LRRK2 Gene Variants Associated With a Higher Risk for Alcohol Dependence in Multiethnic Populations

Background: Genetics influence the vulnerability to alcohol use disorders, and among the implicated genes, three previous studies have provided evidences for the involvement of LRRK2 in alcohol dependence (AD). LRRK2 expression is broadly dysregulated in postmortem brain from AD humans, as well as in the brain of mice with alcohol dependent-like behaviors and in a zebrafish model of alcohol preference. The aim of the present study was to evaluate the association of variants in the LRRK2 gene with AD in multiethnic populations from South and North America. Methods: Alcohol-screening questionnaires [such as CAGE and Alcohol Use Disorders Identification Test (AUDIT)] were used to determine individual risk of AD. Multivariate logistic regression analyses were done in three independent populations (898 individuals from Bambuí, Brazil; 3,015 individuals from Pelotas, Brazil; and 1,316 from the United States). Linkage disequilibrium and conditional analyses, as well as in silico functional analyses, were also conducted. Results: Four LRRK2 variants were significantly associated with AD in our discovery cohort (Bambuí): rs4768231, rs4767971, rs7307310, and rs1465527. Two of these variants (rs4768231 and rs4767971) were replicated in both Pelotas and US cohorts. The consistent association signal (at the LRRK2 locus) found in populations with different genetic backgrounds reinforces the relevance of our findings. Conclusion: Taken together, these results support the notion that genetic variants in the LRRK2 locus are risk factors for AD in humans.

Is the serotonin transporter polymorphism (5-HTTLPR) a potential marker for suicidal behavior in bipolar disorder patients?

BACKGROUND

Suicide prediction is a huge challenge for mental health workers. Structured interviews based on epidemiological and clinical factors don't show effectiveness for suicide prevention. Biological markers, such as 5-HTTLPR, could help for identification of potential suicide attempters.

METHODS

We evaluated 198 bipolar patients and 103 health controls, using a structured interview according to DSM-IV criteria. Genotyping, blind of clinical assessment for identification of S carriers and structured interviews were performed in order to describe clinical and epidemiological factors which could be associated with suicide behavior. Statistical analyses were calculated by the x(2) test and logistic regression model.

RESULTS

We found that 26.77% and 16.67% had a lifetime history of non violent suicide attempt and violent suicide attempt, respectively. The clinical factors associated with violent and non violent suicide attempt had several differences. Violent suicide attempters had an earlier illness onset and had a higher number of psychiatric comorbidities (borderline personality disorder, panic disorder and alcoholism). The frequency of S allele carriers was higher only in those patients who had made a violent suicide attempt in their lifetime (x(2)=16.969; p=0.0001). In a logistic regression model including these factors, S allele carrier (5-HTTLPR) was the only factor associated with violent suicide attempt.

LIMITATIONS

Sample size and retrospective assessment of suicide behavior history are the limitations of this study.

CONCLUSIONS

Our study showed that serotonin polymorphism (5-HTTLPR) is strongly associated with violent suicidal behavior in BD patients. If confirmed, our results could be an important step to create a genetic tool for long-term suicide prediction.