Institute for Innovation, Ajinomoto Co., Inc., Japan.
J Pharmacol Sci. 2012;118(2):138-44. doi: 10.1254/jphs.11r06fm. Epub 2012 Jan 27.
The gustatory and visceral stimulation from food regulates digestion and nutrient utilization, and free glutamate (Glu) release from food is responsible for the umami taste perception that increases food palatability. The results of recent studies reveal a variety of physiological roles for Glu. For example, luminal applications of Glu into the mouth, stomach, and intestine increase the afferent nerve activities of the glossopharyngeal nerve, the gastric branch of the vagus nerve, and the celiac branch of the vagus nerve, respectively. Additionally, luminal Glu evokes efferent nerve activation of each branch of the abdominal vagus nerve. The intragastric administration of Glu activates several brain areas (e.g., insular cortex, limbic system, and hypothalamus) and has been shown to induce flavor-preference learning in rats. Functional magnetic resonance imaging of rats has shown that the intragastric administration of Glu activates the nucleus tractus solitarius, amygdala, and lateral hypothalamus. In addition, Glu may increase flavor preference as a result of its postingestive effect. Considering these results, we propose that dietary Glu functions as a signal for the regulation of the gastrointestinal tract via the gut-brain axis and contributes to the maintenance of a healthy life.
食物的味觉和内脏刺激调节消化和营养利用，食物中游离谷氨酸 (Glu) 的释放负责鲜味感知，从而增加食物的美味。最近的研究结果揭示了 Glu 的多种生理作用。例如，将 Glu 应用于口腔、胃和肠道的腔内会分别增加舌咽神经、迷走神经胃支和迷走神经腹腔支的传入神经活动。此外，腔内 Glu 会引起腹部迷走神经各个分支的传出神经激活。胃内给予 Glu 会激活多个脑区（如脑岛皮质、边缘系统和下丘脑），并已证明可诱导大鼠产生味觉偏好学习。对大鼠的功能性磁共振成像显示，胃内给予 Glu 会激活孤束核、杏仁核和外侧下丘脑。此外，Glu 可能会通过其摄食后作用来增加风味偏好。考虑到这些结果，我们提出膳食 Glu 通过肠-脑轴作为胃肠道调节的信号，有助于维持健康的生活。
