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Raw data for manuscript : "Serine synthesis via reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in MASLD"

ABSTRACT: Metabolic dysfunction-associated steatotic liver disease (MASLD) affects one third of the global population. Understanding metabolic pathways involved can provide insights into disease progression and treatment. Untargeted metabolomics of livers from mice with early-stage steatosis uncovered decreased methylated metabolites, suggesting altered one-carbon metabolism. The levels of glycine, a central component of one-carbon metabolism, were lower in mice with hepatic steatosis, consistent with clinical evidence. Stable-isotope tracing demonstrated that increased serine synthesis from glycine via reverse serine hydroxymethyltransferase (SHMT) is the underlying cause for decreased glycine in steatotic livers. Consequently, limited glycine availability in steatotic livers impaired glutathione synthesis under acetaminophen-induced oxidative stress, enhancing acute hepatotoxicity. Glycine supplementation or hepatocyte-specific ablation of the mitochondrial SHMT2 isoform in mice with hepatic steatosis mitigated acetaminophen-induced hepatotoxicity by supporting de novo glutathione synthesis. Thus, early metabolic changes in MASLD that limit glycine availability sensitize mice to xenobiotics even at the reversible stage of this disease.

INSTRUMENT(S): Orbitrap Exploris 240, Q Exactive

ORGANISM(S): Mus Musculus (ncbitaxon:10090)

SUBMITTER: Eyal Gottlieb Oren Rom Inbal Mor

PROVIDER: MSV000093653 | MassIVE | Tue Dec 12 18:36:00 GMT 2023

REPOSITORIES: MassIVE

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Project description:Hepatic fat accumulation has been widely associated with diabetes and hepatocellular carcinoma (HCC). Here, we aim to characterize the metabolic response that high fat availability elicits in livers prior to development of these diseases. We find that, after a short term on high fat diet, otherwise healthy mice show elevated hepatic glucose metabolization, activated glucose uptake, glycolysis and glucose contribution to serine as well as elevated pyruvate carboxylase activity compared to control diet mice. To understand other changes in the liver tissue after high fat diet exposure, we conducted untargeted transcriptomics and proteomics. This glucose phenotype occurred independent from transcriptional or proteomic programming, which identified increased peroxisomal and lipid metabolism pathways. Interestingly, we observe that high fat diet fed mice exhibit an increased lactate production when challenged with glucose. This trait seems to find a parallel in a human cohort, where we observe a correlation between waist circumference and lactate secretion after an oral glucose bolus across healthy individuals. In an in vitro model of hepatoma cells, we found physiologically relevant palmitate exposure stimulated production of reactive oxygen species (ROS) and glucose uptake, a similar glycolytic phenotype to the in vivo study. This effect is inhibited upon interference with peroxisomal lipid metabolism and ROS production. Furthermore, we find that with exposure to an HCC-inducing hepatic carcinogen, continuation of high fat diet enhances the formation of HCC (100% with resectable tumors) as compared to control (50% with resectable tumors) in mice. However, regardless of the dietary background, all murine tumors showed similar alterations in glucose metabolism compared to those identified in fat exposed non-transformed mouse livers. Further, the presence of tumors in high fat diet exposed mice normalized glucose tolerance. Lipidomics analysis of tumor tissue and liver tissue from high fat diet exposed mice identified tumor tissue enrichment of diacylglycerol (DG) and phosphatidylcholine (PC) species. Some of these species were also increased in high fat diet liver tissue compared to control diet liver tissue. These findings suggest that fat can induce similar metabolic changes in non-transformed liver cells than found in HCC, and that peroxisomal metabolism of lipids may be a factor in driving a glycolytic metabolism In conclusion, we show that normal, non-transformed livers respond to fat by inducing glucose metabolism.

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Raw data for manuscript : "Serine synthesis via reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in MASLD"

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