Search

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease caused by mutations to the dystrophin gene, resulting in deficiency of dystrophin protein, loss of myofiber integrity in skeletal and cardiac muscle, and eventual cell death and replacement with fibrotic tissue. Pathologic cardiac manifestations occur in nearly every DMD patient, with the development of cardiomyopathy—the leading cause of death—inevitable by adulthood. As early cardiac abnormalities are difficult to detect, timely diagnosis and appropriate treatment modalities remain a challenge. There is no cure for DMD; treatment is aimed at delaying disease progression and alleviating symptoms. A comprehensive understanding of the pathophysiological mechanisms is crucial to the development of targeted treatments. While established hypotheses of underlying mechanisms include sarcolemmal weakening, upregulation of pro-inflammatory cytokines, and perturbed ion homeostasis, mitochondrial dysfunction is thought to be a potential key contributor. Several experimental compounds targeting the skeletal muscle pathology of DMD are in development, but the effects of such agents on cardiac function remain unclear. The synergistic integration of small molecule- and gene-target-based drugs with metabolic-, immune-, or ion balance-enhancing compounds into a combinatorial therapy offers potential for treating dystrophin deficiency-induced cardiomyopathy, making it crucial to understand the underlying mechanisms driving the disorder. [ABSTRACT FROM AUTHOR]

Abstract Background Diagnosis of subclinical hypocalcemia in cattle is based on concentration of total Ca ([TCa]) in serum or plasma below the reference range, with [TCa] serving as proxy for the concentration of ionized Ca ([iCa]). Hypothesis/Objectives To investigate the relation between [iCa] and [TCa] in periparturient cows over time, and its association with various metabolites. Animals Thirty periparturient dairy cows. Methods Prospective observational study. Blood from periparturient cows was obtained between 4 days before and 7 days after calving. Samples underwent blood gas analysis and blood biochemical analysis. The ratio of [iCa] : [TCa] was computed. Repeated measures linear regression analyses, spearman correlation‐, Deming regression‐ and receiver operating characteristic (ROC) analyses were conducted. Results Correlations between [iCa] and [TCa] ranged from r = 0.55 to r = 0.84. The diagnostic value of [TCa] to identify cows with [iCa] below the arbitrary cut‐off of 1.1 mmol/L was weak in particular during the first 24 hours of lactation, but continuously improved toward the end of the study with areas under the ROC curve increasing from 0.64 at d 0 to 0.93 at d +4 after calving. Strongest association with [iCa] : [TCa] were found for albumin (r2 = 0.58, P

Background: Diagnosis of subclinical hypocalcemia in cattle is based on concentration of total Ca ([TCa]) in serum or plasma below the reference range, with [TCa] serving as proxy for the concentration of ionized Ca ([iCa]). Hypothesis/Objectives: To investigate the relation between [iCa] and [TCa] in periparturient cows over time, and its association with various metabolites. Animals: Thirty periparturient dairy cows. Methods: Prospective observational study. Blood from periparturient cows was obtained between 4 days before and 7 days after calving. Samples underwent blood gas analysis and blood biochemical analysis. The ratio of [iCa] : [TCa] was computed. Repeated measures linear regression analyses, spearman correlation‐, Deming regression‐ and receiver operating characteristic (ROC) analyses were conducted. Results: Correlations between [iCa] and [TCa] ranged from r = 0.55 to r = 0.84. The diagnostic value of [TCa] to identify cows with [iCa] below the arbitrary cut‐off of 1.1 mmol/L was weak in particular during the first 24 hours of lactation, but continuously improved toward the end of the study with areas under the ROC curve increasing from 0.64 at d 0 to 0.93 at d +4 after calving. Strongest association with [iCa] : [TCa] were found for albumin (r2 = 0.58, P <.0001), pCO2 (r2 = 0.45, P =.0003), the standard [HCO3] (r2 = 0.22, P =.01), lactate (r2 = 0.16, P =.04) and [NEFA] (r2 = 0.15, P =.05). Conclusion and Clinical Importance: The [TCa] is of limited value to identify cows with subnormal [iCa] in the first hours and days of lactation, a finding apparently attributable to the increased variation of a number of metabolic variables that affect the ratio of [iCa] : [TCa]. [ABSTRACT FROM AUTHOR]

Abstract The use of citrate, through reversible binding of calcium, has become the preferred choice for anticoagulation in continuous renal replacement therapy in the critically ill patient. Though generally considered as very efficacious in acute kidney injury, this type of anticoagulation can cause acid–base disorders as well as citrate accumulation and overload, phenomena which have been well described. The purpose of this narrative review is to provide an overview of some other, non-anticoagulation effects of citrate chelation during its use as anticoagulant. We highlight the effects seen on the calcium balance and hormonal status, phosphate and magnesium balance, as well as oxidative stress resulting from these unapparent effects. As most of these data on these non-anticoagulation effects have been obtained in small observational studies, new and larger studies documenting both short- and long-term effects should be undertaken. Subsequent future guidelines for citrate-based continuous renal replacement therapy should take not only the metabolic but also these unapparent effects into account.

Objective: To study the effects of dietary fibers with different structures on calcium balance and biomechanical properties. Methods: Rats were fed a basal diet supplemented with 50 g/kg wheat bran, cellulose, xylan, pectin, inulin, konjac gum or their mixture. The contents of calcium in diets, feces, urine and femur were detected by atomic absorption spectrometry (AAS). The levels of total calcium, free calcium and bound calcium in serum were measured by an electrolyte analyzer. The maximum load of femur was measured by a three-point bending method. The effects of different dietary fibers on calcium absorption, blood calcium level, urinary calcium loss, calcium retention, bone calcium content and bone biomechanical properties were compared. Results: The calcium absorption rates in the wheat bran and cellulose supplementation groups were higher than those in the xylan, pectin, inulin and konjac supplementation groups, and the difference between the xylan and konjac supplementation groups and the wheat bran supplementation group was significant (P 0.05), but the concentrations of bound calcium and total calcium in the wheat bran supplementation group were higher than those in the other groups. The bone calcium content and bone biomechanical properties in the pectin supplementation group were significantly lower than those in the other groups, and the maximum load of femur was the highest in the xylan supplementation group. Conclusion: The intestinal calcium absorption of low fermentable dietary fibers such as wheat bran and cellulose is higher than that of high fermentable dietary fibers such as xylan, pectin, inulin and konjac. Xylan can improve the biomechanical properties of rat bones. Different dietary fibers have different effects on calcium absorption, bone calcium content and calcium balance in rats.

The use of citrate, through reversible binding of calcium, has become the preferred choice for anticoagulation in continuous renal replacement therapy in the critically ill patient. Though generally considered as very efficacious in acute kidney injury, this type of anticoagulation can cause acid–base disorders as well as citrate accumulation and overload, phenomena which have been well described. The purpose of this narrative review is to provide an overview of some other, non-anticoagulation effects of citrate chelation during its use as anticoagulant. We highlight the effects seen on the calcium balance and hormonal status, phosphate and magnesium balance, as well as oxidative stress resulting from these unapparent effects. As most of these data on these non-anticoagulation effects have been obtained in small observational studies, new and larger studies documenting both short- and long-term effects should be undertaken. Subsequent future guidelines for citrate-based continuous renal replacement therapy should take not only the metabolic but also these unapparent effects into account. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Home Economics of Japan is the property of Japan Society of Home Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inadequate dietary calcium intake is a global public health problem that disproportionately affects low‐ and middle‐income countries. However, the calcium status of a population is challenging to measure, and there are no standard methods to identify high‐risk communities even in settings with an elevated prevalence of a disease caused or exacerbated by low calcium intake (e.g., rickets). The calcium status of a population depends on numerous factors, including intake of calcium‐rich foods; the bioavailability of the types of calcium consumed in foods and supplements; and population characteristics, including age, sex, vitamin D status, and genetic attributes that influence calcium retention and absorption. The aim of this narrative review was to assess candidate indicators of population‐level calcium status based on a range of biomarkers and measurement methods, including dietary assessment, calcium balance studies, hormonal factors related to calcium, and health outcomes associated with low calcium status. Several promising approaches were identified, but there was insufficient evidence of the suitability of any single indicator to assess population calcium status. Further research is required to develop and validate specific indicators of calcium status that could be derived from the analysis of data or samples that are feasibly collected in population‐based surveys. [ABSTRACT FROM AUTHOR]

This article discusses the importance of calcium balance in the bone response to exercise, particularly in preventing stress fractures in military populations, especially female recruits. The study used dual calcium isotope methodology to assess calcium kinetics in 21 healthy women during load carriage exercise or rest. The results showed that exercise increased total and fractional calcium absorption and improved calcium balance compared to rest. However, the study also highlighted the need for further research to understand calcium kinetics during exercise in different populations and modes of exercise, as well as the role of calcium intake and supplementation in the bone response to exercise. [Extracted from the article]

Introduction: The composition of the dialysate is a crucial feature in the dialysis treatment. Two of its most debated elements are the optimal calcium concentration and the use of acetate as a buffer. Moreover, among the different alternatives to achieve acetate-free dialysis, the use of citrate is postulated as the most suitable option. The objective of this study is to identify the potential beneficial effects of citrate when compared to acetate dialysate (AD) both in short-term effects (especially regarding intradialytic calcium balance and cardiac damage biomarkers) and in medium-term ones with CKD-mineral and bone disorder (CKD-MBD) and inflammatory biomarkers measured after twelve sessions performed with each dialysate. Methods: This is a unicentric, cross-over, prospective study. Each patient underwent 24 dialysis sessions, 12 with each dialysate buffer. Blood samples were taken in 2 different sessions with each acidifier. They include CKD-MBD and inflammatory biomarkers. The calcium concentration of both dialysates was 1.5 mmol/L, while all other dialysis parameters and patients' treatment remained unchanged during the study period. Results: When comparing AD and citrate dialysate (CD), there were no differences in pre-dialysis ionized calcium (iCa) (1.11 vs. 1.08 mmol/L) in both groups. However, there was a significant increase in iCa with the use of AD in immediate and 30-min post-dialysis blood samples. In contrast, iCa levels remained stable with the use of citrate. Inflammatory biomarkers were also reduced after the use of CD. Conclusions: The use of citrate provides interesting advantages when compared to acetate. It maintains iCa levels stable during dialysis sessions with a neutral or negative effect on calcium balance, and it improves the chronic inflammatory condition that comes with long-time hemodialysis treatment. These beneficial effects may lead to an improvement in clinical outcomes. [ABSTRACT FROM AUTHOR]

There is controversy about the choice of dialysate calcium concentration (DCa), with strong arguments both in favor of and against the use of a low or high DCa, as they can both be potentially harmful. Evidence suggests that calcium mass balance is positive with a DCa 3.5 mEq/L, negative or neutral with the use of DCa 2.5 mEq/L, whereas both positive and negative balances have been observed with the use of DCa 3.0 mEq/L. Overall, the use of DCa >2.5 mEq/L is usually associated with an increase in serum calcium level and a decrease in serum PTH level and use of lower vitamin D analogue dose, with the opposite effects usually observed with the use of lower DCa. Most of the available evidence is from small-sized and crossover studies; hence, evidence should be regarded with caution and applied in a patient-specific manner. As there are a lot of significant unanswered questions regarding calcium balance and the optimal DCa in hemodialysis patients, further high-quality research is needed to clarify many still unclear aspects of calcium homeostasis and balance in these patients. In conclusion, with the existing evidence the choice of DCa needs to be individualized and contextualized in the setting of each patient's calcium balance needs and homeostatic response, taking also into account oral calcium intake (dietary and medicinal), any other relevant therapy administered, such as vitamin D analogues, the type of renal mineral bone disorder, and associated cardiovascular comorbidity. [ABSTRACT FROM AUTHOR]

Oleanolic acid (OA) and ursolic acid (UA) are the major chemical constituents in Fructus Ligustri Lucidi (FLL), a kidney-tonifying Chinese herb that is previously shown to improve bone properties and enhance calcium balance in aged female rats. The present study was designed to study if OA and UA act as the active ingredients in FLL to exert the positive effects on bone and mineral metabolism in aged rats. Aged (13-month-old) Sprague-Dawley female rats were randomly assigned to four groups with oral administration of drug or vehicle treatment for 12 weeks: medium calcium diet (MCD, 0.6% calcium), high calcium diet (HCD, 1.2% calcium), MCD + FLL (700 mg/kg/day), MCD + OA (23.6 mg/kg/day) + UA (8.6 mg/kg/day). A group of mature (3-month-old) female rats fed with MCD was included as positive control. The results demonstrated that FLL and OA+UA increased bone mineral density and improved microarchitectural properties of aged female rats. The osteoprotective effects of FLL and OA+UA might be, at least in part, associated with their actions on enhancing calcium balance and suppressing age-induced secondary hyperparathyroidism in aged female rats. FLL and OA+UA also significantly induced renal CYP27B1 protein expression and OA+UA treatment decreased CYP24A1 mRNA and protein expressions in aged female rats. In addition, FLL and OA+UA significantly increased the promoter activity, mRNA and protein expressions of renal CYP27B1 in vitro in human proximal tubule HKC-8 cells. The present findings suggest that OA+UA can be regarded as the active ingredients of FLL and might be a potential drug candidate for prevention and treatment of osteoporosis.

Background: Dysregulated serum calcium and FGF23 are associated with increased mortality and morbidity rates in patients receiving hemodialysis. Preliminary data suggest serum calcium regulates FGF23 secretion independently of serum phosphate, parathyroid hormone, and 25-OH vitamin D. It is unclear to what extent dietary and prescription sources of calcium influence calcium and FGF23 levels, and whether they confound this relationship. In this cross-sectional analysis of a multi-ethnic cohort of prevalent hemodialysis patients, association of dietary calcium and prescribed calcium were examined against serum calcium and FGF23. Bi- and multivariable linear regression was used for all analyses. Results: 81 patients (mean age 58 years, dialysis vintage 2 years, 51 men) participated. Dietary calcium was inversely associated with FGF23 (p = 0.04) however association of FGF23 with prescribed calcium did not reach statistical significance (0.08). In multivariable models, dietary calcium and prescribed calcium were associated in opposing directions with serum calcium (prescribed calcium; ß-coefficient = −0.35, p = 0.005 versus dietary calcium; ß-coefficient = 0.35, p = 0.03). FGF23 was independently associated with serum calcium (p = 0.007). Conclusions: We found differing, sometimes opposing, associations between serum calcium and FGF23 levels when considering prescribed versus dietary sources of calcium. Serum calcium and FGF23 were strongly correlated regardless of possible confounders examined in this hemodialysis cohort. Dietary calcium was associated with higher serum calcium and lower FGF23 concentrations, while prescribed calcium was only inversely associated with serum calcium. Further studies are required to confirm these associations and determine causality.

The purpose of this study was to investigate the antihypertensive mecha-nisms of piperitenone oxide in spontaneously hypertensive rat (SHR). Compared to control SHR, piperitenone oxide reduced the systolic blood pressure and serum endothelium-1 (ET-1). The nitric oxide (NO) production and ET-1 secretion were significantly inhibited in the noradrenaline-exposed bovine aortic endothelial cells. Piperitenone oxide showed endothelium-independent but concentration-dependent relaxation of the artery rings. The responsible mechanisms appear to be related to the modulation of ET-1 and NO levels. The vasorelaxant effect of piperitenone oxide is independent of endothelium-derived mediators, which is associated with interfering intracellular calcium homeostasis by blocking Ca2+ influx, as well as intracellular Ca2+ release. Video Clip of Methodology: 2 min 58 sec: Full Screen Alternate

In coeliac disease (CD), the risk of adverse calcium balance and reduced bone density is induced mainly by the disease, but also by a gluten-free diet (GFD), the only accepted CD therapy. Prebiotics through the beneficial impact on intestinal microbiota may stimulate calcium (Ca) absorption. In the present study, we hypothesised that the dietary inulin in GFD would influence positively the intestinal microbiota, and by that will stimulate the absorption of calcium (Ca), especially in the conditions of Ca malnutrition. In a six-weeks nutritional experiment on growing a significant (p < 0.05) luminal acidification, decrease in ammonia concentration and stimulation of short chain fatty acids formation indicated inulin-mediated beneficial effects on the caecal microbiota. However, the effect of inulin on characteristics of intestinal microbiota and mineral utilization depended on the dietary Ca intake from GFDs. Inulin stimulated bifidobacteria, in particular B. animalis species, only if a recommended amount of Ca was provided. Most benefits to mineral utilization from inulin consumption were seen in rats fed Ca-restricted GFD where it increased the relative Ca absorption. Administration of inulin to a GFDs could be a promising dietary strategy for beneficial modulation of intestinal ecosystem and by that for the improvement the Ca absorption. [ABSTRACT FROM AUTHOR]

Purpose of Review: The kidneys play a critical role in the balance between the internal milieu and external environment. Kidney failure is known to disrupt a number of homeostatic mechanisms that control serum calcium and normal bone metabolism. However, our understanding of calcium balance throughout the stages of chronic kidney disease is limited and the concept of balance itself, especially with a cation as complex as calcium, is often misunderstood. Both negative and positive calcium balance have important implications in patients with chronic kidney disease, where negative balance may increase risk of osteoporosis and fracture and positive balance may increase risk of vascular calcification and cardiovascular events. Here, we examine the state of current knowledge about calcium balance in adults throughout the stages of chronic kidney disease and discuss recommendations for clinical strategies to maintain balance as well as future research needs in this area. Recent Findings: Recent calcium balance studies in adult patients with chronic kidney disease show that neutral calcium balance is achieved with calcium intake near the recommended daily allowance. Increases in calcium through diet or supplements cause high positive calcium balance, which may put patients at risk for vascular calcification. However, heterogeneity in calcium balance exists among these patients. Summary: Given the available calcium balance data in this population, it appears clinically prudent to aim for recommended calcium intakes around 1000 mg/day to achieve neutral calcium balance and avoid adverse effects of either negative or positive calcium balance. Assessment of patients' dietary calcium intake could further equip clinicians to make individualized recommendations for meeting recommended intakes. [ABSTRACT FROM AUTHOR]

The rare, long-lived radiotracer, Ca, measured by accelerator mass spectrometry in the urine or serum following incorporation into the bone provides an ultra-sensitive tool to assess changes in bone calcium balance in response to an intervention. Changes in bone balance can be followed for years with one small dose that is both radiologically and biologically non-invasive. Sequential interventions can be compared, with greater precision than they can with biochemical markers of bone turnover and with greater power than with bone densitometry. This method is especially useful to screen interventions over a period of weeks. The development and validation of this tool and its applications are reviewed. Mini abstract: Use of Ca measured in the urine or blood by accelerator mass spectrometry to assess bone balance provides a tool to compare the relative efficacy of multiple interventions. This perspective provides insights in the use of this novel method and comparisons with more traditional methods for evaluating the efficacy of interventions. [ABSTRACT FROM AUTHOR]

Currently ground limestone and oyster shell are the common sources of calcium for laying hens. Processed whelk (Buccinum undatum) shell contains approximately 34.8% calcium, very similar to the 38% value for commercial oyster shell and ground limestone. The objective of this study was to evaluate the effect of feeding whelk shells to laying hens on performance, egg and bone quality, and calcium balance. White Leghorn hens were fed a basal diet and either one-third large particle oyster shell (>1.4-4 mm) + two-thirds ground limestone (OS/GL), one-third large particle whelk shells (>1.4-4 mm) + two-thirds ground whelk (W/GW), 100% ground limestone (GL), or 100% ground whelk shells (GW) starting at 20 wk of age for 14 28 d periods. Production data were comparable among calcium sources for the first 8 periods of production. During periods 9 to 14, feed consumption for hens fed GW was lower (P < 0.05) than for hens fed OS/GL. For periods 12 to 14, hens fed W/GW consumed less feed (P < 0.05) than those fed OS/GL and GL. Body weights were less (P < 0.05) for hens fed both forms of whelks at the end of periods 12 to 14. Egg production was not affected (P < 0.05) by treatment up to period 10. During period 11, egg production was lower (P < 0.05) for the hens fed GW compared to OS/GL and GL. For periods 12 to 14, hens fed both forms of whelks produced lower (P < 0.05) numbers of eggs than those fed OS/GL and GL. Hens fed GW produced fewer (P < 0.05) eggs than those fed W/GW. Feed conversions for hens fed W/GW and GW were less efficient (P < 0.05) during periods 12 to 14. Higher environmental temperatures occurred during periods 12 to 13, which may have negatively affected the performance of hens fed whelks. However, there were no differences (P < 0.05) among treatment means for egg weight, egg specific gravity, and shell breaking strength. GW resulted in a lower (P < 0.05) calcium balance than the other treatments for period 14. [ABSTRACT FROM AUTHOR]

Concern has recently arisen about the potential adverse effects of excessive calcium intakes, i.e., calcium loading from supplements, on arterial calcification and risks of cardiovascular diseases (CVD) in older adults. Published reports that high calcium intakes in free-living adults have relatively little or no beneficial impact on bone mineral density (BMD) and fracture rates suggest that current recommendations of calcium for adults may be set too high. Because even healthy kidneys have limited capability of eliminating excessive calcium in the diet, the likelihood of soft-tissue calcification may increase in older adults who take calcium supplements, particularly in those with age or disease-related reduction in renal function. The maintenance of BMD and bone health continues to be an important goal of adequate dietary calcium consumption, but eliminating potential risks of CVDs from excessive calcium intakes needs to be factored into policy recommendations for calcium by adults.

Animal models fed low calcium diets demonstrate a negative calcium balance and gross bone loss while the combination of calcium deficiency and oophorectomy enhances overall bone loss. Following oophorectomy the dietary calcium intake required to remain in balance increases some 5 fold, estimated to be approximately 1.3% dietary calcium. In the context of vitamin D and dietary calcium depletion, osteomalacia occurs only when low dietary calcium levels are combined with low vitamin D levels and osteoporosis occurs with either a low level of dietary calcium with adequate vitamin D status or when vitamin D status is low in the presence of adequate dietary calcium intake. Maximum bone architecture and strength is only achieved when an adequate vitamin D status is combined with sufficient dietary calcium to achieve a positive calcium balance. This anabolic effect occurs without a change to intestinal calcium absorption, suggesting dietary calcium and vitamin D have activities in addition to promoting a positive calcium balance. Each of the major bone cell types, osteoblasts, osteoclasts and osteocytes are capable of metabolizing 25 hydroxyvitamin D (25D) to 1,25 dihydroxyvitamin D (1,25D) to elicit biological activities including reduction of bone resorption by osteoclasts and to enhance maturation and mineralization by osteoblasts and osteocytes. Each of these activities is consistent with the actions of adequate circulating levels of 25D observed in vivo.

Inulin, a dietary fibre found in the roots of many plants, has positive effects on health. It is particularly noteworthy due to its positive impact on calcium metabolism. Inulin has significant functions, such as improving calcium absorption through passive diffusion, bolstering calcium absorption via ion exchange and expanding the absorption surface of the colon by stimulating cell growth. In addition, inulin boosts calcium absorption by increasing calcium solubility, stimulating levels of calcium-binding protein expression and increasing useful microorganisms. It increases calbindin levels and stimulates transcellular active calcium transport. An inulin intake of least 8-10 g/day supports calcium absorption and total body bone mineral content/density in adolescents through its known mechanisms of action. It also significantly enhances calcium absorption and improves bone health in postmenopausal women and adult men. Sustained and sufficient inulin supplementation in adults has a positive effect on calcium metabolism and bone mineral density.

Two experiments were conducted to determine the requirement for standardized total tract digestible (STTD) Ca by 11- to 25-kg pigs based on growth performance, bone ash, or Ca and P retention and to determine the effect of dietary Ca on expression of genes related to Ca transport in the jejunum and kidneys. Six diets were formulated to contain 0.36% STTD P and 0.32, 0.40, 0.48, 0.56, 0.64, or 0.72% STTD Ca by including increasing quantities of calcium carbonate in the diets at the expense of cornstarch. Two additional diets contained 0.72% STTD Ca and 0.33% or 0.40% STTD P to determine if 0.36% STTD P had negative effects on the Ca requirement. The same batch of all diets was used in both experiments. In Exp. 1, 256 pigs (11.39 ± 1.21 kg initial BW) were randomly allotted to the 8 diets with 4 pigs per pen and 8 replicate pens per diet in a randomized complete block design. On the last day of the experiment, 1 pig from each pen was euthanized and the right femur and intestine and kidney samples were collected. Results indicated that ADG and G:F started to decline (linear and quadratic, P < 0.05) at 0.54 and 0.50% STTD Ca, respectively. In contrast, bone ash increased (quadratic, P < 0.05) as dietary Ca increased and reached a plateau indicating that the requirement for STTD Ca to maximize bone ash was 0.48%. Bone ash, but not ADG or G:F, increased (linear, P < 0.01) as STTD P increased in the diets. The mRNA expression of genes related to transcellular Ca transport decreased (linear, P < 0.01) in the jejunum and in kidneys (linear and quadratic, P < 0.01) as dietary Ca increased. In Exp. 2, 80 pigs (13.12 ± 1.79 kg initial BW) were placed in metabolism crates and randomly allotted to the 8 diets with 10 replicate pigs per diet in a randomized complete block design. Fecal and urine samples were collected using the marker-to-marker approach. Results indicated that the requirement for STTD Ca to maximize Ca and P retention (g/d) was 0.60 and 0.49%, respectively. In conclusion, the STTD Ca requirement by 11- to 25-kg pigs to maximize bone ash was 0.48%; however, ADG and G:F declined if more than 0.54 or 0.50% STTD Ca, respectively, was fed, and the minimum concentration of Ca needed to maximize ADG and G:F could not be determined under the conditions of this experiment. Increasing dietary Ca decreased the mRNA expression of several genes related to transcellular Ca transport in the jejunum and the kidneys. [ABSTRACT FROM AUTHOR]

In children with chronic kidney disease (CKD) optimal control of mineral and bone disorder (MBD) is essential not only for the prevention of debilitating skeletal complications and for achieving adequate growth, but also for preserving long-term cardiovascular health. The growing skeleton is particularly vulnerable to the effects of CKD, and bone pain, fractures and deformities are common in children on dialysis. Defective bone mineralisation has been linked with ectopic calcification, which in turn leads to significant morbidity and mortality. Despite national and international guidelines for the management of CKD-MBD, the management of mineral dysregulation in CKD can be extremely challenging, and a significant proportion of patients have calcium, phosphate or parathyroid hormone levels outside the normal ranges. Clinical and experimental studies have shown that, in the setting of CKD, low serum calcium levels are associated with poor bone mineralisation, whereas high serum calcium levels can lead to arterial calcification, even in children. The role of calcium in CKD-MBD is the focus of this review. [ABSTRACT FROM AUTHOR]

Calcium is an essential element in the diet, but there is continuing controversy regarding its optimal intake, and its role in the pathogenesis of osteoporosis. Most studies show little evidence of a relationship between calcium intake and bone density, or the rate of bone loss. Re-analysis of data from the placebo group from the Auckland Calcium Study demonstrates no relationship between dietary calcium intake and rate of bone loss over 5 years in healthy older women with intakes varying from <400 to >1500 mg day−1. Thus, supplements are not needed within this range of intakes to compensate for a demonstrable dietary deficiency, but might be acting as weak anti-resorptive agents via effects on parathyroid hormone and calcitonin. Consistent with this, supplements do acutely reduce bone resorption and produce small short-term effects on bone density, without evidence of a cumulative density benefit. As a result, anti-fracture efficacy remains unproven, with no evidence to support hip fracture prevention (other than in a cohort with severe vitamin D deficiency) and total fracture numbers are reduced by 0-10%, depending on which meta-analysis is considered. Five recent large studies have failed to demonstrate fracture prevention in their primary analyses. This must be balanced against an increase in gastrointestinal side effects (including a doubling of hospital admissions for these problems), a 17% increase in renal calculi and a 20-40% increase in risk of myocardial infarction. Each of these adverse events alone neutralizes any possible benefit in fracture prevention. Thus, calcium supplements appear to have a negative risk-benefit effect, and so should not be used routinely in the prevention or treatment of osteoporosis. [ABSTRACT FROM AUTHOR]

After adulthood, changes in the skeleton are slow and takes years for accruing or losing any appreciable amount of bone mass. Proper interpretation of studies that evaluate the effect of nutrients (like calcium, vitamin D) and anti-resorptive agents (like bisphosphonates) on bone mass is important so that the true effect of the agent is measured correctly. In this report, we are highlighting two issues of utmost importance for correctly interpreting interventional studies for osteoporosis. One issue is the bone remodelling transient (BRT). It refers to a transient change in bone mineral density (BMD) by any agent that reduces remodeling space temporarily. This change is, however, not sustained for a long period and can be misinterpreted as a true gain in bone mass. The second issue is difference between calcium balance and bone balance. Calcium balance is the difference between the amount of calcium ingested in a day and the amount of calcium lost in that day. Recommendations for dietary calcium intake are based on calcium balance studies that presume calcium balance as an equivalent for bone balance. However, these are two different entities and need to be distinguished. Dietary calcium requirements should be established by bone balance studies using bone densitometry, not by calcium balance studies. [ABSTRACT FROM AUTHOR]