The C-Peptide of Insulin Enzyme-Linked Immunosorbent (ELISA) Kit provides materials for the quantitative measurement of C-peptide of insulin in human serum. The kit is intended for research use only.
For Research Use Only. Not for use in diagnostic or therapeutic procedures.
96 well microtiter
HRP-based ELISA, colorimetric detection by dual wavelength absorbance at 450 nm and 630 nm as reference filter
6, 0.2-10.9 ng/mL
|Limit of Detection||
Bovine, Canine, Caprine, Human, Rabbit
Insulin is a member of a family of structurally-related regulatory proteins; other proteins in this group include the insulin-like growth factors and relaxin. Insulin is produced by the β-cells of the pancreatic islets and is initially synthesized as a 12 kDa pre-prohormone, which undergoes intracellular processing to a 9 kDa, 86-amino acid prohormone and subsequent packaging in storage granules. Within these granules, disulfide bonds are formed between the A and B chains of the insulin molecule and the C-peptide region is cleaved, resulting in the 51-amino acid, 6 kDa mature insulin molecule. Upon stimulation, the islet cells release equimolar amounts of insulin and C-peptide, and small amounts of proinsulin and other intermediates (<5% of normal total insulin secretion)1.
Insulin is the most important hormone of the fed-state, and is the only physiologic hormone which significantly lowers blood glucose levels. In response to a number of substrates and other stimuli, including glucose and amino acids, insulin is secreted into the hepatic portal circulation1,2. Fifty-percent of the insulin is removed on first-pass through the liver, the remainder enters the general circulation and is carried to other target tissues. Insulin then binds to specific cell-surface receptors3 and, through incompletely defined mechanisms, facilitates substrate uptake and intracellular utilization, resulting in net increases in intracellular lipid, protein and glycogen1-4. In addition to its role in peripheral metabolism, insulin may influence central regulation of energy balance5. Insulin is rapidly cleared both by liver uptake, tissue utilization and renal clearance (T1/2 of about 4 mins), and circulating insulin levels are very low during fasting. In contrast, C-peptide of insulin does not undergo significant liver or extra-renal metabolism and, therefore, has a much longer circulating half-life (~30 min).1
Basal- and glucose-stimulated circulating insulin concentrations are relatively stable during infancy and childhood, and increase during puberty due to decreased insulin sensitivity . Insulin concentrations tend to be higher in obese individuals, particularly those with an increased proportion of visceral (abdominal) fat7. Glucose counter-regulatory hormones, such as glucagon, glucocorticoids, growth hormone and epinephrine, decrease insulin sensitivity and action; insulin levels may increase during exogenous administration of these substances. 1,2
Measurement of circulating insulin concentrations may be useful in the clinical evaluation of several conditions. Elevated serum insulin levels in the presence of low glucose concentrations may be indicative of pathologic hyperinsulinism, e.g. nesidioblastosis and islet-cell tumor . Elevated serum fasting insulin levels with normal or elevated glucose concentrations, and exaggerated insulin and glucose response to exogenous glucose administration are characteristic of the insulin-resistant forms of glucose intolerance and diabetes mellitus and other insulin resistant conditions.7, 9, 10 High circulating insulin concentrations may be involved in the pathogenesis of hypertension and cardiovascular disease10,11. Conversely, low insulin concentrations in the presence of hyperglycemia suggests insulin-deficiency, e.g. insulin-dependent or Type I diabetes mellitus.
Although the C-peptide of insulin is biologically inactive, it has a longer circulating half-life than insulin and undergoes relatively minimal hepatic metabolism. In addition, C-peptide of insulin assays may be analytically more sensitive than insulin assays. Because of these factors, measurement of C-peptide of insulin may be useful in evaluating insulin secretion in a variety of clinical conditions.12-14
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