C-Peptide as a Remedy for Diabetic Microangiopathy?

Insulin, connecting peptide (C-peptide) is part of theproinsulin molecule from which it is cleaved bya serine protease within the pancreatic b-cells andsubsequently released in equimolar amounts with insulin (1–3). Primarily, C-peptide, which is predominantly cleared by the kidney, was regarded a biologically inert byproduct of insulin secretion and an unneeded contami-nant of commercial insulin preparations (1,4), neither af-fecting glucose metabolism nor lipolysis (5). In contrast, radioimmunological determination of C-peptide turned out to be a useful tool for diagnostic purposes in diabetes re-search at large, including the estimation of insulin pro-duction rates in healthy humans (6) and of residual insulin release in type 1 diabetic patients (7) as well as in vitro (8). From 1995 onwards the question of C-peptide’s bi-ological activity was raised again, and it was assigned a multitude of physiological actions affecting renal, neural, and circulatory functions as well as a wide spectrum o