In article: <09960716233524.OUI22.mplewins at concentric.net> mplewins at concentric.net (M. Plewinska) writes:
> Martin Bansbach wrote:
>> >>Just about every biochemistry textbook will state that the brain uses
> mostly ketone bodies for energy during starvation but I'm not sure that
> this has ever been proven (it's mostly by inference).<<
>> It has actually been proven in patients with type I Glycogen Storage
> Disease. These patients are persistently hypoglycemic and have very high
> lactic acid levels. When lactate content of the carotid artery was
> compared to the lactate content of the jugular vain in these patients,
> it was found to be higher in the carotid. This is exactly trhe opposite
> from the normal situation, where lactate in the jugular is greater than
> in the carotid as a result of the brain converting glucose into lactate.
> Anyway, these patients have induced the enzymatic pathways to use
> lactate instead of glucose for energy production in the brain. This is
> how they tolerate extremely low glucose levels without major ill-effects
> to their mentation.
>> - Magda Plewinska, MD
> Genetics/ Miami, FL, USA?
>>>Thank you for this input
It is interesting that the brain can change fuels when presented with an excess of lactate. However that the
brain can metabolise lactate doesn't, on the face of it, appear to be proof that the brain uses ketone bodies
during starvation abnd that protein is spared. All this evidence indicates is that the brian can adapt to
different energy sources which could just as well be lactate / pyruvate etc from protein as ketone bodies from
fat. In fact surely the observation that the brain can use lactate lends some support to the fact that ketone
bodies are not the only alternative source of energy for the brain and therefore lower glucose oxidation rates
are not necessarily synonymous with increased fat metabolism and protein sparing.
yours
steve collins
