Independent associations of alanine aminotransferase (ALT) levels with cardiovascular risk factor clustering in Chinese adolescents

Background/Aims To establish the prevalence of elevated serum alanine aminotransferase (ALT) concentrations in Chinese adolescents, and to explore the nature of associations amongst ALT, obesity and cardiovascular risk factors. Methods Anthropometric measurements and fasting plasma glucose, insulin, lipids and ALT were measured in 2102 Chinese adolescents, aged 12–18 years, randomly selected from 14 secondary schools in Hong Kong. Results The prevalence of elevated ALT levels was 3.2% and 5.9% if abnormal ALT levels were defined as >40 IU/L and >30 IU/L respectively. Using the <25th, 25–75th and >75th percentile values of ALT, all subjects were divided into 3 ALT strata. Using the lowest ALT stratum as referent, the top ALT stratum was associated with obesity and clustering of cardiometabolic–inflammatory risk markers in both genders. After adjusting for age and body mass index (BMI), the highest ALT stratum remained independently associated with diastolic blood pressure and insulin resistance (fasting insulin and Homeostasis Model Assessment, HOMA-IR, HOMA-beta) in boys (p < 0.05); and serum triglyceride and HOMA-beta (p = 0.008 and 0.014, respectively) in girls. Repeat analysis after excluding subjects with ALT > 30 (n = 123) or >40 IU/L (n = 67) yielded comparable results. Conclusions In adolescents, top ALT stratum, albeit within normal range, is associated with clustering of cardiovascular risk factors, independent of obesity.