Biological activity versus physiological function of proinsulin C-peptide

Abstract

Proinsulin C-peptide (C-peptide) has drawn much research attention. Even if the peptide has turned out not to be important in the treatment of diabetes, every phase of C-peptide research has changed our view on insulin and peptide hormone biology. The first phase revealed that peptide hormones can be subject to processing, and that their pro-forms may involve regulatory stages. The second phase revealed the possibility that one prohormone could harbor more than one activity, and that the additional activities should be taken into account in the development of hormone-based therapies. In the third phase, a combined view of the evolutionary patterns in hormone biology allowed an assessment of C-peptide´s role in physiology, and of how biological activities and physiological functions are shaped by evolutionary processes. In addition to this distinction, C-peptide research has produced further advances. For example, C-peptide fragments are successfully administered in immunotherapy of type I diabetes, and plasma C-peptide levels remain a standard for measurement of beta cell activity in patients. Even if the concept of C-peptide as a hormone is presently not supported, some of its bioactivities continue to influence our understanding of evolutionary changes of also other peptides.

Future clinical prospects of C-peptide testing in the early diagnosis of gestational diabetes

“…Besides its contribution to insulin structure, the exact biological actions of C-peptide in normal physiology remain only partially understood[ 14 ]. Available data indicate that C-peptide may bind to the cell membrane, possibly via a surface receptor coupled with a G-protein.…”

Association between Serum C-peptide Level and Diabetic Nephropathy in Type 2 Diabetes Mellitus Patients on Oral Anti-diabetic Drug

“…It is generally agreed upon that C-peptide has very little, if any, biological activity and plays no other role outside its participation in the production of insulin. This function is underlined by the name of the peptide itself, which translates to "connection peptide" 8 . The information that is presently at our access demonstrates that C-peptide is not as physiologically inert as was previously supposed to be the case.…”

Food-Derived Bioactive Peptides with Antioxidative Capacity, Xanthine Oxidase and Tyrosinase Inhibitory Activity

“…Many BPs exhibit a peptide residue length of 2-20 amino acids [4,6]. BPs may have longer amino acid chains such as proinsulin C-peptide fragments, which are successful for type I diabetes immunotherapy, and plasma C-peptide levels remain a measurement standard for beta cell bioactivity in patients [7]. Furthermore, many bioactive functions of BPs have been systematically reviewed [5,8].…”