Role of vagal innervation in diurnal rhythm of intestinal peptide transporter 1 (PEPT1).
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.
Qandeel
Hisham G
HG
Gastrointestinal Research Unit and Department of Surgery, Mayo Clinic, 200 1st Street SW, Rochester, MN 55905, USA.
Alonso
Fernando
F
Hernandez
David J
DJ
Duenes
Judith A
JA
Zheng
Ye
Y
Scow
Jeffrey S
JS
Sarr
Michael G
MG
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*
D000074011:Peptide Transporter 1; C489940:Slc15a1 protein, rat; D027981:Symporters
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