An immunoassay for the measurement of human proinsulin and C-peptide is described. By a combination of this system and an insulin immunoassay, proinsulin, insulin, and C-peptide were identified in acid-ethanol extracts of serum after gel filtration. In keeping with the results of biosynthetic studies, insulin and C-peptide were found to be present in equimolar amounts. The absolute values of se...

Islets isolated from human cadaver pancreas were pulse-labeled (10 min with [3H]leucine) and then incubated for a 180-min chase. Islets and chase medium were collected every 15 min and analyzed by reversed-phase HPLC to quantify the percentage of radioactively labeled proinsulin, conversion intermediates, and fully processed insulin. Release of proinsulin-related labeled products into the chase...

OBJECTIVE The aim of this study was to determine the effect of gestational diabetes mellitus (GDM) on fetal insulin resistance or β-cell function in Chinese pregnant women with GDM. MEASUREMENTS Maternal fasting blood and venous cord blood samples (reflecting fetal condition) were collected in 65 well-controlled Chinese GDM mothers (only given dietary intervention) and 83 control subjects. Th...

The cause of disproportionate hyperproinsulinemia in patients with type II diabetes is controversial. To examine whether increased b cell demand might contribute, we measured proinsulin and insulin concentrations in clinically healthy humans who had undergone hemipancreatectomy for the purpose of organ donation, a procedure previously demonstrated to increase b cell demand and diminish insulin ...

By quantitative immunoelectron microscopy and HPLC, we have studied the effect of disrupting pH gradients, by ammonium chloride, on proinsulin conversion in the insulin-producing B-cells of the islets of Langerhans. Proinsulin content and pH in single secretory vesicles were measured on consecutive serial sections immunostained alternately with antiproinsulin or anti-dinitrophenol (to reveal th...

1. The reversible interaction of zinc with pig insulin and proinsulin has been studied at pH7 by equilibrium dialysis (ultrafiltration) and by sedimentation equilibrium and velocity measurements in the ultracentrifuge. Binding values calculated from equilibria, where the ratio of free to bound zinc was varied in the range 0.01:1-10:1, indicated that proinsulin and insulin each contained two mai...

Protein minimization highlights essential determinants of structure and function. Minimal models of proinsulin and insulin-like growth factor I contain homologous A and B domains as single-chain analogues. Such models (designated mini-proinsulin and mini-IGF-I) have attracted wide interest due to their native foldability but complete absence of biological activity. The crystal structure of mini...

BACKGROUND Acute hyperglycemia (AHG) is associated with mortality in patients with acute coronary syndrome (ACS). The extent to which hyperproinsulinemia contributes to worse clinical outcomes for this specific patient population is unknown. METHODS We included 308 consecutive ACS patients who underwent coronary angioplasty in this pilot observational study. Patients were separated into 3 gro...

The actions of thyroid hormone (TH) on pancreatic beta cells have not been thoroughly explored, with current knowledge being limited to the modulation of insulin secretion in response to glucose, and beta cell viability by regulation of pro-mitotic and pro-apoptotic factors. Therefore, the effects of TH on proinsulin gene expression are not known. This led us to measure: a) proinsulin mRNA expr...