Complement Component C1q as a Potential Diagnostic Tool for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Subtyping, 2021, Castro-Marrero et al

It's good that the article is open access, and that it's possible to read the feedback of reviewers. The study was partly funded by a patient group, although I bear in mind the previous studies by Castro-Marrero that were funded by a supplement manufacturer.

The study was of a good size (250 people), all females.

The paper is a bit frustrating in that the charts shown in the paper relate to efforts at subgrouping the sample and really don't tell us much, whereas the scatter plots are hidden away in a supplementary file. It's disappointing to see peer reviewers simply say 'Well done!' or focus on the fact that numbers under nine should be spelled out as text rather than given as a number, when the paper could have been improved a lot by better choice of figures.

Vitamin D
A high percentage of the patients were low in vitamin D. While it is likely that that is a result of a lot of time being spent indoors rather than being a cause of ME/CFS or shedding light on the pathology of the illness, it does suggest that people with ME/CFS may need to try to spend more time in the sun, or take supplements.

While Vitamin D deficiency is very common in populations, references I found suggest levels should be over 40 ng/ml. That suggests this sample of people (living in Spain, a sunny country) really are quite deficient. Given the symptoms of Vitamin D deficiency do overlap substantially with the symptoms of ME/CFS, it would be good to see some more attention being paid to this. I'd like to see a well-conducted supplementation trial, and guidelines should note that people with ME/CFS are at risk of vitamin D deficiency.

 

Complement factor C1Q
The main finding of interest though was the high levels of C1q.

 

Sorry but "need to try to spend more time in the sun" I'm surprised at these numbers from Spain, but even in sunny parts of the world vitamin D deficiency is not uncommon due to clothing, sunscreen use and what time of day people are typically outdoors. Not least what time of year the samples were collected.

Many of those patients look to be deficient, although reference ranges for vitamin D vary a lot by country (I assume the red lines are the range used in Spain). If one only cares about skeletal health, the reference range for sufficiency is >7.5 ng/ml (25 nmol/L), but most countries use >20 ng/ml (50 nmol/L) "to be on the safe side" while taking into account that vitamin D might have extraskeletal effects. 35-40 ng/ml (>75 nmol/L) are advocated by some specifically due to extraskeletal effects and I think @Mij mentioned it had been implemented in Canada. I think it has been also in other countries. In Norway it is seen as a bit fringe to advocate for people to have such high levels of vitamin D (our threshold for sufficiency is >16-20 ng/ml depending on what lab is used).

I do with people would have their vitamin/mineral status checked (this will include a diet interview as there isn't a blood test for many nutrients), so deficiencies could be discovered and treated. Having those on top of ME feels so unnecessary

 

So C1Q -
thanks to wikipedia, this is my understanding, which may be wrong and will certainly be incomplete, so do correct me:

1. CIQ binds to molecules that suggest the immune system needs to do something
C1Q can bind directly to bacterial and viral surface proteins, dying cells, and acute-phase proteins*. C1Q can also bind to [antibody (an IgM or IgG) + antigen] complexes.

* Acute-phase proteins - proteins associated with inflammation which include CRP, and the mannose-binding lectin that another recent study looked at in ME/CFS).


2. The binding sets a cascade of reactions off
The binding activates the C1 complex which activates the 'classical complement pathway'.

Classical complement pathway: That's a series of reactions that produces molecules that
1. attract phagocytes;
2. tags cells for phagocytosis;
3. forms the Membrane Attack Complex that damages a cell membrane to kill the cell

3. So, C1Q is a useful thing
A lack of C1Q is therefore not a good thing, as the immune system won't work so well. A deficiency of C1Q apparently leads to lupus, where, Wikipedia says, there is an accumulation of autoantibodies and dying cells that aren't being cleaned up.

4. But too much won't be good either
Some of the molecules produced along in the cascade of reactions are called anaphylatoxins (fragments of C3,C4,C5 - namely C3a, C4a, C5a)

A deficiency of C1-inhibitor can cause angioedema. C1-inhibitor defiency can be hereditary or acquired.

So, it looks as though a substantial proportion of the women in this study had high levels of C1Q. I guess one question is, are the levels high enough to be contributing to their ME/CFS symptoms? Another one is 'why are the levels elevated?'

 

Is the level of elevation of the C1Q significant?

The unit of measure in this study is miligrams/dL. (1 mg/dL =10 ug/ml)

This study suggested the normal range is 10 to 25 mg/dL.
Mayo clinic's normal range is 12 -22 mg/dL. Using that range, most of this study population have high C1Q.
Medscape suggests the normal level is 7 mg/dL, and the acute phase serum level is 13% higher.
Clearly, there's variation in the ranges, maybe depending on the test method.

It doesn't seem like the C1Q level in serum needs to be massively higher to suggest something is going on. C1Q levels can be much higher at the site where the action is taking place.

(The Medscape article also talks about the lectin/ mannose-binding pathway, as an alternative to the classic pathway that involves C1Q. In that pathway, the acute phase serum level of MBL is 1000% of that of the normal level. So, you'd probably be wanting to see much higher levels in ME/CFS compared to controls in order to be convinced that higher levels of MBL are important.)

 

I've made a thread for a Sorensen paper from 2003 here:
Complement activation in a model of chronic fatigue syndrome, 2003, Sorensen et al

It's an interesting paper with an exercise challenge. It looks as though they tested C1Q and did not find a significant difference - but I couldn't find any data reported for the C1Q comparison. The Medscape article suggested that the difference between normal and activated levels serum may not be big, and some of the articles I read suggested that levels change with age. So, perhaps the smallish sample size of the Sorensen study made it hard to get a significant difference given background noise.

 

I don't think it is used routinely in Norway, although mine was checked before I was eventually diagnosed with ME (I apparently presented with lupus-like symptoms).

The Wikipedia article (sans the lupus part, which I found a bit oversimplified) is in line with what we learned about the complement system in immunology @Hutan. A bit off topic, but recently some Norwegian researchers proved that a "truth" about the complement system and coagulation is in fact not true, and they discussed how it came to be a truth in the first place (bad data) https://www.jimmunol.org/content/207/6/1641 so I wonder if there are other things we don't know about these proteins.

Vitamin D can regulate the immune system, so vitamin D status may be important to see certain differences? This is where the threshold for >75 nmol/L may be important. Since endothelium permeability was mentioned, vitamin D may play a role in that too. Vitamin D has been found to regulate epithelium permeability in response to various pathogens, but only when above a certain threshold (in cell culture and animal models, I've also seen it in human studies but they are often of poor quality. Such as the one that gave supplements, said "vitamin D levels and epithelium integrity improved" but did not provide any measurements on vitamin D serum levels pre/post supplementation...). I'm not 100% sure but I think some of the proteins between epithelium cells that can be regulated by vitamin D is also found between endothelium cells.

 

It's not clear to me what that slide is suggesting. That exercise and anti-C1q antibodies reduce levels of functioning C1q? So C1q can't do it's job helping to defeat pathogens and clear the rubbish up?
But, I don't think we have any evidence of high levels of Anti-C1Q antibodies in ME/CFS (unlike the situation with Lupus). I mean, if we had high levels of Anti-C1q antibodies, wouldn't we have been diagnosed with Lupus?

 

Responding to a deleted post

Thank you, that's really interesting. My son and I get generalised swelling when in PEM - I don't wear rings, and lately now don't wear my watch either for that reason. There is facial swelling too, around the eyes. My son has had a couple of episodes of very obvious facial swelling when exhausted. And I know some other members here have problems with oedema too.

So, you have normal levels of the C1 inhibitor but it isn't functioning well? How is that tested for? Does it mean that you have high levels of C1Q? From what I read, problems with C1 inhibitor don't seem to automatically mean high levels of C1Q, and in fact levels of C1Q can be low in people with angioedema.

It's certainly complicated.

 

Responding to a deleted post

Doctors don't seem to be interested. My record of lab tests doesn't have any complement-related tests, but I've been slack about copying results into it these last couple of years. I don't recall any complement-related tests.