The H-1 NMR serum metabolomics response to a two meal challenge: a cross-over dietary intervention study in healthy human volunteers

Background: Metabolomics represents a powerful tool for exploring modulation of the human metabolome in response to food intake. However, the choice of multivariate statistical approach is not always evident, especially for complex experimental designs with repeated measurements per individual. Here we have investigated the serum metabolic responses to two breakfast meals: an egg and ham based breakfast and a cereal based breakfast using three different multivariate approaches based on the Projections to Latent Structures framework. Methods: In a cross over design, 24 healthy volunteers ate the egg and ham breakfast and cereal breakfast on four occasions each. Postprandial serum samples were subjected to metabolite profiling using H-1 nuclear magnetic resonance spectroscopy and metabolites were identified using 2D nuclear magnetic resonance spectroscopy. Metabolic profiles were analyzed using Orthogonal Projections to Latent Structures with Discriminant Analysis and Effect Projections and ANOVA-decomposed Projections to Latent Structures. Results: The Orthogonal Projections to Latent Structures with Discriminant Analysis model correctly classified 92 and 90% of the samples from the cereal breakfast and egg and ham breakfast, respectively, but confounded dietary effects with inter-personal variability. Orthogonal Projections to Latent Structures with Effect Projections removed inter-personal variability and performed perfect classification between breakfasts, however at the expense of comparing means of respective breakfasts instead of all samples. ANOVA-decomposed Projections to Latent Structures managed to remove inter-personal variability and predicted 99% of all individual samples correctly. Proline, tyrosine, and N-acetylated amino acids were found in higher concentration after consumption of the cereal breakfast while creatine, methanol, and isoleucine were found in higher concentration after the egg and ham breakfast. Conclusions: Our results demonstrate that the choice of statistical method will influence the results and adequate methods need to be employed to manage sample dependency and repeated measurements in cross-over studies. In addition, H-1 nuclear magnetic resonance serum metabolomics could reproducibly characterize postprandial metabolic profiles and identify discriminatory metabolites largely reflecting dietary composition

NMR-Based Metabolomics: The Foodome and the Assessment of Dietary Exposure as a Key Step to Evaluate the Effect of Diet on Health

NMR-based metabolomics has gained important insight into the associations between the metabolic status and health, as metabolomics signatures are found in blood, urine, stools, or saliva, differentiating healthy subjects from those affected by diseases or disorders. Although health status has been linked to diet, a measurable fingerprint is rarely found within the metabolome, demonstrating that the diet is curing or, at least, is modifying the subject metabolome away from or closer to a healthy status. The success in finding the correlation between the metabolome and a diet-related disease has, as the main obstacle, the inability to characterize the actual diet followed by the subject. Thus, a big scientific effort has been launched to find metabolite patterns which are characterizing precisely the personal food consumption in order to classify people according to their actual diet. Most of the studies based on NMR-metabolomics are focused on finding biomarkers within the dietary exposome, e.g., originating from food or gut microbiota, without a specific focus on the endogenous metabolome. The main drawback in such approach is a combination of: (i) the actual composition of the meal, (ii) the bioaccessibility of bioactive compounds, and (iii) the processing capability of the gut microbiota. In this chapter, these three aspects are illustrated, where NMR spectroscopy (effectively or potentially) gains relevant information in the discovery of biomarkers for the true food consumption, as a preliminary step in successful \u201cdietary effect studies.\u201