bims-mepmim 2023-11-12 papers

bims-mepmim

Biomed News

on Metabolites in pathological microenvironments and immunometabolism

Issue of 2023–11–12
33 papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

Effects of hepatic mitochondrial pyruvate carrier deficiency on de novo lipogenesis and gluconeogenesis in mice.
Vitamin B5 supports MYC oncogenic metabolism and tumor progression in breast cancer.
Metabolic dependencies of metastasis-initiating cells in female breast cancer.
The inhibition of inner mitochondrial fusion in hepatocytes reduces NAFL and improves metabolic profile during obesity by modulating bile acid conjugation.
IL-6/JAK2-dependent G6PD phosphorylation promotes nucleotide synthesis and supports tumor growth.
Immuno-metabolic dendritic cell vaccine signatures associate with overall survival in vaccinated melanoma patients.
Spatial and single-cell profiling of the metabolome, transcriptome and epigenome of the aging mouse liver.
Fumarate hydratase as a metabolic regulator of immunity.
Hepatic palmitoyl-proteomes and acyl-protein thioesterase protein proximity networks link lipid modification and mitochondria.
Glial metabolism checkpoints memory.
MicroRNA-206-3p suppresses hepatic lipogenesis and cholesterol synthesis while driving cholesterol efflux.
Pharmacologic activation of a compensatory integrated stress response kinase promotes mitochondrial remodeling in PERK-deficient cells.
PDP1 is a key metabolic gatekeeper and modulator of drug resistance in FLT3-ITD-positive acute myeloid leukemia.
Inflammation-induced TRIM21 represses hepatic steatosis by promoting the ubiquitination of lipogenic regulators.
Spatially resolved mapping of proteome turnover dynamics with subcellular precision.
Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation.
The Role of KLF2 in Regulating Hepatic Lipogenesis and Blood Cholesterol Homeostasis via the SCAP/SREBP Pathway.
Breast adipose tissue-derived extracellular vesicles from obese women alter tumor cell metabolism.
A Guide to Ferroptosis, the biological rust of cellular membranes.
Transcriptomes and metabolism define mouse and human MAIT cell populations.
Tissue-resident B cells orchestrate macrophage polarisation and function.
Palmitoylation-Dependent Regulation of Cardiomyocyte Rac1 Signaling Activity and Minor Effects on Cardiac Hypertrophy.
Aster-dependent nonvesicular transport facilitates dietary cholesterol uptake.
Colonic macrophages eat and feed.
The bidirectional immune crosstalk in metabolic dysfunction-associated steatotic liver disease.
NRF2 is essential for adaptative browning of white adipocytes.
A role for the cystathionine-β-synthase /H2S axis in astrocyte dysfunction in the aging brain.
Glucose-dependent insulinotropic polypeptide regulates body weight and food intake via GABAergic neurons in mice.
Skeletal muscle-derived extracellular vesicles transport glycolytic enzymes to mediate muscle-to-bone crosstalk.
Loss of ADAR1 in macrophages in combination with interferon gamma suppresses tumor growth by remodeling the tumor microenvironment.
Glutamate secretion by embryonic stem cells as an autocrine signal to promote proliferation.
Failure to apply standard limit-of-detection or limit-of-quantitation criteria to specialized pro-resolving mediator analysis incorrectly characterizes their presence in biological samples.
Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter.

iScience. 2023 Nov 17. 26(11): 108196

Effects of hepatic mitochondrial pyruvate carrier deficiency on de novo lipogenesis and gluconeogenesis in mice.

Nicole K H Yiew, Stanislaw Deja, Daniel Ferguson, Kevin Cho, Chaowapong Jarasvaraparn, Miriam Jacome-Sosa, Andrew J Lutkewitte, Sandip Mukherjee, Xiaorong Fu, Jason M Singer, Gary J Patti, Shawn C Burgess, Brian N Finck.

  The liver coordinates the systemic response to nutrient deprivation and availability by producing glucose from gluconeogenesis during fasting and synthesizing lipids via de novo lipogenesis (DNL) when carbohydrates are abundant. Mitochondrial pyruvate metabolism is thought to play important roles in both gluconeogenesis and DNL. We examined the effects of hepatocyte-specific mitochondrial pyruvate carrier (MPC) deletion on the fasting-refeeding response. Rates of DNL during refeeding were impaired by hepatocyte MPC deletion, but this did not reduce intrahepatic lipid content. During fasting, glycerol is converted to glucose by two pathways; a direct cytosolic pathway and an indirect mitochondrial pathway requiring the MPC. Hepatocyte MPC deletion reduced the incorporation of 13C-glycerol into TCA cycle metabolites, but not into new glucose. Furthermore, suppression of glycerol and alanine metabolism did not affect glucose concentrations in fasted hepatocyte-specific MPC-deficient mice, suggesting multiple layers of redundancy in glycemic control in mice.

Keywords:  Cellular physiology; Human metabolism

DOI:  https://doi.org/10.1016/j.isci.2023.108196
Nat Metab. 2023 Nov 09.

Vitamin B5 supports MYC oncogenic metabolism and tumor progression in breast cancer.

CRUK Rosetta Grand Challenge Consortium

Tumors are intrinsically heterogeneous and it is well established that this directs their evolution, hinders their classification and frustrates therapy1-3. Consequently, spatially resolved omics-level analyses are gaining traction4-9. Despite considerable therapeutic interest, tumor metabolism has been lagging behind this development and there is a paucity of data regarding its spatial organization. To address this shortcoming, we set out to study the local metabolic effects of the oncogene c-MYC, a pleiotropic transcription factor that accumulates with tumor progression and influences metabolism10,11. Through correlative mass spectrometry imaging, we show that pantothenic acid (vitamin B5) associates with MYC-high areas within both human and murine mammary tumors, where its conversion to coenzyme A fuels Krebs cycle activity. Mechanistically, we show that this is accomplished by MYC-mediated upregulation of its multivitamin transporter SLC5A6. Notably, we show that SLC5A6 over-expression alone can induce increased cell growth and a shift toward biosynthesis, whereas conversely, dietary restriction of pantothenic acid leads to a reversal of many MYC-mediated metabolic changes and results in hampered tumor growth. Our work thus establishes the availability of vitamins and cofactors as a potential bottleneck in tumor progression, which can be exploited therapeutically. Overall, we show that a spatial understanding of local metabolism facilitates the identification of clinically relevant, tractable metabolic targets.

DOI: https://doi.org/10.1038/s42255-023-00915-7
Nat Commun. 2023 Nov 04. 14(1): 7076

Metabolic dependencies of metastasis-initiating cells in female breast cancer.

C Megan Young, Laurent Beziaud, Pierre Dessen, Angela Madurga Alonso, Albert Santamaria-Martínez, Joerg Huelsken.

Understanding the mechanisms that enable cancer cells to metastasize is essential in preventing cancer progression. Here we examine the metabolic adaptations of metastasis-initiating cells (MICs) in female breast cancer and how those shape their metastatic phenotype. We find that endogenous MICs depend on the oxidative tricarboxylic acid cycle and fatty acid usage. Sorting tumor cells based upon solely mitochondrial membrane potential or lipid storage is sufficient at identifying MICs. We further identify that mitochondrially-generated citrate is exported to the cytoplasm to yield acetyl-CoA, and this is crucial to maintaining heightened levels of H3K27ac in MICs. Blocking acetyl-CoA generating pathways or H3K27ac-specific epigenetic writers and readers reduces expression of epithelial-to-mesenchymal related genes, MIC frequency, and metastatic potential. Exogenous supplementation of a short chain carboxylic acid, acetate, increases MIC frequency and metastasis. In patient cohorts, we observe that higher expression of oxidative phosphorylation related genes is associated with reduced distant relapse-free survival. These data demonstrate that MICs specifically and precisely alter their metabolism to efficiently colonize distant organs.

DOI: https://doi.org/10.1038/s41467-023-42748-8
Cardiovasc Res. 2023 Oct 31. pii: cvad169. [Epub ahead of print]

The inhibition of inner mitochondrial fusion in hepatocytes reduces NAFL and improves metabolic profile during obesity by modulating bile acid conjugation.

Lorenzo Da Dalt, Annalisa Moregola, Monika Svecla, Silvia Pedretti, Francesca Fantini, Mirko Ronzio, Patrizia Uboldi, Diletta Dolfini, Elena Donetti, Andrea Baragetti, Nico Mitro, Luca Scorrano, Giuseppe Danilo Norata.

   BACKGROUND AND AIM: Mitochondria are plastic organelles that continuously undergo biogenesis, fusion, fission, and mitophagy to control cellular energy metabolism, calcium homeostasis, hormones, sterols and bile acids (BAs) synthesis. Here we evaluated how the impairment of mitochondrial fusion in hepatocytes affect diet induced liver steatosis and obesity.
METHODS AND RESULTS: Male mice selectively lacking the key protein involved in inner mitochondrial fusion, OPA1, (OPA1ΔHep) on a High Fat Diet (HFD) for 20 weeks. OPA1ΔHep mice were protected from the development of hepatic steatosis and obesity because of reduced lipid absorption; a profile which was accompanied by increased respiratory exchange ratio in vivo, suggesting a preference for carbohydrate in OPA1ΔHep in agreement with the defect in mitochondrial fusion. At the molecular level, this phenotype emerged as a consequence of poor mitochondrial-peroxisome-ER tethering in OPA1 deficient hepatocytes thus impairing bile acid conjugation and therefore its release in the bile, thus impacting lipid absorption from the diet. Concordantly the liver of NAFLD subjects presented an increased expression of OPA1 and of the network of proteins involved in mitochondrial when compared to controls.
CONCLUSION: Patients with NAFLD present increased expression of proteins involved in mitochondrial fusion in the liver. The selective inhibition of liver mitochondrial fusion observed in hepatocyte OPA1 deficient mice protects mice from HFD-induced metabolic dysfunction by reducing lipid dietary absorption and bile acid secretion as a consequence of reduced liver mitochondria-peroxisome-ER tethering.

Keywords:  Bile Acids; Dietary Lipid Absorption; Liver; Mitochondria

DOI:  https://doi.org/10.1093/cvr/cvad169
Mol Metab. 2023 Nov 08. pii: S2212-8778(23)00170-9. [Epub ahead of print] 101836

IL-6/JAK2-dependent G6PD phosphorylation promotes nucleotide synthesis and supports tumor growth.

Xuemei Qiu, Hongping Ye, Xiaofei Li, Dan Li, Lu Jiang, Rui Liu, Zhe Zhao, Dan He.

  Tumor cells hijack inflammatory mechanisms to promote their own growth. IL-6 is one of the major cytokines, and is frequently upregulated in tumors. The pentose phosphate pathway (PPP) generates the indispensable building blocks to produce various nucleotides. However, whether and how PPP is timely tuned in response to IL-6 to support tumor growth remains largely unknown. Here we show that the metabolic flux of PPP and enzymatic activity of glucose-6-phosphate dehydrogenase (G6PD) is rapidly induced under IL-6 treatment, without obvious changes in G6PD expression level. Mechanistically, Janus kinase 2 (JAK2) phosphorylates G6PD Y437 under IL-6 treatment, which accentuates G6PD enzymatic activity by promoting G6PD binding with its substrate G6P. Further, JAK2-dependent G6PD Y437 phosphorylation is required for IL-6-induced nucleotide biosynthesis and tumor cell proliferation, and is associated with the progression of oral squamous cell carcinoma. Our findings report a new mechanism implicated in the crosstalk between tumor cells and inflammatory microenvironment, by which JAK2-dependent activation of G6PD governs nucleotide synthesis to support tumor cell proliferation, thereby highlighting its value as a potential anti-tumor target.

Keywords:  G6PD; JAK2; nucleotide metabolism; pentose phosphate pathway; tumorigenesis

DOI:  https://doi.org/10.1016/j.molmet.2023.101836
Nat Commun. 2023 Nov 08. 14(1): 7211

Immuno-metabolic dendritic cell vaccine signatures associate with overall survival in vaccinated melanoma patients.

Juraj Adamik, Paul V Munson, Deena M Maurer, Felix J Hartmann, Sean C Bendall, Rafael J Argüello, Lisa H Butterfield.

Efficacy of cancer vaccines remains low and mechanistic understanding of antigen presenting cell function in cancer may improve vaccine design and outcomes. Here, we analyze the transcriptomic and immune-metabolic profiles of Dendritic Cells (DCs) from 35 subjects enrolled in a trial of DC vaccines in late-stage melanoma (NCT01622933). Multiple platforms identify metabolism as an important biomarker of DC function and patient overall survival (OS). We demonstrate multiple immune and metabolic gene expression pathway alterations, a functional decrease in OCR/OXPHOS and increase in ECAR/glycolysis in patient vaccines. To dissect molecular mechanisms, we utilize single cell SCENITH functional profiling and show patient clinical outcomes (OS) correlate with DC metabolic profile, and that metabolism is linked to immune phenotype. With single cell metabolic regulome profiling, we show that MCT1 (monocarboxylate transporter-1), a lactate transporter, is increased in patient DCs, as is glucose uptake and lactate secretion. Importantly, pre-vaccination circulating myeloid cells in patients used as precursors for DC vaccine generation are significantly skewed metabolically as are several DC subsets. Together, we demonstrate that the metabolic profile of DC is tightly associated with the immunostimulatory potential of DC vaccines from cancer patients. We link phenotypic and functional metabolic changes to immune signatures that correspond to suppressed DC differentiation.

DOI: https://doi.org/10.1038/s41467-023-42881-4
Nat Aging. 2023 Nov 09.

Spatial and single-cell profiling of the metabolome, transcriptome and epigenome of the aging mouse liver.

Chrysa Nikopoulou, Niklas Kleinenkuhnen, Swati Parekh, Tonantzi Sandoval, Christoph Ziegenhain, Farina Schneider, Patrick Giavalisco, Kat-Folz Donahue, Anna Juliane Vesting, Marcel Kirchner, Mihaela Bozukova, Christian Vossen, Janine Altmüller, Thomas Wunderlich, Rickard Sandberg, Vangelis Kondylis, Achim Tresch, Peter Tessarz.

Tissues within an organism and even cell types within a tissue can age with different velocities. However, it is unclear whether cells of one type experience different aging trajectories within a tissue depending on their spatial location. Here, we used spatial transcriptomics in combination with single-cell ATAC-seq and RNA-seq, lipidomics and functional assays to address how cells in the male murine liver are affected by age-related changes in the microenvironment. Integration of the datasets revealed zonation-specific and age-related changes in metabolic states, the epigenome and transcriptome. The epigenome changed in a zonation-dependent manner and functionally, periportal hepatocytes were characterized by decreased mitochondrial fitness, whereas pericentral hepatocytes accumulated large lipid droplets. Together, we provide evidence that changing microenvironments within a tissue exert strong influences on their resident cells that can shape epigenetic, metabolic and phenotypic outputs.

DOI: https://doi.org/10.1038/s43587-023-00513-y
Trends Cell Biol. 2023 Nov 06. pii: S0962-8924(23)00209-X. [Epub ahead of print]

Fumarate hydratase as a metabolic regulator of immunity.

Christian G Peace, Shane M O'Carroll, Luke A J O'Neill.

  Tricarboxylic acid (TCA) cycle metabolites have been implicated in modulating signalling pathways in immune cells. Notable examples include succinate and itaconate, which have pro- and anti-inflammatory roles, respectively. Recently, fumarate has emerged as having specific roles in macrophage activation, regulating the production of such cytokines as interleukin (IL)-10 and type I interferons (IFNs). Fumarate hydratase (FH) has been identified as a control point. Notably, FH loss in different models and cell types has been found to lead to DNA and RNA release from mitochondria which are sensed by cytosolic nucleic acid sensors including retinoic acid-inducible gene (RIG)-I, melanoma differentiation-associated protein (MDA)5, and cyclic GMP-AMP synthase (cGAS) to upregulate IFN-β production. These findings may have relevance in the pathogenesis and treatment of diseases associated with decreased FH levels such as systemic lupus erythematosus (SLE) or FH-deficient kidney cancer.

Keywords:  immunometabolism; innate immunity; interferon; mitochondria

DOI:  https://doi.org/10.1016/j.tcb.2023.10.005
Cell Rep. 2023 Nov 04. pii: S2211-1247(23)01401-8. [Epub ahead of print]42(11): 113389

Hepatic palmitoyl-proteomes and acyl-protein thioesterase protein proximity networks link lipid modification and mitochondria.

Sarah L Speck, Dhaval P Bhatt, Qiang Zhang, Sangeeta Adak, Li Yin, Guifang Dong, Chu Feng, Wei Zhang, M Ben Major, Xiaochao Wei, Clay F Semenkovich.

  Acyl-protein thioesterases 1 and 2 (APT1 and APT2) reverse S-acylation, a potential regulator of systemic glucose metabolism in mammals. Palmitoylation proteomics in liver-specific knockout mice shows that APT1 predominates over APT2, primarily depalmitoylating mitochondrial proteins, including proteins linked to glutamine metabolism. miniTurbo-facilitated determination of the protein-protein proximity network of APT1 and APT2 in HepG2 cells reveals APT proximity networks encompassing mitochondrial proteins including the major translocases Tomm20 and Timm44. APT1 also interacts with Slc1a5 (ASCT2), the only glutamine transporter known to localize to mitochondria. High-fat-diet-fed male mice with dual (but not single) hepatic deletion of APT1 and APT2 have insulin resistance, fasting hyperglycemia, increased glutamine-driven gluconeogenesis, and decreased liver mass. These data suggest that APT1 and APT2 regulation of hepatic glucose metabolism and insulin signaling is functionally redundant. Identification of substrates and protein-protein proximity networks for APT1 and APT2 establishes a framework for defining mechanisms underlying metabolic disease.

Keywords:  CP: Metabolism; acyl-protein thioesterase 1; acyl-protein thioesterase 2; gluconeogenesis; glutamine; insulin; liver; palmitoylation; proximity labeling

DOI:  https://doi.org/10.1016/j.celrep.2023.113389
Nat Metab. 2023 Nov 06.

Glial metabolism checkpoints memory.

L Felipe Barros.

DOI: https://doi.org/10.1038/s42255-023-00886-9
Hepatology. 2023 Nov 09.

MicroRNA-206-3p suppresses hepatic lipogenesis and cholesterol synthesis while driving cholesterol efflux.

Ningning Liu, Jing Tian, Clifford J Steer, Qinghua Han, Guisheng Song.

BACKGROUND AND AIMS: Hepatosteatosis, hypertriglyceridemia, and hypertriglyceridemia are interconnected metabolic disorders. This study is designed to characterize how microRNA-206-3p (miR-206) simultaneously prevents de novo lipogenesis (DNL), cholesterol synthesis, and VLDL production in hepatocytes while promoting cholesterol efflux in macrophages.
APPROACH AND RESULTS: MiR-206 levels were reduced in hepatocytes and macrophages of mice subjected to a high-fat, high-cholesterol diet (HFHC). A negative feedback between LXRα (liver X receptor) and miR-206 is formed to maintain high LXRα and low miR-206 in hepatocytes. Systemic administration of miR-206 alleviated hepatosteatosis, hypertriglyceridemia and hypercholesterolemia in mice. A significant reduction in LDL-cholesterol and VLDL-cholesterol but unaltered HDL-cholesterol was observed in miR-206-treated mice. Mirroring these findings, miR-206 reprogrammed the transcriptome of hepatocytes towards inhibition of DNL, cholesterol synthesis, and assembly and secretion of VLDL. In macrophages, miR-206 activated expression of genes regulating cholesterol efflux. Hepatocyte-specific expression of miR-206 reduced hepatic and circulating triglycerides and cholesterol as well as VLDL production, while transplantation of macrophages bearing miR-206 facilitated cholesterol efflux. Mechanistically, miR-206 directly targeted Lxrα and Hmgcr in hepatocytes but facilitated expression of Lxrα in macrophages by targeting macrophage-specific TRPS1 (tricho-rhino-phalangeal syndrome 1), a transcription repressor of Lxrα. By targeting Hmgcr and Lxrα, miR-206 inhibited DNL, VLDL production and cholesterol synthesis in hepatocytes, whereas it drove cholesterol efflux by activating the TRPS1-LXRα axis.
CONCLUSIONS: MiR-206, through differentially modulating LXRα signaling in hepatocytes and macrophages, inhibits DNL, promotes cholesterol efflux, and concurrently hinders cholesterol synthesis and VLDL production. MiR-206 simulates the functions of lipid-lowering medications, statins and LXRα agonists.

DOI: https://doi.org/10.1097/HEP.0000000000000672
Cell Chem Biol. 2023 Oct 26. pii: S2451-9456(23)00367-7. [Epub ahead of print]

Pharmacologic activation of a compensatory integrated stress response kinase promotes mitochondrial remodeling in PERK-deficient cells.

Valerie Perea, Kelsey R Baron, Vivian Dolina, Giovanni Aviles, Grace Kim, Jessica D Rosarda, Xiaoyan Guo, Martin Kampmann, R Luke Wiseman.

  The integrated stress response (ISR) comprises the eIF2α kinases PERK, GCN2, HRI, and PKR, which induce translational and transcriptional signaling in response to diverse insults. Deficiencies in PERK signaling lead to mitochondrial dysfunction and contribute to the pathogenesis of numerous diseases. We define the potential for pharmacologic activation of compensatory eIF2α kinases to rescue ISR signaling and promote mitochondrial adaptation in PERK-deficient cells. We show that the HRI activator BtdCPU and GCN2 activator halofuginone promote ISR signaling and rescue ER stress sensitivity in PERK-deficient cells. However, BtdCPU induces mitochondrial depolarization, leading to mitochondrial fragmentation and activation of the OMA1-DELE1-HRI signaling axis. In contrast, halofuginone promotes mitochondrial elongation and adaptive mitochondrial respiration, mimicking regulation induced by PERK. This shows halofuginone can compensate for deficiencies in PERK signaling and promote adaptive mitochondrial remodeling, highlighting the potential for pharmacologic ISR activation to mitigate mitochondrial dysfunction and motivating the pursuit of highly selective ISR activators.

Keywords:  ISR; UPR; integrated stress response; pharmacologic activator; stress-responsive signaling pathway; unfolded protein response

DOI:  https://doi.org/10.1016/j.chembiol.2023.10.006
Leukemia. 2023 Nov 07.

PDP1 is a key metabolic gatekeeper and modulator of drug resistance in FLT3-ITD-positive acute myeloid leukemia.

Islam Alshamleh, Nina Kurrle, Philipp Makowka, Raj Bhayadia, Rahul Kumar, Sebastian Süsser, Marcel Seibert, Damian Ludig, Sebastian Wolf, Sebastian E Koschade, Karoline Stoschek, Johanna Kreitz, Dominik C Fuhrmann, Rosa Toenges, Marco Notaro, Federico Comoglio, Jan Jacob Schuringa, Tobias Berg, Bernhard Brüne, Daniela S Krause, Jan-Henning Klusmann, Thomas Oellerich, Frank Schnütgen, Harald Schwalbe, Hubert Serve.

High metabolic flexibility is pivotal for the persistence and therapy resistance of acute myeloid leukemia (AML). In 20-30% of AML patients, activating mutations of FLT3, specifically FLT3-ITD, are key therapeutic targets. Here, we investigated the influence of FLT3-ITD on AML metabolism. Nuclear Magnetic Resonance (NMR) profiling showed enhanced reshuffling of pyruvate towards the tricarboxylic acid (TCA) cycle, suggesting an increased activity of the pyruvate dehydrogenase complex (PDC). Consistently, FLT3-ITD-positive cells expressed high levels of PDP1, an activator of the PDC. Combining endogenous tagging of PDP1 with genome-wide CRISPR screens revealed that FLT3-ITD induces PDP1 expression through the RAS signaling axis. PDP1 knockdown resulted in reduced cellular respiration thereby impairing the proliferation of only FLT3-ITD cells. These cells continued to depend on PDP1, even in hypoxic conditions, and unlike FLT3-ITD-negative cells, they exhibited a rapid, PDP1-dependent revival of their respiratory capacity during reoxygenation. Moreover, we show that PDP1 modifies the response to FLT3 inhibition. Upon incubation with the FLT3 tyrosine kinase inhibitor quizartinib (AC220), PDP1 persisted or was upregulated, resulting in a further shift of glucose/pyruvate metabolism towards the TCA cycle. Overexpression of PDP1 enhanced, while PDP1 depletion diminished AC220 resistance in cell lines and peripheral blasts from an AC220-resistant AML patient in vivo. In conclusion, FLT3-ITD assures the expression of PDP1, a pivotal metabolic regulator that enhances oxidative glucose metabolism and drug resistance. Hence, PDP1 emerges as a potentially targetable vulnerability in the management of AML.

DOI: https://doi.org/10.1038/s41375-023-02041-5
JCI Insight. 2023 Nov 08. pii: e164694. [Epub ahead of print]8(21):

Inflammation-induced TRIM21 represses hepatic steatosis by promoting the ubiquitination of lipogenic regulators.

Kostas C Nikolaou, Svenja Godbersen, Muthiah Manoharan, Stefan Wieland, Markus H Heim, Markus Stoffel.

  Nonalcoholic steatohepatitis (NASH) is a leading cause for chronic liver diseases. Current therapeutic options are limited due to an incomplete mechanistic understanding of how steatosis transitions to NASH. Here we show that the TRIM21 E3 ubiquitin ligase is induced by the synergistic actions of proinflammatory TNF-α and fatty acids in livers of humans and mice with NASH. TRIM21 ubiquitinates and degrades ChREBP, SREBP1, ACC1, and FASN, key regulators of de novo lipogenesis, and A1CF, an alternative splicing regulator of the high-activity ketohexokinase-C (KHK-C) isoform and rate-limiting enzyme of fructose metabolism. TRIM21-mediated degradation of these lipogenic activators improved steatosis and hyperglycemia as well as fructose and glucose tolerance. Our study identifies TRIM21 as a negative regulator of liver steatosis in NASH and provides mechanistic insights into an immunometabolic crosstalk that limits fatty acid synthesis and fructose metabolism during metabolic stress. Thus, enhancing this natural counteracting force of steatosis through inhibition of key lipogenic activators via TRIM21-mediated ubiquitination may provide a therapeutic opportunity to treat NASH.

Keywords:  Diabetes; Hepatology

DOI:  https://doi.org/10.1172/jci.insight.164694
Nat Commun. 2023 Nov 08. 14(1): 7217

Spatially resolved mapping of proteome turnover dynamics with subcellular precision.

Feng Yuan, Yi Li, Xinyue Zhou, Peiyuan Meng, Peng Zou.

Cellular activities are commonly associated with dynamic proteomic changes at the subcellular level. Although several techniques are available to quantify whole-cell protein turnover dynamics, such measurements often lack sufficient spatial resolution at the subcellular level. Herein, we report the development of prox-SILAC method that combines proximity-dependent protein labeling (APEX2/HRP) with metabolic incorporation of stable isotopes (pulse-SILAC) to map newly synthesized proteins with subcellular spatial resolution. We apply prox-SILAC to investigate proteome dynamics in the mitochondrial matrix and the endoplasmic reticulum (ER) lumen. Our analysis reveals a highly heterogeneous distribution in protein turnover dynamics within macromolecular machineries such as the mitochondrial ribosome and respiratory complexes I-V, thus shedding light on their mechanism of hierarchical assembly. Furthermore, we investigate the dynamic changes of ER proteome when cells are challenged with stress or undergoing stimulated differentiation, identifying subsets of proteins with unique patterns of turnover dynamics, which may play key regulatory roles in alleviating stress or promoting differentiation. We envision that prox-SILAC could be broadly applied to profile protein turnover at various subcellular compartments, under both physiological and pathological conditions.

DOI: https://doi.org/10.1038/s41467-023-42861-8
Redox Biol. 2023 Oct 30. pii: S2213-2317(23)00350-6. [Epub ahead of print]68 102949

Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation.

Shafiul Alam, Sibile Pardue, Xinggui Shen, John D Glawe, Takashi Yagi, Mohammad Alfrad Nobel Bhuiyan, Rakesh P Patel, Paari S Dominic, Chiranjiv S Virk, Md Shenuarin Bhuiyan, A Wayne Orr, Chad Petit, Gopi K Kolluru, Christopher G Kevil.

  Hydropersulfide and hydropolysulfide metabolites are increasingly important reactive sulfur species (RSS) regulating numerous cellular redox dependent functions. Intracellular production of these species is known to occur through RSS interactions or through translational mechanisms involving cysteinyl t-RNA synthetases. However, regulation of these species under cell stress conditions, such as hypoxia, that are known to modulate RSS remain poorly understood. Here we define an important mechanism of increased persulfide and polysulfide production involving cystathionine gamma lyase (CSE) phosphorylation at serine 346 and threonine 355 in a substrate specific manner, under acute hypoxic conditions. Hypoxic phosphorylation of CSE occurs in an AMP kinase dependent manner increasing enzyme activity involving unique inter- and intramolecular interactions within the tetramer. Importantly, both cellular hypoxia and tissue ischemia result in AMP Kinase dependent CSE phosphorylation that regulates blood flow in ischemic tissues. Our findings reveal hypoxia molecular signaling pathways regulating CSE dependent persulfide and polysulfide production impacting tissue and cellular response to stress.

Keywords:  AMP kinase; Cystathionine gamma lyase; Ischemia; Molecular modeling; Persulfide; Phosphorylation; Polysulfide

DOI:  https://doi.org/10.1016/j.redox.2023.102949
J Lipid Res. 2023 Nov 08. pii: S0022-2275(23)00145-1. [Epub ahead of print] 100472

The Role of KLF2 in Regulating Hepatic Lipogenesis and Blood Cholesterol Homeostasis via the SCAP/SREBP Pathway.

Yuhong Huang, Yi Fan Wang, Xiong-Zhong Ruan, Chi Wai Lau, Li Wang, Yu Huang.

  Liver steatosis is a common metabolic disorder resulting from imbalanced lipid metabolism, which involves various processes such as de novo lipogenesis, fatty acid uptake, fatty acid oxidation, and VLDL secretion. In this study, we discovered that KLF2, a transcription factor, plays a crucial role in regulating lipid metabolism in the liver. Overexpression of KLF2 in the liver of db/db mice, C57BL/6J mice, and CD36-/- mice fed on a normal diet resulted in increased lipid content in the liver. Additionally, transgenic mice (ALB-Klf2) that overexpressed KLF2 in the liver developed liver steatosis after being fed a normal diet. We found that KLF2 promotes lipogenesis by increasing the expression of SCAP, a chaperone that facilitates the activation of SREBP, the master transcription factor for lipogenic gene expression. Our mechanism studies revealed that KLF2 enhances lipogenesis in the liver by binding to the promoter of SCAP and increasing the expression of genes involved in fatty acid synthesis. Reduction of KLF2 expression led to a decrease in SCAP expression and a reduction in the expression of SREBP1 target genes involved in lipogenesis. Overexpression of KLF2 also increased the activation of SREBP2 and the mRNA levels of its downstream target SOAT1. In C57BL/6J mice fed a high-fat diet, overexpression of KLF2 increased blood VLDL secretion, while reducing its expression decreased blood cholesterol levels. Our study emphasizes the novelty that hepatic KLF2 plays a critical role in regulating lipid metabolism through the KLF2/SCAP/SREBPs pathway, which is essential for hepatic lipogenesis and maintaining blood cholesterol homeostasis.

Keywords:  KLF2; SCAP; SREBPs; blood cholesterol; lipogenesis; steatosis

DOI:  https://doi.org/10.1016/j.jlr.2023.100472
EMBO Rep. 2023 Nov 06. e57339

Breast adipose tissue-derived extracellular vesicles from obese women alter tumor cell metabolism.

Shuchen Liu, Alberto Benito-Martin, Fanny A Pelissier Vatter, Sarah Z Hanif, Catherine Liu, Priya Bhardwaj, Praveen Sethupathy, Alaa R Farghli, Phoebe Piloco, Paul Paik, Malik Mushannen, Xue Dong, David M Otterburn, Leslie Cohen, Rohan Bareja, Jan Krumsiek, Leona Cohen-Gould, Samuel Calto, Jason A Spector, Olivier Elemento, David C Lyden, Kristy A Brown.

  Breast adipose tissue is an important contributor to the obesity-breast cancer link. Extracellular vesicles (EVs) are nanosized particles containing selective cargo, such as miRNAs, that act locally or circulate to distant sites to modulate target cell functions. Here, we find that long-term education of breast cancer cells with EVs obtained from breast adipose tissue of women who are overweight or obese (O-EVs) results in increased proliferation. RNA-seq analysis of O-EV-educated cells demonstrates increased expression of genes involved in oxidative phosphorylation, such as ATP synthase and NADH: ubiquinone oxidoreductase. O-EVs increase respiratory complex protein expression, mitochondrial density, and mitochondrial respiration in tumor cells. The mitochondrial complex I inhibitor metformin reverses O-EV-induced cell proliferation. Several miRNAs-miR-155-5p, miR-10a-3p, and miR-30a-3p-which promote mitochondrial respiration and proliferation, are enriched in O-EVs relative to EVs from lean women. O-EV-induced proliferation and mitochondrial activity are associated with stimulation of the Akt/mTOR/P70S6K pathway, and are reversed upon silencing of P70S6K. This study reveals a new facet of the obesity-breast cancer link with human breast adipose tissue-derived EVs causing metabolic reprogramming of breast cancer cells.

Keywords:  breast cancer; extracellular vesicles; mitochondrial respiration; obesity; proliferation

DOI:  https://doi.org/10.15252/embr.202357339
FEBS J. 2023 Nov 07.

A Guide to Ferroptosis, the biological rust of cellular membranes.

Geraldine Veeckmans, Emily Van San, Tom Vanden Berghe.

  Unprotected iron can rust due to oxygen exposure. Similarly, in our body, oxidative stress can kill cells in an iron-dependent manner, which can give rise to devastating diseases. This type of cell death is referred to as ferroptosis. Generally, ferroptosis is defined as an iron-catalyzed form of regulated necrosis that occurs through excessive peroxidation of polyunsaturated fatty acids within cellular membranes. This review summarizes how ferroptosis is executed by a rather primitive biochemical process, under tight regulation of lipid, iron, and redox metabolic processes. An overview is given of major classes of ferroptosis inducers and inhibitors, and how to detect ferroptosis. Finally, its detrimental role in disease is briefly discussed.

Keywords:  FSP1; Ferroptosis; GPX4; iron; lipid; lipid peroxidation; metabolism; radical trapping antioxidant; redox

DOI:  https://doi.org/10.1111/febs.16993
Sci Immunol. 2023 Nov 10. 8(89): eabn8531

Transcriptomes and metabolism define mouse and human MAIT cell populations.

Shilpi Chandra, Gabriel Ascui, Thomas Riffelmacher, Ashu Chawla, Ciro Ramírez-Suástegui, Viankail C Castelan, Gregory Seumois, Hayley Simon, Mallory P Murray, Goo-Young Seo, Ashmitaa L R Premlal, Benjamin Schmiedel, Greet Verstichel, Yingcong Li, Chia-Hao Lin, Jason Greenbaum, John Lamberti, Raghav Murthy, John Nigro, Hilde Cheroutre, Christian H Ottensmeier, Stephen M Hedrick, Li-Fan Lu, Pandurangan Vijayanand, Mitchell Kronenberg.

Mucosal-associated invariant T (MAIT) cells are a subset of T lymphocytes that respond to microbial metabolites. We defined MAIT cell populations in different organs and characterized the developmental pathway of mouse and human MAIT cells in the thymus using single-cell RNA sequencing and phenotypic and metabolic analyses. We showed that the predominant mouse subset, which produced IL-17 (MAIT17), and the subset that produced IFN-γ (MAIT1) had not only greatly different transcriptomes but also different metabolic states. MAIT17 cells in different organs exhibited increased lipid uptake, lipid storage, and mitochondrial potential compared with MAIT1 cells. All these properties were similar in the thymus and likely acquired there. Human MAIT cells in lung and blood were more homogeneous but still differed between tissues. Human MAIT cells had increased fatty acid uptake and lipid storage in blood and lung, similar to human CD8 T resident memory cells, but unlike mouse MAIT17 cells, they lacked increased mitochondrial potential. Although mouse and human MAIT cell transcriptomes showed similarities for immature cells in the thymus, they diverged more strikingly in the periphery. Analysis of pet store mice demonstrated decreased lung MAIT17 cells in these so-called "dirty" mice, indicative of an environmental influence on MAIT cell subsets and function.

DOI: https://doi.org/10.1126/sciimmunol.abn8531
Nat Commun. 2023 Nov 04. 14(1): 7081

Tissue-resident B cells orchestrate macrophage polarisation and function.

Ondrej Suchanek, John R Ferdinand, Zewen K Tuong, Sathi Wijeyesinghe, Anita Chandra, Ann-Katrin Clauder, Larissa N Almeida, Simon Clare, Katherine Harcourt, Christopher J Ward, Rachael Bashford-Rogers, Trevor Lawley, Rudolf A Manz, Klaus Okkenhaug, David Masopust, Menna R Clatworthy.

B cells play a central role in humoral immunity but also have antibody-independent functions. Studies to date have focused on B cells in blood and secondary lymphoid organs but whether B cells reside in non-lymphoid organs (NLO) in homeostasis is unknown. Here we identify, using intravenous labeling and parabiosis, a bona-fide tissue-resident B cell population in lung, liver, kidney and urinary bladder, a substantial proportion of which are B-1a cells. Tissue-resident B cells are present in neonatal tissues and also in germ-free mice NLOs, albeit in lower numbers than in specific pathogen-free mice and following co-housing with 'pet-store' mice. They spatially co-localise with macrophages and regulate their polarization and function, promoting an anti-inflammatory phenotype, in-part via interleukin-10 production, with effects on bacterial clearance during urinary tract infection. Thus, our data reveal a critical role for tissue-resident B cells in determining the homeostatic 'inflammatory set-point' of myeloid cells, with important consequences for tissue immunity.

DOI: https://doi.org/10.1038/s41467-023-42625-4
J Biol Chem. 2023 Nov 03. pii: S0021-9258(23)02454-7. [Epub ahead of print] 105426

Palmitoylation-Dependent Regulation of Cardiomyocyte Rac1 Signaling Activity and Minor Effects on Cardiac Hypertrophy.

Tanya A Baldwin, James P Teuber, Yasuhide Kuwabara, Araskumar Subramani, Suh-Chin J Lin, Onur Kanisicak, Ronald J Vagnozzi, Weiqi Zhang, Matthew J Brody, Jeffery D Molkentin.

  S-palmitoylation is a reversible lipid modification catalyzed by 23 S-acyltransferases with a conserved zinc finger aspartate-histidine-histidine-cysteine (zDHHC) domain that facilitates targeting of proteins to specific intracellular membranes. Here we performed a gain-of-function screen in the mouse and identified the Golgi-localized enzymes zDHHC3 and zDHHC7 as regulators of cardiac hypertrophy. Cardiomyocyte-specific transgenic mice overexpressing zDHHC3 show cardiac disease and S-acyl proteomics identified the small GTPase Rac1 as a novel substrate of zDHHC3. Notably, cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice is preceded by enhanced Rac1 S-palmitoylation, membrane localization, activity, downstream hypertrophic signaling and concomitant induction of all Rho family small GTPases whereas mice overexpressing an enzymatically-dead zDHHC3 mutant show no discernible effect. However, loss of Rac1 or other identified zDHHC3 targets Gαq/11 or galectin-1 does not diminish zDHHC3-induced cardiomyopathy, suggesting multiple effectors and pathways promoting decompensation with sustained zDHHC3 activity. Genetic deletion of Zdhhc3 in combination with Zdhhc7 reduces cardiac hypertrophy during the early response to pressure overload stimulation but not over longer time periods. Indeed, cardiac hypertrophy in response to 2 weeks of angiotensin-II infusion is not diminished by Zdhhc3/7 deletion, again suggesting other S-acyltransferases or signaling mechanisms compensate to promote hypertrophic signaling. Taken together, these data indicate that the activity of zDHHC3 and zDHHC7 at the cardiomyocyte Golgi promote Rac1 signaling and maladaptive cardiac remodeling but redundant signaling effectors compensate to maintain cardiac hypertrophy with sustained pathological stimulation in the absence of zDHHC3/7.

Keywords:  Cardiac hypertrophy; Cardiomyocyte; Cardiomyopathy; Cell signaling; G protein‐coupled receptor (GPCR); GTPase; Palmitoylation; Ras homolog gene family, member A (RhoA); Ras‐related C3 botulinum toxin substrate 1 (Rac1); S-acylation; proteomics

DOI:  https://doi.org/10.1016/j.jbc.2023.105426
Science. 2023 Nov 10. 382(6671): eadf0966

Aster-dependent nonvesicular transport facilitates dietary cholesterol uptake.

Alessandra Ferrari, Emily Whang, Xu Xiao, John P Kennelly, Beatriz Romartinez-Alonso, Julia J Mack, Thomas Weston, Kai Chen, Youngjae Kim, Marcus J Tol, Lara Bideyan, Alexander Nguyen, Yajing Gao, Liujuan Cui, Alexander H Bedard, Jaspreet Sandhu, Stephen D Lee, Louise Fairall, Kevin J Williams, Wenxin Song, Priscilla Munguia, Robert A Russell, Martin G Martin, Michael E Jung, Haibo Jiang, John W R Schwabe, Stephen G Young, Peter Tontonoz.

Intestinal absorption is an important contributor to systemic cholesterol homeostasis. Niemann-Pick C1 Like 1 (NPC1L1) assists in the initial step of dietary cholesterol uptake, but how cholesterol moves downstream of NPC1L1 is unknown. We show that Aster-B and Aster-C are critical for nonvesicular cholesterol movement in enterocytes. Loss of NPC1L1 diminishes accessible plasma membrane (PM) cholesterol and abolishes Aster recruitment to the intestinal brush border. Enterocytes lacking Asters accumulate PM cholesterol and show endoplasmic reticulum cholesterol depletion. Aster-deficient mice have impaired cholesterol absorption and are protected against diet-induced hypercholesterolemia. Finally, the Aster pathway can be targeted with a small-molecule inhibitor to manipulate cholesterol uptake. These findings identify the Aster pathway as a physiologically important and pharmacologically tractable node in dietary lipid absorption.

DOI: https://doi.org/10.1126/science.adf0966
Cell Metab. 2023 Nov 07. pii: S1550-4131(23)00375-3. [Epub ahead of print]35(11): 1847-1848

Colonic macrophages eat and feed.

Jan Van den Bossche.

Macrophages not only secure host defense via phagocytosis but also play a key role in tissue homeostasis. A comprehensive study by Fritsch et al. reveals a novel mechanism by which macrophages in the colon deliver polyamines to epithelial cells to support self-renewal of the epithelium during periods of high proliferation.

DOI: https://doi.org/10.1016/j.cmet.2023.10.006
Cell Metab. 2023 Nov 07. pii: S1550-4131(23)00378-9. [Epub ahead of print]35(11): 1852-1871

The bidirectional immune crosstalk in metabolic dysfunction-associated steatotic liver disease.

Keisuke Sawada, Hak Chung, Samir Softic, Maria E Moreno-Fernandez, Senad Divanovic.

  Metabolic dysfunction-associated steatotic liver disease (MASLD) is an unabated risk factor for end-stage liver diseases with no available therapies. Dysregulated immune responses are critical culprits of MASLD pathogenesis. Independent contributions from either the innate or adaptive arms of the immune system or their unidirectional interplay are commonly studied in MASLD. However, the bidirectional communication between innate and adaptive immune systems and its impact on MASLD remain insufficiently understood. Given that both innate and adaptive immune cells are indispensable for the development and progression of inflammation in MASLD, elucidating pathogenic contributions stemming from the bidirectional interplay between these two arms holds potential for development of novel therapeutics for MASLD. Here, we review the immune cell types and bidirectional pathways that influence the pathogenesis of MASLD and highlight potential pharmacologic approaches to combat MASLD based on current knowledge of this bidirectional crosstalk.

Keywords:  MASH; MASLD; NAFLD; NASH; adaptive immunity; immune crosstalk; innate immunity

DOI:  https://doi.org/10.1016/j.cmet.2023.10.009
Redox Biol. 2023 Oct 31. pii: S2213-2317(23)00352-X. [Epub ahead of print]68 102951

NRF2 is essential for adaptative browning of white adipocytes.

Marco Bauzá-Thorbrügge, Eduard Peris, Shabnam Zamani, Peter Micallef, Alexandra Paul, Stefano Bartesaghi, Anna Benrick, Ingrid Wernstedt Asterholm.

  White adipose tissue browning, defined by accelerated mitochondrial metabolism and biogenesis, is considered a promising mean to treat or prevent obesity-associated metabolic disturbances. We hypothesize that redox stress acutely leads to increased production of reactive oxygen species (ROS), which activate electrophile sensor nuclear factor erythroid 2-Related Factor 2 (NRF2) that over time results in an adaptive adipose tissue browning process. To test this, we have exploited adipocyte-specific NRF2 knockout mice and cultured adipocytes and analyzed time- and dose-dependent effect of NAC and lactate treatment on antioxidant expression and browning-like processes. We found that short-term antioxidant treatment with N-acetylcysteine (NAC) induced reductive stress as evident from increased intracellular NADH levels, increased ROS-production, reduced oxygen consumption rate (OCR), and increased NRF2 levels in white adipocytes. In contrast, and in line with our hypothesis, longer-term NAC treatment led to a NRF2-dependent browning response. Lactate treatment elicited similar effects as NAC, and mechanistically, these NRF2-dependent adipocyte browning responses in vitro were mediated by increased heme oxygenase-1 (HMOX1) activity. Moreover, this NRF2-HMOX1 axis was also important for β3-adrenergic receptor activation-induced adipose tissue browning in vivo. In conclusion, our findings show that administration of exogenous antioxidants can affect biological function not solely through ROS neutralization, but also through reductive stress. We also demonstrate that NRF2 is essential for white adipose tissue browning processes.

Keywords:  Adipose tissue; Lactate; N-acetylcysteine; NRF2; Redox stress

DOI:  https://doi.org/10.1016/j.redox.2023.102951
Redox Biol. 2023 Nov 06. pii: S2213-2317(23)00359-2. [Epub ahead of print]68 102958

A role for the cystathionine-β-synthase /H2S axis in astrocyte dysfunction in the aging brain.

Anindya Dey, Pijush Kanti Pramanik, Shailendra Kumar Dhar Dwivedi, Fiifi Neizer-Ashun, Tamas Kiss, Abhrajit Ganguly, Heather Rice, Priyabrata Mukherjee, Chao Xu, Mohiuddin Ahmad, Anna Csiszar, Resham Bhattacharya.

  Astrocytic dysfunction is central to age-related neurodegenerative diseases. However, the mechanisms leading to astrocytic dysfunction are not well understood. We identify that among the diverse cellular constituents of the brain, murine and human astrocytes are enriched in the expression of CBS. Depleting CBS in astrocytes causes mitochondrial dysfunction, increases the production of reactive oxygen species (ROS) and decreases cellular bioenergetics that can be partially rescued by exogenous H2S supplementation or by re-expressing CBS. Conversely, the CBS/H2S axis, associated protein persulfidation and proliferation are decreased in astrocytes upon oxidative stress which can be rescued by exogenous H2S supplementation. Here we reveal that in the aging brain, the CBS/H2S axis is downregulated leading to decreased protein persulfidation, together augmenting oxidative stress. Our findings uncover an important protective role of the CBS/H2S axis in astrocytes that may be disrupted in the aged brain.

Keywords:  Aging; Astrocyte; Hydrogen sulfide; Oxidative stress; Protein persulfidation

DOI:  https://doi.org/10.1016/j.redox.2023.102958
Nat Metab. 2023 Nov 09.

Glucose-dependent insulinotropic polypeptide regulates body weight and food intake via GABAergic neurons in mice.

Arkadiusz Liskiewicz, Ahmed Khalil, Daniela Liskiewicz, Aaron Novikoff, Gerald Grandl, Gandhari Maity-Kumar, Robert M Gutgesell, Mostafa Bakhti, Aimée Bastidas-Ponce, Oliver Czarnecki, Konstantinos Makris, Heiko Lickert, Annette Feuchtinger, Monica Tost, Callum Coupland, Lisa Ständer, Seun Akindehin, Sneha Prakash, Faiyaz Abrar, Russell L Castelino, Yantao He, Patrick J Knerr, Bin Yang, Wouter F J Hogendorf, Shiqi Zhang, Susanna M Hofmann, Brian Finan, Richard D DiMarchi, Matthias H Tschöp, Jonathan D Douros, Timo D Müller.

The development of single-molecule co-agonists for the glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) is considered a breakthrough in the treatment of obesity and type 2 diabetes. But although GIPR-GLP-1R co-agonism decreases body weight with superior efficacy relative to GLP-1R agonism alone in preclinical1-3 and clinical studies4,5, the role of GIP in regulating energy metabolism remains enigmatic. Increasing evidence suggests that long-acting GIPR agonists act in the brain to decrease body weight through the inhibition of food intake3,6-8; however, the mechanisms and neuronal populations through which GIP affects metabolism remain to be identified. Here, we report that long-acting GIPR agonists and GIPR-GLP-1R co-agonists decrease body weight and food intake via inhibitory GABAergic neurons. We show that acyl-GIP decreases body weight and food intake in male diet-induced obese wild-type mice, but not in mice with deletion of Gipr in Vgat(also known as Slc32a1)-expressing GABAergic neurons (Vgat-Gipr knockout). Whereas the GIPR-GLP-1R co-agonist MAR709 leads, in male diet-induced obese wild-type mice, to greater weight loss and further inhibition of food intake relative to a pharmacokinetically matched acyl-GLP-1 control, this superiority over GLP-1 vanishes in Vgat-Gipr knockout mice. Our data demonstrate that long-acting GIPR agonists crucially depend on GIPR signaling in inhibitory GABAergic neurons to decrease body weight and food intake.

DOI: https://doi.org/10.1038/s42255-023-00931-7
Cell Metab. 2023 Nov 07. pii: S1550-4131(23)00382-0. [Epub ahead of print]35(11): 2028-2043.e7

Skeletal muscle-derived extracellular vesicles transport glycolytic enzymes to mediate muscle-to-bone crosstalk.

Shixing Ma, Xiaotao Xing, Haisen Huang, Xin Gao, Xun Xu, Jian Yang, Chengcheng Liao, Xuanhao Zhang, Jinglun Liu, Weidong Tian, Li Liao.

  Identification of cues originating from skeletal muscle that govern bone formation is essential for understanding the crosstalk between muscle and bone and for developing therapies for degenerative bone diseases. Here, we identified that skeletal muscle secreted multiple extracellular vesicles (Mu-EVs). These Mu-EVs traveled through the bloodstream to reach bone, where they were phagocytized by bone marrow mesenchymal stem/stromal cells (BMSCs). Mu-EVs promoted osteogenic differentiation of BMSCs and protected against disuse osteoporosis in mice. The quantity and bioactivity of Mu-EVs were tightly correlated with the function of skeletal muscle. Proteomic analysis revealed numerous proteins in Mu-EVs, some potentially regulating bone metabolism, especially glycolysis. Subsequent investigations indicated that Mu-EVs promoted the glycolysis of BMSCs by delivering lactate dehydrogenase A into these cells. In summary, these findings reveal that Mu-EVs play a vital role in BMSC metabolism regulation and bone formation stimulation, offering a promising approach for treating disuse osteoporosis.

Keywords:  aerobic glycolysis; bone marrow mesenchymal stem/stromal cells; extracellular vesicles; glycolytic enzyme; lactate dehydrogenase A; skeletal muscle

DOI:  https://doi.org/10.1016/j.cmet.2023.10.013
J Immunother Cancer. 2023 Nov;pii: e007402. [Epub ahead of print]11(11):

Loss of ADAR1 in macrophages in combination with interferon gamma suppresses tumor growth by remodeling the tumor microenvironment.

Weiwei Lin, Yikai Luo, Jie Wu, Haowan Zhang, Ge Jin, Chahua Guo, Hang Zhou, Han Liang, Xiaoyan Xu.

   BACKGROUND: ADAR1, the major enzyme for RNA editing, has emerged as a tumor-intrinsic key determinant for cancer immunotherapy efficacy through modulating interferon-mediated innate immunity. However, the role of ADAR1 in innate immune cells such as macrophages remains unknown.
METHODS: We first analyzed publicly accessible patient-derived single-cell RNA-sequencing and perturbed RNA sequencing data to elucidate the ADAR1 expression and function in macrophages. Subsequently, we evaluated the combined effects of ADAR1 conditional knockout in macrophages and interferon (IFN)-γ treatment on tumor growth in three distinct disease mouse models: LLC for lung cancer, B16-F10 for melanoma, and MC38 for colon cancer. To gain the mechanistic insights, we performed human cytokine arrays to identify differentially secreted cytokines in response to ADAR1 perturbations in THP-1 cells. Furthermore, we examined the effects of ADAR1 loss and IFN-γ treatment on vessel formation through immunohistochemical staining of mouse tumor sections and tube-forming experiments using HUVEC and SVEC4-10 cells. We also assessed the effects on CD8+ T cells using immunofluorescent and immunohistochemical staining and flow cytometry. To explore the translational potential, we examined the consequences of injecting ADAR1-deficient macrophages alongside IFN-γ treatment on tumor growth in LLC-tumor-bearing mice.
RESULTS: Our analysis on public data suggests that ADAR1 loss in macrophages promotes antitumor immunity as in cancer cells. Indeed, ADAR1 loss in macrophages combined with IFN-γ treatment results in tumor regression in diverse disease mouse models. Mechanistically, the loss of ADAR1 in macrophages leads to the differential secretion of key cytokines: it inhibits the translation of CCL20, GDF15, IL-18BP, and TIM-3 by activating PKR/EIF2α signaling but increases the secretion of IFN-γ through transcriptional upregulation and interleukin (IL)-18 due to the 5'UTR uORF. Consequently, decreased CCL20 and GDF15 and increased IFN-γ suppress angiogenesis, while decreased IL-18BP and TIM-3 and increased IL-18 induce antitumor immunity by enhancing cytotoxicity of CD8+ T cells. We further demonstrate that combination therapy of injecting ADAR1-deficient macrophages and IFN-γ effectively suppresses tumors in vivo.
CONCLUSION: This study provides a comprehensive elucidation of how ADAR1 loss within macrophages contributes to the establishment of an antitumor microenvironment, suggesting the therapeutic potential of targeting ADAR1 beyond the scope of cancer cells.

Keywords:  cytokines; immunity, innate; immunotherapy; macrophages; tumor microenvironment

DOI:  https://doi.org/10.1136/jitc-2023-007402
Sci Rep. 2023 11 04. 13(1): 19069

Glutamate secretion by embryonic stem cells as an autocrine signal to promote proliferation.

Lin Teng, Qin Qin, Ziyi Zhou, Fei Zhou, Chunyu Cao, Jian Yang, Jiawang Ding.

Glutamate, the major excitatory neurotransmitter in the central nervous system, has also been found to play a role in embryonic stem (ES) cells. However, the exact mechanism and function of glutamatergic signaling in ES cells remain poorly understood. In this study, we identified a glutamatergic transmission circuit in ES cells that operates through an autocrine mechanism and regulates cell proliferation. We performed biological analyses to identify the key components involved in glutamate biosynthesis, packaging for secretion, reaction, and reuptake in ES cells, including glutaminase, vesicular glutamate transporter, glutamate N-methyl-D-aspartate (NMDA) receptor, and cell membrane excitatory amino-acid transporter (EAAT). We directly quantified the released glutamate signal using microdialysis-high performance liquid chromatography-tandem mass spectrometry (MD-HPLC-MS-MS). Pharmacological inhibition of endogenous glutamate release and the resulting tonic activation of NMDA receptors significantly affected ES cell proliferation, suggesting that ES cells establish a glutamatergic autocrine niche via releasing and responding to the transmitter for their own regulation.

DOI: https://doi.org/10.1038/s41598-023-46477-2
Nat Commun. 2023 Nov 09. 14(1): 7172

Failure to apply standard limit-of-detection or limit-of-quantitation criteria to specialized pro-resolving mediator analysis incorrectly characterizes their presence in biological samples.

Valerie B O'Donnell, Nils H Schebb, Ginger L Milne, Michael P Murphy, Christopher P Thomas, Dieter Steinhilber, Stacy L Gelhaus, Hartmut Kühn, Michael H Gelb, Per-Johan Jakobsson, Ian A Blair, Robert C Murphy, Bruce A Freeman, Alan R Brash, Garret A FitzGerald.

DOI: https://doi.org/10.1038/s41467-023-41766-w
Nat Commun. 2023 Nov 08. 14(1): 7184

Asymmetric conformations and lipid interactions shape the ATP-coupled cycle of a heterodimeric ABC transporter.

Qingyu Tang, Matt Sinclair, Hale S Hasdemir, Richard A Stein, Erkan Karakas, Emad Tajkhorshid, Hassane S Mchaourab.

Here we used cryo-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy (DEER), and molecular dynamics (MD) simulations, to capture and characterize ATP- and substrate-bound inward-facing (IF) and occluded (OC) conformational states of the heterodimeric ATP binding cassette (ABC) multidrug exporter BmrCD in lipid nanodiscs. Supported by DEER analysis, the structures reveal that ATP-powered isomerization entails changes in the relative symmetry of the BmrC and BmrD subunits that propagates from the transmembrane domain to the nucleotide binding domain. The structures uncover asymmetric substrate and Mg2+ binding which we hypothesize are required for triggering ATP hydrolysis preferentially in one of the nucleotide-binding sites. MD simulations demonstrate that multiple lipid molecules differentially bind the IF versus the OC conformation thus establishing that lipid interactions modulate BmrCD energy landscape. Our findings are framed in a model that highlights the role of asymmetric conformations in the ATP-coupled transport with general implications to the mechanism of ABC transporters.

DOI: https://doi.org/10.1038/s41467-023-42937-5