Basal and insulin-stimulated glucose metabolism of isolated human fat cells

Glucose-U-14C-activity added to the incubation medium of isolated human fat cells was studied for its conversion to CO2 and its incorporation into fat cell triglyceride. In view of the wide scatter of the figures found under basal conditions as well as in the presence of 100 muU/ml of insulin, the correlations of fat cell glucose metabolism to ponderal index, total body fat mass weight, mean fat cell diameter, fat cell TG-content and age were analysed. The activity of glucose metabolism in obese individuals was found to be inversely related to the degree of obesity under basal conditions as well as under the effect of insulin. According to partial regression analysis, of all these parameters it was the ponderal index which showed the most significant inverse correlation to the activity of fat cell glucose metabolism. No appreciable relationship was found between the production of CO2 from glucose and age. Incorporation of 14C-activity into fat cell triglyceride showed a slight age-related increase under basal conditions as well as on insulin stimulation. It is concluded that at the cellular level it is the triglyceride saturation of fat cells which constitutes the endogenous regulatory factor responsible for the impaired biological action exerted by insulin on the enlarged fat cells in obesity.