DRD2 Gene in Alcohol Dependence 국립중앙의료원 이 소 희

Background Dopamine – Reward behavior (Wise & Rompre, 1989) – Alcoholism Mesolimbic dopamine system – 5 dopamine receptors – DRD2 : most widely studied

Background DRD2 TaqIA – 3´ untranslated region – A1 : ↓ DRD2 density DRD2 141C ins/del – Promoter polymorphism – Related to DRD2 density DRD2 exon 8 (E8) A/G – 52 bp downstream of the stop codon – E8A : ↓ DRD2 expression

DRD2 gene

Objectives Investigate the association of 3 SNPs – -141C (rs ), – exon 8 (rs6276) – TaqIA (rs ) in DRD2 with alcohol dependence, depression, craving Haplotypes associated with AD

Materials and Methods Subjects 245 AD and 110 HC AD from the KARF hospital – Exclusion : other SUD, bipolar I disorder, schizophrenia. HC among volunteers – Exclusion : over 11 in AUDIT-K

Materials and Methods The semi-structured questionnaire Clinical details AUDIT-K Penn Alcohol Craving Scale (PACS) Beck Depression Inventory (BDI)

Materials and Methods Lesch typology 1.allergy model 2.conflict resolution and anxiety model 3.depressive model 4.conditioning model

Materials and Methods Genotypic profiles obtained for DRD2 polymorphisms SNPPrimers -141C (rs ) Forward: 5’-GACCCAGCCTGCAATCAC-3’ Reverse: 5’-AGGAGCTGTACCTCCTCGG-3’ Exon 8 (rs6276) Forward: 5’-GCCGTGCCTCCCCGGCTCTG-3’ Reverse: 5’-GGCAGTGAGGAGCATGGAGCCAAG-3’ Taql A (rs ) Forward: 5’-CCGTCGACGGCTGGCCAAGTTGTCCA-3’ Reverse: 5’-CCGTCGACCCTTCCTGAGTGTCATCA-3’

Materials and Methods Statistical Analysis a chi-square test or a student’s t-test and Mann Whitney test AVOVA, a Kruskal-Wallis test Fisher’ exact test Logistic regression analysis the software SNP Analyzer-Pro TM

Results Clinical Characteristics ADHCStatistics Gender (M/F)195/50108/2χ 2 = , p <0.01 Age (years)45.7 ± ± 10.1t=-1.258, p=0.210 Age at FUA19.6 ± ± 3.1t= 0.807, p=0.420 Age of onset35.9 ± 11.0 Duration of illness9.3 ± 8.2 SD/week111.4 ± PACS21.5 ± 8.5 AUDIT-K31.6 ± ± 3.7t= , p<0.01

Results Lesch typology – Type 1 : 188 (77%) – Type II : 12 (4.9%) – Type III : 23 (9.4%) – Type IV : 21 (8.6%)

Results Genotype and allele frequencies of SNPs in DRD2 SNPsGenotypesStatisticsAllelesStatistics -141CC/C (%)C/- (%)-/- (%)C (%)- (%) AD 167 (69.0) 67 (27.7) 8 (3.3) χ 2 = , p < (82.9) 83 (17.1) χ 2 = , p < HC 49 (44.5) 55 (50.0) 6 (5.5) 153 (69.5) 67 (30.5)

Results Genotype and allele frequencies of SNPs in DRD2 SNPsGenotypesStatisticsAllelesStatistics Exon 8A/A (%)A/G (%)G/G (%)A (%)G (%) AD 62 (25.5) 118 (48.6) 63 (25.9) χ 2 = 3.344, p = (49.8) 244 (50.2) χ 2 = 3.436, p = HC 20 (18.2) 53 (48.2) 37 (33.6) 93 (42.3) 127 (57.7)

Results Genotype and allele frequencies of SNPs in DRD2 SNPsGenotypesStatisticsAllelesStatistics Taql A A1/A1 (%) A1/A2 (%) A2/A2 (%) A1 (%)A2 (%) AD 62 (25.5) 119 (49.0) 62 (25.5) χ 2 = 8.569, p = (50.0) χ 2 = 7.243, p = HC 21 (19.1) 44 (40.0) 45 (40.9) 86 (39.1) 134 (60.9)

Results Significant SNP haplotypes in DRD2 gene associated with AD Haplotype a Haplotype frequencies χ2χ2 p Odds ratio (9 5% CI) AD HC -141C Ins-A-A x10 -5* ( ) -141C Del-G-A x10 -4 * ( )

Results Differences in clinical variables among patients with AD Exon8 A (49.8%)G (50.2%)Statistics Age of onset χ 2 =0.205, p=0.651 < 25 years (%) ≥ 25 years (%) BDI20.8 ± ± 10.8t=2.073, p=0.040 PACS21.5 ± ± 8.3t=-0.065, p=0.949

Conclusion Significant differences in the genotype a nd allele frequencies of -141C & Taq1A between AD and control groups Two haplotypes (-141C Ins-A-A1 and -141C Del-G-A2) were significantly asso ciated with AD AD patients with A allele in exon8 had si gnificantly higher BDI scores.

Discussion -141C Ins-A-A1 haplotype – Seems to confer 2.5 times more risk to develop alcohol dependence in India (Prasad et al.,2010) – the haplotype containing SNPs, previously sh own to reduce DRD2 availability, are associa ted with AD

A1 allele of DRD2 A1 allele of DRD2 (Blum et al, 1990) – Presence : 77% of the alcoholics – Absence : 72% of the nonalcoholics ↓ D2 dopamine receptor numbers Replicated by several groups Failed to replicate by many studies

A1 allele of DRD2 Factors contributing to inconsistencies – Type of alcoholics, type of controls Severe type only? (Blum et al, 1996) – Involved in alcohol-related phenotype Reward deficiency syndrome – Different Frequency among populations

Reward deficiency SD Addictive behavior Impulsive behavior Compulsive behavior Personality disorder Severe alcoholism ADHDAberrant sexual behavior Conduct disorder Polysubsta nce abuse Tourette’s SD Antisocial personality Pathologic al gambling smoking AutismAggressive behavior obesity

-141C Ins/Del of DRD2 -141C Del – alter gene expression in vitro –↑ striatal dopamine receptor density in vivo -141C Ins – Predisposing to AD (Prasad et al.,2010 ; Konishi et al.,2004)

A/G in exon 8 of DRD2 E8AA : German alcoholics (Finckh et al.,1997) –↑ Depressiveness, anxiety, suicidality, withdrawal severity –↓ growth hormone responses after a challenge with apomorphine E8A : ↓ DRD2 expression (Samochowieca et al.,2000)

Reference Blum K et al (1990) Allelic association of human dopamine D2 receptor gene in alcoholism. JAMA 263:2055–2060. Blum K et al (1996) Reward deficiency syndrome. Am Sci 84:132–145. Wise RA, Rompre P-P (1989) Brain dopamine and reward. Annu Rev Psychol 40:191–225. Samochowiec J et al (2000) Predominant influence of the 3'- region of dopamine D2 receptor gene (DRD2) on the clinical p henotype in German alcoholics. Pharmacogenetics. 10(5): Prasad P et al (2010) Dopamine D2 receptor polymorphisms a nd susceptibility to alcohol dependence in Indian males: a pre liminary study. BMC Med Genet 11:24.

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