Use of Calcium Isotopic Tracers To Determine Factors That Perturb Calcium Metabolism

Effects of Dietary Colostrum Basic Protein on Bone Growth and Calcium Absorption in Mice

Colostrum basic protein (CBP) is a trace protein extracted from bovine colostrum. Previous studies have shown that CBP can promote bone cell differentiation and increase bone density. However, the mechanism by which CBP promotes bone activity remains unclear. This study investigated the mechanism of the effect of CBP on bone growth in mice following dietary supplementation of CBP at doses that included 0.015%, 0.15%, 1.5%, and 5%. Compared with mice fed a normal diet, feeding 5% CBP significantly enhanced bone rigidity and improved the microstructure of bone trabeculae. Five-percent CBP intake triggered significant positive regulation of calcium metabolism in the direction of bone calcium accumulation. The expression levels of paracellular calcium transport proteins CLDN2 and CLDN12 were upregulated nearly 1.5-fold by 5% CBP. We conclude that CBP promotes calcium absorption in mice by upregulating the expression of the calcium-transporting paracellular proteins CLND2 and CLND12, thereby increasing bone density and promoting bone growth. Overall, CBP contributes to bone growth by affecting calcium metabolism.

The Postprandial Calcium Absorption of a Milk-Derived Calcium Permeate - The Acute RENEW Double-Blinded Randomized Controlled Cross-Over Study

BACKGROUND

Studies suggest that dairy-derived calcium supplements have additional beneficial properties compared with other calcium supplements in relation to bone health.

OBJECTIVES

We investigated the postprandial calcium absorption from a milk-derived calcium permeate (CP) compared with calcium carbonate (CC).

METHODS

In this randomized double-blinded cross-over study, 10 healthy postmenopausal females (age 50-65 y) received maltodextrin (placebo), 800 mg calcium from CP or from CC provided in 6 capsules on separate days. A fasting blood sample was collected at baseline, 60, 120, 240, and 360 min after ingestion. At baseline and 360 min, spot-urine samples were collected. Serum-ionized calcium, intact parathyroid hormone, phosphorus, and magnesium were analyzed, as were urinary calcium, phosphorus, and magnesium. A linear mixed model was applied.

RESULTS

Serum-ionized calcium concentration after the CC supplement was higher at 240 min compared with the CP supplement [between-group difference; 95% confidence interval (CI): 0.039 mmol/L; 95% CI: 0.017-0.061; P = 0.00078]. Serum-ionized calcium concentration after the CC supplement was significantly higher than placebo at all postprandial time points except at 60 min. Urinary calcium concentration in 360 min spot urine was higher after intake of CC compared with CP [between-group difference; 95% CI: 2.47 mmol/L; 95% CI: 1.90-3.03; P = 0.0042].

CONCLUSIONS

Postprandial calcium absorption from CP was lower than that of CC, and concurrently, urinary concentration reflected increased serum appearance by CC compared with CP, highlighting different metabolic responses. The long-term and clinical implications should be studied further.

Preparation of synbiotic milk powder and its effect on calcium absorption and the bone microstructure in calcium deficient mice

Calcium deficiency can lead to osteoporosis. Adequate calcium intake can improve calcium deficiency and prevent osteoporosis. Milk powder is the best source of dietary calcium supplements. Probiotics and prebiotics are considered to be beneficial substances for promoting calcium absorption. In this study, synbiotic milk powder (SMP) was prepared by combining the three, and its calcium supplementation effect and osteogenic activity were evaluated in calcium deficient mice. Through prebiotic screening experiments in vitro, after adding 1.2% iso-malto-oligosaccharide, the number of viable bacteria and the calcium enrichment of Lactobacillus plantarum JJBYG12 increased by 8.15% and 94.53% compared with those of the control group. Long-term calcium deficiency led to a significant reduction in calcium absorption and bone calcium content in mice, accompanied by structural deterioration of bone trabeculae. SMP significantly improved apparent calcium absorption, increased serum calcium and phosphorus levels, and decreased ALP activity and CTX-1 levels. In the meantime, the bone mineral density increased significantly, and the number of bone trabeculae and the proliferation and differentiation of osteoblasts also increased. SMP has good dietary calcium supplementation capacity and bone remodeling ability without significant side effects on major organs. These findings provide insights into using SMP as a dietary calcium source to improve bone health.

Calcium isotope ratio in kidney stones: preliminary exploration of mechanism from the geochemical perspective

Stable calcium (Ca) isotope ratios are sensitive and radiation-free biomarkers in monitoring biological processes in human bodies. Recently, the Ca isotope ratios of bone, blood, and urine have been widely reported to study bone mineral balance. However, as a pure Ca crystallization product, there is no report on the Ca isotope ratios of kidney stones, even though the prevalence of kidney stones is currently on the rise. Here, we measured Ca isotope data of 21 kidney stone samples collected in Beijing, China. The δ44/42CaNIST 915a values ranged from 0.25‰ to 2.85‰ for calcium oxalate, and from 0.38‰ to 3.00‰ and 0.61‰ to 0.69‰ for carbonate apatite and uric acid, respectively. Kidney stones have heavier Ca isotope ratios than bone or blood, which is probably because complexed Ca contains more heavy Ca isotopes than free Ca2+. Ca isotope evidence suggests that magnesium (Mg) affects kidney stone formation, as the δ44/42CaNIST 915a value is inversely correlated with the Ca/Mg ratio. This study provides important preliminary reference values on the Ca isotopic composition of kidney stones and proposes a factor influencing Ca isotope fractionation in biological processes for future research.

Fracture Risk in Vegetarians and Vegans: the Role of Diet and Metabolic Factors

PURPOSE OF REVIEW

There is strong evidence that poor dietary intake of certain micro- and macro-nutrients can negatively affect bone health. It is unclear if diet is the primary culprit for poor bone health in the vegan population.

RECENT FINDINGS

Plant-based diets are gaining public interest since they may improve metabolic health. Studies that examine vegetarians and vegans together show a lower bone mineral density (BMD), but not always increased fracture risk compared to omnivores. However, vegans consistently have higher risk of fracture at multiple bone sites, especially at the hip. There is higher fracture risk in vegans which may be due to calcium and vitamin D intake, as well as amount of dietary protein and quality. Other nutrients (B vitamins, Se, Zn, Fe, iodine) or physiological factors (lower body mass index, microbiome, or endocrine profile) may also play a role but have not been examined and require further study.

Fructus Ligustri Lucidi aqueous extract promotes calcium balance and short-chain fatty acids production in ovariectomized rats

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Ligustri Lucidi (FLL) is an edible herb with anti-osteoporotic activity, yet whether and how the aqueous extract of this herb affect calcium metabolism in preservation of bone quality remain unclear.

AIM OF THE STUDY

To investigate the effects of FLL aqueous extract on calcium balance and short-chain fatty acids (SCFAs) production in ovariectomized (OVX) rats.

MATERIALS AND METHODS

OVX rats were daily and orally administrated with FLL aqueous extract (3.5 g/kg) for 14 weeks. The levels of N-terminal propeptide of type I collagen (PINP) and C-terminal telopeptide of type I collagen (CTx-I) in rat serum were evaluated by ELISA assays. The concentration of calcium in serum, urine, and feces were determined by biochemical assays. Bone quality was determined by Micro-CT, a three-point bending assay, and Fourier Transform Infrared (FTIR) Spectrometry. The expressions of Calbindin D28K and Calcium-sensing receptor (CaSR) in kidney as well as the Vitamin D receptor (VDR), the transient receptor potential vanilloid receptor 6 (TRPV6), Calbindin D9k in the duodenum were measured by immunohistochemistry, western blotting, or real-time PCR. The short-chain fatty acids (SCFAs) levels in the feces of the cecum were tested by gas chromatograghy.

RESULTS

The administration of FLL to OVX rats resulted in a significant improvement in bone mineral density and biomechanical strength as well as in maintaining bone microstructures and material quality. Meanwhile, the decreased levels of PINP and increased levels of CTx-I in OVX rats were restored by FLL treatment. Additionally, FLL treatment increased calcium absorption, upregulated VDR, TRPV6, Calbindin D9k expressions in the duodenum, Calbindin D28K in kidney, and down-regulated CaSR expression in the kidney, as well as enhanced SCFAs levels in the feces of OVX rats.

CONCLUSIONS

FLL aqueous extract may preserve bone quality through regulation of the calcium balance and intestinal SCFAs production in OVX rats. This offers translational value of FLL into osteoporosis clinical trial.