Altered amino acid homeostasis in subjects affected by fibromyalgia.

OBJECTIVES To evaluate plasma amino acid (AA) concentrations in patients affected by fibromyalgia (FM) and to study the relationships between their levels and FM clinical parameters. DESIGN AND METHODS 20 AAs were assessed in 34 FM patients and in 18 healthy volunteers by means of a modified version of the Waters picotag method. RESULTS Significant lower plasma taurine, alanine, tyrosine (Tyr), valine, methionine, phenylalanine and threonine concentrations, and the sum of essential AAs were observed in FM patients vs healthy controls (P<0.05). Tyr CAA' ratio and the sum of AAs competing with tryptophan for brain uptake were significantly reduced in FM (P<0.05). A significant correlation was found between FM clinical parameters and certain AAs. CONCLUSIONS Our results suggest probable defects of gut malabsorption of certain AAs in FM patients. Moreover, given the reduced Tyr CAA' ratio in FM patients, a possible impairment of the cathecolaminergic system in the FM syndrome may be suggested.