Cobalamin-binding proteins in normal and cobalamin-deficient older subjects

Ann Clin Biochem 2003;40:65-69
doi:10.1258/000456303321016187
© 2003 Association for Clinical Biochemistry

 

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Original Articles


Dieneke Z.B. van Asselt,
Chris M.G. Thomas,
Martin F.G. Segers,
Henk J. Blom,
Ron A. Wevers and
Willibrord H.L. Hoefnagels


Geriatric Medicine, University Medical Centre Nijmegen, Nijmegen, The Netherlands;
Chemical Endocrinology, University Medical Centre Nijmegen, Nijmegen, The Netherlands;
Chemical Endocrinology, University Medical Centre Nijmegen, Nijmegen, The Netherlands;
Pediatrics and Neurology, University Medical Centre Nijmegen, Nijmegen, The Netherlands;
Pediatrics and Neurology, University Medical Centre Nijmegen, Nijmegen, The Netherlands;
Geriatric Medicine, University Medical Centre Nijmegen, Nijmegen, The Netherlands


Background: The causes of cobalamin (vitamin B12) deficiencyin older people are only partly understood. We investigatedthe role of the cobalamin-binding proteins and tested the hypothesisthat low saturated transcobalamin concentration is an earlymarker of cobalamin deficiency.

Methods: We measured saturated (holo) and unsaturated (apo)transcobalamin and haptocorrin concentrations in healthy middle-agedvolunteers, healthy older volunteers, cobalamin-deficient oldervolunteers and cobalamin-deficient older patients.

Results: Holo and apo concentrations of transcobalamin and haptocorrinwere similar in healthy middle-aged and older subjects. Holotranscobalaminconcentrations were significantly decreased in cobalamin-deficientsubjects 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 proteinsare not a cause of cobalamin deficiency in the aged. Plasmaholotranscobalamin concentration did not differ between stagesof cobalamin deficiency in older persons. Therefore, plasmaholotranscobalamin is not an early marker of cobalamin deficiencyin older people and has no additional value in the diagnosticwork-up of reduced plasma cobalamin concentrations in olderpeople.


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