C-peptide ELISA Kits

C-peptide is a peptide co-produced with insulin from its precursor, proinsulin. For a long time, C-peptide was thought to have no physiological role beyond facilitating S-S bond formation and peptide folding during insulin biosynthesis. However, recent studies have revealed that C-peptide has various physiological effects. For example, C-peptide was found to bind to receptors on endothelial cells, renal tubular cells, and fibroblasts at nanomolar concentrations (~10-9 M), activating intracellular calcium-dependent signaling pathways, and to activate Na⁺/K⁺-ATPase and promote nitric oxide (NO) synthesis in endothelial cells^1-2). Furthermore, C-peptide administration in patients with type 1 diabetes, who lack endogenous C-peptide, reduces glomerular hyperfiltration and suppresses urinary albumin excretion³⁾. These findings suggest that co-administration of C-peptide with insulin may help prevent complications in patients with type 1 diabetes.

C-peptide is released in equimolar amounts with insulin; however, it has a several-fold longer half-life in the bloodstream compared to insulin. Therefore, measuring blood levels of C-peptide is useful for evaluating insulin synthesis and secretion. This is particularly relevant when analyzing insulin secretion from cultured pancreatic islets of Langerhans, as it is necessary to distinguish between secreted insulin and insulin added to the culture medium. In such cases, measuring C-peptide offers a more precise measurement of secreted insulin. In mice, two isoforms of C-peptide are produced: C-peptide 1 (29 amino acids) and C-peptide 2 (31 amino acids). FUJIFILM Wako’s ELISA kit recognizes the common region between C-peptide 1 and C-peptide 2, allowing for the measurement of total C-peptide levels.

Key points for measuring C-peptide and insulin are available in "All about Insulin Assay Kits"

The LBIS™ Mouse C-Peptide ELISA Kit is a sandwich ELISA kit designed to quantify mouse C-peptide. It provides high sensitivity and a broad dynamic range, ensuring high accuracy and reproducibility. Additionally, it shows negligible cross-reactivity with insulin, proinsulin, and other related peptides.

Kit Performance

Standard curve range	46.9-3,000 pg/mL
Assay target	C-peptide
Sample	Serum, Plasma (Mouse)
Sample volume	10 μL
Measurement duration	Approx. 5 hours
Wavelength	Primary wavelength 450 nm Reference wavelength 620 nm

Example of Calibration Curve

Example of measurement using mouse serum

Cross-reactivity with similar peptides

1. Ohtomo, Y. et al.: Diabetologia, 39, 199(1996).
   C-peptide stimulates rat renal tubular Na⁺, K⁺-ATPase activity in synergism with neuropeptide Y
2. Rigler, R. et al.: Proc. Natl. Acad. Sci. USA., 96(23), 13318(1999).
   Specific binding of proinsulin C-peptide to human cell membranes
3. Wahren, J. et al.: Am. J. Physiol. Endocrinol. Metab., 278(5), E759(2000).
   Role of C-peptide in human physiology