Beyond energy storage: roles of glycogen metabolism in health and disease

Reyanning mixture inhibits M1 macrophage polarization through the glycogen synthesis pathway to improve lipopolysaccharide-induced acute lung injury

ETHNOPHARMACOLOGICAL RELEVANCE

Reyanning (RYN) mixture is a traditional Chinese medicine composed of Taraxacum, Polygonum cuspidatum, Scutellariae Barbatae and Patrinia villosa and is used for the treatment of acute respiratory system diseases with significant clinical efficacy.

AIM OF THE STUDY

Acute lung injury (ALI) is a common clinical disease characterized by acute respiratory failure. This study was conducted to evaluate the therapeutic effects of RYN on ALI and to explore its mechanism of action.

MATERIALS AND METHODS

Ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to analyze the chemical components of RYN. 7.5 mg/kg LPS was administered to induce ALI in rats. RYN was administered by gavage at doses of 2 ml/kg, 4 ml/kg or 8 ml/kg every 8 h for a total of 6 doses. Observations included lung histomorphology, lung wet/dry (W/D) weight ratio, lung permeability index (LPI), HE staining, Wright-Giemsa staining. ELISA was performed to detect the levels of TNF-α, IL-6, IL-10, Arg-1,UDPG. Immunohistochemical staining detected IL-6, F4/80 expression. ROS, MDA, SOD, GSH/GSSG were detected in liver tissues. Multiple omics techniques were used to predict the potential mechanism of action of RYN, which was verified by in vivo closure experiments. Immunofluorescence staining detected the co-expression of CD86 and CD206, CD86 and P2Y14, CD86 and UGP2 in liver tissues. qRT-PCR detected the mRNA levels of UGP2, P2Y14 and STAT1, and immunoblotting detected the protein expression of UGP2, P2Y14, STAT1, p-STAT1.

RESULTS

RYN was detected to contain 1366 metabolites, some of the metabolites with high levels have anti-inflammatory, antibacterial, antiviral and antioxidant properties. RYN (2, 4, and 8 ml/kg) exerted dose-dependent therapeutic effects on the ALI rats, by reducing inflammatory cell infiltration and oxidative stress damage, inhibiting CD86 expression, decreasing TNF-α and IL-6 levels, and increasing IL-10 and Arg-1 levels. Transcriptomics and proteomics showed that glucose metabolism provided the pathway for the anti-ALI properties of RYN and that RYN inhibited lung glycogen production and distribution. Immunofluorescence co-staining showed that RYN inhibited CD86 and UGP2 expressions. In vivo blocking experiments revealed that blocking glycogen synthesis reduced UDPG content, inhibited P2Y14 and CD86 expressions, decreased P2Y14 and STAT1 mRNA and protein expressions, reduced STAT1 protein phosphorylation expression, and had the same therapeutic effect as RYN.

CONCLUSION

RYN inhibits M1 macrophage polarization to alleviate ALI. Blocking glycogen synthesis and inhibiting the UDPG/P2Y14/STAT1 signaling pathway may be its molecular mechanism.

EDI3 knockdown in ER-HER2+ breast cancer cells reduces tumor burden and improves survival in two mouse models of experimental metastasis

BACKGROUND

Despite progress understanding the mechanisms underlying tumor spread, metastasis remains a clinical challenge. We identified the choline-producing glycerophosphodiesterase, EDI3 and reported its association with metastasis-free survival in endometrial cancer. We also observed that silencing EDI3 slowed cell migration and other cancer-relevant phenotypes in vitro. Recent work demonstrated high EDI3 expression in ER-HER2+ breast cancer compared to the other molecular subtypes. Silencing EDI3 in ER-HER2+ cells significantly reduced cell survival in vitro and decreased tumor growth in vivo. However, a role for EDI3 in tumor metastasis in this breast cancer subtype was not explored. Therefore, in the present work we investigate whether silencing EDI3 in ER-HER2+ breast cancer cell lines alters phenotypes linked to metastasis in vitro, and metastasis formation in vivo using mouse models of experimental metastasis.

METHODS

To inducibly silence EDI3, luciferase-expressing HCC1954 cells were transduced with lentiviral particles containing shRNA oligos targeting EDI3 under the control of doxycycline. The effect on cell migration, adhesion, colony formation and anoikis was determined in vitro, and significant findings were confirmed in a second ER-HER2+ cell line, SUM190PT. Doxycycline-induced HCC1954-luc shEDI3 cells were injected into the tail vein or peritoneum of immunodeficient mice to generate lung and peritoneal metastases, respectively and monitored using non-invasive bioluminescence imaging. Metabolite levels in cells and tumor tissue were analyzed using targeted mass spectrometry and MALDI mass spectrometry imaging (MALDI-MSI), respectively.

RESULTS

Inducibly silencing EDI3 reduced cell adhesion and colony formation, as well as increased susceptibility to anoikis in HCC1954-luc cells, which was confirmed in SUM190PT cells. No influence on cell migration was observed. Reduced luminescence was seen in lungs and peritoneum of mice injected with cells expressing less EDI3 after tail vein and intraperitoneal injection, respectively, indicative of reduced metastasis. Importantly, mice injected with EDI3-silenced cells survived longer. Closer analysis of the peritoneal organs revealed that silencing EDI3 had no effect on metastatic organotropism but instead reduced metastatic burden. Finally, metabolic analyses revealed significant changes in choline and glycerophospholipid metabolites in cells and in pancreatic metastases in vivo.

CONCLUSIONS

Reduced metastasis upon silencing supports EDI3's potential as a treatment target in metastasizing ER-HER2+ breast cancer.

Nanozyme as a rising star for metabolic disease management

Nanozyme, characterized by outstanding and inherent enzyme-mimicking properties, have emerged as highly promising alternatives to natural enzymes owning to their exceptional attributes such as regulation of oxidative stress, convenient storage, adjustable catalytic activities, remarkable stability, and effortless scalability for large-scale production. Given the potent regulatory function of nanozymes on oxidative stress and coupled with the fact that reactive oxygen species (ROS) play a vital role in the occurrence and exacerbation of metabolic diseases, nanozyme offer a unique perspective for therapy through multifunctional activities, achieving essential results in the treatment of metabolic diseases by directly scavenging excess ROS or regulating pathologically related molecules. The rational design strategies, nanozyme-enabled therapeutic mechanisms at the cellular level, and the therapies of nanozyme for several typical metabolic diseases and underlying mechanisms are discussed, mainly including obesity, diabetes, cardiovascular disease, diabetic wound healing, and others. Finally, the pharmacokinetics, safety analysis, challenges, and outlooks for the application of nanozyme are also presented. This review will provide some instructive perspectives on nanozyme and promote the development of enzyme-mimicking strategies in metabolic disease therapy.

HBV DNA polymerase regulates tumor cell glycogen to enhance the malignancy of HCC cells

BACKGROUND

The essential function of HBV DNA polymerase (HBV-DNA-Pol) is to initiate viral replication by reverse transcription; however, the role of HBV-DNA-Pol in HBV-associated HCC has not been clarified. Glycogen phosphorylase L (PYGL) is a critical regulator of glycogenolysis and is involved in tumorigenesis, including HCC. However, it is unknown whether HBV-DNA-Pol regulates PYGL to contribute to HCC tumorigenesis.

METHODS

Bioinformatic analysis, real-time quantitative PCR, western blotting, and oncology functional assays were performed to determine the contribution of HBV-DNA-Pol and PYGL to HCC development and glycolysis. The mechanisms of co-immunoprecipitation and ubiquitination were employed to ascertain how HBV-DNA-Pol upregulated PYGL.

RESULTS

Overexpression of HBV-DNA-Pol enhanced HCC progression in vitro and in vivo. Mechanistically, HBV-DNA-Pol interacted with PYGL and increased PYGL protein levels by inhibiting PYGL ubiquitination, which was mediated by the E3 ligase TRIM21. HBV-DNA-Pol competitively impaired the binding of PYGL to TRIM21 due to its stronger binding affinity to TRIM21, suppressing the ubiquitination of PYGL. Moreover, HBV-DNA-Pol promoted glycogen decomposition by upregulating PYGL, which led to an increased flow of glucose into glycolysis, thereby promoting HCC development.

CONCLUSIONS

Our study reveals a novel mechanism by which HBV-DNA-Pol promotes HCC by controlling glycogen metabolism in HCC, establishing a direct link between HBV-DNA-Pol and the Warburg effect, thereby providing novel targets for HCC treatment and drug development.

Hyperglycemia - A culprit of podocyte pathology in the context of glycogen metabolism

Prolonged disruption in the balance of glucose can result in metabolic disorders. The kidneys play a significant role in regulating blood glucose levels. However, when exposed to chronic hyperglycemia, the kidneys' ability to handle glucose metabolism may be impaired, leading to an accumulation of glycogen. Earlier studies have shown that there can be a significant increase in glucose storage in the form of glycogen in the kidneys in diabetes. Podocytes play a crucial role in maintaining the integrity of filtration barrier. In diabetes, exposure to elevated glucose levels can lead to significant metabolic and structural changes in podocytes, contributing to kidney damage and the development of diabetic kidney disease. The accumulation of glycogen in podocytes is not a well-established phenomenon. However, a recent study has demonstrated the presence of glycogen granules in podocytes. This review delves into the intricate connections between hyperglycemia and glycogen metabolism within the context of the kidney, with special emphasis on podocytes. The aberrant storage of glycogen has the potential to detrimentally impact podocyte functionality and perturb their structural integrity. This review provides a comprehensive analysis of the alterations in cellular signaling pathways that may potentially lead to glycogen overproduction in podocytes.

Kinetic 18F-FDG PET/CT imaging of hepatocellular carcinoma: a dual input four-compartment model

BACKGROUND

The endoplasmic reticulum plays an important role in glucose metabolism and has not been explored in the kinetic estimation of hepatocellular carcinoma (HCC) via 18F-fluoro-2-deoxy-D-glucose PET/CT.

METHODS

A dual-input four-compartment (4C) model, regarding endoplasmic reticulum was preliminarily used for kinetic estimation to differentiate 28 tumours from background liver tissue from 24 patients with HCC. Moreover, parameter images of the 4C model were generated from one patient with negative findings on conventional metabolic PET/CT.

RESULTS

Compared to the dual-input three-compartment (3C) model, the 4C model has better fitting quality, a close transport rate constant (K1) and a dephosphorylation rate constant (k6/k4), and a different removal rate constant (k2) and phosphorylation rate constant (k3) in HCC and background liver tissue. The K1, k2, k3, and hepatic arterial perfusion index (HPI) from the 4C model and k3, HPI, and volume fraction of blood (Vb) from the 3C model were significantly different between HCC and background liver tissues (all P < 0.05). Meanwhile, the 4C model yielded additional kinetic parameters for differentiating HCC. The diagnostic performance of the top ten genes from the most to least common was HPI(4C), Vb(3C), HPI(3C), SUVmax, k5(4C), k3(3C), k2(4C), v(4C), K1(4C) and Vb(4C). Moreover, a patient who showed negative findings on conventional metabolic PET/CT had positive parameter images in the 4C model.

CONCLUSIONS

The 4C model with the endoplasmic reticulum performed better than the 3C model and produced additional useful parameters in kinetic estimation for differentiating HCC from background liver tissue.

Hepatic glycogenesis antagonizes lipogenesis by blocking S1P via UDPG

The identification of mechanisms to store glucose carbon in the form of glycogen rather than fat in hepatocytes has important implications for the prevention of nonalcoholic fatty liver disease (NAFLD) and other chronic metabolic diseases. In this work, we show that glycogenesis uses its intermediate metabolite uridine diphosphate glucose (UDPG) to antagonize lipogenesis, thus steering both mouse and human hepatocytes toward storing glucose carbon as glycogen. The underlying mechanism involves transport of UDPG to the Golgi apparatus, where it binds to site-1 protease (S1P) and inhibits S1P-mediated cleavage of sterol regulatory element-binding proteins (SREBPs), thereby inhibiting lipogenesis in hepatocytes. Consistent with this mechanism, UDPG administration is effective at treating NAFLD in a mouse model and human organoids. These findings indicate a potential opportunity to ameliorate disordered fat metabolism in the liver.

Aryl hydrocarbon receptor sulfenylation promotes glycogenolysis and rescues cancer chemoresistance

Elevation of reactive oxygen species (ROS) levels is a general consequence of tumor cells' response to treatment and may cause tumor cell death. Mechanisms by which tumor cells clear fatal ROS, thereby rescuing redox balance and entering a chemoresistant state, remain unclear. Here, we show that cysteine sulfenylation by ROS confers on aryl hydrocarbon receptor (AHR) the ability to dissociate from the heat shock protein 90 complex but to bind to the PPP1R3 family member PPP1R3C of the glycogen complex in drug-treated tumor cells, thus activating glycogen phosphorylase to initiate glycogenolysis and the subsequent pentose phosphate pathway, leading to NADPH production for ROS clearance and chemoresistance formation. We found that basic ROS levels were higher in chemoresistant cells than in chemosensitive cells, guaranteeing the rapid induction of AHR sulfenylation for the clearance of excess ROS. These findings reveal that AHR can act as an ROS sensor to mediate chemoresistance, thus providing a potential strategy to reverse chemoresistance in patients with cancer.

The placental vasculature is affected by changes in gene expression and glycogen-rich cells in a diet-induced obesity mouse model

Maternal obesity is a risk factor for pregnancy complications. Obesity caused by a high-fat diet (HFD) may alter maternal glucose/glycogen metabolism. Here, our objective was to investigate whether the placental vasculature is altered via changes in gene expression and glycogen-rich cells using a preclinical mouse model of diet-induced obesity. We subjected female FVB/N mice to one of three feeding regimens: regular chow (RC) given at preconception and during pregnancy (Control); RC given at preconception and then a HFD during pregnancy (HFD-P); or HFD initiated 4 weeks preconception and during pregnancy (HFD-PreCP). Daily food consumption and weekly maternal weights were recorded. Maternal blood glucose levels were measured at preconception and 4 gestational epochs (E6.5-E9.5, E10.5-E12.5, E13.5-E15.5, E16.5-E19.5). At E8.5-E16.5, total RNA in placentas were isolated for gene expression analyses. Placentas were also collected for HE and periodic acid Schiff's (PAS) staining and glycogen content assays. Dams in the HFD-P and HFD-PreCP groups gained significantly more weight than controls. Pre- and antenatal glucose levels were also significantly higher (15%-30%) in HFD-PreCP dams. Expression of several placental genes were also altered in HFD dams compared with controls. Consumption of the HFD also led to phenotypic and morphologic changes in glycogen trophoblasts (GlyTs) and uterine natural killer (uNK) cells. Alterations in vascularity were also observed in the labyrinth of HFD-PreCP placentas, which correlated with decreased placental efficiency. Overall, we observed that a HFD induces gestational obesity in mice, alters expression of placental genes, affects glucose homeostasis, and alters glycogen-positive GlyTs and uNK cells. All these changes may lead to impaired placental vascular development, and thus heighten the risk for pregnancy complications.

Dose-dependent stress response of esfenvalerate insecticide on common carp (Cyprinus carpio): Evaluating blood parameters and gene expression

Esfenvalerate is a pyrethroid insecticide used primarily in the agriculture sector for insect management. Esfenvalerate is effective against a wide range of harmful insects, including flies, cockroaches, locusts, and many other types of bugs. It is also known that esfenvalerate has toxic effects on aquatic organisms and poses significant environmental concerns. In this study, the aim is to subchronically examine the effects of sublethal concentrations of esfenvalerate insecticide on common carp (Cyprinus carpio) by assessing changes in blood parameters and resulting gene expression. For this purpose, common carp (Cyprinus carpio) were divided into 5 groups and exposed to 0.025, 0.05, 0.1, and 0.15 μg/L concentrations of esfenvalerate for a period of 14 days. Blood and liver tissue samples were collected from the fish that underwent weight and length measurements. The effects on gene expression levels of immune, antioxidant, and stress-related genes in the liver tissue, including SOD, GST, Cortisol receptor, HSP70, H+-ATPase, Na+/K+-ATPase, Catalase, and GpX, were evaluated, as were the hematological and serum biochemical parameters. Significant decreases were observed in the levels of hematocrit, hemoglobin, erythrocytes, triglycerides and total protein and catalase, H+-ATPase, and GpX gene expression. Glucose, cholesterol, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase (LDH) and alkaline phosphatase (ALP), SOD, Cortisol receptor, Na+/K+-ATPase gene expression levels increased. As a result, it has been revealed that esfenvalerate insecticide causes oxidative stress in carp at all dose ranges.

Spatial metabolomics reveals glycogen as an actionable target for pulmonary fibrosis

Matrix assisted laser desorption/ionization imaging has greatly improved our understanding of spatial biology, however a robust bioinformatic pipeline for data analysis is lacking. Here, we demonstrate the application of high-dimensionality reduction/spatial clustering and histopathological annotation of matrix assisted laser desorption/ionization imaging datasets to assess tissue metabolic heterogeneity in human lung diseases. Using metabolic features identified from this pipeline, we hypothesize that metabolic channeling between glycogen and N-linked glycans is a critical metabolic process favoring pulmonary fibrosis progression. To test our hypothesis, we induced pulmonary fibrosis in two different mouse models with lysosomal glycogen utilization deficiency. Both mouse models displayed blunted N-linked glycan levels and nearly 90% reduction in endpoint fibrosis when compared to WT animals. Collectively, we provide conclusive evidence that lysosomal utilization of glycogen is required for pulmonary fibrosis progression. In summary, our study provides a roadmap to leverage spatial metabolomics to understand foundational biology in pulmonary diseases.

Abnormalities of glucose and lipid metabolism in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury is a common condition in cardiovascular diseases, and the mechanism of its occurrence involves multiple complex metabolic pathways and signaling pathways. Among these pathways, glucose metabolism and lipid metabolism play important roles in regulating myocardial energy metabolism. Therefore, this article focuses on the roles of glucose metabolism and lipid metabolism in myocardial ischemia-reperfusion injury, including glycolysis, glucose uptake and transport, glycogen metabolism and the pentose phosphate pathway; and triglyceride metabolism, fatty acid uptake and transport, phospholipid metabolism, lipoprotein metabolism, and cholesterol metabolism. Finally, due to the different alterations and development of glucose metabolism and lipid metabolism in myocardial ischemia-reperfusion, there are also complex interregulatory relationships between them. In the future, modulating the equilibrium between glucose metabolism and lipid metabolism in cardiomyocytes and ameliorating aberrations in myocardial energy metabolism represent highly promising novel strategies for addressing myocardial ischemia-reperfusion injury. Therefore, a comprehensive exploration of glycolipid metabolism can offer novel theoretical and clinical insights into the prevention and treatment of myocardial ischemia-reperfusion injury.

The role of metabolic reprogramming of tumor-associated macrophages in shaping the immunosuppressive tumor microenvironment

Macrophages are potent immune effector cells in innate immunity and exert dual-effects in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) make up a significant portion of TME immune cells. Similar to M1/M2 macrophages, TAMs are also highly plastic, and their functions are regulated by cytokines, chemokines and other factors in the TME. The metabolic changes in TAMs are significantly associated with polarization towards a protumour or antitumour phenotype. The metabolites generated via TAM metabolic reprogramming in turn promote tumor progression and immune tolerance. In this review, we explore the metabolic reprogramming of TAMs in terms of energy, amino acid and fatty acid metabolism and the potential roles of these changes in immune suppression.

Hepatic Leucine Carboxyl Methyltransferase 1 (LCMT1) contributes to high fat diet-induced glucose intolerance through regulation of glycogen metabolism

Impaired glucose regulation is one of the most important risk factors for type 2 diabetes mellitus (T2DM) and cardiovascular diseases, which have become a major public health issue worldwide. Dysregulation of carbohydrate metabolism in liver has been shown to play a critical role in the development of glucose intolerance but the molecular mechanism has not yet been fully understood. In this study, we investigated the role of hepatic LCMT1 in the regulation of glucose homeostasis using a liver-specific LCMT1 knockout mouse model. The hepatocyte-specific deletion of LCMT1 significantly upregulated the hepatic glycogen synthesis and glycogen accumulation in liver. We found that the liver-specific knockout of LCMT1 improved high fat diet-induced glucose intolerance and insulin resistance. Consistently, the high fat diet-induced downregulation of glucokinase (GCK) and other important glycogen synthesis genes were reversed in LCMT1 knockout liver. In addition, the expression of GCK was significantly upregulated in MIHA cells treated with siRNA targeting LCMT1 and improved glycogen synthesis. In this study, we provided evidences to support the role of hepatic LCMT1 in the development of glucose intolerance induced by high fat diet and demonstrated that inhibiting LCMT1 could be a novel therapeutic strategy for the treatment of glucose metabolism disorders.

Effect of gluten on the digestive tract and fat body of Telodeinopus aoutii (Diplopoda)

Adult specimens or larvae of invertebrates used as food for vertebrates are often maintained close to gluten so they might become vectors for cereal proteins. However, the tissues and internal organs can respond differently in animals with different feeding habits. The midgut epithelium might be a first and sufficient barrier preventing uptake and effects of gluten on the whole body, while the fat body is the main organ that accumulates different xenobiotics. Good models for such research are animals that do not feed on gluten-rich products in their natural environment. The project's goal was to investigate alterations in the midgut epithelium and fat body of the herbivorous millipede Telodeinopus aoutii (Diplopoda) and analyze cell death processes activated by gluten. It enabled us to determine whether changes were intensified or reversed by adaptive mechanisms. Adult specimens were divided into control and experimental animals fed with mushrooms supplemented with gluten and analyzed using transmission electron microscopy, flow cytometry, and confocal microscopy. Two organs were isolated for the qualitative and quantitative analysis: the midgut and the fat body. Our study of the herbivorous T. aoutii which does not naturally feed on gluten containing diet showed that continuous and prolonged gluten feeding activates repair processes that inhibit the processes of cell death (apoptosis and necrosis) and induce an increase in cell viability.

Reprogramming T-Cell Metabolism for Better Anti-Tumor Immunity

T cells play central roles in the anti-tumor immunity, whose activation and differentiation are profoundly regulated by intrinsic metabolic reprogramming. Emerging evidence has revealed that metabolic processes of T cells are generally altered by tumor cells or tumor released factors, leading to crippled anti-tumor immunity. Therefore, better understanding of T cell metabolic mechanism is crucial in developing the next generation of T cell-based anti-tumor immunotherapeutics. In this review, we discuss how metabolic pathways affect T cells to exert their anti-tumor effects and how to remodel the metabolic programs to improve T cell-mediated anti-tumor immune responses. We emphasize that glycolysis, carboxylic acid cycle, fatty acid oxidation, cholesterol metabolism, amino acid metabolism, and nucleotide metabolism work together to tune tumor-reactive T-cell activation and proliferation.

mTOR Participates in the Formation, Maintenance, and Function of Memory CD8+T Cells Regulated by Glycometabolism

Memory CD8⁺T cells participate in the fight against infection and tumorigenesis as well as in autoimmune disease progression because of their efficient and rapid immune response, long-term survival, and continuous differentiation. At each stage of their formation, maintenance, and function, the cell metabolism must be adjusted to match the functional requirements of the specific stage. Notably, enhanced glycolytic metabolism can generate sufficient levels of adenosine triphosphate (ATP) to form memory CD8⁺T cells, countering the view that glycolysis prevents the formation of memory CD8⁺T cells. This review focuses on how glycometabolism regulates memory CD8+T cells and highlights the key mechanisms through which the mammalian target of rapamycin (mTOR) signaling pathway affects memory CD8+T cell formation, maintenance, and function by regulating glycometabolism. In addition, different subpopulations of memory CD8⁺T cells exhibit different metabolic flexibility during their formation, survival, and functional stages, during which the energy metabolism may be critical. These findings which may explain why enhanced glycolytic metabolism can give rise to memory CD8⁺T cells. Modulating the metabolism of memory CD8⁺T cells to influence specific cell fates may be useful for disease treatment.

TCR activation directly stimulates PYGB-dependent glycogenolysis to fuel the early recall response in CD8+ memory T cells

Glycolysis facilitates the rapid recall response of CD8⁺ memory T (Tm) cells. However, it remains unclear whether Tm cells uptake exogenous glucose or mobilize endogenous sugar to fuel glycolysis. Here, we show that intracellular glycogen rather than extracellular glucose acts as the major carbon source for the early recall response. Following antigenic stimulation, Tm cells exhibit high glycogen phosphorylase (brain form, PYGB) activity, leading to glycogenolysis and release of glucose-6-phosphate (G6P). Elevated G6P mainly flows to glycolysis but is also partially channeled to the pentose phosphate pathway, which maintains the antioxidant capacity necessary for later recall stages. Mechanistically, TCR signaling directly induces phosphorylation of PYGB by LCK-ZAP70. Functionally, the glycogenolysis-fueled early recall response of CD8⁺ Tm cells accelerates the clearance of OVA-Listeria monocytogenes in an infected mouse model. Thus, we uncover a specific dependency on glycogen for the initial activation of memory T cells, which may have therapeutic implications for adaptive immunity.

Characterization of a novel type of glycogen-degrading amylopullulanase from Lactobacillus crispatus

Glycogen is one of the major carbohydrates utilized by the human vaginal microbiota, which is commonly dominated by Lactobacillus, especially L. crispatus. An in silico analysis predicted that a type I pullulanase was involved in glycogen degradation in L. crispatus. The biochemical and genetic properties of the pullulanase still need to be determined. Here, we de novo identified the glycogen (Glg)-utilization enzyme (named GlgU) from L. crispatus through a biochemical assay. GlgU was optimally active at acidic pH, approximately 4.0 ~ 4.5, and was able to hydrolyze glycogen into low-molecular-weight malto-oligosaccharides. Actually, GlgU was a type II pullulanase (amylopullulanase) with just one catalytic domain that possessed substrate specificity toward both α-1,4 and α-1,6-glucosidic bonds. Phylogenetically, GlgU was obviously divergent from the known amylases and pullulanases (including amylopullulanases) in lactobacilli. In addition, we confirmed the catalytic activity of glgU in a nonglycogen-utilizing lactobacilli strain, demonstrating the essential role of glgU in glycogen metabolism. Overall, this study characterized a novel type of amylopullulanases, contributing to the knowledge of the glycogen utilization mechanism of the dominant species of human vaginal microbiota. KEY POINTS: • GlgU was a type II pullulanase, not a type I pullulanase predicted before. • GlgU was able to completely hydrolyze glycogen into malto-oligosaccharides. • GlgU played a key role in the metabolism of extracellular glycogen.

Astrocytic glycogen mobilization participates in salvianolic acid B-mediated neuroprotection against reperfusion injury after ischemic stroke

Astrocytic glycogen serves as an important glucose reserve, and its degradation provides extra support for neighboring neurons during energy deficiency. Salvianolic acid B (SAB) exerts a neuroprotective effect on reperfusion insult after cerebrovascular occlusion, but the effect of SAB on astrocytic glycogen and its relationship with neuroprotection are not completely understood. Here, we knocked down astrocyte-specific glycogen phosphorylase (GP, the rate-limiting enzyme in glycogenolysis) in vitro and in vivo and investigated the changes in key enzymes in glycogen metabolism by performing immunoblotting in vitro and immunofluorescence in vivo. Neurobehavioral and morphological assessments were conducted to uncover the outcomes during brain reperfusion. SAB accelerated astrocytic glycogenolysis by upregulating GP activity but not GP expression after reperfusion. Suppression of astrocytic glycogenolysis weakened SAB-mediated neuroprotection against the reperfusion insult. In addition, activation of glycogenolysis by SAB contributed to the survival of astrocytes and surrounding neurons by increasing antioxidant levels in astrocytes. Our data reveal that astrocytic GP represents an important metabolic target in SAB-induced protection against brain damage after cerebrovascular recanalization.

A Novel Microcrystalline BAY-876 Formulation Achieves Long-Acting Antitumor Activity Against Aerobic Glycolysis and Proliferation of Hepatocellular Carcinoma

BAY-876 is an effective antagonist of the Glucose transporter type 1 (GLUT1) receptor, a mediator of aerobic glycolysis, a biological process considered a hallmark of hepatocellular carcinoma (HCC) together with cell proliferation, drug-resistance, and metastasis. However, the clinical application of BAY-876 has faced many challenges. In the presence study, we describe the formulation of a novel microcrystalline BAY-876 formulation. A series of HCC tumor models were established to determine not only the sustained release of microcrystalline BAY-876, but also its long-acting antitumor activity. The clinical role of BAY-876 was confirmed by the increased expression of GLUT1, which was associated with the worse prognosis among advanced HCC patients. A single dose of injection of microcrystalline BAY-876 directly in the HCC tissue achieved sustained localized levels of Bay-876. Moreover, the single injection of microcrystalline BAY-876 in HCC tissues not only inhibited glucose uptake and prolonged proliferation of HCC cells, but also inhibited the expression of epithelial-mesenchymal transition (EMT)-related factors. Thus, the microcrystalline BAY-876 described in this study can directly achieve promising localized effects, given its limited diffusion to other tissues, thereby reducing the occurrence of potential side effects, and providing an additional option for advanced HCC treatment.

Hypoxia promotes breast cancer cell growth by activating a glycogen metabolic program

Hypoxia is known to be commonly present in breast tumor microenvironments. Stem-like cells that repopulate breast tumors, termed tumor-repopulating cells (TRC), thrive under hypoxic conditions, but the underlying mechanism remains unclear. Here we show that hypoxia promotes the growth of breast TRCs through metabolic reprogramming. Hypoxia mobilized transcription factors HIF-1α and FoxO1 and induced epigenetic reprogramming to upregulate cytosolic phosphoenolpyruvate carboxykinase (PCK1), a key enzyme that initiates gluconeogenesis. PCK1 subsequently triggered retrograde carbon flow from gluconeogenesis to glycogenesis, glycogenolysis, and the pentose phosphate pathway. The resultant NADPH facilitated reduced glutathione production, leading to a moderate increase of reactive oxygen species that stimulated hypoxic breast TRC growth. Notably, this metabolic mechanism was absent in differentiated breast tumor cells. Targeting PCK1 synergized with paclitaxel to reduce the growth of triple-negative breast cancer (TNBC). These findings uncover an altered glycogen metabolic program in breast cancer, providing potential metabolic strategies to target hypoxic breast TRCs and TNBC.

From Prokaryotes to Eukaryotes: Insights Into the Molecular Structure of Glycogen Particles

Glycogen is a highly-branched polysaccharide that is widely distributed across the three life domains. It has versatile functions in physiological activities such as energy reserve, osmotic regulation, blood glucose homeostasis, and pH maintenance. Recent research also confirms that glycogen plays important roles in longevity and cognition. Intrinsically, glycogen function is determined by its structure that has been intensively studied for many years. The recent association of glycogen α-particle fragility with diabetic conditions further strengthens the importance of glycogen structure in its function. By using improved glycogen extraction procedures and a series of advanced analytical techniques, the fine molecular structure of glycogen particles in human beings and several model organisms such as Escherichia coli, Caenorhabditis elegans, Mus musculus, and Rat rattus have been characterized. However, there are still many unknowns about the assembly mechanisms of glycogen particles, the dynamic changes of glycogen structures, and the composition of glycogen associated proteins (glycogen proteome). In this review, we explored the recent progresses in glycogen studies with a focus on the structure of glycogen particles, which may not only provide insights into glycogen functions, but also facilitate the discovery of novel drug targets for the treatment of diabetes mellitus.

Reprogramming of Central Carbon Metabolism in Myeloid Cells upon Innate Immune Receptor Stimulation

Immunometabolism is a relatively new field of research that aims at understanding interconnections between the immune system and cellular metabolism. This is now well-documented for innate immune cells of the myeloid lineage such as macrophages and myeloid dendritic cells (DCs) when they engage their differentiation or activation programs. Several studies have shown that stimulation of DCs or macrophages by the binding of pathogen-associated molecular patterns (PAMPs) to pattern recognition receptors (PRRs) leads to increased glycolytic activity and rewiring of central carbon metabolism. These metabolic modulations are essential to support and settle immunological functions by providing energy and immunoregulatory metabolites. As the understanding of molecular mechanisms progressed, significant differences between cell types and species have also been discovered. Pathways leading to the regulation of central carbon metabolism in macrophages and DCs by PRR signaling and consequences on cellular functions are reviewed here.