Effects of GH on the Aging Process in Several Organs: Mechanisms of Action.

ABSTRACT

In order to investigate the possible beneficial effects of GH administration on the aging process, 24-month-old rats of both sexes and 10-month-old SAMP8 mice were used. Male rats showed increased fat content and decreased lean body mass together with enhanced vasoconstriction and reduced vasodilation of their aortic rings compared to young adult animals. Chronic GH treatment for 10 weeks increased lean body mass and reduced fat weight together with inducing an enhancement of the vasodilatory response by increasing eNOS and a reduction of the constrictory responses. Old SAMP8 male mice also showed insulin resistance together with a decrease in insulin production by the endocrine pancreas and a reduced expression of differentiation parameters. GH treatment decreased plasma levels and increased pancreatic production of insulin and restored differentiation parameters in these animals. Ovariectomy plus low calcium diet in rabbits induced osteoporosis Titanium implants inserted into these rabbit tibiae showed after one month lesser bone to implant (BIC) surface and bone mineral density (BMD). Local application of GH in the surgical opening was able to increase BIC in the osteoporotic group. The hippocampus of old rats showed a reduction in the number of neurons and also in neurogenesis compared to young ones, together with an increase of caspases and a reduction of Bcl-2. GH treatment was able to enhance significantly only the total number of neurons. In conclusion, GH treatment was able to show beneficial effects in old animals on all the different organs and metabolic functions studied.