Neuroendocrine Dysregulation in Irritable Bowel Syndrome Patients: A Pilot Study

BACKGROUND/AIMS: Irritable bowel syndrome (IBS) is a multifactorial disorder, involving dysregulation of brain-gut axis. Our aim was to evaluate the neuroendocrine activity in IBS. METHODS: Thirty IBS and 30 healthy subjects were enrolled. Psychological symptoms were evaluated by questionnaires. Urinary 5-hydroxyindoleacetic acid (5-HIAA), plasma serotonin, endothelin, neuropeptide Y (NPY), plasma, and urinary cortisol levels were evaluated. Fourteen IBS subjects underwent microneurography to obtain multiunit recordings of efferent postganglionic muscle sympathetic nerve activity (MSNA). RESULTS: Prevalent psychological symptoms in IBS were maladjustment (60%), trait (40%) and state (17%) anxiety, obsessive compulsive-disorders (23%), and depressive symptoms (23%). IBS showed increased NPY (31.9 [43.7] vs 14.8 [18.1] pmol/L, P = 0.006), serotonin (214.9 [182.6] vs 141.0 [45.5] pg/mL, P = 0.010), and endothelin [1.1 [1.4] vs 2.1 [8.1], P = 0.054], compared to healthy subjects. Moreover, plasma NPY, endothelin, cortisol and serotonin, and urinary 5-HIAA were associated with some psychological disorders (P < 0.05). Despite a similar resting MSNA, after cold pressor test, IBS showed a blunted increase in MSNA burst frequency (+4.1 vs +7.8 bursts/minute, P = 0.048; +30.1% vs +78.1%, P = 0.023). Baseline MSNA tended to be associated with urinary cortisol (ρ = 0.557, P = 0.059), and moreover, changes in heart rate and MSNA after mental stress were associated with urinary (ρ = 0.682, P = 0.021) and plasma cortisol (ρ = 0.671, P = 0.024), respectively. CONCLUSION: Higher concentrations of endothelin, NPY, and serotonin were found to be associated with some psychological disorders in IBS patients together with an altered cardiovascular autonomic reactivity to acute stressors compared to healthy subjects.