Around 2 billion people around the world eat insects to supplement their diet, according to the United Nations' Food and Agriculture Organization. This practice, known as entomophagy, is not only due to food scarcity, since insects are already a staple food in Africa, Asia, and Latin America.
Researchers have been considering insects as a potential source of alternative proteins and other vitamins and minerals. A recent study also suggests that the shells of insects contain nutrients that can improve a mammal's metabolism.
Bug Diet for Improved Metabolism
At the Washington University in St. Louis (WUSL), a study was conducted by a team of researchers where they fed mice with a diet that included chitin. It resulted in the animal's stomach being distended, triggering a specialized immune response. The diet led to the production of a unique gut enzyme called AMCase which is needed in digesting chitin. Additionally, it also resulted in the activation of cells that regulate fat tissues.
The team wanted to figure out which parts of the insects are most nutritious in order to develop ways of reaping their nutritional benefits. To answer this question, the mice were fed chitin along with a high-fat diet. They found out that this group of mice showed improved metabolic activities compared to mice that were fed a high-fat diet without chitin.
To explore more into the mechanisms, the scientists impaired the ability of some mice to produce AMCase enzyme, reducing their ability to digest chitin. After feeding these mice with a high-fat diet alongside chitin, these mice showed resistance to weight gain even when fed a high-fat diet simultaneously.
The team noted an increase in type 2 innate lymphoid cells (ILC2) in this group of mice. These cells, which were a byproduct of the chitin-triggered immune response, were recently found to be involved in regulating fat tissues.
According to immunologist Steven Van Dyken, it is possible that chitin digestion mainly depends on the host's own chitinases. In this mechanism, the enzymatic outputs are changed by the stomach cells through the process of adaptation. However, it is surprising to discover that this process happens without the need for microbial input, since bacteria in the gastrointestinal tract also provide chitinases that degrade chitin.
In the mouse models, it was not bacteria which produced the enzymes needed to break down chitin. When the mammal's ability to digest dietary chitin was disrupted, scientists figured out a possible way to extend the immune and metabolic benefits of chitin in the gut.
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Evolutionary History of Chitin Digestion
Chitin is an abundant polysaccharide present in the exoskeletons of insects and in crustacean shells and fungal cell walls. It is also the second most abundant biopolymer after cellulose.
Mammals do not normally produce enzymes which are strong enough to break down polysaccharides in their diet, but chitin seems to be an exception as it has deep evolutionary origins. Studies suggest that before the dinosaurs got extinct, the ancient mammals once fed on insects at much higher rates than they do today. It was also believed that some mammals adapted to chitin digestions long ago.
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