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 (mmol · 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.

Key words

Exertion - exercise - lipoproteins - HDL-C - lipolytic enzymes