There is growing interest in relating taste perception to diet and healthy aging. However, there is still limited information on the influence of age, sex and genetics on taste acuity as well as on ...the relationship between taste perception and taste preferences. We have analysed the influence of age on the intensity rating of the five basic tastes: sweet, salty, bitter, sour and umami (separately and jointly in a "total taste score") and their modulation by sex and genetics in a relatively healthy population (men and women) aged 18⁻80 years (
= 1020 Caucasian European participants). Taste perception was determined by challenging subjects with solutions of the five basic tastes using standard prototypical tastants (6-n-propylthiouracil (PROP), NaCl, sucrose, monopotassium glutamate and citric acid) at 5 increasing concentrations (I to V). We also measured taste preferences and determined the polymorphisms of the genes taste 2 receptor member 38 (TAS2R38), taste 1 receptor member 2 (TAS2R38) and sodium channel epithelial 1 beta subunit (SCNN1B), as TAS2R38-rs713598, TAS1R2-rs35874116 and SCNN1B-rs239345 respectively. We found a statistically significant decrease in taste perception ("total taste score") with increasing age for all the concentrations analysed. This association was stronger for the higher concentrations (
= 0.028;
= 0.012;
= 0.005;
= 4.20 × 10
and
= 1.48 × 10
, for I to V in the multivariable-adjusted models). When we analysed taste qualities (using concentration V), the intensity rating of all the 5 tastes was diminished with age (
0.05 for all). This inverse association differed depending on the test quality, being higher for bitter (PROP) and sour. Women perceived taste significantly more intense than men (
= 1.4 × 10
for total taste score). However, there were differences depending on the taste, umami being the lowest (
= 0.069). There was a complex association between the ability to perceive a taste and the preference for the same. Significant associations were, nevertheless, found between a higher perception of sour taste and a higher preference for it in women. In contrast, the higher perception of sweet was significantly associated with a higher preference for bitter in both, men and women. The TAS2R38-rs713598 was strongly associated with bitter (PROP) taste (
= 1.38 × 10
), having a significant interaction with sex (
= 0.030). The TAS1R2-rs35874116 was not significantly associated with sweet, whereas the SCNN1B-rs239345 was associated (
= 0.040) with salty taste. In conclusion, the inverse association between age and perceived taste intensity as well as the additional influence of sex and some genetic polymorphisms give rise to large inter-individual differences in taste perception and taste preferences that should be taken into account in future studies and for applications in precision nutrition for healthy aging.
The human taste experience is the result of five basic taste qualities, namely sweet, salty, bitter, sour and umami. Sweet, bitter, and umami are mediated by G protein-coupled receptors (GPCRs), ...whereas sour and salt are modulated by specialized membrane channels. Taste perception starts with the interaction between a taste-active molecule (substance) and a specialized receptor located on the taste buds at the level of the cell membrane. Once the interaction has occurred, taste receptor cells are able to transduce the information content of the chemical stimulus into nerve signals directly to the brain. Therefore, the receptor-mediated recognition of taste molecules is the first episode leading to taste perception.
In this review, we provide a complete overview of in silico molecular modeling techniques applied to the study of umami, sweet, and bitter taste receptors. Structure-based computational tools, usually applied to investigate the binding mode of bioactive molecules into their targets and to rationally design new drug molecules, are proven equally useful in the field of chemical senses to shed light on the molecular acknowledgment of tastants.
The recent computational advancements in the taste research field, and particularly the computation-driven investigations of the tastant-receptor binding, provided a better understanding of the molecular mechanisms underlying food tastants’ sensing and could have an impressive contribution to the identification of new taste modulators in the future.
•Structure prediction of sweet, umami, and bitter taste receptors.•Binding modes' predictions of sweet, umami, and bitter molecules into their respective receptors.•Contribution of computational approaches to the identification of new taste modulators.
The variety of taste sensations, including sweet, umami, bitter, sour, and salty, arises from diverse taste cells, each of which expresses specific taste sensor molecules and associated components ...for downstream signal transduction cascades. Recent years have witnessed major advances in our understanding of the molecular mechanisms underlying transduction of basic tastes in taste buds, including the identification of the bona fide sour sensor H
+
channel OTOP1, and elucidation of transduction of the amiloride-sensitive component of salty taste (the taste of sodium) and the TAS1R-independent component of sweet taste (the taste of sugar). Studies have also discovered an unconventional chemical synapse termed “channel synapse” which employs an action potential-activated CALHM1/3 ion channel instead of exocytosis of synaptic vesicles as the conduit for neurotransmitter release that links taste cells to afferent neurons. New images of the channel synapse and determinations of the structures of CALHM channels have provided structural and functional insights into this unique synapse. In this review, we discuss the current view of taste transduction and neurotransmission with emphasis on recent advances in the field.
Aging may coincide with a declining gustatory function that can affect dietary intake and ultimately have negative health consequences. Taste loss is caused by physiological changes and worsened by ...events often associated with aging, such as polypharmacy and chronic disease. The most pronounced increase in elderly people's detection threshold has been observed for sour and bitter tastes, but their perception of salty, sweet, and umami tastes also seems to decline with age. It has often been suggested that elderly people who lose their sense of taste may eat less food or choose stronger flavors, but the literature has revealed a more complicated picture: taste loss does not appear to make elderly people prefer stronger flavors, but nutrition surveys have pointed to a greater consumption of sweet and salty foods.
Real-life eating habits thus seem to be more influenced by other, social and psychological factors. Elderly gustatory function is worth investigating to identify dietary strategies that can prevent the consequences of unhealthy eating habits in the elderly.
This paper discusses age-related changes in taste perception, focusing on their consequences on food preferences, and pointing to some strategies for preserving appropriate dietary habits in elderly people.
Taste buds are the transducing endorgans of gustation. Each taste bud comprises 50–100 elongated cells, which extend from the basal lamina to the surface of the tongue, where their apical microvilli ...encounter taste stimuli in the oral cavity. Salts and acids utilize apically located ion channels for transduction, while bitter, sweet and umami (glutamate) stimuli utilize G‐protein‐coupled receptors (GPCRs) and second‐messenger signalling mechanisms. This review will focus on GPCR signalling mechanisms. Two classes of taste GPCRs have been identified, the T1Rs for sweet and umami (glutamate) stimuli and the T2Rs for bitter stimuli. These low affinity GPCRs all couple to the same downstream signalling effectors that include Gβγ activation of phospholipase Cβ2, 1,4,5‐inositol trisphosphate mediated release of Ca2+ from intracellular stores and Ca2+‐dependent activation of the monovalent selective cation channel, TrpM5. These events lead to membrane depolarization, action potentials and release of ATP as a transmitter to activate gustatory afferents. The Gα subunit, α‐gustducin, activates a phosphodiesterase to decrease intracellular cAMP levels, although the precise targets of cAMP have not been identified. With the molecular identification of the taste GPCRs, it has become clear that taste signalling is not limited to taste buds, but occurs in many cell types of the airways. These include solitary chemosensory cells, ciliated epithelial cells and smooth muscle cells. Bitter receptors are most abundantly expressed in the airways, where they respond to irritating chemicals and promote protective airway reflexes, utilizing the same downstream signalling effectors as taste cells.
Taste receptor cells use multiple signaling pathways to detect chemicals in potential food items. These cells are functionally grouped into different types: Type I cells act as support cells and have ...glial-like properties; Type II cells detect bitter, sweet, and umami taste stimuli; and Type III cells detect sour and salty stimuli. We have identified a new population of taste cells that are broadly tuned to multiple taste stimuli including bitter, sweet, sour, and umami. The goal of this study was to characterize these broadly responsive (BR) taste cells. We used an IP.sub.3 R3-KO mouse (does not release calcium (Ca.sup.2+) from internal stores in Type II cells when stimulated with bitter, sweet, or umami stimuli) to characterize the BR cells without any potentially confounding input from Type II cells. Using live cell Ca.sup.2+ imaging in isolated taste cells from the IP.sub.3 R3-KO mouse, we found that BR cells are a subset of Type III cells that respond to sour stimuli but also use a PLCbeta signaling pathway to respond to bitter, sweet, and umami stimuli. Unlike Type II cells, individual BR cells are broadly tuned and respond to multiple stimuli across different taste modalities. Live cell imaging in a PLCbeta3-KO mouse confirmed that BR cells use this signaling pathway to respond to bitter, sweet, and umami stimuli. Short term behavioral assays revealed that BR cells make significant contributions to taste driven behaviors and found that loss of either PLCbeta3 in BR cells or IP.sub.3 R3 in Type II cells caused similar behavioral deficits to bitter, sweet, and umami stimuli. Analysis of c-Fos activity in the nucleus of the solitary tract (NTS) also demonstrated that functional Type II and BR cells are required for normal stimulus induced expression.
The mammalian tongue contains gustatory receptors tuned to basic taste types, providing an evolutionarily old hedonic compass for what and what not to ingest. Although representation of these ...distinct taste types is a defining feature of primary gustatory cortex in other animals, their identification has remained elusive in humans, leaving the demarcation of human gustatory cortex unclear. Here we used distributed multivoxel activity patterns to identify regions with patterns of activity differentially sensitive to sweet, salty, bitter, and sour taste qualities. These were found in the insula and overlying operculum, with regions in the anterior and middle insula discriminating all tastes and representing their combinatorial coding. These findings replicated at super-high 7 T field strength using different compounds of sweet and bitter taste types, suggesting taste sensation specificity rather than chemical or receptor specificity. Our results provide evidence of the human gustatory cortex in the insula.
Understanding taste is key for optimizing the palatability of seaweeds and other non‐animal‐based foods rich in protein. The lingual papillae in the mouth hold taste buds with taste receptors for the ...five gustatory taste qualities. Each taste bud contains three distinct cell types, of which Type II cells carry various G protein‐coupled receptors that can detect sweet, bitter, or umami tastants, while type III cells detect sour, and likely salty stimuli. Upon ligand binding, receptor‐linked intracellular heterotrimeric G proteins initiate a cascade of downstream events which activate the afferent nerve fibers for taste perception in the brain. The taste of amino acids depends on the hydrophobicity, size, charge, isoelectric point, chirality of the alpha carbon, and the functional groups on their side chains. The principal umami ingredient monosodium l‐glutamate, broadly known as MSG, loses umami taste upon acetylation, esterification, or methylation, but is able to form flat configurations that bind well to the umami taste receptor. Ribonucleotides such as guanosine monophosphate and inosine monophosphate strongly enhance umami taste when l‐glutamate is present. Ribonucleotides bind to the outer section of the venus flytrap domain of the receptor dimer and stabilize the closed conformation. Concentrations of glutamate, aspartate, arginate, and other compounds in food products may enhance saltiness and overall flavor. Umami ingredients may help to reduce the consumption of salts and fats in the general population and increase food consumption in the elderly.
PDF
