Effects of OPRM1 and DRD2 on brain structure in drug-naïve adolescents: Genetic and neural vulnerabilities to substance use

Polymorphic variants of the dopamine receptor gene DRD2 (rs6277, rs1800497) in adolescents with problematic video game use

Problematic video games use, as a specific form of problematic Internet use, is widespread among adolescents and can have negative effects on their mental and somatic well-being. An increasing incidence of addictive video gaming, as well as the overuse of the Internet, among the young population makes the current study of susceptibility factors, including the genetic component, relevant. There has been a number of investigations related to the involvement of gene variants of the neurotransmitter system in the development of Internet addiction, with the results being different for various ethnic groups. The dopamine type 2 receptor gene (DRD2) is one of the candidate genes for susceptibility to video game addiction. The aim of the work was to study polymorphic variants of the dopamine receptor gene DRD2 (rs6277, rs1800497) in Russian adolescents with problematic use of computer video games. A sampling of 407 adolescents aged 14.1 ± 1.8 years was tested, of which 56 (13.8 %) were identified as having problems with the pathological use of video games use based on the GASA scale results. Boys in the sample proved to be addicted to video games more than girls (p = 0.041). As a result of comparing the allele frequency of DRD2 (rs6277), a tendency to a higher frequency of the minor allele T was revealed in the group of adolescents with problematic video game use compared with adolescents without problematic video game use (i. e. 0.563 and 0.466, respectively, p = 0.06). When using the dominant inheritance model, it was revealed that adolescents with problematic use of video games were statistically significantly more likely to carry the T (CT+TT) allele (p = 0.04, OR = 2.14, CI = 1.01-4.53). The T allele DRD2 (rs6277) is associated with low expression of the dopamine receptor D2 and leads to decreasing the density and affinity of extrastriatal dopamine type 2 receptors, which is associated with impaired social communication as well. We suggest that the presence of CT and TT genotypes of rs6277 DRD2 may be a potential risk factor for developing problematic video game use in adolescents.

Endogenous opiates and behavior: 2022

This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Ethnicity-dependent effect of rs1799971 polymorphism on OPRM1 expression in the postmortem brain and responsiveness to antipsychotics

Schizophrenia is associated with aberration of inhibitory neurons. Although the mu-opioid receptor (MOR) is an essential modulator of inhibitory neurons, the effect of rs1799971 polymorphism in the MOR gene on risk of schizophrenia is controversial. Moreover, the disturbance of opioids systems in patients with schizophrenia has not been fully examined. We firstly conducted preliminary meta-analyses integrating Asian and European populations separately over 12,000 subjects to assess the effect of rs1799971 on risk of schizophrenia. Based on the above result, we also investigated the effect on the expression levels of MOR mRNA in the prefrontal cortex (PFC) and caudate nucleus of 41 postmortem brains. In addition, we determined whether these levels were related to antemortem schizophrenia symptoms and pharmacotherapeutic effects. The rs1799971 G-allele reduced the risk of schizophrenia in Asian populations (OR: 0.56, 95%CI: 0.32-0.98, p = 0.042) but increased it in European populations (OR: 1.66, 95%CI: 1.08-2.56, p = 0.022). It decreased MOR mRNA levels in PFC in the Japanese population (p = 0.031). Increased MOR mRNA level in PFC correlated with higher total score of antemortem schizophrenia symptoms (p = 0.017). Furthermore, the pharmacotherapeutic effect of first-generation antipsychotics was higher for genotype AA than AG/GG of rs1799971 (p = 0.036). The rs1799971 affects risk of schizophrenia and MOR mRNA expression and the effect varies according to ethnicity. Overexpression of MOR might induce severe schizophrenia symptoms. Therefore, MOR modulation may be the key clue for treating antipsychotics-resistant schizophrenia, and genotyping rs1799971 may provide a better pharmacotherapeutic strategy.

Prenatal Effects of Nicotine on Obesity Risks: A Narrative Review

Nicotine usage by mothers throughout pregnancy has been observed to relate to numerous deleterious effects in children, especially relating to obesity. Children who have prenatally been exposed to nicotine tend to have lower birth weights, with an elevated risk of becoming overweight throughout development and into their adolescent and adult life. There are numerous theories as to how this occurs: catch-up growth theory, thrifty phenotype theory, neurotransmitter or endocrine imbalances theory, and a more recent examination on the genetic factors relating to obesity risk. In addition to the negative effect on bodyweight and BMI, individuals with obesity may also suffer from numerous comorbidities involving metabolic disease. These may include type 1 and 2 diabetes, high cholesterol levels, and liver disease. Predisposition for obesity with nicotine usage may also be associated with genetic risk alleles for obesity, such as the DRD2 A1 variant. This is important for prenatally nicotine-exposed individuals as an opportunity to provide early prevention and intervention of obesity-related risks.