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We are interested in information about levels of C-peptide and glucagon in the blood of children with diabetes.

Sooner or later, people who are interested in diabetes learn that insulin is made in a specialized area of the pancreas, called the islet cells. These islet cells can be subdivided into different types, called alpha cells, and beta cells, and delta cells. Insulin is made in the beta cells of the islets.

Other proteins, including C-peptide and glucagon, are also made in islet cells. The levels of these other substances can be measured in kids with diabetes, but these lab tests are relatively expensive, and it takes a while to get the results back from the lab. So, these tests are usually used by researchers to help analyze what goes wrong in diabetes, rather than to help your Diabetes Team care for you as an individual person.


Insulin is initially made in the beta cells as a huge protein called proinsulin. Proinsulin develops like stringing beads onto a necklace: it is a string of amino acids, strung one after another. As the proinsulin protein is being strung together, the molecule curls around on itself so that amino acids that were added early are adjacent to amino acids that were added later. Then, two permanent chemical attachments develop between some of these adjacent amino acids, tying the proinsulin together in a complicated knot. Next, a piece is chopped out from about the middle of the curled-up, tied-together proinsulin: this piece (that is not needed for the active insulin molecule) is called C-peptide. If you think about it, every molecule of proinsulin should become one molecule of insulin plus one molecule of C-peptide.

Since the problem that causes Type 1 diabetes is the destruction of the pancreas's ability to make insulin, you can now realize that really, the beta cells of the pancreas aren't making proinsulin, and if there's no proinsulin to be tied up and then have a chunk split out, there's also no C-peptide made. Indeed, most people with Type 1 diabetes have little or no C-peptide in their bloodstream. (And the insulin that comes in a bottle from the drugstore doesn't add any C-peptide, since it's so highly purified by the manufacturer that almost all the C-peptide has been removed.)


Glucagon is made in a different type of cell than insulin and C-peptide: the alpha cell. You may already know of glucagon as the substance that can be given by injection to treat low blood sugar. Glucagon acts as a natural reverser of the effects of insulin on the blood sugar level, but it also has additional effects on other nutrients. Since it's not made in the beta cells, it's unpredictable how much of the glucagon production will be affected in people with diabetes. In fact, in the complication of diabetes called diabetic ketoacidosis, the amount of glucagon is higher than usual.


So, to summarize, most people with Type 1 diabetes have little or no C-peptide, and variable amounts of glucagon, in their bloodstream. Although these substances are very helpful for researchers who are figuring out what goes wrong in diabetes, individual measurements are rarely helpful in the individual case.

Original posting 30 Dec 95


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Last Updated: Tuesday April 06, 2010 15:08:52
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