C Peptide is a 3020 Da endoplasmic reticulum pancreatic peptide expressed in beta cells of the pancreas; Antibodies to C Peptide can be used to study treatment of diabetic peripheral neuropathy, nephropathy and other decrements associated with long-term complications of type I diabetes. C Peptide, also known as proinsulin C-peptide, is a symbol for Connecting Peptide.