Low 25-hydroxyvitamin D level is associated with insulin sensitivity in obese adolescents with non-alcoholic fatty liver disease

The aim of this study was to investigate the relationships between 25-hydroxy-vitamin D (25(OH)D) and insulin resistance in obese adolescents with non-alcoholic fatty liver disease (NAFLD).

Eighty-seven obese adolescents (45 girls and 42 boys, mean age: 12.7 ± 1.3 years, mean body mass index standard deviation score (BMI-SDS): 2.1 ± 0.3) and 30 lean subjects (15 girls and 15 boys, mean age: 12.3 ± 1.45 years, mean BMI-SDS: 0.5 ± 0.7) were enrolled for the study. The obese subjects were divided into two subgroups based on the presence or absence of fatty liver with high transaminases (NAFLD group and non-NAFLD group). Fasting blood samples were assayed for 25(OH)D, transaminases, glucose, and insulin levels. Insulin resistance was calculated by the homeostasis model assessment (HOMA-IR).

25(OH)D measurements were decreased in both obese groups (NAFLD and non-NAFLD) in comparison with the lean group (29.5 ± 18.4 vs. 41.0 ± 17.9 vs. 48.1 ± 22.2 ng/mL). However; the NAFLD group had significantly lower measurements of 25(OH)D than the non-NAFLD group (p < 0.001) and lean group (p < 0.001). 25(OH)D was negatively correlated with HOMA-IR (r = 0.158, p = 0.01) and with alanine aminotransferase (r = 0.794, p = 0.03) in the NAFLD obese group. There was no significant associations between fasting insulin, BMI-SDS and 25(OH)D in obese groups.

We suggest that low 25(OH)D occurs commonly in obese adolescents with NAFLD and we demonstrated an association between insufficient vitamin D status and low insulin sensitivity in obese adolescents with NAFLD.