Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women

Effects of lacto-vegetarian and vegan diets on glycemic responses and metabolite profiles in healthy adults: A randomized trial using continuous glucose monitoring and targeted metabolomics

BACKGROUND

Our previous studies have demonstrated that dairy products protect against type 2 diabetes (T2D) and improve cardiometabolic health outcomes. Given that continuous glucose monitoring (CGM) and metabolomics analysis capture different aspects of T2D, this study investigated the effects of dairy and non-dairy products on the glycemic and metabolite profiles in healthy adults following lacto-vegetarian and vegan diets.

METHODS

A parallel randomized feeding trial with 30 participants compared isoenergetic vegan and lacto-vegetarian diets. All participants wore CGM sensors for 14 days to track glucose concentrations. Anthropometric and biochemical characteristics were also measured. In a subgroup of 13 individuals, fasting and postprandial blood samples were collected on days 1 and 15 for metabolomics analysis.

RESULTS

Our CGM data showed higher mean glucose concentrations in the vegan group over 14 days compared to the lacto-vegetarian group (p = 0.0399), after adjusting for age, sex, body mass index, and baseline glucose concentrations. Metabolomics analysis from day 1 to day 15 showed increased postprandial phenylalanine (Phe; p = 0.0189) in the vegan group, while the lacto-vegetarian group showed increased acetyl carnitine (C2; p = 0.00704) and decreased argininosuccinic acid (p = 0.0149).

CONCLUSIONS

Our pilot CGM data suggest a lacto-vegetarian diet may offer better glycemic control, potentially explained by our preliminary metabolomics findings. The increased Phe observed in the vegan group may be explained by a hypothetical mechanism in which higher glucose induces oxidative stress, whereas the increased C2 from dairy in the lacto-vegetarian group may protect against oxidative stress, contributing to lower glucose concentrations. However, larger, longer-term studies with more diverse populations, along with in vitro investigations into biomolecular mechanisms, are needed to confirm these findings.

Plant-based diet and erectile dysfunction: a narrative review

Evidence shows that the consumption of plant foods, particularly those in their whole form (fruits, vegetables, whole grains, nuts, seeds, and legumes from which no edible part has been removed) improves cardiometabolic risk factors and is associated with reduced risk of cardiovascular diseases (CVDs), diabetes, cancer, chronic kidney disease and mortality compared to animal (meat, fish, eggs and dairy) and non-whole plant foods (sugar-sweetened beverages, refined grains, etc.). Erectile dysfunction (ED) is considered a strong predictor of CVD. The underlying defect in arteriogenic ED is endothelial dysfunction. A plant-based diet focused on whole plant foods could enhance penile erection as it improves endothelial function through various mechanisms. First, it provides nitrates, L-arginine, and L-citrulline, substrates for nitric oxide production. In addition, this diet lowers low-density-lipoprotein cholesterol (LDL-C), trimethylamine N-oxide (TMAO), postprandial triglycerides, advanced glycation end-product (AGEs), inflammation, and vasoconstrictors levels, contributing to higher nitric oxide concentrations, increased endothelial progenitor cells preservation and decreased arterial stiffness. This review explores the epidemiological evidence of a plant-based diet emphasizing whole plant foods on ED and the potential biological pathways involved.

Plasma reference interval of Trimethylamine-N-oxide in healthy adults: A multicenter study using Trimethylamine-N-oxide assay kit for analysis and validation

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a potential cardiovascular biomarker in Chinese people without a defined plasma reference range. Its clinical application is restricted due to incomplete knowledge of pre-analytical factors' impact on measurement.

METHODS

Assess the effects of standard anticoagulants and pre-analytical factors on TMAO test outcomes to determine optimal conditions. Plasma TMAO levels in 649 healthy Chinese individuals were analyzed using a non-parametric approach to set a 95% reference interval. Examine how age, gender, region, and BMI affect TMAO levels and their correlation with clinical metrics like blood pressure, glucose, lipemia, and liver-kidney function.

RESULTS

Anticoagulants had minimal effect on TMAO assay results. TMAO concentrations remain stable during sample storage at 4 °C for 24 h, 25 °C for 12 h, or 35 °C for six h before centrifugation -prolonged storage at 25 °C or 35 °C results in changes below the acceptable limit. The 95 % reference interval for plasma TMAO is 5.72 µM, with a median of 1.70 µM and an interquartile range of 1.09-2.53 µM. Age, sex, region, and BMI do not affect TMAO levels. SBP, FPG, TC, and BUN positively correlate, while HDL-C, ALT, AST, and TBIL negatively correlate with TMAO.

CONCLUSIONS

This guides for selecting blood collection tubes for TMAO detection and optimal pre- centrifugation storage conditions. We set a 95% reference interval for plasma TMAO in healthy adults in China and examined the correlation between TMAO levels and demographic and biochemical markers.

The Association Between Lifestyle Interventions and Trimethylamine N-Oxide: A Systematic-Narrative Hybrid Literature Review

BACKGROUND

Trimethylamine N-oxide (TMAO) is a gut- and food-derived molecule. Elevated TMAO concentrations have been associated with an increased risk of cardiovascular disease (CVD) and all-cause mortality, highlighting its significance as a potential biomarker for adverse health outcomes. Given these associations, it is hypothesized that lifestyle interventions, such as healthy dietary patterns and exercise, could reduce TMAO concentrations. The aim of this systematic-narrative hybrid literature review was to evaluate the relationship between various lifestyle interventions and TMAO.

METHODS

MEDLINE (via PubMed®), Scopus®, and grey literature were searched until July 2024 for eligible clinical trials. Case reports, case series, case studies and observational studies were excluded, as well as studies that investigated food products, nutraceuticals, dietary supplements or have been conducted in the pediatric population.

RESULTS

In total, 27 studies were included in this review. While some dietary interventions, such as plant-based, high-dairy, very low-calorie ketogenic diet or the Mediterranean diet, were associated with lower TMAO concentrations, others-including high-protein and high-fat diets-were linked to an increase in TMAO concentrations. Studies that incorporated a combination of nutrition and exercise-based intervention presented neutral results.

CONCLUSIONS

The relationship between dietary interventions and TMAO concentration remains controversial. While certain interventions show promise in reducing TMAO levels, others yield mixed or contradictory outcomes. Further research, including well-structured RCTs, is needed to investigate the aforementioned associations.

Trimethylamine N-Oxide Plasma Levels Following Red Meat and Cod Fish Intake: A Pilot Crossover Trial in Hemodialysis Patients

SCOPE

The uremic toxin trimethylamine N-oxide (TMAO) accumulates in patients with chronic kidney disease (CKD) and is associated with its progression, cardiovascular disease, and other complications. The gut microbiota produces TMAO from substrates mainly found in red meat, eggs, and dairy. However, some saltwater fish also contain high levels of TMAO. Although fish consumption is generally linked to beneficial effects, its effects on CKD patients require further research.

METHODS AND RESULTS

This study compares the effect of red meat and cod fish intake on TMAO plasma levels in CKD patients undergoing hemodialysis (HD). Participants received a single animal protein source (red meat vs. cod fish) for lunch and dinner for four consecutive days (each intervention), with a 2-week washout period in between. TMAO plasma levels were analyzed using LC-MS/MS. All 14 patients concluded the red meat intervention, while one refused to participate in the fish intervention. No significant difference in TMAO plasma levels was found post-red meat (p = 0.21) or fish intervention (p = 0.91), as well as between groups (p = 0.43).

CONCLUSION

In this study, 4 days of red meat and cod fish intake did not significantly impact TMAO levels in HD patients, while other factors may be associated with their circulating levels.

Development of a Disease Model for Predicting Postoperative Delirium Using Combined Blood Biomarkers

OBJECTIVE

Postoperative delirium, a common neurocognitive complication after surgery and anesthesia, requires early detection for potential intervention. Herein, we constructed a multidimensional postoperative delirium risk-prediction model incorporating multiple demographic parameters and blood biomarkers to enhance prediction accuracy.

METHODS

We included 555 patients undergoing radical surgery for colorectal cancer. Demographic characteristics and lipid profiles were collected preoperatively, and perioperative anesthesia and surgical conditions were recorded; blood biomarkers were measured before and after surgery. The 3D-CAM scale was used to assess postoperative delirium occurrence within 3 days after surgery. Patients were divided into the postoperative delirium (N = 100) and non-postoperative delirium (N = 455) groups. Based on machine learning, linear and nine non-linear models were developed and compared to select the optimal model. Shapley value-interpretation methods and mediation analysis were used to assess feature importance and interaction.

RESULTS

The median age of the participants was 65 years (interquartile range: 56-71 years; 57.8% male). Among the 10 machine-learning models, the random forest model performed the best (validation cohort, area under the receiver operating characteristic curve of 0.795 [0.704-0.885]). Lipid profile (total cholesterol, triglycerides, and trimethylamine-N-oxide) levels were identified as key postoperative delirium predictors. Mediation analysis further confirmed mediating effects among total cholesterol, trimethylamine-N-oxide, and postoperative delirium; a nomogram model was developed as a web-based tool for external validation and use by other clinicians.

INTERPRETATION

Blood biomarkers are crucial in predicting postoperative delirium and aid anesthesiologists in identifying its risks in a timely manner. This model facilitates personalized perioperative management and reduces the occurrence of postoperative delirium.

TRIAL REGISTRATION

ChiCTR2300075723.

Comprehensive review of the expanding roles of the carnitine pool in metabolic physiology: beyond fatty acid oxidation

Traditionally, the carnitine pool is closely related to fatty acid metabolism. However, with increasing research, the pleiotropic effects of the carnitine pool have gradually emerged. The purpose of this review is to comprehensively investigate of the emerging understanding of the pleiotropic role of the carnitine pool, carnitine/acylcarnitines are not only auxiliaries or metabolites of fatty acid oxidation, but also play more complex and diverse roles, including energy metabolism, mitochondrial homeostasis, epigenetic regulation, regulation of inflammation and the immune system, tumor biology, signal transduction, and neuroprotection. This review provides an overview of the complex network of carnitine synthesis, transport, shuttle, and regulation, carnitine/acylcarnitines have the potential to be used as communication molecules, biomarkers and therapeutic targets for multiple diseases, with profound effects on intercellular communication, metabolic interactions between organs and overall metabolic health. The purpose of this review is to comprehensively summarize the multidimensional biological effects of the carnitine pool beyond its traditional role in fatty acid oxidation and to summarize the systemic effects mediated by carnitine/acylcarnitine to provide new perspectives for pharmacological research and treatment innovation and new strategies for the prevention and treatment of a variety of diseases.

Plasma metabolite profiles of meat intake and their association with cardiovascular disease risk: A population-based study in Swedish cohorts

BACKGROUND

Higher meat intake has been associated with adverse health outcomes, including cardiovascular disease (CVD). This study investigated plasma metabolites associated with meat intake and their relation with cardiometabolic biomarkers, subclinical CVD markers, and incident CVD.

METHODS

Associations between self-reported meat intake and 1272 plasma metabolites were investigated in the SCAPIS cohort (n = 8,819; ages 50-64). Meat-associated metabolites were further examined for relation with subclinical CVD markers in the POEM cohort (n = 502; age 50) and incident CVD in the EpiHealth cohort (n = 2,278; ages 45-75; 107 incident cases over 9.6 years follow-up). Meat intake was categorized into white, unprocessed red, and processed red meat. Linear regression analyzed associations between meat intake, metabolites and cardiometabolic biomarkers, and subclinical CVD markers, while Cox models evaluated association between meat-associated metabolites and incident CVD.

RESULTS

After correction for multiple testing, 458, 368, and 403 metabolites were associated with white, unprocessed red, and processed red meat, respectively. Processed red meat-associated metabolites were associated with higher levels of fasting insulin, hemoglobin A1c, and lipoprotein(a), and were inversely associated with maximal oxygen consumption. Two metabolites, 1-palmitoyl-2-linoleoyl-GPE (16:0/18:2) (hazard ratios (HR: 1.32; 95 % CI: 1.08, 1.62)) and glutamine degradant (HR: 1.35; 95 % CI: 1.07, 1.72), that were inversely associated with intake of all meat types, were also associated with a higher risk of incident CVD.

CONCLUSIONS

This study provides comprehensive analysis of self-reported meat intake and plasma metabolites. The findings may enhance our understanding of the relationship between meat intake and CVD, and provide insights into underlying mechanisms.

The microbial metabolite trimethylamine N-oxide and the kidney diseases

Trimethylamine N-oxide (TMAO), a metabolite, is a co-metabolite produced by both gut microbiota and livers, originating from foods rich in choline or carnitine. Emerging evidence suggests that TMAO may play a role in the pathogenesis of various kidney diseases, including acute kidney injury and chronic kidney disease. Research has demonstrated that heightened levels of TMAO are correlated with a heightened likelihood of kidney disease advancement and cardiovascular incidents among individuals with chronic kidney disease. Furthermore, TMAO has been observed to stimulate inflammation, oxidative stress, and fibrosis in animal models of kidney disease. Mechanistically, TMAO may contribute to kidney disease pathogenesis by inhibiting autophagy, activating the NLRP3 inflammasome, and inducing mitochondrial dysfunction. Therefore, targeting TMAO may represent a promising therapeutic strategy for the treatment of kidney diseases. Future studies are needed to further investigate the role of TMAO in kidney disease pathogenesis and to develop TMAO-targeted therapies for the prevention and treatment of kidney diseases.

Role of Gut Microbial Metabolites in Ischemic and Non-Ischemic Heart Failure

The effect of the gut microbiota extends beyond their habitant place from the gastrointestinal tract to distant organs, including the cardiovascular system. Research interest in the relationship between the heart and the gut microbiota has recently been emerging. The gut microbiota secretes metabolites, including Trimethylamine N-oxide (TMAO), short-chain fatty acids (SCFAs), bile acids (BAs), indole propionic acid (IPA), hydrogen sulfide (H2S), and phenylacetylglutamine (PAGln). In this review, we explore the accumulating evidence on the role of these secreted microbiota metabolites in the pathophysiology of ischemic and non-ischemic heart failure (HF) by summarizing current knowledge from clinical studies and experimental models. Elevated TMAO contributes to non-ischemic HF through TGF-ß/Smad signaling-mediated myocardial hypertrophy and fibrosis, impairments of mitochondrial energy production, DNA methylation pattern change, and intracellular calcium transport. Also, high-level TMAO can promote ischemic HF via inflammation, histone methylation-mediated vascular fibrosis, platelet hyperactivity, and thrombosis, as well as cholesterol accumulation and the activation of MAPK signaling. Reduced SCFAs upregulate Egr-1 protein, T-cell myocardial infiltration, and HDAC 5 and 6 activities, leading to non-ischemic HF, while reactive oxygen species production and the hyperactivation of caveolin-ACE axis result in ischemic HF. An altered BAs level worsens contractility, opens mitochondrial permeability transition pores inducing apoptosis, and enhances cholesterol accumulation, eventually exacerbating ischemic and non-ischemic HF. IPA, through the inhibition of nicotinamide N-methyl transferase expression and increased nicotinamide, NAD+/NADH, and SIRT3 levels, can ameliorate non-ischemic HF; meanwhile, H2S by suppressing Nox4 expression and mitochondrial ROS production by stimulating the PI3K/AKT pathway can also protect against non-ischemic HF. Furthermore, PAGln can affect sarcomere shortening ability and myocyte contraction. This emerging field of research opens new avenues for HF therapies by restoring gut microbiota through dietary interventions, prebiotics, probiotics, or fecal microbiota transplantation and as such normalizing circulating levels of TMAO, SCFA, BAs, IPA, H2S, and PAGln.

Heart Failure and Gut Microbiota: What Is Cause and Effect?

Emerging evidence highlights the central role of gut microbiota in maintaining physiological homeostasis within the host. Disruptions in gut microbiota can destabilize systemic metabolism and inflammation, driving the onset and progression of cardiometabolic diseases. In heart failure (HF), intestinal dysfunction may induce the release of endotoxins and metabolites, leading to dysbiosis and exacerbating HF through the gut-heart axis. Understanding the relationship between gut microbiota and HF offers critical insights into disease mechanisms and therapeutic opportunities. Current research highlights promising potential to improve patient outcomes by restoring microbiota balance. In this review, we summarize the current studies in understanding the gut microbiota-HF connection and discuss avenues for future investigation.

Healthful vs. Unhealthful Plant-Based Restaurant Meals

Background: Vegan/vegetarian (VEG) restaurants and VEG options in omnivore (OMNI) restaurants may serve unhealthful plant-based food that may be more harmful than a typical American diet. Methods: A sample of 561 restaurants with online menus were analyzed over a 3-year period. Each plant-based menu entrée was counted, up to a maximum of ten entrées per restaurant, meaning that a restaurant customer could select from ten or more healthful plant-based choices. Entrées containing refined grains (e.g., white rice and refined flour), saturated fat (e.g., palm oil and coconut oil), or deep-fried foods were counted as zero. Results: We evaluated 278 VEG and 283 OMNI restaurants. A full menu (10 or more plant-based entrées) was available in 59% of the VEG, but only 16% of the OMNI (p < 0.0001). Zero healthful options occurred in 27% of OMNI, but only 14% of VEG (p = 0.0002). The mean healthy entrée count for all restaurants was 3.2, meaning that, on average, there were only about three healthful plant-based choices of entrées on the menu, significantly more in VEG (4.0 vs. 2.4 p < 0.0001). The most common entrée reduction was for refined grains (e.g., white flour in veggie-burger buns or white rice in Asian entrées, n = 1408), followed by fried items (n = 768) and saturated fat (n = 318). VEG restaurants had a significantly higher frequency of adequate VEG options (≥7 options, 24% vs. 13%, p = 0.0005). Conclusions: Restaurants listed as VEG have a slightly higher number of healthful entrées than OMNI restaurants, which offer more limited vegan/vegetarian options. Given the published relationship between unhealthful dietary patterns, chronic illness, and mortality, we propose that detailed nutrition facts be publicly available for every restaurant.

Cardiovascular Risk Assessment and Prevention in Cardio-Oncology: Beyond Traditional Risk Factors

This review goes beyond traditional approaches in cardio-oncology, highlighting often-neglected factors impacting patient care. Social determinants, environment, health care access, and gut microbiome significantly influence patient outcomes. Powerful tools like multi-omics and wearable technologies offer deeper insights into real-world experiences. The future lies in integrating these advancements with established practices to achieve precision cardio-oncology care. By crafting tailored therapies and continuously updating comprehensive management plans based on real-time data, we can unlock the full potential of personalized care for all patients.

The associations between nutrition and circulating gut microbiota-derived uremic toxins in patients undergoing kidney replacement therapy: An observational, cross-sectional study

BACKGROUND

Gut microbiota generates a series of bioactive metabolites that can be converted into uremic toxins such as trimethylamine-N-oxide (TMAO), p-cresyl sulfate (pCS), and indoxyl sulfate (IS). The aim of the study was to examine the association between diet and the concentrations of the mentioned gut microbiota-derived uremic toxins.

METHODS

An observational cross-sectional study was conducted involving 210 participants: 84 hemodialysis (HD) patients, 44 peritoneal dialysis (PD) patients, 52 kidney transplant recipients (KTR), and 30 healthy controls. Dietary intake was assessed using a 3-day food diary and a food frequency questionnaire with 6 answers (FFQ-6). The alternate Mediterranean diet (aMED) score was calculated based on data obtained from the 3-day food diary and FFQ-6. Blood samples were analyzed for TMAO, pCS, and IS concentrations using liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS

Significant differences in TMAO, pCS, and IS concentrations were observed among the study groups. HD and PD patients exhibited higher levels of these metabolites compared to KTR and healthy controls. The median aMED score was 4 (3-5) points in the HD group, 4.5 (4-6) points in the PD group, 5 (4-6) points in the KTRs, and 6 (5-7) points in the control group. Higher adherence to the Mediterranean diet (aMED score) was associated with lower pCS levels in dialysis patients. Vegetable intake several times a day was found to mitigate the effects of phenylalanine and tyrosine intake on pCS concentration among dialysis patients.

CONCLUSIONS

The diet of patients undergoing kidney replacement therapy (KRT) significantly affects the concentrations of gut microbiota-derived uremic toxins. These findings highlight the importance of dietary management in mitigating the adverse effects of these toxins in patients with chronic kidney disease (CKD).

Impact of the Healthy Lifestyle Community Program (HLCP-3) on Trimethylamine N-Oxide (TMAO) and Risk Profile Parameters Related to Lifestyle Diseases During the Six Months Following an Intervention Study

RATIONALE

The dietary components choline, betaine, and L-carnitine are converted by intestinal microbiota into the molecule trimethylamine (TMA). In the human liver, hepatic flavin-containing monooxygenase 3 oxidizes TMA to trimethylamine-N-oxide (TMAO). TMAO is considered a candidate marker for the risk of cardiovascular disease.

METHODOLOGY

The Healthy Lifestyle Community Program cohort 3 (HLCP-3) intervention was conducted with participants recruited from the general population in Germany (intervention: n = 99; control: n = 48). The intervention included intensive educational workshops, seminars, and coaching activities. The assessment was conducted using a complete case analysis (CCA) of the participants. The intervention was carried out for a ten-week intensive phase and an alumni phase. The interventional program emphasizes adopting a healthy plant-based diet and reducing meat consumption, as adherence to such a diet may lead to lowering TMAO levels. Additionally, it provides general recommendations about physical activity, stress management, and community support. The control group did not receive any intervention. TMAO was evaluated using stable isotope dilution liquid chromatography, and tandem mass spectrometry was used to measure fasting plasma levels of TMAO.

OBJECTIVES

The present study aimed to determine the impact of the Healthy Lifestyle Community Program (HLCP-3) on risk profiles for lifestyle-related diseases and TMAO plasma levels.

RESULTS

Significant decreases in most risk profile parameters were detected, and a non-significant decrease in plasma TMAO levels was observed in the intervention group (0.37 (-1.33; 0.59) µmol/L). Furthermore, for the intervention group, after a six-month follow-up period, there was a significant negative correlation between higher healthy plant diet index (hPDI) scores and a decrease in plasma TMAO (ß = -0.200, p = 0.027). Additionally, a significant negative correlation was observed between the TMAO level and the scores for adherence to the plant diet index (PDI) (r = -0.195; p = 0.023).

CONCLUSIONS

HLCP-3 is effective at improving adherence to a plant-based diet and improving risk profile parameters. However, long-term interventions involving stricter dietary programs in the sense of a plant-based diet are recommended if significant decreases in TMAO levels are to be obtained.

Influence of dietary protein and fiber intake interactions on the human gut microbiota composition and function: a systematic review and network meta-analysis of randomized controlled trials

Quantity and source of dietary protein intakes impact the gut microbiota differently. However, these effects have not been systematically studied. This review aimed to investigate these effects whilst controlling for fiber intake. Seven databases were searched, with 50 and 15 randomized controlled trials selected for the systematic review and network meta-analysis respectively. Most gut microbiota-related outcomes showed no significant differences between different protein and fiber intake combinations. Compared to Normal Protein, High Fiber intakes, High Protein, Low Fiber (HPLF) intakes showed greater fecal valerate (SMD = 0.79, 95% CrI: 0.35, 1.24) and plasma trimethylamine N-oxide (TMAO) (SMD = 2.90, 95% CrI: 0.16, 5.65) levels. HPLF intakes also showed greater fecal propionate (SMD = 0.49, 95% CrI: 0.02, 1.07) and valerate (SMD = 0.79, 95% CrI: 0.31, 1.28) levels compared to High Protein, High Fiber intakes. Greater plasma TMAO levels were observed with greater animal protein intakes. Overall, protein quantity and source do not generally alter the gut microbiota composition, although protein quantity can influence microbiota function via modulations in proteolytic fermentation. Both protein and fiber intake should be considered when assessing the impact of dietary protein on the gut microbiota. This trial was registered at PROSPERO (CRD42023391270).

Trimethylamine N-oxide in cardiovascular disease: Pathophysiology and the potential role of statins

Cardiovascular diseases are one of the leading causes of mortality and morbidity worldwide, with the total number of cases increasing to 523 million in 2019. Despite the advent of new drugs, cardiovascular mortality has increased at an alarming rate of 53.7 % from 12.1 million deaths in 1990. Recently, the role of gut microbiome metabolites, such as Trimethylamine N-Oxide (TMAO), in the pathogenesis of cardiovascular disease (CVD) has attracted significant attention. The gut microbiome is critical in various physiological processes including metabolism, immune function, and inflammation. Elevated TMAO levels are associated with atherosclerosis, heart failure, arrhythmia, and atrial fibrillation. TMAO accelerates atherosclerosis by promoting vascular inflammation and reducing reverse cholesterol transport, which leads to lipid accumulation and vessel narrowing. Previous research has indicated that a Mediterranean diet rich in fiber and phytochemicals can reduce TMAO levels by limiting precursors and fostering beneficial gut microbiota. Prebiotics and probiotics also decrease TMAO, while drugs such as meldonium, aspirin, and antibiotics have shown promise. However, recent studies have demonstrated major potential for the use of statins in reducing TMAO levels. Statin therapy can significantly reduce TMAO levels independent of their cholesterol-lowering effects. This reduction may involve direct interactions with the gut microbiome, changes in cholesterol metabolism, and changes in bile acid composition. This review aims to comprehensively evaluate the therapeutic potential of statins in reducing TMAO levels to improve CV outcomes.

The gut-heart axis: a review of gut microbiota, dysbiosis, and cardiovascular disease development

Background

Cardiovascular diseases (CVDs) are a major cause of morbidity and mortality worldwide and there are strong links existing between gut health and cardiovascular health. Gut microbial diversity determines gut health. Dysbiosis, described as altered gut microbiota, causes bacterial translocations and abnormal gut byproducts resulting in systemic inflammation.

Objective

To review the current literature on the relationships between gut microbiota, dysbiosis, and CVD development, and explore therapeutic methods to prevent dysbiosis and support cardiovascular health.

Summary

Dysbiosis increases levels of pro-inflammatory substances while reducing those of anti-inflammatory substances. This accumulative inflammatory effect negatively modulates the immune system and promotes vascular dysfunction and atherosclerosis. High Firmicutes to Bacteroidetes ratios, high trimethylamine-n-oxide to short-chain fatty acid ratios, high indole sulfate levels, low cardiac output, and polypharmacy are all associated with worse cardiovascular outcomes. Supplementation with prebiotics and probiotics potentially alleviates some CVD risk. Blood and stool samples may be used in clinical practice to quantify and qualify gut bacterial ratios and byproducts, assess patients' risk for adverse cardiovascular outcomes, and track their gut health progress. Further research is required to set population-based cutoffs for normal and abnormal gut microbiota and byproduct ratios.

Potential effects of probiotics on atherosclerosis

The rising global incidence of atherosclerosis highlights the inadequacies in our understanding of the pathophysiology and treatment of the disease. Increasing evidence outlines the importance of the intestinal microbiome in atherosclerosis, wherein gut-derived uremic toxins (GDUTs) may be of concern. Plasma levels of the GDUTs trimethylamine n-oxide (TMAO), p-cresyl sulfate, and indoxyl sulfate are associated with accelerated renal function decline and increased cardiovascular risk. Thus, reducing the amount of GDUTs in circulation is expected to benefit patients with atherosclerosis. Because some beneficial bacteria can clear GDUTs in vitro and in vivo, orally administered probiotics targeting the intestinal tract represent a promising way to bring about these changes. Atherosclerosis such, this perspective reviews the potential use of probiotics to treat atherosclerosis, particularly in patients with non-traditional risk factors and/or impaired renal function.

The Gut-Heart Axis: Effects of Intestinal Microbiome Modulation on Cardiovascular Disease-Ready for Therapeutic Interventions?

Recent reports demonstrate an association between distinct bacteria or bacteria-derived metabolites originating from the gut microbiome and the onset or progression of cardiovascular disease (CVD). This raises the opportunity to modulate the gut microbiome to prevent or treat CVD. To investigate whether intestinal microbiome modulation can prevent or treat CVD, this systematic literature review includes all randomized clinical trials on microbiome modulation and its effects on CVD risk published between August 2018 and August 2023. Within this review, we report the modulation of the gut microbiome by a variety of interventions and their effects on CVD, focusing on cardiovascular risk factors and risk markers of CVD. Beneficial effects were observed upon lifestyle intervention and probiotics use. The most promising diets for reducing risk factors of CVD were the Mediterranean diet, high-fiber diets, polyphenol-rich diets, and diets containing polyunsaturated fatty acids. Among drug interventions, only empagliflozin showed beneficial effects on CVD risk factors. Many dietary interventions were less conclusive because of the heterogeneity of study populations, small sample sizes, and short intervention windows or follow-up. Diet, lifestyle, probiotics, or drug interventions can modulate the gut microbiome and decrease risk markers or risk factors related to CVD. Yet, their effects on clinical endpoints remain to be determined.

Association between plasma trimethylamine N-oxide and cerebral white matter hyperintensity: a cross-sectional study

Background

Cerebral white matter hyperintensity (WMH) is a pivotal imaging feature of cerebral small vessel disease (CSVD), closely correlated with an elevated risk of ischemic stroke (IS). Trimethylamine N-oxide (TMAO), a metabolite of gut microbiota, is increasingly associated with IS and atherosclerosis. However, the intricate relationship between TMAO and WMH remains ambiguous. This study aimed to study the connection between plasma TMAO and WMH. Furthermore, it assessed the potential of TMAO as a risk evaluation instrument for WMH.

Methods

In this cross-sectional study, we categorized WMH into periventricular WMH (P-WMH) and deep WMH (D-WMH), based on its locations. The severity of WMH was assessed and grouped according to the Fazekas scale. Plasma TMAO levels were quantitatively determined. We established the correlation between plasma TMAO levels and WMH severity using a Logistic regression model. Additionally, we employed ROC curves to evaluate the diagnostic efficacy of plasma TMAO concentration in distinguishing the severity of WMH.

Results

A higher plasma TMAO tertile was significantly linked to a higher Fazekas score, encompassing the overall score, P-WMH score, and D-WMH score (p < 0.001). A logical regression analysis revealed that plasma TMAO levels were independently associated with overall moderate and severe WMH, compared to overall non-mild WMH, in the unadjusted model (OR = 1.373, 95%CI 1.183-1.594 for moderate; OR = 1.384, 95%CI 1.192-1.607 for severe), the adjusted model a (OR = 1.436, 95%CI 1.214-1.669 for moderate; OR = 1.446, 95%CI 1.222-1.711 for severe) and the adjusted model b (OR = 1.490, 95%CI 1.234-1.800 for moderate; OR = 1.494, 95%CI 1.237-1.805 for severe). The analysis also showed an independent correlation between plasma TMAO levels and WMH severity, irrespective of the unadjusted model, adjusted model a, or adjusted model b, when considering P-WMH and D-WMH severity. The ROC indicated that, in overall WMH and P-WMH, the area under curve (AUC) for non-mild and severe WMH were both>0.5, while the AUC for moderate WMH was<0.5. In contrast, in D-WMH, the AUC for non-mild, moderate, and severe WMH were all>0.5.

Conclusion

Plasma TMAO levels exhibited a significant correlation with both overall and region-specific WMH severity. Furthermore, the plasma TMAO levels displayed robust predictive capability for D-WMH.

Reaction-Based Fluorescence Assays for the Determination of Food Trimethylamine Oxide

Trimethylamine oxide (TMAO), a microbial metabolite commonly found in foods, has been attracting increasing attention as it is associated with the risk of several diseases. Simple and accurate analytical methods are crucial for TMAO study. In the present study, we proposed a chemical reaction-based fluorescence assay for TMAO detection using synthetic small molecular probes. After systematic screening and optimization, the sensitive and selective quantification of TMAO has been achieved based on a fluorescence probe P6 (3-iodopropanyl group modified resorufin). Excellent linearity (R2 = 0.997) was found between 6.25 and 50 μM, and the limit of detection (LOD) was 0.20 μM. Using this method, TMAO levels in several marine fishes and shellfishes have been successfully analyzed. The probe-based assay offers a simple and useful way for TMAO determination. The design is inspired by the unique oxidation reaction between TMAO and halogen, which opens a new perspective in the development of more advanced analytical assays for TMAO in the future.

Gut Microbe-Generated Metabolite Trimethylamine-N-Oxide and Ischemic Stroke

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite, the production of which in vivo is mainly regulated by dietary choices, gut microbiota, and the hepatic enzyme flavin monooxygenase (FMO), while its elimination occurs via the kidneys. The TMAO level is positively correlated with the risk of developing cardiovascular diseases. Recent studies have found that TMAO plays an important role in the development of ischemic stroke. In this review, we describe the relationship between TMAO and ischemic stroke risk factors (hypertension, diabetes, atrial fibrillation, atherosclerosis, thrombosis, etc.), disease risk, severity, prognostic outcomes, and recurrence and discuss the possible mechanisms by which they interact. Importantly, TMAO induces atherosclerosis and thrombosis through lipid metabolism, foam cell formation, endothelial dysfunction (via inflammation, oxidative stress, and pyroptosis), enhanced platelet hyper-reactivity, and the upregulation and activation of vascular endothelial tissue factors. Although the pathogenic mechanisms underlying TMAO's aggravation of disease severity and its effects on post-stroke neurological recovery and recurrence risk remain unclear, they may involve inflammation, astrocyte function, and pro-inflammatory monocytes. In addition, this paper provides a summary and evaluation of relevant preclinical and clinical studies on interventions regarding the gut-microbiota-dependent TMAO level to provide evidence for the prevention and treatment of ischemic stroke through the gut microbe-TMAO pathway.

Unraveling the Role of the Human Gut Microbiome in Health and Diseases

The human gut is a complex ecosystem that supports billions of living species, including bacteria, viruses, archaea, phages, fungi, and unicellular eukaryotes. Bacteria give genes and enzymes for microbial and host-produced compounds, establishing a symbiotic link between the external environment and the host at both the gut and systemic levels. The gut microbiome, which is primarily made up of commensal bacteria, is critical for maintaining the healthy host's immune system, aiding digestion, synthesizing essential nutrients, and protecting against pathogenic bacteria, as well as influencing endocrine, neural, humoral, and immunological functions and metabolic pathways. Qualitative, quantitative, and/or topographic shifts can alter the gut microbiome, resulting in dysbiosis and microbial dysfunction, which can contribute to a variety of noncommunicable illnesses, including hypertension, cardiovascular disease, obesity, diabetes, inflammatory bowel disease, cancer, and irritable bowel syndrome. While most evidence to date is observational and does not establish direct causation, ongoing clinical trials and advanced genomic techniques are steadily enhancing our understanding of these intricate interactions. This review will explore key aspects of the relationship between gut microbiota, eubiosis, and dysbiosis in human health and disease, highlighting emerging strategies for microbiome engineering as potential therapeutic approaches for various conditions.

Puerarin alleviates atherosclerosis via the inhibition of Prevotella copri and its trimethylamine production

OBJECTIVE

Puerarin (PU) is a natural compound that exhibits limited oral bioavailability but has shown promise in the treatment of atherosclerosis (AS). However, the precise mechanisms underlying its therapeutic effects remain incompletely understood. This study aimed to investigate the effects of PU and its mechanisms in mitigating AS in both mice and humans.

DESIGN

The impact of PU on AS was examined in ApoE -/- mice fed a high-fat diet (HFD) and in human patients with carotid artery plaque. To explore the causal link between PU-associated gut microbiota and AS, faecal microbiota transplantation (FMT) and mono-colonisation of mice with Prevotella copri (P. copri) were employed.

RESULTS

PU alleviated AS by modulating the gut microbiota, as evidenced by alterations in gut microbiota composition and the amelioration of AS following FMT from PU-treated mice into ApoE-/- mice fed HFD. Specifically, PU reduced the abundance of P. copri, which exacerbated AS by producing trimethylamine (TMA). Prolonged mono-colonisation of P. copri undermines the beneficial effects of PU on AS. In clinical, the plaque scores of AS patients were positively correlated with the abundance of P. copri and plasma trimethylamine-N-oxide (TMAO) levels. A 1-week oral intervention with PU effectively decreased P. copri levels and reduced TMAO concentrations in patients with carotid artery plaque.

CONCLUSION

PU may provide therapeutic benefits in combating AS by targeting P. copri and its production of TMA.

TRIAL REGISTRATION NUMBER

ChiCTR1900022488.

Dietary patterns and diabetic microvascular complications risk: a Mendelian randomization study of European ancestry

Purpose

Previous observational studies about the link between dietary factors and diabetic microvascular complications (DMCs) is controversial. Thus, we systemically assessed the potential causal relationship between diet and DMCs risk using Mendelian randomization (MR) methods.

Methods

We used genome-wide association studies (GWAS) statistics to estimate the causal effects of 17 dietary patterns on three common DMCs in European. Summary statistics on dietary intakes were obtained from the UK biobank, and data on DMCs [diabetic retinopathy (DR), diabetic nephropathy (DN), and diabetic neuropathy (DNP)] were obtained from the FinnGen Consortium. A two-sample MR (TSMR) was conducted to explore the causal relationships of dietary habits with DMCs. In addition, multivariable MR analysis (MVMR) was performed to adjust for traditional risk factors for eating habits, and evaluated the direct or indirect effects of diet on DMCs.

Results

TSMR analysis revealed that salad/raw vegetable intake (odd ratio [OR]: 2.830; 95% confidence interval [CI]: 1.102-7.267; p = 0.0306) and fresh fruit intake (OR: 2.735; 95% CI: 1.622-4.611; p = 0.0002; false discovery rate [FDR] = 0.0082) increased the risk of DR, whereas cheese intake (OR: 0.742; 95% CI: 0.563-0.978; p = 0.0339) and cereal intake (OR: 0.658; 95% CI: 0.444-0.976; p = 0.0374) decreased the risk of DR. Salad/raw vegetable (OR: 6.540; 95% CI: 1.061-40.300; p = 0.0430) and fresh fruit consumption (OR: 3.573; 95% CI: 1.263-10.107; p = 0.0164) are risk factors for DN, while cereal consumption (OR: 0.380; 95% CI: 0.174-0.833; p = 0.0156) is the opposite. And genetically predicted higher pork intake increased the risk of DNP (OR: 160.971; 95% CI: 8.832-2933.974; p = 0.0006; FDR = 0.0153). The MVMR analysis revealed that cheese intake may act as an independent protective factor for DR development. Moreover, fresh fruit intake, salad/raw vegetable intake and pork intake may be independent risk factors for DR, DN and DNP, respectively. Other causal associations between dietary habits and DMCs risk may be mediated by intermediate factors.

Conclusion

This causal relationship study supports that specific dietary interventions may reduce the risk of DMCs.

Genetics, diet, microbiota, and metabolome: partners in crime for colon carcinogenesis

Colorectal cancer (CRC) ranks among the most prevalent malignant tumors worldwide, with a multifactorial etiology encompassing genetic, environmental, and life-style factors, as well as the intestinal microbiota and its metabolome. These risk factors often work together in specific groups of patients, influencing how CRC develops and progresses. Importantly, alterations in the gut microbiota act as a critical nexus in this interplay, significantly affecting susceptibility to CRC. This review highlights recent insights into unmodifiable and modifiable risk factors for CRC and how they might interact with the gut microbiota and its metabolome. Understanding the mechanisms of these interactions will help us develop targeted, precision-medicine strategies that can adjust the composition of the gut microbiota to meet individual health needs, preventing or treating CRC more effectively.

Elevated Circulating Levels of Gut Microbe-Derived Trimethylamine N-Oxide Are Associated with Systemic Sclerosis

Background/Objectives: Alterations in fecal microbial communities in patients with systemic sclerosis (SSc) are common, but the clinical significance of this observation is poorly understood. Gut microbial production of trimethylamine (TMA), and its conversion by the host to trimethylamine N-oxide (TMAO), has clinical and mechanistic links to cardiovascular and renal diseases. Direct provision of TMAO has been shown to promote fibrosis and vascular injury, hallmarks of SSc. We sought to determine levels of TMAO and related metabolites in SSc patients and investigate associations between the metabolite levels with disease features. Methods: This is an observational case:control study. Adults with SSc (n = 200) and non-SSc controls (n = 400) were matched for age, sex, indices of renal function, diabetes mellitus, and cardiovascular disease. Serum TMAO, choline, betaine, carnitine, γ-butyrobetaine, and crotonobetaine were measured using stable isotope dilution liquid chromatography tandem mass spectrometry. Results: Median TMAO concentration was higher (p = 0.020) in SSc patients (3.31 [interquartile range 2.18, 5.23] µM) relative to controls (2.85 [IQR 1.88, 4.54] µM). TMAO was highest among obese and male SSc participants compared to all other groups. Following adjustment for sex, BMI, age, race, and eGFR in a quantile regression model, elevated TMAO levels remained associated with SSc at each quantile of TMAO. Conclusions: Patients with SSc have increased circulating levels of TMAO independent of comorbidities including age, sex, renal function, diabetes mellitus, and cardiovascular disease. As a potentially modifiable factor, further studies examining the link between TMAO and SSc disease severity and course are warranted.

Trimethylamine-N-Oxide and Related Metabolites: Assessing Cardiovascular Risk in the Dallas Heart Study

OBJECTIVE

To evaluate the association between trimethylamine N-oxide (TMAO) and related metabolites with adverse cardiovascular events in a multiethnic urban primary prevention population.

METHODS

We performed a case-control study of 361 participants of the Dallas Heart Study, including 88 participants with an incident atherosclerotic cardiovascular disease (ASCVD) event and 273 controls matched for age, sex, and body mass index without an ASCVD event during 12 years of follow-up (January 1, 2000, through December 31, 2015). Plasma levels of TMAO, choline, carnitine, betaine, and butyrobetaine were measured by mass spectrometry. The differential odds for incident ASCVD by metabolite levels between cases and controls were compared by a conditional logistic regression model adjusted for cardiovascular risk factors.

RESULTS

Participants with incident ASCVD had higher levels of TMAO and related metabolites compared with those without ASCVD (P<.05 for all). Those with plasma TMAO concentrations in quartile 4 had a more than 2-fold higher odds of ASCVD compared with those in quartile 1 (odds ratio, 2.77 [95% CI, 1.05 to 7.7; P=.04] for hard ASCVD and 2.41 [95% CI, 1.049 to 5.709; P=.04]). Similar trends were seen with the related metabolites choline, betaine, carnitine, and butyrobetaine.

CONCLUSION

Our results suggest that TMAO and related metabolites are independently associated with ASCVD events. Although further studies are needed, measurement of TMAO and related metabolites may have a role in ASCVD risk stratification for primary prevention.

Terrestrial Animal Source Foods and Health Outcomes for Those with Special Nutrient Needs in the Life Course

Background. Animal source foods are under scrutiny for their role in human health, yet some nutritionally vulnerable populations are largely absent from consideration. Methods. Applying a Population Intervention/Exposure Comparator Outcome (PICO/PECO) framework and prioritizing systematic review and meta-analyses, we reviewed the literature on terrestrial animal source foods (TASFs) and human health, by life course phase. Results. There were consistent findings for milk and dairy products on positive health outcomes during pregnancy and lactation, childhood, and among older adults. Eggs were found to promote early childhood growth, depending on context. Unprocessed meat consumption was associated with a reduced risk for anemia during pregnancy, improved cognition among school-age children, and muscle health in older adults. Milk and eggs represent a risk for food sensitivities/allergies, though prevalence is low, and individuals tend to outgrow the allergies. TASFs affect the human microbiome and associated metabolites with both positive and negative health repercussions, varying by type and quantity. Conclusions. There were substantial gaps in the evidence base for studies limiting our review, specifically for studies in populations outside high-income countries and for several TASF types (pig, poultry, less common livestock species, wild animals, and insects). Nonetheless, sufficient evidence supports an important role for TASFs in health during certain periods of the life course.

The Effect of Dietary Types on Gut Microbiota Composition and Development of Non-Communicable Diseases: A Narrative Review

INTRODUCTION

The importance of diet in shaping the gut microbiota is well established and may help improve an individual's overall health. Many other factors, such as genetics, age, exercise, antibiotic therapy, or tobacco use, also play a role in influencing gut microbiota.

AIM

This narrative review summarizes how three distinct dietary types (plant-based, Mediterranean, and Western) affect the composition of gut microbiota and the development of non-communicable diseases (NCDs).

METHODS

A comprehensive literature search was conducted using the PubMed, Web of Science, and Scopus databases, focusing on the keywords "dietary pattern", "gut microbiota" and "dysbiosis".

RESULTS

Both plant-based and Mediterranean diets have been shown to promote the production of beneficial bacterial metabolites, such as short-chain fatty acids (SCFAs), while simultaneously lowering concentrations of trimethylamine-N-oxide (TMAO), a molecule associated with negative health outcomes. Additionally, they have a positive impact on microbial diversity and therefore are generally considered healthy dietary types. On the other hand, the Western diet is a typical example of an unhealthy nutritional approach leading to an overgrowth of pathogenic bacteria, where TMAO levels rise and SCFA production drops due to gut dysbiosis.

CONCLUSION

The current scientific literature consistently highlights the superiority of plant-based and Mediterranean dietary types over the Western diet in promoting gut health and preventing NCDs. Understanding the influence of diet on gut microbiota modulation may pave the way for novel therapeutic strategies.

Developing and evaluating the construct validity of a dietary pattern predictive of plasma TMAO and choline

BACKGROUND AND AIMS

The metabolism of choline (highly present in animal products) can produce trimethylamine N-oxide (TMAO), a metabolite with atherosclerotic effects; however, dietary fiber may suppress this metabolic pathway. This study aimed to develop a dietary pattern predictive of plasma TMAO and choline concentrations using reduced rank regression (RRR) and to evaluate its construct validity.

METHODS AND RESULTS

Diet and plasma concentrations of choline (μmol/L) and TMAO (μmol/L) were assessed in 1724 post-menopausal women who participated in an ancillary study within the Women's Health Initiative Observational Study (1993-1998). The TMAO dietary pattern was developed using RRR in half of the sample (Training Sample) and applied to the other half of the sample (Validation Sample) to evaluate its construct validity. Energy-adjusted food groups were the predictor variables and plasma choline and TMAO, the response variables. ANCOVA and linear regression models were used to assess associations between each biomarker and the dietary pattern score. Discretionary fat, potatoes, red meat, and eggs were positively associated with the dietary pattern, while yogurt, fruits, added sugar, and starchy vegetables were inversely associated. Mean TMAO and choline concentrations significantly increased across increasing quartiles of the dietary pattern in the Training and Validation samples. Positive associations between the biomarkers and the TMAO dietary pattern were also observed in linear regression models (Validation Sample: TMAO, adjusted beta-coefficient = 0.037 (p-value = 0.0088); Choline, adjusted beta-coefficient = 0.011 (p-value = 0.0224).

CONCLUSION

We established the TMAO dietary pattern, a dietary pattern reflecting the potential of the diet to contribute to plasma concentrations of TMAO and choline.

Health Benefits of a Plant-Based Dietary Pattern and Implementation in Healthcare and Clinical Practice

The American College of Lifestyle Medicine recommends eating a predominantly plant-based diet with a variety of minimally processed vegetables, fruits, whole grains, legumes, nuts and seeds. At any level, adoption of a plant-based diet can improve one's health through a variety of mechanisms. Increasing intake of plant-based foods often results in increases in fiber intake, decreases in saturated fat intake, and increased intake of essential vitamins and minerals, among other healthful benefits. Despite such potential benefits, many individuals are reluctant or resistant to change their usual dietary behaviors or unable to sustain diet changes over time. This is largely because an individual's decision to adopt a plant-based diet is influenced by a diverse array of motivating factors, priorities, and/or misconceptions about nutrient adequacy of plant-based diets. Here, we discuss key points from a session at the American College of Lifestyle Medicine's annual conference LM2023. Specifically, we review common preconceptions about plant-based diets, provide guidance on removing the barriers to adopting and adhering to plant-based diets, and highlight key literature findings supporting the health benefits of plant-based diets. Last, we discuss how plant-based diets are increasingly being implemented within health care and clinical practice to support Food is/as Medicine approaches.

Circulating Gut Microbe-Derived Metabolites Are Associated with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death worldwide. The gut microbiome has been implicated in outcomes for HCC, and gut microbe-derived products may serve as potential non-invasive indices for early HCC detection. This study evaluated differences in plasma concentrations of gut microbiota-derived metabolites.

METHODS

Forty-one patients with HCC and 96 healthy controls were enrolled from surgical clinics at the Cleveland Clinic from 2016 to 2020. Gut microbiota-derived circulating metabolites detectable in plasma were compared between patients with HCC and healthy controls. Hierarchical clustering was performed for generating heatmaps based on circulating metabolite concentrations using ClustVis, with Euclidean and Ward settings and significant differences between metabolite concentrations were tested using a binary logistic regression model.

RESULTS

In patients with HCC, 25 (61%) had histologically confirmed cirrhosis. Trimethylamine (TMA)-related metabolites were found at higher concentrations in those with HCC, including choline (p < 0.001), betaine (p < 0.001), carnitine (p = 0.007), TMA (p < 0.001) and trimethylamine N-oxide (TMAO, p < 0.001). Notably, concentrations of P-cresol glucuronide (p < 0.001), indole-lactic acid (p = 0.038), 5-hydroxyindoleacetic acid (p < 0.0001) and 4-hydroxyphenyllactic acid (p < 0.001) were also increased in those with HCC compared to healthy controls. Hierarchical clustering of the metabolite panel separated patients based on the presence of HCC (p < 0.001), but was not able to distinguish between patients with HCC based on the presence of cirrhosis (p = 0.42).

CONCLUSIONS

Gut microbiota-derived metabolites were differentially abundant in patients with HCC versus healthy controls. The observed perturbations of the TMAO pathway in HCC seem particularly promising as a target of future research and may have both diagnostic and therapeutic implications.

Trimethylamine N-oxide: a meta-organismal axis linking the gut and fibrosis

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.

Western diets and chronic diseases

'Westernization', which incorporates industrial, cultural and dietary trends, has paralleled the rise of noncommunicable diseases across the globe. Today, the Western-style diet emerges as a key stimulus for gut microbial vulnerability, chronic inflammation and chronic diseases, affecting mainly the cardiovascular system, systemic metabolism and the gut. Here we review the diet of modern times and evaluate the threat it poses for human health by summarizing recent epidemiological, translational and clinical studies. We discuss the links between diet and disease in the context of obesity and type 2 diabetes, cardiovascular diseases, gut and liver diseases and solid malignancies. We collectively interpret the evidence and its limitations and discuss future challenges and strategies to overcome these. We argue that healthcare professionals and societies must react today to the detrimental effects of the Western diet to bring about sustainable change and improved outcomes in the future.

Trimethylamine N-Oxide and Related Gut Microbe-Derived Metabolites and Incident Heart Failure Development in Community-Based Populations

BACKGROUND

Growing evidence indicates that trimethylamine N-oxide, a gut microbial metabolite of dietary choline and carnitine, promotes both cardiovascular disease and chronic kidney disease risk. It remains unclear how circulating concentrations of trimethylamine N-oxide and its related dietary and gut microbe-derived metabolites (choline, betaine, carnitine, γ-butyrobetaine, and crotonobetaine) affect incident heart failure (HF).

METHODS

We evaluated 11 768 participants from the Cardiovascular Health Study and the Multi-Ethnic Study of Atherosclerosis with serial measures of metabolites. Cox proportional hazard models were used to examine the associations between metabolites and incident HF, adjusted for cardiovascular disease risk factors.

RESULTS

In all, 2102 cases of HF occurred over a median follow-up of 15.9 years. After adjusting for traditional risk factors, higher concentrations of trimethylamine N-oxide (hazard ratio, 1.15 [95% CI, 1.09-1.20]; P<0.001), choline (hazard ratio, 1.44 [95% CI, 1.26-1.64]; P<0.001), and crotonobetaine (hazard ratio, 1.24 [95% CI, 1.16-1.32]; P<0.001) were associated with increased risk for incident HF. After further adjustment for renal function (potential confounder or mediator), these associations did not reach Bonferroni-corrected statistical significance (P=0.01, 0.049, and 0.006, respectively). Betaine and carnitine were nominally associated with a higher incidence of HF (P<0.05). In exploratory analyses, results were similar for subtypes of HF based on left ventricular ejection fraction, and associations appeared generally stronger among Black and Hispanic/Latino versus White adults, although there were no interactions for any metabolites with race.

CONCLUSIONS

In this pooled analysis of 2 well-phenotyped, diverse, community-based cohorts, circulating concentrations of gut microbe-derived metabolites such as trimethylamine N-oxide, choline, and crotonobetaine were independently associated with a higher risk of developing HF.

REGISTRATION

URL: https://www.clinicaltrials.gov/; Unique identifiers: NCT00005133 and NCT00005487.

New Modifiable Risk Factors Influencing Coronary Artery Disease Severity

Cardiovascular diseases (CVDs) remain the leading cause of death worldwide with coronary artery disease (CAD) being the first culprit in this group. In terms of CAD, not only its presence but also its severity plays a role in the patient's treatment and prognosis. CAD complexity can be assessed with the indicator named the SYNTAX score (SS). A higher SS is associated with major adverse cardiovascular event (MACE) occurrence in short- and long-term observations. Hence, the risk factors affecting CAD severity based on SS results may help lower the risk among patients with already developed CAD to reduce their impact on coronary atherosclerosis progression. The well-established risk factors of CAD are consistent with those associated with the coronary plaque burden. However, recently, it was shown that new indicators exist, which we present in this paper, that significantly contribute to CAD complexity such as inflammatory parameters, C-reactive protein (CRP), ratios based on blood smear results, and uric acid. Moreover, microbiota alteration, vitamin D deficiency, and obstructive sleep apnea (OSA) also predicted CAD severity. However, sometimes, certain indicators were revealed as significant only in terms of chronic coronary syndromes (CCSs) or specific acute coronary syndromes (ACSs). Importantly, there is a need to apply the interdisciplinary and translational approach to the novel CAD severity risk assessment to maximize the impact of secondary prevention among patients at risk of coronary atherosclerosis progression.

Xylitol is prothrombotic and associated with cardiovascular risk

BACKGROUND AND AIMS

The pathways and metabolites that contribute to residual cardiovascular disease risks are unclear. Low-calorie sweeteners are widely used sugar substitutes in processed foods with presumed health benefits. Many low-calorie sweeteners are sugar alcohols that also are produced endogenously, albeit at levels over 1000-fold lower than observed following consumption as a sugar substitute.

METHODS

Untargeted metabolomics studies were performed on overnight fasting plasma samples in a discovery cohort (n = 1157) of sequential stable subjects undergoing elective diagnostic cardiac evaluations; subsequent stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) analyses were performed on an independent, non-overlapping validation cohort (n = 2149). Complementary isolated human platelet, platelet-rich plasma, whole blood, and animal model studies examined the effect of xylitol on platelet responsiveness and thrombus formation in vivo. Finally, an intervention study was performed to assess the effects of xylitol consumption on platelet function in healthy volunteers (n = 10).

RESULTS

In initial untargeted metabolomics studies (discovery cohort), circulating levels of a polyol tentatively assigned as xylitol were associated with incident (3-year) major adverse cardiovascular event (MACE) risk. Subsequent stable isotope dilution LC-MS/MS analyses (validation cohort) specific for xylitol (and not its structural isomers) confirmed its association with incident MACE risk [third vs. first tertile adjusted hazard ratio (95% confidence interval), 1.57 (1.12-2.21), P < .01]. Complementary mechanistic studies showed xylitol-enhanced multiple indices of platelet reactivity and in vivo thrombosis formation at levels observed in fasting plasma. In interventional studies, consumption of a xylitol-sweetened drink markedly raised plasma levels and enhanced multiple functional measures of platelet responsiveness in all subjects.

CONCLUSIONS

Xylitol is associated with incident MACE risk. Moreover, xylitol both enhanced platelet reactivity and thrombosis potential in vivo. Further studies examining the cardiovascular safety of xylitol are warranted.

Role of Trimethylamine N-Oxide in Heart Failure

Heart failure (HF) is a clinical syndrome characterizing by typical physical signs and symptomatology resulting from reduced cardiac output and/or intracardiac pressure at rest or under stress due to structural and/or functional abnormalities of the heart. HF is often the final stage of all cardiovascular diseases and a significant risk factor for sudden cardiac arrest, death, and liver or kidney failure. Current pharmacological treatments can only slow the progression and recurrence of HF. With advancing research into the gut microbiome and its metabolites, one such trimethylamine N-oxide (TMAO)-has been implicated in the advancement of HF and is correlated with poor prognosis in patients with HF. However, the precise role of TMAO in HF has not yet been clarified. This review highlights and concludes the available evidence and potential mechanisms associated with HF, with the hope of contributing new insights into the diagnosis and prevention of HF.

Human Gut Microbiota in Cardiovascular Disease

The gut ecosystem, termed microbiota, is composed of bacteria, archaea, viruses, protozoa, and fungi and is estimated to outnumber human cells. Microbiota can affect the host by multiple mechanisms, including the synthesis of metabolites and toxins, modulating inflammation and interaction with other organisms. Advances in understanding commensal organisms' effect on human conditions have also elucidated the importance of this community for cardiovascular disease (CVD). This effect is driven by both direct CV effects and conditions known to increase CV risk, such as obesity, diabetes mellitus (DM), hypertension, and renal and liver diseases. Cardioactive metabolites, such as trimethylamine N -oxide (TMAO), short-chain fatty acids (SCFA), lipopolysaccharides, bile acids, and uremic toxins, can affect atherosclerosis, platelet activation, and inflammation, resulting in increased CV incidence. Interestingly, this interaction is bidirectional with microbiota affected by multiple host conditions including diet, bile acid secretion, and multiple diseases affecting the gut barrier. This interdependence makes manipulating microbiota an attractive option to reduce CV risk. Indeed, evolving data suggest that the benefits observed from low red meat and Mediterranean diet consumption can be explained, at least partially, by the changes that these diets may have on the gut microbiota. In this article, we depict the current epidemiological and mechanistic understanding of the role of microbiota and CVD. Finally, we discuss the potential therapeutic approaches aimed at manipulating gut microbiota to improve CV outcomes. © 2024 American Physiological Society. Compr Physiol 14:5449-5490, 2024.

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

BACKGROUND

Elevations in the gut metabolite trimethylamine-N-oxide (TMAO) have been linked to cardiovascular and metabolic diseases. Whether elevated TMAO levels reflect early mechanistic involvement or a sequela of evolving disease awaits elucidation. The purpose of this study was to further explore these potential associations.

METHODS

We investigated relationships between circulating levels of TMAO and its pre-cursor substrates, dietary factors, gut microbiome profiles and disease risk in individuals with a Healthy BMI (18.5 < BMI < 25, n = 41) or key precursor states for cardiometabolic disease: Overweight (25 < BMI < 30 kg/m2, n = 33), Obese (BMI > 30, n = 27) and Metabolic Syndrome (MetS; ≥ 3 ATPIII report criteria, n = 39).

RESULTS

Unexpectedly, plasma [TMAO] did not vary substantially between groups (means of 3-4 µM; p > 0.05), although carnitine was elevated in participants with MetS. Gut microbial diversity and Firmicutes were also significantly reduced in the MetS group (p < 0.05). Exploratory analysis across diverse parameters reveals significant correlations between circulating [TMAO] and seafood intake (p = 0.007), gut microbial diversity (p = 0.017-0.048), and plasma [trimethylamine] (TMA; p = 0.001). No associations were evident with anthropometric parameters or cardiometabolic disease risk. Most variance in [TMAO] within and between groups remained unexplained.

CONCLUSIONS

Data indicate that circulating [TMAO] may be significantly linked to seafood intake, levels of TMA substrate and gut microbial diversity across healthy and early disease phenotypes. However, mean concentrations remain < 5 µM, with little evidence of links between TMAO and cardiometabolic disease risk. These observations suggest circulating TMAO may not participate mechanistically in cardiometabolic disease development, with later elevations likely a detrimental sequela of extant disease.

Trimethylamine oxide supplementation differentially regulates fat deposition in liver, longissimus dorsi muscle and adipose tissue of growing-finishing pigs

Trimethylamine oxide (TMAO) is a microbiota-derived metabolite, and numerous studies have shown that it could regulate fat metabolism in humans and mice. However, few studies have focused on the effects of TMAO on fat deposition in growing-finishing pigs. This study aimed to investigate the effect of TMAO on fat deposition and intestinal microbiota in growing-finishing pigs. Sixteen growing pigs were randomly divided into 2 groups and fed with a basal diet with 0 or 1 g/kg TMAO for 149 d. The intestinal microbial profiles, fat deposition indexes, and fatty acid profiles were measured. These results showed that TMAO supplementation had a tendency to decrease lean body mass (P < 0.1) and significantly increased backfat thickness (P < 0.05), but it did not affect growth performance. TMAO significantly increased total protein (TP) concentration, and reduced alkaline phosphatase (ALP) concentration in serum (P < 0.05). TMAO increased the α diversity of the ileal microbiota community (P < 0.05), and it did not affect the colonic microbial community. TMAO supplementation significantly increased acetate content in the ileum, and Proteobacteria and Escherichia-Shigella were significantly enriched in the TMAO group (P < 0.05). In addition, TMAO decreased fat content, as well as the ratio of linoleic acid, n-6 polyunsaturated fatty acids (PUFA), and PUFA in the liver (P < 0.05). On the contrary, TMAO increased intramuscular fat content of the longissimus dorsi muscle, whereas the C18:2n6c ratio was increased, and the n-6 PUFA:PUFA ratio was decreased (P < 0.05). In vitro, 1 mM TMAO treatment significantly upregulated the expression of FASN and SREBP1 in C2C12 cells (P < 0.05). Nevertheless, TMAO also increased adipocyte area and decreased the CPT-1B expression in subcutaneous fat (P < 0.05). Taken together, TMAO supplementation regulated ileal microbial composition and acetate production, and regulated fat distribution and fatty acid composition in growing-finishing pigs. These results provide new insights for understanding the role of TMAO in humans and animals.

Effect of resistance training and chicken meat on muscle strength and mass and the gut microbiome of older women: A randomized controlled trial

This study investigated the effects of white meat, such as chicken, intake combined with resistance training on muscle mass and strength in the elderly women, and whether the underlying mechanism involves changes in the gut microbiota. Ninety-three volunteers (age 59-79 years) were randomly allocated to sedentary control with placebo (Sed + PL) or chicken meat (Sed + HP) and resistance training with placebo (RT + PL) or chicken meat (RT + HP). Resistance training sessions were performed 3 d/week for 12 weeks using leg extensions and curls. Boiled chicken meat (110 g, containing 22.5 g protein) was ingested 3 d/week for 12 weeks. Maximal muscle strength and whole-body lean mass increased significantly in the RT + PL group compared to the Sed + HP group, and the RT + HP group showed a significantly greater increase than the Sed + HP and RT + PL groups. Additionally, the gut microbiota composition did not change before or after the interventions in any of the four groups. Moreover, the individual comparison of gut bacteria using false discovery rate-based statistical analysis showed no alterations before or after the interventions in the four groups. Resistance training combined with chicken meat intake may effective have increased muscle mass and strength without drastically modifying the gut microbiota composition in elderly women.

The Gut Microbial Metabolite Trimethylamine N -oxide, Incident CKD, and Kidney Function Decline

Key Points

In community-based US adults, higher plasma trimethylamine N -oxide levels associated with higher risk of incident CKD and greater rate of kidney function decline. Findings from our study support future clinical trials to examine whether lowering plasma trimethylamine N -oxide levels may prevent CKD development and progression.

Background

Trimethylamine N -oxide (TMAO) is a gut microbiota–derived metabolite of dietary phosphatidylcholine and carnitine. Experimentally, TMAO causes kidney injury and tubulointerstitial fibrosis. Little is known about prospective associations between TMAO and kidney outcomes, especially incident CKD. We hypothesized that higher plasma TMAO levels would be associated with higher risk of incident CKD and greater rate of kidney function decline.

Methods

We included 10,564 participants from two community-based, prospective cohorts with eGFR ≥60 ml/min per 1.73 m2 to assess incident CKD. TMAO was measured using targeted mass spectrometry at baseline and one follow-up visit. Creatinine and cystatin C were measured up to four times during follow-up and used to compute eGFR. Incident CKD was defined as an eGFR decline ≥30% from baseline and a resulting eGFR <60 ml/min per 1.73 m2. Time-varying Cox models assessed the association of serial TMAO measures with incident CKD, adjusting for sociodemographic, lifestyle, diet, and cardiovascular disease risk factors. Linear mixed models assessed the association with annualized eGFR change in 10,009 participants with at least one follow-up eGFR measure without exclusions for baseline eGFR levels.

Results

During a median follow-up of 9.4 years (interquartile range, 9.1–11.6 years), 979 incident CKD events occurred. Higher TMAO levels were associated with higher risk of incident CKD (second to fifth versus first quintile hazard ratio [95% confidence interval]=1.65 [1.22 to 2.23], 1.68 [1.26 to 2.25], 2.28 [1.72 to 3.02], and 2.24 [1.68 to 2.98], respectively) and greater annualized eGFR decline (second to fifth versus first quintile annualized eGFR change=−0.21 [−0.32 to −0.09], −0.17 [−0.29 to −0.05], −0.35 [−0.47 to −0.22], and −0.43 [−0.56 to −0.30] ml/min per 1.73 m2, respectively) with monotonic dose–response relationships. These associations were consistent across different racial/ethnic groups examined. The association with eGFR decline was similar to or larger than that seen for established CKD risk factors, including diabetes, per 10 mm Hg of higher systolic BP, per 10 years of older age, and Black race.

Conclusions

In community-based US adults, higher serial measures of plasma TMAO were associated with higher risk of incident CKD and greater annualized kidney function decline.

An inverse association of dietary choline with atherosclerotic cardiovascular disease among US adults: a cross-sectional NHANES analysis

BACKGROUND

The role of diet choline in atherosclerotic cardiovascular disease (ASCVD) is uncertain. Findings from animal experiments are contradictory while there is a lack of clinical investigations. This study aimed to investigate the association between choline intake and ASCVD based on individuals from the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

This cross-sectional study was conducted in 5525 individuals from the NHANES between 2011 and 2018. Participants were categorized into the ASCVD (n = 5015) and non-ASCVD (n = 510) groups. Univariable and multivariable-adjusted regression analyses were employed to investigate the relationship between diet choline and pertinent covariates. Logistic regression analysis and restricted cubic spline analysis were used to evaluate the association between choline intake and ASCVD.

RESULTS

ASCVD participants had higher choline intake compared to those without ASCVD. In the higher tertiles of choline intake, there was a greater proportion of males, married individuals, highly educated individuals, and those with increased physical activity, but a lower proportion of smokers and drinkers. In the higher tertiles of choline intake, a lower proportion of individuals had a history of congestive heart failure and stroke. After adjusting for age, gender, race, ethnicity, and physical activity, an inverse association between choline intake and heart disease, stroke, and ASCVD was found. A restricted cubic spline analysis showed a mirrored J-shaped relationship between choline and ASCVD, stroke and congestive heart failure in males. There was no association between dietary choline and metabolic syndrome.

CONCLUSION

An inverse association was observed between choline intake and ASVCD among U.S. adults. Further large longitudinal studies are needed to test the causal relationship of choline and ASVCD.

Circulating Trimethylamine-N-Oxide Is Elevated in Liver Transplant Recipients

Liver transplant recipients (LTRs) have lower long-term survival rates compared with the general population. This underscores the necessity for developing biomarkers to assess post-transplantation mortality. Here we compared plasma trimethylamine-N-oxide (TMAO) levels with those in the general population, investigated its determinants, and interrogated its association with all-cause mortality in stable LTRs. Plasma TMAO was measured in 367 stable LTRs from the TransplantLines cohort (NCT03272841) and in 4837 participants from the population-based PREVEND cohort. TMAO levels were 35% higher in LTRs compared with PREVEND participants (4.3 vs. 3.2 µmol/L, p < 0.001). Specifically, TMAO was elevated in LTRs with metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, and polycystic liver disease as underlying etiology (p < 0.001 for each). Among LTRs, TMAO levels were independently associated with eGFR (std. β = -0.43, p < 0.001) and iron supplementation (std. β = 0.13, p = 0.008), and were associated with mortality (29 deaths during 8.6 years follow-up; log-rank test p = 0.017; hazard ratio of highest vs. lowest tertile 4.14, p = 0.007). In conclusion, plasma TMAO is likely elevated in stable LTRs, with impaired eGFR and iron supplementation as potential contributory factors. Our preliminary findings raise the possibility that plasma TMAO could contribute to increased mortality risk in such patients, but this need to be validated through a series of rigorous and methodical studies.

Dynamic Changes in Gut Microbiota-Derived Metabolite Trimethylamine-N-Oxide and Risk of Type 2 Diabetes Mellitus: Potential for Dietary Changes in Diabetes Prevention

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.