Effects of aging on intracellular transport of vitamin B12(B12) in rat enterocytes.

Abstract

SummaryTo elucidate the effect of aging on the vitamin B12 (B12) transport in enterocytes, young and old (3-4 months and over 1 .5 years, respectively) female rats were studied. Two units of rat intrinsic factor (IF), saturated with 57Co-labeled cyanocobalamin were orally adminis tered, and the amount of B12 absorbed into each subcellular fraction of enterocytes was assayed. Concentration of endogenous B12 in each subcellular fraction was also studied. Absorption of radioactive B12 in the lysosomal fraction was maximum between 2 and 4hr in each age group . In the older rats, the amount absorbed was lower than in the young rats . The older rats showed a significantly lower value of endogenous B12 in the mitochondria. It has already been reported by us that there exist two B12 binders in enterocytes: lysosomal and microsomal binders. The con centrations of lysosomal and microsomal binders as well as B12 uptake in the mitochondria were significantly lower in the older rats than in the young rats. These data might help to explain the lower B12 absorption in the lysosomal fraction and lower B12 contents in the mitochondrial fraction.

Aging Biology and Geriatric Clinical Pharmacology

“…On the other hand, the active transport of some nutrients [glucose (Yuasa et al, 1997), calcium (Armbrecht et al, 1999), vitamin B 12 (Toyoshima et al, 1983), leucine (Sacchi and Magagnin, 1992)] is impaired. The effect of old age on the efflux pump, P-glycoprotein, in the intestine has not been reported.…”

Coenzyme B12 synthesis as a baseline to study metabolite contribution of animal microbiota

“…In parallel, cobalamin and biotin biosynthesis was decreased (Langille et al ., ). Intestinal uptake of B12 is also modified with age, with lower transport in aged rat enterocytes, for example (Toyoshima et al ., ). This has important consequences for carnivorous animals because the input of cobalamin will depend on prey age, a parameter that is seldom taken into account in the metadata of microbiome metagenome studies.…”