Mucosal expression of p21, p27, p53, Bcl-2, and bax after small bowel resection and autotransplantation in pigs

p38 MAPK regulates Bax activity and apoptosis in enterocytes at baseline and after intestinal resection

Increased apoptosis in crypt enterocytes is a key feature of intestinal adaptation following massive small bowel resection (SBR). Expression of the proapoptotic factor Bax has been shown to be required for resection-induced apoptosis. It has also been demonstrated that p38-α MAPK (p38) is necessary for Bax activation and apoptosis in vitro. The present studies were designed to test the hypothesis that p38 is a key regulator of Bax activation during adaptation after SBR in vivo. Enterocyte expression of p38 was deleted by tamoxifen administration to activate villin-Cre in adult mice with a floxed Mapk14 (p38-α) gene. Proximal 50% SBR or sham operations were performed on wild-type (WT) and p38 intestinal knockout (p38-IKO) mice under isoflurane anesthesia. Mice were killed 3 or 7 days after operation, and adaptation was analyzed by measuring intestinal morphology, proliferation, and apoptosis. Bax activity was quantified by immunoprecipitation, followed by Western blotting. After SBR, p38-IKO mice had deeper crypts, longer villi, and accelerated proliferation compared with WT controls. Rates of crypt apoptosis were significantly lower in p38-IKO mice, both at baseline and after SBR. Levels of activated Bax were twofold higher in WT mice after SBR relative to sham. In contrast, activated Bax levels were reduced by 67% in mice after p38 MAPK deletion. Deleted p38 expression within the intestinal epithelium leads to enhanced adaptation and reduced levels of enterocyte apoptosis after massive intestinal resection. p38-regulated Bax activation appears to be an important mechanism underlying resection-induced apoptosis.

GLP-2 administration results in increased proliferation but paradoxically an adverse outcome in a juvenile piglet model of short bowel syndrome

OBJECTIVE

The objective of the present study was to examine the effect of glucagon-like peptide-2 (GLP-2) administration in a piglet, juvenile model of short bowel syndrome.

MATERIALS AND METHODS

Four-week-old piglets underwent either a sham operation or 75% small bowel resection. Postoperatively, piglets received either polymeric infant formula diet or the diet and subcutaneous human recombinant GLP-2 (1600 microg/day for 7 days, 800 microg/day thereafter). Food intake was monitored throughout the experiment, and stool and serum samples obtained fortnightly. After the piglets were killed, tissues were obtained from the duodenum, jejunum, ileum, and terminal ileum, and used for morphological and functional analysis.

RESULTS

Treatment with GLP-2 resulted in significantly increased numbers of proliferating and apoptotic cells in the ileum of sham and small bowel resection piglets (P < 0.05). GLP-2 administration resulted in decreased weight gain, serum albumin, and disaccharidases in both sham and small bowel resection piglets (P < 0.001 compared with polymeric infant formula diet alone).

CONCLUSIONS

This is the first study to our knowledge to examine the effect of GLP-2 administration in a juvenile short bowel syndrome model. Contrary to adult rodent studies, administration of GLP-2 resulted in adverse outcomes including reduced ability to gain weight; decreased serum albumin, tissue maltase, and sucrase; and villous atrophy. We anticipate this information will have important implications for future paediatric clinical trials.