Skin Biology TRC, Johnson & Johnson Consumer Companies Worldwide, Skillman, New Jersey, U.S.A.

Correspondence: Dr Apostolos Pappas, MBT Munich Biotechnology, Fraunhoferstr. 10, 82152, Martinsried, Germany. Email: Apostolos.Pappas@mbiotech.de

Received 23 May 2001; Revised 16 August 2001; Accepted 10 September 2001.

Abstract

The sebaceous gland is an integral part of the pilosebaceous unit of mammalian skin, which produces and secretes a unique mixture of lipids, known as sebum. Wax esters, which account for approximately 25% of human sebaceous lipids, are unique in that they are not synthesized by other cells in the body. To explore the biosynthesis of wax esters, the metabolic fate of exogenously supplied saturated (16:0, 18:0), mono-unsaturated 9 (16:1, 18:1), and polyunsaturated (18:2, 9,12) fatty acids was followed in biopsy punches from human facial skin rich in sebaceous glands. Acetate was incorporated into all of the cellular and secreted lipids and 16:0 was incorporated into all of the fatty-acid-containing lipids. The 16:0 was elongated to 18:0 and the 16:1 was incorporated primarily into polar lipids, secondarily into triglycerides, but not into other lipids and was elongated to 18:1 (11). As proven by HPTLC analysis, both 18:0 and 18:1 were incorporated into the cellular lipids but at a lower rate into wax esters. Moreover, addition of exogenous 18:1 was not further processed following initial incorporation. Linoleic acid (18:2, 9,12) was the only fatty acid tested that appeared to be subjected to -oxidation. This was proven to be specific to linoleic acid, as it did not induce the oxidation of other fatty acids. The ability of the sebaceous cells to synthesize wax esters correlated with the -oxidation activity in these cells. Thus, the oxidation of linoleic acid is specific for the sebaceous cells and correlates with their function and differentiation. Our results provide evidence that the sebaceous gland selectively utilizes fatty acids as 16:0 is the preferred fatty acid that is incorporated into wax esters and linoleic acid undergoes -oxidation.