Beta-cells Don’t Quit Completely in Diabetic Patients

Patients with long-standing type 1 diabetes still make small amounts of insulin…. 

It has long been thought that patients with type 1 diabetes will eventually progress to total insulin deficiency due to the destruction of pancreatic beta cells. C-peptide, which is a byproduct of insulin production and has a longer half-life than insulin, is measured to detect how high or low insulin levels are in patients. In most patients with a diagnosis of type 1 diabetes for five years or more, C-peptide levels are thought to be below 200 pmol/L. Normal values are 260 – 620 pmol/L. The prevalence of this byproduct depends on factors which include duration of diabetes, age at diagnosis, type and timing of sample collection and the sensitivity of the assay used.

In a recent study that examined levels of C-peptide in patients with a mean diagnosis of type 1 diabetes for 15 years, researchers aimed to determine how common low levels of C-peptide are in this patient population and whether they responded to mixed-meal stimuli. The 74 patients included in the study fasted from midnight, did not take their usual morning insulin and emptied their bladder upon waking in order to obtain fasting blood glucose, C-peptide, creatinine, glucose, HbA1c, islet antigen 2 autobodies levels and a urine sample prior to taking the mixed-meal tolerance test. Ninety minutes after the completion of the meal, patients had blood drawn to analyze for C-peptide and glucose. Additionally, a urine sample was collected two hours post-meal.

Analysis of C-peptide was completed using a direct electrochemiluminescence immunoassay (Roche) on an E170 analyser which had a limit of detection of 3.3 pmol/L. In 54 of 74 (73%) patients, C-peptide was detectable when measured post-meal; whereas 49 (66%) patients had detectable levels in a fasted state. These results are consistent with previous studies and support the notion that residual beta-cells are still functional. According to the researchers, these patients should be called insulin microsecretors. Moreover, further studies are needed in order to determine the benefits of insulin microsecretion and whether the beta cells are escaping immune attack or undergoing regeneration in patients with long-standing type 1 diabetes.

Practice Pearls:

• Small amounts of insulin may still be produced by beta cell in patients with long-standing type 1 diabetes.
• Close to 75% have some kind of function that may be worth paying attention to.
• Reactivation of beta-cells may be a possibility.