“…Emerging studies have shown the differential expression of miRNAs in blood between patients with PD and healthy controls. The expression levels of miRNAs, including Homo sapiens (hsa)-miR-7-5p, hsa-miR-22-3p, hsa-miR-136-3p, hsa-miR-139-5p, hsa-miR-330-5p, hsa-miR-433-3p, hsa-miR-495-3p (Ravanidis et al, 2019), hsa-miR-27a (Chen et al, 2018), hsa-miR-137 (Li et al, 2017), hsa-miR-331-5p (Cardo et al, 2013), hsa-miR-19b-3p (Uwatoko et al, 2019), hsa-miR-520d-5p (Jin et al, 2018), hsa-miR-195 (Ding et al, 2016), hsa-miR-29a-3p, hsa-miR-30b-5p, hsa-miR-103a-3p (Serafin et al, 2015), and hsa-miR-105-5p (Yang et al, 2019a), were up-regulated, while hsa-let-7a, hsa-let-7f, hsa-miR-142-3p, hsa-miR-222 (Chen et al, 2018), hsa-miR-433, hsa-miR-133b (Zhang et al, 2017), hsa-miR-671-5p (Uwatoko et al, 2019), hsa-miR-141, hsa-miR-214, hsa-miR-146b-5p, hsa-miR-193a-3p , hsa-miR-29 (Bai et al, 2017), hsa-miR-15b, hsa-miR-181a, hsa-miR-185, hsa-miR-221 (Ding et al, 2016), hsa-miR-153, hsa-miR-223 (Cressatti et al, 2019), and hsa-miR-133b (Zhao et al, 2014) were found to be down-regulated in the blood of patients with PD compared with that of healthy controls (Figure 1). Hsa-miR-7 is down-regulated in the peripheral blood and regulates the expression of brain-derived neurotrophic factor (BDNF) through an auto-regulatory mechanism.…”