Dietary Restriction and Beta-Cell Sensitivity to Glucose in Adult Male Rhesus Monkeys

We examined the effects of dietary restriction (DR) and age on ß-cell function and peripheral insulin sensitivity in rhesus monkeys. A semipurified diet was provided either ad libitum for ∼8 hours/day to controls (C) or as ∼70% of baseline intake to restricted (R) animals for 10 years. The minimal model of C-peptide secretion and kinetics and the labeled 2-compartment minimal model of glucose kinetics were identified using plasma glucose, C-peptide, and insulin concentrations during an intravenous glucose tolerance test. R monkeys had less body fat, lower basal ß-cell sensitivity to glucose (Øb), greater insulin sensitivity, and lower first-phase plasma insulin response. DR did not significantly affect first-phase and second-phase ß-cell sensitivity to glucose. Indices of body fatness were highly predictive of the effect of DR on Øb, fasting insulin concentration and insulin responses to glucose. Enhanced peripheral insulin sensitivity among R monkeys was strongly correlated with lower Øb.