Department of Nutrition, Faculty of Health Sciences, Kio University, 4-2-4 Umami-naka, Koryo, Kitakatsuragi, Nara 635-0832, Japan.
Health Science Research Center, Kio University, 4-2-4 Umami-naka, Koryo, Kitakatsuragi, Nara 635-0832, Japan.
Chem Senses. 2022 Jan 1;47. doi: 10.1093/chemse/bjac008.
In addition to the well-accepted taste receptors corresponding to the 6 basic taste qualities, sweet, salty, sour, bitter, umami, and fatty, another type of taste receptor, calcium-sensing receptor (CaSR), is located in taste bud cells. CaSR is called the kokumi receptor because its agonists induce koku (or kokumi), a Japanese word meaning the enhancement of flavor characteristics, such as thickness, mouthfulness, and continuity. Kokumi is an important factor in enhancing food palatability. γ-Glu-Val-Gly (EVG) is the most potent agonist of CaSR, which induces a strong kokumi flavor. However, no behavioral studies have been documented in animals using EVG. Here, we show that EVG at low concentrations that do not elicit a taste of its own enhances preferences for umami, fat, and sweet taste solutions in rats. An increased preference for inosine monophosphate (IMP) and Intralipos was the most dominant effect. NPS-2143, an antagonist of CaSR, abolished the additive effect of EVG on IMP and Intralipos solutions. These effects of EVG on taste stimuli are thought to occur in the oral cavity, because the effects of EVG were confirmed in a brief exposure test. The additive effects on IMP and Intralipos remained after the transection of the chorda tympani, indicating that these effects also occur in the palate and/or posterior part of the tongue. Moreover, the additive effects of EVG were verified in electrophysiological taste nerve responses. These results may partially provide the underlying mechanisms for EVG to induce kokumi flavor in humans.
除了与 6 种基本味觉（甜、咸、酸、苦、鲜、脂）相对应的公认味觉受体外，另一种味觉受体，钙敏感受体（CaSR），位于味蕾细胞中。CaSR 被称为“浓厚味受体”，因为其激动剂能诱导浓厚味（或浓厚味），这是一个日语词，意思是增强风味特征，如醇厚、浓郁和连续性。浓厚味是增强食物可口性的一个重要因素。γ-谷氨酰-缬氨酰-甘氨酸（EVG）是 CaSR 的最强激动剂，能诱导强烈的浓厚味。然而，在动物中还没有使用 EVG 进行行为研究的记录。在这里，我们发现，低浓度的 EVG 本身不会产生味道，但能增强大鼠对鲜味、脂肪和甜味溶液的偏好。最主要的效果是增加对肌苷单磷酸（IMP）和 Intralipos 的偏好。CaSR 的拮抗剂 NPS-2143 消除了 EVG 对 IMP 和 Intralipos 溶液的增效作用。EVG 对味觉刺激的这些作用被认为发生在口腔中，因为在短暂暴露测试中证实了 EVG 的作用。EVG 对 IMP 和 Intralipos 的增效作用在切断鼓索神经后仍然存在，表明这些作用也发生在腭和/或舌后部。此外，在味觉神经电生理反应中也验证了 EVG 的增效作用。这些结果可能部分解释了 EVG 在人类中诱导浓厚味的潜在机制。
