Insulin C-Peptides

Insulin C-peptide, also known as linker peptide, is secreted by islet β cells and has a common precursor proinsulin with insulin. C-peptides are made up of compounds called amino acids. When the pancreas produces insulin, it releases C-peptides into the blood, just as heat from burning coal or wood releases smoke into the atmosphere. Proinsulin is split into one molecule of insulin and one molecule of C-peptide, so the molar amount of C-peptide is consistent with that of its own insulin. Because C-peptide is not easily degraded by the liver, so the measurement of C-peptide is to measure the content of insulin, which can accurately reflect the function of islet cells.

Clinical significance of Insulin C-Peptides

C-peptide can reflect the secretory function of islet β cells, and has guiding significance for the classification of diabetic patients and the differentiation of hypoglycemia.

• Diabetes

The determination of C-peptide level can be used to classify diabetes mellitus and understand the function of islet β cells in patients with diabetes mellitus. In patients with type Ⅰ or type Ⅱ diabetes, islet β-cell function should be judged by measuring the level of C-peptide or insulin at the beginning of the disease.

• Low blood sugar

When hypoglycemia occurs in patients suspected of having insulinoma, the determination of the ratio of blood glucose to insulin is helpful for diagnosis. On the other hand, hypoglycemia occurred in patients treated with exogenous insulin, and the cause of hypoglycemia could be identified by measuring C-peptide.

• Islet transplantation

In order to understand the survival of islet transplantation, in addition to monitoring blood glucose, C-peptide should also be measured to understand the secretory function of islet β cells after transplantation.

• Liver and kidney disease

In patients with hepatitis or liver cirrhosis, liver insulin uptake decreased, blood insulin level increased, but C-peptide was less affected by it, and the ratio of C-peptide to insulin in blood decreased. During the onset of nephropathy, the degradation of C-peptide slowed down, the level of C-peptide in blood increased, and the ratio of C-peptide to insulin was significantly higher than normal.

References

1. Moroder, L., & Musiol, H. J. (2017). Insulin—From its Discovery to the Industrial Synthesis of Modern Insulin Analogues. Angewandte Chemie International Edition, 56(36), 10656-10669.
2. Di Sebastiano, K. M., Pinthus, J. H., Duivenvoorden, W. C., Patterson, L., Dubin, J. A., & Mourtzakis, M. (2017). Elevated C‐Peptides, Abdominal Obesity, and Abnormal Adipokine Profile are Associated With Higher Gleason Scores in Prostate Cancer. The Prostate, 77(2), 211-221.