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Background: Bile acids (BAs) are steroid-derived molecules with important roles in digestion, the maintenance of host metabolism, and immunomodulation. Primary BAs are synthesized by the host, while secondary BAs are produced by the gut microbiome through transformation of the former. The regulation of microbial production of secondary BAs is not well understood, particularly the production of 7-dehydroxylated BAs, which are the most potent agonists for host BA receptors. The 7-dehydroxylation of cholic acid (CA) is well established and is linked to the expression of a bile acid-inducible (bai) operon responsible for this process. However, little to no 7-dehydroxylation has been reported for other host-derived BAs (e.g., chenodeoxycholic acid, CDCA or ursodeoxycholic acid, UDCA)., Results: Here, we demonstrate that the 7-dehydroxylation of CDCA and UDCA by the human isolate Clostridium scindens is induced when CA is present, suggesting that CA-dependent transcriptional regulation is required for substantial 7-dehydroxylation of these primary BAs. This is supported by the finding that UDCA alone does not promote expression of bai genes. CDCA upregulates expression of the bai genes but the expression is greater when CA is present. In contrast, the murine isolate Extibacter muris exhibits a distinct response; CA did not induce significant 7-dehydroxylation of primary BAs, whereas BA 7-dehydroxylation was promoted upon addition of germ-free mouse cecal content in vitro. However, E. muris was found to 7-dehydroxylate in vivo., Conclusions: The distinct expression responses amongst strains indicate that bai genes are regulated differently. CA promoted bai operon gene expression and the 7-dehydroxylating activity in C. scindens strains. Conversely, the in vitro activity of E. muris was promoted only after the addition of cecal content and the isolate did not alter bai gene expression in response to CA. The accessory gene baiJ was only upregulated in the C. scindens ATCC 35704 strain, implying mechanistic differences amongst isolates. Interestingly, the human-derived C. scindens strains were also capable of 7-dehydroxylating murine bile acids (muricholic acids) to a limited extent. This study shows novel 7-dehydroxylation activity in vitro resulting from the presence of CA and suggests distinct bai gene expression across bacterial species., (© 2024. The Author(s).)

Background: Optimal stent deployment in left main (LM) bifurcation is paramount, and incomplete stent apposition may cause major adverse cardiac events (MACE). Bench studies show that the proximal optimization technique (POT) provides the best stent apposition., Aims: We aimed to investigate the impact of POT on clinical outcomes in patients treated for unprotected LM (ULM) disease at our institution., Methods: We identified 162 patients who underwent percutaneous coronary intervention (PCI) for ULM coronary disease in the Cardio-FR database. Out of these, 99 (61%) had undergone POT, while 63 patients were treated without POT. The primary outcome was the bifurcation-oriented composite endpoint (BOCE) of cardiac death, target-bifurcation myocardial infarction and target-bifurcation revascularization at maximal follow-up., Results: Mean age was 76 years, and 69% presented with acute coronary syndrome. Mean follow-up was 2.25 years (822 days). The BOCE occurred in 43 (27%) of which 20 (20%) in the POT group and 23 (37%) in the no-POT group (p = 0.009). Cardiac death occurred in 15 (15%) patients in the POT- and 17 (27%) in no-POT group (p = 0.26). Target bifurcation revascularization occurred in 4 (4%) patients in the POT- and 6 (10%) patients in the no-POT group (p = 0.19). POT In the multivariate analysis, POT was the strongest parameter and was associated with BOCE, cardiac death, occurrence of any revascularization and all-cause mortality., Conclusion: The POT improves clinical outcomes. These findings strongly support the systematic use of POT in patients undergoing ULM-PCI., (© 2024 The Authors. Catheterization and Cardiovascular Interventions published by Wiley Periodicals LLC.)

Bile acid transformation is a common gut microbiome activity that produces secondary bile acids, some of which are important for human health. One such process, 7α-dehydroxylation, converts the primary bile acids, cholic acid and chenodeoxycholic acid, to deoxycholic acid and lithocholic acid, respectively. This transformation requires a number of enzymes, generally encoded in a bile acid-inducible ( bai ) operon and consists of multiple steps. Some 7α-dehydroxylating bacteria also harbor additional genes that encode enzymes with potential roles in this pathway, but little is known about their functions. Here, we purified 11 enzymes originating either from the bai operon or encoded at other locations in the genome of Clostridium scindens strain ATCC 35704. Enzyme activity was probed in vitro under anoxic conditions to characterize the biochemical pathway of chenodeoxycholic acid 7α-dehydroxylation. We found that more than one combination of enzymes can support the process and that a set of five enzymes, including BaiJ that is encoded outside the bai operon, is sufficient to achieve the transformation. We found that BaiJ, an oxidoreductase, exhibits an activity that is not harbored by the homologous enzyme from another C. scindens strain. Furthermore, ligation of bile acids to coenzyme A (CoA) was shown to impact the product of the transformation. These results point to differences in the 7α-dehydroxylation pathway among microorganisms and the crucial role of CoA ligation in the process.