bims-mepmim 2023-10-08 papers

bims-mepmim

Biomed News

on Metabolites in pathological microenvironments and immunometabolism

Issue of 2023–10–08
23 papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

Comprehensive quantification of metabolic flux during acute cold stress in mice.
Peroxisomal ROS control cytosolic Mycobacterium tuberculosis replication in human macrophages.
Cholesterol-dependent homeostatic regulation of very long chain sphingolipid synthesis.
Cystine/Glutamate antiporter system xc- deficiency impairs macrophage glutathione metabolism and cytokine production.
Depletion of slow-cycling PDGFRα+ADAM12+ mesenchymal cells promotes antitumor immunity by restricting macrophage efferocytosis.
Amino acid transporter SLC38A5 is a tumor promoter and a novel therapeutic target for pancreatic cancer.
Neutrophils resist ferroptosis and promote breast cancer metastasis through aconitate decarboxylase 1.
TSC2 S1365A mutation potently regulates CD8+T cell function and differentiation improving adoptive cellular cancer therapy.
The glyoxylate shunt protein ICL-1 protects from mitochondrial superoxide stress through activation of the mitochondrial unfolded protein response.
ARL8B mediates lipid droplet contact and delivery to lysosomes for lipid remobilization.
Spatially resolved metabolomics and isotope tracing reveal dynamic metabolic responses of dentate granule neurons with acute stimulation.
CysQuant: Simultaneous quantification of cysteine oxidation and protein abundance using data dependent or independent acquisition mass spectrometry.
High dietary fructose promotes hepatocellular carcinoma progression by enhancing O-GlcNAcylation via microbiota-derived acetate.
Perilipin 2-positive mononuclear phagocytes accumulate in the diabetic retina and promote PPARγ-dependent vasodegeneration.
Structure of the ceramide-bound SPOTS complex.
Voltage-dependent anion channel 1 (VDAC1) overexpression alleviates cardiac fibroblast activation in cardiac fibrosis via regulating fatty acid metabolism.
A subpopulation of lipogenic brown adipocytes drives thermogenic memory.
Hypoxia activates SREBP2 through Golgi disassembly in bone marrow-derived monocytes for enhanced tumor growth.
An early-life microbiota metabolite protects against obesity by regulating intestinal lipid metabolism.
Decreased liver B vitamin-related enzymes as a metabolic hallmark of cancer cachexia.
Spatially Resolved Metabolomics Combined with the 3D Tumor-Immune Cell Coculture Spheroid Highlights Metabolic Alterations during Antitumor Immune Response.
Acetylation-dependent coupling between G6PD activity and apoptotic signaling.
Raman spectroscopy and mass spectrometry identifies a unique group of epidermal lipids in active discoid lupus erythematosus.

Cell Metab. 2023 Sep 27. pii: S1550-4131(23)00337-6. [Epub ahead of print]

Comprehensive quantification of metabolic flux during acute cold stress in mice.

Marc R Bornstein, Michael D Neinast, Xianfeng Zeng, Qingwei Chu, Jessie Axsom, Chelsea Thorsheim, Kristina Li, Megan C Blair, Joshua D Rabinowitz, Zoltan Arany.

  Cold-induced thermogenesis (CIT) is widely studied as a potential avenue to treat obesity, but a thorough understanding of the metabolic changes driving CIT is lacking. Here, we present a comprehensive and quantitative analysis of the metabolic response to acute cold exposure, leveraging metabolomic profiling and minimally perturbative isotope tracing studies in unanesthetized mice. During cold exposure, brown adipose tissue (BAT) primarily fueled the tricarboxylic acid (TCA) cycle with fat in fasted mice and glucose in fed mice, underscoring BAT's metabolic flexibility. BAT minimally used branched-chain amino acids or ketones, which were instead avidly consumed by muscle during cold exposure. Surprisingly, isotopic labeling analyses revealed that BAT uses glucose largely for TCA anaplerosis via pyruvate carboxylation. Finally, we find that cold-induced hepatic gluconeogenesis is critical for CIT during fasting, demonstrating a key functional role for glucose metabolism. Together, these findings provide a detailed map of the metabolic rewiring driving acute CIT.

Keywords:  FBP1; brown adipose tissue; cold exposure; flux; gluconeogenesis; glucose; metabolomics; pyruvate carboxylase; thermogenesis

DOI:  https://doi.org/10.1016/j.cmet.2023.09.002
J Cell Biol. 2023 Dec 04. pii: e202303066. [Epub ahead of print]222(12):

Peroxisomal ROS control cytosolic Mycobacterium tuberculosis replication in human macrophages.

Enrica Pellegrino, Beren Aylan, Claudio Bussi, Antony Fearns, Elliott M Bernard, Natalia Athanasiadi, Pierre Santucci, Laure Botella, Maximiliano G Gutierrez.

Peroxisomes are organelles involved in many metabolic processes including lipid metabolism, reactive oxygen species (ROS) turnover, and antimicrobial immune responses. However, the cellular mechanisms by which peroxisomes contribute to bacterial elimination in macrophages remain elusive. Here, we investigated peroxisome function in iPSC-derived human macrophages (iPSDM) during infection with Mycobacterium tuberculosis (Mtb). We discovered that Mtb-triggered peroxisome biogenesis requires the ESX-1 type 7 secretion system, critical for cytosolic access. iPSDM lacking peroxisomes were permissive to Mtb wild-type (WT) replication but were able to restrict an Mtb mutant missing functional ESX-1, suggesting a role for peroxisomes in the control of cytosolic but not phagosomal Mtb. Using genetically encoded localization-dependent ROS probes, we found peroxisomes increased ROS levels during Mtb WT infection. Thus, human macrophages respond to the infection by increasing peroxisomes that generate ROS primarily to restrict cytosolic Mtb. Our data uncover a peroxisome-controlled, ROS-mediated mechanism that contributes to the restriction of cytosolic bacteria.

DOI: https://doi.org/10.1083/jcb.202303066
J Cell Biol. 2023 Dec 04. pii: e202308055. [Epub ahead of print]222(12):

Cholesterol-dependent homeostatic regulation of very long chain sphingolipid synthesis.

Yeongho Kim, Grace Mavodza, Can E Senkal, Christopher G Burd.

Sphingomyelin plays a key role in cellular cholesterol homeostasis by binding to and sequestering cholesterol in the plasma membrane. We discovered that synthesis of very long chain (VLC) sphingomyelins is inversely regulated by cellular cholesterol levels; acute cholesterol depletion elicited a rapid induction of VLC-sphingolipid synthesis, increased trafficking to the Golgi apparatus and plasma membrane, while cholesterol loading reduced VLC-sphingolipid synthesis. This sphingolipid-cholesterol metabolic axis is distinct from the sterol responsive element binding protein pathway as it requires ceramide synthase 2 (CerS2) activity, epidermal growth factor receptor signaling, and was unaffected by inhibition of protein translation. Depletion of VLC-ceramides reduced plasma membrane cholesterol content, reduced plasma membrane lipid packing, and unexpectedly resulted in the accumulation of cholesterol in the cytoplasmic leaflet of the lysosome membrane. This study establishes the existence of a cholesterol-sphingolipid regulatory axis that maintains plasma membrane lipid homeostasis via regulation of sphingomyelin synthesis and trafficking.

DOI: https://doi.org/10.1083/jcb.202308055
PLoS One. 2023 ;18(10): e0291950

Cystine/Glutamate antiporter system xc- deficiency impairs macrophage glutathione metabolism and cytokine production.

Axel de Baat, Daniel T Meier, Adriano Fontana, Marianne Böni-Schnetzler, Marc Y Donath.

System xc-, encoded by Slc7a11, is an antiporter responsible for exporting glutamate while importing cystine, which is essential for protein synthesis and the formation of thiol peptides, such as glutathione. Glutathione acts as a co-factor for enzymes responsible for scavenging reactive oxygen species. Upon exposure to bacterial products, macrophages exhibit a rapid upregulation of system xc-. This study investigates the impact of Slc7a11 deficiency on the functionality of peritoneal and bone marrow-derived macrophages. Our findings reveal that the absence of Slc7a11 results in significantly reduced glutathione levels, compromised mitochondrial flexibility, and hindered cytokine production in bone marrow-derived macrophages. Conversely, system xc- has a lesser impact on peritoneal macrophages in vivo. These results indicate that system xc- is essential for maintaining glutathione levels, mitochondrial functionality, and cytokine production, with a heightened importance under atmospheric oxygen tension.

DOI: https://doi.org/10.1371/journal.pone.0291950
Nat Immunol. 2023 Oct 05.

Depletion of slow-cycling PDGFRα+ADAM12+ mesenchymal cells promotes antitumor immunity by restricting macrophage efferocytosis.

Selene E Di Carlo, Jerome Raffenne, Hugo Varet, Anais Ode, David Cabrerizo Granados, Merle Stein, Rachel Legendre, Jan Tuckermann, Corinne Bousquet, Lucie Peduto.

The capacity to survive and thrive in conditions of limited resources and high inflammation is a major driver of tumor malignancy. Here we identified slow-cycling ADAM12+PDGFRα+ mesenchymal stromal cells (MSCs) induced at the tumor margins in mouse models of melanoma, pancreatic cancer and prostate cancer. Using inducible lineage tracing and transcriptomics, we demonstrated that metabolically altered ADAM12+ MSCs induced pathological angiogenesis and immunosuppression by promoting macrophage efferocytosis and polarization through overexpression of genes such as Gas6, Lgals3 and Csf1. Genetic depletion of ADAM12+ cells restored a functional tumor vasculature, reduced hypoxia and acidosis and normalized CAFs, inducing infiltration of effector T cells and growth inhibition of melanomas and pancreatic neuroendocrine cancer, in a process dependent on TGF-β. In human cancer, ADAM12 stratifies patients with high levels of hypoxia and innate resistance mechanisms, as well as factors associated with a poor prognosis and drug resistance such as AXL. Altogether, our data show that depletion of tumor-induced slow-cycling PDGFRα+ MSCs through ADAM12 restores antitumor immunity.

DOI: https://doi.org/10.1038/s41590-023-01642-7
Sci Rep. 2023 Oct 06. 13(1): 16863

Amino acid transporter SLC38A5 is a tumor promoter and a novel therapeutic target for pancreatic cancer.

Tyler Sniegowski, Devaraja Rajasekaran, Souad R Sennoune, Sukumaran Sunitha, Fang Chen, Mohamed Fokar, Sudhir Kshirsagar, P Hemachandra Reddy, Ksenija Korac, Mosharaf Mahmud Syed, Tanima Sharker, Vadivel Ganapathy, Yangzom D Bhutia.

Pancreatic ductal adenocarcinoma (PDAC) cells have a great demand for nutrients in the form of sugars, amino acids, and lipids. Particularly, amino acids are critical for cancer growth and, as intermediates, connect glucose, lipid and nucleotide metabolism. PDAC cells meet these requirements by upregulating selective amino acid transporters. Here we show that SLC38A5 (SN2/SNAT5), a neutral amino acid transporter is highly upregulated and functional in PDAC cells. Using CRISPR/Cas9-mediated knockout of SLC38A5, we show its tumor promoting role in an in vitro cell line model as well as in a subcutaneous xenograft mouse model. Using metabolomics and RNA sequencing, we show significant reduction in many amino acid substrates of SLC38A5 as well as OXPHOS inactivation in response to SLC38A5 deletion. Experimental validation demonstrates inhibition of mTORC1, glycolysis and mitochondrial respiration in KO cells, suggesting a serious metabolic crisis associated with SLC38A5 deletion. Since many SLC38A5 substrates are activators of mTORC1 as well as TCA cycle intermediates/precursors, we speculate amino acid insufficiency as a possible link between SLC38A5 deletion and inactivation of mTORC1, glycolysis and mitochondrial respiration, and the underlying mechanism for PDAC attenuation. Overall, we show that SLC38A5 promotes PDAC, thereby identifying a novel, hitherto unknown, therapeutic target for PDAC.

DOI: https://doi.org/10.1038/s41598-023-43983-1
Cell Metab. 2023 Oct 03. pii: S1550-4131(23)00336-4. [Epub ahead of print]35(10): 1688-1703.e10

Neutrophils resist ferroptosis and promote breast cancer metastasis through aconitate decarboxylase 1.

Yun Zhao, Zhongshun Liu, Guoqiang Liu, Yuting Zhang, Sheng Liu, Dailin Gan, Wennan Chang, Xiaoxia Peng, Eun Suh Sung, Keegan Gilbert, Yini Zhu, Xuechun Wang, Ziyu Zeng, Hope Baldwin, Guanzhu Ren, Jessica Weaver, Anna Huron, Toni Mayberry, Qingfei Wang, Yujue Wang, Maria Elena Diaz-Rubio, Xiaoyang Su, M Sharon Stack, Siyuan Zhang, Xuemin Lu, Ryan D Sheldon, Jun Li, Chi Zhang, Jun Wan, Xin Lu.

  Metastasis causes breast cancer-related mortality. Tumor-infiltrating neutrophils (TINs) inflict immunosuppression and promote metastasis. Therapeutic debilitation of TINs may enhance immunotherapy, yet it remains a challenge to identify therapeutic targets highly expressed and functionally essential in TINs but under-expressed in extra-tumoral neutrophils. Here, using single-cell RNA sequencing to compare TINs and circulating neutrophils in murine mammary tumor models, we identified aconitate decarboxylase 1 (Acod1) as the most upregulated metabolic enzyme in mouse TINs and validated high Acod1 expression in human TINs. Activated through the GM-CSF-JAK/STAT5-C/EBPβ pathway, Acod1 produces itaconate, which mediates Nrf2-dependent defense against ferroptosis and upholds the persistence of TINs. Acod1 ablation abates TIN infiltration, constrains metastasis (but not primary tumors), bolsters antitumor T cell immunity, and boosts the efficacy of immune checkpoint blockade. Our findings reveal how TINs escape from ferroptosis through the Acod1-dependent immunometabolism switch and establish Acod1 as a target to offset immunosuppression and improve immunotherapy against metastasis.

Keywords:  Acod1; MDSC; breast cancer; ferroptosis; immune checkpoint blockade; immune metabolism; itaconate; metastasis; neutrophil; single-cell RNA sequencing

DOI:  https://doi.org/10.1016/j.cmet.2023.09.004
JCI Insight. 2023 Oct 03. pii: e167829. [Epub ahead of print]

TSC2 S1365A mutation potently regulates CD8+T cell function and differentiation improving adoptive cellular cancer therapy.

Chirag H Patel, Yi Dong, Navid Koleini, Xiaoxu Wang, Brittany L Dunkerly-Eyring, Jiayu Wen, Mark J Ranek, Laura M Bartle, Daniel B Henderson, Jason G Sagert, David A Kass, Jonathan D Powell.

  MTORC1 integrates signaling from the immune microenvironment to regulate T cell activation, differentiation, and function. TSC2 in the tuberous sclerosis complex tightly regulates mTORC1 activation. CD8+ T cells lacking TSC2 have constitutively enhanced mTORC1 activity and generate robust effector T cells; however sustained mTORC1 activation prevents generation of long-lived memory CD8+ T cells. Here we show manipulating TSC2 at Ser1365 potently regulates activated but not basal mTORC1 signaling in CD8+ T cells. Unlike non-stimulated TSC2 knockout cells, CD8+ T cells expressing a phospho-silencing mutant TSC2-S1365A (SA) retain normal basal mTORC1 activity. PKC and T-cell Receptor (TCR) stimulation induces TSC2 S1365 phosphorylation and preventing this with the SA mutation markedly increases mTORC1 activation and T-cell effector function. Consequently, SA CD8+ T cells display greater effector responses while retaining their capacity to become long-lived memory T cells. SA CD8+ T cells also display enhanced effector function under hypoxic and acidic conditions. In murine and human solid-tumor models, CD8+ SA T cells used as adoptive cell therapy display greater anti-tumor immunity than WT CD8+ T cells. These findings reveal an upstream mechanism to regulate mTORC1 activity in T cells. The TSC2-SA mutation enhances both T cell effector function and long-term persistence/memory formation, supporting an approach to engineer better CAR-T cells for treating cancer.

Keywords:  Adaptive immunity; Cancer immunotherapy; Cell Biology; Immunology; T cells

DOI:  https://doi.org/10.1172/jci.insight.167829
Free Radic Biol Med. 2023 Sep 25. pii: S0891-5849(23)00654-8. [Epub ahead of print]208 771-779

The glyoxylate shunt protein ICL-1 protects from mitochondrial superoxide stress through activation of the mitochondrial unfolded protein response.

Guoqiang Wang, Ricardo Laranjeiro, Stephanie LeValley, Jeremy M Van Raamsdonk, Monica Driscoll.

Disrupting mitochondrial superoxide dismutase (SOD) causes neonatal lethality in mice and death of flies within 24 h after eclosion. Deletion of mitochondrial sod genes in C. elegans impairs fertility as well, but surprisingly is not detrimental to survival of progeny generated. The comparison of metabolic pathways among mouse, flies and nematodes reveals that mice and flies lack the glyoxylate shunt, a shortcut that bypasses part of the tricarboxylic acid (TCA) cycle. Here we show that ICL-1, the sole protein that catalyzes the glyoxylate shunt, is critical for protection against embryonic lethality resulting from elevated levels of mitochondrial superoxide. In exploring the mechanism by which ICL-1 protects against ROS-mediated embryonic lethality, we find that ICL-1 is required for the efficient activation of mitochondrial unfolded protein response (UPRmt) and that ATFS-1, a key UPRmt transcription factor and an activator of icl-1 gene expression, is essential to limit embryonic/neonatal lethality in animals lacking mitochondrial SOD. In sum, we identify a biochemical pathway that highlights a molecular strategy for combating toxic mitochondrial superoxide consequences in cells.

DOI: https://doi.org/10.1016/j.freeradbiomed.2023.09.029
Cell Rep. 2023 Sep 30. pii: S2211-1247(23)01215-9. [Epub ahead of print]42(10): 113203

ARL8B mediates lipid droplet contact and delivery to lysosomes for lipid remobilization.

Dilip Menon, Apoorva Bhapkar, Bhoomika Manchandia, Gitanjali Charak, Surabhi Rathore, Rakesh Mohan Jha, Arpita Nahak, Moumita Mondal, Mohyeddine Omrane, Akash Kumar Bhaskar, Lipi Thukral, Abdou Rachid Thiam, Sheetal Gandotra.

  Lipid droplets (LDs) play a crucial role in maintaining cellular lipid balance by storing and delivering lipids as needed. However, the intricate lipolytic pathways involved in LD turnover remain poorly described, hindering our comprehension of lipid catabolism and related disorders. Here, we show a function of the small GTPase ARL8B in mediating LD turnover in lysosomes. ARL8B-GDP localizes to LDs, while ARL8-GTP predominantly favors lysosomes. GDP binding induces a conformation with an exposed N-terminal amphipathic helix, enabling ARL8B to bind to LDs. By associating with LDs and lysosomes, and with its property to form a heterotypic complex, ARL8B mediates LD-lysosome contacts and efficient lipid transfer between these organelles. In human macrophages, this ARL8B-dependent LD turnover mechanism appears as the major lipolytic pathway. Our finding opens exciting possibilities for understanding the molecular mechanisms underlying LD degradation and its potential implications for inflammatory disorders.

Keywords:  ARL8B; CP: Cell biology; CP: Immunology; lipid droplet; lysosome; macrophage; microlipophagy; small GTPase

DOI:  https://doi.org/10.1016/j.celrep.2023.113203
Nat Metab. 2023 Oct 05.

Spatially resolved metabolomics and isotope tracing reveal dynamic metabolic responses of dentate granule neurons with acute stimulation.

Anne Miller, Elisa M York, Sylwia A Stopka, Juan Ramón Martínez-François, Md Amin Hossain, Gerard Baquer, Michael S Regan, Nathalie Y R Agar, Gary Yellen.

Neuronal activity creates an intense energy demand that must be met by rapid metabolic responses. To investigate metabolic adaptations in the neuron-enriched dentate granule cell (DGC) layer within its native tissue environment, we employed murine acute hippocampal brain slices, coupled with fast metabolite preservation and followed by mass spectrometry (MS) imaging, to generate spatially resolved metabolomics and isotope-tracing data. Here we show that membrane depolarization induces broad metabolic changes, including increased glycolytic activity in DGCs. Increased glucose metabolism in response to stimulation is accompanied by mobilization of endogenous inosine into pentose phosphates via the action of purine nucleotide phosphorylase (PNP). The PNP reaction is an integral part of the neuronal response to stimulation, because inhibition of PNP leaves DGCs energetically impaired during recovery from strong activation. Performing MS imaging on brain slices bridges the gap between live-cell physiology and the deep chemical analysis enabled by MS.

DOI: https://doi.org/10.1038/s42255-023-00890-z
Redox Biol. 2023 Sep 27. pii: S2213-2317(23)00309-9. [Epub ahead of print]67 102908

CysQuant: Simultaneous quantification of cysteine oxidation and protein abundance using data dependent or independent acquisition mass spectrometry.

Jingjing Huang, An Staes, Francis Impens, Vadim Demichev, Frank Van Breusegem, Kris Gevaert, Patrick Willems.

Protein cysteinyl thiols are susceptible to reduction-oxidation reactions that can influence protein function. Accurate quantification of cysteine oxidation is therefore crucial for decoding protein redox regulation. Here, we present CysQuant, a novel approach for simultaneous quantification of cysteine oxidation degrees and protein abundancies. CysQuant involves light/heavy iodoacetamide isotopologues for differential labeling of reduced and reversibly oxidized cysteines analyzed by data-dependent acquisition (DDA) or data-independent acquisition mass spectrometry (DIA-MS). Using plexDIA with in silico predicted spectral libraries, we quantified an average of 18% cysteine oxidation in Arabidopsis thaliana by DIA-MS, including a subset of highly oxidized cysteines forming disulfide bridges in AlphaFold2 predicted structures. Applying CysQuant to Arabidopsis seedlings exposed to excessive light, we successfully quantified the well-established increased reduction of Calvin-Benson cycle enzymes and discovered yet uncharacterized redox-sensitive disulfides in chloroplastic enzymes. Overall, CysQuant is a highly versatile tool for assessing the cysteine modification status that can be widely applied across various mass spectrometry platforms and organisms.

DOI: https://doi.org/10.1016/j.redox.2023.102908
Cell Metab. 2023 Sep 29. pii: S1550-4131(23)00340-6. [Epub ahead of print]

High dietary fructose promotes hepatocellular carcinoma progression by enhancing O-GlcNAcylation via microbiota-derived acetate.

Peng Zhou, Wen-Yi Chang, De-Ao Gong, Jie Xia, Wei Chen, Lu-Yi Huang, Rui Liu, Yi Liu, Chang Chen, Kai Wang, Ni Tang, Ai-Long Huang.

  Emerging studies have addressed the tumor-promoting role of fructose in different cancers. The effects and pathological mechanisms of high dietary fructose on hepatocellular carcinoma (HCC) remain unclear. Here, we examined the effects of fructose supplementation on HCC progression in wild-type C57BL/6 mice using a spontaneous and chemically induced HCC mouse model. We show that elevated uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) and O-GlcNAcylation levels induced by high dietary fructose contribute to HCC progression. Non-targeted metabolomics and stable isotope tracing revealed that under fructose treatment, microbiota-derived acetate upregulates glutamine and UDP-GlcNAc levels and enhances protein O-GlcNAcylation in HCC. Global profiling of O-GlcNAcylation revealed that hyper-O-GlcNAcylation of eukaryotic elongation factor 1A1 promotes cell proliferation and tumor growth. Targeting glutamate-ammonia ligase or O-linked N-acetylglucosamine transferase (OGT) remarkably impeded HCC progression in mice with high fructose intake. We propose that high dietary fructose promotes HCC progression through microbial acetate-induced hyper-O-GlcNAcylation.

Keywords:  GLUL; O-GlcNAcylation; acetate; eEF1A1; fructose; hepatocellular carcinoma

DOI:  https://doi.org/10.1016/j.cmet.2023.09.009
J Clin Invest. 2023 Oct 02. pii: e161348. [Epub ahead of print]133(19):

Perilipin 2-positive mononuclear phagocytes accumulate in the diabetic retina and promote PPARγ-dependent vasodegeneration.

Guillaume Blot, Rémi Karadayi, Lauriane Przegralek, Thérèse-Marie Sartoris, Hugo Charles-Messance, Sébastien Augustin, Pierre Negrier, Frédéric Blond, Frida Paulina Muñiz-Ruvalcaba, David Rivera-de la Parra, Lucile Vignaud, Aude Couturier, José-Alain Sahel, Niyazi Acar, Aida Jimenez-Corona, Cécile Delarasse, Yonathan Garfias, Florian Sennlaub, Xavier Guillonneau.

  Type 2 diabetes mellitus (T2DM), characterized by hyperglycemia and dyslipidemia, leads to nonproliferative diabetic retinopathy (NPDR). NPDR is associated with blood-retina barrier disruption, plasma exudates, microvascular degeneration, elevated inflammatory cytokine levels, and monocyte (Mo) infiltration. Whether and how the diabetes-associated changes in plasma lipid and carbohydrate levels modify Mo differentiation remains unknown. Here, we show that mononuclear phagocytes (MPs) in areas of vascular leakage in DR donor retinas expressed perilipin 2 (PLIN2), a marker of intracellular lipid load. Strong upregulation of PLIN2 was also observed when healthy donor Mos were treated with plasma from patients with T2DM or with palmitate concentrations typical of those found in T2DM plasma, but not under high-glucose conditions. PLIN2 expression correlated with the expression of other key genes involved in lipid metabolism (ACADVL, PDK4) and the DR biomarkers ANGPTL4 and CXCL8. Mechanistically, we show that lipid-exposed MPs induced capillary degeneration in ex vivo explants that was inhibited by pharmaceutical inhibition of PPARγ signaling. Our study reveals a mechanism linking dyslipidemia-induced MP polarization to the increased inflammatory cytokine levels and microvascular degeneration that characterize NPDR. This study provides comprehensive insights into the glycemia-independent activation of Mos in T2DM and identifies MP PPARγ as a target for inhibition of lipid-activated MPs in DR.

Keywords:  Diabetes; Inflammation; Macrophages; Microcirculation; Ophthalmology

DOI:  https://doi.org/10.1172/JCI161348
Nat Commun. 2023 Oct 04. 14(1): 6196

Structure of the ceramide-bound SPOTS complex.

Jan-Hannes Schäfer, Carolin Körner, Bianca M Esch, Sergej Limar, Kristian Parey, Stefan Walter, Dovile Januliene, Arne Moeller, Florian Fröhlich.

Sphingolipids are structural membrane components that also function in cellular stress responses. The serine palmitoyltransferase (SPT) catalyzes the rate-limiting step in sphingolipid biogenesis. Its activity is tightly regulated through multiple binding partners, including Tsc3, Orm proteins, ceramides, and the phosphatidylinositol-4-phosphate (PI4P) phosphatase Sac1. The structural organization and regulatory mechanisms of this complex are not yet understood. Here, we report the high-resolution cryo-EM structures of the yeast SPT in complex with Tsc3 and Orm1 (SPOT) as dimers and monomers and a monomeric complex further carrying Sac1 (SPOTS). In all complexes, the tight interaction of the downstream metabolite ceramide and Orm1 reveals the ceramide-dependent inhibition. Additionally, observation of ceramide and ergosterol binding suggests a co-regulation of sphingolipid biogenesis and sterol metabolism within the SPOTS complex.

DOI: https://doi.org/10.1038/s41467-023-41747-z
Redox Biol. 2023 Sep 26. pii: S2213-2317(23)00308-7. [Epub ahead of print]67 102907

Voltage-dependent anion channel 1 (VDAC1) overexpression alleviates cardiac fibroblast activation in cardiac fibrosis via regulating fatty acid metabolism.

Geer Tian, Junteng Zhou, Yue Quan, Qihang Kong, Junli Li, Yanguo Xin, Wenchao Wu, Xiaoqiang Tang, Xiaojing Liu.

  Cardiac fibrosis is characterized by the excessive deposition of extracellular matrix in the myocardium with cardiac fibroblast activation, leading to chronic cardiac remodeling and dysfunction. However, little is known about metabolic alterations in fibroblasts during cardiac fibrosis, and there is a lack of pharmaceutical treatments that target metabolic dysregulation. Here, we provided evidence that fatty acid β-oxidation (FAO) dysregulation contributes to fibroblast activation and cardiac fibrosis. With transcriptome, metabolome, and functional assays, we demonstrated that FAO was downregulated during fibroblast activation and cardiac fibrosis, and that perturbation of FAO reversely affected the fibroblast-to-myofibroblast transition. The decrease in FAO may be attributed to reduced long-chain fatty acid (LCFA) uptake. Voltage-dependent anion channel 1 (VDAC1), the main gatekeeper of the outer mitochondrial membrane (OMM), serves as the transporter of LCFA into the mitochondria for further utilization and has been shown to be decreased in myofibroblasts. In vitro, the addition of exogenous VDAC1 was shown to ameliorate cardiac fibroblast activation initiated by transforming growth factor beta 1 (TGF-β1) stimuli, and silencing of VDAC1 displayed the opposite effect. A mechanistic study revealed that VDAC1 exerts a protective effect by regulating LCFA uptake into the mitochondria, which is impaired by an inhibitor of carnitine palmitoyltransferase 1A. In vivo, AAV9-mediated overexpression of VDAC1 in myofibroblasts significantly alleviated transverse aortic constriction (TAC)-induced cardiac fibrosis and rescued cardiac function in mice. Finally, we treated mice with the VDAC1-derived R-Tf-D-LP4 peptide, and the results showed that R-Tf-D-LP4 prevented TAC-induced cardiac fibrosis and dysfunction in mice. In conclusion, this study provides evidence that VDAC1 maintains FAO metabolism in cardiac fibroblasts to repress fibroblast activation and cardiac fibrosis and suggests that the VDAC1 peptide is a promising drug for rescuing fibroblast metabolism and repressing cardiac fibrosis.

Keywords:  Cardiac fibroblasts; Cardiac fibrosis; Fatty acid metabolism; Voltage-dependent anion channel 1 (VDAC1)

DOI:  https://doi.org/10.1016/j.redox.2023.102907
Nat Metab. 2023 Oct 02.

A subpopulation of lipogenic brown adipocytes drives thermogenic memory.

Patrick Lundgren, Prateek V Sharma, Lenka Dohnalová, Kyle Coleman, Giulia T Uhr, Susanna Kircher, Lev Litichevskiy, Klaas Bahnsen, Hélène C Descamps, Christina Demetriadou, Jacqueline Chan, Karthikeyani Chellappa, Timothy O Cox, Yael Heyman, Sarshan R Pather, Clarissa Shoffler, Christopher Petucci, Ophir Shalem, Arjun Raj, Joseph A Baur, Nathaniel W Snyder, Kathryn E Wellen, Maayan Levy, Patrick Seale, Mingyao Li, Christoph A Thaiss.

Sustained responses to transient environmental stimuli are important for survival. The mechanisms underlying long-term adaptations to temporary shifts in abiotic factors remain incompletely understood. Here, we find that transient cold exposure leads to sustained transcriptional and metabolic adaptations in brown adipose tissue, which improve thermogenic responses to secondary cold encounter. Primary thermogenic challenge triggers the delayed induction of a lipid biosynthesis programme even after cessation of the original stimulus, which protects from subsequent exposures. Single-nucleus RNA sequencing and spatial transcriptomics reveal that this response is driven by a lipogenic subpopulation of brown adipocytes localized along the perimeter of Ucp1hi adipocytes. This lipogenic programme is associated with the production of acylcarnitines, and supplementation of acylcarnitines is sufficient to recapitulate improved secondary cold responses. Overall, our data highlight the importance of heterogenous brown adipocyte populations for 'thermogenic memory', which may have therapeutic implications for leveraging short-term thermogenesis to counteract obesity.

DOI: https://doi.org/10.1038/s42255-023-00893-w
EMBO J. 2023 Oct 02. e114032

Hypoxia activates SREBP2 through Golgi disassembly in bone marrow-derived monocytes for enhanced tumor growth.

Ryuichi Nakahara, Sho Aki, Maki Sugaya, Haruka Hirose, Miki Kato, Keisuke Maeda, Daichi M Sakamoto, Yasuhiro Kojima, Miyuki Nishida, Ritsuko Ando, Masashi Muramatsu, Melvin Pan, Rika Tsuchida, Yoshihiro Matsumura, Hideyuki Yanai, Hiroshi Takano, Ryoji Yao, Shinsuke Sando, Masabumi Shibuya, Juro Sakai, Tatsuhiko Kodama, Hiroyasu Kidoya, Teppei Shimamura, Tsuyoshi Osawa.

  Bone marrow-derived cells (BMDCs) infiltrate hypoxic tumors at a pre-angiogenic state and differentiate into mature macrophages, thereby inducing pro-tumorigenic immunity. A critical factor regulating this differentiation is activation of SREBP2-a well-known transcription factor participating in tumorigenesis progression-through unknown cellular mechanisms. Here, we show that hypoxia-induced Golgi disassembly and Golgi-ER fusion in monocytic myeloid cells result in nuclear translocation and activation of SREBP2 in a SCAP-independent manner. Notably, hypoxia-induced SREBP2 activation was only observed in an immature lineage of bone marrow-derived cells. Single-cell RNA-seq analysis revealed that SREBP2-mediated cholesterol biosynthesis was upregulated in HSCs and monocytes but not in macrophages in the hypoxic bone marrow niche. Moreover, inhibition of cholesterol biosynthesis impaired tumor growth through suppression of pro-tumorigenic immunity and angiogenesis. Thus, our findings indicate that Golgi-ER fusion regulates SREBP2-mediated metabolic alteration in lineage-specific BMDCs under hypoxia for tumor progression.

Keywords:  Golgi-ER fusion; SREBP2; cholesterol biosynthesis; hypoxia; myeloid differentiation

DOI:  https://doi.org/10.15252/embj.2023114032
Cell Host Microbe. 2023 Sep 28. pii: S1931-3128(23)00369-4. [Epub ahead of print]

An early-life microbiota metabolite protects against obesity by regulating intestinal lipid metabolism.

Catherine D Shelton, Elizabeth Sing, Jessica Mo, Nicolas G Shealy, Woongjae Yoo, Julia Thomas, Gillian N Fitz, Pollyana R Castro, Tara T Hickman, Teresa P Torres, Nora J Foegeding, Jacob K Zieba, M Wade Calcutt, Simona G Codreanu, Stacy D Sherrod, John A McLean, Sun H Peck, Fan Yang, Nicholas O Markham, Min Liu, Mariana X Byndloss.

  The mechanisms by which the early-life microbiota protects against environmental factors that promote childhood obesity remain largely unknown. Using a mouse model in which young mice are simultaneously exposed to antibiotics and a high-fat (HF) diet, we show that Lactobacillus species, predominant members of the small intestine (SI) microbiota, regulate intestinal epithelial cells (IECs) to limit diet-induced obesity during early life. A Lactobacillus-derived metabolite, phenyllactic acid (PLA), protects against metabolic dysfunction caused by early-life exposure to antibiotics and a HF diet by increasing the abundance of peroxisome proliferator-activated receptor γ (PPAR-γ) in SI IECs. Therefore, PLA is a microbiota-derived metabolite that activates protective pathways in the small intestinal epithelium to regulate intestinal lipid metabolism and prevent antibiotic-associated obesity during early life.

Keywords:  Lactobacillus; antibiotics; arachnoid barrier; brain fibroblasts; early-life; intestinal epithelium; leptomeninges; metabolism; microbiota; obesity; single-cell RNA sequencing; tricellular junction

DOI:  https://doi.org/10.1016/j.chom.2023.09.002
Nat Commun. 2023 Oct 06. 14(1): 6246

Decreased liver B vitamin-related enzymes as a metabolic hallmark of cancer cachexia.

Yasushi Kojima, Emi Mishiro-Sato, Teruaki Fujishita, Kiyotoshi Satoh, Rie Kajino-Sakamoto, Isao Oze, Kazuki Nozawa, Yukiya Narita, Takatsugu Ogata, Keitaro Matsuo, Kei Muro, Makoto Mark Taketo, Tomoyoshi Soga, Masahiro Aoki.

Cancer cachexia is a complex metabolic disorder accounting for ~20% of cancer-related deaths, yet its metabolic landscape remains unexplored. Here, we report a decrease in B vitamin-related liver enzymes as a hallmark of systemic metabolic changes occurring in cancer cachexia. Metabolomics of multiple mouse models highlights cachexia-associated reductions of niacin, vitamin B6, and a glycine-related subset of one-carbon (C1) metabolites in the liver. Integration of proteomics and metabolomics reveals that liver enzymes related to niacin, vitamin B6, and glycine-related C1 enzymes dependent on B vitamins decrease linearly with their associated metabolites, likely reflecting stoichiometric cofactor-enzyme interactions. The decrease of B vitamin-related enzymes is also found to depend on protein abundance and cofactor subtype. These metabolic/proteomic changes and decreased protein malonylation, another cachexia feature identified by protein post-translational modification analysis, are reflected in blood samples from mouse models and gastric cancer patients with cachexia, underscoring the clinical relevance of our findings.

DOI: https://doi.org/10.1038/s41467-023-41952-w
Anal Chem. 2023 Oct 06.

Spatially Resolved Metabolomics Combined with the 3D Tumor-Immune Cell Coculture Spheroid Highlights Metabolic Alterations during Antitumor Immune Response.

Panpan Chen, Yuhao Han, Lei Wang, Yurong Zheng, Zihan Zhu, Yuan Zhao, Mingqi Zhang, Xiangfeng Chen, Xiao Wang, Chenglong Sun.

The metabolic cross-talk between tumor and immune cells plays key roles in immune cell function and immune checkpoint blockade therapy. However, the characterization of tumor immunometabolism and its spatiotemporal alterations during immune response in a complex tumor microenvironment is challenging. Here, a 3D tumor-immune cell coculture spheroid model was developed to mimic tumor-immune interactions, combined with mass spectrometry imaging-based spatially resolved metabolomics to visualize tumor immunometabolic alterations during immune response. The inhibition of T cells was simulated by coculturing breast tumor spheroids with Jurkat T cells, and the reactivation of T cells can be monitored through diminishing cancer PD-L1 expressions by berberine. This system enables simultaneously screening and imaging discriminatory metabolites that are altered during T cell-mediated antitumor immune response and characterizing the distributions of berberine and its metabolites in tumor spheroids. We discovered that the transport and catabolism of glutamine were significantly reprogrammed during the antitumor immune response at both metabolite and enzyme levels, corresponding to its indispensable roles in energy metabolism and building new biomass. The combination of spatially resolved metabolomics with the 3D tumor-immune cell coculture spheroid visually reveals metabolic interactions between tumor and immune cells and possibly helps decipher the role of immunometabolic alterations in tumor immunotherapy.

DOI: https://doi.org/10.1021/acs.analchem.2c05734
Nat Commun. 2023 Oct 05. 14(1): 6208

Acetylation-dependent coupling between G6PD activity and apoptotic signaling.

Fang Wu, Natali H Muskat, Inbar Dvilansky, Omri Koren, Anat Shahar, Roi Gazit, Natalie Elia, Eyal Arbely.

Lysine acetylation has been discovered in thousands of non-histone human proteins, including most metabolic enzymes. Deciphering the functions of acetylation is key to understanding how metabolic cues mediate metabolic enzyme regulation and cellular signaling. Glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the pentose phosphate pathway, is acetylated on multiple lysine residues. Using site-specifically acetylated G6PD, we show that acetylation can activate (AcK89) and inhibit (AcK403) G6PD. Acetylation-dependent inactivation is explained by structural studies showing distortion of the dimeric structure and active site of G6PD. We provide evidence for acetylation-dependent K95/97 ubiquitylation of G6PD and Y503 phosphorylation, as well as interaction with p53 and induction of early apoptotic events. Notably, we found that the acetylation of a single lysine residue coordinates diverse acetylation-dependent processes. Our data provide an example of the complex roles of acetylation as a posttranslational modification that orchestrates the regulation of enzymatic activity, posttranslational modifications, and apoptotic signaling.

DOI: https://doi.org/10.1038/s41467-023-41895-2
Sci Rep. 2023 09 30. 13(1): 16452

Raman spectroscopy and mass spectrometry identifies a unique group of epidermal lipids in active discoid lupus erythematosus.

Hannah U Holtkamp, Claude Aguergaray, Kalita Prangnell, Christopher Pook, Satya Amirapu, Angus Grey, Cather Simpson, Michel Nieuwoudt, Paul Jarrett.

Discoid lupus erythematosus (DLE) is the most common form of cutaneous lupus1. It can cause permanent scarring. The pathophysiology of is not fully understood. Plasmacytoid dendritic cells are found in close association with apoptotic keratinocytes inferring close cellular signalling. Matrix Associated Laser Desorption Ionisation (MALDI) combined with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) is an exquisitely sensitive combination to examine disease processes at the cellular and molecular level. Active areas of discoid lupus erythematosus were compared with normal perilesional skin using MALDI combined with FT-ICR-MS. A unique set of biomarkers, including epidermal lipids is identified in active discoid lupus. These were assigned as sphingomyelins, phospholipids and ceramides. Additionally, increased levels of proteins from the keratin, and small proline rich family, and aromatic amino acids (tryptophan, phenylalanine, and tyrosine) in the epidermis are observed. These techniques, applied to punch biopsies of the skin, have shown a distinctive lipid profile of active discoid lupus. This profile may indicate specific lipid signalling pathways. Lipid rich microdomains (known as lipid rafts) are involved in cell signalling and lipid abnormalities have been described with systemic lupus erythematosus which correlate with disease activity.

DOI: https://doi.org/10.1038/s41598-023-43331-3