Ca Metabolism Research Articles

Effects of dietary cation-anion differences at the early stage of transitional period on dry matter intake and plasma Ca metabolism in beef cows

The present study investigated the effects of dietary cation-anion differences (DCADs) on dry matter intake (DMI), nutrient digestibility, body condition score (BCS), body fat, plasma ion metabolism, and relative hormone levels through a perinatal feeding experiment. Eighteen healthy Simmental crossbred cows (Simmental ♂ × native Yunnan Yellow ♀; body weight, 325.4 ± 27.63 kg) were allocated to one of three treatment groups with six replicates each. The control (CON) group received basal diet without anionic salt supplementation, with a DCAD of 127.56 mEq kg−1 DM. The T2% and T4% groups received basal diet supplemented with 2% and 4% anionic salts, with DCADs of −1.60 and −129.10 mEq kg−1 DM, respectively. All groups received isoenergetic and isonitrogenous diets. Blood samples were collected on prepartum days 7 and 3; on the day of calving; and on postpartum days 1, 3, 7, 14, and 42. Prenatal urine pH decreased with decreasing DCAD (P < 0.001). Compared with that in the CON group, DMI in the T2% and T4% groups was decreased by respectively 11.4 % and 17.8 % (P = 0.005) at the early stages of perinatal period (−21 to 0 days), but DMI in the T2% group was increased by 9.4 % (P < 0.046) at the later stages of perinatal period (0–21 days). The postpartum BCS in the T2% and T4% groups was 25 % lower than that in the CON group (P = 0.038). Prepartum apparent P digestibility was increased in the T2% and T4% groups (P = 0.017) and prepartum apparent Ca digestibility was increased in the T2% group (P = 0.022). The content of colostrum fat, Ca, lactose, and immunoglobulin G was increased in the T2% group (P < 0.05). On postpartum day 1, the plasma ionized (i) Ca concentrations were increased by 20.4 % and 19.4 % (P < 0.05), the plasma 1,25(OH)2D3 concentrations were increased by 15.6 % and 12.7 % (P < 0.05), and the plasma iK concentrations were decreased by 8.8 % and 9.8 % (P = 0.003) in the T2% and T4% groups, respectively, compared with values in the CON group. In addition, the iMg, iP, and parathyroid hormone levels in the T2% group were increased (P < 0.05). On prepartum day 7, the plasma glucose concentration in the T2% group was higher than that in the CON group (P = 0.010), and on the day of calving, the plasma glucose concentration in the T4% group was higher than that in the T2% group (P = 0.041). On postpartum day 1, the plasma non-esterified fatty acid (NEFA) concentration in the T2% group was lower than that in the CON group (P = 0.021), but there was no significant difference in this concentration between the T4% and CON groups (P > 0.05). The postpartum plasma β-hydroxybutyric acid (BHB) concentrations in the T2% and T4% groups were lower than those in the CON group (P < 0.001). On postpartum day 42, progesterone levels in the T2% and T4% groups were respectively 27.3 % and 16.7 % lower than those in the CON group (P < 0.001). Therefore, the addition of anionic salts to reduce DCAD accelerated the recovery of postpartum DMI, decreased plasma NEFA and BHB concentrations, and increased plasma iCa concentration. Under the present experimental conditions, 2% anionic salt supplementation was more appropriate.

Impact of dietary calcium tetraborate supplementation on the mineral content of egg and eggshell of laying quails

Boron (B) is a trace element that plays an important role in the mineral, cell membrane, hormone, and enzyme metabolism of animals and humans. The aim of this study was to examine the effect of dietary calcium tetraborate (CaB4O7) supplementation on the mineral composition of egg content and eggshell of laying quails. For this purpose, a total of 20 male and 40 female quails, 6-week-old, were equally divided into 2 groups (control and additive groups) in 5 replicates (6 birds/replicate) and given CaB4O7 300 mg/kg feed in additive group. The experiment was conducted for 56 days. The eggs were collected and the mineral composition [B, calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), potassium (K), manganese (Mn), copper (Cu), zinc (Zn)] of egg content and eggshell samples were determined at the end of the experiment in randomly collected 6 eggs per group. Results of this study indicated dietary supplementation of CaB4O7 increased Mg (P&lt;0.01), Na (P&lt;0.01), and K (P&lt;0.05) contents of edible parts of eggs compared to the control group, but B concentration were not determined in edible parts of eggs in both groups. Moreover, B (P&lt;0.01), Mg (P&lt;0.01), Na (P&lt;0.01), Fe (P&lt;0.01), K (P&lt;0.05), Cu (P&lt;0.05) and Zn (P&lt;0.01) of eggshell were higher in the additive group than control. There were also significant correlations between examined minerals both edible and eggshell parts of the eggs. It may be concluded that supplementing diets with CaB4O7 could improve Ca metabolism, producing eggs enriched in minerals, promoting B, Mg, Na, Fe, K, Cu, and Zn deposition in eggshells, and improving eggshells quality. The effective B supplementation doses for functional egg production could be determined and B could be advantageous in terms of beneficial physiological effects.

The partial replacement of sodium chloride with sodium bicarbonate or sodium sulfate in laying hen diets improved laying performance, and eggshell quality and ultrastructure

This study investigated the effects of dietary chloride (Cl) reduction on laying performance and eggshell quality by substitution of sodium bicarbonate (NaHCO3) or sodium sulfate (Na2SO4) for part of dietary sodium chloride (NaCl), and further explored its mechanism for improving eggshell quality. A total of 360 29-wk-old Hy-line Brown laying hens were randomly allocated to 5 dietary treatments, including a basal diet contained 0.33% NaCl (control group, 0.27% dietary Cl), and 4 experimental diets that contained 0.21% and 0.15% dietary Cl by substituting Na2SO4 or NaHCO3 for part of NaCl in the basal diet. No significant differences were observed in blood Na+, Cl−, K+ and Ca2+ levels and pH value as well as serum creatinine and uric acid contents among 5 treatments (P > 0.05). Dietary Cl reduction increased egg production and ADFI during wk 33 to 36, 37 to 40 and 29 to 40 of age and decreased feed conversion ratio during wk 37 to 40 of age (P < 0.05). The hens fed with diets containing 0.15% Cl increased eggshell breaking strength, thickness and weight ratio in wk 40 of age (P < 0.05). Birds fed with dietary 0.21% and 0.15% Cl exhibited higher effective layer thickness and lower mammillary layer thickness of eggshell than those fed with dietary 0.27% Cl (P < 0.05). Apparent Ca metabolizability of hens was increased with dietary Cl reduction (P < 0.05). Total Ca of eggshell of dietary 0.15% Cl group was higher than that of dietary 0.27% Cl group (P < 0.05). No significant differences in laying performance, eggshell quality and Ca metabolism of layers were observed between Na2SO4 and NaHCO3 replacement groups (P > 0.05). Overall, dietary Cl reductions could improve laying performance and eggshell quality by substitution of NaHCO3 or Na2SO4 for part of NaCl, and there were no differences in the improvements between these two substitutes. The improved eggshell quality may be attributed to improved eggshell ultrastructure and increased supply of eggshell Ca2CO3.

Periodontal inflammation triggers a site-specific and wide radius of calcium metabolic effects on alveolar bone.

There is a close relationship between inflammation and bone remodeling in the periodontium. However, previous studies have not delineated the alterations in calcium (Ca) metabolism during periodontitis progression. The aim of this current investigation was to examine Ca dynamics in alveolar bone of rats during progression of ligature-induced periodontal inflammation by using 45 Ca, which is an index of hard tissue neogenesis. To induce periodontitis, the maxillary right first molar (M1) of 8-week-old male rats was ligated with a silk suture for 1, 3, 7, and 28days. The left M1 was not ligated as a control. To evaluate resultant changes in bone neogenesis, 45 CaCl2 was injected intraperitoneally 24hours before euthanasia. The left-and-right palatal mucosa, molar teeth (M1 and M2), and alveolar bone were harvested for evaluation of 45 Ca radioactivity using a liquid scintillation counter. The distribution of 45 Ca in maxillary tissues was evaluated using autoradiography (ARG). In addition, we analyzed the bone volume fraction (BV/TV) and bone mineral density (BMD) of the alveolar bone by micro-computed tomography. To investigate the number of osteoclasts and osteoblasts, tartrate-resistant acid phosphatase (TRAP) and bone-specific alkaline phosphatase (BAP) were measured by an enzymatic assay and immunohistochemistry, respectively. 45 Ca radioactivity in the alveolar bone of the ligature side decreased by 8% compared to the unligated control-side on day 1, whereas on day 7, it markedly increased by 33%. The 45 Ca levels in the gingival tissue and molar teeth were slightly but significantly lower than the control-side on day 1 and higher from day 3 to 28. The variation in 45 Ca levels for the alveolar bone was greater and specific compared with other tissues. Furthermore, on day 7, ARG data revealed that 45 Ca on the control side was primarily localized to the periodontal ligament (PDL) space and alveolar bone crest and barely detected in the gingival tissues and deeper parts of the alveolar bone. On the ligature side, 45 Ca disappeared from the PDL and alveolar crest, but instead was broadly and significantly increased within the deeper zones of the alveolar bone and furcation areas and distant from the site of ligature placement and periodontal inflammation. In the shallow zone of the alveolar bone, these changes in 45 Ca levels on day 7 were consistent with decreases in the bone structural parameters (BV/TV and BMD), enhanced osteoclast presence, and suppressed levels of BAP expression in osteoblasts. In contrast, the deep zone and furcation area showed that TRAP-positive cells increased, but BAP expression was maintained in the resorption lacunae of the alveolar bone. During periodontitis progression in rats, 45 Ca levels in the alveolar bone exhibited biphasic alterations, namely decreases and increases. These data indicate that periodontitis induces a wide range of site-specific Ca metabolism alterations within the alveolar bone.

Increased expression of fibroblast growth factor 23 is the signature of a deteriorated Ca/P balance in ageing laying hens

The present study concerned the effect of ageing in laying hens, from 23 to 90 weeks of age, on the regulation of Ca metabolism related to the requirement for eggshell mineralization. Samples were collected from parathyroid gland (PG), liver, jejunum, medullary bone (MB) and kidney for a quantitative study of candidate gene expression. Although parathyroid hormone (PTH) gene expression in the PG did not vary with age, a stronger challenge to Ca homeostasis was suggested in aged hens. Indeed gene expression of Ca transporters , Vitamin D Receptor (VDR) in the jejunum, and that of transient receptor potential channel subfamily V member 5 (TRPV5) in the kidney decreased. This could exacerbate bone resorption and impair bone accretion, as attested by a higher expression of the Carbonic Anhydrase 2 (CA2) gene and a lower expression of collagen type I alpha 1 chain (COL1A1) in the MB. The increased expression of Fibroblast Growth Factor 23 (FGF23) in the MB likely contributed to the decreased plasma levels of 1.25(OH)2D3 and the altered expression of target genes under its regulation. Our data highlights the molecular mechanisms underlying the osteoporotic syndrome previously documented in aged laying hens, thus providing new perspectives for future interventions.

Effect of duration of exposure to diets differing in dietary cation-anion difference on Ca metabolism after a parathyroid hormone challenge in dairy cows

Objectives of the experiment were to determine the length of exposure to an acidogenic diet that would elicit changes in acid-base balance, mineral digestion, and response to parathyroid hormone (PTH)-induced changes in blood Ca and vitamin D3 in prepartum dairy cows. Nonlactating parous Holstein cows (n = 20) at 242 d of gestation were blocked by lactation (1 or >1) and pretreatment dry matter (DM) intake and, within block, they were randomly assigned to a diet with a dietary cation-anion difference (DCAD) of +200 mEq/kg of DM (DCAD +200) or an acidogenic diet with -150 mEq/kg of DM (DCAD -150). Water and DM intake were measured and blood was sampled daily. Urine was sampled every 3 h for 36 h, and then daily. During PTH challenges on d 3, 8, and 13, cows received i.v. PTH 1-34 fragment at 0.05 µg/kg of body weight every 20 min for 9 h to mimic the pulsatile release of endogenous PTH. Blood was sampled at 0 h, and hourly thereafter until 10 h, and at 12, 18, 24, 36, and 48 h relative to each challenge. Acid-base measures and concentrations of ionized Ca (iCa) in whole blood, and total Ca, Mg, P, and vitamin D metabolites in plasma were evaluated. On d 2 and 7, Ca, Mg, and P balances were evaluated. Cows fed DCAD -150 had smaller blood pH (7.431 vs. 7.389) and HCO3- (27.4 vs. 22.8 mM) compared with DCAD +200, and metabolic acidosis in DCAD -150 was observed 24 h after dietary treatments started. Concentrations of iCa begin to increase 24 h after feeding the acidogenic diet, and it was greater in DCAD -150 compared with DCAD +200 by 3 d in the experiment (1.23 vs. 1.26 mM). During the PTH challenges, cows fed DCAD -150 had greater concentration of iCa and area under the curve for iCa than those fed DCAD +200 (48.2 vs. 50.7 mmol/L × hour), and there was no interaction between treatment and challenge day. Concentration of 1,25-dihydroxyvitamin D3 in plasma did not differ during the PTH challenge, but change in 1,25-dihydroxyvitamin D3 relative to h 0 of the challenge was smaller in cows fed DCAD -150 than cows fed DCAD +200 (44.1 vs. 32.9 pg/mL). Urinary loss of Ca was greater in cows fed DCAD -150 compared with DCAD +200 (1.8 vs. 10.8 g/d); however, because digestibility of Ca increased in cows fed DCAD -150 (19.7 vs. 36.6%), the amount of Ca retained did not differ between treatments. Diet-induced metabolic acidosis was observed by 24 h after dietary treatment started, resulting in increases in concentration of iCa in blood observed between 1 and 3 d. Collectively, present results indicate that tissue responsiveness to PTH and changes in blood concentrations of iCa and digestibility of Ca are elicited within 3 d of exposure to an acidogenic diet. The increased apparent digestibility of Ca compensated for the increased urinary loss of Ca resulting in similar Ca retention.

Trehalose as an osmolyte in Candidatus Accumulibacter phosphatis

Candidatus Accumulibacter phosphatis is an important microorganism for enhanced biological phosphorus removal (EBPR). In a previous study, we found a remarkable flexibility regarding salinity, since this same microorganism could thrive in both freshwater- and seawater-based environments, but the mechanism for the tolerance to saline conditions remained unknown. Here, we identified and described the role of trehalose as an osmolyte in Ca. Accumulibacter phosphatis. A freshwater-adapted culture was exposed to a single batch cycle of hyperosmotic and hypo-osmotic shock, which led to the release of trehalose up to 5.34 mg trehalose/g volatile suspended solids (VSS). Long-term adaptation to 30% seawater-based medium in a sequencing batch reactor (SBR) gave a stable operation with complete anaerobic uptake of acetate and propionate along with phosphate release of 0.73 Pmol/Cmol, and complete aerobic uptake of phosphate. Microbial analysis showed Ca. Accumulibacter phosphatis clade I as the dominant organism in both the freshwater- and seawater-adapted cultures (> 90% presence). Exposure of the seawater-adapted culture to a single batch cycle of hyperosmotic incubation and hypo-osmotic shock led to an increase in trehalose release upon hypo-osmotic shock when higher salinity is used for the hyperosmotic incubation. Maximum trehalose release upon hypo-osmotic shock was achieved after hyperosmotic incubation with 3× salinity increase relative to the salinity in the SBR adaptation reactor, resulting in the release of 11.9 mg trehalose/g VSS. Genome analysis shows the possibility of Ca. Accumulibacter phosphatis to convert glycogen into trehalose by the presence of treX, treY, and treZ genes. Addition of trehalose to the reactor led to its consumption, both during anaerobic and aerobic phases. These results indicate the flexibility of the metabolism of Ca. Accumulibacter phosphatis towards variations in salinity.Key points• Trehalose is identified as an osmolyte in Candidatus Accumulibacter phosphatis.• Ca. Accumulibacter phosphatis can convert glycogen into trehalose.• Ca. Accumulibacter phosphatis clade I is present and active in both seawater and freshwater.

Exacerbation of Hyperparathyroidism, Secondary to a Reduction in Kidney Function, in Individuals With Vitamin D Deficiency.

Aims/Introduction: Chronic kidney disease (CKD)-mineral and bone disorders (CKD-MBD) are an adverse outcome derived from decreases in kidney function, where abnormality of serum concentrations of calcium (Ca), phosphorus, parathyroid hormone (PTH), and vitamin D can be seen simultaneously. To identify individuals at risk for CKD-MBD or secondary hyperparathyroidism, the relationships between estimated glomerular filtration rate (eGFR) and serum PTH concentration were evaluated, allowing for confounding factors, in particular vitamin D status, in a general Japanese population.Materials and Methods: Nine-hundred-and-thirty participants in the population-based Iwaki study conducted in 2016 who were not on drugs affecting mineral metabolism nor hemodialysis, were included in the study (326 men and 604 women; age: 55.4 ± 15.9 years).Results: Regression analysis showed a significant correlation between eGFR and serum intact PTH concentration, after adjustment for possible confounding factors (β = −0.122, p < 0.001). The smoothed spline curve applied for the correlation analysis revealed a biphasic correlation, with a division at an eGFR of ~60 mL/min/1.73 m2, below which the correlation coefficient was higher (β = −0.405, p < 0.001). Stratification on the basis of vitamin D status showed that the correlation was present only in participants with vitamin D deficiency (25-dihydroxyvitamin D3: <15 pg/mL) (β = −0.154, p < 0.001).Conclusions: These results indicate that a reduction in eGFR is a significant risk factor for an increase in serum PTH concentration when it is <60 mL/min/1.73 m2 and vitamin D is deficient, in the general Japanese population.

Dietary Phytase and Lactic Acid-Treated CerealGrains Differently Affected Calcium and PhosphorusHomeostasis from Intestinal Uptake to SystemicMetabolism in a Pig Model.

High intestinal availability of dietary phosphorus (P) may impair calcium (Ca) homeostasis and bone integrity. In the present study, we investigated the effect of phytase supplementation in comparison to the soaking of cereal grains in 2.5% lactic acid (LA) on intestinal Ca and P absorption; intestinal, renal, and bone gene expression regarding Ca and P homeostasis; bone parameters; and serum levels of regulatory hormones in growing pigs. Thirty-two pigs were randomly assigned to one of four diets in a 2 × 2 factorial design in four replicate batches for 19 days. The diets comprised either untreated or LA-treated wheat and maize without and with phytase supplementation (500 phytase units/kg). Although both treatments improved the P balance, phytase and LA-treated cereals differently modulated gene expression related to intestinal absorption, and renal and bone metabolism of Ca and P, thereby altering homeostatic regulatory mechanisms as indicated by serum Ca, P, vitamin D, and fibroblast growth factor 23 levels. Moreover, phytase increased the gene expression related to reabsorption of Ca in the kidney, whereas LA-treated cereals decreased the expression of genes for osteoclastogenesis in bones, indicating an unbalanced systemic availability of minerals. In conclusion, high intestinal availability of dietary P may impair Ca homeostasis and bone integrity.

SUN-096 Incidentally Found Severe Hypercalcemia in a Pediatric Patient, Diagnostic Challenge

Introduction: Idiopathic infantile hypercalcemia is an intriguing feature of Williams syndrome (WS), occurring in ~15% of diagnoses and is typically not clinically severe. Symptomatic hypercalcemia usually resolves during childhood, but lifelong abnormalities of calcium(Ca) and vitamin D metabolism may persist. The cause of the abnormality in Ca metabolism is still unknown. Hypercalciuria generally accompanies hypercalcemia, but isolated hypercalciuria, especially after infancy, can also occur. Nephrocalcinosis is relatively rare, found in less than 10% of patients undergoing renal ultrasonography. We report a 13-month-old female infant with a history of peripheral pulmonary stenosis and constipation, who presented with severe hypercalcemia that led to a new diagnosis of WS. Case presentation: A 13-month-old girl with a history of peripheral pulmonary stenosis, global developmental delay, and constipation presented to the neurology clinic for evaluation of gross motor delay. She was found to have upper body part hypotonia, decreased reflexes, and on laboratory evaluation, severe hypercalcemia with Ca level of 15.0 mg/dL (8.7 - 10.7). The patient was admitted for management of severe hypercalcemia. Physical exam was also remarkable for subtle features of WS: a happy baby, very social, with prominent eyes, full cheeks, flat nasal bridge, round nasal tip, full lips, and a wide smile. Repeated Ca level on admission was 15.9 mg/dL, with normal albumin level of 4.6 g/dL (2.9-5.5), elevated ionized calcium (iCal) of 1.99 mmol/L (0.95 - 1.32), and intact parathyroid hormone (PTH) of <4.0 pg/mL (8.0 - 85.0). Further evaluation revealed a normal 25 hydroxy-vitamin D:41 ng/mL (30-80) and low 1,25-dihydroxy vitamin D:10pg/mL (31-87). Further evaluation revealed elevated urine calcium to creatinine ratio of 0.7 (normal for age <0.56) and renal ultrasound remarkable for medullary nephrocalcinosis. The patient had a complete blood count within normal limits and a PTH related protein of 26 pg/mL (14-27), ruling out malignancy. Hypercalcemia responded well to intravenous fluids and diuretics, the patient being discharged home after two days on furosemide and potassium supplements with close electrolytes monitoring. The patient required calcium reducing therapy for four months to maintain Ca levels within 9-12 range. The medication was decreased gradually based on calcium and ical levels. The patient is currently doing well, with a normal calcium level, and has being off medication for the past three months. Conclusion: This is a rare case of severe hypercalcemia, which led to the diagnosis of WS. Although idiopathic infantile hypercalcemia occurs in 15% of patients with WS, usually the presentation is mild, and the patients do not require medical interventions. Our patient presented with severe hypercalcemia and subtle physical features of WS that led to genetic testing and final diagnosis.

Two-year retrospective study of the effect of preemptive kidney transplantation and pretransplant mineral bone factors on calcium in post-kidney transplant recipients.

Preemptive kidney transplantation (PEKT) incidence has recently increased in Japan. The effect of PEKT and mineral bone factors before kidney transplantation (KTx) on long-term calcium (Ca) levels remains unknown. Eighty-one consecutive patients at Nagoya Daini Red Cross Hospital were included in this study (PEKT group with 41 patients and non PEKT group with 40 patients). Ca metabolism, including intact fibroblast growth factor 23 (iFGF23), were measured before KTx and intact parathyroid hormone (iPTH), and corrected Ca (cCa) were measured before KTx and 6months (M), 12M, and 24M after KTx. In PEKT group, cCa levels at 24M were higher from the baseline level. At baseline, cCa levels had a positive correlation with iFGF23 levels (r = 0.51; p < 0.001) and a negative correlation with iPTH levels (r = 0.51; p < 0.001). The cCa difference between baseline and 24M was 0.8 ± 0.6mg/dL in PEKT group and 0.3 ± 0.7mg/dL in non-PEKT group (p = 0.001). A multivariate linear regression analysis showed iFGF23 and iPTH at baseline in entire groups were useful markers on calcium levels at 24M. However, in PEKT group, both markers were found to be not associated with Ca at 24M, whereas in non PEKT group, iPTH was the only effective marker. This study suggested that iFGF23 and iPTH may be useful markers of the calcium status after KTx. However, no correlation was noted in PEKT group.

Intestinal responses to 1,25 dihydroxyvitamin D are not improved by higher intestinal VDR levels resulting from intestine-specific transgenic expression of VDR in mice

Intestinal calcium (Ca) absorption depends upon vitamin D signaling through the vitamin D receptor (VDR) in the proximal and distal intestine while lower VDR content causes intestinal resistance to 1,25 dihydroxyvitamin D (1,25(OH)2 D) action. We tested whether intestinal responsiveness to 1,25(OH)2 D is increased in mice with higher than normal VDR levels resulting from transgenic VDR expression in the whole intestine (villin promoter-human VDR transgene, HV2). Wild type (WT) and HV2 mice were treated with 0, 0.15, or 0.3 ng 1,25(OH)2 D/g body weight (BW) (n = 6/dose) for 6 h. 1,25(OH)2 D significantly induced Cyp24a1, Trpv6, and S100 g mRNA in duodenum (Dd) of WT mice but induction was not higher in HV2 mice. We next tested whether higher intestinal VDR could protect mice from the consequences of low dietary Ca intake. WT and HV2 mice were fed diets with 0.125, 0.25, 0.5 (reference), or 1% Ca from weaning to 3 months of age (n = 9/diet/genotype). Dietary Ca restriction caused a dose dependent increase in serum 1,25(OH)2 D, Dd TRPV6, and Dd S100 g mRNA in WT mice and the effect was greater in HV2 mice. While Ca absorption was increased by low Ca intake, there was no difference in Ca absorption between HV2 and WT mice. Similarly, while bone density and microstructure were reduced by low Ca intake in WT mice, high intestinal VDR in HV2 mice did not protect bone in mice fed low Ca diets. Thus, while intestinal VDR and vitamin D signaling are essential for normal Ca metabolism during growth, our data demonstrate that higher than normal intestinal VDR levels do not improve the intestinal response to either 1,25(OH)2 D injection or to elevated 1,25(OH)2 D levels resulting from the physiologic adaptation to low Ca diets.

Peripartum Ca and P homeostasis in multiparous sows fed adequate or excess dietary Ca

The recent increased prevalence of uterine prolapses in sows around parturition has led to inferences that the prolapses may be associated with hypocalcemia. However, limited data are available to support that hypocalcemia occurs in sows. Hypocalcemia in dairy cows is associated with feeding excess dietary Ca during late gestation. The excess Ca is assumed to suppress homeostatic mechanisms critical to maintain serum Ca concentrations as the Ca demand increases during the early stages of lactation. In this experiment, sows were fed diets with excess Ca during late gestation and early lactation to assess the potential development of hypocalcemia in the peripartum period. Twelve crossbred (Large White × Landrace) multiparous gestating sows were fed a control diet (CON), 0.65% Ca to 0.38% standardized total tract digestible P (STTD P) and 0.67% Ca to 0.38% STTD P in gestation and lactation diets, respectively) or a high Ca diet (HCa, 1.75% Ca to 0.46% STTD P and 1.75% Ca to 0.45% STTD P in gestation and lactation diets, respectively). The diets were fed from gestation day 86 þ ± 1 until the end of lactation (27 þ ± 2 days period). On day 112 of gestation, indwelling venous catheters were placed in each sow. Blood samples were collected at 15-min intervals within four designated times (0700, 1000, 1300 and 1700 h) on gestation day 113 and lactation days 1, 3 and 5. Venous blood pH, gases (pO2, pCO2 and HCO3−), electrolytes (K+, Na+ and Cl−), ionized Ca (iCa), metabolites (glucose and lactate), plasma total Ca (tCa), and P were analyzed. Overall, sows fed HCa diet had greater (P < 0.001) concentrations of blood iCa and plasma tCa than sows fed CON diets. No clinical signs of Ca metabolism disorders were observed. Unexpectedly, concentrations of plasma P in sows fed HCa diets were lower (P < 0.001) than in sows fed CON diets. Plasma P tended to decrease (P = 0.057) as day of lactation increased. Differences between dietary treatments for blood pH, gases, electrolytes and metabolites were not detected (P > 0.05). No evidence for hypocalcemia was detected in peripartum sows fed CON or HCa diets. These data imply that excess Ca in late gestation diets did not result in hypocalcemia during the peripartum period. Future experiments should focus on factors other than hypocalcemia to identify causes of uterine prolapses in sows.

Upper Zone of Growth Plate and Cartilage Matrix (UCMA) Levels in Patients with Chronic Kidney Disease

Abstract Chronic kidney disease (CKD) is an important health problem across the world affecting the adult population with an enormous social and economic burden. Calcium regulation is also affected in patients with CKD, and related to several disorders including vascular calcifications, mineral bone disorders, and cardiovascular diseases (CVD). Upper zone of growth plate and cartilage matrix (UCMA) is vitamin K-dependent protein (VKDP) and acts as a calcification inhibitor in the cardiovascular system. The molecular mechanism of UCMA action remains unclear in CKD. In the current study, we aimed to investigate serum total UCMA levels and its association with calcium metabolism parameters in CKD patients including hemodialysis (HD) patients. Thirty-seven patients with CKD stage 3-5, 41 HD patients, and 34 healthy individuals were enrolled in this cross-sectional study. Serum UCMA and calcification related protein levels (Matrix Gla Protein (MGP), Osteocalcin (OC), and Fetuin-A) were analyzed with enzyme-linked immunosorbent assay (ELISA). Calcium mineral disorder parameters (Serum Ca, P, iPTH) were quantified with routine techniques. We, for the first time, report the potential biomarker role of UCMA in CKD including HD. Serum total UCMA levels were significantly higher in patients with CKD including HD patients than the healthy controls. Also, serum UCMA levels showed negative correlations with serum calcium, and eGFR, while showed positive relationships with P, iPTH, MGP, OC. Increased total UCMA levels may have a role in the Ca metabolism disorder and related to the pathogenesis of Vascular Calcification in patients with CKD.

Possible roles of parathyroid hormone, 1.25(OH)2D3, and fibroblast growth factor 23 on genes controlling calcium metabolism across different tissues of the laying hen

This study provides an integrative description of candidate gene expression across tissues involved in calcium (Ca) metabolism during the egg laying cycle, using the well-defined model of Ca supply as fine or coarse particles of calcium carbonate (CaCO3). Plasma and tissue samples were collected from hens at the peak of laying at 0 to 1, 9 to 10, and 18 to 19 h postovulation (PO). After mRNA preparation from the parathyroid gland, medullary bone, liver, kidney, duodenum, and jejunum, gene expressions were quantified using RT-qPCR. The highest levels of parathyroid hormone (PTH) mRNA in the parathyroid gland (P < 0.05), and of the active form of vitamin D3 1.25(OH)2D3 in the plasma (P < 0.01) were observed at 18 to 19 h PO. During this active phase of eggshell formation, bone resorption was attested to high levels of plasma inorganic phosphorus (iP) and the receptor activation of nuclear factor-κB expression in the bone (P < 0.001 and P < 0.05, respectively). At this stage, 5 genes of the transcellular and the paracellular Ca absorption pathways in the intestine (P < 0.05) and the Ca channel transient receptor potential cation channel subfamily V member 5 (P < 0.05), involved in its reabsorption in the kidney, were overexpressed. At 0 to 1 h PO during the subsequent daylight period, 2 candidates of the transcellular and the paracellular Ca pathways (P < 0.05) remained at high levels in the intestine, while calbindin D 28K expression was the highest in the kidney (P < 0.05). As PTH mRNA and 1.25(OH)2D3 were low, bone accretion was likely active at this stage. The phosphaturic hormone fibroblast growth factor 23 (FGF23) was overexpressed at 18 to 19 h PO (P < 0.05) in the bone when plasma iP was high, which suggested a role in the subsequent reduction of P reabsorption in the kidney, as attested to the decreased expression of P cotransporters, leading to iP clearance from the plasma at 0 to 1 h PO (P < 0.05). The low levels of 1.25(OH)2D3 at this stage coincided with increased expression of the 24-hydroxylase gene in the kidney (P < 0.05). In hens fed fine particles of CaCO3, higher plasma levels of 1,25(OH)2D3 and higher expression of several genes involved in bone turnover reflected a stronger challenge to Ca homeostasis. Altogether, these data support the hypothesis that FGF23 could drive vitamin D metabolism in the laying hen, as previously documented in other species and explain the tight link between P and Ca metabolisms.

Mathematical Modeling and Optimization of Active Calcium Absorption in Human Body

Active calcium (Ca) absorption is the first process in Ca metabolism, which regulates the whole Ca absorption. There are a few notable models which depict the mechanism of active Ca absorption; it is still required to update it for human metabolism and optimal conditions to propose an adequate amount of absorbed Ca. In this study, we were to develop a mathematical model describing the active Ca absorption and optimized the active Ca absorption. The developed model explained the active Ca absorption with 3 steps: Ca entry by electrochemical diffusion, intracellular Ca diffusion in cell by facilitated diffusion, and Ca extrusion in Ca pump by Michaelis–Menten equation. Model simulation was validated by showing similar responses with a previous model; then, the model was applied to simulate the active Ca absorption with parameters estimated based on human studies. In addition, the simulated Ca absorption was optimized as a function of Ca load in intestine and regulatory molecule, i.e., Ca-binding protein. This study provides a mechanistic point of view in human active Ca absorption and is expected to be a useful tool for analyzing the whole Ca metabolism and for designing Ca-related clinical experiment.

Metabolic Calcium Balance in Rats with Chronic Renal Failure Assessed Using 42Ca Tracer

Objective: This study's objective is to explore the effect of venous calcium (Ca) load on Ca metabolism using an isotope tracer in both healthy rats and rats with chronic renal failure (CRF). Materials and Methods: The methods included inducing CRF by feeding rats with food that containing 0.75% adenine. Both the rats in the control and CRF group received an intravenous injection of 100 mg/kg CaCl2 mixed with 0.5 mg/kg 42Ca for over 2 minutes in order to induce hypercalcemia. Blood samples, urine, and feces were collected for Ca kinetics and metabolism testing before and 24 hours after the injection. Results: Peak blood Ca levels were presented at 5 minutes in both groups but returned to baseline levels differently: within 3 hours in the CRF group and 1 hour in the control group. 24-hour hypercalciuria and a higher weight-corrected fecal Ca loss were consistently detected in the CRF rats before and after the injection, along with a decrease in the percent fractional Ca absorption and true fractional calcium absorption compared to the control group. The increased fecal Ca in the CRF rats primarily resulted from changes in decreased absorption rate, which indirectly lead to an increase in endogenous fecal Ca (EFC). Body weightcorrected EFC levels in the CRF group were significantly higher than those in the control group (207.58 ± 107.18 mg/kg/day vs. 62.44 ± 20.49 mg/kg/day). In addition, EFC was 22.6% and 26.02% of the total fecal Ca in the CRF group and the control group. Conclusion: These results may be useful in the evaluation of calcium metabolism and may have important implications for stable isotopes that are widely used in exploring calcification studies in the CRF.

The crosstalk between aldosterone and calcium metabolism in primary aldosteronism: A possible calcium metabolism-associated aberrant “neoplastic” steroidogenesis in adrenals

Intracellular calcium (Ca) levels play pivotal roles in aldosterone biosynthesis. Several somatic mutations of ion channels associated with aldosterone over-production were reported to result in over-inflow of Ca ion. Recently, the main regulators of extracellular Ca including VDR, CaSR and PTH1R were also reported to regulate steroidogenesis including aldosterone production. Therefore, not only intracellular but also extracellular Ca levels could regulate aldosterone biosynthesis. In addition, primary aldosteronism (PA) is clinically associated with not only more frequent cardiovascular events but also secondary metabolic disorders including abnormal calcium metabolism, osteoporosis and others. However, the details of Ca metabolic abnormalities associated with, including the potential correlation between those abnormalities and aldosterone overproduction, have remained virtually unknown. Therefore, in this study, we first immunolocalized Ca metabolism-related receptors (CaSR, VDR and PTH1R) in normal adrenal glands (NAs), aldosterone-producing adenomas (APAs) and cortisol-producing adenoma (CPA). We then compared the findings with clinicopathological parameters of these patients and the patterns of KCNJ5 somatic mutation of the tumors among APA patients. In vitro study was also performed to further explore the potential effects of extracellular Ca, PTH, Vitamin D and ionophore on aldosterone production. Ca metabolism-related receptors were predominantly localized in aldosterone-producing cells (ZG and APA) in both immunohistochemistry and qRT-PCR analysis. CYP11B2 mRNA was significantly increased by CaCl2 treatment and further by adding ionophore. All the key enzymes related to aldosterone and cortisol biosynthesis including CYP11B2, CYP17A1 and CYP11B1 were upregulated by PTH treatment in this model and PTH could serve as a co-stimulator of ANG II to increase CYP11B2 expression. VDR mRNA levels were positively correlated with those of CYP11B2, CYP17A1 and CYP11B1 in APA tumor tissues and significantly higher in KCNJ5 mutated APAs than wild type. CYP11B1 levels were also significantly increased by VitD treatment. PTH1R mRNA levels were positively correlated with those of CYP17A1 and CYP11B1, both involved in cortisol production. In addition, the status of VDR was correlated with TRACP-5b levels, and that of PTH1R with serum Ca levels as well as urinary Ca excretion, respectively. Results of our present study did firstly demonstrate that aldosterone-producing cells were more sensitive to the fluctuations of extracellular Ca levels and Ca metabolism could directly influence steroidogenesis, especially “neoplastic” co-secretion of aldosterone and cortisol in APA patients.

The ultrastructural anatomy of the nuclear envelope in the masseter muscle indicates its role in the metabolism of the intracellular Ca++

Specific ultrastructural anatomy of masticatory muscles is commonly referred to a general pattern assigned to striated muscles. Junctional feet consisting of calcium channels of the sarcoplasmic reticulum (i.e. the ryanodine receptors, RyRs) physically connected to the calcium channels of the t-tubules build triads within striated muscles. Functional RyRs were demonstrated in the nuclear envelopes of pancreas and of a skeletal muscle derived cell line, but not in muscle in situ. It was hypothesized that ryanodine receptors (RyRs) could also exist in the nuclear envelope in the masseter muscle, thus aiming at studying this by transmission electron microscopy. There were identified paired and consistent subsarcolemmal clusters of mitochondria, appearing as outpockets of the muscle fibers, usually flanking an endomysial microvessel. It was observed on grazing longitudinal cuts that the I-band-limited mitochondria were not strictly located in a single intermyofibrillar space but continued transversally over the I-band to the next intermyofibrillar space. It appeared that the I-band-limited transverse mitochondria participate with the column-forming mitochondria in building a rather incomplete mitochondrial reticulum of the masseter muscle. Subsarcolemmal nuclei presented nuclear envelope-associated RyRs. Moreover, t-tubules were contacting the nuclear envelope and they were seemingly filled from the perinuclear space. This could suggest that nucleoplasmic calcium could contribute to balance the cytosolic concentration via pre-built anatomical routes: (i) indirectly, via the RyRs of the nuclear envelope and (ii) directly via the communication of t-tubules and sarcoplasmic reticulum through the perinuclear space.

Intravenous calcium infusion in a calving protocol disrupts calcium homeostasis compared with an oral calcium supplement

Hypocalcemia is a common postpartum condition in dairy cows, which negatively affects health and production. Intravenous Ca infusions are commonly included in calving protocols to prevent or mitigate the effect of hypocalcemia in multiparous cows. Thus, we sought to contrast the effect of intravenous Ca infusion against voluntary oral Ca intake on Ca metabolism. Serum total Ca (tCa) and whole-blood ionized Ca (iCa) were monitored in 24 multiparous Holstein cows after parturition. Precalving diets were formulated with a positive dietary cation-anion difference of 172 mEq/kg of DM and contained 4.1 g of Ca/kg of DM. At parturition, cows were blocked by calving sequence and calcemic status as either normocalcemic (cutoff threshold of iCa ≥1.10 mmol/L) or hypocalcemic (cutoff threshold of iCa <1.10 mmol/L). Cows in each block were randomly assigned to 1 of 2 treatments: either an oral source of Ca (Ca-Oral; n = 12) or an intravenous source of Ca (Ca-IV; n = 12). Cows in the Ca-Oral group were offered a 20-L commercial Ca suspension (48 g of Ca) for voluntary consumption. The supplement contained Ca carbonate, Ca formate, Ca propionate, and other minerals and vitamins (Farm-O-San Reviva, Trouw Nutrition, Amersfoort, the Netherlands). Cows in the Ca-IV group received a 450-mL intravenous Ca solution (13 g of Ca) that contained 298 mg/mL of Ca gluconate, 33 mg/mL of magnesium chloride, and 82 mg/mL of boric acid (AmosCAL, Kommer-Biopharm BV, Heiloo, the Netherlands). Both treatments were initiated within 25 ± 10 min after calving. The oral Ca suspension was offered to cows in a 25-L bucket and was available for 10 min. All cows in the Ca-Oral group voluntarily consumed the entire 20 L of the Ca suspension within 5 min. Blood samples for Ca analyses were collected at 0 (before treatment initiation), 1, 3, 10, and 18 h relative to treatment, and at 0700 and 1900 h for the next 2 consecutive days, to represent the 24-, 36-, 48-, and 60-h sampling time points. In Ca-IV cows, both iCa and tCa concentrations peaked at 1 h (1.54 mmol/L for iCa and 2.85 mmol/L for tCa) and declined to a nadir at 24 h following treatment initiation (0.94 mmol/L for iCa and 1.74 mmol/L for tCa). Although whole-blood iCa and serum tCa were higher at 1 and 3 h in Ca-IV cows, concentrations of iCa were greater for Ca-Oral cows at 18, 24, and 36 h and for tCa at 24 and 36 h. Our data indicate that intravenous Ca infusion immediately induced a state of hypercalcemia followed by lower whole-blood iCa and serum tCa concentrations 24 h later compared with oral Ca.