Short Update on C-Peptide and its Clinical Value

Abstract

C-Peptide (“connecting” peptide – molecular formula C112H179N35O46) is a peptide made of 31 aminoacids, making the bond between A and B chains of insulin from the pro-insulin molecule. Pro-insulin is the precursor of the insulin that is synthesized in the beta-pancreatic cells. After its discovery in 1967 by Steiner et al, together with the discovery of insulin biosynthesis, C-peptide seemed to bring new benefits, having similar effects as those of insulin. Unfortunately, the subsequent studies have classified C-peptide as a biologically inactive peptide. After the ‘90s, however, both studies on animals and those on human subjects with type 1 diabetes where C-peptide had been administered showed that it played important biological parts in improving kidney function and nerve conduction velocity, as well as in increasing blood flow in muscles, skin, kidneys, thus being seen as a possible treatment for chronic complications of type 1 diabetes. Although for a long time C-peptide has been considered to be an inert biological product, recent research has emphasized its active biological function. C-peptide bonds to the membrane of certain types of cells (neuronal, endothelial, renal tubular cells, fibroblasts) through a surface receptor coupled with a G protein, and it determines multiple effects at the cellular level: it improves the quality of red cells, generating a better oxygenation of tissues; it has a vasodilator effect for muscles, skin, kidneys; it generates blood flow increase in skeletal muscles and at the skin level; it decreases glomerular hyper-filtering; it reduces albumin urinary excretion; it improves the function and structure of nerves in patients with type 1 diabetes and C-peptide deficiency, but not in healthy subjects. Therefore, C-peptide could have a therapeutic potential in preventing some of the late complications of diabetes mellitus.

FIGURE 1.

Normal values of basal C-peptide in children (18)

TABLE 1.

Normal values of basal C-peptide in children (18)

TABLE 2.

Normal values of C-peptide in adults (18)