bims-glecem Biomed News
on Glycogen metabolism in exercise, cancer and energy metabolism
Issue of 2023–08–20
seven papers selected by
Dipsikha Biswas, Københavns Universitet
  1. Analysis of Cell Glycogen with Quantitation and Determination of Branching Using Liquid Chromatography-Mass Spectrometry.
  2. Harnessing dual-energy CT for glycogen quantification: a phantom analysis.
  3. SGLT5 is the renal transporter for 1,5-anhydroglucitol, a major player in two rare forms of neutropenia.
  4. Neprilysin deficiency reduces hepatic gluconeogenesis in high fat-fed mice.
  5. Whole-Exome sequencing identifies GYS2 biallelic variants in individuals with suspected epilepsy.
  6. A novel mutation of glycogen synthase kinase-3β leads to a reduced level of GSK3β protein in a patient with dilated cardiomyopathy.
  7. The Neurobiology and Therapeutic Potential of Multi-Targeting β-secretase, Glycogen Synthase Kinase 3β and Acetylcholinesterase in Alzheimer's Disease.
  1. Anal Chem. 2023 Aug 16.
    Analysis of Cell Glycogen with Quantitation and Determination of Branching Using Liquid Chromatography-Mass Spectrometry.
    Siyu Chen, Yasmine Bouchibti, Yixuan Xie, Ye Chen, Vincent Chang, Carlito B Lebrilla.
      Glycogen is a highly branched biomacromolecule that functions as a glucose buffer. It is involved in multiple diseases such as glycogen storage disorders, diabetes, and even liver cancer, where the imbalance between biosynthetic and catabolic enzymes results in structural alterations and abnormal accumulation of glycogen that can be toxic to cells. Accurate and sensitive glycogen quantification and structural determination are prerequisites for understanding the phenotypes and biological functions of glycogen under these conditions. In this research, we furthered cell glycogen characterization by presenting a highly sensitive method to measure the glycogen content and degree of branching. The method employed a novel fructose density gradient as an alternative to the traditional sucrose gradient to fractionate glycogen from cell mixtures using ultracentrifugation. Fructose was used to avoid the large glucose background, allowing the method to be highly quantitative. The glycogen content was determined by quantifying 1-phenyl-3-methyl-5-pyrazolone (PMP)-derivatized glucose residues obtained from acid-hydrolyzed glycogen using ultra-high-performance liquid chromatography/triple quadrupole mass spectrometry (UHPLC/QqQ-MS). The degree of branching was determined through linkage analysis where the glycogen underwent permethylation, hydrolysis, PMP derivatization, and UHPLC/QqQ-MS analysis. The new approach was used to study the effect of insulin on the glycogen phenotypes of human hepatocellular carcinoma (Hep G2) cells. We observed that cells produced greater amounts of glycogen with less branching under increasing insulin levels before reaching the cell's insulin-resistant state, where the trend reversed and the cells produced less but higher-branched glycogen. The advantage of this method lies in its high sensitivity in characterizing both the glycogen level and the structure of biological samples.
    DOI:  https://doi.org/10.1021/acs.analchem.3c02230
  2. Quant Imaging Med Surg. 2023 Aug 01. 13(8): 4933-4942
    Harnessing dual-energy CT for glycogen quantification: a phantom analysis.
    Meiqin Li, Zhoulei Li, Luyong Wei, Lujie Li, Meng Wang, Shaofu He, Zhenpeng Peng, Shi-Ting Feng.
       Background: Non-invasive glycogen quantification in vivo could provide crucial information on biological processes for glycogen storage disorder. Using dual-energy computed tomography (DECT), this study aimed to assess the viability of quantifying glycogen content in vitro.
    Methods: A fast kilovolt-peak switching DECT was used to scan a phantom containing 33 cylinders with different proportions of glycogen and iodine mixture at varying doses. The virtual glycogen concentration (VGC) was then measured using material composition images. Additionally, the correlations between VGC and nominal glycogen concentration (NGC) were evaluated using least-square linear regression, then the calibration curve was constructed. Quantitative estimation was performed by calculating the linearity, conversion factor (inverse of curve slope), stability, sensitivity (limit of detection/limit of quantification), repeatability (inter-class correlation coefficient), and variability (coefficient of variation).
    Results: In all conditions, excellent linear relationship between VGC and NGC were observed (P<0.001, coefficient of determination: 0.989-0.997; residual root-mean-square error of glycogen: 1.862-3.267 mg/mL). The estimated conversion factor from VGC to NGC was 3.068-3.222. In addition, no significant differences in curve slope were observed among different dose levels and iodine densities. The limit of detection and limit of quantification had respective ranges of 6.421-15.315 and 10.95-16.46 mg/mL. The data demonstrated excellent scan-repeat scan agreement (inter-class correlation coefficient, 0.977-0.991) and small variation (coefficient of variation, 0.1-0.2%).
    Conclusions: The pilot phantom analysis demonstrated the feasibility and efficacy of detecting and quantifying glycogen using DECT and provided good quantitative performance with significant stability and reproducibility/variability. Thus, in the future, DECT could be used as a convenient method for glycogen quantification to provide more reliable information for clinical decision-making.
    Keywords:  Glycogen; dual-energy computed tomography (DECT); quantification
    DOI:  https://doi.org/10.21037/qims-22-1234
  3. Cell Mol Life Sci. 2023 Aug 18. 80(9): 259
    SGLT5 is the renal transporter for 1,5-anhydroglucitol, a major player in two rare forms of neutropenia.
    Jennifer Diederich, Pierre Mounkoro, Hernan A Tirado, Nathalie Chevalier, Emile Van Schaftingen, Maria Veiga-da-Cunha.
      Neutropenia and neutrophil dysfunction in glycogen storage disease type 1b (GSD1b) and severe congenital neutropenia type 4 (SCN4), associated with deficiencies of the glucose-6-phosphate transporter (G6PT/SLC37A4) and the phosphatase G6PC3, respectively, are the result of the accumulation of 1,5-anhydroglucitol-6-phosphate in neutrophils. This is an inhibitor of hexokinase made from 1,5-anhydroglucitol (1,5-AG), an abundant polyol in blood. 1,5-AG is presumed to be reabsorbed in the kidney by a sodium-dependent-transporter of uncertain identity, possibly SGLT4/SLC5A9 or SGLT5/SLC5A10. Lowering blood 1,5-AG with an SGLT2-inhibitor greatly improved neutrophil counts and function in G6PC3-deficient and GSD1b patients. Yet, this effect is most likely mediated indirectly, through the inhibition of the renal 1,5-AG transporter by glucose, when its concentration rises in the renal tubule following inhibition of SGLT2. To identify the 1,5-AG transporter, both human and mouse SGLT4 and SGLT5 were expressed in HEK293T cells and transport measurements were performed with radiolabelled compounds. We found that SGLT5 is a better carrier for 1,5-AG than for mannose, while the opposite is true for human SGLT4. Heterozygous variants in SGLT5, associated with a low level of blood 1,5-AG in humans cause a 50-100% reduction in 1,5-AG transport activity tested in model cell lines, indicating that SGLT5 is the predominant kidney 1,5-AG transporter. These and other findings led to the conclusion that (1) SGLT5 is the main renal transporter of 1,5-AG; (2) frequent heterozygous mutations (allelic frequency > 1%) in SGLT5 lower blood 1,5-AG, favourably influencing neutropenia in G6PC3 or G6PT deficiency; (3) the effect of SGLT2-inhibitors on blood 1,5-AG level is largely indirect; (4) specific SGLT5-inhibitors would be more efficient to treat these neutropenias than SGLT2-inhibitors.
    Keywords:  1,5-Anhydroglucitol; Empagliflozin; G6PC3-deficiency; GSD1b; Glycogen storage disease type Ib; Neutropenia; SCN4; SGLT2-inhibitors; SGLT4; SGLT5
    DOI:  https://doi.org/10.1007/s00018-023-04884-8
  4. Peptides. 2023 Aug 10. pii: S0196-9781(23)00139-0. [Epub ahead of print]168 171076
    Neprilysin deficiency reduces hepatic gluconeogenesis in high fat-fed mice.
    Nathalie Esser, Stephen M Mongovin, Thomas O Mundinger, Breanne M Barrow, Sakeneh Zraika.
      Neprilysin is a peptidase that cleaves glucoregulatory peptides, including glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK). Some studies suggest that its inhibition in diabetes and/or obesity improves glycemia, and that this is associated with enhanced insulin secretion, glucose tolerance and insulin sensitivity. Whether reduced neprilysin activity also improves hepatic glucose metabolism has not been explored. We sought to determine whether genetic deletion of neprilysin suppresses hepatic glucose production (HGP) in high fat-fed mice. Nep+/+ and Nep-/- mice were fed high fat diet for 16 weeks, and then underwent a pyruvate tolerance test (PTT) to assess hepatic gluconeogenesis. Since glycogen breakdown in liver can also yield glucose, we assessed liver glycogen content in fasted and fed mice. In Nep-/- mice, glucose excursion during the PTT was reduced when compared to Nep+/+ mice. Further, liver glycogen levels were significantly greater in fasted but not fed Nep-/- versus Nep+/+ mice. Since gut-derived factors modulate HGP, we tested whether gut-selective inhibition of neprilysin could recapitulate the suppression of hepatic gluconeogenesis observed with whole-body inhibition, and this was indeed the case. Finally, the gut-derived neprilysin substrates, GLP-1 and CCK, are well-known to suppress HGP. Having previously demonstrated elevated plasma GLP-1 levels in Nep-/- mice, we now measured plasma CCK bioactivity and reveal an increase in Nep-/- versus Nep+/+ mice, suggesting GLP-1 and/or CCK may play a role in reducing HGP under conditions of neprilysin deficiency. In sum, neprilysin modulates hepatic gluconeogenesis and strategies to inhibit its activity may reduce HGP in type 2 diabetes and obesity.
    Keywords:  Cholecystokinin; Glucagon-like peptide-1; Gluconeogenesis; Glycogenolysis; Liver; Neprilysin
    DOI:  https://doi.org/10.1016/j.peptides.2023.171076
  5. Seizure. 2023 Jul 27. pii: S1059-1311(23)00209-1. [Epub ahead of print]
    Whole-Exome sequencing identifies GYS2 biallelic variants in individuals with suspected epilepsy.
    Muhammad Ilyas, Dorothea Holzwarth, Rafaqat Ishaq, Yasir Ali, Umme Habiba, Asad Mehmood Raja, Sadia Saeed, Uzma Abdullah, Sadiq Noor Khan, Ata Ullah, Ghazala Kaukab Raja, Shahid Mehmood Baig, Walid Fazeli, Wolfram S Kunz, Pakeeza Arzoo Shaiq.
       BACKGROUND: Adequate glucose supply is essential for brain function, therefore hypoglycemic states may lead to seizures. Since blood glucose supply for brain is buffered by liver glycogen, an impairment of liver glycogen synthesis by mutations in the liver glycogen synthase gene (GYS2) might result in a substantial neurological involvement. Here, we describe the phenotypes of affected siblings of two families harboring biallelic mutations in GYS2.
    METHODS: Two suspected families - a multiplex Pakistani family (family A) with three affected siblings and a family of Moroccan origin (family B) with a single affected child who presented with seizures and reduced fasting blood glucose levels were genetically characterized. Whole exome sequencing (WES) was performed on the index patients, followed by Sanger sequencing-based segregation analyses on all available members of both families.
    RESULTS: The variant prioritization of WES and later Sanger sequencing confirmed three mutations in the GYS2 gene (12p12.1) consistent with an autosomal recessive pattern of inheritance. A homozygous splice acceptor site variant (NM_021957.3, c. 1646 -2A>G) segregated in family A. Two novel compound heterozygous variants (NM_021957.3: c.343G>A; p.Val115Met and NM_021957.3: c.875A>T; p.Glu292Val) were detected in family B, suggesting glycogen storage disorder. A special diet designed to avoid hypoglycemia, in addition to change of the anti-seizure medication led to reduction in seizure frequency.
    CONCLUSIONS: This study suggests that the seizures in patients initially diagnosed with epilepsy might be directly caused, or influenced by hypoglycemia due to pathogenic variants in the GYS2 gene.
    Keywords:  Biallelic GYS2 mutations; Coma; Compound heterozygous; Hypoglycemia; Seizure; Splice-site mutation; Whole-Exome sequencing
    DOI:  https://doi.org/10.1016/j.seizure.2023.07.020
  6. Genes Dis. 2024 Jan;11(1): 84-86
    A novel mutation of glycogen synthase kinase-3β leads to a reduced level of GSK3β protein in a patient with dilated cardiomyopathy.
    Ke Gong, Zhiping Tan, Haidan Liu, Xiaobo Liao, Xinmin Zhou, Bangliang Yin, Shi Zeng, Yao Yao, Yifeng Yang, Li Xie.
      
    DOI:  https://doi.org/10.1016/j.gendis.2023.02.040
  7. Ageing Res Rev. 2023 Aug 16. pii: S1568-1637(23)00192-7. [Epub ahead of print] 102033
    The Neurobiology and Therapeutic Potential of Multi-Targeting β-secretase, Glycogen Synthase Kinase 3β and Acetylcholinesterase in Alzheimer's Disease.
    Mariana G Fronza, Diego Alves, Domenico Praticò, Lucielli Savegnago.
      Alzheimer's Disease (AD) is the most common form of dementia, affecting almost 50 million of people around the world, characterized by a complex and age-related progressive pathology with projections to duplicate its incidence by the end of 2050. AD pathology has two major hallmarks, the amyloid beta (Aβ) peptides accumulation and tau hyperphosphorylation, alongside with several sub pathologies including neuroinflammation, oxidative stress, loss of neurogenesis and synaptic dysfunction. In recent years, extensive research pointed out several therapeutic targets which have shown promising effects on modifying the course of the disease in preclinical models of AD but with substantial failure when transposed to clinic trials, suggesting that modulating just an isolated feature of the pathology might not be sufficient to improve brain function and enhance cognition. In line with this, there is a growing consensus that an ideal disease modifying drug should address more than one feature of the pathology. Considering these evidence, β-secretase (BACE1), Glycogen synthase kinase 3β (GSK-3β) and acetylcholinesterase (AChE) has emerged as interesting therapeutic targets. BACE1 is the rate-limiting step in the Aβ production, GSK-3β is considered the main kinase responsible for Tau hyperphosphorylation, and AChE play an important role in modulating memory formation and learning. However, the effects underlying the modulation of these enzymes are not limited by its primarily functions, showing interesting effects in a wide range of impaired events secondary to AD pathology. In this sense, this review will summarize the involvement of BACE1, GSK-3β and AChE on synaptic function, neuroplasticity, neuroinflammation and oxidative stress. Additionally, we will present and discuss new perspectives on the modulation of these pathways on AD pathology and future directions on the development of drugs that concomitantly target these enzymes.
    Keywords:  Alzheimer’s disease; Amyloid-β peptides; Multi-target therapy; Neurogenesis; Neuroinflammation; Oxidative Stress; Synapse; Tau protein
    DOI:  https://doi.org/10.1016/j.arr.2023.102033
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