Regulation of mammalian fatty-acid synthetase. The roles of carbohydrate and insulin.

The regulation of fatty-acid synthetase has been studied in liver, adipose tissue, and brain of diabetic and normal rats in relation to insulin administration and glucose or fructose feeding. The data indicate that: (1) insulin is not necessary for regulation of synthetase activity in liver but may be necessary in adipose tissue; (2) synthetase of liver can be regulated by carbohydrate, which can enter the glycolytic scheme in the absence of insulin (e.g., fructose), suggesting the possibility that regulation of synthetase may depend on the concentration of certain intermediates of the glycolytic pathway or beyond; (3) fructose feeding affects the synthetase by causing an increase in the rate of synthesis of fatty-acid synthetase; and (4) unlike fatty-acid synthetase of liver and adipose tissue, the enzyme of brain is unaffected by the diabetic state or by glucose or fructose feeding.