title: Cobalamin-binding proteins in normal and cobalamin-deficient older subjects.
abstract: 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.
authors.affiliation: Geriatric Medicine, University Medical Centre Nijmegen, Nijmegen, The Netherlands. Dieneke.van.Asselt@znb.nl
authors.forename: Dieneke Z B
authors.initials: DZ
authors.lastname: van Asselt
authors.forename: Chris M G
authors.initials: CM
authors.lastname: Thomas
authors.forename: Martin F G
authors.initials: MF
authors.lastname: Segers
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Blom
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.forename: Willibrord H L
authors.initials: WH
authors.lastname: Hoefnagels
mesh_terms: 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
chemical_list: D014155:Transcobalamins; D014805:Vitamin B 12