Clinical staging and serum cytokines in bipolar patients during euthymia

Aims: Changes in serum cytokines and altered neutrophin concentration have been associated with bipolar disorder (BD). Our aim here was to analyze peripheral blood biomarkers according to the clinical stages of BD. Method: Euthymic BD-I patients were grouped according to their level of functioning in early-stage (n = 25) and late-stage (n = 23), and compared to healthy siblings (n = 23) and genetically unrelated healthy controls (n = 21). Neurotrophin (neurotrophin-3 and BDNF) concentration and biomarkers of inflammation, including cytokines (IL-6, IL-10 and TNF-alpha), leukocytes count and acute phase proteins, were measured. Results: IL-10 concentration was significantly increased in early-stage patients compared to late-stage patients, healthy siblings and controls whereas TNF-alpha concentration was significantly increased in late-stage patients compared to controls. Total leukocytes, neutrophil and monocyte count were significantly increased in late-stage patients compared to healthy siblings and controls. The concentration of IL-6, neurotrophin-3 and BDNF was unchanged in euthymia. Healthy siblings did not show significant changes in any biomarker. Conclusions: The concentration of IL-10, TNF-alpha, neutrophil and monocytes subtype count in blood is altered in patients with BD during euthymic state. The link between peripheral inflammation and different stages in BD deserves further studies.