Project 1

HPA DYSREGULATION IN IBS AND RELATED ANIMAL MODELS, WITH EMPHASIS ON SEX DIFFERENCES
PI: Lin Chang, Co-I: Yvette Taché

SPECIFIC AIMS

Aim A. To conduct comprehensive genetic, molecular and functional phenotyping of HPA axis in male and female patients with IBS, with IC/PBS and healthy controls (HCs).

  1. To validate our previous findings that increased methylation of (glucocorticoid receptor, GR) NR3C1 promoter from peripheral blood mononuclear cells (PBMCs) is a potential biomarker for IBS in a new set of IBS patients and HCs.
  2. To determine if GR mRNA expression from PBMCs correlates with the degree of GR methylation, and if it is significantly different in IBS and IC/PBS patients compared to HCs.
  3. To compare (GR) NR3C1 gene methylation and mRNA expression in the colonic mucosa of IBS patients and HCs to determine if these alterations are site specific.
  4. To identify alterations in the HPA axis and autonomic nervous system (ANS) response systems in male and female IBS patients compared to HCs and its relationship to (GR) NR3C1 methylation and expression.
  5. To determine the relationships between GR gene methylation and HPA axis response with EAL, prolonged adult stressor, and IBS and psychological symptoms in IBS.
  6. Provide data collected in IBS patients from #1-5 to Project 3 to populate a comprehensive endophenotype data base, with the goal to identify phenotypic subsets based on HPA axis, ANS tone, GR gene methylation, visceral adiposity (Project 2), and brain imaging data (Project 3).

Aim B. To establish that perinatal stress alters the pattern of regional brain CRF and CRF-R1 expression, and DNA methylation of GR promoter region in male and female rats.

  1. To test the hypothesis that MS stress-induced dysregulation of HPA axis and CRF-R1-mediated visceral hypersensitivity are associated with a sex dependent differential upregulation of CRF and CRF-R1 isoforms in specific brain nuclei which can be curtailed by CRF-R1 antagonist treatment.
  2. To determine that DNA methylation of the GR promoter region in MS rats contributes to the altered HPA responsiveness and CRF/CRF-R1 regulation with sex-dependent modulation.

Aim C. To evaluate increased engagement of central stress responsiveness/arousal circuits in the perinatal stress model. Emphasis is on identifying homologies of these mechanisms between rodent and human brain (Project 3).

  1. To characterize functional activation and connectivity of central stress/arousal circuits in adult male and female rats with and without history of perinatal stress, during acute visceral pain.
  2. To delineate the effects of CRF-R1 receptor antagonism on altered stress/arousal circuits and identify the moderating effect of sex.
Project 2

HPA AXIS-DEPENDENT VISCERAL ADIPOSE TISSUE AND BRAIN CHANGES IN IBS AND RELATED ANIMAL MODELS, WITH EMPHASIS ON SEX DIFFERENCES
PI: Harry Pothoulakis, Co-I: Sylvie Bradesi

SPECIFIC AIMS

Aim A. Correlate changes in visceral adiposity, HPA axis activity and regional brain morphology in a rodent model of chronic unpredictable stress, in adult male and female rats.

  1. Assess sex differences on total body, VAT accumulation and VAT mediators in chronic unpredictable stress.
  2. Characterize alterations in HPA axis at baseline and under stimulation, and assess glucocorticoid receptor (GR) gene methylation in VAT and circulating lymphocytes.
  3. Quantify regional brain morphometry changes following chronic unpredictable stress using MRI, and correlate with peripheral measures from 1 and 2.

Aim B. Characterize the role of visceral fat products in stress-induced changes in the HPA axis and brain structural and functional changes in male and female rodents.

  1. Assess the effect of blockade of selective adipose tissue – derived molecules on HPA axis dysregulation.
  2. Assess the effect of selective blockage of visceral fat derived mediators on regional brain morphometry.

Aim C. To establish a CRF-related sex differences in visceral adipose adipokine expression and differential brain regional alterations correlated with IBS-like symptoms in a mouse model of constitutive HPA overactivity.

  1. To demonstrate sex-dependent immune cell composition and cytokine expression in visceral adipose tissue (VAT), and the role of CRF) receptors in CRF-overexpressing (OE) mice.

Aim D. Correlate HPA axis with VAT accumulation, circulating adipokines, and regional brain structural and resting state functional changes in male and female IBS patients.

  1. Compare plasma adipokine levels (ELISA) and visceral fat accumulation (abdominal computerized tomography [CT] scan) between male and female IBS patients and HCs.
  2. Characterize the HPA axis activity of the subjects using CRF and ACTH stimulation tests and measure glucocorticoid receptor (GR) gene methylation and GR mRNA expression in peripheral blood T cells (in collaboration with Project 1).
  3. Determine resting state and structural MRI scan of the brain in all subjects and correlate these results to results obtained from Subaims 1 and 2.
Project 3

IBS SUBGROUPING BASED ON ENDOPHENOTYPE CLUSTERS AND INTERVENTIONAL PHENOTYPING, WITH EMPHASIS ON SEX DIFFERENCES
PI: Emeran Mayer; Co-Is: Kirsten Tillisch, Jennifer Labus

SPECIFIC AIMS

Aim A. Prospectively perform comprehensive endophenotyping of 120 IBS patients.

  1. Assess structural and functional brain and neuropsychological endophenotypes in 120 IBS patients meeting symptom criteria for IBS (60 women). These endophenotypes will be combined in a comprehensive data base with neuroendocrine (including HPA axis parameters studied in Project 1, and peripheral endophenotypes (including visceral adipose tissue [VAT] and adipokines, studied in Project 2).

Aim B – Deleted due to budget cuts and unavailability of a FDA approved CRF-R1 antagonist)

Aim C. Apply advanced mathematical modeling techniques to identify patient subgroups from endophenotypes identified in Aims A and B.

  1. Develop the most accurate predictor of disease status.
  2. Identify patient subgroups based on clusters of endophenotype from complete list of endophenotypes,
  3. Test hypothesis of a stress hyperresponsive patient subgroup which shows greatest response to CRF-R1 antagonism (from Aim B).
  4. Determine which endophenotypes determine sex related differences.

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