Age modifies the genotype-phenotype relationship for the bitter receptor TAS2R38

Background: The purpose of this study was to investigate the effect of TAS2R38 haplotypes and age on human bitter taste perception. Results: Children (3 to 10 yrs), adolescents (11 to 19 yrs) and adults (mostly mothers, 20 to 55 yrs (N = 980) were measured for bitter taste thresholds for 6-n-propylthiouracil (PROP) and genotyped for three polymorphisms of the AS2R38 gene (A49P, V262A, I296V). Subjects were grouped by haplotype and age, as well as sex and race/ethnicity, and compared for PROP thresholds. Subjects with the same haplotype were similar in bitter threshold regardless of race/ethnicity (all ages) or sex (children and adolescents; all p-values > 0.05) but age was a modifier of the genotype-phenotype relationship. Specifically, AVI/PAV heterozygous children could perceive a bitter taste at lower PROP concentrations than could heterozygous adults, with the thresholds of heterozygous adolescents being intermediate (p < 0.001). Similar age effects were not observed for subjects with the PAV/PAV or AVI/AVI homozygous haplotypes (p > 0.05) perhaps because there is less variation in taste perception among these homozygotes. Conclusions: These data imply that the change in PROP bitter sensitivity which occurs over the lifespan (from bitter sensitive to less so) is more common in people with a particular haplotype combination, i.e., AVI/PAV heterozygotes.