What they did and how they did it
ApoE4 is a genetic isoform of the ApoE protein that is most associated with the develpment of Alzheimers disease (AD). This paper is a systematic review by Rhonda Patrick proposing a mechanism explaing why ApoE4 carriers respond better to docosahexaenoic acid (DHA) present in fish rather than in supplement form.
What they found
- Alzheimers disease is associated with impaired glucose uptake in neurons due to decrease glucose transports (GLUT1).
- Glucose is actually very important in neurons and prevents Tau phosphorylation, a known contributing factor to AD development.
- DHA helps increase GLUT1 transports, allowing more glucose into the neurons (a good thing).
- There are two common forms of DHA that are supplemented: Free DHA and DHA-lysoPC (the type found in fish).
- They are transported differently through the blood brain barrier differently.
- Think of this like getting to the VIP section of a Party. Free DHA wasn’t invited so it has to go through a side door when no one is looking to sneak though–biologically speaking, it goes through a tight junction between cells. DHA-lysoPC was invited to the party, so the bouncer lets him through and in with no problem–biologically speaking through the cell.
- This works well most of the time. But what if that side door was broken. That’s what happens in ApoE4. Now DHA-lysoPC is able to get through to the brain while Free-DHA is left hanging outside, unable to help with glucose metabolism.
Questions left unanswered
We still need outcome data in the for of RCTs to see if this proposed theory actually results in less incidence of alzheimer’s in ApoE4 carriers. However, it would be nearly impossible to have a high-powered enough study with a long enough duration to see any meaningful results.
Takeaway
It has been found that people with Alzheimer’s disease have impaired glucose metabolism in the brain. DHA from fish seems to have a unique mechanism to improve glucose metabolism in ApoE4 carriers, which may help prevent Alzheimer’s. Given the evidence surrounding omega-3 fat intake an improved health, ingestion of DHA in the phospholipid form (that found in fish) may be beneficial.
