Study On Leukocyte Mitochondrial DNA Copy Number And Deletion Of4977Bp In Major Depressive Disorder

Background:Major depressive disorder (MDD) is the leading cause of disability worldwide, and has significant genetic predisposition. Mitochondria may have a role in MDD and so mitochondrial DNA (mtDNA) defection has been suggested as a possible biomarker for this disease. We aimed to test whether the mtDNA copy number and mtDNA4977bp deletion of peripheral blood leukocytes is related to MDD.Method:A case-control study was conducted with253MDD patients and257healthy controls (HC). The mtDNA copy number was measured by quantitative polymerase chain reaction (qPCR) method, while the mtDNA4977bp deletion was test by ordinary polymeras chain reaction (PCR) and agarose gel electrophoresis (AGE). Depression severity was assessed by the Hamilton-17Depression Rating Scale (HDRS-17), while psychological, social, and occupational function was assessed with Global Assessment of Function Scale (GAF).Results:We found no significant differences in mtDNA copy number between MDD patients and HC, though the power analysis showed that our sample size has enough power to detect the difference. There were also no significant correlations between mtDNA copy number and the clinical characteristics (such as age, age of onset, episodes, Hamilton Depression Rating Scale (HDRS) score and Global Assessment of Function Scale (GAF) score) in MDD patients. But MDD patients’ mtDNA4977bp deletion seem to be more frequent than HC, although it’s still have no correlations with age and other characteristics.Conclusions:Our study suggests that leukocyte mtDNA copy number is unlikely to contribute to MDD, while mtDNA4977bp deletion seem to have something to do with MDD. But it doesn’t mean that we can ensure the possibility of involvement of mtDNA in the disease. Further studies are required to elucidate whether mtDNA4977bp deletion can be a potential diagnostic marker of MDD.