Insulin resistance and ferritin as major determinants of abnormal serum aminotransferase in severely obese children.

OBJECTIVES: Liver involvement is a common complication of obesity related in part to insulin resistance. The role of ferritin has not been investigated in children. The aim was to determine the prevalence of liver enzyme abnormalities in severely obese children and to look for relationships between fat mass distribution, insulin resistance, and plasma ferritin.

METHODS: 197 children with severe obesity (defined as a body mass index Z-score (BMI-Z) > 3.0) were studied prospectively from 2001 to 2004. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) values were measured, as well as anthropometric characteristics: blood pressure; body composition by dual energy X-ray absorptiometry, and plasma fasting glucose, insulin, leptin, lipid, and ferritin concentrations.

RESULTS: Serum ALT and AST values were abnormal in 23 (11.7%) and 13 (6.6%) children, respectively. By univariate analysis, serum ALT and AST values were positively correlated with android fat mass distribution (P < 0.0001 and P = 0.005, respectively) after adjustment for age, sex, ethnicity, and Tanner stage. Using the same model, a positive correlation and a positive trend linked plasma ferritin to serum AST (P = 0.02) and serum ALT (P = 0.06), respectively. Serum ALTwas positively correlated to insulin resistance (P = 0.03). Using a multivariate model, with the android/gynoid fat mass ratio as an additional independent variable, ferritin remained correlated with serum AST and ALT (P = 0.001 and P = 0.008, respectively).

CONCLUSIONS: Abnormal serum aminotransferase values are uncommon in severely obese children in France. Android fat mass distribution, insulin resistance, and higher ferritin concentrations are significantly associated with liver abnormalities in our cohort.