Balloon-like micro-device to study "gut feeling" in fruit flies

Two researchers at Bio-X, Stanford University's pioneering interdisciplinary biosciences institute, are using a balloon-like micro-device to explore the signals that trigger changes of small intestine in fruit flies.

Our small intestine, among other organs, is malleable; responding to nutrition, it changes in size depending on how much we are eating.

The researchers, an engineer and a biologist, hope to isolate factors that regulate changes in the small intestine's growth, with potential long-term impacts to human health research.

"Even as fully grown adult animals, our bodies are continually adapting. Understanding how a mature organ senses the need to grow is an important question in biology," said Lucy O'Brien, assistant professor of molecular and cellular physiology.

In both fruit flies and humans, eating stimulates intestinal cells to release a hormone closely related to insulin, which helps cells of the body take up sugar. This insulin relative produced by the intestines activates stem cell division, enlarging the intestines so they can absorb more food. The intestines of a starved fly or human, conversely, will shrink.

This process is reversible and repeatable, allowing organisms to adapt to changing environmental conditions. Maintaining a large gut when food is not available is energetically wasteful.

While the role of the insulin-like hormone in regulating intestine growth is understood, what causes its release is not. Prior research has not been able to distinguish whether the hormones are generated as a result of the physical force of intestine stretching or the sensing of nutrients.

O'Brien has teamed up with Beth Pruitt, associate professor of mechanical engineering. "Beth's superpower is developing micro-scale devices, the size of a single cell or chunk of tissue, that can deliver mechanical forces to tissue and look at the response," O'Brien was quoted as saying in a news release from Stanford.

The two have proposed creating a "gut micro-balloon" to study adaptive gut responses in fruit flies. The micro-balloon, a tiny tube-like device, would be inserted into a chunk of fly gut floating in a media bath. Once inserted, the tube could be used to deliver nutrients or to blow up like a balloon, creating pressure inside the gut.

"In the universe of possibilities, the insulin-like signal gets turned on either from the sensing of nutrients, or the mechanical forces of the gut getting stretched out," O'Brien said. "Using these tools from engineering, we can isolate potential causes and test each one."

A seed grant from the Stanford Bio-X Interdisciplinary Initiatives Program would help the researchers develop prototypes for the micro-balloon for their project, known as "A gut feeling: Mechano- and chemo-sensory inputs controlling adaptive intestinal growth." Enditem