Skin lipid profiling in normal and seborrhoeic shih tzu dogs

Background - Seborrhoea is a clinical condition resulting in excessive lipid and/or scale on the skin and is a common and important skin disease of dogs. However, there is little information on the skin surface lipid composition of dogs with seborrhoea. Hypothesis/Objectives - To compare skin surface lipid profiles in normal and seborrhoeic shih tzu dogs. Methods - Fourteen client-owned dogs (seven seborrhoeic and seven normal) were investigated. Lipids in sebaceous glands (SGs) were extracted from homogenized tissues of SG hyperplasia. Surface lipid was collected by tape stripping [stratum corneum (SC)-enriched fraction] and acetone-wetted cotton swab (acetone-extracted fraction). Lipids in SGs, SC-enriched fractions and acetone-extracted fractions were evaluated by high-performance thin-layer chromatography. Results - Lipids in SGs mainly consisted of cholesterol esters, wax esters and triglycerides, whereas lipids in the SC-enriched fraction mainly consisted of ceramides. The acetone-extracted fraction contained a mixture of lipid classes recognized in SG- and SC-enriched fractions. In seborrhoeic dogs, concentrations of wax esters andtriglycerides in the acetone-extracted fraction were significantly higher than in control dogs (P=0.0285). Amounts of total ceramides (in micrograms) per milligram of SC were not significantly different between the two groups (P=0.5204). Interestingly, two unknown ceramide fractions, which accounted for 20% of the total ceramides, were recognized exclusively in seborrhoeic dogs. Conclusions and clinical importance - These results provide evidence that the skin surface lipid profiles are altered in shih tzu dogs with seborrhoea.