Fly Fitness

The researchers have identified a protein in fruit flies that has a significant impact on exercise in cold conditions. This protein is closely related to human irisin, which is known to play a crucial role in exercise benefits and cold adaptation. The study highlights the evolutionary significance of this gene family in both invertebrates and mammals, indicating its vital role in repairing muscle damage during intense exercise.

The gene, known as Iditarod, appears to be accountable for the capacity of physical activity to eliminate impaired cells.

As the days grow shorter and colder in the northern hemisphere, individuals who opt to exercise in the mornings may encounter difficulties in getting started. The recent study published in PNAS has identified a protein that, when absent, makes exercising in the cold considerably more challenging, at least in fruit flies.

The discovery of a protein in flies, which has been named Iditarod after the renowned long-distance dog sled race across Alaska, was made by a team comprising members from the University of Michigan Medical School and Wayne State University School of Medicine. The team was engaged in a study of metabolism and the impact of stress on the human body.

• Between Autophagy and Iditarod

The researchers displayed a specific interest in a physiological phenomenon known as autophagy, which involves the elimination of damaged cellular components from the organism. During their examination of the fly genome, they identified a potential candidate responsible for regulating this crucial maintenance procedure.

To establish a connection between autophagy and the Iditarod gene, or Idit for short, they manipulated the genetic composition of certain flies to excessively activate autophagy in their eyes. Consequently, flies with heightened autophagy experienced extensive cell death, resulting in visible deterioration of the eye. However, when the Idit gene was deactivated, the eye structure returned to its normal state, indicating the involvement of the Idit gene in the autophagy process.

• Human Connection & Excercise Benefits

The subsequent course of action for the team involved searching for a comparable gene, known as a homolog, in the human genome.

According to Jun Hee Lee, Ph.D, from the U-M Department of Molecular and Integrative Physiology, "Upon investigating this gene in the human genome, we discovered that a gene called FNDC5, which serves as a precursor to the protein irisin, emerged as the most prominent result."

Previous studies have demonstrated the significance of irisin as a hormone involved in generating musculoskeletal benefits and other advantages of exercise in mammals, as well as its role in adapting to cold temperatures.

Lee's laboratory had previously expressed interest in exploring exercise as a mild form of physiological stress.

Lee stated that it was realized that this particular gene may also have significance in relation to exercise. If this is the case, it should be possible to observe a similar physiological effect in flies.

Collaborating with Dr. Robert Wessells' team at Wayne State University, who have developed an innovative method for training fruit flies, the researchers utilized a device resembling a cliff climber for flies. This device takes advantage of the insect's natural instinct to climb upwards out of a test tube.

The findings revealed that flies bred without the Idit gene exhibited impaired endurance during exercise and did not demonstrate the typical improvement seen after training. Additionally, it is known that irisin in mammals stimulates thermogenic processes, which are crucial for cold resistance. Interestingly, flies lacking the Idit gene also displayed an inability to tolerate cold temperatures.

According to Lee, this information indicates that this gene family, present in both invertebrates and mammals, has been conserved throughout evolution and serves a significant function.

Lee stated that they believe exercise plays a role in cleansing the cellular environment through the process of autophagy. According to Lee, intense exercise can cause damage to the muscles and result in malfunctioning mitochondria. In response, the autophagy process is activated to eliminate any damaged organelles or toxic byproducts. Lee also mentioned the significance of the Idit gene in this process.

Furthermore, Lee expressed their intention to establish a connection between this research and their previous work on exercise and physiological stress.

• Reference : Cobb, T., Hwang, I., Soukar, M., Namkoong, S., Cho, U., Safdar, M., Kim, M., Wessells, R. J., & Lee, J. H. (2023). Iditarod, a Drosophila homolog of the Irisin precursor FNDC5, is critical for exercise performance and cardiac autophagy. Proceedings of the National Academy of Sciences, 18 September 2023.