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C-peptide

An indirect measure of viable beta cell function.

Measurements of C-peptide responses to glucose stimulation are helpful to determine the decision to use insulin in both elderly and middle-aged patients with diabetes.

Blunted insulin responses identify those patients who require insulin treatment, whereas high C-peptide values in insulin-treated patients suggest the possibility of discontinuing insulin therapy.

The connecting peptide, or C-peptide, is a short 31-amino-acid protein that connects insulin’s A-chain to its B-chain in the proinsulin molecule.

In the insulin synthesis pathway: first preproinsulin is translocated into the endoplasmic reticulum of beta cells of the pancreas with an A-chain, a C-peptide, a B-chain, and a signal sequence.

The signal sequence is cleaved from the N-terminus of the peptide by a signal peptidase, leaving proinsulin.

After proinsulin is packaged into vesicles in the Golgi apparatus, the C-peptide is removed, leaving the A-chain and B-chain, bound together by disulfide bonds, that constitute the insulin molecule.

Proinsulin C-peptide serves as a linker between the A- and the B- chains of insulin and facilitates the efficient assembly, folding, and processing of insulin in the endoplasmic reticulum.

Equimolar amounts of C-peptide and insulin are stored in secretory granules of the pancreatic beta cells and both are eventually released to the portal circulation.

C-peptide is a marker of insulin secretion.

C-peptide is a bioactive peptide with effects on microvascular blood flow and tissue health.

Following autologous nonmyeloblative hematopoietic stem cell transplantation in patients with type I diabetes mellitus a follow-up at 29.8 months C-peptide levels increased significantly and majority of patients achieved insulin independence with good glycemic control (Couri E).

Late microvascular complications are inversely related to C-peptide levels.

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