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Alleviation of a polyglucosan storage disorder by enhancement of autophagic glycogen catabolism.

ABSTRACT: This work employs adult polyglucosan body disease (APBD) models to explore the efficacy and mechanism of action of the polyglucosan-reducing compound 144DG11. APBD is a glycogen storage disorder (GSD) caused by glycogen branching enzyme (GBE) deficiency causing accumulation of poorly branched glycogen inclusions called polyglucosans. 144DG11 improved survival and motor parameters in a GBE knockin (Gbe^ys/ys ) APBD mouse model. 144DG11 reduced polyglucosan and glycogen in brain, liver, heart, and peripheral nerve. Indirect calorimetry experiments revealed that 144DG11 increases carbohydrate burn at the expense of fat burn, suggesting metabolic mobilization of pathogenic polyglucosan. At the cellular level, 144DG11 increased glycolytic, mitochondrial, and total ATP production. The molecular target of 144DG11 is the lysosomal membrane protein LAMP1, whose interaction with the compound, similar to LAMP1 knockdown, enhanced autolysosomal degradation of glycogen and lysosomal acidification. 144DG11 also enhanced mitochondrial activity and modulated lysosomal features as revealed by bioenergetic, image-based phenotyping and proteomics analyses. As an effective lysosomal targeting therapy in a GSD model, 144DG11 could be developed into a safe and efficacious glycogen and lysosomal storage disease therapy.

SUBMITTER: Kakhlon O

PROVIDER: S-EPMC8495453 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Alleviation of a polyglucosan storage disorder by enhancement of autophagic glycogen catabolism

Project description:This work employs Adult Polyglucosan Body Disease (APBD) models to explore the efficacy and mechanism of action of the polyglucosan-reducing compound 144DG11. APBD is a glycogen storage disorder (GSD) caused by glycogen branching enzyme (GBE) deficiency causing accumulation of poorly branched glycogen inclusions called polyglucosans. 144DG11 improved survival and motor parameters in a GBE knockin (Gbeys/ys) APBD mouse model. 144DG11 reduced polyglucosan and glycogen in brain, liver, heart, and peripheral nerve. Indirect calorimetry experiments revealed that 144DG11 increases carbohydrate burn at the expense of fat burn, suggesting metabolic mobilization of pathogenic polyglucosan. At the cellular level, 144DG11 increased glycolytic, mitochondrial, and total ATP production. The molecular target of 144DG11 is the lysosomal membrane protein LAMP1, whose interaction with the compound, similar to LAMP1 knockdown, enhanced autolysosomal degradation of glycogen and lysosomal acidification. 144DG11 also enhanced mitochondrial activity and modulated lysosomal features as revealed by bioenergetic, image-based phenotyping and proteomics analyses. As an effective lysosomal targeting therapy in a GSD model, 144DG11 could be developed into a safe and efficacious glycogen and lysosomal storage disease therapy.

| S-SCDT-EMM-2021-14554 | biostudies-other

Glycogenin is Dispensable for Glycogen Synthesis in Human Muscle, and Glycogenin Deficiency Causes Polyglucosan Storage.

Project description:Glycogenin is considered to be an essential primer for glycogen biosynthesis. Nevertheless, patients with glycogenin-1 deficiency due to biallelic GYG1 (NM_004130.3) mutations can store glycogen in muscle. Glycogenin-2 has been suggested as an alternative primer for glycogen synthesis in patients with glycogenin-1 deficiency. The objective of this article is to investigate the importance of glycogenin-1 and glycogenin-2 for glycogen synthesis in skeletal and cardiac muscle. Glycogenin-1 and glycogenin-2 expression was analyzed by Western blot, mass spectrometry, and immunohistochemistry in liver, heart, and skeletal muscle from controls and in skeletal and cardiac muscle from patients with glycogenin-1 deficiency. Glycogenin-1 and glycogenin-2 both were found to be expressed in the liver, but only glycogenin-1 was identified in heart and skeletal muscle from controls. In patients with truncating GYG1 mutations, neither glycogenin-1 nor glycogenin-2 was expressed in skeletal muscle. However, nonfunctional glycogenin-1 but not glycogenin-2 was identified in cardiac muscle from patients with cardiomyopathy due to GYG1 missense mutations. By immunohistochemistry, the mutated glycogenin-1 colocalized with the storage of glycogen and polyglucosan in cardiomyocytes. Glycogen can be synthesized in the absence of glycogenin, and glycogenin-1 deficiency is not compensated for by upregulation of functional glycogenin-2. Absence of glycogenin-1 leads to the focal accumulation of glycogen and polyglucosan in skeletal muscle fibers. Expression of mutated glycogenin-1 in the heart is deleterious, and it leads to storage of abnormal glycogen and cardiomyopathy.

| S-EPMC7046021 | biostudies-literature

Pathogenesis of Lafora Disease: Transition of Soluble Glycogen to Insoluble Polyglucosan.

Project description:Lafora disease (LD, OMIM #254780) is a rare, recessively inherited neurodegenerative disease with adolescent onset, resulting in progressive myoclonus epilepsy which is fatal usually within ten years of symptom onset. The disease is caused by loss-of-function mutations in either of the two genes EPM2A (laforin) or EPM2B (malin). It characteristically involves the accumulation of insoluble glycogen-derived particles, named Lafora bodies (LBs), which are considered neurotoxic and causative of the disease. The pathogenesis of LD is therefore centred on the question of how insoluble LBs emerge from soluble glycogen. Recent data clearly show that an abnormal glycogen chain length distribution, but neither hyperphosphorylation nor impairment of general autophagy, strictly correlates with glycogen accumulation and the presence of LBs. This review summarizes results obtained with patients, mouse models, and cell lines and consolidates apparent paradoxes in the LD literature. Based on the growing body of evidence, it proposes that LD is predominantly caused by an impairment in chain-length regulation affecting only a small proportion of the cellular glycogen. A better grasp of LD pathogenesis will further develop our understanding of glycogen metabolism and structure. It will also facilitate the development of clinical interventions that appropriately target the underlying cause of LD.

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Impaired Very-Low-Density Lipoprotein catabolism links hypoglycemia to hypertriglyceridemia in Glycogen Storage Disease type Ia.

Project description:Prevention of hypertriglyceridemia is one of the biomedical targets in Glycogen Storage Disease type Ia (GSD Ia) patients, yet it is unclear how hypoglycemia links to plasma triglyceride (TG) levels. We analyzed whole-body TG metabolism in normoglycemic (fed) and hypoglycemic (fasted) hepatocyte-specific glucose-6-phosphatase deficient (L-G6pc-/- ) mice. De novo fatty acid synthesis contributed substantially to hepatic TG accumulation in normoglycemic L-G6pc-/- mice. In hypoglycemic conditions, enhanced adipose tissue lipolysis was the main driver of liver steatosis, supported by elevated free fatty acid concentrations in GSD Ia mice and GSD Ia patients. Plasma very-low-density lipoprotein (VLDL) levels were increased in GSD Ia patients and in normoglycemic L-G6pc-/- mice, and further elevated in hypoglycemic L-G6pc-/- mice. VLDL-TG secretion rates were doubled in normo- and hypoglycemic L-G6pc-/- mice, while VLDL-TG catabolism was selectively inhibited in hypoglycemic L-G6pc-/- mice. In conclusion, fasting-induced hypoglycemia in L-G6pc-/- mice promotes adipose tissue lipolysis and arrests VLDL catabolism. This mechanism likely contributes to aggravated liver steatosis and dyslipidemia in GSD Ia patients with poor glycemic control and may explain clinical heterogeneity in hypertriglyceridemia between GSD Ia patients.

| S-EPMC8360207 | biostudies-literature

Glycogen metabolism and glycogen storage disorders.

Project description:Glucose is the main energy fuel for the human brain. Maintenance of glucose homeostasis is therefore, crucial to meet cellular energy demands in both - normal physiological states and during stress or increased demands. Glucose is stored as glycogen primarily in the liver and skeletal muscle with a small amount stored in the brain. Liver glycogen primarily maintains blood glucose levels, while skeletal muscle glycogen is utilized during high-intensity exertion, and brain glycogen is an emergency cerebral energy source. Glycogen and glucose transform into one another through glycogen synthesis and degradation pathways. Thus, enzymatic defects along these pathways are associated with altered glucose metabolism and breakdown leading to hypoglycemia ± hepatomegaly and or liver disease in hepatic forms of glycogen storage disorder (GSD) and skeletal ± cardiac myopathy, depending on the site of the enzyme defects. Overall, defects in glycogen metabolism mainly present as GSDs and are a heterogenous group of inborn errors of carbohydrate metabolism. In this article we review the genetics, epidemiology, clinical and metabolic findings of various types of GSD, and glycolysis defects emphasizing current treatment and implications for future directions.

| S-EPMC6331362 | biostudies-literature

Abnormal glycogen in astrocytes is sufficient to cause adult polyglucosan body disease.

Project description:BACKGROUND:A 45-year old woman of Cambodian ethnic background presented with fatal respiratory failure due to a severe diaphragmatic dysfunction. Two years before, she had developed early onset of urinary symptoms. METHODS AND RESULTS:Neuroimaging showed atrophy of the spine and medulla as well as a leukodystrophy affecting both supra- and infra-tentorial regions. At autopsy, polyglucosan bodies (PB) were seen in several peripheral tissues, including the diaphragm, and nervous tissues such as peripheral nerves, cerebral white matter, basal ganglia, hippocampus, brainstem and cerebellum. Immunohistochemistry and electron microscopy of the brain revealed an exclusive astrocytic localization of the PB. The diagnosis of adult polyglucosan body disease (APBD) was confirmed by enzymatic and molecular studies. CONCLUSION:Storage of abnormal glycogen in astrocytes is sufficient to cause the leukodystrophy of APBD. Since brain glycogen is almost exclusively metabolized in astrocytes, this observation sheds light on the pathophysiology of APBD. In addition, this is the first report of an APBD patient presenting with a subacute diaphragmatic failure.

| S-EPMC7126849 | biostudies-literature

The glycogen scaffolding protein PTG coordinately regulates glycogen and lipid storage

Project description:Glycogen and lipid are major storage forms of energy that are tightly regulated by hormones and metabolic signals. Here, we evaluate the role of the glycogenic scaffolding protein PTG/R5 in energy homeostasis. We demonstrate that feeding mice a high-fat diet (HFD) increases hepatic glycogen, corresponding to increased PTG levels, increased activity of the mechanistic target of rapamycin complex 1 (mTORC1) and induced expression of sterol regulatory element binding protein 1c (SREBP1c). PTG promoter activity was increased by activation of mTORC1 and SREBP1, and PTG and glycogen levels were augmented in mice and cells in which mTORC1 is constitutively active. HFD-dependent increases in hepatic glycogen were prevented by deletion of the PTG gene in mice. Interestingly, PTG knockout mice fed HFD exhibited improved liver steatosis and decreased lipid levels in muscle, in coordination with decreased glycogen, suggesting possible crosstalk between glycogen and lipid stores in the overall control of energy metabolism. Together, these data suggest that transcriptional regulation of PTG by dietary and nutritional cues has profound effects on energy storage and metabolism.fi RNA-Seq analysis was used to characterize hepatic diet-associated gene expression changes between wild-type and PTG KO mice. Mice were maintained on a normal chow diet or a high-fat diet as indicated. 2-3 biological replicates per genotype/diet.

2014-06-13 | E-GEOD-45319 | biostudies-arrayexpress

The glycogen scaffolding protein PTG coordinately regulates glycogen and lipid storage

2014-06-13 | GSE45319 | GEO

Feeding Difficulties and Orofacial Myofunctional Disorder in Patients with Hepatic Glycogen Storage Diseases.

Project description:Hepatic glycogen storage diseases (GSDs) are inborn errors of metabolism whose dietary treatment involves uncooked cornstarch administration and restriction of simple carbohydrate intake. The prevalence of feeding difficulties (FDs) and orofacial myofunctional disorders (OMDs) in these patients is unknown.ObjectiveTo ascertain the prevalence of FDs and OMDs in GSD.MethodsThis was a cross-sectional, prospective study of 36 patients (19 males; median age, 12.0 years; range, 8.0-18.7 years) with confirmed diagnoses of GSD (type Ia = 22; Ib = 8; III = 2; IXa = 3; IXc = 1). All patients were being treated by medical geneticists and dietitians. Evaluation included a questionnaire for evaluation of feeding behavior, the orofacial myofunctional evaluation (AMIOFE), olfactory and taste performance (Sniffin' Sticks and Taste Strips tests), and facial anthropometry.ResultsNine (25%) patients had decreased olfactory perception, and four (11%) had decreased taste perception for all flavours. Eight patients (22.2%) had decreased perception for sour taste. Twenty-six patients (72.2%) had FD, and 18 (50%) had OMD. OMD was significantly associated with FD, tube feeding, selective intake, preference for fluid and semisolid foods, and mealtime stress (p < 0.05). Thirteen patients (36.1%) exhibited mouth or oronasal breathing, which was significantly associated with selective intake (p = 0.011) and not eating together with the rest of the family (p = 0.041). Lower swallowing and chewing scores were associated with FD and with specific issues related to eating behavior (p < 0.05).ConclusionThere is a high prevalence of FDs and OMDs in patients with GSD. Eating behavior, decreased taste and smell perception, and orofacial myofunctional issues are associated with GSD.

| S-EPMC6336547 | biostudies-literature

Pathomorphogenesis of Glycogen-Ground Glass Hepatocytic Inclusions (Polyglucosan Bodies) in Children after Liver Transplantation.

Project description:Seventeen out of 764 liver biopsies from transplanted (Tx) livers in children showed glycogen-ground glass (GGG) hepatocytic inclusions. The inclusions were not present in pre-Tx or in the explanted or donor's liver. Under the electron microscope (EM), the stored material within the cytosol appeared as non-membrane-bound aggregates of electron-lucent globoid or fibrillar granules, previously described as abnormally structured glycogen and identified as Polyglucosan bodies (PB). The appearance of GGG in our children was analogous to that of PB-GGG occurring in a number of congenital diseases due to gene mutations such as Lafora's d., Andersen's d., Adult Polyglucosan Body Disease and glycogenin deficiency. The same type of GGG was previously reported in the liver of patients undergoing transplants, immunosuppressive or antiblastic treatment. To explore the potential mechanism of GGG formation, we examined whether the drugs after whose treatment this phenomenon was observed could have a role. By carrying out molecular docking, we found that such drugs somehow present a high binding affinity for the active region of glycogenin, implicating that they can inactivate the protein, thus preventing its interaction with glycogen synthase (GS), as well as the maturation of the nascent glycogen towards gamma, beta or alfa glycogen granules. We could also demonstrate that PG inclusions consist of a complex of PAS positive material (glycogen) and glycogen-associated proteins, i.e., glicogenin-1 and -2 and ubiquitin. These features appear to be analogous to congenital GGG, suggesting that, in both cases, they result from the simultaneous dysregulation of glycogen synthesis and degradation. Drug-induced GGG appear to be toxic to the cell, despite their reversibility.

| S-EPMC9456521 | biostudies-literature

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