Polyphenols such as quercetin and resveratrol are dietary antioxidants known to confer numerous health benefits and to activate sirtuins, thus playing a role in the caloric restriction longevity extension mechanism; their capacity to influence or extend lifespan has been shown in simple organisms but not consistently, as yet, in humans or other mammals (J. Cosmet. Dermatol. 2008;7:2-7; Genes Nutr. 2006;1:85-93).
However, work in mice (discussed in an episode of the television show "60 Minutes" in early 2009) performed by Sirtris Pharmaceuticals, a research company founded on recent discoveries related to sirtuins, demonstrated that resveratrol fed to mice on a high-fat diet improved insulin resistance, increased mitochondrial content, and prolonged life. In two groups of mice fed a high-fat diet, both groups wound up obese, but the mice administered resveratrol as part of their diet were able to run twice as far and fast, and survived 20% longer. In other studies by Sirtris, mice fed resveratrol as part of a high-fat diet gained less weight than mice administered a high-fat diet without resveratrol. Investigators at Sirtris also have identified small-molecule activators of SIRT1 that are 1,000 times as strong as resveratrol (Nature 2007;450:712-6).
Many other companies, such as Avon, have studied ingredients that upregulate sirtuin expression. By using human skin biopsies and immunohistochemical analysis, Avon has shown that its own proprietary botanical extracts promote the expression of dermal matrix proteins. The company claims that a 12-week clinical study using a product formulated to stimulate sirtuin expression displayed efficacy that warrants use in an antiaging product.
It remains to be seen what such claims - and products - will mean for the skin. For now, I would continue to recommend oral resveratrol and red wine supplements. In particular, I suggest OPC Synergy by Standard Process Inc., which contains grape seed and red wine extracts.
Conclusions
The family of proteins known as sirtuins appears to play an important role in the increased lifespan of various species, particularly, as recent research suggests, in calorie-restricted animals. The polyphenolic antioxidant resveratrol, which is abundant in red wine and is now included in some cosmeceutical agents, upregulates sirtuin expression and may protect cells from DNA damage.
The discovery of the role of sirtuin expression in slowing the pace of aging, in the experimental setting, strikes me as a very significant advance, and may lead to further elucidation of the aging process overall as well as cutaneous aging.
However, it is unknown at this time what role sirtuin and sirtuin activators play in skin care. Early data suggest that the activation of sirtuins may improve the appearance of skin, but the mechanism, if known, is unclear to me. The potential of Avon's botanically derived agent in upregulating sirtuin expression in skin cell cultures appears promising, because the company's study did reveal that patients experienced improvement in wrinkles. I was not the investigator in this study, so it is difficult to comment on the validity of the observations, as I am unsure of the exact study design.
I will be interested to see further work in this area, and it's always good to have a medically sound reason to drink wine.
Recently, investigators attempted to stimulate the expression of sirtuin, specifically SIRT1, in human skin cells in a culture of yeast Kluyveromyces biopetides, and to identify cutaneous benefits from an active skin care product containing such biopeptides. They also tested healthy skin samples ex vivo. Immunostaining, Western blotting, and cytometry were used to assess SIRT1 in culture and in ex vivo samples. Comet assays were used to evaluate cellular aging and integrity. Sir2 protein (Sir2p), present in yeast, is the founding member of the sirtuin family. SIRT1 was the first homolog found in humans and other mammals (Mol. Endocrinol. 2007;21:1745-55; Mol. Cell Biol. 2003;23:3173-85; Biochem. Biophys. Res. Commun. 2000;273:793-8). Now there are seven known mammalian sirtuins: SIRT1-SIRT7. Sirtuins are found in organisms ranging from bacteria to humans. Much sirtuin research has been done in the yeast Saccharomyces cerevisiae, the fruit fly Drosophila melanogaster, and the nematode Caenorhabditis elegans. In these organisms, sirtuins have been identified as molecules that mediate the effects of caloric restriction on aging processes (Genes Nutr. 2006;1:85-93).