title: Morin hydrate inhibits amyloid formation by islet amyloid polypeptide and disaggregates amyloid fibers.
abstract: The polypeptide hormone Islet Amyloid Polypeptide (IAPP, amylin) is responsible for islet amyloid formation in type-2 diabetes and in islet cell transplants, where it may contribute to graft failure. Human IAPP is extremely amyloidogenic and fewer inhibitors of IAPP amyloid formation have been reported than for the Alzheimer's Aβ peptide or for α-synuclein. The ability of a set of hydroxyflavones to inhibit IAPP amyloid formation was tested. Fluorescence detected thioflavin-T-binding assays are the most popular methods for measuring the kinetics of amyloid formation and for screening potential inhibitors; however, we show that they can lead to false positives with hydroxyflavones. Several of the compounds inhibit thioflavin-T fluorescence, but not amyloid formation; a result which highlights the hazards of relying solely on thioflavin-T assays to screen potential inhibitors. Transmission electron microscopy (TEM) and right-angle light scattering show that Morin hydrate (2',3,4',5,7-Pentahydroxyflavone) inhibits amyloid formation by human IAPP and disaggregates preformed IAPP amyloid fibers. In contrast, Myricetin, Kaempferol, and Quercetin, which differ only in hydroxyl groups on the B-ring, are not effective inhibitors. Morin hydrate represents a new type of IAPP amyloid inhibitor and the results with the other compounds highlight the importance of the substitution pattern on the B-ring.
authors.affiliation: Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
authors.forename: Harris
authors.initials: H
authors.lastname: Noor
authors.forename: Ping
authors.initials: P
authors.lastname: Cao
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Raleigh
mesh_terms: D000682:Amyloid / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000187:drug effects; D052160:Benzothiazoles; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D058228:Islet Amyloid Polypeptide / Q000037:antagonists & inhibitors*; D044949:Kaempferols / Q000494:pharmacology; D008027:Light; D046529:Microscopy, Electron, Transmission; D011794:Quercetin / Q000494:pharmacology; D012542:Scattering, Radiation; D013844:Thiazoles / Q000737:chemistry; D047309:Flavones
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D005419:Flavonoids; D058228:Islet Amyloid Polypeptide; D044949:Kaempferols; D011794:Quercetin; D013844:Thiazoles; C009462:thioflavin T; C006552:kaempferol; C040015:myricetin; C008548:morin; D047309:Flavones