Metabolomics of Exhaled Breath Condensate by Nuclear Magnetic Resonance Spectroscopy and Mass Spectrometry: A Methodological Approach.

Respiratory diseases present a very high prevalence in the general population, with an increase in morbidity, mortality and health-care expenses worldwide. They are complex and heterogeneous pathologies that may present different pathological facets in different subjects, often with personal evolution. Therefore, there is a need to identify patients with similar characteristics, prognosis or treatment, defining the so-called phenotype, but also to mark specific differences within each phenotype, defining the endotypes. Biomarkers are very useful to study respiratory phenotypes and endotypes. Metabolomics, one of the recently introduced "omics", is becoming a leading technique for biomarker discovery. For the airways, metabolomics appears to be well suited as the respiratory tract offers a natural matrix, the Exhaled Breath Condensate (EBC), in which several biomarkers can be measured. In this review, we will discuss the main methodological issues related to the application of Nuclear Magnetic Resonance (NMR) spectroscopy and Mass Spectrometry (MS) to EBC metabolomics for investigating respiratory diseases.

Coexistence of obesity and asthma determines a distinct respiratory metabolic phenotype.

BACKGROUND: Epidemiologic and clinical evidence supports the existence of an obesity-related asthma phenotype. No distinct pathophysiologic elements or specific biomarkers have been identified thus far, but increased oxidative stress has been reported. OBJECTIVE: We aimed at verifying whether metabolomics of exhaled breath condensate from obese asthmatic (OA) patients, lean asthmatic (LA) patients, and obese nonasthmatic (ONA) subjects could recognize specific and statistically validated biomarkers for a separate "asthma-obesity" respiratory metabolic phenotype, here defined as "metabotype." METHODS: Twenty-five OA patients, 30 ONA subjects, and 30 mild-to-moderate LA age-matched patients participated in a cross-sectional study. Nuclear magnetic resonance (NMR) profiles were analyzed by using partial least-squares discriminant analysis, and the results were validated with an independent patient set. RESULTS: From NMR profiles, we obtained strong regression models that distinguished OA patients from ONA subjects (quality parameters: goodness-of-fit parameter [R2] = 0.81 and goodness-of-prediction parameter [Q2] = 0.79), as well as OA patients from LA patients (R2 = 0.91 and Q2 = 0.89). The all-classes comparison (R2 = 0.86 and Q2 = 0.83) indicated that OA patients possess a respiratory metabolic profile fully divergent from those obtained in the other patient groups. We also identified specific biomarkers for between-class separation, which are independent from clinical bias. They are involved in the methane, pyruvate, and glyoxylate and dicarboxylate metabolic pathways. CONCLUSIONS: NMR-based metabolomics indicates that OA patients are characterized by a respiratory metabolic fingerprint fully different from that of patients independently affected by asthma or obesity. Such a phenotypic difference strongly suggests unique pathophysiologic pathways involved in the pathogenesis of asthma in adult obese subjects. Furthermore, the OA metabotype could define a strategy for patient stratification based on unbiased biomarkers, with important diagnostic and therapeutic implications.

Vitamin C and l-Proline Antagonistic Effects Capture Alternative States in the Pluripotency Continuum.

Metabolites and cofactors are emerging as key regulators of cell plasticity and reprogramming, and their role in the control of pluripotency is just being discovered. Here we provide unprecedented evidence that embryonic stem cell (ESC) pluripotency relies on the relative levels of two physiological metabolites, namely ascorbic acid (vitamin C, VitC) and l-proline (l-Pro), which affect global DNA methylation, transcriptional profile, and energy metabolism. Specifically, while a high VitC/l-Pro ratio drives ESCs toward a naive state, the opposite condition (l-Pro excess) captures a fully reversible early primed pluripotent state, which depends on autocrine fibroblast growth factor and transforming growth factor ß signaling pathways. Our findings highlight the pivotal role of metabolites availability in controlling the pluripotency continuum from naive to primed states.