Food restriction, pituitary hormones and ageing

Reducing the intake of food in rodents inhibitsbody growth, retards most physiologicalageing processes, delays the onset ofpathology and prolongs life. Food restriction(FR) reduces pituitary hormone secretion andin consequence has been called`functional hypophysectomy'. Direct life-longcomparisons in the rat showedthat hypophysectomy (HYP) (a complete absenceof pituitary hormones) has a greateranti-ageing action than FR (a partial lack ofpituitary hormones) on collagen, kidneyand muscle. This suggests that pituitaryhormones accelerate ageing. Recent Americanresearch on genetic variants of the mouseindicates that pituitary growth hormone (GH)may accelerate ageing and shorten life. Boththe Snell and Ames dwarf mice have adeficiency of pituitary GH and live 50%longer than normal mice. The Snell dwarfmouse has retarded ageing of both collagen andimmune functions. The Ames dwarfmouse has high antioxidant enzyme activitiesin liver and kidney. A transgenic humanGH mouse is short lived, has a low activity ofantioxidant enzymes in liver and kidneyand an early development of disease in theseorgans. It is postulated that FR byreducing the secretion of pituitary hormones,such as GH, diminishes the oxidativedamage of certain tissues, thereby delayingthe development of age-related diseases inthese tissues and by this means extendslife.