Development of a gut microbe-targeted nonlethal therapeutic to inhibit thrombosis potential

Dietary bioactive ingredients to modulate the gut microbiota-derived metabolite TMAO. New opportunities for functional food development

There is a growing body of clinical evidence that supports a strong association between elevated circulating trimethylamine N-oxide (TMAO) levels with increased risk of developing adverse cardiovascular outcomes such as atherosclerosis and thrombosis. TMAO is synthesized through a meta-organismal stepwise process that involves (i) the microbial production of TMA in the gut from dietary precursors and (ii) its subsequent oxidation to TMAO by flavin-containing monooxygenases in the liver. Choline, l-carnitine, betaine, and other TMA-containing compounds are the major dietary precursors of TMA. TMAO can also be absorbed directly from the gastrointestinal tract after the intake of TMAO-rich foods such as fish and shellfish. Thus, diet is an important factor as it provides the nutritional precursors to eventually produce TMAO. A number of studies have attempted to associate circulating TMAO levels with the consumption of diets rich in these foods. On the other hand, there is growing interest for the development of novel food ingredients that reduce either the TMAO-induced damage or the endogenous TMAO levels through the interference with microbiota and host metabolic processes involved in TMAO pathway. Such novel functional food ingredients would offer great opportunities to control circulating TMAO levels or its effects, and potentially contribute to decrease cardiovascular risk. In this review we summarize and discuss current data regarding the effects of TMA precursors-enriched foods or diets on circulating TMAO levels, and recent findings regarding the circulating TMAO-lowering effects of specific foods, food constituents and phytochemicals found in herbs, individually or in extracts, and their potential beneficial effect for cardiovascular health.

Changes and roles of intestinal fungal microbiota in coronary heart disease complicated with nonalcoholic fatty liver disease

BACKGROUND

Patients who suffered coronary heart disease (CHD) complicated with non-alcoholic fatty liver disease (NAFLD) were reported to have worse cardiac function and clinical outcomes than patients with CHD only. The mechanism was unclear. Previous study focused on the metabolism and showed it could be regulated by the microbiota. Few studies related to fungi. We aimed to investigate the characteristics of intestinal fungal microbiota in CHD patients complicated with NAFLD (CHD-NAFLD).

METHODS

72 People were recruited and equally divided into three groups, including CHD patients (without NAFLD), CHD-NAFLD patients, and healthy controls (HCs). Fecal samples were collected. The Illumina sequencing of the internal transcribed spacer 3-4 rRNA was applied.

RESULTS

The BMI, uric acid and triglyceride in CHD-NAFLD patients increased compared with CHD patients. The abundance of Exophiala attenuata and Malassezia restricta in all CHD-NAFLD and CHD patients significantly reduced. The intestinal fungal microbiota in CHD-NAFLD patients showed an increase in the abundance of Preussia, Xylodon and Cladorrhinum, and a reduction in the abundance of Candida glabrata and Ganoderma. Among them, the abundance of Ganoderma was significantly lower than that in CHD patients. The ejection fraction was negatively correlated to the abundance of Xylodon. Uric acid was positively correlated with the abundance of Cladorrhinum and Preussia.

CONCLUSIONS

These changes of intestinal fungal microbiota in CHD-NAFLD patients may be important factors affecting the degree of metabolic disorder. But there are few reports on these fungi. More studies are needed to confirm the effects of these fungi on human.

Reduction of intestinal trimethylamine by probiotics ameliorated lipid metabolic disorders associated with atherosclerosis

OBJECTIVES

The purpose of this study was to explore the effect of trimethylamine (TMA)-degrading probiotic agents on trimethylamine oxide (TMAO) and the related lipid metabolism in mice.

METHODS

Ten lipid-lowering strains were detected with TMA-degradation capacity in vitro. After probiotic intervention for the mice on a high-choline diet, TMA content in cecum and TMA and TMAO in serum was explored, as well as the expression of key gene flavin-containing monooxygenase 3 (FMO3) of the TMA-TMAO metabolism. The expression of genes related to the lipid metabolism was also investigated by real-time polymerase chain reaction and Western blot. Finally, the colonization of functional strains in the intestine were examined.

RESULTS

Five of 10 lipid-lowering strains effectively degraded TMA in vitro, and the TMA level in the cecum of mice were reduced after probiotic intervention. TMA level and TMAO in serum were also significantly reduced by the strains (P < 0.05), but not due to the regulation of FMO3. Probiotic agents could improve the lipid metabolism by acting on the Farnesoid X receptor and cholesterol 7-alpha hydroxy-lase. Among the strains, Bifidobacterium animalis subsp. lactis F1-3-2 showed the most prominent performance and colonized in the cecum of mice.

CONCLUSIONS

Bif. animalis subsp. lactis F1-3-2 could be colonized in the cecum, and might directly degrade TMA or change the structure of intestinal flora. The strain had an effect on TMA and TMAO levels in vivo by decreasing cecum TMA. The strain was demonstrated to participate in the TMA-TMAO regulation, improve the lipid metabolism, and alleviate atherosclerosis caused by TMAO. However, FMO3 had not changed in this process, and needs further study.

Biosynthesis, Mechanism of Action, and Inhibition of the Enterotoxin Tilimycin Produced by the Opportunistic Pathogen Klebsiella oxytoca

Tilimycin is an enterotoxin produced by the opportunistic pathogen Klebsiella oxytoca that causes antibiotic-associated hemorrhagic colitis (AAHC). This pyrrolobenzodiazepine (PBD) natural product is synthesized by a bimodular nonribosomal peptide synthetase (NRPS) pathway composed of three proteins: NpsA, ThdA, and NpsB. We describe the functional and structural characterization of the fully reconstituted NRPS system and report the steady-state kinetic analysis of all natural substrates and cofactors as well as the structural characterization of both NpsA and ThdA. The mechanism of action of tilimycin was confirmed using DNA adductomics techniques through the detection of putative N-2 guanine alkylation after tilimycin exposure to eukaryotic cells, providing the first structural characterization of a PBD-DNA adduct formed in cells. Finally, we report the rational design of small-molecule inhibitors that block tilimycin biosynthesis in whole cell K. oxytoca (IC50 = 29 ± 4 μM) through the inhibition of NpsA (KD = 29 ± 4 nM).

Association of Gut Microbiota-Dependent Metabolite Trimethylamine N-Oxide with First Ischemic Stroke

AIM

We aimed to investigate the relationship of trimethylamine N-oxide (TMAO) concentrations with ischemic stroke in a large-scale case-control study conducted among the hospital-based general population.

METHODS

We recruited 953 case-control sex- and age-matched pairs, and cases were confined to first acute ischemic stroke in this study. Fasting plasma TMAO was measured using high-performance liquid chromatography-tandem mass spectroscopy. Conditional logistic regression analysis was conducted to calculate odds ratios (OR) for the association of plasma TMAO with ischemic stroke.

RESULTS

We found that plasma TMAO concentrations in patients with ischemic stroke were significantly higher than that in the control group (median: 2.85 µmol/L vs. 2.33 µmol/L, P＜0.001). In multivariable conditional logistic regression models, higher plasma TMAO concentrations were associated with increased odds of ischemic stroke [fully adjusted OR for highest vs. lowest TMAO quartile: 1.81; 95% confidence interval (CI): 1.27, 2.59; P for trend ＜0.001]. The multivariable-adjusted OR for ischemic stroke per 1 µmol/L increment of plasma TMAO was 1.05 (95% CI: 1.02, 1.08). Additionally, the positive association also persisted in subgroups stratified by age, sex, body mass index, smoking status, alcohol habits, history of diabetes, and history of hypertension.

CONCLUSIONS

This study suggested a positive association between plasma TMAO and ischemic stroke. Further studies are required to explore the role of plasma TMAO concentrations in predicting stroke risk.

Plasma Trimethylamine N-Oxide and Risk of Cardiovascular Events in Patients With Type 2 Diabetes

OBJECTIVE

Even though trimethylamine N-oxide (TMAO) has been demonstrated to interfere with atherosclerosis and diabetes pathophysiology, the association between TMAO and major adverse cardiovascular events (MACE) has not been specifically established in type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

We examined the association of plasma TMAO concentrations with MACE and all-cause mortality in a single-center prospective cohort of consecutively recruited patients with T2D.

RESULTS

The study population consisted in 1463 SURDIENE participants (58% men), aged 65 ± 10 years. TMAO concentrations were significantly associated with diabetes duration, renal function, high-density lipoprotein cholesterol, soluble tumor necrosis factor receptor 1 (sTNFR1) concentrations (R2 = 0.27) and were significantly higher in patients on metformin, even after adjustment for estimated glomerular filtration rate (eGFR): 6.7 (8.5) vs 8.5 (13.6) µmol/L, respectively (PeGFR-adjusted = 0.0207). During follow-up (median duration [interquartile range], 85 [75] months), 403 MACE and 538 deaths were registered. MACE-free survival and all-cause mortality were significantly associated with the quartile distribution of TMAO concentrations, patients with the highest TMAO levels displaying the greatest risk of outcomes (P < 0.0001). In multivariate Cox models, compared with patients from the first 3 quartiles, those from the fourth quartile of TMAO concentration had an independently increased risk for MACE: adjusted hazard ratio (adjHR) 1.32 (1.02-1.70); P = 0.0325. Similarly, TMAO was significantly associated with mortality in multivariate analysis: adjHR 1.75 (1.17-2.09); P = 0.0124, but not when sTNFR1 and angiopoietin like 2 were considered: adjHR 1.16 (0.95-1.42); P = 0.1514.

CONCLUSIONS

We revealed an association between higher TMAO concentrations and increased risk of MACE and all-cause mortality, thereby opening some avenues on the role of dysbiosis in cardiovascular risk, in T2D patients.

Microbiota in cerebrovascular disease: A key player and future therapeutic target

Stroke is the second leading cause of death and a significant cause of disability worldwide. Recent advances in DNA sequencing, proteomics, metabolomics, and computational tools are dramatically increasing access to the identification of host-microbiota interactions in systemic diseases. In this review, we describe the accumulating evidence showing how human microbiota plays an essential role in cerebrovascular diseases. We introduce the symbiotic relationships between microbiota and the mucosal immune system, focusing on differences by anatomical sites. Microbiota directly or indirectly contributes to the pathogenesis of traditional vascular risk factors including age, obesity, diabetes mellitus, dyslipidemia, and hypertension. Moreover, recent studies proposed independent effects of the microbiome on the progression of various subtypes of stroke through direct microbial invasion, exotoxins, functional amyloids, inflammation, and microbe-derived metabolites. We propose the critical concept of gene-microbial interaction to elucidate the heterogeneity of stroke and provide possible therapeutic avenues. We suggest ways to resolve the vast inter-individual diversity of cerebrovascular disease and mechanisms for personalized prevention and treatment.

[Gut-heart axis : How gut bacteria influence cardiovascular diseases]

The view of humans as holobionts consisting of eukaryotic host cells and associated prokaryotic organisms, has opened up a new perspective on cardiovascular pathophysiology. In particular, intestinal bacteria influence the cell and organ functions of the host. Intestinal bacteria represent a metabolically active community whose composition and function can influence cardiovascular health and disease. The interaction between the intestinal microbiota and the heart occurs via metabolites of bacterial origin, which are resorbed in the intestine and distributed via the circulation. Bacterial metabolites are produced from food components, which in turn emphasizes the importance of nutrition. Some of these metabolites, such as trimethylamine N‑oxide (TMAO), can exacerbate cardiovascular pathologies. Short-chain fatty acids (SCFA) in turn are considered to be protective metabolites. The host's immune system is an important target for these metabolites and explains much of their effects. In the future, the targeted manipulation of intestinal bacteria could help to prevent the development and progression of cardiovascular diseases.

The microbiome in pediatric oncology

The human microbiome comprises a diverse set of microorganisms, which play a mostly cooperative role in processes such as metabolism and host defense. Next-generation genomic sequencing of bacterial nucleic acids now can contribute a much broader understanding of the diverse organisms composing the microbiome. Emerging evidence has suggested several roles of the microbiome in pediatric hematology/oncology, including susceptibility to infectious diseases, immune response to neoplasia, and contributions to the tumor microenvironment as well as changes to the microbiome from chemotherapy and antibiotics with unclear consequences. In this review, the authors have examined the evidence of the role of the microbiome in pediatric hematology/oncology, discussed how the microbiome may be modulated, and suggested key questions in need of further exploration.

Nonlethal Inhibition of Gut Microbial Trimethylamine N-oxide Production Improves Cardiac Function and Remodeling in a Murine Model of Heart Failure

Background

Patients at increased risk for coronary artery disease and adverse prognosis during heart failure exhibit increased levels of circulating trimethylamine N‐oxide (TMAO), a metabolite formed in the metabolism of dietary phosphatidylcholine. We investigated the efficacy of dietary withdrawal of TMAO as well as use of a gut microbe‐targeted inhibitor of TMAO production, on cardiac function and structure during heart failure.

Methods and Results

Male C57BLK/6J mice were fed either control diet, a diet containing TMAO (0.12% wt/wt), a diet containing choline (1% wt/wt), or a diet containing choline (1% wt/wt) plus a microbial choline trimethylamine lyase inhibitor, iodomethylcholine (0.06% wt/wt), starting 3 weeks before transverse aortic constriction. At 6 weeks after transverse aortic constriction, a subset of animals in the TMAO group were switched to a control diet for the remainder of the study. Left ventricular structure and function were monitored at 3‐week intervals. Withdrawal of TMAO from the diet attenuated adverse ventricular remodeling and improved cardiac function compared with the TMAO group. Similarly, inhibiting gut microbial conversion of choline to TMAO with a choline trimethylamine lyase inhibitor, iodomethylcholine, improved remodeling and cardiac function compared with the choline‐fed group.

Conclusions

These experimental findings are clinically relevant, and they demonstrate that TMAO levels are modifiable following long‐term exposure periods with either dietary withdrawal of TMAO or gut microbial blockade of TMAO generation. Furthermore, these therapeutic strategies to reduce circulating TMAO levels mitigate the negative effects of dietary choline and TMAO in heart failure.

Targeted Inhibition of Gut Microbial Trimethylamine N-Oxide Production Reduces Renal Tubulointerstitial Fibrosis and Functional Impairment in a Murine Model of Chronic Kidney Disease

OBJECTIVE

Gut microbial metabolism of dietary choline, a nutrient abundant in a Western diet, produces trimethylamine (TMA) and the atherothrombosis- and fibrosis-promoting metabolite TMA-N-oxide (TMAO). Recent clinical and animal studies reveal that elevated TMAO levels are associated with heightened risks for both cardiovascular disease and incident chronic kidney disease development. Despite this, studies focusing on therapeutically targeting gut microbiota-dependent TMAO production and its impact on preserving renal function are limited. Approach and Results: Herein we examined the impact of pharmacological inhibition of choline diet-induced gut microbiota-dependent production of TMA, and consequently TMAO, on renal tubulointerstitial fibrosis and functional impairment in a model of chronic kidney disease. Initial studies with a gut microbial choline TMA-lyase mechanism-based inhibitor, iodomethylcholine, confirmed both marked suppression of TMA generation, and consequently TMAO levels, and selective targeting of the gut microbial compartment (ie, both accumulation of the drug in intestinal microbes and limited systemic exposure in the host). Dietary supplementation of either choline or TMAO significantly augmented multiple indices of renal functional impairment and fibrosis associated with chronic subcutaneous infusion of isoproterenol. However, the presence of the gut microbiota-targeting inhibitor iodomethylcholine blocked choline diet-induced elevation in TMAO, and both significantly improved decline in renal function, and significantly attenuated multiple indices of tubulointerstitial fibrosis. Iodomethylcholine treatment also reversed many choline diet-induced changes in cecal microbial community composition associated with TMAO and renal functional impairment.

CONCLUSIONS

Selective targeting of gut microbiota-dependent TMAO generation may prevent adverse renal structural and functional alterations in subjects at risk for chronic kidney disease.

Microbiota Metabolites in Health and Disease

Metabolism is one of the strongest drivers of interkingdom interactions-including those between microorganisms and their multicellular hosts. Traditionally thought to fuel energy requirements and provide building blocks for biosynthetic pathways, metabolism is now appreciated for its role in providing metabolites, small-molecule intermediates generated from metabolic processes, to perform various regulatory functions to mediate symbiotic relationships between microbes and their hosts. Here, we review recent advances in our mechanistic understanding of how microbiota-derived metabolites orchestrate and support physiological responses in the host, including immunity, inflammation, defense against infections, and metabolism. Understanding how microbes metabolically communicate with their hosts will provide us an opportunity to better describe how a host interacts with all microbes-beneficial, pathogenic, and commensal-and an opportunity to discover new ways to treat microbial-driven diseases.

Role of gut microbiota in cardiovascular diseases

The human gut is colonized by a community of microbiota, primarily bacteria, that exist in a symbiotic relationship with the host. Intestinal microbiota-host interactions play a critical role in the regulation of human physiology. Deleterious changes to the composition of gut microbiota, referred to as gut dysbiosis, has been linked to the development and progression of numerous diseases, including cardiovascular disease (CVD). Imbalances in host-microbial interaction impair homeostatic mechanisms that regulate health and can activate multiple pathways leading to CVD risk factor progression. Most CVD risk factors, including aging, obesity, dietary patterns, and a sedentary lifestyle, have been shown to induce gut dysbiosis. Dysbiosis is associated with intestinal inflammation and reduced integrity of the gut barrier, which in turn increases circulating levels of bacterial structural components and microbial metabolites, including trimethylamine-N-oxide and short-chain fatty acids, that may facilitate the development of CVD. This article reviews the normal function and composition of the gut microbiome, mechanisms leading to the leaky gut syndrome, its mechanistic link to CVD and potential novel therapeutic approaches aimed towards restoring gut microbiome and CVD prevention. As CVD is the leading cause of deaths globally, investigating the gut microbiota as a locus of intervention presents a novel and clinically relevant avenue for future research.

Small molecule inhibition of gut microbial choline trimethylamine lyase activity alters host cholesterol and bile acid metabolism

The gut microbe-derived metabolite trimethylamine-N-oxide (TMAO) has recently been linked to cardiovascular disease (CVD) pathogenesis, prompting the development of therapeutic strategies to reduce TMAO. Previous work has shown that experimental alteration of circulating TMAO levels via dietary alterations or inhibition of the host TMAO producing enzyme flavin containing monooxygenase 3 (FMO3) is associated with reorganization of host cholesterol and bile acid metabolism in mice. In this work, we set out to understand whether recently developed nonlethal gut microbe-targeting small molecule choline trimethylamine (TMA) lyase inhibitors also alter host cholesterol and bile acid metabolism. Treatment of mice with the mechanism-based choline TMA lyase inhibitor, iodomethylcholine (IMC), increased fecal neutral sterol loss in the form of coprostanol, a bacteria metabolite of cholesterol. In parallel, IMC treatment resulted in marked reductions in the intestinal sterol transporter Niemann-pick C1-like 1 (NPC1L1) and reorganization of the gut microbial community, primarily reversing choline supplemented diet-induced changes. IMC also prevented diet-driven hepatic cholesterol accumulation, causing both upregulation of the host hepatic bile acid synthetic enzyme CYP7A1 and altering the expression of hepatic genes critical for bile acid feedback regulation. These studies suggest that the gut microbiota-driven TMAO pathway is closely linked to both microbe and host sterol and bile acid metabolism. Collectively, as gut microbe-targeting choline TMA lyase inhibitors move through the drug discovery pipeline from preclinical models to human studies, it will be important to understand how these drugs impact both microbe and host cholesterol and bile acid metabolism.NEW & NOTEWORTHY The gut microbe-dependent metabolite trimethylamine-N-oxide (TMAO) has been strongly associated with cardiovascular mortality, prompting drug discovery efforts to identify points of therapeutic intervention within the microbe host TMAO pathway. Recently, mechanism-based small molecule inhibitors of the major bacterial trimethylamine (TMA) lyase enzymes have been developed, and these drugs show efficacy as anti-atherothrombotic agents. The novel findings of this study are that small molecule TMA lyase inhibition results in beneficial reorganization of host cholesterol and bile acid metabolism. This study confirms previous observations that the gut microbial TMAO pathway is intimately linked to host cholesterol and bile acid metabolism and provides further rationale for the development of small molecule choline TMA lyase inhibitors for the treatment of cardiometabolic disorders.

Impact of trimethylamine N-oxide (TMAO) metaorganismal pathway on cardiovascular disease

Host-microbes interaction plays a crucial role in cardiovascular disease (CVD) pathogenesis, mechanistically via metaorganismal pathways. The trimethylamine N-oxide (TMAO) metaorganismal pathway is the most deeply investigated one, which comprises trimethylamine precursors, such as choline, trimethylamine lyase, trimethylamine, host liver FMO3, TMAO, and downstream effectors involving unfolded protein response (UPR), NF-κB and NLRP3 inflammasome. Accumulating data from clinical investigations of CVD patient cohorts and rodent models have supported the critical role of this metaorganismal pathway in the pathogenesis of CVD. We summarize an array of significant animal studies especially for arthrosclerosis with an emphasis on downstream molecular effectors of this metaorganismal pathway. We highlight clinical investigations of the prognostic value of plasma TMAO levels in predicting prospective risk for future major adverse cardiac events (MACE) indicated by composite end points of myocardial infarction (MI), stroke, heart failure (HF), other ischemic cardiovascular events, or death. Further, we discuss the latest advances of preclinical models targeting the gut microbiota trimethylamine lyase of the TMAO metaorganismal pathway for CVD intervention, as well as the catalog of gut microbiota TMA lyase genes and microbes in the human gut as the prerequisite for potential clinical intervention. In-depth characterization of TMAO metaorganismal pathway holds great promise for CVD clinical metagenomics, diagnostics and therapeutics.

Simultaneous Measurement of Urinary Trimethylamine (TMA) and Trimethylamine N-Oxide (TMAO) by Liquid Chromatography-Mass Spectrometry

Trimethylamine (TMA) is a gut microbial metabolite—rendered by the enzymatic cleavage of nutrients containing a TMA moiety in their chemical structure. TMA can be oxidized as trimethylamine N-oxide (TMAO) catalyzed by hepatic flavin monooxygenases. Circulating TMAO has been demonstrated to portend a pro-inflammatory state, contributing to chronic diseases such as cardiovascular disease and chronic kidney disease. Consequently, TMAO serves as an excellent candidate biomarker for a variety of chronic inflammatory disorders. The highly positive correlation between plasma TMAO and urine TMAO suggests that urine TMAO has the potential to serve as a less invasive biomarker for chronic disease compared to plasma TMAO. In this study, we validated a method to simultaneously measure urine TMA and TMAO concentrations by liquid chromatography–mass spectrometry (LC/MS). Urine TMA and TMAO can be extracted by hexane/butanol under alkaline pH and transferred to the aqueous phase following acidification for LC/MS quantitation. Importantly, during sample processing, none of the nutrients with a chemical structure containing a TMA moiety were spontaneously cleaved to yield TMA. Moreover, we demonstrated that the acidification of urine prevents an increase of TMA after prolonged storage as was observed in non-acidified urine. Finally, here we demonstrated that TMAO can spontaneously degrade to TMA at a very slow rate.

Archaea, specific genetic traits, and development of improved bacterial live biotherapeutic products: another face of next-generation probiotics

Trimethylamine (TMA) and its oxide TMAO are important biomolecules involved in disease-associated processes in humans (e.g., trimethylaminuria and cardiovascular diseases). TMAO in plasma (pTMAO) stems from intestinal TMA, which is formed from various components of the diet in a complex interplay between diet, gut microbiota, and the human host. Most approaches to prevent the occurrence of such deleterious molecules focus on actions to interfere with gut microbiota metabolism to limit the synthesis of TMA. Some human gut archaea however use TMA as terminal electron acceptor for producing methane, thus indicating that intestinal TMA does not accumulate in some human subjects. Therefore, a rational alternative approach is to eliminate neo-synthesized intestinal TMA. This can be achieved through bioremediation of TMA by these peculiar methanogenic archaea, either by stimulating or providing them, leading to a novel kind of next-generation probiotics referred to as archaebiotics. Finally, specific components which are involved in this archaeal metabolism could also be used as intestinal TMA sequesters, facilitating TMA excretion along with stool. Referring to a standard pharmacological approach, these TMA traps could be synthesized ex vivo and then delivered into the human gut. Another approach is the engineering of known probiotic strain in order to metabolize TMA, i.e., live engineered biotherapeutic products. These alternatives would require, however, to take into account the necessity of synthesizing the 22nd amino acid pyrrolysine, i.e., some specificities of the genetics of TMA-consuming archaea. Here, we present an overview of these different strategies and recent advances in the field that will sustain such biotechnological developments. KEY POINTS: • Some autochthonous human archaea can use TMA for their essential metabolism, a methyl-dependent hydrogenotrophic methanogenesis. • They could therefore be used as next-generation probiotics for preventing some human diseases, especially cardiovascular diseases and trimethylaminuria. • Their genetic capacities can also be used to design live recombinant biotherapeutic products. • Encoding of the 22nd amino acid pyrrolysine is necessary for such alternative developments.

Measurement of gut microbial metabolites in cardiometabolic health and translational research

The human gut microbiota is a functioning endocrine organ and stands at the intersection between dietary components and health or disease. There are very many microbial metabolites with numerous structures and functions arising from the gut microbial fermentation of foods and become signals for biological communication in the human body. These small molecules can be absorbed and delivered to distant organs through the circulatory system to build the gut-systemic axis. The gut microbial metabolomes are thus believed to play important roles in regulating cardiometabolic health and provide opportunities in mechanistic research and new drug discovery. Measurement of these novel microbial metabolites in clinical samples may serve as a tool for investigating disease biomarkers. In the past decade, the development of untargeted and targeted metabolomics approaches using NMR, LC/MS, and GC/MS has contributed to the exploration of gut microbial metabolomes in cardiometabolic health and disease. Some important targets are currently being translated into clinical applications. In this review article, we introduce an oral carnitine challenge test developed as an example to demonstrate the potential applications in personalized nutrition based on the function of gut microbiota. It is a method taking the gut microbiota as a bioreactor and provides fermentable materials as inputs and measures the outputs of targeted microbial byproducts in the blood or urine. This challenge test may be extended to measure metabolites from microbial fermentation related to other endocrinological or inflammatory diseases. We review current gut metabolome research approaches and propose a gut microbial functional measurement using a challenge test. We suggest that the maturation in measuring gut microbial metabolites may provide an important piece to complete the puzzle of precision medicine.

Gut microbiota in atherosclerosis: focus on trimethylamine N-oxide

The increasing prevalence of cardiovascular diseases cannot adequately be explained by traditional risk factors. Recently, accumulating evidence has suggested that gut microbiota‐derived numerous metabolites are contributors to atherosclerotic events. Among them, the role of trimethylamine N‐oxide (TMAO) in promoting atherosclerosis has gained attention. TMAO is reported to exert the proatherogenic effects by impacting on the traditional risk factors of atherosclerosis and is associated with high risk of cardiovascular events. Besides that, TMAO is involved in the complex pathological processes of atherosclerotic lesion formation, such as endothelial dysfunction, platelet activation and thrombus generation. In light of these promising findings, TMAO may serve as a potential target for atherosclerosis prevention and treatment, which is conceptually novel, when compared with existing traditional treatments. It is likely that regulating TMAO production and associated gut microbiota may become a promising strategy for the anti‐atherosclerosis therapy.

The gut microbiome and thromboembolism

The gut microbiome plays a critical role in various inflammatory conditions, and its modulation is a potential treatment option for these conditions. The role of the gut microbiome in the pathogenesis of thromboembolism has not been fully elucidated. In this review, we summarize the evidence linking the gut microbiome to the pathogenesis of arterial and venous thrombosis. In a human host, potentially pathogenic bacteria are normal residents of the human gut microbiome, but significantly outnumbered by commensal anaerobic bacteria. Several disease states with an increased risk of venous thromboembolism (VTE) are associated with an imbalance in the gut microbiome characterized by a decrease in commensal anaerobic bacteria and an increase in the abundance of pathogenic bacteria of which the most common is the gram-negative Enterobacteriaceae (ENTERO) family. Bacterial lipopolysaccharides (LPS), the glycolipids found on the outer membrane of gram-negative bacteria, is one of the links between the microbiome and hypercoagulability. LPS binds to toll-like receptors to activate endothelial cells and platelets, leading to activation of the coagulation cascade. Bacteria in the microbiome can also metabolite compounds in the diet to produce important metabolites like trimethylamine-N-oxide (TMAO). TMAO causes platelet hyperreactivity, promotes thrombus formation and is associated with cardiovascular disease. Modulating the gut microbiome to target LPS and TMAO levels may be an innovative approach for decreasing the risk of thrombosis.

Gut microbiota in surgical and critically ill patients

Microbiota-defined as a collection of microbial organisms colonising different parts of the human body-is now recognised as a pivotal element of human health, and explains a large part of the variance in the phenotypic expression of many diseases. A reduction in microbiota diversity, and replacement of normal microbes with non-commensal, pathogenic or more virulent microbes in the gastrointestinal tract-also known as gut dysbiosis-is now considered to play a causal role in the pathogenesis of many acute and chronic diseases. Results from animal and human studies suggest that dysbiosis is linked to cardiovascular and metabolic disease through changes to microbiota-derived metabolites, including trimethylamine-N-oxide and short-chain fatty acids. Dysbiosis can occur within hours of surgery or the onset of critical illness, even without the administration of antibiotics. These pathological changes in microbiota may contribute to important clinical outcomes, including surgical infection, bowel anastomotic leaks, acute kidney injury, respiratory failure and brain injury. As a strategy to reduce dysbiosis, the use of probiotics (live bacterial cultures that confer health benefits) or synbiotics (probiotic in combination with food that encourages the growth of gut commensal bacteria) in surgical and critically ill patients has been increasingly reported to confer important clinical benefits, including a reduction in ventilator-associated pneumonia, bacteraemia and length of hospital stay, in small randomised controlled trials. However, the best strategy to modulate dysbiosis or counteract its potential harms remains uncertain and requires investigation by a well-designed, adequately powered, randomised controlled trial.

The intestinal microbiome potentially affects thrombin generation in human subjects

BACKGROUND

The intestinal microbiome plays a versatile role in the etiology of arterial thrombosis. In venous thrombosis, driven chiefly by plasma coagulation, no such role has yet been established. We hypothesized that the intestinal microbiome composition affects coagulation in humans.

METHODS

We used healthy donor fecal microbiota transplant (FMT) to experimentally change the microbiome composition in metabolic syndrome patients. Thirty-five subjects were randomized in a blinded fashion to healthy donor FMT or autologous FMT as a control in a 2:1 ratio. We measured thrombin generation at baseline and after 6 weeks using automated calibrated thrombinography, and we determined plasma abundance of 32 coagulation related proteins using a targeted mass spectrometry-based quantitative proteomics assay with heavy labeled internal standards.

RESULTS

Healthy donor FMT prolonged the thrombinography lag time (median delta 0.0 versus 0.25 minutes, P = .039). The other thrombinography parameters showed no significant difference. Unsupervised cluster analysis suggested overall downregulation of coagulation related plasma proteins in subject clusters containing predominantly subjects that had a metabolic response to healthy donor FMT. FMT treatment status itself showed no clear clustering pattern with up- or downregulation, however, and proteins did not cluster according to an apparent biological grouping.

DISCUSSION

A single healthy donor FMT tends to modestly suppress the onset thrombin generation in metabolic syndrome patients, representing initial proof-of-principle that the intestinal microbiota composition might affect the coagulation system in humans. The findings merit external validation as a role for intestinal microbiota in coagulation can have clinically important implications.

Relationship Between the Gut Microbiome and Systemic Chemotherapy

The intestinal microbiome encodes vast metabolic potential, and multidisciplinary approaches are enabling a mechanistic understanding of how bacterial enzymes impact the metabolism of diverse pharmaceutical compounds, including chemotherapeutics. Microbiota alter the activity of many drugs and chemotherapeutics via direct and indirect mechanisms; some of these alterations result in changes to the drug's bioactivity and bioavailability, causing toxic gastrointestinal side effects. Gastrointestinal toxicity is one of the leading complications of systemic chemotherapy, with symptoms including nausea, vomiting, diarrhea, and constipation. Patients undergo dose reductions or drug holidays to manage these adverse events, which can significantly harm prognosis, and can result in mortality. Selective and precise targeting of the gut microbiota may alleviate these toxicities. Understanding the composition and function of the microbiota may serve as a biomarker for prognosis, and predict treatment efficacy and potential adverse effects, thereby facilitating personalized medicine strategies for cancer patients.

Gut Microbiota and Stroke

Ischemic stroke remains a significant health problem, which is expected to increase owing to an aging population. A considerable proportion of stroke patients suffer from gastrointestinal complications, including dysphagia, gastrointestinal hemorrhage, and constipation. Often, these complications adversely affect stroke outcomes. Recent research postulates the role of “brain-gut axis” in causing gut microbiota dysbiosis and various complications and outcomes. In this review, we present our current understanding about the interaction between commensal gut microbiome and brain in determining the course of stroke.

Development of a covalent inhibitor of gut bacterial bile salt hydrolases

Bile salt hydrolase (BSH) enzymes are widely expressed by human gut bacteria and catalyze the gateway reaction leading to secondary bile acid formation. Bile acids regulate key metabolic and immune processes by binding to host receptors. There is an unmet need for a potent tool to inhibit BSHs across all gut bacteria in order to study the effects of bile acids on host physiology. Here, we report the development of a covalent pan-inhibitor of gut bacterial BSH. From a rationally designed candidate library, we identified a lead compound bearing an alpha-fluoromethyl ketone warhead that modifies BSH at the catalytic cysteine residue. Strikingly, this inhibitor abolished BSH activity in conventional mouse feces. Mice gavaged with a single dose of this compound displayed decreased BSH activity and decreased deconjugated bile acid levels in feces. Our studies demonstrate the potential of a covalent BSH inhibitor to modulate bile acid composition in vivo.

Dynamic Changes and Prognostic Value of Gut Microbiota-Dependent Trimethylamine-N-Oxide in Acute Ischemic Stroke

Background: Acute ischemic stroke (AIS) is an atherothrombotic disease. Trimethylamine-N-oxide (TMAO), a gut microbiota-dependent metabolite, has been shown to be proatherogenic and prothrombotic. However, the involvement of TMAO in AIS remains unclear. This study aimed to observe the dynamic changes of TMAO in AIS patients and identify the prognostic value of TMAO for major ischemic events and unfavorable functional outcomes. Methods: This study included 204 AIS patients and 108 healthy controls. Blood samples for TMAO analyses were drawn at admission, 2 and 7 days of admission. Logistic regression models and receiver operating characteristic curves were established to identify associations between TMAO levels and major ischemic events (ischemic stroke, myocardial infarction, or death from an ischemic vascular event), as well as unfavorable functional outcomes (modified Rankin Scale score ≥3), at 90 days and 12 months. Results: TMAO levels showed no significant changes before and within 24 h of AIS treatment (at admission) but decreased significantly thereafter. Elevated log₂-transformed baseline TMAO levels were associated with increased risks of 90-day [odds ratio (OR), 2.62; 95% confidence interval (CI), 1.55-4.45; p < 0.001] and 12-month (OR, 3.59; 95% CI, 2.12-6.09; p < 0.001) major ischemic events, as well as 90-day (OR, 2.89; 95% CI, 1.46-5.71; p = 0.002) and 12-month (OR, 2.58; 95% CI, 1.50-4.46; p = 0.001) unfavorable functional outcomes, after adjustments for confounding factors. The areas under curve of baseline TMAO levels for predicting 90-day and 12-month major ischemic events were 0.72 (95% CI, 0.61-0.83; p < 0.001) and 0.76 (95% CI, 0.66-0.85; p < 0.001). Baseline TMAO levels improved the prognostic accuracy of conventional risk factors, National Institutes of Health Stroke Scale (NIHSS) score and N-terminal B-type natriuretic peptide (NT-proBNP) level. Conclusions: TMAO levels decreased with time since stroke onset. Elevated TMAO levels at an earlier period portended poor stroke outcomes, broadening the potential clinical utility of TMAO as an independent prognostic marker and therapeutic target.

Genetic Deficiency of Flavin-Containing Monooxygenase 3 ( Fmo3) Protects Against Thrombosis but Has Only a Minor Effect on Plasma Lipid Levels-Brief Report

Objective- FMO (flavin-containing monooxygenase) 3 converts bacterial-derived trimethylamine to trimethylamine N-oxide (TMAO), an independent risk factor for cardiovascular disease. We generated FMO3 knockout (FMO3KO) mouse to study its effects on plasma TMAO, lipids, glucose/insulin metabolism, thrombosis, and atherosclerosis. Approach and Results- Previous studies with an antisense oligonucleotide (ASO) knockdown strategy targeting FMO3 in LDLRKO (low-density lipoprotein receptor knockout) mice resulted in major reductions in TMAO levels and atherosclerosis, but also showed effects on plasma lipids, insulin, and glucose. Although FMO3KO mice generated via CRISPR/Cas9 technology bred onto the LDLRKO background did exhibit similar effects on TMAO levels, the effects on lipid metabolism were not as pronounced as with the ASO knockdown model. These differences could result from either off-target effects of the ASO or from a developmental adaptation to the FMO3 deficiency. To distinguish these possibilities, we treated wild-type and FMO3KO mice with control or FMO3 ASOs. FMO3-ASO treatment led to the same extent of lipid-lowering effects in the FMO3KO mice as the wild-type mice, indicating off-target effects. The levels of TMAO in LDLRKO mice fed an atherogenic diet are very low in both wild-type and FMO3KO mice, and no significant effect was observed on atherosclerosis. When FMO3KO and wild-type mice were maintained on a 0.5% choline diet, FMO3KO showed a marked reduction in both TMAO and in vivo thrombosis potential. Conclusions- FMO3KO markedly reduces systemic TMAO levels and thrombosis potential. However, the previously observed large effects of an FMO3 ASO on plasma lipid levels appear to be due partly to off-target effects.

Plasma Trimethylamine N-Oxide as a Novel Biomarker for Plaque Rupture in Patients With ST-Segment-Elevation Myocardial Infarction

BACKGROUND

Trimethylamine N-oxide (TMAO) is reported to promote the pathogenesis of atherosclerosis and be associated with cardiovascular events risk. It is unknown whether plasma TMAO is associated with plaque morphology in patients with acute myocardial infarction. We investigated the relationship between the culprit plaque morphology and plasma TMAO concentration in patients with ST-segment-elevation myocardial infarction.

METHODS AND RESULTS

A prospective series of 211 patients with ST-segment-elevation myocardial infarction who underwent preintervention optical coherence tomography examination for the culprit lesion were enrolled; 77 and 69 patients were categorized as plaque rupture and plaque erosion, respectively. Plasma TMAO levels, detected using stable isotope dilution liquid chromatography tandem mass spectrometry, were significantly higher in patients with plaque rupture than in those with plaque erosion (3.33 μM; interquartile range: 2.48-4.57 versus 1.21 μM; interquartile range: 0.86-1.91; P<0.001). After adjustments for traditional risk factors, elevated TMAO levels remained independently correlated with plaque rupture (adjusted odds ratio: 4.06, 95% CI, 2.38-6.91; P<0.001). The area under the receiver operating characteristic curve for plaque rupture versus plaque erosion was 0.89. At a cutoff level of 1.95 μM, TMAO had a sensitivity of 88.3% and specificity of 76.8% in discriminating plaque rupture from plaque erosion.

CONCLUSIONS

High levels of plasma TMAO independently correlated with plaque rupture in patients with ST-segment-elevation myocardial infarction. Moreover, TMAO might be a useful biomarker for plaque rupture to improve risk stratification and management in patients with ST-segment-elevation myocardial infarction.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifiers: NCT03593928.

Relationship between elevated plasma trimethylamine N-oxide levels and increased stroke injury

Objective

To investigate whether elevated plasma trimethylamine N-oxide (TMAO) levels are associated with initial stroke severity and infarct volume.

Methods

This cross-sectional study included 377 patients with acute ischemic stroke and 50 healthy controls. Plasma TMAO levels were assessed at admission. Stroke infarct size and clinical stroke severity were measured with diffusion-weighted imaging and the NIH Stroke Scale (NIHSS). Mild stroke was defined as an NIHSS score <6.

Results

Plasma TMAO levels were higher in patients with ischemic stroke than in healthy controls (median 5.1 vs 3.0 μmol/L; p < 0.001). Every 1–µmol/L increase in TMAO was associated with a 1.13-point increase in NIHSS score (95% confidence interval [CI] 1.04–1.29; p < 0.001) and 1.69-mL increase in infarct volume (95% CI 1.41–2.03; p < 0.001) after adjustment for vascular risk factors. At admission, 159 patients (42.2%) had experienced a mild stroke, and their plasma TMAO levels were lower compared to those with moderate to severe stroke (median 3.6 vs 6.5 µmol/L; p < 0.001). The area under the receiver operating characteristics curve of plasma TMAO level in predicting moderate to severe stroke was 0.794 (95% CI 0.748–0.839; p < 0.001), and the optimal cutoff value was 4.95 μmol/L. The sensitivity and specificity of TMAO levels ≥4.95 μmol/L for moderate to severe stroke were 70.2% and 79.9%, respectively.

Conclusions

Patients with ischemic stroke had higher plasma TMAO levels compared to healthy controls. Higher plasma TMAO level at admission is an independent predictor of stroke severity and infarct volume in patients with acute ischemia.

Our Microbiome: On the Challenges, Promises, and Hype

The microbiome field is increasingly raising interest among scientists, clinicians, biopharmaceutical entities, and the general public. Technological advances from the past two decades have enabled the rapid expansion of our ability to characterize the human microbiome in depth, highlighting its previously underappreciated role in contributing to multifactorial diseases including those with unknown etiology. Consequently, there is growing evidence that the microbiome could be utilized in medical diagnosis and patient stratification. Moreover, multiple gut microbes and their metabolic products may be bioactive, thereby serving as future potential microbiome-targeting or -associated therapeutics. Such therapies could include new generation probiotics, prebiotics, fecal microbiota transplantations, postbiotics, and dietary modulators. However, microbiome research has also been associated with significant limitations, technical and conceptual challenges, and, at times, "over-hyped" expectations that microbiome research will produce quick solutions to chronic and mechanistically complex human disorders. Herein, we summarize these challenges and also discuss some of the realistic promises associated with microbiome research and its applicability into clinical application.

The Gut Microbiota Affects Host Pathophysiology as an Endocrine Organ: A Focus on Cardiovascular Disease

It is widely recognized that the microorganisms inhabiting our gastrointestinal tract-the gut microbiota-deeply affect the pathophysiology of the host. Gut microbiota composition is mostly modulated by diet, and gut microorganisms communicate with the different organs and tissues of the human host by synthesizing hormones and regulating their release. Herein, we will provide an updated review on the most important classes of gut microbiota-derived hormones and their sensing by host receptors, critically discussing their impact on host physiology. Additionally, the debated interplay between microbial hormones and the development of cardiovascular disease will be thoroughly analysed and discussed.

Urinary TMAO Levels Are Associated with the Taxonomic Composition of the Gut Microbiota and with the Choline TMA-Lyase Gene (cutC) Harbored by Enterobacteriaceae

Gut microbiota metabolization of dietary choline may promote atherosclerosis through trimethylamine (TMA), which is rapidly absorbed and converted in the liver to proatherogenic trimethylamine-N-oxide (TMAO). The aim of this study was to verify whether TMAO urinary levels may be associated with the fecal relative abundance of specific bacterial taxa and the bacterial choline TMA-lyase gene cutC. The analysis of sequences available in GenBank grouped the cutC gene into two main clusters, cut-Dd and cut-Kp. A quantitative real-time polymerase chain reaction (qPCR) protocol was developed to quantify cutC and was used with DNA isolated from three fecal samples collected weekly over the course of three consecutive weeks from 16 healthy adults. The same DNA was used for 16S rRNA gene profiling. Concomitantly, urine was used to quantify TMAO by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). All samples were positive for cutC and TMAO. Correlation analysis showed that the cut-Kp gene cluster was significantly associated with Enterobacteriaceae. Linear mixed models revealed that urinary TMAO levels may be predicted by fecal cut-Kp and by 23 operational taxonomic units (OTUs). Most of the OTUs significantly associated with TMAO were also significantly associated with cut-Kp, confirming the possible relationship between these two factors. In conclusion, this preliminary method-development study suggests the existence of a relationship between TMAO excreted in urine, specific fecal bacterial OTUs, and a cutC subgroup ascribable to the choline-TMA conversion enzymes of Enterobacteriaceae.

Potential Correlation between Dietary Fiber-Suppressed Microbial Conversion of Choline to Trimethylamine and Formation of Methylglyoxal

Dietary interventions alter the formation of the disease-associated metabolite, trimethylamine (TMA), via intestinal microbial TMA lyase activity. Nevertheless, the mechanisms regulating microbial enzyme production are still unclear. Sequencing of the gut bacteria 16S rDNA demonstrated that dietary intervention changed the composition of the gut microbiota and the functional metagenome involved in the choline utilization pathway. Characterization of the functional profile of the metagenomes and metabonomics analysis revealed that a series of Kyoto Encyclopedia of Genes and Genomes orthologous groups and enzyme groups related to accumulation of methylglyoxal (MG) and glycine were enriched in red meat diet-fed animals, whereas fiber-rich diet suppressed glycine formation via the MG-dependent pathway. Our observations suggest associations between choline-TMA lyase expression and MG formation, which are indicative of a novel role of the gut microbiota in choline metabolism and highlight it as a potential target for inhibiting TMA production.

Inflammaging as a common ground for the development and maintenance of sarcopenia, obesity, cardiomyopathy and dysbiosis

Sarcopenia, obesity and their coexistence, obese sarcopenia (OBSP) as well as atherosclerosis-related cardio-vascular diseases (ACVDs), including chronic heart failure (CHF), are among the greatest public health concerns in the ageing population. A clear age-dependent increased prevalence of sarcopenia and OBSP has been registered in CHF patients, suggesting mechanistic relationships. Development of OBSP could be mediated by a crosstalk between the visceral and subcutaneous adipose tissue (AT) and the skeletal muscle under conditions of low-grade local and systemic inflammation, inflammaging. The present review summarizes the emerging data supporting the idea that inflammaging may serve as a mutual mechanism governing the development of sarcopenia, OBSP and ACVDs. In support of this hypothesis, various immune cells release pro-inflammatory mediators in the skeletal muscle and myocardium. Subsequently, the endothelial structure is disrupted, and cellular processes, such as mitochondrial activity, mitophagy, and autophagy are impaired. Inflamed myocytes lose their contractile properties, which is characteristic of sarcopenia and CHF. Inflammation may increase the risk of ACVD events in a hyperlipidemia-independent manner. Significant reduction of ACVD event rates, without the lowering of plasma lipids, following a specific targeting of key pro-inflammatory cytokines confirms a key role of inflammation in ACVD pathogenesis. Gut dysbiosis, an imbalanced gut microbial community, is known to be deeply involved in the pathogenesis of age-associated sarcopenia and ACVDs by inducing and supporting inflammaging. Dysbiosis induces the production of trimethylamine-N-oxide (TMAO), which is implicated in atherosclerosis, thrombosis, metabolic syndrome, hypertension and poor CHF prognosis. In OBSP, AT dysfunction and inflammation induce, in concert with dysbiosis, lipotoxicity and other pathophysiological processes, thus exacerbating sarcopenia and CHF. Administration of specialized, inflammation pro-resolving mediators has been shown to ameliorate the inflammatory manifestations. Considering all these findings, we hypothesize that sarcopenia, OBSP, CHF and dysbiosis are inflammaging-oriented disorders, whereby inflammaging is common and most probably the causative mechanism driving their pathogenesis.

Gut Microbiota-Dependent Marker TMAO in Promoting Cardiovascular Disease: Inflammation Mechanism, Clinical Prognostic, and Potential as a Therapeutic Target

Cardiovascular disease (CVD) is the leading cause of death worldwide, especially in developed countries, and atherosclerosis (AS) is the common pathological basis of many cardiovascular diseases (CVDs) such as coronary heart disease (CHD). The role of the gut microbiota in AS has begun to be appreciated in recent years. Trimethylamine N-oxide (TMAO), an important gut microbe-dependent metabolite, is generated from dietary choline, betaine, and L-carnitine. Multiple studies have suggested a correlation between plasma TMAO levels and the risk of AS. However, the mechanism underlying this relationship is still unclear. In this review, we discuss the TMAO-involved mechanisms of atherosclerotic CVD from the perspective of inflammation, inflammation-related immunity, cholesterol metabolism, and atherothrombosis. We also summarize available clinical studies on the role of TMAO in predicting prognostic outcomes, including major adverse cardiovascular events (MACE), in patients presenting with AS. Finally, since TMAO may be a novel therapeutic target for AS, several therapeutic strategies including drugs, dietary, etc. to lower TMAO levels that are currently being explored are also discussed.

Role and Effective Therapeutic Target of Gut Microbiota in Heart Failure

Although the mechanism of the occurrence and development of heart failure has been continuously explored in the past ten years, the mortality and readmission rate of heart failure is still very high. Modern studies have shown that gut microbiota is associated with a variety of cardiovascular diseases, among which the study of gut microbiota and heart failure attracts particular attention. Therefore, understanding the role of gut microbiota in the occurrence and development of heart failure will help us further understand the pathogenesis of heart failure and provide new ideas for its treatment. This paper introduced intestinal flora and its metabolites, summarized the changes of intestinal flora in patients with heart failure, clarified that intestinal barrier damage and bacterial translocation induced inflammation and immune response aggravated heart failure, and altered intestinal microflora affected various metabolic pathways including trimethylamine/TMAO, SCFA, and Bile acid pathway leads to heart failure. At the same time, regulating intestinal microflora through diet, probiotics, antibiotics, fecal transplantation and microbial enzyme inhibitors has grown up to be a potential treatment for many metabolic disorders.

Changes of intestinal bacterial microbiota in coronary heart disease complicated with nonalcoholic fatty liver disease

Background

Previous study reported that patients who suffered coronary heart disease (CHD) complicated with non-alcoholic fatty liver disease (NAFLD) had worse cardiac function and clinical outcomes than patients with CHD only. Notably, the mechanism is still unclear. This study aimed to investigate the changes and roles of intestinal bacterial microbiota in CHD-NAFLD patients.

Methods and results

People were recruited and divided into three groups, including CHD patients (without NAFLD), CHD-NAFLD patients and healthy controls (HCs). Each group contained 24 people. Fecal samples and clinical information were carefully collected. The Illumina sequencing of 16S rRNA was applied to profile the overall structure of the fecal bacterial microbiota and the characteristics of the bacterial microbiota based on the Operational Taxonomic Units. In clinical information, the CHD-NAFLD patients showed an increase in BMI, uric acid and triglyceride. There was a significant reduction in the abundance of Parabacteroides and Collinsella in overall CHD patients (including CHD-NAFLD and CHD patients). The intestinal bacterial microbiota in CHD-NAFLD patients showed an increase in the abundance of Copococcus and Veillonella, and a reduction in the abundance of Parabacteroides, Bacteroides fragilis, Ruminococcus gnavus, Bacteroides dorei, and Bifidobacterium longum subsp infantis. Among them, the abundance of Ruminococcus gnavus and Bacteroides dorei was significantly lower than that in CHD patients. Additionally, BMI positively correlated with the abundance of Copococcus and negatively correlated with the abundance of Bifidobacterium longum subsp infantis. The abundance of Veillonella positively correlated with AST. The abundance of Bacteroides dorei negatively correlated with ALT and AST. It indicates that the abundance of intestinal microbiota was related to the changes in clinical indexes.

Conclusions

Changes of intestinal bacterial microbiota in CHD-NAFLD patients may be important factors affecting the degree of metabolic disorder, which may be one of the important reasons for the worse clinical outcome and disease progression in CHD-NAFLD patients than in CHD patients.

The Microbiota Promotes Arterial Thrombosis in Low-Density Lipoprotein Receptor-Deficient Mice

Atherosclerotic plaque development depends on chronic inflammation of the arterial wall. A dysbiotic gut microbiota can cause low-grade inflammation, and microbiota composition was linked to cardiovascular disease risk. However, the role of this environmental factor in atherothrombosis remains undefined. To analyze the impact of gut microbiota on atherothrombosis, we rederived low-density lipoprotein receptor-deficient (Ldlr^-/- ) mice as germfree (GF) and kept these mice for 16 weeks on an atherogenic high-fat Western diet (HFD) under GF isolator conditions and under conventionally raised specific-pathogen-free conditions (CONV-R). In spite of reduced diversity of the cecal gut microbiome, caused by atherogenic HFD, GF Ldlr^-/- mice and CONV-R Ldlr^-/- mice exhibited atherosclerotic lesions of comparable sizes in the common carotid artery. In contrast to HFD-fed mice, showing no difference in total cholesterol levels, CONV-R Ldlr^-/- mice fed control diet (CD) had significantly reduced total plasma cholesterol, very-low-density lipoprotein (VLDL), and LDL levels compared with GF Ldlr^-/- mice. Myeloid cell counts in blood as well as leukocyte adhesion to the vessel wall at the common carotid artery of GF Ldlr^-/- mice on HFD were diminished compared to CONV-R Ldlr^-/- controls. Plasma cytokine profiling revealed reduced levels of the proinflammatory chemokines CCL7 and CXCL1 in GF Ldlr^-/- mice, whereas the T-cell-related interleukin 9 (IL-9) and IL-27 were elevated. In the atherothrombosis model of ultrasound-induced rupture of the common carotid artery plaque, thrombus area was significantly reduced in GF Ldlr^-/- mice relative to CONV-R Ldlr^-/- mice. Ex vivo, this atherothrombotic phenotype was explained by decreased adhesion-dependent platelet activation and thrombus growth of HFD-fed GF Ldlr^-/- mice on type III collagen.IMPORTANCE Our results demonstrate a functional role for the commensal microbiota in atherothrombosis. In a ferric chloride injury model of the carotid artery, GF C57BL/6J mice had increased occlusion times compared to colonized controls. Interestingly, in late atherosclerosis, HFD-fed GF Ldlr^-/- mice had reduced plaque rupture-induced thrombus growth in the carotid artery and diminished ex vivo thrombus formation under arterial flow conditions.

Microbial Contribution to the Human Metabolome: Implications for Health and Disease

The human gastrointestinal tract is home to an incredibly dense population of microbes. These microbes employ unique strategies to capture energy in this largely anaerobic environment. In the process of breaking down dietary- and host-derived substrates, the gut microbiota produce a broad range of metabolic products that accumulate to high levels in the gut. Increasingly, studies are revealing that these chemicals impact host biology, either by acting on cells within the gastrointestinal tract or entering circulation and exerting their effects at distal sites within the body. Given the high level of functional diversity in the gut microbiome and the varied diets that we consume, the repertoire of microbiota-derived molecules within our bodies varies dramatically across individuals. Thus, the microbes in our gut and the metabolic end products they produce represent a phenotypic lever that we can potentially control to develop new therapeutics for personalized medicine. Here, we review current understanding of how microbes in the gastrointestinal tract contribute to the molecules within our gut and those that circulate within our bodies. We also highlight examples of how these molecules affect host physiology and discuss potential strategies for controlling their production to promote human health and to treat disease.

The Gut Microbiome Influences Host Endocrine Functions

The gut microbiome is considered an organ contributing to the regulation of host metabolism. Since the relationship between the gut microbiome and specific diseases was elucidated, numerous studies have deciphered molecular mechanisms explaining how gut bacteria interact with host cells and eventually shape metabolism. Both metagenomic and metabolomic analyses have contributed to the discovery of bacterial-derived metabolites acting on host cells. In this review, we examine the molecular mechanisms by which bacterial metabolites act as paracrine or endocrine factors, thereby regulating host metabolism. We highlight the impact of specific short-chain fatty acids on the secretion of gut peptides (i.e., glucagon-like peptide-1, peptide YY) and other metabolites produced from different amino acids and regulating inflammation, glucose metabolism, or energy homeostasis. We also discuss the role of gut microbes on the regulation of bioactive lipids that belong to the endocannabinoid system and specific neurotransmitters (e.g., γ-aminobutyric acid, serotonin, nitric oxide). Finally, we review the role of specific bacterial components (i.e., ClpB, Amuc_1100) also acting as endocrine factors and eventually controlling host metabolism. In conclusion, this review summarizes the recent state of the art, aiming at providing evidence that the gut microbiome influences host endocrine functions via several bacteria-derived metabolites.

Microbial Transplantation With Human Gut Commensals Containing CutC Is Sufficient to Transmit Enhanced Platelet Reactivity and Thrombosis Potential

RATIONALE

Gut microbes influence cardiovascular disease and thrombosis risks through the production of trimethylamine N-oxide (TMAO). Microbiota-dependent generation of trimethylamine (TMA)-the precursor to TMAO-is rate limiting in the metaorganismal TMAO pathway in most humans and is catalyzed by several distinct microbial choline TMA-lyases, including the proteins encoded by the cutC/D (choline utilization C/D) genes in multiple human commensals.

OBJECTIVE

Direct demonstration that the gut microbial cutC gene is sufficient to transmit enhanced platelet reactivity and thrombosis potential in a host via TMA/TMAO generation has not yet been reported.

METHODS AND RESULTS

Herein, we use gnotobiotic mice and a series of microbial colonization studies to show that microbial cutC-dependent TMA/TMAO production is sufficient to transmit heightened platelet reactivity and thrombosis potential in a host. Specifically, we examine in vivo thrombosis potential employing germ-free mice colonized with either high TMA-producing stable human fecal polymcrobial communities or a defined CutC-deficient background microbial community coupled with a CutC-expressing human commensal±genetic disruption of its cutC gene (ie, Clostridium sporogenes Δ cutC).

CONCLUSIONS

Collectively, these studies point to the microbial choline TMA-lyase pathway as a rational molecular target for the treatment of atherothrombotic heart disease.

Antibiotic Treatment Protocols and Germ-Free Mouse Models in Vascular Research

The gut microbiota influence host vascular physiology locally in the intestine, but also evoke remote effects that impact distant organ functions. Amongst others, the microbiota affect intestinal vascular remodeling, lymphatic development, cardiac output and vascular function, myelopoiesis, prothrombotic platelet function, and immunovigilance of the host. Experimentally, host-microbiota interactions are investigated by working with animals devoid of symbiotic bacteria, i.e., by the decimation of gut commensals by antibiotic administration, or by taking advantage of germ-free mouse isolator technology. Remarkably, some of the vascular effects that were unraveled following antibiotic treatment were not observed in the germ-free animal models and vice versa. In this review, we will dissect the manifold influences that antibiotics have on the cardiovascular system and their effects on thromboinflammation.

The gut microbiome and cardiovascular disease: current knowledge and clinical potential

Cardiovascular disease (CVD) is the leading cause of death worldwide. The human body is populated by a diverse community of microbes, dominated by bacteria, but also including viruses and fungi. The largest and most complex of these communities is located in the gastrointestinal system and, with its associated genome, is known as the gut microbiome. Gut microbiome perturbations and related dysbiosis have been implicated in the progression and pathogenesis of CVD, including atherosclerosis, hypertension, and heart failure. Although there have been advances in the characterization and analysis of the gut microbiota and associated bacterial metabolites, the exact mechanisms through which they exert their action are not well understood. This review will focus on the role of the gut microbiome and associated functional components in the development and progression of atherosclerosis. Potential treatments to alter the gut microbiome to prevent or treat atherosclerosis and CVD are also discussed.

Gut Microbiome and Response to Cardiovascular Drugs

The gut microbiome is emerging as an important contributor to both cardiovascular disease risk and metabolism of xenobiotics. Alterations in the intestinal microbiota are associated with atherosclerosis, dyslipidemia, hypertension, and heart failure. The microbiota have the ability to metabolize medications, which can results in altered drug pharmacokinetics and pharmacodynamics or formation of toxic metabolites which can interfere with drug response. Early evidence suggests that the gut microbiome modulates response to statins and antihypertensive medications. In this review, we will highlight mechanisms by which the gut microbiome facilitates the biotransformation of drugs and impacts pharmacological efficacy. A better understanding of the complex interactions of the gut microbiome, host factors, and response to medications will be important for the development of novel precision therapeutics for targeting CVD.