Ketones from Aminos...

[CowPimp]

So I have a class in progress called Scientific Basis of Atheletic Conditioning. Pretty good stuff so far. The professor seems quite knowledgeable, and he seems up on current research. In fact, a lot of the lecture slides simply contain graphs and stuff from recent studies that he uses to back up his points. His wife is also a dietitian who he can talk with if he wants more information.

Anyway, enough preface. He got to talking about protein synthesis and degradation, and somehow started getting questioned about low carbohydrate diets and such. He said something about protein losses during starvation. Having read up a bit on ketogenic dieting I asked a question about it.

Basically he told me that ketones are generally not formed as a by-product of fat metabolism. He said that during starvation or when lacking carbohydrate the ketones will be formed from ketogenic amino acids. The only time you see a lot of ketone formation from fat is in diabetics when in a state of ketoacidosis. He was suggesting that without adequate protein intake you are asking to piss away your muscle in ketosis. I just found it interesting, as I always assumed ketones were formed primarily from fats.

 

[danzik17]

As far as I know ketones are formed from fatty acids - what source/sources was he citing for that?

 

[CowPimp]

As far as I know ketones are formed from fatty acids - what source/sources was he citing for that?

That wasn't exactly part of the lecture, so he wasn't citing a source, just his knowledge. It was in response to a question I posed.

 

[StacyCaliman]

Ketones are the result of carb depletion.

 

[Jodi]

Ketones are formed from fat deposits usually due to starvation or the absence of glucose.

 

[Marat]

Ketones are formed from fat deposits usually due to starvation or the absence of glucose.

Yep, they are short chained fatty acids. They can provide energy to the brain due to their ability to pass through the blood-brain barrier.

Suggesting that ketones are not formed as a by product of of fat metabolism is correct, for all intents and purposes.

Under normal metabolic conditions, the fatty acids get involved with chylomicrons etc. and get sent to the liver or to adipocytes and muscle tissue.

Under glucose deprivation, fatty acids that make it to the liver are converted to ketone bodies. Similarly, fatty acids and glycerol within adipocytes are pulled out and also turned into ketone bodies and glucose, respectively.

EDIT: I lost my train of thought at some point. I meant to touch on ketogenic amino acids, but I forgot. However, I believe that ketone bodies that are created from amino acids occur more so with dietary protein intake than stored amino acids when one is in a positive nitrogen balance.

Here is a tiny bit on glucogenic/ketogenic amino acids: SparkNotes: Amino Acids and Proteins: Functions of Proteins

 

[Built]

From Lyle MdDonald's "An Introduction to the Ketogenic Diet"
What are ketone bodies?

There are three main ketone bodies (which will be referred to more generally as ketones) that we are concerned with acetoacetate (AcAc), beta-hydroxybutyrate (BHB) and acetone. AcAc and BHB are both produced in the liver from the condensation of acetyl-CoA, a product of incomplete breakdown of free fatty acids (FFA) in the liver. When AcAc rises to high levels, roughly one-third will be converted to acetone. Acetone is excreted in the breath and urine, giving some individuals on a ketogenic diet a 'fruity' smell to their breath.

Wikipedia: Ketosis - Wikipedia, the free encyclopedia
Ketosis

In biology, ketosis (pronounced /kɪˈtəʊsɪs/) is a state of the organism characterised by elevated levels of ketone bodies in the blood, occurring when the liver converts fat into fatty acids and ketone bodies (which can be used by all of the body for energy as an alternative to glucose). These ketone bodies are a by-product of the lipid metabolic pathway after the fat is converted to energy.[1][2][3][4][5]

 

[CowPimp]

I've read all that stuff. Where are you suggesting that ketogenic amino acids come into play then? They obviously play some kind of role, as they certainly do exist.

 

[Marat]

They come into play as described in the third paragraph of your first post.

During the negative nitrogen balance that occurs during starvation, the stored ketogenic amino acids will be converted to ketones. The glucogenic amino acids will be converted to glucose. Just an fyi: not all amino acids fall in just one category (e.g. isoleucine is both ketogenic and glucogenic).

I feel like this post may not fully answer your question. If that is the case, can you clarify where your confusion lies?

 

[CowPimp]

They come into play as described in the third paragraph of your first post.

During the negative nitrogen balance that occurs during starvation, the stored ketogenic amino acids will be converted to ketones. The glucogenic amino acids will be converted to glucose. Just an fyi: not all amino acids fall in just one category (e.g. isoleucine is both ketogenic and glucogenic).

I feel like this post may not fully answer your question. If that is the case, can you clarify where your confusion lies?

I dunno I guess it seems like there is conflicting information here as to the primary source of ketone formation during starvation, that's all. It seems like my professor is at odds with most that I've read and heard, but he seems to know his shit when talking about most subjects.

 

[Marat]

Starvation implies insufficient intake of all macronutrients.
Low carbohydrate diets imply adequate protein and fat intake with low carbohydrate intake.

Those two different scenarios change the source of ketone body formation.

 

[Marat]

Basically he told me that ketones are generally not formed as a by-product of fat metabolism.

I agree with this statement

He said that during starvation or when lacking carbohydrate the ketones will be formed from ketogenic amino acids.

As I mentioned above, starvation and 'lacking carbohydrates' are not interchangeable.

I just found it interesting, as I always assumed ketones were formed primarily from fats.

Practically speaking, if one where to properly do a ketogenic diet, ketones would be formed from their stored fatty acids. Their protein intake would keep them in a positive nitrogen balance, limiting the ketogenosis from amino acids.

However, when one is starving (i.e. not taking in adequate amounts of any of the macronutrients) the individual would be in negative nitrogen balance, causing muscle wasting due to ketogenosis of amino acids. This would be occuring in addition to the ketogenosis from fatty acids.


Just an aside: I'm reasonably sure that ketogenosis only applies to fatty acid breakdown. However, I can't think of another term that would describe ketone formation from amino acids, so that's why I'm going with 'ketogenosis from amino acids'.

 

[Built]

ketoacidosis?

 

[Marat]

Well, ketoacidosis just describes an overly acidic metabolic state as a result of a high concentration of ketones. Additionally it can describe an increase in pH as a result of deamination, but that mechanism describes amino acid oxidation more so than the mechanism of converting amino acids to ketone bodies.

 

[Built]

Yeah, I new it wasn't quite right as soon as I posted, but I figured I'd leave it up for discussion.

 

[CowPimp]

I agree with this statement


As I mentioned above, starvation and 'lacking carbohydrates' are not interchangeable.



Practically speaking, if one where to properly do a ketogenic diet, ketones would be formed from their stored fatty acids. Their protein intake would keep them in a positive nitrogen balance, limiting the ketogenosis from amino acids.

However, when one is starving (i.e. not taking in adequate amounts of any of the macronutrients) the individual would be in negative nitrogen balance, causing muscle wasting due to ketogenosis of amino acids. This would be occuring in addition to the ketogenosis from fatty acids.


Just an aside: I'm reasonably sure that ketogenosis only applies to fatty acid breakdown. However, I can't think of another term that would describe ketone formation from amino acids, so that's why I'm going with 'ketogenosis from amino acids'.

So you are suggesting that ketones are quite often formed from protein, but assuming sufficient protein intake, it's not going to come from stored muscle mass? I mean I figured as much, and the professor even said something along those lines.

This also seems to be posited by Lyle McDonald in his book about ketogenic dieting. In it he suggests that the muscle wasting you see on low carbohydrate diets only takes place in studies where protein intake is inadequate. He ends up suggesting .9g/lb of body mass (Or maybe lean body mass? I forget which...) as a sufficient protein intake to prevent this muscle wasting.

 

[Marat]

Yes, exactly.


And just for reference: In The Ketogenic Diet, Lyle recommends .9g/lb of bodyweight for those exercising and .8g/lb of bodyweight for those who are not.

 

[CowPimp]

Yes, exactly.


And just for reference: In The Ketogenic Diet, Lyle recommends .9g/lb of bodyweight for those exercising and .8g/lb of bodyweight for those who are not.

Gotcha. I never even consider those who aren't exercising. If you are dropping weight without resistance training, that's just stupid in my opinion.

 

[Marat]

Certainly.