Analysis of T102C 5HT2A polymorphism in Brazilian psychiatric inpatients: relationship with suicidal behavior

Association study of gene polymorphisms and depression with abnormal humor in traditional Uighur medicine

Background

According to the humor theory of Traditional Uighur Medicine (TUM), a same disease is classified into different abnormal humor types and corresponding methods are applied to treat the diseases according to the type of abnormal humor characteristics. To date the biological foundation of classification of diseases by humor theory has been little studied and the mechanism of action is still unclear. In the present study, we aimed to investigate the association between some related gene polymorphisms and depression with abnormal humor in TUM.

Methods

201 cases of depression patients in a Uighur population were divided into two groups as: 107 cases of depression patients with abnormal black bile (ABB), 94 cases of depression patients with none abnormal black bile (nABB), and 50 healthy people were served as control group. Venous blood was used to isolate DNA samples, and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used for genotyping of single nucleotide polymorphisms (SNPs). Polymorphisms in the serotonin 2A (5-HT_2A) receptor gene, brain derived neurotrophic factor (BDNF), serotonin 1A (5-HT_1A) receptor gene were investigated in each groups, respectively.

Results

The 5-HT_2A A-1438G, 5-HT_2A T102C, BDNF Val66Met, and 5-HT_1A C-1019G gene polymorphisms showed significant association with ABB. However, no difference between nABB and controls was found for those genotype distribution and allele frequency. Moreover, the T102C and A1438G SNPs in the 5-HT_2A receptor gene polymorphisms were in linkage disequilibrium. In addition, the OR associated with the combination of Val66Met-Val/Val genotype plus the presence of -1019C allele was 8.393 for ABB compared with controls (OR 8.393; 95% CI 1.807 ~ 38.991; P= 0.003). Moreover, the OR associated with the presence of -Met plus -1019C alleles was 12.194 for ABB compared with controls (OR 12.194; 95% CI 1.433 ~ 103.776; P= 0.005). The OR associated with the presence of -1438C/C plus Val/Val genotypes was 7.738 for ABB compared with controls (OR 7.738; 95% CI 1.566 ~ 38.241; P= 0.005).

Conclusion

It was concluded that there were significant relationship between the gene polymorphisms and classification of depression with abnormal humor in TUM. The 5-HT_2A A-1438G, 5-HT_2A T102C, BDNF Val66Met, and 5-HT_1A C-1019G gene polymorphisms might predict the incidence of depression with ABB.

Association of the 5HTR2A gene with suicidal behavior: case-control study and updated meta-analysis

BACKGROUND

The polymorphism rs6313 (T102C) has been associated with suicidal behavior in case-control and meta-analysis studies, but results and conclusions remain controversial. The aim of the present study was to examine the association between T102C with suicidal behavior in a case-control study and, to assess the combined evidence - this case-control study and available data from other related studies - we carried out a meta-analysis.

METHODS

We conducted a case-control study that included 161 patients with suicide attempts and 244 controls; we then performed a meta-analysis. The following models were evaluated in the meta-analysis: A) C allele vs T allele; B) T allele vs C allele; C) Caucasian population, D) Asian population, and E) suicide attempters with schizophrenia.

RESULTS

We found an association between attempted suicide and control participants for genotype (χ2=6.28, p=0.04, df=2) and allele (χ2=6.17, p=0.01, df=1, OR 1.48 95% IC: 1.08-2.03) frequencies in the case-control study. The meta-analysis, comprising 23 association studies (including the present one), showed that the rs6313 polymorphism is not associated with suicidal behavior for the following comparisons:T allele vs C allele (OR: 1.03; 95% CI 0.93-1.13; p(Z)=0.44); C allele vs T allele: (OR:0.99; 95% CI: 0.90-1.08; p(Z)=0.22); Caucasians (OR:1.09; 95% CI: 0.96-1.23), and Asians (OR:0.96; 95% CI: 0.84-1.09).

CONCLUSION

Our results showed association between the rs6313 (T102C) polymorphism and suicidal behavior in the case-control study. However, the meta-analysis showed no evidence of association. Therefore, more studies are necessary to determine conclusively an association between T102C and suicidal behavior.

A review of psychiatric genetics research in the Brazilian population

OBJECTIVE AND METHOD: A large increase in the number of Brazilian studies on psychiatric genetics has been observed in the 1970's since the first publications conducted by a group of researchers in Brazil. Here we reviewed the literature and evaluated the advantages and difficulties of psychiatric genetic studies in the Brazilian population. CONCLUSION: The Brazilian population is one of the most heterogeneous populations in the world, formed mainly by the admixture between European, African and Native American populations. Although the admixture process is not a particularity of the Brazilian population, much of the history and social development in Brazil underlies the ethnic melting pot we observe nowadays. Such ethnical heterogeneity of the Brazilian population obviously brings some problems when performing genetic studies. However, the Brazilian population offers a number of particular characteristics that are of major interest when genetic studies are carried out, such as the presence of isolated populations. Thus, differences in the genetic profile and in the exposure to environmental risks may result in different interactions and pathways to psychopathology.

TPH2 -703G/T SNP may have important effect on susceptibility to suicidal behavior in major depression

BACKGROUND

Serotonergic system-related genes can be good candidate genes for both major depressive disorder (MDD) and suicidal behavior. In this study, we aimed to investigate the association of serotonin 2A receptor gene -1438A/G SNP (HTR2A -1438A/G), tryptophan hydroxylase 2 gene -703G/T SNP (TPH2 -703G/T) and serotonin 1A receptor C-1019G (HTR1A C-1019G) with suicidal behavior.

METHODS

One hundred and eighty one suicidal depressed patients and 143 non-suicidal depressed patients who met DSM-IV criteria for major depressive disorder were recruited from patients who were admitted to Korea University Ansan Hospital. One hundred seventy six normal controls were healthy volunteers who were recruited by local advertisement. Patients and normal controls were genotyped for HTR2A -1438A/G, TPH2 -703G/T and 5-HT1A C-1019G. The suicidal depressed patients were evaluated by the lethality of individual suicide attempts using Weisman and Worden's risk-rescue rating (RRR) and the Lethality Suicide Attempt Rating Scale-updated (LSARS-II). In order to assess the severity of depressive symptoms of patients, Hamilton's Depression Rating Scale (HDRS) was administered. Genotype and allele frequencies were compared between groups by chi(2) statistics. Association of genotype of the candidate genes with the lethality of suicidal behavior was examined with ANOVA by comparing the mean scores of LSARS and RRR according to the genotype.

RESULTS

There were statistically significant differences in the genotype distributions and allele frequencies of TPH2 -703G/T between the suicidal depressive group and the normal control group. The homozygous allele G (G/G genotype) frequency was significantly higher in suicidal depressed patients than in controls. However, no differences in either genotype distribution or in allele frequencies of HTR2A -1438A/G and HTR1A C-1019G were observed between the suicidal depressed patients, the non-suicidal depressed patients, and the normal controls. There were no differences in the lethality of suicidal behavior in suicidal depressed patients according to the genotypes of three polymorphisms.

CONCLUSION

Our results suggest that TPH2 -703G/T SNP may have an important effect on susceptibility to suicidal behavior. Furthermore, an increased frequency of G allele of TPH2 SNP may be associated with elevated suicidal behavior itself rather than with the diagnosis of major depression and may increase risk of suicidality, independent of diagnosis.

Stress, genes and the biology of suicidal behavior

Suicidal behavior is partly heritable. Studies seeking the responsible candidate genes have examined genes involved in neurotransmitter systems shown to have altered function in suicide and attempted suicide. These neurotransmitter systems include the serotonergic, noradrenergic, and dopaminergic systems and the hypothalamic-pituitary-adrenal axis. With some exceptions, most notably the serotonin transporter gene promoter polymorphism (HTTLPR), replication of candidate gene association studies findings has been difficult. This article reviews current knowledge of specific gene effects and gene-environment interactions that influence risk for suicidal behavior. Effects of childhood stress on development and how it influences adult responses to current stress are shown to be relevant for mood disorders, aggressive/impulsive traits, and suicidal behavior.

The genetics of suicide: a critical review of molecular studies

Genetic epidemiology research has shown that genes contribute to suicide risk. Unfortunately, the first 30 years of candidate-based association studies have provided little information about the specific genetic contributors. This article reviews genetic association studies of suicidal phenotypes published to date. Possible theoretical, methodological, and operational challenges accounting for the modest success of association studies in the field are also discussed. The authors conclude that future research may benefit from using a more systematic and comprehensive selection of candidate genes and variants, examining gene-environment and gene-gene interactions, and investigating higher-order moderators.

Decision-making impairment is related to serotonin transporter promoter polymorphism in a sample of patients with obsessive-compulsive disorder

OBJECTIVE

Decision-making impairment is an important feature of some psychiatric disorders, such as attention-deficit/hyperactivity disorder and substance-use disorders, and is associated with dysfunction of the fronto-subcortical circuit, mainly the orbitofrontal cortex (OFC). Several data reports support significant correlations between decision-making impairment and the serotonin system. Thus, this neurotransmission system may be a major step in some cognitive features, particularly in OCD because serotonin is associated with this disorder. Therefore, the serotonin transporter promoter polymorphism (5-HTTLPR) may be related to the modulation of these cognitive characteristics. In a sample of Caucasian OCD patients, we explored the link between decision-making and the 5-HTTLPR.

METHOD

We used the Iowa Gambling Task (IGT) to measure decision-making in 49 OCD patients, according to the DSM-IV criteria. All patients were submitted to Y-BOCS, BDI, BAI, the Raven Progressive Matrices, the Continuous Performance Task, and the Trail Making Test. We grouped S- and/or Lg-carriers in view of the fact that these act in a nearly dominant way.

RESULTS

On IGT, S- and/or Lg-carriers had significantly lower scores on the third, fourth, and fifth blocks. These findings were confirmed after adjusting for clinical and cognitive variables.

DISCUSSION

Inconclusive findings about the link between OCD and 5-HTTLPR may be better elucidated by studying OCD subgroups that could be more related in some genetic characteristics. Based on our study, low performance on IGT is associated with S- and/or Lg-carriers.

CONCLUSION

Our results corroborate the hypothesis that the pattern of neuropsychological functioning observed in previous studies may constitute a biological marker or heritable endophenotype of OCD.

Lack of association between three serotonin genes and suicidal behavior in Chinese psychiatric patients

BACKGROUND

Suicide is a significant health problem throughout the world. The serotoninergic system is believed to be involved in suicidal behavior and there is evidence of biological abnormalities of two serotonin receptors (HTR2A, HTR2C) and one serotonin transporter (5HTT) in suicide victims. Rs6313 (T102C) of HTR2A and rs6318 (Cys23Ser) of HTR2C have been investigated in suicide behavior in other studies.

METHODS

Here, we investigated rs6313 and rs6318 and other 10 randomly chosen SNPs, of those three genes in a study of 329 psychiatric patients who had never attempted suicide and 297 patients who had attempted suicide.

RESULTS

No associations were found for the 12 SNPS.

CONCLUSIONS

Our results do not support the involvement of HTR2A, 5HTT or HTR2C in suicidal behavior in Han Chinese subjects.

Genetics of suicide

The concept that genetic factors contribute to the complex trait of suicidal behaviour has stimulated much work aimed at identifying susceptibility genes. So far molecular genetic studies focused on the serotonergic pathway as the intent to die and the lethality of suicide acts were related to the serotonergic system. Two genes have so far emerged as being involved in the vulnerability for suicidality: first, the intronic polymorphisms (A218C or A779C) of the tryptophan hydroxylase 1 (TPH1) gene, which was suggested as a quantitative risk factor for suicidal behaviour; second, the insertion/deletion polymorphism of the serotonin transporter gene (5-HTTLPR), which does not seem to be involved in general suicidal behaviour, but in violent and repeated suicide attempts. The data have further shown that the MAOA gene, which is consistently associated with impulsive-aggressive personality traits, is not related to suicide but might induce violent methods in subjects with other suicide risk factors. Predominantly negative were the findings with any type of the serotonin receptors and inconsistent with catecholamine-synthesizing and -metabolizing enzymes or with the dopaminergic receptors. This paper reviews the status of current knowledge in this area, points to the weakness of the investigations and presents new approaches beyond the serotonergic system.

Association study of serotonin 2A receptor (5-HT2A) gene with schizophrenia and suicidal behavior using systematic meta-analysis

Serotonin 2A receptor (5-HT2A) gene was implicated to be associated with both schizophrenia and suicidal behavior due to its role of key neurotransmitter in many physiologic processes. Association studies were reported in different populations, however, a great number of subsequent studies have produced contrary results, possibly reflecting inadequate statistical power. With the cumulative data in recent years in both European and Asian populations, particularly in Asian populations, it was necessary to carry out a comprehensive analysis of previous findings. The meta-analysis, therefore, combined all English and Chinese studies using multiple research methods published up to July 2005 to give a new picture of the role of the 5-HT2A gene. Compared with significant results reported previously, the current large samples (73 studies in all) failed to find significant association of the T102C polymorphism with either schizophrenia or suicidal behavior. Evidence of significant association was only detected between A-1438G and suicidal behavior. The current study did not support the association of the 5-HT2A gene with either schizophrenia or suicidal behavior.

Association of serotonin 5-HT2A receptor binding and the T102C polymorphism in depressed and healthy Caucasian subjects

Serotonin 5-HT2A receptor (5-HT2A) binding is reported to be altered in individuals with suicidal behavior, mood disorders, and aggressive-impulsive traits. Genetic association with major depression, suicidal behavior, and aggressive-impulsive traits has not been established. This study examines the possible association of the 5-HT2A gene C102T polymorphism with the receptor binding kinetics, and clinical overt phenotypes. The study population included 63 healthy volunteers and 152 subjects with mood disorders, 56 of whom had a history of suicide attempts. All were Caucasian. Platelet 5-HT2A binding kinetics (Bmax and KD) were assayed and adjusted for seasonal variation. All subjects were genotyped for the T102C polymorphism. Clinical phenotype was determined by structured clinical interview. The TT genotype was associated with higher Bmax in all subjects (F=3.53, df=2,211; p=0.03), controlling for diagnosis. Bonferroni-adjusted post hoc testing showed higher binding in the TT compared with TC genotype in the control group (F=7.56, df=2,60, p=0.001), but not in the mood-disordered subjects. No difference was found in genotype and allele distribution between the mood-disordered subjects, with and without suicide attempt history, and controls. Bmax was not related to a diagnosis of mood disorders. The TT genotype appears associated with higher platelet 5-HT2A Bmax in the healthy population, but this genotypic effect appears absent in mood disorders and unrelated to psychopathology.

Familial suicide behaviour: association with probands suicide attempt characteristics and 5-HTTLPR polymorphism

OBJECTIVE

There is compelling evidence that a serotonergic dysfunction may play a major role in suicide behaviour and it has also been demonstrated that suicide is, at least partially, genetically determined. Thus, the serotonin-related genes are the major candidates. Previously a functional polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) was identified and the presence of the short allele (S) was found to be associated with a lower level of expression of the gene and lower levels of 5-HT uptake when compared with the long allele (L). The purpose of this study was to evaluate the association between family suicide behaviour history and probands' suicide attempt (SA) history, SA characteristics and 5-HTTLPR genotype.

METHOD

We genotyped 237 probands (major depressed or schizophrenic patients) and used a semistructured interview to determine probands' SA characteristics and first- and second-degree family suicidal behaviour.

RESULTS

An association between suicidal family history and proband's SA but not with SA characteristics and probands genotype was found.

CONCLUSION

Our results suggest that multiple biological and environmental factors underlie familial transmission of suicidal behaviour.