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

Background & Aims: Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been reported in irritable bowel syndrome (IBS). Enhanced HPA axis responses have 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

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

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

BackgroundThere 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.PurposeTo 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