Coconut oil decreases expression of amyloid precursor protein (APP) and secretion of amyloid peptides through inhibition of ADP-ribosylation factor 1 (ARF1)

Abstract

Alzheimer's disease (AD), affecting 5.3 million people in the U.S., impairs portions of the brain controlling memories. In humans, mutations in the amyloid precursor protein (APP) gene has been implicated in increased plaque formation, which can block the communication between nerve cells, decrease dendritic formation and increase cell death, and promote neuroinflammation. As coconut oil has been suggested to alleviate the symptoms in AD patients, we examined the impact of coconut oil on APP expression and secretion of amyloid peptides in N2a cells expressing the human APP gene (N2a/APP695). We found that coconut oil treatment decreased APP expression in N2a cells and reduced the secretion of amyloid peptides Aβ₄₀ and Aβ₄₂. Moreover, coconut oil treatment promoted differentiation of N2a cells. Our data suggest that ADP-Ribosylation Factor 1 (ARF1) may contribute to the effects of coconut oil on APP expression and secretion of Aβ. A high ARF1 expression was also detected in the primary neuronal cells from the mice overexpressing the Swedish mutant APP. Immunostaining results revealed that APP is co-localized with ARF1 in the Golgi apparatus and this interaction is impaired after coconut oil treatment. Furthermore, knockdown of ARF-1 using siRNA decreased secretion of amyloid peptides, confirming the impact of ARF1 on the secretion of amyloid peptides. CONCLUSION: These results suggest that coconut oil decreases intracellular ARF1 expression, thereby resulting in an inhibition of APP and amyloid β secretion. This study reveals a novel mechanism for intracellular APP processing in neuronal cells.

Keywords: ADP-ribosylation factor 1; Amyloid peptides; Amyloid precursor protein; N2a Cells.