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Age-related augmentation of phosphorylase b kinase in hepatic tissue from the glycogen-storage-disease (gsd/gsd) rat.

ABSTRACT: The effects of food deprivation on body weight, liver weight, hepatic glycogen content, glycogenolytic enzymes and blood metabolites were compared in young and old phosphorylase b kinase-deficient (gsd/gsd) rats. Although the concentration of glycogen in liver from 9-week-old female gsd/gsd rats (730 mumol of glucose equivalents/g wet wt.) was increased by 7-8% during starvation, total hepatic glycogen was decreased by 12% after 24 h without food. In 12-month-old male gsd/gsd rats the concentration of liver glycogen (585 mumol of glucose equiv./g wet wt.) was decreased by 16% and total hepatic glycogen by nearly 40% after food deprivation for 24 h. Phosphorylase b kinase and phosphorylase a were present at approx. 10% of the control activities in 9-week-old gsd/gsd rats, but both enzyme activities were increased more than 3-fold in 12-month-old affected rodents. It is concluded that the age-related ability to mobilize hepatic glycogen appears to result from the augmentation of phosphorylase b kinase during maturation of the gsd/gsd rat.

SUBMITTER: Clark DG

PROVIDER: S-EPMC1147208 | biostudies-other | 1986 Sep

REPOSITORIES: biostudies-other

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Activation of hepatic glycogen phosphorylase b in vivo by sodium sulphate in normal (Wistar) and phosphorylase b kinase-deficient (gsd/gsd) rats.

Project description:Sulphate ions have been known for some years to enhance the activity of hepatic glycogen phosphorylase b in vitro. Here we report that intravenous injections of 4.92 mmol of Na2SO4/kg body wt. to rats induced marked hepatic glycogenolysis in vivo, accompanied by polyuria, glycosuria and a mild hyperglycaemia. These effects were observed both in normal (Wistar) rats and in gsd/gsd rats that lacked hepatic phosphorylase kinase. In both rat strains the activity of glycogen phosphorylase in liver extracts was enhanced by pretreatment of the animals with Na2SO4, but in phosphorylase kinase-deficient livers the enhancement was solely in phosphorylase b activity, whereas both the a and b forms of the enzyme were activated in normal livers. Hepatic glycogenolysis was also induced by perfusing rat livers, both normal and gsd/gsd, with 25 mM-Na2SO4. Under these conditions both the rat strains showed only enhanced activities of glycogen phosphorylase b. This suggested that the increased activity of phosphorylase a in the extracts of normal livers after Na2SO4 administration in vivo was due to a hormonally mediated conversion of the b form into the a form. The activation of glycogen phosphorylase b was stable to dilution and appeared to be due to a long-lasting structural change in the enzyme or very tight binding of an activator.

| S-EPMC1147309 | biostudies-other

Hepatic carbon flux after re-feeding in the glycogen-storage-disease (gsd/gsd) rat.

Project description:In this study we utilized the phosphorylase b kinase-deficient (gsd/gsd) rat as a model of hepatic substrate utilization where there is a constraint on glycogenesis imposed by the maintenance of high glycogen concentrations. Glucose re-feeding of 48 h-starved gsd/gsd rats led to suppression of hepatic glucose output. In contrast with the situation in normal rats, activation of the pyruvate dehydrogenase complex and lipogenesis was observed. It is suggested that impeding glycogenic flux may divert substrate into lipogenesis, possibly via activation of the pyruvate dehydrogenase complex.

| S-EPMC1148646 | biostudies-other

Hormonal regulation of L-type pyruvate kinase in hepatocytes from phosphorylase kinase-deficient (gsd/gsd) rats.

Project description:The hormonal regulation of L-type pyruvate kinase in hepatocytes from phosphorylase b kinase-deficient (gsd/gsd) rats was investigated. Adrenaline (10 microM) and glucagon (10 nM) each led to an inactivation and phosphorylation of pyruvate kinase. Dose-response curves for adrenaline-mediated inactivation of pyruvate kinase, phosphorylation of pyruvate kinase and the stimulation of gluconeogenesis from 1.8 mM-lactate were similar for hepatocytes from control and gsd/gsd rats. Time-course studies indicated that adrenaline-mediated inactivation and phosphorylation of pyruvate kinase proceeded more slowly in phosphorylase kinase-deficient hepatocytes than in control hepatocytes. The age-dependent change in the adrenergic control of pyruvate kinase was similar between control and phosphorylase kinase-deficient hepatocytes. Adrenaline, glucagon and noradrenaline activated the cyclic AMP-dependent protein kinase and inhibited pyruvate kinase in phosphorylase kinase-deficient hepatocytes. Vasopressin (0.2-2 nM), angiotensin (10nM) and A23187 (10 microM) had no effect on the activity ratio of the cyclic AMP-dependent protein kinase or pyruvate kinase in these cells. It is concluded that phosphorylase kinase plays no significant role in the hormonal control of pyruvate kinase and that phosphorylation and inactivation of this enzyme results predominantly from the action of the cyclic AMP-dependent protein kinase.

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Effects in vivo of food deprivation and 3-mercaptopicolinate in the glycogen-storage-disease (gsd/gsd) rat.

Project description:Intraperitoneal injection of 3-mercaptopicolinate into 24 h-food-deprived 27-week-old female control (GSD/GSD) rats lowered the concentration of circulating glucose by 66%, but glycerol and lactate concentrations were increased up to 3- and 4-fold respectively. In phosphorylase b kinase-deficient (gsd/gsd) rats the corresponding changes for blood glucose, lactate and glycerol were half those observed in the controls. Although the concentration of liver glycogen (approx. 12%, w/w) in the gsd/gsd rats was not altered during food deprivation, total hepatic glycogen was decreased by 17%. It is suggested that the gradual breakdown of the extensive hepatic glycogen stores during starvation assists in the maintenance of normoglycaemia in the gsd/gsd rat.

| S-EPMC1152812 | biostudies-other

Glycogen-storage disease in rats, a genetically determined deficiency of liver phosphorylase kinase.

Project description:Rats from an inbred strain (NZR/Mh) were found to have high concentrations of glycogen in their livers, even after 24 h of starvation. Despite this, blood glucose concentrations were well maintained on starvation for up to 72 h. The primary defect is a deficiency of liver phosphorylase kinase, causing a lack of active glycogen phosphorylase, although total phosphorylase is normal. The intravenous injection of glucagon caused a rapid activation of cyclic AMP-dependent protein kinase in the liver, but no increase in either phosphorylase kinase or phosphorylase a activity. Although total glycogen synthase activity in the livers of affected rats was higher than normal, glycogen synthase in the active form was very low, presumably as a result of the high liver glycogen content. The condition is transmitted as autosomal recessive and, apart from hepatomegaly, the affected rats appear healthy.

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Glycogen storage diseases with liver involvement: a literature review of GSD type 0, IV, VI, IX and XI.

Project description:BackgroundGlycogen storage diseases (GSDs) with liver involvement are classified into types 0, I, III, IV, VI, IX and XI, depending on the affected enzyme. Hypoglycemia and hepatomegaly are hallmarks of disease, but muscular and renal tubular involvement, dyslipidemia and osteopenia can develop. Considering the paucity of literature available, herein we provide a narrative review of these latter forms of GSDs.Main bodyDiagnosis is based on clinical manifestations and laboratory test results, but molecular analysis is often necessary to distinguish the various forms, whose presentation can be similar. Compared to GSD type I and III, which are characterized by a more severe impact on metabolic and glycemic homeostasis, GSD type 0, VI, IX and XI are usually known to be responsive to the nutritional treatment for achieving a balanced metabolic homeostasis in the pediatric age. However, some patients can exhibit a more severe phenotype and an important progression of the liver and muscular disease. The effects of dietary adjustments in GSD type IV are encouraging, but data are limited.ConclusionsEarly diagnosis allows a good metabolic control, with improvement of quality of life and prognosis, therefore we underline the importance of building a proper knowledge among physicians about these rare conditions. Regular monitoring is necessary to restrain disease progression and complications.

| S-EPMC9208159 | biostudies-literature

Alpha 1-Adrenergic stimulation of Ca2+ mobilization without phosphorylase activation in hepatocytes from phosphorylase b kinase-deficient gsd/gsd rats.

Project description:Phenylephrine, vasopressin and the bivalent cation ionophore A23187 mobilized Ca2+ normally, but failed to activate phosphorylase, in hepatocytes from gsd/gsd rats with a deficiency of liver phosphorylase b kinase. These data provide strong evidence that phosphorylase b kinase is the site of action of the Ca2+ mobilized intracellularly during alpha 1-adrenergic activation of phosphorylase in liver cells.

| S-EPMC1163259 | biostudies-other

Fenofibrate rapidly decreases hepatic lipid and glycogen storage in neonatal mice with glycogen storage disease type Ia.

Project description:Glycogen storage disease type Ia (GSD Ia) is caused by autosomal mutations in glucose-6-phosphatase ? catalytic subunit (G6PC) and can present with severe hypoglycemia, lactic acidosis and hypertriglyceridemia. In both children and adults with GSD Ia, there is over-accumulation of hepatic glycogen and triglycerides that can lead to steatohepatitis and a risk for hepatocellular adenoma or carcinoma. Here, we examined the effects of the commonly used peroxisomal proliferated activated receptor ? agonist, fenofibrate, on liver and kidney autophagy and lipid metabolism in 5-day-old G6pc -/- mice serving as a model of neonatal GSD Ia. Five-day administration of fenofibrate decreased the elevated hepatic and renal triglyceride and hepatic glycogen levels found in control G6pc -/- mice. Fenofibrate also induced autophagy and promoted ?-oxidation of fatty acids and stimulated gene expression of acyl-CoA dehydrogenases in the liver. These findings show that fenofibrate can rapidly decrease hepatic glycogen and triglyceride levels and renal triglyceride levels in neonatal G6pc -/- mice. Moreover, since fenofibrate is an FDA-approved drug that has an excellent safety profile, our findings suggest that fenofibrate could be a potential pharmacological therapy for GSD Ia in neonatal and pediatric patients as well as for adults. These findings may also apply to non-alcoholic fatty liver disease, which shares similar pathological and metabolic changes with GSD Ia.

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Liver Glycogen Phosphorylase Deficiency Leads to Profibrogenic Phenotype in a Murine Model of Glycogen Storage Disease Type VI.

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.

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Project description:The selective phosphorylation of glycogen phosphorylase (GP) by its only known kinase, phosphorylase kinase (PhK), keeps glycogen catabolism tightly regulated. In addition to the obligatory interaction between the catalytic γ subunit of PhK and the phosphorylatable region of GP, previous studies have suggested additional sites of interaction between this kinase and its protein substrate. Using short chemical crosslinkers, we have identified direct interactions of GP with the large regulatory α and β subunits of PhK. These newfound interactions were found to be sensitive to ligands that bind PhK.

| S-EPMC5195864 | biostudies-literature

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