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dimanche 17 février 2013

More on Fructose

Introduction of fructose induces epigenetic changes in the expression or activity of GLUT5.

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Biochemical Journal 2011 Volume 435, 43-53
Under normal conditions (red line), the intestinal fructose transporter GLUT5 is expressed at low baseline levels throughout suckling (0–14 days of age) and weaning (14–28 days) stages in neonatal rats. GLUT5 expression and activity increase normally after weaning has been completed and then can be enhanced by increases in consumption of dietary fructose (orange). Between 14 and 28 days old (blue), GLUT5 expression and activity are dramatically enhanced by precocious introduction of its substrate fructose into the intestinal lumen. GLUT5 cannot be enhanced by luminal fructose in rats <14 days="" dexamethasone="" green="" gut="" is="" old="" primed="" span="" the="" unless="" with="">

Fructose diet do have epigenetic consequences.

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Figure 8 Schematic model of Glut5 regulation in small intestinal cells of 20-day-old pups
Age-related increases in corticosterone levels lead to binding with and dimerization of the GR in the cytosol, which then translocate to the nuclei and simultaneously stimulate modest levels of histone H3 acetylation. This step is required for Glut5 regulation as fructose is unable to stimulate Glut5 in 10-day-old rats without the GR in the nuclei. Injecting 10-day-old rats with the glucocorticoid analogue dexamethasone relieves the age-related inhibition of Glut5 by fructose [13]. Perfusion with fructose leads to recruitment of unknown transcription factors (TF) which have HAT activity, thereby increasing the magnitude of age-related increases in histone H3 acetylation in the Glut5 promoter.

Biochemical Journal 2011 Volume 435, 43-53

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