Small bowel transit time

Association of serotonin transporter promoter polymorphism (5-HTTLPR) with orocecal transit time in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a multifactorial disorder with altered intestinal motility, secretion, and sensation. Serotonin (5-HT) stimulates gut motility and alters serotonin signaling that may lead to both intestinal and extraintestinal symptoms in IBS.

AIM

The aim of this study was to examine the association of serotonin transporter gene promoter polymorphism (5-HTTLPR) in IBS with orocecal transit time (OCTT) measured by lactulose hydrogen breath test.

METHOD

This prospective case-control study included 151 IBS patients (mean±SD 37.4±11.6 years, median 36, range 19-68). Ninety-two patients were diarrhea-predominant IBS (D-IBS), 44 constipation-predominant IBS (C-IBS), 15 alternating diarrhea and constipation IBS (M-IBS), and 100 healthy controls (mean±SD 37.2±11.4 years, median 36, range 20-64 years). 5-HTTLPR gene polymorphism was studied by polymerase chain reaction-based method. 5-HT levels were measured by enzyme-linked immunosorbent assay (ELISA). Orocecal transit time (OCTT) was measured by a non-invasive lactulose hydrogen breath test. OCTT was also compared with respect to 5-HTTLPR genotypes in different IBS phenotypes.

RESULTS

Serum serotonin levels were significantly higher in overall IBS patients (152±77 ng/mL, p<0.001), D-IBS (184±76 ng/mL, p<0.001), compared to healthy controls (129±56 ng/mL). There was no difference in 5-HT levels between C-IBS (124±53 ng/mL) and controls. In the case of M-IBS, 5-HT levels were (88±49 ng/mL p<0.05) significantly lower than that of controls. OCTT was significantly shorter in D-IBS patients (95±36 min) as compared to controls (112±41 min). In contrast, C-IBS showed significantly prolonged OCTT (136±54 min). There was a significant difference in OCTT between D-IBS and C-IBS patients (p<0.001). There was no significant association found between OCTT and 5-HTTLPR.

CONCLUSIONS

Serum serotonin concentrations were increased in D-IBS compared to controls and C-IBS. OCTT was shorter in D-IBS and delayed in C-IBS patients. There was no association of 5-HTLPR polymorphism with OCTT.

Influence of antidepressants on whole gut and orocaecal transit times in health and irritable bowel syndrome

BACKGROUND

Antidepressants are used in the treatment of irritable bowel syndrome but it is unclear whether any symptomatic improvement is due solely to correction of an associated affective disorder, or whether these drugs have effects on bowel function which may be of therapeutic benefit. Intestinal transit is known to be abnormal in some irritable bowel syndrome patients.

METHODS

We have studied the effects of imipramine, a tricyclic antidepressant with mixed pharmacological properties, and paroxetine, a selective 5-hydroxytryptamine re-uptake inhibitor, on intestinal transit times.

RESULTS

Median (range) whole gut transit time was lower in 10 diarrhoea-predominant irritable bowel syndrome patients, 22.2 (3.6-51.6) h, compared to 28 control subjects 39.6 (7.2-68.4) h, (P < 0.05). Similarly, orocaecal transit time was shorter at 55 (30-90) min in diarrhoea-predominant irritable bowel syndrome patients compared to 75 (40-150) min in controls, (P < 0.05). Four days' administration of imipramine increasing to a daily dose of 100 mg prolonged both orocaecal and whole gut transit times in 12 control subjects and six diarrhoea-predominant irritable bowel syndrome patients. In contrast, 30 mg paroxetine daily for 4 days reduced orocaecal transit time in ten controls and eight irritable bowel syndrome patients, but had no effect on whole gut transit time.

CONCLUSION

Short-term administration of antidepressants alters intestinal transit, but the selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, has different effects to the tricyclic drug, imipramine. These effects on transit precede any effects on mood. Although there is a high prevalence of affective disorder in irritable bowel syndrome clinic patients, these drugs may have additional therapeutic actions on the gut. These actions might be taken into account when prescribing antidepressants in irritable bowel syndrome.