Moderate exercise increases affinity of large very low-density lipoproteins for hydrolysis by lipoprotein lipase

Abstract

Context: Postprandial triglyceride (TG) concentration is independently associated with cardiovascular disease risk. Exercise reduces postprandial TG concentrations, but the mechanisms responsible are unclear. Objective: The objective was to determine the effects of exercise on affinity of chylomicrons, large very low-density lipoproteins (VLDL1), and smaller VLDL (VLDL2) for lipoprotein lipase (LPL)-mediated TG hydrolysis. Design: This was designed as a within-participant crossover study. Setting: The setting was a university metabolic investigation unit. Participants: Participants were 10 overweight/obese men. Interventions: Participants undertook two oral fat tolerance tests, separated by 7-14 days, in which they had blood taken while fasting and for 4 hours after a high-fat mixed meal. On the afternoon before one test, they performed a 90-minute treadmill walk at 50% maximal oxygen uptake (exercise trial [EX]); no exercise was performed before the control trial (CON). Main Outcome Measures: We measured circulating TG-rich lipoprotein concentrations and affinity of chylomicrons, VLDL1, and VLDL2 for LPL-mediated TG hydrolysis. Results: Exercise significantly reduced fasting VLDL1-TG concentration (CON, 0.49 [0.33-0.72] mmol.L-1; EX, 0.36 [0.22-0.59] mmol.L-1; geometric means [95% confidence interval]; P = .04). Time-averaged postprandial chylomicron-TG (CON, 0.55 ± 0.10 mmol.L-1; EX, 0.39 ± 0.08 mmol.L-1; mean ± SEM; P = .03) and VLDL1-TG (CON, 0.85 ± 0.13 mmol.L-1; EX, 0.66 ± 0.10 mmol.L-1 P = .01) concentrations were both lower in EX than CON. Affinity of VLDL1 for LPL-mediated TG hydrolysis increased by 2.2 (1.3-3.7)-fold [geometric mean (95% confidence interval)] (P = .02) in the fasted state and 2.6 (1.8-2.6)-fold (P = .001) postprandially. Affinity of chylomicrons and VLDL2 was not significantly different between trials. Conclusions: Exercise increases affinity of VLDL1 for LPL-mediated TG hydrolysis both fasting and postprandially. This mechanism is likely to contribute to the TG-lowering effect of exercise.