Rumen microbiome-driven insight into bile acid metabolism and host metabolic regulation

Supplementation with ursodeoxycholic acid and bile salt benefits lactation performance, health, and rumen and fecal microbiota of transition dairy cows

This study investigated the effects of ursodeoxycholic acid (UDCA) and bile salt (BAS) supplementation on lactation performance, health, and gut microbiota in periparturient dairy cows. Fifty-one Holstein dairy cows were selected at d -28 before parturition and blocked into 3 dietary treatments, including the control (CON; n = 17) received a basal diet, whereas the UDCA (n = 17) and BAS groups (n = 17) were supplemented with 10 g/d UDCA and 20 g/d BAS from d -21 to +21, with an observation phase until d +35. Milk yield and composition were recorded weekly, whereas the DMI were measured biweekly. Blood samples were collected at d +7 and +21, whereas rumen fluid and fecal samples were collected at d +21. Milk yield was significantly higher in the UDCA group at d +21 compared with the CON group, whereas on d +28, milk yield was significantly higher in both the UDCA and BAS groups compared with the CON group, and the DMI of the UDCA group showed an increased tendency at prepartum. Plasma nonesterified fatty acids were significantly higher in the BAS group, whereas Ala aminotransferase content were significantly lower in the UDCA group compared with the control. Furthermore, the cholesterol, malondialdehyde, oxidative stress index, serum amyloid A, and haptoglobin content were significantly lower in the UDCA and BAS groups. In total, 35, 43, and 45 plasma bile acids (BA) were detected in the control, UDCA, and BAS groups, respectively. Compared with the control, 8 key BA, including UDCA, tauroursodeoxycholic acid, glycoursodeoxycholic acid, and 5 key BA, including tauro-β-muricholic acid and hyocholic acid, were identified in the UDCA and BAS groups, respectively. The concentrations of total VFA and acetate in the UDCA and BAS groups were higher than that in the CON group, and the concentration of propionate tended to be higher. The β-diversity of both rumen and gut microbiota was significantly higher in the CON, UDCA, and BAS groups, whereas no significant changes were observed in α-diversity. Key rumen VFA-production bacteria, including Prevotella_7, Succinivibrionaceae_UCG-001, and Selenomonas, were enriched in the UDCA and BAS groups, along with an increase in beneficial gut microbiota, such as Butyrivibrio, Ruminococcus, and Caproiciproducen, and a reduction in harmful bacteria, such as Stenotrophomonas and Chryseobacterium. These findings suggest that the observed improvements in production performance and health may be mediated by alterations in peripheral BA and rumen and gut microbiota, offering insights for optimizing the nutrition and health of transitional dairy cows.

Bile Acids Modulate Hepatic Glycolipid Metabolism via the Microbiota-Gut-Liver Axis in Lambs

BACKGROUND

Bile acids are essential molecules that facilitate lipid emulsification and function as signaling molecules mediating host-microbiota interactions. They shape the gut microbial structure and function, playing a critical role in metabolic regulation via the gut-liver axis.

OBJECTIVES

This study aimed to investigate the effects of exogenous bile acids, primarily hyocholic acid (HCA), on the microbiota-gut-liver metabolism in male Tan-lambs fed a high-grain diet.

METHODS

Thirty six-mo-old male Tan lambs (Ovis aries) were randomly allocated into either a control group or an HCA-supplemented group (n = 15 per group). The trial lasted 84 d, including a 14-d adaptation period. On day 70, 6 lambs from each group were randomly selected for slaughtering. Rumen and ileal contents were collected for microbial profiling via 16S rRNA sequencing, and liver tissue samples were harvested for transcriptomic and metabolomic analyses.

RESULTS

The HCA intervention significant altered the composition and structure of ruminal and ileal bacteria. Notable increases were observed in Turicibacter species [linear discriminant analysis (LDA) score = 2.48; P < 0.05] and Muribaculaceae (LDA score = 3.75; P < 0.05) in the rumen, and Eubacterium fissicatena group (LDA score = 2.50; P < 0.05) in the ileum. Key hepatic genes and metabolites targeted by HCA were identified, including ENPP3, RFK, Ifi203, LIPG, CYP1A1, and CYP4A11, nordeoxycholic acid (log-fold change = 6.30; P < 0.005), α-muricholic acid (log-fold change = 5.60; P < 0.001), and β-muricholic acid (log-fold change = 5.60; P < 0.001).

CONCLUSIONS

Exogenous bile acids regulate the microbiota-gut-liver axis, influencing hepatic glycolipid metabolism in sheep. Specifically, nordeoxycholic acid demonstrates potential as a dietary intervention to promote metabolic homeostasis in ruminants. These findings highlight the potential of HCA and nordeoxycholic acid as functional feed additives or prebiotic agents for improving metabolic health in ruminants and potentially other species.

The Effect of Microbiome-Derived Metabolites in Inflammation-Related Cancer Prevention and Treatment

Chronic inflammation plays a crucial role in cancer development, yet the mechanisms linking the microbiome to inflammation-related carcinogenesis remain unclear. Emerging evidence suggests that microbiome-derived metabolites influence inflammatory pathways, presenting both challenges and opportunities for therapy. However, a deeper understanding of how these metabolites regulate inflammation and contribute to cancer prevention is still needed. This review explores recent advances in microbiome-derived metabolites and their roles in inflammation-related carcinogenesis. It highlights key molecular mechanisms, emerging therapies, and unresolved challenges. Synthesizing current research, including clinical trials and experimental models, bridges the gap between microbiome science and cancer therapy. Microbial metabolites such as short-chain fatty acids (SCFAs), polyamines, indoles, and bile acids play vital roles in regulating inflammation and suppressing cancer. Many metabolites exhibit potent anti-inflammatory and immunomodulatory effects, demonstrating therapeutic potential. Case studies show promising results, but challenges such as metabolite stability, bioavailability, and individual variability remain. Understanding microbiome-metabolite interactions offers novel strategies for cancer prevention and treatment. This review identifies knowledge gaps and proposes future research directions to harness microbiome-derived metabolites for innovative cancer therapies. Addressing these issues may pave the way for microbiome-targeted cancer interventions.

Metabolic pathways associated with Firmicutes prevalence in the gut of multiple livestock animals and humans

Dynamic interspecific interactions and environmental factors deeply impact the composition of microbiotic communities in the gut. These factors intertwined with the host's genetic background and social habits cooperate synergistically as a hidden force modulating the host's physiological and health determinants, with certain bacterial species being maintained from generation to generation. Firmicutes, one of the dominant bacterial phyla present across vertebrate classes, exhibits a wide range of functional capabilities and colonization strategies. While ecological scenarios involving microbial specialization and metabolic functions have been hypothesized, the specific mechanisms that sustain the persistence of its microbial taxa in a high diversity of hosts remain elusive. This study fills this gap by investigating the Firmicutes metabolic mechanisms contributing to their prevalence and heritability in the host gut on metagenomes-assembled bacterial genomes collected from 351 vertebrate samples, covering 18 food-producing animals and humans, specific breeds and closely-related species. We observed that taxa belonging to Acetivibrionaceae, Clostridiaceae, Lachnospiraceae, Ruminococcaceae, and the not well understood CAG-74 family were evolutionarily shared across all hosts. These prevalent taxa exhibit metabolic pathways significantly correlated with extra-host survival mechanisms, cell adhesion, colonization and host transmission, highlighted by sporulation, glycan biosynthesis, bile acid metabolism, and short-chain fatty acid encoded genes. Our findings provide a deeper understanding of the ecological foundations governing distinct transmission modes, effective colonization establishment, and maintenance of Firmicutes, offering new perspectives on both well-known and poorly characterized species.