GPR120 agonists enhance the fatty orosensation when added to fat-containing system, but do not evoke it by themselves in humans

Involvement of GPR91 in the perception of the umami-like shellfish taste of succinate

Succinate is a key component of the characteristic umami-like taste of shellfish, which is similar to the umami taste elicited by glutamate, but is slightly more persistent and astringent. The taste receptors involved in the perception of succinate currently remain unknown. Therefore, we herein attempted to identify the taste receptors for succinate. We investigated whether cells heterologously expressing receptors associated with umami taste or succinate were activated by succinate and selected GPR91 as a candidate receptor. To verify the contribution of GPR91 to taste perception, the relationship between GPR91 activation and sensory activity was assessed using receptor assays and sensory evaluations. Our results suggest that the taste of succinate depends on the activation of GPR91. We propose that GPR91 functions as a gustatory receptor involved in the perception of the umami-like shellfish taste of succinate.

[Causes of taste hyposensitivity in daily life and health risks: including the taste of ‍fatty acids]

The sensory system detects the internal and external environment of the body and the stimulus trigger feedback loops toward the set point to maintain homeostasis, but if taste sensitivity has changed, we may consume more nutrients or loss of appetite. These can lead metabolic syndrome or malnutrition, which can lead to frailty. In this review, we examined which of the five basic tastes (sweet, umami, bitter, sour, and salty) is affected by aging. Next, we summarize the effects of oral bacteria and tongue coating on taste, which can cause problems such as bad breath and aspiration pneumonia. Even healthy people can change their taste sensitivity and pose health risks if they continue to eat certain taste substances on a daily basis. Furthermore, we summarize research from the discovery of the taste of fatty acids to the present, and discuss how the involvement of taste in food intake regulation contributes to homeostasis through a literature survey. Recently, a gut-brain circuit for fat preference has been identified. In the intestine, fatty acids are sensed by the same receptors as those in the taste buds of the tongue, and nutritional information is sent to the brain via the vagus nerve. It is very interesting that nerves that convey fatty acid-specific information have been discovered. In this way, taste system of the tongue and nutrition-sensing in the digestive tract are very similar, so we think it will be very meaningful to progress research by referring to each other.

Free fatty acid receptors beyond fatty acids: A computational journey to explore peptides as possible binders of GPR120

Free fatty acids receptors, with members among G protein-coupled receptors (GPCRs), are crucial for biological signaling, including the perception of the so called "fatty taste". In recent years, GPR120, a protein belonging to the GPCR family, drew attention as an interesting pharmacological target to cope with obesity, satiety and diabetes. Apart from long chain fatty acids, which are GPR120 natural agonists, other synthetic molecules were identified as agonists expanding the chemical space of GPR120's ligands. In this scenario, we unveiled peptides as possible GPR120 binders toward a better understanding of this multifaceted and relevant target. This study analyzed a virtual library collecting 531 441 low-polar hexapeptides, providing mechanistic insights on the GPR120 activation and further extending the possible chemical space of GPR120 agonists. The computational pipeline started with a narrow filtering of hexapeptides based on their chemical similarity with known GPR120 agonists. The best hits were tested through docking studies, molecular dynamics and umbrella sampling simulations, which pointed to G[I,L]FGGG as a promising GPR120 agonist sequence. The presence of both peptides in food-related proteins was thoroughly assessed, revealing they may occur in mushrooms, food-grade bacteria and rice. Simulations on the counterparts with D-amino acids were also performed. Umbrella sampling simulations described that GdIFGGG may have a better interaction compared to its all-L counterpart (-13 kCal/mol ΔG and -6 kCal/mol ΔG, respectively). Overall, we obtained a predictive model to better understand the underpinning mechanism of GPR120-hexapeptides interaction, hierarchizing novel potential agonist peptides for further analysis and describing promising food sources worth of further dedicated investigations.

Effects of TUG-891, a potent GPR120 agonist, on the physical and oral lipid- coating properties, and secretion of saliva

GPR120 agonists were recently shown to enhance the fatty orosensation in humans when added to vegetable oil or a low-fat food system, but did not evoke it by themselves. Furthermore, an emulsion prepared from vegetable oil had a stronger fatty orosensation than that prepared from mineral oil even though the physical properties of both emulsions were similar. To clarify the mechanisms underlying the enhancement of the fatty orosensation by GPR120 agonists, the present study investigated the effects of TUG-891, a potent GPR120 agonist, on physical and oral lipid-coating properties and the secretion of saliva. The addition of TUG-891 to a vegetable oil emulsion did not significantly change its physical properties, such as viscosity, particle distribution, interfacial tension, contact angle, frictional load, and ζ-electric potential, or the amount of the lipid coating remaining in the oral cavity. These results indicate that TUG-891 enhanced the fatty orosensation without changing the physical or oral lipid-coating properties of the emulsion. The addition of TUG-891 to a vegetable oil emulsion and whipped cream significantly increased the amount of saliva secreted. Therefore, TUG-891, a potent GPR120 agonist, may enhance the fatty orosensation by increasing the amount of saliva secreted.