Proinsulin Intact Human ELISA

Research topic

Diabetology

Features

• The total assay time is less than three hours.
• The kit measures total intact human proinsulin.
• Calibrators are human serum based.
• No dilution of serum samples.
• Components of the kit are in the lyophilized, concentrated and ready-to-use states.
• Convenient for automatization.

Storage/Shipping

Store the kit at 2–8°C. Under these conditions, the kit is stable until the expiration date (see label on the box).

Summary

Proinsulin (PI), a polypeptide of 9390 MW (86 amino acids) is synthetized in the β cells of the Islets of Langerhans in the pancreas. The sequence of proinsulin is highly conserved in mammalian species and is homologous with IGF-1 and IGF-2. This protein is processed to C-peptide and insulin forms. Both are secreted in equimolar amounts into the blood. In normal individuals, proinsulin is present in the circulatioon in very low concentrations (typical basal values 2–6 pmol/l). The level of proinsulin in serum can be a reflection of β cell status and a consequence of disfunction of PI processing and/or secretion. Proinsulin like material is increased in clinical conditions as insulinoma, familial hyperinsulinemia, non-insulin dependent diabetes mellitus.

Clinical applications: Proinsulin is the precursor of insulin, which is the principal hormone responsible for the control of glucose metabolism. The measurement of Proinsulin in serum provides useful valuable information for the diagnosis of insulinomas. Proinsulin levels have also been shown to be elevated in non-insulin dependent diabetics (NIDDM), in insulin dependent diabetics (IDDM) and other clinical situations.

Assay format

Sandwich ELISA, HRP-labelled antibody

Sample requirements

100 µl/well

Applications

Serum

Calibration Curve

Calibration range

0 – 110 pmol/l

Limit of detection

Analytical Limit of Detection is calculated from the real Proinsulin values in wells and is 0.60 pmol/l

Limit of quantification

Assay Sensitivity takes the dilution of samples into consideration and is calculated according to the formula: Assay Sensitivity = Analytical Limit of Detection x sample dilution = 0.60 pmol/l x 1 = 0.60 pmol/l

Intra-assay (Within-Run, n=20)

CV = 3.0 %

Inter-assay (Run-to-Run, n=9)

CV = 1.8 %

Spiking Recovery

102.8 %

Dilution Linearity

105 %

Cross-Reactivity

Human, Chicken

References to summary

• Kitabschi A.E.: Proinsulin and C-peptide: a review. Metabolism, 26(5): 547–587 (1977)
• Stiles A.D., D’Ercole A.J.: The insulin-like growth factors and the lung. Am. J. Respir. Cell Mol. Biol., 3(2): 93–100 (1990)
• Linde S. et al.: Separation and quantitation of serum proinsulin and proinsulin intermediates in humans. J. Chromatogr., 548(1–2): 371–380 (1991)
• Robbins D.C. et al.: Biologic and clinical importance of proinsulin. N. Engl. J. Med., 10(18): 1165–1175 (1984)
• Haffner S.M. et al.: Proinsulin and specific insulin concentration in high- and low risk populations for NIDDM. Diabetes, 43(12): 1490–1493 (1994)
• Hanley A.J. et al.: Increased proinsulin levels and decreased acute insulin response independently predict the incidence of type 2 diabetes in the insulin resistance atherosclerosis study. Diabetes, 51(4): 1263–1270 (2002)
• Cohen R.M. et al.: Proinsulin radioimmunoassay in the evaluation of insulinoma and familial hyperproinsuli­nemia. Metabolism, 35(12): 1137–1146 (1986)
• Houssa P. et al.: First direct assay for intact human proinsulin. Clinical Chemistry, 44(7): 15414–1519 (1998)
• Klee G.: “Human anti-mouse antibodies”Ar­chives of pathology Laboratoire Medicine: Vol. 124 No.6, pp 921–923
• Kricka L.: Human anti-animal antibody interferences in immunological assays.Clinical Chemistry (1999); 45: 942–956