Transcutaneous auricular vagus nerve stimulation augments postprandial inhibition of ghrelin

Transcutaneous auricular vagus nerve stimulation as a novel therapy connecting the central and peripheral systems: a review

Currently, clinical practice and scientific research mostly revolve around a single disease or system, but the single disease-oriented diagnostic and therapeutic paradigm needs to be revised. This review describes how transcutaneous auricular vagus nerve stimulation (taVNS), a novel non-invasive neuromodulation approach, connects the central and peripheral systems of the body. Through stimulation of the widely distributed vagus nerve from the head to the abdominal cavity, this therapy can improve and treat central system disorders, peripheral system disorders, and central-peripheral comorbidities caused by autonomic dysfunction. In the past, research on taVNS has focused on the treatment of central system disorders by modulating this brain nerve. As the vagus nerve innervates the heart, lungs, liver, pancreas, gastrointestinal tract, spleen and other peripheral organs, taVNS could have an overall modulatory effect on the region of the body where the vagus nerve is widespread. Based on this physiological basis, the authors summarize the existing evidence of the taVNS ability to regulate cardiac function, adiposity, glucose levels, gastrointestinal function, and immune function, among others, to treat peripheral system diseases, and complex diseases with central and peripheral comorbidities. This review shows the successful examples and research progress of taVNS using peripheral neuromodulation mechanisms from more perspectives, demonstrating the expanded scope and value of taVNS to provide new ideas and approaches for holistic therapy from both central and peripheral perspectives.

Impact of optimized transcutaneous auricular vagus nerve stimulation on cardiac autonomic profile in healthy subjects and heart failure patients

Objective.To determine the optimal frequency and site of stimulation for transcutaneous vagus nerve stimulation (tVNS) to induce acute changes in the autonomic profile (heart rate (HR), heart rate variability (HRV)) in healthy subjects (HS) and patients with heart failure (HF).Approach.We designed three single-blind, randomized, cross-over studies: (1) to compare the acute effect of left tVNS at 25 Hz and 10 Hz (n= 29, age 60 ± 7 years), (2) to compare the acute effect of left and right tVNS at the best frequency identified in study 1 (n= 28 age 61 ± 7 years), and (3) to compare the acute effect of the identified optimal stimulation protocol with sham stimulation in HS and HF patients (n= 30, age 59 ± 5 years, andn= 32, age 63 ± 7 years, respectively).Main results.In study 1, left tragus stimulation at 25 Hz was more effective than stimulation at 10 Hz in decreasing HR (-1.0 ± 1.2 bpm,p< 0.001 and -0.5 ± 1.6 bpm, respectively) and inducing vagal effects (significant increase in RMSSD, and HF power). In study 2, the HR reduction was greater with left than right tragus stimulation (-0.9 ± 1.5 bpm,p< 0.01 and -0.3 ± 1.4 bpm, respectively). In study 3 in HS, left tVNS at 25 Hz significantly reduced HR, whereas sham stimulation did not (-1.1 ± 1.2 bpm,p< 0.01 and -0.2 ± 2.9 bpm, respectively). In HF patients, both active and sham stimulation produced negligible effects.Significance.Left tVNS at 25 Hz is effective in acute modulation of cardiovascular autonomic control (HR, HRV) in HS but not in HF patients (NCT05789147).

Bibliometric analysis of auriculotherapy research trends over the past 20 years

OBJECTIVES

Auriculotherapy has long been used to treat various diseases. We analyzed and visualized auriculotherapy's geographical distribution, key contributors, and thematic trends over the past 20 years to provide current trends in auriculotherapy field and to offer recommendations for future research directions.

DESIGN/SETTING

We searched for relevant studies in the Web of Science between January 10, 2003, and December 31, 2022. A bibliometric analysis was performed using VOSviewer for annual publications, journals, countries, institutions, authors, and keywords.

RESULTS

A total of 800 studies were included in the analysis, and the number of studies steadily increased over the 20 examined years. In 2018, there was a noteworthy rise in publications, nearly twice as many as the preceding year. Integrative & complementary medicine was the most researched area, with most articles published in Evidence-Based Complementary and Alternative Medicine. China was the country with the most published research, and the most active organization was Guangzhou University of Chinese Medicine in China, followed by Kyung Hee University in South Korea. The most prolific author was Yeh Mei-ling, who reported the effects of auriculotherapy on dysmenorrhea and smoking cessation. Keyword analysis revealed four clusters: pain, mental health, obesity, and smoking cessation.

CONCLUSION

Auriculotherapy research primarily focused on clinical studies related to pain, obesity, smoking cessation, and depression. Future research should place greater emphasis on verifying the mechanisms of auriculotherapy for specific ailments and may require efforts to enhance the robustness of clinical trials. Through visual analysis, our study may serve as a foundational resource, offering valuable insights into the trajectory of auriculotherapy research.

[Research advances in neuromodulation techniques for blood glucose regulation and diabetes intervention]

Diabetes and its complications that seriously threaten the health and life of human, has become a public health problem of global concern. Glycemic control remains a major focus in the treatment and management of patients with diabetes. The traditional lifestyle interventions, drug therapies, and surgeries have benefited many patients with diabetes. However, due to problems such as poor patient compliance, drug side effects, and limited surgical indications, there are still patients who fail to effectively control their blood glucose levels. With the development of bioelectronic medicine, neuromodulation techniques have shown great potential in the field of glycemic control and diabetes intervention with its unique advantages. This paper mainly reviewed the research advances and latest achievements of neuromodulation technologies such as peripheral nerve electrical stimulation, ultrasound neuromodulation, and optogenetics in blood glucose regulation and diabetes intervention, analyzed the existing problems and presented prospects for the future development trend to promote clinical research and application of neuromodulation technologies in the treatment of diabetes.

Combining Celiac and Hepatic Vagus Nerve Neuromodulation Reverses Glucose Intolerance and Improves Glycemic Control in Pre- and Overt-Type 2 Diabetes Mellitus

Neurological disorders and type 2 diabetes mellitus (T2DM) are deeply intertwined. For example, autonomic neuropathy contributes to the development of T2DM and continued unmanaged T2DM causes further progression of nerve damage. Increasing glycemic control has been shown to prevent the onset and progression of diabetic autonomic neuropathies. Neuromodulation consisting of combined stimulation of celiac vagal fibers innervating the pancreas with concurrent electrical blockade of neuronal hepatic vagal fibers innervating the liver has been shown to increase glycemic control in animal models of T2DM. The present study demonstrated that the neuromodulation reversed glucose intolerance in alloxan-treated swine in both pre- and overt stages of T2DM. This was demonstrated by improved performance on oral glucose tolerance tests (OGTTs), as assessed by area under the curve (AUC). In prediabetic swine (fasting plasma glucose (FPG) range: 101-119 mg/dL) the median AUC decreased from 31.9 AUs (IQR = 28.6, 35.5) to 15.9 AUs (IQR = 15.1, 18.3) p = 0.004. In diabetic swine (FPG range: 133-207 mg/dL) the median AUC decreased from 54.2 AUs (IQR = 41.5, 56.6) to 16.0 AUs (IQR = 15.4, 21.5) p = 0.003. This neuromodulation technique may offer a new treatment for T2DM and reverse glycemic dysregulation at multiple states of T2DM involved in diabetic neuropathy including at its development and during progression.

Neuroimmunomodulation of vagus nerve stimulation and the therapeutic implications

Vagus nerve stimulation (VNS) is a technology that provides electrical stimulation to the cervical vagus nerve and can be applied in the treatment of a wide variety of neuropsychiatric and systemic diseases. VNS exerts its effect by stimulating vagal afferent and efferent fibers, which project upward to the brainstem nuclei and the relayed circuits and downward to the internal organs to influence the autonomic, neuroendocrine, and neuroimmunology systems. The neuroimmunomodulation effect of VNS is mediated through the cholinergic anti-inflammatory pathway that regulates immune cells and decreases pro-inflammatory cytokines. Traditional and non-invasive VNS have Food and Drug Administration (FDA)-approved indications for patients with drug-refractory epilepsy, treatment-refractory major depressive disorders, and headaches. The number of clinical trials and translational studies that explore the therapeutic potentials and mechanisms of VNS is increasing. In this review, we first introduced the anatomical and physiological bases of the vagus nerve and the immunomodulating functions of VNS. We covered studies that investigated the mechanisms of VNS and its therapeutic implications for a spectrum of brain disorders and systemic diseases in the context of neuroimmunomodulation.

A systematic review of the effects of transcutaneous auricular vagus nerve stimulation on baroreflex sensitivity and heart rate variability in healthy subjects

PURPOSE

This systematic review aimed to evaluate the effect of transcutaneous auricular vagus nerve stimulation on heart rate variability and baroreflex sensitivity in healthy populations.

METHOD

PubMed, Scopus, the Cochrane Library, Embase, and Web of Science were systematically searched for controlled trials that examined the effects of transcutaneous auricular vagus nerve stimulation on heart rate variability parameters and baroreflex sensitivity in apparently healthy individuals. Two independent researchers screened the search results, extracted the data, and evaluated the quality of the included studies.

RESULTS

From 2458 screened studies, 21 were included. Compared with baseline measures or the comparison group, significant changes in the standard deviation of NN intervals, the root mean square of successive RR intervals, the proportion of consecutive RR intervals that differ by more than 50 ms, high-frequency power, low-frequency to high-frequency ratio, and low-frequency power were found in 86%, 75%, 69%, 47%, 36%, and 25% of the studies evaluating the effects of transcutaneous auricular vagus nerve stimulation on these indices, respectively. Baroreflex sensitivity was evaluated in six studies, of which a significant change was detected in only one. Some studies have shown that the worse the basic autonomic function, the better the response to transcutaneous auricular vagus nerve stimulation.

CONCLUSION

The results were mixed, which may be mainly attributable to the heterogeneity of the study designs and stimulation delivery dosages. Thus, future studies with comparable designs are required to determine the optimal stimulation parameters and clarify the significance of autonomic indices as a reliable marker of neuromodulation responsiveness.

Pediatric Vagus Nerve Stimulation: Case Series Outcomes and Future Directions

BACKGROUND

Vagus nerve stimulation (VNS) is a neuromodulatory procedure most extensively studied as an adjunct to medically refractory epilepsy. Despite widespread adoption and decades of clinical experience, clinical predictors of response to VNS remain unclear.

OBJECTIVE

To evaluate a retrospective cohort of pediatric patients undergoing VNS at our institution to better understand who may benefit from VNS and identify factors which may predict response to VNS.

METHODS

We conducted a retrospective cohort study examining pediatric patients undergoing VNS over nearly a 20-year span at a single institution. Presurgical evaluation, including demographics, clinical history, and diagnostic electroencephalogram, and imaging findings were examined. Primary outcomes included VNS response.

RESULTS

Two hundred ninety-seven subjects were studied. The mean age at surgery was 10.1 (SD = 4.9, range = 0.8-25.3) years; length of follow-up was a mean of 4.6 years (SD = 3.5, median = 3.9 years, range 1 day-16.1 years). There was no association between demographic factors, epilepsy etiology, or genetic basis and VNS outcomes. There was an association between reduction in main seizure type with positive MRI finding. Of all MRI findings analyzed, brain atrophy was significantly associated with worse VNS outcomes, whereas dysplastic hippocampus and chronic periventricular leukomalacia findings were found to be associated with improved outcomes. Increased seizure semiology variability and seizure type were also associated with improved seizure outcomes.

CONCLUSION

Predicting response to VNS remains difficult, leading to incompletely realized benefits and suboptimal resource utilization. Specific MRI findings and increased seizure semiology variability and type can help guide clinical decision making and patient counseling.