MDH1 Research Articles

MDH2 Promotes Hepatocellular Carcinoma Growth Through Ferroptosis Evasion via Stabilizing GPX4

The crosstalk between tumor progression and ferroptosis is largely unknown. Here, we identify malate dehydrogenase 2 (MDH2) as a key regulator of ferroptosis. MDH2 deficiency inhibits the growth of hepatocellular carcinoma (HCC) cells and enhances their sensitivity to ferroptosis induced by RAS-selective lethal 3 (RSL3), a compound known to cause ferroptosis. MDH2 knock-down enhances RSL3-induced intracellular reactive oxygen species, free iron ions and lipid per-oxides levels, leading to HCC ferroptotic cell death which is rescued by ferrostatin-1 and iron chelator deferiprone. Importantly, the inhibition of HCC cell growth caused by MDH2 deficiency is partially rescued by ferroptosis blockade. Mechanistically, MDH2 resists RSL3-induced ferroptosis sensitivity dependent on glutathione peroxidase 4 (GPX4), an enzyme responsible for scavenging lipid peroxides, which is stabilized by MDH2 in HCC. The protein expressions of MDH2 and GPX4 are positively correlated with each other in HCC cell lines. Furthermore, through our UALCAN website analysis, we found that MDH2 and GPX4 are highly expressed in HCC samples. These findings reveal a critical mechanism by which HCC evades ferroptosis via MDH2-mediated stabilization of GPX4 to promote tumor progression and underscore the potential of MDH2 inhibition in combi-nation with ferroptosis inducers for the treatment of HCC.

Dexmedetomidine Ameliorates Myocardial Ischemia-Reperfusion Injury by Inhibiting MDH2 Lactylation via Regulating Metabolic Reprogramming.

Myocardial ischemia-reperfusion injury (MIRI) significantly worsens the outcomes of patients with cardiovascular diseases. Dexmedetomidine (Dex) is recognized for its cardioprotective properties, but the related mechanisms, especially regarding metabolic reprogramming, have not been fully clarified. A total of 60 patients with heart valve disease are randomly assigned to Dex or control group. Blood samples are collected to analyze cardiac injury biomarkers and metabolomics. In vivo and vitro rat models of MIRI are utilized to assess the effects of Dex on cardiac function, lactate production, and mitochondrial function. It is found that postoperative CK-MB and cTNT levels are significantly lower in the Dex group. Metabolomics reveals that Dex regulates metabolic reprogramming and reduces lactate level. In Dex-treated rats, the myocardial infarction area is reduced, and myocardial contractility is improved. Dex inhibits glycolysis, reduces lactate, and improves mitochondrial function following MIRI. Lactylation proteomics identifies that Dex reduces the lactylation of Malate Dehydrogenase 2（MDH2), thus alleviating myocardial injury. Further studies reveal that MDH2 lactylation induces ferroptosis, leading to MIRI by impairing mitochondrial function. Mechanistic analyses reveal that Dex upregulates Nuclear Receptor Subfamily 3 Group C Member 1（NR3C1)phosphorylation, downregulates Pyruvate Dehydrogenase Kinase 4 (PDK4), and reduces lactate production and MDH2 lactylation. These findings provide new therapeutic targets and mechanisms for the treatment for MIRI.

Metabolic regulation of the glioblastoma stem cell epitranscriptome by malate dehydrogenase 2

Tumors reprogram their metabolism to generate complex neoplastic ecosystems. Here, we demonstrate that glioblastoma (GBM) stem cells (GSCs) display elevated activity of the malate-aspartate shuttle (MAS) and expression of malate dehydrogenase 2 (MDH2). Genetic and pharmacologic targeting of MDH2 attenuated GSC proliferation, self-renewal, and invivo tumor growth, partially rescued by aspartate. Targeting MDH2 induced accumulation of alpha-ketoglutarate (αKG), a critical co-factor for dioxygenases, including the N6-methyladenosine (m6A) RNA demethylase AlkB homolog 5, RNA demethylase (ALKBH5). Forced expression of MDH2 increased m6A levels and inhibited ALKBH5 activity, both rescued by αKG supplementation. Reciprocally, targeting MDH2 reduced global m6A levels with platelet-derived growth factor receptor-β (PDGFRβ) as a regulated transcript. Pharmacological inhibition of MDH2 in GSCs augmented efficacy of dasatinib, an orally bioavailable multi-kinase inhibitor, including PDGFRβ. Collectively, stem-like tumor cells reprogram their metabolism to induce changes in their epitranscriptomes and reveal possible therapeutic paradigms.

Biomarkers and pathways in autism spectrum disorder: An individual meta-analysis based on proteomic and metabolomic data.

The utilization of biomarkers for the diagnosis and management of autism spectrum disorders (ASD) remains a relatively unexplored frontier in clinical practice. Proteomics and metabolomics are important tools for revealing key biomarkers and evaluating biological pathways in ASD. We conducted an individual meta-analysis to compare the consistency of biomarkers of ASD from central nervous system (brain and cerebrospinal fluid), circulatory system (blood), and non-invasive samples (urine, saliva, and faeces) and performed pathway enrichment analyses to identify pathways enriched in ASD. After screening 926 proteomics and 619 metabolomics articles, we collected data from 10 studies involving 940 differential proteins and 16 studies assessing a total of 748 differential metabolites. In brain tissue, blood, and urine of ASD cases and controls, flotillin-2 (FLOT2), apolipoprotein E (ApoE), and EH domain-containing protein 3 (EHD3) exhibit differential expression, while vinculin (VCL) displays variations in saliva, blood, and urine. Similarly, in case-control studies, gelsolin (GSN) shows differential expression in brain tissue, saliva, and urine, and malate dehydrogenase 2 (MDH2) in brain tissue, blood, and saliva. Hippuric acid and salicyluric acid were simultaneously found in the brain, blood, urine, and faeces. In terms of pathways, glycolysis/gluconeogenesis, carbon metabolism, and glutathione metabolism were enriched in the brain as well as in saliva or urine. In our study, we identified six shared protein and two metabolic markers in central nervous system, circulatory system, and non-invasive samples, underscoring their potential value for ASD diagnosis and management, warranting further research.

An fusaric acid-based CRISPR library screen identifies MDH2 as a broad-spectrum regulator of Fusarium toxin-induced cell death

Fusarium mycotoxins are of great concern because they are the most common food-borne mycotoxins and environmental contaminants worldwide. Fusaric acid (FA), Deoxynivalenol (DON), Zearalenone (ZEA), T-2 toxin (T-2), and Fumonisin B1 (FB1) are important Fusarium toxins contaminating feeds and food and can cause serious health problems. FA can synergize with some other Fusarium toxins to enhance overall toxicity. However, the underlying molecular mechanism remains poorly understood. In this study, our CRISPR screening revealed Malate dehydrogenase 2 (MDH2) and Pyruvate dehydrogenase E1 subunit beta (PDHB) are the key genes for FA-induced cell death. Pathways associated with mitochondrial function, notably the TCA cycle, play a significant role in FA cytotoxicity. We found that MDH2 and PDHB depletion reduced FA-induced cell death, ROS accumulation, and the expression of caspase-3 and HIF-1α. The cell viability assays and flow cytometry demonstrated that MDH2 knockout but not PDHB decreased DON, ZEA, T-2, and FB1-induced cytotoxicity, apoptosis, and ROS accumulation. MDH2 inhibitor LW6 also decreased DON, ZEA, T-2, and FB1-induced toxicity. This suggested that MDH2, but not PDHB, is a common regulator of broad-spectrum Fusarium toxin (FA, DON, ZEA, T-2, and FB1)-induced cell death. Our work provides new avenues for the treatment of Fusarium toxin toxicity.

Malate dehydrogenase-2 inhibition shields renal tubular epithelial cells from anoxia-reoxygenation injury by reducing reactive oxygen species.

Ischemia-reperfusion (I-R) injury is the most common cause of acute kidney injury. In experiments involving primary human renal proximal tubular epithelial cells (RPTECs) exposed to anoxia-reoxygenation, we explored the hypothesis that mitochondrial malate dehydrogenase-2 (MDH-2) inhibition redirects malate metabolism from the mitochondria to the cytoplasm, towards the malate-pyruvate cycle and reversed malate-aspartate shuttle. Colorimetry, fluorometry, and western blotting showed that MDH2 inhibition accelerates the malate-pyruvate cycle enhancing cytoplasmic NADPH, thereby regenerating the potent antioxidant reduced glutathione. It also reversed the malate-aspartate shuttle and potentially diminished mitochondrial reactive oxygen species (ROS) production by transferring electrons, in the form of NADH, from the mitochondria to the cytoplasm. The excessive ROS production induced by anoxia-reoxygenation led to DNA damage and protein modification, triggering DNA damage and unfolded protein response, ultimately resulting in apoptosis and senescence. Additionally, ROS induced lipid peroxidation, which may contribute to the process of ferroptosis. Inhibiting MDH-2 proved effective in mitigating ROS overproduction during anoxia-reoxygenation, thereby rescuing RPTECs from death or senescence. Thus, targeting MDH-2 holds promise as a pharmaceutical strategy against I-R injury.

Phillyrin and its metabolites exert antipyretic effects by targeting the NAD+ binding domain of GAPDH, MDH2 and IDH2

BackgroundFever is one of the main pathophysiological reactions that occurs during the acute phase of various diseases. Excessive body temperature can lead to various adverse consequences such as brain tissue damage and abnormal immune responses. Phillyrin (Phr) is the main active ingredient in Forsythia suspensa (Thunb.) Vahl (Lian Qiao) and has antipyretic effects; however, its antipyretic mechanism of action remains unclear. PurposeThis study aimed to explore the antipyretic mechanisms of Phr and provide a new treatment plan for fever. MethodsThe antipyretic effects of Phr were evaluated using a mouse model of pneumonia fever. The main metabolites of Phr involved in its antipyretic function were identified using a mitochondrial temperature-sensitive probe. Further synthesis of the main metabolite, phillygenin (Phg), an alkynylated probe, was performed, and chemical proteomics was used to capture and analyze its direct target for antipyretic effects. The mechanism of action of Phg and its antipyretic targets was explored using metabolomics and various molecular biology methods. ResultsPhr showed significant antipyretic and anti-inflammatory effects in a mouse model of lipopolysaccharide-induced fever. Phg reversibly targeted the nicotinamide adenine dinucleotide (NAD+) binding domain of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), malate dehydrogenase 2 (MDH2), and isocitrate dehydrogenase 2 (IDH2) to inhibit their enzymatic activity. In-depth analysis of cellular metabolomics and mitochondrial stress testing indicated that inhibition of GAPDH, MDH2, and IDH2 enzyme activity by Phg led to a decrease in cellular energy supply and heat production regulated by glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation signaling pathways. Phg specifically targeted macrophages and inhibited LPS-induced macrophage activation by downregulating GAPDH enzyme activity, thereby exerting anti-inflammatory effects. In vivo experiments also confirmed that the antipyretic effect of Phr in LPS-induced fever model mice was related to its main metabolites, Phg and Phg-sulfonate (Phg-S), which directly targeted the NAD+ binding domain of GAPDH, IDH2, and MDH2, inhibiting the activity of these enzymes, thereby reducing energy supply and regulating febrile-related inflammatory factors. ConclusionThis study reported for the first time that the antipyretic effect of Phr is produced by targeting GAPDH, IDH2, and MDH2 to regulate energy supply and febrile-related inflammatory factors through its main metabolites Phg and Phg-S. This study not only provides potential drugs for fever treatment but also provides new ideas for improving clinical fever treatment plans.

Participation of the transcription factor CREB1 in the regulation of the Mdh2 gene encoding malate dehydrogenase in the liver of rats with alloxan diabetes

The aim of the study was to study the role of transcription factor CREB1 in regulating the expression of the gene encoding the mitochondrial form of malate dehydrogenase (MDH, EC 1.1.1.37) in the liver of rats with experimental diabetes. An increase in the rate of work of NAD-dependent malate dehydrogenase in rat liver cells during the development of experimental diabetes was shown, associated with the activation of the Mdh1 and Mdh2 genes encoding this enzyme. The analysis of the promoters of these genes showed that only in the Mdh2 gene there is a specific binding site with the transcription factor CREB1. It was found that in the liver of rats with pathology, there is an increase in the rate of expression of the gene encoding this transcription factor, which correlates with the expression of the Mdh2 gene. Thus, the data obtained by us confirm the possibility of positive regulation of the rate of the Mdh2 gene by the transcription factor CREB1.

Metabolic and transcriptomic reprogramming during contact inhibition-induced quiescence is mediated by YAP-dependent and YAP-independent mechanisms.

Metabolic rewiring during the proliferation-to-quiescence transition is poorly understood. Here, using a model of contact inhibition-induced quiescence, we conducted 13C-metabolic flux analysis in proliferating (P) and quiescent (Q) mouse embryonic fibroblasts (MEFs) to investigate this process. Q cells exhibit reduced glycolysis but increased TCA cycle flux and mitochondrial respiration. Reduced glycolytic flux in Q cells correlates with reduced glycolytic enzyme expression mediated by yes-associated protein (YAP) inhibition. The increased TCA cycle activity and respiration in Q cells is mediated by induced mitochondrial pyruvate carrier (MPC) expression, rendering them vulnerable to MPC inhibition. The malate-to-pyruvate flux, which generates NADPH, is markedly reduced by modulating malic enzyme 1 (ME1) dimerization in Q cells. Conversely, the malate dehydrogenase 1 (MDH1)-mediated oxaloacetate-to-malate flux is reversed and elevated in Q cells, driven by high mitochondrial-derived malate levels, reduced cytosolic oxaloacetate, elevated MDH1 levels, and a high cytoplasmic NAD+/NADH ratio. Transcriptomic analysis revealed large number of genes are induced in Q cells, many of which are associated with the extracellular matrix (ECM), while YAP-dependent and cell cycle-related genes are repressed. The results suggest that high TCA cycle flux and respiration in Q cells are required to generate ATP and amino acids to maintain de-novo ECM protein synthesis and secretion.

Exploring the anxiolytic mechanism of Fructus gardeniae based on metabolomics, network pharmacology, and molecular docking.

To explore the effect and anxiolytic mechanism of a natural remedy called Fructus gardeniae (FG). The elevated-plus maze (EPM) test was used to confirm the anxiolytic effect of FG. The potential and anxiolytic components, targets, and route processes of FG were investigated using the network pharmacology method in conjunction with metabolomics and molecular docking technologies. FG could greatly enhance the proportion of time and times of opening arms, according to the EPM data. As to the metabolomics findings, a total of 61 distinct metabolites were found, mainly involved in glycine, serine, and threonine metabolism as well as alanine, aspartate, and glutamate metabolism. The primary active ingredients of FG, nicotiflorin, jasminodiol, and crocetin, demonstrated substantial binding affinities with monoamine oxidase A (MAOA), monoamine oxidase A (ACHE), malate dehydrogenase 2 (MDH2), glutamate decarboxylase 2 (GAD2), glutamate decarboxylase 1 (GAD1), and nitric oxide synthase (NOS1), according to the findings of network pharmacology and molecular docking. FG exerts an anxiolytic action via targeting MAOA, ACHE, MDH2, GAD2, GAD1, and NOS1, and regulating the metabolism of glycine, serine, and threonine as well as alanine, aspartic acid, and glutamic acid.

Deacetylated MDH1 and IDH1 aggravates PANoptosis in acute liver failure through endoplasmic reticulum stress signaling

Acute liver failure (ALF) is a disease with a high mortality rate and poor prognosis, whose pathogenesis is not fully understood. PANoptosis is a recently proposed mode of cell death characterized by pyroptosis, apoptosis, and necroptosis, but it cannot be explained by any of them alone. This study aims to explore the role of PANoptosis in ALF and the impact and mechanism of deacetylated malate dehydrogenase 1 (MDH1) and isocitrate dehydrogenase 1 (IDH1) on PANoptosis. Our results found that, compared with the control group, the cell viability in the lipopolysaccharide (LPS)/D-galactosamine (D-Gal) group decreased, lactate dehydrogenase (LDH) release increased, cell death increased, and the levels of PANoptosis-related molecules RIPK1, GSDMD, caspase-3, MLKL, IL-18, IL-1β increased, indicating that PANoptosis increased during ALF. Deacetylated MDH1 at K118 and IDH1 at K93 increased the expression of PANoptosis-related molecules RIPK1, GSDMD, caspase-3, MLKL, IL-18, and IL-1β in vivo and in vitro. The deacetylation weakened the inhibitory effect of histone deacetylase (HDAC) inhibitor ACY1215 on PANoptosis-related molecules, suggesting that deacetylated MDH1 at K118 and IDH1 at K93 aggravated PANoptosis during ALF. Deacetylated MDH1 at K118 and IDH1 at K93 also promoted the expression of endoplasmic reticulum stress-related molecules BIP, ATF6, XBP1, and CHOP in vivo and in vitro. The use of endoplasmic reticulum stress inhibitor 4-PBA weakened the promotion effect of deacetylated MDH1 K118 and IDH1 K93 on PANoptosis. The results suggested that deacetylated MDH1 at K118 and IDH1 at K93 may aggravate PANoptosis in ALF through endoplasmic reticulum stress signaling. In conclusion, deacetylated MDH1 and IDH1 may aggravate PANoptosis in ALF, and the mechanism may act through endoplasmic reticulum stress signaling.

Proteomics of tumor and serum samples from isocitrate dehydrogenase-wildtype glioblastoma patients: is the detoxification of reactive oxygen species associated with shorter survival?

Proteomics has been little used for the identification of novel prognostic and/or therapeutic markers in isocitrate dehydrogenase (IDH)-wildtype glioblastoma (GB). In this study, we analyzed 50 tumor and 30 serum samples from short- and long-term survivors of IDH-wildtype GB (STS and LTS, respectively) by data-independent acquisition mass spectrometry (DIA-MS)-based proteomics, with the aim of identifying such markers. DIA-MS identified 5422 and 826 normalized proteins in tumor and serum samples, respectively, with only three tumor proteins and 26 serum proteins displaying significant differential expression between the STS and LTS groups. These dysregulated proteins were principally associated with the detoxification of reactive oxygen species (ROS). In particular, GB patients in the STS group had high serum levels of malate dehydrogenase 1 (MDH1) and ribonuclease inhibitor 1 (RNH1) and low tumor levels of fatty acid-binding protein 7 (FABP7), which may have enabled them to maintain low ROS levels, counteracting the effects of the first-line treatment with radiotherapy plus concomitant and adjuvant temozolomide. A blood score built on the levels of MDH1 and RNH1 expression was found to be an independent prognostic factor for survival based on the serum proteome data for a cohort of 96 IDH-wildtype GB patients. This study highlights the utility of circulating MDH1 and RNH1 biomarkers for determining the prognosis of patients with IDH-wildtype GB. Furthermore, the pathways driven by these biomarkers, and the tumor FABP7 pathway, may constitute promising therapeutic targets for blocking ROS detoxification to overcome resistance to chemoradiotherapy in potential GB STS.

SpCTP3 from the hyperaccumulator Sedum plumbizincicola positively regulates cadmium tolerance by interacting with SpMDH1

Cadmium (Cd) is a heavy metal pollutant mainly originating from the discharge of industrial sewage, irrigation with contaminated water, and the use of fertilizers. The phytoremediation of Cd polluted soil depends on the identification of the associated genes in hyperaccumulators. Here, a novel Cd tolerance gene (SpCTP3) was identified in hyperaccumulator Sedum plumbizincicola. The results of Cd2+ binding and thermodynamic analyses, revealed the CXXC motif in SpCTP3 functions is a Cd2+ binding site. A mutated CXXC motif decreased binding to Cd by 59.93%. The subcellular localization analysis suggested that SpCTP3 is primarily a cytoplasmic protein. Additionally, the SpCTP3-overexpressing (OE) plants were more tolerant to Cd and accumulated more Cd than wild-type Sedum alfredii (NHE-WT). The Cd concentrations in the cytoplasm of root and leaf cells were significantly higher (53.75% and 71.87%, respectively) in SpCTP3-OE plants than in NHE-WT. Furthermore, malic acid levels increased and decreased in SpCTP3-OE and SpCTP3-RNAi plants, respectively. Moreover, SpCTP3 interacted with malate dehydrogenase 1 (MDH1). Thus, SpCTP3 helps regulate the subcellular distribution of Cd and increases Cd accumulation when it is overexpressed in plants, ultimately Cd tolerance through its interaction with SpMDH1. This study provides new insights relevant to improving the Cd uptake by Sedum plumbizincicola.

Targeting c-Myc transactivation by LMNA inhibits tRNA processing essential for malate-aspartate shuttle and tumour progression.

A series of studies have demonstrated the emerging involvement of transfer RNA (tRNA) processing during the progression of tumours. Nevertheless, the roles and regulating mechanisms of tRNA processing genes in neuroblastoma (NB), the prevalent malignant tumour outside the brain in children, are yet unknown. Analysis of multi-omics results was conducted to identify crucial regulators of downstream tRNA processing genes. Co-immunoprecipitation and mass spectrometry methods were utilised to measure interaction between proteins. The impact of transcriptional regulators on expression of downstream genes was measured by dual-luciferase reporter, chromatin immunoprecipitation, western blotting and real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) methods. Studies have been conducted to reveal impact and mechanisms of transcriptional regulators on biological processes of NB. Survival differences were analysed using the log-rank test. c-Myc was identified as a transcription factor driving tRNA processing gene expression and subsequent malate-aspartate shuttle (MAS) in NB cells. Mechanistically, c-Myc directly promoted the expression of glutamyl-prolyl-tRNA synthetase (EPRS) and leucyl-tRNA synthetase (LARS), resulting in translational up-regulation of glutamic-oxaloacetic transaminase 1 (GOT1) as well as malate dehydrogenase 1 (MDH1) via inhibiting general control nonrepressed 2 or activating mechanistic target of rapamycin signalling. Meanwhile, lamin A (LMNA) inhibited c-Myc transactivation via physical interaction, leading to suppression of MAS, aerobic glycolysis, tumourigenesis and aggressiveness. Pre-clinically, lobeline was discovered as a LMNA-binding compound to facilitate its interaction with c-Myc, which inhibited aminoacyl-tRNA synthetase expression, MAS and tumour progression of NB, as well as growth of organoid derived from c-Myc knock-in mice. Low levels of LMNA or elevated expression of c-Myc, EPRS, LARS, GOT1 or MDH1 were linked to a worse outcome and a shorter survival time of clinical NB patients. These results suggest that targeting c-Myc transactivation by LMNA inhibits tRNA processing essential for MAS and tumour progression.

Cytosolic RNA binding of the mitochondrial TCA cycle enzyme malate dehydrogenase.

Several enzymes of intermediary metabolism have been identified to bind RNA in cells, with potential consequences for the bound RNAs and/or the enzyme. In this study, we investigate the RNA-binding activity of the mitochondrial enzyme malate dehydrogenase 2 (MDH2), which functions in the tricarboxylic acid (TCA) cycle and the malate-aspartate shuttle. We confirmed in cellulo RNA binding of MDH2 using orthogonal biochemical assays and performed enhanced cross-linking and immunoprecipitation (eCLIP) to identify the cellular RNAs associated with endogenous MDH2. Surprisingly, MDH2 preferentially binds cytosolic over mitochondrial RNAs, although the latter are abundant in the milieu of the mature protein. Subcellular fractionation followed by RNA-binding assays revealed that MDH2-RNA interactions occur predominantly outside of mitochondria. We also found that a cytosolically retained N-terminal deletion mutant of MDH2 is competent to bind RNA, indicating that mitochondrial targeting is dispensable for MDH2-RNA interactions. MDH2 RNA binding increased when cellular NAD+ levels (MDH2's cofactor) were pharmacologically diminished, suggesting that the metabolic state of cells affects RNA binding. Taken together, our data implicate an as yet unidentified function of MDH2-binding RNA in the cytosol.

Metabolic priming by multiple enzyme systems supports glycolysis, HIF1α stabilisation, and human cancer cell survival in early hypoxia

Adaptation to chronic hypoxia occurs through changes in protein expression, which are controlled by hypoxia-inducible factor 1α (HIF1α) and are necessary for cancer cell survival. However, the mechanisms that enable cancer cells to adapt in early hypoxia, before the HIF1α-mediated transcription programme is fully established, remain poorly understood. Here we show in human breast cancer cells, that within 3 h of hypoxia exposure, glycolytic flux increases in a HIF1α-independent manner but is limited by NAD+ availability. Glycolytic ATP maintenance and cell survival in early hypoxia rely on reserve lactate dehydrogenase A capacity as well as the activity of glutamate-oxoglutarate transaminase 1 (GOT1), an enzyme that fuels malate dehydrogenase 1 (MDH1)-derived NAD+. In addition, GOT1 maintains low α-ketoglutarate levels, thereby limiting prolyl hydroxylase activity to promote HIF1α stabilisation in early hypoxia and enable robust HIF1α target gene expression in later hypoxia. Our findings reveal that, in normoxia, multiple enzyme systems maintain cells in a primed state ready to support increased glycolysis and HIF1α stabilisation upon oxygen limitation, until other adaptive processes that require more time are fully established.

A novel HDAC6 inhibitor attenuate APAP-induced liver injury by regulating MDH1-mediated oxidative stress

Glutathione (GSH) depletion, mitochondrial damage, and oxidative stress have been implicated in the pathogenesis of acetaminophen (APAP) hepatotoxicity. Here, we demonstrated that the expression of histone deacetylase 6 (HDAC6) is highly elevated, whereas malate dehydrogenase 1 (MDH1) is downregulated in liver tissues and AML-12 cells induced by APAP. The therapeutic benefits of LT-630, a novel HDAC6 inhibitor on APAP-induced liver injury, were also substantiated. On this basis, we demonstrated that LT-630 improved the protein expression and acetylation level of MDH1. Furthermore, after overexpression of MDH1, an upregulated NADPH/NADP+ ratio and GSH level and decreased cell apoptosis were observed in APAP-stimulated AML-12 cells. Importantly, MDH1 siRNA clearly reversed the protection of LT-630 on APAP-stimulated AML-12 cells. In conclusion, LT-630 could ameliorate liver injury by modulating MDH1-mediated oxidative stress induced by APAP.

Transcription Factor STAT3-Activated LDHB Promotes Tumor Properties of Endometrial Cancer Cells by Inducing MDH2 Expression.

The pathogenesis of endometrial cancer (EC) involves the regulation of lactate dehydrogenases. However, the role and mechanism of lactate dehydrogenase-B (LDHB) in EC progression have not been studied. The mRNA levels of LDHB and malate dehydrogenase 2 (MDH2) were detected by quantitative real-time polymerase chain reaction. Protein expression was checked by western blotting and immunohistochemistry assays. Cell proliferation, apoptosis, and invasion were analyzed by 5-Ethynyl-2'-deoxyuridine, transwell, and flow cytometry assay, respectively. Glycolysis was investigated using Glucose Assay Kit, CheKine™ Micro Lactate Assay Kit, and ADP/ATP ratio assay kit. An in vivo tumor formation assay was conducted to disclose the effect of LDHB on tumor growth in vivo. The associations among signal transducer and activator of transcription 3 (STAT3), LDHB, and MDH2 were predicted through JASPAR or GeneMANIA online database and identified by chromatin immunoprecipitation assay, dual-luciferase reporter assay, and co-immunoprecipitation assay. LDHB expression was increased in EC tissues and cells in comparison with normal endometrial tissues and human endometrial stromal cells. LDHB had the potential as a biomarker to predict the prognosis of EC patients. In addition, LDHB knockdown inhibited the proliferation, invasion, and glycolysis and promoted apoptosis of RL95-2 and Ishikawa cells. LDHB knockdown inhibited tumor property of Ishikawa cells in vivo. STAT3 bound to the promoter region of LDHB, and STAT3 silencing-induced effects were relieved after LDHB upregulation. LDHB interacted with and regulated MDH2 expression. Moreover, MDH2 overexpression rescued LDHB knockdown-induced effects on EC cell phenotypes. STAT3-activated LDHB promoted endometrial cancer cell malignancy by inducing MDH2 production.

Participation of the Transcription Factor CREB1 in the Regulation of the Mdh2 Gene Encoding Malate Dehydrogenase in the Liver of Rats with Alloxan-Induced Diabetes

Participation of the Transcription Factor CREB1 in the Regulation of the Mdh2 Gene Encoding Malate Dehydrogenase in the Liver of Rats with Alloxan-Induced Diabetes

The malate-aspartate shuttle is important for de novo serine biosynthesis

The malate-aspartate shuttle (MAS) is a redox shuttle that transports reducing equivalents across the inner mitochondrial membrane while recycling cytosolic NADH to NAD+. We genetically disrupted each MAS component to generate a panel of MAS-deficient HEK293 cell lines in which we performed [U-13C]-glucose tracing. MAS-deficient cells have reduced serine biosynthesis, which strongly correlates with the lactate M+3/pyruvate M+3 ratio (reflective of the cytosolic NAD+/NADH ratio), consistent with the NAD+ dependency of phosphoglycerate dehydrogenase in the serine synthesis pathway. Among the MAS-deficient cells, those lacking malate dehydrogenase 1 (MDH1) show the most severe metabolic disruptions, whereas oxoglutarate-malate carrier (OGC)- and MDH2-deficient cells are less affected. Increasing the NAD+-regenerating capacity using pyruvate supplementation resolves most of the metabolic disturbances. Overall, we show that the MAS is important for de novo serine biosynthesis, implying that serine supplementation could be used as a therapeutic strategy for MAS defects and possibly other redox disorders.