How does the body manage insulin-producing cells to swiftly adapt to changing situations? This is a question that researchers have been exploring.
Insulin is a vital hormone involved in the metabolism of various living organisms. When food is abundant, insulin facilitates the uptake and storage of energy. Conversely, when food is scarce, insulin secretion diminishes, prompting the body to conserve energy or seek alternative energy sources. It’s essential for survival that this regulatory mechanism is precise. Any disruption can lead to conditions such as diabetes and other metabolic disorders.
In humans, insulin is synthesized in the pancreas. In contrast, the fruit fly Drosophila generates this hormone in specialized nerve cells within the brain. These nerve cells release insulin directly into the haemolymph, which serves the role of blood in insects. Despite these differences, the insulin regulatory systems in flies and humans share many similarities.
Researchers at Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, have examined the insulin-producing cells in fruit flies closely. Their goal was to understand how these cells in the fly’s brain cooperate with other neurons to create a coordinated response to metabolic changes and the internal state of the organism.
The findings have been published in the scientific journal eLife. Dr. Jan Ache, who leads an Emmy Noether group in the Department of Neurobiology and Genetics at the JMU Biocentre, headed the study.
Monitoring Individual Cell Activity
How do insulin-producing cells (IPC) in living insects respond to shifts in energy balance? There is limited information available on this topic. To bridge this knowledge gap, Jan Ache’s team adopted a method that allows them to observe the activity of individual IPCs in live fruit flies under various conditions.
The researchers discovered that IPCs secrete insulin when flies consume sugar with their food, but not when sugar is simply injected into the haemolymph.
‘This effect is comparable to the incretin effect observed in humans,’ explains Jan Ache. It indicates that insulin release is not just triggered by rising blood sugar levels but involves more intricate processes that include gut hormones.
The JMU researchers also observed that IPC activity decreases in older flies, suggesting that the way these insects metabolize sugar may alter with age, akin to what happens in humans.
Examining the Impact on Foraging Behavior
The foraging behavior of fruit flies is intrinsically connected to variations in their energy stores, which are also associated with insulin release. The Würzburg team sought to learn more about these dynamics.
The scientists stimulated the IPCs using optogenetic techniques, simulating conditions that typically follow a meal when sugar levels rise. Their findings revealed that the role of insulin-producing cells in influencing foraging behavior is relatively minor compared to other nerve cells.
Implications for Human Health
‘Through our experiments, we’ve enhanced our understanding of the neural pathways that govern insulin secretion in fruit flies,’ states Jan Ache. This insight opens avenues for further research, potentially leading to discoveries that could benefit human health and address diseases like diabetes. Despite the visible differences between humans and fruit flies, both share genetic and metabolic similarities, especially regarding the nervous system and fundamental aspects of metabolic regulation.
