Cystatin-C some thoughts and some references (blog post 17/8/26)

#1

Cystatin-C has interested me for some time. It is used as a marker of Kidney function and in theory is a better marker than Creatinine. Creatinine has its problems, but it appears so does Cystatin-C. What I found interesting about Cystatin-C is that it is also a signalling molecule whilst Creatinine is a metabolic by product. Creatinine is produced mainly inside skeletal muscle by the spontaneous, non-enzymatic breakdown of creatine and phosphocreatine. Creatinine is also produced in blood samples between the sample being taken and then tested. As it is excreted by the kidneys a low value is an indicator of good kidney function or low muscle mass. High values can result from exercise and high muscle mass as well as bad kidney function.

I have tasked three LLMs to produce some summaries of research and I attach those below. However, there is only one relatively straighforward conclusion I can come to at this point which is that Cystatin-C is a complex molecule and although there is an argument that low levels correlate with a longer healthier life that does not mean that lower levels are always the better thing to have.

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#2

Standalone CysC doesn’t mean much on its own, just as long as it’s not too high. Usually it’s just an input feature when training ML models. An easy way to use it is CCR = Cr / CysC, and the higher the better. That simple division turns it right into a linear metric.

#3

I assume you mean Creatinine for Cr, but I still think that is simplistic. If we are really trying to get into what is going on.

#4

Also, MVM can actually lower CysC. Just out of curiosity, how many people on this forum are currently taking a daily MVM? (MULTIVITAMIN)

#5

I have solgar VM1000 I take on mondays and Thursdays unless I am fasting un which case i am to move it by a day. But multi vitamins depend on the contents

#6

I thought I would add a little more to this. A few years ago I was quite happy with Cystatin-C

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But then it went wrong. I decided to ignore it as I was too busy messing around with other biomarkers and you cannot sensibly try to do too many things at once.

However, then more recently I gave it some attention:

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What has happened over the past two weeks is that it has dropped from 1.29 to 0.95. I did have it at nice 0.73 a few years ago. I will still keep an eye on it, but what is important to learn from this is that it can move a long way without necessarily any change to kidney function itself.

I think there is probably a link between alcohol consumption and Cystatin-C

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#7

Getting a Cystatin-C based eGFR is also useful. Mine is much higher than the eGFR on my regular panel because I am muscular. Sure, a low reading can be a false sense of security but it is still better than a high one. I am pleased with my 0.69 reading and I have tested for it three times in my life now. It’s always been roughly the same number.

#8

The problem with eGFR from either Creatinine or Cystatin - C is that they are vulnerable to changes in the biomarker not related to kidney function.

Both have a number of problems.