Triglyceride Metabolism in the Alloxan-Diabetic Rat

Diabetes mellitus of graded severity was produced by withdrawing insulin from alloxan diabetic rats previously maintained on Protamine Zinc Insulin. The tissue distribution of H-3 palmitate-labeled chyle in the diabetic animals and in normal animals was compared fifteen minutes after its intravenous administration. Although hyperglycemia wasapparent forty-eight hours after insulin withdrawal, it was only at seventy-two and ninety-six hours after insulin withdrawal that marked retention of radioactivity was apparent in blood and that adipose tissue, carcass and hepatic uptake of fatty acid was lower thannormal. Lipoprotein lipase content of epididymal fat pads was significantly higher than normal in insulin-treated and lower than normal in the insulin-deprived rats. The findingsindicate that insulin withdrawal in the alloxan diabetic rat results in delayed clearing of intravenously administered chylomicrons from blood. Initially this may be related in part to the defective uptake by adipose tissue which becomes depleted of lipoprotein lipase. More prolonged insulin deprivation, however, leads to a greatly expanded serum triglyceride pool which in itself could account for the markedly delayed clearing of chylomicrons in severe diabetes.