The ingestible “electroceutical” capsule stimulates hunger-regulating hormones. MIT News

Hormones released by the stomach, such as ghrelin, play an important role in stimulating appetite. These hormones are produced by endocrine cells, part of the enteric nervous system that control hunger, nausea, and satiety.

Engineers at the Massachusetts Institute of Technology have shown that these endocrine cells can be stimulated to produce ghrelin using ingestible capsules that supply the cells with electrical current. This approach may help treat conditions that involve nausea and anorexia, such as cachexia (weight loss that can occur in patients with cancer and other chronic diseases).

In animal studies, researchers have shown that this “electroceutical” capsule can significantly boost ghrelin production in the stomach. They believe this approach could also be applied to provide electrical stimulation to other parts of the digestive tract.

“This study helps establish electrical stimulation with ingestible electroceuticals as a mode of inducing hormone release through the gastrointestinal tract. We provide an example of how to release , which we anticipate could be used in other parts of the gastrointestinal tract not investigated here.”

Khalil Ramadi SM ’16, PhD ’19, graduated from Harvard MIT programs in Mechanical Engineering and Health Science and Technology, and is currently Assistant Professor of Bioengineering at New York University (NYU) Tandon School of Engineering and Advanced Neuroengineering at NYU Abu Dhabi. and Director of the Institute for Translational Medicine, James McRae, a graduate student at the Massachusetts Institute of Technology, said: paperappeared today science robotics.

electrical stimulation

The enteric nervous system controls all aspects of digestion, including the movement of food through the digestive tract. Some patients with gastroparesis, a disorder of the gastric nerve that makes food move very slowly, experience improvement after electrical stimulation produced by a pacemaker-like device that can be surgically implanted in the stomach. is showing.

Doctors theorized that electrical stimulation would help the stomach contract and push food out. A team from the Massachusetts Institute of Technology hypothesized that electrical stimulation of the stomach could lead to the release of ghrelin, which is known to promote hunger and reduce nausea. rice field.

To test that hypothesis, the researchers used an electrical probe to electrically stimulate the stomachs of animals. They found that ghrelin levels in the bloodstream rose significantly after 20 minutes of stimulation.They also found that electrical stimulation did not cause significant inflammation or other adverse effects.

After confirming that electrical stimulation was causing ghrelin release, researchers set out to see if the same could be achieved using a device that could be swallowed and temporarily lodged in the stomach. One of the main challenges in designing such a device is ensuring that the electrodes on the capsule can contact the liquid-coated stomach tissue.

To create a drier surface on which the electrodes can interact, the researchers gave the capsules grooved surfaces that allowed fluid to escape from the electrodes. The surface they designed is inspired by the skin of Australian spiny devil lizards, which use their ribbed scales to collect water. When the lizard touches water on any part of its skin, water is transported by capillary action along channels to the lizard’s mouth.

“We were inspired to incorporate surface textures and patterns on the outside of this capsule,” says McRae. “Its surface can manage fluids that could potentially prevent the electrodes from touching the stomach tissue, so we can deliver reliable electrical stimulation.”

The capsule surface consists of grooves with a hydrophilic coating. These grooves act as channels that draw fluid away from the stomach tissue. Inside the device are battery-powered electronics that generate a current that flows between the electrodes on the surface of the capsule. In the prototype used in the study, the current was always flowing, but the researchers say future versions may be designed to turn the current on and off wirelessly.

hormone boost

Researchers tested the capsules by administering them to the stomachs of large animals and found that the capsules produced significant spikes in ghrelin levels in the bloodstream.

“To our knowledge, it is the first example of using electrical stimulation via an ingestible device to increase endogenous levels of hormones such as ghrelin in the body. , has the effect of utilizing the body’s own systems,” says Ramadi.

Researchers have found that the vagus nerve, which controls digestion, must be intact for this stimulation to work. They theorize that electrical pulses are transmitted to the brain via the vagus nerve, which stimulates endocrine cells in the stomach to produce ghrelin.

Traverso’s lab now plans to explore using this approach in other parts of the gastrointestinal tract, and researchers hope to test the device on human patients within the next three years. . If developed for use in human patients, this type of therapy would replace some of the existing drugs used to prevent nausea and stimulate appetite in people with cachexia or anorexia. or complement it, researchers say.

“Because it’s a relatively simple device, we think it’s something that humans can take relatively quickly,” says Traverso.

This work was funded by the National Cancer Institute, the National Institute of Diabetes and Digestive and Kidney Diseases, the Department of Engineering, New York University Abu Dhabi, the National Science Foundation Graduate Research Fellowship, and a Koch Institute Supporting (Core) grant from Novo. I was. Nordisk, and the Department of Mechanical Engineering at MIT.