“Cells” study refreshes understanding of intestines

A new paper in the leading academic journal, Cell, gives us a new insight into the big things in life : eating. Strange to say, although eating and eating in our lives occupy an indispensable position, the body is how not hungry, full, on this question, there is no exact answer.

You might say, feel the stomach support, you know it’s time to stop. Facts differ from intuition. The new study, led by Professor Zachary Knight of the University of California, San Francisco, found that the gut’s signal of “eating support” plays a greater role in suppressing eating. The unexpected findings also provide a powerful explanation for how bariatric surgery works.

In the stomach and intestines, there are a large number of nerve endings that monitor the internal organs, such as stress, disassociation, pain, temperature, specific chemicals, etc., which collect information on the nerves, known as the vagus nerve, that sends signals to the brain’s central center.

The scientists looked at the morphological structure of nerve endings and found that the vagus nerves that report gastrointestinal information can be divided into three categories: in the gut lining, arranged with mucous membrane endings, which detect hormone levels to reflect nutrient absorption to the brain; Known as the intra-neural plate-shaped endings (IGLE) for short, the sensation of pulling dilatation, and a class of nerve endings (IMa) arranged in the muscle, the function is not yet clear.

Typical types of lost neuronal sensory ends (Image Source: Resources 1)

As the main neural pathway for information from the intestines to the brain, the vagus nerve is blocked or stimulated, altering an animal’s appetite. But what kind of vagus nerve, what kind of signals do you collect, let the brain know that we are not eating enough?

To solve this unknown puzzle, “we decided to use modern genetic techniques for the first time to systematically study the types of cells that make up this pathway. Lead author Dr Ling Bai said.

With the help of single-cellRNA sequencing, the researchers conducted a “census” of stray nerve cells in mice, linking different molecular characteristics to different nerve endings and functions.

Next, with specific molecular labels, Dr. Bai and his colleagues used optogenetics to selectively stimulate various types of lost neurons with special light to test what kind of cells could stop mice from eating.

Different molecular markers can distinguish between different locations of the gastrointestinal tract and different types of vagus incoming nerves (Photo: Resources 1)

As expected, IGLE neurons that stimulate the stomach, the “gastric propped” signal, inhibit the mice from eating. Surprisingly, however, when the IGLE neurons in the intestines were stimulated, the “intestinal prognosis” signal was more effective in stopping the mice from eating, even if they were hungry after fasting;

At the same time, when stimulating these mechanical receptors in the gut, the researchers observed that the neurons responsible for hunger in the brain’s heart are indeed subject to lasting effects, further confirming that the brain is strongly “awakened” to eat the gut.

What the researchers didn’t expect was that the mucous membrane endings in the gut that feel various hormones did not affect animal seating when stimulated. “This is completely unexpected, because for decades, it has been generally believed that the gastric dilation receptors perceive the amount of food eaten, while the hormone receptors in the gut perceive the energy of the intake. Dr. Bai said.

The vagus nerve (Oxtr marker) that feels intestinal dilation is stimulated and the mice’s feeding is inhibited (Photo: Supplied)

These unexpected results also provide a whole new explanation for determining why bariatric surgery works.

In the treatment of extremely obese patients, one type of bariatric surgery is to remove part of the gastrointestinal tract to reduce the intestines, can effectively help patients reduce appetite and lose weight. There has been speculation in the past that this surgery magically curbs hunger may be due to the fact that food can quickly move from the stomach into the intestines, but the reasonbehind for the odd effect is not clear. The study found that food quickly enters the intestines, stretching the intestines quickly, activating the mechanical receptors of the vagus nerve, which powerfully signals stopping eating. But Professor Knight is also careful to say that this view needs to be further tested.

Dr. Ling Bai, the first author of the study, and Professor Zachary Knight, author of the newsletter (Photo: UCSF, Knight Task Force)

Interestingly, not so long ago Professor Knight’s team discovered that the feeling of “thirsty” was not just a signal from the throat, but that it was regulated by the intestines. Read: “Nature” on the same day two “heavy taste” study, scientists found the neural mechanism to control salt and water

Our understanding of the “diet” event is constantly improving.

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