Interindividualidad asociada al metabolismo de polifenoles por la microbiota intestinalnuevos metabotipos y sus agrupaciones, metabolitos y bacterias, y posibles implicaciones en salud

Abstract

(Poly)phenols are bioactive compounds present in plant-foods. Clinical and intervention studies have shown the preventive effects of (poly)phenol-rich diets, such as the Mediterranean diet, against cardiometabolic, inflammatory, and neurodegenerative diseases. However, these effects do not occur equally in all individuals, mainly due to the interindividual variability in the metabolism of (poly)phenols. One of the primary factors contributing to the variability in the metabolism and bioactivity of (poly)phenols is the composition and functionality of the gut microbiota (GM), which varies among individuals. Individuals can be grouped according to “metabotypes”, based on their GM's differential capacity to metabolize certain (poly)phenols, such as isoflavones (soy) to equol (“equol-producers or non-producers”) and ellagitannins (pomegranate, berries, and nuts) to urolithins (UROs) (“URO metabotypes”: UMA, UMB (according to UROs produced) or UM0 (UROs non-producers). Some bacteria that metabolize these (poly)phenols have also been identified, such as certain species of Adlercreutzia and Slackia, which produce equol, and Gordonibacter and Ellagibacter, which produce some UROs. The bioactivity of (poly)phenols is also conditioned by their low bioavailability since, in addition to bacterial metabolism, they are also metabolized by the body’s cells into phase-II conjugates such as sulfates and glucuronides, which exhibit much lower activity than their precursors. In this Doctoral Thesis, our objectives included to investigating the existence of new metabotypes and metabolites of (poly)phenols related to microbial metabolism, new bacteria involved in UROs metabolism, and their use for in vivo replication of UROs metabotypes. Also, the presence of different combinations of metabotypes within the same individual, their prevalence in the population, their associated GM composition, functionality, and distinctive microbial networks were explored. In addition, we investigated the use of milk exosomes (EXOs-L) to encapsulate and transport resveratrol (RSV) and curcumin (CUR) to systemic tissues, and evaluated their anticancer effects at detected concentrations. Finally, the possible encapsulation and transport of (poly)phenols and(or) their metabolites in human exosome-containing EVs (E-EVs) were also explored. Human, animal, and in vitro studies were carried out to achieve these goals. Two human intervention studies were performed: stratification of metabotypes and GM modulation (7 days), as well as a pharmacokinetic study (transport in E-EVs). The participants consumed capsules containing (poly)phenol-rich plant extracts in both trials. Two animal studies: one where rats consumed two sources of (poly)phenols and URO-producing bacteria, and another, where they were administered with RSV and CUR, encapsulated in EXOs-L. Finally, one in vitro study with bacterial cultures and another with breast cancer cell models were also performed. Blood samples, exosomes, urine, feces, and in vitro incubations were analyzed using metabolomics (HPLC-DAD-ESI-Q-MS, UPLC-ESI-QTOF-MS, and GC-MS), GM analysis by genomic sequencing (16S rRNA) and real-time polymerase chain reaction (qPCR), as well as bioinformatics and statistical analysis were applied, among other techniques and approaches. The main findings were: identification of a new metabolite (4-hydroxydibenzyl) derived from the gut microbial metabolism of RSV; new GM metabotypes associated with RSV metabolism (“lunularin-producers or non-producers”); identification of 10 different clusters of existing metabotypes, as well as their distinctive associated GM; identification of the new Uro-G, and the isolation and identification of new bacteria (several Enterocloster species) involved in the metabolism of UROs and characterization of bacterial consortia responsible for UMs; in vivo replication of the metabolic profile of UROs production using said consortia and evaluation of their safety; use of EXOs-L loaded with RSV and CUR, increasing their bioavailability and anticancer activity; and finally, identification of human E-EVs as new carriers of RSV and its metabolites through the bloodstream. The research outcomes of this Thesis contribute in a pioneering way to identify personalized strategies aimed at improving the health effects of (poly)phenols.