The Flavanol (−)-Epigallocatechin 3-Gallate Inhibits Amyloid Formation by Islet Amyloid Polypeptide, Disaggregates Amyloid Fibrils, and Protects Cultured Cells against IAPP-Induced Toxicity

Type II diabetes mellitus is associated with the deposition of fibrillar aggregates in pancreatic islets. The major protein component of islet amyloids is the glucomodulatory hormone islet amyloid polypeptide (IAPP). Islet amyloid fibrils are virtually always associated with several biomolecules, including apolipoprotein E, metals, glycosaminoglycans, and various lipids. IAPP amyloidogenesis has been originally perceived as a self-assembly homogeneous process in which the inherent aggregation propensity of the peptide and its local concentration constitute the major driving forces to fibrillization. However, over the last two decades, numerous studies have shown a prominent role of amyloid cofactors in IAPP fibrillogenesis associated with the etiology of type II diabetes. It is increasingly evident that the biochemical microenvironment in which IAPP amyloid formation occurs and the interactions of the polypeptide with various biomolecules not only modulate the rate and extent of aggregation, but could also remodel the amyloidogenesis process as well as the structure, toxicity, and stability of the resulting fibrils.

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Extended life span is associated with insulin resistance in a transgenic mouse model of insulinoma secreting human islet amyloid polypeptide

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00137.2003 ◽

2004 ◽

Vol 286 (3) ◽

pp. E418-E424 ◽

Cited By ~ 3

Author(s):

Sofianos Andrikopoulos ◽

Rebecca L. Hull ◽

C. Bruce Verchere ◽

Feng Wang ◽

Shani M. Wilbur ◽

...

Keyword(s):

Insulin Resistance ◽

Life Span ◽

Amyloid Fibrils ◽

Islet Amyloid Polypeptide ◽

Transgenic Animals ◽

Human Islet ◽

Amyloid Formation ◽

Islet Amyloid ◽

Glucose Levels ◽

Human Islet Amyloid Polypeptide

Pancreatic amyloid is found in patients with insulinomas and type 2 diabetes. To study mechanisms of islet amyloidogenesis, we produced transgenic mice expressing the unique component of human islet amyloid, human islet amyloid polypeptide (hIAPP). These mice develop islet amyloid after 12 mo of high-fat feeding. To determine whether we could accelerate the rate of islet amyloid formation, we crossbred our hIAPP transgenic animals with RIP-Tag mice that develop islet tumors and die at 12 wk of age from hypoglycemia. At 12 wk of age, this new line of hIAPP×RIP-Tag mice was heavier (29.7 ± 1.0 vs. 25.0 ± 1.3 g, P < 0.05) and had increased plasma glucose levels (4.6 ± 0.4 vs. 2.9 ± 0.6 mmol/l, P < 0.05) compared with littermate RIP-Tag mice. However, the hIAPP×RIP-Tag mice did not display islet amyloid or amyloid fibrils despite high circulating hIAPP levels (24.6 ± 7.0 pmol/l). Interestingly, hIAPP×RIP-Tag mice had a longer life span than RIP-Tag mice (121 ± 8 vs. 102 ± 5 days, P < 0.05). This increase in life span in hIAPP×RIP-Tag was positively correlated with body weight ( r = 0.48, P < 0.05) and was associated with decreased insulin sensitivity compared with RIP-Tag mice. hIAPP×RIP-Tag mice did not develop amyloid during their 4-mo life span, suggesting that increased hIAPP secretion is insufficient for islet amyloid formation within such a short time. However, hIAPP×RIP-Tag mice did have an increase in life span that was associated with insulin resistance, suggesting that hIAPP has extrapancreatic effects, possibly on peripheral glucose metabolism.

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The Role of the 14–20 Domain of the Islet Amyloid Polypeptide in Amyloid Formation

Experimental Diabetes Research ◽

10.1155/2008/256954 ◽

2008 ◽

Vol 2008 ◽

pp. 1-8 ◽

Cited By ~ 29

Author(s):

Sharon Gilead ◽

Ehud Gazit

Keyword(s):

Molecular Recognition ◽

Molecular Mechanism ◽

Amyloid Fibrils ◽

Recent Literature ◽

Islet Amyloid Polypeptide ◽

Supporting Evidence ◽

Amyloid Formation ◽

Islet Amyloid ◽

Human And Mouse

The molecular mechanism of amyloid formation by the islet amyloid polypeptide (IAPP) has been intensively studied since its identification in the late 1980s. The IAPP(20–29) region is considered to be the central amyloidogenic module of the polypeptide. This assumption is mainly based on the amyloidogenic properties of the region and on the large sequence diversity within this region between the human and mouse IAPP, as the mouse IAPP does not form amyloids. A few years ago, another region within IAPP was identified that seems to be at least as important as IAPP(20–29) in facilitation of molecular recognition that leads to amyloid formation. Here, we reinforce our and others' previous findings by analyzing supporting evidence from the recent literature. Moreover, we provide new proofs to our hypothesis by comparing between the amyloidogenic properties of the two regions derived from the IAPP of cats, which is also known to form amyloid fibrils.

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Matrix Metalloproteinase-9 Reduces Islet Amyloid Formation by Degrading Islet Amyloid Polypeptide

Journal of Biological Chemistry ◽

10.1074/jbc.m112.438457 ◽

2012 ◽

Vol 288 (5) ◽

pp. 3553-3559 ◽

Cited By ~ 23

Author(s):

Kathryn Aston-Mourney ◽

Sakeneh Zraika ◽

Jayalakshmi Udayasankar ◽

Shoba L. Subramanian ◽

Pattie S. Green ◽

...

Keyword(s):

Matrix Metalloproteinase ◽

Islet Amyloid Polypeptide ◽

Matrix Metalloproteinase 9 ◽

Amyloid Formation ◽

Islet Amyloid ◽

Metalloproteinase 9

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

Biochemical Journal ◽

10.1042/bj20030852 ◽

2004 ◽

Vol 377 (3) ◽

pp. 709-716 ◽

Cited By ~ 67

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.

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