Residual β-cell function after 10 years of autoimmune type 1 diabetes: prevalence, possible determinants, and implications for metabolism.

backgroundType 1 diabetes (T1D) has long been considered a progressive autoimmune disease resulting in the failure of pancreatic β-cell function and absolute endogenous insulin deficiency. However, several studies have demonstrated patients with T1D have detectable C-peptide levels long after diagnosis, which has remarkable clinical significance. Since this issue has not been systematically explored in non-Caucasian populations, we aimed to identify the prevalence of residual β-cell function and its related clinical features in Chinese long-term T1D patients.

methodsWe enrolled 109 patients with T1D for ≥10 years and administered a mixed-meal tolerance test (MMTT). Fasting and postprandial C-peptide (FCP/PCP) levels were measured to evaluate the insulin secretion function of β-cells. Patients whose FCP and PCP levels were both below the lower detection limit (16.7 pmol/L) were grouped as 'β-cell function depleted', while others were thought to have 'residual β-cell function'. Demographic data, metabolic status, and diabetic complications were compared between patients with or without residual β-cell function.

results38.5% of subjects retained residual β-cell function, and among those, 33.3% responded to MMTT by a two-fold or greater rise of their FCP levels. Clinical features associated with residual β-cell function were older age of diagnosis [27.5 (interquartile range:11.5-37.0)

conclusionsResidual β-cell function can be found in nearly 40% of long-term patients with T1D in China and is associated with older age at diagnosis and better glucose control. The relationship between residual β-cell function and chronic diabetic complications remains to be explored.