Interesting article, CaliReader.
But I have a few things to add: insulin does cross the blood-brain barrier; in fact, some insulin is actually secreted in the brain (although the bulk of it is made in the pancreas).
As grandsons4 pointed out, ketones are an alternate fuel for the brain; in fact, I have read they are the preferred form of fuel (preferred over glucose).
But my greatest concern comes from research finding that amyloid-beta (implicated as a possible cause in Alzheimer's), as well as insulin, is broken down by the Insulin-Degrading Enzyme (IDE); however, INSULIN is the preferential (first) target of IDE. If excess insulin requires all the IDE, amyloid-beta is left to accumulate in the brain. I fear that adding more insulin to the brain may result in MORE cases of Alzheimer's!
My hypothesis: excess insulin (hyperinsulinemia) plays a major role in MS, as developed in my initial post: http://www.thisisms.com/forum/general-discussion-f1/topic1878.html "Insulin – Could This Be the Key?"