The relative abundance of fecal bacterial species belonging to the Firmicutes and Bacteroidetes phyla is related to plasma levels of bile acids in young adults Osuna Prieto, Francisco J. Xu, Huiwen Ortiz Álvarez, Lourdes Jurado Fasoli, Lucas Rubio‑Lopez, Jose Plaza Díaz, Julio Gil Hernández, Ángel Ruiz, Jonatan R. Martínez Téllez, Borja Manuel 7-α-Dehydroxylases Bile salt hydrolases Gut microbiota Microbiome The online version contains supplementary material available at https://doi.org/10.1007/s11306-023-02016-8. Funding for open access publishing: Universidad de Granada/CBUA. The study was supported by the Spanish Ministry of Economy and Competitiveness via Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III (PI13/01393) and PTA 12264-I, Retos de la Sociedad (DEP2016-79512-R), and European Regional Development Funds (ERDF), by the Spanish Ministry of Education (FPU16/05159, FPU16/02828, FPU17/01523 and FPU19/01609), the Fundacion Iberoamericana de Nutricion (FINUT), the University of Granada Plan Propio de Investigacion 2016-Excellence actions: Unit of Excellence on Exercise and Health (UCEES), AstraZeneca HealthCare Foundation, and by the Junta de Andalucia, Consejeria de Economia, Conocimiento, Empresas y Universidad (ref. P18-RT-4455), the Chinese Scholarship Council (CSC, No. 201707060012 to XD), Fundacion Alfonso Martin Escudero and Maria Zambrano fellowship by the Ministerio de Universidades y la Union Europea -NextGenerationEU (RR_C_2021_04). We would like to thank the team of Data Integration Center of University Medicine Magdeburg for local data-analysis solutions; they are supported by MIRACUM and funded by the German Federal Ministry of Education and Research (BMBF) within the "Medical Informatics Funding Scheme" (FKZ 01ZZ1801H). This study is part of a Ph.D. thesis conducted within the Biomedicine Doctoral Studies Program of the University of Granada, Spain. AL was supported by the funds from European Commission through the "European funds for regional development" (EFRE) Project ID: ZS/2018/11/95324. Background Gut bacteria play a crucial role in the metabolism of bile acids (BA). Whether an association exists between the fecal microbiota composition and circulating BA levels in humans is poorly understood. Here, we investigated the relationship between fecal microbiota diversity and composition with plasma levels of BA in young adults. Methods Fecal microbiota diversity/composition was analyzed with 16S rRNA sequencing in 80 young adults (74% women; 21.9 +/- 2.2 years old). Plasma levels of BA were measured using liquid chromatography-tandem mass spectrometry. PERMANOVA and Spearman correlation analyses were used to investigate the association between fecal microbiota parameters and plasma levels of BA. Results Fecal microbiota beta (P = 0.025) and alpha diversity indexes of evenness (rho = 0.237, P = 0.033), Shannon (rho = 0.313, P = 0.004), and inverse Simpson (rho = 0.283, P = 0.010) were positively associated with plasma levels of the secondary BA glycolithocholic acid (GLCA). The relative abundance of genera belonging to the Firmicutes and Bacteroidetes phyla was positively correlated with plasma levels of GLCA (all rho = 0.225, P = 0.049). However, the relative abundance of species from Firmicutes and Bacteroidetes phyla were negatively correlated with plasma levels of primary and secondary BA (all rho = - 0.220, P = 0.045), except for the relative abundance of Bacteroides vulgatus, Alistipes onderdonkii, and Bacteroides xylanisolvens species (Bacteroidetes phylum) that were positively correlated with the plasma levels of GLCA. Conclusions The relative abundance of specific fecal bacteria species is associated with plasma levels of BA in young adults. However, further investigations are required to validate whether the composition of the gut microbiota can regulate the plasma concentrations of BA in humans. 2023-07-18T07:43:26Z 2023-07-18T07:43:26Z 2023-06-06 journal article Osuna-Prieto, F.J., Xu, H., Ortiz-Alvarez, L. et al. The relative abundance of fecal bacterial species belonging to the Firmicutes and Bacteroidetes phyla is related to plasma levels of bile acids in young adults. Metabolomics 19, 54 (2023). [https://doi.org/10.1007/s11306-023-02016-8] https://hdl.handle.net/10481/83830 10.1007/s11306-023-02016-8 eng info:eu-repo/grantAgreement/EC/NextGenerationEU/RR_C_2021_04 info:eu-repo/grantAgreement/EC/EuropeanCommission/ZS/2018/11/95324 http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Springer Nature