Glycogen Metabolism Research Articles

Gys1 regulates maternal glycogen reserve essential for embryonic development in zebrafish

The reserve of glycogen is essential for embryonic development. In oviparous fish, egg is an isolated system after egg laying with all the required energy deposits by their mothers. However, the key regulated factor mediates the storage of maternal glycogen reserve which support for embryogenesis in the offspring is largely unknown. Glycogen synthase (GYS) is a central enzyme for glycogen synthesis. In our previous study, we generated a gys1 knockout zebrafish line, showed an embryonic developmental defect in F3 generation. In this study, firstly we determined that the gys1 was maternal origin by backcrossing the F2 mutant with wildtype lines. PAS staining and glycogen content measurement showed that glycogen reserve was reduced both in ovaries and embryos in the mutant group compared to wildtypes. Free glucose measurement analysis showed a 50 % of reduction in gys1 mutant embryos compared to wildtype embryos at 24 hpf; showed an approximal 50 % of reduction in gys1 mutant adults compared to wildtypes. Microinjection of 2-NBDG in embryos and comparison of fluorescent signal demonstrated that glucose uptake ability was decreased in the mutant embryos, indicating an impaired glucose metabolism. Untargeted metabolomics analysis then was employed and revealed that key modified metabolites enriched into vitamin B pathway, carbohydrate and unsaturated fatty acid pathways. These results demonstrated that gys1 played a role on glycogen metabolism, involved into the maternal glycogen reserve which essentially contribute to embryonic development.

O-Mannosyltransferase CfPmt4 Regulates the Growth, Development and Pathogenicity of Colletotrichum fructicola.

Camellia oleifera is a woody, edible-oil plant native to China. Anthracnose is the major disease of Ca. oleifera, and Colletotrichum fructicola is the main epidemic pathogen. Our previous research indicated that CfHac1 (homologous to ATF/CREB1) and CfGcn5 (general control nonderepressible 5, Gcn5) are integral to key cellular processes that govern fungal development and pathogenesis. Further transcriptomic analyses of the CfHac1 and CfGcn5 mutants, particularly under conditions of endoplasmic reticulum (ER) stress, hold the potential to unveil additional genes implicated in this critical cellular response. We identified all OST/PMT (oligosaccharyltransferase/Protein O-Mannosyltransferases) genes in C. fructicola and analyzed their expression levels. To elucidate novel glycosylation-related genes that may be important for the virulence of C. fructicola, we took an unbiased transcriptomic approach comparing wild-type and the ∆Cfhac1 mutant. Notably, all OST/PMT genes were induced by dithiothreitol and down-regulated in the ΔCfhac1 mutant, yet only the CfPMT4 (Protein O-Mannosyltransferases 4) gene (A04626) was unaffected in the ΔCfgcn5. The results of targeted gene deletion experiments indicate that CfPMT4 plays a crucial role in both vegetative growth and conidiation. Additionally, our investigation revealed that the ΔCfpmt4 exhibits deficiencies in appressorium formation, as well as in its response to cell wall integrity and endoplasmic reticulum stresses. Furthermore, the mutant displayed impaired glycogen metabolism, which may contribute to reduced penetration ability. Overall, CfPmt4, an O-mannosyltransferase, controls the growth, development, and pathogenicity of Colletotrichum fructicola. Understanding the function of the CfPMT4 homolog could provide a potential molecular target for controlling Ca. oleifera anthracnose.

Cellular Mechanisms for pH Regulation and Energy Metabolism in Sharks and Rays

Similar to mammalian kidney distal tubule cells, specialized shark and ray gill epithelial cells maintain blood pH homeostasis. These shark and ray gill cells are either enriched with the Na+/K+-ATPase (NKA) and responsible for acid secretion or enriched for the vacuolar H+-ATPase (VHA) and responsible for base secretion. Moreover, both cell types contain abundant mitochondria and glycogen, and glycogen content decreases in active acid-base regulatory cells in vivo. Additional experiments with isolated gill cells in vitro show that glycogen coincides with the subcellular localization of NKA and VHA. Under control conditions, glycogen and NKA are at the cell membrane of acid-secreting cells while glycogen and VHA are in the cytoplasm of base-secreting cells. During exposure to alkalosis, NKA and glycogen localization remains unchanged in acid-secreting cells; however, both VHA and glycogen translocate to the cell membrane of base-secreting cells. Interestingly, this process is prevented by pharmacological inhibition of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC). This suggests a novel mechanism, a coupling of glycogen metabolism with acid-base regulation that sustains ATPase function during sudden periods of increased energy demand. Since VHA, sAC, and glycogen are evolutionarily widespread, this mechanism is likely to apply broadly to other organisms and systems, perhaps including chronic kidney disease. APS Porter Predoctoral Fellowship and National Science Foundation Postdoctoral Research Fellowship in Biology #1709911 to JR, National Science Foundation Grant IOS 1354181 to MT. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Neutrophil specific glycogen metabolism supports antifungal function in the infected tissues

Abstract Neutrophils are critical for controlling systemic candidiasis (candidiasis), a bloodstream infection caused by Candida albicans. Neutrophils rely on extracellular glucose to fuel their antifungal activities at tissues. However, C. albicans consumes glucose, making it challenging for the neutrophils to survive and function at infected tissues. Hence, encountering fungal pathogens in glucose-depleted tissues exert metabolic challenges for neutrophils. It is unknown how neutrophils dynamically reprogram their metabolic pathways to function in glucose-deprived tissues in candidiasis. We show that neutrophils activate PYGL, an enzyme essential for the breakdown of intracellular glycogen storage to glucose, when glucose supply is limited. C. albicans regulate glycogenolysis in neutrophil in a dectin-1/Syk/Ca2+/PKA-axis dependent manner. Blockade of PYGL function in neutrophils inhibits fungicidal activities only when glucose availability is low and neutrophil specific PYGL ablated mice show increased susceptibility to candidiasis due to impaired ROS formation. Finally, treatment with β2-adrenergic receptor agonist, an approved drug and activator of PYGL function, improved antifungal activities of neutrophils in candidiasis. These results provide insights on how glycogenolysis supports compensatory metabolic reprograming required for antifungal function of neutrophils in the glucose-depleted infected tissues, a knowledge that can be therapeutically exploited by an approved drug.

OA25 Transcriptome analysis of peripheral blood and renal tissue identifies genes that predict treatment response in proliferative lupus nephritis: a prospective observational study

Abstract Background/Aims Mechanisms contributing to non-response in lupus nephritis (LN) are not clear. Peripheral blood mononuclear cells (PBMCs) serve as easily available less invasive alternative to kidney biopsy in monitoring treatment response. However, it is unclear to what extent peripheral blood mirrors the inflamed kidney. This study aims to identify changes in functional pathways from PBMCs and renal tissues after cyclophosphamide treatment and to identify baseline genes that predict treatment response by RNA-sequencing. Methods RNA from PBMCs and renal biopsies was extracted from 16 treatment-naïve proliferative LN at baseline, 6-months and at the time of flare within 2 years of follow-up. Patients were classified as clinical-responders (CR) (n = 4) or non-responders (NR) (n = 8) at 6-months using EULAR/EDTA criteria. CR who developed renal flare on follow-up were considered FL (n = 4). RNA was sequenced on Illumina Novaseq-6000 platform. Healthy control datasets were taken from public databases. Differentially expressed genes (DEGs) and enriched pathways were analysed using Reactome database-v74. Comparisons for each group were performed before vs after treatment. Weighted gene co-expression network analysis (WGCNA) was used to identify baseline hub genes that predict treatment-response and ROC analysis was used to test their prognostic utility. Results Functional enrichment analysis identified neutrophil degranulation, autophagy, regulation of NF-κβ signalling, FCGR-dependent phagocytosis and TNF signalling upregulated and IFN-γ signalling and ECM molecules downregulated in PBMCs of CR. ECM molecules and proteoglycans, neddylation and BCR signalling were enriched in PBMCs of NR. In NR renal tissue, apoptosis, NF-κβ signalling, IKK complex formation upon TLR signalling and MAPK signalling were enriched. In FL PBMCs, neutrophil degranulation, ROS and RNS production in phagocytes, antimicrobial peptide and immune system pathways were downregulated. In FL renal tissue, glycogen metabolism, viral mRNA translation, cell-ECM interactions, cell-cell communications, apoptosis and ISG15 antiviral mechanism were downregulated. Clinical traits for WGCNA were BCR, BNR, BFL and HC. The most correlated modules and hub genes from baseline PBMC were: green (BCR- IFI27, CD24, AZU1, MT2A, SNRNP70), brown (BNR- AC090809.1, TENM2, NLGN1, LSAMP, DLGAP2, AP005230.1, TMEM132D, AL445255.1, LINC00536, AC013287.1, BX470102.1, TM4SF20) and blue module (BFL- AC092436.3, AC046158.3, LINC01147). From baseline renal tissues, the most correlated modules and genes were: green (BCR- AP003068.1, BX470102.1, AC009088.3, AC136475.1, AC073611.1, AP000757.2) and turquoise module (BNR & BFL: TRDN-AS1, AC107973.1, AL672167.1, AC020637.1, AL137100.3, AC018437.3, LINC01982, TPH2, AC136759). From PBMCs, ROC analysis showed that combinational model of TENM2, NLGN1 and AP005230.1 predicted NR (AUC-0.94; 95% CI: 0.80-1; p = 0.02) and AC092436.3 predicted FL (AUC-0.81; 95% CI: 0.53-1; p = 0.036). AP005230.1 from renal tissue also predicted NR (AUC-0.94; 95% CI: 0.82-1; p = 0.01). Conclusion Type I IFN and fibrosis pathways were enriched in NR and downregulated in CR and FL. Baseline PBMC markers TENM2, NLGN1 & AP005230.1 predicted NR and FL. AP005230.1 from PBMCs & renal tissue predicted NR. Disclosure S. Bulusu: None. A. Bavikatte: None. S. Shah: None. S. Murthy: None. C.M. Mariaselvam: None. C. Kavadichanda: None. S. Vembar: None. M. Thabah: None. V.S. Negi: None.

MiR-141/200c contributes to ethanol-mediated hepatic glycogen metabolism

ObjectiveHepatic glucose metabolism is profoundly perturbed by excessive alcohol intake. miR-141/200c expression is significantly induced by chronic ethanol feeding. This study aimed at identifying the role of miR-141/200c in glucose homeostasis during chronic ethanol exposure. MethodsWT and miR-141/200c KO mice were fed a control or an ethanol diet for 30 days, followed by a single binge of maltose dextrin or ethanol, respectively. Untargeted metabolomics analysis of hepatic primary metabolites was performed along with analyses for liver histology, gene expression, intracellular signaling pathways, and physiological relevance. Primary hepatocytes were used for mechanistic studies. ResultsmiR-141/200c deficiency rewires hepatic glucose metabolism during chronic ethanol feeding, increasing the abundance of glucose intermediates including G6P, an allosteric activator for GS. miR-141/200c deficiency replenished glycogen depletion during chronic ethanol feeding accompanied by reduced GS phosphorylation in parallel with increased expression of PP1 glycogen targeting subunits. Moreover, miR-141/200c deficiency prevented ethanol-mediated increases in AMPK and CaMKK2 activity. Ethanol treatment reduced glycogen content in WT-hepatocytes, which was reversed by dorsomorphin, a selective AMPK inhibitor, while KO-hepatocytes displayed higher glycogen content than WT-hepatocytes in response to ethanol treatment. Furthermore, treatment of hepatocytes with A23187, a calcium ionophore activating CaMKK2, lowered glycogen content in WT-hepatocytes. Notably, the suppressive effect of A23187 on glycogen deposition was reversed by dorsomorphin, demonstrating that the glycogen depletion by A23187 is mediated by AMPK. KO-hepatocytes exhibited higher glycogen content than WT-hepatocytes in response to A23187. Finally, miR-141/200c deficiency led to improved glucose tolerance and insulin sensitivity during chronic ethanol feeding. ConclusionsmiR-141/200c deficiency replenishes ethanol-mediated hepatic glycogen depletion through the regulation of GS activity and calcium signaling coupled with the AMPK pathway, improving glucose homeostasis and insulin sensitivity. These results underscore miR-141/200c as a potential therapeutic target for the management of alcohol intoxication.

Empagliflozin in children with glycogen storage disease-associated inflammatory bowel disease: a prospective, single-arm, open-label clinical trial

Glycogen storage disease type Ib (GSD-Ib) is a rare inborn error of glycogen metabolism caused by mutations in SLC37A4. Patients with GSD-Ib are at high risk of developing inflammatory bowel disease (IBD). We evaluated the efficacy of empagliflozin, a renal sodium‒glucose cotransporter protein 2 (SGLT2) inhibitor, on colonic mucosal healing in patients with GSD-associated IBD. A prospective, single-arm, open-label clinical trial enrolled eight patients with GSD-associated IBD from Guangdong Provincial People's Hospital in China from July 1, 2022 through December 31, 2023. Eight patients were enrolled with a mean age of 10.34 ± 2.61 years. Four male and four female. The endoscopic features included deep and large circular ulcers, inflammatory hyperplasia, obstruction and stenosis. The SES-CD score significantly decreased at week 48 compared with before empagliflozin. Six patients completed 48 weeks of empagliflozin therapy and endoscopy showed significant improvement or healing of mucosal ulcers, inflammatory hyperplasia, stenosis, and obstruction. One patient had severe sweating that required rehydration and developed a urinary tract infection. No serious or life-threatening adverse events. This study suggested that empagliflozin may promote colonic mucosal healing and reduce hyperplasia, stenosis, and obstruction in children with GSD-associated IBD.

Architecture, Function, Regulation, and Evolution of α-Glucans Metabolic Enzymes in Prokaryotes.

Bacteria have acquired sophisticated mechanisms for assembling and disassembling polysaccharides of different chemistry. α-d-Glucose homopolysaccharides, so-called α-glucans, are the most widespread polymers in nature being key components of microorganisms. Glycogen functions as an intracellular energy storage while some bacteria also produce extracellular assorted α-glucans. The classical bacterial glycogen metabolic pathway comprises the action of ADP-glucose pyrophosphorylase and glycogen synthase, whereas extracellular α-glucans are mostly related to peripheral enzymes dependent on sucrose. An alternative pathway of glycogen biosynthesis, operating via a maltose 1-phosphate polymerizing enzyme, displays an essential wiring with the trehalose metabolism to interconvert disaccharides into polysaccharides. Furthermore, some bacteria show a connection of intracellular glycogen metabolism with the genesis of extracellular capsular α-glucans, revealing a relationship between the storage and structural function of these compounds. Altogether, the current picture shows that bacteria have evolved an intricate α-glucan metabolism that ultimately relies on the evolution of a specific enzymatic machinery. The structural landscape of these enzymes exposes a limited number of core catalytic folds handling many different chemical reactions. In this Review, we present a rationale to explain how the chemical diversity of α-glucans emerged from these systems, highlighting the underlying structural evolution of the enzymes driving α-glucan bacterial metabolism.

Impaired malin expression and interaction with partner proteins in Lafora disease

Lafora disease (LD) is an autosomal recessive myoclonus epilepsy with onset in the teenage years leading to death within a decade of onset. LD is characterized by the overaccumulation of hyperphosphorylated, poorly branched, insoluble, glycogen-like polymers called Lafora bodies. The disease is caused by mutations in either EPM2A, encoding laforin, a dual specificity phosphatase that dephosphorylates glycogen, or EMP2B, encoding malin, an E3-ubiquitin ligase. While glycogen is a widely accepted laforin substrate, substrates for malin have been difficult to identify partly due to the lack of malin antibodies able to detect malin invivo. Here we describe a mouse model in which the malin gene is modified at the C-terminus to contain the c-myc tag sequence, making an expression of malin-myc readily detectable. Mass spectrometry analyses of immunoprecipitates using c-myc tag antibodies demonstrate that malin interacts with laforin and several glycogen-metabolizing enzymes. To investigate the role of laforin in these interactions we analyzed two additional mouse models: malin-myc/laforin knockout and malin-myc/LaforinCS, where laforin was either absent or the catalytic Cys was genomically mutated to Ser, respectively. The interaction of malin with partner proteins requires laforin but is not dependent on its catalytic activity or the presence of glycogen. Overall, the results demonstrate that laforin and malin form a complex invivo, which stabilizes malin and enhances interaction with partner proteins to facilitate normal glycogen metabolism. They also provide insights into the development of LD and the rescue of the disease by the catalytically inactive phosphatase.

Immunometabolic crosstalk in Aedes fluviatilis and Wolbachia pipientis symbiosis

Wolbachia pipientis is a maternally transmitted symbiotic bacterium that mainly colonizes arthropods, potentially affecting different aspects of the host's physiology, e.g., reproduction, immunity, and metabolism. It has been shown that Wolbachia modulates glycogen metabolism in mosquito Aedes fluviatilis (Ae. fluviatilis). Glycogen synthesis is controlled by the enzyme GSK3, which is also involved in immune responses in both vertebrate and invertebrate organisms. Here we investigated the mechanisms behind immune changes mediated by glycogen synthase kinase β (GSK3β) in the symbiosis between Ae. fluviatilis and W.pipientis using a GSK3β inhibitor or RNAi-mediated gene silencing. GSK3β inhibition or knockdown increased glycogen content and Wolbachia population, together with a reduction in Relish2 and gambicin transcripts. Furthermore, knockdown of Relish2 or Caspar revealed that the immunodeficiency pathway acts to control Wolbachia numbers in the host. In conclusion, we describe for the first time the involvement of GSK3β in Ae. fluviatilis immune response, acting to control the Wolbachia endosymbiotic population.

Genotypic and phenotypic features of 39 Chinese patients with glycogen storage diseases type I, VI, and IX.

Glycogen storage diseases (GSDs) are abnormally inherited glycogen metabolism mainly affecting the liver, muscles, and heart. Deficiency of proteins involved in glycogen metabolism caused by genetic mutations are responsible for different subtype of GSDs. However, there are still some challenges in diagnosing GSD. This study includes 39 suspected GSDs patients from unrelated families in China. Next-generation sequencing (NGS) was used to investigate the reason for their diseases at the genetic level. Finally, all 39 patients were diagnosed with GSDs, including 20 GSD-Ia, 4 GSD-VI, and 15 GSD IX (12 GSD-IXa patients and 3 GSD-IXb patients). Thirty-two mutations in G6PC1, PYGL, PHKA2, and PHKB genes were identified, with 14 of them being novel variants. The pathogenicity of novel variants was classified according to ACMG guildlines and predicted by in slico algorithms. Mutations p.L216L and p.R83H in G6PC1 gene may be the hot spot mutation in Chinese. Hearing impairment is a rare clinical feature of GSD Ia, which has also been observed in our cohort. The severity of GSD VI and IX was indicated by our patients. Close follow-up should be applied to GSD VI and IX patients. Our findings provided evidence for building the phenotype-genotype of GSDs and expanded the mutation spectrum of related genes.

Architecture and activation of human muscle phosphorylase kinase

The study of phosphorylase kinase (PhK)-regulated glycogen metabolism has contributed to the fundamental understanding of protein phosphorylation; however, the molecular mechanism of PhK remains poorly understood. Here we present the high-resolution cryo-electron microscopy structures of human muscle PhK. The 1.3-megadalton PhK α4β4γ4δ4 hexadecamer consists of a tetramer of tetramer, wherein four αβγδ modules are connected by the central β4 scaffold. The α- and β-subunits possess glucoamylase-like domains, but exhibit no detectable enzyme activities. The α-subunit serves as a bridge between the β-subunit and the γδ subcomplex, and facilitates the γ-subunit to adopt an autoinhibited state. Ca2+-free calmodulin (δ-subunit) binds to the γ-subunit in a compact conformation. Upon binding of Ca2+, a conformational change occurs, allowing for the de-inhibition of the γ-subunit through a spring-loaded mechanism. We also reveal an ADP-binding pocket in the β-subunit, which plays a role in allosterically enhancing PhK activity. These results provide molecular insights of this important kinase complex.

What can pediatricians learn from adult inherited metabolic diseases?

The field of inherited metabolic diseases (IMD) has initially emerged and developed over decades in pediatric departments. Still, today, about 50% of patients with IMD are adults, and adult metabolic medicine (AMM) is getting more structured at national and international levels. There are several domains in which pediatricians can learn from AMM. First, long-term evolution of IMD patients, especially those treated since childhood, is critical to determine nutritional and neuropsychiatric outcomes in adults so that these outcomes can be better monitored, and patient care adjusted as much as possible from childhood. Conversely, the observation of attenuated phenotypes in adults of IMD known to present with severe phenotypes in children calls for caution in the development of newborn screening programs and, more largely, in the interpretation of next-generation sequencing data. Third, it is important for pediatricians to be familiar with adult-onset IMD as they expand our understanding of metabolism, including in children, such as oxysterols and glycogen metabolism. Last, the identification of common molecular and cellular mechanisms in neurodevelopment and neurodegeneration opens the way to synergistic therapeutic developments that will benefit both fields of pediatric and adult medicine. Overall, these observations underline the need of strong interdisciplinarity between pediatricians and adult specialists for the diagnosis and the treatment of IMD well beyond the issues of patient transition from pediatric to adult medicine.

Abstract 3345: PP1 phosphatase complex at the hub of the integrated stress response: A potential therapeutic target in multiple myeloma

Abstract Protein phosphatase-1 (PP1) is a class of eukaryotic enzyme that catalyzes more than half of the phosphoserine/threonine dephosphorylation reactions, and plays essential roles in cell division, glycogen metabolism and protein synthesis. The substrate specificity of PP1 holoenzyme complex is mediated by PP1-interacting proteins and its catalytic subunits. Of note, PPP1R15B/CReP and PPP1R15A/GADD34 are regulatory subunits of PP1 complex that regulates global protein synthesis and mRNA translation through eIF2α dephosphorylation. Notably, PPP1R15B is constitutively expressed, whereas the expression of PPP1R15A is stress-inducible. Previous studies showed that multiple myeloma (MM), a hematological malignancy arising from immunoglobulin-secreting plasma cells, is characterized by continual ER stress and high dependency on the unfolded protein response (UPR). The integrated stress response (ISR) activated by eIF2α phosphorylation is the fastest reaction pathway of the UPR; however, its functional role and therapeutic potential in MM remains largely unknown. In this study, we performed gene expression analysis and super-enhancer (SE) profiling in MM cell lines, primary patient samples, normal CD138+ plasma cells and memory B cells. we found that PPP1R15B is highly expressed in MM cells as compared to healthy controls, but did not observe significant upregulation of PPP1R15A in MM cells. In addition, higher expression of PPP1R15B predicted poor overall survival of MM patients, suggesting its clinical relevance in MM pathogenesis. Depletion of PPP1R15B significantly reduced cell viability, proliferation and induced G2/M phase cell cycle arrest. Gene Ontology analysis of downregulated genes in response to PPP1R15B knockdown indicates significant association with the UPR pathway. Immunoblot analysis showed activation of ER stress pro-apoptotic executors PUMA, NOXA, and cleavage of caspase-12 in PPP1R15B knockdown cells. Furthermore, we examined the therapeutic effects of eIF2α dephosphorylation inhibitors, Salubrinal and Raphin1, on MM cells. Raphin1 is a selective inhibitor of PPP1R15B that binds strongly to the PPP1R15B-PP1c complex, whereas Salubrinal inhibits both PPP1R15A-PP1c and PPP1R15B-PP1c complex. Our data showed that both Salubrinal and Raphin1 inhibited MM cell proliferation in a dose-dependent manner, while sparing normal plasma cells. MM cell lines with elevated PPP1R15B expression level were more sensitive to Salubrinal or Raphin1 than those with lower PPP1R15B level. Similar changes in the expression patterns of ISR-related genes were observed in response to eIF2α dephosphorylation inhibitors. Taken together, our study suggests that targeting PPP1R15B-PP1c complex or maintaining eIF2α hyperphosphorylation may serve as a new therapeutic approach in MM, which warrants further investigation. Citation Format: Sinan Xiong, Jianbiao Zhou, Tze King Tan, Sabrina Hui-Min Toh, Tae-Hoon Chung, Takaomi Sanda, Wee Joo Chng. PP1 phosphatase complex at the hub of the integrated stress response: A potential therapeutic target in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3345.

Study of two glycosyltransferases related to polysaccharide biosynthesis in Rhodococcus jostii RHA1.

The bacterial genus Rhodococcus comprises organisms performing oleaginous behaviors under certain growth conditions and ratios of carbon and nitrogen availability. Rhodococci are outstanding producers of biofuel precursors, where lipid and glycogen metabolisms are closely related. Thus, a better understanding of rhodococcal carbon partitioning requires identifying catalytic steps redirecting sugar moieties to storage molecules. Here, we analyzed two GT4 glycosyl-transferases from Rhodococcus jostii (RjoGlgAb and RjoGlgAc) annotated as α-glucan-α-1,4-glucosyl transferases, putatively involved in glycogen synthesis. Both enzymes were produced in Escherichia coli cells, purified to homogeneity, and kinetically characterized. RjoGlgAb and RjoGlgAc presented the "canonical" glycogen synthase activity and were actives as maltose-1P synthases, although to a different extent. Then, RjoGlgAc is a homologous enzyme to the mycobacterial GlgM, with similar kinetic behavior and glucosyl-donor preference. RjoGlgAc was two orders of magnitude more efficient to glucosylate glucose-1P than glycogen, also using glucosamine-1P as a catalytically efficient aglycon. Instead, RjoGlgAb exhibited both activities with similar kinetic efficiency and preference for short-branched α-1,4-glucans. Curiously, RjoGlgAb presented a super-oligomeric conformation (higher than 15 subunits), representing a novel enzyme with a unique structure-to-function relationship. Kinetic results presented herein constitute a hint to infer on polysaccharides biosynthesis in rhodococci from an enzymological point of view.

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

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. 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. 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. 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.

Change and pathological significance of glycogen content in oral squamous cell carcinoma and oral submucous fibrosis

ObjectiveThis study aimed to investigate the change and pathological significance of glycogen content in oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF). Methods and materials13 normal oral mucosa (NOM), 12 OSF mucosa, and 35 pairs of OSCC tissues and their corresponding adjacent mucosa tissues (AT) were collected from Xiangya Hospital for PAS staining to detect glycogen. Transcriptome sequencing data from OSCC were used to compare glycogen metabolism gene expression differences. Kaplan–Meier method was conducted to estimate Recurrence-free survival (RFS). ResultsGlycogen levels were lower in OSF than in NOM and lower in OSCC than in AT. Transcriptome sequencing data analysis showed the expression of most glycogenolysis genes was increased and the expression of glycogen synthesis genes including PPP1R3C and GBE1 was decreased in OSCC tissues. High glycogen level was correlated with poor prognosis in OSCC patients under the background of OSF. ConclusionGlycogen may be used as a potential diagnostic biomolecule for OSF and OSCC, as well as a potential prognostic factor for OSCC in the context of OSF.

Genetic investigation into the broad health implications of caffeine: evidence from phenome-wide, proteome-wide and metabolome-wide Mendelian randomization

BackgroundCaffeine is one of the most utilized drugs in the world, yet its clinical effects are not fully understood. Circulating caffeine levels are influenced by the interplay between consumption behaviour and metabolism. This study aimed to investigate the effects of circulating caffeine levels by considering genetically predicted variation in caffeine metabolism.MethodsLeveraging genetic variants related to caffeine metabolism that affect its circulating levels, we investigated the clinical effects of plasma caffeine in a phenome-wide association study (PheWAS). We validated novel findings using a two-sample Mendelian randomization framework and explored the potential mechanisms underlying these effects in proteome-wide and metabolome-wide Mendelian randomization.ResultsHigher levels of genetically predicted circulating caffeine among caffeine consumers were associated with a lower risk of obesity (odds ratio (OR) per standard deviation increase in caffeine = 0.97, 95% confidence interval (CI) CI: 0.95—0.98, p = 2.47 × 10−4), osteoarthrosis (OR = 0.97, 95% CI: 0.96—0.98, P=1.10 × 10−8) and osteoarthritis (OR: 0.97, 95% CI: 0.96 to 0.98, P = 1.09 × 10−6). Approximately one third of the protective effect of plasma caffeine on osteoarthritis risk was estimated to be mediated through lower bodyweight. Proteomic and metabolomic perturbations indicated lower chronic inflammation, improved lipid profiles, and altered protein and glycogen metabolism as potential biological mechanisms underlying these effects.ConclusionsWe report novel evidence suggesting that long-term increases in circulating caffeine may reduce bodyweight and the risk of osteoarthrosis and osteoarthritis. We confirm prior genetic evidence of a protective effect of plasma caffeine on risk of overweight and obesity. Further clinical study is warranted to understand the translational relevance of these findings before clinical practice or lifestyle interventions related to caffeine consumption are introduced.

Jellyfish stings‐induced cardiac failure was ameliorated through AAG‐mediated glycogen‐driven ATP production

AbstractThis article published in Early View in error. The article is under legal issues and the content is temporarily unavailable.4 April 2024

Current state of the epilepsy drug and device pipeline.

The field of epilepsy has undergone substantial advances as we develop novel drugs and devices. Yet considerable challenges remain in developing broadly effective, well-tolerated treatments, but also precision treatments for rare epilepsies and seizure-monitoring devices. We summarize major recent and ongoing innovations in diagnostic and therapeutic products presented at the seventeenth Epilepsy Therapies & Diagnostics Development (ETDD) conference, which occurred May 31 to June 2, 2023, in Aventura, Florida. Therapeutics under development are targeting genetics, ion channels and other neurotransmitters, and many other potentially first-in-class interventions such as stem cells, glycogen metabolism, cholesterol, the gut microbiome, and novel modalities for delivering electrical neuromodulation.