Dietary Exposure to Antibiotic Residues Facilitates Metabolic Disorder by Altering the Gut Microbiota and Bile Acid Composition.

Antibiotics used as growth promoters in livestock and animal husbandry can be detected in animal-derived food. Epidemiological studies have indicated that exposure to these antibiotic residues in food may be associated with childhood obesity. Herein, the effect of exposure to a residual dose of tylosin-an antibiotic growth promoter-on host metabolism and gut microbiota was explored in vivo. Theoretical maximal daily intake (TMDI) doses of tylosin were found to facilitate high-fat-diet-induced obesity, induce insulin resistance, and perturb gut microbiota composition in mice. The obesity-related phenotypes were transferrable to germfree recipient mice, indicating that the effects of a TMDI dose of tylosin on obesity and insulin resistance occurred mainly via alteration of the gut microbiota. Tylosin TMDI exposure restricted to early life, the critical period of gut microbiota development, altered the abundance of specific bacteria related to host metabolic homeostasis later in life. Moreover, early-life exposure to tylosin TMDI doses was sufficient to modify the ratio of primary to secondary bile acids, thereby inducing lasting metabolic consequences via the downstream FGF15 signaling pathway. Altogether, these findings demonstrate that exposure to very low doses of antibiotic residues, whether continuously or in early life, could exert long-lasting effects on host metabolism by altering the gut microbiota and its metabolites. IMPORTANCE This study demonstrates that even with limited exposure in early life, a residual dose of tylosin might cause long-lasting metabolic disturbances by altering the gut microbiota and its metabolites. Our findings reveal that the gut microbiota is susceptible to previously ignored environmental factors.

Differences in the gut microbiome and reduced fecal butyrate in elders with low skeletal muscle mass.

BACKGROUND AND AIMS: Despite animal studies revealing a causal link between the gut microbiota and skeletal muscle mass, the role of the gut microbiome and its metabolites in humans having low muscle mass remains unclear. METHODS: Eighty-eight subjects older than 65 years were measured for sarcopenia-related parameters, including body composition, grip strength, gait speed and flexibility. Participants were divided into normal muscle mass group (NM, n = 52) and low muscle mass group (LM, n = 36) and fresh fecal samples were collected for metagenome and short chain fatty acids (SCFAs) analysis. RESULTS: The richness and evenness of gut microbiota diversity were significantly decreased in the subjects with low muscle mass, including observed ASVs, Shannon and Chao 1 index. A significant difference of gut microbiota profile was noted between NM group and LM group. The Firmicutes/Bacteroidetes ratio was significantly reduced in the LM group. A significant decrease in the abundance of a SCFA-producer, Marvinbryantia spp., whereas a remarkable enrichment of a flavonoid degrader, Flavonifractor spp., was observed in the LM elders. Comparing with the NM group, the fecal butyrate significantly diminished in the LM group and correlated with skeletal muscle mass index. CONCLUSIONS: This is the first study that demonstrates the reduced fecal butyrate in elders with low muscle mass and highlights the associated gut microbiome changes. The identified gut microbial features and fecal butyrate level may serve as potential biomarkers for early detection of sarcopenic patients.

Atherosclerosis amelioration by allicin in raw garlic through gut microbiota and trimethylamine-N-oxide modulation.

Cardiovascular disease (CVD) is strongly associated with the gut microbiota and its metabolites, including trimethylamine-N-oxide (TMAO), formed from metaorganismal metabolism of ʟ-carnitine. Raw garlic juice, with allicin as its primary compound, exhibits considerable effects on the gut microbiota. This study validated the benefits of raw garlic juice against CVD risk via modulation of the gut microbiota and its metabolites. Allicin supplementation significantly decreased serum TMAO in ʟ-carnitine-fed C57BL/6 J mice, reduced aortic lesions, and altered the fecal microbiota in carnitine-induced, atherosclerosis-prone, apolipoprotein E-deficient (ApoE-/-) mice. In human subjects exhibiting high-TMAO production, raw garlic juice intake for a week reduced TMAO formation, improved gut microbial diversity, and increased the relative abundances of beneficial bacteria. In in vitro and ex vivo studies, raw garlic juice and allicin inhibited γ-butyrobetaine (γBB) and trimethylamine production by the gut microbiota. Thus, raw garlic juice and allicin can potentially prevent cardiovascular disease by decreasing TMAO production via gut microbiota modulation.