Synthesis and Composition of Surface Lipids of Human Skin

Abstract

The composition and biosynthesis of lipids in human skin have long been of considerable interest, both because of the highly unusual structures these lipids contain and because of the possible involvement of the lipids in disease processes of the skin. Despite the exceptionally complex nature of surface lipid, its composition is now known in detail. In addition, since efficient procedures are now available for analyzing the class composition of skin lipid and the individual members of these classes, the changes in composition that may occur under specialized circumstances can now be studied in large groups of subjects. Because of the unusual compounds in skin lipids. the pathways of lipogenesis that have been elucidated in other tissues cannot confidently be accepted for skin. Therefore, direct examination of lipogenesis in skin has been desirable, but the numerous studies that have been conducted have been only moderately successful in delineating pathways of lipid biosynthesis. Moreover, because of the extreme variation in surface lipid composition between species, studies of sebaceous lipogenesis in other animals have only limited application to man. Howe\'er, useful inferences regarding the biosynthesis have been based on observations of the composition of human surface I ipid collected under specific conditions. This review emphasizes the results of investigations of the composition of surface fipids from human skin from which deductions concerning their origin and biosynthesis can be made. Some of the more direct examinations of lipogenesis based on in vitro studies in skin are discussed by Wheatley (this issue).