Context:
Postprandial triglyceride (TG) concentration is independently associated with cardiovascular disease risk. Exercise reduces postprandial TG concentrations but the mechanisms responsible are unclear.
Objective:
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:
Within-participant cross-over study.
Setting:
A University metabolic investigation unit.
Participants:
Ten overweight/obese men.
Interventions:
Participants undertook two oral fat tolerance tests, separated by 7–14 days, in which they had blood taken 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 (EX); no exercise was performed before the control test (CON).
Main outcome measures:
Circulating TG-rich lipoprotein concentrations; affinity of chylomicrons, VLDL1, 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=0.04). Time-averaged postprandial chylomicron-TG (CON: 0.55±0.10 mmol.l−1, EX: 0.39±0.08 mmol.l−1, [mean±SEM], p=0.03) and VLDL1-TG (CON: 0.85±0.13 mmol.l−1, EX: 0.66±0.10 mmol.l−1, p=0.01) 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=0.02) in the fasted state and 2.6(1.8–2.6) fold (p=0.001) 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 exercise's TG-lowering effect
