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.