Alanine transferase: An independent indicator of adiposity related comorbidity risk in youth

Background: Elevated levels of alanine aminotransferase (ALT) are associated with obesity and are often a consequence of non-alcoholic fatty liver disease (NAFLD). The aim of the present study was to assess the relationship between ALT and risk factors for adiposity-related co-morbidities in a diverse population of middle school children. Methods: We measured height, weight, body fatness (bioelectrical impedance), waist circumference, insulin sensitivity, phase 1 insulin release (acute insulin response following intravenous glucose), beta-cell function (acute insulin response corrected for insulin sensitivity), ALT, lipid profiles, and circulating concentrations of interleukin-6 (IL-6), C-reactive protein, adiponectin, and tumor necrosis factor-α (TNF-α) in a multi-ethnic/racial population of 106 middle school students (aged 11-14 years, 45female) of varying body mass indexes (BMI). Results: Alanine aminotransferase was significantly correlated with BMI, % body fat, fat mass, waist circumference, fasting insulin, insulin resistance, triglycerides, and was inversely correlated with high-density lipoprotein cholesterol in children, even though all values of ALT were "normal" (range of 4.0-33.0U/L). ALT was significantly higher in males than females even when corrected for body fatness. Significant correlations with lipids and insulin resistance persisted even when adjusted for age, gender, and body fatness. Conclusion: Even within the normative range, ALT levels were significantly correlated with anthropomorphic and biochemical risk factors for adiposity-related co-morbidities in youth. Therefore, because ALT is correlated with dyslipidemia, insulin resistance, and central fat distribution, it might also serve as a marker of risk for adiposity-related co-morbidities beyond NAFLD.