Effect of Acute Exercise on Uncoupling Protein 3 Is a Fat Metabolism Mediated Effect

American Journal of Physiology-Endocrinology and Metabolism. 2002;282(1):E11-E17

Uncoupling proteins (UCP), which uncouple respiration from ATP production thereby stimulating heat production, are likely contributors to the variability in human energy metabolism. In animals, UCPs have also been implicated in the metabolism of fatty acids and glucose. This project will evaluate changes in UCP3 and GLUT4 mRNA and protein levels in skeletal muscle biopsies from humans following a 36-hour feeding period with either high-carbohydrate or low-carbohydrate diet in a respiration chamber. A third diet that combines the low-carbohydrate food pattern with an inhibitor of fatty acid oxidation will also be evaluated. This will allow separation of the effect of carbohydrate intake from the effect of carbohydrate oxidation on the regulation of UCP. A second experiment examines the acute effect of glucose infusion on UCP3 mRNA and protein expression. A third experiment examines the effect of exercise, with and without carbohydrate intake, on UCP3 mRNA and protein expression.

Findings

• In the fasted state, plasma free fatty acid levels significantly increase during exercise whereas they were unchanged after glucose ingestion.
• Increasing dietary carbohydrate did not affect UCP3
• UCP3 regulated more by ↑ FFA &/or FA ox than glucose metabolism, UCP3 most likely related to FA metabolism
• Abolishing the commonly observed increase in plasma free fatty acid levels and/or fatty acid oxidation during and after exercise prevents the upregulation of UCP3 after acute exercise
• A post-exercise induced increase in UCP3 expression appears to be an effect of prolonged elevation of plasma FFA levels and/or increased fatty acid oxidation and not by carbohydrate intake or glucose metabolism.

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