Steinbach E. auteur aut IRD Belda Eugeni auteur aut IRD Alili R. auteur aut IRD Adriouch S. auteur aut IRD Dauriat C. J. G. auteur aut IRD Donatelli G. auteur aut IRD Dumont J. L. auteur aut IRD Pacini F. auteur aut IRD Tuszynski T. auteur aut IRD Pelloux V. auteur aut IRD Jacques F. auteur aut IRD Creusot L. auteur aut IRD Coles E. auteur aut IRD Taillandier P. auteur aut IRD Gomez M. V. auteur aut IRD Masi D. auteur aut IRD Mateo V. auteur aut IRD André S. auteur aut IRD Kordahi M. auteur aut IRD Rouault C. auteur aut IRD Zucker Jean-Daniel auteur aut IRD Sokol H. auteur aut IRD Genser L. auteur aut IRD Chassaing B. auteur aut IRD Le Roy T. auteur aut IRD Clément K. auteur aut IRD text journalArticle eng text/pdf reformatted digital access The intestinal microbiota is increasingly recognized as a crucial player in the development and maintenance of various chronic conditions, including obesity and associated metabolic diseases. While most research focuses on the fecal microbiota due to its easier accessibility, the small intestine, as a major site for nutrient sensing and absorption, warrants further investigation to determine its microbiota composition and functions. Here, we conducted a clinical research project in 30 age- and sex-matched participants with (n = 15) and without (n = 15) obesity. Duodenojejunal fluid was obtained by aspiration during endoscopy. Phenotyping included clinical variables related to metabolic status, lifestyle, and psychosocial factors using validated questionnaires. We performed metagenomic analyses of the oral, duodenojejunal, and fecal microbiome, alongside metabolomic data from duodenojejunal fluid and feces, integrating these data with clinical and lifestyle information. Our results highlight significant associations between duodenojejunal microbiota composition and usual dietary intake, as well as clinical phenotypes, with larger effect sizes than the associations between these variables and fecal microbiota. Notably, we found that the duodenojejunal microbiota of patients with obesity exhibited higher diversity and showed distinct differences in the abundance of several duodenojejunal microbiota species compared with individuals without obesity. Our findings support the relevance of studying the role of the small intestinal microbiota in the pathogenesis of nutrition-related diseases. specialized Small intestine microbiota duodenojejunal microbiome oral microbiome microbiota microbiome nutrition metabolomics dietary quality obesity metabolic diseases 054 084 16 1 2405547 [19 ] 2024 1949-0976 https://www.documentation.ird.fr/hor/fdi:010091899 10.1080/19490976.2024.2405547 1949-0976 [F B010091899] https://www.documentation.ird.fr/hor/fdi:010091899 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2024-11/010091899.pdf IRD - Base Horizon / Pleins textes 2024-11-13 2026-06-12 fdi:010091899 fre