Mammalian Target of Rapamycin Complex 2 Signaling Is Required for Liver Regeneration in a Cholestatic Liver Injury Murine Model

Molecular insights into experimental models and therapeutics for cholestasis

Cholestatic liver disease (CLD) is a range of conditions caused by the accumulation of bile acids (BAs) or disruptions in bile flow, which can harm the liver and bile ducts. To investigate its pathogenesis and treatment, it is essential to establish and assess experimental models of cholestasis, which have significant clinical value. However, owing to the complex pathogenesis of cholestasis, a single modelling method can merely reflect one or a few pathological mechanisms, and each method has its adaptability and limitations. We summarize the existing experimental models of cholestasis, including animal models, gene-knockout models, cell models, and organoid models. We also describe the main types of cholestatic disease simulated clinically. This review provides an overview of targeted therapy used for treating cholestasis based on the current research status of cholestasis models. In addition, we discuss the respective advantages and disadvantages of different models of cholestasis to help establish experimental models that resemble clinical disease conditions. In sum, this review not only outlines the current research with cholestasis models but also projects prospects for clinical treatment, thereby bridging basic research and practical therapeutic applications.

Silencing of GDF11 suppresses hepatocyte apoptosis to relieve LPS/D-GalN acute liver failure

In this paper, we generated a short hairpin RNA growth differentiation factor-11 (sh-GDF11) and evaluated the effects of sh-GDF11 on the pathogenesis of acute liver failure (ALF) in vitro and in vivo. Through bioinformatics study, the key gene related to ALF was assayed. Lipopolysaccharide (LPS) and D-galactoamine (D-GalN) were applied to establish the mouse model of LPS/D-GalN-induced liver injury, and TNF-α and D-Gal were used to construct an in vitro cell model, followed by treatment of sh-GDF11 for analysis of liver cell proliferation. Bioinformatics analysis showed that the protective effect of sh-GDF11 on ALF may be mediated by phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway. The results of in vitro study found that sh-GDF11 could promote cell proliferation and inhibit death by blocking the PI3K/Akt/mTOR signaling pathway. In vivo animal experiments further confirmed that sh-GDF11 could suppress hepatocyte apoptosis by inhibiting the PI3K/Akt/mTOR signaling pathway. sh-GDF11 relieved LPS/D-GalN-induced ALF by blocking the PI3K/Akt/mTOR signaling pathway, emphasizing its critical role in LPS/D-GalN-induced ALF treatment.

Lipid droplet deposition in the regenerating liver: A promoter, inhibitor, or bystander?

Liver regeneration (LR) is a complex process involving intricate networks of cellular connections, cytokines, and growth factors. During the early stages of LR, hepatocytes accumulate lipids, primarily triacylglycerol, and cholesterol esters, in the lipid droplets. Although it is widely accepted that this phenomenon contributes to LR, the impact of lipid droplet deposition on LR remains a matter of debate. Some studies have suggested that lipid droplet deposition has no effect or may even be detrimental to LR. This review article focuses on transient regeneration-associated steatosis and its relationship with the liver regenerative response.

Metabolic regulation of cholestatic liver injury by D-2-hydroxyglutarate with the modulation of hepatic microenvironment and the mammalian target of rapamycin signaling

Biliary atresia (BA) is a cholestatic liver disease in neonates with devastating obstructive intrahepatic and extrahepatic biliary ducts. Owing to the lack of an early diagnostic marker and limited understanding of its pathogenesis, BA often leads to death within 2 years. Therefore, this study aimed to develop early diagnostic methods and investigate the underlying pathogenesis of liver injury in BA using metabolomics. Metabolomics and organoid combined energy metabolism analysis was used to obtain new insights into BA diagnosis and pathobiology using patient samples, mice liver organoids, and a zebrafish model. Metabolomics revealed that D-2-hydroxyglutarate (D-2-HG) levels were significantly elevated in the plasma and liver of patients with BA and closely correlated with liver injuries and impaired liver regeneration. D-2-HG suppressed the growth and expansion of liver organoids derived from the intrahepatic biliary ducts. The energy metabolism analysis demonstrated that D-2-HG inhibited mitochondrial respiration and ATP synthase; however, it increased aerobic glycolysis in organoids. In addition, D-2-HG exposure caused liver degeneration in zebrafish larvae. Mechanistically, D-2-HG inhibited the activation of protein kinase B and the mammalian target of rapamycin signaling. These findings reveal that D-2-HG may represent a novel noninvasive diagnostic biomarker and a potential therapeutic target for infants with BA.

Metabonomics Study on the hepatoprotective effect mechanism of polysaccharides from different processed products of Angelica Sinensis on the layer chickens based on UPLC-Q/TOF-MS/MS, multivariate statistical analysis and conjoint analysis

Chicken colibacillosis is one of the most severe diseases in the poultry industry. Ceftiofur sodium (CS) is often used to treat it in clinical practice and lipopolysaccharide (LPS) accumulates in the chicken's body. Previous experimental studies found that CS combined with LPS could induce liver injury in layer chickens, and polysaccharides from charred Angelica sinensis(CASP) had a better hepatoprotective effect than polysaccharides from unprocessed Angelica sinensis(UASP). However, the intervention mechanism was unclear. Thus, UPLC–Q/TOF–MS/MS‐based metabonomics and transcriptomics were used in this study to clarify the hepatoprotective effect mechanism of CASP and UASP in layer chickens. Transcriptomics and enzyme‐linked immunosorbent assay were used for biological verification of some critical mutual metabolic pathways screened with metabonomics. The comprehensive analysis results showed that in a layer chicken liver injury model built with LPS and CS, 12 critical metabolic pathways were disturbed, involving 10 important differential metabolites. The hepatoprotective effect mechanism of CASP is related to the arachidonic acid metabolism and mTOR signaling pathways, involving nine important differential metabolites. In contrast, the hepatoprotective effect mechanism of UASP is related to the arachidonic acid metabolism pathway, involving six important differential metabolites.

Liver regeneration biology: Implications for liver tumour therapies

The liver has remarkable regenerative potential, with the capacity to regenerate after 75% hepatectomy in humans and up to 90% hepatectomy in some rodent models, enabling it to meet the challenge of diverse injury types, including physical trauma, infection, inflammatory processes, direct toxicity, and immunological insults. Current understanding of liver regeneration is based largely on animal research, historically in large animals, and more recently in rodents and zebrafish, which provide powerful genetic manipulation experimental tools. Whilst immensely valuable, these models have limitations in extrapolation to the human situation. In vitro models have evolved from 2-dimensional culture to complex 3 dimensional organoids, but also have shortcomings in replicating the complex hepatic micro-anatomical and physiological milieu. The process of liver regeneration is only partially understood and characterized by layers of complexity. Liver regeneration is triggered and controlled by a multitude of mitogens acting in autocrine, paracrine, and endocrine ways, with much redundancy and cross-talk between biochemical pathways. The regenerative response is variable, involving both hypertrophy and true proliferative hyperplasia, which is itself variable, including both cellular phenotypic fidelity and cellular trans-differentiation, according to the type of injury. Complex interactions occur between parenchymal and non-parenchymal cells, and regeneration is affected by the status of the liver parenchyma, with differences between healthy and diseased liver. Finally, the process of termination of liver regeneration is even less well understood than its triggers. The complexity of liver regeneration biology combined with limited understanding has restricted specific clinical interventions to enhance liver regeneration. Moreover, manipulating the fundamental biochemical pathways involved would require cautious assessment, for fear of unintended consequences. Nevertheless, current knowledge provides guiding principles for strategies to optimise liver regeneration potential.

YAP Accelerates Notch-Driven Cholangiocarcinogenesis via mTORC1 in Mice

Intrahepatic cholangiocarcinoma (iCCA) is a lethal malignant neoplasm with limited therapeutic options. Previous studies have found that Notch1 overexpression alone suffices to induce iCCA in the mouse, albeit after long latency. The current study found that activation of the Yes-associated protein (Yap) proto-oncogene occurs during Notch1-driven iCCA progression. After co-expressing activated Notch1 intracellular domain (Nicd) and Yap (YapS127A) in the mouse liver, rapid iCCA formation and progression occurred in Nicd/Yap mice. Mechanistically, an increased expression of amino acid transporters and activation of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway was detected in Nicd/Yap mouse liver tumors. Significantly, the genetic deletion of Raptor, the major mTORC1 component, completely suppressed iCCA development in Nicd/Yap mice. Elevated expression of Notch1, YAP, amino acid transporters, and members of the mTORC1 pathway was also detected ubiquitously in a collection of human iCCA specimens. Their levels were associated with a poor patient outcome. This study demonstrates that Notch and YAP concomitant activation is frequent in human cholangiocarcinogenesis. Notch and YAP synergize to promote iCCA formation by activating the mTORC1 pathway.