| FUTURISTIC APPROACHES TO SKIN CARE | arTicle The most recent
scientific upgrade makes use of ingredients that
activate the expression of master genes that affect life span and
improve resistance to stress.
Cell longevity genes in skin care
A study showing the efficacy of a cosmetic formulation in activating a cell longevity gene (SIRT1) in human skin cells has recently been reported (25). This section presents an overview of how enzyme activators of the SIRT1 gene enhance cell longevity and summarizes the results of this study.
Ageing and skin care Ageing has traditionally been considered part of a genetic program as well as a ‘wear and tear’ phenomenon. The genetically programmed component has been partially discredited, and current thought attributes ageing to an organism’s declining ability to repair damage caused by environmental stress. As the skin ages, proteins, DNA, lipids, and glycans are
damaged, primarily by free radicals induced by UV radiation and internal metabolism (25,26). First-generation skin care products were therefore formulated to include natural scavengers of free radicals. As research progressed, more sophisticated products emerged with ingredients that went one step further: they reinforced natural cellular enzymes that detoxified free radicals. Examples of these cellular enzymes are superoxide dismutase, which detoxifies oxygen free radicals; catalase; and glutathione peroxidase, which detoxifies hydrogen peroxide. Subsequent formulations activated chaperone proteins (27) that protect cellular proteins or they activate detoxifying proteins such as proteasome (28), which assists in recycling damaged proteins. The most recent scientific upgrade makes use of
ingredients that activate the expression of master genes that affect life span and improve resistance to stress (25). These activators are enzymes called sirtuins, which are involved in gene silencing, fatty acid metabolism, apoptosis, and cellular life span regulation (25,29). Up to
seven sirtuin enzymes (Sir1–Sir7) have been described in humans (30).
The role of sirtuins The importance of sirtuins in ageing is supported by a study in which a yeast cell’s life span was increased 30% after an extra copy of a sirtuin gene was added to the cell. A later study showed that extra copies of the same gene extended the life span of roundworms by up to 50% (31). Additional support comes from the increased activity of sirtuin enzymes observed in yeast when food is reduced. This is important because caloric reduction is known to increase life span as well as to lower the incidence and postpone the onset of age-related diseases (25,31). Finally, recent human genomic research shows that high-activity sirtuin genes are significantly increased in humans with the greatest longevity (32). Sirtuins exert their anti-ageing effects by adding acetyl
groups to and removing them from histones, a group of proteins that wrap around cellular DNA (31). Adding acetyl groups to histones allows transcription to occur, and removing them from histones inhibits transcription. Sir1, for example, regulates gene silencing by removing acetyl groups from histones. (Genes are “silenced” when they are in a region of the genome that cannot be activated due to deacetylation (31).) Sir1 also regulates chromatin remodeling and the activity of a large range of transcription factors (e.g., p53) involved in the regulation of apoptosis, cell repair, cell cycle progression, and senescence (33).
The skin care product Sirtuins occur in keratinocytes and fibroblasts of the lower epidermis, upper dermis, and the epidermal–dermal junction. In these three layers, collectively called the ageing- responsible interface (ARI), are located 20 “youth
sirtuins
exert their anti- ageing effects by adding acetyl groups to and removing them from histones, a group of proteins that wrap around cellular dna.
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