Altered circulating concentrations of active glucagon-like peptide (GLP-1) and dipeptidyl peptidase 4 (DPP4) in obese subjects and their association with insulin resistance

Objectives: Soluble DPP4 (sDPP4) is a novel adipokine that degrades glucagon-like peptide (GLP-1). We evaluated the fasting serum levels of active GLP-1 and sDPP4 in obese, overweight and normal weight subjects to assess the association between sDPP4 levels, active GLP-1 levels and insulin resistance in obese subjects. Methods: The study involved 235 Malaysian subjects who were randomly selected (66 normal weight subjects, 97 overweight, 59 obese subjects, and 13 subjects who were underweight). Serum sDPP4 and active GLP-1 levels were examined by enzyme-linked immunosorbent assay (ELISA). Also, body mass index kg/m(2) (BMI), lipid profiles, insulin and glucose levels were evaluated. Insulin resistance (IR) was estimated via the homeostasis model assessment for insulin resistance (HOMA-IR). Results: Serum sDPP4 levels were significantly higher in obese subjects compared to normal weight subjects (p = 0.034), whereas serum levels of active GLP-1 were lower (p = 0.021). In obese subjects, sDPP4 levels correlated negatively with active GLP-1 levels (r(2) = -0.326, p = 0.015). Furthermore, linear regression showed that sDPP4 levels were positively associated with insulin resistance (B = 82.28, p = 0.023) in obese subjects. Conclusion: Elevated serum sDPP4 levels and reduced GLP-1 levels were observed in obese subjects. In addition, sDPP4 levels correlated negatively with active GLP-1 levels but was positively associated with insulin resistance. This finding provides evidence that sDPP4 and GLP-1 may play an important role in the pathogenesis of obesity, suggesting that sDPP4 may be valuable as an early marker for the augmented risk of obesity and insulin resistance. (C) 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.