P4‐003: Modulation of Amyloid Beta (Aβ) Structure and Toxicity by a Dairy‐derived Peptide Product

In 2008, Alzheimer's disease (AD)-related dementia affected over 200,000 Australians with over a million projected to be affected by 2050. The rise in AD sufferers is likely to be disproportionate to the rise in population by a factor of 8 with major implications for social and health care costs. The development of preventative and therapeutic interventions represents a priority. There are challenges with lengthy timeframes associated with clinical interventions research. Protective factors discovered from dietary sources can possibly shorten the time for required substantiation. The ‘amyloid hypothesis’ has evolved to implicate oligomeric versus fibrillar forms of amyloid beta (Aβ) 1-42 as the preferred target for inhibition with a host of known and new chemical species with capacity to modulate self-assembly including peptide analogues and small molecules. Furthermore, as the ‘chaperone’ properties of several intra-cellular proteins appear to regulate the toxicity of Aβ, and particular dairy milk proteins (i.e., alpha S1 and beta caseins) can also prevent amyloid-like self-assembly of other milk proteins (e.g. kappa casein), we have undertaken to evaluate the anti-fibril capacity of dairy-derived peptides. We report here our discovery of a heterogeneous peptide fraction from enzyme-hydrolysed bovine whey with interesting anti-fibril properties. The dose-dependent modulation of Aβ1-42 self-assembly by a low molecular weight (<6 kDa) mixture of hydrophobic dairy whey protein-derived peptides from the total hydrolysate P0147 (SPE40 and SPE100) was studied using a combination of physicochemical techniques (circular dichroism); in vitro (ThT binding assay, Western blot and TEM imaging) and cell-based assay (yeast toxicity rescue). ThT-binding assay and yeast toxicity results revealed interesting dose-dependent capacity for modulation of Aβ fibril morphology and toxicity, respectively, by SPE40 and SPE100, apparently driving self-assembly progressively from relatively more toxic to less toxic forms of Aβ1-42. The suppression of ThT binding by dairy peptides correlated with (1) loss of beta sheet absorbance by CD, (2) suppression of oligomeric Aβ1-42 by Western blot with 6E10 antibody and disappearance of macroscopic fibril structures by TEM. The modulation of Aβ1-42 self-assembly by dairy peptides, eliciting either potentiation or suppression of amyloid self-assembly, can assist in understanding the transitional toxicity of self-assembled forms of Aβ1-42.