Glucose-6-phosphatase deficiency

Glucose-6-phosphatase deficiency (G6P deficiency), or glycogen storage disease type I (GSDI), is a group of inherited metabolic diseases, including types Ia and Ib, characterized by poor tolerance to fasting, growth retardation and hepatomegaly resulting from accumulation of glycogen and fat in the liver. Prevalence is unknown and annual incidence is around 1/100,000 births. GSDIa is the more frequent type, representing about 80% of GSDI patients. The disease commonly manifests, between the ages of 3 to 4 months by symptoms of hypoglycemia (tremors, seizures, cyanosis, apnea). Patients have poor tolerance to fasting, marked hepatomegaly, growth retardation (small stature and delayed puberty), generally improved by an appropriate diet, osteopenia and sometimes osteoporosis, full-cheeked round face, enlarged kydneys and platelet dysfunctions leading to frequent epistaxis. In addition, in GSDIb, neutropenia and neutrophil dysfunction are responsible for tendency towards infections, relapsing aphtous gingivostomatitis, and inflammatory bowel disease. Late complications are hepatic (adenomas with rare but possible transformation into hepatocarcinoma) and renal (glomerular hyperfiltration leading to proteinuria and sometimes to renal insufficiency). GSDI is caused by a dysfunction in the G6P system, a key step in the regulation of glycemia. The deficit concerns the catalytic subunit G6P-alpha (type Ia) which is restricted to expression in the liver, kidney and intestine, or the ubiquitously expressed G6P transporter (type Ib). Mutations in the genes G6PC (17q21) and SLC37A4 (11q23) respectively cause GSDIa and Ib. Many mutations have been identified in both genes,. Transmission is autosomal recessive. Diagnosis is based on clinical presentation, on abnormal basal values and absence of hyperglycemic response to glucagon. It can be confirmed by demonstrating a deficient activity of a G6P system component in a liver biopsy. To date, the diagnosis is most commonly confirmed by G6PC (GSDIa) or SLC37A4 (GSDIb) gene analysis, and the indications of liver biopsy to measure G6P activity are getting rarer and rarer. Differential diagnoses include the other GSDs, in particular type III (see this term). However, in GSDIII, glycemia and lactacidemia are high after a meal and low after a fast period (often with a later occurrence than that of type I). Primary liver tumors and Pepper syndrome (hepatic metastases of neuroblastoma) may be evoked but are easily ruled out through clinical and ultrasound data. Antenatal diagnosis is possible through molecular analysis of amniocytes or chorionic villous cells. Pre-implantatory genetic diagnosis may also be discussed. Genetic counseling should be offered to patients and their families. The dietary treatment aims at avoiding hypoglycemia (frequent meals, nocturnal enteral feeding through a nasogastric tube, and later oral addition of uncooked starch) and acidosis (restricted fructose and galactose intake). Liver transplantation, performed on the basis of poor metabolic control and/or hepatocarcinoma, corrects hypoglycemia, but renal involvement may continue to progress and neutropenia is not always corrected in type Ib. Kidney transplantation can be performed in case of severe renal insufficiency. Combined liver-kidney grafts have been performed in a few cases. Prognosis is usually good: late hepatic and renal complications may occur, however, with adapted management, patients have almost normal life span

Glucose-6-phosphatase deficiency

Glucose-6-phosphatase deficiency (G6P deficiency), or glycogen storage disease type I (GSDI), is a group of inherited metabolic diseases, including types Ia and Ib, characterized by poor tolerance to fasting, growth retardation and hepatomegaly resulting from accumulation of glycogen and fat in the liver. Prevalence is unknown and annual incidence is around 1/100,000 births. GSDIa is the more frequent type, representing about 80% of GSDI patients. The disease commonly manifests, between the ages of 3 to 4 months by symptoms of hypoglycemia (tremors, seizures, cyanosis, apnea). Patients have poor tolerance to fasting, marked hepatomegaly, growth retardation (small stature and delayed puberty), generally improved by an appropriate diet, osteopenia and sometimes osteoporosis, full-cheeked round face, enlarged kydneys and platelet dysfunctions leading to frequent epistaxis. In addition, in GSDIb, neutropenia and neutrophil dysfunction are responsible for tendency towards infections, relapsing aphtous gingivostomatitis, and inflammatory bowel disease. Late complications are hepatic (adenomas with rare but possible transformation into hepatocarcinoma) and renal (glomerular hyperfiltration leading to proteinuria and sometimes to renal insufficiency). GSDI is caused by a dysfunction in the G6P system, a key step in the regulation of glycemia. The deficit concerns the catalytic subunit G6P-alpha (type Ia) which is restricted to expression in the liver, kidney and intestine, or the ubiquitously expressed G6P transporter (type Ib). Mutations in the genes G6PC (17q21) and SLC37A4 (11q23) respectively cause GSDIa and Ib. Many mutations have been identified in both genes,. Transmission is autosomal recessive. Diagnosis is based on clinical presentation, on abnormal basal values and absence of hyperglycemic response to glucagon. It can be confirmed by demonstrating a deficient activity of a G6P system component in a liver biopsy. To date, the diagnosis is most commonly confirmed by G6PC (GSDIa) or SLC37A4 (GSDIb) gene analysis, and the indications of liver biopsy to measure G6P activity are getting rarer and rarer. Differential diagnoses include the other GSDs, in particular type III (see this term). However, in GSDIII, glycemia and lactacidemia are high after a meal and low after a fast period (often with a later occurrence than that of type I). Primary liver tumors and Pepper syndrome (hepatic metastases of neuroblastoma) may be evoked but are easily ruled out through clinical and ultrasound data. Antenatal diagnosis is possible through molecular analysis of amniocytes or chorionic villous cells. Pre-implantatory genetic diagnosis may also be discussed. Genetic counseling should be offered to patients and their families. The dietary treatment aims at avoiding hypoglycemia (frequent meals, nocturnal enteral feeding through a nasogastric tube, and later oral addition of uncooked starch) and acidosis (restricted fructose and galactose intake). Liver transplantation, performed on the basis of poor metabolic control and/or hepatocarcinoma, corrects hypoglycemia, but renal involvement may continue to progress and neutropenia is not always corrected in type Ib. Kidney transplantation can be performed in case of severe renal insufficiency. Combined liver-kidney grafts have been performed in a few cases. Prognosis is usually good: late hepatic and renal complications may occur, however, with adapted management, patients have almost normal life span

TNF-α- and tumor-induced skeletal muscle atrophy involves sphingolipid metabolism

Additional filesInternational audienceUNLABELLED: ABSTRACT: BACKGROUND: Muscle atrophy associated with various pathophysiological conditions represents a major health problem, because of its contribution to the deterioration of patient status and its effect on mortality. Although the involvement of pro-inflammatory cytokines in this process is well recognized, the role of sphingolipid metabolism alterations induced by the cytokines has received little attention. RESULTS: We addressed this question both in vitro using differentiated myotubes treated with TNF-α, and in vivo in a murine model of tumor-induced cachexia. Myotube atrophy induced by TNF-α was accompanied by a substantial increase in cell ceramide levels, and could be mimicked by the addition of exogenous ceramides. It could be prevented by the addition of ceramide-synthesis inhibitors that targeted either the de novo pathway (myriocin), or the sphingomyelinases (GW4869 and 3-O-methylsphingomyelin). In the presence of TNF-α, ceramide-synthesis inhibitors significantly increased protein synthesis and decreased proteolysis. In parallel, they lowered the expression of both the Atrogin-1 and LC3b genes, involved in muscle protein degradation by proteasome and in autophagic proteolysis, respectively, and increased the proportion of inactive, phosphorylated Foxo3 transcription factor. Furthermore, these inhibitors increased the expression and/or phosphorylation levels of key factors regulating protein metabolism, including phospholipase D, an activator of mammalian target of rapamycin (mTOR), and the mTOR substrates S6K1 and Akt. In vivo, C26 carcinoma implantation induced a substantial increase in muscle ceramide, together with drastic muscle atrophy. Treatment of the animals with myriocin reduced the expression of the atrogenes Foxo3 and Atrogin-1, and partially protected muscle tissue from atrophy. CONCLUSIONS: Ceramide accumulation induced by TNF-α or tumor development participates in the mechanism of muscle-cell atrophy, and sphingolipid metabolism is a logical target for pharmacological or nutritional interventions aiming at preserving muscle mass in pathological situations

Острый рабдомиолиз

Rhabdomyolysis results from the rapid breakdown of skeletal muscle fibers, which leads to leakage of potentially toxic cellular contents into the systemic circulation. Acquired causes by direct injury to the sarcolemma are the most frequent. The inherited causes are: metabolic with failure of energy production, including mitochondrial fatty acid ß-oxidation defects, LPIN1 mutations, inborn errors of glycogenolysis and glycolysis, more rarely mitochondrial respiratory chain deficiency, purine defects and peroxysomalα-Methylacyl-CoA-racemase defect (AMACR); dystrophinopathies and myopathies; calcic causes with RYR1 mutations; inflammatory with myositis. Irrespective of the cause of rhabdomyolysis, the pathophysiologic events follow a common pathway, the ATP depletion leading to an increased intracellular calcium concentration and necrosis. Most episodes of rhabdomyolysis are triggered by an environmental stress, mostly fever. This condition is associated with two events, elevated temperature and high circulating levels of pro-inflammatory mediators such as cytokines and chemokines. We describe here an example of rhabdomyolysis related to high temperature, aldolase deficiency, in 3 siblings with episodic rhabdomyolysis without hemolytic anemia. Myoglobinuria was always triggered by febrile illnesses. We show that the underlying mechanism involves an exacerbation of aldolase A deficiency at high temperatures that affected myoblasts but not erythrocytes. Thermolability was enhanced in patient myoblasts compared to control. The aldolase A deficiency was rescued by arginine supplementation in vitro. Lipid droplets accumulated in patient myoblasts relative to control and this was increased by cytokines. Lipotoxicity may participate to myolysis. Our results expand the clinical spectrum of aldolase A deficiency to isolated temperature-dependent rhabdomyolysis, and suggest that thermolability may be tissue specific. We also propose a treatment for this severe disease. Some other diseases involved in rhabdomyolysis may implicate pro-inflammatory cytokines and may be proinflammatory diseases.Острый рабдомиолиз – драматичное внезапное разрушение мышечных волокон скелетных мышц. К генетическим этиологическим факторам относят: метаболические расстройства, сопровождаемые дефицитом окисления жирных кислот, дефицитом липина-1, аномалии гликогенолиза и гликолиза, реже – дефицит митохондриальной дыхательной цепи, дефицит пурина и пероксизмальный дефицит α-метил-ацил-КоА-рацемазы (α-methyl-acyl-CoA-acemase, AMACR); структурные патологии в рамках дистрофинопатий и миопатий; аномалии кальциевого обмена с мутациями в гене RYR1; воспалительные реакции, ассоциированные с миозитом. Независимо от причины, дефицит аденозинтрифосфата в миоците приводит к повышению содержания внутриклеточного кальция и некрозу мышечных волокон. Провоцирующим фактором рабдомиолиза могут быть экзогенные факторы, среди которых травматизация мышц является самой частой причиной рабдомиолиза метаболического генеза. В случае лихорадки следует учитывать 2 фактора: повышение температуры тела и существование провоспалительных цитокинов. В статье описан случай рабдомиолиза у 3 детей от близкородственного брака, спровоцированный гипертермией и вызванный дефицитом альдолазы А, не сопровождаемой гемолитической анемией. В рассматриваемом случае миоглобинурия была всегда вызвана фебрильной температурой. В свою очередь, фермент альдолаза-А обладает тканеспецифичной термолабильностью: при тестируемых температурах он обнаружен в миобластах, но не в эритроцитах, что объясняет специфическую симптоматику у описываемых пациентов. Существуют предположения, что в клеточной липотоксичности участвуют так называемые жировые капли. В ходе исследований in vitro дефицит альдолазы А был возмещен добавлением аргинина. Другие типы рабдомиолиза метаболического генеза, вероятно, являются провоспалительными заболеваниями.перевод: Мария Олеговна Ковальчу

Cerebral Changes Occurring in Arginase and Dimethylarginine Dimethylaminohydrolase (DDAH) in a Rat Model of Sleeping Sickness

Involvement of nitric oxide (NO) in the pathophysiology of human African trypanosomiasis (HAT) was analyzed in a HAT animal model (rat infected with Trypanosoma brucei brucei). With this model, it was previously reported that trypanosomes were capable of limiting trypanocidal properties carried by NO by decreasing its blood concentration. It was also observed that brain NO concentration, contrary to blood, increases throughout the infection process. The present approach analyses the brain impairments occurring in the regulations exerted by arginase and N(G), N(G)-dimethylarginine dimethylaminohydrolase (DDAH) on NO Synthases (NOS). In this respect: (i) cerebral enzymatic activities, mRNA and protein expression of arginase and DDAH were determined; (ii) immunohistochemical distribution and morphometric parameters of cells expressing DDAH-1 and DDAH-2 isoforms were examined within the diencephalon; (iii) amino acid profiles relating to NOS/arginase/DDAH pathways were established.Arginase and DDAH activities together with mRNA (RT-PCR) and protein (western-blot) expressions were determined in diencephalic brain structures of healthy or infected rats at various days post-infection (D5, D10, D16, D22). While arginase activity remained constant, that of DDAH increased at D10 (+65%) and D16 (+51%) in agreement with western-blot and amino acids data (liquid chromatography tandem-mass spectrometry). Only DDAH-2 isoform appeared to be up-regulated at the transcriptional level throughout the infection process. Immunohistochemical staining further revealed that DDAH-1 and DDAH-2 are contained within interneurons and neurons, respectively.In the brain of infected animals, the lack of change observed in arginase activity indicates that polyamine production is not enhanced. Increases in DDAH-2 isoform may contribute to the overproduction of NO. These changes are at variance with those reported in the periphery. As a whole, the above processes may ensure additive protection against trypanosome entry into the brain, i.e., maintenance of NO trypanocidal pressure and limitation of polyamine production, necessary for trypanosome growth

Dosage du globotriaosylcéramide dans l’urine

La maladie de Fabry est une maladie de surchargedue à un déficit de l’α-galactosidase A.Un traitement par enzyme de substitution estdésormais possible. Le dosage du globotriaosylcéramidedans l’urine peut être effectué parspectrométrie de masse en tandem (MS/MS).Cette technique, particulièrement sensible etspécifique, est décrite, ainsi que les résultatschez des patients atteints, des femmes hétérozygoteset des malades traités par enzyme desubstitution

Fast urinary screening of oligosaccharidoses by MALDI-TOF/TOF mass spectrometry.

International audienceBACKGROUND: Oligosaccharidoses, which belong to the lysosomal storage diseases, are inherited metabolic disorders due to the absence or the loss of function of one of the enzymes involved in the catabolic pathway of glycoproteins and indirectly of glycosphingolipids. This enzymatic deficiency typically results in the abnormal accumulation of uncompletely degraded oligosaccharides in the urine. Since the clinical features of many of these disorders are not specific for a single enzyme deficiency, unambiguous screening is critical to limit the number of costly enzyme assays which otherwise must be performed. METHODS: Here we provide evidence for the advantages of using a MALDI-TOF/TOF (matrix-assisted laser desorption ionization time-of-flight) mass spectrometric (MS) method for screening oligosaccharidoses. Urine samples from previously diagnosed patients or from unaffected subjects were randomly divided into a training set and a blind testing set. Samples were directly analyzed without prior treatment. RESULTS: The characteristic MS and MS/MS molecular profiles obtained allowed us to identify fucosidosis, aspartylglucosaminuria, GM1 gangliosidosis, Sandhoff disease, α-mannosidosis, sialidosis and mucolipidoses type II and III. CONCLUSIONS: This method, which is easily run in less than 30 minutes, is performed in a single step, and is sensitive and specific. Invaluable for clinical chemistry purposes this MALDI-TOF/TOF mass spectrometry procedure is semi-automatizable and suitable for the urinary screening of oligosacharidoses