A Korea-U.S. joint team has become the first in the world to find glucose-sensing neurons in the fruit fly's brain that directly function in the body's blood glucose level.

Professors Suh Seong-bae (right) and Oh Yang-kyun

The study, conducted by Korea Advanced Institute of Science and Technology and New York University, is the first of its kind to reveal how blood glucose-sensing neurons in the brain are involved in glucose regulation by activating insulin-producing tissues and inhibiting glucagon-producing tissue activity.

The team, led by Professors Suh Seong-bae from KAIST and Oh Yang-kyun from NYU, expect that the research will open up new possibilities for the diagnosis and treatment of diabetes in the future.

The prevalence of diabetes among Koreans is 14 percent, and the nation has recorded the fastest increase in diabetes patients in the world, as one in four Koreans is potential diabetes patients. The total number of diabetes patients also surpassed five million last year.

Genetics and environmental factors exist, but most diabetic cases begin with decreased pancreatic insulin secretory function. Recent studies have also found that stress affects the diabetes process, as it makes it difficult for patients to control blood sugar. Researchers remain unclear, however, on which part of the brain function controls blood sugar levels.

Suh's team had used fruit flies to study the presence of cells and receptors that detect glucose in the animal brain, as well as in the tongue and internal organs.

Based on the study, the team predicted that there might be glucose-sensing neurons in the hypothalamus or posterior brain of the human brain as well. They then set out to examine how these cells sense glucose and give orders to different parts of the body.

Through extensive screening of the entire brain neurons in the fruit fly, the team discovered a pair of neurons essential for determining the nutritional value of glucose. The researchers also found that these neurons activated in response to increased glucose levels in the body.

They confirmed that these cells recognized glucose through a molecular system similar to human pancreatic cells. Such findings allowed the researchers to study glucose-sensing neurons to see which neurons and tissues they signal.

Afterward, the team confirmed that the neurons form axons in the nerve tissue responsible for insulin production in fruit flies and in tissues that produce proteins that function as glucagon. The researchers also learned that a pair of glucose-sensing neurons could deliver nutritional information directly to tissues that produce hormones that are important for blood sugar control.

To verify their theory, the team examined the physical and functional interactions between glucose-sensing neurons and two hormone-secreting tissues.

The results demonstrated that when a pair of glucose-sensing neurons is activated, insulin-producing tissues are also activated, while glucagon-producing tissues are inhibited.

In a situation where the team surpassed the glucose-sensing neurons, blood insulin levels decrease due to inhibition of insulin-producing tissues, and blood glucagon concentrations increase as the inhibition of glucagon-producing tissues disappears.

By regulating the activity of only a pair of glucose-sensing neurons in the brain, it was possible to create fruit flies with diabetes artificially, according to its press release.

Professor Suh said, "The research allows us to change the paradigm of diagnosing and treating diabetes fundamentally. If the signals produced by the brain are found to play a fundamental role in regulating blood sugar in the body, it is possible to treat even treat obesity and metabolic diseases as well as diabetes."

The journal Nature published the results of the trial.

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