A review of new research says there is growing evidence to support the idea that the brain plays a key role in normal glucose regulation and the development of type 2 diabetes.
In the latest online issue of Nature, researchers from the Universities of Washington, Cincinnati and Michigan in the US, and the Technical University of Munich in Germany, present evidence of a brain-centered system that can lower blood sugar or glucose via insulin and non-insulin mechanisms.
They propose that normal glucose regulation relies on "highly coordinated interactions" between this brain system and the insulin-producing islets in the pancreas.
Should their suggestion be correct, it could open the door to completely new approaches to prevent and treat type 2 diabetes, perhaps even to reverse it, say the researchers.
Type 2 diabetes develops when the body does not produce enough insulin or the body's cells do not react to insulin (known as insulin resistance), with the result that blood sugar levels become too high (hyperglycemia).
Current treatments only control type 2 diabetes
In their paper, the researchers note that about a century ago, scientists believed the brain played an important role in keeping glucose in check. But since its discovery in 1920, the focus shifted to insulin, and today nearly all treatments for diabetes are devised either to increase insulin or increase the body's sensitivity to the glucose-regulating hormone.
The researchers write:
"These drugs enjoy wide use and are effective in controlling hyperglycemia, the hallmark of type 2 diabetes, but they address the consequence of diabetes more than the underlying causes and thus control rather than cure the disease."
However, the researchers say new research brings back the idea that the brain is involved - it suggests that normal glucose regulation depends on a partnership between the insulin-producing cells (the islet cells) of the pancreas and key circuits in the hypothalamus and other brain areas.
The authors argue that type 2 diabetes is the result of failure of both the pancreatic islet cell system and this brain-centered system for regulating blood sugar levels.
They review animal and human studies that document how the brain-centered regulatory system has a powerful effect on blood sugar levels independent of insulin.
Brain system 'fails first'
One brain-centered mechanism uses a process called "glucose effectiveness" to promote glucose uptake in tissues. As this process accounts for nearly half of normal glucose uptake, it is on par with the insulin-dependent processes of the pancreatic islet cells.
The researchers propose a two-system model - the pancreatic islet system reacts to rising blood glucose by releasing insulin, and the brain-centered system enhances insulin-dependent glucose metabolism while also stimulating glucose effectiveness independently of insulin.
They say type 2 diabetes appears to be the result of failure of both systems.
According to the research, the brain system is the one most likely to fail first. This puts pressure on the islet system, which can compensate and carry on for a while, but then also fails, causing further decompensation in the brain system. The result is a vicious cycle of deterioration that ends in type 2 diabetes.
Introducing insulin reduces blood sugar back to normal levels but is only half the problem, say the researchers. You also need to tackle the brain-centered system failure. It may be possible not only to keep blood glucose under control, but also to cause a reversal of the type 2 diabetes, they write.
Medical News Today reported that in another Nature paper published recently, US researchers describe how they discovered a biological link between diabetes and heart disease. They found a biological pathway through which abnormally high blood sugar can trigger irregular heartbeats.