Effects and mechanisms of auricular vagus nerve stimulation on high-fat-diet—induced obese rats

Effects of transcutaneous auricular vagus nerve stimulation on postoperative delirium in older patients with hip fracture: protocol for a randomised controlled trial

BACKGROUND

Postoperative delirium (POD) is an acute neurocognitive impairment and is commonly observed in older patients with hip fractures. POD is associated with poor outcomes, including increased postoperative complications, prolonged hospitalisation, high costs and increased perioperative mortality. Therefore, reducing the occurrence of POD and improving cognitive abilities in older patients are critical and urgent. Transcutaneous auricular vagus nerve stimulation (TAVNS) is a simple, safe, non-invasive treatment and has great potential to improve cognitive function. This clinical study will evaluate the effectiveness of TAVNS in reducing the incidence of POD in older patients and further elucidate the possible underlying mechanisms.

METHODS AND ANALYSIS

This randomised, double-blind, single-centre controlled trial will enroll 154 older patients undergoing hip fracture surgery, who will be randomly assigned to the TAVNS group (n=77), receiving TAVNS from 1 hour before anaesthetic induction to the end of the surgery, or the sham stimulation group (n=77), receiving sham stimulation in the same manner. The primary outcome measure will be the incidence of POD during the first 7 days post-surgery, as assessed by the confusion assessment method for the intensive care unit. The secondary outcomes include the incidence of delayed neurocognitive recovery; serum acetylcholinesterase and butyrylcholinesterase levels; the concentrations of tumour necrosis factor-α, interleukin-1β, interleukin-6 and S100β; unplanned intensive care unit admission rates; the length and cost of hospital stay; the incidence of postoperative complications during hospitalisation; and mortality at 1 month, 6 months and 1 year after surgery.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of the Chongqing Traditional Chinese Medicine Hospital on 15 May 2024 (2024-KY-HY-13). The findings will be published in the international peer-reviewed academic journals and presented orally at academic conferences.

TRIAL REGISTRATION NUMBER

ChiCTR2400085508.

Decorin alleviates non-alcoholic fatty liver disease in rats with polycystic ovary syndrome

Endocrine multisystem defect polycystic ovary syndrome (PCOS) causes hyperandrogenism and infertility. Half of PCOS women have (non-alcoholic fatty liver disease) NAFLD, which increases metabolic disease risk. We tested decorin's effect on NAFLD and related processes in PCOS. NAFLD+PCOS, PCOS+decorin, and control rats were studied. Decorin was evaluated on NAFLD/PCOS rats. Test group rats received HF for eight weeks to generate NAFLD. The rats got 1 mg/kg letrozole orally daily for 21 days to diagnosis PCOS. Afterward, rats got injectable decorin for 14 days. Body weight, liver weight, liver coefficient Abdominal Circumference (AC) and body mass index (BMI) were determined. Blood triglycerides (TG), total cholesterol, LDL-c, AST, and glucose were measured. The insulin, testosterone, estrogen, LH, and FSH were measured by ELISA. GPx, SOD, MDA, TNF-, and Caspase-3 liver immunohistochemistry were evaluated. NAFLD liver tissues in PCOS models showed biochemical and histological alterations. NAFLD+PCOS raised BMI, AC, liver weight, and coefficient. Blood glucose, insulin resistance, TG, ALT, and AST increased. Lipid abnormalities (TG, cholesterol, LDL-c, and HDL-c), oxidative stress markers (MDA, SOD, and GPx), and liver dysfunction were found. Low serum E2 and high T supported PCO. Decorin reduced model rat BMI, liver weight, coefficient, insulin resistance, TG, ALT, and AST. It reduced liver inflammation, improved liver extract lipids, and normalized MDA, SOD, and GPx. In the model group, decorin lowered serum T, E2, LH, caspase 3, and TNF-alpha. Decorating improved NAFLD/PCOS group liver histology and function. Decorin reduces hepatosteatosis by reducing liver inflammation, oxidative stress, and dyslipidemia.

Autonomic neuromodulation for cardiomyopathy associated with metabolic syndrome - Prevention of precursors for heart failure with preserved ejection fraction

Metabolic syndrome (MetS) induces a systemic inflammatory state which can lead to cardiomyopathy, manifesting clinically as heart failure (HF) with preserved ejection fraction (HFpEF). MetS components are intricately linked to the pathophysiologic processes of myocardial remodeling. Increased sympathetic nervous system activity, which is noted as an upstream factor of MetS, has been linked to adverse myocardial structural changes. Since renal denervation and vagus nerve stimulation have a sympathoinhibitory effect, attention has been paid to the cardioprotective effects of autonomic neuromodulation. In this review, the pathophysiology underlying the relationship between MetS and HF is elucidated, and the evidence regarding autonomic neuromodulation in HFpEF is summarized.

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.

Vagus Nerve and Gut-Brain Communication

The vagus nerve, as an important component of the gut-brain axis, plays a crucial role in the communication between the gut and brain. It influences food intake, fat metabolism, and emotion by regulating the gut-brain axis, which is closely associated with the development of gastrointestinal, psychiatric, and metabolism-related disorders. In recent years, significant progress has been made in understanding the vagus-mediated regulatory pathway, highlighting its profound implications in the development of many diseases. Here, we summarize the latest advancements in vagus-mediated gut-brain pathways and the novel interventions targeting the vagus nerve. This will provide valuable insights for future research on treatment of obesity and gastrointestinal and depressive disorders based on vagus nerve stimulation.

Vagal Stimulation Ameliorates Non-Alcoholic Fatty Liver Disease in Rats

BACKGROUND

The harmful consequences of non-alcoholic fatty liver disease (NAFLD) are posing an increasing threat to public health as the incidence of diabetes and obesity increases globally. A non-invasive treatment with a range of autonomic and metabolic benefits is transcutaneous vagus nerve stimulation (tVNS).

AIM OF THE STUDY

To investigate the possible preventive impacts of VNS against adult rats' NAFLD caused by a high-fat diet (HFD) and to clarify the underlying mechanisms.

METHODS

A total of thirty-two adult male rats were split into two groups: the HFD-induced NAFLD group (n = 24) and the control normal group (n = 8). The obesogenic diet was maintained for 12 weeks to induce hepatic steatosis. The HFD-induced NAFLD group (n = 24) was separated into three groups: the group without treatment (n = 8), the group with sham stimulation (n = 8), and the group with VNS treatment (n = 8). VNS was delivered for 30 min per day for 6 weeks after the establishment of NAFLD using a digital TENS device. The subsequent assessments included hepatic triglyceride, cholesterol content, serum lipid profile, and liver function testing. In this context, inflammatory biomarkers (TNF-α, IL-6) and hepatic oxidative stress (MDA, SOD, and GPx) were also assessed. To clarify the possible mechanisms behind the protective benefits of VNS, additional histological inspection and immunohistochemistry analysis of TNF-α and Caspase-3 were performed.

RESULTS

In the NAFLD-affected obese rats, VNS markedly decreased the rats' body mass index (BMI) and abdominal circumference (AC). Liver function markers (albumin, ALT, and AST) and the serum lipid profile-which included a notable decrease in the amounts of hepatic triglycerides and cholesterol-were both markedly improved. Additionally, oxidative stress and inflammatory indicators showed a considerable decline with VNS. Notably, the liver tissues examined by histopathologists revealed that there is evidence of the protective impact of VNS on the oxidative and inflammatory states linked to HFD-induced NAFLD while maintaining the architectural and functional condition of the liver.

CONCLUSIONS

Our findings suggest that VNS may represent a promising therapeutic candidate for managing NAFLD induced by obesity. It can be considered to be an effective adjuvant physiological intervention for the obese population with NAFLD to spare the liver against obesity-induced deleterious injury.

Application of Vagus Nerve Stimulation in Spinal Cord Injury Rehabilitation

Spinal cord injury (SCI) is a prevalent devastating condition causing significant morbidity and mortality, especially in developing countries. The pathophysiology of SCI involves ischemia, neuroinflammation, cell death, and scar formation. Due to the lack of definitive therapy for SCI, interventions mainly focus on rehabilitation to reduce deterioration and improve the patient's quality of life. Currently, rehabilitative exercises and neuromodulation methods such as functional electrical stimulation, epidural electrical stimulation, and transcutaneous electrical nerve stimulation are being tested in patients with SCI. Other spinal stimulation techniques are being developed and tested in animal models. However, often these methods require complex surgical procedures and solely focus on motor function. Vagus nerve stimulation (VNS) is currently used in patients with epilepsy, depression, and migraine and is being investigated for its application in other disorders. In animal models of SCI, VNS significantly improved locomotor function by ameliorating inflammation and improving plasticity, suggesting its use in human subjects. SCI patients also suffer from nonmotor complications, including pain, gastrointestinal dysfunction, cardiovascular disorders, and chronic conditions such as obesity and diabetes. VNS has shown promising results in alleviating these conditions in non-SCI patients, which makes it a possible therapeutic option in SCI patients.

GLP-1 Increases Circulating Leptin Levels in Truncal Vagotomized Rats

GLP-1 is a gastro-intestinal hormone acting within the gut/brain axis for energy balance regulation. We aimed to evaluate the role of the vagus nerve in whole-body energy homeostasis and in mediating GLP-1 effects. For this, rats submitted to truncal vagotomy and sham-operated controls underwent a comprehensive evaluation, including eating behavior, body weight, percentage of white (WAT) and brown adipose tissue (BAT), resting energy expenditure (REE) and acute response to GLP-1. Truncal vagotomized rats had significantly lower food intake, body weight, body weight gain, WAT and BAT, with a higher BAT/WAT ratio, but no significant difference in REE when compared to controls. Vagotomized rats also had significantly higher fasting ghrelin and lower glucose and insulin levels. After GLP-1 administration, vagotomized rats depicted a blunted anorexigenic response and higher plasma leptin levels, as compared to controls. However, in vitro stimulation of VAT explants with GLP-1 resulted in no significant changes in leptin secretion. In conclusion, the vagus nerve influences whole-body energy homeostasis by modifying food intake, body weight and body composition and by mediating the GLP-1 anorectic response. The higher leptin levels in response to acute GLP-1 administration observed after truncal vagotomy suggest the existence of a putative GLP-1-leptin axis that relies on the integrity of gut-brain vagal pathway.

Nutritional Supplements and Complementary Therapies in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) affects 1 in 5 women of reproductive age, and is characterized by menstrual irregularities, clinical or biochemical hyperandrogenism, and the presence of polycystic ovary morphology. One of the recommended treatment strategies in the international evidence-based guidelines is lifestyle modification, which includes diet and exercise, with the aim of improving a range of health outcomes. The incurable nature of PCOS reinforces the importance of developing novel and innovative symptomatic relief strategies, which are currently the only available approaches for improving quality of life for these women. Women with PCOS tend to be nutrient deficient in many common vitamins and minerals, thought to be associated with the psychological (depression, anxiety, etc.) and physiological (insulin resistance, diabetes, infertility, etc.) sequelae of the condition. Nutrient supplementation and the integration of complementary medicine as adjuncts to traditional lifestyle-based therapies in PCOS could therefore provide additional benefits to these women. In this review, we synthesize the evidence regarding nutrient supplementation and complementary therapies in PCOS, predominantly from randomized controlled trials, systematic reviews, and meta-analyses, to provide an overview of the state of knowledge in this field. The evidence to date suggests that specific vitamins (B-12, inositols, folate, vitamins D, E, and K), vitamin-like nutrients (bioflavonoids and α-lipoic acid), minerals (calcium, zinc, selenium, and chromium picolinate), and other formulations (melatonin, ω-3 fatty acids, probiotics, and cinnamon), as well as some complementary approaches such as acupuncture and yoga may be beneficial in PCOS. However, there remain areas of uncertainty and key limitations in the literature that must be overcome before these therapies can be integrated into routine clinical practice.

Obesity as a premature aging phenotype - implications for sarcopenic obesity

Obesity and aging have both seen dramatic increases in prevalence throughout society. This review seeks to highlight common pathologies that present with obesity, along with the underlying risk factors, that have remarkable similarity to what is observed in the aged. These include skeletal muscle dysfunction (loss of quantity and quality), significant increases in adiposity, systemic alterations to autonomic dysfunction, reduction in nitric oxide bioavailability, increases in oxidant stress and inflammation, dysregulation of glucose homeostasis, and mitochondrial dysfunction. This review is organized by the aforementioned indices and succinctly highlights literature that demonstrates similarities between the aged and obese phenotypes in both human and animal models. As aging is an inevitability and obesity prevalence is unlikely to significantly decrease in the near future, these two phenotypes will ultimately combine as a multidimensional syndrome (a pathology termed sarcopenic obesity). Whether the pre-mature aging indices accompanying obesity are additive or synergistic upon entering aging is not yet well defined, but the goal of this review is to illustrate the potential consequences of a double aged phenotype in sarcopenic obesity. Clinically, the modifiable risk factors could be targeted specifically in obesity to allow for increased health span in the aged and sarcopenic obese populations.

Clinical perspectives on vagus nerve stimulation: present and future

The vagus nerve, the great wanderer, is involved in numerous processes throughout the body and vagus nerve stimulation (VNS) has the potential to modulate many of these functions. This wide-reaching capability has generated much interest across a range of disciplines resulting in several clinical trials and studies into the mechanistic basis of VNS. This review discusses current preclinical and clinical evidence supporting the efficacy of VNS in different diseases and highlights recent advancements. Studies that provide insights into the mechanism of VNS are considered.

Toward Diverse or Standardized: A Systematic Review Identifying Transcutaneous Stimulation of Auricular Branch of the Vagus Nerve in Nomenclature

OBJECTIVES

After 20 years of development, there is confusion in the nomenclature of transcutaneous stimulation of the auricular branch of the vagus nerve (ABVN). We performed a systematic review of transcutaneous stimulation of ABVN in nomenclature.

MATERIALS AND METHODS

A systematic search of the literature was carried out, using the bibliographic search engine PubMed. The search covered articles published up until June 11, 2020. We recorded the full nomenclature and abbreviated nomenclature same or similar to transcutaneous stimulation of ABVN in the selected eligible studies, as well as the time and author information of this nomenclature.

RESULTS

From 261 studies, 67 full nomenclatures and 27 abbreviated nomenclatures were finally screened out, transcutaneous vagus nerve stimulation and tVNS are the most common nomenclature, accounting for 38.38% and 42.06%, respectively. In a total of 97 combinations of full nomenclatures and abbreviations, the most commonly used nomenclature for the combination of transcutaneous vagus nerve stimulation and tVNS, accounting for 30.28%. Interestingly, the combination of full nomenclatures and abbreviations is not always a one-to-one relationship, there are ten abbreviated nomenclatures corresponding to transcutaneous vagus nerve stimulation, and five full nomenclatures corresponding to tVNS. In addition, based on the analysis of the usage habits of nomenclature in 21 teams, it is found that only three teams have fixed habits, while other different teams or the same team do not always use the same nomenclature in their paper.

CONCLUSIONS

The phenomenon of confusion in the nomenclature of transcutaneous stimulation of ABVN is obvious and shows a trend of diversity. The nomenclature of transcutaneous stimulation of ABVN needs to become more standardized in the future.

A Qualitative Study Exploring Feasibility and Acceptability of Acupuncture, Yoga, and Mindfulness Meditation for Managing Weight After Breast Cancer

Introduction:

Weight gain is common after breast cancer. Yoga, mindfulness meditation, and acupuncture may assist with managing weight. However, evidence on effectiveness is limited. This study assessed the feasibility and acceptability of recruiting for and implementing a randomized controlled trial (RCT) evaluating these interventions as adjuncts to lifestyle interventions (diet and exercise) for weight management in women with breast cancer.

Methods:

Qualitative study involving virtual focus groups or semi-structured interviews. Participants were recruited via email invitation from a breast cancer consumer organization and breast cancer center in Australia. Eligible participants had received treatment for breast cancer, and were fluent in English. A purposive sample of culturally and linguistically diverse (CALD) participants was also recruited. Focus groups and interviews were audio-recorded, transcribed verbatim and analyzed using thematic analysis with the constant comparison method.

Results:

Emails were sent to 1415 women of which 37 provided data in 5 focus groups and 1 semi-structured interview, including 1 focus group (n = 6) with only women from CALD backgrounds. Yoga and mindfulness meditation were perceived as feasible and acceptable for weight management, but acupuncture was seen to be too invasive to be acceptable. A focus on wellness rather than weight reduction, flexible program delivery, trusted advice, consideration of participant burden and benefit, and peer-support were key factors perceived to increase feasibility and acceptability.

Conclusions:

Yoga and mindfulness meditation are acceptable and useful adjuncts to lifestyle interventions for weight management after breast cancer. This research places end-users at the forefront of trial design, and will inform future trials using these interventions for weight management and improving health and wellbeing after breast cancer.

Acute vagus nerve stimulation does not affect liking or wanting ratings of food in healthy participants

The vagus nerve plays a vital role in the regulation of food intake and vagal afferent signals may help regulate food cue reactivity by providing negative homeostatic feedback. Despite strong evidence from preclinical studies on vagal afferent "satiety" signals in guiding food intake, evidence from human studies is largely inconclusive to date. Here, we investigated the acute effects of left or right transcutaneous auricular vagus nerve stimulation (taVNS) on subjective ratings of wanting and liking of various food and non-food items in 82 healthy participants (46 women, M_BMI = 23.1 kg/m²). In contrast to previous reports in patients with depression, we found moderate to anecdotal evidence supporting the absence of taVNS-induced changes in food ratings. To test whether the absence of taVNS effects on food ratings is due to heterogeneity in the sample, we conducted post hoc subgroup analyses by splitting the data according to stimulation side and sex (between-subject factors) as well as caloric density, perceived healthiness, and flavor (sweet vs. savory) of the food (within-subject factors). This multiverse analysis largely supported the absence of taVNS-induced changes since the strongest subgroup effects provided only anecdotal evidence in favor of taVNS-induced changes. We conclude that acute taVNS only has a marginal effect on subjective ratings of food, suggesting that it is an unlikely mechanism for the reported long-term effects of VNS on body weight. In light of an absence of acute taVNS effects on conscious food liking and wanting, our results call for future research on the correspondence between acute and chronic effects of vagal afferent stimulation.

Obesity Animal Models for Acupuncture and Related Therapy Research Studies

Obesity and related diseases are considered as pandemic representing a worldwide threat for health. Animal models are critical to validate the effects and understand the mechanisms related to classical or innovative preventive and therapeutic strategies. It is, therefore, important to identify the best animal models for translational research, using different evaluation criteria such as the face, construct, and predictive validity. Because the pharmacological treatments and surgical interventions currently used for treating obesity often present many undesirable side effects, relatively high relapse probabilities, acupuncture, electroacupuncture (EA), and related therapies have gained more popularity and attention. Many kinds of experimental animal models have been used for obesity research studies, but in the context of acupuncture, most of the studies were performed in rodent obesity models. Though, are these obesity rodent models really the best for acupuncture or related therapies research studies? In this study, we review different obesity animal models that have been used over the past 10 years for acupuncture and EA research studies. We present their respective advantages, disadvantages, and specific constraints. With the development of research on acupuncture and EA and the increasing interest regarding these approaches, proper animal models are critical for preclinical studies aiming at developing future clinical trials in the human. The aim of the present study is to provide researchers with information and guidance related to the preclinical models that are currently available to investigate the outcomes of acupuncture and related therapies.

Modulation of visual processing of food by transcutaneous vagus nerve stimulation (tVNS)

Present project is concerned with the possibility to modulate the neural regulation of food intake by non-invasive stimulation of the vagus nerve. This nerve carries viscero-afferent information from the gut and other internal organs and therefore serves an important role in ingestive behavior. The electrical stimulation of the vagus nerve (VNS) is a qualified procedure in the treatment of drug-resistant epilepsy and depression. Since weight loss is a known common side effect of VNS treatment in patients with implanted devices, VNS is evaluated as a treatment of obesity. To investigate potential VNS-related changes in the cognitive processing of food-related items, 21 healthy participants were recorded in a 3-Tesla scanner in two counterbalanced sessions. Participants were presented with 72 food pictures and asked to rate how much they liked that food. Before entering the scanner subjects received a 1-h sham or verum stimulation, which was implemented transcutanously with a Cerbomed NEMOS® device. We found significant activations in core areas of the vagal afferent pathway, including left brainstem, thalamus, temporal pole, amygdala, insula, hippocampus, and supplementary motor area for the interaction between ratings (high vs low) and session (verum vs sham stimulation). Significant activations were also found for the main effect of verum compared to sham stimulation in the left inferior and superior parietal cortex. These results demonstrate an effect of tVNS on food image processing even with a preceding short stimulation period. This is a necessary prerequisite for a therapeutic application of tVNS which has to be evaluated in longer-term studies.

Vagus Nerve Stimulation with Mild Stimulation Intensity Exerts Anti-Inflammatory and Neuroprotective Effects in Parkinson's Disease Model Rats

Background: The major surgical treatment for Parkinson’s disease (PD) is deep brain stimulation (DBS), but a less invasive treatment is desired. Vagus nerve stimulation (VNS) is a relatively safe treatment without cerebral invasiveness. In this study, we developed a wireless controllable electrical stimulator to examine the efficacy of VNS on PD model rats. Methods: Adult female Sprague-Dawley rats underwent placement of a cuff-type electrode and stimulator on the vagus nerve. Following which, 6-hydroxydopamine (6-OHDA) was administered into the left striatum to prepare a PD model. VNS was started immediately after 6-OHDA administration and continued for 14 days. We evaluated the therapeutic effects of VNS with behavioral and immunohistochemical outcome assays under different stimulation intensity (0.1, 0.25, 0.5 and 1 mA). Results: VNS with 0.25–0.5 mA intensity remarkably improved behavioral impairment, preserved dopamine neurons, reduced inflammatory glial cells, and increased noradrenergic neurons. On the other hand, VNS with 0.1 mA and 1 mA intensity did not display significant therapeutic efficacy. Conclusions: VNS with 0.25–0.5 mA intensity has anti-inflammatory and neuroprotective effects on PD model rats induced by 6-OHDA administration. In addition, we were able to confirm the practicality and effectiveness of the new experimental device.

The evolving obesity challenge: targeting the vagus nerve and the inflammatory reflex in the response

Obesity and the metabolic syndrome (MetS), which have reached pandemic proportions significantly increase the risk for type 2 diabetes, cardiovascular disease, and other serious conditions. Recent data with COVID-19 patients indicate that obesity also is a significant risk factor for this novel viral disease and poor outcome of associated critical illness. These findings considerably change the view of obesity as a driver of serious, but slowly-progressing chronic diseases, and emphasize the urgency to explore new therapeutic approaches. Inflammation is a recognized driver of metabolic derangements in obesity and MetS, and a core feature of COVID-19 pathobiology. Recent advances in our understanding of inflammatory regulation have highlighted the role of the nervous system and the vagus nerve-based inflammatory reflex. Current bioelectronic and pharmacological therapeutic explorations centered on the inflammatory reflex offer new approaches for conditions characterized by immune and metabolic dysregulation and for ameliorating the escalating burden of obesity, MetS, and COVID-19.

Transcutaneous auricular vagal nerve stimulation inhibits hypothalamic P2Y1R expression and attenuates weight gain without decreasing food intake in Zucker diabetic fatty rats

Zucker diabetic fatty (ZDF) rats that harbor a mutation in the leptin receptor innately develop type 2 diabetes (T2D) with obesity. Transcutaneous auricular vagal nerve stimulation (taVNS) has an antidiabetic effect in ZDF rats. However, the underlying mechanisms of the weight-gain attenuating effect in ZDF rats by taVNS is still unclear. This study aimed to assess whether the weight-gain attenuating effect of taVNS in ZDF rats is associated with changes in the central nervous system (CNS) expression of P2Y1 receptors (P2Y1R). Adult male ZDF rats were subjected to taVNS and transcutaneous non-vagal nerve stimulation (tnVNS). Their food intake and body weight were recorded daily and weekly, respectively. P2Y1R expression in the hypothalamus, amygdala, and hippocampus was evaluated by western blotting. Hypothalamic P2Y1R expressing cells were detected using immunohistochemistry. Naïve ZDF rats were much heavier (p < 0.05) than their lean littermates (ZL rats), with elevated hypothalamic P2Y1R expression (p < 0.05). Further, taVNS but not tnVNS attenuated weight gain (p < 0.05) without decreasing food intake (p > 0.05) and suppressed hypothalamic P2Y1R expression in ZDF rats (p < 0.05). Moreover, P2Y1R showed major expression in astrocytes of ZDF rats' hypothalamus. ZDF rats innately develop obesity associated with elevated hypothalamic P2Y1R expression. taVNS attenuates weight gain in ZDF rats without changes in food intake, suggesting increased energy expenditure. Whether the reduced hypothalamic P2Y1R expression in response to taVNS is mechanistically linked to the increased energy expenditure remains to be determined.

Effects of transcutaneous vagus nerve stimulation in individuals aged 55 years or above: potential benefits of daily stimulation

Ageing is associated with attenuated autonomic function. Transcutaneous vagal nerve stimulation (tVNS) improved autonomic function in healthy young participants. We therefore investigated the effects of a single session of tVNS (studies 1 and 2) and tVNS administered daily for two weeks (study 3) in volunteers aged ≥ 55 years. tVNS was performed using modified surface electrodes on the tragus and connected to a transcutaneous electrical nerve stimulation (TENS) machine. Study 1: participants (n=14) received a single session of tVNS and sham. Study 2: all participants (n=51) underwent a single session of tVNS. Study 3: participants (n=29) received daily tVNS for two weeks. Heart rate variability and baroreflex sensitivity were derived. Quality of life (QoL), mood and sleep were assessed in study 3. tVNS promoted increases in measures of vagal tone and was associated with greater increases in baroreflex sensitivity than sham. Two weeks of daily tVNS improved measures of autonomic function, and some aspects of QoL, mood and sleep. Importantly, findings showed that improvements in measures of autonomic balance were more pronounced in participants with greater baseline sympathetic prevalence. This suggests it may be possible to identify individuals who are likely to encounter significant benefits from tVNS.

Non-invasive Auricular Vagus Nerve Stimulation as a Potential Treatment for Covid19-Originated Acute Respiratory Distress Syndrome

Background: Covid-19 is an infectious disease caused by an invasion of the alveolar epithelial cells by coronavirus 19. The most severe outcome of the disease is the Acute Respiratory Distress Syndrome (ARDS) combined with hypoxemia and cardiovascular damage. ARDS and co-morbidities are associated with inflammatory cytokine storms, sympathetic hyperactivity, and respiratory dysfunction. Hypothesis: In the present paper, we present and justify a novel potential treatment for Covid19-originated ARDS and associated co-morbidities, based on the non-invasive stimulation of the auricular branch of the vagus nerve. Methods: Auricular vagus nerve stimulation activates the parasympathetic system including anti-inflammatory pathways (the cholinergic anti-inflammatory pathway and the hypothalamic pituitary adrenal axis) while regulating the abnormal sympatho-vagal balance and improving respiratory control. Results: Along the paper (1) we expose the role of the parasympathetic system and the vagus nerve in the control of inflammatory processes (2) we formulate our physiological and methodological hypotheses (3) we provide a large body of clinical and preclinical data that support the favorable effects of auricular vagus nerve stimulation in inflammation, sympatho-vagal balance as well as in respiratory and cardiac ailments, and (4) we list the (few) possible collateral effects of the treatment. Finally, we discuss auricular vagus nerve stimulation protective potential, especially in the elderly and co-morbid population with already reduced parasympathetic response. Conclusions: Auricular vagus nerve stimulation is a safe clinical procedure and it could be either an effective treatment for ARDS originated by Covid-19 and similar viruses or a supplementary treatment to actual ARDS therapeutic approaches.

Effect of Short-Term Transcutaneous Vagus Nerve Stimulation (tVNS) on Brain Processing of Food Cues: An Electrophysiological Study

Background: The vagus nerve plays an important role in the regulation of food intake. Modulating vagal activity via electrical stimulation (VNS) in patients and animal studies caused changes in food intake, energy metabolism, and body weight. However, the moderating impact of cognitive processes on VNS effects on eating behavior has not been investigated so far.

Hypothesis: We hypothesized that transcutaneous VNS (tVNS) affects food intake by altering cognitive functions relevant to the processing of food-related information.

Methods: Using a repeated-measurement design, we applied tVNS and a sham stimulation for 2 h on two different days in normal-weight subjects. We recorded standard scalp EEG while subjects watched food and object pictures presented in an oddball task. We analyzed the event-related potentials (ERPs) P1, P2, N2, and LPP and also examined the amount of consumed food and eating duration in a free-choice test meal.

Results: Significant differences between stimulations were observed for the P1, P2, and N2 amplitudes. However, we found no tVNS-dependent modulation of food intake nor a specific food-related stimulation effect on the ERPs. Further analyses revealed a negative relationship between P2 amplitude and food intake for the sham stimulation. Significant effects are additionally confirmed by Bayesian statistics.

Conclusion: Our study demonstrates tVNS’ impact on visual processing. Since the effects were similar between food and object stimuli, a general effect on visual perceptual processing can be assumed. More detailed investigations of these effects and their relationship with food intake and metabolism seem reasonable for future studies.

Acupuncture or auricular electro-acupuncture as adjuncts to lifestyle interventions for weight management in PCOS: protocol for a randomised controlled feasibility study

BACKGROUND

Polycystic ovary syndrome (PCOS) is a prevalent women's health condition with reproductive, metabolic, and psychological manifestations. Weight loss can improve these symptoms and is a key goal; however, many women find this difficult to achieve. Acupuncture is a Chinese medical treatment that involves insertion of very fine metal needles into specific areas of the body and has been shown to be efficacious for weight loss in non-PCOS populations. However, few studies have been conducted in women with PCOS. A variant of acupuncture, auricular electro-acupuncture (AEA), may have beneficial effects on sympathetic tone, which is associated with insulin resistance, obesity and PCOS.

METHODS

This prospective three-arm open label parallel randomised controlled trial will assess feasibility and acceptability of acupuncture and/or AEA for weight loss in women with PCOS. We will enrol 39 women from the community aged between 18 and 45 years, with physician diagnosis of PCOS according to the Rotterdam criteria: body mass index (BMI) between 25 and 40 kg/m2. Women will be randomly allocated to receive one of three treatments for 12 weeks duration: body electro-acupuncture + lifestyle interventions, AEA + lifestyle interventions, or lifestyle interventions alone. The lifestyle intervention in this study is telephone-based health coaching (between 4 and 13 phone calls, depending on individual need), provided by the Get Healthy Service. Primary outcomes of the study are feasibility and acceptability of trial methods as determined by recruitment and retention rates, adherence, acceptability, credibility, and safety. Secondary outcomes include anthropometric (body weight, BMI, waist and hip circumference), metabolic (glucose tolerance and insulin sensitivity obtained from a 2-h 75 g oral glucose tolerance test with area under the curve insulin calculated using the trapezoid rule), reproductive (androgen levels, menstrual cyclicity, clinical hyperandrogenism using the Ferriman-Gallwey scoring system), autonomic (heart rate variability, blood pressure), lifestyle (physical activity levels, diet quality, weight self-efficacy), quality of life, and psychological (depression and anxiety symptoms, internal health locus of control).

DISCUSSION

This study addresses the feasibility and acceptability of novel interventions to treat overweight/obesity in PCOS. Study findings have the potential to generate a new understanding of the role of acupuncture and auricular acupuncture in weight management.

TRIAL REGISTRATION

Australian New Zealand Clinical Trial Registry, 8/6/18 ACTRN12618000975291.

Auricular acupuncture induces FNDC5/irisin and attenuates obese inflammation in mice

OBJECTIVE

To investigate whether auricular acupuncture (AA) attenuates bodyweight and obese inflammation through the release of irisin from muscle tissue in mice.

METHODS

Sixty 4-week-old mice were fed a high fat diet (HFD) for 4 weeks. These animals were divided into six groups that remained untreated (HFD) or underwent electrical AA (HFD+EAA), sham EAA (HFD+SEAA), adrenalectomy (HFD+AD), adrenalectomy and EAA (HFD+AD+EAA), or adrenalectomy and injection of recombinant lentivirus expressing fibronectin type III domain-containing protein 5 (rFNDC) (HFD+AD+rFNDC) in the ninth week. The EAA and SEAA were performed at two traditional auricular acupuncture points daily for 4 weeks. An additional 10 mice fed a control diet were included as a normal control (NC) group. At the end of the study, norepinephrine (NE) in the serum, tumour necrosis factor α (TNFα) and interleukin 1β (IL-1β) in the serum and white adipose tissue, irisin in the serum and muscle, uncoupling protein-1 (UCP-1) in the brown adipose tissue (BAT), and FNDC5 in the muscle, were analysed.

RESULTS

The AD+EAA group exhibited better control of bodyweight and inflammation compared with the AD+SEAA and untreated HFD model groups (P<0.05), especially regarding the increased expression of NE, FNDC5, irisin and UCP-1 (P<0.05). After adrenalectomy, mice receiving EAA had less NE, FNDC5, irisin and UCP-1 as well as greater expression of inflammatory cytokines and bodyweight. However, lentiviral overexpression of rFNDC successfully reversed this situation in the AD mice and mimicked the effects of EAA on bodyweight, inflammation and expression of FNDC5, irisin and UCP-1, although it did not impact NE.

CONCLUSIONS

EAA promoted NE release from the adrenal gland leading to further expression of FNDC5, irisin and UCP-1, which contributed to weight management and inflammatory inhibition.

Prevalence of and attitudes towards complementary therapy use for weight after breast cancer in Australia: a national survey

BACKGROUND

Weight gain is common after breast cancer (BC) treatment and may increase the risk of disease recurrence. Complementary medicine (CM) use is high amongst BC patients. This paper describes the use of CM from a cross-sectional self-administered survey on prevalence and management of weight after BC.

METHODS

Use of CM was assessed using a question modified from the I-CAM Questionnaire. Participants were asked to rate perceived effectiveness, advantages and disadvantages, and which CM they were willing to use for weight management if there was evidence for effectiveness. The survey was emailed to members of the Breast Cancer Network Australia Survey and Review Group, the largest consumer advocacy group in Australia for people with breast cancer.

RESULTS

There were a total of 309 responses. Three quarters had used CM in the past 12 months. One third had tried CM for weight loss. Yoga, meditation and pilates were perceived to be effective for weight loss. Perceived advantages of CMs for weight loss were the ability to improve general wellbeing, relaxation, and being non-pharmacological while disadvantages were financial cost, finding a reliable practitioner, and lack of research for effectiveness. Three quarters would be willing to try CM for weight loss if there was evidence for effectiveness, with the most popular CMs being acupuncture, relaxation, yoga, supplements, and meditation.

CONCLUSIONS

The high use of CM in this group is consistent with previous research. Our research suggests that BC survivors would use acupuncture, meditation, supplements and yoga for weight loss if supported by scientifically-credible evidence. Research into the effectiveness of these treatments on weight loss after BC is warranted.

Identification of Suitable Reference Genes for Quantitative Gene Expression Analysis in Innervated and Denervated Adipose Tissue from Cafeteria Diet-Fed Rats

Our previous studies show that cafeteria diet increases body adiposity, plasma insulin levels, and sympathetic activity to brown adipose tissue (BAT) and white adipose tissue (WAT) of Wistar rats, leading to rapid and progressive changes in the metabolic profile. The identification of suitable reference genes that are not affected by the experimental conditions is a critical step in accurate normalization of the reverse transcription quantitative real-time PCR (qRT-PCR), a commonly used assay to elucidate changes in the gene expression profile. In the present study, the effects of the cafeteria diet and sympathetic innervation on the gene expression of adrenoceptor beta 3 (Adrb3) from BAT and WAT were assessed using one of the most stable and one of the least stable genes as normalizers. Rats were fed the cafeteria diet and on the 17th day, interscapular BAT or retroperitoneal WAT was denervated and, 7 days after surgery, the contralateral innervated tissue was used as control. Ten reference genes were evaluated (18S, B2m, Actb, CypA, Gapdh, Hprt1, Rpl32, Tbp, Ubc, and Ywhaz) and ranked according to their stability using the following algorithms: geNorm, NormFinder, BestKeeper, and comparative delta threshold cycle (ΔC _t ) method. According to the algorithms employed, the normalization of Adrb3 expression by the least stable genes produced opposite results compared with the most stable genes and literature data. In cafeteria and control diet-fed rats, the three most stable genes were Hprt1, Tbp, and Rpl32 for interscapular BAT and Tbp, B2m, and Hprt1 for retroperitoneal WAT, while the least stable genes were 18S, Actb, and Gapdh for both tissues.

Current Directions in the Auricular Vagus Nerve Stimulation I - A Physiological Perspective

Electrical stimulation of the auricular vagus nerve (aVNS) is an emerging technology in the field of bioelectronic medicine with applications in therapy. Modulation of the afferent vagus nerve affects a large number of physiological processes and bodily states associated with information transfer between the brain and body. These include disease mitigating effects and sustainable therapeutic applications ranging from chronic pain diseases, neurodegenerative and metabolic ailments to inflammatory and cardiovascular diseases. Given the current evidence from experimental research in animal and clinical studies we discuss basic aVNS mechanisms and their potential clinical effects. Collectively, we provide a focused review on the physiological role of the vagus nerve and formulate a biology-driven rationale for aVNS. For the first time, two international workshops on aVNS have been held in Warsaw and Vienna in 2017 within the framework of EU COST Action "European network for innovative uses of EMFs in biomedical applications (BM1309)." Both workshops focused critically on the driving physiological mechanisms of aVNS, its experimental and clinical studies in animals and humans, in silico aVNS studies, technological advancements, and regulatory barriers. The results of the workshops are covered in two reviews, covering physiological and engineering aspects. The present review summarizes on physiological aspects - a discussion of engineering aspects is provided by our accompanying article (Kaniusas et al., 2019). Both reviews build a reasonable bridge from the rationale of aVNS as a therapeutic tool to current research lines, all of them being highly relevant for the promising aVNS technology to reach the patient.

Effect of auriculotherapy and intervention types on weight control: A systematic review and meta-analysis protocol

BACKGROUND

Overweight and obesity characterized by abnormal or excessive fat accumulation, can cause many complications. Auriculotherapy, as the traditional Chinese technique, is widely applied in clinical trials for the management of body weight. The program aims to evaluate the effect and safety of auriculotherapy therapy and intervention types on weight control.

METHODS

All randomized controlled trials related to auriculotherapy targeting overweight and obesity will be searched in online databases, such as Medline, EMbase, Cochrane Central Register of Controlled Trials, AMED, CBM, Wanfang Data, and other databases from their inception to July 2019. The primary outcome is the difference in BMI from baseline to the end of studies. Secondary outcomes include the change of weight, percentage of body fat, waist circumference, serum lipid before and after treatment. Study selection, data extraction, and assessment of risk of bias will be performed independently by 2 reviewers. Comprehensive Meta-Analysis software (Version 3; Biostat Inc.) will be used for data synthesis.

RESULTS

This study will provide a comprehensive review of the available evidence for the treatment of obesity with auriculotherapy.

CONCLUSION

The conclusion of this study will provide evidence to judge whether auriculotherapy is an effective therapeutic intervention for obesity.

PROSPERO REGISTRATION NUMBER

CRD42019136827.

Effectiveness of Acupuncture in Treatment of Simple Obesity in Animal Models: A Systematic Review and Meta-Analysis

BACKGROUND

Simple obesity has become a global risk to health of human beings. Acupuncture, as one of traditional Chinese medicine therapies, has been widely used in obesity treatment in recent years. However, the individual heterogeneity which makes acupuncture's efficiency unstable leads to some controversy. So more evidence-based results are necessary to judge the effectiveness of acupuncture in treatment of simple obesity. Compared with clinical trials, animal experiments are controllable, and the underlying mechanism is more likely to be explored. Last but not the least, more and more experimental studies on acupuncture for animal obesity have been published. Therefore, we conducted the systematic review and meta-analysis to evaluate the effectiveness of acupuncture in treating simple obesity in animal experiments.

METHODS

Randomized Controlled Trials (RCTs) on acupuncture for simple obesity animal models were searched from six databases: PubMed, MEDLINE, CNKI, VIP, WanFang Date, and CMB from inception to February 2017 and updated on April 12, 2019. RevMan 5.3 software was used for meta-analysis. Treatment effects were summarized as relative risk (RR) and Standard mean difference (SMD) with 95% of confidence interval (CI).

RESULTS

A total of 108 trials involving 5731 rats were included. Meta-analysis showed that acupuncture had better effect on reducing weight (SMD -2.60, 95%CI: -2.93 to -2.26, p<0.00001) and Lee's index (SMD -2.62, 95%CI:-3.18 to -2.06, p<0.00001) compared with control group. However, the methodological quality of included studies was generally poor. Details of blinding were not reported in most studies. In spite of high heterogeneity being observed on the merged data, sensitivity analysis using the leave-one-out approach, subgroup analysis based on different acupuncture techniques, and rat strains and meta-regression all failed to find the sources of heterogeneity. The asymmetric funnel plot suggested publication bias. Besides, adverse events were not reported in any reports.

CONCLUSIONS

Our review provided positive evidence of acupuncture for simple obesity. Unfortunately, none of the firm conclusions can be drawn due to methodological flaws, high heterogeneity, and publication bias. More high-quality trials are needed in future to get objective conclusions.

Vagal mechanisms as neuromodulatory targets for the treatment of metabolic disease

With few effective treatments available, the global rise of metabolic diseases, including obesity, type 2 diabetes mellitus, and cardiovascular disease, seems unstoppable. Likely caused by an obesogenic environment interacting with genetic susceptibility, the pathophysiology of obesity and metabolic diseases is highly complex and involves crosstalk between many organs and systems, including the brain. The vagus nerve is in a key position to bidirectionally link several peripheral metabolic organs with the brain and is increasingly targeted for neuromodulation therapy to treat metabolic disease. Here, we review the basics of vagal functional anatomy and its implications for vagal neuromodulation therapies. We find that most existing vagal neuromodulation techniques either ignore or misinterpret the rich functional specificity of both vagal efferents and afferents as demonstrated by a large body of literature. This lack of specificity of manipulating vagal fibers is likely the reason for the relatively poor beneficial long‐term effects of such therapies. For these therapies to become more effective, rigorous validation of all physiological endpoints and optimization of stimulation parameters as well as electrode placements will be necessary. However, given the large number of function‐specific fibers in any vagal branch, genetically guided neuromodulation techniques are more likely to succeed.

Complementary Medicine Therapies That May Assist With Weight Loss: A Narrative Review

Objective

The purpose of this study was to review the potential effects of traditional Chinese medicine-which includes acupuncture; electroacupuncture; plum blossom needle hammer; auricular acupuncture; herbs that balance hormones, regulate neurotransmitters, induce sedative effects, and increase thermogenesis; and functional foods that can suppress the appetite-as an adjunct therapy for weight loss.

Methods

A narrative review of the current literature was performed using searches of MEDLINE and 4 scholarly texts. The inclusion criteria for the review consisted of studies that were performed from 2005 to 2016.

Results

In general, some traditional Chinese medicine modalities claim to promote weight loss. Acupuncture, electroacupuncture, and herbs aim to reduce stress-related food cravings. These therapeutic approaches aim to downregulate dopamine and leptin levels, suppressing the appetite. Other attributes of these therapies are increasing uncoupling protein-1 activity promoting thermogenesis, which contributes to weight loss. In addition, acupuncture, electroacupuncture, and Cimicifuga racemosa may regulate estrogen, which could attenuate the appetite, assisting in weight-loss programs.

Conclusion

The literature reviewed includes information that describes how traditional Chinese medicine, herbal medicine, or functional foods as adjunct therapies may be beneficial for weight-loss programs.

Body thermal responses and the vagus nerve

While thermosensation from external environment has been extensively studied, physiological responses to temperature changes inside the body and the underlying regulatory mechanisms are less understood. As a critical link between body and brain that relays visceral organ information and regulates numerous physiological functions, the vagus nerve has been proposed to mediate diverse visceral thermal reflexes and indirectly regulate body temperature. However, the precise role of the vagus nerve in body thermal responses or visceral organ-related thermoregulation is still under debate due to extensive contradictory results. This data discrepancy is likely due to the high cell heterogeneity in the vagus nerve, as diverse vagal neuron types mediate numerous and sometimes opposite physiological functions. Here, we will review evidences that support and against the role of the vagus nerve in body thermosensation and thermoregulation and discuss potential future approaches for better understanding of this critical issue.

Electric stimulation of ears accelerates body weight loss mediated by high-fat to low-fat diet switch accompanied by increased white adipose tissue browning in C57BL/6 J mice

Background

Weight reduction frequently occurs in patients receiving vagus nerve stimulation (VNS) therapy. Therefore, we hypothesized that during dietary intervention for weight loss, auricular electric stimulation (AES), an alternative of VNS, accelerates weight loss by increasing white adipose tissue (WAT) browning and increases energy expenditure.

Methods

C57BL/6J male mice were fed a high-fat diet for 5 wk. to induce obesity, then switched to a low-fat diet for 5 wk. and allocated into 3 groups to receive 2 Hz electric stimulation on ears, electrode clamps only, or nothing (AES, Sham and Ctrl, respectively).

Results

Switching to a low-fat diet reduced body weight progressively in all 3 groups, with the greatest reduction in the AES group. In accordance with a mild decrease in feed intake, hypothalamus mRNA levels of Npy, AgRP tended to be reduced, while Pomc tended to be increased by AES. Mice in the AES group had the highest concentrations of norepinephrine in serum and inguinal WAT, and expression levels of uncoupling protein-1 (UCP-1) and tyrosine hydroxylase in inguinal WAT. Furthermore, their subcutaneous adipocytes had multilocular and UCP-1⁺ characteristics, along with a smaller cell size.

Conclusion

AES, by increasing WAT browning, could be used in conjunction with a low-fat diet to augment weight loss in addition to suppressing appetite.

Feasibility and acceptability of a proposed trial of acupuncture as an adjunct to lifestyle interventions for weight loss in Polycystic Ovary Syndrome: a qualitative study

BACKGROUND

Polycystic Ovary Syndrome (PCOS) is a common female reproductive disorder with multiple manifestations. Weight management is a key therapeutic goal. Acupuncture is a potential adjunctive weight loss treatment in non-PCOS populations. We aimed to engage patients in co-design and assess the feasibility and acceptability of methods for a randomised controlled trial (RCT) on acupuncture and telephone-based health coaching for weight management in overweight or obese women with PCOS using qualitative methods.

METHODS

We recruited women who had PCOS and were aged 18-45 years and with a body mass index of 25 kg/m² and over, using social media. Two face-to-face focus group meetings and three semi-structured telephone interviews were conducted (n = 10). We analysed data using thematic analysis and aimed to compare and contrast motivations for joining the trial between women who were actively trying to conceive (n = 7) and not trying to conceive (n = 3). Attitudes to, knowledge and experiences of acupuncture; perceptions and attitudes towards the interventions in the RCT (real acupuncture, sham acupuncture and telephone-based health coaching); the outcomes of importance; and barriers and facilitators to successful trial recruitment and retention were collected.

RESULTS

Women were both acupuncture-naive and acupuncture-experienced. Overall, attitudes towards acupuncture were positive, and the trial design was acceptable with appointment flexibility requested. Ideal enrolment time, if women were trying to conceive, was six months prior to conception. Women supported three-month intervention and the use of sham acupuncture as a control. Financial incentives were not believed to be necessary, and women spoke of altruistic intentions in enrolling for such a trial. Women who were trying to conceive voiced a need for support from their family, health coaches, and peers. The telephone-based health coaching offered welcome support and accountability, noted as possible facilitators of weight loss.

CONCLUSIONS

Our findings show that acupuncture is a likely acceptable adjunct to lifestyle interventions for weight loss in PCOS, and that a sham-controlled trial is feasible and acceptable to PCOS women. Further research is required in order to evaluate the efficacy of acupuncture together with lifestyle for weight management in PCOS.

Vagal afferent activation decreases brown adipose tissue (BAT) sympathetic nerve activity and BAT thermogenesis

In urethane/α-chloralose anesthetized rats, electrical stimulation of cervical vagal afferent fibers inhibited the increases in brown adipose tissue sympathetic nerve activity and brown adipose tissue thermogenesis evoked by cold exposure, by nanoinjection of the GABA_A receptor antagonist, bicuculline, in the dorsomedial hypothalamus, and by nanoinjection of N-methyl-D-aspartate in the rostral raphe pallidus. Vagus nerve stimulation-evoked inhibition of brown adipose tissue sympathetic nerve activity was prevented by blockade of ionotropic glutamate receptors in the termination site of vagal afferents in the nucleus of the solitary tract, and by nanoinjection of GABA_A receptor antagonists in the rostral raphe pallidus. In conclusion, the brown adipose tissue sympathoinhibitory effect of cervical afferent vagal nerve stimulation is mediated by glutamatergic activation of second-order sensory neurons in the nucleus of the solitary tract and by a GABAergic inhibition of brown adipose tissue sympathetic premotor neurons in the rostral raphe pallidus, but does not require GABAergic inhibition of the brown adipose tissue sympathoexcitatory neurons in the dorsomedial hypothalamus.

Novel developments in vagal afferent nutrient sensing and its role in energy homeostasis

Vagal afferent neurons (VANs) play an important role in the control of food intake by signaling nutrient type and quantity to the brain. Recent findings are broadening our view of how VANs impact not only food intake but also energy homeostasis. This review focuses exclusively on studies of the vagus nerve from the past 2 years that highlight major new advancements in the field. We firstly discuss evidence that VANs can directly sense nutrients, and we consider new insights into mechanisms affecting sensing of gastric distension and signaling by gastrointestinal hormones ghrelin and GLP1. We discuss evidence that disrupting vagal afferent signaling increases long-term control of food intake and body weight management, and the importance of this gut-brain pathway in mediating beneficial effects of bariatric surgery. We conclude by highlighting novel roles for vagal afferent neurons in circadian rhythm, thermogenesis, and reward that may provide insight into mechanisms by which VAN nutrient sensing controls long-term control of energy homeostasis.

Role of the vagus nerve in the development and treatment of diet-induced obesity

This review highlights evidence for a role of the vagus nerve in the development of obesity and how targeting the vagus nerve with neuromodulation or pharmacology can be used as a therapeutic treatment of obesity. The vagus nerve innervating the gut plays an important role in controlling metabolism. It communicates peripheral information about the volume and type of nutrients between the gut and the brain. Depending on the nutritional status, vagal afferent neurons express two different neurochemical phenotypes that can inhibit or stimulate food intake. Chronic ingestion of calorie-rich diets reduces sensitivity of vagal afferent neurons to peripheral signals and their constitutive expression of orexigenic receptors and neuropeptides. This disruption of vagal afferent signalling is sufficient to drive hyperphagia and obesity. Furthermore neuromodulation of the vagus nerve can be used in the treatment of obesity. Although the mechanisms are poorly understood, vagal nerve stimulation prevents weight gain in response to a high-fat diet. In small clinical studies, in patients with depression or epilepsy, vagal nerve stimulation has been demonstrated to promote weight loss. Vagal blockade, which inhibits the vagus nerve, results in significant weight loss. Vagal blockade is proposed to inhibit aberrant orexigenic signals arising in obesity as a putative mechanism of vagal blockade-induced weight loss. Approaches and molecular targets to develop future pharmacotherapy targeted to the vagus nerve for the treatment of obesity are proposed. In conclusion there is strong evidence that the vagus nerve is involved in the development of obesity and it is proving to be an attractive target for the treatment of obesity.