Absence of retbindin blocks glycolytic flux, disrupts metabolic homeostasis, and leads to photoreceptor degeneration

We previously reported a model of progressive retinal degeneration resulting from the knockout of the retina-specific riboflavin binding protein, retbindin (Rtbdn−/−). We also demonstrated a reduction in neural retinal flavins as a result of the elimination of RTBDN. Given the role of flavins in metabolism, herein we investigated the underlying mechanism of this retinal degeneration by performing metabolomic analyses on predegeneration at postnatal day (P) 45 and at the onset of functional degeneration in the P120 retinas. Metabolomics of hydrophilic metabolites revealed that individual glycolytic products accumulated in the P45 Rtbdn−/− neural retinas along with the elevation of pentose phosphate pathway, while TCA cycle intermediates remained unchanged. This was confirmed by using 13C-labeled flux measurements and immunoblotting, revealing that the key regulatory step of phosphoenolpyruvate to pyruvate was inhibited via down-regulation of the tetrameric pyruvate kinase M2 (PKM2). Separate metabolite assessments revealed that almost all intermediates of acylcarnitine fatty acid oxidation, ceramides, sphingomyelins, and multiple toxic metabolites were significantly elevated in the predegeneration Rtbdn−/− neural retina. Our data show that lack of RTBDN, and hence reduction in flavins, forced the neural retina into repurposing glucose for free-radical mitigation over ATP production. However, such sustained metabolic reprogramming resulted in an eventual metabolic collapse leading to neurodegeneration.

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β-Hydroxybutyrate Oxidation Promotes the Accumulation of Immunometabolites in Activated Microglia Cells

Metabolites ◽

10.3390/metabo10090346 ◽

2020 ◽

Vol 10 (9) ◽

pp. 346

Author(s):

Adrian Benito ◽

Nabil Hajji ◽

Kevin O’Neill ◽

Hector C. Keun ◽

Nelofer Syed

Keyword(s):

Metabolic Regulation ◽

Marker Gene ◽

Tca Cycle ◽

Metabolic Reprogramming ◽

Glycolytic Flux ◽

Dihydroxyacetone Phosphate ◽

Glycolytic Intermediate ◽

Critical Set ◽

The Tca Cycle ◽

Bv2 Cells

Metabolic regulation of immune cells has arisen as a critical set of processes required for appropriate response to immunological signals. While our knowledge in this area has rapidly expanded in leukocytes, much less is known about the metabolic regulation of brain-resident microglia. In particular, the role of alternative nutrients to glucose remains poorly understood. Here, we use stable-isotope (13C) tracing strategies and metabolomics to characterize the oxidative metabolism of β-hydroxybutyrate (BHB) in human (HMC3) and murine (BV2) microglia cells and the interplay with glucose in resting and LPS-activated BV2 cells. We found that BHB is imported and oxidised in the TCA cycle in both cell lines with a subsequent increase in the cytosolic NADH:NAD+ ratio. In BV2 cells, stimulation with LPS upregulated the glycolytic flux, increased the cytosolic NADH:NAD+ ratio and promoted the accumulation of the glycolytic intermediate dihydroxyacetone phosphate (DHAP). The addition of BHB enhanced LPS-induced accumulation of DHAP and promoted glucose-derived lactate export. BHB also synergistically increased LPS-induced accumulation of succinate and other key immunometabolites, such as α-ketoglutarate and fumarate generated by the TCA cycle. Finally, BHB upregulated the expression of a key pro-inflammatory (M1 polarisation) marker gene, NOS2, in BV2 cells activated with LPS. In conclusion, we identify BHB as a potentially immunomodulatory metabolic substrate for microglia that promotes metabolic reprogramming during pro-inflammatory response.

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PO-153 The metabolic changes in the hippocampus of an atherosclerotic rat model and the regulation of exercise

Exercise Biochemistry Review ◽

10.14428/ebr.v1i4.11773 ◽

2018 ◽

Vol 1 (4) ◽

Author(s):

Beibei Liu ◽

Shujie Lou

Keyword(s):

Arachidonic Acid ◽

Rat Model ◽

Methyl Stearate ◽

Tca Cycle ◽

Pentose Phosphate ◽

Metabolic Changes ◽

Nonanoic Acid ◽

Control Group ◽

Acid Oxidation ◽

Running Exercise

Objective atherosclerosis has been associated with the progression of cognitive impairment and dementia. Several features, such as high oxygen consumption, a large content of peroxidation-sensitive polyunsaturated fatty acids (PUFAs) and a strong dependency on the supply of glucose make the brain vulnerable to even small metabolic changes. The hippocampus is closely related to memory and learning function, and prone to ischemic injury. However, using metabolomics technology to explore metabolites of hippocampus from atherosclerosis animals is rarely reported. We aim to reveal the metabolic changes during atherosclerosis, and clarify the possible role of exercise in regulating hippocampus metabolism. Methods we established a rat model of atherosclerosis(n=18) along with control group (n=10). The model group was assigned into the AS group (n=8) and the TAS group (n=8), which was intervened by running exercise for 4 weeks. A Y maze test was performed to evaluate initial memory. Metabolomics based on GC-MS was applied to detect small molecules metabolites in rat hippocampus. Results we found that the AS and TAS group both showed elevation in HDL, meanwhile decrement in TC and LDL after 4 weeks’ intervention. The behavioral test showed rats from AS group entered less frequently into and spent less time in the novel arm than rats from C group (P<0.01), while other indexes showed no difference. Compared to the C group, metabolites including xylulose 5-phosphate, threonine, succinate and nonanoic acid were markedly elevated, whereas methyl arachidonic acid and methyl stearate decreased in the AS group. Meanwhile, the levels of succinic acid, branched chain amino acids, nonanoic acid and desmosterol decreased, whereas methyl arachidonic acid, methyl stearate, and glyceraldehyde-3-phosphate elevated in the hippocampus of the TAS group in comparison with the AS group. Conclusions A series of metabolic changes implicated in the hippocampus of atherosclerotic rats, including a decrease in anaerobic glycolysis and TCA cycle, an activation of pentose phosphate pathway, and a disturbance in fatty acid oxidation and cholesterol synthesis, which could lead to insufficient ATP in the hippocampus and related to the behavioral changes of atherosclerotic rats, while running exercise may take part in regulating metabolism to normal state in the hippocampus of atherosclerotic rats.

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Targeted deletion of PD-1 in myeloid cells induces antitumor immunity

Science Immunology ◽

10.1126/sciimmunol.aay1863 ◽

2020 ◽

Vol 5 (43) ◽

pp. eaay1863 ◽

Cited By ~ 45

Author(s):

Laura Strauss ◽

Mohamed A. A. Mahmoud ◽

Jessica D. Weaver ◽

Natalia M. Tijaro-Ovalle ◽

Anthos Christofides ◽

...

Keyword(s):

T Cell ◽

Antitumor Immunity ◽

Myeloid Cells ◽

Suppressor Cells ◽

Myeloid Cell ◽

Tca Cycle ◽

Pentose Phosphate ◽

Metabolic Reprogramming ◽

Effector Memory ◽

Emergency Myelopoiesis

PD-1, a T cell checkpoint receptor and target of cancer immunotherapy, is also expressed on myeloid cells. The role of myeloid-specific versus T cell–specific PD-1 ablation on antitumor immunity has remained unclear because most studies have used either PD-1–blocking antibodies or complete PD-1 KO mice. We generated a conditional allele, which allowed myeloid-specific (PD-1f/fLysMcre) or T cell–specific (PD-1f/fCD4cre) targeting of Pdcd1 gene. Compared with T cell–specific PD-1 ablation, myeloid cell–specific PD-1 ablation more effectively decreased tumor growth. We found that granulocyte/macrophage progenitors (GMPs), which accumulate during cancer-driven emergency myelopoiesis and give rise to myeloid-derived suppressor cells (MDSCs), express PD-1. In tumor-bearing PD-1f/fLysMcre but not PD-1f/fCD4cre mice, accumulation of GMP and MDSC was prevented, whereas systemic output of effector myeloid cells was increased. Myeloid cell–specific PD-1 ablation induced an increase of T effector memory cells with improved functionality and mediated antitumor protection despite preserved PD-1 expression in T cells. In PD-1–deficient myeloid progenitors, growth factors driving emergency myelopoiesis induced increased metabolic intermediates of glycolysis, pentose phosphate pathway, and TCA cycle but, most prominently, elevated cholesterol. Because cholesterol is required for differentiation of inflammatory macrophages and DC and promotes antigen-presenting function, our findings indicate that metabolic reprogramming of emergency myelopoiesis and differentiation of effector myeloid cells might be a key mechanism of antitumor immunity mediated by PD-1 blockade.

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Metabolic Reprogramming of Chemoresistant Cancer Cells and the Potential Significance of Metabolic Regulation in the Reversal of Cancer Chemoresistance

Metabolites ◽

10.3390/metabo10070289 ◽

2020 ◽

Vol 10 (7) ◽

pp. 289 ◽

Cited By ~ 2

Author(s):

Xun Chen ◽

Shangwu Chen ◽

Dongsheng Yu

Keyword(s):

Drug Resistance ◽

Cancer Cells ◽

Tumor Cells ◽

Metabolic Regulation ◽

Metabolic Response ◽

Pentose Phosphate ◽

Metabolic Reprogramming ◽

Acid Oxidation ◽

Drug Resistant ◽

Chemotherapy Drugs

Metabolic reprogramming is one of the hallmarks of tumors. Alterations of cellular metabolism not only contribute to tumor development, but also mediate the resistance of tumor cells to antitumor drugs. The metabolic response of tumor cells to various chemotherapy drugs can be analyzed by metabolomics. Although cancer cells have experienced metabolic reprogramming, the metabolism of drug resistant cancer cells has been further modified. Metabolic adaptations of drug resistant cells to chemotherapeutics involve redox, lipid metabolism, bioenergetics, glycolysis, polyamine synthesis and so on. The proposed metabolic mechanisms of drug resistance include the increase of glucose and glutamine demand, active pathways of glutaminolysis and glycolysis, promotion of NADPH from the pentose phosphate pathway, adaptive mitochondrial reprogramming, activation of fatty acid oxidation, and up-regulation of ornithine decarboxylase for polyamine production. Several genes are associated with metabolic reprogramming and drug resistance. Intervening regulatory points described above or targeting key genes in several important metabolic pathways may restore cell sensitivity to chemotherapy. This paper reviews the metabolic changes of tumor cells during the development of chemoresistance and discusses the potential of reversing chemoresistance by metabolic regulation.

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The SDHB Arg230His mutation causing familial paraganglioma alters glycolysis in a new Caenorhabditis elegans model

Disease Models & Mechanisms ◽

10.1242/dmm.044925 ◽

2020 ◽

Vol 13 (10) ◽

pp. dmm044925 ◽

Cited By ~ 1

Author(s):

Éva Saskői ◽

Zoltán Hujber ◽

Gábor Nyírő ◽

István Likó ◽

Barbara Mátyási ◽

...

Keyword(s):

Tricarboxylic Acid Cycle ◽

Familial Cancer ◽

Tca Cycle ◽

Metabolic Reprogramming ◽

Sdhb Mutation ◽

Mutation Site ◽

Atp Production ◽

B Subunit ◽

Mitochondrial Number

ABSTRACTThe conserved B-subunit of succinate dehydrogenase (SDH) participates in the tricarboxylic acid cycle (TCA) cycle and mitochondrial electron transport. The Arg230His mutation in SDHB causes heritable pheochromocytoma/paraganglioma (PPGL). In Caenorhabditiselegans, we generated an in vivo PPGL model (SDHB-1 Arg244His; equivalent to human Arg230His), which manifests delayed development, shortened lifespan, attenuated ATP production and reduced mitochondrial number. Although succinate is elevated in both missense and null sdhb-1(gk165) mutants, transcriptomic comparison suggests very different causal mechanisms that are supported by metabolic analysis, whereby only Arg244His (not null) worms demonstrate elevated lactate/pyruvate levels, pointing to a missense-induced, Warburg-like aberrant glycolysis. In silico predictions of the SDHA-B dimer structure demonstrate that Arg230His modifies the catalytic cleft despite the latter's remoteness from the mutation site. We hypothesize that the Arg230His SDHB mutation rewires metabolism, reminiscent of metabolic reprogramming in cancer. Our tractable model provides a novel tool to investigate the metastatic propensity of this familial cancer and our approach could illuminate wider SDH pathology.This article has an associated First Person interview with the first author of the paper.

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Sema7A is crucial for resolution of severe inflammation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2017527118 ◽

2021 ◽

Vol 118 (9) ◽

pp. e2017527118

Author(s):

Andreas Körner ◽

Alice Bernard ◽

Julia C. Fitzgerald ◽

Juan Carlos Alarcon-Barrera ◽

Sarantos Kostidis ◽

...

Keyword(s):

Inflammatory Responses ◽

Tricarboxylic Acid Cycle ◽

Pentose Phosphate ◽

Tissue Homeostasis ◽

Metabolic Reprogramming ◽

Lipid Mediator ◽

Acid Oxidation ◽

Guidance Cue ◽

Metabolic Remodeling ◽

Inflammation Resolution

Endogenous mediators regulating acute inflammatory responses in both the induction and resolution phases of inflammatory processes are pivotal in host defense and tissue homeostasis. Recent studies have identified neuronal guidance proteins characterized in axonal development that display immunomodulatory functions. Here, we identify the neuroimmune guidance cue Semaphorin 7A (Sema7A), which appears to link macrophage (MΦ) metabolic remodeling to inflammation resolution. Sema7A orchestrated MΦ chemotaxis and chemokinesis, activated MΦ differentiation and polarization toward the proresolving M2 phenotype, and promoted leukocyte clearance. Peritoneal MΦSema7A−/− displayed metabolic reprogramming, characterized by reductions in fatty acid oxidation and oxidative phosphorylation, increases in glycolysis and the pentose phosphate pathway, and truncation of the tricarboxylic acid cycle, which resulted in increased levels of the intermediates succinate and fumarate. The low accumulation of citrate in MΦSema7A−/− correlated with the decreased synthesis of prostaglandins, leading to a reduced impact on lipid-mediator class switching and the generation of specialized pro resolving lipid mediators. Signaling network analysis indicated that Sema7A induced the metabolic reprogramming of MΦ by activating the mTOR- and AKT2-signaling pathways. Administration of Sema7ASL4cd orchestrated the resolution response to tissue homeostasis by shortening the resolution interval, promoting tissue protection in murine peritonitis, and enhancing survival in polymicrobial sepsis.

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FABP3 Deficiency Exacerbates Metabolic Derangement in Cardiac Hypertrophy and Heart Failure via PPARα Pathway

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.722908 ◽

2021 ◽

Vol 8 ◽

Author(s):

Lingfang Zhuang ◽

Ye Mao ◽

Zizhu Liu ◽

Chenni Li ◽

Qi Jin ◽

...

Keyword(s):

Fatty Acid ◽

Cardiac Hypertrophy ◽

Metabolic Reprogramming ◽

Acid Oxidation ◽

Transverse Aortic Constriction ◽

Aortic Constriction ◽

Metabolic Derangement ◽

Fatty Acid Binding ◽

Atp Production ◽

Incidence And Mortality

Background: Cardiac hypertrophy was accompanied by various cardiovascular diseases (CVDs), and due to the high global incidence and mortality of CVDs, it has become increasingly critical to characterize the pathogenesis of cardiac hypertrophy. We aimed to determine the metabolic roles of fatty acid binding protein 3 (FABP3) on transverse aortic constriction (TAC)-induced cardiac hypertrophy.Methods and Results: Transverse aortic constriction or Ang II treatment markedly upregulated Fabp3 expression. Notably, Fabp3 ablation aggravated TAC-induced cardiac hypertrophy and cardiac dysfunction. Multi-omics analysis revealed that Fabp3-deficient hearts exhibited disrupted metabolic signatures characterized by increased glycolysis, toxic lipid accumulation, and compromised fatty acid oxidation and ATP production under hypertrophic stimuli. Mechanistically, FABP3 mediated metabolic reprogramming by directly interacting with PPARα, which prevented its degradation and synergistically modulated its transcriptional activity on Mlycd and Gck. Finally, treatment with the PPARα agonist, fenofibrate, rescued the pro-hypertrophic effects of Fabp3 deficiency.Conclusions: Collectively, these findings reveal the indispensable roles of the FABP3–PPARα axis on metabolic homeostasis and the development of hypertrophy, which sheds new light on the treatment of hypertrophy.

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Pulmonary artery smooth muscle cell hyperproliferation and metabolic shift triggered by pulmonary overcirculation

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00040.2016 ◽

2016 ◽

Vol 311 (4) ◽

pp. H944-H957 ◽

Cited By ~ 15

Author(s):

Jason Boehme ◽

Xutong Sun ◽

Kathryn V. Tormos ◽

Wenhui Gong ◽

Manuela Kellner ◽

...

Keyword(s):

Smooth Muscle ◽

Pulmonary Artery ◽

Smooth Muscle Cell ◽

Muscle Cell ◽

Lactate Production ◽

Pentose Phosphate ◽

Metabolic Reprogramming ◽

Glycolytic Flux ◽

Pulmonary Artery Smooth Muscle

Vascular cell hyperproliferation and metabolic reprogramming contribute to the pathophysiology of pulmonary arterial hypertension (PAH). An important cause of PAH in children with congenital heart disease (CHD) is increased pulmonary blood flow (PBF). To better characterize this disease course we studied early changes in pulmonary artery smooth muscle cell (PASMC) proliferation and metabolism using a unique ovine model of pulmonary overcirculation. Consistent with PAH in adults, PASMCs derived from 4-wk-old lambs exposed to increased PBF (shunt) exhibited increased rates of proliferation. While shunt PASMCs also exhibited significant decreases in mitochondrial oxygen consumption, membrane potential, and tricarboxylic acid (TCA) cycle function, suggesting a switch to Warburg metabolism as observed in advanced PAH in adults, they unexpectedly demonstrated decreased glycolytic lactate production, likely due to enhanced flux through the pentose phosphate pathway (PPP). This may be a response to the marked increase in NADPH oxidase (Nox) activity and decreased NADPH/NADP+ ratios observed in shunt PASMCs. Consistent with these findings, pharmacological inhibition of Nox activity preferentially slowed the growth of shunt PASMCs in vitro. Our results therefore indicate that PASMC hyperproliferation is observed early in the setting of pulmonary overcirculation and is accompanied by a unique metabolic profile that is independent of HIF-1α, PDHK1, or increased glycolytic flux. Our results also suggest that Nox inhibition may help prevent pulmonary overcirculation-induced PAH in children born with CHD.

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Schistosoma mansoni infection reprograms the metabolic potential of the myeloid lineage in a mouse model of metabolic syndrome

10.1101/2020.04.20.050898 ◽

2020 ◽

Author(s):

Diana Cortes-Selva ◽

Lisa Gibbs ◽

J. Alan Maschek ◽

Tyler Van Ry ◽

Bartek Rajwa ◽

...

Keyword(s):

Bone Marrow ◽

Myeloid Cells ◽

Tca Cycle ◽

Underlying Mechanism ◽

Metabolic Reprogramming ◽

Metabolic Potential ◽

Infected Male ◽

Biological Sex ◽

Tca Cycle Intermediates ◽

Uninfected Host

SummaryDespite evidence that helminths protect from metabolic disease, a major gap exists in understanding the underlying mechanism(s). Here we demonstrate that bone marrow derived macrophages (BMDM) from S. mansoni infected male ApoE-/- mice have dramatically increased mitochondrial respiration compared to those from uninfected mice. This change associates with increased glucose and palmitate shuttling into TCA cycle intermediates and decreased accumulation of cellular cholesterol esters. Moreover, systemic metabolic modulation by schistosomes is a function of biological sex, where infection protects ApoE-/- male, but not female, mice from obesity and glucose intolerance. Sex-dependence extends to myeloid cells, where reprogramming leads to opposite cholesterol phenotypes in BMDM from females and males. Finally, the metabolic reprogramming of male myeloid cells is transferrable via bone marrow transplantation to an uninfected host, indicating maintenance of reprogramming in the absence of sustained antigen exposure. This work reveals that S. mansoni systemic reprograming of myeloid metabolism is sex-dependent.

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Slow TCA flux implies low ATP production in tumors

10.1101/2021.10.04.463108 ◽

2021 ◽

Author(s):

Caroline R. Bartman ◽

Yihui Shen ◽

Won Dong Lee ◽

Tara TeSlaa ◽

Connor S.R. Jankowski ◽

...

Keyword(s):

Electron Transport ◽

Warburg Effect ◽

Electron Transport Chain ◽

Aerobic Glycolysis ◽

Tca Cycle ◽

High Energy ◽

Glycolytic Flux ◽

Atp Production ◽

Transport Chain ◽

The Warburg Effect

SummaryThe tricarboxylic acid (TCA) cycle oxidizes carbon substrates to carbon dioxide, with the resulting high energy electrons fed into the electron transport chain to produce ATP by oxidative phosphorylation. Healthy tissues derive most of their ATP from oxidative metabolism, and the remainder from glycolysis. The corresponding balance in tumors remains unclear. Tumors upregulate aerobic glycolysis (the Warburg effect), yet they also typically require an intact TCA cycle and electron transport chain1–6. Recent studies have measured which nutrients contribute carbon to the tumor TCA metabolites7,8, but not tumor TCA flux: how fast the cycle turns. Here, we develop and validate an in vivo dynamic isotope tracing-mass spectrometry strategy for TCA flux quantitation, which we apply to all major mouse organs and to five tumor models. We show that, compared to the tissue of origin, tumor TCA flux is markedly suppressed. Complementary glycolytic flux measurements confirm tumor glycolysis acceleration, but the majority of tumor ATP is nevertheless made aerobically, and total tumor ATP production is suppressed compared to healthy tissues. In murine pancreatic cancer, this is accommodated by downregulation of the major energy-using pathway in the healthy exocrine pancreas, protein synthesis. Thus, instead of being hypermetabolic as commonly assumed, tumors apparently make ATP at a lower than normal rate. We propose that, as cells de-differentiate into cancer, they eschew ATP-intensive processes characteristic of the host tissue, and that the resulting suppressed ATP demand contributes to the Warburg effect and facilitates cancer growth in the nutrient-poor tumor microenvironment.

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