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Protein tyrosine phosphatase receptor kappa regulates glycolysis, de novo lipogenesis and promotes hepatocyte metabolic reprogramming in obesity.

ABSTRACT: 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.

INSTRUMENT(S): Orbitrap Eclipse

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Liver

SUBMITTER: Thibaut Vignane

LAB HEAD: Milos Filipovic

PROVIDER: PXD046506 | Pride | 2024-10-21

REPOSITORIES: Pride

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Project description: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:Recent studies have reported that glycosphingolipids (GSL) might be involved in obesity induced insulin resistance. Those reports suggested that inhibition of GSL biosynthesis in animals ameliorated insulin sensitivity accompanied with improved glycemic control leading to decreased liver steatosis in obese mice. In addition, GSL depletion altered hepatic secretory function. In those studies, ubiquitously acting inhibitors for GSL-biosynthesis have been used to inhibit function of the enzyme Ugcg (UDP-glucose:ceramide glucosyltransferase), catalyzing the first step of the glucosylceramide based GSL-synthesis pathway. In the present study, a genetic approach for GSL deletion in hepatocytes was chosen to achieve full inhibition of GSL synthesis and to prevent possible adverse effects caused by Ugcg-inhibitors. Using the Cre/loxP system under control of the albumin promoter, GSL biosynthesis in hepatocytes and their release into the plasma could be effectively blocked. Deletion of GSL in hepatocytes did not change quantity of bile excretion through the biliary duct. Total bile salt content in bile-, feces- and plasma from mutant mice showed no difference as compared to control animals. Cholesterol concentration in liver-, bile-, feces- and plasma-samples remained unaffected. Lipoprotein concentration in plasma-samples in mutant animals reached similar levels as in their control littermates. No alteration in glucose tolerance after intraperitoneal application of glucose and insulin appeared in mutant animals. A preventive effect of GSL-deficiency on development of liver steatosis after high fat diet feeding could not be observed. Conclusion: The data suggest that GSL in hepatocytes are not essential for sterol, glucose and lipoprotein metabolism and do not prevent high fat diet-induced liver steatosis, indicating that Ugcg inhibitors exert their effect on hepatocytes either independently of GSL or mediated by other (liver) cell types. Comparison of wildtype mouse liver function versus Ugcg-deficient

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Protein tyrosine phosphatase receptor kappa regulates glycolysis, de novo lipogenesis and promotes hepatocyte metabolic reprogramming in obesity.

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