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.