Circulating Level of Soluble Leptin Receptor and its Association with Cardiometabolic Risk Factors among Obese Subjects in Kerala, South India

Background and Aims: Leptin, the peptide hormone secreted mainly by adipose tissue is reported to play the central role in the pathogenesis of obesity. Leptin exerts its biological effects through specific receptor molecules present in target tissues. Among the different isoforms of leptin receptor, the Soluble Leptin Receptor (SLR) is the major leptin binding protein seen in circulation which modulates the bioavailability of leptin. Our objectives were to analyse the level of circulating SLR among obese subjects and its association with biomarkers of obesity, serum leptin, insulin and cardiometabolic risk factors in comparison with healthy age and sex matched control subjects.

Methods: About 173 study participants of both genders were selected and grouped as case (n=102) and control (n=71) with a cut off point of BMI 25kg/m2. Waist to hip ratio (WHR) and body fat percentage (BF%) were calculated from anthropometric measurements. Leptin, insulin, soluble leptin receptor were estimated in fasting blood samples by sandwich ELISA method. Fasting plasma glucose and lipid profile were measured by standard enzymatic methods in autoanalyzer. Homeostasis Model Assessment of Insulin resistance (HOMA-IR) was calculated. Comparison between groups was done by independent sample ‘t’ test. P values <.05 were considered statistically significant.

Results: The SLR level was found to be increased in obese group in comparison with control group(P =.001). A significant increase in serum leptin and insulin level was observed in obese group when compared to control (P =.001). Obese group showed more than two fold increase in insulin resistance expressed as HOMA-IR when compared to control subjects (P =.001). But no significant difference in the synthesis of insulin expressed as HOMA-beta between the groups. No significant difference in serum lipoprotein levels was observed between the two groups.

Conclusion: Increased level of circulating soluble leptin receptor has been observed in obese subjects in comparison with control subjects and is associated with hyperleptinemia, hypertension and insulin resistance.