Abstract
Despite the ever-increasing number of patients with dementia worldwide, fundamental therapeutic approaches to this condition have not been established. Epidemiological studies suggest that intake of fermented dairy products prevents cognitive decline in the elderly. However, the active compounds responsible for the effect remain to be elucidated. The present study aims to elucidate the preventive effects of dairy products on Alzheimer’s disease and to identify the responsible component. Here, in a mouse model of Alzheimer’s disease (5xFAD), intake of a dairy product fermented with Penicillium candidum had preventive effects on the disease by reducing the accumulation of amyloid β (Aβ) and hippocampal inflammation (TNF-α and MIP-1α production), and enhancing hippocampal neurotrophic factors (BDNF and GDNF). A search for preventive substances in the fermented dairy product identified oleamide as a novel dual-active component that enhanced microglial Aβ phagocytosis and anti-inflammatory activity towards LPS stimulation in vitro and in vivo. During the fermentation, oleamide was synthesized from oleic acid, which is an abundant component of general dairy products owing to lipase enzymatic amidation. The present study has demonstrated the preventive effect of dairy products on Alzheimer’s disease, which was previously reported only epidemiologically. Moreover, oleamide has been identified as an active component of dairy products that is considered to reduce Aβ accumulation via enhanced microglial phagocytosis, and to suppress microglial inflammation after Aβ deposition. Because fermented dairy products such as camembert cheese are easy to ingest safely as a daily meal, their consumption might represent a preventive strategy for dementia.
Highlights
With aged populations growing rapidly around the world, cognitive decline and dementia are becoming an increasing burden on patients and their families, and on national healthcare systems
Because cognitive function declines in accordance with an accumulation of Amyloid β (Aβ) in the brain, Aβ deposition is a crucial part of the pathology [1]
In the Alzheimer’s brain, microglia infiltrate the region around the Aβ plaques, become excessively activated, and produce large amounts of inflammatory cytokines and chemokines, such as tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-1α (MIP-1α), reactive oxygen (ROS) and nitric oxide (NO) [7,8,9]
Summary
With aged populations growing rapidly around the world, cognitive decline and dementia are becoming an increasing burden on patients and their families, and on national healthcare systems. In the Alzheimer’s brain, microglia infiltrate the region around the Aβ plaques, become excessively activated, and produce large amounts of inflammatory cytokines and chemokines, such as tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-1α (MIP-1α), reactive oxygen (ROS) and nitric oxide (NO) [7,8,9]. These products, which are chronically generated by microglia, after Aβ deposition are toxic to neurons and cause neuronal cell death [7, 10,11]
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