The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
William C Duckworth - One of the best experts on this subject based on the ideXlab platform.
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an Insulin degrading enzyme inhibitor decreases amylin Degradation increases amylin induced cytotoxicity and increases amyloid formation in Insulinoma cell cultures
Diabetes, 2003Co-Authors: Robert G Bennett, Frederick G Hamel, William C DuckworthAbstract:Amylin (islet amyloid polypeptide) is the chief component of the islet amyloid found in type 2 diabetes, and amylin fibril precursors may be cytotoxic to pancreatic beta-cells. Little is known about the prevention of amylin aggregation. We investigated the role of Insulin-degrading enzyme (IDE) in amylin Degradation, amyloid deposition, and cytotoxicity in RIN-m5F Insulinoma cells. Human (125)I-labeled amylin Degradation was inhibited by 46 and 65% with the addition of 100 nmol/l human amylin or Insulin, respectively. (125)I-labeled Insulin Degradation was inhibited with 100 nmol/l human amylin, rat amylin, and Insulin (by 50, 50, and 73%, respectively). The IDE inhibitor bacitracin inhibited amylin Degradation by 78% and Insulin Degradation by 100%. Amyloid staining by Congo red fluorescence was detectable at 100 nmol/l amylin and was pronounced at 1,000 nmol/l amylin treatment for 48 h. Bacitracin treatment markedly increased staining at all amylin concentrations. Bacitracin with amylin caused a dramatic decrease in cell viability compared with amylin alone (68 and 25%, respectively, at 10 nmol/l amylin). In summary, RIN-m5F cells degraded both amylin and Insulin through a common proteolytic pathway. IDE inhibition by bacitracin impaired amylin Degradation, increased amyloid formation, and increased amylin-induced cytotoxicity, suggesting a role for IDE in amylin clearance and the prevention of amylin aggregation.
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Degradation of Amylin by Insulin-degrading Enzyme
The Journal of biological chemistry, 2000Co-Authors: Robert G Bennett, William C Duckworth, Frederick G HamelAbstract:A pathological feature of Type 2 diabetes is deposits in the pancreatic islets primarily composed of amylin (islet amyloid polypeptide). Although much attention has been paid to the expression and secretion of amylin, little is known about the enzymes involved in amylin turnover. Recent reports suggest that Insulin-degrading enzyme (IDE) may have specificity for amyloidogenic proteins, and therefore we sought to determine whether amylin is an IDE substrate. Amylin-degrading activity co-purified with IDE from rat muscle through several chromatographic steps. Metalloproteinase inhibitors inactivated amylin-degrading activity with a pattern consistent with the enzymatic properties of IDE, whereas inhibitors of acid and serine proteases, calpains, and the proteasome were ineffective. Amylin Degradation was inhibited by Insulin in a dose-dependent manner, whereas Insulin Degradation was inhibited by amylin. Other substrates of IDE such as atrial natriuretic peptide and glucagon also competitively inhibited amylin Degradation. Radiolabeled amylin and Insulin were both covalently cross-linked to a protein of 110 kDa, and the binding was competitively inhibited by either unlabeled Insulin or amylin. Finally, a monoclonal anti-IDE antibody immunoprecipitated both Insulin- and amylin-degrading activities. The data strongly suggest that IDE is an amylin-degrading enzyme and plays an important role in the clearance of amylin and the prevention of islet amyloid formation.
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Insulin Degradation progress and potential
Endocrine Reviews, 1998Co-Authors: Robert G Bennett, William C Duckworth, Frederick G HamelAbstract:I. Introduction II. Insulin Clearance A. Liver B. Kidney C. Other tissues D. Extracellular Insulin Degradation III. Cellular Insulin Uptake IV. Cellular Insulin Degradation A. Degradation products B. Assay for Insulin Degradation C. Insulin-degrading enzymes V. Biological Role of Insulin Degradation VI. Insulin-IDE-Proteasome Interactions and Control of Protein Degradation VII. Summary and Conclusions
Anna Ardevol - One of the best experts on this subject based on the ideXlab platform.
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procyanidins modify Insulinemia by affecting Insulin production and Degradation
Journal of Nutritional Biochemistry, 2012Co-Authors: Anna Castellauvi, Lidia Cedo, Victor Pallares, Teresa M Blay, Montserrat Pinent, Jose M Motilva, Santiago Garciavallve, Gerard Pujadas, Pierre Maechler, Anna ArdevolAbstract:Previous studies from our research group have suggested that procyanidins modify glycemia and Insulinemia. The aim of this work was to evaluate the effects of procyanidins on β-cell functionality in a nonpathological system. Four groups of healthy rats were studied. The animals were given daily acute doses of grape seed procyanidin extract (GSPE) for different time periods and at different daily amounts. A β-cell line (INS-1E) was treated with 25 mg GSPE/L for 24 h to identify possible mechanisms of action for the procyanidins. In vivo experiments showed that different doses of GSPE affected Insulinemia in different ways by modifying β-cell functionality and/or Insulin Degradation. The islets isolated from rats that were treated with 25 mg GSPE/kg of body weight for 45 days exhibited a limited response to glucose stimulation. In addition, Insulin gene expression, Insulin synthesis and expression of genes related to Insulin secretion were all down-regulated. In vitro studies revealed that GSPE decreased the ability of β-cells to secrete Insulin in response to glucose. GSPE increased glucose uptake in β-cells under high-glucose conditions but impaired glucose-induced mitochondrial hyperpolarization, decreased adenosine triphosphate (ATP) synthesis and altered cellular membrane potentials. GSPE also modified Glut2, glucokinase and Ucp2 gene expression as well as altered the expression of hepatic Insulin-degrading enzyme (Ide), thereby altering Insulin Degradation. At some doses, procyanidins changed β-cell functionality by modifying Insulin synthesis, secretion and Degradation under nonpathological conditions. Membrane potentials and Ide provide putative targets for procyanidins to induce these effects.
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procyanidins modify Insulinemia by affecting Insulin production and Degradation
Journal of Nutritional Biochemistry, 2012Co-Authors: Anna Castellauvi, Lidia Cedo, Victor Pallares, Teresa M Blay, Montserrat Pinent, Jose M Motilva, Santiago Garciavallve, Gerard Pujadas, Pierre Maechler, Anna ArdevolAbstract:Previous studies from our research group have suggested that procyanidins modify glycemia and Insulinemia. The aim of this work was to evaluate the effects of procyanidins on β-cell functionality in a nonpathological system. Four groups of healthy rats were studied. The animals were given daily acute doses of grape seed procyanidin extract (GSPE) for different time periods and at different daily amounts. A β-cell line (INS-1E) was treated with 25 mg GSPE/L for 24 h to identify possible mechanisms of action for the procyanidins. In vivo experiments showed that different doses of GSPE affected Insulinemia in different ways by modifying β-cell functionality and/or Insulin Degradation. The islets isolated from rats that were treated with 25 mg GSPE/kg of body weight for 45 days exhibited a limited response to glucose stimulation. In addition, Insulin gene expression, Insulin synthesis and expression of genes related to Insulin secretion were all down-regulated. In vitro studies revealed that GSPE decreased the ability of β-cells to secrete Insulin in response to glucose. GSPE increased glucose uptake in β-cells under high-glucose conditions but impaired glucose-induced mitochondrial hyperpolarization, decreased adenosine triphosphate (ATP) synthesis and altered cellular membrane potentials. GSPE also modified Glut2, glucokinase and Ucp2 gene expression as well as altered the expression of hepatic Insulin-degrading enzyme (Ide), thereby altering Insulin Degradation. At some doses, procyanidins changed β-cell functionality by modifying Insulin synthesis, secretion and Degradation under nonpathological conditions. Membrane potentials and Ide provide putative targets for procyanidins to induce these effects.
Bradley D. Anderson - One of the best experts on this subject based on the ideXlab platform.
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solid state stability of human Insulin ii effect of water on reactive intermediate partitioning in lyophiles from ph 2 5 solutions stabilization against covalent dimer formation
Journal of Pharmaceutical Sciences, 1997Co-Authors: Robert G. Strickley, Bradley D. AndersonAbstract:Abstract Previous studies have established that at low pH human Insulin decomposition proceeds through a two-step mechanism involving rate-limiting intramolecular formation of a cyclic anhydride intermediate at the C-terminal Asn A21 followed by intermediate partitioning to various products, most notably desamido Insulin and covalent dimers, in both aqueous solution and in the amorphous (lyophilized) solid state. This study examines the product distribution resulting from Insulin Degradation in lyophilized powders as a function of water content and the phase behavior of the solid (glassy versus rubbery) between pH 3 and 5. In amorphous solids at low water content (glassy state), the cyclic anhydride intermediate of Insulin reacts predominantly with water to form deamidated Insulin, whereas the intermolecular reaction with another Insulin molecule to form a covalent dimer accounts for ≤15% of the total Degradation. Increasing water content reduces the glass transition temperature of Insulin to A21 position requires only short-range conformational flexibility and thus is only modestly restricted even in the glassy state. On the other hand, the competing bimolecular reactions involving either water or another molecule of Insulin combining with the intermediate anhydride are dependent on molecular mobility of the reactants, in accord with predictions of free volume theory. In the glassy state, deamidation (reaction with water) is favored because of the restricted molecular mobility of proteins in rigid matrices. Increasing plasticization with increasing water content favors covalent aggregate formation because of the higher dependence of protein mobility on free volume within the solid matrix.
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Solid-State Stability of Human Insulin I. Mechanism and the Effect of Water on the Kinetics of Degradation in Lyophiles from pH 2–5 Solutions
Pharmaceutical Research, 1996Co-Authors: Robert G. Strickley, Bradley D. AndersonAbstract:Purpose . Previous studies have established that in aqueous solution at low pH human Insulin decomposition proceeds through a cyclic anhydride intermediate leading to the formation of both deamidated and covalent dimer products. This study examines the mechanism and kinetics of Insulin Degradation in the amorphous solid state (lyophilized powders) as a function of water content over a similar pH range. Methods . Solutions of 1.0 mg/mL Insulin were adjusted to pH 2–5 using HC1, freeze-dried, then exposed to various relative humidities at 35°C. The water content within the powders was determined by Karl Fischer titration, and the concentrations of Insulin and its Degradation products were determined by HPLC. Degradation kinetics were determined by both the initial rates of product formation and Insulin disappearance. Results . Semi-logarithmic plots of Insulin remaining in lyophilized powders versus time were non-linear, asymptotically approaching non-zero apparent plateau values, mathematically describable by a reversible, first-order kinetic model. The rate of Degradation of Insulin in the solid state was observed to increase with decreasing apparent pH (‘pH’) yielding, at any given water content, solid-state ‘pH’-rate profiles parallel to the solution pH-rate profile. This ‘pH’ dependence could be accounted for in terms of the fraction of the Insulin A21 carboxyl in its neutral form, with an apparent pKa of ≈4, independent of water content. Aniline trapping studies established that the mechanism of Degradation of human Insulin in lyophilized powders between pH 3–5 and at 35°C involves rate-limiting intramolecular nucleophilic attack of the Asn_A21 C-terminal carboxylic acid onto the side-chain amide carbonyl to form a reactive cyclic anhydride intermediate, which further reacts with either water or an N-terminal primary amino group (e.g., Phe_B1, and Gly_Al) of another Insulin molecule to generate either deamidated Insulin (Asp_A21) or an amide-linked covalent dimer (e.g., [Asp_A21-Phe_B1] or [Asp_A21-Gly_A1]), respectively. The rate of Insulin Degradation in lyophilized powders at 35°C increases with water content at levels of hydration well below the suspected glass transition and approaches the rate in solution at or near the water content (20–50%) required to induce a glass transition. Conclusions . The decomposition of human Insulin in lyophilized powders between pH 3–5 is a water induced solid-state reaction accelerated by the plasticization effect of sorbed water. The formation of the cyclic anhydride intermediate at A21 occurs readily even in the glassy state, presumably due to the conformational flexibility of the A21 segment even under conditions in which the Insulin molecules as a whole are largely immobile.
Anna Castellauvi - One of the best experts on this subject based on the ideXlab platform.
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procyanidins modify Insulinemia by affecting Insulin production and Degradation
Journal of Nutritional Biochemistry, 2012Co-Authors: Anna Castellauvi, Lidia Cedo, Victor Pallares, Teresa M Blay, Montserrat Pinent, Jose M Motilva, Santiago Garciavallve, Gerard Pujadas, Pierre Maechler, Anna ArdevolAbstract:Previous studies from our research group have suggested that procyanidins modify glycemia and Insulinemia. The aim of this work was to evaluate the effects of procyanidins on β-cell functionality in a nonpathological system. Four groups of healthy rats were studied. The animals were given daily acute doses of grape seed procyanidin extract (GSPE) for different time periods and at different daily amounts. A β-cell line (INS-1E) was treated with 25 mg GSPE/L for 24 h to identify possible mechanisms of action for the procyanidins. In vivo experiments showed that different doses of GSPE affected Insulinemia in different ways by modifying β-cell functionality and/or Insulin Degradation. The islets isolated from rats that were treated with 25 mg GSPE/kg of body weight for 45 days exhibited a limited response to glucose stimulation. In addition, Insulin gene expression, Insulin synthesis and expression of genes related to Insulin secretion were all down-regulated. In vitro studies revealed that GSPE decreased the ability of β-cells to secrete Insulin in response to glucose. GSPE increased glucose uptake in β-cells under high-glucose conditions but impaired glucose-induced mitochondrial hyperpolarization, decreased adenosine triphosphate (ATP) synthesis and altered cellular membrane potentials. GSPE also modified Glut2, glucokinase and Ucp2 gene expression as well as altered the expression of hepatic Insulin-degrading enzyme (Ide), thereby altering Insulin Degradation. At some doses, procyanidins changed β-cell functionality by modifying Insulin synthesis, secretion and Degradation under nonpathological conditions. Membrane potentials and Ide provide putative targets for procyanidins to induce these effects.
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procyanidins modify Insulinemia by affecting Insulin production and Degradation
Journal of Nutritional Biochemistry, 2012Co-Authors: Anna Castellauvi, Lidia Cedo, Victor Pallares, Teresa M Blay, Montserrat Pinent, Jose M Motilva, Santiago Garciavallve, Gerard Pujadas, Pierre Maechler, Anna ArdevolAbstract:Previous studies from our research group have suggested that procyanidins modify glycemia and Insulinemia. The aim of this work was to evaluate the effects of procyanidins on β-cell functionality in a nonpathological system. Four groups of healthy rats were studied. The animals were given daily acute doses of grape seed procyanidin extract (GSPE) for different time periods and at different daily amounts. A β-cell line (INS-1E) was treated with 25 mg GSPE/L for 24 h to identify possible mechanisms of action for the procyanidins. In vivo experiments showed that different doses of GSPE affected Insulinemia in different ways by modifying β-cell functionality and/or Insulin Degradation. The islets isolated from rats that were treated with 25 mg GSPE/kg of body weight for 45 days exhibited a limited response to glucose stimulation. In addition, Insulin gene expression, Insulin synthesis and expression of genes related to Insulin secretion were all down-regulated. In vitro studies revealed that GSPE decreased the ability of β-cells to secrete Insulin in response to glucose. GSPE increased glucose uptake in β-cells under high-glucose conditions but impaired glucose-induced mitochondrial hyperpolarization, decreased adenosine triphosphate (ATP) synthesis and altered cellular membrane potentials. GSPE also modified Glut2, glucokinase and Ucp2 gene expression as well as altered the expression of hepatic Insulin-degrading enzyme (Ide), thereby altering Insulin Degradation. At some doses, procyanidins changed β-cell functionality by modifying Insulin synthesis, secretion and Degradation under nonpathological conditions. Membrane potentials and Ide provide putative targets for procyanidins to induce these effects.
Suzanne Y Guenette - One of the best experts on this subject based on the ideXlab platform.
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Insulin degrading enzyme regulates the levels of Insulin amyloid β protein and the β amyloid precursor protein intracellular domain in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Wesley Farris, Dennis J Selkoe, Matthew P Frosch, Stefan Mansourian, Yang Chang, Loren Lindsley, Elizabeth A Eckman, Christopher B Eckman, Rudolph E Tanzi, Suzanne Y GuenetteAbstract:Two substrates of Insulin-degrading enzyme (IDE), amyloid beta-protein (Abeta) and Insulin, are critically important in the pathogenesis of Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2), respectively. We previously identified IDE as a principal regulator of Abeta levels in neuronal and microglial cells. A small chromosomal region containing a mutant IDE allele has been associated with hyperInsulinemia and glucose intolerance in a rat model of DM2. Human genetic studies have implicated the IDE region of chromosome 10 in both AD and DM2. To establish whether IDE hypofunction decreases Abeta and Insulin Degradation in vivo and chronically increases their levels, we characterized mice with homozygous deletions of the IDE gene (IDE --). IDE deficiency resulted in a >50% decrease in Abeta Degradation in both brain membrane fractions and primary neuronal cultures and a similar deficit in Insulin Degradation in liver. The IDE -- mice showed increased cerebral accumulation of endogenous Abeta, a hallmark of AD, and had hyperInsulinemia and glucose intolerance, hallmarks of DM2. Moreover, the mice had elevated levels of the intracellular signaling domain of the beta-amyloid precursor protein, which was recently found to be degraded by IDE in vitro. Together with emerging genetic evidence, our in vivo findings suggest that IDE hypofunction may underlie or contribute to some forms of AD and DM2 and provide a mechanism for the recently recognized association among hyperInsulinemia, diabetes, and AD.
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Insulin degrading enzyme regulates the levels of Insulin amyloid β protein and the β amyloid precursor protein intracellular domain in vivo
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Wesley Farris, Dennis J Selkoe, Matthew P Frosch, Stefan Mansourian, Yang Chang, Loren Lindsley, Elizabeth A Eckman, Christopher B Eckman, Rudolph E Tanzi, Suzanne Y GuenetteAbstract:Two substrates of Insulin-degrading enzyme (IDE), amyloid β-protein (Aβ) and Insulin, are critically important in the pathogenesis of Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2), respectively. We previously identified IDE as a principal regulator of Aβ levels in neuronal and microglial cells. A small chromosomal region containing a mutant IDE allele has been associated with hyperInsulinemia and glucose intolerance in a rat model of DM2. Human genetic studies have implicated the IDE region of chromosome 10 in both AD and DM2. To establish whether IDE hypofunction decreases Aβ and Insulin Degradation in vivo and chronically increases their levels, we characterized mice with homozygous deletions of the IDE gene (IDE −/−). IDE deficiency resulted in a >50% decrease in Aβ Degradation in both brain membrane fractions and primary neuronal cultures and a similar deficit in Insulin Degradation in liver. The IDE −/− mice showed increased cerebral accumulation of endogenous Aβ, a hallmark of AD, and had hyperInsulinemia and glucose intolerance, hallmarks of DM2. Moreover, the mice had elevated levels of the intracellular signaling domain of the β-amyloid precursor protein, which was recently found to be degraded by IDE in vitro. Together with emerging genetic evidence, our in vivo findings suggest that IDE hypofunction may underlie or contribute to some forms of AD and DM2 and provide a mechanism for the recently recognized association among hyperInsulinemia, diabetes, and AD.