[Christmas 2016] Sniffing out significant “Pee values”: genome wide association study of asparagus anosmia [嗅出显著的“P值”：芦笋嗅觉缺失症的全基因组关联分析]

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BMJ 2016; 355 doi: http://dx.doi.org/10.1136/bmj.i6071 (Published 13 December 2016)
Cite this as: BMJ 2016;355:i6071

Authors
Sarah C Markt, Elizabeth Nuttall, Constance Turman, Jennifer Sinnott, Eric B Rimm, Ethan Ecsedy, Robert H Unger, Katja Fall, Stephen Finn, Majken K Jensen, Jennifer R Rider, Peter Kraft, Lorelei A Mucci

Abstract
Objective To determine the inherited factors associated with the ability to smell asparagus metabolites in urine.

Design Genome wide association study.

Setting Nurses’ Health Study and Health Professionals Follow-up Study cohorts.

Participants 6909 men and women of European-American descent with available genetic data from genome wide association studies.

Main outcome measure Participants were characterized as asparagus smellers if they strongly agreed with the prompt “after eating asparagus, you notice a strong characteristic odor in your urine,” and anosmic if otherwise. We calculated per-allele estimates of asparagus anosmia for about nine million single nucleotide polymorphisms using logistic regression. P values <5×10-8 were considered as genome wide significant.

Results 58.0% of men (n=1449/2500) and 61.5% of women (n=2712/4409) had anosmia. 871 single nucleotide polymorphisms reached genome wide significance for asparagus anosmia, all in a region on chromosome 1 (1q44: 248139851-248595299) containing multiple genes in the olfactory receptor 2 (OR2) family. Conditional analyses revealed three independent markers associated with asparagus anosmia: rs13373863, rs71538191, and rs6689553.

Conclusion A large proportion of people have asparagus anosmia. Genetic variation near multiple olfactory receptor genes is associated with the ability of an individual to smell the metabolites of asparagus in urine. Future replication studies are necessary before considering targeted therapies to help anosmic people discover what they are missing.