bims-mepmim Biomed News
on Metabolites in pathological microenvironments and immunometabolism
Issue of 2022‒07‒24
thirty papers selected by
Erika Mariana Palmieri
NIH/NCI Laboratory of Cancer ImmunoMetabolism

  1. Cell Death Discov. 2022 Jul 19. 8(1): 327
      Compared to cancer cells, macrophages are inert to lipid peroxidation-triggered, iron-dependent cell death known as ferroptosis. Mechanisms underlying macrophage resistance towards ferroptosis are largely obscure. Here, we show that human primary macrophages respond to RSL3, a ferroptosis-inducing inhibitor of glutathione peroxidase 4, by upregulating mRNA expression of the iron transporter ferroportin. RSL3 induces lipid peroxidation, and both, lipid peroxidation as well as ferroportin induction were attenuated by liproxstatin-1, an inhibitor of lipid peroxidation and ferroptosis blocker. At the same time, system xc- inhibitor erastin fails to elicit lipid peroxidation or ferroportin expression. Ferroportin induction in response to RSL3 demands nuclear accumulation of the redox-sensitive transcription factor Nrf2 and downregulation of the transcriptional repressor BACH1. Silencing ferroportin or Nrf2 increases the cellular labile iron pool and lipid peroxidation, thereby sensitizing cells towards ferroptosis following RSL3 treatments. In contrast, silencing BACH1 decreases the labile iron pool and lipid peroxidation, enhancing macrophage resistance towards ferroptosis. Our findings reveal Nrf2, BACH1, and ferroportin as important regulators, protecting human macrophages against ferroptosis.
  2. Mol Cell. 2022 Jul 13. pii: S1097-2765(22)00609-8. [Epub ahead of print]
      NAD+ kinases (NADKs) are metabolite kinases that phosphorylate NAD+ molecules to make NADP+, a limiting substrate for the generation of reducing power NADPH. NADK2 sustains mitochondrial NADPH production that enables proline biosynthesis and antioxidant defense. However, its molecular architecture and mechanistic regulation remain undescribed. Here, we report the crystal structure of human NADK2, revealing a substrate-driven mode of activation. We find that NADK2 presents an unexpected dimeric organization instead of the typical tetrameric assemblage observed for other NADKs. A specific extended segment (aa 325-365) is crucial for NADK2 dimerization and activity. Moreover, we characterize numerous acetylation events, including those on Lys76 and Lys304, which reside near the active site and inhibit NADK2 activity without disrupting dimerization, thereby reducing mitochondrial NADP(H) production, proline synthesis, and cell growth. These findings reveal important molecular insight into the structure and regulation of a vital enzyme in mitochondrial NADPH and proline metabolism.
    Keywords:  NAD kinases; NADK2; NADPH metabolism; crystal structure; mitochondrial metabolism; post-translational modifications; proline metabolism
  3. Cell Metab. 2022 Jul 18. pii: S1550-4131(22)00301-1. [Epub ahead of print]
      Obesity is accompanied by inflammation in adipose tissue, impaired glucose tolerance, and changes in adipose leukocyte populations. These studies of adipose tissue from humans and mice revealed that increased frequencies of T-bet+ B cells in adipose tissue depend on invariant NKT cells and correlate with weight gain during obesity. Transfer of B cells enriched for T-bet+ cells exacerbates metabolic disorder in obesity, while ablation of Tbx21 specifically in B cells reduces serum IgG2c levels, inflammatory cytokines, and inflammatory macrophages in adipose tissue, ameliorating metabolic symptoms. Furthermore, transfer of serum or purified IgG from HFD mice restores metabolic disease in T-bet+ B cell-deficient mice, confirming T-bet+ B cell-derived IgG as a key mediator of inflammation during obesity. Together, these findings reveal an important pathological role for T-bet+ B cells that should inform future immunotherapy design in type 2 diabetes and other inflammatory conditions.
    Keywords:  B cells; CD11c(+) T-bet(+) B cells; IgG2c; adipose tissue; glucose intolerance; iNKT cells; inflammation; metabolic disorder; obesity; type 2 diabetes
  4. Nat Commun. 2022 Jul 19. 13(1): 4174
      Regulation of fatty acid uptake, lipid production and storage, and metabolism of lipid droplets (LDs), is closely related to lipid homeostasis, adipocyte hypertrophy and obesity. We report here that stomatin, a major constituent of lipid raft, participates in adipogenesis and adipocyte maturation by modulating related signaling pathways. In adipocyte-like cells, increased stomatin promotes LD growth or enlargements by facilitating LD-LD fusion. It also promotes fatty acid uptake from extracellular environment by recruiting effector molecules, such as FAT/CD36 translocase, to lipid rafts to promote internalization of fatty acids. Stomatin transgenic mice fed with high-fat diet exhibit obesity, insulin resistance and hepatic impairments; however, such phenotypes are not seen in transgenic animals fed with regular diet. Inhibitions of stomatin by gene knockdown or OB-1 inhibit adipogenic differentiation and LD growth through downregulation of PPARγ pathway. Effects of stomatin on PPARγ involves ERK signaling; however, an alternate pathway may also exist.
  5. Front Microbiol. 2022 ;13 919424
      Energy and anabolic metabolism are essential for normal cellular homeostasis but also play an important role in regulating immune responses and cancer development as active immune and cancer cells show an altered metabolic profile. Mitochondria take a prominent position in these metabolic reactions. First, most key energetic reactions take place within or in conjunction with mitochondria. Second, mitochondria react to internal cues from within the cell but also to external cues originating from the microbiota, a vast diversity of associated microorganisms. The impact of the microbiota on host physiology has been largely investigated in the last decade revealing that the microbiota contributes to the extraction of calories from the diet, energy metabolism, maturation of the immune system and cellular differentiation. Thus, changes in the microbiota termed dysbiosis have been associated with disease development including metabolic diseases, inflammation and cancer. Targeting the microbiota to modulate interactions with the mitochondria and cellular metabolism to delay or inhibit disease development and pathogenesis appears an attractive therapeutic approach. Here, we summarize recent advances in developing the therapeutic potential of microbiota-mitochondria interactions for inflammation and cancer.
    Keywords:  cancer; inflammation; metabolites; microbiota; mitochondria
  6. J Nutr Biochem. 2022 Jul 17. pii: S0955-2863(22)00174-7. [Epub ahead of print] 109106
      A high-fat diet (HFD) is reported to exacerbate ulcerative colitis by inducing obesity, which conceals the effect of the diet itself. Ferroptosis, a type of regulated cell death induced by lipid hydroperoxides, has recently been reported in colitis. Here, we aimed to determine whether HFD affects ferroptosis and colitis progression in an obesity-independent manner. We subjected male C57BL/6J mice to either an HFD (60% fat diet) or isocaloric control diet (10% fat diet) for 4 weeks, followed by inducing colitis with 2.5% dextran sulfate sodium (DSS). Compared with the isocaloric control diet, non-obesogenic HFD reduced DSS-induced colonic mucosal injury, as shown by disease activity index, colon thickness, inflammatory infiltrations, and mucosal damage index; however, there were no differences in body weight, Lee's index, and omental fat weight between the two groups. HFD mice exhibited decreased lipid peroxidation and ferroptosis marker expression in colon tissues. Furthermore, a lipid mixture protected gut organoids and normal colonic epithelial cells from RSL3-induced ferroptosis. Mechanistically, the lipid mixture prevented glutathione deficiency by upregulating the cysteine transporter, solute carrier family 7 member 11. Collectively, these findings suggest that an HFD ameliorates DSS-induced colitis through ferroptosis repression in an obesity-independent manner and provide new evidence to evaluate the effects of an HFD on colitis.
    Keywords:  High-fat diet; colitis; ferroptosis; gut organoid; solute carrier family 7 member 11
  7. Nat Metab. 2022 Jul 21.
      Successful elimination of bacteria in phagocytes occurs in the phago-lysosomal system, but also depends on mitochondrial pathways. Yet, how these two organelle systems communicate is largely unknown. Here we identify the lysosomal biogenesis factor transcription factor EB (TFEB) as regulator for phago-lysosome-mitochondria crosstalk in macrophages. By combining cellular imaging and metabolic profiling, we find that TFEB activation, in response to bacterial stimuli, promotes the transcription of aconitate decarboxylase (Acod1, Irg1) and synthesis of its product itaconate, a mitochondrial metabolite with antimicrobial activity. Activation of the TFEB-Irg1-itaconate signalling axis reduces the survival of the intravacuolar pathogen Salmonella enterica serovar Typhimurium. TFEB-driven itaconate is subsequently transferred via the Irg1-Rab32-BLOC3 system into the Salmonella-containing vacuole, thereby exposing the pathogen to elevated itaconate levels. By activating itaconate production, TFEB selectively restricts proliferating Salmonella, a bacterial subpopulation that normally escapes macrophage control, which contrasts TFEB's role in autophagy-mediated pathogen degradation. Together, our data define a TFEB-driven metabolic pathway between phago-lysosomes and mitochondria that restrains Salmonella Typhimurium burden in macrophages in vitro and in vivo.
  8. J Biol Chem. 2022 Jul 19. pii: S0021-9258(22)00728-1. [Epub ahead of print] 102286
      In the mammalian retina, a metabolic ecosystem exists in which photoreceptors acquire glucose from the choriocapillaris with the help of the retinal pigment epithelium (RPE). While the photoreceptor cells are primarily glycolytic, exhibiting Warburg-like metabolism, the RPE is reliant on mitochondrial respiration. However, the ways in which mitochondrial metabolism affect RPE cellular functions are not clear. We first used the human RPE cell line, ARPE-19, to examine mitochondrial metabolism in the context of cellular differentiation. We show that nicotinamide induced rapid differentiation of ARPE-19 cells, which was reversed by removal of supplemental nicotinamide. During the nicotinamide-induced differentiation, we observed using quantitative PCR, western blotting, electron microscopy, and metabolic respiration and tracing assays that (1) mitochondrial gene and protein expression increased, (2) mitochondria became larger with more tightly-folded cristae, and (3) mitochondrial metabolism was enhanced. Additionally, we show primary cultures of human fetal RPE cells responded similarly in the presence of nicotinamide. Furthermore, disruption of mitochondrial oxidation of pyruvate attenuated the nicotinamide-induced differentiation of the RPE cells. Together, our results demonstrate a remarkable effect of nicotinamide on RPE metabolism. We also identify mitochondrial respiration as a key contributor to the differentiated state of the RPE, and thus to many of the RPE functions that are essential for retinal health and photoreception.
    Keywords:  RPE; differentiation; mitochondria; nicotinamide; retina
  9. J Gen Physiol. 2022 Oct 03. pii: e202213104. [Epub ahead of print]154(10):
      Ca2+ signals regulate the function of many immune cells and promote immune responses to infection, cancer, and autoantigens. Ca2+ influx in immune cells is mediated by store-operated Ca2+ entry (SOCE) that results from the opening of Ca2+ release-activated Ca2+ (CRAC) channels. The CRAC channel is formed by three plasma membrane proteins, ORAI1, ORAI2, and ORAI3. Of these, ORAI1 is the best studied and plays important roles in immune function. By contrast, the physiological role of ORAI3 in immune cells remains elusive. We show here that ORAI3 is expressed in many immune cells including macrophages, B cells, and T cells. To investigate ORAI3 function in immune cells, we generated Orai3-/- mice. The development of lymphoid and myeloid cells in the thymus and bone marrow was normal in Orai3-/- mice, as was the composition of immune cells in secondary lymphoid organs. Deletion of Orai3 did not affect SOCE in B cells and T cells but moderately enhanced SOCE in macrophages. Orai3-deficient macrophages, B cells, and T cells had normal effector functions in vitro. Immune responses in vivo, including humoral immunity (T cell dependent or independent) and antitumor immunity, were normal in Orai3-/- mice. Moreover, Orai3-/- mice showed no differences in susceptibility to septic shock, experimental autoimmune encephalomyelitis, or collagen-induced arthritis. We conclude that despite its expression in myeloid and lymphoid cells, ORAI3 appears to be dispensable or redundant for physiological and pathological immune responses mediated by these cells.
  10. J Lipid Res. 2022 Jul 15. pii: S0022-2275(22)00088-8. [Epub ahead of print] 100255
      Friedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a triplet guanine-adenine-adenine (GAA) repeat expansion in intron 1 of the FXN gene, which leads to decreased levels of the frataxin protein. Frataxin is involved in the formation of iron-sulfur (Fe-S) cluster prosthetic groups for various metabolic enzymes. To provide a better understanding of the metabolic status of FRDA patients, here we used patient-derived fibroblast cells as a surrogate tissue for metabolic and lipidomic profiling by liquid-chromatography high resolution-mass spectrometry (LC-HRMS). We found elevated HMG-CoA and β-hydroxybutyrate (BHB)-CoA levels, implying dysregulated fatty acid oxidation, which was further demonstrated by elevated acyl-carnitine levels. Lipidomic profiling identified dysregulated levels of several lipid classes in FRDA fibroblast cells when compared with non-FRDA fibroblast cells. For example, levels of several ceramides were significantly increased in FRDA fibroblast cells; these results positively correlated with the GAA repeat length and negatively correlated with the frataxin protein levels. Furthermore, stable isotope tracing experiments indicated increased ceramide synthesis, especially for long chain fatty acid-ceramides, in FRDA fibroblast cells compared to ceramide synthesis in healthy control fibroblast cells. In addition, PUFA containing triglycerides and phosphatidylglycerols were enriched in FRDA fibroblast cells and negatively correlated with frataxin levels, suggesting lipid remodeling as a result of FXN deficiency. Altogether, we demonstrate patient-derived fibroblast cells exhibited dysregulated metabolic capabilities, and their lipid dysfunction predicted the severity of FRDA, making them a useful surrogate to study the metabolic status in FRDA.
    Keywords:  ceramides; fatty acids oxidation; frataxin; lipid remodeling; lipidomics; neurodegenerative disorders; phospholipids; stable isotope tracing; triglycerides; triplet repeat expansion
  11. Int Immunopharmacol. 2022 Jul 18. pii: S1567-5769(22)00546-X. [Epub ahead of print]110 109062
      The inflammatory focus is similar to the tumor microenvironment, which contains a complex milieu with immune cells and macrophages. The accumulation of cells promotes local pH and O2 tension decline (hypoxia). Local O2 tension decline activates hypoxia-inducible factor α and β (HIF-1α and HIF-1β adenosine triphosphate (ATP) release. ATP activates the P2X7 receptor and modulates ischemic/hypoxic conditions. Similarly, α1α may regulate P2X7 receptor expression in the hypoxic microenvironment. Therefore, we investigated P2X7 receptor function under simulated hypoxic conditions by pretreating peritoneal macrophages with mitochondrial electron transport chain complex inhibitors (simulated hypoxia). Treatment with mitochondrial electron transport chain complex inhibitors until three hours of exposure did not cause LDH release. Additionally, mitochondrial electron transport chain complex inhibitors increased ATP-induced P2X7 receptor function without being able to directly activate this receptor. Other P2 receptor subtypes do not appear to participate in this mechanism. Simulated hypoxia augmented HIF-1α levels and suppressed HIF-1α and P2X7 receptor antagonists. Similarly, simulated hypoxia increased ATP-induced dye uptake and inhibited HIF-1α antagonists. Another factor activated in simulated hypoxic conditions was the intracellular P2X7 receptor regulator PIP2. Treatment with HIF-1α agonists increased PIP2 levels and reversed the effects of HIF-1α and P2X7 receptor antagonists. Additionally, the improved ATP-induced dye uptake caused by the simulated hypoxia stimulus was inhibited by P2X7 receptor and PIP2 antagonists. Therefore, simulated hypoxia may augment P2X7 receptor activity for a pathway dependent on HIF-1α and PIP2 activation.
    Keywords:  ATP release; HIF-1α; Hypoxia; Purinergic receptors; ROS
  12. Cancer Res. 2022 Jul 21. pii: CAN-22-1427. [Epub ahead of print]
      Tumor-associated macrophages (TAM) play a detrimental role in triple-negative breast cancer (TNBC). In-depth analysis of TAM characteristics and interactions with stromal cells, such as cancer-associated fibroblast (CAF), could provide important biological and therapeutic insights. Here we identify at the single-cell level a monocyte-derived-STAB1+TREM2high lipid-associated macrophage (LAM) subpopulation with immune suppressive capacities that is expanded in patients resistant to immune checkpoint blockade (ICB). Genetic depletion of this LAM subset in mice suppressed TNBC tumor growth. Flow cytometry and bulk-RNA sequencing data demonstrated that co-culture with TNBC-derived CAFs led to reprogramming of blood monocytes towards immune suppressive STAB1+TREM2high LAMs, which inhibit T cell activation and proliferation. Cell-to-cell interaction modeling and assays in vitro demonstrated the role of the inflammatory CXCL12-CXCR4 axis in CAF-myeloid cell crosstalk and recruitment of monocytes in tumor sites. Altogether, these data suggest an inflammation model whereby monocytes recruited to the tumor via the CAF-driven CXCL12-CXCR4 axis acquire pro-tumorigenic LAM capacities to support an immunosuppressive microenvironment.
  13. Rheumatology (Oxford). 2022 Jul 21. pii: keac359. [Epub ahead of print]
      Synovial macrophages are key mediators of OA pathology, and skewing of macrophage phenotype in favour of an M1-like phenotype is thought to underlie the chronicity of synovial inflammation in OA. Components of the metabolic syndrome (MetS), such as dyslipidaemia, can affect macrophage phenotype and function, which could explain the link between MetS and OA development. Recently published studies have provided novel insights into the different origins and heterogeneity of synovial macrophages. Considering these findings, we propose an important role for monocyte-derived macrophages in particular, as opposed to yolk-sac derived residential macrophages, in causing a pro-inflammatory phenotype shift, and explain how this can start even prior to synovial infiltration. In the circulation, monocytes can be trained by metabolic factors such as low-density lipoprotein (LDL) to become extra responsive to chemokines and damage associated molecular patterns (DAMPs). The concept of innate immune training has been widely studied and implicated in atherosclerosis pathology, but its involvement in OA remains uncharted territory. Finally, we evaluate the implications of all this for targeted therapy directed to macrophages and metabolic factors.
    Keywords:  Innate immune training; LDL-cholesterol; Macrophages; Metabolic syndrome; Monocytes; Osteoarthritis; Synovitis
  14. J Inherit Metab Dis. 2022 Jul 22.
      Patients with urea cycle disorders intermittently develop episodes of decompensation with hyperammonemia. Although such an episode is often associated with starvation and catabolism, its molecular basis is not fully understood. First, we attempted to elucidate the mechanism of such starvation-associated hyperammonemia. Using a mouse embryonic fibroblast (MEF) culture system, we found that glucose starvation increases ammonia production, and that this increase is associated with enhanced glutaminolysis. These results led us to focus on α-ketoglutarate (AKG), a glutamate dehydrogenase inhibitor and a major anaplerotic metabolite. Hence, we sought to determine the effect of dimethyl α-ketoglutarate (DKG), a cell-permeable AKG analog, on MEFs and found that DKG mitigates ammonia production primarily by reducing flux through glutamate dehydrogenase. We also verified that DKG reduces ammonia in an NH4 Cl-challenged hyperammonemia mouse model and observed that DKG administration reduces plasma ammonia concentration to 22.8% of the mean value for control mice that received only NH4 Cl. In addition, we detected increases in ornithine concentration and in the ratio of ornithine to arginine following DKG treatment. We subsequently administered DKG intravenously to a newborn pig with hyperammonemia due to ornithine transcarbamylase deficiency and found that blood ammonia concentration declined significantly over time. We determined that this effect is associated with facilitated reductive amination and glutamine synthesis. Our present data indicate that energy starvation triggers hyperammonemia through enhanced glutaminolysis and that DKG reduces ammonia accumulation via pleiotropic mechanisms both in vitro and in vivo. Thus, cell-permeable forms of AKG are feasible candidates for a novel hyperammonemia treatment.
    Keywords:  anaplerosis; glutamate dehydrogenase; glutaminase; glutaminolysis; hyperammonemia; ornithine transcarbamylase deficiency; α-ketoglutarate
  15. Front Mol Biosci. 2022 ;9 917818
      Sepsis, the most common life-threatening multi-organ dysfunction syndrome secondary to infection, lacks specific therapeutic strategy due to the limited understanding of underlying mechanisms. It is currently believed that inflammasomes play critical roles in the development of sepsis, among which NLRP3 inflammasome is involved to most extent. Recent studies have revealed that dramatic reprogramming of macrophage metabolism is commonly occurred in sepsis, and this dysregulation is closely related with the activation of NLRP3 inflammasome. In view of the fact that increasing evidence demonstrates the mechanism of metabolism reprogramming regulating NLRP3 activation in macrophages, the key enzymes and metabolites participated in this regulation should be clearer for better interpreting the relationship of NLRP3 inflammasome and sepsis. In this review, we thus summarized the detail mechanism of the metabolic reprogramming process and its important role in the NLRP3 inflammasome activation of macrophages in sepsis. This mechanism summarization will reveal the applicational potential of metabolic regulatory molecules in the treatment of sepsis.
    Keywords:  NLRP3 inflammasome; macrophages; metabolism reprogramming; sepsis; targeted therapy
  16. ACS Omega. 2022 Jul 12. 7(27): 24020-24026
      Oncolytic virotherapy was approved as a localized treatment for advanced melanoma by the US Food and Drug Administration (FDA) in 2015. Granulocyte macrophage colony stimulating factor (GM-CSF) encoded by clinical virus-infected tumor cells, acting as a pro-inflammatory cytokine or growth factor, increases tumor antigen presentation, leading to the activation of macrophages and T cells. Notably, tumor-secreted lactate can promote the suppressive functions of M2-polarized tumor-associated macrophages and subsequently promote tumor growth. Furthermore, the consumption of tumor-secreted lactate has been implicated in the beneficial polarization of macrophages. Here, we report that GM-CSF-encoded recombinant adeno-associated virus (AAV2-GM-CSF) infection in B16-F10 mouse melanoma cells combined with lactate oxidase (LOX) leads to the recruitment of M1 macrophages for the inhibition of cancer cell growth. This study suggests that GM-CSF combined with LOX has potential as cancer virotherapy.
  17. Nature. 2022 Jul 20.
      Oocytes form before birth and remain viable for several decades before fertilization1. Although poor oocyte quality accounts for most female fertility problems, little is known about how oocytes maintain cellular fitness, or why their quality eventually declines with age2. Reactive oxygen species (ROS) produced as by-products of mitochondrial activity are associated with lower rates of fertilization and embryo survival3-5. Yet, how healthy oocytes balance essential mitochondrial activity with the production of ROS is unknown. Here we show that oocytes evade ROS by remodelling the mitochondrial electron transport chain through elimination of complex I. Combining live-cell imaging and proteomics in human and Xenopus oocytes, we find that early oocytes exhibit greatly reduced levels of complex I. This is accompanied by a highly active mitochondrial unfolded protein response, which is indicative of an imbalanced electron transport chain. Biochemical and functional assays confirm that complex I is neither assembled nor active in early oocytes. Thus, we report a physiological cell type without complex I in animals. Our findings also clarify why patients with complex-I-related hereditary mitochondrial diseases do not experience subfertility. Complex I suppression represents an evolutionarily conserved strategy that allows longevity while maintaining biological activity in long-lived oocytes.
  18. Sci Adv. 2022 Jul 15. 8(28): eabo3064
      Alveolar macrophages (AMs) are critical mediators of pulmonary inflammation. Given the unique lung tissue environment, whether there exist AM-specific mechanisms that control inflammation is not known. Here, we found that among various tissue-resident macrophage populations, AMs specifically expressed Lepr, encoding receptor for a key metabolic hormone leptin. AM-intrinsic Lepr signaling attenuated pulmonary inflammation in vivo, manifested as subdued acute lung injury yet compromised host defense against Streptococcus pneumoniae infection. Lepr signaling protected AMs from necroptosis and thus constrained neutrophil recruitment and tissue damage secondary to release of proinflammatory cytokine interleukin-1α. Mechanistically, Lepr signaling sustained activation of adenosine monophosphate-activated protein kinase in a Ca2+ influx-dependent manner and rewired cellular metabolism, thus preventing excessive lipid droplet formation and overloaded metabolic stress in a lipid-rich alveolar microenvironment. In conclusion, our results defined AM-expressed Lepr as a metabolic checkpoint of pulmonary inflammation and exemplified a macrophage tissue adaptation strategy for maintenance of immune homeostasis.
  19. J Biol Chem. 2022 Jul 18. pii: S0021-9258(22)00725-6. [Epub ahead of print] 102283
      Knockout of the transcription factor X-box binding protein (XBP1) is known to decrease liver glucose production and lipogenesis. However, whether insulin can regulate gluconeogenesis and lipogenesis through XBP1 and how insulin activates the inositol-requiring enzyme (IRE1)-XBP1 ER stress pathway remain unexplored. Here we report that in the fed state, insulin-activated kinase AKT directly phosphorylates IRE1 at S724, which in turn mediates the splicing of XBP1u mRNA, thus favoring the generation of the spliced form, XBP1s, in the liver of mice. Subsequently, XBP1s stimulates the expression of lipogenic genes and upregulates liver lipogenesis as previously reported. Intriguingly, we find that fasting leads to an increase in XBP1u along with a drastic decrease in XBP1s in the liver of mice, and XBP1u, not XBP1s, significantly increases PKA-stimulated CRE reporter activity in cultured hepatocytes. Furthermore, we demonstrate overexpression of XBP1u significantly increases cAMP-stimulated expression of rate-limiting gluconeogenic genes, G6pc and Pck1, and glucose production in primary hepatocytes. Re-expression of XBP1u in the liver of mice with XBP1 depletion significantly increases fasted blood glucose levels and gluconeogenic gene expression. These data support an important role of XBP1u in upregulating gluconeogenesis in the fasted state. Taken together, we reveal that insulin signaling via AKT controls the expression of XBP1 isoforms, and that XBP1u and XBP1s function in different nutritional states to regulate liver gluconeogenesis and lipogenesis, respectively.
    Keywords:  AKT; IRE1; XBP1; insulin; liver glucose production; triglyceride
  20. Redox Biol. 2022 Jul 15. pii: S2213-2317(22)00175-6. [Epub ahead of print]55 102403
      Defects in Coenzyme Q (CoQ) metabolism have been associated with primary mitochondrial disorders, neurodegenerative diseases and metabolic conditions. The consequences of CoQ deficiency have not been fully addressed, and effective treatment remains challenging. Here, we use mice with primary CoQ deficiency (Coq9R239X), and we demonstrate that CoQ deficiency profoundly alters the Q-junction, leading to extensive changes in the mitochondrial proteome and metabolism in the kidneys and, to a lesser extent, in the brain. CoQ deficiency also induces reactive gliosis, which mediates a neuroinflammatory response, both of which lead to an encephalopathic phenotype. Importantly, treatment with either vanillic acid (VA) or β-resorcylic acid (β-RA), two analogs of the natural precursor for CoQ biosynthesis, partially restores CoQ metabolism, particularly in the kidneys, and induces profound normalization of the mitochondrial proteome and metabolism, ultimately leading to reductions in gliosis, neuroinflammation and spongiosis and, consequently, reversing the phenotype. Together, these results provide key mechanistic insights into defects in CoQ metabolism and identify potential disease biomarkers. Furthermore, our findings clearly indicate that the use of analogs of the CoQ biosynthetic precursor is a promising alternative therapy for primary CoQ deficiency and has potential for use in the treatment of more common neurodegenerative and metabolic diseases that are associated with secondary CoQ deficiency.
    Keywords:  Coenzyme Q; Mitochondrial disease; Omics; Phenolic compound; Therapy
  21. Physiol Rep. 2022 Jul;10(14): e15394
      Little is known how acute exercise-induced inflammation and metabolic stress affect immune cell bioenergetics and the portion of its components. Therefore, we investigated acute effects of eccentric-only (E), concentric-only (C) and combined eccentric-concentric resistance exercise (E + C) bouts on cellular respiration of peripheral blood mononuclear cells (PBMCs). Twelve strength-trained young men performed bench press resistance exercises in randomized order. Venous blood samples were drawn at pre-, 5 min post- and 24 h post-exercise. Several PBMC respiration states were measured using high-resolution respirometry. Levels of leukocytes, interleukin 6 (IL-6), C-reactive protein (CRP), creatine kinase (CK), blood lactate and maximum voluntary isometric force were measured from the same time points. Effects of blood lactate and pH change on bioenergetics of PBMCs were investigated ex vivo. PBMC routine respiration (p = 0.017), free routine capacity (p = 0.025) and ET-capacity (p = 0.038) decreased immediately after E + C. E responded in opposite manner 5 min post-exercise compared to E + C (p = 0.013) and C (p = 0.032) in routine respiration, and to E + C in free routine activity (p = 0.013). E + C > C > E was observed for increased lactate levels and decreased isometric force that correlated with routine respiration (R = -0.369, p = 0.035; R = 0.352, p = 0.048). Lactate and pH change did not affect bioenergetics of PBMCs. Acute resistance exercise affected cellular respiration of PBMCs, with training volume and the amount of metabolic stress appear influential. Results suggest that acute inflammation response does not contribute to changes seen in cellular respiration, but the level of peripheral muscle fatigue and metabolic stress could be explaining factors.
    Keywords:  bioenergetics; mitochondria; resistance training; training volume; white blood cells
  22. Int J Biol Macromol. 2022 Jul 18. pii: S0141-8130(22)01532-X. [Epub ahead of print]
      The effect of low and high molecular weight hyaluronic acid on glutamine metabolism in luminal and basal breast cancer and cancer stem cells is being investigated. In luminal cell lines (MCF-7), HA enhances the intracellular utilization of gln in redox metabolism and decreases its use in TCA. On the contrary, in MDAMB-231 cells, HA induces the uptake of gln to be utilized in anaplerosis rather than ROS maintenance. However, in MCF-7 CSCs, HA induces up-regulation of xCT, further, it uses gln-derived glutamate for the exchange of cystine, thus maintaining ROS levels through xCT. MDA-MB-231 CSCs reduce the secretion of glutamate in response to HA and decrease the gln flux towards reductive carboxylation. Conclusively, our study demonstrated that although the uptake of gln is enhanced by HA, it is differentially utilized intracellularly in breast cancer cells. This study could significantly influence the therapeutics involving HA and Gln in breast cancer.
    Keywords:  Alanine-serine-cysteine transporter; Breast cancer stem cells; Cystine–glutamate exchanger transporter; Glutamine; Hyaluronic acid; Reductive carboxylation
  23. Front Immunol. 2022 ;13 923481
      Triple negative breast cancer (TNBC) remains the worst molecular subtype due to high heterogeneity and lack of effective therapeutic targets. Here we investigated the tumor and immune microenvironment heterogeneity of TNBC using scRNA-seq and bulk RNA-seq data from public databases and our cohort. Macrophage subpopulations accounted for a high proportion of tumor immune microenvironment (TIME), and M1 macrophages were associated with better clinical outcomes. Furthermore, three maker genes including IFI35, PSMB9, and SAMD9L showed a close connection with M1 macrophages. Specifically, IFI35 was positively associated with macrophage activation, chemotaxis, and migration. Also, patients with high IFI35 expression had a better prognosis. In vitro studies subsequently demonstrated that IFI35 was upregulated during the M1 subtype differentiation of macrophages. In summary, our data suggested that IFI35 maybe a promising novel target that helps to reshape macrophage polarization towards the M1 subtype for anti-tumor effects.
    Keywords:  IFI35; ScRNA-seq analysis; bulk-RNA sequencing; macrophages; triple negative breast cancer; tumor immune microenvironment
  24. J Pharm Biomed Anal. 2022 Jul 16. pii: S0731-7085(22)00365-X. [Epub ahead of print]219 114944
      One-carbon metabolism is an important metabolic pathway involved in many diseases, such as congenital malformations, tumours, cardiovascular diseases, anaemia, depression, cognitive diseases and liver disease. However, the current methods have specific defects in detecting and qualifying the related compounds of one-carbon metabolism. In this study, a validated method was established to simultaneously quantify 22 one-carbon metabolites & co-factors in human plasma and applied to the study of correlation between one-carbon metabolism and colorectal cancer in human plasma samples, which were from 44 healthy subjects and 55 colorectal cancer patients. The method used ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-MS/MS), and the analytes included betaine, L-carnitine, L-cystathionine, L-cysteine, dimethylglycine, DL-homocysteic acid, homocysteine, methionine, pyridoxal hydrochloride, pyridoxamine dihydrochloride, pyridoxine dihydrochloride, S-(5'-Adenosyl)-L-homocysteine, serine, choline chloride, folic acid, glycine, pyridoxal phosphate monohydrate, riboflavin, taurine, 5-methyltetrahydrofolate, S-(5'-adenosyl)-L-methionine disulfate salt, trimethylamine oxide. The developed method was successfully applied to the quantification of 22 one-carbon metabolites & co-factors in human plasma from colorectal cancer patients and healthy individuals. The plasma concentrations of dimethylglycine was significantly decreased in the patients compared with the healthy individuals, while L-cystathionine was increased.
    Keywords:  Folic acid; Homocysteine; Human plasma; LC-MS/MS; One-carbon metabolism
  25. Sci Immunol. 2022 Jul 22. 7(73): eabo2787
      Acne affects 1 in 10 people globally, often resulting in disfigurement. The disease involves excess production of lipids, particularly squalene, increased growth of Cutibacterium acnes, and a host inflammatory response with foamy macrophages. By combining single-cell and spatial RNA sequencing as well as ultrahigh-resolution Seq-Scope analyses of early acne lesions on back skin, we identified TREM2 macrophages expressing lipid metabolism and proinflammatory gene programs in proximity to hair follicle epithelium expressing squalene epoxidase. We established that the addition of squalene induced differentiation of TREM2 macrophages in vitro, which were unable to kill C. acnes. The addition of squalene to macrophages inhibited induction of oxidative enzymes and scavenged oxygen free radicals, providing an explanation for the efficacy of topical benzoyl peroxide in the clinical treatment of acne. The present work has elucidated the mechanisms by which TREM2 macrophages and unsaturated lipids, similar to their involvement in atherosclerosis, may contribute to the pathogenesis of acne.
  26. J Comp Neurol. 2022 Jul 20.
      Astrocytes are the main homeostatic cell of the brain involved in many processes related to cognition, immune response, and energy expenditure. It has been suggested that the distribution of astrocytes is associated with brain size, and that they are specialized in humans. To evaluate these, we quantified astrocyte density, soma volume, and total glia density in layer I and white matter in Brodmann's area 9 of humans, chimpanzees, baboons, and macaques. We found that layer I astrocyte density, soma volume, and ratio of astrocytes to total glia cells were highest in humans and increased with brain size. Overall glia density in layer I and white matter were relatively invariant across brain sizes, potentially due to their important metabolic functions on a per volume basis. We also quantified two transporters involved in metabolism through the astrocyte-neuron lactate shuttle, excitatory amino acid transporter 2 (EAAT2) and glucose transporter 1 (GLUT1). We expected these transporters would be increased in human brains due to their high rate of metabolic consumption and associated gene activity. While humans have higher EAAT2 cell density, GLUT1 vessel volume, and GLUT1 area fraction compared to baboons and chimpanzees, they did not differ from macaques. Therefore, EAAT2 and GLUT1 are not related to increased energetic demands of the human brain. Taken together, these data provide evidence that astrocytes play a unique role in both brain expansion and evolution among primates, with an emphasis on layer I astrocytes having a potentially significant role in human-specific metabolic processing and cognition.
    Keywords:  EAAT2; GFAP; GLUT1; astrocyte; glia; human; prefrontal cortex; primate
  27. Biol Trace Elem Res. 2022 Jul 19.
      Macrophages are important innate immune cells which can be polarized into heterogeneous populations. The inflammatory-activated M1 cells are known to be involved in all kinds of inflammatory diseases, which were also found to be associated with dysregulation of iron metabolism. While iron overload is known to induce M1 polarization, the valence states of iron and its intracellular dynamics during macrophage inflammatory activation have not been identified. In this study, THP-1-derived macrophages were polarized into M1, M2a, M2b, M2c, and M2d cells, and intracellular ferrous iron (Fe(II)) was measured by our previously developed ultrasensitive Fe(II) fluorescent probe. Significant accumulation of Fe(II) was only observed in M1 cells, which was different from the alterations of total iron. Time-dependent change of intracellular Fe(II) during the inflammatory activation was also consistent with the expression shifts of transferrin receptor CD71, ferrireductase Steap3, and Fe(II) exporter Slc40a1. In addition, accumulation of Fe(II) was also found in the colon macrophages of mice with ulcerative colitis, which was positively correlated to inflammatory phenotypes, including the productions of NO, IL-1β, TNF-α, and IL-6. Collectively, these results demonstrated the specific accumulation of Fe(II) in inflammatory-activated macrophages, which not only enriched our understanding of iron homeostasis in macrophages, but also indicated that Fe(II) could be further developed as a potential biomarker for inflammatory-activated macrophages.
    Keywords:  Ferrous iron; Inflammatory activation; Iron metabolism; Macrophages; Polarization; Ulcerative colitis
  28. Front Mol Biosci. 2022 ;9 894207
      Coronavirus disease 2019 (COVID 19) is a systemic infection that exerts a significant impact on cell metabolism. In this study we performed metabolomic profiling of 41 in vitro cultures of peripheral blood mononuclear cells (PBMC), 17 of which displayed IgG memory for spike-S1 antigen 60-90 days after infection. By using mass spectrometry analysis, a significant up-regulation of S-adenosyl-Homocysteine, Sarcosine and Arginine was found in leukocytes showing IgG memory. These metabolites are known to be involved in physiological recovery from viral infections and immune activities, and our findings might represent a novel and easy measure that could be of help in understanding SARS-Cov-2 effects on leukocytes.
    Keywords:  COVID-19; cell-ELISA; in vitro B-cell memory; mass spectrometry; metabolomics
  29. Proc Natl Acad Sci U S A. 2022 Jul 26. 119(30): e2200512119
      Epstein-Barr virus (EBV) is a human tumor virus which preferentially infects resting human B cells. Upon infection in vitro, EBV activates and immortalizes these cells. The viral latent protein EBV nuclear antigen 2 (EBNA2) is essential for B cell activation and immortalization; it targets and binds the cellular and ubiquitously expressed DNA-binding protein CBF1, thereby transactivating a plethora of viral and cellular genes. In addition, EBNA2 uses its N-terminal dimerization (END) domain to bind early B cell factor 1 (EBF1), a pioneer transcription factor specifying the B cell lineage. We found that EBNA2 exploits EBF1 to support key metabolic processes and to foster cell cycle progression of infected B cells in their first cell cycles upon activation. The α1-helix within the END domain was found to promote EBF1 binding. EBV mutants lacking the α1-helix in EBNA2 can infect and activate B cells efficiently, but activated cells fail to complete the early S phase of their initial cell cycle. Expression of MYC, target genes of MYC and E2F, as well as multiple metabolic processes linked to cell cycle progression are impaired in EBVΔα1-infected B cells. Our findings indicate that EBF1 controls B cell activation via EBNA2 and, thus, has a critical role in regulating the cell cycle of EBV-infected B cells. This is a function of EBF1 going beyond its well-known contribution to B cell lineage specification.
    Keywords:  B cell activation; Epstein-Barr virus; MYC expression; RNA sequencing; transcription factor
  30. Mucosal Immunol. 2022 Jul 18.
      Environmental microbial triggers shape the development and functionality of the immune system. Alveolar macrophages (AMs), tissue-resident macrophages of the lungs, are in constant and direct contact with inhaled particles and microbes. Such exposures likely impact AM reactivity to subsequent challenges by immunological imprinting mechanisms referred to as trained immunity. Here, we investigated whether a ubiquitous microbial compound has the potential to induce AM training in vivo. We discovered that intranasal exposure to ambient amounts of lipopolysaccharide (LPS) induced a pronounced AM memory response, characterized by enhanced reactivity upon pneumococcal challenge. Exploring the mechanistic basis of AM training, we identified a critical role of type 1 interferon signaling and found that inhibition of fatty acid oxidation and glutaminolysis significantly attenuated the training effect. Notably, adoptive transfer of trained AMs resulted in increased bacterial loads and tissue damage upon subsequent pneumococcal infection. In contrast, intranasal pre-exposure to LPS promoted bacterial clearance, highlighting the complexity of stimulus-induced immune responses, which likely involve multiple cell types and may depend on the local immunological and metabolic environment. Collectively, our findings demonstrate the profound impact of ambient microbial exposure on pulmonary immune memory and reveal tissue-specific features of trained immunity.