B12 def and Myelin synthesis

[SwissB4]

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I was wondering if during B12 deficency is the reason for the neuro defects due to decreased a problem with odd-chain fatty acids (which B12 is needed to breakdown)? Thanks..

 

[Taus]

there are a few more specifics to it but you're basically correct

 

[SwissB4]

Thanks...

 

[Buckeye(OH)]

Thanks...

Though I haven't taken the test, as Taus said you will need to know the details, seems to be fairly high yield.

 

[blz]

here's probably all the details you have to know:

odd chain fatty acids broken down to propionyl CoA --> methylmalonyl CoA --> succinyl CoA (enzyme for this reaction is methymalony CoA mutase - which needs B12)

so you get a buildup of methylmalonyl CoA and propionyl CoA. goljan's book said propionyl CoA replaces acetyl CoA in neuronal membranes resulting in demyelination. i think i also read somewhere that methylmalony coa is toxic to schwann cells.

also of course, don't forget folate isn't involved in this so the megaloblastic anemia from folate deficiency has no neurologic problems.

 

[winsicle]

odd chain fatty acids broken down to propionyl CoA --> methylmalonyl CoA --> succinyl CoA (enzyme for this reaction is methymalony CoA mutase - which needs B12)

so you get a buildup of methylmalonyl CoA and propionyl CoA.

Yeah - the actual pathophys on the Subacute Combined Degeneration hasn't been conclusively discerned, so I think knowing the association w/ B12 (and lack thereof w/ folate), and the above reaction sequence is more than sufficient....

if anyone is interested there is an interesting association b/t Nitrous Oxide anesthesia -> precipitating B12 deficiency and subsequent SCD:
http://jnnp.bmj.com/cgi/content/full/64/4/563