scholarly journals Pancreatic beta-cell granule peptides form heteromolecular complexes which inhibit islet amyloid polypeptide fibril formation

2004 ◽  
Vol 377 (3) ◽  
pp. 709-716 ◽  
Author(s):  
Emma T. A. S. JAIKARAN ◽  
Melanie R. NILSSON ◽  
Anne CLARK
Keyword(s):  
Type 2 Diabetes ◽  
Amyloid Fibrils ◽  
Secretory Granules ◽  
Pancreatic Beta Cell ◽  
Islet Amyloid Polypeptide ◽  
Fibril Formation ◽  
Islet Amyloid ◽  
Β Sheet

Islet amyloid polypeptide (IAPP), or ‘amylin’, is co-stored with insulin in secretory granules of pancreatic islet β-cells. In Type 2 diabetes, IAPP converts into a β-sheet conformation and oligomerizes to form amyloid fibrils and islet deposits. Granule components, including insulin, inhibit spontaneous IAPP fibril formation in vitro. To determine the mechanism of this inhibition, molecular interactions of insulin with human IAPP (hIAPP), rat IAPP (rIAPP) and other peptides were examined using surface plasmon resonance (BIAcore), CD and transmission electron microscopy (EM). hIAPP and rIAPP complexed with insulin, and this reaction was concentration-dependent. rIAPP and insulin, but not pro-insulin, bound to hIAPP. Insulin with a truncated B-chain, to prevent dimerization, also bound hIAPP. In the presence of insulin, hIAPP did not spontaneously develop β-sheet secondary structure or form fibrils. Insulin interacted with pre-formed IAPP fibrils in a regular repeating pattern, as demonstrated by immunoEM, suggesting that the binding sites for insulin remain exposed in hIAPP fibrils. Since rIAPP and hIAPP form complexes with insulin (and each other), this could explain the lack of amyloid fibrils in transgenic mice expressing hIAPP. It is likely that IAPP fibrillogenesis is inhibited in secretory granules (where the hIAPP concentration is in the millimolar range) by heteromolecular complex formation with insulin. Alterations in the proportions of insulin and IAPP in granules could disrupt the stability of the peptide. The increase in the proportion of unprocessed pro-insulin produced in Type 2 diabetes could be a major factor in destabilization of hIAPP and induction of fibril formation.

scholarly journals BRICHOS domain of Bri2 inhibits islet amyloid polypeptide (IAPP) fibril formation and toxicity in human beta cells

2018 ◽  
Vol 115 (12) ◽  
pp. E2752-E2761 ◽  
Author(s):  
Marie E. Oskarsson ◽  
Erik Hermansson ◽  
Ye Wang ◽  
Nils Welsh ◽  
Jenny Presto ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Beta Cells ◽  
Transmembrane Protein ◽  
Islet Amyloid Polypeptide ◽  
Fibril Formation ◽  
Islet Amyloid ◽  
Peripheral Tissues ◽  
Beta Cell Line

Aggregation of islet amyloid polypeptide (IAPP) into amyloid fibrils in islets of Langerhans is associated with type 2 diabetes, and formation of toxic IAPP species is believed to contribute to the loss of insulin-producing beta cells. The BRICHOS domain of integral membrane protein 2B (Bri2), a transmembrane protein expressed in several peripheral tissues and in the brain, has recently been shown to prevent fibril formation and toxicity of Aβ42, an amyloid-forming peptide in Alzheimer disease. In this study, we demonstrate expression of Bri2 in human islets and in the human beta-cell line EndoC-βH1. Bri2 colocalizes with IAPP intracellularly and is present in amyloid deposits in patients with type 2 diabetes. The BRICHOS domain of Bri2 effectively inhibits fibril formation in vitro and instead redirects IAPP into formation of amorphous aggregates. Reduction of endogenous Bri2 in EndoC-βH1 cells with siRNA increases sensitivity to metabolic stress leading to cell death while a concomitant overexpression of Bri2 BRICHOS is protective. Also, coexpression of IAPP and Bri2 BRICHOS in lateral ventral neurons of Drosophila melanogaster results in an increased cell survival. IAPP is considered to be the most amyloidogenic peptide known, and described findings identify Bri2, or in particular its BRICHOS domain, as an important potential endogenous inhibitor of IAPP aggregation and toxicity, with the potential to be a possible target for the treatment of type 2 diabetes.

scholarly journals Islet Amyloid Polypeptide: Structure, Function, and Pathophysiology

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Rehana Akter ◽  
Ping Cao ◽  
Harris Noor ◽  
Zachary Ridgway ◽  
Ling-Hsien Tu ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Cell Death ◽  
Type 1 Diabetes ◽  
Islet Amyloid Polypeptide ◽  
Amyloid Formation ◽  
Islet Amyloid

The hormone islet amyloid polypeptide (IAPP, or amylin) plays a role in glucose homeostasis but aggregates to form islet amyloid in type-2 diabetes. Islet amyloid formation contributes toβ-cell dysfunction and death in the disease and to the failure of islet transplants. Recent work suggests a role for IAPP aggregation in cardiovascular complications of type-2 diabetes and hints at a possible role in type-1 diabetes. The mechanisms of IAPP amyloid formationin vivoorin vitroare not understood and the mechanisms of IAPP inducedβ-cell death are not fully defined. Activation of the inflammasome, defects in autophagy, ER stress, generation of reactive oxygen species, membrane disruption, and receptor mediated mechanisms have all been proposed to play a role. Open questions in the field include the relative importance of the various mechanisms ofβ-cell death, the relevance of reductionist biophysical studies to the situationin vivo, the molecular mechanism of amyloid formationin vitroandin vivo, the factors which trigger amyloid formation in type-2 diabetes, the potential role of IAPP in type-1 diabetes, the development of clinically relevant inhibitors of islet amyloidosis toxicity, and the design of soluble, bioactive variants of IAPP for use as adjuncts to insulin therapy.

Islet Amyloid Polypeptide, Islet Amyloid, and Diabetes Mellitus

2011 ◽  
Vol 91 (3) ◽  
pp. 795-826 ◽  
Author(s):  
Per Westermark ◽  
Arne Andersson ◽  
Gunilla T. Westermark
Keyword(s):  
Type 2 Diabetes ◽  
Pancreatic Islets ◽  
Amyloid Fibrils ◽  
Mammalian Species ◽  
Islet Amyloid Polypeptide ◽  
Glucagon Secretion ◽  
Β Cells ◽  
Islet Amyloid ◽  
Pancreatic Islets Of Langerhans

Islet amyloid polypeptide (IAPP, or amylin) is one of the major secretory products of β-cells of the pancreatic islets of Langerhans. It is a regulatory peptide with putative function both locally in the islets, where it inhibits insulin and glucagon secretion, and at distant targets. It has binding sites in the brain, possibly contributing also to satiety regulation and inhibits gastric emptying. Effects on several other organs have also been described. IAPP was discovered through its ability to aggregate into pancreatic islet amyloid deposits, which are seen particularly in association with type 2 diabetes in humans and with diabetes in a few other mammalian species, especially monkeys and cats. Aggregated IAPP has cytotoxic properties and is believed to be of critical importance for the loss of β-cells in type 2 diabetes and also in pancreatic islets transplanted into individuals with type 1 diabetes. This review deals both with physiological aspects of IAPP and with the pathophysiological role of aggregated forms of IAPP, including mechanisms whereby human IAPP forms toxic aggregates and amyloid fibrils.

scholarly journals Molecular Docking Studies of Possible Treatment of Diabetes using Vasicine against Islet Amyloid Polypeptide

2021 ◽  
Vol 9 (VI) ◽  
pp. 4202-4209
Author(s):  
Tushar Kumar
Keyword(s):  
Type 2 Diabetes ◽  
Insulin Secretion ◽  
Molecular Docking ◽  
Islet Amyloid Polypeptide ◽  
Docking Studies ◽  
Islet Amyloid ◽  
Molecular Docking Studies ◽  
The World ◽  
Treatment Of Diabetes

Diabetes is the becoming one of the most common problem all over the world. About 1 in 10 persons are suffering from diabetes and most from type 2 diabetes. It occurs due to problem in pancreas which further results defect in the insulin secretion, as insulin maintains blood glucose level. The effect of Alpha-Amyrin Acetate, Myrcene and Vasicine compounds against Islet Amyloid polypeptide (IAPP) protein was seen through molecular docking studies. IAPP acts as complementary to insulin in regulating the sugar level for the treatment of diabetes disease by virtual screening. Different tools and software used in this research were Uniprot, Pubchem, Swiss ADMS, PyRx, Auto dock Vina/MGL tool and PyMOL.

scholarly journals Dietary Supplementation with Curcumin Reduce Circulating Levels of Glycogen Synthase Kinase-3β and Islet Amyloid Polypeptide in Adults with High Risk of Type 2 Diabetes and Alzheimer’s Disease

Nutrients ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1032 ◽  
Author(s):  
Rohith N Thota ◽  
Jessica I Rosato ◽  
Cintia B Dias ◽  
Tracy L Burrows ◽  
Ralph N Martins ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Placebo Group ◽  
Glycogen Synthase ◽  
Islet Amyloid Polypeptide ◽  
Dietary Supplementation ◽  
Islet Amyloid ◽  
Gsk 3Β ◽  
Circulating Levels

Dietary supplementation with curcumin has been previously reported to have beneficial effects in people with insulin resistance, type 2 diabetes (T2D) and Alzheimer’s disease (AD). This study investigated the effects of dietary supplementation with curcumin on key peptides implicated in insulin resistance in individuals with high risk of developing T2D. Plasma samples from participants recruited for a randomised controlled trial with curcumin (180 mg/day) for 12 weeks were analysed for circulating glycogen synthase kinase-3 β (GSK-3β) and islet amyloid polypeptide (IAPP). Outcome measures were determined using ELISA kits. The homeostasis model for assessment of insulin resistance (HOMA-IR) was measured as parameters of glycaemic control. Curcumin supplementation significantly reduced circulating GSK-3β (−2.4 ± 0.4 ng/mL vs. −0.3 ± 0.6, p = 0.0068) and IAPP (−2.0 ± 0.7 ng/mL vs. 0.4 ± 0.6, p = 0.0163) levels compared with the placebo group. Curcumin supplementation significantly reduced insulin resistance (−0.3 ± 0.1 vs. 0.01 ± 0.05, p = 0.0142) compared with placebo group. Dietary supplementation with curcumin reduced circulating levels of IAPP and GSK-3β, thus suggesting a novel mechanism through which curcumin could potentially be used for alleviating insulin resistance related markers for reducing the risk of T2D and AD.

scholarly journals Islet amyloid polypeptide gene promoter polymorphisms are not associated with Type 2 diabetes or with the severity of islet amyloidosis

2005 ◽  
Vol 1740 (1) ◽  
pp. 74-78 ◽  
Author(s):  
Christopher Esapa ◽  
Jennifer H. Moffitt ◽  
Anna Novials ◽  
Catherine M. McNamara ◽  
Jonathan C. Levy ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Islet Amyloid Polypeptide ◽  
Gene Promoter ◽  
Promoter Polymorphisms ◽  
Islet Amyloid
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