No increase in risk of hip fracture at high serum retinol concentrations in community-dwelling older Norwegians: the Norwegian Epidemiologic Osteoporosis Studies

Elucidating causal relationships of diet-derived circulating antioxidants and the risk of osteoporosis: A Mendelian randomization study

Background

Osteoporosis (OP) is typically diagnosed by evaluating bone mineral density (BMD), and it frequently results in fractures. Here, we investigated the causal relationships between diet-derived circulating antioxidants and the risk of OP using Mendelian randomization (MR).

Methods

Published studies were used to identify instrumental variables related to absolute levels of circulating antioxidants like lycopene, retinol, ascorbate, and β-carotene, as well as antioxidant metabolites such as ascorbate, retinol, α-tocopherol, and γ-tocopherol. Outcome variables included BMD (in femoral neck, lumbar spine, forearm, heel, total body, total body (age over 60), total body (age 45-60), total body (age 30-45), total body (age 15-30), and total body (age 0-15)), fractures (in arm, spine, leg, heel, and osteoporotic fractures), and OP. Inverse variance weighted or Wald ratio was chosen as the main method for MR analysis based on the number of single nucleotide polymorphisms (SNPs). Furthermore, we performed sensitivity analyses to confirm the reliability of the findings.

Results

We found a causal relationship between absolute retinol levels and heel BMD (p = 7.6E-05). The results of fixed effects IVW showed a protective effect of absolute retinol levels against heel BMD, with per 0.1 ln-transformed retinol being associated with a 28% increase in heel BMD (OR: 1.28, 95% CI: 1.13-1.44). In addition, a sex-specific effect of the absolute circulating retinol levels on the heel BMD has been observed in men. No other significant causal relationship was found.

Conclusion

There is a positive causal relationship between absolute retinol levels and heel BMD. The implications of our results should be taken into account in future studies and in the creation of public health policies and OP prevention tactics.

Vitamin A - discovery, metabolism, receptor signaling and effects on bone mass and fracture susceptibility

The first evidence of the existence of vitamin A was the observation 1881 that a substance present in small amounts in milk was necessary for normal development and life. It was not until more than 100 years later that it was understood that vitamin A acts as a hormone through nuclear receptors. Unlike classical hormones, vitamin A cannot be synthesized by the body but needs to be supplied by the food as retinyl esters in animal products and ß-carotene in vegetables and fruits. Globally, vitamin A deficiency is a huge health problem, but in the industrialized world excess of vitamin A has been suggested to be a risk factor for secondary osteoporosis and enhanced susceptibility to fractures. Preclinical studies unequivocally have shown that increased amounts of vitamin A cause decreased cortical bone mass and weaker bones due to enhanced periosteal bone resorption. Initial clinical studies demonstrated a negative association between intake of vitamin A, as well as serum levels of vitamin A, and bone mass and fracture susceptibility. In some studies, these observations have been confirmed, but in other studies no such associations have been observed. One meta-analysis found that both low and high serum levels of vitamin A were associated with increased relative risk of hip fractures. Another meta-analysis also found that low levels of serum vitamin A increased the risk for hip fracture but could not find any association with high serum levels of vitamin A and hip fracture. It is apparent that more clinical studies, including large numbers of incident fractures, are needed to determine which levels of vitamin A that are harmful or beneficial for bone mass and fracture. It is the aim of the present review to describe how vitamin A was discovered and how vitamin A is absorbed, metabolized and is acting as a ligand for nuclear receptors. The effects by vitamin A in preclinical studies are summarized and the clinical investigations studying the effect by vitamin A on bone mass and fracture susceptibility are discussed in detail.

Vitamin A and Bone Health: A Review on Current Evidence

Vitamin A is a fat-soluble micronutrient essential for growth, immunity, and good vision. The preformed retinol is commonly found in food of animal origin whereas provitamin A is derived from food of plant origin. This review summarises the current evidence from animal, human and cell-culture studies on the effects of vitamin A towards bone health. Animal studies showed that the negative effects of retinol on the skeleton were observed at higher concentrations, especially on the cortical bone. In humans, the direct relationship between vitamin A and poor bone health was more pronounced in individuals with obesity or vitamin D deficiency. Mechanistically, vitamin A differentially influenced the stages of osteogenesis by enhancing early osteoblastic differentiation and inhibiting bone mineralisation via retinoic acid receptor (RAR) signalling and modulation of osteocyte/osteoblast-related bone peptides. However, adequate vitamin A intake through food or supplements was shown to maintain healthy bones. Meanwhile, provitamin A (carotene and β-cryptoxanthin) may also protect bone. In vitro evidence showed that carotene and β-cryptoxanthin may serve as precursors for retinoids, specifically all-trans-retinoic acid, which serve as ligand for RARs to promote osteogenesis and suppressed nuclear factor-kappa B activation to inhibit the differentiation and maturation of osteoclasts. In conclusion, we suggest that both vitamin A and provitamin A may be potential bone-protecting agents, and more studies are warranted to support this hypothesis.

Non-Pharmacological Interventions towards Preventing the Triad Osteoporosis-Falls Risk-Hip Fracture, in Population Older than 65. Scoping Review

Osteoporosis leads to increased risk of falls, and thus an increase in fractures, highlighting here hip fractures, that result in high mortality, functional disability, and high medical expenditure. The aim is to summarise the available evidence on effective non-pharmacological interventions to prevent the triad osteoporosis/falls risk/hip fracture. A scoping review was conducted consulting the Scientific Electronic Library Online (Scielo), National Institute for Health and Care Excellence (NICE), Cumulative Index to Nursing & Allied Health Literature (CINAHL) y PubMed.databases. Inclusion criteria were articles published between 2013 and 2019, in Spanish or English. In addition, publications on a population over 65 years of age covering non-pharmacological interventions aimed at hip fracture prevention for both institutionalised patients in long-stay health centres or hospitals, and patients cared for at home, both dependent and non-dependent, were included. Sixty-six articles were selected and 13 non-pharmacological interventions were identified according to the Nursing Interventions Classification taxonomy, aimed at preventing osteoporosis, falls, and hip fracture. The figures regarding the affected population according to the studies are alarming, reflecting the importance of preventing the triad osteoporosis, falls risk, and hip fracture among the population over 65 years of age. The most effective interventions were focused on increasing Bone Mineral Density through diet, exercise, and falls prevention. As a conclusion, primary prevention should be applied to the entire adult population, with special emphasis on people with osteoporosis.

Maternal serum retinol, 25(OH)D and 1,25(OH)2D concentrations during pregnancy and peak bone mass and trabecular bone score in adult offspring at 26-year follow-up

Background

Vitamin A and D deficiency is prevalent in pregnant women worldwide. Both vitamins are involved in fetal skeletal development. A positive association between maternal vitamin D levels and offspring bone mineral density (BMD) at adulthood has been observed. The impact of maternal vitamin A status in pregnancy on offspring peak bone mass remains unclear.

Method and findings

Forty-one mother-child pairs were recruited from a population-based prospective cohort study in Trondheim, Norway, where pregnant women were followed from gestational week 17. Their term-born infants were followed from birth (1986–88). Regression analyses were performed for vitamin A (retinol), 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)₂D] in maternal serum (gestational weeks 17, 33, 37) and cord blood. Offspring BMD and spine trabecular bone score (TBS), a measure of bone quality, were analyzed by dual x-ray absorptiometry at 26 years. Average levels during pregnancy of retinol, 25(OH)D and 1,25(OH)₂D were 1.66 (0.32) μmol/L, 59.0 (20.6) nmol/L, and 251.3 (62.4) pmol/L, respectively. 1,25(OH)₂D levels were similar in those with 25(OH)D levels <30 and >75 nmol/L. After adjustment for maternal age, BMI, smoking, and education, and offspring birth weight, maternal serum retinol was positively associated with offspring spine BMD [mean change 30.8 (CI 7.6, 54.0) mg/cm² per 0.2 μmol/L retinol], and with offspring TBS, although non-significant (p = 0.08). No associations were found between maternal 25(OH)D and 1,25(OH)₂D levels and offspring bone parameters. Vitamin levels in cord blood were not associated with offspring BMD or TBS.

Conclusions

This is the first study to show an association between maternal vitamin A status and offspring peak bone mass. Our findings may imply increase future risk for osteoporotic fracture in offspring of mothers with suboptimal vitamin A level. No associations were observed between 25(OH)D and 1,25(OH)₂D and offspring BMD.

Creatinine, total cysteine and uric acid are associated with serum retinol in patients with cardiovascular disease

Purpose

We hypothesized that biomarkers and dietary factors related to cardiovascular disease risk were associated with serum retinol and evaluated these potential associations in patients with suspected coronary artery disease (CAD).

Methods

We used cross-sectional data from 4116 patients hospitalised for suspected CAD. Dietary data were obtained from a subgroup of 1962 patients using a food frequency questionnaire. Potential biomarkers and dietary factors were explored using linear regression modelling adjusted for age and sex. Regression coefficients and corresponding confidence intervals (CI) are given as  % change in serum retinol per unit change in the predictors. Analyses were performed in the total population and in strata of serum retinol tertiles.

Results

In age- and sex-adjusted models, serum creatinine (standardized β: 0.38, 95% CI [0.35, 0.42]), plasma total cysteine (0.26, [0.23, 0.29]), serum uric acid (0.30, [0.26, 0.33]) and plasma neopterin (0.22, [0.18, 0.25]) were positively associated, whereas plasma serine (− 0.15, [− 0.18, − 0.12]) and serum C-reactive protein (− 0.15, [− 0.18, − 0.12]) were inversely associated with serum retinol. When we included the significant biomarkers in a multivariate model, the model explained 33% of the variability (R² = 0.33) in serum retinol. The results were similar in the lower and upper tertiles of serum retinol. Weak or no associations were observed for dietary factors.

Conclusions

In patients with suspected CAD, concentrations of creatinine, cysteine and uric acid were positively associated with serum retinol. Future studies should assess whether retinol concentrations are influenced by metabolic alterations in patients at risk of cardiovascular disease.

Effects of Rhizoma Drynariae Cataplasm on Fracture Healing in a Rat Model of Osteoporosis

BACKGROUND Osteoporosis is an increasingly prevalent disease characterized by decreased bone mass and deterioration of the bone microstructure, which contribute to increased fragility and subsequent fragility fractures, especially in elderly individuals. Rhizoma Drynariae (DRE) is among the most frequently used herbal medicines for the treatment of osteoporosis. Transdermal delivery is a proven novel pathway for drug treatment and has several advantages over traditional drug delivery routes. MATERIAL AND METHODS Female Sprague-Dawley osteoporotic fracture model rats were divided into 3 groups: the control group, the DRE (90 mg/kg/day) group and the DRE cataplasm (containing 30 mg DRE, administered at right femur site daily) group. At 3 and 6 weeks after operation, we performed x-ray, histological, and biomechanical analyses, and evaluated bone marrow density of the femur. RESULTS Treatment with DRE increased callus formation and bone union compared with the control group. Moreover, DRE enhanced bone strength at the femoral diaphysis in the osteoporotic fractures in rats by increasing the ultimate load and stiffness compared with the control group. Furthermore, DRE restored the trabecular bone mineral density in the femur compared with the control group. DRE cataplasm application further enhanced the therapeutic effects against osteoporotic fracture in this rat model. CONCLUSIONS DRE cataplasm application might be useful against osteoporotic fracture.

Circulating serum level of retinoic acid and hip fractures among postmenopausal women

PURPOSE

The aim of this study was to evaluate the serum levels of retinoic acid (RA), an active form of vitamin A, in postmenopausal women with hip fractures from Zhengzhou, China.

METHODS

This was a case-control study from the Affiliated Hospital of Zhengzhou University. Serum samples were drawn from 375 postmenopausal women who were diagnosed as having hip fracture and 750 matched controls without fracture. Serum RA levels were evaluated as both a continuous variable and a categorical variable in quintiles.

RESULTS

The results showed that the serum levels of RA were significantly (P = .039) higher in patients with hip fracture compared with controls. In univariate and multivariate logistic regression analysis, for each 1 ng/mL increase of serum level of RA, the unadjusted and adjusted risk of hip fracture would be increased by 5% (odds ratio [OR] = 1.05; 95% confidence interval [CI] = 1.00-1.10; P = .035) and 2% (OR = 1.02; 95% CI = 0.95-1.11; P = .096), respectively. In multivariate models comparing the fifth with the third quintiles of RA, the RA was associated with hip fracture, and adjusted risk of hip fracture would be increased by 52% (OR = 1.52; 95% CI = 1.13-1.42; P = .011).

CONCLUSIONS

The results of our study suggest that subclinical higher levels of RA may increase the risk of hip fracture in postmenopausal women, particularly among the top quintile of serum RA. J Am Geriatr Soc 67:336-341, 2019.

Vitamin D status and its management for achieving optimal health benefits in the elderly

INTRODUCTION

Vitamin D deficiency is common, world-wide, but vitamin D repletion throughout life, and into older age, has accepted health benefits for bone. Many mechanisms through which vitamin D also benefits soft tissues are understood, and clinical evidence of such benefits is now accumulating, especially following re-analyses of trial data, which are revealing previously missed health benefits with correction of deficiency.

AREAS COVERED

The sources of vitamin D, its activation, mechanistic effects; problems of trials of supplementation for reducing health risks, the benefits shown for mortality, cardiovascular disease, infection and cancer; the global problem of vitamin D deficiency; age-related reductions in vitamin D efficacy, and currently recommended intakes.

EXPERT COMMENTARY

High prevalence of vitamin D deficiency and insufficiency worldwide have proven ill-effects on health. Governmental efforts to improve population repletion by recommending minimal daily intakes does benefit some but is not effective at the population-level. However, food fortification with vitamin D3, already implemented in some countries, can solve this highly avoidable problem cost-effectively and is probably the best way to abolish vitamin D inadequacy, allowing public health benefits to emerge over time, thereby allowing future research on vitamin D to be directed at emerging issues on vitamin D.

The risk association of plasma total homocysteine with acute myocardial infarction is modified by serum vitamin A

Background

Plasma total homocysteine (tHcy) has been implicated in the development of cardiovascular disease, but the mechanisms remain unclear. Vitamin A (Vit-A) is involved in homocysteine metabolism and we therefore explored the potential interaction between plasma tHcy and serum Vit-A in relation to incident acute myocardial infarction.

Methods

Cox proportional hazards models were used to assess the prospective relationships between tHcy and acute myocardial infarction in 2205 patients from Western Norway undergoing elective coronary angiography for suspected stable angina pectoris. Results are reported as hazard ratio per standard deviation increase in log-transformed tHcy. An interaction term for tHcy × Vit-A was added to multivariate models including age, sex, smoking, apolipoprotein B fasting, statin and aspirin prescription and estimated glomerular filtration rate.

Results

Geometric mean (geometric standard deviation) age of the participants (64.3% men) was 62.3 (1.24) years. Plasma tHcy was higher among participants in the upper versus lower Vit-A tertile. During 7 (2.4) years of follow-up, 15.1% suffered an AMI. A significant association of plasma tHcy with AMI in the total study population was observed. When we stratified the population according to Vit-A tertiles, plasma tHcy was associated with acute myocardial infarction only in the upper Vit-A tertile (hazard ratio per SD: 1.25, 95% confidence interval: 1.04–1.53, pinteraction = 0.03).

Conclusions

The risk relationship between plasma tHcy and acute myocardial infarction was modified by serum concentrations of Vit-A in patients with suspected stable angina pectoris. This finding may clarify the relationship between tHcy and cardiovascular disease.

Overfed but undernourished: recognizing nutritional inadequacies/deficiencies in patients with overweight or obesity

Overweight and obesity are highly prevalent throughout the world and can adversely affect the nutritional status of individuals. Studies have shown that many people with obesity have inadequate intake of iron, calcium, magnesium, zinc, copper, folate and vitamins A and B₁₂, likely as a result of poor diet quality. Nutritional inadequacies or deficiencies may also occur due to altered pharmacokinetics in the individual with obesity and due to interactions in those with overweight or obesity with various pharmaceuticals. However, it has been demonstrated that the adult population in the United States as a whole is deficient in certain micronutrients as a result of the availability and overconsumption of high-calorie, low-nutrient processed foods. Poor nutrition may contribute to the development of certain chronic conditions, such as type 2 diabetes, which is already more prevalent in those with obesity. Clinicians need to be aware of these gaps, particularly in those individuals with obesity who are undergoing bariatric surgery or taking pharmaceutical products long term to facilitate weight loss. Patients with overweight or obesity likely struggle to achieve a balanced diet and may benefit from consultation with a dietitian. Along with providing recommendations for healthy eating and exercise, supplementation with specific micronutrients or multivitamins should be considered for individuals at the highest risk for or with established deficiencies. Further research is needed to understand the factors underlying nutritional inadequacies in individuals with overweight or obesity, as well as the outcomes of treatment strategies employed to address them.

The Effect of Vitamin A on Fracture Risk: A Meta-Analysis of Cohort Studies

This meta-analysis evaluated the influence of dietary intake and blood level of vitamin A (total vitamin A, retinol or β-carotene) on total and hip fracture risk. Cohort studies published before July 2017 were selected through English-language literature searches in several databases. Relative risk (RR) with corresponding 95% confidence interval (CI) was used to evaluate the risk. Heterogeneity was checked by Chi-square and I² test. Sensitivity analysis and publication bias were also performed. For the association between retinol intake and total fracture risk, we performed subgroup analysis by sex, region, case ascertainment, education level, age at menopause and vitamin D intake. R software was used to complete all statistical analyses. A total of 319,077 participants over the age of 20 years were included. Higher dietary intake of retinol and total vitamin A may slightly decrease total fracture risk (RR with 95% CI: 0.95 (0.91, 1.00) and 0.94 (0.88, 0.99), respectively), and increase hip fracture risk (RR with 95% CI: 1.40 (1.02, 1.91) and 1.29 (1.06, 1.57), respectively). Lower blood level of retinol may slightly increase total fracture risk (RR with 95% CI: 1.11 (0.94, 1.30)) and hip fracture risk (RR with 95% CI: 1.27 (1.05, 1.53)). In addition, higher β-carotene intake was weakly associated with the increased risk of total fracture (RR with 95% CI: 1.07 (0.97, 1.17)). Our data suggest that vitamin A intake and level may differentially influence the risks of total and hip fractures. Clinical trials are warranted to confirm these results and assess the clinical applicability.

Maternal and neonatal vitamin D status, genotype and childhood celiac disease

Background

Low concentration of 25-hydroxyvitamin D during pregnancy may be associated with offspring autoimmune disorders. Little is known about environmental triggers except gluten for celiac disease, a common immune-mediated disorder where seasonality of birth has been reported as a risk factor. We therefore aimed to test whether low maternal and neonatal 25-hydroxyvitamin D predicted higher risk of childhood celiac disease.

Methods and Findings

In this Norwegian nationwide pregnancy cohort (n = 113,053) and nested case-control study, we analyzed 25-hydroxyvitamin D in maternal blood from mid-pregnancy, postpartum and cord plasma of 416 children who developed celiac disease and 570 randomly selected controls. Mothers and children were genotyped for established celiac disease and vitamin D metabolism variants. We used mixed linear regression models and logistic regression to study associations.

There was no significant difference in average 25-hydroxyvitamin D between cases and controls (63.1 and 62.1 nmol/l, respectively, p = 0.28), and no significant linear trend (adjusted odds ratio per 10 nM increase 1.05, 95% CI: 0.93–1.17). Results were similar when analyzing the mid-pregnancy, postpartum or cord plasma separately. Genetic variants for vitamin D deficiency were not associated with celiac disease (odds ratio per risk allele of the child, 1.00; 95% CI, 0.90 to 1.10, odds ratio per risk allele of the mother 0.94; 95% CI 0.85 to 1.04). Vitamin D intake in pregnancy or by the child in early life did not predict later celiac disease. Adjustment for established genetic risk markers for celiac disease gave similar results.

Conclusions

We found no support for the hypothesis that maternal or neonatal vitamin D status is related to the risk of childhood celiac disease.

Effect of icariin on fracture healing in an ovariectomized rat model of osteoporosis

Osteoporosis is frequently asymptomatic, presenting a significant clinical and economic burden, particularly following an osteoporosis-associated fracture. Icariin has been reported to inhibit osteoporosis in vitro, and the present study investigated whether icariin also promoted bone fracture healing in ovariectomized osteoporotic (OVX) rats in vivo. A total of 30 female rats were randomly divided into three groups (n=10 per group): i) Sham surgery; ii) OVX; and iii) OVX with icariin (OVX + ICA) groups. At 3 months after the ovariectomy, a unilateral cross-tibia fracture was made at the proximal right tibia. Animals were then sacrificed after 5 weeks of oral treatment. X-rays were taken at 1 week, 3 weeks and 5 weeks of treatment, and dual energy X-ray absorptiometry was used to measure the bone mineral density (BMD). Changes to the osteocalcin (BGLAP), alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP) and estradiol levels in blood were measured. Callus formation and bone union were observed, the BMD was significantly higher and the BGLAP, ALP and TRAP levels were reduced, but no significant increase was observed in the blood estradiol level in the OVX + ICA group compared with the OVX group. The present findings indicate that icariin has potential as a novel alternative therapeutic agent for fracture healing in postmenopausal osteoporosis.

Nuclear Receptors in Skeletal Homeostasis

Nuclear receptors are a family of transcription factors that can be activated by lipophilic ligands. They are fundamental regulators of development, reproduction, and energy metabolism. In bone, nuclear receptors enable bone cells, including osteoblasts, osteoclasts, and osteocytes, to sense their dynamic microenvironment and maintain normal bone development and remodeling. Our views of the molecular mechanisms in this process have advanced greatly in the past decade. Drugs targeting nuclear receptors are widely used in the clinic for treating patients with bone disorders such as osteoporosis by modulating bone formation and resorption rates. Deficiency in the natural ligands of certain nuclear receptors can cause bone loss; for example, estrogen loss in postmenopausal women leads to osteoporosis and increases bone fracture risk. In contrast, excessive ligands of other nuclear receptors, such as glucocorticoids, can also be detrimental to bone health. Nonetheless, the ligand-induced osteoprotective effects of many other nuclear receptors, e.g., vitamin D receptor, are still in debate and require further characterizations. This review summarizes previous studies on the roles of nuclear receptors in bone homeostasis and incorporates the most recent findings. The advancement of our understanding in this field will help researchers improve the applications of agonists, antagonists, and selective modulators of nuclear receptors for therapeutic purposes; in particular, determining optimal pharmacological drug doses, preventing side effects, and designing new drugs that are more potent and specific.