Discovery of ethyl urea derivatives as inhibitors of islet amyloid polypeptide fibrillization and cytotoxicity

2016 ◽  
Vol 94 (3) ◽  
pp. 341-346 ◽  
Author(s):  
Jessica S. Fortin ◽  
Marie-Odile Benoit-Biancamano ◽  
René C.-Gaudreault
Keyword(s):  
Small Molecules ◽  
Islet Amyloid Polypeptide ◽  
Islet Amyloid ◽  
Cytotoxic Effects ◽  
Urea Derivatives ◽  
Amyloid Deposits ◽  
Survival Assay

Islet amyloid polypeptide (IAPP) has been shown to form amyloid deposits in pancreatic islets, thereby furthering type 2 diabetes disease progression. Further discovery of new molecules is needed to create a diverse set of molecules that impede pancreatic amyloidosis. We have recently designed and synthesized N-phenyl-N′-(2-ethyl)ureas (EU) that are non-cytotoxic small molecules, to evaluate the role of the aryl-substituted moiety on the inhibition of hIAPP fibrillization. Several EUs were tested in vitro for their anti-amyloidogenic activity using the fluorometric ThT assay, the photo-induced cross-linking (PIUCP) assay, and cell survival assay in pancreatic MIN-6 cells. EU-362 and EU-418 were able to significantly inhibit the formation of hIAPP fibrils and protected cells from amyloid cytotoxic effects. Our results suggest that increasing the nucleophilic potency of the aryl moiety significantly enhances the anti-amyloidogenic activity of the molecules.

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 Amyloid damage to islet β-cells in type 2 diabetes: hypoxia or pseudo-hypoxia?

2019 ◽  
Author(s):  
Vittorio Bellotti ◽  
Alessandra Corazza ◽  
Beatrice Foglia ◽  
Erica Novo ◽  
J. Paul Simons ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Amyloid Deposition ◽  
Β Cells ◽  
Islet Amyloid ◽  
Good Tool ◽  
Amyloid Deposits ◽  
Oxygen Perfusion

ABSTRACTAggregation of islet amyloid polypeptide (IAPP) and amyloid deposition in the islets of Langerhans may significantly contribute to the multifactorial pathogenic mechanisms leading to type 2 diabetes. A direct toxic effect on β-cells of oligomeric IAAP has been demonstrated in in vitro models, but the mechanism operating in vivo is still unclear. Mice models presenting amyloid deposition and glucose intolerance represent a good tool for exploring in vivo a putative mechanism of toxicity directly related to the physical expansion of the extracellular matrix by the amyloid fibrillar aggregates. Based on our hypothesis that deposition of amyloid may influence the oxygen perfusion, we have calculated that the mean distribution of oxygen partial pressure would drop by more than 50 % in the presence of amyloid deposits in the islet. This condition of hypoxia caused by the remodelling of the extracellular space may explain the metabolic abnormalities in the Langerhans islets, otherwise interpreted as pseudo-hypoxic response to IAPP oligomers.

scholarly journals Extracellular vesicles from human pancreatic islets suppress human islet amyloid polypeptide amyloid formation

2017 ◽  
Vol 114 (42) ◽  
pp. 11127-11132 ◽  
Author(s):  
Diana Ribeiro ◽  
Istvan Horvath ◽  
Nikki Heath ◽  
Ryan Hicks ◽  
Anna Forslöw ◽  
...  
Keyword(s):  
Pancreatic Islets ◽  
Extracellular Vesicles ◽  
Islet Amyloid Polypeptide ◽  
Cell Communication ◽  
Human Islet ◽  
Amyloid Formation ◽  
Islet Amyloid ◽  
Human Islet Amyloid Polypeptide ◽  
Amyloid Deposits

Extracellular vesicles (EVs) are small vesicles released by cells to aid cell–cell communication and tissue homeostasis. Human islet amyloid polypeptide (IAPP) is the major component of amyloid deposits found in pancreatic islets of patients with type 2 diabetes (T2D). IAPP is secreted in conjunction with insulin from pancreatic β cells to regulate glucose metabolism. Here, using a combination of analytical and biophysical methods in vitro, we tested whether EVs isolated from pancreatic islets of healthy patients and patients with T2D modulate IAPP amyloid formation. We discovered that pancreatic EVs from healthy patients reduce IAPP amyloid formation by peptide scavenging, but T2D pancreatic and human serum EVs have no effect. In accordance with these differential effects, the insulin:C-peptide ratio and lipid composition differ between EVs from healthy pancreas and EVs from T2D pancreas and serum. It appears that healthy pancreatic EVs limit IAPP amyloid formation via direct binding as a tissue-specific control mechanism.

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.

scholarly journals Molecular Structure, Membrane Interactions, and Toxicity of the Islet Amyloid Polypeptide in Type 2 Diabetes Mellitus

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Lucie Caillon ◽  
Anais R. F. Hoffmann ◽  
Alexandra Botz ◽  
Lucie Khemtemourian
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Membrane Damage ◽  
Islet Amyloid Polypeptide ◽  
Amyloid Formation ◽  
Membrane Interactions ◽  
Islet Amyloid ◽  
Amyloid Deposits

Human islet amyloid polypeptide (hIAPP) is the major component of the amyloid deposits found in the pancreatic islets of patients with type 2 diabetes mellitus (T2DM). Mature hIAPP, a 37-aa peptide, is natively unfolded in its monomeric state but forms islet amyloid in T2DM. In common with other misfolded and aggregated proteins, amyloid formation involves aggregation of monomers of hIAPP into oligomers, fibrils, and ultimately mature amyloid deposits. hIAPP is coproduced and stored with insulin by the pancreatic isletβ-cells and is released in response to the stimuli that lead to insulin secretion. Accumulating evidence suggests that hIAPP amyloid deposits that accompany T2DM are not just an insignificant phenomenon derived from the disease progression but that hIAPP aggregation induces processes that impair the functionality and the viability ofβ-cells. In this review, we particularly focus on hIAPP structure, hIAPP aggregation, and hIAPP-membrane interactions. We will also discuss recent findings on the mechanism of hIAPP-membrane damage and on hIAPP-induced cell death. Finally, the development of successful antiamyloidogenic agents that prevent hIAPP fibril formation will be examined.

scholarly journals Islet amyloid deposits preferentially in the highly functional and most blood-perfused islets

2017 ◽  
Vol 6 (7) ◽  
pp. 458-468 ◽  
Author(s):  
Sara Ullsten ◽  
Sara Bohman ◽  
Marie E Oskarsson ◽  
K Peter R Nilsson ◽  
Gunilla T Westermark ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
High Fat Diet ◽  
Islet Amyloid Polypeptide ◽  
Prohormone Convertase ◽  
Amyloid Formation ◽  
High Fat ◽  
Islet Amyloid ◽  
Amyloid Deposits ◽  
Release Capacity

Islet amyloid and beta cell death in type 2 diabetes are heterogeneous events, where some islets are affected early in the disease process, whereas others remain visibly unaffected. This study investigated the possibility that inter-islet functional and vascular differences may explain the propensity for amyloid accumulation in certain islets. Highly blood-perfused islets were identified by microspheres in human islet amyloid polypeptide expressing mice fed a high-fat diet for three or 10 months. These highly blood-perfused islets had better glucose-stimulated insulin secretion capacity than other islets and developed more amyloid deposits after 10 months of high-fat diet. Similarly, human islets with a superior release capacity formed more amyloid in high glucose culture than islets with a lower release capacity. The amyloid formation in mouse islets was associated with a higher amount of prohormone convertase 1/3 and with a decreased expression of its inhibitor proSAAS when compared to islets with less amyloid. In contrast, levels of prohormone convertase 2 and expression of its inhibitor neuroendocrine protein 7B2 were unaltered. A misbalance in prohormone convertase levels may interrupt the normal processing of islet amyloid polypeptide and induce amyloid formation. Preferential amyloid load in the most blood-perfused and functional islets may accelerate the progression of type 2 diabetes.

Photodegradation of porphyrin-bound hIAPP(1–37) fibrils

2020 ◽  
Vol 44 (22) ◽  
pp. 9438-9443
Author(s):  
Yongxiu Song ◽  
Ping Li ◽  
Zhiming Zhang ◽  
Yin Wang ◽  
Zhefei Zhang ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Pancreatic Islets ◽  
Islet Amyloid Polypeptide ◽  
Human Islet ◽  
Preventive Strategy ◽  
Islet Amyloid ◽  
Amyloid Deposits

Amyloid deposits in pancreatic islets of type 2 diabetes mellitus (T2DM) are mainly comprised of human islet amyloid polypeptide (hIAPP), the degradation of hIAPP fibrils by photoactive porphyrin could be a preventive strategy against T2DM.

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.

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