Interaction of the level of dietary fat and type of carbohydrate in the regulation of hepatic lipogenesis in the mouse

Abstract

We have studied hepatic and extrahepatic lipogenesis in mice fed diets containing 0, 5, 10, or 15% corn oil in which the carbohydrate was one of fructose, sucrose, glucose, or wheat starch. Meal-fed animals were trained to eat a quantity of food such that at a given level of fat ail animals consumed the same amount of carbohydrate. Fatty acids synthesis in vivo, acetyl CoA carboxylase, fatty acid synthetase, ATP citrate lyase, glucose-6-phosphate dehydrogenase, and malic enzyme were determined. At 0 and 5% corn oil the values generally decreased in the order fructose > sucrose > glucose > wheat starch. At 10 and 15% corn oil differences due to the type of carbohydrate were less pronounced. The effect of dietary carbohydrate on glucokinase activity followed the reverse pattern with the values decreasing in the order wheat starch > glucose > sucrose > fructose. The results obtained demonstrate that hepatic lipogenesis was increased in mice consuming fructose or sucrose independent of carbohydrate intake or the level of dietary fat. However, total capacity for lipogenesis was greater in glucose-fed mice than those consuming wheat starch, fructose, or sucrose. Regardless of the carbohydrate in the diet, as dietary fat increased all the lipogenic parameters measured declined.Increasing corn oil from 0 to 15% caused a greater change in lipogenic capacity than the change due to the various carbohydrates. The percentage of total synthesis which occurred in liver was greater in mice fed fructose or sucrose. This increased contribution by the liver was unaltered by dietary fat which may contribute to the hypertriglyceridemia in such animals. Compared with diets based on glucose or wheat starch, diets based on fructose or sucrose do not cause increased lipogenesis in meal-fed mice if the diets contain more than 30 calorie percent fat. Our results suggest that when diets contain fat a a level similar to that in North American diets, the effects of the type of dietary carbohydrate on lipogenesis are minimal.