"Our findings suggest that, in individuals with diabetes, the ability of insulin to lower blood sugar involves the brain," said senior author of the study, Michael Schwartz of the University of Washington at Seattle. "This effect is not trivial; the brain makes a substantial contribution to insulin response."
The findings in rats suggest that therapies that boost the brain response to insulin in patients with diabetes might improve blood sugar control while lowering the required dose of the hormone, the researchers said. That advance, in turn, might help to reduce side effects of insulin treatment, such as weight gain, they added.
Scientists once thought that insulin's effects were limited to peripheral body tissues that respond to the hormone by importing glucose. However, more recent studies have revealed that insulin receptors in the brain also play an important role in normal blood sugar control.
To extend those findings to the disease state in the current study, the researchers examined the brain's effect on insulin sensitivity in rats with diabetes due to a lack of so-called pancreatic beta cells, which normally secrete insulin. The rats' condition mimics type I diabetes.
The researchers infused the brains of the diabetic rats with a chemical that limits the function of an enzyme involved in the normal insulin response before injecting the animals with the hormone. Without the normal brain response to insulin, the hormone therapy's efficacy for reducing blood sugar fell by about 35%, Schwartz said. Furthermore, they found that gene therapy interventions designed to increase the brain's insulin response heightened the animals' response to therapy about 2-fold.
Strategies that target the molecules involved in the brain's response to insulin "may therefore prove beneficial in the management of diabetes in humans," the researchers said.
MEDICA.de; Source: Cell Press