Vitamin D: direct effects of vitamin D metabolites on bone: lessons from genetically modified mice

Comparative proteomic exploration of plasma proteins in different levels of vitamin D with type 2 diabetes mellitus using iTRAQ-coupled LC-MS/MS

Objectives

Due to the variety of modern diet and lifestyle changes, China has become the world's largest number of people with T2DM. How to prevent and cure T2DM has become one of the urgent public health events in China. Numerous studies have demonstrated vitamin D (VitD) was independently correlated with insulin sensitivity and β cells function. VitD deficiency occurs in about 70% to 80% of patients with T2DM. However, the reason of T2DM patients suffering from VitD deficiency is not very clear. The aim of this project is to identify biomarkers to explore potential mechanism of VitD deficiency in patients with T2DM.

Methods

We used the iTRAQ-coupled LC-MS/MS technique to screen differential expression proteins between VitD deficiency group and VitD sufficiency group in T2DM patients. Then we carried out hierarchical clustering analysis, Gene Ontology classification and enrichment analysis, KEGG pathway enrichment analysis, protein-protein interaction network (PPI) analysis and ELISA validation.

Results

We identified 63 differentially expressed proteins, 17 proteins were up-regulated and 46 proteins were down-regulated (VitD sufficiency vs. VitD deficiency). We ultimately selected four proteins, Podocalyxin (PODXL), ICAM3, MMP9, ApoF for further verification. As a result, the level of MMP9 and ICAM3 was higher in VitD sufficiency group than VitD deficiency group.

Conclusions

Our study provided a solid theoretical foundation for the study of biomarkers and their mechanisms in most patients with T2DM who suffer from vitamin D deficiency. In addition, MMP9 and ICAM3 may play critical roles in the process of VitD deficiency in T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01456-w.

The multi-faceted nature of age-associated osteoporosis

Age-associated osteoporosis (AAOP) poses a significant health burden, characterized by increased fracture risk due to declining bone mass and strength. Effective prevention and early treatment strategies are crucial to mitigate the disease burden and the associated healthcare costs. Current therapeutic approaches effectively target the individual contributing factors to AAOP. Nonetheless, the management of AAOP is complicated by the multitude of variables that affect its development. Main intrinsic and extrinsic factors contributing to AAOP risk are reviewed here, including mechanical unloading, nutrient deficiency, hormonal disbalance, disrupted metabolism, cognitive decline, inflammation and circadian disruption. Furthermore, it is discussed how these can be targeted for prevention and treatment. Although valuable as individual targets for intervention, the interconnectedness of these risk factors result in a unique etiology for every patient. Acknowledgement of the multifaceted nature of AAOP will enable the development of more effective and sustainable management strategies, based on a holistic, patient-centered approach.

Association of vitamins with bone mineral density and osteoporosis measured by dual-energy x-ray absorptiometry: a cross-sectional study

BACKGROUND

We aimed to assess the associations of vitamins intake with osteoporosis based on a national sample from US adults.

METHODS

A total of 1536 participants were included in this cross-sectional study to investigate the relationship between vitamins intake and osteoporosis from National Health and Nutrition Examination Survey, including vitamin A, C, D. Logistic regression models were used to assess the associations between dietary vitamin intake and osteoporosis.

RESULTS

We found that vitamins intake were negatively associated with osteoporosis. For vitamin A, compared with the first tertile, the odds ratios (ORs) and 95% confidential intervals (CIs) were 0.93 (0.81-1.04) for the second tertile and 0.85 (0.78-0.96) for the third tertile (P < 0.01). For vitamin C, compared with the first tertile, the ORs and 95% CIs were 0.89 (0.78-1.05) for the second tertile and 0.79 (0.67-0.93) for the third tertile (P < 0.01). For vitamin D, compared with the first tertile, the odds ratios (ORs) and 95% confidential intervals (CIs) were 0.94 (0.82-1.07) for the second tertile and 0.88 (0.75-0.98) for the third tertile (P < 0.01). And the negative association between vitamins intake and osteoporosis were more evident for female, aged ≥ 60, and BMI > 30, including vitamin A, C and D.

CONCLUSIONS

Our findings provide evidence that vitamins intake is linked with decreased prevalence of osteoporosis, including vitamin A, C, D. Further large-scale prospective cohort studies are needed to verify our findings.

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Association of bone turnover markers and cognitive function in Chinese chronic schizophrenia patients with or without vitamin D insufficiency

BACKGROUND

Increasing evidence shows that bone turnover markers (BTMs) and vitamin D can affect human cognitive function. However, there are few studies that have investigated the association between BTMs and cognitive function in chronic schizophrenia patients. The aim of this study was to investigate the relationship between BTMs and cognitive function in chronic schizophrenia patients with or without vitamin D insufficiency (VDI).

METHODS

In all, 118 chronic schizophrenia patients were enrolled in this cross-sectional study. Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was applied to evaluate the cognitive function of the subjects. Blood analysis included bone turnover markers, vitamin D levels, and glycolipid levels.

RESULTS

Relative to 72 vitamin D-sufficient (VDS) patients, 46 VDI patients had higher bone resorption markers levels and lower bone formation markers levels. Regression analysis showed that, in the total sample, CTX and language function exhibited independent positive correlation (p = 0.027, R2 change = 0.042), and in the VDS group, procollagen type I N-terminal propeptide (PINP) was independently negatively correlated with language function (p = 0.031, R2 change = 0.065), while the positive correlation between osteopontin (OPN) and delayed memory remained in the VDI group (p = 0.036, R2 change = 0.083).

CONCLUSION

Our study showed an association between the levels of BTMs and cognitive function among chronic schizophrenia patients. This correlation may have different mechanisms of action at different vitamin D levels.

Effects of intermittent or single high-dose vitamin D supplementation on risk of falls and fractures: a systematic review and meta-analysis

Previous randomized controlled trials have reported inconsistent findings regarding the effects of high-dose vitamin D supplementation on a risk of falls and fractures. This meta-analysis of 15 trials shows that intermittent or single high-dose vitamin D supplementation had no preventive effect on the risk of falls and fractures and might even increase the risk of falls.

PURPOSE

Randomized controlled trials (RCTs) have reported controversial findings regarding the associations between intermittent or single high-dose vitamin D supplementation and a risk of falls and fractures in adults. This study aimed to investigate those associations using a systematic review and meta-analysis.

METHODS

We searched PubMed, EMBASE, and Cochrane Library from inception to May 25, 2022. Data were extracted for a random-effects meta-analysis to calculate a pooled relative risk (RR) with a 95% confidence interval (CI).

RESULTS

Out of 527 articles, a total of 15 RCTs were included in the final analysis. In a meta-analysis of RCTs, intermittent or single high-dose vitamin D supplementation showed no significant beneficial effect in the prevention of either falls (RR, 1.03 [95% CI, 0.98-1.09]; I² = 56.6%; n = 11) or fractures (RR, 0.99 [95% CI, 0.87-1.14]; I² = 48.3%; n = 11). Among the subgroup meta-analyses by various factors, intermittent or single high-dose vitamin D supplementation reduced the risk of fractures in the subgroup meta-analysis of RCTs that included fewer than 1000 participants (RR, 0.74 [95% CI 0.57-0.96]; I² = 0.0%; n = 5). However, its beneficial effect was not observed in those including 1000 or more participants (RR, 1.06 [95% CI 0.92-1.21]; I² = 57.5%; n = 6). In contrast, intermittent or single high-dose vitamin D3 supplementation increased the risk of falls on the borderline of statistical significance (RR, 1.06 [95% CI 0.99-1.15]; P = 0.051; I² = 50.0%; n = 7).

CONCLUSIONS

Intermittent or single high-dose vitamin D supplementation had no preventive effect on the risk of falls and fractures and might even increase the risk of falls.

Vitamin D and Bone: A Story of Endocrine and Auto/Paracrine Action in Osteoblasts

Despite its rigid structure, the bone is a dynamic organ, and is highly regulated by endocrine factors. One of the major bone regulatory hormones is vitamin D. Its renal metabolite 1α,25-OH2D3 has both direct and indirect effects on the maintenance of bone structure in health and disease. In this review, we describe the underlying processes that are directed by bone-forming cells, the osteoblasts. During the bone formation process, osteoblasts undergo different stages which play a central role in the signaling pathways that are activated via the vitamin D receptor. Vitamin D is involved in directing the osteoblasts towards proliferation or apoptosis, regulates their differentiation to bone matrix producing cells, and controls the subsequent mineralization of the bone matrix. The stage of differentiation/mineralization in osteoblasts is important for the vitamin D effect on gene transcription and the cellular response, and many genes are uniquely regulated either before or during mineralization. Moreover, osteoblasts contain the complete machinery to metabolize active 1α,25-OH2D3 to ensure a direct local effect. The enzyme 1α-hydroxylase (CYP27B1) that synthesizes the active 1α,25-OH2D3 metabolite is functional in osteoblasts, as well as the enzyme 24-hydroxylase (CYP24A1) that degrades 1α,25-OH2D3. This shows that in the past 100 years of vitamin D research, 1α,25-OH2D3 has evolved from an endocrine regulator into an autocrine/paracrine regulator of osteoblasts and bone formation.

Study on the relationship between vitamin D level and macrophage typing in patients with type 2 diabetes mellitus

Objective

Population studies have shown that vitamin D (VitD) deficiency is associated with an increased incidence of type 2 diabetes mellitus (T2DM), VitD deficiency is a potential risk factor for T2DM, and the proportion of M1-type macrophages and M2-type macrophages in T2DM patients is imbalanced. Another study reported that VitD can affect the differentiation of macrophages into M1 and M2 types. However, there is no definitive result about the correlation between plasma VitD levels and macrophage typing in patients with T2DM. Whether VitD affects the progression of T2DM by regulating the polarization type of macrophages and the specific regulatory mechanism is not very clear. Therefore, we carried out the following research.

Methods

We first used flow cytometry to detect the proportions of M1 and M2 macrophages in peripheral blood of T2DM patients with different VitD levels. Furthermore, we used ELISA to detect the inflammatory factors affecting macrophage differentiation in patients’ plasma, including IL-6 secreted by M1-type macrophages and TGF-β secreted by M2-type macrophages. Mononuclear cells were separated from human peripheral blood with immunomagnetic beads, cultured in vitro, and treated with different concentrations of VitD, and the ratio of differentiation into M1 and M2 macrophages was detected by flow cytometry.

Results

With the increase of serum 25(OH)D levels in patients with T2DM, the proportion of M1 and M2 macrophages in peripheral blood decreased, that is, the polarized phenotype of macrophages was more inclined to M2 type, while plasma IL-6 gradually decreased, and TGF-β gradually increased. In addition, VitD can promote the differentiation of CD14-positive monocytes cultured in vitro into M2 macrophages.

Conclusions

When the level of VitD in T2DM patients is low, there are more M1-type macrophages in peripheral blood, and when the level of VitD is increased, M2-type macrophages are increased. Changes in related inflammatory factors were also consistent. In vitro culture of monocytes further confirmed that VitD can promote the differentiation of macrophages to M2 type in T2DM patients.

Vitamin D-Related Risk Factors for Maternal Morbidity and Mortality during Pregnancy: Systematic Review and Meta-Analysis

Vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] levels <20 ng/mL in serum) is a common health condition among pregnant women, especially in high-risk groups. Evidence has connected vitamin D levels with many health-related problems during pregnancy, including gestational diabetes and preeclampsia. Because of vitamin D’s effect on both mother and fetus, we systematically review the association between 25(OH)D level and its health effects. From a total of 143 studies, 43 came from PubMed, 4 from Cochrane, and 96 from EMBASE. After screening, we identified 38 studies as candidates for inclusion. Ultimately, we limited this review to 23 articles originating from 12 countries, written in English or Spanish, and conducted between 2010 and 2022. We conducted this review according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and evaluated the quality and strength of the evidence by using the Navigation Guide Systematic Review Methodology (SING). These systematic reviews summarize findings that support vitamin D’s role in reducing risks of multiple outcomes and the possible contribution of adequate vitamin D levels to a healthy pregnancy.

Bone Fragility in Chronic Kidney Disease Stage 3 to 5: The Use of Vitamin D Supplementation

Frequently silent until advanced stages, bone fragility associated with chronic kidney disease-mineral and bone disease (CKD-MBD) is one of the most devastating complications of CKD. Its pathophysiology includes the reduction of active vitamin D metabolites, phosphate accumulation, decreased intestinal calcium absorption, renal alpha klotho production, and elevated fibroblast growth factor 23 (FGF23) levels. Altogether, these factors contribute firstly to secondary hyperparathyroidism, and ultimately, to micro- and macrostructural bone changes, which lead to low bone mineral density and an increased risk of fracture. A vitamin D deficiency is common in CKD patients, and low circulating 25(OH)D levels are invariably associated with high serum parathyroid hormone (PTH) levels as well as with bone mineralization defects, such as osteomalacia in case of severe forms. It is also associated with a variety of non-skeletal diseases, including cardiovascular disease, diabetes mellitus, multiple sclerosis, cancer, and reduced immunological response. Current international guidelines recommend supplementing CKD patients with nutritional vitamin D as in the general population; however, there is no randomized clinical trial (RCT) evaluating the effect of vitamin D (or vitamin D+calcium) supplementation on the risk of fracture in the setting of CKD. It is also unknown what level of circulating 25(OH)D would be sufficient to prevent bone abnormalities and fractures in these patients. The impact of vitamin D supplementation on other surrogate endpoints, including bone mineral density and bone-related circulating biomarkers (PTH, FGF23, bone-specific alkaline phosphatase, sclerostin) has been evaluated in several RTCs; however, the results were not always translated into an improvement in long-term outcomes, such as reduced fracture risk. This review provides a brief and comprehensive update on CKD-related bone fragility and the use of natural vitamin D supplementation in these patients.

Modern India and Dietary Calcium Deficiency-Half a Century Nutrition Data-Retrospect-Introspect and the Road Ahead

Calcium and vitamin D are inseparable nutrients required for bone health. In the past half a century, the dietary calcium intake of rural, tribal, and urban India has declined. Though India is the largest producer of milk and cereals, the major source of calcium in India is through non-dairy products. The highest intake of cereals and lowest intake of milk & milk products was observed in rural and tribal subjects whereas, the intake of cereals, milk & milk products were similar in both urban and metropolitan subjects. One of the reasons for lower calcium intake was the proportion of calcium derived from dairy sources. Over the past half a century, the average 30-day consumption of cereals in the rural and urban population has declined by 30%. The Per Capita Cereal Consumption (PCCC)has declined despite sustained raise in Monthly Per capita Consumption Expenditure (MPCE) in both rural and urban households. The cereal consumption was the highest in the lowest income group, despite spending smaller portion of their income, as cereals were supplied through public distribution system (PDS). About 85% of the Indian population are vitamin D deficient despite abundant sunlight. Dietary calcium deficiency can cause secondary vitamin D deficiency. Though India as a nation is the largest producer of milk, there is profound shortage of calcium intake in the diet with all negative consequences on bone health. There is a decline in dietary calcium in the background of upward revision of RDI/RDA. There is a gap in the production-consumption-supply chain with respect to dietary calcium. To achieve a strong bone health across India, it is imperative to have population based strategies addressing different segments including supplementing dietary/supplemental calcium in ICDS, mid-day-meals scheme, public distribution system, educational strategies. Other measures like mass food fortification, biofortification, bioaddition, leveraging digital technologies, investments from corporate sector are some measures which can address this problem. India is a vast country with diverse social, cultural and dietary habits. No single measure can address this problem and requires a multi-pronged strategic approach to tackle the dietary calcium deficiency to achieve strong bone health while solving the problem of nutritional deficiency.

Fat-Soluble Vitamins

The fat-soluble vitamins are vitamins A, D, E, and K. Each vitamin has unique characteristics and contributes to the overall health of an individual. These vitamins have complex absorption, metabolism, and distribution elements that provide protection to the cells in the body as well as many organs. Fat-soluble vitamins, once ingested and processed, are stored in the body for use. Most fat-soluble vitamins are obtained from fruits, vegetables, nuts, and animals.

Cholecalciferol (vitamin D3) has a direct protective activity against interleukin 6-induced atrophy in C2C12 myotubes

We previously determined that different vitamin D metabolites can have opposite effects on C2C12 myotubes, depending on the sites of hydroxylation or doses. Specifically, 25(OH)D₃ (25VD) has an anti-atrophic activity, 1,25(OH)₂D₃ induces atrophy, and 24,25(OH)₂D₃ is anti-atrophic at low concentrations and atrophic at high concentrations. This study aimed to clarify whether cholecalciferol (VD3) too, the non-hydroxylated upstream metabolite, has a direct effect on muscle cells.

Assessing the effects of VD3 treatment on mouse C2C12 skeletal muscle myotubes undergoing atrophy induced by interleukin 6 (IL6), we demonstrated that VD3 has a protective action, preserving C2C12 myotubes size, likely through promoting the differentiation and fusion of residual myoblasts and by modulating the IL6-induced autophagic flux. The lack, in C2C12 myotubes, of the hydroxylase transforming VD3 in the anti-atrophic 25VD metabolite suggests that VD3 may have a direct biological activity on the skeletal muscle. Furthermore, we found that the protective action of VD3 depended on VDR, implying that VD3 too might bind to and activate VDR. However, despite the formation of VDR-RXR heterodimers, VD3 effects do not depend on RXR activity.

In conclusion, VD3, in addition to its best-known metabolites, may directly impact on skeletal muscle homeostasis.

Maternal vitamin D deficiency increases the risk of obesity in male offspring mice by affecting the immune response

OBJECTIVES

Recently, many epidemiologic and animal studies have indicated that obesity has its origin in early stages of life, including the inappropriate balance of some nutrients. So the objectives of this study were to determine the risk of obesity in male offspring mice as a consequence of maternal vitamin D (VD) deficiency mediating the disordered immune response.

METHODS

C57BL/6J female mice 4 wk old were fed VD-deficient or normal reproductive diets during pregnancy and lactation. Their male offspring were given control and high-fat diets for 16 wk after weaning and then weighed and euthanized. The serum was collected for biochemical analyses. Epididymal (eWAT) and inguinal white adipose tissue (iWAT) were excised for histologic examination, immunohistochemistry, gene expression of inflammatory factors, and determination by flow cytometry of the proportions of immune cells.

RESULTS

Insufficient maternal VD intake exacerbated the development of obesity in male offspring mice that were both obese and non-obese, as evidenced by larger adipose cells and abnormal glucose and lipid metabolisms. Also, the expressions of proinflammatory cytokines were increased and that of anti-inflammatory cytokines was decreased in eWAT and/or iWAT in the maternal VD-deficient group, accompanied by higher levels of tumor necrosis factor-α and/or interferon-γ and lower levels of interleukin-4 and interleukin-10. Insufficient maternal VD intake was also observed to induce a shift in the profiles of immune cells in the eWAT and/or iWAT of male offspring that were both obese and non-obese, resulting in increased percentages of M1 macrophages, adipose tissue dendritic cells, and CD4⁺ and CD8⁺ T cells but a significant decrease in the percentages of M2 macrophages. All these changes in the immune cell profile were more obvious in the eWAT than those in the iWAT.

CONCLUSIONS

Maternal VD deficiency might promote the development of obesity in male offspring mice partly by modulating the immune cell populations and causing a polarization in the adipose depots.

Impact of the 25-Hydroxycholecalciferol Concentration and Vitamin D Deficiency Treatment on Changes in the Bone Level at the Implant Site during the Process of Osseointegration: A Prospective, Randomized, Controlled Clinical Trial

INTRODUCTION

The most important factor which is responsible for the positive course of implant treatment is the process of osseointegration between the implant structure and the host's bone tissue. The aim of this study was to assess what effect the 25-hydroxycholecalciferol concentration and vitamin D deficiency treatment have on changes in the bone level at the implant site during the process of osseointegration in the mandible.

MATERIALS AND METHODS

The study was with 122 people qualified for implant surgery, who were assigned to three research groups (A, B, and C). Laboratory, clinical, and radiological tests were performed on the day of surgery, and after 6 and 12 weeks. The bone level in the immediate proximity of the implant was determined by radiovisiography (RVG).

RESULTS

The bone level after 12 weeks in Groups B and C was significantly higher than after 6 weeks. The bone level in the study Group B was significantly higher than in Group A. The study showed that the higher the levels of 25-hydroxycholecalciferol were observed on the day of surgery, the higher was the level of bone surrounding the implant after 6 and 12 after surgery.

CONCLUSION

The correct level of 25-hydroxycholecalciferol on the day of surgery and vitamin D deficiency treatment significantly increase the bone level at the implant site in the process of radiologically assessed osseointegration.

Effect of supplementation with vitamins D3 and K2 on undercarboxylated osteocalcin and insulin serum levels in patients with type 2 diabetes mellitus: a randomized, double-blind, clinical trial

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) are characterized by chronic hyperglycemia as a consequence of decreased insulin sensitivity, which contributes to bone demineralization and could also be related to changes in serum levels of osteocalcin and insulin, particularly when coupled with a deficiency in the daily consumption of vitamins D3 and K2. The objective of this study was to evaluate the effect of vitamin D3 and vitamin K2 supplements alone or in combination on osteocalcin levels and metabolic parameters in patients with T2DM.

METHODS

A double-blind, randomized clinical trial was carried out in 40 patients aged between 30 and 70 years old for 3 months. Clinical and laboratory assessment was carried out at the beginning and at the end of the treatment. The patients were divided into three groups: (a) 1000 IU vitamin D3 + a calcinated magnesium placebo (n = 16), (b) 100 µg of Vitamin K2 + a calcinated magnesium placebo (n = 12), and (c) 1000 IU vitamin D3 + 100 µg vitamin K2 (n = 12).

RESULTS

After treatment in the total studied population, a significant decrease in glycemia (p = 0.001), HOMA-IR (Homeostatic model assessment-insulin resistance) (p = 0.040), percentage of pancreatic beta cells (p < 0.001), uOC/cOC index and diastolic blood pressure (p = 0.030) were observed; in vitamin D3 group, differences in serum undercarboxylated osteocalcin (p = 0.026), undercarboxylated to carboxylated osteocalcin index (uOC/cOC) (p = 0.039) glucose (p < 0.001) and  % of functional pancreatic beta cells (p < 0.001) were demonstrated. In vitamin K2 group a significant decrease in glycemia (p = 0.002), HOMA-IR (p = 0.041), percentage of pancreatic beta cells (p = 0.002), and in cOC (p = 0.041) were observed, conversely cOC concentration was found high. Finally, in the vitamins D3 + K2 a significant decrease in glycemia (p = 0.002), percentage of pancreatic beta cells (p = 0.004), and in the uOC/cOC index (p = 0.023) were observed.

CONCLUSION

Individual or combined supplementation with vitamins D3 and K2 significantly decreases the glucose levels and  % of functional pancreatic beta cells, while D3 and D3 + K2 treatments also induced a reduction in the uOC/cOC index. Only in the group with vitamin D3 supplementation, it was observed a reduction in undercarboxylated osteocalcin while vitamin K2 increased the carboxylated osteocalcin levels.Trial registration NCT04041492.

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

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

Effect of Chronic Vitamin D Deficiency on the Development and Severity of DSS-Induced Colon Cancer in Smad3-/- Mice

Both human epidemiologic data and animal studies suggest that low serum vitamin D increases the risk of inflammatory bowel disease (IBD) and consequently IBD-associated colorectal cancer. We tested the hypothesis that vitamin D deficiency increases the risk for colitis-associated colon cancer (CAC) by using an established CAC mouse model, 129-Smad3tm1Par/J (Smad3-/-) mice, which have defective transforming growth factor β-signaling and develop colitis and CAC after the administration of dextran sodium sulfate (DSS). After determining a dietary regimen that induced chronic vitamin D deficiency in Smad3-/- mice, we assessed the effects of vitamin D deficiency on CAC. Decreasing dietary vitamin D from 1 IU/g diet (control diet) to 0.2 IU /g diet did not decrease serum 25-hydroxyvitamin D (25(OH)D) levels in Smad3-/- mice. A diet devoid of vitamin D (< 0.02 IU/g diet [no added vitamin D]; vitamin D-null) significantly decreased serum 25(OH)D levels in mice after 2 wk (null compared with control diet: 8.4 mg/mL compared with 12.2 ng/mL) and further decreased serum levels to below the detection limit after 9 wk but did not affect weight gain, serum calcium levels, bone histology, or bone mineral density. In light of these results, Smad3-/- mice were fed a vitamin D-null diet and given DSS to induce colitis. Unexpectedly, DSS-treated Smad3-/- mice fed a vitamin D-null diet had improved survival, decreased colon tumor incidence (8% compared with 36%), and reduced the incidence and severity of colonic dysplasia compared with mice fed the control diet. These effects correlated with increased epithelial cell proliferation and repair early in the disease, perhaps reducing the likelihood of developing chronic colitis and progression to cancer. Our results indicate that vitamin D deficiency is beneficial in some cases of CAC, possibly by promoting intestinal healing.

Effect of circulating 25-hydroxyvitamin D and antioxidant capacity level on cognitive function parameters of children with idiopathic short stature

Background

An optimal level of vitamin D is necessary for normal bone growth. Recently, vitamin D has been linked to many neurological disorders, changes in antioxidant capacity levels, and cognitive function decline in old age; thus, the aim was to evaluate the effect of vitamin D and antioxidant levels on the cognitive function parameters of children with idiopathic short stature (ISS).

Results

A prospective case-control study was conducted with 60 primary school-aged children with ISS who were compared to 60 unrelated healthy age- and sex-matched children as a control group. A complete clinical evaluation; anthropometric measurements; neurocognitive function parameters using the Stanford-Binet test, fifth edition; vitamin D level; total antioxidant capacity (TAC); total oxidative stress (TOS); and oxidative stress index (OSI) were measured. A total of 83.3% of children with ISS had a vitamin D level < 30 ng/ml with significantly lower vitamin D levels than the control group. The TAC level was significantly lower in children with ISS than in healthy children. Children with ISS had an average level for all of the cognitive function parameters but a lower non-verbal IQ, full-scale IQ, fluid reasoning, knowledge, quantitative reasoning, and working memory than healthy controls. A positive correlation was found between vitamin D level and all anthropometric measurements, all IQ parameters, and TAC levels in the studied children. A positive correlation was found between TAC and all IQ parameters.

Conclusion

Vitamin D level and antioxidant capacity level have a major impact on cognitive function parameters in children with ISS.

WY 1048, a 17-methyl 19-nor D-ring analog of vitamin D3, in combination with risedronate restores bone mass in a mouse model of postmenopausal osteoporosis

Bisphosphonates like risedronate inhibit osteoclast-mediated bone resorption and are therefore used in the prevention and treatment of osteoporosis. Also vitamin D₃ and calcium supplementation is commonly used in the prevention or treatment of osteoporosis. Combined therapy of risedronate with 1,25(OH)₂D₃, the active metabolite of vitamin D₃, may be advantageous over the use of either monotherapy, but bears a risk of causing hypercalcemia thereby decreasing the therapeutic window for osteoporosis treatment. In this study, we evaluated the effect on bone mass of the combination of risedronate with the 17-methyl 19-nor five-membered D-ring vitamin D₃ analog WY 1048 in a mouse ovariectomy model for postmenopausal osteoporosis. Ovariectomy-induced bone loss was restored by administration of risedronate or a combination of risedronate with 1,25(OH)₂D_3. However, the combination of WY 1048 with risedronate induced an even higher increase on total body and spine bone mineral density and on trabecular and cortical bone mass. Our data indicate that combination therapy of risedronate with WY 1048 was superior in restoring and improving bone mass over a combination of risedronate with 1,25(OH)₂D₃ with minimal calcemic side effects.

Enhancement of bone mineral density and body mass in newborn chickens by in ovo injection of ionic-hydroxyapatite nanoparticles of bacterial origin

Using non-drug, non-surgical treatments for improving bone mineral diseases in newborn babies is an important topic for neonatologists. The present study introduces bacterial synthesized ionic nano-hydroxyapatite (Bio-HA) for the development of bone mineral density in the chicken embryo model. In vitro cytotoxicity analyses were demonstrated the optimal concentrations of Bio-HA compared to a chemically-synthesized hydroxyapatite (Ch-HA). Toxicity of Bio-HA on MCF-7 human cell lines was negligible at the concentrations less than 500 μg/mL whereas Ch-HA showed similar results at the concentrations less than 100 μg/mL. Therefore, concentrations at 50 μg/mL and 100 μg/mL were selected for in ovo injection of both materials into the fertilized eggs. The newly hatched chickens were sacrificed in order to monitor their serological factors, total body mass, bone mineral contents and bone mineral density. The results confirmed that Bio-HA increased the average body weight and bone mineral indices of chickens in comparison to the Ch-HA and negative controls (normal saline and intact groups). In view of the intact group, no liver or kidney damage occurred in the groups receiving Bio-HA which promises the effectiveness of these nanoparticles for the treatment of afterbirth bone mineral deficiency.

Vitamin D insufficiency: Definition, diagnosis and management

Severe vitamin D deficiency can be defined as the dose of vitamin D or serum 25OHD concentrations needed to prevent nutritional rickets or osteomalacia. There is large international consensus that these diseases can be prevented by 400 IU of vitamin D/d and 25OHD above 30 nmol/l (12 ng/ml). Vitamin D deficiency can also accelerate the risk of fractures and probably also of falls in elderly subjects but there is no consensus on the required daily doses or minimal 25OHD threshold for these endpoints. The majority of experts consider 800 IU/d and serum 25OHD above 50 nmol/l (20 ng/ml) as sufficient, with a minority opinion aiming for 75 nmol/l or even higher. For other extra-skeletal endpoints, no hard evidence is available to define whether or not this is causally related to vitamin D status. Therefore, for these endpoints no minimal dosage or 25OHD threshold can be defined.

Exogenous Vitamin D signaling alters skeletal patterning, differentiation, and tissue integration during limb regeneration in the axolotl

Urodele amphibians such as the axolotl regenerate complete limbs as adults, and understanding how the "blueprint", or pattern, of the regenerate is established and manipulated are areas of intense interest. Nutrient signaling plays an important role in pattern formation during regeneration. Retinoic acid signaling is the most characterized pathway during this process. Exogenous retinoic acid (RA) reprograms the pattern information in regenerating cells to a more posterior, ventral, and proximal identity. Vitamin D signaling shares several molecular similarities with RA and has been shown to alter pattern formation during zebrafish pectoral fin regeneration. To determine if exogenous Vitamin D signaling is capable of reprograming pattern in the axolotl limb blastema, we treated regenerating limbs with a potent Vitamin D agonist. Under the studied conditions, exogenous Vitamin D did not act in a manner similar to RA and failed to proximalize the pattern of the resulting regenerates. The Vitamin D treatment did result in several skeletal defects during regeneration, including carpal fusions along the A/P axis; failure to integrate the newly regenerated tissue with the existing tissue, formation of ectopic nodules of cartilage at the site of amputation, and altered bone morphology in uninjured skeletal tissue.

VDR and TNFSF11 polymorphisms are associated with osteoporosis in Thai patients

Determining molecular markers for osteoporosis may be valuable for improving the quality of life of affected elderly patients by aiding in early detection and disease management. In the present study, the association between single nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) and tumour necrosis factor superfamily number 11 (TNFSF11) genes and the susceptibility of developing osteoporosis was investigated in a Thai female cohort. The study group consisted of 105 Thai postmenopausal patients diagnosed with osteoporosis and 132 healthy Thai postmenopausal female volunteers. DNA extracted from blood samples was used to genotype the VDR and TNFSF11 genes using polymerase chain reaction-restriction fragment length polymorphism and sequencing analysis. For VDR, the frequencies of the genotypes TT, CT and CC for the TaqI SNP (rs731236) were 87.88, 11.36 and 0.76%, respectively, in the control group, while in the osteoporosis cohort were 92.38, 5.71 and 1.91%, respectively. For the FokI SNP (rs2228570), the frequencies of the genotypes CC, CT and TT were 31.06, 55.30 and 13.64%, respectively, in the control group, and in the osteoporosis group were 29.52, 43.81 and 26.67%, respectively. For BsmI SNP (rs1544410), the frequencies of the genotypes GG, GA and AA were 78.03, 18.94 and 3.03%, respectively, in control group, and in the osteoporosis group were 80.95, 18.10 and 0.95%, respectively. The significant risk of osteoporosis associated with the FokI SNP was determined. The odds ratio (95% confidence interval) was 2.30 (1.14-4.69; P=0.01) among patients with osteoporosis with TT as the susceptibility genotype. For TNFSF11, the frequencies of the genotypes TT, CT and CC for the -290C>T SNP (rs9525641) in the control group were 36.36, 50.76 and 12.88%, respectively, while in the osteoporosis group were 31.43, 56.19 and 12.38%, respectively. For the -643C>T SNP (rs9533156), the frequencies of the genotypes TT, CT and CC in the control group were 35.61, 48.48 and 15.91%, respectively, while in the osteoporosis group were 32.38, 55.24 and 12.38%, respectively. For the -693G>C SNP (rs9533155), the frequencies of the genotypes CC, CG, and GG in the control group were 39.39, 46.97 and 13.64%, respectively, and in the osteoporosis group were 36.19, 53.33 and 10.48%, respectively. No significant associations of the TNFSF11 SNPs with osteoporosis were determined; however, it was notable that the GCT haplotype of TNFSF11 may be a protective haplotype for osteoporosis. Therefore, it was concluded that the SNP FokI of VDR may be a potential molecular biomarker for the development of osteoporosis in Thai females.

Vitamin D Supplementation in Pregnancy and Lactation and Infant Growth

BACKGROUND

It is unclear whether maternal vitamin D supplementation during pregnancy and lactation improves fetal and infant growth in regions where vitamin D deficiency is common.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial in Bangladesh to assess the effects of weekly prenatal vitamin D supplementation (from 17 to 24 weeks of gestation until birth) and postpartum vitamin D supplementation on the primary outcome of infants' length-for-age z scores at 1 year according to World Health Organization (WHO) child growth standards. One group received neither prenatal nor postpartum vitamin D (placebo group). Three groups received prenatal supplementation only, in doses of 4200 IU (prenatal 4200 group), 16,800 IU (prenatal 16,800 group), and 28,000 IU (prenatal 28,000 group). The fifth group received prenatal supplementation as well as 26 weeks of postpartum supplementation in the amount of 28,000 IU (prenatal and postpartum 28,000 group).

RESULTS

Among 1164 infants assessed at 1 year of age (89.5% of 1300 pregnancies), there were no significant differences across groups in the mean (±SD) length-for-age z scores. Scores were as follows: placebo, -0.93±1.05; prenatal 4200, -1.11±1.12; prenatal 16,800, -0.97±0.97; prenatal 28,000, -1.06±1.07; and prenatal and postpartum 28,000, -0.94±1.00 (P=0.23 for a global test of differences across groups). Other anthropometric measures, birth outcomes, and morbidity did not differ significantly across groups. Vitamin D supplementation had expected effects on maternal and infant serum 25-hydroxyvitamin D and calcium concentrations, maternal urinary calcium excretion, and maternal parathyroid hormone concentrations. There were no significant differences in the frequencies of adverse events across groups, with the exception of a higher rate of possible hypercalciuria among the women receiving the highest dose.

CONCLUSIONS

In a population with widespread prenatal vitamin D deficiency and fetal and infant growth restriction, maternal vitamin D supplementation from midpregnancy until birth or until 6 months post partum did not improve fetal or infant growth. (Funded by the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT01924013 .).

The impact of the intestinal microbiome on bone health

Intestinal microbial flora, known as the second gene pool of the human body, play an important role in immune function, nutrient uptake, and various activities of host cells, as well as in human disease. Intestinal microorganisms are involved in a variety of mechanisms that affect bone health. Gut microbes are closely related to genetic variation, and gene regulation plays an important part in the development of bone-related diseases such as osteoporosis. Intestinal microorganisms can disrupt the balance between bone formation and resorption by indirectly stimulating or inhibiting osteoblasts and osteoclasts. In addition, intestinal microorganisms affect bone metabolism by regulating growth factors or altering bone immune status and can also alter the metabolism of serotonin, cortisol, and sex hormones, thereby affecting bone mass in mice. Moreover, probiotics, antibiotics, and diet can change the composition of the intestinal microbial flora, thus affecting bone health and also potentially helping to treat bone disease. Studying the relationship between intestinal flora and osteoblasts, osteoclasts, and bone marrow mesenchymal stem cells may provide a basis for preventing and treating bone diseases. This paper reviews recent advances in the study of the relationship between intestinal microflora and bone disease.

Deterioration of Cortical Bone Microarchitecture: Critical Component of Renal Osteodystrophy Evaluation

BACKGROUND

Cortical bone is a significant determinant of bone strength and its deterioration contributes to bone fragility. Thin cortices and increased cortical porosity have been noted in patients with chronic kidney disease (CKD), but the "Turnover Mineralization Volume" classification of renal osteodystrophy does not emphasize cortical bone as a key parameter. We aimed to assess trabecular and cortical bone microarchitecture by histomorphometry and micro-CT in patients with CKD G5 and 5D (dialysis).

METHODS

Transiliac bone biopsies were performed in 14 patients undergoing kidney transplantation (n = 12) and parathyroidectomy (n = 2). Structural parameters were analysed by histomorphometry and micro-CT including trabecular bone volume, thickness (TbTh), number (TbN) and separation and cortical thickness (CtTh) and porosity (CtPo). Indices of bone remodelling and mineralisation were obtained and relationships to bone biomarkers examined. Associations were determined by Spearman's or Pearson's rank correlation coefficients.

RESULTS

By micro-CT, trabecular parameters were within normal ranges in most patients, but all patients showed very low CtTh (127 ± 44 µm) and high CtPo (60.3 ± 22.5%). CtPo was inversely related to TbN (r = -0.56; p = 0.03) by micro-CT and to TbTh (r = -0.60; p = 0.024) by histomorphometry and correlated to parathyroid hormone values (r = 0.62; p = 0.021). By histomorphometry, bone turnover was high in 50%, low in 21% and normal in 29%, while 36% showed abnormal patterns of mineralization. Significant positive associations were observed between osteoblast surface, osteoclast surface, mineralization surface and bone turnover markers.

CONCLUSIONS

Deterioration of cortical -microarchitecture despite predominantly normal trabecular parameters reinforces the importance of comprehensive cortical evaluation in patients with CKD.

Cholecalciferol Supplementation Promotes Bone Turnover in Chinese Adults with Vitamin D Deficiency

BACKGROUND

Bone turnover markers (BTMs) are proposed as alternative indicators for bone mineral density in diagnosis and management of osteoporosis. However, little is known about the effects of vitamin D supplementation on BTMs in nonwhite populations.

OBJECTIVE

We aimed to investigate the responses in BTMs after vitamin D supplementation in Asians.

METHODS

In this secondary data analysis of a randomized, double-blind, placebo-controlled trial, 448 Chinese adults [mean ± SD age: 31.9 ± 8.0 y; mean ± SD body mass index (kg/m2): 22.1 ± 2.6; 69% were women] with vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] <50 nmol/L) received 2000 IU/d cholecalciferol or placebo for 20 wk. Serum concentrations of 25(OH)D, parathyroid hormone (PTH), calcium, and markers of bone formation and resorption were measured at weeks 0 and 20. Intention-to-treat analysis was applied, and between-group differences were compared by general linear models with adjustments.

RESULTS

Cholecalciferol supplementation increased the serum bone alkaline phosphatase (BALP) concentration (+1.7 ± 1.9 µg/L) significantly more than placebo (+1.1 ± 1.7 µg/L; P = 0.004), but not circulating concentrations of procollagen type I N-terminal propeptide (PINP), β-isomerized C-terminal telopeptide of type I collagen (β-CTX), or tartrate-resistant acid phosphatase 5b (TRAP5b) (P ≥ 0.53). Notably, a pooled analysis indicated that changes in serum 25(OH)D were positively associated with changes in serum BALP, PINP, and TRAP5b (r = 0.07-0.16, P ≤ 0.02), but inversely with changes in PTH (r = -0.15, P < 0.001). Among cholecalciferol-treated participants, individuals who achieved serum 25(OH)D ≥75 nmol/L had greater increases in serum β-CTX (224% compared with 146%; P = 0.02) and TRAP5b (22.2% compared with 9.1%; P = 0.007), but smaller decreases in serum calcium (-1.3% compared with -1.9%; P = 0.005) and calcium-phosphorus product (-2.6% compared with -3.3%; P = 0.02) compared with those with serum 25(OH)D <75 nmol/L.

CONCLUSIONS

Daily supplementation with 2000 IU cholecalciferol for 20 wk may promote bone formation in Chinese adults with vitamin D deficiency. More studies are needed to elucidate the potential clinical implications of BTMs.This trial was registered at clinicaltrials.gov as NCT01998763.

Association of low penetrance vitamin D receptor Tru9I (rs757343) gene polymorphism with risk of premenopausal breast cancer

Objective The aim of this study was to determine whether a novel polymorphism ( Tru9I) in the low penetrance vitamin D receptor (VDR) gene is associated with risk of premenopausal breast cancer (BC). Methods This case-control study included 228 patients with BC and 503 healthy women living in Pakistan who were analyzed for the VDR Tru9I (rs757343) single nucleotide polymorphism. BC cases were histopathologically confirmed, and all healthy controls were age-matched with patients (age range, 20-45 years). DNA was extracted, and the polymerase chain reaction and restriction fragment length polymorphism assays were performed. Results The VDR Tru9I polymorphism was not significantly associated with premenopausal BC. However, the risk of BC was associated with the 'uu' genotype (odds ratio [OR], 1.141; 95% confidence interval [95% CI], 0.206-6.317). Further, mutant Tru9I was significantly associated with Grade IV carcinoma (OR, 5.36; 95% CI, 1.181-24.338). Conclusion The VDR Tru9I 'uu' genotype may increase the risk of premenopausal BC.

The bone remodelling cycle

The bone remodelling cycle replaces old and damaged bone and is a highly regulated, lifelong process essential for preserving bone integrity and maintaining mineral homeostasis. During the bone remodelling cycle, osteoclastic resorption is tightly coupled to osteoblastic bone formation. The remodelling cycle occurs within the basic multicellular unit and comprises five co-ordinated steps; activation, resorption, reversal, formation and termination. These steps occur simultaneously but asynchronously at multiple different locations within the skeleton. Study of rare human bone disease and animal models have helped to elucidate the cellular and molecular mechanisms that regulate the bone remodelling cycle. The key signalling pathways controlling osteoclastic bone resorption and osteoblastic bone formation are receptor activator of nuclear factor-κB (RANK)/RANK ligand/osteoprotegerin and canonical Wnt signalling. Cytokines, growth factors and prostaglandins act as paracrine regulators of the cycle, whereas endocrine regulators include parathyroid hormone, vitamin D, calcitonin, growth hormone, glucocorticoids, sex hormones, and thyroid hormone. Disruption of the bone remodelling cycle and any resulting imbalance between bone resorption and formation leads to metabolic bone disease, most commonly osteoporosis. The advances in understanding the cellular and molecular mechanisms underlying bone remodelling have also provided targets for pharmacological interventions which include antiresorptive and anabolic therapies. This review will describe the remodelling process and its regulation, discuss osteoporosis and summarize the commonest pharmacological interventions used in its management.

Regulation of bone remodeling by vitamin K2

All living tissues require essential nutrients such as amino acids, fatty acids, carbohydrates, minerals, vitamins, and water. The skeleton requires nutrients for development, maintaining bone mass and density. If the skeletal nutritional requirements are not met, the consequences can be quite severe. In recent years, there has been growing interest in promotion of bone health and inhibition of vascular calcification by vitamin K2. This vitamin regulates bone remodeling, an important process necessary to maintain adult bone. Bone remodeling involves removal of old or damaged bone by osteoclasts and its replacement by new bone formed by osteoblasts. The remodeling process is tightly regulated, when the balance between bone resorption and bone formation shifts to a net bone loss results in the development of osteoporosis in both men and women. In this review, we focus on our current understanding of the effects of vitamin K2 on bone cells and its role in prevention and treatment of osteoporosis.

Class 3 semaphorins are transcriptionally regulated by 1,25(OH)2D3 in osteoblasts

The vitamin D endocrine system is essential for calcium metabolism and skeletal integrity. 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] regulates bone mineral homeostasis and acts directly on osteoblasts. In the present study we characterized the transcriptional regulation of the class 3 semaphorin (Sema3) gene family by 1,25(OH)₂D₃ in osteoblastic cells. Class 3 semaphorins are secreted proteins that regulate cell growth, morphology and migration, and were recently shown to be involved in bone homeostasis. In ST2, MC3T3-E1 and primary calvarial osteoblast cell cultures we found that all members of the Sema3 gene family were expressed, and that Sema3e and Sema3f were the most strongly induced 1,25(OH)₂D₃ target genes among the studied cell types. In addition, transcription of Sema3b and Sema3c was upregulated, whereas Sema3d and Sema3g was downregulated by 1,25(OH)₂D₃ in different osteoblastic cells. Chromatin immunoprecipitation analysis linked to DNA sequencing (ChIP-seq analysis) revealed the presence of the vitamin D receptor at multiple genomic loci in the proximity of Sema3 genes, demonstrating that the genes are primary 1,25(OH)₂D₃ targets. Furthermore, we showed that recombinant SEMA3E and SEMA3F protein were able to inhibit osteoblast proliferation. However, recombinant SEMA3s did not affect ST2 cell migration. The expression of class 3 semaphorins in osteoblasts together with their regulation by 1,25(OH)₂D₃ suggests that these genes, involved in the regulation of bone homeostasis, are additional mediators for 1,25(OH)₂D₃ signaling in osteoblasts.

Vitamin D endocrinology of bone mineralization

Bone is a dynamic tissue that is strongly influenced by endocrine factors to restore the balance between bone resorption and bone formation. Bone formation involves the mineralization of the extracellular matrix formed by osteoblasts. In this process the role of vitamin D (1α,25(OH)₂D₃) is both direct and indirect. The direct effects are enabled via the Vitamin D Receptor (VDR); the outcome is dependent on the presence of other factors as well as origin of the osteoblasts, treatment procedures and species differences. Vitamin D stimulates mineralization of human osteoblasts but is often found inhibitory for mineralization of murine osteoblasts. In this review we will overview the current knowledge of the role of the vitamin D endocrine system in controlling the mineralization process in bone.

Vitamin D: Musculoskeletal health

Perhaps the role of Vitamin D supplementation has been most exhaustively studied in calcium absorption, skeletal wellbeing, muscular potency, balance and risk of falling. Nonetheless, new data has emerged and the recent research on sarcopenia makes the topic increasingly interesting. Given the socioeconomic burden of the musculoskeletal consequences of hypovitaminosis D it is vital to keep abreast with the latest literature in the field. The recommended Vitamin D supplementation dose should suffice to increase the serum 25 hydroxyvitamin D level to 30 ng/mL (75 nmol/L) and this level should be optimally maintained with a maintenance dose, particularly for those diagnosed with osteoporosis.

Korean Society for Bone and Mineral Research Task Force Report: Perspectives on Intermittent High-dose Vitamin D Supplementation

An adequate supply of vitamin D is considered necessary for osteoporosis management and fracture prevention. Intermittent high-dose vitamin D supplementation is an effective and convenient way to achieve and maintain sufficient vitamin D status. However, the long-term effectiveness of supplementation for preventing falls and fractures is unclear, and some deleterious effects of such treatments have been reported. Concerning these issues, the Korean Society for Bone and Mineral Research task force team reviewed previous clinical trials and provided the following perspectives based on current evidence: 1) An adequate supply of vitamin D is necessary for preventing falls and fractures in postmenopausal women and men older than 50 years. An oral intake of 800 to 1,000 IU/day of vitamin D is generally recommended. 2) Care should be taken concerning the routine use of intermittent high-dose vitamin D, as large-scale clinical trials showed increased risk of falls or fractures after high-dose vitamin D administration. Intermittent high-dose vitamin D supplementation is recommendable only in cases of malabsorption or when oral administration is not suitable. 3) Monitoring of the serum level of 25-hydroxy-vitamin D (25[OH]D) is advisable, especially when intermittent high-dose vitamin D is used for supplementation. The task force team suggests that a serum 25(OH)D level of >20 ng/mL is generally appropriate for the prevention of osteoporosis, and that a serum 25(OH)D level of >30 ng/mL is probably helpful both for the management of osteoporosis and the prevention of fractures and falls. However, serum 25(OH)D level >50 ng/mL (this value can vary depending on the measurement method used) is unnecessary and may be undesirable. These perspectives are relevant for the management of osteoporosis, falls, or fractures. Other metabolic bone diseases or non-skeletal disorders are not within the scope of these perspectives.

Vitamin D Supplementation Enhances C18(dihydro)ceramide Levels in Type 2 Diabetes Patients

Sphingolipids are characterized by a broad range of bioactive properties. Particularly, the development of insulin resistance, a major pathophysiological hallmark of Type 2 Diabetes mellitus (T2D), has been linked to ceramide signaling. Since vitamin D supplementation may slow down T2D progression by improving glucose concentrations and insulin sensitivity, we investigated whether vitamin D supplementation impacts on plasma sphingolipid levels in T2D patients. Thus, plasma samples of 59 patients with non-insulin-requiring T2D from a placebo-controlled, randomized, and double-blind study were retrospectively analyzed. Once per week, patients received either 20 drops of Vigantol oil, corresponding to a daily dose of 1904 IU/d vitamin D (verum: n = 31), or a placebo oil consisting of medium chain triglycerides (placebo: n = 28). Blood samples were taken from all of the participants at three different time points: 1) at the beginning of the study (baseline), 2) after 6 months supplementation, and 3) after an additional 6 months of follow-up. Plasma sphingolipids were measured by high-performance liquid chromatography tandem mass spectrometry. At baseline and 6 months follow-up, no significant differences in plasma sphingolipid species were detected between the placebo and verum groups. After 6 months, vitamin D supplementation significantly enhanced plasma C18dihydroceramide (dhCer; N-stearoyl-sphinganine (d18:0/18:0)) and C18ceramide (Cer; N-stearoyl-sphingosine (d18:1/18:0)) levels were observed in the verum group compared to the placebo group. This was accompanied by significantly higher 25-hydroxyvitamin D₃ (25(OH)D₃) blood levels in patients receiving vitamin D compared to the placebo group. Taken together, vitamin D supplementation induced changes of the C18 chain-length-specific dhCer and Cer plasma levels in patients with T2D. The regulation of sphingolipid signaling by vitamin D may thus unravel a novel mechanism by which vitamin D can influence glucose utilization and insulin action. Whether this acts favorably or unfavorably for the progression of T2D needs to be clarified.

VDR in Osteoblast-Lineage Cells Primarily Mediates Vitamin D Treatment-Induced Increase in Bone Mass by Suppressing Bone Resorption

Long-term treatment with active vitamin D [1α,25(OH)₂ D₃ ] and its derivatives is effective for increasing bone mass in patients with primary and secondary osteoporosis. Derivatives of 1α,25(OH)₂ D₃ , including eldecalcitol (ELD), exert their actions through the vitamin D receptor (VDR). ELD is more resistant to metabolic degradation than 1α,25(OH)₂ D₃ . It is reported that ELD treatment causes a net increase in bone mass by suppressing bone resorption rather than by increasing bone formation in animals and humans. VDR in bone and extraskeletal tissues regulates bone mass and secretion of osteotropic hormones. Therefore, it is unclear what types of cells expressing VDR preferentially regulate the vitamin D-induced increase in bone mass. Here, we examined the effects of 4-week treatment with ELD (50 ng/kg/day) on bone using osteoblast lineage-specific VDR conditional knockout (Ob-VDR-cKO) and osteoclast-specific VDR cKO (Ocl-VDR-cKO) male mice aged 10 weeks. Immunohistochemically, VDR in bone was detected preferentially in osteoblasts and osteocytes. Ob-VDR-cKO mice showed normal bone phenotypes, despite no appreciable immunostaining of VDR in bone. Ob-VDR-cKO mice failed to increase bone mass in response to ELD treatment. Ocl-VDR-cKO mice also exhibited normal bone phenotypes, but normally responded to ELD. ELD-induced FGF23 production in bone was regulated by VDR in osteoblast-lineage cells. These findings suggest that the vitamin D treatment-induced increase in bone mass is mediated by suppressing bone resorption through VDR in osteoblast-lineage cells. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Feed additives regulating calcium homeostasis in the bones of poultry – a review

The strength of leg bones is not only genetically determined but it also depends on the gender, age, health condition and nutrition of slaughter birds. Calcium ions deficit in bones results in the deterioration of skeleton structure and reduction of bone strength. The presented work compiles the results of studies concerning the effect of feed additives on the level of calcium in the bones of broiler chickens, published during the past 10 years. From the analysis of available literature it follows that some additives had a positive effect on the accumulation of calcium (e.g. vitamin D, probiotics, prebiotics and synbiotics), some were not very explicit (e.g. ascorbic acid and phytase), while others did not have a significant effect on the accumulation of calcium in bones (e.g. herbs and chelates). It is concluded from our collected information that the use of probiotics, prebiotics and synbiotics offers the best advantages for poultry. These additives, apart from stimulating the accumulation of calcium in bones, also benefit animal health.

Unique Regenerative Mechanism to Replace Bone Lost During Dietary Bone Depletion in Weanling Mice

The present study was undertaken to determine the mechanism whereby calcitropic hormones and mesenchymal stem cell progeny changes are involved in bone repletion, a regenerative bone process that restores the bone lost to calcium deficiency. To initiate depletion, weanling mice with a mixed C57BL/6 (75%) and CD1 (25%) genetic background were fed a calcium-deficient diet (0.01%) for 14 days. For repletion, the mice were fed a control diet containing 1.2% calcium for 14 days. Depletion decreased plasma calcium and increased plasma parathyroid hormone, 1,25(OH)2D (calcitriol), and C-terminal telopeptide of type I collagen. These plasma parameters quickly returned toward normal on repletion. The trabecular bone volume and connectivity decreased drastically during depletion but were completely restored by the end of repletion. This bone repletion process largely resulted from the development of new bone formation. When bromodeoxyuridine (BrdU) was administered in the middle of depletion for 3 days and examined by fluorescence-activated cell sorting at 7 days into repletion, substantial increases in BrdU incorporation were seen in several CD105 subsets of cells of osteoblastic lineage. When BrdU was administered on days 1 to 3 of repletion and examined 11 days later, no increases in BrdU were seen in these subsets. Additionally, osteocytes that stained positively for BrdU were increased during depletion. In conclusion, the results of the present study have established a unique regenerative mechanism to initiate bone repair during the bone insult. Calcium homeostatic mechanisms and the bone repletion mechanism are opposing functions but are simultaneously orchestrated such that both endpoints are optimized. These results have potential clinical relevance for disease entities such as type 2 osteoporosis.

Screening for nutritional rickets in a community

Concern has been expressed about the rising incidence of nutritional rickets with its associated long-term sequelae in children globally. In order to address the condition worldwide, it is imperative that accurate figures of its incidence are available particularly in at-risk communities. In order to obtain these figures, various screening tools and diagnostic criteria have been used with no standardization of methodologies, resulting in varying prevalences which may under- or over-estimate the prevalence depending of the techniques used. This review discusses the advantages and disadvantages of various screening tests used to diagnose rickets in communities. Clinical signs characteristic of rachitic deformities have been used extensively, but are likely to over-estimate the prevalence and are dependent on the clinical skills of the observer. Biochemical tests such as alkaline phosphatase and 25-hydroxyvitamin D have also been proposed. There is no consensus on the usefulness of alkaline phosphatase as a screening tool, while there is general agreement that the measurement of vitamin D status is unhelpful in screening for rickets. Finally, the confirmation of the presence of active rickets in suspected infants and children is dependent on radiographic findings, although these may be less helpful in adolescents whose growth plates might be closed or nearly so. In order to obtain uniformity in screening for rickets globally, the is a need for consensus among public health specialists, paediatric endocrinologists and those interested in paediatric bone disease as to the best methods to be employed to determine the prevalence of rickets, particularly in communities with limited resources.

Protective links between vitamin D, inflammatory bowel disease and colon cancer

Vitamin D deficiency has been associated with a wide range of diseases and multiple forms of cancer including breast, colon, and prostate cancers. Relatively recent work has demonstrated vitamin D to be critical in immune function and therefore important in inflammatory diseases such as inflammatory bowel disease (IBD). Because vitamin D deficiency or insufficiency is increasingly prevalent around the world, with an estimated 30%-50% of children and adults at risk for vitamin D deficiency worldwide, it could have a significant impact on IBD. Epidemiologic studies suggest that low serum vitamin D levels are a risk factor for IBD and colon cancer, and vitamin D supplementation is associated with decreased colitis disease activity and/or alleviated symptoms. Patients diagnosed with IBD have a higher incidence of colorectal cancer than the general population, which supports the notion that inflammation plays a key role in cancer development and underscores the importance of understanding how vitamin D influences inflammation and its cancer-promoting effects. In addition to human epidemiological data, studies utilizing mouse models of colitis have shown that vitamin D is beneficial in preventing or ameliorating inflammation and clinical disease. The precise role of vitamin D on colitis is unknown; however, vitamin D regulates immune cell trafficking and differentiation, gut barrier function and antimicrobial peptide synthesis, all of which may be protective from IBD and colon cancer. Here we focus on effects of vitamin D on inflammation and inflammation-associated colon cancer and discuss the potential use of vitamin D for protection and treatment of IBD and colon cancer.

Epigenetic histone modifications and master regulators as determinants of context dependent nuclear receptor activity in bone cells

Genomic annotation of unique and combinatorial epigenetic modifications along with transcription factor occupancy is having a profound impact on our understanding of the genome. These studies have led to a better appreciation of the dynamic nature of the epigenetic and transcription factor binding components that reveal overarching principles of the genome as well as tissue specificity. In this minireview, we discuss the presence and potential functions of several of these features across the genome in osteoblast lineage cells. We examine how these features are modulated during cellular maturation, affect transcriptional output and phenotype, and how they alter the ability of cells to respond to systemic signals directed by calcemic hormones such as 1,25-dihydroxyvitamin D3 and PTH. In particular, we describe recent experiments which indicate that progressive stages of bone cell differentiation affect RUNX2 binding to the genome, modify and restrict patterns of gene expression, and dramatically alter cellular response to the vitamin D hormone. These studies expand our understanding of mechanisms that govern steroid hormone regulation of gene expression, while highlighting the increasing complexity that is evident relative to these basic cellular processes. The results also have profound implications with respect to the impact of skeletal diseases on transcriptional outcomes as well. This article is part of a Special Issue entitled Epigenetics and Bone.

The clinical use of vitamin D metabolites and their potential developments: a position statement from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and the International Osteoporosis Foundation (IOF)

Several compounds are produced along the complex pathways of vitamin D3 metabolism, and synthetic analogs have been generated to improve kinetics and/or vitamin D receptor activation. These metabolites display different chemical properties with respect to the parental or native vitamin D3, i.e., cholecalciferol, which has been, so far, the supplement most employed in the treatment of vitamin D inadequacy. Hydrophilic properties of vitamin D3 derivatives facilitate their intestinal absorption and their manageability in the case of intoxication because of the shorter half-life. Calcidiol is a more hydrophilic compound than parental vitamin D3. Active vitamin D analogs, capable of binding the vitamin D receptor evoking vitamin D-related biological effects, are mandatorily employed in hypoparathyroidism and kidney failure with impaired 1α-hydroxylation. They have been shown to increase BMD, supposedly ameliorating calcium absorption and/or directly affecting bone cells, although their use in these conditions is jeopardized by the development of hypercalciuria and mild hypercalcemia. Further studies are needed to assess their overall safety and effectiveness in the long-term and new intermittent regimens, especially when combined with the most effective antifracture agents.

Associations of 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D With Bone Mineral Density, Bone Mineral Density Change, and Incident Nonvertebral Fracture

Relationships between 1,25-dihydroxyvitamin D (1,25(OH)2 D) and skeletal outcomes are uncertain. We examined the associations of 1,25(OH)2 D with bone mineral density (BMD), BMD change, and incident non-vertebral fractures in a cohort of older men and compared them with those of 25-hydroxyvitamin D (25OHD). The study population included 1000 men (aged 74.6 ± 6.2 years) in the Osteoporotic Fractures in Men (MrOS) study, of which 537 men had longitudinal dual-energy X-ray absorptiometry (DXA) data (4.5 years of follow-up). A case-cohort design and Cox proportional hazards models were used to test the association between vitamin D metabolite levels and incident nonvertebral and hip fractures. Linear regression models were used to estimate the association between vitamin D measures and baseline BMD and BMD change. Interactions between 25OHD and 1,25(OH)2 D were tested for each outcome. Over an average follow-up of 5.1 years, 432 men experienced incident nonvertebral fractures, including 81 hip fractures. Higher 25OHD was associated with higher baseline BMD, slower BMD loss, and lower hip fracture risk. Conversely, men with higher 1,25(OH)2 D had lower baseline BMD. 1,25(OH)2 D was not associated with BMD loss or nonvertebral fracture. Compared with higher levels of calcitriol, the risk of hip fracture was higher in men with the lowest 1,25(OH)2 D levels (8.70 to 51.60 pg/mL) after adjustment for baseline hip BMD (hazard ratio [HR] = 1.99, 95% confidence interval [CI] 1.19-3.33). Adjustment of 1,25(OH)2 D data for 25OHD (and vice versa) had little effect on the associations observed but did attenuate the hip fracture association of both vitamin D metabolites. In older men, higher 1,25(OH)2 D was associated with lower baseline BMD but was not related to the rate of bone loss or nonvertebral fracture risk. However, with BMD adjustment, a protective association for hip fracture was found with higher 1,25(OH)2 D. The associations of 25OHD with skeletal outcomes were generally stronger than those for 1,25(OH)2 D. These results do not support the hypothesis that measures of 1,25(OH)2 D improve the ability to predict adverse skeletal outcomes when 25OHD measures are available. © 2015 American Society for Bone and Mineral Research.

Vitamin D, muscle and bone: Integrating effects in development, aging and injury

Beyond the established effects of muscle loading on bone, a complex network of hormones and growth factors integrates these adjacent tissues. One such hormone, vitamin D, exerts broad-ranging effects in muscle and bone calcium handling, differentiation and development. Vitamin D also modulates muscle and bone-derived hormones, potentially facilitating cross-talk between these tissues. In the clinical setting, vitamin D deficiency or mutations of the vitamin D receptor result in generalized atrophy of muscle and bone, suggesting coordinated effects of vitamin D at these sites. In this review, we discuss emerging evidence that vitamin D exerts specific effects throughout the life of the musculoskeletal system - in development, aging and injury. From this holistic viewpoint, we offer new insights into an old debate: whether vitamin D's effects in the musculoskeletal system are direct via local VDR signals or indirect via its systemic effects in calcium and phosphate homeostasis.

Physiological functions of vitamin D: what we have learned from global and conditional VDR knockout mouse studies

The physiological role of vitamin D depends on calcium supply and calcium balance. When the calcium balance is normal, the major target of vitamin D is intestine. Vitamin D stimulates mainly active intestinal calcium transport mechanism. During a negative calcium balance, bone effects of vitamin D become dominant. Thus, the role of vitamin D in maintaining normocalcemia appears to have priority over skeletal integrity in these situations.