[Note: The full text of the Jul 30, 2009 report abstracted below is now available via PubMed Central at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2757484/?tool=pubmed. It may take on new relevance in the context of controversy regarding the Feb 2011 PACE Trial report on exercise therapy for ME/CFS. To read an explanation of this post-exertion study at the University of Utah (which "suggests that a blood test for muscle fatigue and pain is possible") – written by CFIDS Association Scientific Director Suzanne D. Vernon, PhD, and published in the August 2009 CFIDSLink e-newsletter – go to www.cfids.org/cfidslink/2009/080503.asp.]
Chronic fatigue syndrome (CFS) is characterized by debilitating fatigue, often accompanied by widespread muscle pain that meets criteria for fibromyalgia syndrome (FMS). Symptoms become markedly worse after exercise.
Previous studies implicated dysregulation of the sympathetic nervous system (SNS), and immune system (IS) in CFS and FMS.
We recently demonstrated that acid sensing ion channel (probably ASIC3), purinergic type 2X receptors (probably P2X4 and P2X5) and the transient receptor potential vanilloid type 1 (TRPV1) are molecular receptors in mouse sensory neurons detecting metabolites that cause acute muscle pain and possibly muscle fatigue.
These molecular receptors are found on human leukocytes along with sympathetic nervous system and immune system genes.
Real-time, quantitative PCR (polymerase chain reaction test) showed that 19 CFS patients had lower expression of beta-2 adrenergic receptors but otherwise did not differ from 16 control subjects before exercise.
After a sustained moderate exercise test, CFS patients showed greater increases than control subjects in gene expression for metabolite detecting receptors ASIC3, P2X4, and P2X5, for SNS receptors alpha-2A, beta-1, beta-2, and COMT and IS genes for IL10 and TLR4 lasting from 0.5 to 48 hours (P < .05).
These increases were also seen in the CFS subgroup with comorbid FMS and were highly correlated with symptoms of physical fatigue, mental fatigue, and pain.
These new findings suggest dysregulation of metabolite detecting receptors as well as SNS and IS in CFS and CFS-FMS.
Perspective: Muscle fatigue and pain are major symptoms of CFS. After moderate exercise, CFS and CFS-FMS patients show enhanced gene expression for receptors detecting muscle metabolites and for SNS and IS, which correlate with these symptoms.
These findings suggest possible new causes, points for intervention, and objective biomarkers for these disorders.
Source: The Journal of Pain, Jul 30, 2009. PMID: 19647494, by Light AR, White AT, Hughen RW, Light KC. Departments of Anesthesiology and Neurobiology & Anatomy, University of Utah Salt Lake City, Utah, USA. [E-mail: email@example.com]