In mammals, sebaceous glands (SG) and keratinocytes produce a protective lipid layer that covers the skin, which is critical for maintaining the skin’s barrier function. Research has suggested that SG abnormalities contribute to disease. One of the most common dog breeds with seborrhea is the shih tzu, in which primary seborrhea is complicated by Malassezia spp dermatitis and/or atopic dermatitis. Fourteen client-owned shih tzu dogs (7 normal, 7 affected) were investigated. Skin lipids were collected via tape stripping then evaluated via high performance thin layer chromatography. The study found that low polar lipids (eg, ceramides, wax esters, triglycerides) were the main components of sebaceous glands while ceramides were the main component of lipids in the stratum corneum. The study also found that lipid profiles of affected dogs were different from those of normal dogs; specifically, concentrations of wax esters and triglycerides were significantly higher than in normal dogs. Of interest, the total amounts of ceramides was not different between normal and affected dogs. However, 2 unknown ceramide fractions accounted for 20% of total ceramides in the affected dogs and were found exclusively in this group.

Commentary
Until this report, it was merely hypothesized that skin lipids of seborrhoeic dogs were abnormal; this study provides evidence. The ability to tell clients with certainty that topical therapy is necessary for these dogs and that it will be lifelong is advantageous. If the investigators pursue this research, a genetic marker could be identified, making selective breeding or early detection possible.—Karen Moriello, DVM, DACVD

Source
Skin lipid profiling in normal and seborrhoeic shih tzu dogs. Yoon J-S, Nishifuji K, Ishioroshi S. VET DERMATOL 24:84-e22, 2013.