In assessing the relationship
between calcium supplementation and maintaining bone mass or reducing the risk of
fracture, the effectiveness of calcium supplementation has never been decisive.
Freshwater crayfish rely on amorphous calcium
carbonate (ACC), an instable polymorph of calcium carbonate, as the main mineral
in the exoskeleton and in the temporary storage organ, the gastrolith. Inspired
by the crayfish model, we have previously shown an increase in calcium bioavailability
in rats administered with synthetic stable ACC vs. crystalline calcium carbonate
(CCC). The current study compared the effects of amorphous calcium derived from
either gastrolith or synthetic ACC with those of crystalline calcium, found in
commercial CCC or calciumcitrate supplements,
in a bone loss prevention model. Rats were subjected to either sham or ovariectomy
(OVX) operation (n~20/ group) followed by administration of food pellets supplemented
with 0.5% calcium from either source over 12 weeks. Micro-computed tomography (μCT) and histomorphometric
analyses revealed bone loss prevention by both gastrolith and ACC treatments, manifested by an increase in morphometric bone parameters, compared to both CCC- and calcium citrate-treated groups.
Both gastrolith and ACC treatments resulted in bone formation in the tibia cancellous
bone, indicated by dynamic histomorphometry parameters, compared to either the CCC or calcium citrate
treatments. Levels of urine deoxypyridinoline (DPD), suggested
an anti-resorptive effect of ACC, which
was also the only treatment that led to a significant increase in vertebral mechanical strength, as supported
by μCT analysis of topology and orientation
parameters of the vertebral trabeculae. To our knowledge, such levels of bone
loss prevention by calcium supplements have never
been reported. These findings thus suggest the potential of both natural
(crayfish gastrolith) and, to a greater extent, synthetic ACC sources for the prevention
of metabolic bone disorders and possibly of osteoporotic processes.