Effect of intravenously administered glucose on glucagon and insulin secretion during fat absorption

The intravenous infusion of glucose was found to alter profoundly the response of insulin and glucagon to an intraduodenally administered fat meal in conscious dogs from that of dogs given only intravenous saline as a control. In the latter, insulin rose only 4 muu/ml and glucagon rose from 142 SEM plus or minus 8 to a peak of 221 pg/ml SEM plus or minus 50. When glucose was infused, raising plasma glucose above 173 mg/100 ml, the administration of fat was associated with a rise in mean insulin to 344 muu/ml, and glucagon remained suppressed by hyperglycemia to below baseline level, despite the fat meal. The peak insulin response to a fat meal plus glucose infusion was more than three times the peak level observed when glucose was infused alone without a meal or with a nonabsorbable intraduodenal volume load in the form of mineral oil. This suggests that the absorption of fat elicits an entero-insular signal that is greatly potentiated by exogenous glucose. These glucose-induced changes in the hormonal response to a fat meal may mediate certain of the metabolic effects of carbohydrates.