A pellet has been used to electrically stimulate stomach cells in pigs to increase levels of ghrelin, a hormone that regulates appetite and reduces nausea. If the technology translates to humans, it could treat nausea, vomiting and loss of appetite in people who suffer from eating disorders, or who are receiving treatment for cancer.
Current interventions that use electrical stimulation to reduce gastrointestinal symptoms require invasive surgery. Therefore, Giovanni Traverso He and his colleagues at the Massachusetts Institute of Technology designed a non-invasive capsule the size of a raisin that provides tiny gaps.
Inside the capsule, a battery generates electric currents that travel along a gold wire coiled around the outside. Grooves etched into the surface of the capsule divert the fluid so that the wires can electrically stimulate receptors in the stomach tissue that trigger the release of ghrelin. The device is coated in a thin casing that dissolves once it reaches the stomach to ensure that it does not stimulate the tissues in the esophagus.
Traverso and his team tested the capsule in 13 pigs that fasted overnight and were given anesthetics. Eleven animals received 20 minutes of stimulation while the other two received no stimulation.
The researchers measured blood levels of ghrelin before and 10 minutes after the stimulation. They found that on average, ghrelin increased by about 40 percent in the pigs that underwent the stimulation, while ghrelin decreased by about 50 percent in the pigs that did not.
“The levels we see are comparable to the levels we would expect to induce appetite or suppress nausea, but we didn’t evaluate [symptoms] in animals,” Traverso says. “Part of the next steps involves understanding in humans whether nausea, for example, can be treated using this system.”
All the animals expelled the capsule within two weeks, Traverso says—a typical time period for pigs. Tissue samples collected from his stomach, duodenum and colon showed no changes or signs of trauma, suggesting the therapy was safe.
“To my knowledge, this is the first ingested device that can provide gastrointestinal electrical stimulation,” says Stavros Zanos at the Feinstein Institutes for Medical Research in New York. The technique can be tweaked to deliver electrical stimulation to other gastrointestinal tissues, such as the colon.