Obesity in psoriasis: Leptin and resistin as mediators of cutaneous inflammation

Background: Obesity is a significant risk factor for psoriasis and body mass index (BMI) correlates with disease severity. Objectives: To investigate the relationship between obesity and psoriasis, focusing on the role of adipokines such as leptin and resistin. Patients/methods: Patients with psoriasis (n = 30) were recruited and their BMI, waist circumference and disease severity [Psoriasis Area and Severity Index (PASI)] were recorded. Fasting serum samples were obtained on enrolment and after a course of ultraviolet (UV) B treatment. Age-, sex- and BMI-matched healthy controls were also recruited. Results: On enrolment, serum leptin and soluble leptin receptor levels were not raised compared with the controls. However, resistin, interleukin (IL)-1β, IL-6, and chemokines CCL2, CXCL8 and CXCL9 were all significantly elevated in the patient group and serum resistin correlated with disease severity (r = 0.372, P = 0.043). Improvement after UVB treatment was accompanied by decreased serum CXCL8. In vitro, both leptin and resistin could induce CXCL8 and tumour necrosis factor-α production by blood monocytes, and leptin could additionally induce IL-1β and IL-1 receptor antagonist production. Leptin also dose dependently increased secretion of the growth factor amphiregulin by ex vivo-cultured lesional psoriasis skin. Conclusions: These data support the view that leptin and resistin may be involved in the pathogenesis of psoriasis in overweight individuals, possibly by augmenting the cytokine expression by the inflammatory infiltrate.