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Tenuous link between chronic fatigue syndrome and pyruvate dehydrogenase deficiency

Murph

:)
Messages
1,799
This is a rebuttal to Fluge and Mella's PDH deficiency idea, from a guy at Oslo Hospital, published in Norwegian and English. (Found it via PubMed so I assume the site is a medical journal or similar.).

http://tidsskriftet.no/en/2017/12/d...yndrome-and-pyruvate-dehydrogenase-deficiency

Researchers studying the energy metabolism of patients with chronic fatigue syndrome have reached the conclusion that these patients have impaired pyruvate dehydrogenase function, but their measurements are not consistent with the changes we see in patients with primary genetic pyruvate dehydrogenase deficiency.

A cross-sectional study published in December 2016 found a change in the pattern of amino acids in the plasma of patients with chronic fatigue syndrome. Gene expression in white blood cells and energy metabolism in muscle cells was also found to have changed (1). The authors interpret the results as an expression of functional inhibition of the enzyme pyruvate dehydrogenase, and they postulate dysregulation of the enzyme complex as a possible key factor in the pathogenesis associated with chronic fatigue syndrome.

The study received extensive media coverage (2, 3), and the link to pyruvate dehydrogenase is published without reservations as an established fact (4, 5). At our laboratory we are now receiving samples for metabolic screening from patients with suspected fatigue syndrome. On the basis of my own experience with biochemical diagnostic workup for pyruvate dehydrogenase deficiency, I would like to point out weaknesses in the study that should have prompted much greater caution in the conclusions.

Criticism of method and interpretation
The plasma amino acid concentrations of 200 patients and 102 healthy control persons were examined in the study. The researchers found significant differences between the two groups, but the implications of this are uncertain because they did not adhere to established diagnostic workup for pyruvate dehydrogenase deficiency, and because the samples were not taken in a standardised manner.

The amino acid pattern is not consistent with what we see in patients with primary pyruvate dehydrogenase deficiency
Pyruvate dehydrogenase deficiency results in an increased concentration of pyruvate, in muscle and nerve cells, for example. Pyruvate is converted into lactate and the amino acid alanine. Alanine is the only amino acid that is expected to be outside the reference range in plasma and cerebrospinal fluid in cases of primary pyruvate dehydrogenase deficiency (one and a half times to twice the upper reference limit) (6). However, the study reports a tendency to a lower alanine level in these patients. It is surprising that this striking discrepancy is not mentioned in the article.

Failure to standardise sampling may explain the difference between the groups
A fasting sample is strongly recommended for assaying plasma amino acid concentrations, because levels vary substantially with diet, and also naturally over a 24-hour period, by up to 10–15 % (6). In the study, non-fasting amino acid patterns with small differences are compared; significance is attached to differences down to 3 %.

It is very strange that the authors do not make greater reservations about diet as a confounding factor, when they themselves have shown that diet affects precisely the group of amino acids that they use in their argument for pyruvate dehydrogenase deficiency.

The study found significant differences between fasting and non-fasting patients. The fasting patients were therefore excluded in subsequent statistical work. The authors should then also have made clearer reservations to the effect that a possible concealed discrepancy between patient group and control group with respect to diet and sampling might be an alternative explanation for several of the differences they found. Systematic dietary differences between the groups are not inconceivable.

Gastrointestinal symptoms (abdominal pain, nausea, irritable bowel etc.) are some of the consensus criteria for the diagnosis (7). There have been earlier reports of special dietary habits among patients with chronic fatigue syndrome (8).

What about the pyruvate/lactate ratio and direct measurement of pyruvate dehydrogenase activity?
The pyruvate/lactate ratio in plasma may distinguish patients with pyruvate dehydrogenase deficiency from other patients with hyperlactacidaemia. The ratio therefore plays a central part in the biochemical workup of pyruvate dehydrogenase deficiency (9).

The pyruvate/lactate ratio was not determined in the study. This is unfortunate, because the ratio could have provided important evidence for, or against, pyruvate dehydrogenase deficiency. Direct determination of enzyme activity in cells is also a key factor in routine diagnosis of pyruvate dehydrogenase deficiency. It is strange that this was not performed in the study of muscle cells cultured in the presence of patient serum.

Specific link to chronic fatigue syndrome requires several control groups
The expression pattern of genes associated with the pyruvate dehydrogenase complex differed between the patient group and the control group in the study. This is an interesting result, but the study does not provide grounds for interpreting the difference as specific to chronic fatigue syndrome.

According to the consensus criteria, the patients have had a “substantially reduced activity level” lasting for “at least six months” (7). It is well known that genes associated with the entire energy metabolism (including pyruvate dehydrogenase complex) are changed by immobilisation (10). Musculature grows and dwindles depending on the activity level; different expression patterns between the two groups in this study are therefore only to be expected. Before the expression pattern can be linked specifically to chronic fatigue syndrome, the patients must be compared not only with healthy subjects, but also with other patient groups who experience a similar reduced activity level, for example patients with stroke, broken bones, renal failure or severe depression.

The study also found that the energy metabolism of muscle cells in vitro changed in the presence of serum from patients with chronic fatigue syndrome. It is interesting that this can be shown experimentally, but this observation cannot be used either as a link specifically to chronic fatigue syndrome. Here, too, more control groups consisting of patients with a reduced activity level for other reasons are needed. For example, the study shows reduced production of high-energy phosphates (ATP) in vitro. In a mouse model in which cultivated muscle cells are exposed to serum from individuals with muscular atrophy and chronic renal failure, ATP production is also reduced (11).

Chronic fatigue syndrome is not typical of primary genetic pyruvate dehydrogenase deficiency
The authors suggest that pyruvate dehydrogenase deficiency is a key to the pathophysiology of chronic fatigue syndrome. Chronic fatigue is not a typical symptom of patients with primary genetic pyruvate dehydrogenase deficiency, either the severe or the mild form (9). This requires a comment, but is not mentioned at all.

Objective assessments called for
Research on metabolic mechanisms associated with chronic fatigue syndrome is interesting, and the major work of Fluge et al. may generate hypotheses that are well worth investigating further. But the authors have been too quick to state almost categorically that pyruvate dehydrogenase deficiency is a part of the pathophysiology underlying chronic fatigue syndrome. At present, the link between detected amino acid changes and pyruvate dehydrogenase deficiency is too tenuous, and the change in gene expression and energy metabolism too non-specific for so categorical a conclusion.
 

Dolphin

Senior Member
Messages
17,567
http://tidsskriftet.no/en/2017/12/d...pyruvate-dehydrogenase-deficiency/kommentarer

Chronic fatigue syndrome and pyruvate dehydrogenase function
13.12.2017

Karl Johan Tronstad, Øystein Fluge, Olav Mella

We appreciate the comments, but wonder why this kind of debate is raised in Tidsskriftet (The Journal of the Norwegian Medical Association) rather than the journal which published the original

article. Bliksrud gives an inaccurate image of the findings, with partially uncritical use of sources and an incomplete description of a complex research field.

We have suggested the hypothesis that impaired pyruvate dehydrogenase function may play a role in chronic fatigue syndrome. We have not made any statements “without reservations”. The hypothesis is based on scientific arguments and will be tested thoroughly through further research. We have stressed that there is no indication of a structural defect in, nor a lack of, the pyruvate dehydrogenase enzyme in patients with chronic fatigue syndrome. We argue that our results may imply a dysregulation of the enzyme function. We have repeatedly emphasized that these findings at present do not justify new methods for treatment or diagnostics. How the media chose to report on the findings was evidently difficult to control.

We have made every effort to describe our results in a clear and precise manner in order to avoid misunderstandings. Terms like “pyruvate dehydrogenase deficiency” are misleading in this context, and it is unfortunate that Bliksrud applies this particular term in his comment, and even in the title. There is no indication of an enzyme deficiency. Rather, we have explained why we believe the results to be consistent with a partial impairment of the enzyme function, as a result of changes in the underlying regulatory mechanisms.

Pyruvate dehydrogenase is an essential enzyme in energy metabolism, and is carefully regulated both allosterically, post-translationally and through gene transcription, partly via energy-sensitive signaling pathways (1, 2). When Bliksrud narrows the enzyme’s role in disease mechanisms to what is seen in genetic primary pyruvate dehydrogenase deficiency, the basis for comparison is limited. It is not obvious that that such a systemic, permanent condition should be comparable to a more fluctuating, perhaps local and context dependent impairment of the enzyme function. In a number of conditions, pyruvate dehydrogenase is associated with other potentially pathogenic mechanisms. One example is primary biliary cirrhosis, which involves autoantibodies against components of the pyruvate dehydrogenase complex, and where fatigue is a characteristic symptom (3). It is also relevant to look at other conditions involving glucose metabolism and regulation of pyruvate dehydrogenase, such as diabetes and cancer (2), and also normal adaptation to variable metabolic and physiological circumstances (4). In the article, we have elaborated on how these mechanisms may play a part in chronic fatigue syndrome.

There are no published systematic studies suggesting increased blood lactate at rest in chronic fatigue syndrome, but many patients describe a sensation of rapid accumulation of lactate upon activity. The accumulation of lactate may occur at a considerably lower muscular effort than among healthy. Alanine levels normally increase in plasma as a result of muscular work, in parallel with lactate (1), but we anticipate such an increase to be considerably more permanent in genetic primary pyruvate dehydrogenase deficiency than in chronic fatigue syndrome, where the effects are context dependent and triggered by activity. Since alanine plays a specific role in transporting amino groups to the liver, from amino acid catabolism in the muscles, the serum level is expected to vary independently of changes in glucose catabolism. In order to limit possible misinterpretations, we therefore chose not to include alanine in the statistical analyses of the amino acid categories. Studies of both lactate and alanine in chronic fatigue syndrome should preferentially be performed using standardized protocols for physical exercise testing. We would also like to point out that measurements of citric acid cycle substrate consumption are used in laboratory investigations to detect mitochondrial pyruvate oxidation defects (5).

Direct measurement of pyruvate dehydrogenase activity would of course be relevant, but is complicated. A method developed to detect genetic primary dehydrogenase deficiency would not necessarily be suitable for measurement of reversible and contextual enzyme inhibition, which may be caused by altered phosphorylation state. Therefore, as shown in the article, we are working with living cell cultures exposed to serum from either patients with chronic fatigue syndrome or healthy controls, to assess central parameters of energy metabolism.

Although individual patients describe avoidance of certain foods, there are no systematic studies which show that patients with chronic fatigue syndrome, with a body mass index equivalent to that of the general population, have a significantly different diet compared to healthy controls. Surprisingly, Bliksrud refers to a case series describing four patients with known eating disorder who developed chronic fatigue syndrome. Needless to say, this article does not constitute relevant evidence of the dietary habits of this patient population in general, nor of our study sample. Nevertheless, as we have not performed a detailed dietary anamnesis, we cannot categorically rule out that dietary factors could play a role. However, as there are no known or expected systematic differences in dietary habits, the number of included patients (153) and controls (102) will counteract significant bias in the analyses.

We observed that overnight fasting led to reduced levels of several amino acids, and therefore included only non-fasting patients in the comparison (see supplementary tables in the article). The altered amino acid profile was primarily observed in non-fasting women with chronic fatigue syndrome as compared to healthy women. Some changes were highly significant, of moderate effect sizes, with differences in mean values of approximately 15%. Yet the values were within the normal ranges. Thus, there are no amino acid deficiencies, but the data rather reflect compensation mechanisms for an altered metabolism. In the same samples, we observed no differences in triglyceride levels which increase after meals, or free fatty acids which increase upon fasting (1). We therefore find it unlikely that differences in fasting state should explain the findings. Also, our results are consistent with other reports, including studies where only fasting individuals were included (see references in article).

Our study included more patients than previous metabolism reports. The changes in amino acid profiles could not be explained by disease severity or duration, age, BMI or physical activity level (see supplementary tables in article). Bliksrud mentions, without further specification, that immobilization leads to metabolic changes, and refers to a study of mRNA analysis of muscle biopsies after limb immobilization. There are more relevant and comparable studies of serum metabolites after immobilization, where the results do not correspond to our findings in patients with chronic fatigue syndrome (6, 7).

We have not found reports showing an amino acid pattern equivalent to what we observed in patients with chronic fatigue syndrome, in healthy subjects after exercise, inactivity or dietary changes, nor in other patient groups. That does not signify that the observed changes are exclusive for patients with chronic fatigue syndrome. We have not maintained that these changes are specific to chronic fatigue syndrome, and we entirely agree with Bliksrud that it would be interesting to investigate whether similar changes take place in other groups suffering substantial fatigue.

We hope we have conveyed a more nuanced image than reflected in Bliksrud’s comments, and we confirm that our hypothesis still stands.

Litterature
1. Berg JM, Tymoczko JL, Gatto GJ, Stryer L. Biochemistry. 8. utgave. New York: W.H. Freeman & Company, 2015.
2. Gray LR, Tompkins SC, Taylor EB. Regulation of pyruvate metabolism and human disease. Cell Mol Life Sci. 2014;71(14):2577-604.
3. Bjorkland A, Loof L, Mendel-Hartvig I, Totterman TH. Primary biliary cirrhosis. High proportions of B cells in blood and liver tissue produce anti-mitochondrial antibodies of several Ig classes. J Immunol. 1994;153(6):2750-7.
4. Zhang S, Hulver MW, McMillan RP et al. The pivotal role of pyruvate dehydrogenase kinases in metabolic flexibility. Nutr Metab (Lond). 2014;11(1):10.
5. Sperl W, Fleuren L, Freisinger P et al. The spectrum of pyruvate oxidation defects in the diagnosis of mitochondrial disorders. J Inherit Metab Dis. 2015;38(3):391-403.
6. Glover EI, Yasuda N, Tarnopolsky MA et al. Little change in markers of protein breakdown and oxidative stress in humans in immobilization-induced skeletal muscle atrophy. Appl Physiol Nutr Metab. 2010;35(2):125-33.
7. Kujala UM, Makinen VP, Heinonen I et al. Long-term leisure-time physical activity and serum metabolome. Circulation. 2013;127(3):340-8.
 

alex3619

Senior Member
Messages
13,810
Location
Logan, Queensland, Australia
Deficiency would be about having low PDH levels, or associated complexes and enzymes. I suspect we might have poor associated complexes and enzymes, but not absolute deficiency, though this should be testable. The hypothesis here really goes to PDH suppression, and it might be variable even in a single patient. So direct comparison to PDH deficiency is potentially problematic.

I am particularly concerned about lipoic acid levels.
 

pattismith

Senior Member
Messages
3,930
I found this really good picture about how PDH is inhibited by PDK4 activation.
I wonder if PDK4 is activated in ME, do we know?

1743-7075-11-10-2.jpg


Transcriptional regulation pathways of PDK4 in different tissues under various nutritional states.

Inactivation of PDC by up-regulation of PDK4 can switch glucose catabolism to fatty acid utilization.

There are different transcriptional regulation pathways in skeletal muscle, liver, white adipose tissue and heart under various nutritional conditions (energy deprivation, high fat diet consumption, exercise, diseases, drugs). Akt/PKB: protein kinase B; AMPK: 5’-AMP-activated protein kinase; CD36: Cluster of differentiation 36; C/EBPβ: CCAAT/enhancer-binding protein β; eIF4E: Eukaryotic initiation factor 4E; ERRα: Estrogen related receptor α; FAT: Fatty acid transporter; FoxO1: Forkhead box protein O1; LXR: Liver X receptor; MAPK: p38 mitogen-activated protein kinase; PDC: Pyruvate dehydrogenase complex; PDK4: Pyruvate dehydrogenase kinase 4; PGC1α: PPARγ co-activator 1α; PPARs: Peroxisome proliferator-activated receptors; SHP: Small heterodimer partner; STAT5: Signal transducer and activator of transcription 5.


 
Messages
25
I have increased pyruvate and slightly low lactate. Also decreased citrate, cis aconitate, isocitrate in kreb's cycle. You can see in image.
 

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bertiedog

Senior Member
Messages
1,738
Location
South East England, UK
@bostjan01 Your results are the exact opposite of mine. There was no pyruvate detected and I had high levels of the others you mention.

I am however quite active and average 8000 steps daily so this might have a bearing. I do, of course have periods when I suffer with PEM and then my steps will be quite a bit less.

Pam