Inflammatory Bowel Disease: Role of Vagus Nerve Stimulation

Inflammatory bowel disease and neuropsychiatric disorders: Mechanisms and emerging therapeutics targeting the microbiota-gut-brain axis

Crohn's disease (CD) and ulcerative colitis (UC) are the two major entities of inflammatory bowel disease (IBD). These disorders are known for their relapsing disease course and severe gastrointestinal symptoms including pain, diarrhoea and bloody stool. Accumulating evidence suggests that IBD is not only restricted to the gastrointestinal tract and that disease processes are able to reach distant organs including the brain. In fact, up to 35 % of IBD patients also suffer from neuropsychiatric disorders such as generalized anxiety disorder and major depressive disorder. Emerging research in this area indicates that in many cases these neuropsychiatric disorders are a secondary condition as a consequence of the disturbed communication between the gut and the brain via the microbiota-gut-brain axis. In this review, we summarise the current knowledge on IBD-associated neuropsychiatric disorders. We examine the role of different pathways of the microbiota-gut-brain axis in the development of CNS disorders highlighting altered neural, immunological, humoral and microbial communication. Finally, we discuss emerging therapies targeting the microbiota-gut-brain axis to alleviate IBD and neuropsychiatric symptoms including faecal microbiota transplantation, psychobiotics, microbial metabolites and vagus nerve stimulation.

A single dose of nicotine modulates heart rate variability in rats with induced-ulcerative colitis

BACKGROUND AND AIMS

Nicotine, a widely used toxic substance, has various receptors scattered throughout the body that have shown opposite effects on inflammatory disorders. However, the effects of nicotine on heart rate variability in ulcerative colitis are unclear. Therefore, the present study aimed to determine the effect of acute nicotine injection on heart rate variability in a rat model of ulcerative colitis.

METHODS

Six male Wistar rat groups, containing vehicle, UC (induction of ulcerative colitis without treatment), and nicotine (0.5, 1, 1.5, and 2 mg/kg), were assessed. First, the rats were anesthetized and the initial electrocardiogram was recorded. Twenty-four hours after the induction of ulcerative colitis with 4 % acetic acid by rectal injection, a second electrocardiogram was recorded. Finally, 15 min after nicotine injection in each group, the last electrocardiogram was recorded. Linear and nonlinear indices of heart rate variability were extracted from the recorded R-R intervals.

RESULTS

A single injection of nicotine at high doses increased the standard deviation of R-R intervals, root mean square of successive differences between normal heartbeats, ratio of the short-term deviation to the long-term deviation of R-R intervals, and entropy of R-R intervals in ulcerative colitis animals (at least P < 0.05).

CONCLUSIONS

Acute injection of nicotine at doses 1.5 and 2 mg/kg can improve R-R interval linear indices, balance the ratio of short-term deviation to long-term deviation, and modify the entropy in the induced ulcerative colitis rats. However, further research is needed for the clinical use of acute nicotine injection in ulcerative colitis.

Physical Exercise Alleviates Oxidative Stress and Autonomic Dysregulation in a Rat Model of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) induces immunological and autonomic imbalances. Exercise is a beneficial strategy for controlling IBD symptoms. We investigated the role of exercise on gastrointestinal (GI) motility changes and autonomic parameters in rats with ileitis. Rats were divided into control, ileitis, and exercise+ileitis groups. Ileitis was induced by TNBS (40 mM, intraileally). The exercise was swimming (1 h/day/4 weeks, 5%/bw). We assessed eating behaviour and oxidative stress. Body composition was assessed by bioimpedance. Autonomic balance and ECG parameters were measured by an electrocardiogram (ECG). Gastrointestinal motility was evaluated using the phenol red technique. In terms of body composition, total body water (TBW), body mass index (BMI), and fat-free mass (FFM) were higher in the ileitis group (216.80 ± 11.44 mL; 24.09 ± 2.15 g/cm2; 287.1 ± 14.66 g) (p < 0.05) vs. control rats (130.06 ± 28.23 mL; 16.38 ± 2.50 g/cm2; 193 ± 42.21 g) and exercise prevented (91.33 ± 12.33 mL; 11.73 ± 0.47 g/cm2; 133.8 ± 16.82 g) (p < 0.05) these changes. The exercise+ileitis group induces a reduction (p < 0.05) in gastric retention vs. ileitis and control (11.22 ± 1.91% vs. 35.17 ± 1.01% and 33.96 ± 1.77%). Ileitis increased intestinal retention in the duodenum (46.3 ± 2.56% vs. 24.98 ± 1.78%) and jejunum (34.22 ± 2.33% and 34.72 ± 2.83% vs. 47.32 ± 1.48%) (p < 0.05) and decreased intestinal retention in the ileum (p < 0.05) vs. the control group. Exercise+ileitis prevented (p < 0.05) changes in the duodenum (24.96 ± 1.66% vs. 46.3 ± 2.56%) and ileum (40.32 ± 3.75% vs. 14.08 ± 0.88%). Ileitis induces high MDA levels (p < 0.05) vs. control rats (4.43 ± 0.69 vs. 2.15 ± 0.12 nmol/mg of the tissue). This effect was prevented (p < 0.05) in the exercise+ileitis group (2.75 ± 0.21 vs. 4.43 ± 0.69 nmol/mg of the tissue). We observed a reduction in the LF component (p < 0.05) in the ileitis group vs. control group (31.32 ± 3.99 vs. 43.43 ± 3.86). The correlation indicated a stronger interrelationship between the autonomic parameter and intestinal retention in the ileum (r: 0.68; p: 0.04). The current study suggests intestinal ileitis alters GI motility and autonomic balance, and physical exercise can represent an essential non-pharmacological approach to IBD treatment.

Vagus nerve stimulation: A targeted approach for reducing tissue-specific ischemic reperfusion injury

Vagus Nerve Stimulation (VNS), a neuromodulation technique of applying controlled electrical impulses to the vagus nerve, has now emerged as a potential therapeutic approach for ischemia-reperfusion insults. It provides a pivotal link in improving functional outcomes for the central nervous system and multiple target organs affected by ischemia-reperfusion injury (I/RI). Reduced blood flow during ischemia and subsequent resumption of blood supply during reperfusion to the tissue compromises cellular health because of the combination of mitochondrial dysfunction, oxidative stress, cytokine release, inflammation, apoptosis, intracellular calcium overload, and endoplasmic reticulum stress, which ultimately leads to cell death and irreversible tissue damage. Furthermore, inflammation and apoptosis also play critical roles in the acute progression of ischemic injury pathology. Emerging evidence indicates that VNS in I/RI may act in an anti-inflammatory capacity, reducing oxidative stress and apoptosis, while also improving endothelial and mitochondrial function leading to reduced infarct sizes and cytoprotection in skeletal muscle, gastrointestinal tract, liver, kidney, lung, heart, and brain tissue. In this review, we attempt to shed light on the mechanistic links between tissue-specific damage following I/RI and the therapeutic approach of VNS in attenuating damage, considering both direct and remote I/RI scenarios. Thus, we want to advance the understanding of VNS that could further warrant its clinical implementation, especially as a treatment for I/RI.

Evaluating PEMF vagus nerve stimulation through neck application: A randomized placebo study with volunteers

This study investigates the effects of pulsed electromagnetic field (PEMF) therapy on vagus nerve stimulation through non-invasive neck applications. Exploring the efficacy of PEMF across different frequencies (6 hz, 16 hz, and 32 hz), this double-blind placebo-controlled trial included 485 volunteers to assess its impact on autonomic nervous system functions, particularly targeting sleep disturbances and anxiety. Results demonstrated significant improvements in sleep quality and reduction in anxiety levels, especially notable at 16 hz. These findings suggest that PEMF therapy, by modulating autonomic activity, offers a beneficial non-pharmacological treatment option for related disorders.

Electroceuticals and Magnetoceuticals in Gastroenterology

In the realm of gastroenterology, the inadequacy of current medical treatments for gastrointestinal (GI) motility disorders and inflammatory bowel disease (IBD), coupled with their potential side effects, necessitates novel therapeutic approaches. Neuromodulation, targeting the nervous system's control of GI functions, emerges as a promising alternative. This review explores the promising effects of vagal nerve stimulation (VNS), magnetic neuromodulation, and acupuncture in managing these challenging conditions. VNS offers targeted modulation of GI motility and inflammation, presenting a potential solution for patients not fully relieved from traditional medications. Magnetic neuromodulation, through non-invasive means, aims to enhance neurophysiological processes, showing promise in improving GI function and reducing inflammation. Acupuncture and electroacupuncture, grounded in traditional medicine yet validated by modern science, exert comprehensive effects on GI physiology via neuro-immune-endocrine mechanisms, offering relief from motility and inflammatory symptoms. This review highlights the need for further research to refine these interventions, emphasizing their prospective role in advancing patient-specific management strategies for GI motility disorders and IBD, thus paving the way for a new therapeutic paradigm.

AxoDetect: an automated nerve image segmentation and quantification workflow for computational nerve modeling

Objective.Bioelectronic treatments targeting near-organ innervation have unprecedented clinical applications. Particularly in the spleen, the inhibition of the cholinergic inflammatory response by near-organ nerve stimulation has potential to replace pharmacological treatments in chronic and autoimmune diseases. A caveat is that the optimization of therapeutic stimulation parameters relies onin vivoexperimentation, which becomes challenging due to the small nerve diameters (2 μm), complex anatomy, and mixed axon type composition of the autonomic nerves. Effective development ofin silicomodels requires tools which allow for fast and efficient quantification of axonal composition of specific nerves. Current approaches to generate such information rely on manual image segmentation and quantification.Approach.We developed a combined image-segmentation and model-generation software called AxoDetect: a target- and format-agnostic computer vision algorithm which can segment myelin, endo/epineurium, and both myelinated and unmyelinated fibers from a nerve image without training.Main results.AxoDetect is over 10 times faster on average when compared with current automatic methods while maintaining flexibility through the use of tunable pixel threshold filters to detect different types of tissue. When compared to a distribution-based and a manually segmented model of the splenic nerve terminal branch 1, the model generated with AxoDetect had comparable threshold prediction and was able to accurately detect an increase in activation threshold caused by the addition of surrounding fat tissue to the modeled nerve.Significance.AxoDetect contributes to the acceleration of neuromodulation treatment development through faster model design and iteration without requiring training. Furthermore, the computer vision approach and tunable nature of the filters in our method allow for its use in a variety of histological applications. Our approach will impact not only the study of nerves but also the design of implantable neural interfaces to enhance bioelectronic therapeutic options.

Optimal Management of Refractory Crohn's Disease: Current Landscape and Future Direction

Refractory Crohn's disease, defined as ongoing inflammation despite the trial of multiple advanced therapies, impacts a number of individuals with Crohn's disease, and leads to significant burden in quality of life and cost. Interventions such as early implementation of advanced therapies, optimization of current therapies prior to switching to an alternative, as well as understanding the overlapping pathophysiology between immune-mediated disorders, however, can help shift the current landscape and reduce the number of patients with refractory disease. As such, in this review we summarize the key takeaways of the latest research in the management of moderate-to-severe Crohn's disease, focusing on maximization of our currently available medications, while also exploring topics such as combination advanced therapies. We also describe evidence for emerging and alternative therapeutic modalities, including fecal microbiota transplant, exclusive enteral feeding, hyperbaric oxygen, stem cell therapy, bone marrow transplant, and posaconazole, with a focus on both the potential impact and specific indications for each.

Bioelectronic Medicine: a multidisciplinary roadmap from biophysics to precision therapies

Bioelectronic Medicine stands as an emerging field that rapidly evolves and offers distinctive clinical benefits, alongside unique challenges. It consists of the modulation of the nervous system by precise delivery of electrical current for the treatment of clinical conditions, such as post-stroke movement recovery or drug-resistant disorders. The unquestionable clinical impact of Bioelectronic Medicine is underscored by the successful translation to humans in the last decades, and the long list of preclinical studies. Given the emergency of accelerating the progress in new neuromodulation treatments (i.e., drug-resistant hypertension, autoimmune and degenerative diseases), collaboration between multiple fields is imperative. This work intends to foster multidisciplinary work and bring together different fields to provide the fundamental basis underlying Bioelectronic Medicine. In this review we will go from the biophysics of the cell membrane, which we consider the inner core of neuromodulation, to patient care. We will discuss the recently discovered mechanism of neurotransmission switching and how it will impact neuromodulation design, and we will provide an update on neuronal and glial basis in health and disease. The advances in biomedical technology have facilitated the collection of large amounts of data, thereby introducing new challenges in data analysis. We will discuss the current approaches and challenges in high throughput data analysis, encompassing big data, networks, artificial intelligence, and internet of things. Emphasis will be placed on understanding the electrochemical properties of neural interfaces, along with the integration of biocompatible and reliable materials and compliance with biomedical regulations for translational applications. Preclinical validation is foundational to the translational process, and we will discuss the critical aspects of such animal studies. Finally, we will focus on the patient point-of-care and challenges in neuromodulation as the ultimate goal of bioelectronic medicine. This review is a call to scientists from different fields to work together with a common endeavor: accelerate the decoding and modulation of the nervous system in a new era of therapeutic possibilities.

Inflammatory Bowel Disease and Irritable Bowel Syndrome: What Differences in Mentalization Abilities? A Scoping Review

Mentalization is a psychological process that enables individuals to understand the self and others in terms of intentional mental states. The aim of this scoping review was to provide an overview of the findings on mentalization in patients with inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). A literature search, in line with the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols extension for Scoping Review guidelines, was conducted in the following bibliographic databases: PubMed, PsycINFO, and Scopus. Databases were queried using the following strings (with Boolean operators): ("mentaliz*" OR "metacogniti*" OR "theory of mind" OR "ToM" OR "reflective function*") AND ("irritable bowel syndrome" OR "IBS" OR "inflammatory bowel disease" OR "IBD"). In line with the eligibility criteria, seven articles were included. Results showed that no significant differences in metacognitive ability were found between patients in the IBD and IBS groups. This review revealed the mentalizing difficulties for patients with IBD and IBS. These results should be interpreted with caution since they are based on a few studies that used different instruments to assess mentalizing processes. Future studies are needed to clarify the role of mentalization in patients with these gastrointestinal conditions.

[Vagus Nerve Stimulation (VNS) in Depression]

Major depressive disorder is a common mental health disease with a chronic and treatment-resistant course in about one-third of patients. Invasive vagus nerve stimulation (VNS) as a long-term adjunctive treatment option has increasingly been used in the last years. VNS was CE-certified in the European Union for use in chronic and treatment-resistant depression in 2001. Method In this narrative literature review we provide an overview on VNS as a treatment option in patients with depression. We particularly focus on aspects with high clinical relevance. Results Indication to conduct VNS is determined after comprehensive evaluation of the patients' symptoms and psychiatric history. After education of patients and caregivers and obtaining informed consent, a pacemaker-like pulse generator is implanted in the left chest in a short surgical procedure. In the first weeks after implantation, the stimulation is turned on stepwise in an outpatient setting. The left vagal nerve is stimulated for 30 sec. every 5 minutes. Hoarseness during stimulation is the most frequent side-effect. There is a delay in the onset of antidepressant action of about 6-12 months. In a large registry, the cumulative response rate after 5 years was significantly higher (67.6%) in patients treated with VNS plus treatment-as-usual (TAU) than TAU alone (40.9%). Long-term benefits of VNS on quality of life, cognition, morbidity and mortality have been described previously. Conclusion VNS is a long-term safe treatment option in severely affected patients with depression with positive impact on depression severity, quality of life and cognitive function. Increase of monoaminergic transmission and anti-inflammatory effects of VNS are possible mechanisms of action.

Enlarged cross-sectional area of the left vagus nerve in patients with major depressive disorder

Purpose

Autonomic dysfunction and a chronic low-grade inflammation are supposed to play a role in the etiology of major depressive disorder (MDD). The vagus nerves (VN) form a major part of the parasympathetic nervous system and of the gut-brain axis. They are supposed to exert anti-inflammatory and epithelial barrier protective effects in the gut. A reduced vagal activity was described in patients with MDD. We aimed to examine the VN in patients with MDD with high-resolution ultrasound (HRUS) and hypothesized that the cross-sectional area (CSA) and the echogenicity of the VNs were altered in comparison to healthy controls.

Materials and methods

The echogenicity (gray scale mean) and the CSA of the cervical VNs at the level of the thyroid gland and both median nerves were examined with HRUS in 50 patients with MDD and 50 matched healthy controls.

Results

The left VN-CSA was significantly larger in the MDD group compared to the control group (1.7 ± 0.4 mm2 versus 1.5 ± 0.4 mm2; p = 0.045). The CSA of the right VN and both median nerves (MN) were similar between groups. In MDD subgroup analyses, recurrent depressive disorders were the main contributing factor for the left VN-CSA enlargement. Echogenicity was not altered in the VN and MN between groups.

Conclusion

The enlargement of the left VN-CSA in patients with MDD, and especially in these patients with recurrent depressive disorders, might turn out as a promising imaging biomarker. Longitudinal studies are warranted to examine whether the VNs-CSA change in the course of MDD.

Mental Illnesses in Inflammatory Bowel Diseases: mens sana in corpore sano

Background and aims: Inflammatory bowel diseases (IBD) are chronic disorders associated with a reduced quality of life, and patients often also suffer from psychiatric comorbidities. Overall, both mood and cognitive disorders are prevalent in chronic organic diseases, especially in the case of a strong immune component, such as rheumatoid arthritis, multiple sclerosis, and cancer. Divergent data regarding the true incidence and prevalence of mental disorders in patients with IBD are available. We aimed to review the current evidence on the topic and the burden of mental illness in IBD patients, the role of the brain-gut axis in their co-existence, and its implication in an integrated clinical management. Methods: PubMed was searched to identify relevant studies investigating the gut-brain interactions and the incidence and prevalence of psychiatric disorders, especially of depression, anxiety, and cognitive dysfunction in the IBD population. Results: Among IBD patients, there is a high prevalence of psychiatric comorbidities, especially of anxiety and depression. Approximately 20-30% of IBD patients are affected by mood disorders and/or present with anxiety symptoms. Furthermore, it has been observed that the prevalence of mental illnesses increases in patients with active intestinal disease. Psychiatric comorbidities continue to be under-diagnosed in IBD patients and remain an unresolved issue in the management of these patients. Conclusions: Psychiatric illnesses co-occurring in IBD patients deserve acknowledgment from IBD specialists. These comorbidities highly impact the management of IBD patients and should be studied as an adjunctive therapeutic target.

Transauricular vagus nerve stimulation for patients with disorders of consciousness: A randomized controlled clinical trial

Introduction

Disorders of consciousness (DoCs) are a frequent complication of brain injury disease, and effective treatments are currently lacking. Transauricular vagus nerve stimulation (tVNS) has been proposed as a promising therapeutic method for neurological disorders such as epilepsy and depression. In our previous study, we demonstrated that vagus nerve stimulation promoted recovery in rats with DoCs caused by traumatic brain injury. However, the clinical effect of vagus nerve stimulation on consciousness disorders is unclear. We aimed to investigate the therapeutic efficacy and safety of tVNS in patients with DoCs.

Methods

We conducted a randomized, double-blinded, sham-controlled trial. Patients (N = 60) with DoCs, including minimally conscious state (MCS) and vegetative state/unresponsive wakefulness syndrome, were enrolled and randomized to groups receiving either active or sham tVNS. A frequency of 20 Hz and pulse wave of 200 us was used in the active-tVNS protocol, which was performed in the auricular branch of the vagus nerve in the left outer ear. The sham-tVNS protocol was the same as the active-tVNS protocol although without current input. Both groups of patients also received conventional treatments. Consciousness was evaluated according to the Coma Recovery Scale-Revised before and after the 4-week intervention. We also recorded the type and number of behavioral responses. Safety was primarily assessed according to the incidence of treatment-emergent adverse events. Each patient's heart rate and blood pressure were monitored during all treatment sessions.

Results

Ultimately, 57 patients completed the study: 28 patients underwent active tVNS and 29 patients underwent sham tVNS. No significant differences were observed in Coma Recovery Scale-Revised scores between the active- and sham-tVNS groups before the tVNS sessions. Compared with patients in the sham-tVNS group (9.28 ± 4.38), patients with DoCs treated with active tVNS showed improved consciousness (10.93 ± 4.99), although not statistically significant. Further analysis revealed obvious differences between patients with MCS receiving active and sham tVNS, but no significant difference in patients with vegetative state/unresponsive wakefulness syndrome in both groups. All side effects were considered common medical conditions with no obvious correlation to tVNS.

Conclusion

These preliminary data provide early evidence that tVNS may be an effective and safe approach for promoting the recovery of consciousness, especially in patients with MCS.

Clinical trial registration

https://www.chictr.org.cn/edit.aspx?pid=175938&htm=4, identifier: ChiCTR2200066629.