Mechanisms on the chemical reception of dietary fat in the oral cavity and its signaling to the brain

虽然大家都知道我们偏爱高脂肪的饮食，但我们仍然不知道是什么让饮食中的脂肪如此美味。最近的证据表明，膳食脂肪，特别是脂肪酸，可能在口腔中被识别出来。这些结果在脂肪酸的接收机制上有些不一致但它们至少支持了一个理论，即舌头对脂肪的化学接收不是以甘油三酯为中心，即能量储存形式，而是以新陈代谢更活跃的形式，脂肪酸为中心。然而，食物中绝大多数的脂肪成分是甘油三酯，这与口腔中越来越多的脂肪酸接收结果相矛盾。甘油三酯被认为是脂肪酸的机制尚不清楚。在本研究中，我们检测到少量但显著量的脂肪酸~由叶氏腺分泌的舌脂酶裂解。把放射性甘油三酯涂在乳突上，在1到3秒内就能产生接近芽细胞的脂肪酸，这个速度足以让人尝到脂肪的味道。在人乳头叶状叶中也观察到类似的酶活性，认为其产生的脂肪酶较少。此外，给甘油三酯和奥利司他（一种唇部抑制剂）的小鼠没有表现出对它的偏好。奥利司他本身并没有抑制液体的摄入。这些发现表明舌脂肪酶对于品尝高脂肪食物很重要。

Though it is generally known that we have a preference for high fat diets, we still do not know what makes dietary fat so tasty. Recent evidence suggests that dietary fat, especially fatty acids, may be recognized in the oral cavity. These results has some inconsistency about mechanisms on, reception of fatty acids but they at least support the theory that chemical reception of fats in the tongue centers not on triglycerides, the energy storage form, but on the, more metabolically active form, fatty acids. However, vast majority of fat component in foods is triglycerides, contradicting with the growing results of being fatty acid reception in oral cavity. Mecanisms have been unclear underlying the,acception of, triglycerides as fatty acids. In the present study, we detected small but significant amount of fatty acids ~ cleaved by lingual lipase secreted from Ebner's gland opening papillae vallatae and papillae foliate. Radioactive triglycerides applied on the papillae vallatae produced fatty acids close on bud cells within 1 to 3 sec which is enough speed to taste fat. The similar enzyme activity was observed in the human papillae foliate which was, beleaved producing few lipase. Moreover, mice offered triglycerides with orlistat a lipse-inhibitor did not show any preference to it. Orlistat, itself did not inhibit the fluid intake. These findings suggest that lingual lipase is important for tasting the fatty foods.