Background: Rheumatoid arthritis (RA) is associated with a high risk of cardiovascular (CV) risks, including accelerated atherosclerosis, left ventricular hypertrophy and decreased heart rate variability (HRV). HRV decrease reflects the inability of the autonomic nervous system (ANS) to adapt cardiac function and lower HRV is associated with a higher risk of CV events. Autonomic dysfunction is observed in RA with a prevalence of 60–80% and precedes the onset of symptoms.

Objectives: Given that gut microbiota (GM) dysbiosis also occurs before disease and inflammation in subjects who will develop RA, and that activity of vagus nerve can be modulated by the GM, we hypothesized that GM impairs the ANS balance in RA.

Methods: We investigated whether fecal microbiota transplantation (FMT) of RA patients in mice modulates the electrocardiographic profile, the HRV and cardiac function compared to FMT of healthy subjects (age-and-sex-matched controls). Using electrocardiogram (ECG) acquired by telemetry, we characterized the impact of FMT on sympathetic and/or vagal outflow using temporal and spectral domain analyses of HRV. High resolution echocardiography allowed to assess both cardiac structural and contractile function. A pharmacological study was conducted to test the integrity of the cardiac muscarinic and adrenergic pathways (carbachol and isoproterenol injection). In parallel, FMT consequences on pro- or anti-inflammatory immune cells and early markers of atherosclerosis were assessed to correlate with potential changes in the inflammatory profile. Intestinal permeability (ZO-1 in situ and FITC-dextran in vivo) was also analysed. Finally, 16S RNA sequencing of the GM after FMT was performed to identify differentially affected bacterial genera.

Results: HRV analysis showed that FMT from RA patients altered the ANS activity in mice, reproducing a defect of vagal tone. Indeed, we observed an increase of heart rate in mice with fecal transfer of RA microbiota (RA-FMT), only during resting time (444.82(±20.07) bpm vs 477.12(±30), p=0.0001, n=34/group). This tachycardia results from a reduction of HRV reflecting altered ANS activity with a decrease in SDNN index (SDNN 23.88±9.97 vs 10.22±4.05 ms, p<0.0001, n=34/group). Time domain and spectral domain analyses of HRV confirmed a decrease in the parasympathetic activity resulting in a drop of sympathovagal balance. These alterations were independent of cardiac structural or contractile modifications and remodeling of cardiac muscarinic or adrenergic signalling pathways. Furthermore, this dysfunction of vagal tone was independent of inflammation as RA-FMT did not induce major immune dysfunction or change in the aortic expression of early markers of atherosclerosis (VCAM and ICAM). On the other hand, RA-FMT had an impact on the intestinal barrier, with an increase in the passage of FITC-Dextran into the blood of mice with RA-FMT (p<0.01, n=12-13/group). We identified Parabacteroides distasonis as a candidate to explain the dysautonomia observed in our model.

Conclusion: We demonstrate for the first time that the MI of RA patients contributes to autonomic dysfunction, independently of the inflammatory status and without structural or contractile modification of the heart. This opens new therapeutic perspectives, such as dietary modifications, for example by adding fibre or the use of probiotics, to prevent autonomic dysfunction and CV risk in RA. In addition, P. distasonis has been shown to protect against inflammation, particularly in RA, via succinate and secondary bile acids, which will be investigated in our model.

REFERENCES: NIL.

Acknowledgements: NIL.

Disclosure of Interests: None declared.