Identification of Proinsulin and C-Peptide in Human Serum by a Specific Immunoassay

Melani, F; Rubenstein, Arthur H.; Oyer, Philip E.; Steiner, Donald F.

doi:10.1073/pnas.67.1.148

Cited by 154 publications

(67 citation statements)

References 18 publications

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“…Insulin is the key hormone regulating intermediary metabolism; it coordinates the uptake and storage of glucose, and provides an integrated signal of energy balance to the brain (Norman and Litwack, 1997;Schwartz et al, 1992;Strack et al, 1995). When insulin is produced from proinsulin in the pancreas, the C-peptide molecule is cleaved off and released into the bloodstream on an equimolar basis (Melani et al, 1970;Rubenstein et al, 1969). Unlike insulin, C-peptide does not undergo significant clearance by the liver, meaning that it is probably a better indicator of pancreatic insulin secretion than circulating insulin itself (Polonsky et al, 1986).…”

Section: Introductionmentioning

confidence: 99%

Urinary C-peptide tracks seasonal and individual variation in energy balance in wild chimpanzees

Thompson

Muller

Wrangham

et al. 2009

Hormones and Behavior

105

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C-peptide of insulin presents a promising new tool for behavioral ecologists that allows for regular, noninvasive assessment of energetic condition in wild animals. C-peptide is produced on an equimolar basis with insulin, thus is indicative of the body's response to available glucose and, with repeated measurement, provides a biomarker of energy balance. As yet, few studies have validated the efficacy of C-peptide for monitoring energy balance in wild animals. Here, we assess seasonal and interindividual variation in urinary C-peptide concentrations of East African chimpanzees (Pan troglodytes schweinfurthii). We assayed 519 urine samples from 13 adult male chimpanzees in the Kanyawara community of Kibale National Park, Uganda. Cpeptide levels were significantly predicted by the total amount of fruit and the amount of preferred fruit in the diet. However, chimpanzees had very low C-peptide titers during an epidemic of severe respiratory illness, despite highly favorable feeding conditions. Kanyawara males had significantly lower C-peptide levels than males at Ngogo, a nearby chimpanzee community occupying a more productive habitat. Among Kanyawara males, low-ranking males had consistently higher C-peptide levels than dominant males. While counterintuitive, this result supports previous findings of costs associated with dominance in male chimpanzees. Our preliminary investigations demonstrate that C-peptide has wide applications in field research, providing an accessible tool for evaluating seasonal and individual variation in energetic condition, as well as the costs of processes such as immune function and reproduction.

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Section: Introductionmentioning

confidence: 99%

Urinary C-peptide tracks seasonal and individual variation in energy balance in wild chimpanzees

Thompson

Muller

Wrangham

et al. 2009

Hormones and Behavior

105

View full text Add to dashboard Cite

show abstract

“…We performed asystematic review of the English literature from 1970 (C-peptide assay first described) through March 2004 [12]. The Ovid search engine (Ovid Technologies™, 2000-2003 was used to search the Medline database.…”

Section: Methodsmentioning

confidence: 99%

Insulin & C-peptide levels in sulfonylurea-induced hypoglycemia: A systematic review

DeWitt

Heard

Waksman³

2007

J. Med. Toxicol.

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Objectives: We will describe insulin and C-peptide levels observed in sulfonylurea-induced hypoglycemia and determine whether these levels differed if obtained before or after hypoglycemic therapy.Methods: We performed a systematic review of the English literature to identify Medline articles containing "sets" (glucose Ͻ 60 mg/dL with insulin and C-peptide levels). These "sets" were categorized as being obtained BEFORE, AFTER, or UNKNOWN with respect to hypoglycemic therapy.Results: 22 articles, 76 patients, and 97 "sets" were included. Mean glucose (mg/dL), insulin ( IU/mL), and C-peptide (ng/mL) for all "sets' were 28.6 (Ϯ12.6; 26.1 to 31.2), 54.4 (Ϯ126.3; 28.3 to 80.5), 7.2 (Ϯ6.2; 5.9 to 8.5).I The BEFORE measures were 24.3 (Ϯ7.3; 18.7 to 30.0), 36.6 (Ϯ26.2; 16.5 to 56.7), 5.4 (Ϯ4.6; 1.5 to 9.2). I The AFTER measures were 33.1 (Ϯ9.8; 28.2 to 38.0), 126.7 (Ϯ278.1; 0 to 265.0), 10.3 (Ϯ10.5; 5.1 to 15.4). I The UNKNOWN measures were 28.0 (Ϯ13.5; 24.7 to 31.3), 37.1 (Ϯ21.8; 31.7 to 42.5), 6.5 (Ϯ4.3; 5.4 to 7.6). I Only one "set" (glucose 49 mg/dL) had insulin Ͻ 3.9 IU/mL and C-peptide Ͻ 1.4 ng/mL. Conclusions:Insulin Ն 3.9 IU/mL, C-peptide Ն 1.4 ng/mL, and glucose Ͻ 49 mg/dl are consistent with sulfonylurea-induced hypoglycemia. BEFORE levels were lower, but they were consistent with sulfonylurea-induced hypoglycemia.

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“…Normal islets of Langerhans secrete proinsulin only to a small extent [24] but insulinomas often secrete a large percentage of proinsulin [25]. Recent experiments on the secretion of plasmid-coded rat proinsulin from Escherichia coli cells also show that no conversion to insulin is required 126,271.…”

Section: Absence Of Insulin In Oocytesmentioning

confidence: 99%

Intracellular Compartmentation and Secretion of Carp Proinsulin Synthesized in Xenopus Oocytes

Rapoport

2005

European Journal of Biochemistry

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Carp proinsulin and rabbit globin, synthesized in Xrnopus oocyies in response to simultaneously injected mRNAs, are found in membrane vesicles and in the cytosol respectively. After 24 h of incubation labeled proinsulin, but not globin, is found also in the medium, indicating specific secretion from the oocytes. N o insulin could be found either within or outside the oocytes.The results provide further evidence that the mRNA for a given protein contains the information for its intracellular destination and its eventual secretion.It is generally assumed that the mRNA for a given protein contains the information for its final destination within a cell or for its secretion out of a cell. This information is probably encoded in defined amino acid sequences which are called 'topogenic' sequences [I]. There is some evidence to support this hypothesis. Experiments in vitro have shown that most secretory proteins are synthesized via precursors which contain at their N-termini cleavable hydrophobic signal sequences. These are recognized by a signal receptor in the rough endoplasmic reticulum membrane [2,3] and direct the nascent polypeptide cotranslationally into the lumen of the endoplasmic reticulum membrane [4,5]. It is clear that the signal for the vectorial transport across the membrane is entirely localized in the nascent secretory protein. Accordingly, studies both in viiro and zn vivo have shown that there is no species or tissue specificity of the translocation or processing activity of the endoplasmic reticulum membrane.The further pathway of a secretory protein, which involves its transport to the smooth endoplasmic reticulum, to the Golgi apparatus and finally to the plasma membrane, has not yet been studied successfully in vitro. The Xenopus oocyte system may be a valuable tool for the investigation of these steps in vivo. In Xenopus oocytes foreign eucaryotic mRNAs are translated faithfully after their injection and many cotranslational and posttranslational protein modifications are carried out [6,7]. For example, in Xenopus oocytes the signal peptidase of precursors of some secretory proteins are split off and there is only one report which claimed that human and rat preproinsulins can be detected in oocytes [30]. Furthermore, Lane and his associates have demonstrated for some secretory proteins that the newly made and processed polypeptides are contained within membrane vesicles [I 3,141. Recently, Colman and Morser extended a previous study [I51 and reported the secretion of human interferon and guineapig milk proteins from oocytes into the medium [16].We have previously shown that mRNA isolated from carp islets (Brockmann bodies of Cyprinus carpio) directs the syn- thesis of carp proinsulin in Xenopus oocytes [lo]. In the present paper it is demonstrated that the proinsulin is contained within membrane vesicles. Moreover, after some time it is found in the surrounding medium, On the other hand, newly synthesized rabbit globin is contained within the oocytes in the cyto.;olic compartment and is not s...

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Identification of Proinsulin and C-Peptide in Human Serum by a Specific Immunoassay

Cited by 154 publications

References 18 publications

Urinary C-peptide tracks seasonal and individual variation in energy balance in wild chimpanzees

Urinary C-peptide tracks seasonal and individual variation in energy balance in wild chimpanzees

Insulin & C-peptide levels in sulfonylurea-induced hypoglycemia: A systematic review

Intracellular Compartmentation and Secretion of Carp Proinsulin Synthesized in Xenopus Oocytes

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