According to the study, published in the journal Immunity, mice that were switched to a so-called ketogenic diet showed significantly reduced inflammation of the respiratory tract.
Asthma patients react even to low concentrations of some allergens with severe inflammation of the bronchi. This is also accompanied by increased mucus production, which makes breathing even more difficult, the researchers said.
A central role here is played by cells of the innate immune system, which were only discovered a few years ago and are called Innate Lymphoid Cells (ILC). They perform an important protective function in the lungs by regenerating damaged mucous membranes. For this purpose, they produce inflammatory messengers from the group of cytokines, which stimulate the division of the mucosal cells and promote mucus production.
This mechanism is normally very useful: It allows the body to quickly repair damage caused by pathogens or harmful substances. The mucus then transports the pathogens out of the bronchial tubes and protects the respiratory tract against re-infection.
"With asthma, however, the inflammatory reaction is much stronger and longer than normal. The consequences are extreme breathing difficulties, which can even be life-threatening," said study researcher Christoph Wilhelm from the University of Bonn in Germany.
The ILCs multiply rapidly during this process and produce large amounts of proinflammatory cytokines. Scientists hope that if their division could be slowed down, it may be possible to bring the excessive reaction under control. In fact, the results now published point in exactly this direction.
"We have investigated which metabolic processes are active in the ILCs when they switch to reproduction mode. Then we tried to block these metabolic pathways and thereby reduce the speed at which the cells divide," explained said study researcher Fotios Karagiannis.
Some metabolic pathways were in fact significantly more active in dividing ILCs. They primarily ensure that the cells are supplied with energy and with the building blocks they require for reproduction. The latter include, for example, fatty acids that are needed to make the cell membrane. This forms a thin skin with which cells separate themselves from their surroundings.
"Activated ILCs, therefore, absorb fatty acids from their environment and store them in their interior in small droplets for a short time, before they utilise them for energy or building membranes," explained Karagiannis.
But what happens if cells are forced to use these fatty acids elsewhere? To answer this question, the researchers put asthmatic mice on a diet that contained mainly fats, but hardly any carbohydrates or proteins.
With this diet, also known as a ketogenic diet, the cell metabolism changes: The cells now get the energy they need from burning fat. However, this means that they lack fatty acids, which they need for the formation of new membranes during cell division."
As a consequence, the division activity of the ILCs in the rodents fed a special diet decreased - dramatically: Normally, contact with allergens increases the number of ILCs in the bronchi fourfold," said Wilhelm. "In our experimental animals, however, it remained almost unchanged. Both mucus production and other asthma symptoms decreased accordingly," Wilhelm added.