EFFECTS OF A PROTEIN MEAL ON PLASMA AMINO ACIDS, GLUCOSE AND INSULIN IN CONTROL AND NON INSULIN DEPENDENT DIABETES MELLITUS

This study is concerned with the influence of a protein meal (250g beef steak) on plasma glucose, insulin and amino acids measured before and for 3 hours after feeding in control (C) and non insulin dependent diabetes mellitus (NIDDM) subjects. Plasma glucose which was 4.2±0.3 for C and 8.0±0.4 mM/l for NIDDM subjects during the fasting state, remained unchanged for the duration of the postprandial period. At that time plasma insulin levels were at 35.6±10.5 for C and at 98.2±13.6 μmol/l for NIDDM subjects. A rapid insulin release identified as the early cephalic phase of feeding was observed in both groups even if it was slightly delayed in NIDDM subjects. Two hours after feeding plasma insulin was increased by approximately 100% in both groups. At 180 min the plasma levels remained elevated in the NIDDM subjects but significantly declined in the controls. This increase in insulin in the presence of unchanged glycemia suggests an increase glucose utilization supported by an enhanced gluconeogenesis. Plasma levels of all branched-chain amino acids as well as of alanine and arginine, were significantly higher during the fasting state and increased more after the protein meal in NIDDM than in control subjects. The results for both groups of subjects show on the whole a high correlation between the plasma levels of insulin on one hand and those of arginine and alanine. The nature of this relationship is not different between the two groups; for instance the high values for plasma insulin observed in the NIDDM group correspond to high values for plasma arginine, alanine and total amino acids. Taken together these results suggest that in both groups, the unchanged glycemia following the protein meal, in spite of increased glucose utilization as evidenced by increased insulin secretion, is caused by enhanced gluconeogenesis possibly regulated primarily by alanine and arginine with the participation of branched-chain amino acids.