bims-mepmim Biomed News
on Metabolites in pathological microenvironments and immunometabolism
Issue of 2023‒08‒20
eighteen papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

  1. Cell Rep. 2023 Aug 12. pii: S2211-1247(23)00982-8. [Epub ahead of print]42(8): 112971
      Fatty acid synthase (FASN) maintains de novo lipogenesis (DNL) to support rapid growth in most proliferating cancer cells. Lipogenic acetyl-coenzyme A (CoA) is primarily produced from carbohydrates but can arise from glutamine-dependent reductive carboxylation. Here, we show that reductive carboxylation also occurs in the absence of DNL. In FASN-deficient cells, reductive carboxylation is mainly catalyzed by isocitrate dehydrogenase-1 (IDH1), but IDH1-generated cytosolic citrate is not utilized for supplying DNL. Metabolic flux analysis (MFA) shows that FASN deficiency induces a net cytosol-to-mitochondria citrate flux through mitochondrial citrate transport protein (CTP). Previously, a similar pathway has been shown to mitigate detachment-induced oxidative stress in anchorage-independent tumor spheroids. We further report that tumor spheroids show reduced FASN activity and that FASN-deficient cells acquire resistance to oxidative stress in a CTP- and IDH1-dependent manner. Collectively, these data indicate that by inducing a cytosol-to-mitochondria citrate flux, anchorage-independent malignant cells can gain redox capacity by trading off FASN-supported rapid growth.
    Keywords:  CP: Metabolism; CP: Molecular biology; DNL; FASN inhibitor; IDH1 inhibitor; MFA; SLC25A1; anchorage-independent growth; cytosol-to-mitochondria citrate flux; de novo lipogenesis; metabolic flux analysis; redox; reductive carboxylation
  2. ACS Sens. 2023 Aug 14.
      Mitochondrial oxidative phosphorylation (OXPHOS) is sensitive to a variety of biological factors, and dysregulated OXPHOS is observed during the development of numerous pathological conditions. ATP production via OXPHOS is intrinsically dependent on the availability of acetyl-coenzyme A (CoA), which can enter the tricarboxylic acid (TCA) cycle to drive the oxidative pathway. Acetyl-l-carnitine (ALCAR) is an interchangeable endogenous source of acetyl-CoA, and therefore, ALCAR-derived probes are uniquely positioned for the assessment of OXPHOS. In this report, we develop hyperpolarized (HP) [1-13C]ALCAR as a noninvasive probe to investigate cardiac TCA cycle activity in vivo. We initially synthesized the isotopically labeled substrate and demonstrated that the 13C nucleus maintained a suitable T1 value (50.1 ± 0.8 s at 3 T) and polarization levels (21.3 ± 5.3%) to execute in vivo metabolic measurements. HP [1-13C]ALCAR was employed for cardiac analyses of OXPHOS in rats under fed and fasted conditions. [5-13C]Glutamate was successfully detected, and the metabolite was used to analyze the TCA cycle activity in both nutritional states. These assessments were compared to analogous experiments with the HP [1-13C]pyruvate. Our report represents the first study to demonstrate that HP methods using [1-13C]ALCAR enable direct analyses of mitochondrial function and TCA cycle activity, which are fundamental to cardiac cell homeostasis.
    Keywords:  acetyl-CoA; acetyl-l-carnitine; carbon-13 MRS; cardiac oxidative metabolism; hyperpolarization; oxidative phosphorylation
  3. Nat Commun. 2023 Aug 15. 14(1): 4943
      Metabolic flexibility of muscle tissue describes the adaptive capacity to use different energy substrates according to their availability. The disruption of this ability associates with metabolic disease. Here, using a Drosophila model of systemic metabolic dysfunction triggered by yorkie-induced gut tumors, we show that the transcription factor REPTOR is an important regulator of energy metabolism in muscles. We present evidence that REPTOR is activated in muscles of adult flies with gut yorkie-tumors, where it modulates glucose metabolism. Further, in vivo studies indicate that sustained activity of REPTOR is sufficient in wildtype muscles to repress glycolysis and increase tricarboxylic acid (TCA) cycle metabolites. Consistent with the fly studies, higher levels of CREBRF, the mammalian ortholog of REPTOR, reduce glycolysis in mouse myotubes while promoting oxidative metabolism. Altogether, our results define a conserved function for REPTOR and CREBRF as key regulators of muscle energy metabolism.
  4. Sci Adv. 2023 Aug 18. 9(33): eadg8631
      Abundant formation of endogenous supersulfides, which include reactive persulfide species and sulfur catenated residues in thiols and proteins (supersulfidation), has been observed. We found here that supersulfides catalyze S-nitrosoglutathione (GSNO) metabolism via glutathione-dependent electron transfer from aldehydes by exploiting alcohol dehydrogenase 5 (ADH5). ADH5 is a highly conserved bifunctional enzyme serving as GSNO reductase (GSNOR) that down-regulates NO signaling and formaldehyde dehydrogenase (FDH) that detoxifies formaldehyde in the form of glutathione hemithioacetal. C174S mutation significantly reduced the supersulfidation of ADH5 and almost abolished GSNOR activity but spared FDH activity. Notably, Adh5C174S/C174S mice manifested improved cardiac functions possibly because of GSNOR elimination and consequent increased NO bioavailability. Therefore, we successfully separated dual functions (GSNOR and FDH) of ADH5 (mediated by the supersulfide catalysis) through the biochemical analysis for supersulfides in vitro and characterizing in vivo phenotypes of the GSNOR-deficient organisms that we established herein. Supersulfides in ADH5 thus constitute a substantial catalytic center for GSNO metabolism mediating electron transfer from aldehydes.
  5. Cell Rep. 2023 Aug 16. pii: S2211-1247(23)01016-1. [Epub ahead of print]42(8): 113005
      The intricate interplay between gut microbes and the onset of experimental autoimmune encephalomyelitis (EAE) remains poorly understood. Here, we uncover remarkable similarities between CD4+ T cells in the spinal cord and their counterparts in the small intestine. Furthermore, we unveil a synergistic relationship between the microbiota, particularly enriched with the tryptophan metabolism gene EC:, and intestinal cells. This symbiotic collaboration results in the biosynthesis of kynurenic acid (KYNA), which modulates the recruitment and aggregation of GPR35-positive macrophages. Subsequently, a robust T helper 17 (Th17) immune response is activated, ultimately triggering the onset of EAE. Conversely, modulating the KYNA-mediated GPR35 signaling in Cx3cr1+ macrophages leads to a remarkable amelioration of EAE. These findings shed light on the crucial role of microbial-derived tryptophan metabolites in regulating immune responses within extraintestinal tissues.
    Keywords:  CD4(+) T cells; CP: Immunology; CP: Microbiology; GPR35; encephalomyelitis; gut microbes; immune system; kynurenic acid; macrophages; multiple sclerosis; spinal cord; tryptophan metabolites
  6. Cell Death Dis. 2023 08 12. 14(8): 515
      Anaplastic thyroid cancer (ATC) is one of the most aggressive tumors with an extremely poor prognosis. Based on the several biological features related to glutamine metabolism in ATC, we hypothesized glutaminolysis inhibition induces cell death in ATC cells. However, glutamine metabolism inhibition triggered cell growth arrest independent of cell death in ATC, suggesting that other signaling pathways avoid glutamine metabolism inhibition-induced stress exist. To investigate the functional mechanism against glutamine metabolism inhibition, we conducted mRNA and ATAC-Sequencing data analysis and found that glutamine deprivation increased ATF4-mediated one-carbon metabolism. When we inhibited PHGDH, the first rate-limiting enzyme for one-carbon metabolism, cell growth arrest was promoted upon glutamine metabolism inhibition by accumulating intracellular ROS. We next observed that the co-inhibition of glutamine and one-carbon metabolism could augment the anticancer effects of drugs used in patients with ATC. Finally, single-cell RNA sequencing analysis revealed that one-carbon metabolism was strengthened through the evolutionary process from PTC to ATC. Collectively, our data demonstrate that one-carbon metabolism has a potential role of modulation of cell fate in metabolic stress and can be a therapeutic target for enhancing antitumor effects in ATC.
  7. Nat Commun. 2023 Aug 17. 14(1): 4634
      Deregulated oxidative metabolism is a hallmark of leukaemia. While tyrosine kinase inhibitors (TKIs) such as imatinib have increased survival of chronic myeloid leukaemia (CML) patients, they fail to eradicate disease-initiating leukemic stem cells (LSCs). Whether TKI-treated CML LSCs remain metabolically deregulated is unknown. Using clinically and physiologically relevant assays, we generate multi-omics datasets that offer unique insight into metabolic adaptation and nutrient fate in patient-derived CML LSCs. We demonstrate that LSCs have increased pyruvate anaplerosis, mediated by increased mitochondrial pyruvate carrier 1/2 (MPC1/2) levels and pyruvate carboxylase (PC) activity, in comparison to normal counterparts. While imatinib reverses BCR::ABL1-mediated LSC metabolic reprogramming, stable isotope-assisted metabolomics reveals that deregulated pyruvate anaplerosis is not affected by imatinib. Encouragingly, genetic ablation of pyruvate anaplerosis sensitises CML cells to imatinib. Finally, we demonstrate that MSDC-0160, a clinical orally-available MPC1/2 inhibitor, inhibits pyruvate anaplerosis and targets imatinib-resistant CML LSCs in robust pre-clinical CML models. Collectively these results highlight pyruvate anaplerosis as a persistent and therapeutically targetable vulnerability in imatinib-treated CML patient-derived samples.
  8. Oncogene. 2023 Aug 17.
      Proliferating cells have metabolic dependence on glutamine to fuel anabolic pathways and to refill the mitochondrial carbon pool. The Hippo pathway is essential for coordinating cell survival and growth with nutrient availability, but no molecular connection to glutamine deprivation has been reported. Here, we identify a non-canonical role of YAP, a key effector of the Hippo pathway, in cellular adaptation to perturbation of glutamine metabolism. Whereas YAP is inhibited by nutrient scarcity, enabling cells to restrain proliferation and to maintain energy homeostasis, glutamine shortage induces a rapid YAP dephosphorylation and activation. Upon glutaminolysis inhibition, an increased reactive oxygen species production inhibits LATS kinase via RhoA, leading to YAP dephosphorylation. Activated YAP promotes transcriptional induction of ATF4 to induce the expression of genes involved in amino acid homeostasis, including Sestrin2. We found that YAP-mediated Sestrin2 induction is crucial for cell viability during glutamine deprivation by suppressing mTORC1. Thus, a critical relationship between YAP, ATF4, and mTORC1 is uncovered by our findings. Finally, our data indicate that targeting the Hippo-YAP pathway in combination with glutaminolysis inhibition may provide potential therapeutic approaches to treat tumors.
  9. Nature. 2023 Aug 16.
      Endothelial cells (ECs) line the blood and lymphatic vasculature, and act as an essential physical barrier, control nutrient transport, facilitate tissue immunosurveillance, and coordinate angiogenesis/ lymphangiogenesis1,2. In the intestine, dietary and microbial cues are particularly important in the regulation of organ homeostasis. However, whether enteric ECs actively sense and integrate such signals is currently unknown. Here, we show that the aryl hydrocarbon receptor (AHR) acts as a critical node for EC-sensing of dietary metabolites in adult mice and human primary ECs. We first established a comprehensive single-cell endothelial atlas of the mouse small intestine, uncovering the cellular complexity and functional heterogeneity of blood and lymphatic ECs. Analyses of AHR mediated responses at single-cell resolution identified tissue-protective transcriptional signatures and regulatory networks promoting cellular quiescence and vascular normalcy at steady state. Endothelial AHR-deficiency in adult mice resulted in dysregulated inflammatory responses, and the initiation of proliferative pathways. Furthermore, endothelial sensing of dietary AHR ligands was required for optimal protection against enteric infection. In human ECs, AHR signalling promoted quiescence and restrained activation by inflammatory mediators. Together, our data provide a comprehensive dissection of the impact of environmental sensing across the spectrum of enteric endothelia, demonstrating that endothelial AHR signalling integrates dietary cues to maintain tissue homeostasis by promoting EC quiescence and vascular normalcy.
  10. Nat Metab. 2023 Aug 14.
      The genomic landscape of colorectal cancer (CRC) is shaped by inactivating mutations in tumour suppressors such as APC, and oncogenic mutations such as mutant KRAS. Here we used genetically engineered mouse models, and multimodal mass spectrometry-based metabolomics to study the impact of common genetic drivers of CRC on the metabolic landscape of the intestine. We show that untargeted metabolic profiling can be applied to stratify intestinal tissues according to underlying genetic alterations, and use mass spectrometry imaging to identify tumour, stromal and normal adjacent tissues. By identifying ions that drive variation between normal and transformed tissues, we found dysregulation of the methionine cycle to be a hallmark of APC-deficient CRC. Loss of Apc in the mouse intestine was found to be sufficient to drive expression of one of its enzymes, adenosylhomocysteinase (AHCY), which was also found to be transcriptionally upregulated in human CRC. Targeting of AHCY function impaired growth of APC-deficient organoids in vitro, and prevented the characteristic hyperproliferative/crypt progenitor phenotype driven by acute deletion of Apc in vivo, even in the context of mutant Kras. Finally, pharmacological inhibition of AHCY reduced intestinal tumour burden in ApcMin/+ mice indicating its potential as a metabolic drug target in CRC.
  11. Cell Rep. 2023 Aug 15. pii: S2211-1247(23)00993-2. [Epub ahead of print]42(8): 112982
      In daylight, demand for visual chromophore (11-cis-retinal) exceeds supply by the classical visual cycle. This shortfall is compensated, in part, by the retinal G-protein-coupled receptor (RGR) photoisomerase, which is expressed in both the retinal pigment epithelium (RPE) and in Müller cells. The relative contributions of these two cellular pools of RGR to the maintenance of photoreceptor light responses are not known. Here, we use a cell-specific gene reactivation approach to elucidate the kinetics of RGR-mediated recovery of photoreceptor responses following light exposure. Electroretinographic measurements in mice with RGR expression limited to either cell type reveal that the RPE and a specialized subset of Müller glia contribute both to scotopic and photopic function. We demonstrate that 11-cis-retinal formed through photoisomerization is rapidly hydrolyzed, consistent with its role in a rapid visual pigment regeneration process. Our study shows that RGR provides a pan-retinal sink for all-trans-retinal released under sustained light conditions and supports rapid chromophore regeneration through the photic visual cycle.
    Keywords:  11-cis-retinal; CP: Cell biology; CP: Neuroscience; Müller cells; chromophore; cone opsin; photic visual cycle; photoisomerization; retina; retinal pigmented epithelium; vision; visual cycle
  12. Sci Adv. 2023 Aug 18. 9(33): eadg7997
      Understanding mechanisms of epigenetic regulation in embryonic stem cells (ESCs) is of fundamental importance for stem cell and developmental biology. Here, we identify Spic, a member of the ETS family of transcription factors (TFs), as a marker of ground state pluripotency. We show that Spic is rapidly induced in ground state ESCs and in response to extracellular signal-regulated kinase (ERK) inhibition. We find that SPIC binds to enhancer elements and stabilizes NANOG binding to chromatin, particularly at genes involved in choline/one-carbon (1C) metabolism such as Bhmt, Bhmt2, and Dmgdh. Gain-of-function and loss-of-function experiments revealed that Spic controls 1C metabolism and the flux of S-adenosyl methionine to S-adenosyl-L-homocysteine (SAM-to-SAH), thereby, modulating the levels of H3R17me2 and H3K4me3 histone marks in ESCs. Our findings highlight betaine-dependent 1C metabolism as a hallmark of ground state pluripotency primarily activated by SPIC. These findings underscore the role of uncharacterized auxiliary TFs in linking cellular metabolism to epigenetic regulation in ESCs.
  13. Mol Cancer. 2023 08 12. 22(1): 133
      Prostate cancer (PCa) is a common and fatal type of cancer in men. Metastatic PCa (mPCa) is a major factor contributing to its lethality, although the mechanisms remain poorly understood. PTEN is one of the most frequently deleted genes in mPCa. Here we show a frequent genomic co-deletion of PTEN and STAT3 in liquid biopsies of patients with mPCa. Loss of Stat3 in a Pten-null mouse prostate model leads to a reduction of LKB1/pAMPK with simultaneous activation of mTOR/CREB, resulting in metastatic disease. However, constitutive activation of Stat3 led to high LKB1/pAMPK levels and suppressed mTORC1/CREB pathway, preventing mPCa development. Metformin, one of the most widely prescribed therapeutics against type 2 diabetes, inhibits mTORC1 in liver and requires LKB1 to mediate glucose homeostasis. We find that metformin treatment of STAT3/AR-expressing PCa xenografts resulted in significantly reduced tumor growth accompanied by diminished mTORC1/CREB, AR and PSA levels. PCa xenografts with deletion of STAT3/AR nearly completely abrogated mTORC1/CREB inhibition mediated by metformin. Moreover, metformin treatment of PCa patients with high Gleason grade and type 2 diabetes resulted in undetectable mTORC1 levels and upregulated STAT3 expression. Furthermore, PCa patients with high CREB expression have worse clinical outcomes and a significantly increased risk of PCa relapse and metastatic recurrence. In summary, we have shown that STAT3 controls mPCa via LKB1/pAMPK/mTORC1/CREB signaling, which we have identified as a promising novel downstream target for the treatment of lethal mPCa.
    Keywords:  AMPK; AR; CREB; LKB1; Metformin; Prostate Cancer; STAT3; mTORC1
  14. Nat Commun. 2023 Aug 14. 14(1): 4895
      The opportunistic fungal pathogen Cryptococcus neoformans causes lethal infections in immunocompromised patients. Macrophages are central to the host response to cryptococci; however, it is unclear how C. neoformans is recognised and phagocytosed by macrophages. Here we investigate the role of TLR4 in the non-opsonic phagocytosis of C. neoformans. We find that loss of TLR4 function unexpectedly increases phagocytosis of non-opsonised cryptococci by murine and human macrophages. The increased phagocytosis observed in Tlr4-/- cells was dampened by pre-treatment of macrophages with oxidised-LDL, a known ligand of scavenger receptors. The scavenger receptor, macrophage scavenger receptor 1 (MSR1) (also known as SR-A1 or CD204) was upregulated in Tlr4-/- macrophages. Genetic ablation of MSR1 resulted in a 75% decrease in phagocytosis of non-opsonised cryptococci, strongly suggesting that it is a key non-opsonic receptor for this pathogen. We go on to show that MSR1-mediated uptake likely involves the formation of a multimolecular signalling complex involving FcγR leading to SYK, PI3K, p38 and ERK1/2 activation to drive actin remodelling and phagocytosis. Altogether, our data indicate a hitherto unidentified role for TLR4/MSR1 crosstalk in the non-opsonic phagocytosis of C. neoformans.
  15. J Cell Biol. 2023 10 02. pii: e202301091. [Epub ahead of print]222(10):
      Mitochondria are dynamic organelles regulated by fission and fusion processes. The fusion of membranes requires elaborative coordination of proteins and lipids and is particularly crucial for the function and quality control of mitochondria. Phosphatidic acid (PA) on the mitochondrial outer membrane generated by PLD6 facilitates the fusion of mitochondria. However, how PA promotes mitochondrial fusion remains unclear. Here, we show that a mitochondrial outer membrane protein, NME3, is required for PLD6-induced mitochondrial tethering or clustering. NME3 is enriched at the contact interface of two closely positioned mitochondria depending on PLD6, and NME3 binds directly to PA-exposed lipid packing defects via its N-terminal amphipathic helix. The PA binding function and hexamerization confer NME3 mitochondrial tethering activity. Importantly, nutrient starvation enhances the enrichment efficiency of NME3 at the mitochondrial contact interface, and the tethering ability of NME3 contributes to fusion efficiency. Together, our findings demonstrate NME3 as a tethering protein promoting selective fusion between PLD6-remodeled mitochondria for quality control.
  16. J Biol Chem. 2023 Aug 14. pii: S0021-9258(23)02190-7. [Epub ahead of print] 105162
      Sphingomyelin synthase (SMS)-related protein (SMSr) is a phosphatidylethanolamine phospholipase C (PE-PLC) molecule that is conserved and ubiquitous in mammals. However, its biological function is still not clear. We previously observed that SMS1 deficiency-mediated glucosylceramide accumulation caused nonalcoholic fatty liver diseases (NAFLD), including nonalcoholic steatohepatitis (NASH) and liver fibrosis. Here, first, we evaluated high-fat diet/fructose-induced NAFLD in Smsr knock out (KO) and WT mice. Second, we evaluated whether SMSr deficiency can reverse SMS1 deficiency-mediated NAFLD, using Sms1/Sms2 double and Sms1/Sms2/Smsr triple KO mice. We found that SMSr/PE-PLC deficiency attenuated high-fat diet/fructose-induced fatty liver and NASH, and attenuated glucosylceramide accumulation-induced NASH, fibrosis, and tumor formation. Further, we found that SMSr/PE-PLC deficiency reduced the expression of many inflammatory cytokines and fibrosis-related factors, and PE supplementation in vitro or in vivo mimicked the condition of SMSr/PE-PLC deficiency. Furthermore, we demonstrated that SMSr/PE-PLC deficiency or PE supplementation effectively prevented membrane-bound β-catenin transfer to the nucleus, thereby preventing tumor-related gene expression. Finally, we observed that patients with NASH had higher SMSr protein levels in the liver, lower plasma PE levels, and lower plasma PE/phosphatidylcholine (PC) ratios, and that human plasma PE levels are negatively associated with TNF-α and TGFβ1 levels. In conclusion, SMSr/PE-PLC deficiency causes PE accumulation, which can attenuate fatty liver, NASH, and fibrosis. These results suggest that SMSr/PE-PLC inhibition therapy may mitigate NAFLD.
    Keywords:  Sphingomyelin synthase related protein; liver fibrosis; nonalcoholic fatty liver disease (NAFLD); nonalcoholic steatohepatitis (NASH); phosphatidylethanolamine; phosphatidylethanolamine phospholipase C
  17. Mol Cell. 2023 Aug 17. pii: S1097-2765(23)00527-0. [Epub ahead of print]83(16): 2837-2839
      A recent study by Yang et al.1 uncovers the pyrimidinosome, a multienzyme complex where enzymes from different subcellular compartments collaborate to enable efficient pyrimidine biosynthesis and ferroptosis defense, highlighting the remarkable adaptability of cellular metabolism and new therapeutic opportunities.
  18. Nature. 2023 Aug 16.
      Disruption of the lung endothelial-epithelial cell barrier following respiratory virus infection causes cell and fluid accumulation in the air spaces and compromises vital gas exchange function1. Endothelial dysfunction can exacerbate tissue damage2,3, yet it is unclear whether the lung endothelium promotes host resistance against viral pathogens. Here we show that the environmental sensor aryl hydrocarbon receptor (AHR) is highly active in lung endothelial cells and protects against influenza-induced lung vascular leakage. Loss of AHR in endothelia exacerbates lung damage and promotes the infiltration of red blood cells and leukocytes into alveolar air spaces. Moreover, barrier protection is compromised and host susceptibility to secondary bacterial infections is increased when endothelial AHR is missing. AHR engages tissue-protective transcriptional networks in endothelia, including the vasoactive apelin-APJ peptide system4, to prevent a dysplastic and apoptotic response in airway epithelial cells. Finally, we show that protective AHR signalling in lung endothelial cells is dampened by the infection itself. Maintenance of protective AHR function requires a diet enriched in naturally occurring AHR ligands, which activate disease tolerance pathways in lung endothelia to prevent tissue damage. Our findings demonstrate the importance of endothelial function in lung barrier immunity. We identify a gut-lung axis that affects lung damage following encounters with viral pathogens, linking dietary composition and intake to host fitness and inter-individual variations in disease outcome.