Substrate oxidation and cardiac performance during exercise in disorders of long chain fatty acid oxidation

Abstract

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.

Objectives: 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.

Design: 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.

Trial registration: ClinicalTrials.gov NCT00654004.

Conflict of interest statement

Conflict of Interest:

The authors have no conflicts of interest relevant to this article to disclose.

Copyright © 2011 Elsevier Inc. All rights reserved.

Figures

Fig 1

Change in respiratory exchange ratio (RER) with and without MCT (*indicates significant difference). Standard deviation (SD) represented by error bars.

Fig 2

Change in oxygen utilization during exercise.

Fig 3

(A) Change in total serum ketone bodies (B) acetylcarnitines and (C) free fatty acids, with and without MCT, measured immediately before, immediately after, and 20 minutes post exercise (*indicates significant difference).

Fig 4

Difference in glycolytic intermediates during exercise with and without MCT; (A) change serum lactate, (B) change in serum pyruvate, measured immediately before, immediately after, and 20 minutes post exercise (*indicates significant difference).

Fig 5

Difference in heart function during exercise with and without MCT; (A) change in heart rate, (B) change in double product.