title: Genotyping the Mu-opioid receptor A118G polymorphism using the real-time amplification refractory mutation system: allele frequency distribution among Brazilians.
abstract: BACKGROUND
  The mu-opioid receptor (OPRM1) A118G polymorphism has been associated with decreased analgesic effects of opioids and predisposition to addiction. However, its role in specific clinical scenarios and in different ethnicities must be better defined. No studies evaluating the A118G polymorphism in the Brazilian population have yet been published.
  
  
  METHODS
  Genomic DNA was isolated from peripheral leukocytes of 200 surgical patients of the Center-West region of Brazil. Our genotyping protocol was developed based on the real-time amplification refractory mutation system and validated by comparison with cycle sequencing. Functional consequences of the A118G polymorphism were studied by comparing tobacco smoking prevalence and exposure between genotype groups.
  
  
  RESULTS
  We observed perfect correlation between genotyping and sequencing results. Frequency of the G allele was 16% (IC 95% 12.7-19.9%) in our sample. Genotype distribution revealed 146 (73%) patients 118A homozygous, 44 (22%) heterozygous, and 10 (5%) homozygous for the G variant. After grouping patients according to the presence of the G allele, we did not observe differences in smoking prevalence; however, patients with one or two copies of the 118G allele reported higher tobacco exposure than patients 118A homozygous measured in pack-years (28.9 ± 12.5 vs. 21.5 ± 10.8, respectively, P = 0.02).
  
  
  CONCLUSIONS
  We developed a fast and reliable genotyping method to identify the allele frequency distribution of the OPRM1 A118G polymorphism among patients from Center-West Brazil. Our preliminary results suggest functional consequences of the polymorphism on smoking behavior among Brazilians.
authors: Department of Anesthesiology, University Hospital of Brasilia, University of Brasilia, Brasilia, Brazil.
authors: Mauricio
authors: M
authors: Daher
authors: Felipe M M
authors: FM
authors: Costa
authors: Francisco A R
authors: FA
authors: Neves
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D009293:Opioid-Related Disorders / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D017450:Receptors, Opioid, mu / Q000235:genetics*; D055815:Young Adult
chemical_list: D017450:Receptors, Opioid, mu
keywords: addiction behavior; genetic polymorphisms; genotyping techniques; mu-opioid receptor; opioid analgesics; pain management