Effect of short-and long-term caloric restriction on insulin resistance in male fisher-344 rats

The effect of short- and long-term caloric restriction (CR) on insulin resistance in male Fisher-344 rats was studied. The short- and long-term CR rats had not only significantly lower blood glucose and insulin levels, but also lower body and liver weights as compared with ad libitum (AL) rats. The insulin resistance index (IRI) was markedly lower, but the insulin sensitive index (ISI) was significantly higher in CR rats than in AL ones. The results indicate that CR rats can ultilize glucose and adapt themselves to the condition of lower insulin and glucose concentrations. They have higher ISI and lower IRI, which probably result from decreased body fat and increased exercise. Insulin resistance increased with aging, and this phenomenon could be retarted through CR. It is concluded that rats on CR show decreased body and liver weights, lowered glucose and insulin concentrations, lowered insulin resistance, and elevated insulin sensitivity.