C-Peptide (C-peptide), also known as linking peptide, is secreted by islet beta cells and shares a common precursor with insulin. It is A polypeptide composed of 31 amino acids that connects the A and B chains of insulin in the proinsulin molecule. C-peptide has been shown to bind at nanomolar concentrations to G-protein-coupled receptors on the surface of many cell types, such as neurons, endothelial cells, fibroblasts, and renal tubules. C-peptide plays an anti-inflammatory role by down-regulating endothelial cell surface adhesion molecules, reducing inflammatory cytokine production and protecting vascular smooth muscle cells from harmful insulin action. In animals with C-peptide-deficient (type 1 model) nephropathy, administration of C-peptide improves renal function and structure, reduces urinary albumin excretion, and also prevents or reduces glomerular changes due to diabetes with mesangial stroma dilatation.