Plasma Trimethylamine N-oxide Levels Research Articles

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.

Trimethylamine N-oxide (TMAO) in patients with subarachnoid hemorrhage: a prospective observational study

BackgroundIt is suspected that microbiome-derived trimethylamine N-oxide (TMAO) may enhance platelet responsiveness and accordingly be thrombophilic. The purpose of this prospective observational study is to evaluate TMAO in patients with subarachnoid hemorrhage (SAH) and compare it with a control group. A secondary aim was to investigate TMAO in the cerebrospinal fluid (CSF) from SAH patients. This should provide a better understanding of the role of TMAO in the pathogenesis of SAH and its thrombotic complications.MethodsThe study included patients with diagnosed spontaneous SAH recruited after initial treatment on admission and patients with nerve, nerve root, or plexus disorders serving as controls. Blood samples were gathered from all patients at recruitment. Additionally, sampling of SAH patients in the intensive care unit continued daily for 14 days. The CSF was collected out of existing external ventricular drains whenever possible.ResultsThirty-four patients diagnosed with SAH, and 108 control patients participated in this study. Plasma TMAO levels at baseline were significantly lower in the SAH group (1.7 μmol/L) compared to the control group (2.9 μmol/L). TMAO was detectable in the CSF (0.4 μmol/L) and significantly lower than in plasma samples of the SAH group at baseline. Plasma and CSF TMAO levels correlated positively. The TMAO levels did not differ significantly during the observation period of 15 days.ConclusionsAlthough we assumed that patients with higher TMAO levels were at higher risk for SAH a priori, plasma TMAO levels were lower in patients with SAH compared with control subjects with nerve, nerve root, or plexus disorders on admission to the hospital. A characteristic pattern of plasma TMAO levels in patients with SAH was not found.

Dietary Methionine Restriction Alleviates Choline-Induced Tri-Methylamine-N-Oxide (TMAO) Elevation by Manipulating Gut Microbiota in Mice

Dietary methionine restriction (MR) has been shown to decrease plasma trimethylamine-N-oxide (TMAO) levels in high-fat diet mice; however, the specific mechanism used is unknown. We speculated that the underlying mechanism is related with the gut microbiota, and this study aimed to confirm the hypothesis. In this study, we initially carried out an in vitro fermentation experiment and found that MR could reduce the ability of gut microbiota found in the contents of healthy mice and the feces of healthy humans to produce trimethylamine (TMA). Subsequently, mice were fed a normal diet (CON, 0.20% choline + 0.86% methionine), high-choline diet (H-CHO, 1.20% choline + 0.86% methionine), or high-choline + methionine-restricted diet (H-CHO+MR, 1.20% choline + 0.17% methionine) for 3 months. Our results revealed that MR decreased plasma TMA and TMAO levels in H-CHO-diet-fed mice without changing hepatic FMO3 gene expression and enzyme activity, significantly decreased TMA levels and expression of choline TMA-lyase (CutC) and its activator CutD, and decreased CutC activity in the intestine. Moreover, MR significantly decreased the abundance of TMA-producing bacteria, including Escherichia-Shigella (Proteobacteria phylum) and Anaerococcus (Firmicutes phylum), and significantly increased the abundance of short-chain fatty acid (SCFA)-producing bacteria and SCFA levels. Furthermore, both MR and sodium butyrate supplementation significantly inhibited bacterial growth, down-regulated CutC gene expression levels in TMA-producing bacteria, including Escherichia fergusonii ATCC 35469 and Anaerococcus hydrogenalis DSM 7454 and decreased TMA production from bacterial growth under in vitro anaerobic fermentation conditions. In conclusion, dietary MR alleviates choline-induced TMAO elevation by manipulating gut microbiota in mice and may be a promising approach to reducing circulating TMAO levels and TMAO-induced atherosclerosis.

Mangiferin alleviates trimethylamine-N-oxide (TMAO)-induced atherogenesis and modulates gut microbiota in mice.

Trimethylamine-N-oxide (TMAO), originating from dietary trimethylamine-containing nutrients such as choline, has been recognized as a risk factor for atherosclerosis. Mangiferin is a bioactive xanthone initially extracted from mango (Mangifera indica). The present study aimed to investigate the effect of mangiferin on TMAO-induced atherogenesis in mice fed a high-choline diet. Female ApoE-/- mice were randomly divided into three groups and fed either a control diet, a high-choline diet with 1% free choline, or an experimental diet with 1% free choline plus 0.5% mangiferin for 15 weeks. Our results showed that a high-choline diet elevated plasma TMAO levels, accelerated atherogenesis, promoted cholesterol accumulation, and reduced the generation of short-chain fatty acids (SCFAs) by gut microbes. Mangiferin alleviated inflammation, and lowered plasma total cholesterol levels by facilitating the elimination of neutral and acidic sterols in feces, resulting in a 16.7-29.0% reduction in aortic atherosclerotic lesions. Notably, mangiferin could favorably remodel the composition of the gut microbiota by fostering the growth of the beneficial taxa Akkermansia, Parabacteroides, and Bifidobacteriaceae, while reducing the relative abundance of the pathogenic genus Helicobacter. This modulation led to a decrease in plasma lipopolysaccharide levels, enhanced the production of total SCFAs by gut microbes, and reduced susceptibility to atherosclerosis. In conclusion, mangiferin exhibited its ability to alleviate TMAO-induced atherosclerosis through its anti-inflammatory, cholesterol-lowering, and gut microbial modulatory activities.

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

BackgroundStudies 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). ObjectivesTo 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. MethodsWe 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. ResultsDuring 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. ConclusionsHigher 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.

Association of Circulating Trimethylamine-N Oxide With Malnutrition and the Risk of Coronary Artery Disease in Patients With Maintenance Hemodialysis

Malnutrition is a serious complication frequently observed in dialysis patients. Therefore, nutrition status evaluation and the early identification of malnutrition are clinically important. Trimethylamine N-oxide (TMAO) is reportedly associated with deteriorating metabolic profiles and cardiovascular diseases. The aim of our study was to investigate correlations between circulating TMAO levels and malnutrition and the risk of major adverse cardiovascular events in patients on maintenance hemodialysis. This retrospective observational study involved 228 subjects. Fasting plasma TMAO levels were detected using liquid chromatography-tandem mass spectrometry. TMAO levels were significantly elevated in patients with malnutrition (8728.78±704.12ng/mL) when compared with those without (6532.1±570.41ng/mL, P<.01). TMAO levels were positively correlated with Subjective Global Assessment scores (ρ=0.56, P=.02) and were independent risk factors for malnutrition after adjustment for multiple traditional risk factors (odds ratio=2.07, 95% confidence interval: 1.41-3.62, P<.01). Furthermore, TMAO levels were good predictors of major adverse cardiovascular events in a 2-year follow-up period (area under the curve=0.68, P<.01) and accuracy was increased to 74% when TMAO levels were combined with Subjective Global Assessment scores (area under the curve=0.74, P=.02). Elevated TMAO levels were independently associated with a risk of malnutrition and cardiovascular disease, and could be a useful predictive biomarker for risk stratification and cardiovascular disease management for patients on dialysis.

342 TMAO PLASMA LEVELS PREDICT RECURRENT ISCHEMIC EVENTS IN SURVIVORS OF MYOCARDIAL INFARCTION

Abstract Background Recent studies have highlighted a direct link between dietary nutrients, microbiota and cardiovascular disease (CVD). In this context, trimethylamine-N-oxide (TMAO), a metabolite derived from the intestinal microbiota, stands out, paving its way as one of the important biomarkers associated with atherosclerosis, increased risk of CVD, recurrent events and adverse outcomes. Methods 81 patients who survived acute myocardial infarction (AMI), (both STEMI 50 / NSTEMI 31) were enrolled in this study together with 10 healthy individuals. Further, we evaluated the relationship between plasma TMAO levels and cardiovascular events during the follow-up. The measurement of plasma levels of TMAO was performed using liquid chromatography-tandem mass spectrometry (LC-MS). Results The median plasma concentration of TMAO were significantly higher in patients with AMI compared with healthy control (1.62 (1.37–2.25) µM. vs 0.55 (0.35–0.74) µM, p &amp;lt; 0.0001). During a median follow-up of 61.74 (59.34–64.24) months, 10 out of 81 patients (12.3%) had a re-infarction. Patients who had another ischemic event had higher TMAO values compared with individuals who did not (2.29 (1.60–6.49) µM vs 1.60 (1.34–2.09) µM, p = 0.026). Further, TMAO values positively correlate with CRP, a pro-inflammatory marker. However, at multivariate Cox regression analysis, plasma TMAO values were not predictive of re-infarction. Conclusions The data of our pilot study show that higher TMAO values are associated with the risk of recurrent ischemic event. A future prospective study, including larger cohort is necessary to analyze this issue.

Abstract 13248: The Association of Serial Measures of Plasma Trimethylamine N-Oxide With Incident Chronic Kidney Disease and Renal Function Decline Among Older Adults: The Cardiovascular Health Study

Introduction: Trimethylamine N-oxide (TMAO) is a gut microbiota-derived metabolite of dietary phosphatidylcholine and carnitine. Experimentally, TMAO causes renal tubulointerstitial fibrosis and kidney injury. Yet, little is known about prospective associations between TMAO and renal outcomes. Hypothesis: Higher plasma TMAO levels are prospectively associated with higher risk of incident chronic kidney disease (CKD) and greater renal function decline. Methods: We included 4,131 US adults from the Cardiovascular Health Study, a community-based cohort, with normal baseline renal function (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73m 2 ). TMAO was measured using liquid chromatography-mass spectrometry at baseline and year 7. Creatinine and Cystatin C were measured 4 times during serial follow-up and used to compute eGFR. Incident CKD was defined by eGFR (decline ≥ 30% plus eGFR&lt;60 at a follow-up visit) or presence of CKD hospitalization ICD codes. Time-varying Cox models assessed how serial TMAO measures related to incident CKD, adjusting for sociodemographic, lifestyle, diet, and CVD risk factors. Linear regression models assessed how baseline TMAO related to annualized eGFR change in 3,997 participants with at least one follow-up eGFR measure. Results: During a median follow-up of 14 years, 1,136 participants developed CKD. There was a non-linear dose-response relationship of TMAO with CKD incidence: higher TMAO levels were associated with higher risk of incident CKD with a plateauing of risk above the ~75 th percentile of TMAO levels (top Figure ). Higher baseline TMAO levels were also associated with greater annualized eGFR decline (P-linearity=0.004. bottom Figure ) after adjusting for baseline eGFR and other covariates. Conclusions: In this community-based cohort of older US adults, higher serial measures of plasma TMAO were associated with a higher risk of incident CKD and a greater rate of annualized renal function decline.

Abstract 12480: Changes in Tmao Levels Following Bariatric Surgery Vary by Procedure Type

Introduction: Trimethylamine-N-oxide (TMAO), a metabolite generated by the gut microbiota from dietary phosphatidylcholine and carnitine, is linked to atherosclerosis and thrombosis. Although bariatric surgery improves CV outcomes, several studies in both animals and humans have shown increased TMAO levels after bariatric surgery. We tested the impact of the two most common bariatric procedures on plasma TMAO. Methods: This study included 93 severely obese non-diabetic individuals who did not take diabetes or lipid-lowering medications and underwent Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). Plasma TMAO was measured before and ≥ six months after bariatric surgery. Results: Mean age of the subjects was 31.4 ± 7.2 years and 90% were female. At baseline, average weight and BMI were 117.1 ± 24.4 kg and 43.4 ± 8.0 kg/m 2 respectively. Average baseline plasma TMAO level was 2.2 ± 1.4 μM. 29 patients underwent RYGB and 64 patients underwent SG. There were no significant differences in baseline weight, BMI, or TMAO between procedures. RYGB patients lost significantly more weight than SG patients (37.5 ± 8.6 kg for RYGB vs 32.8 ± 9.0 kg for SG, p = 0.03). TMAO levels did not change following SG, whereas they increased after RYGB ( Figure ). Changes in TMAO were not associated with changes in other clinical measures, for example, body weight and BMI ( Figure ) for either RYGB or SG patients. Conclusions: We found contrasting responses in circulating TMAO following bariatric surgical procedures employing dissimilar anatomical alterations. Given TMAO-associated CVD risk, these differences may lead to contrasting CV outcomes in the future. Additional research to understand changes in TMAO and the microbiota after bariatric surgery, and their clinical relevance, are warranted.

Trimethylamine N-oxide is associated with impaired cognitive function in patients with atrial fibrillation

Abstract Introduction Since patients with atrial fibrillation (AF) are predisposed to suffer from major adverse cerebrovascular events (MACE), they are more likely to suffer MACE linked sequelae, such as cognitive impairment. We hypothesised that the gut microbiome derivate trimethylamine N-oxide (TMAO) may amplify this pathomechanism given its hypercoagulative, proinflammatory and proatherogenic effects. Methods Patients of the Swiss-AF cohort with determined TMAO plasma levels, cognitive scores (n=2'379) and cerebral magnetic resonance imaging (cMRI) (n=1'722) collected at baseline were included. TMAO levels were measured by liquid chromatography-mass spectrometry (HPLC). Overall cognitive performance was evaluated using the Cognitive Construct (CoCo) score reflecting different cognitive functions measured by four validated neuropsychological assessments, namely the Montreal Cognitive Assessment (MoCA), Trail Making Test (TMT parts A and B), Semantic Fluency Test (SFT) and Digital Symbol Substitution Test (DSST). The scores were compared with the quartiles of patients' TMAO plasma levels (Q1: 0.6–4, Q2: 4–5.8, Q3: 5.8–9.1, Q4: 9.1–164μmol/l) in linear effect models. All models were adjusted for multiple covariates correlating with this association: For TMAO (overall meat consumption &amp;gt;3 times per week, physical activity, glomerular filtration rate, presence of diabetes mellitus), cognitive function (EQ-5D-5L score, geriatric depression scale, education level) and cerebral affects (white matter lesions volume and total brain volume in cMRI). The relevance of high TMAO plasma levels in different stroke groups in cMRI (i.e., clinically overt, silent, or no stroke) were analysed in a subgroup analysis. The subgroups were additionally adjusted for total brain volume to eliminate the effect of simultaneous decrease of cerebral white matter. Results After multivariable adjustment, AF patients in the highest quartile of TMAO levels performed significantly poorer in the global cognitive score (CoCo: estimate −0.11, 95% CI [−0.17, −0.05], p=0.002) compared to patients in the lowest quartile. This was observed also in the MoCA, SFT, DSST, TMT-A and TMT-B. In the subgroup analysis, an association between the highest TMAO quartile (compared with the lowest quartile) and lower CoCo score was found in the group of patients with overt strokes (−0.18, 95% CI [−0.33, −0.04], p=0.012). Weak evidence of the same association was found in the group of patients with silent strokes (−0.13, 95% CI [−0.25, 0.002], p=0.053) and patients with no strokes (−0.08, 95% CI [−0.16, 0.01], p=0.07). After adjustment for decreased brain volume, the association remained for silent strokes (−0.14, 95% CI [−0.28, −0.01], p=0.036) indicating the impact of TMAO in this subgroup. Conclusion TMAO plasma levels were associated with cognitive impairment in patients with AF. Longitudinal data will clarify dynamics and likely causality between TMAO and cognitive impairment. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Swiss National Science Foundation

Brown adipose tissue dysfunction promotes heart failure via a trimethylamine N-oxide-dependent mechanism

Low body temperature predicts a poor outcome in patients with heart failure, but the underlying pathological mechanisms and implications are largely unknown. Brown adipose tissue (BAT) was initially characterised as a thermogenic organ, and recent studies have suggested it plays a crucial role in maintaining systemic metabolic health. While these reports suggest a potential link between BAT and heart failure, the potential role of BAT dysfunction in heart failure has not been investigated. Here, we demonstrate that alteration of BAT function contributes to development of heart failure through disorientation in choline metabolism. Thoracic aortic constriction (TAC) or myocardial infarction (MI) reduced the thermogenic capacity of BAT in mice, leading to significant reduction of body temperature with cold exposure. BAT became hypoxic with TAC or MI, and hypoxic stress induced apoptosis of brown adipocytes. Enhancement of BAT function improved thermogenesis and cardiac function in TAC mice. Conversely, systolic function was impaired in a mouse model of genetic BAT dysfunction, in association with a low survival rate after TAC. Metabolomic analysis showed that reduced BAT thermogenesis was associated with elevation of plasma trimethylamine N-oxide (TMAO) levels. Administration of TMAO to mice led to significant reduction of phosphocreatine and ATP levels in cardiac tissue via suppression of mitochondrial complex IV activity. Genetic or pharmacological inhibition of flavin-containing monooxygenase reduced the plasma TMAO level in mice, and improved cardiac dysfunction in animals with left ventricular pressure overload. In patients with dilated cardiomyopathy, body temperature was low along with elevation of plasma choline and TMAO levels. These results suggest that maintenance of BAT homeostasis and reducing TMAO production could be potential next-generation therapies for heart failure.

Implications of trimethylamine N-oxide (TMAO) and Betaine in Human Health: Beyond Being Osmoprotective Compounds.

Osmolytes are naturally occurring small molecular weight organic molecules, which are accumulated in large amounts in all life forms to maintain the stability of cellular proteins and hence preserve their functions during adverse environmental conditions. Trimethylamine N-oxide (TMAO) and N,N,N-trimethylglycine (betaine) are methylamine osmolytes that have been extensively studied for their diverse roles in humans and have demonstrated opposing relations with human health. These osmolytes are obtained from food and synthesized endogenously using dietary constituents like choline and carnitine. Especially, gut microbiota plays a vital role in TMAO synthesis and contributes significantly to plasma TMAO levels. The elevated plasma TMAO has been reported to be correlated with the pathogenesis of numerous human diseases, including cardiovascular disease, heart failure, kidney diseases, metabolic syndrome, etc.; Hence, TMAO has been recognized as a novel biomarker for the detection/prediction of several human diseases. In contrast, betaine acts as a methyl donor in one-carbon metabolism, maintains cellular S-adenosylmethionine levels, and protects the cells from the harmful effects of increased plasma homocysteine. Betaine also demonstrates antioxidant and anti-inflammatory activities and has a promising therapeutic value in several human diseases, including homocystinuria and fatty liver disease. The present review examines the multifarious functions of TMAO and betaine with possible molecular mechanisms towards a better understanding of their emerging and diverging functions with probable implications in the prevention, diagnosis, and treatment of human diseases.

Finasteride Alleviates High Fat Associated Protein-Overload Nephropathy by Inhibiting Trimethylamine N-Oxide Synthesis and Regulating Gut Microbiota.

Unhealthy diet especially high-fat diet (HFD) is the major cause of hyperlipidemia leading to deterioration of chronic kidney diseases (CKD) in patients. Trimethylamine N-oxide (TMAO) is a gut-derived uremic toxin. Our previous clinical study demonstrated that the elevation of TMAO was positively correlated with CKD progression. Finasteride, a competitive and specific inhibitor of type II 5a-reductase, has been reported recently to be able to downregulate plasma TMAO level thus preventing the onset of atherosclerosis by our research group. In this study, we established a protein-overload nephropathy CKD mouse model by bovine serum albumin (BSA) injection to investigate whether hyperlipidemia could accelerate CKD progression and the underlying mechanisms. Finasteride was administrated to explore its potential therapeutic effects. The results of biochemical analyses and pathological examination showed that HFD-induced hyperlipidemia led to aggravated protein-overload nephropathy in mice along with an elevated level of circulating TMAO, which can be alleviated by finasteride treatment possibly through inhibition of Fmo3 in liver. The 16 S rRNA sequencing results indicated that HFD feeding altered the composition and distribution of gut microbiota in CKD mice contributing to the enhanced level of TMAO precursor TMA, while finasteride could exert beneficial effects via promoting the abundance of Alistipes_senegalensis and Akkermansia_muciniphila. Immunofluorescence staining (IF) and qRT-PCR results demonstrated the disruption of intestinal barrier by decreased expression of tight junction proteins including Claudin-1 and Zo-1 in HFD-fed CKD mice, which can be rescued by finasteride treatment. Cytokine arrays and redox status analyses revealed an upregulated inflammatory level and oxidative stress after HFD feeding in CKO mice, and finasteride-treatment could alleviate these lesions. To summarize, our study suggested that finasteride could alleviate HFD-associated deterioration of protein-overload nephropathy in mice by inhibition of TMAO synthesis and regulation of gut microbiota.

Trimethylamine N-oxide facilitates the progression of atrial fibrillation in rats with type 2 diabetes by aggravating cardiac inflammation and connexin remodeling.

Diabetes is an independent risk factor for atrial fibrillation (AF). This study aimed to elucidate the pathophysiology of diabetes-related AF from the perspective of the gut microbial metabolite trimethylamine N-oxide (TMAO). In the present study, male rats received either a normal diet to serve as the control group or a high-fat diet/streptozotocin to induce type 2 diabetes mellitus. Then, diabetic rats were divided into two groups based on the presence or absence of 3,3-dimethyl-1-butanol (DMB, a specific TMAO inhibitor) in drinking water: the diabetic cardiomyopathy (DCM) group and the DCM + DMB group. Eight weeks later, compared with control rats, rats in the DCM group exhibited gut microbiota dysbiosis and systemic TMAO elevation. The inflammatory cytokines IL-1β, IL-6, and TNF-α were markedly increased in the atria of rats in the DCM group. Downregulated expression of connexin 40 and lateralized distribution of connexin 43 were also observed in the atria of DCM rats. AF inducibility was significantly higher in DCM rats than in control rats. Furthermore, DMB treatment effectively ameliorated atrial inflammation and connexin remodeling while markedly reducing plasma TMAO levels. DMB treatment also decreased the vulnerability of diabetic rats to AF. In conclusion, TMAO might promote atrial inflammation and connexin remodeling in the development of diabetes, which may play a key role in mediating diabetes-related AF.

Deferiprone has less benefits on gut microbiota and metabolites in high iron-diet induced iron overload thalassemic mice than in iron overload wild-type mice: A preclinical study

AimsThis study aimed to investigate the changes in gut microbiota in iron-overload thalassemia and the roles of an iron chelator on gut dysbiosis/inflammation, and metabolites, including short-chain fatty acids (SCFAs) and trimethylamine N-oxide (TMAO). Main methodsAdult male C57BL/6 mice both wild-type (WT: n = 15) and heterozygous β-thalassemia (BKO: n = 15) were fed on either a normal (ND: n = 5/group) or a high‑iron diet for four months (HFe: n = 10/group). HFe-treated WT and HFe-treated BKO groups were further subdivided into two subgroups and each subgroup given either vehicle (n = 5/subgroup) or deferiprone (n = 5/subgroup) during the last month. Gut microbiota profiles, gut barrier characteristics, levels of proinflammatory cytokines, and plasma SCFAs and TMAO were determined at the end of the study. Key findingsHFe-fed WT mice showed distinct gut microbiota profiles from those of ND-fed WT mice, whereas HFe-fed BKO mice showed slightly different gut microbiota profiles from ND-fed BKO. Gut inflammation and barrier disruption were found only in HFe-fed BKO mice, however, an increase in plasma TMAO levels and decreased levels of SCFAs were observed in both WT and BKO mice with HFe-feeding. Treatment with deferiprone, gut dysbiosis and disturbance of metabolites were attenuated in HFe-fed WT mice, but not in HFe-fed BKO mice. Increased Verrucomicrobia and Ruminococcaceae were associated with the beneficial effects of deferiprone. SignificanceIron-overload leads to gut dysbiosis/inflammation and disturbance of metabolites, and deferiprone alleviates those conditions more effectively in WT than in those that are thalassemic.

Akkermansia muciniphila prevents cold-related atrial fibrillation in rats by modulation of TMAO induced cardiac pyroptosis.

SummaryBackgroundCold exposure is one of the most important risk factors for atrial fibrillation (AF), and closely related to the poor prognosis of AF patients. However, the mechanisms underlying cold-related AF are poorly understood.MethodsVarious techniques including 16S rRNA gene sequencing, fecal microbiota transplantation, and electrophysiological examination were used to determine whether gut microbiota dysbiosis promotes cold-related AF. Metabonomics were performed to investigate changes in fecal trimethylamine (TMA) and plasma trimethylamine N-oxide (TMAO) during cold exposure. The detailed mechanism underlying cold-related AF were examined in vitro. Transgenic mice were constructed to explore the role of pyroptosis in cold-related AF. The human cohort was used to evaluate the correlation between A. muciniphila and cold-related AF.FindingsWe found that cold exposure caused elevated susceptibility to AF and reduced abundance of Akkermansia muciniphila (A. muciniphila) in rats. Intriguingly, oral supplementation of A. muciniphila ameliorated the pro-AF property induced by cold exposure. Mechanistically, cold exposure disrupted the A. muciniphila, by which elevated the level of trimethylamine N-oxide (TMAO) through modulation of the microbial enzymes involved in trimethylamine (TMA) synthesis. Correspondingly, progressively increased plasma TMAO levels were validated in human subjects during cold weather. Raised TMAO enhanced the infiltration of M1 macrophages in atria and increased the expression of Casp1-p20 and cleaved-GSDMD, ultimately causing atrial structural remodeling. Furthermore, the mice with conditional deletion of caspase1 exhibited resistance to cold-related AF. More importantly, a cross-sectional clinical study revealed that the reduction of A. muciniphila abundance was an independent risk factor for cold-related AF in human subjects.InterpretationOur findings revealed a novel causal role of aberrant gut microbiota and metabolites in pathogenesis of cold-related AF, which raises the possibility of selectively targeting microbiota and microbial metabolites as a potential therapeutic strategy for cold-related AF.FundingThis work was supported by grants from the State Key Program of National Natural Science Foundation of China (No.81830012), and National Natural Science Foundation of China (No.82070336, No.81974024), Youth Program of the National Natural Science Foundation of China (No.81900374, No.81900302), and Excellent Young Medical Talents supporting project in the First Affiliated Hospital of Harbin Medical University (No. HYD2020YQ0001).

Relation of Statin Use to Gut Microbial Trimethylamine N-Oxide and Cardiovascular Risk

Accumulating evidence suggests that statins can influence the microbiota. We investigated the effects of statin therapy on circulating levels of atherogenic gut microbial metabolite, trimethylamine N-oxide (TMAO), and subsequent clinical outcomes. We examined the effects of statin use on plasma TMAO in patients who are statin-naive with dyslipidemia previously enrolled in 2 intervention studies, International Medical Innovations (n=79) and Advances in Atorvastatin Research Group (n=27) in a post hoc analysis. A propensity score matching model stratified by statin use was used to validate the associations between statin use, plasma TMAO, and major adverse cardiovascular events across 4,007 patients who underwent elective coronary angiography. In the International Medical Innovations cohort, at 4weeks, statin use was associated with decreased plasma TMAO (p=0.03) and a return to baseline after statin discontinuation. In both intervention cohorts, patients with higher baseline TMAO (predefined cutoff 6.18μM) showed significant reductions in TMAO (all p &lt;0.05). Propensity score matching on statin use (1,196 patient-pairs) revealed lower plasma TMAO (p=0.002) with statin use. An adjusted cox regression model including statin use, TMAO, and cholesterol showed preserved association of statin use and TMAO but not cholesterol with major adverse cardiovascular events (p=0.005, p &lt;0.001, p=0.24, respectively). A likelihood ratio test showed improved model fit (p &lt;0.001) with the addition of TMAO. In conclusion, our findings demonstrate that statin therapy significantly decreases plasma TMAO levels, suggesting the potential contribution of a statin-mediated reduction of TMAO production in cardiovascular benefits in addition to improved lipid profile and attenuated inflammation.

Associations of plasma betaine, plasma choline, choline intake, and MTHFR polymorphism (rs1801133) with anthropometric parameters of healthy adults are sex-dependent.

Choline and its metabolites apppear to have relationships with body mass index (BMI), body fat, and body weight, but the research results have proved inconsistent. We thus investigated the associations of plasma levels of trimethylamine N-oxide (TMAO), choline, and betaine with anthropometric measurements, including modulatory effects of genetics and diet. The study was performed on a group of 421 adults, aged 20-40 years, who had been recruited in Poland. Plasma concentrations of choline, betaine, and TMAO were determined using reverse-phase ultra-high-performance liquid chromatography electrospray ionisation mass spectrometry. The following polymorphisms were genotyped using TaqMan probes: rs180113 (MTHFR), rs70991108 (DHFR), rs2236225 (MTHFD1), and rs7946 and rs12325817 (PEMT). We employed multivariate linear regression to examine the associations between anthropometric measurements, one-carbon metabolism metabolites, and genotypes. Higher plasma choline was associated with higher BMI (β = 0.17; p < 0.01), body weight (β = 0.11; p < 0.05), body fat mass (FM) (β = 0.10; p < 0.05), and waist circumference (WC) (β = 0.14; p < 0.01), whereas higher choline intake was associated with lower body FM (β = -0.14; p < 0.01) and lower WC (β = -0.12; p < 0.01). After stratification by sex, plasma betaine was found to be associated with lower BMI (β = -0.20; p < 0.05) and body weight (β = -0.16; p < 0.05) in men only, whereas choline intake was associated with lower body FM (β = -0.19; p < 0.05) and waist-to-hip ratio (WHR) (β = -0.19; p < 0.05) and MTHFR CC genotype was associated with WHR (β = 0.15; p < 0.05) in women only. Higher plasma betaine and higher dietary choline are associated with lower FM and body weight, whereas higher plasma choline is positively associated with body weight status and adiposity. Moreover, these associations appear to be sex-specific.

Association between trimethylamine N-oxide and prognosis of patients with acute myocardial infarction and heart failure.

This study aimed to investigate the association between trimethylamine N-oxide (TMAO) and the prognosis and association between high-sensitivity C-reactive protein (hsCRP) and TMAO-associated cardiovascular risk in patients with acute myocardial infarction (AMI) complicated by heart failure (HF). A total of 985 patients presenting with AMI and HF were consecutively enrolled at the Fuwai Hospital between March 2017 and January 2020. Patients were stratified into groups according to tertiles of TMAO levels and the median hsCRP levels. The primary endpoint was major adverse cardiac events (MACE), including all-cause death, recurrence of myocardial infarction, and rehospitalization due to HF. During a median follow-up of 716days, 138 (14.0%) patients experienced MACE. Cox regression analyses showed that the adjusted hazard ratio (HR) for MACE was higher in patients in tertile 3 [TMAO>9.52μmol/L, HR: 1.85, 95% confidence interval (CI): 1.18-2.89; P=0.007] than in tertile 1 (TMAO<4.74μmol/L), whereas no significant differences were detected between the patients in tertiles 1 and 2 (TMAO=4.74-9.52μmol/L, HR: 0.96, 95% CI: 0.59-1.58; P=0.874). Restricted cubic spline regression depicted an S-shaped association between TMAO and MACE (P for nonlinearity=0.012). In the setting of hsCRP above the median level (6.68mg/L), per unit increase of TMAO was associated with a 20% increase of MACE risk (HR: 1.20, 95% CI: 1.05-1.37, P=0.009); increasing tertiles of TMAO were significantly associated with a higher risk of MACE (adjusted P=0.007 for interaction; P<0.001 for trend across tertiles). The Kaplan-Meier analysis indicated that patients in tertile 3 had a significantly lower event-free survival (P=0.001) when the hsCRP level was above the median level. No similar association between TMAO and MACE was observed when the hsCRP level was below the median level. High plasma TMAO levels were independently correlated with poor prognosis in patients with AMI complicated by HF, especially in those with higher hsCRP levels. There was an S-shaped relationship between TMAO and HR for MACE.

Deficiency of proline/serine-rich coiled-coil protein 1 (PSRC1) accelerates trimethylamine N-oxide-induced atherosclerosis in ApoE−/− mice

AimsThe main therapeutic strategies for coronary artery disease (CAD) are mainly based on the correction of abnormal cholesterol levels; however, residual risks remain. The newly proven gut microbial metabolite trimethylamine N-oxide (TMAO) linked with CAD has broadened our horizons. In this study, we determined the role of proline/serine-rich coiled-coil protein 1 (PSRC1) in TMAO-driven atherosclerosis. Methods and resultsWe first analyzed the levels of TMAO and PSRC1 in patients with or without atherosclerosis with a target LDL-C < 1.8 mmol/L. Plasma TMAO levels were increased and negatively associated with decreased PSRC1 in peripheral blood mononuclear cells. Animals and in vitro studies showed that TMAO inhibited macrophage PSRC1 expression due to DNA hypermethylation of CpG islands. ApoE−/− mice fed a choline-supplemented diet exhibited reduced PSRC1 expression accompanied by increased atherosclerotic lesions and plasma TMAO levels. We further deleted PSRC1 in apoE−/− mice and PSRC1 deficiency significantly accelerated choline-induced atherogenesis, characterized by increased macrophage infiltration, foam cell formation and M1 macrophage polarization. Mechanistically, we overexpressed and knocked out PSRC1 in cultured macrophages to explore the mechanisms underlying TMAO-induced cholesterol accumulation and inflammation. PSRC1 deletion impaired reverse cholesterol transport and enhanced cholesterol uptake and inflammation, while PSRC1 overexpression rescued the proatherogenic phenotype observed in TMAO-stimulated macrophages, which was partially attributed to sulfotransferase 2B1b (SULT2B1b) inhibition. ConclusionsHerein, clinical data provide evidence that TMAO may participate in the development of CAD beyond well-controlled LDL-C levels. Our work also suggests that PSRC1 is a negative regulator mediating the unfavorable effects of TMAO-containing diets. Therefore, PSRC1 overexpression and reduced choline consumption may further alleviate atherosclerosis.