EFFECTS OF AN ACUTE INCREASE IN PLASMA TRIGLYCERIDE LEVELS ON GLUCOSE-METABOLISM IN MAN

The aim of the study was to evaluate the effects of an acute increase in triglyceride levels induced by Intralipid (Kabivitrum, Stockholm, S weden) infusion on forearm glucose uptake, glucose oxidative metabolis m, and hepatic glucose production independent of circulating free fatt y acid (FFA) levels in man. Six normal subjects underwent three differ ent tests in random order. Each test consisted of a control period of 120 minutes followed by a euglycemic, hyperinsulinemic clamp lasting 1 20 minutes. In test 1, a high-dose intravenous Intralipid infusion was performed to increase triglyceride and FFA levels. In test 2, heparin (30 U/min) plus low-dose Intralipid infusions were performed to maint ain triglyceride at normal levels and increase only FFA levels. Test 3 was performed as a control study. During the 120-minute control perio d, forearm glucose uptake and hepatic glucose production were not affe cted by increasing only FFA levels (test 2) or FFA and triglyceride le vels (test 1) as compared with the control study. On the contrary, glu cose oxidation was significantly decreased as compared with the contro l study during tests 1 and 2, without a further significant decrease d uring simultaneously increased FFA and triglyceride levels. Concomitan tly, lipid oxidation was similar in tests 1 and 2, at values significa ntly greater than in test 3. During the euglycemic clamp, forearm gluc ose uptake and glucose oxidation were significantly lower during tests 1 and 2 than test 3. At variance with the control period, the increas e of triglyceride levels during test 1 caused a significant 30% to 40% decrease of both parameters as compared with test 2. Opposite results were found for lipid oxidation, which remained unchanged during test 1 as compared with the control period but significantly decreased duri ng tests 2 and 3. Hepatic glucose production was less inhibited during test 1 than during tests 2 and 3, and less so during test 2 than test 3. In conclusion, at least under these particular conditions, acute h ypertriglyceridemia induced by Intralipid infusion seems to decrease f orearm glucose uptake, glucose oxidation, and insulin-induced suppress ibility of hepatic glucose production. Taking our results together, it seems that the triglyceride effect on carbohydrate metabolism occurs via triglyceride hydrolysis using the intracellular pathways of FFA wi thout interference with the circulating FFA pool. Copyright (C) 1995 b y W.B. Saunders Company