However, although moderate overexpression of SIRT1 protected against age-related diseases such as osteoporosis, glucose intolerance, and metabolic syndrome-related cancers, it did not extend lifespan.35 Thus, either SIRT1 has no role in regulating lifespan; or under the weak expression of the transgene (threefold) SIRT1 has no effect of longevity, and stronger expression of the transgene may be necessary to achieve lifespan extension. The gene discussed is SIRT1; the disease is cancer.