Variability in the fatty acid composition of wax esters from vernix caseosa and its possible relation to sebaceous gland activity.

Wax ester/sterol ester (WE/SE) ratios were measured in samples of vernix caseosa lipid obtained from 21 full-term infants. The mean WE/SE ratio was twice as high in males as in females, suggesting higher average fetal sebum production rates in males, but individual values varied widely and there was considerable overlap between the sexes. Wax esters (a class of lipid produced only by the sebaceous glands) were isolated from 6 of the 21 samples of vernix caseosa lipid and analyzed for fatty acid composition. The percentages of iso and anteiso branched saturated fatty acids and of delta 9-type monounsaturated fatty acids were found to be correlated negatively with the WE/SE ratios of the original lipid samples. Values for the percentages of the major delta 9-type monounsaturates, plotted as a function of WE/SE ratios, fell near a curve of the shape which would be expected if a limited quantity of delta 9-type monounsaturates were available for sebum synthesis, and were diluted with varying amounts of delta 6-type monounsaturates, the amount of the delta 6-type monounsaturates being proportional to the amount of wax esters synthesized by the sebaceous glands. The results suggested that the rate of sebum production may be the sole determinant of the percentage of delta 9-type monounsaturates in sebaceous wax esters and a partial determinant of the percentage of iso and anteiso branched saturates.