Analysis of epidermal lipids in normal and atopic dogs, before and after administration of an oral omega-6/omega-3 fatty acid feed supplement. A pilot study.

Alterations of the lipid expression in the skin of human and canine atopic subjects may be one of the key factors in the disease development. We have analyzed the ultrastructure of the clinically uninvolved skin of atopic dogs and compared it with the lipid composition of their tape-stripped stratum corneum (SC). The effect of a 2 month treatment of atopic dogs by food supplementation with a mixture of essential fatty acids was evaluated on skin samples taken before and after the treatment period. Electron microscopy revealed that the non-lesional skin of atopic dogs exhibited an abnormal and largely incomplete structure of the lamellar lipids with little cohesion between the corneocyte strata. The SC of atopic dogs was characterized by a significant decrease in the lipid content when compared to the healthy controls. Following oral supplementation with the mixture of essential fatty acids, the overall lipid content of the SC markedly increased. This feature was observed both with the free and, most importantly, with the protein-bound lipids (cholesterol, fatty acids and ceramides), the latter constituting the corneocyte-bound scaffold for ordinate organisation of the extracellular lipid bi-layers. Indeed, the semi-quantitative electron microscopy study revealed that the treatment resulted in a significantly improved organization of the lamellar lipids in the lower SC, comparable to that of the healthy dogs. Our results indicate the potential interest of long-term alimentary supplementation with omega-6 and omega-3 essential fatty acids in canine atopic dermatitis.