Suicide attempt, smoking, comorbid depression, and platelet serotonin in alcohol dependence

The risk of suicide in patients with alcoholism increases if alcoholism is related to comorbid depression. Both alcoholism and suicidal behavior are associated with reduced serotonin (5-hydroxytryptamine [5-HT]) function. Because suicide is enormous public health problem worldwide, to prevent suicide attempts, it is important to find peripheral marker of suicidal behavior. The aim of this study was to assess whether platelet 5-HT concentration is altered in alcoholic patients with or without suicide attempt. Platelet 5-HT concentration was evaluated in 397 male and 108 female ethnically homogenous medication-free patients with alcoholism, subdivided according to smoking status, comorbid depression, and a history of suicide attempt and in 450 male and 139 female healthy control (nonsuicidal) subjects. Suicide attempt was assessed by two measures: according to the score 4 on the item 3 from the Hamilton Rating Scale for Depression and according to the Structured Clinical Interview regarding suicidal attempt during lifetime. Both male and female patients with alcoholism who were nonsmokers had significantly lower platelet 5-HT concentration than the corresponding healthy subjects. Multifactor analyses of variance revealed the significant effects of alcoholism and smoking, but the lack of significant effects of suicide attempt, sex, or comorbid depression, and no interactions between variables, on platelet 5-HT concentration. Platelet 5-HT concentration did not differ significantly between suicidal patients compared with nonsuicidal patients with alcoholism. Because the results from the present study showed similar platelet 5-HT values between patients with or without a history of suicide attempt, our data did not support the hypothesis that platelet 5-HT concentration might be used as a peripheral marker of the pronounced suicidal behavior in alcoholism.

Brain derived neurotrophic factor Val66Met polymorphism and psychotic symptoms in Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative disorder with a high prevalence. Since behavioral disturbances, such as psychotic symptoms, represent a key feature of AD, genes related to dopamine, serotonin and brain derived neurotrophic factor (BDNF), are considered as candidate genes for AD. BDNF is a neurotrophin that regulates neurodevelopment, neuroplasticity, and neuronal functions. BDNF is involved in the etiopathogenesis of psychiatric and neurodegenerative disorders. A single base pair polymorphism (BDNF Val66Met) was reported to be associated with AD and/or schizophrenia, as well as other psychoses, although some studies failed to replicate these findings. The aim of the study was to evaluate the association between BDNF Val66Met variants and AD, as well as onset of AD or presence of psychotic symptoms in AD.

METHOD

BDNF Val66Met was analyzed in 211 patients with AD and in 402 aged healthy control subjects. All subjects were ethnically homogenous Caucasians from Croatia, and were subdivided according to the gender, onset of AD, and presence of psychotic symptoms. A χ(2) test, with Bonferroni correction and standardized residuals were used to evaluate the data.

RESULTS

Distribution of the BDNF Val66Met genotypes differed significantly between male and female AD patients with or without psychotic symptoms. This difference was due to the significant contribution of the Met/Val genotype and the combined Met/Met and Met/Val genotypes between psychotic and non-psychotic symptoms in male, but not in female patients with AD. The frequency of the gene variants of the BDNF Val66Met did not differ significantly among male and female patients with AD and control subjects, or between male and female patients with early or late onset AD. There were significant sex related differences in age, duration of illness and scores of dementia between patients with AD.

CONCLUSION

Our male patients were younger, had shorter duration of illness, and had less severe dementia and higher cognitive performance than female AD patients. The gene variants of the BDNF Val66Met polymorphism were significantly associated with the presence of psychotic symptoms in male, but not in female patients with AD. The results had adequate statistical power to suggest that BDNF Val66Met was not related to susceptibility to AD or the onset of AD, but that presence of one or two Met alleles of BDNF Val66Met polymorphism might present a risk factor for psychosis in AD.

Ethnic differences in the serotonin transporter polymorphism (5-HTTLPR) in several European populations

The serotonin transporter (5-HTT) is a protein that has a major role in divergent psychiatric disorders, personality traits and behaviors, by regulating serotonergic synaptic function. Transcriptional activity of the 5-HTT gene (5-HTT or SLC6A4) is modulated by a polymorphic repetitive element (5-HTT gene-linked polymorphic region, 5-HTTLPR), which consists of a 44-base pairs insertion-deletion in the promoter region, creating a short (S) allele and a long (L) allele. Ethnic differences in the allele frequencies of the 5-HTTLPR exist between Caucasian and Asian populations. This study investigated ethnic differences in 5-HTTLPR in 1804 healthy Caucasian subjects from several European populations living in Croatia and the Russian Federation. The genotype and allele frequency of the 5-HTTLPR differed significantly (P<0.001) between male and female Croats, Russians, Tatars and Bashkirs, due to the lower frequency of the S allele (38% and 37%) and S/S genotype (14% and 15%) in Croat men and women compared to other studied groups. When male and female data were collapsed, Russians had marginally different allele and genotype distribution compared to Bashkirs and Tatars. Bashkirs and Tatars had similar allele and genotype frequency. The higher frequency of the S/S genotype was found in Tatars and Bashkirs compared to Croats and Russians. Gender related differences occurred only in the allele distribution within Bashkir population. These ethnic differences might be responsible for the inconsistent findings in the studies of the association between various psychiatric disorders, personality traits, behaviors and 5-HTTLPR across different ethnicities, and should be controlled to enable the generalization of results across various population groups.