Amyloid-β colocalizes with apolipoprotein B in absorptive cells of the small intestine

Background: Amyloid-beta is recognized as the major constituent of senile plaque found in subjects with Alzheimer's disease. However, there is increasing evidence that in a physiological context amyloid-beta may serve as regulating apolipoprotein, primarily of the triglyceride enriched lipoproteins. To consider this hypothesis further, this study utilized an in vivo immunological approach to explore in lipogenic tissue whether amyloid-beta colocalizes with nascent triglyceride-rich lipoproteins. Results: In murine absorptive epithelial cells of the small intestine, amyloid-beta had remarkable colocalization with chylomicrons (Manders overlap coefficient = 0.73 +/- 0.03 (SEM)), the latter identified as immunoreactive apolipoprotein B. A diet enriched in saturated fats doubled the abundance of both amyloid-beta and apo B and increased the overlap coefficient of the two proteins (0.87 +/- 0.02). However, there was no evidence that abundance of the two proteins was interdependent within the enterocytes (Pearson's Coefficient < 0.02 +/- 0.03), or in plasma (Pearson's Coefficient < 0.01). Conclusion: The findings of this study are consistent with the possibility that amyloid-beta is secreted by enterocytes as an apolipoprotein component of chylomicrons. However, secretion of amyloid. appears to be independent of chylomicron biogenesis.