Association between Antipsychotics-Induced Restless Legs Syndrome and Tyrosine Hydroxylase Gene Polymorphism

Restless Legs Syndrome among patients receiving antipsychotic and antidepressant drugs

BACKGROUND

Patients with Restless Legs Syndrome (RLS) experience psychological distress and diminished quality of life. Antipsychotics and antidepressants are known to be linked to RLS.

AIMS

This study aims to investigate the presence of RLS in psychiatric patients who receive antipsychotic and antidepressant drugs and to determine potential risk factors for its occurrence.

METHODS

Two hundred patients who received antipsychotic and antidepressant drugs for more than 1 month were recruited from two tertiary psychiatric centers in Cairo, Egypt. One hundred apparently healthy volunteers were also included. All patients and controls were screened using the four-items questionnaire (Arabic version) for RLS. RLS severity was scored according to the validated Arabic version of International Restless Legs Syndrome Study Group rating scale (IRLS). Mimicking conditions were carefully investigated and excluded.

RESULTS

Forty-one percent of the patients who receive antipsychotic and antidepressant drugs were found to have RLS. Family history, past history and smoking are potential risk factors. Trazodone and haloperidol were less associated with RLS.

CONCLUSIONS

Although limited by its cross-sectional design, these findings suggest that patients who receive antipsychotic and antidepressant are susceptible to RLS. However, these results need to be replicated on a wider scale.

Genetic Variations Associated with Sleep Disorders in Patients with Schizophrenia: A Systematic Review

Background: Schizophrenic patients commonly suffer from sleep disorders which are associated with acute disease severity, worsening prognoses and a poorer quality of life. Research is attempting to disentangle the complex interplay between schizophrenia and sleep disturbances by focusing not only on demographic and clinical characteristics, but also on the identification of genetic factors. Methods: Here, we performed a systematic literature review on the topic of genetic variations in sleep-disordered schizophrenic patients in an attempt to identify high quality investigations reporting scientifically sound and clinically useful data. For this purpose, we conducted a thorough search of PubMed, ScienceDirect and GoogleScholar databases, according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) protocol. Results: Our search yielded 11 eligible studies. Certain genetic variations were reported to be associated with schizophrenia-related sleep disorders. Antipsychotic-induced restless legs syndrome was linked to polymorphisms located on CLOCK, BTBD9, GNB3, and TH genes, clozapine-induced somnolence was correlated with polymorphisms of HNMT gene, while insomnia was associated with variants of the MTNR1 gene. Conclusions: There are significant genetic associations between schizophrenia and co-morbid sleep disorders, implicating the circadian system, dopamine and histamine metabolism and signal transduction pathways.

Haplotype Association of the MAP2K5 Gene with Antipsychotics-Induced Symptoms of Restless Legs Syndrome among Patients with Schizophrenia

OBJECTIVE

Restless legs syndrome (RLS) is considered a genetic disease and, following a genome-wide association study conducted in 2007, the mitogen-activated protein kinase 5 (MAP2K5) gene has been regarded as the promising candidate gene for RLS. The present study investigated whether polymorphisms of MAP2K5 are associated with antipsychotics-induced RLS in schizophrenia.

METHODS

We assessed antipsychotics-induced RLS symptoms in 190 Korean schizophrenic patients using the diagnostic criteria of the International Restless Legs Syndrome Study Group. Five single-nucleotide polymorphisms (SNPs) of MAP2K5 were genotyped. We investigated genetic and haplotypic associations of these five SNPs with the risk of antipsychotics-induced RLS symptoms.

RESULTS

We divided the 190 subjects into 2 groups: 1) those with RLS symptoms (n=96) and 2) those without RLS symptoms (n=94). There were no significant intergroup differences in the distributions of the genotypes and alleles of the rs1026732, rs11635424, rs12593813, rs4489954, and rs3784709 SNPs. However, the haplotype analysis showed that the G-G-G-G-T (rs1026732-rs11635424-rs12593813-rs4489954-rs3784709) haplotype was associated with RLS symptoms (permutation p=0.033).

CONCLUSION

These data suggest that a haplotype of MAP2K5 polymorphisms confers increased susceptibility to antipsychotics-induced RLS symptoms in schizophrenic patients.

MEIS1, a Promising Candidate Gene, Is Not Associated with the Core Symptoms of Antipsychotic-Induced Restless Legs Syndrome in Korean Schizophrenia Patients

OBJECTIVE

Restless legs syndrome (RLS) is a distressing sleep disorder to which individuals appear to be genetically predisposed. In the present study, we assumed that antipsychotic-induced RLS symptoms were attributable to differences in individual genetic susceptibility, and investigated whether MEIS1, a promising candidate gene, was associated with antipsychotic-induced RLS symptoms in schizophrenia patients.

METHODS

All subjects were diagnosed with schizophrenia by board-certified psychiatrists using the Korean version of the Structured Clinical Interview for DSM-IV. We assessed antipsychotic-induced RLS symptoms in 190 Korean schizophrenic patients using the diagnostic criteria of the International Restless Legs Syndrome Study Group. Genotyping was performed for the rs2300478 and rs6710341 polymorphisms of the MEIS1 gene.

RESULTS

We divided subjects into RLS symptom (n=96) and non-symptom (n=94) groups. There was no significant between-group difference in the genotype or allele frequencies of the two polymorphisms investigated, nor in the frequency of the rs2300478-rs6710341 haplotype.

CONCLUSION

Our data do not suggest that the rs2300478 and rs6710341 polymorphisms of the MEIS1 gene are associated with the core symptoms of antipsychotic-induced RLS in schizophrenia; different genetic mechanisms may underlie antipsychotic-induced vs. primary RLS.

Association between restless legs syndrome and CLOCK and NPAS2 gene polymorphisms in schizophrenia

Previous studies have suggested that there is a genetic basis to restless legs syndrome (RLS) development. Occurrence of antipsychotic-induced RLS could also be due to differences in genetic susceptibility. We investigated whether CLOCK and NPAS2 gene polymorphisms are associated with RLS in schizophrenic patients on antipsychotics because RLS symptoms usually manifest during the evening and night. We assessed symptoms of RLS in 190 Korean schizophrenic patients on antipsychotics and divided the subjects into two groups according to the International Restless Legs Syndrome Study Group diagnostic criteria: (i) subjects who met all the criteria and (ii) the remaining subjects who did not meet all the criteria. We found a significant difference in the number of subjects with different genotype and allele carrier frequencies for the CLOCK gene (rs2412646) between the two groups (p = 0.031 and 0.010, respectively). Distribution of CLOCK haplotypes (rs2412646-rs1801260) was significantly different between schizophrenic patients with and without RLS (p = 0.021). However, the distributions of allelic, genotypic, and haplotypic variants of NPAS2 (rs2305160 and rs6725296) were not significantly different between the two groups. Our results suggest that CLOCK polymorphisms are associated with increased susceptibility of schizophrenic patients to RLS. We hypothesize that RLS in schizophrenia patients treated with antipsychotics may be a very mild akathisia that manifests during the night and is under control of circadian oscillation.

The BTBD9 gene may be associated with antipsychotic-induced restless legs syndrome in schizophrenia

OBJECTIVE

A genome-wide association study and several replication studies have shown significant association between BTBD9 gene single nucleotide polymorphisms and restless legs syndrome (RLS). The aim of this study is to investigate the association between the BTBD9 gene polymorphisms and antipsychotic-induced RLS in schizophrenic patients.

METHODS

Restless legs syndrome symptoms were evaluated using the diagnostic criteria of the International Restless Legs Syndrome Study Group in 190 Korean schizophrenic patients. We genotyped the rs9357271 and rs3923809 polymorphisms of the BTBD9 gene in schizophrenic patients with (n = 96) and without (n = 94) RLS symptoms.

RESULTS

There was a significant difference in the allele frequency (χ(2) = 8.14, p = 0.004) of the rs9357271 polymorphism between schizophrenic patients with and without RLS symptoms. Significant genotypic association of this single nucleotide polymorphisms with RLS symptoms was also observed for the dominant model (χ(2) = 10.32, p = 0.001) and heterozygous model (χ(2) = 10.9, p = 0.001). When we compared the frequencies of the rs3923809-rs9357271 haplotypes between the two groups, the overall haplotype frequencies were significantly different (permuted p = 0.037), and the A-T haplotype was significantly more frequent in the RLS symptom group than in the no RLS symptom group (0.112 vs. 0.041, permuted p = 0.007).

CONCLUSIONS

These data suggest that the BTBD9 gene is associated with antipsychotic-induced RLS symptoms in schizophrenic patients.

Association study between antipsychotic-induced restless legs syndrome and polymorphisms of monoamine oxidase genes in schizophrenia

OBJECTIVE

This study aimed to investigate whether the monoamine oxidase (MAO) A and B genes are associated with antipsychotic-induced restless legs syndrome (RLS) in schizophrenia.

METHODS

We assessed antipsychotic-induced RLS symptoms in 190 Korean schizophrenic patients and divided the subjects into two groups: those with RLS symptoms (n = 96) and those without RLS symptoms (n = 94). Genotyping was performed for the variable number of tandem repeat (VNTR) polymorphism of the MAOA gene and A644G polymorphism of the MAOB gene.

RESULTS

There was no significant difference in the genotype and allele frequencies of all polymorphisms investigated between these two groups. However, the result of global haplotype analysis showed a significant difference in haplotype frequencies between male subjects with and without RLS symptoms (p = 0.013). The interaction between two polymorphisms had a significant effect on the RLS scores of both male (p = 0.047) and female (p = 0.028) patients.

CONCLUSIONS

These data do not suggest that the MAOA gene VNTR and MAOB gene A644G polymorphisms are associated with antipsychotic-induced RLS symptoms in schizophrenia. However, we found that the haplotype frequencies differed between the male schizophrenic patients with and without RLS symptom and the interaction between the two polymorphisms had a significant influence on the RLS scores of patients with schizophrenia.