Association of elevated serum alanine aminotransferase with metabolic factors in obese children: sex-related analysis.

Alanine aminotransferase (ALT) elevations are considered a surrogate marker of nonalcoholic liver disease and predict later development of diabetes and metabolic syndrome in adults. The aim of the present study is to evaluate the prevalence of high ALT levels in obese children using updated and sex-related cutoff ALT value (ALT >30 IU/L for boys and >19 IU/L for girls). We also analyzed the association between ALT levels and metabolic factors in the 2 sexes. Three-hundred fifty-eight obese children (168 boys and 190 girls; age range, 6-16 years) were studied. Inclusion criteria were as follows: obesity, defined by an individual body mass index (BMI) greater than or equal to the 95th percentile for age and sex; negativity of markers for viral hepatitis; and no alcohol consumption. Two hundred six nonobese children (92 boys and 114 girls; age range, 6-16 years) served as a control group for ALT levels. The percentage of obese children with elevated ALT was 36% in boys and 55% in girls. Obese boys with ALT greater than 30 IU/L showed higher mother's BMI (P < .025), BMI, waist circumference, insulin resistance evaluated with homeostasis model assessment (HOMA-IR) index (P < .0001, for all), and systolic and diastolic blood pressure (P < .025, for both) compared with those with ALT not exceeding 30 IU/L. The ALT levels correlated positively with mother's BMI, BMI, waist circumference, HOMA-IR, triglycerides, and blood pressure. In linear regression analysis, waist circumference was the only independent factor associated with ALT level (beta = 0.370, t = 3,905, P < .0001). Obese girls with ALT greater than 19 IU/L exhibited lower age (P < .025) and higher triglycerides (P < .0001) than girls with ALT not exceeding 19 IU/L. The ALT levels correlated positively with triglycerides and HOMA-IR and negatively with age and Tanner stage. In linear regression analysis, ALT levels were independently associated only with triglycerides (beta = 0.330, t = 4.588, P < .0001). Our study shows that a high proportion of obese children present elevated ALT levels. This abnormality is associated in boys, more than in girls, with preclinical traits of the metabolic syndrome. The adoption of sex-related cutoff of ALT levels is desirable also for the pediatric population.