Protective Effect of a Phytoestrogen-Enriched Diet on the Increase in Visceral Sensitivity and Intestinal Permeability Induced by Acute Stress in Female Rats

INTRODUCTION: Irritable bowel syndrome (IBS) is frequently associated with psychological distress and is characterized by abdominal pain and increased gut permeability.IBS prevalence is higher in women, suggesting a sex hormone influence.It has been shown that estrogens reduce intestinal permeability in female rats, but their effect on visceral sensitivity remains controversial.The aim of this study was to evaluate the effects of a phytoestrogen-enriched diet (PED) on increased visceral sensitivity and intestinal permeability induced by acute stress in female rats.METHODS: Female Wistar rats received orally for 15 days either PED (0.45mg isoflavone aglycone forms equivalent/day), or 17B-estradiol benzoate (EB; 0.6mg/ kg/day) or PED vehicle (1ml water), with or without the estrogen receptor antagonist ICI182,780 (2mg/kg/day, s.c), administered from days 10 to 15 of treatment.Rats were submitted or not (controls) to a restraint stress during 2h.Rats were used for visceral pain assessment, or measurements of intestinal permeability.In a first series of experiments, rats were equipped with NiCr electrodes implanted on abdominal muscle to record electromyographic activity as an index of visceral pain.Twenty minutes after the stress session, colorectal distensions (CRD) were performed using an embolectomy probe inserted into the rectum and inflated from 0 to 1.2ml (0.4ml intervals).A second experimental design was devoted to In Vivo intestinal permeability measurement using 51 Cr-EDTA and expressed as the percentage of the total radioactivity collected in the 24h urines.In a third series of experiments, colonic segments were mounted in Ussing chambers for In Vitro evaluation of colonic paracellular permeability (CPP) to FITC-dextran.RESULTS: Acute stress significantly increased i) intestinal permeability to 51 Cr-EDTA (P