Early downregulation of P-glycoprotein facilitates bacterial attachment to intestinal epithelial cells and thereby triggers barrier dysfunction in a rodent model of total parenteral nutrition

Altered hepatic and intestinal homeostasis in a neonatal murine model of short-term total parenteral nutrition and antibiotics

Parenteral nutrition (PN) prevents starvation and supports metabolic requirements intravenously when patients are unable to be fed enterally. Clinically, infants are frequently provided PN in intensive care settings along with exposure to antibiotics (ABX) to minimize infection during care. Unfortunately, neonates experience extremely high rates of hepatic complications. Adult rodent and piglet models of PN are well-established but neonatal models capable of leveraging the considerable transgenic potential of the mouse remain underdeveloped. Utilizing our newly established neonatal murine PN mouse model, we administered ABX or controlled drinking water to timed pregnant dams to disrupt the maternal microbiome. We randomized mouse pups to PN or sham surgery controls +/- ABX exposure. ABX or short-term PN decreased liver and brain organ weights, intestinal length, and mucosal architecture (vs. controls). PN significantly elevated evidence of hepatic proinflammatory markers, neutrophils and macrophage counts, bacterial colony-forming units, and evidence of cholestasis risk, which was blocked by ABX. However, ABX uniquely elevated metabolic regulatory genes resulting in accumulation of hepatocyte lipids, triglycerides, and elevated tauro-chenoxycholic acid (TCDCA) in serum. Within the gut, PN elevated the relative abundance of Akkermansia, Enterococcus, and Suterella with decreased Anaerostipes and Lactobacillus compared with controls, whereas ABX enriched Proteobacteria. We conclude that short-term PN elevates hepatic inflammatory stress and risk of cholestasis in early life. Although concurrent ABX exposure protects against hepatic immune activation during PN, the dual exposure modulates metabolism and may contribute toward early steatosis phenotype, sometimes observed in infants unable to wean from PN.NEW & NOTEWORTHY This study successfully established a translationally relevant, murine neonatal parenteral nutrition (PN) model. Short-term PN is sufficient to induce hepatitis-associated cholestasis in a neonatal murine model that can be used to understand disease in early life. The administration of antibiotics during PN protects animals from bacterial translocation and proinflammatory responses but induces unique metabolic shifts that may predispose the liver toward early steatosis.

Multi-Omics Unravels Metabolic Alterations in the Ileal Mucosa of Neonatal Piglets Receiving Total Parenteral Nutrition

Total parenteral nutrition (TPN) is life-saving therapy for the pediatric patients with intestinal failure (IF) who cannot tolerate enteral nutrition (EN). However, TPN-induced metabolic alterations are also a critical issue for the maintenance of intestinal homeostasis, and thus the global metabolomic signatures need to be addressed. In this study, ileal mucosal biopsies were collected from 12 neonatal Bama piglets receiving either EN or TPN for 14 days, and changes in the intestinal metabolism were examined by multi-omics (HM350 Metabolomics + Tandem Mass Tag (TMT)-based proteomics). As a result, a total of 240 compounds were identified by metabolomics, including 56 down-regulated and 9 up-regulated metabolites. Notably, tissue levels of fatty acyl-carnitines (decreased by 35-85%) and succinate (decreased by 89%) dramatically decreased in the TPN group, suggestive of disrupted processes of fatty acid oxidation (FAO) and the citrate cycle, respectively. Interestingly, however, no differences were found in the production of adenosine 5'-triphosphate (ATP) between groups, suggesting that these dysregulated metabolites may have mainly led to the loss of bioactive compounds rather than energy deficit. Additionally, 4813 proteins were identified by proteomics in total, including 179 down-regulated and 329 up-regulated proteins. The analysis of protein-protein interactions (PPI) indicated that most of the differentially expressed proteins were clustered into "lipid metabolism" and "innate immune responses". In summary, this work provided new findings in TPN-induced intestinal metabolic alterations, which would be useful to the improvement of nutritional management for IF patients.

Small noncoding vault RNA2-1 disrupts gut epithelial barrier function via interaction with HuR

Vault RNAs (vtRNAs) are small noncoding RNAs and highly expressed in many eukaryotes. Here, we identified vtRNA2-1 as a novel regulator of the intestinal barrier via interaction with RNA-binding protein HuR. Intestinal mucosal tissues from patients with inflammatory bowel diseases and from mice with colitis or sepsis express increased levels of vtRNAs relative to controls. Ectopically expressed vtRNA2-1 decreases the levels of intercellular junction (IJ) proteins claudin 1, occludin, and E-cadherin and causes intestinal epithelial barrier dysfunction in vitro, whereas vtRNA2-1 silencing promotes barrier function. Increased vtRNA2-1 also decreases IJs in intestinal organoid, inhibits epithelial renewal, and causes Paneth cell defects ex vivo. Elevating the levels of tissue vtRNA2-1 in the intestinal mucosa increases the vulnerability of the gut barrier to septic stress in mice. vtRNA2-1 interacts with HuR and prevents HuR binding to claudin 1 and occludin mRNAs, thus decreasing their translation. These results indicate that vtRNA2-1 impairs intestinal barrier function by repressing HuR-facilitated translation of claudin 1 and occludin.

Impaired FXR-CPT1a signaling contributes to parenteral nutrition-induced villus atrophy in short-bowel syndrome

Parenteral nutrition (PN)-induced villus atrophy is a major cause of intestinal failure (IF) for children suffering from short bowel syndrome (SBS), but the precise mechanism remains unclear. Herein, we report a pivotal role of farnesoid X receptor (FXR) signaling and fatty acid oxidation (FAO) in PN-induced villus atrophy. A total of 14 pediatric SBS patients receiving PN were enrolled in this study. Those patients with IF showed longer PN duration and significant intestinal villus atrophy, characterized by remarkably increased enterocyte apoptosis concomitant with impaired FXR signaling and decreased FAO genes including carnitine palmitoyltransferase 1a (CPT1a). Likewise, similar changes were found in an in vivo model of neonatal Bama piglets receiving 14-day PN, including villus atrophy and particularly disturbed FAO process responding to impaired FXR signaling. Finally, in order to consolidate the role of the FXR-CPT1a axis in modulating enterocyte apoptosis, patient-derived organoids (PDOs) were used as a mini-gut model in vitro. Consequently, pharmacological inhibition of FXR by tauro-β-muricholic acid (T-βMCA) evidently suppressed CPT1a expression leading to reduced mitochondrial FAO function and inducible apoptosis. In conclusion, impaired FXR/CPT1a axis and disturbed FAO may play a pivotal role in PN-induced villus atrophy, contributing to intestinal failure in SBS patients.