NR McGregor, RH Dunstan, HL Butt , TK Roberts, M Zerbes, IJ Klineberg.
Collaborative Pain Research Unit:
Department of Biological Sciences
The University of Newcastle
NSW 2308, Australia.
Neurobiology Research Unit
Centre for Oral Health Research
University of Sydney
NSW 2084, Australia.
1 Division of Microbiology and Infectious Diseases
Hunter Area Pathology Service
John Hunter Hospital
NSW 2305, Australia.
Chronic Facial Muscle Pain and Dysregulated Cellular Proteolysis
Chronic muscle pain is a common condition for which there is no known aetiology although its onset has been associated with infectious events, trauma and increasing life stresses. CFS patients have increased prevalence of facial muscle pain compared with the normal population. Muscle pain has been associated with reductions in muscle protein and RNA concentrations. Thirty-five chronic facial pain patients (MP group) and 34 age and sex-matched control subjects were assessed by GCMS for variations in urinary organic and amino acid excretion which could provide evidence of increased energy utilisation or proteolysis.
Compared with the controls, the MP patients had reductions in the excretion of leucine which is an important amino acid for the regulation of proteolysis. The MP patients also had increases in tyrosine excretion, which is a marker of proteolysis. The visual analogue pain scale of average pain intensity (VAS) was inversely correlated with the reduction in leucine excretion. The VAS score was positively correlated with the increased excretion of tyrosine, as well as the increased excretion of glutamic and aspartic acids, which are excitatory amino acids. No association was found between the VAS score and the fibrillar proteolysis marker, 3-methyl-histidine. Increasing VAS scores were associated with an increased total amino acid out-put which is consistent with the reductions in the serum amino acid levels observed in other studies and suggestive of a low grade aminoaciduria. The depletion of leucine may represent a significant anomaly in the regulation of proteolysis.
These data provide evidence to support the hypothesis that dysregulated non-fibrillar proteolysis occurs in chronic facial muscle pain patients which was associated with increasing severity of chronic pain as assessed by VAS scores.
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