Microbe-Derived Butyrate and Its Receptor, Free Fatty Acid Receptor 3, But Not Free Fatty Acid Receptor 2, Mitigate Neointimal Hyperplasia Susceptibility After Arterial Injury.

Background Arterial restenosis after vascular surgery is a common cause of midterm restenosis and treatment failure. Herein, we aim to investigate the role of microbe-derived butyrate, FFAR2 (free fatty acid receptor 2), and FFAR3 (free fatty acid receptor 3) in mitigating neointimal hyperplasia development in remodeling murine arteries after injury. Methods and Results C57BL/6 mice treated with oral vancomycin before unilateral femoral wire injury to deplete gut microbiota had significantly diminished serum and stool butyrate and more neointimal hyperplasia development after arterial injury, which was reversed by concomitant butyrate supplementation. Deficiency of FFAR3 but not FFAR2, both receptors for butyrate, exacerbated neointimal hyperplasia development after injury. FFAR3 deficiency was also associated with delayed recovery of the endothelial layer in vivo. FFAR3 gene expression was observed in multiple peripheral arteries, and expression was increased after arterial injury. Treatment of endothelial but not vascular smooth muscle cells with the pharmacologic FFAR3 agonist 1-methylcyclopropane carboxylate stimulated cellular migration and proliferation in scratch assays. Conclusions Our results support a protective role for butyrate and FFAR3 in the development of neointimal hyperplasia after arterial injury and delineate activation of the butyrate-FFAR3 pathway as a valuable strategy for the prevention and treatment of neointimal hyperplasia.

Microbiota composition modulates inflammation and neointimal hyperplasia after arterial angioplasty.

BACKGROUND: Neointimal hyperplasia is a major contributor to restenosis after arterial interventions, but the genetic and environmental mechanisms underlying the variable propensity for neointimal hyperplasia between individuals, including the role of commensal microbiota, are not well understood. We sought to characterize how shifting the microbiome using cage sharing and bedding mixing between rats with differing restenosis phenotypes after carotid artery balloon angioplasty could alter arterial remodeling. METHODS: We co-housed and mixed bedding between genetically distinct rats (Lewis [LE] and Sprague-Dawley [SD]) that harbor different commensal microbes and that are known to have different neointimal hyperplasia responses to carotid artery balloon angioplasty. Sequencing of the 16S ribosomal RNA gene was used to monitor changes in the gut microbiome. RESULTS: There were significant differences in neointimal hyperplasia between non-co-housed LE and SD rats 14 days after carotid artery angioplasty (mean intima + media [I + M] area, 0.117 ± 0.014 mm2 LE vs 0.275 ± 0.021 mm2 SD; P < .001) that were diminished by co-housing. Co-housing also altered local adventitial Ki67 immunoreactivity, local accumulation of leukocytes and macrophages (total and M2), and interleukin 17A concentration 3 days after surgery in each strain. Non-co-housed SD and LE rats had microbiomes distinguished by both weighted (P = .012) and unweighted (P < .001) UniFrac beta diversity distances, although without significant differences in alpha diversity. The difference in unweighted beta diversity between the fecal microbiota of SD and LE rats was significantly reduced by co-housing. Operational taxonomic units that significantly correlated with average I + M area include Parabacteroides distasonis, Desulfovibrio, Methanosphaera, Peptococcus, and Prevotella. Finally, serum concentrations of microbe-derived metabolites hydroxyanthranilic acid and kynurenine/tryptophan ratio were significantly associated with I + M area in both rat strains independent of co-housing. CONCLUSIONS: We describe a novel mechanism for how microbiome manipulations affect arterial remodeling and the inflammatory response after arterial injury. A greater understanding of the host inflammatory-microbe axis could uncover novel therapeutic targets for the prevention and treatment of restenosis.

Microbial Colonization of Germ-Free Mice Restores Neointimal Hyperplasia Development After Arterial Injury.

Background The potential role of the gut microbiome in cardiovascular diseases is increasingly evident. Arterial restenosis attributable to neointimal hyperplasia after cardiovascular procedures such as balloon angioplasty, stenting, and bypass surgery is a common cause of treatment failure, yet whether gut microbiota participate in the development of neointimal hyperplasia remains largely unknown. Methods and Results We performed fecal microbial transplantation from conventionally raised male C57BL/6 mice to age-, sex-, and strain-matched germ-free mice. Five weeks after inoculation, all mice underwent unilateral carotid ligation. Neointimal hyperplasia development was quantified after 4 weeks. Conventionally raised and germ-free cohorts served as comparison groups. Conclusions Germ-free mice have significantly attenuated neointimal hyperplasia development compared with conventionally raised mice. The arterial remodeling response is restored by fecal transplantation. Our results describe a causative role of gut microbiota in contributing to the pathogenesis of neointimal hyperplasia.

The relationship of preoperative versus postoperative hyperglycemia on clinical outcomes after elective colorectal surgery.

BACKGROUND: The relationship between preoperative hyperglycemia and complications after surgery is not well defined. We compared the relationship of preoperative versus postoperative hyperglycemia on clinical outcomes and assessed if preoperative hyperglycemia was a predictor for postoperative hyperglycemia in patients undergoing elective colorectal surgery. METHODS: We performed a retrospective review of an institutional database for patients who underwent elective colorectal resection between July 2015 and June 2017. Data regarding patient characteristics, history of diabetes, preoperative and postoperative hyperglycemic events, and postoperative complications were collected. Bivariate and multivariate logistic analyses were used to assess relationships. RESULTS: Of 755 surgical operations reviewed, preoperative hyperglycemia >180 mg/dL was not significantly associated with adverse outcomes in an adjusted model. Only postoperative hyperglycemia >180 mg/dL was significantly associated with complications, including acute kidney injury (odds ratio 2.58, P < 0.001), anastomotic leak (odds ratio 2.64, P = 0.01), arrhythmia (odds ratio 2.40, P = 0.009), and sepsis (odds ratio 3.86, P < 0.001). Preoperative hyperglycemia remained a significant predictor of postoperative hyperglycemia (odds ratio 4.91, P < 0.001). CONCLUSION: Postoperative hyperglycemia was more significantly associated with adverse clinical outcomes after elective colorectal surgery than was preoperative hyperglycemia. However, preoperative hyperglycemia was associated with postoperative hyperglycemia, suggesting that improved glycemic management preoperatively may help reduce hyperglycemic events after surgery.

Microbiota control acute arterial inflammation and neointimal hyperplasia development after arterial injury.

BACKGROUND: The microbiome has a functional role in a number of inflammatory processes and disease states. While neointimal hyperplasia development has been linked to inflammation, a direct role of the microbiota in neointimal hyperplasia has not yet been established. Germ-free (GF) mice are an invaluable model for studying causative links between commensal organisms and the host. We hypothesized that GF mice would exhibit altered neointimal hyperplasia following carotid ligation compared to conventionally raised (CONV-R) mice. METHODS: Twenty-week-old male C57BL/6 GF mice underwent left carotid ligation under sterile conditions. Maintenance of sterility was assessed by cultivation and 16S rRNA qPCR of stool. Neointimal hyperplasia was assessed by morphometric and histologic analysis of arterial sections after 28 days. Local arterial cell proliferation and inflammation was assessed by immunofluorescence for Ki67 and inflammatory cell markers at five days. Systemic inflammation was assessed by multiplex immunoassays of serum. CONV-R mice treated in the same manner served as the control cohort. GF and CONV-R mice were compared using standard statistical methods. RESULTS: All GF mice remained sterile during the entire study period. Twenty-eight days after carotid ligation, CONV-R mice had significantly more neointimal hyperplasia development compared to GF mice, as assessed by intima area, media area, intima+media area, and intima area/(intima+media) area. The collagen content of the neointimal lesions appeared qualitatively similar on Masson's trichrome staining. There was significantly reduced Ki67 immunoreactivity in the media and adventitia of GF carotid arteries 5 days after ligation. GF mice also had increased arterial infiltration of anti-inflammatory M2 macrophages compared to CONV-R mouse arteries and a reduced proportion of mature neutrophils. GF mice had significantly reduced serum IFN-γ-inducible protein (IP)-10 and MIP-2 5 days after carotid ligation, suggesting a reduced systemic inflammatory response. CONCLUSIONS: GF mice have attenuated neointimal hyperplasia development compared to CONV-R mice, which is likely related to altered kinetics of wound healing and acute inflammation. Recognizing the role of commensals in the regulation of arterial remodeling will provide a deeper understanding of the pathophysiology of restenosis and support strategies to treat or reduce restenosis risk by manipulating microbiota.

Current State of Knowledge on Implications of Gut Microbiome for Surgical Conditions.

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.

Increased mammalian lifespan and a segmental and tissue-specific slowing of aging after genetic reduction of mTOR expression.

We analyzed aging parameters using a mechanistic target of rapamycin (mTOR) hypomorphic mouse model. Mice with two hypomorphic (mTOR(Δ/Δ)) alleles are viable but express mTOR at approximately 25% of wild-type levels. These animals demonstrate reduced mTORC1 and mTORC2 activity and exhibit an approximately 20% increase in median survival. While mTOR(Δ/Δ) mice are smaller than wild-type mice, these animals do not demonstrate any alterations in normalized food intake, glucose homeostasis, or metabolic rate. Consistent with their increased lifespan, mTOR(Δ/Δ) mice exhibited a reduction in a number of aging tissue biomarkers. Functional assessment suggested that, as mTOR(Δ/Δ) mice age, they exhibit a marked functional preservation in many, but not all, organ systems. Thus, in a mammalian model, while reducing mTOR expression markedly increases overall lifespan, it affects the age-dependent decline in tissue and organ function in a segmental fashion.