Limei Wang, Ph.D., from Massachusetts General Hospital in Boston, and colleagues used an ultrasensitive assay (lower detection limit, 1.5 pmol/L; 22 times more sensitive than standard assays), to measure the serum levels of C-peptide, a marker of insulin production, in 182 patients with type 1 diabetes.
The researchers found that C-peptide levels declined with longer durations of disease, with C-peptide detected in 10 percent of patients 31 to 40 years after disease onset. However, patients who developed diabetes after 40 had low levels of C-peptide, in spite of short disease duration. Increased C-peptide production was seen in response to hyperglycemia, even in those with levels as low as 2.8 ± 1.1 pmol/L. Several analyses indicated that β-cells were able to function. Disease duration and level of zinc transporter 8 autoantibodies correlated significantly with C-peptide production.
"The ultrasensitive assay revealed that C-peptide production persists for decades after disease onset and remains functionally responsive," Wang and colleagues conclude. "These findings suggest that patients with advanced disease, whose β-cell function was thought to have long ceased, may benefit from interventions to preserve β-cell function or to prevent complications."
