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

Probiotic interventions in peritoneal dialysis: A review of underlying mechanisms and therapeutic potentials

Peritoneal dialysis (PD) is a commonly used modality for kidney replacement therapy for patients with end-stage kidney disease (ESKD). PD offers many benefits, including home-based care, greater flexibility, and preservation of residual kidney function compared to in-center hemodialysis. Nonetheless, patients undergoing PD often face significant challenges, including systemic inflammation, PD-related peritonitis, metabolic disorders, and cardiovascular issues that can negatively affect their quality of life and treatment outcomes. Recent studies have demonstrated the crucial role of the gut microbiome in overall health and treatment results, supporting the hypothesis that probiotics may bring potential benefits to the general population of ESKD patients. However, specific data on probiotic use in PD patients are limited. This opinion review aims to summarize the current knowledge on the relationship between PD and the gut microbiome and offers a novel perspective by specifically exploring how probiotic interventions could improve the outcomes of PD treatment. The review also outlines some clinical data supporting the effectiveness of probiotics in patients undergoing PD and considers the difficulties and restrictions in their application. Based on the current knowledge gaps, this study seeks to explore future research directions and their implications for clinical practice.

The Association Between Serum Trimethylamine N-Oxide and Arterial Stiffness in Chronic Peritoneal Dialysis Patients: A Cross-Sectional Study

Trimethylamine N-oxide (TMAO), a gut microbiome-derived metabolite, participates in the atherogenesis and vascular stiffening that is closely linked with cardiovascular (CV) complications and related deaths in individuals with kidney failure undergoing peritoneal dialysis (PD) therapy. In these patients, arterial stiffness (AS) is also an indicator of adverse CV outcomes. This study assessed the correlation between serum TMAO concentration quantified with high-performance liquid chromatography and mass spectrometry and central AS measured by carotid-femoral pulse wave velocity (cfPWV) in patients with chronic PD. Of the 160 participants included, 23.8% had a cfPWV of ≥10 m/s, which fulfilled the AS criteria. Multivariable logistic regression analysis revealed that TMAO, age, and waist circumference were positively associated with AS. Multivariable stepwise linear regression showed that underlying diabetes, advanced age, waist circumference, systolic blood pressure, and logarithmic-transformed TMAO were independently correlated with cfPWV. The area under the receiver operating characteristic curve for TMAO in differentiating AS from non-AS was 0.737. In conclusion, serum TMAO level was significantly independently correlated with central AS among participants undergoing PD for end-stage kidney failure.

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, I2 = 43%) and (HR: 1.55, 95% CI 1.37-1.75, P < .00001, I2 = 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.

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

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