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'''Authors:''' [[Axelrod Christopher L]] … '''Authors:''' [[Axelrod Christopher L]], [[Kirwan John P]] Obesity mediates the onset of lipid-induced insulin resistance, increasing the risk of type 2 diabetes. The inability of mitochondria to maintain core functions such as ATP synthesis, redox homeostasis, organelle quality control, and/or preservation of inheritance is proposed to link obesity-related insulin resistance to the onset and progression of type 2 diabetes, yet evidence remains elusive. To parse out the contributions of obesity versus peripheral insulin resistance, healthy weight adults were infused with an intralipid solution followed by evaluation of skeletal muscle mitochondrial function. The lipid infusion reduced insulin sensitivity and dampened mitochondrial membrane potential while increasing markers of mitochondrial fission and increasing the presence of autophagic vesicles, consistent with activation of the quality control machinery. Despite this, respiratory capacity and mitochondrial content were unaltered. From these studies, we concluded that activation of mitochondrial fission and quality control were early events in the onset of insulin resistance to defend cellular energy homeostasis. Subsequently, we conducted a cross-sectional analysis of individuals across the insulin sensitivity spectrum. We observed that markers of fission and quality control were markedly altered in patients with obesity and type 2 diabetes relative to obesity alone and healthy weight despite no apparent differences in respiratory capacity. Mitochondrial volume was incrementally lower in patients with obesity and type 2 diabetes relative to healthy weight. Collectively, we conclude that preservation of bioenergetic function in patients with obesity and type 2 diabetes is achieved by chronic activation of the quality control machinery which occurs at the expense of mitochondrial volume.y which occurs at the expense of mitochondrial volume. +
'''Authors:''' [[Barkova Daria]] … '''Authors:''' [[Barkova Daria]], [[Ukropec Jozef]], [[Nemec Michal]], [[Slobodova L]], [[Schoen M]], [[Tirpakova V]], [[Krumpolec P]], [[Sumbalova Zuzana]], [[Vician M]], [[Sedliak M]], [[Ukropcova Barbara]] '''Introduction:''' Regular exercise supports healthy ageing and reduces risk of elderly chronic diseases. Respirometry is an important tool in understanding the physiological adaptations in response to physical activity at cellular level. Previously, we showed that 3-month exercise training increases muscle metabolism in the elderly. Present study is aimed to assess the effects of long-term training on muscle oxidative capacity in the subset of individuals continuing regular training for 5 years. '''Methods:''' Volunteers (n=60, 66.9±1.2 years, 27.1±3.9 kg/m2) were recruited for 3-month intervention study: 36 of them underwent aerobic-strength training, 24 volunteers were active controls. A volunteer subpopulation continued aerobic-strength training for next 5 years (n=15), and is compared to non-exercising controls (n=15). Body composition, glucose tolerance, insulin sensitivity and other metabolic parameters were assessed. Samples of m. vastus lateralis obtained by biopsy were used for measurement of muscle mitochondria oxygen consumption by O2k high-resolution respirometry, applying RP1 SUIT protocol. '''Results and discussion:''' Three-month exercise training enhanced muscle mitochondrial respiration rate in the elderly undergoing exercise training compared to controls. So far, two individuals completed follow up phenotyping after 5 years training. A slight deterioration in anthropometric (increased BMI by ~ 8 % and visceral fat content by ~ 36%) and metabolic parameters was observed, together with a reduction in muscle mitochondrial respiration (by ~ 15 %). Short-term training improved the whole-body and muscle metabolism in the elderly. Obtaining data from exercising and non-exercising cohorts (currently ongoing) will allow us to assess the impact of a long-term intervention.ongoing) will allow us to assess the impact of a long-term intervention. +
'''Authors:''' [[Brunetta Henver Simionato]] … '''Authors:''' [[Brunetta Henver Simionato]], [[Palermo Ruiz Gabriel]], [[Ludwig Raissa]], [[Ruberti Olivia]], [[Bechara Luiz]], [[Consonni Silvio]], [[Rodrigues Bruno]], [[Ferreira Julio Cesar B]], [[Mori Marcelo AS]] The negative effects of high-fat high-sucrose (HFHS) diet consumption on heart function are exacerbated in mice lacking DICER in adipocytes (AdicerKO). These findings suggest a protective role of adipocyte-derived microRNAs on heart physiology. Exercise training is known to have a protective role in cardiometabolic diseases. However, it is not known whether chronic aerobic training is able to rescue heart dysfunction in HFHS-fed AdicerKO mice. Here, we fed AdicerKO mice with a HFHS diet for 12 weeks, after confirming the deleterious effects of the diet on these mice, we submitted them to moderate aerobic training for 8 weeks, 5 days/week for 60 minutes each section while keeping them on HFHS-diet. Chronic aerobic training restored end-systolic volume and stroke volume in the hearts of HFHS-fed AdicerKO mice without changing ejection fraction. In addition, aerobic exercise increased left ventricle diameter in both, systolic and diastolic, phases. Notably, HFHS-fed AdicerKO-trained mice presented lower heart rate with no differences in systolic blood pressure compared to HFHS-fed AdicerKO sedentary mice. Mechanistically, chronic exercise training lowered mitochondrial H2O2 emission and oxidative stress alongside greater lipid- and succinate-supported mitochondrial respiration. Importantly, these effects were not followed by changes in triacylglycerol content within the left ventricle or fibrosis. In summary, chronic aerobic training is capable to rescue heart function of HFHS-fed AdicerKO mice in association with improvements in mitochondrial bioenergetics and redox balance.ssociation with improvements in mitochondrial bioenergetics and redox balance. +
'''Authors:''' [[Cardoso Luiza HD]] … '''Authors:''' [[Cardoso Luiza HD]], [[Donnelly Chris]], [[Komlodi Timea]], [[Doerrier Carolina]], [[Gnaiger Erich]] '''Introduction:''' Multiple mt-matrix dehydrogenases reduce NAD+ to NADH+H+, which is oxidized by CI (N-junction). Convergent electron flow through several mt-Complexes (CI, CII, CETF, etc) reduces electron transfer system (ETS)-reactive ubiquinone (UQ) to ubiquinol (UQH2), which is oxidized by CIII (Q-junction). The aim of our study was to analyze the relationships between the N- and Q-redox states and electron transfer rates. '''Methods:''' Respiration and N- or Q-redox fractions were measured simultaneously with the Oroboros NextGen-O2k. Multiple protocols were used with sequential titrations of substrates, inhibitors, and uncouplers [1, 2]: N-pool with pyruvate&glutamate&malate, mouse liver mitochondria; Q-pool with succinate&rotenone, octanoylcarnitine&malate or palmitoylcarnitine&malate, permeabilized HEK 293T. After substrates, ADP, CCCP and antimycin A were titrated. '''Results and discussion:''' Varying energy supply upstream of the Q-junction by using combinations of substrates and ETS-inhibitors in the noncoupled state, the Q-pool became reduced in direct proportion to respiration. In contrast, varying downstream energy demand in the absence of ADP (LEAK), by ADP activation (OXPHOS), and by uncoupler titrations (ET capacity), the N- and Q-pools were reduced in indirect proportion to respiration. The opposite correlations between redox state and respiratory rate were explained by the contrasting effects of varying electron push from different fuel substrates of the ETS or electron pull modulated by coupling and corresponding energy demand. Special emphasis on the interaction between fatty acid oxidation, CI, and CII – all involving separate electron entries into the Q-junction [3] – is particularly relevant in the context of obesity and bioenergetics studies.# Komlódi T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2021) Coupling and pathway control of coenzyme Q redox state and respiration in isolated mitochondria. https://doi.org/10.26124/bec:2021-0003# Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. https://doi.org/10.26124/bec:2020-0002 # Gnaiger E (2023) Complex II ambiguities ― FADH2 in the electron transfer system. https://doi.org/10.26124/mitofit:2023-0003.v4 E (2023) Complex II ambiguities ― FADH2 in the electron transfer system. https://doi.org/10.26124/mitofit:2023-0003.v4 +
'''Authors:''' [[Chicco Adam J]] … '''Authors:''' [[Chicco Adam J]], [[Le Catherine H]], [[Mulligan Christopher M]], [[Whitcomb Luke A]], [[Evans Amanda E]], [[Routh Melissa A]], [[Sparanga Genevieve C]] Cardiolipin (CL) is a tetra-acyl mitochondrial phospholipid that supports the optimal function of several mitochondrial membrane proteins and processes. In the healthy mammalian heart, the majority of CL species contain four linoleate acyl chains (L4CL). A marked depletion of cardiac L4CL is paralleled by an increase in CL species containing docosahexaenoic acid (DHA) in hyperphagic obese (''Lepob''; OB) mice despite no change in dietary fat composition [1], but the mechanisms and functional relevance of these changes are unclear. We hypothesized that this shift in CL composition results from increased activity of delta-6 desaturase (D6D), the rate limiting enzyme in the biosynthesis of DHA and conversion of linoleate into highly unsaturated ω-6 fatty acids, by altering the distribution of fatty acids available for CL remodeling. To test this, we administered the selective D6D inhibitor SC-26196 (100 mg/kg/d in chow) to 4-5 month-old OB or lean (C57Bl/6) mice for 4 weeks. As hypothesized, D6D inhibition reversed obesity-related changes in cardiac CL composition, restoring L4CL and DHA-enriched CL species to within 5 % of levels in lean mice, which paralleled reciprocal shifts in the linoleate and DHA levels of total myocardial phospholipids. Obesity-related decreases in cardiac mitochondrial respiratory control by ADP (with NS pathway substrates) and greater mitochondrial H2O2 release during both LEAK and OXPHOS states were also abolished by D6D inhibition. These results corroborate accumulating evidence that cardiac CL composition is strongly influenced by the membrane fatty acids available for CL remodeling [2-3], and may impact the bioenergetic efficiency of mitochondrial respiration. # Han X, Yang J, Yang K, ZhongdancZ, Abendschein DR, Gross RW (2007) Alterations in Myocardial Cardiolipin Content and Composition Occur at the Very Earliest Stages of Diabetes: A Shotgun Lipidomics Study Biochemistry https://doi.org/10.1021/bi7004015 # Le CH et al. (2014) Delta-6-desaturase links PUFA metabolism with phospholipid remodeling and disease progression in heart failure. https://doi.org/10.1161/CIRCHEARTFAILURE.113.000744 # Oemer G, Edenhofer ML, Wohlfarter Y, Lackner K, Leman G, Koch J, Cardoso LHD, Lindner HH, Gnaiger E, Dubrac S, Zschocke J, Keller MA (2021) Fatty acyl availability modulates cardiolipin composition and alters mitochondrial function in HeLa cells. https://doi.org/10.1016/j.jlr.2021.100111 and alters mitochondrial function in HeLa cells. https://doi.org/10.1016/j.jlr.2021.100111 +
'''Authors:''' [[Giordano Luca]] … '''Authors:''' [[Giordano Luca]], [[Nolte A]], [[Wittig Ilka]], [[Pak Oleg]], [[Knoepp F]], [[Ramser K]], [[Wahl J]], [[Cabrera A]], [[Huettemann Maik]], [[Grossman Lawrence]], [[Pecina Petr]], [[Ghofrani HA]], [[Seeger W]], [[Weissmann Norbert]], [[Giehl K]], [[Sommer Natascha]] '''Introduction:''' Hypoxia in the lung alveoli triggers the contraction of the small precapillary pulmonary arteries, i.e., hypoxic pulmonary vasoconstriction (HPV), avoiding life-threatening hypoxemia. Pulmonary arterial smooth muscle cells (PASMCs) are involved in HPV, with the mitochondrial cytochrome c oxidase (COX) subunit 4 isoform 2 (Cox4i2) playing an essential role in the acute oxygen sensing1. Nonetheless, the molecular mechanism by which Cox4i2 sensitizes the whole COX remains unclear. '''Methods:''' We analysed superoxide production by MitoSOX, oxygen consumption by high-resolution respirometry, redox changes of the electron transport system (ETS) by RAMAN spectroscopy, and supercomplex formation by blue native gel analysis of PASMCs isolated from wild type (WT) and Cox4i2 knockout mice (Cox4i2 KO) exposed to normoxia or hypoxia. To figure out the role of Cox4i2-specific cysteine residues we generated mouse epithelial (CMT167) cells overexpressing either Cox4i1, or WT Cox4i2, or Cox4i2 mutants (C41S, C55A, C109S), and we tested their superoxide production and oxygen affinity. '''Results:''' Respiration, abundance, and COX assembly were similar in WT and Cox4i2 KO PASMCs. On the contrary, hypoxia-induced production of superoxide and the reduction of ETS components (NADH, ubiquinol, cytochrome c) was prevented in Cox4i2 KO PASMCs. CMT167 cells expressing either Cox4i1, or Cox4i2 mutants lacked hypoxia-induced superoxide production, which was detected only in cells expressing WT Cox4i2. Overexpression of Cox4i1, or Cox4i2, or Cox4i2 mutants did not affect oxygen affinity. Our findings suggests that Cox4i2 does not alter superoxide production by rearrangement of supercomplexes, but by the reduction of the ETS, likely mediated by the cysteine residues.Sommer N, Hüttemann M, et al. Mitochondrial Complex IV Subunit 4 Isoform 2 Is Essential for Acute Pulmonary Oxygen Sensing. Circ Res. 2017;121(4):424-38.r Acute Pulmonary Oxygen Sensing. Circ Res. 2017;121(4):424-38. +
'''Authors:''' [[Guerrier Lisa]] … '''Authors:''' [[Guerrier Lisa]], [[Malpuech-Brugere C]], [[Bacoeur-Ouzillou O]], [[Cassagnes L]], [[Pezet D]], [[Gagniere J]], [[Richard R]], [[Touron Julianne]] '''Introduction:''' Adipose tissue (AT), as an endocrine organ, plays an important role in health and diseases, but unlike skeletal muscle, its energy metabolism have been under investigated due to technical limitations. Nevertheless, according to recent studies, mitochondria could play a predominant role in AT disorders and their activity could depend on adiposity level (1-3). This study aims to evaluate mitochondrial activity and metabolism of human visceral and subcutaneous white AT and their relationship with body mass index (BMI) and composition. '''Methods:''' Sixty-two patients undergoing digestive surgery, without chemotherapy, nor parietal infection, have been included in the study with BMI ranging from 15.4 to 51.9 kg·m-2. Their body composition was assessed by computed tomographic (CT) image at third lumbar vertebra (L3). Mitochondrial function was measured in situ in digitonin-permeabilized adipocytes using high resolution respirometry and a substrate/inhibitor titration approach (Figure) (4,5). Protein accumulation of mitochondrial and lipid metabolism key elements was evaluated by Western-blot. '''Results and discussion:''' Results showed a negative correlation between maximal mitochondrial respiration and BMI (p<0.05) as well as with AT surface, regardless of the anatomical location, though, OXPHOS respiration was significantly higher in visceral (2.22±0.15 pmol·sec-1·mg-1) than in the subcutaneous AT (1.79±0.17 pmol·sec-1·mg-1). Thus, mitochondrial function can be studied with small amount of AT despite its low mitochondrial density and can be discriminated according to AT depot and BMI. Further analyses are required to know whether the observed differences are quantitative and/or qualitative, as well as to identify the mechanisms involved # Ling Y et al. (2019) Persistent low body weight in humans is associated with higher mitochondrial activity in white adipose tissue. https://doi.org/10.1093/ajcn/nqz144# Fischer B, Schöttl T, Schempp C, Fromme T, Hauner H, Klingenspor M, Skurk T (2015) Inverse relationship between body mass index and mitochondrial oxidative phosphorylation capacity in human subcutaneous adipocytes. https://doi.org/10.1152/ajpendo.00524.2014# Wessels B, Honecker J, Schöttl T, Stecher L, Klingenspor M, Hauner H, Skurk T (2019) Adipose Mitochondrial Respiratory Capacity in Obesity is Impaired Independently of Glycemic Status of Tissue Donors. https://doi.org/10.1002/oby.22435# Kraunsøe R, Boushel R, Neigaard Hansen C, Schjerling P, Qvortrup K, Støckel M, Mikines KJ, Dela F (2010) Mitochondrial respiration in subcutaneous and visceral adipose tissue from patients with morbid obesity. https://doi.org/10.1113/jphysiol.2009.184754# Sahl RE, Frederikke Høy Helms E, Schmücker M, Flensted-Jensen M, Ingersen A, Morville T, Dela F, Wulff Helge J, Larsen S (2021) Reliability and variation in mitochondrial respiration in human adipose tissue. https://doi.org/10.1080/21623945.2021.1991617en S (2021) Reliability and variation in mitochondrial respiration in human adipose tissue. https://doi.org/10.1080/21623945.2021.1991617 +
'''Authors:''' [[Holloway Graham P]] … '''Authors:''' [[Holloway Graham P]], [[Petrick Heather L]], [[van Loon LJC]] Mitochondria play a key role in metabolic homeostasis, with impaired mitochondrial biology directly linked with numerous pathological conditions, including skeletal muscle atrophy, insulin resistance and heart dysfunction. Our team has focused on identifying nutritional approaches that preserve mitochondrial bioenergetics as a preventative medicine approach. In particular, we have studied dietary nitrate, which can be consumed through foods such as beets and green leafy vegetables or supplementation, as this compound appears to positively affect mitochondrial bioenergetics in diverse tissues. Additionally, we have shown that dietary nitrate can prevent high-fat diet-induced cardiac dysfunction, whole-body insulin resistance, dyslipidemia, and hepatic dysfunction. Moreover, we have recently uncovered that nitrate prevents skeletal muscle disuse-mediated reductions in mitochondrial protein synthesis rates (FSR), mitochondrial protein content, respiration and prevented the normal increase mitochondrial reactive oxygen species (ROS) emission during limb immobilization. While these physiological outcomes are likely in part linked to the serial reduction of nitrate to systemic nitric oxide (NO)-mediated vasodilation, we have also utilized fecal microbial transplantation from nitrate-fed donors to prevent HFD-induced cardiac dysfunction in the absence of increasing serum nitrate or reducing blood pressure. Given these systemic, reproducible, and consistent effects, nitrate appears to represent a viable therapeutic approach to improve mitochondrial bioenergetics to combat compromised cardiometabolic health in diverse situations.promised cardiometabolic health in diverse situations. +
'''Authors:''' [[Jasinska Joanna]] … '''Authors:''' [[Jasinska Joanna]], [[Bednarczyk Piotr]], [[Kalenik B]], [[Kulawiak Bogusz]], [[Wrzosek A]], [[Szewczyk Adam]] Recent studies point out that mitochondria are not only a source of ATP in the cell, but more and more data indicate their role related to Ca2+ buffering, production of reactive oxygen species (ROS) and activation of intracellular signaling pathways of necrosis and apoptosis. Recent studies clearly indicate that mitochondrial potassium channels (mitoK) present in the inner mitochondrial membrane play an important protective role in the ischemia-reperfusion processes of myocardial cell damage. These results were obtained using low molecular weight chemicals. Due to the lack of selective modulators of potassium channels, we opted for an alternative approach to modulate the activity of mitoK channels by changing the redox state of the respiratory chain, which we have demonstrated in previous studies. Some respiratory chain proteins are thought to absorb infrared (IR) light. Cytochrome c oxidase (COX) may be important in these mechanisms because it has four metal redox centers: binuclear CuA, CuB, heme a, and heme a3. All these metal centers are able to absorb light waves in the IR region. Data obtained in our laboratory indicate that COX may be functionally linked to mitochondrial high-conductance Ca2+-activated potassium channels (mitoBKCa) in the U87 cell line1. Using the patch-clamp technique with the illumination system, we exposed the mitoBKCa channel. We observed that in the presence of ferricyanide, channel activity was inhibited and that mitoBK channel activity could be restored by 820 nm illumination, suggesting that COX is involved in the modulation of mitoBK channel activity.# Szewczyk A and Bednarczyk P (2018) Modulation of the Mitochondrial Potassium Channel Activity by Infrared Light. https://doi.org/10.1016/j.bpj.2017.11.288ed Light. https://doi.org/10.1016/j.bpj.2017.11.288 +
'''Authors:''' [[Karabatsiakis Alexander]] … '''Authors:''' [[Karabatsiakis Alexander]], [[Manrique Juan-Salinas]], [[Stoll Thomas]], [[Hennessy Thomas]], [[Hill Michelle M]], [[Dietrich Detlef E]] Major depressive disorder (MDD) is characterized by impairments in mental and physical performance. Despite intensified hypothesis-driven research, applicable biomarkers for MDD are missing. Research showed that MD is associated with impaired mitochondrial bioenergetic functioning in peripheral blood mononuclear cells (PBMC). However, deeper biomolecular insights into bioenergetic and associated biochemical changes in blood underlying the pathophysiology of MDD are necessary to identify new biomarker candidates. Here, the biochemistry of PBMC-surrounding blood was analyzed using a hypothesis-free biomarker identification approach combining metabolite and lipid fingerprinting. Biochemical fingerprints of serum were compared between female individuals (N = 44) with and without MDD. Serum extracts were separated by liquid chromatography and detected with time-of-flight mass spectrometry. The data was analyzed by multiple group comparisons and correlations, as well as two multivariate classification procedures. Next, our previously identified alterations in mitochondrial bioenergetics in PBMC were co-considered as an outcome for our biomarker identification approach. Consequently, the most promising compound was tested for correlation with mitochondrial respiration. Nine biomarker candidates discriminated between MDD and non-MDD with high predictive accuracy (90.9 %). The detected compounds are involved in lipid and amino acid-metabolism. ''9,10-dihydroxy-octadenedioic acid'' was revealed as a robust biomarker candidate with a predictive accuracy of 81.8 % and significant mean positive correlation with parameters of mitochondrial respiration (r = 0.31-0.48, p<0.01). Our fingerprinting results highlight novel biomarker candidates and associated pathways for MDD research. The unraveled biochemical pathways indicate a modulated association of MDD with inflammation, oxidative stress, and mitochondrial bioenergetics. The biomarker candidates have to be replicated in independent cohorts of all ages & sexes.be replicated in independent cohorts of all ages & sexes. +
'''Authors:''' [[Kopecky Jan]] … '''Authors:''' [[Kopecky Jan]], [[Zouhar Petr]], [[Janovska Petra]], [[Bardova K]], [[Otahal J]], [[Vrbacky Marek]], [[Mracek Tomas]], [[Adamcova K]], [[Lenkova L]], [[Funda J]], [[Cajka T]], [[Drahota Zdenek]], [[Stanic S]], [[Rustan Arild C]], [[Horakova Olga]], [[Houstek Josef]], [[Rosmeissl M]] Heat production is essential for maintaining a constant body temperature, and is an important component of energy balance. Well-described mechanisms involved in heat generation include shivering of muscle and non-shivering thermogenesis (NST) in brown adipose tissue (BAT). Thermogenesis in BAT, which is dependent on the presence of the mitochondrial protein UCP1, is the focus of interest for its potential use in the treatment of obesity. Other mechanisms of NST and their significance are relatively poorly understood. We have shown [1] that obesity-resistant A/J mice acclimated to cold failed to increase adrenergically stimulated NST in BAT and activated NST in skeletal muscle instead. Heat generation in muscle involved increased calcium ion cycling in the endoplasmic reticulum associated with higher mitochondrial oxidative activity. The involvement of different thermogenic mechanisms could be related to the different susceptibility to obesity. The resistance of A/J mice to obesity may result, at least in part, from their ability to activate NST in muscle. Such mechanism may provide a more promising way to treat obesity than potential therapies based on increasing thermogenesis in BAT, as the capacity of skeletal muscle of adult human to burn fat energy stores is several fold greater than in BAT. Thus, only a relatively small increase in thermogenesis in muscle could significantly reduce adipose tissue deposition. How to achieve such an increase is a challenge for further research. # Janovska P et al., 2023, Mol Metab. https://doi.org/10.1016/j.molmet.2023.101683Metab. https://doi.org/10.1016/j.molmet.2023.101683 +
'''Authors:''' [[Mahapatra Gargi]] … '''Authors:''' [[Mahapatra Gargi]], [[Gao Zhengrong]], [[Bateman James R III]], [[Lockhart Samuel Neal]], [[Bergstrom Jaclyn]], [[Craft Suzanne]], [[Molina Anthony JA]] Impaired glucose tolerance (IGT), including prediabetes and diabetes, increases risk of developing age related disorders, including Alzheimer’s disease (AD). We analyzed mitochondrial bioenergetics in platelets collected from 208 adults, 55 years and older, with or without insulin sensitivities (112 normoglycemics (NG), 96 IGTs). Platelets from IGT participants exhibited unique bioenergetic profiles exemplified by higher mitochondrial respiration than NG. IGT platelets exhibited higher glucose-dependent maximal (Max) and spare respiratory (SRC) capacities compared to NG, and higher fatty acid oxidation-dependent maximal coupled (MaxOXPHOS) and uncoupled (MaxETS) respiration compared to NG. Correlating bioenergetics from all 208 participants combined with glucose measures (OGTT_120, OGTT_AUC, and HbA1c) revealed significant positive associations. Most associations were unaltered with age, sex, and BMI adjustments. Further separating NG and IGT participants and correlating platelet respiration with glucose measures revealed distinct trends in NG versus IGT group. In NG, previously observed associations remained intact, and new significant positive associations emerged between platelet bioenergetics and HbA1c. Associations in IGT group were overall negative. Identifying systemic mitochondrial mechanisms that associate with glucose intolerance in older adults will help in monitoring pathological progression of AD in relation to comorbidities such as insulin sensitivity, and supports the development of minimally invasive biomarkers of AD.# Mahapatra G, Gao, Bateman JR III, Lockhart SN, Bergstrom J, DeWitt AR, Piloso JE, Kramer PA, Gonzalez-Armenta JL, Amick A, Casanova R, Craft S, Molina AJA (2022) Blood-Based Bioenergetic Profiling Reveals Differences in Mitochondrial Function Associated with Cognitive Performance and Alzheimer’s Disease Alzheimer's & Dementia 2022. https://doi.org/10.1002/alz.12731 & Dementia 2022. https://doi.org/10.1002/alz.12731 +
'''Authors:''' [[Nagwani Amit K]] … '''Authors:''' [[Nagwani Amit K]], [[Kaczmarek L]], [[Kmita H]] '''Introduction:''' Tardigrades are considered as one of the toughest animals on Earth due to their remarkable ability to withstand extreme condition. An example of these conditions is hypomagnetic field (HMF, static magnetic field with an intensity <5 μT), which is known to influence the metabolic processes including mitochondria functioning. However, very few studies considering HMF impact were performed for organisms able to survive under extreme conditions and considered as suitable for outer space colonization. Therefore, we decided to check the impact of HMF on the tardigrade ''Paramacrobiotus experimentalis'' focusing on mitochondria functionality reflected by the mitochondrial inner membrane potential (ΔΨ) having regard to age and sex. '''Methods:''' Females and males from 3 different age classes (i.e., 30-60, 150-180 and >300 days) were extracted from laboratory culture and divided into experimental and control groups exposed to HMF and standard magnetic field (SMF), respectively, for three different durations i.e., 7 days, 15 days and 30 days. The HMF treatment was performed in a special anti-magnetic chamber whereas SMF treatment was performed in a climate chamber. TMRM staining of intact animals was used to estimate ΔΨ. '''Results and discussion:''' The calculated FITMRM index indicated HMF-related changes in Δψ dependent on age and sex. Accordingly, HMF effect was most pronounced for the oldest animals and males appeared to be more sensitive to HMF than females that correlated with the survival rate. The results provide an insight into mechanisms of HMF effect that could be useful for organization of space travels and living outside the Earth. # Mo W, Liu Y, He R. (2014) Hypomagnetic field, an ignorable environmental factor in space? https://doi.org/10.1007/s11427-014-4662-x# Binhi VN, Prato FS (2017) Biological effects of the hypomagnetic field: An analytical review of experiments and theories. https://doi.org/10.1371/journal.pone.0179340# Conley CC (1970) A Review of the biological effects of very low magnetic fields. NASA. Technical Note; TN D-5902: 1–27. https://ntrs.nasa.gov/citations/19700024915# Erdmann W, Idzikowski B, Kowalski W, Kosicki J, Kaczmarek Ł (2021) Tolerance of two anhydrobiotic tardigrades Echiniscus testudo and Milnesium inceptum to hypomagnetic conditions. https://doi.org/10.7717/peerj.10630scus testudo and Milnesium inceptum to hypomagnetic conditions. https://doi.org/10.7717/peerj.10630 +
'''Authors:''' [[Owesny Patricia]] … '''Authors:''' [[Owesny Patricia]], [[Hegemann N]], [[Kuebler WM]], [[Ost Mario]], [[Grune T]], [[Ott C]] Cardiac aging is a multifactorial process, which is associated with increased oxidative stress, cell death and mitochondrial abnormalities. These factors can lead to an overall impairment of cardiac function and substrate utilization [1,2]. With the increased prevalence of obesity and related comorbidities, especially coronary heart disease, it was proposed that obesity could present a condition of premature heart aging [3]. Therefore, our aim is to compare the impact of obesity and aging on heart function, as well as the cardiac energy metabolism, focusing on mitochondria. Our experimental design of diet-induced obesity contains three different age groups (22, 76 and 106 weeks), where male C57BL/6J mice receive either a High fat/High-carb or a Standard diet for 8 weeks. After dietary intervention, mice underwent echocardiographic or metabolic treadmill analysis. Heart tissue was used for the Oroboros O2k measurement of mitochondrial bioenergetics. In further studies of cardiac energy metabolism Western blot and qPCR in heart tissue and isolated cardiomyocytes were performed. Echocardiography revealed a decline in cardiac output in mice 76 and 106 weeks of age with a further decrease by High fat/High-carb diet. Interestingly, these effects were more pronounced in 76 weeks group. In the same group we investigated indications of an impaired mitochondrial energy metabolism, specifically associated with cardiomyocytes. Although, loss of cardiac function with age has been previously described, we demonstrate here a key role for mitochondrial energy metabolism in this loss of function. # Houtkooper R H, Argmann C, Houten S M, Cantó C, Jeninga E H, Andreux P A, Thomas C, Doenlen R, Schoonjans K, Auwerx J (2011), The metabolic footprint of aging in mice. https://doi.org/10.1038/srep00134. # Lazzeroni D, Villatore A, Souryal G, Pili G, Peretto G (2022), The Aging Heart: A Molecular and Clinical Challenge. https://doi.org/10.3390/ijms232416033.# Ren J, Dong F, Cai G-J, Zhao P, Nunn J M, Wold L E, Pei J (2010), Interaction between age and obesity on cardiomyocyte contractile function: role of leptin and stress signaling. https://doi.org/10.1371/journal.pone.0010085.n and stress signaling. https://doi.org/10.1371/journal.pone.0010085. +
'''Authors:''' [[Petrick Heather L]] … '''Authors:''' [[Petrick Heather L]], [[Aussieker T]], [[Fuchs CJ]], [[Hermans WJ]], [[Betz MW]], [[Pinckaers PJM]], [[Snijders T]], [[van Loon LJC]], [[Holloway Graham P]] '''Introduction:''' Mitochondrial ADP sensitivity represents an important control point in oxidative phosphorylation. The sensitivity of mitochondria to ADP is lower in high-lipid environments, in aging males, and in young females compared to young males. However, the interaction between sex, age, and body composition (fat mass) in the regulation of mitochondrial ADP sensitivity remains unknown. '''Methods:''' Vastus lateralis muscle biopsies were obtained from healthy, recreationally active, young males (n=21, 24±4 y, 22.7±2.2 kg/m2 BMI), young females (n=20, 21±2 y, 21.7±2.2 kg/m2), older males (n=13, 76±5 y, 25.8±2.5 kg/m2), and older females (n=6, 70±6 y, 23.4±3.0 kg/m2). Permeabilized fibers were prepared to measure mitochondrial ADP sensitivity. Whole-body DEXA scans were performed. Data (mean±SD) were analyzed using two-way ANOVAs. '''Results and discussion:''' Body fat percentage was higher in females and older individuals (main effects). While maximal mitochondrial respiration did not differ between groups, mitochondrial ADP sensitivity was affected by sex and age. Specifically, in younger individuals mitochondrial ADP sensitivity was lower in females compared with males (~15 % higher apparent ADP Km, p=0.02). Older males also showed ~15% lower mitochondrial ADP sensitivity compared with young males (p=0.04). In contrast to young individuals, mitochondrial ADP sensitivity was numerically greater (~15 %) in older females when compared with older males (p=0.14) and younger females (p=0.12). However, there were no correlations between body fat percentage and mitochondrial apparent ADP Km in any group. We speculate that sex-based differences in mitochondrial ADP sensitivity are impacted by estrogen as opposed to body composition, as this response is lost with aging. ADP sensitivity are impacted by estrogen as opposed to body composition, as this response is lost with aging. +
'''Authors:''' [[Phang Howard J]] … '''Authors:''' [[Phang Howard J]], [[Gerwick W]], [[Molina Anthony JA]] Mitochondrial bioenergetic decline is a well known biological hallmark of aging, suggesting that mitochondria-targeting therapeutics have great potential in treating age-related diseases and conditions [1]. Despite this, their efficacy within the context of human aging remains largely unknown. We sought to develop a phenotypic screening platform to identify agents that directly modulate mitochondrial function in human cells. Marine natural products (MNP) represent a large, under-explored chemical space with immense therapeutic potential [2]. We screened a MNP library of 125 pure compounds at 10, 1, and 0.1 µg/mL incubated for 24 hours with with primary human dermal fibroblasts (pHDF) as summarized in Figure 1. We leveraged the San Diego Nathan Shock Center which houses 50+ pHDF lines derived from healthy donors across a spectrum of adult age. Cultured pHDF retain age-related phenotypes including mitochondrial bioenergetic decline, which presents a robust opportunity to identify bioenergetic effects within the context of human aging [3]. Thus, we used pHDF from a donor representative of an “older” phenotype (74 years of age) to ensure aging relevance. We identified numerous compounds that modulate mitochondrial function in a dose-dependent manner. Our primary outcomes were change in basal or maximal respiration using high throughput respirometry (Agilent Seahorse XFe96). This screening platform successfully identified compounds with stimulatory as well as inhibitory effects on respiratory capacity. Future steps include further validation of hit compounds using high-resolution respirometry on the Oroboros O2k. These studies will elucidate mechanistic effects on the electron transfer system as well as effects on cells of different donor ages. # Murphy MP, Hartley RC (2018) Mitochondria as a therapeutic target for common pathologies. https://doi.org/10.1038/nrd.2018.174.# Liang X, Luo D, Luesch H (2018) Advances in exploring the therapeutic potential of marine natural products. https://doi.org/10.1016/j.phrs.2019.104373. # Auburger G, Klinkenberg M, Drost J, Marcus K, Morales-Gordo B, Kunz WS, Brandt U, Broccoli V, Reichmann H, Gispert S, Jendrach M (2012). Primary Skin Fibroblasts as a Model of Parkinson's Disease. https://doi.org/10.1007/s12035-012-8245-1. Parkinson's Disease. https://doi.org/10.1007/s12035-012-8245-1. +
'''Authors:''' [[Piel Sarah]] … '''Authors:''' [[Piel Sarah]], [[cManus Meagan J]], [[Heye K]], [[Beaulieu F]], [[Fazeliniae H]], [[Janowska Joanna I]], [[McTurk B]], [[Starr Jonathan]], [[Gaudio H]], [[Patel N]], [[Hefti MM]], [[Smalley M]], [[Hook JF]], [[Kohli NV]], [[Bruton J]], [[Hallowell T]], [[Delso N]], [[Roberts A]], [[Lin Y]], [[Ehinger Johannes K]], [[Karlsson Michael]], [[Berg RA]], [[Morgan RW]], [[Kilbaugh Todd J]] '''Introduction:''' Despite advancements in cardiopulmonary resuscitation (CPR), secondary neurological injury remains the key determinant of successful recovery from cardiac arrest (CA) [1-3]. Currently, there are no established clinical therapies that preserve neurological function [4]. We previously found that acute decline in mitochondrial health up to 24 hours post-CA correlated with poor neurological outcome [5-6]. Here, we tested the potential of dimethyl fumarate (DMF), a derivative of the TCA-cycle intermediate fumaric acid shown to enhance mitochondrial bioenergetics [7], to improve mitochondrial injury in brain and heart following successful resuscitation after CA. '''Methods:''' Female piglets representing toddler age underwent asphyxia, followed by ventricular fibrillation, cardiopulmonary resuscitation and defibrillation until return of spontaneous circulation. Subsequently, animals received daily treatment with DMF or vehicle. Sham animals underwent identical anesthesia protocols and instrumentation without CA. After 4 days, animals (n=5 of each group) were euthanized, tissues were harvested and their mitochondrial function, quantity and proteomic profile was analyzed. '''Results and discussion:''' Mitochondrial content and function, as measured by citrate synthase activity and high-resolution respirometry, was reduced at 4 days following CA. In contrast, myocardial mitochondria demonstrated a complete restoration of mitochondrial content and function despite persistent changes in mitochondrial ultrastructure. DMF treatment prevented 25 % of the long-term proteomic changes in the brain, including proteins related to mitochondrial bioenergetics and oxidative stress. In addition, myocardial mitochondrial morphology was normalized by DMF. In this model of CA, mitochondria sustained persistent damage in an organ-specific manner. DMF partially prevents these long-term mitochondrial changes in myocardium and brain.# Berg RA et al: Incidence and Outcomes of Cardiopulmonary Resuscitation in PICUs. Crit Care Med 2016; 44(4):798-808# Slomine BS, Silverstein FS, Christensen JR, et al: Neurobehavioural outcomes in children after In-Hospital cardiac arrest. Resuscitation 2018; 124:80-89# Laver S, Farrow C, Turner D, et al: Mode of death after admission to an intensive care unit following cardiac arrest. Intensive Care Med 2004; 30(11):2126-2128# Neumar RW et al: Post-Cardiac Arrest Syndrome. Circulation 2008; 118(23):2452-2483# Lautz AJ, Morgan RW, Karlsson M, et al: Hemodynamic-Directed Cardiopulmonary Resuscitation Improves Neurologic Outcomes and Mitochondrial Function in the Heart and Brain. Critical care medicine 2019; 47(3):e241-e249# Kilbaugh TJ, Sutton RM, Karlsson M, et al: Persistently Altered Brain Mitochondrial Bioenergetics After Apparently Successful Resuscitation From Cardiac Arrest. Journal of the American Heart Association 2015; 4(9):e002232# Hayashi G, Jasoliya M, Sahdeo S, et al: Dimethyl fumarate mediates Nrf2-dependent mitochondrial biogenesis in mice and humans. Human molecular genetics 2017; 26(15):2864-2873ice and humans. Human molecular genetics 2017; 26(15):2864-2873 +
'''Authors:''' [[Pytlak Karolina]] … '''Authors:''' [[Pytlak Karolina]], [[Maliszewska – Olejniczak K]], [[Sek Aleksandra]], [[Szewczyk Adam]], [[Bednarczyk Piotr]], [[Kulawiak Bogusz]] Human bronchial epithelial (HBE) cells form an external barrier in the airways and are constantly exposed to factors such as urban dust. Recently, the large conductance calcium-activated potassium (mitoBKCa) channel has been identified in the inner mitochondrial membrane of HBE cells. The pore-forming subunit of the channel is encoded by the ''KCNMA1'' gene, which also encodes plasma membrane BKCa channels. Mitochondrial potassium channels regulate mitochondrial membrane potential, oxygen consumption, mitochondrial volume and reactive oxygen species synthesis. Activation of mitoBKCa induces cytoprotection of cardiac and brain tissue. In our project, we applied CRISPR/Cas9 technique to disrupt ''KCNMA1'' gene in the HBE cell line (16HBE14o- cells). The newly formed line showed no mitoBKCa channel activity. We also noticed changes related to the deregulation of the cell cycle. The loss of mitoBKCa significantly affected mitochondrial function. We observed a decrease in the rate of mitochondrial respiration. Furthermore, we analyzed the organization of respiratory chain complexes using Blue Native electrophoresis. In addition, analysis of the expression of selected genes encoding mitochondrial proteins showed changes in cells with disrupted ''KCNMA1'' gene. Nevertheless, a thorough understanding of the observed mitochondrial dysfunction requires further study.We conclude that the presence of the mitoBKCa channel in HBE cells is essential for the preservation of mitochondrial function and is important for the proper function of these cells as part of the human airways. for the preservation of mitochondrial function and is important for the proper function of these cells as part of the human airways. +
'''Authors:''' [[Sadler Daniel]] … '''Authors:''' [[Sadler Daniel]], [[Treas L]], [[Ross T]], [[Sikes JD]], [[Britton SL]], [[Koch LG]], [[Borsheim Elisabet]], [[Porter Craig]] '''Introduction:''' Low cardiorespiratory fitness (CRF) is associated with a greater risk for metabolic disease. The potential for early life exercise training to overcome metabolic perturbations imparted by low intrinsic CRF remains unknown. We tested the hypothesis that early life exercise training would overcome whole-body and tissue metabolic defects imparted by low CRF.'''Methods:''' At 26 days of age, rat low-capacity runners (LCR, ''n''=20) and high-capacity runners (HCR, ''n''=20) generated by artificial selection were assigned to either sedentary control (CTRL, n=10) or voluntary wheel running (VWR, ''n''=10) for 6 weeks. Post-intervention, whole-body metabolic phenotyping was performed, and the respiratory function of isolated skeletal muscle and liver mitochondria assayed. Quantitative proteomics were performed on tissue samples.'''Results and discussion:''' HCR-VWR performed 1.8-fold greater volume of wheel running than LCR-VWR (P<0.001). In LCR, VWR reduced body fat (''P''<0.001), increased total daily energy expenditure (+16 %, ''P''=0.030), and enhanced glucose tolerance (''P''=0.040). Muscle mitochondrial respiratory function was unaffected by VWR in both strains, although VWR increased muscle mitochondrial protein content (both ''P''<0.05). VWR enhanced the respiratory capacity of HCR hepatic mitochondria (+23 %, ''P''=0.040). Proteomic analyses revealed lower capacity for fatty acid oxidation in muscle and liver of LCR-CTRL versus HCR-CTRL, which was not rescued by VWR. VWR reduced hepatic pyruvate kinase abundance in both strains (both ''P''<0.013), indicating VWR may shift fuel preferences of hepatic mitochondria. These results reveal early life exercise training partially overcomes the metabolic phenotype imparted by low intrinsic CRF, although proteomic adaptations to early exercise training remain influenced by intrinsic CRF. to early exercise training remain influenced by intrinsic CRF. +
'''Authors:''' [[Saleem Ranim]] … '''Authors:''' [[Saleem Ranim]], [[Scott Graham R]] '''Introduction:''' High-altitude environments are characterized by cold temperatures and low O2 levels (hypoxia). Small mammals at high altitude thus face the metabolic challenge of maintaining thermogenesis to cope with cold in a hypoxic environment that can constrain aerobic ATP supply. Circulatory O2 delivery by the heart is essential for supporting tissue O2 demands, but it is unclear whether evolved or plastic changes in cardiac mitochondria help overcome constraints on thermogenesis in high-altitude environments. '''Method:''' We examined this issue in deer mice (Peromyscus maniculatus). Mice from populations native to high altitude and low altitude were born and raised in captivity, and adults were acclimated to warm (25 °C) normoxia or cold (5 °C) hypoxia (~12 kPa O2 for 5-6 weeks) in a full-factorial design. Mitochondrial function was studied by high-resolution respirometry and fluorometry in permeabilized tissue from left ventricles and was complemented by assays of several metabolic and antioxidant enzymes. '''Results and discussion:''' Mitochondrial capacities for oxidative phosphorylation and electron transport were similar between populations and were unaffected by acclimation to cold hypoxia, as were activities of citrate synthase and cytochrome oxidase. However, exposure to cold hypoxia increased activities of lactate dehydrogenase, which were also greater in highlanders than in lowlanders, likely to augment capacities for lactate oxidation. Furthermore, mitochondrial emission of reactive oxygen species was lower in highlanders than in lowlanders across environments, associated with lower levels of lipid peroxidation and protein carbonyls. Therefore, phenotypic plasticity and evolved changes in cardiac mitochondria help deer mice cope with metabolic challenges at high altitude. evolved changes in cardiac mitochondria help deer mice cope with metabolic challenges at high altitude. +
'''Authors:''' [[Saucedo-Rodriguez Maria Jose]] … '''Authors:''' [[Saucedo-Rodriguez Maria Jose]], [[Pecina Petr]], [[Cunatova Kristyna]], [[Vrbacky Marek]], [[Cajka T]], [[Mracek Tomas]], [[Pecinova Alena]] '''Introduction:''' Succinate dehydrogenase (SDH) connects the TCA cycle by oxidizing succinate to fumarate and the respiratory chain by transferring electrons to ubiquinone. Mutations in SDH subunits have been associated with tumorigenesis as well as mitochondrial diseases. In this project, we focused on the flavoprotein subunit A of SDH (SDHA) which is primarily associated with inherited mitochondrial disease [1] and investigated the consequences of this subunit loss in HEK cells (SDHA KO). '''Methods:''' We performed structural and functional characterizations of the SDHA KO model involving protein electrophoresis to study OXPHOS complexes and subcomplexes, label-free quantification of protein levels, measurement of cellular respiration using high-resolution respirometry and determination of NAD+/NADH levels. '''Results and discussion:''' Together with SDHA, other SDH subunits were downregulated as well, leading to the absence of assembled SDH. Moreover, a secondary downregulation of the majority of complex I and IV subunits was observed. The cellular respiratory capacity was severely decreased in the model, with SDH-dependent respiration completely abolished and complex I-dependent respiration attenuated reflecting the downregulation of respiratory chain complexes in general. Finally, the NAD+/NADH ratio was increased in SDHA KO compared to the controls, indicating complex rearrangement of the TCA. The SDHA KO cells thus represent a suitable model to study metabolic rewiring and the effect of pathogenic SDHA mutations. # Rustin, P., Munnich, A., & Rötig, A. (2002). Succinate dehydrogenase and human diseases: new insights into a well-known enzyme. https://doi.org/10.1038/sj.ejhg.5200793 d human diseases: new insights into a well-known enzyme. https://doi.org/10.1038/sj.ejhg.5200793 +
'''Authors:''' [[Schoenfeld Peter|Schönfeld P]], … '''Authors:''' [[Schoenfeld Peter|Schönfeld P]], [[Reiser G]] Distinct hypothalamic neurons sense blood levels of fatty acids (FA) and, thereby regulate caloric intake. Astrocytes have some capacity of β-oxidation. But, there are ongoing discussions on this question: Do neurons generally burn FA for energy generation?Respiration and membrane potential of mitochondria of rat brain (RBM) and, for comparison, of liver (RLM) were measured without and with octanoate (l-octanoylcarnitine). In addition, H2O2 generation was measured with Amplex Red.In line with previous studies, we found no evidence for a noteworthy β-oxidation of FA by RBM. This fits with theoretical considerations (1) and values obtained for capacities of enzymes of β-oxidation (2). But, these results contradict those of a previous study (3), reporting that RBM incubated with mixtures of FA (carnitine derivatives) plus other substrates (e.g. succinate) show substantial β-oxidation. What could be possible reasons for disregarding FA as energy substrates by neurons? These are mainly: (a) Harmful activities of non-esterified long-chain FA on mitochondria. (b) Burning of FA costs more oxygen than glucose burning with respect to the energy yield. (c) FA oxidation by mitochondria is associated with more sites of superoxide generation. (d) Neurons are equipped with poor antioxidative capacity. In conclusion, burning of FA would expose neurons to intolerably high oxidative stress.# Speijer D (2011] Oxygen radicals shaping evolution: Why fatty acid catabolism leads to peroxisomes while neurons do without it. https://doi.org/10.1002/bies.201000097# Yang SY, He XY, Schultz H (1987) Fatty acid oxidation in rat brain is limited by the low activity of 3-ketoacyl-coenzyme A thiolase. https://doi.org/10.1016/S0021-9258(18)45161-7# Panov A, Orynbayeva Z, Vavilin V, Lyakhovich V (2014) Fatty acids in energy metabolism of the central nervous system. https://doi.org/10.1155/2014/472459tabolism of the central nervous system. https://doi.org/10.1155/2014/472459 +
'''Authors:''' [[Sobotka Lubos]] … '''Authors:''' [[Sobotka Lubos]], [[Sobotka Ondrej]] Obesity is associated with insulin resistance, which is the cause of subsequent metabolic complications, including increased morbidity. Despite several decades of efforts to prevent the growth of obesity, its incidence continues to increase. We do not even know what ratio of nutrients is optimal for preventing obesity and insulin resistance, and the optimal ratio of carbohydrates to lipids has not been proven. Some studies, including calorimetric measurements performed at our workplace, have shown that the oxidation of individual substrates does not correspond to their ratio in the given diet. However, this apparent paradox makes sense because food intake in humans is intermittent and usually does not occur during increased or even maximal physical activity. Energy and metabolic substrates are stored in the body during intake and are subsequently mobilized during periods of starvation and physical activity. As a result, the human body is never in true energy balance; storage and subsequent mobilization of energy is necessary for a functioning organism. In addition, carbohydrates, fats and proteins are not only a source of energy, but also important substances with many functions [1]. After ingestion of a mixed meal, carbohydrates (especially glucose) are used for both oxidation and non-oxidative pathways (antioxidant, anaplerotic, cataplerotic processes). Only a relatively small fraction of glucose is a source for new lipid synthesis. Ingested fats are preferentially stored in adipose tissue and does not influence carbohydrate oxidation. The lack of glucose can explain more insulin resistance in whole organism than Randle cycle measured in vitro conditions [2].# Sobotka L, Sobotka O. The predominant role of glucose as a building block and precursor of reducing equivalents. https://doi.org/10.1097/mco.0000000000000786 # Sobotka O, et al. Should Carbohydrate Intake Be More Liberal during Oral and Enteral Nutrition in Type 2 Diabetic Patients? https://doi.org/10.3390/nu15020439in Type 2 Diabetic Patients? https://doi.org/10.3390/nu15020439 +
'''Authors:''' [[Stanic Sara]] … '''Authors:''' [[Stanic Sara]], [[Janovska Petra]], [[Zouhar Petr]], [[Bardova K]], [[Otahal J]], [[Vrbacky Marek]], [[Mracek Tomas]], [[Adamcova K]], [[Lenkova L]], [[Funda J]], [[Cajka T]], [[Drahota Zdenek]], [[Rustan Arlid C]], [[Horakova Olga]], [[Houstek Josef]], [[Rosmeissl M]], [[Kopecky Jan]] '''Introduction:''' Non-shivering thermogenesis (NST) is an energy-dissipating process that occurs in brown adipose tissue (BAT) and is activated by the adrenergic system. Earlier studies found that cold induces adrenergically activated NST in obesity-prone C57BL/6 (B6) mice, but not in obesity-resistant A/J mice. To investigate this difference, we studied the effect of cold acclimation on muscle NST. '''Methods:''' Palmitoyl carnitine oxidation and cytochrome c oxidase (COX) activity (TMPD+ascorbate and KCN) was measured in muscle homogenates of A/J and B6 mice acclimated to 30 °C or to 6 °C using Oroboros Oxygraph. In parallel, amount of mitochondrial supercomplexes was assessed by Blue native electrophoresis. '''Results and discussion:''' As expected, muscle of A/J mice exhibited higher amount of Scaf1 dependent supercomplex III2IV than muscle of B6 mice, and this amount was further increased by cold acclimation. Both palmitoyl carnitine oxidation and COX activity were induced by cold in A/J but not in B6 mice. The higher oxidation capacity of muscle of cold acclimated A/J mice, possibly connected with supercomplex composition, may indicate that muscle represents the site of alternative NST instead of BAT in these mice. The distinct mechanism of NST could correspond to obesity resistance of this strain. # Janovska P. et al (2023) Impairment of adrenergically-regulated thermogenesis in brown fat of obesity-resistant mice is compensated by non-shivering thermogenesis in skeletal muscle. https://doi.org/10.1016/j.molmet.2023.101683rmogenesis in skeletal muscle. https://doi.org/10.1016/j.molmet.2023.101683 +
'''Authors:''' [[Stankova Pavla]] … '''Authors:''' [[Stankova Pavla]], [[Peterova E]], [[Dusek J]], [[Elkalaf Moustafa]], [[Cervinkova Zuzana]], [[Kucera Otto]] '''Introduction:''' In our previous study in a murine model of nonalcoholic steatohepatitis (NASH), we found reduced succinate-activated hepatic mitochondrial respiration and accumulation of succinate, a proinflammatory, profibrogenic, and oncogenic metabolite [1]. According to preliminary studies, telmisartan, an angiotensin II type 1 receptor blocker, positively affects insulin resistance and liver steatosis. This project aimed to investigate the effect of telmisartan on NASH in mice. '''Methods:''' The NASH was induced in male mice fed a western-style diet (WD) for 36 weeks. During the last 6 weeks of the experiments, mice were administered daily telmisartan (oral gavage, 5 mg/kg b.w./day). Liver and epididymal fat histological changes were evaluated (Hematoxylin-eosin, Sirius red). Body parameters, plasma liver profile (VetScan), hepatic triglycerides, cholesterol, and the expression of selected proteins (WB/ELISA) and genes (qRT-PCR) were assessed. Mitochondrial respiration of liver homogenates was measured by high-resolution respirometry (OROBOROS Oxygraph-2k). Using Reporter Gene assay, telmisartan's activation of nuclear receptors was evaluated on HepG2 cells. '''Results and discussion:''' Administration of telmisartan to mice fed a WD reduced absolute and relative liver weight and visceral adipose tissue weight, activities of ALT and AST, liver steatosis, and inflammation grade. These effects were accompanied by a significant increase in succinate-activated respiration in the ET state and the activity of succinate dehydrogenase. We confirmed that telmisartan is a PPAR-γ partial agonist and described the activating effect of telmisartan on the CAR receptor for the first time. Telmisartan appears to be a promising safety drug for treating NASH that affects metabolism at multiple levels. # Staňková P, Kučera O, Peterová E, Elkalaf M, Rychtrmoc D, Melek J, Podhola M, Zubáňová V, Červinková Z (2021) Western Diet Decreases the Liver Mitochondrial Oxidative Flux of Succinate: Insight from a Murine NAFLD Model. https://doi.org/10.3390/ijms22136908ght from a Murine NAFLD Model. https://doi.org/10.3390/ijms22136908 +
'''Authors:''' [[Stiles Linsey]] … '''Authors:''' [[Stiles Linsey]], [[Fernandez-del-Rio L]], [[Beninca C]], [[Acin-Perez R]], [[Shirihai Orian]] Impaired mitochondrial function has been shown to play a key role in diseases of metabolism and aging. Respirometry is the gold standard measurement of mitochondrial function, as it is an integrated metabolic readout of the final step of the electron transport chain (ETC). However, analysis of mitochondrial respiratory function in tissue requires processing and measurement of freshly isolated mitochondria. This requirement makes respirometry impracticable for standard clinical practice, clinical studies, retrospective studies, and higher throughput respirometry. We have validated a methodology to measure maximal mitochondrial oxygen consumption rates through Complex I, II, and IV of the ETC in previously frozen biological samples using Agilent XF Analyzers. Additionally, Complex V (CV) ATP hydrolytic activity can be measured with the pH channel. These measurements of Complex I-V activities are specific as demonstrated by inhibition with ETC inhibitors. Additionally, these approaches can be applied to tissue homogenates, which simplifies the sample preparation and reduces the required starting material compared with isolating mitochondria. We find that primary changes in the maximal respiratory capacity, detected in fresh tissue, are preserved in frozen samples. These techniques to measure mitochondrial maximal respiratory function and CV hydrolytic activity in frozen samples makes clinical mitochondrial assessment more feasible and adds a complementary approach to investigate the role of mitochondrial function in disease onset and progression.tochondrial function in disease onset and progression. +
'''Authors:''' [[Timon-Gomez Alba]] … '''Authors:''' [[Timon-Gomez Alba]], [[Cardoso Luiza HD]], [[Doerrier Carolina]], [[Garcia-Souza Luiz F]], [[Gnaiger Erich]] '''Introduction:''' Mitochondrial dysfunction in muscle tissue is associated with obesity (mitObesity) and its comorbidities. Many drugs and nutraceuticals used to treat these conditions target mitochondria. Early diagnosis of mitObesity is crucial for understanding the link between obesity, mitochondrial dysfunction, and its associated chronic comorbidities. Respirometry of mitochondrial preparations can assess electron transfer pathways and coupling in oxidative metabolism with high diagnostic resolution [1]. '''Methods:''' We developed a standardized protocol for functional diagnosis of mitochondrial defects using high-resolution respirometry [2]. This substrate-uncoupler-inhibitor titration (SUIT) protocol analyzes fatty acid oxidation (FAO) by adding 0.1 mM malate and octanoylcarnitine, with consideration of malate-linked anaplerosis to avoid overestimation of FAO [3-4]. The protocol is extended to stimulate the NADH-linked pathway by adding pyruvate and glutamate. Then succinate and glycerophosphate are titrated to investigate convergent CoQ-reducing pathways. A stepwise titration of uncoupler CCCP allows quantification of the electron transfer capacity. Residual oxygen consumption is assessed after inhibition by rotenone and antimycin A. '''Results and discussion:''' To quantify FAO, malate was needed to avoid inhibition by accumulating acetyl-CoA. However, in the presence of mitochondrial malic enzyme, 2 mM malate stimulated respiration through the NADH-linked pathway in liver and brain mitochondria. Anaplerotic activity above endogenous respiration was minimized at a low (0.1 mM) malate concentration and subtracted from respiration obtained after addition of octanoylcarnitine. This SUIT reference protocol can be used as a general diagnostic tool for bioenergetic profiling in various sample preparations from different cell types, tissues, and organisms. # Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. https://doi.org/10.26124/bec:2020-0002# Doerrier C, Garcia-Souza LF, Krumschnabel G, Wohlfarter Y, Mészáros AT, Gnaiger E (2018) High-Resolution FluoRespirometry and OXPHOS protocols for human cells, permeabilized fibers from small biopsies of muscle, and isolated mitochondria. https://doi.org/10.1007/978-1-4939-7831-1_3 # Ojuka E, Andrew B, Bezuidenhout N, George S, Maarman G, Madlala HP, Mendham A, Osiki PO (2016) Measurement of β-oxidation capacity of biological samples by respirometry: a review of principles and substrates. https://doi.org/10.1152/ajpendo.00475.2015# Bernstine EG, Koh C, Lovelace CC (1979) Regulation of mitochondrial malic enzyme synthesis in mouse brain. https://www.doi.org/10.1073/pnas.76.12.6539synthesis in mouse brain. https://www.doi.org/10.1073/pnas.76.12.6539 +
'''Authors:''' [[Torres-Quesada Omar]] … '''Authors:''' [[Torres-Quesada Omar]], [[Strich Sophie]], [[Feichtner Andreas]], [[Schwaighofer Selina]], [[Doerrier Carolina]], [[Schmitt Sabine]], [[Gnaiger Erich]], [[Stefan Eduard]] Protein kinases play an important role in numerous signaling pathways regulating cell proliferation, cell cycle, and metabolism. Deregulation of kinase functions have been connected to various human diseases, such as cancer [1]. In recent years, kinase inhibitors have gained recognition by aiming to block single or multiple oncogenic kinase pathways [2]. In these lines, blockade of kinase activities has been shown to converge on the central energetic organelle, the mitochondria [3, 4]. Furthermore, colon cancer cells rely on mitochondrial OXPHOS as major source of energy, contradicting the Warburg effect [5]. To increase the understanding of small molecule-based kinase blockers and their cell-type-specific adverse effects, we set out to record the impact of kinase drugs on mitochondrial respiration using High-resolution FluoRespirometry in several colon cancer cell models. We observed that the impact of kinase inhibitors depends on the mutational background of the tested cancer cell lines as well as on cell culture medium formulations [6]. First, we detected off-target effects of sunitinib, an FDA-approved multikinase blocker, only in a more physiological cell culture medium as compared with classical formulations. Second, mitochondrial profiling of the glycolytic kinase inhibitor PFK158 revealed off-target mitochondrial dysfunction. Third, we were able to show that inhibition of kinase signaling is connected to mitochondrial reactive oxygen species (ROS), which can be influenced by protein kinase modulators. In summary, cell-based mitochondrial bioenergetic profiles have the power to identify off-target effects of kinase inhibitors and allow a detailed mechanistic insight on drug-induced perturbations in cancer cell metabolism.# Cohen, P, Cross, D, Jänne, PA (2021). Kinase drug discovery 20 years after imatinib: progress and future directions. Nat Rev Drug Discov. 20(7):551-569. https://doi.org/10.1038/s41573-021-00195-4 # Zhang J, Yang PL, Gray NS (2009). Targeting cancer with small molecule kinase inhibitors. https://doi.org/10.1038/nrc2559 # Wallace, DC (2012). Mitochondria and Cancer Nat. Rev. Cancer, 12, 685–698. https://doi.org/10.1038/nrc3365 # Torres-Quesada O, Strich S, Stefan E (2022). Kinase perturbations redirect mitochondrial function in cancer. Bioenerg. Commun. 2022,13. https://doi.org/10.26124/bec:2022-0013# Sun, X., Zhan, L., Chen, Y. et al. (2018) Increased mtDNA copy number promotes cancer progression by enhancing mitochondrial oxidative phosphorylation in microsatellite-stable colorectal cancer. Sig Transduct Target Ther 3, 8. https://doi.org/10.1038/s41392-018-0011-z # Torres-Quesada, O, Doerrier, C, Strich, S, Gnaiger, E, Stefan, E (2022). Physiological Cell Culture Media Tune Mitochondrial Bioenergetics and Drug Sensitivity in Cancer Cell Models. Cancers, 14, 3917. https://doi.org/10.3390/cancers14163917ancers, 14, 3917. https://doi.org/10.3390/cancers14163917 +
'''Authors:''' [[Ullrich Volker]] … '''Authors:''' [[Ullrich Volker]], [[Heidler Juliana]], [[Schildknecht S]], [[Daiber Andreas]], [[Frensch M]], [[Wittig Ilka]], [[Bruene B]] '''Introduction:''' Micelles containing cardiolipin (CL) and phosphatidylcholine in presence of cytochrome ''c'' (Cytc) and H2O2 were reported to catalyze peroxidationes of typical peroxidase substrates but also of CL itself (Kagan et. al, Biochem. 45,4998, 2006). This can be explained by complex formation of CL with Cytc under removal of the Met80 sixth ligand of the heme. '''Methods:''' O2 consumption was measured polarographically (Orobos Instruments) and diene formation spectrally at 237 nm. '''Results and Discussion:''' Cytc addition to CL micelles caused a burst of O2 uuptake that could be repeated until CL or O2 were depleted. About 4.5 mol of O2/mol CL were taken up forming products with mainly 2,4,6 or 8 additional O-atoms. Diene formation initially followed the same kinetics but stopped or was reversed before O2 uptake was completed. In presence of 2 M KCl Cytc acted catalytically with slower kinetics in three phases and showed oxidative modifications of the protein. The required peroxide tone originated from autoxidized CL and was upregulated during progress of the reaction. Significance for the process of opening of the permeability pore is suggested. autoxidized CL and was upregulated during progress of the reaction. Significance for the process of opening of the permeability pore is suggested. +
'''Authors:''' [[Valencia Ana P]] … '''Authors:''' [[Valencia Ana P]], [[Melhorn Susan J]], [[Schur Ellen A]], [[Marcinek David J]] '''Introduction:''' Weight loss (WL) promotes counterregulatory mechanisms that may involve mitochondrial (MITO) function to limit cardiometabolic benefit. This study compared T-cell MITO function in states of obesity (OB), active weight loss (OB-WL), weight loss plateau (OB-PL), regain (OB-RG), and healthy weight (HWC). '''Methods:''' Participants with obesity (61.5%female, 39.5±10.8 yr, BMI 36.7±6.4) underwent a 24-week WL intervention and transmitted their daily weight for 18 months. T-cells (CD3+) were isolated from blood samples obtained at baseline, 6-month, or 12-months. We measured MITO respiratory capacity (MITO-RC) (XFe Analyzer) and sensitivity of membrane depolarization with ADP (IC50) (O2K Fluorespirometer). '''Results:''' Compared to HWC, MITO-RC was lower in OB T-cells (4.1±1.7 vs. 3.3±1.0 pmol O2/106 cells, p<0.05), and even lower in OB-PL (3.0±0.7, p<0.05) and OB-RG (2.7±0.3, p<0.05). Maximal membrane potential was also lower in the OB group and remained low in all phases of WL. IC50 did not differ in T-cells between HWC and OB but was lower in OB-WL and OB-PL (156±15 vs. 7±1 & 22±5, p<0.05). '''Conclusions:''' T-cell MITO respiratory capacity is reduced in obesity and further aggravated in response to WL, particularly following a plateau. However, WL improved ADP sensitivity, suggesting a potential counterregulatory mechanism to meet energy demand. Findings suggest that the MITO function of T-cells is not restored by WL to resemble HWC and is rather altered in a way that could potentially limit cardiometabolic benefit of WL. L to resemble HWC and is rather altered in a way that could potentially limit cardiometabolic benefit of WL. +
'''Authors:''' [[Vujacic-Mirski Ksenija]] … '''Authors:''' [[Vujacic-Mirski Ksenija]], [[Sudowe S]] The impairment of mitochondrial respiration, observed in neurodegenerative and cardiovascular disease, diabetes, cancer and migraine headaches, has emerged as a biomarker of mitochondrial dysfunctions [1]. Newer research are also trying to link conditions such as chronic fatigue, depression and other behaviour/mood disorders with mitochondrial malfunctioning [2]. In our study, we examined 88 (relatively) healthy volunteers, ages from 23 to 68, from which 36 individuals were taking some sort of medication (such as for asthma, high blood pressure, mood disorders), but they considered themselves fit and healthy. Volunteers were ask to follow their normal routines day prior the test. The blood was drawn 3 h before PBMCs isolation, followed by immediate Seahorse XF Cell Mito Stress Test (Agilent) on SeahorseXF96e instrument (Agilent). Our analysis consisted of carefully examining parameters of mitochondrial respiration: basal respiration, ATP-linked respiration, reserve capacity, maximal respiration, proton leak, non-mitochondrial respiration as well as bioenergetics health index (BHI) [3]. We observed difference between people who took some sort of medication for chronic but manageable comorbidities and completely healthy individuals. There was significant difference between BHI, reserve capacity, coupling efficiency and proton leak. We also observed that people who had regular sport activities (in the healthy group without any medication) seem to have lower proton leak. This difference was not significant but points out to the lifestyle impact to mitochondria [4]. # Petrus, A T et al. (2019) Assessment of platelet respiration as emerging biomarker of disease. https://doi.org/10.33549/physiolres.934032# Zvěřová M et al. (2019) Disturbances of mitochondrial parameters to distinguish patients with depressive episode of bipolar disorder and major depressive disorder. https://doi.org/10.2147/NDT.S188964# Chacko, Balu K et al. (2014) The Bioenergetic Health Index: a new concept in mitochondrial translational research. https://doi.org/10.1042/CS20140101 # Janssen, Joëlle J E et al. (2022) Extracellular flux analyses reveal differences in mitochondrial PBMC metabolism between high-fit and low-fit females. https://doi.org/10.1152/ajpendo.00365.2021w-fit females. https://doi.org/10.1152/ajpendo.00365.2021 +
'''Authors:''' [[Whitcomb Luke A]] … '''Authors:''' [[Whitcomb Luke A]], [[Li Puma Lance C]], [[Zilhaver PT]], [[Izon CS]], [[Chicco Adam J]] Myocardial ischemia causes pathological increases in cardiomyocyte mitochondrial calcium (Ca++), which trigger a series of events that contribute to cell death and myocardial necrosis. Previous studies in our lab and others indicate that metabolites of phosholipid-derived arachidonic acid (AA), an omega-6 polyunsaturated fatty acid (PUFA), contribute to mitochondrial permeability transition pore (mPTP) opening in response to Ca++ overload, leading to mitochondrial swelling, rupture, and release of reactive oxygen species (ROS) [1,2]. We hypothesized that age-related increases in these parameters result in part from greater mitochondrial production of AA from its abundant membrane PUFA precursor linoleic acid (LA) in response to Ca++ overload. To test this hypothesis, we evaluated effects of 50-400 µM Ca++ on O2 consumption, ROS release and mPTP opening in cardiac mitochondria isolated from young (3 mo) and aged (24 mo) BALB/c mice in the presence or absence of an inhibitor of delta-6 desaturase (D6D), the rate-limiting enzyme in AA biosynthesis from LA. Results demonstrate that cardiac mitochondria from old mice release more ROS during oxidative phosphorylation and undergo more mPTP opening in response to Ca++ overload than mitochondria from young mice. D6D inhibition significantly attenuates these responses in both young and old mitochondria, but had greater impacts on old, largely abolishing the effect of aging on both ROS release and mPTP opening. Similar attenuation of mPTP opening was seen following inhibition of lipoxygenase enzymes (Baicalein), consistent with the hypothesized links between mitochondrial AA synthesis, eicosanoid production and mPTP in regulating responses of cardiac mitochondria to Ca++ overload. # Moon SH, Jenkins CM, Liu X, Guan S, Mancuso DJ, Gross RW (2012) Activation of mitochondrial calcium-independent phospholipase A2 gamma by divalent cations mediating arachidonate release and production of downstream eicosanoids. https://10.1074/jbc.M111.336776 # Moon SH, Jenkins CM, Kiebish MA, Sims HF, Mancuso DJ, Gross RW (2012) Genetic Ablation of Calcium-independent Phospholipase A2γ (iPLA2γ) attenuates calcium-induced opening of the mitochondrial permeability transition pore and resultant cytochrome ''c''. https://doi.org/10.1074/jbc.M112.373654 uced opening of the mitochondrial permeability transition pore and resultant cytochrome ''c''. https://doi.org/10.1074/jbc.M112.373654 +
'''Authors:''' [[Wohlfarter Yvonne]] … '''Authors:''' [[Wohlfarter Yvonne]], [[Eidelpes R]], [[Yu RD]], [[Sailer S]], [[Koch Jakob]], [[Karall Daniela]], [[Scholl‑Buergi S]], [[Amberger A]], [[Hillen HS]], [[Zschocke J]], [[Keller Markus A]] '''Introduction:''' Human 17β-Hydroxysteroid dehydrogenase 10 (HSD10) is a crucial enzyme located in mitochondria that participates in isoleucine catabolism and is part of the mitochondrial RNase P complex [1,2]. Mutations in the ''HSD10B17'' gene have been linked to HSD10 disease, which causes progressive cardiomyopathy and cognitive function loss [3]. Recently, HSD10 has been reported to possess a phospholipase C-like activity towards cardiolipins, which are essential mitochondrial membrane lipids involved in various processes such as super-complex assembly, cristae formation, and apoptotic signaling cascades [4]. The transacylase tafazzin is remodeling cardiolipin side chains, and its deficiency leads to high levels of monolyso-cardiolipins and abnormal cardiolipin patterns [5]. '''Methods:''' To explore the role of HSD10 in cardiolipin homeostasis, we carried out a comprehensive analysis of cardiolipin profiles in different cellular contexts by means of LC-MS/MS [6]: We investigated the impact of HSD10 knockdown in wild-type cells, in a tafazzin-deficient background, and in fibroblasts derived from HSD10-deficient patients. Additionally, by supplementation with fatty acids such as linoleic acid and palmitic acid we simulated different lipid environments. '''Results and Discussion:''' We found no evidence for the enzyme function of HSD10 to be involved in cardiolipin homeostasis in all conditions examined [6]. Thus, its previously reported cardiolipin cleaving function is likely to be regarded as an ''in vitro'' artefact. However, the HSD10's structural importance in the mitochondrial RNase P complex underscores its essential role in cellular function [7]. We show that the enzyme has evolved with significant evolutionary constraints to maintain this structure, possibly at the expense of achieving a high degree of substrate specificity and reaction rates [6].# Zschocke J, Ruiter JPN, Brand J, et al (2000) Progressive Infantile Neurodegeneration Caused by 2-Methyl-3-Hydroxybutyryl-CoA Dehydrogenase Deficiency: A Novel Inborn Error of Branched-Chain Fatty Acid and Isoleucine Metabolism. https://doi.org/10.1203/00006450-200012000-00025# Bhatta A, Dienemann C, Cramer P, Hillen HS. (2021) Structural basis of RNA processing by human mitochondrial RNase P. https://doi.org/10.1038/s41594-021-00637-y# Zschocke J. (2012) HSD10 disease: clinical consequences of mutations in the HSD17B10 gene. https://doi.org/10.1007/s10545-011-9415-4# Boynton TO, Shimkets LJ. (2015) Myxococcus CsgA, Drosophila Sniffer, and human HSD10 are cardiolipin phospholipases. https://doi.org/10.1101/gad.268482.115# Oemer G, Koch J, Wohlfarter Y, Lackner K, Gebert REM, Geley S, et al. (2022) The lipid environment modulates cardiolipin and phospholipid constitution in wild type and tafazzin-deficient cells. https://doi.org/10.1002/jimd.12433# Wohlfarter Y, Eidelpes R, Yu RD, Sailer S, Koch J, Karall D, et al. (2022) Lost in promiscuity? An evolutionary and biochemical evaluation of HSD10 function in cardiolipin metabolism. https://doi.org/10.1007/s00018-022-04682-8# Zschocke J, Byers PH, Wilkie AOM. (2023) Mendelian inheritance revisited: dominance and recessiveness in medical genetics. https://doi.org/10.1038/s41576-023-00574-0 n medical genetics. https://doi.org/10.1038/s41576-023-00574-0 +
'''Authors:''' [[Yardeni Tal]] … '''Authors:''' [[Yardeni Tal]] Both mitochondrial DNA (mtDNA) lineages and the gut microbiota have been correlated with altered risk for a variety of human diseases including obesity. However, the mechanisms by which mtDNA variation and the gut microbiota modulate disease risk remains unknown. Our hypothesis is that both the gut microbiota and the immune system are modulated by the mitochondrial genome, in part through mitochondrial reactive oxygen species (mtROS) production, forming a critical link between the gut microbiota and disease initiation and progression.Our studies showed significant differences in gut microbiota in our conplastic mice which differ in their mtDNA lineages. Further, the transfer of the gut microbiota from a host of one mitochondrial genotype to a host of different mitochondrial genotypes shifted the gut microbiota composition toward that of the recipient animal. Moreover, we showed that host mtROS levels modulated the composition of the gut microbiota. Those conplastic mice also exhibit markedly different capacities to sustain melanoma tumor growth. Relative to control mtDNA (mtDNAB6) mice, the mice harboring NZB mtDNAs (mtDNANZB) have strong anti-tumor immune response while those with129 mtDNA (mtDNA129) are the opposite. Reduction of mtROS by expression of mitochondrial catalase (mtCAT)Tg only in the hematopoietic cells changed the gut microbiota and obviated the anti-tumor effects on the mtDNANZB and mtDNAB6 mice. These observations suggest that disease severity (melanoma), and gut microbiota are regulated by the mtDNA's regulation of mtROS production in host immune cells, pointing to new potential pathways for understanding diseases etiology.lation of mtROS production in host immune cells, pointing to new potential pathways for understanding diseases etiology. +
'''Authors:''' [[Zweck Elric]] … '''Authors:''' [[Zweck Elric]], [[Piel Sarah]], [[Chadt A]], [[Al-Hasani H]], [[Kelm M]], [[Szendroedi Julia]], [[Roden Michael]], [[Granata Cesare]] '''Introduction:''' Ketone bodies (KB) are important substrates for the heart, particularly during heart failure [1], kidney [2], brain, skeletal muscle, and other organs [3]. Despite their significant role in health and disease [4], very limited research is available investigating KB-linked ATP production in mammalian tissues [5]; moreover, no optimized protocols exist to assess the interplay of key enzymes involved in ketolysis and their respective contribution to OXPHOS capacity. '''Methods:''' β-hydroxybutyrate (HBA)- and acetoacetate (ACA)-linked mitochondrial respiration was assessed in the heart left ventricle (LV), kidney, liver, brain, and soleus of ~18-24-week-old C57BL/6J female mice (n=6-8). A novel protocol combining KB-linked and complex I (CI)+CII-linked mitochondrial respiration was also devised. '''Results and discussion:''' The Km for HBA was similar (~1 mM) in all tested organs. However, maximal HBA-linked respiration was different between organs (p<0.001), i.e., greater in the LV and liver (~32 pmol O2·s-1·mg-1), and lowest in the brain (5.2 pmol O2·s-1·mg-1). This protocol allows to determine β-hydroxybutyrate dehydrogenase activity in the liver. The Km for ACA and maximal ACA-linked respiration were greater in the kidney compared to the other tested organs (all p<0.050). Our novel KB+CI+CII combined respiration protocol indicated that the KB contribution to maximal respiration is 2- to 4-fold greater in the kidney (37.4 %) compared to all other organs (all p<0.050), confirming the kidney’s reliance on KB metabolism [2]. Taken together, our novel protocols demonstrate an organ-specific response of mitochondrial respiration to different KBs. # Aubert, G., et al., The failing heart relies on ketone bodies as a fuel. Circulation, 2016. 133(8): p. 698-705. https://doi.org/10.1161/CIRCULATIONAHA.115.017355# Forbes, J.M. and D.R. Thorburn, Mitochondrial dysfunction in diabetic kidney disease. Nature Reviews Nephrology, 2018. 14(5): p. 291-312. https://doi.org/10.1038/nrneph.2018.9# Robinson, A.M. and D.H. Williamson, Physiological roles of ketone bodies as substrates and signals in mammalian tissues. Physiological reviews, 1980. 60(1): p. 143-187. https://doi.org/10.1152/physrev.1980.60.1.143# Puchalska, P. and P.A. Crawford, Metabolic and signaling roles of ketone bodies in health and disease. Annual review of nutrition, 2021. 41: p. 49-77. https://doi.org/10.1146/annurev-nutr-111120-111518# Petrick, H.L., et al., In vitro ketone‐supported mitochondrial respiration is minimal when other substrates are readily available in cardiac and skeletal muscle. The Journal of Physiology, 2020. 598(21): p. 4869-4885. https://doi.org/10.1113/JP280032en other substrates are readily available in cardiac and skeletal muscle. The Journal of Physiology, 2020. 598(21): p. 4869-4885. https://doi.org/10.1113/JP280032 +
'''Authors:'''[[Kolonics Attila]] … '''Authors:'''[[Kolonics Attila]], [[Kawamura T]], [[Szipoecs R]], [[Radak Z]] Aging leads to a loss of muscle mass and a decline in skeletal muscle function (1) leading to imbalance between glucose and lipid metabolism (2). Low exercise capacity is highly correlated with skeletal muscle dysfunction and metabolic disorders (3). Age-associated factors intrinsic to the muscle, including defects in NAD+ synthesis (4), reduced mitochondrial copy number (5), and epigenomic changes affecting the expression of metabolic genes (6) reported. We aimed to characterize mitochondrial fitness of liver in an inborn low- versus high-capacity runners (LCR/HCR) aged female rats to study the spread of metabolic dysfunction. LCR/HCR rats (44th generation, 24 months old) used were artificially selected from genetically heterogeneous N:NIH stock (7). NAD(P)H lifetime imaging (FLIM) characterized liver metabolism in frozen tissues; basal and succinate induced ROS production was evaluated by Amplex Red in the presence of horseradish peroxidase, ΔΨmt by TMRE in intact liver mitochondria. HCR group was less vulnerable to metabolic disorder comparing to LCR group proofed by decreased body mass and increased VO2max. It was further supported by mitochondrial analysis of intact liver mitochondria. Basal ROS production showed no difference between LCR and HCR groups although succinate induced ROS production was higher in LCR group at identical ΔΨmt. NAD(P)H FLIM uncovered subtle alterations: LCR groups had significantly less free NADH comparing to HCR groups (Fig.1). In conclusion, epigenetic changes induced decline of metabolism correlated with deterioration of liver mitochondrial fitness. Succinate induced ROS-production at same membrane potential negatively correlated with free NADH-level. # Frontera WR, Hughes VA, Lutz KJ, Evans WJ (1985) A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women. J Appl Physiol. 1991 Aug;71(2):644-50 http://doi.org/10.1152/jappl.1991.71.2.644 # Gheller BJ, Riddle ES, Lem MR, Thalacker-Mercer AE (2016) Understanding Age-Related Changes in Skeletal Muscle Metabolism: Differences Between Females and Males. Annu Rev Nutr. 2016 Jul 17;36:129-56 http://doi.org/10.1146/annurev-nutr-071715-050901# Biolo G, Cederholm T, Muscaritoli M (2014) Muscle contractile and metabolic dysfunction is a common feature of sarcopenia of aging and chronic diseases: from sarcopenic obesity to cachexia. Clin Nutr. 2014 Oct;33(5):737-48 http://doi.org/10.1016/j.clnu.2014.03.007# Yoshino J, Mills KF, Yoon MJ, Imai S (2011) Nicotinamide mononucleotide, a key NAD(+) intermediate, treats the pathophysiology of diet- and age-induced diabetes in mice. Cell Metab. 2011 Oct 5;14(4):528-36 http://doi.org/10.1016/j.cmet.2011.08.014# Barazzoni R, Short KR, Nair KS (2000) Effects of aging on mitochondrial DNA copy number and cytochrome c oxidase gene expression in rat skeletal muscle, liver, and heart. J Biol Chem. 2000 Feb4; 275(5): 3343-7 http://doi.org/10.1074/jbc.275.5.3343# Jiang MH, Fei J, Lan MS, Lu ZP, Liu M, Fan WW, Gao X, Lu DR (2008) Hypermethylation of hepatic Gck promoter in ageing rats contributes to diabetogenic potential. Diabetologia. 2008 Aug;51(8):1525-33 http://doi.org/10.1007/s00125-008-1034-8# Koch LG, Britton SL (2007) Artificial selection for intrinsic aerobic endurance running capacity in rats. Physiol Genomics. 2001 Feb 7;5(1):45-52 http://doi.org/10.1152/physiolgenomics.2001.5.1.45 running capacity in rats. Physiol Genomics. 2001 Feb 7;5(1):45-52 http://doi.org/10.1152/physiolgenomics.2001.5.1.45 +
'''Authours:''' [[Kayastha Pushpalata]] … '''Authours:''' [[Kayastha Pushpalata]], [[Wieczorkiewicz Filip]], [[Kaczmarek Lukasz]], [[Poprawa Izabela]] Tardigrada (water bears) are well known for their ability to undergo cryptobiosis and survival in extreme conditions. The best-known type of cryptobiosis for their survival is anhydrobiosis i.e. response to lack of water. In this state tardigrades are able to tolerate high pressure, very high and low temperatures, space vacuum, and high levels of UV, and ionizing radiation. These results in various ultrastructural changes in tardigrades, including in mitochondria. We analyzed the effect of different temperatures (20 °C, 35 °C, 37 °C, 40 °C and 42 °C) on the ultrastructure of mitochondria in the tardigrade ''Paramacrobiotus experimentalis'' Kaczmarek et al. 2020. Analyzes were conducted in active specimens, specimens in anhydrobiosis (tun), and rehydrated specimens. The analysis will provide knowledge about changes in the ultrastructure of tardigrades caused by different temperatures. Our results will also determine whether anhydrobiosis protects against temperature-induced ultrastructural changes.s against temperature-induced ultrastructural changes. +
'''BACKGROUND & AIMS:''' Liver ischemi … '''BACKGROUND & AIMS:''' Liver ischemia/reperfusion (I/R) injury is a frequent cause of organ dysfunction. Loss of the oxygen sensor prolyl hydroxylase domain enzyme 1 (PHD1) causes tolerance of skeletal muscle to hypoxia. We assessed whether loss or short-term silencing of PHD1 could likewise induce hypoxia tolerance in hepatocytes and protect them against hepatic I/R damage.'''METHODS:''' Hepatic ischemia was induced in mice by clamping of the portal vessels of the left lateral liver lobe; 90 minutes later livers were reperfused for 8 hours for I/R experiments. Hepatocyte damage following ischemia or I/R was investigated in PHD1-deficient (PHD1(-/-)) and wild-type mice or following short hairpin RNA-mediated short-term inhibition of PHD1 ''in vivo''.'''RESULTS:''' PHD1(-/-) livers were largely protected against acute ischemia or I/R injury. Among mice subjected to hepatic I/R followed by surgical resection of all nonischemic liver lobes, more than half of wild-type mice succumbed, whereas all PHD1(-/-) mice survived. Also, short-term inhibition of PHD1 through RNA interference-mediated silencing provided protection against I/R. Knockdown of PHD1 also induced hypoxia tolerance of hepatocytes ''in vitro''. Mechanistically, loss of PHD1 decreased production of oxidative stress, which likely relates to a decrease in oxygen consumption as a result of a reprogramming of hepatocellular metabolism.'''CONCLUSIONS:''' Loss of PHD1 provided tolerance of hepatocytes to acute hypoxia and protected them against I/R-damage. Short-term inhibition of PHD1 is a novel therapeutic approach to reducing or preventing I/R-induced liver injury.ducing or preventing I/R-induced liver injury. +
'''BACKGROUND AND AIMS:'''We investigated … '''BACKGROUND AND AIMS:'''We investigated whether in patients with liver cirrhosis reduced muscle strength is related to dysfunction of muscle mitochondria.'''METHODS:''' The mitochondrial respiratory capacity of the tibial anterior muscle was evaluated in seven patients and eight healthy control subjects by 31P nuclear magnetic resonance spectroscopy (31PMRS) to express ATP turnover in vivo and by respirometry of permeabilized fibres from the same muscle to express the in vitro capacity for oxygen consumption.'''RESULTS:''' Maximal voluntary contraction force for plantar extension was low in the patients (46% of the control value; P < 0.05), but neither the capacity for mitochondrial ATP synthesis, V(max-ATP) (0.38 ± 0.26 vs. 0.50 ± 0.07 mM s(-1) ; P = 0.13) nor the in vitro VO(2max) (0.52 ± 0.21 vs. 0.48 ± 0.21 μmol O2 (min g wet wt.)(-1) P = 0.25) were lowered correspondingly. Also, the activity of citrate synthesis and the respiratory chain complexes II and IV were similar in patients and controls. However during the contractions, the contribution to initial anaerobic ATP production from glycolysis relative to that from PCr was reduced in the patients (0.73 ± 0.22 vs. 0.99 ± 0.09; P < 0.01).'''CONCLUSIONS:''' The results demonstrate that the markedly lower capacity for force generation in patients with liver cirrhosis is unrelated to their capacity for muscle ATP turnover, but the attenuated initial acceleration of anaerobic glycolysis suggests that these patients could be affected by a central limitation to force generation.ted by a central limitation to force generation. +
'''BACKGROUND:''' Mild cold exposure and o … '''BACKGROUND:''' Mild cold exposure and overfeeding are known to elevate energy expenditure in mammals, including humans. This process is called adaptive thermogenesis. In small animals, adaptive thermogenesis is mainly caused by mitochondrial uncoupling in brown adipose tissue and regulated via the sympathetic nervous system. In humans, skeletal muscle is a candidate tissue, known to account for a large part of the epinephrine-induced increase in energy expenditure. However, mitochondrial uncoupling in skeletal muscle has not extensively been studied in relation to adaptive thermogenesis in humans. Therefore we hypothesized that cold-induced adaptive thermogenesis in humans is accompanied by an increase in mitochondrial uncoupling in skeletal muscle.'''METHODOLOGY/PRINCIPAL FINDINGS:''' The metabolic response to mild cold exposure in 11 lean, male subjects was measured in a respiration chamber at baseline and mild cold exposure. Skeletal muscle mitochondrial uncoupling (state 4) was measured in muscle biopsies taken at the end of the respiration chamber stays. Mild cold exposure caused a significant increase in 24h energy expenditure of 2.8% (0.32 MJ/day, range of -0.21 to 1.66 MJ/day, ''p''<0.05). The individual increases in energy expenditure correlated to state 4 respiration (''p''<0.02, ''R''(2) = 0.50).'''CONCLUSIONS/SIGNIFICANCE:''' This study for the first time shows that in humans, skeletal muscle has the intrinsic capacity for cold induced adaptive thermogenesis via mitochondrial uncoupling under physiological conditions. This opens possibilities for mitochondrial uncoupling as an alternative therapeutic target in the treatment of obesity. therapeutic target in the treatment of obesity. +
'''BEC tutorial-Living Communications. Fro … '''BEC tutorial-Living Communications. From Peter Mitchell’s protonmotive force to protonmotive pressure: elements of the science of bioenergetics. Preceding the '''[[MiPNet27.04 IOC155 Schroecken AT |Oroboros O2k-Workshop on high-resolution respirometry]]'''. Schroecken, Austria; 2022.[[File:Gnaiger 2020 BEC MitoPathways.jpg|left|100px|link=Gnaiger_2020_BEC_MitoPathways|Gnaiger 2020 BEC MitoPathways]]The [[mitochondrial membrane potential]] is an element of the science of bioenergetics, linked to the control of respiratory flux and related mitochondrial functions. A [https://pubmed.ncbi.nlm.nih.gov/?term=mitochondrial+membrane+potential PubMed search] on ‘mitochondrial membrane potential’ yields 40 000 results and 3452 for 2021 (search 2022-09-20), with a linear increase during the past 20 years. [[Gnaiger_2020_BEC_MitoPathways#Chapter_8._Protonmotive_pressure_and_respiratory_control |Chapter 8]] on ‘Protonmotive pressure and respiratory control’ of [[Mitochondrial Pathways]] (Gnaiger 2020) introduces a novel perspective on Peter Mitchell’s protonmotive force, which incorporates the mitochondrial membrane potential. If you find the reading is tough, you are not alone. Join this BEC tutorial-Living Communications for a fundamental introduction into the relevant concepts of physical chemistry, which differ from [[Force#Thermodynamic_ignorance |misleading chapters in bioenergetics textbooks]]. A retreat with plenty of informal discussions and group interactions takes you on a journey to visit chemical potential differences versus potential gradients, Gibbs [[energy]] versus Gibbs [[force]], quantities of capacity versus intensity, protonmotive force and [[motive unit]]s, [[flow]]s and [[force]]s, and finally protonmotive [[pressure]]. This will introduce students (and teachers) to a new understanding of mitochondrial membrane potential and the protonmotive force, connecting the ideal gas equation, osmotic pressure, the [[Boltzmann constant]] and [[gas constant]] with [[Fick 1855 Pogg Ann |Fick’s]] and [[Einstein 1905 Ann Physik 549 |Einstein’s diffusion equation]]. If theory gets dry and grey, join for a swim in lake Körbersee, for a Walk&Talk in the colorful alpine environment of the Schröcken-Tannberg region, and a visit to the [https://www.alpmuseum.at/ Alpmuseum ufm Tannberg].s://www.alpmuseum.at/ Alpmuseum ufm Tannberg]. +
'''BEC tutorial-Living Communications. Mit … '''BEC tutorial-Living Communications. Mitochondrial membrane potential and Peter Mitchell’s protonmotive force: elements of the science of bioenergetics. Preceding the [[EMC2022 Prague CZ |EMC 2022 49th European Muscle Conference]], Prague, Czech Republic.[[File:Gnaiger 2020 BEC MitoPathways.jpg|left|100px|link=Gnaiger_2020_BEC_MitoPathways|Gnaiger 2020 BEC MitoPathways]]The [[mitochondrial membrane potential]] is an element of the science of bioenergetics, linked to the control of respiratory flux and related mitochondrial functions. A [https://pubmed.ncbi.nlm.nih.gov/?term=mitochondrial+membrane+potential PubMed search] on ‘mitochondrial membrane potential’ yields 40 000 results and 3452 for 2021 (search 2022-09-20), with a linear increase during the past 20 years. [[Gnaiger_2020_BEC_MitoPathways#Chapter_8._Protonmotive_pressure_and_respiratory_control |Chapter 8]] on ‘Protonmotive pressure and respiratory control’ of [[Mitochondrial Pathways]] (Gnaiger 2020) introduces a novel perspective on Peter Mitchell’s protonmotive force, which incorporates the mitochondrial membrane potential. If you find the reading is tough, you are not alone. Join this BEC tutorial-Living Communications for an introduction into the relevant concepts of physical chemistry, which differ from [[Force#Thermodynamic_ignorance |misleading chapters in bioenergetics textbooks]] on potential gradients, Gibbs ''[[energy]]'', protonmotive [[flow]] and [[force]], and finally protonmotive [[pressure]]. This will introduce students (and teachers) to a new understanding of mitochondrial membrane potential and the protonmotive force, connecting the ideal gas equation, osmotic pressure, the [[Boltzmann constant]] and [[gas constant]] with [[Fick 1855 Pogg Ann |Fick’s]] and [[Einstein 1905 Ann Physik 549 |Einstein’s diffusion equation]]. If theory gets tough, join for a [[MiPNet27.05 BEC tutorial-Living Communications pmF |follow-up retreat]].C tutorial-Living Communications pmF |follow-up retreat]]. +
'''BEC tutorial-Living Communications. Mit … '''BEC tutorial-Living Communications. Mitochondrial membrane potential and Peter Mitchell’s protonmotive force: elements of the science of bioenergetics. [[File:Gnaiger 2020 BEC MitoPathways.jpg|left|100px|link=Gnaiger_2020_BEC_MitoPathways|Gnaiger 2020 BEC MitoPathways]]The [[mitochondrial membrane potential]] is an element of the science of bioenergetics, linked to the control of respiratory flux and related mitochondrial functions. A PubMed search on ‘mitochondrial membrane potential’ yields nearly 40 000 results and 3442 for 2021 (search 2022-07-04), with a linear increase during the past 20 years. [[Gnaiger_2020_BEC_MitoPathways#Chapter_8._Protonmotive_pressure_and_respiratory_control |Chapter 8]] on ‘Protonmotive pressure and respiratory control’ of [[Mitochondrial Pathways]] (Gnaiger 2020) introduces a novel perspective on Peter Mitchell’s protonmotive force, which incorporates the mitochondrial membrane potential. If you find the reading is tough, you are not alone. Join this BEC tutorial-Living Communications for an introduction into the relevant concepts of physical chemistry, which differ from [[Force#Thermodynamic_ignorance |misleading chapters in bioenergetics textbooks]] on potential gradients, Gibbs ''[[energy]]'', protonmotive [[flow]] and [[force]], and finally protonmotive [[pressure]]. This will introduce students (and teachers) to a new understanding of mitochondrial membrane potential and the protonmotive force, connecting the ideal gas equation, osmotic pressure, the [[Boltzmann constant]] and [[gas constant]] with [[Fick 1855 Pogg Ann |Fick’s]] and [[Einstein 1905 Ann Physik 549 |Einstein’s diffusion equation]]. If theory gets tough, join for a [[MiPNet27.05 BEC tutorial-Living Communications pmF |follow-up retreat]].C tutorial-Living Communications pmF |follow-up retreat]]. +
'''Background ''' Mitochondrial dysfuncti … '''Background ''' Mitochondrial dysfunction is one of the most characteristic properties of the cancer cell. However, it is not known whether oxidative energy metabolism has already become altered in conditions of atrophic gastritis, a precancerous state of gastric disease. The purpose of our study was to comparatively characterize oxidative phosphorylation (OXPHOS) in the atrophic and nonatrophic gastric corpus mucosa.'''Methods''' Mucosal biopsies were taken from 12 patients with corpus dominant atrophic gastritis and from 12 patients with nonatrophic mucosa (controls). One part of the tissue samples was permeabilized with saponin for analysis of the function of the respiratory chain using high-resolution respirometry, and another part was used for histopathological examination. The serum level of pepsinogen I (S-PGI) was determined with a specific enzyme immunoassay (EIA).'''Results''' Compared to the control group, the maximal capacity of OXPHOS in the atrophy group was almost twofold lower, the respiratory chain complex I-dependent respiration, normalized to complex II-dependent respiration, was reduced, and respiratory control by ADP in the presence of succinate was increased in the atrophic corpus mucosa. In the whole cohort of the patients studied, serum S-PGI level correlated positively with complex I-dependent respiration or complex Idependent to complex II-dependent respiration ratio.'''Conclusions''' Corpus dominant atrophic gastritis is characterized by decreased respiratory capacity and relative deficiency of the respiratory complex I of mitochondria in the mucosa, the latter defect probably limiting mitochondrial ATP production and energetic support of the secretory function of the zymogenic mucosal cells.y function of the zymogenic mucosal cells. +
'''Background''' Mitochondrial dysfunction … '''Background''' Mitochondrial dysfunction and degradation takes a central role in current paradigms of neurodegeneration in Parkinson's disease (PD). Loss of DJ-1 function is a rare cause of familial PD. Although a critical role of DJ-1 in oxidative stress response and mitochondrial function has been recognized, the effects on mitochondrial dynamics and downstream consequences remain to be determined.'''Methodology/Principal Findings''' Using DJ-1 loss of function cellular models from knockout (KO) mice and human carriers of the E64D mutation in the DJ-1 gene we define a novel role of DJ-1 in the integrity of both cellular organelles, mitochondria and lysosomes. We show that loss of DJ-1 caused impaired mitochondrial respiration, increased intramitochondrial reactive oxygen species, reduced mitochondrial membrane potential and characteristic alterations of mitochondrial shape as shown by quantitative morphology. Importantly, ultrastructural imaging and subsequent detailed lysosomal activity analyses revealed reduced basal autophagic degradation and the accumulation of defective mitochondria in DJ-1 KO cells, that was linked with decreased levels of phospho-activated ERK2.'''Conclusions/Significance''' We show that loss of DJ-1 leads to impaired autophagy and accumulation of dysfunctional mitochondria that under physiological conditions would be compensated via lysosomal clearance. Our study provides evidence for a critical role of DJ-1 in mitochondrial homeostasis by connecting basal autophagy and mitochondrial integrity in Parkinson's disease.hondrial integrity in Parkinson's disease. +
'''Background''': "Open peer review" (OPR) … '''Background''': "Open peer review" (OPR), despite being a major pillar of Open Science, has neither a standardized definition nor an agreed schema of its features and implementations. The literature reflects this, with numerous overlapping and contradictory definitions. While for some the term refers to peer review where the identities of both author and reviewer are disclosed to each other, for others it signifies systems where reviewer reports are published alongside articles. For others it signifies both of these conditions, and for yet others it describes systems where not only "invited experts" are able to comment. For still others, it includes a variety of combinations of these and other novel methods. '''Methods''': Recognising the absence of a consensus view on what open peer review is, this article undertakes a systematic review of definitions of "open peer review" or "open review", to create a corpus of 122 definitions. These definitions are systematically analysed to build a coherent typology of the various innovations in peer review signified by the term, and hence provide the precise technical definition currently lacking. '''Results''': This quantifiable data yields rich information on the range and extent of differing definitions over time and by broad subject area. Quantifying definitions in this way allows us to accurately portray exactly how ambiguously the phrase "open peer review" has been used thus far, for the literature offers 22 distinct configurations of seven traits, effectively meaning that there are 22 different definitions of OPR in the literature reviewed. '''Conclusions''': I propose a pragmatic definition of open peer review as an umbrella term for a number of overlapping ways that peer review models can be adapted in line with the aims of Open Science, including making reviewer and author identities open, publishing review reports and enabling greater participation in the peer review process. participation in the peer review process. +
'''Background''': Atherosclerosis is one o … '''Background''': Atherosclerosis is one of the major complications of diabetes, which may result from insulin resistance via mitochondrial dysfunction. Although a strong association between insulin resistance and cardiovascular disease has been suggested, it is not clear yet whether stress-inducing factors damage mitochondria and insulin signaling pathway in cardiovascular tissues.'''Methods''': We investigated whether stress-induced mitochondrial dysfunction might alter the insulin/Akt signaling pathway in A10 rat vascular smooth muscle cells (VSMC).'''Results''': The treatment of oxidized low density lipoprotein (oxLDL) decreased ATP contents, mitochondrial respiration activity, mRNA expressions of OXPHOS subunits and IRS-1/2 and insulin-mediated phosphorylations of Akt and AMP-activated protein kinase (AMPK). Similarly, dideoxycytidine (ddC), the mtDNA replication inhibitor, or rotenone, OXPHOS complex I inhibitor, inhibited the insulin-mediated pAkt while increased pAMPK regardless of insulin. Reciprocally, an inhibitor of Akt, triciribine (TCN), decreased cellular ATP contents. Overexpression of Akt dominant positive reversed the oxLDL- or ddC-mediated ATP decrease but AMPK activator did not. Akt activation also normalized the aberrant VSMC migration induced by ddC.'''Conclusions''': Defective insulin signaling and mitochondrial function may collectively contribute to developing cardiovascular disease.'''General significance''': Akt may be a possible therapeutic target for treating insulin resistance-associated atherosclerosis.lin resistance-associated atherosclerosis. +
'''Background''': It has been hypothesized … '''Background''': It has been hypothesized that reduced axonal transport contributes to the degeneration of neuronal processes in Parkinson's disease (PD). Mitochondria supply the adenosine triphosphate (ATP) needed to support axonal transport and contribute to many other cellular functions essential for the survival of neuronal cells. Furthermore, mitochondria in PD tissues are metabolically and functionally compromised. To address this hypothesis, we measured the velocity of mitochondrial movement in human transmitochondrial cybrid "cytoplasmic hybrid" neuronal cells bearing mitochondrial DNA from patients with sporadic PD and disease-free age-matched volunteer controls (CNT). The absorption of low level, near-infrared laser light by components of the mitochondrial electron transport chain (mtETC) enhancesmitochondrial metabolism, stimulates oxidative phosphorylation and improves redox capacity. PD and CNT cybrid neuronal cells were exposed to near-infrared laser light to determine if the velocity of mitochondrial movement can be restored by low level light therapy (LLLT). Axonal transport of labeled mitochondria was documented by time lapse microscopy in dopaminergic PD and CNT cybrid neuronal cells before and after illumination with an 810 nm diode laser (50 mW/cm2) for 40 s. Oxygen utilization and assembly of mtETS complexes were also determined.'''Results''': The velocity of mitochondrial movement in PD cybrid neuronal cells (0.175 +/- 0.005 SEM) was significantly reduced (p < 0.02) compared to mitochondrial movement in disease free CNT cybrid neuronal cells (0.232 +/- 0.017 SEM). For two hours after LLLT, the average velocity of mitochondrial movement in PD cybrid neurites was significantly (p < 0.003) increased (to 0.224 +/- 0.02 SEM) and restored to levels comparable to CNT. Mitochondrial movement in CNT cybrid neurites was unaltered by LLLT (0.232 +/- 0.017 SEM). Assembly of complexes in the mtETC was reduced and oxygen utilization was altered in PD cybrid neuronal cells. PD cybrid neuronal cell lines with the most dysfunctional mtETC assembly and oxygen utilization profiles were least responsive to LLLT.'''Conclusion''': The results from this study support our proposal that axonal transport is reduced in sporadic PD and that a single, brief treatment with near-infrared light can restore axonal transport to control levels. These results are the first demonstration that LLLT can increase axonal transport in model human dopaminergic neuronal cells and they suggest that LLLT could be developed as a novel treatmentto improve neuronal function in patients with PD. treatment to improve neuronal function in patients with PD. +
'''Background''': Reactive oxygen species … '''Background''': Reactive oxygen species (ROS) are among the main determinants of cellular damage during ischemia and reperfusion. There is also ample evidence that mitochondrial ROS production is involved in signaling during ischemic and pharmacological preconditioning. In a previous study we analyzed the mitochondrial effects of the efficient preconditioning drug diazoxide and found that it increased the mitochondrial oxidation of the ROS-sensitive fluorescent dye 2′,7′-dichlorodihydrofluorescein (H2DCF) but had no direct impact on the H2O2 production of submitochondrial particles (SMP) or intact rat heart mitochondria (RHM).'''Methods''': H2O2 generation of bovine SMP and tightly coupled RHM was monitored under different conditions using the amplex red/horseradish peroxidase assay in response to diazoxide and a number of inhibitors.'''Results''': We show that diazoxide reduces ROS production by mitochondrial Complex I under conditions of reverse electron transfer in tightly coupled RHM, but stimulates mitochondrial ROS production at the Qo site of Complex III under conditions of oxidant-induced reduction; this stimulation is greatly enhanced by uncoupling. These opposing effects can both be explained by inhibition of Complex II by diazoxide. 5-Hydroxydecanoate had no effect, and the results were essentially identical in the presence of Na+ or K+ excluding a role for putative mitochondrial KATP-channels.'''General significance''': A straightforward rationale is presented to mechanistically explain the ambivalent effects of diazoxide reported in the literature. Depending on the metabolic state and the membrane potential of mitochondria, diazoxide-mediated inhibition of Complex II promotes transient generation of signaling ROS at Complex III (during preconditioning) or attenuates the production of deleterious ROS at Complex I (during ischemia and reperfusion).x III (during preconditioning) or attenuates the production of deleterious ROS at Complex I (during ischemia and reperfusion). +
'''Background''': Restriction of intracell … '''Background''': Restriction of intracellular diffusion of adenine nucleotides has been studied intensively on adult rat cardiomyocytes. However, their cause and role ''in vivo'' is still uncertain. Intracellular membrane structures have been suggested to play a role. We therefore chose to study cardiomyocytes from rainbow trout (''Oncorhynchus mykiss''), which are thinner and have fewer intracellular membrane structures than adult rat cardiomyocytes. Previous studies suggest that trout permeabilized cardiac fibers also have diffusion restrictions. However, results from fibers may be affected by incomplete separation of the cells. This is avoided when studying permeabilized, isolated cardiomyocytes. The aim of this study was to verify the existence of diffusion restrictions in trout cardiomyocytes by comparing ADP-kinetics of mitochondrial respiration in permeabilized fibers, permeabilized cardiomyocytes and isolated mitochondria from rainbow trout heart. Experiments were performed at 10, 15 and 20°C in the absence and presence of creatine.'''Results''': Trout cardiomyocytes hypercontracted in the solutions used for mammalian cardiomyocytes. We developed a new solution in which they retained their shape and showed stable steady state respiration rates throughout an experiment. The apparent ADP-affinity of permeabilized cardiomyocytes was different from that of fibers. It was higher, independent of temperature and not increased by creatine. However, it was still about ten times lower than in isolated mitochondria.'''Conclusions''': The differences between fibers and cardiomyocytes suggest that results from trout heart fibers were affected by incomplete separation of the cells. However, the lower ADP-affinity of cardiomyocytes compared to isolated mitochondria indicate that intracellular diffusion restrictions are still present in trout cardiomyocytes despite their lower density of intracellular membrane structures. The lack of a creatine effect indicates that trout heart lacks mitochondrial creatine kinase tightly coupled to respiration. This argues against diffusion restriction by the outer mitochondrial membrane. These results from rainbow trout cardiomyocytes resemble those from other low-performance hearts such as neonatal rat and rabbit hearts. Thus, it seems that metabolic regulation is related to cardiac performance, and it is likely that rainbow trout can be used as a model animal for further studies of the localization and role of diffusion restrictions in lowperformance hearts.ion restrictions in lowperformance hearts. +