bims-mepmim Biomed News
on Metabolites in pathological microenvironments and immunometabolism
Issue of 2022‒07‒31
43 papers selected by
Erika Mariana Palmieri
NIH/NCI Laboratory of Cancer ImmunoMetabolism

  1. Cell Rep. 2022 Jul 26. pii: S2211-1247(22)00907-X. [Epub ahead of print]40(4): 111105
      A functional electron transport chain (ETC) is crucial for supporting bioenergetics and biosynthesis. Accordingly, ETC inhibition decreases proliferation in cancer cells but does not seem to impair stem cell proliferation. However, it remains unclear how stem cells metabolically adapt. In this study, we show that pharmacological inhibition of complex III of the ETC in skeletal stem and progenitor cells induces glycolysis side pathways and reroutes the tricarboxylic acid (TCA) cycle to regenerate NAD+ and preserve cell proliferation. These metabolic changes also culminate in increased succinate and 2-hydroxyglutarate levels that inhibit Ten-eleven translocation (TET) DNA demethylase activity, thereby preserving self-renewal and multilineage potential. Mechanistically, mitochondrial malate dehydrogenase and reverse succinate dehydrogenase activity proved to be essential for the metabolic rewiring in response to ETC inhibition. Together, these data show that the metabolic plasticity of skeletal stem and progenitor cells allows them to bypass ETC blockade and preserve their self-renewal.
    Keywords:  CP: Metabolism; CP: Stem cell research; NAD regeneration; TCA rerouting; TET activity; cell-based regenerative medicine; electron transport chain; metabolic plasticity; proliferation; reverse succinate dehydrogenase; self-renewal; skeletal stem cells
  2. J Leukoc Biol. 2022 Jul 28.
      Adipose tissue macrophages (ATMs) play key roles in metabolic inflammation, insulin resistance, adipose tissue fibrosis, and immune disorders associated with obesity. Research on ATM biology has mostly been conducted in the setting of adult obesity, since adipocyte hypertrophy is associated with a significant increase in ATM number. Signals that control ATM activation toward a proinflammatory or a proresolving phenotype also determine the developmental program and lipid metabolism of adipocytes after birth. ATMs are present at birth and actively participate in the synthesis of mediators, which induce lipolysis, mitobiogenesis, and mitochondrial uncoupling in adipocytes. ATMs in the newborn and the infant promote a lipolytic and fatty acid oxidizing adipocyte phenotype, which is essential to support the lipid-fueled metabolism, to maintain nonshivering thermogenesis and counteract an excessive adipose tissue expansion. Since adipose tissue metabolism in the early postnatal life determines obesity status in adulthood, early-life ATM functions may have a life-long impact.
    Keywords:  inflammation; macrophage; obesity; pediatric adiposity
  3. Cell Commun Signal. 2022 Jul 27. 20(1): 114
      Metabolic reprogramming and immune escape play a major role in tumorigenesis. Increasing number of studies have shown that reprogramming of glutamine metabolism is a putative determinant of the anti-tumor immune response in the tumor microenvironment (TME). Usually, the predatory uptake of glutamine by tumor cells in the TME results in the limited utilization of glutamine by immune cells and affects the anti-tumor immune response. The cell-programmed glutamine partitioning also affects the anti-tumor immune response. However, the reprogramming of glutamine metabolism in tumors modulates immune escape by regulating tumor PD-L1 expression. Likewise, the reprogramming of glutamine metabolism in the immune cells also affects their immune function. Additionally, different types of glutamine metabolism inhibitors extensively regulate the immune cells in the TME while suppressing tumor cell proliferation. Herein, we discuss how metabolic reprogramming of tumor and immune cells regulates anti-tumor immune responses, as well as functional changes in different immune cells in the context of targeting tumor glutamine metabolism, which can better explain the potential of targeting glutamine metabolism in combination with immunotherapy for cancer. Video abstract.
    Keywords:  Glutamine metabolism; Glutamine metabolism inhibitors; Immune response; Immunity; Reprogramming; Tumor microenvironment
  4. Carcinogenesis. 2022 Jul 28. pii: bgac061. [Epub ahead of print]
      Hepatocellular carcinoma (HCC) is a common form of liver cancer. The incidence of HCC is increasing and effective prevention methods are needed. The solute carrier family 38 member 6 (SLC38A6) plays an important role in the metabolism of glutamine, which is a central nutrient for many cancers. However, the regulation and function of SLC38A6 in HCC are unclear. SLC38A6 levels in human HCC tissue arrays and cells were determined. SLC38A6 was silenced or overexpressed to determine its role in regulating cell viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration. A luminescence assay was used to study the interaction between SLC38A6 and EP300. The interactions between SLC38A6, H3K27ac, and EP300 were determined using chromatin immunoprecipitation assays. Quantitative RT-PCR and immunoblots were performed to measure mRNAs and proteins, respectively. SLC38A6 expression was higher in HCC compared with expression in normal tissue. Silencing SLC38A6 inhibited cell viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration, while SLC38A6 overexpression had the opposite effects. Silencing SLC38A6 also inhibited tumor growth in vivo. Silencing EP300 significantly suppressed the interaction between H3K27ac and the SLC38A6 promoter, leading to decreased SLC38A6. SLC38A6 is regulated by EP300-mediated modifications of H3K27ac and promotes viability, colony formation, cell cycle progression, glutamine metabolism, and mitochondrial respiration in HCC cells.
    Keywords:  acetylation; glutamine metabolism; hepatocellular carcinoma; solute carrier family 38 member 6
  5. Nutrients. 2022 Jul 09. pii: 2825. [Epub ahead of print]14(14):
      Vitamin B12 (VB12) is a micronutrient that is essential for DNA synthesis and cellular energy production. We recently demonstrated that VB12 oral supplementation coordinates ileal epithelial cells (iECs) and gut microbiota functions to resist pathogen colonization in mice, but it remains unclear whether VB12 directly modulates the cellular homeostasis of iECs derived from humans. Here, we integrated transcriptomic, metabolomic, and epigenomic analyses to identify VB12-dependent molecular and metabolic pathways in human iEC microtissue cultures. RNA sequencing (RNA-seq) revealed that VB12 notably activated genes involved in fatty acid metabolism and epithelial cell proliferation while suppressing inflammatory responses in human iECs. Untargeted metabolite profiling demonstrated that VB12 facilitated the biosynthesis of amino acids and methyl groups, particularly S-adenosylmethionine (SAM), and supported the function of the mitochondrial carnitine shuttle and TCA cycle. Further, genome-wide DNA methylation analysis illuminated a critical role of VB12 in sustaining cellular methylation programs, leading to differential CpG methylation of genes associated with intestinal barrier function and cell proliferation. Together, these findings suggest an essential involvement of VB12 in directing the fatty acid and mitochondrial metabolisms and reconfiguring the epigenome of human iECs to potentially support cellular oxygen utilization and cell proliferation.
    Keywords:  DNA methylation; cell proliferation; ileal epithelial cells; mitochondrial metabolism; vitamin B12
  6. Nat Commun. 2022 Jul 26. 13(1): 4327
      Mutant KRAS (KM), the most common oncogene in lung cancer (LC), regulates fatty acid (FA) metabolism. However, the role of FA in LC tumorigenesis is still not sufficiently characterized. Here, we show that KMLC has a specific lipid profile, with high triacylglycerides and phosphatidylcholines (PC). We demonstrate that FASN, the rate-limiting enzyme in FA synthesis, while being dispensable in EGFR-mutant or wild-type KRAS LC, is required for the viability of KMLC cells. Integrating lipidomic, transcriptomic and functional analyses, we demonstrate that FASN provides saturated and monounsaturated FA to the Lands cycle, the process remodeling oxidized phospholipids, such as PC. Accordingly, blocking either FASN or the Lands cycle in KMLC, promotes ferroptosis, a reactive oxygen species (ROS)- and iron-dependent cell death, characterized by the intracellular accumulation of oxidation-prone PC. Our work indicates that KM dictates a dependency on newly synthesized FA to escape ferroptosis, establishing a targetable vulnerability in KMLC.
  7. Nature. 2022 Jul 27.
      In response to hormones and growth factors, the class I phosphoinositide-3-kinase (PI3K) signalling network functions as a major regulator of metabolism and growth, governing cellular nutrient uptake, energy generation, reducing cofactor production and macromolecule biosynthesis1. Many of the driver mutations in cancer with the highest recurrence, including in receptor tyrosine kinases, Ras, PTEN and PI3K, pathologically activate PI3K signalling2,3. However, our understanding of the core metabolic program controlled by PI3K is almost certainly incomplete. Here, using mass-spectrometry-based metabolomics and isotope tracing, we show that PI3K signalling stimulates the de novo synthesis of one of the most pivotal metabolic cofactors: coenzyme A (CoA). CoA is the major carrier of activated acyl groups in cells4,5 and is synthesized from cysteine, ATP and the essential nutrient vitamin B5 (also known as pantothenate)6,7. We identify pantothenate kinase 2 (PANK2) and PANK4 as substrates of the PI3K effector kinase AKT8. Although PANK2 is known to catalyse the rate-determining first step of CoA synthesis, we find that the minimally characterized but highly conserved PANK49 is a rate-limiting suppressor of CoA synthesis through its metabolite phosphatase activity. Phosphorylation of PANK4 by AKT relieves this suppression. Ultimately, the PI3K-PANK4 axis regulates the abundance of acetyl-CoA and other acyl-CoAs, CoA-dependent processes such as lipid metabolism and proliferation. We propose that these regulatory mechanisms coordinate cellular CoA supplies with the demands of hormone/growth-factor-driven or oncogene-driven metabolism and growth.
  8. Nature. 2022 Jul 28.
    Bonn COVIMMUNE Consortium
      Anorexia and fasting are host adaptations to acute infection, inducing a metabolic switch towards ketogenesis and the production of ketone bodies, including β-hydroxybutyrate (BHB) 1-6. However, whether ketogenesis metabolically influences the immune response in pulmonary infections remains unclear. Here we report impaired production of BHB in humans with SARS-CoV-2-induced but not influenza-induced acute respiratory distress syndrome (ARDS). CD4+ T cell function is impaired in COVID-19 and BHB promotes both survival and production of Interferon-γ from CD4+ T cells. Using metabolic tracing analysis, we uncovered that BHB provides an alternative carbon source to fuel oxidative phosphorylation (OXPHOS) and the production of bioenergetic amino acids and glutathione, which is important for maintaining the redox balance. T cells from patients with SARS-CoV-2-induced ARDS were exhausted and skewed towards glycolysis, but can be metabolically reprogrammed by BHB to perform OXPHOS, thereby increasing their functionality. Finally, we demonstrate that ketogenic diet (KD) and delivery of BHB as ketone ester drink restores CD4+ T cell metabolism and function in respiratory infections, ultimately reducing the mortality of SARS-CoV-2 infected mice. Altogether, our data reveal BHB as alternative carbon source promoting T cell responses in pulmonary viral infections, highlighting impaired ketogenesis as a potential confounder of severe COVID-19.
  9. Cells. 2022 Jul 16. pii: 2213. [Epub ahead of print]11(14):
      Vascular aging is based on the development of endothelial dysfunction, which is thought to be promoted by senescent cells accumulating in aged tissues and is possibly affected by their environment via inflammatory mediators and oxidative stress. Senescence appears to be closely interlinked with changes in cell metabolism. Here, we describe an upregulation of both glycolytic and oxidative glucose metabolism in replicative senescent endothelial cells compared to young endothelial cells by employing metabolic profiling and glucose flux measurements and by analyzing the expression of key metabolic enzymes. Senescent cells exhibit higher glycolytic activity and lactate production together with an enhanced expression of lactate dehydrogenase A as well as increases in tricarboxylic acid cycle activity and mitochondrial respiration. The latter is likely due to the reduced expression of pyruvate dehydrogenase kinases (PDHKs) in senescent cells, which may lead to increased activity of the pyruvate dehydrogenase complex. Cellular and mitochondrial ATP production were elevated despite signs of mitochondrial dysfunction, such as an increased production of reactive oxygen species and extended mitochondrial mass. A shift from glycolytic to oxidative glucose metabolism induced by pharmacological inhibition of PDHKs in young endothelial cells resulted in premature senescence, suggesting that alterations in cellular glucose metabolism may act as a driving force for senescence in endothelial cells.
    Keywords:  aging; dichloroacetate; endothelial cell; glucose metabolism; lactate; lactate dehydrogenase; pyruvate dehydrogenase kinase; replicative senescence
  10. Cancer Res. 2022 Jul 27. pii: CAN-22-0042. [Epub ahead of print]
      Hepatocellular carcinoma (HCC) is one of the primary liver malignancies with a poor prognosis. Glutamic-oxaloacetic transaminase 2 (GOT2) is a highly tissue-specific gene in the liver, but the roles GOT2 plays in the progression of HCC remain unclear. Here, we report that GOT2 is downregulated in HCC tumor tissues and that low expression of GOT2 is associated with advanced progression and poor prognosis. In HCC cells, knockdown of GOT2 promoted proliferation, migration, and invasion. In mouse models of HCC, loss of GOT2 promoted tumor growth as well as hematogenous and intrahepatic metastasis. Mechanistically, silencing of GOT2 enhanced glutaminolysis, nucleotide synthesis, and GSH synthesis by reprogramming glutamine metabolism to support the cellular antioxidant system, which activated the PI3K/AKT/mTOR pathway to contribute to HCC progression. Furthermore, HCC with low expression of GOT2 was highly dependent on glutamine metabolism and sensitive to the glutaminase inhibitor CB-839 in vitro and in vivo. Overall, GOT2 is involved in glutamine metabolic reprogramming to promote HCC progression and may serve as a therapeutic and diagnostic target for HCC.
  11. Antioxidants (Basel). 2022 Jul 21. pii: 1410. [Epub ahead of print]11(7):
      Respiratory syncytial virus (RSV) can cause severe respiratory illness in infants, immunocompromised, and older adults. Despite its burden, no vaccine or specific treatment is available. RSV infection is associated with increased reactive oxygen species (ROS) production, degradation of the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2), and decreased antioxidant enzymes (AOEs), leading to oxidative damage and lung injury. Hydrogen sulfide (H2S) is an endogenous gaseous molecule that plays a physiological role in numerous cellular processes and a protective role in multiple pathological conditions, displaying vasoactive, cytoprotective, anti-inflammatory, and antioxidant activities. H2S can promote NRF2 activation through the sulfhydration of Kelch-like ECH-associated protein 1, the cytoplasmic repressor of NRF2. Here we investigated whether increasing cellular H2S levels could rescue NRF2 and NRF2-dependent gene expression in RSV-infected primary airway epithelial cells. We found that treatment with the H2S donor GYY4137 significantly increased NRF2 levels and AOEs gene expression by decreasing KEAP1 levels, and by modulating pathways involved in RSV-induced NRF2 degradation, such as NRF2 ubiquitination, and promyelocytic leukemia (PML) protein levels. These results suggest that the administration of exogenous H2S can positively impact the altered redox balance associated with RSV infection, which represents an important determinant of RSV-induced lung disease.
    Keywords:  GYY4137; H2S donor; NRF2; antioxidant enzymes; hydrogen sulfide; respiratory syncytial virus
  12. Cancers (Basel). 2022 Jul 10. pii: 3355. [Epub ahead of print]14(14):
      HCC is well known for low glycolysis in the tumors, whereas hypoxia induces glycolytic phenotype and tumor progression. This study was conducted to evaluate the expression of SLCs in human HCCs and investigated whether extracellular nutrient administration related to SLCs in low-glycolytic HCC can prevent hypoxic tumor progression. SLCs expression was screened according to the level of glycolysis in HCCs. Then, whether extracellular nutrient treatment can affect hypoxic tumor progression, as well as the mechanisms, were evaluated in an in vitro cell line and an in vivo animal model. Low-glycolytic HCCs showed high SLC13A5/NaCT and SLC16A1/MCT1 but low SLC2A1/GLUT1 and HIF1α/HIF1α expression. Especially, high SLC13A5 expression was significantly associated with good overall survival in the Cancer Genome Atlas (TCGA) database. In HepG2 cells with the highest NaCT expression, extracellular citrate treatment upon hypoxia induced HIF1α degradation, which led to reduced glycolysis and cellular proliferation. Finally, in HepG2-animal models, the citrate-treated group showed smaller tumor with less hypoxic areas than the vehicle-treated group. In patients with HCC, SLC13A5/NaCT is an important SLC, which is associated with low glycolysis and good prognosis. Extracellular citrate treatment induced the failure of metabolic adaptation to hypoxia and tumor growth inhibition, which can be a potential therapeutic strategy in HCCs.
    Keywords:  SLC13A5/NaCT; cancer metabolism; citrate; hepatocellular carcinoma; hypoxia
  13. J Clin Biochem Nutr. 2022 Jul;71(1): 48-54
      Glutathione (GSH) is synthesized from three amino acids and the overall process is highly dependent on the availability of l-cysteine (l-Cys). GSH serves as an essential cofactor for glutathione peroxidase 4 (Gpx4), which reduces phospholipid hydroperoxides. The inactivation of Gpx4 or an insufficient supply of l-Cys results in the accumulation of lipid hydroperoxides, eventually leading to iron-dependent cell death, ferroptosis. In this study, we investigated the anti-ferroptotic properties of d-cysteine (d-Cys) under conditions of dysfunction in cystine transporter, xCT. l-Cys supplementation completely rescued ferroptosis that had been induced by the erastin-mediated inhibition of xCT in Hepa 1-6 cells. Upon d-Cys supplementation, the erastin-treated cells remained completely viable for periods of up to 24 h but eventually died after 48 h. d-Cys supplementation suppressed the production of lipid peroxides, thereby ferroptosis. The addition of d-Cys sustained intracellular Cys and GSH levels to a certain extent. When Hepa 1-6 cells were treated with a combination of buthionine sulfoximine and erastin, the anti-ferroptotic effect of d-Cys was diminished. These collective results indicate that, although d-Cys is not the direct source of GSH, d-Cys supplementation protects cells from ferroptosis in a manner that is dependent on GSH synthesis via stimulating the uptake of l-Cys.
    Keywords:  cystine; d-‍cysteine; ferroptosis; glutathione; l-cysteine
  14. Front Immunol. 2022 ;13 840029
      Macrophages are one of the most important cells in the innate immune system, they are converted into two distinct subtypes with completely different molecular phenotypes and functional features under different stimuli of the microenvironment: M1 macrophages induced by IFN-γ/lipopolysaccharides(LPS) and M2 macrophages induced by IL-4/IL-10/IL-13. Tumor-associated macrophages (TAMs) differentiate from macrophages through various factors in the tumor microenvironment (TME). TAMs have the phenotype and function of M2 macrophages and are capable of secreting multiple cytokines to promote tumor progression. Both tumor cells and macrophages can meet the energy needs for rapid cell growth and proliferation through metabolic reprogramming, so a comprehensive understanding of pro-tumor and antitumor metabolic switches in TAM is essential to understanding immune escape mechanisms. This paper focuses on the functions of relevant signaling pathways and cytokines during macrophage polarization and metabolic reprogramming, and briefly discusses the effects of different microenvironments and macrophage pathogenicity, in addition to describing the research progress of inhibitory drugs for certain metabolic and polarized signaling pathways.
    Keywords:  immune escape; macrophage polarization; metabolic reprogramming; tumor microenvironment; tumor-associated macrophages
  15. Biochim Biophys Acta Mol Cell Res. 2022 Jul 25. pii: S0167-4889(22)00120-3. [Epub ahead of print] 119328
      Ferroptosis is a unique iron-dependent cell death mechanism characterized by the generation of lipid reactive oxygen species (ROS) in cancer cells, which leads to mitochondrial metabolic dysregulation. However, how could the tumor immune microenvironment (TIME) modulates ferroptosis remains unclear. Thus, by integrating multiple algorithms, we revealed the novel functional and immune patterns of the ferroptosis-related genes (FRGs) in breast cancer. Five prognostic FRGs were finally selected for the prognostic signature and four of which were identified as the independent biomarkers for immunotherapies. The consensus cluster analysis illustrated the FRGs were characterized by the metabolism dysfunction and immune infiltration cells, meanwhile, these FRGs have the same stem cell characteristics and response efficacy to the immunotherapies. In conclusion, a comprehensive analysis of the FRGs in breast cancer was conducted to develop a prognostic gene signature. Functional and immunological evidence of vulnerabilities in the interaction between ferroptosis and the TIME was also revealed. Further data and research are required.
    Keywords:  Breast cancer; Ferroptosis; Immune cell infiltration; Immunotherapy; Tumor immune microenvironment
  16. Obesity (Silver Spring). 2022 Aug;30(8): 1647-1658
      OBJECTIVE: Aldose reductase (AKR1B1 in humans; Akr1b3 in mice), a key enzyme of the polyol pathway, mediates lipid accumulation in the murine heart and liver. The study objective was to explore potential roles for AKR1B1/Akr1b3 in the pathogenesis of obesity and its complications.METHODS: The study employed mice treated with an inhibitor of aldose reductase or mice devoid of Akr1b3 were used to determine their response to a high-fat diet. The study used subcutaneous adipose tissue-derived adipocytes to investigate mechanisms by which AKR1B1/Akr1b3 promotes diet-induced obesity.
    RESULTS: Increased expression of aldose reductase and senescence in the adipose tissue of humans and mice with obesity were demonstrated. Genetic deletion of Akr1b3 or pharmacological blockade of AKRIB3 with zopolrestat reduced high-fat-diet-induced obesity, attenuated markers of adipose tissue senescence, and increased lipolysis.
    CONCLUSIONS: AKR1B1/Akr1b3 modulation of senescence in subcutaneous adipose tissue contributes to aberrant metabolic responses to high-fat feeding. These data unveil new opportunities to target these pathways to combat obesity.
  17. Stem Cells Int. 2022 ;2022 3674931
      Dental follicle cells (DFCs) are stem/progenitor cells of the periodontium and give rise to alveolar osteoblasts. However, understanding of the molecular mechanisms of osteogenic differentiation, which is required for cell-based therapies, is delimited. This study is aimed at analyzing the energy metabolism during the osteogenic differentiation of DFCs. Human DFCs were cultured, and osteogenic differentiation was induced by either dexamethasone or bone morphogenetic protein 2 (BMP2). Previous microarray data were reanalyzed to examine pathways that are regulated after osteogenic induction. Expression and activity of metabolic markers were evaluated by western blot analysis and specific assays, relative amount of mitochondrial DNA was measured by real-time quantitative polymerase chain reaction, the oxidative state of cells was determined by a glutathione assay, and the lipidome of cells was analyzed via mass spectrometry (MS). Moreover, osteogenic markers were analyzed after the inhibition of fatty acid synthesis by 5-(tetradecyloxy)-2-furoic acid or C75. Pathway enrichment analysis of microarray data revealed that carbon metabolism was amongst the top regulated pathways after osteogenic induction in DFCs. Further analysis showed that enzymes involved in glycolysis, citric acid cycle, mitochondrial activity, and lipid metabolism are differentially expressed during differentiation, with most markers upregulated and more markedly after induction with dexamethasone compared to BMP2. Moreover, the cellular state was more oxidized, and mitochondrial DNA was distinctly upregulated during the second half of differentiation. Besides, MS of the lipidome revealed higher lipid concentrations after osteogenic induction, with a preference for species with lower numbers of C-atoms and double bonds, which indicates a de novo synthesis of lipids. Concordantly, inhibition of fatty acid synthesis impeded the osteogenic differentiation of DFCs. This study demonstrates that energy metabolism is highly regulated during osteogenic differentiation of DFCs including changes in the lipidome suggesting enhanced de novo synthesis of lipids, which are required for the differentiation process.
  18. Metabolites. 2022 Jun 25. pii: 593. [Epub ahead of print]12(7):
      Tracer metabolomics is a powerful technology for the biomedical community to study and understand disease-inflicted metabolic mechanisms. However, the interpretation of tracer metabolomics results is highly technical, as the metabolites' abundances, tracer incorporation and positions on the metabolic map all must be jointly interpreted. The field is currently lacking a structured approach to help less experienced researchers start the interpretation of tracer metabolomics datasets. We propose an approach using an intuitive visualization concept aided by a novel open-source tool, and provide guidelines on how researchers can apply the approach and the visualization tool to their own datasets. Using a showcase experiment, we demonstrate that the visualization approach leads to an intuitive interpretation that can ease researchers into understanding their tracer metabolomics data.
    Keywords:  biochemical pathways; data visualization; tracer metabolomics
  19. Biomedicines. 2022 Jul 07. pii: 1627. [Epub ahead of print]10(7):
      Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the "resting" state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.
    Keywords:  PEP cycle; diabetes; insulin secretion; lipids; mitochondrial dysfunction; uncoupling proteins
  20. Brain. 2022 Jul 28. pii: awac222. [Epub ahead of print]
      Malignant brain tumours are the cause of a disproportionate level of morbidity and mortality among cancer patients, an unfortunate statistic that has remained constant for decades. Despite considerable advances in the molecular characterization of these tumours, targeting the cancer cells has yet to produce significant advances in treatment. An alternative strategy is to target cells in the glioblastoma microenvironment, such as tumour-associated astrocytes. Astrocytes control multiple processes in health and disease, ranging from maintaining the brain's metabolic homeostasis, to modulating neuroinflammation. However, their role in glioblastoma pathogenicity is not well understood. Here we report that depletion of reactive astrocytes regresses glioblastoma and prolongs mouse survival. Analysis of the tumour-associated astrocyte translatome revealed astrocytes initiate transcriptional programmes that shape the immune and metabolic compartments in the glioma microenvironment. Specifically, their expression of CCL2 and CSF1 governs the recruitment of tumour-associated macrophages and promotes a pro-tumourigenic macrophage phenotype. Concomitantly, we demonstrate that astrocyte-derived cholesterol is key to glioma cell survival, and that targeting astrocytic cholesterol efflux, via ABCA1, halts tumour progression. In summary, astrocytes control glioblastoma pathogenicity by reprogramming the immunological properties of the tumour microenvironment and supporting the non-oncogenic metabolic dependency of glioblastoma on cholesterol. These findings suggest that targeting astrocyte immunometabolic signalling may be useful in treating this uniformly lethal brain tumour.
    Keywords:  astrocytes; cholesterol; glioma
  21. Diabetes. 2022 Jul 26. pii: db220035. [Epub ahead of print]
      Caveolin-1 (cav1) is an important structural and signaling component of plasma membrane invaginations called caveolae and is abundant in adipocytes. As previously reported, adipocyte-specific ablation of the cav1 gene (ad-cav1KO mouse) does not result in elimination of the protein, as cav1 protein traffics to adipocytes from neighboring endothelial cells. However, this mouse is a functional knockout as adipocyte caveolar structures are depleted. Compared to controls, ad-cav1KO mice on a high-fat diet (HFD) display improved whole-body glucose clearance despite complete loss of glucose-stimulated insulin secretion, blunted insulin-stimulated AKT activation in metabolic tissues and partial lipodystrophy. The cause is increased insulin-independent glucose uptake by white adipose tissue (AT) and reduced hepatic gluconeogenesis. Furthermore, high fat fed ad-cav1KO mice display significant AT inflammation, fibrosis, mitochondrial dysfunction, and dysregulated lipid metabolism. The glucose clearance phenotype of the ad-cav1KO mice is at least partially mediated by AT small extracellular vesicles (AT-sEVs). Injection of control mice with AT-sEVs from ad-cav1KO mice phenocopies ad-cav1KO characteristics. Interestingly, AT-sEVs from ad-cav1KO mice propagate the phenotype of the AT to the liver. These data indicate that adipocyte cav1 is essential for healthy adaptation of the AT to overnutrition and prevents aberrant propagation of negative phenotypes to other organs by EVs.
  22. Front Pharmacol. 2022 ;13 920113
      Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in the nicotinamide adenine dinucleotide (NAD) salvage pathway in mammals. It is of great significance in the metabolic homeostasis and cell survival via synthesizing nicotinamide mononucleotide (NMN) through enzymatic activities, serving as a key protein involved in the host's defense mechanism. The NAMPT metabolic pathway connects NAD-dependent sirtuin (SIRT) signaling, constituting the NAMPT-NAD-SIRT cascade, which is validated as a strong intrinsic defense system. Neurodegenerative diseases belong to the central nervous system (CNS) disease that seriously endangers human health. The World Health Organization (WHO) proposed that neurodegenerative diseases will become the second leading cause of human death in the next two decades. However, effective drugs for neurodegenerative diseases are scant. NAMPT is specifically highly expressed in the hippocampus, which mediates cell self-renewal and proliferation and oligodendrocyte synthesis by inducing the biosynthesis of NAD in neural stem cells/progenitor cells. Owing to the active biological function of NAMPT in neurogenesis, targeting NAMPT may be a powerful therapeutic strategy for neurodegenerative diseases. This study aims to review the structure and biological functions, the correlation with neurodegenerative diseases, and treatment advance of NAMPT, aiming to provide a novel idea for targeted therapy of neurodegenerative diseases.
    Keywords:  agonists; inhibitors; neurodegenerative diseases; nicotinamide adenine dinucleotide; nicotinamide phosphoribosyltransferase
  23. Biomolecules. 2022 Jul 15. pii: 986. [Epub ahead of print]12(7):
      The association between neurodegenerative diseases (NDs) and obesity has been well studied in recent years. Obesity is a syndrome of multifactorial etiology characterized by an excessive accumulation and release of fatty acids (FA) in adipose and non-adipose tissue. An excess of FA generates a metabolic condition known as lipotoxicity, which triggers pathological cellular and molecular responses, causing dysregulation of homeostasis and a decrease in cell viability. This condition is a hallmark of NDs, and astrocytes are particularly sensitive to it, given their crucial role in energy production and oxidative stress management in the brain. However, analyzing cellular mechanisms associated with these conditions represents a challenge. In this regard, metabolomics is an approach that allows biochemical analysis from the comprehensive perspective of cell physiology. This technique allows cellular metabolic profiles to be determined in different biological contexts, such as those of NDs and specific metabolic insults, including lipotoxicity. Since data provided by metabolomics can be complex and difficult to interpret, alternative data analysis techniques such as machine learning (ML) have grown exponentially in areas related to omics data. Here, we developed an ML model yielding a 93% area under the receiving operating characteristic (ROC) curve, with sensibility and specificity values of 80% and 93%, respectively. This study aimed to analyze the metabolomic profiles of human astrocytes under lipotoxic conditions to provide powerful insights, such as potential biomarkers for scenarios of lipotoxicity induced by palmitic acid (PA). In this work, we propose that dysregulation in seleno-amino acid metabolism, urea cycle, and glutamate metabolism pathways are major triggers in astrocyte lipotoxic scenarios, while increased metabolites such as alanine, adenosine, and glutamate are suggested as potential biomarkers, which, to our knowledge, have not been identified in human astrocytes and are proposed as candidates for further research and validation.
    Keywords:  astrocytes; lipotoxicity; metabolomics; neurodegenerative diseases; obesity
  24. Prog Neurobiol. 2022 Jul 21. pii: S0301-0082(22)00117-4. [Epub ahead of print] 102331
      Astrocytes contribute to the complex cellular pathology of Alzheimer's disease (AD). Neurons and astrocytes function in close collaboration through neurotransmitter recycling, collectively known as the glutamate/GABA-glutamine cycle, which is essential to sustain neurotransmission. Neurotransmitter recycling is intimately linked to astrocyte energy metabolism. In the course of AD, astrocytes undergo extensive metabolic remodeling, which may profoundly affect the glutamate/GABA-glutamine cycle. The consequences of altered astrocyte function and metabolism in relation to neurotransmitter recycling are yet to be comprehended. Metabolic alterations of astrocytes in AD deprive neurons of metabolic support, thereby contributing to synaptic dysfunction and neurodegeneration. In addition, several astrocyte-specific components of the glutamate/GABA-glutamine cycle, including glutamine synthesis and synaptic neurotransmitter uptake, are perturbed in AD. Integration of the complex astrocyte biology within the context of AD is essential for understanding the fundamental mechanisms of the disease, while restoring astrocyte metabolism may serve as an approach to arrest or even revert clinical progression of AD.
    Keywords:  Neurotransmitter recycling; alternative substrates; astrogliosis; dementia; excitotoxicity; mitochondria; neurodegeneration
  25. Cancers (Basel). 2022 Jul 11. pii: 3369. [Epub ahead of print]14(14):
      Background: A high adenosine level is an important characteristic of the tumor microenvironment (TME) in breast cancer. Pannexin 1 (PANX1) can release intracellular ATP to the extracellular space and elevate extracellular ATP (exATP) levels under physiological conditions. Methods: We performed public database bioinformatics analysis, surgical specimen histological validation, RNA sequencing, and exATP/extracellular adenosine (exADO) assays to reveal the role of PANX1 in regulating the immune microenvironment of basal-like breast cancer. Results: Our results revealed that PANX1 acted as a poor prognostic factor for breast cancer and had high expression in basal-like breast cancer. PANX1 expression was positively correlated with exATP and exADO levels in basal-like breast cancer TME. PANX1 expression was also positively correlated with tumor-associated neutrophil (TAN) infiltration in breast cancer TME and TANs highly expressed ENTPD1 (CD39)/NT5E (CD73). Conclusions: This study suggests that high PANX1 expression is associated with high TAN infiltration and adenosine production to induce local immunosuppression in basal-like breast cancer TME.
    Keywords:  adenosine; breast cancer; neutrophils; pannexin 1 (PANX1); tumor microenvironment (TME)
  26. Cancers (Basel). 2022 Jul 13. pii: 3410. [Epub ahead of print]14(14):
      Hepatocellular carcinoma (HCC) is a common malignant tumor worldwide. Chromosome 8 open reading frame 76 (C8orf76), a novel gene located in the nucleus, is highly expressed in many tumor types. However, the specific mechanisms and functions of C8orf76 in HCC remain unclear. Here, we reported for the first time that C8orf76 gene expression levels were frequently upregulated in liver cancer and significantly correlated with HCC development. C8orf76 downregulation induced G1-S arrest and inhibited cell proliferation. Intriguingly, C8orf76 deficiency could accelerate erastin or sorafenib-induced ferroptosis through increasing lipid reactive oxygen species (ROS) levels. Moreover, although C8orf76 overexpression did not affect tumorigenesis under normal conditions, it increased resistance to lipid disturbance and ferroptosis triggered by erastin or sorafenib, which further facilitated HCC cell growth and tumor progression. Mechanistically, C8orf76 bound to the promoter region of the solute carrier family 7 member 11 (SLC7A11) gene and upregulated SLC7A11 transcriptionally. SLC7A11-dependent cystine import led to sufficient GSH synthesis and lipid peroxidation inhibition, thus accelerating tumor growth. Our study indicated that C8orf76 could be a novel marker for HCC diagnosis. In addition, a better comprehensive understanding of the potential role of C8orf76 in HCC helped us develop novel therapeutic strategies for this intractable cancer.
    Keywords:  C8orf76; SLC7A11; ferroptosis; ferroptosis resistance; hepatocellular carcinoma; oxidative stress
  27. ChemMedChem. 2022 Jul 27.
      A series of derivatives of the substrate amino acid Ltryptophan have been investigated for inhibition of the L-type amino acid transporter LAT1 (SLC7A5), which is an emerging target in anticancer drug discovery. Of the four isomeric 4-, 5-, 6-, or 7benzyloxy-L-tryptophans, the 5-substituted derivative was the most potent, with an IC 50 of 19 μM for inhibition of [ 3 H]-L-leucine uptake into HT-29 human colon carcinoma cells. The replacement of the carboxy group in 5-benzyloxy-L-tryptophan by a bioisosteric tetrazole moiety led to a complete loss in potency. Likewise, the corresponding tetrazolide derived from L-tryptophan itself was found to be neither a substrate nor an inhibitor of the transporter. Increasing the steric bulk at the 5-position, while reasonably well tolerated in some cases, did not result in an improvement in potency. At the same time, none of these derivatives was found to be substrates of LAT1-mediated transport.
    Keywords:  Amino acid transporter; LAT1 inhibitor; Structure-activity relationships; cancer; tryptophan
  28. Metabolites. 2022 Jul 07. pii: 625. [Epub ahead of print]12(7):
      Fetuin-A, a plasma multifunctional protein known to play a role in insulin resistance, is usually presented as a liver secreted protein. However, fetuin-A adipose tissue production has been also described. Here, we evaluated fetuin-A production by the liver and the adipose tissue during metabolic dysfunction-associated fatty liver disease (MAFLD)-non-alcoholic steatohepatitis (NASH) development. Fetuin-A was evaluated by enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), Western blot, and immunofluorescence in male foz-/- mice fed a normal diet (ND) or a high fat diet (HFD) at various timepoints and in MAFLD-NASH patients. Foz-/- mice fed a short-term HFD developed liver steatosis, insulin resistance, and increased circulating levels of fetuin-A compared to ND-fed mice. In mice and patients with NASH, fetuin-A was located not only in healthy or steatotic hepatocytes but also in some macrophages forming lipogranulomas. In both mice and humans, a significant amount of fetuin-A was present in the adipose tissue compared to the liver. However, messenger ribonucleic acid levels and cell culture experiments indicate that fetuin-A is produced by the liver but not by the adipose tissue. In conclusion, fetuin-A is produced by steatotic hepatocytes at early timepoints in MAFLD and correlates with insulin resistance both in mice and humans. In NASH, fetuin-A also co-localizes with activated liver macrophages and could be interpreted as a signal released by damaged hepatocytes.
    Keywords:  adipose tissue; diabetes; fetuin-A; foz mice; humans; insulin resistance; liver; metabolic dysfunction-associated fatty liver disease; non-alcoholic steatohepatitis
  29. J Immunol. 2022 Jul 27. pii: ji2100795. [Epub ahead of print]
      Colonization by Helicobacter pylori is associated with gastric diseases, ranging from superficial gastritis to more severe pathologies, including intestinal metaplasia and adenocarcinoma. The interplay of the host response and the pathogen affect the outcome of disease. One major component of the mucosal response to H. pylori is the activation of a strong but inefficient immune response that fails to control the infection and frequently causes tissue damage. We have shown that polyamines can regulate H. pylori-induced inflammation. Chemical inhibition of ornithine decarboxylase (ODC), which generates the polyamine putrescine from l-ornithine, reduces gastritis in mice and adenocarcinoma incidence in gerbils infected with H. pylori However, we have also demonstrated that Odc deletion in myeloid cells enhances M1 macrophage activation and gastritis. Here we used a genetic approach to assess the specific role of gastric epithelial ODC during H. pylori infection. Specific deletion of the gene encoding for ODC in gastric epithelial cells reduces gastritis, attenuates epithelial proliferation, alters the metabolome, and downregulates the expression of immune mediators induced by H. pylori Inhibition of ODC activity or ODC knockdown in human gastric epithelial cells dampens H. pylori-induced NF-κB activation, CXCL8 mRNA expression, and IL-8 production. Chronic inflammation is a major risk factor for the progression to more severe pathologies associated with H. pylori infection, and we now show that epithelial ODC plays an important role in mediating this inflammatory response.
  30. Sci Adv. 2022 Jul 29. 8(30): eabo0340
      Mitochondrial quality in skeletal muscle is crucial for maintaining energy homeostasis during metabolic stresses. However, how muscle mitochondrial quality is controlled and its physiological impacts remain unclear. Here, we demonstrate that mitoprotease LONP1 is essential for preserving muscle mitochondrial proteostasis and systemic metabolic homeostasis. Skeletal muscle-specific deletion of Lon protease homolog, mitochondrial (LONP1) impaired mitochondrial protein turnover, leading to muscle mitochondrial proteostasis stress. A benefit of this adaptive response was the complete resistance to diet-induced obesity. These favorable metabolic phenotypes were recapitulated in mice overexpressing LONP1 substrate ΔOTC in muscle mitochondria. Mechanistically, mitochondrial proteostasis imbalance elicits an unfolded protein response (UPRmt) in muscle that acts distally to modulate adipose tissue and liver metabolism. Unexpectedly, contrary to its previously proposed role, ATF4 is dispensable for the long-range protective response of skeletal muscle. Thus, these findings reveal a pivotal role of LONP1-dependent mitochondrial proteostasis in directing muscle UPRmt to regulate systemic metabolism.
  31. Cancer Res. 2022 Jul 27. pii: CAN-21-3914. [Epub ahead of print]
      Glutamine synthase 2 (GLS2) is a key regulator of glutaminolysis and has been previously implicated in activities consistent with tumor suppression. Here we generated Gls2 knockout (KO) mice that develop late-occurring B cell lymphomas and hepatocellular carcinomas (HCC). Further, Gls2 KO mice subjected to the hepatocarcinogenic Stelic Animal Model (STAM) protocol produce larger HCC tumors than seen in wild-type mice. GLS2 has been shown to promote ferroptosis, a form of cell death characterized by iron-dependent accumulation of lipid peroxides. In line with this, GLS2 deficiency, either in cells derived from Gls2 KO mice or in human cancer cells depleted of GLS2, conferred significant resistance to ferroptosis. Mechanistically, GLS2, but not GLS1, increased lipid ROS production by facilitating the conversion of glutamate to α-ketoglutarate, thereby promoting ferroptosis. Ectopic expression of wild-type GLS2 in a human hepatic adenocarcinoma xenograft model significantly reduced tumor size; this effect was nullified by either expressing a catalytically inactive form of GLS2 or by blocking ferroptosis. Furthermore, analysis of cancer patient datasets supported a role for GLS2-mediated regulation of ferroptosis in human tumor suppression. These data suggest that GLS2 is a bona fide tumor suppressor and that its ability to favor ferroptosis by regulating glutaminolysis contributes to its tumor suppressive function.
  32. Biofabrication. 2022 Jul 27.
      Obesity prevalence has reached pandemic proportions, leaving individuals at high risk for the development of diseases such as cancer and type 2 diabetes. In obesity, to accommodate excess lipid storage, adipocytes become hypertrophic, which is associated with an increased pro-inflammatory cytokine secretion and dysfunction of metabolic processes such as insulin signaling and lipolysis. Targeting adipocyte dysfunction is an important strategy to prevent the development of obesity-associated disease. However, it is unclear how accurately animal models reflect human biology, and the long-term culture of human hypertrophic adipocytes in an in vitro 2D monolayer is challenging due to the buoyant nature of adipocytes. Here we describe the development of a human 3D in vitro disease model that recapitulates hallmarks of obese adipocyte dysfunction. First, primary human adipose-derived mesenchymal stromal cells are embedded in hydrogel, and infiltrated into a thin cellulose scaffold. The thin microtissue profile allows for efficient assembly and image-based analysis. After adipocyte differentiation, the scaffold is stimulated with oleic or palmitic acid to mimic caloric overload. Using functional assays, we demonstrated that this treatment induced important obese adipocyte characteristics such as a larger lipid droplet size, increased basal lipolysis, insulin resistance and a change in macrophage gene expression through adipocyte-conditioned media. This 3D disease model mimics physiologically relevant hallmarks of obese adipocytes, to enable investigations into the mechanisms by which dysfunctional adipocytes contribute to disease.
    Keywords:  Adipocyte; Fatty acid stimulation; In vitro disease model; obesity; paper-based scaffold
  33. Nat Rev Immunol. 2022 Jul 25.
      Numerous mitochondrial constituents and metabolic products can function as damage-associated molecular patterns (DAMPs) and promote inflammation when released into the cytosol or extracellular milieu. Several safeguards are normally in place to prevent mitochondria from eliciting detrimental inflammatory reactions, including the autophagic disposal of permeabilized mitochondria. However, when the homeostatic capacity of such systems is exceeded or when such systems are defective, inflammatory reactions elicited by mitochondria can become pathogenic and contribute to the aetiology of human disorders linked to autoreactivity. In addition, inefficient inflammatory pathways induced by mitochondrial DAMPs can be pathogenic as they enable the establishment or progression of infectious and neoplastic disorders. Here we discuss the molecular mechanisms through which mitochondria control inflammatory responses, the cellular pathways that are in place to control mitochondria-driven inflammation and the pathological consequences of dysregulated inflammatory reactions elicited by mitochondrial DAMPs.
  34. JCI Insight. 2022 Jul 26. pii: e158737. [Epub ahead of print]
      Increased red cell distribution width (RDW), which measures erythrocyte volume (MCV) variability (anisocytosis), has been linked to early mortality in many diseases and in older adults through unknown mechanisms. Hypoxic stress has been proposed as a potential mechanism. However, experimental models to investigate the link between increased RDW and reduced survival are lacking. Here, we show that lifelong hypobaric hypoxia (~10% O2) increases erythrocyte numbers, hemoglobin and RDW, while reducing longevity in male mice. Compound heterozygous knockout (chKO) mutations in succinate dehydrogenase (Sdh; mitochondrial complex II) genes Sdhb, Sdhc and Sdhd reduce Sdh subunit protein levels, RDW, and increase healthy lifespan compared to wild-type (WT) mice in chronic hypoxia. RDW-SD, a direct measure of MCV variability, and the standard deviation of MCV (1SD-RDW) show the most statistically significant reductions in Sdh hKO mice. Tissue metabolomic profiling of 147 common metabolites shows the largest increase in succinate with elevated succinate to fumarate and succinate to oxoglutarate (2-ketoglutarate) ratios in Sdh hKO mice. These results demonstrate that mitochondrial complex II level is an underlying determinant of both RDW and healthy lifespan in hypoxia, and suggest that therapeutic targeting of Sdh might reduce high RDW-associated clinical mortality in hypoxic diseases.
    Keywords:  Hematology; Hypoxia; Mitochondria; Pulmonology
  35. J Xenobiot. 2022 Jul 06. 12(3): 158-180
      Replication is a fundamental aspect of cancer, and replication is about reproducing all the elements and structures that form a cell. Among them are DNA, RNA, enzymes, and coenzymes. All the DNA is doubled during each S (synthesis) cell cycle phase. This means that six billion nucleic acids must be synthesized in each cycle. Tumor growth, proliferation, and mutations all depend on this synthesis. Cancer cells require a constant supply of nucleotides and other macromolecules. For this reason, they must stimulate de novo nucleotide synthesis to support nucleic acid provision. When deregulated, de novo nucleic acid synthesis is controlled by oncogenes and tumor suppressor genes that enable increased synthesis and cell proliferation. Furthermore, cell duplication must be achieved swiftly (in a few hours) and in the midst of a nutrient-depleted and hypoxic environment. This also means that the enzymes participating in nucleic acid synthesis must work efficiently. pH is a critical factor in enzymatic efficiency and speed. This review will show that the enzymatic machinery working in nucleic acid synthesis requires a pH on the alkaline side in most cases. This coincides with many other pro-tumoral factors, such as the glycolytic phenotype, benefiting from an increased intracellular pH. An increased intracellular pH is a perfect milieu for high de novo nucleic acid production through optimal enzymatic performance.
    Keywords:  de novo nucleotide synthesis; intracellular alkalosis; pH deregulation; pyrimidine
  36. Front Nutr. 2022 ;9 925908
      A decrease in TCA cycle activity may lead to impaired nutrition metabolism and cellular energy shortage. Herein, we aimed to characterize the detailed metabolic changes that compensate for energy shortages in energy-consuming organs (heart and skeletal muscles) in mice with knockout of citrate synthase (CS), an important enzyme in the TCA cycle. CS hetero knockout (CS +/-) mice and wild-type mice were fed a low-carbohydrate ketogenic diet (LCKD) or high-fat, high-carbohydrate diet (HFHCD) to induce metabolic changes. Body weight, blood serum parameters, metabolic gene expression, and adenosine triphosphate (ATP) levels were measured in the heart and skeletal muscles. Glycogen content, anabolic and catabolic biomarkers, and morphological changes were also assessed in the skeletal muscles. After diet feeding, there were no differences observed in the body weight and blood serum parameters between wild-type and CS +/- mice. The cardiac expression of genes related to the utilization of fatty acids, monocarboxylates, and branched amino acids increased in LCKD-fed CS +/- mice. In contrast, no significant differences in gene expression were observed in the muscles of LCKD-fed mice or the heart and muscles of HFHCD-fed mice. ATP levels decreased only in the skeletal muscles of LCKD-fed CS +/- mice. Additionally, the decrease in glycogen content, suppression of p70 S6 kinase, and presence of type I fiber atrophy were observed in the muscles of LCKD-fed CS +/- mice. These results suggest that the energy-consuming organs with CS insufficiency may undergo tissue-specific adaption to compensate for energy shortages when the carbohydrate supply is limited.
    Keywords:  TCA cycle; citrate synthase; heart; knockout mice; skeletal muscle
  37. Cancers (Basel). 2022 Jul 15. pii: 3449. [Epub ahead of print]14(14):
      Prostate cancer (PCa) affects an estimated 250,000 men every year and causes 34,000 deaths annually. A high-fat diet and obesity are associated with PCa progression and mortality. This study's premise was the novel observation of crosstalk between PCa epithelia and cancer-associated fibroblasts (CAF) in response to palmitate-mediated lineage plasticity. We found that cholesterol activated canonical Hedgehog (Hh) signaling by increasing cilium Gli activity in PCa cells, while palmitate activated Hh independent of Gli. Exogenous palmitate activated SOX2, a known mediator of lineage plasticity, in PCa cells cocultured with CAF. Stroma-derived Wnt5a was upregulated in CAF while cocultured with PCa cells and treated with palmitate. Wnt5a knockdown in CAF inhibited Hh and SOX2 expression in PCa cells from cocultures. These findings supported our proposed mechanism of a high-fat diet promoting Hh signaling-mediated transformation within the tumor microenvironment. SOX2 and Wnt5a expression were limited by the CD36 neutralizing antibody. Mice xenografted with PCa epithelia and CAF tumors were fed a high-fat diet, leading to elevated SOX2 expression and lineage plasticity reprogramming compared to mice fed an isocaloric rodent diet. CD36 inhibition with enzalutamide elevated apoptosis by TUNEL, but limited proliferation and SOX2 expression compared to enzalutamide alone. This study revealed a mechanism for a high-fat diet to affect prostate cancer progression. We found that saturated fat induced lineage plasticity reprogramming of PCa by interaction with CAF through Wnt5a and Hh signaling.
    Keywords:  Wnt; androgen; cancer associated fibroblast; cholesterol; free fatty acid; hedgehog; prostate cancer
  38. Biomedicines. 2022 Jul 12. pii: 1675. [Epub ahead of print]10(7):
      Background: the endocannabinoid 2-arachidonoylglycerol (2-AG) plays a pivotal role in immune cells regulation. The plasma levels of 2-AG are increased in patients with systemic lupus erythematosus (SLE) and correlate with disease activity. Moreover, in plasmacytoid dendritic cells from SLE patients, 2-AG is able to control the production of type 1 interferon (IFN) through CB2 activation. The aim of this study was to evaluate the potential role of 2-AG on T lymphocytes from SLE patients. Methods: peripheral blood mononuclear cells (PBMCs) from SLE participants and age- and sex-matched healthy donors (HD) were isolated by Ficoll-Hypaque density-gradient centrifugation. The PBMCs were treated with increasing concentrations of 2-AG, and AM251 and AM630 were used to antagonize CB1 and CB2, respectively. Flow cytometry was used to assess the expression of CD3, CD4, CD8, CD25, IFN-ɣ, IL-4, and IL-17A. Results: 2-AG (1 μM) decreased IFN-ɣ expression (p = 0.0005) in the Th1 lymphocytes of SLE patients. 2-AG did not modulate the cytokine expression of any other T lymphocyte population from either SLE or HD. Treatment with both 2-AG and AM630 increased the IFN-ɣ expression in Th1 lymphocytes of SLE patients (p = 0.03). Discussion: 2-AG is able to modulate type 2 IFN production from CD4+ T lymphocytes from SLE patients through CB2 activation.
    Keywords:  2-arachidonoylglycerol; T cell; endocannabinoids; inflammation; interferon-ɣ; systemic lupus erythematosus
  39. Development. 2022 Jul 25. pii: dev.200519. [Epub ahead of print]
      Epithelial tube formation requires Rho1-dependent actomyosin contractility to generate the cellular forces that drive cell shape changes and rearrangement. Rho1 signaling is activated by G protein-coupled receptor (GPCR) signaling at the cell surface. During Drosophila embryonic salivary gland (SG) invagination, the GPCR ligand Folded gastrulation (Fog) activates Rho1 signaling to drive apical constriction. The SG receptor that transduces the Fog signal into Rho1-dependent myosin activation has not been identified. Here, we reveal that the Smog GPCR transduces Fog signal to regulate Rho kinase accumulation and myosin activation in the medioapical region of cells to control apical constriction during SG invagination. We also report on unexpected Fog-independent roles for Smog in maintaining epithelial integrity and organizing cortical actin. Our data supports a model wherein Smog regulates distinct myosin pools and actin cytoskeleton in a ligand-dependent manner during epithelial tube formation.
    Keywords:  Actomyosin; Drosophila; Fog signaling; GPCR; Salivary gland
  40. Int J Mol Sci. 2022 Jul 07. pii: 7539. [Epub ahead of print]23(14):
      Particulate matter (PM) pollutants impose a certain degree of destruction and toxicity to the skin. Mast cells in the skin dermis could be activated by PMs that diffuse across the blood vessel after being inhaled. Mast cell degranulation in the dermis provides a kind of inflammatory insult to local fibroblasts. In this study, we evaluated human dermal fibroblast responses to conditioned medium from KU812 cells primed with PM. We found that PM promoted the production of proinflammatory cytokines in mast cells and that the cell secretome induced reactive oxygen species and mitochondrial reactive oxygen species production in dermal fibroblasts. Nicotinamide mononucleotide or coenzyme Q10 alleviated the generation of excessive ROS and mitochondrial ROS induced by the conditioned medium from PM-activated KU812 cells. PM-conditioned medium treatment increased the NF-κB expression in dermal fibroblasts, whereas NMN or Q10 inhibited p65 upregulation by PM. The reduced sirtuin 1 (SIRT 1) and nuclear factor erythroid 2-related Factor 2 (Nrf2) expression induced by PM-conditioned medium was reversed by NMN or Q10 in HDFs. Moreover, NMN or Q10 attenuated the expression of senescent β-galactosidase induced by PM-conditioned KU812 cell medium. These findings suggest that NMN or Q10 ameliorates PM-induced inflammation by improving the cellular oxidative status, suppressing proinflammatory NF-κB, and promoting the levels of the antioxidant and anti-inflammatory regulators Nrf2 and SIRT1 in HDFs. The present observations help to understand the factors that affect HDFs in the dermal microenvironment and the therapeutic role of NMN and Q10 as suppressors of skin aging.
    Keywords:  NF-κB; PM; human dermal fibroblast; oxidative stress; senescence
  41. Antioxidants (Basel). 2022 Jul 14. pii: 1369. [Epub ahead of print]11(7):
      Irisin, a novel myokine, is secreted by the muscle following proteolytic cleavage of fibronectin type III domain containing 5 (FNDC5) and is considered a novel regulator of glucose homeostasis. Cystathionine γ-lyase (CSE) produces hydrogen sulfide (H2S) and is involved in glucose homeostasis. We examined the hypothesis that H2S deficiency leads to decreased FNDC5 and irisin secretion, and thereby alters glucose metabolism. High-fat diet-fed mice exhibited elevated blood glucose and significantly reduced levels of CSE, H2S, and PGC-1α, with decreased FNDC5/irisin levels and increased oxidative stress in the muscle compared with those of normal diet-fed mice (control). High glucose or palmitate decreases CSE/PGC-1α/FNDC5 levels and glucose uptake in myotubes. Inhibitors (propargylglycine and aminooxyacetate) of H2S producing enzymes or CSE siRNA significantly decreased levels of H2S and FNDC5 along with PGC-1α; similar H2S-deficient conditions also resulted in decreased GLUT4 and glucose uptake. The levels of H2S, PGC-1α, and FNDC5 and glucose uptake were significantly upregulated after treatment with l-cysteine or an H2S donor. Myoblast differentiation showed upregulation of PGC-1α and FNDC5, which was consistent with the increased expression of CSE/H2S. These findings suggest that the upregulation of H2S levels can have beneficial effects on glucose homeostasis via activation of the PGC-1α/FNDC5/irisin signaling pathway.
    Keywords:  CSE; FNDC5; GLUT4; Irisin; PGC-1α; T2DM; hydrogen sulfide; l-cysteine; muscle; obesity
  42. Nat Commun. 2022 Jul 25. 13(1): 4273
      3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) is the rate-limiting enzyme in cholesterol synthesis and target of cholesterol-lowering statin drugs. Accumulation of sterols in endoplasmic reticulum (ER) membranes accelerates degradation of HMGCR, slowing the synthesis of cholesterol. Degradation of HMGCR is inhibited by its binding to UBIAD1 (UbiA prenyltransferase domain-containing protein-1). This inhibition contributes to statin-induced accumulation of HMGCR, which limits their cholesterol-lowering effects. Here, we report cryo-electron microscopy structures of the HMGCR-UBIAD1 complex, which is maintained by interactions between transmembrane helix (TM) 7 of HMGCR and TMs 2-4 of UBIAD1. Disrupting this interface by mutagenesis prevents complex formation, enhancing HMGCR degradation. TMs 2-6 of HMGCR contain a 170-amino acid sterol sensing domain (SSD), which exists in two conformations-one of which is essential for degradation. Thus, our data supports a model that rearrangement of the TMs in the SSD permits recruitment of proteins that initate HMGCR degradation, a key reaction in the regulatory system that governs cholesterol synthesis.
  43. Prog Lipid Res. 2022 Jul 25. pii: S0163-7827(22)00037-6. [Epub ahead of print] 101182
      The inflammatory response is a complex regulated effector mechanism of the innate immune system that is initiated after tissue injury or infection. The NLRP3 inflammasome is an important initiator of inflammation by regulating the activation of caspase-1, the maturation of pro-inflammatory cytokines and the induction of pyroptotic cell death. Numerous studies demonstrate that the NLRP3 inflammasome could be modulated by lipids, existing a relation between lipids and the activation of different inflammatory processes. In this review we will summarize how the mechanism of NLRP3 inflammasome activation is regulated by different lipids and how these lipids control specific cellular localization of NLRP3 during activation. Although being a cytosolic protein, NLRP3 interacts with lipids accessible in neighbor membranes. Also, the modulation of NLRP3 by endogenous lipids has been found causative of different metabolic diseases and bacterial-pathogenic lipids lead to NLRP3 activation during infection. The understanding of the modulation of the NLRP3 inflammasome by lipids has resulted not only in a better knowledge about the mechanism of NLRP3 activation and its implication in disease, but also opens a new avenue for the development of novel therapeutics and vaccines, as NLRP3 could be modulated by synthetic lipids used as adjuvants.
    Keywords:  25-hydroxycholesterol; Cardiolipin; Caspase; Ceramide; Cholesterol; Inflammasome; Inflammation; Interleukin-1; Linoleic acid; Lipophosphoglycan; Lipopolysaccharide; Non-canonical inflammasome; Oleic acid; Ornithine lipid; Phosphatidylcholine; Phosphatidylinositol-4-phosphate; Polyunsaturated fatty acid; Pyroptosis; Saturated fatty acid; Sphingosine