Tryptophan as a link between psychopathology and somatic states.
OBJECTIVE
Several somatic illnesses are associated with psychiatric comorbidity. Evidence is provided that availability of the essential amino acid tryptophan, which is the precursor of serotonin, may cause this phenomenon.


METHODS
We performed a database search to find relevant articles published between 1966 and 2002. For our search strategy, we combined several diseases from the categories hormonal, gastrointestinal, and inflammatory with the search terms "tryptophan" and "serotonin."


RESULTS
The catabolism of tryptophan is stimulated under the influence of stress, hormones and inflammation by the induction of the enzymes tryptophan pyrrolase (in the liver) and IDO (ubiquitous). Because of the reduction in blood levels of tryptophan under these circumstances the formation of cerebral serotonin is decreased.


CONCLUSIONS
It is argued that the coupling of peripheral tryptophan levels and cerebral serotonin levels has physiological significance. The clinical implications and therapeutic consequences of changes in tryptophan and consequently serotonin metabolism are discussed.
Russo
Sascha
S
Department of Biological Psychiatry, University Hospital Groningen, The Netherlands. s.r.russo@acggn.azg.nl
Kema
Ido P
IP
Fokkema
M Rebecca
MR
Boon
Jim C
JC
Willemse
Pax H B
PH
de Vries
Elisabeth G E
EG
den Boer
Johannes A
JA
Korf
Jakob
J
D000818:Animals; D001007:Anxiety / Q000209:etiology / Q000378:metabolism; D001923:Brain Chemistry; D003863:Depression / Q000139:chemically induced / Q000209:etiology / Q000378:metabolism; D004194:Disease / Q000523:psychology*; D004700:Endocrine System Diseases / Q000378:metabolism / Q000523:psychology; D005260:Female; D005767:Gastrointestinal Diseases / Q000378:metabolism / Q000523:psychology; D006801:Humans; D006854:Hydrocortisone / Q000502:physiology; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007239:Infections / Q000378:metabolism / Q000523:psychology; D007249:Inflammation / Q000378:metabolism / Q000523:psychology; D007372:Interferons / Q000009:adverse effects / Q000627:therapeutic use; D007508:Irritable Mood / Q000502:physiology; D007737:Kynurenine / Q000096:biosynthesis; D008297:Male; D051381:Rats; D012701:Serotonin / Q000096:biosynthesis*; D013312:Stress, Physiological / Q000378:metabolism / Q000523:psychology; D014364:Tryptophan / Q000172:deficiency / Q000378:metabolism*; D014365:Tryptophan Hydroxylase / Q000378:metabolism; D014366:Tryptophan Oxygenase / Q000378:metabolism
D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D012701:Serotonin; D007737:Kynurenine; D014364:Tryptophan; D007372:Interferons; D014366:Tryptophan Oxygenase; D014365:Tryptophan Hydroxylase; D006854:Hydrocortisone