Influences of Dietary Carbohydrate-fat Combinations on Various Functions Associated with Glycolysis and Lipogenesis in Rats

Abstract

The purpose of this study was to determine whether changes in the dietary source of fat would affect the activities of some of the enzymes involved in the metabolism of carbohydrates. Male, weanling rats were fed rations in which levels of all nutrients were identical. Dietary fats were corn oil and hydrogenated coconut oil with and without added cholesterol. Each of the 4 fats was fed with rice starch, as a direct source of glucose, and with sucrose, as partially indirect source. During the third week of the experiment, livers from all animals were assayed for activities of the glucose-6-phosphatase and fructose diphosphatase enzyme systems, glycogen, total lipid, phospholipid, and cholesterol; and serum was analyzed for total cholesterol. Responses of the two enzyme systems and glycogen levels in the liver to changes in dietary carbohydrate were modified by the type of fat fed. Similarly, changes in liver lipids and serum cholesterol concentration were influenced by the combination of fat and carbohydrate in the diet. Possible interrelationships among the above effects were discussed, and the importance of considering dietary constituents other than the specific nutrient under investigation in metabolic studies was stressed.