Reduction of dietary magnesium by only 50% in the rat disrupts bone and mineral metabolism

The Importance of Vitamin D and Magnesium in Athletes

Vitamin D and magnesium are essential nutrients that play key roles in an athlete's performance, recovery, and overall health. Vitamin D is crucial for bone health (aiding calcium absorption and preventing stress fractures), muscle function (preventing weakness and injury), and reducing respiratory infections. Magnesium is fundamental in muscle function, adenosine triphosphate production for muscle contraction, electrolyte balance, bone strength, and cardiovascular health. The magnesium requirement of healthy adults is estimated at 300-400 mg/day, but there is evidence that athletes may have higher magnesium needs compared to sedentary persons. Magnesium and vitamin D are closely linked-vitamin D aids magnesium absorption, while magnesium is vital for vitamin D synthesis, transport, and activation. Given their importance in athletes, this article explores their functions, interactions, and the effects of deficiencies and supplementation in athletic populations.

Magnesium biology

Magnesium (Mg2+) is essential for energy metabolism, muscle contraction and neurotransmission. As part of the Mg-ATP complex, it is involved in over 600 enzymatic reactions. Serum Mg2+ levels are tightly regulated between 0.7 and 1.1 mmol/L by interplay of intestinal absorption and renal excretion. In the small intestine, Mg2+ is absorbed paracellularly via claudin-2 and -12. In the colon, transcellular absorption of Mg2+ is facilitated by TRPM6/7 and CNNM4. In the kidney, the proximal tubule reabsorbs only 20% of the filtered Mg2+. The majority of the filtered Mg2+ is reabsorbed in the thick ascending limb, where the lumen-positive transepithelial voltage drives paracellular transport via claudin-16/-19. Fine-tuning of Mg2+ reabsorption is achieved in the distal convoluted tubule (DCT). Here, TRPM6/7 tetramers facilitate apical Mg2+ uptake, which is hormonally regulated by insulin and epidermal growth factor. Basolateral Mg2+ extrusion is Na+ dependent and achieved by CNNM2 and/or SLC41A3. Hypomagnesemia (serum Mg2+ <0.7 mmol/L) develops when intestinal and/or renal Mg2+ (re)absorption is disturbed. Common causes include alcoholism, type 2 diabetes mellitus and the use of pharmacological drugs, such as proton-pump inhibitors, calcineurin inhibitors and thiazide diuretics. Over the last decade, research on rare genetic and acquired Mg2+ disorders have identified Mg2+ channel and transporter activity, DCT length, mitochondrial function and autoimmunity as mechanisms explaining hypomagnesemia. Classically, treatment of hypomagnesemia depended on oral or intravenous Mg2+ supplementation. Recently, prebiotic dietary fibers and sodium-glucose cotransporter 2 inhibitors have been proposed as promising new therapeutic pathways to treat hypomagnesemia.

Modeling calcium and magnesium balance: Regulation by calciotropic hormones and adaptations under varying dietary intake

Magnesium (Mg2+) is crucial for several cellular and physiological processes and is tightly regulated due to health risks associated with imbalances. Mg2+, calcium (Ca2+), parathyroid hormone, and vitamin D3 are tightly coupled, ensuring proper bone metabolism and intestinal and renal absorption of Mg2+ and Ca2+. While several Ca2+ homeostasis models exist, no computational model has been developed to study Mg2+ homeostasis. We developed a computational model of Mg2+ homeostasis in male rats, integrating it with an existing Ca2+ homeostasis model, to understand the interconnected physiological processes regulating their homeostasis. We then analyzed adaptations in these interconnected processes under (1) dietary Mg2+ deficiency, (2) low/high dietary Ca2+ with Mg2+ deficiency, and (3) vitamin D3 deficiency. Model simulations predicted severe hypomagnesemia and mild hypocalcemia with significant dietary Mg2+ deficiency. Low dietary Ca2+ improved, while high dietary Ca2+ worsened Mg2+ deficiency. Finally, vitamin D3 deficiency caused severe hypocalcemia, with minimal impact on Mg2+ homeostasis.

Biocompatibility and osteogenic capacity of additively manufactured biodegradable porous WE43 scaffolds: An in vivo study in a canine model

Magnesium is the most promising absorbable metallic implant material for bone regeneration and alloy WE43 is already FDA approved for cardiovascular applications. This study investigates the cyto- and biocompatibility of novel additively manufactured (AM) porous WE43 scaffolds as well as their osteogenic potential and degradation characteristics in an orthotopic canine bone defect model. The cytocompatibility was demonstrated using modified ISO 10993-conform extract-based indirect and direct assays, respectively. Additionally, degradation rates of WE43 scaffolds were quantified in vitro prior to absorption tests in vivo. Complete blood cell counts, blood biomarker analyses, blood trace element analyses as well as multi-organ histopathology demonstrated excellent biocompatibility of porous y WE43 scaffolds for bone defect repair. Micro-CT analyses further showed a relatively higher absorption rate during the initial four weeks upon implantation (i.e., 36 % ± 19 %) than between four and 12 weeks (41 % ± 14 %), respectively. Of note, the porous WE43 implants were surrounded by newly formed bony tissue as early as four weeks after implantation when unmineralized trabecular ingrowth was detected. After 12 weeks, a substantial amount of mineralized bone was detected inside and around the gradually disappearing implants. This first study on AM porous WE43 implants in canine bone defects demonstrates the potential of this alloy for in vivo applications in humans. Our data further underscore the need to control initial bulk absorption kinetics through surface modifications.

Magnesium-Titanium Alloys: A Promising Solution for Biodegradable Biomedical Implants

Magnesium (Mg) has attracted considerable attention as a biodegradable material for medical implants owing to its excellent biocompatibility, mitigating long-term toxicity and stress shielding. Nevertheless, challenges arise from its rapid degradation and low corrosion resistance under physiological conditions. To overcome these challenges, titanium (biocompatibility and corrosion resistance) has been integrated into Mg. The incorporation of titanium significantly improves mechanical and corrosion resistance properties, thereby enhancing performance in biological settings. Mg-Ti alloys are produced through mechanical alloying and spark plasma sintering (SPS). The SPS technique transforms powder mixtures into bulk materials while preserving structural integrity, resulting in enhanced corrosion resistance, particularly Mg80-Ti20 alloy in simulated body fluids. Moreover, Mg-Ti alloy revealed no more toxicity when assessed on pre-osteoblastic cells. Furthermore, the ability of Mg-Ti-based alloy to create composites with polymers such as PLGA (polylactic-co-glycolic acid) widen their biomedical applications by regulating degradation and ensuring pH stability. These alloys promote temporary orthopaedic implants, offering initial load-bearing capacity during the healing process of fractures without requiring a second surgery for removal. To address scalability constraints, further research is necessary to investigate additional consolidation methods beyond SPS. It is essential to evaluate the relationship between corrosion and mechanical loading to confirm their adequacy in physiological environments. This review article highlights the importance of mechanical characterization and corrosion evaluation of Mg-Ti alloys, reinforcing their applicability in fracture fixation and various biomedical implants.

Association Between Combined Polymetallic Exposure and Osteoporosis

Combined polymetallic exposure may be an influential factor in osteoporosis. This study aimed to explore the association between polymetallic combined exposure and osteoporosis. A total of 2115 participants were included. Plasma concentrations of 22 metals were determined by inductively coupled plasma mass spectrometry. Osteoporosis was defined as a T ≤  - 2.5. The least absolute shrinkage and selection operator (LASSO) regression, binary logistics regression, and Bayesian kernel machine regression (BKMR) model were used to explore the association between plasma metals and osteoporosis. LASSO regression showed that 10 metals were associated with osteoporosis in the total population (magnesium, calcium, manganese, nickel, cobalt, arsenic, selenium, rubidium, cadmium, aluminum) and women (magnesium, calcium, molybdenum, nickel, cobalt, arsenic, selenium, rubidium, cadmium, aluminum), and four metals associated with men (magnesium, cobalt, aluminum, iron). Logistics regression showed that in total population, magnesium (ORQ3 = 0.653, 95% CI = 0.446-0.954) was negatively correlated with osteoporosis, while aluminum (ORQ2 = 1.569, 95% CI = 1.095-2.248, ORQ4 = 1.616, 95% CI = 1.109-2.354) and cadmium (ORQ4 = 1.989, 95% CI = 1.379-2.870) were positively correlated; in women, magnesium (ORQ3 = 0.579, 95% CI = 0.379-0.883) was negatively correlated with osteoporosis, while aluminum (ORQ2 = 1.563, 95% CI = 1.051-2.326, ORQ4 = 1.543, 95% CI = 1.024-2.326) and cadmium (ORQ3 = 1.482, 95% CI = 1.003-2.191, ORQ4 = 1.740, 95% CI = 1.167-2.596) were positively correlated. BKMR model showed that combined polymetallic exposure had an overall positive effect on osteoporosis, magnesium was negatively associated with osteoporosis, and cadmium, selenium, and aluminum were positively associated with osteoporosis. Metal mixtures in plasma were associated with osteoporosis risk. Magnesium may reduce the risk of osteoporosis, while cadmium, selenium, and aluminum may increase the risk of osteoporosis. Future studies needed to explore correlations and mechanisms.

The association between dietary approaches to stop hypertension diet and bone mineral density in US adults: evidence from the National Health and Nutrition Examination Survey (2011-2018)

This study aimed to investigate the relationship between the dietary approaches to stop hypertension (DASH) dietary patterns and bone mineral density (BMD) in adults residing in the United States. To achieve this, data from the National Health and Nutrition Examination Survey (NHANES) database for 2011-2018 were utilized. This study utilized the NHANES database from 2011 to 2018, with a sample size of 8,486 US adults, to investigate the relationship between the DASH diet and BMD. The DASH diet was assessed based on nine target nutrients: total fat, saturated fat, protein, fiber, cholesterol, calcium, magnesium, sodium and potassium. The primary outcome measures were BMD values at the total BMD, thoracic spine, lumbar spine, and pelvis. Multivariable linear models were employed to analyze the association between the DASH diet and BMD. Interaction tests, subgroup, and sensitivity analysis were also followed. A negative correlation was observed between the DASH diet and total BMD (OR: - 0.003 [95%CI: - 0.005, - 0.001), pelvic (OR: - 0.005 [95%CI: - 0.007, - 0.002]), and thoracic BMD (OR: - 0.003 [95%CI: - 0.005, - 0.001]). However, the DASH diet does not appear to have a particular effect on lumbar spine BMD (OR: - 0.002 [95%CI: - 0.004, 0.001]). Similarly, when the DASH diet was categorized into tertiles groups, the relationship with total BMD, pelvic BMD, thoracic BMD, and lumbar spine BMD remained consistent. Furthermore, we performed a sensitivity analysis by converting BMD to Z-scores, and the results remained unchanged. Subgroup analyses and interaction tests indicated no significant dependence of BMI, gender, smoking, hypertension, and diabetes on the observed association (all p for interactions > 0.05). The DASH diet has been identified as potentially reducing total BMD, while specifically impacting thoracic and pelvic BMD. However, it appears to have no significant effect on lumbar spine BMD.

Titanium alloy cannulated screws and biodegrade ceramic nails for treatment of femoral neck fractures: A finite element analysis

BACKGROUND

Our previous studies have demonstrated the mechanical effect of sclerosis around screw paths on the healing of femoral neck fractures (FNF) after internal fixation. Furthermore, we discussed the possibility of using bioceramic nails (BNs) to prevent sclerosis. However, all these studies were conducted under static conditions as the patient was standing on one leg, while the effect of the stress generated during movement is unknown. The purpose of this study was to evaluate the stress and displacement under dynamic stress loading conditions.

METHODS

Two types of internal fixation, namely cannulated screws and bioceramic nails, were utilized in conjunction with various finite element models of the femur. These models included the femoral neck fracture healing model, the femoral neck fracture model, and the sclerosis around screws model. The resulting stress and displacement were analyzed by applying the contact forces associated with the most demanding activities during gait, including walking, standing, and knee bending. The present study establishes a comprehensive framework for investigating the biomechanical properties of internal fixation devices in the context of femoral fractures.

RESULTS

The stress at the top of the femoral head in the sclerotic model was increased by roughly 15 MPa during the knee bend and walking phases and by about 30 MPa during the standing phase compared to the healing model. The area of high stress at the top of the femoral head was increased during the sclerotic model's walking and standing phases. Additionally, the stress distribution throughout the dynamic gait cycle was comparable before and after the removal of internal fixations following the healing of the FNF. The overall stress distribution of the entire fractured femoral model was lower and more evenly distributed in all combinations of internal fixation. Furthermore, the internal fixation stress concentration was lower when more BNs were used. In the fractured model with three cannulated screws (CSs), however, the majority of the stress was concentrated around the ends of the fractures.The maximal stress in the healing model with one CS and two BNs was the highest at all stages of gait over three combinations of internal fixation, and the stress was mainly carried by CS.

CONCLUSIONS

The presence of sclerosis around screw paths increases the risk of femoral head necrosis. Removal of CS has little effect on the mechanics of the femur after healing of the FNF. BNs have several advantages over conventional CSs after FNF. Replacing all internal fixations with BNs after the healing of FNF may solve the problem of sclerosis formation around CSs to improve bone reconstruction owing to their bioactivity.

A narrative review on the role of magnesium in immune regulation, inflammation, infectious diseases, and cancer

BACKGROUND

Magnesium (Mg) has gained much importance recently because of its unique range of biological functions. It is one of the most significant micronutrients in biological systems. This review aims to outline the immune-regulating actions of Mg and its crucial role in regulating inflammation and immune response to infectious agents and malignancies.

METHODS

We conducted a literature review on MEDLINE, PubMed, EMBASE, Web of Science to determine the impact of Mg on immune regulation in three settings of inflammation, infection, and cancer. We thoroughly examined all abstracts and full-text articles and selected the most relevant ones for inclusion in this review.

RESULTS

Mg has long been associated with immunological responses, both nonspecific and specific. It plays a pivotal role in diverse immune responses by participating in multiple mechanisms. It facilitates substance P binding to lymphoblasts, promotes T helper, B cell, and macrophage responses to lymphokines, and facilitates antibody-dependent cytolysis and immune cell adherence. Besides, Mg serves as a cofactor for C'3 convertase and immunoglobulin synthesis. It additionally boasts a significant anti-cancer effect. Chronic Mg deficiency leads to enhanced baseline inflammation associated with oxidative stress, related to various age-associated morbidities. A deficiency of Mg in rodents has been observed to impact the cell-mediated immunity and synthesis of IgG adversely. This deficiency can lead to various complications, such as lymphoma, histaminosis, hypereosinophilia, increased levels of IgE, and atrophy of the thymus. The immunological consequences of Mg deficiency in humans can be influenced by the genetic regulation of Mg levels in blood cells. Mg can also mediate cell cycle progression. There has been a renewed interest in the physiology and therapeutic efficacy of Mg. However, the in-depth mechanisms, their clinical significance, and their importance in malignancies and inflammatory disorders still need to be clarified.

CONCLUSIONS

Mg is essential for optimal immune function and regulating inflammation. Deficiency in Mg can lead to temporary or long-term immune dysfunction. A balanced diet usually provides sufficient Mg, but supplementation may be necessary in some cases. Excessive supplementation can have negative impacts on immune function and should be avoided. This review provides an update on the importance of Mg in an immune response against cancer cells and infectious agents and how it regulates inflammation, oxidative stress, cell progression, differentiation, and apoptosis.

Prevention of sclerosis around cannulated screw after treatment of femoral neck fractures with bioceramic nails: a finite element analysis

PURPOSE

Conventional cannulated screws (CS) are the main treatment method for femoral neck fractures (FNF). However, the rate of femoral head necrosis remains high after FNF treatment. The study aimed to compare the biomechanical features of different internal fixation materials for the treatment of Pauwel type III FNF to explore new strategies for clinical management.

METHODS

A new material was prepared by applying casting, freeze drying and sintering process. The independently developed calcium magnesium silicate ceramic powder and hydrogel solution were evenly mixed to obtain a high-viscosity bio-ink, and a bioceramic nail (BN) with high mechanical strength and high fracture toughness was successfully prepared. Four internal fixations were developed to establish the Pauwel type III FNF and healed fracture finite element models: A, three CSs; B, three BNs; C, two BNs and one CS; D, one BN and two CSs. Von Mises stress and displacement of the implants and femur were observed.

RESULTS

The measured Mg content in ceramic powder was 2.08 wt%. The spectral data confirmed that the ceramic powder has high crystallinity, which coincides with the wollastonite-2 M (PDF# 27-0088). The maximum von Mises stresses for the four models were concentrated in the lower part of the fracture surface, at 318.42 Mpa, 103.52 MPa, 121.16 MPa, and 144.06 MPa in models A, B, C, and D, respectively. Moreover, the maximum Von-mises stresses of the implants of the four models were concentrated near the fracture end at 243.65 MPa (A) and 58.02 MPa (B), 102.18 MPa (C), and 144.06 MPa (D). The maximum displacements of the four models were 5.36 mm (A), 3.41 mm (B), 3.60 mm (C), and 3.71 mm (D). The displacements of the three models with BNs were similar and smaller than that of the triple CS fracture model. In the fracture healing models with and without three CSs, the greatest stress concentration was scattered among the lowest screw tail, femoral calcar region, and lateral femur shaft. The displacement and stress distributions in both models are generally consistent. The stress distribution and displacement of the three healed femoral models with BNs were essentially identical to the healing models with three CSs. The maximum von Mises stresses were 65.94 MPa (B), 64.61 MPa (C), and 66.99 MPa (D) while the maximum displacements of the three healed femoral models were 2.49 mm (B), 2.56 mm (C), and 2.49 mm (D), respectively.

CONCLUSIONS

Bioceramic nails offer greater advantages than conventional canulated screws after femoral neck fractures. However, the combination of bioceramic nails and CSs is more clinically realistic; replacing all internal fixations with bioceramic nails after the healing of femoral neck fractures can solve the problem of sclerosis formation around CSs and improve bone reconstruction by their bioactivity.

Association between Serum Magnesium and Fractures: A Systematic Review and Meta-Analysis of Observational Studies

Magnesium, an essential cation for numerous cellular processes, is a major component of bone. However, its relationship with the risk of fractures is still uncertain. The present systematic review and meta-analysis aim to investigate the impact of serum Mg on the risk of incident fractures. A systematic search was conducted using several databases including PubMed/Medline and Scopus from inception to 24 May 2022, including observational studies investigating serum Mg and the incidence of fractures considered as outcomes. Abstract and full-text screenings, data extractions, and risk of bias assessments were conducted by two investigators independently. Any inconsistencies were resolved by consensus with a third author. The Newcastle-Ottawa Scale was used to assess the study quality/risk of bias. Among 1332 records initially screened, 16 were retrieved as full-texts; of them, four papers were included in the systematic review with a total of 119,755 participants. We found that lower serum Mg concentrations were associated with a significantly higher risk of incident fractures (RR = 1.579; 95%CI: 1.216-2.051; p = 0.001; I2 = 46.9%). Our systematic review with meta-analysis suggests a strong association of serum Mg concentrations with incident fractures. Further research is needed to confirm our results among other populations and to assess whether serum Mg is potentially relevant in the prevention of fractures, which continue to increase and represent a significant health burden due to the associated disability.

The Localized Ionic Microenvironment in Bone Modelling/Remodelling: A Potential Guide for the Design of Biomaterials for Bone Tissue Engineering

Bone is capable of adjusting size, shape, and quality to maintain its strength, toughness, and stiffness and to meet different needs of the body through continuous remodeling. The balance of bone homeostasis is orchestrated by interactions among different types of cells (mainly osteoblasts and osteoclasts), extracellular matrix, the surrounding biological milieus, and waste products from cell metabolisms. Inorganic ions liberated into the localized microenvironment during bone matrix degradation not only form apatite crystals as components or enter blood circulation to meet other bodily needs but also alter cellular activities as molecular modulators. The osteoinductive potential of inorganic motifs of bone has been gradually understood since the last century. Still, few have considered the naturally generated ionic microenvironment's biological roles in bone remodeling. It is believed that a better understanding of the naturally balanced ionic microenvironment during bone remodeling can facilitate future biomaterial design for bone tissue engineering in terms of the modulatory roles of the ionic environment in the regenerative process.

Divergent effects of sex and calcium/vitamin D supplementation on serum magnesium and markers of bone structure and function during initial military training

Maintaining Mg status may be important for military recruits, a population that experiences high rates of stress fracture during initial military training (IMT). The objectives of this secondary analysis were to (1) compare dietary Mg intake and serum Mg in female and male recruits pre- and post-IMT, (2) determine whether serum Mg was related to parameters of bone health pre-IMT, and (3) whether Ca and vitamin D supplementation (Ca/vitamin D) during IMT modified serum Mg. Females (n 62) and males (n 51) consumed 2000 mg of Ca and 25 μg of vitamin D/d or placebo during IMT (12 weeks). Dietary Mg intakes were estimated using FFQ, serum Mg was assessed and peripheral quantitative computed tomography was performed on the tibia. Dietary Mg intakes for females and males pre-IMT were below the estimated average requirement and did not change with training. Serum Mg increased during IMT in females (0·06 ± 0·08 mmol/l) compared with males (-0·02 ± 0·10 mmol/l; P < 0·001) and in those consuming Ca/vitamin D (0·05 ± 0·09 mmol/l) compared with placebo (0·001 ± 0·11 mmol/l; P = 0·015). In females, serum Mg was associated with total bone mineral content (BMC, β = 0·367, P = 0·004) and robustness (β = 0·393, P = 0·006) at the distal 4 % site, stress-strain index of the polaris axis (β = 0·334, P = 0·009) and robustness (β = 0·420, P = 0·004) at the 14 % diaphyseal site, and BMC (β = 0·309, P = 0·009) and stress-strain index of the polaris axis (β = 0·314, P = 0·006) at the 66 % diaphyseal site pre-IMT. No significant relationships between serum Mg and bone measures were observed in males. Findings suggest that serum Mg may be modulated by Ca/vitamin D intake and may impact tibial bone health during training in female military recruits.

Magnesium Status and Ca/Mg Ratios in a Series of Children and Adolescents with Chronic Diseases

Magnesium (Mg) is an essential divalent cation involved in various enzymatic reactions that regulate vital biological functions. The main goal was to evaluate Mg status and its association with nutritional indicators in 78 children and adolescents with chronic diseases. We assessed anthropometric, biochemical, diet, body composition, and bone densitometry valuations. Serum Mg and Ca levels were determined using the standardized method and diet calcium (Ca) and Mg consumption by a prospective 72 h diet survey. Mean serum Ca (9.9 mg/dL), Mg (2.08 mg/dL) dietary Ca (102% DRI: Dietary Reference Intake), and Mg intake (105% DRI) were normal. A total of 45% had hypomagnesemia, 12% had hypermagnesemia, and 26% and 24% had inadequate and high Mg intake, respectively. Only 6% of patients had poor Mg intake and hypomagnesemia, and 54% and 90% of our series had an elevated serum Ca/Mg ratio > 4.70 (mean 4.79) and a low Ca/Mg intake ratio < 1.70 (mean 1.06), respectively. Both Ca/Mg ratios were linked with the risk of developing other chronic conditions such as cardiovascular disease, type 2 diabetes, syndrome metabolic, and even several cancers. Therefore, 79% of children and adolescents with chronic diseases were at elevated risk of having abnormal Mg status and developing other chronic illnesses.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Antimicrobial Polymeric Composites with Embedded Nanotextured Magnesium Oxide

Nanotextured magnesium oxide (MgO) can exhibit both antibacterial and tissue regeneration activity, which makes it very useful for implant protection. To successfully combine these two properties, MgO needs to be processed within an appropriate carrier system that can keep MgO surface available for interactions with cells, slow down the conversion of MgO to the less active hydroxide and control MgO solubility. Here we present new composites with nanotextured MgO microrods embedded in different biodegradable polymer matrixes: poly-lactide-co-glycolide (PLGA), poly-lactide (PLA) and polycaprolactone (PCL). Relative to their hydrophilicity, polarity and degradability, the matrices were able to affect and control the structural and functional properties of the resulting composites in different manners. We found PLGA matrix the most effective in performing this task. The application of the nanotextured 1D morphology and the appropriate balancing of MgO/PLGA interphase interactions with optimal polymer degradation kinetics resulted in superior bactericidal activity of the composites against either planktonic E. coli or sessile S. epidermidis, S. aureus (multidrug resistant-MRSA) and three clinical strains isolated from implant-associated infections (S. aureus, E. coli and P. aeruginosa), while ensuring controllable release of magnesium ions and showing no harmful effects on red blood cells.

The Role of Disturbed Mg Homeostasis in Chronic Kidney Disease Comorbidities

Some of the critical mechanisms that mediate chronic kidney disease (CKD) progression are associated with vascular calcifications, disbalance of mineral metabolism, increased oxidative and metabolic stress, inflammation, coagulation abnormalities, endothelial dysfunction, or accumulation of uremic toxins. Also, it is widely accepted that pathologies with a strong influence in CKD progression are diabetes, hypertension, and cardiovascular disease (CVD). A disbalance in magnesium (Mg) homeostasis, more specifically hypomagnesemia, is associated with the development and progression of the comorbidities mentioned above, and some mechanisms might explain why low serum Mg is associated with negative clinical outcomes such as major adverse cardiovascular and renal events. Furthermore, it is likely that hypomagnesemia causes the release of inflammatory cytokines and C-reactive protein and promotes insulin resistance. Animal models have shown that Mg supplementation reverses vascular calcifications; thus, clinicians have focused on the potential benefits that Mg supplementation may have in humans. Recent evidence suggests that Mg reduces coronary artery calcifications and facilitates peripheral vasodilation. Mg may reduce vascular calcification by direct inhibition of the Wnt/β-catenin signaling pathway. Furthermore, Mg deficiency worsens kidney injury induced by an increased tubular load of phosphate. One important consequence of excessive tubular load of phosphate is the reduction of renal tubule expression of α-Klotho in moderate CKD. Low Mg levels worsen the reduction of Klotho induced by the tubular load of phosphate. Evidence to support clinical translation is yet insufficient, and more clinical studies are required to claim enough evidence for decision-making in daily practice. Meanwhile, it seems reasonable to prevent and treat Mg deficiency. This review aims to summarize the current understanding of Mg homeostasis, the potential mechanisms that may mediate the effect of Mg deficiency on CKD progression, CVD, and mortality.

General Aspects of Metal Ions as Signaling Agents in Health and Disease

This review focuses on the current knowledge on the involvement of metal ions in signaling processes within the cell, in both physiological and pathological conditions. The first section is devoted to the recent discoveries on magnesium and calcium-dependent signal transduction-the most recognized signaling agents among metals. The following sections then describe signaling pathways where zinc, copper, and iron play a key role. There are many systems in which changes in intra- and extra-cellular zinc and copper concentrations have been linked to important downstream events, especially in nervous signal transduction. Iron signaling is mostly related with its homeostasis. However, it is also involved in a recently discovered type of programmed cell death, ferroptosis. The important differences in metal ion signaling, and its disease-leading alterations, are also discussed.

Magnesium, Oxidative Stress, Inflammation, and Cardiovascular Disease

Hypomagnesemia is commonly observed in heart failure, diabetes mellitus, hypertension, and cardiovascular diseases. Low serum magnesium (Mg) is a predictor for cardiovascular and all-cause mortality and treating Mg deficiency may help prevent cardiovascular disease. In this review, we discuss the possible mechanisms by which Mg deficiency plays detrimental roles in cardiovascular diseases and review the results of clinical trials of Mg supplementation for heart failure, arrhythmias and other cardiovascular diseases.

Magnesium Deficiency Causes Transcriptional Downregulation of Kir2.1 and Kv4.2 Channels in Cardiomyocytes Resulting in QT Interval Prolongation

BACKGROUND

Mechanisms for QT interval prolongation and cardiac arrhythmogenesis in hypomagnesemia are poorly understood. This study investigated the potential molecular mechanism for QT prolongation caused by magnesium (Mg) deficiency in rats by using the patch clamp technique and molecular biology.

METHODS AND RESULTS

Male Wistar rats were fed an Mg-free diet or a normal diet for up to 12 weeks. There was QT prolongation in the ECG of Mg-deficient rats, and cardiomyocytes from these rats showed prolongation of action potential duration. Electrophysiological studies showed that inward-rectifying K+current (IK1) and transient outward K+current (Ito) were decreased in Mg-deficient cardiomyocytes, and these findings were consistent with the downregulation of mRNA, as well as protein levels of Kir2.1 and Kv4.2. In Mg-deficient cardiomyocytes, transcription factors, GATA4 and NFAT, were upregulated, whereas CREB was downregulated. In contrast to Mg deficiency, cellular Mg2+overload in cultured cardiomyocytes resulted in the upregulation of Kir2.1 and Kv4.2, which was accompanied by the downregulation of GATA4 and NFATc4, and the upregulation of CREB. Activation of NFAT and inhibition of CREB reduced Kv4.2-Ito, whereas Kir2.1-IK1was reduced by CREB inhibition but not by NFTA activation.

CONCLUSIONS

Intracellular Mg deficiency downregulates IK1and Itoin cardiomyocytes, and this is mediated by the transcription factors, NFAT and CREB. These results provide a novel mechanism for the long-term QT interval prolongation in hypomagnesemia.

Dietary Magnesium, Vitamin D, and Animal Protein Intake and Their Association to the Linear Growth Trajectory of Children from Birth to 24 Months of Age: Results From MAL-ED Birth Cohort Study Conducted in Dhaka, Bangladesh

BACKGROUND

Evidence suggests lack of understanding of the association of specific nutrients with different time points of linear growth trajectory.

OBJECTIVE

We investigated the role of dietary macro- and micronutrients on length-for-age z (LAZ) score trajectory of children across first 24 months of their life.

METHODS

The MAL-ED Bangladesh birth cohort study recruited 265 healthy newborn children after birth. The linear growth trajectory of those children was modeled using latent growth curve modeling (LGCM) technique.

RESULTS

Dietary magnesium intake at 9 to 11 months was positively associated (coefficient β = 0.006, P < .02) with LAZ at 12 months. Animal protein intake at 15 to 17 months, in turn, was positively associated (β = 0.03, P < .03) with LAZ at 18 months. However, vitamin D intake at 15 to 17 months was negatively associated (β = -0.06, P < .02) with LAZ at 18 months. Other micro- and macronutrients did not show any statistically significant association with the linear growth trajectory. We also found that birth weight (β = 0.91, P < .01), treating water (β = 0.35, P < 0.00), and maternal height (β = 3.4, P < .00) were positively associated with intercept. Gender had a significant negative association with the intercept, but a positive association with the slope (β = -0.39, P < .01; β = 0.08, P < .04), respectively. Conversely, birth weight had negative association with the slope (β = -0.12, P < .01).

CONCLUSIONS

Dietary magnesium and animal protein were positively and vitamin D was negatively associated with the linear growth trajectory. Maternal height, birth weight, gender, and treatment of drinking water also played significant roles in directing the trajectory.

Magnesium: An old player revisited in the context of CKD-MBD

Chronic kidney disease (CKD) is associated with a wide number of abnormalities in mineral metabolism. Often, these alterations are the leading players in the development of comorbidities associated with CKD, which are risk factors of mortality. In this context, mineral and bone disorder associated with CKD (CKD-MBD) are highlighted, connecting bone, renal, and cardiovascular disorders. Many studies have been led to propose strategies to avoid, reduce, or slow down CKD-MBD progression using different compositions of metallic elements-based P binders such as aluminum, magnesium, or calcium. Magnesium, the aim of this review, has been used by nephrologists to treat CKD-MBD with a variable acceptation due mainly to different results on bone homeostasis. Nowadays, we have new evidence about the efficacy of magnesium supplementation on vascular calcification, renal function, and bone disorders, suggesting potential beneficial effects of Magnesium in the management of CKD-MBD.

The effect of increasing dialysate magnesium on calciprotein particles, inflammation and bone markers: post hoc analysis from a randomized controlled clinical trial

Background

The formation of calciprotein particles (CPPs) may be an important component of the humoral defences against ectopic calcification. Although magnesium (Mg) has been shown to delay the transition of amorphous calcium-/phosphate-containing primary CPP (CPP-1) to crystalline apatite-containing secondary CPP (CPP-2) ex vivo, effects on the endogenous CPP pool are unknown.

Methods

We used post hoc analyses from a randomized double-blind parallel-group controlled clinical trial of 28 days treatment with high dialysate Mg of 2.0 mEq/L versus standard dialysate Mg of 1.0 mEq/L in 57 subjects undergoing maintenance hemodialysis for end-stage kidney disease. CPP load, markers of systemic inflammation and bone turnover were measured at baseline and follow-up.

Results

After 28 days of treatment with high dialysate Mg, serum total CPP (−52%), CPP-1 (−42%) and CPP-2 (−68%) were lower in the high Mg group (all P &lt; 0.001) but were unchanged in the standard dialysate Mg group. Tumour necrosis factor-α (−20%) and interleukin-6 (−22%) were also reduced with high dialysate Mg treatment (both P &lt; 0.01). High dialysate Mg resulted in higher levels of bone-specific alkaline phosphatase (a marker of bone formation) (+17%) but lower levels of tartrate-resistant acid phosphatase 5 b (a marker of bone resorption; −33%) (both P &lt; 0.01). Inflammatory cytokines and bone turnover markers were unchanged in the standard dialysate Mg group over the same period.

Conclusions

In this exploratory analysis, increasing dialysate Mg was associated with reduced CPP load and systemic inflammation and divergent changes in markers of bone formation and resorption.

Anthropometry before Day 46 and Growth Velocity before 6 Months of Guatemalan Breastfed Infants Are Associated with Subclinical Mastitis and Milk Cytokines, Minerals, and Trace Elements

BACKGROUND

Subclinical mastitis (SCM) is an inflammatory condition of the mammary gland, but its association with human milk composition and infant growth is not well described.

OBJECTIVES

We investigated whether SCM, milk cytokines, and/or estimated intakes of milk minerals and trace elements were associated with infant anthropometry or growth velocity before 6 mo.

METHODS

Breast milk was collected from Mam-Mayan mothers (n = 114) at both early (2-46 d) and established (4-6 mo) lactation. Concentrations of 9 elements (sodium, potassium, calcium, magnesium, copper, iron, manganese, selenium, zinc) analyzed by inductively-coupled plasma mass spectrometry were used to estimate infants' daily intakes. Concentrations of 4 cytokines were measured. Milk concentrations and infants' estimated elemental intakes and anthropometric measurements during early and established lactation were compared by SCM status. Multiple regression was used to identify factors associated with infant growth attainment (<46 d) for infant weight- (WAZ), length- (LAZ), and head circumference-for-age (HCAZ) and weight-for-length (WLZ) z scores and with growth velocity (expressed as Δ/d) from early to established lactation.

RESULTS

SCM prevalence was higher in early (30%) than established (10%) lactation. Breast milk of SCM mothers had higher cytokine concentrations and higher magnesium in early and higher selenium concentrations in both early and established lactation (Padj < 0.0121). At day 46, regression models showed inverse associations of SCM with WLZ and IL-1β with LAZ (Padj < 0.0150). In contrast, linear growth velocity was positively associated with IL-1β measured in early lactation (Padj < 0.0124), whereas cranial growth velocity was positively associated with IL-8 measured during established lactation ( Padj < 0.0124).

CONCLUSIONS

Despite a high prevalence of inadequate intakes, only infants' intake of milk magnesium during early lactation was associated with linear growth velocity in breastfed infants <6 mo. Evidence shows that SCM, breast-milk cytokines, and infants' estimated intakes of select elements are independently associated with growth attainment and growth velocity during lactation.

A Direct Quantitative Analysis of Erythrocyte Intracellular Ionized Magnesium in Physiological and Pathological Conditions

Magnesium (Mg²⁺) is an endogenous cation that is involved in many essential biological reactions. Abnormal Mg²⁺ metabolisms in the body affect important physiological and pathological processes. However, most endogenous Mg²⁺ markers fail to represent body Mg²⁺ status; they are disadvantageous in terms of representational capacity, applied range, operational convenience, etc. In this article, we evaluated some of the most popular Mg²⁺ marker candidates. A logical model of the blood Mg²⁺ compartments was established, which consisted of unstable Mg²⁺ pools, representative Mg²⁺ pools, and conserved Mg²⁺ pools. These pools were based on the metabolic efficiency of Mg²⁺ in an acute Mg²⁺ intake test. The results of this study showed that only the erythrocyte intracellular ionized Mg²⁺ (RBC [Mg²⁺]_i), a representative Mg²⁺ pool, could effectively represent abnormal body Mg²⁺ metabolisms in various conditions, including dietary Mg²⁺ adjustments, aging and metabolic syndrome. These results suggest that RBC [Mg²⁺]_i might be a widely applicable marker of body Mg²⁺ levels. On unified technology platform and evaluation system, this research compared the representative capacities of RBC [Mg²⁺]_i, plasma Mg²⁺ concentration (plasma [Mg²⁺]), erythrocyte intracellular total Mg (RBC [Mg]_total) and Mg retention in rats and mice under various Mg²⁺-metabolism-related physiological and pathological conditions. Our technique for the direct quantitative analysis of RBC [Mg²⁺]_i may prove valuable for basic physiological research, dietary Mg²⁺ regulation, as well as clinical monitoring/intervention of Mg²⁺-metabolism-related pathology.

In vitro Chondrocyte Responses in Mg-doped Wollastonite/Hydrogel Composite Scaffolds for Osteochondral Interface Regeneration

The zone of calcified cartilage (ZCC) is the mineralized region between the hyaline cartilage and subchondral bone and is critical in cartilage repair. A new non-stoichiometric calcium silicate (10% Ca substituted by Mg; CSi-Mg10) has been demonstrated to be highly bioactive in an osteogenic environment in vivo. This study is aimed to systematically evaluate the potential to regenerate osteochondral interface with different amount of Ca-Mg silicate in hydrogel-based scaffolds, and to compare with the scaffolds containing conventional Ca-phosphate biomaterials. Hydrogel-based porous scaffolds combined with 0-6% CSi-Mg10, 6% β-tricalcium phosphate (β-TCP) or 6% nanohydroxyapatite (nHAp) were made with three-dimensional (3D) printing. An increase in CSi-Mg10 content is desirable for promoting the hypertrophy and mineralization of chondrocytes, as well as cell proliferation and matrix deposition. Osteogenic and chondrogenic induction were both up-regulated in a dose-dependent manner. In comparison with the scaffolds containing 6% β-TCP or nHAp, human deep zone chondrocytes (hDZCs) seeded on CSi-Mg10 scaffold of equivalent concentration exhibited higher mineralization. It is noteworthy that the hDZCs in the 6% CSi-Mg10 scaffolds maintained a higher expression of the calcified cartilage zone specific extracellular matrix marker and hypertrophic marker, collagen type X. Immunohistochemical and Alizarin Red staining reconfirmed these findings. The study demonstrated that hydrogel-based hybrid scaffolds containing 6% CSi-Mg10 are particularly desirable for inducing the formation of calcified cartilage.

Dietary Magnesium and Chronic Disease

Although official magnesium (Mg) dietary reference intakes are open to question, a significant number of adults likely have intakes that are in the range of 50%-99% of the requirement. This moderate or marginal (subclinical) deficient Mg intake generally is asymptomatic. Animal studies, however, indicate that moderate or subclinical Mg deficiency primes phagocytic cells for the release of proinflammatory cytokines leading to chronic inflammatory and oxidative stress. Human studies have found that dietary Mg is inversely related to serum or plasma C-reactive protein (CRP). Individuals with apparently deficient Mg intakes have an increased likelihood of serum or plasma CRP ≥3.0 mg/L, considered an indicator of chronic inflammatory stress that increases the risk for chronic disease. In addition, elevated serum or plasma CRP in individuals with chronic disease is decreased by Mg supplementation, which suggests that Mg decreases the risk for chronic disease. The importance of dietary Mg intake on the risk for chronic disease through affecting inflammatory and oxidative stress is supported by numerous meta-analyses and systematic reviews that have found dietary Mg is inversely associated with chronic diseases such hypertension, ischemic heart disease, stroke, metabolic syndrome, diabetes, and colorectal cancer.

Magnesium as a Calcification Inhibitor

Vascular calcification (VC) is associated with elevated cardiovascular mortality rates in patients with CKD. Recent clinical studies of patients with advanced CKD have observed an association between low serum magnesium (Mg) levels on one hand and elevated VC and cardiovascular mortality on the other. These findings have stimulated interest in understanding Mg's impact on CKD in general and the associated VC in particular. In vitro and preclinical in vivo data indicate that Mg has the potential to protect vascular smooth muscle cells against calcification via several different molecular mechanisms. Accordingly, data from pilot interventional studies in the clinic suggest that oral Mg supplementation reduces VC in patients with CKD. The present review provides an overview of our current understanding of the impact of Mg on the development of VC in patients with CKD.

Applications of Metals for Bone Regeneration

The regeneration of bone tissue is the main purpose of most therapies in dental medicine. For bone regeneration, calcium phosphate (CaP)-based substitute materials based on natural (allo- and xenografts) and synthetic origins (alloplastic materials) are applied for guiding the regeneration processes. The optimal bone substitute has to act as a substrate for bone ingrowth into a defect, as well as resorb in the time frame needed for complete regeneration up to the condition of restitution ad integrum. In this context, the modes of action of CaP-based substitute materials have been frequently investigated, where it has been shown that such materials strongly influence regenerative processes such as osteoblast growth or differentiation and also osteoclastic resorption due to different physicochemical properties of the materials. However, the material characteristics needed for the required ratio between new bone tissue formation and material degradation has not been found, until now. The addition of different substances such as collagen or growth factors and also of different cell types has already been tested but did not allow for sufficient or prompt application. Moreover, metals or metal ions are used differently as a basis or as supplement for different materials in the field of bone regeneration. Moreover, it has already been shown that different metal ions are integral components of bone tissue, playing functional roles in the physiological cellular environment as well as in the course of bone healing. The present review focuses on frequently used metals as integral parts of materials designed for bone regeneration, with the aim to provide an overview of currently existing knowledge about the effects of metals in the field of bone regeneration.

Magnesium deficiency and increased inflammation: current perspectives

Animal studies have shown that magnesium deficiency induces an inflammatory response that results in leukocyte and macrophage activation, release of inflammatory cytokines and acute-phase proteins, and excessive production of free radicals. Animal and in vitro studies indicate that the primary mechanism through which magnesium deficiency has this effect is through increasing cellular Ca²⁺, which is the signal that results in the priming of cells to give the inflammatory response. Primary pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL)-1; the messenger cytokine IL-6; cytokine responders E-selectin, intracellular adhesion molecule-1 and vascular cell adhesion molecule-1; and acute-phase reactants C-reactive protein and fibrinogen have been determined to associate magnesium deficiency with chronic low-grade inflammation (inflammatory stress). When magnesium dietary intake, supplementation, and/or serum concentration suggest/s the presence of magnesium deficiency, it often is associated with low-grade inflammation and/or with pathological conditions for which inflammatory stress is considered a risk factor. When magnesium intake, supplementation, and/or serum concentration suggest/s an adequate status, magnesium generally has not been found to significantly affect markers of chronic low-grade inflammation or chronic disease. The consistency of these findings can be modified by other nutritional and metabolic factors that affect inflammatory and oxidative stress. In spite of this, findings to date provide convincing evidence that magnesium deficiency is a significant contributor to chronic low-grade inflammation that is a risk factor for a variety of pathological conditions such as cardiovascular disease, hypertension, and diabetes. Because magnesium deficiency commonly occurs in countries where foods rich in magnesium are not consumed in recommended amounts, magnesium should be considered an element of significant nutritional concern for health and well-being in these countries.

Dual modulation of bone formation and resorption with zoledronic acid-loaded biodegradable magnesium alloy implants improves osteoporotic fracture healing: An in vitro and in vivo study

Osteoporotic fracture (OPF) remains a major clinical challenge for skeletal regeneration. Impaired osteogenesis and excessive remodeling result in prolonged and poor quality of fracture healing. To augment bone formation and inhibit excessive resorption simultaneously, we constructed a biodegradable magnesium-based implant integrated with the anti-catabolic drug zoledronic acid (ZA); this implant exhibits controllable, sustained release of magnesium degradation products and ZA in vitro. The extracts greatly stimulate the osteogenic differentiation of rat-bone marrow-derived mesenchymal stem cells (rBMSCs), while osteoclastogenesis is inhibited by ZA. Implantation of intramedullary nails to fix femur fracture in ovariectomy-induced osteoporotic rats for up to 12 weeks demonstrates magnesium implants alone can enhance OPF repair through promoting callus formation compared to conventional stainless steel, while the combinatory treatment with local ZA release from implant coating further increases bone regeneration rate and callus size, remarkably improves bone quality and mechanical strength and suppresses osteoclasts and bone remodeling, due to the synergistic effect of both agents. The slow and uniform degradation of the implant ensures a steady decrease in bending force, which meets clinical requirements. In summary, biodegradable magnesium-based implants can locally co-deliver magnesium degradation products and zoledronic acid in a controlled manner, and can be superior alternatives for the reconstruction of osteoporosis-related fracture.

STATEMENT OF SIGNIFICANCE

Management of osteoporotic fracture has posed a major challenge in orthopedics, as the imbalance between diminished osteogenesis and excessive bone remodeling often leads to delayed and compromised fracture repair. Among various efforts expended on augmenting osteoporotic fracture healing, herein we reported a new strategy by engineering and utilizing a biodegradable magnesium-based implant integrated with local drug delivery, specifically, zoledronic acid (ZA)-loaded polylactic acid/brushite bilayer coating on a biodegradable Mg-Nd-Zn-Zr alloy (denoted as Mg/ZA/CaP), aiming to combine the favorable properties of Mg and zoledronic acid for simultaneous modulation of bone formation and bone resorption. In vitro and in vivo studies demonstrated its superior treatment efficacy along with adequate degradation. It stimulated new bone formation while suppressing remodeling, ascribed to the local release of magnesium degradation products and zoledronic acid. To our knowledge, the enhanced fracture repair capability of Mg-based implants was for the first time demonstrated in an osteoporotic fracture animal model. This innovative biodegradable Mg-based orthopedic implant presents great potential as a superior alternative to current internal fixation devices for treating osteoporotic fracture.

Magnesium and Risk of Hip Fracture among Patients Undergoing Hemodialysis

Magnesium is an essential mineral for bone metabolism. However, little is known about the relationship between magnesium and the risk of fractures. In this cohort study, we elucidated the association between serum magnesium level and the risk of incident hip fracture among patients undergoing hemodialysis. We identified 113,683 patients undergoing hemodialysis with no history of hip fracture from a nation-wide database of patients undergoing dialysis in Japan. During a 2-year follow-up, a total of 2305 (2%) new hip fractures occurred. The crude incidence rate was significantly higher among patients in the lower quartiles of serum magnesium levels (2.63%, 2.08%, 1.76%, and 1.49% in Q1-Q4, respectively; P<0.001 for trend). The range of serum magnesium levels (in milligrams per deciliter) in each quartile was as follows: Q1, <2.3; Q2, 2.4-2.6; Q3, 2.7-2.8, and Q4, >2.9. After adjustment for demographic and clinical factors, patients in Q1 had a 1.23-fold higher risk for hip fracture than those in Q4 (95% confidence interval, 1.06 to 1.44; P<0.01). Similarly, an inverse probability weighting analysis showed an increased risk of hip fracture among patients in the lower magnesium quartiles. We did not observe significant effect modifications in subgroup analyses. The population-attributable fraction of serum magnesium level for incident hip fractures was 13.7% (95% confidence interval, 3.7% to 22.7%), which was much higher than that of serum calcium, serum phosphate, and parathyroid hormone levels. Thus, mild hypermagnesemia is associated with a lower risk of hip fracture among patients undergoing hemodialysis.

Biocompatibility and bioactivity of porous polymer-derived Ca-Mg silicate ceramics

Magnesium is a trace element in the human body, known to have important effects on cell differentiation and the mineralisation of calcified tissues. This study aimed to synthesise highly porous Ca-Mg silicate foamed scaffolds from preceramic polymers, with analysis of their biological response. Akermanite (Ak) and wollastonite-diopside (WD) ceramic foams were obtained from the pyrolysis of a liquid silicone mixed with reactive fillers. The porous structure was obtained by controlled water release from selected fillers (magnesium hydroxide and borax) at 350°C. The homogeneous distribution of open pores, with interconnects of modal diameters of 160-180μm was obtained and maintained after firing at 1100°C. Foams, with porosity exceeding 80%, exhibited compressive strength values of 1-2MPa. In vitro studies were conducted by immersion in SBF for 21days, showing suitable dissolution rates, pH and ionic concentrations. Cytotoxicity analysis performed in accordance with ISO10993-5 and ISO10993-12 standards confirmed excellent biocompatibility of both Ak and WD foams. In addition, MC3T3-E1 cells cultured on the Mg-containing scaffolds demonstrated enhanced osteogenic differentiation and the expression of osteogenic markers including Collagen Type I, Osteopontin and Osteocalcin, in comparison to Mg-free counterparts. The results suggest that the addition of magnesium can further enhance the bioactivity and the potential for bone regeneration applications of Ca-silicate materials.

STATEMENTS OF SIGNIFICANCE

Here, we show that the incorporation of Mg in Ca-silicates plays a significant role in the enhancement of the osteogenic differentiation and matrix formation of MC3T3-E1 cells, cultured on polymer-derived highly porous scaffolds. Reduced degradation rates and improved mechanical properties are also observed, compared to Mg-free counterparts, suggesting the great potential of Ca-Mg silicates as bone tissue engineering materials. Excellent biocompatibility of the new materials, in accordance to the ISO10993-5 and ISO10993-12 standard guidelines, confirms the preceramic polymer route as an efficient synthesis methodology for bone scaffolds. The use of hydrated fillers as porogens is an additional novelty feature presented in the manuscript.

Effects of Treatment of Treadmill Combined with Electro-Acupuncture on Tibia Bone Mass and Substance PExpression of Rabbits with Sciatic Nerve Injury

The peripheral nervous system may play an important role in normal bone maintenance and remodeling. Substance P (SP) is a neuropeptide associated with bone loss and formation that may mediate the effects of the nervous system. The purpose of this study is to determine if treadmill running combined with electro-acupuncture at Jiaji acupoints (Jiaji-EA) affects tibial bone mass and SP expression in rabbits with sciatic nerve injury. Twenty-four juvenile male New Zealand white rabbits were randomly assigned to one of 4 groups: sham injury control (sham), sciatic never crush control (SNCr), treadmill running (treadmill), and Jiaji-EA combined with treadmill running (ET group). The SNCr, treadmill, and ET groups all had an induced sciatic never crush injury of approximately 2mm. Control groups received no intervention; the treadmill and ET groups were trained by treadmill; the ET group also received Jiaji-EA. After the 4 weeks of treatment, toe-spreading index (TSI), BMD, bone strength, and SP expression in the tibia were significantly lower in the nerve injury groups (SNCr, treadmill, and ET) compared to the sham groups (p<0.05). Treatment (treadmill and ET groups) increased all measures compared to the SNCr group (p<0.05). Further, TSI, BMD, bone strength, and SP expression in the ET group were higher than the treadmill group (p<0.05). Our results indicate that treadmill therapy combined with electro-acupuncture at Jiaji acupoints prevents bone loss in rabbit tibias after sciatic nerve injury. This may occur in two ways: indirectly in association with axon regeneration and directly via loading on the bone mediated through increased SP expression. This study provides important evidence for the clinical treatment of bone loss after peripheral nerve injury.

Perspective: The Case for an Evidence-Based Reference Interval for Serum Magnesium: The Time Has Come

The 2015 Dietary Guidelines Advisory Committee indicated that magnesium was a shortfall nutrient that was underconsumed relative to the Estimated Average Requirement (EAR) for many Americans. Approximately 50% of Americans consume less than the EAR for magnesium, and some age groups consume substantially less. A growing body of literature from animal, epidemiologic, and clinical studies has demonstrated a varied pathologic role for magnesium deficiency that includes electrolyte, neurologic, musculoskeletal, and inflammatory disorders; osteoporosis; hypertension; cardiovascular diseases; metabolic syndrome; and diabetes. Studies have also demonstrated that magnesium deficiency is associated with several chronic diseases and that a reduced risk of these diseases is observed with higher magnesium intake or supplementation. Subclinical magnesium deficiency can exist despite the presentation of a normal status as defined within the current serum magnesium reference interval of 0.75-0.95 mmol/L. This reference interval was derived from data from NHANES I (1974), which was based on the distribution of serum magnesium in a normal population rather than clinical outcomes. What is needed is an evidenced-based serum magnesium reference interval that reflects optimal health and the current food environment and population. We present herein data from an array of scientific studies to support the perspective that subclinical deficiencies in magnesium exist, that they contribute to several chronic diseases, and that adopting a revised serum magnesium reference interval would improve clinical care and public health.

Moderately Low Magnesium Intake Impairs Growth of Lean Body Mass in Obese-Prone and Obese-Resistant Rats Fed a High-Energy Diet

The physical and biochemical changes resulting from moderately low magnesium (Mg) intake are not fully understood. Obesity and associated co-morbidities affect Mg metabolism and may exacerbate Mg deficiency and physiological effects. Male rats selectively bred for diet-induced obesity (OP, obese-prone) or resistance (OR, obese-resistant) were fed a high-fat, high-energy diet containing moderately low (LMg, 0.116 ± 0.001 g/kg) or normal (NMg, 0.516 ± 0.007 g/kg) Mg for 13 weeks. The growth, body composition, mineral homeostasis, bone development, and glucose metabolism of the rats were examined. OP and OR rats showed differences (p < 0.05) in many physical and biochemical measures regardless of diet. OP and OR rats fed the LMg diet had decreased body weight, lean body mass, decreased femoral size (width, weight, and volume), and serum Mg and potassium concentrations compared to rats fed the NMg diet. The LMg diet increased serum calcium (Ca) concentration in both rat strains with a concomitant decrease in serum parathyroid hormone concentration only in the OR strain. In the femur, Mg concentration was reduced, whereas concentrations of Ca and sodium were increased in both strains fed the LMg diet. Plasma glucose and insulin concentrations in an oral glucose tolerance test were similar in rats fed the LMg or NMg diets. These results show that a moderately low Mg diet impairs the growth of lean body mass and alters femoral geometry and mineral metabolism in OP and OR rats fed a high-energy diet.

Unraveling the role of Mg(++) in osteoarthritis

Mg(++) is widely involved in human physiological processes that may play key roles in the generation and progression of diseases. Osteoarthritis (OA) is a complex joint disorder characterized by articular cartilage degradation, abnormal mineralization and inflammation. Magnesium deficiency is considered to be a major risk factor for OA development and progression. Magnesium deficiency is active in several pathways that have been implicated in OA, including increased inflammatory mediators, cartilage damage, defective chondrocyte biosynthesis, aberrant calcification and a weakened effect of analgesics. Abundant in vitro and in vivo evidence in animal models now suggests that the nutritional supplementation or local infiltration of Mg(++) represent effective therapies for OA. The goal of this review is to summarize the current understanding of the role of Mg(++) in OA with particular emphasis on the related molecular mechanisms involved in OA progression.

Effects of thirty elements on bone metabolism

The human skeleton, made of 206 bones, plays vital roles including supporting the body, protecting organs, enabling movement, and storing minerals. Bones are made of organic structures, intimately connected with an inorganic matrix produced by bone cells. Many elements are ubiquitous in our environment, and many impact bone metabolism. Most elements have antagonistic actions depending on concentration. Indeed, some elements are essential, others are deleterious, and many can be both. Several pathways mediate effects of element deficiencies or excesses on bone metabolism. This paper aims to identify all elements that impact bone health and explore the mechanisms by which they act. To date, this is the first time that the effects of thirty minerals on bone metabolism have been summarized.

Dietary intakes of expeditioners during prolonged sunlight deprivation in polar enviroments do not support bone health

Background

Early Antarctic expeditions were plagued by nutrient deficiencies, due to lack of fresh food and reliance on preserved foods. Modern Antarctic expeditioners also require provisions to be shipped in, but improved knowledge and storage options ensure foods are nutritionally sound. Despite this, nutritional imbalances are observed.

Objectives

To determine the adequacy of dietary intake of Antarctic expeditioners, with reference to bone health.

Design

Dietary intake was determined on 225 adults (mean age 42±11 years, 16% female) during 12-month deployments at Australian Antarctic stations from 2004 to 2010, using weighed 3-day food records. Nutrient intake was analysed using FoodWorks. Foods were divided into the 5 food groups according to the Australian Guide to Healthy Eating.

Results

Men consumed below the recommended levels [recommended daily intake (RDI)/adequate intakes (AI)] of calcium (79±42% of RDI, p<0.001), magnesium (83±34% of RDI, p<0.001), potassium (86±29% of AI, p<0.001) and fibre (75±30% of AI, p<0.001), and above the upper limit (UL) for sodium (125±48% of UL p<0.001), whereas women consumed below the recommended levels of calcium (68±21% of RDI, p<0.001) and iron (73±37% of RDI, p<0.001). Vitamin D intake is not substantial (<150 IU/d). Men consumed more alcohol than women (18±24 g/d vs. 10±13 g/d, p<0.05), nearer the guideline of ≤20 g/d. Men and women consumed approximately 1 serving of dairy food per day, and 3 of 5 recommended vegetable servings. Discretionary foods were consumed in excess of recommended.

Conclusions

Improving consumption of calcium-rich (dairy) foods better supports bone health during sunlight deprivation. Increasing vegetable intake to recommended levels will increase fibre, potassium and magnesium intakes. The challenge is the logistics of providing these foods throughout the year.

Dietary magnesium and potassium intakes and circulating magnesium are associated with heel bone ultrasound attenuation and osteoporotic fracture risk in the EPIC-Norfolk cohort study

BACKGROUND

In our aging population, maintenance of bone health is critical to reduce the risk of osteoporosis and potentially debilitating consequences of fractures in older individuals. Among modifiable lifestyle and dietary factors, dietary magnesium and potassium intakes are postulated to influence bone quality and osteoporosis, principally via calcium-dependent alteration of bone structure and turnover.

OBJECTIVE

We investigated the influence of dietary magnesium and potassium intakes, as well as circulating magnesium, on bone density status and fracture risk in an adult population in the United Kingdom.

DESIGN

A random subset of 4000 individuals from the European Prospective Investigation into Cancer and Nutrition-Norfolk cohort of 25,639 men and women with baseline data was used for bone density cross-sectional analyses and combined with fracture cases (n = 1502) for fracture case-cohort longitudinal analyses (mean follow-up 13.4 y). Relevant biological, lifestyle, and dietary covariates were used in multivariate regression analyses to determine associations between dietary magnesium and potassium intakes and calcaneal broadband ultrasound attenuation (BUA), as well as in Prentice-weighted Cox regression to determine associated risk of fracture. Separate analyses, excluding dietary covariates, investigated associations of BUA and fractures with serum magnesium concentration.

RESULTS

Statistically significant positive trends in calcaneal BUA for women (n = 1360) but not men (n = 968) were apparent across increasing quintiles of magnesium plus potassium (Mg+K) z score intake (P = 0.03) or potassium intake alone (P = 0.04). Reduced hip fracture risk in both men (n = 1958) and women (n = 2755) was evident for individuals in specific Mg+K z score intake quintiles compared with the lowest. Statistically significant trends in fracture risk in men across serum magnesium concentration groups were apparent for spine fractures (P = 0.02) and total hip, spine, and wrist fractures (P = 0.02). None of these individual statistically significant associations remained after adjustment for multiple testing.

CONCLUSIONS

These findings enhance the limited literature studying the association of magnesium and potassium with bone density and demonstrate that further investigation is warranted into the mechanisms involved and the potential protective role against osteoporosis.

Magnesium and cardiovascular complications of chronic kidney disease

Cardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). Abundant experimental evidence suggests a physiological role of magnesium in cardiovascular function, and clinical evidence suggests a role of the cation in cardiovascular disease in the general population. The role of magnesium in CKD-mineral and bone disorder, and in particular its impact on cardiovascular morbidity and mortality in patients with CKD, is however not well understood. Experimental studies have shown that magnesium inhibits vascular calcification, both by direct effects on the vessel wall and by indirect, systemic effects. Moreover, an increasing number of epidemiologic studies in patients with CKD have shown associations of serum magnesium levels with intermediate and hard outcomes, including vascular calcification, cardiovascular events and mortality. Intervention trials in these patients conducted to date have had small sample sizes and have been limited to the study of surrogate parameters, such as arterial stiffness, vascular calcification and atherosclerosis. Randomized controlled trials are clearly needed to determine the effects of magnesium supplementation on hard outcomes in patients with CKD.