fictiondurden
Forum Junior
Topics: 19
Posts: 20
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Why is the GLUT in the blood brain barrier not regulated by insulin?
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| NeimanPicksMOM
Topics: 5
Posts: 24
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Isn't it simply because as a rule the brain is always using glucose no matter the insulin concentration...
Even if you are starving, the brain is feeding on any glucose you have whether it has to create it from amino acids or WHATEVER.
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| babydoc4usmle
Forum Guru
Topics: 18
Posts: 634
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GLUT-1 and GLUT-3 have very low Km for Glu (about 1, i think), which vives you very high affinity Glu-transporter @ base line Glu concentration (insulin level @that concentration is very low)
in order for Glu to get into liver for further processing Glu concentration has to be elevated to 15 and higher (well fed state) - very high Km-->low affinity Glu-transporter
for adipose and muscle you also required insulin, which will not change transporter in any way other than just make them appear on the surfase of the cell to increase Glu uptake for storage in well fed state and postabsorbtive state when Glu is still high.
this is just short overview, don't take numbers i gave as is, it might be different, but i put it for illustration
hope it helps
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| Clozapine
Forum Elite
Topics: 15
Posts: 164
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I agree with babydoc.
To my understanding only GLUT 4 in adipose tissue and muscle is insulin regulated (among the first 5 GLUTs, donno about the rest of them) rest of them are regulated by blood glucose level regardless of presence of insulin or not.
As babydoc said. GLUT 2 has a bigger Km and for GLUT 1 and 3, its <1 I guess ... If the basal glucose intake (regulated by GLUT 1 and 3) was also regulated by insulin, would the diabetics (specially type 1) even survive ?
Edited by Clozapine on 02/07/07 - 08:36 AM
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| nandrolone
Forum Junior
Topics: 8
Posts: 51
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Since we are on the GLUT topic i would like to add...
GLUT 2 receptors are present on islets of pancreas B cell as well
Glucose take in by them=> glycolysis=> products of glycolysis accumulate=> mere the products of glycolysis more is the blood glucose hence more insulin is producsed. Thus GLUT receptors on B cell act as Glucose sensors and abviously can not b e synthesized under the influence of glucose.
Thanx
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