Galactosemia: Biochemistry, Molecular Genetics, Newborn Screening, and Treatment

Genetic background of neonatal hypokalemia

Neonatal hypokalemia (defined as a serum potassium level <3.5 mEq/L) is the most common electrolyte disorder encountered in clinical practice. In addition to common secondary causes, primary genetic etiologies are also closely associated with hypokalemia. Currently, a systematic characterization of these genetic disorders is lacking, making early recognition challenging and clinical management uncertain. This review will aid clinicians by summarizing the genetic background of neonatal hypokalemia from two aspects: (1) increased excretion of K+, whereby genetic factors primarily lead to increased renal Na+ influx, decreased H+ efflux, or reduced Cl- influx, ultimately resulting in increased K+ efflux; and (2) decreased extracellular distribution of K+, whereby genetic factors result in abnormalities in transmembrane ion channels, reducing outward potassium currents or generating inward cation leak currents. We describe over ten genetic diseases associated with neonatal hypokalemia, which involve pathogenic variants in dozens of genes and affect multiple target organs, including the kidneys, intestines, and skeletal muscle. For example, in the renal tubules, pathogenic variants in the SLC12A1 gene encoding the Na+-K+-2Cl- cotransporter lead to renal K+ loss, causing Bartter syndrome type I; in intestinal epithelial cells, pathogenic variants in the SLC26A3 gene result in a defective Cl⁻-HCO₃⁻ exchanger, causing congenital chloride diarrhea; and in skeletal muscle, pathogenic variants in the CACNA1S gene impact membrane calcium ion channels resulting in hypokalemic periodic paralysis. Given the wide variety of organs and genetic alterations that can contribute to neonatal hypokalemia, we believe this review will provide valuable insights for clinical diagnosis and treatment.

Biogenesis and roles of tRNA queuosine modification and its glycosylated derivatives in human health and diseases

Various types of post-transcriptional modifications contribute to physiological functions by regulating the abundance and function of RNAs. In particular, tRNAs have the widest variety and largest number of modifications, with crucial roles in protein synthesis. Queuosine (Q) is a characteristic tRNA modification with a 7-deazaguanosine core structure bearing a bulky side chain with a cyclopentene group. Q and its derivatives are found in the anticodon of specific tRNAs in both bacteria and eukaryotes. In metazoan tRNAs, Q is further glycosylated with galactose or mannose. The functions of these glycosylated Qs remained unknown for nearly half a century since their discovery. Recently, our group identified the glycosyltransferases responsible for these tRNA modifications and elucidated their biological roles. We, here, review the biochemical and physiological functions of Q and its glycosylated derivatives as well as their associations with human diseases, including cancer and inflammatory and neurological diseases.

Glucose Disorders

Glucose disorders are the most common endocrine condition in the primary care setting. The conditions overlap and are better viewed as a spectrum rather than discrete entities. Multiple treatment agents are now available for diabetes mellitus which include long-acting and short-acting insulins and medications targeting the various pathways of diabetes including liver gluconeogenesis, increasing peripheral insulin sensitivity, stimulating pancreatic insulin production, eliminating glucose renally, decreasing carbohydrate gastrointestinal absorption, and targeting the body's incretin system. Various endocrine conditions can cause secondary hyperglycemia or hypoglycemia. Medications and physiologic stress can affect glucose levels. Genetic syndromes causing enzyme deficiencies underlie a small portion of glucose disorders.

Genetic insights into the complexity of premature ovarian insufficiency

Premature Ovarian Insufficiency (POI) is a highly heterogeneous condition characterized by ovarian dysfunction in women occurring before the age of 40, representing a significant cause of female infertility. It manifests through primary or secondary amenorrhea. While more than half of POI cases are idiopathic, genetic factors play a pivotal role in all instances with known causes, contributing to approximately 20-25% of cases. This article comprehensively reviews the genetic factors associated with POI, delineating the primary candidate genes. The discussion delves into the intricate relationship between these genes and ovarian development, elucidating the functional consequences of diverse mutations to underscore the fundamental impact of genetic effects on POI. The identified genetic factors, encompassing gene mutations and chromosomal abnormalities, are systematically classified based on whether the resulting POI is syndromic or non-syndromic. Furthermore, this paper explores the genetic interplay between mitochondrial genes, such as Required for Meiotic Nuclear Division 1 homolog Gene (RMND1), Mitochondrial Ribosomal Protein S22 Gene (MRPS22), Leucine-rich Pentapeptide Repeat Gene (LRPPRC), and non-coding RNAs, including both microRNAs and Long non-coding RNAs, with POI. The insights provided serve to consolidate and enhance our understanding of the etiology of POI, contributing to establishing a theoretical foundation for diagnosing and treating POI patients, as well as for exploring the mechanisms underlying the disease.

Galactokinase 1 is the source of elevated galactose-1-phosphate and cerebrosides are modestly reduced in a mouse model of classic galactosemia

Classic galactosemia (CG) arises from loss-of-function mutations in the Galt gene, which codes for the enzyme galactose-1-phosphate uridylyltransferase (GALT), a central component in galactose metabolism. The neonatal fatality associated with CG can be prevented by galactose dietary restriction, but for decades it has been known that limiting galactose intake is not a cure and patients often have lasting complications. Even on a low-galactose diet, GALT's substrate galactose-1-phosphate (Gal1P) is elevated and one hypothesis is that elevated Gal1P is a driver of pathology. Here we show that Gal1P levels were elevated above wildtype (WT) in Galt mutant mice, while mice doubly mutant for Galt and the gene encoding galactokinase 1 (Galk1) had normal Gal1P levels. This indicates that GALK1 is necessary for the elevated Gal1P in CG. Another hypothesis to explain the pathology is that an inability to metabolize galactose leads to diminished or disrupted galactosylation of proteins or lipids. Our studies reveal that levels of a subset of cerebrosides-galactosylceramide 24:1, sulfatide 24:1, and glucosylceramide 24:1-were modestly decreased compared to WT. In contrast, gangliosides were unaltered. The observed reduction in these 24:1 cerebrosides may be relevant to the clinical pathology of CG, since the cerebroside galactosylceramide is an important structural component of myelin, the 24:1 species is the most abundant in myelin, and irregularities in white matter, of which myelin is a constituent, have been observed in patients with CG. Therefore, impaired cerebroside production may be a contributing factor to the brain damage that is a common clinical feature of the human disease.

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.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

mRNA therapies: Pioneering a new era in rare genetic disease treatment

Rare genetic diseases, often referred to as orphan diseases due to their low prevalence and limited treatment options, have long posed significant challenges to our medical system. In recent years, Messenger RNA (mRNA) therapy has emerged as a highly promising treatment approach for various diseases caused by genetic mutations. Chemically modified mRNA is introduced into cells using carriers like lipid-based nanoparticles (LNPs), producing functional proteins that compensate for genetic deficiencies. Given the advantages of precise dosing, biocompatibility, transient expression, and minimal risk of genomic integration, mRNA therapies can safely and effectively correct genetic defects in rare diseases and improve symptoms. Currently, dozens of mRNA drugs targeting rare diseases are undergoing clinical trials. This comprehensive review summarizes the progress of mRNA therapy in treating rare genetic diseases. It introduces the development, molecular design, and delivery systems of mRNA therapy, highlighting their research progress in rare genetic diseases based on protein replacement and gene editing. The review also summarizes research progress in various rare disease models and clinical trials. Additionally, it discusses the challenges and future prospects of mRNA therapy. Researchers are encouraged to join this field and collaborate to advance the clinical translation of mRNA therapy, bringing hope to patients with rare genetic diseases.

Enzymatic biosynthesis of D-galactose derivatives: Advances and perspectives

D-Galactose derivatives, including galactosyl-conjugates and galactose-upgrading compounds, provide various physiological benefits and find applications in industries such as food, cosmetics, feed, pharmaceuticals. Many research on galactose derivatives focuses on identification, characterization, development, and mechanistic aspects of their physiological function, providing opportunities and challenges for the development of practical approaches for synthesizing galactose derivatives. This study focuses on recent advancements in enzymatic biosynthesis of galactose derivatives. Various strategies including isomerization, epimerization, transgalactosylation, and phosphorylation-dephosphorylation were extensively discussed under the perspectives of thermodynamic feasibility, theoretical yield, cost-effectiveness, and by-product elimination. Specifically, the enzymatic phosphorylation-dephosphorylation cascade is a promising enzymatic synthesis route for galactose derivatives because it can overcome the thermodynamic equilibrium of isomerization and utilize cost-effective raw materials. The study also elucidates the existing challenges and future trends in enzymatic biosynthesis of galactose derivatives. Collectively, this review provides a real-time summary aimed at promoting the practical biosynthesis of galactose derivatives through enzymatic catalysis.

Effect of Protection Polymer Coatings on the Performance of an Amperometric Galactose Biosensor in Human Plasma

Galactose monitoring in individuals allows the prevention of harsh health conditions related to hereditary metabolic diseases like galactosemia. Current methods of galactose detection need development to obtain cheaper, more reliable, and more specific sensors. Enzyme-containing amperometric sensors based on galactose oxidase activity are a promising approach, which can be enhanced by means of their inclusion in a redox polymer coating. This strategy simultaneously allows the immobilization of the biocatalyst to the electroactive surface and hosts the electron shuttling units. An additional deposition of capping polymers prevents external interferences like ascorbic or uric acid as well as biofouling when measuring in physiological fuels. This work studies the protection effect of poly(2-methacryloyloxyethyl phosphorylcholine-co-glycidyl methacrylate (MPC) and polyvinylimidazole-polysulfostyrene (P(VI-SS)) when incorporated in the biosensor design for the detection of galactose in human plasma.

Carriers of autosomal recessive conditions: are they really 'unaffected?'

Mendel's Law of Dominance suggests that recessive disease expression requires the inheritance of two mutated alleles as the dominant, wildtype allele suppresses disease presentation leading to the expression of physiological normal phenotypes. However, there is existing evidence that challenges this school of thought. Here, we summarise existing literature evaluating metabolic and health impacts among carriers of autosomal recessive conditions, focusing on phenylketonuria (PKU), classical homocystinuria, galactosemia and Usher syndrome as examples. Our findings suggest that carriers, often described as 'unaffected', may actually display attenuated symptoms for the recessive disease they are carrying. For instance, PKU is an inborn error of metabolism characterised by the build-up of plasma phenylalanine attributed to the deficiency of the phenylalanine hydroxylase (PAH) enzyme. While less severe, PKU carriers also exhibit this impaired enzymatic activity, leading to elevated plasma phenylalanine levels, especially after phenylalanine consumption. Related to these metabolic alterations in the PAH pathway, there is early evidence to suggest that PKU carriers may have compromised cognitive and mental health outcomes. Overall, research on the health and metabolic impacts of PKU carriers is sparse, with most studies conducted several decades ago. However, early evidence suggests that intermediate phenotypes among carriers of autosomal recessive conditions are plausible. The illustrated possible intermediate phenotypes observed among carriers necessitates future research to determine possible clinical implications among this population.

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.

Glycosylated queuosines in tRNAs optimize translational rate and post-embryonic growth

Transfer RNA (tRNA) modifications are critical for protein synthesis. Queuosine (Q), a 7-deaza-guanosine derivative, is present in tRNA anticodons. In vertebrate tRNAs for Tyr and Asp, Q is further glycosylated with galactose and mannose to generate galQ and manQ, respectively. However, biogenesis and physiological relevance of Q-glycosylation remain poorly understood. Here, we biochemically identified two RNA glycosylases, QTGAL and QTMAN, and successfully reconstituted Q-glycosylation of tRNAs using nucleotide diphosphate sugars. Ribosome profiling of knockout cells revealed that Q-glycosylation slowed down elongation at cognate codons, UAC and GAC (GAU), respectively. We also found that galactosylation of Q suppresses stop codon readthrough. Moreover, protein aggregates increased in cells lacking Q-glycosylation, indicating that Q-glycosylation contributes to proteostasis. Cryo-EM of human ribosome-tRNA complex revealed the molecular basis of codon recognition regulated by Q-glycosylations. Furthermore, zebrafish qtgal and qtman knockout lines displayed shortened body length, implying that Q-glycosylation is required for post-embryonic growth in vertebrates.

Micronutrient Deficiency in Inherited Metabolic Disorders Requiring Diet Regimen: A Brief Critical Review

Many inherited metabolic disorders (IMDs), including disorders of amino acid, fatty acid, and carbohydrate metabolism, are treated with a dietary reduction or exclusion of certain macronutrients, putting one at risk of a reduced intake of micronutrients. In this review, we aim to provide available evidence on the most common micronutrient deficits related to specific dietary approaches and on the management of their deficiency, in the meanwhile discussing the main critical points of each nutritional supplementation. The emerging concepts are that a great heterogeneity in clinical practice exists, as well as no univocal evidence on the most common micronutrient abnormalities. In phenylketonuria, for example, micronutrients are recommended to be supplemented through protein substitutes; however, not all formulas are equally supplemented and some of them are not added with micronutrients. Data on pyridoxine and riboflavin status in these patients are particularly scarce. In long-chain fatty acid oxidation disorders, no specific recommendations on micronutrient supplementation are available. Regarding carbohydrate metabolism disorders, the difficult-to-ascertain sugar content in supplementation formulas is still a matter of concern. A ketogenic diet may predispose one to both oligoelement deficits and their overload, and therefore deserves specific formulations. In conclusion, our overview points out the lack of unanimous approaches to micronutrient deficiencies, the need for specific formulations for IMDs, and the necessity of high-quality studies, particularly for some under-investigated deficits.

Elucidating response mechanisms at the metabolic scale of Eisenia fetida in typical oil pollution sites: A native driver in influencing carbon flow

Previous investigations on the stress response patterns of earthworms (Eisenia fetida) in practical petroleum hydrocarbon (PH) contamination systems were less focused. Therefore, this study investigated the ecotoxicological effect of PH contamination on earthworms based on metabonomics and histological observation, followed by correlation analysis between the earthworm metabolism, PH types and concentrations, soil physicochemical characteristics, and the microbial community structures (i.e., diversity and abundance) and functions. The results showed that due to the abundant PH organics, the cell metabolism of earthworms shifts under PH contamination conditions, leading them to use organic acids as alternative energy sources (i.e., gluconeogenesis pathway). Simultaneously, biomarker metabolites related to cellular uptake, stress response, and membrane disturbance were identified. In addition, when compared to the controls, considerable epicuticle and cuticle layer disruption was observed, along with PH internalization. It was demonstrated that PH pollution preferentially influences the physiological homeostasis of earthworms through indirect (i.e., microbial metabolism regulation) than direct (i.e., direct interaction with earthworms) mechanisms. Moreover, the varied CO2 releasement was verified, which highlights the potential role of earthworms in influencing carbon transformation and corresponds with the considerably enriched energy metabolism-related pathway. This study indicated that PH contamination can induce a strong stress response in earthworms through both direct and indirect mechanisms, which in turn, substantially influences carbon transformation in PH contamination sites.

Hypoglycemia in Children: Major Endocrine-Metabolic Causes and Novel Therapeutic Perspectives

Hypoglycemia is due to defects in the metabolic systems involved in the transition from the fed to the fasting state or in the hormone control of these systems. In children, hypoglycemia is considered a metabolic-endocrine emergency, because it may lead to brain injury, permanent neurological sequelae and, in rare cases, death. Symptoms are nonspecific, particularly in infants and young children. Diagnosis is based on laboratory investigations during a hypoglycemic event, but it may also require biochemical tests between episodes, dynamic endocrine tests and molecular genetics. This narrative review presents the age-related definitions of hypoglycemia, its pathophysiology and main causes, and discusses the current diagnostic and modern therapeutic approaches.

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.

Optical Coherence Tomography: Retinal Imaging Contributes to the Understanding of Brain Pathology in Classical Galactosemia

It remains unresolved whether central nervous system involvement in treated classical galactosemia (CG) is a progressive neurodegenerative process. This study aimed to investigate retinal neuroaxonal degeneration in CG as a surrogate of brain pathology. Global peripapillary retinal nerve fibre layer (GpRNFL) and combined ganglion cell and inner plexiform layer (GCIPL) were analysed in 11 CG patients and 60 controls (HC) using spectral-domain optical coherence tomography. Visual acuity (VA) and low-contrast VA (LCVA) were acquired to test visual function. GpRNFL and GCIPL did not differ between CG and HC (p > 0.05). However, in CG, there was an effect of intellectual outcome on GCIPL (p = 0.036), and GpRNFL and GCIPL correlated with neurological rating scale scores (p < 0.05). A single-case follow-up analysis showed GpRNFL (0.53-0.83%) and GCIPL (0.52-0.85%) annual decrease beyond the normal aging effect. VA and LCVA were reduced in CG with intellectual disability (p = 0.009/0.006), likely due to impaired visual perception. These findings support that CG is not a neurodegenerative disease, but that brain damage is more likely to occur early in brain development. To clarify a minor neurodegenerative component in the brain pathology of CG, we propose multicenter cross-sectional and longitudinal studies using retinal imaging.

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.

Biomarker discovery in galactosemia: Metabolomics with UPLC/HRMS in dried blood spots

Introduction:Galactosemia (GAL) is a genetic disorder that results in disturbances in galactose metabolism and can lead to life-threatening complications. However, the underlying pathophysiology of long-term complications in GAL remains poorly understood. Methods: In this study, a metabolomics approach using ultra-performance liquid chromatography coupled with high-resolution mass spectrometry was used to investigate metabolomic changes in dried blood spots of 15 patients with GAL and 39 healthy individuals. Results: The study found that 2,819 metabolites underwent significant changes in patients with GAL compared to the control group. 480 human endogenous metabolites were identified, of which 209 and 271 were upregulated and downregulated, respectively. PA (8:0/LTE4) and ganglioside GT1c (d18:0/20:0) metabolites showed the most significant difference between GAL and the healthy group, with an area under the curve of 1 and 0.995, respectively. Additionally, the study identified potential biomarkers for GAL, such as 17-alpha-estradiol-3-glucuronide and 16-alpha-hydroxy DHEA 3-sulfatediphosphate. Conclusion: This metabolomics study deepened the understanding of the pathophysiology of GAL and presented potential biomarkers that might serve as prognostic biomarkers to monitor the progression or support the clinical diagnosis of GAL.

Gut dysmotility in children with neurological impairment: the nutritional management

Intestinal motility disorders represent a frequent problem in children with neurological impairment. These conditions are characterized by abnormal movements of the gut, which can result in symptoms such as constipation, diarrhea, reflux, and vomiting. The underlying mechanisms leading to dysmotility are various, and the clinical manifestations are often nonspecific. Nutritional management is an important aspect of care for children with gut dysmotility, as it can help to improve their quality of life. Oral feeding, when safe and in the absence of risk of ingestion or severe dysphagia, should always be encouraged. When oral nutrition is insufficient or potentially harmful, it is necessary to switch to an enteral by tube or parenteral nutrition before the onset of malnutrition. In most cases, children with severe gut dysmotility may require feeding via a permanent gastrostomy tube to ensure adequate nutrition and hydration. Drugs may be necessary to help manage gut dysmotility, such as laxatives, anticholinergics and prokinetic agents. Nutritional management of patients with neurological impairment often requires an individualized care plan to optimize growth and nutrition and to improve overall health outcomes. This review tries to sum up most significant neurogenetic and neurometabolic disorders associated with gut dysmotility that may require a specific multidisciplinary care, identifying a proposal of nutritional and medical management.

The Importance of Neonatal Screening for Galactosemia

Galactosemia is an inborn metabolic disorder caused by a deficient activity in one of the enzymes involved in the metabolism of galactose. The first description of galactosemia in newborns dates from 1908, ever since complex research has been performed on cell and animal models to gain more insights into the molecular and clinical bases of this challenging disease. In galactosemia, the newborn appears to be born in proper health, having a window of opportunity before developing major morbidities that may even be fatal following ingestion of milk that contains galactose. Galactosemia cannot be cured, but its negative consequences on health can be avoided by establishing precocious diagnosis and treatment. All the foods that contain galactose should be eliminated from the diet when there is a suspicion of galactosemia. The neonatal screening for galactosemia can urge early diagnosis and intervention, preventing complications. All galactosemia types may be detected during the screening of newborns for this disorder. The major target is, however, galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia, which is diagnosed by applying a combination of total galactose and GALT enzyme analysis as well as, in certain programs, mutation screening. Most critically, infants who exhibit symptoms suggestive of galactosemia should undergo in-depth testing for this condition even when the newborn screening shows normal results. The decision to enroll global screening for galactosemia among the specific population still faces many challenges. In this context, the present narrative review provides an updated overview of the incidence, clinical manifestations, diagnosis, therapy, and prognosis of galactosemia, questioning under the dome of these aspects related to the disease the value of its neonatal monitoring.

The use of pharmacological chaperones in rare diseases caused by reduced protein stability

Rare diseases are most often caused by inherited genetic disorders that, after translation, will result in a protein with altered function. Decreased protein stability is the most frequent mechanism associated with a congenital pathogenic missense mutation and it implies the destabilization of the folded conformation in favour of unfolded or misfolded states. In the cellular context and when experimental data is available, a mutant protein with altered thermodynamic stability often also results in impaired homeostasis, with the deleterious accumulation of protein aggregates, metabolites and/or metabolic by-products. In the last decades, a significant effort has enabled the characterization of rare diseases associated to protein stability defects and triggered the development of innovative therapeutic intervention lines, say, the use of pharmacological chaperones to correct the intracellular impaired homeostasis. Here, we review the current knowledge on rare diseases caused by reduced protein stability, paying special attention to the thermodynamic aspects of the protein destabilization, also focusing on some examples where pharmacological chaperones are being tested.

Current Understanding on the Genetic Basis of Key Metabolic Disorders: A Review

Simple Summary

Metabolic disorders (MD) are a challenge to healthcare systems; the emergence of the modern socio-economic system has led to a profound change in lifestyles in terms of dietary habits, exercise regimens, and behavior, all of which complement the genetic factors associated with MD. Diabetes Mellitus and Familial hypercholesterolemia are two of the 14 most widely researched MD, as they pose the greatest challenge to the public healthcare system and have an impact on productivity and the economy. Research findings have led to the development of new therapeutic molecules for the mitigation of MD as well as the invention of experimental strategies, which target the genes themselves via gene editing and RNA interference. Although these approaches may herald the emergence of a new toolbox to treat MD, the current therapeutic approaches still heavily depend on substrate reduction, dietary restrictions based on genetic factors, exercise, and the maintenance of good mental health. The development of orphan drugs for the less common MD such as Krabbe, Farber, Fabry, and Gaucher diseases, remains in its infancy, owing to the lack of investment in research and development, and this has driven the development of personalized therapeutics based on gene silencing and related technologies.

Abstract

Advances in data acquisition via high resolution genomic, transcriptomic, proteomic and metabolomic platforms have driven the discovery of the underlying factors associated with metabolic disorders (MD) and led to interventions that target the underlying genetic causes as well as lifestyle changes and dietary regulation. The review focuses on fourteen of the most widely studied inherited MD, which are familial hypercholesterolemia, Gaucher disease, Hunter syndrome, Krabbe disease, Maple syrup urine disease, Metachromatic leukodystrophy, Mitochondrial encephalopathy lactic acidosis stroke-like episodes (MELAS), Niemann-Pick disease, Phenylketonuria (PKU), Porphyria, Tay-Sachs disease, Wilson’s disease, Familial hypertriglyceridemia (F-HTG) and Galactosemia based on genome wide association studies, epigenetic factors, transcript regulation, post-translational genetic modifications and biomarker discovery through metabolomic studies. We will delve into the current approaches being undertaken to analyze metadata using bioinformatic approaches and the emerging interventions using genome editing platforms as applied to animal models.