The pain profile in fibromyalgia : Painomic studies of pain characteristics and proteins in blood

Abstract: Chronic widespread pain (CWP), including fibromyalgia (FM), is a complex pain condition, where little is known about the molecular mechanisms contributing to its pathophysiology. To date, there are no established biomarkers for CWP/FM. This thesis has investigated potential molecular mechanisms and biomarkers in blood for chronic pain in women with CWP/FM. Furthermore, investigations are made to evaluate whether common pain characteristics such as pain intensity, sensitivity, and psychological distress in CWP/FM are correlated with specific proteins in blood.The pain profile of CWP/FM, which includes the plasma proteome and clinical characteristics, is analyzed using proteomics, advanced multivariate statistics, and bioinformatics. The results from paper I, III, and IV indicate that there are prominent systemic changes related to immunity, inflammation, and metabolic processes in women with CWP/FM compared to healthy controls. Furthermore, paper II and III show that in CWP/FM, pain intensity is related to protein profiles involved in immunity processes, psychological distress with metabolic and immunity processes, and pain sensitivity with inflammatory processes.In paper IV, the plasma proteome is investigated before and after a 15 weeks resistance exercise intervention in FM and healthy controls. Both at baseline and post exercise in FM and controls, prominent protein alterations are found that are involved in immunity, stress, mRNA stability, and muscle structure development. Exercise seems to influence clinical characteristics and circulating proteins in FM. Furthermore, specific plasma proteome profile is found related to grade of chronification, pain sensitivity, and improved muscle force of the quadriceps muscle.To summarize, the results from this thesis suggest that in CWP/FM there might be a dysregulation in the biological processes involved in the immune system and metabolic processes, which are tightly linked to several proteins in the complement system and blood coagulation cascade. These results shed light on potential ongoing mechanisms involved in the pathophysiology of the complex pain condition CWP/FM. This type of biomarker research has a large potential in increasing knowledge about mechanisms involved in CWP/FM and can hereby open for better clinical understanding and management of this and other chronic pain states. The clinical value of collecting a blood sample and measuring stable pain mechanism markers in combination with evaluation of anamnesis and clinical examination would in the future help clinicians and patients receive a faster and more precise diagnosis and ultimately better treatment strategies.