Acute effects of endurance exercise on human adipose tissue metabolism

In order to study the acute effects of exercise on adipose tissue metabolism, 27 sedentary male subjects, 18 to 27 years of age, performed a prolonged aerobic exercise test. Biopsies of adipose tissue were obtained from the suprailiac fat depot before and immediately after a 90-minute period of exercise on ergocycle at an average intensity of 88% of maximal heart rate. Fat cells, isolated by collagenase digestion, were measured for their glucose conversion into triglycerides and for lipolytic activity. Adipose tissue lipoprotein lipase activity released by heparin was also determined. Mean basal and insulin-stimulated glucose conversion into triglycerides decreased significantly with exercise (P less than .05) while adipose tissue lipoprotein lipase activity increased (P less than .01). Fat cell lipolysis increased during exercise only for its epinephrine-stimulated values (P less than .05). The total amount of work performed during the test was correlated only with changes in lipoprotein lipase activity (r = .42, P less than .05). Finally, the changes induced by exercise in lipoprotein lipase activity (r = .37, P less than .05) and insulin-stimulated glucose conversion into triglycerides (r = .61, P less than .01) were positively correlated with fat cell weight. These results indicate that adipose tissue metabolic activities are selectively influenced by endurance exercise. They also suggest that these metabolic changes are not closely coupled with the amount of work performed in a prolonged exercise bout.