Search

Background: Tissue fibrosis is a common pathway to failure in many organ systems and is the cellular and molecular driver of myriad chronic diseases that are incompletely understood and lack effective treatment. Recent studies suggest that gut microbe-dependent metabolites might be involved in the initiation and progression of fibrosis in multiple organ systems. Main body of the manuscript: In a meta-organismal pathway that begins in the gut, gut microbiota convert dietary precursors such as choline, phosphatidylcholine, and L-carnitine into trimethylamine (TMA), which is absorbed and subsequently converted to trimethylamine N-oxide (TMAO) via the host enzyme flavin-containing monooxygenase 3 (FMO3) in the liver. Chronic exposure to elevated TMAO appears to be associated with vascular injury and enhanced fibrosis propensity in diverse conditions, including chronic kidney disease, heart failure, metabolic dysfunction-associated steatotic liver disease, and systemic sclerosis. Conclusion: Despite the high prevalence of fibrosis, little is known to date about the role of gut dysbiosis and of microbe-dependent metabolites in its pathogenesis. This review summarizes recent important advances in the understanding of the complex metabolism and functional role of TMAO in pathologic fibrosis and highlights unanswered questions. [ABSTRACT FROM AUTHOR]

Trimethylamine-n-oxide (TMAO) is a metabolite of intestinal flora following the consumption of phosphatidylcholine-rich foods. Clinical cohort studies have shown that plasma TMAO may be a risk factor for cancer development, including hepatocellular carcinoma (HCC), but fundamental research data supporting this hypothesis are lacking. In this study, HCC cells were treated with TMAO in vivo and in vitro to evaluate the effect on some indicators related to the malignancy degree of HCC, and the relevant molecular mechanisms were explored. In vitro, TMAO promoted the proliferation and migration of HCC cells and significantly upregulated the expression of proteins related to epithelial–mesenchymal transformation (EMT). In vivo, after HCC cells were inoculated subcutaneously in nude mice given water containing TMAO, the tumors grew faster and larger than those in the mice given ordinary water. The immunohistochemistry analysis showed that proliferation, migration and EMT-related proteins in the tumor tissues were significantly upregulated by TMAO. Furthermore, TMAO obviously enhanced the phosphorylation of MAPK signaling molecules in vivo and in vitro. In conclusion, TMAO promotes the proliferation, migration and EMT of HCC cells by activating the MAPK pathway. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Gut microbiota has significant impact on the cardio-metabolism and inflammation, and is implicated in the pathogenesis and progression of atherosclerosis. However, the long-term prospective association between trimethylamine N-oxide (TMAO) level and major adverse clinical events (MACEs) in patients with coronary artery disease (CAD) with or without diabetes mellitus (DM) habitus remains to be investigated. Methods: This prospective, single-center cohort study enrolled 2090 hospitalized CAD patients confirmed by angiography at Beijing Hospital from 2017-2020. TMAO levels were performed using liquid chromatography-tandem mass spectrometry. The composite outcome of MACEs was identified by clinic visits or interviews annually. Multivariate Cox regression analysis, Kaplan-Meier analysis, and restricted cubic splines were mainly used to explore the relationship between TMAO levels and MACEs based on diabetes mellitus (DM) habitus. Results: During the median follow-up period of 54 (41, 68) months, 266 (12.7%) developed MACEs. Higher TMAO levels, using the tertile cut-off value of 318.28 ng/mL, were significantly found to be positive dose-independent for developing MACEs, especially in patients with DM (HR 1.744, 95%CI 1.084-2.808, p = 0.022). Conclusions: Higher levels of TMAO are significantly associated with long-term MACEs among CAD patients with DM. The combination of TMAO in patients with CAD and DM is beneficial for risk stratification and prognosis. [ABSTRACT FROM AUTHOR]

Choline is essential for proper liver, muscle, brain, lipid metabolism, cellular membrane composition, and repair. Understanding genetic determinants of circulating choline metabolites can help identify new determinants of choline metabolism, requirements, and their link to disease endpoints. We conducted a scoping review to identify studies assessing the association of genetic polymorphisms on circulating choline and choline-related metabolite concentrations and subsequent associations with health outcomes. This study follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement scoping review extension. Literature was searched to September 28, 2022, in 4 databases: Embase, MEDLINE, Web of Science, and the Biological Science Index. Studies of any duration in humans were considered. Any genome-wide association study (GWAS) investigating genetic variant associations with circulating choline and/or choline-related metabolites and any Mendelian randomization (MR) study investigating the association of genetically predicted circulating choline and/or choline-related metabolites with any health outcome were considered. Qualitative evidence is presented in summary tables. From 1248 total reviewed articles, 53 were included (GWAS = 27; MR = 26). Forty-two circulating choline-related metabolites were tested in association with genetic variants in GWAS studies, primarily trimethylamine N-oxide, betaine, sphingomyelins, lysophosphatidylcholines, and phosphatidylcholines. MR studies investigated associations between 52 total unique choline metabolites and 66 unique health outcomes. Of these, 47 significant associations were reported between 16 metabolites (primarily choline, lysophosphatidylcholines, phosphatidylcholines, betaine, and sphingomyelins) and 27 health outcomes including cancer, cardiovascular, metabolic, bone, and brain-related outcomes. Some articles reported significant associations between multiple choline types and the same health outcome. Genetically predicted circulating choline and choline-related metabolite concentrations are associated with a wide variety of health outcomes. Further research is needed to assess how genetic variability influences choline metabolism and whether individuals with lower genetically predicted circulating choline and choline-related metabolite concentrations would benefit from a dietary intervention or supplementation.

Abstract Background Tissue fibrosis is a common pathway to failure in many organ systems and is the cellular and molecular driver of myriad chronic diseases that are incompletely understood and lack effective treatment. Recent studies suggest that gut microbe-dependent metabolites might be involved in the initiation and progression of fibrosis in multiple organ systems. Main body of the manuscript In a meta-organismal pathway that begins in the gut, gut microbiota convert dietary precursors such as choline, phosphatidylcholine, and L-carnitine into trimethylamine (TMA), which is absorbed and subsequently converted to trimethylamine N-oxide (TMAO) via the host enzyme flavin-containing monooxygenase 3 (FMO3) in the liver. Chronic exposure to elevated TMAO appears to be associated with vascular injury and enhanced fibrosis propensity in diverse conditions, including chronic kidney disease, heart failure, metabolic dysfunction-associated steatotic liver disease, and systemic sclerosis. Conclusion Despite the high prevalence of fibrosis, little is known to date about the role of gut dysbiosis and of microbe-dependent metabolites in its pathogenesis. This review summarizes recent important advances in the understanding of the complex metabolism and functional role of TMAO in pathologic fibrosis and highlights unanswered questions.

Abstract Trimethylamine-n-oxide (TMAO) is a metabolite of intestinal flora following the consumption of phosphatidylcholine-rich foods. Clinical cohort studies have shown that plasma TMAO may be a risk factor for cancer development, including hepatocellular carcinoma (HCC), but fundamental research data supporting this hypothesis are lacking. In this study, HCC cells were treated with TMAO in vivo and in vitro to evaluate the effect on some indicators related to the malignancy degree of HCC, and the relevant molecular mechanisms were explored. In vitro, TMAO promoted the proliferation and migration of HCC cells and significantly upregulated the expression of proteins related to epithelial–mesenchymal transformation (EMT). In vivo, after HCC cells were inoculated subcutaneously in nude mice given water containing TMAO, the tumors grew faster and larger than those in the mice given ordinary water. The immunohistochemistry analysis showed that proliferation, migration and EMT-related proteins in the tumor tissues were significantly upregulated by TMAO. Furthermore, TMAO obviously enhanced the phosphorylation of MAPK signaling molecules in vivo and in vitro. In conclusion, TMAO promotes the proliferation, migration and EMT of HCC cells by activating the MAPK pathway.

Abstract 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.

Abstract Dapagliflozin (DAPA) demonstrates promise in the management of diabetic mellitus (DM) and cardiomyopathy. Trimethylamine N-oxide (TMAO) is synthesized by the gut microbiota through the metabolic conversion of choline and phosphatidylcholine. Ferroptosis may offer novel therapeutic avenues for the management of diabetes and myocardial ischemia–reperfusion injury (IRI). However, the precise mechanism underlying ferroptosis in cardiomyocytes and the specific role of TMAO generated by gut microbiota in the therapeutic approach for DM and myocardial IRI utilizing DAPA need to be further explored. Nine male SD rats with specific pathogen-free (SPF) status were randomly divided equally into the normal group, the DM + IRI (DIR) group, and the DAPA group. The diversity of the gut microbiota was analyzed using 16S rRNA gene sequencing. Additionally, the Wekell technique was employed to measure the levels of TMAO in the three groups. Application of network pharmacology to search for intersection targets of DAPA, DIR, and ferroptosis, and RT-PCR experimental verification. Ultimately, the overlapping targets that were acquired were subjected to molecular docking analysis with TMAO. The changes of Bacteroidetes and Firmicutes in the gut microbiota of DIR rats were most significantly affected by DAPA. Escherichia-Shigella and Prevotella_9 within the phylum Bacteroidetes could be identified as the primary effects of DAPA on DIR. Compared with the normal group, the TMAO content in the DIR group was significantly increased, while the TMAO content in the DAPA group was decreased compared to the DIR group. For the network pharmacology analysis, DAPA and DIR generated 43 intersecting target genes, and then further intersected with ferroptosis-related genes, resulting in 11 overlapping target genes. The mRNA expression of ALB, HMOX1, PPARG, CBS, LCN2, and PPARA decreased in the DIR group through reverse transcription polymerase chain reaction (RT-PCR) validation, while the opposite trend was observed in the DAPA group. The docking score between TMAO and DPP4 was − 5.44, and the MM-GBSA result of − 22.02 kcal/mol. It epitomizes the finest docking performance among all the target genes with the lowest score. DAPA could reduce the levels of metabolite TMAO produced by gut microbiota, thereby regulating related target genes to decrease ferroptosis in DIR cardiomyocytes.

Abstract Background Patients with pulmonary arterial hypertension (PAH) exhibit a distinct gut microbiota profile; however, the causal association between gut microbiota, associated metabolites, and PAH remains elusive. We aimed to investigate this causal association and to explore whether dietary patterns play a role in its regulation. Methods Summary statistics of gut microbiota, associated metabolites, diet, and PAH were obtained from genome-wide association studies. The inverse variance weighted method was primarily used to measure the causal effect, with sensitivity analyses using the weighted median, weighted mode, simple mode, MR pleiotropy residual sum and outlier (MR-PRESSO), and MR-Egger methods. A reverse Mendelian randomisation analysis was also performed. Results Alistipes (odds ratio [OR] = 2.269, 95% confidence interval [CI] 1.100–4.679, P = 0.027) and Victivallis (OR = 1.558, 95% CI 1.019–2.380, P = 0.040) were associated with an increased risk of PAH, while Coprobacter (OR = 0.585, 95% CI 0.358–0.956, P = 0.032), Erysipelotrichaceae (UCG003) (OR = 0.494, 95% CI 0.245–0.996, P = 0.049), Lachnospiraceae (UCG008) (OR = 0.596, 95% CI 0.367–0.968, P = 0.036), and Ruminococcaceae (UCG005) (OR = 0.472, 95% CI 0.231–0.962, P = 0.039) protected against PAH. No associations were observed between PAH and gut microbiota-derived metabolites (trimethylamine N-oxide [TMAO] and its precursors betaine, carnitine, and choline), short-chain fatty acids (SCFAs), or diet. Although inverse variance-weighted analysis demonstrated that elevated choline levels were correlated with an increased risk of PAH, the results were not consistent with the sensitivity analysis. Therefore, the association was considered insignificant. Reverse Mendelian randomisation analysis demonstrated that PAH had no causal impact on gut microbiota-derived metabolites but could contribute to increased the levels of Butyricicoccus and Holdemania, while decreasing the levels of Clostridium innocuum, Defluviitaleaceae UCG011, Eisenbergiella, and Ruminiclostridium 5. Conclusions Gut microbiota were discovered suggestive evidence of the impacts of genetically predicted abundancy of certain microbial genera on PAH. Results of our study point that the production of SCFAs or TMAO does not mediate this association, which remains to be explained mechanistically.

Dapagliflozin (DAPA) demonstrates promise in the management of diabetic mellitus (DM) and cardiomyopathy. Trimethylamine N-oxide (TMAO) is synthesized by the gut microbiota through the metabolic conversion of choline and phosphatidylcholine. Ferroptosis may offer novel therapeutic avenues for the management of diabetes and myocardial ischemia–reperfusion injury (IRI). However, the precise mechanism underlying ferroptosis in cardiomyocytes and the specific role of TMAO generated by gut microbiota in the therapeutic approach for DM and myocardial IRI utilizing DAPA need to be further explored. Nine male SD rats with specific pathogen-free (SPF) status were randomly divided equally into the normal group, the DM + IRI (DIR) group, and the DAPA group. The diversity of the gut microbiota was analyzed using 16S rRNA gene sequencing. Additionally, the Wekell technique was employed to measure the levels of TMAO in the three groups. Application of network pharmacology to search for intersection targets of DAPA, DIR, and ferroptosis, and RT-PCR experimental verification. Ultimately, the overlapping targets that were acquired were subjected to molecular docking analysis with TMAO. The changes of Bacteroidetes and Firmicutes in the gut microbiota of DIR rats were most significantly affected by DAPA. Escherichia-Shigella and Prevotella_9 within the phylum Bacteroidetes could be identified as the primary effects of DAPA on DIR. Compared with the normal group, the TMAO content in the DIR group was significantly increased, while the TMAO content in the DAPA group was decreased compared to the DIR group. For the network pharmacology analysis, DAPA and DIR generated 43 intersecting target genes, and then further intersected with ferroptosis-related genes, resulting in 11 overlapping target genes. The mRNA expression of ALB, HMOX1, PPARG, CBS, LCN2, and PPARA decreased in the DIR group through reverse transcription polymerase chain reaction (RT-PCR) validation, while the opposite trend was observed in the DAPA group. The docking score between TMAO and DPP4 was − 5.44, and the MM-GBSA result of − 22.02 kcal/mol. It epitomizes the finest docking performance among all the target genes with the lowest score. DAPA could reduce the levels of metabolite TMAO produced by gut microbiota, thereby regulating related target genes to decrease ferroptosis in DIR cardiomyocytes. [ABSTRACT FROM AUTHOR]

It is inconclusive whether trimethylamine N-oxide (TMAO) and choline and related metabolites, namely trimethylamine (TMA), l-carnitine, betaine and dimethylglycine (DMG), are associated with non-alcoholic fatty liver disease (NAFLD). Our objective was to investigate these potential associations. Additionally, we sought to determine the mediating role of TMAO. In this 1:1 age- and sex-matched case–control study, a total of 150 pairs comprising NAFLD cases and healthy controls were identified. According to the fully adjusted model, after the highest tertile was compared with the lowest tertile, the plasma TMAO concentration (OR = 2·02 (95 % CI 1·04, 3·92); P trend = 0·003), l-carnitine concentration (OR = 1·79 (1·01, 3·17); P trend = 0·020) and DMG concentration (OR = 1·81 (1·00, 3·28); P trend = 0·014) were significantly positively associated with NAFLD incidence. However, a significantly negative association was found for plasma betaine (OR = 0. 50 (0·28, 0·88); P trend = 0·001). The restricted cubic splines model consistently indicated positive dose–response relationships between exposure to TMAO, l-carnitine, and DMG and NAFLD risk, with a negative association being observed for betaine. The corresponding AUC increased significantly from 0·685 (0·626, 0·745) in the traditional risk factor model to 0·769 (0·716, 0·822) when TMAO and its precursors were included (l-carnitine, betaine and choline) (P = 0·032). Mediation analyses revealed that 14·7 and 18·6 % of the excess NAFLD risk associated with l-carnitine and DMG, respectively, was mediated by TMAO (the P values for the mediating effects were 0·021 and 0·036, respectively). These results suggest that a higher concentration of TMAO is associated with increased NAFLD risk among Chinese adults and provide evidence of the possible mediating role of TMAO. [ABSTRACT FROM AUTHOR]

A notable shift in understanding the human microbiome's influence on cardiovascular disease (CVD) is underway, although the causal association remains elusive. A systematic review and meta-analysis were conducted to synthesise current knowledge on microbial taxonomy and metabolite variations between healthy controls (HCs) and those with CVD. An extensive search encompassing three databases identified 67 relevant studies (2012–2023) covering CVD pathologies from 4707 reports. Metagenomic and metabolomic data, both qualitative and quantitative, were obtained. Analysis revealed substantial variability in microbial alpha and beta diversities. Moreover, specific changes in bacterial populations were shown, including increased Streptococcus and Proteobacteria and decreased Faecalibacterium in patients with CVD compared with HC. Additionally, elevated trimethylamine N-oxide levels were reported in CVD cases. Biochemical parameter analysis indicated increased fasting glucose and triglycerides and decreased total cholesterol and low- and high-density lipoprotein cholesterol levels in diseased individuals. This study revealed a significant relationship between certain bacterial species and CVD. Additionally, it has become clear that there are substantial inconsistencies in the methodologies employed and the reporting standards adhered to in various studies. Undoubtedly, standardising research methodologies and developing extensive guidelines for microbiome studies are crucial for advancing the field. [ABSTRACT FROM AUTHOR]

Background: Trimethylamine-N-oxide (TMAO) is produced by hepatic flavin-containing monooxygenase 3 (FMO3) from trimethylamine (TMA). High TMAO level is a biomarker of cardiovascular diseases and metabolic disorders, and it also affects periodontitis through interactions with the gastrointestinal microbiome. While recent findings indicate that periodontitis may alter systemic TMAO levels, the specific mechanisms linking these changes and particular oral pathogens require further clarification. Methods: In this study, we established a C57BL/6J male mouse model by orally administering Porphyromonas gingivalis (P. gingivalis, Pg), Fusobacterium nucleatum (F. nucleatum, Fn), Streptococcus mutans (S. mutans, Sm) and PBS was used as a control. We conducted LC-MS/MS analysis to quantify the concentrations of TMAO and its precursors in the plasma and cecal contents of mice. The diversity and composition of the gut microbiome were analyzed using 16S rRNA sequencing. TMAO-related lipid metabolism and enzymes in the intestines and liver were assessed by qPCR and ELISA methods. We further explored the effect of Pg on FMO3 expression and lipid molecules in HepG2 cells by stimulating the cells with Pg-LPS in vitro. Results: The three oral pathogenic bacteria were orally administered to the mice for 5 weeks. The Pg group showed a marked increase in plasma TMAO, betaine, and creatinine levels, whereas no significant differences were observed in the gut TMAO level among the four groups. Further analysis showed similar diversity and composition in the gut microbiomes of both the Pg and Fn groups, which were different from the Sm and control groups. The profiles of TMA-TMAO pathway- related genera and gut enzymes were not significantly different among all groups. The Pg group showed significantly higher liver FMO3 levels and elevated lipid factors (IL-6, TG, TC, and NEFA) in contrast to the other groups. In vitro experiments confirmed that stimulation of HepG2 cells with Pg-LPS upregulated the expression of FMO3 and increased the lipid factors TC, TG, and IL-6. Conclusion: This study conclusively demonstrates that Pg, compared to Fn and Sm, plays a critical role in elevating plasma TMAO levels and significantly influences the TMA-TMAO pathway, primarily by modulating the expression of hepatic FMO3 and directly impacting hepatic lipid metabolism. [ABSTRACT FROM AUTHOR]

Background: A gut-microbial metabolite, trimethylamine N-oxide (TMAO), has been associated with type 2 diabetes mellitus (T2DM). Few previous prospective studies have addressed associations between the changes in TMAO and T2DM incidence. Methods: Data were derived from a longitudinal cohort conducted from 2019 to 2021 in rural areas of Fuxin County, Liaoning Province, China, and 1515 diabetes-free participants aged above 35 years were included. The concentrations of serum TMAO and its precursors were measured at two time points, namely in 2019 and 2021. TMAO and TMAO changes (ΔTMAO) were separately tested in a logistic regression model. For further examination, the odds ratios (ORs) for T2DM were calculated according to a combination of TMAO levels and ΔTMAO levels. Results: During a median follow-up of 1.85 years, 81 incident cases of T2DM (5.35%) were identified. Baseline TMAO levels exhibited a nonlinear relationship, first decreasing and then increasing, and only at the highest quartile was it associated with the risk of T2DM. The OR for T2DM in the highest quartile of serum TMAO was 3.35 (95%CI: 1.55–7.26, p = 0.002), compared with the lowest quartile. As for its precursors, only choline level was associated with T2DM risk and the OR for T2DM in the Q3 and Q4 of serum choline was 3.37 (95%CI: 1.41–8.05, p = 0.006) and 4.72 (95%CI: 1.47–15.13, p = 0.009), respectively. When considering both baseline TMAO levels and ΔTMAO over time, participants with sustained high TMAO levels demonstrated a significantly increased risk of T2DM, with a multivariable-adjusted OR of 8.68 (95%CI: 1.97, 38.34). Conclusion: Both initial serum TMAO levels and long-term serum TMAO changes were collectively and significantly associated with the occurrence of subsequent T2DM events. Interventions aimed at normalizing TMAO levels, such as adopting a healthy dietary pattern, may be particularly beneficial in T2DM prevention. [ABSTRACT FROM AUTHOR]

The Mediterranean diet (MD), rich in minimally processed plant foods and in monounsaturated fats but low in saturated fats, meat, and dairy products, represents one of the most studied diets for cardiovascular health. It has been shown, from both observational and randomized controlled trials, that MD reduces body weight, improves cardiovascular disease surrogates such as waist-to-hip ratios, lipids, and inflammation markers, and even prevents the development of fatal and nonfatal cardiovascular disease, diabetes, obesity, and other diseases. However, it is unclear whether it offers cardiovascular benefits from its individual components or as a whole. Furthermore, limitations in the methodology of studies and meta-analyses have raised some concerns over its potential cardiovascular benefits. MD is also associated with characteristic changes in the intestinal microbiota, mediated through its constituents. These include increased growth of species producing short-chain fatty acids, such as Clostridium leptum and Eubacterium rectale, increased growth of Bifidobacteria, Bacteroides, and Faecalibacterium prausnitzii species, and reduced growth of Firmicutes and Blautia species. Such changes are known to be favorably associated with inflammation, oxidative status, and overall metabolic health. This review will focus on the effects of MD on cardiovascular health through its action on gut microbiota. [ABSTRACT FROM AUTHOR]

Background: Patients with pulmonary arterial hypertension (PAH) exhibit a distinct gut microbiota profile; however, the causal association between gut microbiota, associated metabolites, and PAH remains elusive. We aimed to investigate this causal association and to explore whether dietary patterns play a role in its regulation. Methods: Summary statistics of gut microbiota, associated metabolites, diet, and PAH were obtained from genome-wide association studies. The inverse variance weighted method was primarily used to measure the causal effect, with sensitivity analyses using the weighted median, weighted mode, simple mode, MR pleiotropy residual sum and outlier (MR-PRESSO), and MR-Egger methods. A reverse Mendelian randomisation analysis was also performed. Results: Alistipes (odds ratio [OR] = 2.269, 95% confidence interval [CI] 1.100–4.679, P = 0.027) and Victivallis (OR = 1.558, 95% CI 1.019–2.380, P = 0.040) were associated with an increased risk of PAH, while Coprobacter (OR = 0.585, 95% CI 0.358–0.956, P = 0.032), Erysipelotrichaceae (UCG003) (OR = 0.494, 95% CI 0.245–0.996, P = 0.049), Lachnospiraceae (UCG008) (OR = 0.596, 95% CI 0.367–0.968, P = 0.036), and Ruminococcaceae (UCG005) (OR = 0.472, 95% CI 0.231–0.962, P = 0.039) protected against PAH. No associations were observed between PAH and gut microbiota-derived metabolites (trimethylamine N-oxide [TMAO] and its precursors betaine, carnitine, and choline), short-chain fatty acids (SCFAs), or diet. Although inverse variance-weighted analysis demonstrated that elevated choline levels were correlated with an increased risk of PAH, the results were not consistent with the sensitivity analysis. Therefore, the association was considered insignificant. Reverse Mendelian randomisation analysis demonstrated that PAH had no causal impact on gut microbiota-derived metabolites but could contribute to increased the levels of Butyricicoccus and Holdemania, while decreasing the levels of Clostridium innocuum, Defluviitaleaceae UCG011, Eisenbergiella, and Ruminiclostridium 5. Conclusions: Gut microbiota were discovered suggestive evidence of the impacts of genetically predicted abundancy of certain microbial genera on PAH. Results of our study point that the production of SCFAs or TMAO does not mediate this association, which remains to be explained mechanistically. [ABSTRACT FROM AUTHOR]

AIMS: Little is known about associations of trimethylamine N-oxide (TMAO), a novel gut microbiota-generated metabolite of dietary phosphatidylcholine and carnitine, and its changes over time with all-cause and cause-specific mortality in the general population or in different race/ethnicity groups. The study aimed to investigate associations of serially measured plasma TMAO levels and changes in TMAO over time with all-cause and cause-specific mortality in a multi-ethnic community-based cohort. METHODS AND RESULTS: The study included 6,785 adults from the Multi-Ethnic Study of Atherosclerosis. TMAO was measured at baseline and year 5 using mass spectrometry. Primary outcomes were adjudicated all-cause mortality and cardiovascular disease (CVD) mortality. Secondary outcomes were deaths due to kidney failure, cancer, or dementia obtained from death certificates. Cox proportional hazards models with time-varying TMAO and covariates assessed the associations with adjustment for sociodemographics, lifestyles, diet, metabolic factors, and comorbidities. During a median follow-up of 16.9 years, 1704 participants died and 411 from CVD. Higher TMAO levels associated with higher risk of all-cause mortality [hazard ratio (HR): 1.12, 95% confidence interval (CI): 1.08-1.17], CVD mortality (HR: 1.09, 95% CI: 1.00-1.09), and death due to kidney failure (HR: 1.44, 95% CI: 1.25-1.66) per inter-quintile range, but not deaths due to cancer or dementia. Annualized changes in TMAO levels associated with higher risk of all-cause mortality (HR: 1.10, 95% CI: 1.05-1.14) and death due to kidney failure (HR: 1.54, 95% CI: 1.26-1.89) but not other deaths. CONCLUSION: Plasma TMAO levels were positively associated with mortality, especially deaths due to cardiovascular and renal disease, in a multi-ethnic US cohort.

An expanding body of research indicates a correlation between the gut microbiota and various diseases. Metabolites produced by the gut microbiota act as mediators between the gut microbiota and the host, interacting with multiple systems in the human body to regulate physiological or pathological functions. However, further investigation is still required to elucidate the underlying mechanisms. One such metabolite involved in choline metabolism by gut microbes is trimethylamine (TMA), which can traverse the intestinal epithelial barrier and enter the bloodstream, ultimately reaching the liver where it undergoes oxidation catalyzed by flavin-containing monooxygenase 3 (FMO3) to form trimethylamine N-oxide (TMAO). While some TMAO is eliminated through renal excretion, remaining amounts circulate in the bloodstream, leading to systemic inflammation, endoplasmic reticulum (ER) stress, mitochondrial stress, and disruption of normal physiological functions in humans. As a representative microbial metabolite originating from the gut, TMAO has significant potential both as a biomarker for monitoring disease occurrence and progression and for tailoring personalized treatment strategies for patients. This review provides an extensive overview of TMAO sources and its metabolism in human blood, as well as its impact on several major human diseases. Additionally, we explore the latest research areas related to TMAO along with future directions.

Xiaoxiao Zhao,1 Hanjun Zhao,1 Runzhen Chen,1 Jiannan Li,1 Jinying Zhou,1 Nan Li,1 Shaodi Yan,2 Chen Liu,1 Peng Zhou,1 Yi Chen,1 Li Song,1 Hongbing Yan2 1Department of Cardiology, Fuwai Hospital, National Center for Cardiovascular Diseases, Peking Union Medical College & Chinese Academy of Medical Sciences, BeiJing, People’s Republic of China; 2Department of Cardiology, Fuwai Hospital Chinese Academy of Medical Sciences, ShenZhen, People’s Republic of ChinaCorrespondence: Hanjun Zhao, Department of Cardiology, Fuwai Hospital, Chinese Academy of Medical Sciences, No. 167, Beijing, 100037, People’s Republic of China, Tel +86-15210020808, Email 15210020808@163.com Hongbing Yan, Fuwai Hospital, Chinese Academy of Medical Sciences, 12 Langshan Road, Shenzhen, 518000, People’s Republic of China, Tel +86-1301339287, Email hbyanfuwai2018@163.comBackground and Aim: An elevated triglyceride-glucose (TyG) level is associated with increased risk of mortality in patients with CAD. Trimethylamine N-oxide (TMAO) has mechanistic links to atherosclerotic coronary artery disease (CAD) pathogenesis and is correlated with adverse outcomes. However, the incremental prognostic value of TMAO and TyG in the cohort of optical coherence tomography (OCT)-defined high-risk ST-segment elevation myocardial infarction (STEMI) patients is unknown.Methods: We studied 274 consecutive aged ≥ 18 years patients with evidence of STEMI and detected on pre-intervention OCT imaging of culprit lesions between March 2017 and March 2019.Outcomes: There were 22 (22.68%), 27 (27.84%), 26 (26.80%), and 22 (22.68%) patients in groups A-D, respectively. The baseline characteristics according to the level of TMAO and TyG showed that patients with higher level in both indicators were more likely to have higher triglycerides (p < 0.001), fasting glucose (p < 0.001) and higher incidence of diabetes (p = 0.008). The group with TMAO > median and TyG ≤ median was associated with higher rates of MACEs significantly (p = 0.009) in fully adjusted analyses. During a median follow-up of 2.027 years, 20 (20.6%) patients experienced MACEs. To evaluate the diagnostic value of the TyG index combined with TMAO, the area under the receiver operating characteristic curve for predicting MACEs after full adjustment was 0.815 (95% confidence interval, 0.723– 0.887; sensitivity, 85.00%; specificity, 72.73%; cut-off level, 0.577). Among the group of patients with TMAO > median and TyG ≤ median, there was a significantly higher incidence of MACEs (p= 0.033). A similar tendency was found in the cohort with hyperlipidemia (p= 0.016) and diabetes mellitus (p= 0.036).Conclusion: This study demonstrated the usefulness of combined measures of the TyG index and TMAO in enhancing risk stratification in STEMI patients with OCT-defined high-risk plaque characteristics.Trial Registration: This study was registered at ClinicalTrials.gov as NCT03593928.Keywords: optical coherence tomography, triglyceride glucose index, trimethylamine N-oxide, high risk plaque feature, major adverse cardiovascular events, prospective study

Abstract Background Cervical cancer (CC) is a danger to women’s health, especially in many developing countries. Metabolomics can make the connection between genotypes and phenotypes. It provides a wide spectrum profile of biological processes under pathological or physiological conditions. Method In this study, we conducted plasma metabolomics of healthy volunteers and CC patients and integratively analyzed them with public CC tissue transcriptomics from Gene Expression Omnibus (GEO). Result Here, we screened out a panel of 5 metabolites to precisely distinguish CC patients from healthy volunteers. Furthermore, we utilized multi-omics approaches to explore patients with stage I-IIA1 and IIA2-IV4 CC and comprehensively analyzed the dysregulation of genes and metabolites in CC progression. We identified that plasma levels of trimethylamine N-oxide (TMAO) were associated with tumor size and regarded as a risk factor for CC. Moreover, we demonstrated that TMAO could promote HeLa cell proliferation in vitro. In this study, we delineated metabolic profiling in healthy volunteers and CC patients and revealed that TMAO was a potential biomarker to discriminate between I-IIA1 and IIA2-IV patients to indicate CC deterioration. Conclusion Our study identified a diagnostic model consisting of five metabolites in plasma that can effectively distinguish CC from healthy volunteers. Furthermore, we proposed that TMAO was associated with CC progression and might serve as a potential non-invasive biomarker to predict CC substage. Impact These findings provided evidence of the important role of metabolic molecules in the progression of cervical cancer disease, as well as their ability as potential biomarkers.

Yue Yue,1,&ast; Han-Bo Cui,2,&ast; Yue-Jie Chu,2 Gui-Ling Zheng1 1Department of Endocrinology, The 983 Hospital of the Joint Logistics Force of the Chinese People’s Liberation Army, Tianjin, People’s Republic of China; 2Department of Diabetes, Tianjin Academy of Traditional Chinese Medicine Affiliated Hospital, Tianjin, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Yue-Jie Chu, Department of Diabetes, Tianjin Academy of Traditional Chinese Medicine Affiliated Hospital, 354 North Road, Hongqiao District, Tianjin, 300120, People’s Republic of China, Tel +8613920513352, Email chuyuejie0710@126.comObjective: We aimed to analyze the mechanisms underlying spleen-and-stomach-tonifying, yin-fire-purging, and yang-raising decoction derived from the trimethylamine N-oxide (TMAO) metabolic pathway of intestinal microbiota in the treatment of macrovascular lesions caused by type 2 diabetes mellitus (T2DM).Methods: Hartley-guinea pigs were randomly divided into 3 groups—the blank, model, and intervention groups. The T2DM combined with atherosclerosis guinea pig models were established in the model and intervention groups. After successful modeling, spleen-and-stomach-tonifying, yin-fire-purging, and yang-raising decoction were administered intragastrically to the intervention group, while the same volume of normal saline was administered via gavage to the blank and model groups. After 6 weeks of continuous gavage, guinea pigs were sacrificed in all groups, the colon contents were obtained, and the diversity and structural differences of intestinal microbiota were analyzed via bioinformatics. Serum was collected to detect differences in lipids, TMAO, oxidative stress, and inflammation markers between groups.Results: Compared to the blank group, the species diversity of the intestinal microbiota in the model and intervention groups was significantly reduced. Based on the results of Analysis of Similarities and Multiple Response Permutation Procedure, the microbiota structure of the intervention group was closer to that of the blank group. After modeling, the blood lipid levels of guinea pigs increased significantly, and drug intervention significantly reduced the levels of TC, TG, and LDL-C (P < 0.05). TMAO expression was significantly increased after modeling (P < 0.05), while drug intervention reduced TMAO expression (P < 0.05). Compared to the model group, drug intervention significantly increased the concentrations of SOD while decreasing the concentrations of MDA, ICAM-1, VCAM-1, IL-6, and hs-CRP.Conclusion: Spleen-and-stomach-tonifying, yin-fire-purging, and yang-raising decoction can reduce the risk of macrovascular lesions in T2DM, and its mechanism may be associated with its ability to regulate the TMAO metabolic pathway of intestinal microbiota.Keywords: intestinal microbiota, macrovascular lesions, spleen-and-stomach-tonifying, yin-fire-purging, and yang-raising decoction, trimethylamine N-oxide, type 2 diabetes mellitus

AIM: To provide the direct evidence for the crucial role of trimethylamine N-oxide (TMAO) in vascular permeability and endothelial cell dysfunction under diabetic condition. METHODS: The role of TMAO on the in vitro biological effect of human retinal microvascular endothelial cells (HRMEC) under high glucose conditions was tested by a cell counting kit, wound healing, a transwell and a tube formation assay. The inflammation-related gene expression affected by TMAO was tested by real-time polymerase chain reaction (RT-PCR). The expression of the cell junction was measured by Western blotting (WB) and immunofluorescence staining. In addition, two groups of rat models, diabetic and non-diabetic, were fed with normal or 0.1% TMAO for 16wk, and their plasma levels of TMAO, vascular endothelial growth factor (VEGF), interleukin (IL)-6 and tumor necrosis factor (TNF)-α were tested. The vascular permeability of rat retinas was measured using FITC-Dextran, and the expression of zonula occludens (ZO)-1 and claudin-5 in rat retinas was detected by WB or immunofluorescence staining. RESULTS: TMAO administration significantly increased the cell proliferation, migration, and tube formation of primary HRMEC either in normal or high-glucose conditions. RT-PCR showed elevated inflammation-related gene expression of HRMEC under TMAO stimulation, while WB or immunofluorescence staining indicated decreased cell junction ZO-1 and occludin expression after high-glucose and TMAO treatment. Diabetic rats showed higher plasma levels of TMAO as well as retinal vascular leakage, which were even higher in TMAO-feeding diabetic rats. Furthermore, TMAO administration increased the rat plasma levels of VEGF, IL-6 and TNF-α while decreasing the retinal expression levels of ZO-1 and claudin-5. CONCLUSION: TMAO enhances the proliferation, migration, and tube formation of HRMEC, as well as destroys their vascular integrity and tight connection. It also regulates the expression of VEGF, IL-6, and TNF-α.

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

Background: Cervical cancer (CC) is a danger to women's health, especially in many developing countries. Metabolomics can make the connection between genotypes and phenotypes. It provides a wide spectrum profile of biological processes under pathological or physiological conditions. Method: In this study, we conducted plasma metabolomics of healthy volunteers and CC patients and integratively analyzed them with public CC tissue transcriptomics from Gene Expression Omnibus (GEO). Result: Here, we screened out a panel of 5 metabolites to precisely distinguish CC patients from healthy volunteers. Furthermore, we utilized multi-omics approaches to explore patients with stage I-IIA1 and IIA2-IV4 CC and comprehensively analyzed the dysregulation of genes and metabolites in CC progression. We identified that plasma levels of trimethylamine N-oxide (TMAO) were associated with tumor size and regarded as a risk factor for CC. Moreover, we demonstrated that TMAO could promote HeLa cell proliferation in vitro. In this study, we delineated metabolic profiling in healthy volunteers and CC patients and revealed that TMAO was a potential biomarker to discriminate between I-IIA1 and IIA2-IV patients to indicate CC deterioration. Conclusion: Our study identified a diagnostic model consisting of five metabolites in plasma that can effectively distinguish CC from healthy volunteers. Furthermore, we proposed that TMAO was associated with CC progression and might serve as a potential non-invasive biomarker to predict CC substage. Impact: These findings provided evidence of the important role of metabolic molecules in the progression of cervical cancer disease, as well as their ability as potential biomarkers. [ABSTRACT FROM AUTHOR]

Intracerebral hemorrhagic stroke, characterized by acute hemorrhage in the brain, has a significant clinical prevalence and poses a substantial threat to individuals' well-being and productivity. Recent research has elucidated the role of gut microorganisms and their metabolites in influencing brain function through the microbiota-gut-brain axis (MGBA). This article provides a comprehensive review of the current literature on the common metabolites, short-chain fatty acids (SCFAs) and trimethylamine-N-oxide (TMAO), produced by gut microbiota. These metabolites have demonstrated the potential to traverse the blood-brain barrier (BBB) and directly impact brain tissue. Additionally, these compounds have the potential to modulate the parasympathetic nervous system, thereby facilitating the release of pertinent substances, impeding the buildup of inflammatory agents within the brain, and manifesting anti-inflammatory properties. Furthermore, this scholarly analysis delves into the existing dearth of investigations concerning the influence of gut microorganisms and their metabolites on cerebral functions, while also highlighting prospective avenues for future research. [ABSTRACT FROM AUTHOR]

Aim: Phenylacetylglutamine (PAGln) is a phenylalanine‐derived metabolite produced by gut microbiota with mechanistic links to heart failure (HF)‐relevant phenotypes. We sought to investigate the prognostic value of PAGln in patients with stable HF. Methods and results: Fasting plasma PAGln levels were measured by stable‐isotope‐dilution liquid chromatography–tandem mass spectrometry (LC‐MS/MS) in patients with stable HF from two large cohorts. All‐cause mortality was assessed at 5‐year follow‐up in the Cleveland cohort, and HF, hospitalization, or mortality were assessed at 3‐year follow‐up in the Berlin cohort. Within the Cleveland cohort, median PAGln levels were 4.2 (interquartile range [IQR] 2.4–6.9) μM. Highest quartile of PAGln was associated with 3.09‐fold increased mortality risk compared to lowest quartile. Following adjustments for traditional risk factors, as well as race, estimated glomerular filtration rate, amino‐terminal pro‐B‐type natriuretic peptide, high‐sensitivity C‐reactive protein, left ventricular ejection fraction, ischaemic aetiology, and HF drug treatment, elevated PAGln levels remained predictive of 5‐year mortality in quartile comparisons (adjusted hazard ratio [HR] [95% confidence interval, CI] for Q4 vs Q1: 1.64 [1.07–2.53]). In the Berlin cohort, a similar distribution of PAGln levels was observed (median 3.2 [IQR 2.0–4.8] μM), and PAGln levels were associated with a 1.92‐fold increase in 3‐year HF hospitalization or all‐cause mortality risk (adjusted HR [95% CI] for Q4 vs Q1: 1.92 [1.02‐3.61]). Prognostic value of PAGln appears to be independent of trimethylamine N‐oxide levels. Conclusion: High levels of PAGln are associated with adverse outcomes independent of traditional cardiac risk factors and cardio‐renal risk markers. [ABSTRACT FROM AUTHOR]

Background: Gut microbiota assumes an essential role in the development and progression of pulmonary arterial hypertension (PAH). Trimethylamine N-oxide (TMAO), a gut microbiota-dependent metabolite, is correlated with the prognosis of patients with PAH. However, the correlation between changes in TMAO (ΔTMAO) and the prognosis of PAH remains elusive. Objectives: To investigate the association between ΔTMAO and prognosis of PAH, and explore whether dynamic assessment of TMAO level was superior to measurement at a single time point in predicting prognosis. Design: Single-center cohort study. Methods: Consecutive patients diagnosed with PAH and had at least two TMAO measurements taken from May 2019 to June 2020 were eligible. The outcome events of this study were defined as adverse clinical events. Results: A total of 117 patients with PAH who had two TMAO measurements and follow-up were included in this study. Patients with ΔTMAO ⩾1.082 μmol/L had over four times increased risk of adverse clinical events than their counterparts after adjusting for confounders [hazard ratio (HR) 4.050, 95% confidence interval (CI): 1.468–11.174; p = 0.007]. Patients with constant high TMAO levels at both time points had the highest risk of adverse clinical events compared with patients with constant low TMAO levels (HR 3.717, 95% CI: 1.627–8.492; p = 0.002). ΔTMAO was also associated with changes in parameters reflecting PAH severity (p < 0.05). Conclusion: Changes in TMAO were independently correlated with prognosis in patients with PAH, irrespective of baseline level of TMAO. ΔTMAO also correlated with alteration in disease severity. Repeated assessment of TMAO level contributes to better identification of patients with increased risk of adverse clinical events. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to determine whether trimethylamine N-oxide (TMAO) was involved in sympathetic activation in aging and the underlying mechanisms. Our hypothesis is TMAO reduces P2Y12 receptor (P2Y12R) and induces microglia-mediated inflammation in the paraventricular nucleus (PVN), then leading to sympathetic activation in aging. This study involved 18 young adults and 16 old adults. Aging rats were established by injecting D-galactose (D-gal, 200 mg/kg/d) subcutaneously for 12 weeks. TMAO (120 mg/kg/d) or 1% 3, 3-dimethyl-l-butanol (DMB) was administrated via drinking water for 12 weeks to investigate their effects on neuroinflammation and sympathetic activation in aging rats. Plasma TMAO, NE and IL-1β levels were higher in old adults than in young adults. In addition, standard deviation of all normal to normal intervals (SDNN) and standard deviation of the average of normal to normal intervals (SDANN) were lower in old adults and negatively correlated with TMAO, indicating sympathetic activation in old adults, which is associated with an increase in TMAO levels. Treatment of rats with D-gal showed increased senescence-associated protein levels and microglia-mediated inflammation, as well as decreased P2Y12R protein levels in PVN. Plasma TMAO, NE and IL-1β levels were increased, accompanied by enhanced renal sympathetic nerve activity (RSNA). While TMAO treatment exacerbated the above phenomenon, DMB mitigated it. These findings suggest that TMAO contributes to sympathetic hyperactivity in aging by downregulating P2Y12R in microglia and increasing inflammation in the PVN. These results may provide promising new target for the prevention and treatment of aging and aging-related diseases.

BACKGROUND: Effects of animal source foods (ASF) on atherosclerotic cardiovascular disease (ASCVD) and underlying mechanisms remain controversial. We investigated prospective associations of different ASF with incident ASCVD and potential mediation by gut microbiota-generated trimethylamine N-oxide, its L-carnitine-derived intermediates γ-butyrobetaine and crotonobetaine, and traditional ASCVD risk pathways. METHODS: Among 3931 participants from a community-based US cohort aged 65+ years, ASF intakes and trimethylamine N-oxide-related metabolites were measured serially over time. Incident ASCVD (myocardial infarction, fatal coronary heart disease, stroke, other atherosclerotic death) was adjudicated over 12.5 years median follow-up. Cox proportional hazards models with time-varying exposures and covariates examined ASF-ASCVD associations; and additive hazard models, mediation proportions by different risk pathways. RESULTS: After multivariable-adjustment, higher intakes of unprocessed red meat, total meat, and total ASF associated with higher ASCVD risk, with hazard ratios (95% CI) per interquintile range of 1.15 (1.01-1.30), 1.22 (1.07-1.39), and 1.18 (1.03-1.34), respectively. Trimethylamine N-oxide-related metabolites together significantly mediated these associations, with mediation proportions (95% CI) of 10.6% (1.0-114.5), 7.8% (1.0-32.7), and 9.2% (2.2-44.5), respectively. Processed meat intake associated with a nonsignificant trend toward higher ASCVD (1.11 [0.98-1.25]); intakes of fish, poultry, and eggs were not significantly associated. Among other risk pathways, blood glucose, insulin, and C-reactive protein, but not blood pressure or blood cholesterol, each significantly mediated the total meat-ASCVD association. CONCLUSIONS: In this large, community-based cohort, higher meat intake associated with incident ASCVD, partly mediated by microbiota-derived metabolites of L-carnitine, abundant in red meat. These novel findings support biochemical links between dietary meat, gut microbiome pathways, and ASCVD.

CONTEXT: Gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) may adversely affect bone by inducing oxidative stress. Whether this translates into increased fracture risk in older adults is uncertain. OBJECTIVE: Determine the associations of plasma TMAO with hip fracture and bone mineral density (BMD) in older adults. DESIGN AND SETTING: Cox hazard models and linear regression stratified by sex examined the associations of TMAO with hip fracture and BMD in the longitudinal cohort of the Cardiovascular Health Study. PARTICIPANTS: 5019 U.S. adults aged ≥65 years. EXPOSURE: Plasma TMAO. MAIN OUTCOME MEASURES: Incident hip fractures; total hip BMD dual x-ray absorptiometry in a subset (n = 1400). RESULTS: Six hundred sixty-six incident hip fractures occurred during up to 26 years of follow-up (67,574 person-years). After multivariable adjustment, TMAO was not significantly associated with hip fracture (women: hazard ratio (HR) [95% confidence interval (CI)] of 1.00[0.92,1.09] per TMAO doubling; men: 1.12[0.95,1.33]). TMAO was also not associated with total hip BMD (women: BMD difference [95% CI] of 0.42 g/cm2*100 [-0.34,1.17] per TMAO doubling; men: 0.19[-1.04,1.42]). In exploratory analyses, we found an interaction between body mass index (BMI) and the association of TMAO with hip fracture (P

Trimethylamine N-oxide (TMAO), the oxidized form of trimethylamine (TMA), was previously thought to be a waste product but is now considered an important risk factor for cardiovascular disease (CVD) and its comorbidities. Foods or supplements containing choline and carnitine are major precursors of TMA in the diet and are metabolized by gut microbiota. Trimethylamine N-oxide is produced through the oxidation of this compound by flavin-containing monooxygenase (FMO) in the liver. The organ responsible for the removal of TMAO from body fluids is the kidneys. Therefore, plasma TMAO levels are influenced by multiple complex factors, especially the amount of TMA precursors and dietary TMAO sources in the diet, the dominant genera in the gut microbiota, FMO3 enzyme activity, and kidney functions. Among these, the quantity of TMAO and its precursors in the diet and microbiota can be considered modifiable risk factors. However, discussions continue regarding how plasma TMAO levels reach pathological levels and their role (consequence or cause) in CVD. This review presents the current scientific evidence on the relationship and underlying mechanisms between CVD and TMAO and provides an overview of the association of plasma TMAO levels with modifiable risk factors, such as dietary TMAO precursors, dietary TMAO sources, and microbiota. [ABSTRACT FROM AUTHOR]

Trimethylamine N-oxide (TMAO) derived from gut microbiota causes kidney-heart damage in chronic kidney disease (CKD) patients. However, it is controversial whether CKD patients with higher TMAO are associated with a higher risk of death. We aimed to assess the correlation between circulating TMAO concentration and the risk of all-cause and cardiovascular death in CKD patients of different dialysis statuses and different races by dose-response analyses, and the underlying mechanisms were also explored by analyzing the correlations of TMAO with glomerular filtration rate (GFR) and inflammation. PubMed, Web of Science, and EMBASE were systematically searched up to 1 July 2022. A total of 21 studies involving 15,637 individuals were included. Stata 15.0 was used to perform the meta-analyses and dose-response analyses with extracted data. Subgroup analyses were conducted to recognize possible sources of heterogeneity. The risk of all-cause mortality was increased in non-dialysis CKD patients (RR = 1.26, 95%CI = 1.03–1.54, p = 0.028) and non-black dialysis patients (RR = 1.62, 95%CI = 1.19–2.22, p = 0.002) with the highest circulating TMAO concentration, and the association was confirmed to be linear. In addition, an increased risk of cardiovascular mortality was also found in non-black dialysis patients with the highest circulating TMAO concentration (RR = 1.72, 95%CI = 1.19–2.47, p = 0.004), likewise, a linear association was identified. However, for dialysis patients including blacks with high TMAO concentrations, there was no significant increase in either all-cause mortality (RR = 0.98, 95%CI = 0.94-1.03, p = 0.542) or cardiovascular mortality (RR = 0.87, 95% CI = 0.65–1.17, p = 0.362). Meanwhile, we verified strong correlations between TMAO and both GFR (r= −0.49; 95% CI= −0.75, −0.24; p < 0.001) and inflammatory markers (r = 0.43; 95% CI= 0.03, 0.84; p = 0.036) in non-dialysis patients. Increased circulating TMAO concentrations increase the risk of all-cause mortality in non-dialysis and non-black dialysis CKD patients. Moreover, elevated TMAO levels raise the cardiovascular mortality risk in non-black dialysis patients. Non-dialysis and non-black dialysis CKD patients with higher circulating TMAO concentrations are associated with an increased risk of all-cause mortality. Non-black dialysis patients with higher concentrations of TMAO are associated with an increased risk of cardiovascular mortality. Circulating TMAO concentrations have a strong negative correlation with GFR and a positive correlation with inflammation biomarkers in non-dialysis CKD patients. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Sichuan University (Medical Science Edition) is the property of Editorial Board of Journal of Sichuan University (Medical Sciences) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Intestinal bacteria produce metabolites such as trimethylamine N-oxide (TMAO), which have been found to impact the pathological process of coronary artery atherosclerotic disease through various signaling pathways. TMAO has been shown to induce vascular endothelial cell damage, contribute to lipid deposition in the vascular wall, promote inflammation, and stimulate smooth muscle cell aging and migration. Research suggests that modulation of TMAO metabolism and associated signaling pathways may offer potential therapeutic interventions for the prevention and treatment of atherosclerotic disease. This article will provide a brief overview of the TMAO mechanism in atherosclerosis, offering new research insights for the prevention and treatment of this disease. [ABSTRACT FROM AUTHOR]

Background: The incidence of heart failure, the terminal stage of several cardiovascular diseases, is increasing owing to population growth and aging. Bidirectional crosstalk between the gut and heart plays a significant role in heart failure. This study aimed to analyze the gut-heart axis and heart failure from a bibliometric perspective. Methods: We extracted literature regarding the gut-heart axis and heart failure from the Web of Science Core Collection database (January 1, 1993, to June 30, 2023) and conducted bibliometric and visualization analyses using Microsoft Excel, CiteSpace, VOSviewer, and the R package “bibliometrix.” Results: The final analysis included 1646 articles with an average of 35.38 citations per article. Despite some fluctuations, the number of articles published per year has steadily increased over the past 31 years, particularly since 2018. A total of 9412 authors from 2287 institutions in 86 countries have contributed to this field. The USA and China have been the most productive countries, with the Cleveland Clinic in the USA and Charité-Universitätsmedizin Berlin in Germany being the most active institutions. The cooperation between countries/regions and institutions was relatively close. Professor Tang WHW was the most productive author in the field and the journal Shocks published the highest number of articles. ''Heart failure,'' ''gut microbiota,'' ''trimethylamine N-oxide,'' and ''inflammation'' were the most common keywords, representing the current research hotspots. The keyword burst analysis indicated that ''gut microbiota'' and ''short-chain fatty acids'' are the current frontier research topics in this field. Conclusion: Research on the gut-heart axis and heart failure is increasing. This bibliometric analysis indicated that the mechanisms associated with the gut-heart axis and heart failure, particularly the gut microbiota, trimethylamine N-oxide, inflammation, and short-chain fatty acids, will become hotspots and emerging trends in research in this field. These findings provide valuable insights into current research and future directions.

BackgroundEpidemiologic research suggests that gut microbiota alteration (dysbiosis) may play a role in the pathogenesis of metabolic syndrome (MetS). Dysbiosis can influence Trimethylamine N-oxide (TMAO) a gut microbiota-derived metabolite, as well as kynurenine pathways (KP), which are known as a new marker for an early predictor of chronic diseases. Hence, the current study aimed to investigate the association between KYN and TMAO with MetS and its components.MethodsThis case-control study was conducted on 250 adults aged 18 years or over of Tehran University of Medical Sciences (TUMS) Employee’s Cohort study (TEC) in the baseline phase. 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 FFQ with 144 items. MetS was defined according to the NCEP ATP criteria. Serum profiles TMAO and KYN were measured by standard protocol.ResultThe mean level of TMAO and KYN in subjects with MetS was 51.49 pg/mL and 417.56 nmol/l. High levels of TMAO (≥30.39 pg/mL) with MetS were directly correlated, after adjusting for confounding factors, the odds of MetS in individuals 2.37 times increased (OR: 2.37, 95% CI: 1.31–4.28, P-value = 0.004), also, high levels of KYN (≥297.18 nmol/L) increased odds of Mets+ 1.48 times, which is statistically significant (OR: 1.48, 95% CI: 0.83–2.63, P-value = 0.04). High levels of TMAO compared with the reference group increased the odds of hypertriglyceridemia and low HDL in crude and adjusted models (P < 0.05). Additionally, there was a statistically significant high level of KYN increased odds of abdominal obesity (P < 0.05).ConclusionOur study revealed a positive association between serum TMAO and KYN levels and MetS and some of its components. For underlying mechanisms and possible clinical implications of the differences. Prospective studies in healthy individuals are necessary.

BackgroundEggs are a rich source of choline, an essential nutrient important for child growth and development. In a randomized trial of 1 egg/d in young children in Ecuador, an egg intervention led to significant improvements in growth, which were partially mediated by increased plasma choline concentration. A similar trial in Malawi (clinicaltrials.gov: NCT03385252) found little improvement in child growth or development.ObjectivesWe aimed to evaluate the effect of 1 egg/d for 6 mo on plasma choline concentrations in Malawian children enrolled in a randomized trial.MethodsInfants aged 6-9 mo in rural Malawi were randomly assigned to receive 1 egg/d (n = 331) or serve as a nonintervention control (n = 329) for 6 mo. Anthropometric, developmental, and dietary data were collected at baseline and 6-mo follow-up, along with a blood draw. Plasma choline, betaine, dimethylglycine, trimethylamine N-oxide (TMAO), and DHA were measured at both time points using ultrahigh performance liquid chromatography-tandem MS (n = 200 per group). Linear regression analysis was used to determine the difference in plasma choline and related metabolites between groups after 6 mo of intervention.ResultsPlasma choline, betaine, dimethylglycine, and DHA concentrations did not differ between groups at 6-mo follow-up. Plasma TMAO was significantly (26%; 95% CI: 7%, 48%) higher in the egg intervention group in a fully adjusted model.ConclusionsProvision of 1 egg/d for 6 mo did not result in increases in plasma choline or related metabolites, except TMAO. This could partially explain the lack of effect on growth and development. Additional interventions are needed to improve choline status, growth, and development in this population.

TMAO is elevated in individuals with cardiometabolic diseases, but it is unknown whether the metabolite is a biomarker of concern in healthy individuals. We conducted a cross-sectional study in metabolically healthy adults aged 18-66 years with BMI 18-44 kg/m2 and assessed the relationship between TMAO and diet, the fecal microbiome, and cardiometabolic risk factors. TMAO was measured in fasted plasma samples by liquid chromatography mass spectrometry. The fecal microbiome was assessed by 16S ribosomal RNA sequencing and recent food intake was captured by multiple ASA24 dietary recalls. Endothelial function was assessed via EndoPAT. Descriptive statistics were computed by fasting plasma TMAO tertiles and evaluated by ANOVA and Tukey's post-hoc test. Multiple linear regression was used to assess the relationship between plasma TMAO and dietary food intake and metabolic health parameters. TMAO concentrations were not associated with average intake of animal protein foods, fruits, vegetables, dairy, or grains. TMAO was related to the fecal microbiome and the genera Butyribrio, Roseburia, Coprobaciullus, and Catenibacterium were enriched in individuals in the lowest versus the highest TMAO tertile. TMAO was positively associated with α-diversity and compositional differences were identified between groups. TMAO was not associated with classic cardiovascular risk factors in the healthy cohort. Similarly, endothelial function was not related to fasting TMAO, whereas the inflammatory marker TNF-α was significantly associated. Fasting plasma TMAO may not be a metabolite of concern in generally healthy adults unmedicated for chronic disease. Prospective studies in healthy individuals are necessary.

ObjectiveTo investigate the diagnostic value of trimethylamine N-Oxide （TMAO） and serum amyloid A （SAA） levels in peripheral blood of patients with chronic cerebral hypoperfusion （CCH）. MethodsThe patients attending the Department of Neurology of Sichuan Provincial Peoples Hospital from February 2022 to June 2022 were divided into CCH group （n=55） and control group （n=42） based on the results of magnetic resonance arterial spin labeling （ASL）. The levels of TMAO and SAA were detected by ELISA and their diagnostic value for CCH were anaylzed by ROC curve. ResultsThe levels of TMAO （47.24±8.84 vs 40.81±8.33, t=3.639, P＜0.05） and SAA （14.04±2.70 vs 12.20±2.30, t=3.542, P＜0.05） in CCH group were significantly higher than those in control group. High levels of TMAO and SAA and history of primary hypertension were independent risk factors for the occurrence of CCH （P＜0.05）. The areas under ROC curve （AUC） of TMAO and SAA for diagnosing CCH were 0.701 （95%CI: 0.594-0.809） respectively and 0.675 （95%CI: 0.565-0.786）. The combined detection of TMAO and SAA achieved the highest AUC of 0.765 （95%CI: 0.667-0.863）. ConclusionBoth TMAO and SAA are related to the occurrence of CCH and can be used as auxiliary diagnostic indicators for CCH.

Abstract Background Higher circulating levels of trimethylamine N-oxide (TMAO), which is a metabolite that can be produced by the gut microbiota from L-carnitine (LC), have been associated with bone mineral density (BMD). Because LC supplementation can improve bone density and microstructural properties in animal models, this study aimed to examine the effects of 12 weeks of LC supplementation on BMD and selected blood markers involved in bone metabolism of postmenopausal women participating in a resistance training (RT) program. Methods Twenty-seven postmenopausal women, who had not been treated for osteoporosis, with a total T-score above − 3.0 and no diet differences completed 12 weeks of RT. The participants’ diets were supplemented with either 1 g of LC-L-tartrate and 3 g of leucine per day (LC group) or 4 g of leucine per day as a placebo (PLA group), in a double-blind fashion. Results After the intervention in the LC group, plasma total carnitine and serum decorin levels were higher than the corresponding preintervention values (p = 0.040 and p = 0.042, respectively). Moreover, plasma TMAO and serum SPARC levels were higher in the LC group than the corresponding postintervention values in the PLA group (p

Abstract Introduction The relationship between sodium glucose co-transporter 2 inhibitors (SGLT2i) and trimethylamine N-oxide (TMAO) following acute myocardial infarction (AMI) is not yet explored. Methods In this secondary analysis of the EMMY trial (ClinicalTrials.gov registration: NCT03087773), changes in serum TMAO levels were investigated in response to 26-week Empagliflozin treatment following an AMI compared to the standard post-MI treatment. Additionally, the association of TMAO changes with clinical risk factors and cardiorenal biomarkers was assessed. Results The mean age of patients (N = 367) was 57 ± 9 years, 82% were males, and 14% had type 2 diabetes. In the Empagliflozin group, the median TMAO value was 2.62 µmol/L (IQR: 1.81) at baseline, 3.74 µmol/L (2.81) at 6 weeks, and 4.20 µmol/L (3.14) at 26 weeks. In the placebo group, the median TMAO value was 2.90 µmol/L (2.17) at baseline, 3.23 µmol/L (1.90) at 6 weeks, and 3.35 µmol/L (2.50) at 26 weeks. The serum TMAO levels increased significantly from baseline to week 6 (coefficient: 0.233; 95% confidence interval 0.149–0.317, p

Background: Diabetic kidney disease (DKD) has become a major cause of chro nic kidney disease. However, early diagnosis of DKD is challenging. Trimethylamine oxide (TMAO) is an intestinal microbial metabolite which might be ass ociated with diabetes complications. The aim of this study was to investigate the cor relation between TMAO and DKD. Methods: A cross-sectional study was conducted. A total of 108 T2DM pati ents and 33 healthy subjects were enrolled in this study. Multiple logistic regression analyses and area under receiver operating characteristic curves (AUROC) wer e performed to evaluate the correlation between serum TMAO and DKD. Results: Serum TMAO levels were significantly higher in DKD patients than healthy control group and the NDKD (T2DM without combined DKD) group (P < 0.05). TMAO levels were negatively correlated with eGFR and positively correlated with urea nitrogen, ACR and DKD (P < 0.05). Logistic regression analysis indicated that serum TMA O was one of the independent risk factors for DKD patients (P < 0.05). In the diagnostic model, the AUROC of TMAO for the diagnosis of DKD was 0.691. Conclusion: Elevated levels of serum TMAO levels were positively associated with the risk of DKD in T2DM patients, which might be a potential biomarker for DKD.

Background Trimethylamine-N-oxide (TMAO) is a small molecule derived from the metabolism of dietary nutrients by gut microbes and contributes to cardiovascular disease. Plasma TMAO increases following consumption of red meat. This metabolic change is thought to be partly because of the expansion of gut microbes able to use nutrients abundant in red meat. Methods and Results We used data from a randomized crossover study to estimate the degree to which TMAO can be estimated from fecal microbial composition. Healthy participants received a series of 3 diets that differed in protein source (red meat, white meat, and non-meat), and fecal, plasma, and urine samples were collected following 4 weeks of exposure to each diet. TMAO was quantitated in plasma and urine, while shotgun metagenomic sequencing was performed on fecal DNA. While the cai gene cluster was weakly correlated with plasma TMAO (rho=0.17, P=0.0007), elastic net models of TMAO were not improved by abundances of bacterial genes known to contribute to TMAO synthesis. A global analysis of all taxonomic groups, genes, and gene families found no meaningful predictors of TMAO. We postulated that abundances of known genes related to TMAO production do not predict bacterial metabolism, and we measured choline- and carnitine-trimethylamine lyase activity during fecal culture. Trimethylamine lyase genes were only weakly correlated with the activity of the enzymes they encode. Conclusions Fecal microbiome composition does not predict systemic TMAO because, in this case, gene copy number does not predict bacterial metabolic activity. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01427855.

A notable shift in understanding the human microbiome’s influence on cardiovascular disease (CVD) is underway, although the causal association remains elusive. A systematic review and meta-analysis were conducted to synthesise current knowledge on microbial taxonomy and metabolite variations between healthy controls (HCs) and those with CVD. An extensive search encompassing three databases identified 67 relevant studies (2012–2023) covering CVD pathologies from 4707 reports. Metagenomic and metabolomic data, both qualitative and quantitative, were obtained. Analysis revealed substantial variability in microbial alpha and beta diversities. Moreover, specific changes in bacterial populations were shown, including increased Streptococcus and Proteobacteria and decreased Faecalibacterium in patients with CVD compared with HC. Additionally, elevated trimethylamine N-oxide levels were reported in CVD cases. Biochemical parameter analysis indicated increased fasting glucose and triglycerides and decreased total cholesterol and low- and high-density lipoprotein cholesterol levels in diseased individuals. This study revealed a significant relationship between certain bacterial species and CVD. Additionally, it has become clear that there are substantial inconsistencies in the methodologies employed and the reporting standards adhered to in various studies. Undoubtedly, standardising research methodologies and developing extensive guidelines for microbiome studies are crucial for advancing the field.

Background: A gut-microbial metabolite, trimethylamine N-oxide (TMAO), has been associated with type 2 diabetes mellitus (T2DM). Few previous prospective studies have addressed associations between the changes in TMAO and T2DM incidence. Methods: Data were derived from a longitudinal cohort conducted from 2019 to 2021 in rural areas of Fuxin County, Liaoning Province, China, and 1515 diabetes-free participants aged above 35 years were included. The concentrations of serum TMAO and its precursors were measured at two time points, namely in 2019 and 2021. TMAO and TMAO changes (ΔTMAO) were separately tested in a logistic regression model. For further examination, the odds ratios (ORs) for T2DM were calculated according to a combination of TMAO levels and ΔTMAO levels. Results: During a median follow-up of 1.85 years, 81 incident cases of T2DM (5.35%) were identified. Baseline TMAO levels exhibited a nonlinear relationship, first decreasing and then increasing, and only at the highest quartile was it associated with the risk of T2DM. The OR for T2DM in the highest quartile of serum TMAO was 3.35 (95%CI: 1.55–7.26, p = 0.002), compared with the lowest quartile. As for its precursors, only choline level was associated with T2DM risk and the OR for T2DM in the Q3 and Q4 of serum choline was 3.37 (95%CI: 1.41–8.05, p = 0.006) and 4.72 (95%CI: 1.47–15.13, p = 0.009), respectively. When considering both baseline TMAO levels and ΔTMAO over time, participants with sustained high TMAO levels demonstrated a significantly increased risk of T2DM, with a multivariable-adjusted OR of 8.68 (95%CI: 1.97, 38.34). Conclusion: Both initial serum TMAO levels and long-term serum TMAO changes were collectively and significantly associated with the occurrence of subsequent T2DM events. Interventions aimed at normalizing TMAO levels, such as adopting a healthy dietary pattern, may be particularly beneficial in T2DM prevention.

The Mediterranean diet (MD), rich in minimally processed plant foods and in monounsaturated fats but low in saturated fats, meat, and dairy products, represents one of the most studied diets for cardiovascular health. It has been shown, from both observational and randomized controlled trials, that MD reduces body weight, improves cardiovascular disease surrogates such as waist-to-hip ratios, lipids, and inflammation markers, and even prevents the development of fatal and nonfatal cardiovascular disease, diabetes, obesity, and other diseases. However, it is unclear whether it offers cardiovascular benefits from its individual components or as a whole. Furthermore, limitations in the methodology of studies and meta-analyses have raised some concerns over its potential cardiovascular benefits. MD is also associated with characteristic changes in the intestinal microbiota, mediated through its constituents. These include increased growth of species producing short-chain fatty acids, such as Clostridium leptum and Eubacterium rectale, increased growth of Bifidobacteria, Bacteroides, and Faecalibacterium prausnitzii species, and reduced growth of Firmicutes and Blautia species. Such changes are known to be favorably associated with inflammation, oxidative status, and overall metabolic health. This review will focus on the effects of MD on cardiovascular health through its action on gut microbiota.