| BackgroundSuicide is a complex social and public problem, which is considered to be related to genetic and environmental factors. Studies of attempted suicide have developed from the sociological and psychological researches to the molecular biology and genetic researches. Biomarkers of attempted suicide have been come up with continuously, but the results have been inconsistent.Recently, the correlation of lipid and suicide behaviors has become a hot topic in the study of suicide behaviors. A number of studies have concluded that the elevated high density lipoprotein (HDL) concentration in serum may be associated with the occurrence of suicidal behaviors, and the lower concentration of total cholesterol in serum may also be related to the occurrence of suicidal behavior. But the results of previous studies are uncertain and controversial. Considering the serum cholesterol is influenced by diet, exercise habits, and other living habits, which may lead the results to unstable, we are trying to find a relatively stable biological marker.The cholesterol ester transfer protein CETP Taq1B (rs708272) gene polymorphism which is closely related to regulation of serum cholesterol concentration was selected as a biomarker in our study. The relationship between the gene polymorphism and attempted suicide was explored in the research.MethodsSelection of research subjects:Zoucheng, Tengzhou, Lijin, Jyunan, Penglai, Ningyang, Xintai, Zhangqiu, and Yishui counties were selected in Shandong province. The subjects were obtained in two stages. The subjects in the first stage conducted suicide during October 1,2009 to March 31,2011 and the second subjects conducted their suicide during January 1,2014 to June 30,2015. The controls were selected randomly in the same area with the same age (±3 years) and the same gender without a history of attempted suicide with the cases.Investigation and survey tools:Face-to-face interview was used to collect the information of subjects. The general demographic Questionnaire (personal basic situation including gender, age, occupation, marital status, level of education, religion, family status, health status, suffering from severe body, acute or chronic disease, professional organization diagnosis of mental illness, family economic condition, family history of suicidal behavior, home storage of pesticides, etc.), Suicide Intent Scale (SIS), Interview for Recent Life Events (IRLE), Self-esteem Scale (SES), Trait Anxiety Inventory (STAI), Center Epidemiological Studies of Depression (CES-D), Simplified Coping Style Questionnaire and DSM-Ⅳ Axis I Clinical Interview examination in the diagnosis of Scale Research Version (Structural Clinical Interview for DSM-Ⅳ Axis I Disorder,2001, Research Version (SCID) used to collect the information.DNA Extraction and Genotyping:l ml venous blood of the subjects was used to extract DNA. DNA was extracted by Blood genomic DNA extraction Kit (TIANamp Blood DNA Kit, centrifugal type; directory number:DP318), according to the Kit standard procedure. The polymerase chain reaction-ligase detection reaction (PCR-LDR) method was used for genotyping. The specific process of genotyping was conducted by Shanghai Biowing Applied biotechnology Co., Ltd.Data Statistical Analysis:SPSS16.0 software was used for data analysis. Descriptive analysis used single Chi-Square test and t test; Genotype and allele frequency distribution between case and control compared with Chi-Square test. Univariate conditional Logistic regression was used for selecting risk factors of attempted suicide. The variables which were significant in univariate analysis were included in the multivariate conditional Logistic regression model by stepwise method. In this way, the effect of gene polymorphism after controlling for the influence of other environment variables was explored. The crossover analysis method was used to calculate interaction effect of gene (rs708272) and environment (negative life events) interaction based on the additive and the multiplication model.Results1. The behavior characteristics of suicide attemptersIn the 411 suicide attempters, the female was accounted for 69.53%; suicidal behavior on the time distribution in different gender, different age had the same trend. There were two peaks in the months February to March and September to October. The most patients conducted suicide at home, in which the male accounted for 84.00% and the female accounted for 87.28%. But the attempters aged 15-35 years old tended to conduct the suicide in other places than 36-50 year-old age group (17.61% vs.11.24%,χ2= 3.32, P=0.068). No matter in the male or in the female, there were no different in suicide method, and most attempters took the non-violent method (oral pesticide) to suicide.In the suicidal intent, the male seemed to have the more hidden in conduct time (P=0.073) and to mention his suicide intent (P=0.051, and in other items the suicidal intent of the male were similar to the female. The patients aged 36-50 years old tended to have more isolated in place of suicide than the patients aged 15-35 years old (P=0.071), and there were no significant differences between the other items.There were 119 attempters which were diagnosed with SCID standard for mental illness, and only 36 of them reported that he/she had been diagnosed by the professional medical institution. These who had been diagnosed accounted for only 30.23% of all patients with mental illness, and attempters with mental illness accounted for 28.95% in all the suicide attempters. In different gender, more male patients with mental illness ignored his mental illness than the female (χ2=5.04, P=5.04). There was no difference in different aged groups.2. The genes and the relevance of attempted suicideCETP Taq1B (rs708272) allele frequency and genotype frequency distribution had no significant difference between the suicide attempters and controls. The genotype frequency was included in the multivariate conditional Logistic regression model according to the genetic model of codominant model (TT vs. CT vs. CC), recessive model (CT+TT vs. CC), and dominant model (TT vs. CT+CC), respectively, to adjust the role of other factors and get the real effect value of genotype to suicide attempt. The results had no significant.3. The interaction of rs708272 polymorphism and negative life events and attempted suicideBased on multivariate conditional Logistic regression model to adjust education, occupation, mental illness and personality psychological variables first principal component and second principal component, the 2×4 gene-environment crossover interaction analysis table was used which contained the rs708272 gene separate effect (ORg), negative life events separate effect (ORe), mutual effect (OReg) of rs708272 gene and negative life events and their 95% confidence interval. Then the effect of the interaction of rs708272 gene and negative life event to attempted suicide based on the multiplication model and additive model were calculated separately. The results didn’t support negative life events and the CETP TaqlB (rs708272) interaction effect existing in attempted suicide.Conclusions(1) Low education level, farmers, negative life events and mental illness are the main environmental risk factors for the people aged 15 to 50 suicide attempts in Shandong Province, and the personality traits and emotions (self-esteem, positive coping, trait anxiety, and depression) are also the important influence factors of the attempted suicide;(2) Because of the economic conditions and the limitation of the accessibility of health services and different sense for searching professional mental health help in rural population, the awareness rate of mental illness in the rural population is still very low;(3) In allele frequency and genotype frequency distribution of rs708272, there are no significant differences between suicide attempters and controls. There are still no significant in the effect of rs708272 gene to attempted suicide after adjusting possible confounding factors in multivariate conditional Logistic regression. These results don’t support the association of gene rs708272 and attempted suicide. The interaction between negative life events and rs708272 is not supported in this study. |
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