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A Small Molecule Impedes Insulin Fibrillation: Another New Role of Phenothiazine Derivatives.

ABSTRACT: Protein misfolding is interrelated to several diseases, including neurodegenerative diseases and type?II diabetes. Misfolded/unfolded proteins produce soluble oligomers that accumulate into "amyloid plaques". Inhibition of amyloid-plaque formation by those misfolded/unfolded proteins will lead to the invention of new therapeutic approaches for amyloid-related diseases. Herein, methylene blue (MB), a well-defined drug against multiple diseases and disorders, is used to impede insulin fibrillation. In this study, we perform an array of in?vitro experiments to monitor the effects of MB on the fibrillation of bovine insulin. Our results confirm that MB distresses the kinetics of insulin fibrillation by interacting with insulin in its monomeric form. A thioflavin?T assay indicates that insulin fibrillation is interrupted upon the addition of MB. The same results are confirmed by circular dichroism, dynamic light scattering (DLS), and size-exclusion chromatography (SEC). According to the DLS data, the insulin fibrils are 800?nm in diameter, and the addition of MB reduces the size of the fibrils, which remain 23?nm in size, and this indicates that no fibrillation of insulin occurs in the presence of MB. This data is also supported by SEC. Saturation transfer difference NMR spectroscopy and molecular dynamics simulations demonstrate the interactions between insulin and MB at the atomic level.

SUBMITTER: Mukherjee M

PROVIDER: S-EPMC5754551 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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A Small Molecule Impedes Insulin Fibrillation: Another New Role of Phenothiazine Derivatives.

Mukherjee Meghomukta M Jana Jagannath J Chatterjee Subhrangsu S

ChemistryOpen 20171207 1

Protein misfolding is interrelated to several diseases, including neurodegenerative diseases and type II diabetes. Misfolded/unfolded proteins produce soluble oligomers that accumulate into "amyloid plaques". Inhibition of amyloid-plaque formation by those misfolded/unfolded proteins will lead to the invention of new therapeutic approaches for amyloid-related diseases. Herein, methylene blue (MB), a well-defined drug against multiple diseases and disorders, is used to impede insulin fibrillation ...[more]

PMID: 29318099

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Project description:Type 2 diabetes (T2D) is major cause of mortality and morbidity. The key manifestations of this disease are insulin resistance (IR), hyperglycemia and hyperinsulinemia. Secretion of insulin from the endocrine pancreas is triggered by elevated circulating glucose and acts on skeletal muscle and adipose tissues to remove excess glucose from the blood (1). This is achieved through a series of intracellular events that trigger the translocation of vesicles containing the glucose transporter 4 (GLUT4) to the surface of skeletal muscle cells and adipocytes (2,3). This process is impaired in patients with IR or T2D and insulin fails to promote GLUT4 translocation, thus resulting in inefficient glucose uptake in storage tissue and hyperglycemia (4). Chronic hyperglycemic condition increases the risk of cardiovascular disease, stroke, neuropathy, and death (5). Previously developed insulin sensitizer like thiazolidinediones (TZDs) have proven effective in improving glycemic control, however, they significantly increase the risk of cardiovascular disease due to their agonist activity at PPAR(6-8). Consequently, identifying insulin sensitizers that restore insulin-stimulated GLUT4 translocation in diabetic patients without targeting PPAR is urgently needed. The discovery of such molecules has been challenging due to the lack of a GLUT4 translocation assay amenable to high throughput screening (HTS). For this reason, we have developed a new luminescence based HTS assay that allows real time monitoring of GLUT4 translocation in mammalian cells and further adapted the assay to measure GLUT4 translocation in live mice. Using this assay, we identified a new insulin sensitizer which greatly improves insulin-dependent glucose uptake in storage tissues and glucose tolerance in insulin resistant rodents. This new insulin sensitizers acts through interaction with the Unc119 family of proteins which are known to facilitate the transport of specific cargos (9) but had not yet been implicated in insulin action or GLUT4 translocation. This study identifies new PPAR-independent insulin sensitizers with in-vivo efficacy and identify Unc119 proteins as new targets for the treatment of T2D.

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A Small Molecule Impedes Insulin Fibrillation: Another New Role of Phenothiazine Derivatives.

Publications

A Small Molecule Impedes Insulin Fibrillation: Another New Role of Phenothiazine Derivatives.

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