Chitin, which provides crucial exoskeletal structure and protection to soft-bodied arthropods such as crustaceans, spiders and insects, may have a surprising role in being able to modulate metabolism and fight weight gain in mammals.
Chitin has been the focus of research into everything from stronger materials to better drug delivery. It's even been tabled to help fight malaria. In their mouse study, scientists from the Washington University School of Medicine in St. Louis have found that chitin triggers an immune system response in the gut, and suppressing the body's enzymes that fight chitin breakdown could provide a new avenue for obesity treatment.
“Obesity is an epidemic,” said Steven Van Dyken, an assistant professor of pathology and immunology. “What we put into our bodies has a profound effect on our physiology and on how we metabolize food. We’re investigating ways to counteract obesity based on what we learn about how the immune system is engaged by diet.”
When chitin is ingested, stomach cells activate production of chitinases, enzymes which break down the polysaccharide. The human body has two chitinases, chitotriosidase 1 (CHIT1) and acid mammalian chitinase (AMCase), which have long played roles in fighting pathogens containing chitin in their cell walls, including toxic fungi and the gut lining of parasitic nematodes. They've also been linked to inflammation associated with asthma and other immune response disorders.
In this study, three cohorts of mice were fed a high-fat diet; one group had their chitinase ability suppressed to be unable to break down chitin, another had regular chitinase production, and a third were not given any chitin. The animals that ate chitin and couldn’t break it down gained the least amount of weight and had the lowest body fat, compared to those that either didn’t eat chitin or did but could break it down.
The scientists believe that the immune response triggered by the animals that couldn’t degrade the chitin is key to how they were able to resist obesity despite their diet.
“We think chitin digestion mainly relies on the host's own chitinases," Van Dyken said. “The stomach cells change their enzymatic output through a process we refer to as adaptation. But it is surprising that this process is happening without microbial input, because bacteria in the gastrointestinal tract are also sources of chitinases that degrade chitin.”
The researchers now hope to take this to a human study, to see if adding chitin to diets while blocking chitinase production could have similar weight-control benefits.
Fortunately, while some adventurous eaters wouldn’t mind a bowl of crunchy crickets, chitin is also found in yeast and algae, in common edible mushrooms, and can be easily adapted into more palatable dietary supplements.
“We have several ways to inhibit stomach chitinases,” Van Dyken said. “Pairing those approaches with a chitin-containing food might have a very real metabolic benefit.”
The study was published in the journal Science.
Source: Washington University School of Medicine in St. Louis
