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                               Ketones

                                  by
                          Arturo R. Rolla, MD
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LAST UPDATED: 21Nov95, corrected length of ketoacids, paragraph 3
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Ketones, ketones! So much interest for these little buggers! I hate
them because for me they always mean trouble. Nevertheless, since so
many of you are so interested, let's talk some more about them.

What we call ketones are really two acids and a ketone. The acids are
called hydroxybutyric and acetoacetic. Butyric is related to butter
because it's formed in rancid butter from the milk fat. Acetoacetic is
related to the acid in vinegar. The ketone is acetone, the same that is
use to clean up nail polish.

The ketoacids are short - they are four carbons long. This is important
because in that way they are able to penetrate cells to feed them when
there is no sugar. The fat stores accumulate fat as very long fatty
acids. They are hard to digest - if you know what I mean - because they
are so long. So, in situations of energy crisis (not enough food, not
enough sugar), the fat cells start releasing these long fatty acids
into the blood.

To be used, particularly by the brain, the fatty acids go to the liver
where they are literally cut into two carbon fragments (ketoacids).
They are then utilized (burned) by many tissues, including the brain.
The brain can do its computer work equally as good being fed sugar or
ketones! Isn't that remarkable? You can be a mathematics genious while
starving and your brain is consuming short fats.

If the production of ketoacids equals the utilization of ketones by the
tissue, there is no problem. They don't accumulate in the blood, and
some of the ketoacids are excreted in the urine. (You test positive
with Acetest or Ketodiastix). This is exactly what happens during
starvation in a non-diabetic person.

In IDDM without insulin, the levels of insulin in the blood are so low
that the release of fatty acids from the fat stores is massive. The
liver can then only produce tremendous amounts of ketoacids because it
has to get rid of all this extra fat. The production of ketoacids is
therefore exaggerated.

At the same time, the tissues decrease their utilization of ketoacids,
and they start accumulating in the blood. This constitutes an "acid
pollution" as a result of the burning of fat. As long as you can
excrete them in the urine, you are OK. But because of all the sugar in
the urine, you start getting dehydrated and the kidneys run out of
water to make more urine.

At that point, the kidneys cannot excrete ketoacids as well. They pile
up in the blood and start making it acid ---> Ketoacidosis is the name!
Voila!