Propionic Acidemia, Methylmalonic Acidemia, and cblC Defect: Comparison of Untargeted Metabolomic Profiles

Abstract

Methylmalonic acidemia (MMA), propionic acidemia (PA), and cobalamin C deficiency (cblC) share a defect in propionic acid metabolism. In addition, cblC is also involved in the process of homocysteine remethylation. These three diseases produce various phenotypes and complex downstream metabolic effects. In this study we used an untargeted metabolomics approach to investigate the biochemical differences and the possible connections with the pathophysiology of each disease. Untargeted urine metabolomic profiles of 21 patients (7 MMA, 7 PA, 7 cblC) were identified through statistical analysis (p<0.05; log2FC >|1|) and then used for the annotation. Annotated features were associated with different metabolic pathways potentially involved in the diseases development. Comparative statistic showed markedly different metabolomic profiles between MMA, PA and cblC, highlighting characteristic species for each disease. The most affected pathways were related to the metabolism of organic acids (MMA, PA, cblC), amino acids (MMA, PA, cblC), glycine and its conjugates (PA), transsulfuration pathway (cblC), oxidative processes (cblC) and neurosteroid hormones (cblC). The untargeted metabolomics study highlighted the presence of significant differences between the three diseases, pointing to the most relevant contrast of cblC profile compared to MMA and PA. Some new biomarkers are proposed for PA, while novel data regarding the alterations of steroid hormone profiles and biomarkers of oxidative stress were obtained for cblC disease. The elevation of neurosteroids in cblC may indicate a potential connection with the development of ocular and neuronal deterioration.