Lipoprotein lipase and lipid metabolism in muscle and adipose tissues of Zucker rats.

To determine the relative rates of lipid metabolism in muscle and adipose tissues in obesity, we measured uptake and oxidation of free palmitate or tripalmitin into tissue slices in vitro. We also measured lipoprotein lipase (LPL) activity of soleus muscle and perirenal adipose tissues. Muscle took up more liquid from tripalmitin than from free palmitate (FFA) at 6 and 12 wk of age, whereas adipose took up more from FFA. The relative uptake of tripalmitin in adipose decreased from twofold that of muscle at 6 wk to 60% of muscle at 12 wk. Uptake from FFA in adipose was faster than in soleus at both ages. LPL/g of soleus muscle at 12 wk was higher than that of adipose. LPL/g protein was higher in adipose tissue than in muscle at 12 wk. Muscle oxidized 15-32% of FFA, obese muscles more than lean at 12 wk. AT 15-h fast decreased lean adipose tripalmitin uptake 50%, did not affect obese adipose lipid uptake, and decreased obese soleus palmitate uptake. In soleus muscle, triglyceride uptake is as active as in adipose. Obese muscles at 12 wk oxidized more FFA than lean and respond to a short fast by increasing the percent lipid oxidized.