MicroRNA-134 plasma levels before and after treatment for bipolar mania

Studies have previously documented that microRNAs (miRNAs), with their key roles in regulating both synaptic plasticity and brain development, are candidate genetic contributors to the etiopathology of bipolar disorder (BD). Moreover, miRNA identified as targets for the actions of chronic lithium and VPA are known to play diverse and intriguing roles in brain function. In particular, the brain specific miR-134 has recently been identified as a potential regulator of dendritic spine volume and synapse formation. Recently, circulating miRNAs have been reported as promising biomarkers for various pathologic conditions. We assessed the hypothesis that miRNA-134 may be present and detectable in circulating blood, and that miRNA-134 may serve as a biomarker of mania episodes in BD. In the present study, we recruited 21 bipolar I, manic (DSM-IV) patients and controls matched by sex and age for quantification of miR-134 level in plasma using real-time RT-PCR method. We found that: Plasma miR-134 levels in drug-free, 2-week medicated, and 4-week medicated bipolar mania patients were significantly decreased when compared with controls, and the level was increased on following medication. Decreased circulating miR-134 level both in drug-free and medicated patients did presented negative correlation with the clinical scales. Overall, these results suggest that the decreased plasma miR-134 levels may be directly associated with the pathophysiology and severity of manic symptoms in BD. Plasma miRNA-134 in BD may be considered as a potential peripheral marker that can respond to acute manic episodes and associate with effective mood stabilizers treatment.