Wheat gluten is capable of triggering the destruction of your tissues in your GI tract as in celiac disease. This is not hypothetical.
This is another "poorly understood" area.
With the issues surrounding the permeability of the Gut barrier and the BBB, it is no stretch to imagine protein molecules from gluten finding their way into the brain. Since permeability fluctuates, this could be a gradual process. Maybe stretching over decades. Would medical science know if it was happening? An intermittent process, slow moving, not detectable by testing, controversial? SUURE they would!
This is an ideal White Rat area. Try a day or two with a paleolithic diet - meat and leafy greens. Keep notes.