Summary: Ingested non-essential amino acids reduce appetite and promote movement in mouse models.
Source: ETH Zurich
In experiments with mice, the ETH Zurich researchers show that non-essential amino acids act as appetite suppressants and promote the urge to move.
His research is published in current biology and provides information about the neural mechanism that controls this behavior.
Protein can suppress appetite, so a high-protein diet can help people lose weight. That’s just one of the reasons this type of diet has become increasingly popular in recent years. Working with mice, the ETH Zurich researchers have now demonstrated a new mechanism by which the building blocks of protein, amino acids, curb appetite. Specifically, these are what are known as non-essential amino acids.
Of the 21 amino acids that our body requires, there are nine that it cannot produce on its own. They are called essential amino acids. Because we must obtain them through our diet, they have long been the focus of nutritional research. The other 12 amino acids are considered non-essential. The body can produce them on its own by altering other molecules.
Shown in mice
Both essential and non-essential amino acids are known to suppress appetite. However, for non-essential amino acids, the mode of action has not yet been demonstrated in living organisms.
Now, a group of researchers led by Denis Burdakov, professor of neuroscience at ETH Zurich, has shown for the first time in a living organism that non-essential amino acids influence the brain in a way that curbs appetite and promotes exercise.
The researchers first fed the mice a mixture of various non-essential amino acids or a sugar solution with the same number of calories (control group). Both groups of mice were then allowed to drink a shake, which they normally love.
While the control group drank large amounts, the mice that had been fed non-essential amino acids avoided theirs. Instead, they scoured their compound for alternative livelihood.
Rooted in evolutionary history
With additional experiments, the researchers were able to tease out the underlying mechanism, in which specialized nerve cells in the brain, orexin neurons, play the main role. Proteins that mice ingest through food are broken down in the intestine into their amino acids, which then enter the bloodstream. From there, the blood carries them to the brain.
Orexin neurons in the hypothalamus have receptors that specifically recognize nonessential amino acids. In response, they initiate a neural circuit that produces the behavioral changes described.
It is likely that this mechanism has its roots in evolutionary history. “Today we have enough access to all the nutrients and we have plenty of time to eat. In prehistoric times, when this mechanism was developed, that probably wasn’t the case,” says Paulius Viskaitis, a postdoc in Burdakov’s group and lead author of the study.
“Back then, it was advantageous for people to spend little time on a food source that consisted mostly of non-essential amino acids.” If eating non-essential amino acids promotes the need to move, the animal will seek out other food sources, which potentially contain more essential nutrients and are more important to the individual.
Viskaitis highlights that the results are transferable to humans and other animals, since this mechanism affects a region of the brain that is very old in terms of evolutionary history and occurs equally in all mammals and many other vertebrates.
Still, for people who want to lose weight, a diet that includes especially many non-essential amino acids cannot be recommended, says Viskaitis. Nutritional recommendations must be made on an individual basis and must also take into account health aspects.
About this appetite research news
Author: press office
Source: ETH Zurich
Contact: Press Office – ETH Zurich
Image: The image is in the public domain.
original research: Open access.
“Ingested nonessential amino acids recruit brain orexin cells to suppress feeding in mice” by Paulius Viskaitis et al. current biology
Summary
See also
Ingested nonessential amino acids recruit brain orexin cells to suppress feeding in mice
Reflexes
- Ingested nonessential amino acids (nAAs) activate orexin cells
- Cell optostimulation with nAAs or orexin increases exploration and reduces feeding
- CCK-sensitive vagal afferents are not required for nAA effects
- Ablation of orexin cells abolishes nAA modulation of feeding and scanning
Summary
Ingested nutrients are proposed to control mammalian behavior by modulating the activity of hypothalamic orexin/hypocretin neurons (HON). Previous in vitro The studies showed that nutrients ubiquitous in mammalian diets, such as non-essential amino acids (AAs) and glucose, modulate HON in different ways. Glucose inhibits HONs, while non-essential (but non-essential) AAs activate HONs. This latter effect is of particular interest because its purpose is unknown.
Here, we show that ingestion of a relevant dietary mix of non-essential AAs activates HONs and changes behavior from eating to exploring.
These effects persisted despite the ablation of a key communication pathway between the neural gut and the brain, cholecystokinin-sensitive vagal afferents. Behavioral change induced by ingested non-essential AAs was recapitulated by HON-targeted optostimulation and abolished in HON-deficient mice.
Furthermore, licking microstructure analysis indicated that intragastric optostimulation of non-essential AAs and HON reduces the size, but not the frequency, of eating episodes, implying that modulation of food palatability is a mechanism. for the suppression of food consumption. Taken together, these results suggest that a key purpose of HON activation by ingested nonessential AAs is to suppress food intake and restart food seeking.
We propose and discuss possible evolutionary advantages of this, such as optimizing the limited capacity of the stomach for the ingestion of essential nutrients.
