Association of plasma dipeptidyl peptidase-4 activity with non-alcoholic fatty liver disease in nondiabetic Chinese population

Objective. The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is attributed to a "multi-hits hypothesis" involving insulin resistance, oxidative stress and inflammation. Dipeptidyl peptidase-4 (DPP4) was identified as a novel adipokine capable of enhancing the "multi-hits". Hence, we investigated the association between plasma DPP4 activity and NAFLD in nondiabetic Chinese population. Design and methods. We performed a cross-sectional study using data from 1105 subjects (36-79 years) in Guilin between 2015 and 2016. Plasma DPP4 activity, homeostatic model assessment of insulin resistance (HOMA-IR), oxidative stress parameters, and inflammatory markers were measured in all participants. NAFLD and its severity were diagnosed by ultrasound after the exclusion of alcohol abuse and other liver diseases. Results. Participants in the highest quartile of DPP4 activity had higher HOMA-IR, nitrotyrosine, 8-iso-PGF2a, interleukin-6, CRP, alanine aminotransferase, aspartate aminotransferase and gamma-glutamyltransferase compared with those in the lowest quartile (all P < 0.05). Plasma DPP4 activity gradually increased across the groups according to the ultrasonographic severity of steatosis (P < 0.001 for the trend). In the highest DPP4 quartile, NAFLD risk was higher (odds ratio 1.88; 95% CI 1.04-3.37) than in the lowest quartile after adjustment for confounders. The risk for NAFLD increased more with higher levels of DPP4 activity, HOMA-IR, nitrotyrosine, 8-iso-PGF2a, interleukin-6 and CRP. Conclusions. Plasma DPP4 activity is significantly associated with NAFLD. The underlying mechanisms may be partly attributed to the interactions between insulin resistance, oxidative stress, inflammation, and DPP4. (C) 2017 Elsevier Inc. All rights reserved.