Modest changes in high-density lipoprotein concentration and metabolism with prolonged exercise training.

Abstract

High-density lipoprotein (HDL) metabolism was studied in eight sedentary men before and after 14 and 32-48 weeks of exercise training. Subjects rode stationary bicycles 1 hour daily, 5 days each week for 14 weeks (n = 8), and 4 days each week thereafter for a total of 32-48 weeks (n = 7) of training. HDL metabolism was assessed with 125I-radiolabeled autologous HDL while subjects consumed defined diets. Maximal oxygen uptake increased 26 +/- 7% (p less than 0.001) after 14 weeks but did not increase further with more prolonged training. Body weight and estimated body fat did not change. HDL cholesterol increased 5 +/- 3 mg/dl, and triglycerides decreased 19 +/- 23 mg/dl after 14 weeks (p less than 0.025 for both), but there were no additional changes with continued training. Postheparin plasma lipoprotein lipase activity was 22% higher than baseline activity after both 14 (p less than 0.025) and 32 or more weeks of exercise. In contrast, hepatic triglyceride lipase activity was 16 +/- 8% and 15 +/- 8% lower than baseline at each measurement (p less than 0.005 for both). The disappearance rate of triglycerides after an intravenously administered fat solution was 24 +/- 24% higher at 14 weeks and 49 +/- 18% (p less than 0.005) higher after more prolonged training. Total and low-density lipoprotein cholesterol and apolipoprotein A-I and A-II concentrations at the end of study were not different from initial values. Plasma volume was 8% above initial values at both post-training measurements. The biological half-life of apolipoprotein A-I was unchanged at 14 weeks but was 10 +/- 13% longer (p = 0.07) and increased in all but one subject at the end of the study. Half-life for apolipoprotein A-II was 8 +/- 8% (p = 0.031) and 11 +/- 14% (p = 0.06) above baseline at 14 and 32 or more weeks, respectively. The synthetic rates for apolipoproteins A-I and A-II were not different from baseline values at 32-48 weeks. We conclude that 8-11 months of exercise training in previously sedentary men enhances fat tolerance and increases HDL cholesterol concentrations by prolonging HDL survival. The changes in HDL apolipoprotein survival, however, do not approximate the differences previously noted between elite endurance athletes and sedentary men. Changes in HDL cholesterol concentration were not large and suggest that the potential for exercise-related changes in HDL may be modest in many subjects.