Since the 1960s, scientists have studied the endocannabinoid system to better understand the collection of molecules and receptors in the body that respond to marijuana. As one paper put it, "the endocannabinoids are literally a bridge between body and mind." A recent study suggests a new use for that bridge: It may help calm the gut, offering potential treatments for type 1 diabetes and colitis, a type of inflammatory bowel disease. Even more importantly, it suggests important connections between the brain, gut, and immune system.
Researchers at the University of Connecticut looked at receptors for capsaicin, the chemical in chili peppers that provokes that mouth-on-fire sensation when you take a bite. When mice were fed capsaicin, it bonded with receptors throughout the gastrointestinal tract and produced an endocannabinoid compound called anandamide. Mice fed capsaicin had less inflammation in their guts than mice who didn't get it. When researchers looked at what was going on at the molecular level, it was the anandamide that calmed the mice's immune systems; feeding the mice anandamide directly had the same gut-calming effects. Overall, the researchers said capsaicin (and the resulting anandamide) effectively cured the mice of type 1 diabetes—an autoimmune disease where immune cells attack the pancreas—by reducing inflammation in the pancreatic lymph node.
The brain also has receptors for anandamide, which is how you actually recognize that chili peppers are spicy: The receptor triggers a nerve that tells your brain as much. "We have found a common language in the molecules and the receptors in the immune system and the nervous system," says Pramod Srivastava, professor of immunology and medicine at UConn Health School of Medicine and an author of the paper, published in Proceedings of the National Academy of Sciences. "That itself has enormous potential for the whole field."
Anandamide is just one part of that language, which scientists are still investigating. While feeding rats anandamide did call on immune cells that fight inflammation, it's not yet clear how or why anandamide can relay messages between the gut and the brain. There are still open questions about the precise molecular pathway involved—and whether, say, eating marijuana might have similar effects.
Colitis is an inflammatory bowel disorder that Srivastava wants to investigate. That means continuing to work with mice to see whether anandamide has an effect on their gut inflammation; it also might mean looking for effects in humans. Though it's difficult to get federal permission for clinical marijuana research, researchers could draw on data about people who are already using it. He's thinking about gathering data from Colorado, where recreational weed dispensaries have been open since 2014, to see whether the severity of colitis has changed for regular users.
Once collected, that kind of evidence could suggest whether anandamide or other cannabinoids could treat some disorders in the stomach, pancreas, intestines, and colon. (It might also validate some of the anecdotal advice about using weed for the same problems.) Simply knowing that communication pathways exist among the immune system, brain, and gut—well, that opens up fascinating new realms for study.
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