Wheel lets researchers measure fruit-fly exercise

A new study led by corresponding author Dr. Laura Reed, assistant professor of biological sciences, suggests that a device called the TreadWheel can be used to study the benefits of exercise on Drosophila -- fruit flies.

"With this study, we have established the TreadWheel as a useful tool to study the effect of exercise in flies, shown significant genotype-specific and sex-specific impacts of exercise, and have laid the groundwork for more extensive studies of how genetics, sex, environment and aging interact with exercise to influence metabolic fitness in Drosophila," Reed said.

The study -- "The TreadWheel: A novel apparatus to measure genetic variation in response to gently induced exercise for Drosophila" -- was published Oct. 13 in the journal PLOS ONE. Basically, scientists in two labs -- one at UA and one at The University of Alabama at Birmingham -- used two identical TreadWheels, invented by recent UA graduate Sean Mendez.

They placed vials containing fruit flies on the wheels and rotated them slowly -- like rotisserie chickens -- creating a constant gravitational change that impelled the fruit flies to climb. The fruit flies represented both sexes and several different genotypes -- fat and not so fat, or active and not-so-active. The fruit flies engaged in five-day sessions of gentle exercise.

"Flies are intrinsically motived to move to the top of their enclosures," Reed said. "Thus the TreadWheel induces exercise in adult Drosophila by slowly turning their enclosures."

The results? Reed and her fellow authors observed that across all genotypes the gentle TreadWheel exerciser helped to reduce the fruit flies' weight and increased metabolism, and improved climbing ability.

"Exercised flies showed decreased stored triglycerides, glycogen and body weight, as well as increased stored protein and climbing ability," Reed said. "In addition to demonstrating an overall effect of TreadWheel exercise on flies, we found significant interactions of exercise with genotype, sex, or genotype-by-sex effects for most of the measured phenotypes."

In addition, the researchers saw effects of exercise on "gene expression" -- how a genetic trait is expressed in a fruit-fly body. The expression patterns indicated a modified mitochondrial function -- meaning exercise can influence how genes affect a body's metabolism.

The study points the way for other researchers to use TreadWheels or other gentle-exercise devices to see what effect exercise has on genetically differing individuals and how it interacts with diet and feeding behavior in fruit flies. The ultimate goal is to study how exercise influences how genes are expressed in humans to see if lessons can be learned in the fight against obesity.

"Some people enjoy and respond well to exercise as a method to maintain a healthy body weight," Reed said. "Others find exercise to be ineffective or unpleasant. We are interested in understanding how variation in exercise response is influenced by genetic and other environmental factors, like diet. By understanding how these factors affect fruit flies, we will also develop a better understanding of how they affect people."