Association Between GABA_A Receptor Gene Polymorphism And Affective Network In Patients With Anxious Depression

Objective:The GABA_A receptor deficiency hypothesis in the occurrence and development of anxiety and depression has been widely recognized,but its neuropathological mechanism is still unclear.The purpose of this study was to investigate the association between GABA_A receptor gene polymorphism and anxious depression by combining genetic and imaging methods in the special subtype of depression.At the same time,the abnormal brain function of emotional network in patients with anxiety depression was used as endophenotype to explore the influence of gene polymorphism on brain imaging and the potential relationship among gene polymorphism,abnormal brain function and clinical symptom groups.The aim of this study is to explain the neuropathological mechanism of GABA_A receptor gene polymorphism in anxiety depression from the perspective of brain imaging.Methods:A total of 153 patients with major depressive disorder who met the DSM-?were recruited from the inpatients of the Brain Hospital Affiliated to Nanjing Medical University.Meanwhile 62 cases of healthy control group were recruited matched in the sex and age with patients.Demographic and clinical information of the two groups were collected.According to whether the anxiety/somatization factor score of HAMD-17 was?7,the patients group was further divided into anxious depression group and non-anxious depression group.The data of elbow vein blood and resting state MRI were collected from the both groups.Twenty-two SNP sites of GABA_A receptor were selected as candidate gene sites.DNA extraction,PCR amplification,sequencing and other processing were carried out on blood samples of the two groups to obtain the information of each gene locus.The brain imaging data of the two groups were preprocessed by format conversion,slice timing,head movement correction and normalize.Then,all data were analyzed as follows:1 Association analysis of GABA_A receptor gene polymorphism with susceptibility to anxious depression and clinical symptomsThe 22 sites of GABA_A receptor subunits were sequenced by second generation sequencing.The risk gene loci of anxious depression were analyzed by case-control analysis.MGPS was used to calculate the effect of all the loci,and the MGPS of each subject was obtained.Correlation analysis was made with the clinical characteristics of patients with anxious depression,and the combination of GABA_A receptor SNP sites related to clinical characteristics was obtained.The significant MGPS entered into the following imaging analysis.2 Abnormality of emotional network and its resting state index and its correlation with clinical characteristics in patients with anxious depression.According to the situation of group divided,the differences of resting state brain structure,functional connectivity of amygdala subregion and brain activity in emotional network among the three groups were investigated.Post-hoc analysis was used to obtain the differences of the above indexes between anxious and non-anxious depression groups.The abnormal indexes of significant different brain regions in anxious depression group were extracted,and correlation analysis was made with clinical characteristics.3 To investigate the relationship between MGPS and affective network related brain dysfunction in patients with anxious depression.Taking gender,age and years of education as covariates,partial correlation analysis was made between MGPS score obtained in the first step and brain structural and functional abnormalities of anxious depression obtained in the second part to explore the association between gene polymorphism and abnormal brain image of emotional network related brain regions.4 To investigate the mediating effect of brain abnormalities of resting state emotional network between GABA_A receptor subunit gene polymorphism and clinical phenotype in patients with anxious depression.The MGPS of the risk gene locus with statistical significance obtained in the first step was used as the independent variable(X).Abnormal resting state MRI indexes,including gray matter volume,functional connectivity and brain activity,were used as mediators(M).The total score of HAMD-17 and the scores of each factor were taken as dependent variables(Y).The mediating effect model was constructed in spss19.0software to explore the brain imaging mechanism of GABA_A receptor gene associated with anxious depression.Result:1 Association between GABA_A receptor gene polymorphism and anxious depression.After the quality control of the data and the detection of Hardy-Weinberg equilibrium test,17 loci met the analysis requirements.Association analysis showed that two SNP loci(rs140682,rs140685)were associated with anxious depression group,non-anxious depression group and depressive group,so these two SNP loci were not specific risk sites for anxious depression.After linkage equilibrium analysis of 17 loci,13 loci were obtained which met the requirements of MGPS analysis.According to the genotypes of SNPs carried by the subjects,different values were assigned.The specific principles of assignment are as follows:the value of wild homozygote is"0",the value of heterozygote is"1",and the value of mutation homozygote is"2".In this way,the MGPS values of different SNP combinations are obtained.Pearson correlation method was used to calculate the correlation between MGPS and clinical symptoms.The results showed that MGPS was positively correlated with anxiety/somatization factor score(r=0.223,P=0.043),but not with other clinical features(P>0.05).2 The relationship between the abnormal resting state indexes of emotion network and clinical features in patients with anxious depression.2.1 Correlation of gray matter volume abnormality and clinical symptoms in patients with anxious depression.The gray matter volume of right middle frontal gyrus(MFG)and left dorsolateral superior frontal gyrus(SFG)were significantly different among the three groups(GRF corrected,P<0.05),Comparisons of different brain regions in each group revealed that:The order of gray matter volume in the two different brain regions of the three groups was AD<HC<NAD(Bonferroni multiple comparison correction,P<0.05/3).The volume values of the two brain regions in the anxiety depression group were extracted,and the correlation analysis was made between the volume value and the clinical feature.The volume of right MFG was positively correlated with the insight score(r=-0.36,P=0.001),but no correlation was found with HAMD-17 and it's factor scores.2.2 Abnormal functional connectivity in amygdala and its correlation with clinical symptoms in patients with anxious depression.Compared with the non-anxious depression group,the functional connectivity between the right CM and the right LB with the right middle frontal gyrus was decreased(P<0.001,K?6,P<0.05,Alphasim correction).Compared with HC group,functional connectivity between right CM and right anterior central gyrus was significantly decreased in non-anxious depression group(P<0.001,K?6,P<0.05,Alphasim correction).Compared with HC group,functional connectivity between right SF and right anterior central gyrus was decreased in non-anxious depression group(P<0.001,K?6 voxel,P<0.05,Alphasim correction).The functional connectivity values of amygdala subregions between anxious depression patients and non-anxious depression patients were extracted.Then the correlation analysis with clinical characteristics showed that the functional connectivity between right CM and right MFG was negatively correlated with anxiety somatization factor(r=-0.30,P=0.006).2.3 The analysis of the relationship between brain activity and clinical symptoms Compared with NAD group,the activity of the right superior frontal gyrus(SFG med)in AD group was decreased.Compared with HC group,the activity of right thalamus(THA)and left posterior cingulate gyrus were increased in AD group.Compared with HC group,the activity of right SFG Med was increased in NAD group.The correlation analysis between SFG Med activity and clinical indexes in anxiety depression group showed that there was no correlation between two indexes.3 To investigate the relationship between MGPS and affective network related brain dysfunction in patients with anxious depression.After removing the influence of gender,age and education years,partial correlation analysis showed that there was a negative correlation between MGPS and right MFG and right cm brain area(r=-0.24,P=0.034)4 The mediating effect of resting state MRI abnormal index characteristics between GABA_A receptor gene polymorphism and clinical symptoms in patients with anxious depression.The mediation analysis showed that the coefficient of total effect was established according to the masking effect(c=0.168,P=0.034).The coefficients a(P=0.035)and b(P=0.005)were both significant in the model.The result also showed a significant indirect effect of coefficient ab(ab=0.068,95%CI:0.00283-0.14,P=0.034),The coefficient of direct effect was not significant(c'=0.11,P=0.17).To sum up,The functional connectivity between right MFG and right CM was completely mediated between GABA_A receptor MGPS and anxiety/somatization factors.Conclusion:1.The cumulative effect of 13 SNPs of GABA_A receptor subunits(GABRA2,GABRA3,GABRA5,GABRB3,GABRD,GABRG,GABRG2)was associated with the susceptibility to anxious depression,rather than a single SNP.2.Through the study of different brain imaging indexes,it is found that the coordination of the related brain regions in the affective network of patients with anxious depression is abnormal,and the abnormal coordination of these brain regions is related to the disorder of inhibitory regulation in the network,and the abnormality of these indexes is related to the pathological mechanism of anxious depression.3.The mediating effect model found that the functional connection between the right middle frontal gyrus and the right amygdala CM subunit mediates the susceptibility of GABA_A receptor to clinical features.