Relationship between water-soluble primary metabolites in feces, gut microbiota, and dietary history in healthy female university students using gas chromatography–mass spectrometry: A cross-sectional study

<b>Background & Aims:</b> The ingested food substances and the substances produced by the action of organisms and gut bacteria on the ingested food can impact health and increase chronic disease risk. Metabolomics is used to elucidate metabolic profiles altered by diet; however, there is no clear consensus regarding the samples and the analytical and dietary survey methods used. This study aimed to assess the effect on metabolic profiling of feces with or without cell disruption and to evaluate the correlation between the annotated metabolites and the gut microbiota and dietary habits. <b>Methods:</b> This study included 50 healthy female university students. Metabolomic analysis using gas chromatography-mass spectrometry was performed under two conditions: with and without cell disruption. The annotated metabolites were designated as X1 and X2, respectively, and underwent principal component analysis (PCA). Orthogonal partial least squares regression (OPLS) analysis was performed between each metabolite and data on dietary habits and gut microbiota. <b>Results:</b> PCA using X1 and X2 metabolites showed generally consistent profiles of metabolites detected under the two extraction conditions. The OPLS analysis showed that the X1 metabolites were significantly associated with terms of α-diversity indices of the gut microbiota and with some food groups, whereas the X2 metabolites were significantly associated with only the α-diversity indices of the gut microbiota. Furthermore, using variable importance of projection values, several characteristic metabolites were detected in each significant OPLS model. <b>Conclusion:</b> For extraction of primary metabolites in feces, extraction methods without cell disruption may be strongly associated with food intake.