Thiol-Disulfide Balance in Fibromyalgia: A Case-Control Study

Abstract

Aim. We aimed to examine the thiol-disulfide (SS) balance, a recognized marker of oxidative stress, in fibromyalgia syndrome (FMS). Methods. The study comprised 98 female participants (61 newly diagnosed patients and 37 patients under treatment) with FMS, along with 82 apparently healthy female volunteers. In both groups, assessments were conducted using the Fibromyalgia Impact Questionnaire (FIQ), Visual Analogue Scale (VAS), Pittsburgh Sleep Quality Index (PSQI), Fatigue Severity Scale (FSS), Short Form-36 (SF-36), Tender Point Count, Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI). Native thiol (NT) and total thiol (TT) levels were measured, SS levels and SS/NT ratio were calculated. Results. FMS patients demonstrated significantly lower NT levels, higher SS levels, and an elevated SS/NT ratio compared to the control group (p< 0.05 for all groups). In FMS patients, a statistically significant correlation was found between SS level and the SS/NT ratio, as well as the number of tender points (r=-0.24, p=0.02; r=-0.21, p=0.04), SF-36 pain subscales (r=0.22, p=0.032; r=0.21, p=0.04), and BAI scores (r=-0.22, p=0.01; r=-0.23 p=0.03). In the subgroup analysis, all health assessment scales were observed to exhibit statistically significant differences between the under-treatment group and newly-diagnosed group when compared to the control group (p< 0.05 for all groups). The FIQ, VAS, FSS, and BAI scores were found to be significantly lower in the under-treatment group as compared to the newly-diagnosed group (p< 0.05 for all groups). In the newly-diagnosed group, NT was significantly lower and the SS/NT ratio was significantly higher than those in the control group (p< 0.05). In the under-treatment group, SS levels and SS/NT ratio were significantly higher as compared to the control group (p< 0.05). In the multivariate regression analysis, which incorporated age, health assessment scales, patient subgroups, tender points, and duration of symptoms to predict the SS/NT ratio, variabes such as being in the under-treatment group, tender points, and BAI score were identified as significant predictors (p< 0.05). Conclusions. The thiol-SS balance was observed to shift in the oxidative direction, and oxidative stress was higher in the FMS group. The absence of a significant difference between the under-treatment group and the newly-diagnosed group in terms of thiol-SS balance parameters suggests a shift to oxidative stress in patients, independent of the treatment status.

Keywords

• disulfide
• fibromyalgia
• oxidative stress
• pain
• thiol