The Effect of Diabetes and Insulin on the Biosynthesis of Individual Fatty Acids in Adipose Tissue

Abstract

Adipose tissue has been found to be exquisitely responsive to changes in the physiological state of the whole organism. Thus, fatty acid oxidation, synthesis, and release, oxygen uptake and glucose utilization, are profoundly and characteristically affected by temperature (l), nutrition (2, 3), hormones (4), age (5, 6), and the genetic constitution (7). The mechanism by which each adaptation is made in metabolism by adipose tissue is poorly understood. Recent studies of lipid metabolism in adipose tissue indicate that there may be a common change in lipid biosynthesis with aging and diabetes for, in both, the rate of fatty acid synthesis (5, 8) and oxygen uptake (9, 10) is markedly decreased. It has also been shown that there is a marked decrease in the synthesis of palmitoleic and oleic acids de noso in adipose tissue from old rats compared to young, which is repaired by the administration of insulin or by the feeding of a fat-free diet (6). In this report, studies on the incorporation of acetate-1-i4C and stearic acid-l-% in vitro into the individual fatty acids of the epididymal fat pad from normal, alloxan-diabetic, and insulin-treated rats are presented. These experiments show a marked depression in the amount and synthesis of the monounsaturated fatty acids of adipose tissue from diabetic rats. This defect is not repaired by the addition of insulin in