Miller Joshua W, Ramos Marisa I, Garrod Marjorie G, Flynn Margaret A, Green Ralph
Department of Medical Pathology, School of Medicine, University of California, Davis, CA 95817, USA.
Blood. 2002 Jul 15;100(2):718-20. doi: 10.1182/blood-2002-01-0209.
A common polymorphism (775G>C) in the vitamin B12 transport protein, transcobalamin II (TCII), has been identified in which proline replaces arginine at codon 259. We determined the influence of TCII genotype on indices of B12 status, including total serum B12, the amount of B12 bound to TCII (holoTCII), methylmalonic acid, and homocysteine, in 128 healthy older adults (ages 40-88 years). Mean total B12 and homocysteine concentrations were not significantly different among the 3 genotypes. Mean holoTCII concentration was significantly higher in those subjects homozygous for the proline form of TCII (PP) compared with those homozygous for the arginine form (RR) and heterozygotes (PR) (P <or=.006). In addition, mean methylmalonic acid concentrations were significantly lower in the PP and PR groups compared with the RR group (P <or=.02). The PP genotype may be more efficient in delivering B12 to tissues, resulting in enhanced B12 functional status. TCII genotype may thus influence susceptibility to B12 deficiency.
在维生素B12转运蛋白转钴胺素II（TCII）中已鉴定出一种常见的多态性（775G>C），其中第259位密码子的脯氨酸取代了精氨酸。我们测定了128名健康老年人（年龄40 - 88岁）中TCII基因型对维生素B12状态指标的影响，这些指标包括血清总维生素B12、与TCII结合的维生素B12量（全结合型TCII）、甲基丙二酸和同型半胱氨酸。在这三种基因型中，平均血清总维生素B12和同型半胱氨酸浓度无显著差异。与精氨酸形式纯合子（RR）和杂合子（PR）相比，TCII脯氨酸形式纯合子（PP）的受试者平均全结合型TCII浓度显著更高（P≤0.006）。此外，PP组和PR组的平均甲基丙二酸浓度与RR组相比显著更低（P≤0.02）。PP基因型在将维生素B12输送到组织方面可能更有效，从而导致维生素B12功能状态增强。因此，TCII基因型可能影响维生素B12缺乏的易感性。
