Summary Sex differences strongly influence susceptibility to metabolic dysfunction-associated steatotic liver disease (MASLD), yet the regulatory mechanisms underlying these differences remain incompletely understood. To examine sex-specific hepatic adaptation to a high-fat (HF) diet mouse model of MASLD, we integrated proteomics, transcriptomics, and Oxford Nanopore direct RNA sequencing for transcriptome-wide m6A profiling in male and female mouse livers. Female mice were relatively protected from HF diet–induced hepatic steatosis and exhibited distinct proteome remodeling enriched for peroxisomal pathways. In contrast, transcriptomic responses in females were dominated by inflammatory signatures and did not recapitulate the metabolic adaptations observed at the protein level, revealing extensive RNA–protein discordance and post-transcriptional remodeling. Integrated RNA–protein analyses identified female-specific amplification of peroxisomal proteins despite modest transcript-level changes. HF diet also induced sex-specific remodeling of m6A RNA methylation and altered regulation of the m6A methylation system. Notably, reduced 3′ UTR m6A methylation of peroxisomal transcripts inversely correlated with increased protein abundance relative to RNA expression in female mice. Together, these findings implicate m6A-associated post-transcriptional regulation in sex-specific hepatic adaptation to HF diet exposure and the basis for discordance between many of the mRNAs and proteins in the liver.

Coenzyme A is an essential cofactor synthesized from pantothenate, cysteine, and ATP, and is involved in numerous processes of cellular metabolism through its ability to carry activated acyl groups. Coenzyme A participates in catabolism of carbohydrate, fat and amino acids; biosynthesis of fatty acids, cholesterol and heme; and protein modification including acetylation and 4-phosphopantetheinylation. Despite CoA's critical functions, the regulation of CoA levels and the rate of CoA synthesis in different cell types and disease states are not well understood. One reason for this gap is that many acyl-CoA species are analytically challenging to measure due to factors including instability, poor ionization, and the wide range of biochemical properties conferred by different acyl chain lengths. In addition, most current methods do not support analysis of CoA isotopic labeling, which is required to quantify CoA synthesis rate or to measure absolute concentration using isotope-labeled internal standards. Here, we describe a method to quantify the concentration and isotopic labeling of total CoA, defined as the sum of CoASH plus all acyl-CoA species. Acyl-CoA species are hydrolyzed using sodium hydroxide to remove acyl chains, then CoA is derivatized on the thiol with N-ethylmaleimide (NEM). Following protein precipitation and solid phase extraction, samples are analyzed by liquid chromatography-mass spectrometry. This method is linear in a wide range that captures mouse tissue CoA levels, with accuracy within 15% error and precision below 15% relative standard deviation for both pure standards and tissue samples. We applied this method to measure total CoA concentration in five tissues from male and female mice, and total CoA synthesis rate in mouse liver via infusion of 13C-15N-pantothenate. Overall, this method offers a tractable approach to measure total CoA concentration and isotopic labeling to enable study of total CoA synthesis rates and concentrations in health and disease.

Cellular senescence is a consequence of many chemotherapeutics that plays context-dependent roles in cancer. Senescent cells secrete an array of factors collectively known as the senescence-associated secretory phenotype (SASP). Here we show that the cisplatin-induced SASP enhances the detachment of high-grade serous ovarian cancer (HGSOC) cells in vitro and dissemination in vivo. We identify fructose as a metabolic component of the SASP that facilitates cell detachment and show that a high-fructose diet increases HGSOC dissemination in vivo. We identified complex I as the driver of SASP-mediated cell detachment and HGSOC dissemination. Mechanistically, this effect was driven by SASP-mediated inhibition of an NAD+-SIRT-SREBP axis, leading to decreased plasma membrane cholesterol that increased cell detachment. These findings reveal that the SASP reprograms the metabolic microenvironment, promoting metastatic dissemination in a paracrine fashion, and highlight a pro-tumorigenic metabolic effect of fructose in the SASP that may contribute to the high recurrence rate of HGSOC.

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce mortality in heart failure, but their pharmacological target remains unclear. In this study, we showed that SGLT2i directly activate pantothenate kinase 1 (PANK1), the rate-limiting enzyme in coenzyme A (CoA) synthesis. Using stable isotope infusions, we established that SGLT2i activate CoA synthesis and broadly stimulate fuel use in human cardiac tissue. We also demonstrated that SGLT2i bind PANK1 at physiological concentrations, directly inducing conformational changes and increasing enzymatic activity. In silico modeling identified the site of SGLT2i binding on PANK1, which was confirmed by amino acid mutagenesis. Finally, we showed that SGLT2i-mediated PANK activation is necessary and sufficient to increase contractility of human cardiomyocytes. In summary, we demonstrate off-target activation of PANK1 and promotion of CoA synthesis by SGLT2i, which may explain their marked clinical benefits.

Homologous recombination (HR) deficiency increases sensitivity to DNA-damaging agents that are commonly used to treat cancer1. In HR-proficient cancers, the metabolic mechanisms that drive response or resistance to DNA-damaging agents remain unclear. Here we have identified that depletion of α-ketoglutarate (αKG) sensitizes HR-proficient cells to DNA-damaging agents by metabolic regulation of histone acetylation. αKG is required for the activity of αKG-dependent dioxygenases2 (αKGDDs), and previous work has focused almost exclusively on the demethylase functions of αKGDD. Using a targeted CRISPR knockout library consisting of 64 αKGDDs, we discovered that trimethyllysine hydroxylase epsilon (TMLHE), the first and rate-limiting enzyme in de novo carnitine synthesis, is necessary for the survival of HR-proficient cells in the presence of DNA-damaging agents. Unexpectedly, αKG-mediated TMLHE-dependent carnitine synthesis was required for histone acetylation and was non-redundant with other nucleo-cytosolic acetyl-CoA-generating pathways. The increase in histone acetylation by means of the αKG-carnitine axis promoted HR-mediated DNA repair through site-specific histone acetylation. Finally, we observed a positive correlation between TMLHE and histone acetylation in patient samples and found that high TMLHE or acetylcarnitine correlates with worse progression-free survival in patients treated with DNA-damaging agents. This study demonstrates for the first time, to our knowledge, that αKG affects site-specific histone acetylation and provides a mechanism of HR proficiency through carnitine synthesis. Moreover, these data provide a metabolic avenue for inducing HR deficiency and promoting sensitivity to DNA-damaging agents.

Copper (Cu) is an essential cofactor for mitochondrial cytochrome c oxidase, yet whether it directly regulates mitochondrial metabolism beyond respiration remains unclear. Here we show that mitochondrial Cu, delivered by SLC25A3, is required to maintain the stability of lipoylated TCA cycle proteins. Loss of Slc25a3 or pharmacological Cu depletion selectively destabilized the lipoylated E2 subunits of mitochondrial dehydrogenases and the lipoylation enzymes LIPT1 and LIPT2, an effect not reproduced by acute electron transport chain inhibition. Mechanistically, we find that Cu directly engages the reduced lipoyl moiety using chemical probes and synthetic peptide approaches. Cu depletion impaired PDH and OGDH activity, rewired TCA cycle metabolism, and imposed a dependence on pyruvate carboxylase for anaplerosis. This metabolic defect depleted aspartate, suppressed mTORC1 signaling, and limited proliferation. Conversely, selective delivery of Cu to the mitochondria restored lipoylation, TCA cycle function, and cell growth. Together, these findings identify mitochondrial Cu as a structural regulator of the lipoylation machinery and reveal a direct link between Cu homeostasis and central carbon metabolism.

Mitochondrial matrix Ca2+ concentration ([Ca2+](m)) is theorized to be an essential regulator of mitochondrial metabolism by positively regulating key mitochondrial dehydrogenases. However, ablation or functional inhibition of the mitochondrial calcium uniporter channel (mtCU) fails to significantly perturb basal metabolism and is largely phenotypically silent in the absence of stress. Here we demonstrate that MICU proteins, the reported gatekeepers of mtCU, function in coordination to impart calcium-dependent regulation to FADH(2)-dependent mitochondrial dehydrogenases through metabolon formation independently of the mtCU and [Ca2+](m). Our results demonstrate that MICU proteins differentially localize to mitochondrial microdomains and form heterodimers and interactomes in response to intermembrane space Ca2+ binding their respective EF-hand domains. Using an equimolar expression platform coupled with unbiased proteomics, we reveal unique interactomes for MICU1/MICU2 versus MICU1/MICU3 heterodimers and demonstrate that MICU proteins control coupling of mitochondrial glycerol-3-phosphate dehydrogenase and succinate dehydrogenase/complex II and impart calcium-dependent changes in activity. We propose that MICU-mediated mitochondrial metabolons are a fundamental system facilitating matching of mitochondrial energy production with cellular demand and is the primary physiological calcium signaling mechanism regulating homeostatic energetics, not mtCU-dependent changes in [Ca2+](m).

Herein we uncover a relationship between histone succinylation and Jumonji (JmjC) domain-containing histone demethylases. We used quantitative proteomics and peptide pull-down assays to identify JmjC demethylases as candidate interactors with succinylated histone peptides. Succinyl-lysine peptides bind and inhibit the catalytic activity of JmjC demethylases in a dose-dependent manner. This includes KDM4D and KDM6B, which are responsible for the removal of the silencing marks H3K9me2/3 and H3K27me2/3. Supraphysiological sodium succinate treatment of HepG2/C3A cells increased the relative abundance of histone succinylation, H3K9me2/3, and H3K27me2/3. CUT&Tag and ChIP-mass spectrometry revealed the co-occurrence of succinylation with these repressive methylation marks, in addition to reduced transcriptional output. This work establishes a novel mechanistic link between metabolite abundance and chromatin regulation and suggests a role for histone succinylation in the maintenance of heterochromatin.

Abstract CAR-T cell therapy has transformed the treatment landscape for hematologic malignancies, yet its efficacy in solid tumors remains challenged. Aspartate is one of the most critically depleted metabolites in the solid tumor microenvironment; its deficiency impairs T cell proliferation, redox balance, and mitochondrial fitness. GOT2, a mitochondrial enzyme in the malate-aspartate shuttle, plays a critical role in T cell metabolism, as it catalyzes the conversion of oxaloacetate to aspartate. In doing so, GOT2 also helps maintain redox balance and energy production. In addition to its canonical role in aspartate biosynthesis, recent studies in cancer cells suggest that GOT2 regulates fatty acid metabolism through the activation of the transcription factor PPARδ. In T cells, PPARδ is shown to regulate the formation of central memory phenotype and long-term survival. In this study, we examined whether GOT2 overexpression enhances CAR-T cell metabolic fitness and antitumor activity. We found that GOT2-overexpressing CAR-T cells (CART19-GOT2) exhibit superior cytolytic function in both in vitro hypoxic conditions and in vivo tumor models. In xenograft models of NALM6 leukemia, CART19-GOT2 was able to sustain tumor control and prevented regrowth even after rechallenge. Compared to standard CART19 cells, CART19-GOT2 show enhanced mitochondrial respiration and spare respiratory capacity, indicating better mitochondrial fitness. GOT2 overexpression also elevated intracellular aspartate levels in CAR-T cells in normal growth conditions and under hypoxic stress. Using isotypically labeled nutrients as tracers, we found that aspartate is replenished through a cooperative interplay of fuels in primary human T cells, with glutamine serving as the preferred substrate. Collectively, these findings indicate that GOT2 overexpression is a promising strategy for metabolic enhancement of CAR-T cells for solid tumor immunotherapy. Citation Format: Xiangyi Fang, Shadab Kazmi, Andre Kelly, Xiaoling Jin, Alison Jaccard, Nathaniel W. Snyder, Alexander A. Shestov, Saba Ghassemi, Roddy S. O'Connor. Glutamic-oxaloacetic transaminase 2 (GOT2) as a dual-functional enhancer for CAR-T cell metabolic fitness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4272.

Reactive cysteines serve important functions in proteins, and characterizing their engagement by different electrophiles facilitates biological discovery and covalent drug development. Here, we show that the common lysis buffer components phenylmethylsulfonyl fluoride (PMSF) and orthovanadate generate a lysis-derived oxidant that engages cysteines during cell lysis. This oxidant sulfonylates N-acetyl-D-glucosamine kinase (NAGK) C217, producing a mobility shift on SDS-PAGE. C217 lies within the ATP-binding pocket, and a C217S mutant exhibits reduced ATP affinity and enzymatic activity. Competitive iodoacetamide-alkyne activity-based protein profiling (IAA-ABPP) chemoproteomics further showed that the PMSF/orthovanadate oxidant defines a cysteine-engagement profile that partially differs from that of pervanadate. These findings reveal an unrecognized source of chemical reactivity during protein extraction that expands the toolkit for cysteine-engagement profiling and underscores how sample preparation chemistry shapes chemoproteomic measurements.

Levels of pancreatic ductal adenocarcinoma (PDAC) are increasing, with epidemiological studies nominating obesity, altered cholesterol metabolism, and elevated lipids as risk factors. In prior studies, we determined that elevated expression of sterol regulatory element binding protein 2 (SREBP2), a transcription factor directing lipid biosynthesis, promoted epithelial-mesenchymal transition and aggressive tumorigenesis in the KPC (LSL-KrasG12D;Trp53f/f;Pdx1-Cre) mouse model of PDAC. We analyzed the consequences of deleting SCAP, a scaffolding protein required for SREBP activation, in KPC mice. Unexpectedly tumorigenesis in KPCS mice was significantly accelerated, with a preponderance of sarcomatoid carcinomas. To better understand SCAP action, we analyzed loss of pancreatic SCAP in isolation in ScapΔpanc (Pdx1-Cre;Scapf/f) mice. Pancreata of ScapΔpanc mice had rapid progressive loss of acinar cells, acinar-ductal metaplasia (ADM), infiltration of adipose cells, increased fibrosis, and infiltration of immune cells, indicative of chronic pancreatitis. Single cell RNA sequencing indicated that loss of SCAP suppressed SREBP-dependent transcriptional programs in endocrine and exocrine precursors, but was associated with enhanced SREBP2 activity in fibroblastic populations, compatible with formation of a pro-tumorigenic tumor microenvironment. Together, these results implicate lipid metabolism via SCAP-SREBP signaling as an important metabolic regulator of acinar-ductal differentiation and pancreatic carcinogenesis.

AbstractToll-like receptor (TLR)-dependent macrophage responses rely on acute increases in oxidative mitochondrial glucose metabolism that epigenetically support rapid proinflammatory transcriptional programming via histone acetylation. Subsequent suppression of oxidative metabolism restrains this metabolic-epigenetic support of proinflammatory gene transcription to enforce tolerance, an immunosuppressed state of innate immune memory. Identifying biology that promotes or counters these metabolic-epigenetic changes will inform therapeutic approaches to influence proinflammatory, antimicrobial, and immunosuppressed myeloid cellular states. Here, we demonstrate that Coenzyme A (CoA) is a “metabolic adjuvant”, as supplying exogenous CoA to macrophages both enhances the magnitude of TLR-driven proinflammatory and antimicrobial responses, and reverse tolerance, via promotion of oxidative metabolism. Extracellular CoA, which we isotopically trace to show its direct uptake by macrophages, works synergistically with tonic TLR signaling, which we demonstrate is a critical regulator of nutrient uptake, metabolism, histone acetylation, and gene expression in macrophages. Together, TLR signaling and exogenous CoA promote mitochondrial glucose oxidation, acetyl-CoA production, and TLR target gene-specific histone acetylation, enhancing metabolic-epigenetic support of proinflammatory transcriptional programming. Exogenous CoA unlocks tumor-associated macrophage (TAM)-dependent TLR agonist anti-tumor activity in anin vivobreast cancer model, and promotes macrophage restriction of the intracellular bacterial pathogenLegionella pneumophila in vitrovia anIrg1-dependent antimicrobial state of CoA-augmented itaconate biosynthesis. Our findings demonstrate direct acquisition of intact extracellular CoA, and the ability of this exogenously supplemented metabolic cofactor to augment a key oxidative metabolic-epigenetic pathway supporting proinflammatory and antimicrobial macrophage phenotypes. This may inform host-targeted metabolic adjuvant therapies to reverse myeloid immunosuppression.

Pancreatic ductal adenocarcinoma (PDA) is a deadly cancer for which development of effective therapies is urgently needed. Metabolic programs are vastly remodeled in pancreatic cancer to favor the production of certain metabolites that support tumor progression. Previous studies reported that catabolism of branched-chain amino acids (BCAAs) is the major carbon source for energy production in healthy pancreatic acinar cells. However, in PDA cells, BCAA metabolism is reprogrammed and its contribution to the TCA cycle is suppressed. Our labs recently showed that BCAAs, primarily isoleucine, are a primary supplier of propionyl-CoA (pr-CoA), which accumulates in the nuclei of cancer cells and is utilized for site-specific histone lysine propionylation (Kpr). Yet, the metabolic route through which BCAA catabolism supplies pr-CoA to the nucleus, as well as the distinct function of BCAA-derived Kpr in promoting tumor growth, are currently unknown. Here, we find that disrupting BCAA catabolism in PDA cells by either nutrient deprivation or genetic manipulation significantly decreases pr-CoA pools and the global levels of selective Kpr marks. Loss of BCAA-derived Kpr downregulates the expression of specific genes associated with lipid metabolism and immunosuppression. Accordingly, defective BCAA oxidation inhibits PDA tumor growth in vitro and in vivo, signifying the potential of targeting BCAA metabolism to attenuate PDA progression. Remarkably, we show that, in addition to their expected location in the mitochondria, BCAA metabolic enzymes also are detectable in the nuclear compartment of PDA cells and primary patient tissues, suggesting on-site synthesis of pr-CoA for Kpr. Overall, our findings support a novel link between metabolism and epigenetics in which segregation of a nuclear specific BCAA metabolic sub-network is harnessed by PDA cells to boost histone propionylation and shape malignant gene expression signatures. Christina Demetriadou, Michael Noji, Erick Mitchell-Velasquez, Sharan Venkatesh, Austin Good, Taku Harada, Daniel Kantner, Zoltan Arany, Irfan Asangani, Ben Stanger, Nathaniel Snyder, Kathryn Wellen. Branched-chain amino acid metabolism and histone propionylation in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3798.

DNA damaging agents remain the mainstay for high grade serous ovarian cancer (HGSOC) therapy. While many HGSOCs are sensitized to DNA damaging agents via dysregulated DNA repair, those patients harboring tumors with amplification or overexpression of CCNE1 (encoding cyclin E1) respond poorly in part due to proficiency in the homologous recombination (HR) DNA repair pathway. Here, we put forth a novel paradigm that HR proficiency of CCNE1-driven HGSOCs is promoted by altered cellular metabolism. We found that alpha-ketoglutarate (aKG) is upregulated in cyclin E1-driven HGSOC cells, and suppression of aKG sensitized these cells to DNA damaging agents both in vitro and in vivo, demonstrating that aKG drives chemoresistance in these models. aKG is required for the activity of aKG-dependent dioxygenases (aKGDD). There are >60 known aKGDD, and prior work has almost exclusively focused on aKGDD-mediated histone demethylation. Through a targeted CRISPR knockout library, we discovered that Trimethyllysine Hydroxylase Epsilon (TMLHE), the first and rate-limiting enzyme in de novo carnitine synthesis, is necessary for chemoresistance to DNA damaging agents in cyclin E1-driven cells. Unexpectedly, aKG-mediated TMLHE-dependent carnitine synthesis was required for histone acetylation, while histone methylation was affected but dispensable. These data point to a previously unrecognized role for aKG in acetylation reactions. The increase in histone acetylation via aKG-dependent carnitine synthesis promoted HR-mediated repair through site-specific histone acetylation. Additionally, analysis of HGSOC patient samples demonstrated that TMLHE positively correlates with histone acetylation, and both high tumor TMLHE or high serum acetylcarnitine are associated with worse progression free survival (PFS) in HGSOC patients treated with DNA damaging agents. Pharmacological targeting of carnitine synthesis via mildronate in vivo was sufficient to decrease tumor burden >30% in combination with cisplatin. Since mildronate is a non-toxic and extensively used drug in humans, this combination shows potential applicability of inhibition of this axis in humans. These data demonstrate for the first time that HR-proficiency in cyclin E1-driven HGSOCs is mediated through a metabolic axis that directly influences histone acetylation and highlight the translational potential of targeting this axis to induce HR deficiency and sensitize these tumors to DNA damaging agents. Apoorva Uboveja, Nathaniel W. Snyder, Katherine M. Aird. aKG-mediated carnitine synthesis promotes chemoresistance in CCNE1-high ovarian cancers via enhancing histone acetylation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr B031.

Excessive androgen levels can severely affect female health. However, most existing models of androgen excess rely on exogenous androgen administration, which does not fully capture the effect of elevated local ovarian testosterone on reproductive and metabolic functions. Here, we report the development of a novel hyperandrogenic mouse model, Cyp17TM-625, generated by combining CRISPR-Cas9 and a Tet-On doxycycline system to induce Cyp17A1 overexpression in ovarian theca-interstitial cells. As a result, Cyp17TM-625 mice exhibited significantly elevated Cyp17A1 messenger RNA and protein levels, accompanied by increased testosterone concentrations without alterations in basal levels of estradiol, progesterone, luteinizing hormone, or follicle-stimulating hormone. These mice demonstrated subfertility, evident by smaller and fewer litters, prolonged estrous cycles, and an increased number of unhealthy follicles with abnormally shaped oocytes. Despite these marked reproductive changes, body weight and glucose homeostasis remained comparable to Con-625 mice. Notably, withdrawal of doxycycline reversed testosterone overexpression and restored fertility over time. This model recapitulates reproductive dysfunction but not the metabolic disturbances, commonly observed in exogenous androgen models. The Cyp17TM-625 mouse line is a unique model for investigating the effects of local excess androgens on ovarian function. It also serves as a valuable tool for studying fertility restoration following the withdrawal of testosterone.

Cellular senescence, characterized by a stable cell cycle arrest, is a well-documented consequence of several widely used chemotherapeutics that has context-dependent roles in cancer. Although senescent cells are non-proliferative, they remain biologically active and secrete a complex and diverse array of factors collectively known as the senescence-associated secretome (SAS), which exerts pro-tumorigenic effects. Here, we aimed to mechanistically investigate how the SAS contributes to metastatic dissemination of high grade serous ovarian cancer (HGSOC) using standard-of-care cisplatin as a senescence inducer. Our findings demonstrate that the cisplatin-induced SAS enhances the dissemination of HGSOC in vivo without affecting cell proliferation or viability. We found that the SAS facilitates cell detachment, an effect that is mediated by a metabolic component. Using a metabolically focused CRISPR knockout screen, we identified complex I as the key driver of SAS-mediated cell detachment in bystander cells and validated that inhibition of complex I activity decreases HGSOC dissemination in vivo. Mechanistically, this effect was driven by SAS-mediated inhibition of an NAD+-SIRT-SREBP axis, leading to decreased plasma membrane cholesterol that increased cell detachment. Excitingly, we found that fructose is the key SAS component upstream of the NAD+-SIRT-SREBP-cholesterol axis mediating increased detachment of bystander cells, and a high fructose diet increases HGSOC dissemination in vivo. These findings reveal that the cisplatin-induced SAS reprograms the metabolic microenvironment in HGSOC, driving cancer cell detachment and promoting metastatic dissemination in a paracrine fashion. They also point to a previously unrecognized pro-tumorigenic effect of the SAS that may contribute to the high recurrence rate of HGSOC patients.

Nicotinamide adenine dinucleotide (NAD+) precursor supplementation shows metabolic and functional benefits in rodent models of disease and is being explored as potential therapeutic strategy in humans. However, the wide range of processes that involve NAD+ in every cell and subcellular compartment make it difficult to narrow down the mechanisms of action. Here we show that the rate of liver regeneration is closely associated with the concentration of NAD+ in hepatocyte mitochondria. We find that the mitochondrial NAD+ concentration in hepatocytes of male mice is determined by the expression of the transporter SLC25A51 (MCART1). The heterozygous loss of SLC25A51 modestly decreases mitochondrial NAD+ content in multiple tissues and impairs liver regeneration, whereas the hepatocyte-specific overexpression of SLC25A51 is sufficient to enhance liver regeneration comparably to the effect of systemic NAD+ precursor supplements. This benefit is observed even though NAD+ levels are increased only in mitochondria. Thus, the hepatocyte mitochondrial NAD+ pool is a key determinant of the rate of liver regeneration.

Succinate dehydrogenase (SDH) is both Complex II in the electron transport chain (ETC) and a key metabolic enzyme in the tricarboxylic acid cycle. SDH is a heterotetrameric enzyme consisting of four subunits SDHA, SDHB, SDHC, and SDHD, all encoded in the nuclear genome. In addition, the SDH complex requires two assembly factors, SDHAF1 and SDHAF2, which are required for assembly of SDHA and SDHB onto the inner mitochondrial-embedded subunits SDHC and SDHD. Once assembled, SDH catalyzes the conversion of succinate to fumarate coupled to the reduction of ubiquinone to ubiquinol via FAD/FADH2 and ultimately the generation of ATP via ATP synthase through a functioning ETC. Given the unique dual metabolic role of SDH, loss of activity results in major metabolic rewiring, potentially uncovering metabolic vulnerabilities that could be targeted for pharmacological manipulation in disease states. SDH is a tumor suppressor and SDH-loss is a driver of oncogenesis for cancers including pheochromocytomas, paragangliomas, gastrointestinal stromal tumors, and clear cell renal cell carcinomas. SDH deficiency also plays a role in the pathogenesis in non-neoplastic diseases, including Leigh syndrome and other neurometabolic disorders. Considering the implications of SDH function in both normal physiology and disease, understanding SDH function has fundamental and translational implications. This review seeks to summarize SDH deficiency, focusing on the role SDH plays in metabolism, the metabolic consequences of SDH deficiency, the proteomic consequences of SDH loss, thereby highlight potential therapeutic vulnerabilities in SDH-deficient cells.

Cellular metabolism produces reactive metabolites as both main and side products, requiring recycling pathways to detoxify these products. A study uncovers a recycling pathway that protects vitamin B12 from inactivating covalent modification.

Branched-chain amino acid (BCAA) metabolism is perturbed in patients with pancreatic cancer, but the contribution of systemic or pancreas-intrinsic BCAA catabolism to pancreatic carcinogenesis is unclear. We show here that pancreas-specific loss of DBT, the E2 subunit of the branched-chain keto-acid dehydrogenase (BCKDH) complex required for BCAA oxidation, strikingly exacerbates premalignant pancreatic intraepithelial neoplasia (PanIN) lesions in KC (p48-Cre;Kras LSL-G12D/+ ) mice. However, deletion of upstream enzyme BCAT2 neither phenocopied nor rescued loss of DBT in KC mice, ruling out involvement of both upstream and downstream metabolites as mediators of PanIN promotion. Instead, we observed that DBT deficiency led to loss of the kinase BCKDK, a negative regulator of the BCKDH complex, and that, remarkably, pancreas-specific loss of BCKDK phenocopied DBT deficiency in accelerating PanIN formation. These data thus support a model in which pancreas BCKDK restrains tumorigenesis. In contrast, systemic treatment of KC mice with the BCKDK inhibitor BT2, which inhibits BCKDH phosphorylation across many tissues except the pancreas, reduced PanIN formation and preserved normal acinar area. Together the data reveal the promotion of BCAA catabolism systemically, but not within the pancreas, as a promising intervention strategy to suppress tumor initiation.