Is melatonin involved in the irritable bowel syndrome?

There is a substantial evidence that large quantities of melatonin are produced in gastrointestinal tract, however, is still unclear which is the role of melatonin in digestive system in human physiology and pathophysiology. In the present study we investigated urinary excretion of a main melatonin metabolite, 6-sulphatoxymelatonin, in patients with irritable bowel syndrome (IBS). The investigation was carried out in 67 persons, both sexes, aged 20-45 years old who according to Rome III Criteria were diagnosed as sufferers of constipation (C-IBS, n=21 persons) or diarrhoea (D-IBS, n=24 persons) form of irritable bowel syndrome and as healthy subjects (K, n=22), matched for control. Samples were obtained from the collected diurnal urine. The concentration of 6-sulphatoxymelatonin (6-SMLT) was measured with ELISA method, creatinine (crea) was automatically analyzed with biochemical analyzer and 6-SMLT/crea calculated. There were statistically significant differences between groups: the 6-SMLT/crea level was lower in C-IBS (103.86+/- 82.83 ng/mg) and D-IBS (112.72+/-85.29 ng/mg) groups compared to K group (202.7+/-89.28 ng/mg), respectively, p=0.002, p=0.003. There were no differences between C-IBS and D-IBS groups, however, there were observed differences between men and women with C-IBS. The 6-SMLT/crea. level was higher in women with C-IBS (139.31+/-96.45) compared to men with C-IBS (35.51+/-41.05) (p=0.04). These results suggest that different melatonin secretion and metabolism may be involved in the pathogenesis of irritable bowel syndrome.