title: Role of vagal innervation in diurnal rhythm of intestinal peptide transporter 1 (PEPT1).
abstract: BACKGROUND
  Protein is absorbed predominantly as di/tripeptides via H(+)/peptide cotransporter-1 (PEPT1). We demonstrated previously diurnal variations in expression and function of duodenal and jejunal but not ileal PEPT1; neural regulation of this pattern is unexplored.
  
  
  OBJECTIVE
  Complete abdominal vagotomy abolishes diurnal variations in gene expression and transport function of PEPT1.
  
  
  METHODS
  Twenty-four rats maintained in a 12-h light/dark room [6AM-6PM] underwent abdominal vagotomy; 24 other rats were controls. Four weeks later, mucosal levels of mRNA and protein were measured at 9AM, 3PM, 9PM, and 3AM (n = 6 each) by quantitative real-time PCR and Western blots, respectively; transporter-mediated uptake of dipeptide (Gly-Sar) was measured by the everted-sleeve technique.
  
  
  RESULTS
  Diurnal variation in mRNA, as in controls, was retained post-vagotomy in duodenum and jejunum (peak at 3PM, p < 0.05) but not in ileum. Diurnal variations in expression of protein and Gly-Sar uptake, however, were absent post-vagotomy (p > 0.3). Similar to controls, maximal uptake was in jejunum after vagotomy (V (max), nmol/cm/min: jejunum vs. duodenum and ileum; 163 vs. 88 and 71 at 3AM; p < 0.04); K (m) remained unchanged.
  
  
  CONCLUSIONS
  Vagal innervation appears to mediate in part diurnal variations in protein expression and transport function of PEPT1, but not diurnal variation in mRNA expression of PEPT1.
authors.affiliation: Gastrointestinal Research Unit and Department of Surgery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
authors.forename: Hisham G
authors.initials: HG
authors.lastname: Qandeel
authors.forename: Fernando
authors.initials: F
authors.lastname: Alonso
authors.forename: David J
authors.initials: DJ
authors.lastname: Hernandez
authors.forename: Judith A
authors.initials: JA
authors.lastname: Duenes
authors.forename: Ye
authors.initials: Y
authors.lastname: Zheng
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Scow
authors.forename: Michael G
authors.initials: MG
authors.lastname: Sarr
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004386:Duodenum / Q000502:physiology; D007082:Ileum / Q000502:physiology; D007583:Jejunum / Q000502:physiology; D008297:Male; D000074011:Peptide Transporter 1; D051381:Rats; D011917:Rats, Inbred Lew; D027981:Symporters / Q000502:physiology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D000074011:Peptide Transporter 1; C489940:Slc15a1 protein, rat; D027981:Symporters
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