Distinct Patterns of Gene Expression Changes in the Colon and Striatum of Young Mice Overexpressing Alpha-Synuclein Support Parkinson's Disease as a Multi-System Process.

BACKGROUND: Evidence supports a role for the gut-brain axis in Parkinson's disease (PD). Mice overexpressing human wild type α- synuclein (Thy1-haSyn) exhibit slow colonic transit prior to motor deficits, mirroring prodromal constipation in PD. Identifying molecular changes in the gut could provide both biomarkers for early diagnosis and gut-targeted therapies to prevent progression. OBJECTIVE: To identify early molecular changes in the gut-brain axis in Thy1-haSyn mice through gene expression profiling. METHODS: Gene expression profiling was performed on gut (colon) and brain (striatal) tissue from Thy1-haSyn and wild-type (WT) mice aged 1 and 3 months using 3' RNA sequencing. Analysis included differential expression, gene set enrichment and weighted gene co-expression network analysis (WGCNA). RESULTS: At one month, differential expression (Thy1-haSyn vs. WT) of mitochondrial genes and pathways related to PD was discordant between gut and brain, with negative enrichment in brain (enriched in WT) but positive enrichment in gut. Linear regression of WGCNA modules showed partial independence of gut and brain gene expression changes. Thy1-haSyn-associated WGCNA modules in the gut were enriched for PD risk genes and PD-relevant pathways including inflammation, autophagy, and oxidative stress. Changes in gene expression were modest at 3 months. CONCLUSIONS: Overexpression of haSyn acutely disrupts gene expression in the colon. While changes in colon gene expression are highly related to known PD-relevant mechanisms, they are distinct from brain changes, and in some cases, opposite in direction. These findings are in line with the emerging view of PD as a multi-system disease.

Experimental models of gut-first Parkinson's disease: A systematic review.

BACKGROUND: There is strong support from studies in humans and in animal models that Parkinson's disease (PD) may begin in the gut. This brings about a unique opportunity for researchers in the field of neurogastroenterology to contribute to advancing the field and making contributions that could lead to the ability to diagnose and treat PD in the premotor stages. Lack of familiarity with some of the aspects of the experimental approaches used in these studies may present a barrier for neurogastroenterology researchers to enter the field. Much remains to be understood about intestinal-specific components of gut-first PD pathogenesis and the field would benefit from contributions of enteric and central nervous system neuroscientists. PURPOSE: To address these issues, we have conducted a systematic review of the two most frequently used experimental models of gut-first PD: transneuronal propagation of α-synuclein preformed fibrils and oral exposure to environmental toxins. We have reviewed the details of these studies and present methodological considerations for the use of these models. Our aim is that this review will serve as a framework and useful reference for neuroscientists, gastroenterologists, and neurologists interested in applying their expertise to advancing our understanding of gut-first PD.

Risk Factors for Abdominal Pain-Related Disorders of Gut-Brain Interaction in Adults and Children: A Systematic Review.

BACKGROUND & AIMS: Many studies have assessed risk factors of irritable bowel syndrome (IBS) and other abdominal pain-related disorders of gut-brain interaction (AP-DGBI); however, the role of these factors is unclear due to heterogeneous study designs. The aim of this systematic review was to extensively evaluate the literature and determine clinical risk and protective factors for the presence and persistence of AP-DGBI in children and adults. METHODS: A PubMed search identified studies investigating potential risk and protective factors for AP-DGBI in adults and children. Inclusion criteria included fully published studies with a control group; exclusion criteria included poor-quality studies (using a validated scale). For each factor, the proportion of studies that found the factor to be a risk factor, protective factor, or neither was summarized. The number of studies, diagnostic criteria, number of subjects, and average study quality rating provided further context. Whenever possible, a meta-analysis generated pooled odds ratios or mean difference. RESULTS: The systematic review included 348 studies. Female sex, gastroenteritis, abuse, stress, psychological disorders, somatic symptoms, and poor sleep were consistent risk factors for developing AP-DGBI in adults and children. In adults, additional risk factors included obesity, smoking, and increased use of medical resources. Protective AP-DGBI factors in adults included social support and optimism; no studies for protective factors were found for children. CONCLUSIONS: There are multiple risk factors for AP-DGBI in adults and children. These include female sex, gastroenteritis, abuse, stress, poor sleep, obesity, psychological disorders, and somatic symptoms. Additional studies are needed in children, on protective factors, and on factors associated with persistence of AP-DGBI.

Latest Insights on the Pathogenesis of Irritable Bowel Syndrome.

The pathogenesis of irritable bowel syndrome is multifactorial and complex. Our understanding of its pathophysiology has evolved, but remains incompletely understood. Symptoms result from a dysregulation of brain-gut interactions. Evidence has identified alterations in central and peripheral (gut) mechanisms in irritable bowel syndrome and the bidirectional communication between the brain and the gut. Pertinent mechanisms include disturbed gut motility, visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, and altered central nervous system processing. This review addresses factors that increase the risk of irritable bowel syndrome and the central and peripheral mechanisms thought to underlie its symptoms.

Importance of trauma-related fear in patients with irritable bowel syndrome and early adverse life events.

BACKGROUND: Although early adverse life events (EALs) are prevalent among patients with irritable bowel syndrome (IBS), the impact of fear or dissociation experienced during the trauma has not been evaluated. We investigated the prevalence of fear at the time of trauma and its association with IBS status among individuals with early-life trauma before the age of 18. METHODS: Among participants with ≥1 EAL, association of fear and dissociation with IBS status was determined with logistic regression, and improvement in prediction of IBS over ETI score alone was determined with the likelihood ratio test. Controlling for age, sex, and IBS status, we then examined the association of each EAL with reported fear. KEY RESULTS: Compared to healthy controls (HCs), IBS subjects reported a higher prevalence of fear (60.4% vs 36.2%, P < .0005) and dissociation (23.5% vs 13.0%, P < .0005) at the time of EAL. Fear, but not dissociation, improved prediction of IBS over the total number of EALs (odds ratio = 2.00, P < .0001). CONCLUSIONS AND INFERENCES: This study highlights the importance of EAL-related factors such as fear in addition to the presence or absence of EALs in IBS pathophysiology.

Negative Events During Adulthood Are Associated With Symptom Severity and Altered Stress Response in Patients With Irritable Bowel Syndrome.

BACKGROUND & AIMS: Irritable bowel syndrome (IBS) is a stress-sensitive disorder associated with dysregulation of the hypothalamic-pituitary-adrenal axis. We studied the cumulative effect of events during adulthood on this pathway in patients with IBS. METHODS: We studied 129 patients with IBS, based on Rome III criteria (mean age 28.1 years, 66% women), and 108 healthy individuals (controls; mean age 29.8 years, 60% women) who completed the Life Experiences Survey from August 2013 to September 2017. Data were collected on the presence and effects of events since age 18, IBS severity scores, and IBS-related quality of life. For a subset of subjects, we measured serum cortisol and adrenocorticotropic hormone (ACTH) production in response to administration of corticotropin-releasing factor and ACTH. RESULTS: Compared with controls, patients with IBS perceived more adulthood life events as negative and had a significantly higher negative life event impact score (14.17 ± 12.04 vs 10.83 ± 9.98; P=.022). In patients with IBS, the presence of more-negatively perceived adulthood life events was associated with worse IBS symptom severity (ß = 1.53, 95% CI, 0.21-2.84; P = .025) and IBS-related quality of life (ß = -0.70; 95% CI, -1.02 to -0.38; P < .001). Negatively perceived adulthood life events were associated with reduced production of ACTH in response to corticotropin-releasing factor in patients with IBS compared with controls (P < .05). CONCLUSION: In a study of more than 200 subjects, we associated more-negatively perceived events during adulthood with an increased risk for IBS, worse symptom severity and quality of life, and a dysregulated stress response. Understanding the effects of events that cause stress in adults and their perceived effects on IBS may help guide disease management.

Sigmoid colon mucosal gene expression supports alterations of neuronal signaling in irritable bowel syndrome with constipation.

Peripheral factors likely play a role in at least a subset of irritable bowel syndrome (IBS) patients. Few studies have investigated mucosal gene expression using an unbiased approach. Here, we performed mucosal gene profiling in a sex-balanced sample to identify relevant signaling pathways and gene networks and compare with publicly available profiling data from additional cohorts. Twenty Rome III+ IBS patients [10 IBS with constipation (IBS-C), 10 IBS with diarrhea (IBS-D), 5 men/women each), and 10 age-/sex-matched healthy controls (HCs)] underwent sigmoidoscopy with biopsy for gene microarray analysis, including differential expression, weighted gene coexpression network analysis (WGCNA), gene set enrichment analysis, and comparison with publicly available data. Expression levels of 67 genes were validated in an expanded cohort, including the above samples and 18 additional participants (6 each of IBS-C, IBS-D, HCs) using NanoString nCounter technology. There were 1,270 differentially expressed genes (FDR < 0.05) in IBS-C vs. HCs but none in IBS or IBS-D vs. HCs. WGNCA analysis identified activation of the cAMP/protein kinase A signaling pathway. Nine of 67 genes were validated by the NanoString nCounter technology (FDR < 0.05) in the expanded sample. Comparison with publicly available microarray data from the Mayo Clinic and University of Nottingham supports the reproducibility of 17 genes from the microarray analysis and three of nine genes validated by nCounter in IBS-C vs. HCs. This study supports the involvement of peripheral mechanisms in IBS-C, particularly pathways mediating neuronal signaling. NEW & NOTEWORTHY Peripheral factors play a role in the pathophysiology of irritable bowel syndrome (IBS), which, to date, has been mostly evident in IBS with diarrhea. Here, we show that sigmoid colon mucosal gene expression profiles differentiate IBS with constipation from healthy controls. These profiling data and analysis of additional cohorts also support the concept that peripheral neuronal pathways contribute to IBS pathophysiology.

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.

Effects of linaclotide in patients with irritable bowel syndrome with constipation or chronic constipation: a meta-analysis.

BACKGROUND & AIMS: Linaclotide is a minimally absorbed, 14-amino acid peptide used to treat patients with irritable bowel syndrome with constipation (IBS-C) or chronic constipation (CC). We performed a meta-analysis to determine the efficacy of linaclotide, compared with placebo, for patients with IBS-C or CC. METHODS: MEDLINE, EMBASE, and the Cochrane central register of controlled trials were searched for randomized, placebo-controlled trials examining the effect of linaclotide in adults with IBS-C or CC. Dichotomous results were pooled to yield a relative risk (RR), 95% confidence intervals (CIs), and number needed to treat (NNT). RESULTS: The search identified 7 trials of linaclotide in patients with IBS-C or CC; 6 were included in the analysis. Two of 3 trials of IBS-C used the end point recommended by the U.S. Food and Drug Administration: an increase from baseline of 1 or more complete spontaneous bowel movement (CSBM)/week and a 30% or more reduction from baseline in the weekly average of daily worst abdominal pain scores for 50% of the treatment weeks. On the basis of this end point, the RR for response to treatment with 290 µg linaclotide, compared with placebo, was 1.95 (95% CI, 1.3-2.9), and the NNT was 7 (95% CI, 5-11). For CC, on the basis of data from 3 trials of patients with CC, the RR for the primary end point (more than 3 CSBMs/week and an increase in 1 or more CSBM/week, for 75% of weeks) was 4.26 for 290 µg linaclotide vs placebo (95% CI, 2.80-6.47), and the NNT was 7 (95% CI, 5-8). Linaclotide also improved stool form and reduced abdominal pain, bloating, and overall symptom severity in patients with IBS-C or CC. CONCLUSIONS: On the basis of a meta-analysis, linaclotide improves bowel function and reduces abdominal pain and overall severity of IBS-C or CC, compared with placebo.

Association between early adverse life events and irritable bowel syndrome.

BACKGROUND & AIMS: Although childhood and adult abuse are more prevalent among patients with irritable bowel syndrome (IBS) than healthy individuals (controls), other types of early adverse life events (EALs) have not been well characterized. We investigated whether different types of EALs, before age 18 years, are more prevalent among patients with IBS, and the effects of sex and nongastrointestinal symptoms on the relationship between EALs and IBS. METHODS: EALs were evaluated in 294 IBS patients (79% women) and 435 controls (77% women) using the Early Trauma Inventory Self-Report Form, which delineates subcategories of general trauma and physical, emotional, and sexual abuse. Validated questionnaires assessed gastrointestinal, psychological, and somatic symptoms. RESULTS: Compared with controls, IBS patients reported a higher prevalence of general trauma (78.5% vs 62.3%), physical punishment (60.6% vs 49.2%), emotional abuse (54.9% vs 27.0%), and sexual events (31.2% vs 17.9%) (all P < .001). These significant differences were observed mainly in women. Of the EAL domains, emotional abuse was the strongest predictor of IBS (P < .001). Eight of the 27 EAL items were significant (P < .001) and increased the odds of having IBS by 108% to 305%. Although EALs and psychological variables were related, EALs had an independent association with IBS (P = .04). CONCLUSIONS: Various types of EALs are associated with the development of IBS-particularly among women. Psychological distress and somatic symptoms might contribute to this relationship. When appropriate, EALs and nongastrointestinal symptoms should be assessed in IBS patients.

Serum and colonic mucosal immune markers in irritable bowel syndrome.

OBJECTIVES: Low-grade colonic mucosal inflammation has been postulated to have an important role in the pathophysiology of irritable bowel syndrome (IBS). The objectives of this study were (i) to identify serum and tissue-based immunological and neuroendocrine markers associated with mucosal inflammation in male (M) and female (F) patients with non-post-infectious IBS (non-PI-IBS) compared with healthy controls and (ii) to assess possible correlations of such markers with IBS symptoms. METHODS: Sigmoid mucosal biopsies were obtained from 45 Rome II positive IBS patients without a history of PI-IBS (26 F, 35.5% IBS-C, 33.3% IBS-D, 31.1% IBS-A/M) and 41 healthy controls (22 F) in order to measure immunological markers (serum cytokine levels, colonic mucosal mRNA levels of cytokines, mucosal immune cell counts) and neuroendocrine markers associated with mucosal inflammation (corticotropin releasing factor- and neurokinin (NK)-related ligands and receptors, enterochromaffin cells). Symptoms were measured using validated questionnaires. RESULTS: Of all the serum and mucosal cytokines measured, only interleukin-10 (IL-10) mRNA expression showed a group difference, with female, but not male, patients showing lower levels compared with female controls (18.0±2.9 vs. 29.5±4.0, P=0.006). Mucosal mRNA expression of NK-1 receptor was significantly lower (1.15±0.19 vs. 2.66±0.56, P=0.008) in female, but not male, patients compared with healthy controls. No other significant differences were observed. CONCLUSIONS: Immune cell counts and levels of cytokines and neuropeptides that are associated with inflammation were not significantly elevated in the colonic mucosa of non-PI-IBS patients, and did not correlate with symptoms. Thus, these findings do not support that colonic mucosal inflammation consistently has a primary role in these patients. However, the finding of decreased IL-10 mRNA expression may be a possible biomarker of IBS and warrants further investigation.

Childhood trauma is associated with hypothalamic-pituitary-adrenal axis responsiveness in irritable bowel syndrome.

BACKGROUND & AIMS: A history of early adverse life events (EALs) is associated with a poorer outcome and higher levels of distress in adult patients with functional gastrointestinal disorders. An EAL is thought to predispose individuals to develop a range of chronic illnesses by inducing persistent changes in the central stress response systems, including the hypothalamic-pituitary-adrenal (HPA) axis. We sought to determine if EALs affect the HPA axis response to a visceral stressor in irritable bowel syndrome (IBS) patients and healthy controls, and to determine if this is affected by sex or related to symptoms or quality of life. METHODS: Forty-four IBS patients (25 women, 19 men) and 39 healthy controls (21 women, 18 men) were assessed for gastrointestinal and psychological symptoms and EALs by validated questionnaires and interview. All subjects underwent a visceral stressor (sigmoidoscopy). Salivary cortisol was collected at baseline and serially for 1 hour poststressor. RESULTS: Twenty-one IBS patients and 18 controls had EALs. In subjects with and without IBS, an EAL was associated with higher mean (+/-SD) cortisol levels (0.32 +/- 0.2 vs 0.20 +/- 0.1 microg/dL; P = .003) and higher area under the curve (28.1 +/- 17 vs 18.6 +/- 13 microg x min/dL; P = .005) after the stressor compared with subjects without EALs. In IBS, a faster resolution of cortisol to basal values corresponded to lower symptom severity (r = -0.36, P < .05) and better disease-specific quality of life (r = 0.33, P < .05). CONCLUSIONS: HPA axis hyperresponsiveness to a visceral stressor is related more to a history of EALs than to the presence of IBS. However, HPA axis reactivity has a moderating effect on IBS symptoms.

Stress hormones and post-traumatic stress disorder in civilian trauma victims: a longitudinal study. Part II: the adrenergic response.

The aim of the study was to prospectively evaluate the association between the occurrence of post-traumatic stress disorder (PTSD) and the adrenergic response to the traumatic event, and additionally, to explore the link between PTSD and the initial norepinephrine:cortisol ratio. Plasma levels and urinary excretion of norepinephrine (NE) were measured in 155 survivors of traumatic events during their admission to a general hospital emergency room (ER) and at 10 d, 1 month and 5 months later. Symptoms of peri-traumatic dissociation, PTSD and depression were assessed in each follow-up session. The Clinician-Administered PTSD Scale (CAPS) conferred a diagnosis of PTSD at 5 months. Trauma survivors with (n=31) and without (n=124) PTSD had similar levels of plasma NE, urinary NE excretion, and NE:cortisol ratio in the ER. Plasma NE levels were lower in subjects with PTSD at 10 d, 1 month, and 5 months. There was a weak but significant positive correlation between plasma levels of NE in the ER and concurrent heart rate, and a negative correlation between NE in the ER and dissociation symptoms. Peripheral levels of NE, shortly after traumatic events, are poor risk indicators of subsequent PTSD among civilian trauma victims. Simplified biological models may not properly capture the complex aetiology of PTSD.

Stress hormones and post-traumatic stress disorder in civilian trauma victims: a longitudinal study. Part I: HPA axis responses.

The aim of the study was to evaluate the association between post-traumatic disorder (PTSD) and hypothalamic-pituitary-adrenal (HPA) axis responses to the triggering trauma. A companion paper evaluates the adrenergic response and interactions between the two. We measured plasma and saliva cortisol, hourly urinary excretion of cortisol, plasma levels of adrenocorticotropin (ACTH), and the leukocyte glucocorticoid receptor (GR) density of 155 non-injured survivors of traumatic events (91 males and 64 females; 125 road traffic accidents, 19 terrorist attacks, 11 others). Measurements were taken during survivors' admissions to an emergency room (ER) of a general hospital, and in the mornings, 10 d, 1 month, and 5 months later. Symptoms of peri-traumatic dissociation, PTSD, and depression were assessed on each follow-up session. The clinician-administered PTSD scale (CAPS) conferred a diagnosis of PTSD at 5 months. Survivors with (n=31) and without (n=124) PTSD at 5 months had similar levels of hormones at all times. Plasma cortisol levels decreased with time in both groups. Female subjects had lower ACTH levels than males. PTSD in females was associated with higher levels of ACTH. In unselected cohorts of trauma survivors, PTSD is not preceded by a detectable abnormality of peripheral HPA axis hormones.

Irritable bowel syndrome: current approach to symptoms, evaluation, and treatment.

There are frequent advances in knowledge about the clinical presentation, pathophysiology, and treatment of irritable bowel syndrome. It is important for clinicians to be aware of available therapies and the supporting evidence for those therapies to increase patient satisfaction. This is best achieved with a collaborative and long-term clinician-patient relationship and mutual commitment to modify therapy and try new modalities until the greatest relief of symptoms and improvement in health-related quality of life is achieved. This article reviews symptoms, comorbidities, gender differences, and measure of severity in irritable bowel syndrome and current and evidence-based approaches to evaluation and treatment, and the new symptom-based Rome III diagnostic criteria are reviewed and explained.

Identification of a molecular recognition role for the activation loop phosphotyrosine of the SRC tyrosine kinase.

A human cDNA phage display library screen, using a phosphopeptide designed to mimic the activation loop phosphotyrosine of the Src tyrosine kinase, has identified the N-terminal SH2 domain of the p85 regulatory subunit of phosphatidyl inositol-3 kinase (PI3K) as an interacting recognition domain. Activation loop phosphorylation is known to play a conformational role in kinase activation, but is largely not thought to play a role in protein/protein recognition. Affinity chromatography and biochemical evaluation in mouse fibroblast cells has confirmed the dependence of this interaction on both the Src activation loop phosphotyrosine and the N-terminal SH2 domain of PI3K.

Two-dimensional diversity: screening human cDNA phage display libraries with a random diversity probe for the display cloning of phosphotyrosine binding domains.

A random phosphopeptide probe (bio-pYZZZ) has been used for the isolation and identification of multiple SH2 domains from human cDNA-displaying phage libraries. In addition, on-phage analysis and quantification of binding affinities for these phage-displayed proteins has shown them to be functional domains, retaining the same characteristics as in their native state.