C-peptide and residual β-cell function in pediatric diabetes - state of the art.

C-peptide, the molecule produced in an equimolar concentration to insulin, has become an established insulin secretion biomarker in diabetic patients. Measurement of C-peptide level can be helpful in clinical practice for assessing insulin-producing b-cells residual function, especially in the patients who have already started exogenous insulin therapy. Advances in assays have made measurement of C-peptide more reliable and inexpensive. Traditionally, C-peptide is widely used to differentiate between type 1, type 2 and monogenic types in diabetic patients of all ages, both when the diabetes occurs and even months and years after the initial diagnosis. Moreover, in the patients with type 1 diabetes, the C-peptide secretion can become a reliable predictor of the clinical partial remission in the first months after diagnosis, although noteworthy, its' any specified level is not included in the definition of this phase of the disease. Many other clinical factors such as age, use of innovative technologies, the intensity of physical activity or body mass influence the concentration of C-peptide as well as diabetes remission occurrence and duration. They may interfere the interpretation of C-peptide level in the diabetes course. There is a great need to assess the new, adjusted C-peptide levels in these situations. A multitude novel therapies including immunomodulative factors and stem cell transplants can also use C-peptide in the patient selection and post-therapeutic monitoring of the outcome in researches aimed in extension of remission period. Recent research proves C-peptide presence and preserved function and being the possible important player in better metabolic control in long-lasting diabetes type 1. These findings may open the area for trials to regenerate b-cells and save endogenous insulin secretion for many years after diagnosis. Last but not the least, C-peptide presents its own physiological effect on other tissues, among others on the endothelial function, thus participates in inhibiting micro- and macrovascular diabetes complications. The idea of C-peptide as a new, additional to insulin cure remains as much attractive as elusive.