Posted by Jim Dryden
Patients with a rare, genetic form of diabetes often are misdiagnosed as having type 2 diabetes because the two share symptoms.
Now, scientists say treating these patients with therapies designed for type 2 diabetes is potentially harmful and that treatment guidelines need to change.
The underlying problems in patients with the genetic form of the disease—called maturity-onset diabetes of the young (MODY1)—are very different from those in type 2 diabetes. And treating MODY1 patients with drugs for type 2 diabetes appears to lead to destruction of insulin-secreting beta cells that regulate blood sugar.
“People diagnosed with type 2 diabetes are treated with oral medications that make insulin-secreting beta cells very active,” says first author Benjamin D. Moore, a former postdoctoral fellow at Washington University in St. Louis who is now at Massachusetts General Hospital.
“But the MODY1 pathway we’ve uncovered shows that stimulating those cells with those drugs can lead to beta cell death. That means these patients can become dependent on insulin injections much sooner.”
It’s common for patients with MODY1—who make up 3 to 5 percent of all patients with diabetes—to transition from oral medications to insulin injections within 10 years of diagnosis as a way to keep their blood sugar in check. The new research suggests, however, that revving up the beta cells with oral medications increases cellular stress levels, eventually kills those cells, and precipitates the need to switch to insulin much sooner.
Instead, patients with MODY1 might benefit from therapies that target a specific pathway that appears to be essential to the function of insulin-secreting cells. The researchers note a relationship between a pair of proteins that regulate cells that secrete insulin and enzymes in the stomach, liver, kidney, and intestines. One of those proteins is made by the gene that’s altered in patients who have MODY1 diabetes.
Moore originally was studying cells in the stomach when he identified the insulin-secretion pathway disrupted in the genetic form of diabetes. Now he and Jason C. Mills, associate professor of medicine, believe the new pathway may be important in disorders that involve cells that secrete other enzymes.
“Nature doesn’t re-invent the wheel,” Mills says. “What these different cells secrete is very different, but the machinery is very similar. As with auto plants, although a BMW is very different from a Volkswagen, the factories where those cars are built are not really that different. It appears the same thing may be true for a number of these cells that secrete key enzymes in the gastrointestinal tract.”
The researchers are continuing to conduct experiments to determine whether the same pathways are active in different types of secretory cells. For now, they say doctors need to determine if diabetes patients have the MODY1 form of the disorder before moving ahead with treatment.
“It’s important to diagnose patients as accurately as possible and to attempt to target the correct pathway,” Moore says.
The National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health funded the work.