Substrate oxidation and cardiac performance during exercise in disorders of long chain fatty acid oxidation.
BACKGROUND
The use of long-chain fatty acids (LCFAs) for energy is inhibited in inherited disorders of long-chain fatty acid oxidation (FAO). Increased energy demands during exercise can lead to cardiomyopathy and rhabdomyolysis. Medium-chain triglycerides (MCTs) bypass the block in long-chain FAO and may provide an alternative energy substrate to exercising muscle.


OBJECTIVE
To determine the influence of isocaloric MCT versus carbohydrate (CHO) supplementation prior to exercise on substrate oxidation and cardiac workload in participants with carnitine palmitoyltransferase 2 (CPT2), very long-chain acyl-CoA dehydrogenase (VLCAD) and long-chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiencies.


METHODS
Eleven subjects completed two 45-minute, moderate intensity, treadmill exercise studies in a randomized crossover design. An isocaloric oral dose of CHO or MCT-oil was administered prior to exercise; hemodynamic and metabolic indices were assessed during exertion.


RESULTS
When exercise was pretreated with MCT, respiratory exchange ratio (RER), steady state heart rate and generation of glycolytic intermediates significantly decreased while circulating ketone bodies significantly increased.


CONCLUSIONS
MCT supplementation prior to exercise increases the oxidation of medium chain fats, decreases the oxidation of glucose and acutely lowers cardiac workload during exercise for the same amount of work performed when compared with CHO pre-supplementation. We propose that MCT may expand the usable energy supply, particularly in the form of ketone bodies, and improve the oxidative capacity of the heart in this population.
Graduate Programs in Human Nutrition, OHSU, USA. behrenda@ohsu.edu
Annie M
AM
Behrend
Cary O
CO
Harding
James D
JD
Shoemaker
Dietrich
D
Matern
David J
DJ
Sahn
Diane L
DL
Elliot
Melanie B
MB
Gillingham
D000108:Acetylcarnitine / Q000378:metabolism; D044942:Acyl-CoA Dehydrogenase, Long-Chain / Q000097:blood / Q000172:deficiency / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D002648:Child; D003402:Creatine Kinase / Q000378:metabolism; D003710:Demography; D015444:Exercise / Q000502:physiology*; D005227:Fatty Acids / Q000097:blood / Q000378:metabolism*; D005260:Female; D006019:Glycolysis; D006334:Heart Function Tests; D006339:Heart Rate; D006801:Humans; D007659:Ketones / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008052:Lipid Metabolism, Inborn Errors / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D019289:Pyruvic Acid / Q000097:blood; D012119:Respiration; D013379:Substrate Specificity; D055815:Young Adult
D005227:Fatty Acids; D007659:Ketones; D019344:Lactic Acid; D000108:Acetylcarnitine; D019289:Pyruvic Acid; D044942:Acyl-CoA Dehydrogenase, Long-Chain; D003402:Creatine Kinase