Leptin and insulin resistance are being discussed to be involved in the pathogenesis of nonalcoholic fatty liver disease, which is frequently characterized by moderately elevated transaminases. However, longitudinal studies proving an association between leptin, insulin resistance, and transaminases are scarce. We examined weight status, aspartate aminotransferase (AST), alanine aminotransferase (ALT), leptin, glucose, and insulin in 180 overweight children at baseline and 1 year later. Relationships between these parameters at baseline and their changes in the course of 1 year were determined by multiple regression analysis adjusted for age, sex, pubertal stage, and body mass index (BMI). Leptin but not homeostasis model assessment of insulin resistance index correlated significantly to transaminases in both cross-sectional and longitudinal analyses. The same findings were observed in 30 children with suspected nonalcoholic fatty liver disease by ultrasound. The 130 children who participated in a 1-year lifestyle intervention reduced their overweight (standard deviation score [SDS]-BMI, -0.37 +/- 0.11). In the course of 1 year, their changes of transaminases depended on change of weight status (SDS-BMI decrease >0.5: ALT 12 [10-15] --> 9 [8-13] U/L, AST 11 [9-12] --> 9 [8-12] U/L; SDS-BMI decrease >0 but <or=0.5: ALT 14 [11-18] --> 16 [12-26] U/L, AST 10 [8-14] --> 10 [8-24] U/L; no SDS-BMI decrease: ALT 13 [11-20] --> 20[13-33] U/L, AST 11 [9-21] --> 15 [9-24] U/L; data as median and interquartile range). The 50 children without intervention increased their SDS-BMI (+0.02 +/- 0.18) and transaminases (ALT 14 [11-18] --> 19 [15-25] U/L, AST 10 [8-15] --> 16 [10-25] U/L). These findings suggest that leptin may be involved in the pathogenesis of liver diseases. However, to test this hypothesis, careful histologic assessments in correlation to leptin levels are needed.
Trial registration: ClinicalTrials.gov NCT00435734.