過敏性腸症候群における心理社会的ストレスに対する副腎皮質および自律神経反応  [in Japanese] Adrenal and Autonomic Responses to Psychosocial Stress in Individuals with Irritable Bowel Syndrome  [in Japanese]

本研究では,過敏性腸症候群(irritable bowel syndrome ; IBS)における心理社会的ストレス負荷時の副腎皮質ホルモン〔コルチゾールおよびデヒドロエピアンドロステロン(DHEA)〕,自律神経活動の反応を検討した.DHEAおよび自律神経指標についてはIBS群と統制群の差は認められなかったが,IBS群のコルチゾールの反応性は統制群よりも低下していた.本研究の結果から,IBS群において心理社会的ストレス負荷時のコルチゾールとDHEAの反応は一致していないことが示唆された.

Introduction : In the previous researches on irritable bowel syndrome (IBS), it was reported that Hypothalamus-Pituitary-Adrenal (HPA) axis related to IBS symptoms. However, the results of previous researches on cortisol level of IBS were inconsistent and dehydroepiandrosterone (DHEA) level of IBS has not been measured in these researches. In this study, we investigated adrenal (including cortisol and DHEA) and autonomic response to stress in individuals with IBS. Methods : The participants were 33 male college students (mean age=22.64yrs.) including 10 individuals with IBS met Rome II criteria and 23 individuals without IBS (control group). All of the participants were nonsmokers. All experiments were conducted after 15 : 00. The participants were exposed to a standardized laboratory stressor (Trier Social Stress Test : TSST) including a speech and a mental arithmetic task. We measured subjective stress level (visual analogue scale : 0-1), salivary cortisol and DHEA, and autonomic nerve activity (Cardiac Sympathetic Index : CSI, Cardiac Vagal Index : CVI) repeatedly during the experiment, and asked participants to complete perceived stress scale (PSS : measuring stress level during the recent week). The area under the curve on the basis of the ground (AUC_G) of cortisol level and DHEA level was calculated to assess the responsiveness of them. Statistical analyses were made using 2way ANOVA and t test. Results : There were no significant interactions between groups and time in cortisol, DHEA, CSI, CVI, and subjective stress level. However, there were significant main effect of groups in cortisol (F [1, 31]=4.39, p<0.05), and significant main effects of time in all dependent variables (cortisol : F [6, 26]=4.75, p<0.01, DHEA : F [6, 26]= 7.58, p<0.001, subjective stress : F [6, 26]=16.87, p<0.001). IBS group had lower AUC_G of cortisol than control group (t [31]=2.72, p<0.05). There were no significant differences between IBS and control group in AUC_G of DHEA, DHEA and cortisol at rest, and PSS score. Conclusion : Although individuals with IBS had lower responsiveness of cortisol, they showed about the same responsiveness of DHEA level and autonomic nerve activity as control groups. Therefore, it was suggested that individuals with IBS had the discrepancy between secretion of cortisol and DHEA in response to psychosocial stress.