Stranded
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#1
Report Thread starter 13 years ago
#1
Is fructose the main energy source in brain? Just want to confirm
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Tom H
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#2
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I always thought it was Glucose
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nikk
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#3
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Blood glucose....although it does end up being transiently converted to fructose (phosphates) during glycolysis.

In the normal fed state, the brain uses approximately 100g of glucose per day. During times of starvation, this may drop to 60g per day as the brain can synthesis enzymes to begin utilising ketone bodies. But under normal circumstances, glucose is used exclusively.
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Comp_Genius
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glucose, so yes, fructose as well.... perhaps one should say 'pyruvate'.
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Stranded
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#5
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(Original post by nikk)
Blood glucose....although it does end up being transiently converted to fructose (phosphates) during glycolysis.

In the normal fed state, the brain uses approximately 100g of glucose per day. During times of starvation, this may drop to 60g per day as the brain can synthesis enzymes to begin utilising ketone bodies. But under normal circumstances, glucose is used exclusively.
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nikk
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(Original post by darkenergy)
glucose, so yes, fructose as well.... perhaps one should say 'pyruvate'.
I think saying fructose would be inaccurate as that would suggest an absolute requirement for fructose in the diet, which is not the case (luckily considering humans are pretty bad at uptaking fructose!). Again, to say pyruvate suggests that glycolysis is not required by the brain, which I believe also to be incorrect.

/pick pick pick :p:
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Comp_Genius
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yes, but without fructose, regardless of its origin, will not result in glycolysis. similarly without enolase, puruvate won't be formed which means that the citric acid cycle cannot occur.

:p:
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oxymoron
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(Original post by darkenergy)
yes, but without fructose, regardless of its origin, will not result in glycolysis. similarly without enolase, puruvate won't be formed which means that the citric acid cycle cannot occur.

:p:
Although pyruvate isn't the only possible input for the citric acid cycle. The brain can use ketone bodies in certain situations (ie starvation) so the citric acid cycle could still work without pyruvate!
Also, if we're being this picky then fructose isn't actually required, but fructose-6-phosphate is :p:

I can be pedantic too if I want to
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Comp_Genius
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#9
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Yes but our brain only use ketones for so long, and also, the brain needs both glucose and ketones for energy production, but ketones only lowers the glucose requirement.

oops, yes, i meant F6P since F is not actually in glycolysis. :p:
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