The association of serum FGF 23 and non‐alcoholic fatty liver disease is independent of vitamin D in type 2 diabetes patients

Summary Recent studies have shown that circulating fibroblast growth factor ( FGF ) 23 and vitamin D levels are closely correlated with insulin resistance. The aim of this study was to investigate the relationship among serum FGF 23 levels, serum 25‐hydroxyvitamin D [25( OH )D] levels, and non‐alcoholic fatty liver disease ( NAFLD ) in Chinese patients with type 2 diabetes mellitus (T2 DM ). This study enrolled 331 hospitalized T2 DM patients (209 patients with NAFLD and 122 patients without NAFLD ). Serum FGF 23 levels were measured using a sandwich enzyme‐linked immunosorbent assay. Serum 25( OH )D levels were determined by an electrochemiluminescence immunoassay. NAFLD was diagnosed by hepatic ultrasound, and the fatty liver index ( FLI ) was calculated to quantify hepatic steatosis. Results showed that T2 DM patients with NAFLD had significantly higher serum FGF 23 levels (44.17 [37.92‐51.30] pg/ mL vs 40.21 [34.07‐48.33] pg/ mL , P  = .002), but lower serum 25( OH )D levels (16.43 [12.70‐21.37] ng/ mL vs 19.59 [13.78‐26.26] ng/ mL , P  = .002) than those without NAFLD . Moreover, the incidence rate of NAFLD increased with increasing serum FGF 23 levels and decreased with increasing 25( OH )D levels (both P  < .05). Logistic regression analysis showed that both serum FGF 23 and 25( OH )D levels were independent factors for NAFLD (both P  < .05). Furthermore, a multiple stepwise regression analysis also revealed that both serum FGF 23 and 25( OH )D levels were independently correlated with FLI (both P  < .01). In conclusion, both high FGF 23 and low vitamin D levels showed an independent relationship with NAFLD in Chinese T2 DM patients, indicating that FGF 23 and vitamin D function via different regulatory pathways in the liver.