Clinical Use of Genetic Polymorphisms as Markers of Refractoriness in Schizophrenia

Abstract

Background: Pharmacogenetics studies have demonstrated the importance of various neurotransmitter systems in mediating drug effectiveness. Due to the importance of the dopaminergic system in the activity of antipsychotics, proteins that regulate the availability of dopamine may influence the response to drug treatment, as the enzyme catechol-O-methyl-transferase (COMT), which catalyzes the breakdown of dopamine. Some associations have already been described between Val108/158Met polymorphism and response, with individuals carrying the Met allele presenting the best answer. However, most of the findings reported have not been universally replicated. Methods: The study enrolled 89 schizophrenia patients divided in two groups: 59 refractory patients according to IPAP algorithm (International Psychopharmacology Algorithm Project) and 30 non-refractory patients. Polymorphisms in COMT (rs4680), HTR2A (T102C, rs6314, rs1928042), HTR2C (rs6318, rs3813929), CHRNA7(rs7164043), BDNF (rs6265), DRD3 (rs6280) and GRM8 (rs7778604) genes were evaluated by allelic discrimination using the TaqMan® system. Results: regarding the polymorphism rs4680 (Val158Met) of the COMT gene, among the non-refractory patients we found 7% AA, 50% AG and 43% GG genotypes. Among refractory patients we found 20% AA, 59% AG and 21% GG. After the X2 test, we found a difference in the genotype distribution between the two groups (p=0.043). For the other polymorphisms in genes HTR2A, HTR2C, CHRNA7, BDNF, DRD3, and GRM8, no significant difference was found. Conclusions: Our findings do not confirm previous data. In our study there is a higher prevalence of individuals homozygous for Met in the refractory group and a higher prevalence of individuals homozygous for Val the non-refractory (p=0.043).