Conversion of glucose to lipid by human adipose tissue in vitro

Abstract

The rates of incorporation in vitro of glucose carbons into carbon dioxide and glyceride-glycerol and fatty acids by specimens of omental adipose tissue obtained from patients undergoing elective surgery were studied in the absence and presence of insulin. The basal (absence of insulin) activity for each parameter of glucose metabolism in the individual specimens correlated significantly with the insulin-stimulated increments. The glucose metabolism of specimens of subcutaneous adipose tissue, obtained under local anesthesia from normal volunteers in the fasting state and after ingestion of a standard breakfast, was also studied. In the absence of added insulin the incorporation of the glucose carbons into glyceride-fatty acids was consistently greater in specimens obtained after feeding, but incorporation into carbon dioxide and glyceride-glycerol was not significantly increased. In the presence of maximally effective amounts of insulin, there was no significant difference between the elevated rates of incorporation of glucose carbons into carbon dioxide and glyceride-glycerol and fatty acids between the specimens obtained before and after feeding. It was concluded that feeding did not enhance the maximal capacity for lipogenesis in adipose tissue. The modest increase in glyceride-fatty acid production in specimens obtained after feeding was probably due to effects of endogenous insulin. A hypothetical rate of lipogenesis from glucose derived from these data suggests that the production of fatty acids from glucose in human adult adipose tissue occurs on a very small scale relative to the intake of carbohydrate in normal man.