Department of Clinical Medicine

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 moderate intensity exercise in healthy women and men. VLDL-TG kinetics were assessed using a primed-constant infusion of ex-vivo labeled [1-(14)C] triolein VLDL-TG. Fractional VLDL-TG derived fatty acid oxidation was measured from (14)CO2 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 post-absorptive 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.