Sepsis caused by Phytobacter diazotrophicus complicated with galactosemia type 1 in China: a case report.

BACKGROUND: Phytobacter diazotrophicus (P. diazotrophicus) is an opportunistic pathogen that causes nosocomial outbreaks and sepsis. However, there are no reports of P. diazotrophicus isolated from human blood in China. CASE PRESENTATION: A 27-day-old female infant was admitted to our hospital with fever and high bilirubin levels. The clinical features included jaundice, abnormal coagulation, cholestasis, fever, convulsions, weak muscle tension, sucking weakness, ascites, abnormal tyrosine metabolism, cerebral oedema, abnormal liver function, clavicle fracture, and haemolytic anaemia. The strain isolated from the patient's blood was identified as P. diazotrophicus by whole-genome sequencing (WGS). Galactosemia type 1 (GALAC1) was diagnosed using whole-exome sequencing (WES). Based on drug sensitivity results, 10 days of anti-infective treatment with meropenem combined with lactose-free milk powder improved symptoms. CONCLUSION: P. diazotrophicus was successfully identified in a patient with neonatal sepsis combined with galactosemia. Galactosemia may be an important factor in neonatal sepsis. This case further expands our understanding of the clinical characteristics of GALAC1.

Simple and sensitive galactose monitoring based on capillary SERS sensor.

Galactosemia, a severe genetic metabolic disorder, results from the absence of galactose-degrading enzymes, leading to harmful galactose accumulation. In this study, we introduce a novel capillary-based surface-enhanced Raman spectroscopy (SERS) sensor for convenient and sensitive galactose detection. The developed sensor enhances SERS signals by introducing gold nanoparticles (Au NPs) onto the surface of silver nanoshells (Ag NSs) within a capillary, creating Ag NSs with Au NPs as satellites. Utilizing 4-mercaptophenylboronic acid (4-MPBA) as a Raman reporter molecule, the detection method relies on the conversion of 4-MPBA to 4-mercaptophenol (4-MPhOH) driven by hydrogen peroxide (H2O2) generated during galactose oxidation by galactose oxidase (GOx). A new SERS signal was observed, which was generated by H2O2 produced when galactose and GOx reacted. Our strategy yielded a quantitative change in the SERS signal, specifically in the band intensity ratio of 998 to 1076 cm-1 (I998/I1076) as the galactose concentration increased. Our capillary-based SERS biosensor provides a promising platform for early galactosemia diagnosis.

Classical Hereditary galactosemia: findings in patients and animal models.

Classic galactosemia is a rare inborn error of metabolism that affects the metabolism of galactose, a sugar derived from milk and derivates. Classic galactosemia is caused by variants of the GALT gene, which lead to absent or misfolded forms of the ubiquitously present galactose-1-phosphate uridylyltransferase enzyme (GALT) driving galactose metabolites to accumulate, damaging cells from neurons to hepatocytes. The disease has different prevalence around the world due to different allele frequencies among populations and its symptoms range from cognitive and psychomotor impairment to hepatic, ophthalmological, and bone structural damage. The practice of newborn screening still varies among countries, dairy restriction treatment is a consensus despite advances in preclinical treatment strategies. Recent clinical studies in Duarte variant suggest dairy restriction could be reconsidered in these cases. Despite noteworthy advances in the classic galactosemia understanding, preclinical trials are still crucial to fully understand the pathophysiology of the disease and help propose new treatments. This review aims to report a comprehensive analysis of past studies and state of art research on galactosemia screening, its clinical and preclinical trials, and treatments with the goal of shedding light on this complex and multisystemic innate error of the metabolism.

A case report of classic galactosemia with a GALT gene variant and a literature review.

BACKGROUND: Galactosemia is an autosomal recessive disorder resulting from an enzyme defect in the galactose metabolic pathway. The most severe manifestation of classic galactosemia is caused by galactose-1-phosphate uridylyltransferase (GALT) deficiency, and this condition can be fatal during infancy if left untreated. It also may result in long-term complications in affected individuals. CASE PRESENTATION: This report describes a patient whose initial clinical symptoms were jaundice and liver dysfunction. The patient's liver and coagulation functions did not improve after multiple admissions and treatment with antibiotics, hepatoprotective and choleretic agents and blood transfusion. Genetic analysis revealed the presence of two variants in the GALT gene in the compound heterozygous state: c.377 + 2dup and c.368G > C (p.Arg123Pro). Currently, the variant locus (c.377 + 2dup) in the GALT gene has not been reported in the Human Gene Mutation Database (HGMD), while c.368G > C (p.Arg123Pro) has not been reported in the Genome Aggregation Database (GnomAD) nor the HGMD in East Asian population. We postulated that the two variants may contribute to the development of classical galactosemia. CONCLUSIONS: Applications of whole-exome sequencing to detect the two variants can improve the detection and early diagnosis of classical galactosemia and, more specifically, may identify individuals who are compound heterozygous with variants in the GALT gene. Variants in the GALT gene have a potential therapeutic significance for classical galactosemia.

Long-term complications in classic galactosemia are not progressive.

Classic galactosemia (CG) is a potentially lethal genetic disorder that results from profound deficiency of galactose-1-P uridylyltransferase. Despite early detection and life-long dietary restriction of galactose, which is the current standard of care, many patients with CG grow to experience a range of long-term developmental complications that can include difficulties with speech/voice/language, cognitive, motor, and psychosocial outcomes, among other problems. That these complications are common in CG is well-documented, but whether they are also progressive has been a point of controversy for decades. Here, we addressed the question of whether long-term outcomes in CG are progressive by analyzing a robust data set in each of 4 ways. First, we compared cross-sectional Vineland-3 Adaptive Behavior Scales scores for 101 cases and 65 unaffected sibling controls and found no evidence of consistently declining scores with age. Second, we analyzed longitudinal Vineland-3 subdomain scores for 45 cases and 34 controls to see if individual participants demonstrated developmental gains (positive slope) or losses (negative slope) over time. The changes in most growth scale value (GSV) scores, which are not normed, were positive for both cases and controls <10y, and either positive or near zero for participants ≥10y. In contrast, the slopes of most v-Scale scores, which are normed, were negative for many cases <10y, indicating that these children, while gaining milestones, were gaining them at a slower pace than their counterparts in the reference population. Third, we analyzed medical records from 76 cases, assigning ordinal scores for complications and gathering the quantitative results of relevant formal assessments where available. Both cross-sectional and longitudinal analyses of both ordinal and formal assessment scores confirmed that outcomes were mostly stable, albeit with some ups and downs in isolated cases. Finally, we analyzed data collected via custom family-response surveys from 124 cases and 67 controls regarding each participant's perceived symptom severity over time. Among cases, the percentages of respondents reporting worsening symptoms over time for speech, cognitive, motor, and psychosocial outcomes were 0.8%, 6.6%, 5.2%, and 9.8%, respectively. Among controls, the corresponding percentages were 0.0%, 1.5%, 1.5%, and 6.5%, respectively. These results provide compelling evidence that long-term developmental complications are not progressive for a majority of patients with CG.

Racial and ethnic diversity of classic and clinical variant galactosemia in the United States.

Classic and clinical variant galactosemia (CG/CVG) are allelic, autosomal recessive disorders that result from deficiency of galactose-1-P uridylyltransferase (GALT). CG/CVG has been reported globally among patients of diverse ancestries, but most large studies of outcomes have included, almost exclusively, patients categorized as White or Caucasian. As a first step to explore whether the cohorts studied are representative of the CG/CVG population at large, we sought to define the racial and ethnic makeup of CG/CVG newborns in a diverse population with essentially universal newborn screening (NBS) for galactosemia: the United States (US). First, we estimated the predicted racial and ethnic distribution of CG/CVG by combining the reported demographics of US newborns from 2016 to 2018 with predicted homozygosity or compound heterozygosity of pathogenic, or likely pathogenic, GALT alleles from the relevant ancestral groups. Incorporating some simplifying assumptions, we predicted that of US newborns diagnosed with CG/CVG, 65% should be White (non-Hispanic), 23% should be Black (non-Hispanic), 10% should be Hispanic, and 2% should be Asian (non-Hispanic). Next, we calculated the observed racial and ethnic distribution of US newborns diagnosed with CG/CVG using available de-identified data from state NBS programs from 2016 to 2018. Of the 235 newborns in this cohort, 41 were categorized as other or unknown. Of the remaining 194, 66% were White (non-Hispanic or ethnicity unknown), 16% were Black (non-Hispanic or ethnicity unknown),15% were Hispanic, and 2% were Asian (non-Hispanic or ethnicity unknown). This observed distribution was statistically indistinguishable from the predicted distribution. To the limits of our study, these data confirm the racial and ethnic diversity of newborns with CG/CVG in the US, demonstrate an approach for estimating CG/CVG racial and ethnic diversity in other populations, and raise the troubling possibility that current understanding of long-term outcomes in CG/CVG may be skewed by ascertainment bias of the cohorts studied.

Development, optimization and validation of LC-MS/MS method for the determination of DBS GALT enzyme activity.

Galactosemia is a carbohydrate metabolism disorder often caused by galactose-1-phosphate uridyl transferase (GALT) deficiency. Detecting GALT deficiency involves measuring intra-erythrocyte enzyme activity. We aimed to create a robust liquid chromatography-mass spectrometry (LC-MS/MS) method to assess GALT activity in dried blood spot (DBS) samples. We validated this method and compared it to the fluorometric approach. We investigated the impact of K2EDTA and lithium heparin tubes on enzyme activity to identify the best sample collection tube. We also assessed the reaction-stopping method. The developed approach employed [13C6]-galactose-1-phosphate as a substrate and UDP-N-acetylglycosamine as an internal standard (IS). The mean ± SD value for GALT activity of DBS samples was determined as 6.37 ± 1.96 µmol/gHb/hour. The linear range was 0.4-50 µM (2.4-310% of normal) in the DBS method. The % coefficient of variation (%CV) values were less than 15 for intra-day and inter-day repeatability studies. Over 90% recovery was achieved in recovery studies, and no ion suppression from matrix was detected. DBS samples were quite stable for 31 days under different storage conditions. Enzyme activity results reported as <3.5 U/g Hb by fluorometric method, were quantitatively determined for even very low concentrations by LC-MS/MS method.

Addition of galactose-1-phosphate measurement enhances newborn screening for classical galactosemia.

Galactosemia is an inborn disorder of carbohydrate metabolism of which early detection can prevent severe illness. Although the assay for galactose-1-phosphate uridyltransferase (GALT) enzyme activity has been available since the 1960s, many issues prevented it from becoming universal. In order to develop the Israeli newborn screening pilot algorithm for galactosemia, flow injection analysis tandem mass spectrometry measurement of galactose-1-phosphate in archived dried blood spots from newborns with classical galactosemia, galactosemia variants, epimerase deficiency, and normal controls, was conducted. Out of 431 330 newborns screened during the pilot study (30 months), two with classical galactosemia and four with epimerase deficiency were identified and confirmed. Five false positives and no false negatives were recorded. Following this pilot study, the Israeli final and routine newborn screening algorithm, as recommended by the Advisory Committee to the National Newborn Screening Program, now consists of galactose-1-phosphate measurement integrated into the routine tandem mass spectrometry panel as the first-tier screening test, and GALT enzyme activity as the second-tier performed to identify only newborns suspected to be at risk for classical galactosemia. The GALT enzyme activity cut-off used in the final algorithm was lowered in order to avoid false positives.

Grip strength in patients with galactosemia and in a galactose-1-phosphate uridylyltransferase (GALT)-null rat model.

Classic galactosemia (CG) and clinical variant galactosemia (CVG) are allelic inborn errors of metabolism that result from profound deficiency, and near-profound deficiency, respectively, of galactose-1-P uridylyltransferase (GALT). Despite early detection and lifelong dietary restriction of galactose, which is the current standard of care, most patients with CG/CVG grow to experience a range of long-term developmental and other complications. One of the less well-understood complications of CG/CVG is decreased hand grip strength, as reported by Potter et al. (2013). Here, we confirm this phenotype in an independent cohort of 36 cases (4-18 years) and 19 controls (4-17 years), and further demonstrate that the grip strength deficit observed in cases may be secondary to growth delay. Specifically, we found that when grip strength of cases and controls in a new cohort recruited in 2022 was plotted by weight, rather than age, the difference between cases and controls for both sexes disappeared. Reanalyzing data from the original 2013 cohort, we found that differences in weight accounted for grip strength differences between cases and controls in girls and young women, but not in boys and young men. Finally, we tested whether a GALT-null rat model of CG also showed a grip strength deficit-it did-and again the difference between GALT-null and wild-type rats associated with differences in body mass. Combined, these results confirm that GALT deficiency is associated with a grip strength deficit in both young patients with CG/CVG and GALT-null rats, and further demonstrate that this phenotype may be secondary to growth delay, and therefore not evidence of a muscle abnormality.

GALE variants associated with syndromic manifestations, macrothrombocytopenia, bleeding, and platelet dysfunction.

GALE gene encodes the uridine diphosphate [UDP]-galactose-4-epimerase, which catalyzes the bidirectional interconversion of UDP-glucose to UDP-galactose, and UDP-N-acetyl-glucosamine to UDP-N-acetyl-galactosamine. In that way, GALE balances, through reversible epimerization, the pool of four sugars that are essential during the biosynthesis of glycoproteins and glycolipids. GALE-related disorder presents an autosomal recessive inheritance pattern, and it is commonly associated with galactosemia. Peripheral galactosemia generally associates with non-generalized forms or even asymptomatic presentations, while classical galactosemia may be related to complications such as learning difficulties, developmental delay, cardiac failure, or dysmorphic features. Recently, GALE variants have been related to severe thrombocytopenia, pancytopenia, and in one patient, to myelodysplastic syndrome.

What is the context? GALE gene encodes for the UDP-Galactose 4-Epimerase, an enzyme involved in the Leloir pathway of galactose catabolism and protein glycosylation.Homozygous or compound heterozygous GALE variants associate with the disorder known as galactosemia type III.Three types of galactosemia can be distinguished: the peripheral, the intermediate, and the generalized form, which associate with different clinical symptoms and GALE genetic variants.Peripheral form is considered benign, while the intermediate and the generalized form is associated with severe and syndromic manifestations, including learning difficulties, delayed growth, sensorineural hearing loss, and early-onset cataracts, among others.What is new? In the last few years, GALE variants have been linked to hematological manifestations, such as anemia, febrile neutropenia, and severe thrombocytopenia.To date, the only GALE variants described in patients presenting hematological disorders are GALE p.Arg51Trp, p.Lys78ValfsX32, p.Val128Met, p.Thr150Met, p.Leu223Pro, and p.Gly237Asp.The thrombocytopenia observed in GALE patients is associated with reduced GPIbα and ß1 integrin glycosylation and externalization to the megakaryocyte and platelet surface, disrupting the actin cytoskeleton remodeling.What is the impact? GALE is an essential protein for the correct megakaryocyte and platelet glycosylation.

Caregivers' nutrition-related knowledge, perceptions, practices and barriers regarding the therapeutic diet for classical galactosaemia.

BACKGROUND: Classical galactosaemia is a life-threatening disorder of carbohydrate metabolism, and the primary treatment is a lifelong galactose-restricted diet commenced in infancy. Adherence to restrictive diets can be burdensome for patients and their families; however, little is known about the impact on caregivers. AIM: This study aims to determine the nutrition-related knowledge, perceptions, practices, and barriers of caregivers related to the therapeutic diet for classical galactosaemia. METHODS: An online survey was conducted among 98 eligible members of the Galactosaemia Support Group using a novel questionnaire. Descriptive and inferential analyses were performed using Microsoft Excel 2021 and Stata/MP (version 17.0), respectively. Forty-three caregivers participated in the study. RESULTS AND CONCLUSION: Of those who participated, 98% had high levels of dietary knowledge. Caregivers' knowledge scores ( x ¯ $\bar{{\rm{x}}}$ = 17.9, standard deviation [SD] = 1.7) were positively correlated with educational level (r = 0.383, p = 0.013). High attitudinal scores ( x ¯ $\bar{{\rm{x}}}$ = 32.5, SD = 5.5) obtained by most caregivers (65%) revealed an overall positive attitude towards the galactosaemia diet. Negative perceptions of being unable to feed their child breast milk (49%) were apparent, and this perception was positively correlated with caregivers' intention to feed their child breast milk (r = 0.450, p = 0.003). Caregivers' concerns about the safety of their child in social settings (79%) and feeling that their child was excluded in social settings (49%) were clear barriers. A multidisciplinary approach to galactosaemia management is warranted, with healthcare interventions focusing on addressing caregivers' negative perceptions and barriers related to the diet to enable tailored support and facilitate lifelong compliance.

Classic Galactosemia: Clinical and Computational Characterization of a Novel GALT Missense Variant (p.A303D) and a Literature Review.

Classic galactosemia is an autosomal recessive inherited liver disorder of carbohydrate metabolism caused by deficient activity of galactose-1-phosphate uridylyltransferase (GALT). While a galactose-restricted diet is lifesaving, most patients still develop long-term complications. In this study, we report on a two-week-old female patient who is a compound heterozygote for a known pathogenic variant (p.K285N) and a novel missense variant (p.A303D) in the GALT gene. Segregation analysis showed that the patient inherited the p.K285N pathogenic variant from her father and the p.A303D variant from her mother. A bioinformatics analysis to predict the impact of the p.A303D missense variant on the structure and stability of the GALT protein revealed that it may be pathogenic. Based on this finding, we performed a literature review of all GALT missense variants identified in homozygous and compound heterozygous galactosemia patients carrying the p.K285N pathogenic variant to explore their molecular effects on the clinical phenotype of the disease. Our analysis revealed that these missense variants are responsible for a wide range of molecular defects. This study expands the clinical and mutational spectrum in classic galactosemia and reinforces the importance of understanding the molecular consequences of genetic variants to incorporate genetic analysis into clinical care.

[Clinical characteristics and genetic analysis of a child with Galactosemia due to compound heterozygous variants of GALT gene].

OBJECTIVE: To explore the clinical features and genetic basis of a child with Galactosemia. METHODS: A child who had presented at the Children's Hospital Affiliated to Zhengzhou University on November 20, 2019 was selected as the study subject. Clinical data of the child was collected. Whole exome sequencing was carried out for the child. Candidate variants were validated by Sanger sequencing. RESULTS: Clinical manifestations of the child have included anemia, feeding difficulty, jaundice, hypomyotonia, abnormal liver function and coagulation abnormality. Tandem mass spectrometry showed increased citrulline, methionine, ornithine and tyrosine. Urine organic acid analysis showed increased phenyllactic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenyllactic acid, 4-hydroxyphenylpyruvate and N-acetyltyrosine. Genetic testing revealed that the child has harbored compound heterozygous variants of the GALT gene, namely c.627T>A (p.Y209*) and c.370G>C (p.G124R), which were respectively inherited from her healthy parents. Among these, c.627T>A (p.Y209*) was known as a likely pathogenic variant, while c.370G>C (p. G124R) was unreported previously and also predicted as a likely pathogenic variant(PM1+PM2_Supporting+PP3_Moderate+PPR). CONCLUSION: Above discovery has expanded the spectrum of the GALT gene variants underlying Galactosemia. Patients with thrombocytopenia, feeding difficulties, jaundice, abnormal liver function and coagulation abnormality without obvious causes should be analyzed by screening of metabolic diseases in combination with genetic testing.

Endocrine Disorders in a Newborn with Heterozygous Galactosemia, Down Syndrome and Complex Cardiac Malformation: Case Report.

Down syndrome is the most common chromosomal abnormality diagnosed in newborn babies. Infants with Down syndrome have characteristic dysmorphic features and can have neuropsychiatric disorders, cardiovascular diseases, gastrointestinal abnormalities, eye problems, hearing loss, endocrine and hematologic disorders, and many other health issues. We present the case of a newborn with Down syndrome. The infant was a female, born at term through c-section. She was diagnosed before birth with a complex congenital malformation. In the first few days of life, the newborn was stable. In her 10th day of life, she started to show respiratory distress, persistent respiratory acidosis, and persistent severe hyponatremia, and required intubation and mechanical ventilation. Due to her rapid deterioration our team decided to do a screening for metabolic disorders. The screening was positive for heterozygous Duarte variant galactosemia. Further testing on possible metabolic and endocrinologic issues that can be associated with Down syndrome was performed, leading to hypoaldosteronism and hypothyroidism diagnoses. The case was challenging for our team because the infant also had multiple metabolic and hormonal deficiencies. Newborns with Down syndrome often require a multidisciplinary team, as besides congenital cardiac malformations they can have metabolic and hormonal deficiencies that can negatively impact their short- and long-term prognosis.

Pathophysiology of long-term complications in classic galactosemia: What we do and do not know.

Despite many decades of research involving both human subjects and model systems, the underlying pathophysiology of long-term complications in classic galactosemia (CG) remains poorly understood. In this review, intended for those already familiar with galactosemia, we focus on the big questions relating to outcomes, mechanism, and markers, drawing on relevant literature where available, attempting to navigate inconsistencies where they appear, and acknowledging gaps in knowledge where they persist.

A multinational study of acute and long-term outcomes of Type 1 galactosemia patients who carry the S135L (c.404C > T) variant of GALT.

Patients with galactosemia who carry the S135L (c.404C > T) variant of galactose-1-P uridylyltransferase (GALT), documented to encode low-level residual GALT activity, have been under-represented in most prior studies of outcomes in Type 1 galactosemia. What is known about the acute and long-term outcomes of these patients, therefore, is based on very limited data. Here, we present a study comparing acute and long-term outcomes of 12 patients homozygous for S135L, 25 patients compound heterozygous for S135L, and 105 patients homozygous for two GALT-null (G) alleles. This is the largest cohort of S135L patients characterized to date. Acute disease following milk exposure in the newborn period was common among patients in all 3 comparison groups in our study, as were long-term complications in the domains of speech, cognition, and motor outcomes. In contrast, while at least 80% of both GALT-null and S135L compound heterozygous girls and women showed evidence of an adverse ovarian outcome, prevalence was only 25% among S135L homozygotes. Further, all young women in this study with even one copy of S135L achieved spontaneous menarche; this is true for only about 33% of women with classic galactosemia. Overall, we observed that while most long-term outcomes trended milder among groups of patients with even one copy of S135L, many individual patients, either homozygous or compound heterozygous for S135L, nonetheless experienced long-term outcomes that were not mild. This was true despite detection by newborn screening and both early and life-long dietary restriction of galactose. This information should empower more evidence-based counseling for galactosemia patients with S135L.

AAV-mediated expression of galactose-1-phosphate uridyltransferase corrects defects of galactose metabolism in classic galactosemia patient fibroblasts.

Classic galactosemia (CG) is a rare disorder of autosomal recessive inheritance. It is caused predominantly by point mutations as well as deletions in the gene encoding the enzyme galactose-1-phosphate uridyltransferase (GALT). The majority of the more than 350 mutations identified in the GALT gene cause a significant reduction in GALT enzyme activity resulting in the toxic buildup of galactose metabolites that in turn is associated with cellular stress and injury. Consequently, developing a therapeutic strategy that reverses both the oxidative and ER stress in CG cells may be helpful in combating this disease. Recombinant adeno-associated virus (AAV)-mediated gene therapy to restore GALT activity offers the potential to address the unmet medical needs of galactosemia patients. Here, utilizing fibroblasts derived from CG patients we demonstrated that AAV-mediated augmentation of GALT protein and activity resulted in the prevention of ER and oxidative stress. We also demonstrate that these CG patient fibroblasts exhibit reduced CD109 and TGFßRII protein levels and that these effectors of cellular homeostasis could be restored following AAV-mediated expression of GALT. Finally, we show initial in vivo proof-of-concept restoration of galactose metabolism in a GALT knockout mouse model following treatment with AAV-GALT.

Novel mRNA therapy restores GALT protein and enzyme activity in a zebrafish model of classic galactosemia.

Messenger RNA (mRNA) has emerged as a novel therapeutic approach for inborn errors of metabolism. Classic galactosemia (CG) is an inborn error of galactose metabolism caused by a severe deficiency of galactose-1-phosphate:uridylyltransferase (GALT) activity leading to neonatal illness and chronic impairments affecting the brain and female gonads. In this proof of concept study, we used our zebrafish model for CG to evaluate the potential of human GALT mRNA (hGALT mRNA) packaged in two different lipid nanoparticles to restore GALT expression and activity at early stages of development. Both one cell-stage and intravenous single-dose injections resulted in hGALT protein expression and enzyme activity in the CG zebrafish (galt knockout) at 5 days post fertilization (dpf). Moreover, the levels of galactose-1-phosphate (Gal-1-P) and galactonate, metabolites that accumulate because of the deficiency, showed a decreasing trend. LNP-packaged mRNA was effectively translated and processed in the CG zebrafish without signs of toxicity. This study shows that mRNA therapy restores GALT protein and enzyme activity in the CG zebrafish model, and that the zebrafish is a suitable system to test this approach. Further studies are warranted to assess whether repeated injections safely mitigate the chronic impairments of this disease.

ß-Galactosidase therapy can mitigate blood galactose elevation after an oral lactose load in galactose mutarotase deficiency.

Galactose mutarotase (GALM) deficiency (MIM# 618881), also known as type IV galactosemia, is caused by biallelic pathogenic variants of GALM. Cataracts are observed in patients with GALM deficiency as well as in other conditions associated with high levels of blood galactose and can be prevented by consuming a galactose-restricted diet or formula. Galactose restriction is the only known treatment for GALM deficiency and other types of galactosemia. We incidentally found that ß-galactosidase might reduce blood galactose levels caused by lactose loading in GALM deficiency. Consequently, we investigated the effectiveness of ß-galactosidase in decreasing the level of blood galactose in three patients with GALM deficiency. We performed two lactose loading tests per case: one with and one without ß-galactosidase. The add-on administration of ß-galactosidase significantly mitigated blood galactose elevations after lactose loading. Although urine galactitol was mildly elevated in all patients with GALM deficiency, ß-galactosidase did not prevent increased levels of urine galactitol during the loading tests. No adverse events, including cataracts, were observed during or after the tests. Therefore, ß-galactosidase could be a potential novel treatment agent for blood galactose elevation caused by lactose in patients with GALM deficiency. The effectiveness of ß-galactosidase could possibly result in loosening of the galactose dietary restrictions or treatment for patients with GALM deficiency.

Neonatal GALT gene replacement offers metabolic and phenotypic correction through early adulthood in a rat model of classic galactosemia.

Classic galactosemia (CG) results from profound deficiency of galactose-1-P uridylyltransferase (GALT). Despite early detection by newborn screening and lifelong dietary restriction of galactose, most patients grow to experience a range of long-term complications. Recently, we developed and characterized a GALT-null rat model of CG and demonstrated that AAV9-hGALT, administered by tail vein injection to neonatal pups, dramatically improved plasma, liver, and brain galactose metabolites at 2 weeks posttreatment. Here we report a time-course study of GALT restoration in rats treated as neonates with scAAV9-hGALT and harvested at 8, 14, 30, and 60 days. Cohorts of rats in the two older groups were weaned to diets containing either 1% or 3% of calories from galactose. As expected, GALT activity in all treated animals peaked early and then diminished over time, most notably in liver, ostensibly due to dilution of the nonreplicating episomal vector as transduced cells divided. All treated rats showed dramatic metabolic rescue through 1 month, and those weaned to the lower galactose diet showed continued strong metabolic rescue into adulthood (2 months). Prepubertal growth delay and cataracts were both partially rescued by treatment. Finally, we found that UDP glucose pyrophosphorylase (UGP), which offers a metabolic bypass around missing GALT, was 3-fold more active in brain samples from adult rats than from young pups, offering a possible explanation for the improved ability of older GALT-null rats to metabolize galactose. Combined, these results document promising metabolic and phenotypic efficacy of neonatal GALT gene replacement in a rat model of classic galactosemia.