Sulfated polysaccharide ascophyllan prevents amyloid fibril formation of human insulin and inhibits amyloid-induced hemolysis and cytotoxicity in PC12 cells

We found that ascophyllan significantly inhibited the fibrillation of human insulin, and was the most effective among the sulfated polysaccharides tested. Gel-filtration analysis suggested that ascophyllan was capable of forming a complex with insulin through a weak interaction. Secondary structure transition from native α-helix to β-sheet predominant structure of insulin under the fibrillation conditions was suppressed in the presence of ascophyllan. Interestingly, ascophyllan attenuated insulin fibrils-induced hemolysis of human erythrocytes. Moreover ascophyllan attenuated insulin amyloid induced cytotoxicity on rat pheochromocytoma PC12 cells and reduced the level of intracellular reactive oxygen species (ROS). This is the first report indicating that a sulfated polysaccharide, ascophyllan can suppress the insulin amyloid fibril formation and inhibit the fibril-induced detrimental bioactivities.