Increasing muscle carnitine availability in humans and its impact on muscle fuel... - Prof. Stephens

Invited Session at ECSS MetropolisRuhr 2017 "Muscle Carnitine: The Key Player in Muscle Fuel Selection?"
Increasing muscle carnitine availability in humans and its impact on muscle fuel selection and regulation in exercise and health
Stephens, F.
University of Exeter
More than 95% of the body’s carnitine pool is confined to skeletal muscle, where it fulfils metabolic roles in the regulation of both fat
and carbohydrate oxidation, the major fuel sources utilised for mitochondrial ATP resynthesis during exercise. Firstly, as a substrate for carnitine palmitoyltransferase 1 (CPT1), carnitine facilitates the translocation of long-chain fatty acids across the otherwise impermeable mitochondrial membrane. Secondly, during high intensity exercise, carnitine buffers acetyl-CoA from excessive carbohydrate flux to acetylcarnitine, thereby maintaining a viable pool of free co-enzyme A (CoASH) to enable pyruvate
dehydrogenase complex (PDC) flux and mitochondrial ATP resynthesis to continue. It is, therefore, not surprising that carnitine
supplementation has been advocated as an ergogenic aid. This presentation will focus on studies that have increased skeletal
muscle carnitine content in humans to provide insight into the importance of these metabolic roles. In particular, studies
demonstrating that increasing skeletal muscle carnitine content by 15 to 20%, via 24 weeks of L-carnitine feeding in combination with
an insulinogenic beverage, can increase fat oxidation and energy expenditure during low intensity exercise, and result in a greater
acetylcarnitine accumulation and PDC activation during high intensity exercise. The implications of these metabolic effects for
exercise performance and health will also be discussed.

[@countrycorner9337]

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[@stefanweilhartner4415]

during HIIT the mitochondria switch almost to 100% glucose burning and therefore the limiting factor is not carnetine but the amount and size of mitochondria. also the purpose of HIIT is not to achieve a higher workload but running out of ATP while building up more AMP. to activate AMPK/PGC1-Alpha ==> mitochondrial biogenesis

[@stefanweilhartner4415]

the question for me is also, if the measurement method can detect a shift in body composition if there is only a shift in intermyofibral fatty acid content. i guess a DEXA cannot do this. the DEXA probably can not distinguish between a lean or fatty muscle.

[@Hellraiser3331]

Can medium chain triglycerides increase the absorption?

[@stefanweilhartner4415]

mct does not need carnitine to get into the mitochondria. and to my knowledge it does not have an effect on transporting stuff into the cell. that is the role of insulin. but sprint interval training increases insulin sensitivity. so insulin gets more effective to make stuff go into the cell. one day fasted LISS and one day fasted SIT and using whey protein to get a high insulin response together with carnitine could do the trick

[@davelane4055]

And the shit is cheaper than creatinine at your local Walmart