Effects of exercise on VLDL-triglyceride oxidation and turnover

Effects of exercise on VLDL-triglyceride oxidation and turnover. Am J Physiol Endocrinol Metab 300: E939-E944, 2011. First published March 8, 2011; doi: 10.1152/ajpendo.00031.2011.-Lipids are important substrates for oxidation at rest and during exercise. Aerobic exercise mediates a delayed onset decrease in total and VLDL-triglyceride (TG) plasma concentration. However, the acute effects of exercise on VLDL-TG oxidation and turnover remain unclear. Here, we studied the acute effects of 90 min of moderate-intensity exercise in healthy women and men. VLDL-TG kinetics were assessed using a primed constant infusion of ex vivo labeled [1-C-14] triolein VLDL-TG. Fractional VLDL-TG-derived fatty acid oxidation was measured from (CO2)-C-14 specific activity in expired air. VLDL-TG concentration was unaltered during exercise and early recovery, whereas non-VLDL-TG concentration decreased significantly. VLDL-TG secretion rate decreased significantly during exercise and remained suppressed during recovery. Total VLDL-TG oxidation rate was unaffected by exercise. However, the contribution of VLDL-TG oxidation to total energy expenditure fell from 14 +/- 9% at rest to 3 +/- 4% during exercise. We conclude that VLDL-TG fatty acids are quantitatively important oxidative substrates under basal postabsorptive conditions but remain unaffected during 90-min moderate-intensity exercise and, thus, become relatively less important during exercise. Lower VLDL secretion rate during exercise may contribute to the decrease in TG concentrations during and after exercise.