D2.2 Report about the effects produced by the consumption of sourdough breads on rat’s gut microbiota / gut-derived metabolites – Abstract

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• Create Date July 10, 2023
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In the previous project, PANSALUD, we evaluated the postprandial and chronic response to different sourdough breads. For this purpose, seven groups of rats were fed a conventional refined-wheat bread (PSMMC_H), a Rebola sourdough-leavened bread made from spelt (PH_1), tritordeum (PH_2) or durum wheat (PH_3), or a multigrain bread leavened with Rebola (PH_4), Carla (PH_5) or San Francisco (PH_6) sourdoughs. We found, in rats, that the intake of the sourdough breads PH_1), PH_3, PH_4 and PH_6 improved postprandial blood glucose and insulin responses compared to the PSMMC_H consumption. Furthermore, we also demonstrated for the first time that the effects of a multigrain bread leavened with Rebola (PH_4), Carla (PH_5) or San Francisco (PH_6) sourdoughs on these acute responses as well as on relative apparent absorption (RAA), serum insulin, triacylglycerols and MCP-1 levels after a 3-week intake were sourdough-specific.
The aim of the present study is to gain knowledge about the mechanism of action by which the sourdough breads can exert their health effects, analysing the gut microbiota and the gut-derived metabolism in faeces using an omics approach (metabolomics and metagenomics).For this purpose, the intestinal microbiota and the metabolite profile of the faeces from the 6 groups of rats that were used during the execution of the PANSALUD project were analysed.

In the present omics study we reported important changes in faecal amino acids and metabolites as well as in the circulating levels of acetate and hexanoic acids in rats in response to the chronic consumption of the multigrain bread leavened with the Carla sourdough (PH_5). These changes were accompanied with very slight changes in the gut microbiota composition. Similar results were found after PH_6 intake concerning fecal amino acids, but to a lesser extent. These effects could be potentially attributed to a lower amino acid absorption in the small intestine or to a lower protein digestibility of these breads. These results would not support PH5 and PH6 breads as the first choices to enrich the Mediterranean diet that will be implemented in obese adolescents.

Overall, the 3-week intake intake of a Rebola sourdough-leavened bread made from spelt (PH_1), tritordeum (PH_2) or durum wheat (PH_3), or a multigrain bread leavened with Rebola (PH_4) produced scarce changes in faecal amino acids and metabolites, circulating SCFAs and gut microbiota composition. Taking into account that, compared to PSMMC_H-fed rats, PH_1, PH_3 and PH_4-fed animals showed lower postprandial blood glucose levels, and that this beneficial effect was not observed in response to the consumption of PH_2 bread, the choice of the Rebola sourdough-leavened bread made from tritordeum (PH_2) for the nutritional intervention study with obese adolescents would be discarded.

Interestingly, rats chronically fed the PH_4 bread also displayed significant lower circulating levels of MCP-1 (a pro-inflammatory marker) than their control counterparts, and effect that was not observed in PH_1 and PH_3-fed animals. This result could put the multigrain bread leavened with Rebola (PH_4) as first choice to be included in the Mediterranean diet. Nevertheless, it is suggested to take into account the results concerning the surveys about bread preferences carried out in adolescents from Spain, Portugal and Italy as well as the results about the adolescents’ sensory acceptability evaluation of the sourdough breads that will performed in the short term to make the final choice among the Rebola sourdough-leavened bread made from spelt (PH_1), durum wheat (PH_3), or multigrain (PH_4).