Serum vitamin D is associated with ultrasound-defined hepatic fibrosis

Evidences from population-based investigations on the exact relationship between vitamin D and the severity of liver fibrosis remain debated and conflicting. Here, we aim to explore the relationship between serum vitamin D and ultrasound - defined advanced hepatic fibrosis in the US participants with nonalcoholic fatty liver disease (NAFLD). In the retrospective study, individuals with intact information on interesting variables from the 2017 – 2018 National Health and Nutrition Examination Survey (NHANES) were included. NAFLD was diagnosed on the basis of controlling attenuation parameter (CAP) value≥ 274 dB/m without causes of other chronic hepatic diseases. We identified advanced fibrosis grades (F2) by liver stiffness measurement (LSM) score of ≥ 8.2 kPa in NAFLD patients. The impact of elevated serum vitamin D on the prevalence of hepatic fibrosis was assessed by multivariate logistic regression models on the basis of the NHANES recommended weights. The study involved 1624 subjects with NAFLD in total, and 305 (18.28 %, weighted%) of whom were diagnosed with advanced hepatic fibrosis according to the definition based on parameters obtained from vibration controlled transient elastography (VCTE). In the multivariate logistic regression analysis, serum vitamin D presented a negative relationship to hepatic fibrosis with lower odds in patients with hepatic steatosis after being adjusted for potential confounding factors (fully adjusted: OR=0.47, 95 % CI: 0.24–0.90, p  = 0.034). Our subgroup analysis revealed that the inverse relationship was still existed in males (fully adjusted: OR = 0.34, 95 % CI: 0.17–0.70, p  = 0.014), non-obese subjects (fully adjusted: OR = 0.20, 95 % CI: 0.04–0.89, p  = 0.042) and participants below 60 years (fully adjusted: OR = 0.43, 95 % CI: 0.21–0.90, p  = 0.033), whereas in models adjusted for the potential confounding factors, no statistically significant correlation was noted in females, obese subjects or subjects with age≥ 60 years. This large population-based investigation indicated that elevated serum vitamin D reduced the onset of advanced fibrosis diagnosed by ultrasound in males, non-obese subjects and younger participants with NAFLD.