Leptin and Atopic Dermatitis in Korean Elementary School Children

The prevalence of atopic dermatitis (AD) and obesity have been increasing considerably in Korean school-children. AD is a chronic pruritic recurrent inflammatory skin disorder. Leptin is secreted by adipocytes which has been suggested to be immunologically active; however, their role in AD has not yet been well understood. A total of 227 subjects out of 2,109 elementary school children were defined as having AD based on the ISAAC questionnaire survey. Ninety subjects with AD, aged between 6 and 12 years, completed scoring of severity of AD (SCORAD), skin prick testing, blood tests for total IgE, eosinophil counts, eosinophil cationic protein (ECP) and lipid profiles. Serum leptin levels were also measured. A subject with atopic AD was defined as an AD patient showing at least 1 positive reaction to allergens in skin prick testing. There were no significant differences in age, body mass index, percentage of breast milk feeding, mode of delivery, prevalence of atopy, and lipid profiles between atopic AD and non-atopic AD subjects. The serum leptin levels (log mean±SD) were significantly higher in non-atopic AD group than in the atopic AD group (0.86±0.57 ng/mL vs 0.53±0.72 ng/mL, p=0.045). Subjects with mild-to-moderate AD showed significantly higher serum leptin levels than those with severe AD (0.77±0.67 ng/mL vs 0.33±0.69 ng/mL, p=0.028). There was a marginal inverse correlation between the SCORAD index and the serum leptin concentration in total AD subjects (r=-0.216, p=0.053). The serum leptin levels were significantly higher in non-atopic AD subjects or mild-to-moderate AD subjects. Leptin did not seem to be associated with IgE-mediated inflammation in AD. Obesity-associated high leptin differed between non-atopic AD and atopic AD subjects.