Growth Hormone Key to Calorie-Restricted Longevity
Growth hormone receptor deficiency extends life in calorie-restricted mice
TUESDAY, May 9 (HealthDay News) -- Growth hormone signaling could be key to the life-extending effects of calorie restriction, since mice lacking its receptor live as long as calorie-restricted mice, according to a report published online May 8 in the Proceedings of the National Academy of Sciences.
Andrzej Bartke, Ph.D., from Southern Illinois University School of Medicine in Springfield, Ill., and colleagues tested growth hormone receptor-deficient (GHRKO) mice in controlled feeding assays to determine if the pathway participates in the known effects of calorie restriction on longevity.
Calorie restriction increased the life span of normal mice by 18.8 percent (males) to 28 percent (females), as has been previously shown. GHRKO mice had a similar increase in longevity, although the effect was not dependent on calorie restriction. Calorie-restricting GHRKO mice did not increase longevity, further suggesting that growth hormone perturbation alone is sufficient for the life-extending effect of calorie restriction.
Insulin sensitivity in GHRKO mice mirrored the longevity effects, where free-feeding GHRKO mice had enhanced sensitivity similar to calorie-restricted normal mice that was independent of feeding regimen. The authors conclude that their findings "support the notion that enhanced sensitivity to insulin plays a prominent role in the actions of calorie restriction and growth hormone resistance on longevity".