An acronym for Silent Information Regulator Two proteins. They are a class of proteins thought to influence aging and regulation of the life and death cycle of cells. Sirtuins act as cellular energy sensors that regulate numerous other proteins involved in energy and glucose balance, which in turn induce a wide range of physiological changes that counteract detrimental effects of metabolic stressors. Some cosmetic companies are claiming they contain ingredients that can stimulate sirtuins in skin to prevent and reduce wrinkles. The major ingredient known to affect sirtuins is resveratrol. However those studies have been about oral consumption and not topical application. The research about its effect on skin has been done by the cosmetic companies themselves. (Source: Current Opinion in Clinical Nutrition and Metabolic Care, July 2009, pages 431-437 and Journal of Cosmetic Dermatology, March 2008, pages 2-7).