Octreotide diminishes luminal nutrient transport activity, which is reversed by epidermal growth factor

Enhancement of Colonic Absorptive Function after the Massive Resection of the Small Intestine Based on the Creation of an Artificial Colonic Valve

The colon can have an absorptive function similar to that of the small intestine after the massive resection of the small bowel. To improve colonic absorptive function, we created a valve in the colon (artificial colonic valve, ACV). ACVs were created in 20 rats that had 80 percent of their small intestine resected, with an observation time of 30 weeks. The ACV rats were compared with those in the non-operated control group, the short bowel syndrome (SBS) group and the colon interposition (CI) group. The ACV rats were much heavier than those in the control group, SBS group and CI group. In terms of histology and the levels of α-amylase and the Na⁺-dependent bile salt transporter, the absorptive function of the colons before the valves resembled that of the small intestine. The colonic absorptive function was more obvious in ACV rats than in CI rats. An ACV can enhance colonic absorptive function after the massive resection of the small intestine. The colonic absorptive function of ACV rats was better than that of the rats in the CI group.

Anastomotic ulcers in short bowel syndrome: New suggestions from a multidisciplinary approach

BACKGROUND AND AIMS

Anastomotic ulceration (AU) is a rare potential life-threatening complication that may occur after intestinal resection. The diagnosis is often delayed after a long-lasting history of refractory anemia. The pathogenesis remains unknown and there are no established therapies. The aim of the study was to analyze the medical history of children with short bowel syndrome (SBS) who were experiencing AU.

METHODS

Records of SBS children were retrospectively reviewed. Demographics, baseline characteristics, presentation, diagnosis and treatment of AU cases were analyzed.

RESULTS

Eight out of 114 children with SBS were identified as having AU. Mean gestational age was 32.5weeks. Underlying diseases were: 5 necrotising enterocolitis, 2 gastroschisis and 1 multiple intestinal atresia. The mean age at AU diagnosis was 6.5years (diagnosis delay of 35months). All but 2 patients had AU persistency after medical treatment. Endoscopic treatment (2 argon plasma coagulation; 1 platelet-rich fibrin instillation; 2 endoscopic hydrostatic dilations) was effective in 3 out of 5 children. Surgery was required in 3 patients.

CONCLUSIONS

Severe bowel ischemic injury, especially in preterm infant, could predispose to AU development. Medical treatment showed discouraging results. We firstly described that different endoscopic treatment could be attempted before resorting to further surgery.

LEVEL OF EVIDENCE

IV.

Pharmacologic management of diarrhea in patients with short bowel syndrome

Diarrhea associated with short bowel syndrome (SBS) can have multiple etiologies, including accelerated intestinal transit, gastric acid hypersecretion, intestinal bacterial overgrowth, and malabsorption of fats and bile salts. As a result, patients may need multiple medications to effectively control fecal output. The armamentarium of antidiarrheal drugs includes antimotility agents, antisecretory drugs, antibiotics and probiotics, bile acid-binding resins, and pancreatic enzymes. An antidiarrheal regimen must be individualized for each patient and should be developed using a methodical, stepwise approach. Treatment should be initiated with a single first-line medication at the low end of its dosing range. Dosage and/or dosing frequency can then be slowly escalated to achieve maximal effect while minimizing adverse events. If diarrhea remains poorly controlled, additional agents can be incorporated sequentially. If modification of the regimen is required, a single medication should be altered or exchanged at a time. After each adjustment of the regimen, sufficient time should be permitted to fully assess response (≥3-5 days) before initiating additional changes. SBS-associated malabsorption is a major obstacle to optimization of an antidiarrheal regimen because drug absorption is impaired. Patients may benefit from high dosages and/or frequent dosing intervals, liquid preparations, or nonoral routes of drug delivery. Although the diarrhea associated with SBS can be debilitating, effective pharmaceutical management has the potential to substantially improve health outcomes and quality of life for these patients.

Novel therapies for the management of short bowel syndrome in children

Short bowel syndrome (SBS) is the most common cause of intestinal failure in children. It is defined as the inability to maintain adequate nutrition enterally as a result of a major loss of the small intestine. SBS is a life-threatening entity associated with potential significant morbidity and mortality. The etiology in the pediatric age group includes necrotizing enterocolitis (32%), atresia (20%), volvulus (18%), gastroschisis (17%), and aganglionosis (6%). It is characterized by substrate malabsorption, electrolyte imbalance, intestinal bacterial overgrowth, steatorrhea, and weight loss. Current medical management includes parenteral nutrition, progressive feeds as tolerated, various medications, and surgical manipulations. However, frequently this management is not successful in achieving the goal of attaining normal growth and development without parenteral nutrition. It has been known for decades that there is a normal physiologic response of the residual intestine to massive bowel resection referred to as intestinal adaptation. The mechanisms that control this process are unknown. Unfortunately, intestinal adaptation and the current management are not always successful. As a result of new knowledge regarding the pathophysiology of SBS over the past two decades, several novel strategies have been developed in experimental animal models as well as limited clinical trials in infants and children. They can be divided into several categories that potentially influence intestinal (1) absorption, (2) secretion, (3) motility, and (4) adaptation. More recently, newer modalities have been studied including small intestine transplantation, and the use of specific intestinal growth factors. Ultimately, tissue and organ engineering will become the treatment for infants and children with SBS.

Dietary and medical management of short bowel syndrome in adult patients

Resection of the small bowel can lead to malabsorption of fluid, electrolytes, minerals, and other essential nutrients, resulting in malnutrition and dehydration. Individualized and tailored nutritional management for patients with short bowel syndrome (SBS) helps to optimize intestinal absorption, leading to nutritional independence such that a patient can resume as normal a lifestyle as possible. Parenteral nutrition (PN), used to supply the required nutrients following resection, is associated with a number of complications affecting patient morbidity and mortality. Attempts should be made to wean patients from PN to an oral diet as soon as possible. Dietary management is complex and needs to be individualized for each patient on the basis of his or her specific gastrointestinal anatomy, underlying disease, and lifestyle. In addition to nutrient intake, management of SBS also requires appropriate oral rehydration, vitamin and mineral supplementation, and pharmacotherapy. Several medications provide a useful adjunctive function to dietary intervention, including antidiarrheal agents, H2 antagonists and proton pump inhibitors, pancreatic enzymes, somatostatin analogs, antimicrobials, and trophic factors.

ATB0/ASCT2 expression in residual rabbit bowel is decreased after massive enterectomy and is restored by growth hormone treatment

Two weeks after 70% enterectomy, glutamine (Gln) transport is downregulated in rabbit residual bowel due to a decrease in system B(0) activity. Providing epidermal growth factor (EGF) and growth hormone (GH) restores Gln transport by increasing systems A and B(0,+) activities. We hypothesized that changes in Na(+)-dependent broad-spectrum neutral amino acid transporter (ATB(0)/ASCT2) protein and mRNA expression correlate with system B(0) activity. New Zealand White rabbits underwent 70% jejunoileal resection or no resection. Resected rabbits immediately received parenteral EGF, GH, both, or neither agent for 2 wk. Tissues harvested from jejunum, ileum, and colon were subjected to Western and Northern blot analyses for ATB(0)/ASCT2 protein and mRNA. In all tissues, ATB(0)/ASCT2 mRNA was reduced by approximately 50% in resected rabbits compared with nonresected controls. Similar reductions in protein amount occurred in the ileum and cecum. None of the growth factor treatments restored ATB(0)/ASCT2 protein, but GH treatment increased ATB(0)/ASCT2 mRNA abundance 250% in the residual ileum. Because changes in the ATB(0)/ASCT2 protein amount paralleled those in the system B(0) activity in this model, it is likely that this is the protein responsible for this transport system. The increase in mRNA abundance in rabbits treated with GH for 2 wk may be a harbinger of subsequent increases in transporter protein and activity. Unlike reported upregulation of transporters in human colon after small bowel resection, ATB(0)/ASCT2 protein and mRNA expression in rabbit colon are decreased, suggesting different regulatory pathways.

Growth factor regulation of enterocyte nutrient transport during intestinal adaptation

BACKGROUND

Intestinal adaptation occurs in response to injury or alteration in nutrient availability. It is both morphologic and physiologic in nature and can be mediated by growth factors and nutrients. Pathologic conditions such as short-bowel syndrome and inflammatory bowel disease lead to derangements in nutrient absorption that may exceed the body's regenerative and adaptive capacity. Failure to fully adapt often results in long-term dependence on parenteral nutrition, leading to decreased quality of life and excessive medical expenses. The therapeutic use of appropriate growth factors may increase the adaptive capabilities of the gut.

DATA SOURCE

Medline and current literature review.

CONCLUSIONS

The major known nutrient transporters present in the gut and the mechanisms by which growth factors alter transport activity during intestinal adaptation are summarized. Growth factors have the potential to improve nutrient absorption in some bowel diseases.

Nutritional management of short bowel syndrome in adults

Short bowel syndrome (SBS) comprises the sequelae of nutrient, fluid, and weight loss that occurs subsequent to greatly reduced functional surface area of the small intestine. Signs and symptoms of SBS include electrolyte disturbances; deficiencies of calcium, magnesium, zinc, iron, vitamin B12, or fat-soluble vitamin deficiency; malabsorption of carbohydrates, lactose, and protein; metabolic acidosis, gastric acid hypersecretion; formation of cholesterol biliary calculi and renal oxalate calculi; and dehydration, steatorrhea, diarrhea, and weight loss. Thorough nutritional management is the key factor in achieving an optimal outcome in SBS. Total parenteral nutrition is necessary in the early stages, as is replacement of excess fluid and electrolyte losses. Nutritional management of SBS has traditionally been divided into three phases: an acute phase when total parenteral nutrition is usually begun, an adaptation phase, and a maintenance phase. Recommendations regarding the need for parenteral nutrition vary depending on the presence or absence of certain factors: the ileocecal valve, jejunum, and functional colon. Patients with residual small bowel length of 100 cm or less usually require the administration of parenteral nutrition at home with good results. The total parenteral nutrition diet should consist of a majority of calories from fat, followed by protein, and the remaining as carbohydrates. Vitamins, minerals, and trace elements should also be added accordingly. Although total parenteral nutrition is initially necessary, treatment goals should focus on early transition to enteral nutrition followed by oral feeds. Other recent advances in the medical management of SBS include pharmacologic treatment and the use of specific nutrients and growth factors to stimulate intestinal absorption and adaptation. Both animal studies and clinical trials in humans have shown much promise in supplementation with growth factors and hormones. This strategy is likely to play a greater role in the treatment of SBS in the future.

Pharmacotherapy and growth factors in the treatment of short bowel syndrome

A review of the pharmacologic substances and growth factors that have been studied experimentally and administered clinically for the management of short bowel syndrome is presented. The medical management of short bowel syndrome is multifaceted. In the acute phase, efforts focus on fluid and electrolyte management and the reduction of gastric acid output. As enteral feeding is initiated, antimotility and antisecretory agents may be effective in reducing gastrointestinal losses. Additional modalities of management, including nutrients and growth factors, may be directed at maximizing absorptive function beyond that which occurs with intestinal adaptation. Continued research aimed at further elucidating the process of intestinal adaptation may allow us to use the various peptides and hormones that act as growth factors for the bowel mucosa. Knowledge gained from these studies combined with gene therapy techniques will result in the permanent enhancement of intestinal function beyond the normal adaptation process, eliminate the dependence on total parenteral nutrition, and avoid the need for intestine transplantation.

Growth factors regulation of rabbit sodium-dependent neutral amino acid transporter ATB0 and oligopeptide transporter 1 mRNAs expression after enteretomy

BACKGROUND

Sucessful intestinal adaptation after massive enterectomy is dependent on increased efficiency of nutrient transport. However, midgut resection (MGR) in rabbits induces an initial decrease in sodium-dependent brush border neutral amino acid transport, whereas parenteral epidermal growth factor (EGF) and growth hormone (GH) reverse this downregulation. We investigated intestinal amino acid transporter B0 (ATB0) and oligopeptide transporter 1 (PEPT 1) mRNA expression after resection and in response to EGF and/or GH.

METHODS

Rabbits underwent anesthesia alone (control) or proximal, midgut, and distal resections. Full-thickness intestine was harvested from all groups on postoperative day (POD) 7, and on POD 14 from control and MGR rabbits. A second group of MGR rabbits received EGF and/or GH for 7 days, beginning 7 days after resection. ATB0 and PEPT 1 mRNA levels were determined by Northern blot analysis.

RESULTS

In control animals, ileal ATB0 mRNA abundance was three times higher than jejunal mRNA, whereas PEPT 1 mRNA expression was similar. By 7 and 14 days after MGR, jejunal ATB0 mRNA abundance was decreased by 50% vs control jejunum. A 50% decrease in jejunal PEPT 1 message was delayed until 14 days after MGR. Treatment with EGF plus GH did not alter ATB0 mRNA expression but doubled PEPT 1 mRNA in the jejunum.

CONCLUSION

The site of resection, time postresection, and growth factors treatment differentially influence ATB0 and PEPT 1 mRNA expression. Enhanced sodium-dependent brush border neutral amino acid transport with GH plus EGF administration is independent of increased ATB0 mRNA expression in rabbit small intestine after enterectomy.

Interactions between nutrients and peptide growth factors in intestinal growth, repair, and function

Several lines of evidence demonstrate that general nutritional status, specific nutrients (eg, zinc, glutamine), and certain trophic growth factors (eg, growth hormone, insulin-like growth factor I, keratinocyte growth factor, and glucagon-like peptide-2) have important interactions relevant for intestinal growth and function. Adequate nutritional status is critical for endogenous growth factor synthesis in the gut and other tissues and is an important mediator of organ responsiveness to exogenous growth factor administration. Both endogenously synthesized and exogenously administered growth factors upregulate nutrient uptake and utilization by gut mucosa, skeletal muscle, and other organs. Emerging data from both animal and human studies indicate that combinations of selected growth factors and specific nutrients may improve the growth, adaptation, and repair of the intestinal mucosa. Additional studies to determine basic mechanisms of nutrient-growth factor interactions and the safety and efficacy of treatment with combinations of specific nutrients and recombinant growth factors are needed. Results of these investigations should define new methods for support of the intestinal tract during short bowel syndrome (SBS), catabolic illness, and malnutrition.

Small bowel adaptation is dependent on site of massive enterectomy

BACKGROUND

Changes in amino acid transport after massive enterectomy occur in a nutrient-dependent fashion and may affect long-term outcome. Epidermal growth factor (EGF) can enhance nutrient transport and a defective epidermal growth factor receptor (EGF-R) has been noted to attenuate adaptation. Most animal studies, however, have examined only a single site of resection. This does not mimic the clinical situation where disease dictates the site of resection leading to proximal, middle, or distal enterectomies. We hypothesize that the site of massive enterectomy will alter nutrient transport and EGF-R levels in the residual gut.

MATERIALS AND METHODS

New Zealand White rabbits were randomized to control, midgut division, or 70% resection (proximal, midgut, or distal). After 1 week, sodium-dependent transport of glucose, glutamine, alanine, and leucine into brush border membrane vesicles was quantitated. EGF-R protein was determined by Western blot analysis.

RESULTS

At baseline, amino acid transport was greater in ileum than jejunum. Surgery alone elevated glutamine and leucine jejunal transport by 130 and 97%, respectively, over controls (P < 0.05). Midgut resection increased jejunal glutamine transport 61% over control (P < 0.05). In contrast, distal resection increased jejunal alanine transport by 150% over controls with no change in glutamine (P < 0.05). After midgut resection, EGF-R was significantly greater (124%) in ileum then in jejunum in whole mucosa homogenates. Proximal resection significantly lowered ileal EGF-R compared to that seen in midgut resected residual ileum.

CONCLUSIONS

Site of massive resection is important in determining postoperative changes in nutrient transport and EGF-R.

Growth factors and the gastrointestinal tract

This paper reviews areas of interest in gut mucosal growth factor physiology. Several epidermal growth factor (EGF)-like peptides (EGF, transforming growth factor [TGF]-alpha, heparin-binding EGF-like peptide, amphiregulin, and betacellulin) have been identified in the gut, EGF is produced by the salivary glands and is present in milk. It may act on the mucosa from the lumen as a surveillance peptide promoting mucosal repair. A stem-cell-derived "ulcer-associated cell lineage" develops adjacent to ulcers and produces EGF, which may play a role in ulcer healing. TGF-alpha is expressed by villus enterocytes and may have an important role in mucosal healing. The Trefoil peptides (pS2, spasmolytic polypeptide, intestinal trefoil factor) are protease resistant molecules secreted by mucin cells throughout the gut, with a role in mucosal healing. The TGF-beta family inhibit cell proliferation, and promote cell differentiation. TGF-beta has a gradient of expression along the crypt villus axis, with maximum production at the villus tip. It is suspected that it may prevent cell proliferation and support differentiation of villus enterocytes. Hepatocyte growth factor is a multifunctional growth factor expressed in many tissues, including the gastrointestinal tract. It has a role in organogenesis. Intestinal adaptation is highly dependent on enteral nutrition, and it is likely that growth factors are involved in adaptation. Little is known, however, about interactions between nutrients and growth factors. Milk contains a range of potentially important growth factors. Their biological significance is uncertain, and this is an area of active research.

Epidermal growth factor and human growth hormone induce two sodium-dependent arginine transport systems after massive enterectomy

BACKGROUND

A combination of epidermal growth factor (EGF) and human growth hormone (hGH) after massive enterectomy induces a 400% increase in arginine transport in the remnant distal small intestine. The kinetic mechanism(s) responsible for enhanced arginine transport under these conditions is unknown.

METHODS

New Zealand White rabbits underwent 70% midjejunoileal resection. After a 1-week recovery period, animals received hGH (0.2 mg/kg/d IM), EGF (1.5 microg/kg/h SC), hGH + EGF, or vehicle (equal volume) for 7 days. Transport of tritiated arginine into brush border membrane vesicles prepared from distal remnant small intestinal mucosa was quantified in the presence and absence of a sodium gradient over a range of arginine concentrations (25 to 5000 micromol/L).

RESULTS

Eadie-Hofstee transformation of the kinetic data demonstrates two sodium-dependent arginine transport systems, comprising a high-capacity, low-affinity system and a low-capacity, high-affinity system. A combination of EGF and hGH significantly upregulates both the high-capacity (685%) and low-capacity (350%) maximum transport velocity (Vmax). Additionally, EGF alone significantly upregulates Vmax by 200% in the low-capacity system. There were no significant changes in transport affinity (Km) in either system.

CONCLUSIONS

There are two quiescent sodium-dependent arginine transport systems in the distal small intestine. A combination of EGF and hGH after massive enterectomy increase arginine transport by Vmax upregulation in both the high-capacity/low-affinity and low-capacity/high-affinity systems.

Epidermal growth factor and human growth hormone accelerate adaptation after massive enterectomy in an additive, nutrient-dependent, and site-specific fashion

BACKGROUND

After massive enterectomy (ME), remnant intestine undergoes compensatory adaptation. Epidermal growth factor (EGF) and human growth hormone (hGH) have each been shown to enhance total length small intestine nutrient transport after ME. This study aims to determine the differential effects of EGF and hGH on proximal and distal small intestinal remnants after ME.

METHODS

New Zealand white rabbits underwent 70% mid-jejunoileal resection. After 1 week, animals received hGH (0.2 mg/kg/day), EGF (1.5 micrograms/kg/hr), hGH + EGF, or vehicle (equal volume) for 7 days. Sodium-dependent uptake of glucose, glutamine, alanine, leucine, and arginine into brush border membrane vesicles was quantitated. Serum insulin-like growth factor-I concentrations as well as proximal and distal villus and microvillus heights were measured. IGF binding protein-3 and -4 mRNA expression was determined in full-thickness proximal and distal gut remnants.

RESULTS

Concomitant hGH and EGF treatment up-regulates glucose (100%), glutamine (80%), and leucine (60%) transport in the proximal remnant; alanine (150%) and arginine (400%) transport in the distal remnant; and microvillus height (25% to 35%) both proximally and distally. Serum IGF-I levels and gross villus heights were not different among groups.

CONCLUSIONS

Co-infusion of hGH and EGF accelerates intestinal adaptation after ME in an additive, nutrient-dependent, and site-specific fashion via enhanced nutrient transport as well as microvillus hypertrophy.

Human growth hormone induces system B transport in short bowel syndrome

BACKGROUND

After massive enterectomy, remnant intestine undergoes compensatory adaptation. A combination of human growth hormone (hGH) and a glutamine-enriched modified diet induces further adaptation in patients with short bowel syndrome (SBS) on long-term total parenteral nutrition. The specific actions of each component, however, are not well-defined.

METHODS

New Zealand White rabbits were randomized to control, sham operation, or SBS (70% midjejunoileal resection) groups and treated with either hGH or saline. Sodium-dependent uptake of glucose, glutamine, alanine, leucine, and arginine into brush border membrane vesicles was quantitated. Serum insulin-like growth factor-I (IGF-I) levels were determined by immunoradiometric assay. Mucosal mRNA expression of IGF-I and IGF binding protein 4 (IGFBP-4) was evaluated by northern blot analysis using rat cDNA probes.

RESULTS

Glutamine and leucine transports were 33 and 39% greater, respectively, in the hGH-treated versus saline-treated SBS group (P < 0.05), supporting induction of system B amino acid transport. This upregulation was due, in part, to an 88% increase in glutamine carrier capacity (Vmax) with no change in carrier affinity (Km). Both hGH treatment and SBS increased serum IGF-I levels without direct correlation with increased nutrient transport. IGFBP-4 mRNA expression in small bowel mucosa of saline-treated SBS animals was significantly greater than saline-treated unoperated control values. Mucosal IGFBP-4 mRNA was not significantly altered from control in the other study groups. IGF-I mRNA expression was not detected in mucosa, but weak hybridization was noted in rabbit liver.

CONCLUSIONS

Human growth hormone accelerates early adaptation in SBS by upregulation of system B carrier capacity. Serum IGF-I levels and mucosal IGF-I and IGFBP-4 mRNA expression did not directly correlate with this enhanced nutrient transport, suggesting that hGH might exert its adaptive effects by mechanisms that are independent from the IGF system in this model.