Effect of Short-Term Vitamin D Correction on Hepatic Steatosis as Quantified by Controlled Attenuation Parameter (CAP)

Introduction: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in Western countries. A meta-analysis has confirmed decreased serum 25-hydroxyvitamin D levels in NAFLD patients. This intervention study investigates whether vitamin D correction ameliorates hepatic steatosis. Methods: We prospectively recruited 40 patients from an outpatient liver clinic with vitamin D deficiency (serum 25-hydroxyvitamin D < 20 ng/ml). Controlled attenuation parameter (CAP) during transient elastography quantified hepatic steatosis. Patients with significant liver fat accumulation were included, which was defined by a CAP value ≥ 280 dB/m. Patients received 20,000 IU vitamin D/week for six months, while vitamin D status, liver function tests (LFTs), CAP and body composition were monitored. Results: The cohort comprised 47.5% women (age 54.9 ± 12.1 years; BMI 29.5 ± 3.0 kg/m2). Mean serum vitamin D level was 11.8 ± 4.8 ng/ml. CAP decreased significantly from baseline (330 ± 32 vs. 307 ± 41 dB/m) during supplementation (P = 0.007). A mean CAP reduction relative to baseline was demonstrated at four weeks and three and six months: -5.3 ± 13.8%; -6.0 ± 14.6% and -6.4 ± 13.0%, respectively. During these time points, restoration of serum vitamin D levels was observed (34.6 ± 12.9, 36.3 ± 10.2, 34.8 ± 9.8 ng/ml; P < 0.0001). Liver function tests and body composition remained unchanged. Conclusions: Hepatic steatosis, as assessed by CAP, significantly improves after only 4 weeks of vitamin D correction. Hepatic steatosis is a dynamic process, that can be monitored in the short-term using such non-invasive methods. Abbreviations: ALT: alanine aminotransferase; ANOVA: analysis of variance; AP: alkaline phosphatase; AST: aspartate aminotransferase; CAP: controlled attenuation parameter; CRP: C-reactive protein; FFA: free fatty acids; γ-GT: gamma-glutamyl transpeptidase; ITT: intention-to-treat; LFT: liver function test; LSM: liver stiffness measurement; NAFLD: non-alcoholic fatty liver disease; PPAR-γ: peroxisome proliferator-activated receptor gamma; PP: per protocol; PTH: parathyroid hormone; VDR: vitamin D receptor