Fraction of Total Plasma Vitamin B12 Bound to Transcobalamin Correlates with Cognitive Function in Elderly Latinos with Depressive Symptoms

Abstract

BACKGROUND:The fraction of total plasma vitamin B 12 bound to transcobalamin (holoTC/B12 ratio) may reflect tissue levels of the vitamin, but its clinical relevance is unclear.

Metabolic evidence of vitamin B-12 deficiency, including high homocysteine and methylmalonic acid and low holotranscobalamin, is more pronounced in older adults with elevated plasma folate

“…Many factors affect cognitive function in older adults, including Alzheimer's disease, vascular disease, diabetes, depression, and genetics (eg, apolipoprotein E genotype). These conditions are highly prevalent in the SALSA population (20)(21)(22)(23)(24). Coupled with the fact that the low vitamin B-12/elevated-folate group consisted of only 22 subjects, our power to see associations with cognitive function scores may have been inadequate.…”

“…The remainder and majority of plasma vitamin B-12 is bound to a second vitamin B-12 transport protein, haptocorrin, which is taken up nonspecifically by the liver. Holotranscobalamin has therefore received significant attention in recent years as a potential alternative measure of vitamin B-12 status (15,(24)(25)(26). The finding that the lowest holotranscobalamin and the lowest holotranscobalamin:total vitamin B-12 are observed in the low vitamin B-12/elevated-folate group indicates that the metabolic associations observed by Selhub et al (19) may extend beyond intracellular metabolism of vitamin B-12 (as reflected by homocysteine and methylmalonic acid concentrations) to relative availability and delivery of vitamin B-12 to the tissues.…”

“…Data analyzed for this study came from the Sacramento Area Latino Study on Aging (SALSA), a cohort study of physical and cognitive functioning in community-dwelling elderly Latinos (n = 1789; age 60 y) (20)(21)(22)(23)(24)(25). Baseline recruitment occurred between February 1998 and August 1999-ie, after the start of mandatory folic acid fortification of cereals and grains in the United States.…”

Cobalamin deficiency, hyperhomocysteinemia, and dementia

“…Since serum TC II levels decrease with advancing age, a given serum B12 level in an elder may represent a deficiency, compared with the same level in a younger adult 30,380. Directly measuring serum TC II may be helpful in these cases and others 17,38,308,335,351,372,374,380–383…”

Vitamin B-12 Status Differs among Pregnant, Lactating, and Control Women with Equivalent Nutrient Intakes

“…Data that deviated from the normal distribution or homogeneity of variance (i.e., all serum/urinary vitamin B-12 biomarkers and breast milk vitamin B-12) were natural log transformed and used in the models. In addition to serum vitamin B-12 and holotranscobalamin, their ratio (i.e., holotranscobalamin-tovitamin B-12) was included in the models (after log transformation) as an additional vitamin B-12 status indicator because this ratio (vs. individual metabolite alone) is suggested to better reflect the tissue availability of circulating vitamin B-12 (32). Reproductive states (pregnant, lactating, or control), time (baseline or study-end), and the interaction of reproductive state and time (reproductive state 3 time) were entered as fixed factors, and participant identification was entered as a random factor.…”