Abstract
PURPOSE: Dipeptidyl peptidase 4 (DPP4) is expressed and secreted by adipocytes. DPP4 induces insulin resistance independently of its effect on glucagon-like peptide 1, thus it is conceivable that DPP4 directly contributes to metabolic dysfunction in patients with morbid obesity. The aim of this study was to investigate the impact of weight loss induced by bariatric surgery on DPP4 activity, and whether these changes are associated with improvements in markers of metabolic dysfunction and fatty liver disease. MATERIALS AND METHODS: We included 68 non-diabetic patients who underwent bariatric surgery. Serum DPP4 activity was measured using a fluorogenic substrate before and after surgery. RESULTS: Results: After a median follow-up period of 12 (IQR 11-17) months, median serum DPP4 activity decreased from 230 (IQR: 194-273) to 193 (164-252) pmol/min (p=0.012). The decrease in DPP4 activity was significantly correlated with decreases in BMI, improved cholesterol levels, reduced hepatic injury markers as well as improved post-prandial insulin sensitivity. After multivariable adjustment, ΔDPP4 activity remained significantly associated with Δcholesterol (beta=0.341, p=0.025), ΔLDL cholesterol (beta=0.350, p=0.019), Δgamma-glutamyltransferase (beta=0.323, p=0.040) and ΔMatsuda index (beta=-0.386, p=0.045). CONCLUSION: We demonstrated that weight loss induced by bariatric surgery results in decreased circulating DPP4 activity beyond the initial phase of weight loss. The associations between decreased DPP4 activity and improved cholesterol levels as well as hepatic injury markers point towards pleiotropic effects of DPP4 beyond glucose metabolism which warrant further investigation.