Is dietary deficiency of calcium a factor in rickets? Use of current evidence for our understanding of the disease in the past

Isolation, characterization, and molecular docking analyses of novel calcium-chelating peptide from soy yogurt and the study of its calcium chelation mechanism

BACKGROUND

Calcium is an essential dietary mineral nutrient for humans. Digestive instability limits the bioavailability of calcium ions. Peptide-calcium chelate has been proven to excite higher calcium absorption than amino acid-calcium chelate, organic and inorganic calcium. Soy yogurt, which is produced via liquid-state fermentation using lactic acid bacteria, has a high amount of bioavailable calcium. In this study, a novel peptide with high calcium binding affinity was purified and identified from soy yogurt. The binding mechanism of peptide and calcium was then analyzed by bioinformatics and spectral analysis. Furthermore, the effect of the novel peptide on gastrointestinal stability by the Caco-2 cell model and calcium bioavailability in vivo were investigated by the zebrafish model.

RESULTS

The results showed that a novel peptide was purified and identified as DEDEQIPSHPPR (CBP). Calcium ions probably coordinate with Glu-2 and Glu-4 carboxyl groups via salt bridges and interact with Asp-1, Asp-3, and Arg-12 in CBP via charge pairing. The calcium binding activity of the CBP was 36.64 ± 0.04 mg g^-1 . Fourier transform infrared (FTIR) spectra showed that calcium spontaneously bound to the amino group nitrogen and oxygen atoms of the carboxyl group. The binding mode is either bidentate or unidentate, depending on the circumstances. More importantly, the CBP peptide substantially increased the bone mass in a zebrafish osteoporosis model.

CONCLUSION

The more glutamic acid and aspartic acid, the high was the calcium affinity with peptide. Soy yogurt-derived peptides can be used as carriers of calcium ions throughout the gastrointestinal tract, which may be clinically useful for osteoporosis therapy. © 2022 Society of Chemical Industry.

The role of dietary calcium in the etiology of childhood rickets in the past and the present

For more than two centuries, lack of sunlight has been understood to cause vitamin D deficiency and documented as a primary cause of rickets. As such, evidence of rickets in the archeological record has been used as a proxy for vitamin D status in past individuals and populations. In the last decade, a clinical global consensus has emerged wherein it is recognized that dietary calcium deficiency also plays a role in the manifestation of rickets and classic skeletal deformities may not form if dietary calcium is normal even if vitamin D is deficient. This disease is now clinically called "nutritional rickets" to reflect the fact that rickets can take calcium deficiency-predominant or vitamin D deficiency-predominant forms. However, there are currently no paleopathological studies wherein dietary calcium deficiency is critically considered a primary etiology of the disease. We review here the interplay of calcium, vitamin D, and phosphorous in bone homeostasis, examine the role of dietary calcium in human health, and critically explore the clinical literature on calcium deficiency-predominant rickets. Finally, we report a case of rickets from the late Formative Period (~2500-1500 years ago) of the Atacama Desert and argue the disease in this infant is likely an example of calcium deficiency-predominant rickets. We conclude that most archeological cases of rickets are the result of multiple micronutrient deficiencies that compound to manifest in macroscopic skeletal lesions. For clinicians, these factors are important for implementing best treatment practice, and for paleopathologists they are necessary for appropriate interpretation of health in past communities.