Hexose transporter expression and function in mouse small intestine: role of diurnal rhythm.
BACKGROUND
Expression and function of hexose transporters vary diurnally in rat small intestine; however, this subject remains unexplored in mice.


OBJECTIVE
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: .


CONCLUSIONS
Hexose transporter expression and function vary diurnally with nocturnal feeding patterns of mice.
Fatima
Javairiah
J
Gastroenterology Research Unit (GU 1001), Department of Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. fatima.javairiah@mayo.edu
Iqbal
Corey W
CW
Houghton
Scott G
SG
Kasparek
Michael S
MS
Duenes
Judith A
JA
Zheng
Ye
Y
Sarr
Michael G
MG
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004386:Duodenum / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000378:metabolism / Q000502:physiology*; D051273:Glucose Transporter Type 2 / Q000378:metabolism / Q000502:physiology*; D051296:Glucose Transporter Type 5; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1 / Q000378:metabolism / Q000502:physiology*
D051246:Glucose Transport Proteins, Facilitative; D051273:Glucose Transporter Type 2; D051296:Glucose Transporter Type 5; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495682:Slc2a2 protein, mouse; C465351:Slc2a5 protein, mouse; C495675:Slc5a1 protein, mouse; D051269:Sodium-Glucose Transporter 1