Increased inflammatory biomarkers and changes in biological rhythms in bipolar disorder: A case-control study

•BD shows changes in biological rhythms.•BD has increase in inflammatory markers.•Increased COX-2 and AA in BD.•Increased IL-6 and TNF-α in BD.•No difference in IL-4, IL-5, IL-10 and IL-33 levels in the BD and control groups. Bipolar Disorder (BD) is a chronic psychiatric disorder characterized by mood disturbances that include depressive, manic, and hypomanic episodes. Despite the severity of the symptoms, there is still a gap in the literature on the precise neurobiology and treatment of BD. The investigations of inflammatory changes in BD has increased in the last decade, evincing the importance of its role in the pathophysiology of the disorder. The present study aimed to investigate the inflammatory role in BD, through the evaluation of biomarkers and their relation to biological rhythms. It was conducted a case-control study that included 36 BD and 46 healthy controls (HC). The Cyclooxygenase 2 (COX-2) enzyme, Arachidonic Acid (AA), interleukins (IL) IL-4, IL-5, IL-6, IL-10, IL-33, and Tumor Necrosis Factor Alpha (TNF-α) in the serum of individuals. It also was administered the Biological Rhythm Interview of Assessment in Neuropsychiatry (BRIAN) to the BD and healthy control groups. Results: The results indicated that the individuals with BD showed increased COX-2, AA, IL-6, and TNF-α levels in comparison to the HC without psychiatric disorders, as well as significant commitments in all domains evaluated by BRIAN. Uncontrolled pharmacotherapy used by the included bipolar participants, which had important effects on participants’ inflammatory systems and the lack of cases with bipolar manic episodes. The results of the present study reaffirm that inflammation has an important role in BD, as well as the significant changes in biological rhythms. It is still necessary to better characterize the inflammatory pathway of AA.