title: Coordinated, diurnal hexose transporter expression in rat small bowel: implications for small bowel resection.
abstract: BACKGROUND
  Hexose transporter mRNA and protein levels follow a diurnal rhythm in rat jejunum. Their coordinated expression and resultant function throughout the small bowel is not well understood. We hypothesized that hexose transporter levels and glucose absorption follow a coordinated, site-specific diurnal rhythm in rat duodenum and jejunum, but not in ileum.
  
  
  METHODS
  Sprague-Dawley rats were housed in a strictly maintained, 12-h, light/dark room [light 6 am to 6 pm] with free access to water and chow. Mucosa was harvested from duodenum, jejunum, and ileum at 3 am, 9 am, 3 pm, and 9 pm, and full thickness 1-cm segments were harvested at 9 am, and 9 pm (n = 6 for each segment at each time point). mRNA levels were determined by reverse-transcription, real-time polymerase chain reaction (n > or = 5), protein levels by semiquantitative Western blotting (n > or = 5), and transporter-mediated glucose uptake by everted sleeve technique (n = 6).
  
  
  RESULTS
  mRNA levels of SGLT1 and GLUT5 followed a temporally coordinated, diurnal rhythm in all 3 segments (P < .01), while mRNA for GLUT2 and protein levels for SGLT1 and GLUT2 varied diurnally only in duodenum and jejunum (P > .05) but not in ileum (P > .10). SGLT1 and GLUT5 mRNA induction decreased aborally. Baseline SGLT1 and GLUT5 mRNA levels and SLGT1 and GLUT2 protein levels did not vary aborally (P > .05 for all). GLUT2 mRNA baseline levels were decreased in ileum (P < .01). Glucose uptake varied diurnally in duodenum and jejunum with no difference in ileum. Transporter-mediated glucose uptake was greater in duodenum and jejunum compared with ileum.
  
  
  CONCLUSIONS
  Regulation of hexose absorption in rat small bowel seems to be site-specific and mediated by multiple mechanisms.
authors.affiliation: Department of Surgery, GI Research Unit, Alfred 2, St Mary's Hospital, Mayo Clinic College of Medicine, Rochester, Minn 55905, USA.
authors.forename: Scott G
authors.initials: SG
authors.lastname: Houghton
authors.forename: Corey W
authors.initials: CW
authors.lastname: Iqbal
authors.forename: Judith A
authors.initials: JA
authors.lastname: Duenes
authors.forename: Javairiah
authors.initials: J
authors.lastname: Fatima
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kasparek
authors.forename: Michael G
authors.initials: MG
authors.lastname: Sarr
mesh_terms: D000042:Absorption; D000818:Animals; D002940:Circadian Rhythm; D004386:Duodenum / Q000378:metabolism*; D005947:Glucose / Q000493:pharmacokinetics; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D051296:Glucose Transporter Type 5 / Q000378:metabolism; D007421:Intestine, Small / Q000601:surgery; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051269:Sodium-Glucose Transporter 1 / Q000235:genetics / Q000378:metabolism
chemical_list: D051273:Glucose Transporter Type 2; D051296:Glucose Transporter Type 5; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D051269:Sodium-Glucose Transporter 1; D005947:Glucose