The influence of diet and diabetes on stearoyl Conenzyme A desaturase (EC 1.14.99.5) activity and fatty acid composition in rat tissues.

1. Rats were given low-fat diets for 3 d in which the carbohydrate source was starch. The livers of animals given the fructose or sucrose had increased hepatic activities of the fatty acid synthetase and stearoyl CoA desaturase (EC 1.14.99.5) enzyme complexes: in those given fructose there was a lower activity of the enzymes in adipose tissue. 2. Similar results were obtained in rats given fructose diets for 30 d, but in animals which had previously been made diabetic with streptozotocin, the activities were lower. The dietary treatment made little difference to the fatty acid profiles of the tissue lipids. The diabetic condition on the other hand produced considerable changes in fatty acid profile. 3. With diets containing approximately 200 g fat/kg in the form of butter or of polyunsaturated margarine, the tissue lipids from rats given sucrose had less linoleic acid than those from rats given starch. In addition, there was the expected difference between the rats given butter or margarine. The results are discussed in relation to the current literature.