Psoriasis vulgaris severity and body mass index: evaluating the role of leptin, tumor necrosis factor-a, and interleukin-6

Background Psoriasis is one of the dermatologic diseases that are aggravated by overweight or obesity. Leptin, a hormone secreted from the adipocytes of white fat, has been implicated in obesity. It has been recognized as a cytokine-like hormone that modulates both innate and adaptive immunity by enhancing T-cell survival and stimulating the production of proinflammatory cytokines. Psoriasis and obesity are both immune-mediated diseases. However, the relationship between these two entities is not yet clearly defined. Objective This study aims at investigating the relationship between psoriasis vulgaris severity and BMI by measuring the levels of leptin, tumor necrosis factor-a (TNF-a), and interleukin-6 (IL-6) in patients’ serum. Patients and methods The study included 30 patients with chronic psoriasis vulgaris. Seventeen patients were either overweight or obese. Thirteen were of normal weight, and these constituted the control group. Both BMI and the psoriasis area and severity index (PASI) were scored for all patients. Fasting serum leptin, TNF-a, and IL-6 levels were estimated using an enzyme-linked immunosorbant assay technique. Results PASI score, serum leptin, TNF-a, and IL-6 levels were all found to be significantly higher in overweight and obese psoriatic patients when compared with normal weight psoriatic patients (Po0.001, Po0.001, P= 0.002, and P = 0.04, respectively). A statistically significant correlation was found between BMI and each of PASI score, serum leptin level, TNF-a, and IL-6 in all patients (r =0.755, Po0.001; r = 0.759, Po0.001; r= 0.757, Po0.001; r= 0.374, P= 0.042, respectively). Moreover, a statistically significant correlation was observed between serum leptin level and each of BMI, PASI score, TNF-a, and IL-6 in all patients (r = 0.759, Po0.001; r = 0.722, Po0.001; r= 0.737, Po0.001; r= 0.554, P= 0.002, respectively). Conclusion The present study strongly suggests the relationship between the severity of psoriasis vulgaris and BMI. The current data support the view that serum leptin may contribute to the induction and maintenance of psoriatic lesions, possibly by increasing the production of TNF-a and IL-6, the key cytokines in the pathogenesis of psoriasis.