Effects Of Exercise On Depressive Behavior And Gene Expression Profile In ASMT Gene Knockout Mice

Background: It focused on the depression that increasingly serious problem on World Health Day of 2017,according to statistics released by the World Health Organization(WHO),the number of people is at least 322 million suffering from the disease around the world,and it was expected that depression will become the first largest health burden for human disease by 2030.In the same year,“the Molecular Mechanism of Biological Rhythm”was awarded by the Nobel Prize in Physiology or Medicine.Rhythm disorders can induce the risk of neurodegenerative diseases such as depression,while regular exercise can regulate rhythm disorders,restore homeostasis and improve depression,but the mechanism has not yet been elucidated.Acetyl serotonin methyltransferase(ASMT)is a key rate-limiting enzyme in the synthesis of melatonin(MT),a circadian rhythm output signal.ASMT can catalyze serotonin(5-HT)to MT.but whether the ASMT gene knockout does cause disorder of circadian rhythm and induce depression behavior needs further confirmation by experiments,which the depression and exercise anti-depression mechanism still need to be further explored.Objective: The purpose of this study was to investigate the effects of ASMT knockout and swimming exercise intervention on depression behavior,and further explore the mechanism of depression regulation that ASMT knockout and swimming exercise intervention may involve,which will bring new discoveries to the study of exerciseanti-depressant mechanisms,and also open up ideas for clarifying the therapeutic mechanisms of seasonal affective disorders and insomnia depression.Methods: There were 11 male homozygous ASMT knockout mice and 9 littermate wild-type mice,6-7 weeks old,24-25 g.They were divided into 4 groups:(1)WT group(n=5),ie wild control group,normal feeding,no intervention;(2)WE group(n=4),ie wild exercise group,experimental mice began to receive 5 weeks swimming exercise at 6-7 weeks of age;(3)KO group(n = 5),ie the gene knockout group, identified as ASMT knockout mice,normal feeding,no intervention;(4)The KE group(n=6),ie the knockout exercise group,the ASMT knockout mice began to receive 5-week swimming exercise at 6-7 weeks of age.After the end of the experimental intervention,all groups of mice received behavioral tests.After the behavioral test was completed,killed mice by decapitation after taking blood from heart and then extracted the hypothalamus tissue.Elisa was used to detect the levels of serum MT,5-HT and NE;Agilent expression profiling chip was used to detect m RNA expression in hypothalamic tissue,bioinformatics method was used to predict target genes and perform functions and pathway enrichment analysis relating depression and exercise anti-depression.RT-PCR was used to check the m RNA expression of some genes,including ASMT and the genes that were selected from the results of gene chip screening.Results:(1)Behavioral experiment results showed that compared with the WT group,sucrose preference of KO group in the sucrose preference test(SPT)was significantly lower(P<0.01);immobility time in the forced swimming test(FST)was increased,but no significant difference was found,struggling time in the FST was reduced,but no significant difference was found;The number of poking into holes in the open field test(OFT)was significantly reduced(P<0.01),distance in center in the OFT was reduced,but no significant difference was found.Compared with the KO group,sucrose preference of KE group in the SPT was significantly increased(P<0.01);immobility time in the FST was significantly reduced(P<0.05),struggling time in the FST was significantly increased(P<0.05);the number of poking into holes in the OFT was significantly increased(P<0.01),distance in center in the OFT was increased,but no significant difference was found.(2)Serum Elisa results showed that the serum level of MT and 5-HT in the KO group was decreased but did not reach a significant difference compared with the WT group,the serum level of norepinephrine(NE)increased but did not reach a significant difference;compared with the KO group,the MT(P<0.05)and 5-HT(P<0.01)serum level of the KE group increased significantly,and the NE serum level decreased significantly(P<0.05).(3)The results of microarray showed that compared with the WT group,17 genes showed significant changes in the gene expression of KO group,8 genes were up-regulated and 9 genes were down-regulated.Compared with the KO group,51 genes showed significant changes in the gene expression of KE group,35 genes were up-regulated and 16 genes were down-regulated.Compared with the WT group,715 genes showed significant changes in the gene expression of WE group,687 genes were up-regulated and 28 genes were down-regulated.Compared with the WE group,49 genes showed significant changes in the gene expression of KE group,17 genes were up-regulated and 32 were down-regulated.Compared with the WT group,880 genes showed significant changes in the gene expression of KE group,841 genes were up-regulated and 39 genes were down-regulated.The screening criteria of differential gene was P?0.05 and FC(abs)?2.0.(4)Combined with the results of GO enrichment analysis,the differentially expressed genes with high correlation with the study were selected by the chip detection:EPS8L-1,STYL2,PLC-?2,CHEK1,CDKN1 A,ITPR2,MDM4,PIDD1,HSPA1 B.Among them,EPS8L-1 was partly consistent with the checking results by RT-PCR,PLC-?2 was completely consistent with the checking results by RT-PCR,HSPA1 B did not reach significant difference in RT-PCR checking results,but it showed down-regulation trend consistent with the chip checking results after exercise in the KO mice.Pathway analysis results showed that the enriched signaling pathways with high correlation with this study were: p53 signaling pathway,long-term depression and estrogen signaling pathway.Conclusion:(1)ASMT gene knockout can induce depressive behavior in mice,swimming exercise has a significant improvement effect,and the effect may be related to the serum levels of MT and monoamine neurotransmitters 5-HT and NE.(2)ASMT gene knockout and swimming exercise can affect the gene expression profile of mice hypothalamus.EPS8L-1 and PLC-?2 genes may affect the depressive behavior,and participate in the exercise anti-depression mechanism through p53 signaling pathway,long-term depression and estrogen signaling pathway.