A newborn with severe liver failure, cardiomyopathy and transaldolase deficiency

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Liver Disease and Risk of Hepatocellular Carcinoma in Children With Mutations in TALDO1

Mutations in the transaldolase 1 (TALDO1) gene have been described in a limited number of cases. Several organs can be affected and clinical manifestations are variable, but often include liver dysfunction and/or hepatosplenomegaly. We report 4 patients presenting with liver disease: 2 with early-onset hepatocellular carcinoma (HCC). Patients with cholestasis and mutations in TALDO1 were identified by next-generation sequencing. Clinical, laboratory, and histological data were collected. Four (1 male) patients were identified with variants predicted to be damaging in TALDO1. Three patients were homozygous (two protein truncating/one missense mutations), 1 one was compound heterozygous (two missense mutations). Median age at presentation was 4 months (range, 2-210 days) with jaundice (3), hepatosplenomegaly (3), and pancytopaenia (1). The diagnosis was corroborated by detection of minimal transaldolase enzyme activity in skin fibroblasts in two cases and raised urine polyols in the third. Three patients underwent liver transplantation (LT), 2 of whom had confirmed HCC on explanted liver. One patient suddenly died shortly after LT. The nontransplanted case has a chronic liver disease with multiple dysplastic liver nodules, but normal liver biochemistry and alpha-fetoprotein. Median follow-up was 4 years (range, 1-21). Conclusion: Transaldolase deficiency can include early-onset normal gamma-glutamyltransferase liver disease with multisystem involvement and variable progression. Patients with this disease are at risk of early-onset HCC and may require early LT.

Prenatal Diagnosis of Fetus With Transaldolase Deficiency Identifies Compound Heterozygous Variants: A Case Report

Transaldolase (TALDO) deficiency is a rare autosomal recessive disorder caused by variants in the TALDO1 gene that commonly results in multisystem dysfunction. Herein, we reported compound heterozygous variants in a Chinese prenatal case with TALDO deficiency using whole-exome sequencing (WES) for trios and Sanger sequencing. The heterozygous variants were located on the TALDO1 gene: NM_006755.2:c.574C > T(Chr11:g.763456C > T), a missense variant in exon 5 paternally inherited; NM_006755.2:c.462-2A > G(Chr11:g.763342A > G), a splicing aberration in intron 4 maternally inherited. The qualitative analysis of urinary polyols in neonatal urine indicated that xylitol + arabitol and ribitol in the proband’s urine were significantly increased. These findings expand the variation spectrum of the TALDO1 gene, provide solid evidence for the counseling of the family in regard to future pregnancies, strongly support the application of WES in prenatal diagnosis, and further prove that effective postpartum treatments could improve prognosis.

Hypergonadotrophic hypogonadism in a patient with transaldolase deficiency: novel mutation in the pentose phosphate pathway

BACKGROUND

Transaldolase (TALDO) deficiency (OMIM #606003) is a rare autosomal recessive multi-systemic disorder of carbohydrate metabolism. It has a vast phenotypic spectrum ranging from neonatal liver failure to slowly progressive liver cirrhosis and is characterized by intrauterine growth restriction, hepatosplenomegaly, bicytopenia, nephrolithiasis, and congenital heart disease.

METHODS AND RESULTS

We report a patient with a late-onset form of TALDO deficiency characterized by hypergonadotropic hypogonadism and slightly elevated levels of alpha-fetoprotein (AFP). A novel TALDO1 mutation was detected through the application of reverse genetics with the use of clinical exome sequencing (CES).

CONCLUSION

This report provides further evidence that reverse genetics is a useful approach in patients who do not manifest the hallmark features of known and recognizable syndromes. TALDO deficiency should be considered in the differential diagnosis of unexplained elevated AFP levels and hypergonadotropic hypogonadism with microlithiasis.

Transaldolase haploinsufficiency in subjects with acetaminophen-induced liver failure

Transaldolase (TAL) is an enzyme in the pentose phosphate pathway (PPP) that generates NADPH for protection against oxidative stress. While deficiency of other PPP enzymes, such as transketolase (TKT), are incompatible with mammalian cell survival, mice lacking TAL are viable and develop progressive liver disease attributed to oxidative stress. Mice with homozygous or heterozygous TAL deficiency are predisposed to cirrhosis, hepatocellular carcinoma (HCC) and acetaminophen (APAP)-induced liver failure. Both mice and humans with complete TAL deficiency accumulate sedoheptulose 7-phosphate (S7P). Previous human studies relied on screening patients with S7P accumulation, thus excluding potentially pathogenic haploinsufficiency. Of note, mice with TAL haploinsufficiency are also predisposed to HCC and APAP-induced liver failure which are preventable with oral N-acetylcysteine (NAC) administration. Based on TALDO1 DNA sequencing, we detected functional TAL deficiency due to novel, heterozygous variations in two of 94 healthy adults and four of 27 subjects with APAP-induced liver failure (P = .022). The functional consequences of these variations were individually validated by site-directed mutagenesis of normal cDNA and loss of activity by recombinant enzyme. All four patients with TAL haplo-insufficiency with APAP-induced liver failure were successfully treated with NAC. We also document two novel variations in two of 15 children with previously unexplained liver cirrhosis. Examination of the National Center for Biotechnology Information databases revealed 274 coding region variations have been documented in 1125 TALDO1 sequences relative to 25 variations in 2870 TKT sequences (P < .0001). These findings suggest an unexpected prevalence and variety of genetic changes in human TALDO1 with relevance for liver injury that may be preventable by treatment with NAC.

Clinical, biochemical, and molecular overview of transaldolase deficiency and evaluation of the endocrine function: Update of 34 patients

BACKGROUND

Transaldolase deficiency (TALDO-D) is a rare autosomal recessive inborn error of the pentose phosphate pathway. Since its first description in 2001, several case reports have been published, but there has been no comprehensive overview of phenotype, genotype, and phenotype-genotype correlation.

METHODS

We performed a retrospective questionnaire and literature study of clinical, biochemical, and molecular data of 34 patients from 25 families with proven TALDO-D. In some patients, endocrine abnormalities have been found. To further evaluate these abnormalities, we performed biochemical investigations on blood of 14 patients.

RESULTS AND CONCLUSIONS

Most patients (n = 22) had an early-onset presentation (prenatally or before 1 month of age); 12 patients had a late-onset presentation (3 months to 9 years). Main presenting symptoms were intrauterine growth restriction, dysmorphic facial features, congenital heart disease, anemia, thrombocytopenia, and hepato(spleno)megaly. An older sib of two affected patients was asymptomatic until the age of 9 years, and only after molecular diagnosis was hepatomegaly noted. In some patients, there was gonadal dysfunction with low levels of testosterone and secondary luteinizing hormone (LH) and follicle-stimulating hormone (FSH) abnormalities later in life. This overview provides information that can be helpful for managing patients and counseling families regarding prognosis. Diagnostic guidelines, possible genotype-phenotype correlations, treatment options, and pathophysiological disease mechanisms are proposed.

Acute Liver Failure: An Update

Pediatric acute liver failure (PALF) is a dynamic, life-threatening condition of disparate etiology. Management of PALF is dependent on intensive collaborative clinical care and support. Proper recognition and treatment of common complications of liver failure are critical to optimizing outcomes. In parallel, investigations to identify underlying cause and the implementation of timely, appropriate treatment can be life-saving. Predicting patient outcome in the era of liver transplantation has been unfulfilling and better predictive models must be developed for proper stewardship of the limited resource of organ availability.

Apparent Acetaminophen Toxicity in a Patient with Transaldolase Deficiency

Transaldolase deficiency (MIM#: 606003) is a rare autosomal recessive defect in the pentose phosphate pathway. Affected individuals are at risk for progressive liver failure and hepatocarcinoma. In the transaldolase-deficient mouse model (Taldo1 ^-/-), these hepatic complications are accentuated by oxidative stress related to acetaminophen administration. We report a 13-month-old transaldolase-deficient male who developed mild liver failure after receiving standard doses of acetaminophen during a febrile respiratory syncytial virus infection. He was admitted for respiratory distress with neutropenia and thrombocytopenia, but developed an enlarged nodular liver with accompanying splenomegaly and rising alpha-fetoprotein which peaked 2 weeks after acetaminophen exposure. Whole exome sequencing revealed compound heterozygous variants c.512_514delCCT (p.Ser171del) and c.931G > T (p.Gly311Trp) in TALDO1 (HGNC:11559), which encodes transaldolase (EC 2.2.1.2), a key enzyme in ribose metabolism. Urine polyols and plasma metabolomics confirmed the diagnosis of transaldolase deficiency. Studies on the Taldo1 ^-/- mouse model demonstrate acetaminophen-induced liver failure can be prevented by administration of the antioxidant N-acetylcysteine. Moreover, a published report showed treatment of a transaldolase-deficient patient with N-acetylcysteine was associated with a decrease in alpha-fetoprotein levels. After discontinuation of acetaminophen and prior to initiation of N-acetylcysteine treatment, our patient demonstrated resolving alpha-fetoprotein levels suggesting acetaminophen incited the liver failure. Conclusion: Our observations support the conclusion from mouse model studies that transaldolase-deficient patients are uniquely sensitive to acetaminophen and should avoid this antipyretic. Recognition of this individualized toxicity and avoidance of acetaminophen are essential for management of these patients.

Long-Term Systematic Monitoring of Four Polish Transaldolase Deficient Patients

INTRODUCTION

Transaldolase deficiency (TALDO; OMIM 606003) is a rare inborn autosomal recessive error of the pentose phosphate pathway that, to date, has been diagnosed in 33 patients. Tżhere are few reports regarding the long-term follow-up of these patients.The aim of our study is to present the disease progression in the form of a systematic long-term follow-up of four Polish patients with TALDO.

METHODS AND RESULTS

We report four patients who manifested early onset TALDO. They were monitored with systematic clinical and laboratory examinations for 4-13 years. The dominant feature was an early liver injury, with subsequent renal tubulopathy. All patients presented with osteopenia and poor physical development. Our data shows that polyol concentrations seem to decrease with age.

CONCLUSIONS

In our patients, a progressive coagulopathy was the most sensitive parameter of liver dysfunction. Nodular fibrosis of the liver developed over the natural course of TALDO. This is the first report of long-term systematic clinical and biochemical monitoring of the disease progress in patients with TALDO.

Human Metabolic Enzymes Deficiency: A Genetic Mutation Based Approach

One of the extreme challenges in biology is to ameliorate the understanding of the mechanisms which emphasize metabolic enzyme deficiency (MED) and how these pretend to have influence on human health. However, it has been manifested that MED could be either inherited as inborn error of metabolism (IEM) or acquired, which carries a high risk of interrupted biochemical reactions. Enzyme deficiency results in accumulation of toxic compounds that may disrupt normal organ functions and cause failure in producing crucial biological compounds and other intermediates. The MED related disorders cover widespread clinical presentations and can involve almost any organ system. To sum up the causal factors of almost all the MED-associated disorders, we decided to embark on a less traveled but nonetheless relevant direction, by focusing our attention on associated gene family products, regulation of their expression, genetic mutation, and mutation types. In addition, the review also outlines the clinical presentations as well as diagnostic and therapeutic approaches.

Transaldolase Deficiency: A New Case Expands the Phenotypic Spectrum

Transaldolase (TALDO) deficiency has various clinical manifestations including liver dysfunction, hepatosplenomegaly, anemia, thrombocytopenia, and dysmorphic features. We report a case presenting prenatally with hyperechogenic bowel and intrauterine growth restriction. The infant was born small for gestational age, with cutis laxa and hypertrichosis. Postnatally, meconium plug was identified, complicated with intestinal obstruction necessitating laparotomy, partial resection of the intestine, and ileostomy. Liver biopsy revealed cholangiolar proliferation and portal fibrosis. He also suffered from persistent congenital thrombocytopenia requiring platelet transfusions and severe hypothyroidism with normal anatomical and structural gland responding only to the combination of T3 and T4 treatment. Neurologically, severe hypotonia and anisocoria were noted at the age of 2 months. Brain MRI was normal. Shortly after the abdominal surgery, a rapid liver failure ensued, which eventually led to his death. Specific metabolic tests ruled out glycosylation disorders, yet urine analysis using 1H NMR showed accumulation of sedoheptulose which was previously described in patients with transaldolase deficiency. Sequencing of the gene-encoding transaldolase (TALDO1) revealed a homozygous stop mutation c.669C>G; p.Tyr223*. In conclusion, we present an infant with a novel homozygous mutation in TALDO1, causing TALDO deficiency, and extend the clinical characteristics of this rare syndrome.

Effects of Mutations of 3 Amino Acids on Hepatocellular Carcinoma

In recent years, over 1000 reports have been published on the association between hepatic diseases and gene mutations which may result in pathogenic amino acids. Most of the studies focus on the hepatocellular carcinoma (HCC). The aim was to systematically examine the published literature on the association between the mutations of arginine, serine, and threonine and hepatic diseases, particularly HCC. The Biosciences information service database was systematically searched before July 10, 2012. Of the initially selected 471 publications, 112 articles were included in this study. Meta-analyses were conducted for 3 amino acids. Risk ratios were used to analyze the association between amino acids and liver diseases. We analyze the literature on the association between gene mutations and hepatic diseases, especially in patients with HCC. Full-text articles were analyzed by 4 independent researchers. Some amino acid mutations were found only in people with liver diseases—not in the general population. Arginine and threonine mutations occurred more frequently in patients with hepatic diseases, compared to the normal population. There is a statistically significant association between arginine mutations and the risk of HCC and serine mutations and the risk of HCC.

Transaldolase deficiency caused by the homozygous p.R192C mutation of the TALDO1 gene in four Emirati patients with considerable phenotypic variability

Transaldolase deficiency is a heterogeneous disorder of carbohydrate metabolism characterized clinically by dysmorphic features, cutis laxa, hepatosplenomegaly, hepatic fibrosis, pancytopenia, renal and cardiac abnormalities, and urinary excretion of polyols. This report describes four Emirati patients with transaldolase deficiency caused by the homozygous p.R192C missense mutation in TALDO1 displaying wide phenotypic variability. The patients had variable clinical presentations including hepatosplenomegaly, pancytopenia, liver failure, proteinuria, hydrops fetalis, cardiomyopathy, and skin manifestations (e.g., dryness, cutis laxa, ichthyosis, telangiectasias, and hemangiomas). Biochemical analyses including urinary concentration of polyols were consistent with transaldolase deficiency. The mutation p.R192C was previously identified in an Arab patient, suggesting a founder effect in Arab populations.

CONCLUSION

The above findings support the premise that biallelic mutations in TALDO1 are responsible for transaldolase deficiency and confirm the broad phenotypic variability of this condition, even with the same genotype.

Clinical and molecular characteristics of two transaldolase-deficient patients

Transaldolase (TALDO) deficiency is a rare metabolic disease in the pentose phosphate pathway, which manifests as a severe, early-onset multisystem disease. The body fluids of affected patients contain increased polyol concentrations and seven-carbon chain carbohydrates. We report the molecular and clinical findings in two recently diagnosed transaldolase-deficient children, both presented at birth. During infancy, they presented thin skin with a network of visible vessels, spider telangiectasias and multiple haemangiomas. Such unusual skin changes are characteristic of liver damage. Later, the patients developed rapidly progressive nodular liver fibrosis, tubulopathy and severe clotting disturbances. The clinical features of these patients were in line with previously studied patients with transaldolase deficiency. The diagnosis was established by detecting high concentrations of erythritol, ribitol, arabitol, sedoheptitol, perseitol, sedoheptulose and sedoheptulose-7-phosphate in the urine. Detection was made by gas chromatography and liquid chromatography-tandem mass spectrometry and then confirmed by molecular analysis of the TALDO gene.

CONCLUSION

Transaldolase deficiency, a rare early-onset multisystem disease, should be considered by neonatologists, paediatricians, hepatologists and nephrologists in the differential diagnosis of patients presenting hepatosplenomegaly, thrombocytopenia, anaemia, bleeding diathesis, liver failure and tubulopathy.

Transaldolase deficiency: report of 12 new cases and further delineation of the phenotype

PURPOSE

Transaldolase deficiency is a recently described inborn error of pentose phosphate pathway. We conducted this study to further delineate the associated phenotype.

METHODS AND RESULTS

We report on 12 new cases representing six families with this metabolic defect that were observed over an 8 year span. None of these cases received the correct diagnosis initially because of significant overlap in the presenting symptoms (growth retardation, dysmorphic features, cutis laxa, congenital heart disease, hepatosplenomegaly, pancytopenia, and bleeding tendency) with a wide range of genetic disorders. However, the consanguineous nature of these families allowed us to pursue autozygome analysis, which highlighted TALDO as the likely candidate gene and sequencing confirmed segregation of a novel homozygous mutation with the disease in all the studied families. Biochemical analysis was also consistent with transaldolase deficiency.

CONCLUSION

This study expands the clinical definition of transaldolase deficiency, and adds to its allelic heterogeneity. In addition, we emphasize the diagnostic challenge posed by this rare and pleiotropic metabolic disorder.

Novel association of early onset hepatocellular carcinoma with transaldolase deficiency

We evaluated a family with a 16-month-old boy with cirrhosis and hepatocellular carcinoma and his 30-month-old brother with cirrhosis. After failing to identify a diagnosis after routine metabolic evaluation, we utilized a combination of RNA-Seq and whole exome sequencing to identify a novel homozygous p.Ser171Phe Transaldolase (TALDO1) variant in the proband, his brother with cirrhosis, as well as a clinically asymptomatic older 8-year-old brother. Metabolite analysis and enzymatic testing of TALDO1 demonstrated elevated ribitol, sedoheptitol, and sedoheptulose-7P, and lack of activity of TALDO1 in the three children homozygous for the p.Ser171Phe mutation. Our findings expand the phenotype of transaldolase deficiency to include early onset hepatocellular carcinoma in humans and demonstrate that, even within the same family, individuals with the same homozygous mutation demonstrate a wide range of phenotypes.

Sensitive measurement of polyols in urine by capillary zone electrophoresis coupled with amperometric detection using on-column complexation with borate

Little is known about human polyol metabolism, but recent studies indicate that abnormal polyol concentrations in body fluids are related to several diseases. In this study, a rapid and sensitive method for the determination of seven major polyols in urine including two groups of polyol isomers, C5-polyols (Rib+Arb+Xyl) and C6-polyols (Sor+Gal+Man), was developed using capillary zone electrophoresis coupled with amperometric detection (CZE-AD). The effects of the working electrode potential, pH, running buffer components and concentrations, separation voltage and injection times were investigated. Under the optimised conditions, seven types of polyols could be perfectly separated via the formation of anionic polyol-borate complexes in a borate buffer solution. Highly linear current responses to the polyol concentrations were obtained with good correlation (0.9984<R(2)<0.9997), and the limits of detection (LODs) ranged from 1.33×10(-6) to 5.8×10(-7) mol L(-1) (S/N=3). The proposed method has been successfully used to detect polyols in urinary samples from healthy subjects and diabetes patients, demonstrating accurate and reliable results. This method has potential applications in the recognition of inborn errors affecting polyol metabolism.

Evidence for transaldolase activity in the isolated heart supplied with [U-13C3]glycerol

Studies of glycerol metabolism in the heart have largely emphasized its role in triglyceride synthesis. However, glycerol may also be oxidized in the citric acid cycle, and glycogen synthesis from glycerol has been reported in the nonmammalian myocardium. The intent of this study was to test the hypothesis that glycerol may be metabolized to glycogen in mammalian heart. Isolated rat hearts were supplied with a mixture of substrates including glucose, lactate, pyruvate, octanoate, [U-(13)C(3)]glycerol, and (2)H(2)O to probe various metabolic pathways including glycerol oxidation, glycolysis, the pentose phosphate pathway, and carbon sources of stored glycogen. NMR analysis confirmed that glycogen production from the level of the citric acid cycle did not occur and that the glycerol contribution to oxidation in the citric acid cycle was negligible in the presence of alternative substrates. Quite unexpectedly, (13)C from [U-(13)C(3)]glycerol appeared in glycogen in carbon positions 4-6 of glucosyl units but none in positions 1-3. The extent of [4,5,6-(13)C(3)]glucosyl unit enrichment in glycogen was enhanced by insulin but decreased by H(2)O(2). Given that triose phosphate isomerase is generally assumed to fully equilibrate carbon tracers in the triose pool, the marked (13)C asymmetry in glycogen can only be attributed to conversion of [U-(13)C(3)]glycerol to [U-(13)C(3)]dihydroxyacetone phosphate and [U-(13)C(3)]glyceraldehyde 3-phosphate followed by rearrangements in the nonoxidative branch of the pentose phosphate pathway involving transaldolase that places this (13)C-enriched 3-carbon unit only in the bottom half of hexose phosphate molecules contributing to glycogen.

Nephrological abnormalities in patients with transaldolase deficiency

BACKGROUND

Transaldolase deficiency (OMIM 606003) is a multisystem disorder first described in 2001. Transaldolase is an enzyme of the reversible part of the pentose phosphate pathway. Affected patients have abnormal polyol concentrations in body fluids, mostly in urine. The clinical presentation is variable. The leading symptoms are coagulopathy, thrombocytopenia, hepatosplenomegaly, hepatic fibrosis and dysmorphic features. The objective of our study was to attempt to characterize the renal phenotype of patients with transaldolase deficiency.

METHODS

Clinical and laboratory data of all nine patients with transaldolase deficiency presently known were gathered by retrospective chart analysis.

RESULTS

Nephrological abnormalities were present in seven of the nine patients. The most common findings were low molecular weight (LMW) proteinuria and hypercalciuria. The two oldest patients had moderate chronic kidney failure. In two patients, generalized aminoaciduria was found, two patients had renal phosphate wasting and three patients had hyperchloremic metabolic acidosis. Three patients had anatomical abnormalities.

CONCLUSIONS

Renal tubular dysfunction is present in the majority of patients with transaldolase deficiency and may lead to chronic renal failure. The combination of unexplained liver dysfunction with LMW proteinuria should prompt metabolic screening for transaldolase deficiency by measuring urinary polyols. In patients with transaldolase deficiency, monitoring of kidney function is mandatory.

The tissue and plasma concentration of polyols and sugars in sheep intrauterine growth retardation

In an ovine model of placental insufficiency-induced intrauterine growth retardation (PI-IUGR), characterized by hypoxia, hypoglycemia and a significant reduction in fetal weight, we assessed alterations in fetal and placental polyols. Arterial maternal–fetal concentration differences of glucose and mannose were greater in the PI-IUGR fetus; glucose: C ( n = 7), 2.68 ± 0.14 mmol/L versus PI-IUGR ( n = 9), 3.18 ± 0.16 mmol/L ( P < 0.02) and mannose: C, 42.9 ± 8.1 μmol/L versus PI-IUGR, 68.5 ± 19.1 μmol/L ( P < 0.001). For PI-IUGR fetuses, fetal arterial plasma myo-inositol concentrations were significantly increased ( P < 0.001). The concentrations of sorbitol, glucose and fructose were significantly reduced ( P < 0.03, 0.01, 0.02, respectively). The cotyledons of IUGR placentas had a significantly increased concentration of myo-inositol ( P < 0.003) and decreased concentrations of sorbitol, fructose and glycerol ( P < 0.01, 0.02, 0.01, respectively). Fetal hepatic concentrations of sorbitol ( P < 0.001) and fructose ( P < 0.03) were also significantly reduced. These profound changes in both placental and fetal concentrations of polyols and sugars in sheep PI-IUGR pregnancies support the conclusion that within the PI-IUGR placenta there is an increased flux through the glucose 6-P:inositol 1-P cyclase system and decreased flux through the polyol dehydrogenase system, leading to increased placental myo-inositol production and decreased sorbitol production. The decreased placental supply of sorbitol to the fetal liver may lead to decreased fetal hepatic fructose production. These observations highlight that, in association with hypoxic and hypoglycemic PI-IUGR fetuses, there are major placental and fetal alterations in polyol production. The manner in which these alterations in fetoplacental carbohydrate metabolism contribute to the pathophysiology of PI-IUGR is currently unknown.

Mitochondrial involvement and erythronic acid as a novel biomarker in transaldolase deficiency

BACKGROUND

Sedoheptulose, arabitol, ribitol, and erythritol have been identified as key diagnostic metabolites in TALDO deficiency.

METHOD

Urine from 6 TALDO-deficient patients and TALDO-deficient knock-out mice were analyzed using ¹H-NMR spectroscopy and GC-mass spectrometry.

RESULTS

Our data confirm the known metabolic characteristics in TALDO-deficient patients. The β-furanose form was the major sedoheptulose anomer in TALDO-deficient patients. Erythronic acid was identified as a major abnormal metabolite in all patients and in knock-out TALDO mice implicating an as yet unknown biochemical pathway in this disease. A putative sequence of enzymatic reactions leading to the formation of erythronic acid is presented. The urinary concentration of the citric acid cycle intermediates 2-oxoglutaric acid and fumaric acid was increased in the majority of TALDO-deficient patients but not in the knock-out mice.

CONCLUSION

Erythronic acid is a novel and major hallmark in TALDO deficiency. The pathway leading to its production may play a role in healthy humans as well. In TALDO-deficient patients, there is an increased flux through this pathway. The finding of increased citric acid cycle intermediates hints toward a disturbed mitochondrial metabolism in TALDO deficiency.

Prevention of hepatocarcinogenesis and increased susceptibility to acetaminophen-induced liver failure in transaldolase-deficient mice by N-acetylcysteine

Although oxidative stress has been implicated in acute acetaminophen-induced liver failure and in chronic liver cirrhosis and hepatocellular carcinoma (HCC), no common underlying metabolic pathway has been identified. Recent case reports suggest a link between the pentose phosphate pathway (PPP) enzyme transaldolase (TAL; encoded by TALDO1) and liver failure in children. Here, we show that Taldo1-/- and Taldo1+/- mice spontaneously developed HCC, and Taldo1-/- mice had increased susceptibility to acetaminophen-induced liver failure. Oxidative stress in Taldo1-/- livers was characterized by the accumulation of sedoheptulose 7-phosphate, failure to recycle ribose 5-phosphate for the oxidative PPP, depleted NADPH and glutathione levels, and increased production of lipid hydroperoxides. Furthermore, we found evidence of hepatic mitochondrial dysfunction, as indicated by loss of transmembrane potential, diminished mitochondrial mass, and reduced ATP/ADP ratio. Reduced beta-catenin phosphorylation and enhanced c-Jun expression in Taldo1-/- livers reflected adaptation to oxidative stress. Taldo1-/- hepatocytes were resistant to CD95/Fas-mediated apoptosis in vitro and in vivo. Remarkably, lifelong administration of the potent antioxidant N-acetylcysteine (NAC) prevented acetaminophen-induced liver failure, restored Fas-dependent hepatocyte apoptosis, and blocked hepatocarcinogenesis in Taldo1-/- mice. These data reveal a protective role for the TAL-mediated branch of the PPP against hepatocarcinogenesis and identify NAC as a promising treatment for liver disease in TAL deficiency.

Transaldolase deficiency in two new patients with a relative mild phenotype

Transaldolase (TALDO) deficiency is a recently described inborn error of metabolism of the pentose phosphate pathway that so far has been diagnosed in only eight patients. In this article, we report the clinical course and biochemical findings of two newly identified patients with TALDO deficiency-two sons of consanguineous parents from Polish origin, presenting with neonatal onset of bleeding diathesis, haemolytic anemia, thrombocytopenia and hepatosplenomegaly. Subsequently the patients had persistent thrombocytopenia, a bleeding tendency, impaired liver function and fibrosis. Their physical and psychomotor development progressed normally.

Transaldolase: from biochemistry to human disease

The role of the enzyme transaldolase (TAL) in central metabolism, its biochemical properties, structure, and role in human disease is reviewed. The nearly ubiquitous enzyme transaldolase is a part of the pentose phosphate pathway and transfers a dihydroxyacetone group from donor compounds (fructose 6-phosphate or sedoheptulose 7-phosphate) to aldehyde acceptor compounds. The phylogeny of transaldolases shows that five subfamilies can be distinguished, three of them with proven TAL enzyme activity, one with unclear function, and the fifth subfamily comprises transaldolase-related enzymes, the recently discovered fructose 6-phosphate aldolases. The three-dimensional structure of a bacterial (Escherichia coli TAL B) and the human enzyme (TALDO1) has been solved. Based on the 3D-structure and mutagenesis studies, the reaction mechanism was deduced. The cofactor-less enzyme proceeds with a Schiff base intermediate (bound dihydroxyacetone). While a transaldolase deficiency is well tolerated in many microorganisms, it leads to severe symptoms in homozygous TAL-deficient human patients. The involvement of TAL in oxidative stress and apoptosis, in multiple sclerosis, and in cancer is discussed.

The biochemistry, metabolism and inherited defects of the pentose phosphate pathway: a review

The recent discovery of two defects (ribose-5-phosphate isomerase deficiency and transaldolase deficiency) in the reversible part of the pentose phosphate pathway (PPP) has stimulated interest in this pathway. In this review we describe the functions of the PPP, its relation to other pathways of carbohydrate metabolism and an overview of the metabolic defects in the reversible part of the PPP.

Replacement of a phenylalanine by a tyrosine in the active site confers fructose-6-phosphate aldolase activity to the transaldolase of Escherichia coli and human origin

Based on a structure-assisted sequence alignment we designed 11 focused libraries at residues in the active site of transaldolase B from Escherichia coli and screened them for their ability to synthesize fructose 6-phosphate from dihydroxyacetone and glyceraldehyde 3-phosphate using a newly developed color assay. We found one positive variant exhibiting a replacement of Phe(178) to Tyr. This mutant variant is able not only to transfer a dihydroxyacetone moiety from a ketose donor, fructose 6-phosphate, onto an aldehyde acceptor, erythrose 4-phosphate (14 units/mg), but to use it as a substrate directly in an aldolase reaction (7 units/mg). With a single amino acid replacement the fructose-6-phosphate aldolase activity was increased considerably (>70-fold compared with wild-type). Structural studies of the wild-type and mutant protein suggest that this is due to a different H-bond pattern in the active site leading to a destabilization of the Schiff base intermediate. Furthermore, we show that a homologous replacement has a similar effect in the human transaldolase Taldo1 (aldolase activity, 14 units/mg). We also demonstrate that both enzymes TalB and Taldo1 are recognized by the same polyclonal antibody.

Transaldolase deficiency influences the pentose phosphate pathway, mitochondrial homoeostasis and apoptosis signal processing

TAL (transaldolase) was originally described in the yeast as an enzyme of the PPP (pentose phosphate pathway). However, certain organisms and mammalian tissues lack TAL, and the overall reason for its existence is unclear. Recently, deletion of Ser(171) (TALDeltaS171) was found in five patients causing inactivation, proteasome-mediated degradation and complete deficiency of TAL. In the present study, microarray and follow-up Western-blot, enzyme-activity and metabolic studies of TALDeltaS171 TD (TAL-deficient) lymphoblasts revealed co-ordinated changes in the expression of genes involved in the PPP, mitochondrial biogenesis, oxidative stress, and Ca(2+) fluxing. Sedoheptulose 7-phosphate was accumulated, whereas G6P (glucose 6-phosphate) was depleted, indicating a failure to recycle G6P for the oxidative branch of the PPP. Nucleotide analysis showed depletion of NADPH and NAD(+) and accumulation of ADP-ribose. TD cells have diminished Deltapsi(m) (mitochondrial transmembrane potential) and increased mitochondrial mass associated with increased production of nitric oxide and ATP. TAL deficiency resulted in enhanced spontaneous and H(2)O(2)-induced apoptosis. TD lymphoblasts showed increased expression of CD38, which hydrolyses NAD(+) into ADP-ribose, a trigger of Ca(2+) release from the endoplasmic reticulum that, in turn, facilitated CD20-induced apoptosis. By contrast, TD cells were resistant to CD95/Fas-induced apoptosis, owing to a dependence of caspase activity on redox-sensitive cysteine residues. Normalization of TAL activity by adeno-associated-virus-mediated gene transfer reversed the elevated CD38 expression, ATP and Ca(2+) levels, suppressed H(2)O(2)- and CD20-induced apoptosis and enhanced Fas-induced cell death. The present study identified the TAL deficiency as a modulator of mitochondrial homoeostasis, Ca(2+) fluxing and apoptosis.

Transaldolase deficiency in a two-year-old boy with cirrhosis

Transaldolase (TALDO) deficiency is a rare inborn error of the pentose phosphate pathway. We report the clinical presentation and laboratory findings of a new patient with TALDO deficiency. The two-year-old Arabic boy presented with neonatal onset of anemia and thrombocytopenia, tubulopathy, and rickets and was subsequently found to have cirrhosis and deafness. A comparison with other TALDO deficient patients is given.

Sedoheptulokinase deficiency due to a 57-kb deletion in cystinosis patients causes urinary accumulation of sedoheptulose: elucidation of the CARKL gene

The most common mutation in the nephropathic cystinosis (CTNS) gene is a homozygous 57-kb deletion that also includes an adjacent gene carbohydrate kinase-like (CARKL). The latter gene encodes a protein that is predicted to function as a carbohydrate kinase. Cystinosis patients with the common 57-kb deletion had strongly elevated urinary concentrations of sedoheptulose (28-451 mmol/mol creatinine; controls and other cystinosis patients <9) and erythritol (234-1110 mmol/mol creatinine; controls and other cystinosis patients <148). Enzyme studies performed on fibroblast homogenates derived from patients carrying the 57-kb deletion revealed 80% reduction in their sedoheptulose phosphorylating activity compared to cystinosis patients with other mutations and controls. This indicates that the CARKL-encoded protein, sedoheptulokinase (SHK), is responsible for the reaction: sedoheptulose + ATP --> sedoheptulose-7-phosphate + ADP and that deletion of CARKL causes urinary accumulation of sedoheptulose and erythritol.

Detection of transaldolase deficiency by quantification of novel seven-carbon chain carbohydrate biomarkers in urine

Transaldolase deficiency, a recently discovered disorder of carbohydrate metabolism with multisystem involvement, has been diagnosed in 6 patients. Affected patients have abnormal concentrations of polyols in body fluids and in all patients we have previously found increased amounts of a seven-carbon chain carbohydrate which we suspected of being sedoheptulose. We report development of a liquid chromatography-tandem mass spectrometry method for quantitation of the seven-carbon carbohydrates sedoheptulose and mannoheptulose in urine. Additionally, other seven-carbon chain carbohydrates were characterized in urine, including sedoheptitol, perseitol and sedoheptulose 7-phosphate. Transaldolase-deficient patients had significantly increased urinary sedoheptulose and sedoheptulose 7-phosphate, associated with subtle elevations of mannoheptulose, sedoheptitol and perseitol. Our findings reveal novel urinary biomarkers for identification of transaldolase deficiency.

Epidemiology of acute liver failure

Acute liver failure (ALF) is an uncommon disorder that leads to jaundice, coagulopathy, and multisystem organ failure. Its definition is based on the timing from onset of jaundice to encephalopathy. In 2005, ALF accounted for 6% of liver-related deaths and 7% of orthotopic liver transplants (OLT) in the United States. Several classification systems have been developed for ALF, with the King's College criteria most widely used for prediction of OLT. Specific diagnostic tests should be implemented to identify the cause of ALF, which will help to determine its treatment and prognosis. Viral hepatitis was previously reported to be the most common cause of ALF in the United States, but acetaminophen overdose and idiosyncratic drug reactions have emerged as the most frequent causes in recent studies. Malignancy is an uncommon cause of ALF, and thus imaging studies may not be useful in this setting, but liver biopsy may be beneficial in selected cases. An overall strategy for ALF should start with identifying the cause, assessing the prognosis, and early transfer to a transplantation center for suitable candidates. OLT has emerged as a life-saving procedure leading to marked improvement in survival rates. Improved surgical techniques, immunosuppression, and comprehensive care have led to an overall survival rate of approximately 65% with OLT. N-acetylcysteine is effective in ALF caused by acetaminophen overdose, with results strongly related to how soon it is given rather than the route of administration. Liver support systems show potential for the treatment of ALF, but their role needs validation in large multicenter randomized trials.

Transaldolase deficiency: a new cause of hydrops fetalis and neonatal multi-organ disease

Transaldolase (TALDO) deficiency is a newly recognized metabolic disease, which has been reported so far in 2 patients presenting with liver failure and cirrhosis. We report a new sibship of 4 infants born to the same consanguineous parents; all presented at birth or in the antenatal period with dysmorphic features, cutis laxa and hypertrichosis, hepatomegaly, splenomegaly, liver failure, hemolytic anemia, thrombocytopenia, and genitourinary malformations. The clinical courses were variable: the first child died of liver failure at 4 months of age; the second pregnancy was medically terminated at 28 weeks gestation because of hydrops fetalis with oligohydramnios. The third child is doing well at age 7 with liver fibrosis and mild kidney failure. The fourth child is now 21 months old and has hepatosplenomegaly, mild anemia, and thrombocytopenia. Urine assessment of polyols showed elevations of erythritol, arabitol, and ribitol consistent with TALDO deficiency. TALDO activity was undetectable in the patients' tissues, and mutation in the TALDO1 gene was found in the 4 patients.

[Radiological innovations in the screening and diagnosis of the inborn errors of metabolism]

New metabolic diseases are regularly identified by a genetic or biochemical approach. Indeed, the metabolic diseases result from an enzymatic block with accumulation of a metabolite upstream to the block and deficit of a metabolite downstream. The characterization of these abnormal metabolites by MRI spectroscopy permitted to identify the deficient enzyme in two new groups of diseases, creatine deficiencies and polyol anomalies. Creatine deficiency is implicated in unspecific mental retardation. A low peak of creatine at MRI spectroscopy is evocating of creatine deficiency which is treatable by creatine administration. Deficiency of synthesis of polyols, metabolites on the pentose pathway, represent new described metabolic diseases with variable symptoms including a neurological distress, liver disease, splenomegaly, cutis laxa and renal insufficiency. The deficit of ribose-5-phosphate isomerase, one of the enzymes whose diagnosis is evoked in front of the accumulation of ribitol, arabitol and xylitol leads to a leucodystrophy in adults. This new deficit was highlighted by the identification of an abnormal peak in cerebral MRI-spectroscopy corresponding to the abnormal accumulation of polyols in brain. Congenital hyperinsulinism (HI) is characterized by profound hypoglycaemia related to inappropriate insulin secretion. Focal and diffuse forms of hyperinsulinism share a similar clinical presentation but their treatment is dramatically different. Until recently, preoperative differential diagnosis was based on pancreatic venous sampling, an invasive and technically demanding technique. Positron emission tomography (PET) after injection of [18F]Fluoro-L-DOPA has been evaluated for the preoperative differentiation between focal and diffuse HI, by imaging uptake of radiotracer and the conversion of [18F]Fluoro-L-DOPA into dopamine by DOPA decarboxylase. PET with [18F]Fluoro-L-DOPA has been validated as a reliable test to differentiate diffuse and focal HI and is now a major differential diagnosis tool in infantile hyperinsulinemic hypoglycaemia.

Analysis of polyols in urine by liquid chromatography-tandem mass spectrometry: a useful tool for recognition of inborn errors affecting polyol metabolism

Several inborn errors of metabolism with abnormal polyol concentrations in body fluids are known to date. Most of these defects can be diagnosed by the assessment of urinary concentrations of polyols. We present two methods using tandem mass spectrometry for screening for inborn errors affecting polyol metabolism. Urine samples supplemented with internal standards ([13C4]erythritol, [13C2]arabitol and [2H3]sorbitol) were desalted by a mixed-bed ion-exchange resin. Separation was achieved by two different columns. Sugar isomers could not be separated using a Prevail Carbohydrate ES 54 column (method 1), whereas with the other column (Aminex HPX-87C) separation of the isomers was achieved (method 2). Multiple reaction monitoring polyol detection was achieved by tandem mass spectrometry with an electron ion-spray source operating in the negative mode. Age-related reference ranges of polyols (erythritol, treitol, arabitol, ribitol, xylitol, galactitol, mannitol, sorbitol, sedoheptitol and perseitol) in urine were established. The applicability of the method was demonstrated by the abnormal polyol concentrations observed in patients with transaldolase deficiency, ribose-5-phosphate isomerase deficiency and classical galactosaemia. This paper describes two methods for the analysis of urinary polyols by liquid chromatography-tandem mass spectrometry. Method 1 is a fast screening method with the quantification of total isomers and method 2 is a more selective method with the separate quantification of the polyols. Both methods can be used for diagnosing inborn errors of metabolism affecting polyol metabolism.