Fruit flys give insight into human metabolism

Although scientists have known for some time that there are as many as 500 million nerve cells in our gut, the sheer complexity that this presents means that little is known about the different types of nerve cell and their functions.

Now, researchers at the University of Cambridge led by Dr Irene Miguel-Aliaga, with funding from the Wellcome Trust and the Biotechnology and Biological Sciences Research Council, have used the fruit fly, Drosophila melanogaster, to investigate the function of these intestinal neurons. The fly has simpler versions of our nervous and digestive systems, which lend it to genetic manipulation.*

"We reasoned that what comes out of the gut may be able to tell us about what is going on inside," explained Dr Miguel-Aliaga. "So, we devised a method to extract information about several metabolic features from the flies’ faecal deposits - which are actually rather pretty and don’t smell bad. Then we turned specific neurons on and off and examined what came out."

Dr Miguel-Aliaga and colleagues found that these intestinal neurons have very important and specialised functions, such as regulating appetite or adjusting intestinal water balance during reproduction.

"Humans and fruit flies reproduce in very different ways, yet the associated symptoms of constipation and bloating and their cause - a reproductive hormone - are the same," explained Dr Miguel-Aliaga. "This suggests that this mechanism has been conserved through evolution. These intestinal changes may provide a benefit at a time of high nutritional demand by maximising nutrient absorption."

"A mechanism that maximises nutrient absorption by slowing the passage of food through the intestine is fine when food is scarce or during reproduction," said Dr Miguel-Aliaga, "but when we are eating a normal diet, constipation may lead to the build up of waste products produced during internal metabolism. Similarly, it could lead to changes in the composition of the gut bacteria, which are essential to regulating metabolism. Our research suggests that in addition to paying attention to what we eat, which has been the focus of longevity research, we may also have to consider what our body does with the food and what goes on in our guts." Cambridge University.

*Findings published in Cell Metabolism