Vitamin D and non-alcoholic fatty liver disease in children
Background: Insulin resistance (IR) plays a key role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Hypovitaminosis D is associated with several diseases, including hepatic steatosis and obesity. Vitamin D (VD) affects insulin secretion and improves tissue sensitivity to insulin, suggesting that hypovitaminosis D is also associated with IR. The leptin-to-adiponectin ratio (LAR) was investigated as a new marker of IR. Aim: The aim of our study was to determine the association between the VD status, NAFLD and IR in paediatric overweight or obese patients. Methods: The study ran from January 2018 to August 2020 and included 100 subjects. We measured their anthropometric parameters, determined their basic laboratory parameters and the level of leptin and adiponectin, calculated BMI, WHR, WHtR, LAR and HOMA-IR. We measured the degree of hepatic steatosis by obtaining the hepatorenal index (HRI) using ultrasonography, and used real-time elastography to determine the elasticity of the liver parenchyma (LFI). Subsequently, we compared the groups of patients with and without hepatic steatosis and looked for correlations in relation to the level of VD and IR. Results: 4.4% of patients had a severe VD deficiency, 55% of the children had hypovitaminosis D, 28.6% had VD insufficiency and 12% of patients had sufficient VD levels. Patients with significant hepatic steatosis (HRI 1.5 and more) had the lowest level of VD (16.61 ±5.62 μg/l, P = 0.015). The level of VD in patients with hepatic steatosis was inversely correlated with waist circumference, hip circumference, height, weight, triacylglycerols, GMT, C-peptide, insulin, HOMA-IR, HRI and LFI. Leptin levels were highest in patients with hepatic pre-steatosis. LAR was highest in the group with hepatic steatosis, but we did not observe significant correlations in relation to other parameters. Conclusion: VD levels are inversely associated with the degree of hepatic steatosis in overweight or obese paediatric patients. HOMA-IR inversely correlates with VD levels and positively with LFI. The LAR value was highest in the group of patients with steatosis, although we did not find out any significant correlations in relation to VD status and HRI. Key words: vitamin D – non-alcoholic fatty liver disease – insulin resistance – leptin – adiponectin – obesity – childhood