Elevated Trimethylamine N-oxide Levels Research Articles

Gut microbiota-derived metabolite trimethylamine N-oxide aggravates cognitive dysfunction induced by femoral fracture operation in mice.

An increasing number of elderly individuals are experiencing postoperative cognitive dysfunction (POCD) problems after undergoing hip replacement surgery, with gut microbiota metabolites playing a role in its pathogenesis. Among these, the specific effects of trimethylamine N-oxide (TMAO) on POCD are still unclear. This study aimed to explore the role of TMAO on cognitive dysfunction and underlying mechanisms in mice. The POCD model was created through femoral fracture surgery in elderly mice, followed by cognitive function assessments using the Morris Water Maze and Novel Object Recognition tests. The gut microbiota depletion and fecal microbiota transplantation were performed to examine the relationship between TMAO levels and cognitive outcomes. The effects of TMAO treatment on cognitive dysfunction, microglial activation, and inflammatory cytokine levels in the brain were also evaluated, with additional assessment of the role of microglial ablation in reducing TMAO-induced cognitive impairment. Elevated TMAO levels were found to be associated with cognitive decline in mice following femoral fracture surgery, with gut microbiota depletion mitigating both TMAO elevation and cognitive dysfunction. In contrast, fecal microbiota transplantation from postoperative mice resulted in accelerated cognitive dysfunction and TMAO accumulation in germ-free mice. Furthermore, TMAO treatment worsened cognitive deficits, neuroinflammation, and promoted microglial activation, which were reversed through the ablation of microglia. TMAO exacerbates cognitive dysfunction and neuroinflammation in POCD mice, with microglial activation playing a crucial role in this process. Our findings may provide new therapeutic strategies for managing TMAO-related POCD and improving the quality of life for elderly patients.

The Brain-Gut Axis, an Important Player in Alzheimer and Parkinson Disease: A Narrative Review.

Neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are severe age-related disorders with complex and multifactorial causes. Recent research suggests a critical link between neurodegeneration and the gut microbiome, via the gut-brain communication pathway. This review examines the role of trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite, in the development of AD and PD, and investigates its interaction with microRNAs (miRNAs) along this bidirectional pathway. TMAO, which is produced from dietary metabolites like choline and carnitine, has been linked to increased neuroinflammation, protein misfolding, and cognitive decline. In AD, elevated TMAO levels are associated with amyloid-beta and tau pathologies, blood-brain barrier disruption, and neuronal death. TMAO can cross the blood-brain barrier and promote the aggregation of amyloid and tau proteins. Similarly, TMAO affects alpha-synuclein conformation and aggregation, a hallmark of PD. TMAO also activates pro-inflammatory pathways such as NF-kB signaling, exacerbating neuroinflammation further. Moreover, TMAO modulates the expression of various miRNAs that are involved in neurodegenerative processes. Thus, the gut microbiome-miRNA-brain axis represents a newly discovered mechanistic link between gut dysbiosis and neurodegeneration. MiRNAs regulate the key pathways involved in neuroinflammation, oxidative stress, and neuronal death, contributing to disease progression. As a direct consequence, specific miRNA signatures may serve as potential biomarkers for the early detection and monitoring of AD and PD progression. This review aims to elucidate the complex interrelationships between the gut microbiota, trimethylamine-N-oxide (TMAO), microRNAs (miRNAs), and the central nervous system, and the implications of these connections in neurodegenerative diseases. In this context, an overview of the current neuroradiology techniques available for studying neuroinflammation and of the animal models used to investigate these intricate pathologies will also be provided. In summary, a bulk of evidence supports the concept that modulating the gut-brain communication pathway through dietary changes, the manipulation of the microbiome, and/or miRNA-based therapies may offer novel approaches for implementing the treatment of debilitating neurological disorders.

Targeting the Gut-Kidney Axis in Diarrhea with Kidney-Yang Deficiency Syndrome: The Role of Sishen Pills in Regulating TMAO-Mediated Inflammatory Response.

BACKGROUND Sishen Pills (SSPs) are commonly used to treat diarrhea with kidney-yang deficiency syndrome. Trimethylamine-N-oxide (TMAO) is produced through the metabolism of gut microbiota and can participate in diarrhea in kidney-yang deficiency syndrome by mediating the "gut-kidney axis" to transmit inflammatory factors. This study combined network pharmacology with animal experiments to explore whether SSPs can treat diarrhea with kidney-yang deficiency syndrome by affecting the interaction between TMAO and gut microbiota. MATERIAL AND METHODS A mouse model of diarrhea with kidney-yang deficiency syndrome was constructed by using adenine and Folium sennae decoction, and SSP decoction was used for treatment. This study utilized network pharmacology to predict the potential mechanisms of SSPs in treating diarrhea with kidney-yang deficiency syndrome. 16S rRNA high-throughput sequencing was used to analyze gut mucosal microbial characteristics. ELISA was used to measure TMAO, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), interleukin-1ß (IL-1ß), and transforming growth factor-ß1 (TGF-ß1) levels. We performed Masson and immunohistochemical (Occludin, ZO-1) staining of kidney and small intestinal tissues. The fluorescein diacetate (FDA) hydrolysis spectrophotometric method was used to assess the microbial activity in contents of the small intestine. RESULTS Network pharmacology analysis revealed that SSPs can modulate 108 target points involved in the development of diarrhea, including IL-1ß and TNF. The experimental results demonstrated that SSP decoction significantly improved the general behavioral profiles of the mice, and also reduced TMAO, NLRP3, IL-1ß, and TGF-ß1 levels (P<0.05). Correlation analysis revealed significant positive correlations between TMAO concentrations and NLRP3, IL-1ß and TGF-ß1 levels (P<0.05). Pathological analysis revealed improvements in renal fibrosis and increased expression of the Occludin and ZO-1 proteins in intestinal tissue. In the SSP group, there was a significant increase in microbial activity (P<0.001). According to the sequencing results, the characteristic bacteria of the SSP and NR groups included Succinatimonas hippei, uncultured Solirubrobacter sp., and Clostridium tyrobutyricum. Furthermore, TMAO, NLRP3, IL-1ß, and TGF-ß1 were significantly positively correlated (P<0.05) with Succinatimonas hippei and Clostridium tyrobutyricum. By modulating Firmicutes, Succinatimonas hippei, and Clostridium tyrobutyricum, SSP decoction lowers TMAO levels to alleviate diarrhea with kidney-yang deficiency syndrome. CONCLUSIONS TMAO likely plays a significant role in the "gut-kidney axis" of diarrhea with kidney-yang deficiency syndrome. By adjusting gut microbiota to reduce the inflammatory response that is transmitted through the "gut-kidney axis" as a result of elevated TMAO levels, SSP decoction can alleviate diarrhea with kidney-yang deficiency syndrome.

Circulating TMAO, the gut microbiome and cardiometabolic disease risk: an exploration in key precursor disorders

BackgroundElevations in the gut metabolite trimethylamine-N-oxide (TMAO) have been linked to cardiovascular and metabolic diseases. Whether elevated TMAO levels reflect early mechanistic involvement or a sequela of evolving disease awaits elucidation. The purpose of this study was to further explore these potential associations.MethodsWe investigated relationships between circulating levels of TMAO and its pre-cursor substrates, dietary factors, gut microbiome profiles and disease risk in individuals with a Healthy BMI (18.5 < BMI < 25, n = 41) or key precursor states for cardiometabolic disease: Overweight (25 < BMI < 30 kg/m2, n = 33), Obese (BMI > 30, n = 27) and Metabolic Syndrome (MetS; ≥ 3 ATPIII report criteria, n = 39).ResultsUnexpectedly, plasma [TMAO] did not vary substantially between groups (means of 3–4 µM; p > 0.05), although carnitine was elevated in participants with MetS. Gut microbial diversity and Firmicutes were also significantly reduced in the MetS group (p < 0.05). Exploratory analysis across diverse parameters reveals significant correlations between circulating [TMAO] and seafood intake (p = 0.007), gut microbial diversity (p = 0.017–0.048), and plasma [trimethylamine] (TMA; p = 0.001). No associations were evident with anthropometric parameters or cardiometabolic disease risk. Most variance in [TMAO] within and between groups remained unexplained.ConclusionsData indicate that circulating [TMAO] may be significantly linked to seafood intake, levels of TMA substrate and gut microbial diversity across healthy and early disease phenotypes. However, mean concentrations remain < 5 µM, with little evidence of links between TMAO and cardiometabolic disease risk. These observations suggest circulating TMAO may not participate mechanistically in cardiometabolic disease development, with later elevations likely a detrimental sequela of extant disease.

Gut microbiota metabolites and risk of major adverse cardiovascular events and death: A systematic review and meta-analysis

Background: Gut microbial metabolites such as trimethylamine N-oxide (TMAO) and its precursors, namely betaine, L-carnitine, and choline, have been implicated as risk factors for cardiovascular events and mortality development. Therefore, we aim to perform a systematic review and meta-analysis to assess the validity of these associations. Methods: MEDLINE and Scopus were queried from their inception to August 2023 to identify studies that quantified estimates of the associations of TMAO with the development of major adverse cardiovascular events (MACE) or death. A random-effects meta-analysis was conducted to pool unadjusted or multivariable-adjusted hazard ratios (HR) and their 95% confidence intervals. The primary endpoint was the risk of MACE and all-cause death. Results: 30 prospective observational studies (n = 48 968) were included in the analysis. Elevated TMAO levels were associated with a significantly greater risk of MACE and all-cause death compared to low TMAO levels (HR: 1.41, 95% CI 1.2–1.54, P &lt; .00001, I 2 = 43%) and (HR: 1.55, 95% CI 1.37–1.75, P &lt; .00001, I 2 = 46%), respectively. Furthermore, high levels of either L-carnitine or choline were found to significantly increase the risk of MACE. However, no significant difference was seen in MACE in either high or low levels of betaine. Conclusion: Elevated concentrations of TMAO were associated with increased risks of MACE and all-cause mortality. High levels of L-carnitine/choline were also significantly associated with an increased risk of MACE. However, no significant difference was found between high or low levels of betaine for the outcome of MACE.

Empagliflozin Mitigates TMAO-Induced NLRP3 Inflammation and Alters Transporter Expression in Renal Proximal Tubular Cells

The gut-microbe-derived metabolite, trimethylamine N-oxide (TMAO), not only exhibits elevated levels but also serves as a predictor of higher mortality in patients with chronic kidney disease (CKD). In additional to CKD, elevated TMAO levels were also observed in organic anion transporter 3 (OAT 3) knockout mice and in the presence of trimethoprim, an antibiotic known for inhibiting multiple transporters on renal proximal tubule (PT) cells. These findings suggest that plasma TMAO level is a marker for diminished transporter function in PT cells. Moreover, the pro-inflammatory effects of TMAO on PT cells is relatively underexplored. Besides reno-protective effect, a recent study has shown that the sodium-glucose cotransporter 2 (SGLT2) inhibitor empagliflozin attenuates hyperuricemia by enhancing efflux transporter function. Therefore, we propose that empagliflozin can ameliorate TMAO-induced inflammation in PT cells by regulating the expression of membrane transporters. Western blotting results revealed that empagliflozin mitigated TMAO-induced NLRP3 inflammatory cytokines IL-1β, and IL-18. Additionally, empagliflozin reduced the elevated serum levels of TMAO in a CKD mouse model resulting from 5/6 nephrectomy (5/6Nx). Immuno-fluorescent staining demonstrated that TMAO decreased the expression of the basolateral transporter organic anion transporter 1 (OAT1) but increased the expression of apical membrane transporters ATP-binding cassette super-family G member 2 (ABCG2) on the PT cells of 5/6Nx mice. Our in vitro study indicated that TMAO reduced the expression of basolateral membrane transporters OAT1 and OAT3. But empagliflozin significantly increased the expression of OAT3 and ABCG2 in TMAO-treated HK-2 cells. In summary, TMAO induced NLRP3 inflammation in PT cells, while empagliflozin ameliorated the inflammation. Empagliflozin also lowered TMAO levels and influenced transporter expressions in a CKD mouse model. In conclusion, we have shown that empagliflozin mitigate TMAO-induced NLRP3 inflammation. Beyond inhibiting SGLT2, empagliflozin possesses additional effect on the expression of membrane transporters in PT, particularly in CKD mice. This research was funded by Chang Gung Medical Foundation CMRPG8K0011 and CMRPG8M0311. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 128: Blood TMAO Predicts Abdominal Aortic Aneurysm Growth Rate And Need For Surgical Intervention

Background: Patients known to have abdominal aortic aneurysms (AAAs) undergo surveillance imaging to predict both the risk for acute aortic syndromes including aortic dissection and aortic rupture, and the need for surgical intervention. Aortic rupture is a feared consequence of rapidly expanding AAAs. Aims: A blood biomarker that predicts risk for AAA and distinguishes slow from fast AAA growth does not exist but could be a valuable tool for risk stratification. We recently reported systemic levels of the gut microbe-generated metabolite trimethylamine N-oxide (TMAO) are associated with the presence of AAA in humans, and directly contribute to AAA progression in animal models. Methods: We leveraged access 805 patients in two cohorts from Europe (n=237) and the United States (n=658) undergoing serial aortic imaging surveillance. Blood TMAO concentration was measured by stable isotope dilution mass spectrometry. Results: TMAO was positively associated with larger baseline and follow-up abdominal aortic diameter beyond traditional factors (Adjusted OR 3.87, 95% CI, 2.70-5.58, P&lt;0.001). In addition, TMAO predicted rapid AAA growth (HR 1.81, 95%CI, 1.23-2.67, P=0.0029). When TMAO was added to a predictive model of traditional risk factors for AAA, we saw a significant improvement in the net reclassification index (NRI, 0.43, P &lt; 0.001; C statistic, 0.77 (0.72–0.81) with TMAO vs. NRI 0.73 (0.69–0.78) without TMAO, P =0.005). Finally, including TMAO in a predictive model for assessing need for surgical intervention among AAA patients significantly improved the prognostic performance of the model (NRI, 0.44, P &lt; 0.001; C statistic, 0.78 (0.73–0.82) with TMAO vs. 0.75 (0.70–0.79) without TMAO, P =0.004) (Fig. 1). Conclusions: Elevated TMAO levels predict increased risk of AAA, and identify patients with fast-growing AAA and those who may benefit from early surgical intervention to prevent acute aortic syndromes.

The prediction value of combined serum levels of TMAO and TML for poor prognosis in patients with heart failure

Objective: To evaluate the predictive value of combined serum levels of trimethylamine N-oxide (TMAO) and trimethyllysine (TML) for poor prognosis in patients with heart failure. Methods: This single-center prospective cohort study included hospitalized patients with heart failure and complete baseline data from the Department of Cardiology at Ruijin Hospital, Shanghai Jiao Tong University School of Medicine from June 2017 to December 2020. Patients were categorized into four groups based on median serum levels of TMAO and TML after admission: TMAO low level TML low level group (TMAO<9.7 μmol/L, TML<0.73 μmol/L), TMAO low level TML high level group (TMAO<9.7 μmol/L, TML≥0.73 μmol/L), TMAO high level TML low level group (TMAO≥9.7 μmol/L, TML<0.73 μmol/L) and TMAO high level TML high level group (TMAO≥9.7 μmol/L, TML≥0.73 μmol/L). The primary endpoint was a composite endpoint of cardiovascular death and readmission for heart failure. Multiple factor Cox regression analysis was conducted to evaluate the correlation between serum TMAO and TML levels and poor prognosis in patients with heart failure. Results: A total of 471 patients with heart failure were included, with an mean age of (62.5±12.0) years and a median follow-up time of 1.61 (1.06, 2.90) years. Multivariate Cox regression analysis showed that after adjusting for age, gender, and traditional risk factors, the TMAO high level TML high level group had a higher incidence of primary endpoint events compared to the TMAO low level TML low level group (HR=1.71, 95%CI 1.05-2.77, P=0.03). Conclusion: Elevated serum levels of both TMAO and TML can effectively predict the occurrence of long-term adverse events in patients with heart failure.

Gut-Derived Trimethylamine N-Oxide Promotes CCR2-Mediated Macrophage Infiltration in acute kidney injury.

Inflammation is crucial in the development of AKI and subsequent CKD following renal ischemia-reperfusion (IR) injury. Gut microbiota metabolites trigger inflammation and affect IR-induced renal damage. Yet, the driving factors and mechanisms are unclear. Trimethylamine N-oxide (TMAO), a gut-derived choline metabolite, is a strong pro-inflammatory factor that increases in patients with AKI and CKD. We hypothesized that TMAO can promote renal injury caused by IR. Mice subjected to unilateral renal IR to induce AKI and CKD were fed a high-choline diet to observe the effects of TMAO on kidney inflammation, fibrosis, and macrophage dynamics. A choline-rich diet altered the gut microbiota and elevated TMAO levels, which exacerbated IR-induced AKI and subsequent CKD. Single-cell analysis identified a distinct subset of CCR2+ macrophages derived from monocytes as key responders to TMAO, intensifying immune cell interactions and worsening renal injury. TMAO promoted sustained CCR2 expression after IR, increasing macrophage infiltration. CCR2 deletion and antagonist RS-102895 improved TMAO-induced inflammation and fibrosis, alleviated renal injury induced by IR. Our study provides valuable insights into the link between TMAO and IR-incited renal inflammation and fibrosis, emphasizing the critical role of TMAO-mediated macrophage infiltration via CCR2 as a key therapeutic target in the acute and chronic phase after IR.

Research progress in the relationship between gut microbiota metabolite trimethylamine N-oxide and ischemic stroke.

Ischemic stroke (IS) is a severe cerebrovascular disease that seriously endangers human health. Gut microbiota plays a key role as an intermediate mediator in bidirectional regulation between the brain and the intestine. In recent years, trimethylamine N-oxide (TMAO) as a gut microbiota metabolite has received widespread attention in cardiovascular diseases. Elevated levels of TMAO may increase the risk of IS by affecting IS risk factors such as atherosclerosis, atrial fibrillation, hypertension, and type 2 diabetes. TMAO exacerbates neurological damage in IS patients, increases the risk of IS recurrence, and is an independent predictor of post-stroke cognitive impairment (PSCI) in patients. Current research suggests that the mechanisms of TMAO action include endothelial dysfunction, promoting of foam cell formation, influence on cholesterol metabolism, and enhancement of platelet reactivity. Lowering plasma TMAO levels through the rational use of traditional Chinese medicine, dietary management, vitamins, and probiotics can prevent and treat IS.

The association of dietary nitrates/nitrites intake and the gut microbial metabolite trimethylamine N-oxide and kynurenine in adults: a population-based study.

Dietary nitrate and nitrite may affect the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO) and kynurenine (KYN). However, this association and the exact mechanism are still unclear. Therefore, this study aimed to assess the association between dietary consumption of nitrite and nitrate on TMAO and KYN levels in adults. This cross-sectional study was employed on a subsample baseline phase of the Tehran University of Medical Sciences (TUMS) Employee's Cohort Study (TEC). A total of 250 adults aged 18 years or older were included in the current analysis. Data on the dietary intakes were collected using a validated dish-based food frequency questionnaire (FFQ), and dietary intakes of nitrite and nitrate were estimated using the FFQ with 144 items. Serum profiles and TMAO and KYN were measured using a standard protocol. The findings of this study demonstrate a significant association between the intake of animal sources of nitrate and nitrite and the likelihood of having elevated levels of TMAO and KYN. Specifically, after adjustment, individuals with the highest intake adherence to nitrates from animal sources exhibited increased odds of having the highest level of TMAO (≥51.02 pg/ml) (OR = 1.51, 95% CI = 0.59-3.88, P = 0.03) and KYN (≥417.41 pg/ml) (OR = 1.75, 95% CI = 0.73-4.17, P = 0.02). Additionally, subjects with the highest animal intake from nitrite sources have 1.73 and 1.45 times higher odds of having the highest levels of TMAO and KYN. These results emphasize the potential implications of animal-derived nitrate and nitrite consumption on the levels of TMAO and KYN. The present evidence indicates that a high level of nitrate and nitrite intake from animal sources can increase the odds of high levels of TMAO and KYN. Further studies suggest that we should better evaluate and understand this association.

Association of serum trimethylamine N-oxide levels and bone mineral density in type 2 diabetes mellitus.

The relationship between trimethylamine N-oxide (TMAO) and bone mineral density (BMD) in type 2 diabetes mellitus (T2DM) is unclear. We explore the relationship between TMAO levels and BMD in T2DM. This is a cross-sectional study. 254 T2DM patients were enrolled and divided into three groups by TMAO tertiles, and the clinical data were collected. BMD was determined by dual-energy X-ray absorptiometry (DXA) and serum TMAO levels was determined by stable isotope dilution high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Patients in the highest tertile of TMAO levels (TMAO > 6.72 μmol/L) showed relatively low BMD and a higher number of fracture history, osteoporosis (OP) than those in the lower tertiles. Spearman correlation analysis showed that serum TMAO was negatively correlated with BMD of whole body (WB), lumbar spine (LS) and femoral neck (FN), while TMAO was positive correlated with osteoporotic fracture (p < 0.05). Logistic regression models showed that TMAO was an independent influencing factor of fracture history after adjusting for confounders in TMAO > 6.72 μmol/L group. There is a significant linear correlation between TMAO levels and BMD in T2DM patients. Especially in TMAO > 6.72 μmol/L group, TMAO was negatively correlated with WB, LS, and FN BMD, and was positive correlated with osteoporotic fracture in T2DM patients. The findings suggest that elevated TMAO levels are associated with OP and osteoporotic fracture in T2DM patients.

1H NMR Serum Metabolomic Change of Trimethylamine N-oxide (TMAO) Is Associated with Alcoholic Liver Disease Progression.

Without early detection and treatment, chronic and excessive alcohol consumption can lead to the development of alcoholic liver disease (ALD). With this in mind, we exploit the recent concept of the liver-gut axis and analyze the serum profile of ALD patients for identification of microbiome-derived metabolites that can be used as diagnostic biomarkers for onset of ALD. 1H-NMR was used to analyze serum metabolites of 38 ALD patients that were grouped according to their Child-Turcotte-Pugh scores (CTP): class A (CTP-A; 19), class B(CTP-B; 10), and class C (CTP-C; 9). A partial least squares-discriminant analysis (PLS-DA) and a variable importance of projection (VIP) score were used to identify significant metabolites. A receiver operating characteristic (ROC) curve and correlation heatmap were used to evaluate the predictability of identified metabolites as ALD biomarkers. Among 42 identified metabolites, 6 were significantly correlated to exacerbation of ALD. As ALD progressed in CTP-C, the levels of trimethylamine N-oxide (TMAO), malate, tyrosine, and 2-hydroxyisovalerate increased, while isobutyrate and isocitrate decreased. Out of six metabolites, elevated levels of TMAO and its precursors (carnitine, betaine, choline) were associated with severity of ALD. This indicates that TMAO can be used as an effective biomarker for the diagnosis of ALD progression.

Trimethylamine-N-oxide (TMAO) and basic fibroblast growth factor (bFGF) are possibly involved in corticosteroid resistance in adult patients with immune thrombocytopenia

PurposeImmune thrombocytopenia (ITP) is an autoimmune disease characterized by accelerated platelet clearance. Gut dysbiosis was associated with its pathogenesis, but the underlying mechanisms have not been fully elucidated. Patients with ITP exhibit varying degrees of responsiveness to corticosteroid treatment. Therefore, prognostic indexes for corticosteroid responsiveness in ITP could offer valuable guidance for clinical practices. MethodsThe present study examined the signature of six types of gut-microbiota metabolites and forty-eight types of cytokines, chemokines, and growth factors and their clinical significance in patients with ITP. ResultsBoth patients with good and poor corticosteroid responsiveness exhibited significantly elevated/suppressed secretion of twenty-two cyto(chemo)kins/growth factors in comparison to healthy controls. Additionally, patients with ITP demonstrated a significant decrease in plasma levels of trimethylamine-N-oxide (TMAO), which was found to be negatively correlated to circulating platelet counts, and positively correlated with Interleukin (IL)-1β and IL-18. Notably, patients who exhibited poor response to corticosteroid treatment displayed elevated levels of TMAO and basic fibroblast growth factor (bFGF) in comparison to responders. Additionally, we found that the amalgamation of TMAO, bFGF and interleukin (IL)-13 could serve as a valuable prognostic tool for predicting CS responsiveness. ConclusionPatients with ITP were characterized overall by an imbalanced secretion of cyto(cheo)kins/growth factors and inadequate levels of TMAO. The varying degrees of responsiveness to corticosteroid treatment can be attributed to different profiles of basic FGF and TMAO that might be related to overburdened oxidative stress and inflammasome overactivation, and ultimately mediate corticosteroid resistance.

Abstract 13681: Association of Serum Trimethylamine N-oxide Levels With Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

Background: Trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite of red meat, has emerged as a potential biomarker for CVD and all-cause mortality. It is also found in preformed amounts in fish. However, the association between serum TMAO levels and CVD outcomes remain unclear. Aim: To conduct a systematic review and dose-response meta-analysis evaluating the association between serum TMAO and CVD and all-cause mortality in prospective cohort studies. Methods: A comprehensive literature search was conducted in MEDLINE, EMBASE, and Cochrane Library up to and including March 6, 2023. A manual search through references found in reviews and meta-analyses was also conducted. Studies reporting hazard ratios (HRs) or relative risks (RRs) with 95% confidence intervals (CIs) for the association between serum TMAO levels and CVD or all-cause mortality in adults ≥ 18 years with follow-up of ≥ 1 year were included. Random-effects models were utilized for pooled risk estimates and assess the dose-response. GRADE was used to evaluate certainty of evidence. Results: 2459 papers, 44 prospective cohort studies were included involving 84771 participants included in final analysis (fig.1). Pooled analyses revealed a significant positive association between elevated serum TMAO levels and the risk of total CVD (RR 1.29 [1.16-1.44]), CVD mortality (RR 1.51 [1.23-1.87]) and all-cause mortality (RR 1.30 [1.21,1.39]). Non-significant associations were found for MI, stroke, total CHD, MI mortality and CHD mortality. All outcomes were of low to very low certainty.Dose response analysis revealed a significant linear association with all-cause mortality (RR 1.01 [95% CI 1.01, 1.02] per 2μM/L) up to a threshold of 6μM/L and total CVD (RR 1.04 [1.02-1.06]). Conclusion: This study provides evidence supporting the positive association of serum TMAO levels with increased risk of total CVD, CVD mortality and all-cause mortality. A recent review found 13/15 studies demonstrated a strong positive correlation between TMAO and fish intake, complicating the hypotheses relating TMAO in red meat and CVD risk. Thus, further assessments of diet components are needed to explore the clinical implications of the associations found in our study.

The relationship between trimethylamine-N-oxide and the risk of acute ischemic stroke: A dose‒response meta-analysis.

Although trimethylamine-N-oxide (TMAO) shows a notable correlation with cardiovascular disease, its association with acute ischemic stroke (AIS) remains uncertain and necessitates further investigation. A meta-analysis was conducted to assess the relationship between trimethylamine-N-oxide and acute ischemic stroke. We conducted a comprehensive search in PubMed, Embase, Cochrane, CNKI, VIP, Wanfang, and CBM, spanning from their inception to 23 September 2023. The search was consistently updated and supplemented by bibliographies of retrieved articles and previous reviews. A total of 20 eligible studies, including 17 case‒controls and 3 cohort studies, were selected, involving 9141 participants (5283 case group, 3858 control group). For the dose‒response analysis, three case-control studies were eligible. We extracted and pooled TMAO mean and standard deviation from observational studies for control and ischemic stroke groups. The effect sizes were combined using the random-effects model. Where possible, dose‒response analysis was performed. Overall, the pooled standardized mean difference (SMD) demonstrated significantly higher concentrations of serum/plasma TMAO in AIS compared to the control group (SMD = 1.27; 95% CI: 0.9, 1.61, P<0.001). Additionally, the dose‒response meta-analysis revealed a 12.1% relative increase in the risk of acute ischemic stroke per 1 μmol/L rise in TMAO concentration (RR = 1.12; 95% CI 1.07-1.17; P<0.05; I2 = 1.6%, P = 0.4484). These findings indicate a potential increased risk of AIS associated with elevated TMAO levels.

Trimethylamine N-oxide generation process was influenced by the proportion and source of macronutrients in the diet

Trimethylamine N-oxide (TMAO) is a risk factor of various chronic diseases, which was produced by metabolism from precursors to trimethylamine (TMA) in gut and the oxidation from TMA in liver. The TMA generation was influenced by diet, mainly due to the rich TMAO precursors in diet. However, it was still unclear that the effects of different proportion and source of macronutrients in different dietary pattern on the production process of TMAO. Here, the generation of TMA from precursors and TMAO from TMA was determined after single oral choline chloride and intraperitoneal injection TMA, respectively, in mice fed with carbohydrates, proteins and fats in different proportion and sources. The results suggested that the generation of TMAO was increased by low non-meat protein and high fat via enhancing the production of TMAO from TMA, and decreased by plant protein and refined sugar via reducing TMA production from precursors in gut and TMAO transformation from TMA in liver. The high fat and high sugar diets accelerating the development of atherosclerosis did not increase the production of TMAO, the risk factor for atherosclerosis, which indicated that the dietary compositions rather than the elevated TMAO level might be a more key risk factor for atherosclerosis.

Connections between serum Trimethylamine N-Oxide (TMAO), a gut-derived metabolite, and vascular biomarkers evaluating arterial stiffness and subclinical atherosclerosis in children with obesity.

Childhood obesity leads to early subclinical atherosclerosis and arterial stiffness. Studying biomarkers like trimethylamine N-oxide (TMAO), linked to cardio-metabolic disorders in adults, is crucial to prevent long-term cardiovascular issues. The study involved 70 children aged 4 to 18 (50 obese, 20 normal-weight). Clinical examination included BMI, waist measurements, puberty stage, the presence of acanthosis nigricans, and irregular menstrual cycles. Subclinical atherosclerosis was assessed by measuring the carotid intima-media thickness (CIMT), and the arterial stiffness was evaluated through surrogate markers like the pulse wave velocity (PWV), augmentation index (AIx), and peripheral and central blood pressures. The blood biomarkers included determining the values of TMAO, HOMA-IR, and other usual biomarkers investigating metabolism. The study detected significantly elevated levels of TMAO in obese children compared to controls. TMAO presented positive correlations to BMI, waist circumference and waist-to-height ratio and was also observed as an independent predictor of all three parameters. Significant correlations were observed between TMAO and vascular markers such as CIMT, PWV, and peripheral BP levels. TMAO independently predicts CIMT, PWV, peripheral BP, and central SBP levels, even after adding BMI, waist circumference, waist-to-height ratio, puberty development and age in the regression model. Obese children with high HOMA-IR presented a greater weight excess and significantly higher vascular markers, but TMAO levels did not differ significantly from the obese with HOMA-IR<cut-offs. TMAO did not correlate to HOMA-IR and insulin levels but presented a negative correlation to fasting glucose levels. An increase in TMAO was shown to be associated with an increase in the probability of the presence of acanthosis nigricans. TMAO levels are not influenced by other blood biomarkers. Our study provides compelling evidence supporting the link between serum TMAO, obesity, and vascular damage in children. These findings highlight the importance of further research to unravel the underlying mechanisms of this connection.

Excessive consumption of certain sea fishes and mushrooms may pose significant health risks

Trimethylamine N-oxide (TMAO) is a diet-dependent molecule that causes atherosclerosis in human bodies. Elevated TMAO levels in the blood of type 2 diabetes and chronic renal disease patients have also been documented. This study examines trimethylamine (TMA) and TMAO levels in several edible mushrooms and marine fishes. According to the quantitative study, TMA and TMAO levels are high in the fish and mushroom samples. Although the examined marine fishes and mushrooms are considered nutritious and healthy, our data indicate that significant TMA/TMAO in those healthy foods may pose major health risks if ingested in excess. Bangladesh J. Sci. Ind. Res. 58(3), 187-190, 2023

The role of trimethylamine-N-oxide in the development of cerebrovascular disease (brief review)

Trimethylamine-N-oxide (TMO) is one of the best studied metabolites of the gut microbiota. It increases the risk of stroke and dyscirculatory encephalopathy, independent of traditional cardiovascular risk factors. The mechanisms of the negative effects of TMO on the cardiovascular system are related to the acceleration of atherosclerosis progression, platelet activation, and the development of aseptic inflammation. Currently, elevated TMO levels are an indication for a strict diet with restriction of foods rich in TMO precursors. Future research should clarify the role of TMO in the development of cerebrovascular disease (CVD). It is necessary to continue the investigation of new compounds that can reduce TMO levels in patients at high risk for developing CVD.