Pancreatic Beta cell Function and c- peptide
Beta cells of the human pancreas produce and secrete insulin. The product of the insulin gene is a peptide known
as Preproinsulin. As with other secretory peptides, the prepeptide or signal peptide is cleaved off early in the biosynthetic process, yielding proinsulin. Proinsulin is an 86-amino acid protein that is subsequently cleaved at two sites to yield insulin and a 31-amino acid peptide know as c-peptide. Insulin and c-peptide are, therefore, localized within the same secretory vesicle and are co-secreted into the bloodstream.
For these reasons, measurements of the circulating c-peptide levels can provide a valuable indirect assessment of beta cell insulin secretory capacity. In diabetes mellitus patients who are receiving exogenous insulin injections, the measurement of circulating insulin levels would not provide and useful information about their own pancreatic function because it would primarily be the injected insulin that would be measured. However, an evaluation of C-Peptide levels in such patients would provide an indirect measure of how well the beta cells were functioning with regard to insulin production and secretion.
* In above figure, red shows insulin and yellow represents C-peptide.
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Filed Under: Endocrine
