Rapid diagnosis of late-onset Pompe disease by fluorometric assay of alpha-glucosidase activities in dried blood spots

The enzymatic defect in Pompe disease is insufficient lysosomal acid alpha-glucosidase (GAA) activity which leads to lysosomal glycogen accumulation. We recently introduced a simple and reliable method to measure GAA activity in dried blood spots using Acarbose, a highly selective alpha-glucosidase inhibitor, to eliminate isoenzyme interference. Here we demonstrate that this method efficiently detects late-onset Pompe patients who are frequently misdiagnosed by conventional methods due to residual GAA activity in other tissue types.     

The glycogen synthase kinase-3β/nuclear factor-kappa B pathway is involved in cinobufagin-induced apoptosis in cultured osteosarcoma cells

Cinobufagin, a major component of cinobufacini (huachansu), is an important cardenolidal steroid. Several studies have suggested that cinobufagin has potent anti-cancer effects. The present study examines the apoptosis-inducing activity and the underlying mechanism of action of cinobufagin in osteosarcoma (OS) cells. Our results showed that cinobufagin potently inhibited the proliferation of U2OS, MG63 and SaOS-2 cells. Significant increases in G₂/M cell-cycle arrest and apoptosis in OS cells were also observed. The expression levels of several apoptotic proteins were assessed after cinobufagin treatment in U2OS cells. Among them, xIAP, cIAP-1, survivin and Bcl-2 levels decreased remarkably, while the levels of Bax and cleaved-PARP increased. Furthermore, we validated the inhibition of GSK-3β/NF-κB signaling following cinobufagin treatment. Western blots showed a decrease in nuclear p65 protein expression after exposure to different concentrations of cinobufagin, while the phosphorylation of GSK-3β was simultaneously increased. Transduction with constitutively active forms of GSK-3β could protect against the downregulation of p65 and upregulation of cleaved-PARP that are induced by cinobufagin treatment. However, combined treatment with cinobufagin and SB216367 resulted in a significant reduction in p65 and an increase in cleaved-PARP in U2OS cells. Altogether, these results show that cinobufagin is a promising agent for the treatment of OS. These studies are the first to reveal the involvement of the GSK-3β/NF-κB pathway in cinobufagin-induced apoptosis.     

Exercising with blocked muscle glycogenolysis: Adaptation in the McArdle mouse

Background

McArdle disease (glycogen storage disease type V) is an inborn error of skeletal muscle metabolism, which affects glycogen phosphorylase (myophosphorylase) activity leading to an inability to break down glycogen. Patients with McArdle disease are exercise intolerant, as muscle glycogen-derived glucose is unavailable during exercise. Metabolic adaptation to blocked muscle glycogenolysis occurs at rest in the McArdle mouse model, but only in highly glycolytic muscle. However, it is unknown what compensatory metabolic adaptations occur during exercise in McArdle disease.

Glycogen synthase kinase 3β promotes liver innate immune activation by restraining AMP-activated protein kinase activation

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Enhanced insulin-stimulated glycogen synthesis in response to insulin, metformin or rosiglitazone is associated with increased mRNA expression of GLUT4 and peroxisomal proliferator activator receptor gamma co-activator 1

Aims/hypothesis The aim of this study was to determine the effect of several antidiabetic agents on insulin-stimulated glycogen synthesis, as well as on mRNA expression.Methods Cultured primary human skeletal myotubes obtained from six healthy subjects were treated for 4 or 8 days without or with glucose (25 mmol/l), insulin (400 pmol/l), rosiglitazone (10 mol/l), metformin (20 mol/l) or the AMP-activated kinase activator 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) (200 mol/l). After this, insulin-stimulated glycogen synthesis was determined. mRNA levels of the glucose transporters GLUT1 and GLUT4, the peroxisomal proliferator activator receptor gamma (PPAR gamma) co-activator 1 (PGC1) and the myocyte-specific enhancer factors (MEF2), MEF2A, MEF2C and MEF2D were determined using real-time PCR analysis after 8 days exposure to the various antidiabetic agents.Results Insulin-stimulated glycogen synthesis was significantly increased in cultured human myotubes treated with insulin, rosiglitazone or metformin for 8 days, compared with non-treated cells. Furthermore, an 8-day exposure of myotubes to 25 mmol/l glucose impaired insulin-stimulated glycogen synthesis. In contrast, treatment with AICAR was without effect on insulin-mediated glycogen synthesis. Exposure to insulin, rosiglitazone or metformin increased mRNA expression of PGC1 and GLUT4, while AICAR or 25 mmol/l glucose treatment increased GLUT1 mRNA expression. Metformin also increased mRNA expression of the MEF2 isoforms.Conclusions/interpretation Enhanced insulin-stimulated glycogen synthesis in human skeletal muscle cell culture coincides with increased GLUT4 and PGC1 mRNA expression following treatment with various antidiabetic agents. These data show that chronic treatment of human myotubes with insulin, metformin or rosiglitazone has a direct positive effect on insulin action and mRNA expression.     

Endogenous glycogen prevents Ca2+ overload and hypercontracture in harp seal myocardial cells during simulated ischemia

The purpose of this study was to determine if elevated myocardial glycogen content could obviate Ca(2+) overload and subsequent myocardial injury in the setting of low oxygen and diminished exogenous substrate supplies. Isolated harp seal cardiomyocytes, recognized as having large glycogen stores, were incubated under conditions simulating ischemia (oxygen and substrate deprivation) for 1 h. Rat cardiomyocytes were used for comparison. Freshly isolated seal cardiomyocytes contained approximately 10 times more glycogen than those from rats (479 +/- 39 vs. 48 +/- 5 nmol glucose/mg dry weight (dry wt), mean +/- S.E., n = 6), and during ischemia lactate production was significantly greater in seal compared to rat cardiomyocytes (660 +/- 99 vs. 97 +/- 14 nmol/mg dry wt), while glycogen content decreased both in seal (from 479 +/- 39 to 315 +/- 58 nmol glucose/mg dry wt) and rat cardiomyocytes (from 48 +/- 5 to 18 +/- 5 nmol glucose/mg dry wt). Cellular ATP was well maintained in ischemic seal cardiomyocytes, whereas it showed a 65% decline (from 31 +/- 3 to 11 +/- 1 nmol ATP/mg dry wt) in rat cardiomyocytes. Similarly, total seal cardiomyocyte Ca(2+) content was not affected by ischemia, while Ca(2+) increased from 8.5 +/- 2.0 to 13.3 +/- 2.0 nmol/mg dry wt in ischemic rat myocytes. Rat cardiomyocytes also showed a notable decline in the percentage of rod-shaped cells in response to ischemia (from 66 +/- 4% to 30 +/- 3%), and cell morphology was unaffected in seal incubations. Addition of iodoacetate (IAA, an inhibitor of glycolysis) to seal cardiomyocytes, on top of substrate and oxygen deprivation, reduced the cellular content of ATP by 52.9 +/- 4.4% (from 25 +/- 4 to 11 +/- 2 nmol ATP/mg dry wt) and the percentage of rod-shaped myocytes from 51 +/- 3% to 28 +/- 4%, while total Ca(2+) content was unchanged by these conditions. Seal cardiomyocytes thus tolerate low oxygen conditions better than rat cardiomyocytes. This finding is most likely due to a higher glycolysis rate in seals, fueled by larger myocardial glycogen stores.     

糖原累积症Ⅰ型心血管受累的临床分析

目的 分析糖原累积症Ⅰ型心血管疾病损害的危险因素.方法 收集62 例糖原累积症Ⅰ型患者的临床资料,分析其心脏损害的发生率及可能诱发心血管疾病的高危因素.结果 62例患者中,女性26例,男性36例,平均年龄(8.4±6.9)岁,平均病程(6.7±6.2)年,接受治疗时间(38.3±35.2)个月.其中17.7%的患者有心电图异常,24.2%的患者超声心动图有异常发现;治疗前后患者的血总胆固醇、甘油三酯、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇和血尿酸分别为(6.18±2.47)mmol/L与(5.61±1.84)mmol/L,P=0.020;(11.17±9.85)mmol/L与(6.81±5.97)mmol/L,P=0.010;(2.55±1.27)mmol/L与(2.78±1.07)mmol/L,P=0.617;(0.98±0.37)mmol/L与(0.96±0.23)mmol/L,P=0.005;(526.53±127.09)μmol/L与(490.78±129.79)μmol/L,P=0.977.高敏C反应蛋白水平则由治疗前的(2.33±3.30)mg/L升至(3.35±3.39)mg/L,P=0.431.结论 糖原累积症Ⅰ型患者可能是心血管疾病的高危人群,应重视糖原累积症Ⅰ型引起的心血管系统受累及相关的危险因素.

Abstract：

Objective To investigate the cardiovascular risk profile in patients with glycogen storage disease (GSD) type Ⅰ.Method The clinical information of 62 patients with GSD type Ⅰ who admitted to Peking Union Medical Hospital were reviewed and the cardiovascular risk profile was analyzed.Results The age of the 26.The median disease duration was (6.7±6.2) years and treatment duration was (38.3±35.2) months. The rate of abnormal change in electrocardiogram and echocardiography was 17.7% and 24.2%, respectively. The serum concentration of total cholesterol(TC), triglyceride(TG), low-density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) and uric acid in patient before and after treatment were (6.18±2.47)mmol/L vs. (5.61±1.84)mmol/L(P=0.020),(11.17±9.85)mmol/L vs. (6.81±5.97)mmol/L(P=0.010),(2.55±1.27)mmol/L vs. (2.78±1.07)mmol/L(P=0.617),(0.98±0.37)mmol/L vs. (0.96±0.23)mmol/L(P=0.005),(526.53±127.09)μmol/L vs. (490.78±129.79)μmol/L(P=0.977), respectively. The high-sensitivity C-reactive protein levels tended to be higher after therapy compared before treatment (2.33±3.30)mg/L vs. (3.35±3.39)mg/L, P=0.431.Conclusion Patients with GSD Ⅰ are associated with an increased risk for cardiovascular disease.     

Type I glycogen storage disease: Kidney involvement,pathogenesis and its treatment

Type I glycogen storage disease (GSD-I) is due to the deficiency of glucose-6-phosphatase activity in the liver, kidney and intestine. Although kidney enlargement occurs in GSD-I, renal disease has not been considered a major problem until recently. In older patients (more than 20 years of age) whose GSD-I disease has been ineffectively treated, virtually all have disturbed renal function, manifested by persistent proteinuria; many also have hypertension, renal stones, altered creatinine clearance or a progressive renal insufficiency. Glomerular hyperfiltration is seen in the early stage of the renal dysfunction and can occur before proteinuria. In younger GSD-I patients, the hyperfiltration is usually the only renal abnormality found; and, in some patients, microalbuminuria develops before clinical proteinuria. The predominant underlying renal pathology is focal segmental glomerulosclerosis. Renal stones and/or nephrocalcinosis are also common findings. Amyloidosis and Fanconi-like syndrome can occur, but rarely. The risk factors for developing the glomerulosclerosis in GSD-I include hyperfiltration, hypertension, hyperlipidemia and hyperuricemia. Dietary therapy with cornstarch and/or nasogastric infusion of glucose, aimed at maintaining normoglycemia, corrects metabolic abnormalities and improves the proximal renal tubular function. Long-term trial will be needed to assess whether the dietary therapy may prevent the evolution or the progression of the renal disease.     

Regulation of glycogen content in rat pineal gland by norepinephrine

In the rat pineal gland the glycogen stores were cytochemically localized in astrocytes and pinealocytes. Moreover, it was found that norepinephrine (NE) induced a time- and concentration-dependent reduction in pineal glycogen content and yielded lactic acid. The NE effect was prevented by blocking ₁- but not ₂ or β-adrenoceptors. Activation of ₂-adrenoceptors induced a small decrease in glycogen levels that could have pre- and postsynaptic components. Activation of β-adrenoceptors with 10⁻¹²–10⁻³ M isoproterenol (ISO) induced a bell shape concentration-response curve, presumably due to desensitization, since the response induced by 10⁻⁴ M ISO was greater with shorter period of stimulation. On the other hand, activation of ₁-adrenoceptors with 10⁻¹²–10⁻³ M phenylephrine (PHN) induced a hyperbolic concentration-response curve with a maximum at concentrations above 10⁻⁸ M. Moreover, treatment with ISO drastically reduced the response induced by PHN concentrations lower but not higher than 10⁻⁶ M, favoring a concentration-dependent response between 10⁻⁶ and 10⁻⁴ M PHN, similar to that induced by equimolar NE concentrations. Thus, the NE-induced reduction in glycogen content of the rat pineal gland is mainly mediated by ₁-adrenoceptors and modulated by intracellular mechanisms activated by β-adrenoceptors.     

A complex rearrangement in GBE1 causes both perinatal hypoglycemic collapse and late-juvenile-onset neuromuscular degeneration in glycogen storage disease type IV of Norwegian forest cats

Deficiency of glycogen branching enzyme (GBE) activity causes glycogen storage disease type IV (GSD IV), an autosomal recessive error of metabolism. Abnormal glycogen accumulates in myocytes, hepatocytes, and neurons, causing variably progressive, benign to lethal organ dysfunctions. A naturally occurring orthologue of human GSD IV was described previously in Norwegian forest cats (NFC). Here, we report that while most affected kittens die at or soon after birth, presumably due to hypoglycemia, survivors of the perinatal period appear clinically normal until onset of progressive neuromuscular degeneration at 5 months of age. Molecular investigation of affected cats revealed abnormally spliced GBE1 mRNA products and lack of GBE cross-reactive material in liver and muscle. Affected cats are homozygous for a complex rearrangement of genomic DNA in GBE1, constituted by a 334 bp insertion at the site of a 6.2 kb deletion that extends from intron 11 to intron 12 (g. IVS11+1552_IVS12-1339 del6.2kb ins334 bp), removing exon 12. An allele-specific, PCR-based test demonstrates that the rearrangement segregates with the disease in the GSD IV kindred and is not found in unrelated normal cats. Screening of 402 privately owned NFC revealed 58 carriers and 4 affected cats. The molecular characterization of feline GSD IV will enhance further studies of GSD IV pathophysiology and development of novel therapies in this unique animal model.