insulin and the brain

[Douglas Fitts]

sfm at manduca.neurobio.arizona.edu (Stephen Matheson) writes:

>From article <41iaji$ccl at fremont.ohsu.edu>,
>by Matt Jones <jonesmat at ohsu.edu>:
>> In article <41hpov$mqk at whitbeck.ncl.ac.uk> erasmus harland,
>> p.s.e.harland at ncl.ac.uk writes:
>>>I am interested in brain metabolism, how does insulin function in 

>> My understanding was that insulin doesn't cross the blood/brain

>I estimate it to be about 50% wrong :-).  While I'm pretty sure
>that insulin does not cross the BBB, that does *not* mean that
>it doesn't have direct effects on neurons.  There are 2 ways
>that insulin could have direct neuronal effects without
>breaching the BBB: 1) by affecting neurons that are outside
>the BBB; 2) via cellular synthesis and release within the
>brain.  The first is most definitely the case for various
>hypothalamic neurons.  The second is hinted at by reports of
>expression of insulin mRNA by CNS neurons and by demonstrations
>of mRNA expression and insulin secretion by some cultured
>neurons.

A BBB uptake mechanism for insulin has been identified, but I believe 
you're correct that it has little to do with glucose uptake by brain 
cells.  It's an endocrine signal to the brain.

Doug