Classical galactosaemia revisited

Semisynthetic sensor proteins enable metabolic assays at the point of care

Monitoring metabolites at the point of care could improve the diagnosis and management of numerous diseases. Yet for most metabolites, such assays are not available. We introduce semisynthetic, light-emitting sensor proteins for use in paper-based metabolic assays. The metabolite is oxidized by nicotinamide adenine dinucleotide phosphate, and the sensor changes color in the presence of the reduced cofactor, enabling metabolite quantification with the use of a digital camera. The approach makes any metabolite that can be oxidized by the cofactor a candidate for quantitative point-of-care assays, as shown for phenylalanine, glucose, and glutamate. Phenylalanine blood levels of phenylketonuria patients were analyzed at the point of care within minutes with only 0.5 microliters of blood. Results were within 15% of those obtained with standard testing methods.

Profiling of intracellular metabolites produced from galactose and its potential for galactosemia research

BACKGROUND

Clinical outcome of patients with a classical presentation of galactosemia (classical patients) varies substantially, even between patients with the same genotype. With current biomarkers, it is not possible to predict clinical outcome early in life. The aim of this study was to develop a method to provide more insight into galactose metabolism, which allows quantitative assessment of residual galactose metabolism in galactosemia patients. We therefore developed a method for galactose metabolite profiling (GMP) in fibroblasts using [U-13C]-labeled galactose.

METHODS

GMP analysis was performed in fibroblasts of three classical patients, three variant patients and three healthy controls. The following metabolites were analyzed: [U13C]-galactose, [U13C]-galactose-1-phosphate (Gal-1-P) and [13C6]- uridine diphosphate(UDP)-galactose. The ratio of [U13C]-Gal-1-P/ [13C6]-UDP-galactose was defined as the galactose index (GI).

RESULTS

All patient cell lines could be distinguished from the control cell lines and there was a clear difference between variant and classical patients. Variant patients had lower levels of [U13C]-galactose and [U13C]-Gal-1-P than classical patients (though substantially higher than healthy controls) and higher levels of [13C6]-UDP-galactose than classical patients (though substantially lower than healthy controls) resulting in a different GI in all groups.

CONCLUSIONS

GMP in fibroblasts is a sensitive method to determine residual galactose metabolism capacity, which can discriminate between patients with a classical presentation of galactosemia, patients with a variant presentation and healthy controls. GMP may be a useful method for early prognostication after further validation in a larger cohort of patients representing the full phenotypic spectrum of galactosemia.

Antioxidant effects on the intracerebroventricular galactose damage in rats

We investigated the effects of the intracerebroventricular infusion of galactose and the influence of pretreatment with antioxidants on oxidative stress parameters and acethylcholinesterase (AChE) activity in the brain of 60-day-old Wistar rats (6 per group). The animals were divided into naïve group (did not undergo surgery); procedure group (only underwent surgery); sham group (underwent surgery and received 5 μL saline) and galactose group (received 5 μL of galactose solution (5.0 mM) by intracerebroventricular injection), and were killed by decapitation after 1 h. Other groups were pretreated daily for 1 week with saline (sham and galactose groups) or antioxidants, α-tocopherol (40 mg/kg) plus ascorbic acid (100 mg/kg, i.p.) (antioxidants and galactose + antioxidants groups). Twelve hours after the last antioxidants injection, animals received an intracerebroventricular infusion of 5 μL of galactose solution (galactose and galactose + antioxidants groups) or saline (sham and antioxidants groups) and were sacrificed 1 h later. Galactose elevated thiobarbituric acid reactive substances (TBA-RS), protein carbonyl content and glutathione peroxidase (GSH-Px) activity and decreased total sulfhydryl content and catalase (CAT) activity in the cerebral cortex. In the hippocampus, galactose enhanced TBA-RS, decreased total sulfhydryl content and increased AChE activity, while in the cerebellum it decreased total sulfhydryl content and increased CAT and superoxide dismutase (SOD) activities. Pretreatment with antioxidants prevented the majority of these alterations, indicating the participation of free radicals in these effects. Thus, intracerebroventricular galactose infusion impairs redox homeostasis in the brain; the administration of antioxidants should be considered as an adjuvant therapy to specific diets in galactosemia.

Extreme neonatal hyperbilirubinemia, acute bilirubin encephalopathy, and kernicterus spectrum disorder in children with galactosemia

BACKGROUND

Galactosemia has not been recognized as a cause of extreme neonatal hyperbilirubinemia, although growing evidence supports this association.

METHODS

In a retrospective cohort study, we identified children with galactosemia due to GALT deficiency using the Danish Metabolic Laboratory Database. Among these, we identified children with extreme neonatal hyperbilirubinemia or symptoms of ABE. Extreme neonatal hyperbilirubinemia was defined as maximum total serum bilirubin (TSB_max)) level ≥450 µmol/L and a ratio of conjugated serum bilirubin/TSB <0.30.

RESULTS

We identified 21 children with galactosemia (incidence:1:48,000). Seven children developed extreme neonatal hyperbilirubinemia (median [range] TSB_max level: 491 [456-756] µmol/L), accounting for 1.7% of all extreme neonatal hyperbilirubinemia cases. During the first 10 days of life, hyperbilirubinemia was predominantly of unconjugated type. Four children developed symptoms of intermediate/advanced ABE. One additional child had symptoms of intermediate/advanced ABE without having extreme neonatal hyperbilirubinemia. On follow-up, one child had KSD.

CONCLUSIONS

Galactosemia is a potential cause of extreme neonatal hyperbilirubinemia, ABE, and KSD. It is crucial that putative galactosemic children are treated aggressively with phototherapy to prevent ABE and KSD. Thus it is important that galactosemia is part of the work up for unconjugated hyperbilirubinemia.

The need for additional care in patients with classical galactosaemia

Purpose: Classical galactosaemia is an inborn error of galactose metabolism which may lead to impairments in body functions and accordingly, need for additional care. The primary aim of this study was to establish the type and intensity of this additional care. Materials and methods: Patients with classical galactosaemia aged ≥2 years were evaluated with the Capacity Profile, a standardised method to classify additional care needs according to type and intensity. Based on a semi-structured interview, current impairments in five domains of body functions were determined. The intensity of additional care was assessed (from 0, usual care, to 5, total dependence). Results: Forty-four patients with classical galactosaemia, 18 males and 26 females (median age 15 years, range 2-49 years), were included. There was a wide spectrum of impairments in mental functions. Motor function impairments were present in four patients, and mild speech impairments in eight patients. Additional care for sensory functions was uncommon. All patients needed a diet, which care is scored in the physical health domain. Conclusions: Apart from the diet all patients need, classical galactosaemia leads to the need for additional care mainly in the domains of mental functions and speech and voice functions. Implications for rehabilitation The Capacity Profile is a useful tool to demonstrate additional care needs in classical galactosaemia. In classical galactosaemia additional care is mostly indicated by mental impairments and speech and voice functions. One-fifth of patients have impairment of speech and voice functions at time of the study, and half of all patients had received speech therapy in childhood. Over 70% of patients need additional care/help due to impairment of mental functions, ranging from coaching due to social vulnerability to full day care.

Molecular basis and clinical presentation of classic galactosemia in a Croatian population

BACKGROUND

Classic galactosemia is an autosomal recessive disorder of galactose metabolism caused by severely decreased activity of galactose-1-phosphate uridylyltransferase (GALT) due to pathogenic mutations in the GALT gene. To date more than 330 mutations have been described, with p.Q188R and p.K285N being the most common in Caucasian populations. Although acute manifestations can be fully avoided by a galactose-restricted diet, chronic complications, such as neurological ones, cannot be prevented in a significant number of patients despite compliance with the dietary treatment.

METHODS

A cohort of 16 galactosemic Croatian patients, including one pair of siblings, was studied. Molecular characterization was performed by direct sequence analysis of the GALT gene.

RESULTS

Sixteen patients were analyzed and only four different mutations were detected. As expected, p.Q188R and p.K285N were common, accounting for 40% and 37% of unrelated alleles, respectively. The third mutation accounting for 20% of mutant alleles was p.R123X causing a premature stop codon, is thus considered to be severe, which is in accordance with the phenotype presented by the homozygous patient described here. The fourth mutation p.E271D was found in a single allele. More than half of our patients manifested some chronic neurological complications.

CONCLUSIONS

This is the first report on mutational and phenotypic spectra of classic galactosemia in Croatia that expands the knowledge on the mutational map of the GALT gene across Europe and reveals the genetic homogeneity of the Croatian population.

Effects of d-galactose-induced ageing on the heart and its potential interventions

Ageing is a strong independent risk factor for disability, morbidity and mortality. Post-mitotic cells including those in the heart are a particular risk to age-related deterioration. As the occurrence of heart disease is increasing rapidly with an ageing population, knowledge regarding the mechanisms of age-related cardiac susceptibility and possible therapeutic interventions needs to be acquired to prevent advancing levels of heart disease. To understand more about the ageing heart, numerous aged animal models are being used to explore the underlying mechanisms. Due to time-consuming for investigations involving naturally aged animals, mimetic ageing models are being utilized to assess the related effects of ageing on disease occurrence. d-galactose is one of the substances used to instigate ageing in various models, and techniques involving this have been widely used since 1991. However, the mechanism through which d-galactose induces ageing in the heart remains unclear. The aim of this review was to comprehensively summarize the current findings from in vitro and in vivo studies on the effects of d-galactose-induced ageing on the heart, and possible therapeutic interventions against ageing heart models. From this review, we hope to provide invaluable information for future studies and based on the findings from experiments involving animals, we can inform possible therapeutic strategies for the prevention of age-related heart diseases in clinical settings.

Multi-Protection of DL0410 in Ameliorating Cognitive Defects in D-Galactose Induced Aging Mice

D-galactose has been reported to accelerate senescence in rodents, accompanied by a decline in learning and memory. We used a model of D-galactose-induced amnesia for the efficacy evaluation and pharmacologic studies of active compounds against Alzheimer's disease (AD). DL0410 is a potent inhibitor against acetylcholinesterase (AChE) and, in the present study, the effect of DL0410 was evaluated in this model. We found that DL0410 could significantly improve the learning and memory of D-galactose induced aging mice in a series of behavioral tests: novel-object recognition test, nest-building test, Morris water maze test and step-through test. Pharmacologic studies were conducted from several aspects: the cholinergic system, mitochondrial respiration, oxidative stress, neuroinflammation, apoptosis and synaptic loss. The acetylcholine level and AChE activity were not altered by D-galactose but were slightly affected by DL0410 in the brain. DL0410 could significantly improve decreased mitochondrial respiration in the NADH chain and FADH2 chain, and protect mitochondrial ultrastructure. DL0410 reduced the accumulation of advanced glycation end products (AGEs) and malondialdehyde (MDA) and increase the total antioxidant capability of the brain via an increase in activity of catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD). RAGE expression was inhibited by DL0410, followed by the decreased activation of astrocytes and microglia. Subsequent phosphorylation of NF-κB was also reversed by DL0410, with lower expression of cyclooxygenase-2 (COX2) and iNOS. With respect to apoptosis, the activation of caspase 3 and cleavage of PARP were downregulated significantly by DL0410, after the inhibition of phosphorylation of JNK induced by inflammation and oxidative stress. Synaptic protection by DL0410 was also demonstrated. These data suggest that mitochondrial protection has a primary role in the ameliorating effect of DL0410 on the impaired learning and memory, oxidative stress, inflammation, apoptosis and synaptic loss induced by D-galactose. DL0410 is a promising candidate for the treatment of aging-related AD, and this study lays an important foundation for its further research and development.

Sweet and sour: an update on classic galactosemia

Classic galactosemia is a rare inherited disorder of galactose metabolism caused by deficient activity of galactose-1-phosphate uridylyltransferase (GALT), the second enzyme of the Leloir pathway. It presents in the newborn period as a life-threatening disease, whose clinical picture can be resolved by a galactose-restricted diet. The dietary treatment proves, however, insufficient in preventing severe long-term complications, such as cognitive, social and reproductive impairments. Classic galactosemia represents a heavy burden on patients' and their families' lives. After its first description in 1908 and despite intense research in the past century, the exact pathogenic mechanisms underlying galactosemia are still not fully understood. Recently, new important insights on molecular and cellular aspects of galactosemia have been gained, and should open new avenues for the development of novel therapeutic strategies. Moreover, an international galactosemia network has been established, which shall act as a platform for expertise and research in galactosemia. Herein are reviewed some of the latest developments in clinical practice and research findings on classic galactosemia, an enigmatic disorder with many unanswered questions warranting dedicated research.

Intensive Care Management of Pediatric Acute Liver Failure

Pediatric acute liver failure is rare but life-threatening illness that occurs in children without preexisting liver disease. The rarity of the disease, along with its severity and heterogeneity, presents unique clinical challenges to the physicians providing care for pediatric patients with acute liver failure. In this review, practical clinical approaches to the care of critically ill children with acute liver failure are discussed with an organ system-specific approach. The underlying pathophysiological processes, major areas of uncertainty, and approaches to the critical care management of pediatric acute liver failure are also reviewed.

A novel splicing mutation in GALT gene causing Galactosemia in Ecuadorian family

Classic Galactosemia (OMIM 230400) is an autosomal recessive disorder of galactose metabolism caused by mutations in the galactose-1-phosphate uridyl transferase (GALT) gene. This disease caused by the inability to metabolize galactose is potentially life-threatening but its pathophysiology has not been clearly defined. GALT gene presents high allelic heterogeneity and around 336 variations have been identified. Here, we report the case of a patient with Classic Galactosemia who was detected during a neonatal screening in Ecuador. Molecular study revealed a mutation in GALT gene intron 1, c.82+3A>G in homozygous condition, this mutation has not been previously reported. This gene variation was not found in any of the 119 healthy Ecuadorian individuals used as control. Furthermore, the mutation was the only alteration detected in the propositus's GALT after sequencing all exons and introns of this gene. In silico modeling predicted that the mutation was pathogenic.

Systematic Review and Meta-analysis of Intelligence Quotient in Early-Treated Individuals with Classical Galactosemia

INTRODUCTION

Cognitive impairment is a well-known complication of classical galactosemia (CG). Differences in patient characteristics and test methods have hampered final conclusions regarding the extent of intellectual disabilities in CG. The primary aim of this systematic review was to assess intellectual performance in early-treated (≤4 weeks of life) individuals with confirmed CG (defined by absent or barely detectable GALT enzyme activity and/or the presence of two null or severe missense variations), assessed with comparable test instruments. The full-scale IQ (FSIQ) was the variable of interest.

METHODS

A clinical librarian developed search strategies, and two independent investigators performed the study selection, risk of bias assessment and data extraction. Individual patient data were pooled for meta-analysis using linear mixed-effect models with a random intercept per study and including covariates (age or gender) as fixed effects where appropriate.

RESULTS

Four articles were included in this meta-analysis. Data of 87 individuals (median age 13 years, range 3-38 years) were used to assess mean FSIQ in CG. The FSIQ ranged from 47 to 122, and the mean score was 87 (95% CI, 81-94). Forty-five percent of individuals attained scores <85, almost 40% attained scores of 85-100, and a minority (15%) attained scores above 100. There was no significant correlation between FSIQ and age.

CONCLUSIONS

Results from this meta-analysis fortify conclusions from previous studies that early-treated individuals with CG are at risk for having impaired cognitive abilities. However, IQ varies considerably between affected individuals.

Nine years of newborn screening for classical galactosemia in the Netherlands: Effectiveness of screening methods, and identification of patients with previously unreported phenotypes

INTRODUCTION

Newborn screening (NBS) for classical galactosemia (CG) was introduced in the Netherlands in 2007. Multiple screening methods have been used since, and currently a two-tier system is used, with residual enzyme activity of galactose-1-phosphate-uridyltransferase (GALT) and total galactose concentration in dried blood spots as the primary and secondary markers. As it is essential to monitor effectiveness of NBS programs, we assessed the effectiveness of different screening methods used over time (primary aim), and aimed to identify and investigate patients identified through NBS with previously unreported clinical and biochemical phenotypes (secondary aim).

METHODS

The effectiveness of different screening methods and their cut-off values (COVs), as used from 2007 through 2015, was determined, and the clinical and biochemical data of all identified patients were retrospectively collected.

RESULTS

All screening methods and COVs resulted in relatively high false-positive rates and low positive predictive values. Total galactose levels in dried blood spots were far above the COV for NBS in all true positive cases. A total of 31 galactosemia patients were identified, and when corrected for a family with three affected siblings, 14% had a previously unreported phenotype and genotype. These individuals did not demonstrate any symptoms at the time of diagnosis while still being exposed to galactose, had galactose-1-phosphate values below detection limit within months after the start of diet, and had previously unreported genotypes.

CONCLUSION

Optimization of NBS for CG in the Netherlands is warranted because of the high false-positive rate, which may result in significant harm. Furthermore, a surprising 14% of newborns identified with CG by screening had previously unreported clinical and biochemical phenotypes and genotypes. For them, individualized prognostication and treatment are warranted, in order to avoid unnecessary stringent galactose restriction.

The galactose-induced decrease in phosphate levels leads to toxicity in yeast models of galactosemia

Classic galactosemia is an inborn error of metabolism caused by deleterious mutations in the GALT gene. A number of evidences indicate that the galactose-1-phosphate accumulation observed in patient cells is a cause of toxicity in this disease. Nevertheless, the consequent molecular events caused by the galactose-1-phosphate accumulation remain elusive. Here we show that intracellular inorganic phosphate levels decreased when yeast models of classic galactosemia were exposed to galactose. The decrease in phosphate levels is probably due to the trapping of phosphate in the accumulated galactose-1-phosphate since the deletion of the galactokinase encoding gene GAL1 suppressed this phenotype. Galactose-induced phosphate depletion caused an increase in glycogen content, an expected result since glycogen breakdown by the enzyme glycogen phosphorylase is dependent on inorganic phosphate. Accordingly, an increase in intracellular phosphate levels suppressed the galactose effect on glycogen content and conferred galactose tolerance to yeast models of galactosemia. These results support the hypothesis that the galactose-induced decrease in phosphate levels leads to toxicity in galactosemia and opens new possibilities for the development of better treatments for this disease.

Classical galactosemia in a Thai infant: case report and review of the literature

Background

Classic galactosemia is an inherited disorder of galactose metabolism that is caused by a deficiency of galactose-1-phosphate uridyl transferase (GALT). As in other Asians, the prevalence of galactosemia in Thai people is very low. An accumulation of its toxic metabolites leads to acute neonatal toxicity and long-term complications.

Objective

To present the fourth known published case of classical galactosemia in a Thai infant and review the English language literature.

Method

A 4-month-old boy who was born into a Thai family with no history of consanguinity developed persistent jaundice, hepatosplenomegaly, and lethargy, since introduction to breast-feeding.

Result

Urine gas chromatography-mass spectrometry demonstrated a high level of galactose, galactitol, and galactonate. Liver biopsy confirmed severe hepatocellular damage and fibrosis. Breast-feeding was immediately replaced by a lactose-free diet and soy milk. His clinical features and subsequent laboratory measurements improved. Developmental delays and defects on speech presented at the last followed up.

Conclusion

Long-term complications are diet-independent and inevitable. However early recognition and immediate withdraw of galactose from the diet can prevent serious morbidity and mortality.

False-Positive Newborn Screen Using the Beutler Spot Assay for Galactosemia in Glucose-6-Phosphate Dehydrogenase Deficiency

Classical galactosemia is detected through newborn screening by measuring galactose-1-phosphate uridylyltransferase (GALT) in the USA primarily via the Beutler spot assay. We report on an 18-month-old patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency that was originally diagnosed with classical galactosemia. The patient presented with elevated liver function enzymes and bilirubinemia and was immediately treated with soy-based formula. Confirmatory tests revealed deficiency of the GALT enzyme, however, full-sequencing of GALT was normal, suggestive of a different ideology. The Beutler spot assay uses three other enzymatic steps in addition to GALT. A deficiency in either of these enzymes can result in suspected decreased GALT activity when using the Beutler assay. Congenital Disorders of Glycosylation screening for phosphoglucomutase-1 deficiency was negative. Quantitative analysis of G6PD enzyme in red blood cells showed a severe deficiency and a deletion in G6PD. Soy-formula, the standard treatment for galactosemia, has been reported to trigger hemolysis in G6PD deficient patients. G6PD and phosphoglucomutase-1 deficiencies should be considered when confirmatory tests are negative for pathogenic variants in GALT and galactose-1-phosphate level is normal.

Clinical, molecular, and genetic evaluation of galactosemia in Turkish children

AIM

Galactosemia is a carbohydrate metabolism disorder with autosomal recessive inheritance. The most frequent enzyme deficiency is galactose-1-phosphate-uridylytransferase, which causes classic galactosemia. When the enzyme is absent, an infant cannot metabolize galactose-1-phosphate and it cumulates in liver, kidney, brain, tongue, lens, and skin. This study aimed to evaluate the clinical and molecular characteristics of patients with galactosemia, which is observed more frequently in our country than anywhere else in the world.

MATERIAL AND METHODS

This is a retrospective study that includes the moleculer and genetic charcteristics of 14 patient who were diagnosed as having galactosemia between January 2009 and January 2011.

RESULTS

Nine patients were male and 5 female. Consanguineous marriage was detected in the family history of 7 patients. One patient had a history of a deceased sibling with a confirmed diagnosis of galactosemia. The main reasons for admission to the hospital were jaundice in 9, hypoglycemia in 2, sepsis in 2, and elevated liver enzymes in 1 patient. The Beutler test was positive in all patients. The mean enzyme activity was 0.36±0.26 μmol/mL. Only 6 of our cases were diagnosed in the early period (first 15 days). Cataract was present in four patients. Q188R mutation was observed in 13 patients, and homozygote N314D and homozygote E340X mutations were observed in one patient. Three patients had impaired neurologic development according to the Denver Developmental Screening Test II.

CONCLUSION

The most common genetic abnormality was Q188R mutation. Only 43% of our patients's disease could be diagnosed at an early stage. We suggest that galactosemia should be included in the national newborn screening program in order to make earlier diagnoses.

Immunological aspects of congenital disorders of glycosylation (CDG): a review

Congenital disorders of glycosylation (CDG) are a rapidly growing family of genetic diseases comprising more than 85 known distinct disorders. They show a great phenotypic variability ranging from multi-organ/system to mono-organ/system involvement with very mild to extremely severe expression. Immunological dysfunction has a significant impact on the phenotype in a minority of CDG. CDG with major immunological involvement are ALG12-CDG, MAGT1-CDG, MOGS-CDG, SLC35C1-CDG and PGM3-CDG. This review discusses the variety of immunological abnormalities reported in human CDG. Understanding the immunological aspects of CDG may contribute to a better management/treatment of these pathologies and possibly of more common diseases, such as inflammatory diseases.

Acute and long-term outcomes in a Drosophila melanogaster model of classic galactosemia occur independently of galactose-1-phosphate accumulation

Classic galactosemia (CG) is a potentially lethal inborn error of metabolism that results from the profound loss of galactose-1-phosphate uridylyltransferase (GALT), the second enzyme in the Leloir pathway of galactose metabolism. Neonatal detection and dietary restriction of galactose minimizes or resolves the acute sequelae of CG, but fails to prevent the long-term complications experienced by a majority of patients. One of the substrates of GALT, galactose-1-phosphate (Gal-1P), accumulates to high levels in affected infants, especially following milk exposure, and has been proposed as the key mediator of acute and long-term pathophysiology in CG. However, studies of treated patients demonstrate no association between red blood cell Gal-1P level and long-term outcome severity. Here, we used genetic, epigenetic and environmental manipulations of a Drosophila melanogaster model of CG to test the role of Gal-1P as a candidate mediator of outcome in GALT deficiency. Specifically, we both deleted and knocked down the gene encoding galactokinase (GALK) in control and GALT-null Drosophila, and assessed the acute and long-term outcomes of the resulting animals in the presence and absence of dietary galactose. GALK is the first enzyme in the Leloir pathway of galactose metabolism and is responsible for generating Gal-1P in humans and Drosophila. Our data confirmed that, as expected, loss of GALK lowered or eliminated Gal-1P accumulation in GALT-null animals. However, we saw no concomitant rescue of larval survival or adult climbing or fecundity phenotypes. Instead, we saw that loss of GALK itself was not benign and in some cases phenocopied or exacerbated the outcome seen in GALT-null animals. These findings strongly contradict the long-standing hypothesis that Gal-1P alone underlies pathophysiology of acute and long-term outcomes in GALT-null Drosophila and suggests that other metabolite(s) of galactose, and/or other pathogenic factors, might be involved.

Summary: In a GALT-deficient Drosophila model of classic galactosemia, Gal-1P accumulation is not required for compromised larval survival following galactose exposure or adult movement and fecundity phenotypes.

Coordinated movement, neuromuscular synaptogenesis and trans-synaptic signaling defects in Drosophila galactosemia models

The multiple galactosemia disease states manifest long-term neurological symptoms. Galactosemia I results from loss of galactose-1-phosphate uridyltransferase (GALT), which converts galactose-1-phosphate + UDP-glucose to glucose-1-phosphate + UDP-galactose. Galactosemia II results from loss of galactokinase (GALK), phosphorylating galactose to galactose-1-phosphate. Galactosemia III results from the loss of UDP-galactose 4'-epimerase (GALE), which interconverts UDP-galactose and UDP-glucose, as well as UDP-N-acetylgalactosamine and UDP-N-acetylglucosamine. UDP-glucose pyrophosphorylase (UGP) alternatively makes UDP-galactose from uridine triphosphate and galactose-1-phosphate. All four UDP-sugars are essential donors for glycoprotein biosynthesis with critical roles at the developing neuromuscular synapse. Drosophila galactosemia I (dGALT) and II (dGALK) disease models genetically interact; manifesting deficits in coordinated movement, neuromuscular junction (NMJ) development, synaptic glycosylation, and Wnt trans-synaptic signalling. Similarly, dGALE and dUGP mutants display striking locomotor and NMJ formation defects, including expanded synaptic arbours, glycosylation losses, and differential changes in Wnt trans-synaptic signalling. In combination with dGALT loss, both dGALE and dUGP mutants compromise the synaptomatrix glycan environment that regulates Wnt trans-synaptic signalling that drives 1) presynaptic Futsch/MAP1b microtubule dynamics and 2) postsynaptic Frizzled nuclear import (FNI). Taken together, these findings indicate UDP-sugar balance is a key modifier of neurological outcomes in all three interacting galactosemia disease models, suggest that Futsch homolog MAP1B and the Wnt Frizzled receptor may be disease-relevant targets in epimerase and transferase galactosemias, and identify UGP as promising new potential therapeutic target for galactosemia neuropathology.

Establishing New Cut-Off Limits for Galactose 1-Phosphate-Uridyltransferase Deficiency for the Dutch Newborn Screening Programme

Newborn screening for classical galactosemia in the Netherlands is performed by five laboratories and is based on the measurement of galactose 1-phosphate-uridyltransferase (GALT) activity and total galactose (TGAL) in heel prick blood spots. Unexpected problems with the GALT assay posed a challenge to switch to a new assay. The aim of this study was to make an analytical and clinical evaluation of GALT assays to replace the current assay and to establish new cut-off values (COVs).First, the manual assay from PerkinElmer (NG-1100) and the GSP assay were compared by analyzing 626 anonymous heel prick samples in parallel. Secondly, a manual GSP method was evaluated and 2,052 samples were compared with the automated GSP assay. Finally, a clinical evaluation was performed by collecting data from 93 referred newborns.No satisfactory correlation was observed between GALT activity measured with the manual NG-1100 assay and the automated GSP assay. An acceptable correlation was found between the manual and automated GSP assay. Intra- and inter-assay variation of the automated GSP were 1.8-10.0% and 3.1-13.9%, respectively. Evaluation of clinical data demonstrated that adjusting the COVs for GALT to 2.0 U/dl and TGAL to 1,100 μmol/l improved specificity of screening for classical galactosemia.An assay designed for automated processing to measure GALT activity in heel prick samples works equally well when processed manually. We therefore adopted both methods in the Dutch screening laboratories. As a result of this evaluation new COVs for GALT and TGAL have been introduced and are valid from July 2015.

Clinical profile and molecular characterization of Galactosemia in Brazil: identification of seven novel mutations

Background

Classical Galactosemia (CG) is an inborn error of galactose metabolism caused by the deficiency of the galactose-1-phosphate uridyltransferase enzyme. It is transmitted as an autosomal recessive disease and is typically characterized by neonatal galactose intolerance, with complications ranging from neonatal jaundice and liver failure to late complications, such as motor and reproductive dysfunctions. Galactosemia is also heterogeneous from a molecular standpoint, with hundreds of different mutations described in the GALT gene, some of them specific to certain populations, reflecting consequence of founder effect.

Methods

This study reviews the main clinical findings and depicts the spectrum of mutations identified in 19 patients with CG, six with Duarte Galactosemia and one with type 2 Galactosemia in Brazil. Some individuals were diagnosed through expanded newborn screening test, which is not available routinely to all newborns.

Results

The main classical Galactosemia mutations reported to date were identified in this study, as well as the Duarte variant and seven novel mutations - c.2 T > C (p.M1T), c.97C > A (p.R33S), c.217C > T (p.P73S), c.328 + 1G > A (IVS3 + 1G > A), c.377 + 4A > C (IVS4 + 4A > C), c.287_289delACA (p.N97del) and c.506A > C (p.Q169P). This was expected, given the high miscegenation of the Brazilian population.

Conclusions

This study expands the mutation spectrum in GALT gene and reinforces the importance of early diagnosis and introduction of dietary treatment, what is possible with the introduction of Galactosemia in neonatal screening programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0300-8) contains supplementary material, which is available to authorized users.

Differential Proteomics of Urinary Exovesicles from Classical Galactosemic Patients Reveals Subclinical Kidney Insufficiency

Classical galactosemia is caused by a nearly complete deficiency of galactose-1-phosphate uridyltransferase (GALT; EC 2.7.712), resulting in a severely impaired galactose metabolism with galactose-1-phosphate and galactitol accumulation. Even on a galactose-restricted diet, patients develop serious long-term complications of the central nervous system and ovaries that may result from chronic cell-toxic effects exerted by endogenous galactose. To address the question of whether disease-associated cellular perturbations could affect the kidney function of the patients, we performed differential proteomics of detergent-resistant membranes from urinary exovesicles. Galactosemic samples (showing drastic shifts from high-mannose to complex-type N-glycosylation on exosomal N-glycoproteins) and healthy, sex-matched controls were analyzed in quadruplex iTRAQ experiments performed in biological and technical replicates. Particularly in the female patient group, the most striking finding was a drastic increase of abundant serum (glyco)proteins, like albumin, leucine-rich α-2-glycoprotein, fetuin, immunoglobulins, prostaglandin H2 d-isomerase, and α-1-microglobulin protein (AMBP), pointing to a subclinical failure of kidney filter function in galactosemic patients and resulting in a heavy overload of exosomal membranes with adsorbed serum (glyco)proteins. Several of these proteins are connected to TBMN and IgAN, proteinuria, and renal damage. The impairment of renal protein filtration was also indicated by increased protein contents derived from extracellular matrices and lysosomes.

Identification of a Large SLC25A13 Deletion via Sophisticated Molecular Analyses Using Peripheral Blood Lymphocytes in an Infant with Neonatal Intrahepatic Cholestasis Caused by Citrin Deficiency (NICCD): A Clinical and Molecular Study

Background. Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) is a Mendelian disorder arising from biallelic SLC25A13 mutations, and SLC25A13 genetic analysis was indispensable for its definite diagnosis. However, conventional SLC25A13 analysis could not detect all mutations, especially obscure large insertions/deletions. This paper aimed to explore the obscure SLC25A13 mutation in an NICCD infant. Methods. Genomic DNA was extracted to screen for 4 high-frequency SLC25A13 mutations, and then all 18 exons and their flanking sequences were analyzed by Sanger sequencing. Subsequently, cDNA cloning, SNP analyses, and semiquantitative PCR were performed to identify the obscure mutation. Results. A maternally inherited mutation IVS16ins3kb was screened out, and then cDNA cloning unveiled paternally inherited alternative splicing variants (ASVs) featuring exon 5 skipping. Ultimately, a large deletion c.329-1687_c.468+3865del5692bp, which has never been described in any other references, was identified via intensive study on the genomic DNA around exon 5 of SLC25A13 gene. Conclusions. An NICCD patient was definitely diagnosed as a compound heterozygote of IVS16ins3kb and c.329-1687_c.468+3865del5692bp. The large deletion enriched the SLC25A13 mutation spectrum, and its identification supported the concept that cDNA cloning analysis, along with other molecular tools such as semiquantitative PCR, could provide valuable clues, facilitating the identification of obscure SLC25A13 deletions.

Anti-Apoptotic and Pro-Survival Effect of Alpinate Oxyphyllae Fructus (AOF) in a d-Galactose-Induced Aging Heart

Aging, a natural biological/physiological phenomenon, is accelerated by reactive oxygen species (ROS) accumulation and identified by a progressive decrease in physiological function. Several studies have shown a positive relationship between aging and chronic heart failure (HF). Cardiac apoptosis was found in age-related diseases. We used a traditional Chinese medicine, Alpinate Oxyphyllae Fructus (AOF), to evaluate its effect on cardiac anti-apoptosis and pro-survival. Male eight-week-old Sprague–Dawley (SD) rats were segregated into five groups: normal control group (NC), d-Galactose-Induced aging group (Aging), and AOF of 50 (AL (AOF low)), 100 (AM (AOF medium)), 150 (AH (AOF high)) mg/kg/day. After eight weeks, hearts were measured by an Hematoxylin–Eosin (H&E) stain, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-assays and Western blotting. The experimental results show that the cardiomyocyte apoptotic pathway protein expression increased in the d-Galactose-Induced aging groups, with dose-dependent inhibition in the AOF treatment group (AL, AM, and AH). Moreover, the expression of the pro-survival p-Akt (protein kinase B (Akt)), Bcl-2 (B-cell lymphoma 2), anti-apoptotic protein (Bcl-xL) protein decreased significantly in the d-Galactose-induced aging group, with increased performance in the AOF treatment group with levels of p-IGFIR and p-PI3K (Phosphatidylinositol-3′ kinase (PI3K)) to increase by dosage and compensatory performance. On the other hand, the protein of the Sirtuin 1 (SIRT1) pathway expression decreased in the aging groups and showed improvement in the AOF treatment group. Our results suggest that AOF strongly works against ROS-induced aging heart problems.

Gene Transcriptional and Metabolic Profile Changes in Mimetic Aging Mice Induced by D-Galactose

D-galactose injection has been shown to induce many changes in mice that represent accelerated aging. This mouse model has been widely used for pharmacological studies of anti-aging agents. The underlying mechanism of D-galactose induced aging remains unclear, however, it appears to relate to glucose and 1ipid metabolic disorders. Currently, there has yet to be a study that focuses on investigating gene expression changes in D-galactose aging mice. In this study, integrated analysis of gas chromatography/mass spectrometry-based metabonomics and gene expression profiles was used to investigate the changes in transcriptional and metabolic profiles in mimetic aging mice injected with D-galactose. Our findings demonstrated that 48 mRNAs were differentially expressed between control and D-galactose mice, and 51 potential biomarkers were identified at the metabolic level. The effects of D-galactose on aging could be attributed to glucose and 1ipid metabolic disorders, oxidative damage, accumulation of advanced glycation end products (AGEs), reduction in abnormal substance elimination, cell apoptosis, and insulin resistance.

Inborn errors of metabolism

Inborn errors of metabolism (IEM) are individually rare but collectively common. Approximately 25% of IEMs can have manifestations in the neonatal period. Neonates with IEM are usually healthy at birth; however, in hours to days after birth they can develop nonspecific signs that are common to several other neonatal conditions. Therefore, maintaining a high index of suspicion is extremely important for early diagnosis and the institution of appropriate therapy, which are mandatory to prevent death and ameliorate complications from many IEMs.

Neurologic sequela in a patient with galactosemia potentially mediated by interleukin-11 dysfunction

A 16-year-old galactosemic patient, homozygous for the 5.5-kb gene deletion, suffered severe neurologic regression following streptococcal infection. Since the gene deletion includes the promoter of interleukin-11a receptor involved in neuronal apoptosis, we questioned whether this patient had no interleukin-11a receptor activity-resulting in neuronal toxicity during septicemia. We hypothesized that interleukin-11 levels would be elevated because of a loss of feedback induced by the absent interleukin-11Ra receptor complex. To assess this, we compared interleukin-11 levels in the proband and 2 of his siblings with the same genetic deletion, to age-matched controls. No differences were found in interleukin-11 levels between groups. Our study was not carried out during acute infective states, when the disrupted immunoregulation triggered by sepsis is relevant, and is thus limited. In conclusion, although interleukin-11 was not chronically elevated in individuals with galactosemia and 5.5-kb gene deletion, data do not rule out potential interleukin-11 dysfunction during acute infection.

Galactose-1-phosphate uridyltransferase dried blood spot quality control materials for newborn screening tests

OBJECTIVES

We aimed to prepare dried-blood-spot (DBS) quality control (QC) materials for galactose-1-phosphate uridyltransferase (GALT), to evaluate their stability during storage and use, and to evaluate their performance in five DBS GALT test methods.

DESIGN AND METHODS

We prepared and characterized GALT-normal and GALT-deficient DBS materials and compared GALT activities in DBSs after predetermined storage intervals at controlled temperatures and humidities. External evaluators documented the suitability of the DBS QC materials for use in five GALT test methods.

RESULTS

GALT activity losses from DBSs stored in low (<30%) humidity for 14 days at 45°C, 35 days at 37°C, 91 days at room temperature, 182 days at 4°C, and 367 days at -20°C were 54%, 53%, 52% 23%, and 7% respectively. In paired DBSs stored in high humidity (>50%) for identical intervals, losses were: 45°C-68%; 37°C-79%; room temperature-72%, and 4°C-63%. GALT activities in DBSs stored at 4°C were stable throughout 19 excursions to room temperature. Twenty-five of 26 external evaluators, using five different GALT test methods, classified the GALT-deficient DBSs as "outside normal limits". All evaluators classified the GALT-normal DBSs as "within normal limits".

CONCLUSIONS

Most of the GALT activity loss from DBSs stored at elevated or room temperature was attributable to the effects of storage temperature. Most of the loss from DBSs stored at 4°C was attributable to the effects of elevated humidity. Loss from DBSs stored at -20°C was insignificant. The DBS materials were suitable for monitoring performance of all five GALT test methods.

Arginine Functionally Improves Clinically Relevant Human Galactose-1-Phosphate Uridylyltransferase (GALT) Variants Expressed in a Prokaryotic Model

Classic galactosemia is a rare genetic disease of the galactose metabolism, resulting from deficient activity of galactose-1-phosphate uridylyltransferase (GALT). The current standard of care is lifelong dietary restriction of galactose, which however fails to prevent the development of long-term complications. Structural-functional studies demonstrated that the most prevalent GALT mutations give rise to proteins with increased propensity to aggregate in solution. Arginine is a known stabilizer of aggregation-prone proteins, having already shown a beneficial effect in other inherited metabolic disorders.Herein we developed a prokaryotic model of galactose sensitivity that allows evaluating in a cellular context the mutations' impact on GALT function, as well as the potential effect of arginine in functionally rescuing clinically relevant variants.This study revealed that some hGALT variants, previously described to exhibit no detectable activity in vitro, actually present residual activity when determined in vivo. Furthermore, it revealed that arginine presents a mutation-specific beneficial effect, particularly on the prevalent p.Q188R and p.K285N variants, which led us to hypothesize that it might constitute a promising therapeutic agent in classic galactosemia.

Assessing Psychological Functioning in Metabolic Disorders: Validation of the Adaptive Behavior Assessment System, Second Edition (ABAS-II), and the Behavior Rating Inventory of Executive Function (BRIEF) for Identification of Individuals at Risk

Long-term follow-up of neuropsychological functioning in metabolic disorders remains difficult due to limited opportunities for comprehensive neuropsychological evaluations. This study examined the validity of using the Adaptive Behavior Assessment System, Second Edition (ABAS-II), and the Behavior Rating Inventory of Executive Function (BRIEF) for assessing developmental status in metabolic disorders and for identifying individuals at risk for cognitive deficits. Results from individuals with urea cycle disorders, phenylketonuria, galactosemia, and fatty acid oxidation disorders were obtained on the ABAS-II and BRIEF and were compared to results obtained from neuropsychological testing performed on the same day. Correlations between scores on the ABAS-II and developmental or IQ tests for individuals with urea cycle disorders ranged from 0.48 to 0.72 and concordance rates for scores greater than a standard deviation below the normative mean ranged from 69 to 89%. Correlations ranged from 0.20 to 0.68 with concordance ranging from 73 to 90% in the other metabolic disorders. For the BRIEF, correlations with other tests of executive functioning were significant for urea cycle disorders, with concordance ranging from 52 to 80%. For the other metabolic disorders, correlations ranged from -0.09 to -0.55. Concordance rates for at-risk status on the BRIEF and executive functioning tests ranged from 55% in adults to 80% in children with other metabolic disorders. These results indicate that the ABAS-II and BRIEF together can confidently be used as an adjunct or supplementary method for clinical follow-up and for research on functional status involving infants, children, and adults with metabolic disorders.

Consensus on the guidelines for the dietary management of classical galactosemia

BACKGROUND AND AIM

Worldwide there is scientific discussion about the dietary management of galactosemia. The dietary management is very different in several countries among Europe, the US and Canada. The main points of discussion are related to the fact that i) despite a strict diet some patients still have poor outcomes; ii) there is lack of scientific knowledge about the role of endogenous production of galactose on disease evolution, with or without diet. The aim of the current work was the creation of a Belgian consensus on dietary guidelines for the management of galactosemia.

METHODS

A step-wise approach was used to achieve a consensus, including: a workshop, a Delphi round, discussion groups and a round table of different Belgian experts.

RESULTS

The consensus is an agreement between strict guidelines (strict limitation of fruits, vegetables and soybean products/French guidelines) and the more liberal guidelines (comparable with a diet free of lactose/guidelines of UK and the Netherlands). The consensus document consists of different modules, including the medical context, the theoretical background of dietary guidelines and the age-specific practical dietary guidelines.

CONCLUSION

A Belgian consensus on the guidelines for the dietary management of classical galactosemia was developed despite the uncertainties of the efficacy and practical application of these guidelines. The final consensus is based on scientific knowledge and practical agreement among experts. In the future, regular revision of the guidelines is recommended and a uniform European guideline is desirable.

Galactose oxidation using (13)C in healthy and galactosemic children

Galactosemia is an inborn error of galactose metabolism that occurs mainly as the outcome of galactose-1-phosphate uridyltransferase (GALT) deficiency. The ability to assess galactose oxidation following administration of a galactose-labeled isotope (1-(13)C-galactose) allows the determination of galactose metabolism in a practical manner. We aimed to assess the level of galactose oxidation in both healthy and galactosemic Brazilian children. Twenty-one healthy children and seven children with galactosemia ranging from 1 to 7 years of age were studied. A breath test was used to quantitate (13)CO2 enrichment in exhaled air before and at 30, 60, and 120 min after the oral administration of 7 mg/kg of an aqueous solution of 1-(13)C-galactose to all children. The molar ratios of (13)CO2 and (12)CO2 were quantified by the mass/charge ratio (m/z) of stable isotopes in each air sample by gas-isotope-ratio mass spectrometry. In sick children, the cumulative percentage of (13)C from labeled galactose (CUMPCD) in the exhaled air ranged from 0.03% at 30 min to 1.67% at 120 min. In contrast, healthy subjects showed a much broader range in CUMPCD, with values from 0.4% at 30 min to 5.58% at 120 min. The study found a significant difference in galactose oxidation between children with and without galactosemia, demonstrating that the breath test is useful in discriminating children with GALT deficiencies.

Compound heterozygosity with a novel S222N GALT mutation leads to atypical galactosemia with loss of GALT activity in erythrocytes but little evidence of clinical disease

Galactosemia is an inborn error of galactose metabolism caused by mutations in the GALT gene. Though early detection and galactose restriction prevent severe liver disease, affected individuals have persistently elevated biomarkers and often neuro-developmental symptoms. We present a teenage compound heterozygote for a known pathogenic mutation (H132Q) and a novel variant of unknown significance (S222N), with nearly absent erythrocyte GALT enzyme activity but normal biomarkers and only mild anxiety despite diet non-adherence. This case is similar to a previously reported S135L mutation. In this report we investigate the novel S222N variant and critically evaluate a clinically puzzling case.

Untargeted metabolomic analysis of urine samples in the diagnosis of some inherited metabolic disorders

BACKGROUND

Metabolomics is becoming an important tool in clinical research and the diagnosis of human diseases. It has been used in the diagnosis of inherited metabolic disorders with pronounced biochemical abnormalities. The aim of this study was to determine if it could be applied in the diagnosis of inherited metabolic disorders (IMDs) with less clear biochemical profiles from urine samples using an untargeted metabolomic approach.

METHODS

A total of 14 control urine samples and 21 samples from infants with cystinuria, maple syrup urine disease, adenylosuccinate lyase deficiency and galactosemia were tested. Samples were analyzed by liquid chromatography on aminopropyl column in aqueous normal phase separation system using gradient elution of acetonitrile/ammonium acetate. Detection was performed by time-of-flight mass spectrometer fitted with electrospray ionisation in positive mode. The data were statistically processed using principal component analysis (PCA), principal component discriminant function analysis (PCA-DFA) and partial least squares (PLS) regression.

RESULTS

All patient samples were first distinguished from controls using unsupervised PCA. Discrimination of the patient samples was then unambiguously verified using supervised PCA-DFA. Known markers of the diseases in question were successfully confirmed and a potential new marker emerged from the PLS regression.

CONCLUSION

This study showed that untargeted metabolomics can be applied in the diagnosis of mild IMDs with less clear biochemical profiles.

Overelaborated synaptic architecture and reduced synaptomatrix glycosylation in a Drosophila classic galactosemia disease model

Classic galactosemia (CG) is an autosomal recessive disorder resulting from loss of galactose-1-phosphate uridyltransferase (GALT), which catalyzes conversion of galactose-1-phosphate and uridine diphosphate (UDP)-glucose to glucose-1-phosphate and UDP-galactose, immediately upstream of UDP-N-acetylgalactosamine and UDP-N-acetylglucosamine synthesis. These four UDP-sugars are essential donors for driving the synthesis of glycoproteins and glycolipids, which heavily decorate cell surfaces and extracellular spaces. In addition to acute, potentially lethal neonatal symptoms, maturing individuals with CG develop striking neurodevelopmental, motor and cognitive impairments. Previous studies suggest that neurological symptoms are associated with glycosylation defects, with CG recently being described as a congenital disorder of glycosylation (CDG), showing defects in both N- and O-linked glycans. Here, we characterize behavioral traits, synaptic development and glycosylated synaptomatrix formation in a GALT-deficient Drosophila disease model. Loss of Drosophila GALT (dGALT) greatly impairs coordinated movement and results in structural overelaboration and architectural abnormalities at the neuromuscular junction (NMJ). Dietary galactose and mutation of galactokinase (dGALK) or UDP-glucose dehydrogenase (sugarless) genes are identified, respectively, as critical environmental and genetic modifiers of behavioral and cellular defects. Assaying the NMJ extracellular synaptomatrix with a broad panel of lectin probes reveals profound alterations in dGALT mutants, including depletion of galactosyl, N-acetylgalactosamine and fucosylated horseradish peroxidase (HRP) moieties, which are differentially corrected by dGALK co-removal and sugarless overexpression. Synaptogenesis relies on trans-synaptic signals modulated by this synaptomatrix carbohydrate environment, and dGALT-null NMJs display striking changes in heparan sulfate proteoglycan (HSPG) co-receptor and Wnt ligand levels, which are also corrected by dGALK co-removal and sugarless overexpression. These results reveal synaptomatrix glycosylation losses, altered trans-synaptic signaling pathway components, defective synaptogenesis and impaired coordinated movement in a CG neurological disease model.

Pre-linguistic communication skill development in an infant with a diagnosis of galactosaemia

BACKGROUND

Neonatal screening for galactosaemia (GAL) identifies the condition early, but subsequent biomedical and genetic testing fails to identify which subgroup of infants with GAL are at most risk of the language disorders associated with the condition. This study aims to present preliminary data on an infant with GAL based on assessment of pre-linguistic communication behaviours known to underpin language development.

METHODS

This single case-control study profiles the pre-linguistic skills of a 13-month-old infant with GAL. The Index Infant's performance was descriptively compared to that of a typically developing, suitably matched control infant.

RESULTS

The Index Infant was identified as presenting with clinically significant delays on 9 of the 11 pre-linguistic skills assessed.

DISCUSSION AND CONCLUSION

The early identification of risk of developmental language difficulties in the Index Infant allows for the implementation of early intervention using the infant's parents as facilitators of language stimulation. Monitoring of the infant's progress is warranted.