EFFECTS OF EXERCISE TRAINING AND FEEDING ON LIPOPROTEIN-LIPASE GENE-EXPRESSION IN ADIPOSE-TISSUE, HEART, AND SKELETAL-MUSCLE OF THE RAT

Lipoprotein lipase (LPL) is found in adipose tissue and muscle, and is important for the uptake of triglyceride-rich lipoproteins from plasm a. This study examined the regulation of LPL in adipose tissue and mus cle by exercise training in combination with the fed or fasted state. After training male rats on a treadmill for 6 weeks, LPL activity, mas s, and mRNA levels were measured in adipose tissue, heart, soleus, and extensor digitorum longus (EDL) muscles and compared with levels in s edentary rats. Tissue LPL was measured as the heparin-released (HR) an d cellular-extracted (EXT) fractions 16 hours following the last bout of exercise, during which time some animals were fasted and others wer e allowed free access to food. Training led to an increase in HR LPL a ctivity and LPL protein mass in soleus and EDL, but had no effect on a dipose tissue and heart LPL. The increase in soleus LPL with exercise was in the HR fraction only, whereas the increase in EDL LPL with trai ning was in both the HR and EXT fractions. All these changes in LPL ac tivity were accompanied by similar changes in LPL immunoreactive mass. However, there were no changes in LPL mRNA levels with training. Feed ing induced a large increase in adipose tissue LPL activity and mass i n both the HR and EXT fractions; however, there was no change in mRNA levels. In heart, feeding yielded a decrease in HR but no consistent c hange in EXT activity or mass, and a consistent decrease in mRNA level s. As compared with control rats, trained rats demonstrated different responses to feeding in all tissues, especially in soleus and EDL. Whe reas feeding had no effect on LPL in soleus and EDL of control rats, f eeding induced a decrease in HR and EXT LPL in the soleus of trained r ats. In addition, feeding yielded a significant decrease in EXT LPL of the EDL of trained rats. Thus, these data demonstrate that adipose ti ssue and heart LPL are highly regulated by feeding and are not respons ive to long-term exercise training. On the other hand, skeletal muscle LPL is increased in trained rats, but this increase is blunted consid erably by feeding following the last bout of exercise. These changes i n LPL activity and mass are mostly unaccompanied by changes in LPL mRN A levels, demonstrating that much physiologic regulation occurs posttr anscriptionally. Copyright (C) 1995 by W.B. Saunders Company