Plasma Circular RNA DYM Related to Major Depressive Disorder and Rapid Antidepressant Effect Treated by Visual Cortical Repetitive Transcranial Magnetic Stimulation

Background: Reduced plasma circular RNA DYM (circDYM) has been detected in patients with major depressive disorder (MDD). Mechanism research has demonstrated that circDYM, acting as a microRNA-9 sponge, sup- pressed microglial activation by increasing Heat Shock Protein 90 ubiquitination, indicating that circDYM could be a potential biomarker of MDD. Methods: Thirty-two normal controls (NCs) and 60 MDD patients were recruited. Enrolled patients were ran- domly allocated to the real or sham repetitive transcranial magnetic stimulation (rTMS) group, followed by continuous five-day visual cortical rTMS or sham treatment. All participants underwent multidimensional neuropsychological assessments and detection of circDYM levels. Results: Initial scores on all emotional and psychosocial assessments in MDD were significantly different from those of NCs. As compared with the NC group, baseline plasma circDYM levels in MDD patients decreased remarkably (p=0.030) and showed significant positive correlations with the scores of the 24 -item Hamilton Depression Rating Scale (r=0.318, p=0.031) and retardation subscale (r=0.323, p=0.029). The increase in circDYM was noteworthy after rTMS (p=0.006), while downregulation with no statistical significance was observed after sham treatment (p=0.170). Limitations: It was not estimated on the correlation between plasma circDYM levels and long-term efficacy of rTMS. The mechanism of upregulated circDYM expression in response to visual cortical rTMS remained un- revealed, and the sample size was relatively small. Conclusions: This study verified the reduced circDYM levels in MDD patients, and further determined the up - regulated circDYM expression after rTMS treatment, revealing the potential of circDYM as a biomarker for MDD diagnosis and antidepressant effect of visual cortical rTMS.