CHANGES IN LIPOPROTEIN-LIPASE ACTIVITIES IN ADIPOSE-TISSUE, HEART ANDSKELETAL-MUSCLE DURING CONTINUOUS OR INTERRUPTED FEEDING

Lipoprotein lipase (LPL) activities in parametrial and interscapular a dipose tissue, soleus and adductor longus muscles and hearts of female rats were measured during progressive starvation, chow re-feeding aft er 24 h starvation and throughout dark and light phases in rats permit ted unrestricted access to chow. Adipose-tissue LPL activities decline d by 50 % after 6 h starvation and continued to fall as the starvation period was extended to 24 h. Skeletal-muscle LPL activities dramatica lly increased between 9 and 12 h of starvation. Cardiac LPL activities increased 2.5-fold within 6 h of starvation, reaching a maximum after 12 h of starvation. Adipose-tissue LPL activities increased rapidly w ithin 2 h of re-feeding chow ad libitum after 24 h starvation, achievi ng 'fed ad libitum' values after 6 h. Oxidative-skeletal-muscle LPL ac tivities also increased after 2 h of re-feeding and exceeded 'fed ad l ibitum' values throughout the 6 h re-feeding period. Cardiac LPL activ ities remained up-regulated for the 6 h of re-feeding. Adipose-tissue LPL activities exceeded those of cardiac or skeletal muscle throughout both light and dark phases. The lowest adipose-tissue LPL activities were observed at 9 h into the light phase. In contrast, cardiac LPL ac tivity declined throughout the dark phase, with a minimum at 9 h into the dark phase. No such variation was observed for skeletal-muscle LPL activities. A diurnal nadir in plasma triacyl-glycerol (TG) concentra tions coincided with the peak in cardiac LPL activities. The results d emonstrate that, during unrestricted feeding and re-feeding after prol onged starvation, changes in skeletal-muscle and adipose-tissue LPL ac tivities are neither reciprocal nor co-ordinate. Regulation of cardiac LPL activity during the diurnal cycle may be an important aspect of b oth of cardiac fuel selection and whole-body TG metabolism.