L-2-hydroxyglutarate Dehydrogenase Research Articles

Renal L-2-hydroxyglutarate dehydrogenase activity promotes hypoxia tolerance and mitochondrial metabolism in Drosophila melanogaster

ObjectivesThe mitochondrial enzyme L-2-hydroxyglutarate dehydrogenase (L2HGDH) regulates the abundance of L-2-hydroxyglutarate (L-2HG), a potent signaling metabolite capable of influencing chromatin architecture, mitochondrial metabolism, and cell fate decisions. Loss of L2hgdh activity in humans induces ectopic L-2HG accumulation, resulting in neurodevelopmental defects, altered immune cell function, and enhanced growth of clear cell renal cell carcinomas. To better understand the molecular mechanisms that underlie these disease pathologies, we used the fruit fly Drosophila melanogaster to investigate the endogenous functions of L2hgdh. MethodsL2hgdh mutant adult male flies were analyzed under normoxic and hypoxic conditions using a combination of semi-targeted metabolomics and RNA-seq. These multi-omic analyses were complemented by tissue-specific genetic studies that examined the effects of L2hgdh mutations on the Drosophila renal system (Malpighian tubules; MTs). ResultsOur studies revealed that while L2hgdh is not essential for growth or viability under standard culture conditions, L2hgdh mutants are hypersensitive to hypoxia and expire during the reoxygenation phase with severe disruptions of mitochondrial metabolism. Moreover, we find that the fly renal system is a key site of L2hgdh activity, as L2hgdh mutants that express a rescuing transgene within the MTs survive hypoxia treatment and exhibit normal levels of mitochondrial metabolites. We also demonstrate that even under normoxic conditions, L2hgdh mutant MTs experience significant metabolic stress and are sensitized to aberrant growth upon Egfr activation. ConclusionsThese findings present a model in which renal L2hgdh activity limits systemic L-2HG accumulation, thus indirectly regulating the balance between glycolytic and mitochondrial metabolism, enabling successful recovery from hypoxia exposure, and ensuring renal tissue integrity.

L2-hydroxyglutaric aciduria presenting with learning disability and cerebellar signs: A case report

L-2-hydroxyglutaric aciduria (L2HGA) is a rare, autosomal recessive neurometabolic disorder due to variants in the L2HGDH gene, which encodes L-2-hydroxyglutarate dehydrogenase (L2HGDH), an enzyme involved in tricarboxylic acid cycle. Deficiency of L2HGDH causes leukoencephalopathy predominantly affecting the cerebellum. This case presents L2HGA in a 12-year-old Sri Lankan boy born to third-degree consanguineous parents, who also showed learning disability and bilateral cerebellar signs. Magnetic resonance imaging (MRI) of the brain revealed T2/FLAIR hyperintensities in bilateral symmetrical subcortical white matter involving the cerebellum. A diagnosis of 2-hydroxyglutaric aciduria was made after a massive peak of 2-hydroxyglutaric acid (2HG) was observed in the analysis of urine organic acids (UOA) using gas chromatography/mass spectrometry. Genetic variant analysis revealed two heterozygous pathogenic variants in the L2HGDH gene, confirming the genetic diagnosis of autosomal recessive L2HGA. Parental genetic testing confirmed the trans phase of the variants in the index patient and their carrier status of a pathogenic L2HGDH variant. Despite typical clinical features and classical MRI findings, initial clues toward the diagnosis are mainly derived from the UOA analysis. In conclusion, this case underscores the paramount importance of analyzing the UOA profile in the process of identifying rare metabolic causes, such as L2HGA, that contribute to learning disability with neurological involvement in children.

L-2-hydroxyglutaric aciduria: a report of clinical, radiological, and genetic characteristics of two siblings from Egypt

ABSTRACT L-2-hydroxyglutaric aciduria (L-2-HGA) is a rare autosomal recessive disease characterized by elevated levels of hydroxyglutaric acid in the body fluids and brain with abnormal white matter. We present two siblings with psychomotor retardation and quadriparesis. Their brain imaging showed diffuse bilateral symmetrical involvement of the cerebral cortex, white matter, basal ganglia and cerebellum. The whole exome sequence studies revealed a homozygous likely pathogenic variant on chromosome 14q22.1 (NM_024884.2: c.178G > A; pGly60Arg) in the gene encoding for L-2-hydroxyglutarate dehydrogenase (L2HGDH) (OMIM #236792). Therefore, using the L2HGDH gene study is beneficial for L2HGA diagnosis.

Structure and biochemical characterization of l-2-hydroxyglutarate dehydrogenase and its role in the pathogenesis of l-2-hydroxyglutaric aciduria

l-2-hydroxyglutarate dehydrogenase (L2HGDH) is a mitochondrial membrane-associated metabolic enzyme, which catalyzes the oxidation of l-2-hydroxyglutarate (l-2-HG) to 2-oxoglutarate (2-OG). Mutations in human L2HGDH lead to abnormal accumulation of l-2-HG, which causes a neurometabolic disorder named l-2-hydroxyglutaric aciduria (l-2-HGA). Here, we report the crystal structures of Drosophila melanogaster L2HGDH (dmL2HGDH) in FAD-bound form and in complex with FAD and 2-OG and show that dmL2HGDH exhibits high activity and substrate specificity for l-2-HG. dmL2HGDH consists of an FAD-binding domain and a substrate-binding domain, and the active site is located at the interface of the two domains with 2-OG binding to the re-face of the isoalloxazine moiety of FAD. Mutagenesis and activity assay confirmed the functional roles of key residues involved in the substrate binding and catalytic reaction and showed that most of the mutations of dmL2HGDH equivalent to l-2-HGA-associated mutations of human L2HGDH led to complete loss of the activity. The structural and biochemical data together reveal the molecular basis for the substrate specificity and catalytic mechanism of L2HGDH and provide insights into the functional roles of human L2HGDH mutations in the pathogeneses of l-2-HGA.

TMET-02. CLINICAL EFFICACY OF ONC201 IN H3K27M-MUTANT DIFFUSE MIDLINE GLIOMAS IS DRIVEN BY DISRUPTION OF INTEGRATED METABOLIC AND EPIGENETIC PATHWAYS

Abstract H3K27M-mutant diffuse midline glioma (DMG) patients have no proven effective therapies beyond radiation. ONC201, a mitochondrial protease ClpP agonist, has recently demonstrated efficacy in these patients, but the mechanism behind this remains unknown. We assessed clinical outcomes, tumor sequencing, and tissue samples from patients treated in two completed multi-site clinical studies (n=71). Patients treated with ONC201 monotherapy following initial radiation but prior to recurrence (n=35) demonstrated a median overall survival of 21.7 months and a median progression-free survival of 12.2 months. Radiographic response was associated with increased expression of key tricarboxylic acid cycle-related genes in baseline tumor sequencing. Similar survival benefits were observed using in utero electroporation and orthotopic mouse models of H3K27M-DMG (median 107 versus 77 days [p=0.02] and median 97 versus 141 days [p=0.004], respectively). Integrated transcriptomic and metabolomic analysis of ONC201-treated H3K27M-DMG cells revealed downregulation of TCA cycle, glycolysis, and pyruvate metabolism genes, most notably oxoglutarate dehydrogenase (OGDH), and concomitant changes in levels of associated metabolites including ɑ-ketoglutarate (ɑ-KG). Interestingly, L-2-hydroxyglutarate (L-2HG), a known inhibitor of the Jumonji C domain family of histone lysine demethylases, was also increased. This corresponded with increases in repressive H3K27me3 in vitro and in human tumors accompanied by epigenetic downregulation of cell cycle regulation and neuro-glial differentiation genes. Genetic knockdown of OGDH recapitulated ONC201-mediated increases in H3K27me3. In contrast, genetic knockdown of ClpP or lactate dehydrogenase A or overexpression of L-2-hydroxyglutarate dehydrogenase (L-2HGDH), but not D-2HGDH, abrogated ONC201-mediated increases in H3K27me3, demonstrating that ONC201 induces the production of L-2HG in H3K27M-DMG cells leading to increased H3K27me3. Overall, our data demonstrates the efficacy of ONC201 in H3K27M-mutant DMG and supports ONC201 as the first monotherapy to improve outcomes in patients with H3K27M-mutant DMG for whom few therapeutic options currently exist. Mechanistically, ONC201 disrupts integrated metabolic and epigenetic pathways and reverses pathognomonic H3K27me3 reduction.

Abstract B005: Metabolic liabilities in high L-2HG kidney cancer

Abstract Renal cell carcinoma (RCC) is among the top 10 cancers in the USA. Despite several approved therapies, patients with the advanced disease rarely have durable responses and therefore, face a poor prognosis (median survival 2-3 years). This underscores the need for new strategies. Alterations in metabolism are well-established in cancers including RCC. The oncometabolite, L-2-hydroxyglutarate (L-2HG) is elevated in the most common form of RCC (clear cell histology) and promotes tumor progression. However, L-2HG’s roles in RCC progression and its mediated therapeutic vulnerability are yet to be explored. RCC cell lines lack the L-2HG dehydrogenase enzyme (L2HGDH) which results in their high L-2HG level. RNA-seq of control (high L-2GH) and an L2HGDH reconstituted (low L-2HG) RCC cell line reveals that L-2HG suppresses the expression of serine biosynthesis genes, PHGDH and PSAT1. In agreement, high L-2HG renal tumors demonstrate lower levels of serine biosynthesis enzymes compared to their matched normal kidneys. Mechanistic studies reveal L-2HG-mediated remodeling of both the epigenome and epitranscriptome suppress serine biosynthesis genes. Consistently, 13C-metabolomics labeling studies demonstrate that raised L-2HG suppresses de novo serine biosynthesis. Moreover, LC-MS analysis of the metabolites isolated from the kidneys of L2hgdh KO and wild-type (WT) mice revealed lower serine levels in L2hgdh KO kidneys. In accordance with these data, found that high L-2HG RCC cells require exogenous serine for in vitro proliferation and in vivo tumor growth. Likewise, the pharmacologic blockade of serine uptake decreases the proliferation of high L-2HG RCC cells. Furthermore, this serine liability can be rescued upon lowering cellular L-2HG levels. Untargeted metabolomics analyses demonstrate that exogenous serine is required to maintain cellular pools of glutathione (GSH+GSSG) in high L-2HG RCC. This is particularly relevant as glutathione is among the most highly enriched metabolites in RCC compared to normal kidneys. Our metabolomics data also suggest that serine might be essential for the transsulfuration process of glutathione biosynthesis in RCC that lacks the xCT system required to uptake cysteine for transsulfuration. In vivo, we find that intratumoral levels of glutathione are reduced in mice fed a chow diet lacking serine compared to regular chow diet-fed mice. Pharmacologic inhibition of glutathione synthesis ablates the growth of high L-2HG RCC cells even in the presence of serine, suggesting the importance of redox homeostasis for RCC proliferation. The data indicate that the L-2HG elevation in RCC reconfigures tumor metabolism, resulting in serine liability. Collectively, our data unmask a metabolic vulnerability that can be harnessed for precision-based approaches to kidney cancer. Citation Format: Anirban Kundu, Garrett J. Brinkley, Hyeyoung Nam, Suman Karki, Devin Absher, William J. Placzek, Jason Locasale, Dinesh Rakheja, Victor Darley-Usmarc, Jason Tennessen, Sunil Sudarshan. Metabolic liabilities in high L-2HG kidney cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr B005.

Nrf2 sensitizes ferroptosis through l-2-hydroxyglutarate–mediated chromatin modifications in sickle cell disease

AbstractSickle cell disease (SCD) is a chronic hemolytic and systemic hypoxia condition with constant oxidative stress and significant metabolic alterations. However, little is known about the correlation between metabolic alterations and the pathophysiological symptoms. Here, we report that Nrf2, a master regulator of cellular antioxidant responses, regulates the production of the metabolite l-2-hydroxyglutarate (L2HG) to mediate epigenetic histone hypermethylation for gene expression involved in metabolic, oxidative, and ferroptotic stress responses in SCD. Mechanistically, Nrf2 was found to regulate the expression of L2HG dehydrogenase (L2hgdh) to mediate L2HG production under hypoxia. Gene expression profile analysis indicated that reactive oxygen species (ROS) and ferroptosis responses were the most significantly affected signaling pathways after Nrf2 ablation in SCD. Nrf2 silencing and L2HG supplementation sensitize human sickle erythroid cells to ROS and ferroptosis stress. The absence of Nrf2 and accumulation of L2HG significantly affect histone methylation for chromatin structure modification and reduce the assembly of transcription complexes on downstream target genes to regulate ROS and ferroptosis responses. Furthermore, pharmacological activation of Nrf2 was found to have protective effects against ROS and ferroptosis stress in SCD mice. Our data suggest a novel mechanism by which Nrf2 regulates L2HG levels to mediate SCD severity through ROS and ferroptosis stress responses, suggesting that targeting Nrf2 is a viable therapeutic strategy for ameliorating SCD symptoms.

Abstract 715: Genetically Proxied Inhibition Of L-2-Hydroxyglutarate Dehydrogenase Reduces The Risk Of Coronary Artery Disease: A Mendelian Randomization And Network Medicine Study

Introduction: L-2-hydroxyglutarate dehydrogenase (L2HGDH) deletion-induced L-2-hydroxyglutarate accumulation plays a cardioprotective role in hypoxic conditions by eliminating reactive oxygen species. However, there has been no causal evidence in real-world clinical data. Hypothesis: We examined the potential therapeutic effects of L2HGDH inhibition on coronary artery disease (CAD) using Mendelian randomization (MR) and network medicine analyses. Methods: We used nine L2HGDH -proxied genetic variants associated with blood 2-hydroxyglutarate levels (6,287 European individuals) as genetic instruments, and performed a two-sample MR analysis using the CARDIoGRAMplusC4D meta-analysis datasets of CAD (60,801 cases and 123,504 controls). A protein-protein interaction network analysis was also performed to determine the potential therapeutic effects of L2HGDH inhibition on a CAD disease module. Results: Genetically proxied inhibition of L2HGDH associated with 2-hydroxyglutarate levels decreased the risk of CAD (odds ratio [OR] 0.486, 95% confidence interval [CI] 0.242-0.977, P=0.043). This potential causal association between L2HGDH inhibition and CAD was unlikely to be biased by horizontal pleiotropy. Network proximity analysis showed that L2HGDH is significantly closer to the CAD disease module in the human heart protein-protein interactome (P=0.016). Conclusions: In conclusion, our MR and network analyses suggest potential causal and pathobiological associations between genetically proxied inhibition of L2HGDH and CAD. Our findings may have therapeutic implications for L2HGDH inhibitors in CAD.

Abstract 3705: L-2HG, oncometabolite-driven epigenetic and epitranscriptomic reprogramming creates metabolic vulnerability in renal cancer

Abstract The oncometabolite, L-2-hydroxyglutarate (L-2HG) is elevated in the most common form of renal cell carcinoma-RCC (clear cell histology) and promotes tumor progression. L-2HG is structurally similar to α-ketoglutarate (α-KG). Therefore, L-2HG can competitively inhibit enzymes that utilize α-KG as a cofactor including α-KG-dependent dioxygenases that can profoundly impact gene expression via effects on the epigenome and epitranscriptome. RCC cell lines lack the L-2HG dehydrogenase enzyme (L2HGDH), resulting in their high L-2HG level. RNA-seq of control (high L-2GH) and an L2HGDH reconstituted (low L-2HG) RCC cell line has revealed that L-2HG suppresses the expression of serine biosynthesis genes, PHGDH and PSAT1. The findings were consistent in the patient samples where high L-2HG renal tumors had lower levels of PHGDH and PSAT1 expressions than that of the low L-2HG renal tumors and the patient-matched normal kidneys. Consistently, 13C-metabolomics labeling studies demonstrate that raised L-2HG suppresses de novo serine biosynthesis. Moreover, LC-MS analysis of the metabolites isolated from the kidneys of L2HGDH KO and wild-type (WT) mice revealed less serine content in the absence of L2HGDH, further confirming that high L-2HG suppresses serine biosynthesis in vivo. We found that L-2HG-mediated inhibition of the α-KG-dependent histone demethylase KDM4C silences ATF4 transcription. ATF4 is a master regulator of amino acid biosynthetic genes including PHGDH and PSAT1. Using ATF4 gain of function analysis, we confirmed that high L-2HG causes the suppression of PHGDH and PSAT1 in an ATF4-dependent manner. In addition, we demonstrate that L-2HG promotes the accumulation of the epitranscriptomic mark N⁶-methyladenosine (m6A) via inhibiting α-KG-dependent RNA demethylases ALKBH5 and FTO. In the setting of high L-2HG, m6A is enriched in the 3’-UTR region of transcripts including PSAT1. Using mutational analysis, we demonstrate that L-2HG promotes m6A accumulation at a specific site within the 3’UTR of PSAT1 that silences its translation. In accord with these data, found that high L-2HG RCC cells require exogenous serine for in vitro proliferation and in vivo tumor growth. Furthermore, this serine liability can be rescued upon lowering cellular L-2HG levels. Metabolomics analyses demonstrate that exogenous serine is required to maintain cellular pools of glutathione in high L-2HG RCC which supports both proliferation and resistance to oxidative stress. The data indicate that the L-2HG elevation in RCC reconfigures tumor metabolism through a bimodal mechanism via remodeling of both the epigenome and epitranscriptome. This results in a serine liability in the setting of raised L-2HG. Collectively, our data unmask a metabolic vulnerability that can be harnessed for precision-based approaches to kidney cancer. Citation Format: Anirban Kundu, Garrett J. Brinkley, Hyeyoung Nam, Suman Karki, Richard Kirkman, Hayley Widden, Michelle Johnson, Juan Liu, Yasaman Heidarian, Nader Mahmoudzadeh, Devin Absher, Han-Fei Ding, David Crosman, William J. Placzek, Jason Locasale, Dinesh Rakheja, Victor Darley-Usmar, Jason Tennessen, Sunil Sudarshan. L-2HG, oncometabolite-driven epigenetic and epitranscriptomic reprogramming creates metabolic vulnerability in renal cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3705.

L-2hydroxyglutaric acid rewires amino acid metabolism in colorectal cancer via the mTOR-ATF4 axis

Oncometabolites, such as D/L-2-hydroxyglutarate (2HG), have directly been implicated in carcinogenesis; however, the underlying molecular mechanisms remain poorly understood. Here, we showed that the levels of the L-enantiomer of 2HG (L2HG) were specifically increased in colorectal cancer (CRC) tissues and cell lines compared with the D-enantiomer of 2HG (D2HG). In addition, L2HG increased the expression of ATF4 and its target genes by activating the mTOR pathway, which subsequently provided amino acids and improved the survival of CRC cells under serum deprivation. Downregulating the expression of L-2-hydroxyglutarate dehydrogenase (L2HGDH) and oxoglutarate dehydrogenase (OGDH) increased L2HG levels in CRC, thereby activating mTOR-ATF4 signaling. Furthermore, L2HGDH overexpression reduced L2HG-mediated mTOR-ATF4 signaling under hypoxia, whereas L2HGDH knockdown promoted tumor growth and amino acid metabolism in vivo. Together, these results indicate that L2HG ameliorates nutritional stress by activating the mTOR-ATF4 axis and thus could be a potential therapeutic target for CRC.

In Silico Analysis of the L-2-Hydroxyglutarate Dehydrogenase Gene Mutations and Their Biological Impact on Disease Etiology.

The L-2-hydroxyglutarate dehydrogenase (L2HGDH) gene encodes an important mitochondrial enzyme. However, its altered activity results in excessive levels of L-2-hydroxyglutarate, which results in diverse psychiatric features of intellectual disability. In the current study, we executed an in-silico analysis of all reported L2HGDH missense and nonsense variants in order to investigate their biological significance. Among the superimposed 3D models, the highest similarity index for a wild-type structure was shown by the mutant Glu336Lys (87.26%), while the lowest similarity index value was shown by Arg70* (10.00%). Three large active site pockets were determined using protein active site prediction, in which the 2nd largest pocket was shown to encompass the substrate L-2-hydroxyglutarate (L2HG) binding residues, i.e., 89Gln, 195Tyr, 402Ala, 403Gly and 404Val. Moreover, interactions of wild-type and mutant L2HGDH variants with the close functional interactor D2HGDH protein resulted in alterations in the position, number and nature of networking residues. We observed that the binding of L2HG with the L2HGDH enzyme is affected by the nature of the amino acid substitution, as well as the number and nature of bonds between the substrate and protein molecule, which are able to affect its biological activity.

Myelodysplastic Syndromes: A More Global 5-Hydroxymethylcytosine Deficiency Disorder Than Suggested By the Presence of TET2 Mutations

Myelodysplastic Syndromes: A More Global 5-Hydroxymethylcytosine Deficiency Disorder Than Suggested By the Presence of TET2 Mutations

HIF1\u03b1 is not a target of 14q deletion in clear cell renal cancer

HIF1α has been termed a tumor-suppressor in clear cell renal cell carcinoma (ccRCC), primarily based on functional proliferation studies in cell lines (in vitro and in vivo) with genetic manipulation, and the adverse prognosis of 14q-deleted ccRCC patients. In other malignancies, however, HIF1α has an established tumor-promoting role. Therefore, this study sought to further examine the role of HIF1α in ccRCC using bioinformatic analyses of 530 ccRCC patients from The Cancer Genome Atlas (TCGA) and The Cancer Proteome Atlas (TCPA) registries. Although lower copy numbers of HIF1A (encoding HIF1α, located at 14q23.2) was associated with worse survival, there was no survival difference based on either HIF1A mRNA or HIF1α protein expression. Interestingly, L2HGDH (L-2-Hydroxyglutarate Dehydrogenase), a recently characterized epigenetic modulating ccRCC tumor-suppressor with a marked impact on survival, was found to be located only ~ 11.5Mbp from HIF1A on 14q (at 14q21.3). L2HGDH was therefore co-deleted in ~ 95% of 14q deletions involving HIF1A locus. Remarkably, HIF1A CNV had a markedly stronger correlation with L2HGDH expression (Rho = 0.55) than its own gene expression (Rho = 0.27), indicating high preserved-allele compensation of HIF1A. Genetic loss of HIF1A was therefore associated with a much greater reduction of L2HGDH gene expression than its own gene expression, providing a possible explanation for survival differences based on HIF1A CNV and mRNA expression. Furthermore, in 14q-deleted ccRCC patients with complete (uncensored) survival data, in the relatively rare cases where genetic loss of HIF1A occurred without genetic loss of L2HGDH (n = 5), the survival was significantly greater than where there was simultaneous genetic loss of both (n = 87) (mean survival 1670.8 ± 183.5 days vs 885.1 ± 78.4 days; p = 0.007). In addition, there was no correlation between HIF1A mRNA and HIF1α protein expression in ccRCC (R = 0.02), reflecting the primarily post-translational regulation of HIF1α. Lastly, even between L2HGDH and HIF1A loci, 14q was found to have several other yet-to-be-characterized potential ccRCC tumor-suppressors. Taken together, the data indicate that HIF1α is not a target of 14q deletion in ccRCC and that it is not a tumor-suppressor in this malignancy.

P1616L-2-hydroxyglutarate dehydrogenase (L2HGDH) is a novel target for heart failure due to pressure overload

Abstract Background We have found L-2-hydroxyglutarate dehydrogenase (L2HGDH) to be downregulated in the myocardium of mice subjected to transverse aortic constriction (TAC). L2HGDH is an important regulator of mitochondrial bioenergetics by catalyzing the conversion of L-2-hydroxyglutarate (L2-HG) to α-ketoglutarate. However, the connection between L2-HG accumulation and heart failure is not yet understood. Purpose Purpose of our study was to investigate the role of increased L2-HG levels in heart failure and the potential role of L2HGDH overexpression as therapeutic strategy. Methods For in vitro studies, primary rat neonatal cardiomyocytes (NRVCMs) were incubated with L2-HG. L2HGDH was overexpressed using adeno-associated virus (AAV) 6 vectors. Mitochondrial membrane potential was measured using TMRE (tetramethylrhodamine ethyl ester) dye. Mitochondrial reactive oxygen species production was monitored using MitoSOX. We further determined activation of fetal gene program by real time qPCR and macrophage migration using RAW 264.7 cells and transwell inserts. mTOR activation was analyzed by Western blot with antibodies against phosphorylated mTOR and ribosomal protein S6. AAV9 expressing L2HGDH or luciferase was injected in C57BL/6N mice two weeks prior to TAC and heart function was monitored by echocardiography for 6 weeks. Results L2-HG acts as a pro-hypertrophic stimulus in NRVCMs as shown by upregulation of a fetal gene expression pattern and an increase in cardiomyocyte cross-sectional area upon L2-HG treatment. Furthermore, mRNA levels of macrophage chemoattractant protein 1 were increased in L2-HG treated cells, which correlated with enhanced macrophage migration towards supernatant of L2-HG treated NRVCMs. Furthermore, we could confirm that L2-HG augmented mTOR signaling by affecting the phosphorylation status of ribosomal protein S6. AAV-mediated L2HGDH overexpression in NRVCMs led to a significant 2.1-fold decrease in the accumulation of ROS production. Moreover, we found an inhibition of endothelin-1 induced mitochondrial membrane depolarization in AAV6-L2HGDH transduced cells. Pretreatment of mice with AAV9-L2HGDH prior to TAC resulted in significantly reduced heart weight to tibia length ratios (HW/TL) and cardiomyocyte area. Importantly, heart function was notably improved in mice receiving gene therapy (ejection fraction, EF: 36.18±6.63%, fractional shortening, FS: 16.72±4.01%) whereas control animals showed marked decline in myocardial contractility (EF: 20.14±8.24%, FS: 12.66±6.66%). Conclusion L2-HG causes cardiomyocyte dysfunction by activating mTOR signaling pathway, a well-characterized critical inducer of myocyte hypertrophy, and enhancing macrophage migration, leading to establishment of a pro-inflammatory environment in the myocardium. Moreover, our results point out towards a novel preventive approach for cardiac hypertrophy and heart failure by cardiomyocyte-specific L2HGDH overexpression. Acknowledgement/Funding DZHK (Deutsches Zentrum für Herz-Kreislaufforschung)

Abstract 4364: Oncometabolite L-2-hydroxyglutarate blocks differentiation of renal proximal tubule cells in matrigel

Abstract Previously, the Sudarshan laboratory has identified elevations in the level of the oncometabolite L-2-hydroxyglutarate (L-2HG) in human renal cell carcinomas (RCCs). Of particular interest in these regards, both L-2HG inhibits 2-oxoglutarate-dependent dioxygenases (2-OGDs), including histone demethylases, which regulate the epigenetic landscape of cells, and cellular differentiation. Thus, it was of interest to determine whether the accumulation of L-2HG alters the differentiation of the normal renal proximal tubule (RPT), ultimately affecting the phenotype of the RCC. Towards these ends, L-2HG dehydrogenase (L2HGDH) was knocked down in primary cultures of normal rabbit RPT cells, and their capacity for cellular differentiation was examined. Initially, we examined the ability of primary RPT cells to form tubules in matrigel following an L2HGDH knockdown (KD). While tubulogenesis was stimulated by Epidermal Growth Factor (EGF) in primary RPT cells transduced with a control lentiviral vector, tubulogenesis in matrigel was dramatically impaired in primary RPT cells when L2HGDH was knocked down by lentiviral L2HGDH shRNA. In order to determine whether the expression of differentiated transport functions was affected, RealTime PCR (RTPCR) was conducted. The results indicated that an L2HGDH knockdown (80%) resulted in a reduction in the expression of the Na+/Pi cotransporter NaPi2a (81%), the Na+/glucose cotransporter SGLT2 (88%), the water transporter Aquaporin 1 (AQP1) (95%), and the Na,K-ATPase ß1 subunit (atp1b1) (43%), whereas the expression of the p-Aminohippurate transporter OAT1 was not significantly affected. Similar results were obtained when using L2HGDH siRNA and lentiviral shRNA. Not only is tissue architecture critical for the maintenance of functional differentiation, but alterations in tissue architecture are a necessary component of tumor formation. Thus, we are examining the underlying causes for the reduced tubulogenesis in matrigel cultures with an L2HGDH KD. In our initial studies, we examined the expression of differentiated transport functions in matrigel vs. monolayer cultures. Notably, while the expression such transporters as AQP2 increased dramatically in matrigel (as opposed to monolayer cultures), the expression of other transporters such as NaPi2a, SGLT2 and atp1b1 was affected to a much smaller extent. Of particular interest in these regards, is the known role of AQP1 in the migration of renal proximal tubule cells, tumor spread, and wound healing. We are currently studying the effects of an L2HGDH KD on the expression of such genes as AQP1 during tubulogenesis in matrigel.This work has been funded by Grant # 1RO1CA200653-01A1 to Dr. Sunil Sudarshan (PI) with a subaward to Dr. Mary Taub. Citation Format: Mary L. Taub, Sunil Sudarshan. Oncometabolite L-2-hydroxyglutarate blocks differentiation of renal proximal tubule cells in matrigel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4364.

Ascorbic acid-induced TET activation mitigates adverse hydroxymethylcytosine loss in renal cell carcinoma.

Although clear cell renal cell carcinoma (ccRCC) has been shown to result in widespread aberrant cytosine methylation and loss of 5-hydroxymethylcytosine (5hmC), the prognostic impact and therapeutic targeting of this epigenetic aberrancy has not been fully explored. Analysis of 576 primary ccRCC samples demonstrated that loss of 5hmC was strongly associated with aggressive clinicopathologic features and was an independent adverse prognostic factor. Loss of 5hmC also predicted reduced progression-free survival after resection of nonmetastatic disease. The loss of 5hmC in ccRCC was not due to mutational or transcriptional inactivation of ten eleven translocation (TET) enzymes, but to their functional inactivation by l-2-hydroxyglutarate (L2HG), which was overexpressed due to the deletion and underexpression of L2HG dehydrogenase (L2HGDH). Ascorbic acid (AA) reduced methylation and restored genome-wide 5hmC levels via TET activation. Fluorescence quenching of the recombinant TET-2 protein was unaffected by L2HG in the presence of AA. Pharmacologic AA treatment led to reduced growth of ccRCC in vitro and reduced tumor growth in vivo, with increased intratumoral 5hmC. These data demonstrate that reduced 5hmC is associated with reduced survival in ccRCC and provide a preclinical rationale for exploring the therapeutic potential of high-dose AA in ccRCC.

Abstract 16722: L-2-Hydroxyglutarate Protects Against Myocardial Ischemia-Reperfusion Injury

Background: L-2-hydroxyglutarate (L2HG) couples mitochondrial (Mito) and cytoplasmic energy metabolism in a model of cellular redox regulation. Under conditions of limited oxygen availability, mammalian cells generate L2HG to counteract the adverse effects of Mito reductive stress induced by hypoxia. L2HG is oxidized to α-ketoglutarate by L2HG dehydrogenase (L2HGDH) in a variety of mammalian tissues, including the heart. Myocardial ischemia/reperfusion injury (MIRI) is a consequence of coronary vascular disease and vascular procedures. Mito oxidative stress plays a critical role in MIRI. Here we hypothesized that L2HG protects against MIRI. Methods and Results: We induced accumulation of L2HG by heterozygous (HET) and homozygous (KO) deletion of L2HGDH gene in mice. The hearts isolated from HET, KO, and wild-type (WT) littermate mice were subjected to 30 min global thermal ischemia followed by 60 min reperfusion. Cardiac function and energy metabolism were simultaneously measured using a Langendorff heart perfusion model and 31 P-NMR spectroscopy. We found that female HET and KO exhibited better recovery of cardiac function post-MIRI in consistent with better preservation of intracellular ATP and phosphocreatine (Table). Using HPLC, we measured compounds representative of cellular redox state (GSG, GSSG, NAD, NADH, NADP, NADPH, coenzyme A and ascorbate), cellular energy state (ATP, ADP, AMP, GTP, GDP, GMP, UTP, UDP, UMP, CTP, CDP, CMP, IMP, malonyl-CoA and acetyl-CoA), and nucleotide catabolism (adenosine, hypoxanthine, xanthine and inosine) in freeze-clamped hearts. We found that ratios of GSH/GSSG and ATP/ADP increased in HET and KO hearts (Table). Interestingly, the ratios of NADH/NAD and NADPH/NADP increased only in KO but not in HET hearts. Consistent with the increased ratio of ATP/AMP, hypoxanthine and xanthine decreased only in KO hearts but not in HET hearts (Table). Conclusion: The accumulation of L2HG in a genetic mouse model protects against MIRI though increasing cellular antioxidative capacity and preserving high energy phosphates. The underlying mechanism of these beneficial adaptive phenomena warrants further study. Targeting L2HG levels and L2HGDH expression may serve as new therapeutic strategies for MIRI protection.

Identification of novel L2HGDH mutation in a large consanguineous Pakistani family- a case report

BackgroundL-2-hydroxyglutaric aciduria (L2HGA) is a progressive neurometabolic disease of brain caused by mutations of in L-2-hydroxyglutarate dehydrogenase (L2HGDH) gene. Cardinal clinical features include cerebellar ataxia, epilepsy, neurodevelopmental delay, intellectual disability, and other clinical neurological deficits.Case presentationWe describe an index case of the family presented with generalised tonic-clonic seizure, developmental delay, intellectual disability, and ataxia. Initially, the differential diagnosis was difficult to be established and a SNP genome wide scan identified the candidate region on chromosome 14q22.1. DNA sequencing showed a novel homozygous mutation in the candidate gene L2HGDH (NM_024884.2: c.178G > A; p.Gly60Arg). The mutation p.Gly60Arg lies in the highly conserved FAD/NAD(P)-binding domain of this mitochondrial enzyme, predicted to disturb enzymatic function.ConclusionsThe combination of homozygosity mapping and DNA sequencing identified a novel mutation in Pakistani family with variable clinical features. This is second report of a mutation in L2HGDH gene from Pakistan and the largest family with L2HGA reported to date.

L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration.

l-2-Hydroxyglutarate aciduria (L-2-HGA) is an autosomal recessive neurometabolic disorder caused by a mutation in the l-2-hydroxyglutarate dehydrogenase (L2HGDH) gene. In this study, we generated L2hgdh knockout (KO) mice and observed a robust increase of l-2-hydroxyglutarate (L-2-HG) levels in multiple tissues. The highest levels of L-2-HG were observed in the brain and testis, with a corresponding increase in histone methylation in these tissues. L2hgdh KO mice exhibit white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and an expansion of oligodendrocyte progenitor cells (OPCs). Moreover, L2hgdh deficiency leads to impaired adult hippocampal neurogenesis and late-onset neurodegeneration in mouse brains. Our data provide in vivo evidence that L2hgdh mutation leads to L-2-HG accumulation, leukoencephalopathy, and neurodegeneration in mice, thereby offering new insights into the pathophysiology of L-2-HGA in humans.

Acidúria L2-hidroxiglutárica: circulação do gene em cães da raça Staffordshire Bull Terrier no Brasil em 2008-2015

RESUMO: O objetivo do trabalho foi identificar a presença no Brasil do gene mutante L2HGDH em cães da raça Staffordshire Bull Terrier (SBT). Para tanto foi feito o teste genético em 76 cães provenientes de diferentes regiões do Brasil, no período de 2008 a 2015, sendo encontrados 55 animais (72,37%) livres do gene mutante L2-HGDH ou homozigotos dominantes, e 21(27,63%) portadores do gene mutante ou heterozigotos. Não foi encontrado nenhum animal homozigoto recessivo (afetado), porém pode-se observar que o gene circula no Brasil e que cães afetados podem aparecer.