Trimethylamine N-oxide is associated with impaired cognitive function in patients with atrial fibrillation

Introduction

Since patients with atrial fibrillation (AF) are predisposed to suffer from major adverse cerebrovascular events (MACE), they are more likely to suffer MACE linked sequelae, such as cognitive impairment. We hypothesised that the gut microbiome derivate trimethylamine N-oxide (TMAO) may amplify this pathomechanism given its hypercoagulative, proinflammatory and proatherogenic effects.

Methods

Patients of the Swiss-AF cohort with determined TMAO plasma levels, cognitive scores (n=2'379) and cerebral magnetic resonance imaging (cMRI) (n=1'722) collected at baseline were included. TMAO levels were measured by liquid chromatography-mass spectrometry (HPLC). Overall cognitive performance was evaluated using the Cognitive Construct (CoCo) score reflecting different cognitive functions measured by four validated neuropsychological assessments, namely the Montreal Cognitive Assessment (MoCA), Trail Making Test (TMT parts A and B), Semantic Fluency Test (SFT) and Digital Symbol Substitution Test (DSST). The scores were compared with the quartiles of patients' TMAO plasma levels (Q1: 0.6–4, Q2: 4–5.8, Q3: 5.8–9.1, Q4: 9.1–164μmol/l) in linear effect models. All models were adjusted for multiple covariates correlating with this association: For TMAO (overall meat consumption >3 times per week, physical activity, glomerular filtration rate, presence of diabetes mellitus), cognitive function (EQ-5D-5L score, geriatric depression scale, education level) and cerebral affects (white matter lesions volume and total brain volume in cMRI). The relevance of high TMAO plasma levels in different stroke groups in cMRI (i.e., clinically overt, silent, or no stroke) were analysed in a subgroup analysis. The subgroups were additionally adjusted for total brain volume to eliminate the effect of simultaneous decrease of cerebral white matter.

Results

After multivariable adjustment, AF patients in the highest quartile of TMAO levels performed significantly poorer in the global cognitive score (CoCo: estimate −0.11, 95% CI [−0.17, −0.05], p=0.002) compared to patients in the lowest quartile. This was observed also in the MoCA, SFT, DSST, TMT-A and TMT-B.

In the subgroup analysis, an association between the highest TMAO quartile (compared with the lowest quartile) and lower CoCo score was found in the group of patients with overt strokes (−0.18, 95% CI [−0.33, −0.04], p=0.012). Weak evidence of the same association was found in the group of patients with silent strokes (−0.13, 95% CI [−0.25, 0.002], p=0.053) and patients with no strokes (−0.08, 95% CI [−0.16, 0.01], p=0.07).

After adjustment for decreased brain volume, the association remained for silent strokes (−0.14, 95% CI [−0.28, −0.01], p=0.036) indicating the impact of TMAO in this subgroup.

Conclusion

TMAO plasma levels were associated with cognitive impairment in patients with AF. Longitudinal data will clarify dynamics and likely causality between TMAO and cognitive impairment.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Swiss National Science Foundation

Trimethylamine-N-oxide (TMAO) is associated with cardiovascular mortality and vascular brain lesions in patients with atrial fibrillation

Introduction

Trimethylamine-N-oxide (TMAO) is a well characterized pro-atherogenic metabolite derived from the microbial processing of phosphatidylcholine and carnitine (usually present in red meat) and subsequent hepatic oxydation, which promotes endothelial dysfunction, platelet activation and thrombosis initiation. Its role concerning cerebral and cardiovascular adverse events has been assessed in various patient subpopulations but not for long term in patients with atrial fibrillation.

Methods

Baseline TMAO plasma levels were measured by high-performance liquid chromatography/mass spectrometry in plasmas of 2,379 subjects from our multicentric study. Among them, 1,722 participants at time of recruitment underwent brain MRI. Participants were stratified into TMAO tertiles and Cox PH models, linear mixed effect models or logistic mixed effect models were employed adjusting for several risk factors (age, sex, BMI, active and past smoke habit, cystatin c levels, heart failure, diabetes mellitus, hypertension, coronary artery disease and history of TIA/stroke). Subjects were prospectively followed with a median observation time of 4 years.

Results

Subjects in the highest tertile of TMAO were older (75.4 vs. 70.6 years in low tertile p<0.001) and had significantly more often comorbidities, (26.9% of subjects were diabetic vs. 9.1% in low tertile p<0.001), with higher BMI (28.1 vs 27.0, p<0.001) and worse renal function as assessed by serum cystatin C (1.46 vs 1.07, mg/dl; p<0.001). Heart failure was present in 37.9% participants in the upper compared to 15.8% in the lower tertile. (p<0.001). As shown in Figure 1, Kaplan Meier estimates showed increased cardiovascular mortality with increasing TMAO tertiles (p<0.0001). After adjustment for the abovementioned factors the upper tertile (T3) had an increased hazard ratio (HR) compared to the lowest one (HR 2.36 95% CI 1.56–3.58 p<0.01). Similar trends for global and ischemic stroke occurrences were not found although TMAO levels positively weakly correlated with NIHSS severity (Spearman's coefficient 0.31 p=0.02). Concerning brain MRI findings, TMAO tertiles identified individuals with different prevalence of small non-cortical infarcts (30.5%, 18.1% and 17.4% in high, middle and low tertiles respectively; p<0.001) and when present, larger white matter lesions volumes (5061 mm3, 4158 mm3 and 2970 mm3; p<0.001). After adjustment, the association with small non-cortical infarcts with TMAO levels remained significant in the highest tertile (T3) (OR 1.48 95% CI 1.07–2.05; p=0.02) and a trend towards larger white matter lesions volumes was observed (estimate 1307 95% CI −90–2705; p=0.07).

Conclusions

TMAO represents a robust prognostic independent biomarker identifying multimorbid, high risk patients for cardiovascular mortality and brain damage.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Swiss National Science Foundation (SNSF) and Theodor und Ida Herzog-Egli Foundation Figure 1. CV mortality according to TMAOFigure 2. Brain lesions assessment