Published in:
01-11-2009 | 2009 SSAT Quick Shot Presentation
Role of Vagal Innervation in Diurnal Rhythm of Intestinal Peptide Transporter 1 (PEPT1)
Published in: Journal of Gastrointestinal Surgery | Issue 11/2009
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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.
Hypothesis
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.