Specific microbe-derived metabolite signatures associate with advanced human atherosclerosis and postoperative cardiac complications. We suggest that these metabolites are potential novel biomarkers for atherosclerotic disease burden and that further investigation into mechanistic links between defined microbial metabolic pathways and cardiovascular disease is warranted.

The role of the microbiome in human health has become a central tenant of current medical research, infiltrating a diverse disciplinary base whereby microbiology, computer science, ecology, gastroenterology, immunology, neurophysiology and psychology, metabolism, and cardiovascular medicine all intersect. Traditionally, commensal gut microbiota have been assumed to play a significant role only in the metabolic processing of dietary nutrients and host metabolites, the fortification of gut epithelial barrier function, and the development of mucosal immunity. However, over the last 20 years, new technologies and renewed interest have uncovered a considerably broader influence of the microbiota on health maintenance and disease development, many of which are of particular relevance for surgeons. This article provides a broad overview of the current state of knowledge and a review of the technology that helped in their formation.

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Neointimal hyperplasia is a major contributor to restenosis after arterial interventions. The genetic and environmental mechanisms underlying the variable propensity for neointimal hyperplasia between individuals are not well understood. One possible modulator could be commensal gut microbes. To address whether microbes mediate neointimal hyperplasia, we cohoused genetically different rats (Lewis [LE] and Sprague-Dawley [SD]) which harbor different commensal microbes and compared neointimal hyperplasia 2 weeks after carotid angioplasty in the cohoused and non-cohoused cohorts. Cohousing is a means of microbial transfer between cage inhabitants. We observed that differences in neointimal hyperplasia between non-cohoused LE and SD rats (median intima+media [I+M] area 0.12 mm 2 LE vs. 0.26 mm 2 SD, P<.0001;Mann-Whitney) were mitigated when rats are cohoused for 1 month (Figure 1A), suggesting an environmental effect that outweighs the genetic influence. Specifically, I+M area decreased by 23% in SD rats that were cohoused with LE rats (P<.0001;Mann-Whitney), and there was a trend towards a 10% increase in I+M area in cohoused LE rats. To identify specific bacteria associated with the change in neointimal hyperplasia, we monitored fecal bacteria over time using 16S rRNA sequencing. Principal component analysis revealed that fecal samples from cohoused rats diverged from non-cohoused rats in both strains (P<.001 SD, P=.008 LE;PERMANOVA) (Figure 1B). The greatest change was cohoused SD samples becoming similar to non-cohoused LE samples over time, which correlates with the carotid morphometric data. Comparative analysis showed that abundance of the bacterial genera Peptococcus and Blautia negatively correlated with I+M area in both strains (P<.001;Fisher z transform, Bonferroni corrected, Spearman’s ρ -0.8 for both). Ongoing studies will further delineate the potential causative relationship between these microbes and neointimal hyperplasia.