Metabolic perturbations in classic galactosemia beyond the Leloir pathway: Insights from an untargeted metabolomic study

Abstract

Classic galactosemia (CG) is an autosomal recessive disorder that impacts close to 1/50000 live births in the United States, with varying prevalence in other countries. Following exposure to milk, which contains high levels of galactose, affected infants may experience rapid onset and progression of potentially lethal symptoms. With the benefit of early diagnosis, generally by newborn screening, and immediate and lifelong dietary restriction of galactose, the acute sequelae of disease can be prevented or resolved. However, long‐term complications are common, and despite many decades of research, the bases of these complications remain unexplained. As a step toward defining the underlying pathophysiology of long‐term outcomes in CG, we applied an untargeted metabolomic approach with mass spectrometry and dual liquid chromatography, comparing thousands of small molecules in plasma samples from 183 patients and 31 controls. All patients were on galactose‐restricted diets. Using both univariate and multivariate statistical methods, we identified 252 differentially abundant features from anion exchange chromatography and 167 differentially abundant features from C18 chromatography. Mapping these discriminatory features to putative metabolites and biochemical pathways revealed 14 significantly perturbed pathways; these included multiple redox, amino acid, and mitochondrial pathways, among others. Finally, we tested whether any discriminatory features also distinguished cases with mild vs more severe long‐term outcomes and found multiple candidates, of which one achieved false discovery rate‐adjusted q < 0.1. These results extend substantially from prior targeted studies of metabolic perturbation in CG and offer a new approach to identifying candidate modifiers and targets for intervention.

Multi‐omics in classical galactosemia: Evidence for the involvement of multiple metabolic pathways

“…The results of our metabolomics analysis revealed that CG does not only compromise the Leloir pathway, but also involves other metabolic pathways including the glycolytic pathway, the pentose phosphate pathway, and nucleotide metabolism. Our results confirm the finding of the only previous metabolomics study in CG that multiple pathways are affected 8 . The earlier metabolomics study reported perturbations in glutathione metabolism, amino acids and mitochondrial pathways, which were not replicated in our study.…”

“…Since galactose plays a central role in metabolism being involved in multiple different pathways, a full analysis of the metabolome may well shed new light on CG. Until now, the only published metabolomics study in CG patients evaluated plasma samples only 8 . It was demonstrated that not only the Leloir pathway is affected in CG, but that other metabolic pathways including amino acid metabolism and mitochondrial function are involved as well.…”

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

“…Metabolomics has emerged as a potentially useful diagnostic and prognostic tool that might explain disease pathogenesis ( Masood et al, 2021 ; Jacob et al, 2022 ; Jans et al, 2022 ). There currently needs to be more investigations on the pathophysiology of GAL that concentrate on urine or blood metabolomics profiling ( Taylor Fischer et al, 2019 ; Hermans et al, 2022 ). Therefore, investigating the GAL metabolomics profile may aid in finding potential biomarkers, shed light on the mechanisms behind the disease’s progression, and ultimately aid in its early detection.…”

Untargeted LC/MS-Based Metabolic Phenotyping of Hypopituitarism in Young Males

“…As one of them, the determination of cortisol content in human scalp hair was recently used ( Ibrahim and Van Uum, 2014 ). Metabolomics studies provide novel tools in identifying biomarkers of diseases early diagnosis and treatment efficacy ( Taylor Fischer et al, 2019 ). Dooijeweert et al found that untargeted metabolomics in dried blood spots is a useful tool for pyruvate kinase deficiency diagnosis ( Van Dooijeweert et al, 2020 ).…”