Abstract
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.
Highlights
Strategies for preventing osteoporotic processes include a balanced diet rich in calcium, vitamin-D and regular exercise [1]
A significant increase in morphometric bone parameters, studied by μCT and structural histomorphometry was observed for the gastrolith and amorphous calcium carbonate (ACC) compared to calcium carbonate (CCC) and calcium citrate treatments
Urinary DPD levels suggested an anti-resorptive effect for the synthetic ACC compared to the other treatments, and this was the only treatment that prevented the loss of vertebral mechanical strength following OVX, supported by microarchitectural analysis of topology and orientation parameters
Summary
Strategies for preventing osteoporotic processes include a balanced diet rich in calcium, vitamin-D and regular exercise [1]. Calcium supplementation with and without vitamin-D has become a widely recognized strategy for realizing adequate calcium intake. The effectiveness of calcium supplementation for the prevention of progressive skeletal disease has never been decisive. The effectiveness of calcium supplements with or without vitamin-D in reducing bone loss and preventing fractures has been the focus of many clinical trials and several meta-analyses [4,5,6,7,8]. According to an extensive meta-analysis, calcium combined with vitamin-D was associated with a 12% reduction of fracture risk [4]
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