Levels of N-acylethanolamines in the interstitium of trapezius muscle during the tissue trauma: A microdialysis study on women with chronic widespread pain

Abstract

Abstract Aims Since the insertion of MD probes causes an acute tissue trauma, analyses of microdialysates during this period has previously been disregarded in favour of waiting until stable baselines are achieved. The aim of this study is to compare the levels of NAEs in women with chronic widespread pain (CWP) to the healthy controls (CON) during the tissue trauma period. Methods 18 women with CWP were included in this study. Inclusion criteria were female sex, age range 20–65 years, and widespread pain according to the American College of Rheumatology (ACR) classification. 20 CON were recruited. Inclusion criteria were female sex age range 20–65 years, and pain-free. All participants were examined by a standard and validated clinical examination of the upper extremities. MD was conducted in trapezius muscle and dialysate were sampled every 20 min, and the samples of interest in this study were collected in the two first hour after catheter insertion. CMA 63 (catheter: membrane 30 mm length, 0.5 mm diameter, 20 kDa cut-off, flow rate: 5 μl/min) was used. The levels of NAEs were analyzed by liquid chromatography tandem mass spectrometry (LC–MS/MS). Results Oleoylethanolamine (OEA) and Palmitoylethanolamine (PEA) levels were significantly higher in CWP compered to CON during tissue trauma period (Mann–Whitney U-test: P > 0.001 for OEA and P ≤ 0.05 for PEA). Conclusions Previous biochemical studies of patients with CWP have often focused on sensitizing substances. Here we investigated the levels of lipid signaling molecules, with anti-inflammatory and pain-relieving properties, during acute tissue trauma. The results demonstrate that the levels of OEA and PEA differ significantly between CWP and CON. A better understanding of the interplay between these lipids and peripheral pain signaling might provide new therapeutic opportunities for patients with CWP.