Intestinal Adaptation for Oligopeptide Absorption via PepT1 After Massive (70%) Mid-Small Bowel Resection

Abstract

Introduction Proteins are absorbed primarily as short peptides via PepT1. Hypothesis Intestinal adaptation for peptide absorption after massive mid-small intestinal resection occurs by increased expression of PepT1 in the remnant small intestine and colon. Methods Peptide uptake was measured in duodenum, jejunum, ileum, and colon using Glycyl-Sarcosine 1 wk (n=9) and 4 wk (n=11) after 70% mid-small bowel resection, and in corresponding segments from unoperated rats (n=12) and after transection and reanastomosis of jejunum and ileum (n=8). Expression of PepT1 (mRNA, protein) and villus height were measured. Results Intestinal transection/reanastomosis did not alter gene expression. Compared to non-operated controls, 70% mid-small bowel resection increased jejunal peptide uptake (p<0.05) associated with increased villus height (1.13 vs 1.77 and 1.50 mm resp, p<0.01). In ileum although villus height increased at 1 and 4 wk (1.03 vs 1.21 and 1.35 mm resp; p<0.01), peptide uptake was not altered. PepT1 mRNA and protein were decreased at 1 wk, and PepT1 protein continued low at 4 wk. Gene expression, peptide uptake, and histomorphology were unchanged in the colon. Conclusions Jejunal adaptation for peptide absorption occurs by hyperplasia. Distal Ileum and colon do not have a substantive role in adaptation for peptide absorption.

Peptide absorption after massive proximal small bowel resection: Mechanisms of ileal adaptation

“…There was not enough ileal length to evaluate differences in the proximal and distal aspects of the remnant ileum. Only PepT1 expression was studied in the colonic mucosal samples; colonic uptake was not evaluated, because our prior study [14] showed virtually no colonic absorption of the model dipeptide. The mucosa was scraped bluntly using a glass slide into cold, phosphate-buffered saline (PBS); although the mucosal scrapings include some nonenterocytes in the sample, PepT1 is expressed almost exclusively in the enterocyte only.…”

“…Levels of total cellular protein for PepT1 were measured semi-quantitatively using our wellcharacterized technique with Western blots [14,[20][21]. Tissue samples stored in RIPA buffer containing Halt protease inhibitors and PMSF were thawed on ice; the presence of protease inhibitors was used to minimize protein degradation.…”

“…We measured transporter-mediated uptake of the di-peptide Glycyl-Sarcosine (Gly-Sar), a non-hydrolysable substrate for PepT1 [19], using a modified everted sleeve technique as we described previously [14,[20][21]. Ileal segments (1 cm) were everted over a pre-grooved steel rod and secured with silk ties, thereby exposing the mucosal surface externally.…”

“…Ileal segments (1 cm) were everted over a pre-grooved steel rod and secured with silk ties, thereby exposing the mucosal surface externally. Colonic uptake studies were not performed, because our prior work showed very little if any colonic uptake of dipeptides [14]. The intestinal "sleeves" were kept in cold (4ºC) Ringer's solution bubbled with 95% O 2 /5% CO 2 .…”

“…In our laboratory, we investigated previously the mechanisms of ileal adaptation for glucose absorption after extensive resection of the proximal intestine in a rat model [13]. Recently, we examined the response of the proximal jejunum to a massive, mid-small bowel resection by evaluating gene expression of the peptide transporter PepT1 and peptide absorption [14], but to the best of our knowledge, this current study is the first comprehensive investigation of the effect of massive, proximal, jejunoileal resection on ileal gene expression of peptide transporter-1 (PepT1), the exclusive peptide transporter in the brush border of enterocytes and peptide uptake. Colonic gene expression of PepT1 was also investigated in this study before and after massive proximal small bowel resection.…”