This paper describes a potential new explanation for Alzheimer’s disease (AD), referred to here as the lipid leakage model. It proposes that AD is caused by the influx of lipids following the breakdown of the blood brain barrier (BBB).The model argues that a principle role of the BBB is to protect the brain from external lipid access. When the BBB is damaged, it allows a mass influx of free fatty acids (FFAs) and lipid-rich lipoproteins to the brain, which in turn causes neurodegeneration, amyloidosis, tau tangles and other AD characteristics. The model also argues that, whilst β-amyloid causes neurodegeneration, as is widely argued, its principal role in the disease lies in damaging the BBB. It is the external lipids, entering as a consequence, that are the primary drivers of neurodegeneration in AD, especially FFAs, which stimulate microglia-driven neuroinflammation, inhibit neurogenesis and cause endosomal-lysosomal abnormalities, all characteristic of AD. In most cases amyloidosis and tau tangle formation lie downstream of these lipids and are in many ways as much symptomatic of the disease as causative. In support of this, it is argued that the pattern of damage caused by the influx of FFAs into the brain is likely to resemble the neurodegeneration seen in alcohol-related brain damage (ARBD), a disease that shows many similarities to AD, including the areas of the brain it affects. The fact that anterograde amnesia is far more pronounced in AD than ARBD results from the greater hydrophobicity of FFAs, in an anaesthesia-related manner.
Role of dietary fatty acids in microglial polarization in Alzheimer’s disease