What is C-P/Ins?

Insulin is a protein hormone secreted by pancreatic beta cells in the pancreas stimulated by endogenous or exogenous substances such as glucose, lactose, ribose, arginine, and glucagon. Insulin is the only hormone in the body that lowers blood glucose while promoting glycogen, fat, and protein synthesis. Exogenous insulin is mainly used to treat diabetes.

C-Peptide is a secretory product of pancreatic β-cells. Both of them are derived from a common precursor - insulinogen, and one molecule of insulinogen is cleaved into one molecule of insulin and one molecule of C-Peptide after enzymatic cleavage. Since the two are secreted in equal molecules, the level of endogenous insulin secretion can be determined by measuring the C peptide.

The C-peptide has no antigenic crossover with insulin and the results are not interfered by exogenous insulin or insulin antibodies, and at the same time, C-peptide is secreted isomolecularly with insulin and is not readily degraded by the liver (unlike insulin), and the concentration in the bloodstream is relatively stable.

Clinical application of C-P/Ins

After oral administration of glucose, Insulin and C-peptide levels rise rapidly, reaching peak secretion in 0.5 ~ 1 hour, with peak insulin and C-peptide levels 5 ~ 10 times the fasting level and 5 ~ 8 times the fasting level respectively, and then decline gradually to return to the fasting level in 2 ~ 3 hours.

Insulin and C-peptide are isomolecularly secreted, but their metabolic pathways are different: insulin enters the liver via the portal vein, of which 40%~50% is degraded by hepatic uptake, and the rest of insulin enters the circulation, with a half-life of 5~6 minutes; whereas, C-peptide is seldom degraded by hepatic uptake, and most of it enters the circulation directly, and is then metabolised and cleared by the kidneys, with a half-life that is about twice as long as that of insulin.

Specific clinical applications of C-P/Ins are shown below:

C-P:

① The C-P test reflects the secretory function of the body's pancreatic β-cells, and is a guide to the typing of diabetes mellitus and the identification of hypoglycaemia.

② The C-P test identifies the cause of hypoglycaemia in patients treated with exogenous insulin.

③ In addition to blood glucose monitoring, C-peptide should be tested to understand the secretory function of islet β-cells after transplantation.

④ Because C-peptide is less affected by the liver, the degradation of C-peptide is slowed down and the blood level of C-peptide increases when kidney disease occurs, so C-peptide can have a better diagnostic value for liver and kidney diseases such as hepatitis or cirrhosis compared with insulin.

 Insulin：

① Fasting blood insulin levels reflect the basal level of insulin secretion in the body:Used primarily to determine the glucose/insulin ratio to illustrate questions about insulin secretion.

② Fasting blood insulin levels are informative in the diagnosis and monitoring of diabetes: predict the development of type 2 diabetes and assess patient status and predicting diabetes susceptibility.

③ Fasting blood insulin levels can also be used to assess the degree of insulin resistance: high fasting blood insulin levels may be a marker of insulin resistance.

C-peptide/Insulin combo test is complementary, and is valuable for typing diabetes, guiding insulin application, identifying the causes of hypoglycaemia, diagnosing pancreatic islet cell tumours, and determining postoperative outcomes, as well as providing a more accurate diagnosis of diabetes mellitus and other diseases.

Factors affecting C-P/Ins

Increased C-P/Ins levels may also be due to:

Endocrine metabolic diseases

(Type 2 diabetes, Cushing's syndrome, hypokalaemia)

Hepatitis, cirrhosis

Diabetic kidney disease, renal failure

Oncological disease(insulinoma)

Diet, Drug effects

Summary

C-peptide and Insulin are generally used to check the specific typology of diabetes, as well as to assess the subject's pancreatic islet function, which is an important screening measure for diabetic patients, and the results of which allow for a better assessment of the patient's physical condition.

The ReLIA C-P/INS(2 in 1) Immunoassay is CE-marked cleared. For more details on ReLIA C-P/INS(2 in 1)  Immunoassay products and prices please contact us at  marketing@ReLIAchina.com

References

[1] Wei Yihan,Quan Li,Zhou Ting,Du Guoli,Jiang Sheng. The relationship between different C-peptide level and insulin dose of insulin pump[J]. Nutrition & Diabetes,2021,11(1).

[2] Kazuma Ogiso,Nobuyuki Koriyama,Takahiko Obo,Akinori Tokito,Yoshihiko Nishio. Basal insulin ameliorates post-breakfast hyperglycemia via suppression of post-breakfast proinsulin/C-peptide ratio and fasting serum free fatty acid levels in patients with type 2 diabetes[J]. Diabetology International,2020(prepublish).

[3] Liao Jing,Ding Fei,Luo Wei,Nie Xin,He Yong,Li Guixing. Using the Secretion Ratios of Insulin and C-peptide During the 2-h Oral Glucose Tolerance Test to Diagnose Insulinoma.[J]. Digestive diseases and sciences,2020.

[4] Wenying Yang,Pengfei Ruan,Xia Zhang,Nan Cui. 1048-P: Fasting C-Peptide as a Predictor for Hypoglycemia Risk and HbA1c Reduction in Chinese T2DM Patients Switching from Premixed to Basal Insulin: A Post Hoc Analysis from the Optimization Study[J]. Diabetes,2020,69.

[5] Charlotte Perkins,Erin Campbell,David P Cistola. 1444-P: Discordance between Insulin and C-Peptide Is Associated with Liver Function and Ethnicity[J]. Diabetes,2020,69.

[6] Lynda Guildford,Catherine Crofts,Jun Lu. Can the Molar Insulin: C-Peptide Ratio Be Used to Predict Hyperinsulinaemia [J]. Biomedicines,2020,8(5).