Cobalamin-binding proteins in normal and cobalamin-deficient older subjects.
BACKGROUND
The causes of cobalamin (vitamin B(12)) deficiency in older people are only partly understood. We investigated the role of the cobalamin-binding proteins and tested the hypothesis that low saturated transcobalamin concentration is an early marker of cobalamin deficiency.


METHODS
We measured saturated (holo) and unsaturated (apo) transcobalamin and haptocorrin concentrations in healthy middle-aged volunteers, healthy older volunteers, cobalamin-deficient older volunteers and cobalamin-deficient older patients.


RESULTS
Holo and apo concentrations of transcobalamin and haptocorrin were similar in healthy middle-aged and older subjects. Holotranscobalamin concentrations were significantly decreased in cobalamin-deficient subjects but did not differ between healthy volunteers and patients. Furthermore, the relative amount of cobalamin on transcobalamin (i.e. holotranscobalamin/holotranscobalamin + holohaptocorrin) was similar in all four groups.


CONCLUSIONS
Abnormalities of the cobalamin-binding proteins are not a cause of cobalamin deficiency in the aged. Plasma holotranscobalamin concentration did not differ between stages of cobalamin deficiency in older persons. Therefore, plasma holotranscobalamin is not an early marker of cobalamin deficiency in older people and has no additional value in the diagnostic work-up of reduced plasma cobalamin concentrations in older people.
van Asselt
Dieneke Z B
DZ
Geriatric Medicine, University Medical Centre Nijmegen, Nijmegen, The Netherlands. Dieneke.van.Asselt@znb.nl
Thomas
Chris M G
CM
Segers
Martin F G
MF
Blom
Henk J
HJ
Wevers
Ron A
RA
Hoefnagels
Willibrord H L
WH
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002624:Chemistry, Clinical / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014155:Transcobalamins / Q000172:deficiency* / Q000378:metabolism*; D014805:Vitamin B 12 / Q000097:blood* / Q000378:metabolism
D014155:Transcobalamins; D014805:Vitamin B 12