Metabolic profiling indicates impaired pyruvate dehydrogenase function in myalgic encephalopathy/CFS (Fluge et al., 2016)

[alicec]

then it is only the acetyl-CoA anaplerotic pathway of pyruvate which provides energy to drive the Krebs cycle;

Yes, the thioester bond which links the acetyl group to coenzyme A is a high energy bond which is highly reactive. When it reacts it releases energy - it is an exergonic reaction.

 

[Hip]

Anyway, given all that. If oxaloacetate feeds into the Krebs cycle, by definition wouldn't it be aiding in the process of generating high-energy molecules?

My understanding (which may not be correct) is that all the processes that supply energy to the Krebs cycle, in order to turn the wheels of the Krebs cycle, do so via creation of acetyl-CoA. That includes pyruvate converted to acetyl-CoA, fatty acids converted to acetyl-CoA, and ketogenic amino acids converted to acetyl-CoA.

It says here that:

Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle.

I also read that acetyl-CoA is the only molecule that gets used up by the Krebs cycle; whereas all Krebs cycle intermediates are not used up, but are converted from one to another, as the Krebs cycle runs through its motions. So this means that if you replenish one of the Krebs cycle intermediates, such as say alpha-ketoglutarate, then you actually replenish all the intermediates, because the alpha-ketoglutarate you added to the Krebs cycle will get converted to every other intermediate.

So replenishing just one of the Krebs cycle intermediates replenishes all of them.

But then given this, what I don't understand is what they found in the Fluge and Mella study, namely:

The anaplerotic amino acids, which serve to maintain TCA cycle capacity (category III), were reduced in female ME/CFS patients.

Anaplerotic amino acids are defined as those which replenish the Krebs cycle intermediates. See: Anaplerotic reactions - Wikipedia. So the fact that there is this shortage of anaplerotic amino acids in female ME/CFS patients suggests they are being used up at a higher rate, in order to replenish the Krebs cycle intermediates.

However, as far as we know, only the pyruvate > acetyl-CoA conversion is inhibited in ME/CFS, but the pyruvate > oxaloacetate and the pyruvate > alpha-ketoglutarate replenishment conversions are still functional. So there should be plenty of pyruvate available for the purpose of replenishing the Krebs cycle intermediates.

In fact, if anything, there should be excess pyruvate available for replenishing the Krebs cycle intermediates, because the usual pyruvate conversion to acetyl-CoA is being blocked in ME/CFS.

So why then are the anaplerotic amino acids (category III amino acids) being used up in female ME/CFS patients, presumably for Krebs cycle intermediate replenishment?

I understand why the category II amino acids, which can be converted to acetyl-CoA to fuel the Krebs cycle, are low in female ME/CFS patients: because these category II amino acids are being used for energy, to make up for the blocked pyruvate > acetyl-CoA conversion.

But I don't see why the anaplerotic amino acids (category III amino acids) are being used up.

 

[alicec]

So why then are the anaplerotic amino acids (category III amino acids) being used up in female ME/CFS patients, presumably for Krebs cycle intermediate replenishment?

The Kreb's cycle is not a carbon sink. Anaplerosis is balanced by cataplerosis; anions exit as well as enter the cycle in a balanced way.

The principle cataplerotic enzymes are phosphoenolpyruvate carboxykinase, aspartate aminotransferase and glutamate dehydrogenase. The two former drain oxalaoacetate, the latter drains alpha keto glutarate.

Citrate also exits the cycle and is used in fatty acid synthesis in the cytosol.

So it is wrong to think of the Kreb's cycle only as a metabolic furnace. Cataplerosis feeds synthetic pathways, namely gluconeogenesis, glyceroneogenesis, lipogenesis and ammoniagenesis.

What exactly is going on in female patients that is leading to consumption of the anaplerotic amino acids is undoubtedly complex but understanding that intermediates are both drained and replenished is probably a useful first step in figuring this out.

 

[nandixon]

@Hip

The other pathway for pyruvate, besides conversion to acetyl-CoA , is to be converted to lactate (lactic acid).

Fluge & Mella wrote in the study:

Although lactate production tended to be low under resting conditions, it was excessively induced by energetic strain in muscle cells exposed to ME/CFS serum. These observations are compatible with a metabolic obstruction at the level of PDH, causing increased conversion of pyruvate to lactate, and amplified demand for alternative substrates downstream of PDH.

 

[nandixon]

There are clues but also countervailing evidence. For example wikipedia says it can be activated by carbs and inhibited by curcumin, which many of us take.

I tried curcumin several times over the course of a year or so and always had the same result: I initially felt better from it, but within 2 or 3 days I felt worse than baseline. So curcumin being bad due to inhibition of mTORC1 is very consistent for me personally.

(At the time, I thought the ill effects of curcumin might have been due to its ability to inhibit some cytochrome P450 enzymes. I believe this product was the last one I tried, taken with a meal and a spoonful of olive oil for maximum absorption.)

 

[nandixon]

Does Fluge & Mella's study mention anything about alpha-ketoglutarate dehydrogenase complex (alpha-KDC) aka oxoglutarate dehydrogenase complex (OGDC) and its enzymes?

I ask this because the OGDC is almost identical to the pyruvate dehydrogenase complex (PDC) (as well as the branched-chain α-ketoacid dehydrogenase complex (BCKDC)). Each of these complexes uses the same subunit structure and same cofactors as PDC. The OGDC is also implicated in primary biliary cirrhosis. 2-Oxo-glutarate dehydrogrenase is an [URL='https://en.wikipedia.org/wiki/Autoantigen']autoantigen in the disease.[/URL]

The OGDC is later in the citric acid cycle than PDC, so maybe there aren't as many indicators that may point to a problem in its biochemistry too.

Fluge & Mella don't mention it directly, I don't think. But in the 2014 reference they site for SIRT4's newly found ability to inhibit the PDH complex by removing the lipoyl functionality ("cofactor") from the second (E2) subunit, the authors of that paper seem to think that SIRT4 might have the same ability to inhibit the OGDC (OGDH complex):

Thus, it is tempting to speculate that this regulation may also involve SIRT4 lipoamidase activity towards OGDH, which contains DLST-lipoyl and feeds 2-oxoglutarate [alpha-ketoglutarate] into the TCA cycle.

So perhaps increased SIRT4 inhibits both the PDH complex and the OGDC as well. (I guess we'll have to wait until someone publishes some experimental results to find out.)

Generally it looks like OGDC is regulated by the balance of its reactants and products, and by the level of reactive oxygen species (e.g., free radicals) it is exposed to, which are inhibitory and likely to be high in ME/CFS patients anyway.

 

[JaimeS]

My understanding (which may not be correct) is that all the processes that supply energy to the Krebs cycle, in order to turn the wheels of the Krebs cycle, do so via creation of acetyl-CoA.

At least from my perspective, we may have a problem of semantics. I'd clarify that Acetyl-CoA can't supply energy per se; it just supplies itself at what is usually drawn at the 'top' of the Krebs cycle, and supplies its acetyl group to make citrate in the citric acid cycle. Acetyl Co-A does also help oxidize fatty acids in situations of lower glucose, so it is in part responsible for fat breakdown as well.

Acetyl CoA is even responsible for the production of cholesterol, which goes on to make hormones (which I'm sure you know @Hip but I'm stating for the purposes of clarity here).

The only one where Acetyl CoA isn't absolutely required is the digestion of proteins.

Some amino acids break down into keto acids. Some will enter the cycle above pyruvate and therefore still 'pass through' Acetyl CoA. Others enter the cycle at oxaloacetate, further on in the cycle; and others enter at alpha-ketoglutarate, even further down.

I wouldn't say that Acetyl CoA isn't involved because they're all part of a cycle, which means every part of the process 'leans' on every other part. But there are places for amino acids to enter the cycle that are after (or depending on your point of view, before) Acetyl CoA.

Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle.

I find that to be a weird statement in general. Note there's nothing about proteins, our other macronutrient. Proteins would not be a macronutrient if they didn't play a part in cellular respiration someplace.

This is from an explanation I made regarding (I think) C Armstrong's paper before last. You can see that amino acids enter the cycle at various points, though:

I also read that acetyl-CoA is the only molecule that gets used up by the Krebs cycle; whereas all Krebs cycle intermediates are not used up, but are converted from one to another

"Not used up" BUT "converted from one form into another".

Since Acetyl CoA is a molecule, the only way you can use it up is to convert it from one form to another. Since matter is never created or destroyed, this is the only way in which a molecule can be used up.

this means that if you replenish one of the Krebs cycle intermediates, such as say alpha-ketoglutarate, then you actually replenish all the intermediates, because the alpha-ketoglutarate you added to the Krebs cycle will get converted to every other intermediate.

Arguably the case, PROVIDED that all of the enzymes that help catalyze those reactions are present and accounted for, and not blocked by inhibitors; which F & M say is not the case.

However, as far as we know, only the pyruvate > acetyl-CoA conversion is inhibited in ME/CFS, but the pyruvate > oxaloacetate and the pyruvate > alpha-ketoglutarate replenishment conversions are still functional. So there should be plenty of pyruvate available for the purpose of replenishing the Krebs cycle intermediates.

Pyruvate to oxaloacetate requires that there first be pyruvate, which would be lower without Acetyl CoA.

Ditto for pyruvate to alpha-ketoglutarate.

You can feed amino acids straight to alpha-ketoglutarate in the cycle. But since, in a healthy person, you'd also be getting additional alpha-ketoglutarate as the result of glucose metabolism, without proper glucose metabolism (and without increased amino acid uptake) you'd have lower alpha-ketoglutarate.

As you say, if you increase alpha-ketoglutarate you increase everything in the CAC (without errors in enzymes) -- but you have to have some way of increasing it! Women, at least, are feeding it allll their protein, according to F & M.

Note: all of this is upper-level-high-school knowledge and may be incomplete. Take with a grain of salt!

-J

 

[eljefe19]

N=1 but since starting Leucine and cutting most carbs out of my diet, I've gained 6-7 pounds and have been insatiably hungry. Starting Florinef tomorrow. I'll find the source later, but Phosphaditic Acid and Creatine also activate mTorc1 for anyone trying nandixons idea.

 

[eljefe19]

https://topbrainboosters.com/metaprot/

As a result, the processes of physiological and reparative regeneration and adaptation to the new conditions accelerate. Metaprot improves ATP formation and resynthesis of glucose from lactate and pyruvate, which reducing acidosis, lactacidemia, oxygen debt and lead to fast normalization of performance.

 

[eljefe19]

Metaprot is an adaptogen. It works by direct stimulating the synthesis of Ribonucleic acid (RNA) and proteins, including enzymes and related to the immune system. This process activates the synthesis of gluconeogenesis enzymes which provides lactate utilization (a factor limiting performance) and carbohydrate resynthesis (a source of intense energy at loads). These all increases physical performance. Antihypoxic and antiischemic activity in severe oxygen deficiency is provided by keeping a high level of ATP synthesis. Metaprot is non-exhaustive agent - it doesn't increase oxygen consumption or heat production.

 

[JaimeS]

https://topbrainboosters.com/metaprot/

https://www.ncbi.nlm.nih.gov/pubmed/?term=metaprot

 

[nandixon]

N=1 but since starting Leucine and cutting most carbs out of my diet, I've gained 6-7 pounds and have been insatiably hungry.

Just to be clear, I wouldn't think a ketogenic diet (i.e., very low carbohydrate and high fat) would work very well, on average, for most people with ME/CFS, especially women, since fatty acid oxidation may be impaired. (Everyone is different, though, as we all know.) As Fluge & Mella note:

However, there were also indications of reduced mitochondrial fatty acid oxidation only in female ME/CFS patients (32). Adding to PDH inhibition, reduced mitochondrial fatty acid oxidation would expectedly compromise the supply of acetyl-CoA further and thereby increase the dependency of category II amino acids for alternative fueling of the TCA cycle, as shown in our study.

The possible work around might be the incorporation of medium-chain triglycerides into such a diet.

Also, I haven't researched it but if the Wikipedia source @Murph mentioned earlier is correct about carbs activating mTORC1, then low carbs could be shooting yourself in the foot.

Edited to add: Reference 32 is the 2016 Naviaux study.

 

[JaimeS]

Just to be clear, I wouldn't think a ketogenic diet (i.e., very low carbohydrate and high fat) would work very well, on average, for most people with ME/CFS, especially women, since fatty acid oxidation may be impaired.

In my case, I take in the MOST protein, then fats, then carbs. Works quite well for me.

 

[eljefe19]

@nandixon @JaimeS started my diet off with MCT oil and leucine. Now just Leucine and ALCAR. It's highest protein, high fat, low to normal carbs. Gluten free. I intend to add MCT oil again at some point.

 

[Hip]

understanding that intermediates are both drained and replenished is probably a useful first step in figuring this out.

I do understand that, but it doesn't on its own provide any obvious explanation of why anaplerotic amino acids (category III amino acids) are being used up faster in female ME/CFS patients than in healthy controls.

The other pathway for pyruvate, besides conversion to acetyl-CoA , is to be converted to lactate (lactic acid).

So perhaps in ME/CFS, if more pyruvate is routed into the anaerobic glycolysis, lactic acid-producing pathway (rather than routed into the mitochondria to complete aerobic glycolysis), then that might lead to a shortage of pyruvate in the mitochondria, resulting in reduced availability of pyruvate for anaplerotic purposes (ie, for replenishing the Krebs cycle intermediate compounds).

So that might explain why anaplerotic amino acids are being used up faster in female ME/CFS patients.

Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle.

I find that to be a weird statement in general.

Fuel means a substance that can be burnt with oxygen to produce energy. So that statement is saying that acetyl CoA is the only substance entering the Krebs cycle which can be burnt to produce energy.

So it seems from that statement that acetyl CoA is the only source of fuel for the Krebs cycle.

This Britannica article says a similar thing:

The TCA cycle plays a central role in the breakdown, or catabolism, of organic fuel molecules—i.e., glucose and some other sugars, fatty acids, and some amino acids. Before these rather large molecules can enter the TCA cycle they must be degraded into a two-carbon compound called acetyl coenzyme A (acetyl CoA). Once fed into the TCA cycle, acetyl CoA is converted into carbon dioxide and energy.

But I have very limited understanding of the Krebs cycle, so am just quoting statements from other articles.

 

[JaimeS]

So it seems from that statement that acetyl CoA is the only source of fuel for the Krebs cycle.

I see why you'd think so. I see why anyone reading what you've quoted would think so!

I understand what is meant by 'fuel', but I still can't quite grasp why they'd say that. This biochemistry text, available from PubMed, states multiple times that "many" and sometimes that "most" of the fuel comes from Acetyl CoA, rather than 'all'. That would jive with everything but certain amino acids entering the cycle at that point.

 

[Hip]

This biochemistry text, available from PubMed, states multiple times that "many" and sometimes that "most" of the fuel comes from Acetyl CoA, rather than 'all'.

Yes, I came across that PubMed article previously, and was puzzled by their use the word "most" in this statement:

The citric acid cycle is the final common pathway for the oxidation of fuel molecules—amino acids, fatty acids, and carbohydrates. Most fuel molecules enter the cycle as acetyl coenzyme A.

When I saw the Fluge and Mella paper, my first thought was to see if there were any other pathways that you could use to input fuel or input energy into the Krebs cycle, because if this were possible, then if might be helpful for ME/CFS.

But in my Googling, I could not find any definitive statements about alternative pathways (other than acetyl CoA) that can be used to supply fuel or energy to the Krebs cycle.

But if anyone can find a definitive statements on alternative pathways to energize the Krebs cycle, please do post.

 

[nandixon]

So perhaps in ME/CFS, if more pyruvate is routed into the anaerobic glycolysis, lactic acid-producing pathway (rather than routed into the mitochondria to complete aerobic glycolysis), then that might lead to a shortage of pyruvate in the mitochondria, resulting in reduced availability of pyruvate for anaplerotic purposes (ie, for replenishing the Krebs cycle intermediate compounds).

So that might explain why anaplerotic amino acids are being used up faster in female ME/CFS patients.

That's right, and in men it may not show up as well because of their greater muscle mass which can be broken down for the same purpose.

 

[JaimeS]

But in my Googling, I could not find any definitive statements about alternative pathways (other than acetyl CoA) that can be used to supply fuel or energy to the Krebs cycle.

Since it's a cycle you could say that ANY molecule in the cycle is offering up fuel / energy, directly or indirectly. Regardless, since Acetyl CoA is part of the cycle, we can't remove it from the equation; no matter what, from a certain angle we would say it is involved in cellular metabolism.

If you're looking for a quotation that states that proteins are utilized in metabolism to produce energy-rich molecules, here is a statement from another biology text on PubMed:

Amino acids that are not utilized in biosynthesis can be oxidized to generate metabolic energy.

That section in general is a great overview.

-J

 

[Helen]

At the time, I thought the ill effects of curcumin might have been due to its ability to inhibit some cytochrome P450 enzymes.

Thanks for this important information.