Vitamin D insufficiency together with high serum levels of vitamin A increases the risk for osteoporosis in postmenopausal women

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.

Osteocyte-Like Cells Differentiated From Primary Osteoblasts in an Artificial Human Bone Tissue Model

In vitro models of primary human osteocytes embedded in natural mineralized matrix without artificial scaffolds are lacking. We have established cell culture conditions that favored the natural 3D orientation of the bone cells and stimulated the cascade of signaling needed for primary human osteoblasts to differentiate into osteocytes with the characteristically phenotypical dendritic network between cells. Primary human osteoblasts cultured in a 3D rotating bioreactor and incubated with a combination of vitamins A, C, and D for up to 21 days produced osteospheres resembling native bone. Osteocyte-like cells were identified as entrapped, stellate-shaped cells interconnected through canaliculi embedded in a structured, mineralized, collagen matrix. These cells expressed late osteoblast and osteocyte markers such as osteocalcin (OCN), podoplanin (E11), dentin matrix acidic phosphoprotein 1 (DMP1), and sclerostin (SOST). Organized collagen fibrils, observed associated with the cell hydroxyapatite (HAp) crystals, were found throughout the spheroid and in between the collagen fibrils. In addition to osteocyte-like cells, the spheroids consisted of osteoblasts at various differentiation stages surrounded by a rim of cells resembling lining cells. This resemblance to native bone indicates a model system with potential for studying osteocyte-like cell differentiation, cross-talk between bone cells, and the mineralization process in a bonelike structure in vitro without artificial scaffolds. In addition, natural extracellular matrix may allow for the study of tissue-specific biochemical, biophysical, and mechanical properties. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Vitamin A Nutritional Status Is a Key Determinant of Bone Mass in Children

The bone mass increases that occur during the period of childhood are of great significance for maximizing the peak bone mass in adults and preventing for osteoporosis. Studies have reported that VA can improve the bone health in adults. Moreover, limited studies have assessed such associations in children. In this cross-sectional study including 426 children, we assessed the children’s plasma retinol concentration by liquid chromatography–mass spectrometry and the dietary intake of VA and carotenoids using a structured Food Frequency Questionnaire. Their bone mineral content and bone mineral density (BMD) were measured using dual-energy X-ray absorptiometry. After adjusting for potential confounders, the restricted cubic spline revealed an inverted U-shaped association between plasma retinol concentration and BMD; the estimated effects on the TBLH BMD per μmol/L increase in the plasma retinol concentration were 1.79 × 10⁻² g/cm² below 1.24 μmol/L and −5.78 × 10⁻³ g/cm² above this point (p for non-linearity = 0.046). A multiple linear regression analysis revealed a positive association between the plasma retinol concentration and the TBLH BMC (β = 1.89, 95% CI: 1.64 × 10⁻¹–3.62, p = 0.032). In conclusion, an appropriate plasma retinol concentration and greater intakes of dietary VA and β-carotene may enhance the bone mineral status of children who are aged 6–9 years.

Characterization of methylation patterns associated with lifestyle factors and vitamin D supplementation in a healthy elderly cohort from Southwest Sweden

Numerous studies have shown that lifestyle factors, such as regular physical activity and vitamin D intake, may remarkably improve overall health and mental wellbeing. This is especially important in older adults whose vitamin D deficiency occurs with a high prevalence. This study aimed to examine the influence of lifestyle and vitamin D on global DNA methylation patterns in an elderly cohort in Southwest of Sweden. We also sought to examine the methylation levels of specific genes involved in vitamin D's molecular and metabolic activated pathways. We performed a genome wide methylation analysis, using Illumina Infinium DNA Methylation EPIC 850kBeadChip array, on 277 healthy individuals from Southwest Sweden at the age of 70–95. The study participants also answered queries on lifestyle, vitamin intake, heart medication, and estimated health. Vitamin D intake did not in general affect methylation patterns, which is in concert with other studies. However, when comparing the group of individuals taking vitamin supplements, including vitamin D, with those not taking supplements, a difference in methylation in the solute carrier family 25 (SCL25A24) gene was found. This confirms a previous finding, where changes in expression of SLC25A24 were associated with vitamin D treatment in human monocytes. The combination of vitamin D intake and high physical activity increased methylation of genes linked to regulation of vitamin D receptor pathway, the Wnt pathway and general cancer processes. To our knowledge, this is the first study detecting epigenetic markers associated with the combined effects of vitamin D supplementation and high physical activity. These results deserve to be further investigated in an extended, interventional study cohort, where also the levels of 25(OH)D₃ can be monitored.

Effects of Extracellular Osteoanabolic Agents on the Endogenous Response of Osteoblastic Cells

The complex multidimensional skeletal organization can adapt its structure in accordance with external contexts, demonstrating excellent self-renewal capacity. Thus, optimal extracellular environmental properties are critical for bone regeneration and inextricably linked to the mechanical and biological states of bone. It is interesting to note that the microstructure of bone depends not only on genetic determinants (which control the bone remodeling loop through autocrine and paracrine signals) but also, more importantly, on the continuous response of cells to external mechanical cues. In particular, bone cells sense mechanical signals such as shear, tensile, loading and vibration, and once activated, they react by regulating bone anabolism. Although several specific surrounding conditions needed for osteoblast cells to specifically augment bone formation have been empirically discovered, most of the underlying biomechanical cellular processes underneath remain largely unknown. Nevertheless, exogenous stimuli of endogenous osteogenesis can be applied to promote the mineral apposition rate, bone formation, bone mass and bone strength, as well as expediting fracture repair and bone regeneration. The following review summarizes the latest studies related to the proliferation and differentiation of osteoblastic cells, enhanced by mechanical forces or supplemental signaling factors (such as trace metals, nutraceuticals, vitamins and exosomes), providing a thorough overview of the exogenous osteogenic agents which can be exploited to modulate and influence the mechanically induced anabolism of bone. Furthermore, this review aims to discuss the emerging role of extracellular stimuli in skeletal metabolism as well as their potential roles and provide new perspectives for the treatment of bone disorders.

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.

Coexistence of metabolic syndrome and osteopenia associated with social inequalities and unhealthy lifestyle among postmenopausal women in South Korea: the 2008 to 2011 Korea National Health and Nutritional Examination Survey (KNHANES)

OBJECTIVE

The prevalence of metabolic syndrome (MetS) and osteoporosis (OP) among postmenopausal women has been rapidly increasing. We examined the associations between socioeconomic status-related factors, unhealthy lifestyle, and the coexistence of MetS and osteopenia or OP.

METHODS

One thousand nine hundred ninety-one postmenopausal women aged 45 to 65 years were used to select a representative sample of the civilian, noninstitutionalized South Korean population from the 2008 to 2011 Korea National Health and Nutrition Examination Survey data. Women were grouped as neither MetS nor OP (normal), MetS, OP, and both MetS and OP (MetS + OP). Socioeconomic status (education, household income, place of residence, employment status), health-related behaviors (physical activity, alcohol consumption, smoking), and diet-related factors (intake of nutrients and food groups, eating habits, food insecurity) were obtained. Logistic regression models were used to examine the odds ratio (OR) and 95% confidence interval (CI).

RESULTS

The prevalence of MetS + OP was 32.5%. The average number of MetS risk factors in MetS + OP was 3.5, higher than that of normal and OP groups (P < 0.001). Bone mineral density at all sites was significantly lower in MetS + OP than normal and MetS groups (P < 0.001). Also, calcium, phosphorus, vitamin A, riboflavin, and niacin levels were lowest in the MetS + OP group compared with the three other groups (P < 0.05). After controlling for covariates, low-income and low-education women were more likely to have MetS + OP (OR 1.97, 95% CI 1.04-3.72); high-income and high-education group was 70% less likely to have MetS + OP (OR 0.30, 95% CI 0.10-0.86) compared with the middle-income and middle-education group.

CONCLUSIONS

Social inequalities might be powerful contributors in Korean postmenopausal women with coexistence of MetS and OP. Therefore, social and political perspective approaches are required in this population for prevention and treatment of MetS and OP. Future studies should explore to find controllable factors and thereby improve health status in postmenopausal women.

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.

Antifibrotic Effects of 1,25(OH)2D3 on Nonalcoholic Steatohepatitis in Female Mice

BACKGROUND

Postmenopausal women have a higher risk of nonalcoholic steatohepatitis (NASH) along with an increase in age, and vitamin D deficiency occurs in some patients with NASH.

AIM

We performed ovariectomy (OVX) surgery on female mice to mimic menopause, fed them a choline-deficient high-fat (CDHF) diet to induce NASH, and then investigated the effects of treatment with 1,25(OH)₂D₃.

METHODS

Seven-week-old C57BL/6J female mice were separated into five experimental groups: SHAM, OVX, and OVX + intraperitoneal (i.p.) injection of 1,25(OH)₂D₃ (0.0008, 0.004, and 0.02 μg/kg). All groups were fed a CDHF diet for 8 weeks. Injections took place twice per week throughout the experimental period. Blood samples and liver tissue were collected for analyzing liver histological changes, serum biochemical indicators of hepatic function, and hepatic genes associated with fibrosis.

RESULTS

Supplementation of 1,25(OH)₂D₃ in CDHF-diet mice showed decreased serum levels of ALT, AST, indicating the improvement in overall liver function, and suppressed histological NASH regarding fibrosis stage, lobular inflammation, and steatosis compared to the OVX group. Primary fibrotic markers of TGF-β, TIMP-1, α-SMA, and COL1A1 were significantly lower in the 1,25(OH)₂D₃ groups than in the OVX group. Furthermore, down-regulated levels of SMAD2 and SMAD3 were also observed in 1,25(OH)₂D₃ groups.

CONCLUSION

Supplementation of 1,25(OH)₂D₃ may ameliorate liver fibrosis and improve liver function in OVX mice with NASH induced by a CDHF diet, suggesting the therapeutic effects on postmenopause with NASH.

Prevalence of hypovitaminosis D in postmenopausal women: a systematic review

BACKGROUND

Hypovitaminosis D is considered a global public health issue. Knowledge of its true dimensions will allow us to design interventions and plan preventive measures that can have a significant impact on human health.

OBJECTIVES

The aim of this study was to evaluate the prevalence of hypovitaminosis D, defined as a serum 25-hydroxyvitamin D concentration < 30 ng/ml, in postmenopausal women around the world, as well as to identify the potential associated factors.

METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses recommendations. Specific search terms were consulted in Medline, Excerpta Medica, and Latin-American and Caribbean Health Sciences Literature databases, with no restriction for the year or language of publication.

RESULTS

Of 451 studies initially identified, 32 were selected for analysis. Collectively, those 32 studies evaluated 21,236 postmenopausal women, of whom 16,440 (77.4%) had serum 25-hydroxyvitamin D concentrations < 30 ng/ml. The reported prevalence of hypovitaminosis D ranged from 29% (in the United States) to 99.4% (in China). In six of the studies, the prevalence was above 90%.

CONCLUSIONS

If the criterion is the 30 ng/ml cut-off point, the majority of postmenopausal women in the world could be classified as having hypovitaminosis D. Among the studies evaluated, the lowest prevalence reported was nearly 30%. Neither latitude, region of the world, nor laboratory methodology were found to be associated with the prevalence of hypovitaminosis D.

High Serum Retinol as a Relevant Contributor to Low Bone Mineral Density in Postmenopausal Osteoporotic Women

There is controversial information about the impact of vitamin A on bone. Some epidemiological studies show that excessive intake of vitamin A, or an excess of serum vitamin A, has related with adverse impact on bone mass; however, other studies did not find these links, and some authors have proposed that this vitamin might promote a better bone health. The present work aims to contribute to clarify the real role of vitamin A in bone tissue. For this purpose, a cross-sectional study of 154 osteoporotic non-treated postmenopausal women (> 65 years old) was carried out. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. We assessed concentrations of serum retinol, osteocalcin, parathyroid hormone, alkaline phosphatase, calcium, and phosphorus. We also studied demographic and anthropometric parameters. Spearman's correlations between retinol levels and other variables found negative correlations with BMD in both lumbar spine (R = - 0.162, P < 0.01) and femoral neck (R = - 0.182, P < 0.01), as well as alkaline phosphatase (R = - 0.110; P < 0.05) and phosphorus (R = - 0.110; P < 0.05). A positive correlation between retinol and fertile window was observed (R = 0.158; P < 0.01). After multivariable adjustment, we still found a negative correlation between serum retinol and BMD, both at the lumbar spine (R = - 0.210; P < 0.01) and at the femoral neck (R = - 0.324, P < 0.001). It is concluded that elevated serum-retinol levels are associated with an increased risk of low bone mass and thus with osteoporotic fractures. Therefore, osteoporosis-risk assessment should include quantification of serum metabolite of vitamin A.

Survey on the levels of 25-hydroxy vitamin D and bone metabolic markers and evaluation of their correlations with osteoporosis in perimenopausal woman in Xi'an region

It has been accepted that vitamin D (VD) plays an important role in bone metabolism. However, the levels of VD in people of different regions are quite different and there is still no final conclusion on the significant correlation between VD and osteoporosis. 245 cases of peri-menopausal women were collected to study the relationship between VD and osteoporosis in western China. The mean value of 25-hydroxyvitamin D for the participants was 14.39 ng/mL. The average values of parathyroid hormone (PTH), calcium (Ca) and phosphorus (P) were 47.62 pg/mL, 2.26 mmol/L and 1.18 mmol/L, respectively. The average value of bone mineral density (BMD) in lumbar vertebrae was -1.20 SD and that in femoral neck was -0.04 SD. Compared with normal group, PTH of VD deficiency group was significantly increased (P < 0.05), Ca was remarkably decreased (P < 0.01) while the BMD between these two groups showed no significant difference (P > 0.05). VD was in positive correlation with the age (P < 0.01) and Ca (< 0.01) of the participants, negative correlation with PTH (P < 0.01) while no significant correlation with the BMD of lumbar vertebrae and femoral neck (P > 0.05). The risk factors resulting in the occurrence of osteoporosis in the lumbar vertebrae of the participants covered Ca increase (OR = 66.247, P<0.05), age growth (OR = 1.194, P<0.01) and menopause (OR = 2.285, P<0.05). This study has found that the status of VD deficiency showed no significant correlation with the level of BMD, which hinted that independent measurement of the bone metabolic markers, including Ca, P, VD and PTH, was difficult to accurately reflect the status of BMD in peri-menopausal women of this region. It's necessary to combine multi-site bone scanning to diagnose the patients' status of osteoporosis so as to provide reasonable guidance for early clinical prevention and treatment.

Correlations Between Clinical Parameters and Health-Related Quality of Life in Postmenopausal Osteoporotic Women

The purpose of this study was to assess the correlation between health-related quality of life (HRQoL) and clinically relevant osteodensitometric and biochemical parameters in postmenopausal osteoporotic women. Bone mineral density (BMD) and T scores of the lumbar vertebrae and femoral neck were assessed in 100 osteoporotic women (56 without previous fractures and 44 with previous fractures) using dual x-ray absorptiometry. The Fracture Risk Assessment Tool (FRAX) index for major osteoporotic and hip fractures was calculated based on demographic data and hip BMD. Venous blood samples were taken from each subject for biochemical analysis (serum calcium, phosphorus, alkaline phosphatase and vitamin D levels). HRQoL was assessed using the QUALEFFO-41 questionnaire (domains: Health perception, Pain, and Physical, Social and Mental function). Basic participant characteristics (age, menopause length, body mass index, smoking habits, hereditary tendency towards fracture, fracture history) correlated with some of the QUALEFFO-41 domains, but the correlation coefficients were low (r<0.3), except in the case of the correlation between Pain and fracture history (r=0.638). Of the six variables included in the multiple regression model, fracture history was shown to be the most significant predictor with respect to the following three QUALEFFO-41 domains: Pain (b=20.511), Social function (b=2.548) and Health perception (b=3.185). Correlation analysis showed that after adjustment for basic characteristics, BMD and T score of the femoral neck and Pain (r=0.331 and r=0.449, respectively), Social function (r=0.422 and r=0.419) and Health perception (r=0.434 for T score of the femoral neck) exhibited the strongest correlations. Vitamin D was negatively correlated with Mental function, while the other biochemical parameters exhibited variable correlations with the QUALEFFO- 41 domains (r≈0.2-0.5). Our study confirmed the previously established relationship between BMD of the femoral neck and HRQoL in patients with osteoporosis and demonstrated correlations between various blood bone metabolism parameters and HRQoL that have not been previously investigated.

Effect of Calcitriol Supplementation on Blood Pressure in Older Adults

Recent studies suggest that vitamin D plays an important role in the control of blood pressure. Unfortunately, because older adults are more likely to have low 25-hydroxyvitamin-D [25(OH)D] levels, this study investigated whether calcitriol supplementation reduces blood pressure in older adults with hypertension. The design was a double-blind placebo-controlled randomized clinical trial with 36 randomly assigned subjects (71.7 ± 10 years). Blood pressure and serum levels of 25(OH)D before and after calcitriol intervention (1,000 IU daily for 6 weeks; n = 22) or placebo (n = 23) for 6 weeks were analyzed. At the end of the study, the calcitriol group presented a significant decrease of systolic blood pressure [20.25 mmHg (p = 0.001)] and diastolic blood pressure [7 mmHg (p = 0.01)], compared with the placebo group. In conclusion, 1,000 IU/day of calcitriol for 6 weeks efficiently reduced systolic and diastolic blood pressure levels in this population of older adults presenting with high blood pressure (Clinical Trial Approbation NCT02047799).

Association of dietary consumption and serum levels of vitamin A and β-carotene with bone mineral density in Chinese adults

BACKGROUND

Former studies suggested an adverse effect of hypervitaminosis A on bone health, while the effects of retinol and its precursor (β-carotene) remain uncertain in populations consuming vitamin A (VA) mainly from plant sources.

OBJECTIVE

We investigated the association of serum, dietary retinol, and β-carotene with bone mineral density (BMD) in Chinese adults.

METHODS

We recruited 2101 women and 1053 men (aged 40-75 years) in Guangzhou, China. Dietary intake was assessed through face-to-face interviews with food-frequency questionnaires at baseline and 3 years later. Serum levels of retinol and β-carotene were determined by HPLC using a baseline specimen, and the BMD for the whole body (WB), lumbar spine (LS), total hip (TH), and femur neck (FN) were measured using dual energy X-ray absorptiometry at follow-up.

RESULTS

In general, greater levels of serum retinol, β-carotene, and the β-carotene-to-retinol ratio were associated with a higher BMD after adjustment for potential covariates in the total sample. BMD values in the top (vs. bottom) quartile were increased by 2.06% (TH) for retinol; 2.87% (WB), 2.51% (LS), 3.10% (FN) for β-carotene; 2.21% (WB) and 2.05% (FN) for the β-carotene-to-retinol ratio in the total sample (all p<0.05). A significant positive association with BMD was observed for dietary intake of β-carotene and total VA in retinol equivalents at the hip sites in the total sample.

CONCLUSION

Higher circulating and dietary levels of VA and β-carotene and higher serum β-carotene-to-retinol ratios were positively associated with BMD in Chinese adults consuming relatively low levels of VA, mainly from plant foods.

Continuous Positive Airway Pressure Treatment Increases Serum Vitamin D Levels in Male Patients with Obstructive Sleep Apnea

STUDY OBJECTIVE

Recent studies report a link between obstructive sleep apnea (OSA) syndrome, low vitamin D levels, and high parathyroid hormone (PTH) concentrations. The aim of the current study is to evaluate the effect of 7-night continuous positive airway pressure (CPAP) therapy on serum vitamin D, PTH, and calcium levels in patients with severe OSA syndrome.

METHODS

Patients with severe OSA were enrolled into the study and compared to control subjects. Patients with OSA underwent CPAP therapy for 7 nights and were consequently divided into responders (OSA-R, mean residual AHI < 5/h) and nonresponders (OSA-nR, mean residual AHI > 5/h). Serum vitamin D, PTH, and calcium levels were measured at baseline in patients with severe OSA (apnea-hypopnea index > 30/h) and control subjects. Patients with OSA underwent a final morning blood sample after 7-night CPAP therapy.

RESULTS

We enrolled 90 patients with OSA into the study (65 OSA-R and 25 OSA-nR) compared to 32 control subjects. At baseline, lower vitamin D and higher PTH levels were detected in the OSA group compared to controls. After 7-night CPAP therapy, male OSA-R patients showed a significant increase in vitamin D levels. Conversely, female OSA-R patients did not show the same increase in vitamin D levels. It was also observed that OSA-nR subjects did not show modifications of serum markers after nCPAP-therapy.

CONCLUSIONS

The study demonstrates that short-term nCPAP treatment is able to promote the recovery of vitamin D homeostasis in male patients with OSA. The mediation of sexual hormones in regulating vitamin D is a possible explanation of the lack of recovery of vitamin D homeostasis in female patients with OSA as it often affects postmenopausal women.

Vitamin A intake, serum vitamin D and bone mineral density: analysis of the Korea National Health and Nutrition Examination Survey (KNHANES, 2008-2011)

The association of high vitamin A intake and low bone mineral density (BMD) is still controversial. To determine the association of dietary vitamin A intake and serum 25-hydroxyvitamin D (25(OH)D) concentration with BMD, a total of 6481 subjects (2907 men and 3574 women) aged ≥50 years from the Korean National Health and Nutrition Examination Survey (2008–2011) were divided into groups according to dietary vitamin A intake (tertiles) and serum 25(OH)D (<50, 50–75, >75 nmol/L), and evaluated for BMD after adjusting for relevant variables. Mean dietary vitamin A intakes were 737 and 600 μg RE (Retinol Equivalents) in men and women, respectively. Total hip and femoral neck BMD in men and lumbar spine BMD in women were both positively correlated with dietary vitamin A intake in subjects with serum 25(OH)D >75 nmol/L. Among men with serum 25(OH)D <50 nmol/L, both the top (mean 1353 μg RE) and bottom (mean 218 μg RE) tertiles of dietary vitamin A intake had lower BMD than the middle group (mean 577 μg RE). In this population, BMD was the highest among men and women with serum 25(OH)D = 50–75 nmol/L and that there were no differences in BMD by vitamin A intake in these vitamin D adequate groups. This cross-sectional study indicates that vitamin A intake does not affect bone mineral density as long as the serum 25(OH)D concentration is maintained in the moderate level of 50–75 nmol/L.

Serum levels of 25-hydroxyvitamin D and functional outcome among postmenopausal women with hip fracture

Objective

The main objective of the current study was to assess the distribution and its prognostic value of serum 25-hydroxyvitamin D (25[OH] D) levels assessed at admission in Chinese postmenopausal women with hip fracture.

Methods

From January 1, 2012 to December 31, 2013, all postmenopausal women with first-ever hip fracture were recruited to participate in the study. Serum 25[OH] D levels were measured at admission. The functional evaluation at the time of discharge was performed by the Barthel Index (BI). The prognostic value of 25[OH] D to predict the functional outcome within discharge was analyzed by logistic regression analysis, after adjusting for the possible confounders.

Results

In our study, 261 patients were included and assessed. In the 76 patients with an unfavorable functional outcome, serum 25(OH) D levels were lower compared with those in patients with a favorable outcome [11.8(IQR, 9.9–16.1)ng/ml; 16.8(IQR, 13.6–21.4)ng/ml, respectively; P<0.0001]. In multivariate analysis, there was an increased risk of unfavorable outcome associated with serum 25(OH) D levels ≤ 20ng/ml (OR 5.24, 95%CI: 3.11–8.15; P<0.0001) after adjusting for possible confounders.

Conclusions

Our data support an association between serum 25[OH] D levels and prognosis in Chinese postmenopausal women with hip fracture.

Retinoid receptors in bone and their role in bone remodeling

Vitamin A (retinol) is a necessary and important constituent of the body which is provided by food intake of retinyl esters and carotenoids. Vitamin A is known best for being important for vision, but in addition to the eye, vitamin A is necessary in numerous other organs in the body, including the skeleton. Vitamin A is converted to an active compound, all-trans-retinoic acid (ATRA), which is responsible for most of its biological actions. ATRA binds to intracellular nuclear receptors called retinoic acid receptors (RARα, RARβ, RARγ). RARs and closely related retinoid X receptors (RXRα, RXRβ, RXRγ) form heterodimers which bind to DNA and function as ligand-activated transcription factors. It has been known for many years that hypervitaminosis A promotes skeleton fragility by increasing osteoclast formation and decreasing cortical bone mass. Some epidemiological studies have suggested that increased intake of vitamin A and increased serum levels of retinoids may decrease bone mineral density and increase fracture rate, but the literature on this is not conclusive. The current review summarizes how vitamin A is taken up by the intestine, metabolized, stored in the liver, and processed to ATRA. ATRA's effects on formation and activity of osteoclasts and osteoblasts are outlined, and a summary of clinical data pertaining to vitamin A and bone is presented.

Micronutrient Needs of the Elderly

Older adults are becoming a significant percentage of the world's population. A multitude of factors, from the normal aging process to the progression of chronic disease, influence the nutrition needs of this very diverse group of people. Appropriate micronutrient intake is of particular importance but is often suboptimal. Here we review the available data regarding micronutrient needs and the consequences of deficiencies in the ever growing aged population.

Vitamin a metabolism, action, and role in skeletal homeostasis

Vitamin A (retinol) is ingested as either retinyl esters or carotenoids and metabolized to active compounds such as 11-cis-retinal, which is important for vision, and all-trans-retinoic acid, which is the primary mediator of biological actions of vitamin A. All-trans-retinoic acid binds to retinoic acid receptors (RARs), which heterodimerize with retinoid X receptors. RAR-retinoid X receptor heterodimers function as transcription factors, binding RAR-responsive elements in promoters of different genes. Numerous cellular functions, including bone cell functions, are mediated by vitamin A; however, it has long been recognized that increased levels of vitamin A can have deleterious effects on bone, resulting in increased skeletal fragility. Bone mass is dependent on the balance between bone resorption and bone formation. A decrease in bone mass may be caused by either an excess of resorption or decreased bone formation. Early studies indicated that the primary skeletal effect of vitamin A was to increase bone resorption, but later studies have shown that vitamin A can not only stimulate the formation of bone-resorbing osteoclasts but also inhibit their formation. Effects of vitamin A on bone formation have not been studied in as great a detail and are not as well characterized as effects on bone resorption. Several epidemiological studies have shown an association between vitamin A, decreased bone mass, and osteoporotic fractures, but the data are not conclusive because other studies have found no associations, and some studies have suggested that vitamin A primarily promotes skeletal health. In this presentation, we have summarized how vitamin A is absorbed and metabolized and how it functions intracellularly. Vitamin A deficiency and excess are introduced, and detailed descriptions of clinical and preclinical studies of the effects of vitamin A on the skeleton are presented.

Evidence of overtesting for vitamin D in Australia: an analysis of 4.5 years of Medicare Benefits Schedule (MBS) data

OBJECTIVE

To comprehensively examine pathology test utilisation of 25-hydroxyvitamin D (25(OH)D) testing in each state of Australia to determine the cost impact and value and to add evidence to enable the development of vitamin D testing guidelines.

DESIGN

Longitudinal analysis of all 25(OH)D pathology tests in Australia.

SETTING

Primary and Tertiary Care.

MEASUREMENTS

The frequency of 25(OH)D testing between 1 April 2006 and 30 October 2010 coded for each individual by provider, state and month between 2006 and 2010. Rate of tests per 100 000 individuals and benefit for 25(OH)D, full blood count (FBC) and bone densitometry by state and quarter between 2000 and 2010.

RESULTS

4.5 million tests were performed between 1 April 2006 and 30 October 2010. 42.9% of individuals had more than one test with some individuals having up to 79 tests in that period. Of these tests, 80% were ordered by general practitioners and 20% by specialists. The rate of 25(OH)D testing increased 94-fold from 2000 to 2010. Rate varied by state whereby the most southern state represented the highest increase and northern state the lowest increase. In contrast, the rate of a universal pathology test such as FBC remained relatively stable increasing 2.5-fold. Of concern, a 0.5-fold (50%) increase in bone densitometry was seen.

CONCLUSIONS

The marked variation in the frequency of testing for vitamin D deficiency indicates that large sums of potentially unnecessary funds are being expended. The rate of 25(OH)D testing increased exponentially at an unsustainable rate. Consequences of such findings are widespread in terms of cost and effectiveness. Further research is required to determine the drivers and cost benefit of such expenditure. Our data indicate that adoption of specific guidelines may improve efficiency and effectiveness of 25(OH)D testing.