The effect of two isocaloric evening meals (low protein-high fat vs. high protein-low fat content) on plasma glucose regulation during the night were compared. Eight C-peptide-defïcient type-I diabetic subjects without autonomic neuropathy were treated with fixed doses of continuous infusions of insulin during 2 nights. At 7 p.m. they received in random order either a low protein-high fat (5% of total energy protein, 60% fat, 35% carbohydrate) or a high protein-low fat (35% protein, 30% fat, 35% carbohydrate) evening meal. Venous plasma samples were drawn hourly thereafter. Plasma glucose concentrations were similar postprandially during the 2 nights between 7 p.m. and 11 p.m., but they were higher in the early morning hours after the high protein meal (p < 0.02 vs. the low protein meal). Two subjects developed symptomatic hypoglycemia after the low protein meal. Plasma glucagon concentrations were higher (p = 0.023) and serum free insulin lower (p < 0.05) after the high protein-low fat meal. Plasma cortisol and growth hormone were not significantly different between the two diets. Therefore, an increase in the protein content of the evening meal (fat content diminished) increases plasma glucose concentrations several hours later in the night, possibly due to protein-induced glucagon secretion and to lower plasma free insulin levels. Patients with type-I diabetes with a tendency to develop hypoglycemia during the night may avoid this problem by increasing the protein content of the evening meal.

By means of transumbilical portal catheterization immunoreactive insulin (IRI) concentrations in portal vein (POV) and in peripheral vein (PEV) were compared after administration of glucose, galactose, xylitol and tolbutamide. Fasting portal IRI concentration was about twice that found in PEV. After ß.cell-stimulation the maximal IRI rise in POV was several times greater compared to PEV. Xylitol produced a significant IRI rise in POV but non in PEV. Thus, absence of IRI elevation in PEV does not exc1ude stimulation of IRI secretion. Factors affecting the difference between portal and peripheral venous IRI concentrations are discussed.

Relative 01 absolute hyperglucagonemia is a characteristic feature in diabetics (Aguilar-Parada, Eisentraut and Unger 1969, Miiller, Faloona and Unger 1970). Therefore we were interested to study, whether an effect of biguanides on alpha cell function might be an additional factor in their hypoglycemic action.

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To assess mechanisms leading to the ‘dawn phenomenon’ in type 1 diabetes mellitus, overnight insulin clearance, hepatic blood flow and insulin sensitivity of glucose metabolism were determined in 9 type 1 diabetic subjects treated with continuous subcutaneous insulin infusions. Glucose clamp studies were performed twice, once after midnight (from 24.00 to 02.00 h), and once in the early morning (from 06.00 to 08.00 h) during insulin infusion at 15 mU/m²/min. Insulin clearance was 482 ± 57 ml/m²/min during the first, and 528 ± 56 ml/m²/min during the second clamp (nonsignificant). Hepatic plasma flow assessed by measuring indocyanine green clearance was 984 ± 115 and 1,040 ± 163ml/min, after the first and after the second clamp, respectively (nonsignificant). Glucose uptake during the two clamps was not significantly different. Since hepatic blood flow is known to influence insulin clearance and hepatic glucose metabolism, the data demonstrate that overnight changes in hepatic blood flow and insulin clearance do not contribute to the previously described early morning increase in insulin requirements in type 1 diabetic subjects (dawn phenomenon).