Serum Vitamin D Levels Are Inversely Related With Non-alcoholic Fatty Liver Disease Independent Of Visceral Obesity In Postmenopausal Women

Objective: Vitamin D, a fat-soluble steroid hormone with a broad range of biological effects, is closely associated with ectopic fat deposition. The aim of this study was to investigate the association between serum vitamin D levels and visceral adipose as well as nonalcoholic fatty liver disease(NAFLD) in Shanghai postmenopausal women.Subjects and Methods: All subjects enrolled in this study had participated in the Shanghai Obesity Study between June and August 2011 and received abdominal magnetic resonance imaging scans and abdominal ultrasonography examination. NAFLD was diagnosed according to the work definition in the 2010 Revised Guidelines for the Diagnosis and Management of NAFLD. Visceral fat area(VFA) ≥ 80 cm2 was defined as abdominally obese. Serum 25-hydroxyvitamin D3(25(OH)D3) levels were measured by electrochemiluminescence immunoassay. Simple correlation and partial correlation analysis were performed to explore the relationship between serum 25(OH)D3 level and clinical parameters. Multivariate logistic regression analysis was performed to identify the independent factors of serum 25(OH)D3 level.Results: Finally, 451 postmenopausal women were enrolled in this study. The age of the study participants ranged between 45 and 74 years(mean±SD: 57.3±4.6 years). The prevalence of NAFLD in this study population was 34.81%(n=157). Compared with non-abdominal obesity group, abdominal obesity group shows significantly lower serum 25(OH)D3 levels(11.23(8.64-14.12) ng/m L vs. 12.56(9.41-15.98) ng/m L; P < 0.01). Whether in abdominal-obesity group or non-abdominal-obesity group, serum 25(OH)D3 levels of NAFLD subgroup were lower than that of non-NAFLD subgroup(abdominal obesity group: 10.86(8.61-13.56) ng/m L vs.11.55(8.82-16.38) ng/m L; non-abdominal-obesity group: 11.14(8.63-13.81) ng/m L vs. 12.92(9.48-16.37) ng/m L, P < 0.05). Simple correlation analyses indicated that serum 25(OH)D3 levels negatively correlated with body mass index, waist circumference, VFA, glycated hemoglobin, triglycerides, alanine aminotransferase, glutamyltranspeptidase, and alkaline phosphatase(P < 0.05-0.01). After adjustment for age and body mass index, partial correlation analysis demonstrated a negative correlation of serum 25(OH)D3 levels with VFA(P < 0.05). Logistic regression analysis showed high serum 25(OH)D3 levels were a protective factor for NAFLD after adjusting risk factors such as VFA. Moreover, regardless of abdominal obesity status, an independent inverse correlation between serum 25(OH)D3 levels and NAFLD persisted(OR 0.906(95% CI 0.823–0.995; P = 0.038) and OR 0.868(95% CI 0.765–0.986; P = 0.029) in the abdominal obesity groups and non-abdominal obesity groups, respectively).Conclusions: Serum vitamin D levels of abdominal obesity group were significantly lower. Vitamin D is a protective factor for NAFLD in postmenopausal women, independent of visceral obesity.