Metabolomics by 1H-NMR in human pleural effusions: preliminary results

1H NMR-based metabolomics has been applied, for the first time to our knowledge of published literature, to investigate lung cancer metabolic signatures in human pleural effusions (PE) collected by thoracentesis, with the aim to assess the diagnostic potential of this approach and to gain novel insights into lung cancer metabolism and related systemic effects. The innovative aspect of this preliminary work is based on the usage of pleural effusions as biofluid samples. Generally, the biofluids used for NMR metabolomic investigations are urine and plasma or serum: the pleural effusions have the advantage, when compared with the urine samples, of being much less influenced, if not at all, by the diet and lifestyle of the patients and, when compared with the plasma or serum samples, of having a very low content of proteins, that generally cover, at different extent depending on protein type and concentration, the NMR metabolite signals. Pleural effusions samples obtained from cancer patients (n 36) and from a control healthy group (n 30) were analyzed by high resolution 1H-NMR (300 MHz) with standard NMR pulse sequences (1D NOESY sequence, CPMG spin-echo sequence), at 310 °K and pH 7.4. The spectral profiles were subjected to multivariate statistics (AMIX software) according to Principal Component Analysis (PCA). A partial separation between patients and control group was achieved by the multivariate modeling of the pleural effusion profiles (Fig.2). The possible confounding influence of other factors (e.g., gender and age) on the PCA results have been taken into account and excluded by our results. Four spectral regions (0.80-0.90, 1.30-1.40, 2.00-2.10 and 4.10-4.20 ppm) emerged as the most interesting for the individuation of the metabolites involved in the pathology (Fig.1) The metabolites mainly contributing to this discrimination, as highlighted by multivariate analysis, seem to be lactate, triglycerides (increased in patients), some amino acids and metabolites that have yet to be identified. Such preliminary results should be confirmed by applying the investigation to a wider patient cohort, and reinforced by the identification of as much as possible of the metabolites emerged as significant in the present study.