Glycogen Accumulation Research Articles

Pediatric Considerations in Pompe Disease: A Comprehensive Review

Pompe disease, also known as glycogen storage disease type II, is a rare inherited disorder caused by a deficiency of the enzyme acid alpha-glucosidase (GAA), leading to the accumulation of glycogen in various tissues, particularly muscles. While Pompe disease can affect individuals of all ages, its presentation and management in pediatric patients present unique challenges. This review aims to provide a comprehensive overview of the clinical manifestations, diagnosis, and management of Pompe disease in pediatric populations. Special considerations in the areas of respiratory support, nutrition, physical therapy, and long-term outcomes will be discussed. Understanding these aspects is crucial for optimizing the care and quality of life for children with Pompe disease

Decreased pancreatic amylase activity after acute high-intensity exercise and its effects on post-exercise muscle glycogen recovery.

Our prior results showed that an acute bout of endurance exercise for 6h, but not 1h, decreased pancreatic amylase activity, indicating that acute endurance exercise may affect carbohydrate digestive capacity in an exercise duration-dependent manner. Here, we investigated the effects of acute endurance exercise of different intensities on mouse pancreatic amylase activity. Male C57BL/6J mice performed low- or high-intensity running exercise for 60min at either 10 (Ex-Low group) or 20m/min (Ex-High group). The control group comprised sedentary mice. Immediately after acute exercise, pancreatic amylase activity was significantly decreased in the Ex-High group and not the Ex-Low group in comparison with the control group. To determine whether the decreased amylase activity induced by high-intensity exercise influenced muscle glycogen recovery after exercise, we investigated the rates of muscle glycogen resynthesis in Ex-High group mice administered either oral glucose or starch solution (2.0mg/g body weight) immediately after exercise. The starch-fed mice exhibited significantly lower post-exercise glycogen accumulation rates in the 2-h recovery period compared with the glucose-fed mice. This difference in the glycogen accumulation rate was absent for starch- and glucose-fed mice in the sedentary (no exercise) control group. Furthermore, the plasma glucose AUC during early post-exercise recovery (0-60min) was significantly lower in the starch-fed mice than in the glucose-fed mice. Thus, our findings suggest that acute endurance exercise diminishes the carbohydrate digestive capacity of the pancreas in a manner dependent on exercise intensity, with polysaccharides leading to delayed muscle glycogen recovery after exercise.

Glycogen synthesis is required for adaptive thermogenesis in beige adipose tissue and affects diet-induced obesity.

Glycogen is a form of energy storage for glucose in different tissues such as liver and skeletal muscle. It remains incompletely understood how glycogen impacts on adipose tissue functionality. Cold exposure elevated the expression of Gys1 that encodes glycogen synthase 1 in brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT). The in vivo function of Gys1 was analyzed using a mouse model in which Gys1 was deleted specifically in adipose tissues. Under normal chow conditions, Gys1 deletion caused little changes to body weight and glucose metabolism. Deletion of Gys1 abrogated upregulation of UCP1 and other thermogenesis-related genes in iWAT upon prolonged cold exposure or treatment with β3-adrenergic receptor agonist CL-316,243. Stimulation of UCP1 by CL-316,243 in adipose-derived stromal cells (stromal vascular fractions, SVFs) was also reduced by Gys1 deletion. Both the basal glycogen content and CL-316,243-stimulated glycogen accumulation in adipose tissues were reduced by Gys1 deletion. High-fat diet-induced obesity and insulin resistance were aggravated in Gys1-deleted mice. The loss of body weight upon CL-316,243 treatment was also abrogated by the loss of Gys1. In conclusion, our results underscore the pivotal role of glycogen synthesis in adaptive thermogenesis in beige adipose tissue and its impact on diet-induced obesity in mice.NEW & NOTEWORTHY Glycogen is one of major types of fuel reserve in the body and its classical function is to maintain blood glucose level. This study uncovers that glycogen synthesis is required for beige fat tissue to generate heat upon cold exposure. Such a function of glycogen is linked to development of high-fat diet-induced obesity, thus extending our understanding about the physiological functions of glycogen.

A New Mutation of Pompe Disease in a 2-Month-Old Infant

Pompe disease, also known as type 2 glycogen storage disease (GSD), is an autosomal recessive disorder. It occurs due to the deficiency of an enzyme, acid maltase, which degrades glycogen in lysosomes. This deficiency leads to glycogen accumulation in several tissues, such as cardiac muscle cells [1]. The disease is classified into infantile and late-onset types. Infantile Pompe disease (IPD) can manifest with feeding problems, hepatomegaly, generalized muscle weakness, hypotonia, macroglossia, and hypertrophic cardiomyopathy [1-3], from the first day to weeks of life [1]. If left untreated, IPD leads to cardiorespiratory failure and death within one year. Late-onset Pompe disease (LOPD), which includes juvenile-, childhood-, and adult-onset disease, is characterized by proximal muscle weakness, respiratory muscle involvement (especially the diaphragm), and arrhythmia. The prognosis of LOPD is less severe than that of IPD [1]. Diagnosis can be made by gene sequencing of the acid alpha-glucosidase (GAA) gene and enzyme assay in dried blood, muscle, skin, and blood cells [5,6]. During pregnancy, diagnosis can also be made by amniocentesis [1]. Treatment with enzyme replacement using recombinant human acid α-glucosidase is effective. As IPD is rapidly progressive, treatment should be initiated as soon as possible. Enzyme therapy can prevent and reverse cardiac and muscle involvement [1]. According to the information the authors have about Pompe disease, in most cases, the initial signs and symptoms are common with other diseases. In these cases, genetic testing significantly helps to definitively diagnose the disease. With the progress made in genetic tests, sometimes new mutations are added to the existing genetic bank. In this case report, the authors introduce a Pompe patient with a new genetic mutation of pathogenic types. This patient had presented with signs of severe hypotonia and cardiomegaly, increased cardiac enzymes, and abnormal liver tests. Despite enzyme therapy immediately after diagnosis, the patient died.

Infantile-onset pompe disease: a case report emphasizing the role of genetic counseling and prenatal testing

BackgroundPompe disease, classified as glycogen storage disease type II, arises from a deficiency in the acid alpha-glucosidase (GAA) enzyme, leading to glycogen accumulation in multiple tissues. The unique correlation between genotype and enzyme activity is a key feature. This case highlights an infantile-onset form, emphasizing genetic counseling and prenatal testing importance.Case PresentationAn 18-week-old infant with respiratory distress, cyanosis, and fever was admitted. Born healthy, her sibling died from Pompe disease. She presented with cardiomegaly, hypotonia, and absent reflexes. Diagnosis was confirmed by significantly reduced GAA activity. Despite treatment initiation, the patient succumbed to cardiac arrest.ConclusionsThe case underscores genetic counseling’s role, offering insights into prenatal testing advancements, antenatal diagnosis through echocardiography, and the significance of early intervention, particularly in infantile-onset Pompe disease.SynopsisGenetic risk assessment and prenatal testing are crucial for families with a history of Pompe disease to improve early diagnosis and management outcomes.

Glycogen Granules Are Degraded by Non-Selective Autophagy in Nitrogen-Starved Komagataella phaffii.

Autophagy was initially recognized as a bulk degradation process that randomly sequesters and degrades cytoplasmic material in lysosomes (vacuoles in yeast). In recent years, various types of selective autophagy have been discovered. Glycophagy, the selective autophagy of glycogen granules, is one of them. While autophagy of glycogen is an important contributor to Pompe disease, which is characterized by the lysosomal accumulation of glycogen, its selectivity is still a matter of debate. Here, we developed the Komagataella phaffii yeast as a simple model of glycogen autophagy under nitrogen starvation conditions to address the question of its selectivity. For this, we turned the self-glucosylating initiator of glycogen synthesis, Glg1, which is covalently bound to glycogen, into the Glg1-GFP autophagic reporter. Our results revealed that vacuolar delivery of Glg1-GFP and its processing to free GFP were strictly dependent on autophagic machinery and vacuolar proteolysis. Notably, this process was independent of Atg11, the scaffold protein common for many selective autophagy pathways. Importantly, the non-mutated Glg1-GFP (which synthesizes and marks glycogen) and mutated Glg1Y212F-GFP (which does not synthesize glycogen and is degraded by non-selective autophagy as cytosolic Pgk1-GFP) were equally well delivered to the vacuole and had similar levels of released GFP. Therefore, we concluded that glycogen autophagy is a non-selective process in K. phaffii yeast under nitrogen starvation conditions.

Neuron–astrocyte metabolic coupling facilitates spinal plasticity and maintenance of inflammatory pain

Long-lasting pain stimuli can trigger maladaptive changes in the spinal cord, reminiscent of plasticity associated with memory formation. Metabolic coupling between astrocytes and neurons has been implicated in neuronal plasticity and memory formation in the central nervous system, but neither its involvement in pathological pain nor in spinal plasticity has been tested. Here we report a form of neuroglia signalling involving spinal astrocytic glycogen dynamics triggered by persistent noxious stimulation via upregulation of the Protein Targeting to Glycogen (PTG) in spinal astrocytes. PTG drove glycogen build-up in astrocytes, and blunting glycogen accumulation and turnover by Ptg gene deletion reduced pain-related behaviours and promoted faster recovery by shortening pain maintenance in mice. Furthermore, mechanistic analyses revealed that glycogen dynamics is a critically required process for maintenance of pain by facilitating neuronal plasticity in spinal lamina 1 neurons. In summary, our study describes a previously unappreciated mechanism of astrocyte–neuron metabolic communication through glycogen breakdown in the spinal cord that fuels spinal neuron hyperexcitability.

Effect on Endoplasmic Reticulum Stress of the Combined Oral Contraceptives in the Kidney

Objective: This study aimed to analyze the effects of combined oral contraceptive active ingredients, Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone, on liver histopathological changes and endoplasmic reticulum stress levels. Material and Methods: In the study, 37 Balb/c female mice were used. Mice were randomly divided into the Control, Sham, Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone groups. The experimental groups were administered with gavage to 8-week-old female mice for 35 days. Kidney tissue sections were applied with Hematoxylin&Eosin, Orcein, Mallory’s Azan, and Periodic Acid-Schiff to detect histopathological changes, and Chop and Grp78 were used to detect Endoplasm Reticulum Stress. Results: Significant loss of microvilli and a decrease in glycogen accumulation were observed in the apical part of some of the proximal tubules of animals in the Drospirenone and Ethinyl Estradiol+Drospirenone groups. The amount of collagen fiber stained with Mallory’s Azan increased in the parietal layer of Bowman’s capsule of the kidney tissues of the Drospirenone and Ethinyl Estradiol+Drospirenone applied groups, but no difference was observed in elastic fibers in all groups. The expression level of Grp78 and Chop proteins in the kidney tubules of female mice given Drospirenone, Ethinyl Estradiol, and Ethinyl Estradiol+Drospirenone was significantly higher compared to the control group. Conclusion: In this study, it was shown that the expression of Grp78 and Chop markers detected in the mouse kidney increased as a result of Drospirenone, Ethinyl Estradiol and Ethinyl Estradiol + Drospirenone administration, thus causing kidney cell apoptosis by inducing ER-dependent death pathway activity.

Dietary bile acids inclusion improves dietary carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass (Micropterus salmoides)

The study explored the role of dietary bile acids inclusion in improving dietary carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass (Micropterus salmoides). Two isonitrogenous (50.40%) and isolipidic (12.00%) diets were formulated, containing a positive control with 5% α-starch and a negative control with 10% α-starch, respectively. The other three diets were supplemented with 200 mg, 500 mg, or 1000 mg bile acids kg−1 based on 10% α-starch diet. Different experiment diets were fed to cultured fish twice daily for 8 weeks. The results showed that the growth of cultured fish was inhibited by high carbohydrate diet and hepatic glycogen and lipid inordinate accumulation were induced. Meanwhile, high carbohydrate diet caused liver oxidative damage, but supplementation of bile acids significantly improved the antioxidant capacity. Compared with the negative control group, dietary bile acids supplementation didn't affect the growth of largemouth bass, but significantly reduced hepatic glycogen and lipid inordinate accumulation and the viscerosomatic index and hepatosomatic index. In addition, the increase of dietary carbohydrate increased liver bile acids content, and dietary bile acids inclusion could linearly increase liver bile acids content. Results showed that bile acids supplementation regulated liver bile acid synthesis and metabolism of largemouth bass through activating FXR-FGFR4-CYP7A1 pathway. Meanwhile, bile acids inclusion inhibited the expression of foxo1 and genes related to gluconeogenesis, including g6pc, fbp1 and gs, enhanced the expression of genes related to glycolysis, including pfkl and gk through activating insulin pathway. Moreover, high carbohydrate diet with bile acids supplementation also increased gut microbial diversity, and changed the relative abundance of some phyla and genera related to carbohydrate utilization and energy balance, and improved the intestinal inflammatory response. Those findings indicated that dietary bile acids inclusion improved carbohydrate utilization, antioxidant capacity and intestinal microbiota and inflammation of largemouth bass.

Double blocking of carbon metabolism causes a large increase of Calvin-Benson cycle compounds in cyanobacteria.

Carbon-flow-regulator A (CfrA) adapts carbon flux to nitrogen conditions in nondiazotrophic cyanobacteria. Under nitrogen deficiency, CfrA leads to the storage of excess carbon, which cannot combine with nitrogen, mainly as glycogen. cfrA overexpression from the arsenite-inducible, nitrogen-independent ParsB promoter allows analysis of the metabolic effects of CfrA accumulation. Considering that the main consequence of cfrA overexpression is glycogen accumulation, we examined carbon distribution in response to cfrA expression in Synechocystis sp. PCC 6803 strains impaired in synthesizing this polymer. We carried out a comparative phenotypic analysis to evaluate cfrA overexpression in the wild-type strain and in a mutant of ADP-glucose pyrophosphorylase (ΔglgC), which is unable to synthesize glycogen. The accumulation of CfrA in the wild-type background caused a photosynthetic readjustment although growth was not affected. However, in a ΔglgC strain, growth decreased depending on CfrA accumulation and photosynthesis was severely affected. An elemental analysis of the H, C, and N content of cells revealed that cfrA expression in the wild-type caused an increase in the C/N ratio, due to decreased nitrogen assimilation. Metabolomic study indicated that these cells store sucrose and glycosylglycerol, in addition to the previously described glycogen accumulation. However, cells deficient in glycogen synthesis accumulated large amounts of Calvin-Benson cycle intermediates as cfrA was expressed. These cells also showed increased levels of some amino acids, mainly alanine, serine, valine, isoleucine, and leucine. The findings suggest that by controlling cfrA expression, in different conditions and strains, we could change the distribution of fixed carbon, with potential biotechnological benefits.

Treatment of infantile-onset Pompe disease in a rat model with muscle-directed AAV gene therapy

ObjectivePompe disease (PD) is caused by deficiency of the lysosomal enzyme acid α-glucosidase (GAA), leading to progressive glycogen accumulation and severe myopathy with progressive muscle weakness. In the Infantile-Onset PD (IOPD), death generally occurs <1 year of age. There is no cure for IOPD. Mouse models of PD do not completely reproduce human IOPD severity. Our main objective was to generate the first IOPD rat model to assess an innovative muscle-directed adeno-associated viral (AAV) vector-mediated gene therapy. MethodsPD rats were generated by CRISPR/Cas9 technology. The novel highly myotropic bioengineered capsid AAVMYO3 and an optimized muscle-specific promoter in conjunction with a transcriptional cis-regulatory element were used to achieve robust Gaa expression in the entire muscular system. Several metabolic, molecular, histopathological, and functional parameters were measured. ResultsPD rats showed early-onset widespread glycogen accumulation, hepato- and cardiomegaly, decreased body and tissue weight, severe impaired muscle function and decreased survival, closely resembling human IOPD. Treatment with AAVMYO3-Gaa vectors resulted in widespread expression of Gaa in muscle throughout the body, normalizing glycogen storage pathology, restoring muscle mass and strength, counteracting cardiomegaly and normalizing survival rate. ConclusionsThis gene therapy holds great potential to treat glycogen metabolism alterations in IOPD. Moreover, the AAV-mediated approach may be exploited for other inherited muscle diseases, which also are limited by the inefficient widespread delivery of therapeutic transgenes throughout the muscular system.

Defect in degradation of glycogenin-exposed residual glycogen in lysosomes is the fundamental pathomechanism of Pompe disease.

Pompe disease is a lysosomal storage disorder that preferentially affects muscles, and it is caused by GAA mutation coding acid alpha-glucosidase in lysosome and glycophagy deficiency. While the initial pathology of Pompe disease is glycogen accumulation in lysosomes, the special role of the lysosomal pathway in glycogen degradation is not fully understood. Hence, we investigated the characteristics of accumulated glycogen and the mechanism underlying glycophagy disturbance in Pompe disease. Skeletal muscle specimens were obtained from the affected sites of patients and mouse models with Pompe disease. Histological analysis, immunoblot analysis, immunofluorescence assay, and lysosome isolation were utilized to analyze the characteristics of accumulated glycogen. Cell culture, lentiviral infection, and the CRISPR/Cas9 approach were utilized to investigate the regulation of glycophagy accumulation. We demonstrated residual glycogen, which was distinguishable from mature glycogen by exposed glycogenin and more α-amylase resistance, accumulated in the skeletal muscle of Pompe disease. Lysosome isolation revealed glycogen-free glycogenin in wild typemouse lysosomes and variously sized glycogenin in Gaa-/- mouse lysosomes. Our study identified that a defect in the degradation of glycogenin-exposed residual glycogen in lysosomes was the fundamental pathological mechanism of Pompe disease. Meanwhile, glycogenin-exposed residual glycogen was absent in other glycogen storage diseases caused by cytoplasmic glycogenolysis deficiencies. In vitro, the generation of residual glycogen resulted from cytoplasmic glycogenolysis. Notably, the inhibition of glycogen phosphorylase led to a reduction in glycogenin-exposed residual glycogen and glycophagy accumulations in cellular models of Pompe disease. Therefore, the lysosomal hydrolysis pathway played a crucial role in the degradation of residual glycogen into glycogenin, which took place in tandem with cytoplasmic glycogenolysis. These findings may offer a novel substrate reduction therapeutic strategy for Pompe disease. © 2024 The Pathological Society of Great Britain and Ireland.

A possible case of glycogenic hepatopathy in a schoolboy with poorly controlled type 1 diabetes mellitus

Glycogenic hepatopathy (GH) is a rare condition that can occur in individuals with poorly controlled diabetes mellitus, particularly in those with type 1 diabetes mellitus(T1DM). This condition is characterised by hepatomegaly and elevated liver enzymes. GH is associated with the accumulation of glycogen in the liver, which is a result of uncontrolled hyperglycemia and excessive glycogen storage in liver cells. We present a case of a 15-year-old boy who has been diagnosed with T1DM at the age of 8 and has experienced recurrent episodes of diabetic ketoacidosis (DKA). In this specific instance, he was admitted for treatment of DKA and was also diagnosed with GH.

Real-world outcomes from a series of patients with late onset Pompe disease who switched from alglucosidase alfa to avalglucosidase alfa.

Introduction: Pompe disease is an inherited, progressive neuromuscular disorder caused by deficiency of lysosomal acid α-glucosidase and accumulation of glycogen in tissues, resulting in cellular dysfunction, muscle damage, and functional disabilities. Enzyme replacement therapy with alglucosidase alfa (Myozyme/Lumizyme) has led to better outcomes, but many patients have plateaued or declined despite treatment. The second-generation ERT avalglucosidase alfa (Nexviazyme) was designed to have enhanced cellular uptake via the conjugation of additional bis-mannose-6-phosphate residues. There have been trials comparing the efficacy of alglucosidase and avalglucosidase, but there remains a need for more real-world data on patients who switched from alglucosidase to avalglucosidase. Methods: A chart review was conducted on n = 15 patients with late-onset Pompe disease followed at a single center who switched from alglucosidase to avalglucosidase and continued for at least 6months. Results: A total of n = 8/15 patients received alglucosidase for more than 3years prior to switching, and n = 7/15 received it for more than 5years prior to switching. There were statistically significant improvements in CK, Hex4, and AST with mean differences of -104.8U/L, -3.0mmol/molCr, and -14.7U/L, respectively, post-switch. 6-Minute Walk Test; comfortable gait speed; Gait, Stairs, Gower, Chair; and Quick Motor Function Test scores improved or stabilized in most patients post-switch (n = 8/12, n = 11/12, n = 9/12, n =7/11, respectively). Of n = 7 patients with pulmonary function testing, n = 4/7 had improved upright FVC. Patient-reported outcomes revealed improvements in dyspnea (n = 4/4), physical function (n = 3/4), fatigue (n = 2/3), and lower back pain (n = 3/3). Avalglucosidase was well tolerated without infusion-associated reactions, and all n = 7 patients on home infusions continued receiving ERT at home. Anti-drug antibodies were seen in n = 9/10 of patients on alglucosidase and n = 8/13 of those on avalglucosidase, with titers below 12,800 in a majority of patients. We also present the first outcome data for a patient with LOPD who is non-ambulatory and a full-time wheelchair user; she demonstrated meaningful improvements in quality of life and motor function with the switch. Discussion: In summary, improved outcomes were seen in most patients, with a subset whose decline persisted. This study presents evidence that switching from alglucosidase to avalglucosidase may be associated with improved outcomes in certain patients with LOPD.

Epac2 activation mediates glucagon-induced glucogenesis in primary rat hepatocytes.

Glucagon plays an essential role in hepatic glucogenesis by enhancing glycogen breakdown, inducing gluconeogenesis, and suppressing glycogenesis. Moreover, glucagon increases cyclic adenosine monophosphate (cAMP) levels, thereby activating protein kinase A (PKA) and cAMP guanine nucleotide exchange factor (also known as Epac). Although the function of PKA in the liver has been studied extensively, the function of hepatic Epac is poorly understood. The aim of this study was to elucidate the role of Epac in mediating the action of glucagon on the hepatocytes. Epac mRNA and protein expression, localization, and activity in the hepatocytes were analyzed by reverse transcription polymerase chain reaction, western blotting, immunofluorescence staining, and Rap1 activity assay, respectively. Additionally, we investigated the effects of an Epac-specific activator, 8-CPT, and an Epac-specific inhibitor, ESI-05, on glycogen metabolism in isolated rat hepatocytes. Further mechanisms of glycogen metabolism were evaluated by examining glucokinase (GK) translocation and mRNA expression of gluconeogenic enzymes. Epac2, but not Epac1, was predominantly expressed in the liver. Moreover, 8-CPT inhibited glycogen accumulation and GK translocation and enhanced the mRNA expression of gluconeogenic enzymes. ESI-05 failed to reverse glucagon-induced suppression of glycogen storage and partially inhibited glucagon-induced GK translocation and the mRNA expression of gluconeogenic enzymes. Epac signaling plays a role in mediating the glucogenic action of glucagon in the hepatocytes.

Histotopographic Organization of Levator Ani Muscle in Laboratory Rats

Morphological organization of the levator ani muscle still remains unclear due to methodological problems in the study of the pelvic floor muscles. Therefore, the study of the histological structure of muscle tissue m. levator ani in animals is of not only theoretical but also practical importance for the study and modeling of pelvic floor dysfunction conditions in animal models. The aim is to study the enzymohistochemical and ultramicroscopic organization of the levator ani muscle in white laboratory rats. Material and methods. The study was performed on 10 laboratory Wistar rats (5 females and 5 males) aged 12–14 months. The metabolic profile of muscle fibers was determined using the Nachlass succinate dehydrogenase test. Imaging and linear measurements were carried out on a Leica UC 7 microscope (Germany), using its software. Ultrathin sections were counterstained with uranyl acetate and lead citrate, viewed nd photographed using a Hitachi HT 7700 Exalens (Japan) electron microscope. Results. All types of muscle fibers are present in levator ani muscle: slow fibers and rapid muscle fibers of typs IIA and IIB. It has been established that the total cross-sectional area of white type fibers is 3 times greater than the total area of other fibers. Significant sex differences were found in relative square parameters of glycolytic fibers in m. levator ani (p=0,009). At the ultrastructural level, it was found that in some muscle fibers the mitochondrial apparatus is well developed, in others, mitochondria are few in number, have smaller sizes, are located singly between myofibrils, without forming clusters. In such fibers, there are large accumulations of glycogen between the myofibrils. Conclusion. In the laboratory rat, the levator ani muscle is heterogeneous both in metabolic activity of muscle fibers and in ultrastructural organization. This feature of the muscle involves not only static work in creating intra-abdominal pressure and retaining the pelvic organs, but also isotonic contraction, acting as a synergist to ensure the movement of the tail.

Small-molecule inhibition of glycogen synthase 1 for the treatment of Pompe disease and other glycogen storage disorders.

Glycogen synthase 1 (GYS1), the rate-limiting enzyme in muscle glycogen synthesis, plays a central role in energy homeostasis and has been proposed as a therapeutic target in multiple glycogen storage diseases. Despite decades of investigation, there are no known potent, selective small-molecule inhibitors of this enzyme. Here, we report the preclinical characterization of MZ-101, a small molecule that potently inhibits GYS1 in vitro and in vivo without inhibiting GYS2, a related isoform essential for synthesizing liver glycogen. Chronic treatment with MZ-101 depleted muscle glycogen and was well tolerated in mice. Pompe disease, a glycogen storage disease caused by mutations in acid α glucosidase (GAA), results in pathological accumulation of glycogen and consequent autophagolysosomal abnormalities, metabolic dysregulation, and muscle atrophy. Enzyme replacement therapy (ERT) with recombinant GAA is the only approved treatment for Pompe disease, but it requires frequent infusions, and efficacy is limited by suboptimal skeletal muscle distribution. In a mouse model of Pompe disease, chronic oral administration of MZ-101 alone reduced glycogen buildup in skeletal muscle with comparable efficacy to ERT. In addition, treatment with MZ-101 in combination with ERT had an additive effect and could normalize muscle glycogen concentrations. Biochemical, metabolomic, and transcriptomic analyses of muscle tissue demonstrated that lowering of glycogen concentrations with MZ-101, alone or in combination with ERT, corrected the cellular pathology in this mouse model. These data suggest that substrate reduction therapy with GYS1 inhibition may be a promising therapeutic approach for Pompe disease and other glycogen storage diseases.

Prenatal EGCG consumption impacts hepatic glycogen synthesis and lipid metabolism in adult mice

In this study, the impact of prenatal exposure to Epigallocatechin gallate (EGCG) on the liver of adult offspring mice was investigated. While EGCG is known for its health benefits, its effects of prenatal exposure on the liver remain unclear. Pregnant C57BL/6 J mice were exposed to 1 mg/kg of EGCG for 16 days to assess hepatotoxicity effects of adult offspring. Transcriptomics and metabolomics were employed to elucidate the hepatotoxicity mechanisms. The findings revealed that prenatal EGCG exposure led to a decrease in liver somatic index, enhanced inflammatory responses and disrupted liver function through increased glycogen accumulation in adult mice. The integrated omics analysis revealed significant alterations in key pathways involved in liver glucose lipid metabolism, such as gluconeogenesis, dysregulation of insulin signaling, and induction of liver inflammation. Furthermore, the study found a negative correlation between the promoter methylation levels of Ppara and their mRNA levels, suggesting that EGCG could reduce hepatic lipid content through epigenetic modifications. The findings suggest that prenatal EGCG exposure can have detrimental impacts on the liver among adult individuals and emphasize the need for a comprehensive evaluation of the potential risks associated with EGCG consumption during pregnancy.

The adc1 knockout with proC overexpression in Synechocystis sp. PCC 6803 induces a diversion of acetyl-CoA to produce more polyhydroxybutyrate

BackgroundLack of nutrients, in particular nitrogen and phosphorus, has been known in the field to sense glutamate production via 2-oxoglutarate and subsequently accelerate carbon storage, including glycogen and polyhydroxybutyrate (PHB), in cyanobacteria, but a few studies have focused on arginine catabolism. In this study, we first time demonstrated that gene manipulation on proC and adc1, related to proline and polyamine syntheses in arginine catabolism, had a significant impact on enhanced PHB production during late growth phase and nutrient-modified conditions. We constructed Synechocystis sp. PCC 6803 with an overexpressing proC gene, encoding Δ1pyrroline-5-carboxylate reductase in proline production, and adc1 disruption resulted in lower polyamine synthesis.ResultsThree engineered Synechocystis sp. PCC 6803 strains, including a ProC-overexpressing strain (OXP), adc1 mutant, and an OXP strain lacking the adc1 gene (OXP/Δadc1), certainly increased the PHB accumulation under nitrogen and phosphorus deficiency. The possible advantages of single proC overexpression include improved PHB and glycogen storage in late phase of growth and long-term stress situations. However, on day 7 of treatment, the synergistic impact created by OXP/Δadc1 increased PHB synthesis by approximately 48.9% of dry cell weight, resulting in a shorter response to nutrient stress than the OXP strain. Notably, changes in proline and glutamate contents in engineered strains, in particular OXP and OXP/Δadc1, not only partially balanced the intracellular C/N metabolism but also helped cells acclimate under nitrogen (N) and phosphorus (P) stress with higher chlorophyll a content in comparison with wild-type control.ConclusionsIn Synechocystis sp. PCC 6803, overexpression of proC resulted in a striking signal to PHB and glycogen accumulation after prolonged nutrient deprivation. When combined with the adc1 disruption, there was a notable increase in PHB production, particularly in situations where there was a strong C supply and a lack of N and P.

Regulatory Role of GgaR (YegW) for Glycogen Accumulation in Escherichia coli K-12.

Glycogen, the stored form of glucose, accumulates upon growth arrest in the presence of an excess carbon source in Escherichia coli and other bacteria. Chromatin immunoprecipitation screening for the binding site of a functionally unknown GntR family transcription factor, YegW, revealed that the yegTUV operon was a single target of the E. coli genome. Although none of the genes in the yegTUV operon have a clear function, a previous study suggested their involvement in the production of ADP-glucose (ADPG), a glycogen precursor. Various validation through in vivo and in vitro experiments showed that YegW is a single-target transcription factor that acts as a repressor of yegTUV, with an intracellular concentration of consistently approximately 10 molecules, and senses ADPG as an effector. Further analysis revealed that YegW repressed glycogen accumulation in response to increased glucose concentration, which was not accompanied by changes in the growth phase. In minimal glucose medium, yegW-deficient E. coli promoted glycogen accumulation, at the expense of poor cell proliferation. We concluded that YegW is a single-target transcription factor that senses ADPG and represses glycogen accumulation in response to the amount of glucose available to the cell. We propose renaming YegW to GgaR (repressor of glycogen accumulation).