Vagal blocking improves glycemic control and elevated blood pressure in obese subjects with type 2 diabetes mellitus

Malignant tumors in vagal-innervated organs: Exploring its homeostatic role

Cancer remains a significant global health challenge, with its progression shaped by complex and multifactorial mechanisms. Recent research suggests that the vagus nerve could play a critical role in mediating communication between the tumor microenvironment and the central nervous system (CNS). This review highlights the diversity of vagal afferent receptors, which could position the vagus nerve as a unique pathway for transmitting immune, metabolic, mechanical, and chemical signals from tumors to the CNS. Such signaling could influence systemic disease progression and tumor-related responses. Additionally, the vagus nerve's interactions with the microbiome and the renin-angiotensin system (RAS)-both implicated in cancer biology-further underscore its potential central role in modulating tumor-related processes. Contradictions in the literature, particularly concerning vagal fibers, illustrate the complexity of its involvement in tumor progression, with both tumor-promoting and tumor-suppressive effects reported depending on cancer type and context. These contradictions often overlook certain experimental biases, such as the failure to distinguish between vagal afferent and efferent fibers during vagotomies or the localized parasympathetic effects that cannot always be extrapolated to the systemic level. By focusing on the homeostatic role of the vagus nerve, understanding these mechanisms could open the door to new perspectives in cancer research related to the vagus nerve and lead to potential therapeutic innovations.

Recent advances in targeting obesity, with a focus on TGF-β signaling and vagus nerve innervation

Over a third of the global population is affected by obesity, fatty liver disease (Metabolic Dysfunction-Associated Steatotic Liver Disease, MASLD), and its severe form, MASH (Metabolic Dysfunction-Associated Steatohepatitis), which can ultimately progress to hepatocellular carcinoma (HCC). Recent advancements include therapeutics such as glucagon-like peptide 1 (GLP-1) agonists and neural/vagal modulation strategies for these disorders. Among the many pathways regulating these conditions, emerging insights into transforming growth factor-β (TGF-β) signaling highlight potential future targets through its role in pathophysiological processes such as adipogenesis, inflammation, and fibrosis. Vagus nerve innervation in the gastrointestinal tract is involved in satiety regulation and energy homeostasis, and vagus nerve stimulation has been applied in weight loss and diabetes. This review explores clinical trials in obesity, novel therapeutic targets, and the role of TGF-β signaling and vagus nerve modulation in obesity-related liver diseases and HCC.

Vagal Splenic-Dependent Effects Influence Glucose Homeostasis, Insulin Secretion, and Histopathology of the Endocrine Pancreas in Hypothalamic Obese Male Rats: Vagus Nerve and Spleen Interactions Affect the Endocrine Pancreas

Vagus nerve (VN) and spleen dysfunctions are often associated with obesity (Ob). Aim: We evaluated the effects of VN and spleen ablation on adiposity, metabolism, and insulin secretion in hypothalamic obese male rats. Methods: Ob was induced by neonatal subcutaneous injection of monosodium glutamate (4 g/kg). At 60 days of life, Ob animals were randomly distributed into four groups (n = 16 rats/group): sham operation (SHAM), vagotomy (VAG), splenectomy (SPL), and VAG + SPL. Body weight and food intake were monitored for 8 weeks postsurgery. Intraperitoneal glucose tolerance test (ipGTT) and intraperitoneal pyruvate tolerance test (ipPTT) were performed at 148 days of life, and VN activity was recorded at 150 days. After euthanasia (150 days), adiposity, plasma biochemical parameters, glucose-induced insulin secretion (GIIS), and cholinergic and adrenergic islet responsiveness were evaluated. The pancreas was submitted for histopathological analysis, and the protein content of OXPHOS and IL-10 was evaluated in isolated pancreatic islets. Results: Decreased VN activity was confirmed in the Ob-VAG groups, associated with lower visceral adiposity, triglycerides, and plasma insulin, together with improved insulin sensibility and pyruvate tolerance, compared to Ob-SHAM rats. Spleen absence reduced VN activity and cholinergic insulinotropic responses, with deleterious effects on the endocrine pancreas. Furthermore, Ob-VAG + SPL rats presented greater reductions in GIIS and more severe endocrine pancreas histopathology, compared to the Ob-SHAM group, without altered islet size or number or protein content of OXPHOS or IL-10. Conclusion: Vagal and splenic interactions contribute to glucose homeostasis control in hypothalamic obese rats, modulating insulin secretion and pancreas histology.

Possible Glycemic Effects of Vagus Nerve Stimulation Evaluated by Continuous Glucose Monitoring in People with Diabetes and Autonomic Neuropathy: A Randomized, Sham-Controlled Trial

Objective: Autonomic neuropathy is associated with dysglycemia that is difficult to control. We investigated if transcutaneous vagus nerve stimulation (tVNS) could improve glycemic levels. Methods: We randomized 145 individuals with type 1 diabetes (T1D) (n = 70) or type 2 diabetes (T2D) (n = 75) and diabetic autonomic neuropathy (DAN) to self-administered treatment with active cervical tVNS (n = 68) or sham (n = 77) for 1 week (4 daily stimulations) and 8 weeks (2 daily stimulations), separated by a wash-out period of at least 2 weeks. Continuous glucose monitoring (CGM) indices were measured for 104 participants starting 5 days prior to intervention periods, during the 1-week period, and at end of the 8-week period. Primary outcomes were between-group differences in changes in coefficient of variation (CV) and in time in range (TIR 3.9-10 mmol/L). Secondary outcomes were other metrics of CGM and HbA1c. Results: For the 1-week period, median [interquartile range] changes of CV from baseline to follow-up were -1.1 [-4.3;2.0] % in active and -1.5 [-4.4;2.5] % in sham, with no significance between groups (P = 0.54). For TIR, the corresponding changes were 2.4 [-2.1;7.4] % in active and 5.1 [-2.6;8.8] in sham group (P = 0.84). For the 8-week treatment period, changes in CV and TIR between groups were also nonsignificant. However, in the subgroup analysis, persons with T1D receiving active tVNS for 8 weeks had a significant reduction in CV compared with the T1D group receiving sham stimulation (estimated treatment effect: -11.6 [95% confidence interval -20.2;-2.0] %, P = 0.009). None of the changes in secondary outcomes between treatment groups were significantly different. Conclusions: Overall, no significant changes were observed in CGM metrics between treatment arms, while individuals with T1D and DAN decreased their CV after 8 weeks of tVNS treatment.

Vagus nerve stimulation (VNS): recent advances and future directions

PURPOSE

Vagus nerve stimulation (VNS) is emerging as a unique and potent intervention, particularly within neurology and psychiatry. The clinical value of VNS continues to grow, while the development of noninvasive options promises to change a landscape that is already quickly evolving. In this review, we highlight recent progress in the field and offer readers a glimpse of the future for this bright and promising modality.

METHODS

We compiled a narrative review of VNS literature using PubMed and organized the discussion by disease states with approved indications (epilepsy, depression, obesity, post-stroke motor rehabilitation, headache), followed by a section highlighting novel, exploratory areas of VNS research. In each section, we summarized the current role, recent advancements, and future directions of VNS in the treatment of each disease.

RESULTS

The field continues to gain appreciation for the clinical potential of this modality. VNS was initially developed for treatment-resistant epilepsy, with the first depression studies following shortly thereafter. Overall, VNS has gained approval or clearance in the treatment of medication-refractory epilepsy, treatment-resistant depression, obesity, migraine/cluster headache, and post-stroke motor rehabilitation.

CONCLUSION

Noninvasive VNS represents an opportunity to bridge the translational gap between preclinical and clinical paradigms and may offer the same therapeutic potential as invasive VNS. Further investigation into how VNS parameters modulate behavior and biology, as well as how to translate noninvasive options into the clinical arena, are crucial next steps for researchers and clinicians studying VNS.

Spinal afferent neurons: emerging regulators of energy balance and metabolism

Recent advancements in neurophysiology have challenged the long-held paradigm that vagal afferents serve as the primary conduits for physiological signals governing food intake and energy expenditure. An expanding body of evidence now illuminates the critical role of spinal afferent neurons in these processes, necessitating a reevaluation of our understanding of energy homeostasis regulation. This comprehensive review synthesizes cutting-edge research elucidating the multifaceted functions of spinal afferent neurons in maintaining metabolic equilibrium. Once predominantly associated with nociception and pathological states, these neurons are now recognized as integral components in the intricate network regulating feeding behavior, nutrient sensing, and energy balance. We explore the role of spinal afferents in food intake and how these neurons contribute to satiation signaling and meal termination through complex gut-brain axis pathways. The review also delves into the developing evidence that spinal afferents play a crucial role in energy expenditure regulation. We explore the ability of these neuronal fibers to carry signals that can modulate feeding behavior as well as adaptive thermogenesis in adipose tissue influencing basal metabolic rate, and thereby contributing to overall energy balance. This comprehensive analysis not only challenges existing paradigms but also opens new avenues for therapeutic interventions suggesting potential targets for treating metabolic disorders. In conclusion, this review highlights the need for a shift in our understanding of energy homeostasis, positioning spinal afferent neurons as key players in the intricate web of metabolic regulation.

The Ablation of Sensory Neurons Expressing the Nav1.8 Sodium Channel Improves Glucose Homeostasis and Amplifies the GLP-1 Signaling in Obese Female Mice

SCOPE

Sensory neurons expressing the sodium channel Nav1.8 contain a repertoire of receptors for nutrient, hormonal, and inflammatory ligands. However, their function in key regulators of energy homeostasis control is not well understood and is completely unexplored in females.

METHODS AND RESULTS

Mice lacking neurons expressing the sodium channel Nav1.8 were generated using an ablation strategy based on cre recombinase-mediated expression of diphtheria toxin fragment A (DTA) (Nav1.8-cre/DTA mice) to investigate whether these neurons modulate body weight, food intake, gut hormone secretion, gastrointestinal transit, and glucose tolerance in response to nutrient challenges in a sex-dependent manner. Male Nav1.8-cre/DTA mice show resistance to gain weight in response to high-fat high-sugar diet (HFHSD), whereas females lacking Nav1.8+ neurons have improved oral glucose tolerance accompanied by higher insulin levels and attenuated glucagon secretion after an oral glucose load. Female Nav1.8-cre/DTA mice also show higher fasting and postprandial glucagon like peptide-1 (GLP-1) levels with an increased number of GLP-1-positive cells. Finally, ablation of Nav1.8-expressing neurons accelerates the gastrointestinal transit in female mice under HFHSD.

CONCLUSION

This data demonstrates sex-dependent differences in the Nav1.8-mediated regulation of energy metabolism, and provides new insights that may help in the design of sex-specific neuromodulation therapies for metabolic disorders induced by diets rich in fats and simple sugars.

Vagal Nerve Therapy in the Management of Obesity: A Systematic Review and Meta-Analysis

INTRODUCTION

The vagus nerve has an important role in satiety, metabolism, and autonomic control in upper gastrointestinal function. However, the role and effects of vagal nerve therapy on weight loss remain controversial. This systematic review and meta-analysis assessed the effects of vagal nerve therapy on weight loss, body mass index (BMI), and obesity-related conditions.

METHODS

MEDLINE, EMBASE, and CINAHL databases were searched for studies up to April 2022 that reported on percentage excess weight loss (%EWL) or BMI at 12 months or remission of obesity-related conditions following vagal nerve therapy from January 2000 to April 2022. Weighted mean difference (WMD) was calculated, meta-analysis was performed using random-effects models, and between-study heterogeneity was assessed.

RESULTS

Fifteen studies, of which nine were randomised controlled trials, of 1,447 patients were included. Vagal nerve therapy led to some improvement in %EWL (WMD 17.19%; 95% confidence interval [CI]: 10.94-23.44; p < 0.001) and BMI (WMD -2.24 kg/m2; 95% CI: -4.07 to -0.42; p = 0.016). There was a general improvement found in HbA1c following vagal nerve therapy when compared to no treatment given. No major complications were reported.

CONCLUSIONS

Vagal nerve therapy can safely result in a mild-to-moderate improvement in weight loss. However, further clinical trials are required to confirm these results and investigate the possibility of the long-term benefit of vagal nerve therapy as a dual therapy combined with standard surgical bariatric interventions.

Stimulation parameters for directional vagus nerve stimulation

BACKGROUND

Autonomic nerve stimulation is used as a treatment for a growing number of diseases. We have previously demonstrated that application of efferent vagus nerve stimulation (eVNS) has promising glucose lowering effects in a rat model of type 2 diabetes. This paradigm combines high frequency pulsatile stimulation to block nerve activation in the afferent direction with low frequency stimulation to activate the efferent nerve section. In this study we explored the effects of the parameters for nerve blocking on the ability to inhibit nerve activation in the afferent direction. The overarching aim is to establish a blocking stimulation strategy that could be applied using commercially available implantable pulse generators used in the clinic.

METHODS

Male rats (n = 20) had the anterior abdominal vagus nerve implanted with a multi-electrode cuff. Evoked compound action potentials (ECAP) were recorded at the proximal end of the electrode cuff. The efficacy of high frequency stimulation to block the afferent ECAP was assessed by changes in the threshold and saturation level of the response. Blocking frequency and duty cycle of the blocking pulses were varied while maintaining a constant 4 mA current amplitude.

RESULTS

During application of blocking at lower frequencies (≤ 4 kHz), the ECAP threshold increased (ANOVA, p < 0.001) and saturation level decreased (p < 0.001). Application of higher duty cycles (> 70%) led to an increase in evoked neural response threshold (p < 0.001) and a decrease in saturation level (p < 0.001). During the application of a constant pulse width and frequency (1 or 1.6 kHz, > 70% duty cycle), the charge delivered per pulse had a significant influence on the magnitude of the block (ANOVA, p = 0.003), and was focal (< 2 mm range).

CONCLUSIONS

This study has determined the range of frequencies, duty cycles and currents of high frequency stimulation that generate an efficacious, focal axonal block of a predominantly C-fiber tract. These findings could have potential application for the treatment of type 2 diabetes.

Prevalence of excess weight and associated socio-demographic factors among postmenopausal women: A population-based study in Ghana

BACKGROUND

Excess weight (obesity and overweight) is a pervasive condition that is considered a global epidemic and a threat to public health. Furthermore, numerous changes in fat deposits occur with the advent of menopause, leading to a change in the distribution of body fat. Knowledge of sociodemographic factors and prevalence can inform the effective management of these women.

AIM

This study aimed to investigate the prevalence of excess weight among postmenopausal women in Ghana's Bono East (Techiman) region.

SETTING

This study was conducted in Bono East regional capital, Techiman, Ghana.

METHODS

This is a cross-sectional study conducted over 5 months at Bono East regional capital, Techiman in Ghana. Anthropometric parameters such as body mass index (BMI), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) were obtained using physical measurements while socio-demographic data were gathered using questionnaires. Data analysis was performed using IBM SPSS 25.

RESULTS

The mean age of the 378 women who participated in the study was 60.09 ± 6.24 years. Body mass index, WHtR and WHR indicated excess weight of 73.2%, 91.8% and 91.0%, respectively. Education and ethnicity were predictors of excess weight (WHR). Women of the Ga tribe with high school education have 4.7- and 8.6-times increased odds of having excess weight.

CONCLUSIONS

There are higher prevalence rates of excess weight (obesity and overweight) among postmenopausal women using BMI, WHtR and WHR. Education and ethnicity are predictors of excess weight.Contribution: The study's findings can be used to develop interventions that focus on addressing excess weight in postmenopausal women within the Ghanaian context.

Metabolic effects of truncal vagotomy when combined with bariatric-metabolic surgery

Bariatric-metabolic surgery (BMS) in patients with obesity frequently leads to remission of concurrent type 2 diabetes mellitus (T2DM), even before body weight loss takes place. This is probably based on the correction of a dysmetabolic cycle in the gastrointestinal physiology of T2DM that includes increased vagus-dependent exocrine pancreatic secretion (EPS) and, hence, amplified digestion and nutrient absorption. The resultant chronic exposure of tissues to high plasma levels of glucose, fatty acids and amino acids causes tissue resistance to the actions of insulin and, at a later stage, β-cell dysfunction and reduction of insulin release. We hypothesize that the addition of a surgical truncal vagotomy (TV) may improve and solidify the beneficial results of BMS on T2DM by stably decreasing EPS, - hence reducing the digestion and absorption of nutrients -, and increasing incretin secretion as a result of increased delivery of unabsorbed nutrients to the distal intestine. This hypothesis is supported by surgical data from gastrointestinal malignancies and peptic ulcer operations that include TV, as well as by vagal blockade studies. We suggest that TV may result in a stable reduction of EPS, and that its combination with the appropriate type of BΜS, may enhance and sustain the salutary effects of the latter on T2DM.

Impact of Vagotomy on Postoperative Weight Loss, Alimentary Intake, and Enterohormone Secretion After Bariatric Surgery in Experimental Translational Models

Obesity may be treated by bariatric procedures and is related to enterohormone release modulation. Nevertheless, a majority of commonly used surgical procedures have a significant impact on vagus nerve function by breaking the connections with its gastric branches. In the case of an intragastric balloon (BAL), this interaction is unclear. However, BAL-induced weight reduction is not long-lasting. Interestingly, this method has not been used in combination with vagotomy (VAG). Thus, we evaluated, for the first time, the short- and long-term effects of combined BAL and VAG using the animal-based translational model and compared these effects with sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). Wistar rats were fed a high-calorie diet for 8 weeks to induce obesity before SG, RYGB, BAL + / - VAG. Animals' weight and eating behaviors were monitored weekly. After 90 days, serum samples were collected to evaluate postprandial and fasting GLP-1, GIP, PYY, ghrelin, glucagon, insulin, leptin, and pancreatic polypeptide concentrations by fluorescent assay. VAG, SG, RYGB, and BAL + VAG significantly reduced body weight 30 and 90 days after surgery. BAL alone induced temporal weight reduction observed after 30 days, reversed after 90 days. Calories intake was reduced at the first half of the observation period in all groups. Fluid intake was reduced in all groups except SG and BAL. Enterohormone profile for BAL + VAG was comparable to SG and RYGB but not BAL. VAG and BAL + VAG but not BAL alone maintain weight reduction, alimentary intake changes, and enterohormone release after long-term observation. VAG may improve the effectiveness of bariatric procedures for obesity treatment in clinical practice.

Molecular mechanisms linking stress and insulin resistance

To date, there is ample evidence to support the strong relationship between stress and insulin resistance. While diabetes mellitus acts as a potent stress inducer, stress may be an upstream event for insulin resistance as well. It is widely recognized that diabetes mellitus is more prevalent among people who have a stressful lifestyle; however, the underlying mechanisms are not well understood. In the current study, we surveyed the scientific literature for possible interactions between stress and insulin resistance and found that stress can impair glucose homeostasis, working through at least six molecular pathways.

Central Nervous System Control of Glucose Homeostasis: A Therapeutic Target for Type 2 Diabetes?

Historically, pancreatic islet beta cells have been viewed as principal regulators of glycemia, with type 2 diabetes (T2D) resulting when insulin secretion fails to compensate for peripheral tissue insulin resistance. However, glycemia is also regulated by insulin-independent mechanisms that are dysregulated in T2D. Based on evidence supporting its role both in adaptive coupling of insulin secretion to changes in insulin sensitivity and in the regulation of insulin-independent glucose disposal, the central nervous system (CNS) has emerged as a fundamental player in glucose homeostasis. Here, we review and expand upon an integrative model wherein the CNS, together with the islet, establishes and maintains the defended level of glycemia. We discuss the implications of this model for understanding both normal glucose homeostasis and T2D pathogenesis and highlight centrally targeted therapeutic approaches with the potential to restore normoglycemia to patients with T2D.

Impact of the Hepatic Branch of the Vagus Nerve Transection in Laparoscopic Sleeve Gastrectomy for Patients with Obesity and Type 2 Diabetes Mellitus

BACKGROUND

An increase in gastroesophageal reflux disease (GERD) after laparoscopic sleeve gastrectomy (LSG) has been reported, and concomitant hiatal hernia repair (HHR) during LSG is expected to reduce the incidence of post-LSG GERD. In HHR, the hepatic branch of the vagus nerve is anatomically transected. Recent experimental animal models suggest that vagotomy may affect glycemic control and weight loss through a neuroendocrine response.

OBJECTIVES

To examine whether LSG with/without hepatic branch vagotomy (HV) has a clinical impact on glycemic control in patients with obesity and type 2 diabetes mellitus (T2DM). Furthermore, the impact on weight loss and post-LSG GERD were evaluated.

METHODS

A total of 204 Japanese patients with obesity and T2DM, who underwent LSG and completed 1-year follow-up, were retrospectively analyzed. Operative outcomes, weight loss, glycemic, and GERD-related parameters were compared between the LSG/HHR/HV group (n = 89) and the LSG group (n = 115).

RESULTS

There was no significant difference in the background factors in terms of anthropometric and T2DM-related parameters between the groups. The median operation times in the LSG/HHR/HV and LSG groups were 133 and 124 minutes, respectively (p = 0.236). At 1 year, the diabetes remission rate, HbA1c, fasting glucose, and C-peptide levels were all comparable between the groups. The weight loss effect was also comparable. The patients in the LSG/HHR/HV group achieved significant improvement and prevention of GERD and hiatus hernia (p < 0.001).

CONCLUSION

HV does not appear to have a clinical impact on glycemic control and weight loss. Concomitant HHR with LSG serves to reduce post-LSG GERD.

International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020)

Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

Bioelectronic medicine for the autonomic nervous system: clinical applications and perspectives

Bioelectronic medicine (BM) is an emerging new approach for developing novel neuromodulation therapies for pathologies that have been previously treated with pharmacological approaches. In this review, we will focus on the neuromodulation of autonomic nervous system (ANS) activity with implantable devices, a field of BM that has already demonstrated the ability to treat a variety of conditions, from inflammation to metabolic and cognitive disorders. Recent discoveries about immune responses to ANS stimulation are the laying foundation for a new field holding great potential for medical advancement and therapies and involving an increasing number of research groups around the world, with funding from international public agencies and private investors. Here, we summarize the current achievements and future perspectives for clinical applications of neural decoding and stimulation of the ANS. First, we present the main clinical results achieved so far by different BM approaches and discuss the challenges encountered in fully exploiting the potential of neuromodulatory strategies. Then, we present current preclinical studies aimed at overcoming the present limitations by looking for optimal anatomical targets, developing novel neural interface technology, and conceiving more efficient signal processing strategies. Finally, we explore the prospects for translating these advancements into clinical practice.

Glucose Sensing Mediated by Portal Glucagon-Like Peptide 1 Receptor Is Markedly Impaired in Insulin-Resistant Obese Animals

The glucose portal sensor informs the brain of changes in glucose inflow through vagal afferents that require an activated glucagon-like peptide 1 receptor (GLP-1r). The GLP-1 system is known to be impaired in insulin-resistant conditions, and we sought to understand the consequences of GLP-1 resistance on glucose portal signaling. GLP-1-dependent portal glucose signaling was identified, in vivo, using a novel 68Ga-labeled GLP-1r positron-emitting probe that supplied a quantitative in situ tridimensional representation of the portal sensor with specific reference to the receptor density expressed in binding potential units. It also served as a map for single-neuron electrophysiology driven by an image-based abdominal navigation. We determined that in insulin-resistant animals, portal vagal afferents failed to inhibit their spiking activity during glucose infusion, a GLP-1r-dependent function. This reflected a reduction in portal GLP-1r binding potential, particularly between the splenic vein and the entrance of the liver. We propose that insulin resistance, through a reduction in GLP-1r density, leads to functional portal desensitization with a consequent suppression of vagal sensitivity to portal glucose.

Therapeutic potential of α7 nicotinic acetylcholine receptor agonists to combat obesity, diabetes, and inflammation

The cholinergic anti-inflammatory reflex (CAIR) represents an important homeostatic regulatory mechanism for sensing and controlling the body's response to inflammatory stimuli. Vagovagal reflexes are an integral component of CAIR whose anti-inflammatory effects are mediated by acetylcholine (ACh) acting at α7 nicotinic acetylcholine receptors (α7nAChR) located on cells of the immune system. Recently, it is appreciated that CAIR and α7nAChR also participate in the control of metabolic homeostasis. This has led to the understanding that defective vagovagal reflex circuitry underlying CAIR might explain the coexistence of obesity, diabetes, and inflammation in the metabolic syndrome. Thus, there is renewed interest in the α7nAChR that mediates CAIR, particularly from the standpoint of therapeutics. Of special note is the recent finding that α7nAChR agonist GTS-21 acts at L-cells of the distal intestine to stimulate the release of two glucoregulatory and anorexigenic hormones: glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). Furthermore, α7nAChR agonist PNU 282987 exerts trophic factor-like actions to support pancreatic β-cell survival under conditions of stress resembling diabetes. This review provides an overview of α7nAChR function as it pertains to CAIR, vagovagal reflexes, and metabolic homeostasis. We also consider the possible usefulness of α7nAChR agonists for treatment of obesity, diabetes, and inflammation.

Differential effects of vagus nerve stimulation strategies on glycemia and pancreatic secretions

Despite advancements in pharmacotherapies, glycemia is poorly controlled in type 2 diabetic patients. As the vagus nerve regulates energy metabolism, here we evaluated the effect various electrical vagus nerve stimulation strategies have on glycemia and glucose-regulating hormones, as a first step to developing a novel therapy of type 2 diabetes. Sprague-Dawley rats were anesthetized, the abdominal (anterior) vagus nerve implanted, and various stimulation strategies applied to the nerve: (a) 15 Hz; (b) 4 kHz, or 40 kHz and; (c) a combination of 15 Hz and 40 kHz to directionally activate afferent or efferent vagal fibers. Following a glucose bolus (500 mg/kg, I.V.), stimulation strategies were applied (60 min) and serial blood samples taken. No stimulation was used as a crossover control sequence. Applying 15 Hz stimulation significantly increased glucose (+2.9 ± 0.2 mM·hr, p = .015) and glucagon (+17.1 ± 8.0 pg·hr/ml, p = .022), compared to no stimulation. Application of 4 kHz stimulation also significantly increased glucose levels (+1.5 ± 0.5 mM·hr, p = .049), while 40 kHz frequency stimulation resulted in no changes to glucose levels but did significantly lower glucagon (-12.3 ± 1.1 pg·hr/ml, p = .0009). Directional afferent stimulation increased glucose (+2.4 ± 1.5 mM·hr) and glucagon levels (+39.5 ± 15.0 pg·hr/ml). Despite hyperglycemia resulting when VNS, aVNS, and 4 kHz stimulation strategies were applied, the changes in insulin levels were not significant (p ≥ .05). In summary, vagus nerve stimulation modulates glycemia by effecting glucagon and insulin secretions, and high-frequency 40 kHz stimulation may have potential application for the treatment of type 2 diabetes.

Chronic vagus nerve stimulation for drug-resistant epilepsy may influence fasting blood glucose concentration

Background

Cervical vagus nerve stimulation (VNS) has been widely accepted as adjunctive therapy for drug-resistant epilepsy and major depression. Its effects on glycemic control in humans were however poorly understood. The aim of our study was to investigate the potential effects of VNS on fasting blood glucose (FBG) in patients with drug-resistant epilepsy.

Methods

Patients with drug-resistant epilepsy who had received VNS implants at the same hospital were retrospectively studied. Effects on FBG, weight, body mass index and blood pressure were evaluated at 4, 8 and 12 months of follow-up.

Results

32 subjects (11 females/21 males, 19 ± 9 years, body mass index 22.2 ± 4.0 kg/m²) completed 12-month follow-up. At the 4 months, there were no significant changes in FBG concentrations from baseline to follow-up in both Sham-VNS (4.89 ± 0.54 vs. 4.56 ± 0.54 mmol/L, N = 13, p = 0.101) and VNS (4.80 ± 0.54 vs. 4.50 ± 0.56 mmol/L, N = 19, p = 0.117) groups. However, after 8 (4.90 ± 0.42 mmol/L, N = 32, p = 0.001) and 12 (4.86 ± 0.40 mmol/L, N = 32, p = 0.002) months of VNS, FBG levels significantly increased compared to baseline values (4.52 ± 0.54 mmol/L, N = 32). Changes in FBG concentrations at both 8 (R² = 0.502, N = 32, p < 0.001) and 12 (R² = 0.572, N = 32, p < 0.001) months were negatively correlated with baseline FBG levels.

Conclusions

Our study suggests that chronic cervical VNS elevates FBG levels with commonly used stimulation parameters in patients with epilepsy.

Trial registration VNSRE, NCT02378792. Registered 4 March 2015—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02378792

Closed-loop bioelectronic medicine for diabetes management

Modulation of the nervous system by delivering electrical or pharmaceutical agents has contributed to the development of novel treatments to serious health disorders. Recent advances in multidisciplinary research has enabled the emergence of a new powerful therapeutic approach called bioelectronic medicine. Bioelectronic medicine exploits the fact that every organ in our bodies is neurally innervated and thus electrical interfacing with peripheral nerves can be a potential pathway for diagnosing or treating diseases such as diabetes. In this context, a plethora of studies have confirmed the important role of the nervous system in maintaining a tight regulation of glucose homeostasis. This has initiated new research exploring the opportunities of bioelectronic medicine for improving glucose control in people with diabetes, including regulation of gastric emptying, insulin sensitivity, and secretion of pancreatic hormones. Moreover, the development of novel closed-loop strategies aims to provide effective, specific and safe interfacing with the nervous system, and thereby targeting the organ of interest. This is especially valuable in the context of chronic diseases such as diabetes, where closed-loop bioelectronic medicine promises to provide real-time, autonomous and patient-specific therapies. In this article, we present an overview of the state-of-the-art for closed-loop neuromodulation systems in relation to diabetes and discuss future related opportunities for management of this chronic disease.

Closed-Loop Implantable Therapeutic Neuromodulation Systems Based on Neurochemical Monitoring

Closed-loop or intelligent neuromodulation allows adjustable, personalized neuromodulation which usually incorporates the recording of a biomarker, followed by implementation of an algorithm which decides the timing (when?) and strength (how much?) of stimulation. Closed-loop neuromodulation has been shown to have greater benefits compared to open-loop neuromodulation, particularly for therapeutic applications such as pharmacoresistant epilepsy, movement disorders and potentially for psychological disorders such as depression or drug addiction. However, an important aspect of the technique is selection of an appropriate, preferably neural biomarker. Neurochemical sensing can provide high resolution biomarker monitoring for various neurological disorders as well as offer deeper insight into neurological mechanisms. The chemicals of interest being measured, could be ions such as potassium (K⁺), sodium (Na⁺), calcium (Ca²⁺), chloride (Cl⁻), hydrogen (H⁺) or neurotransmitters such as dopamine, serotonin and glutamate. This review focusses on the different building blocks necessary for a neurochemical, closed-loop neuromodulation system including biomarkers, sensors and data processing algorithms. Furthermore, it also highlights the merits and drawbacks of using this biomarker modality.

Peripheral and central compensatory mechanisms for impaired vagus nerve function during peripheral immune activation

BACKGROUND

Determining the etiology and possible treatment strategies for numerous diseases requires a comprehensive understanding of compensatory mechanisms in physiological systems. The vagus nerve acts as a key interface between the brain and the peripheral internal organs. We set out to identify mechanisms compensating for a lack of neuronal communication between the immune and the central nervous system (CNS) during infection.

METHODS

We assessed biochemical and central neurotransmitter changes resulting from subdiaphragmatic vagotomy and whether they are modulated by intraperitoneal infection. We performed a series of subdiaphragmatic vagotomy or sham operations on male Wistar rats. Next, after full, 30-day recovery period, they were randomly assigned to receive an injection of Escherichia coli lipopolysaccharide or saline. Two hours later, animal were euthanized and we measured the plasma concentration of prostaglandin E2 (with HPLC-MS), interleukin-6 (ELISA), and corticosterone (RIA). We also had measured the concentration of monoaminergic neurotransmitters and their metabolites in the amygdala, brainstem, hippocampus, hypothalamus, motor cortex, periaqueductal gray, and prefrontal medial cortex using RP-HPLC-ED. A subset of the animals was evaluated in the elevated plus maze test immediately before euthanization.

RESULTS

The lack of immunosensory signaling of the vagus nerve stimulated increased activity of discrete inflammatory marker signals, which we confirmed by quantifying biochemical changes in blood plasma. Behavioral results, although preliminary, support the observed biochemical alterations. Many of the neurotransmitter changes observed after vagotomy indicated that the vagus nerve influences the activity of many brain areas involved in control of immune response and sickness behavior. Our studies show that these changes are largely eliminated during experimental infection.

CONCLUSIONS

Our results suggest that in vagotomized animals with blocked CNS, communication may transmit via a pathway independent of the vagus nerve to permit restoration of CNS activity for peripheral inflammation control.

Electroceutical Targeting of the Autonomic Nervous System

Autonomic nerves are attractive targets for medical therapies using electroceutical devices because of the potential for selective control and few side effects. These devices use novel materials, electrode configurations, stimulation patterns, and closed-loop control to treat heart failure, hypertension, gastrointestinal and bladder diseases, obesity/diabetes, and inflammatory disorders. Critical to progress is a mechanistic understanding of multi-level controls of target organs, disease adaptation, and impact of neuromodulation to restore organ function.

A comparative study of subsequent liver cirrhosis risk in non-Helicobacter pylori-infected peptic ulcer patients with and without vagotomy: An Asian population cohort study

OBJECTIVES

Hepatic parasympathetic nerves branch off the vagus nerve. The vagal and hepatic nervous systems are important in liver physiological processes and some diseases such as diabetes, obesity, and liver cirrhosis. We were interested in vagal nerve integrity and subsequent diseases in peptic ulcer patients. Herein, we used National Health Insurance database in Taiwan and retrospectively assessed the risk of developing liver cirrhosis in peptic ulcer patients with and without complications by surgical treatments.

METHODS

A cohort of 357 423 peptic ulcer patients without Helicobacter pylori, hepatitis B/C virus infection, and alcoholism from 2001 to 2008 was established. A randomly selected cohort of 357 423 people without peptic ulcer that matched by age, gender, comorbidities, and index year was used for comparison. The risks of developing liver cirrhosis were assessed both in cohorts and in peptic ulcer patients with and without vagotomy at the end of 2011.

RESULTS

Peptic ulcer patients were with higher incidence of liver cirrhosis than those without peptic ulcer (2.63 vs 0.96 per 1000 person-years) and with a 2.79-fold adjusted hazard ratio (HR) (95% confidence interval = 2.66-2.93) based on the multivariable Cox proportional hazards regression analysis. Comparing with different peptic ulcer management strategies, the HR value for subsequent liver cirrhosis risk was the lowest in vagotomy group (HR = 0.46, 95% confidence interval = 0.33-0.64).

CONCLUSIONS

Peptic ulcer patients have an increased risk of developing liver cirrhosis. Moreover, there were association of vagotomy and decreased risk of subsequent liver cirrhosis in complicated peptic ulcer patients. However, further studies are warranted.

Glucose Activates Vagal Control of Hyperglycemia and Inflammation in Fasted Mice

Sepsis is a leading cause of death in hospitalized patients. Many experimental treatments may have failed in clinical trials for sepsis, in part, because they focused on immune responses of healthy animals that did not mimic the metabolic settings of septic patients. Epidemiological studies show an association between metabolic and immune alterations and over 1/3 of septic patients are diabetic, but the mechanism linking these systems is unknown. Here, we report that metabolic fasting increased systemic inflammation and worsened survival in experimental sepsis. Feeding and administration of glucose in fasted mice activated the vagal tone without affecting blood pressure. Vagal stimulation attenuated hyperglycemia and serum TNF levels in sham but only hyperglycemia in splenectomized mice. Vagal stimulation induced the production of dopamine from the adrenal glands. Experimental diabetes increased hyperglycemia and systemic inflammation in experimental sepsis. Fenoldopam, a specific dopaminergic type-1 agonist, attenuated hyperglycemia and systemic inflammation in diabetic endotoxemic mice. These results indicate that glucose activates vagal control of hyperglycemia and inflammation in fasted septic mice via dopamine.

Effective weight control via an implanted self-powered vagus nerve stimulation device

In vivo vagus nerve stimulation holds great promise in regulating food intake for obesity treatment. Here we present an implanted vagus nerve stimulation system that is battery-free and spontaneously responsive to stomach movement. The vagus nerve stimulation system comprises a flexible and biocompatible nanogenerator that is attached on the surface of stomach. It generates biphasic electric pulses in responsive to the peristalsis of stomach. The electric signals generated by this device can stimulate the vagal afferent fibers to reduce food intake and achieve weight control. This strategy is successfully demonstrated on rat models. Within 100 days, the average body weight is controlled at 350 g, 38% less than the control groups. This work correlates nerve stimulation with targeted organ functionality through a smart, self-responsive system, and demonstrated highly effective weight control. This work also provides a concept in therapeutic technology using artificial nerve signal generated from coordinated body activities.

Developing new technologies for the neuromodulation of the vagus nerve can enable therapeutic strategies for body weight control in obese patients. Here, the authors present a battery-free self-powered implantable vagus nerve stimulation system that electrically responds to stomach movement.

A SIRT1 agonist reduces cognitive decline in type 2 diabetic rats through antioxidative and anti‑inflammatory mechanisms

Sirtuin 1 (SIRT1) is an NAD+‑dependent protein deacetylase that is involved in cell differentiation, aging, apoptosis, physiological rhythms, metabolic regulation, oxidative stress and numerous other important biological processes. In the present study, the ability of a sirtuin‑1 (SIRT1) agonist, SRT1720, to reduce cognitive decline in type 2 diabetes mellitus (T2DM) was investigated. Streptozotocin‑induced male Sprague‑Dawley rats were used to establish a T2DM model and the protective effect of SRT1720 and its underlying mechanisms were investigated. Body weight and fasting blood glucose (FBG) were recorded and cognitive function was measured with the Morris water maze. Levels of oxidative stress, inflammation, caspase‑3 activity and nuclear factor κB (NF‑κB) mRNA expression were detected with a series of commercial assay kits and reverse transcription‑quantitative polymerase chain reaction, respectively. Western blot analysis was performed to determine the protein expression of NF‑κB, endothelial nitric oxide synthase (eNOS), peroxisome proliferator‑activated receptor γ (PPARγ), AMP‑activated protein kinase (AMPK), heat shock 70 kDa protein (HSP70), SIRT1, nuclear factor erythroid 2‑related factor 2 (Nrf2) and heme oxygenase 1 (HO‑1). The results revealed that SRT1720 significantly increased body weight, decreased FBG, improved cognitive function and reduced the levels of proteins associated with oxidative stress and inflammation damage in T2DM rats. Additionally, SRT1720 significantly decreased NF‑κB p65 mRNA expression and increased eNOS and PPARγ expression. SRT1720 significantly reduced caspase‑3 activity and HSP70 protein expression, and increased p‑AMPK, SIRT1, Nrf2 and HO‑1 protein expression. Collectively, the results indicate that SRT1720 may reduce cognitive decline in T2DM rats through antioxidative and anti‑inflammatory action via NF‑κB and AMPK‑dependent mechanisms.

Selective Vagotomy Worsens Glucose Control After Ileal Transposition

PURPOSES

Our aim was to investigate the effects of selective celiac branch vagotomy on food intake and glycemic control after ileal transposition (IT) and the possible roles of the vagus on the improvement of diabetes.

MATERIALS AND METHODS

Forty non-obese rats with diabetes underwent either IT, IT + celiac branch vagotomy (ITV), sham IT (SI), or sham IT + celiac branch vagotomy (SIV). They were pair fed, and the food intake, body weight, fasting plasma glucose, and glucagon-like peptide 1 (GLP-1) level were monitored. The number of activated pro-opiomelanocortin (POMC) neurons and POMC-derived peptides were measured after sacrifice.

RESULTS

The fasting glucose level of the ITV group was higher (7.0 ± 0.7 mmol/L vs. 5.7 ± 0.3, P = 0.01), and the area under the curve of the oral glucose tolerance test (AUCOGTT) value was greater than that of the IT group (1101.8 ± 90.3 (mmol/l) min vs. 986.9 ± 47.7 (mmol/l) min, P = 0.01). There was no significant difference in the postprandial GLP-1 level between these two groups, but the number of activated neurons in the ITV group was less than that of the IT group (10.3 ± 2.1 vs. 14.9 ± 2.3, P < 0.01), while the relative content level of POMC-derived peptides in the ITV group was half that of the IT group (P < 0.01).

CONCLUSIONS

The celiac branches of the vagus might contribute to less eating and improvement of diabetes after IT. The activating vagus strategy might be a goal for the treatment of diabetes.

Metabolic syndrome emerges after artificial selection for low baroreflex sensitivity

AIMS

It is unclear whether the impaired BRS plays a key role in the incidence of cardiovascular diseases. The molecular mechanism of impaired BRS remains to be fully elucidated. We hypothesized that selection of rats based on deficient and normal intrinsic BRS would yield models that reflect cardiovascular diseases risk.

METHODS AND RESULTS

Twenty generations of selection produced arterial baroreflex low rats and normal rats that differed in BRS by about 2.5-fold change. Metabolic syndrome (including hypertension, overweight, hyperlipemia, and hyperglycemia) emerged in ABR-DRs. Although ABR-DRs consumed less food, they gained significantly more body weight.

CONCLUSION

Our study demonstrated that intrinsic low BRS induced hypertension and metabolic disorder. Restoration of impaired BRS might be a potent target of therapeutic intervention in metabolic syndrome.

The vagus neurometabolic interface and clinical disease

The nervous system both monitors and modulates body metabolism to maintain homoeostasis. In disease states such as obesity and diabetes, the neurometabolic interface is dysfunctional and contributes to clinical illness. The vagus nerve, in particular, with both sensory and motor fibres, provides an anatomical substrate for this interface. Its sensory fibres contain receptors for important circulating metabolic mediators, including leptin and cholecystokinin, and provide real-time information about these mediators to the central nervous system. In turn, efferent fibres within the vagus nerve participate in a brain-gut axis to regulate metabolism. In this review, we describe these vagus nerve-mediated metabolic pathways and recent clinical trials of vagus nerve stimulation for the management of obesity. These early studies suggest that neuromodulation approaches that employ electricity to tune neurometabolic circuits may represent a new tool in the clinical armamentarium directed against obesity.

The Gastrointestinal Tract as an Integrator of Mechanical and Hormonal Response to Nutrient Ingestion

Glucose tolerance after meal ingestion in vivo is the result of multiple processes that occur in parallel. Insulin secretion together with reciprocal inhibition of glucagon secretion contributes to glucose tolerance. However, other factors beyond glucose effectiveness and insulin action require consideration. The absorption of ingested nutrients and their subsequent systemic rate of appearance largely depend on the rate of delivery of nutrients to the proximal small intestine. This is determined by the integrated response of the upper gastrointestinal tract to a meal. While gastric emptying is probably the most significant component, other factors need to be considered. This review will examine all processes that could potentially alter the fraction and rate of appearance of ingested nutrients in the peripheral circulation. Several of these processes may be potential therapeutic targets for the prevention and treatment of diabetes. Indeed, there is increased interest in gastrointestinal contributions to nutritional homeostasis, as demonstrated by the advent of antidiabetes therapies that alter gastrointestinal motility, the effect of bariatric surgery on diabetes remission, and the potential of the intestinal microbiome as a modulator of human metabolism. The overall goal of this review is to examine current knowledge of the gastrointestinal contributions to metabolic control.

Two-Year Outcomes of Vagal Nerve Blocking (vBloc) for the Treatment of Obesity in the ReCharge Trial

Background

The ReCharge Trial demonstrated that a vagal blocking device (vBloc) is a safe and effective treatment for moderate to severe obesity. This report summarizes 24-month outcomes.

Methods

Participants with body mass index (BMI) 40 to 45 kg/m², or 35 to 40 kg/m² with at least one comorbid condition were randomized to either vBloc therapy or sham intervention for 12 months. After 12 months, participants randomized to vBloc continued open-label vBloc therapy and are the focus of this report. Weight loss, adverse events, comorbid risk factors, and quality of life (QOL) will be assessed for 5 years.

Results

At 24 months, 123 (76 %) vBloc participants remained in the trial. Participants who presented at 24 months (n = 103) had a mean excess weight loss (EWL) of 21 % (8 % total weight loss [TWL]); 58 % of participants had ≥5 % TWL and 34 % had ≥10 % TWL. Among the subset of participants with abnormal preoperative values, significant improvements were observed in mean LDL (−16 mg/dL) and HDL cholesterol (+4 mg/dL), triglycerides (−46 mg/dL), HbA1c (−0.3 %), and systolic (−11 mmHg) and diastolic blood pressures (−10 mmHg). QOL measures were significantly improved. Heartburn/dyspepsia and implant site pain were the most frequently reported adverse events. The primary related serious adverse event rate was 4.3 %.

Conclusions

vBloc therapy continues to result in medically meaningful weight loss with a favorable safety profile through 2 years.

Trial Registration

https://clinicaltrials.gov/ct2/show/NCT01327976

The Role of the Autonomic Nervous System in the Pathophysiology of Obesity

Obesity is reaching epidemic proportions globally and represents a major cause of comorbidities, mostly related to cardiovascular disease. The autonomic nervous system (ANS) dysfunction has a two-way relationship with obesity. Indeed, alterations of the ANS might be involved in the pathogenesis of obesity, acting on different pathways. On the other hand, the excess weight induces ANS dysfunction, which may be involved in the haemodynamic and metabolic alterations that increase the cardiovascular risk of obese individuals, i.e., hypertension, insulin resistance and dyslipidemia. This article will review current evidence about the role of the ANS in short-term and long-term regulation of energy homeostasis. Furthermore, an increased sympathetic activity has been demonstrated in obese patients, particularly in the muscle vasculature and in the kidneys, possibily contributing to increased cardiovascular risk. Selective leptin resistance, obstructive sleep apnea syndrome, hyperinsulinemia and low ghrelin levels are possible mechanisms underlying sympathetic activation in obesity. Weight loss is able to reverse metabolic and autonomic alterations associated with obesity. Given the crucial role of autonomic dysfunction in the pathophysiology of obesity and its cardiovascular complications, vagal nerve modulation and sympathetic inhibition may serve as therapeutic targets in this condition.

Vagotomy Reduces Insulin Clearance in Obese Mice Programmed by Low-Protein Diet in the Adolescence

The aim of this study was to investigate the effect of subdiaphragmatic vagotomy on insulin sensitivity, secretion, and degradation in metabolic programmed mice, induced by a low-protein diet early in life, followed by exposure to a high-fat diet in adulthood. Weaned 30-day-old C57Bl/6 mice were submitted to a low-protein diet (6% protein). After 4 weeks, the mice were distributed into three groups: LP group, which continued receiving a low-protein diet; LP + HF group, which started to receive a high-fat diet; and LP + HFvag group, which underwent vagotomy and also was kept at a high-fat diet. Glucose-stimulated insulin secretion (GSIS) in isolated islets, ipGTT, ipITT, in vivo insulin clearance, and liver expression of the insulin-degrading enzyme (IDE) was accessed. Vagotomy improved glucose tolerance and reduced insulin secretion but did not alter adiposity and insulin sensitivity in the LP + HFvag, compared with the LP + HF group. Improvement in glucose tolerance was accompanied by increased insulinemia, probably due to a diminished insulin clearance, as judged by the lower C-peptide : insulin ratio, during the ipGTT. Finally, vagotomy also reduced liver IDE expression in this group. In conclusion, when submitted to vagotomy, the metabolic programmed mice showed improved glucose tolerance, associated with an increase of plasma insulin concentration as a result of insulin clearance reduction, a phenomenon probably due to diminished liver IDE expression.

Modeling the response of small myelinated axons in a compound nerve to kilohertz frequency signals

OBJECTIVE

There is growing interest in electrical neuromodulation of peripheral nerves, particularly autonomic nerves, to treat various diseases. Electrical signals in the kilohertz frequency (KHF) range can produce different responses, including conduction block. For example, EnteroMedics' vBloc® therapy for obesity delivers 5 kHz stimulation to block the abdominal vagus nerves, but the mechanisms of action are unclear.

APPROACH

We developed a two-part computational model, coupling a 3D finite element model of a cuff electrode around the human abdominal vagus nerve with biophysically-realistic electrical circuit equivalent (cable) model axons (1, 2, and 5.7 µm in diameter). We developed an automated algorithm to classify conduction responses as subthreshold (transmission), KHF-evoked activity (excitation), or block. We quantified neural responses across kilohertz frequencies (5-20 kHz), amplitudes (1-8 mA), and electrode designs.

MAIN RESULTS

We found heterogeneous conduction responses across the modeled nerve trunk, both for a given parameter set and across parameter sets, although most suprathreshold responses were excitation, rather than block. The firing patterns were irregular near transmission and block boundaries, but otherwise regular, and mean firing rates varied with electrode-fibre distance. Further, we identified excitation responses at amplitudes above block threshold, termed 're-excitation', arising from action potentials initiated at virtual cathodes. Excitation and block thresholds decreased with smaller electrode-fibre distances, larger fibre diameters, and lower kilohertz frequencies. A point source model predicted a larger fraction of blocked fibres and greater change of threshold with distance as compared to the realistic cuff and nerve model.

SIGNIFICANCE

Our findings of widespread asynchronous KHF-evoked activity suggest that conduction block in the abdominal vagus nerves is unlikely with current clinical parameters. Our results indicate that compound neural or downstream muscle force recordings may be unreliable as quantitative measures of neural activity for in vivo studies or as biomarkers in closed-loop clinical devices.

Effects of sleeve gastrectomy plus trunk vagotomy compared with sleeve gastrectomy on glucose metabolism in diabetic rats

AIM

To investigate the effects of sleeve gastrectomy plus trunk vagotomy (SGTV) compared with sleeve gastrectomy (SG) in a diabetic rat model.

METHODS

SGTV, SG, TV and Sham operations were performed on rats with diabetes induced by high-fat diet and streptozotocin. Body weight, food intake, oral glucose tolerance test, homeostasis model assessment of insulin resistance (HOMA-IR), hepatic insulin signaling (IR, IRS1, IRS2, PI3K and AKT), oral glucose stimulated insulin secretion, GLP-1 and ghrelin were compared at various postoperative times.

RESULTS

Both SG and SGTV resulted in better glucose tolerance, lower HOMA-IR, up-regulated hepatic insulin signaling, higher levels of oral glucose-stimulated insulin secretion, higher postprandial GLP-1 and lower fasting ghrelin levels than the TV and Sham groups. No significant differences were observed between the SG and SGTV groups. In addition, no significant differences were found between the TV and Sham groups in terms of glucose tolerance, HOMA-IR, hepatic insulin signaling, oral glucose-stimulated insulin secretion, postprandial GLP-1 and fasting ghrelin levels. No differences in body weight and food intake were noted between the four groups.

CONCLUSION

SGTV is feasible for diabetes control and is independent of weight loss. However, SGTV did not result in a better improvement in diabetes than SG alone.

Ghrelin, CCK, GLP-1, and PYY(3-36): Secretory Controls and Physiological Roles in Eating and Glycemia in Health, Obesity, and After RYGB

The efficacy of Roux-en-Y gastric-bypass (RYGB) and other bariatric surgeries in the management of obesity and type 2 diabetes mellitus and novel developments in gastrointestinal (GI) endocrinology have renewed interest in the roles of GI hormones in the control of eating, meal-related glycemia, and obesity. Here we review the nutrient-sensing mechanisms that control the secretion of four of these hormones, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine [PYY(3-36)], and their contributions to the controls of GI motor function, food intake, and meal-related increases in glycemia in healthy-weight and obese persons, as well as in RYGB patients. Their physiological roles as classical endocrine and as locally acting signals are discussed. Gastric emptying, the detection of specific digestive products by small intestinal enteroendocrine cells, and synergistic interactions among different GI loci all contribute to the secretion of ghrelin, CCK, GLP-1, and PYY(3-36). While CCK has been fully established as an endogenous endocrine control of eating in healthy-weight persons, the roles of all four hormones in eating in obese persons and following RYGB are uncertain. Similarly, only GLP-1 clearly contributes to the endocrine control of meal-related glycemia. It is likely that local signaling is involved in these hormones' actions, but methods to determine the physiological status of local signaling effects are lacking. Further research and fresh approaches are required to better understand ghrelin, CCK, GLP-1, and PYY(3-36) physiology; their roles in obesity and bariatric surgery; and their therapeutic potentials.

Intermittent Vagal Nerve Block for Improvements in Obesity, Cardiovascular Risk Factors, and Glycemic Control in Patients with Type 2 Diabetes Mellitus: 2-Year Results of the VBLOC DM2 Study

BACKGROUND

One-year results of the VBLOC DM2 study found that intermittent vagal blocking (VBLOC therapy) was safe among subjects with obesity and type 2 diabetes mellitus (T2DM) and led to significant weight loss and improvements in glycemic parameters and cardiovascular risk factors. Longer-term data are needed to determine whether the results are sustained.

METHODS

VBLOC DM2 is a prospective, observational study of 28 subjects with T2DM and body mass index (BMI) between 30 and 40 kg/m(2) to assess mid-term safety and weight loss and improvements in glycemic parameters, and other cardiovascular risk factors with VBLOC therapy. Continuous outcome variables are reported using mixed models.

RESULTS

At 24 months, the mean percentage of excess weight loss was 22% (95% CI, 15 to 28, p < 0.0001) or 7.0% total body weight loss (95% CI, 5.0 to 9.0, p < 0.0001). Hemoglobin A1c decreased by 0.6 percentage points (95% CI, 0.2 to 1.0, p = 0.0026) on average from 7.8% at baseline. Fasting plasma glucose declined by 15 mg/dL (95% CI, 0 to 29, p = 0.0564) on average from 151 mg/dL at baseline. Among subjects who were hypertensive at baseline, systolic blood pressure declined 10 mmHg (95% CI, 2 to 19, p = 0.02), diastolic blood pressure declined by 6 mmHg (95% CI, 0 to 12, p = 0.0423), and mean arterial pressure declined 7 mmHg (95% CI, 2 to 13, p = 0.014). Waist circumference was significantly reduced by 7 cm (95% CI, 4 to 10, p < 0.0001) from a baseline of 120 cm. The most common adverse events were mild or moderate heartburn, implant site pain, and constipation.

CONCLUSIONS

Improvements in obesity and glycemic control were largely sustained after 2 years of treatment with VBLOC therapy with a well-tolerated risk profile.

Effect of Vagal Nerve Blockade on Moderate Obesity with an Obesity-Related Comorbid Condition: the ReCharge Study

Background

Vagal nerve blockade (vBloc) therapy was shown to be a safe and effective treatment for moderate to severe obesity. This report summarizes the safety and efficacy of vBloc therapy in the prespecified subgroup of patients with moderate obesity.

Methods

The ReCharge Trial is a double-blind, randomized controlled clinical trial of participants with body mass index (BMI) of 40–45 or 35–40 kg/m² with at least one obesity-related comorbid condition. Participants were randomized 2:1 to implantation with either a vBloc or sham device with weight management counseling. Eighty-four subjects had moderate obesity (BMI 35–40 kg/m²) at randomization.

Results

Fifty-three participants were randomized to vBloc and 31 to sham. Qualifying obesity-related comorbidities included dyslipidemia (73 %), hypertension (58 %), sleep apnea (33 %), and type 2 diabetes (8 %). The vBloc group achieved a percentage excess weight loss (%EWL) of 33 % (11 % total weight loss (%TWL)) compared to 19 % EWL (6 % TWL) with sham at 12 months (treatment difference 14 percentage points, 95 % CI, 7–22; p < 0.0001). Common adverse events of vBloc through 12 months were heartburn/dyspepsia and implant site pain; the majority of events were reported as mild or moderate.

Conclusions

vBloc therapy resulted in significantly greater weight loss than the sham control among participants with moderate obesity and comorbidities with a well-tolerated safety profile.

Association of vagus nerve severance and decreased risk of subsequent type 2 diabetes in peptic ulcer patients: An Asian population cohort study

Vagus nerve may play a role in serum glucose modulation. The complicated peptic ulcer patients (with perforation or/and bleeding) who received surgical procedures with or without vagotomy provided 2 patient populations for studying the impact of vagus nerve integrity. We assessed the risk of developing type 2 diabetes in peptic ulcer patients without and with complications by surgical treatment received in a retrospective population study using the National Health Insurance database in Taiwan.A cohort of 163,385 patients with peptic ulcer and without Helicobacter pylori infection in 2000 to 2003 was established. A randomly selected cohort of 163,385 persons without peptic ulcer matched by age, sex, hypertension, hyperlipidemia, Charlson comorbidity index score, and index year was utilized for comparison. The risks of developing diabetes in both cohorts and in the complicated peptic ulcer patients who received truncal vagotomy or simple suture/hemostasis (SSH) were assessed at the end of 2011.The overall diabetes incidence was higher in patients with peptic ulcer than those without peptic ulcer (15.87 vs 12.60 per 1000 person-years) by an adjusted hazard ratio (aHR) of 1.43 (95% confidence interval [CI] = 1.40-1.47) based on the multivariable Cox proportional hazards regression analysis (competing risk). Comparing ulcer patients with truncal vagotomy and SSH or those without surgical treatment, the aHR was the lowest in the vagotomy group (0.48, 95% CI = 0.41-0.56).Peptic ulcer patients have an elevated risk of developing type 2 diabetes. Moreover, there were associations of vagus nerve severance and decreased risk of subsequent type 2 diabetes in complicated peptic ulcer patients.

A Novel Endoscopic Bariatric Procedure: Results of an Experimental Study

BACKGROUND

Surgical treatment of obesity is characterized by both early and late complications, and thus, there is a need to develop safe and non-invasive techniques. Ghrelin is an orexigenic hormone produced by the fundus of the stomach, which may represent a novel target for obesity management. Unfortunately, numerous attempts to alter ghrelin levels have failed to present significant clinical results. We describe a novel procedure that involves modifying arterial blood flow to the gastric fundus for limiting plasma ghrelin levels.

METHODS

A gastroscope was advanced into the gastric fundus of 13 healthy Yorkshire swine, and the fundus was clipped under direct visualization to restrict left gastric artery blood flow. Body weights and ghrelin levels were recorded before and once a week for 4 weeks after the procedure.

RESULTS

Compared to controls, gastroscopic clipping of the fundus decreased plasma ghrelin levels and prevented further weight gain in the 4 weeks of follow-up. Immunohistochemistry and histomorphometry revealed reduced numbers of ghrelin-positive cells in the fundus of experimental animals. We also observed thrombosis in submucosal arteries and submucosal fibrosis. Histological studies demonstrated minimal gastric mucosal injury.

CONCLUSION

Gastroscopic clipping of the fundus in an experimental porcine model resulted in sustained weight loss and a reduction in plasma ghrelin levels at 1 month post-procedure, with no adverse events. Further experimental studies in human patients are needed to examine the clinical utility of this procedure and to optimize a technique, which can facilitate adequate weight loss while minimizing the risk of mucosal injury.

Vagotomy and subsequent development of diabetes - A nested case-control study

BACKGROUND

Vagal signaling is involved in gastric emptying and the secretion and effect of a number of hormones regulating gluco-metabolic processes and, thus, crucial for metabolic homeostasis.

PURPOSE

We hypothesized that vagotomy would increase the risk of developing type 2 diabetes and examined the association between vagotomy and subsequent development of diabetes.

METHODS

A nested case-control study was conducted with information on cases and controls from the Danish National Patient Registry. Cases included individuals with a diabetes diagnosis subsequent (>12months) to the first registration of vagotomy and/or upper gastrointestinal disease in the period 1977-2011. Controls had no subsequent diagnosis of diabetes and were matched by incidence density sampling, age and gender. Logistic regression analyses were conducted.

RESULTS

501,724 diabetes patients and 1,375,567 matched controls were included in the analysis. Vagotomy was performed on 2772 individuals and 148,489 individuals had an upper gastrointestinal diagnosis. In this combined population, 30,902 were diagnosed with diabetes. The mean follow-up was 16years. The unadjusted odds ratio for developing diabetes following vagotomy was 0.64 (95% confidence interval (CI): 0.58-0.71) and did not change in an adjusted analysis (0.64, 95% CI: 0.58-0.70). When restricting the multivariate-adjusted analysis to patients with type 2 diabetes and type 1 diabetes, respectively, the multivariate odds ratios were 0.79 (95% CI: 0.70-0.89) and 0.75 (95% CI 0.53-1.08), respectively.

CONCLUSION

Vagotomy was associated with a significantly decreased risk of developing type 2 diabetes in a population of patients with upper gastrointestinal disease.

Vagus nerve stimulation: state of the art of stimulation and recording strategies to address autonomic function neuromodulation

OBJECTIVE

Neural signals along the vagus nerve (VN) drive many somatic and autonomic functions. The clinical interest of VN stimulation (VNS) is thus potentially huge and has already been demonstrated in epilepsy. However, side effects are often elicited, in addition to the targeted neuromodulation.

APPROACH

This review examines the state of the art of VNS applied to two emerging modulations of autonomic function: heart failure and obesity, especially morbid obesity.

MAIN RESULTS

We report that VNS may benefit from improved stimulation delivery using very advanced technologies. However, most of the results from fundamental animal studies still need to be demonstrated in humans.