Nutrient regulation of post-heparin lipoprotein lipase activity in obese subjects.

This study examines the immediate effect of ingestion of oral carbohydrate and fat on lipoprotein lipase (LPL) activity post-heparin in six lean and six obese age-matched women. Subjects were given, on two separate occasions, 340 kcal carbohydrate or an equicaloric amount of fat, both in 300 ml of water. Post-heparin LPL activity (10,000 U) was measured on each occasion 120 minutes after ingestion of the meal. Following oral carbohydrate postprandial plasma insulin levels were significantly higher in obese subjects than in lean (p < 0.01). Impaired glucose tolerance was seen in the obese group. GIP secretion was similar in lean and obese subjects both during oral fat and carbohydrate ingestion. GLP-1 secretion post-carbohydrate was lower in obese subjects. Total LPL activity unadjusted for body weight was similar in the two groups after carbohydrate administration but was significantly lower when adjusted per kg body weight. Total LPL activity was lower in the lean group at 130 minutes after fat administration (p < 0.02). Fasting serum triglycerides were higher in the obese group and were inversely related to the post-carbohydrate LPL activity (r = - 0.65, p < 0.02). Intraluminal lipoprotein lipase activity is not increased in established obesity. Fat and carbohydrate nutrients may affect LPL activity differently in lean and obese subjects.