Polyphenolic gallotannins 1,3,6-Tri-O-galloyl-β-D-glucose and corilagin attenuate

IAPP amyloid formation and cytotoxicity by primarily targeting secondary

nucleation

Jihane Khalifa1,2,3, Ridwan Sulaimon4, Mélanie Côté-Cyr1,3, Phuong Trang Nguyen1,3,

Gilles Peslherbe4, Steve Bourgault1,3*, and Roger Gaudreault1,2*.

1Department of Chemistry, Université du Québec à Montréal, 2101 Jeanne-Mance Street, Montreal, QC H2X

2J6, Canada.

2Quebec Centre for Advanced Materials, QCAM, Canada

3Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Canada

4Centre for Research in Molecular Modeling (CERMM) & Department of Chemistry and Biochemistry,

Concordia University, Montreal H4B 1R6, QC, Canada

*Corresponding authors: Bourgault.steve@uqam.ca, Gaudreault.roger@uqam.ca

ABSTRACT

Protein misfolding and subsequent aggregation into insoluble amyloid deposits are

associated with various diseases, including Alzheimer’s disease, systemic amyloidosis and

type 2 diabetes mellitus (T2DM). In T2DM, the peptide hormone islet amyloid polypeptide

(IAPP), which regulates glucose homeostasis, aggregates in the pancreas, forming soluble

cytotoxic aggregates and amyloid fibrils that contribute to β-cell dysfunction and death.

Thus, the inhibition of IAPP aggregation consists of a promising strategy for treating

T2DM. Natural gallotannins are potential amyloid modulators, though their effects on

amyloid self-assembly are not fully understood. This study examines two gallotannins,

1,3,6-tri-O-Galloyl-β-D-glucose (β-TGG) and corilagin, and their inhibitory effects on

IAPP aggregation. Using thioflavin T fluorescence, atomic force microscopy, and circular

dichroism, it was found that the gallotannins delay IAPP self-assembly and reduce the

length and quantity of amyloid fibrils. Despite structural similarity, corilagin exhibited

markedly higher anti-aggregative activity at lower concentrations compared to β-TGG.

Peptide monomer-gallotannin interactions were further investigated using all-atom explicit

solvent molecular dynamics simulations, providing valuable insight into the binding of

both gallotannins to monomeric IAPP. Furthermore, corilagin provided significant

cytoprotective effects against IAPP-induced cytotoxicity and membrane damage in

pancreatic β-cells. Mechanistic analysis revealed that corilagin exerts its effects primarily

by inhibiting secondary nucleation and facilitating off-pathway aggregation into

cytocompatible proteospecies. Together, these findings highlight the potential of both

gallotannins in inhibiting amyloid self-assembly and inspiring the development of antiaggregative

agents for neurodegenerative Alzheimer’s disease