The association of circulating levels of complement-C1q TNF-related protein 5 (CTRP5) with nonalcoholic fatty liver disease and type 2 diabetes: a case-control study

Background: It is well-established that nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes mellitus (T2DM). Complement-C1q TNF-related protein 5 (CTRP5) is a novel adipokine involved in the regulation of lipid and glucose metabolism. We aimed to assess plasma levels of CTRP5 in patients with NAFLD (n = 22), T2DM (n = 22) and NAFLD with T2DM (NAFLD + T2DM) (n = 22) in comparison with healthy subjects (n = 21) and also to study the association between CTRP5 levels and NAFLD and diabetes-related parameters. Methods: All subjects underwent anthropometric assessment, biochemical evaluation and liver stiffness (LS) measurement. Insulin resistance (IR) was determined by the homeostasis model assessment (HOMA). Plasma CTRP5 levels were measured by enzyme-linked immunosorbent assay. Results: We found significantly lower plasma levels of CTRP5 in patients with NAFLD + T2DM, NAFLD and T2DM (122.52 +/- 1.92, 124.7 +/- 1.82 and 118.31 +/- 1.99 ng/ml, respectively) in comparison with controls (164.96 +/- 2.95 ng/ml). In the whole study population, there was a significant negative correlations between CTRP5 and body mass index (r = -0.337; p = 0.002), fasting blood glucose (FBG) (r = -0.488; p < 0.001), triglyceride (TG) (r = -0.245; p = 0.031), HOMA-IR (r = -0.492; p < 0.001), insulin(r = -0.338; p = 0.002), LS (r = -0.544; p < 0.001), alanine aminotransferase (ALT) (r = -0.251; p = 0.027), waist-to-hip ratio (WHR) (r = -0.352; p = 0.002) and waist circumference (WC) (r = -0.357; p = 0.001). After adjustment for BMI, decrease in circulating levels of CTRP5 remained as a significant risk factor for NAFLD, T2DM and NAFLD + T2DM. The receiver operating characteristic (ROC) curves of circulating CTRP5 in predicting NAFLD and T2DM demonstrated an area under the curve (AUC) of 0.763 in T2DM, and 0.659 in NAFLD + T2DM. Conclusions: It appears that the decreased levels of CTRP5 contribute to the increased risk of T2DM and NAFLD.