Association of serum fibroblast growth factor 19 with DKD as assessed by the UACR and eGFR in patients with type 2 diabetes

Background Diabetic kidney disease (DKD) is a major complication of type 2 diabetes (T2D). Fibroblast growth factor 19 (FGF19) is a key metabolic regulator, but its relationship with DKD, as defined by estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR), remains unclear.Methods This cross-sectional study included 330 T2D inpatients and 60 normal controls (NC group). Serum FGF19 levels were measured by ELISA. Renal function was evaluated according to eGFR (CKD-EPI equation) and UACR. Associations between FGF19 levels and renal parameters were analyzed according to Spearman’s correlation, partial correlation, and multiple linear regression analyses adjusted for confounders.Results Serum FGF19 levels were lower in the T2D group than in the NC group (110.25 [68.40–169.32] vs. 242.06 [143.74–319.51] pg/mL, p < 0.001). Among those with T2D, patients with DKD had higher FGF19 levels than those without DKD (122.61 [83.38–189.02] vs. 106.97 [66.54–164.22] pg/mL, p = 0.023). In T2D patients, FGF19 was positively correlated with UACR (r = 0.185; p = 0.005) and inversely correlated with eGFR (r = -0.210; p = 0.001), and these correlations persisted after adjustment for confounders. In fully adjusted linear regression models, FGF19 remained independently associated with a higher UACR (β = 0.203, t = 2.286, p = 0.024) and a lower eGFR (β = -0.170, t = -2.542, p = 0.012). Restricted cubic spline analyses confirmed linear relationships between lnFGF19 and both lnUACR (p = 0.480) and eGFR (p = 0.162).Conclusion Serum FGF19 levels are independently associated with DKD status in T2D patients; the serum FGF19 level is decreased in T2D patients but relatively elevated in those with DKD. FGF19 levels are independently associated with a higher UACR and a lower eGFR. Restricted cubic spline analyses confirmed linear, rather than nonlinear, associations. These cross-sectional findings suggest an association between FGF19 and diabetic kidney pathology, though the modest effect sizes and study design limit causal interpretation.