Taste and smell synergistically increase appetite, meaning and application to animals

Taste and smell synergistically increase appetite, meaning and application to animals

Taste cells can also “smell”

The sense of smell can be subdivided into pre-nasal smell and post-nasal smell. Pre-nasal smell means that the aroma enters from the nasal cavity and reaches the olfactory cortex of the nose. In short, it is what we usually smell. Enter, through the oral and nasal passages into the olfactory skin cells, also known as oral olfaction. Many people equate smell with taste, but the unique flavor of most foods and beverages comes more from smell than taste. As many as 80% of the time we are eating olfactory stimuli rather than taste. Taste detects sweet, salty, sour, bitter and umami molecules on the tongue, helping to assess the nutritional value and potential toxicity of foods we put in our mouths. Smell provides detailed information about the flavor quality of the food, for example, is it banana, licorice or cherry? The brain combines taste, smell, and other sensory inputs to create multimodal taste sensations. Until now, it was generally accepted that taste and smell are separate sensory systems that do not interact until their respective information reaches the brain. However, researchers at the Monell Research Center used genetic and biochemical methods to probe taste cell cultures and found that cultured taste cells can respond to odorant molecules in a manner similar to olfactory receptor cells. These findings are the first to demonstrate functional olfactory receptors in human taste cells, suggesting that a single taste cell can contain both taste and olfactory receptors. These results suggest that we can make improvements based on odor when developing taste modulators. The relationship between smell and taste is very important. For example, if you taste apple mash and mashed potatoes with your nose, you will find that the difference between the two is less obvious, and the taste of the two tastes is also different than when you do not pinch your nose. This suggests that olfactory functions are correlated with taste discrimination.

Why do animals like sweetness?

From an evolutionary point of view: Substances with sweet taste tend to have higher energy. For example, carbohydrates are the first choice for many organisms to obtain energy, which is why we gradually like sweet tastes during the long evolutionary process. From a physiological point of view: Sweetness as a sensation begins on the tongue. When sweet taste ligands stimulate receptors on taste cells such as T1R2, T1R3, the resulting signal is transmitted through the G protein, which activates pleasure-producing brain pathways, where sweetness perception and pleasure are produced. The cerebral cortex translates “need” and “like” signals. Studies have shown that sweet taste receptors are also present in the gastrointestinal tract as well as in the nasal epithelium, islet cells, sperm and testis. The sweet taste receptors in different parts play different physiological functions.

Why animals prefer sucrose

We often use sucrose’s sweetness as a standard when evaluating sweeteners, so why animals tend to prefer sucrose between sucrose and artificial sweeteners. Scientists found that when fruit flies lick real sugar, six neurons are activated to release the corresponding hormone, which has receptors in the gut and brain. This hormone promotes digestion, allowing the flies to lick more nutrients. Drosophila flies, on the other hand, were unable to activate these neurons when they licked the sweetener, nor could they generate a hormone-digestive response, because the sweetener has no nutritional or energy value. In another experiment, the researchers fed the rats with glucose and sucralose, respectively, and found that when the rats were fed with glucose, the dopamine was secreted in both the dorsal and ventral regions of the striatum; When sucralose-fed rats, only the ventral region of the striatum secretes dopamine. From these experiments we can learn that sweetness and energy respond differently in brain neurons, with the dorsal striatal region responsible for sugar energy response and the ventral striatum region responsible for sugar response. Sweetness reacts. Nutritious sweeteners activate both regions simultaneously, causing a digestive response in the gastrointestinal tract.

Differences in the body’s sensitivity to sweetness

There are differences in sweet taste sensitivity and preference among different animals. Monell scientists conducted an experiment and selected 243 pairs of identical twins, 452 pairs of fraternal twins and 511 individuals. A total of 1901 people, of which 53.8% female. They studied changes in the intensity of sweetness perception in these individuals, using nutritive sugars such as glucose and fructose; and non-nutritive sweeteners such as NHDC and aspartame. Test results showed that the perceived intensity of all four sweeteners decreased with age (2-5% per year). At the same time, patients with a history of otitis were more sensitive to sweet taste, and the heritability of nutritive sugars and high-potency sweeteners was similar, suggesting that a genetic pathway may be shared between nutritive sugars and high-potency sweeteners perception. At the same time, this result also suggests whether we should not be limited to a small range of sensory evaluation in the evaluation of sweeteners, and consider more instrument-assisted evaluation methods.

The meaning of bitterness to animals

Bitterness can prevent animals from ingesting toxic and harmful substances, and plays a particularly important role in the survival of animals. The production of bitter taste depends on the interaction between bitter substances and bitter taste receptors. Bitter taste receptors exist in human taste bud cells. Bitter taste receptors are a class of G protein-coupled receptors, and their activation can convert extracellular stimuli into intracellular signals. Therefore, it has been regarded as an important drug target to regulate various physiological functions of organisms. Bitter taste receptor genes are not only expressed in the oral cavity, but also in tissues such as the respiratory tract, digestive tract, heart, brain, and even testis. Its function is also different in different parts.

Differences in animal tolerance to bitterness

The study found that the number of bitter receptor genes was related to the proportion of plants in the food. Herbivorous species had more bitter receptor genes than carnivorous species. This may be because bitter substances are widely distributed in the food of herbivores, so herbivore bears are able to recognize a higher number of bitter compounds. A modest reduction in the sensitivity of herbivores to bitterness could prevent starvation, and more importantly, herbivores may have acquired detoxification mechanisms, such as fermentation by rumen microorganisms in ruminants, to dispose of ingested toxins. In conclusion, herbivores are able to recognize higher numbers of bitter compounds and are also behaviorally and physiologically more tolerant of bitter compounds.

Common bitter substances in feed

There are many common bitter substances in feed. Tannins are one of the most common bitter anti-nutritional factors. This anti-nutritional effect has a dose effect. Low concentrations of condensed tannins can produce a certain positive nutritional effect on animals, but high concentrations can lead to anti-nutritional effects. Soy isoflavones are widely present in energy feed containing soybean, and have a certain bitter taste, which makes animals have a certain aversion to energy feed containing soybean. There are also some bitter substances in the feed, such as some bitter alkaloids in the feed containing leguminous plants, which have a certain antioxidant effect on animal feed.

Inhibit bitterness in feed

Low concentrations of bitter substances can have certain health care effects on animals, but high concentrations can lead to poisoning and even death. Therefore, it is particularly important to inhibit the production of bitterness in the feed. Amino acid derivatives and peptides are known bitterness masking agents, which can inhibit the expression of bitterness receptor genes, and are widely used in animal feed additives to eliminate bitterness in feeds. AMP and its analogs can attach to bitter taste receptor cells and reduce bitter taste perception by reducing the level of taste neurotransduction. Phosphatidic acid inhibits the bitter taste effect by competitive binding. GIV3727 is a small molecule bitter receptor antagonist that inhibits the response of bitter substances in saccharin and acesulfame potassium to receptors. Besides, there are some substances such as cyclodextrin, fructan, tannin, etc., which can reduce the bitter taste by inhibiting the reaction between bitter molecules and receptors, without affecting other taste receptors on acid, sweet and salty. , umami perception

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