Effect of transforming growth factor-alpha on intestinal adaptation in a rat model of short bowel syndrome

Proteomic biomarkers in short bowel syndrome : are we ready to use them in clinical activity?

Introduction: Short bowel syndrome (SBS) is a clinical condition that can affect childhood and adult patients. Biomarker research is expected to be a new frontier in the clinical application, helpful for patients and health-care systems.Areas covered: SBS is usually a consequence of a massive intestinal resection that leads to an intestinal failure because of the reduction of absorptive surface, bacterial overgrowth, and faster intestinal transit. This new condition requires a multidisciplinary expertise to achieve again digestive autonomy. Parental nutrition (PN) supports nutritional status in SBS patients while the new guidelines on intestinal transplantation confirm its strict indication only for patients at actual risk of death on PN. A PubMed literature review from the 1980s up to date was performed, highlighting proteomic biomarkers and growth factor therapies that have shown so far promising results in SBS patients.Expert opinion: Apart from a few specific biomarkers and growth factors, the discovery of specific molecular events is currently under investigation of the proteomic analysis and could potentially represent fundamental, future changes in prevention, diagnosis, therapeutic management, and experimental practices in SBS.

Host-Gut Microbiota Crosstalk in Intestinal Adaptation

Short-bowel syndrome represents the most common cause of intestinal failure and occurs when the remaining intestine cannot support fluid and nutrient needs to sustain adequate physiology and development without the use of supplemental parenteral nutrition. After intestinal loss or damage, the remnant bowel undergoes multifactorial compensatory processes, termed adaptation, which are largely driven by intraluminal nutrient exposure. Previous studies have provided insight into the biological processes and mediators after resection, however, there still remains a gap in the knowledge of more comprehensive mechanisms that drive the adaptive responses in these patients. Recent data support the microbiota as a key mediator of gut homeostasis and a potential driver of metabolism and immunomodulation after intestinal loss. In this review, we summarize the emerging ideas related to host-microbiota interactions in the intestinal adaptation processes.

Effect of Splenectomy to Short Bowel Syndrome in Rats

The aim of this study was to determine the effect of splenectomy in the short bowel syndrome. Twenty-four Wistar-albino rats weighing between 210 and 375 g were used. They were divided into three groups. In group A, short bowel syndrome (SBS) was created by 75 % bowel resection. In group B, SBS and splenectomy was performed. In group C, after transecting the bowel, it was anastomosed. Before and 45 days after the procedures, all rats were weighed. In all three groups, the first and final weight of the rats, the final bowel weight and length, the ileal and jejunal crypt depths, the villus height, the luminal diameter, the bowel wall thickness, and the number of apoptotic cells and mitosis per 100 crypt cell were compared. Periportal fibrosis, infiltration, bile stasis, and bile duct proliferation were detected in liver samples. The rat intestinal length and weight was the least in group B while the jejunal crypt depth was higher in group B than in group A and it was exactly the opposite for the jejunal and ileal villus heights. The ileal and jejunal luminal diameter, the ileal bowel wall thickness, the jejunal and ileal apoptotic cell number, the jejunal mitosis, and the periportal fibrosis were highest in group B. Adding splenectomy to an SBS model has a negative impact on bowel adaptation.

Success of serial transverse enteroplasty in an adult with extreme short bowel syndrome: a case report

Since its introduction as an alternative intestinal lengthening technique, serial transverse enteroplasty has been increasingly used as the surgical treatment of choice for children with refractory short bowel syndrome, but there have been few reports about the adult patients. This report describes the case of a 71-year-old man with a short bowel after distal gastrectomy with Billroth II reconstruction for gastric cancer, followed by extensive intestinal resection. The serial transverse enteroplasty operation was performed and lengthened the small intestine from 49 to 67 cm. The patient tolerated the procedure well and weaned off total parenteral nutrition. Liver function also improved. This case shows that the serial transverse enteroplasty procedure increases intestinal length. This procedure should be considered a surgical option for adult patients with extreme short bowel syndrome.

Angiotensin II induces apoptosis in intestinal epithelial cells through the AT2 receptor, GATA-6 and the Bax pathway

Angiotensin II (Ang II) has been shown to play an important role in cell apoptosis. However, the mechanisms of Ang-II-induced apoptosis in intestinal epithelial cells are not fully understood. GATA-6 is a zinc finger transcription factor expressed in the colorectal epithelium, which directs cell proliferation, differentiation and apoptosis. In the present study we investigated the underlying mechanism of which GATA-6 affects Ang-II induced apoptosis in intestinal epithelial cells. The in vitro intestinal epithelial cell apoptosis model was established by co-culturing Caco-2 cells with Ang II. Pretreatment with Angiotensin type 2 (AT2) receptor antagonist, PD123319, significantly reduced the expression of Bax and prevented the Caco-2 cells apoptosis induced by Ang II. In addition, Ang II up-regulated the expression of GATA-6. Interestingly, GATA-6 short hairpin RNA prevented Ang II-induced intestinal epithelial cells apoptosis and reduced the expression of Bax, but not Bcl-2. Taken together, the present study suggests that Angiotensin II promotes apoptosis in intestinal epithelial cells through GATA-6 and the Bax pathway in an AT2 receptor-dependent manner.

Complications of enterocutaneous fistulas and their management

Complications related to enterocutaneous fistulas are common and include sepsis, malnutrition, and fluid or electrolyte abnormalities. Intestinal failure is one of the most feared complications of enterocutaneous fistula management and results in significant patient morbidity and mortality. The authors review emerging trends in the medical and surgical management of patients with intestinal failure.

Bilirubin impairs intestinal regrowth following massive small bowel resection in a rat model

OBJECTIVES

The purpose of the present study was to evaluate the effects of exogenous bilirubin on structural intestinal adaptation, cell proliferation, and apoptosis in a rat model of short bowel syndrome (SBS).

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into 5 experimental groups: Sham rats underwent bowel transection and reanastomosis, sham multiple doses of bilirubin (MDB) rats underwent bowel transection and were treated with bilirubin, SBS rats underwent a 75% small bowel resection, SBS-SDB (single dose bilirubin) rats underwent a bowel resection and were treated with a single dose of bilirubin, and SBS-MDB underwent a bowel resection and were treated with 3 doses of bilirubin. Bilirubin was administered intraperitoneally from the 7th day through the 14th day postoperatively. Serum total bilirubin concentration over time was evaluated in 5 SBS-SDB rats following a single intraperitoneal dose. Total bilirubin, alanine aminotransferase, and aspartate aminotransferase in serum and parameters of intestinal adaptation, enterocyte proliferation, and enterocyte apoptosis were determined on day 15.

RESULTS

SBS-SDB and SBS-MDB animals demonstrated lower ileal bowel and mucosal weights, jejunal mucosal DNA and ileal mucosal protein, and jejunal and ileal villus height and crypt depth (vs SBS animals). Bilirubin-treated rats showed a lower apoptotic index in jejunum and ileum and a trend toward an increase in cell proliferation in jejunum and ileum (vs SBS group).

CONCLUSIONS

In a rat model of SBS, exogenous bilirubin inhibits structural intestinal adaptation. Increased cell proliferation and decreased apoptosis may be considered adaptive mechanisms that maintain cell mass.

The role of Angiotensin II type 1a receptor on intestinal epithelial cells following small bowel resection in a mouse model

AIM

We have previously shown that inhibition of angiotensin converting enzyme (ACE) significantly reduced intestinal epithelial cell (EC) apoptosis and improved morphometric intestinal adaptation in a mouse model of massive small-bowel resection (SBR). This study attempted to further examine the downstream signaling factors in this system by blocking the action of angiotensin II (ATII), hypothesizing that this would lead to similar improvement of intestinal adaptation after SBR.

METHOD

Two groups of mice (C57BL/6J) underwent either a 60% mid-intestinal resection (SBR group) or a transection/re-anastomosis (Sham group). Because real-time PCR studies showed that only ATII receptor type 1a (ATII-1a) expression was significantly increased after SBR, compared to SHAM mice, we decided to use the specific ATII-1a receptor antagonist Losartan to block this signaling pathway. An additional two groups of mice received daily i.p. injections of Losartan (SBR + Losartan and Sham + Losartan group). At 7 days, the adaptive response was assessed in the remnant gut including villus height, crypt depth, EC apoptosis (TUNEL staining) and proliferation (BrdU incorporation). The apoptotic and proliferation signaling pathways were addressed by analysis of EC mRNA expression.

RESULT

SBR (with and without Losartan) led to a significant increase in villus height and crypt depth. Losartan treatment did not significantly change EC proliferation, but did significantly reduce EC apoptosis rates as compared to the non-treated SBR group. Losartan treatment was associated with a significant reduction of the bax-to-bcl-2 ratio and TNF-alpha expression after SBR compared to non-treated groups. Interestingly, Losartan-treated groups showed a tremendous increase in proliferation of signaling factors EGFR, KGFR and IL7R, which may indicate an expanded potential for further intestinal adaptation also beyond 7 days after SBR.

CONCLUSION

This study showed that the ATII-1a receptor may be of crucial importance for the modulation of intestinal EC apoptosis, and for regulating the post-resectional EC adaptive response.

Dietary palmitic acid modulates intestinal re-growth after massive small bowel resection in a rat

PURPOSE

Among factors promoting intestinal adaptation after bowel resection, dietary fatty acids have a special role. The purpose of the present study was to evaluate the effects of palmitic acid (PA) on early intestinal adaptation in rats with short bowel syndrome (SBS).

MATERIALS

Male Sprague-Dawley rats underwent either a bowel transection with re-anastomosis (sham rats) or 75% small bowel resection (SBS rats). Animals were randomly assigned to one of four groups: sham rats fed normal chow (sham-NC); SBS rats fed NC (SBS-NC), SBS rats fed high palmitic acid diet (SBS-HPA), and SBS rats fed low palmitic acid diet (SBS-LPA). Rats were sacrificed on day 14. Parameters of intestinal adaptation, overall bowel and mucosal weight, mucosal DNA and protein, villus height and crypt depth, cell proliferation and apoptosis were determined at sacrifice. RT-PCR and Western blotting were used to determine the level of bax and bcl-2 mRNA and protein (parameters of apoptosis), and ERK protein levels (parameter of proliferation). Statistical analysis was performed using Kruskal-Wallis test followed by post hoc test for multiple comparisons with P values of less than 0.05 considered statistically significant.

RESULTS

SBS-HFD rats demonstrated higher bowel and mucosal weight, mucosal DNA and protein in ileum, while deprivation of PA (SBS-LPA) inhibited intestinal re-growth both in jejunum and ileum compared to SBS-NC rats. A significant up-regulation of ERK protein coincided with increased cell proliferation in SBS-HFD rats (vs. SBS-NC). Also, the initial decreased levels of apoptosis corresponded with the early decrease in bax and increase in bcl-2 at both mRNA and protein levels.

CONCLUSION

Early exposure to HPA both augments and accelerates structural bowel adaptation in a rat model of SBS. Increased cell proliferation and decreased cell apoptosis may be responsible for this effect. Deprivation of PA in the diet inhibits intestinal re-growth.

Effect of lactulose on bacterial translocation and intestinal adaptation in a rat model of short bowel syndrome

BACKGROUND

It is frequently assumed that dietary nondigestible carbohydrates improve host resistance to intestinal infections by stimulating proliferation of the protective gut microflora. Therefore, the aim of this study was to define the effect of lactulose, a nondigestible carbohydrate, on bacterial translocation and intestinal adaptation in a rat model of short bowel syndrome (SBS).

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into 3 experimental groups. Sham rats underwent bowel transection, SBS rats underwent 75% small bowel resection, and SBS-LAC rats underwent bowel resection and were treated with oral lactulose given in drinking water at a dose of 1.5 g x kg(-1) x day(-1) from the 3rd to the 15th postoperative day. Bacterial translocation (to mesenteric lymph nodes, liver, and portal and peripheral blood) and parameters of intestinal adaptation were determined on day 15.

RESULTS

Treatment with lactulose did not change bacterial translocation, but decreased ileal mucosal weight (20%; P < 0.05), ileal mucosal DNA (2-fold decrease; P < 0.05) and protein (26%; P < 0.05), villus height in jejunum (21%; P < 0.05) and crypt depth in ileum (17%; P < 0.05), proliferation rates in jejunum (18%; P < 0.05) and ileum (15%; P < 0.05), and apoptotic index in jejunum (40%; P < 0.05) and ileum (36%; P < 0.05) compared with SBS animals. Bax expression was upregulated in SBS rats compared with control animals, but decreased following treatment with lactulose.

CONCLUSIONS

In a rat model of SBS, oral lactulose does not improve bacterial translocation from the intestine, but inhibits intestinal adaptation.

Responsiveness of intestinal epithelial cell turnover to TGF-alpha after bowel resection in a rat is correlated with EGF receptor expression along the villus-crypt axis

Recent evidence suggests that transforming growth factor alpha (TGF-alpha) enhances enterocyte proliferation and stimulates intestinal adaptation after massive bowel resection. In the present study, we evaluated the effects of TGF-alpha on enterocyte turnover and correlated it with epidermal-growth factor (EGF) receptor expression along the villus-crypt axis in a rat model of short bowel syndrome (SBS). Male rats were divided into three groups, sham rats underwent bowel transection (group A); SBS rats underwent a 75% bowel resection (group B); and SBS/TGF-alpha rats underwent bowel resection and were treated with TGF-alpha (75 microg/kg) (group C) from the seventh postoperative day. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined on day 15. Villus tips, lateral villi and crypts were separated using laser capture microdissection. EGF receptor expression for each compartment was assessed by quantitative real-time PCR (Taqman). Statistical analysis was performed using one-way ANOVA test, with P < 0.05 considered statistically significant. Treatment with TGF-alpha resulted in a significant increase in all parameters of intestinal adaptation. EGF receptor expression in crypts significantly increased in SBS rats (vs sham rats) (0.035 +/- 0.013 vs 0.010 +/- 0.002 Log ng Total RNA/18 s) and was accompanied by a significant increase in enterocyte proliferation (169 +/- 8 vs 138 +/- 5 BrdU positive cells/per 10 crypts, P < 0.05) and decreased apoptosis following TGF-alpha administration (group C). A significant decrease in EGF receptor expression at the tip of the villus (0.005 +/- 0.002 vs 0.029 +/- 0.014 Log ng Total RNA/18 s) and in the lateral villus (0.003 +/- 0.001 vs 0.028 +/- 0.006 Log ng Total RNA/18 s) in SBS (group B) rats (vs sham, group A) was accompanied by increased cell apoptosis in these compartments following treatment with TGF-alpha (group C). In a rat model of SBS, TGF-alpha increased enterocyte proliferation and stimulated intestinal adaptation. The effect of TGF-alpha on enterocyte turnover is correlated with EGF receptor expression along the villus-crypt axis.

Bombesin stimulates enterocyte turnover following massive small bowel resection in a rat

Recent evidence suggests that bombesin (BBS) is involved in modulation of growth and differentiation of normal small intestine. The purpose of the present study was to evaluate the effects of BBS on enterocyte turnover after massive small bowel resection in a rat. Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and re-anastomosis, short bowel syndrome (SBS) rats underwent a 75% small bowel resection, and SBS-BBS rats underwent bowel resection and were treated with BBS given subcutaneously at a dose of 20 mug/kg, once daily, from postoperative day 3 through 14. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height and crypt depth), enterocyte proliferation and enterocyte apoptosis were determined in jejunum and ileum on day 15 following operation. RT-PCR technique was used to determine Bax and Bcl-2 gene expression in ileal mucosa. Statistical analysis was performed using the non-parametric Kruskal-Wallis ANOVA test, with P less than 0.05 considered statistically significant. Treatment with BBS resulted in a significant increase in ileal bowel and mucosal weight, ileal mucosal DNA and protein, jejunal and ileal villus height, jejunal crypt depth, and jejunal and ileal proliferation index compared to SBS-animals. SBS rats showed a significant increase in Bax and Bcl-2 expression in ileum that was accompanied by a significant increase in cell apoptosis compared to sham animals. SBS-BBS rats demonstrated a significant decrease in Bax and Bcl-2 expression in ileum and a decrease in apoptotic index compared to SBS-animals. In conclusion, in a rat model of SBS, BBS enhances enterocyte turnover and stimulates structural intestinal adaptation. Decreased Bax expression may be responsible for the inhibitory effect of BBS on enterocyte apoptosis.

Local glutathione redox status does not regulate ileal mucosal growth after massive small bowel resection in rats

Glutathione (GSH) concentration affects cell proliferation and apoptosis in intestinal and other cell lines in vitro. However, in vivo data on gut mucosal GSH redox status and cell turnover are limited. We investigated the effect of altered GSH redox status on the ileal mucosa in a rat model of short bowel syndrome following massive small bowel resection (SBR). Rats underwent 80% mid-jejunoileal resection (RX) or small bowel transection (TX; as operative controls), with administration of either saline or D, L-buthionine-sulfoximine (BSO), a specific inhibitor of cellular GSH synthesis. Ileal mucosal redox, morphology, and indices of cell proliferation and apoptosis were determined at different days after surgery. Ileal GSH redox status was assessed by GSH and GSH disulfide (GSSG) concentrations and the redox potential of GSH/GSSG (Eh). Ileal lipid peroxidation [free malondialdehyde (MDA)] was measured as an index of lipid peroxidation. BSO markedly decreased ileal mucosal GSH, oxidized GSH/GSSG Eh, and increased MDA content without inducing morphological damage as assessed by light or electron microscopy. As expected, SBR stimulated adaptive growth of ileal villus height and total mucosal height at 7 d after surgery, but this response was unaffected by BSO treatment despite a modest increase in crypt cell apoptosis. Ileal cell proliferation (crypt cell bromodeoxyuridine incorporation) increased at 2 d after SBR but was unaffected by BSO. Collectively, our in vivo data show that marked depletion of ileal GSH and oxidation of the GSH redox pool does not alter indices of ileal epithelial proliferation or SBR-induced ileal mucosal adaptive growth.

Short bowel syndrome: current medical and surgical trends

Short bowel syndrome is a chronic malabsorptive state usually resulting from extensive small bowel resections. A combination of diarrhea, nutrient malabsorption, dysmotility, and bowel dilatation may constitute the clinical symptomatology of this syndrome. The remaining bowel undergoes a process called adaptation, which may replace lost intestinal function. Chronic complications include nutrient, electrolyte, and vitamin deficiencies. Therapy depends largely on the administration of various factors stimulating intestinal adaptation of the remaining bowel. If the patient despite medical therapy fails to return to oral diet alone, then long-term parenteral nutrition is required. However, long-term parenteral nutrition may gradually induce cholestatic liver disease. Surgical methods may be required for treatment including intestinal transplantation, as a last resort for the treatment of end-stage intestinal failure. The goal of this review is to analyze the clinical spectrum and pathophysiologic aspects of the syndrome, the process of intestinal adaptation, and to outline the medical and surgical methods currently used to treat this complicated group of patients.

Effect of leptin on intestinal re-growth following massive small bowel resection in rat

Recent evidence suggests that the adipose tissue-derived cytokine leptin (LEP) is involved in modulation of growth and differentiation of normal small intestine. The purpose of the present study was to evaluate the effects of parenteral LEP on structural intestinal adaptation, cell proliferation and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and re-anastomosis, SBS-rats underwent a 75% small bowel resection, and SBS-LEP-rats underwent bowel resection and were treated with LEP given subcutaneously at a dose of 20 mug/kg, once daily, from day 3 through 14. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height and crypt depth in jejunum and ileum), enterocyte proliferation and enterocyte apoptosis were determined on day 15 following operation. Ileal tissue samples were taken for detection of bax and bcl-2 gene expression using RT-PCR technique. Statistical analysis was performed using the non-parametric Kruskal-Wallis ANOVA test, with P<0.05 considered statistically significant. Treatment with subcutaneous LEP resulted in a significant increase in jejunal (17%, P<0.05) and ileal (13%, P<0.05) bowel weight, jejunal (10%, P<0.05) and ileal (25%, P<0.05) mucosal weight, jejunal (26%, P<0.05) and ileal (38%, P<0.05) mucosal DNA, ileal (25%, P<0.05) mucosal protein, jejunal (41%, P<0.05) and ileal (21%, P<0.05) villus height, jejunal (37%, P<0.05) crypt depth, and jejunal (24%, P<0.05) and ileal (21%, P<0.05) enterocyte proliferation compared to SBS-animals. Enterocyte apoptosis increased significantly after bowel resection in jejunum and ileum compared to sham animals and was accompanied by an increased bax gene expression and a decreased bcl-2 gene expression in ileal samples. SBS-LEP rats showed a trend toward a decrease in enterocyte apoptosis in ileum and a mild decrease in bax gene expression compared to SBS-untreated animals. In conclusion, in a rat model of SBS parenteral LEP stimulates structural intestinal adaptation. Increased cell proliferation and decreased cell death via apoptosis may be responsible for this increased cell mass.

Advances in short bowel syndrome: an updated review

Short bowel syndrome (SBS) continues to be an important clinical problem due to its high mortality and morbidity as well as its devastating socioeconomic effects. The past 3 years have witnessed many advances in the investigation of this condition, with the aim of elucidating the cellular and molecular mechanisms of intestinal adaptation. Such information may provide opportunities to exploit various factors that act as growth agents for the remaining bowel mucosa and may suggest new therapeutic strategies to maintain gut integrity, eliminate dependence on total parenteral nutrition, and avoid the need for intestinal transplantation. This review summarizes current research on SBS over the last few years.

Oral insulin enhances intestinal regrowth following massive small bowel resection in rat

Experimental studies have suggested that insulin (INS) plays an important role in small intestinal growth and development. In the present study we investigated the effect of oral INS on structural intestinal adaptation and enterocyte proliferation and loss via apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection, SBS rats underwent 75% small bowel resection, and SBS-INS rats underwent bowel resection and were treated with oral INS given in the drinking water from the 3rd to the 15th postoperative day. Parameters of intestinal adaptation (bowel and mucosal weight, mucosal DNA and protein, villous height, and crypt depth), enterocyte proliferation, and apoptosis were determined on day 15. SBS-INS rats demonstrated a significant increase (vs SBS rats) in jejunal and ileal overall bowel and mucosal weight, ileal mucosal DNA and protein, ileal villous height, and crypt depth. SBS-INS rats also showed an increased cell proliferation index in jejunum and ileum and decreased apoptotic index in jejunum compared to SBS animals. In conclusion, in a rat model of SBS, oral INS strongly enhances intestinal adaptation. Possible mechanisms may include increased cell proliferation and decreased enterocyte loss via apoptosis.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

Intestinal adaptation after massive intestinal resection

Patients with short bowel syndrome require long term parenteral nutrition support. However, after massive intestinal resection the intestine undergoes adaptation and nutritional autonomy may be obtained. Given that the complications of parenteral nutrition may be life threatening or result in treatment failure and the need for intestinal transplantation, a more attractive option is to wean patients off nutrition support by optimising the adaptive process. The article examines the evidence that after extensive small bowel resection adaptation occurs in humans and focuses on the factors that influence adaptation and the strategies that have been used to optimise this process. The review is based on an English language Medline search with secondary references obtained from key articles. There is evidence that adaptation occurs in humans. Adaptation is a complex process that results in response to nutrient and non-nutrient stimuli. Successful and reproducible strategies to improve adaptation remain elusive despite an abundance of experimental data. Nevertheless given the low patient survival and quality of life associated with other treatments for irreversible intestinal failure it is imperative that clinical research continues into the optimisation of the adaptation.

Parenteral arginine impairs intestinal adaptation following massive small bowel resection in a rat model

The nitric oxide precursor L-arginine (ARG) has been shown to influence intestinal structure and absorptive function. It is also well known that the route of administration modulates the effects of ARG. The present study evaluated the effects of parenteral ARG on structural intestinal adaptation, cell proliferation, and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and reanastomosis, SBS rats underwent a 75% small bowel resection, and SBS-ARG rats underwent a 75% small bowel resection and were treated with ARG given subcutaneously at a dose of 300 mug/kg, once daily, from days 3 to 14. Parameters of intestinal adaptation, enterocyte proliferation, and enterocyte apoptosis were determined on day 15 following operation. The SBS rats demonstrated a significant increase in jejunal and ileal bowel and mucosal weight, villus height and crypt depth, and cell proliferation index compared with the sham group. The SBS-ARG animals demonstrated lower ileal bowel and mucosal weights, jejunal mucosal DNA and ileal mucosal protein, and jejunal and ileal villus height and crypt depth compared with SBS animals. The SBS-ARG rats also had a lower cell proliferation index in both jejunum and ileum and a greater enterocyte apoptotic index in ileum compared with the SBS-untreated group. In conclusion, in a rat model of SBS, parenteral arginine inhibits structural intestinal adaptation. Decreased cell proliferation and increased apoptosis are the main mechanisms responsible for decreased cell mass.

Effect of subcutaneous insulin on intestinal adaptation in a rat model of short bowel syndrome

Insulin has been shown to influence intestinal structure and absorptive function. The purpose of the present study was to evaluate the effects of parenteral insulin on structural intestinal adaptation, cell proliferation, and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection and reanastomosis, SBS rats underwent a 75% small bowel resection, and SBS-INS rats underwent a 75% small bowel resection and were treated with insulin given subcutaneously at a dose of 1 U/kg, twice daily, from day 3 through day 14. Parameters of intestinal adaptation, enterocyte proliferation, and enterocyte apoptosis were determined on day 15 following operation. SBS rats demonstrated a significant increase in jejunal and ileal bowel and mucosal weight, villus height and crypt depth, and cell proliferation index compared with the sham group. SBS-INS animals demonstrated higher jejunal and ileal bowel and mucosal weights, jejunal and ileal mucosal DNA and protein, and jejunal and ileal crypt depth compared with SBS animals. SBS-INS rats also had a greater cell proliferation index in both jejunum and ileum and a trend toward a decrease in enterocyte apoptotic index in jejunum and ileum compared with the SBS untreated group. In conclusion, parenteral insulin stimulates structural intestinal adaptation in a rat model of SBS. Increased cell proliferation is the main mechanism responsible for increased cell mass.

Effect of sex and sex hormones on structural intestinal adaptation after massive small bowel resection in rats

PURPOSE

The gonadal steroids play a major role in the regulation of many functions. The purpose of the current study was to evaluate the effect of sex and sex hormones on intestinal adaptation in a rat model of short bowel syndrome (SBS).

METHODS

In the first experiment, male and female Sprague-Dawley rats underwent bowel transection and re-anastomosis (sham group) or 75% small bowel resection and anastomosis (SBS group). Relative changes in parameters of intestinal adaptation (overall bowel and mucosal weight, mucosal DNA and protein, villus height, and crypt depth) were measured on day 15 and were compared with respect to sex. In the second experiment, male rats were divided into 4 experimental groups: SBS rats, SBS castrated rats, SBS castrated rats treated with testosterone, and SBS castrated rats treated with estradiol. Parameters of intestinal adaptation were compared with respect to hormonal treatment. Statistical significance was determined by Student's t test and analysis of variance with P < .05 considered significant.

RESULTS

Sex had minimal effects on intestinal adaptation. Both male and female rats showed a comparable increase in all parameters of intestinal adaptation. In the second experiment, castration led to significant decrease in bowel and mucosal weight, mucosal DNA and protein in both jejunum and ileum compared with SBS animals. Castrated rats also had lower jejunal villus height and crypt depth compared with SBS animals. Testosterone attenuated this negative effect of castration on bowel regrowth. Rats treated with testosterone showed a significant increase in bowel and mucosal weight, mucosal protein in both jejunum and ileum, mucosal DNA, villus height, and crypt depth in jejunum compared with castrated nontreated animals. Treatment with estradiol after resection and castration had minimal effect on bowel regrowth.

CONCLUSIONS

Bowel regrowth after massive small bowel resection is not sex-related. Depletion of androgens by castration inhibited intestinal adaptation. Testosterone has shown a strong stimulating effect on bowel regrowth.

Bax deficiency rescues resection-induced enterocyte apoptosis in mice with perturbed EGF receptor function

BACKGROUND

Adaptation after massive smallbowel resection (SBR) is associated with increased cell turnover, increased rates of enterocyte proliferation, and apoptosis. Epidermal growth factor receptor (EGFR) inhibition attenuates adaptation and increases apoptosis. Intestinal levels of bax appear to correlate with EGFR signaling. This study tested the hypothesis that bax is required for the exaggerated postresection apoptosis induced by perturbed EGFR signaling.

METHODS

Waved-2 mice with impaired EGFR signaling were crossbred with bax-null mice. Offspring were subjected to either 50% proximal SBR or sham operation (bowel transection and reanastomosis). After 7 days, parameters of adaptation (villus height, wet weight), proliferation (% Ki-67 immunostaining of crypt cells), and apoptosis (# apoptotic bodies per crypt) were recorded in the remnant ileum.

RESULTS

Enterocyte apoptosis was increased in waved-2 mice and prevented in bax-null mice after SBR. The accelerated apoptosis in the waved-2 mice was rescued in the context of deficient bax expression. Other parameters of adaptation were restored in the bax-null/waved-2 mice.

CONCLUSION

Bax is required for the induction of postresection enterocyte apoptosis. Defective EGFR signaling augments resection-induced enterocyte apoptosis via a mechanism that also requires bax expression. These data implicate a link between EGFR signaling and bax in the genesis of postresection apoptosis and adaptation.

A genetic mechanism for cecal atresia: the role of the Fgf10 signaling pathway

BACKGROUND

Intestinal atresia represents a significant surgically correctable cause of intestinal obstruction in neonates. Intestinal development proceeds as a tube-like structure with differentiation along its axis. As the intestine differentiates, the cecum develops at the transition from small to large intestine. Fgf10 is known to serve a key role in budding morphogenesis; however, little is known about its role in the development of this transitional structure. Here we evaluate the effect of Fgf10/Fgfr2b invalidation on the developing cecum.

MATERIALS AND METHODS

Wild-type C57Bl/6, Fgf10(-/-), and Fgfr2b(-/-) embryos harvested from timed pregnant mothers were analyzed for cecal phenotype, Fgf10 expression, and differentiation of smooth muscle actin.

RESULTS

Wt cecal development is first evident at E11.5. FGF10 is discreetly expressed in the area of the developing cecum at early stages of development. One hundred percent of Fgf10(-/-) and Fgfr2b(-/-) mutant embryos demonstrate cecal atresia with absence of epithelial and muscular layers. The development of neighboring anatomical structures such as the ileocecal valve is not affected by Fgf10/Fgfr2b invalidation.

CONCLUSIONS

FGF10 expression is localized to the cecum early in the normal development of the cecum. Fgf10(-/-) and Fgfr2b(-/-) mutant embryos demonstrate cecal atresia with complete penetrance. Epithelial and muscular layers of the cecum are not present in the atretic cecum. The Fgf10(-/-) and Fgfr2b(-/-) mutants represent a genetically reproducible animal model of autosomal recessive intestinal atresia.

Preventing enterocyte apoptosis after massive small bowel resection does not enhance adaptation of the intestinal mucosa

BACKGROUND

After massive small bowel resection (SBR), increased rates of enterocyte apoptosis are observed in the remnant bowel via a mechanism requiring bax gene expression. This study tested the hypothesis that adaptive mucosal growth could be enhanced by the novel strategy of preventing postresection enterocyte apoptosis.

METHODS

Male bax-null and corresponding wild-type (WT) mice underwent a 50% proximal SBR or sham operation (bowel transaction with reanastomosis alone). Mice were killed after a full adaptation interval of 1 month. Adaptation was measured in the remnant ileum as alterations in villus height, crypt depth, and wet weight. Rates of enterocyte proliferation were derived by immunostaining of crypt enterocytes for Ki-67 and apoptosis by the presence of apoptosis bodies.

RESULTS

The expected increase in enterocyte apoptosis after SBR occurred in the WT mice but was unchanged in the bax-null mice. Despite the prevention of postresection apoptosis in the bax-null mice, all parameters of adaptation and proliferation increased equally after SBR in both groups of mice.

CONCLUSIONS

Bax deficiency prevents the increase in enterocyte apoptosis that occurs after massive SBR throughout the entire adaptation period. Attenuation of postresection enterocyte apoptosis does not augment mucosal adaptation to massive intestinal loss.

Factors enhancing intestinal adaptation after bowel compensation

Intestinal failure (IF) refers to the condition in which certain causes lead to derangements in nutrient absorption capacity. Gut adaptation occurs in response to IF and it is both morphologic and physiologic in nature and can be mediated by growth factors and nutrients. Our paper reviews certain trophic growth factors that have important interactions relevant for intestinal growth, function and adaptation.

DATA SOURCE

The literature was reviewed (data from both animal and human studies) and certain trophic factors that modulate intestinal adaptation are summarized. The factors reviewed are: epidermal growth factor, insulin-like growth factor I and II, transforming growth factor alpha and beta, neurotensin, interleukin-11, glucagon-like peptide-2, keratinocyte growth factor, human growth hormone, short-chain fatty acids, and glutamine.

CONCLUSIONS

Growth factors augment intestinal proliferation, diminish programmed apoptosis, and modulate the adaptive process. They also have the potential to improve nutrient absorption in some bowel disease. The enhancement of gut adaptation may allow patients to transition of parenteral/enteral to normal nutrition, in a shorter period of time, which reduce the rate of adverse effects caused by artificial nutrition and improve quality of life.