Biomaterial

Homocysteine, vitamin B12, MMA


Data files
LASAC866

Contact: Natasja van Schoor

Background
In the general population, a mildly elevated plasma level of homocysteine, termed hyperhomocysteinemia, is a common condition. Hyperhomocysteinemia is recognized as a major risk factor for atherosclerosis, cognitive impairment and Alzheimer’s disease, and osteoporosis. Deficiencies of vitamin B6, B12, and folic acid cause a rise in homocysteine levels. Those vitamins are involved in the homocysteine metabolism. Methylmalonic acid has been recognized as a better marker of availability of vitamin B12 in the cell, compared to vitamin B12 itself. This document describes the determination of homocysteine, vitamin B12, and MMA in LASA.

Measurements in LASA

Blood collection
Morning blood samples were collected in 1995 and 1996. Subjects were allowed to eat toast or drink tea, but no dairy products. Samples had been kept deep-frozen until determination 2001/2002.

Measurement procedure & variable information
EDTA plasma samples were analyzed for total homocysteine (tHcy) with the Abbott IMx analyzer at the Laboratory of Clinical Chemistry of the VUMC. The IMx method uses fluorescence polarization immunoassay (FPIA) technology. The between-assay CV was 4%.
Serum levels of vitamin B12 were determined at the Endocrine Laboratory of the VUMC with a competitive immunoassay luminescence on the automated ACS 180 System (Bayer Diagnostics, Mijdrecht, The Netherlands). The between-assay CV was 5%.
Methylmalonic acid (MMA), which was determined in subjects living in the Amsterdam region, was measured in 0.5-mL plasma by stable-isotope-dilution capillary gas chromatography-mass spectrometry. The between-assay CV was 9%.

All values can be seen and used as valid values, including the extreme high values that occur. Hcy and MMA are metabolites, and metabolites can reach high extremes. The same is true for vitamin B12: when a subject uses multivitamin or vitamin B-complex tablets, or receives B12 injections, his or her plasma B12 level can be very high (f.i. 1500 pmol/L instead of around 400-500 pmol/L). In some studies, persons having levels above 800 pmol/L were excluded, in order to exclude those using vitamin B supplements.(1)

Please note that vitamin B12 and folic acid has also been determined directly after blood sampling for the Zwolle region only, both in 1992/93 and 1995/96, at the Isala Clinic, Zwolle (datafile LASAX860).

Availability of data per wave

Numbers per wave

B

C


2B*

G



3B*

Total homocysteine (tHcy)

1301

Vitamin B12

1276

MMA (Amsterdam only)

582

* 2B=baseline second cohort;
   3B=baseline third cohort

Previous use in LASA
A study on the association between Hcy and osteoporotic fractures in both LASA and the Rotterdam Study has been published in the New England Journal of Medicine (Van Meurs et al., 2004). The combination of high Hcy and low vitamin B12concentrations were significantly associated with low broadband ultrasound attenuation, high markers of bone turnover, and increased fracture risk (Dhonukshe-Rutten et al., 2005). Furthermore, Hcy has been associated with lower physical performance in older women (Van Schoor et al., 2012), a lower hand grip strength in older men, and more functional limitation in both older men and women (Swart et al., 2013).
Also, a LASA paper on the association of vitamin B12 and folic acid on cognition has been published. However, data used for that paper were data from determinations directly after blood sampling in the Zwolle region at baseline; thus data from file B860 and not from file C866, which is described here (Jelicic et al., 2001).

References

  1. Dhonukshe-Rutten RA, Pluijm SM, de Groot LC, Lips P, Smit JH, van Staveren WA. Homocysteine and vitamin B12 status relate to bone turnover markers, broadband ultrasound attenuation, and fractures in healthy elderly people. J Bone Miner Res. 2005;20(6):921-9.