Expression of the candidate fat taste receptors in human fungiform papillae and the association with fat taste function

Abstract

Significant experimental evidence supports fat as a taste modality; however, the associated peripheral mechanisms are not well established. Several candidate taste receptors have been identified, but their expression pattern and potential functions in human fungiform papillae remain unknown. The aim of this study is to identify the fat taste candidate receptors and ion channels that were expressed in human fungiform taste buds and their association with oral sensory of fatty acids. For the expression analysis, quantitative RT-PCR (qRT-PCR) from RNA extracted from human fungiform papillae samples was used to determine the expression of candidate fatty acid receptors and ion channels. Western blotting analysis was used to confirm the presence of the proteins in fungiform papillae. Immunohistochemistry analysis was used to localise the expressed receptors or ion channels in the taste buds of fungiform papillae. The correlation study was analysed between the expression level of the expressed fat taste receptors or ion channels indicated by qRT-PCR and fat taste threshold, liking of fatty food and fat intake. As a result, qRT-PCR and western blotting indicated that mRNA and protein of CD36, FFAR4, FFAR2, GPR84 and delayed rectifying K+ channels are expressed in human fungiform taste buds. The expression level of CD36 was associated with the liking difference score (R -0·567, β=-0·04, P=0·04) between high-fat and low-fat food and FFAR2 was associated with total fat intake (ρ=-0·535, β=-0·01, P=0·003) and saturated fat intake (ρ=-0·641, β=-0·02, P=0·008).

Keywords: DRK delayed rectifying K+; GPCR G-protein-coupled receptors; qRT-PCR quantitative RT-PCR; Delayed rectifying K+ channels; Fat taste; Fat taste receptors; Fatty acid metabolism; Immunohistochemistry; RT-PCR; Western blot.