Ok, since I haven´t got very far with this series of blogs, I have decided to skip straight ahead to the juicy stuff. I had two additional reasons for this: 1.) the stuff in the fourth episode is what motivated me to start writing this series; and 2.) I was worried someone on the forum might ´scoop´ me (it´s all about keeping/earning a reputation for relevancy in the cut throat world of PR). As I am skipping ahead to part 4, there will be a couple of parts missing (from my current understanding of ME), but seeing as the crucial one with regards to this part, the gut, has quite a lot of evidence already pointing towards what I am claiming (check out Lipkin´s, KDM´s and Hanson´s gut studies if you haven´t already), I thought I could get away with skipping to the end.
I was motivated to look into the metabolic problems in ME when I this read blog on Health Rising:
Basically, the studies authors found that immune cells free of serum were producing twice as much ATP in patients as in controls. If you are interested (and haven´t already) you can read the article or the study yourself, but to my mind the most important conclusion was this:
(Cort) I asked Dr. Wang if by-products of glycolytic production such as lactate could be causing issues in ME/CFS.
(Dr. Wang, the study´s lead author) That’s indeed my speculation. There might be some intrinsic triggers in the patients, such as activation of immune cells, and/or elevation of cellular activities, that promote glycolysis – a similar situation when we exercise too vigorously and we feel sore and tired.
Dr. Wang elaborated on this later in the interview:
It is possible that those immune cells (PBMCs) are activated, maybe due to a virus infection or other pathological conditions. It has been shown that when activated, immune cells shift from catabolism to anabolism which requires more energy, and become increasingly dependent on glycolysis for ATP production. This theory was raised by Dr. Maureen Hanson via personal communications.
So, being biologically ignorant as I am, I did not understand the full implication of these statements when I first read the article, and it was only after staying up late googling stuff on Pubmed that I understood them (at which point I thought I had come up with the basic idea myself, when clearly I hadn´t).
To make it clear for people as biologically ignorant as me: something is causing the serum-free immune cells in ME patients to increase glycolysis and produce lactic acid.
When Cort asked about the significance of the cells being serum-free, Dr. Wang said this:
It is difficult to directly compare our results from cultured PBMCs with those from patients in vivo. The reason is that the cells we studied were dissociated from the patients and thus they didn’t have the same environment as those cells inside the body. To be precise, other cells, serum, and the environment surrounding PBMCs were not present anymore.
And when she was asked about the possibility that the immune cells may be acting oddly both in and out of the serum she said this:
I’m not an expert in immunity so I’ll have to speculate. The immune cells undergo significant structural and signaling changes after activation – such as receptor binding to a ligand on the plasma membrane, intracellular transduction of signals, and eventually the signals end up in nucleus to change gene transcriptions. I don’t know how long these changes last once the cells are out of the body, but maybe the cells still keep some of the internal changes in our culture so we are able to detect it. It’s also entirely possible that these phenomena are responses of the cells after removing inhibitory factors in the serum – to prove this theory, a direct comparison with and without serum is needed.
I am going to assume that the first possibility (odd in and out of the serum) is true. Of course, this might turn out to be wrong, but since the first possibility fits so well with what we know about ME, I´m fairly confident in this prediction.
Ok, I will now stop just rehashing Cort´s article, and try to contribute myself to ME patients´ (and who knows, perhaps a couple of researchers´ too, I can dream, can´t I?) understanding of this glycolysis/lactic acid problem. Dr. Wang has already suggested where the problem is occurring (the immune cells) and by which mechanism (the switch from catabolism to anabolism when activated); I will try to illustrate why I think this this activation is occurring in the immune cells of people with ME.
To do this I have to go back to the blog on the gut that I haven´t wrote yet (oops). Briefly, first KDM reported (6 years ago, I think), and then Hanson last year showed that ME patients have higher levels of LPS in their blood than controls do. According to KDM, this was positively correlated with the severity of the patient´s condition, and since he was right on the LPS in general I am willing to bet that he is right on this too. This led me to look into whether LPS can cause the immune cell activation mentioned above.
The answer was an unequivocal ´yes´:
This study is well worth reading in its entirety. I am not going to detail them all here, but there are several changes in the immune cells mentioned that seem to correspond to the results of Naviaux´s metabolic study.
I also found the following study very intriguing, particularly this statement:
The findings indicate that the early (2 and 6 h) elevation in muscle lactate concentration during LPS infusion was not attributable to limited muscle oxygen availability or ATP production (evidenced by unchanged ATP and phosphocreatine (PCr) concentrations) or to PDC inhibition, whereas after 24 h, muscle lactate accumulation appears to have resulted from PDC activation status limiting pyruvate flux, most probably due to cytokine-mediated up-regulation of PDK4 transcription.
I can feel everyone´s (and most importantly, my own) patience starting to wane, so I will just list the steps that I think probably make up an ME attack or PEM episode, and that are probably present to some extent all the time, at least in those with more severe ME.
1. Exercise or diet causes changes in intestinal permeability. This has been shown in healthy people in the first instance, and I willing to bet that when this is measured in people with ME, it will be found that not only do people with ME have leakier guts than controls, but that exercise makes them far leakier. I do not have a detailed explanation for this yet as the gut is a very complicated area, but in people like me (with those gut infections that Lipkin is looking at as the cause of the IBS present in some ME patients), it might be either a direct or indirect result of infection with one of these bugs. In others it may be an autoimmune process, or perhaps something else entirely. Regardless, I think we will see that there will be some separation between cases and controls with regards to measures of intestinal permeability (which would explain the differences observed by Hanson in levels of LPS) and that all of these measures (including the LPS) will show a much greater separation between patients and controls after exercise (as was suggested by the Vernon gut study).
2. The increased level of LPS ´aggravates´ the ongoing immune process in the blood whereby lactic acid is produced by these immune cells through the ramping up of glycolysis. This process also causes changes in cytokine production, which I believe account for the sleep disturbances (see the other blog I haven´t written yet), and also very likely other symptoms as well.
3. This increased production of lactic acid by the immune cells results in increased amounts in the blood (I´ve forgotten which study it was, but I found good evidence that the increased glycolysis in the immune cells result in changes in blood lactate levels).
4. This increased level of lactic acid in the blood results in changes in the lactate gradient between the muscles and the blood, resulting in lactate levels increasing in the muscles as well (see the unpublished observations in the second study I posted).
5. The early LPS-induced increase in TNF-a results in a delayed upregulation of PDK4 in the muscle (see the second study for a proposal for how this might work).
6.This upregulation of PDK4 results in the inhibition of PDC, contributing further to muscle lactate accumulation.
Things this might explain
- Observed increases in blood lactate levels in ME patients, both before and, more dramatically, after exercise.
- Some of the metabolic changes observed in Naviaux´s study.
Things that this does not explain because I couldn´t be bothered/had forgotten why I came to that conclusion, but which may be the true anyway
- The delayed onset of PEM. I do not have a explanation yet for why the delayed, possibly PDK4-induced inhibition of muscle PDC activity should be more disabling in ME patients than in controls (if indeed it is), but if I had to guess I would go back to the mooted intestinal permeability changes (and the suggestion of longer lasting changes in the blood microbiota after exercise in the Vernon study). In rats, the PDC inhibition did not compensate fully for the ramping down of the first mechanism (suggested to be the change in the lactate gradient), but perhaps in ME patients this situation is reserved, with lactate levels climbing not falling. The delayed onset could of course be caused by something other than increasing lactate levels, but it definitely feels like there is more lactate in my muscles a day or two after exercise than there is immediately afterwards.
- The contradiction between the seemingly well-founded assumption that mTOR is downregulated in ME patients, and the fact that some people seem to improve on mTOR inhibitors such as Rapamycin and Azithromycin. I forgot exactly how I came to this conclusion, but it seemed to me when I stayed up late researching this (sleep deprivation might be a factor here) that the Akt-mTor-HIF-1a pathway may be downregulated in the muscle*, but upregulated in the immune cells in the blood. A possible mechanism for the positive effects of mTOR inhibitors (one I mentioned in one of the mTOR threads, although not explicitly with reference to LPS-induced activation of immune cells), could then be that these mTOR inhibitors suppress the LPS-induced increase in glycolysis in the immune cells.
* I think this quote from the second study may have had something to do with it:
In the context of cytokines, it has recently been demonstrated that TNF-α decreases Akt protein levels and/or signalling in apidocytes (Medina et al. 2005) and human skeletal muscle (Plomgaard et al. 2005) thereby presumably activating (dephosphorylating) the family of FOXO transcription factors.
My Current Understanding of ME: Part 4 - Lactic Acid
Blog entry posted by msf, Jun 25, 2017.