Effects of aging on fatty acids in skin surface lipids

Abstract

The effects of aging on skin surface lipids have been studied by analysis (thin-layer chromatography and photodensitometry) of the lipid composition of skin specimens from 194 individuals, divided into groups by age and sex, and in 22 specimens of vernix caseosa. In 100 of these skin lipid samples and in 10 vernix caseosa samples, the fatty acid compositions of triglycerides, wax esters, and sterol esters were analyzed by gas-liquid chromatography on capillary and packed columns. The structures of the unsaturated fatty acids were studied by an original method based on gas chromatographic-mass spectrometric analysis of trimethylsilyloxy derivatives of fatty acid methyl esters. Our results show that either the amount and composition of skin surface lipids or the structures of the fatty acids vary according to age and sex, and that the skin surface lipids of very old individuals are similar to those of prepubertal children. The variations were especially evident in the structures of the unsaturated fatty acids. In the monoenes with chain lengths less than C16=, the double bond was always at the Δ6 position; in the longer chains, different positional isomers were found. In the unsaturated fatty acids of triglycerides, wax esters, and sterol esters, the Δ9 level, always higher in women and girls then in men and boys, reached its maximum in the prepubertal stages; from adolescence to senility the Δ9 level was at its lowest (it was superseded by the highly predominant Δ6 unsaturation pattern), but with advancing senescence, it tended to rise again.