Loss of weight restores GLUT 4 content in insulin-sensitive tissues of monosodium glutamate treated obese mice

OBJECTIVE: To investigate the effect of weight loss on GLUT 4 content of insulin sensitive tissues of obese mice. SUBJECTS: Mice were made obese by neonatal treatment with monosodium glutamate (MSG). In addition, one group of obese animals was submitted to a caloric restriction to promote 20% weight loss (MSG-L). Both groups were compared to age-matched control mice. MEASUREMENTS: Anthropometric data, glycaemia and insulinaemia were measured. The GLUT 4 protein was assessed by Western blotting analysis in white (WAT) and brown (BAT) adipose tissue, and skeletal (SM) and cardiac (CM) muscles. RESULTS: The MSG mice were very obese according to their morphometric analysis, showing moderate hyperglycaemia with severe hyperinsulinaemia, and reduced (P < 0.001) glucose/insulin (G/I) ratio. The procedure for weight loss promoted a significant (P < 0.001) reduction of both glycaemic and insulinaemic levels, and an increase in G/I ratio. Compared to control animals, the GLUT 4 content in obese MSG mice, was decreased by 30% (P < 0.05) in SM and CM, by 80% (P < 0.001) in BAT and in different subcellular membrane fractions of WAT. On the other hand, transporter protein content was restored to normal levels in MSG-L animals. CONCLUSION: The reduced GLUT 4 content of insulin sensitive tissues from MSG-treated obese mice is recovered by a 20% loss in weight. This mechanism can be involved in the observed increase of insulin sensitivity.