Ghrelin Gly90Leu and Ghrelin Receptor Gly57Gly Gene Variants Are Not Associated with Saltiness Intensity Perception and Pleasantness Ratings

Abstract

Aims: The salty taste modality is modulated by epithelial sodium channel (ENaC) and Transient Receptor Potential Vanniloid (TRPV1) ionic channel and more recently, the gastric hormone ghrelin and its signaling system are also thought to play a role. Taste perception plays an important role in modulating food preference, and intake and is partly determined by genetic variations in chemoreceptor genes. For the salty taste modality, no studies have yet identified any genetic determinants of salt taste in humans. Nevertheless, a single study has identified that common variations in genes encoding for TRPV1 (TRPV1) and ENaC (SCNN1B) may influence the perception of salt solutions in humans, while it is currently unknown whether it would be the same for ghrelin and its cognate receptor, GHSR. Therefore, the primary objective of this study was to investigate the association of Ghrelin Gly90Leu and GHSR Gly57Gly gene polymorphisms with individual’s saltiness intensity perception and pleasantness ratings. Study Design: A convenience sampling method was practiced in this study. The sampling was carried out among students between the age of 18–25. Place and Duration of Study: Universiti Tunku Abdul Rahman (UTAR), Perak campus, between January to December, 2011. Methodology: We recruited 166 Malaysian university students (mean age: 20.33±1.68; 75 males, 91 females; 152 ethnic Chinese, 14 Indians; 113 normal weight, 53 overweight) by convenience sampling. Low and high sodium concentrations of foods, solutions and broths were tasted and rated for their perceived intensity and pleasantness using generalized Labeled Magnitude Scale and Labeled Affective Magnitude scale, respectively. Results: The minor allele frequencies (MAF) of Ghrelin Gly90Leu and GHSR Gly57Gly were 0.48 and 0.31, respectively. Only the perceived intensity of salted egg was significantly different among Ghrelin Gly90Leu genotypes, where the individuals with T318T and A318T genotypes rated the intensity significantly higher than those with the A318A genotype.  Conclusion: In conclusion, Ghrelin Gly90Leu and GHSR Gly57Gly SNPs did not serve as markers for individual’s saltiness intensity perception and pleasantness ratings, at least among Malaysian subjects in this study. This suggests that the ghrelin signaling mechanism in modulating salty taste responsivity in inconclusive at the moment, as the positive findings in mice might not be translatable to humans.