Studies of human adipose tissue in culture. 3. Influence of insulin and medium glucose concentration on cellular metabolism.

Explants of human adipose tissue were maintained in culture for 1 wk in different glucose concentrations with or without the addition of insulin. After this period of time the explants were carefully washed and then subjected to short-term incubations in the same glucose concentration and in the absence of insulin. With this experimental design the influence of long-term exposure to insulin and different glucose concentrations on adipose tissue metabolism could be studied. The results of these studies show that an increase in the glucose concentration of the culture medium enhanced the basal as well as the catecholamine-stimulated lipolysis in the short-term incubations. The presence of insulin in the culture medium enhanced the lipolytic process as well. Analogous results were obtained with the cellular rate of glucose conversion to triglycerides in the short-term incubations. The stimulating effects of insulin and glucose were most pronounced in the larger adipose cells possibly due to their enlarged surface areas. The data suggest that the metabolism of adipose tissue as revealed by short-term studies may be profoundly influenced by the antecedent biochemical environment.