Role of small intestine in pathogenesis of hyperlipidemia in diabetic rats

The small intestine can utilize endogenous substrates for triglyceride synthesis. In diabetes mellitus, potential endogenous substrates are elevated. This study was designed to investigate whether intestinal triglyceride production utilizing endogenous substrates contributes to the pathogenesis of hyperlipidemia in diabetes. Intestinal fatty acid esterification as well as activities of acyl-CoA synthetase and acyl-CoA monoglyceride acyltransferase are the same in diabetic and control rats when the results are expressed per milligram protein. However, due to marked intestinal hypertrophy these activities are increased when the results are expressed as per centimeter gut length. In the mesenteric lymph fistula rat model, we found that during fasting diabetic rats have a greater than twofold increase in triglyceride output that is carried mainly by very low-density lipoproteins (VLDL). During lipid infusion, total triglyceride fatty acid output was not different between diabetic and control rats, although there were significant differences in the patterns of partition of endogenous and exogenous triglyceride into chylomicrons and VLDL. Endogenous triglyceride production did not increase in diabetic rats during lipid infusion. In contrast, there was a substantial increase in endogenous triglyceride production in the control group to a level comparable with that of the diabetic rats. There was a significant reduction in incorporation of exogenous triglyceride into chylomicrons in diabetic rats.