Altered psychobiological responsiveness in women with irritable bowel syndrome

Neuroendocrine System Adaptation during Consecutive Extrinsic Stimuli: A Pilot Dynamic Study

This pilot repeated measures study aims to evaluate the dynamics of the autonomic nervous system (ANS), the hypothalamic-pituitary-adrenal (HPA) axis, and/or their interplay with low-level inflammation in healthy schoolchildren during consecutive extrinsic stimuli. Twenty healthy schoolchildren and adolescents aged 11-14 years (12.5 ± 1.5) were consecutively exposed to an oral task (#2) and an arithmetic task (#3) (Trier Social Stress Test for Children (TSST-C)), lasting 5 min each, and a three-minute cellular phone call (#4). Salivary cortisol (SC) was sampled at baseline (#1) and immediately after each exposure (#2, 3, and 4). Baseline serum high-sensitivity C-reactive protein (hsCRP) and cortisol levels were also assessed. ANS dynamics and complexity were measured using Sample Entropy (SampEn) at each experimental time period (#1-4). Baseline serum hCRP and cortisol correlated negatively to each other, while the ANS and HPA axis acute reactions to the three consecutive stimuli differed over time. The ANS adaptation to these stimuli included complexity modulation, which was not dependent on baseline hsCRP or cortisol, and weakened during the third stimulation. However, baseline hsCRP and cortisol had a weakening and an increasing effect on the HPA axis over time, respectively. We conclude that low-level inflammation and baseline morning cortisol level have no effect on ANS dynamics but influence the HPA axis response to consecutive external stimuli.

Interactions between symptoms and psychological status in irritable bowel syndrome: An exploratory study of the impact of a probiotic combination

BACKGROUND

Stress is an exacerbator of irritable bowel syndrome (IBS) symptoms, and anxiety and depression are co-morbidities. Bifidobacterium longum strains 1714® and 35642® attenuate stress responses in healthy people and reduce symptoms in IBS, respectively. Here, we explore relationships between the psychological and visceral effects of the two strains (COMBO) in IBS subjects and biomarkers of stress and inflammation.

METHODS

We recruited 40 patients with IBS (Rome III) and mild to moderate anxiety (HADS-A) and/or depression (HADS-D) and 57 asymptomatic female controls with low or moderate stress. IBS patients were fed COMBO (1 × 10⁹ cfu/day) for 8 weeks with an 8-week washout. IBS symptoms, psychometric measures, salivary cortisol awakening response (CAR), and plasma inflammatory biomarkers were assessed every 4 weeks.

KEY RESULTS

Compared to healthy controls, IBS subjects had a blunted CAR. Treatment with COMBO restored CAR and improved IBS symptoms compared to baseline during the treatment phase. The COMBO reduced HADS-D, HADS-A score, and TNF-α, while sleep quality improved significantly from baseline to the end of the intervention. Surprisingly, these parameters improved further once treatment ended and maintained this improvement by Week 16.

CONCLUSIONS AND INFERENCES

These findings suggest that the stress response is a major driver of IBS symptoms. The time course of the beneficial effect of COMBO on IBS symptoms suggests that this is achieved through a restoration of the stress response. In contrast, the time course of the effects of COMBO on anxiety and depression in IBS paralleled an anti-inflammatory effect as indicated by a reduction in circulating levels of TNF-α.

Emotional stress responsivity of patients with IBS - a systematic review

OBJECTIVE

Irritable bowel syndrome (IBS) is a highly prevalent disorder of the gut-brain interaction characterized by abdominal discomfort and pain associated with altered bowel habits in the absence of structural abnormalities. Chronic psychological stress is considered a risk factor for the development of IBS. The multifactorial pathogenesis involves complex interactions between biological, psychological and social factors, yet the underlying mechanisms have not been fully understood.

METHODS

We systematically reviewed the literature from the databases MEDLINE, Embase and PsycINFO to assess stress responsivity of patients with IBS in comparison to healthy individuals, specifically focusing acute psychological stressors.

RESULTS

A total of 37 case-control studies were included in the narrative synthesis. Findings comprised subjective changes in emotion (k = 18) and of gastrointestinal symptoms (k = 8) as well as objective parameters of gastrointestinal motility (k = 10), autonomic nervous system (k = 23), hypothalamic-pituitary-adrenal axis (k = 11), functional brain activity (k = 7) and immune system (k = 3). Mental stress was found to increase IBS-specific symptomatology and alter gastrointestinal motility. Some patients with IBS showed stress-induced emotional hyperresponsivity and different patterns of neural activation. Autonomic and endocrine stress responses depend on the type of stressor and showed no clear evidence of differential reactivity, partly due to confounding factors. Data on acute immunological changes remains sparse and requires further investigation.

CONCLUSIONS

Current evidence suggests altered stress reactivity in patients with IBS however, it remains unclear whether it can be attributed to the syndrome itself or the high prevalence of psychiatric comorbidities.

Concordant pattern of the HPA axis response to visceral stimulation and CRH administration

The physiological and psychological mechanisms explaining the individual variability in the stress response are poorly understood. We tested the hypothesis that hypothalamic-pituitary- adrenal (HPA) axis responses to colorectal stimulation affect HPA axis reactivity to corticotropin-releasing hormone (CRH), the visceral pain threshold, and perceived stress. We examined 31 healthy volunteers and 27 individuals with irritable bowel syndrome. According to the ACTH response to colorectal stimulation, the participants were classified into three groups: flattened, decreased, and increased. We found significant differences in the abdominal pain threshold, discomfort threshold, and sensitivity to anxiety among the groups. There were significant differences in the ACTH change and peak level after CRH administration among the groups. The area under the curve of the cortisol response to CRH was significantly different among the groups. The increased group showed a higher basal ACTH level, earlier peak level in the CRH administration test, and higher stress rating during the experiment. The increased group had an exaggerated psychological and physiological stress response, whereas the decreased group had a higher anticipatory endocrine response, stress, and sensitivity to anxiety. Further studies are needed to determine factors including gut microbiota on the individual difference in HPA response.

Sex Hormones, BDNF, Leptin, and TGF-β1 in Females With IBS: A Pilot Investigation

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic gastrointestinal condition predominantly affecting the female sex, and is characterized by brain-gut axis dysregulation. Relevance of hormones along the hypothalamic-pituitary gonadal axis and hypothalamic-pituitary adrenal axis to IBS symptomatology remain unclear, as does the significance of other modulators including brain derived neurotrophic factor (BDNF), leptin, and transforming growth factor βeta 1 (TGF-β1).

METHODS

Females with IBS were compared with female healthy controls (HC) on age, race, hormonal contraceptive use, body mass index, adrenocorticotropic hormone, cortisol, estradiol, follicular stimulating hormone, luteinizing hormone, progesterone, total cholesterol, Center for Epidemiological Studies Depression Scale (CES-D) and Perceived Stress Scale (PSS). BDNF, leptin, and TGF-β1 were quantified using enzyme-linked immunosorbent assay. Descriptive statistics, non-parametric techniques, and regression analyses were performed.

RESULTS

Participants with IBS (n = 12) displayed higher estradiol (p = .027) than did HC (n = 21). Direction of associations among study variables often differed between groups: BDNF and progesterone in HC (r_s = .623) and in IBS (r_s = -.723). The relationship between log (CES-D) and log (estradiol) varied by IBS status (interaction term p = 0.019).

DISCUSSION

Elevated estradiol in participants with IBS, and differential patterns of biological and psychological indices between groups, encourages further inquiry on the relevance of sex hormones, BDNF, leptin, and TGF-β1 to symptoms of IBS. Future research endeavors should conduct longitudinal quantification of sex hormones with subjective symptom assessment to facilitate insight on the pathophysiology and female sex bias in IBS.

Effects of cognitive-behavioral stress management training in individuals with functional somatic symptoms - an exploratory randomized controlled trial

Stress is discussed as a risk factor in the manifestation and maintenance of functional somatic (FS) symptoms. However, there is a lack of evidence regarding the effects of cognitive-behavioral stress management training (CBSM) on FS symptoms and the (potentially mediating) role of the neuroendocrine system. This study aims to examine stress-related psychological and neuroendocrine changes after receiving a brief CBSM in individuals with FS symptoms. Forty-three participants of both sexes, who reported at least one current FS symptom, were analyzed (treatment group (TG) n = 21, waitlist control group (WCG) n = 22) using mixed models. Number of symptoms, psychological stress, and salivary cortisol levels were assessed at pretreatment, posttreatment, and 6 months later. Mixed model analyses did not reveal significant differences between the TG and the WCG regarding number of FS symptoms (p > 0.05), psychological stress measures (p > 0.05) or the cortisol awakening response (CAR) (p > 0.05). The TG presented lower diurnal cortisol levels at pretreatment, posttreatment and 6 months later (p < 0.05). We did not find significant beneficial effects that were specific to CBSM. Further research should be undertaken to investigate the effects of CBSM on real life stress or laboratory stressors in subjects with FS symptoms. Moreover, learning cognitive restructuring and establishing new coping strategies into everyday life might require more time. This study is a first step in filling the gap in understanding the influences of CBSM as a brief intervention on psychological and biological aspects of stress in participants with FS symptoms and will hopefully inform larger trials of CBSM for FS symptoms.

Does Irritable Bowel Syndrome Exist? Identifiable and Treatable Causes of Associated Symptoms Suggest It May Not

Significant shortcomings in irritable bowel syndrome (IBS) diagnosis and treatment may arise from IBS being an “umbrella” diagnosis that clusters several underlying identifiable and treatable causes for the same symptom presentation into one classification. This view is compatible with the emerging understanding that the pathophysiology of IBS is heterogeneous with varied disease mechanisms responsible for the central pathological features. Collectively, these converging views of the pathophysiology, assessment and management of IBS render the traditional diagnosis and treatment of IBS less relevant; in fact, they suggest that IBS is not a disease entity per se and posit the question “does IBS exist?” The aim of this narrative review is to explore identifiable and treatable causes of digestive symptoms, including lifestyle, environmental and nutritional factors, as well as underlying functional imbalances, that may be misinterpreted as being IBS.

Perceived Stress, Its Physiological Correlates, and Quality of Life in Patients With Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic, common disorder of the gastrointestinal tract associated with high psychological comorbidity and diminished quality of life. Patients with IBS display a heightened sensitivity to stress, although the literature is inconsistent as to whether they have a dysregulated stress response. The purpose of the present investigation, a substudy of a larger research effort, was to examine physiological correlates of perceived stress in patients with IBS (cortisol and adrenocorticotropic hormone) and to explore associations between perceived stress and quality of life. A total of 101 participants (35 with IBS [predominant subtypes IBS-constipation and IBS-diarrhea] and 66 healthy controls [HCs]) completed self-report inventories regarding perceived stress and quality of life, and fasting peripheral blood was drawn. Participants with IBS did not differ from the HC in demographic or physiological measures but did differ in psychological measures, reporting significantly higher levels of perceived stress and lower levels of quality of life. Perceived stress and quality of life were not significantly associated in IBS participants. However, differential findings of the stress response were found within IBS participants by sex, race, and subtype. These findings illustrate the heterogeneity of the IBS patient population, underscore the necessity of evaluating larger sample sizes and increasing the diversity of such samples to include males and ethnic minorities, and demonstrate the importance of taking an individualized approach to evaluation and treatment in the IBS patient population.

A psychology of the human brain-gut-microbiome axis

In recent years, we have seen increasing research within neuroscience and biopsychology on the interactions between the brain, the gastrointestinal tract, the bacteria within the gastrointestinal tract, and the bidirectional relationship between these systems: the brain-gut-microbiome axis. Although research has demonstrated that the gut microbiota can impact upon cognition and a variety of stress-related behaviours, including those relevant to anxiety and depression, we still do not know how this occurs. A deeper understanding of how psychological development as well as social and cultural factors impact upon the brain-gut-microbiome axis will contextualise the role of the axis in humans and inform psychological interventions that improve health within the brain-gut-microbiome axis. Interventions ostensibly aimed at ameliorating disorders in one part of the brain-gut-microbiome axis (e.g., psychotherapy for depression) may nonetheless impact upon other parts of the axis (e.g., microbiome composition and function), and functional gastrointestinal disorders such as irritable bowel syndrome represent a disorder of the axis, rather than an isolated problem either of psychology or of gastrointestinal function. The discipline of psychology needs to be cognisant of these interactions and can help to inform the future research agenda in this emerging field of research. In this review, we outline the role psychology has to play in understanding the brain-gut-microbiome axis, with a focus on human psychology and the use of research in laboratory animals to model human psychology.

The Trier Social Stress Test: Principles and practice

Researchers interested in the neurobiology of the acute stress response in humans require a valid and reliable acute stressor that can be used under experimental conditions. The Trier Social Stress Test (TSST) provides such a testing platform. It induces stress by requiring participants to make an interview-style presentation, followed by a surprise mental arithmetic test, in front of an interview panel who do not provide feedback or encouragement. In this review, we outline the methodology of the TSST, and discuss key findings under conditions of health and stress-related disorder. The TSST has unveiled differences in males and females, as well as different age groups, in their neurobiological response to acute stress. The TSST has also deepened our understanding of how genotype may moderate the cognitive neurobiology of acute stress, and exciting new inroads have been made in understanding epigenetic contributions to the biological regulation of the acute stress response using the TSST. A number of innovative adaptations have been developed which allow for the TSST to be used in group settings, with children, in combination with brain imaging, and with virtual committees. Future applications may incorporate the emerging links between the gut microbiome and the stress response. Future research should also maximise use of behavioural data generated by the TSST. Alternative acute stress paradigms may have utility over the TSST in certain situations, such as those that require repeat testing. Nonetheless, we expect that the TSST remains the gold standard for examining the cognitive neurobiology of acute stress in humans.

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The TSST is the human experimental gold standard for evaluating the neurobiology of acute stress.

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The HPA axis response to the TSST is higher in males and lower in older adults.

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Genotype and epigenetic factors moderate the neurobiological response to the TSST.

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Multiple adaptations of the TSST are available for different testing contexts.

The effect of sex and irritable bowel syndrome on HPA axis response and peripheral glucocorticoid receptor expression

BACKGROUND AND AIMS

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been reported in irritable bowel syndrome (IBS). Enhanced HPA axis response has been associated with reduced glucocorticoid receptor (GR) mediated negative feedback inhibition. We aimed to study the effects of IBS status, sex, or presence of early adverse life events (EAL) on the cortisol response to corticotropin-releasing factor (CRF) and adrenocorticotropic hormone (ACTH), and on GR mRNA expression in peripheral blood mononuclear cells (PBMCs).

METHODS

Rome III+ IBS patients and healthy controls underwent CRF (1μg/kg ovine) and ACTH (250μg) stimulation tests with serial plasma ACTH and cortisol levels measured (n=116). GR mRNA levels were measured using quantitative PCR (n=143). Area under the curve (AUC) and linear mixed effects models were used to compare ACTH and cortisol response measured across time between groups.

RESULTS

There were divergent effects of IBS on the cortisol response to ACTH by sex. In men, IBS was associated with an increased AUC (p=0.009), but in women AUC was blunted in IBS (p=0.006). Men also had reduced GR mRNA expression (p=0.007). Cumulative exposure to EALs was associated with an increased HPA response. Lower GR mRNA was associated with increased pituitary HPA response and increased severity of overall symptoms and abdominal pain in IBS.

CONCLUSION

This study highlights the importance of considering sex in studies of IBS and the stress response in general. Our findings also provide support for PBMC GR mRNA expression as a peripheral marker of central HPA response.

Biopsychosocial Aspects of Functional Gastrointestinal Disorders

In this paper, we provide a general framework for understanding the functional gastrointestinal disorders (FGID) from a biopsychosocial perspective. More specifically, we provide an overview of the recent research on how the complex interactions of environmental, psychological, and biological factors contribute to the development and maintenance of the FGID. We emphasize that considering and addressing all these factors is a conditio sine qua non for appropriate treatment of these conditions. First, we provide an overview of what is currently known about how each of these factors - the environment, including the influence of those in an individual's family, the individual's own psychological states and traits, and the individual's (neuro)physiological make-up - interact to ultimately result in the generation of FGID symptoms. Second, we provide an overview of commonly used assessment tools which can assist clinicians in obtaining a more comprehensive assessment of these factors in their patients. Finally, the broader perspective outlined earlier is applied to provide an overview of centrally acting treatment strategies, both psychological and pharmacological, which have been shown to be efficacious to treat FGID.

Aspects of the non-pharmacological treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most commonly diagnosed gastrointestinal conditions. It represents a significant healthcare burden and remains a clinical challenge. Over the years IBS has been described from a variety of different perspectives; from a strict illness of the gastrointestinal tract (medical model) to a more complex multi-symptomatic disorder of the brain-gut axis (biopsychosocial/psychosomatic model). In this article we present aspects of the pathophysiology and the non-pharmacological treatment of IBS based on current knowledge. Effects of conditioned stress and/or traumatic influences on the emotional system (top-down) as well as effects on the intestine through stressors, infection, inflammation, food and dysbiosis (bottom-up) can affect brain-gut communication and result in dysregulation of the autonomic nervous system (ANS), playing an important role in the pathophysiology of IBS. Conditioned stress together with dysregulation of the autonomic nervous system and the emotional system may involve reactions in which the distress inside the body is not recognized due to low body awareness. This may explain why patients have difficulty identifying their symptoms despite dysfunction in muscle tension, movement patterns, and posture and biochemical functions in addition to gastrointestinal symptoms. IBS shares many features with other idiopathic conditions, such as fibromyalgia, chronic fatigue syndrome and somatoform disorders. The key to effective treatment is a thorough examination, including a gastroenterological examination to exclude other diseases along with an assessment of body awareness by a body-mind therapist. The literature suggests that early interdisciplinary diagnostic co-operation between gastroenterologists and body-mind therapists is necessary. Re-establishing balance in the ANS is an important component of IBS treatment. This article discusses the current knowledge of body-mind treatment, addressing the topic from a practical point of view.

Interoception and stress

Afferent neural signals are continuously transmitted from visceral organs to the brain. Interoception refers to the processing of visceral-afferent neural signals by the central nervous system, which can finally result in the conscious perception of bodily processes. Interoception can, therefore, be described as a prominent example of information processing on the ascending branch of the brain–body axis. Stress responses involve a complex neuro-behavioral cascade, which is elicited when the organism is confronted with a potentially harmful stimulus. As this stress cascade comprises a range of neural and endocrine pathways, stress can be conceptualized as a communication process on the descending branch of the brain–body axis. Interoception and stress are, therefore, associated via the bi-directional transmission of information on the brain–body axis. It could be argued that excessive and/or enduring activation (e.g., by acute or chronic stress) of neural circuits, which are responsible for successful communication on the brain–body axis, induces malfunction and dysregulation of these information processes. As a consequence, interoceptive signal processing may be altered, resulting in physical symptoms contributing to the development and/or maintenance of body-related mental disorders, which are associated with stress. In the current paper, we summarize findings on psychobiological processes underlying acute and chronic stress and their interaction with interoception. While focusing on the role of the physiological stress axes (hypothalamic-pituitary-adrenocortical axis and autonomic nervous system), psychological factors in acute and chronic stress are also discussed. We propose a positive feedback model involving stress (in particular early life or chronic stress, as well as major adverse events), the dysregulation of physiological stress axes, altered perception of bodily sensations, and the generation of physical symptoms, which may in turn facilitate stress.

Effect of experimental stress on the small bowel and colon in healthy humans

BACKGROUND

Symptoms of irritable bowel syndrome (IBS) are frequently reported to be exacerbated by stress. Animal studies suggest that corticotrophin releasing hormone (CRH) mediates the effect of stress on the bowel. We have shown that stressed IBS patients with diarrhea have constricted small bowels. We hypothesized that we could mimic this effect by applying experimental stress in the form of either hand immersion in ice water or CRH injection in healthy volunteers (HV).

METHODS

The postprandial effect of the cold pressor test (repeated hand immersion in ice cold water) and injection of CRH, were assessed vs control in two groups of 18 HVs.

KEY RESULTS

CRH produced a significant rise from baseline salivary cortisol levels (p = 0.004) not seen with the cold pressor test. Small bowel water content (SBWC) fell postprandially on all four treatments. SBWC was significantly reduced by both stressors but CRH caused a greater effect (anova, p < 0.003 vs p = 0.02). Ascending colon (AC) volume was greater after CRH injection compared with saline (p = 0.002) but no differences were seen with the cold pressor test vs warm water. Postprandial increase in colon volume was also reduced by CRH which also increased the sensations of distension and bloating.

CONCLUSIONS & INFERENCES

Two experimental stressors were shown to constrict the small bowel, mimicking the effect previously seen in IBS-D patients. CRH increased the volume of the AC. We speculate that stress accelerates transfer of water from the small bowel to the AC.

Effect of prolonged stress on the adrenal hormones of individuals with irritable bowel syndrome

Background

The purpose of this study was to investigate the effect of prolonged stress on the salivary adrenal hormones (cortisol, dehydroepiandrosterone [DHEA], DHEA-sulfate [DHEA-S]) of individuals with irritable bowel syndrome (IBS).

Methods

The participants were female college students, including 10 with IBS and 16 without IBS (control group), who were scheduled for a 2-week teaching practice at a kindergarten. Participants were asked to collect saliva for determining adrenal hormones immediately and 30 min after awakening and before sleep, 2 weeks before the practice, the first week of the practice, the second week of the practice, and a few days after the practice.

Results

Regarding cortisol/DHEA ratio, significantly increased levels were found during the first week of the practice, and a significant interaction between group and time was found; the ratio at 30 min after awakening in the IBS group was higher than that in the control group. For the other adrenal hormone indexes, no significant differences due to the presence of IBS were found.

Conclusions

Individuals with IBS showed an elevated cortisol/DHEA ratio after awakening compared with individuals without IBS, and the elevated ratio peaked under the prolonged stress. The present study suggests that the cortisol effect is dominant in individuals with IBS under prolonged stress.

Stress and resilience in functional somatic syndromes--a structural equation modeling approach

BACKGROUND

Stress has been suggested to play a role in the development and perpetuation of functional somatic syndromes. The mechanisms of how this might occur are not clear.

PURPOSE

We propose a multi-dimensional stress model which posits that childhood trauma increases adult stress reactivity (i.e., an individual's tendency to respond strongly to stressors) and reduces resilience (e.g., the belief in one's competence). This in turn facilitates the manifestation of functional somatic syndromes via chronic stress. We tested this model cross-sectionally and prospectively.

METHODS

Young adults participated in a web survey at two time points. Structural equation modeling was used to test our model. The final sample consisted of 3'054 participants, and 429 of these participated in the follow-up survey.

RESULTS

Our proposed model fit the data in the cross-sectional (χ2(21)  = 48.808, p<.001, CFI  = .995, TLI  = .992, RMSEA  = .021, 90% CI [.013.029]) and prospective analyses (χ2(21)  =  32.675, p<.05, CFI  = .982, TLI  = .969, RMSEA  = .036, 90% CI [.001.059]).

DISCUSSION

Our findings have several clinical implications, suggesting a role for stress management training in the prevention and treatment of functional somatic syndromes.

A sustained hypothalamic-pituitary-adrenal axis response to acute psychosocial stress in irritable bowel syndrome

BACKGROUND

Despite stress being considered a key factor in the pathophysiology of the functional gastrointestinal (GI) disorder irritable bowel syndrome (IBS), there is a paucity of information regarding the ability of IBS patients to respond to acute experimental stress. Insights into the stress response in IBS could open the way to novel therapeutic interventions. To this end, we assessed the response of a range of physiological and psychological parameters to the Trier Social Stress Test (TSST) in IBS.

METHOD

Thirteen female patients with IBS and 15 healthy female age-matched control participants underwent a single exposure to the TSST. Salivary cortisol, salivary C-reactive protein (CRP), skin conductance level (SCL), GI symptoms, mood and self-reported stress were measured pre- and post-exposure to the TSST.

RESULTS

The hypothalamic-pituitary-adrenal (HPA) axis response to the TSST was sustained in IBS, as shown by a greater total cortisol output throughout (p = 0.035) and higher cortisol levels measured by an area under the curve with respect to ground (AUCG) analysis (p = 0.044). In IBS patients, GI symptoms increased significantly during the recovery period following exposure to the TSST (p = 0.045). Salivary CRP and SCL activity showed significant changes in relation to stress but with no differential effect between experimental groups.

CONCLUSIONS

Patients with IBS exhibit sustained HPA axis activity, and an increase in problematic GI symptoms in response to acute experimental psychosocial stress. These data pave the way for future interventional studies aimed at identifying novel therapeutic approaches to modulate the HPA axis and GI symptom response to acute psychosocial stress in IBS.

Irritable bowel syndrome and symptom severity: evidence of negative attention bias, diminished vigour, and autonomic dysregulation

OBJECTIVE

To determine if cognitive processing, and subjective and physiological responses to stress and relaxation differed between an irritable bowel syndrome (IBS) group and control group. How these variables relate to the severity of IBS symptoms was also determined.

METHODS

Twenty-one IBS participants and 20 controls provided cognitive (attention and processing), subjective (perceived stress and vigour), and physiological (heart rate, blood pressure, and skin conductance) data during a relaxation and stress phase. Logistic regression analyses determined which variables are related to the IBS group and hierarchical linear regression assessed how the variables are related to the severity of IBS symptoms.

RESULTS

Subjective and cognitive factors (drowsiness at baseline, total vigour, and reduced Stroop colour-naming accuracy for negative words) are significantly related to IBS, χ2 (3, N=41)=23.67, p<.001, accurately categorising 85% of participants. IBS symptom severity was associated with both subjective (drowsiness at baseline and a smaller reduction in tiredness from relaxation to stress) and physiological (smaller increase in systolic blood pressure from baseline to stress phase and lower skin conductance at baseline) variables. This model predicted IBS severity, F (4, 16)=11.20, p<.001, and accounted for 74% of the variability in scores.

CONCLUSIONS

A negative attention bias, which may be related to a negative self-schema, as well as perceived low vigour were important in categorising IBS. Low subjective vigour and reduced physiological reactivity to both relaxation and stress conditions were associated with IBS severity, suggestive of illness-related allostatic load.

Gender-related differences in irritable bowel syndrome: Potential mechanisms of sex hormones

According to epidemiological studies, twice as many women as men are affected by irritable bowel syndrome (IBS) in western countries, suggesting a role for sex hormones in IBS pathophysiology. Despite growing evidence about the implications of sex hormones in IBS symptom modulation, data on mechanisms by which they influence disease development are sparse. This review aims to determine the state of knowledge about the role of sex hormones in sensorimotor dysfunctions and to address the possible interplay of sex hormones with common risk factors associated with IBS. The scientific bibliography was searched using the following keywords: irritable bowel syndrome, sex, gender, ovarian hormone, estradiol, progesterone, testosterone, symptoms, pain, sensitivity, motility, permeability, stress, immune system, brain activity, spinal, supraspinal, imaging. Ovarian hormones variations along the menstrual cycle affect sensorimotor gastrointestinal function in both healthy and IBS populations. They can modulate pain processing by interacting with neuromodulator systems and the emotional system responsible for visceral pain perception. These hormones can also modulate the susceptibility to stress, which is a pivotal factor in IBS occurrence and symptom severity. For instance, estrogen-dependent hyper-responsiveness to stress can promote immune activation or impairments of gut barrier function. In conclusion, whereas it is important to keep in mind that ovarian hormones cannot be considered as a causal factor of IBS, they arguably modulate IBS onset and symptomatology. However, our understanding of the underlying mechanisms remains limited and studies assessing the link between IBS symptoms and ovarian hormone levels are needed to improve our knowledge of the disease evolution with regard to gender. Further studies assessing the role of male hormones are also needed to understand fully the role of sex hormones in IBS. Finally, investigation of brain-gut interactions is critical to decipher how stress, ovarian hormones, and female brain processing of pain can translate into gut dysfunctions.

The role of stress in absenteeism: cortisol responsiveness among patients on long-term sick leave

OBJECTIVE

This study aimed to (1) See whether increased or decreased variation relate to subjective reports of common somatic and psychological symptoms for a population on long-term sick leave; and (2) See if this pattern in variation is correlated with autonomic activation and psychological appraisal.

METHODS

Our participants (n = 87) were referred to a 3.5-week return-to-work rehabilitation program, and had been on paid sick leave >8 weeks due to musculoskeletal pain, fatigue and/or common mental disorders. An extensive survey was completed, addressing socio-demographics, somatic and psychological complaints. In addition, a physician and a psychologist examined the participants, determining baseline heart rate, medication use and SCID-I diagnoses. During the 3.5-week program, the participants completed the Trier Social Stress Test for Groups. Participants wore heart rate monitors and filled out Visual Analogue Scales during the TSST-G.

RESULTS

Our participants presented a low cortisol variation, with mixed model analyses showing a maximal increase in free saliva cortisol of 26% (95% CI, 0.21-0.32). Simultaneously, the increase in heart rate and Visual Analogue Scales was substantial, indicating autonomic and psychological activation consistent with intense stress from the Trier Social Stress Test for Groups.

CONCLUSIONS

The current findings are the first description of a blunted cortisol response in a heterogeneous group of patients on long-term sick leave. The results suggest lack of cortisol reactivity as a possible biological link involved in the pathway between stress, sustained activation and long-term sick leave.

Cognitive performance in irritable bowel syndrome: evidence of a stress-related impairment in visuospatial memory

BACKGROUND

Central nervous system (CNS) dysfunction is a prominent feature of the functional gastrointestinal (GI) disorder, irritable bowel syndrome (IBS). However, the neurobiological and cognitive consequences of key pathophysiological features of IBS, such as stress-induced changes in hypothalamic-pituitary-adrenal (HPA)-axis functioning, is unknown. Our aim was to determine whether IBS is associated with cognitive impairment, independently of psychiatric co-morbidity, and whether cognitive performance is related to HPA-axis function.

METHOD

A cross-sectional sample of 39 patients with IBS, a disease control group of 18 patients with Crohn's disease (CD) in clinical remission and 40 healthy age- and IQ-matched control participants were assessed using the Paired Associates Learning (PAL), Intra-Extra Dimensional Set Shift (IED) and Spatial Working Memory (SWM) tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a computerized Stroop test. HPA-axis function was determined by measuring the cortisol awakening response (CAR).

RESULTS

IBS patients exhibited a subtle visuospatial memory deficit at the PAL six- pattern stage (p = 0.03), which remained after psychiatric co-morbidity was controlled for (p = 0.04). Morning cortisol levels were lower in IBS (p = 0.04) and significantly associated with visuospatial memory performance within IBS only (p = 0.02).

CONCLUSIONS

For the first time, altered cognitive function on a hippocampal-mediated test of visuospatial memory, which was related to cortisol levels and independent of psychiatric co-morbidity, has been identified in IBS. Visuospatial memory impairment may be a common, but currently neglected, component of IBS. Further elucidation of the nature of this impairment may lead to a greater understanding of the underlying pathophysiology of IBS, and may provide novel therapeutic approaches.

Physiological underpinnings of irritable bowel syndrome: neurohormonal mechanisms

The gastrointestinal tract is a vast neuroendocrine organ with extensive extrinsic and intrinsic neural circuits that interact to control its function. Circulating and paracrine hormones (amine and peptide) provide further control of secretory, absorptive, barrier, motor and sensory mechanisms that are essential to the digestion and assimilation of nutrients, and the transport and excretion of waste products. Specialized elements of the mucosa (including enteroendocrine cells, enterocytes and immune cells) and the microbiome interact with other intraluminal contents derived from the diet, and with endogenous chemicals that alter the gut's functions. The totality of these control mechanisms is often summarized as the brain-gut axis. In irritable bowel syndrome (IBS), which is the most common gastrointestinal disorder, there may be disturbances at one or more of these diverse control mechanisms. Patients present with abdominal pain in association with altered bowel function. This review documents advances in understanding the pathophysiological mechanisms in the brain-gut axis in patients with IBS. It is anticipated that identification of one or more disordered functions in clinical practice will usher in a renaissance in the management of IBS, leading to effective therapy tailored to the needs of the individual patient.

Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test

Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.

Biomarkers of stress in behavioural medicine

PURPOSE OF REVIEW

In recent years, a growing interest has emerged in behavioural medicine to examine the role of acute and chronic stress as a predisposing and contributing factor to physical health and illness. For a deeper understanding of these associations, research is in need of biological markers for alterations in biological stress systems. This review will summarize a selection of important recent findings in this area of research.

RECENT FINDINGS

We will focus on essential peripheral stress-sensitive physiological systems, that is, the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and the immune system. We will present findings on commonly used stress biomarkers (cortisol, alpha-amylase, pro-inflammatory cytokines) regarding alterations in basal activity and stress-dependent reactivity in these systems, and discuss selected findings on intervention-induced changes of these biomarkers.

SUMMARY

This review will highlight new developments and guide readers in their choice of suitable study designs and outcomes in behavioural medicine. The reviewed studies included here encourage optimism that the employment of stress biomarkers in behavioural medicine has the potential to significantly improve our understanding of physical health and illness.

Urinary proteome analysis of irritable bowel syndrome (IBS) symptom subgroups

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by chronic abdominal pain associated with alterations in bowel function. Given the heterogeneity of the symptoms, multiple pathophysiologic factors are suspected to play a role. We classified women with IBS into four subgroups based on distinct symptom profiles. In-depth shotgun proteomic analysis was carried out to profile the urinary proteomes to identify possible proteins associated with these subgroups. First void urine samples with urine creatinine level≥100 mg/dL were used after excluding samples that tested positive for blood. Urine from 10 subjects representing each symptom subgroup was pooled for proteomic analysis. The urine proteome was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a data-independent method known as Precursor Acquisition Independent From Ion Count (PAcIFIC) that allowed extended detectable dynamic range. Differences in protein quantities were determined by peptide spectral counting followed by validation of select proteins with ELISA or a targeted single reaction monitoring (LC-SRM/MS) approach. Four IBS symptom subgroups were selected: (1) Constipation, (2) Diarrhea+Low Pain, (3) Diarrhea+High Pain, and (4) High Pain+High Psychological Distress. A fifth group consisted of Healthy Control subjects. From comparisons of quantitative spectral counting data among the symptom subgroups and controls, a total of 18 proteins that showed quantitative differences in relative abundance and possible physiological relevance to IBS were selected for further investigation. Three of the 18 proteins were chosen for validation by either ELISA or SRM. An elevated expression of gelsolin (GSN) was associated with the high pain groups. Trefoil Factor 3 (TFF3) levels were higher in IBS groups compared to controls. In this study, the IBS patients subclassified by predominant symptoms showed differences in urine proteome levels. Proteins showing distinctive changes are involved in homeostasis of intestinal function and inflammatory response. These findings warrant future studies with larger, independent cohorts to enable more extensive assessment and validation of urinary protein markers as a diagnostic tool in adults with IBS.

Differential effects of early environmental enrichment on emotionality related behaviours in Huntington's disease transgenic mice

Psychiatric disorders such as depression and anxiety are reported in patients with Huntington's disease (HD). Recent studies suggest beneficial effects of environmental enrichment (EE) on HD progression possibly through the serotonergic system. We investigated the potential effectiveness of EE in correcting the affective-like phenotype of female R6/1 HD mice. In addition to a behavioural battery of tests assessing depression and anxiety-related endophenotypes, we recorded physiological measures, including body temperature regulation and defecation rate as indices of stress reactivity. Finally, following identification of changes in serotonin (5-HT) receptor gene expression we measured the function of 5-HT(1A) auto- and hetero-receptors. We found that 8-week-old female HD mice exhibited higher immobility time in the forced swimming test and a decreased preference for saccharin solution. EE did not correct those depressive-like behaviours but reduced anxiety-related measures in unconditioned approach/avoidance conflict situations. Defecation rate in a large open field and change in temperature during exposure to the tail suspension test were both enhanced in HD compared to wild-type animals. Despite the enhanced hypothermic response to the 5-HT(1A) receptor agonist 8-OH-DPAT exhibited by HD mice, we found a reduction in 5-HT(1A) receptor-mediated stimulation of [(35)S]GTP-γ-S binding in the dorsal raphe nucleus and the hippocampus of HD animals. EE did not change 5-HT(1A) receptor function. Our data suggest that early EE has beneficial effects on the anxiety-like, but not on depression-like, behaviours in HD. This is the first evidence that these affective endophenotypes can be dissociated via this form of environmental stimulation. As 5-HT(1A) receptor dysfunction was not affected by EE, this receptor is unlikely to underlie the anxiety-related phenotype of HD. However, the specific regulatory role of the 5-HT(1A) autoreceptor in mediating depressive-like behaviour in HD remains to be elucidated. Interestingly, by comparing in vivo and in vitro results, our findings suggest that 8-OH-DPAT-induced hypothermia could be mediated by other targets besides the 5-HT(1A) autoreceptor, including hippocampal 5-HT(7) receptors.