Small-bowel resection. Oral intake is the stimulus for hyperplasia

Antimicrobial Pharmacokinetic Considerations in Extracorporeal Membrane Oxygenation

Critical illness creates challenges for healthcare providers in determining the optimal treatment of severe disease, particularly in determining the most appropriate selection and dosing of medications. Critically ill patients experience endogenous physiologic changes that alter the pharmacokinetics (PKs) of medications. These alterations can be further compounded by mechanical support modalities such as extracorporeal membrane oxygenation (ECMO). Specific components of the ECMO circuit have the potential to affect drug PKs through drug sequestration and an increase in the volume of distribution. Factors related to the medications themselves also play a role. These PK alterations create problems when trying to properly utilize antimicrobials in this patient population. The literature seeking to identify appropriate antimicrobial dosing regimens is both limited and difficult to evaluate due to patient variability and an inability to determine the exact role of the ECMO circuit in reduced drug concentrations. Lipophilic and highly protein bound medications are considered more likely to undergo significant drug sequestration in an ECMO circuit, and this general trend represents a logical starting point in antimicrobial selection and dosing in patients on ECMO support. This should not be the only consideration, however, as identifying infection and evaluating the efficacy of treatments in this population is challenging. Due to these challenges, therapeutic drug monitoring should be utilized whenever possible, particularly in cases with severe infection or high concern for drug toxicity.

Anatomical and physiological considerations in short bowel syndrome: Emphasis on intestinal adaptation and the role of enterohormones

Short bowel syndrome (SBS)-associated intestinal failure (IF) is a complex, life-threatening condition that requires complex care of multiple factors impacting the patient's long-term prognosis. Various etiologies result in SBS-IF, with three primary anatomical subtypes occurring following intestinal resection. Depending on the extent and segment(s) of the intestine resected, malabsorption can be nutrient specific or sweeping; however, such issues and the associated prognosis for the patient can be predicted with analysis of the residual intestine, along with baseline nutrient and fluid deficits and extent of malabsorption. The provision of parenteral nutrition/intravenous (PN-IV) fluids and antisymptomatic agents is fundamental; however, optimal management should focus on intestinal rehabilitation, wherein intestinal adaptation is prioritized and PN-IV fluids are weaned over time. Key strategies to maximize intestinal adaptation include hyperphagic consumption of an individualized SBS diet and the appropriate use of trophic agents, such as a glucagon-like peptide 2 analog.

The effect of probiotics on ıntestinal motility in an experimental short bowel model

PURPOSE

To investigate the effect of probiotics on spontaneous contractions of smooth muscle isolated from jejunum and ileum of rat model.

METHODS

Four rat groups were created (n=8, in each) including control (Group 1), control+probiotic (Group 2), short bowel (Group 3), and short bowel+probiotic (Group 4). Groups 1 and 2 underwent sham operation, Groups 3 and 4 underwent massive bowel resection. Bifidobacterium Lactis was administered in Groups 2 and 4 daily (P.O.) for three weeks. On postoperative week 3, rats were sacrificed, and jejunum and ileum smooth muscle were isolated for organ bath. Muscle contraction changes were analyzed before and after addition of antagonists.

RESULTS

Short bowel group exhibited increased amplitude and frequency of spontaneous contractions. The addition of probiotics significantly decreased enhanced amplitude and frequency of bowel contraction in short bowel group and returned to control values. L-NNA increased amplitude and frequency of contractions in all groups. While indomethacin and nimesulide increased the amplitude in all groups, the frequency was only increased in jejunum. Hexamethonium and tetrodotoxin did not change the contraction characteristics in all groups.

CONCLUSION

We suggest that early use of probiotics may significantly regulate bowel motility, and accordingly improve absorption of nutrients in short bowel syndrome.

Ghrelin and glucagon-like peptide-2 increase immediately following massive small bowel resection

Children with short bowel syndrome face life-threatening complications. Therefore, there is an urgent need for a new therapy to induce effective adaptation of the remnant intestine. Adaptation occurs only during feeding. We focused on preprandial acyl ghrelin and des-acyl ghrelin, and postprandial glucagon-like peptide-2 (GLP-2), which are known to have active orexigenic and trophic actions. This study aims to clarify the secretion trends of these hormones after massive small bowel resection and to obtain basic data for developing a new treatment. Sixty-three growing male rats were used: 3 were designated as controls receiving no operation and 60 were randomized into the 80% small bowel resection (80% SBR) group and the transection and re-anastomosis group. Changes in body weight, food intake, and remnant intestine morphology were also assessed for 15 days after the operation. Acyl ghrelin and des-acyl ghrelin levels increased immediately, equivalently in both operation groups (P=0.09 and 0.70). Interestingly, in 80% SBR animals, des-acyl ghrelin peaked on day 1 and acyl ghrelin peaked on day 4 (P=0.0007 and P=0.049 vs controls). GLP-2 secretion was obvious in 80% SBR animals (P=2.25×10(-6)), which increased immediately and peaked on day 4 (P=0.009 vs. controls). Body weight and food intake in 80% SBR animals recovered to preoperative levels on day 4. Morphological adaptations were evident after day 4. Our results may suggest a management strategy to reinforce these physiological hormone secretion patterns in developing a new therapy for short bowel syndrome.

Dietary supplementation with vitamin D stimulates intestinal epithelial cell turnover after massive small bowel resection in rats

PURPOSE

While the endocrine action of the active metabolite 1,25-dihydroxyvitamin D (VtD) has been well characterized in relation to the maintenance of plasma calcium and phosphate homeostasis through regulation of intestinal absorption, recent research has focused on its autocrine and/or paracrine activities. Such activities have been best characterized in intestine, where VtD regulates cell differentiation and maturation. The purpose of this study was to evaluate the effect of VtD on enterocyte turnover in a rat model of short bowel syndrome (SBS).

METHODS

Male rats were divided into four groups: sham rats underwent bowel transection, sham-VtD rats underwent bowel transection and were treated oral VtD, SBS rats underwent a 75 % bowel resection, and SBS-VtD rats underwent bowel resection and were treated with VtD. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined at sacrifice. Illumina's digital gene expression (DGE) analysis was used to determine VtD pathway-related gene expression profiling. VtD receptor (VDR) and its promoter, Bax and Bcl-2 mRNA expression were determined using real-time PCR. Western blotting was used to determine p-ERK, Bax and β-catenin protein levels.

RESULTS

From the total of 20,000 probes, 11 genes related to VtD signaling were investigated. Of these genes, five were found to be up-regulated in SBS versus sham animals with a relative change in gene expression level of 20 %, five remained unchanged, and one was down-regulated. VtD treatment in sham and SBS rats resulted in significant up-regulation of the VDR gene and its promoter's expression. SBS-VtD rats demonstrated a significant increase in all intestinal mucosal parameters compared to SBS animals. A significant increase in cell proliferation in SBS-VtD rats was accompanied by increased β-catenin protein levels. A significant decrease in cell apoptosis in this group was correlated with lower Bax/Bcl-2 mRNA and protein levels.

CONCLUSION

In a rat model of SBS, dietary supplementation with VtD stimulates enterocyte turnover, which correlates with up-regulated VtD receptor expression in the remaining small intestine.

Inflammation enhances resection-induced intestinal adaptive growth in IL-10 null mice

BACKGROUND

Surgical resection of the ileum, cecum, and proximal right colon (ICR) is common in the management of Crohn's disease, yet little is known about the effect of active inflammation on the adaptive response following intestinal loss. We recently developed a surgical model of ICR in germ-free (GF) IL-10 null mice that develop small intestinal inflammation only when mice undergo conventionalization with normal fecal microflora (CONV) before surgical intervention. In this study, we examined the effects of postsurgical small bowel inflammation on adaptive growth after ICR.

METHODS

GF 129SvEv IL-10 null mice, 8-10 wk old, were allocated to GF or CONV groups. Nonoperated GF and CONV mice provided baseline controls. Two wk later, GF and CONV mice were further allocated to ICR or sham operation. Small intestine and colon were harvested 7 d after surgery for histological analysis.

RESULTS

All mice within the gnotobiotic facility maintained GF status and did not develop small intestinal or colonic inflammation. CONV resulted in colitis in all groups, whereas small intestinal inflammation was only observed following ICR. Resection-induced small intestinal inflammation in CONV mice was associated with increases in proliferation, crypt depth, and villus height compared with GF mice after ICR. Resection-induced increases in crypt fission only occurred in CONV mice.

CONCLUSION

ICR-dependent small intestinal inflammation in CONV IL-10 null mice dramatically enhances early adaptive growth of the small intestine. Additional studies utilizing our model may provide clinical insight leading to optimal therapies in managing IBD patients after surgical resection.

Morphological adaptation with preserved proliferation/transporter content in the colon of patients with short bowel syndrome

In short bowel syndrome (SBS), although a remaining colon improves patient outcome, there is no direct evidence of a mucosal colonic adaptation in humans. This prospective study evaluates morphology, proliferation status, and transporter expression level in the epithelium of the remaining colon of adult patients compared with controls. The targeted transporters were Na+/H+ exchangers (NHE2 and 3) and oligopeptide transporter (PepT1). Twelve adult patients with a jejuno-colonic anastomosis were studied at least 2 yr after the last surgery and compared with 11 healthy controls. The depth of crypts and number of epithelial cells per crypt were quantified. The proliferating and apoptotic cell contents were evaluated by revealing Ki67, PCNA, and caspase-3. NHE2, NHE3, PepT1 mRNAs, and PepT1 protein were quantified by quantitative RT-PCR and Western blot, respectively. In patients with SBS compared with controls, 1) hyperphagia and severe malabsorption were documented, 2) crypt depth and number of cells per crypt were 35% and 22% higher, respectively (P < 0.005), whereas the proliferation and apoptotic levels per crypt were unchanged, and 3) NHE2 mRNA was unmodified; NHE3 mRNA was downregulated near the anastomosis and unmodified distally, and PepT1 mRNA and protein were unmodified. We concluded that, in hyperphagic patients with SBS with severe malabsorption, adaptive colonic changes include an increased absorptive surface with an unchanged proliferative/apoptotic ratio and well-preserved absorptive NHE2, NHE3, and PepT1 transporters. This is the first study showing a controlled nonpharmacological hyperplasia in the colon of patients with SBS.

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.

Expansion of intestinal stem cells associated with long-term adaptation following ileocecal resection in mice

Sustained increases in mucosal surface area occur in remaining bowel following massive intestinal loss. The mechanisms responsible for expanding and perpetuating this response are not presently understood. We hypothesized that an increase in the number of intestinal stem cells (ISC) occurs following intestinal resection and is an important component of the adaptive response in mice. This was assessed in the jejunum of mice 2-3 days, 4-5 days, 6-7 days, 2 wk, 6 wk, and 16 wk following ileocecal resection (ICR) or sham operation. Changes in ISC following ICR compared with sham resulted in increased crypt fission and were assayed by 1) putative ISC population (SP) by flow cytometry, 2) Musashi-1 immunohistochemistry, and 3) bromodeoxyuridine (BrdU) label retention. Observed early increases in crypt depth and villus height were not sustained 16 wk following operation. In contrast, long-term increases in intestinal caliber and overall number of crypts per circumference appear to account for the enhanced mucosal surface area following ICR. Flow cytometry demonstrated that significant increases in SP cells occur within 2-3 days following resection. By 7 days, ICR resulted in marked increases in crypt fission and Musashi-1 immunohistochemistry staining. Separate label-retention studies confirmed a 20-fold increase in BrdU incorporation 6 wk following ICR, confirming an overall increase in the number of ISC. These studies support that expansion of ISC occurs following ICR, leading to an overall increase number of crypts through a process of fission and intestinal dilation. Understanding the mechanism expanding ISCs may provide important insight into management of intestinal failure.

Intestine-specific ablation of mouse atonal homolog 1 (Math1) reveals a role in cellular homeostasis

BACKGROUND & AIMS

Math1 (Atoh1) is a basic helix-loop-helix transcription factor important for intestinal secretory cell differentiation. We hypothesized that Math1 is important in cell fate commitment, and therefore mediates proliferative homeostasis and the adaptive response following intestinal resection in the adult intestine.

METHODS

We generated mice with an intestine-specific mosaic deletion of Math1 (Math1(Delta intestine)) using the Cre/loxP system. Histologic analysis in adult Math1(Delta intestine) and wild-type littermates at baseline and following small bowel resection or sham surgery was performed.

RESULTS

We observed loss of Paneth, goblet, and enteroendocrine cells in Math1-null crypts. In addition, aberrant activation of the Math1 promoter occurred in absorptive enterocytes derived from Math1-null crypts, suggesting a change in cell fate. Proliferation was increased but apoptosis unchanged in Math1-mutant crypts compared to adjacent wild-type crypts. Math1(Delta intestine) mice and wild-type littermates displayed similar physiologic adaptive responses to small bowel resection as measured by changes in body weight and ileal wet weight. In contrast, Math1-mutant crypts displayed a blunted adaptive response compared to adjacent wild-type crypts.

CONCLUSIONS

We show that Math1 is essential for adult intestinal secretory cell production, and in its absence cells destined to a secretory phenotype instead adopt an absorptive phenotype. Subtle abnormalities of proliferation within Math1-null crypts in Math1(Delta intestine) mice were identified, together with a substantial defect in the adaptive response of Math1-null crypts following small bowel resection. Our results suggest that Math1 is critical for both cell fate determination within the intestinal epithelium and for regulation of the response to intestinal resection.

Rapid expansion of intestinal secretory lineages following a massive small bowel resection in mice

Following massive small bowel resection (SBR) in mice, there are sustained increases in crypt depth and villus height, resulting in enhanced mucosal surface area. The early mechanisms responsible for resetting and sustaining this increase are presently not understood. We hypothesized that expansion of secretory lineages is an early and sustained component of the adaptive response. This was assessed in the ileum by quantitative morphometry at 12 h, 36 h, 7 days, and 28 days and by quantitative RT-PCR of marker mRNAs for proliferation and differentiated goblet, Paneth cell, and enterocyte genes at 12 h after 50% SBR or sham operation. As predicted, SBR elicited increases of both crypt and villus epithelial cells, which were sustained though the 28 days of the experiment. Significant increases in the overall number and percentage of both Paneth and goblet cells within intestinal epithelium occurred by 12 h and were sustained up to 28 days after SBR. The increases of goblet cells after SBR were initially observed within villi at 12 h, with marked increases occurring in crypts at 36 h and 7 days. Consistent with this finding, qRT-PCR demonstrated significant increases in the expression of mRNAs associated with proliferation (c-myc) and differentiated goblet cells (Tff3, Muc2) and Paneth cells (lysozyme), whereas mRNA associated with differentiated enterocytes (sucrase-isomaltase) remained unchanged. From these data, we speculate that early expansion of intestinal secretory lineages within the epithelium of the ileum occurs following SBR, possibly serving to amplify the signal responsible for initiating and sustaining intestinal adaptation.

Pharmacokinetic changes in critical illness

Physiologic alterations in critically ill patients can significantly affect the pharmacokinetics of drugs used in the critically ill patient population. Understanding these pharmacokinetic changes is essential relative to optimizing drug therapy. This article outlines the major differences seen in the absorption, distribution, metabolism, and excretion of drugs in critically ill patients. Important strategies for drug therapy dosing and monitoring in these patients are also addressed.

Extensive small bowel resection in dogs and cats: 20 cases (1998–2004)

OBJECTIVE

To determine outcome in dogs and cats that underwent extensive (ie, > 50%) resection of the small intestine and identify factors associated with outcome.

DESIGN

Retrospective case series.

ANIMALS

13 dogs and 7 cats.

PROCEDURE

Medical records were reviewed, and follow-up information was obtained.

RESULTS

In all 7 cats and in 8 of the 13 dogs, extensive intestinal resection was performed because of a foreign body. Mean+/-SD estimated percentage of intestine that was removed was 68+/-14% (range, 50% to 90%). Two dogs were euthanized 3 days after surgery because of dehiscence of the surgical site and development of septic peritonitis; 1 dog died of acute respiratory distress syndrome 5 days after surgery. The remaining 10 dogs and 7 cats were discharged from the hospital, and follow-up information was available for 15 of the 17. Median survival time was 828 days, and 12 of the 15 animals for which long-term follow-up information was available had good outcomes. However, none of the factors examined, including percentage of intestine resected, were significantly associated with outcome.

CONCLUSIONS AND CLINICAL RELEVANCE

Most dogs and cats that underwent extensive resection of the small intestine had a good outcome. The amount of intestine resected was not associated with outcome. These data may be useful in providing prognostic information in cases of extensive small intestinal resection.

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.

Effect of dietary fat on early morphological intestinal adaptation in a rat with short bowel syndrome

Among factors promoting mucosal hyperplasia after bowel resection, long-chain fatty acids may have a special role. The purpose of the present study was to evaluate the effects of high-fat diet (HFD) on early intestinal adaptation in rats with short bowel syndrome (SBS). 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 three groups: Sham rats fed normal chow (Sham-NC); SBS rats fed NC (SBS-NC); and SBS rats fed HFD (SBS-HFD). Rats were killed on days 3 or 14. Body weight and parameters of intestinal adaptation (overall bowel and mucosal weight, mucosal DNA and protein, villus height, and crypt depth) were determined at time of killing. By day 3, SBS-HFD rats demonstrated higher duodenal and jejunal bowel and mucosal weights and ileal villus height and jejunal crypt depth vs SBS-NC rats. By day 14 SBS-HFD rats continued to demonstrate increased duodenal and jejunal bowel weight and duodenal mucosal weight vs SBS-NC animals. We conclude that early exposure to HFD both augmented and accelerated structural bowel adaptation in a rat model of SBS.

Enhancing bowel adaptation in short bowel syndrome

Malabsorption of both nonessential and essential nutrients, fluid, and electrolytes will, if not compensated for by increased intake, lead to diminished body stores and to subclinical and eventually clinical deficiencies. By definition, intestinal failure prevails when parenteral support is necessary to maintain nutritional equilibrium. After intestinal resection, adaptation, a progressive recovery from the malabsorptive disorder, may be seen. Research has focused on optimizing remnant intestinal function through dietary or pharmacologic interventions. In this review, factors responsible for the morphologic and functional changes in the adaptive processes are described. Results of clinical trials employing either growth hormone and glutamine or glucagon-like peptide-2 in short bowel patients are presented.

Time-dependent intestinal adaptation and GLP-2 alterations after small bowel resection in rats

Existing data on morphological adaptation after small bowel resection are obtained by potentially biased methods. Using stereological techniques, we examined segments of bowel on days 0, 4, 7, 14, and 28 after 80% jejunoileal resection or sham operation in rats and correlated intestinal growth with plasma levels of glucagon-like peptide-2 (GLP-2). In the jejunum and ileum of the resected rats, the mucosal weight increased by 120 and 115% during the first week, and the weight of muscular layer increased by 134 and 83%, compared with sham-operated controls. The luminal surface area increased by 190% in the jejunum and by 155% in the ileum after 28 days. The GLP-2 level was increased by 130% during the entire study period in the resected rats. Small bowel resection caused a pronounced and persistent transmural growth response in the remaining small bowel, with the most prominent growth occurring in the jejunal part. The significantly elevated GLP-2 level is consistent with an important role of GLP-2 in the adaptive response.

Intestinal permeability in adult patients with growth hormone deficiency

Pathological disruption of the intestinal mucosa increases the paracellular pathway, leading to an increase in the penetration of large molecules. Since growth hormone (GH) has a trophic intestinal effect, we used a double marker test to enable examination of intestinal permeability, which reflects the state of integrity of the intestinal mucosa. We recruited 22 adult patients, mean age 54+/-13.3 years, with GH deficiency due to partial or total hypopituitarism. None had received GH treatment at any time, although they were all in optimized replacement therapy. A control group was composed of 19 healthy age-matched relatives. The intestinal permeability test was performed with lactulose (5 g) and mannitol (1 g) after an oral load of 100 ml of aqueous solution. The urinary lactulose/mannitol ratio and the percentages of lactulose and mannitol excreted were determined on a 5-h urine collection. There were no significant differences between the patients and the control group in the lactulose/mannitol ratio (0.087+/-0.059 vs 0.077+/-0.064, respectively) or in the urinary excretion percentages of lactulose (0.067+/-0.048% vs 0.073+/-0.070%, respectively) or mannitol (5.127+/-3.269% vs 5.068+/-2.985%, respectively). In conclusion, no increase in intestinal permeability was detected in patients with GH deficiency, so that in spite of the known trophic effects of GH on the epithelial crypt cells, there was no intestinal hyperpermeability in these patients.

Autotransplantation modulates ileal enteroendocrine cell expression in the pig

BACKGROUND

Enteroendocrine cell-derived peptides modulate postresectional small bowel adaptation, which may be attenuated by transplantation. We investigated whether autotransplantation modulates the number and distribution of ileal enteroendocrine cells in pigs with proximal small bowel resection.

MATERIALS AND METHODS

Fifteen pigs were assigned into either small intestinal transection or 75% proximal small intestinal resection with or without autotransplantation of the remaining ileum. After 14 weeks the number and subtype distribution of enteroendocrine cells, crypt cell proliferation, and mucosal histology were analyzed from the proximal and distal ends of the remaining ileum.

RESULTS

When compared to resected controls, autotransplantation of the ileum decreased the absolute (P < 0.05 in proximal ileum) and proportional (P < 0.05 in distal ileum) crypt enteroendocrine cell number. In addition, autotransplantation reduced somatostatin and glicentin expressing cell counts and abolished the proximodistal gradient of the enteroendocrine cell number. When compared to transected controls, villus height, crypt depth, number of proliferating crypt cells, and crypt cell proliferation index increased after the proximal resection (P < 0.05 in all except in crypt depth and proliferation index of the distal ileum) but remained virtually unchanged after autotransplantation of the ileal remnant.

CONCLUSIONS

Autotransplantation decreases the crypt enteroendocrine cell number and alters their proximodistal and subtype distribution in the remaining ileum in pigs with proximal small bowel resection. These alterations are associated with attenuated adaptive response of the autotransplanted ileum.

Recombinant human interleukin-11 prevents mucosal atrophy and bowel shortening in the defunctionalized intestine

BACKGROUND

Mucosal atrophy and bowel shortening are the hallmark of proximal intestinal diversion for extensive necrotizing enterocolitis (NEC) or Thiry-Vella fistulas (TVF), in which the ends of a defunctionalized loop of intestine are exteriorized as stomas. Recombinant human interleukin-11 (rhIL-11) is a pleiotropic cytokine that promotes epithelial regeneration and enhances adaptation after bowel resection. The authors hypothesized that rhIL-11 may prevent mucosal atrophy and bowel shortening in rats with TVF METHODS: After creation of ileal TVF, Sprague-Dawley rats were selected randomly to receive either rhIL-11 or equal volume of 0.1% bovine serum albumin (BSA) subcutaneously daily. On day 14, the TVF were excised and examined morphologically. Enterocyte apoptosis was measured using the TUNEL assay. Mucosal DNA and protein content were measured.

RESULTS

Administration of rhIL-11 resulted in a significantly greater weight gain and less shortening of TVF than BSA treatment. TVF from the rhIL-11-treated group showed evidence of hyperplasia and hypertrophy and increased crypt to villus ratio. The BSA group had substantial mucosal atrophy. There was a qualitative decrease in the incidence of apoptosis in the rhIL-11 group.

CONCLUSIONS

Recombinant human IL-11 prevents mucosal atrophy and shortening of defunctionalized intestinal loops. It may help reduce the incidence of short gut syndrome in infants with extensive NEC.

Malnutrition impairs postresection intestinal adaptation

BACKGROUND

Postresection intestinal adaptation is influenced by several factors, including luminal nutrients. Adaptation is impaired in the absence of luminal nutrients, even if the nutrition is maintained via total parenteral nutrition (TPN). Reduced enteral intake also inhibits adaptation if malnutrition is present, but the mechanism has not been completely defined. Our aim was to study the effect of reduced enteral nutrition on adaptation and enterocyte production and death after 50% proximal resection in rats.

METHODS

Eighteen Lewis rats underwent either transection (n =6) or 50% proximal resection (n =12). The resected animals either ate ad libitum (n = 6) or were offered 75% of ad libitum intake (n =6). Nutritional status and intestinal adaptation were determined 14 days after surgery.

RESULTS

Resected animals receiving 75% normal intake had decreased body weight (89% +/- 4% vs 112% +/- 2% and 112% +/- 1%, p < .05) and serum albumin (2.7 +/- 0.1 vs 3.2 +/- 0.0 g/dL and 3.0 +/- 0.1 g/dL, p < .05) compared with resection with normal intake and transection, respectively. Intestinal weight (0.32 +/- 03 vs 0.22 +/- 0.02 g/cm and 0.19 +/- 0.03 g/cm, p < .05) and diameter (10.5 +/- 0.5 vs 8.5 +/- 1.0 mm and 7.8 +/- 0.8 mm, p < .05) increased after resection alone compared with transection and malnourished resection groups. Gut weight and diameter and villus height were lower in malnourished resected animals than with transection. Crypt cell production rate was significantly lower in the reduced intake animals. Apoptosis was increased in both crypt and villus enterocytes in normally nourished but not malnourished resected animals. Villus apoptosis correlated with villus height.

CONCLUSIONS

Intestinal adaptation is impaired by a 25% reduction in enteral nutrients, confirming that both the route and quantity of nutrient intake are important in this process. Both enterocyte production and loss via apoptosis are decreased by reduced enteral intake and malnutrition after resection. The correlation between villus height and apoptosis suggests that the reduced apoptosis reflects the smaller enterocyte number in malnourished animals rather than an adaptive response to maintain intestinal structure.

Prospective evaluation of faecal fatty acid excretion in short bowel syndrome in newborns

Short bowel syndrome (SBS) in the newborn results in limited intestinal absorptive capacity, leading especially to fatty acid (FA) malabsorption. It is unknown whether adaptation occurs in time in FA absorption, and whether this adaptation is chain-length dependent. The aid of the present study was to prospectively evaluate FA absorption and excretion during SBS in the newborn. Twenty-one neonates who underwent small bowel resection (of variable length) for various reasons (necrotizing enterocolitis, intestinal atresia, meconium peritonitis, cloacal extrophy, etc) were studied. Eight neonates had SBS, defined as a small bowel remnant of less than 50% of the original small bowel length related to gestational age. The mean remaining small bowel length in the SBS group was 34% (24% to 42%). The non-SBS control group consisted of 13 neonates who had only minor small bowel resections. The mean remaining bowel length for the non-SBS group was 95% (70% to 100%). The results show that the total fractional excretion of FA (FE-FA) at 2 weeks and 1, 2, 3, and 4 months postsurgery was 51% +/- 37%, 33% +/- 24%, 51% +/- 65%, 53% +/- 27%, and 7% +/- 2% in patients with SBS, versus 12% +/- 8%, 24% +/- 10%, 9% +/- 3%, 8% +/- 3% and 17% +/- 14% in the non-SBS controls, respectively (P < .05 by ANOVA). There appeared to be an amelioration in time in FA absorption, especially in the SBS group, after 3 months. FE-FA was chain-length related, being considerably less for C10 and C12 than for C14 and longer amounts. An amelioration of absorption occurred in the SBS patients, especially with the longer-chain FA. On the basis of the study data, the authors conclude that in the initial adaptation phase shorter chain lengths are better absorbed than longer chain lengths; however, in the latter FA group, substantial adaptation occurs with time.

Microvesiculation of the microvilli provides a membranous medium within the lumen during digestion

A hypothesis is presented which states that there is a membranous medium within the intestinal lumen which occurs during digestion. The medium is thought to be generated by the microvesiculation of the microvilli.

Morphologic and cytoproliferative patterns of duodenal mucosa in two patients after long-term total parenteral nutrition: changes with oral refeeding and relation to intestinal resection

The morphologic and cytoproliferative patterns of the duodenal mucosa of two adult patients, one of whom had a short bowel, were evaluated after more than 2 months of postoperative total parenteral nutrition and 2 and 12 months after the resumption of oral alimentation. Morphometric analysis was performed on routinely processed duodenal biopsies. Cell proliferation was evaluated by means of in vitro bromodeoxyuridine uptake. The results were compared with those obtained in five healthy controls. After parenteral nutrition, patients showed significantly lower villus height and crypt depth than those of controls and a normal bromodeoxyuridine labeling index. After 2 months of refeeding, villus and crypt returned to normal, and the labeling index was increased. After 12 months of oral refeeding, labeling index, villus height, and crypt depth were similar to those of controls. The patient with the short bowel showed a number of cells per unit length of villus and crypt significantly greater than those of the controls and of the patient who underwent shorter intestinal resection. In human duodenal mucosa, (1) hypoplasia develops after long-term total parenteral nutrition; (2) mucosal recovery occurs through an increased cell proliferation after oral refeeding; and (3) extensive small bowel resection determines the development of relative hyperplasia.

Trophic effects of neurotensin in massive bowel resection in the rat

The trophic effect of the administration of exogenous neurotensin on the intestinal mucosa was studied in rats following an 80% bowel resection. Villus length and mucosal DNA content were assessed in the jejunal and ileal mucosa of the remnant intestine 14 days after resection. The data obtained in an 80% resected control group (80% group) and an experimental group receiving an infusion of neurotensin (300 micrograms/kg/day) for 14 days subcutaneously (80% + NT group) were compared. The results indicate that the administration of exogenous neurotensin (80% + NT) increases villus length (jejunum: 920 +/- 77 vs 861 +/- 25 microns and ileum length: 975 +/- 23 vs 875 +/- 99 microns) to an extent greater than that observed in the 80% resected group not receiving exogenous neurotensin. The levels of mucosal DNA per milligram of protein increased significantly in both groups but was paradoxically less in the 80% + NT group than in the 80% resection group (jejunum: 8.12 +/- 0.56 vs 10.18 +/- 0.80; ileum: 8.63 +/- 0.43 vs 10.05 +/- 0.46). These data suggest that the administration of exogenous neurotensin to the rat potentiates the growth of intestinal villi and accelerates the intestinal trophic response seen following massive bowel resection. The increase in circulating enteroglucagon levels noted after neurotensin administration (80% + NT: 547 +/- 48 pg/ml vs 80%: 341 +/- 41 pg/ml) suggests that some of the trophic effects of neurotensin may be mediated, at least in part, by enteroglucagon. These data also suggest a potential role for the use of neurotensin in the initial treatment of individuals with short bowel syndrome.

Small intestinal mucosa changes, including epithelial cell proliferative activity, of children receiving total parenteral nutrition (TPN)

We examined the small intestinal histology disaccharidase activities as well as the incorporation of [3H]thymidine into DNA of biopsies maintained in organ culture from seven children (ages 9 months to 5 years) receiving total parenteral nutrition (TPN). Three children suffered from inflammatory bowel disease and received TPN for one month (short term). Four required long-term TPN (> 9 months) for short-bowel syndrome. DNA was extracted from the samples following serial precipitation with perchloric acid. Results were compared to those from 22 age-matched children investigated for abdominal pain or chronic diarrhea. Short-term TPN resulted in slightly lower lactase, sucrase, and palatinase activities that were not statistically different from controls. Long-term TPN resulted in focal mild villus atrophy and a decrease in disaccharidase activity in two patients. Biopsies from long-term TPN patients incorporated less thymidine compared to those of controls (P < 0.001) when data was expressed per total biopsy (3.6 +/- 1.1 vs. 8.4 +/- 1.1 fmol) or per milligram of tissue (1.0 +/- 0.12 vs 2.7 +/- 0.7 fmol). The above data are in general agreement with the hypoplastic effect of TPN in animals. However, in children, much longer periods of TPN are required to realize the changes.

Principles of nutrition therapy for short-bowel syndrome

Short-bowel syndrome is characterized by maldigestion, malabsorption, dehydration, electrolyte abnormalities, and both macronutrient and micronutrient deficiencies. Nutritional and hydration status are difficult to maintain without the provision of specialized nutrition support when more than 75% of the small intestine has been resected. Each patient's response to small-bowel resection is unique; therefore, the type of therapy must be tailored to each individual's bowel resection, complications that ensue, and specific nutrient needs. Clinical management should be guided by principles of nutrition assessment and treatment of nutrient deficiencies as well as routine monitoring of the patient's clinical course and response to therapy.

Short-chain fatty acids, lactate, and ammonia in ileorectal and ileal pouch contents: a model of cecal fermentation

Fecal concentrations of total short-chain fatty acids were normal in 16 patients with ileorectal anastomoses (mean +/- SEM, 99.7 +/- 10.3 mmol/L) and 28 patients with ileal pouch-anal anastomoses (138.8 +/- 8.5 mmol/L) and did not differ from those in 14 healthy noncolectomized controls (130.7 +/- 12.6 mmol/L). Acetate:propionate:butyrate:isobutyrate+valerate+isovalerate ratios were similar in the ileorectum (71:12:12:5%) and in the colorectum (66:14:13:7%) of healthy noncolectomized controls, whereas the concentration of acetate was increased at the expense of the polypeptide-derived isobutyrate, valerate, and isovalerate in the ileal pouch (77:12:11:1%). Ammonia was accordingly significantly diminished in ileal pouch contents (28.8 +/- 3.2 mmol/L vs 45.2 +/- 4.1 mmol/L in controls) in contrast to concentrations in ileorectal contents (36.2 +/- 5.3 mmol/L). Concentrations of lactate were normal and low. Twenty-four-hour productions of total short-chain fatty acids in 16.6% fecal homogenates from both groups of patients were normal. Addition of saccharides (eg, glucose, starch, pectin, ispaghula husk) increased the production of acetate, propionate, and butyrate and decreased the production of ammonia and isobutyrate, valerate, and isovalerate, which was increased in homogenates with albumin added. This pattern of substrate fermentation was similar in homogenates from ileal pouch, ileorectum, and control colorectum. In conclusion, the concentrations of short-chain fatty acids, lactate, and ammonia indicate that ileorectal fermentation resembles normal colorectal fermentation in noncolectomized healthy individuals, whereas the fermentation in ileal pouch contents seems to be more carbohydrate predominated.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related changes in duodenal adaptation after distal small bowel resection in rat

Two groups of male Fisher 344 rats (young: 4 months old; aged: 25 months old) underwent either 70% distal small bowel resection or sham operation (small bowel transection). Rats from each treatment group of each age were sacrificed on the 10th (N = 15: young rats; N = 13: aged rats) or 20th (N = 15: young; N = 13: aged) postoperative day (POD), and the duodenal mucosa was weighed and assayed for DNA, RNA, and protein contents, as well as for specific activities of the disaccharidase, sucrase, maltase, and lactase. Compared to the sham operation, distal small bowel resection significantly increased DNA by 48%, RNA by 122%, and protein by 75% in young rats and DNA by 40%, RNA by 92%, and protein by 71% in aged rats on the 20th POD. Both young and aged rats showed similar adaptive hyperplasia on the 10th POD. On the 20th POD after distal small bowel resection, specific activities of all tested enzymes were significantly increased in young rats (sucrase +86%, maltase +110% and lactase +64%), but showed no significant changes in aged rats. These findings suggest that the duodenum of aged rats may have sufficient proliferative potential to respond to distal small bowel resection, but that the mechanisms governing return of function in response to distal small bowel resection are inhibited in aged rats, compared to those mechanisms in the young.

Nutrient-independent increases in proglucagon and ornithine decarboxylase messenger RNAs after jejunoileal resection

To assess potential mediators of adaptive bowel growth, ileal proglucagon messenger RNA (mRNA) ornithine decarboxylase (ODC) mRNA, plasma enteroglucagons, and plasma glucagonlike peptide I (GLP-I) were analyzed in rats soon after jejunoileal resection or control transection. Analyses were performed before and after refeeding to establish whether responses are nutrient dependent. The elevation of ileal proglucagon and ODC mRNAs within 12 hours after resection and before refeeding shows a nutrient-independent component of the adaptive response. The onset of adaptive growth of the ileum required luminal nutrient but occurred very rapidly, within 4 hours of refeeding. The onset of adaptive growth was accompanied by transient elevation of ileal ODC mRNAs. Ileal proglucagon mRNA and plasma GLP-I levels were also elevated, and these increases were sustained up to 8 days after resection. These early and sustained increases in proglucagon mRNA and plasma GLP-I indicate that in addition to the enteroglucagons, other intestinal proglucagon-derived peptides must be considered as potential mediators of adaptive growth after jejunoileal resection.

Effects of pectin and cellulose on fat absorption after massive small-bowel resection in weanling rats

The effects of pectin and cellulose on fat absorption after massive small-bowel resection were studied in rats. Weanling Wistar rats underwent 80% resection of the small intestine with gastrostomy, and fat emulsion labeled with 14C-linoleate was given via a gastrostomy tube for the fat absorption test on the 10th postoperative day. They were classified into three groups by diet as follows: E group, a fiber-free, chemically defined diet (CDD); EP group, CDD with 2% pectin; and EC group, CDD with 2% cellulose. The cumulative and hourly output of 14C in the expired air, the absorption rate of 14C in the intestine, and the metabolic utilization rate of 14C were calculated. The cumulative 14CO2 output was significantly lower in the EC group than in the E and EP groups. However, there was no significant difference in the 14CO2 output between the E and EP groups. The highest hourly 14CO2 output in the E and EP groups was observed during the first 2 hours. However, in the EC group, this fluctuated at low levels. No significant difference in the 1-14C-linoleate absorption rate was observed between the E and EP groups, whereas it was significantly lower in the EC group than in the E and EP groups. The metabolic utilization rate of 1-14C-linoleate showed no significant difference among the three groups. These data suggest that an addition of pectin to CDD does not impair small intestinal absorption of 1-14C-linoleate after massive small-bowel resection, and an addition of cellulose decreases absorption of 1-14C-linoleate.

Intestinal absorption of free oral hyperalimentation in the very short bowel syndrome

Ten adult ambulatory patients with the nonactive digestive disease short bowel syndrome were prospectively studied to quantitatively assess their free oral intake and their net digestive absorption of total calories, fat, protein, and carbohydrate during a 3-day period at least 6 months after a resection. The remaining portions of small bowel had a mean length of 75 cm (range, 0-200 cm); the remaining colon lengths had a mean of 67% of normal (range, 0%-100%). The experimental diets were formulated according to a home dietary inquiry. During the study period, pooled intakes and digestive losses were measured for total calories, fat, and protein using the bomb calorimetry, Van de Kamer, and Kjeldahl techniques, respectively. The ingested diet provided 58 +/- 14 kcal.kg-1.day-1 (mean +/- SD) and consisted of 46% carbohydrate, 31% fat, and 23% protein. Net digestive absorption was 67% +/- 12% for total calories, 79% +/- 15% for carbohydrate, 52% +/- 16% for fat, and 61% +/- 19% for protein. The larger net digestive absorption of carbohydrate (P less than or equal to 0.004) compared with fat and protein suggests salvage of colonic cholesterol in short bowel syndrome patients. It is concluded that these patients with the short bowel syndrome adapted to a hypercaloric, hyperprotein diet to compensate for increased fecal losses and that this hyperphagia does not seem to have impaired their net digestive absorption.

Immediate enteral feeding in burn patients is safe and effective

Recent animal studies indicate that immediate enteral feeding may be beneficial in patients with major burns. Yet, largely because of the fear of complications, immediate enteral feeding is not commonly performed in patients with major burns until after the resuscitation period. The purpose of this study was to evaluate the safety and efficacy of immediate enteral tube feedings in patients with burns larger than 20% of their body surface area. The daily intake of enteral feedings begun immediately (less than 6 hours) after burn was measured during the first 7 days after burn in 106 consecutive patients with a mean +/- SD burn size of 40% +/- 21%. The incidence of complications related to enteral feeding was low; aspiration pneumonia did not occur. Vomiting was the major complication observed and occurred 21 times in 16 patients during the 745 study days (2.8% daily incidence). The mean number of calories absorbed enterally increased daily and met the patient's calculated resting energy expenditure (REE) on day 3 after burn (99% +/- 7% REE). The results of this study indicate that immediate enteral feeding is a safe and effective method of delivering nutritional support to burn victims with major burns.

The effect of intestinal anastomosis on gut growth and maturation

We evaluated the effect of intestinal anastomosis without resection on gut morphometry (muscle thickness, villus height, and crypt depth), growth indices (DNA, protein, and protein:DNA ratio), and disaccharidase activity (maltase, sucrase, and lactase) in the growing animal. A group of 10 weanling Sprague-Dawley rats at 21 days of age was subjected to intestinal transection and anastomosis in the upper jejunum, 10 cm distal to the ligament of Treitz. A second group of 10 similar rats was used as a control group. All rats were fed a regular diet and kept under the same conditions. They were sacrificed 2 weeks later. Body weight, intestinal weight, and intestinal length measurements were obtained. The intestine was divided into two sections: preanastomotic (section A) and postanastomotic (section B) in the surgery group and equivalent sections A and B in the control group. Specimens were subjected to morphometric evaluation and mucosal scrapings for biochemical analysis. Despite significant weight gain in the control group, there were no differences in intestinal length, intestinal weight, and mucosal weight between the two groups. Muscle thickness, villus height, and crypt depth were significantly increased in the preanastomotic segment. Protein and DNA were also higher in the preanastomotic segment, but the protein:DNA ratio was less affected. There was significantly decreased enzymatic activity in the preanastomotic segment. Intestinal anastomosis has a significant effect on gut growth and maturation in the growing animal and may have important implications in the postoperative management of newborns and infants following intestinal surgery.

The effect of pinealectomy and jejunal loop diversion on rat small bowel crypt cell kinetics

Previously, it was found that diversion of an isolated loop of jejunum into the colon was associated with a significantly diminished crypt cell proliferation rate in the isolated loop, probably principally because of the diminished amount of nutrient available to the diverted mucosa. It has also been shown previously that removal of the pineal gland is associated with a considerable increase in the jejunal crypt cell mitotic rate. In the present investigation it was found that following pinealectomy, whilst the rise in crypt cell proliferation elsewhere in the rat small intestine was maintained at the expected level, the mitotic rate in the crypts of an isolated jejunal loop attached to the colon was also increased to a similar level, despite the fact that this isolated loop was in contact with a considerably diminished level of luminal nutrients. Thus, the expected hypoproliferative effects of jejunal isolation were overridden by the hyperproliferative effects of pinealectomy and the effects of pinealectomy appeared to be independent of the particular changes in luminal environment produced in this experiment. The significance of these findings is discussed in the light of the available literature.

Effect of parenteral nutrition supplemented with short-chain fatty acids on adaptation to massive small bowel resection

After massive small bowel resection, total parenteral nutrition (TPN) is prescribed to maintain nutritional status. However, TPN reduces the mass of the remaining intestinal mucosa, whereas adaptation to small bowel resection is associated with increased mucosal mass. Short-chain fatty acids (SCFAs) have been shown to stimulate mucosal cell mitotic activity. This study determined whether the addition of SCFAs to TPN following small bowel resection would prevent intestinal mucosal atrophy produced by TPN. Adult rats underwent an 80% small bowel resection and then received either standard TPN or TPN supplemented with SCFAs (sodium acetate, propionate, and butyrate). After 1 wk, jejunal and ileal mucosal weights, deoxyribonucleic acid, ribonucleic acid, and protein contents were measured and compared with the parameters obtained at the time of resection. Animals receiving TPN showed significant loss of jejunal mucosal weight, deoxyribonucleic acid, ribonucleic acid, and protein and ileal mucosal weight and deoxyribonucleic acid after small bowel resection, whereas animals receiving SCFA-supplemented TPN showed no significant change in the jejunal mucosal parameters and a significant increase in ileal mucosal protein. These data demonstrate that SCFA-supplemented TPN reduces the mucosal atrophy associated with TPN after massive bowel resection and thys may facilitate adaptation to small bowel resection.

The effects of diet on the residual small intestine following massive resection

The midportions of rat small intestines were resected by 90 per cent, and the residual intestines studied for the effects of diet on mucosal morphology, nutrition and gastrointestinal hormones. Groups of rats were fed chow, an elemental diet (ED), or an ED + dietary fiber (EDF) for 1 or 3 weeks. Nonresected rats which were fed chow or ED for 3 weeks were used as controls. Nutritional parameters, such as concentrations of serum total protein, albumin and transferrin were favorable but gain in body weight was not. The parameters indicated that resected rats fed EDF fared better than resected rats fed ED. Mucosal villous height in the residual jejunum, similar in all the resected groups after 1 week, was significantly increased in the resected rats fed chow or EDF after 3 weeks, but did not differ between 1 and 3 weeks in the resected rats fed ED. Changes in the number of villous epithelial cells and villous width were also examined. The level of plasma enteroglucagon was high in the rats fed chow or EDF after both 1 and 3 weeks, and was positively correlated with the increases in villous height. Levels of serum gastrin were not affected by dietary change. Luminal nutrients were significantly associated with the adaptive changes in the mucosa of the residual intestine, and mucosal morphology was also considerably influenced by dietary change.

Role of food in appearance of growth-stimulating activity in rat proximal intestine after small-bowel resection

The oral intake of food is important for the observed compensatory hyperplasia in the remnant small intestine after resection but the molecular events governing this response are not known. Peptides, of molecular weight 4500 and 1000 daltons, present in the the proximal intestine for 96 hr after resection and mitogenic for the intestine have been implicated in the adaptive hyperplasia. In this study, the role of food in the appearance of these peptides was assessed. The results show that after resection, rats nourished intravenously demonstrated neither a significant adaptation nor any of the detectable mucosal mitogens, whereas the rats nourished intragastrically demonstrated both hyperplasia and the mitogenic peptide(s). The association of the hyperplasia with the appearance of the mitogenic peptides in the small intestine suggests that they are important in the mechanism by which food promotes the adaptive hyperplasia.

Use of a 3T3 cell growth factor assay for the delineation and characterization of humoral trophic factors involved in intestinal adaptation in the rat

Indirect evidence has suggested that circulating trophic factors are involved in intestinal adaptation. A 3T3 fibroblast cell culture system was used to more directly delineate the presence of such factors. Rats were divided into four groups: C-unop, those undergoing no surgery; S, those in which a dorsal slit was made; C-op, those in which the peritoneum was incised; and R, those undergoing 80% intestinal resection. At the time of death at 24 h, 1 wk, and 2 wk postoperative, stimulation of DNA synthesis in the 3T3 cells was noted after incubation with platelet-free plasma from the C-op and R groups, and simultaneously an increase in ileal DNA specific activity occurred. Characterization of the plasma fraction with growth factor activity revealed it to have a molecular weight of greater than 6000 but less than 14,000. The factors were resistant to reduction with dithiothreitol, and were partially inactivated by heating to 60 degrees C. The use of a 3T3 cell growth factor assay system now makes it possible to further characterize circulating factors involved in intestinal adaptation.