Squalene as a pollution protection marker

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Sebum, the lipid film produced by sebaceous glands in the skin, has important functions including reducing water loss from the skin surface, serving as a vehicle for lipophilic antioxidants, protecting against harmful microorganisms and shielding against environmental aggressors. Human sebum is a complex mixture of lipids consisting of triglycerides, diacylglycerols and fatty acids (50–60% altogether); wax esters (20–30%); squalene (10–16%); and cholesterol esters (2–4%). Variations in sebum production and composition have been reported among different ethnic groups. For example, African-American skin produces more sebum than Asian skin, which in turn produces more than Caucasian skin. African-American skin also contains higher squalene content.3 The presence of squalene in sebum is of particular interest since it is unique to humans and has recently been identified as a reliable marker of environmental damage to the skin. Squalene is a triterpene comprising six non-conjugated double bonds, making it one of the most unsaturated lipids. However, this means that squalene is highly prone to oxidative damage. Indeed, squalene is particularly sensitive to singlet oxygen (1O2), which is generated in the skin upon exposure to UVB and UVA radiation. Atmospheric pollutants, ozone (O3) and cigarette smoke are also powerful oxidizing agents of squalene. When squalene is oxidized, peroxides are formed, creating important biological consequences. First, peroxidized by-products are potent inflammatory mediators associated with acne, hyperpigmentation, skin roughness and wrinkle formation. Moreover, in response to squalene deterioration, sebaceous glands are activated, resulting in excess sebum production to compensate for its poor quality. This creates an unbalanced sebum composition abnormally rich in peroxidation-prone squalene and glycerides that can only perpetuate oily skin problems. Reference: May, 22th, 2018 by Joan Attia-Vigneau Ph.D., Marty Shortt, Rachelle Seguin, Isabelle Lacasse and Estelle Loing, Ph.D