Cell: new research reveals for the first time that gut stretch tells us we're full

November 20, 2019 / BIOON / - -- we usually think that feeling full will stop us eating In a new study, however, researchers from institutions such as the University of California, San Francisco, found that stretch of the gut may play a greater role in making us feel full The relevant research results were published in the cell Journal on November 14, 2019, with the title of "genetic identification of vagal sensor neurons that control feeding" The corresponding author is Dr Zachary knight, neuroscientist at the University of California, San Francisco Picture from cell, 2019, DOI: 10.1016/j.cell.2019.10.031 You may not believe this, especially in the coming holiday season, but in the long run, your body is very good at keeping your weight in a very narrow range, which can be achieved by balancing how much you eat and how much energy you consume every day There are a lot of nerve endings in your gut, which play an important role in controlling your food intake These nerve endings monitor the contents of the stomach and intestines, and then send signals to the brain to promote or reduce your appetite Most scientists believe that this feedback involves hormone sensitive nerve endings in the gut that track the nutrients you eat and calculate when you're full, but so far no one has tracked the exact type of neurons that send these signals to the brain "Given the importance of diet in our lives, we still don't understand how our bodies know they're not hungry anymore when we eat," Knight said One of the challenges in answering this question is that thousands of sensory nerves are involved in collecting sensory information from the stomach and intestines There are many different types of sensory nerves, but they all transmit information back to the brain through a huge nerve bundle called vagus nerve Scientists can block or stimulate the activity of this nerve bundle and change the appetite of animals, but how to find out which vagal nerve endings caused this change? To solve this mystery, knight and his team (including the first author of the paper, Dr Ling BAI) have mapped the molecular and anatomical characteristics of neurons of vagal sensory cell type distributed in the stomach and intestine Their maps allow people to selectively stimulate different types of vagal neurons in mice, revealing that the intestinal stretch sensor can prevent hungry mice from eating A comprehensive map of the gut nervous system has revealed surprising new insights Scientists have previously classified gut sensory neurons into three categories based on the anatomical structure of their nerve endings: the nerve endings of the mucosal endings are arranged in the inner layer of the gut, and the kinin reflecting nutrient absorption is detected; IgE (endogenous laser array, The nerve endings are located in the muscle layer surrounding the stomach and intestines, sensing the physical stretch of the intestines; the function of ima (intramuscular array) is not clear, but they may also perceive stretch "The vagus nerve is the main neural pathway that carries information from the gut to the brain, but the identity and function of specific neurons that carry these signals are still poorly understood," Bai said We decided to use modern genetic technology for the first time to systematically characterize the cell types that make up the pathway " Bai and colleagues used these techniques to find that there are actually different types of mucosal ends - four of which were studied in detail by the researchers Some of these types are mainly found in the stomach, while others are mainly found in different parts of the intestine Each type is specifically used to sense specific combinations of nutrients related hormones They found that there were at least two different types of stretch sensitive IgE, one mainly in the stomach and the other in the gut To understand how these different types of nerves in the gut control appetite, Bai and her team used a technique called photogenetics, which involves genetically modifying specific populations of neurons so that they can be stimulated optically In the new study, they used this selective stimulation to test their ability to stop hungry mice from eating The researchers hope that stimulating IgE neurons that sense stretch in the stomach will stop the animal from eating But when they turned to stimulating different types of hormone sensitive mucosal endings in the gut, which are supposed to control appetite, they found that they did not affect animal feeding at all Instead, to their surprise, they found that stimulating the Igle stretch receptor in the gut was more effective in eliminating the appetite of hungry mice than eliminating the stretch receptor in the stomach "It's unexpected because for decades the traditional view in this field has been that the stretch receptor in the stomach can sense the amount of food you eat, and the gut hormone receptor can sense the energy content of food," Bai said These results raise important questions about how these stretch receptors are usually activated during eating and how to manipulate them to treat obesity The findings also offer a possible explanation for bariatric surgery, which treats extreme obesity by reducing the size of the intestine - why it is so effective in promoting long-term appetite and weight loss Scientists have been speculating for some time that one of the reasons why the operation is so effective in preventing hunger is that it causes food to enter the intestine quickly from the stomach, but its mechanism is not clear These new findings offer an answer: rapidly entering food stretches the gut, activating the vagal stretch sensor and powerfully preventing eating "Identifying the mechanism of weight loss caused by bariatric surgery is one of the biggest unsolved problems in metabolic disease research, so it's exciting that our research work can propose a new mechanism for this kind of surgery," Knight said However, at present, this idea still needs to be tested " These findings add to the scientific study of hunger and thirst Knight studies how the brain perceives the needs of the body and then produces specific behaviors to restore physiological balance, sometimes in surprising ways In the past few years, his lab has overturned the long-standing textbook theories of hunger and thirst For example, it was once thought that neurons in the brain stimulate diet by responding to nutrients and water balance in the body However, by accurately recording the activity of specific neurons in mice, Knight's team found that hunger neurons shut down after mice saw or smelled food, which seemed to predict food intake Similarly, thirsty neurons turn off when they first taste water, much earlier than any change in body fluid balance Knight's team also found warm sensing neurons that control temperature regulation, including the animal's response to heat More recently, his lab has turned its attention to the gut, studying how nutrients, salts and stretching in the stomach and gut affect these diet controlling neurons Knight, "we like to use unbiased methods like in vivo imaging to see how these systems work naturally It creates the chance to discover 'the unknown unknowns' -- we don't know what we should be looking for " (BIOON Com) reference: 1 Ling Bai et al Genetic identification of vagal sensor neurons that control feeding Cell, 2019, DOI: 10.1016/j.cell.2019.10.031 2 We know we're full because a streched Intel tell us so https://mediaexpress.com/news/2019-11-full-intel.html