Received on October 4, 2005
Accepted on March 8, 2006

Endocrinology and Metabolism

Effect of Vitamin B₁₂ Treatment on Haptocorrin

Anne L. Mørkbak ^1*, Anne-Mette Hvas ², Zouë Lloyd-Wright ³, Tom A.B. Sanders ³, yvind Bleie ⁴, Helga Refsum ⁵, Ottar K. Nygaard ⁴, Ebba Nexø ¹

¹ Department of Clinical Biochemistry, Aarhus Sygehus, Aarhus University Hospital, Aarhus, Denmark
² Department of Clinical Biochemistry, Skejby Sygehus, Aarhus University Hospital, Aarhus, Denmark
³ Nutrition, Food and Health Research Centre, King's College, London, United Kingdom
⁴ Department of Heart Disease, Haukeland University Hospital, Bergen, Norway, and Institute of Medicine, University of Bergen, Bergen, Norway
⁵ Institute of Medicine, University of Bergen, Bergen, Norway, and Institute of Basic Medical Sciences, Department of Nutrition, University of Oslo, Oslo, Norway

^* To whom correspondence should be addressed. E-mail: almor{at}as.aaa.dk.

Background: Haptocorrin (HC) carries the major part of circulating cobalamin, but whether HC is altered on treatment with vitamin B₁₂ remains unknown.

Methods: Our study included 3 populations: a population of vegan men (n = 174; vegan population), of whom 63 were treated daily with 5 mg of oral vitamin B₁₂ for 3 months; a group of patients with a previous methylmalonic acid (MMA) concentration >0.4 µmol/L (n = 140; population with suspected deficiency), of which 69 were treated with weekly vitamin B₁₂ injections (1 mg) for 4 weeks; and a subgroup of participants in a vitamin B intervention study (n = 88; nondeficient population), of whom 45 were treated daily with 0.4 mg of oral vitamin B₁₂ for 3 months. Total HC and holoHC were measured by ELISA. Cobalamin was measured by an intrinsic factor (IF)-based assay. Samples were collected at baseline and 3 months after start of treatment.

Results: Compared with baseline results for the 3 study populations, total HC and holoHC increased 30 pmol/L for every 100 pmol/L increase in cobalamin. After treatment with vitamin B₁₂, holoHC (P <0.0001) and total HC (P <0.0001) increased significantly in the vegan population. Only holoHC increased in the population with suspected deficiency (P <0.0001), whereas no alteration was observed in the nondeficient population.

Conclusions: The HC concentration is decreased in severely cobalamin-deficient individuals and increases on treatment. The concentration of cobalamin also relates significantly to the HC concentration in nondeficient individuals.