Gluten

For individuals with the gluten related disorders mentioned above, it is apparent that gluten has a negative effect on the brain and should be avoided.  However, what about the rest of us? What about Apoe4 carriers?  Does gluten affect our risk of getting Alzheimer’s?

To answer this, let’s first take a closer look at zonulin.  As we have read above, zonulin increases the permeability of the intestine, but researchers have also found that patients with MCI and Alzheimer’s have elevated levels of Zonulin and that increased zonulin concentrations have also been correlated with reduced MMSE scores.  In addition, zonulin as well as some immune system signaling molecules (known as cytokines) can increase the permeability of the blood brain barrier.3,4  

The majority of blood vessels in the brain are surrounded by endothelial cells that are collectively called blood brain barrier (BBB).  The BBB separates the central nervous system from the circulatory system in the rest of the body.  However, just like with the intestine, nutrients must be able to pass through the BBB so that the brain can function.  Oxygen and carbon dioxide as well as small lipid-soluble molecules can cross the BBB, but larger molecules will need to be transported across using dedicated transporter proteins.  For example, omega-3 fatty acids are transported across the BBB by a protein called Sodium-dependent lysophosphatidylcholine symporter 1.  When the BBB is broken down and becomes too permeable, toxins, microbes, antigens, and cells can pass through into the brain.  In addition, the very specific chemical environment within the brain will be disrupted.  A disrupted BBB leads to increasing neuroinflammation, neuronal injury, synaptic dysfunction, loss of neuronal connectivity and neurodegeneration.5    

Both Alzheimer’s and MCI patients have a disrupted BBB.  Unfortunately, Apoe4 carriers, as well as Alzheimer’s patients in general, are prone to microhemorrhages of the brain which can lead to the breakdown of the BBB.  Microhemorrhages can be caused by amyloid beta clogging up the brain’s blood vessels.  In fact, the number of amyloid plaques in the brain have been correlated with the number of microbleeds a patients has had.5  

Protecting the blood brain barrier is critical in fighting Alzheimer’s.  Anything that might breakdown the blood brain barrier should be avoided.  Zonulin has been shown to be destructive to the BBB by making it more permeable.  Zonulin has been shown to be increased in Alzheimer’s patients, but also in diabetes type II patients, people that are insulin resistant, obese people, in people with coronary artery disease, in people with glioma, in people that suffer from irritable bowel syndrome and also people that have non-celiac gluten sensitivity (NCGS).  Gluten containing foods also contains gliadin which has shown to increase the concentration of zonulin which not only makes the intestine more permeable but also makes the BBB more permeable.   In addition, zonulin has been shown to be associated with hyperlipidemia which is a comorbidity of Alzheimer’s.6,7,8