Inhibition of the TOR signalling pathway by genetic or pharmacological intervention extends lifespan in invertebrates, including yeast, nematodes and fruit flies1–5. However, whether inhibition of mTOR signalling can extend life in a mammalian species was unknown. We report here that rapamycin, an inhibitor of the mTOR pathway, extends median and maximal lifespan of both male and female mice when fed beginning at 600 days of age. Based on age at 90% mortality, rapamycin led to an increase of 14% for females and 9% for males. The effect was seen at three independent test sites in genetically heterogeneous mice, chosen to avoid genotype-specific effects on disease susceptibility. Disease patterns of rapamycin-treated mice did not differ from those of control mice. In a separate study, rapamycin fed to mice beginning at 270 days of age also increased survival in both males and females, based on an interim analysis conducted near the median survival point. Rapamycin may extend lifespan by postponing death from cancer, by retarding mechanisms of ageing, or both. These are the first results to demonstrate a role for mTOR signalling in the regulation of mammalian lifespan, as well as pharmacological extension of lifespan in both genders. These findings have implications for further development of interventions targeting mTOR for the treatment and prevention of age-related diseases.

Rapamycin was administered in food to genetically heterogeneous mice from the age of 9 months and produced significant increases in life span, including maximum life span, at each of three test sites. Median survival was extended by an average of 10% in males and 18% in females. Rapamycin attenuated age-associated decline in spontaneous activity in males but not in females. Causes of death were similar in control and rapamycin-treated mice. Resveratrol (at 300 and 1200 ppm food) and simvastatin (12 and 120 ppm) did not have significant effects on survival in male or female mice. Further evaluation of rapamycin's effects on mice is likely to help delineate the role of the mammalian target of rapamycin complexes in the regulation of aging rate and age-dependent diseases and may help to guide a search for drugs that retard some or all of the diseases of aging.

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Single-gene mutations that extend lifespan provide valuable tools for the exploration of the molecular basis for age-related changes in cell and tissue function and for the pathophysiology of agedependent diseases. We show here that mice homozygous for loss-of-function mutations at the Pit1 (Snell dwarf) locus show a >40% increase in mean and maximal longevity on the relatively long-lived (C3H͞HeJ ؋ DW͞J)F1 background. Mutant dw J ͞dw animals show delays in age-dependent collagen cross-linking and in six age-sensitive indices of immune system status. These findings thus demonstrate that a single gene can control maximum lifespan and the timing of both cellular and extracellular senescence in a mammal. Pituitary transplantation into dwarf mice does not reverse the lifespan effect, suggesting that the effect is not due to lowered prolactin levels. In contrast, homozygosity for the Ghrhr lit mutation, which like the Pit1 dw mutation lowers plasma growth hormone levels, does lead to a significant increase in longevity. Male Snell dwarf mice, unlike calorically restricted mice, become obese and exhibit proportionately high leptin levels in old age, showing that their exceptional longevity is not simply due to alterations in adiposity per se. Further studies of the Pit1 dw mutant, and the closely related, long-lived Prop-1 df (Ames dwarf) mutant, should provide new insights into the hormonal regulation of senescence, longevity, and late life disease.T he analysis of single-gene mutations in flies (1) and nematode worms (2-4) has begun to yield important clues to the molecular basis of aging and genetic control of longevity in invertebrates. At present there are four examples of single gene mutations that extend longevity in mammals (5-8). The best documented of these is the Ames dwarf mutation, now known as Prop-1 df , which in homozygous form has been shown to extend longevity by Ͼ50% in both males and females (5). Homozygous df͞df mice show defects in embryonic development of the anterior pituitary that lead to an absence of cells responsible for the production of growth hormone (GH), thyroid-stimulating hormone, and prolactin (PRL). The small body size of these mice is apparent within the first 3 weeks of age, and young adults are approximately one-third of the size of ϩ͞df or ϩ͞ϩ littermates, which are themselves phenotypically indistinguishable from one another. Extended longevity (about 20%) and small body size also are seen in transgenic mice that express high brain levels of urokinase-type plasminogen activator (6); in this case the phenotypes are thought to reflect a loss of appetite and diminished food intake similar to that seen in genetically normal mice and rats subjected to involuntary food restriction (9). In a third instance, targeted deletion of the p66 shc signal transduction protein has been shown to lead to increased lifespan presumably mediated by increased cellular resistance to apoptosis (7).The fourth example, the Snell dwarf mutation Pit1 dw and the coallelic mutation Pit1 dwJ are the topic of...