Vitamin D Status and Bone Mineral Density in Obese Children with Nonalcoholic Fatty Liver Disease

Whether nonalcoholic fatty liver disease (NAFLD) is related to vitamin D and bone health in obese children is unknown. The aim of this study was to evaluate vitamin D status and bone mineral density (BMD) in obese children according to their condition within the NAFLD spectrum. Anthropometric data, laboratory tests, and abdominal ultrasonography were obtained from 94 obese children. The subjects were divided into three groups according to NAFLD spectrum: normal liver, simple steatosis, and nonalcoholic steatohepatitis (NASH). Although there were no differences in vitamin D levels between the three groups, these groups showed significant differences in highly sensitive C-reactive protein (P = 0.044), homeostasis model assessment of insulin resistance (HOMA-IR) (P = 0.02), hepatic fibrosis scores (P < 0.05), and trunk fat percentage (P = 0.025). Although there were significant differences in BMDs, the age-matched BMD z-scores were not significantly different between the three groups. Serum vitamin D levels were negatively correlated with age (r = -0.368, P = 0.023), serum uric acid levels (r = -0.371, P = 0.022), fibrosis 4 (FIB4) (r = -0.406, P = 0.011), and HOMA-IR (r = -0.530, P = 0.001) in obese children with NASH. Multiple regression analysis for vitamin D in the NASH group revealed age and HOMA-IR as significant factors. In conclusion, inflammatory markers, hepatic fibrosis scores, trunk fat, and insulin resistance may reflect the spectrum of NAFLD in obese children, whereas vitamin D levels and BMD may not. In patients with NASH, however, low serum vitamin D is associated with hepatic fibrosis and insulin resistance, but not with bone health status.