Circulating zinc-α2-glycoprotein levels are low in newly diagnosed patients with metabolic syndrome and correlate with adiponectin

BACKGROUND: Zinc-α2-glycoprotein (ZAG) is a novel adipokine that reduces insulin resistance, protecting against type 2 diabetes. However, past studies have been contradictory. This cross-sectional study aims to investigate the association of circulating ZAG with metabolic syndrome (MetS) in middle-aged and older Chinese adults. METHODS: Four hundred eighty nine individuals (234 healthy controls and 255 MetS patients) were examined. All individuals were screened for MetS according to the diagnostic guidelines of the United States National Cholesterol Education Program (NCEP) Expert Panel Adult Treatment Panel (ATP) III criteria. Circulating ZAG and ADI levels were measured by ELISA. Blood fat, glucose and insulin were measured with a commercial kit. Circulating ZAG levels were compared with various parameters in study subjects. RESULTS: Plasma ZAG levels were lower in MetS patients compared to those of the healthy controls (35.0 ± 11.7 vs. 46.1 ± 18.6 mg/L, P < 0.01). ZAG showed a positive correlation with age, HDL-C, HOMA-β and ADI, but a negative correlation with Fat%, BMI, WHR, blood pressure, triglycerides, FFA, FBG, 2 h–BG, fasting insulin, 2 h–Ins, HbA1c and HOMA-IR (P < 0.01). When the population was divided according to tertiles of ADI, subjects in the highest tertile had the highest ZAG levels. The analysis of ROC curves revealed that the best cutoff value for plasma ZAG to predict MetS was 45.2 mg/L (sensitivity 92%, specificity 59%, and AUC 0.80). CONCLUSIONS: We found that circulating ZAG levels were decreased in patients with MetS. In fact, circulating ZAG decreased progressively with an increasing number of MetS components and associated with ADI levels, suggesting that ZAG is related to IR and MetS and may be a sensitizer. TRIAL REGISTRATION: ChiCTR-OCC-11001422. Registered 23 June 2011.