Association Between Osteocalcin And Major Depression And Its Potential Mechanism

Background:Depression is a genetic and environmental interaction of major psychiatric disorder.As to the pathogenesis of depression,it includes of disorders neurogenesis and breakdown of the immune system,with different opinions.Traditionally,most of the researches involve in vivo environment disorders,ignoring the influence of genes and dynamic external environment,so that in 40% of patients clinical phenomenon of antidepressant treatment is invalid.Recently,some studies found that osteocalcin gene knockout(OCN-/-)mice exhibit anxiety-like behaviours,accompanied with increased levels of neurotransmitter GABA and decreased levels of neurotransmitter serotonin.And there symptom could be reversed and improved by administration of OCN.Thus we speculated that osteocalcin may played an important role in the pathophysiological mechanism of the depression,as well as make an antidepressant effect.Thus we try to study the relation between depression and osteocalcin,and explore the potential antidepressant mechanism of osteocalcin.Objectives:1.Assess the association of osteocalcin and major depression by measuring the levels of osteocalcin in the serum from two cohorts.2.Assess the rapid antidepressant effect of osteocalcin combining with behavior testing based on the acute stress depression mice model.3.Explore the antidepressant mechanism of osteocalcin by western blotting,ELISA and GC-MS-based metabonomic methods.Methods:1.By commercial electro-chemiluminescence immunoassay kit method,we measured the levels of osteocalcin expression in the serum from MDD(drug naive,n=199)and healthy control(n=354).2.Through the construction of rapid stress mice model of depression,we tried to find out the best concentration of osteocalcin,best type and potential mechanism of osteocalcin in three steps,and the mice were divided according to the different experimental purposes.3.Western Blotting,ELISA and the protein-chip methods were firstly used to screen and find possible antidepressant mechanism.Moreover,GC-MS-based metabolic methods were used to test metabolites expression level in the hippocampus of mice of different groups,studying the effect of osteocalcin on metabolism in the brain to explore the potential mechanism of osteocalcin deeply.Results:1.By commercial electro-chemiluminescence immunoassay kit method,compared to healthy controls,decreased expression level of osteocalcin wasfound to be significantin the serum from MDD.2.By assessing the data from FST,TST and OFT,it is noticed that compared with normal saline group,carboxylation osteocalcin and ketamine group mice showed a significant reduction in immobility time of FST and TST,while no significant change was found in OFT.Meanwhile,no significant change was found in the uncarboxylation osteocalcins groups.After treatment of antagonist NBQX,the antidepressant effect of carboxylation osteocalcin and ketamine were both offset.Carboxylation osteocalcin can quickly reverse behavior in mouse models of depression;it is likely to make similar rapid antidepressant effect as ketamine.3.Based on in vitro cell experiment and animal experiment,the results of Werstern Blotting showed that carboxylated osteocalcin can significantly inhibit the expression of NMDAR2 A and increase the expression of GluR1,GluR3 and GluR4.What's more,the administration of osteocalcin could enhance the expression of BDNF in the hippocampus of mice.These symptoms could be reversed by using NBQX.As results of GC-MS revealed that,24 metabolites were significantly changed in the OCN treated mice,including 1-Methylhydantoin,4-aminobutyric acid,adenosine DL-dihydrosphingosine,Ethanolamine,glutamic acid,glutamine,creatine,4-Vinylphenol dimer,ascorbate,aspartic acid,D-(glycerol-phosphate),glycine,lactic acid,Methyl Phosphate,myo-inositol,L-Allothreonine,L-Malic acid,N-acetyl-L-aspartic acid,oxoproline,phosphate,serine,succinic acid,urea.Conclusions:1.The expression of osteocalcin was significantly lower in MDD serum than healthy controls.2.Carboxylated osteocalcin show a significant rapid antidepressant effect,but not uncarboxylated osteocalcin.3.Carboxylation osteocalcin may exhibit the rapid antidepressant effect by down regulating the expression of the NMDA glutamate receptor and enhance the expression of AMA receptors,so as to promote the release of BDNF and glutamate,and reduce the expression of GABA.