DIETARY-PROTEIN RESTRICTION ALTERS GLUCOSE BUT NOT PROTEIN-METABOLISMIN NON-INSULIN-DEPENDENT DIABETES-MELLITUS

We determined whether a customary diet high or low in protein (1) infl uences postabsorptive amino acid catabolism, nitrogen (N) balance, and hepatic glucose output (HGO) in normal subjects or patients with non- insulin-dependent diabetes mellitus (NIDDM) or (2) alters blood glucos e levels in NIDDM, Eight normal young adults and five obese middle-age d persons with NIDDM consumed low-protein (0.8 g/kg lean body mass [LB M]) or high-protein (3.0 g/kg LBM) diets at maintenance energy for con secutive 7-day periods, Easting and average blood glucose and N balanc e were measured daily, The level of dietary protein had no effect on t he basal plasma leucine rate of appearance (Ra) or urinary 3-methylhis tidine excretion in either subject group, Basal leucine oxidation (and by inference, whole-body amino acid catabolism) was reduced on the lo w-protein diet but basal HGO was not, and although exogenous glucose e ffectively suppressed HGO, it did not reduce leucine oxidation with ei ther diet. After adaptation to the low-protein diet, N balance in both the normal and NIDDM subjects was close to zero, The low-protein diet reduced the fasting and daily blood glucose of the diabetic subjects by approximately 2 mmol/L (P < .05). We conclude that physiologic vari ation in dietary protein does not affect basal whole-body protein turn over or HGO in either normal young adults or obese middle-aged NIDDM s ubjects. However, protein restriction to the level of the average dail y requirement significantly reduces postabsorptive and average daily b lood glucose concentrations in persons with NIDDM. Copyright (C) 1998 by W.B. Saunders Company.