Combined metabolomic and correlation networks analyses reveal fumarase insufficiency altered amino acid metabolism

Networks as Biomarkers: Uses and Purposes

Networks-based approaches are often used to analyze gene expression data or protein-protein interactions but are not usually applied to study the relationships between different biomarkers. Given the clinical need for more comprehensive and integrative biomarkers that can help to identify personalized therapies, the integration of biomarkers of different natures is an emerging trend in the literature. Network analysis can be used to analyze the relationships between different features of a disease; nodes can be disease-related phenotypes, gene expression, mutational events, protein quantification, imaging-derived features and more. Since different biomarkers can exert causal effects between them, describing such interrelationships can be used to better understand the underlying mechanisms of complex diseases. Networks as biomarkers are not yet commonly used, despite being proven to lead to interesting results. Here, we discuss in which ways they have been used to provide novel insights into disease susceptibility, disease development and severity.

High-salt diet contributes to excess oxidative stress and abnormal metabolism in mouse ovaries

High-salt diets (HSDs) are associated with elevated levels of reactive oxygen species (ROS), which play a key role in ovarian disorders. However, it is not yet clear whether HSDs impact ovarian redox balance and metabolism. Accordingly, in this study, we analyzed the effect of HSDs on ovarian redox balance by biochemical analysis and further dissected its possible mechanism by metabolic analysis combined with correlation network method. We found that ROS and H₂ O₂ levels were significantly increased in the ovarian tissue of mice receiving an HSD for 4 weeks. The enhanced activity of NADPH oxidase may contribute to an increase in ROS in ovarian tissue after excessive salt consumption. Meanwhile, the activities of key antioxidant enzymes, including superoxide dismutase 2, glutathione peroxidase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase increased significantly. The apparent activation of antioxidant defense appeared insufficient as the glutathione, GSH/GSSG ratio, and NADPH/NADP⁺ ratio decreased significantly. In addition, HSDs significantly altered the metabolic patterns of ovarian tissue in mice, and pathways were mainly enriched in fatty acid metabolism. Arachidonic acid was an altered hub metabolite according to Pearson correlation network analysis. Mechanistically, an HSD increased the concentration of arachidonic acid in ovarian tissue, inducing high NADPH oxidase activity, which increased the levels of ROS and H₂ O₂ . Our results indicate that HSDs can lead to increased oxidative stress and dramatically alter the metabolic patterns in mouse ovarian tissues.

Metabolomics and correlation network analysis of follicular fluid reveals associations between l-tryptophan, l-tyrosine and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is an endocrine and metabolic disorder in women of reproductive age. Some studies have investigated metabolic alterations in plasma and follicular fluid from PCOS patients, but they did not control for obesity or insulin resistance (IR); additionally, correlation analysis of metabolites is sparse. Accordingly, in this study, we aimed to examine metabolic differences owing to the pathogenesis of PCOS, identify the hub metabolites and investigate its associations with androgens. We applied GC-MS platform coupled with a correlation network approach to analyze follicular fluid samples from 32 PCOS patients without obesity and IR and 31 healthy women. Thirty significantly altered metabolites in PCOS patients were enriched in amino acid metabolism. l-Phenylalanine, l-tryptophan, pyroglutamic acid, l-tyrosine, l-leucine and l-valine were screened as hub metabolites in metabolic correlation network. Among them, increased l-tryptophan and l-tyrosine were altered hub metabolites, and they had a more significant impact on the metabolic change of PCOS. In addition, l-tryptophan and l-tyrosine were significantly positively associated with serum androgens levels in the PCOS. Our results suggest that disorders of amino acid metabolism, especially tryptophan and tyrosine metabolism, might play an important role in the development of PCOS in predisposed women without obesity and IR.