Trimethylamine N-Oxide and Cardiovascular Events in Hemodialysis Patients

Reduction in Serum Concentrations of Uremic Toxins Driven by Bifidobacterium Longum Subsp. Longum BL21 is Associated with Gut Microbiota Changes in a Rat Model of Chronic Kidney Disease

Gut microbiota dysbiosis and consequent impairment of gut barrier function, culminating in elevated levels of uremic toxins, are prevalent in chronic kidney disease (CKD) patients. These toxins, notably indoxyl sulphate (IS), indole-3-acetic acid (IAA), and trimethylamine oxide (TMAO), are implicated in a spectrum of CKD-related complications, including cardiovascular disease, bone and mineral disorders, and inflammation. The specific impacts of various probiotics on these CKD manifestations remain unexplored. This study delved into the potential of dietary probiotic interventions, particularly Bifidobacterium longum subsp. longum BL21, to modulate gut microbiota and mitigate metabolic disorders in a CKD rat model. Over a six-week period, we administered a dietary regimen of BL21 and conducted comprehensive analyses, including serum uremic toxin quantification and 16S rRNA gene sequencing, to systematically profile gut microbial alterations at the phylogenetic level. Our findings reveal that BL21 intervention significantly ameliorated CKD-induced disruptions in gut microbial populations, enhancing both microbial richness and the relative abundance of key taxa. Importantly, BL21 appeared to exert its beneficial effects by modulating the abundance of crucial species such as Barnesiella and Helicobacter. Functionally, the intervention markedly normalized serum levels of IS, IAA, and TMAO, while potentially attenuating p-cresol sulphate (PCS) and p-cresol glucuronide (PCG) concentrations. Consequently, BL21 demonstrated efficacy in regulating gut microbiota and curtailing the accumulation of uremic toxins. Our results advocate for the utilization of BL21 as a dietary intervention to diminish serum uremic toxins and re-establish gut microbiota equilibrium at the phylogenetic level, underscoring the promise of probiotic strategies in the management of CKD.

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

Background:

Gut microbial metabolites such as trimethylamine N-oxide (TMAO) and its precursors, namely betaine, L-carnitine, and choline, have been implicated as risk factors for cardiovascular events and mortality development. Therefore, we aim to perform a systematic review and meta-analysis to assess the validity of these associations.

Methods:

MEDLINE and Scopus were queried from their inception to August 2023 to identify studies that quantified estimates of the associations of TMAO with the development of major adverse cardiovascular events (MACE) or death. A random-effects meta-analysis was conducted to pool unadjusted or multivariable-adjusted hazard ratios (HR) and their 95% confidence intervals. The primary endpoint was the risk of MACE and all-cause death.

Results:

30 prospective observational studies (n = 48 968) were included in the analysis. Elevated TMAO levels were associated with a significantly greater risk of MACE and all-cause death compared to low TMAO levels (HR: 1.41, 95% CI 1.2–1.54, P  < .00001, I 2 = 43%) and (HR: 1.55, 95% CI 1.37–1.75, P  < .00001, I 2 = 46%), respectively. Furthermore, high levels of either L-carnitine or choline were found to significantly increase the risk of MACE. However, no significant difference was seen in MACE in either high or low levels of betaine.

Conclusion:

Elevated concentrations of TMAO were associated with increased risks of MACE and all-cause mortality. High levels of L-carnitine/choline were also significantly associated with an increased risk of MACE. However, no significant difference was found between high or low levels of betaine for the outcome of MACE.

Plasma Concentrations of Trimethylamine-N-Oxide, Choline, and Betaine in Patients With Moderate to Advanced Chronic Kidney Disease and Their Relation to Cardiovascular and Renal Outcomes

OBJECTIVES

Trimethylamine N-oxide (TMAO) is a gut bacteria-mediated liver metabolite of dietary betaine, choline, and carnitine, which is excreted by glomerular filtration. We studied whether TMAO is excreted by cardiovascular disease (CVD) in patients with chronic kidney disease (CKD).

METHODS

Among 478 patients with CKD stage G2 (n = 104), G3a (n = 163), G3b (n = 123), and G4 (n = 88), we studied the association between fasting plasma concentrations of TMAO, choline, or betaine at baseline and kidney function, prevalent CVD, and future renal outcomes during a mean follow-up of 5.1 years.

RESULTS

Decreased glomerular filtration rate was associated with higher plasma concentrations of TMAO, choline, and betaine. Baseline concentrations of TMAO were higher in participants with preexisting CVD compared to those without CVD (8.4 [10.1] vs. 7.8 [8.0] μmol/L; P = .047), but the difference was not significant after adjusting for confounders. During the follow-up, 147 participants experienced CVD or died, and 144 reached the predefined renal endpoint. In the adjusted regression analyses, TMAO or choline concentrations in the upper three quartiles (vs. the lowest quartile) were not associated with any of the study's clinical endpoints. In contrast, the adjusted hazard ratio of plasma betaine in the highest quartile versus the lowest quartile was 2.14 (1.32, 3.47) for the CVD endpoint and 1.64 (1.00, 2.67) for the renal endpoint.

CONCLUSIONS

Elevated plasma TMAO concentrations were explained by impaired kidney function. Elevated plasma concentrations of betaine, but not those of TMAO or choline, constituted a risk factor for adverse outcomes. TMAO might not be an appropriate target to reduce CVD or renal outcomes in patients with preexisting CKD.

Food to Prevent Vascular Calcification in Chronic Kidney Disease

Vascular calcification (VC) is a consequence of chronic kidney disease (CKD) which is of paramount importance regarding the survival of CKD patients. VC is far from being controlled with actual medication; as a result, in recent years, diet modulation has become more compelling. The concept of medical nutritional therapy points out the idea that food may prevent or treat diseases. The aim of this review was to evaluate the influence of food habits and nutritional intervention in the occurrence and progression of VC in CKD. Evidence reports the harmfulness of ultra-processed food, food additives, and animal-based proteins due to the increased intake of high absorbable phosphorus, the scarcity of fibers, and the increased production of uremic toxins. Available data are more supportive of a plant-dominant diet, especially for the impact on gut microbiota composition, which varies significantly depending on VC presence. Magnesium has been shown to prevent VC but only in experimental and small clinical studies. Vitamin K has drawn considerable attention due to its activation of VC inhibitors. There are positive studies; unfortunately, recent trials failed to prove its efficacy in preventing VC. Future research is needed and should aim to transform food into a medical intervention to eliminate VC danger in CKD.

Choline metabolites and incident cardiovascular disease in a prospective cohort of adults: Coronary Artery Risk Development in Young Adults (CARDIA) Study

BACKGROUND

The potential role for choline metabolite trimethylamine N-oxide (TMAO) in cardiovascular disease (CVD) has garnered much attention, but there have been limited data from diverse population-based cohorts. Furthermore, few studies have included circulating choline and betaine, which can serve as precursors to TMAO and may independently influence CVD.

OBJECTIVE

We quantified prospective associations between 3 choline metabolites and 19-y incident CVD in a population-based cohort and tested effect modification of metabolite-CVD associations by kidney function.

METHODS

Data were from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a prospective cohort with recruitment from 4 US urban centers (year 0: 1985-1986, n = 5115, ages 18-30). The analytic sample included 3444 White and Black males and females, aged 33 to 45, who attended the year 15 follow-up exam and did not have prevalent CVD. TMAO, choline, and betaine were quantitated from stored plasma (-70°C) using liquid-chromatography mass-spectrometry. Nineteen-year incident CVD events (n = 221), including coronary heart disease and stroke, were identified through adjudicated hospitalization records and linkage with the National Death Register.

RESULTS

Plasma choline was positively associated with CVD in Cox proportional hazards regression analysis adjusted for demographics, health behaviors, CVD risk factors, and metabolites (hazard ratio: 1.24; 95% CI: 1.09, 1.40 per standard deviation-unit choline). TMAO and betaine were not associated with CVD in an identically adjusted analysis. There was statistical evidence for effect modification by kidney function with CVD positively associated with TMAO and negatively associated with betaine at lower values of estimated glomerular filtration rate (interaction P values: 0.0046 and 0.020, respectively).

CONCLUSIONS

Our findings are consistent with a positive association between plasma choline and incident CVD. Among participants with lower kidney function, TMAO was positively, and betaine negatively, associated with CVD. These results further our understanding of the potential role for choline metabolism on CVD risk.

Relationship between gut microbiota and vascular calcification in hemodialysis patients

INTRODUCTION

Vascular calcification (VC) is an independent risk factor for cardiovascular mortality in end-stage renal disease (ESRD) patients. The pathogenesis of VC is complicated and unclear. Uremic toxins produced by gut microbiota can promote VC. This study aims to identify the differences in gut microbiota between the different VC groups and the main bacteria associated with VC in hemodialysis (HD) patients in an attempt to open up new preventive and therapeutic approaches and define the probable mechanism for VC in HD patients in the future.

METHODS

A total of 73 maintenance HD patients were enrolled in this cross-sectional study. According to the abdominal aortic calcification (AAC) scores, the participants were divided into the high AAC score group and the low AAC score group. High-throughput sequencing of the gut microbiota was performed and the results were evaluated by alpha diversity, beta diversity, species correlation, and model predictive analyses.

RESULTS

The prevalence of VC was 54.79% (40/73) in the study. The majority of phyla in the two groups were the same, including Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota. The microbial diversity in the high AAC score group had a decreasing trend (p = 0.050), and the species abundance was significantly lower (p = 0.044) than that in the low AAC score group. The HD patients with high AAC scores showed an increased abundance of Proteobacteria and decreased abundances of Bacteroidota and Synergistota at the phylum level; increased abundances of Escherichia-Shigella, Ruminococcus_gnavus_group, and Lactobacillus; and decreased abundances of Ruminococcus and Lachnospiraceae_NK4A136_group at the genus level (p<0.05). Escherichia-Shigella and Ruminococcus_gnavus_group were positively correlated with VC, and Ruminococcus, Adlercreutzia, Alistipes, and norank_f__Ruminococcaceae were negatively correlated with VC. Escherichia-Shigella had the greatest influence on VC in HD patients, followed by Ruminococcus and Butyricimonas.

CONCLUSIONS

Our results provide clinical evidence that there was a difference in gut microbiota between the different VC groups in HD patients. Escherichia-Shigella, a lipopolysaccharide (LPS)-producing bacterium, was positively correlated with VC and had the greatest influence on VC. Ruminococcus, a short-chain fatty acid (SCFA)-producing bacterium, was negatively correlated with VC and had the second strongest influence on VC in HD patients. The underlying mechanism is worth studying. These findings hint at a new therapeutic target.

Serum Trimethylamine N-Oxide Level Is Positively Associated with Aortic Stiffness Measured by Carotid-Femoral Pulse Wave Velocity in Patients Undergoing Maintenance Hemodialysis

Trimethylamine N-oxide (TMAO) is a biomarker that is effective in predicting major adverse cardiovascular (CV) events. Age-related vascular problems are significantly affected by aortic stiffness (AS), which is independently linked to CV morbidity and mortality. This study aimed to determine the association between serum TMAO levels and carotid-femoral pulse wave velocity (cfPWV) in patients receiving hemodialysis (HD) therapy. In total, 115 patients with HD were enrolled in this study. The AS group included patients whose cfPWV was >10 m/s. Using high-performance liquid chromatography and mass spectrometry, the levels of serum TMAO were measured. The AS group included 42 (36.5%) patients, and compared with the non-AS group, the rates of diabetes, hypertension, older age, systolic blood pressure, serum glucose, and TMAO levels were high. In the multivariate logistic regression analysis, serum TMAO and age were independently linked with AS after correcting for the factors significantly associated with AS. Following multivariate stepwise linear regression analysis, serum TMAO in these individuals was found to be strongly correlated with cfPWV values (p < 0.001). In patients on chronic HD, serum TMAO level is an independent measure of AS and strongly correlated with cfPWV.

Effect of replacement therapy (CRRT) and hemodialysis (IHD) on severe acute renal failure

Hyperkalemia, metabolic acidosis, and acute uremia are the main symptoms in patients with severe acute renal failure (SARF). Its clinical symptoms are obvious, and it is extremely harmful. It needs to take active and effective measures for treatment. CRRT refers to any extracorporeal blood purification treatment technique designed to replace impaired renal function for 24 h or nearly 24 h. Hemodialysis treatment is a treatment process in which the patient's blood is discharged from the body, passes through the dialysis membrane and dialysis machine, removes excess toxins and water in the body, corrects electrolyte and acid-base disorders, and then returns the blood to the body. In order to explore the efficacy of replacement therapy and hemodialysis in the treatment of severe acute renal failure, the data samples were randomly divided into observation group and control group, who were given conventional treatment, hemodialysis and replacement therapy, respectively. Clinical data show that after replacement therapy and hemodialysis in patients with severe acute renal failure in the observation group, the levels of parathyroid hormone, renin, and quality of life were all improved, with an improvement rate of 9.47%, which has certain promotional value.

Major cardiovascular events and associated factors among routine hemodialysis patients with end-stage renal disease at tertiary care hospital in Somalia

Introduction

Cardiovascular complications are the most significant cause of death in patients undergoing routine hemodialysi (HD) with end-stage renal disease (ESRD). The main objective of this study is to determine the significant cardiac events and risk factors in patients undergoing routine hemodialysis in Somalia.

Methods

We carried out a cross-sectional retrospective study in a single dialysis center in Somalia. Two hundred out of 224 were included. All of them had ESRD and were on hemodialysis during the study period between May and October 2021. The records of all patients were reviewed, and the following parameters were analyzed socio-demographic factors, risk factors for cardiovascular disease, and the presence of cardiovascular diseases.

Results

The mean age was 54 ± 17.5 years (range 18-88 years), and 106 (53%) patients were males. The prevalence of a cardiovascular disease among hemodialysis patients was 29.5%. Moreover, the distribution of cardiovascular diseases was different; heart failure was the most common, about 27.1%, followed by coronary artery disease (17%), pericarditis and pericardial-effusion (13.6%), dysrhythmia (10.2%), cerebrovascular-accident (8.5%), and peripheral vascular disease (3.4%). About 176 (88%) participants had at least one modifiable cardiovascular risk factor. The most common modifiable cardiovascular risk factor was hypertension (n = 45, 25.1%), followed by anemia (n = 28, 15.6%) and diabetes (n = 26, 14.5%). Younger (18-30) participants were six times less likely to have cardiovascular events among hemodialysis than older age 0.4 (0.11-1.12).

Conclusion

Low prevalence rate of cardiovascular complications was confirmed in ESRD patients receiving hemodialysis in the main HD center in Somalia. Diabetes, anemia, and hypertension were the highest significant risk factors for CVD in HD patients with ESRD in Somalia.

Icariin, the main prenylflavonoid of Epimedii Folium, ameliorated chronic kidney disease by modulating energy metabolism via AMPK activation

ETHNOPHARMACOLOGICAL RELEVANCE

Epimedii Folium is a famous traditional Chinese medicine (TCM) widely used in classic formulas, Chinese patent drugs and health care products for treating kidney diseases. Therefore, we speculated that icariin, its main component, might also have a good therapeutic effect on chronic kidney disease (CKD).

AIM OF STUDY

To investigate the efficacy and potential mechanism of icariin on CKD.

MATERIALS AND METHODS

A CKD model was established by intragastric administration of adenine (200 mg/kg/d) to adult male SD rats for 28 consecutive days. TGF-β1-induced fibrotic HK-2 cells were applied to establish the renal fibrosis model in vitro. Biochemical determination, pathological staining, flow cytometry and ELISA were performed to preliminarily evaluate the renoprotection of icariin. The intervention effect of icariin on renal fibrosis progression was assessed by cell stiffness determination and multiple immunological methods. The potential mechanism of icariin on CKD was revealed by means of ¹H NMR metabolomics, qRT-PCR and Western blotting analysis.

RESULTS

Icariin at the dosage of 100 mg/kg/d and 200 mg/kg/d markedly ameliorated rat renal function in a dose-dependent manner. Based on renal pathological features, the mechanism of icariin intervention in CKD was initially revealed by metabolomics, which was closely related to energy metabolism pathways. Furthermore, the detection results of AMPK and related factors in its mediated signaling pathways indicated that icariin exerted a therapeutic effect on CKD by attenuating inflammation and oxidative stress responses and retarding renal fibrosis progression through regulating AMPK/SIRT1/NF-κB and AMPK/ACC signaling pathways.

CONCLUSION

It was the first time to demonstrate that icariin could treat adenine-induced CKD by modulating energy metabolism via AMPK activation in a dose-dependent manner.

Gut Microbiota-Targeted Interventions in the Management of Chronic Kidney Disease

Recent advances in microbiome research have informed the potential role of the gut microbiota in the regulation of metabolic, cardiovascular, and renal systems, and, when altered, in the pathogenesis of various cardiometabolic disorders, including chronic kidney disease (CKD). The improved understanding of gut dysbiosis in cardiometabolic pathologies in turn has led to a vigorous quest for developing therapeutic strategies. These therapeutic strategies aim to investigate whether interventions targeting gut dysbiosis can shift the microbiota toward eubiosis and if these shifts, in turn, translate into improvements in (or prevention of) CKD and its related complications, such as premature cardiovascular disease. Existing evidence suggests that multiple interventions (eg, plant-based diets; prebiotic, probiotic, and synbiotic supplementation; constipation treatment; fecal microbiota transplantation; and intestinal dialysis) might result in favorable modulation of the gut microbiota in patients with CKD, and thereby potentially contribute to improving clinical outcomes in these patients. In this review, we summarize the current understanding of the characteristics and roles of the gut microbiota in CKD and discuss the potential of emerging gut microbiota-targeted interventions in the management of CKD.

The role of gut-dependent molecule trimethylamine N-oxide as a novel target for the treatment of chronic kidney disease

Trimethylamine N-oxide (TMAO) is an intestinal uremic toxin molecule mainly excreted by the kidney. Therefore, the plasma TMAO concentration is significantly increased in chronic kidney disease (CKD) patients, and plasma TMAO can be cleared by dialysis. Furthermore, TMAO damage the kidney mainly through three mechanisms: oxidative stress, inflammation and endoplasmic reticulum stress. Clinical experiments have indicated that higher TMAO levels are strongly related to the elevated incidence and mortality of cardiovascular (CV) events in CKD patients. Moreover, experimental data have shown that high levels of TMAO directly aggravate atherosclerosis, thrombosis and enhance myocardial contractility, resulting in myocardial ischemia and stroke. Specially, there are currently four potential ways to reduce blood TMAO concentration or block the effect of TMAO, including reducing the intake of trimethylamine (TMA) precursors in the diet, regulating the intestinal flora to reduce TMA production, interrupting the role of flavin-dependent monooxygenase isoforms (FMOs) to reduce the generation of TMAO, and blocking the TMAO receptor protein kinase R-like endoplasmic reticulum kinase (PERK). We hope that more clinical studies and clinicians will focus on clinical treatment to reduce the concentration of TMAO and alleviate renal damage.

Contribution of Trimethylamine N-Oxide (TMAO) to Chronic Inflammatory and Degenerative Diseases

Trimethylamine N-oxide (TMAO) is a metabolite produced by the gut microbiota and has been mainly associated with an increased incidence of cardiovascular diseases (CVDs) in humans. There are factors that affect one's TMAO level, such as diet, drugs, age, and hormones, among others. Gut dysbiosis in the host has been studied recently as a new approach to understanding chronic inflammatory and degenerative diseases, including cardiovascular diseases, metabolic diseases, and Alzheimer's disease. These disease types as well as COVID-19 are known to modulate host immunity. Diabetic and obese patients have been observed to have an increase in their level of TMAO, which has a direct correlation with CVDs. This metabolite is attributed to enhancing the inflammatory pathways through cholesterol and bile acid dysregulation, promoting foam cell formation. Additionally, TMAO activates the transcription factor NF-κB, which, in turn, triggers cytokine production. The result can be an exaggerated inflammatory response capable of inducing endoplasmic reticulum stress, which is responsible for various diseases. Due to the deleterious effects that this metabolite causes in its host, it is important to search for new therapeutic agents that allow a reduction in the TMAO levels of patients and that, thus, allow patients to be able to avoid a severe cardiovascular event. The present review discussed the synthesis of TMAO and its contribution to the pathogenesis of various inflammatory diseases.

Probiotic Bifidobacteria Mitigate the Deleterious Effects of para-Cresol in a Drosophila melanogaster Toxicity Model

Renal impairment associated with chronic kidney disease (CKD) causes the buildup of uremic toxins that are deleterious to patient health. Current therapies that manage toxin accumulation in CKD offer an incomplete therapeutic effect against toxins such as para-cresol (p-cresol) and p-cresyl sulfate. Probiotic therapies can exploit the wealth of microbial diversity to reduce toxin accumulation. Using in vitro culture techniques, strains of lactobacilli and bifidobacteria from a 24-strain synbiotic were investigated for their ability to remove p-cresol. Four strains of bifidobacteria internalized p-cresol from the extracellular environment. The oral supplementation of these toxin-clearing probiotics was more protective than control strains in a Drosophila melanogaster toxicity model. Bifidobacterial supplementation was also associated with higher abundance of lactobacilli in the gut microbiota of p-cresol-exposed flies. The present findings suggest that these strains might reduce p-cresol in the gut in addition to increasing the prevalence of other beneficial bacteria, such as lactobacilli, and should be tested clinically to normalize the dysbiotic gut microbiota observed in CKD patients. IMPORTANCE Chronic kidney disease (CKD) affects approximately 10% of the global population and has limited treatment options. The accumulation of gut microbiota-derived uremic toxins, such as para-cresol (p-cresol) and p-cresyl sulfate, is associated with the onset of comorbidities (i.e., atherosclerosis and cognitive disorders) in CKD. Unfortunately, dialysis, the gold standard therapy is unable to remove these toxins from the bloodstream due to their highly protein-bound nature. Some strains of Bifidobacterium have metabolic properties that may be useful in managing uremic toxicity. Using a Drosophila model, the present work highlights why dosing with certain probiotic strains may be clinically useful in CKD management.

Dietary choline, via gut microbe- generated trimethylamine-N- oxide, aggravates chronic kidney disease-induced cardiac dysfunction by inhibiting hypoxia-induced factor 1α

Chronic kidney disease (CKD) is a global public health problem that shortens lifespan primarily by increasing the risk of cardiovascular diseases. Trimethylamine-N-oxide (TMAO), a gut microbiota-derived toxin produced by metabolizing high-choline or carnitine foods, is associated with cardiovascular events in patients with CKD. Although the deleterious effect of TMAO on CKD-induced cardiac injury has been confirmed by various researches, the mechanisms remain unclear. Here, we tested the hypothesis that TMAO aggravates CKD-induced cardiac injury and explores the potential mechanism. CD1 mice underwent 5/6 nephrectomy to induce CKD, and then fed with a diet supplemented with choline (1.2% total) for 8 weeks. Serum TMAO levels were elevated in CKD mice compared with SHAM group, and higher TMAO levels were found in choline-supplemented CKD mice compared with CKD group. Dietary choline aggravated CKD-induced cardiac dysfunction, and reducing TMAO levels via medicinal charcoal tablets improved cardiac dysfunction. RNA-seq analysis revealed that dietary choline affected cardiac angiogenesis in CKD mice. Reduced cardiac capillary density and expressions of angiogenesis-related genes were observed in choline-treated CKD mice. Furthermore, dietary choline inhibited cardiac Hif-1α protein level in CKD mice, and Hif-1α stabilizer FG-4592 could improve cardiac angiogenesis and dysfunction in CKD mice on a high-choline diet. In conclusion, these data indicate that dietary choline, via gut microbe-generated TMAO, inhibits cardiac angiogenesis by reducing Hif-1α protein level, ultimately aggravates cardiac dysfunction in CKD mice.

Physiological Mechanisms of Hypertension and Cardiovascular Disease in End-Stage Kidney Disease

PURPOSE OF REVIEW

In this article, we summarize recent advances in understanding hypertension and cardiovascular disease in patients with end-stage kidney disease.

RECENT FINDINGS

Factors such as anemia, valvular and vascular calcification, vasoconstrictors, uremic toxins, hypoglycemia, carbamylated proteins, oxidative stress, and inflammation have all been associated with the progression of cardiovascular disease in end-stage kidney disease but the causality of these mechanisms has not been proven. The high risk of cardiovascular mortality has not improved as in the general population despite many advancements in cardiovascular care over the last two decades. Mechanisms that increase hypertension risk in these patients are centered on the control of extracellular fluid volume; however, over-correction of volume with dialysis can increase risks of intradialytic hypotension and death in these patients. This review presents both recent and classic work that increases our understanding of hypertension and cardiovascular disease in end-stage kidney disease.

The association between TMAO, CMPF, and clinical outcomes in advanced chronic kidney disease: results from the European QUALity (EQUAL) Study

BACKGROUND

Trimethylamine N-oxide (TMAO), a metabolite from red meat and fish consumption, plays a role in promoting cardiovascular events. However, data regarding TMAO and its impact on clinical outcomes are inconclusive, possibly due to its undetermined dietary source.

OBJECTIVES

We hypothesized that circulating TMAO derived from fish intake might cause less harm compared with red meat sources by examining the concomitant level of 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), a known biomarker of fish intake, and investigated the association between TMAO, CMPF, and outcomes.

METHODS

Patients were recruited from the European QUALity (EQUAL) Study on treatment in advanced chronic kidney disease among individuals aged ≥65 y whose estimated glomerular filtration rate (eGFR) had dropped for the first time to ≤20 mL/min per 1.73 m2 during the last 6 mo. The association between TMAO, CMPF, and outcomes including all-cause mortality and kidney replacement therapy (KRT) was assessed among 737 patients. Patients were further stratified by median cutoffs of TMAO and CMPF, suggesting high/low red meat and fish intake.

RESULTS

During a median of 39 mo of follow-up, 232 patients died. Higher TMAO was independently associated with an increased risk of all-cause mortality (multivariable HR: 1.46; 95% CI: 1.17, 1.83). Higher CMPF was associated with a reduced risk of both all-cause mortality (HR: 0.79; 95% CI: 0.71, 0.89) and KRT (HR: 0.80; 95% CI: 0.71, 0.90), independently of TMAO and other clinically relevant confounders. In comparison to patients with low TMAO and CMPF, patients with low TMAO and high CMPF had reduced risk of all-cause mortality (adjusted HR: 0.49; 95% CI: 0.31, 0.73), whereas those with high TMAO and high CMPF showed no association across adjusted models.

CONCLUSIONS

High CMPF conferred an independent role in health benefits and might even counteract the unfavorable association between TMAO and outcomes. Whether higher circulating CMPF concentrations are due to fish consumption, and/or if CMPF is a protective factor, remains to be verified.

Association between nutritional, inflammatory and oxidative status (NIOS) and risk of adverse outcomes in patients on haemodialysis (HD): the NIOS-HD prospective cohort study protocol

INTRODUCTION

The mortality of patients on chronic haemodialysis is 10-30 times greater than that of the general population and over 60% of these individuals die within the first 5 years of beginning haemodialysis. Although causes for excessive mortality in haemodialysis patients are not clearly defined, it seems that nutrition, inflammation and oxidative stress play key roles in this regard. Until now, no cohort study has focused on the association between nutritional, inflammatory or oxidative status and risk of complications and adverse outcomes in Iranian haemodialysis patients. Therefore, we sought to fill this gap and designed the Nutritional, Inflammatory, and Oxidative Status in Hemodialysis (NIOS-HD) prospective cohort study to determine the association of dietary factors, malnutrition, anthropometric indices, body composition, inflammation and oxidative stress with quality of life, dialysis access infections, hospitalisation, potential years of life lost and mortality in adults on maintenance haemodialysis in Isfahan, Iran.

METHODS AND ANALYSIS

The sample size of this cohort was estimated to be 300 participants. At baseline, demographic, medical and dialysis-related data of eligible patients will be recorded. In addition, participants will undergo anthropometric measurements, malnutrition assessment and body composition analysis. Also, their dietary intake and quality of life will be evaluated through interviewer-administered questionnaires. Moreover, their fasting blood samples will be collected and stored for biochemical assays including transthyretin, albumin, serum amyloid A, pentraxin-3, trimethylamine N-oxide, myeloperoxidase, paraoxonase-1 and superoxide dismutase. After baseline evaluation, patients will be followed up to 3 years to update exposure information (except biochemical assays) and measure adverse outcomes. Finally, collected data will be analysed using descriptive and inferential statistics.

ETHICS AND DISSEMINATION

The NIOS-HD is in agreement with the Declaration of Helsinki and has been approved by the Ethics Committee of Isfahan University of Medical Sciences (reference number: IR.MUI.

RESEARCH

REC.1399.605). Findings of this study will be published in academic journals.

Trimethylamine N-Oxide and Its Precursors Are Associated with Gestational Diabetes Mellitus and Pre-Eclampsia in the Boston Birth Cohort

Background

Trimethylamine N-oxide (TMAO) and its precursors choline, betaine, and carnitine have been associated with cardiometabolic disease in nonpregnant adults. However, studies examining TMAO and its precursors in relation to cardiometabolic conditions during pregnancy are lacking.

Objectives

The primary objective was to estimate the association of TMAO and its precursors in maternal and cord plasma with gestational diabetes mellitus (GDM) and pre-eclampsia (PE) among women in the Boston Birth Cohort. A secondary objective was to determine whether associations vary by race/ethnicity.

Methods

ORs for each outcome according to tertiles and to an SD increment of TMAO, choline, betaine, and carnitine were estimated using logistic regression. Final models were adjusted for covariates.

Results

Among 1496 women, 115 women had GDM and 159 had PE during the index pregnancy. Intermetabolite correlations of TMAO and its precursors were stronger within cord plasma (r = 0.38-0.87) than within maternal plasma (r = 0.08-0.62). Maternal TMAO was associated with higher odds of GDM (third compared with first tertile OR: 1.75; 95% CI: 1.04, 2.94), whereas maternal choline, betaine, and carnitine were not associated with GDM. Maternal TMAO and choline were not associated with PE, whereas carnitine was associated with higher (OR: 1.86; 95% CI: 1.18, 2.94) and betaine with lower odds of PE (OR: 0.37; 95% CI: 0.23, 0.59). In cord plasma, TMAO was not associated with GDM or PE, but choline, betaine, and carnitine were associated with higher odds of PE (OR: 3.11; 95% CI: 1.62, 5.96; OR: 2.65; 95% CI: 1.42, 4.93; OR: 2.56; 95% CI: 1.39, 4.69, respectively). Cord choline was associated with lower odds of GDM (OR: 0.52; 95% CI: 0.27, 0.99), whereas other cord metabolites were not significantly associated with GDM. Associations did not vary by race/ethnicity.

Conclusions

TMAO and its precursors were associated with GDM and PE, but the associations differed based on the metabolite medium (maternal compared with cord plasma).This trial was registered at clinicaltrials.gov as NCT03228875.

Novel Mechanisms and Therapeutic Targets for Ischemic Stroke: A Focus on Gut Microbiota

Ischemic stroke is the most common type of stroke with limited treatment options. Although the pathological mechanisms and potential therapeutic targets of ischemic stroke have been comprehensively studied, no effective therapies were translated into clinical practice. Gut microbiota is a complex and diverse dynamic metabolic ecological balance network in the body, including a large number of bacteria, archaea, and eukaryotes. The composition, quantity and distribution in gut microbiota are found to be associated with the pathogenesis of many diseases, such as individual immune abnormalities, metabolic disorders, and neurodegeneration. New insight suggests that ischemic stroke may lead to changes in the gut microbiota and the alterations of gut microbiota may determine stroke outcomes in turn. The link between gut microbiota and stroke is expected to provide new perspectives for ischemic stroke treatment. In this review, we discuss the gut microbiota alterations during ischemic stroke and gut microbiota-related stroke pathophysiology and complications. Finally, we highlight the role of the gut microbiota as a potential therapeutic target for ischemic stroke and summarize the microbiome-based treatment options that can improve the recovery of stroke patients.

Association of Trimethylamine N-Oxide and Metabolites With Mortality in Older Adults

IMPORTANCE

Little is known about the association of trimethylamine N-oxide (TMAO), a novel plasma metabolite derived from L-carnitine and phosphatidylcholine, and related metabolites (ie, choline, betaine, carnitine, and butyrobetaine) with risk of death among older adults in the general population.

OBJECTIVE

To investigate the associations of serial measures of plasma TMAO and related metabolites with risk of total and cause-specific death (ie, deaths from cardiovascular diseases [CVDs] and non-CVDs) among older adults in the US.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study involved 5333 participants from the Cardiovascular Health Study-a community-based longitudinal cohort of adults aged 65 years or older-who were followed up from June 1, 1989, to December 31, 2015. Participants were from 4 communities in the US (Forsyth County, North Carolina; Sacramento County, California; Washington County, Maryland; and Allegheny County, Pennsylvania). Data were analyzed from March 17 to June 23, 2021.

EXPOSURES

Plasma TMAO, choline, betaine, carnitine, and butyrobetaine levels were measured using stored samples from baseline (June 1, 1989, to May 31, 1990, or November 1, 1992, to June 31, 1993) and follow-up examination (June 1, 1996, to May 31, 1997). Measurements were performed through stable-isotope dilution liquid chromatography with tandem mass spectrometry using high-performance liquid chromatography with online electrospray ionization tandem mass spectrometry.

MAIN OUTCOMES AND MEASURES

Deaths (total and cause specific) were adjudicated by a centralized Cardiovascular Health Study events committee based on information from medical records, laboratory and diagnostic reports, death certificates, and/or interviews with next of kin. The associations of each metabolite with mortality were assessed using Cox proportional hazards regression models.

RESULTS

Among 5333 participants in the analytic sample, the mean (SD) age was 73 (6) years; 2149 participants (40.3%) were male, 3184 (59.7%) were female, 848 (15.9%) were African American, 4450 (83.4%) were White, and 35 (0.01%) were of other races (12 were American Indian or Alaska Native, 4 were Asian or Pacific Islander, and 19 were of other races or ethnicities). During a median follow-up of 13.2 years (range, 0-26.9 years), 4791 deaths occurred. After adjustment for potential confounders, the hazard ratios for death from any cause (ie, total mortality) comparing extreme quintiles (fifth vs first) of plasma concentrations were 1.30 (95% CI, 1.17-1.44) for TMAO, 1.19 (95% CI, 1.08-1.32) for choline, 1.26 (95% CI, 1.15-1.40) for carnitine, and 1.26 (95% CI, 1.13-1.40) for butyrobetaine. Plasma betaine was not associated with risk of death. The extent of risk estimates was similar for CVD and non-CVD mortality.

CONCLUSIONS AND RELEVANCE

In this cohort study, plasma concentrations of TMAO and related metabolites were positively associated with risk of death. These findings suggest that circulating TMAO is an important novel risk factor associated with death among older adults.

Uremic Toxins and Cardiovascular Risk in Chronic Kidney Disease: What Have We Learned Recently beyond the Past Findings?

Patients with chronic kidney disease (CKD) have an elevated prevalence of atheromatous (ATH) and/or non-atheromatous (non-ATH) cardiovascular disease (CVD) due to an array of CKD-related risk factors, such as uremic toxins (UTs). Indeed, UTs have a major role in the emergence of a spectrum of CVDs, which constitute the leading cause of death in patients with end-stage renal disease. The European Uremic Toxin Work Group has identified over 100 UTs, more than 25 of which are dietary or gut-derived. Even though relationships between UTs and CVDs have been described in the literature, there are few reviews on the involvement of the most toxic compounds and the corresponding physiopathologic mechanisms. Here, we review the scientific literature on the dietary and gut-derived UTs with the greatest toxicity in vitro and in vivo. A better understanding of these toxins’ roles in the elevated prevalence of CVDs among CKD patients might facilitate the development of targeted treatments. Hence, we review (i) ATH and non-ATH CVDs and the respective levels of risk in patients with CKD and (ii) the mechanisms that underlie the influence of dietary and gut-derived UTs on CVDs.

Circulating Trimethylamine-N-Oxide and Risk of All-Cause and Cardiovascular Mortality in Patients With Chronic Kidney Disease: A Systematic Review and Meta-Analysis

Background

Trimethylamine-N-oxide (TMAO) is expected to be a prognostic biomarker among patients suffering from chronic kidney disease (CKD). However, investigations on the association between TMAO and CKD prognosis are conflicting. In the present article, we aimed to assess the relationship of circulating TMAO with the risk of all-cause and cardiovascular mortality among CKD patients by a meta-analysis.

Methods

Data were collected from PubMed, EMBASE, and Web of Science for systematically searching related literature (last update: February 2022). The multivariable-adjusted hazard risks (HR) and their 95% confidence intervals (CI) were pooled using random effects models.

Results

Eleven prospective cohort studies covering 7,899 CKD patients were enrolled in this meta-analysis. When comparing individuals in the top and bottom baseline TMAO levels thirds, the multivariate adjusted pooled HR was 1.29 (95% CI 1.11–1.51, P = 0.001) for all-cause mortality, and 1.45 (95% CI 1.01–2.09, P = 0.043) for cardiovascular death. For continuous variables, per 1 unit increase of circulating TMAO levels was associated with a 3% higher all-cause mortality (HR 1.03, 95% CI 1.00–1.06, P = 0.032), but not significantly associated with cardiovascular death (HR 1.08, 95% CI 0.92–1.27, P = 0.346). Stratified analyses revealed that the positive relationship between TMAO and all-cause mortality remained significant after adjusting for diabetes, blood pressure, blood lipid, renal function, or inflammatory parameters.

Conclusion

Higher circulating TMAO was associated with an increased mortality risk among patients with CKD, and this relationship may be dependent on TMAO dose and independent of renal function, inflammation, diabetes, hypertension, and dyslipidemia.

Systematic Review Registration

[https://www.INPLASY.COM], identifier [INPLASY2021100049].

The Microbiome and Uremic Solutes

Uremic retention solutes, especially the protein-bound compounds, are toxic metabolites, difficult to eliminate with progressive renal functional decline. They are of particular interest because these uremic solutes are responsible for the pathogenesis of cardiovascular and chronic kidney diseases. Evidence suggests that the relation between uremic toxins, the microbiome, and its host is altered in patients with chronic kidney disease, with the colon’s motility, epithelial integrity, and absorptive properties also playing an important role. Studies found an alteration of the microbiota composition with differences in species proportion, diversity, and function. Since uremic toxins precursors are generated by the microbiota, multiple therapeutic options are currently being explored to address dysbiosis. While an oral adsorbent can decrease the transport of bacterial metabolites from the intestinal lumen to the blood, dietary measures, supplements (prebiotics, probiotics, and synbiotics), and antibiotics aim to target directly the gut microbiota composition. Innovative approaches, such as the modulation of bacterial enzymes, open new perspectives to decrease the plasma level of uremic toxins.

Gut microbiota-derived metabolite trimethylamine-N-oxide and multiple health outcomes: an umbrella review and updated meta-analysis

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite produced from dietary nutrients. Many studies have discovered that circulating TMAO concentrations are linked to a wide range of health outcomes.

OBJECTIVES

This study aimed to summarize health outcomes related to circulating TMAO concentrations.

METHODS

We searched the Embase, Medline, Web of Science, and Scopus databases from inception to 15 February, 2022 to identify and update meta-analyses examining the associations between TMAO and multiple health outcomes. For each health outcome, we estimated the summary effect size, 95% prediction CI, between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias. These metrics were used to evaluate the evidence credibility of the identified associations.

RESULTS

This umbrella review identified 24 meta-analyses that investigated the association between circulating TMAO concentrations and health outcomes including all-cause mortality, cardiovascular diseases (CVDs), diabetes mellitus (DM), cancer, and renal function. We updated these meta-analyses by including a total of 82 individual studies on 18 unique health outcomes. Among them, 14 associations were nominally significant. After evidence credibility assessment, we found 6 (33%) associations (i.e., all-cause mortality, CVD mortality, major adverse cardiovascular events, hypertension, DM, and glomerular filtration rate) to present highly suggestive evidence.

CONCLUSIONS

TMAO might be a novel biomarker related to human health conditions including all-cause mortality, hypertension, CVD, DM, cancer, and kidney function. Further studies are needed to investigate whether circulating TMAO concentrations could be an intervention target for chronic disease.This review was registered at www.crd.york.ac.uk/prospero/ as CRD42021284730.

Acute Kidney Injury and Gut Dysbiosis: A Narrative Review Focus on Pathophysiology and Treatment

Acute kidney injury (AKI) and gut dysbiosis affect each other bidirectionally. AKI induces microbiota alteration in the gastrointestinal (GI) system, while gut dysbiosis also aggravates AKI. The interplay between AKI and gut dysbiosis is not yet well clarified but worthy of further investigation. The current review focuses on the pathophysiology of this bidirectional interplay and AKI treatment in this base. Both macrophages and neutrophils of the innate immunity and the T helper type 17 cell from the adaptive immunity are the critical players of AKI-induced gut dysbiosis. Conversely, dysbiosis-induced overproduction of gut-derived uremic toxins and insufficient generation of short-chain fatty acids are the main factors deteriorating AKI. Many novel treatments are proposed to deter AKI progression by reforming the GI microbiome and breaking this vicious cycle. Data support the benefits of probiotic treatment in AKI patients, while the results of postbiotics are mainly limited to animals. Prebiotics and synbiotics are primarily discussed in chronic kidney disease patients rather than AKI patients. The effect of adsorbent treatment seems promising, but more studies are required before the treatment can be applied to patients. Immune therapy and some repurposed drugs such as allopurinol are prospects of future treatments and are worth more discussion and survey.

Balancing the Equation: A Natural History of Trimethylamine and Trimethylamine-N-oxide

Trimethylamine (TMA) and its N-oxide (TMAO) are ubiquitous in prokaryote and eukaryote organisms as well as in the environment, reflecting their fundamental importance in evolutionary biology, and their diverse biochemical functions. Both metabolites have multiple biological roles including cell-signaling. Much attention has focused on the significance of serum and urinary TMAO in cardiovascular disease risk, yet this is only one of the many facets of a deeper TMA-TMAO partnership that reflects the significance of these metabolites in multiple biological processes spanning animals, plants, bacteria, and fungi. We report on analytical methods for measuring TMA and TMAO and attempt to critically synthesize and map the global functions of TMA and TMAO in a systems biology framework.

Gut microbial metabolite TMAO increases peritoneal inflammation and peritonitis risk in peritoneal dialysis patients

Trimethylamine-N-oxide (TMAO), a gut microbiota-produced metabolite, is accumulated in chronic kidney disease (CKD) patients. It is well known to contribute to CKD-related cardiovascular complications. However, the effect of TMAO on peritoneal dialysis (PD)-related peritonitis remains largely unknown. Here, we demonstrate that serum concentrations of TMAO were positively correlated with C-reactive protein levels, and the appearance rate of dialysate IL-6 and PAI-1, in PD patients. During the follow-up period of 28.3 ± 8.0 months, patients with higher TMAO levels (≥50 μM) had a higher risk of new-onset peritonitis (HR, 3.60; 95%CI, 1.18-10.99; P=0.025) after adjusting for sex, age, diabetes, PD duration, BUN, rGFR, C-reactive protein, BMI and β2-M. In CKD rat models, TMAO significantly promoted peritoneal dialysate-induced inflammatory cell infiltration, inflammatory cytokines production in the peritoneum. In vitro study revealed that TMAO directly induced primary peritoneal mesothelial cell necrosis, together with increased production of pro-inflammatory cytokines including CCL2, TNF-α, IL-6, and IL-1β. In addition, TMAO significantly increased TNF-α-induced P-selectin production in mesothelial cells, as well as high glucose-induced TNF-α and CCL2 expression in endothelial cells. In conclusion, our data demonstrate that higher levels of TMAO exacerbate peritoneal inflammation and might be a risk factor of incidence of peritonitis in PD patients.

Association Between Plasma Trimethyllysine and Prognosis of Patients With Ischemic Stroke

Background

Trimethyllysine, a trimethylamine N‐oxide precursor, has been identified as an independent cardiovascular risk factor in acute coronary syndrome. However, limited data are available to examine the role of trimethyllysine in the population with stroke. We aimed to examine the relationship between plasma trimethyllysine levels and stroke outcomes in patients presenting with ischemic stroke or transient ischemic attack.

Methods and Results

Data of 10 027 patients with ischemic stroke/transient ischemic attack from the CNSR‐III (Third China National Stroke Registry) and 1‐year follow‐up data for stroke outcomes were analyzed. Plasma levels of trimethyllysine were measured with mass spectrometry. The association between trimethyllysine and stroke outcomes was analyzed using Cox regression models. Mediation analysis was performed to examine the mediation effects of risk factors on the associations of trimethyllysine and stroke outcomes. Elevated trimethyllysine levels were associated with increased risk of cardiovascular death (quartile 4 versus quartile 1: adjusted hazard ratio [HR], 1.72; 95% CI, 1.03–2.86) and all‐cause mortality (quartile 4 versus quartile 1: HR, 1.97; 95% CI, 1.40–2.78) in multivariate Cox regression model. However, no associations were found between trimethyllysine and nonfatal stroke recurrence or nonfatal myocardial infarction. Trimethyllysine was associated with cardiovascular death independent of trimethylamine N‐oxide. Both estimated glomerular filtration rate and hs‐CRP (high‐sensitivity C‐reactive protein) had significant mediation effects on the association of trimethyllysine with cardiovascular death, with a mediation effect of 37.8% and 13.4%, respectively.

Conclusions

Elevated trimethyllysine level is associated with cardiovascular death among patients with ischemic stroke/transient ischemic attack. Mediation analyses propose that trimethyllysine contributes to cardiovascular death through inflammation and renal function, suggesting a possible pathomechanistic link.

Trimethylamine-N-Oxide Aggravates Kidney Injury via Activation of p38/MAPK Signaling and Upregulation of HuR

BACKGROUND

Trimethylamine-N-oxide (TMAO) is an intestinal metabolic toxin, which is produced by gut flora via metabolizing high-choline foods. TMAO is known to increase the risk of atherosclerosis and cardiovascular events in chronic kidney disease (CKD) patients.

OBJECTIVES

The objective of this study was to explore the role and mechanism of TMAO aggravating kidney injury.

METHOD

We used the five-sixths nephrectomy (5/6 Nx)-induced CKD rats to investigate whether TMAO could aggravate kidney damage and its possible mechanisms. Six weeks after the operation, the two groups of 5/6 Nx rats were subjected to intraperitoneal injection with 2.5% glucose peritoneal dialysis fluid (2.5% PDF) and 2.5% PDF plus TMAO 20 mg/kg/day.

RESULTS

In this study, we provided evidence showing TMAO significantly aggravated renal failure as well as inflammatory cell infiltration and in five-sixths nephrectomy-induced CKD rats. We found that TMAO could upregulate inflammatory factors including MCP-1, TNF-α, IL-6, IL-1β, and IL-18 by activating p38 phosphorylation and upregulation of human antigen R. TMAO could aggravate oxidative stress by upregulating NOX4 and downregulating SOD. The result also confirmed that TMAO promoted NLRP3 inflammasome formation as well as cleaved caspase-1 and IL-1β activation in the kidney tissue.

CONCLUSIONS

Taken together, the present study validates TMAO as a pro-inflammatory factor that causes renal inflammatory injury and renal function impairment. Inhibition of TMAO synthesis or promoting its clearance may be a potential therapeutic approach of CKD in the future.

Trimethylamine-N-oxide (TMAO) and clinical outcomes in patients with end-stage kidney disease receiving peritoneal dialysis

BACKGROUND

Trimethylamine-N-oxide (TMAO) is a gut bacteria-derived metabolite of l-carnitine and choline. A high concentration of TMAO has been proven to relate to cardiovascular disease (CVD), all-cause mortality and chronic kidney disease progression. We aimed to investigate the relation between the value of serum TMAO and outcomes for peritoneal dialysis (PD) patients.

METHODS

This is a prospective cohort study with data retrospectively analysed. All incident PD patients were enrolled and followed up. Log-rank test, competing risk survival analysis and COX regression were performed to test the effect of serum TMAO on developing first-episode peritonitis, all-cause and CVD mortality.

RESULTS

A wide distribution of serum TMAO concentration was observed in 513 PD patients, with a median level of 72.3 (43.7, 124.7) µmol/L. Patients with lower TMAO concentration were more likely to be without diabetes and hypertension. Patients with lower TMAO concentration showed better residual kidney function and solute clearance at baseline. Participants in the higher three TMAO quartiles showed an increased risk for first-episode peritonitis (p = 0.039). By competing risk survival analysis, after adjusting for age, sex, diabetes mellitus, CVD, body mass index, albumin, high-sensitive C-reactive protein, potassium, phosphorus, residual kidney function, normalised protein equivalent of total nitrogen appearance and calendar year of catheter implantation, patients in the higher three TMAO quartiles had a statistically or marginally higher risk for first-episode peritonitis compared with patients in the lowest quartile, with hazard ratio (HR) 1.65 (1.05, 2.58), 1.46 (0.92, 2.31) and 1.66 (1.05, 2.61), respectively. In the COX model, patients in the third quartile TMAO group had significantly higher CVD mortality risk compared with the lowest quartile group, as HR 2.27 (1.02, 5.05) after adjusting for various factors. As for all-cause mortality, TMAO did not show any associated effects.

CONCLUSIONS

Serum TMAO concentration is associated with the risk of first-episode peritonitis and CVD mortality in PD patients. No obvious association between serum TMAO and all-cause mortality was observed.

Ventricular arrhythmias in mouse models of diabetic kidney disease

Chronic kidney disease (CKD) affects more than 20 million people in the US, and it is associated with a significantly increased risk of sudden cardiac death (SCD). Despite the significance, the mechanistic relationship between SCD and CKD is not clear and there are few effective therapies. Using optical mapping techniques, we tested the hypothesis that mouse models of progressive diabetic kidney disease (DKD) exhibit enhanced ventricular arrhythmia incidence and underlying arrhythmia substrates. Compared to wild-type mice, both Lepr^db/db eNOS^−/− (2KO) and high fat diet plus low dose streptozotocin (HFD + STZ) mouse models of DKD experienced sudden death and greater arrhythmia inducibility, which was more common with isoproterenol than programmed electrical stimulation. 2KO mice demonstrated slowed conduction velocity, prolonged action potential duration (APD), and myocardial fibrosis; both 2KO and HFD + STZ mice exhibited arrhythmias and calcium dysregulation with isoproterenol challenge. Finally, circulating concentrations of the uremic toxin asymmetric dimethylarginine (ADMA) were elevated in 2KO mice. Incubation of human cardiac myocytes with ADMA prolonged APD, as also observed in 2KO mice hearts ex vivo. The present study elucidates an arrhythmia-associated mechanism of sudden death associated with DKD, which may lead to more effective treatments in the vulnerable DKD patient population.

Longitudinal Plasma Measures of Trimethylamine N-Oxide and Risk of Atherosclerotic Cardiovascular Disease Events in Community-Based Older Adults

Background

Trimethylamine N‐oxide (TMAO) is a gut microbiota‐dependent metabolite of dietary choline, L‐carnitine, and phosphatidylcholine‐rich foods. On the basis of experimental studies and patients with prevalent disease, elevated plasma TMAO may increase risk of atherosclerotic cardiovascular disease (ASCVD). TMAO is also renally cleared and may interact with and causally contribute to renal dysfunction. Yet, how serial TMAO levels relate to incident and recurrent ASCVD in community‐based populations and the potential mediating or modifying role of renal function are not established.

Methods and Results

We investigated associations of serial measures of plasma TMAO, assessed at baseline and 7 years, with incident and recurrent ASCVD in a community‐based cohort of 4131 (incident) and 1449 (recurrent) older US adults. TMAO was measured using stable isotope dilution liquid chromatography–tandem mass spectrometry (laboratory coefficient of variation, <6%). Incident ASCVD (myocardial infarction, fatal coronary heart disease, stroke, sudden cardiac death, or other atherosclerotic death) was centrally adjudicated using medical records. Risk was assessed by multivariable Cox proportional hazards regression, including time‐varying demographics, lifestyle factors, medical history, laboratory measures, and dietary habits. Potential mediating effects and interaction by estimated glomerular filtration rate (eGFR) were assessed. During prospective follow‐up, 1766 incident and 897 recurrent ASCVD events occurred. After multivariable adjustment, higher levels of TMAO were associated with a higher risk of incident ASCVD, with extreme quintile hazard ratio (HR) compared with the lowest quintile=1.21 (95% CI, 1.02–1.42; P‐trend=0.029). This relationship appeared mediated or confounded by eGFR (eGFR‐adjusted HR, 1.07; 95% CI, 0.90–1.27), as well as modified by eGFR (P‐interaction <0.001). High levels of TMAO were associated with higher incidence of ASCVD in the presence of impaired renal function (eGFR <60 mL/min per 1.73 m²: HR, 1.56 [95% CI, 1.13–2.14]; P‐trend=0.007), but not normal or mildly reduced renal function (eGFR ≥60 mL/min per 1.73 m²: HR, 1.03 [95% CI, 0.85–1.25]; P‐trend=0.668). Among individuals with prior ASCVD, TMAO associated with higher risk of recurrent ASCVD (HR, 1.25 [95% CI, 1.01–1.56]; P‐trend=0.009), without significant modification by eGFR.

Conclusions

In this large community‐based cohort of older US adults, serial measures of TMAO were associated with higher risk of incident ASCVD, with apparent modification by presence of impaired renal function and with higher risk of recurrent ASCVD.

The role of carnitine in maintenance dialysis therapy

Carnitine metabolism and homeostasis is significantly altered in patients receiving maintenance dialysis. Current literature in the adult and pediatric dialysis populations suggest a high prevalence of carnitine deficiency, which may lead to erythropoietin-resistant anemia, cardiomyopathy, and muscle weakness. However, the results of pediatric dialysis studies are limited and have not provided the evidence necessary to support strong recommendations or guidelines pertaining to carnitine management. The characteristics and function of carnitine, the definition and consequences of deficiency, a brief overview of recent adult studies, and current studies on carnitine supplementation in pediatric hemodialysis (HD) and peritoneal dialysis (PD) populations are discussed in this review.

Possible Biochemical Processes Underlying the Positive Health Effects of Plant-Based Diets-A Narrative Review

Plant-based diets are becoming more popular for many reasons, and epidemiological as well as clinical data also suggest that a well-balanced vegan diet can be adopted for the prevention, and in some cases, in the treatment of many diseases. In this narrative review, we provide an overview of the relationships between these diets and various conditions and their potential biochemical background. As whole plant foods are very rich in food-derived antioxidants and other phytochemicals, they have many positive physiological effects on different aspects of health. In the background of the beneficial health effects, several biochemical processes could stand, including the reduced formation of trimethylamine oxide (TMAO) or decreased serum insulin-like growth factor 1 (IGF-1) levels and altered signaling pathways such as mechanistic target of rapamycin (mTOR). In addition, the composition of plant-based diets may play a role in preventing lipotoxicity, avoiding N-glycolylneuraminic acid (Neu5Gc), and reducing foodborne endotoxin intake. In this article, we attempt to draw attention to the growing knowledge about these diets and provide starting points for further research.

Association of trimethylamine N-Oxide with cardiovascular and all-cause mortality in hemodialysis patients

Background

Trimethylamine-N-Oxide (TMAO) is a proatherogenic and prothrombotic metabolite. Our study examined the association of plasma TMAO level with cardiovascular and all-cause mortality in hemodialysis (HD) patients.

Methods

Patients who were at least 18 years-old and received HD for at least 6 months were enrolled within 6 months. Patients with coronary heart disease, congestive heart failure, arrhythmia, or stroke within 3 months before study onset were excluded. The primary endpoints were cardiovascular and all-cause death, and the secondary endpoint was cerebrovascular death.

Results

We recruited 252 patients and divided them into a high-TMAO group (>4.73 μg/mL) and a low-TMAO group (≤4.73 μg/mL). The median follow-up time was 73.4 months (interquartile range: 42.9, 108). A total of 123 patients died, 39 from cardiovascular disease, 19 from cerebrovascular disease, and 65 from other causes. Kaplan-Meier analysis indicated that the high-TMAO group had a greater incidence of cardiovascular death (Log-Rank: p = 0.006) and all-cause death (Log-Rank: p < 0.001). Cox regression analysis showed that high TMAO level was significantly associated with cardiovascular and all-cause mortality. After adjustment for confounding, this association remained significant for cardiovascular mortality (TMAO as a continuous variable: HR: 1.18, 95%CI: 1.07, 1.294, p < 0.001; TMAO as a dichotomous variable: HR: 3.44, 95%CI: 1.68, 7.08, p < 0.001) and all-cause mortality (TMAO as a continuous variable: HR: 1.14, 95%CI: 1.08, 1.21, p < 0.001; TMAO as a dichotomous variable: HR: 2.54, 95%CI: 1.71, 3.76, p < 0.001).

Conclusions

High plasma TMAO level is significantly and independently associated with cardiovascular and all-cause mortality in HD patients.

FMO3-TMAO axis modulates the clinical outcome in chronic heart-failure patients with reduced ejection fraction: evidence from an Asian population

The association among plasma trimethylamine-N-oxide (TMAO), FMO3 polymorphisms, and chronic heart failure (CHF) remains to be elucidated. TMAO is a microbiota-dependent metabolite from dietary choline and carnitine. A prospective study was performed including 955 consecutively diagnosed CHF patients with reduced ejection fraction, with the longest follow-up of 7 years. The concentrations of plasma TMAO and its precursors, namely, choline and carnitine, were determined by liquid chromatography-mass spectrometry, and the FMO3 E158K polymorphisms (rs2266782) were genotyped. The top tertile of plasma TMAO was associated with a significant increment in hazard ratio (HR) for the composite outcome of cardiovascular death or heart transplantation (HR = 1.47, 95% CI = 1.13-1.91, P = 0.004) compared with the lowest tertile. After adjustments of the potential confounders, higher TMAO could still be used to predict the risk of the primary endpoint (adjusted HR = 1.33, 95% CI = 1.01-1.74, P = 0.039). This result was also obtained after further adjustment for carnitine (adjusted HR = 1.33, 95% CI = 1.01-1.74, P = 0.039). The FMO3 rs2266782 polymorphism was associated with the plasma TMAO concentrations in our cohort, and lower TMAO levels were found in the AA-genotype. Thus, higher plasma TMAO levels indicated increased risk of the composite outcome of cardiovascular death or heart transplantation independent of potential confounders, and the FMO3 AA-genotype in rs2266782 was related to lower plasma TMAO levels.

Plasma trimethylamine N-oxide (TMAO) levels predict future risk of coronary artery disease in apparently healthy individuals in the EPIC-Norfolk prospective population study

BACKGROUND

Recent studies show a mechanistic link between gut microbiota-dependent formation of the atherosclerosis- and thrombosis-promoting metabolite trimethylamine N-oxide (TMAO) and cardiovascular disease (CVD). The clinical utility of TMAO in apparently healthy subjects for predicting incident CVD risks is unclear.

METHODS AND RESULTS

In the EPIC-Norfolk community-based study, we examined baseline fasting levels of TMAO and two of its nutrient precursors, choline and betaine, in a case:control design study comparing apparently European healthy middle-aged participants who subsequently develop CVD (Cases, n = 908) vs those who did not (Controls, n = 1,273) over an ensuing average follow-up period of 8 years. In participants who developed CVD vs controls, higher plasma TMAO (3.70 [IQR 2.50-6.41]μM vs 3.25 [IQR 2.19-52,1.15]μM; P < .001) and choline levels (9.09 [IQR 7.87-10.53]μM vs 8.89 [IQR 7.66-10.13]μM; P = .001) were observed. Following adjustments for traditional risk factors, elevated TMAO (adjusted odds ratio (OR) 1.58 [95% confidence interval (CI) 1.21-2.06], P < .001) and choline levels (adjusted OR 1.31 [95%CI 1.00-1.72], P < .05) remained predictive of incident CVD development. The clinical prognostic utility of TMAO remained significant and essentially unchanged regardless of the level of cutoff chosen between 1.5 uM (10%ile) to 10.5 uM (90%ile).

CONCLUSION

In apparently healthy participants of the community-based middle-aged EPIC-Norfolk population, elevated plasma levels of the gut microbe-dependent metabolite TMAO, and its nutrient precursor choline, predict incident risk for CVD development independent of traditional risk factors.

Circulating Trimethylamine N-Oxide Is Associated with Increased Risk of Cardiovascular Mortality in Type-2 Diabetes: Results from a Dutch Diabetes Cohort (ZODIAC-59)

Trimethylamine N-oxide (TMAO), a novel cardiovascular (CV) disease and mortality risk marker, is a gut microbiota-derived metabolite as well. Recently, plasma concentrations of branched-chain amino acids (BCAA) have been reported to be affected by microbiota. The association of plasma TMAO with CV mortality in Type 2 Diabetes (T2D) and its determinants are still incompletely described. We evaluated the association between plasma BCAA and TMAO, and the association of TMAO with CV mortality in T2D individuals. We used data of 595 participants (mean age 69.5 years) from the Zwolle Outpatient Diabetes project Integrating Available Care (ZODIAC) cohort were analyzed. Plasma TMAO and BCAA were measured with nuclear magnetic resonance spectroscopy. CV mortality risk was estimated using multivariable-adjusted Cox regression models. Cross-sectionally, TMAO was independently associated with BCAA standardized (Std) β = 0.18 (95% Confidence Interval (CI) 0.09; 0.27), p <0.001. During a median follow-up of 10 years, 113 CV deaths were recorded. In Cox regression analyses, adjusted for multiple clinical and laboratory variables including BCAA, TMAO was independently associated with CV mortality: adjusted hazard ratio (_adjHR) 1.93 (95% CI 1.11; 3.34), p = 0.02 (for the highest vs. the lowest tertile of the TMAO distribution). The same was true for analyses with TMAO as continuous variable: _adjHR 1.32 (95% CI 1.07; 1.63), p = 0.01 (per 1 SD increase). In contrast, BCAAs were not associated with increased CV mortality. In conclusion, higher plasma TMAO but not BCAA concentrations are associated with an increased risk of CV mortality in individuals with T2D, independent of clinical and biochemical risk markers.

Significance of the Gut Microbiota in Acute Kidney Injury

Recent studies have revealed that the gut microbiota plays a crucial role in maintaining a healthy, as well as diseased condition. Various organs and systems, including the kidney, are affected by the gut microbiota. While the impacts of the gut microbiota have been reported mainly on chronic kidney disease, acute kidney injury (AKI) is also affected by the intestinal environment. In this review, we discussed the pathogenesis of AKI, highlighting the relation to the gut microbiota. Since there is no established treatment for AKI, new treatments for AKI are highly desired. Some kinds of gut bacteria and their metabolites reportedly have protective effects against AKI. Current studies provide new insights into the role of the gut microbiota in the pathogenesis of AKI.

Contribution of Gut Microbiota-Derived Uremic Toxins to the Cardiovascular System Mineralization

Chronic kidney disease (CKD) affects more than 10% of the world population and leads to excess morbidity and mortality (with cardiovascular disease as a leading cause of death). Vascular calcification (VC) is a phenomenon of disseminated deposition of mineral content within the media layer of arteries preceded by phenotypic changes in vascular smooth muscle cells (VSMC) and/or accumulation of mineral content within the atherosclerotic lesions. Medial VC results in vascular stiffness and significantly contributes to increased cardio-vascular (CV) morbidity, whereas VC of plaques may rather increase their stability. Mineral and bone disorders of CKD (CKD-MBD) contribute to VC, which is further aggravated by accumulation of uremic toxins. Both CKD-MBD and uremic toxin accumulation affect not only patients with advanced CKD (glomerular filtration rate (GFR) less than 15 mL/min/1.72 m², end-stage kidney disease) but also those on earlier stages of a disease. The key uremic toxins that contribute to VC, i.e., p-cresyl sulphate (PCS), indoxyl sulphate (IS) and trimethylamine-N-oxide (TMAO) originate from bacterial metabolism of gut microbiota. All mentioned toxins promote VC by several mechanisms, including: Transdifferentiation and apoptosis of VSMC, dysfunction of endothelial cells, oxidative stress, interaction with local renin–angiotensin–aldosterone system or miRNA profile modification. Several attractive methods of gut microbiota manipulations have been proposed in order to modify their metabolism and to limit vascular damage (and VC) triggered by uremic toxins. Unfortunately, to date no such method was demonstrated to be effective at the level of “hard” patient-oriented or even clinically relevant surrogate endpoints.

Gut microbial metabolite TMAO portends prognosis in acute ischemic stroke

BACKGROUND

Over the recent years, the role of trimethylamine N-oxide (TMAO) as a gut-derived metabolite mediating cardiovascular disease pathogenesis has been under particularly intense scrutiny. The aim was to explore whether TMAO levels were associated with clinical severity or functional outcome in Chinese patients with ischemic stroke.

METHODS

This is a single-center, prospective cohort study from Xiamen, China. We examined the relationship between fasting TMAO and 2 of its nutrient precursors, choline and betaine, vs. 3-month functional outcome and mortality in 351 first-ever patients with acute ischemic stroke.

RESULTS

The median value of the plasma level of TMAO was 6.1 μM (IQR, 3.7-9.9 μM), which was higher than in those control cases (4.0; 2.4-5.9 μM). Patients with a poor outcome and nonsurvivors had significantly increased TMAO levels on admission (P < 0.001). Following adjustments for traditional risk factors, increased TMAO concentrations remained predictive of both poor outcome and mortality risks in stroke patients [e.g., quartiles 4 vs 1, odd ratio 5.65 (95% CI, 2.87-13.45), P < 0.001; and 5.84 (95% CI, 3.05-16.12), P < 0.001, respectively]. In multivariate analysis, TMAO was an independent predictor of functional outcome and mortality and improved the prognostic accuracy of the NIHSS to predict functional outcome (combined areas under the curve, 0.82; 95% CI 0.77-0.89, P = 0.003) and mortality (combined areas under the curve, 0.85; 95% CI: 0.80-0.90, P = 0.002).

CONCLUSIONS

Fasting plasma concentrations of gut microbial TMAO are higher in patients with ischemic stroke and portend higher poor functional outcome events and mortality.

Elevated Serum Trimethylamine N-Oxide Levels Are Associated with Mortality in Male Patients on Peritoneal Dialysis

BACKGROUND

Elevated levels of serum trimethylamine N-oxide (TMAO) have been previously linked to adverse cardiovascular (CV) and all-cause mortality in hemodialysis patients. However, the clinical significance of serum TMAO levels in patients treated with peritoneal dialysis (PD) is unclear.

METHODS

A total of 1,032 PD patients with stored serum samples at baseline were enrolled in this prospective study. Serum concentrations of TMAO were quantified by ultra-performance liquid chromatography-tandem mass spectrometry. Cox proportional hazards and competing-risk regression models were performed to examine the association of TMAO levels with all-cause and CV mortality.

RESULTS

The median level of serum TMAO in our study population was 34.5 (interquartile range (IQR), 19.8-61.0) μM. During a median follow-up of 63.7 months (IQR, 43.9-87.2), 245 (24%) patients died, with 129 (53%) deaths resulting from CV disease. In the entire cohort, we observed an association between elevated serum TMAO levels and all-cause mortality (adjusted subdistributional hazard ratio [SHR], 1.22; 95% confidence interval [95% CI], 1.01-1.48; p = 0.039) but not CV mortality. Further analysis revealed such association differed by sex; the elevation of serum TMAO levels was independently associated with increased risk of both all-cause (SHR, 1.37; 95% CI, 1.07-1.76; p = 0.013) and CV mortality (SHR, 1.41; 95% CI, 1.02-1.94; p = 0.038) in men but not in women.

CONCLUSIONS

Higher serum TMAO levels were independently associated with all-cause and CV mortality in male patients treated with PD.

Loop Diuretics Inhibit Renal Excretion of Trimethylamine N-Oxide

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Uremic retention solutes predominantly eliminate through the kidneys largely via specific efflux channels in the proximal renal tubules.

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For the first time, we demonstrated in vivo that renal tubular excretion of TMAO can be inhibited by concomitant loop diuretic administration via competition at the level of renal transporters.

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We further observed accumulation of TMAO in the renal parenchyma, which implied differential distributions of TMAO across various tissues and/or systems as a consequence of efflux channel control.

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Poorer outcomes in patients who receive long-term loop diuretic agents may therefore be associated with metabolic perturbations, such as retention of metabolites like TMAO, beyond impaired glomerular filtration.

This study demonstrates, for the first time, that renal tubular excretion of trimethylamine N-oxide (TMAO) is inhibited by concomitant loop diuretic administration. The observed marked accumulation in the renal parenchyma, and to lesser extent, plasma, implies differential distributions of TMAO across various tissues and/or systems as a consequence of efflux channel control. A better understanding of TMAO renal clearance and its potential interactions with current and future therapies in patients with heart failure are warranted.

Association of Circulating Trimethylamine N-Oxide and Its Dietary Determinants with the Risk of Kidney Graft Failure: Results of the TransplantLines Cohort Study

Background. Due to the critical shortage of kidneys for transplantation, the identification of modifiable factors related to graft failure is highly desirable. The role of trimethylamine-N-oxide (TMAO) in graft failure remains undetermined. Here, we investigated the clinical utility of TMAO and its dietary determinants for graft failure prediction in renal transplant recipients (RTRs). Methods. We included 448 RTRs who participated in the TransplantLines Cohort Study. Cox proportional-hazards regression analyses were performed to study the association of plasma TMAO with graft failure. Net Benefit, which is a decision analysis method, was performed to evaluate the clinical utility of TMAO and dietary information in the prediction of graft failure. Results. Among RTRs (age 52.7 ± 13.1 years; 53% males), the baseline median TMAO was 5.6 (3.0–10.2) µmol/L. In multivariable regression analysis, the most important dietary determinants of TMAO were egg intake (Std. β = 0.09 [95%CI, 0.01; 0.18]; p = 0.03), fiber intake (Std. β = −0.14 [95%CI, −0.22, −0.05]; p = 0.002), and fish and seafood intake (Std. β = 0.12 [95%CI, 0.03,0.21]; p = 0.01). After a median follow-up of 5.3 (4.5–6.0) years, graft failure was observed in 58 subjects. TMAO was associated with an increased risk of graft failure, independent of age, sex, the body mass index (BMI), blood pressure, lipids, albuminuria, and the Estimated Glomerular Filtration Rate (eGFR) (Hazard Ratio per 1-SD increase of TMAO, 1.62 (95% confidence interval (CI): 1.22; 2.14, p < 0.001)). A TMAO and dietary enhanced prediction model offered approximately double the Net Benefit compared to a previously reported, validated prediction model for future graft failure, allowing the detection of 21 RTRs per 100 RTRs tested, with no false positives versus 10 RTRs, respectively. Conclusions. A predictive model for graft failure, enriched with TMAO and its dietary determinants, yielded a higher Net Benefit compared with an already validated model. This study suggests that TMAO and its dietary determinants are associated with an increased risk of graft failure and that it is clinically meaningful.

Trimethylamine N-Oxide Was Not Associated With 30-Day Left Ventricular Systolic Dysfunction in Patients With a First Anterior ST-Segment Elevation Myocardial Infarction After Primary Revascularization: A Sub-analysis From an Optical Coherence Tomography Registry

Objective: Left ventricular systolic dysfunction (LVSD) after ST-segment elevation myocardial infarction (STEMI) is associated with poor outcome. Trimethylamine N-oxide (TMAO), a gut metabolite, is linked to cardiovascular diseases but its relationship with LVSD after STEMI remains unclear. The present study therefore aimed to investigate the relationship between TMAO and LVSD at 30 days after a first anterior STEMI.

Methods: This was a sub-study from the OCTAMI (Optical Coherence Tomography Examination in Acute Myocardial Infarction) registry. Eligible patients were included in current study if they: (1) presented with a first anterior STEMI; (2) had available baseline TMAO concentration; (3) completed a cardiovascular magnetic resonance examination at 30 days after STEMI. LVSD was defined as left ventricular ejection fraction < 50%. Associations between TMAO and left ventricular ejection fraction, infarct size and left ventricular global strain were examined.

Results: In total, 78 patients were included in final analysis. Overall, TMAO was moderately associated with peak cTnI (r = 0.27, p = 0.01), age (r = 0.34, p < 0.01), and estimated glomerular filtration rate (r = −0.30, p < 0.01). At 30-day follow-up, 41 patients were in the LVSD group and 37 in the non-LVSD group. Baseline TMAO levels were not significantly different between the two groups (LVSD vs. non-LVSD: median 1.9 μM, 25−75th percentiles 1.5–3.3 μM vs. median 1.9 μM, 25−75th percentiles 1.5–2.7 μM; p = 0.46). Linear regression analyses showed that TMAO was not associated with left ventricular ejection fraction, infarct size or left ventricular global strain at 30 days (all p > 0.05).

Conclusions: TMAO was not significantly correlated with 30-day LVSD in patients with a first anterior STEMI after primary revascularization.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03593928.

The Links between Microbiome and Uremic Toxins in Acute Kidney Injury: Beyond Gut Feeling-A Systematic Review

The last years have brought an abundance of data on the existence of a gut-kidney axis and the importance of microbiome in kidney injury. Data on kidney-gut crosstalk suggest the possibility that microbiota alter renal inflammation; we therefore aimed to answer questions about the role of microbiome and gut-derived toxins in acute kidney injury. PubMed and Cochrane Library were searched from inception to October 10, 2020 for relevant studies with an additional search performed on ClinicalTrials.gov. We identified 33 eligible articles and one ongoing trial (21 original studies and 12 reviews/commentaries), which were included in this systematic review. Experimental studies prove the existence of a kidney-gut axis, focusing on the role of gut-derived uremic toxins and providing concepts that modification of the microbiota composition may result in better AKI outcomes. Small interventional studies in animal models and in humans show promising results, therefore, microbiome-targeted therapy for AKI treatment might be a promising possibility.