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 344 mts, the influence of brief (20 days) and prolonged (similar to 15 months) calorie restriction (CR; consuming similar to 60% of ad libitum, AL, intake) on circulating levels of glucose, insulin, C-peptide, and free fatty acids (FFA); age-matched AL rats were also studied. In the prolonged CR group, there was an similar to 85% decline in felt pad masses (epididymal and retroperitoneal) compared to AL and brief CR mts (these latter groups did not differ significantly). Compared to AL levels, glucose was 15% lower with prolonged CR (p < 0.05) while the brief 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 of each CR group exceeded that for the AL rats. These results demonstrate that: the CR-induced reduction in plasma insulin is attributable in large part to reduced insulin secretion; these decreases in insulin secretion and concentration are essentially undiminished when brief CR is initiated rather late in life, and the reductions are independent of substantial reductions in body fat. (Aging Clin. Exp. Res. 10: 303-307, 1998) (C) 1998, Editrice Kurtis.