Autophagy May Protect Against Parenteral Nutrition-Associated Liver Disease by Suppressing Endoplasmic Reticulum Stress

Targeting GPX4-mediated Ferroptosis Alleviates Liver Steatosis in a Rat Model of Total Parenteral Nutrition

BACKGROUND

Parenteral nutrition-associated liver disease (PNALD) is a common hepatobiliary complication resulting from long-term parenteral nutrition (PN) that is associated with significant morbidity and mortality. Ferroptosis plays a significant role in the pathogenesis of various liver diseases. This study aims to explore the role of ferroptosis in PNALD and to uncover its underlying mechanisms.

METHODS

Ferroptosis was evaluated in pediatric patients with PNALD and in rats administered with total parenteral nutrition (TPN) as an animal model of PNALD. In TPN-fed rats, we applied liproxstatin-1 (Lip-1) to inhibit ferroptosis for 7 days and assessed its impact on liver steatosis. We performed RNA-seq analysis to profile the alterations in miRNAs in livers from TPN-fed rats. The ferroptosis-promoting effects of miR-431 were evaluated in HepG2 cells and the direct targeting effects on glutathione peroxidase 4 (GPX4) were evaluated in HEK293T cells.

RESULTS

RNA-seq analysis and experimental validation suggested that ferroptosis was increased in the livers of pediatric patients and rats with PNALD. Inhibiting ferroptosis with Lip-1 attenuated liver steatosis by regulating PPARα expression. RNA-seq analysis uncovered miR-431 as the most upregulated miRNA in the livers of TPN-fed rats, showing a negative correlation with hepatic GPX4 expression. In vitro studies demonstrated that miR-431 promoted ferroptosis by directly binding to the 3'UTR of GPX4 mRNA, resulting in the suppression of its expression.

CONCLUSIONS

Our study demonstrates that TPN induces the upregulation of miR-431 in rats, leading to activation of ferroptosis through downregulation of GPX4. Inhibition of ferroptosis attenuates TPN-induced liver steatosis by regulating PPARα expression.

Pharmacological effects of mTORC1/C2 inhibitor in a preclinical model of NASH progression

Knowledge of the benefits of mTOR inhibition concerning adipogenesis and inflammation has recently encouraged the investigation of a new generation of mTOR inhibitors for non-alcoholic steatohepatitis (NASH). We investigated whether treatment with a specific mTORC1/C2 inhibitor (Ku-0063794; KU) exerted any beneficial impacts on experimentally-induced NASH in vitro and in vivo. The results indicated that KU decreases palmitic acid-induced lipotoxicity in cultivated primary hepatocytes, thus emerging as a successful candidate for testing in an in vivo NASH dietary model, which adopted the intraperitoneal KU dosing route rather than oral application due to its significantly greater bioavailability in mice. The pharmacodynamics experiments commenced with the feeding of male C57BL/6 mice with a high-fat atherogenic western-type diet (WD) for differing intervals over several weeks aimed at inducing various phases of NASH. In addition to the WD, the mice were treated with KU for 3 weeks or 4 months. Acute and chronic KU treatments were observed to be safe at the given concentrations with no toxicity indications in the mice. KU was found to alleviate NASH-related hepatotoxicity, mitochondrial and oxidative stress, and decrease the liver triglyceride content and TNF-α mRNA in at least one set of in vivo experiments. The KU modulated liver expression of selected metabolic and oxidative stress-related genes depended upon the length and severity of the disease. Although KU failed to completely reverse the histological progression of NASH in the mice, we demonstrated the complexity of mTORC1/C2 signaling regulation and suggest a stratified therapeutic management approach throughout the disease course.

Down regulation of NDUFS1 is involved in the progression of parenteral-nutrition-associated liver disease by increasing Oxidative stress

Parenteral nutrition (PN)-associated liver disease (PNALD) is a common and life-threatening complication of patients receiving PN. However, its definitive pathology remains unclear. Ubiquinone oxidoreductase core subunit S1 (NDUFS1), which is the largest core subunit of mitochondrial complex I, could alter the mitochondrial reactive oxygen species (ROS) formation. The purpose of this study was to investigate the role of NDUFS1 in the pathogenesis of PNALD and its underlying mechanism. We performed hepatic proteomics analysis of PNALD patients, and established a PNALD rat model to verify the role of oxidative stress, NDUFS1, pyrin inflammasome, and IL-1β in the progression of PNALD. Proteomics analysis revealed the NDUFS1 expression was decreased in PNALD patients, and the differentially espressed proteins were involved in mitochondrial respiratory chain complex Ⅰ. Treatment with MitoQ or overexpression of NDUFS1 can alleviate the progression of PNALD by reducing oxidative stress. The expression of pyrin, caspase-1, and IL-1β was increased in PN rats. Pharmacological antagonism of pyrin by colchicine can alleviate liver injury and hepatic steatosis. NDUFS1 prevents PNALD pathogenesis by regulating oxidative stress. Pyrin inflammasome and IL-1β may participate in the process of PNALD development by suppressing the transcription of MTTP and impairing the secretion of VLDL. Oxidative stress reduction may be employed as a strategy in the prevention and treatment of PNALD.

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.

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.

Lactobacillus plantarum supplementation alleviates liver and intestinal injury in parenteral nutrition-fed piglets

OBJECTIVE

Long-term parenteral nutrition (PN) causes parenteral nutrition-associated liver disease (PNALD) for which therapeutic approaches are limited. This study aimed to investigate the effects of Lactobacillus plantarum CGMCC 1258 (LP) on liver and intestinal injury in the PN-fed neonatal piglets.

METHODS

The piglets received PN with or without oral LP for 14 days. The levels of liver enzymes and inflammatory markers were measured using biochemical kits and q-RT-PCR. Serum fibroblast growth factor 19 (FGF19) was detected using an enzyme-linked immunosorbent assay (ELISA). The bile acid profiles in the liver, serum, and intestinal contents were determined using ultraperformance liquid chromatography coupled with mass spectrometry (UPLC-MS). The composition of intestinal bacteria was analyzed with 16S rRNA gene amplicon sequencing.

RESULTS

LP supplementation was associated with improved markers of liver disease, inflammation, and oxidative stress in PN-fed piglets. Moreover, markers of intestinal injury and inflammation were alleviated by LP in PN-fed piglets. Mechanistically, LP increased the abundance of Lactobacillus in ileal contents and stimulated FGF19 expression in ileal mucosa. Subsequently, it increased the expression of small heterodimer partner (SHP) and inhibited cholesterol 7α-hydroxylase (CYP7A1) expression in the liver. Additionally, LP altered the systemic composition and metabolism of bile acids.

CONCLUSIONS

LP alleviated liver and intestinal injury in PN-fed neonatal piglets by altering the composition of intestinal bacteria and bile acids. This article is protected by copyright. All rights reserved.

Liver PP2A-Cα Protects From Parenteral Nutrition-associated Hepatic Steatosis

BACKGROUND & AIMS

Parenteral nutrition (PN) is a lifesaving therapy for patients with intestinal failure. Hepatic steatosis is a potentially fatal complication of long-term PN, but the involved pathological mechanisms are incompletely unclarified. Herein, we identify the role of protein phosphatase 2A (PP2A) in the pathogenesis of parenteral nutrition-associated hepatic steatosis (PNAHS).

METHODS

Proteomic/phosphoproteomic analyses of liver samples from patients with PNAHS were applied to identify the mechanism of PNAHS. Total parenteral nutrition (TPN) mice model, in vivo, and in vitro experiments were used to assess the effect of PP2A-Cα on liver fatty acid metabolism.

RESULTS

Reduced expression of PP2A-Cα (catalytic subunit) enhanced activation of serine/threonine kinase Akt2 and decreased activation of adenosine monophosphate-activated protein kinase (AMPK) were associated with hepatic steatosis in patients with PNAHS. Mice given PN for 14 days developed hepatic steatosis, down-regulation of PP2A-Cα, activation of Akt2, and inhibition of AMPK. Hepatocyte-specific deletion of PP2A-Cα in mice given PN exacerbated Akt2 activation, AMPK inhibition, and hepatic steatosis through an effect on fatty acid degradation, whereas hepatocyte-specific PP2A-Cα overexpression significantly ameliorated hepatic steatosis accompanied with Akt2 suppression and AMPK activation. Additionally, pharmacological activation of Akt2 in mice overexpressing PP2A-Cα led to the aggravation of hepatic steatosis.

CONCLUSIONS

Our findings demonstrate that hepatic PP2A-Cα serves as a protective factor of PNAHS due to ameliorating hepatic steatosis and improving liver function. Our study provides a strong rationale that PP2A-Cα may be involved in the pathogenesis of PNAHS.

Alterations of gut microbiota and serum bile acids are associated with parenteral nutrition-associated liver disease

BACKGROUND

Parenteral nutrition-associated liver disease (PNALD) is a major complication of long-term parenteral nutrition (PN). The pathogenesis of PNALD remains unclear. We investigated the changes in taxonomic and functional composition of gut microbiota and serum bile acid levels in a rat model of PNALD.

METHODS

Male 4-week-old Sprague Dawley rats received either total parenteral nutrition or standard chow with 0.9% saline for 7 days. The taxonomic composition of cecal microbiota and its functional composition associated with bile acid metabolism were measured.

RESULTS

There were differences in taxonomic composition between the two groups. The abundance of the secondary bile acid biosynthesis pathway was higher in the TPN group (p < 0.05) with an increase in the percentage of bacteria expressing 7-alpha-hydroxysteroid dehydrogenase (p < 0.05). The abundance of enzymes associated with bile salt hydrolase was also higher (p < 0.05) in the TPN group. The TPN group showed a distinct bile acid profile characterized by a higher ratio of secondary bile acids to primary bile acids.

CONCLUSIONS

The alteration of bile acid-associated microbiota may lead to increased secondary bile acid production in a rat model of PNALD.

Lin 28A/Occludin axis: An aberrantly activated pathway in intestinal epithelial cells leading to impaired barrier function under total parenteral nutrition

Disassembly of tight junctions is a major cause of intestinal barrier dysfunction under total parenteral nutrition (TPN), but the precise mechanisms have not been fully understood. Normally, RNA binding protein Lin 28A is highly restricted to embryonic stem cells and dramatically decreases as differentiation progresses; however, in our preliminary study it was found aberrantly increased in the intestinal epithelial cells of TPN rats, and thus its mechanism of action needs to be addressed. Herein, we report a pivotal role of Lin 28A in the regulation of tight junctions, which induces a sustained translational repression of Occludin, leading to disruption of intestinal barrier function under TPN. Using a rat model of TPN, we found time-dependent upregulation of Lin 28A, negatively correlated with Occludin. Using mouse intestinal organoids and human gut-derived Caco-2 cells as in vitro models, we found that expression of Occludin could be significantly suppressed by ectopic overexpression of Lin 28A. The underlying mechanisms may be partially attributed to translational repression, as the abundance of Occludin transcripts in polysomes was dramatically reduced by Lin 28A (polysomal profiling). Furthermore, Lin 28A was found to directly bind to Occludin mRNA 3' untranslated coding region (UTR), thereby repressing the translation of Occludin transcripts through decapping enzyme 1A (DCP1a). Taken together, our findings revealed that Lin 28A/Occludin axis may be a novel mechanism accounting for the development of barrier dysfunction under TPN.

Differential Metabolomic Analysis of Liver Tissues from Rat Models of Parenteral Nutrition-Associated Liver Disease

Parenteral nutrition (PN) is a life-saving therapy for patients with intestinal failure, but parenteral nutrition-associated liver disease (PNALD) limits its long-term use. The present study is aimed at determining which pathways are altered most notably in a rat model of PNALD. We randomly assigned male Sprague-Dawley (SD) rats into two different groups, whereby they received either enteral nutrition (EN) or PN. Liver tissues were harvested from all rats 7 days later for metabolomic profiling. The composition of primary conjugated bile acids was altered, the synthesis of polyunsaturated fatty acids was reduced, the conversion of pyruvate to acetyl-CoA was blocked, and the synthesis of phosphatidylcholine was inhibited in rats with PNALD. Riboflavin, which is involved in the electron transfer process in the mitochondrial electron transport chain, was remarkably decreased in PNALD rats. A deficiency of polyunsaturated fatty acids, riboflavin, choline, and taurine might be involved in the progression of PNALD. The implications of these findings for the field of medicine are that supplementation with polyunsaturated fatty acids, riboflavin, choline, and taurine might have potential as therapeutic strategies for PNALD and also shed light on the mechanisms of PNALD.

Suppression of IRE1α Attenuated the Fatty Degeneration in Parenteral Nutrition-Related Liver Disease (PNALD) Cell Model

Aims

To model the parenteral nutrition-associated liver disease (PNALD) in rat normal hepatocytes BRL and investigate the role of endoplasmic reticulum stress- (ERS-) related IRE1α signal in the process of PNALD.

Methods

The BRL cells were treated with different concentrations of soybean oil emulsion (SO) to induce hepatocyte fatty degeneration. The PNALD cell disease model was further confirmed by analysis of Oil Red O staining and biochemical parameters. Next, the IRE1α signal in the process of PNALD. α signal in the process of PNALD. α signal in the process of PNALD. α signal in the process of PNALD.

Results

The results of Oil Red O staining indicated that the PNALD was successfully established in BRL cells and the CCK-8 data indicated which 0.6% that SO was further applied to the experiment owing to its better induction of PNALD and less toxicity to the cells. Besides, the value of biochemical parameters (TBIL, DBIL, ALT, and AST) was also elevated in the SO group compared with the NG group. After knockdown of IRE1α signal in the process of PNALD. α signal in the process of PNALD.

Conclusion

IRE1α was induced in PNALD cell model and suppression of IRE1α resulted in reduced steatosis in this cell disease model. Taken together, our data suggested that the IRE1α pathway may be involved in the development of PNALD.α signal in the process of PNALD. α signal in the process of PNALD. α signal in the process of PNALD.