Serotonin Metabolism and Serotonin Receptors Expression Are Altered in Colon Diverticulosis.

Background and Objectives: Diverticulosis is frequently accompanied by altered bowel habits. The biogenic amines within colonic mucosa control bowel motility, and in particular, alterations in serotonin signaling may play a role in colon diverticulosis. The aim of the study was to assess the concentration of biogenic amines and serotonin receptor expression in the colonic mucosa in patients with diverticulosis and healthy controls. Materials and Methods: This prospective, comparative study included 59 individuals: 35 with sigmoid diverticulosis and 24 healthy controls. The study was held at the Department of Gastroenterology and Internal Medicine, Medical University of Warsaw, Poland. Mucosal samples were taken from the right and left colon during a colonoscopy in all patients. Concentrations of norepinephrine, 3-methoxy-4-hydroxyphenylglycol, dopamine, homovanillic acid, serotonin, and 5 - hydroxyindoleacetic acid were measured with high-performance liquid chromatography. Expressions of human 5-hydroxytryptamine receptor 3A, 5-hydroxytryptamine receptor 4, 5-hydroxytryptamine receptor 7, solute carrier family 6 member 4 (SERT) for serotonin, as well as the neuroglia activation markers glial fibrillary acidic protein, S100 calcium-binding protein B, and proteolipid protein 1, were assessed with polymerase chain reaction. Results: The median age and sex distribution were comparable in both study groups (median 69 y vs. 52 y; p < 0.455 and males/females in cases 11/17 vs. 18/19 in controls; p < 0.309). In diverticulosis patients, there was a higher concentration of serotonin in the left affected colon compared to the right healthy part of the colon (median 8239 pg/mg vs. 6326 pg/mL; p < 0.01). The SERT expression was lower in the affected left segment compared to the right colon (median 0.88 vs. 1.36; p < 0.01). There was a higher colonic mucosa concentration of serotonin (median 8239 pg/mg vs. 6000 pg/mL; p < 0.02) and 5 - hydroxyindoleacetic acid/serotonin ratio (median 0.27 vs. 0.47; p < 0.01) in diverticulosis patients compared to controls in the left side of the colon. Conclusions: The concentration of serotonin in the mucosa of the colon segment affected by diverticula is higher than in the healthy segment in the same individuals and higher than in healthy controls. These results underline serotonin signaling in colon diverticulosis pathophysiology.