The Role of Microbiota-Related Co-Metabolites in MASLD Progression: A Narrative Review.

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a growing health concern due to its increasing prevalence worldwide. Metabolic homeostasis encompasses the stable internal conditions vital for efficient metabolism. This equilibrium extends to the intestinal microbiota, whose metabolic activities profoundly influence overall metabolic balance and organ health. The metabolites derived from the gut microbiota metabolism can be defined as microbiota-related co-metabolites. They serve as mediators between the gut microbiota and the host, influencing various physiological processes. The recent redefinition of the term MASLD has highlighted the metabolic dysfunction that characterize the disease. Metabolic dysfunction encompasses a spectrum of abnormalities, including impaired glucose regulation, dyslipidemia, mitochondrial dysfunction, inflammation, and accumulation of toxic byproducts. In addition, MASLD progression has been linked to dysregulation in the gut microbiota and associated co-metabolites. Short-chain fatty acids (SCFAs), hippurate, indole derivatives, branched-chain amino acids (BCAAs), and bile acids (BAs) are among the key co-metabolites implicated in MASLD progression. In this review, we will unravel the relationship between the microbiota-related metabolites which have been associated with MASLD and that could play an important role for developing effective therapeutic interventions for MASLD and related metabolic disorders.

Antibiotic-induced intestinal microbiota depletion can attenuate the acute kidney injury to chronic kidney disease transition via NADPH oxidase 2 and trimethylamine-N-oxide inhibition.

Intestinal microbiota and their metabolites affect systemic inflammation and kidney disease outcomes. Here, we investigated the key metabolites associated with the acute kidney injury (AKI)-to chronic kidney disease (CKD) transition and the effect of antibiotic-induced microbiota depletion (AIMD) on this transition. In 61 patients with AKI, 59 plasma metabolites were assessed to determine the risk of AKI-to-CKD transition. An AKI-to-CKD transition murine model was established four weeks after unilateral ischemia-reperfusion injury (IRI) to determine the effects of AIMD on the gut microbiome, metabolites, and pathological responses related to CKD transition. Human proximal tubular epithelial cells were challenged with CKD transition-related metabolites, and inhibitory effects of NADPH oxidase 2 (NOX2) signals were tested. Based on clinical metabolomics, plasma trimethylamine N-oxide (TMAO) was associated with a significantly increased risk for AKI-to-CKD transition [adjusted odds ratio 4.389 (95% confidence interval 1.106-17.416)]. In vivo, AIMD inhibited a unilateral IRI-induced increase in TMAO, along with a decrease in apoptosis, inflammation, and fibrosis. The expression of NOX2 and oxidative stress decreased after AIMD. In vitro, TMAO induced fibrosis with NOX2 activation and oxidative stress. NOX2 inhibition successfully attenuated apoptosis, inflammation, and fibrosis with suppression of G2/M arrest. NOX2 inhibition (in vivo) showed improvement in pathological changes with a decrease in oxidative stress without changes in TMAO levels. Thus, TMAO is a key metabolite associated with the AKI-to-CKD transition, and NOX2 activation was identified as a key regulator of TMAO-related AKI-to-CKD transition both in vivo and in vitro.

TMAO promotes vascular endothelial cell pyroptosis via the LPEAT-mitophagy pathway.

Trimethylamine N-oxide (TMAO) is a novel risk factor for atherosclerosis, and its underlying regulatory mechanisms are under intensive investigation. Inflammation-related vascular endothelial damage is the major driver in atherogenic process. Pyroptosis, a type of proinflammatory programmed cell death, has been proved to promote the initiation and progression of atherosclerosis. In our study, we found that TMAO triggered endothelial cells excessive mitophagy, thereby facilitating pyroptosis. This process is mediated by the upexpression of phosphatidylethanolamine acyltransferase (LPEAT). These findings provide insights into TMAO-induced vascular endothelial cell damage and suggest that LPEAT may be a valuable target for the prevention and treatment of atherosclerosis.

Quinic acid regulated TMA/TMAO-related lipid metabolism and vascular endothelial function through gut microbiota to inhibit atherosclerotic.

BACKGROUND: Quinic acid (QA) and its derivatives have good lipid-lowering and hepatoprotective functions, but their role in atherosclerosis remains unknown. This study attempted to investigate the mechanism of QA on atherogenesis in Apoe-/- mice induced by HFD. METHODS: HE staining and oil red O staining were used to observe the pathology. The PCSK9, Mac-3 and SM22a expressions were detected by IHC. Cholesterol, HMGB1, TIMP-1 and CXCL13 levels were measured by biochemical and ELISA. Lipid metabolism and the HMGB1-SREBP2-SR-BI pathway were detected by PCR and WB. 16 S and metabolomics were used to detect gut microbiota and serum metabolites. RESULTS: QA or low-frequency ABX inhibited weight gain and aortic tissue atherogenesis in HFD-induced Apoe-/- mice. QA inhibited the increase of cholesterol, TMA, TMAO, CXCL13, TIMP-1 and HMGB1 levels in peripheral blood of Apoe-/- mice induced by HFD. Meanwhile, QA or low-frequency ABX treatment inhibited the expression of CAV-1, ABCA1, Mac-3 and SM22α, and promoted the expression of SREBP-1 and LXR in the vascular tissues of HFD-induced Apoe-/- mice. QA reduced Streptococcus_danieliae abundance, and promoted Lactobacillus_intestinalis and Ileibacterium_valens abundance in HFD-induced Apoe-/- mice. QA altered serum galactose metabolism, promoted SREBP-2 and LDLR, inhibited IDOL, FMO3 and PCSK9 expression in liver of HFD-induced Apoe-/- mice. The combined treatment of QA and low-frequency ABX regulated microbe-related Glycoursodeoxycholic acid and GLYCOCHENODEOXYCHOLATE metabolism in HFD-induced Apoe-/- mice. QA inhibited TMAO or LDL-induced HCAECs damage and HMGB1/SREBP2 axis dysfunction, which was reversed by HMGB1 overexpression. CONCLUSIONS: QA regulated the gut-liver lipid metabolism and chronic vascular inflammation of TMA/TMAO through gut microbiota to inhibit the atherogenesis in Apoe-/- mice, and the mechanism may be related to the HMGB1/SREBP2 pathway.

Very low-calorie ketogenic diet (VLCKD) in the management of hidradenitis suppurativa (Acne Inversa): an effective and safe tool for improvement of the clinical severity of disease. Results of a pilot study.

BACKGROUND: Hidradenitis suppurativa (HS), an inflammatory-based dermatological condition often associated with obesity, poses significant challenges in management. The very low-calorie ketogenic diet (VLCKD) has shown efficacy in addressing obesity, related metabolic disorders, and reducing chronic inflammation. However, its effects on HS remain underexplored. In this prospective pilot study, we aimed to investigate the impact of a 28-day active phase of VLCKD on HS in a sample of treatment-naive women with HS and excess weight. METHODS: Twelve women with HS and overweight or obesity (BMI 27.03 to 50.14 kg/m2), aged 21 to 54 years, meeting inclusion/exclusion criteria and agreeing to adhere to VLCKD, were included. Baseline lifestyle habits were assessed. The Sartorius score was used to evaluate the clinical severity of HS. Anthropometric parameters (waist circumference, weight, height, and body mass index), body composition via bioelectrical impedance analysis, levels of trimethylamine N-oxide (TMAO), oxidized low-density lipoprotein (oxLDL), and derivatives of reactive oxygen metabolites (dROMs) were assessed at baseline and after 28 days of the active phase of VLCKD. RESULTS: VLCKD led to general improvements in anthropometric parameters and body composition. Notably, a significant reduction in the Sartorius score was observed after the intervention (Δ%: - 24.37 ± 16.64, p < 0.001). This reduction coincided with significant decreases in TMAO (p < 0.001), dROMs (p = 0.001), and oxLDL (p < 0.001) levels. Changes in the Sartorius score exhibited positive correlations with changes in TMAO (p < 0.001), dROMs (p < 0.001), and oxLDL (p = 0.002). CONCLUSION: The 28-day active phase of VLCKD demonstrated notable improvements in HS severity and associated metabolic markers, highlighting the potential utility of VLCKD in managing HS and its association with metabolic derangements in women with overweight or obesity.

Interactions between the gut microbiome, associated metabolites and the manifestation and progression of heart failure with preserved ejection fraction in ZSF1 rats.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is associated with systemic inflammation, obesity, metabolic syndrome, and gut microbiome changes. Increased trimethylamine-N-oxide (TMAO) levels are predictive for mortality in HFpEF. The TMAO precursor trimethylamine (TMA) is synthesized by the intestinal microbiome, crosses the intestinal barrier and is metabolized to TMAO by hepatic flavin-containing monooxygenases (FMO). The intricate interactions of microbiome alterations and TMAO in relation to HFpEF manifestation and progression are analyzed here. METHODS: Healthy lean (L-ZSF1, n = 12) and obese ZSF1 rats with HFpEF (O-ZSF1, n = 12) were studied. HFpEF was confirmed by transthoracic echocardiography, invasive hemodynamic measurements, and detection of N-terminal pro-brain natriuretic peptide (NT-proBNP). TMAO, carnitine, symmetric dimethylarginine (SDMA), and amino acids were measured using mass-spectrometry. The intestinal epithelial barrier was analyzed by immunohistochemistry, in-vitro impedance measurements and determination of plasma lipopolysaccharide via ELISA. Hepatic FMO3 quantity was determined by Western blot. The fecal microbiome at the age of 8, 13 and 20 weeks was assessed using 16s rRNA amplicon sequencing. RESULTS: Increased levels of TMAO (+ 54%), carnitine (+ 46%) and the cardiac stress marker NT-proBNP (+ 25%) as well as a pronounced amino acid imbalance were observed in obese rats with HFpEF. SDMA levels in O-ZSF1 were comparable to L-ZSF1, indicating stable kidney function. Anatomy and zonula occludens protein density in the intestinal epithelium remained unchanged, but both impedance measurements and increased levels of LPS indicated an impaired epithelial barrier function. FMO3 was decreased (- 20%) in the enlarged, but histologically normal livers of O-ZSF1. Alpha diversity, as indicated by the Shannon diversity index, was comparable at 8 weeks of age, but decreased by 13 weeks of age, when HFpEF manifests in O-ZSF1. Bray-Curtis dissimilarity (Beta-Diversity) was shown to be effective in differentiating L-ZSF1 from O-ZSF1 at 20 weeks of age. Members of the microbial families Lactobacillaceae, Ruminococcaceae, Erysipelotrichaceae and Lachnospiraceae were significantly differentially abundant in O-ZSF1 and L-ZSF1 rats. CONCLUSIONS: In the ZSF1 HFpEF rat model, increased dietary intake is associated with alterations in gut microbiome composition and bacterial metabolites, an impaired intestinal barrier, and changes in pro-inflammatory and health-predictive metabolic profiles. HFpEF as well as its most common comorbidities obesity and metabolic syndrome and the alterations described here evolve in parallel and are likely to be interrelated and mutually reinforcing. Dietary adaption may have a positive impact on all entities.

Metabolomic and genomic insights into TMA degradation by a novel halotolerant strain - Paracoccus sp. PS1.

Trimethylamine N-oxide (TMAO) is a gut metabolite that acts as a biomarker for chronic diseases, and is generated by the oxidation of trimethylamine (TMA) produced by gut microflora. Since, microbial degradation of TMA is predicted to be used to restrict the production of TMAO, we aimed to isolate bacterial strains that could effectively degrade TMA before being oxidized to TMAO. As marine fish is considered to have a rich content of TMAO, we have isolated TMA degrading isolates from fish skin. Out of the fourteen isolates, depending on their rapid TMA utilization capability in mineral salt medium supplemented with TMA as a sole carbon and nitrogen source, isolate PS1 was selected as our desired isolate. Its TMA degrading capacity was further confirmed through spectrophotometric, Electrospray Ionization Time-of-Flight Mass Spectrometry (ESI TOF-MS) and High performance liquid chromatography (HPLC) analysis and in silico analysis of whole genome (WG) gave further insights of protein into its TMA degradation pathways. PS1 was taxonomically identified as Paracoccus sp. based on its 16S rRNA and whole genome sequence analysis. As PS1 possesses the enzymes required for degradation of TMA, clinical use of this isolate has the potential to reduce TMAO generation in the human gut.

Circulating trimethylamine N-oxide is correlated with high coronary artery atherosclerotic burden in individuals with newly diagnosed coronary heart disease.

BACKGROUND: Trimethylamine N-oxide (TMAO) is a metabolite derived from the gut microbiota and has been reported to be correlated with cardiovascular diseases. Although TMAO is associated with the severity of coronary artery disease in subjects with coronary heart disease (CHD) history. However, the correlation between TMAO and the atherosclerotic burden in newly diagnosed cases of CHD is unknown. METHODS: In this hospital-based study, we enrolled 429 individuals newly diagnosed with CHD undergoing coronary angiography. Plasma TMAO was assessed before coronary angiography. SYNTAX score was computed during coronary angiography to estimate the coronary artery atherosclerotic burden. Both linear and logistic regression analyses were conducted to explore the correlation between plasma TMAO levels and SYNTAX score in newly diagnosed CHD population. RESULTS: The TMAO in patients with SYNTAX ≥ 33 and subjects with SYNTAX < 23 were 6.10 (interquartile range [IQR]: 3.53 to 9.15) µmol/L and 4.90 [IQR: 3.25 to 7.68] µmol/L, respectively. Linear regression adjusting for traditional risk factors showed TMAO level was positively correlated with SYNTAX score (ß = 0.179; p = 0.006) in CHD population. When TMAO was added to models with traditional risk factors, the predictive value improved significantly, with the receiver operating characteristic curve (AUC) increased from 0.7312 to 0.7502 (p = 0.003). Stratified analysis showed that the correlations did not hold true for subjects who were non-smoker or with histories of diabetes. None of the stratifying factors significantly altered the correlation (all p for interaction < 0.05). CONCLUSIONS: We found a positive linear correlation between plasma TMAO and SYNTAX score among newly diagnosed CHD individuals in Chinese population.

Correlation between serum trimethylamine-N-oxide and body fat distribution in middle-aged and older adults: a prospective cohort study.

BACKGROUND: Trimethylamine-N-oxide (TMAO) is linked with obesity, while limited evidence on its relationship with body fat distribution. Herein, we investigated the associations between serum TMAO and longitudinal change of fat distribution in this prospective cohort study. METHODS: Data of 1964 participants (40-75y old) from Guangzhou Nutrition and Health Study (GNHS) during 2008-2014 was analyzed. Serum TMAO concentration was quantified by HPLC-MS/MS at baseline. The body composition was assessed by dual-energy X-ray absorptiometry at each 3-y follow-up. Fat distribution parameters were fat-to-lean mass ratio (FLR) and trunk-to-leg fat ratio (TLR). Fat distribution changes were derived from the coefficient of linear regression between their parameters and follow-up duration. RESULTS: After an average of 6.2-y follow-up, analysis of covariance (ANCOVA) and linear regression displayed women with higher serum TMAO level had greater increments in trunk FLR (mean ± SD: 1.47 ± 4.39, P-trend = 0.006) and TLR (mean ± SD: 0.06 ± 0.24, P-trend = 0.011). Meanwhile, for women in the highest TMAO tertile, linear mixed-effects model (LMEM) analysis demonstrated the annual estimated increments (95% CI) were 0.03 (95% CI: 0.003 - 0.06, P = 0.032) in trunk FLR and 1.28 (95% CI: -0.17 - 2.73, P = 0.083) in TLR, respectively. In men, there were no similar significant observations. Sensitivity analysis yielded consistent results. CONCLUSION: Serum TMAO displayed a more profound correlation with increment of FLR and TLR in middle-aged and older community-dwelling women in current study. More and further studies are still warranted in the future. TRIAL REGISTRATION: NCT03179657.

Role of Gut Microbial Metabolites in Cardiovascular Diseases-Current Insights and the Road Ahead.

Cardiovascular diseases (CVDs) are the leading cause of premature morbidity and mortality globally. The identification of novel risk factors contributing to CVD onset and progression has enabled an improved understanding of CVD pathophysiology. In addition to the conventional risk factors like high blood pressure, diabetes, obesity and smoking, the role of gut microbiome and intestinal microbe-derived metabolites in maintaining cardiovascular health has gained recent attention in the field of CVD pathophysiology. The human gastrointestinal tract caters to a highly diverse spectrum of microbes recognized as the gut microbiota, which are central to several physiologically significant cascades such as metabolism, nutrient absorption, and energy balance. The manipulation of the gut microbial subtleties potentially contributes to CVD, inflammation, neurodegeneration, obesity, and diabetic onset. The existing paradigm of studies suggests that the disruption of the gut microbial dynamics contributes towards CVD incidence. However, the exact mechanistic understanding of such a correlation from a signaling perspective remains elusive. This review has focused upon an in-depth characterization of gut microbial metabolites and their role in varied pathophysiological conditions, and highlights the potential molecular and signaling mechanisms governing the gut microbial metabolites in CVDs. In addition, it summarizes the existing courses of therapy in modulating the gut microbiome and its metabolites, limitations and scientific gaps in our current understanding, as well as future directions of studies involving the modulation of the gut microbiome and its metabolites, which can be undertaken to develop CVD-associated treatment options. Clarity in the understanding of the molecular interaction(s) and associations governing the gut microbiome and CVD shall potentially enable the development of novel druggable targets to ameliorate CVD in the years to come.

Effects of Trimethylamine N-Oxide in Improving Exercise Performance in Mice: A 1H-NMR-Based Metabolomic Analysis Approach.

To improve exercise performance, the supplement of nutrients has become a common practice before prolonged exercise. Trimethylamine N-oxide (TMAO) has been shown to ameliorate oxidative stress damage, which may be beneficial in improving exercise capacity. Here, we assessed the effects of TMAO on mice with exhaustive swimming, analyzed the metabolic changes, and identified significantly altered metabolic pathways of skeletal muscle using a nuclear magnetic resonance-based (NMR-based) metabolomics approach to uncover the effects of TMAO improving exercise performance of mice. We found that TMAO pre-administration markedly prolonged the exhaustive time in mice. Further investigation showed that TMAO pre-administration increased levels of 3-hydroxybutyrate, isocitrate, anserine, TMA, taurine, glycine, and glutathione and disturbed the three metabolic pathways related to oxidative stress and protein synthesis in skeletal muscle. Our results provide a metabolic mechanistic understanding of the effects of TMAO supplements on the exercise performance of skeletal muscle in mice. This work may be beneficial in exploring the potential of TMAO to be applied in nutritional supplementation to improve exercise performance. This work will lay a scientific foundation and be beneficial to exploring the potential of TMAO to apply in nutritional supplementation.

Trimethylamine N-Oxide Improves Exercise Performance by Reducing Oxidative Stress through Activation of the Nrf2 Signaling Pathway.

Trimethylamine N-oxide (TMAO) has attracted interest because of its association with cardiovascular disease and diabetes, and evidence for the beneficial effects of TMAO is accumulating. This study investigates the role of TMAO in improving exercise performance and elucidates the underlying molecular mechanisms. Using C2C12 cells, we established an oxidative stress model and administered TMAO treatment. Our results indicate that TMAO significantly protects myoblasts from oxidative stress-induced damage by increasing the expression of Nrf2, heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase (NQO1), and catalase (CAT). In particular, suppression of Nrf2 resulted in a loss of the protective effects of TMAO and a significant decrease in the expression levels of Nrf2, HO-1, and NQO1. In addition, we evaluated the effects of TMAO in an exhaustive swimming test in mice. TMAO treatment significantly prolonged swimming endurance, increased glutathione and taurine levels, enhanced glutathione peroxidase activity, and increased the expression of Nrf2 and its downstream antioxidant genes, including HO-1, NQO1, and CAT, in skeletal muscle. These findings underscore the potential of TMAO to counteract exercise-induced oxidative stress. This research provides new insights into the ability of TMAO to alleviate exercise-induced oxidative stress via the Nrf2 signaling pathway, providing a valuable framework for the development of sports nutrition supplements aimed at mitigating oxidative stress.

Evaluation of the Feasibility of In Vitro Metabolic Interruption of Trimethylamine with Resveratrol Butyrate Esters and Its Purified Monomers.

Resveratrol (RSV), obtained from dietary sources, has been shown to reduce trimethylamine oxide (TMAO) levels in humans, and much research indicates that TMAO is recognized as a risk factor for cardiovascular disease. Therefore, this study investigated the effects of RSV and RSV-butyrate esters (RBE) on the proliferation of co-cultured bacteria and HepG2 cell lines, respectively, and also investigated the changes in trimethylamine (TMA) and TMOA content in the medium and flavin-containing monooxygenase-3 (FMO3) gene expression. This study revealed that 50 µg/mL of RBE could increase the population percentage of Bifidobacterium longum at a rate of 53%, while the rate was 48% for Clostridium asparagiforme. In contrast, co-cultivation of the two bacterial strains effectively reduced TMA levels from 561 ppm to 449 ppm. In addition, regarding TMA-induced HepG2 cell lines, treatment with 50 µM each of RBE, 3,4'-di-O-butanoylresveratrol (ED2), and 3-O-butanoylresveratrol (ED4) significantly reduced FMO3 gene expression from 2.13 to 0.40-1.40, which would also contribute to the reduction of TMAO content. This study demonstrated the potential of RBE, ED2, and ED4 for regulating TMA metabolism in microbial co-cultures and cell line cultures, which also suggests that the resveratrol derivative might be a daily dietary supplement that will be beneficial for health promotion in the future.

Associations of plasma TMAO and its precursors with stroke risk in the general population: A nested case-control study.

BACKGROUND: Trimethylamine N-oxide (TMAO) is a gut-derived atherogenic metabolite. However, the role of TMAO and its precursors in the development of stroke remains unclear. We aimed to examine the associations between metabolites in TMAO biosynthesis and stroke risk. METHODS: A nested case-control study was performed in a community-based cohort (2013-2018, n = 16,113). We included 412 identified stroke cases and 412 controls matched by age and sex. Plasma carnitine, choline, betaine, trimethyl lysine (TML), and TMAO were measured by ultrahigh performance liquid chromatography-tandem mass spectrometry. Conditional logistic regression analyses were used to calculate odds ratios (ORs) and their 95% confidence intervals (CIs) between these biomarkers and stroke risk. RESULTS: After adjustment for body mass index, smoking, hypertension, educational attainment, and estimated glomerular filtration rate, the corresponding OR for the highest versus lowest quartile was 1.74 (95% CI: 1.16-2.61, P trend = 0.006) for total stroke and 1.81 (95% CI: 1.14-2.86, P trend = 0.020) for ischemic stroke in an essentially linear dose-response fashion. A significant association between TMAO and nonischemic stroke was shown as a J-shape with OR for the highest versus second quartile of 5.75 (95% CI: 1.73-19.1). No meaningful significant risk association was found among plasma carnitine, choline, betaine, and TML with stroke risk. CONCLUSIONS: Increased TMAO was associated with higher stroke risk in the community-based population, whereas the TMAO precursors carnitine, choline, betaine, and TML were not associated. Further studies are warranted to confirm these findings and to further elucidate the role of TMAO in the development of stroke.

Phenylacetylglutamine and trimethylamine N-oxide: Two uremic players, different actions.

BACKGROUND: Chronic kidney disease (CKD) patients exhibit a heightened cardiovascular (CV) risk which may be partially explained by increased medial vascular calcification. Although gut-derived uremic toxin trimethylamine N-oxide (TMAO) is associated with calcium-phosphate deposition, studies investigating phenylacetylglutamine's (PAG) pro-calcifying potential are missing. METHODS: The effect of TMAO and PAG in vascular calcification was investigated using 120 kidney failure patients undergoing living-donor kidney transplantation (LD-KTx), in an observational, cross-sectional manner. Uremic toxin concentrations were related to coronary artery calcification (CAC) score, epigastric artery calcification score, and markers of established non-traditional risk factors that constitute to the 'perfect storm' that drives early vascular aging in this patient population. Vascular smooth muscle cells were incubated with TMAO or PAG to determine their calcifying effects in vitro and analyse associated pathways by which these toxins may promote vascular calcification. RESULTS: TMAO, but not PAG, was independently associated with CAC score after adjustment for CKD-related risk factors in kidney failure patients. Neither toxin was associated with epigastric artery calcification score; however, PAG was independently, positively associated with 8-hydroxydeoxyguanosine. Similarly, TMAO, but not PAG, promoted calcium-phosphate deposition in vitro, while both uremic solutes induced oxidative stress. CONCLUSIONS: In conclusion, our translational data confirm TMAO's pro-calcifying effects, but both toxins induced free radical production detrimental to vascular maintenance. Our findings suggest these gut-derived uremic toxins have different actions on the vessel wall and therapeutically targeting TMAO may help reduce CV-related mortality in CKD.

A water-soluble tomato extract rich in secondary plant metabolites lowers trimethylamine-n-oxide and modulates gut microbiota: a randomized, double-blind, placebo-controlled cross-over study in overweight and obese adults.

BACKGROUND: Natural products rich in polyphenols have been shown to lower plasma trimethylamine-n-oxide (TMAO) known for its proatherogenic effects by modulating the intestinal microbiota. OBJECTIVES: We aimed to determine the impact of Fruitflow, a water-soluble tomato extract, on TMAO, fecal microbiota, and plasma and fecal metabolites. METHODS: Overweight and obese adults (n = 22, BMI 28-35 kg/m2) were included in a double-blind, placebo-controlled, cross-over study receiving 2×150 mg Fruitflow per day or placebo (maltodextrin) for 4 wk with a 6-week wash-out between interventions. Stool, blood, and urine samples were collected to assess changes in plasma TMAO (primary outcome) as well as fecal microbiota, fecal and plasma metabolites, and urine TMAO (secondary outcomes). In a subgroup (n = 9), postprandial TMAO was evaluated following a choline-rich breakfast (∼450 mg). Statistical methods included paired t-tests or Wilcoxon signed rank tests and permutational multivariate analysis of variance. RESULTS: Fruitflow, but not placebo, reduced fasting levels of plasma (-1.5 µM, P ≤ 0.05) and urine (-19.1 µM, P ≤ 0.01) TMAO as well as plasma lipopolysaccharides (-5.3 ng/mL, P ≤ 0.05) from baseline to the end of intervention. However, these changes were significant only for urine TMAO levels when comparing between the groups (P ≤ 0.05). Changes in microbial beta, but not alpha, diversity paralleled this with a significant difference in Jaccard distance-based Principal Component (P ≤ 0.05) as well as decreases in Bacteroides, Ruminococccus, and Hungatella and increases in Alistipes when comparing between and within groups (P ≤ 0.05, respectively). There were no between-group differences in SCFAs and bile acids (BAs) in both faces and plasma but several changes within groups such as an increase in fecal cholic acid or plasma pyruvate with Fruitflow (P ≤ 0.05, respectively). An untargeted metabolomic analysis revealed TMAO as the most discriminant plasma metabolite between groups (P ≤ 0.05). CONCLUSIONS: Our results support earlier findings that polyphenol-rich extracts can lower plasma TMAO in overweight and obese adults related to gut microbiota modulation. This trial was registered at clinicaltrials.gov as NCT04160481 (https://clinicaltrials.gov/ct2/show/NCT04160481?term= Fruitflow&draw= 2&rank= 2).

High plasma levels of betaine, a trimethylamine N-Oxide-related metabolite, are associated with the severity of cirrhosis.

BACKGROUND AND AIMS: The gut microbiome-related metabolites betaine and trimethylamine N-oxide (TMAO) affect major health issues. In cirrhosis, betaine metabolism may be diminished because of impaired hepatic betaine homocysteine methyltransferase activity, whereas TMAO generation from trimethylamine may be altered because of impaired hepatic flavin monooxygenase expression. Here, we determined plasma betaine and TMAO levels in patients with end-stage liver disease and assessed their relationships with liver disease severity. METHODS: Plasma betaine and TMAO concentrations were measured by nuclear magnetic resonance spectroscopy in 129 cirrhotic patients (TransplantLines cohort study; NCT03272841) and compared with levels from 4837 participants of the PREVEND cohort study. Disease severity was assessed by Child-Pugh-Turcotte (CPT) classification and Model for End-stage Liver Disease (MELD) score. RESULTS: Plasma betaine was on average 60% higher (p < .001), whereas TMAO was not significantly lower in cirrhotic patients vs. PREVEND population (p = .44). After liver transplantation (n = 13), betaine decreased (p = .017; p = .36 vs. PREVEND population), whereas TMAO levels tended to increase (p = .085) to higher levels than in the PREVEND population (p = .003). Betaine levels were positively associated with the CPT stage and MELD score (both p < .001). The association with the MELD score remained in the fully adjusted analysis (p < .001). The association of TMAO with the MELD score did not reach significance (p = .11). Neither betaine nor TMAO levels were associated with mortality on the waiting list for liver transplantation (adjusted p = .78 and p = .44, respectively). CONCLUSION: Plasma betaine levels are elevated in cirrhotic patients in parallel with disease severity and decrease after liver transplantation.

Gut microbiome and metabolites, the future direction of diagnosis and treatment of atherosclerosis?

Over the past few decades, the treatment of atherosclerotic cardiovascular disease has mainly been through an LDL lowering strategy and treatments targeting other traditional risk factors for atherosclerosis, which has significantly reduced cardiovascular mortality. However, the overall benefit of targeting these risk factors has stagnated, and the discovery of new therapeutic targets for atherosclerosis remains a challenge. Accumulating evidence from clinical and animal experiments has revealed that the gut microbiome play a significant role in human health and disease, including cardiovascular diseases. The gut microbiome contribute to host health and disease through microbial composition and function. The gut microbiome function like an endocrine organ by generating bioactive metabolites that can impact atherosclerosis. In this review, we describe two gut microbial metabolites/pathways by which the gut affects atherosclerotic cardiovascular disease. On the one hand, we discuss the effects of trimethylamine oxide (TMAO), bile acids and aromatic amino acid metabolites on the development of atherosclerosis, and the protective effects of beneficial metabolites short chain amino acids and polyamines on atherosclerosis. On the other hand, we discuss novel therapeutic strategies for directly targeting gut microbial metabolites to improve cardiovascular outcomes. Reducing gut-derived TMAO levels and interfering with the bile acid receptor farnesoid X receptor (FXR) are new therapeutic strategies for atherosclerotic disease. Enzymes and receptors in gut microbiota metabolic pathways are potential new drug targets. We need solid insight into these underlying mechanisms to pave the way for therapeutic strategies targeting gut microbial metabolites/pathways for atherosclerotic cardiovascular disease.

Gut microbiota and stroke: New avenues to improve prevention and outcome.

Despite major recent therapeutic advances, stroke remains a leading cause of disability and death. Consequently, new therapeutic targets need to be found to improve stroke outcome. The deleterious role of gut microbiota alteration (often mentioned as "dysbiosis") on cardiovascular diseases, including stroke and its risk factors, has been increasingly recognized. Gut microbiota metabolites, such as trimethylamine-N-oxide, short chain fatty acids and tryptophan, play a key role. Evidence of a link between alteration of the gut microbiota and cardiovascular risk factors exists, with a possible causality link supported by several preclinical studies. Gut microbiota alteration also seems to be implicated at the acute phase of stroke, with observational studies showing more non-neurological complications, higher infarct size and worse clinical outcome in stroke patients with altered microbiota. Microbiota targeted strategies have been developed, including prebiotics/probiotics, fecal microbiota transplantation, short chain fatty acid and trimethylamine-N-oxide inhibitors. Research teams have been using different time windows and end-points for their studies, with various results. Considering the available evidence, it is believed that studies focusing on microbiota-targeted strategies in association with conventional stroke care should be conducted. Such strategies should be considered according to three therapeutic time windows: first, at the pre-stroke (primary prevention) or post-stroke (secondary prevention) phases, to enhance the control of cardiovascular risk factors; secondly, at the acute phase of stroke, to limit the infarct size and the systemic complications and enhance the overall clinical outcome; thirdly, at the subacute phase of stroke, to prevent stroke recurrence and promote neurological recovery.

Trimethylamine N-oxide: role in cell senescence and age-related diseases.

INTRODUCTION: Hayflick and Moorhead first demonstrated cell senescence as the irreversible growth arrest of cells after prolonged cultivation. Telomere shortening and oxidative stress are the fundamental mechanisms that drive cell senescence. Increasing studies have shown that TMAO is closely associated with cellular aging and age-related diseases. An emerging body of evidence from animal models, especially mice, has identified that TMAO contributes to senescence from multiple pathways and appears to accelerate many neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. However, the specific mechanism of how TMAO speeds aging is still not completely clear. MATERIAL AND METHODS: In this review, we summarize some key findings in TMAO, cell senescence, and age-related diseases. We focused particular attention on the potential mechanisms for clinical transformation to find ways to interfere with the aging process. CONCLUSION: TMAO can accelerate cell senescence by causing mitochondrial damage, superoxide formation, and promoting the generation of pro-inflammatory factors.