Storage and Utilization of Glycogen by Mouse Liver during Adaptation to Nutritional Changes Are GLP-1 and PASK Dependent.
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ABSTRACT:
SUBMITTER: Perez-Garcia A
PROVIDER: S-EPMC8399311 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The liver's high metabolic activity and detoxification functions generate reactive oxygen species, mainly through oxidative phosphorylation in the mitochondria of hepatocytes. In contrast, it also has a potent antioxidant mechanism for counterbalancing the oxidant's effect and relieving oxidative stress. PAS kinase (PASK) is a serine/threonine kinase containing an N-terminal Per-Arnt-Sim (PAS) domain, able to detect redox state. During fasting/feeding changes, PASK regulates the expression and activation of critical liver proteins involved in carbohydrate and lipid metabolism and mitochondrial biogenesis. Interestingly, the functional inactivation of PASK prevents the development of a high-fat diet (HFD)-induced obesity and diabetes. In addition, PASK deficiency alters the activity of other nutrient sensors, such as the AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR). In addition to the expression and subcellular localization of nicotinamide-dependent histone deacetylases (SIRTs). This review focuses on the relationship between oxidative stress, PASK, and other nutrient sensors, updating the limited knowledge on the role of PASK in the antioxidant response. We also comment on glucagon-like peptide 1 (GLP-1) and its collaboration with PASK in preventing the damage associated with hepatic oxidative stress. The current knowledge would suggest that PASK inhibition and/or exendin-4 treatment, especially under fasting conditions, could ameliorate disorders associated with excess oxidative stress.
| S-EPMC8698360 | biostudies-literature
Project description:Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.
| S-EPMC6035741 | biostudies-literature
Project description:Glycogen storage disease type I (GSDI), an inborn error of carbohydrate metabolism, is caused by defects in the glucose-6-transporter/glucose-6-phosphatase complex, which is essential in glucose homeostasis. Two types exist, GSDIa and GSDIb, each caused by different defects in the complex. GSDIa is characterized by fasting intolerance and subsequent metabolic derangements. In addition to these clinical manifestations, patients with GSDIb suffer from neutropenia with neutrophil dysfunction and inflammatory bowel disease.With the feasibility of novel cell-based therapies, including hepatocyte transplantations and liver stem cell transplantations, it is essential to consider long term outcomes of liver replacement therapy. We reviewed all GSDI patients with liver transplantation identified in literature and through personal communication with treating physicians. Our review shows that all 80 GSDI patients showed improved metabolic control and normal fasting tolerance after liver transplantation. Although some complications might be caused by disease progression, most complications seemed related to the liver transplantation procedure and subsequent immune suppression. These results highlight the potential of other therapeutic strategies, like cell-based therapies for liver replacement, which are expected to normalize liver function with a lower risk of complications of the procedure and immune suppression.
| S-EPMC4113191 | biostudies-literature
Project description:Glycogen storage disease type IV (GSD IV) is a rare autosomal recessive disorder caused by glycogen-branching enzyme (GBE) deficiency, leading to accumulation of amylopectin-like glycogen that may damage affected tissues. The clinical manifestations of GSD IV are heterogeneous; one of which is the classic manifestation of progressive hepatic fibrosis. There is no specific treatment available for GSD IV. Currently, liver transplantation is an option. It is crucial to evaluate long-term outcomes of liver transplantation. We reviewed the published literature for GSD IV patients undergoing liver transplantation. To date, some successful liver transplantations have increased the quantity and quality of life in patients. Although the extrahepatic manifestations of GSD IV may still progress after transplantation, especially cardiomyopathy. Patients with cardiac involvement are candidates for cardiac transplantation. Liver transplantation remains the only effective therapeutic option for treatment of GSD IV. However, liver transplantation may not alter the extrahepatic progression of GSD IV. Patients should be carefully assessed before liver transplantation.
| S-EPMC7933444 | biostudies-literature
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
Project description:Autophagy is an intracellular pathway that contributes to the degradation and recycling of unfolded proteins. Based on the knowledge that autophagy affects glycogen metabolism and that alpha(1)-antitrypsin (AAT) deficiency is associated with an autophagic response in the liver, we hypothesized that the conformational abnormalities of the Z-AAT protein interfere with hepatocyte glycogen storage and/or metabolism. Compared with wild-type mice (WT), the Z-AAT mice had lower liver glycogen stores (P < 0.001) and abnormal activities of glycogen-related enzymes, including acid alpha-glucosidase (P < 0.05) and the total glycogen synthase (P < 0.05). As metabolic consequences, PiZ mice demonstrated lower blood glucose levels (P < 0.05), lower body weights (P < 0.001), and lower fat pad weights (P < 0.001) compared with WT. After the stress of fasting or partial hepatectomy, PiZ mice had further reduced liver glycogen and lower blood glucose levels (both P < 0.05 compared WT). Finally, PiZ mice exhibited decreased survival after partial hepatectomy (P < 0.01 compared with WT), but this was normalized with postoperative dextrose supplementation. In conclusion, these observations are consistent with the general concept that abnormal protein conformation and degradation affects other cellular functions, suggesting that diseases in the liver might benefit from metabolic compensation if glycogen metabolism is affected.
| S-EPMC2633144 | biostudies-literature
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
Project description:IntroductionLiver Glycogen Storage Disease Type IX (GSD IX) is one of the most common forms of GSD. It is caused by a deficiency in enzyme phosphorylase kinase (PhK), a complex, hetero-tetrameric enzyme comprised of four subunits - α, β, γ, and δ - each with tissue specific isoforms encoded by different genes. Until the recent availability of gene panels and exome sequencing, the diagnosis of liver GSD IX did not allow for differentiation of these subtypes. This study presents the first comprehensive literature review for liver GSD IX subtypes - GSD IX α2, β, and γ2. We aim to better characterize the natural history of liver GSD IX and further investigate if there are subtype-specific differences in clinical presentation.MethodsA comprehensive literature review was performed with the help of a medical librarian at Duke University Medical Center to gather all published patients of liver GSD IX. Our refined search yielded 74 articles total. Available patient data were compiled into an excel spreadsheet. Data were analyzed via descriptive statistics. The number of patients with specific symptoms were individually summed and reported as a percentage of the total number of patients for which data were available or were averaged and reported as a mean numerical value. Published pathology reports were scored using the International Association of the Study of the Liver Scale.ResultsThere were a total of 183 GSD IX α2 patients, 17 GSD IX β patients, and 30 GSD IX γ2 patients. Average age at diagnosis was 4 years for GSD IX α2 patients, 2.34 years for GSD IX β patients, and 1.81 years for GSD IX γ2 patients. Hepatomegaly was reported in 164/176 (93.2%) of GSD IX α2 patients, 16/17 (94.1%) of GSD IX β patients, and 30/30 (100%) of GSD IX γ2 patients. Fasting hypoglycemia was reported in 53/121 (43.8%) of GSD IX α2 patients, 8/16 (50%) of GSD IX β patients, and 18/19 (94.7%) of GSD IX γ2 patients. Liver biopsy pathology reports were available and interpreted for 46 GSD IX α2 patients, 3 GSD IX β patients, and 24 GSD IX γ2 patients. 22/46 (47.8%) GSD IX α2 patients, 1/3 (33.3%) GSD IX β patients, and 23/24 (95.8%) GSD IX γ2 patients with available pathology reports documented either some degree of fibrosis or cirrhosis.ConclusionOur comprehensive review demonstrates quantitatively that the clinical presentation of GSD IX γ2 patients is more severe than that of GSD IX α2 or β patients. However, our study also shows the existence of a severe phenotype in GSD IX α2, evidenced by early onset liver pathology in conjunction with clinical symptoms. There is need for a more robust natural history study to better understand the variability in liver pathophysiology within liver GSD IX; in addition, further study of mutations and gene mapping could bring a better understanding of the relationship between genotype and clinical presentation.
| S-EPMC7953588 | biostudies-literature
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
2014-06-13 | GSE45319 | GEO
Project description:Mutations in the liver glycogen phosphorylase (Pygl) gene are associated with the diagnosis of glycogen storage disease type VI (GSD-VI). To understand the pathogenesis of GSD-VI, we generated a mouse model with Pygl deficiency (Pygl -/-). Pygl -/- mice exhibit hepatomegaly, excessive hepatic glycogen accumulation, and low hepatic free glucose along with lower fasting blood glucose levels and elevated blood ketone bodies. Hepatic glycogen accumulation in Pygl -/- mice increases with age. Masson's trichrome and picrosirius red staining revealed minimal to mild collagen deposition in periportal, subcapsular, and/or perisinusoidal areas in the livers of old Pygl -/- mice (>40 weeks). Consistently, immunohistochemical analysis showed the number of cells positive for alpha smooth muscle actin (?-SMA), a marker of activated hepatic stellate cells, was increased in the livers of old Pygl -/- mice compared with those of age-matched wild-type (WT) mice. Furthermore, old Pygl -/- mice had inflammatory infiltrates associated with hepatic vessels in their livers along with up-regulated hepatic messenger RNA levels of C-C chemokine ligand 5 (Ccl5/Rantes) and monocyte chemoattractant protein 1 (Mcp-1), indicating inflammation, while age-matched WT mice did not. Serum levels of aspartate aminotransferase and alanine aminotransferase were elevated in old Pygl -/- mice, indicating liver damage. Conclusion: Pygl deficiency results in progressive accumulation of hepatic glycogen with age and liver damage, inflammation, and collagen deposition, which can increase the risk of liver fibrosis. Collectively, the Pygl-deficient mouse recapitulates clinical features in patients with GSD-VI and provides a model to elucidate the mechanisms underlying hepatic complications associated with defective glycogen metabolism.
| S-EPMC6824077 | biostudies-literature