Vitamin B12 unsaturated binding capaciy & holotranscobalamin

[mice]

Are the vitamin B12 unsaturated binding capacity test and the holotranscobalamin test the same test? If someone is able to, could you provide the rational or documentation for your answer? Thank you!!!!

[NHE]

Are the vitamin B12 unsaturated binding capacity test and the holotranscobalamin test the same test? If someone is able to, could you provide the rational or documentation for your answer? Thank you!!!!

Welcome to ThisIsMS. I don't believe that they're the same test. The transcobalamins bind vitamin B12. Holotranscobalamin is transcobalamin with bound B12. To the best of my understanding, unsaturated B12 binding capacity is a measure of transcobalamin without B12.

See https://www.labcorp.com/wps/portal/provider/testmenu and click on "V" and go to the third page for the B12 tests.

Serum transport of vitamin B12 is accomplished by normally occurring proteins termed transcobalamins including I (an α-globulin), II (a β-globulin), and III (a group of transport factors − “R-type” binders or binder III − found also in some tissues, saliva, milk, and tears). The term “R-type” refers to binding protein with “rapid” mobility on electrophoresis. A family of immunologically identical proteins is known, not all of which have the initially described rapid mobility. They are known also as cobalophilins. Transcobalamin I is the major B12 transport protein and bears immunologic identity to granulocyte cobalophilin. Isoelectric focusing has shown that the cobalophilins are a microheterogenous group of plasma binding proteins. Stenman has reviewed this subject in detail.1 Cobalophilin is increased in diseases characterized by excess granulocyte production, reactive leukocytosis, chronic myelogenous leukemia, and other myeloproliferative states, in particular polycythemia vera. UBBC levels were increased in over two-thirds of cases with polycythemia vera, while nearly 90% of secondary/relative polycythemia patients had normal levels.2 Very high levels have been reported in some patients with hepatoma.3,4 The transcobalamins are normally about 25% saturated with vitamin B12.

[mice]

Thank you NHE!

I can find a lot of info on the holotranscobalamin test. However, I find very little information on the vitamin B12 unsaturated binding capacity test. I just got the result of the vitamin B12 unsaturated binding capacity test and my test result is abnormal (very low). I am wondering if this confirms that I have a problem with transport proteins (like a partial transcobalamin ii deficiency). Other tests are probably needed to confirm this. I have severe problems absorbing vitamin B12.

[NHE]

http://www.expertconsultbook.com/expert ... 020-3408-4

Measurement of unsaturated B12 binding capacity is rarely undertaken and is only available in reference laboratories. (Details of the method were given in the 9th edition of this book.) It is mainly of use for detection of transcobalamin I deficiency as a cause for very low serum B12 with no clinical features of cobalamin deficiency. It is also required for diagnosing the rare TCII deficiency.

[NHE]

http://books.google.com/books?id=OBlxCK ... 22&f=false

...the common term "unsaturated B12 binding capacity" refers to the sum of all B12 binders in the apo-form.

[mice]

NHE, thank you so much for taking the time to research my question!

http://www.expertconsultbook.com/expert ... 020-3408-4

Measurement of unsaturated B12 binding capacity is rarely undertaken and is only available in reference laboratories. (Details of the method were given in the 9th edition of this book.) It is mainly of use for detection of transcobalamin I deficiency as a cause for very low serum B12 with no clinical features of cobalamin deficiency. It is also required for diagnosing the rare TCII deficiency.

I was reading this website before I posted my last post. I thought that things might finally be straightforward. Essentially, based on my symptoms and blood test results, this points to me having a partial TCII deficiency.

http://books.google.com/books?id=OBlxCK ... 22&f=false

...the common term "unsaturated B12 binding capacity" refers to the sum of all B12 binders in the apo-form.

This is a very interesting book. But, if ""unsaturated B12 binding capacity" refers to the sum of all B12 binders in the apo-form, things might not be so straightforward after all. Maybe my problem isn't necessarily a partial TCII deficiency but a problem with another binder? I really don't know. I need to read about these other B12 binders to truly understand and make sense this what this could mean.

Anyone can feel free to comment while I wrap my head around this

[Scott1]

Hi,

I think you'll find what you are looking for if you google "megalin".

Regards

[NHE]

Dr. Benjamin Lynch discusses B12 binding capacity.

http://www.seekinghealth.com/media/podcast1-tcn.mp3

[PointsNorth]

It seems like problems with absorption, bind/transport, metabolism etc. are 'solved' with additional B12 supplementation. It hasn't solved my problem! If I go more than 3-4 days without a 1ml injection of cynocobalamin B12 I crash. Numbness in hands and general disability progresses.

Having some luck with high dosing vitD and (Calcitriol+D before) but early days. Wonder if there is a link between D and B12? I know the MS population is deficient in both.

Thx for your ear.

PN

[kengriff]

I know that Vitamin B12 is an Unsaturated Transcobalamin and Holotranscobalamin is a marker of vitamin B-12 status. So, They are not the same test. One is dependent on the other, but it does not mean that they are the same.

[NHE]

It seems like problems with absorption, bind/transport, metabolism etc. are 'solved' with additional B12 supplementation. It hasn't solved my problem! If I go more than 3-4 days without a 1ml injection of cynocobalamin B12 I crash. Numbness in hands and general disability progresses.

Have you tried methylcobalamin? It's available for injection from compounding pharmacies. Perhaps your doctor could switch you over to methylcobalamin if you're not responding well to cyanocobalamin. Note that it's also available as over the counter sublingual tablets in doses up to 10,000 µg though a 1000 µg daily dose is more common.

[PointsNorth]

NHE, Methylcob doesn't work fo me. My Naturopath says that I'm not able to process thise active form of b12.