Genetic Role of BDNF Val66Met and 5-HTTLPR Polymorphisms on Depressive Disorder

Objective

We investigated possible association between depressive disorders and BDNF Val66Met and 5-HTTLPR. Brain derived neurotrophic factor (BDNF) gene and serotonin transporter (SLC6A4) gene are promising candidate genes for depressive disorders. It has been suggested that BDNF promotes the survival and differentiation of serotonergic neurons and that serotonergic transmission exerts powerful control over BDNF gene expression.

Methods

Final analyses were performed on 186 patients with depressive disorders and 1032 controls. Val66Met polymorphism of BDNF gene and 5-HTTLPR polymorphism of serotonin transporter gene were genotyped and allele and genotypic associations on the diagnosis of depression and age at onset of depression were analyzed.

Results

The 5-HTTLPR was positively associated with depressive affected status in the total sample and in females (p=0.038 for allelewise, p=0.015 for genotype-wise associations), but, not in males. The BDNF Val66Met showed no association with depression. BDNF Val66Met and 5-HTTLPR alone were not associated with age at onset of depression. Additional analysis on the interaction between BDNF Val66Met and 5-HTTLPR found a significant association with age at onset of depression in the entire patient group. This association was also found in the female but not in the male patient group. None of the positive results survived Bonferroni correction for multiple testing.

Conclusion

This result suggested that BDNF Val66Met and 5-HTTLPR may contribute to depressive disorders in a complex way and that the genetic effect could differ by gender. Further studies with large number of patients will be necessary.     

No association of serotonin transporter polymorphism (5-HTTVNTR and 5-HTTLPR) with characteristics and treatment response to atypical antipsychotic agents in schizophrenic patients

Background

Serotonin transporter is a candidate gene for the pathogenesis of some psychiatric disorders. The aim of this study was to examine the role of the serotonin transporter gene polymorphism in the clinical aspects of schizophrenia including symptomatology and therapeutic response.

Methods

This study comprised 141 unrelated patients who strictly met the DSM-IV criteria for schizophrenia and 115 control subjects. All subjects were of Korean ethnicity. Serotonin transporter intron 2 VNTR polymorphism (5-HTTVNTR) and serotonin transporter linked polymorphic region polymorphism (5-HTTLPR) were analyzed in schizophrenia patients and control subjects. The Positive and Negative Symptom Scale (PANSS) was used at baseline and 6 weeks after atypical antipsychotic treatment to evaluate the clinical symptoms. Body mass index (BMI), the Barnes Akathisia Rating Scale (BARS), the Simpson–Angus Rating Scale (EPS) for adverse effect and the Calgary Depression rating Scale for Schizophrenia (CDSS) were measured.

Results

There were no significant differences in the frequency of genotypes between schizophrenia patients and control subjects. There were no significant differences in PANSS scores before treatment according to the serotonin transporter genotypes. Treatment response after atypical antipsychotics did not differ among the genotypes. No difference was shown among the genotypes for the scales in adverse effects and depression (BMI, BARS, EPS, CDSS).

Conclusions

Our results suggest that the serotonin transporter polymorphism does not seem to be a susceptibility factor for schizophrenia. Similarly, the serotonin transporter polymorphism might not affect the therapeutic response and adverse effect to atypical antipsychotics in Korean patients with schizophrenia. Further studies with a larger number of subjects are required to better understand the role of the serotonin transporter polymorphism in schizophrenia.     

Epigenetic changes of serotonin transporter in the patients with alcohol dependence: methylation of an serotonin transporter promoter CpG island

Objective

Psychiatric disorders such as depression, anxiety and alcohol dependence are associated with serotonin metabolism. We assessed the methylation level of the serotonin transporter (5-HTT) promoter region in control and alcohol dependent patients.

Methods

Twenty seven male patients who met the Diagnostic and Statistical Manual of Mental Disorder IV (DSM-IV) criteria for alcohol dependence were compared with fifteen controls. Polymerase chain reaction (PCR) assays of bisulfate-modified DNA were designed to amplify a part of the CpG island in the 5HTT gene. Pyrosequencing was performed and the methylation level at seven CpG island sites was measured.

Results

We found no differences in the methylation patterns of the serotonin transporter linked promoter region (5-HTTLPR) between alcohol-dependent and control subjects.

Conclusion

Our negative finding may be because 5-HTT epigenetic variation may not affect the expression for 5-HTT or there may be other methylation site critical for its expression. To find out more conclusive result, repeating the study in more methylation sites with a larger number of samples in a well-controlled setting is needed.     

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 χ² 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.     

No Association between Serotonin Receptor 2C-759C/T Polymorphism and Weight Change or Treatment Response to Mirtazapine in Korean Depressive Patients

Objective

Activation of one or more serotonin (5-HT) receptors may play a role in mediating the antidepressant effects of serotonergic antidepressants. The serotonin 2C (5HT 2C) receptor is known to be associated with antidepressant action and weight gain. We sought to determine whether the 5-HTR 2C receptor -759C/T polymorphism was associated with weight gain and treatment response to mirtazapine in major depressive disorder (MDD) patients.

Methods

The 5-HT 2C receptor -759C/T polymorphism was analyzed in 323 MDD patients. All patients were evaluated using the 21-item Hamilton Depression Rating Scale at the beginning of the study and at 1, 2, 4, and 8 weeks of mirtazapine treatment.

Results

There was no significant difference in the 5-HT 2C receptor -759C/T genotype distribution between responder and non-responder groups. The 5-HT 2C receptor -759C/T polymorphism was not associated with weight change over time after mirtazapine administration.

Conclusion

The 5-HT 2C receptor -759C/T polymorphism does not appear to be a predictor of treatment response to mirtazapine. This polymorphism was not associated with weight change after 8 weeks of mirtazapine treatment. Further investigation on other polymorphisms of the 5-HT 2C gene is required to determine whether the 5-HT 2C gene influences treatment response and weight change after mirtazapine administration in patients with major depressive disorder.     

Association Study between 5-HT1A Receptor Gene C(-1019)G Polymorphism and Panic Disorder in a Korean Population

Objective

Serotonergic dysfunction is quite evident in panic disorder. We investigated whether the C(-1019)G polymorphism of 5-HT1A receptor gene may play a role in the pathogenesis of panic disorder in a Korean population.

Methods

The 5-HT1A receptor genotype for the single nucleotide polymorphism (SNP) C(-1019)G was analyzed in 94 patients and 111 healthy controls. The severity of the patients'' symptoms was examined using the Spielberger State-Trait Anxiety Inventory (STAI), Panic Disorder Severity Scale (PDSS), Anxiety sensitivity index (ASI), Acute Panic Inventory (API) and Hamilton''s Rating Scale for Anxiety (HAM-A).

Results

The distribution of the genotypes of the C/G polymorphism did not differ significantly from those predicted by Hardy-Weinberg equilibrium in patients as well as the controls. No association between the C(-1019)G polymorphism and panic disorder was detected in either the allele frequency or genotype distribution. There was no significant association with genotype distribution in the panic disorder with agoraphobia. However, there was a significant difference of symptom severity between C/C, C/G, and G/G genotype or between C and G allele in panic disorder patients without agoraphobia. PDSS scores were significantly higher in subjects with the G/G genotype or with G allele in patients without agoraphobia, not in total patients or patients with agoraphobia.

Conclusion

Although there were no significant differences in the genotype and allele distributions, we found a significant association between panic symptom severity and the serotonin 1A receptor gene. This result suggests that the serotonin 1A receptor and serotonin may play a role in the pathogenesis of panic disorder.     

Variations in 5-HTTLPR: Relation to familiar risk of affective disorder,life events,neuroticism and cortisol

Background

Variations in the serotonin transporter gene (5-HTTLPR) and stressful life events are associated with affective disorders.

Aim

To investigate whether the distribution of the alleles of the 5-HTTLPR is associated with a genetic predisposition to affective disorder and whether these variations interact with life events in relation to depressive symptoms, neuroticism and salivary cortisol.

Method

In a high-risk population study, healthy monozygotic and dizygotic twins with (high-risk twins) and without (low-risk twins) a co-twin history of affective disorder were identified through nationwide registers.

Results

When comparing the 81 individuals homozygote for the long allele with the 125 individuals hetero- and homozygote for the short allele no associations between the allele distribution and a genetic predisposition were found. The presence of the short allele of the 5-HTTLPR and the experience of SLE was associated with a higher neuroticism score, but not with depressive symptoms nor awakening or evening salivary cortisol.

Conclusion

A combination of variants in 5-HTTLPR and environmental stress seems to increase neuroticism in healthy individuals.     

CYP2D6 P34S Polymorphism and Outcomes of Escitalopram Treatment in Koreans with Major Depression

Objective

Cytochrome P450 (CYP) enzymatic activity, which is influenced by CYP genetic polymorphism, is known to affect the inter-individual variation in the efficacy and tolerability of antidepressants in major depressive disorder (MDD). Escitalopram is metabolized by CYP2D6, and recent studies have reported a correlation between clinical outcomes and CYP2D6 genetic polymorphism. The purpose of this study was to determine the relationship between the CYP2D6 P34S polymorphism (C188T, rs1065852) and the efficacy of escitalopram treatment in Korean patients with MDD.

Methods

A total of 94 patients diagnosed with MDD were recruited for the study and their symptoms were evaluated using the 21-item Hamilton Depression Rating scale (HAMD-21). The association between the CYP2D6 P34S polymorphism and the clinical outcomes (remission and response) was investigated after 1, 2, 4, 8, and 12 weeks of escitalopram treatment using multiple logistic regression analysis and χ² test.

Results

The proportion of P allele carriers (PP, PS) in remission status was greater than that of S allele homozygotes (SS) after 8 and 12 weeks of escitalopram treatment. Similarly, P allele carriers exhibited a greater treatment response after 8 and 12 weeks of escitalopram treatment than S allele homozygotes.

Conclusion

Our results suggest that the P allele of the CYP2D6 P34S polymorphism is a favorable factor in escitalopram treatment for MDD, and that the CYP2D6 P34S polymorphism may be a good genetic marker for predicting escitalopram treatment outcomes.     

Standardization of the Korean Version of the Geriatric Depression Scale: Reliability, Validity, and Factor Structure

Objective

We developed a Revised Korean version of the Geriatric Depression Scale (GDS-KR) and examined its reliability, validity, and factor structures. We also estimated its optimal cutoff scores for major depressive disorder (MDD) and minor depressive disorder (MnDD) stratified by age and education.

Methods

The GDS-KR was administered to 888 subjects (61 MDD patients, 45 MnDD patients, and 782 normal elders). Its internal consistency and test-retest reliability were examined. Its concurrent validity was evaluated using Pearson correlation coefficients with the Korean version of the Center for Epidemiologic Studies Depression Scale (CES-D-K) and Hamilton Depression Rating Scale (HAM-D). The mean GDS-KR scores of the MDD patients, MnDD patients and normal elders were compared to evaluate its discriminant validity. To evaluate its construct validity, a principal component analysis with varimax rotation was performed. Receiver operator characteristic (ROC) curve analyses were performed to evaluate its diagnostic ability.

Results

Chronbach''s coefficient alpha for the GDS-KR was 0.90 and the test-retest reliability was 0.91 (p<0.01). The Pearson correlation coefficients of the GDS-KR scores with the CES-D-K and HAM-D scores were 0.63 (p<0.01) and 0.56 (p<0.01), respectively. The GDS-KR consisted of 5 factors. The optimal cut-off scores of the GDS-KR were 16/17 for MDD only and 15/16 for both MDD and MnDD. The optimal cutoff scores of the GDS-KR were higher in the less educated and younger subjects. The diagnostic accuracy for MDD of the GDS-KR was higher than that of the CES-D.

Conclusion

The GDS-KR was found to be a reliable and valid questionnaire for screening MDD and MnDD in late life.     

Comorbid Depressive Disorders in ADHD: The Role of ADHD Severity,Subtypes and Familial Psychiatric Disorders

Objective

To evaluate the presence of Major Depressive Disorder (MDD) and Dysthymic Disorder (DD) in a sample of Italian children with Attention Deficit Hyperactivity Disorder (ADHD) and to explore specific features of comorbid depressive disorders in ADHD.

Methods

Three hundred and sixty-six consecutive, drug-naïve Caucasian Italian outpatients with ADHD were recruited and comorbid disorders were evaluated using DSM-IV-TR criteria. To evaluate ADHD severity, parents of all children filled out the ADHD Rating Scale. Thirty-seven children with comorbid MDD or DD were compared with 118 children with comorbid conduct disorder and 122 without comorbidity for age, sex, IQ level, family psychiatric history, and ADHD subtypes and severity.

Results

42 of the ADHD children displayed comorbid depressive disorders: 16 exhibited MDD, 21 DD, and 5 both MDD and DD. The frequency of hyperactive-impulsive subtypes was significantly lower in ADHD children with depressive disorders, than in those without any comorbidity. ADHD children with depressive disorders showed a higher number of familial psychiatric disorders and higher score in the Inattentive scale of the ADHD Rating Scale, than children without any comorbidity. No differences were found for age, sex and IQ level between the three groups.

Conclusion

Consistent with previous studies in other countries, depressive disorders affect a significant proportion of ADHD children in Italy. Patient assessment and subsequent treatment should take into consideration the possible presence of this comorbidity, which could specifically increase the severity of ADHD attention problems.     

原发性失眠的5-羟色胺转运体基因遗传多态性研究

目的　探讨原发性失眠与羟色胺转运体( 5 -HTT)基因遗传多态性的关系。方法　对85例病例组和54名对照组提取外周血基因组DNA ,进行PCR扩增,分析相应的基因型,并比较两组不同基因型患者的焦虑和抑郁评分有无差异。结果　两组的5 -HTTLPR和5 -HTTVNTR的基因型、等位基因频率及不同基因型频率的两两比较均无显著性差异(P >0 .0 5) ;病例组5- HTTLPR的S/S(S组)和S/L +L/L(L组)两组之间及5- HTTVNTR的1 0 / 1 0 + 1 0 / 1 2 ( 1 0组)和1 2 / 1 2 ( 1 2组)两组之间的焦虑、抑郁量表评分比较均无显著性差异(P >0 . 0 5)。结论　5- HTTLPR和5 -HTTVNTR两种基因遗传多态性与原发性失眠的关系尚需进一步探讨。     

Genotype over-diagnosis in amygdala responsiveness: affective processing in social anxiety disorder

Background

Although the amygdala is thought to be a crucial brain region for negative affect, neuroimaging studies do not always show enhanced amygdala response to aversive stimuli in patients with anxiety disorders. Serotonin (5-HT)–related genotypes may contribute to interindividual variability in amygdala responsiveness. The short (s) allele of the 5-HT transporter linked polymorphic region (5-HTTLPR) and the T variant of the G-703T polymorphism in the tryptophan hydroxylase-2 (TPH2) gene have previously been associated with amygdala hyperresponsivity to negative faces in healthy controls. We investigated the influence of these polymorphisms on amygdala responsiveness to angry faces in patients with social anxiety disorder (SAD) compared with healthy controls.

Methods

We used positron emission tomography with oxygen 15-labelled water to assess regional cerebral blood flow in 34 patients with SAD and 18 controls who viewed photographs of angry and neutral faces presented in counterbalanced order. We genotyped all participants with respect to the 5-HTTLPR and TPH2 polymorphisms.

Results

Patients with SAD and controls had increased left amygdala activation in response to angry compared with neutral faces. Genotype but not diagnosis explained a significant portion of the variance in amygdala responsiveness, the response being more pronounced in carriers of s and/or T alleles.

Limitations

Our analyses were limited owing to the small sample and the fact that we were unable to match participants on genotype before enrolment. In addition, other imaging techniques not used in our study may have revealed additional effects of emotional stimuli.

Conclusion

Amygdala responsiveness to angry faces was more strongly related to serotonergic polymorphisms than to diagnosis of SAD. Emotion activation studies comparing amygdala excitability in patient and control groups could benefit from taking variation in 5-HT–related genes into account.     

Distinctive Clinical Correlates of Psychotic Major Depression: The CRESCEND Study

Objective

The purpose of this investigation was to identify distinctive clinical correlates of psychotic major depression (PMD) as compared with non-psychotic major depression (NPMD) in a large cohort of Korean patients with major depressive disorder (MDD).

Methods

We recruited 966 MDD patients of age over 18 years from the Clinical Research Center for Depression of South Korea (CRESCEND) study. Diagnoses of PMD (n=24) and NPMD (n=942) were made with the DSM-IV definitions and confirmed with SCID. Psychometric scales were used to assess overall psychiatric symptoms (BPRS), depression (HAMD), anxiety (HAMA), global severity (CGI-S), suicidal ideation (SSI-Beck), functioning (SOFAS), and quality of life (WHOQOL-BREF). Using independent t-tests and χ² tests, we compared clinical characteristics of patients with PMD and NPMD. A binary logistic regression model was constructed to identify factors independently associated with increased likelihood of PMD.

Results

PMD subjects were characterized by a higher rate of inpatient enrollment, and higher scores on many items on BPRS (somatic concern, anxiety, emotional withdrawal, guilt feelings, tension, depression, suspiciousness, hallucination, motor retardation, blunted affect and excitement) global severity (CGI-s), and suicidal ideation (SSI-Beck). The explanatory factor model revealed that high levels of tension, excitement, and suicidal ideation were associated with increased likelihood of PMD.

Conclusion

Our findings partly support the view that PMD has its own distinctive clinical manifestation and course, and may be considered a diagnostic entity separate from NPMD.     

Risk Factors for Suicidal Ideation among Patients with Complex Regional Pain Syndrome

Objective

Chronic pain frequently coexists with psychiatric symptoms in patients diagnosed with complex regional pain syndrome (CRPS). Previous studies have shown a relationship between CRPS and the risk of suicide. The purpose of this study was to assess risk factors for suicidal ideation in patients with CRPS.

Methods

Based on criteria established by the International Association for the Study of Pain, 39 patients diagnosed with CRPS Type 1 or Type 2 were enrolled in this study. Suicidal ideation was assessed using item 3 of the Hamilton Depression Rating Scale (HAMD), and symptoms of pain were evaluated using the short form of the McGill Pain Questionnaire (SF-MPQ). Psychiatric symptoms were assessed in using the Structured Clinical Interview for DSM-IV Disorders (SCID-I, SCID-II), the HAMD, the Hamilton Anxiety Rating Scale (HAMA), the Global Assessment of Functioning Scale (GAF), and the Pittsburgh Sleep Quality Index (PSQI).

Results

Twenty-nine patients (74.4%) were at high risk and 10 (25.6%) were at low risk for suicidal ideation. Risk factors significantly associated with suicidal ideation included depression (p=0.002), severity of pain (p=0.024), and low scores on the GAF (p=0.027). No significant correlations were found between suicidal ideation and anxiety or quality of sleep.

Conclusion

Significant risk factors for suicidal ideation in patients with CRPS include severity of pain, depressive symptoms, and decreased functioning. These results suggest that psychiatric evaluation and intervention should be included in the treatment of CRPS.     

Decreased Total Antioxidant Activity in Major Depressive Disorder Patients Non-Responsive to Antidepressant Treatment

Objective

This study aimed to evaluate the total antioxidant activity (TAA) in patients with major depressive disorder (MDD) and the effect of antidepressants on TAA using a novel potentiometric method.

Methods

Twenty-eight patients with MDD and thirty-one healthy controls were enrolled in this study. The control group comprised 31 healthy individuals matched for gender, drinking and smoking status. We assessed symptoms of depression using the Hamilton Depression Rating Scale (HAMD) and the Beck Depression Inventory (BDI). We measured TAA using potentiometry. All measurements were made at baseline and four and eight weeks later.

Results

There was a significant negative correlation between BDI scores and TAA. TAA was significantly lower in the MDD group than in controls. When the MDD group was subdivided into those who showed clinical response to antidepressant therapy (response group) and those who did not (non-response group), only the non-response group showed lower TAA, while the response group showed no significant difference to controls at baseline. After eight weeks of antidepressant treatment, TAA in both the response and non-response groups was similar, and there was no significant difference among the three groups.

Conclusion

These results suggest that the response to antidepressant treatment in MDD patients might be predicted by measuring TAA.     

Neural Network Based Response Prediction of rTMS in Major Depressive Disorder Using QEEG Cordance

Objective

The combination of repetitive transcranial magnetic stimulation (rTMS), a non-pharmacological form of therapy for treating major depressive disorder (MDD), and electroencephalogram (EEG) is a valuable tool for investigating the functional connectivity in the brain. This study aims to explore whether pre-treating frontal quantitative EEG (QEEG) cordance is associated with response to rTMS treatment among MDD patients by using an artificial intelligence approach, artificial neural network (ANN).

Methods

The artificial neural network using pre-treatment cordance of frontal QEEG classification was carried out to identify responder or non-responder to rTMS treatment among 55 MDD subjects. The classification performance was evaluated using k-fold cross-validation.

Results

The ANN classification identified responders to rTMS treatment with a sensitivity of 93.33%, and its overall accuracy reached to 89.09%. Area under Receiver Operating Characteristic (ROC) curve (AUC) value for responder detection using 6, 8 and 10 fold cross validation were 0.917, 0.823 and 0.894 respectively.

Conclusion

Potential utility of ANN approach method can be used as a clinical tool in administering rTMS therapy to a targeted group of subjects suffering from MDD. This methodology is more potentially useful to the clinician as prediction is possible using EEG data collected before this treatment process is initiated. It is worth using feature selection algorithms to raise the sensitivity and accuracy values.     

No Effect of Serotoninergic Gene Variants on Response to Interpersonal Counseling and Antidepressants in Major Depression

Objective

Gene variants within the serotonin pathway have been associated with major depressive disorder (MDD) treatment outcomes, however a possible different modulation on pharmacological or psychological treatments has never been investigated.

Methods

One hundred sixty MDD patients were partially randomized to either inter-personal counseling (IPC) or antidepressants. The primary outcome was remission at week 8. Five serotonergic polymorphisms were investigated (COMT rs4680, HTR1A rs6295, HTR2A rs2224721, HTR2A rs7997012 and SLC6A4 rs421417).

Results

IPC (n=43) and antidepressant (n=117) treated patients did not show any difference in remission rates at week 8 (corrected for baseline severity, age and center). None of the studied gene variants impacted on response and remission rates at week 8 neither in the IPC nor in the antidepressant group. An analysis of the whole sample showed a trend of association between rs7997012 AA genotype and a better treatment outcome.

Conclusion

Our study confirms that IPC is an effective psychological intervention comparable to antidepressants in mild-moderate MDD. Polymorphisms related to the serotonin system did not exert a major effect on clinical outcomes in none of the treatment groups.     

中国汉族人群5-羟色胺转运体基因多态性与非病灶性颞叶癫痫的关联性

目的　初步探讨颞叶癫痫(temporal lobe epilepsy,TLE)的遗传易感因素。方法　采用聚合酶链反应技术,检测263例TLE患者和296名健康对照者的5-羟色胺转运体(5-hydroxytryptamine transporter,5-HTT) 基因启动子的基因连锁多态区(gene-linked polymorphic region,LPR) 和第2内含子的可变数目串联重复区(variable number tandem repeat,VNTR) 多态性,分别对所得基因型和等位基因的频率进行相关统计学分析。结果　TLE患者5-HTTLPR多态性的基因型和等位基因频率与正常对照组之间的差异无统计学意义(P>0.05)。TLE患者的5-HTTVNTR的基因型12/12频率高于正常对照组(P<0.01),其等位基因12的频率高于正常对照组(P< 0.01)。携12等位基因者患TLE的相对危险度(OR)是1.435,95%可信区间(CI)为1.096～1.880(P<0.05)。 结论　5-HTTLPR可能不是TLE患者的遗传位点,第2内含子VNTR的等位基因12可能与TLE有一定的关联。     

Impaired interhemispheric connectivity in medication-naive patients with major depressive disorder

Background

Abnormalities in the anterior interhemispheric connections provided by the corpus callosum (CC) have long been implicated in major depressive disorder (MDD). The purpose of this study was to investigate interhemispheric connectivity in medication-naive patients with MDD by measuring fractional anisotropy in the CC with diffusion tensor imaging (DTI) techniques.

Methods

We obtained DTI scans from medication-naive patients with MDD and from matched healthy controls. Fractional anisotropy values were compared using semiautomatic region of interest methods to localize the regional CC differences between these 2 groups.

Results

We enrolled 27 patients and 27 controls in our study. Fractional anisotropy values were significantly lower in the anterior genu of the CC in the MDD group than in the control group (p = 0.009, corrected); results were not significantly different in any other CC subregions.

Limitations

As patients with MDD were already experiencing acute episodes, future studies of individuals at risk for MDD are warranted to elucidate the interhemispheric connectivity abnormalities associated with the predisposition to MDD.

Conclusion

The findings demonstrate abnormalities in the structural integrity of the anterior genu of the CC in medication-naive individuals with MDD, which may contribute to impairment of interhemispheric connectivity in patients with this disorder.     

Behavioural therapy based on distraction alleviates impaired fear extinction in male serotonin transporter knockout rats

Background

The “biological susceptibility” model posits that some individuals, by genetic predisposition, are highly sensitive to environmental stimuli. Exposure to adverse stimuli leads to negative outcomes, and better outcomes follow favourable stimuli. Recent studies indicate that individuals carrying the low-activity (short; s) variant of the serotonin transporter (5-HTT)-linked polymorphic region (5-HTTLPR) show an enhanced vulnerability to posttraumatic stress disorder (PTSD). Simultaneously, they respond poorly to exposure therapy, the first-line treatment to enhance fear extinction in individuals with PTSD. Given that s-allele carriers also show improved adaptive responding when exposed to positive stimuli, we hypothesized that this trait could be used to offset impaired fear extinction.

Methods

We explored this hypothesis preclinically using wild-type and 5-HTT knockout (5-HTT^−/−) male rats (n = 36) that share behavioural similarities with 5-HTTLPR s-allele carriers. Subsequent to cued fear conditioning, animals were tested for short- (1 and 2 days postconditioning) and long-term (6 days postconditioning) fear extinction in the absence or presence of a secondary “distracting” stimulus predicting the delivery of sucrose pellets.

Results

Introducing a secondary stimulus predicting sucrose pellets that distracts attention away from the fear-predicting stimulus led to a long-lasting improvement of impaired fear extinction in 5-HTT^−/− male rats.

Limitations

The context-dependency of the efficacy of the “distraction therapy” was not tested. In addition, it remains to be clarified whether the positive valence of the distracting stimulus is critical for the distraction of attention or whether a neutral and/or novel stimulus can induce similar effects. Finally, although of lesser importance from a therapeutic perspective, underlying mechanisms remain to be elucidated.

Conclusion

These data indicate that positive environmental stimuli can be used to offset heightened responses to negative stimuli, particularly in individuals characterized by inherited 5-HTT downregulation and high sensitivity to environmental stimuli.