Endocrine Abstracts (2009) 20 P521

Increased intra-erythrocyte magnesium is associated with gamma-glutamyl transferase in obese children

Maryam Tohidi1, Asghar Ghasemi2, Farzad Hadaegh1, Shamsi Arbabi1, Firoozeh Hosseini Isfahani3 & Fereidoun Azizi2

1Research Institute for Endocrine Sciences, Prevention of Metabolic Disorders Research Center, Shahid Beheshti University (MC), Tehran, Islamic Republic of Iran; 2Research Institute for Endocrine Sciences, Endocrine Research Center, Shahid Beheshti University (MC), Tehran, Islamic Republic of Iran; 3Research Institute for Endocrine Sciences, Obesity Research Center, Shahid Beheshti University (MC), Tehran, Islamic Republic of Iran.

Objective: To determine the association between markers of hepatic injury and serum, urinary, and intra-erythrocyte magnesium concentrations and dietary magnesium intake in obese children.

Methods: In a case–control cross-sectional study, we studied 42 obese children and adolescents and 42 sex- and puberty-matched lean controls. Serum, urinary, and intra-erythrocyte magnesium levels, indexes of insulin sensitivity, and liver enzymes were measured. Dietary magnesium intake was assessed using a food frequency questionnaire.

Results: Obese children 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 children had significantly higher intra-erythrocyte magnesium (IEM) concentration than non-obese ones (3.99±1.05 vs 3.35±1.26 mg/dl of packed cells, P=0.015). Serum, urinary, and dietary magnesium levels were comparable between groups. 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). Positive association was found between GGT and IEM in both groups; however in multivariate analysis, in obese subjects, only GGT (β=0.375; P=0.026, model R=0.38) and, in non-obese subjects, only age (β=−0.466; P=0.006, model R=0.47) remained as significant predictors of IEM.

Conclusions: Increased IEM concentration was seen in insulin resistant obese children; furthermore, serum GGT was associated with IEM independently of body mass index and HOMA-IR.

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