Dietary Gluten-Free Regimen Does Not Affect the Suppression of the Inflammatory Response in the Arachidonic Acid Cascade in Hashimoto’s Disease

The incidence of Hashimoto’s disease (HD) increases with age and in people who have other autoimmune diseases. It is characterized by lymphocytic infiltration, fibrosis, and atrophy of the thyroid parenchyma with the simultaneous presence of thyroid peroxidase antibodies (ATPO) and/or thyroglobulin antibodies (ATG). Eicosanoids are formed via the cyclooxygenase (COX), lipoxygenase (LOX), and monooxygenase (CYP450) pathways with arachidonic acid (ARA), resulting in the production of epoxyeicosatrienoic acids (EETs) or hydroxyeicosatetraenoic acids (HETEs). These eicosanoids can act in an autocrine or paracrine manner on target cells. This study aimed to examine whether a gluten-free diet (GFD) can modulate the enzymatic pathways of the pro-inflammatory ARA cascade. The study material consisted of serum samples from Caucasian female patients with HD aged 18–55 years. Participants were enrolled in the study based on the presence of an ultrasound characteristic of HD, and elevated serum levels of anti-thyroid peroxidase antibodies and anti-thyroglobulin antibodies. Patients with confirmed celiac disease did not participate in the study. A total of 78 samples were analyzed, with 39 collected after 3 months of following a GFD. Eicosanoids (thromboxane B2, prostaglandin E2, leukotriene B4, and 16R-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid (16-RS HETE)) were extracted using high-performance liquid chromatography. The contribution of leukotriene (LTB) was analyzed in the LOX pathway, prostaglandins (PGE2) and thromboxane (TXB2) were selected for the involvement of the COX pathway, and 16RS HETE was used for the CYP450 pathway. All parameters were analyzed before and after a 3-month dietary intervention that included a gluten-free diet. In the obtained results, only one mediator, leukotriene B4, was significant (p < 0.05). The mean level on the initial visit was 0.202 ± 0.11 (SD), while it was 0.421 ± 0.27 (SD) on the subsequent visit, indicating a significant increase in its level after implementing a GFD. Although there was a trend in the CYP 450 pathway of decreased 16-RS HETE, the presented correlations show that thromboxane B4 and 16RS-HETE were positively correlated with the body mass and body fat mass of the examined patients. There was a trend in the CYP 450 pathway of decreased 16-RS HETE after GFD. Thromboxane B4 and 16RS-HETE levels before GFD were positively correlated with the body mass and body fat mass of the examined patients. A gluten-free diet in HD does not suppress the synthetic pathways of LOX, COX, or cytochrome P450 (CYP450). The level of adipose tissue has a greater impact on the inflammatory processes in HD than a gluten-free diet. This study does not confirm the suppressive effect of a gluten-free diet on the pro-inflammatory arachidonic acid cascade in any of the three analyzed mediator synthesis LOX, COX, CYP450 pathways.