An updated review of the long-term neurological effects of galactosemia

Neuroactive metabolites and bile acids are altered in extremely premature infants with brain injury

The gut microbiome is associated with pathological neurophysiological evolvement in extremely premature infants suffering from brain injury. The exact underlying mechanism and its associated metabolic signatures in infants are not fully understood. To decipher metabolite profiles linked to neonatal brain injury, we investigate the fecal and plasma metabolome of samples obtained from a cohort of 51 extremely premature infants at several time points, using liquid chromatography (LC)-high-resolution mass spectrometry (MS)-based untargeted metabolomics and LC-MS/MS-based targeted analysis for investigating bile acids and amidated bile acid conjugates. The data are integrated with 16S rRNA gene amplicon gut microbiome profiles as well as patient cytokine, growth factor, and T cell profiles. We find an early onset of differentiation in neuroactive metabolites between infants with and without brain injury. We detect several bacterially derived bile acid amino acid conjugates in plasma and feces. These results provide insights into the early-life metabolome of extremely premature infants.

Brain function in classic galactosemia, a galactosemia network (GalNet) members review

Classic galactosemia (CG, OMIM #230400, ORPHA: 79,239) is a hereditary disorder of galactose metabolism that, despite treatment with galactose restriction, affects brain function in 85% of the patients. Problems with cognitive function, neuropsychological/social emotional difficulties, neurological symptoms, and abnormalities in neuroimaging and electrophysiological assessments are frequently reported in this group of patients, with an enormous individual variability. In this review, we describe the role of impaired galactose metabolism on brain dysfunction based on state of the art knowledge. Several proposed disease mechanisms are discussed, as well as the time of damage and potential treatment options. Furthermore, we combine data from longitudinal, cross-sectional and retrospective studies with the observations of specialist teams treating this disease to depict the brain disease course over time. Based on current data and insights, the majority of patients do not exhibit cognitive decline. A subset of patients, often with early onset cerebral and cerebellar volume loss, can nevertheless experience neurological worsening. While a large number of patients with CG suffer from anxiety and depression, the increased complaints about memory loss, anxiety and depression at an older age are likely multifactorial in origin.

Comparison of In Vitro and In Silico Assessments of Human Galactose-1-Phosphate Uridylyltransferase Coding Variants

Introduction Human pathogenic coding variations of the galactose-1-phosphate uridylyltransferase (GALT) gene cause classic galactosemia, a recessive disease of galactose metabolism. Unfortunately, there are many variants of uncertain significance (VUS) that need to be characterized in order to be able to predict the likelihood of classic galactosemia for all possible genotypes. There are many bioinformatic resources available that attempt to predict the pathogenicity of a human variant, but it is unclear if these methods realistically predict the consequence of these variants. To determine the clinical application of these resources, we compared the results of in vitro enzymatic assays with in silico predictive models. Methods In all assays, we compared the activity of the three human GALT VUS (Alanine81Threonine, Histidine47Aspartate, Glutamate58Lysine) to native GALT (nGALT) and to a variant of known pathogenic clinical significance (Glutamine188Arginine). The enzymatic activities of VUS recombinant proteins were compared to the results of in silico analytical methods. The in silico methods included the comparison of molecular dynamic simulation root-mean-square deviation (RMSD) results and the results from predictive programs PredictSNP, evolutionary model of variant effect (EVE), ConSurf, and sorting intolerant from tolerant (SIFT). Results The enzymatic assays showed that the variants tested had diminished Vmax relative to the native protein. The VUS RMSD data for both the whole protein and individual residues in the molecular dynamics simulations were not significantly different when compared to nGALT. The other predictive programs had mixed results for each VUS and were not consistent with the enzyme activity or simulation results. Conclusions Our experiments indicated a statistically significant decrease in enzymatic activity of the VUS when compared to nGALT. These experiments also demonstrated significant differences between in silico predictions and in vitro results. These results suggest that the in silico tools used may not be beneficial in determining the pathogenicity of GALT VUS.

North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition Position Paper on the Diagnosis and Management of Pediatric Acute Liver Failure

ABSTRACT

Pediatric acute liver failure (PALF) is a rare, rapidly progressive clinical syndrome with significant morbidity and mortality. The phenotype of PALF manifests as abrupt onset liver dysfunction, which can be brought via disparate etiology. Management is reliant upon intensive clinical care and support, often provided by the collaborative efforts of hepatologists, critical care specialists, and liver transplant surgeons. The construction of an age-based diagnostic approach, the identification of a potential underlying cause, and the prompt implementation of appropriate therapy can be lifesaving; however, the dynamic and rapidly progressive nature of PALF also demands that diagnostic inquiries be paired with monitoring strategies for the recognition and treatment of common complications of PALF. Although liver transplantation can provide a potential life-saving therapeutic option, the ability to confidently determine the certainness that liver transplant is needed for an individual child has been hampered by a lack of adequately tested clinical decision support tools and accurate predictive models. Given the accelerated progress in understanding PALF, we will provide clinical guidance to pediatric gastroenterologists and other pediatric providers caring for children with PALF by presenting the most recent advances in diagnosis, management, pathophysiology, and associated outcomes.

Metabolic Framework for the Improvement of Autism Spectrum Disorders by a Modified Ketogenic Diet: A Pilot Study

The ketogenic diet (KD) can improve the core features of autism spectrum disorders (ASD) in some children, but the effects on the overall metabolism remain unclear. This pilot study investigated the behavioral parameters in relation to blood metabolites and trace elements in a cohort of 10 typically developed controls (TC) and 17 children with ASD at baseline and following 3 months of treatment with a modified KD regimen. A nontargeted, multiplatform metabolomic approach was employed, including gas chromatography-mass spectrometry, ¹H nuclear magnetic resonance spectroscopy, and inductively coupled plasma-mass spectrometry. The associations among plasma metabolites, trace elements, and behavior scores were investigated. Employing a combination of metabolomic platforms, 118 named metabolites and 73 trace elements were assessed. Relative to TC, a combination of glutamate, galactonate, and glycerol discriminated ASD with 88% accuracy. ASD had higher concentrations of galactose intermediates, gut microbe-derived trimethylamine N-oxide and N-acetylserotonin, and lower concentrations of 3-hydroxybutyrate and selenium at baseline. Following 3 months of KD intervention, the levels of circulating ketones and acetylcarnitine were increased. KD restored lower selenium levels in ASD to that of controls, and correlation analysis identified a novel negative correlation between the changes in selenium and behavior scores. Based on the different behavior responses to KD, we found that high responders had greater concentrations of 3-hydroxybutyrate and ornithine, with lower galactose. These findings enhance our current understanding of the metabolic derangements present in ASD and may be of utility in predicting favorable responses to KD intervention.

Early neurological complications in children with classical galactosemia and p.gln188arg mutation

BACKGROUND

Despite implementation of a controlled diet, children with classical galactosemia (CG) may develop a variety of developmental and cognitive problems. In this study, we examined the early developmental status of, as well as the neurological and neuroradiological findings for, children with CG.

METHODS

We retrospectively evaluated 46 galactosemia patients who were followed between 2003 and 2017. We included those who exhibited CG and p.gln188arg homozygous mutation without concomitant disease and who had undergone detailed neurological examination, brain magnetic resonance imaging (MRI), and Denver II developmental testing.

RESULTS

The mean ages at the time of the most recent neurological examination and Denver II testing were 48.5 ± 28.5 months and 34.4 ± 18.2 months, respectively. Developmental delay was defined as developmental age ≥ 20% lower than chronological age. The results were normal in 25 patients and delayed ≥ 20% in least in one domain, primarily in language development, in 21 patients. Brain MRI was abnormal in 22 patients.

CONCLUSIONS

This analysis of the youngest children with the same genetic mutation reported thus far showed that, despite treatment, developmental delays and abnormalities on brain MRI may begin at an early age.

Movement disorders and nonmotor neuropsychological symptoms in children and adults with classical galactosemia

Although movement disorders (MDs) are known complications, the exact frequency and severity remains uncertain in patients with classical galactosemia, especially in children. We determined the frequency, classification and severity of MDs in a cohort of pediatric and adult galactosemia patients, and assessed the association with nonmotor neuropsychological symptoms and daily functioning. Patients from seven centers in the United Kingdom and the Netherlands with a confirmed galactosemia diagnosis were invited to participate. A videotaped neurological examination was performed and an expert panel scored the presence, classification and severity of MDs. Disease characteristics, nonmotor neuropsychological symptoms, and daily functioning were evaluated with structured interviews and validated questionnaires (Achenbach, Vineland, Health Assessment Questionnaire, SIP68). We recruited 37 patients; 19 adults (mean age 32.6 years) and 18 children (mean age 10.7 years). Subjective self-reports revealed motor symptoms in 19/37 (51.4%), similar to the objective (video) assessment, with MDs in 18/37 patients (48.6%). The objective severity scores were moderate to severe in one third (6/37). Dystonia was the overall major feature, with additional tremor in adults, and myoclonus in children. Behavioral or psychiatric problems were present in 47.2%, mostly internalizing problems, and associated with MDs. Daily functioning was significantly impaired in the majority of patients. Only one patient received symptomatic treatment for MDs. We show that MDs and nonmotor neuropsychological symptoms are frequent in both children and adults with classical galactosemia.

Clinical approach to tremor in children

Pediatric Movement Disorders encompass a very large and complex group of diseases, among which Tremor is one of the least studied. Evaluation of tremors in kids carries significant challenges, in particular the fact that many tremor etiologies have other associated movement disorders that make tremor identification more difficult. Also, it is sometimes difficult to differentiate tremors from other shaking disorders. Yet, the correct identification of tremor leads to appropriate treatments and sometimes practical cures. Thus, in this paper we have strived to provide a succinct, clinically useful and practical review of pediatric tremors. The most useful classification of tremors in based on their predominance during rest or activity. By far, the most common tremor in children is during action. We provide a clinical algorithm on how to assess pediatric tremors at the bedside, as well as multiple useful tables. We also review common tremor etiologies.

Discovery of novel inhibitors of human galactokinase by virtual screening

Classic Galactosemia is a potentially lethal autosomal recessive metabolic disorder caused by deficient galactose-1-phosphate uridyltransferase (GALT) that results in the buildup of galactose-1-phosphate (gal-1-p) in cells. Galactokinase (GALK1) is the enzyme responsible for converting galactose into gal-1-p. A pharmacological inhibitor of GALK1 is hypothesized to be therapeutic strategy for treating galactosemia by reducing production of gal-1-p. In this study, we report the discovery of novel series of GALK1 inhibitors by structure-based virtual screening (VS). Followed by an extensive structural modeling and binding mode analysis of the active compounds identified from quantitative high-throughput screen (qHTS), we developed an efficient pharmacophore-based VS approach and applied for a large-scale in silico database screening. Out of 230,000 compounds virtually screened, 350 compounds were cherry-picked based on multi-factor prioritization procedure, and 75 representing a diversity of chemotypes exhibited inhibitory activity in GALK1 biochemical assay. Furthermore, a phenylsulfonamide series with excellent in vitro ADME properties was selected for downstream characterization and demonstrated its ability to lower gal-1-p in primary patient fibroblasts. The compounds described herein should provide a starting point for further development of drug candidates for the GALK1 modulation in the Classic Galactosemia.

Microchip in situ electrosynthesis of silver metallic oxide clusters for ultra-FAST detection of galactose in galactosemic newborns' urine samples

This work describes for the first time the coupling of microfluidic chips (MC) to electrosynthetized silver metallic oxide clusters (AgMOCs). As an early demonstration of this novel approach, the ultrafast detection of galactose in galactosemic newborns' urine samples is proposed. AgMOCs were in situ electrosynthetized on integrated microchip platinum electrodes using a double pulse technique and characterized in full using scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques revealing the presence of silver oxides and electrocatalysis towards galactose as a galactosemia biomarker. Galactose detection in galactosemic newborns' urine samples proceeded in less than 30 s, differentiating between ill and healthy urine samples and requiring negligible urine sample consumption. The significance of the newborns' urine samples confirmed the analytical potency of the MC-AgMOCs approach for future implementation of screening for rare disease diagnosis such as galactosemia.

Galactose-1-phosphate uridyltransferase deficiency: A literature review of the putative mechanisms of short and long-term complications and allelic variants

Galactosemia type 1 is an autosomal recessive disorder of galactose metabolism, determined by a deficiency in the enzyme galactose-1-phosphate uridyltransferase (GALT). GALT deficiency is classified as severe or variant depending on biochemical phenotype, genotype and potential to develop acute and long-term complications. Neonatal symptoms usually resolve after galactose-restricted diet; however, some patients, despite the diet, can develop long-term complications, in particular when the GALT enzyme activity results absent or severely decreased. The mechanisms of acute and long-term complications are still discussed and several hypotheses are presented in the literature like enzymatic inhibition, osmotic stress, endoplasmic reticulum stress, oxidative stress, defects of glycosylation or epigenetic modification. This review summarizes the current knowledge of galactosemia, in particular the putative mechanisms of neonatal and long-term complications and the molecular genetics of GALT deficiency.

Classic Galactosemia: Study on the Late Prenatal Development of GALT Specific Activity in a Sheep Model

Classic galactosemia results from deficient activity of galactose-1-phosphate uridylyltransferase (GALT), a key enzyme of galactose metabolism. Despite early diagnosis and early postnatal therapeutic intervention, patients still develop neurologic and fertility impairments. Prenatal developmental toxicity has been hypothesized as a determinant factor of disease. In order to shed light on the importance of prenatal GALT activity, several studies have examined GALT activity throughout development. GALT was shown to increase with gestational age in 7-28 weeks human fetuses; later stages were not investigated. Prenatal studies in animals focused exclusively on brain and hepatic GALT activity. In this study, we aim to examine GALT specific activity in late prenatal and adult stages, using a sheep model. Galactosemia acute target-organs-liver, small intestine and kidney-had the highest late prenatal activity, whereas the chronic target-organs-brain and ovary-did not exhibit a noticeable pre- or postnatal different activity compared with nontarget organs. This is the first study on GALT specific activity in the late prenatal stage for a wide variety of organs. Our findings suggest that GALT activity cannot be the sole pathogenic factor accounting for galactosemia long-term complications, and that some organs/cells might have a greater susceptibility to galactose toxicity. Anat Rec, 300:1570-1575, 2017. © 2017 Wiley Periodicals, Inc.

Vertically-Oriented and Shape-Tailored Electrocatalytic Metal Nanowire Arrays for Enzyme-Free Galactosemia Rapid Diagnosis

Metallic catalytic nanowires such as nickel and copper nanowires (NWs) for electrochemical detection of carbohydrates involved in metabolic rare diseases are proposed. NWs were electrodeposited using a polycarbonate membrane template, which was cut with the desired shape, stuck in double-sided adhesive tape, pasted into a non-conductive substrate and in situ removed. This simple and versatile approach allowed to obtain NWs vertically oriented (v-NWs), which are contained in the double-sided adhesive tape, becoming highly versatile. The high specific surface of working electrode in which the transduction is supported exclusively by the nanomaterial yielded a high analytical performance [extremely low fouling for galactose (RSD<2 %; n=25)]. Likewise, v-NWs exhibited a superior analytical performance with respect to commercial sputtered thick-film electrodes showing also a clear advantage related with the price, as well as with non-need clean room facilities. The analytical potency of the new approach was clearly demonstrated towards the fast and reliable diagnosis of galactosemia using precious newborn urine samples compared to standard clinical diagnosis. These results revealed new opportunities for future enzyme-free diagnosis and development of future point-of-care applications.

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.

Cholestasis in Infancy

Jaundice is a key manifestation of hepatobiliary disease in all age groups. Jaundice is a common finding in the first 2 weeks after birth, occurring in 2.4% to 15% of newborns. The neonatal liver is at increased susceptibility to cholestasis, with an incidence ranging from 1 in 2,500 to 1 in 5,000 live births. Etiologies vary, but the most common is biliary atresia. In 2004, the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition published guidelines for the evaluation of cholestasis that clearly stated any infant with jaundice persisting beyond age 2 weeks (3 weeks in breast-fed infants with an otherwise normal history and physical examination) should be evaluated with a fractionated serum bilirubin level. Prompt evaluation, diagnosis, and intervention are vital to optimize timely intervention and improve clinical outcomes. This article discusses the etiology, diagnosis and evaluation of cholestatis in infants. [Pediatr Ann. 2016;45(12):e414-e419.].

Evidence of oxidative stress in brain and liver of young rats submitted to experimental galactosemia

Galactosemia is a disorder of galactose metabolism, leading to the accumulation of this carbohydrate. Galactosemic patients present brain and liver damage. For evaluated oxidative stress, 30-day-old males Wistar rats were divided into two groups: galactose group, that received a single injection of this carbohydrate (5 μmol/g), and control group, that received saline 0.9 % in the same conditions. One, twelve or twenty-four hours after the administration, animals were euthanized and cerebral cortex, cerebellum, and liver were isolated. After one hour, it was found a significant increase in TBA-RS levels, nitrate and nitrite and protein carbonyl contents in cerebral cortex, as well as protein carbonyl content in the cerebellum and in hepatic level of TBA-RS, and a significant decrease in nitrate and nitrite contents in cerebellum. TBA-RS levels were also found increased in all studied tissues, as well as nitrate and nitrite contents in cerebral cortex and cerebellum, that also present increased protein carbonyl content and impairments in the activity of antioxidant enzymes of rats euthanized at twelve hours. Finally, animals euthanized after twenty-four hours present an increase of TBA-RS levels in studied tissues, as well as the protein carbonyl content in cerebellum and liver. These animals also present an increased nitrate and nitrite content and impairment of antioxidant enzymes activities. Taken together, our data suggest that acute galactose administration impairs redox homeostasis in brain and liver of rats.

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.

Friedreich Ataxia in Classical Galactosaemia

Movement disorders such as ataxia are a recognized complication of classical galactosaemia, even in diet-compliant patients. Here, we report the coexistence of classical galactosaemia and Friedreich ataxia (FRDA) in nine children from seven Irish Traveller families. These two autosomal recessive disorders, the loci for which are located on either side of the centromere of chromosome 9, appear to be in linkage disequilibrium in this subgroup. Both conditions are known to occur with increased frequency amongst the Irish Traveller population.Each member of our cohort had been diagnosed with galactosaemia in the neonatal period, and all are homozygous for the common Q188R mutation in the GALT gene. Eight of the nine patients later presented with progressive ataxia, between the ages of 5-13 years. Another child presented in cardiac failure secondary to dilated cardiomyopathy at 7 years of age. He was not ataxic at presentation and, one year from diagnosis, his neurological examination remains normal. The diagnosis of FRDA was confirmed by detecting the common pathogenic GAA expansion in both alleles of the frataxin gene (FXN) in each patient.Neurological symptoms are easily attributed to an underlying diagnosis of galactosaemia. It is important to consider a diagnosis of Friedreich ataxia in a child from the Irish Traveller population with galactosaemia who presents with ataxia or cardiomyopathy.

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.

Newborn screening for galactosemia: a 30-year single center experience

BACKGROUND

Galactosemia due to complete or near-complete galactose-1-phosphate uridyltransferase (GALT) deficiency was the first disorder added to the pioneering newborn screening panel besides phenylketonuria. In the last 50 years, many criticisms have been focused on the opportunity of its inclusion. Consequently, long-term single center experiences with this issue are generally lacking.

METHODS

We reviewed the outcome of newborn screening for hypergalactosemia performed at our department since 1982 and the correspondent long-term clinical outcome.

RESULTS

Among 1 123 909 newborns screened for hypergalactosemia, 33 showed abnormal results confirmed at second tier test. Thirteen patients were affected with classic galactosemia, 8 partial GALT deficiency, 3 severe galactokinase deficiency, 7 transient galactosemia, one congenital porto-systemic shunt, and one glucose transporter 2 deficiency. Acute neonatal liver failure in the late first week of life (5.8±1.1 days) unavoidably complicated the clinical course of classic galactosemia, unless in three second-born siblings treated on the basis of presumptive diagnosis immediately after newborn screening sample collection on day 3. Despite early treatment and long-term steadily normal peripheral blood galactose, 77% of patients with severe GALT deficiency present mild to severe intellectual disabilities. All patients with partial GALT deficiency showed normal intellectual development on a regular diet, as well as patients with galactokinase deficiency under treatment.

CONCLUSIONS

Availability of screening results within the fifth day after birth would allow the prevention of acute decompensation in classic galactosemia. A systematic diagnostic work-up in all positive newborns is essential to unravel the etiology of hypergalactosemia.

Clinical and molecular spectra in galactosemic patients from neonatal screening in northeastern Italy: structural and functional characterization of new variations in the galactose-1-phosphate uridyltransferase (GALT) gene

Classical galactosemia is an autosomal recessive inborn error of metabolism due to mutations of the GALT gene leading to toxic accumulation of galactose and derived metabolites. With the benefit of early diagnosis by neonatal screening and early therapy, the acute presentation of classical galactosemia can be prevented. However, despite early diagnosis and treatment, the long term outcome for these patients is still unpredictable because they may go on to develop cognitive disability, speech problems, neurological and/or movement disorders and, in females, ovarian dysfunction. The objectives of the current study were to report our experience with a group of galactosemic patients identified through the neonatal screening programs in northeastern Italy during the last 30years. No neonatal deaths due to galactosemia complications occurred after the introduction of the neonatal screening program. However, despite the early diagnosis and dietary treatment, the patients with classical galactosemia showed one or more long-term complications. A total of 18 different variations in the GALT gene were found in the patient cohort: 12 missense, 2 frameshift, 1 nonsense, 1 deletion, 1 silent variation, and 1 intronic. Six (p.R33P, p.G83V, p.P244S, p.L267R, p.L267V, p.E271D) were new variations. The most common variation was p.Q188R (12 alleles, 31.5%), followed by p.K285N (6 alleles, 15.7%) and p.N314D (6 alleles, 15.7%). The other variations comprised 1 or 2 alleles. In the patients carrying a new mutation, the biochemical analysis of GALT activity in erythrocytes showed an activity of <1%. In silico analysis (SIFT, PolyPhen-2 and the computational analysis on the static protein structure) showed potentially damaging effects of the six new variations on the GALT protein, thus expanding the genetic spectrum of GALT variations in Italy. The study emphasizes the difficulty in establishing a genotype-phenotype correlation in classical galactosemia and underlines the importance of molecular diagnostic testing prior to making any treatment.

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.

GALK inhibitors for classic galactosemia

Classic galactosemia is an inherited metabolic disease for which, at present, no therapy is available apart from galactose-restricted diet. However, the efficacy of the diet is questionable, since it is not able to prevent the insurgence of chronic complications later in life. In addition, it is possible that dietary restriction itself could induce negative side effects. Therefore, there is a need for an alternative therapeutic approach that can avert the manifestation of chronic complications in the patients. In this review, the authors describe the development of a novel class of pharmaceutical agents that target the production of a toxic metabolite, galactose-1-phosphate, considered as the main culprit for the cause of the complications, in the patients.

Imaging manifestations of the leukodystrophies, inherited disorders of white matter

The leukodystrophies are a diverse set of inherited white matter disorders and are uncommonly encountered by radiologists in everyday practice. As a result, it is challenging to recognize these disorders and to provide a useful differential for the referring physician. In this article, leukodystrophies are reviewed from the perspective of 4 imaging patterns: global myelination delay, periventricular/deep white matter predominant, subcortical white matter predominant, and mixed white/gray matter involvement patterns. Special emphasis is placed on pattern recognition and unusual combinations of findings that may suggest a specific diagnosis.

Glucide metabolism disorders (excluding glycogen myopathies)

Glucide metabolism comprises pathways for transport, intermediate metabolism, utilization, and storage of carbohydrates. Defects affect multiple organs and present as systemic diseases. Neurological symptoms result from hypoglycemia, lactic acidosis, or inadequate storage of complex glucide molecules in neurological tissues. In glycogen storage disorders hypoglycemia indicates hepatic involvement, weakness and muscle cramps muscle involvement. Hypoglycemia is also the leading neurological symptom in disorders of gluconeogenesis. Disorders of galactose and fructose metabolism are rare, detectable by neonatal screening, and manifest following dietary intake of these sugars. Rare defects within the pentose metabolism constitute a new area of inborn metabolic disorders and may present with neurological symptoms. Treatment of these disorders involves the avoidance of fasting, dietary treatment eliminating specific carbohydrates, and enzyme replacement therapy in individual glycogen storage diseases.GLUT1 deficiency syndrome, a specific disorder of glucose transport into brain, results in global developmental delay, early-onset epilepsy, and a complex movement disorder. Treatment with a high-fat, low-carbohydrate ketogenic diet provides ketones as an alternative fuel to the brain and restores brain energy metabolism. Recently paroxysmal exertion-induced dyskinesia and stomatin-deficient cryohydrocytosis have been identified as an allelic disorder to GLUT1 deficiency equally responding to a ketogenic diet.

Subfertility and growth restriction in a new galactose-1 phosphate uridylyltransferase (GALT) - deficient mouse model

The first GalT gene knockout (KO) mouse model for Classic Galactosemia (OMIM 230400) accumulated some galactose and its metabolites upon galactose challenge, but was seemingly fertile and symptom free. Here we constructed a new GalT gene-trapped mouse model by injecting GalT gene-trapped mouse embryonic stem cells into blastocysts, which were later implanted into pseudo-pregnant females. High percentage GalT gene-trapped chimera obtained were used to generate heterozygous and subsequently, homozygous GalT gene-trapped mice. Biochemical assays confirmed total absence of galactose-1 phosphate uridylyltransferase (GALT) activity in the homozygotes. Although the homozygous GalT gene-trapped females could conceive and give birth when fed with normal chow, they had smaller litter size (P=0.02) and longer time-to-pregnancy (P=0.013) than their wild-type littermates. Follicle-stimulating hormone levels of the mutant female mice were not significantly different from the age-matched, wild-type females, but histological examination of the ovaries revealed fewer follicles in the homozygous mutants (P=0.007). Administration of a high-galactose (40% w/w) diet to lactating homozygous GalT gene-trapped females led to lethality in over 70% of the homozygous GalT gene-trapped pups before weaning. Cerebral edema, abnormal changes in the Purkinje and the outer granular cell layers of the cerebellum, as well as lower blood GSH/GSSG ratio were identified in the galactose-intoxicated pups. Finally, reduced growth was observed in GalT gene-trapped pups fed with normal chow and all pups fed with high-galactose (20% w/w) diet. This new mouse model presents several of the complications of Classic Galactosemia and will be useful to investigate pathogenesis and new therapies.

Phenotype-genotype correlations in patients with Marinesco-Sjögren syndrome

Marinesco-Sjögren syndrome (MSS; MIM 248800) is an autosomal recessive disorder characterized by congenital cerebellar ataxia, early cataracts, developmental delay, myopathy and short stature. Alterations in the gene SIL1 cause MSS in some patients with typical findings. In this study, molecular investigations including sequencing of the SIL1 gene, western blotting and microscopic investigations in fibroblast cultures were carried out in a cohort of 15 patients from 14 unrelated families, including the large, inbred family reported by Superneau et al., having the clinical features of MSS to provide insights into the pathophysiology of the disorder. A total of seven different mutations were found in eight of the patients from seven families. The mutations caused loss of the BIP-associated protein (BAP) protein in four patients by western blot. Novel clinical features such as dental abnormalities, iris coloboma, eczema and hormonal abnormalities were noticed in some patients, but there was no clear way to distinguish those with and without SIL1 mutations. Cultured fibroblasts contained numerous cytoplasmic inclusion bodies, similar to those identified in the brain of the whoozy mouse in five unrelated patients, three with and two without SIL1 mutations, suggesting some SIL1 negative patients share a common cellular pathogenesis with those who are SIL1 positive.

Differential phonological awareness skills in children with classic galactosemia: a descriptive study of four cases

Educational achievement, which for individuals with the metabolic disorder classic galactosemia (GAL) is significantly lower than in the wider population, correlates with self-reported quality of life. Phonological awareness skills underpin the development of literacy, and although literacy is a key contributor to successful academic outcomes, no study to date has investigated phonological awareness skills in children with GAL. This study investigated phonological awareness (PA) in four school-aged children with the disorder, two of whom were siblings. Age range for the children was 7 years 7 months to 9 years 2 months. Each child was assessed with the Phonological Awareness criterion-referenced subtest from the Clinical Evaluation of Language Fundamentals-Fourth Edition. Included in the data for analysis was each child's performance measures obtained from their most recent assessment of cognitive and lexical development. A number of descriptive analyses were undertaken on the data. One child, who met her age criterion for PA, had cognitive and lexical development skills in the average range. The remaining three children failed to meet their age criteria. Although these three children presented with clinically similar cognitive and lexical development skills, disparate PA skills were identified. The PA skills of one of the sibling pair were notably more advanced than his older sibling. The limitations of relying on behavioural test results in children with GAL to predict those most at risk of reduced skill development are discussed in terms future research directions.

Galactosemia: when is it a newborn screening emergency?

Classic galactosemia is an autosomal recessive disorder of carbohydrate metabolism, due to a severe deficiency of the enzyme, galactose-1-phosphate uridyltransferase (GALT), that catalyzes the conversion of galactose-1-phosphate and uridine diphosphate glucose (UDPglucose) to uridine diphosphate galactose (UDPgalactose) and glucose-1-phosphate. Upon consumption of lactose in the neonatal period, the affected infants develop a potentially lethal disease process with multiorgan involvement. Since the advent of newborn screening (NBS) for galactosemia, we rarely encounter such overwhelmingly ill newborns. After ascertainment that the positive NBS indicates the possibility of galactosemia due to GALT deficiency, the critical question for the physician is whether the infant has the classic or a variant form of GALT deficiency, as classic galactosemia is a medical emergency. However, there are over 230 GALT gene mutations that have been detected around the world. Yet, most positive NBS tests are due to the Duarte biochemical variant condition or a simple false positive. In order to make the correct decision as well as provide informative counseling to parents of infants with a positive NBS, I utilize a relatively simple classification scheme for GALT deficiency. There are three basic forms of GALT deficiency: 1) classic galactosemia; 2) clinical variant galactosemia; and 3) biochemical variant galactosemia. The classic genotype is typified by Q188R/Q188R, the clinical variant by S135L/S135L and the biochemical variant by N314D/Q188R. In classic galactosemia, the erythrocyte GALT enzyme activity is absent or markedly reduced, the blood galactose and erythrocyte galactose-1-phosphate levels are markedly elevated, and the patient is at risk to develop potentially lethal E. coli sepsis, as well as the long-term diet-independent complications of galactosemia. Patients with the clinical variant form require treatment but do not die from E. coli sepsis in the neonatal period. If the clinician suspects galactosemia, even if based on clinical findings alone, then the infant should be immediately placed on a lactose-restricted diet. The purpose of this review is to help the clinician make the correct therapeutic decision after an NBS test has returned positive for galactosemia.

Innovative therapy for Classic Galactosemia - tale of two HTS

Classic Galactosemia is an autosomal recessive disorder caused by the deficiency of galactose-1-phosphate uridylyltransferase (GALT), one of the key enzymes in the Leloir pathway of galactose metabolism. While the neonatal morbidity and mortality of the disease are now mostly prevented by newborn screening and galactose restriction, long-term outcome for older children and adults with this disorder remains unsatisfactory. The pathophysiology of Classic Galactosemia is complex, but there is convincing evidence that galactose-1-phosphate (gal-1P) accumulation is a major, if not the sole pathogenic factor. Galactokinase (GALK) inhibition will eliminate the accumulation of gal-1P from both dietary sources and endogenous production, and efforts toward identification of therapeutic small molecule GALK inhibitors are reviewed in detail. Experimental and computational high-throughput screenings of compound libraries to identify GALK inhibitors have been conducted, and subsequent studies aimed to characterize, prioritize, as well as to optimize the identified positives have been implemented to improve the potency of promising compounds. Although none of the identified GALK inhibitors inhibits glucokinase and hexokinase, some of them cross-inhibit other related enzymes in the GHMP small molecule kinase superfamily. While this finding may render the on-going hit-to-lead process more challenging, there is growing evidence that such cross-inhibition could also lead to advances in antimicrobial and anti-cancer therapies.

Structure-activity analysis and cell-based optimization of human galactokinase inhibitors

Classic Galactosemia is a rare human disease associated with the accumulation of toxic level of galactose-1-phosphate (gal-1P) caused by the inherited deficiency of galactose-1-phosphate uridyltransferase (GALT) activity. To reduce the toxic level of gal-1P in the patients, we have identified, via high-throughput screening, over 200 small molecule GALK inhibitors. We selected a 4-oxo-3,4-dihydro-2H-1,3-thiazine-5-carbonitrile scaffold for further structure-activity relationships characterization, lead optimization with regards to potency and efficacy to reduce gal-1P accumulation in patient cells.

Cerebellar herniation after lumbar puncture in galactosemic newborn

Cerebral edema resulting in elevated intracranial pressure is a well-known complication of galactosemia. Lumbar puncture was performed for the diagnosis of clinically suspected bacterial meningitis. Herniation of cerebral tissue through the foramen magnum is not a common problem in neonatal intensive care units because of the open fontanelle in infants. We present the case of a 3-week-old infant with galactosemia who presented with signs of cerebellar herniation after lumbar puncture.

Prevalence and phenotype of childhood apraxia of speech in youth with galactosemia

PURPOSE

In this article, the authors address the hypothesis that the severe and persistent speech disorder reported in persons with galactosemia meets contemporary diagnostic criteria for childhood apraxia of speech (CAS). A positive finding for CAS in this rare metabolic disorder has the potential to impact treatment of persons with galactosemia and inform explanatory perspectives on CAS in neurological, neurodevelopmental, and idiopathic contexts.

METHOD

Thirty-three youth with galactosemia and significant prior or persistent speech sound disorder were assessed in their homes in 17 states. Participants completed a protocol yielding information on their cognitive, structural, sensorimotor, language, speech, prosody, and voice status and function.

RESULTS

Eight of the 33 participants (24%) met contemporary diagnostic criteria for CAS. Two participants, 1 of whom was among the 8 with CAS, met criteria for ataxic or hyperkinetic dysarthria. Groupwise findings for the remaining 24 participants are consistent with a classification category termed Motor Speech Disorder-Not Otherwise Specified (Shriberg, Fourakis et al., 2010a).

CONCLUSION

The authors estimate the prevalence of CAS in galactosemia at 18 per hundred-180 times the estimated risk for idiopathic CAS. Findings support the need to study risk factors for the high occurrence of motor speech disorders in galactosemia despite early compliant dietary management.

Voice disorders in children with classic galactosemia

Children with classic galactosemia are at risk for motor speech disorders resulting from disruptions in motor planning and programming (childhood apraxia of speech or CAS) or motor execution (dysarthria). In the present study of 33 children with classic galactosemia, 21% were diagnosed with CAS, 3% with ataxic dysarthria, and 3% with mixed CAS-dysarthria. Voice disorders due to laryngeal insufficiency were common in children with dysarthria and co-occurred with CAS. Most (58%) of the children with classic galactosemia had decreased respiratory-phonatory support for speech, and 33% had disturbed vocal quality that was indicative of cerebellar dysfunction. Three children, two diagnosed with CAS and one not diagnosed with a motor speech disorder, had vocal tremors. Treatment of voice dysfunction in neurogenic speech disorders is discussed.

The GALT rush: high carrier frequency of an unusual deletion mutation of the GALT gene in the Ashkenazi population

Classic galactosemia is an autosomal recessive disorder of galactose metabolism manifesting in the first weeks of life following exposure to a milk-based diet. Despite the benefit of avoidance of lactose, many patients suffer from long-term complications including neurological deficits and ovarian failure. To date, over 230 mutations have been described in the GALT gene resulting in galactosemia. Recently, an unusual mutation was characterized causing a 5.5 kb deletion, with a relatively high carrier rate in subjects of Ashkenazi Jewish (AJ) descent. The aim of this study was to estimate the carrier frequency of this mutation in the AJ population in Israel. For this purpose we developed a high-throughput methodology to genotype both normal and deleted alleles using a chip-based matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometer and Multiplex PCR. DNA samples of 760 anonymous AJ subjects were submitted for analysis, subsequently detecting six individuals heterozygous for the GALT deletion mutation, giving a carrier frequency of 1 in 127 (0.79%). Based on these results, we suggest that the method described here provides a basis for genetic screening and prenatal counseling and can potentially reduce the morbidity and mortality associated with delayed diagnosis of galactosemia in this patient population.

The neuropsychological profile of galactosaemia

Long-term follow-up studies of individuals with galactosaemia have indicated that despite a strict galactose-free diet, cognitive functioning is often below average. This study was designed to examine the neuropsychological profile of individuals with galactosaemia in terms of IQ, memory, executive functioning, perceptual abilities and educational outcome. Twenty-eight people with classic galactosaemia and no comorbid neurological or psychiatric disorder took part. A battery of clinical neuropsychological tests was performed. Overall, findings were consistent with previous literature in showing galactosaemia to be linked to below-average functioning across a range of cognitive measures when mean scores were examined. Thus, the mean overall scores for verbal and performance IQ, memory, and executive functions were in the low average range. However, a range of ability was represented across individuals, with some achieving average or above scores and education to A level or above. Further work using longitudinal methodology is needed to address the issue of factors mediating any cognitive weaknesses and to establish the extent of any possible decline in functioning over time.

Galactose toxicity in animals

In most organisms, productive utilization of galactose requires the highly conserved Leloir pathway of galactose metabolism. Yet, if this metabolic pathway is perturbed due to congenital deficiencies of the three associated enzymes, or an overwhelming presence of galactose, this monosaccharide which is abundantly present in milk and many non-dairy foodstuffs, will become highly toxic to humans and animals. Despite more than four decades of intense research, little is known about the molecular mechanisms of galactose toxicity in human patients and animal models. In this contemporary review, we take a unique approach to present an overview of galactose toxicity resulting from the three known congenital disorders of galactose metabolism and from experimental hypergalactosemia. Additionally, we update the reader about research progress on animal models, as well as advances in clinical management and therapies of these disorders.

Longitudinal assessment of intellectual achievement in patients with classical galactosemia

OBJECTIVE

To conduct a longitudinal assessment of long-term cognitive outcome in patients with classical galactosemia.

METHODS

Inclusion criteria were (1) previous assessment of IQ dating back >10 years with tests being comparable with the recent German tests HAWIK-III and HAWIE-R, (2) absence of illnesses other than galactosemia, (3) absence of foreign language problems, (4) enzymatic-metabolic proof of classical galactosemia, (5) compliance with dietary therapy, and (6) written informed consent. Twenty-three patients who fulfilled these criteria were found. They underwent the first IQ test at a mean age of 11 +/- 5 years and the second 13.6 to 15.5 years later at a mean age of 26 +/- 5 years. Results were corrected for the obsolescence of test norms (Flynn effect).

RESULTS

Mean total IQ scores on the first and second tests were 78 +/- 14 and 73 +/- 15, respectively, and not significantly different. IQ scores in the average range were observed for 7 patients on the first test and for 5 patients on the second test. For 17 patients, the intraindividual IQ scores remained essentially unchanged. Five patients showed a decrease and 1 an increase of the IQ score over time. No consistent pattern of change was found with respect to performance or verbal IQ subscores or in achievements in the individual subtest.

CONCLUSIONS

The results confirm the presence of reduced cognitive ability in classical galactosemia and present evidence for an absence of substantial galactosemia-induced aggravation of this impairment with increasing age, at least in patients from 4 to 40 years of age. It remains to be clarified whether a reduction of cognitive function in galactosemia may be initiated by an in utero toxicity of endogenously formed galactose and which role such a process may play in the development of intellectual deficiencies that are later maintained throughout life.