I n an attempt to define the relationship between plasma insulin and triglyceride concentrations, we have studied the effect of suppression of the postprandial insulin response upon the secretion and plasma concentration of very low density lipoprotein (VLDL)-triglycerides. Eight nondiabetic subjects with a wide range of fasting plasma triglyceride levels (100-358 mg/dl) were studied during three dietary periods: base line, high carbohydrate (80% calories), and high carbohydrate (80% calories) with a daily intravenous infusion of somatostatin (SRIF) (1.3 micrograms/min) between 800 and 2,100 h. The significant increase in postprandial insulin response observed during high carbohydrate vs. base line was completely abolished during high carbohydrate-SRIF. However, plasma triglyceride levels rose in all subjects during each high carbohydrate period (with/without SRIF) vs. base line and the mean values reached during each period were the same (476 +/- 165 vs. 482 +/- 152 mg/dl, respectively). The secretion of VLDL-triglyceride into plasma was higher in four subjects, the same in two subjects, and lower in one subject during high carbohydrate-SRIF vs. high carbohydrate alone. The mean production rate of VLDL-triglyceride (mg/kg per h) was 25.6 +/- 4.9 during the high carbohydrate and 40.9 +/- 28.1 during the high carbohydrate-SRIF periods. These values were not significantly different. Postprandial glucose levels were slightly increased during high carbohydrate-SRIF, but overnight glucose concentrations were not affected. Plasma FFA levels were not different during the two high carbohydrate periods. Plasma glucagon levels did not appear to affect the results either. This study indicates that postprandial hyperinsulinemia during a high carbohydrate diet is not necessary for induction of hypertriglyceridemia.