No abstract

The aim of this study was to evaluate the most common ABCB1 (MDR1, P-glycoprotein) polymorphisms in the population of R. Macedonia and compare the allele and haplotype frequencies with the global geographic data reported from different ethnic populations. The total of 107 healthy Macedonian individuals from the general population was included. Genotypes for the ABCB1 for three polymorphisms C1236T [rs1128503], G2677A/T [rs2032582] and C3435T [rs1045642] were analyzed by Real-Time PCR. Obtained allele frequencies for these three SNPs were similar to those observed in other European Caucasians. The detected genotype frequencies were 33.6% for 1236CC, 44.9% for 1236CT and 21.5% for 1236TT in exon 12; 32.7%, 44.9% and 22.4% for 2677GG, 2677GT and 2677GT consecutively in exon 21; and 25.2% for 3435CC, 52.3% for 3435CT and 22.5% for 3435TT in exon 26.Strong LD was observed in our study among all = 0.859, r 2 = 0.711). Eight different haplotypes were identified and the most prominent was the CGC haplotype (45.3%). Our study was the first to have documented the distribution of ABCB1 alleles, genotypes and haplotypes in the population of R. Macedonia. The obtained results can help in the prediction of different response to the drugs that are P-glycoprotein substrates. Additionally, in the era of individualized medicine the determination of the P-glycoprotein genotype might be a good predictive marker for determination of the subpopulations with higher risk to certain diseases.

Antipsychotic drugs are widely used in the treatment of schizophrenia and psychotic disorder. The lack of antipsychotic response and treatment-induced side-effects, such as neuroleptic syndrome, polydipsia, metabolic syndrome, weight gain, extrapyramidal symptoms, tardive dyskinesia or prolactin increase, are the two main reasons for non-compliance and increased morbidity in schizophrenic patients. During the past decades intensive research has been done in order to determine the influence of genetic variations on antipsychotics dosage, treatment efficacy and safety. The present work reviews the molecular basis of treatment response of schizophrenia. It highlights the most important findings about the impact of functional polymorphisms in genes coding the CYP450 metabolizing enzymes, ABCB1 transporter gene, dopaminergic and serotonergic drug targets (DRD2, DRD3, DRD4, 5-HT1, 5HT-2A, 5HT-2C, 5HT6) as well as genes responsible for metabolism of neurotransmitters and G signalling pathways (5-HTTLPR, BDNF, COMT, RGS4) and points their role as potential biomarkers in everyday clinical practice. Pharmacogenetic testing has predictive power in the selection of antipsychotic drugs and doses tailored according to the patient’s genetic profile. In this perception pharmacogenetics could help in the improvement of treatment response by using different medicinal approaches that would avoid potential adverse effects, reduce stabilization time and will advance the prognosis of schizophrenic patients.

The evaluated peripheral markers reflect only state (but not trait) abnormalities in patients with current severe episode of RDD. The observed peripheral α-AR and serotonin abnormalities are mutually not related and they are probably triggered by different mechanisms.

Atypical antipsychotic risperidone is widely used first-line monotherapy in schizophrenia and combined therapy in bipolar disorders. Therapeutic plasma concentrations of risperidone and its active moiety are directly influenced by genetic variations in metabolic CYP450 enzymes (CYP2D6 and CYP3A4/5) and transporter (ABCB1) protein and additional environmental factors. Since active metabolite 9-OH risperidone has a greater percentage of the pharmacologically active fraction and is equipotent to the parent drug risperidone, it is assumed that it contributes significantly to therapeutic and adverse effects. Unpredictable dose/concentration ratio, narrow therapeutic index, number of interactions, along with serious adverse reactions (ADR), raises the need for individualization of risperidone treatment and establishing of good therapeutic regime using TDM. A simple and reliable validated bioanalytical liquide-liquide extraction HPLC/UV method was applied for the simultaneous determination of risperidone and its active metabolite, 9-OH risperidone, in human plasma and urine of 52 hospitalized schizophrenia/bipolar disorder patients treated with risperidone as monotherapy and in polytherapy. All the patients were previously genotyped for CYP2D6 (EM=30, EM/IM=14, IM=4 IM/PM=1 and PM=3) and ABCB1 using Real-Time PCR methods with TaqMan SNP genotyping suitable assays according to the guidelines of the manufacturer (Life Technologies, USA).The influence of CYP2D6 phenotype on metabolic ratio MR (Ris/9-OHRis) in plasma (p=0.012) and in urine (p=0.048) was confirmed. Statistically significant correlation (R2=55.53%, Rho=0.844, p<0,0001) for MR in both plasma and urine indicates that urine may be utilized as appropriate media for initial CYP2D6 phenotype identification and selection of patients on risperidone treatment with high risk for ADR.