scholarly journals Analysis of Amylin Consensus Sequences Suggests That Human Amylin Is Not Optimized to Minimize Amyloid Formation and Provides Clues to Factors That Modulate Amyloidogenicity

2020 ◽  
Vol 15 (6) ◽  
pp. 1408-1416
Author(s):  
Daeun Noh ◽  
Rebekah L. Bower ◽  
Debbie L. Hay ◽  
Alexander Zhyvoloup ◽  
Daniel P. Raleigh
Keyword(s):  
Amyloid Formation ◽  
Consensus Sequences ◽  
Human Amylin

scholarly journals Suppression by polycyclic compounds of the conversion of human amylin into insoluble amyloid

2003 ◽  
Vol 374 (3) ◽  
pp. 779-784 ◽  
Author(s):  
Jacqueline F. AITKEN ◽  
Kerry M. LOOMES ◽  
Barbara KONARKOWSKA ◽  
Garth J. S. COOPER
Keyword(s):  
Acridine Orange ◽  
Congo Red ◽  
Type Ii Diabetes Mellitus ◽  
Significant Inhibition ◽  
Molar Ratio ◽  
Amyloid Formation ◽  
Islet Amyloid ◽  
Polycyclic Compounds ◽  
Molar Excess ◽  
Human Amylin

There is a significant correlation between the occurrence of pancreatic islet amyloid and β-cell failure in advanced type II diabetes mellitus. Islet amyloid is composed primarily of the fibrillar form of the pancreatic hormone, amylin. Using thioflavin-T fluorescence binding and radioprecipitation assays, we investigated whether or not a series of small tricyclic compounds, tetracycline or Congo Red could interfere with the conversion of synthetic human amylin into its insoluble amyloid form. Of the compounds investigated, incubation of human amylin with a 20-fold molar excess of either Congo Red or Acridine Orange resulted in significant inhibition in the rate of amyloid formation. With Congo Red, maximal inhibition effectively occurred at a 1:1 molar ratio or greater over human amylin, whereas inhibition by Acridine Orange was dose-dependent. A 20-fold molar excess of the compound tetracycline also decreased insoluble amyloid content after extended incubation periods of approx. 20 h. Amyloid fibril morphology in the presence of tetracycline, as measured by transmission electron microscopy, was characterized by short fragmented fibrils compared with the longer and denser appearance of fibrils formed by amylin alone. These findings show that polycyclic compounds can suppress the formation of amyloid by human amylin, providing support for an alternative approach to peptide-based strategies by which islet amyloid formation could be modulated.

scholarly journals The Fluorescent Dye 1,6-Diphenyl-1,3,5-Hexatriene Binds to Amyloid Fibrils Formed by Human Amylin and Provides a New Probe of Amylin Amyloid Kinetics

2021 ◽  
Author(s):  
Ming-Hao Li ◽  
Lakshan Manathunga ◽  
Erwin London ◽  
Daniel Raleigh
Keyword(s):  
Time Course ◽  
Amyloid Fibrils ◽  
Fold Increase ◽  
Fluorescent Dye ◽  
Thioflavin T ◽  
Lag Phase ◽  
Amyloid Formation ◽  
Islet Amyloid ◽  
Human Amylin ◽  
Mutant Forms

The fluorescent dye 1,6-diphenyl-1,3,5-hexatriene (DPH) is widely used as a probe of membrane order. We show that DPH also interacts with amyloid fibrils formed by human amylin (also known as islet amyloid polypeptide) in solution and this results in a 100-fold increase in DPH fluorescence for a sample of microM human amylin and 0.25 microM DPH. No increase in DPH fluorescence is observed with the non-amyloidogenic rat amylin or with freshly dissolved, non-fibrillar human amylin. The time course of amyloid formation by amylin was followed by monitoring the fluorescence of added DPH as a function of time and was similar to that monitored by the standard fluorescent probe thioflavin-T. The inclusion of DPH in the buffer did not perturb the time course of amyloid formation under the conditions examined and the time course was independent of the range of DPH concentrations tested (0.25 to 5 microM). Maximum final fluorescence intensity is observed at substoichiometric ratios of DPH to amylin. No significant increase in fluorescence was observed during the lag phase of amyloid formation, and the implications for the structure of amylin pre-fibril oligomers are discussed. Human amylin contains three aromatic residues. A triple aromatic to leucine mutant forms amyloid and DPH binds to the resulting fibrils, indicating that interactions with aromatic side chains are not required for DPH amylin amyloid interactions. DPH may be especially useful for studies on mutant amylins and other polypeptides in which changes in charged residues might complicate interpretation of thioflavin-T fluorescence.

scholarly journals Human Amylin Oligomer Growth and Fibril Elongation Define Two Distinct Phases in Amyloid Formation

2004 ◽  
Vol 279 (13) ◽  
pp. 12206-12212 ◽  
Author(s):  
Janelle D. Green ◽  
Claire Goldsbury ◽  
Joerg Kistler ◽  
Garth J. S. Cooper ◽  
Ueli Aebi
Keyword(s):  
Amyloid Formation ◽  
Human Amylin

scholarly journals Amyloidogenicity and cytotoxicity of des-Lys-1 human amylin provides insight into amylin self-assembly and highlights the difficulties of defining amyloidogenicity

2019 ◽  
Vol 32 (2) ◽  
pp. 87-93 ◽  
Author(s):  
Kyung-Hoon Lee ◽  
Alexander Zhyvoloup ◽  
Daniel Raleigh
Keyword(s):  
Self Assembly ◽  
Amyloid Formation ◽  
Wild Type ◽  
Islet Amyloid ◽  
High Charge Density ◽  
Human Amylin ◽  
Phosphate Buffered Saline

Abstract The polypeptide amylin is responsible for islet amyloid in type 2 diabetes, a process which contributes to β-cell death in the disease. The role of the N-terminal region of amylin in amyloid formation is relatively unexplored, although removal of the disulfide bridged loop between Cys-2 and Cys-7 accelerates amyloid formation. We examine the des Lys-1 variant of human amylin (h-amylin), a variant which is likely produced in vivo. Lys-1 is a region of high charge density in the h-amylin amyloid fiber. The des Lys-1 polypeptide forms amyloid on the same time scale as wild-type amylin in phosphate buffered saline, but does so more rapidly in Tris. The des Lys-1 variant is somewhat less toxic to cultured INS cells than wild type. The implications for the in vitro mechanism of amyloid formation and for comparative analysis of amyloidogenicity are discussed.

scholarly journals Cyanidin-3-O-Glucoside improves the viability of human islet cells treated with amylin or Aβ1-42 in vitro

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258208
Author(s):  
Jennifer Croden ◽  
Josue Rodrigues Silva ◽  
Wenlong Huang ◽  
Nancy Gupta ◽  
Wen Fu ◽  
...  
Keyword(s):  
Cell Viability ◽  
Islet Cells ◽  
Human Islets ◽  
Amyloid Formation ◽  
Post Transplant ◽  
Anti Oxidant ◽  
And Function ◽  
Human Amylin

Islet transplantation is being considered as an alternative treatment for type 1 diabetes. Despite recent progress, transplant recipients continue to experience progressive loss of insulin independence. Cyanidin-3-O-Glucoside (C3G) has shown to be protective against damage that may lead to post-transplant islet loss. In this study, human islets cultured with or without C3G were treated with human amylin, Aβ1-42, H2O2, or rapamycin to mimic stresses encountered in the post-transplant environment. Samples of these islets were collected and assayed to determine C3G’s effect on cell viability and function, reactive oxygen species (ROS), oxidative stress, amyloid formation, and the presence of inflammatory as well as autophagic markers. C3G treatment of human islets exposed to either amylin or Aβ1-42 increased cell viability (p<0.01) and inhibited amyloid formation (p<0.01). A reduction in ROS and an increase in HO-1 gene expression as well as in vitro islet function were also observed in C3G-treated islets exposed to amylin or Aβ1-42, although not significantly. Additionally, treatment with C3G resulted in a significant reduction in the protein expression of inflammatory markers IL-1β and NLRP3 (p<0.01) as well as an increase in LC3 autophagic marker (p<0.05) in human islets treated with amylin, Aβ1-42, rapamycin, or H2O2. Thus, C3G appears to have a multi-faceted protective effect on human islets in vitro, possibly through its anti-oxidant property and alteration of inflammatory as well as autophagic pathways.

Role of Aromatic Interactions in Amyloid Formation by Peptides Derived from Human Amylin†

Biochemistry ◽  
2004 ◽  
Vol 43 (50) ◽  
pp. 15901-15908 ◽  
Author(s):  
Sylvia M. Tracz ◽  
Andisheh Abedini ◽  
Miles Driscoll ◽  
Daniel P. Raleigh
Keyword(s):  
Amyloid Formation ◽  
Aromatic Interactions ◽  
Human Amylin

Effects of pramlintide, an analog of human amylin, on plasma glucose profiles in patients with IDDM: results of a multicenter trial

Diabetes ◽  
1997 ◽  
Vol 46 (4) ◽  
pp. 632-636 ◽  
Author(s):  
R. G. Thompson ◽  
J. Peterson ◽  
A. Gottlieb ◽  
J. Mullane
Keyword(s):  
Plasma Glucose ◽  
Multicenter Trial ◽  
Glucose Profiles ◽  
Human Amylin

Heparin induces amyloid formation in cultured human isletss

2007 ◽  
Vol 30 (4) ◽  
pp. 92 ◽  
Author(s):  
K Potter ◽  
K Park
Keyword(s):  
Cell Death ◽  
B Cells ◽  
Islet Transplantation ◽  
Islet Cell ◽  
Human Islets ◽  
Fibril Formation ◽  
Amyloid Formation ◽  
Secretory Product ◽  
Islet Amyloid ◽  
Heparin Sulfate

Background: Pancreatic islet transplantation offers improved glycemic control in type 1 diabetic patients above standard insulin therapy, ideally minimizing macro- and microvascular complications of diabetes mellitus. However success is limited thus far, with fewer than 10% of patients retaining insulin independence at two years post-transplantation. In addition to immune rejection, many non-immune factors may promote long-term graft secretory dysfunction and loss of viable graft mass. One such important non-immune factor may be the formation of islet amyloid, a pathologic lesion of the islet in type 2 diabetes that contributes to the progressive loss of b cells in that disease and that has been shown to form rapidly in human islets transplanted into NOD.scid mice. Amyloid deposits are composed primarily of the b cell secretory product islet amyloid polypeptide (IAPP), are cytotoxic, and develop in environments in which b cells are stressed. Heparin sulfate is used as an anti-coagulant in clinical islet transplantation and to prevent the instant blood-mediated inflammatory reaction (IBMIR), which occurs upon contact between islets and blood and may destroy a substantial proportion of the grafted islet mass. However, heparin is also known to stimulate amyloid fibril formation. Methods: To determine whether heparin may enhance amyloid formation in human islets and contribute to graft failure, we cultured isolated human islets in the presence or absence of heparin sulfate (42 and 420 units/ml) for 2 weeks in 11.1 mM glucose. Results: Histological assessment of sections of cultured islets for the presence of amyloid (by thioflavin S staining) revealed a marked, concentration-dependent increase in amyloid deposition following culture in the presence of heparin. Quantitative analysis of these sections showed that the proportion of islet area comprised of amyloid was increased approximately 2-fold (0.15%±0.12% vs 0.46%±0.15% of islet area) following culture in 42 units/ml heparin, and the proportion of islets in which amyloid was detectable (amyloid prevalence) was also increased (35%±24% vs 68%±10% of islets). At 420 units/ml heparin, the amyloid area was even greater (0.23%±0.15% vs 0.97%±0.42% of islet area) as was the amyloid prevalence (53%±29% vs 81%±14% of islets). To affirm that heparin can stimulate IAPP fibrillogenesis and enhance IAPP toxicity, we incubated synthetic human IAPP in the presence of heparin and measured amyloid formation in real time by thioflavin T fluorescence, and cell toxicity by Alamar blue viability assay in transformed rat (INS-1) ß-cell cultures. Heparin stimulated IAPP fibril formation and increased death of INS-1 cells exposed to IAPP (78.2%±10.9% vs 51.8%±12.2% of control viability), suggesting that heparin stimulates IAPP aggregation and toxicity. Remarkably, preliminary assessment of human islets cultured in heparin did not show increased islet cell death by TUNEL staining or loss of insulin immunostaining. Conclusion: In summary, heparin increases amyloid formation in cultured human islets. Although our preliminary data does not suggest that heparin-induced amyloid formation contributes to islet cell death, we speculate that heparin-induced amyloid formation may contribute to graft dysfunction and that caution should be used in the clinical application of this drug in islet transplantation.

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