Sex differences of brain serotonin synthesis in patients with irritable bowel syndrome using alpha-[11C]methyl-L-tryptophan, positron emission tomography and statistical parametric mapping.
BACKGROUND
Irritable bowel syndrome (IBS) is the most common functional bowel disorder and has a strong predominance in women. Recent data suggest that the brain may play an important role in the pathophysiology of IBS in the brain-gut axis. It is strongly suspected that serotonin (5-HT), a neurotransmitter found in the brain and gut, may be related to the pathophysiology of IBS. It is reported that a 5-HT3 antagonist is effective only in female patients with diarrhea-predominant IBS.


OBJECTIVE
In the present study, 5-HT synthesis was measured using positron emission tomography, with alpha-[11C]methyl-L-tryptophan as the tracer, in patients with IBS. The aim of the present study was to compare 5-HT synthesis in the IBS patients with that in the controls, and to compare 5-HT synthesis between male and female IBS patients.


METHODS
Six male and six female nonconstipated IBS patients were scanned. Age-matched healthy volunteers were scanned as controls. Eighty minute dynamic scans were performed. Functional 5-HT synthesis images were analyzed using statistical parametric mapping.


RESULTS
5-HT synthesis was greater only in the female IBS patients in the right medial temporal gyrus (multimodal sensory association cortex) compared with the female controls (P<0.001).


CONCLUSIONS
The greater brain 5-HT synthesis in the female IBS patients than in the controls may be related to the pathological visceral pain processing of the IBS patients, a larger female predominance of the disorder, and the sex difference of the efficacy of the 5-HT3 antagonist in treatment.
Nakai
Akio
A
Fukui Medical University School of Medicine, Fukui, Japan.
Kumakura
Yoshikata
Y
Boivin
Michel
M
Rosa
Pedro
P
Diksic
Mirko
M
D'Souza
Doreen
D
Kersey
Kathryn
K
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002908:Chronic Disease; D003109:Colonic Diseases, Functional / Q000000981:diagnostic imaging* / Q000209:etiology / Q000378:metabolism*; D005260:Female; D016166:Free Radical Scavengers / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012701:Serotonin / Q000032:analysis*; D012737:Sex Factors; D014055:Tomography, Emission-Computed; D014364:Tryptophan / Q000031:analogs & derivatives*
D016166:Free Radical Scavengers; C020774:alpha-methyltryptophan; D012701:Serotonin; D014364:Tryptophan