Dietary effects on glycogen and lipoprotein lipase activity in skeletal muscle in man.

The influence of short-term adaptation to a fat and protein enriched diet (F + P) and a carbohydrate enriched diet (CHO) on skeletal muscle lipoprotein lipase (LPL) activity and muscle glycogen levels was evaluated in 7 males. Muscle biopsies were taken from the m. vastus lateralis after an uncontrolled, mixed diet (M), after a 3 day F + P) diet preceded by intense exercise, and after a 3 day CHO diet. After the F + P diet glycogen concentration was 55% that of the M diet while LPL activity increased by 21% (n.s.). After the CHO diet glycogen levels increased by 82% and LPL activity decreased by 55% compared to the M diet (p less than 0.01). The changes in LPL after the CHO diet were related to the changes in glycogen concentration (r = 0.98, p less than 0.01). LPL activity in the control situation was directly related to percent slow twitch (ST) muscle fibre type (r = 0.95, p less than 0.01). The results suggest that the uptake of fat from the circulation may be actively regulated by the muscle as a function of intramuscular substrate availability and that this regulation may be related to muscle fibre type composition.