Natural Logarithm Of Zinc-α2- Glycoprotein/Homa-Ir—A Convenient Predictor Of Insulin Sensitivity

Part 1:A preliminary study of the association between Zinc-a2-glycoprotein and insulin sensitivity in obesity subjects with different degrees of glucose toleranceObjective:To evaluate the correlation between Zinc-a2-glycoprot ein (ZAG) and insulin sensitivity (IS) in obesity subjects with differe nt degrees of glucose tolerance.Methods:We performed a population-based cross-sectional study.67 obesity subjects with normal glucose tolerance,61 obesity subjects with newly diagnosed impaired glucose tolerance, and 83 obesity subjects with newly diagnosed type 2 diabetes mellitus were enrolled. Oral glucose tolerance tests (OGTT), oral glucose insulin releasing (OGIRT), clinical and biochemical characteristics measurement were performed. Circulating ZAG were determined by Enzyme-linked immunoabsorbent Assay (ELISA). Comparisons of ZAG between different groups were performed by t test. The correlation between ZAG, homeostasis model assessment of insulin resistance (HOMA-IR), anthropometric and clinical characteristics was assessed by linear correlation analysis and partial linear correlation analysis. Furthermore, multiple linear regression was performed to evaluate the association between ZAG and IS.Results:Compared with obesity subjects with normal glucose tolerance, waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting plasma glucose (FPG),2-h plasma glucose after glucose overload (2h-PG), HbA1c, total cholesterol (TC), triglyceride (TG), HOMA-IR, fasting insulin (FIns),2-h insulin after glucose overload (2h-Ins) were higher in obesity subjects with type 2 diabetes mellitus group (P＜0.05 or P＜0.01). However, high-density lipoprotein cholesterol (HDL-C) and ZAG were lower (P＜0.01). ZAG was significantly correlated negatively with HOMA-IR after age and sex adjusted. Multiple linear regression showed YZAG= 0.957 XHDL-C-1.290XBMI-2.474XHOMA-IR+87.112 (R=0.583, P＜0.01).Conclusion:ZAG was correlated positively with insulin sensitivity in obesity subjects with different degrees of glucose tolerance.Part 2:Zinc-α2-glycoprotein index——A convenient predictor of insulin sensitivity in poly cystic ovarian syndrome: A preliminary studyObjective:To assess whether ZAG index (Ln [ZAG/HOMA-IR]) can be a new surrogate index for estimating insulin sensitivity (IS) compared with other indices in polycystic ovarian syndrome (PCOS).Methods:The euglycemic-hyperinsulinemic clamp (EHC) was performed for identifying IS on 102 PCOS and 100 healthy subjects. And OGTT, OGIRT, clinical and biochemical characteristics measurement were performed. Circulating ZAG and adiponectin (ADI) were determined by ELISA. Firstly, comparisons of ZAG index between insulin resistance (IR) and non-IR groups were performed by t test. In addition, the correlations between ZAG index, HOMA-IR, ADI/HOMA-IR etc. with M value (the glucose infusion rate during the stable period of the clamp) were assessed by partial correlation analysis and multiple linear regression. Furthermore, logistic regression was performed to evaluate whether ZAG index and other indices is protective factor or not. Moreover, agreement in the categorization of subjects between M value and ZAG index was measured by weighted K test and Pearson correlation coefficient. Finally, the optimal value of ZAG index for diagnosis of IS was established on a receiver operating characteristic (ROC) scatter plot. The area under the ROC curve (AUC), as a summary of the overall diagnostic accuracy of the test, and sensitivity, specificity, Youden index were calculated.Results:ZAG index and ADI/HOMA-IR were significantly lower in participants with IR than in those without IR. On the contrary, TG/HDL-C, TyG, I/G, HOMA-IR were higher in IR group than non-IR group. In addition, partial linear correlation analysis showed that the Pearson correlation coefficient between the ZAG index and M value (r= 0.779, P<0.01) was no less than the Pearson correlation coefficient between HOMA-IR (r=-0.623, P＜0.01), ADI/HOMA-IR (r= 0.604, P<0.01) and M value, and no less than that between TyG (r=-0.394, P<0.01), I/G (r=-0.598, P＜0.01), TG/HDL-C (r=-0.237, P＜0.01) and M value. And multiple regression analysis showed that YZAG index=4.277+0.1 XM value-0.079XFIns-0.248XFPG (R2=0.896, P＜0.001). Furthermore, logistic regression showed ZAG index and ADI/HOMA-IR is protective factors, whereas the others were inversely. Moreover, there is medium agreement between ZAG index and M value measured by weighted K test, and Pearson correlation coefficient showed a strong association between ZAG index and M value. ZAG index has ROC curve that are shifted to the left with AUC near 1, and AUC of ZAG index is no less than other indices’ AUC. Finally, the optimal cutoff value of the ZAG index for detection of IS in all study populations was 2.97, with a sensitivity of 87.8% and a specificity of 90.8%, and the Youden index is 0.786.Conclusion:ZAG index can be a surrogate index for estimating insulin sensitivity in PCOS.