Development of an in vitro model based on fecal slurries to study the metabolism of soy isoflavones by the microbiota of the human gut

Trabajo presentado en la International Scientific Association for Probiotics and Prebiotics (ISAPP) Conference, celebrada en Washington (Estados Unidos), del 19 al 21 de mayo de 2015Isoflavones are a class of polyphenols with estrogenic activity present in relatively high concentration in soy. Consumption of isoflavones has been epidemiologically correlated with a decrease of menopause symptoms in women and a lower incidence of hormonedependent and aging-associated diseases, such as osteoporosis, cardiovascular diseases and cancer. To be active, isoflavones require their transformation by the gut microbiota into more bioavailable and active metabolites, such as S-(-)equol. However, intestinal populations involved in isoflavone metabolism and equol production are not yet well characterized. Indeed, only 25-30% of Western individuals are able to produce equol. Conceivably, these individuals might be those who benefit from the health effects of soy isoflavone intake. The aim of this work was to develop an in vitro colonic model based on fecal slurries to study the role of fecal microbial constituents in the metabolism of isoflavones. Identification of beneficial microbes would lead to their application in functional foods. Fecal slurries from menopausal women were grown in a rich colonic medium (MCB) supplemented or not with isoflavone concentrates. Cultures were carried out in anaerobiosis at 37ºC for 24 h with mild stirring. Microbial communities were analyzed by DGGE and phylogenetic metagenomics. Short-chain fatty acids and isoflavone metabolites were analyzed by GC and UHPLC, respectively. Slurries from equolproducer women yielded equol in vitro. Changes in both microbial communities and isoflavone metabolites were observed. However, clear-cut associations between populations and metabolites were not obtained. This might be due to huge interindividual variations in microbiota composition.Peer reviewe