NMR-based metabolomics applications: from food to human biofluids

Abstract

Metabolomics is the scientific discipline that identifies and quantifies endogenous and exogenous metabolites in different biological samples. Metabolites are crucial components of a biological system and they are highly informative about its functional state, due to their closeness to the organism’s phenotype. This approach finds an increasing number of applications in many areas including medical, pharmaceutical, food and environmental sciences. The combined use of NMR spectroscopy and chemometrics techniques, is able to provide the metabolic “fingerprint” of the various samples. This PhD project focused on the analysis of various samples covering a wide range of fields, namely, food and nutraceutical sciences, cell metabolomics and medicine using a metabolomics approach. Indeed, the first part of the thesis describes two exploratory studies performed on Algerian extra virgin olive oil and apple juice from ancient Danish apple cultivars. Both studies revealed variety-related peculiarities that would have been difficult to detect by means of traditional analysis. The second part of the project includes four metabolomics studies performed on samples of biological origin. In particular, the first study is related to a recent emerging field: cell metabolomics. Indeed, tumour cells (HTC116) were treated with novel anticancer drugs in order to understand their in vitro action. The aim of this study was also the development of a reliable experimental protocol for an efficient harvesting, quenching and extraction of cellular metabolites of human adherent cancer cell lines. The second and the third studies concern the evaluation of the effects of functional food ingredients, namely β-glucans and phytosterols, on in vivo animal models. In particular, the hypocholesterolemic action of β-glucans was investigated by analysing rat plasma and faecal samples. This study confirmed the role of barley β-glucans in increasing faecal bile acids excretion in hypercholesterolemic rats and showed, for the first time, a modulation of the primary and secondary bile acid excretion, depending on the molecular weight of the β-glucan employed. In the other study, the effects of phytosterols on a murine colitis model, was investigated. NMR measurements on the liver metabolome revealed the role of these plant sterols in restoring the homeostatic equilibrium of the living system. Thus, in both cases, the results suggest the appropriate use of these nutraceutical products. The last study explores the differences in the follicular fluid metabolome of hyper- and normoinsulinemic women affected with Polycystic Ovary Syndrome (PCOS). The study provides preliminary but interesting relationships between serum hormones and metabolites in follicular fluids.