Abstract: Objective The aim of this study was to investigate implication of serum retinol binding protein 4 (RBP-4), fibroblast growth factor 21 (FGF21) and nuclear factor kappa B (NF-κB) levels in patients with nonalcoholic fatty liver disease (NAFLD) and concomitant type 2 diabetes mellitus (T2DM). Methods 257 patients with NAFLD, of which NAFLD and T2DM concomitant in 132 cases, were enrolled in our hospital between July 2022 and July 2025, and all underwent Fibrotouch for liver stiffness measurement (LSM). Serum RBP-4, FGF21 and NF-κB levels were assayed by ELISA. Multivariate Logistic regression analysis was applied to find risk factors for liver fibrosis, and receiver operating characteristic (ROC) curve was drawn for evaluating diagnostic efficacy. Results Serum RBP-4, FGF21 and NF-κB levels in patients with NAFLD and T2DM were (15.3±2.7)ng/mL, (314.3±33.6)pg/mL and (4.1±0.5)pg/mL, all significantly higher than [(11.5±1.7)ng/mL, (277.8±31.8)pg/mL and (2.7±0.6)pg/mL, respectively P<0.05] in those with NAFLD; serum total cholesterol, RBP-4, FGF21 and NF-κB levels in 39 patients with moderate/severe liver fibrosis based on LSM were (6.2±1.4)mmol/L, (17.7±2.0)ng/mL, (326.9±35.3)pg/mL and (4.2±0.5)pg/mL, all significantly higher than [(5.7±1.3)mmol/L, (14.3±2.3)ng/mL, (309.0±31.6)pg/mL and (3.8±0.5)pg/mL, respectively, P<0.05] in 93 patients with mild liver fibrosis; multivariate Logistic regression analysis showed that elevated serum RBP-4(OR=1.368), FGF21(OR=1.252) and NF-κB (OR=2.563) levels were all the independent risk factors for liver fibrosis in patients with NAFLD and T2DM (P<0.05); ROC analysis demonstrated that the AUC was 0.910, with sensitivity of 97.4% and specificity of 72.0%, when serum RBP-4 level was combined with serum FGF21 and NF-κB levels in predicting moderate/severe liver fibrosis in patients with NAFLD and T2DM. Conclusion In patients with NAFLD and concomitant T2DM, increased serum RBP-4, FGF21 and NF-κB levels hint moderate-to-severe liver fibrosis existence, which might help clinicians screening liver fibrosis as early as possible.

Key words: Nonalcoholic fatty liver disease, Type 2 diabetes mellitus, Retinol binding protein 4, Fibroblast growth factor 21, Nuclear factor κB, Liver fibrosis, Diagnosis