Comparing high-density lipoprotein and macrophage inflammatory protein-1α in healthy individuals and those affected by chronic pain in relation to physical activity: an experimental study

Background Chronic pain is a widespread problem for both individuals and society. Chronic pain can be defined as pain lasting for three months or more and symptoms can be depression and decreased quality of life. Biomarkers are defined as quantities that can be measured and used to imply normal or pathogenic biological processes. High density lipoproteins (HDLs) main function is to transport excess cholesterol from peripheral tissue back to the liver while Macrophage inflammatory protein-1α (MIP-1α) attracts inflammatory cells to the site of inflammation. Higher levels of HDL have been shown to be associated with lower levels of pain, whilst MIP-1α may have an association with higher pain perception. Aim/objective/purpose The study aimed to investigate if high-density lipoprotein and macrophage inflammatory protein-1α could serve as biomarkers for chronic pain, particularly in studying the role of physical activity by comparing healthy individuals to those with chronic pain (ageing between 35-65 years). Biomarkers were analysed in saliva and capillary blood respectively to see if these associate with self-reported pain prior to and post physical activity using the Åstrand bicycle ergometer test. Method A total of 18 participants were divided into two groups, pain group and control group. A capillary bloodsample, a saliva sample and self-reported pain were obtained prior to, and post a Åstrands bicycle ergometer test. Saliva samples were analysed using Enzyme-linked immunosorbent assay (ELISA) and HDL was analysed using Cardiocheck. The statistical analysis was performed in SPSS using a Wilcoxon-signed ranked test, Spearman's correlation test and a two-way ANOVA. Result The studied population were in the ages between 35-65 years old, baseline pain for the paingroup were 4.11 and 1.22 for the controlgroup. HDL values were significantly higher post the exercise session for both groups and MIP-1α values did not significantly differ post the exercise. HDL was moderately negatively associated with self-reported pain and MIP-1α was strongly positively associated with self-reported pain prior to the exercise intervention but this association was no longer detectable post the intervention. Conclusion HDL was negatively associated with self-reported pain and increased similarly across groups, while MIP-1α was unaffected by exercise. This suggests potential benefits of physical activity for pain reduction and highlights the importance of further research on HDL and