Acute and delayed effects of prolonged exercise on serum lipoproteins. I. Composition and distribution of high density lipoprotein subfractions.

To investigate the effects of a single period of prolonged exercise on lipoprotein concentration and composition, the serum of 13 healthy, endurance-trained men was examined before and after (1 h, 20 h) a field test [running time, 130 (SD 7.4) min]. We found changes in composition of all of the lipoprotein fractions isolated. In detail, all very low density lipoprotein particle components were reduced after exercise; the most pronounced changes found were in the concentrations of phospholipids (PL) and triglycerides (TG) (PL, before vs 20 h after, P < 0.01; TG, before vs 20 h after, P < 0.01). The serum high density lipoprotein (HDL)-cholesterol mass was unchanged after exercise, but both HDL subfractions showed changes in composition. In HDL3 the relative amounts of cholesterol increased (unesterified free cholesterol; FC) before vs 20 h after, P < 0.05; cholesterylester (CE), before vs 20 h after, P < 0.01) and TG and PL decreased (TG and PL, before vs 20 h after, P < 0.05). The HDL2 particles became enriched in the relative amount of CE (before vs 20 h after, P < 0.01) and lost TG after exercise (before vs 20 h after, P < 0.01). The observation that all the changes in lipoprotein concentration and composition reached their maximal differences compared to the pre-exercise values 20 h afterwards would support the assumption that circulating lipoproteins play an important role in the regeneration period, refilling the intramuscular triglyceride stores.