Serotonergic markers and lowered plasma branched-chain-amino acid concentrations in fibromyalgia

The aims of the present study were to examine serotonergic markers, i.e. [H -3]paroxetine binding characteristics and the availability of plasma trypto phan, the precursor of serotonin (5-HT), and the plasma concentrations of t he branched chain amino acids (BCAAs), valine, leucine and isoleucine, in f ibromyalgia. The [H-3]paroxetine binding characteristics, B-max and K-d val ues, and tryptophan and the competing amino acids (CAA), known to compete f or the same cerebral uptake mechanism (i.e. valine, leucine, isoleucine, ph enylalanine and tyrosine), were determined in fibromyalgia patients and nor mal controls. There were no significant differences in the [H-3]paroxetine binding characteristics (B-max and K-d) between fibromyalgia and control su bjects. There were no significant differences in plasma tryptophan or the t ryptophan/CAA ratio between fibromyalgia patients and normal controls. In t he fibromyalgia patients, there were no significant correlations between [H -3]paroxetine binding characteristics or the availability of tryptophan and myalgic or depressive symptoms. Patients with fibromyalgia had significant ly lower plasma concentrations of the three BCAAs (valine, leucine and isol eucine) and phenylalanine than normal controls. It is hypothesized that the relative deficiency in the BCAAs may play a role in the pathophysiology of fibromyalgia, since the BCAAs supply energy to the muscle and regulate pro tein synthesis in the muscles. A supplemental trial with BCAAs in fibromyal gia appears to be justified. (C) 2000 Elsevier Science Ireland Ltd. All rig hts reserved.