From the article:
A research group has revealed that amyloid-β (Aβ) detected in blood is secreted from peripheral tissues (pancreas, adipose tissue, skeletal muscle, liver, etc.) that are sensitive to glucose and insulin. Also, that Aβ secreted from peripheral tissues acts as a regulator on pancreatic β-cells to suppress insulin secretion. The results of this study indicate that blood Aβ levels fluctuate significantly with diet, and special care should be taken when using blood samples as a diagnostic marker for Alzheimer’s disease, such as taking blood samples during fasting.