Comparative Proteomic Analysis Of Plasma From Bipolar Ⅱ And Major Depressive Disorder

BackgroundBipolar Ⅱ disorder is a hypotype of Bipolar disorder, and is characterized by recurrent episodes of depression and hypomania. At present, because the diagnoses of BD and MDD are still largely reliant on behavioral observations and hypomania is always neglected, many BipolarⅡ patients are initially misdiagnosed with MDD.ObjectiveIn this study, a comparative proteomic analysis of plasma from bipolarⅡ and MDD was finished to identify plasma protein biomarker candidates for differential diagnosis between bipolar Ⅱ and MDD in order to provide basis for decreasing chance of misdiagnosis.MethodsPlasma samples from 15 first-episode drug-naive bipolar Ⅱ patients and 15 first-episode drug-naive MDD patients were collected. Plasma proteins were purified and immunodepleted of high-abundance proteins for preparation and then separated by two-dimensional gel electrophoresis.PDQuest software was used to analyse differential expressed protein spots.And then matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF/TOF-MS) was used to identify them. The DAVID Bioinformatics Resource v6.7 was used to analyse the proteomic results. Next, we choose three differentially expressed proteins for ELISA validation by using individual samples from the bipolar Ⅱ(n = 20), MDD(n = 30), and HC groups(n = 30).ResultsWe found 25 differential expressed proteins by 2-DE and MALDI-TOF/TOF-MS. The expression levels of eight proteins were found to be significantly elevated and those of the other 17 proteins were significantly lower in bipolar Ⅱ subjects compared with MDD subjects.Results analysed by the DAVID Bioinformatics Resource gave information that all the differentially expressed proteins were associated with immune regulatory. ELISA results gave information that the expression levels of C3,CFI and C4BPα were significantly different in bipolar Ⅱ subjects compared with MDD subjects and were in accordance with 2-DE.ConclusionDifferentially expressed proteins are associated with immune regulating function, hinting that the pathological process of two kinds of diseases in the immune regulation may have significantly difference. C3,CFI and C4BPαmay be potential biomarkers for differential diagnosisbetween bipolar Ⅱ and MDD.