Intra-erythrocyte magnesium is associated with gamma-glutamyl transferase in obese children and adolescents.

This study aims at determining the association between markers of hepatic injury and serum, urinary, and intra-erythrocyte magnesium concentrations and dietary magnesium intake in obese children and adolescents. In a case-control study, 42 obese children and adolescents (8-18 years) and 42 sex- and puberty-matched controls were studied. Serum, urinary, and intra-erythrocyte magnesium levels, indices of insulin sensitivity, and liver enzymes were measured. Dietary magnesium intake was assessed using a food frequency questionnaire. Obese children and adolescents exhibited insulin resistance as determined by a higher fasting insulin and the HOMA-IR (p<0.001) and lower QUICKI indices (p=0.001); in addition these subjects had significantly higher intra-erythrocyte magnesium (IEM) concentrations, than non-obese ones (3.99±1.05 vs. 3.35±1.26 mg/dL of packed cell; p=0.015). Among liver enzymes, only gamma-glutamyl transferase (GGT) was significantly higher in obese than in non-obese subjects (22.7±9.4 vs. 17.1±7.9 U/l; p=0.002). A positive association was found between GGT and IEM in both groups; however in multivariate analysis, in obese subjects, only GGT (p=0.026) and, in non-obese subjects, only age (p=0.006) remained as significant predictors of IEM. In conclusion, increased IEM concentration was seen in insulin-resistant obese children and adolescents; furthermore, serum GGT was associated with IEM, independently of body mass index and HOMA-IR.