Alanine aminotransferase and metabolic syndrome in adolescents: The Korean National Health and Nutrition Examination Survey Study

What is already known about this subject Adolescent NAFLD has increased in parallel with obesity. Elevated serum ALT level is a surrogate marker for NALFD. Increased ALT levels are closely related to NAFLD and metabolic syndrome. What this study adds Increased ALT within normal range are associated with an increased risk of metabolic syndrome. All of the five components of metabolic syndrome were associated with high ALT within normal range. By elevation of ALT, the prevalence of metabolic syndrome increased in obese adolescents and normal-weight adolescents as well. Background/Aims The potential interactions between alanine aminotransferase (ALT) and components of metabolic syndrome (MetS) have not been fully investigated in healthy adolescents. This study investigated the impact of a mild ALT elevation on the risks of MetS in healthy Korean adolescents. Methods From the Korean National Health and Nutrition Examination Surveys 1998-2009, the data of 5026 adolescents aged 10-18 years (2604 boys and 2422 girls) were analysed. Individuals who had ALT levels equal or more than 40 IU L^-1 were excluded. Results Subjects in the upper ALT tertile had higher mean values of body mass index (BMI), homeostasis model assessment-insulin resistance and prevalence of MetS than subjects in the lower tertile. The risk of each five components of MetS was significantly higher than subjects in the lower tertile. Compared with the subjects in the lower ALT tertile, the prevalence of MetS was higher in the upper tertile among obese adolescents (44.6-50.7% vs. 31.2-40.0%) as well as normal-weight adolescents (5.2-7.7% vs. 2.7-3.2%). Subjects in the upper ALT tertile were at a higher risk of MetS than those in the lower tertile (odds ratio [OR] = 1.95 for boys, OR = 2.00 for girls) after controlling for age and BMI. Conclusions A high serum ALT within normal range increased the risk of all the components of MetS. The prevalence of MetS increased with the elevation of obesity level, and it increased further with the elevation of ALT tertile. Thus, serum ALT levels in addition to BMI might be useful as a marker for early detection of MetS.