The effect of dietary manipulation on hepatic lipid accumulation in rats undergoing small intestinal bypass.

Small intestinal bypass performed for morbid obesity produces hepatic fat infiltration which persists in some patients for more than 5 years. In an attempt to define causative and preventative factors of hepatic steatosis following small intestinal bypass, a rat model was developed. In this study, nutritionally obese rats underwent sham operations or bypass of 90 per cent of their small intestine and postoperatively were fed various diets to determine the effects of dietary manipulations on hepatic lipid content. After 30 days the rats were killed and their hepatic lipid content and lipogenic enzyme activity determined. In rats that underwent intestinal bypass neither a high fat, a high carbohydrate nor a high protein diet increased hepatic lipid content over that present in sham operated animals. A low (4.5 per cent) protein diet increased total hepatic lipid and hepatic triglyceride content. The increased triglyceride levels were not associated with significant changes in lipogenic enzyme activity and were associated with decreased serum triglycerides suggesting impaired triglyceride transport from the liver secondary to decreased lipoprotein formation as a possible etiologic mechanism. A significant inverse relationship was found between hepatic triglyceride content and hepatic protein content. These results support previous reports from human studies of hypoproteinemia associated with hepatic steatosis following small intestinal bypass.