Distinct intestinal adaptation for vitamin B12 and bile acid absorption revealed in a new mouse model of massive ileocecal resection

Nutrition and Intestinal Rehabilitation of Children With Short Bowel Syndrome: A Position Paper of the ESPGHAN Committee on Nutrition. Part 1: From Intestinal Resection to Home Discharge

Short bowel syndrome (SBS) is the leading cause of intestinal failure (IF) in children. The mainstay of treatment for IF is parenteral nutrition (PN). The aim of this position paper is to review the available evidence on managing SBS and to provide practical guidance to clinicians dealing with this condition. All members of the Nutrition Committee of the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) contributed to this position paper. Some renowned experts in the field joined the team to guide with their experience. A systematic literature search was performed from 2005 to May 2021 using PubMed, MEDLINE, and Cochrane Database of Systematic Reviews. In the absence of evidence, recommendations reflect the expert opinion of the authors. Literature on SBS mainly consists of retrospective single-center experience, thus most of the current papers and recommendations are based on expert opinion. All recommendations were voted on by the expert panel and reached >90% agreement. The first part of this position paper focuses on the physiological mechanism of intestinal adaptation after surgical resection. It subsequently provides some clinical practice recommendations for the primary management of children with SBS from surgical resection until discharged home on PN.

Alteration of Ileal lncRNAs After Duodenal–Jejunal Bypass Is Associated With Regulation of Lipid and Amino Acid Metabolism

Metabolic and bariatric surgery (MBS) can generate a drastic shift of coding and noncoding RNA expression patterns in the gastrointestinal system, which triggers organ function remodeling and may induce type 2 diabetes (T2D) remission. Our previous studies have demonstrated that the altered expression profiles of duodenal and jejunal long noncoding RNAs (lncRNAs) after the duodenal–jejunal bypass (DJB), an investigational procedure and research tool of MBS, can improve glycemic control by modulating the entero-pancreatic axis and gut–brain axis, respectively. As an indiscerptible part of the intestine, the ileal lncRNA expression signatures after DJB and the critical pathways associated with postoperative correction of the impaired metabolism need to be investigated too. High-fat diet-induced diabetic mice were randomly assigned into two groups receiving either DJB or sham surgery. Compared to the sham group, 1,425 dysregulated ileal lncRNAs and 552 co-expressed mRNAs were identified in the DJB group. Bioinformatics analysis of the differently expressed mRNAs and predicted target genes or transcriptional factors indicated that the dysregulated ileal lncRNAs were associated with lipid and amino acid metabolism-related pathways. Moreover, a series of lncRNAs and their potential target mRNAs, especially NONMMUT040618, Pxmp4, Pnpla3, and Car5a, were identified on the pathway. In conclusion, DJB can induce remarkable alteration of ileal lncRNA and mRNA expression. The role of the ileum in DJB tends to re-establish the energy homeostasis by regulating the lipid and amino acid metabolism.

Review article: insights into the bile acid-gut microbiota axis in intestinal failure-associated liver disease-redefining the treatment approach

BACKGROUND

Intestinal failure-associated liver disease (IFALD) increases mortality of patients with intestinal failure (IF), but lacks effective prevention or treatment approaches. Bile acids, gut microbiota and the host have close and complex interactions, which play a central role in modulating host immune and metabolic homeostasis. Increasing evidence suggests that derangement of the bile acid-gut microbiota (BA-GM) axis contributes to the development of IFALD.

AIMS

To review the BA-GM axis in the pathogenesis and clinical applications of IFALD, and to explore future directions for effective disease management.

METHODS

We conducted a literature search on bile acid and gut microbiota in IF and liver diseases.

RESULTS

The BA-GM axis demonstrates a unique IF signature manifesting as an increase in primary-to-secondary bile acids ratio, disturbed enterohepatic circulation, blunted bile acid signalling pathways, gut microbial dysbiosis, and altered microbial metabolic outputs. Bile acids and gut microbiota shape the compositional and functional alterations of each other in IF; collaboratively, they promote immune dysfunction and metabolic aberration in the liver. Diagnostic markers and treatments targeting the BA-GM axis showed promising potential in the management of IFALD.

CONCLUSIONS

Bile acids and gut microbiota play a central role in the development of IFALD and make attractive biomarkers as well as therapeutic targets. A multitarget, individualised therapy aiming at different parts of the BA-GM axis may provide optimal clinical benefits and requires future investigation.

Defined serum-free culture of human infant small intestinal organoids with predetermined doses of Wnt3a and R-spondin1 from surgical specimens

PURPOSE

Refinement of organoid technology is important for studying physiology and disease of the intestine. We aimed to optimize defined serum-free conditions for human infant small intestinal (SI) organoid culture with predetermined doses of Wnt3a and Rspo1 from surgical specimens. We further assessed whether intestinal specimens could be stored before use as a source of organoids.

METHODS

Different doses of Wnt3a and Rspo1 in a serum-free medium were tested to establish a condition in which surgically resected SI cells grew as organoids over multiple passages. The expression of marker genes for stem and differentiated cells was assessed by quantitative polymerase chain reaction. We also investigated the organoid-forming efficiency of cells in degenerating intestines stored at 4 °C for various intervals post-resection.

RESULTS

We determined the doses of Wnt3a and Rspo1 required for the continuous growth of infant SI organoids with multi-differentiation potential. We revealed that, despite the time-dependent loss of stem cells, tissues stored for up to 2 days preserved cells capable of generating amplifiable organoids.

CONCLUSION

SI cells can be grown as organoids under defined conditions. This could provide a reproducible and customizable method of using surgical specimens for the study of intestinal maturation and their relevance to pediatric diseases.

Severe Intestinal Dysbiosis in Rat Models of Short Bowel Syndrome with Ileocecal Resection

BACKGROUND

Short bowel syndrome (SBS) resulting from extensive intestinal resection is thought to significantly affect gut microbiota. Data are limited on the signatures of the intestinal microbiome in SBS with different anatomical types.

AIMS

The aim of our investigation was to characterize the composition and function of gut microbiota in SBS with or without ileocecal resection (ICR).

METHODS

Six-week-old male Sprague-Dawley rats underwent 75% small bowel resection (SBR) with the ileocecal junction intact (SBR group, jejunoileal anastomosis, n = 10) or removed (ICR group, jejunocolic anastomosis, n = 10), or sham surgery (sham group, n = 10). Colonic contents of the rats were collected 28 days after operation, and 16S rRNA gene sequencing was performed on the MiSeq Illumina platform to analyze bacterial composition.

RESULTS

Overall structures of the gut microbiome differed significantly among the three groups. The bacterial α-diversity of the ICR group was remarkably lower than that of the sham group. ICR rats were enriched with Lactobacillus and opportunistic pathogens from Proteobacteria but depleted of commensal genera belonging to the Lachnospiraceae, Ruminococcaceae and Erysipelotrichaceae families. Genera from the Bacteroidales S24-7 group, Porphyromonadaceae, Prevotellaceae, Rikenellaceae and Christensenellaceae were prevalent in SBR rats. Functional pathways of branched-chain and aromatic amino acid biosynthesis, lipopolysaccharide biosynthesis and infectious diseases were abundant in the ICR group, while SBR rats featured pathways of C5 branched dibasic acid metabolism, biotin metabolism and one carbon pool folate.

CONCLUSIONS

ICR causes dramatically more severe intestinal dysbiosis than SBR only in SBS rat models, resulting in altered functional profiles of the gut microbiome.

Nod2 deficiency functionally impairs adaptation to short bowel syndrome via alterations of the epithelial barrier function

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) gene mutations are a risk factor for Crohn's disease and also associated with worse outcome in short bowel syndrome (SBS) patients independent of the underlying disease. The aim of this study was to analyze the effect of Nod2 deficiency on barrier function and stool microbiome after extensive ileocecal resection in mice. Male C57BL6/J wild-type (WT) and Nod2-knockout (KO) mice underwent 40% ileocecal resection. Sham control mice received simple transection of the ileum. Clinical outcome was monitored daily. Barrier function was measured with Ussing chambers using FITC-4-kDa-Dextran flux, transmucosal electrical resistance, and dilution potentials. Immunofluorescence of claudin-2 was studied. Composition of the stool microbiome was assessed by 16S rRNA gene sequencing. Resected Nod2-KO mice had impaired clinical outcome compared with resected WT mice. This was accompanied by increased stool water contents and increased plasma aldosterone. Histomorphological adaptation was independent of Nod2. Barrier function studies revealed impaired sodium to chloride permeability and altered claudin-2 localization in the absence of Nod2. Resection induced decreases of bacterial diversity and a shift of bacteriodetes-to-firmicutes ratios. Ileum and cecum resection-induced increase in proteobacteria was absent in Nod2-deficient mice. Verrucomicrobia were temporarily increased in Nod2-KO mice. Nod2 deficiency functionally impairs adaptation to short bowel syndrome via a lesser increase of epithelial sodium pore permeability, altered epithelial barrier function, and the microbiome.NEW & NOTEWORTHYNOD2 gene mutations are associated with the development of severe short bowel syndrome and intestinal failure. The influence of Nod2 mutations on intestinal adaptation in experimental short bowel syndrome has not been studied yet. Here, we provide data that Nod2 deficiency worsens clinical outcome and functional adaptation under SBS conditions in mice, indicating that NOD2 is required for successful adaptation after ileocecal resection.

The colon as an energy salvage organ for children with short bowel syndrome

BACKGROUND

The main cause of intestinal failure is short bowel syndrome (SBS). The management goal for children with SBS is to promote intestinal adaptation while preserving growth and development with the use of parenteral nutrition (PN).

OBJECTIVES

This study evaluated the intestinal absorption rate in children with SBS, focusing on the role of the remnant colon. In addition, the relation between intestinal absorption rate, citrulline concentration, and small bowel length was studied.

METHODS

Thirty-two children with SBS on PN were included. They were divided into 3 groups according to the European Society for Clinical Nutrition and Metabolism (ESPEN) anatomical classification system: type 1 SBS (n = 9), type 2 (n = 13), and type 3 (n = 10). Intestinal absorption rate was assessed by a stool balance analysis of a 3-d collection of stools. Plasma citrulline concentrations were measured and the level of PN dependency was calculated.

RESULTS

The total energy absorption rate did not differ significantly between the 3 groups: 68% (61-79% ) for type 1, 60% (40-77%) for type 2, and 60% (40-77%) for type 3 ( P = 0.45). Children with type 2 or 3 SBS had significantly shorter small bowel length than children with type 1: 28 cm (19-36 cm) and 16 cm (2-29 cm), respectively, compared with 60 cm (45-78 cm) ( P = 0.04). Plasma citrulline concentrations were lower in type 3 SBS but not significantly different: 15 µmol/L (11-25 µmol/L) in type 1, 14 µmol/L (7-21 µmol/L) in type 2 , and 9 µmol/L (6-14 µmol/L) in type 3 ( P = 0.141). A multivariate analysis confirmed the role of the remnant colon in providing additional energy absorption.

CONCLUSION

This study demonstrated the importance of the colon as a salvage organ in children with SBS. Plasma citrulline concentrations should be interpreted according to the type of SBS. Efforts should focus on conservative surgery, early re-establishment of a colon in continuity, and preserving the intestinal microbiota.

Villus Growth, Increased Intestinal Epithelial Sodium Selectivity, and Hyperaldosteronism Are Mechanisms of Adaptation in a Murine Model of Short Bowel Syndrome

BACKGROUND

Short bowel syndrome results from extensive small bowel resection and induces adaptation of the remaining intestine. Ileocecal resection (ICR) is the most frequent situation in humans. Villus hypertrophy is one hallmark of mucosal adaptation, but the functional mechanisms of mucosal adaptation are incompletely understood.

AIMS

The aim of the study was to characterize a clinically relevant model of short bowel syndrome but not intestinal failure in mice and to identify outcome predictors and mechanisms of adaptation.

METHODS

Male C57BL6/J mice underwent 40% ICR and were followed for 7 or 14 days. Small bowel transection served as control. All mice underwent autopsy. Survival, body weight, wellness score, stool water content, plasma aldosterone concentrations, and paracellular permeability were recorded.

RESULTS

Unlike controls, resected mice developed significant diarrhea with increased stool water. This was accompanied by sustained weight loss throughout follow-up. Villus length increased but did not correlate positively with adaptation. Plasma aldosterone concentrations correlated inversely with body weight at day 14. After ICR, intestinal epithelial (i.e., tight junctional) sodium permeability was increased.

CONCLUSIONS

40% ICR results in moderate to severe short bowel syndrome. Successful adaptation to the short bowel situation involves villus elongation but does not correlate with the degree of villus elongation alone. In addition, increased intestinal epithelial sodium permeability facilitates sodium-coupled solute transport. Hyperaldosteronism correlates with the severity of weight loss, indicates volume depletion, and counterregulates water loss.