Rs1800497

From SNPedia

rs1800497, a SNP also known as the TaqIA (or Taq1A) polymorphism of the dopamine D2 receptor DRD2 gene (even though it is actually located over 10,000bp downstream of the gene), gives rise to the DRD2*A1 allele. This allele (rs1800497(T)) is associated with a reduced number of dopamine binding sites in the brain [PMID 9672901], and has been postulated to play a role in alcoholism, smoking, and certain neuropsychiatric disorders.

The reduced number of dopamine binding sites may play a role in nicotine addiction by causing an "understimulated" state that can be relieved by smoking (and/or use of other drugs). [PMID 8873216]

A wide variety of reports have been published over more than ten years either linking rs1800497 to aspects of nicotine use and smoking cessation success, or finding no such association. A meta-analysis of 41 such studies published in 2004 concluded that overall the association of rs1800497 with such phenomena was statistically weak. [PMID 15370155] This same group recently (2009) published a study showing no association between rs1800497 and improved response to nicotine replacement therapy (NRT), contrary to their previous study.[PMID 19273465]

More recently, a relatively large study of over 700 patients attempting to kick their smoking habit using the drug bupropion determined that smokers homozygous for the A2/A2 genotype were more successful than A1/A2 or A1/A1 individuals. The A2/A2 smokers were more than three times as likely, relative to placebo, to be abstinent at end of treatment (35.2% vs. 15.1%; odds ratio = 3.25, CI: 2.00-5.28) and at 6 months of follow-up (26.7% vs. 12.2%; odds ratio = 2.81, CI: 1.66-4.77), whereas not so much by 12 months (16.3% vs. 10.7%; OR = 1.70, CI: 0.95-3.05). Basically, A1/A2 and A1/A1 genotype smokers didn't gain anything from using bupropion versus placebo; bupropion only helped A2/A2 genotypes stop smoking. [PMID 18058343]

In a study of individuals in the Polyp Prevention Trial with any, multiple (>/=2) or advanced colorectal adenoma recurrence after 4 years, compared to those without adenoma recurrence, rs1800497(T;T) individuals were significantly associated with all advanced adenoma recurrence (odds ratio 2.40, CI: 1.11-5.20). The authors speculate this increased risk of adenoma recurrence (and an association with colorectal cancer) may be related to SNP-associated differences in alcohol and fat intake.[PMID 19065655]

[PMID 18698520] A small (54 patient) study of patients with traumatic brain injury concluded that carriers of rs1800497(A) alleles recover slower as assessed by memory and attention tests.

spittoon diminished pleasure response from food

[PMID 19344737] Associations of the DRD2 TaqIA Polymorphism with Impulsivity and Substance Use: Preliminary Results from a Clinical Sample of Adolescents.

[PMID 19373123] Genetic variants altering dopamine D2 receptor expression or function modulate the risk of opiate addiction and the dosage requirements of methadone substitution

[PMID 19796663] Influence of DRD2 and ANKK1 genotypes on apomorphine-induced growth hormone (GH) response in alcohol-dependent patients

[PMID 19925838] Parental Control and the Dopamine D2 Receptor Gene (DRD2) interaction on Emotional Eating in Adolescence

[PMID 19512960] Genetic diagnostics of functional variants of the human dopamine D2 receptor gene