Chicco 2013 Abstract MiP2013

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Chicco AJ, Le CH, Schlater A, Kanatous S (2013) Comparative muscle mitochondrial physiology of the northern elephant seal. Mitochondr Physiol Network 18.08.
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Adam Chicco
MiP2013, Book of Abstracts Open Access

Chicco AJ, Le CH, Schlater A, Kanatous S (2013)

Event: MiPNet18.08_MiP2013

The Northern Elephant seal (Mirounga angustirostis; E-seal) is known for its remarkable capacity for diving in cold water to hunt for up to 2 hours without resurfacing for air. E-seal muscle contains very large quantities of myoglobin, which helps to maintain muscle pO2 prior to and during long dives, but the muscle mitochondrial respiratory phenotype of this species has not been characterized. Ongoing studies in our lab have sought to understand the effects of species, sex and environment on muscle mitochondrial function in E-seals by performing high resolution respirometry (HRR) on samples obtained from individuals at various stages of their life cycle, compared to data obtained from human vastus lateralis muscle biopsies in our laboratory. Seal biopsies were taken from the primary swimming muscle (M. longissimus dorsi) with a 6 mm biopsy cannula and stored on ice-cold BIOPS (0-4 days) prior to being saponin permeabilized for HRR using a variety of SUIT protocols on an Oroboros Oxygraph-2k.

Compared to fibers from young adult humans, young adult E-seal fibers exhibit ~50% lower mass-specific values of maximal ETF+CI and CII-linked OXPHOS and ET-pathway capacity, with trends for higher values in male vs. female E-seals. Despite this, OXPHOS rates with palmitoylcarnitine+malate (PalM) were similar in E-Seals and humans, with a trend for higher rates in female vs. male seals. Respiratory adenylate control ratios (P/LN) with PalM and pyruvate+malate are similar between seals and humans, with trends for higher values in male vs. female seals. ETF+CI OXPHOS flux normalized to ET capacity (P/E) is also similar in seals and humans, but tends to be higher in female vs. male seals. Interestingly, despite similar values of LEAK respiration in the absence of adenylates (LN), E-seal fibers consistently exhibit 50-80% higher indices of CII-linked oligomycin-induced LEAK respiration normalized to OXPHOS or ET capacities (LOmy/E and LOmy/P) compared to humans, indicating a much greater capacity for LEAK respiration in the presence of adenylates. Respiratory LEAK indices are greater in female vs. male seals, despite similar P/LN and higher P/E values. Notably, data from newborn E-seal pups show markedly higher mass-specific OXPHOS and ET capacities and lower indices of LEAK compared to young adults, with values similar to those seen in adult humans, suggesting a strong environmental and/or developmental component to the differences seen in adults.

Taken together, our studies indicate that E-Seals maintain a high capacity for fatty acid oxidation and phosphorylation control of respiration despite a lower overall OXPHOS and ET capacity and a much greater capacity for LEAK respiration compared to humans. This remarkable mitochondrial phenotype may serve to meet both bioenergetic and thermal demands of extended cold water dives routine to this mammalian species. Observed differences between sexes and life-cycle stages parallel known aspects of E-seal biology, suggesting that muscle mitochondrial adaptations likely result from a combination of genetic, hormonal and/or environmental factors.


O2k-Network Lab: US CO Fort Collins Chicco AJ


Labels: MiParea: Respiration, Comparative MiP;environmental MiP, Gender, Developmental biology 

Stress:Ischemia-reperfusion  Organism: Human, Other mammals  Tissue;cell: Skeletal muscle  Preparation: Permeabilized tissue 


Coupling state: LEAK, OXPHOS, ET  Pathway: F, N, Other combinations  HRR: Oxygraph-2k 

MiP2013 

Affiliations and author contributions

1 - Mitochondrial Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA;

2 - Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO, USA;

3 - Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO, USA.

Email: adam.chicco@colostate.edu


References

  1. Butler PJ (2004) Metabolic regulation in diving birds and mammals. Respir Physiol Neurobiol 141: 297-315.
  2. Kelso EJ, Champagne CD, Tift MS, Houser DS, Crocker DE (2012) Sex differences in fuel use and metabolism during development in fasting juvenile northern elephant seals. J Exp Biol 215: 2637-2645.