title: 13C-phenylalanine breath test detects altered phenylalanine kinetics in schizophrenia patients.
abstract: Phenylalanine is an essential amino acid required for the synthesis of catecholamines including dopamine. Altered levels of phenylalanine and its metabolites in blood and cerebrospinal fluid have been reported in schizophrenia patients. This study attempted to examine for the first time whether phenylalanine kinetics is altered in schizophrenia using L-[1-(13)C]phenylalanine breath test ((13)C-PBT). The subjects were 20 chronically medicated schizophrenia patients (DSM-IV) and the same number of age- and sex-matched controls. (13)C-phenylalanine (99 atom% (13)C; 100 mg) was administered orally and the breath (13)CO(2) /(12)CO(2) ratio was monitored for 120 min. The possible effect of antipsychotic medication (risperidone (RPD) or haloperidol (HPD) treatment for 21 days) on (13)C-PBT was examined in rats. Body weight (BW), age and diagnostic status were significant predictors of the area under the curve of the time course of Δ(13)CO(2) (‰) and the cumulative recovery rate (CRR) at 120 min. A repeated measures analysis of covariance controlled for age and BW revealed that the patterns of CRR change over time differed between the patients and controls and that Δ(13)CO(2) was lower in the patients than in the controls at all sampling time points during the 120 min test, with an overall significant difference between the two groups. Chronic administration of RPD or HPD had no significant effect on (13)C-PBT indices in rats. Our results suggest that (13)C-PBT is a novel laboratory test that can detect altered phenylalanine kinetics in chronic schizophrenia patients. Animal experiments suggest that the observed changes are unlikely to be attributable to antipsychotic medication.
authors: Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors: T
authors: T
authors: Teraishi
authors: Y
authors: Y
authors: Ozeki
authors: H
authors: H
authors: Hori
authors: D
authors: D
authors: Sasayama
authors: S
authors: S
authors: Chiba
authors: N
authors: N
authors: Yamamoto
authors: H
authors: H
authors: Tanaka
authors: Y
authors: Y
authors: Iijima
authors: J
authors: J
authors: Matsuo
authors: Y
authors: Y
authors: Kawamoto
authors: Y
authors: Y
authors: Kinoshita
authors: K
authors: K
authors: Hattori
authors: M
authors: M
authors: Ota
authors: M
authors: M
authors: Kajiwara
authors: S
authors: S
authors: Terada
authors: T
authors: T
authors: Higuchi
authors: H
authors: H
authors: Kunugi
mesh_terms: D000328:Adult; D000818:Animals; D014150:Antipsychotic Agents / Q000627:therapeutic use; D001944:Breath Tests; D002247:Carbon Isotopes; D002908:Chronic Disease; D004298:Dopamine / Q000502:physiology; D006220:Haloperidol / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D010649:Phenylalanine / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D018967:Risperidone / Q000627:therapeutic use; D012559:Schizophrenia / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D013055:Spectrophotometry, Infrared
chemical_list: D014150:Antipsychotic Agents; D002247:Carbon Isotopes; D010649:Phenylalanine; D006220:Haloperidol; D018967:Risperidone; D004298:Dopamine