Comparison of exercise and normal variability on HDL cholesterol concentrations and lipolytic activity.

In order to compare the influence of a single bout of exercise on HDL-C metabolism with normal variability, 12 male runners (mean age: 24.9 +/- 4 yr) who ran 15-30 miles per week underwent exercise (E) and control (C) experimental conditions. During the E trial subjects ran on a motor driven treadmill at 75% (42.5 +/- 4.7 ml.kg-1.min-1) VO2max until 800 Kcals were expended. The C trial consisted of no exercise. Subjects were instructed to follow the same diet and keep a four d food diary during each experimental condition. Fasted blood samples were obtained at the same time of day in each condition at time points corresponding to 24 h pre-exercise (24 PRE), 6 h post- (6 h) and 24 h post-exercise (24 h). Plasma was analyzed for HDL-C, HDL2-C and HDL3-C (mg.dl-1). In addition post-heparin plasma samples were analyzed for lipoprotein lipase (LPL) and hepatic lipase (HL) activity (mumol.FFA-1.ml-1). All values were adjusted for changes in plasma volume and compared to Baseline. HDL-C levels were unaltered following the C trial. However, following the E trial, HDL-C increased (p < 0.01) above baseline values at 24 h. The increase in HDL-C was reflected in the HDL3-C subfraction (p < 0.05). Analysis of lipolytic activity revealed an overall greater LPL activity (p < 0.05) in the E trial vs the C trial. In addition, a decrease in HL was observed at 24 h (p < 0.05) but was not different between experimental conditions. These data suggest that exercise and not normal variability are responsible for alterations in lipolytic activity and corresponding increases in HDL-C levels.

The acute effects of exercise intensity on HDL-C metabolism.

To determine whether exercise intensity influences acute HDL-C responses, 12 male recreational runners (24.8 +/- 4 yr) who ran 15-30 miles.wk-1 exercised on a motor driven treadmill at 60% (L) and 75% (H) VO2max. A counterbalanced experimental design was utilized and energy expenditure was 800 Kcal. Fasting blood samples were obtained 24 h before exercise (24 PRE), immediately post-(IPE), 1 h post- (1 h PE), 6 h post- (6 h PE), and 24 h post- (24 h PE) exercise and analyzed for HDL-C and HDL2&3-C. In addition, postheparin plasma samples, obtained 24 h PRE, 6 h PE, and 24 h PE were analyzed for lipolytic activity--LPLA and HTGLA. An exercise trial by time interaction was observed for HDL-C (P < 0.01). Post-hoc analysis revealed no change in HDL-C following the L trial. However, an increase in HDL-C was observed 24 h PE (P < 0.01) following the H trial. The increase in HDL-C was attributed to an elevated HDL3-C (P < 0.01), with no change in HDL2-C. Analysis of plasma lipolytic activity revealed an increase in LPLA 24 h PE (P < 0.05) which may be responsible for the postexercise alterations in HDL-C. However, HTGLA decreased 6 h PE (P < 0.01) and 24 h PE (P < 0.05). We conclude that increases in HDL-C levels following endurance activity are influenced, in part, by the exercise intensity.