Protein tyrosine phosphatase receptor kappa regulates glycolysis, de novo lipogenesis and promotes hepatocyte metabolic reprogramming in obesity
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ABSTRACT: Metabolic dysfunction within the liver is a major cause of human disease worldwide. Fat accumulation, de novo lipogenesis, and glycolysis are key drivers of hepatocyte reprogramming and the consequent metabolic dysfunction-associated steatotic liver disease (MASLD). The underpinning molecular mechanisms affected by steatosis and inflammation in the obese states remain unknown. Here we report that obesity leads to dysregulated expression of protein-tyrosine phosphatases (PTPs) in the liver. Protein Tyrosine Phosphatase Receptor Kappa (PTPRK) expression was increased in hepatocytes during steatosis and inflammation in humans and mice, and positively correlates with PPARγ-induced lipogenic signalling. Supporting this, PTPRK knockout mice displayed reduced fat accumulation in adipose tissue and liver after exposure to an obesogenic diet. Phosphoproteomic analysis in primary hepatocytes and hepatic metabolomics identified specific phosphotyrosine residues in fructose-1,6 bisphosphatase-1 and glycolysis regulation as targets of PTPRK. The changes in glycolysis and de novo lipogenesis revealed PTPRK was a driving force for metabolic reprogramming in hepatocytes. Moreover, hepatoma cell lines showed reduced colony-forming ability after PTPRK silencing in vitro, and PTPRK knockout mice developed smaller tumours after diethylnitrosamine-induced hepatocarcinogenesis in vivo. Through computational modelling, we identified selective PTPRK inhibitors. These compounds decreased glycolytic rates in hepatoma cell lines, PPARγ expression in primary hepatocytes and steatosis in obese mice. In conclusion, our study defines a novel mechanism for the development of MASLD, revealing a key role of PTPRK on hepatic glycolysis regulation with implications in lipid metabolism, and liver tumour development. We propose PTPRK as a potential target for metabolic liver dysfunction, and the identified inhibitors may represent promising candidates for therapy in obesity-associated liver diseases.
Project description:Fat accumulation, de novo lipogenesis, and glycolysis are key contributors to hepatocyte reprogramming and the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD). The molecular mechanisms affected by steatosis and inflammation in the obese states remain unknown. Here we report that obesity leads to dysregulated expression of protein-tyrosine phosphatases (PTPs) in the liver. Protein Tyrosine Phosphatase Receptor Kappa (PTPRK) was increased in hepatocytes by steatosis and inflammation in humans and mice, and positively correlates with PPARγ-induced lipogenic signalling. Mechanistically, PTPRK-PPARγ upregulation by fat accumulation is dependent upon Notch signalling in mouse primary hepatocytes. PTPRK knockout mice have reduced fat accumulation in adipose tissue and liver after exposure to an obesogenic diet. Phosphoproteomic analysis in isolated hepatocytes and hepatic metabolomics identified specific phosphotyrosine residues in fructose-1,6 bisphosphatase-1 and glycolysis regulation as targets of PTPRK. These changes in glycolysis and de novo lipogenesis revealed PTPRK-dependent metabolic reprogramming in hepatocytes. Moreover, hepatoma cell lines showed reduced colony-forming ability after PTPRK silencing in vitro, and PTPRK knockout mice developed smaller tumours after diethylnitrosamine-induced hepatocarcinogenesis in vivo. Computational modelling identified potential PTPRK inhibitors, which selectively reduced PTPRK activity. The compounds decreased glycolytic rates in hepatoma cell lines, PPARγ expression in primary hepatocytes and steatosis in obese mice. In conclusion, our study defines a novel mechanism for the development of MASLD, revealing a key role of PTPRK on hepatic glycolysis regulation with implications in lipid metabolism, and liver tumour development. We propose PTPRK as a potential target for metabolic liver dysfunction, and the identified inhibitors may represent promising candidates for therapy in obesity-associated liver diseases.
Project description:Here, we revealed that Zbtb7b is a suppressor of MASLD-related HCC. Zbtb7b deficiency in mouse hepatocytes increases de novo lipogenesis while hepatic fatty acid oxidation is inhibited. Consequently, lipid deposition in the liver is increased, which facilitating the progression of MASLD and eventually to HCC. Mechanistically, depletion of Zbtb7b drastically induced long noncoding RNA H19 expression, thereby driving hepatic de novo lipogenesis and suppressing fatty acid oxidation program to accelerate MASLD-related HCC progression.
Project description:Metabolic dysfunction-associated steatotic liver disease (MASLD) is a highly prevalent chronic liver disease worldwide that encompasses a spectrum of steatosis, inflammation, and fibrosis. Evidence suggests that weight loss approaches such as dietary restriction (DR) and sleeve gastrectomy (SG) can lead to remission of hepatic steatosis and inflammation. However, it remains unclear about the effects of weight loss on the hepatic immune mechanisms in MASLD. Therefore, this study aims to elucidate the intricate immunometabolic landscape of steatotic livers following DI and BS by employing the sleeve gastrectomy (a typical BS procedure) and comparable food intake after sham surgery in a rat model of MASLD. Single-cell (sc) and single-nuclei (sn) transcriptome analysis together with spatial metabolomics and immunohistochemistry were utilized to depict immunometabolic landscape, while circulating markers were assessed in serum. Furthermore, artificial intelligence (AI)-based image analysis was introduced to characterize the distribution of hepatocytes, myeloid cells and lymphocytes.
Project description:BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH) is a chronic liver disease characterized by hepatic lipid accumulation, inflammation, and progressive fibrosis. Acetyl-CoA carboxylase (ACC) catalyzes the rate-limiting step of de novo lipogenesis and regulates fatty-acid beta-oxidation in hepatocytes. ACC inhibition reduces hepatic fat content and markers of liver injury in NASH patients; however, the effect of ACC inhibition on liver fibrosis has not been reported. METHODS: A direct role for ACC in fibrosis was evaluated by measuring de novo lipogenesis, procollagen production, gene expression, glycolysis, and mitochondrial respiration in hepatic stellate cells (HSCs) in the absence or presence of small-molecule inhibitors of ACC. ACC inhibitors were evaluated in rodent models of liver fibrosis induced by diet or the hepatotoxin, DEN. Fibrosis and hepatic steatosis were evaluated by histological and biochemical assessments. RESULTS: In TGF-beta-stimulated HSCs, ACC inhibition reduced activation and collagen production independent of mitochondrial beta-oxidation by blocking de novo lipogenesis. ACC inhibition prevented a metabolic switch necessary for induction of glycolysis and oxidative phosphorylation during HSC activation. Consistent with this direct anti-fibrotic mechanism in HSCs, ACC inhibition reduced liver fibrosis in a rat CDHFD model and in response to chronic DEN-induced liver injury that lacked hepatic lipid accumulation. CONCLUSIONS: In addition to reducing lipid accumulation in hepatocytes, ACC inhibition also directly impairs the pro-fibrogenic activity of HSCs. Small molecule inhibitors of ACC may reduce liver fibrosis by both reducing lipotoxicity in hepatocytes and directly reducing HSC activation, providing a mechanistic rationale for the treatment of patients with advanced liver fibrosis due to NASH.
Project description:Metabolic dysfunction-associated steatotic liver disease (MASLD) embraces different conditions, including metabolic dysfunction-associated steatohepatitis (MASH), fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The landscape of cellular abnormalities occurring in the different stages of MASLD as well as the processes which drive MASLD evolution are not completely clarified. We used single cell RNAsequencing (scRNAseq) to unravel cellular heterogeneity affecting livers during the switching from simple steatosis towads MASH and and MASH-fibrosis.
Project description:E2F transcription factors are known regulators of the cell cycle, proliferation, apoptosis and differentiation. We reveal an essential role for E2F1 in liver through the regulation of glycolysis and lipogenesis. E2F1 deficiency leads to a decreased in glycolysis and de novo synthesis of fatty acids in hepatocytes. ChIP-Seq was performed to determine direct tagets of E2F1 in hepatocytes. We highlight that E2F1 directly binds the promoters of genes implicated in metabolic process and notably key lipogenic genes to control these pathways.
Project description:Background & Aims:The prevalence of metabolic dysfunction-associated liver disease (MASLD) has been strongly increasing over the last decades. As MASLD is often associated with more severe disease states, such as metabolic dysfunction-associated steato-hepatitis (MASH), insulin resistance and type 2 diabetes, the increasing number of patients will contribute to an epidemic rise in metabolic abnormalities and end stage liver diseases. Despite the high demand, there are still no FDA-approved pharmaceutical treatments for MASLD due to low efficacy and high toxicity of the targets pursued, indicating a lack of appropriate pre-clinical models for selection and validation. To facilitate earlier stop-go decisions for continued target development, we have established and extensively characterized a primary human steatoticin vitrohepatocyte model system that could guide treatment strategies for MASLD. Methods:Cryopreserved primary human hepatocytes of different donors varying in sex and ethnicity were cultured with free fatty acids (FFA) in a 3D collagen sandwich system for 7 days and the development of MASLD was followed by assessing classical hepatocellular functions. As aproof-of-concept, the effects of Firsocostat (GS-0976) onin vitroMASLD phenotypes were evaluated. Results:Incubation with FFA induced known MASLD pathologies, including steatosis, insulin resistance, mitochondrial dysfunction, inflammation and alterations in prominent human gene signatures similar to patients with MASLD/MASH, indicating the recapitulation of human MASLD in this system. As the application of Firsocostat rescued clinically observed fatty liver disease pathologies, it highlights the ability of thein vitrosystem to test drug efficacy and potentially characterize their mode of action. Conclusions:Altogether, our human MASLDin vitromodel system could guide the development and validation of novel targets and drugs for the treatment of MASLD.
Project description:Long non-coding RNAs (lncRNAs) display higher tissue-specificity than mRNAs. In particular, many lncRNAs are specifically expressed in early embryos, but the physiological functions of most of them remain largely unknown. Here, we show that deficiency of Lncenc1, a lncRNA specifically expressed in early embryos, results in an altered glucose and lipid balance in adult mice. Newly weaned lncenc1-deficient mice have been shown to display higher fasting blood glucose levels and to prefer to use lipids as a fuel source. When mice were fed a normal chow diet (NCD), in which glucose was the main energy source, glucose intolerance and insulin resistance were observed in adult lncenc1-deficient mice. Under high-fat diet (HFD) conditions, however, lncenc1-deficient mice became healthier and could resist food-induced obesity and metabolic disturbances, including liver steatosis and hypercholesterolmia. Furthermore, PPARγ-regulated lipogenesis in liver was reduced in lncenc1-deficient mice fed an HFD, as shown by transcriptome analyses. Interestingly, lncenc1-deficient mouse embryonic fibroblasts (MEFs) showed impaired glycolysis and lipogenesis, suggesting that the metabolic defects may already exist in embryos. Our study provides the first piece of evidence showing the essential roles of embryo-specific lncRNAs in adult metabolism, verifying the “fetal origin” of adult metabolic disorders.
Project description:Senescent hepatocytes accumulate in metabolic dysfunction-associated steatotic liver disease (MASLD) and are linked to worse clinical outcomes. However, their heterogeneity and lack of specific markers have made them difficult to target therapeutically. Here, we define a senescent hepatocyte gene signature (SHGS) using in vitro and in vivo models and show that it tracks with MASLD progression/regression across mouse models and large human cohorts. Single-nucleus RNA-sequencing and functional studies reveal that SHGS+ hepatocytes originate from p21+ cells, lose key liver functions and release factors that drive disease progression. One such factor, GDF15, increases in circulation alongside SHGS+ burden and disease progression. Through chemical screening, we identify senolytics that selectively eliminate SHGS+ hepatocytes and improve MASLD in mice. Notably, SHGS enrichment also correlates with dysfunction in other organs. These findings establish SHGS+ hepatocytes as key drivers of MASLD and highlight a potential therapeutic strategy for targeting senescent cells in liver disease and beyond.
Project description:Metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH) are characterized by excessive triglyceride accumulation in the liver. However, due to an incomplete understanding of its pathogenesis, more efforts are still needed to identify specific and effective treatments. N4-acetylcytidine (ac4C) is a newly discovered RNA modification to regulate mRNA stability post-transcriptionally. N-acetyltransferase 10 (NAT10), the sole enzyme catalyzing mRNA acetylation, has not been fully explored in human diseases, especially in MASLD and MASH. In the current study, abundant RNA acetylation was found in lipid metabolism-related genes in the livers of leptin receptor-deficient (db/db) mice. Besides, hepatic NAT10 expression is significantly increased in multiple mouse models of MASLD and MASH. NAT10 expression is also elevated in patients with MASLD and positively correlated with clinical characteristics. Genetic NAT10 knockdown protects against diet-induced hepatic steatosis and steatohepatitis in mice, while its overexpression exacerbates steatosis. Mechanistically, NAT10 could bind to Srebp-1c mRNA to promote its stability and expression, thereby upregulating lipogenic enzymes. In addition, the translational significance of our findings is that treatment of Remodelin, an NAT10 inhibitor, could improve liver steatosis and dyslipidemia in a preclinical mouse model. Together, these findings highlight the significance of ac4C modification and NAT10 in MASLD and MASH, offering a potential therapeutic target for disease treatment.