A new multiplex method for the diagnosis of peroxisomal disorders allowing simultaneous determination of plasma very-long-chain fatty acids, phytanic, pristanic, docosahexaenoic and bile acids by high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

Antioxidant Response in Human X-Linked Adrenoleukodystrophy Fibroblasts

Redox imbalance, mitochondrial dysfunction, and inflammation play a major role in the pathophysiology of X-linked adrenoleukodystrophy (X-ALD), an inherited neurodegenerative disease caused by mutations in the ABCD1 gene, encoding the protein responsible for peroxisomal import and degradation of very long chain fatty acids (VLCFAs). Therefore, VLCFAs accumulate in tissues and plasma, constituting a pathognomonic biomarker for diagnosis. However, the precise role of VLCFA accumulation on the diverse clinical phenotypes of X-ALD and the pathogenic link between VLCFAs and oxidative stress remain currently unclear. This study proposes ferroptosis as a crucial contributor to the disease development and progression. The expression profiles of "GPX4-glutathione" and "NQO1-CoQ₁₀" ferroptosis pathways have been analyzed in fibroblasts of one patient with AMN, the late onset and slowly progressive form of X-ALD, and in two patients with cALD, the cerebral inflammatory demyelinating form of early childhood. Furthermore, as no effective treatments are currently available, especially for the rapidly progressing form of X-ALD (cALD), the efficacy of NAC treatment has also been evaluated to open the way toward novel combined therapies. Our findings demonstrate that lipid peroxides accumulate in X-ALD fibroblasts and ferroptosis-counteracting enzymes are dysregulated, highlighting a different antioxidant response in patients with AMN and cALD.

Metabolomics to Improve the Diagnostic Efficiency of Inborn Errors of Metabolism

Early diagnosis of inborn errors of metabolism (IEM)—a large group of congenital disorders—is critical, given that many respond well to targeted therapy. Newborn screening programs successfully capture a proportion of patients enabling early recognition and prompt initiation of therapy. For others, the heterogeneity in clinical presentation often confuses diagnosis with more common conditions. In the absence of family history and following clinical suspicion, the laboratory diagnosis typically begins with broad screening tests to circumscribe specialised metabolite and/or enzyme assays to identify the specific IEM. Confirmation of the biochemical diagnosis is usually achieved by identifying pathogenic genetic variants that will also enable cascade testing for family members. Unsurprisingly, this diagnostic trajectory is too often a protracted and lengthy process resulting in delays in diagnosis and, importantly, therapeutic intervention for these rare conditions is also postponed. Implementation of mass spectrometry technologies coupled with the expanding field of metabolomics is changing the landscape of diagnosing IEM as numerous metabolites, as well as enzymes, can now be measured collectively on a single mass spectrometry-based platform. As the biochemical consequences of impaired metabolism continue to be elucidated, the measurement of secondary metabolites common across groups of IEM will facilitate algorithms to further increase the efficiency of diagnosis.

Rapid liquid chromatography-tandem mass spectrometry to determine very-long-chain fatty acids in human and to establish reference intervals for the Chinese population

Very-long-chain fatty acids (VLCFAs), including hexacosanoic, tetracosanoic, and docosanoic acids, are peroxisomal disease markers, whose abnormal accumulation warrants prompt detection for timely, effective treatment. This study aimed to establish and validate a robust liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method to simultaneously quantify VLCFAs and provide reference intervals among Chinese individuals, quantify VLCFAs in pregnancy, and explore potential associations between plasma and amniotic fluid. Analytes were extracted via water-bath incubation with HCl and liquid-liquid extraction. Method linearity, limit of detection/quantitation, precision, carryover, and recovery were evaluated according to Clinical and Laboratory Standard Institute (CLSI) guidelines. VLCFAs showed good reproducibility based on low within-run coefficient variations (CVs) and total CVs, and correlation coefficients of linearity were > 0.99. The reference interval of C22:0, C24:0, and C26:0 were 32.0-73.4 μmol/L, 30.3-72.0 μmol/L, and 0.20-0.71 μmol/L, respectively; C24:0/C22:0 and C26:0/C22:0 ratios were 0.75-1.28 and 0.005-0.0139, respectively. Plasma and amniotic fluid of the same pregnant women displayed no significant correlation in the second trimester. This study presents the simple, efficient, accurate, and robust LC-MS/MS method to simultaneously detect C22:0, C24:0, and C26:0 without derivatization; it can be used to establish reference intervals among Chinese individuals and has diagnostic and other clinical applications.