Plasma trimethylamine N-oxide is associated with vulnerable plaque characteristics in CAD patients as assessed by optical coherence tomography

Research development on gut microbiota and vulnerable atherosclerotic plaque

The relationship between gut microbiota and its metabolites with cardiovascular disease (CVD) has been proven. In this review, we aim to conclude the potential mechanism of gut microbiota and its metabolites on inducing the formation of vulnerable atherosclerotic plaque, and to discuss the effect of intestinal metabolites, including trimethylamine-N-oxide (TMAO), lipopolysaccharide (LPS), phenylacetylglutamine (PAG), short-chain fatty acids (SCFAs) on plaque stability. Finally, we include the impact of gut microbiota and its metabolites on plaque stability, to propose a new therapeutic direction for coronary heart disease. Gut microbiota regulation intervenes the progress of arteriosclerosis, especially on coronary atherosclerosis, by avoiding or reducing the formation of vulnerable plaque, to lower the morbidity rate of myocardial infarction.

Trimethylamine N-oxide promotes oxidative stress and lipid accumulation in macrophage foam cells via the Nrf2/ABCA1 pathway

Recently, trimethylamine N-oxide (TMAO) has been considered a risk factor for cardiovascular disease and has a proatherogenic effect. Many studies have found that TMAO is involved in plaque oxidative stress and lipid metabolism, but the specific mechanism is still unclear. In our study, meta-analysis and bioinformatic analysis were firstly conducted in the database, and found that the effect of high plasma TMAO levels on promoting atherosclerotic plaque may be related to the expression of key antioxidant genes nuclear factor erytheroid-derived-2-like 2 (NFE2L2/Nrf2) decreased. Next, we assessed the role of Nrf2-mediated signaling pathway in TMAO-treated foam cells. Our results showed that TMAO can inhibit the expression of Nrf2 and its downstream antioxidant response element such as heme oxygenase-1 (HO-1) and glutathione peroxidase4 (GPX4), resulting in increased production of reactive oxygen species and decreased activity of superoxide dismutase, promoting oxidative stress. And TMAO can also promote lipid accumulation in foam cells by inhibiting cholesterol efflux protein expression. In addition, upregulation of Nrf2 expression partially rescues TMAO-induced oxidative stress and reduces ATP-binding cassette A1 (ABCA1)-mediated lipid accumulation. Therefore, TMAO promotes oxidative stress and lipid accumulation in macrophage foam cells through the Nrf2/ABCA1 pathway, which may provide a potential mechanism for the proatherogenic effect of TMAO.

Protocatechuic acid alleviates TMAO-aggravated atherosclerosis via mitigating inflammation, regulating lipid metabolism, and reshaping gut microbiota

Trimethylamine-N-oxide (TMAO) is a risk factor for atherosclerosis. As a natural phenolic acid, protocatechuic acid (PCA) is abundant in various plant foods. The present study investigated the effect of PCA on TMAO-aggravated atherosclerosis in ApoE-/- mice. The mice were randomly divided into five groups and fed one of the following five diets for 12 weeks: namely a low-fat diet (LFD), a western diet (WD), a WD + 0.2% TMAO diet (WDT), a WDT + 0.5% PCA diet (WDT + LPCA), and a WDT + 1.0% PCA diet (WDT + HPCA). Results demonstrated that dietary TMAO exacerbated the development of atherosclerosis by eliciting inflammation and disturbing lipid metabolism. The diet with PCA at 1% reduced TMAO-induced aortic plaque by 30% and decreased the levels of plasma pro-inflammatory cytokines. PCA also improved lipid metabolism by up-regulating the hepatic gene expression of peroxisome proliferator-activated receptor alpha (PPARα). In addition, PCA supplementation enhanced fecal excretion of fatty acids and decreased hepatic fat accumulation. PCA supplementation favorably modulated gut microbiota by increasing the α-diversity with an increase in the abundance of beneficial genera (Rikenella, Turicibacter, Clostridium_sensu_stricto and Bifidobacterium) and a decrease in the abundance of the harmful Helicobacter genus. In summary, PCA could alleviate the TMAO-exacerbated atherosclerosis and inflammation, improve the lipid metabolism, and modulate gut microbiota.

Gut microbiota and stroke: New avenues to improve prevention and outcome

Despite major recent therapeutic advances, stroke remains a leading cause of disability and death. Consequently, new therapeutic targets need to be found to improve stroke outcome. The deleterious role of gut microbiota alteration (often mentioned as "dysbiosis") on cardiovascular diseases, including stroke and its risk factors, has been increasingly recognized. Gut microbiota metabolites, such as trimethylamine-N-oxide, short chain fatty acids and tryptophan, play a key role. Evidence of a link between alteration of the gut microbiota and cardiovascular risk factors exists, with a possible causality link supported by several preclinical studies. Gut microbiota alteration also seems to be implicated at the acute phase of stroke, with observational studies showing more non-neurological complications, higher infarct size and worse clinical outcome in stroke patients with altered microbiota. Microbiota targeted strategies have been developed, including prebiotics/probiotics, fecal microbiota transplantation, short chain fatty acid and trimethylamine-N-oxide inhibitors. Research teams have been using different time windows and end-points for their studies, with various results. Considering the available evidence, it is believed that studies focusing on microbiota-targeted strategies in association with conventional stroke care should be conducted. Such strategies should be considered according to three therapeutic time windows: first, at the pre-stroke (primary prevention) or post-stroke (secondary prevention) phases, to enhance the control of cardiovascular risk factors; secondly, at the acute phase of stroke, to limit the infarct size and the systemic complications and enhance the overall clinical outcome; thirdly, at the subacute phase of stroke, to prevent stroke recurrence and promote neurological recovery.

Role of glycolysis in diabetic atherosclerosis

Diabetes mellitus is a kind of typical metabolic disorder characterized by elevated blood sugar levels. Atherosclerosis (AS) is one of the most common complications of diabetes. Modern lifestyles and trends that promote overconsumption and unhealthy practices have contributed to an increase in the annual incidence of diabetic AS worldwide, which has created a heavy burden on society. Several studies have shown the significant effects of glycolysis-related changes on the occurrence and development of diabetic AS, which may serve as novel thera-peutic targets for diabetic AS in the future. Glycolysis is an important metabolic pathway that generates energy in various cells of the blood vessel wall. In particular, it plays a vital role in the physiological and pathological activities of the three important cells, Endothelial cells, macrophages and vascular smooth muscle cells. There are lots of similar mechanisms underlying diabetic and common AS, the former is more complex. In this article, we describe the role and mechanism underlying glycolysis in diabetic AS, as well as the therapeutic targets, such as trained immunity, microRNAs, gut microbiota, and associated drugs, with the aim to provide some new perspectives and potentially feasible programs for the treatment of diabetic AS in the foreseeable future.

Prognostic value of gut microbiota-derived metabolites in patients with ST-segment elevation myocardial infarction

BACKGROUND

Studies about the prognostic role of gut microbiota-derived metabolites including phenylacetyl glutamine (PAGln), indoxyl sulfate (IS), lithocholic acid (LCA), deoxycholic acid (DCA), trimethylamine (TMA), trimethylamine N-oxide (TMAO), and its precursor trimethyllysine (TML) are limited in patients with ST-segment elevation myocardial infarction (STEMI).

OBJECTIVES

To examine the relationship between plasma metabolite levels and major adverse cardiovascular events (MACEs), including nonfatal MI, nonfatal stroke, all-cause mortality, and heart failure in patients with STEMI.

METHODS

We enrolled 1004 patients with STEMI undergoing percutaneous coronary intervention (PCI). Plasma levels of these metabolites were determined by targeted liquid chromatography/mass spectrometry. The associations of metabolite levels with MACEs were assessed with the Cox regression model and quantile g-computation.

RESULTS

During a median follow-up of 360 d, 102 patients experienced MACEs. Higher plasma PAGln (hazard ratio [HR], 3.17 [95% CI: 2.05, 4.89]; P < 0.001), IS (2.67 [1.68, 4.24], P < 0.001), DCA (2.36 [1.40, 4.00], P = 0.001), TML (2.66 [1.77,3.99], P < 0.001), and TMAO (2.61 [1.70, 4.00], P < 0.001) levels were significantly associated with MACEs independent of traditional risk factors. According to quantile g-computation, the joint effect of all these metabolites was 1.86 (95% CI: 1.46, 2.27). PAGln, IS and TML had the greatest proportional positive contributions to the mixture effect. Additionally, plasma PAGln and TML combined with coronary angiography scores including the Synergy between PCI with Taxus and cardiac surgery (SYNTAX) score (area under the curve [AUC]: 0.792 vs. 0.673), Gensini score (0.794 vs. 0.647) and Balloon pump-assisted Coronary Intervention Study (BCIS-1) jeopardy score (0.774 vs. 0.573) showed better prediction performance for MACEs.

CONCLUSIONS

Higher plasma PAGln, IS, DCA, TML, and TMAO levels are independently associated with MACEs suggesting that these metabolites may be useful markers for prognosis in patients with STEMI.

Zuogui Jiangtang Shuxin formula Ameliorates diabetic cardiomyopathy mice via modulating gut-heart axis

BACKGROUND

There is growing evidence demonstrating that the gut microbiota plays a crucial role in multiple endocrine disorders, including diabetic cardiomyopathy (DCM). Research shows that the Chinese herb reduces disease occurrence by regulating gut microbiota. Zuogui Jiangtang Shuxin formula (ZGJTSXF), a Chinese medicinal formula, has been clinically used for treatment of DCM for many years. However, there is still no clear understanding of how ZGJTSXF treatment contributes to the prevention and treatment of DCM through its interaction with gut microbiota and metabolism.

METHODS

In this study, mice models of DCM were established, and ZGJTSXF's therapeutic effects were assessed. Specifically, serum glycolipid, echocardiography, histological staining, myocardial apoptosis rate were assessed. Using 16s rRNA sequencing and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), we determined the impact of ZGJTSXF on the structure of gut microbiota and content of its metabolite TMAO. The mechanism of ZGJTSXF action on DCM was analyzed using quantitative real-time PCR and western blots.

RESULTS

We found that ZGJTSXF significantly ameliorated DCM mice by modulating gut-heart axis: ZGJTSXF administration improved glycolipid levels, heart function, cardiac morphological changes, inhibited cardiomyocytes apoptosis, and regulate the gut microbiota in DCM mice. Specifically, ZGJTSXF treatment reverse the significant changes in the abundance of certain genera closely related to DCM phenotype, including Lactobacillus, Alloprevotella and Alistipes. Furthermore, ZGJTSXF alleviated DCM in mice by blunting TMAO/PERK/FoxO1 signaling pathway genes and proteins.

CONCLUSION

ZGJTSXF administration could ameliorate DCM mice by remodeling gut microbiota structure, reducing serum TMAO generation and suppressing TMAO/PERK/FoxO1 signaling pathway.

Natural products against inflammation and atherosclerosis: Targeting on gut microbiota

The gut microbiota (GM) has become recognized as a crucial element in preserving human fitness and influencing disease consequences. Commensal and pathogenic gut microorganisms are correlated with pathological progress in atherosclerosis (AS). GM may thus be a promising therapeutic target for AS. Natural products with cardioprotective qualities might improve the inflammation of AS by modulating the GM ecosystem, opening new avenues for researches and therapies. However, it is unclear what components of natural products are useful and what the actual mechanisms are. In this review, we have summarized the natural products relieving inflammation of AS by regulating the GM balance and active metabolites produced by GM.

Vulnerable Atherosclerotic Plaque: Is There a Molecular Signature?

Atherosclerosis and its clinical manifestations, coronary and cerebral artery diseases, are the most common cause of death worldwide. The main pathophysiological mechanism for these complications is the rupture of vulnerable atherosclerotic plaques and subsequent thrombosis. Pathological studies of the vulnerable lesions showed that more frequently, plaques rich in lipids and with a high level of inflammation, responsible for mild or moderate stenosis, are more prone to rupture, leading to acute events. Identifying the vulnerable plaques helps to stratify patients at risk of developing acute vascular events. Traditional imaging methods based on plaque appearance and size are not reliable in prediction the risk of rupture. Intravascular imaging is a novel technique able to identify vulnerable lesions, but it is invasive and an operator-dependent technique. This review aims to summarize the current data from literature regarding the main biomarkers involved in the attempt to diagnose vulnerable atherosclerotic lesions. These biomarkers could be the base for risk stratification and development of the new therapeutic drugs in the treatment of patients with vulnerable atherosclerotic plaques.

Anti-atherosclerotic effects of geraniin through the gut microbiota-dependent trimethylamine N-oxide (TMAO) pathway in mice

BACKGROUND

Cardiovascular disease is a leading cause of death, which signifies the urgent need for effective anti-atherosclerotic strategies. Gut microbiota-dependent trimethylamine-N-oxide (TMAO) is associated with atherosclerosis, and geraniin, a natural polyphenol with various biological activities, might play key role in this process.

PURPOSE

We aimed to investigate the pharmacological activity of geraniin in atherosclerosis through remodeling the gut microbiota.

METHODS

C57BL/6J ApoE^-/- mice were administrated geraniin for 12 weeks. The colon contents were analyzed via 16S rRNA sequencing. Pathological staining was performed to evaluate the atherosclerotic characteristics. Cytokine assays detected the levels of plasma inflammatory cytokines. RAW264.7 cells were cultured in vitro and treated with TMAO. Tandem Mass Tag quantitative proteomics analysis and western blot were performed to investigate the effect of TMAO in macrophages.

RESULTS

The plasma TMAO level in mice significantly decreased after geraniin intervention. The predominant intestinal microflora from geraniin-treated mice were Bacteroides (65.3%) and Firmicutes (30.6%). Pathological staining demonstrated that administration of geraniin attenuated atherosclerotic characteristics. After geraniin treatment, plasma levels of IL-1β, IL-6, and TNF-α in mice were significantly reduced, and IL-10 levels were significantly increased. Proteomics analysis demonstrated the number of differentially expressed proteins after TMAO administration. In vitro study suggested that the atherogenic effect of TMAO could be attributed to changes in CD36, transmembrane protein 106a, apolipoprotein C1, macrophage scavenger receptor types I and II, and alpha-2-macroglobulin.

CONCLUSION

Geraniin might be an effective prospective drug against cardiovascular diseases, and the gut microbiota is a potential target to reduce the risk of atherosclerotic disease.

Gut microbiota-derived metabolite trimethylamine-N-oxide and multiple health outcomes: an umbrella review and updated meta-analysis

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite produced from dietary nutrients. Many studies have discovered that circulating TMAO concentrations are linked to a wide range of health outcomes.

OBJECTIVES

This study aimed to summarize health outcomes related to circulating TMAO concentrations.

METHODS

We searched the Embase, Medline, Web of Science, and Scopus databases from inception to 15 February, 2022 to identify and update meta-analyses examining the associations between TMAO and multiple health outcomes. For each health outcome, we estimated the summary effect size, 95% prediction CI, between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. These metrics were used to evaluate the evidence credibility of the identified associations.

RESULTS

This umbrella review identified 24 meta-analyses that investigated the association between circulating TMAO concentrations and health outcomes including all-cause mortality, cardiovascular diseases (CVDs), diabetes mellitus (DM), cancer, and renal function. We updated these meta-analyses by including a total of 82 individual studies on 18 unique health outcomes. Among them, 14 associations were nominally significant. After evidence credibility assessment, we found 6 (33%) associations (i.e., all-cause mortality, CVD mortality, major adverse cardiovascular events, hypertension, DM, and glomerular filtration rate) to present highly suggestive evidence.

CONCLUSIONS

TMAO might be a novel biomarker related to human health conditions including all-cause mortality, hypertension, CVD, DM, cancer, and kidney function. Further studies are needed to investigate whether circulating TMAO concentrations could be an intervention target for chronic disease.This review was registered at www.crd.york.ac.uk/prospero/ as CRD42021284730.

Balancing the Equation: A Natural History of Trimethylamine and Trimethylamine-N-oxide

Trimethylamine (TMA) and its N-oxide (TMAO) are ubiquitous in prokaryote and eukaryote organisms as well as in the environment, reflecting their fundamental importance in evolutionary biology, and their diverse biochemical functions. Both metabolites have multiple biological roles including cell-signaling. Much attention has focused on the significance of serum and urinary TMAO in cardiovascular disease risk, yet this is only one of the many facets of a deeper TMA-TMAO partnership that reflects the significance of these metabolites in multiple biological processes spanning animals, plants, bacteria, and fungi. We report on analytical methods for measuring TMA and TMAO and attempt to critically synthesize and map the global functions of TMA and TMAO in a systems biology framework.

Intestinal Flora: A Potential New Regulator of Cardiovascular Disease

Although substantial progress has been made in reducing the burden of the disease by preventing the risk factors of cardiovascular disease (CVD), potential risk factors still exist and lead to its progression. In recent years, numerous studies have revealed that intestinal flora can interfere with the physiological processes of the host through changes in composition and function or related metabolites. Intestinal flora thus affects the occurrence and development of a variety of CVDs, including atherosclerosis, ischemic heart disease, and heart failure. Moreover, studies have found that interventions for intestinal flora and its metabolites provide new opportunities for CVD treatment. This article mainly discusses the interaction between the human intestinal flora and its metabolites, the occurrence and development of CVD, and the potential of intestinal flora as a new target for the diagnosis and treatment of CVD.

The gut microbiome and microbial metabolites in acute myocardial infarction

Emerging evidence has highlighted the role of the gut microbiome in human health. However, the integrative role of the gut microbiome and microbial metabolites in acute myocardial infarction (AMI) remains unclear. The current study profiled the microbial community through 16S rRNA gene sequencing and shotgun metagenomic sequencing, and measured fecal short-chain fatty acids and circulating choline pathway metabolites among 117 new-onset AMI cases and 78 controls. Significant microbial alternations were observed in AMI patients compared with controls (P = 0.001). The abundances of nine species (e.g., Streptococcus salivarius, Klebsiella pneumoniae) were positively associated, and one species (Roseburia hominis) was inversely associated with AMI status and severity. A gut microbial score at disease onset was associated with the risk of major adverse cardiovascular events in 3.2 years (hazard ratio [95% CI]: 2.01 [1.04-4.24]) in AMI patients. The molar proportions of fecal acetate and butyrate were higher, and the circulating levels of choline and carnitine were lower in AMI patients than in controls. In addition, disease classifiers showed that AMI cases and controls had a more distinct pattern in taxonomical composition than in pathways or metabolites. Our findings suggested that microbial composition and functional potentials were associated with AMI status and severity.

Remodelling of gut microbiota by Berberine attenuates trimethylamine N-oxide-induced platelet hyperreaction and thrombus formation

Berberine is an extract derived from Chinese herbs with pleiotropic cardiovascular protective effects. However, the underlying mechanism remains unclear because of its poor bioavailability. Herin, we aimed to investigate whether berberine affects choline diet-induced arterial thrombosis and explore the potential mechanism. Ultrasound and optical coherence tomography were used to assess the potential risk of artery thrombosis in vivo. The plasma concentrations of trimethylamine N-oxide (TMAO) and trimethylamine (TMA) were quantified with mass spectrometry. Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qPCR) were utilized to detect the levels of microbial TMA-lyase choline utilization C (CutC) in faeces. Gut microbiota analysis was performed with 16S rRNA gene sequencing. For in vitro studies, platelet aggregometry, intracellular Ca2+ measurement, ATP release assay, flow cytometry and Western blot were applied to identify the effects of TMAO on platelets. Berberine treatment significantly decreased the CutC levels in the caecal contents, reduced choline diet-induced TMA and TMAO production, and subsequently, reduced the arterial thrombosis potential risk. Berberine administration remodelled the structure of gut microbiota in rats and increased the levels of the genus Lactobacillus. Finally, TMAO enhanced platelet reactivity to collagen by promoting the phosphorylation levels of extracellular signal-regulated kinase 1/2 (ERK1/2) and Jun N-terminal kinase (JNK) in platelets. These results demonstrate that berberine attenuates the risk of choline diet-induced arterial thrombosis by changing the gut microbial composition and reducing TMAO generation.

Addition of Plasma Myeloperoxidase and Trimethylamine N-Oxide to the GRACE Score Improves Prediction of Near-Term Major Adverse Cardiovascular Events in Patients With ST-Segment Elevation Myocardial Infarction

Background: The Global Registry of Acute Coronary Events (GRACE) risk score (GRS) is an established powerful model in predicting prognosis of patients with acute coronary syndrome. However, it does not contain pathophysiological biomarkers. Myeloperoxidase (MPO) and trimethylamine N-oxide (TMAO) are novel biomarkers of different pathophysiological processes of acute myocardial infarction, and each of them predicts risk of adverse clinical outcomes. We aimed to investigate whether the addition of MPO and TMAO could improve a GRS-based prediction model in patients with ST-segment elevation myocardial infarction (STEMI).

Methods: A prospective cohort of 444 consecutive patients with STEMI who underwent primary percutaneous coronary intervention were enrolled in this study. Plasma levels of MPO and TMAO were measured using samples collected before the interventional procedure. GRS at admission was calculated. Death and nonfatal myocardial infarction were recorded as major adverse cardiac events (MACEs). Kaplan–Meier survival analysis with Cox proportional-hazards regression was used to identify predictive values of MPO and TMAO. Area under the receiver-operator characteristic curve (AUC) and net reclassification improvement (NRI) were calculated to evaluate the increment of predictive value for the combination of MPO and TMAO with GRS in predicting adverse clinical outcomes.

Results: During 6 months follow-up, 27 patients suffered MACEs. Both MPO (hazard ratio [HR]: 2.55, 95% confidence interval [CI]: 1.11–5.87; p < 0.05) and TMAO (HR: 4.50, 95% CI: 1.78–11.40, p < 0.01) predicted MACEs at 6 months. The AUC for MPO, TMAO, GRS, and their combination in predicting risk of MACEs at 6 months is 0.642, 0.692, 0.736, and 0.760, respectively. The addition of MPO and TMAO significantly improved the net reclassification of GRS for predicting MACEs at 6 months (NRI: 0.42, p = 0.032).

Conclusion: Plasma MPO and TMAO each predict near-term risk of adverse outcomes in patients with STEMI. Furthermore, the combination of MPO and TMAO with GRS enables more accurate prediction of cardiovascular events compared with GRS alone.

Gut Lactobacillus Level Is a Predictive Marker for Coronary Atherosclerotic Lesions Progress and Prognosis in Patients With Acute Coronary Syndrome

Background

Gut microbiota dysbiosis can contribute to the progression of atherosclerosis. We investigated the association of the gut microbiota and the severity of coronary artery lesions and prognosis of patients with ACS.

Methods

In this case-control study, 402 ACS patients and 100 controls were enrolled from June 2017 to December 2018. The number of bacterial species was determined by real-time PCR. A SYNTAX score was calculated for all ACS patients based on their coronary angiography results.

Results

Compared with the healthy controls, the gut microbial levels in Escherichia coli, Streptococcus, and Enterobacteriaceae were significantly increased in ACS patients, while the Lactobacillus level was significantly decreased. Lactobacillus level was as an independent predictor of disease severity on the coronary angiography [high vs. low SYNTAX score: adjusted odds ratio (aOR) = 0.024, 95% confidence interval (CI): 0.004-0.155] and myocardial necrosis [high vs. low cardiac troponin T (cTNT): aOR = 0.317, 95% CI: 0.099-0.914]. Subsequently, a higher Lactobacillus level was associated with a lower risk of an all-cause death [adjusted hazard ratio (aHR) = 0.239; 95% CI: 0.093-0.617] and major adverse cardiac events (MACE) in ACS patients (aHR = 0.208; 95% CI: 0.081-0.531). After stratifying by the type of ACS, a higher Lactobacillus level was significantly associated with the decreased risks of high SYNTAX score, all-cause death, and MACE in the STEMI subgroup but not in the NSTEMI and UAP subgroups.

Conclusions

Lower Lactobacillus levels may indicate a higher risk of a more severe coronary atherosclerotic lesions and myocardial necrosis and worse prognosis for patients with ACS, particularly in the STEMI subgroup.

Gut Microbiota and Atherosclerosis-Focusing on the Plaque Stability

Cardiovascular diseases (CVDs) are major causes of mortality and morbidity in the modern society. The rupture of atherosclerotic plaque can induce thrombus formation, which is the main cause of acute cardiovascular events. Recently, many studies have demonstrated that there are some relationships between microbiota and atherosclerosis. In this review, we will focus on the effect of the microbiota and the microbe-derived metabolites, including trimethylamine-N-oxide (TMAO), short-chain fatty acids (SCFAs), and lipopolysaccharide (LPS), on the stability of atherosclerotic plaque. Finally, we will conclude with some therapies based on the microbiota and its metabolites.

Vascular endothelial tissue factor contributes to trimethylamine N-oxide-enhanced arterial thrombosis

AIMS

Gut microbiota and their generated metabolites impact the host vascular phenotype. The metaorganismal metabolite trimethylamine N-oxide (TMAO) is both associated with adverse clinical thromboembolic events, and enhances platelet responsiveness in subjects. The impact of TMAO on vascular Tissue Factor (TF) in vivo is unknown. Here, we explore whether TMAO-enhanced thrombosis potential extends beyond TMAO effects on platelets, and is linked to TF. We also further explore the links between gut microbiota and vascular endothelial TF expression in vivo.

METHODS AND RESULTS

In initial exploratory clinical studies, we observed that among sequential stable subjects (n = 2989) on anti-platelet therapy undergoing elective diagnostic cardiovascular evaluation at a single-site referral centre, TMAO levels were associated with an increased incident (3 years) risk for major adverse cardiovascular events (MACE) (myocardial infarction, stroke, or death) [4th quartile (Q4) vs. Q1 adjusted hazard ratio (HR) 95% confidence interval (95% CI), 1.73 (1.25-2.38)]. Similar results were observed within subjects on aspirin mono-therapy during follow-up [adjusted HR (95% CI) 1.75 (1.25-2.44), n = 2793]. Leveraging access to a second higher risk cohort with previously reported TMAO data and monitoring of anti-platelet medication use, we also observed a strong association between TMAO and incident (1 year) MACE risk in the multi-site Swiss Acute Coronary Syndromes Cohort, focusing on the subset (n = 1469) on chronic dual anti-platelet therapy during follow-up [adjusted HR (95% CI) 1.70 (1.08-2.69)]. These collective clinical data suggest that the thrombosis-associated effects of TMAO may be mediated by cells/factors that are not inhibited by anti-platelet therapy. To test this, we first observed in human microvascular endothelial cells that TMAO dose-dependently induced expression of TF and vascular cell adhesion molecule (VCAM)1. In mouse studies, we observed that TMAO-enhanced aortic TF and VCAM1 mRNA and protein expression, which upon immunolocalization studies, was shown to co-localize with vascular endothelial cells. Finally, in arterial injury mouse models, TMAO-dependent enhancement of in vivo TF expression and thrombogenicity were abrogated by either a TF-inhibitory antibody or a mechanism-based microbial choline TMA-lyase inhibitor (fluoromethylcholine).

CONCLUSION

Endothelial TF contributes to TMAO-related arterial thrombosis potential, and can be specifically blocked by targeted non-lethal inhibition of gut microbial choline TMA-lyase.

Trimethylamine/Trimethylamine-N-Oxide as a Key Between Diet and Cardiovascular Diseases

Trimethylamine (TMA) is a gut microbiota-derived metabolite which comes from diets rich of choline, betaine or L-carnitine and could be further converted to Trimethylamine-N-oxide (TMAO) in the liver. As the function of gut microbiota and its metabolites being explored so far, studies suggest that TMAO may be a potential risk factor of cardiovascular diseases independent of other traditional risk factors. However, the precise role of TMAO is controversial as some converse results were discovered. In recent studies, it is hypothesized that TMA may also participate in the progression of cardiovascular diseases and some cytotoxic effect of TMA has been discovered. Thus, exploring the relationship between TMA, TMAO and CVD may bring a novel insight into the diagnosis and therapy of cardiovascular diseases. In this review, we discussed the factors which influence the TMA/TMAO's process of metabolism in the human body. We have also summarized the pathogenic effect of TMA/TMAO in cardiovascular diseases, as well as the limitation of some controversial discoveries.

Gut-microbe derived TMAO and its association with more progressed forms of AF: Results from the AF-RISK study

Introduction

The importance of gut microbiome in cardiovascular disease has been increasingly recognized. Trimethylamine N-oxide (TMAO) is a gut microbe-derived metabolite that is associated with cardiovascular disease, including atrial fibrillation (AF). The role of TMAO in clinical AF progression however remains unknown.

Methods and results

In this study we measured TMAO and its precursor (betaine, choline, and L- carnitine) levels in 78 patients using plasma samples from patients that participated in the AF-RISK study. 56 patients suffered from paroxysmal AF and 22 had a short history of persistent AF. TMAO levels were significantly higher in patients with persistent AF, as compared to those with paroxysmal AF (median [IQR] 5.65 [4.7–9.6] m/z versus 4.31 [3.2–6.2] m/z, p < 0.05), while precursor levels did not differ. In univariate analysis, we observed that for every unit increase in TMAO, the odds for having persistent AF increased with 0.44 [0.14–0.73], p < 0.01. Conclusion: These results suggest that higher levels of TMAO are associated with more progressed forms of AF. We therefore hypothesize that increased TMAO levels may reflect disease progression in humans. Larger studies are required to validate these preliminary findings.

Trial Registration number: Clinicaltrials.gov NCT01510210.

Gut microbiota in coronary artery disease: a friend or foe?

There is a growing interest in the role of gut microbiota in the pathophysiology of several diseases, including coronary artery diseases (CAD). Gut microorganisms may produce beneficial effects in myocardial ischemia either directly in the form of exogenous administration or indirectly by acting on fiber-rich food to produce important cardioprotective components. The harmful effects of gut microbiota in CAD are due to alteration in their composition with a significant decrease in Bacteroidetes and an increase in Firmicutes, Escherichia, Shigella, and Enterococcus. The altered microbiota may produce potentially toxic metabolites, including trimethylamine-N-oxide (TMAO). Indeed, the fasting plasma levels of TMAO are directly correlated to increased risk of major cardiovascular events in CAD patients, and it is proposed as a potential biomarker to predict the onset of major cardiovascular events. It is concluded that the change in the composition of gut microbiota in CAD patients may predispose to more harmful effects. However, exogenous delivery of probiotics may overcome the detrimental effects of myocardial ischemia.

Association of Trimethylamine N-Oxide Levels and Calcification in Culprit Lesion Segments in Patients With ST-Segment-Elevation Myocardial Infarction Evaluated by Optical Coherence Tomography

The presence of calcified plaques is one of the pathological phenotypes of acute coronary syndrome (ACS) and can be frequently found in culprit lesion segments. Trimethylamine N-oxide (TMAO) is reported to be involved in vascular calcification and plaque instability. This study investigated the relationship between plasma TMAO levels and calcified lesions in culprit lesion segments in STEMI patients. A prospective series of 179 patients with STEMI were enrolled, and calcified lesions from 127 patients were analyzed by OCT. The plasma TMAO levels were measured by using stable isotope dilution liquid chromatography tandem mass spectrometry. Patients were divided into two groups according to the median plasma TMAO level. The prevalence of intimal calcified lesions in the high TMAO group was significantly higher than that in the low TMAO group (90.6 vs. 57.1%, p < 0.001; 84.4 vs. 44.4%, p < 0.001). After adjustment of traditional risk factors and medication history, patients with calcification in their culprit lesion segments had higher plasma TMAO levels than those without calcification. Moreover, plasma TMAO levels were significantly positively associated with the parameters of calcium burden, including maximal calcification arc (r = 0.392, p < 0.001), maximal calcification thickness (r = 0.443, p < 0.001), and calcified length (r = 0.466, p < 0.001). These results suggested that the level of TMAO is significantly correlated with the incidence of calcification in the culprit lesion segment, and the measurement of TMAO levels might improve clinical management in patients with heavy calcification. Clinical Trial Registration: This study is registered at ClinicalTrials.gov as NCT03593928.

Plasma levels of trimethylamine-N-oxide can be increased with 'healthy' and 'unhealthy' diets and do not correlate with the extent of atherosclerosis but with plaque instability

AIMS

The microbiome-derived metabolite trimethylamine-N-oxide (TMAO) has attracted major interest and controversy both as a diagnostic biomarker and therapeutic target in atherothrombosis.

METHODS AND RESULTS

Plasma TMAO increased in mice on 'unhealthy' high-choline diets and notably also on 'healthy' high-fibre diets. Interestingly, TMAO was found to be generated by direct oxidation in the gut in addition to oxidation by hepatic flavin-monooxygenases. Unexpectedly, two well-accepted mouse models of atherosclerosis, ApoE-/- and Ldlr-/- mice, which reflect the development of stable atherosclerosis, showed no association of TMAO with the extent of atherosclerosis. This finding was validated in the Framingham Heart Study showing no correlation between plasma TMAO and coronary artery calcium score or carotid intima-media thickness (IMT), as measures of atherosclerosis in human subjects. However, in the tandem-stenosis mouse model, which reflects plaque instability as typically seen in patients, TMAO levels correlated with several characteristics of plaque instability, such as markers of inflammation, platelet activation, and intraplaque haemorrhage.

CONCLUSIONS

Dietary-induced changes in the microbiome, of both 'healthy' and 'unhealthy' diets, can cause an increase in the plasma level of TMAO. The gut itself is a site of significant oxidative production of TMAO. Most importantly, our findings reconcile contradictory data on TMAO. There was no direct association of plasma TMAO and the extent of atherosclerosis, both in mice and humans. However, using a mouse model of plaque instability we demonstrated an association of TMAO plasma levels with atherosclerotic plaque instability. The latter confirms TMAO as being a marker of cardiovascular risk.

Trimethylamine N-Oxide Was Not Associated With 30-Day Left Ventricular Systolic Dysfunction in Patients With a First Anterior ST-Segment Elevation Myocardial Infarction After Primary Revascularization: A Sub-analysis From an Optical Coherence Tomography Registry

Objective: Left ventricular systolic dysfunction (LVSD) after ST-segment elevation myocardial infarction (STEMI) is associated with poor outcome. Trimethylamine N-oxide (TMAO), a gut metabolite, is linked to cardiovascular diseases but its relationship with LVSD after STEMI remains unclear. The present study therefore aimed to investigate the relationship between TMAO and LVSD at 30 days after a first anterior STEMI.

Methods: This was a sub-study from the OCTAMI (Optical Coherence Tomography Examination in Acute Myocardial Infarction) registry. Eligible patients were included in current study if they: (1) presented with a first anterior STEMI; (2) had available baseline TMAO concentration; (3) completed a cardiovascular magnetic resonance examination at 30 days after STEMI. LVSD was defined as left ventricular ejection fraction < 50%. Associations between TMAO and left ventricular ejection fraction, infarct size and left ventricular global strain were examined.

Results: In total, 78 patients were included in final analysis. Overall, TMAO was moderately associated with peak cTnI (r = 0.27, p = 0.01), age (r = 0.34, p < 0.01), and estimated glomerular filtration rate (r = −0.30, p < 0.01). At 30-day follow-up, 41 patients were in the LVSD group and 37 in the non-LVSD group. Baseline TMAO levels were not significantly different between the two groups (LVSD vs. non-LVSD: median 1.9 μM, 25−75th percentiles 1.5–3.3 μM vs. median 1.9 μM, 25−75th percentiles 1.5–2.7 μM; p = 0.46). Linear regression analyses showed that TMAO was not associated with left ventricular ejection fraction, infarct size or left ventricular global strain at 30 days (all p > 0.05).

Conclusions: TMAO was not significantly correlated with 30-day LVSD in patients with a first anterior STEMI after primary revascularization.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03593928.

Novel insights in the relationship of gut microbiota and coronary artery diseases

Atherosclerosis is a chronic, progressive, inflammatory disease in the vasculature and is common in both coronary and peripheral arteries. Human beings harbor a complex and dynamic population of microorganisms defined as the microbiota. Importantly, alterations in the bacterial composition (dysbiosis) and the metabolic compounds produced by these bacteria have been associated with the pathogenesis of many inflammatory diseases and infections. There is also a close relationship between intestinal microbiota and cardiovascular diseases. The aim of this review was to analyze how changes in the gut microbiota and their metabolites might affect coronary artery diseases. The most representative groups of bacteria that make up the intestinal microbiota are altered in coronary artery disease patients, resulting in a decrease in Bacteroidetes and an increase in Firmicutes. In relation to metabolites, trimethylamine-N-oxide plays an important role in atherosclerosis and may act as a cardiovascular risk predictor. In addition, the use of probiotics, prebiotics, diet modulation, and fecal transplantation, which may represent alternative treatments for these diseases, is thoroughly discussed. Finally, the role of lipid-lowering treatments is also analyzed as they may affect and alter the gut microbiota and, conversely, gut microbiota diversity could be associated with resistance or sensitivity to these treatments.

Association of plasma trimethylamine N-Oxide level with healed culprit plaques examined by optical coherence tomography in patients with ST-Segment elevation myocardial infarction

BACKGROUND AND AIMS

Healed plaque is a hallmark of previous regional plaque rupture or erosion. We hypothesized that the plasma level of trimethylamine N-oxide (TMAO) is related to healed culprit plaque in ST-segment elevation myocardial infarction (STEMI) patients.

METHODS AND RESULTS

A prospective cohort of 206 patients with STEMI, who were examined by optical coherence tomography (OCT) was enrolled in our study. After exclusion, 156 patients were categorized into healed plaque (n = 54) and nonhealed plaque (n = 102) groups. Plasma TMAO levels were detected by stable isotope dilution liquid chromatography tandem mass spectrometry in these two groups. Increased age and low BMI were more common in patients with healed plaques than in those without healed plaques. Through OCT observation, plaque rupture (81.5% vs. 45.1%, p < 0.001), thin cap fibroatheroma (TCFA) and macrophages (42.6% vs. 20.6%, p = 0.004, 70.4% vs. 26.5%, p < 0.001, respectively) were more frequently seen in patients with healed plaques than in those without healed plaques. The TMAO level in patients with healed plaques was significantly higher than that in patients with nonhealed plaques (3.9 μM [2.6-5.1] vs. 1.8 μM [1.0-2.7], p < 0.001). Furthermore, the receiver operating characteristic curve showed that TMAO can be used as a potential biomarker to predict healed plaque presence with a cutoff value of 2.9 μM (AUC = 0.810, sensitivity: 72.2%, specificity: 81.4%).

CONCLUSIONS

Healed plaque in STEMI patients is associated with a high level of plaque vulnerability and inflammation. A high level of plasma TMAO can be a useful biomarker to differentiate STEMI patients with healed culprit plaques.

Gut microbiota–associated trimethylamine N-oxide and increased cardiometabolic risk in adults: a systematic review and dose-response meta-analysis

Context

Several studies suggest a relationship between trimethylamine N-oxide (TMAO) concentrations and increased cardiometabolic risk, but findings are controversial.

Objective

The aim of this systematic review and meta-analysis was to summarize evidence of the relationship between circulating TMAO levels and risk of hypertension and increased serum lipids in a dose-response and 2-class meta-analysis of discrete and continuous variables.

Data Sources

PubMed, Scopus, Cochrane, and ProQuest databases were searched.

Study Selection

Observational studies that reported disease status of participants (≥ 18 years), type of sample in which TMAO was measured (serum or plasma), and results based on at least 2 categories of TMAO concentrations, including relative risks, hazard ratios, or odds ratios with 95%CIs for cardiometabolic risk factors in association with circulating TMAO levels were selected. Papers were reviewed independently by both authors. The Newcastle-Ottawa Scale was used to assess the quality of included studies.

Data Extraction

The following data were extracted: first author’s name, publication year, study design, study location, demographic information of participants, and concentrations of circulating TMAO.

Results

Eighteen studies were included in the meta-analysis. There was a dose-response relationship between circulating TMAO and increased odds of hypertension in cohort studies (P  for nonlinearity = 0.049), in plasma-derived TMAO samples (P  for nonlinearity = 0.043), in patients with cardiovascular disease (P  for nonlinearity = 0.048), and in apparently healthy individuals from community-based studies (P  for nonlinearity = 0.005). Moreover, the highest category of TMAO concentrations was associated with a 2.36 mmHg increase in systolic blood pressure when compared with the lowest category. The dose-response meta-analysis of continuous variables revealed that an increase in TMAO is associated with reduced high-density lipoprotein cholesterol in apparently healthy individuals and reduced high-density lipoprotein cholesterol and increased total cholesterol in patients with cardiovascular disease.

Conclusions

Circulating TMAO is positively associated with an increased risk of hypertension and other cardiometabolic disorders in adults.

Systematic Review Registration

PROSPERO identification number CRD42019138296.

Involvement of Gut Microbiota, Microbial Metabolites and Interaction with Polyphenol in Host Immunometabolism

Immunological and metabolic processes are inextricably linked and important for maintaining tissue and organismal health. Manipulation of cellular metabolism could be beneficial to immunity and prevent metabolic and degenerative diseases including obesity, diabetes, and cancer. Maintenance of a normal metabolism depends on symbiotic consortium of gut microbes. Gut microbiota contributes to certain xenobiotic metabolisms and bioactive metabolites production. Gut microbiota-derived metabolites have been shown to be involved in inflammatory activation of macrophages and contribute to metabolic diseases. Recent studies have focused on how nutrients affect immunometabolism. Polyphenols, the secondary metabolites of plants, are presented in many foods and beverages. Several studies have demonstrated the antioxidant and anti-inflammatory properties of polyphenols. Many clinical trials and epidemiological studies have also shown that long-term consumption of polyphenol-rich diet protects against chronic metabolic diseases. It is known that polyphenols can modulate the composition of core gut microbiota and interact with the immunometabolism. In the present article, we review the mechanisms of gut microbiota and its metabolites on immunometabolism, summarize recent findings on how the interaction between microbiota and polyphenol modulates host immunometabolism, and discuss future research directions.

Long-Term Changes in Gut Microbial Metabolite Trimethylamine N-Oxide and Coronary Heart Disease Risk

BACKGROUND

A gut-microbial metabolite, trimethylamine N-oxide (TMAO), has been associated with coronary atherosclerotic burden. No previous prospective study has addressed associations of long-term changes in TMAO with coronary heart disease (CHD) incidence.

OBJECTIVES

The purpose of this study was to investigate whether 10-year changes in plasma TMAO levels were significantly associated with CHD incidence.

METHODS

This prospective nested case-control study included 760 healthy women at baseline. Plasma TMAO levels were measured both at the first (1989 to 1990) and the second (2000 to 2002) blood collections; 10-year changes (Δ) in TMAO were calculated. Incident cases of CHD (n = 380) were identified after the second blood collection through 2016 and were matched to controls (n = 380).

RESULTS

Regardless of the initial TMAO levels, 10-year increases in TMAO from the first to second blood collection were significantly associated with an increased risk of CHD (relative risk [RR] in the top tertile: 1.58 [95% confidence interval (CI): 1.05 to 2.38]; RR per 1-SD increment: 1.33 [95% CI: 1.06 to 1.67]). Participants with elevated TMAO levels (the top tertile) at both time points showed the highest RR of 1.79 (95% CI: 1.08 to 2.96) for CHD as compared with those with consistently low TMAO levels. Further, we found that the ΔTMAO-CHD relationship was strengthened by unhealthy dietary patterns (assessed by the Alternate Healthy Eating Index) and was attenuated by healthy dietary patterns (p interaction = 0.008).

CONCLUSIONS

Long-term increases in TMAO were associated with higher CHD risk, and repeated assessment of TMAO over 10 years improved the identification of people with a higher risk of CHD. Diet may modify the associations of ΔTMAO with CHD risk.

The Association between Trimethylamine N-Oxide and Its Predecessors Choline, L-Carnitine, and Betaine with Coronary Artery Disease and Artery Stenosis

Background

Trimethylamine N-oxide (TMAO) and its predecessor products, choline, L-carnitine, and betaine, were reported to be associated with cardiovascular events risk. However, the association of TMAO and its predecessors with extent of artery stenosis in coronary artery disease (CAD) and in different gender is still unknown. Our aim is to investigate the association of plasma TMAO and its predecessors in CAD and extent of artery lesion in different gender.

Methods

94 CAD patients and 75 healthy controls (CON) were enrolled. Fasting plasma TMAO, choline, L-carnitine, and betaine were detected using liquid chromatography-tandem mass spectrometry.

Results

Elevated plasma TMAO but not choline, L-carnitine, or betaine was observed in CAD (1.46(0.8–2.32) μM) and severe artery stenosis patients (S) (1.62(0.91–2.81) μM) compared with controls and mild artery stenosis (M) (1.18(0.67–1.7) μM in CON; 1.27(0.77–1.82) μM in M, p < 0.05). TMAO was an independent risk factor of CAD and severe artery stenosis (CAD : OR = 1.81, 95%CI: 1.07–3.09, p=0.03; S : OR = 1.36, 95%CI: 1.01–1.84, p=0.04). TMAO was more sensitive in diagnosing CAD and severe artery stenosis from controls in men rather than in women by ROC analysis (AUC for men and women in CAD: 0.64 versus 0.57; AUC for men and women in S: 0.64 versus 0.58), while the combined four metabolites greatly improved diagnostic accuracy in women with CAD and severe artery stenosis (AUC in CAD: 0.64, AUC in S: 0.68).

Conclusion

The associations of TMAO with CAD and severe artery stenosis were sex-related. TMAO alone was more powerful in determining CAD and artery stenosis in men than women, while a combination of TMAO, choline, L-carnitine, and betaine could be potential biomarkers for diagnosing CAD and artery stenosis in both men and women.

Metabolic Profiling of Blood and Urine for Exploring the Functional Role of the Microbiota in Human Health

The quantification of metabolites in blood and urine allows nurses to explore new hypotheses about the microbiome. This review summarizes findings from recent studies with a focus on how the state of the science can influence future nursing research initiatives. Metabolomics can advance nursing research by identifying physiologic/pathophysiologic processes underlying patients' symptoms and can be useful for testing the effects of nursing interventions. To date, metabolomics has been used to study cardiovascular, respiratory, endocrine, autoimmune, and infectious conditions, with research focused on understanding the microbial metabolism of substrates resulting in circulating/excreted biomarkers such as trimethylamine N-oxide. This review provides specific recommendations for the collection of specimens and goals for future studies.

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.

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.

The Gut Microbial Metabolite Trimethylamine N-Oxide and Hypertension Risk: A Systematic Review and Dose-Response Meta-analysis

The gut microbial metabolite trimethylamine N-oxide (TMAO) is increasingly regarded as a novel risk factor for cardiovascular events and mortality. However, little is known about the association between TMAO and hypertension. This meta-analysis was conducted to quantitatively assess the relation between the circulating TMAO concentration and hypertension prevalence. The PubMed, Cochrane Library, and Embase databases were systematically searched up to 17 June 2018. Studies recording the hypertension prevalence in members of a given population and their circulating TMAO concentrations were included. A total of 8 studies with 11,750 individuals and 6176 hypertensive cases were included in the analytic synthesis. Compared with low circulating TMAO concentrations, high TMAO concentrations were correlated with a higher prevalence of hypertension (RR: 1.12; 95% CI: 1.06, 1.17; P < 0.0001; I2 = 64%; P-heterogeneity = 0.007; random-effects model). Consistent results were obtained in all examined subgroups as well as in the sensitivity analysis. The RR for hypertension prevalence increased by 9% per 5-μmol/L increment (RR: 1.09; 95% CI: 1.05, 1.14; P < 0.0001) and 20% per 10-μmol/L increment of circulating TMAO concentration (RR: 1.20; 95% CI: 1.11, 1.30; P < 0.0001) according to the dose-response meta-analysis. To our knowledge, this is the first systematic review and meta-analysis demonstrating a significant positive dose-dependent association between circulating TMAO concentrations and hypertension risk.

The Microbial Metabolite Trimethylamine N-Oxide Links Vascular Dysfunctions and the Autoimmune Disease Rheumatoid Arthritis

Diet and microbiota each have a direct impact on many chronic, inflammatory, and metabolic diseases. As the field develops, a new perspective is emerging. The effects of diet may depend on the microbiota composition of the intestine. A diet that is rich in choline, red meat, dairy, or egg may promote the growth, or change the composition, of microbial species. The microbiota, in turn, may produce metabolites that increase the risk of cardiovascular disease. This article reviews our current understanding of the effects of the molecule trimethylamine-N-oxide (TMAO) obtained from food or produced by the microbiota. We review the mechanisms of actions of TMAO, and studies that associate it with cardiovascular and chronic kidney diseases. We introduce a novel concept: TMAO is one among a group of selective uremic toxins that may rise to high levels in the circulation or accumulate in various organs. Based on this information, we evaluate how TMAO may harm, by exacerbating inflammation, or may protect, by attenuating amyloid formation, in autoimmune diseases such as rheumatoid arthritis.

Is increased plasma TMAO a compensatory response to hydrostatic and osmotic stress in cardiovascular diseases?

Recent clinical studies show a positive correlation between elevated plasma TMAO and increased cardiovascular risk. However, the mechanism of the increase and biological effects of TMAO in the circulatory system are obscure. Plasma TMAO level depends mostly on the following three factors. First, the liver produces TMAO from TMA, a gut bacteria metabolite of dietary choline and carnitine. Second, plasma TMAO increases after ingestion of dietary TMAO from fish and seafood. Finally, plasma TMAO depends on TMAO and TMA excretion by the kidneys. Ample evidence highlights protective functions of TMAO, including the stabilization of proteins and cells exposed to hydrostatic and osmotic stresses, for example in fish exposed to hydrostatic stress (deep water) and osmotic stress (salty water). Osmotic stress and hydrostatic stresses are augmented in cardiovascular diseases such as hypertension. In hypertensive subjects a diastole-systole change in hydrostatic pressure in the heart may exceed 220 mmHg with a frequency of 60-220/min. This produces environment in which hydrostatic pressure changes over 100,000 times per 24 h. Furthermore, cardiovascular diseases are associated with disturbances in water-electrolyte balance which produce changes in plasma osmolarity. Perhaps, the increase in plasma TMAO in cardiovascular diseases is analogous to increased level of plasma natriuretic peptide B, which is both a cardiovascular risk marker and a compensatory response producing beneficial effects for pressure/volume overloaded heart. In this regard, there is some evidence that a moderate increase in plasma TMAO due to TMAO supplementation may be beneficial in animal model of hypertension-related heart failure. Finally, increased plasma TMAO is present in humans consuming seafood-rich diet which is thought to be health-beneficial. We hypothesize that increased plasma TMAO serves as a compensatory response mechanism which protects cells from hydrostatic and osmotic stresses.

Gut microbe-generated metabolite trimethylamine N-oxide and the risk of diabetes: A systematic review and dose-response meta-analysis

Elevated circulating concentrations of the gut bacteria choline metabolite trimethylamine N-oxide (TMAO) were found in patients with type 2 diabetes mellitus (T2DM). However, whether a high level of TMAO is related to the risk of diabetes has not been studied. We aimed to synthesize the evidence on the relation between TMAO levels and the risk of diabetes mellitus (DM) and to investigate the association further in a dose-response meta-analysis. PubMed, Web of Science, and Scopus databases were searched for studies from inception to June 2018. A total of 12 clinical studies were included in this study, and 15 314 enrolled subjects were included. A meta-analysis of two-class variables and continuous variables were used to obtain pooled effects. Dose-response meta-analysis was used to investigate the dose-response relationship between TMAO concentrations and the risk of DM. Meta-regression and subgroup analyses were applied to identify the source of heterogeneity in this study. High levels of circulating TMAO were associated with an increased risk of DM (odds ratio [OR] = 1.89) using the two-class meta-analysis. Plasma levels of TMAO in patients with diabetes were higher than in subjects without diabetes (standardized mean difference [SMD]: 0.36) using a meta-analysis of continuous variables. The OR for DM prevalence increased by 54% per 5 μmol L^-1 increment of plasma TMAO (OR = 1.54) according to the dose-response meta-analysis. This is the first systematic review and meta-analysis to demonstrate a positive dose-dependent association between circulating TMAO levels and increased diabetes risk.

Relation of Circulating Trimethylamine N-Oxide With Coronary Atherosclerotic Burden in Patients With ST-segment Elevation Myocardial Infarction

The gut microbial metabolite trimethylamine N-oxide (TMAO) promotes atherosclerosis and cardiovascular diseases. TMAO levels are associated with the coronary atherosclerotic burden in patients with stable coronary artery disease. However, the relation between TMAO levels and the coronary atherosclerotic burden in patients with ST-segment elevation myocardial infarction (STEMI) is unknown. We prospectively enrolled 2 cohorts in this study, including 335 patients with STEMI and 53 healthy controls. The coronary atherosclerotic burden was quantified by the number of diseased coronary arteries and the SYNTAX score. The median TMAO levels in patients with STEMI and healthy controls were 2.18 (interquartile range [IQR]: 1.34 to 3.90) μM and 1.23 [IQR: 0.84 to 2.42] μM, respectively. Of the 335 patients with STEMI, TMAO levels were significantly higher in the multivessel disease group than in the single-vessel disease group (p <0.001) and in the group with intermediate-high SYNTAX scores (SYNTAX score ≥23) than in the group with low SYNTAX scores (SYNTAX score ≤22; p <0.001). Based on the ordinal logistic regression analysis adjusted for traditional risk factors, elevated TMAO levels predicted both a high SYNTAX score (adjusted odds ratio [OR]: 1.16; 95% confidence interval [CI] 1.06 to 1.29; p = 0.001) and the presence of multivessel disease (adjusted OR: 1.15; 95% CI 1.01 to 1.32; p = 0.035). In conclusion, plasma TMAO levels are associated with a high coronary atherosclerotic burden in patients with STEMI.

Application of optical coherence tomography in clinical diagnosis

BACKGROUND

Optical coherence tomography (OCT) is a non-invasive diagnosing tool used in clinics. Due to its high resolution (<10um), it is appropriate for the early detection of tiny infections. It has been widely used in diagnosis and treatment of diseases, evaluation of therapeutic efficacy, and monitoring of various physiological and pathological processes.

OBJECTIVE

To systemically review literature to summarize the clinic application of OCT in recent years.

METHODS

For clinic applications that OCT has been applied, we selected studies that describe the most relevant works. The discussion included: 1) which tissue could be used in the OCT detection, 2) which character of different tissue could be used as diagnosing criteria, 3) which diseases and pathological process have been diagnosed or monitored using OCT imaging, and 4) the recent development of clinic OCT diagnosing.

RESULTS

The literature showed that the OCT had been listed as a routine test choice for ophthalmic diseases, while the first commercial product for cardiovascular OCT detection had gotten clearance. Meanwhile, as the development of commercial benchtop OCT equipment and tiny fiber probe, the commercial application of OCT in dermatology, dentistry, gastroenterology and urology also had great potential in the near future.

CONCLUSIONS

The analysis and discussions showed that OCT, as an optical diagnosing method, has been used successfully in many clinical fields, and has the potential to be a standard inspection method in several clinic fields, such as dermatology, dentistry and cardiovascular.