Repression Effects of Hydrolysates from Hen-Egg Proteins on Amyloid Fibril Formation

Amyloid fibrils, which are formed from aggregates of aberrant proteins, can cause various forms of amyloidosis (including Alzheimer's disease). Such disorders often occur in elderly populations and are suspected to be lifestyle related. Thus, it has been speculated that some foodstuffs could be beneficial for preventing amyloidosis. In this study, we determine whether fibril formation by the hen egg white lysozyme (HEWL) could be inhibited by conducting a thioflavin T assay followed by fluorescence and electron microscopy observations. The results demonstrated that four peptide specimens prepared by the hydrolysis of crude proteins from the egg white, egg yolk, chalazae, and eggshell membrane of hen eggs effectively inhibited HEWL fibril formation. Among the four specimens, peptides from chalazae exhibited the highest preventive ability. The superiority of chalaza peptides was also observed when fibril formation was assayed using a full-length human lysozyme and human amyloid β peptide 1-42, which is the key factor for the development of Alzheimer's disease. Our study of the fibrillization of the human lysozyme also showed that metal ions (Zn²⁺, Ca²⁺, Co²⁺, Mn²⁺ and Al³⁺) promoted fibrillization, and their effects were abolished by the peptide specimens (especially by chalaza peptides). Thus, we conclude that chicken-egg proteins could be a convenient source of therapeutic materials for amyloidosis.