Genetic and molecular basis of individual differences in human umami taste perception - PubMed (original) (raw)

Genetic and molecular basis of individual differences in human umami taste perception

Noriatsu Shigemura et al. PLoS One. 2009.

Abstract

Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 and TAS1R3, is proposed to function as its receptor. However, little is known about genetic variation of TAS1R1 and TAS1R3 and its potential links with individual differences in umami sensitivity. Here we investigated the association between recognition thresholds for umami substances and genetic variations in human TAS1R1 and TAS1R3, and the functions of TAS1R1/TAS1R3 variants using a heterologous expression system. Our study demonstrated that the TAS1R1-372T creates a more sensitive umami receptor than -372A, while TAS1R3-757C creates a less sensitive one than -757R for MSG and MSG plus IMP, and showed a strong correlation between the recognition thresholds and in vitro dose-response relationships. These results in human studies support the propositions that a TAS1R1/TAS1R3 heterodimer acts as an umami receptor, and that genetic variation in this heterodimer directly affects umami taste sensitivity.

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Conflict of interest statement

Competing Interests: Ajinomoto is a product brand name of monosodium glutamate, and the company has interests directly in the sensing of umami. MSG is used in this study and the study could be used to promote the use of MSG and umami.

Figures

Figure 1

Figure 1. Distributions of individual MSG, IMP and MSG+0.5 mM IMP taste recognition thresholds (254 Japanese subjects).

Bin width concentrations correspond to 0.3 log units. The subjects exhibiting recognition threshold over 100 mM MSG, 10 mM IMP, 1.56 mM MSG+0.5 mM IMP are presented as 100<, 10

Figure 2

Figure 2. Distributions of individual MSG, IMP and MSG+0.5 mM IMP taste recognition thresholds for three groups defined by TAS1R1-372 and TAS1R3-757 haplotypes.

Black, red and green bars indicate human TAS1R1-372A/TAS1R3-757R homozygotes (n = 84), TAS1R1-372T/TAS1R3-757R homozygotes (n = 37) and homo- and heterozygotes containing the TAS1R3-757C (n = 39), respectively. Black, red and green dotted lines indicate the distribution curves for TAS1R1-372A/TAS1R3-757R homozygotes, TAS1R1-372T/TAS1R3-757R homozygotes and homo- and heterozygotes containing the TAS1R3-757C, respectively, which were obtained by gaussian fit analysis. Bin width concentrations correspond to 0.3 log units. The subjects exhibiting recognition threshold over 100 mM MSG, 10 mM IMP, 1.56 mM MSG+0.5 mM IMP are presented as 100<, 10

Figure 3

Figure 3. Concentration-response relationships of the calcium concentrations in HEK293 cells transfected with human TAS1R1 and TAS1R3 variants after stimulation with increasing MSG, and MSG+0.5 mM IMP.

(A) Dose-response curves of MSG, and MSG+0.5 mM IMP concentration series in cells expressing the TAS1R1/TAS1R3 variants [TAS1R1-372A, -372T, TAS1R3-757R and -757C]. Black and red lines indicate the responses to MSG and MSG+0.5 mM IMP, respectively. Responses have been normalized to those of isoproterenol (ISO, 10 µM), which activate the endogenous βadrenergic receptor . Each point represented the mean (±S.E.) from 10∼18 independent experiments. Half maximal responses (EC50) for TAS1R1/TAS1R3 variants were calculated from the dose-response curves. The X-axis triangles present the EC50 values for MSG (black) and MSG+0.5 mM IMP (red). (B) The responses of TAS1R1/TAS1R3 variants at concentrations of MSG (5, 20, 50 mM) and MSG (0.3, 5, 50 mM)+0.5 mM IMP. The values are means (±S.E.) from 14∼18 independent experiments. Asterisks indicate statistically significant differences (*: p<0.05, †: p<0.01, Fisher's PLSD as a Post-hoc test).

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