COMPARISON OF THE EFFECTS OF 20 DAYS AND 15 MONTHS OF CALORIE RESTRICTION AN MALE FISCHER-344 RATS

The aim of this study teas to compare, in 19-month-old merle Fischer 3 44 mts, the influence of brief (20 days) and prolonged (similar to 15 months) calorie restriction (CR; consuming similar to 60% of ad libitu m, AL, intake) on circulating levels of glucose, insulin, C-peptide, a nd free fatty acids (FFA); age-matched AL rats were also studied. In t he prolonged CR group, there was an similar to 85% decline in felt pad masses (epididymal and retroperitoneal) compared to AL and brief CR m ts (these latter groups did not differ significantly). Compared to AL levels, glucose was 15% lower with prolonged CR (p < 0.05) while the b rief CR values tended to be lower (10%) than AL; the CR groups did not differ significantly. Plasma FFA levels were significantly (p < 0.05) greater (85-106%) in the brief CR group compared to each of the other groups. Plasma insulin concentrations for the CR groups were lower (p < 0.05; similar to 50-60%) than AL levels. Plasma concentrations of C -peptide (an indicator of insulin secretion) were also lower for each CR group vs AL levels, and a high correlation was found between plasma insulin and C-peptide concentrations (r(2) = 0.90; p < 0.001). The C- peptide/insulin ratios for the CR groups were similar, and the value o f each CR group exceeded that for the AL rats. These results demonstra te that: the CR-induced reduction in plasma insulin is attributable in large part to reduced insulin secretion; these decreases in insulin s ecretion and concentration are essentially undiminished when brief CR is initiated rather late in life, and the reductions are independent o f substantial reductions in body fat. (Aging Clin. Exp. Res. 10: 303-3 07, 1998) (C) 1998, Editrice Kurtis.