Short-chain fatty acid-supplemented total parenteral nutrition enhances functional adaptation to intestinal resection in rats

Intestinal microbiome in short bowel syndrome: diagnostic and therapeutic opportunities

PURPOSE OF REVIEW

The intestinal microbiome plays a strong, complementary role in the development and integrity of the intestinal epithelium. This biology is crucial for intestinal adaptation, particularly after the mucosal insults that lead to short bowel syndrome (SBS). The purpose of this review is to discuss relationships between the intestinal microbiota and the physiology of intestinal adaptation.

RECENT FINDINGS

We will address interactions between the intestinal microbiome and nutritional metabolism, factors leading to dysbiosis in SBS, and common compositional differences of the gut microbiome in SBS patients as compared to healthy controls. We will also discuss novel opportunities to expand diagnostic and therapeutic interventions in this population, by using our knowledge of the microbiome to manipulate luminal bacteria and study their resultant metabolites. As microbial therapeutics advance across so many fields of medicine, this review is timely in its advocacy for ongoing research that focuses on the SBS population.Our review will discuss 4 key areas: 1) physiology of the intestinal microbiome in SBS, 2) clinical and therapeutic insults that lead to a state of dysbiosis, 3) currently available evidence on microbiome-based approaches to SBS management, and 4) opportunities and innovations to inspire future research.

SUMMARY

The clinical implications of this review are both current, and potential. Understanding how the microbiome impacts intestinal adaptation and host physiology may enhance our understanding of why we experience such clinical variability in SBS patients' outcomes. This review may also expand clinicians' understanding of what 'personalized medicine' can mean for this patient population, and how we may someday consider our nutritional, therapeutic, and prognostic recommendations based on our patients' host, and microbial physiology.

MAFLD and Celiac Disease in Children

Celiac disease (CD) is an immune-mediated systemic disorder elicited by the ingestion of gluten whose clinical presentation ranges from the asymptomatic form to clinical patterns characterized by multiple systemic involvement. Although CD is a disease more frequently diagnosed in patients with symptoms of malabsorption such as diarrhea, steatorrhea, weight loss, or failure to thrive, the raised rate of overweight and obesity among general pediatric and adult populations has increased the possibility to diagnose celiac disease in obese patients as well. Consequently, it is not difficult to also find obesity-related disorders in patients with CD, including "metabolic associated fatty liver disease" (MAFLD). The exact mechanisms linking these two conditions are not yet known. The going assumption is that a gluten-free diet (GFD) plays a pivotal role in determining an altered metabolic profile because of the elevated content of sugars, proteins, saturated fats, and complex carbohydrates, and the higher glycemic index of gluten-free products than gluten-contained foods, predisposing individuals to the development of insulin resistance. However, recent evidence supports the hypothesis that alterations in one of the components of the so-called "gut-liver axis" might contribute to the increased afflux of toxic substances to the liver triggering the liver fat accumulation and to the subsequent hepatocellular damage. The aim of this paper was to describe the actual knowledge about the factors implicated in the pathogenesis of hepatic steatosis in pediatric patients with CD. The presented review allows us to conclude that the serological evaluations for CD with anti-transglutaminase antibodies, should be a part of the general workup in the asymptomatic patients with "non-alcoholic fatty liver disease" (NAFLD) when metabolic risk factors are not evident, and in the patients with steatohepatitis when other causes of liver disease are excluded.

Short-chain fatty acids reprogram metabolic profiles with the induction of reactive oxygen species production in human colorectal adenocarcinoma cells

Short-chain fatty acids (SCFAs) exhibit anticancer activity in cellular and animal models of colon cancer. Acetate, propionate, and butyrate are the three major SCFAs produced from dietary fiber by gut microbiota fermentation and have beneficial effects on human health. Most previous studies on the antitumor mechanisms of SCFAs have focused on specific metabolites or genes involved in antitumor pathways, such as reactive oxygen species (ROS) biosynthesis. In this study, we performed a systematic and unbiased analysis of the effects of acetate, propionate, and butyrate on ROS levels and metabolic and transcriptomic signatures at physiological concentrations in human colorectal adenocarcinoma cells. We observed significantly elevated levels of ROS in the treated cells. Furthermore, significantly regulated signatures were involved in overlapping pathways at metabolic and transcriptomic levels, including ROS response and metabolism, fatty acid transport and metabolism, glucose response and metabolism, mitochondrial transport and respiratory chain complex, one-carbon metabolism, amino acid transport and metabolism, and glutaminolysis, which are directly or indirectly linked to ROS production. Additionally, metabolic and transcriptomic regulation occurred in a SCFAs types-dependent manner, with an increasing degree from acetate to propionate and then to butyrate. This study provides a comprehensive analysis of how SCFAs induce ROS production and modulate metabolic and transcriptomic levels in colon cancer cells, which is vital for understanding the mechanisms of the effects of SCFAs on antitumor activity in colon cancer.

Effects of Clostridium butyricum, Sodium Butyrate, and Butyric Acid Glycerides on the Reproductive Performance, Egg Quality, Intestinal Health, and Offspring Performance of Yellow-Feathered Breeder Hens

Butyrate has been reported to promote the performance and growth of chickens. The specific roles and efficacy of different sources of butyrate remained unclear. Thus, the present study aimed to investigate and compare the effects of Clostridium butyricum (CB), sodium butyrate (SB), and butyric acid glycerides (tributyrin, BAG) on the reproductive performance, egg quality, intestinal health, and offspring performance of yellow-feathered breeder hens. A total of 300 Lingnan yellow-feathered breeder hens were assigned to five treatment groups: control (CL), 1×10⁸CFU/kg CB (CBL), 1×10⁹CFU/kg CB (CBH), 500mg/kg SB, and 300mg/kg BAG. Results showed that the laying performance and egg quality were increased by CBL, CBH, and BAG. Both CB treatments increased the hatchability of fertilized eggs. Maternal supplementation with both levels of CB significantly elevated the growth performance of offspring. Treatment with CBL, CBH, SB, and BAG all improved the oviduct-related variables and reduced the plasmal antioxidant variables. The CBH, CBL, and BAG treatments also improved the intestinal morphology to different degrees. Jejunal contents of IL-6 were decreased by CBH and BAG, while those of IL-4, IL-6, IL-1β, and IgY were decreased by SB. Transcripts of nutrient transporters in jejunal mucosa were also upregulated by CBH, CBL, and SB treatments and expression of Bcl-2-associated X protein was decreased by CBL, CBH, and BAG. In cecal contents, CBL increased the abundance of Firmicutes and Bacillus, while CBH decreased the abundance of Proteobacteria. Also, the co-occurrence networks of intestinal microbes were regulated by CBH and BAG. In conclusion, dietary inclusion of CB and BAG improved the reproductive parameters, egg quality, and intestinal morphology of breeders. CB also influenced the hatching performance of breeders and growth performance of the offspring, while SB improved the oviduct-related variables. These beneficial effects may result from the regulation of cytokines, nutrient transporters, apoptosis, and gut microbiota; high-level CB had more obvious impact. Further study is needed to explore and understand the correlation between the altered gut microbiota induced by butyrate and the performance, egg quality, intestinal health, and also offspring performance.

Short Bowel Syndrome: A Paradigm for Intestinal Adaptation to Nutrition?

Short bowel syndrome (SBS) is a rare disease that results from extensive resection of the intestine. When the remaining absorption surface of the intestine cannot absorb enough macronutrients, micronutrients, and water, SBS results in intestinal failure (IF). Patients with SBS who suffer from IF require parenteral nutrition for survival, but long-term parenteral nutrition may lead to complications such as catheter sepsis and metabolic diseases. Spontaneous intestinal adaptation occurs weeks to months after resection, resulting in hyperplasia of the remnant gut, modification of gut hormone levels, dysbiosis, and hyperphagia. Oral nutrition and presence of the colon are two major positive drivers for this adaptation. This review aims to summarize the current knowledge of the mechanisms underlying spontaneous intestinal adaptation, particularly in response to modifications of luminal content, including nutrients. In the future, dietary manipulations could be used to treat SBS.

Probiotic supplementation increases carbohydrate metabolism in trained male cyclists: a randomized, double-blind, placebo-controlled crossover trial

We hypothesized that probiotic supplementation (PRO) increases the absorption and oxidation of orally ingested maltodextrin during 2 h endurance cycling, thereby sparing muscle glycogen for a subsequent time trial (simulating a road race). Measurements were made of lipid and carbohydrate oxidation, plasma metabolites and insulin, gastrointestinal (GI) permeability, and subjective symptoms of discomfort. Seven male cyclists were randomized to PRO (bacterial composition given in methods) or placebo for 4 wk, separated by a 14-day washout period. After each period, cyclists consumed a 10% maltodextrin solution (initial 8 mL/kg bolus and 2 mL/kg every 15 min) while exercising for 2 h at 55% maximal aerobic power output, followed by a 100-kJ time trial. PRO resulted in small increases in peak oxidation rates of the ingested maltodextrin (0.84 ± 0.10 vs. 0.77 ± 0.09 g/min; P = 0.016) and mean total carbohydrate oxidation (2.20 ± 0.25 vs. 1.87 ± 0.39 g/min; P = 0.038), whereas fat oxidation was reduced (0.40 ± 0.11 vs. 0.55 ± 0.10 g/min; P = 0.021). During PRO, small but significant increases were seen in glucose absorption, plasma glucose, and insulin concentration and decreases in nonesterified fatty acid and glycerol. Differences between markers of GI damage and permeability and time-trial performance were not significant (P > 0.05). In contrast to the hypothesis, PRO led to minimal increases in absorption and oxidation of the ingested maltodextrin and small reductions in fat oxidation, whereas having no effect on subsequent time-trial performance.

Effects of dietary tributyrin on intestinal mucosa development, mitochondrial function and AMPK-mTOR pathway in weaned pigs

Background

The objective of this experiment was to investigate the influence of dietary tributyrin on intestinal mucosa development, oxidative stress, mitochondrial function and AMPK-mTOR signaling pathway.

Methods

Seventy-two pigs were divided into two treatments and received either a basal diet or the same diet supplemented with 750 mg/kg tributyrin. Each treatment has six replicates of six pigs. After 14 days, 6 pigs from each treatment were selected and the jejunal samples were collected.

Results

Results showed that supplemental tributyrin increased (P < 0.05) villus height and villus height: crypt depth of weaned pigs. Pigs fed tributyrin had greater (P < 0.05) RNA/DNA and protein/DNA ratios than pigs on the control group. The mRNA levels of sodium glucose transport protein-1 and glucose transporter-2 in the jejunum were upregulated (P < 0.05) in pigs fed the tributyrin diet. Dietary tributyrin supplementation lowered (P < 0.05) the malondialdehyde and hydrogen peroxide (H₂O₂₎ content in jejunum, enhanced (P < 0.05) the mitochondrial function, as demonstrated by decreased (P < 0.05) reactive oxygen species level and increased (P < 0.05) mitochondrial membrane potential. Furthermore, tributyrin increased (P < 0.05) mitochondrial DNA content and the mRNA abundance of genes related to mitochondrial functions, including peroxisomal proliferator-activated receptor-γ coactivator-1α, mitochondrial transcription factor A, nuclear respiratory factor-1 in the jejunum. Supplementation with tributyrin elevated (P < 0.05) the phosphorylation level of AMPK and inhibited (P < 0.05) the phosphorylation level of mTOR in jejunum compared with the control group.

Conclusions

These findings suggest that dietary supplementation with tributyrin promotes intestinal mucosa growth, extenuates oxidative stress, improves mitochondrial function and modulates the AMPK-mTOR signal pathway of weaned pigs.

Short Bowel Syndrome as the Leading Cause of Intestinal Failure in Early Life: Some Insights into the Management

Intestinal failure (IF) is the critical reduction of the gut mass or its function below the minimum needed to absorb nutrients and fluids required for adequate growth in children. Severe IF requires parenteral nutrition (PN). Pediatric IF is most commonly due to congenital or neonatal intestinal diseases or malformations divided into 3 groups: 1) reduced intestinal length and consequently reduced absorptive surface, such as in short bowel syndrome (SBS) or extensive aganglionosis; 2) abnormal development of the intestinal mucosa such as congenital diseases of enterocyte development; 3) extensive motility dysfunction such as chronic intestinal pseudo-obstruction syndromes. The leading cause of IF in childhood is the SBS. In clinical practice the degree of IF may be indirectly measured by the level of PN required for normal or catch up growth. Other indicators such as serum citrulline have not proven to be highly reliable prognostic factors in children. The last decades have allowed the development of highly sophisticated nutrient solutions consisting of optimal combinations of macronutrients and micronutrients as well as guidelines, promoting PN as a safe and efficient feeding technique. However, IF that requires long-term PN may be associated with various complications including infections, growth failure, metabolic disorders, and bone disease. IF Associated Liver Disease may be a limiting factor. However, changes in the global management of IF pediatric patients, especially since the setup of intestinal rehabilitation centres did change the prognosis thus limiting "nutritional failure" which is considered as a major indication for intestinal transplantation (ITx) or combined liver-ITx.

Effects of Intravenous Infusion With Sodium Butyrate on Colonic Microbiota, Intestinal Development- and Mucosal Immune-Related Gene Expression in Normal Growing Pigs

This study aimed to investigate effects of intravenous infusion with sodium butyrate (SB) on colonic microbiota, intestinal mucosal immune and intestinal development in normal growing pigs. Twelve crossbred barrows (Duroc × Landrace × Large White) fitted with a medical polyethylene cannula via internal jugular vein were daily infused with 10 ml SB (200 mmol/l) or the same volume of physiological saline for 7 days. Results showed that SB infusion had no effects on the short-chain fatty acids concentrations and the number of total bacteria, but significantly increased the microbial richness estimators (ACE and Chao1), and the abundance of genera related to Clostridiales order in the colonic digesta (P < 0.05). SB infusion significantly up-regulated the mRNA expression of monocarboxylate transporter 1 (MCT1) in the colon, while no change was found in the ileum. Only the relative mRNA of pro-inflammatory cytokine IL-6 gene was decreased significantly in the ileum by SB infusion. On the contrary, in the colon, SB infusion significantly decreased the gene expression of histone deacetylase 1 (HDAC1) and pro-inflammatory cytokines IL-6, IL-18, IL-12p40, and TNF-α (P < 0.05), but significantly increased the secretory immunoglobulin A (sIgA) concentration, the gene expression of anti-inflammatory cytokine IL-10, and the expression of intestinal development-related gene zonula occludens-1 (ZO-1), occludin, and epidermal growth factor (EGF) (P < 0.05). The results suggest that systemic SB can modify colonic microbial composition, regulate the inflammatory cytokine- and intestinal development-related gene expression in pigs under the normal physiological condition. This study may provide an alternative strategy for improving the intestinal health of normal piglets.

Sodium butyrate improved performance while modulating the cecal microbiota and regulating the expression of intestinal immune-related genes of broiler chickens

This study evaluated the effect of sodium butyrate (SB) on performance, expression of immune-related genes in the cecal tonsils, and cecal microbiota of broiler chickens when dietary energy and amino acids concentrations were reduced. Day-old male Ross 708 broiler chicks were fed dietary treatments in a 3 × 2 factorial design (8 pens per treatment) with 3 dietary formulations (control diet; reduction of 2.3% of amino acids and 60 kcal/kg; and reduction of 4.6% of amino acids and 120 kcal/kg) with or without the inclusion of 0.1% of SB. Feed intake (FI), body weight gain (BW gain), and feed conversion ratio (FCR) were recorded until 28 d of age. From 14 to 28 d, there was an interaction of nutrient density by SB (P = 0.003) wherein BW gain of birds fed SB was impaired less by the energy/amino acids reduction than unsupplemented birds. A similar result was obtained from 1 to 28 d (P = 0.004). No interaction (P < 0.05) between nutrient density by SB was observed for FCR. Nutritional density of the diets and SB modified the structure, composition, and predicted function of the cecal microbiota. The nutritionally reduced diet altered the imputed function performed by the microbiota and the SB supplementation reduced these variations, keeping the microbial function similar to that observed in chickens fed a control diet. The frequency of bacterial species presenting the butyryl-CoA: acetate CoA-transferase gene increased in the microbiota of chickens fed a nutritionally reduced diet without SB supplementation, and was not changed by nutrient density of the diet when supplemented with SB (interaction; P = 0.01). SB modulated the expression of immune related genes in the cecal tonsils; wherein SB upregulated the expression of A20 in broilers fed control diets (P < 0.05) and increased IL-6 expression (P < 0.05). These results show that SB had positive effects on the productive performance of broilers fed nutritionally reduced diets, partially by modulating the cecal microbiota and exerting immune-modulatory effects.

Marine polysaccharides attenuate metabolic syndrome by fermentation products and altering gut microbiota: An overview

Marine polysaccharides (MPs), including plant, animal, and microbial-derived polysaccharides, can alleviate metabolic syndrome (MetS) by different regulation mechanisms. MPs and their derivatives can attenuate MetS by vary cellular signal pathways, such as peroxisome proliferator-activated receptor, 5' adenosine monophosphate-activated protein kinase, and CCAAT/enhancer binding protein-α. Also, most of MPs cannot be degraded by human innate enzymes, but they can be degraded and fermented by human gut microbiota. The final metabolic products of these polysaccharides are usually short-chain fatty acids (SCFAs), which can change the gut microbiota ecology by altering the existing percentage of special microorganisms. In addition, the SCFAs and changed gut microbiota can regulate enteroendocrine hormone secretion, blood glucose, lipid metabolism levels, and other MetS symptoms. Here, we summarize the up-to-date findings on the effects of MPs, particularly marine microbial-derived polysaccharides, and their metabolites on attenuating MetS.

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.

Enteral Nutrients and Gastrointestinal Physiology

The gastrointestinal (GI) tract is a highly efficient organ system with specialized structures to facilitate digestion and absorption of nutrients to meet the body's needs. The presence of nutrients in the GI tract supports optimal structure and function, stimulates regulatory hormones, and supports the microbiota, the population of microorganisms residing in the GI tract. A lack of enteral nutrition (EN) results in impaired GI integrity and serious patient complications, making EN a priority. Normal GI physiology is reviewed, and the regulatory impact of luminal nutrients on GI function is discussed.

Nutritional strategies to enhance adaptation in intestinal failure

PURPOSE OF REVIEW

This article summarizes the current and potential future nutritional approaches to stimulate adaptation in intestinal failure. Adaptation in this context usually refers to intestinal adaptation but also involves changes in whole body physiology as well as in eating/drinking behavior.

RECENT FINDINGS

Adaptation largely depends on residual functional anatomy. Luminal exposure to complex nutrients is the most important trigger for intestinal adaptation. Enteral fat as well as enteral or parenteral short chain fatty acids have a specific stimulatory effect. Zinc and vitamin A status need to be optimized for adaptation to proceed and be maintained. In the context of maintaining sodium and water homeostasis, flushing the remnant intestine because of uncontrolled thirst/drinking must be avoided. Complications of nutritional care such as malnutrition, intestinal failure-associated liver disease, and recurrent line sepsis also need optimal management.

SUMMARY

Stimulation by luminal nutrients as well as prophylaxis against and treatment of (nutritional) complications are the cornerstones of adaptation to the short bowel situation. Based on ample data from animal studies but only limited evidence in humans specific nutritional stimulators need to be studied more rigorously. As long as such data are missing they can be tried on an individual basis.

Severe Gut Microbiota Dysbiosis Is Associated With Poor Growth in Patients With Short Bowel Syndrome

BACKGROUND

Children with short bowel syndrome (SBS) can vary significantly in their growth trajectory. Recent data have shown that children with SBS possess a unique gut microbiota signature compared with healthy controls. We hypothesized that children with SBS and poor growth would exhibit more severe gut microbiota dysbiosis compared with those with SBS who are growing adequately, despite similar intestinal anatomy.

MATERIALS AND METHODS

Stool samples were collected from children with SBS (n = 8) and healthy controls (n = 3) over 3 months. Gut microbiota populations (16S ribosomal RNA sequencing and metagenomic shotgun sequencing) were compared, including a more in-depth analysis of SBS children exhibiting poor and good growth. Statistical analysis was performed using Mann-Whitney, Kruskal-Wallis, and χ² tests as appropriate.

RESULTS

Children with SBS had a significant deficiency of the commensal Firmicutes order Clostridiales ( P = .025, Kruskal-Wallis) compared with healthy children. Furthermore, children with SBS and poor growth were deficient in beneficial bacteria known to produce short-chain fatty acids and had expansion of proinflammatory Enterobacteriaceae ( P = .038, Kruskal-Wallis) compared with children with SBS who were growing adequately. Using metabolic function analyses, SBS/poor growth microbiomes were deficient in genes needed for gluconeogenesis but enriched in branched and aromatic amino acid synthesis and citrate cycle pathway genes.

CONCLUSIONS

Patients with SBS, particularly those with suboptimal growth, have a marked gut dysbiosis characterized by a paucity of beneficial commensal anaerobes, resulting in a deficiency of key metabolic enzymes found in the gut microbiomes of healthy children.

Gut Microbiota of Nonalcoholic Fatty Liver Disease

The prevalence of nonalcoholic fatty liver disease has been rapidly increasing worldwide. It has become a leading cause of liver transplantation. Accumulating evidence suggests a significant role for gut microbiota in its development and progression. Here we review the effect of gut microbiota on developing hepatic fatty infiltration and its progression. Current literature supports a possible role for gut microbiota in the development of liver steatosis, inflammation and fibrosis. We also review the literature on possible interventions for NAFLD that target the gut microbiota.

Can Bacteriotherapy Using Commercially Available Probiotics, Prebiotics, and Organic Acids Ameliorate the Symptoms Associated With Runting-Stunting Syndrome in Broiler Chickens?

Runting-stunting syndrome (RSS) in poultry has been known for more than 40 years, but the precise etiology remains unknown and a licensed vaccine is consequently not currently available. In order to mitigate the symptoms associated with RSS, a series of experiments was performed to investigate whether a combined bacteriotherapeutic treatment consisting of probiotics, prebiotics, and organic acids could influence the outcome of this disease. Initially two groups of commercial broiler chickens were either left uninoculated or inoculated with filtrate from homogenized intestines of RSS-affected broiler chickens. One group from each of these two challenge groups was treated, with a bacteriotherapeutic regimen. After 12 days chickens were euthanatized, the body weight was measured, and duodenal lesions were enumerated. Five consecutive broiler chicken flocks were then raised either on litter from RSS-affected birds or on fresh wood shavings. Treatment had no beneficial effect on the number and severity of intestinal lesions. There appeared to be a significant build-up of RSS agent(s) in poultry litter, with each consecutive flock placement, independent of bacteriotherapeutic treatment, as more individuals exhibited intestinal lesions on built-up litter in RSS-affected houses (28.9% vs. 44%). While treatment did not appear to consistently reduce intestinal lesions, it did significantly improve the mean body weights (P<0.05) and uniformity of 12-day-old chickens placed on reused litter in houses in which RSS-infected birds were previously raised. A combination of litter management and bacteriotherapy may be needed to ameliorate the adverse effects of RSS on intestinal health and body weight in broiler chickens.

Sex differences in gut fermentation and immune parameters in rats fed an oligofructose-supplemented diet

BACKGROUND

Mechanistic data to support health claims is often generated using rodent models, and the influence of prebiotic supplementation has largely been evaluated using male rodents. Given that sex-based differences in immune parameters are well recognized and recent evidence suggests differences in microbiota composition between sexes, validation of the effectiveness of prebiotics merits assessment in both males and females. Here, we have compared the effect of oligofructose (OF) supplementation on the fecal bacterial community, short chain fatty acid profiles, and gut mucosal and systemic immune parameters in male and female rats.

METHODS

Male and female rats were fed rodent chow or chow supplemented with OF (5 % w/w). Fecal community change was examined by analyzing 16S rRNA gene content. To compare effects of OF between sexes at the gut microbial and mucosal immune level, fecal short chain fatty acid and tissue cytokine profiles were measured. Serum lipopolysaccharide levels were also evaluated by the limulus amebocyte lysate assay as an indirect means of determining gut permeability between sexes.

RESULTS

In the fecal community of females, OF supplementation altered community structure by increasing abundance in the Phylum Bacteroidetes. In male rats, no changes in fecal community structure were observed, although fecal butyrate levels significantly increased. Liver Immunoglobulin A (IgA) levels were higher in males relative to females fed OF, and serum LPS concentrations were higher in males independent of diet. Females had higher basal levels of the regulatory cytokine interleukin-10 (IL-10) in the colon and liver, while males had higher basal levels of the pro-inflammatory cytokines IL-6 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) in the cecum and liver.

CONCLUSIONS

We have shown that male and female rat gut communities metabolize an OF-supplemented diet differently. Sex-specific responses in both the fecal community and systemic immune parameters suggest that this difference may result from an increase in the availability of gut peptidyl-nitrogen in the males. These findings demonstrate the importance of performing sex-comparative studies when investigating potential health effects of prebiotics using rodent models.

Gut microbiome and nonalcoholic fatty liver diseases

We review recent findings and hypotheses on the roles of gut microbiome in the pathogenesis of nonalcoholic fatty liver diseases (NAFLD). Microbial metabolites and cell components contribute to the development of hepatic steatosis and inflammation, key components of nonalcoholic steatohepatitis (NASH), the severe form of NAFLD. Altered gut microbiome can independently cause obesity, the most important risk factor for NAFLD. This capability is attributed to short-chain fatty acids (SCFAs), major gut microbial fermentation products. SCFAs account for a large portion of caloric intake of the host, and they enhance intestinal absorption by activating GLP-2 signaling. However, elevated SCFAs may be an adaptive measure to suppress colitis, which could be a higher priority than imbalanced calorie intake. The microbiome of NASH patients features an elevated capacity for alcohol production. The pathomechanisms for alcoholic steatohepatitis may apply to NASH. NAFLD/NASH is associated with elevated Gram-negative microbiome and endotoxemia. However, many NASH patients exhibited normal serum endotoxin indicating that endotoxemia is not required for the pathogenesis of NASH. These observations suggest that microbial intervention may benefit NAFLD/NASH patients. However, very limited effects were observed using traditional probiotic species. Novel probiotic therapy based on NAFLD/NASH specific microbial composition represents a promising future direction.

Animal models of gastrointestinal and liver diseases. Animal models of infant short bowel syndrome: translational relevance and challenges

Intestinal failure (IF), due to short bowel syndrome (SBS), results from surgical resection of a major portion of the intestine, leading to reduced nutrient absorption and need for parenteral nutrition (PN). The incidence is highest in infants and relates to preterm birth, necrotizing enterocolitis, atresia, gastroschisis, volvulus, and aganglionosis. Patient outcomes have improved, but there is a need to develop new therapies for SBS and to understand intestinal adaptation after different diseases, resection types, and nutritional and pharmacological interventions. Animal studies are needed to carefully evaluate the cellular mechanisms, safety, and translational relevance of new procedures. Distal intestinal resection, without a functioning colon, results in the most severe complications and adaptation may depend on the age at resection (preterm, term, young, adult). Clinically relevant therapies have recently been suggested from studies in preterm and term PN-dependent SBS piglets, with or without a functional colon. Studies in rats and mice have specifically addressed the fundamental physiological processes underlying adaptation at the cellular level, such as regulation of mucosal proliferation, apoptosis, transport, and digestive enzyme expression, and easily allow exogenous or genetic manipulation of growth factors and their receptors (e.g., glucagon-like peptide 2, growth hormone, insulin-like growth factor 1, epidermal growth factor, keratinocyte growth factor). The greater size of rats, and especially young pigs, is an advantage for testing surgical procedures and nutritional interventions (e.g., PN, milk diets, long-/short-chain lipids, pre- and probiotics). Conversely, newborn pigs (preterm or term) and weanling rats provide better insights into the developmental aspects of treatment for SBS in infants owing to their immature intestines. The review shows that a balance among practical, economical, experimental, and ethical constraints will determine the choice of SBS model for each clinical or basic research question.

Short bowel syndrome in infants: the critical role of luminal nutrients in a management program

Short bowel syndrome develops when the remnant mass of functioning enterocytes following massive resections cannot support growth or maintain fluid–electrolyte balance and requires parenteral nutrition. Resection itself stimulates the intestine’s inherent ability to adapt morphologically and functionally. The capacity to change is very much related to the high turnover rate of enterocytes and is mediated by several signals; these signals are mediated in large part by enteral nutrition. Early initiation of enteral feeding, close clinical monitoring, and ongoing assessment of intestinal adaptation are key to the prevention of irreversible intestinal failure. The length of the functional small bowel remnant is the most important variable affecting outcome. The major objective of intestinal rehabilitation programs is to achieve early oral nutritional autonomy while maintaining normal growth and nutrition status and minimizing total parenteral nutrition related comorbidities such as chronic progressive liver disease. Remarkable progress has been made in terms of survivability and quality of life, especially in the context of coordinated multidisciplinary programs, but much work remains to be done.

Intestinal adaptation following resection

Intestinal adaptation is a natural compensatory process that occurs following extensive intestinal resection, whereby structural and functional changes in the intestine improve nutrient and fluid absorption in the remnant bowel. In animal studies, postresection structural adaptations include bowel lengthening and thickening and increases in villus height and crypt depth. Functional changes include increased nutrient transporter expression, accelerated crypt cell differentiation, and slowed transit time. In adult humans, data regarding adaptive changes are sparse, and the mechanisms underlying intestinal adaptation remain to be fully elucidated. Several factors influence the degree of intestinal adaptation that occurs post resection, including site and extent of resection, luminal stimulation with enteral nutrients, and intestinotrophic factors. Two intestinotrophic growth factors, the glucagon-like peptide 2 analog teduglutide and recombinant growth hormone (somatropin), are now approved for clinical use in patients with short bowel syndrome (SBS). Both agents enhance fluid absorption and decrease requirements for parenteral nutrition (PN) and/or intravenous fluid. Intestinal adaptation has been thought to be limited to the first 1-2 years following resection in humans. However, recent data suggest that a significant proportion of adult patients with SBS can achieve enteral autonomy, even after many years of PN dependence, particularly with trophic stimulation.

Pathobiology and potential therapeutic value of intestinal short-chain fatty acids in gut inflammation and obesity

BACKGROUND

The lumen of the gastrointestinal tract contains many substances produced from the breakdown of foodstuffs, from salivary, esophageal, intestinal, hepatic, and pancreatic secretions, and from sloughed cells present in the gastrointestinal lumen. Although these substances were traditionally regarded as waste products, there is increasing realization that many can be biologically active, either as signalling compounds or as nutrients. For example, proteins are broken down into amino acids, which are then sensed by nutrient receptors. The gut microbiome, which is at highest abundance in the ileocecum, has powerful metabolic activity, digesting and breaking down unabsorbed carbohydrates, proteins, and other ingested nutrients into phenols, amines, volatile organic compounds, methane, carbon dioxide, hydrogen, and hydrogen sulfide into volatile fatty acids, also called short-chain fatty acids (SCFAs).

CONCLUSION

These latter substances are the topic of this review. In this review, we will briefly discuss recent advances in the understanding SCFA production, signalling, and absorption, followed by a detailed description and discussion of trials of SCFAs, probiotics, and prebiotics in the treatment of gastrointestinal disease, in particular ulcerative colitis (UC), pouchitis, short bowel syndrome, and obesity.

Intestinal microbiology in early life: specific prebiotics can have similar functionalities as human-milk oligosaccharides

Human milk is generally accepted as the best nutrition for newborns and has been shown to support the optimal growth and development of infants. On the basis of scientific insights from human-milk research, a specific mixture of nondigestible oligosaccharides has been developed, with the aim to improve the intestinal microbiota in early life. The mixture has been extensively studied and has been shown to be safe and to have potential health benefits that are similar to those of human milk. The specific mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides has been found to affect the development of early microbiota and to increase the Bifidobacterium amounts as observed in human-milk-fed infants. The resulting gut ecophysiology is characterized by high concentrations of lactate, a slightly acidic pH, and specific short-chain fatty acid profiles, which are high in acetate and low in butyrate and propionate. Here, we have summarized the main findings of dietary interventions with these specific oligosaccharides on the gut microbiota in early life. The gut ecophysiology in early life may have consequences for the metabolic, immunologic, and even neurologic development of the child because reports increasingly substantiate the important function of gut microbes in human health. This review highlights major findings in the field of early gut colonization and the potential impact of early nutrition in healthy growth and development.

Role of probiotics in short bowel syndrome in infants and children--a systematic review

Short bowel syndrome (SBS) is a cause of significant morbidity and mortality in children. Probiotics, due to their beneficial effects on the gastrointestinal tract (e.g., improving gut barrier function, motility, facilitation of intestinal adaptation and decreasing pathogen load and inflammation) may have a therapeutic role in the management of SBS. To conduct a systematic review of the current evidence for the effects of probiotic supplementation in children with SBS, the standard Cochrane methodology for systematic reviews was used. The databases, Pubmed, Embase, ACTR, CENTRAL, and the international trial registry, and reference lists of articles were searched for randomised (RCT) or quasi-randomised controlled trials reporting on the use of probiotics in SBS. Our search revealed no RCTs on the use of probiotics in children with SBS. We found one small cross-over RCT (placebo controlled crossover clinical trial), one case control study and nine case reports on the use of probiotics in children with SBS. In the crossover RCT, there was no consistent effect on intestinal permeability (primary outcome) after supplementation with Lactobacillus rhamnosus (LGG) in nine children with SBS. The case control study (four cases: four controls) reported a trend for increase in height and weight velocity and improvement in non-clinical outcomes, such as gut flora, lymphocyte count and serum prealbumin. Five of the nine case reports showed that children (n = 12) with SBS were benefited (e.g., cessation of diarrhoea, improved faecal flora, weight gain and weaning from parenteral nutrition) by probiotic supplementation. The remaining four reported on the adverse effects, such as Lactobacillus sepsis (n = 3) and D-lactic acidosis (n = 2). There is insufficient evidence on the effects of probiotics in children with SBS. The safety and efficacy of probiotic supplementation in this high-risk cohort needs to be evaluated in large definitive trials.

Intestinal adaptation is stimulated by partial enteral nutrition supplemented with the prebiotic short-chain fructooligosaccharide in a neonatal intestinal failure piglet model

BACKGROUND

Butyrate has been shown to stimulate intestinal adaptation when added to parenteral nutrition (PN) following small bowel resection but is not available in current PN formulations. The authors hypothesized that pre- and probiotic administration may be a clinically feasible method to administer butyrate and stimulate intestinal adaptation.

METHODS AND MATERIALS

Neonatal piglets (48 hours old, n = 87) underwent placement of a jugular catheter and an 80% jejunoileal resection and were randomized to one of the following treatment groups: control (20% standard enteral nutrition/80% standard PN), control plus prebiotic (10 g/L short-chain fructooligosaccharides [scFOS]), control plus probiotic (1 × 10(9) CFU Lactobacillus rhamnosus GG [LGG]), or control plus synbiotic (scFOS + LGG). Animals received infusions for 24 hours, 3 days, or 7 days, and markers of intestinal adaptation were assessed.

RESULTS

Prebiotic treatment increased ileal mucosa weight compared with all other treatments (P = .017) and ileal protein compared with control (P = .049), regardless of day. Ileal villus length increased in the prebiotic and synbiotic group (P = .011), regardless of day, specifically due to an increase in epithelial proliferation (P = .003). In the 7-day prebiotic group, peptide transport was upregulated in the jejunum (P = .026), whereas glutamine transport was increased in both the jejunum and colon (P = .001 and .003, respectively).

CONCLUSIONS

Prebiotic and/or synbiotic supplementation resulted in enhanced structure and function throughout the residual intestine. Identification of a synergistic prebiotic and probiotic combination may enhance the promising results obtained with prebiotic treatment alone.

Mybl2, downregulated during colon epithelial cell maturation, is suppressed by miR-365

Altered profiles of gene expression reflect the reprogramming of intestinal epithelial cells during their maturation along the crypt-luminal axis. To focus on genes important in this process, and how they in turn are regulated, we identified 14 transcripts commonly downregulated in expression during lineage-specific maturation of the immortalized cell lines Caco-2 (absorptive), HT29Cl16E (goblet), and HT29Cl19A (secretory) induced by contact inhibition of growth or the short-chain fatty acid butyrate. One such gene, Mybl2 (Myb-related protein B), has been linked to the stem cell phenotype, and we report is also markedly suppressed in maturing cells along the crypt-luminal axis in vivo. Mybl2 is not significantly downregulated transcriptionally during colon cell maturation, but we identified a potential micro-RNA (miRNA)-binding sequence in the Mybl2 3'-untranslated region that mediates reporter gene suppression in differentiating colon cells. Accordingly, miRNAs predicted to bind this functional target are upregulated in differentiating colon epithelial cells in vitro and in vivo; expression of one of these, hsa-miR-365 (but not hsa-324-5p), suppresses Mybl2 protein expression in proliferating Caco-2 cells. These data demonstrate that miRNA silencing plays an important role in regulating gene expression in maturing colon epithelial cells, and that utilizing a target-centered approach, rather than profiling global miRNA expression, can identify physiologically relevant, functional miRNAs.

Parenteral nutrition: Revisited

The prevalence of malnutrition among critically ill patients, especially those with a protracted clinical course, has remained largely unchanged over the last two decades. The metabolic response to stress, injury, surgery, or inflammation cannot be accurately predicted and these metabolic alterations may change during the course of illness. Both underfeeding and overfeeding are common in intensive care units (ICU), resulting in large energy and other nutritional imbalances. Systematic research and clinical trials on various aspects of nutritional support in the ICU are limited and make it challenging to compile evidence-based practice guidelines.

[Intestinal microbiota in short bowel syndrome]

Short bowel syndrome (SBS) is the main cause of intestinal failure especially in children. The colon is a crucial partner for small intestine adaptation and function in patients who have undergone extensive small bowel resection. However, SBS predisposes the patient to small intestine bacterial overgrowth (SIBO), explaining its high prevalence in patients with this disorder. SIBO may significantly compromise digestive and absorptive functions and may delay or prevent weaning from total parenteral nutrition (TPN). Moreover, SIBO may be one of the causes of intestinal failure-associated liver disease, requiring liver transplantation in some cases. Traditional tests for assessing SIBO may be unreliable in SBS patients. Management of SIBO with antibiotic therapy as a first-line approach remains a matter of debate, while other approaches, including probiotics, offer potential based on experimental evidence, though only few data from human studies are available.

MYBL2, a link between proliferation and differentiation in maturing colon epithelial cells

Multiple signals, controlling both proliferation and differentiation, must be integrated in the reprogramming of intestinal epithelial cells during maturation along the crypt-luminal axis. The v-myb family member Mybl2, a molecule implicated in the development and maintenance of the stem cell phenotype, has been suggested to play an important role in proliferation and differentiation of several cell types and is a gene we have found is commonly regulated in several systems of colon cell maturation both in vitro and in vivo. Here we show that siRNA silencing of Mybl2 in proliferating Caco-2 cells increases expression of the cell-cycle regulators cdk2, cyclin D2, and c-myc and decreases expression of cdc25B and cyclin B2 with a consequent 10% increase of cells in G2/M and a complementary 10% decrease in G1. Mybl2 occupies sequences upstream of transcriptional start sites of cyclin D2, c-myc, cyclin B2, and cdc25B and regulates reporter activity driven by upstream regions of cdk2, cyclin D2, and c-myc. These data suggest that Mybl2 plays a subtle but key role in linking specific aspects of cell-cycle progression with generation of signals for differentiation and may therefore be fundamental in commitment of intestinal epithelial cells to differentiation pathways during their maturation.

Butyrate increases GLUT2 mRNA abundance by initiating transcription in Caco2-BBe cells

BACKGROUND

Glucose transporter 2 (GLUT2) is a high-capacity, facilitative intestinal monosaccharide transporter, known to be upregulated by short-chain fatty acids (SCFAs) derived from the intestinal microbiota during fermentation. Understanding the mechanisms regulating intestinal function is important to optimize therapies for patients with intestinal failure and ultimately reduce their dependence on parenteral nutrition.

OBJECTIVE

The objective was to examine the mechanism regulating the underlying response of GLUT2 to the SCFA butyrate.

METHODS

GLUT2 messenger RNA (mRNA) abundance was measured in differentiated Caco2-BBe monolayers treated for 0.5-24 hours with 0-20 mM butyrate using quantitative reverse transcription-polymerase chain reaction. Activation of the human GLUT2 promoter was measured using luciferase reporting in transiently transfected Caco2-BBe monolayers.

RESULTS

GLUT2 mRNA abundance was higher (P < .0001) with 1-4 hours of exposure to 2.5, 7.5, and 10 mM butyrate. Butyrate induced (P < .0001) promoter activity in a dose-dependent fashion. Analysis of the GLUT2 promoter indicated that regions -282/+522, -216/+522, and -145/+522 had a heightened (P < .05) response to butyrate compared with 1135/+522 and 564/+522.

CONCLUSIONS

Butyrate upregulates GLUT2 mRNA abundance in Caco2-BBe monolayers by activating specific regions within the human GLUT2 promoter. These results identify a cellular mechanism wherein butyrate upregulates intestinal absorption that may be relevant to patients with reduced function. Additional work is necessary to understand cellular targets of butyrate therapy and define clinically appropriate means of providing such strategies, such as consuming prebiotics and probiotics.

Metabolites produced by probiotic Lactobacilli rapidly increase glucose uptake by Caco-2 cells

Background

Although probiotic bacteria and their metabolites alter enterocyte gene expression, rapid, non-genomic responses have not been examined. The present study measured accumulation of tracer (2 μM) glucose by Caco-2 cells after exposure for 10 min or less to a chemically defined medium (CDM) with different monosaccharides before and after anaerobic culture of probiotic Lactobacilli.

Results

Growth of L. acidophilus was supported by CDM with 110 mM glucose, fructose, and mannose, but not with arabinose, ribose, and xylose or the sugar-free CDM. Glucose accumulation was reduced when Caco-2 cells were exposed for 10 min to sterile CDM with glucose (by 92%), mannose (by 90%), fructose (by 55%), and ribose (by 16%), but not with arabinose and xylose. Exposure of Caco-2 cells for 10 min to bacteria-free supernatants prepared after exponential (48 h) and stationary (72 h) growth phases of L. acidophilus cultured in CDM with 110 mM fructose increased glucose accumulation by 83% and 45%, respectively; exposure to a suspension of the bacteria had no effect. The increase in glucose accumulation was diminished by heat-denaturing the supernatant, indicating the response of Caco-2 cells is triggered by as yet unknown heat labile bacterial metabolites, not by a reduction in CDM components that decrease glucose uptake. Supernatants prepared after anaerobic culture of L. gasseri, L. amylovorus, L. gallinarum, and L. johnsonii in the CDM with fructose increased glucose accumulation by 83%, 32%, 27%, and 14%, respectively.

Conclusion

The rapid, non-genomic upregulation of SGLT1 by bacterial metabolites is a heretofore unrecognized interaction between probiotics and the intestinal epithelium.

Role of the colon in short bowel syndrome and intestinal transplantation

Colon is a crucial partner for small intestinal adaptation and function in patients who underwent extensive small intestinal resection or transplantation. This short review deals with the different properties and roles of the colon in these settings, involving fluid and electrolytes absorption, absorption of medium-chain triglycerides, and production of short-chain fatty acids for malabsorbed energy salvage. The colon may adapt after small intestinal resection, whereas it hosts the most important part of the intestinal microbiota, which plays a crucial role in intestinal function and health. Also, colon may be responsible for D-lactic acidosis as well, as it can be injured by noninfectious colitis. Finally, the relevance of a simultaneous colon grafting is discussed as it is occasionally considered in specific patients requiring intestinal transplantation.

Morphological, kinetic, membrane biochemical and genetic aspects of intestinal enteroplasticity

The process of intestinal adaptation (“enteroplasticity”) is complex and multifaceted. Although a number of trophic nutrients and non-nutritive factors have been identified in animal studies, successful, reproducible clinical trials in humans are awaited. Understanding mechanisms underlying this adaptive process may direct research toward strategies that maximize intestinal function and impart a true clinical benefit to patients with short bowel syndrome, or to persons in whom nutrient absorption needs to be maximized. In this review, we consider the morphological, kinetic and membrane biochemical aspects of enteroplasticity, focus on the importance of nutritional factors, provide an overview of the many hormones that may alter the adaptive process, and consider some of the possible molecular profiles. While most of the data is derived from rodent studies, wherever possible, the results of human studies of intestinal enteroplasticity are provided.

The physiological relevance of the intestinal microbiota--contributions to human health

The intestinal commensal microbiota is a dynamic mixture of essential microbes that develops under key influences of genetics, environment, diet and disease. Population profiles differ along the gastrointestinal tract, from the lumen to the mucosa, and among individuals. The total microbiota population outnumbers the cells in the human body and accounts for 35-50% of the volume of the colonic content. Key physiological functions of the commensal microbiota include protective effects exerted directly by specific bacterial species, control of epithelial cell proliferation and differentiation, production of essential mucosal nutrients, such as short-chain fatty acids and amino acids, prevention of overgrowth of pathogenic organisms, and stimulation of intestinal immunity. Oral probiotics are living microorganisms that upon ingestion in specific numbers exert health benefits beyond those of inherent basic nutrition. Emerging evidence indicates prophylactic and therapeutic utility for probiotic consumption in gastrointestinal health and disease.

Non–digestible oligosaccharides and defense functions: lessons learned from animal models

Animals are constantly exposed to a diversity of health challenges and the gastrointestinal tract (GIT) is a major, if not the principal, site of exposure. Animal models and a limited number of human clinical studies have shown that the assemblages and metabolic activities of the resident bacteria are important determinants of the effectiveness of the various host defense mechanisms and thereby influence the ability of animals to respond to health challenges. The assemblages of bacteria resident in the GIT provide a first line of defense that can exclude invading pathogens, reduce the proliferation of opportunistic pathogens already resident in the GIT, and reduce the availability, carcinogenicity, or toxicity of noxious chemicals. The mucosa of the GIT is a second, multilayered line of defense that includes the mucous and other secretions, the epithelial cells, and immune-associated cells scattered within and under the epithelium. The final line of defense contends with pathogens or noxious chemicals that transcend the mucosal barrier and enter the host and consists of the innate and acquired components of the systemic immune system and the xenobiotic metabolizing enzymes. The lactic acid producing bacteria (LAB) are considered to be immunomodulatory and directly or indirectly influence the GIT and systemic defense functions. Corresponding with this, supplementing the diet with inulin, oligofructose, or other nondigestible oligosaccharides that increase the densities and metabolic capacities of the LAB enhances defense mechanisms of the host, increases resistance to various health challenges, and accelerates recovery of the GIT after disturbances.

Nutritional modulation of the inflammatory response in inflammatory bowel disease- From the molecular to the integrative to the clinical

Nutrient deficiencies are common in patients with inflammatory bowel disease (IBD). Both total parenteral and enteral nutrition provide important supportive therapy for IBD patients, but in adults these are not useful for primary therapy. Dietary intervention with omega-3 polyunsaturated fatty acids contained in fish oil may be useful for the care of IBD patients, and recent studies have stressed the role of PPAR on NFκB activity on the potential beneficial effect of dietary lipids on intestinal function.

Effect of energy substrates on protein degradation in isolated small intestinal enterocytes from rats

BACKGROUND

Nutrients affect small intestinal protein mass and metabolism, but studies on the effect of nutrients on small intestinal protein degradation are very limited due to a lack of a proper method. The objectives of this study were to establish a method to directly estimate protein degradation in isolated enterocytes from rats and to test the effect of energy substrates on protein degradation.

METHODS

Male Sprague-Dawley rats (150-200 g, n>or=8 per treatment) were used. Cell viability, tyrosine release as an indicator of protein degradation, and the effect of osmolarity, 50 mmol/L glucose, 20 mmol/L beta-hydroxybutyrate, 4.7 mmol/L butyrate, and 30 mmol/L glutamine on protein degradation were measured.

RESULTS

The average viability of enterocytes at time 30 minutes was 85.8% (range, 81%-94%). Tyrosine release was linear over the course of experiments, indicating constant protein degradation (R2=0.9943; p<.05). Osmolarity, glucose, and glutamine had no effect on protein degradation in isolated enterocytes. Beta-hydroxybutyrate significantly decreased it (-16%; p<.05), whereas butyrate slightly increased it (+5%; p<.05).

CONCLUSIONS

A high viability and constant protein degradation indicate a successful establishment of a method to estimate protein degradation in isolated small intestinal enterocytes from rats. The large effect of beta-hydroxybutyrate suggests a potential positive role for ketone bodies to limit the loss of small intestinal protein mass by decreasing protein degradation.

Intestinal mucosal adaptation

Intestinal failure is a condition characterized by malnutrition and/or dehydration as a result of the inadequate digestion and absorption of nutrients. The most common cause of intestinal failure is short bowel syndrome, which occurs when the functional gut mass is reduced below the level necessary for adequate nutrient and water absorption. This condition may be congenital, or may be acquired as a result of a massive resection of the small bowel. Following resection, the intestine is capable of adaptation in response to enteral nutrients as well as other trophic stimuli. Identifying factors that may enhance the process of intestinal adaptation is an exciting area of research with important potential clinical applications.

New growth factor therapies aimed at improving intestinal adaptation in short bowel syndrome

Short bowel syndrome (SBS) is used to describe a condition of malabsorption and malnutrition resulting from the loss of absorptive area following massive small bowel resection. The key to improved clinical outcome after massive small bowel resection is the ability of the residual bowel to adapt. Although still in experimental stages, a major goal in the management of SBS may be the augmented use of growth factors to promote increased adaptation. A number of growth factors have been implicated in promoting the adaptation process. The best-described growth factors are reviewed: glucagon-like peptide-2 (GLP-2), epidermal growth factor (EGF), and growth hormone (GH). This article reviews the ability of recombinant GLP-2, EGF and GH to modulate structural and functional aspects of intestinal adaptation following small bowel resection. Although these growth factors have shown promise, small sample size, inconsistent measurement parameters and uncontrolled study designs have hampered the acquisition of strong data advocating the use of growth factor treatment for SBS. Multicenter trials using well-defined outcome measures to assess clinical efficacy are needed to direct the clinical indications, timing and duration of therapy and assess potential risks associated with growth factor therapies.

Dietary supplementation with orotate and uracil increases adaptive growth of jejunal mucosa after massive small bowel resection in rats

BACKGROUND

Massive small-bowel resection (SBR) increases adaptive growth of residual intestine in animal models of short-bowel syndrome (SBS). Pyrimidine nucleotides are critical for DNA and RNA synthesis, but no previous study has evaluated whether supplementation of pyrimidines or their precursors in the diet enhances adaptive gut growth after SBR. This study determined growth responses in jejunal mucosa after 7 days of dietary supplementation with uracil, or its precursor, orotate, after massive SBR in rats.

METHODS

Sprague-Dawley rats ( approximately 200 g) underwent 80% jejunoileal resection (RX) or ileal transection (TX; control). Rats were pair-fed a purified (AIN-93G) powdered diet supplemented with or without 1% (wt/wt) orotate or uracil until killing at 7 days postsurgery. Defined jejunal segments were obtained for analysis of mucosal villus height (VH), crypt depth (CD), total mucosal height, bromodeoxyuridine (BrdU) incorporation, an index of cell proliferation, and full-thickness DNA and protein content as measures of intestinal adaptive growth.

RESULTS

Jejunal VH increased significantly with SBR, as expected, and orotate further stimulated this response. Jejunal CD and total mucosal height increased significantly with both orotate and uracil supplementation compared with resected animals receiving standard diet. Orotate administration also increased jejunal DNA content compared with the increase observed with SBR alone. Finally, orotate, but not uracil, supplementation increased BrdU incorporation compared with resected rats fed standard or uracil-supplemented diet after SBR.

CONCLUSIONS

Supplementation of oral diet with the pyrimidine precursor orotate and uracil stimulated adaptive jejunal growth after massive SBR in rats. Dietary orotate had more potent growth-stimulatory effects than uracil in this animal model. Dietary supplementation with orotate and uracil represents a novel nutrition approach to enhance small-bowel mucosal adaptive growth and absorptive capacity in SBS.