Background: Expression and function of hexose transporters vary diurnally in rat small intestine; however, this subject remains unexplored in mice.
Aim: The aim of the study was to investigate the diurnal expression and function of hexose transporters SGLT1, GLUT2, and GLUT5 in mouse small bowel.
Methods: Twenty-four c57bl6 mice maintained in a 12-h light/dark room (6 AM: -6 PM: ) were sacrificed at 9 AM: , 3 PM: , 9 PM: , and 3 AM: (n = 6 each). In duodenal, jejunal, and ileal mucosa, total cellular mRNA and protein levels were quantitated by real-time PCR and semiquantitative Western blotting, respectively. The everted sleeve technique measured transporter-mediated glucose uptake at 9 AM: and 9 PM: .
Results: mRNA expression of SGLT1, GLUT2, and GLUT5 varied diurnally in all three intestinal segments (p <or= 0.03). SGLT1, GLUT2, and GLUT5 protein levels varied diurnally in duodenum and jejunum (p < 0.05) but not in ileum. Transporter-mediated glucose uptake was greater at 9 PM: than 9 AM: (p <or= 0.04) in all three segments. V (max) was greater in duodenum (10 vs 6 nmol/cm/s) and jejunum (8 vs 5 nmol/cm/s) at 9 PM: compared to 9 AM: (p = 0.01); K (m) remained unchanged. mRNA levels of intestinal hexose transporters varied diurnally. Protein levels peaked 6-12 h later during dark cycle when >70% of food intake occurred; glucose transport followed a similar pattern with increased uptake at 9 PM: .
Conclusion: Hexose transporter expression and function vary diurnally with nocturnal feeding patterns of mice.