Brief periods of transcutaneous auricular vagus nerve stimulation improve autonomic balance and alter circulating monocytes and endothelial cells in patients with metabolic syndrome: a pilot study

BACKGROUND

There is emerging evidence that the nervous system regulates immune and metabolic alterations mediating Metabolic syndrome (MetS) pathogenesis via the vagus nerve. This study evaluated the effects of transcutaneous auricular vagus nerve stimulation (TAVNS) on key cardiovascular and inflammatory components of MetS.

METHODS

We conducted an open label, randomized (2:1), two-arm, parallel-group controlled trial in MetS patients. Subjects in the treatment group (n = 20) received 30 min of TAVNS with a NEMOS® device placed on the cymba conchae of the left ear, once weekly. Patients in the control group (n = 10) received no stimulation. Hemodynamic, heart rate variability (HRV), biochemical parameters, and monocytes, progenitor endothelial cells, circulating endothelial cells, and endothelial micro particles were evaluated at randomization, after the first TAVNS treatment, and again after 8 weeks of follow-up.

RESULTS

An improvement in sympathovagal balance (HRV analysis) was observed after the first TAVNS session. Only patients treated with TAVNS for 8 weeks had a significant decrease in office BP and HR, a further improvement in sympathovagal balance, with a shift of circulating monocytes towards an anti-inflammatory phenotype and endothelial cells to a reparative vascular profile.

CONCLUSION

These results are of interest for further study of TAVNS as treatment of MetS.

Additional Improvement of Respiratory Technique on Vascular Function in Hypertensive Postmenopausal Women Following Yoga or Stretching Video Classes: The YOGINI Study

Background: Hypertension remains highly prevalent in postmenopausal women, along with vascular dysfunction and increased oxidative stress. In such context, regular exercises, yoga practice, and slow breathing have been recommended to treat hypertension. However, the effects of the multiple components of yoga, including the respiratory techniques involved in the practice, on hypertension and on vascular and endothelial function have never been evaluated.

Objective: This study aimed to investigate the additional effects of respiratory technique on vascular function and oxidative stress profile in hypertensive postmenopausal women (HPMWs) following yoga or stretching video classes.

Study Design: Hypertensive postmenopausal women were recruited and randomized for 12 weeks, twice a week, of supervised yoga or stretching video classes of 75 min for 12 weeks associated or not with respiratory technique. Baseline and post-intervention measurements included pulse wave velocity (PWV), flow-mediated dilation (FMD), and oxidative stress parameters. Hypertensive postmenopausal women (59 ± 0.7 years) who ended the protocol were distributed into three groups: (1) control group (yoga or stretching, C, n = 14); (2) yoga + respiratory technique (Y+, n = 10); (3) stretching + respiratory technique (S+, n = 9).

Results: Diastolic blood pressure and FMD [baseline: C: 6.94 ± 1.97%, Y+: 7.05 ± 1.65%, and S+: 3.54 ± 2.01% vs. post: C: 16.59 ± 3.46% (p = 0.006), Y+: 13.72 ± 2.81% (p = 0.005), and S+: 11.79 ± 0.99% (p = 0.0001)] have significantly increased in all groups when baseline and post-practice values were compared. However, resting heart rate and PWV [baseline: Y+: 10.44 ± 3.69 and S+: 9.50 ± 0.53 m/s vs. post: Y+: 9.45 ± 0.39 (p = 0.003) and S+: 8.02 ± 0.47 m/s (p = 0.003)] decreased significantly only in the Y+ and S+ groups (baseline vs. post). Systemic antioxidant enzyme activities (superoxide dismutase and catalase) increased in all groups, and hydrogen peroxide and lipoperoxidation reduced in Y+ and S+ (baseline vs. post).

Conclusions: Twelve weeks of yoga or stretching video classes promoted positive changes in several outcomes generally regarded as cardiovascular risk factors in HPMWs, and these changes were even more pronounced by the association with respiratory technique.