Effect of dietary lipid on response to exercise: relationship to metabolic adaptation.

This study investigates how oil supplementation affects muscle function and fat utilization during exercise in horses. The results show that after receiving oil supplements for 10 weeks, horses displayed improved fat utilization during light and moderate exertion, which was probably linked to increased muscle oxidative capacity.

Oil Supplementation and Exercise Performance

• The study aimed to establish the link between changes in muscle oxidative capacity and free fatty acid flux following oil supplementation and the subsequent fuel usage during exercises of varying intensities.
• The oil supplementation process lasted for 10 weeks. At the end of this period, horses had developed an enhanced capacity for fat utilization during low and moderate intensity exercises.
• The researchers used a measure known as the respiratory exchange ratio (RER) to determine fat and carbohydrate utilization. A lower RER suggests a higher reliance on fat for fuel. With oil supplementation, horses exhibited a lower RER, suggesting improved fat utilization during exercise.

Muscle and Metabolic Adaptations

• According to the researchers, the improved fat utilization might have been facilitated by an increase in muscle oxidative capacity, which was evidenced by a significant growth in the activity of an enzyme called muscle citrate synthase (CS).
• The study also identified a potential increase in the activity of another enzyme, beta-Hydroxy acyl CoA dehydrogenase (beta-HAD), which plays a role in fatty acid oxidation but this increase was not statistically significant.
• In addition, exercises of low and moderate intensity triggered an exercise-induced increase in free fatty acids (FFA) in plasma, which was accompanied with a developed ability for muscle uptake of these FFAs from circulating triglycerides. This was suggested by a significant increase in the activity of another enzyme, TL.
• The results varied from one horse to another. In terms of the RER difference during low intensity exercises, the magnitude of response was closely linked to the increase in CS activity following the oil supplementation.

Further Investigation Needed

• Despite these positive and promising findings, the researchers highlight the lack of a statistically significant correlation between the observed metabolic adaptations and the activities of FFA, TL, or beta-HAD.
• The investigator’s initial hypothesis predicted a concise relationship between metabolic adaptation due to oil supplementation – in terms of exercise response – and individual increases in CS, beta-HAD or TL activity.
• However, this relationship appeared elusive and requires further verification and exploration, preferably with a larger group of horses for increased statistical power.