Liver enzymes and vitamin D levels in metabolically healthy but obese individuals: Korean National Health and Nutrition Examination Survey

Abstract

Objective: Increased liver enzymes and decreased vitamin D levels are associated with insulin resistance and type 2 diabetes. We examined liver enzymes and vitamin D levels in metabolically healthy but obese (MHO) individuals and compared the values with those of other body size phenotypes in the Korean population.

Materials/methods: A total of 16,190 people over the age of 18years were analyzed using data from the Fourth Korean National Health and Nutrition Examination Survey, which is a nationally representative survey. Body size phenotypes were classified into four groups by body mass index (BMI) and number of metabolic syndrome components.

Results: The prevalence of MHO was 14.9% in the entire population and 47.7% in the obese population. In a correlation analysis adjusted for age, sex, and BMI, AST and ALT levels were positively correlated with insulin resistance and cardiometabolic risk factors of the metabolic syndrome, whereas vitamin D level was negatively correlated with these variables. MHO individuals had significantly lower concentrations of AST and ALT compared to metabolically abnormal obese (MAO) subjects, although vitamin D levels were not significantly different. Furthermore, a multiple logistic regression analysis revealed that MHO individuals had lower risk of liver enzyme abnormality compared to MAO after adjusting for potential confounding factors. However, the risk of vitamin D deficiency was not significantly different among groups with different body size phenotypes.

Conclusions: Although both liver enzymes and vitamin D levels are related to insulin resistance and metabolic syndrome, only liver enzymes were independently associated with MHO phenotype.

Keywords: 25(OH)D; 25-hydroxyvitamin D; BMI; Body mass index; Body size phenotype; CI; CVD; Cardiovascular disease; Confidence interval; Fourth Korean National Health and Nutrition Examination Survey; KNHANES IV; MAO; MHO; Metabolically abnormal obese; Metabolically healthy but obese; NAFLD; NHANES III; Nonalcoholic fatty liver disease; OR; Obesity metabolism; Odds ratio; Third National Health and Nutrition Examination Survey in the United States; Vitamin D.