Galactose Metabolism and Clinical Management

Galactose metabolism in humans is principally governed by the Leloir pathway, which converts dietary galactose into glucose-1-phosphate via the sequential action of galactokinase, galactose-1-phosphate uridylyltransferase and UDP-galactose 4′-epimerase. Beyond its role in energy production, galactose supplies essential substrates for glycosylation of proteins and lipids. Inherited defects in this pathway give rise to distinct forms of galactosaemia: GALT deficiency (classic galactosaemia), galactokinase deficiency (type II) and GALE deficiency (type III). Classic galactosaemia typically presents in the neonatal period with liver dysfunction, hypoglycaemia and sepsis, and carries a risk of chronic complications including neurocognitive impairments, primary ovarian insufficiency and reduced bone mineral density. Universal newborn screening facilitates early diagnosis, and prompt initiation of a galactose-restricted diet remains the cornerstone of acute management. Lifelong monitoring of biochemistry, growth and developmental milestones is recommended, alongside skeletal assessments and reproductive surveillance. Emerging therapeutic avenues—such as gene-based interventions, mRNA therapeutics and pharmacological chaperones—aim to correct underlying enzyme deficiencies and mitigate long-term sequelae. International guidelines advocate harmonised protocols for diagnosis, dietary prescriptions and follow-up to optimise patient outcomes globally.

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Galactose Metabolism and Clinical Management publication trend

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Technical terms

Leloir pathway: The enzymatic sequence that converts galactose to glucose-1-phosphate via GALK, GALT and GALE.

Galactokinase (GALK): Enzyme that phosphorylates galactose to form galactose-1-phosphate in the first step of the Leloir pathway.

Galactose-1-phosphate uridylyltransferase (GALT): Enzyme that catalyses the conversion of galactose-1-phosphate and UDP-glucose into UDP-galactose and glucose-1-phosphate.

UDP-galactose 4′-epimerase (GALE): Enzyme that interconverts UDP-galactose and UDP-glucose, completing the Leloir pathway and contributing to glycosylation precursors.

Galactosaemia: A group of inherited disorders resulting from deficient activity of one of the Leloir pathway enzymes, leading to galactose accumulation and toxicity.

Genetically encoded sensor: An engineered protein that emits a measurable signal on binding galactose, enabling in vivo monitoring of sugar dynamics.

Whole-body galactose oxidation (WBGO): A functional assay measuring systemic utilisation of galactose, used to assess therapeutic efficacy in animal models.

Biomarker: A biological molecule whose presence or level indicates normal or pathogenic processes, used for diagnosis or therapy monitoring.

Newborn screening: Population-based testing of infants shortly after birth to identify metabolic disorders such as classic galactosaemia before symptoms arise.

References

1. GALDAR: A genetically encoded galactose sensor for visualizing sugar metabolism in vivo. PLOS Biology (2024).
2. Lactose and Galactose Content in Spanish Cheeses: Usefulness in the Dietary Treatment of Patients with Galactosaemia. Nutrients (2023).
3. Whole-body galactose oxidation as a robust functional assay to assess the efficacy of gene-based therapies in a mouse model of Galactosemia. Molecular Therapy — Methods & Clinical Development (2024).
4. Galactose in human metabolism, glycosylation and congenital metabolic diseases: Time for a closer look. Biochimica et Biophysica Acta (BBA) - General Subjects (2021).
5. Sweet and sour: an update on classic galactosemia. Journal of Inherited Metabolic Disease (2017).
6. International clinical guideline for the management of classical galactosemia: diagnosis, treatment, and follow‐up. Journal of Inherited Metabolic Disease (2016).