Acute tryptophan depletion alters gastrointestinal and anxiety symptoms in irritable bowel syndrome.
OBJECTIVE
To assess the effect of acute changes in serotonin (5-HT) synthesis using the acute tryptophan depletion (ATD) paradigm on gastrointestinal (GI) and mood symptoms in irritable bowel syndrome (IBS).


METHODS
In a randomized double-blind crossover study, 29 subjects (18 patients with ROME II defined IBS and 11 age-matched controls) were studied under ATD and acute tryptophan increase (ATI) conditions. GI symptoms, mood and anxiety ratings, as well as plasma tryptophan concentrations were measured.


RESULTS
Total (and free) plasma tryptophan concentrations decreased on the ATD day in patients (73%[82%]) and controls (73%[80%]), and increased on the ATI day in patients (59%[143%]) and controls (61%[381%]). Compared with the ATD day, IBS patients reported more GI symptoms on the ATI day at +210 (p < 0.001) and at +270 (p < 0.05) min post drink. IBS patients also reported less anxiety on the ATI day compared with the ATD day at +270 min (p < 0.001). ATD and ATI did not affect these ratings in control participants. IBS patients had a lower mood compared with controls (p < 0.05), but this did not differ between the ATI and ATD days in either group.


CONCLUSIONS
IBS patients' GI and anxiety responses to changes in tryptophan load differ from controls. This suggests a difference in serotonergic functioning between these two groups and provides evidence to support the hypothesis that 5-HT dysfunction is involved in IBS.
Shufflebotham
Jonathan
J
Clinical Science at South Bristol, University of Bristol, Bristol, United Kingdom.
Hood
Sean
S
Hendry
Julie
J
Hince
Dana A
DA
Morris
Kelly
K
Nutt
David
D
Probert
Chris
C
Potokar
John
J
D000328:Adult; D000339:Affect; D001007:Anxiety; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D041981:Gastrointestinal Tract / Q000503:physiopathology*; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000378:metabolism* / Q000503:physiopathology / Q000523:psychology; D008297:Male; D012701:Serotonin / Q000096:biosynthesis; D014364:Tryptophan / Q000097:blood / Q000172:deficiency*
D012701:Serotonin; D014364:Tryptophan