EFFECTS OF DIETARY FRUCTOSE OR GLUCOSE ON TRIGLYCERIDE PRODUCTION ANDLIPOGENIC ENZYME-ACTIVITIES IN THE LIVER OF WISTAR FATTY RATS, AN ANIMAL-MODEL OF NIDDM

Effects of dietary carbohydrates on triglyceride production and hepati c lipogenic enzyme activities were examined in Wistar fatty rats, an a nimal model of noninsulin dependent diabetes mellitus, fed fructose or glucose and were compared with those of Wistar lean rats. Carbohydrat es were supplied in 10% drinking solutions for 21 days. As compared wi th lean rats, Wistar fatty rats were characterized by hyperglycemia, h yperinsulinemia and hypertriglyceridemia, the last of which was associ ated with an increased hepatic activity of fatty acid synthetase and a n increased rate of triglyceride secretion from the liver to the circu lation. Feeding fructose to genetically obese diabetic rats produced a threefold increase in the hepatic activity of fatty acid synthetase, a twofold increase in NADPH-generating enzymes (malic enzyme and gluco se-6-phosphate dehydrogenase) and a 56% increase in the rate of trigly ceride secretion, with a resultant 86% increase in plasma triglyceride concentrations. Feeding glucose produced a similar increase in the ac tivity of NADPH-generating enzymes and triglyceride production in the fatty Liver but it differed in producing no change in plasma triglycer ide concentrations or hepatic fatty acid synthetase activity. Neither dietary fructose nor glucose changed glycemia or insulinemia. These re sults show that in genetically obese, diabetic rats feeding fructose a nd glucose is associated with an increase in hepatic lipogenic enzyme activities and triglyceride production, and suggest that fructose stim ulates triglyceride production but impairs triglyceride removal, where as glucose stimulates both of them.