Calorie restriction from a young age preserves the functions of pancreatic β cells in aging rats

Calorie restriction (CR) is a simple method for delaying aging process, extending lifespan, and preventing the onset of aging-related diseases, such as diabetes. However, the mechanism, by which CR influences β-cell functions during the aging process, still remains unclear. In this study, sixteen 8-week-old male Sprague-Dawley rats were randomized to control group with food intake ad libitum and CR group fed with 70% of food intake of the control group. Twenty-four weeks later, the body weights of the rats with CR were significantly lower with the smaller amounts of perirenal and epididymal fats, compared to those of control rats. The β-cell activity, as judged by the early insulin secretion in the intraperitoneal glucose tolerance test, was significantly higher in the CR group than that in control animals. Moreover, CR animals showed the increased β-cell mass and proliferation of β-cells in pancreas. The plasma level of malondialdehyde was lower in CR rats than that in control rats, while the activities of superoxide dismutase, catalase and glutathione peroxidase in plasma were higher in CR rats than control rats. These results indicate that aging is associated with the increases in oxidative stress, which was, however, alleviated by CR. In conclusion, CR from a young age preserves the principal β-cell function of early insulin secretion in rats probably by stimulating the β-cell proliferation. Our observations provide the evidence for clinical significance of CR in preventing β-cell dysfunction during the aging process, which may delay the onset of aging-related disease, including diabetes in humans.