The Relationship Between Trimethylamine-N-Oxide and Prevalent Cardiovascular Disease in a Multiethnic Population Living in Canada

Plasma Concentrations of Trimethylamine-N-Oxide, Choline, and Betaine in Patients With Moderate to Advanced Chronic Kidney Disease and Their Relation to Cardiovascular and Renal Outcomes

OBJECTIVES

Trimethylamine N-oxide (TMAO) is a gut bacteria-mediated liver metabolite of dietary betaine, choline, and carnitine, which is excreted by glomerular filtration. We studied whether TMAO is excreted by cardiovascular disease (CVD) in patients with chronic kidney disease (CKD).

METHODS

Among 478 patients with CKD stage G2 (n = 104), G3a (n = 163), G3b (n = 123), and G4 (n = 88), we studied the association between fasting plasma concentrations of TMAO, choline, or betaine at baseline and kidney function, prevalent CVD, and future renal outcomes during a mean follow-up of 5.1 years.

RESULTS

Decreased glomerular filtration rate was associated with higher plasma concentrations of TMAO, choline, and betaine. Baseline concentrations of TMAO were higher in participants with preexisting CVD compared to those without CVD (8.4 [10.1] vs. 7.8 [8.0] μmol/L; P = .047), but the difference was not significant after adjusting for confounders. During the follow-up, 147 participants experienced CVD or died, and 144 reached the predefined renal endpoint. In the adjusted regression analyses, TMAO or choline concentrations in the upper three quartiles (vs. the lowest quartile) were not associated with any of the study's clinical endpoints. In contrast, the adjusted hazard ratio of plasma betaine in the highest quartile versus the lowest quartile was 2.14 (1.32, 3.47) for the CVD endpoint and 1.64 (1.00, 2.67) for the renal endpoint.

CONCLUSIONS

Elevated plasma TMAO concentrations were explained by impaired kidney function. Elevated plasma concentrations of betaine, but not those of TMAO or choline, constituted a risk factor for adverse outcomes. TMAO might not be an appropriate target to reduce CVD or renal outcomes in patients with preexisting CKD.

Choline consumption reduces CVD risk via body composition modification

Despite extensive research on the relationship between choline and cardiovascular disease (CVD), conflicting findings have been reported. We aim to investigate the relationship between choline and CVD. Our analysis screened a retrospective cohort study of 14,663 participants from the National Health and Nutrition Examination Survey conducted between 2013 and 2018. Propensity score matching and restricted cubic splines was used to access the association between choline intake and the risk of CVD. A two-sample Mendelian randomization (MR) analysis was conducted to examine the potential causality. Additionally, sets of single cell RNA-sequencing data were extracted and analyzed, in order to explore the role of choline metabolism pathway in the progression and severity of the CVD and the underlying potential mechanisms involved. The adjusted odds ratios and 95% confidence intervals for stroke were 0.72 (0.53-0.98; p = 0.035) for quartile 3 and 0.54 (0.39-0.75; p < 0.001) for quartile 4. A stratified analysis revealed that the relationship between choline intake and stroke varied among different body mass index and waist circumference groups. The results of MR analysis showed that choline and phosphatidylcholine had a predominantly negative causal effect on fat percentage, fat mass, and fat-free mass, while glycine had opposite effects. Results from bioinformatics analysis revealed that alterations in the choline metabolism pathway following stroke may be associated with the prognosis. Our study indicated that the consumption of an appropriate quantity of choline in the diet may help to protect against CVD and the effect may be choline-mediated, resulting in a healthier body composition. Furthermore, the regulation of the choline metabolism pathway following stroke may be a promising therapeutic target.

Gut microbiota and metabolic biomarkers in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD), a replacement of the nomenclature employed for NAFLD, is the most prevalent chronic liver disease worldwide. Despite its high global prevalence, NAFLD is often under-recognized due to the absence of reliable noninvasive biomarkers for diagnosis and staging. Growing evidence suggests that the gut microbiome plays a significant role in the occurrence and progression of NAFLD by causing immune dysregulation and metabolic alterations due to gut dysbiosis. The rapid advancement of sequencing tools and metabolomics has enabled the identification of alterations in microbiome signatures and gut microbiota-derived metabolite profiles in numerous clinical studies related to NAFLD. Overall, these studies have shown a decrease in α-diversity and changes in gut microbiota abundance, characterized by increased levels of Escherichia and Prevotella, and decreased levels of Akkermansia muciniphila and Faecalibacterium in patients with NAFLD. Furthermore, bile acids, short-chain fatty acids, trimethylamine N-oxide, and tryptophan metabolites are believed to be closely associated with the onset and progression of NAFLD. In this review, we provide novel insights into the vital role of gut microbiome in the pathogenesis of NAFLD. Specifically, we summarize the major classes of gut microbiota and metabolic biomarkers in NAFLD, thereby highlighting the links between specific bacterial species and certain gut microbiota-derived metabolites in patients with NAFLD.

Choline - a scoping review for Nordic Nutrition Recommendations 2023

Choline is an essential nutrient with metabolic roles as a methyl donor in one carbon metabolism and as a precursor for membrane phospholipids and the neurotransmitter acetylcholine. Choline content is particularly high in liver, eggs, and wheat germ, although it is present in a variety of foods. The main dietary sources of choline in the Nordic and Baltic countries are meat, dairy, eggs, and grain. A diet that is devoid of choline causes liver and muscle dysfunction within 3 weeks. Choline requirements are higher during pregnancy and lactation than in non-pregnant women. Although no randomized controlled trials are available, observational studies in human, supported by coherence from interventional studies with neurodevelopmental outcomes and experimental studies in animals, strongly suggest that sufficient intake of choline during pregnancy is necessary for normal brain development and function in the child. Observational studies suggested that adequate intake of choline could have positive effects on cognitive function in older people. However, prospective data are lacking, and no intervention studies are available in the elderly.

Significant correlation between the gut microbiota-derived metabolite trimethylamine-N-oxide and the risk of stroke: evidence based on 23 observational studies

The gut microbiota-derived metabolite trimethylamine-N-oxide (TMAO) is regarded as a major risk factor for cardiovascular events and diabetes. However, the association of TMAO with stroke has yet to be fully elucidated. The present meta-analysis was conducted to explore the association between TMAO and stroke. The present meta-analysis quantitatively summarized the results of studies that investigated the association between TMAO and stroke. The PubMed, Embase, Cochrane Library and Web of Science databases were systematically searched from January 1, 2001 to June 1, 2021. All studies that evaluated the association between TMAO and stroke were included in the present systematic review. The present meta-analysis included 30,808 participants and revealed that being in the higher TMAO category increased the odds of stroke by 68% (OR 1.83; 95% CI 1.02-3.29; P = 0.04), and that the mean TMAO concentration in stroke patients was 2.20 μmol/L higher than that of non-stroke controls (MD 2.20; 95% CI 1.23-3.16; P < 0.00001). In addition, TMAO plasma levels was associated with the risk of all-cause mortality, with a pooled HR of 1.89 (95% CI 1.15-3.08; P = 0.01). Both univariate analysis (UVA) and multivariate analysis (MVA) indicated that high TMAO levels significantly increased the risk of major adverse cardiovascular events (MACEs), with pooled RRs of 2.26 (95% CI 2.01-2.54; P < 0.00001) with UVA and 1.55 (95% CI 1.17-2.05; P = 0.002) with MVA respectively. In the current meta-analysis we revealed the positive association between circulating TMAO and stroke. Higher TMAO levels increased the risk of stroke and stroke patients experienced higher mean TMAO concentration. In addition, high TMAO plasma level was one of independent risk factors of MACEs and was associated with all-cause mortality.

The Impact of Semicarbazide Sensitive Amine Oxidase Activity on Rat Aortic Vascular Smooth Muscle Cells

Semicarbazide-sensitive amine oxidase (SSAO) is both a soluble- and membrane-bound transmembrane protein expressed in the vascular endothelial and in smooth muscle cells. In vascular endothelial cells, SSAO contributes to the development of atherosclerosis by mediating a leukocyte adhesion cascade; however, its contributory role in the development of atherosclerosis in VSMCs has not yet been fully explored. This study investigates SSAO enzymatic activity in VSMCs using methylamine and aminoacetone as model substrates. The study also addresses the mechanism by which SSAO catalytic activity causes vascular damage, and further evaluates the contribution of SSAO in oxidative stress formation in the vascular wall. SSAO demonstrated higher affinity for aminoacetone when compared to methylamine (Km = 12.08 µM vs. 65.35 µM). Aminoacetone- and methylamine-induced VSMCs death at concentrations of 50 & 1000 µM, and their cytotoxic effect, was reversed with 100 µM of the irreversible SSAO inhibitor MDL72527, which completely abolished cell death. Cytotoxic effects were also observed after 24 h of exposure to formaldehyde, methylglyoxal and H2O2. Enhanced cytotoxicity was detected after the simultaneous addition of formaldehyde and H2O2, as well as methylglyoxal and H2O2. The highest ROS production was observed in aminoacetone- and benzylamine-treated cells. MDL72527 abolished ROS in benzylamine-, methylamine- and aminoacetone-treated cells (**** p < 0.0001), while βAPN demonstrated inhibitory potential only in benzylamine-treated cells (* p < 0.05). Treatment with benzylamine, methylamine and aminoacetone reduced the total GSH levels (**** p < 0.0001); the addition of MDL72527 and βAPN failed to reverse this effect. Overall, a cytotoxic consequence of SSAO catalytic activity was observed in cultured VSMCs where SSAO was identified as a key mediator in ROS formation. These findings could potentially associate SSAO activity with the early developing stages of atherosclerosis through oxidative stress formation and vascular damage.

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.

Gut microbiota: A new target for traditional Chinese medicine in the treatment of depression

ETHNIC PHARMACOLOGICAL RELEVANCE

The causes of depression are complex. Many factors are involved in its pathogenesis, including the individual's biological and social environment. Although numerous studies have reported that the gut microbiota plays a significant role in depression, drugs that regulate the gut microbiota to treat depression have not yet been comprehensively reviewed. At the same time, more and more attention has been paid to the characteristics of traditional Chinese medicine (TCM) in improving depression by regulating gut microbiota. In ancient times, fecal microbiota transplantation was recorded in TCM for the treatment of severe diseases. There are also records in Chinese ancient books about the use of TCM to adjust gut microbiota to treat diseases, which has opened up a unique research field in TCM. Therefore, this article focuses on the pharmacological effects, targets, and mechanisms of TCM in improving depression by mediating the influence of gut microbiota.

AIM OF THIS REVIEW

To summarize the role the gut microbiota plays in depression, highlight potential regulatory targets, and elucidate the anti-depression mechanisms of TCMs through regulation of the gut microbiota.

METHODS

A systematic review of 256 clinical trials and pharmaceutical studies published until June 2022 was conducted in eight electronic databases (Web of Science, PubMed, SciFinder, Research Gate, ScienceDirect, Google Scholar, Scopus, and China Knowledge Infrastructure), according to the implemented PRISMA criteria, using the search terms "traditional Chinese medicine," "depression," and "gut microbiota."

RESULTS

Numerous studies reported the effects of different gut bacteria on depression and that antidepressants work through the gut microbiota. TCM preparations based on compound Chinese medicine, the Chinese Materia Medica, and major bioactive components exerted antidepressant-like effects by improving levels of neurotransmitters, short-chain fatty acids, brain-derived neurotrophic factor, kynurenine, and cytokines via regulation of the gut microbiota.

CONCLUSION

This review summarized the anti-depression effects of TCM on the gut microbiota, providing evidence that TCMs are safe and effective in the treatment of depression and may provide a new therapeutic approach.

Neither Trimethylamine-N-Oxide nor Trimethyllysine Is Associated with Atherosclerosis: A Cross-Sectional Study in Older Japanese Adults

Recent evidence suggests that trimethylamine-N-oxide (TMAO), a metabolite of L-carnitine and choline, is linked to atherosclerosis and cardiovascular diseases. As TMAO content is very high in fish, we raised the following question: why do Japanese people, who consume lots of fish, show a low risk of atherosclerosis? To address this question, we investigated the effects of TMAO and other L-carnitine-related metabolites on carotid intima-media thickness (IMT). Participants were recruited from a small island and a mountainous region. Plasma L-carnitine, γ-butyrobetaine (γBB), TMAO, trimethyllysine (TML), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels were measured using liquid or gas chromatography-mass spectrometry. Plasma L-carnitine concentration was higher in men than in women. TMAO and TML were significantly higher in the residents of the island than in the mountainous people. In multiple linear regression analyses in all participants, TML showed a significant inverse association with max-IMT and plaque score (PS), whereas TMAO did not show any associations. In women, L-carnitine was positively associated with max-IMT and PS. TMAO was correlated with both EPA and DHA levels, implying that fish is a major dietary source of TMAO in Japanese people. Our study found that plasma TMAO was not an apparent risk factor for atherosclerosis in elderly Japanese people, whereas a low level of TML might be a potential risk. L-carnitine may be a marker for atherosclerosis in women.

Inhibition of Trimethylamine N-Oxide Attenuates Neointimal Formation Through Reduction of Inflammasome and Oxidative Stress in a Mouse Model of Carotid Artery Ligation

Aims: Trimethylamine-N-oxide (TMAO) is a metabolite generated from dietary choline, betaine, and l-carnitine, after their oxidization in the liver. TMAO has been identified as a novel independent risk factor for atherosclerosis through the induction of vascular inflammation. However, the effect of TMAO on neointimal formation in response to vascular injury remains unclear. Results: This study was conducted using a murine model of acutely disturbed flow-induced atherosclerosis induced by partial carotid artery ligation. 3,3-Dimethyl-1-butanol (DMB) was used to reduce TMAO concentrations. Wild-type mice were divided into four groups [regular diet, high-TMAO diet, high-choline diet, and high-choline diet+DMB] to investigate the effects of TMAO elevation and its inhibition by DMB. Mice fed high-TMAO and high-choline diets had significantly enhanced neointimal hyperplasia and advanced plaques, elevated arterial elastin fragmentation, increased macrophage infiltration and inflammatory cytokine secretion, and enhanced activation of nuclear factor (NF)-κB, the NLRP3 inflammasome, and endoplasmic reticulum (ER) stress relative to the control group. Mice fed high-choline diets with DMB treatment exhibited attenuated flow-induced atherosclerosis, inflammasome expression, ER stress, and reactive oxygen species expression. Human aortic smooth muscle cells (HASMCs) were used to investigate the mechanism of TMAO-induced injury. The HASMCs were treated with TMAO with or without an ER stress inhibitor to determine whether inhibition of ER stress modulates the TMAO-induced inflammatory response. Innovation: This study demonstrates that TMAO regulates vascular remodeling via ER stress. Conclusion: Our findings demonstrate that TMAO elevation promotes disturbed flow-induced atherosclerosis and that DMB administration mitigates vascular remodeling, suggesting a rationale for a TMAO-targeted strategy for the treatment of atherosclerosis. Antioxid. Redox Signal. 38, 215-233.

Correlation between serum trimethylamine-N-oxide concentration and protein energy wasting in patients on maintenance hemodialysis

Objectives

Chronic kidney disease (CKD) is a serious health problem that is associated with several systemic changes, including protein energy wasting (PEW). However, the exact mechanism of PEW in CKD remains unclear. As one of the important intestinal flora metabolites and uremic toxins, trimethylamine-N-oxide (TMAO) is involved in CKD-associated mortality, which might play a role in the development of PEW in CKD patients especially in patients on maintenance hemodialysis (MHD). However, this possibility has not been investigated.

Methods

PEW was diagnosed in a group of CKD patients on MHD according to the criteria of the International Society of Renal Nutrition and Metabolism. Serum TMAO concentration was assessed by high-performance liquid chromatography and mass spectrometry. The association between TMAO concentration and PEW was assessed using linear regression and logistic analysis after adjustment for confounding factors, including basic characteristics, comorbidities, and laboratory findings.

Results

The circulating TMAO level was higher in the MHD patients than in control (healthy) individuals (5653.76 ± 2853.51 vs. 254.92 ± 197.88 ng/mL, p < 0.001). Further, after the MHD patients were screened for PEW, those with PEW were found to have significantly higher serum TMAO levels than those without PEW (6760.9 vs. 4016.1 ng/mL, p < 0.001). Further, the serum TMAO concentration exhibited a significant negative correlation with body mass index (BMI) and dietary protein intake. In the logistic regression analysis, after adjustment for confounding factors, the serum TMAO concentration was still significantly correlated with PEW occurrence.

Conclusions

The circulating TMAO level is significantly correlated with the prevalence of PEW in MHD patients. TMAO might be a potential target in the prevention and treatment of PEW in CKD especially ESRD.

A novel therapeutic concern: Antibiotic resistance genes in common chronic diseases

Infections caused by multidrug-resistant bacteria carrying antibiotic resistance genes pose a severe threat to global public health and human health. In clinical practice, it has been found that human gut microbiota act as a “reservoir” of antibiotic resistance genes (ARGs) since gut microbiota contain a wide variety of ARGs, and that the structure of the gut microbiome is influenced by the profile of the drug resistance genes present. In addition, ARGs can spread within and between species of the gut microbiome in multiple ways. To better understand gut microbiota ARGs and their effects on patients with chronic diseases, this article reviews the generation of ARGs, common vectors that transmit ARGs, the characteristics of gut microbiota ARGs in common chronic diseases, their impact on prognosis, the current state of treatment for ARGs, and what should be addressed in future research.

The relationship between the number of stenotic coronary arteries and the gut microbiome in coronary heart disease patients

An increasing number of studies have shown that the gut microbiome plays an important role in the development of coronary heart disease (CHD). However, there are no clear studies on the relationship between the gut microbiome and the number of stenotic coronary arteries. To clarify whether the gut microbiome is associated with the number of stenotic coronary arteries in CHD, we performed the 16S rRNA gene sequencing for the V3-V4 region in the gut microbiota from 9 healthy controls (C) and 36 CHD patients, which including 25 CHD patients with multivessel (MV) lesion and 11 CHD patients with single-vessel (SV) lesion. It showed that the abundance of the genus Escherichia-Shigella was significantly increased in the MV and SV groups compared with C group, while the abundance of the genera Subdoligranulum and Collinsella was significantly decreased. Biomarkers based on three gut microbiotas (Escherichia-Shigella, Subdoligranulum, and Collinsella) and three plasma metabolites(left atrial diameter (LA), low density lipoprotein (LDL), and total bile acids (TBA)) were able to distinguish CHD patients with different numbers of stenotic coronary arteries. Functional prediction of the gut microbiome was performed based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The results showed that the gut microbial function of MV and SV group patients was richer than C group in betaine biosynthesis and unsaturated fatty acid biosynthesis, in the contrast less than C group in sphingolipid metabolism and primary bile acid biosynthesis. In summary, our study showed that the composition and function of the gut microbiome changed significantly from healthy controls to CHD patients with different numbers of coronary lesions.

Effects of nutrients on immunomodulation in patients with severe COVID-19: Current knowledge

Recent research has demonstrated that critically ill patients with coronavirus disease 2019 (COVID-19) show significant immune system dysregulation. Due to that, some nutrients that influence immunomodulation have been suggested as a form of treatment against the infection. This review collected the information on the impact of vitamins on the prognosis of COVID-19, with the intention of facilitating treatment and prevention of the disease risk status in patients. The collected information was obtained using the PubMed electronic database by searching for articles that relate COVID-19 and the mechanisms/effects of the nutrients: Proteins, glucose, lipids, vitamin B12, vitamin D, calcium, iron, copper, zinc, and magnesium, including prospective, retrospective, and support articles. The findings reveal an optimal response related mainly to omega-3, eicosapentaenoic acid, docosahexaenoic acid, calcium, and iron that might represent benefits in the treatment of critically ill patients. However, nutrient supplementation should be done with caution due to the limited availability of randomized controlled studies.

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.

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.

Comparison between Egg Intake versus Choline Supplementation on Gut Microbiota and Plasma Carotenoids in Subjects with Metabolic Syndrome

We previously demonstrated that intake of three eggs/d for 4 weeks increased plasma choline and decreased inflammation in subjects with metabolic syndrome (MetS). The purpose of the current study was to further explore the effects of phosphatidylcholine (PC) provided by eggs versus a choline bitartrate (CB) supplement on the gut microbiota, trimethylamine N-oxide (TMAO) formation, and plasma carotenoids lutein and zeaxanthin in MetS. This randomized, controlled crossover clinical trial included 23 subjects with MetS. Following a washout period of 2 weeks without consuming any choline-containing foods, subjects were randomly allocated to consume either three eggs/d or a CB supplement for 4 weeks (both diets had a choline equivalent of 400 mg/day). DNA was extracted from stool samples to sequence the 16S rRNA gene region for community analysis. Operational taxonomic units (OTUs) and the α-diversity of the community were determined using QIIME software. Plasma TMAO, methionine, betaine, and dimethylglycine (DMG) were quantified by stable isotope dilution liquid chromatography with tandem mass spectrometry. Plasma carotenoids, lutein, and zeaxanthin were measured using reversed-phase high-performance liquid chromatography. There were significant increases in plasma lutein and zeaxanthin after egg intake compared to the baseline or intake of CB supplement (p < 0.01). In contrast, TMAO was not different between treatments compared to the baseline (p > 0.05). Additionally, while diet intervention had no effects on microbiota diversity measures or relative taxa abundances, a correlation between bacterial biodiversity and HDL was observed. Following egg intake, the observed increases in plasma lutein and zeaxanthin may suggest additional protection against oxidative stress, a common condition in MetS.

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.

TMAO as a Novel Predictor of Major Adverse Vascular Events and Recurrence in Patients with Large Artery Atherosclerotic Ischemic Stroke

Objectives

To explore the association of plasma trimethylamine N-oxide (TMAO) concentration with large artery atherosclerotic (LAA) ischemic stroke and its role in predicting neurological outcome and major vascular event recurrence.

Materials and Methods

We performed a case-control study that included patients with first-ever LAA stroke as cases (n = 291) and asymptomatic patients as controls (n = 235). Clinical data and venous blood samples were collected within 72 hours after stroke. All subjects were followed for 3 months. TMAO level was detected by liquid chromatography mass spectrometry (LC-MS). Logistic and Cox proportional hazard regression were performed to evaluate plasma TMAO concentration as a predictor of LAA stroke and major vascular event recurrence, respectively. Kaplan–Meier survival analysis was performed to compare major vascular event recurrence between patients with high and low TMAO concentration.

Results

After adjusting for traditional stroke risk factors, the plasma TMAO level was significantly higher in the LAA stroke group than the control group (OR = 1.031, 95% CI 1.024-1.037, P < .001). At a cutoff level of 106.9 pg/ml, TMAO had a sensitivity of 63.23% and specificity of 80.00% in discriminating the LAA stroke subjects from the controls in Receiver operator characteristic (ROC) analysis. Kaplan–Meier survival analysis demonstrated TMAO plasma concentration was significantly relevant with recurrent vascular events (Log Rank, P = .006). Moreover, this association was still existed after adjusting for traditional risks (adjusted HR, 3.128; 95% CI, 1.018-9.610) in Cox regression model. But TMAO plasma levels were not relevant with functional disability after 3 months of the LAA stroke.

Conclusion

Elevated plasma TMAO concentration was independently associated with LAA ischemic stroke. The risk of major vascular event recurrence increased by 2.128 times in the LAA stroke subjects with plasma TMAO level higher than 126.83 pg/mL. Plasma TMAO concentration might be a potential biomarker of major vascular event recurrence.

The Nutritional Supplement L-Alpha Glycerylphosphorylcholine Promotes Atherosclerosis

L-alpha glycerylphosphorylcholine (GPC), a nutritional supplement, has been demonstrated to improve neurological function. However, a new study suggests that GPC supplementation increases incident stroke risk thus its potential adverse effects warrant further investigation. Here we show that GPC promotes atherosclerosis in hyperlipidemic Apoe-/- mice. GPC can be metabolized to trimethylamine N-oxide, a pro-atherogenic agent, suggesting a potential molecular mechanism underlying the observed atherosclerosis progression. GPC supplementation shifted the gut microbial community structure, characterized by increased abundance of Parabacteroides, Ruminococcus, and Bacteroides and decreased abundance of Akkermansia, Lactobacillus, and Roseburia, as determined by 16S rRNA gene sequencing. These data are consistent with a reduction in fecal and cecal short chain fatty acids in GPC-fed mice. Additionally, we found that GPC supplementation led to an increased relative abundance of choline trimethylamine lyase (cutC)-encoding bacteria via qPCR. Interrogation of host inflammatory signaling showed that GPC supplementation increased expression of the proinflammatory effectors CXCL13 and TIMP-1 and activated NF-κB and MAPK signaling pathways in human coronary artery endothelial cells. Finally, targeted and untargeted metabolomic analysis of murine plasma revealed additional metabolites associated with GPC supplementation and atherosclerosis. In summary, our results show GPC promotes atherosclerosis through multiple mechanisms and that caution should be applied when using GPC as a nutritional supplement.

Adopting a Mediterranean-style eating pattern with low, but not moderate, unprocessed, lean red meat intake reduces fasting serum trimethylamine N-oxide (TMAO) in adults who are overweight or obese

A Mediterranean-style eating pattern (MED-EP) may include moderate red meat intake. However, it is unknown if the pro-atherogenic metabolite trimethylamine N-oxide (TMAO) is affected by the amount of red meat consumed with a MED-EP. The results presented are from a secondary, retrospective objective of an investigator-blinded, randomized, crossover, controlled feeding trial (two 5-wk interventions separated by a 4-wk washout) to determine if a MED-EP with 200g unprocessed lean red meat/wk (MED-CONTROL) reduces circulating TMAO concentrations compared to a MED-EP with 500g unprocessed lean red meat/wk (MED-RED). Participants were 27 women and 12 men (n=39 total) who were either overweight or obese (BMI: 30.5 ± 0.3 kg/m2 mean ± SEM). Serum samples were obtained following an overnight fast both before (pre) and after (post) each intervention. Fasting serum TMAO, choline, carnitine, and betaine concentrations were measured using a targeted Liquid chromatography-mass spectrometry. Data were analyzed to assess if (a) TMAO and related metabolites differed by intervention, and (b) if changes in TMAO were associated with changes in Framingham 10-year risk score. Serum TMAO was lower post-intervention following MED-CONTROL compared to MED-RED intervention (post-MED-CONTROL 3.1 ± 0.2 µM vs. post-MED-RED 5.0 ± 0.5 µM, p<0.001), and decreased following MED-CONTROL (pre- vs post-MED-CONTROL, p = 0.025). Exploratory analysis using mixed model analysis of covariance identified a positive association between changes in TMAO and changes in HOMA-IR (p = 0.036). These results suggest that lower amounts of red meat intake leads to lower TMAO concentrations in the context of a MED-EP.

Cardiovascular Health and The Intestinal Microbial Ecosystem: The Impact of Cardiovascular Therapies on The Gut Microbiota

It has become evident over the past several years that the intestinal microbial ecosystem plays a critical role in the development and prevention of cardiovascular diseases (CVDs) and other metabolic disorders, such as hypertension, obesity, diabetes mellitus, and metabolic syndrome. The intestinal microbiota ecosystem functions as a major virtual endocrine organ that interacts and responds to molecules' signals within the host. Several meta-organismal pathways are involved in the gut-host interaction, including trimethylamine-N-oxide (TMAO) and short-chain fatty acids (SCFA). Host phenotype and cardiovascular diseases (CVDs) varying from hypertension, insulin resistance, and obesity to more specific inflammatory processes, such as atherosclerosis and hypercoagulability, have shown to be affected by the gut-host interaction. Additionally, several studies that involved animals and humans demonstrated a striking connection between the development of new CVDs and an imbalance in the gut microbiota composition along with the presence of their derived metabolites. Through this review article, we aim to evaluate the role of the normal gut microbiota ecosystem, its association with CVDs, effects of the therapies used to control and manage CVDs in the gut microbiota environment and explore potential therapeutic interventions to amplify disease outcomes in patients with CVDs.

Polycystic ovary syndrome and cardiovascular risk. Could trimethylamine N-oxide (TMAO) be a major player? A potential upgrade forward in the DOGMA theory

Several studies reported an increase in cardiovascular risk (CVR) in women with polycystic ovary syndrome (PCOS), considered primarily as the result of the combination of all the clinical features that characterize the syndrome, including hyperandrogenism, insulin resistance, diabetes, obesity chronic low-grade inflammation. Interestingly, in 2012 it has been proposed the so-called DOGMA theory, suggesting the pivotal role played by microbiota alteration in the development of PCOS. Subsequently, several authors evidenced the existence in PCOS women of a marked dysbiosis, which is related to the development of metabolic diseases and cardiovascular complications, mainly due to the production of bacteria-derived metabolites that interfere with various pathways. Among these, trimethylamine-N-oxide (TMAO) is emerging as one of the most important and studied microbiota-derived metabolites related to the increase in CVR, due to its pro-atherosclerotic effect. The purpose of the present review is to summarize the evidence in order to support the hypothesis that, in women with PCOS, dysbiosis might be further involved in enhancement of the CVR via contributing to the increase of circulating TMAO. Although no observational studies on a large number of patients directly investigated the serum levels of TMAO in PCOS women, this manuscript aimed to drive future studies in this field, concurring in providing a novel approach for both comprehension and treatment of the CVR in PCOS.

Potential Dietary Interventions for COVID-19 Infection Based on the Gut-Immune Axis: An Update Review on Bioactive Component of Macronutrients

Recently emerged coronavirus, known as SARS-CoV-2 or Covid-19 is considered as a serious threat for human health. Due to unavailable specific drugs for this virus, there is an urgent need for supportive cares. Epigenetic immune boosting approaches and developing anti-inflammatory agents by gut-associated bioactive macronutrients can be plausible protective cares for COVID-19. Suitable intake of bioactive macronutrients including prebiotics, fatty acids, proteins and branched-chain amino acids may result in anti-viral responses through modulating macrophages and dendritic cells via Toll-like receptors, decreasing viral load, inactivating the enveloped viruses, increasing the anti-inflammatory metabolites and inhibiting the proliferation of microbial organisms. Bioactive macronutrients may help in promotion of immunological responses and recovery acceleration against Covid-19. This review focuses on the mechanisms of bioactive macronutrients and related clinical trials on enveloped viruses with emphasis on gut-microbiome-immune axis. Macronutrients and this axis may be conducive strategies to protect host against the viral infection.

The Accumulation and Molecular Effects of Trimethylamine N-Oxide on Metabolic Tissues: It's Not All Bad

Since elevated serum levels of trimethylamine N-oxide (TMAO) were first associated with increased risk of cardiovascular disease (CVD), TMAO research among chronic diseases has grown exponentially. We now know that serum TMAO accumulation begins with dietary choline metabolism across the microbiome-liver-kidney axis, which is typically dysregulated during pathogenesis. While CVD research links TMAO to atherosclerotic mechanisms in vascular tissue, its molecular effects on metabolic tissues are unclear. Here we report the current standing of TMAO research in metabolic disease contexts across relevant tissues including the liver, kidney, brain, adipose, and muscle. Since poor blood glucose management is a hallmark of metabolic diseases, we also explore the variable TMAO effects on insulin resistance and insulin production. Among metabolic tissues, hepatic TMAO research is the most common, whereas its effects on other tissues including the insulin producing pancreatic β-cells are largely unexplored. Studies on diseases including obesity, diabetes, liver diseases, chronic kidney disease, and cognitive diseases reveal that TMAO effects are unique under pathologic conditions compared to healthy controls. We conclude that molecular TMAO effects are highly context-dependent and call for further research to clarify the deleterious and beneficial molecular effects observed in metabolic disease research.

Variability of multi-omics profiles in a population-based child cohort

BACKGROUND

Multiple omics technologies are increasingly applied to detect early, subtle molecular responses to environmental stressors for future disease risk prevention. However, there is an urgent need for further evaluation of stability and variability of omics profiles in healthy individuals, especially during childhood.

METHODS

We aimed to estimate intra-, inter-individual and cohort variability of multi-omics profiles (blood DNA methylation, gene expression, miRNA, proteins and serum and urine metabolites) measured 6 months apart in 156 healthy children from five European countries. We further performed a multi-omics network analysis to establish clusters of co-varying omics features and assessed the contribution of key variables (including biological traits and sample collection parameters) to omics variability.

RESULTS

All omics displayed a large range of intra- and inter-individual variability depending on each omics feature, although all presented a highest median intra-individual variability. DNA methylation was the most stable profile (median 37.6% inter-individual variability) while gene expression was the least stable (6.6%). Among the least stable features, we identified 1% cross-omics co-variation between CpGs and metabolites (e.g. glucose and CpGs related to obesity and type 2 diabetes). Explanatory variables, including age and body mass index (BMI), explained up to 9% of serum metabolite variability.

CONCLUSIONS

Methylation and targeted serum metabolomics are the most reliable omics to implement in single time-point measurements in large cross-sectional studies. In the case of metabolomics, sample collection and individual traits (e.g. BMI) are important parameters to control for improved comparability, at the study design or analysis stage. This study will be valuable for the design and interpretation of epidemiological studies that aim to link omics signatures to disease, environmental exposures, or both.

Plasma trimethylamine N-oxide (TMAO) levels predict future risk of coronary artery disease in apparently healthy individuals in the EPIC-Norfolk prospective population study

BACKGROUND

Recent studies show a mechanistic link between gut microbiota-dependent formation of the atherosclerosis- and thrombosis-promoting metabolite trimethylamine N-oxide (TMAO) and cardiovascular disease (CVD). The clinical utility of TMAO in apparently healthy subjects for predicting incident CVD risks is unclear.

METHODS AND RESULTS

In the EPIC-Norfolk community-based study, we examined baseline fasting levels of TMAO and two of its nutrient precursors, choline and betaine, in a case:control design study comparing apparently European healthy middle-aged participants who subsequently develop CVD (Cases, n = 908) vs those who did not (Controls, n = 1,273) over an ensuing average follow-up period of 8 years. In participants who developed CVD vs controls, higher plasma TMAO (3.70 [IQR 2.50-6.41]μM vs 3.25 [IQR 2.19-52,1.15]μM; P < .001) and choline levels (9.09 [IQR 7.87-10.53]μM vs 8.89 [IQR 7.66-10.13]μM; P = .001) were observed. Following adjustments for traditional risk factors, elevated TMAO (adjusted odds ratio (OR) 1.58 [95% confidence interval (CI) 1.21-2.06], P < .001) and choline levels (adjusted OR 1.31 [95%CI 1.00-1.72], P < .05) remained predictive of incident CVD development. The clinical prognostic utility of TMAO remained significant and essentially unchanged regardless of the level of cutoff chosen between 1.5 uM (10%ile) to 10.5 uM (90%ile).

CONCLUSION

In apparently healthy participants of the community-based middle-aged EPIC-Norfolk population, elevated plasma levels of the gut microbe-dependent metabolite TMAO, and its nutrient precursor choline, predict incident risk for CVD development independent of traditional risk factors.

Circulating trimethylamine N-oxide in association with diet and cardiometabolic biomarkers: an international pooled analysis

BACKGROUND

Trimethylamine N-oxide (TMAO), a diet-derived, gut microbial-host cometabolite, has been linked to cardiometabolic diseases. However, the relations remain unclear between diet, TMAO, and cardiometabolic health in general populations from different regions and ethnicities.

OBJECTIVES

To examine associations of circulating TMAO with dietary and cardiometabolic factors in a pooled analysis of 16 population-based studies from the United States, Europe, and Asia.

METHODS

Included were 32,166 adults (16,269 white, 13,293 Asian, 1247 Hispanic/Latino, 1236 black, and 121 others) without cardiovascular disease, cancer, chronic kidney disease, or inflammatory bowel disease. Linear regression coefficients (β) were computed for standardized TMAO with harmonized variables. Study-specific results were combined by random-effects meta-analysis. A false discovery rate <0.10 was considered significant.

RESULTS

After adjustment for potential confounders, circulating TMAO was associated with intakes of animal protein and saturated fat (β = 0.124 and 0.058, respectively, for a 5% energy increase) and with shellfish, total fish, eggs, and red meat (β = 0.370, 0.151, 0.081, and 0.056, respectively, for a 1 serving/d increase). Plant protein and nuts showed inverse associations (β = -0.126 for a 5% energy increase from plant protein and -0.123 for a 1 serving/d increase of nuts). Although the animal protein-TMAO association was consistent across populations, fish and shellfish associations were stronger in Asians (β = 0.285 and 0.578), and egg and red meat associations were more prominent in Americans (β = 0.153 and 0.093). Besides, circulating TMAO was positively associated with creatinine (β = 0.131 SD increase in log-TMAO), homocysteine (β = 0.065), insulin (β = 0.048), glycated hemoglobin (β = 0.048), and glucose (β = 0.023), whereas it was inversely associated with HDL cholesterol (β = -0.047) and blood pressure (β = -0.030). Each TMAO-biomarker association remained significant after further adjusting for creatinine and was robust in subgroup/sensitivity analyses.

CONCLUSIONS

In an international, consortium-based study, animal protein was consistently associated with increased circulating TMAO, whereas TMAO associations with fish, shellfish, eggs, and red meat varied among populations. The adverse associations of TMAO with certain cardiometabolic biomarkers, independent of renal function, warrant further investigation.

Association of Urinary and Plasma Levels of Trimethylamine N-Oxide (TMAO) with Foods

Introduction: Trimethylamine N-oxide (TMAO) may play a key mediator role in the relationship between the diet, gut microbiota and cardiovascular diseases, particularly in people with kidney failure. The aim of this review is to evaluate which foods have a greater influence on blood or urinary trimethylamine N-oxide (TMAO) levels. Methods: 391 language articles were screened, and 27 were analysed and summarized for this review, using the keywords “TMAO” AND “egg” OR “meat” OR “fish” OR “dairy” OR “vegetables” OR “fruit” OR “food” in December 2020. Results: A strong correlation between TMAO and fish consumption, mainly saltwater fish and shellfish, but not freshwater fish, has been demonstrated. Associations of the consumption of eggs, dairy and meat with TMAO are less clear and may depend on other factors such as microbiota or cooking methods. Plant-based foods do not seem to influence TMAO but have been less investigated. Discussion: Consumption of saltwater fish, dark meat fish and shellfish seems to be associated with an increase in urine or plasma TMAO values. Further studies are needed to understand the relationship between increased risk of cardiovascular disease and plasma levels of TMAO due to fish consumption. Interventions coupled with long-term dietary patterns targeting the gut microbiota seem promising.

Pivotal Role of the Interaction Between Herbal Medicines and Gut Microbiota on Disease Treatment

With the recognition of the important role of gut microbiota in both health and disease progression, attempts to modulate its composition, as well as its co-metabolism with the organism, have attracted special attention. Abundant studies have demonstrated that dysfunction or imbalance of gut microbiota is closely related to disease progression, including endocrine diseases, neurodegenerative diseases, tumors, cardiovascular diseases, etc. Herbal medicines have been applied to prevent and treat diseases worldwide for hundreds of years. Although the underlying mechanism seems to be complex, one of the important ones is through modulating gut microbiota. In this review, co-metabolism between herbal medicines and microbiota, as well as the potential pathways are summarized from most recent published papers.

Use of dietary phytochemicals for inhibition of trimethylamine N-oxide formation

Trimethylamine-N-oxide (TMAO) has been reported as a risk factor for atherosclerosis development, as well as for other cardiovascular disease (CVD) pathologies. The objective of this review is to provide a useful summary on the use of phytochemicals as TMAO-reducing agents. This review discusses the main mechanisms by which TMAO promotes CVD, including the modulation of lipid and bile acid metabolism, and the promotion of endothelial dysfunction and oxidative stress. Current knowledge on the available strategies to reduce TMAO formation are discussed, highlighting the effect and potential of phytochemicals. Overall, phytochemicals (i.e., phenolic compounds or glucosinolates) reduce TMAO formation by modulating gut microbiota composition and/or function, inhibiting host's capacity to metabolize TMA to TMAO, or a combination of both. Perspectives for design of future studies involving phytochemicals as TMAO-reducing agents are discussed. Overall, the information provided by this review outlines the current state of the art of the role of phytochemicals as TMAO reducing agents, providing valuable insight to further advance in this field of study.

Gut Microbiota Functional Dysbiosis Relates to Individual Diet in Subclinical Carotid Atherosclerosis

Gut Microbiota (GM) dysbiosis associates with Atherosclerotic Cardiovascular Diseases (ACVD), but whether this also holds true in subjects without clinically manifest ACVD represents a challenge of personalized prevention. We connected exposure to diet (self-reported by food diaries) and markers of Subclinical Carotid Atherosclerosis (SCA) with individual taxonomic and functional GM profiles (from fecal metagenomic DNA) of 345 subjects without previous clinically manifest ACVD. Subjects without SCA reported consuming higher amounts of cereals, starchy vegetables, milky products, yoghurts and bakery products versus those with SCA (who reported to consume more mechanically separated meats). The variety of dietary sources significantly overlapped with the separations in GM composition between subjects without SCA and those with SCA (RV coefficient between nutrients quantities and microbial relative abundances at genus level = 0.65, p-value = 0.047). Additionally, specific bacterial species (Faecalibacterium prausnitzii in the absence of SCA and Escherichia coli in the presence of SCA) are directly related to over-representation of metagenomic pathways linked to different dietary sources (sulfur oxidation and starch degradation in absence of SCA, and metabolism of amino acids, syntheses of palmitate, choline, carnitines and Trimethylamine n-oxide in presence of SCA). These findings might contribute to hypothesize future strategies of personalized dietary intervention for primary CVD prevention setting.

Trimethylamine N-oxide (TMAO) Is not Associated with Cardiometabolic Phenotypes and Inflammatory Markers in Children and Adults

BACKGROUND

Trimethylamine N-oxide (TMAO) is a diet- and microbiome-derived metabolite and a proposed biomarker of adverse cardiometabolic outcomes. TMAO studies have mainly been conducted in individuals with cardiometabolic disease, and studies in population-derived samples are limited.

OBJECTIVE

We aimed to investigate the associations between plasma TMAO concentrations and its precursors [carnitine, choline, betaine, and dimethylglycine (DMG)] with metabolic syndrome (MetS) scores, preclinical cardiovascular phenotypes, and inflammatory biomarkers (i.e. high-sensitivity C-reactive protein and serum glycoprotein acetyls) in a population-derived cohort of children and their parents.

METHODS

The concentrations of TMAO and its precursors were quantified using UHPLC coupled with tandem MS (UHPLC/MS-MS) in 1166 children (mean age 11 y ± 0.5 y, 51% female) and 1324 adults (44 y ± 5.1 y, 87% female) participating in The Growing Up in Australia's Child Health CheckPoint Study. We developed multivariable fractional polynomial models to analyze associations between TMAO, its precursors, MetS (adjusted for sex and age), and cardiovascular phenotypes (adjusted for sex, age, BMI, household income, and the urinary albumin to creatinine ratio). Pearson's correlations were computed to identify associations between TMAO, its precursors, and inflammatory biomarkers.

RESULTS

The concentrations of TMAO precursors, but not TMAO itself, were associated with MetS, cardiovascular phenotypes, and inflammatory biomarkers in children and adults.

CONCLUSIONS

TMAO precursors, but not TMAO itself, were associated with adverse cardiometabolic and inflammatory phenotypes in children and adults. TMAO precursor concentrations may better reflect cardiovascular health and inflammatory status within the wider population. Replication in other population settings and mechanistic studies are warranted.

Vascular reactivity stimulated by TMA and TMAO: Are perivascular adipose tissue and endothelium involved?

Trimethylamine (TMA), formed by intestinal microbiota, and its Flavin-Monooxygenase 3 (FMO3) product Trimethylamine-N-Oxide (TMAO), are potential modulators of host cardiometabolic phenotypes. High circulating levels of TMAO are associated with increased risk for cardiovascular diseases. We hypothesized that TMA/TMAO could directly change the vascular tone. Perivascular adipose tissue (PVAT) helps to regulate vascular homeostasis and may also possess FMO3. Thoracic aorta with(+) or without(-) PVAT, also + or - the endothelium (E), of male Sprague Dawley rats were isolated for measurement of isometric tone in response to TMA/TMAO (1nM-0.5 M). Immunohistochemistry (IHC) studies were done to identify the presence of FMO3. TMA and TMAO elicited concentration-dependent arterial contraction. However, at a maximally achievable concentration (0.2 M), contraction stimulated by TMA was of a greater magnitude (141.5 ± 16% of maximum phenylephrine contraction) than that elicited by TMAO (19.1 ± 4.03%) with PVAT and endothelium intact. When PVAT was preserved, TMAO-induced contraction was extensively reduced the presence (19.1 ± 4.03%) versus absence of E (147.2 ± 20.5%), indicating that the endothelium plays a protective role against TMAO-induced contraction. FMO3 enzyme was present in aortic PVAT, but the FMO3 inhibitor methimazole did not affect contraction stimulated by TMA in aorta + PVAT. However, the l-type calcium channel blocker nifedipine reduced TMA-induced contraction by ∼50% compared to the vehicle. Though a high concentration of these compounds was needed to achieve contraction, the findings that TMA-induced contraction was independent of PVAT and E and mediated by nifedipine-sensitive calcium channels suggest metabolite-induced contraction may be physiologically important.

Untargeted GC-MS investigation of serum metabolomics of coronary artery disease patients

Recent advances in metabolomics provide tools to investigate human metabolome in order to establish new parameters to study different approaches towards diagnostics, diseases and their treatment. The present study focused on the untargeted identification of metabolites in serum of patients with coronary artery disease who were under treatment at the time of sample collection. AUCs (Area Under the Curves) from different peaks were considered for the analysis and comparison purposes. The metabolome was studied using GC–MS (Gas Chromatography Mass Spectrometry) and the metabolites were identified with NIST (The National Institute of Standards and Technology) and Wiley library matches. A total of 17 metabolites were identified and focused on to compare with the metabolome of healthy individuals. T test analysis found significant differences in alanine, malonic acid, ribitol, D-glucose, mannose (P < 0.001), acetohydroxamic acid, N-carboxyglycine, and aminobutyrate (P < 0.05). Principal Component Analysis of serum metabolites data found three components out of 17 metabolites; RC1 (Acetohydroxamic acid, alanine, D-glucose, malonic acid, mannose, N-carboxy glycine and ribitol), RC2 (Heptadecanoic acid, hexadecanoic acid, octadecanoic acid and Trans-9-octadecanoic acid), RC3 (Aminobutyrate, D-sorbit, gamma lactone, valine, benzene propanoic acid and lactic acid). No correlation was found among the components.

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.

Mutual Interplay of Host Immune System and Gut Microbiota in the Immunopathology of Atherosclerosis

Inflammation is the key for the initiation and progression of atherosclerosis. Accumulating evidence has revealed that an altered gut microbiome (dysbiosis) triggers both local and systemic inflammation to cause chronic inflammatory diseases, including atherosclerosis. There have been some microbiome-relevant pro-inflammatory mechanisms proposed to link the relationships between dysbiosis and atherosclerosis such as gut permeability disruption, trigger of innate immunity from lipopolysaccharide (LPS), and generation of proatherogenic metabolites, such as trimethylamine N-oxide (TMAO). Meanwhile, immune responses, such as inflammasome activation and cytokine production, could reshape both composition and function of the microbiota. In fact, the immune system delicately modulates the interplay between microbiota and atherogenesis. Recent clinical trials have suggested the potential of immunomodulation as a treatment strategy of atherosclerosis. Here in this review, we present current knowledge regarding to the roles of microbiota in contributing atherosclerotic pathogenesis and highlight translational perspectives by discussing the mutual interplay between microbiota and immune system on atherogenesis.

Vitamin D Decreases Plasma Trimethylamine-N-oxide Level in Mice by Regulating Gut Microbiota

As a metabolite generated by gut microbiota, trimethylamine-N-oxide (TMAO) has been proven to promote atherosclerosis and is a novel potential risk factor for cardiovascular disease (CVD). The objective of this study was to examine whether regulating gut microbiota by vitamin D supplementation could reduce the plasma TMAO level in mice. For 16 weeks, C57BL/6J mice were fed a chow (C) or high-choline diet (HC) without or with supplementation of vitamin D₃ (CD3 and HCD3) or a high-choline diet with vitamin D₃ supplementation and antibiotics (HCD3A). The results indicate that the HC group exhibited higher plasma trimethylamine (TMA) and TMAO levels, lower richness of gut microbiota, and significantly increased Firmicutes and decreased Bacteroidetes as compared with group C. Vitamin D supplementation significantly reduced plasma TMA and TMAO levels in mice fed a high-choline diet. Furthermore, gut microbiota composition was regulated, and the Firmicutes/Bacteroidetes ratio was reduced by vitamin D. Spearman correlation analysis indicated that Bacteroides and Akkermansia were negatively correlated with plasma TMAO in the HC and HCD3 groups. Our study provides a novel avenue for the prevention and treatment of CVD with vitamin D.

Gut microbiome and cardiovascular disease

PURPOSE OF REVIEW

This review aims to highlight the association between gut microbiome and cardiovascular disease (CVD) with emphasis on the possible molecular mechanisms by which how gut microbiome contributes to CVD.

RECENT FINDINGS

Increasingly, the roles of gut microbiome in cardiovascular health and disease have gained much attention. Most of the investigations focus on how the gut dysbiosis contributes to CVD risk factors and which gut microbial-derived metabolites mediate such effects.

SUMMARY

In this review, we discuss the molecular mechanisms of gut microbiome contributing to CVD, which include gut microbes translocalization to aortic artery because of gut barrier defect to initiate inflammation and microbial-derived metabolites inducing inflammation-signaling pathway and renal insufficiency. Specifically, we categorize beneficial and deleterious microbial-derived metabolites in cardiovascular health. We also summarize recent findings in the gut microbiome modulation of drug efficacy in treatment of CVD and the microbiome mechanisms by which how physical exercise ameliorates cardiovascular health. Gut microbiome has become an essential component of cardiovascular research and a crucial consideration factor in cardiovascular health and disease.

Effects of gut microbial metabolite trimethylamine N-oxide (TMAO) on platelets and endothelial cells

Thrombotic events result from different pathologies and are the underlying causes of severe diseases like stroke or myocardial infarction. Recent basic research now revealed a link between food uptake, food conversion and gut metabolism. Gut microbial production of trimethylamine N-oxide (TMAO) from dietary nutrients like choline, lecithin and L-carnitine was associated with the development of cardiovascular diseases. Within this review we give a systematic overview about the influence of TMAO on blood components like platelets and endothelial cells which both are involved as key players in thrombotic processes. In summary, a mechanistic correlation between the gut microbiome, TMAO and cardiovascular diseases becomes obvious and emphasizes to the significance of the intestinal microbiome.

Gut microbiota-associated metabolite trimethylamine N-Oxide and the risk of stroke: a systematic review and dose-response meta-analysis

AIMS

Several epidemiological studies have examined the association between trimethylamine N-Oxide (TMAO) and stroke risk; however, the results are still inconclusive. The purpose of this meta-analysis was to evaluate the relationship between TMAO concentrations and stroke risk.

METHODS

PubMed, Scopus, Cochrane and ProQuest search engines were systematically searched up to 18 June 2019. All of the studies that evaluated the relationship between TMAO and stroke were included in the systematic review and eligible studies were included into the meta-analysis. Meta-regression and subgroup analysis were also employed to find the source of heterogeneity.

RESULTS

Eight studies (two cross-sectional studies, two cohort studies, three case-control studies and one nested case-control study) with a total of 6150 participants were included in the meta-analysis. The overall result showed that being in the highest category of TMAO increased the odds of stroke by 68% (OR: 1.675; CI: 0.866-3.243; P = 0.047) and mean TMAO concentrations was 2.201 μmol/L higher in patients with stroke rather than non-stroke controls (weighted mean difference (WMD): 2.20; CI: 1.213-3.188; P < 0.001). Furthermore, we observed revealed a non-linear association between increased TMAO levels and increased odds of stroke (P- for nonlinearity < 0.001). In addition, visual inspection of the funnel plot revealed a significant asymmetry among studies examining the differences in TMAO in patients with stroke versus control group.

CONCLUSION

This is the first meta-analysis to show positive dose-dependent relations between circulating TMAO concentration and stroke risk. However, further interventional studies and long-term studies are needed to better explain causality.

Trimethylamine N-oxide: heart of the microbiota-CVD nexus?

We critically review potential involvement of trimethylamine N-oxide (TMAO) as a link between diet, the gut microbiota and CVD. Generated primarily from dietary choline and carnitine by gut bacteria and hepatic flavin-containing mono-oxygenase (FMO) activity, TMAO could promote cardiometabolic disease when chronically elevated. However, control of circulating TMAO is poorly understood, and diet, age, body mass, sex hormones, renal clearance, FMO3 expression and genetic background may explain as little as 25 % of TMAO variance. The basis of elevations with obesity, diabetes, atherosclerosis or CHD is similarly ill-defined, although gut microbiota profiles/remodelling appear critical. Elevated TMAO could promote CVD via inflammation, oxidative stress, scavenger receptor up-regulation, reverse cholesterol transport (RCT) inhibition, and cardiovascular dysfunction. However, concentrations influencing inflammation, scavenger receptors and RCT (≥100 µm) are only achieved in advanced heart failure or chronic kidney disease (CKD), and greatly exceed pathogenicity of <1-5 µm levels implied in some TMAO-CVD associations. There is also evidence that CVD risk is insensitive to TMAO variance beyond these levels in omnivores and vegetarians, and that major TMAO sources are cardioprotective. Assessing available evidence suggests that modest elevations in TMAO (≤10 µm) are a non-pathogenic consequence of diverse risk factors (ageing, obesity, dyslipidaemia, insulin resistance/diabetes, renal dysfunction), indirectly reflecting CVD risk without participating mechanistically. Nonetheless, TMAO may surpass a pathogenic threshold as a consequence of CVD/CKD, secondarily promoting disease progression. TMAO might thus reflect early CVD risk while providing a prognostic biomarker or secondary target in established disease, although mechanistic contributions to CVD await confirmation.

Plasma Trimethylamine N-Oxide and Its Precursors: Population Epidemiology, Parent-Child Concordance, and Associations with Reported Dietary Intake in 11- to 12-Year-Old Children and Their Parents

BACKGROUND

Trimethylamine N-oxide (TMAO) is a microbiome- and diet-derived metabolite implicated in adverse cardiovascular outcomes. To date, studies of plasma TMAO concentrations have largely focused on individuals with metabolic disease. As such, data on TMAO concentrations in population settings and parent-child dyads are lacking.

OBJECTIVES

This study aimed to investigate parent-child concordance, age, and sex effects on plasma concentrations of TMAO and its precursors [l-carnitine, choline, betaine, and dimethylglycine (DMG)]. Associations between concentrations of TMAO and its precursors and self-reported dietary intakes of animal protein (i.e., red meat, meat products, chicken, fish, milk products, and cheese) and fast-food meals were also investigated.

METHODS

A total of 1166 children (mean ± SD age: 11 ± 0.5 y, 51% female) and 1324 parents (mean ± SD age: 44 ± 5.1 y, 87% female) had a biomedical assessment as part of Growing Up in Australia's Child Health Checkpoint. Plasma TMAO and precursor concentrations were quantified using ultra-high-pressure LC coupled with tandem MS.

RESULTS

Familial dyads significantly contributed to plasma TMAO and precursor concentrations (P < 0.0001), explaining 37% of variance for TMAO concentrations. Least-square mean ± SE plasma TMAO was lower in children (0.79 ± 0.02 µM on the log-scale) than in adults (1.22 ± 0.02 µM). By contrast, children's betaine (40.30 ± 0.34 µM) and DMG concentrations (1.02 ± 0.01 µM on the log-scale) were higher than adults' betaine (37.50 ± 0.32 µM) and DMG concentrations (0.80 ± 0.01 µM) (P < 0.0001). Mean values of all metabolites, except adult TMAO, were higher in males than in females (P < 0.001). Greater reported intake of red meat and fish was associated with higher TMAO concentrations in both children [estimates (95% CIs) for red meat: 0.06 (0.01, 0.10); fish: 0.11 (0.06, 0.17)] and adults [red meat: 0.13 (0.08, 0.17); meat products: 0.07 (0.03, 0.12); and fish: 0.09 (0.04, 0.14)].

CONCLUSIONS

Age, sex, and shared family factors, including diet, contribute to variation in plasma concentrations of TMAO and its precursors.

[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.

Identification of Serum Biomarker in Acute Aortic Dissection by Global and Targeted Metabolomics

BACKGROUND

Acute aortic dissection (AAD) is the most devastating aortic pathology, and the incidence is increasing worldwide. However, the occurrence and development of AAD are unpredictable. A thorough understanding of the serum metabolic landscape through metabolomic analysis may help identify new biomarkers for AAD and offers new insights into its prevention and evaluation.

METHODS

Nineteen patients with Stanford type A aortic dissection and 20 healthy individuals were enrolled in this study. We use global and targeted mass spectrometry-based metabolomics to investigate the serum metabolomics profiles, and the data were analyzed by principal component analysis and orthogonal partial least squares discriminant analysis.

RESULTS

Initial untargeted metabolomics analysis revealed significant changes of lipids and polar metabolites in patients with AAD. Alterations of the phosphatidylcholine metabolic pathway were further observed by targeted metabolomics. Trimethylamine N-oxide (TMAO) levels were obviously increased in patients with AAD compared with controls (P < 0.005), whereas the levels of carnitine (P < 0.005), choline, and betaine (P < 0.05) were decreased. Furthermore, TMAO levels were associated with disease severity in AAD and correlated positively with C-reactive protein levels (r = 0.537, P = 0.018), IL-6 levels (r = 0.546, P = 0.016), D-dimer levels (r = 0.694, P = 0.001), and maximum aortic diameter on admission (r = 0.748, P = 0.002).

CONCLUSIONS

Patients with AAD showed a predominant and consistent change of metabolites levels, especially the compounds in the phosphatidylcholine metabolic pathway. TMAO could potentially serve as a biomarker for the auxiliary diagnosis and evaluation of AAD.

Effects of Alpha-Lipoic Acid Supplementation on Cardiovascular Disease Risk Factors in β-Thalassemia Major Patients: A Clinical Trial Crossover Study

AIM

Thalassemia is one of the most common genetic diseases, and cardiovascular disease (CVD) has been considered as the leading cause of mortality in more than 50% of β-thalassemia patients. The aim of this study was to determine the effects of alpha-lipoic acid (ALA) on CVD risk factors in β-thalassemia major patients.

METHODS

Twenty β-thalassemia major patients participated in this randomized crossover clinical trial study. Participants were randomly assigned to ALA (600 mg/day) or placebo groups for two 8-wk interventions that were separated by a 3-wk washout period. The CVD risk factors including serum osteoprotegerin (OPG), homocysteine, lipoprotein-associated phospholipase A2 and trimethylamine N-oxide were measured at the beginning and the end of each intervention phase according to the standard protocol.

RESULTS

Serum OPG reduced significantly in the ALA group in all participants (5.38 ± 2.79 to 3.27 ± 2.43 ng/mL, P= .003) and in the male subgroup (5.24 ± 2.56 to 3.13 ± 2.5 ng/mL, P= .015); this reduction was significant in comparison with the placebo group (P= .013). The changes in other CVD risk factors were not significant.

CONCLUSION

The results of this study showed that after 8-wk of ALA consumption, the serum OPG reduced significantly in β-thalassemia major patients. Therefore, controlling the serum OPG level with ALA consumption can be an important complementary therapeutic option to prevent the progression of CVD in β-thalassemia major patients.