Cobalamin and osteoblast-specific proteins

R Carmel, KHW Lau, DJ Baylink… - New England Journal …, 1988 - Mass Medical Soc
R Carmel, KHW Lau, DJ Baylink, S Saxena, FR Singer
New England Journal of Medicine, 1988Mass Medical Soc
Cobalamin deficiency has well-known hematologic and neurologic effects, but little is known
about its other effects. We therefore studied the effect of cobalamin on osteoblast-related
proteins. We found that mean (±1 SD) levels of skeletal alkaline phosphatase in the blood
were lower in 12 cobalamin-deficient patients (3.89±2.19 units per liter) than in 5
nondeficient and 5 iron-deficient control subjects (7.55±3.99 units per liter). The degree of
the megaloblastic anemia correlated with the reduction in skeletal alkaline phosphatase …
Abstract
Cobalamin deficiency has well-known hematologic and neurologic effects, but little is known about its other effects. We therefore studied the effect of cobalamin on osteoblast-related proteins. We found that mean (±1 SD) levels of skeletal alkaline phosphatase in the blood were lower in 12 cobalamin-deficient patients (3.89±2.19 units per liter) than in 5 nondeficient and 5 iron-deficient control subjects (7.55±3.99 units per liter). The degree of the megaloblastic anemia correlated with the reduction in skeletal alkaline phosphatase levels (r = 0.67, P<0.01). With cobalamin therapy, levels of skeletal alkaline phosphatase rose in 11 of the 12 cobalamin-deficient subjects but not in the controls.
The cobalamin-deficient patients also had significantly lower osteocalcin levels than the control subjects (1.11 ±0.77 vs. 1.84±0.49 nmol per liter). During cobalamin therapy, these levels rose in the cobalamin-deficient patients but not in the controls. In contrast to the levels of osteoblast-related proteins, hepatic alkaline phosphatase levels were similar in the patients and controls and were usually unaffected by cobalamin therapy. In vitro studies of calvarial cells from chicken embryos showed that their alkaline phosphatase content was cobalamin-dependent, thus supporting our in vivo observations in humans.
Our findings suggest that osteoblast activity depends on cobalamin and that bone metabolism is affected by cobalamin deficiency, but we do not yet know whether cobalamin deficiency produces clinically important bone disease. (N Engl J Med 1988; 319:70–5.)
The New England Journal Of Medicine