Leptin, soluble leptin receptor, and free leptin index in patients with metabolic syndrome

Aim . To assess the levels of leptin, its soluble receptor, and index of the formation of free leptin in metabolic syndrome (MS). Materials and methods . The study included 110 individuals with obesity and overweight. The group 1 consisted of 70 patients with MS (IDF, 2005), the average body mass index (BMI) 38.4 ± 4.4 kg/m 2 , aged 48.2 ± 2.4 years, with arterial hypertension (AH) 1–2 degree, without regular antihypertensive therapy. Group 2 – "healthy" obesity accounted for 40 patients aged 38.4 ± 6.2 years, BMI 36.0 ± 5.5 kg/m 2 without hypertension and metabolic disorders. Group 3 consisted of 30 healthy persons, BMI 27.1 ± 1.3 kg/m2. All patients were evaluated for insulin, HOMA index, leptin, leptin receptor, leptin free index (calculated as the ratio of leptin (ng/ml) to the leptin receptor (ng/ml), multiplied by 100). Results : In patients with MS as compared to other two groups there were higher levels of HOMA IR index, leptin and free leptin index. Values of leptin receptor in groups 1 and 2 did not differ significantly and were lower than in healthy persons. The free leptin index was significantly higher in MS group relative to the group 2 and 15 times higher than in the healthy individuals. Free leptin index correlated with values of BMI (R = 0.32; p = 0.02), blood pressure (R = 0.3; p = 0.04), uric acid (R = 0.27; p = 0.04), triglycerides (R = 0.42; p = 0.02), index HOMA-IR (R = 0.45; p = 0.02). Conclusions : Reduction of soluble leptin receptor, depending on the degree of abdominal obesity, may cause progression of leptin resistance in patients with MS. The levels of leptin and soluble leptin receptor appears to have dramatical gender differences. Calculation of free leptin index should be used for the objective evaluation of leptin resistance, regardless of gender, degree of obesity, and other metabolic parameters.