Effect of chemical interaction between oleic acid and L-Arginine on oral perception, as a function of polymorphisms of CD36 and OBPIIa and genetic ability to taste 6-n-propylthiouracil

Abstract

Oral sensitivity to fats varies in individuals influencing nutritional status and health. Variations in oleic acid perception are associated with CD36 and odorant binding protein (OBPIIa) polymorphisms, and 6-n-propylthiouracil (PROP) sensitivity, which is mediated by TAS2R38 receptor. L-Arginine (L-Arg) supplementation was shown to modify the perception of the five taste qualities. Here we analyzed the effect of three concentrations (5, 10, 15 mmol/L) of L-Arg on oral perception of oleic acid in forty-six subjects classified for PROP taster status and genotyped for TAS2R38, CD36 and OBPIIa polymorphisms. L-Arg supplementation was effective in increasing the perceived intensity of oleic acid in most subjects. The lowest concentration was the most effective, especially in PROP non-tasters or medium tasters, and in subjects with at least an allele A in CD36 and OBPIIa loci. Density Functional Theory (DFT) calculations were exploited to characterize the chemical interaction between L-Arg and oleic acid, showing that a stable 1:1 oleate·ArgH+ adduct can be formed, stabilized by a pair of hydrogen bonds. Results indicate that L-Arg, acting as a 'carrier' of fatty acids in saliva, can selectively modify taste response, and suggest that it may to be used in personalized dietetic strategies to optimize eating behaviors and health.

Fig 1. DFT optimized structure of H-bonded adduct between oleic acid (right) and L-ArgH⁺ (left) calculated in water.

Oxygen atoms are depicted in red, nitrogen atoms in blue, carbon atoms in grey and hydrogen atoms in white.

Fig 2. Effect of L-Arginine (L-Arg) supplementation on oleic acid responsiveness.

(A) Percentage of subjects who showed an effective increase of perceived intensity ratings when the oleic acid was supplemented with three concentrations of L-Arg (5, 10 and 15 mmol/L). (B) Percentage increase of perceived intensity ratings by the subjects in which the three concentrations of L-Arg (5, 10 and 15 mmol/L) were effective. n = 46. Different letters on top of bars (a or b) indicate significant differences (p ≤ 0.0044; Fisher’s exact test). * = Significant difference with respect to the corresponding value assessed before supplementation (F_(1,20) = 8.1696, p = 0.0097; Repeated-measures ANOVA).

Fig 3. Percentage of subjects who showed an effective increase of responsiveness when oleic acid was supplemented with three concentration of L-Arg (5, 10 and 15 mmol/L).

(A) Data shown for each PROP taster group. (B) Data shown for each genotype of TAS2R3 gene. (C) Data shown for each genotype of CD36 gene. (D) Data shown for each genotype of OBPIIa gene. n = 46. Different letters on top of bars (a, b or c) indicate significant differences (p ≤ 0.045; Fisher’s exact test).

Fig 4. Percentage increase of perceived intensity ratings by the subjects in which L-Arg (5 mmol/L) was effective according to PROP taster status or polymorphisms of TAS2R38, CD36 (rs1761667) and OBPIIa (rs2590498) genes.

n = 33. * = Significant difference with respect to the corresponding value assessed before supplementation (p = 0.019; Fisher’s LSD test subsequent to repeated-measures ANOVA).