Alcohol induced alterations to the human fecal VOC metabolome.

Studies have shown that excessive alcohol consumption impacts the intestinal microbiota composition, causing disruption of homeostasis (dysbiosis). However, this observed change is not indicative of the dysbiotic intestinal microbiota function that could result in the production of injurious and toxic products. Thus, knowledge of the effects of alcohol on the intestinal microbiota function and their metabolites is warranted, in order to better understand the role of the intestinal microbiota in alcohol associated organ failure. Here, we report the results of a differential metabolomic analysis comparing volatile organic compounds (VOC) detected in the stool of alcoholics and non-alcoholic healthy controls. We performed the analysis with fecal samples collected after passage as well as with samples collected directly from the sigmoid lumen. Regardless of the approach to fecal collection, we found a stool VOC metabolomic signature in alcoholics that is different from healthy controls. The most notable metabolite alterations in the alcoholic samples include: (1) an elevation in the oxidative stress biomarker tetradecane; (2) a decrease in five fatty alcohols with anti-oxidant property; (3) a decrease in the short chain fatty acids propionate and isobutyrate, important in maintaining intestinal epithelial cell health and barrier integrity; (4) a decrease in alcohol consumption natural suppressant caryophyllene; (5) a decrease in natural product and hepatic steatosis attenuator camphene; and (6) decreased dimethyl disulfide and dimethyl trisulfide, microbial products of decomposition. Our results showed that intestinal microbiota function is altered in alcoholics which might promote alcohol associated pathologies.

The approach to sample acquisition and its impact on the derived human fecal microbiome and VOC metabolome.

Recent studies have illustrated the importance of the microbiota in maintaining a healthy state, as well as promoting disease states. The intestinal microbiota exerts its effects primarily through its metabolites, and metabolomics investigations have begun to evaluate the diagnostic and health implications of volatile organic compounds (VOCs) isolated from human feces, enabled by specialized sampling methods such as headspace solid-phase microextraction (hSPME). The approach to stool sample collection is an important consideration that could potentially introduce bias and affect the outcome of a fecal metagenomic and metabolomic investigation. To address this concern, a comparison of endoscopically collected (in vivo) and home collected (ex vivo) fecal samples was performed, revealing slight variability in the derived microbiomes. In contrast, the VOC metabolomes differ widely between the home collected and endoscopy collected samples. Additionally, as the VOC extraction profile is hyperbolic, with short extraction durations more vulnerable to variation than extractions continued to equilibrium, a second goal of our investigation was to ascertain if hSPME-based fecal metabolomics studies might be biased by the extraction duration employed. As anticipated, prolonged extraction (18 hours) results in the identification of considerably more metabolites than short (20 minute) extractions. A comparison of the metabolomes reveals several analytes deemed unique to a cohort with the 20 minute extraction, but found common to both cohorts when the VOC extraction was performed for 18 hours. Moreover, numerous analytes perceived to have significant fold change with a 20 minute extraction were found insignificant in fold change with the prolonged extraction, underscoring the potential for bias associated with a 20 minute hSPME.

Alterations in the porcine colon microbiota induced by the gastrointestinal nematode Trichuris suis.

Helminth parasites ensure their survival by regulating host immunity through mechanisms that dampen inflammation. These properties have recently been exploited therapeutically to treat human diseases. The biocomplexity of the intestinal lumen suggests that interactions between the parasite and the intestinal microbiota would also influence inflammation. In this study, we characterized the microbiota in the porcine proximal colon in response to Trichuris suis (whipworm) infection using 16S rRNA gene-based and whole-genome shotgun (WGS) sequencing. A 21-day T. suis infection in four pigs induced a significant change in the composition of the proximal colon microbiota compared to that of three parasite-naive pigs. Among the 15 phyla identified, the abundances of Proteobacteria and Deferribacteres were changed in infected pigs. The abundances of approximately 13% of genera were significantly altered by infection. Changes in relative abundances of Succinivibrio and Mucispirillum, for example, may relate to alterations in carbohydrate metabolism and niche disruptions in mucosal interfaces induced by parasitic infection, respectively. Of note, infection by T. suis led to a significant shift in the metabolic potential of the proximal colon microbiota, where 26% of all metabolic pathways identified were affected. Besides carbohydrate metabolism, lysine biosynthesis was repressed as well. A metabolomic analysis of volatile organic compounds (VOCs) in the luminal contents showed a relative absence in infected pigs of cofactors for carbohydrate and lysine biosynthesis, as well as an accumulation of oleic acid, suggesting altered fatty acid absorption contributing to local inflammation. Our findings should facilitate development of strategies for parasitic control in pigs and humans.