bims-mepmim Biomed News
on Metabolites in pathological microenvironments and immunometabolism
Issue of 2022‒11‒13
29 papers selected by
Erika Mariana Palmieri
NIH/NCI Laboratory of Cancer ImmunoMetabolism

  1. Nat Commun. 2022 Nov 07. 13(1): 6723
      Alterations in cellular metabolism underpin macrophage activation, yet little is known regarding how key immunological molecules regulate metabolic programs in macrophages. Here we uncover a function for the antigen presenting molecule CD1d in the control of lipid metabolism. We show that CD1d-deficient macrophages exhibit a metabolic reprogramming, with a downregulation of lipid metabolic pathways and an increase in exogenous lipid import. This metabolic rewiring primes macrophages for enhanced responses to innate signals, as CD1d-KO cells show higher signalling and cytokine secretion upon Toll-like receptor stimulation. Mechanistically, CD1d modulates lipid import by controlling the internalization of the lipid transporter CD36, while blocking lipid uptake through CD36 restores metabolic and immune responses in macrophages. Thus, our data reveal CD1d as a key regulator of an inflammatory-metabolic circuit in macrophages, independent of its function in the control of T cell responses.
  2. Sci Adv. 2022 Nov 11. 8(45): eabo7956
      Mitochondria are dynamic organelles that undergo membrane remodeling events in response to metabolic alterations to generate an adequate mitochondrial network. Here, we investigated the function of mitochondrial fission regulator 1-like protein (MTFR1L), an uncharacterized protein that has been identified in phosphoproteomic screens as a potential AMP-activated protein kinase (AMPK) substrate. We showed that MTFR1L is an outer mitochondrial membrane-localized protein modulating mitochondrial morphology. Loss of MTFR1L led to mitochondrial elongation associated with increased mitochondrial fusion events and levels of the mitochondrial fusion protein, optic atrophy 1. Mechanistically, we show that MTFR1L is phosphorylated by AMPK, which thereby controls the function of MTFR1L in regulating mitochondrial morphology both in mammalian cell lines and in murine cortical neurons in vivo. Furthermore, we demonstrate that MTFR1L is required for stress-induced AMPK-dependent mitochondrial fragmentation. Together, these findings identify MTFR1L as a critical mitochondrial protein transducing AMPK-dependent metabolic changes through regulation of mitochondrial dynamics.
  3. Cell Rep. 2022 Nov 08. pii: S2211-1247(22)01463-2. [Epub ahead of print]41(6): 111598
      Classically activated pro-inflammatory macrophages are generated from naive macrophages by pro-inflammatory cues that dynamically reprogram their fuel metabolism toward glycolysis. This increases their intracellular reactive oxygen species (ROS) levels, which then activate the transcription and release of pro-inflammatory mediators. Our study on mice that lack methionine sulfoxide reductase (Msr)-B1 shows that the resulting partial loss of protein methionine reduction in pro-inflammatory macrophages creates a unique metabolic signature characterized by altered fuel utilization, including glucose and pyruvate. This change also associates with hyper-inflammation that is at least partly due to sustained oxidation of an exposed methionine residue (M44) on glyceraldehyde 3-phosphate dehydrogenase (GAPDH), thereby inducing GAPDH aggregation, inflammasome activation, and subsequent increased interleukin (IL)-1β secretion. Since MsrB1-knockout mice exhibit increased susceptibility to lipopolysaccharide (LPS)-induced sepsis, the MsrB1-GAPDH axis may be a key molecular mechanism by which protein redox homeostasis controls the metabolic profile of macrophages and thereby regulates their functions.
    Keywords:  CP: Metabolism; GAPDH; MsrB1; ROS; inflammasome; macrophage; metabolic reprogramming; sepsis
  4. Immunometabolism (Cobham). 2022 Oct;4(4): e00011
      Hexokinases (HKs) catalyze the first and irreversible step of glucose metabolism. Its product, glucose-6-phosphate (G-6P) serves as a precursor for catabolic processes like glycolysis for adenosine 5'-triphosphate (ATP) production and anabolic pathways including the pentose phosphate pathway (PPP) for the generation of intermediaries like nicotinamide adenine dinucleotide phosphate (NADPH) and ribulose-5-P. Thus, the cellular fate of glucose is important not only for growth and maintenance, but also to determine different cellular activities. Studies in immune cells have demonstrated an intimate linkage between metabolic pathways and inflammation, however the precise molecular mechanisms that determine the cellular fate of glucose during inflammation or aging are not completely understood. Here we discuss a study by De Jesus et al that describes the role of HK1 cytosolic localization as a critical regulator of glucose flux by shunting glucose into the PPP at the expense of glycolysis, exacerbating the inflammatory response of macrophages. The authors convincingly demonstrate a novel mechanism that is independent of its mitochondrial functions, but involve the association to a protein complex that inhibits glycolysis at the level of glyceraldehyde 3-phosphate dehydrogenase. We expand the discussion by comparing previous studies related to the HK2 isoform and how cells have evolved to regulate the mitochondrial association of these two isoforms by non-redundant mechanism.
    Keywords:  glucose; hexokinase
  5. Metabolites. 2022 Nov 04. pii: 1066. [Epub ahead of print]12(11):
      Cell metabolism represents the coordinated changes in genes, proteins, and metabolites that occur in health and disease. The metabolic fluxome, which includes both intracellular and extracellular metabolic reaction rates (fluxes), therefore provides a powerful, integrated description of cellular phenotype. However, intracellular fluxes cannot be directly measured. Instead, flux quantification requires sophisticated mathematical and computational analysis of data from isotope labeling experiments. In this review, we describe isotope-assisted metabolic flux analysis (iMFA), a rigorous computational approach to fluxome quantification that integrates metabolic network models and experimental data to generate quantitative metabolic flux maps. We highlight practical considerations for implementing iMFA in mammalian models, as well as iMFA applications in in vitro and in vivo studies of physiology and disease. Finally, we identify promising new frontiers in iMFA which may enable us to fully unlock the potential of iMFA in biomedical research.
    Keywords:  NMR; fluxomics; isotopic non-stationary metabolic flux analysis; mass spectrometry; metabolic engineering; metabolic flux analysis; metabolomics
  6. Metabolites. 2022 Nov 08. pii: 1081. [Epub ahead of print]12(11):
      Metabolic dysfunction-associated fatty liver disease (MAFLD) is a complex disorder that is implicated in dysregulations in multiple biological pathways, orchestrated by interactions between genetic predisposition, metabolic syndromes and environmental factors. The limited knowledge of its pathogenesis is one of the bottlenecks in the development of prognostic and therapeutic options for MAFLD. Moreover, the extent to which metabolic pathways are altered due to ongoing hepatic steatosis, inflammation and fibrosis and subsequent liver damage remains unclear. To uncover potential MAFLD pathogenesis in humans, we employed an untargeted nuclear magnetic resonance (NMR) spectroscopy- and high-resolution mass spectrometry (HRMS)-based multiplatform approach combined with a computational multiblock omics framework to characterize the plasma metabolomes and lipidomes of obese patients without (n = 19) or with liver biopsy confirmed MAFLD (n = 63). Metabolite features associated with MAFLD were identified using a metabolome-wide association study pipeline that tested for the relationships between feature responses and MAFLD. A metabolic pathway enrichment analysis revealed 16 pathways associated with MAFLD and highlighted pathway changes, including amino acid metabolism, bile acid metabolism, carnitine shuttle, fatty acid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism and steroid metabolism. These results suggested that there were alterations in energy metabolism, specifically amino acid and lipid metabolism, and pointed to the pathways being implicated in alerted liver function, mitochondrial dysfunctions and immune system disorders, which have previously been linked to MAFLD in human and animal studies. Together, this study revealed specific metabolic alterations associated with MAFLD and supported the idea that MAFLD is fundamentally a metabolism-related disorder, thereby providing new perspectives for diagnostic and therapeutic strategies.
    Keywords:  NMR; lipidomics; mass spectrometry; metabolic dysfunction-associated fatty liver disease; metabolomics; multiblock analysis
  7. Metabolites. 2022 Nov 10. pii: 1095. [Epub ahead of print]12(11):
      Metabolic alterations occurring in cancer cells have been seen to also occur in other tissues than cancerous tissue. For instance, cachexia, peripheral insulin resistance, or both are commonly seen in patients with cancer. We explored differences in substrate use in myotubes conditioned with the medium from a pancreatic cancer cell line, PANC-1, or primary human pancreatic cells, hPECs. Protein turnover was assessed using scintillation proximity assay, glucose and oleic acid handling were analyzed by substrate oxidation assay. We performed qPCR to study gene expression and immunoblotting and proteomic analyses to study protein expression. PANC-1-conditioned myotubes had an imbalance in protein turnover with decreased accumulation, increased decay, and decreased MYH2 gene expression. Glucose uptake decreased despite increased insulin-stimulated Akt phosphorylation. Fatty acid uptake increased, whereas fatty acid oxidation was unchanged, leading to accumulation of intracellular lipids (TAG) in PANC-1-conditioned myotubes. Secretome analyses revealed increased release of growth factors and growth factor receptor from PANC-1 cells, potentially affecting muscle cell metabolism. Myotubes exposed to pancreatic cancer cell medium displayed altered energy metabolism with increased protein/leucine turnover and lipid accumulation, while glucose uptake and oxidation reduced. This indicates production and release of substances from pancreatic cancer cells affecting skeletal muscle.
    Keywords:  cachexia; cross talk; energy metabolism; protein metabolism
  8. Methods Mol Biol. 2023 ;2603 163-171
      Cultured primary neurons are a well-established model for the study of neuronal function. Conventional stable isotope labeling with amino acids in cell culture (SILAC) requires nearly complete metabolic labeling of proteins and therefore is difficult to apply to cultured primary neurons, which do not divide in culture. In a multiplex SILAC strategy, two different sets of heavy amino acids are used for labeling cells for the different experimental conditions. This allows for straightforward SILAC quantitation using partially labeled cells because the two cell populations are always equally labeled. When combined with bioorthogonal noncanonical amino acid tagging (BONCAT), it allows for comparative proteomic analysis of de novo protein synthesis. Here we describe protocols that utilize the multiplex SILAC labeling strategy for primary cultured neurons to study steady-state and nascent proteomes.
    Keywords:  BONLAC; Mass spectrometry; Primary neurons; Proteomics; Quantitation; SILAC
  9. Sci Signal. 2022 Nov 08. 15(759): eabj4220
      The role of metabolites exchanged in the tumor microenvironment is largely thought of as fuels to drive the increased biosynthetic and bioenergetic demands of growing tumors. However, this view is shifting as metabolites are increasingly shown to function as signaling molecules that directly regulate oncogenic pathways. Combined with our growing understanding of the essential role of stromal cells, this shift has led to increased interest in how the collective and interconnected metabolome of the tumor microenvironment can drive malignant transformation, epithelial-to-mesenchymal transition, drug resistance, immune evasion, and metastasis. In this review, we discuss how metabolite exchange between tumors and various cell types in the tumor microenvironment-such as fibroblasts, adipocytes, and immune cells-can activate signaling pathways that drive cancer progression.
  10. Cell Death Dis. 2022 Nov 05. 13(11): 925
      The term ferroptosis was put forward in 2012 and has been researched exponentially over the past few years. Ferroptosis is an unconventional pattern of iron-dependent programmed cell death, which belongs to a type of necrosis and is distinguished from apoptosis and autophagy. Actuated by iron-dependent phospholipid peroxidation, ferroptosis is modulated by various cellular metabolic and signaling pathways, including amino acid, lipid, iron, and mitochondrial metabolism. Notably, ferroptosis is associated with numerous diseases and plays a double-edged sword role. Particularly, metastasis-prone or highly-mutated tumor cells are sensitive to ferroptosis. Hence, inducing or prohibiting ferroptosis in tumor cells has vastly promising potential in treating drug-resistant cancers. Immunotolerant cancer cells are not sensitive to the traditional cell death pathway such as apoptosis and necroptosis, while ferroptosis plays a crucial role in mediating tumor and immune cells to antagonize immune tolerance, which has broad prospects in the clinical setting. Herein, we summarized the mechanisms and delineated the regulatory network of ferroptosis, emphasized its dual role in mediating immune tolerance, proposed its significant clinical benefits in the tumor immune microenvironment, and ultimately presented some provocative doubts. This review aims to provide practical guidelines and research directions for the clinical practice of ferroptosis in treating immune-resistant tumors.
  11. Cell Death Dis. 2022 Nov 09. 13(11): 944
      High expression of CD38 in tissues is a characteristic of aging, resulting in a decline in nicotinamide adenine dinucleotide (NAD) and increasing cellular reactive oxygen species (ROS). However, whether CD38 increases susceptibility to ferroptosis remains largely unexplored. Our previous study showed that CD38 overexpression decreased dihydrofolate reductase (DHFR). In the present study, we confirmed that high expression of CD38 increased ROS levels and induced DHFR degradation, which was prevented by nicotinamide mononucleotide (NMN) replenishment. We further revealed that ROS-mediated sulfonation on Cys7 of DHFR induced its degradation via the autophagy and non-canonical proteasome pathways. Mutation of Cys7 to alanine abolished ROS-induced DHFR degradation. Moreover, oxidative degradation of DHFR was responsible for the increased ferroptosis susceptibility of cells in which CD38 was highly expressed. We also found that CD38 expression was higher in bone-marrow-derived macrophages (BMDMs) from aged mice than those from young mice, while the DHFR level was lower. Consequently, we demonstrated that BMDMs from aged mice were more susceptible to ferroptosis that can be reverted by NMN replenishment, suggesting that CD38 high expression rendered cells more susceptible to ferroptosis. Taken together, these results indicated that CD38-mediated NAD+ decline promoted DHFR oxidative degradation, thus resulting in increased cellular susceptibility to ferroptosis and suggesting that NMN replenishment may protect macrophages from ferroptosis in aged mice.
  12. Oncogene. 2022 Nov 08.
      TET2 (ten-eleven-translocation) protein is a Fe(II)- and α-ketoglutarate-dependent dioxygenase that catalyzes DNA demethylation to regulate gene expression. While TET2 gene is frequently mutated in hematological cancer, its enzymatic activity is also compromised in various solid tumors. Whether TET2 deficiency creates vulnerability for cancer cells has not been studied. Here we reported that TET2 deficiency is associated with the change of lipid metabolism processes in acute myeloid leukemia (AML) patient. We demonstrate that statins, the inhibitors of β-Hydroxy β-methylglutaryl-CoA (HMG-CoA) reductase and commonly used cholesterol-lowering medicines, significantly sensitize TET2 deficient tumor cells to apoptosis. TET2 directly regulates the expression of HMG-CoA synthase (HMGCS1) by catalyzing demethylation on its promoter region, and conversely TET2 deficiency leads to significant down-regulation of HMGCS1 expression and the mevalonate pathway. Consistently, overexpression of HMGCS1 in TET2-deficient cells rescues statin-induced apoptosis. We further reveal that decrease of geranylgeranyl diphosphate (GGPP), an intermediate metabolite in the mevalonate pathway, is responsible for statin-induced apoptosis. GGPP shortage abolishes normal membrane localization and function of multiple small GTPases, leading to cell dysfunction. Collectively, our study reveals a vulnerability in TET2 deficient tumor and a potential therapeutic strategy using an already approved safe medicine.
  13. Proc Natl Acad Sci U S A. 2022 11 16. 119(46): e2215528119
      Group 2 innate lymphoid cells (ILC2) are innate counterparts of T helper 2 (Th2) cells that maintain tissue homeostasis and respond to injuries through rapid interleukin (IL)-5 and IL-13 secretion. ILC2s depend on availability of arginine and branched-chain amino acids for sustaining cellular fitness, proliferation, and cytokine secretion in both steady state and upon activation. However, the contribution of amino acid transporters to ILC2 functions is not known. Here, we found that ILC2s selectively express <i>Slc7a8</i>, encoding a transporter for arginine and large amino acids. <i>Slc7a8</i> was expressed in ILC2s in a tissue-specific manner in steady state and was further increased upon activation. Genetic ablation of <i>Slc7a8</i> in lymphocytes reduced the frequency of ILC2s, suppressed IL-5 and IL-13 production upon stimulation, and impaired type 2 immune responses to helminth infection. Consistent with this, <i>Slc7a8-</i>deficient ILC2s also failed to induce cytokine production and recruit eosinophils in a model of allergic lung inflammation. Mechanistically, reduced amino acid availability due to <i>Slc7a8</i> deficiency led to compromised mitochondrial oxidative phosphorylation, as well as impaired activation of mammalian target of rapamycin and c-Myc signaling pathways. These findings identify <i>Slc7a8</i> as a key supplier of amino acids for the metabolic programs underpinning fitness and activation of ILC2s.
    Keywords:  allergy; amino acid; asthma; innate lymphoid cells; transporter
  14. Nutrients. 2022 Nov 01. pii: 4600. [Epub ahead of print]14(21):
      BACKGROUND: Hypoxia is caused by the excessive expansion of the white adipose tissue (AT) and is associated with obesity-related conditions such as insulin resistance, inflammation, and oxidative stress. Docosahexaenoic acid (DHA) is an omega-3 fatty acid reported to have beneficial health effects. However, the effects of DHA in AT against hypoxia-induced immune-metabolic perturbations in adipocytes exposed to low O2 tension are not well known. Consequently, this study aimed to evaluate the impact of DHA on markers of inflammation, metabolism, apoptosis, and oxidative stress in 3T3-L1 cell adipocytes exposed to low O2 tension (1% O2) induced hypoxia.METHODS: The apoptosis and reactive oxygen species (ROS) rates were evaluated. Metabolic parameters such as lactate, FFA, glycerol release, glucose uptake, and ATP content were assessed by a fluorometer. The expression of HIF-1, GLUT1 and the secretion of adipocytokines such as leptin, adiponectin, and pro-inflammatory markers was evaluated.
    RESULTS: DHA-treated hypoxic cells showed significantly decreased basal free fatty acid release, lactate production, and enhanced glucose consumption. In addition, DHA-treatment of hypoxic cells caused a significant reduction in the apoptosis rate and ROS production with decreased lipid peroxidation. Moreover, DHA-treatment of hypoxic cells caused a decreased secretion of pro-inflammatory markers (IL-6, MCP-1) and leptin and increased adiponectin secretion compared with hypoxic cells. Furthermore, DHA-treatment of hypoxic cells caused significant reductions in the expression of genes related to hypoxia (HIF-1, HIF-2), anaerobic metabolism (GLUT1 and Ldha), ATP production (ANT2), and fat metabolism (FASN and PPARY).
    CONCLUSION: This study suggests that DHA can exert potential anti-obesity effects by reducing the secretion of inflammatory adipokines, oxidative stress, lipolysis, and apoptosis.
    Keywords:  3T3-L1 cell adipocytes; adipokines; docosahexaenoic acid (DHA); hypoxia; metabolism; obesity
  15. Front Immunol. 2022 ;13 936167
      In the lungs, macrophages constitute the first line of defense against pathogens and foreign bodies and play a fundamental role in maintaining tissue homeostasis. Activated macrophages show altered immunometabolism and metabolic changes governing immune effector mechanisms, such as cytokine secretion characterizing their classic (M1) or alternative (M2) activation. Lipopolysaccharide (LPS)-stimulated macrophages demonstrate enhanced glycolysis, blocked succinate dehydrogenase (SDH), and increased secretion of interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Glycolysis suppression using 2 deoxyglucose in LPS-stimulated macrophages inhibits IL-1β secretion, but not TNF-α, indicating metabolic pathway specificity that determines cytokine production. In contrast to LPS, the nature of the immunometabolic responses induced by non-organic particles, such as silica, in macrophages, its contribution to cytokine specification, and disease pathogenesis are not well understood. Silica-stimulated macrophages activate pattern recognition receptors (PRRs) and NLRP3 inflammasome and release IL-1β, TNF-α, and interferons, which are the key mediators of silicosis pathogenesis. In contrast to bacteria, silica particles cannot be degraded, and the persistent macrophage activation results in an increased NADPH oxidase (Phox) activation and mitochondrial reactive oxygen species (ROS) production, ultimately leading to macrophage death and release of silica particles that perpetuate inflammation. In this manuscript, we reviewed the effects of silica on macrophage mitochondrial respiration and central carbon metabolism determining cytokine specification responsible for the sustained inflammatory responses in the lungs.
    Keywords:  M1 macrophages; complex II; electron transport chain; macrophage immunometabolism; macrophage metabolic adaptation; mitochondria; respirable crystalline silica
  16. Metabolites. 2022 Oct 23. pii: 1011. [Epub ahead of print]12(11):
      Glucose absorption promoters perform insulin mimic functions to enhance blood glucose transport to skeletal muscle cells and accelerate glucose consumption, thereby reducing blood glucose levels. In our screening exploration of food ingredients for improving glucose transportation and metabolism, we found that the saponins in American ginseng (Panaxquinquefolius L.) showed potential activity to promote glucose uptake, which can be used for stabilizing levels of postprandial blood glucose. The aim of this study was to identify key components of American ginseng with glucose uptake-promoting activity and to elucidate their metabolic regulatory mechanisms. Bio-guided isolation using zebrafish larvae and 2-NBDG indicator identified ginsenoside Rb1 (GRb1) as the most potential promotor of glucose uptake. Using UPLC-QTOF-MS/MS combined with RT-qPCR and phenotypic verification, we found that riboflavin metabolism is the hinge for GRb1-mediated facilitation of glucose transport. GRb1-induced restoration of redox homeostasis was mediated by targeting riboflavin transporters (SLC52A1 and SLC52A3) and riboflavin kinase (RFK).
    Keywords:  Panax quinquefolius L.; bioguided isolation; diabetes; metabolomics; redox; riboflavin
  17. Methods Mol Biol. 2023 ;2603 259-268
      Stable isotope labeling by amino acids in cell culture (SILAC) and iodoacetyl tandem mass tag (iodoTMT) are well-implemented mass spectrometry-based approaches for quantification of proteins and for site-mapping of cysteine modification. We describe here a combination of SILAC and iodoTMT to assess ongoing changes in the global proteome and cysteine modification levels using liquid chromatography separation coupled with high-resolution mass spectrometry (LC-MS/MS).
    Keywords:  Cysteine; Global proteome; IodoTMT; Liquid chromatography; Mass spectrometry; Redox; SILAC
  18. J Biol Chem. 2022 Nov 07. pii: S0021-9258(22)01125-5. [Epub ahead of print] 102682
      Liraglutide, a glucagon-like peptide-1 analog, has beneficial metabolic effects in patients with type 2 diabetes and obesity. Although the high efficacy of liraglutide as an anti-diabetic and anti-obesity drug is well known, liraglutide-induced metabolic alterations in diverse tissues remain largely unexplored. Here, we report the changes in metabolic profiles induced by a two-week subcutaneous injection of liraglutide in diet-induced obese (DIO) mice fed a high-fat diet for eight weeks. Our comprehensive metabolomic analyses of the hypothalamus, plasma, liver, and skeletal muscle showed that liraglutide intervention led to various metabolic alterations in comparison with DIO or non-obese mice. We found that liraglutide remarkably coordinated not only fatty acid metabolism in the hypothalamus and skeletal muscle, but also amino acid and carbohydrate metabolism in plasma and liver. Comparative analyses of metabolite dynamics revealed that liraglutide rewired inter-tissue metabolic correlations. Our study points to a previously unappreciated metabolic alteration by liraglutide in several tissues, which may underlie its therapeutic effects within and across the tissues.
    Keywords:  diabetes; hypothalamus; liraglutide; liver; metabolomics; obesity; plasma; skeletal muscle
  19. Immunometabolism (Cobham). 2022 Oct;4(4): e00008
      An increase in glucose uptake driving aerobic glycolysis is a robust hallmark of immune cell activation. The glycolytic response supports functional alterations of the innate immune cells including the production and release of cytokines. Large inter-individual differences in the magnitude of this cytokine response are known to exist. In addition, the presence of disease is known to impact on immune cell function. Whether variation in metabolic responses of immune cells exist between individuals during health or disease is currently unknown. Here, we explore inter-individual differences in the glycolytic rate of immune cells using lactate production as readout upon activation using a variety of different stimuli. Glycolytic responses are subsequently associated to functional immune cell responses in healthy humans. In addition, we determined the glycolytic rate of immune cells and its association with immune function using patients diagnosed with diabetes mellitus. Based on the relative increase in lactate production after activation, distinct clusters of low, intermediate, and high responders could be identified, illustrating the existence of variation in glycolytic responses in healthy subjects. Interestingly, the production of cytokines mirrored these high-, intermediate-, and low-lactate patterns after pathogenic stimulation. In patients with diabetes mellitus, a reduced correlation was found between lactate and cytokine production, specifically for IL-6. Furthermore, based on the relative increase in lactate production, variability in the glycolytic response was reduced compared to healthy subjects. In conclusion, our results show a specific association between the glycolytic rate and function in human immune cells after stimulation with different pathogens. In addition to demonstrating the existence of glycolytic variability and specificity depending on the type of stimulus, the association between glycolysis and function in innate immune cells is altered during the presence of diabetes.
    Keywords:  glycolysis; human immune cell function; lactate
  20. Nat Commun. 2022 Nov 11. 13(1): 6845
      Targeting the intrinsic metabolism of immune or tumor cells is a therapeutic strategy in autoimmunity, chronic inflammation or cancer. Metabolite repair enzymes may represent an alternative target class for selective metabolic inhibition, but pharmacological tools to test this concept are needed. Here, we demonstrate that phosphoglycolate phosphatase (PGP), a prototypical metabolite repair enzyme in glycolysis, is a pharmacologically actionable target. Using a combination of small molecule screening, protein crystallography, molecular dynamics simulations and NMR metabolomics, we discover and analyze a compound (CP1) that inhibits PGP with high selectivity and submicromolar potency. CP1 locks the phosphatase in a catalytically inactive conformation, dampens glycolytic flux, and phenocopies effects of cellular PGP-deficiency. This study provides key insights into effective and precise PGP targeting, at the same time validating an allosteric approach to control glycolysis that could advance discoveries of innovative therapeutic candidates.
  21. Cell. 2022 Nov 10. pii: S0092-8674(22)01322-8. [Epub ahead of print]185(23): 4259-4279
      The heterogeneity of tissue macrophages, in health and in disease, has become increasingly transparent over the last decade. But with the plethora of data comes a natural need for organization and the design of a conceptual framework for how we can better understand the origins and functions of different macrophages. We propose that the ontogeny of a macrophage-beyond its fundamental derivation as either embryonically or bone marrow-derived, but rather inclusive of the course of its differentiation, amidst steady-state cues, disease-associated signals, and time-constitutes a critical piece of information about its contribution to homeostasis or the progression of disease.
  22. Front Immunol. 2022 ;13 984408
      Metabolomic studies show that rheumatoid arthritis (RA) is associated with metabolic disruption. Metabolic changes in fibroblast-like synoviocytes (FLS) likely contribute to FLS abnormal response and strongly contribute to joint destruction. These changes often involve increased expression of nutrient transporters to meet a high demand for energy or biomolecules. The solute carrier (SLC) transporter families are nutrient transporters and serve as 'metabolic gates' for cells by mediating the transport of several different nutrients such as glucose, amino acids, vitamins, neurotransmitters, and inorganic/metal ions. In RA FLS SLC-mediated transmembrane transport was one pathway associated with different epigenetic landscape between RA and osteoarthritis (OA) FLS. These highlight that transporters from the SLC family offer unique targets for further research and offer the promise of future therapeutic targets for RA.
    Keywords:  FLS; RA; SLC transporters; metabolism; nutrients
  23. Cell Metab. 2022 Nov 02. pii: S1550-4131(22)00461-2. [Epub ahead of print]
      A hostile microenvironment in tumor tissues disrupts endoplasmic reticulum homeostasis and induces the unfolded protein response (UPR). A chronic UPR in both cancer cells and tumor-infiltrating leukocytes could facilitate the evasion of immune surveillance. However, how the UPR in cancer cells cripples the anti-tumor immune response is unclear. Here, we demonstrate that, in cancer cells, the UPR component X-box binding protein 1 (XBP1) favors the synthesis and secretion of cholesterol, which activates myeloid-derived suppressor cells (MDSCs) and causes immunosuppression. Cholesterol is delivered in the form of small extracellular vesicles and internalized by MDSCs through macropinocytosis. Genetic or pharmacological depletion of XBP1 or reducing the tumor cholesterol content remarkably decreases MDSC abundance and triggers robust anti-tumor responses. Thus, our data unravel the cell-non-autonomous role of XBP1/cholesterol signaling in the regulation of tumor growth and suggest its inhibition as a useful strategy for improving the efficacy of cancer immunotherapy.
    Keywords:  ER stress; HMGCR; IRE1α; MDSC; XBP1; cancer immunosuppression; cholesterol; macropinocytosis; small extracellular vesicle; unfolded protein response
  24. FASEB Bioadv. 2022 Nov;4(11): 709-723
      In solid organs, cells of the same "type" can vary in their molecular phenotype. The basis of this state variation is being revealed by characterizing cell features including the expression pattern of mRNAs and the internal distribution of proteins. Here, the variability of metabolic state between cells is probed by enzyme activity profiling. We study individual cells of types that can be identified during the post-mitotic phase of oogenesis in Xenopus laevis. Whole-cell homogenates of isolated oocytes are used for kinetic analysis of enzymes, with a focus on the initial reaction rate. For each oocyte type studied, the activity signatures of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and malate dehydrogenase 1 (MDH1) vary more between the homogenates of single oocytes than between repeat samplings of control homogenates. Unexpectedly, the activity signatures of GAPDH and MDH1 strongly co-vary between oocytes of each type and change in strength of correlation during oogenesis. Therefore, variability of the kinetic behavior of these housekeeping enzymes between "identical" cells is physiologically programmed. Based on these findings, we propose that single-cell profiling of enzyme kinetics will improve understanding of how metabolic state heterogeneity is related to heterogeneity revealed by omics methods including proteomics, epigenomics, and metabolomics.
    Keywords:  cell‐to‐cell variability; development; enzyme; glyceraldehyde 3‐phosphate dehydrogenase; kinetic analysis; malate dehydrogenase 1; metabolism; oogenesis; single‐cell analysis
  25. iScience. 2022 Nov 18. 25(11): 105357
      The cuticle of C. elegans is impermeable to chemicals, toxins, and pathogens. However, increased permeability is a desirable phenotype because it facilitates chemical uptake. Surface lipids contribute to the permeability barrier. Here, we identify the lipid transfer protein GMAP-1 as a critical element setting the permeability of the C. elegans cuticle. A gmap-1 deletion mutant increases cuticular permeability to sodium azide, levamisole, Hoechst, and DiI. Expressing GMAP-1 in the hypodermis or transiently in the adults is sufficient to rescue this gmap-1 permeability phenotype. GMAP-1 protein is secreted from the hypodermis to the aqueous fluid filling the space between collagen fibers of the cuticle. In vitro, GMAP-1 protein binds phosphatidylserine and phosphatidylcholine while in vivo, GMAP-1 sets the surface lipid composition and organization. Altogether, our results suggest GMAP-1 secreted by hypodermis shuttles lipids to the surface to form the permeability barrier of C. elegans.
    Keywords:  Biological sciences; molecular biology; physiology
  26. Biochim Biophys Acta Mol Cell Biol Lipids. 2022 Nov 07. pii: S1388-1981(22)00138-X. [Epub ahead of print] 159248
      Recent trials have reported the ability of triheptanoin to improve clinical outcomes for the severe symptoms associated with long-chain fatty acid oxidation disorders, including very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. However, the milder myopathic symptoms are still challenging to treat satisfactorily. Myopathic pathogenesis is multifactorial, but oxidative stress is an important component. We have previously shown that metabolic stress increases the oxidative burden in VLCAD-deficient cell lines and can deplete the antioxidant glutathione (GSH). We investigated whether medium-chain fatty acids provide protection against GSH depletion during metabolic stress in VLCAD-deficient fibroblasts. To investigate the effect of differences in anaplerotic capacity, we included both even-(octanoate) and odd-numbered (heptanoate) medium-chain fatty acids. Overall, we show that modulation of the concentration of medium-chain fatty acids in culture media affects levels of GSH retained during metabolic stress in VLCAD-deficient cell lines but not in controls. Lowered glutamine concentration in the culture media during metabolic stress led to GSH depletion and decreased viability in VLCAD deficient cells, which could be rescued by both heptanoate and octanoate in a dose-dependent manner. Unlike GSH levels, the levels of total thiols increased after metabolic stress exposure, the size of this increase was not affected by differences in cell culture medium concentrations of glutamine, heptanoate or octanoate. Addition of a PPAR agonist further exacerbated stress-related GSH-depletion and viability loss, requiring higher concentrations of fatty acids to restore GSH levels and cell viability. Both odd- and even-numbered medium-chain fatty acids efficiently protect VLCADdeficient cells against metabolic stress-induced antioxidant depletion.
    Keywords:  Anaplerosis; Fatty acids oxidation deficiency; Glutathione; Heptanoate; Mitochondria; Octanoate; Oxidative stress; VLCAD
  27. Elife. 2022 Nov 08. pii: e81559. [Epub ahead of print]11
      While dysregulation of adipocyte endocrine function plays a central role in obesity and its complications, the vast majority of adipokines remain uncharacterized. We employed bio-orthogonal non-canonical amino acid tagging (BONCAT) and mass spectrometry to comprehensively characterize the secretome of murine visceral and subcutaneous white and interscapular brown adipocytes. Over 600 proteins were identified, the majority of which showed cell type-specific enrichment. We here describe a metabolic role for leucine-rich α-2 glycoprotein 1 (LRG1) as an obesity-regulated adipokine secreted by mature adipocytes. LRG1 overexpression significantly improved glucose homeostasis in diet-induced and genetically obese mice. This was associated with markedly reduced white adipose tissue macrophage accumulation and systemic inflammation. Mechanistically, we found LRG1 binds cytochrome c in circulation to dampen its pro-inflammatory effect. These data support a new role for LRG1 as an insulin sensitizer with therapeutic potential given its immunomodulatory function at the nexus of obesity, inflammation, and associated pathology.
    Keywords:  cell biology; mouse
  28. STAR Protoc. 2022 Dec 16. 3(4): 101799
      This protocol describes CAROM, a computational tool that combines genome-scale metabolic networks (GEMs) and machine learning to identify enzyme targets of post-translational modifications (PTMs). Condition-specific enzyme and reaction properties are used to predict targets of phosphorylation and acetylation in multiple organisms. CAROM is influenced by the accuracy of GEMs and associated flux-balance analysis (FBA), which generate the inputs of the model. We demonstrate the protocol using multi-omics data from E. coli. For complete details on the use and execution of this protocol, please refer to Smith et al. (2022).
    Keywords:  Bioinformatics; Computer sciences; Genomics; Metabolism; Metabolomics; Microbiology; Proteomics; Systems biology