Determination of genotype frequencies of PDYN VNTR polymorphism in heroin and methamphetamine co-users

Substance use disorder is the use of all kinds of chemical substances that cause negative changes in the central nervous system as a pleasure and when they are not used, they show withdrawal symptoms and are psychologically and physically dependent on substance use. Opioid use disorder, which has become a major problem in our country as it is worldwide, affects people of all ages and harms public health. Methamphetamine, a class of amphetamine-type stimulants, is among the most widely consumed illicit substances in the world. In recent years, there has been a significant increase in the use of heroin and methamphetamine together worldwide. Prodynorphin is encoded by the PDYN gene and is a precursor of dynorphin-related peptides. Dynorphins activate kappa-opioid receptors, a member of the endogenous opioid system. Gene expression may vary according to the number of repeats of the 68-bp VNTR polymorphism in the promoter region of PDYN. Therefore, this master's thesis study, it was aimed to determine the genotype frequencies of PDYN 68-bp VNTR polymorphism in individuals using heroin and methamphetamine together and to investigate the effects of substance use. The study included 50 individuals diagnosed with heroin use disorder, 50 individuals diagnosed with methamphetamine use disorder, and 50 individuals using heroin and methamphetamine together who applied to the AMATEM clinic of Ankara Training and Research Hospital. PDYN 68-bp VNTR gene polymorphism was determined by Polymerase Chain Reaction (PCR) method. The data collected were statistically analyzed. In terms of PDYN 68-bp VNTR polymorphism, no significant difference was observed between the three groups of heroin, methamphetamine, and heroin-methamphetamine co-users in terms of genotype frequencies (p=0.55; p=0.77; p=0.72, respectively). Furthermore, the effect of PDYN 68-bp VNTR polymorphism on substance use was investigated by logistic regression analysis in groups of 2 and it was found that this polymorphism had no effect on heroin-methamphetamine co-use (p=0.509; p=0.608; p=0.903, respectively). In conclusion, this is the first time that the PDYN 68-bp VNTR polymorphism has been shown to have an effect on heroin and methamphetamine co-use. However, considering the small number of individuals included in the study, the findings obtained in this study need to be confirmed with new studies including more individuals.