Validating hyperbilirubinemia and gut mucosal atrophy with a novel ultramobile ambulatory total parenteral nutrition piglet model

Intraduodenal fecal microbiota transplantation ameliorates gut atrophy and cholestasis in a novel parenteral nutrition piglet model

Total parenteral nutrition (TPN) provides lifesaving nutritional support intravenously; however, it is associated with significant side effects. Given gut microbial alterations noted with TPN, we hypothesized that transferring fecal microbiota from healthy controls would restore gut-systemic signaling in TPN and mitigate injury. Using our novel ambulatory model (US Patent: US 63/136,165), 31 piglets were randomly allocated to enteral nutrition (EN), TPN only, TPN + antibiotics (TPN-A), or TPN + intraduodenal fecal microbiota transplant (TPN + FMT) for 14 days. Gut, liver, and serum were assessed through histology, biochemistry, and qPCR. Stool samples underwent 16 s rRNA sequencing. Permutational multivariate analysis of variance, Jaccard, and Bray-Curtis metrics were performed. Significant bilirubin elevation in TPN and TPN-A versus EN (P < 0.0001) was prevented with FMT. IFN-G, TNF-α, IL-β, IL-8, and lipopolysaccharide (LPS) were significantly higher in TPN (P = 0.009, P = 0.001, P = 0.043, P = 0.011, P < 0.0001), with preservation upon FMT. Significant gut atrophy by villous-to-crypt ratio in TPN (P < 0.0001) and TPN-A (P = 0.0001) versus EN was prevented by FMT (P = 0.426 vs. EN). Microbiota profiles using principal coordinate analysis demonstrated significant FMT and EN overlap, with the largest separation in TPN-A followed by TPN, driven primarily by Firmicutes and Fusobacteria. TPN-altered gut barrier was preserved upon FMT; upregulated cholesterol 7 α-hydroxylase and bile salt export pump in TPN and TPN-A and downregulated fibroblast growth factor receptor 4, EGF, farnesoid X receptor, and Takeda G Protein-coupled Receptor 5 (TGR5) versus EN was prevented by FMT. This study provides novel evidence of prevention of gut atrophy, liver injury, and microbial dysbiosis with intraduodenal FMT, challenging current paradigms into TPN injury mechanisms and underscores the importance of gut microbes as prime targets for therapeutics and drug discovery.NEW & NOTEWORTHY Intraduodenal fecal microbiota transplantation presents a novel strategy to mitigate complications associated with total parenteral nutrition (TPN), highlighting gut microbiota as a prime target for therapeutic and diagnostic approaches. These results from a highly translatable model provide hope for TPN side effect mitigation for thousands of chronically TPN-dependent patients.

Parenteral Nutrition, Inflammatory Bowel Disease, and Gut Barrier: An Intricate Plot

Malnutrition poses a critical challenge in inflammatory bowel disease, with the potential to detrimentally impact medical treatment, surgical outcomes, and general well-being. Parenteral nutrition is crucial in certain clinical scenarios, such as with patients suffering from short bowel syndrome, intestinal insufficiency, high-yielding gastrointestinal fistula, or complete small bowel obstruction, to effectively manage malnutrition. Nevertheless, research over the years has attempted to define the potential effects of parenteral nutrition on the intestinal barrier and the composition of the gut microbiota. In this narrative review, we have gathered and analyzed findings from both preclinical and clinical studies on this topic. Based on existing evidence, there is a clear correlation between short- and long-term parenteral nutrition and negative effects on the intestinal system. These include mucosal atrophic damage and immunological and neuroendocrine dysregulation, as well as alterations in gut barrier permeability and microbiota composition. However, the mechanistic role of these changes in inflammatory bowel disease remains unclear. Therefore, further research is necessary to effectively address the numerous gaps and unanswered questions pertaining to these issues.

Lower systemic inflammation is associated with gut firmicutes dominance and reduced liver injury in a novel ambulatory model of parenteral nutrition

BACKGROUND

Total Parenteral Nutrition (TPN) provides lifesaving nutritional support to patients unable to maintain regular enteral nutrition (EN). Unfortunately, cholestasis is a significant side effect affecting 20-40% of paediatric patients. While the aetiology of TPN-associated injury remains ill-defined, an altered enterohepatic circulation in the absence of gut luminal nutrient content during TPN results in major gut microbial clonal shifts, resulting in metabolic endotoxemia and systemic inflammation driving liver injury and cholestasis.

HYPOTHESIS

To interrogate the role of gut microbiota, using our novel ambulatory TPN piglet model, we hypothesized that clonal reduction of bacteria in Firmicutes phylum (predominant in EN) and an increase in pathogenic Gram-negative bacteria during TPN correlates with an increase in serum lipopolysaccharide and systemic inflammatory cytokines, driving liver injury.

METHODS

Upon institutional approval, 16 animals were allocated to receive either TPN (n = 7) or EN only (n = 9). The TPN group was subdivided into a low systemic inflammation (TPN-LSI) and high systemic inflammation (TPN-HSI) based on the level of serum lipopolysaccharide. Culture-independent identification of faecal bacterial populations was determined by 16S rRNA.

RESULTS

Piglets on TPN, in the TPN-HSI group, noted a loss of enterocyte protective Firmicutes bacteria and clonal proliferation of potent inflammatory and lipopolysaccharide containing pathogens: Fusobacterium, Bacteroidetes and Campylobacter compared to EN animals. Within the TPN group, the proportion of Firmicutes phylum correlated with lower portal lipopolysaccharide levels (r = -0.89). The TPN-LSI had a significantly lower level of serum bile acids compared to the TPN-HSI group (7.3 vs. 60.4 mg/dL; p = .018), increased day 14 weight (5.67 vs. 5.07 kg; p = .017) as well as a 13.7-fold decrease in serum conjugated bilirubin.

CONCLUSION

We demonstrate a novel relationship between the gut microbiota and systemic inflammation in a TPN animal model. Pertinently, the degree of gut dysbiosis correlated with the severity of systemic inflammation. This study underscores the role of gut microbiota in driving liver injury mechanisms during TPN and supports a paradigm change in therapeutic targeting of the gut microbiota to mitigate TPN-related injury. KEY MESSAGESThis study identified a differential link between gut microbiota and inflammation-the higher the dysbiosis, the worse the systemic inflammatory markers.Higher levels of Firmicutes species correlated with reduced inflammation.

Novel Therapeutic Approaches for Mitigating Complications in Short Bowel Syndrome

Short bowel syndrome (SBS) is a particularly serious condition in which the small intestine does not absorb sufficient nutrients for biological needs, resulting in severe illness and potentially death if not treated. Given the important role of the gut in many signaling cascades throughout the body, SBS results in disruption of many pathways and imbalances in various hormones. Due to the inability to meet sufficient nutritional needs, an intravenous form of nutrition, total parental nutrition (TPN), is administered. However, TPN presents difficulties such as severe liver injury and altered signaling secondary to the continued lack of luminal contents. This manuscript aims to summarize relevant studies into the systemic effects of TPN on systems such as the gut-brain, gut-lung, and gut-liver axis, as well as present novel therapeutics currently under use or investigation as mitigation strategies for TPN induced injury.

Carbamazepine mitigates parenteral nutrition-associated liver disease in a novel ambulatory piglet model

BACKGROUND

Parenteral nutrition (PN) remains a critical therapeutic option in patients who cannot tolerate enteral feeding. However, although lifesaving, PN is associated with significant side effects, including liver injury, the etiology of which is multifactorial. Carbamazepine (CBZ), an antiepileptic medication, is known to modulate hepatic fibrosis and hepatocellular injury in a variety of liver diseases. We hypothesized that CBZ could prevent PN-associated liver disease (PNALD), which we tested by using our novel ambulatory PN piglet model.

METHODS

Piglets were fitted with jugular catheters and infusion pumps for PN and randomized to enteral nutrition (n = 7), PN (n = 6), or PN with parenteral CBZ (n = 6) for 2 weeks. Serum and liver tissue were analyzed via light microscopy, quantification of serum liver injury markers, Ki67 and cytokeratin-7 indexing, and real-time quantitative polymerase chain reaction.

RESULTS

PN-fed piglets in our model developed manifestations of PNALD-particularly, increased serum bilirubin, gamma-glutamyltransferase, liver cholestasis, and Ki67 expression compared with that of EN-fed animals (P < 0.03). CBZ therapy in PN-fed animals led to a significant reduction in these markers of injury (P < 0.05). Investigation into the mechanism of these therapeutic effects revealed increased expression of sterol regulatory element-binding protein 1 (SREBP-1), peroxisome proliferator-activated receptor alpha (PPAR-α), and fatty acid binding protein (FABP) in PN-fed animals receiving CBZ (P < 0.03). Further investigation revealed increased LC3 expression and decreased lysosomal-associated membrane protein (LAMP1) expression with CBZ (P < 0.03).

CONCLUSION

CBZ administration mitigates PNALD severity, suggesting a novel therapeutic strategy targeting PN-associated side effects, and may present a paradigm change to current treatment options.

Beyond lipids: Novel mechanisms for parenteral nutrition-associated liver disease

Parenteral nutrition (PN) is a therapy that delivers essential nutrients intravenously to patients who are unable to meet their nutrition requirements via standard enteral feeding. This methodology is often referred to as PN when accompanied by minimal or no enteral nutrition (EN). Although PN is lifesaving, significant complications can arise, such as intestinal failure-associated liver disease and gut-mucosal atrophy. The exact mechanism of injury remains ill defined. This review was designed to explore the available literature related to the drivers of injury mechanisms. The Farnesoid X receptor and fibroblast growth factor 19 signaling pathway seems to play an important role in gut-systemic signaling, and its alteration during PN provides insights into mechanistic links. Central line infections also play a key role in mediating PN-associated injury. Although lipid reduction strategies, as well as the use of multicomponent lipid emulsions and vitamin E, have shown promise, the cornerstone of preventing injury is the early establishment of EN.

Impaired Gut-Systemic Signaling Drives Total Parenteral Nutrition-Associated Injury

BACKGROUND

Total parenteral nutrition (TPN) provides all nutritional needs intravenously. Although lifesaving, enthusiasm is significantly tempered due to side effects of liver and gut injury, as well as lack of mechanistic understanding into drivers of TPN injury. We hypothesized that the state of luminal nutritional deprivation with TPN drives alterations in gut-systemic signaling, contributing to injury, and tested this hypothesis using our ambulatory TPN model.

METHODS

A total of 16 one-week-old piglets were allocated randomly to TPN (n = 8) or enteral nutrition (EN, n = 8) for 3 weeks. Liver, gut, and serum were analyzed. All tests were two-sided, with a significance level of 0.05.

RESULTS

TPN resulted in significant hyperbilirubinemia and cholestatic liver injury, p = 0.034. Hepatic inflammation (cluster of differentiation 3 (CD3) immunohistochemistry) was higher with TPN (p = 0.021). No significant differences in alanine aminotransferase (ALT) or bile ductular proliferation were noted. TPN resulted in reduction of muscularis mucosa thickness and marked gut atrophy. Median and interquartile range for gut mass was 0.46 (0.30-0.58) g/cm in EN, and 0.19 (0.11-0.29) g/cm in TPN (p = 0.024). Key gut-systemic signaling regulators, liver farnesoid X receptor (FXR; p = 0.021), liver constitutive androstane receptor (CAR; p = 0.014), gut FXR (p = 0.028), G-coupled bile acid receptor (TGR5) (p = 0.003), epidermal growth factor (EGF; p = 0.016), organic anion transporter (OAT; p = 0.028), Mitogen-activated protein kinases-1 (MAPK1) (p = 0.037), and sodium uptake transporter sodium glucose-linked transporter (SGLT-1; p = 0.010) were significantly downregulated in TPN animals, whereas liver cholesterol 7 alpha-hydroxylase (CyP7A1) was substantially higher with TPN (p = 0.011).

CONCLUSION

We report significant alterations in key hepatobiliary receptors driving gut-systemic signaling in a TPN piglet model. This presents a major advancement to our understanding of TPN-associated injury and suggests opportunities for strategic targeting of the gut-systemic axis, specifically, FXR, TGR5, and EGF in developing ameliorative strategies.

A porcine animal model to mimic the restart of enteral nutrition (refeeding-model)

With the aim towards establishing an animal model of total parenteral nutrition (TPN), 12 piglets aged 9 weeks (mean body weight 21 kg) were surgically provided with central venous catheters. Six piglets were nourished parenterally with the objective to reach a 14-d period of TPN; the other six piglets served as control and were fed normally. Only one animal from each group could be monitored over the whole period. Nine piglets were euthanised on d 13 and one on d 12. No animal showed fever or signs of septicaemia during the study. The levels of Ca, Mg, Na and P in the blood were within the normal range as were those for blood glucose and plasma creatinine. Symptoms of the TPN included: transient diarrhoea, occasional appearance of faecal blood and occasional absence of defecation. A reduced small intestine length and altered mucosal morphology and function were observed. One animal showed bile stasis at the end of the study. All TPN animals showed a remarkably high level of blood urea early in the morning. The intestinal symptoms observed may resemble the human situation during TPN. However, due to the fast growth rate, pigs aged 9 weeks have higher nutrient requirements per kg body weight. Consequently, the osmolality of the nutrient solution was necessarily high. Whether the significantly higher blood urea observed in the TPN group reflected a catabolic metabolism during the starving period at night-time could not be conclusively shown. Alternatively, it could reflect a slower growth rate and a resulting quantitative excess of amino acids (AA), or could have been the consequence of a suboptimal AA composition. A permanent infusion would be favourable in order not to overcharge the capacity for glucose uptake and amino acid metabolism during the infusion.

Developing a Novel Ambulatory Total Parenteral Nutrition-Dependent Short Bowel Syndrome Animal Model

BACKGROUND

Short bowel syndrome (SBS) results from extensive bowel resection. Patients with SBS require total parenteral nutrition (TPN) for survival. Understanding mechanisms contributing to TPN-associated liver injury and gut atrophy are critical in developing SBS therapies. Existing SBS models using tethered animals have significant limitations and are unlike ambulatory human SBS patients. We hypothesized that we could induce SBS in piglets and develop an ambulatory TPN-SBS model.

MATERIAL AND METHODS

Eighteen neonatal pigs received duodenal and jugular catheters. They were fitted with a jacket holding TPN and a miniaturized pump. Six piglets had 90% small bowel resection and catheter placement (SBS group). Non-SBS piglets were randomized into enteral nutrition (EN) or TPN.

RESULTS

Bowel resection was successfully accomplished in SBS animals. Weight gain was similar in all groups. SBS animals had increased serum bilirubin compared to EN. Mean conjugated bilirubin ± SD was 0.045 ± 0.01 for EN, (P = 0.03 EN versus TPN and P = 0.03 SBS versus EN) and 1.09 ± 1.25 for TPN, (P = 0.62 TPN versus SBS). Gut density was reduced in the TPN group compared to EN and SBS groups. Mean gut density ± SD was 0.11 ± 0.04 for TPN (P = 0.0004 TPN versus SBS and P = 0.00007 TPN versus EN) and not statistically different for EN versus SBS (P = 0.32).

CONCLUSIONS

We created a novel, ambulatory TPN-SBS model using piglets, mimicking long-term TPN delivery in human SBS patients. Our model demonstrated TPN-related conjugated hyperbilirubinemia and compensatory gut hypertrophy, as noted in humans with SBS. This model holds great potential for future research.

Role of the Gut⁻Liver Axis in Driving Parenteral Nutrition-Associated Injury

For decades, parenteral nutrition (PN) has been a successful method for intravenous delivery of nutrition and remains an essential therapy for individuals with intolerance of enteral feedings or impaired gut function. Although the benefits of PN are evident, its use does not come without a significant risk of complications. For instance, parenteral nutrition-associated liver disease (PNALD)—a well-described cholestatic liver injury—and atrophic changes in the gut have both been described in patients receiving PN. Although several mechanisms for these changes have been postulated, data have revealed that the introduction of enteral nutrition may mitigate this injury. This observation has led to the hypothesis that gut-derived signals, originating in response to the presence of luminal contents, may contribute to a decrease in damage to the liver and gut. This review seeks to present the current knowledge regarding the modulation of what is known as the “gut–liver axis” and the gut-derived signals which play a role in PN-associated injury.

No Gut No Gain! Enteral Bile Acid Treatment Preserves Gut Growth but Not Parenteral Nutrition-Associated Liver Injury in a Novel Extensive Short Bowel Animal Model

BACKGROUND

Parenteral nutrition (PN) provides nutrition intravenously; however, this life-saving therapy is associated with significant liver disease. Recent evidence indicates improvement in PN-associated injury in animals with intact gut treated with enteral bile acid (BA), chenodeoxycholic acid (CDCA), and a gut farnesoid X receptor (FXR) agonist, which drives the gut-liver cross talk (GLCT). We hypothesized that similar improvement could be translated in animals with short bowel syndrome (SBS).

METHODS

Using piglets, we developed a novel 90% gut-resected SBS model. Fifteen SBS piglets receiving PN were given CDCA or control (vehicle control) for 2 weeks. Tissue and serum were analyzed posteuthanasia.

RESULTS

CDCA increased gut FXR (quantitative polymerase chain reaction; P = .008), but not downstream FXR targets. No difference in gut fibroblast growth factor 19 (FGF19; P = .28) or hepatic FXR (P = .75), FGF19 (P = .86), FGFR4 (P = .53), or Cholesterol 7 α-hydroxylase (P = .61) was noted. PN resulted in cholestasis; however, no improvement was noted with CDCA. Hepatic fibrosis or immunostaining for Ki67, CD3, or Cytokeratin 7 was not different with CDCA. PN resulted in gut atrophy. CDCA preserved (P = .04 vs control) gut mass and villous/crypt ratio. The median (interquartile range) for gut mass for control was 0.28 (0.17-0.34) and for CDCA was 0.33 (0.26-0.46).

CONCLUSIONS

We note that, unlike in animals with intact gut, in an SBS animal model there is inadequate CDCA-induced activation of gut-derived signaling to cause liver improvement. Thus, it appears that activation of GLCT is critically dependent on the presence of adequate gut. This is clinically relevant because it suggests that BA therapy may not be as effective for patients with SBS.

Duodenal Disaccharidase Activities During and After Weaning off Parenteral Nutrition in Pediatric Intestinal Failure

OBJECTIVES

Data on factors affecting absorptive function in children with intestinal failure (IF) are sparse. We evaluated duodenal disaccharidase activities and inflammation in relation to parenteral nutrition (PN) and intestinal resection in pediatric onset IF.

METHODS

Disaccharidase (maltase, sucrase, and lactase) activities and histologic inflammation were evaluated from duodenal biopsies in 58 patients during PN (n = 23) or full enteral nutrition (n = 40) and in 43 matched controls. The first and the last postresection biopsies were analyzed separately after 4.3 (1.2-9.7) years and 6.5 (2.3-12.4) years, respectively.

RESULTS

During PN, maltase and sucrase activities were 1.6-fold lower and mucosal inflammation more frequent (22% vs 3%) when compared to matched controls (P < 0.05 for both). In patients on full enteral nutrition, activities of maltase and sucrase were significantly higher than that in patients receiving PN and comparable to those of matched controls. Postresection time correlated positively (r = 0.448 and r = 0.369) and percentage length of the remaining small intestine inversely (r = -0.337 and r = -0.407) with maltase and sucrase activity in patients on full enteral nutrition (P < 0.05 for all), whereas proportional length of remaining colon correlated positively with maltase and lactase activity (r = 0.424-0.544, P < 0.05) in patients receiving PN.

CONCLUSIONS

In children with IF, PN dependency associated with decreased duodenal maltase and sucrase activities and mucosal inflammation, which may disturb intestinal absorptive function. Localization and extent of intestinal resection and post-resection time correlated with duodenal disaccharidase activities.

Preserved Gut Microbial Diversity Accompanies Upregulation of TGR5 and Hepatobiliary Transporters in Bile Acid-Treated Animals Receiving Parenteral Nutrition

BACKGROUND

Parenteral nutrition (PN) is a lifesaving therapy but is associated with gut atrophy and cholestasis. While bile acids (BAs) can modulate intestinal growth via gut receptors, the gut microbiome likely influences gut proliferation and inflammation. BAs also regulate the bile salt export pump (BSEP) involved in cholestasis. We hypothesized that the BA receptor agonist oleanolic acid (OA) regulates gut TGR5 receptor and modulates gut microbiota to prevent PN-associated injury.

MATERIALS AND METHODS

Neonatal piglets were randomized to approximately 2 weeks of isocaloric enteral nutrition (EN), PN, or PN + enteral OA. Serum alanine aminotransferase, bilirubin, BAs, hepatic BSEP, gut TGR5, gut, liver morphology, and fecal microbiome utilizing 16S rRNA sequencing were evaluated. Kruskal-Wallis test, pairwise Mann-Whitney U test, and multilevel logistic regression analysis were performed.

RESULTS

PN support resulted in gut atrophy substantially prevented by OA. The median (interquartile range) for villous/crypt ratio was as follows: EN, 3.37 (2.82-3.80); PN, 1.73 (1.54-2.27); and OA, 2.89 (2.17-3.34; P = .006). Pairwise comparisons yielded P = .002 (EN vs PN), P = .180 (EN vs OA), P = .026 (PN vs OA). OA upregulated TGR5 and BSEP without significant improvement in serum bilirubin ( P = .095). A decreased microbial diversity and shift toward proinflammatory phylum Bacteroidetes were seen with PN, which was prevented by OA.

CONCLUSIONS

OA prevented PN-associated gut mucosal injury, Bacterioides expansion, and the decreased microbial diversity noted with PN. This study demonstrates a novel relationship among PN-associated gut dysfunction, BA treatment, and gut microbial changes.

The Role of Lactoferrin in Gastrointestinal and Immune Development and Function: A Preclinical Perspective

The early postnatal period is a critical time for gastrointestinal (GI) and immune development. Neonates fed mother's milk have more rapid GI and immune development than fed-formula infants. In addition, clinical and epidemiologic data provide strong evidence that breastfeeding reduces the incidence and/or severity of infectious diseases. Lactoferrin is a 77 kDa, iron-binding glycoprotein that is present at high concentration in human milk compared with bovine milk and infant formula. It is a multifunctional protein that mediates many of the physiological processes in which breastfed infants have advantages over their formula-fed peers, including promoting GI and immune development, protection from infections, and improved cognitive development. Feeding bovine lactoferrin or recombinant human lactoferrin was well tolerated and stimulated intestinal cell proliferation and increased villus length and crypt depth in piglets. Lactoferrin also influenced both systemic and GI immune development by stimulating a balanced T-helper-1/T-helper-2 cytokine immune response. Further, there was a tendency for immune cells to secrete more anti-inflammatory cytokines in an unstimulated state, while being primed for a robust pro-inflammatory response when presented with a bacterial trigger in piglets fed lactoferrin. These findings support clinical studies demonstrating benefits of dietary lactoferrin in the prevention of infections, late onset sepsis, and necrotizing enterocolitis.

Oleanolic Acid Improves Gut Atrophy Induced by Parenteral Nutrition

BACKGROUND

Nutrition support with parenteral nutrition (PN) is associated with gut atrophy. Prior studies have shown improvement with enteral chenodeoxycholic acid, a dual agonist for the farnesoid X receptor (FXR) and bile acid receptor TGR5. We hypothesized that gut growth is induced by TGR5 activation, and gut atrophy during PN administration could be prevented with the TGR5-specific agonist oleanolic acid (OA).

METHODS

Neonatal pigs were implanted with duodenal and jugular vein catheters. Animals were provided equi-nutritious PN or enteral swine milk. A PN subgroup received enteral OA at 50 mg/kg/d.

RESULTS

PN caused marked gut atrophy compared with enterally fed (EN) control animals. OA treatment led to preservation of gut mass demonstrated grossly and histologically. The mean ± SD gut weight as a percentage of body weight was 4.30 ± 0.26 for EN, 1.92 ± 0.06 for PN (P < .05, EN vs PN), and 3.39 ± 0.79 for PN+OA (P < .05, PN+OA vs PN). Mean ± SD gut density (g/cm) was 0.31 ± 0.03 for EN, 0.18 ± 0.03 for PN (P < .05 EN vs PN), and 0.27 ± 0.01 for PN+OA (P < .05 PN+OA vs PN). Histologically, a markedly decreased villous to crypt ratio was noted with PN, and OA significantly prevented this decrease. The mean ± SD v/c ratio was 3.51 ± 0.59 for EN, 1.69 ± 0.10 for PN (P < .05, EN vs PN), and 2.90 ± 0.23 for PN+OA (P < .05, PN+OA vs PN). Gut TGR5 messenger RNA expression was significantly elevated with OA treatment compared with both PN and EN.

CONCLUSION

The bile acid-activated G protein-coupled receptor TGR5 agonist OA prevented gut atrophy associated with PN.