Visceral sensitivity, hunger responsiveness, and satiety responsiveness: Associations between facets of gastrointestinal interoception and disordered eating profiles in an undergraduate sample

This preregistered study examined associations between empirically derived profiles of disordered eating in a diverse nonclinical sample and three facets of gastrointestinal (GI) interoception (visceral sensitivity, hunger responsiveness, satiety responsiveness). University students (n = 591; 53.3% women; 23.0% Hispanic) completed the Visceral Sensitivity Index, Adult Eating Behavior Questionnaire, and Eating Pathology Symptom Inventory. Latent profile analysis was conducted in Mplus v8.3 with four behavioral indicators (restricting, binge eating, excessive exercise, purging [binary]). Facets of GI interoception predicting odds of disordered eating profile membership compared to an asymptomatic group were evaluated. Five profiles were identified. Facets of GI interoception differentially predicted odds of membership in disordered eating profiles. However, higher scores on all three facets of GI interoception were associated with increased odds of membership in a high disordered eating profile. The relationship between distinct facets of GI interoception and specific disordered eating patterns appears nuanced, though individuals displaying a range of disordered eating behaviors may exhibit broad GI interoceptive dysfunction. Findings are consistent with the recent emphasis on idiographic treatment approaches for disordered eating and may have implications for screening among university students. Prospective longitudinal work and extension to clinical samples is needed.

Environmental enrichment reverses stress-induced changes in the brain-gut axis to ameliorate chronic visceral and somatic hypersensitivity

Introduction

Behavioral therapies, including cognitive behavioral therapy, hypnotherapy and stress management activities, have emerged as effective treatments for irritable bowel syndrome (IBS), a female predominant disorder of the brain-gut axis. IBS, affecting over 10% of the global population, typically presents with abnormal bowel habits and abdominal pain due to visceral hypersensitivity. While the mechanisms underlying how behavioral therapies treat IBS are still elusive, we had previously shown that chronic stress alters gene expression in brain regions critical for stress processing and nociception. We found that exposure to an enriched environment (EE), the rodent analogue of behavioral therapies, prior to and during the stressor was sufficient to prevent stress-induced changes in glucocorticoid receptor (GR) expression in the central nucleus of the amygdala (CeA) and hippocampus. Pre-exposure to EE also inhibited stress-induced increased colonic permeability and was able to block the induction of stress-induced visceral and somatic hypersensitivity. However, it remains unknown if EE can reverse chronic viscerosomatic hypersensitivity that persists following exposure to stress. We hypothesized that EE after chronic stress would be sufficient to reverse stress-induced changes in i) GR expression in the CeA and hippocampus, ii) ameliorate stress-induced colonic hyperpermeability and iii) restore normal visceral and somatic sensitivity in male and female rats.

Methods

Male and female rats were exposed to daily water avoidance stress (WAS). After confirming the rats had developed visceral hypersensitivity, 50% of the animals were housed in EE for 2 weeks while the other 50% remained in standard housing (SH). At the end of this period, we assessed visceral and somatic sensitivity. We also collected colon tissue to measure colonic permeability. Micro-punches of tissue from the CeA and hippocampus were isolated to measure GR expression. Control animals not exposed to WAS were kept in SH for the duration of the study (n = 8 per group).

Results

In both male and female rats, EE reversed stress-induced visceral (p < 0.001) and somatic (p < 0.01) hypersensitivity when compared to WAS animals housed in SH to levels comparable to control animals. EE exposure also reversed changes in GR expression in both the hippocampus (p < 0.01) and CeA (p < 0.01), normalizing GR expression to control levels. EE exposure ameliorated stress-induced colonic hyperpermeability in both male (p < 0.01) and female (p < 0.01) rats compared to WAS rats in SH.

Conclusion

Our findings suggest that behavioral therapies are viable therapeutic options for IBS as they can counter the stress-induced pathophysiology underlying IBS symptoms including visceral hypersensitivity, increased colonic permeability and altered gene expression.

Environmental enrichment prevents stress-induced epigenetic changes in the expression of glucocorticoid receptor and corticotrophin releasing hormone in the central nucleus of the amygdala to inhibit visceral hypersensitivity

INTRODUCTION

Stress is a known trigger for the symptoms of irritable bowel syndrome (IBS), a gastrointestinal (GI) disorder that presents with abnormal bowel habits and abdominal pain due to visceral hypersensitivity. While behavioral therapies have been used to attenuate IBS symptoms, the underlying mechanisms by which these therapies interact with stress-induced pathology remains to be delineated. Here we use a rat model to test the hypothesis that exposure to environmental enrichment (EE) inhibits stress-induced changes within the brain-gut axis to prevent visceral and somatic hypersensitivity and colonic hyperpermeability.

METHODS

Female rats (n = 8/group) were housed in EE one week before and one week during exposure to water avoidance stress (WAS) while controls were housed in standard cages (SH). One day after the final WAS exposure, colonic and somatic sensitivity were assessed by the visceromotor response (VMR) to colorectal distension (CRD) and withdrawal threshold elicited by an electronic von Frey on the hind paw of the rats respectively. All rats were returned to SH for 3 weeks before colonic and somatic sensitivity were reassessed on day 28. The rats were then immediately euthanized and the spinal cord was collected to assess changes in neuronal activation (assessed via ERK phosphorylation) in response to noxious CRD. A separate cohort of animals (n = 8/group) that did not undergo behavioral assessments was euthanized the day after the final WAS exposure and the central nucleus of the amygdala (CeA) was collected to investigate WAS and EE induced epigenetic changes at the glucocorticoid receptor (GR) and corticotrophin releasing hormone (CRH) promoter. The colon from these rats was also collected to assess colonic permeability via changes in transepithelial electrical resistance (TEER) in vitro.

RESULTS

Exposure to stress persistently increased VMR to CRD (P < 0.01) and decreased the hind paw withdrawal threshold (P < 0.001) in female rats. WAS also decreased TEER in the colon tissue of female rats (p = 0.05). In the CeA, WAS induced a decrease in histone acetylation at the GR promoter but increased histone acetylation at the CRH promoter and reduced GR-CRH interactions in the CeA. Analysis of the spinal cord showed that WAS increased CRD-evoked ERK phosphorylation in the dorsal horn. Exposure to EE prevented WAS-induced changes in the CeA, dorsal horn and colon respectively to prevent visceral and somatic hypersensitivity.

CONCLUSION

Our data reveals that behavioral therapies can produce long lasting molecular and epigenetic changes that can prevent stress-induced pathologies even after completion of the therapy. These results highlight the potential mechanisms by which behavioral therapies may ameliorate visceral pain associated stress-related pathologies such as the irritable bowel syndrome.

Magnetic resonance imaging analysis of brain function in patients with irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional disease of the gastrointestinal tract. The current study aimed to examine the association between visceral hypersensitivity in IBS and cortical activation using functional magnetic resonance imaging (fMRI), and to elucidate the role of psychological factors in the pathogenesis of IBS.

METHODS

The present study included 31 patients with IBS and 20 healthy controls. Cerebral function was assessed using fMRI. During imaging, a Sengstaken-Blakemore tube was placed within the rectum approximately 10 cm from the anus, following which gas was rapidly injected into the airbag using a 150-ml syringe. Images were obtained at 40 ml, 80 ml, and 120 ml of expansion. Psychological status was evaluated using the Hospital Anxiety and Depression Scale (HADS).

RESULTS

Anxiety and depression scores were higher among patients with IBSthan among controls (both P < 0.05), although scores in both groups were below the level of clinical diagnosis. Brain activation in regions of interest (parietal areas, prefrontal cortex, cerebellum, anterior cingulate cortex, insular cortex, and thalamus) increased along with increases in rectal balloon dilation, except in women with IBS and patients with disease duration less than 5 years. Furthermore, region of interest (ROI) activation (such as the parietal region, prefrontal cortex, cerebellum, anterior cingulate cortex, insular cortex, and thalamus) differed significantly between the 40-ml and 120-ml conditions, and between the 80-ml and 120-ml conditions (P < 0.05), among patients with IBS with anxiety or depression scores less than 9 points.

CONCLUSIONS

Overall, our findings indicate that changes in brain activation due to changes in rectal balloon distension can be objectively and accurately measured using fMRI. Although our results indicated that visceral hypersensitivity during IBS is associated with changes in cortical activation, further studies utilizing larger sample sizes are required to more fully elucidate the association between psychological factors and visceral hypersensitivity in IBS.

Visceral sensitivity, anxiety, and smoking among treatment-seeking smokers

It is widely recognized that smoking is related to abdominal pain and discomfort, as well as gastrointestinal disorders. Research has shown that visceral sensitivity, experiencing anxiety around gastrointestinal sensations, is associated with poorer gastrointestinal health and related health outcomes. Visceral sensitivity also increases anxiety symptoms and mediates the relation with other risk factors, including gastrointestinal distress. No work to date, however, has evaluated visceral sensitivity in the context of smoking despite the strong association between smoking and poor physical and mental health. The current study sought to examine visceral sensitivity as a unique predictor of cigarette dependence, threat-related smoking abstinence expectancies (somatic symptoms and harmful consequences), and perceived barriers for cessation via anxiety symptoms. Eighty-four treatment seeking adult daily smokers (M_age=45.1years [SD=10.4]; 71.6% male) participated in this study. There was a statistically significant indirect effect of visceral sensitivity via general anxiety symptoms on cigarette dependence (b=0.02, SE=0.01, Bootstrapped 95% CI [0.006, 0.05]), smoking abstinence somatic expectancies (b=0.10, SE=0.03, Bootstrapped 95% CI [0.03, 0.19]), smoking abstinence harmful experiences (b=0.13, SE=0.05, Bootstrapped 95% CI [0.03, 0.25]), and barriers to cessation (b=0.05, SE=0.06, Bootstrapped 95% CI [0.01, 0.13]). Overall, the present study serves as an initial investigation into the nature of the associations between visceral sensitivity, anxiety symptoms, and clinically significant smoking processes among treatment-seeking smokers. Future work is needed to explore the extent to which anxiety accounts for relations between visceral sensitivity and other smoking processes (e.g., withdrawal, cessation outcome).

Advances in understanding role of brain-derived neurotrophic factor in physiological and pathological processes in the intestinal tract

Brain-derived neurotrophic factor is a kind of neurotrophic substance. In recent years, besides the central nervous system, brain-derived neurotrophic factor was also found to be expressed abundantly in the gastrointestinal tract, and it plays an important role in the development of the enteric nervous system and in regulating intestinal motility and visceral sensitivity. In this article, we review the role of brain-derived neurotrophic factor in the intestinal tract, and discuss its possible role in the pathogenesis of irritable bowel syndrome, with an aim to provide new ideas for clinical treatment of gastrointestinal diseases.

Acupuncture and regulation of gastrointestinal function

In China, acupuncture has been considered an effective method for treating gastrointestinal (GI) dysfunction diseases for thousands of years. In fact, acupuncture has gained progressive acceptance from both practitioners and patients worldwide. However, the therapeutic effects and underlying mechanisms in treating GI dysfunction have not yet been established due to a lack of systematic and comprehensive review articles. Therefore, the aim of this review is to discuss the efficacy of acupuncture as a treatment for GI dysfunction and the associated underlying mechanisms. A search of PubMed was conducted for articles that were published over the past 10 years using the terms “acupuncture”, “gastrointestine”, and other relevant keywords. In the following review, we describe the effect and underlying mechanisms of acupuncture on GI function from the perspectives of GI motility, visceral sensitivity, the GI barrier, and the brain-gut axis. The dual regulatory effects of acupuncture may manifest by promoting gastric peristalsis in subjects with low initial gastric motility, and suppressing peristalsis in subjects with active initial motility. In addition, the regulation of acupuncture on gastric motility may be intensity-dependent. Our findings suggest that further studies are needed to investigate the effects and more systematic mechanisms in treating GI dysfunction, and to promote the application of acupuncture for the treatment of GI diseases.

Rectal tone and compliance affected in patients with fecal incontinence after fistulotomy

AIM: To investigate the anal sphincter and rectal factors that may be involved in fecal incontinence that develops following fistulotomy (FIAF).

METHODS: Eleven patients with FIAF were compared with 11 patients with idiopathic fecal incontinence and with 11 asymptomatic healthy subjects (HS). All of the study participants underwent anorectal manometry and a barostat study (rectal sensitivity, tone, compliance and capacity). The mean time since surgery was 28 ± 26 mo. The postoperative continence score was 14 ± 2.5 (95%CI: 12.4-15.5, St Mark’s fecal incontinence grading system).

RESULTS: Compared with the HS, the FIAF patients showed increased rectal tone (42.63 ± 27.69 vs 103.5 ± 51.13, P = 0.002) and less rectal compliance (4.95 ± 3.43 vs 11.77 ± 6.9, P = 0.009). No significant differences were found between the FIAF patients and the HS with respect to the rectal capacity; thresholds for the non-noxious stimuli of first sensation, gas sensation and urge-to-defecate sensation or the noxious stimulus of pain; anal resting pressure or squeeze pressure; or the frequency or percentage of relaxation of the rectoanal inhibitory reflex. No significant differences were found between the FIAF patients and the patients with idiopathic fecal incontinence.

CONCLUSION: In patients with FIAF, normal motor anal sphincter function and rectal sensitivity are preserved, but rectal tone and compliance are impaired. The results suggest that FIAF is not due to alterations in rectal sensitivity and that the rectum is more involved than the anal sphincters in the genesis of FIAF.

Visceral sensitivity correlates with decreased regional gray matter volume in healthy volunteers: a voxel-based morphometry study

Regional changes in brain structure have been reported in patients with altered visceral sensitivity and chronic abdominal pain, such as in irritable bowel syndrome. It remains unknown whether structural brain changes are associated with visceral sensitivity. Therefore, we present the first study in healthy individuals to address whether interindividual variations in gray matter volume (GMV) in pain-relevant regions correlate with visceral sensitivity. In 92 healthy young adults (52 female), we assessed rectal sensory and pain thresholds and performed voxel-based morphometry (VBM) to compute linear regression models with visceral sensory and pain thresholds, respectively, as independent variable and GMV in a priori-defined regions of interest (ROIs) as dependent variable. All results were familywise error (FWE) corrected at a level of PFWE<.05 and covaried for age. The mean (±SEM) rectal thresholds were 14.78±0.46mm Hg for first sensation and 33.97±1.13mm Hg for pain, without evidence of sex differences. Lower rectal sensory threshold (ie, increased sensitivity) correlated significantly with reduced GMV in the thalamus, insula, posterior cingulate cortex, ventrolateral and orbitofrontal prefrontal cortices, amygdala, and basal ganglia (all PFWE<.05). Lower rectal pain threshold was associated with reduced GMV in the right thalamus (PFWE=.051). These are the first data supporting that increased visceral sensitivity correlates with decreased gray matter volume in pain-relevant brain regions. These findings support that alterations in brain morphology not only occur in clinical pain conditions but also occur according to normal interindividual variations in visceral sensitivity.

Low-grade mucosal inflammation induces colonic PAR-2 activation and visceral hypersensitivity in mice

AIM: To detect the expression of protease-activated receptor-2 (PAR-2) in the colon and substance P (SP) and calcitonin gene-related peptide (CGRP) in the cornu dorsale medullae spinalis and to explore the relationship between the activation of PAR-2 and visceral hypersensitivity in mice with dextran sulfate sodium (DSS)-induced low-glade colonic mucosal inflammation (LGI).

METHODS: Thirty-six C57BL/6 mice were randomly divided into two groups: LGI group and control group. The LGI group was given 1.5% DSS solution for 5 d and distilled water for another 10 d, while the control group was given distilled water only. After treatment, the myoelectric activity of the abdominal wall at different levels of colorectal distension (CRD) was recorded. The expression of SP and CGRP in the cornu dorsale medullae spinalis and PAR-2 in the colonic mucosa was detected by immunohistochemistry.

RESULTS: After treatment, colonic histological index (HI) in the LGI group was 1.500 ± 0.926. When the colon was distended to a pressure of 15 mmHg, the myoelectric activity of the abdominal wall in the LGI group was comparable to that in the control group (27.958 μV ± 1.660 μV vs 26.947 μV ± 0.854 μV, P > 0.05). However, the myoelectric activity of the abdominal wall was significantly higher in the LGI group than in the control group when the colon was distended to a pressure of 30, 45 or 60 mmHg (33.455 μV ± 3.786 μV vs 31.253 μV ± 3.842 μV; 46.848 μV ± 4.038 μV vs 37.267 μV ± 2.542 μV; 47.207 μV ± 18.151 μV vs 33.798 μV ± 8.415 μV, all P < 0.05). The integrated optical density (IA) of PAR-2 staining in the distal colon was significantly higher in the LGI group than in the control group. The IA of SP and CGRP staining in the spine cord was also significantly higher in the LGI group than in the control group (40.769 ± 8.422 vs 21.718 ± 4.131; 30.288 ± 13.530 vs 10.788 ± 4.490; 46.829 ± 26.261 vs 13.997 ± 3.340, all P < 0.05). There is a positive correlation between the expression of PAR-2 and SP and between the expression of PAR-2 and CGRP in the LGI group (r = 0.622, P < 0.05, r = 0.588, P < 0.05). The expression of PAR-2, SP or CGRP was closely correlated with the myoelectric activity of the abdominal wall in the LGI group (r = 0.439-0.835, P < 0.05).

CONCLUSION: Low-grade mucosal inflammation induces visceral hypersensitivity in mice possibly by activating colonic PAR-2.

Visceral sensitivity and expression of 5-hydroxytryptamine and c-fos in the spinal dorsal horn in a rat model with irritable bowel syndrome

AIM: To study the visceral sensitivity by rectal balloon distension and expression of 5-hydroxy-tryptamine (5-HT) and c-fos in the spinal dorsal horn of a rat model with constipation-predominant irritable bowel syndrome (C-IBS).

METHODS: The rat model was established by intragastric injection with ice-cold water (0-4℃). The perception thresholds and the number of abdominal withdrawal reflexes (AWRs) were recorded during rectal balloon distention in order to evaluate visceral sensitivity in the model group (A, n = 10) and control group (B, n = 10). Expression of 5-HT and c-fos in the spinal dorsal horn was shown by immunohistochemical staining, and analyzed semi-quantitatively by computerized color image analyzer using immunoreactive areas and optical density (OD). The statistical difference of the OD and immunoreactive areas between the two groups was examined by t test.

RESULTS: The perception threshold in group A was slightly higher than that in group B during rectal balloon distention, but there was no significant difference (0.59 ± 0.09 vs 0.57 ± 0.13, P > 0.05). The number of AWRs to the lower balloon content (1.0 mL) was much lower in group A than in group B (10.3 ± 3.3 vs 18.3 ± 5.5, P < 0.05), although no difference was found to the higher balloon content (1.5 and 2.0 mL). Immunoreactive area and OD of 5-HT- and c-fos-positive neurons and fibers in group A were significantly higher than those in group B (5-HT immunoreactive area, 146.5 ± 15.1 vs 109.3 ± 18.5; 5-HT OD, 45826 ± 2563.2 vs 29358 ± 8965.5; c-fos immunoreactive area, 125.4 ± 23.3 vs 88.7 ± 23.2; c-fos OD, 46258 ± 4642 vs 33238 ± 4587; all P < 0.05).

CONCLUSION: The model of C-IBS has a decreased visceral sensitivity to rectal balloon distention. The increased expression of 5-HT and c-fos in the spinal dorsal horn is probably involved in the process.