Effects of essential fatty acid deficiency on epidermal O-acylsphingolipids and transepidermal water loss in young pigs.

Linoleate-rich O-acylglucosylceramides and acylceramides are thought to be of major significance for the physical structure and function of the epidermal permeability barrier. In the present investigation, the effects of a linoleate-free diet on O-acylsphingolipids and their associated functions were investigated. Starting at 5 days of age, male pigs were fed diets containing 12% of either lard or hydrogenated coconut oil. Transepidermal water loss was measured with an electrolytic water analyzer at weekly intervals. Pigs were killed at intervals, and epidermal lipids were isolated and analyzed. Fatty acid compositions were determined by gas-liquid chromatography (GLC). Within 2-3 weeks, pigs on the diet containing coconut oil began to display biochemical and physiological symptoms of essential fatty acid deficiency. Within 2 months, this group had extremely scaly skin and transepidermal water loss was elevated to five times that of controls. The progressive increase in transepidermal water loss correlated with replacement of linoleate by oleate in both acylceramide and acylglucosylceramide. The formation of lamellar granules and intercellular lipid sheets in the stratum corneum was not impaired in essential fatty acid deficiency as judged by electron microscopy. These results suggest that the linoleic acid normally found in the O-acylsphingolipids is not essential for formation of the epidermal membrane system. Rather, it appears that the nature of the ester-linked fatty acid in the O-acylsphingolipids regulates the permeability of this membrane system.