Peripheral blood miR-16-5p as a potential biomarker for distinguishing unmedicated bipolar disorder type II from...

major depressive disorder (MDD) and bipolar disorder type II (BD-II) are difficult to distinguish clinically due to similar depressive symptoms and unrecognizable hypomania symptoms in the early stages. The study aims to identify these two disorders in the early stages through differential expression of microRNAs.

93 subjects including 66 unmedicated patients (33 MDD, 33 BD-II), and 27 healthy controls (HC) were enrolled. At the time of enrollment, all subjects' demographic data, HAMD, HCL-32, and YMRS scales were assessed. 5 ml of peripheral blood for all subjects was collected for microRNA second-generation sequencing. MicroRNA differential expression, target gene GO and KEGG analyses were performed.

No statistical differences in demographic data were found except for age (BD-II < MDD, P = 0.002). In terms of clinical data, there are differences in the course of the disease (BD-II > MDD, P = 0.037) and the HCL-32 (BD-II > MDD, P < 0.01). A variance analysis of microRNA expressions across all three groups identified eight highly expressed differential miRNAs (P < 0.001), Pairwise comparisons revealed that the expression level of miR-16-5p was lower in both MDD group (P < 0.05) and BD-II group (P < 0.001) than in HC group, and it was even lower in BD-II group compared to MDD group (P < 0.01). The area under the curve (AUC) for miR-16-5p in differentiating BD-II from MDD groups was 0.723 (P = 0.003).

Peripheral blood miR-16-5p may serve as a potential biomarker for distinguishing unmedicated BD-II from MDD patients.