Ojuka 2016 Am J Physiol Endocrinol Metab

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Publications in the MiPMap
Ojuka E, Andrew B, Bezuidenhout N, George S, Maarman G, Madlala HP, Mendham A, Osiki PO (2016) Measurement of Ξ²-oxidation capacity of biological samples by respirometry: a review of principles and substrates. Am J Physiol Endocrinol Metab 310:E715-23. https://doi.org/10.1152/ajpendo.00475.2015

Β» PMID: 26908505 Open Access

Ojuka E, Andrew B, Bezuidenhout N, George S, Maarman G, Madlala HP, Mendham A, Osiki PO (2016) Am J Physiol Endocrinol Metab

Abstract: Oxidation of fatty acids is a major source of energy in the heart, liver, and skeletal muscle. It can be measured accurately using respirometry in isolated mitochondria, intact cells, and permeabilized cells or tissues. This technique directly measures the rate of oxygen consumption or flux at various respiratory states when appropriate substrates, uncouplers, and inhibitors are used. Acylcarnitines such as palmitoylcarnitine or octanoylcarnitine are the commonly used substrates. The Ξ²-oxidation pathway is prone to feedforward inhibition resulting from accumulation of short-chain acyl-CoA and depletion of CoA, but inclusion of malate or carnitine prevents accumulation of these intermediaries and CoA depletion. β€’ Keywords: Beta-oxidation, Palmitoylcarnitine, Octanylcarnitine, Malate, Carnitine, Substrate combinations, Respirometry

β€’ O2k-Network Lab: ZA Cape Town Smith J, ZA Cape Town Ojuka EO, ZA Cape Town Maarman GJ

Cited by

  • Silva et al (2021) Off-target effect of etomoxir on mitochondrial Complex I. MitoFit Preprints 2021. (in preparation)

Labels: MiParea: Respiration, Instruments;methods 

Organism: Human, Mouse, Rat  Tissue;cell: Skeletal muscle, Liver  Preparation: Permeabilized tissue, Isolated mitochondria 

Regulation: Fatty acid  Coupling state: LEAK, OXPHOS, ET  Pathway:HRR: Oxygraph-2k 

Review, 2016-07, MitoFit 2021 Etomoxir 

  • β€œHowever, the isolation process is tedious and may bring about selective loss of damaged mitochondria, which makes it less likely that the ex vivo data is representative of the in vivo condition”
  • β€œAs mentioned earlier, intact cells allow for assessment of respiration under resting physiological conditions and avoid potential artefacts caused by mitochondrial isolation or cell permeanilization but do not allow for assessment of maximum OXPHOS capacity or functional analysis of various components of the respiratory system.”
  • [Ref.13] β€œBased on these data, they recommended the use of 22 Β΅M palmitoyl- CoA plus 1 mM carnitine in Ξ²-oxidation measurements.”
  • β€œIt remains uncertain whether octanylcarnitine alone is a viable substrate for the assessment of Ξ²-oxidation using respirometry.”
  • β€œβ€¦we hypothesize that the use of chemicals that inhibit the activities of malate dehydrogenase (…), citrate synthase (…), or the tricarboxylate carrier (…) would reduce measured oxygen flux, giving a false reading of the rate of Ξ²-oxidation when malate is used as a cosubstrate.”
  • β€œThe recommended concentration of substrates are 5 M malate, 0.2 M octanoylcarnitine, 15 M palmitoylcarnitine, and 2 mM carnitine (23, 50), although these concentrations could be adjusted accordingly depending on the question being answered and the experimental design being used.”
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