Expanding the role of bitter taste receptor in extra oral tissues: TAS2R38 is expressed in human adipocytes

Raffaella Cancello,Giancarlo Micheletto,Dorela Meta,Rosalia Lavagno,Emanuele Bevilacqua,Valerio Panizzo,Cecilia Invitti

doi:10.1080/21623945.2019.1709253

Abstract

ABSTRACT Increasing evidence indicates that taste receptors mediate a variety of functions in extra-oral tissues. The present study investigated the expression of bitter taste receptor TAS2R38 in human adipocytes, the possible link with genetic background and the role of TAS2R38 in cell delipidation and lipid accumulation rate in vitro. Subcutaneous (SAT) and visceral (VAT) adipose tissues were collected in 32 obese and 18 lean subjects. The TAS2R38 gene expression and protein content were examined in whole tissues, differentiated adipocytes and stroma-vascular fraction cells (SVF). The P49A SNP of TAS2R38 gene was determined in each collected sample. The effect of two bitter agonists (6-n-propylthiouracil and quinine) was tested. TAS2R38 mRNA was more expressed in SAT and VAT of obese than lean subjects and the expression/protein content was greater in mature adipocytes. The expression levels were not linked to P49A variants. In in vitro differentiated adipocytes, bitter agonists induced a significant delipidation. Incubation with 6-n-propylthiouracil induced an inhibition of lipid accumulation rate together with an increase in TAS2R38 and a decrease in genes involved in adipocyte differentiation. In conclusion, TAS2R38 is more expressed in adipocytes of obese than lean subjects and is involved in differentiation and delipidation processes.

Highlights

The sense of taste acts as a nutrient-sensing system and may be considered a kind of detection system, informing us of suitability to swallow or reject food
The TAS2R38 mRNA was more expressed in whole SAT and visceral adipose tissue (VAT) of obese than lean subjects (p < 0.05) (Figure 1(a)), and was not significantly different between sexes in both adipose tissue depots
The P49A variants of TAS2R38 gene were analysed in a total of 47 adipose tissue samples by restriction fragment length polymorphisms (RFLP) (Figure 2 (a))

Summary

Introduction

The sense of taste acts as a nutrient-sensing system and may be considered a kind of detection system, informing us of suitability to swallow or reject food Any alteration of this system might contribute to an excessive energy intake and weight gain [1]. Some evidence demonstrate that overweight/obese subjects have a lower sensitivity to all taste stimuli than normal weight individuals [3,4] suggesting that the higher taste threshold may be involved in the excessive consumption of food This finding, has not been shared by other studies due to the different techniques used and the confounding factors affecting taste perception (i.e. sex, age, smoking/ drinking habits, experiences, socio-cultural habits and genetic differences). PROP sensitivity is considered a proxy of general taste ability as it is associated with the sensitivity to other oro-sensory stimuli [5]

Methods

Results

Conclusion