Mechanisms of increase in plasma triacylglycerol concentrations as a result of high carbohydrate intakes in patients with non-insulin-dependent diabetes mellitus.

To determine the mechanisms of increase in plasma triacylglycerol concentrations after high dietary intakes of carbohydrates, 10 men with non-insulin-dependent diabetes mellitus (NIDDM) were fed an isoenergetic high-carbohydrate diet (55% of energy as carbohydrate and 30% as fat) and a high-monounsaturated-fat diet (45% of energy as fat and 40% as carbohydrates) for 6 wk in a randomized, crossover manner. The high-carbohydrate diet raised fasting plasma triacylglycerol concentrations by 26% (P = 0.007) but did not affect postheparin lipoprotein lipase (P = 0.2) or hepatic lipase activities (P = 0.9). The oral-fat-tolerance test labeled with retinyl palmitate also revealed no differences in postprandial plasma triacylglycerol (P = 0.37) or retinyl palmitate clearances (P = 0.34) between the two diets. We conclude that the increase in plasma triacylglycerol concentrations with high-carbohydrate diets in men with NIDDM is not due to reduced lipolysis or diminished postprandial clearance of triacylglycerol-rich lipoproteins but is primarily due to increased hepatic secretion of very-low-density-lipoprotein triacylglycerols.