By Serena Gordon
WEDNESDAY, Aug. 18 (HealthDay News) -- Although it's long been thought that people with type 1 diabetes cease to produce any insulin after they've had the disease for a while, new research suggests that the insulin-producing beta cells destroyed by type 1 diabetes may actually be in a constant state of turnover, even in people who've had diabetes for decades.
This new research stems from a study of people who've had type 1 diabetes for at least 50 years and have been awarded the Joslin Diabetes Center's "50-Year Medal." In fact, the impetus for the study came from one of the medalists who mentioned to her doctor that she believed her body was still making some insulin.
"I knew I still produced insulin. I don't do it all the time, but sometimes I need a lot less insulin, and the doctors proved on one test that I still did make some insulin," said medalist Elizabeth Saalfeld from Springfield, Va., who was diagnosed with type 1 diabetes in 1945 at age 9.
"In our study, we made the unexpected finding that about two-thirds of the medalists still retained the ability to have positive C-peptide results, which is an indication that they could still be making insulin," said the study's senior author, Dr. George L. King, chief scientific officer at the Joslin Diabetes Center in Boston. "It was a surprise because they've had diabetes for so long."
Results of the study were released online Aug. 10 in advance of publication in an upcoming print issue of the journal Diabetes.
Type 1 diabetes is believed to be an autoimmune disease in which the body's immune system mistakenly attacks the beta cells in the pancreas. When enough beta cells have been destroyed, the body is no longer able to produce sufficient enough amounts of insulin to properly metabolize the carbohydrates in food. Someone with type 1 diabetes must replace that lost insulin through daily injections.
The current study included 411 living diabetes medalists, and a post-mortem pancreas analysis from another nine medalists.
The average age of the medalists was 67, and they'd had diabetes an average of 56 years, according to the study. Half of the study participants were male, and the average body mass index (BMI) was 26, which is considered slightly overweight.
The researchers found that 67.4 percent of the medalists had minimal or sustained C-peptide levels, suggesting that they were still producing some insulin.
Some of the study participants also had their C-peptide levels measured before and after a meal. The researchers also measured C-peptide levels before and after a meal in age-matched non-diabetic people. They found that C-peptide levels increased about fivefold in those without diabetes. In people with type 1 diabetes, the C-peptide levels in those whose bodies responded to the meal rose about threefold.
The people with diabetes who had sustained C-peptide levels saw about a 36 percent response to the meal compared to those with minimal levels who had response levels of 15 percent.
When the researchers examined the donor pancreases, King said they were able to confirm that there were still insulin-producing beta cells present.
"In most, there weren't that many, but at least two had substantial amounts of insulin-producing cells," said King. "The data is quite exciting, indicating that there can be a turnover of beta cells even after such a long time with diabetes."
"This study shows that in this unique cohort of people surviving 50 years or more that some still have a nice balance of beta cells; it's not just a progressive death," said Dr. Joel Zonszein, director of the Clinical Diabetes Center at Montefiore Medical Center in New York City.
But, Zonszein added, this may not apply to everyone with type 1 diabetes. "Some people have a very rapid decay in beta cell function, but many continue to make insulin and their beta cells try to survive. The take-home message is that not all patients with type 1 have no insulin of their own, although they still need [outside] insulin to survive," he said.
Zonszein also noted that good control of blood sugar levels in type 1 diabetes may help preserve beta cell function.
To others living with type 1 diabetes, Saalfeld said, "You can manage diabetes. You definitely have to take care of yourself -- eat what you're supposed to, exercise and take your insulin correctly -- but you can live a normal, or close to normal, life, and a full life, too."