Glycation affects fibril formation of a peptides

Increasing evidence shows that -amyloid (A) peptides, which are associated with Alzheimer disease (AD), are heavily glycated in patients, suggesting a role of this irreversible nonenzymatic post-translational modification in pathology. Previous reports have shown that glycation increases the toxicity of the A peptides, although little is known about the mechanism. Here, we used the natural metabolic by-product methylglyoxal as a glycating agent and exploited various spectroscopic methods and atomic force microscopy to study how glycation affects the structures of the A40 and A42 peptides, the aggregation pathway, and the morphologies of the resulting aggregates. We found that glycation significantly slows down but does not prevent -conversion to mature fibers. We propose that the previously reported higher toxicity of the glycated A peptides could be explained by a longer persistence in an oligomeric form, usually believed to be the toxic species.