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Abstract Background and aims Recent studies have shown that trimethylamine N-oxide (TMAO) is a risk factor for cardiovascular disease (CVD) in different clinical settings, but few studies confirmed the association in a community-based general population. Methods This is a nested case-control study from a prospective cohort design. A total of 86 newly diagnosed CVD cases with a median follow-up period of 4.83 years and 86 matched controls were selected for the present analysis. Results Using the LC-MS/MS assays, we found that new CVD cases had a higher baseline levels of TMAO than controls [median (inter-quartile): 1.57 (0.79–2.29) μmol/L v.s 0.68 (0.23–1.40) μmol/L, p < 0.001]. After multivariable adjustment, individuals with TMAO ≥1.89 μmol/L (Q4) and 1.05–1.89 μmol/L (Q3) had odds ratio (OR) for CVD of 2.735 [95% confidence interval (CI): 1.328–5.630] and 2.544 (95% CI: 1.251–5.172) with the lowest quartile (<0.43 μmol/L) as reference. In addition, comparisons of areas under receiver operator characteristics curves confirmed that a model including TMAO had a better discrimination than one without (0.732 vs. 0.664, p = 0.045). Conclusions In the community-based general population, there was a positive association between TMAO and future risk of CVD. Addition of TMAO improved the prediction of CVD beyond traditional risk factors. We recommend considering TMAO as a potential novel preventive target in the management of low-risk CVD adults. Graphical abstract Image 1 Highlights • TMAO has a dose-dependent relationship with risk of CVD in the general population. • Addition of TMAO significantly improved the predictive ability of CVD risk. • TMAO is a potential novel preventive target for low-risk CVD adults. [ABSTRACT FROM AUTHOR]

Several studies have suggested negative effects of trimethylamine oxide (TMAO) on the circulatory system. However, a number of studies have shown protective functions of TMAO, a piezolyte and osmolyte, in animals exposed to high hydrostatic and/or osmotic stress. We evaluated the effects of TMAO treatment on the development of hypertension and its complications in male spontaneously hypertensive rats (SHRs) maintained on water (SHR-Water) and SHRs drinking TMAO water solution from weaning (SHR-TMAO). Wistar-Kyoto (WKY) rats were used as normotensive controls to discriminate between agedependent and hypertension-dependent changes. Telemetry measurements of blood pressure were performed in rats between the 7th and 16th weeks of life. Anesthetized rats underwent echocardiographic, electrocardiographic, and direct left ventricular end-diastolic pressure (LVEDP) measurements. Hematoxylin and eosin as well as van Gieson staining for histopathological evaluation were performed. Plasma TMAO measured by chromatography coupled with mass spectrometry was significantly higher in the SHR-Water group compared with the WKY group (~20%). TMAO treatment increased plasma TMAO by four- to fivefold and did not affect the development of hypertension in SHRs. Sixteen-week-old rats in the SHR-Water and SHR-TMAO groups (12-wk TMAO treatment) showed similar blood pressures, angiopathy, and cardiac hypertrophy. However, the SHRTMAO group had lower plasma NH2-terminal pro-B-type natriuretic peptide, LVEDP, and cardiac fibrosis. In contrast to age-matched WKY rats, 60-wk-old SHRs showed hypertensive angiopathy and heart failure with preserved ejection fraction. Compared with the SHR-Water group, the SHR-TMAO group (56-wk TMAO treatment) showed significantly lower plasma NH2-terminal pro-B-type natriuretic peptide and vasopressin, significantly lower LVEDP, and cardiac fibrosis. In conclusion, a four- to fivefold increase in plasma TMAO does not exert negative effects on the circulatory system. In contrast, increased dietary TMAO seems to reduce diastolic dysfunction in pressure-overloaded hearts in rats. [ABSTRACT FROM AUTHOR]

High circulating levels of trimethylamine N-oxide (TMAO) have been associated with cardiovascular disease risk. TMAO is formed through a microbiome-host pathway utilizing primarily dietary choline as a substrate. Specific gut microbiota transform choline into trimethylamine (TMA), and, when absorbed, host hepatic flavin-containing monooxygenase 3 (FMO3) oxidizes TMA into TMAO. Chlorogenic acid and its metabolites reduce microbial TMA production in vitro. However, little is known regarding the potential for chlorogenic acid and its bioavailable metabolites to inhibit the last step: hepatic conversion of TMA to TMAO. We developed a screening methodology to study FMO3-catalyzed production of TMAO from TMA. HepG2 cells were unable to oxidize TMA into TMAO due to their lack of FMO3 expression. Although Hepa-1 cells did express FMO3 when pretreated with TMA and NADPH, they lacked enzymatic activity to produce TMAO. Rat hepatic microsomes contained active FMO3. Optimal reaction conditions were: 50 µM TMA, 0.2 mM NADPH, and 33 µL microsomes/mL reaction. Methimazole (a known FMO3 competitive substrate) at 200 µM effectively reduced FMO3-catalyzed conversion of TMA to TMAO. However, bioavailable chlorogenic acid metabolites did not generally inhibit FMO3 at physiological (1 µM) nor supra-physiological (50 µM) doses. Thus, the effects of chlorogenic acid in regulating TMAO levels in vivo are unlikely to occur through direct FMO3 enzyme inhibition. Potential effects on FMO3 expression remain unknown. Intestinal inhibition of TMA production and/or absorption are thus likely their primary mechanisms of action. [ABSTRACT FROM AUTHOR]

The last decade is marked by the significant reinterpretation of the gut microbiota contribution to chronic disease progression. The researchers’ careful attention is focused on improving the understanding of the metabolic pathways of two dietary compounds – choline and L-carnitine, which stand at the origins of trimethylamine N-oxide (TMAO) formation. This small molecule of great expectations has gained an impressive appreciation due to its ability to promote atherogenesis, and thus increasing the risk of major adverse cardiovascular events and affecting patients’ prognosis. This paper aims to discuss updated concept of microbiota-dependent cardiometabolic consequences of consumption of food rich in quaternary amines as well as to touch upon the currently existing interventions in TMAO production, their limitations and future scientific directions.

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

Objective: This review aimed to summarize the relationship between intestinal microbiota metabolism and cardiovascular disease (CVD) and to propose a novel CVD therapeutic target. Data Sources: This study was based on data obtained from PubMed and EMBASE up to June 30, 2015. Articles were selected using the following search terms: "Intestinal microbiota", "trimethylamine N-oxide (TMAO)", "trimethylamine (TMA)", "cardiovascular", and "atherosclerosis". Study Selection: Studies were eligible if they present information on intestinal microbiota metabolism and atherosclerosis. Studies on TMA-containing nutrients were also included. Results: A new CVD risk factor, TMAO, was recently identified. It has been observed that several TMA-containing compounds may be catabolized by specific intestinal microbiota, resulting in TMA release. TMA is subsequently converted to TMAO in the liver. Several preliminary studies have linked TMAO to CVD, particularly atherosclerosis; however, the details of this relationship remain unclear. Conclusions: Intestinal microbiota metabolism is associated with atherosclerosis and may represent a promising therapeutic target with respect to CVD management.

Objective: To investigate the role and mechanism of trimethylamine N-oxide (TMAO), a uremic toxin, in renal fibrosis., Methods: A total of 20 male BALB/c mice were randomly and evenly assigned to a Control group and a TMAO group. Mice in the Control group received intraperitoneal injection of normal saline, while mice in the TMAO group received intraperitoneal injection of TMAO (20 mg/[kg·d]). The injection was given once a day for 8 weeks. Histopathology and fibrosis of kidney were observed by H&E staining and Masson staining. Immunohistochemistry was performed to determine the levels of alpha smooth muscle actin (α-SMA), recombinant human fibronectin fragment (Fibronectin), and sterol-regulatory element binding protein 1 (SREBP1). Western blot was performed to determine α-SMA, SREBP1, phosphatidylinositol 3 kinase (PI3K), phospho-phosphatidylinositol 3 kinase (p-PI3K), protein kinase B (PKB, also known as AKT), and phospho-AKT (p-AKT) protein levels. HK2 cells were treated with SREBP 1 small interfering RNA (siRNA) and PI3K/AKT inhibitor, respectively, and the reversal of the effects of TMAO was examined., Results: Animal experiments showed that, compared with the Control group, the mice treated with TMAO experienced pathological damage and fibrosis of the kidney tissue and the expression levels of fibrosis markers, α-SMA and Fibronectin, in the kidney were increased (all P <0.05). According to the findings from further investigation, the TMAO-treatment group showed increased expression of SREBP1 and an up-regulation of PI3K phosphorylation ratio and AKT phosphorylation ratio compared with those of the Control group (all P <0.05). Cell experiments produced results similar to those of the animal experiment. After siRNA interference with SREBP1 expression, the expression levels of fibrosis marker proteins decreased ( P <0.05). Besides, the high expression of SREBP1 caused by TMAO was inhibited after HK2 cells were incubated with LY294002, a PI3K-AKT pathway inhibitor ( P <0.05)., Conclusion: TMAO may induce renal fibrosis by promoting the PI3K/AKT/SREBP1 pathway., Competing Interests: 利益冲突　所有作者均声明不存在利益冲突, (© 2023《四川大学学报（医学版）》编辑部 版权所有Copyright ©2023 Editorial Board of Journal of Sichuan University (Medical Sciences).)

Background and Purpose: The present study analyzed the relationship between circulating trimethylamine N-oxide (TMAO) levels and stroke severity in diabetic patients with acute ischaemic stroke. A further aim was to investigate whether higher TMAO levels were associated with platelet aggregation and glycemic variability., Methods: This was a cross-sectional analysis of 108 patients with type 2 diabetes mellitus (DM) undergoing acute ischaemic stroke and 60 healthy controls. Fasting plasma TMAO was measured using high-performance liquid chromatography with online electrospray ionization tandem mass spectrometry., Results: Plasma TMAO levels of patients with acute ischaemic stroke were significantly higher than those of healthy controls. Amongst stroke patients, 50 were defined as undergoing mild stroke, and their plasma TMAO levels were lower compared to those with moderate to severe stroke. Platelet aggregation and mean amplitude of glycemic excursions were both correlated with plasma TMAO levels and these relationships remained significant in multiple linear regression analyses. Moreover, in streptozotocin-induced diabetic rats fed a diet enriched with choline to increase TMAO synthesis, platelet aggregation was significantly increased in the DM + choline and fluctuating DM (FDM) + choline groups compared to the control group. This increase was abolished in rats receiving oral antibiotics, which markedly reduced plasma TMAO levels. Importantly, compared with the DM + choline group, the FDM + choline group displayed significantly elevated TMAO levels and higher platelet aggregation., Conclusions: Our results demonstrated that higher plasma TMAO levels were associated with stroke severity and suggested a novel link between plasma TMAO levels and glycemic variability in diabetic patients with acute ischaemic stroke., (© 2022 European Academy of Neurology.)

Background and Purpose: It has been suggested that trimethylamine N-oxide (TMAO) is related to Parkinson's disease (PD) in observational studies. However, the direction of this association is inconsistent. An exploratory Mendelian randomization study was conducted to investigate whether TMAO and its precursors have a causal relationship with PD., Methods: Summary statistics were obtained for single nucleotide polymorphisms related to circulating levels of TMAO, betaine, carnitine and choline, and the corresponding data for the risk, age at onset and progression of PD from genome-wide association studies. Inverse-variance weighting was used as the primary method for effect estimation. The false discovery rate was applied to the correction of multiple testing. A p value of association <0.05 but above the false discovery rate corrected threshold was deemed suggestive evidence of a possible association. A range of robust Mendelian randomization methods were used for sensitivity analysis., Results: Suggestive evidence was observed of an inverse causal effect of TMAO on motor fluctuations (odds ratio [OR] 0.851, 95% confidence interval [CI] 0.731, 0.990, p = 0.037) and carnitine on insomnia (OR 0.817, 95% CI 0.700, 0.954, p = 0.010) and a positive causal effect of betaine on Hoehn-Yahr stage (OR 1.397, 95% CI 1.112, 1.756, p = 0.004), Unified Parkinson's Disease Rating Scale (UPDRS) III score (β = 0.138, 95% CI 0.051, 0.225, p = 0.002), motor fluctuations (OR 1.236, 95% CI 1.011, 1.511, p = 0.039), and choline on UPDRS IV (β = 0.106, 95% CI 0.026, 0.185, p = 0.009) and modified Schwab and England Activities of Daily Living Scale score (β = 0.806, 95% CI 0.127, 1.484, p = 0.020)., Conclusions: Our findings provide suggestive evidence that TMAO and its precursors have a causal effect on the progression of PD. Further investigation of the underlying mechanisms is required., (© 2023 European Academy of Neurology.)

Probiotics are considered to represent important modulators of gastrointestinal health through increased colonization of beneficial bacteria thus altering the gut microflora. Although these beneficial effects of probiotics are now widely recognized, emerging evidence suggests that alterations in the gut microflora also affect numerous other organ systems including the heart through a process generally referred to as the gut-heart axis. Moreover, cardiac dysfunction such as that seen in heart failure can produce an imbalance in the gut flora, known as dysbiosis, thereby further contributing to cardiac remodelling and dysfunction. The latter occurs by the production of gut-derived pro-inflammatory and pro-remodelling factors which exacerbate cardiac pathology. One of the key contributors to gut-dependent cardiac pathology is trimethylamine N-oxide (TMAO), a choline and carnitine metabolic by-product first synthesized as trimethylamine which is then converted into TMAO by a hepatic flavin-containing monooxygenase. The production of TMAO is particularly evident with regular western diets containing high amounts of both choline and carnitine. Dietary probiotics have been shown to reduce myocardial remodelling and heart failure in animal models although the precise mechanisms for these effects are not completely understood. A large number of probiotics have been shown to possess a reduced capacity to synthesize gut-derived trimethylamine and therefore TMAO thereby suggesting that inhibition of TMAO is a factor mediating the beneficial cardiac effects of probiotics. However, other potential mechanisms may also be important contributing factors. Here, we discuss the potential benefit of probiotics as effective therapeutic tools for attenuating myocardial remodelling and heart failure., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Gut microbiota is associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD) through the metabolites, which can induce atherogenesis. One of these metabolites is trimethylamine N-oxide (TMAO). Some studies indicate that statins do not only decrease LDL-cholesterol and thus ASCVD risk, but they also affect gut microbiota. There are only a few studies on humans suggesting that statins might also decrease TMAO, but their results are not unanimous. This meta-analysis aimed to provide an answer as to whether statins do affect decreasing the plasma levels of atherogenic TMAO., Methods: A systematic literature search in PubMed, Scopus, Embase, and Web of Science was performed from inception to January 1st, 2023. To assess the quality of each study included in the meta-analysis, the Cochrane Quality Assessment tool 1 (ROB 1) was used. Comprehensive Meta-Analysis V3 software was used to perform the meta-analysis. The weighted mean difference was also used. A random effects meta-analysis was used to calculate the overall estimate of effect size. In the leave-one-out approach, one study was excluded from each analysis to evaluate the effect of each study on the overall effect size., Results: Random-effects meta-analysis of 3 studies including 244 patients demonstrated a significant decrease in plasma TMAO levels after statin treatment (WMD: -1.839, 95% CI: -2.391, -1.287, p<0.001; I2 :0). The reduction in TMAO was robust in the leaveone-out sensitivity analysis., Conclusion: Statins might reduce TMAO levels, but there is a need for further evidence from long-term studies taking into account different types and doses of statins., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Trimethylamine N -oxide (TMAO) is a biomarker that is effective in predicting major adverse cardiovascular (CV) events. Age-related vascular problems are significantly affected by aortic stiffness (AS), which is independently linked to CV morbidity and mortality. This study aimed to determine the association between serum TMAO levels and carotid-femoral pulse wave velocity (cfPWV) in patients receiving hemodialysis (HD) therapy. In total, 115 patients with HD were enrolled in this study. The AS group included patients whose cfPWV was >10 m/s. Using high-performance liquid chromatography and mass spectrometry, the levels of serum TMAO were measured. The AS group included 42 (36.5%) patients, and compared with the non-AS group, the rates of diabetes, hypertension, older age, systolic blood pressure, serum glucose, and TMAO levels were high. In the multivariate logistic regression analysis, serum TMAO and age were independently linked with AS after correcting for the factors significantly associated with AS. Following multivariate stepwise linear regression analysis, serum TMAO in these individuals was found to be strongly correlated with cfPWV values ( p < 0.001). In patients on chronic HD, serum TMAO level is an independent measure of AS and strongly correlated with cfPWV.

Objective: To investigate the correlation between the plasma levels of trimethylamine N-oxide (TMAO) and lipid levels in hyperlipidemic patients., Methods: A total of 130 patients who received treatment and underwent coronary angiography at the Heart Center, the First Affiliated Hospital of Xinjiang Medical University between March 2019 and March 2021 were enrolled. Patients' plasma TMAO levels were determined by stable isotope liquid chromatography/mass spectrometry. The correlation between plasma TMAO levels and the levels of lipids, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), was analyzed., Results: Patients with hyperlipidemia had higher plasma TMAO levels (μmol/L) than patients without hyperlipidemia did (6.73±5.40 vs. 3.82±2.65), with the difference being statistically significant ( P <0.05). After controlling for the effects of age and body mass index, partial correlation analysis revealed that plasma TMAO levels were positively correlated with plasma TG ( r =0.286, P <0.001) and negatively correlated with HDL-C ( r =-0.366, P <0.001)., Conclusion: There is a correlation between plasma TMAO levels and lipid levels in hyperlipidemic patients., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Neuroinflammation mediated by brain glial cells is one of the pathological drivers of Parkinson's disease (PD). Recent studies have shown that higher circulating trimethylamine N-oxide (TMAO, a gut microbiota-derived metabolite) can induce neuroinflammation and are strongly related to a variety of central nervous system diseases and adverse brain events. Herein, we explored the effect of pre-existing higher circulating TMAO on dopamine system and neuroinflammation in acute PD model mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP). TMAO pretreatment was given by adding 3% (w/v) TMAO to drinking water of mice for 21 days to induce higher circulating TMAO status, then mice were administered with MPTP (20 mg/kg, i.p) for four times in one day to construct an acute PD model mice and treated with TMAO continuously until the end of the experiment. Results demonstrated that TMAO treatment significantly increased serum TMAO levels. Moreover, high serum TMAO significantly increased activation of microglia and astrocytes both in striatum and in substantia nigra. And strikingly, high serum TMAO significantly promoted the metabolism of striatal dopamine (DA) of PD model mice, although it had no significant effect on the number of dopaminergic neurons or the content of DA. Furthermore, immunofluorescence, ELISA, and RT-qPCR results of the hippocampus also showed that high serum TMAO significantly promoted the activation of microglia and astrocytes in the dentate gyrus, increased the levels of TNF-α and IL-1β, and upregulated gene expression of M1 microglia-related markers (including CD16, CD32, and iNOS) and A2 astrocyte-related markers (including S100a10, Ptx3, and Emp1) in mRNA levels. In summary, we found that pre-existing high serum levels of TMAO worsened the PD-related brain pathology by promoting DA metabolism, aggravating neuroinflammation and regulating glial cell polarization., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Quaternary ammonium compounds containing N -trimethylamino moiety, such as choline derivatives and carnitine, abundant in meat and dairy products, are metabolic precursors of trimethylamine (TMA). A similar fate is reported for N ε -trimethyllysine and γ-butyrobetaine. With the aim at investigating the metabolic profile of such metabolites in most employed animal dietary sources, HPLC-ESI-MS/MS analyses on ruminant and non-ruminant milk and meat were performed. Results demonstrate, for the first time, the presence of δ-valerobetaine, occurring at levels higher than γ-butyrobetaine in all ruminant samples compared to non-ruminants. Demonstration of δ-valerobetaine metabolic origin, surprisingly, showed that it originates from rumen through the transformation of dietary N ε -trimethyllysine. These results highlight our previous findings showing the ubiquity of free N ε -trimethyllysine in vegetable kingdom. Furthermore, δ-valerobetaine, similarly to γ-butyrobetaine, can be degraded by host gut microbiota producing TMA, precursor of the proatherogenic trimethylamine N-oxide (TMAO), unveiling its possible role in the biosynthetic route of TMAO. [ABSTRACT FROM AUTHOR]

Clusters of bacterial species within the gut microenvironment, or gut enterotype, have been correlated with cardiometabolic disease risk. The metabolic products and metabolites that bacteria produce, such as short-chain fatty acids, secondary bile acids, and trimethylamine, may also affect the microbial community and disease risk. Diet has a direct impact on the gut microenvironment by providing substrates to and promoting the colonization of resident bacteria. To date, few dietary patterns have been evaluated for their effect on the gut microbiome, but the Mediterranean diet and Vegetarian diets have shown favorable effects for both the gut microbiome and cardiometabolic disease risk. This review examines the gut microbiome as a mediator between these dietary patterns and cardiometabolic disease risk. [ABSTRACT FROM AUTHOR]

Enterococcus faecium WEFA23 is a potential probiotic strain from Chinese infants with the ability to decrease cholesterol levels. Aiming to explore the mechanism of E. faecium WEFA23 in lowering cholesterol in vivo, we examined the gene transcriptions related to cholesterol metabolism, the composition of bile acids in feces, the synthesis of trimethylamine N-oxide (TMAO) in liver, and the composition of the gut microbiota of rats. We found that E. faecium WEFA23 enhanced the synthesis of bile acids by promoting cholesterol excretion, upregulating the genes transcript level relevant to cholesterol decomposition and transportation, and downregulating the genes involved in cholesterol synthesis. In addition, E. faecium WEFA23 not only downregulated the transcript levels of farnesoid X receptor and fibroblast growth factor 15 as well as flavin-containing monooxygenase 3, but also decreased the TMAO production followed by increasing the CYP7A1 transcript level. Furthermore, when orally administered to rats for 35 d, E. faecium WEFA23 improved the gut microbiota diversity of rats fed a high-fat diet. Therein, the ratio of Bacteroidetes to Firmicutes and the abundance of Rikenellaceae increased, whereas the number of Veillonellaceae decreased. These results suggest that reduction of cholesterol level by E. faecium WEFA23 might be related to the changes in the gut microbiota. Our finding provides important information on lowering cholesterol by E. faecium and reveals that Enterococcus spp. might have the potential to decrease the TMAO level. [ABSTRACT FROM AUTHOR]

Background Plaque vulnerability indicates the risk of a cardiovascular event. In the present study, we sought to analyze the relationship between trimethylamine N-oxide (TMAO), a gut microbiota metabolite from dietary phosphatidylcholine, and vulnerable plaque characteristics in patients with coronary artery disease (CAD). Methods One hundred eighty non-culprit plaques from 90 patients with ACS or with stable angina were assessed by optical coherence tomography (OCT). The plasma TMAO levels were measured using rapid resolution liquid chromatography quadrupole time-of-flight mass spectrometry (RRLC-QTOF/MS). Results Patients were divided into two groups (high TMAO group and low TMAO group) according to the median plasma TMAO level (114.73 μg/L). The non-culprit plaques in the high TMAO group exhibited a thinner fibrous cap thickness (FCT) (65.97 ± 25.89 vs. 93.0 ± 28.28 μm, P < 0.001), higher frequency of microvessels (75.6% vs. 31.1%, P < 0.001, per-patient) and increased incidence of thin-cap fibroatheroma (TCFA) (69.2% vs. 18.4%, P < 0.001, per-patient) compared with the low TMAO group. Moreover, the level of TMAO was negatively associated with FCT ( r  = −0.418, P < 0.001). Furthermore, multivariate regression analysis results showed that TMAO (OR: 7.455, 95% CI: 2.753–20.189, P < 0.001) had a significant association with TCFA, with a cut-off point of 118.34 μg/L, specificity of 72.6% and sensitivity of 79.5% in predicting the prevalence of TCFA. Conclusions In conclusion, these findings suggest that the level of TMAO is significantly correlated with the incidence of TCFA. New biomarkers acquired through non-invasive means, such as TMAO, offer the potential to improve risk stratification and clinical management in patients with CAD. [ABSTRACT FROM AUTHOR]

Deep-sea organisms must cope with hydrostatic pressure, up to ~ 110 MPa (~ 1100 atm) at 11 km in the Mariana Trench. Pressure perturbs protein conformations, ligand binding, and can promote damaging protein aggregates. Salinity is another stressor: seawater, averaging ~ 1000 mOsm/kg, is dehydrating towards the ~ 250–400 mOsm/kg of universal cellular solutes. Most marine organisms prevent dehydration by becoming isosmotic with cellular organic osmolytes, which, unlike NaCl, do not perturb proteins and can have chemical chaperone properties, stabilizing proteins against various physicochemical stressors. In shallow-dwelling invertebrates, these osmolytes are typically taurine, glycine, and betaine. Previous work on crustaceans down to 3 km found that “shallow” osmolytes decreased with depth, replaced with trimethylamine N-oxide (TMAO) and other apparent chemical chaperones. In bony fishes, TMAO increases with depth down to 8 km, and is probably a piezolyte (pressure counteractant) as it reverses pressure's inhibitory effects. Here we analyzed amphipods over the full ocean depth range of 0–11 km, from coastal habitats and numerous depths in the Kermadec and Mariana Trenches. We found that “shallow” osmolytes decreased while potential piezolytes, in different combinations in different species, increased with depth. These are TMAO, glycerophosphorylcholine and proline betaine (all methylamine chaperones), glycerophosphorylethanolamine, and scyllo -inositol, a polyol chaperone (being tested for Alzheimer's Disease) that works differently than methylamines by preventing damaging protein aggregations. Though only TMAO has been tested for piezolyte properties, these other solutes may explain how some hadal amphipods live deeper than fish, which appear to be limited to a maximum of 8.4 km. [ABSTRACT FROM AUTHOR]

Background: Metabolic syndrome (MetS), a cardio-metabolic cluster afflicting 35% of American adults, increases cardiovascular disease (CVD) and type-2 diabetes (T2DM) risk. Increased levels of trimethylamine N-oxide (TMAO), a metabolite derived from choline and L-carnitine, correlates with CVD and T2DM. However, the precise role of TMAO and its precursors in MetS remains unclear. We tested the hypothesis that choline, L-carnitine and TMAO in MetS patients without CVD or T2DM would be altered and correlate with inflammatory markers. Materials and methods: This was an exploratory study of 30 patients with nascent MetS (without CVD or T2DM) and 20 matched controls. MetS was defined by the Adult Treatment Panel III criteria. TMAO and its precursors were evaluated from each patient's frozen early morning urine samples and quantified using liquid chromatography/mass spectrometry (LC-MS). These amines were correlated with a detailed repertoire of biomarkers of inflammation and adipokines. Results: L-carnitine was significantly increased (p = 0.0002) compared to controls. There was a trend for a significant increase in TMAO levels (p = 0.08). Choline was not significantly altered in MetS. L-carnitine correlated significantly with soluble tumor necrosis factor 1 (sTNFR1) and leptin, and inversely to adiponectin. TMAO correlated with IL-6, endotoxin and chemerin. Neither choline, nor L-carnitine significantly correlated with TMAO. Conclusion: L-carnitine is directly correlated with markers of inflammation in nascent MetS. Cellular L-carnitine could be a biomediator or marker of inflammation in the pathogenesis of MetS, and the sequelae of CVD and T2DM. [ABSTRACT FROM AUTHOR]

Summary Trimethylamine N-oxide (TMAO) is a circulating metabolite that has been implicated in the development of atherosclerosis and cardiovascular disease (CVD). In this paper, we identify blood markers, metabolites, proteins, gut microbiota patterns, and diets that are significantly associated with levels of plasma TMAO. We find that kidney markers are strongly associated with TMAO and identify CVD-related proteins that are positively correlated with TMAO. We show that metabolites derived by the gut microbiota are strongly correlated with TMAO and that the magnitude of this correlation varies with kidney function. Moreover, we identify diet-associated patterns in the microbiome that are correlated with TMAO. These findings suggest that both the process of TMAO accumulation and the mechanism by which TMAO promotes atherosclerosis are a complex interplay between diet and the microbiome on one hand and other system-level factors such as circulating proteins, metabolites, and kidney function. [ABSTRACT FROM AUTHOR]

Both insufficiency and excess of one-carbon nutrients (folate, choline, vitamins B6 and B12) during pregnancy have been associated with gestational diabetes mellitus (GDM). However, the precise nature of this association has not been clearly established. We hypothesized that GDM may affect one-carbon nutrients concentrations in the fetus, thus possibly participating in epigenetic programing of the offspring. Maternal blood was collected at recruitment (12–16 weeks). At delivery (28–42 weeks), both maternal and cord blood were collected. Blood concentrations of one-carbon nutrients and their metabolites were compared between the two groups. A total of 368 women were included in the study, of whom 19 (5.6%) were later diagnosed with GDM. No significant differences were found in maternal blood concentrations of one-carbon nutrients and their metabolites between the GDM and control groups at recruitment or at delivery. In cord blood, however, serum folate (87.7 [IQR 70.4–103.9] vs 66.6 [IQR 45.5–80.3] nmol/L, P = .025) and plasma TMAO (2.82 [IQR 1.3–3.2] vs 1.35 [IQR 1.0–2.0] μ mol/L, P = .017) concentrations were higher, while plasma betaine concentrations were lower (17.5 [IQR 16.3–19.4] vs 21.1 [IQR 18.0–24.1] μ mol/L, P = .019) in infants born to mothers with GDM compared with control. Our data suggest that while maternal blood concentrations of one-carbon nutrients and their metabolites may not affect the risk of GDM, GDM may alter concentrations of serum folate, plasma betaine and TMAO in cord blood. These alterations in one-carbon nutrient concentrations in fetal circulation may impact epigenetic programing, thereby contributing to physiologic changes and disease susceptibility in adulthood associated with GDM offspring. [ABSTRACT FROM AUTHOR]

The gut microbiome recently has emerged as a novel risk factor that impacts health and disease. Our gut microbiota can function as an endocrine organ through its unique ability to metabolize various dietary precursors, and can fuel the systemic inflammation observed in chronic disease. This is especially important in the setting of chronic kidney disease, in which microbial metabolism can contribute directly to accumulation of circulating toxins that then can alter and shift the balance of microbiota composition and downstream functions. To study this process, advances in -omics technologies are providing opportunities to understand not only the taxonomy, but also the functional diversity of our microbiome. We also reliably can quantify en masse a wide range of uremic byproducts of microbial metabolism. Herein, we examine the bidirectional relationship between the gut microbiome and the failing kidneys. We describe potential approaches targeting gut microbiota for cardiovascular risk reduction in chronic kidney disease using an illustrative example of a novel gut-generated metabolite, trimethylamine N-oxide. [ABSTRACT FROM AUTHOR]

Protein-protein interactions are critical for biological function and depend significantly on environmental factors. A wide variety of small organic molecules that comprise the cellular environment are capable of interacting with proteins to affect folding, binding, and association. The plant lectin concanavalin A (ConA) undergoes a reversible, pH dependent dimer-to-tetramer equilibrium and has been used in our laboratory as a model system to study the effect of osmolytes on protein self-association. Previous research determined that trimethylamine N-oxide (TMAO) stabilizes the tetrameric conformation, while urea favors the dimer. Studying the equilibrium over a range of temperatures allowed quantification of the enthalpy change (ΔH) and entropy change (ΔS) of tetramer formation. Urea increased both the ΔH and ΔS of tetramer formation, while TMAO decreased both. These effects are consistent with preferential hydration of the dimer-dimer interface in TMAO solution and preferential binding of urea to the interface. [ABSTRACT FROM AUTHOR]

Background: Individuals with phenylketonuria (PKU) have a risk of cognitive impairment and inflammation. Many follow a low-phenylalanine (low-Phe) diet devoid of animal protein in combination with medical foods (MFs).Objective: To assess lipid metabolism in participants with PKU consuming amino acid MFs (AA-MFs) or glycomacropeptide MFs (GMP-MFs), we conducted fatty acid and metabolomics analyses.Methods: We used subsets of fasting plasma and urine samples from our randomized crossover trial in which participants with early-treated classical and variant (milder) PKU consumed a low-Phe diet combined with AA-MFs or GMP-MFs for 3 wk each. Fatty acid profiles of red blood cell (RBC) membranes were determined for 25 adults (aged 18-49 y) with PKU and 143 control participants. Metabolomics analyses of plasma and urine samples were conducted by Metabolon for 9-10 adolescent and adult participants with PKU and for 15 control participants.Results: RBC fatty acid profiles were not significantly different with AA-MFs or GMP-MFs. PKU participants showed higher total n-6:n-3 (ω-6:ω-3) fatty acids (mean ± SD percentages of total fatty acids: AA-MF = 5.45% ± 1.07%; controls = 4.33%; P < 0.001) and lower docosahexaenoic acid (DHA; AA-MF = 3.21% ± 0.98%; controls = 3.70% ± 1.01%; P = 0.02) and eicosapentaenoic acid (AA-MF = 0.33% ± 0.12%; controls = 0.60% ± 0.43%; P < 0.001) in RBCs than did control participants. Despite higher carnitine intake from AA-MFs than GMP-MFs (mean ± SE intake: AA-MFs = 58.6 ± 5.3 mg/d; GMP-MFs = 0.3 ± 0.01 mg/d; P < 0.001), plasma concentrations of carnitine were similar and not different from those in the control group (AA-MF compared with GMP-MF, P = 0.73). AA-MFs resulted in higher urinary excretion of trimethylamine N-oxide (TMAO), which is synthesized by bacteria from carnitine, compared with GMP-MFs (mean ± SE scaled intensity-TMAO: AA-MFs = 1.2 ± 0.1, GMP-MFs = 0.9 ± 0.1; P = 0.005). Plasma deoxycarnitine was lower in PKU participants than in control participants, suggesting reduced carnitine biosynthesis in PKU (AA-MF = 0.9 ± 0.1; GMP-MF = 1.0 ± 0.1; controls = 1.3 ± 0.1; AA-MF compared with controls, P = 0.01; GMP-MF compared with controls, P = 0.04).Conclusions: Supplementation with DHA is needed in PKU. Carnitine supplementation of AA-MFs shows reduced bioavailability due, in part, to bacterial degradation to TMAO, whereas the bioavailability of carnitine is greater with prebiotic GMP-MFs. This trial was registered at www.clinicaltrials.gov as NCT01428258. [ABSTRACT FROM AUTHOR]

The human body is an integrated circuit between microbial symbionts and our Homo sapien genome, which communicate bi-directionally to maintain homeostasis within the human meta-organism. There is now strong evidence that microbes resident in the human intestine can directly contribute to the pathogenesis of obesity and associated cardiometabolic disorders. In fact, gut microbes represent a filter of our greatest environmental exposure - the foods we consume. It is now clear that we each experience a given meal differently, based on our unique gut microbial communities. Biologically active gut microbe-derived metabolites, such as short chain fatty acids, secondary bile acids, and trimethylamine-N-oxide (TMAO), are now uniquely recognized as contributors to obesity and related cardiometabolic disorders. However, mechanistic insights into how microbe-derived metabolites promote obesity are largely unknown. Recent work has demonstrated that the meta-organismal production of the bacterial co-metabolite TMAO is linked to suppression of beiging of white adipose tissue in mice and humans. Furthermore, the TMAO pathway is becoming an increasingly attractive therapeutic target in obesity-associated diseases such as type 2 diabetes, kidney failure, and cardiovascular disease. In this commentary we discuss recent findings linking the TMAO pathway to obesity-associated disorders, and provide additional insights into potential mechanisms driving this microbe-host interaction. [ABSTRACT FROM AUTHOR]

Circulating trimethylamine N-oxide (TMAO), a canonical metabolite from gut flora, has been related to the risk of cardiovascular disorders. However, the association between circulating TMAO and the risk of cardiovascular events has not been quantitatively evaluated. We performed a systematic review and meta-analysis of all available cohort studies regarding the association between baseline circulating TMAO and subsequent cardiovascular events. Embase and PubMed databases were searched for relevant cohort studies. The overall hazard ratios for the developing of cardiovascular events (CVEs) and mortality were extracted. Heterogeneity among the included studies was evaluated with Cochran's Q Test and I2 statistics. A random-effect model or a fixed-effect model was applied depending on the heterogeneity. Subgroup analysis and meta-regression were used to evaluate the source of heterogeneity. Among the 11 eligible studies, three reported both CVE and mortality outcome, one reported only CVEs and the other seven provided mortality data only. Higher circulating TMAO was associated with a 23% higher risk of CVEs (HR = 1.23, 95% CI: 1.07-1.42, I2 = 31.4%) and a 55% higher risk of all-cause mortality (HR = 1.55, 95% CI: 1.19-2.02, I2 = 80.8%). Notably, the latter association may be blunted by potential publication bias, although sensitivity analysis by omitting one study at a time did not significantly change the results. Further subgroup analysis and meta-regression did not support that the location of the study, follow-up duration, publication year, population characteristics or the samples of TMAO affect the results significantly. Higher circulating TMAO may independently predict the risk of subsequent cardiovascular events and mortality. [ABSTRACT FROM AUTHOR]

Purpose: Restriction of animal foods and choline may affect plasma trimethylamine- N-oxide (TMAO). In vegetarians, we investigated the association between TMAO concentrations and the strictness of the diet or sex. We also studied the biological variations of TMAO in vegans. Methods: Concentrations of plasma TMAO and choline metabolites were measured in 38 vegans and 67 lacto-ovo-vegetarians (group 1: mean age ± SD = 50 ± 15 years). Group 2 consisted of 66 vegans (29.2 ± 7.3 years) that was tested twice within 3 months of intervention with vitamin B12 or a placebo. Results: In group 1, plasma TMAO did not differ according to the strictness of the diet (both means 3.7 µmol/L). In lacto-ovo-vegetarians, men had higher TMAO and betaine, but lower trimethylamine than women. In group 2, the intervention with vitamin B12 had no effect on plasma TMAO or choline metabolites. The mean within-subject change of TMAO within 3 months was −0.3 (95 % confidence intervals = −0.7-0.1 µmol/L). TMAO increased after 3 months (mean 1.7 to 2.8 µmol/L) in vegans with a lower baseline dimethylglycine (2.2 µmol/L), while it declined (from 2.7 to 1.9 µmol/L) in vegans with a higher dimethylglycine (3.1 µmol/L). The intra-class correlation coefficients were 0.819 for TMAO, 0.885 for betaine and 0.860 for dimethylglycine. Conclusions: Plasma TMAO was not related to the strictness of the vegetarian diet. Metabolisms of TMAO and dimethylglycine are interrelated. Intra-individual variations of TMAO are low in vegans. Changes of fasting plasma TMAO >80 % upon retesting are likely to exceed the biological variations. [ABSTRACT FROM AUTHOR]