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Saturday, May 12, 2012

Association Between In Vivo Alcohol Metabolism and Genetic Variation in Pathways that Metabolize the Carbon Skeleton of Ethanol and NADH Reoxidation i

Variation in alcohol metabolism affects the duration of intoxication and alcohol use. While the majority of genetic association studies investigating variation in alcohol metabolism have focused on polymorphisms in alcohol or aldehyde dehydrogenases, we have now tested for association with genes in alternative metabolic pathways that catalyze the carbon skeleton of ethanol (EtOH) and NADH reoxidation.

Nine hundred fifty single nucleotide polymorphisms (SNPs) spanning 14 genes (ACN9,ACSS1,ACSS2,ALDH1A1, CAT, CYP2E1,GOT1,GOT2,MDH1,MDH2,SLC25A10,SLC25A11,SLC25A12,SLC25A13) were genotyped in 352 young adults who participated in an alcohol challenge study. Traits tested were blood alcohol concentration (BAC), breath alcohol concentration (BrAC), peak alcohol concentration, and rates of alcohol absorption and elimination. Allelic association was tested using quantitative univariate and multivariate methods.

A CYP2E1 promoter SNP (rs4838767, minor allele frequency 0.008) exceeded the threshold for study-wide significance (4.01 × 10−5) for 2 early BAC, 8 BrAC measures, and the peak BrAC. For each phenotype, the minor C allele was related to a lower alcohol concentration, most strongly for the fourth BrAC (p = 2.07 × 10−7) explaining ~8% of the phenotypic variance. We also observed suggestive patterns of association with variants in ALDH1A1 and on chromosome 17 near SLC25A11 for aspects of blood and breath alcohol metabolism. An SNP upstream of GOT1 (rs2490286) reached study-wide significance for multivariate BAC metabolism (p = 0.000040).

Overall, we did not find strong evidence that variation in genes coding for proteins that further metabolize the carbon backbone of acetaldehyde, or contribute to mechanisms for regenerating NAD from NADH, affects alcohol metabolism in our European-descent subjects. However, based on the breath alcohol data, variation in the promoter of CYP2E1 may play a role in preabsorptive or early hepatic alcohol metabolism, but more samples are required to validate this finding.

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