Professor Greg Suh, from the Department of Biological Sciences, and Yangkyun Oh PhD, from New York University, have collaborated to discover the neuron in the brain that directly regulates blood glucose levels and modeled its functions using Drosophila (fruit flies).
The result provided by this research is the first important clue as to how glucose-sensing neurons in the Drosophila brain are involved in the regulation of blood glucose, by activating insulin-producing tissues and inhibiting glucagon-producing tissues. It also opens up new possibilities for the diagnosis and the treatment of diabetes.
Recent discoveries indicate that there is a part of the brain that may affect the degree of diabetes. For most diabetics, academics argue, stress can make it harder to control blood glucose levels – indicating that there may be an unknown ability to control blood sugar levels in the brain.
The research team has long used fruit flies to study the presence of cells and receptors that detect glucose not only in the animal brain, but also in the tongue and in internal organs. It has been predicted that the neurons that detect glucose may exist in the hypothalamus or the hindbrain, but their mechanism was unclear.
Through extensive screening of the Drosophila brain, the researchers found a pair of neurons essential for the determination of the nutritional value of glucose. The pair of neurons were found to be activated in response to increasing glucose levels in the body. Using pharmaceutical and genetic methods, the team confirmed that these cells recognize glucose in a similar molecular mechanism to human pancreatic cells. Based on this, the team found that the insulin-producing cells (IPCs) and the adipokinetic hormone-producing tissue – hormones that have a similar function to glucagon – are connected to the neurons via axons. The findings suggest that a pair of glucose-sensing neurons can deliver nutritional information directly to tissues which produce hormones that are important for blood sugar control.
To confirm this, the team identified physical and functional interactions between glucose-sensing neurons and two hormone-secreting tissues. As a result, when a pair of glucose-sensing neurons are activated, insulin-producing tissue is also activated, whereas glucagon-producing tissues are inhibited.In addition, the researchers found that small Neuropeptide F (sNPF), a type of short protein that functions as a neurotransmitter in Drosophila, is expressed in glucose-sensing neurons and that the neurotransmitter is secreted when exposed to glucose. The team also demonstrated that sNPF receptors play an essential role in receiving signals from the brain.
Professor Suh said, “The results of this study have not only made meaningful findings in Drosophila, but have provided an opportunity to fundamentally change the paradigm of diagnosing and treating diabetes.” If the interaction is specifically identified in humans, it will be possible to treat obesity and metabolic diseases as well as diabetes more effectively.