Altered FXR signalling is associated with bile acid dysmetabolism in short bowel syndrome-associated liver disease

Interactions between gut bacteria and bile in health and disease

Bile acids are synthesized from cholesterol in the liver and released into the intestine to aid the digestion of dietary lipids. The host enzymes that contribute to bile acid synthesis in the liver and the regulatory pathways that influence the composition of the total bile acid pool in the host have been well established. In addition, the gut microbiota provides unique contributions to the diversity of bile acids in the bile acid pool. Gut microbial enzymes contribute significantly to bile acid metabolism through deconjugation and dehydroxylation reactions to generate unconjugated bile acids and secondary bile acids. These microbial enzymes (which include bile salt hydrolase (BSH) and bile acid-inducible (BAI) enzymes) are essential for bile acid homeostasis in the host and represent a vital contribution of the gut microbiome to host health. Perturbation of the gut microbiota in disease states may therefore significantly influence bile acid signatures in the host, especially in the context of gastrointestinal or systemic disease. Given that bile acids are ligands for host cell receptors (including the FXR, TGR5 and Vitamin D Receptor) alterations to microbial enzymes and associated changes to bile acid signatures have significant consequences for the host. In this review we examine the contribution of microbial enzymes to the process of bile acid metabolism in the host and discuss the implications for microbe-host signalling in the context of C. difficile infection, inflammatory bowel disease and other disease states.

Sphingosine Kinases/Sphingosine 1-Phosphate Signaling in Hepatic Lipid Metabolism

The ever-increasing prevalence of metabolic diseases such as dyslipidemia and diabetes in the western world continues to be of great public health concern. Biologically active sphingolipids, such as sphingosine 1-phosphate (S1P) and ceramide, are important regulators of lipid metabolism. S1P not only directly functions as an active intracellular mediator, but also activates multiple signaling pathways via five transmembrane G-protein coupled receptors (GPCRs), S1PR1-5. S1P is exclusively formed by sphingosine kinases (SphKs). Two isoforms of SphKs, SphK1 and SphK2, have been identified. Recent identification of the conjugated bile acid-induced activation of S1PR2 as a key regulator of SphK2 opened new directions for both the sphingolipid and bile acid research fields. The role of SphKs/S1P-mediated signaling pathways in health and various human diseases has been extensively reviewed elsewhere. This review focuses on recent findings related to SphKs/S1P-medaited signaling pathways in regulating hepatic lipid metabolism.

Farnesoid X Receptor Agonist Treatment Alters Bile Acid Metabolism but Exacerbates Liver Damage in a Piglet Model of Short-Bowel Syndrome

BACKGROUND & AIMS

Options for the prevention of short-bowel syndrome-associated liver disease (SBS-ALDs) are limited and often ineffective. The farnesoid X receptor (FXR) is a newly emerging pharmaceutical target and FXR agonists have been shown to ameliorate cholestasis and metabolic disorders. The aim of this study was to assess the efficacy of obeticholic acid (OCA) treatment in preventing SBS-ALDs.

METHODS

Piglets underwent 75% small-bowel resection (SBS) or sham surgery (sham) and were assigned to either a daily dose of OCA (2.4 mg/kg/day) or were untreated. Clinical measures included weight gain and stool studies. Histologic features were assessed. Ultraperformance liquid chromatography tandem mass spectrometry was used to determine bile acid composition in end point bile and portal serum samples. Gene expression of key FXR targets was assessed in intestinal and hepatic tissues via quantitative polymerase chain reaction.

RESULTS

OCA-treated SBS piglets showed decreased stool fat and altered liver histology when compared with nontreated SBS piglets. OCA prevented SBS-associated taurine depletion, however, further analysis of bile and portal serum samples indicated that OCA did not prevent SBS-associated alterations in bile acid composition. The expression of FXR target genes involved in bile acid transport and synthesis increased within the liver of SBS piglets after OCA administration whereas, paradoxically, intestinal expression of FXR target genes were decreased by OCA administration.

CONCLUSIONS

Administration of OCA in SBS reduced fat malabsorption and altered bile acid composition, but did not prevent the development of SBS-ALDs. We postulate that extensive small resection impacts the ability of the remnant intestine to respond to FXR activation.

Unravelling the metabolic impact of SBS-associated microbial dysbiosis: Insights from the piglet short bowel syndrome model

Liver disease is a major source of morbidity and mortality in children with short bowel syndrome (SBS). SBS-associated microbial dysbiosis has recently been implicated in the development of SBS-associated liver disease (SBS-ALD), however the pathological implications of this association have not been explored. In this study high-throughput sequencing of colonic content from the well-validated piglet SBS-ALD model was examined to determine alterations in microbial communities, and concurrent metabolic alterations identified in urine samples via targeted mass spectrometry approaches (GC-MS, LC-MS, FIA-MS) further uncovered impacts of microbial disturbance on metabolic outcomes in SBS-ALD. Multi-variate analyses were performed to elucidate contributing SBS-ALD microbe and metabolite panels and to identify microbe-metabolite interactions. A unique SBS-ALD microbe panel was clearest at the genus level, with discriminating bacteria predominantly from the Firmicutes and Bacteroidetes phyla. The SBS-ALD metabolome included important alterations in the microbial metabolism of amino acids and the mitochondrial metabolism of branched chain amino acids. Correlation analysis defined microbe-metabolite clustering patterns unique to SBS-ALD and identified a metabolite panel that correlates with dysbiosis of the gut microbiome in SBS.

Use of a novel docosahexaenoic acid formulation vs control in a neonatal porcine model of short bowel syndrome leads to greater intestinal absorption and higher systemic levels of DHA

Infants with short bowel syndrome (SBS) are at high risk for malabsorption, malnutrition, and failure to thrive. The objective of this study was to evaluate in a porcine model of SBS, the systemic absorption of a novel enteral Docosahexaenoic acid (DHA) formulation that forms micelles independent of bile salts (DHA-ALT®). We hypothesized that enteral delivery of DHA-ALT® would result in higher blood levels of DHA compared to a control DHA preparation due to improved intestinal absorption. SBS was induced in term piglets through a 75% mid-jejunoileal resection and the piglets randomized to either DHA-ALT® or control DHA formulation (N=5 per group) for 4 postoperative days. The median±IQR difference in final vs starting weight was 696±425 g in the DHA-ALT® group compared to 132±278 g in the controls (P=.08). Within 12 hours, median±IQR DHA and eicosapentaenoic acid plasma levels (mol%) were significantly higher in the DHA-ALT® vs control group (4.1±0.3 vs 2.5±0.5, P=.009; 0.7±0.3 vs 0.2±0.005, P=.009, respectively). There were lower fecal losses of DHA and greater ileal tissue incorporation with DHA-ALT® vs the control. Morphometric analyses demonstrated an increase in proximal jejunum and distal ileum villus height in the DHA-ALT® group compared to controls (P=.01). In a neonatal porcine model of SBS, enteral administration of a novel DHA preparation that forms micelles independent of bile salts resulted in increased fatty acid absorption, increased ileal tissue incorporation, and increased systemic levels of DHA.

Altered systemic bile acid homeostasis contributes to liver disease in pediatric patients with intestinal failure

Intestinal failure (IF)-associated liver disease (IFALD), as a major complication, contributes to significant morbidity in pediatric IF patients. However, the pathogenesis of IFALD is still uncertain. We here investigate the roles of bile acid (BA) dysmetabolism in the unclear pathogenesis of IFALD. It found that the histological evidence of pediatric IF patients exhibited liver injury, which was characterized by liver bile duct proliferation, inflammatory infiltration, hepatocyte apoptosis and different stages of fibrosis. The BA compositions were altered in serum and liver of pediatric IF patients, as reflected by a primary BA dominant composition. In IF patients, the serum FGF19 levels decreased significantly, and were conversely correlated with ileal inflammation grades (r = −0.50, p < 0.05). In ileum, the inflammation grades were inversely associated with farnesoid X receptor (FXR) expression (r = −0.55, p < 0.05). In liver, the expression of induction of the rate-limiting enzyme in bile salt synthesis, cytochrome P450 7a1 (CYP7A1) increased evidently. In conclusion, ileum inflammation decreases FXR expression corresponding to reduce serum FGF19 concentration, along with increased hepatic bile acid synthesis, leading to liver damages in IF patients.

Short bowel syndrome (SBS)-associated alterations within the gut-liver axis evolve early and persist long-term in the piglet model of short bowel syndrome

BACKGROUND AND AIM

Short bowel syndrome (SBS) is primarily characterized by malabsorption and malnutrition, resulting from loss of intestinal absorptive area following massive small bowel resection (SBR). Bile acids and the gut microbiota are functionally linked within the gut-liver axis; however, SBS-associated disturbances within the gut-liver axis remain largely unexplored. The aim of this study was to characterize the evolution of bile acid alterations within the gut-liver axis at both short-term and long-term time points and to relate these changes to alterations in colonic bacterial composition.

METHODS

Four-week-old piglets were assigned to 75% SBR, sham-operation or non-operation control groups. High throughput sequencing was employed to determine bacterial abundance in colonic content and ultra-performance liquid chromatography used to determine the bile acid concentration of gall bladder, portal serum, and fecal samples.

RESULTS

Bile acid complexity and relative abundance are altered in the SBS piglet model at two weeks post-SBR, and these changes persisted at six weeks post-SBR. Our examination of the microbial profile revealed an early and persistent loss in bacteria belonging to the Clostridiales order.

CONCLUSIONS

This study provides evidence of an early and persistent disturbance of the bile acid profile throughout the entero-hepatic circulation with an increase in the proportion of primary bile acids and a decrease in secondary bile acids following SBR. These changes were associated with a loss of bacteria belonging to the Clostridiales order consistent with a disturbance in the bile-microbial axis following SBR.

Intestinal Microbiota Signatures Associated With Histological Liver Steatosis in Pediatric-Onset Intestinal Failure

BACKGROUND

Intestinal failure (IF)-associated liver disease (IFALD) is the major cause of mortality in IF. The link between intestinal microbiota and IFALD is unclear.

METHODS

We compared intestinal microbiota of patients with IF (n = 23) with healthy controls (n = 58) using culture-independent phylogenetic microarray analysis. The microbiota was related to histological liver injury, fecal markers of intestinal inflammation, matrix metalloproteinase 9 and calprotectin, and disease characteristics.

RESULTS

Overabundance of Lactobacilli, Proteobacteria, and Actinobacteria was observed in IF, whereas bacteria related to Clostridium clusters III, IV, and XIVa along with overall diversity and richness were reduced. Patients were segregated into 3 subgroups based on dominating bacteria: Clostridium cluster XIVa, Proteobacteria, and bacteria related to Lactobacillus plantarum. In addition to liver steatosis and fibrosis, Proteobacteria were associated with prolonged current parenteral nutrition (PN) as well as liver and intestinal inflammation. Lactobacilli were related to advanced steatosis and fibrosis mostly after weaning off PN without associated inflammation. In multivariate permutational analysis of variance, liver steatosis, bowel length, PN calories, and antibiotic treatment best explained the microbiota variation among patients with IF.

CONCLUSIONS

Intestinal microbiota composition was associated with liver steatosis in IF and better predicted steatosis than duration of PN or length of the remaining intestine. Our results may be explained by a model in which steatosis is initiated during PN in response to proinflammatory lipopolysaccharides produced by Proteobacteria and progresses after weaning off PN, as the L plantarum group Lactobacilli becomes dominant and affects lipid metabolism by altering bile acid signaling.

Liver steatosis induced by small bowel resection is prevented by oral vancomycin

BACKGROUND

Intestinal failure-associated liver disease causes significant mortality in patients with short bowel syndrome. Steatosis, a major component of intestinal failure-associated liver disease has been shown to persist even after weaning from parenteral nutrition. We sought to determine whether steatosis occurs in our murine model of short bowel syndrome and whether steatosis was affected by manipulation of the intestinal microbiome.

METHODS

Male C57BL6 mice underwent 50% small bowel resection and orogastric gavage with vancomycin or vehicle for 10 weeks. DNA was extracted from stool samples then sequenced using 16s rRNA. Liver lipid content was analyzed. Bile acids were measured in liver and stool.

RESULTS

Compared with unoperated mice, small bowel resection resulted in significant changes in the fecal microbiome and was associated with a >25-fold increase in steatosis. Oral vancomycin profoundly altered the gut microbiome and was associated with a 15-fold reduction in hepatic lipid content after resection. There was a 17-fold reduction in fecal secondary bile acids after vancomycin treatment.

CONCLUSION

Massive small bowel resection in mice is associated with development of steatosis and prevented by oral vancomycin. These findings implicate a critical role for gut bacteria in intestinal failure-associated liver disease pathogenesis and illuminate a novel, operative model for future investigation into this important morbidity.

Effect of artesunate supplementation on bacterial translocation and dysbiosis of gut microbiota in rats with liver cirrhosis

AIM: To evaluate the effect of artesunate (AS) supplementation on bacterial translocation (BT) and gut microbiota in a rat model of liver cirrhosis.

METHODS: Fifty-four male Sprague-Dawley rats were randomly divided into a normal control group (N), a liver cirrhosis group (M) and a liver cirrhosis group intervened with AS (MA). Each group was sampled at 4, 6 and 8 wk. Liver cirrhosis was induced by injection of carbon tetrachloride (CCl₄), intragastric administration of 10% ethanol, and feeding a high fat diet. Rats in the MA group were intragastrically administered with AS (25 mg/kg body weight, once daily). Injuries of the liver and intestinal mucosa were assessed by hematoxylin-eosin or Masson’s trichrome staining. Liver index was calculated as a ratio of the organ weight (g) to body weight (g). The gut microbiota was examined by automated ribosomal intergenic-spacer analysis of fecal DNA. BT was assessed by standard microbiological techniques in the blood, mesenteric lymph nodes (MLNs), liver, spleen, and kidney.

RESULTS: Compared to group N, the body weight was reduced significantly in groups M and MA due to the development of liver cirrhosis over the period of 8 wk. The body weight was higher in group MA than in group M. The liver indices were significantly elevated at 4, 6 and 8 wk in groups M and MA compared to group N. AS supplementation partially decreased the liver indices in group MA. Marked histopathologic changes in the liver and small intestinal mucosa in group M were observed, which were alleviated in group MA. Levels of pro-inflammatory interleukin-6 and tumor necrosis factor-α were significantly elevated at 8 wk in ileal homogenates in group M compared to group N, which were decreased after AS supplementation in group MA. The dysbiosis of gut microbiota indicated by the mean diversity (Shannon index) and mean similarity (Sorenson index) was severe as the liver cirrhosis developed, and AS supplementation had an apparent intervention effect on the dysbiosis of gut microbiota at 4 wk. The occurrence of BT was increased in the liver of group M compared to that of group N. AS supplementation reduced BT in group MA at 8 wk. BT also occurred in the MLNs, spleen, and kidney, which was reduced by AS supplementation. BT was not detected in the blood in any group.

CONCLUSION: Dysbiosis of gut microbiota, injury of intestinal mucosal barrier and BT occurred as liver cirrhosis progressed, which might enhance inflammation and aggravate liver injury. AS may have other non-antimalarial effects that modulate gut microbiota, inhibit BT and alleviate inflammation, resulting in a reduction in CCl₄, alcohol and high fat-caused damages to the liver and intestine.

Cholecystectomy and Liver Disease in Short Bowel Syndrome

BACKGROUND

Recently, an association has been proposed between cholecystectomy and various liver diseases. Our aim was to determine whether cholecystectomy in short bowel patients influences the risk of liver disease.

METHODS

We reviewed 422 adults: 182 underwent cholecystectomy prior to short bowel, 102 after developing short bowel, and 138 patients still had the gallbladder in place.

RESULTS

Compared to pre and post short bowel, gallbladder patients were significantly less likely to have obesity (18 % and 21 % vs 9 %), central line infections (59 % and 69 % vs 46 %), intestine <60 cm (30 % and 39 % vs 26 %), and require parenteral nutrition >1 year (72 % and 77 % vs 64 %). The incidence of fatty liver was similar (31, 26, and 25 %). Fibrosis/cirrhosis was less common in the gallbladder group (26 % and 36 % vs 16 %). Frequency of end-stage liver disease was similar (15, 22, and 11 %). On multivariate analysis, cholecystectomy, parenteral nutrition >1 year, line infection, and intestine <60 cm were predictors of fibrosis/cirrhosis. Parenteral nutrition >1 year, line infection, and intestine <60 cm were predictors of end-stage liver disease.

CONCLUSIONS

Cholecystectomy does not appear to increase the incidence of liver disease in short bowel patients overall. Fibrosis/cirrhosis occurs significantly less frequently in patients with an intact gallbladder.

Total Parenteral Nutrition-Induced Cholestasis: Prevention and Management

When cholestasis occurs in patients receiving total parenteral nutrition, it is the result of many pathogenic pathways converging on the hepatic acinus. The result may be a temporary rise in liver function tests. The resulting fibrosis, portal hypertension, and jaundice are hallmarks of type 3 intestinal-associated liver disease to which children are more susceptible than adults. The key to prevention is in identifying high-risk scenarios, meticulous monitoring, and personalized prescription of parenteral nutrition solutions combined with an active approach in reducing the impact of inflammatory events when they occur by prompt use of antibiotics and line locks.

Bile Acid Modifications at the Microbe-Host Interface: Potential for Nutraceutical and Pharmaceutical Interventions in Host Health

Bile acids have emerged as important signaling molecules in the host, as they interact either locally or systemically with specific cellular receptors, in particular the farnesoid X receptor (FXR) and TGR5. These signaling functions influence systemic lipid and cholesterol metabolism, energy metabolism, immune homeostasis, and intestinal electrolyte balance. Through defined enzymatic activities, the gut microbiota can significantly modify the signaling properties of bile acids and therefore can have an impact upon host health. Alterations to the gut microbiota that influence bile acid metabolism are associated with metabolic disease, obesity, diarrhea, inflammatory bowel disease (IBD), Clostridium difficile infection, colorectal cancer, and hepatocellular carcinoma. Here, we examine the regulation of this gut-microbiota-liver axis in the context of bile acid metabolism and indicate how this pathway represents an important target for the development of new nutraceutical (diet and/or probiotics) and targeted pharmaceutical interventions.

Regulation of Hepatic Stellate Cells and Fibrogenesis by Fibroblast Growth Factors

Fibroblast growth factors (FGFs) are a family of growth factors critically involved in developmental, physiological, and pathological processes, including embryogenesis, angiogenesis, wound healing, and endocrine functions. In the liver, several FGFs are produced basally by hepatocytes and hepatic stellate cells (HSCs). Upon insult to the liver, expression of FGFs in HSCs is greatly upregulated, stimulating hepatocyte regeneration and growth. Various FGF isoforms have also been shown to directly induce HSC proliferation and activation thereby enabling autocrine and paracrine regulation of HSC function. Regulation of HSCs by the endocrine FGFs, namely, FGF15/19 and FGF21, has also recently been identified. With the ability to modulate HSC proliferation and transdifferentiation, targeting FGF signaling pathways constitutes a promising new therapeutic strategy to treat hepatic fibrosis.

Implications of microbiota and bile acid in liver injury and regeneration

Studies examining the mechanisms by which the liver incurs injury and then regenerates usually focus on factors and pathways directly within the liver, neglecting the signaling derived from the gut-liver axis. The intestinal content is rich in microorganisms as well as metabolites generated from both the host and colonizing bacteria. Through the gut-liver axis, this complex "soup" exerts an immense impact on liver integrity and function. This review article summarizes data published in the past 30 years demonstrating the signaling derived from the gut-liver axis in relation to liver injury and regeneration. Due to the intricate networks of implicated pathways as well as scarcity of available mechanistic data, it seems that nutrigenomic, metabolomics, and microbiota profiling approaches are warranted to provide a better understanding regarding the interplay and impact between nutrition, bacteria, and host response in influencing liver function and healing. Therefore elucidating the possible molecular mechanisms that link microbiota alteration to host physiological response and vice versa.

Glucagon-Like Peptide-2 Alters Bile Acid Metabolism in Parenteral Nutrition--Associated Liver Disease

BACKGROUND

We aim to study the mechanisms underlying our previous finding that exogenous glucagon-like peptide-2 (GLP-2) treatment in a preclinical model of neonatal parenteral nutrition-associated liver disease (PNALD) improves cholestasis.

METHODS

Neonatal piglets received 17 days of parenteral nutrition (PN) therapy and either saline control (PN/Saline n = 8) or GLP-2 treatment at 11 nmol/kg/d (PN/GLP-2, n = 7). At terminal laparotomy, bile and liver samples were collected. The relative gene expression of enzymes involved in bile acid synthesis, regulation, and transport was measured in liver by reverse-transcriptase quantitative polymerase chain reaction. Bile acid composition in bile was determined using tandem mass spectrometry. Data were analyzed using 1-way analysis of variance (ANOVA) or Kruskal-Wallis ANOVA.

RESULTS

GLP-2 increased the expression of bile acid export genes: multidrug resistance-associated proteins 2 (MRP2) (P = .002) and 3 (MRP3) (P = .037) over saline control. GLP-2 increased expression of Farnesoid X receptor (FXR) (P < .001) and CYP7A1 (cytochrome P450, family 7, subfamily A, polypeptide 1) (P = .03). GLP-2 treatment was associated with decreased concentrations of taurohyocholic acid and conjugates of toxic lithocholic acid (P < .01). GLP-2 treatment increased the liver bile acid content.

CONCLUSIONS

GLP-2 treatment was associated with alterations in the hepatic expression of genes involved in bile acid metabolism. The transcriptomic results indicate the mechanisms at the transcriptional level acting to regulate bile acid synthesis and increase bile acid export. Differences in bile acid profiles further support a beneficial role for GLP-2 therapy in PNALD.

Loss of ileum decreases serum fibroblast growth factor 19 in relation to liver inflammation and fibrosis in pediatric onset intestinal failure

BACKGROUND & AIMS

The pathogenesis of intestinal failure (IF) associated liver disease (IFALD) is uncertain, we therefore investigated the role of FGF19 and pro-inflammatory cytokines has on this disease state.

METHODS

Serum FGF19, IL-6 and, TNF-α were measured in 52 IF patients at median age 6.0 years (IQR 2.2-13) after 10 months (4.1-39) on parenteral nutrition (PN). Thirty-nine patients underwent liver biopsies.

RESULTS

In IF patients, FGF19 concentrations were lower and those of IL-6 and TNF-α higher compared to healthy matched controls (p ⩽ 0.001 for all). FGF19 concentrations were further decreased in patients without a remaining ileum [37 pg/ml (IQR 30-68) vs. 74 (35-135) p=0.028], and correlated with remaining ileum length (r = 0.333, p = 0.018) and markers of cholesterol synthesis (r = -0.552 to -0.643, p < 0.001). Patients with histological portal inflammation [30 pg/ml (28-45) vs. 48 (33-100), p = 0.019] or fibrosis [35 pg/ml (30-66) vs. 99 (38-163), p = 0.013] had lower serum FGF19 concentrations than others. FGF19 negatively correlated with portal inflammation grade (r = -0.442, p = 0.005), serum TNF-α (r = -0.318, p = 0.025), METAVIR fibrosis stage (r = -0.441, p = 0.005) and APRI (r = -0.328, p = 0.028). IL-6 was higher during PN [6 pg/ml (2-31)] than after weaning off PN [2 pg/ml (1-5), p = 0.009], correlated weakly with cholestasis grade (r = 0.328, p = 0.044), and tended to associate with histological cholestasis [n = 5, 5 pg/ml (5-267) vs. n=34, 2 pg/ml (1-7), p = 0.058].

CONCLUSIONS

In pediatric onset of IF, total or partial loss of ileum decreases serum FGF19 concentration corresponding to hepatic inflammation and fibrosis, along with increased cholesterol synthesis. In contrast, serum IL-6 increases during PN and may associate with concurrent cholestasis. These data suggests that FGF19 may contribute to the pathogenesis of IFALD.

Emerging Piglet Models of Neonatal Short Bowel Syndrome

Short bowel syndrome (SBS) is a growing problem in the human neonatal population. In infants, SBS is the leading cause of intestinal failure, the state of being unable to absorb sufficient nutrients for growth and development. Neonates with SBS are dependent on long-term parenteral nutrition therapy, but many succumb to the complications of sepsis and liver disease. Research in neonatal SBS is challenged by the ethical limits of studying sick human neonates and the heterogeneous nature of the disease process. Outcomes in SBS vary depending on residual intestinal anatomy, intestinal length, patient age, and exposure to nutrition therapies. The neonatal piglet serves as an appropriate translational model of the human neonate because of similarities in gastrointestinal ontogeny, physiological maturity, and adaptive processes. Re-creating the disease process in a piglet model presents a unique opportunity for researchers to discover novel insights and therapies in SBS. Emerging piglet models of neonatal SBS now represent the entire spectrum of disease seen in human infants. This review aims to contextualize these emerging piglet models within the context of SBS as a heterogeneous disease. We first explore the factors that account for SBS heterogeneity and then explore the suitability of the neonatal piglet as an appropriate translational animal model. We then examine differences between the emerging piglet models of neonatal SBS and how these differences affect their translational potential to human neonates with SBS.