Vitamin D, leaky gut and leaky Blood Brain Barrier

The role of Blood Brain Barrier permeability is described in the OMS book. We have much to learn about the BBB, particularly regarding its main structures - tight junctions. I'm interested in how they are regulated, why they break down and can we heal them?
In 'the Autoimmune Fix', Tom O'Bryan explains that Vitamin D heals intestinal permeability by 'supervising' the function of tight junctions. This led me to find an article linking Vitamin D to the upregulation of tight junctions of the BBB which may be of interest.
'Active form of vitamin D directly protects the blood–brain barrier in multiple sclerosis' (S Takahashi et al, 2017)
https://onlinelibrary.wiley.com/doi/ful ... cen3.12398
In 'the Autoimmune Fix', Tom O'Bryan explains that Vitamin D heals intestinal permeability by 'supervising' the function of tight junctions. This led me to find an article linking Vitamin D to the upregulation of tight junctions of the BBB which may be of interest.
'Active form of vitamin D directly protects the blood–brain barrier in multiple sclerosis' (S Takahashi et al, 2017)
https://onlinelibrary.wiley.com/doi/ful ... cen3.12398