Bone structural and metabolic response of caloric restriction in Wistar rats and a GH-IGF-1 axis-suppressed transgenic rat model.Bone structural and metabolic response of caloric restriction in Wistar rats and a GH-IGF-1 axis-suppressed transgenic rat model. カロリー制限を行ったWistar ratとGH-IGF-1系を抑制したトランスジェニックラットの骨構造および骨代謝の変化についての検討
The growth hormone–insulin-like growth factor-1 (GH–IGF-1) axis plays an important role in the effects of caloric restriction (CR) on lifespan extension and may elicit effects on bone metabolism in CR animals. We compared the effects of the GH–IGF-1 axis suppression and CR on bone metabolism. We used Wistar rats fed ad libitum (control group) or fed a 30% calorierestricted diet in CR group and heterozygous transgenic (F1) rats whose GH-IGF-1 axis is moderately suppressed. There was no significant difference in serum IGF-1 concentration between control and CR rats; however, IGF-1 was significantly lower in F1 rats than in other groups. The bone volume fraction (BV/TV) was significantly lower in CR than in the control. The mean SMI value in CR rats was marginally significant difference from that in control rats, Although there was no difference in serum IGF-1 concentrations between CR and control rats, bone volume was lower, and higher SMI was observed in the former. The serum IGF-1 levels in F1 rats were lower than those of controls, but the bone volume and SMI in F1 were not different. Therefore, the effects of bone metabolism in CR rats may be different from those in the GH-IGF-1 suppression rats.