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Proinsulin measurement

With this assay, basal insulin values of 5-15 pU/mL (30-90 pmol/L) are found in normal humans, with a peak rise to 60-90 U/mL (360-540 pmol/L) during meals. Similar assays for measuring all of the known hormones of the endocrine pancreas (including C-peptide and proinsulin) have been developed. [Pg.985]

The most definitive laboratory test to distinguish type 1 from type 2 diabetes is the C-peptide assay, which is a measure of endogenous insulin production. With type 2 diabetes, proinsulin can be split into insulin and C-peptide lack of C-peptide indicates type 1 diabetes. The presence of anti-islet antibodies (to glutamic acid decarboxylase, insulinoma associated peptide-2 or insulin) or absence of insulin resistance (determined by a glucose tolerance test) is also suggestive of type 1. [Pg.48]

Clinical Utility of Measuring Insulin, Proinsulin, C-Peptide, and Glucagon... [Pg.850]

Box 25-1 lists the clinical conditions in which hormones that regulate glucose, namely insulin, proinsulin, C-peptide, and glucagon, have been measured. Although there is interest in the possible clinical value of measurement of the concentrations of insulin and its precursors, the assays are useful primarily for research purposes. There is no role for routine testing for insulin, proinsulin, or C-peptide in patients with diabetes mellitus. It must be emphasized that the diagnostic criteria for diabetes mellitus do not include measurements of hormones, which remain predominantly research tools. [Pg.850]

High proinsulin concentrations are usually noted in patients with benign or malignant j3 ceil tumors of the pancreas. Most patients with fl-cell tumors have increased insuhn, C-peptide, and proinsulin concentrations, but occasionally only proinsulin is increased because the tumors have defective conversion of proinsulin to insulin. Despite its low biological activity, proinsuHn production may be adequate to produce hypoglycemia. In addition, a rare form of familial hyperproinsulinemia, produced by impaired conversion to insulin, has been described. Measurement of proinsulin can... [Pg.850]

Accurate measurement of proinsulin has been difhcult for several reasons the blood concentrations are low antibody production is difficult most antisera cross-react with insulin and C-peptide, which are present in much higher concentrations the assays measure intermediate cleavage forms of proinsulin and reference preparations of pure proinsulin are not readily available. However, a more sensitive nonequiUb-rium RIA method for measuring proinsiilin was developed by adsorbing the initial antiserum with biosynthetic human C-peptide coupled to agarose to eliminate cross-reactivity with C-peptide.An enzyme-linked immunosorbent assay (ELISA) has been described that employs an antibody to C-peptide as the coating antibody and antiinsulin antibody for detection. The detection limit is 0.25 pmol/L. ... [Pg.851]

A stable isotope dilution assay using mass spectrometry to measure insulin, proinsulin, and C-peptide has been developed. The difference in mass among the three analytes allows specific measurement of each protein. Comparison of patient samples revealed that most, but not all, results were higher by immunoassay than mass spectrometry. Thus immunoassays may overestimate insulin, particularly at low concentrations. The high protein concentration in the serum requires extraction of proteins (e.g., by immunoaffinity) and purification by high-performance liquid chromatography (HPLC) before quantification by mass spectrometry. This method is not suitable for routine laboratory analysis. [Pg.852]

Ostrega D, Polonsky K, Nagi D, Yudkin J, Cox LJ, Clark PM, et al. Measurement of proinsulin and intermediates. Validation of immunoassay methods by high-performance liquid chromatography Diabetes 1995 44 437-40. [Pg.898]

The measurement of C-peptide provides a fully validated means of quantifying endogenous insulin secretion, preventing influence of exogenous insulin or insulin antibody. However, most C-peptide assay kits cannot differentiate C-peptide from proinsulin and proinsulin conversion products. The influence of proinsulin may be significant in cases where serum proinsulin is elevated, as in Type 2 diabetes, familial hyperproinsulinemia and in patients with proinsulin antibody. [Pg.467]

Cross-reactivity with proinsulin and insulin was determined by measuring recombinant human proinsulin (Sigma-aldrich Co.) and WHO approved reference material (International Reference Preparation Code 66/304, NIBSC). [Pg.468]

The use of a monoclonal antibody that recognizes the N-terminal of the C-peptide molecule made it possible to realize a low cross-reactivity to proinsulin. Our results indicate that the C-peptide assay on the LUMIPULSE system shows good specificity, sensitivity, precision and linearity. Accordingly, the C-peptide assay enables for the accurate measurement of C-peptide at low concentrations. Especially, it is useful for the presumption of residual P-cell function of diabetic patients who are nearly depleted of insulin secretion. [Pg.470]

The amino acid sequence of prolnsulin has been determined and the amount of the connecting or C peptide can be measured in plasmalS. xhe detection of proinsulin in human plasma in addition to its lower biological activityi suggested that a higher proportion of proinsulin might explain the functional lack of Insulin in some maturity onset diabetics. This has been shown not to be the casel5,16. Evidence has also been presented to show that newly synthesized proinsulin is often released in preference to... [Pg.192]

This approach has been used, for example, to measure tetrahydrocannabinol (the active ingredient of cannabis) in blood plasma in the presence of much higher concentrations of its inactive metabolites, and insulin in the presence of proinsulin and its split products. [Pg.2143]

Desmethylcyproheptadine 10,11-epoxide, a biotransformation product of the antihistaminic and antiserotoninergic drug, cyproheptadine inhibited proinsulin and insulin biosynthesis and insulin release in isolated rat pancreatic islets (Chow et al. 1989). Measurement of (pro)insulin (proinsulin and insulin) synthesis using incorporation of H-leucine showed that desmethylcyproheptadine epoxide, desmethylcyproheptadine and cyproheptadine epoxide were 22,10, and 4 times, respectively, more potent than cyproheptadine in inhibiting hormone synthesis. In man, there was no evidence for metabolic alteration at the tricyclic ethylene bridge (C-10, C-11), whereas dog, cat, and rat all metabolise the drug, at least in part, at this site (Porter et al. 1974). A minor N-oxide conjugate as a metabolite of cyproheptadine has been found in man (Johnson et al. 1962). [Pg.576]

Insulin in the body is derived from its precursor molecule proinsulin. During the conversion of proinsulin to insulin, a small peptide (C-peptide) is released by enzymic action. Measurement of this peptide in serum provides a measure of pancreatic -cell function, even in patients on insulin. C-pep-tide determination can be used in the evaluation of a number of metabolic conditions, e.g. brittle diabetes, insulinoma. [Pg.101]


See other pages where Proinsulin measurement is mentioned: [Pg.350]    [Pg.350]    [Pg.106]    [Pg.765]    [Pg.347]    [Pg.204]    [Pg.229]    [Pg.234]    [Pg.852]    [Pg.853]    [Pg.865]    [Pg.1913]    [Pg.48]    [Pg.273]    [Pg.485]    [Pg.1322]    [Pg.2142]    [Pg.2142]    [Pg.539]    [Pg.183]   
See also in sourсe #XX -- [ Pg.853 ]




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Proinsulin

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