Dysregulation of miR-499, miR-708 and miR-1908 during a depression episode in bipolar disorders.

Affective disorders include unipolar disorder (UP) (depression episodes) and bipolar disorder (BP) (depression and mania episodes). Currently, no biological markers are known that can help to differentiate these disorders. However, recent studies have suggested that psychiatric disorders can be connected with small, non-coding RNA, like microRNA. The objective of this study was to analyse the expression level of three microRNAs (miR-499, miR-708, miR-1908) in bipolar and unipolar disorder during depression episodes and after entering the remission state. The group consisted of adult women only, 17 UP (age: 50±17) and 15 BP (age: 33±13) patients. The expression level of miRNAs was investigated by RT-qPCR with the TaqMan assay. Our study has shown a lower expression level of miR-499 (p=0.008), miR-708 (p=0.02) and miR-1908 (p=0.004) in depression episodes of the bipolar disorder patients in comparison to remission state. We have not found similar differences in unipolar disorder and between those types in acute phase of depression and during remission. Obtained results indicate that miRNAs: miR-499, miR-708 and miR-1908 are the most promising candidates for biomarkers of depression episodes of bipolar disorder.