A three-day insulin-induced normoglycemia improves carbohydrate oxidation in type 2 diabetic subjects

Two months of a better glycemic control improve carbohydrate oxidation in type 2 diabetes. However, this benefit is uncertain for a shorter duration. We tested the effect of 3 days of normoglycemia induced by an insulin infusion. Ten type 2 diabetic subjects (body mass index [BMI], 30.0 [plusmn] 1.1; glycosylated hemoglobin [HbA_1C], 10.1 [plusmn] 0.5) were studied twice, before and after normal glucose levels were maintained by a 72-hour intravenous insulin infusion. Indirect calorimetry was performed 1 hour before (basal) and during the 3 hours after (postprandial) the ingestion of a standard meal (carbohydrates, 72 g; fat, 21 g; protein, 32 g), at noon. Carbohydrate storage was calculated as ingested carbohydrate [minus ] (postprandial glycosuria + suprabasal postprandial carbohydrate oxidation). After normoglycemia, glucose and triglyceride levels were decreased (basal glucose, 13.8 [plusmn] 1.1 mmol/L to 8.8 [plusmn] 0.5; postprandial, 14.9 [plusmn] 0.9 to 11.0 [plusmn] 0.5; basal triglycerides, 2.2 [plusmn] 0.1 mmol/L to 1.6 [plusmn] 0.2; postprandial, 2.7 [plusmn] 0.2 to 1.9 [plusmn] 0.2; all P [lt ] .01), C peptides were unchanged. Glycosuria (before, 0.30 mg/kg/min) was abolished after normoglycemia. Basal carbohydrate, lipid, protein oxidation, and energy production rates were unchanged. Postprandial carbohydrate oxidation was increased after normoglycemia (before, 1.33 [plusmn] 0.38 mg/kg/min; after, 1.77 [plusmn] 0.42; P [lt ] .05). Lipid oxidation and plasma free fatty acids (FFA) tended to be more suppressed by the meal after normoglycemia (not significant [NS]). Carbohydrate storage (before, 67,5 [plusmn] 4.6 g; after, 65.7 [plusmn] 3.6; NS) and diet-induced thermogenesis did not change after normoglycemia. Short-term insulin-induced normoglycemia improves the postprandial oxidation of carbohydrates, but not their storage.