bims-camemi 2023-02-19 papers

bims-camemi

Biomed News

on Mitochondrial metabolism in cancer

Issue of 2023‒02‒19
forty-two papers selected by
Christian Frezza, Universität zu Köln

Mitochondrial metabolism in primary and metastatic human kidney cancers.
MARS2 drives metabolic switch of non-small-cell lung cancer cells via interaction with MCU.
Cytoskeletal association of ATP citrate lyase controls the mechanodynamics of macropinocytosis.
β-cell selective inhibition of DNA damage response signaling by nitric oxide is associated with an attenuation in glucose uptake.
An Overview: The Diversified Role of Mitochondria in Cancer Metabolism.
A novel therapeutic strategy against mitochondrial respiratory chain dysfunction-linked diseases.
FDX1 regulates cellular protein lipoylation through direct binding to LIAS.
Mitochondrial single-cell ATAC-seq for high-throughput multi-omic detection of mitochondrial genotypes and chromatin accessibility.
Dynamics of co-substrate pools can constrain and regulate metabolic fluxes.
The outer mitochondrial membrane protein TMEM11 demarcates spatially restricted BNIP3/BNIP3L-mediated mitophagy.
Mitochondrial cristae morphology reflecting metabolism, superoxide formation, redox homeostasis, and pathology.
Time of day determines postexercise metabolism in mouse adipose tissue.
Mitochondrial function in macrophages controls cardiac repair after myocardial infarction.
ATP synthase inhibitory factor subunit 1 regulates islet β-cell function via repression of mitochondrial homeostasis.
Simultaneous targeting of mitochondrial Kv1.3 and lysosomal acid sphingomyelinase amplifies killing of pancreatic ductal adenocarcinoma cells in vitro and in vivo.
Metabolism and epigenetics at the heart of T cell function.
Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans.
Integrated landscape of cardiac metabolism in end-stage human nonischemic dilated cardiomyopathy.
Essential mitochondrial role in iron-sulfur cluster assembly of the cytoplasmic isopropylmalate isomerase Leu1 in Saccharomyces cerevisiae.
Repair of airway epithelia requires metabolic rewiring towards fatty acid oxidation.
PFKFB2-mediated glycolysis promotes lactate-driven continual efferocytosis by macrophages.
Fibroblast growth factor 21, a stress regulator, inhibits Drp1 activation to alleviate skeletal muscle ischemia/reperfusion injury.
Metabolic heterogeneity and cross-feeding within isogenic yeast populations captured by DILAC.
On the interdependence of ketone body oxidation,glycogen content, glycolysis and energy metabolism in the heart.
Genome-wide screens for mitonuclear co-regulators uncover links between compartmentalized metabolism and mitochondrial gene expression.
Branched chain amino acids alter cellular redox to induce lipid oxidation and reduce de novo lipogenesis in the liver.
Molecular pathways that drive diabetic kidney disease.
Fully accessible fitness landscape of oncogene-negative lung adenocarcinoma.
Reverse electron transfer is activated during aging and contributes to aging and age-related disease.
Bacterial origins of thymidylate metabolism in Asgard archaea and Eukarya.
Circadian regulator CLOCK promotes tumor angiogenesis in glioblastoma.
Tubular Mitochondrial Pyruvate Carrier Disruption Elicits Redox Adaptations that Protect from Acute Kidney Injury.
Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma.
Mitochondrial recovery by the UPRmt: Insights from C. elegans.
Mitochondrial respiration reduces exposure of the nucleus to oxygen.
TMEM164 is an acyltransferase that forms ferroptotic C20:4 ether phospholipids.
Spatial self-organization of metabolism in microbial systems: A matter of enzymes and chemicals.
Cell Survival Enabled by Leakage of a Labile Metabolic Intermediate.
Super-resolution non-linear multimodal imaging platform for studying spatially correlated metabolic reactions.
Palmitate oxidation drives a pro-metastatic post-translational modification.
Mitochondria on the move: Horizontal mitochondrial transfer in disease and health.
Innate immune cell-intrinsic ketogenesis is dispensable for organismal metabolism and age-related inflammation.

bioRxiv. 2023 Feb 07. pii: 2023.02.06.527285. [Epub ahead of print]

Mitochondrial metabolism in primary and metastatic human kidney cancers.

Divya Bezwada, Nicholas P Lesner, Bailey Brooks, Hieu S Vu, Zheng Wu, Ling Cai, Stacy Kasitinon, Sherwin Kelekar, Feng Cai, Arin B Aurora, McKenzie Patrick, Ashley Leach, Rashed Ghandour, Yuanyuan Zhang, Duyen Do, Jessica Sudderth, Dennis Dumesnil, Sara House, Tracy Rosales, Alan M Poole, Yair Lotan, Solomon Woldu, Aditya Bagrodia, Xiaosong Meng, Jeffrey A Cadeddu, Prashant Mishra, Ivan Pedrosa, Payal Kapur, Kevin D Courtney, Craig R Malloy, Vitaly Margulis, Ralph J DeBerardinis.

Most kidney cancers display evidence of metabolic dysfunction 1â€"4 but how this relates to cancer progression in humans is unknown. We used a multidisciplinary approach to infuse 13 C-labeled nutrients during surgical tumour resection in over 70 patients with kidney cancer. Labeling from [U- 13 C]glucose varies across cancer subtypes, indicating that the kidney environment alone cannot account for all metabolic reprogramming in these tumours. Compared to the adjacent kidney, clear cell renal cell carcinomas (ccRCC) display suppressed labelling of tricarboxylic acid (TCA) cycle intermediates in vivo and in organotypic slices cultured ex vivo, indicating that suppressed labeling is tissue intrinsic. Infusions of [1,2- 13 C]acetate and [U- 13 C]glutamine in patients, coupled with respiratory flux of mitochondria isolated from kidney and tumour tissue, reveal primary defects in mitochondrial function in human ccRCC. However, ccRCC metastases unexpectedly have enhanced labeling of TCA cycle intermediates compared to primary ccRCCs, indicating a divergent metabolic program during ccRCC metastasis in patients. In mice, stimulating respiration in ccRCC cells is sufficient to promote metastatic colonization. Altogether, these findings indicate that metabolic properties evolve during human kidney cancer progression, and suggest that mitochondrial respiration may be limiting for ccRCC metastasis but not for ccRCC growth at the site of origin.

DOI: https://doi.org/10.1101/2023.02.06.527285
Redox Biol. 2023 Apr;pii: S2213-2317(23)00029-0. [Epub ahead of print]60 102628

MARS2 drives metabolic switch of non-small-cell lung cancer cells via interaction with MCU.

Juhyeon Son, Okkeun Jung, Jong Heon Kim, Kyu Sang Park, Hee-Seok Kweon, Nhung Thi Nguyen, Yu Jin Lee, Hansol Cha, Yejin Lee, Quangdon Tran, Yoona Seo, Jongsun Park, Jungwon Choi, Heesun Cheong, Sang Yeol Lee.

  Mitochondrial methionyl-tRNA synthetase (MARS2) canonically mediates the formation of fMet-tRNAifMet for mitochondrial translation initiation. Mitochondrial calcium uniporter (MCU) is a major gate of Ca2+ flux from cytosol into the mitochondrial matrix. We found that MARS2 interacts with MCU and stimulates mitochondrial Ca2+ influx. Methionine binding to MARS2 would act as a molecular switch that regulates MARS2-MCU interaction. Endogenous knockdown of MARS2 attenuates mitochondrial Ca2+ influx and induces p53 upregulation through the Ca2+-dependent CaMKII/CREB signaling. Subsequently, metabolic rewiring from glycolysis into pentose phosphate pathway is triggered and cellular reactive oxygen species level decreases. This metabolic switch induces inhibition of epithelial-mesenchymal transition (EMT) via cellular redox regulation. Expression of MARS2 is regulated by ZEB1 transcription factor in response to Wnt signaling. Our results suggest the mechanisms of mitochondrial Ca2+ uptake and metabolic control of cancer that are exerted by the key factors of the mitochondrial translational machinery and Ca2+ homeostasis.

Keywords:  Cancer metabolism; Epithelial-mesenchymal transition; Mitochondrial calcium uniporter; Mitochondrial methionyl-tRNA synthetase; Reactive oxygen species; p53

DOI:  https://doi.org/10.1016/j.redox.2023.102628
Proc Natl Acad Sci U S A. 2023 Feb 21. 120(8): e2213272120

Cytoskeletal association of ATP citrate lyase controls the mechanodynamics of macropinocytosis.

Joseph Puccini, Jia Wei, Liang Tong, Dafna Bar-Sagi.

  Macropinocytosis is an actin-dependent mode of nonselective endocytosis that mediates the uptake of extracellular fluid-phase cargoes. It is now well recognized that tumor cells exploit macropinocytosis to internalize macromolecules that can be catabolized and used to support cell growth and proliferation under nutrient-limiting conditions. Therefore, the identification of molecular mechanisms that control macropinocytosis is fundamental to the understanding of the metabolic adaptive landscape of tumor cells. Here, we report that the acetyl-CoA-producing enzyme, ATP citrate lyase (ACLY), is a key regulator of macropinocytosis and describes a heretofore-unappreciated association of ACLY with the actin cytoskeleton. The cytoskeletal tethering of ACLY is required for the spatially defined acetylation of heterodimeric actin capping protein, which we identify as an essential mediator of the actin remodeling events that drive membrane ruffling and macropinocytosis. Furthermore, we identify a requirement for mitochondrial-derived citrate, an ACLY substrate, for macropinocytosis, and show that mitochondria traffic to cell periphery regions juxtaposed to plasma membrane ruffles. Collectively, these findings establish a mode of metabolite compartmentalization that supports the spatiotemporal modulation of membrane-cytoskeletal interactions required for macropinocytosis by coupling regional acetyl-CoA availability with dynamic protein acetylation.

Keywords:  actin cytoskeleton; macropinocytosis; membrane ruffling

DOI:  https://doi.org/10.1073/pnas.2213272120
J Biol Chem. 2023 Feb 09. pii: S0021-9258(23)00126-6. [Epub ahead of print] 102994

β-cell selective inhibition of DNA damage response signaling by nitric oxide is associated with an attenuation in glucose uptake.

Chay Teng Yeo, Erin M Kropp, Polly A Hansen, Michael Pereckas, Bryndon J Oleson, Aaron Naatz, Jennifer S Stancill, Kyle A Ross, Rebekah L Gundry, John A Corbett.

Nitric oxide plays a dual role in regulating DNA damage response (DDR) signaling in pancreatic β-cells. As a genotoxic agent, nitric oxide activates two types of DDR signaling; however, when produced at micromolar levels by the inducible isoform of nitric oxide synthase (iNOS), nitric oxide inhibits DDR signaling and DDR-induced apoptosis in a β-cell-selective manner. DDR signaling inhibition by nitric oxide correlates with mitochondrial oxidative metabolism inhibition and decreases in ATP and NAD+. Unlike most cell types, β-cells do not compensate for impaired mitochondrial oxidation by increasing glycolytic flux, and this metabolic inflexibility leads to a decrease in ATP and NAD+. Here, we used multiple analytical approaches to determine changes in intermediary metabolites in β-cells and non-β-cells treated with nitric oxide or the complex I inhibitor rotenone. In addition to ATP and NAD+, glycolytic and TCA cycle intermediates as well as NADPH are significantly decreased in β-cells treated with nitric oxide or rotenone. Consistent with glucose-6-phosphate residing at the metabolic branchpoint for glycolysis and the pentose phosphate pathway (NADPH), we show that mitochondrial oxidation inhibitors limit glucose uptake in a β-cell-selective manner. Our findings indicate that the β-cell selective inhibition of DDR signaling by nitric oxide is associated with a decrease in ATP to levels that fall significantly below the Km for ATP of glucokinase (glucose uptake) and suggest that this action places the β-cell in a state of suspended animation where it is metabolically inert until nitric oxide is removed, and metabolic function can be restored.

DOI: https://doi.org/10.1016/j.jbc.2023.102994
Int J Biol Sci. 2023 ;19(3): 897-915

An Overview: The Diversified Role of Mitochondria in Cancer Metabolism.

Yu'e Liu, Yihong Sun, Yadong Guo, Xiaoyun Shi, Xi Chen, Wenfeng Feng, Lei-Lei Wu, Jin Zhang, Shibo Yu, Yi Wang, Yufeng Shi.

  Mitochondria are intracellular organelles involved in energy production, cell metabolism and cell signaling. They are essential not only in the process of ATP synthesis, lipid metabolism and nucleic acid metabolism, but also in tumor development and metastasis. Mutations in mtDNA are commonly found in cancer cells to promote the rewiring of bioenergetics and biosynthesis, various metabolites especially oncometabolites in mitochondria regulate tumor metabolism and progression. And mutation of enzymes in the TCA cycle leads to the unusual accumulation of certain metabolites and oncometabolites. Mitochondria have been demonstrated as the target for cancer treatment. Cancer cells rely on two main energy resources: oxidative phosphorylation (OXPHOS) and glycolysis. By manipulating OXPHOS genes or adjusting the metabolites production in mitochondria, tumor growth can be restrained. For example, enhanced complex I activity increases NAD+/NADH to prevent metastasis and progression of cancers. In this review, we discussed mitochondrial function in cancer cell metabolism and specially explored the unique role of mitochondria in cancer stem cells and the tumor microenvironment. Targeting the OXPHOS pathway and mitochondria-related metabolism emerging as a potential therapeutic strategy for various cancers.

Keywords:  cancer; mitochondria; tumor metabolism; tumor metastasis

DOI:  https://doi.org/10.7150/ijbs.81609
Biophys J. 2023 Feb 10. pii: S0006-3495(22)02620-0. [Epub ahead of print]122(3S1): 302a

A novel therapeutic strategy against mitochondrial respiratory chain dysfunction-linked diseases.

Daniele Bonesso, Andrea Mattarei, Roberta Peruzzo, Marta Favero, Andrea Rossa, Massimo Zeviani, Carlo Viscomi, Ildikò Szabò.

DOI: https://doi.org/10.1016/j.bpj.2022.11.1704
bioRxiv. 2023 Feb 04. pii: 2023.02.03.526472. [Epub ahead of print]

FDX1 regulates cellular protein lipoylation through direct binding to LIAS.

Margaret B Dreishpoon, Nolan R Bick, Boryana Petrova, Douglas M Warui, Alison Cameron, Squire J Booker, Naama Kanarek, Todd R Golub, Peter Tsvetkov.

Ferredoxins are a family of iron-sulfur (Fe-S) cluster proteins that serve as essential electron donors in numerous cellular processes that are conserved through evolution. The promiscuous nature of ferredoxins as electron donors enables them to participate in many metabolic processes including steroid, heme, vitamin D and Fe-S cluster biosynthesis in different organisms. However, the unique natural function(s) of each of the two human ferredoxins (FDX1 and FDX2) are still poorly characterized. We recently reported that FDX1 is both a crucial regulator of copper ionophore induced cell death and serves as an upstream regulator of cellular protein lipoylation, a mitochondrial lipid-based post translational modification naturally occurring on four mitochondrial enzymes that are crucial for TCA cycle function. Here we show that FDX1 regulates protein lipoylation by directly binding to the lipoyl synthase (LIAS) enzyme and not through indirect regulation of cellular Fe-S cluster biosynthesis. Metabolite profiling revealed that the predominant cellular metabolic outcome of FDX1 loss-of-function is manifested through the regulation of the four lipoylation-dependent enzymes ultimately resulting in loss of cellular respiration and sensitivity to mild glucose starvation. Transcriptional profiling of cells growing in either normal or low glucose conditions established that FDX1 loss-of-function results in the induction of both compensatory metabolism related genes and the integrated stress response, consistent with our findings that FDX1 loss-of-functions is conditionally lethal. Together, our findings establish that FDX1 directly engages with LIAS, promoting cellular protein lipoylation, a process essential in maintaining cell viability under low glucose conditions.

DOI: https://doi.org/10.1101/2023.02.03.526472
Nat Protoc. 2023 Feb 15.

Mitochondrial single-cell ATAC-seq for high-throughput multi-omic detection of mitochondrial genotypes and chromatin accessibility.

Caleb A Lareau, Vincent Liu, Christoph Muus, Samantha D Praktiknjo, Lena Nitsch, Pauline Kautz, Katalin Sandor, Yajie Yin, Jacob C Gutierrez, Karin Pelka, Ansuman T Satpathy, Aviv Regev, Vijay G Sankaran, Leif S Ludwig.

Natural sequence variation within mitochondrial DNA (mtDNA) contributes to human phenotypes and may serve as natural genetic markers in human cells for clonal and lineage tracing. We recently developed a single-cell multi-omic approach, called 'mitochondrial single-cell assay for transposase-accessible chromatin with sequencing' (mtscATAC-seq), enabling concomitant high-throughput mtDNA genotyping and accessible chromatin profiling. Specifically, our technique allows the mitochondrial genome-wide inference of mtDNA variant heteroplasmy along with information on cell state and accessible chromatin variation in individual cells. Leveraging somatic mtDNA mutations, our method further enables inference of clonal relationships among native ex vivo-derived human cells not amenable to genetic engineering-based clonal tracing approaches. Here, we provide a step-by-step protocol for the use of mtscATAC-seq, including various cell-processing and flow cytometry workflows, by using primary hematopoietic cells, subsequent single-cell genomic library preparation and sequencing that collectively take ~3-4 days to complete. We discuss experimental and computational data quality control metrics and considerations for the extension to other mammalian tissues. Overall, mtscATAC-seq provides a broadly applicable platform to map clonal relationships between cells in human tissues, investigate fundamental aspects of mitochondrial genetics and enable additional modes of multi-omic discovery.

DOI: https://doi.org/10.1038/s41596-022-00795-3
Elife. 2023 Feb 17. pii: e84379. [Epub ahead of print]12

Dynamics of co-substrate pools can constrain and regulate metabolic fluxes.

Robert West, Hadrien Delattre, Elad Noor, Elisenda Feliu, Orkun Soyer.

  Cycling of co-substrates, whereby a metabolite is converted among alternate forms via different reactions, is ubiquitous in metabolism. Several cycled co-substrates are well known as energy and electron carriers (e.g. ATP and NAD(P)H), but there are also other metabolites that act as cycled co-substrates in different parts of central metabolism. Here, we develop a mathematical framework to analyse the effect of co-substrate cycling on metabolic flux. In the cases of a single reaction and linear pathways, we find that co-substrate cycling imposes an additional flux limit on a reaction, distinct to the limit imposed by the kinetics of the primary enzyme catalysing that reaction. Using analytical methods, we show that this additional limit is a function of the total pool size and turnover rate of the cycled co-substrate. Expanding from this insight and using simulations, we show that regulation of these two parameters can allow regulation of flux dynamics in branched and coupled pathways. To support these theoretical insights, we analysed existing flux measurements and enzyme levels from the central carbon metabolism and identified several reactions that could be limited by the dynamics of co-substrate cycling. We discuss how the limitations imposed by co-substrate cycling provide experimentally testable hypotheses on specific metabolic phenotypes. We conclude that measuring and controlling co-substrate dynamics is crucial for understanding and engineering metabolic fluxes in cells.

Keywords:  E. coli; computational biology; systems biology

DOI:  https://doi.org/10.7554/eLife.84379
J Cell Biol. 2023 Apr 03. pii: e202204021. [Epub ahead of print]222(4):

The outer mitochondrial membrane protein TMEM11 demarcates spatially restricted BNIP3/BNIP3L-mediated mitophagy.

Mehmet Oguz Gok, Olivia M Connor, Xun Wang, Cameron J Menezes, Claire B Llamas, Prashant Mishra, Jonathan R Friedman.

Mitochondria play critical roles in cellular metabolism and to maintain their integrity, they are regulated by several quality control pathways, including mitophagy. During BNIP3/BNIP3L-dependent receptor-mediated mitophagy, mitochondria are selectively targeted for degradation by the direct recruitment of the autophagy protein LC3. BNIP3 and/or BNIP3L are upregulated situationally, for example during hypoxia and developmentally during erythrocyte maturation. However, it is not well understood how they are spatially regulated within the mitochondrial network to locally trigger mitophagy. Here, we find that the poorly characterized mitochondrial protein TMEM11 forms a complex with BNIP3 and BNIP3L and co-enriches at sites of mitophagosome formation. We find that mitophagy is hyper-active in the absence of TMEM11 during both normoxia and hypoxia-mimetic conditions due to an increase in BNIP3/BNIP3L mitophagy sites, supporting a model that TMEM11 spatially restricts mitophagosome formation.

DOI: https://doi.org/10.1083/jcb.202204021
Antioxid Redox Signal. 2023 Feb 15.

Mitochondrial cristae morphology reflecting metabolism, superoxide formation, redox homeostasis, and pathology.

Petr Jezek, Martin Jaburek, Blanka Holendova, Hana Engstová, Andrea Dlasková.

SIGNIFICANCE: Mitochondrial (mt) reticulum network in the cell possesses amazing ultramorphology of parallel lamellar cristae, formed by the invaginated mitochondrial inner membrane (IMM). Its non-invaginated part, the inner boundary membrane (IBM) forms a cylindrical sandwich with the outer mitochondrial membrane (OMM). Crista membranes (CM) meet IBM at crista junctions (CJs) of mt cristae organizing system (MICOS) complexes connected to OMM SAM. Cristae dimensions, shape and CJs have characteristic patterns for different metabolic regimes, physiological, and pathological situations.RECENT ADVANCES: Cristae-shaping proteins were characterized, namely rows of ATP-synthase dimers forming the crista lamella edges, MICOS subunits, OPA1 isoforms and MGM1 filaments, prohibitins and others. Detailed cristae ultramorphology changes were imaged by focused-ion beam/scanning electron microscopy. Dynamics of crista lamellae and mobile CJs were demonstrated by nanoscopy in living cells. With tBID-induced apoptosis a single entirely fused cristae reticulum was observed in a mitochondrial spheroid.
CRITICAL ISSUES: The mobility and composition of MICOS, OPA1, and ATP-synthase dimeric rows regulated by posttranslational modifications might be exclusively responsible for cristae morphology changes, but ion fluxes across CM and resulting osmotic forces might be also involved. Inevitably, cristae ultramorphology should reflect also mitochondrial redox homeostasis, but details are unknown. Disordered cristae typically reflect higher superoxide formation.
FUTURE DIRECTIONS: To link redox homeostasis to cristae ultramorphology and define markers, recent progress will help in uncovering mechanisms involved in proton-coupled electron transfer via the respiratory chain and in regulation of cristae architecture, leading to structural determination of superoxide formation sites and cristae ultramorphology changes in diseases.

DOI: https://doi.org/10.1089/ars.2022.0173
Proc Natl Acad Sci U S A. 2023 Feb 21. 120(8): e2218510120

Time of day determines postexercise metabolism in mouse adipose tissue.

Logan A Pendergrast, Leonidas S Lundell, Amy M Ehrlich, Stephen P Ashcroft, Milena Schönke, Astrid L Basse, Anna Krook, Jonas T Treebak, Lucile Dollet, Juleen R Zierath.

  The circadian clock is a cell-autonomous transcription-translation feedback mechanism that anticipates and adapts physiology and behavior to different phases of the day. A variety of factors including hormones, temperature, food-intake, and exercise can act on tissue-specific peripheral clocks to alter the expression of genes that influence metabolism, all in a time-of-day dependent manner. The aim of this study was to elucidate the effects of exercise timing on adipose tissue metabolism. We performed RNA sequencing on inguinal adipose tissue of mice immediately following maximal exercise or sham treatment at the early rest or early active phase. Only during the early active phase did exercise elicit an immediate increase in serum nonesterified fatty acids. Furthermore, early active phase exercise increased expression of markers of thermogenesis and mitochondrial proliferation in inguinal adipose tissue. In vitro, synchronized 3T3-L1 adipocytes showed a timing-dependent difference in Adrb2 expression, as well as a greater lipolytic activity. Thus, the response of adipose tissue to exercise is time-of-day sensitive and may be partly driven by the circadian clock. To determine the influence of feeding state on the time-of-day response to exercise, we replicated the experiment in 10-h-fasted early rest phase mice to mimic the early active phase metabolic status. A 10-h fast led to a similar lipolytic response as observed after active phase exercise but did not replicate the transcriptomic response, suggesting that the observed changes in gene expression are not driven by feeding status. In conclusion, acute exercise elicits timing-specific effects on adipose tissue to maintain metabolic homeostasis.

Keywords:  adipose tissue; circadian rhythm; exercise; lipolysis; metabolism

DOI:  https://doi.org/10.1073/pnas.2218510120
J Clin Invest. 2023 Feb 15. pii: e167079. [Epub ahead of print]133(4):

Mitochondrial function in macrophages controls cardiac repair after myocardial infarction.

David Weissman, Christoph Maack.

Cardiac healing following acute myocardial infarction (MI) involves the mobilization and activation of immune cells, including macrophages. In the early phase after MI, macrophages adopt a proinflammatory phenotype, while polarizing toward a reparative one in the late stage. Although metabolic reprogramming has been observed during this transition, the mechanistic links to macrophage differentiation are still poorly understood. In this issue of the JCI, Cai, Zhao and colleagues demonstrate that mitochondrial function in macrophages governed the resolution of inflammation and tissue repair by modulating the phagocytic removal of apoptotic cells (so-called efferocytosis) as well as myofibroblast activation. These findings provide important mechanistic insights into the potential relevance of metabolic modulation of macrophage functions following MI, which might lead to alternative therapeutic strategies for MI.

DOI: https://doi.org/10.1172/JCI167079
Lab Invest. 2022 01;pii: S0023-6837(22)00107-6. [Epub ahead of print]102(1): 69-79

ATP synthase inhibitory factor subunit 1 regulates islet β-cell function via repression of mitochondrial homeostasis.

Kailiang Zhang, Rong Bao, Fengyuan Huang, Kevin Yang, Yishu Ding, Lothar Lauterboeck, Masasuke Yoshida, Qinqiang Long, Qinglin Yang.

Mitochondrial homeostasis is crucial for the function of pancreatic β-cells. ATP synthase inhibitory factor subunit 1 (IF1) is a mitochondrial protein interacting with ATP synthase to inhibit its enzyme activity. IF1 may also play a role in maintaining ATP synthase oligomerization and mitochondrial inner membrane formation. A recent study confirmed IF1 expresses in β-cells. IF1 knockdown in cultured INS-1E β-cells enhances glucose-induced insulin release. However, the role of IF1 in islet β-cells remains little known. The present study investigates islets freshly isolated from mouse lines with global IF1 knockout (IF1-/-) and overexpression (OE). The glucose-stimulated insulin secretion was increased in islets from IF1-/- mice but decreased in islets from IF1 OE mice. Transmitted Electronic Microscopic assessment of isolated islets revealed that the number of matured insulin granules (with dense core) was relatively higher in IF1-/-, but fewer in IF1 OE islets than those of controlled islets. The mitochondrial ultrastructure within β-cells of IF1 overexpressed islets was comparable with those of wild-type mice, whereas those in IF1-/- β-cells showed increased mitochondrial mass. Mitochondrial network analysis in cultured INS-1 β-cells showed a similar pattern with an increased mitochondrial network in IF1 knockdown cells. IF1 overexpressed INS-1 β-cells showed a compromised rate of mitochondrial oxidative phosphorylation with attenuated cellular ATP content. In contrast, INS-1 cells with IF1 knockdown showed markedly increased cellular respiration with improved ATP production. These results support that IF1 is a negative regulator of insulin production and secretion via inhibiting mitochondrial mass and respiration in β-cells. Therefore, inhibiting IF1 to improve β-cell function in patients can be a novel therapeutic strategy to treat diabetes.

DOI: https://doi.org/10.1038/s41374-021-00670-x
J Mol Med (Berl). 2023 Feb 15.

Simultaneous targeting of mitochondrial Kv1.3 and lysosomal acid sphingomyelinase amplifies killing of pancreatic ductal adenocarcinoma cells in vitro and in vivo.

Sameer H Patel, Magdalena Bachmann, Stephanie Kadow, Gregory C Wilson, Mostafa M L Abdel-Salam, Kui Xu, Simone Keitsch, Matthias Soddemann, Barbara Wilker, Katrin Anne Becker, Alexander Carpinteiro, Syed A Ahmad, Ildiko Szabo, Erich Gulbins.

  Pancreas ductal adenocarcinoma (PDAC) remains a malignant tumor with very poor prognosis and low 5-year overall survival. Here, we aimed to simultaneously target mitochondria and lysosomes as a new treatment paradigm of malignant pancreas cancer in vitro and in vivo. We demonstrate that the clinically used sphingosine analog FTY-720 together with PAPTP, an inhibitor of mitochondrial Kv1.3, induce death of pancreas cancer cells in vitro and in vivo. The combination of both drugs results in a marked inhibition of the acid sphingomyelinase and accumulation of cellular sphingomyelin in vitro and in vivo in orthotopic and flank pancreas cancers. Mechanistically, PAPTP and FTY-720 cause a disruption of both mitochondria and lysosomes, an alteration of mitochondrial bioenergetics and accumulation of cytoplasmic Ca2+, events that collectively mediate cell death. Our findings point to an unexpected cross-talk between lysosomes and mitochondria mediated by sphingolipid metabolism. We show that the combination of PAPTP and FTY-720 induces massive death of pancreas cancer cells, thereby leading to a substantially delayed and reduced PDAC growth in vivo. KEY MESSAGES: FTY-720 inhibits acid sphingomyelinase in pancreas cancer cells (PDAC). FTY-720 induces sphingomyelin accumulation and lysosomal dysfunction. The mitochondrial Kv1.3 inhibitor PAPTP disrupts mitochondrial functions. PAPTP and FTY-720 synergistically kill PDAC in vitro. The combination of FTY-720 and PAPTP greatly delays PDAC growth in vivo.

Keywords:  Acid sphingomyelinase; Kv1.3; Lysosomes; Mitochondria; Pancreas cancer; Sphingolipids

DOI:  https://doi.org/10.1007/s00109-023-02290-y
Trends Immunol. 2023 Feb 09. pii: S1471-4906(23)00002-9. [Epub ahead of print]

Metabolism and epigenetics at the heart of T cell function.

Leticia Soriano-Baguet, Dirk Brenner.

  T cell subsets adapt and rewire their metabolism according to their functions and surrounding microenvironment. Whereas naive T cells rely on mitochondrial metabolic pathways characterized by low nutrient requirements, effector T cells induce kinetically faster pathways to generate the biomass and energy needed for proliferation and cytokine production. Recent findings support the concept that alterations in metabolism also affect the epigenetics of T cells. In this review we discuss the connections between T cell metabolism and epigenetic changes such as histone post-translational modifications (PTMs) and DNA methylation, as well as the 'extra-metabolic' roles of metabolic enzymes and molecules. These findings collectively point to a new group of potential therapeutic targets for the treatment of T cell-dependent autoimmune diseases and cancers.

Keywords:  DNA; NAD; T cells; acetylation; epigentics; histone; metabolism; methylation

DOI:  https://doi.org/10.1016/j.it.2023.01.002
Cell Death Dis. 2023 Feb 11. 14(2): 110

Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans.

Christina Ploumi, Emmanouil Kyriakakis, Nektarios Tavernarakis.

Mitochondria preserve metabolic homeostasis and integrate stress signals, to trigger cytoprotective, or cell death pathways. Mitochondrial homeostasis and function decline with age. The mechanisms underlying the deterioration of mitochondrial homeostasis during ageing, or in age-associated pathologies, remain unclear. Here, we show that CISD-1, a mitochondrial iron-sulfur cluster binding protein, implicated in the pathogenesis of Wolfram neurodegenerative syndrome type 2, modulates longevity in the nematode Caenorhabditis elegans by engaging autophagy and the mitochondrial intrinsic apoptosis pathway. The anti-apoptotic protein CED-9 is the downstream effector that mediates CISD-1-dependent effects on proteostasis, neuronal integrity and lifespan. Moreover, intracellular iron abundance is critical for CISD-1 function, since mild iron supplementation is sufficient to decelerate ageing and partly ameliorate the disturbed mitochondrial bioenergetics and proteostasis of CISD-1 deficient animals. Our findings reveal that CISD-1 serves as a mechanistic link between autophagy and the apoptotic pathway in mitochondria to differentially modulate organismal proteostasis and ageing, and suggest novel approaches which could facilitate the treatment of Wolfram Syndrome or related diseases.

DOI: https://doi.org/10.1038/s41419-023-05638-x
Nat Cardiovasc Res. 2022 Sep;1(9): 817-829

Integrated landscape of cardiac metabolism in end-stage human nonischemic dilated cardiomyopathy.

Emily Flam, Cholsoon Jang, Danielle Murashige, Yifan Yang, Michael P Morley, Sunhee Jung, Daniel S Kantner, Hannah Pepper, Kenneth C Bedi, Jeff Brandimarto, Benjamin L Prosser, Thomas Cappola, Nathaniel W Snyder, Joshua D Rabinowitz, Kenneth B Margulies, Zolt Arany.

Heart failure (HF) is a leading cause of mortality. Failing hearts undergo profound metabolic changes, but a comprehensive evaluation in humans is lacking. We integrate plasma and cardiac tissue metabolomics of 678 metabolites, genome-wide RNA-sequencing, and proteomic studies to examine metabolic status in 87 explanted human hearts from 39 patients with end-stage HF compared with 48 nonfailing donors. We confirm bioenergetic defects in human HF and reveal selective depletion of adenylate purines required for maintaining ATP levels. We observe substantial reductions in fatty acids and acylcarnitines in failing tissue, despite plasma elevations, suggesting defective import of fatty acids into cardiomyocytes. Glucose levels, in contrast, are elevated. Pyruvate dehydrogenase, which gates carbohydrate oxidation, is de-repressed, allowing increased lactate and pyruvate burning. Tricarboxylic acid cycle intermediates are significantly reduced. Finally, bioactive lipids are profoundly reprogrammed, with marked reductions in ceramides and elevations in lysoglycerophospholipids. These data unveil profound metabolic abnormalities in human failing hearts.

DOI: https://doi.org/10.1038/s44161-022-00117-6
Mitochondrion. 2023 Feb 09. pii: S1567-7249(23)00015-6. [Epub ahead of print]69 104-115

Essential mitochondrial role in iron-sulfur cluster assembly of the cytoplasmic isopropylmalate isomerase Leu1 in Saccharomyces cerevisiae.

Ashutosh K Pandey, Jayashree Pain, Brindha J, Andrew Dancis, Debkumar Pain.

  Iron-sulfur (Fe-S) cluster assembly in mitochondria and cytoplasm is essential for cell viability. In the yeast S. cerevisiae, Leu1 [4Fe-4S] is the cytoplasmic isopropylmalate isomerase involved in leucine biosynthesis. Using permeabilized Δleu1 cells and recombinant apo-Leu1R, here we show that the [4Fe-4S] cluster assembly on Leu1R can be reconstituted in a physiologic manner requiring both mitochondria and cytoplasm, as judged by conversion of the inactive enzyme to an active form. The mitochondrial contribution to this reconstitution assay is abrogated by inactivating mutations in the mitochondrial ISC (iron-sulfur cluster assembly) machinery components (such as Nfs1 cysteine desulfurase and Ssq1 chaperone) or the mitochondrial exporter Atm1. Likewise, depletion of a CIA (cytoplasmic iron-sulfur protein assembly) component Dre2 leads to impaired Leu1R reconstitution. Mitochondria likely make and export an intermediate, called X-S or (Fe-S)int, that is needed for cytoplasmic Fe-S cluster biosynthesis. Here we show that once exported, the same intermediate can be used for both [2Fe-2S] and [4Fe-4S] cluster biogenesis in the cytoplasm, with no further requirement of mitochondria. Our data also suggest that the exported intermediate can activate defective/latent CIA components in cytoplasm isolated from nfs1 or Δatm1 mutant cells. These findings may provide a way to isolate X-S or (Fe-S)int.

Keywords:  Cytoplasm; Fe-S cluster assembly; Iron-sulfur intermediate; Mitochondria; Mitochondrial export; Permeabilized cells

DOI:  https://doi.org/10.1016/j.mito.2023.02.006
Nat Commun. 2023 Feb 13. 14(1): 721

Repair of airway epithelia requires metabolic rewiring towards fatty acid oxidation.

Stefania Crotta, Matteo Villa, Jack Major, Katja Finsterbusch, Miriam Llorian, Peter Carmeliet, Joerg Buescher, Andreas Wack.

Epithelial tissues provide front-line barriers shielding the organism from invading pathogens and harmful substances. In the airway epithelium, the combined action of multiciliated and secretory cells sustains the mucociliary escalator required for clearance of microbes and particles from the airways. Defects in components of mucociliary clearance or barrier integrity are associated with recurring infections and chronic inflammation. The timely and balanced differentiation of basal cells into mature epithelial cell subsets is therefore tightly controlled. While different growth factors regulating progenitor cell proliferation have been described, little is known about the role of metabolism in these regenerative processes. Here we show that basal cell differentiation correlates with a shift in cellular metabolism from glycolysis to fatty acid oxidation (FAO). We demonstrate both in vitro and in vivo that pharmacological and genetic impairment of FAO blocks the development of fully differentiated airway epithelial cells, compromising the repair of airway epithelia. Mechanistically, FAO links to the hexosamine biosynthesis pathway to support protein glycosylation in airway epithelial cells. Our findings unveil the metabolic network underpinning the differentiation of airway epithelia and identify novel targets for intervention to promote lung repair.

DOI: https://doi.org/10.1038/s41467-023-36352-z
Nat Metab. 2023 Feb 16.

PFKFB2-mediated glycolysis promotes lactate-driven continual efferocytosis by macrophages.

Maaike Schilperoort, David Ngai, Marina Katerelos, David A Power, Ira Tabas.

Resolving-type macrophages prevent chronic inflammation by clearing apoptotic cells through efferocytosis. These macrophages are thought to rely mainly on oxidative phosphorylation, but emerging evidence suggests a possible link between efferocytosis and glycolysis. To gain further insight into this issue, we investigated molecular-cellular mechanisms involved in efferocytosis-induced macrophage glycolysis and its consequences. We found that efferocytosis promotes a transient increase in macrophage glycolysis that is dependent on rapid activation of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2), which distinguishes this process from glycolysis in pro-inflammatory macrophages. Mice transplanted with activation-defective PFKFB2 bone marrow and then subjected to dexamethasone-induced thymocyte apoptosis exhibit impaired thymic efferocytosis, increased thymic necrosis, and lower expression of the efferocytosis receptors MerTK and LRP1 on thymic macrophages compared with wild-type control mice. In vitro mechanistic studies revealed that glycolysis stimulated by the uptake of a first apoptotic cell promotes continual efferocytosis through lactate-mediated upregulation of MerTK and LRP1. Thus, efferocytosis-induced macrophage glycolysis represents a unique metabolic process that sustains continual efferocytosis in a lactate-dependent manner. The differentiation of this process from inflammatory macrophage glycolysis raises the possibility that it could be therapeutically enhanced to promote efferocytosis and resolution in chronic inflammatory diseases.

DOI: https://doi.org/10.1038/s42255-023-00736-8
Lab Invest. 2022 09;pii: S0023-6837(22)00274-4. [Epub ahead of print]102(9): 979-988

Fibroblast growth factor 21, a stress regulator, inhibits Drp1 activation to alleviate skeletal muscle ischemia/reperfusion injury.

Baoxiang Li, Limin Liu.

Abnormal Drp1 activation and subsequent excessive mitochondrial fission play a critical role in ischemia-reperfusion injury (I/RI). Although fibroblast growth factor 21 (FGF21) protects organs against I/RI and regulates metabolism, which indicates that FGF21 is involved in mitochondria homeostasis, the detailed mechanism remains unclear. Herein, we investigated whether FGF21 had an effect on Drp1 activation during skeletal muscle I/RI. Drp1 phosphorylation and its translocation to mitochondria, as regulated by FGF21, was examined in mouse and C2C12 cell I/RI models. Mice overexpressing FGF21 displayed alleviation of serum index, histological lesions and apoptosis levels. Moreover, FGF21 markedly decreased cyclin-dependent kinase 1 (CDK1) and Drp1 phosphorylation at Ser616, accompanied by reduced accumulation in mitochondria. In parallel in vitro studies, cells with FGF21 knockdown displayed enhanced Drp1 activation, and the reverse effect was found when FGF21 was added. More importantly, FGF21 attenuated mitochondrial fission with linear mitochondria rather than fragmented mitochondria. Furthermore, a CDK1 inhibitor reduced Drp1 activation and mitochondrial fission due to FGF21 knockdown. This study shows that FGF21 inhibits Drp1 activation to protect mitochondria from fission, thereby rescuing cells from I/RI-induced apoptosis. Our findings may provide a new therapeutic approach to ameliorate skeletal muscle I/RI.

DOI: https://doi.org/10.1038/s41374-022-00787-7
Nat Microbiol. 2023 Feb 16.

Metabolic heterogeneity and cross-feeding within isogenic yeast populations captured by DILAC.

Stephan Kamrad, Clara Correia-Melo, Lukasz Szyrwiel, Simran Kaur Aulakh, Jürg Bähler, Vadim Demichev, Michael Mülleder, Markus Ralser.

Genetically identical cells are known to differ in many physiological parameters such as growth rate and drug tolerance. Metabolic specialization is believed to be a cause of such phenotypic heterogeneity, but detection of metabolically divergent subpopulations remains technically challenging. We developed a proteomics-based technology, termed differential isotope labelling by amino acids (DILAC), that can detect producer and consumer subpopulations of a particular amino acid within an isogenic cell population by monitoring peptides with multiple occurrences of the amino acid. We reveal that young, morphologically undifferentiated yeast colonies contain subpopulations of lysine producers and consumers that emerge due to nutrient gradients. Deconvoluting their proteomes using DILAC, we find evidence for in situ cross-feeding where rapidly growing cells ferment and provide the more slowly growing, respiring cells with ethanol. Finally, by combining DILAC with fluorescence-activated cell sorting, we show that the metabolic subpopulations diverge phenotypically, as exemplified by a different tolerance to the antifungal drug amphotericin B. Overall, DILAC captures previously unnoticed metabolic heterogeneity and provides experimental evidence for the role of metabolic specialization and cross-feeding interactions as a source of phenotypic heterogeneity in isogenic cell populations.

DOI: https://doi.org/10.1038/s41564-022-01304-8
J Physiol. 2023 Feb 17.

On the interdependence of ketone body oxidation,glycogen content, glycolysis and energy metabolism in the heart.

Azrul Abdul Kadir, Brianna J Stubbs, Cher-Rin Chong, Henry Lee, Mark Cole, Carolyn Carr, David Hauton, James McCullagh, Rhys D Evans, Kieran Clarke.

  In heart, glucose and glycolysis are important for anaplerosis and potentially therefore for d-beta-hydroxybutyrate (βHB) oxidation. As a glucose store, glycogen may also furnish anaplerosis. We determined the effects of glycogen content on βHB oxidation and glycolytic rates, and their downstream effects on energetics, in the isolated rat heart. High glycogen (HG) and low glycogen (LG) containing hearts were perfused with 11 mM [5-3 H]-glucose and/or 4mM [14 C]-βHB to measure glycolytic rates or βHB oxidation, respectively, then freeze-clamped for glycogen and metabolomic analyses. Free cytosolic [NAD+ ]/[NADH] and mitochondrial [Q+ ]/[QH2 ] ratios were estimated using the lactate dehydrogenase and succinate dehydrogenase reactions, respectively. Phosphocreatine (PCr) and inorganic phosphate (Pi) concentrations were measured using 31 P-NMR spectroscopy. Rates of βHB oxidation in LG hearts were half that in HG hearts, with βHB oxidation directly proportional to glycogen content. βHB oxidation decreased glycolysis in all hearts. Glycogenolysis in glycogen-replete hearts perfused with βHB alone was twice that of hearts perfused with βHB and glucose, which had significantly higher levels of the glycolytic intermediates, fructose 1,6-bisphosphate and 3-phosphoglycerate, and higher free cytosolic [NAD+ ]/[NADH]. βHB oxidation increased the Krebs cycle intermediates citrate, 2-oxoglutarate and succinate, the total nicotinamide adenine dinucleotide phosphate (NADP/H) pool, reduced mitochondrial [Q+ ]/[QH2 ], and increased the calculated free energy of ATP hydrolysis (∆GATP ). Although βHB oxidation inhibited glycolysis, glycolytic intermediates were not depleted, and cytosolic free NAD remained oxidised. βHB oxidation alone increased Krebs cycle intermediates, reduced mitochondrial Q and increased ∆GATP . We conclude that glycogen facilitates cardiac βHB oxidation by anaplerosis. KEY POINTS: Ketone bodies (D-β-hydroxybutyrate; acetoacetate) are increasingly recognised as important cardiac energetic substrates, in both healthy and diseased hearts. As 2-carbon equivalents they are cataplerotic, causing depletion of Kreb's cycle intermediates; therefore their utilisation requires anaplerotic supplementation. Intra-myocardial glycogen has been suggested as a potential anaplerotic source during ketone oxidation. We demonstrate here that cardiac glycogen does indeed provide anaplerotic substrate to facilitate β-hydroxybutyrate oxidation in isolated perfused rat heart, and utilising a novel pulse-chase metabolic approach, quantify this contribution. Further, using metabolomics and 31 P-MR, we show that glycolytic flux from myocardial glycogen increased the heart's ability to oxidise βHB, and βHB oxidation increased the mitochondrial redox potential, ultimately increasing the free energy of ATP hydrolysis. Abstract figure legend Overview of relationship of glycogen to ketone body oxidation and cardiac energetics in isolated perfused rat hearts. Myocardial glycogen was pre-labelled with tritium and its metabolic fate tracked using a pulse-chase technique. Increased glycolytic flux from glycogen facilitated increased exogenous β-hydroxybutyrate (βHB) oxidation through anaplerosis, and the increased βHB oxidation increased mitochondrial redox potential, and hence increased free energy of ATP hydrolysis. This article is protected by copyright. All rights reserved.

Keywords:  d-β-hydroxybutyrate oxidation; glycogen; glycolysis; metabolomics; redox states

DOI:  https://doi.org/10.1113/JP284270
bioRxiv. 2023 Feb 11. pii: 2023.02.11.528118. [Epub ahead of print]

Genome-wide screens for mitonuclear co-regulators uncover links between compartmentalized metabolism and mitochondrial gene expression.

Nicholas J Kramer, Gyan Prakash, Karine Choquet, Iliana Soto, Boryana Petrova, Hope E Merens, Naama Kanarek, L Stirling Churchman.

Mitochondrial oxidative phosphorylation (OXPHOS) complexes are assembled from proteins encoded by both nuclear and mitochondrial DNA. These dual-origin enzymes pose a complex gene regulatory challenge for cells, in which gene expression must be coordinated across organelles using distinct pools of ribosomes. How cells produce and maintain the accurate subunit stoichiometries for these OXPHOS complexes remains largely unknown. To identify genes involved in dual-origin protein complex synthesis, we performed FACS-based genome-wide screens analyzing mutant cells with unbalanced levels of mitochondrial- and nuclear-encoded subunits of cytochrome c oxidase (Complex IV). We identified novel genes involved in OXPHOS biogenesis, including two uncharacterized genes: PREPL and NME6 . We found that PREPL specifically regulates Complex IV biogenesis by interacting with mitochondrial protein synthesis machinery, while NME6, an uncharacterized nucleoside diphosphate kinase (NDPK), controls OXPHOS complex biogenesis through multiple mechanisms reliant on its NDPK domain. First, NME6 maintains local mitochondrial pyrimidine triphosphate levels essential for mitochondrial RNA abundance. Second, through stabilizing interactions with RCC1L, NME6 modulates the activity of mitoribosome regulatory complexes, leading to disruptions in mitoribosome assembly and mitochondrial RNA pseudouridylation. Taken together, we propose that NME6 acts as a link between compartmentalized mitochondrial metabolites and mitochondrial gene expression. Finally, we present these screens as a resource, providing a catalog of genes involved in mitonuclear gene regulation and OXPHOS biogenesis.

DOI: https://doi.org/10.1101/2023.02.11.528118
Am J Physiol Endocrinol Metab. 2023 Feb 15.

Branched chain amino acids alter cellular redox to induce lipid oxidation and reduce de novo lipogenesis in the liver.

Chaitra Surugihalli, Vaishna Muralidaran, Caitlin E Ryan, Kruti Patel, David Zhao, Nishanth E Sunny.

  Metabolic and molecular interactions between branched chain amino acid (BCAA) and lipid metabolism are evident in insulin resistant tissues. However, it remains unclear whether insulin resistance is a prerequisite for these relationships and whether BCAAs or their metabolic intermediates can modulate hepatic lipid oxidation and synthesis. We hypothesized that BCAAs can alter hepatic oxidative function and de novo lipogenesis, independent of them being anaplerotic substrates for the mitochondria. Mice (C57BL/6NJ) were reared on a low-fat (LF), LF diet plus 1.5X BCAAs (LB), high-fat (HF) or HF diet plus 1.5X BCAAs (HB) for 12-wks. Hepatic metabolism was profiled utilizing stable isotopes coupled to mass-spectrometry and nuclear magnetic resonance, together with fed-to-fasted changes in gene and protein expression. A greater induction of lipid oxidation and ketogenesis upon fasting was evident in the BCAA supplemented, insulin sensitive livers from LB mice, while their rates of hepatic de novo lipogenesis remained lower than their LF counterparts. Onset of insulin resistance in HF and HB mice livers blunted these responses. Whole-body turnover of BCAAs and their ketoacids, their serum concentrations, and the ketogenic flux from BCAA catabolism, all remained similar between fasted LF and LB mice. This suggested that the impact of BCAAs on lipid metabolism can occur independent of them or their degradation products fueling anaplerosis through the liver mitochondria. Further, the greater induction of lipid oxidation in the LB livers accompanied higher mitochondrial NADH/NAD+ ratio and higher fed-to-fasting phosphorylation of AMPKα and ACC. Taken together, our results provide evidence that BCAA supplementation, under conditions of insulin sensitivity, improved the feeding-to-fasting induction of hepatic lipid oxidation through changes in cellular redox, thus providing a favorable biochemical environment for flux through β-oxidation and lower de novo lipogenesis.

Keywords:  branched chain amino acids; fatty acid oxidation; lipogenesis; liver metabolism; mitochondria

DOI:  https://doi.org/10.1152/ajpendo.00307.2022
J Clin Invest. 2023 Feb 15. pii: e165654. [Epub ahead of print]133(4):

Molecular pathways that drive diabetic kidney disease.

Samer Mohandes, Tomohito Doke, Hailong Hu, Dhanunjay Mukhi, Poonam Dhillon, Katalin Susztak.

Kidney disease is a major driver of mortality among patients with diabetes and diabetic kidney disease (DKD) is responsible for close to half of all chronic kidney disease cases. DKD usually develops in a genetically susceptible individual as a result of poor metabolic (glycemic) control. Molecular and genetic studies indicate the key role of podocytes and endothelial cells in driving albuminuria and early kidney disease in diabetes. Proximal tubule changes show a strong association with the glomerular filtration rate. Hyperglycemia represents a key cellular stress in the kidney by altering cellular metabolism in endothelial cells and podocytes and by imposing an excess workload requiring energy and oxygen for proximal tubule cells. Changes in metabolism induce early adaptive cellular hypertrophy and reorganization of the actin cytoskeleton. Later, mitochondrial defects contribute to increased oxidative stress and activation of inflammatory pathways, causing progressive kidney function decline and fibrosis. Blockade of the renin-angiotensin system or the sodium-glucose cotransporter is associated with cellular protection and slowing kidney function decline. Newly identified molecular pathways could provide the basis for the development of much-needed novel therapeutics.

DOI: https://doi.org/10.1172/JCI165654
bioRxiv. 2023 Feb 06. pii: 2023.01.30.526178. [Epub ahead of print]

Fully accessible fitness landscape of oncogene-negative lung adenocarcinoma.

Maryam Yousefi, Laura Andrejka, Monte M Winslow, Dmitri A Petrov, Gábor Boross.

Cancer genomes are almost invariably complex with genomic alterations cooperating during each step of carcinogenesis. In cancers that lack a single dominant oncogene mutation, cooperation between the inactivation of multiple tumor suppressor genes can drive tumor initiation and growth. Here, we shed light on how the sequential acquisition of genomic alterations generates oncogene-negative lung tumors. We couple tumor barcoding with combinatorial and multiplexed somatic genome editing to characterize the fitness landscapes of three tumor suppressor genes NF1, RASA1, and PTEN, the inactivation of which jointly drives oncogene-negative lung adenocarcinoma initiation and growth. The fitness landscape was surprisingly accessible, with each additional mutation leading to growth advantage. Furthermore, the fitness landscapes remained fully accessible across backgrounds with additional tumor suppressor mutations. These results suggest that while predicting cancer evolution will be challenging, acquiring the multiple alterations required for the growth of oncogene-negative tumors can be facilitated by the lack of constraints on mutational order.

DOI: https://doi.org/10.1101/2023.01.30.526178
EMBO Rep. 2023 Feb 16. e55548

Reverse electron transfer is activated during aging and contributes to aging and age-related disease.

Suman Rimal, Ishaq Tantray, Yu Li, Tejinder Pal Khaket, Yanping Li, Sunil Bhurtel, Wen Li, Cici Zeng, Bingwei Lu.

  Mechanisms underlying the depletion of NAD+ and accumulation of reactive oxygen species (ROS) in aging and age-related disorders remain poorly defined. We show that reverse electron transfer (RET) at mitochondrial complex I, which causes increased ROS production and NAD+ to NADH conversion and thus lowered NAD+ /NADH ratio, is active during aging. Genetic or pharmacological inhibition of RET decreases ROS production and increases NAD+ /NADH ratio, extending the lifespan of normal flies. The lifespan-extending effect of RET inhibition is dependent on NAD+ -dependent Sirtuin, highlighting the importance of NAD+ /NADH rebalance, and on longevity-associated Foxo and autophagy pathways. RET and RET-induced ROS and NAD+ /NADH ratio changes are prominent in human induced pluripotent stem cell (iPSC) model and fly models of Alzheimer's disease (AD). Genetic or pharmacological inhibition of RET prevents the accumulation of faulty translation products resulting from inadequate ribosome-mediated quality control, rescues relevant disease phenotypes, and extends the lifespan of Drosophila and mouse AD models. Deregulated RET is therefore a conserved feature of aging, and inhibition of RET may open new therapeutic opportunities in the context of aging and age-related diseases including AD.

Keywords:  Alzheimer's disease; NAD+/NADH ratio; lifespan; mitochondrial complex I; reverse electron transport

DOI:  https://doi.org/10.15252/embr.202255548
Nat Commun. 2023 Feb 15. 14(1): 838

Bacterial origins of thymidylate metabolism in Asgard archaea and Eukarya.

Jonathan Filée, Hubert F Becker, Lucille Mellottee, Rima Zein Eddine, Zhihui Li, Wenlu Yin, Jean-Christophe Lambry, Ursula Liebl, Hannu Myllykallio.

Asgard archaea include the closest known archaeal relatives of eukaryotes. Here, we investigate the evolution and function of Asgard thymidylate synthases and other folate-dependent enzymes required for the biosynthesis of DNA, RNA, amino acids and vitamins, as well as syntrophic amino acid utilization. Phylogenies of Asgard folate-dependent enzymes are consistent with their horizontal transmission from various bacterial groups. We experimentally validate the functionality of thymidylate synthase ThyX of the cultured 'Candidatus Prometheoarchaeum syntrophicum'. The enzyme efficiently uses bacterial-like folates and is inhibited by mycobacterial ThyX inhibitors, even though the majority of experimentally tested archaea are known to use carbon carriers distinct from bacterial folates. Our phylogenetic analyses suggest that the eukaryotic thymidylate synthase, required for de novo DNA synthesis, is not closely related to archaeal enzymes and might have been transferred from bacteria to protoeukaryotes during eukaryogenesis. Altogether, our study suggests that the capacity of eukaryotic cells to duplicate their genetic material is a sum of archaeal (replisome) and bacterial (thymidylate synthase) characteristics. We also propose that recent prevalent lateral gene transfer from bacteria has markedly shaped the metabolism of Asgard archaea.

DOI: https://doi.org/10.1038/s41467-023-36487-z
Cell Rep. 2023 Feb 14. pii: S2211-1247(23)00138-9. [Epub ahead of print]42(2): 112127

Circadian regulator CLOCK promotes tumor angiogenesis in glioblastoma.

Lizhi Pang, Madeline Dunterman, Wenjing Xuan, Annette Gonzalez, Yiyun Lin, Wen-Hao Hsu, Fatima Khan, Robert S Hagan, William A Muller, Amy B Heimberger, Peiwen Chen.

  Glioblastoma (GBM) is one of the most aggressive tumors in the adult central nervous system. We previously revealed that circadian regulation of glioma stem cells (GSCs) affects GBM hallmarks of immunosuppression and GSC maintenance in a paracrine and autocrine manner. Here, we expand the mechanism involved in angiogenesis, another critical GBM hallmark, as a potential basis underlying CLOCK's pro-tumor effect in GBM. Mechanistically, CLOCK-directed olfactomedin like 3 (OLFML3) expression results in hypoxia-inducible factor 1-alpha (HIF1α)-mediated transcriptional upregulation of periostin (POSTN). As a result, secreted POSTN promotes tumor angiogenesis via activation of the TANK-binding kinase 1 (TBK1) signaling in endothelial cells. In GBM mouse and patient-derived xenograft models, blockade of the CLOCK-directed POSTN-TBK1 axis inhibits tumor progression and angiogenesis. Thus, the CLOCK-POSTN-TBK1 circuit coordinates a key tumor-endothelial cell interaction and represents an actionable therapeutic target for GBM.

Keywords:  BMAL1; CLOCK; CP: Cancer; TBK1; and POSTN; angiogenesis; circadian rhythm; glioblastoma; tumor microenvironment

DOI:  https://doi.org/10.1016/j.celrep.2023.112127
bioRxiv. 2023 Jan 31. pii: 2023.01.31.526492. [Epub ahead of print]

Tubular Mitochondrial Pyruvate Carrier Disruption Elicits Redox Adaptations that Protect from Acute Kidney Injury.

Adam J Rauckhorst, Gabriela Vasquez Martinez, Gabriel Mayoral Andrade, Hsiang Wen, Ji Young Kim, Aaron Simoni, Kranti A Mapuskar, Prerna Rastogi, Emily J Steinbach, Michael L McCormick, Bryan G Allen, Navjot S Pabla, Ashley R Jackson, Mitchell C Coleman, Douglas R Spitz, Eric B Taylor, Diana Zepeda-Orozco.

Energy-intensive kidney reabsorption processes essential for normal whole-body function are maintained by tubular epithelial cell metabolism. Tubular metabolism changes markedly following acute kidney injury (AKI), but which changes are adaptive versus maladaptive remain poorly understood. In publicly available data sets, we noticed a consistent downregulation of the mitochondrial pyruvate carrier (MPC) after AKI, which we experimentally confirmed. To test the functional consequences of MPC downregulation, we generated novel tubular epithelial cell-specific Mpc1 knockout (MPC TubKO) mice. 13 C-glucose tracing, steady-state metabolomic profiling, and enzymatic activity assays revealed that MPC TubKO coordinately increased activities of the pentose phosphate pathway and the glutathione and thioredoxin oxidant defense systems. Following rhabdomyolysis-induced AKI, MPC TubKO decreased markers of kidney injury and oxidative damage and strikingly increased survival. Our findings suggest that decreased mitochondrial pyruvate uptake is a central adaptive response following AKI and raise the possibility of therapeutically modulating the MPC to attenuate AKI severity.

DOI: https://doi.org/10.1101/2023.01.31.526492
bioRxiv. 2023 Feb 07. pii: 2023.02.07.527498. [Epub ahead of print]

Nucleotide excision repair deficiency is a targetable therapeutic vulnerability in clear cell renal cell carcinoma.

Aurel Prosz, Haohui Duan, Viktoria Tisza, Pranshu Sahgal, Sabine Topka, Gregory T Klus, Judit Börcsök, Zsofia Sztupinszki, Timothy Hanlon, Miklos Diossy, Laura Vizkeleti, Dag Rune Stormoen, Istvan Csabai, Helle Pappot, Joseph Vijai, Kenneth Offit, Thomas Ried, Nilay Sethi, Kent W Mouw, Sandor Spisak, Shailja Pathania, Zoltan Szallasi.

Purpose: Due to a demonstrated lack of DNA repair deficiencies, clear cell renal cell carcinoma (ccRCC) has not benefitted from targeted synthetic lethality-based therapies. We investigated whether nucleotide excision repair (NER) deficiency is present in an identifiable subset of ccRCC cases that would render those tumors sensitive to therapy targeting this specific DNA repair pathway aberration.Experimental Design: We used functional assays that detect UV-induced 6-4 pyrimidine-pyrimidone photoproducts to quantify NER deficiency in ccRCC cell lines. We also measured sensitivity to irofulven, an experimental cancer therapeutic agent that specifically targets cells with inactivated transcription-coupled nucleotide excision repair (TC-NER). In order to detect NER deficiency in clinical biopsies, we assessed whole exome sequencing data for the presence of an NER deficiency associated mutational signature previously identified in ERCC2 mutant bladder cancer.
Results: Functional assays showed NER deficiency in ccRCC cells. Irofulven sensitivity increased in some cell lines. Prostaglandin reductase 1 (PTGR1), which activates irofulven, was also associated with this sensitivity. Next generation sequencing data of the cell lines showed NER deficiency-associated mutational signatures. A significant subset of ccRCC patients had the same signature and high PTGR1 expression.
Conclusions: ccRCC cell line based analysis showed that NER deficiency is likely present in this cancer type. Approximately 10% of ccRCC patients in the TCGA cohort showed mutational signatures consistent with ERCC2 inactivation associated NER deficiency and also substantial levels of PTGR1 expression. These patients may be responsive to irofulven, a previously abandoned anticancer agent that has minimal activity in NER-proficient cells.
Translational relevance: DNA repair deficiencies can be therapeutically targeted by synthetic lethal-based strategies in cancer. However, clear cell renal cell carcinoma (ccRCC) has not benefitted from this therapeutic approach due to a lack of evidence for the presence of specific DNA repair pathway deficiencies. Here, we demonstrate that ccRCC harbors a therapeutically targetable DNA repair pathway aberration, nucleotide excision repair (NER) deficiency. ccRCC cell lines displayed robust signs of NER deficiency as determined by functional assays and some of these cell lines also displayed NER deficiency induced mutational signatures. These cell lines are also sensitive to irofulven, an abandoned anticancer agent that creates DNA lesions which can only be repaired by the NER pathway. We estimate that up to 10% of ccRCC cases may respond to NER-directed therapy with irofulven based on NER deficiency associated mutational signatures and PTGR1 expression levels, which is an enzyme required to activate irofulven.

DOI: https://doi.org/10.1101/2023.02.07.527498
Semin Cell Dev Biol. 2023 Feb 13. pii: S1084-9521(23)00030-7. [Epub ahead of print]

Mitochondrial recovery by the UPRmt: Insights from C. elegans.

Joshua D Dodge, Nicholas J Browder, Mark W Pellegrino.

  Mitochondria are multifaceted organelles, with such functions as the production of cellular energy to the regulation of cell death. However, mitochondria incur various sources of damage from the accumulation of reactive oxygen species and DNA mutations that can impact the protein folding environment and impair their function. Since mitochondrial dysfunction is often associated with reductions in organismal fitness and possibly disease, cells must have safeguards in place to protect mitochondrial function and promote recovery during times of stress. The mitochondrial unfolded protein response (UPRmt) is a transcriptional adaptation that promotes mitochondrial repair to aid in cell survival during stress. While the earlier discoveries into the regulation of the UPRmt stemmed from studies using mammalian cell culture, much of our understanding about this stress response has been bestowed to us by the model organism Caenorhabditis elegans. Indeed, the facile but powerful genetics of this relatively simple nematode has uncovered multiple regulators of the UPRmt, as well as several physiological roles of this stress response. In this review, we will summarize these major advancements originating from studies using C. elegans.

Keywords:  Aging; C. elegans; Host-pathogen interactions; Infection; Mitochondria; Mitochondrial UPR; Stress response

DOI:  https://doi.org/10.1016/j.semcdb.2023.02.002
J Biol Chem. 2023 Feb 14. pii: S0021-9258(23)00150-3. [Epub ahead of print] 103018

Mitochondrial respiration reduces exposure of the nucleus to oxygen.

Mateus Prates Mori, Rozhin Penjweini, Jin Ma, Greg Alspaugh, Alessio Andreoni, Young-Chae Kim, Ping-Yuan Wang, Jay R Knutson, Paul M Hwang.

  The endosymbiotic theory posits that ancient eukaryotic cells engulfed O2-consuming prokaryotes, which protected them against O2 toxicity. Previous studies have shown that cells lacking cytochrome c oxidase (COX), required for respiration, have increased DNA damage and reduced proliferation, which could be improved by reducing O2 exposure. With recently developed fluorescence lifetime microscopy (FLIM)-based probes demonstrating that the mitochondrial compartment has lower [O2] than the cytosol, we hypothesized that the perinuclear distribution of mitochondria in cells may create a barrier for O2 to access the nuclear core, potentially affecting cellular physiology and maintaining genomic integrity. To test this hypothesis, we utilized myoglobin (MB)-mCherry FLIM O2 sensors without subcellular targeting ("cytosol") or with targeting to the mitochondrion or nucleus for measuring their localized O2 homeostasis. Our results showed that, similar to the mitochondria, the nuclear [O2] was reduced by ∼20-40% compared to the cytosol under imposed O2 levels of ∼0.5-18.6%. Pharmacologic inhibition of respiration increased nuclear O2 levels, and reconstituting O2 consumption by COX reversed this increase. Similarly, genetic disruption of respiration by deleting SCO2, a gene essential for COX assembly, or restoring COX activity in SCO2-/- cells by transducing with SCO2 cDNA also replicated these changes in nuclear O2 levels. The results were further supported by the expression of genes known to be affected by cellular O2 availability. Our study reveals the potential for dynamic regulation of nuclear O2 levels by mitochondrial respiratory activity, which in turn could affect oxidative stress and cellular processes such as neurodegeneration and aging.

Keywords:  Classification: Cell Biology; Metabolism; hypoxia; mitochondria; nucleus; oxygen; respiration

DOI:  https://doi.org/10.1016/j.jbc.2023.103018
Nat Chem Biol. 2023 Feb 13.

TMEM164 is an acyltransferase that forms ferroptotic C20:4 ether phospholipids.

Alex Reed, Timothy Ware, Haoxin Li, J Fernando Bazan, Benjamin F Cravatt.

Ferroptosis is an iron-dependent form of cell death driven by oxidation of polyunsaturated fatty acid (PUFA) phospholipids. Large-scale genetic screens have uncovered a specialized role for PUFA ether phospholipids (ePLs) in promoting ferroptosis. Understanding of the enzymes involved in PUFA-ePL production, however, remains incomplete. Here we show, using a combination of pathway mining of genetic dependency maps, AlphaFold-guided structure predictions and targeted lipidomics, that the uncharacterized transmembrane protein TMEM164-the genetic ablation of which has been shown to protect cells from ferroptosis-is a cysteine active center enzyme that selectively transfers C20:4 acyl chains from phosphatidylcholine to lyso-ePLs to produce PUFA ePLs. Genetic deletion of TMEM164 across a set of ferroptosis-sensitive cancer cell lines caused selective reductions in C20:4 ePLs with minimal effects on C20:4 diacyl PLs, and this lipid profile produced a variable range of protection from ferroptosis, supportive of an important but contextualized role for C20:4 ePLs in this form of cell death.

DOI: https://doi.org/10.1038/s41589-022-01253-7
Cell Syst. 2023 Feb 15. pii: S2405-4712(22)00497-5. [Epub ahead of print]14(2): 98-108

Spatial self-organization of metabolism in microbial systems: A matter of enzymes and chemicals.

Alma Dal Co, Martin Ackermann, Simon van Vliet.

Most bacteria live in dense, spatially structured communities such as biofilms. The high density allows cells to alter the local microenvironment, whereas the limited mobility can cause species to become spatially organized. Together, these factors can spatially organize metabolic processes within microbial communities so that cells in different locations perform different metabolic reactions. The overall metabolic activity of a community depends both on how metabolic reactions are arranged in space and on how they are coupled, i.e., how cells in different regions exchange metabolites. Here, we review mechanisms that lead to the spatial organization of metabolic processes in microbial systems. We discuss factors that determine the length scales over which metabolic activities are arranged in space and highlight how the spatial organization of metabolic processes affects the ecology and evolution of microbial communities. Finally, we define key open questions that we believe should be the main focus of future research.

DOI: https://doi.org/10.1016/j.cels.2022.12.009
Mol Biol Evol. 2023 Feb 15. pii: msad032. [Epub ahead of print]

Cell Survival Enabled by Leakage of a Labile Metabolic Intermediate.

Encarnación Medina-Carmona, Luis I Gutierrez-Rus, Fadia Manssour-Triedo, Matilda S Newton, Gloria Gamiz-Arco, Antonio J Mota, Pablo Reiné, Juan Manuel Cuerva, Mariano Ortega-Muñoz, Eduardo Andrés-León, Jose Luis Ortega-Roldan, Burckhard Seelig, Beatriz Ibarra-Molero, Jose M Sanchez-Ruiz.

  Many metabolites are generated in one step of a biochemical pathway and consumed in a subsequent step. Such metabolic intermediates are often reactive molecules which, if allowed to freely diffuse in the intracellular milieu, could lead to undesirable side reactions and even become toxic to the cell. Therefore, metabolic intermediates are often protected as protein-bound species and directly transferred between enzyme active sites in multi-functional enzymes, multi-enzyme complexes and metabolons. Sequestration of reactive metabolic intermediates thus contributes to metabolic efficiency. It is not known, however, whether this evolutionary adaptation can be relaxed in response to challenges to organismal survival. Here, we report evolutionary repair experiments on E. coli cells in which an enzyme crucial for the biosynthesis of proline has been deleted. The deletion makes cells unable to grow in a culture medium lacking proline. Remarkably, however, cell growth is efficiently restored by many single mutations (12 at least) in the gene of glutamine synthetase. The mutations cause the leakage to the intracellular milieu of a highly reactive phosphorylated intermediate common to the biosynthetic pathways of glutamine and proline. This intermediate is generally assumed to exist only as a protein-bound species. Nevertheless, its diffusion upon mutation-induced leakage enables a new route to proline biosynthesis. Our results support that leakage of sequestered metabolic intermediates can readily occur and contribute to organismal adaptation in some scenarios. Enhanced availability of reactive molecules may enable the generation of new biochemical pathways and the potential of mutation-induced leakage in metabolic engineering is noted.

Keywords:  auxotrophy rescue; evolutionary repair experiments; labile metabolic intermediates; laboratory evolution; metabolic innovation; prototrophy restoration

DOI:  https://doi.org/10.1093/molbev/msad032
Biophys J. 2023 Feb 10. pii: S0006-3495(22)01801-X. [Epub ahead of print]122(3S1): 133a

Super-resolution non-linear multimodal imaging platform for studying spatially correlated metabolic reactions.

Hongje Jang, Zhi Li, Yajuan Li, Pegah Bagheri, Ellen Ackerstaff, Jason A Koutcher, Lingyan Shi.

DOI: https://doi.org/10.1016/j.bpj.2022.11.885
Nat Cancer. 2023 Feb 15.

Palmitate oxidation drives a pro-metastatic post-translational modification.

DOI: https://doi.org/10.1038/s43018-023-00514-1
J Cell Biol. 2023 Mar 06. pii: e202211044. [Epub ahead of print]222(3):

Mitochondria on the move: Horizontal mitochondrial transfer in disease and health.

Lan-Feng Dong, Jakub Rohlena, Renata Zobalova, Zuzana Nahacka, Anne-Marie Rodriguez, Michael V Berridge, Jiri Neuzil.

Mammalian genes were long thought to be constrained within somatic cells in most cell types. This concept was challenged recently when cellular organelles including mitochondria were shown to move between mammalian cells in culture via cytoplasmic bridges. Recent research in animals indicates transfer of mitochondria in cancer and during lung injury in vivo, with considerable functional consequences. Since these pioneering discoveries, many studies have confirmed horizontal mitochondrial transfer (HMT) in vivo, and its functional characteristics and consequences have been described. Additional support for this phenomenon has come from phylogenetic studies. Apparently, mitochondrial trafficking between cells occurs more frequently than previously thought and contributes to diverse processes including bioenergetic crosstalk and homeostasis, disease treatment and recovery, and development of resistance to cancer therapy. Here we highlight current knowledge of HMT between cells, focusing primarily on in vivo systems, and contend that this process is not only (patho)physiologically relevant, but also can be exploited for the design of novel therapeutic approaches.

DOI: https://doi.org/10.1083/jcb.202211044
J Biol Chem. 2023 Feb 10. pii: S0021-9258(23)00137-0. [Epub ahead of print] 103005

Innate immune cell-intrinsic ketogenesis is dispensable for organismal metabolism and age-related inflammation.

Emily L Goldberg, Anudari Letian, Tamara Dlugos, Claire Leveau, Vishwa Deep Dixit.

  Aging is accompanied by chronic low-grade inflammation, but the mechanisms that allow this to persist are not well understood. Ketone bodies are alternative fuels produced when glucose is limited and improve indicators of healthspan in aging mouse models. Moreover, the most abundant ketone body, β-hydroxybutyrate (BHB), inhibits the NLRP3 inflammasome in myeloid cells, a key potentiator of age-related inflammation. Given that myeloid cells express ketogenic machinery, we hypothesized this pathway may serve as a metabolic checkpoint of inflammation. To test this hypothesis, we conditionally ablated ketogenesis by disrupting expression of the terminal enzyme required for ketogenesis, 3-Hydroxy-3-Methylglutaryl-CoA Lyase (HMGCL). By deleting HMGCL in the liver, we validated the functional targeting and establish that the liver is the only organ that can produce the life-sustaining quantities of ketone bodies required for survival during fasting or ketogenic diet feeding. Conditional ablation of HMGCL in neutrophils and macrophages had modest effects on body weight and glucose tolerance in aging, but worsened glucose homeostasis in myeloid cell-specific Hmgcl-deficient mice fed a high-fat diet. Our results suggest that during aging, liver-derived circulating ketone bodies might be more important for deactivating the NLRP3 inflammasome and controlling organismal metabolism.

Keywords:  aging; inflammation; innate immunity; ketone; metabolism

DOI:  https://doi.org/10.1016/j.jbc.2023.103005