Stress and Gastrointestinal Motility in Humans: A Review of the Literature

Single-day and multi-day exposure to orogastric gavages does not affect intestinal barrier function in mice

Animals involved in common laboratory procedures experience minor levels of stress. The direct effect of limited amounts of stress on gastrointestinal function has not been reported yet. Therefore, this study aimed to assess the effect of single-day and multi-day orogastric gavages on gut physiology in mice. To this end, 12-wk-old female C57Bl6/J mice were randomized to receive treatment with sterile water (200 µL) delivered by orogastric gavages twice daily for a total of 1 or 10 day(s). Control animals did not receive any treatment. Subsequently, gastrointestinal function was assessed by measuring fecal pellet production. Furthermore, ex vivo intestinal barrier and secretory function of the distal colon, proximal colon, and terminal ileum were quantified in Ussing chambers. In mice, single-day gavages did neither influence corticosterone levels nor gastrointestinal function. In mice exposed to multi-day gavages, corticosterone levels were slightly but significantly increased compared with controls after 10 days of treatment. Gastrointestinal motor function was altered, as evidenced by increased fecal pellet counts and a small increase in fecal water content. However, exposure to repeated gavages did not lead to detectable alterations in gastrointestinal barrier function as quantified by the paracellular flux of the probe 4 kDa FITC-dextran as well as transepithelial resistance measurements. Thus, the administration of drugs via single-day or multi-day orogastric gavages leads to no or minor stress in mice, respectively. In both cases, it does not hamper the study of the intestinal barrier function and therefore remains a valuable administration route in preclinical pharmacological research.NEW & NOTEWORTHY Exposure of mice to serial orogastric gavages over the course of 10 days leads to a small but significant increase in plasma corticosterone levels, indicating the presence of a limited amount of stress that is absent after a single-day treatment. This minor stress after multi-day gavages results in increased fecal pellet production and fecal water content in exposed compared with nontreated mice but does not affect the intestinal barrier function in the distal colon, proximal colon, or terminal ileum.

Practicing Digital Gastroenterology through Phonoenterography Leveraging Artificial Intelligence: Future Perspectives Using Microwave Systems

Production of bowel sounds, established in the 1900s, has limited application in existing patient-care regimes and diagnostic modalities. We review the physiology of bowel sound production, the developments in recording technologies and the clinical application in various scenarios, to understand the potential of a bowel sound recording and analysis device-the phonoenterogram in future gastroenterological practice. Bowel sound production depends on but is not entirely limited to the type of food consumed, amount of air ingested and the type of intestinal contractions. Recording technologies for extraction and analysis of these include the wavelet-based filtering, autoregressive moving average model, multivariate empirical mode decompression, radial basis function network, two-dimensional positional mapping, neural network model and acoustic biosensor technique. Prior studies evaluate the application of bowel sounds in conditions such as intestinal obstruction, acute appendicitis, large bowel disorders such as inflammatory bowel disease and bowel polyps, ascites, post-operative ileus, sepsis, irritable bowel syndrome, diabetes mellitus, neurodegenerative disorders such as Parkinson's disease and neonatal conditions such as hypertrophic pyloric stenosis. Recording and analysis of bowel sounds using artificial intelligence is crucial for creating an accessible, inexpensive and safe device with a broad range of clinical applications. Microwave-based digital phonoenterography has huge potential for impacting GI practice and patient care.

The Psychobiological Etiology of Gastrointestinal Distress in Sport: A Review

Gastrointestinal (GI) disturbances are common during training and competition, especially among endurance athletes. Historically, little attention has been paid to the psychobiological etiology of GI problems in sport. The aim of this review is to: (1) provide a physiological overview of how psychological stress and anxiety impact GI system function; (2) review the literature that has examined the role of stress and anxiety in GI distress in athletes; and (3) provide suggestions for future research. Animal and human studies have documented that psychological stressors reduce gastric motility and delay stomach emptying while simultaneously increasing large intestine motility. These functional changes are likely mediated through the secretion of corticotropin-releasing factor and subsequent alterations in autonomic nervous system activity, which act to reduce splanchnic blood flow and increase GI permeability. In addition, chronic stress and anxiety may worsen GI discomfort by increasing visceral hypersensitization. Still, only a couple of studies have found modest associations between stress, anxiety, and the occurrence/severity of GI distress in active populations. As such, future work should attempt to confirm that experimentally inducing psychological stress results in the aforementioned GI problems during exercise. Furthermore, studies are needed to determine how psychological stress impacts the tolerance to nutritional fueling and whether it worsens the GI permeability that normally occurs with exercise.

The effects of stress during the mirror drawing test on electrogastrograms of subjects who underwent gastrointestinal surgery involving either total gastrectomy, distal gastrectomy, or total esophagectomy with colonic replacement

Electrogastrograms (EGGs) were recorded from 16 locations on the thoraco-abdominal surface to find the maximum absolute power foci during rest (RAP) and the maximum ratio of the % content during the mirror drawing test (MDT) compared to that during rest (%C-MDT/R) for both the 3 cpm (2.4–4.9) and 6 cpm (5.0–7.4) groups. The maximum foci were obtained from control subjects and those who received gastro-intestinal surgery via total gastrectomy (TG), distal gastrectomy (DG), and total esophagectomy with colonic replacement (CR). The control mean of the infraumbilical channels 10–16 (I) expressed as %C-MDT/R of the 3 cpm group was higher than the mean of the supraumbilical channels 1–9 (S) (I>S, P<0.001). The maximum focus of the 3-cpm %C-MDT/R was in the left umbilical area, while that of the 6-cpm %C-MDT/R was found bilaterally in the right epigastric and left umbilical areas, interposed by the lower %C-MDT/R gastric area. Therefore, the presence of gastric EGG inhibition and colonic facilitation are suggested to occur during MDT. In TG and DG, the foci of the %C-MDT/R in the 3-cpm group were located bilaterally in the right epigastric and left umbilical areas. The shifts of foci suggest colonic EGG facilitation. The mean S of the 3-cpm group was significantly higher than the mean I with CR (S>I, P<0.05). The maximum foci of the 3- and 6-cpm groups were in the epigastrium. These results suggest colonic EGG facilitation in the epigastrium, as the stomach has been removed and the original gastric location is instead occupied by the transverse colon in CR.

[Psychophysiology of visceral pain]

The psychophysiology of visceral pain is--different from cardiac psychophysiology--much less well investigated due to the invasiveness of its methods and problems associated with reliably and reproducibly stimulating as well as recording of the gastrointestinal tract. Despite these problems, the last 30 years have documented a number of psychophysiological phenomena such as the perception (interoception) of visceral stimuli, the effect of emotions and stress on visceral sensations, and the effect of visceral processes on cortical processing. This was mainly due to the application of neurophysiological techniques (cortical imaging and stimulation) in these investigations.

Correlations between anxiety and the stress responses of electrogastrography (EGG) induced by the mirror drawing test (MDT)

Electrogastrograms (EGGs) were recorded at 16 locations on the thoraco-abdominal surface at rest and then both during and after the acute stress of performing the mirror drawing test (MDT). A significant linear correlation with a negative slope was found between the anxiety scores and the ratio of the power content during MDT to the power content at rest (r) (MDTr(-1)) of the 3 cpm component from the epigastric channel 2 recording. In contrast, significant linear correlations with positive slopes were found between the anxiety scores and MDTr(-1) of the 6 cpm component of the recordings from the infraumbilical channels (channels 13, 15, and 16). The epigastric 3-cpm EGG activity reflects gastric myoelectric activity, while the infraumbilical 3- and 6-cpm activity reflects that of the colon. Therefore, these results seem to further support the previous report of the inhibition of gastric EGG by stress and the stress-mediated facilitation of colonic EGG (Homma S, J Smooth Muscle Res. 2012; 48(2-3): 47-57).

Altered psychobiological responsiveness in women with irritable bowel syndrome

OBJECTIVE

Although stress has been considered an important pathophysiological factor in irritable bowel syndrome (IBS), there is incomplete understanding of its physiological mechanisms. The current study was designed to compare diurnal hypothalamic-pituitary-adrenal (HPA) axis activity in IBS patients and controls and their psychobiological response to a psychosocial stressor.

METHODS

Basal and stimulated HPA axis activity was assessed in 57 women with IBS and 20 matched controls. Psychiatric comorbidity was assessed using a standardized clinical interview. Salivary morning cortisol and diurnal profile were obtained, and the Trier Social Stress Test (TSST) was administered. Levels of cortisol and adrenocorticotropic hormone (ACTH) were measured before and within 1 hour after the stressor. Overall stress experience and stress related to the TSST were assessed using standardized questionnaires.

RESULTS

All subjects showed intact circadian variation of cortisol. However, IBS patients with predominant diarrhea exhibited substantially heightened cortisol levels at awakening (p < .03) and a blunted cortisol awakening response. In response to the TSST, patients exhibited significantly blunted cortisol (p < .05) and slightly attenuated ACTH secretion compared with controls. During the recovery period, ACTH levels were significantly lower (p < .04) in patients than those in healthy subjects. Women with IBS perceived higher stress susceptibility than control subjects did (p < .01).

CONCLUSIONS

The enhanced morning cortisol levels in one subgroup of IBS patients may indicate an association between basal HPA axis activity and predominant bowel habit. The downregulated HPA axis reactivity in IBS after the TSST suggests a downregulated sensitivity of the endocrine system. On the contrary, all subjective stress ratings were increased in the IBS group, which may indicate increased stress susceptibility.

Psychophysiology of visceral pain in IBS and health

The psychophysiology of visceral pain as it relates to gastrointestinal motility, visceral sensitivity, and putative mechanisms of the processing of visceral stimuli by the central and peripheral nervous systems are discussed. Peripheral mechanisms may include low-grade mucosal inflammation, and it is likely that central nervous mechanisms such as neuronal plasticity at the level of the spinal cord and attentional bias at the cortical level are relevant for the chronification of visceral pain. From a psychophysiological perspective, visceral pain therefore remains a complex symptom because behavioral variables, such as the way an individual deals with stress, may be as important for the etiology of visceral pain as, for example, a history of inflammation.

[Functional gastrointestinal disorders]

The functional gastrointestinal disorders (FGID) are the most frequent clinical conditions seen in practice. The FGID are associated with significant work absenteeism, impaired quality of life and increased medical costs. Most patients also suffer from psychosocial problems. Therefore it is important to define the patient's complaints in terms of a biopsychosocial disorder rather than just a medical illness. Physicians must acknowledge the relevance of the psychosocial aspects to prepare the patient for a referral to a specialist (in psychosomatic medicine or a psychotherapist) and to get the patient interested in the psychological factors involved as well as further explore their cause. Most of the research on psychotherapy in FGID to date has focused on the irritable bowel syndrome, and different methods of treatments have been studied (e. g., cognitive-behavioral therapy, dynamic psychotherapy, hypnotherapy, and relaxation). Randomised controlled studies have shown that psychotherapy is superior to conventional medical therapy. Hypnotherapy seems to be very successful. Predictors of a positive response to psychological treatment generally are: (1) awareness that stress exacerbates their bowel symptoms, (2) mild anxiety or depression, (3) the predominant bowel symptom is abdominal pain or diarrhea and not constipation, (4) the abdominal pain waxes and wanes in response to eating, defecation, or stress rather than being constant pain, and (5) the symptoms are of relatively short duration. Psychotherapy is initially relatively expensive because it requires multiple, long sessions. However, its benefits persist or even increase over time, and in the long run, there may be a reduction in clinic visits and health care costs which offsets the initial cost of psychological treatment.

[Psychosomatic aspects of bowel diseases]

Functional gastrointestinal disorders (FGID) and inflammatory bowel diseases (IBD) are the most frequently studied bowel disorders in the context of a bio psycho-social model. FGID are associated with significant work absenteeism, impaired quality of life, and increased medical costs. Many patients also suffer from psychosocial problems. Most of the research in FGID to date has focused on the irritable bowel syndrome. Randomised controlled studies have shown that psychotherapy is superior to conventional medical therapy. The gut-focussed hypnotherapy seems to be very successful. For IBD it is increasingly recognized that the psycho-neuro-endocrine network can modulate inflammation and pain perception and that psychosocial factors are related to exacerbation of and coping with IBD. The psychosocial consequences of the illness become more significant with increasing severity of the disease. Therefore integrated psychosomatic care should be provided, the patient's psychosocial status and the demand for additional psychological care should be assessed and offered, if indicated.

The effects of stress in response to mirror drawing test trials on the electrogastrogram, heart rate and respiratory rate of human subjects

Electrogastrograms (EGGs), heart and respiratory rates were recorded simultaneously from human subjects and analyzed spectrally by the maximal entropy method. The stress of the mirror drawing test (MDT) significantly increased both the heart and respiratory rates with an associated increase in LF/HF ratios. MDT stress, however, increased (excited groups) or decreased (inhibited groups) the power amplitude and the power ratio, (peak power during MDT)/(peak power during rest), of the 1-cpm (0-2.4 cpm), 3-cpm (2.5-4.9), 6-cpm (5.0-7.4), 8-cpm (7.5-9.9) and 10-cpm (10.0-12.9) spectral group components of the EGG recording of the electrical activity of the gastrointestinal tract. The depression scores of the subjects in the MDT stress excited group were higher and their resting frequencies were significantly lower than those of the MDT stress inhibited groups in each of the epigastric, supra-umbilical and infra-umbilical 6-cpm frequency groups but not in the epigastric 1-cpm frequency group. Anxiety scores of the MDT stress excited groups were significantly higher and their power ratios were also significantly higher than those of the inhibited groups in each of the epigastric 10-cpm, the supra-umbilical 6-cpm and the infra-umbilical 1- and 3-cpm frequency groups. Therefore, depression scores appeared to have inhibitory effects on the resting EGG frequencies, while anxiety scores appeared to have facilitatory effects on the EGG power ratio during MDT stress. It is suggested that analysis of EGG under MDT stress would provide a measure of the stress sensitivity of the electrical activity of the human gastrointestinal tract.

Reference values for stationary and 24-hour ambulatory esophageal manometry and pH data in Hispanic population

BACKGROUND

It has not yet been determined whether values obtained with stationary esophageal motility test are similar to those obtained with the 24-h procedure. Furthermore, there are no normal values established for esophageal pH and motility parameters in a Hispanic population.

METHODS

Reflux symptoms, endoscopy, Helicobacter pylori, stationary esophageal manometry, and combined 24-h pH-manometry were evaluated in 12 healthy volunteers. Three subjects also underwent 24-h esophageal bilirubin monitoring.

RESULTS

Mean lower esophageal sphincter pressure measured stationary was lower (p<0.05) compared with 24-h ambulatory procedure. Mean duration of contraction waves was greater with stationary method (p<0.05). Esophageal contraction mean amplitude was not different between both procedures. Total percent of time with pH<4 was 0.16+/-0.21. Total 24-h acid reflux episodes were 5.5+/-6.6, with no episodes >5 min. No high bilirubin reflux episodes were recorded.

CONCLUSIONS

These results suggested that physiologic motility parameters differed depending on the method employed for its evaluation. Values obtained with stationary and 24-h ambulatory esophageal manometry are identical when evaluating amplitude of contractions but differ in duration of contractions and lower esophageal sphincter pressure. In addition, these results provide for the first time reference values for stationary and 24-h ambulatory esophageal manometry and pH data in a Hispanic population.

Autonomic control of colonic tone and the cold pressore test

BACKGROUND

Cardiovascular responses to cold stimulation are well characterised. It is unclear, however, whether cold pain stimulates responses in colonic tone in the transverse and sigmoid regions.

AIMS

To assess the effects of cold stimulation on tone nd motility in the transverse and sigmoid colon and on cardiovascular autonomic activity.

METHODS

Phasic and tonic motility of the transverse and sigmoid colon, pulse rate, and beat to beat pulse variability (which are measures of centrally mediated changes in autonomic function) were measured before, during, and after a standard cold pressor test in 22 healthy volunteers.

RESULTS

Cold pain induced a significant increase in colonic tone but not phasic contractility in the transverse and sigmoid regions. Simultaneously, cold pain increased pulse interval variability.

CONCLUSION

The findings are consistent with the hypotheses that cold pain produces coactivation of both the sympathetic and parasympathetic limbs of the autonomic nervous system and that cold induced changes in colonic tone are temporally associated with alterations in central autonomic nervous activity.

Effects of different psychophysiological stressors on the cutaneous electrogastrogram in healthy subjects

To evaluate the effect of psychophysiological stress on the gastric electrical activity, the cutaneous electrogastrography (EGG), a non-invasive technique, was performed in ten healthy subjects. Three different stressful (cold pressor test, arithmetic task, and Stroop color-word test) tests and a non-stressful (reading a booklet) task were administered, and EGG parameters (dominant frequency, coefficient of variation of dominant frequency, and gastric power) were recorded during baseline, task and rest periods. Neutral task did not affect EGG parameters. During stressful stimulations, a slight decrease in the dominant frequency and an increase in the coefficient of variation of the dominant frequency were found. During arithmetic task, the gastric power significantly increased (baseline vs stimulus P = 0.008; stimulus vs rest P = 0.015; baseline vs rest P = 0.011), and a statistically significant difference between gastric power during arithmetic and neutral task was observed (P = 0.007). During Stroop test, the gastric power showed only a trend toward significance (baseline vs stimulus P = 0.018; stimulus vs rest P = 0.018). A wide interindividual variability was recorded during the stress period. Therefore, the individual susceptibility to psychological stress may influence the EGG response and gastric electrical activity. In conclusion, cutaneous electrogastrography may be used as a non-invasive technique to study the effects of acute stressors on the gastric electrical activity.