The triglyceride-glucose index (TyG) and Nonalcoholic fatty liver in the Japanese population: a retrospective cross-sectional study

Abstract Background: Evidences regarding the association between triglyceride-glucose index (TyG) and Nonalcoholic fatty liver (NAFLD) are controversial. Therefore, the goals of this research are to evaluate whether TyG is independently associated with NAFLD and the ability of TyG index to detect NAFLD in the Japanese population. Methods: The present study was a cross-sectional study. The data was downloaded from the DATADRYAD website. A total of 13178 participants was involved in a hospital in Japan from 2004 to 2015. The correlation between TyG and NAFLD was detected by using binary logistic regression and Generalized additive models. The likelihood ration test was used to examine the modification and interaction of subgroups. Furthermore, the ability of TyG to predict NAFLD was evaluated by using receiver operating characteristic (ROC) curves. The formula for the TyG index was ln [fasting triglyceride level (mg / dl) × fasting blood glucose level (mg / dl) / 2] Results: The average age of the selected participants was 43.36±8.89 years old, and about 51.02% of them were male. In fully-adjusted binary logistic regression model, TyG was positively related with the risk of NAFLD (Odds ratio (OR)=2.45, 95%CI 2.12-2.82). The relationship between TyG and NAFLD was a non-linear relationship, and its inflection point was 8.22. The effect sizes and the confidence intervals of the left and right sides of inflection point were 3.26(2.44 - 4.35) and 2.09 (1.72 - 2.54), respectively. By subgroup analysis, the stronger association was found in females, low GGT, non-obesity, non-visceral fat obesity (P for interaction <0.05). Among the total population, the AUC for TyG [0.810 (0.804 - 0.817)] was worse than ALT [ 0.829 (0.822 - 0.835)] but better than TG [ 0.799 (0.792 - 0.805)] and FPG [ 0.715 (0.707 - 0.722)]. A similar result was found for men. In the women, the AUC for the TyG was superior to ALT, FPG, and TG. Conclusion: The association between TyG and NAFLD is non-linear. TyG is stronger positively correlated to the risk of NAFLD when TyG is less than 8.22. TyG is helpful to identify individuals with NAFLD.