The effect of vitamin D supplementation on the bone mineral density of the femoral neck is associated with vitamin D receptor genotype

Genetic variations of vitamin D receptor and vitamin D supplementation interaction in relation to serum vitamin D and metabolic traits: a systematic review and meta-analysis

Background: It is now becoming increasingly recognized that the effects of vitamin D supplementation may vary by several factors including vitamin D deficiency status, ethnicity, and/or the presence of genetic variants, which affect individual responses to supplementation. This study investigates the interaction between metabolic traits and circulating 25-hydroxyvitamin-D (25OHD) concentration with 4 polymorphisms of vitamin D receptor (VDR) including BsmI, ApaI, TaqI, FokI, and vitamin D supplementation. Methods: A systematic review and meta-analysis of papers until August 2021 on PubMed, The Cochrane Library, Scopus, Web of Science, Google Scholar, ProQuest, Science Direct, and Embase about the association between functionally relevant VDR variants and vitamin D supplementation on circulating 25OHD and metabolic traits. Results: A total of 2994 cases from 16 randomized controlled trial (RCT) studies were included in meta-analyses. There were no significant changes in the serum concentrations of 25OHD and metabolic traits after vitamin D supplementation in different variants of BsmI, ApaI, TaqI, and FokI polymorphism in the VDR gene in the overall analysis (p>0.05). However, the results showed there is significant interaction between these above VDR polymorphisms and vitamin D supplement on serum 25OHD level after subgroup analyses based on the study duration, gender, age, BMI, health status, Hardy-Weinberg Equilibrium, PCR, and race (p<0.05). Conclusions: The present meta-analysis demonstrates that the effect of vitamin D supplementation on serum 25OHD and metabolic traits is independent of genetic variants of the VDR gene (BsmI, ApaI, TaqI, and FokI). However, future trials should consider inter-individual differences and, in particular, should aim to clarify whether certain subgroups of individuals may benefit from vitamin D supplementation in the context of metabolic health.

Vitamin D Receptor (VDR) Gene Polymorphisms Modify the Response to Vitamin D Supplementation: A Systematic Review and Meta-Analysis

The vitamin D receptor (VDR), a member of the nuclear receptor superfamily of transcriptional regulators, is crucial to calcitriol signalling. VDR is regulated by genetic and environmental factors and it is hypothesised that the response to vitamin D supplementation could be modulated by genetic variants in the VDR gene. The best studied polymorphisms in the VDR gene are Apal (rs7975232), BsmI (rs1544410), Taql (rs731236) and Fokl (rs10735810). We conducted a systematic review and meta-analysis to evaluate the response to vitamin D supplementation according to the BsmI, TaqI, ApaI and FokI polymorphisms. We included studies that analysed the relationship between the response to vitamin D supplementation and the genotypic distribution of these polymorphisms. We included eight studies that enrolled 1038 subjects. The results showed no significant association with the BsmI and ApaI polymorphisms (p = 0.081 and p = 0.63) and that the variant allele (Tt+tt) of the TaqI polymorphism and the FF genotype of the FokI variant were associated with a better response to vitamin D supplementation (p = 0.02 and p < 0.001). In conclusion, the TaqI and FokI polymorphisms could play a role in the modulation of the response to vitamin D supplementation, as they are associated with a better response to supplementation.

Diet Modulates the Effects of Genetic Variants on the Vitamin D Metabolic Pathway and Bone Mineral Density in Mexican Postmenopausal Women

BACKGROUND

Macro- and micronutrients, such as proteins, vitamin D, and calcium (Ca), are important dietary factors that can modify bone mineral density (BMD). Genetic factors can interact with diet, affecting an individual's predisposition to osteoporosis.

OBJECTIVES

This study aimed to evaluate the associations between macro- and micronutrient intakes and BMD in Mexican postmenopausal women, and their interactions with genetic polymorphisms involved in the vitamin D metabolic pathway.

METHODS

We analyzed data from 317 postmenopausal women from the Health Workers Cohort Study, a longitudinal cohort studied in Cuernavaca, Mexico. Postmenopausal women participated in 2 data collection waves (2004-2006 and 2010-2011), with a mean time of 6.4 years. Dietary intake was assessed with a semi-quantitative FFQ. BMD (femoral neck, hip, and lumbar spine) was measured by DXA. Hybrid mixed-effects regression models were used to assess the associations of dietary macro- and micronutrients on BMD, after adjusting for confounding factors and for diet and single nucleotide polymorphism interactions.

RESULTS

At baseline, the median age was 57 years (IQR, 50-64). Mean femoral neck, hip, and lumbar spine BMDs decreased over time. We observed statistically significant longitudinal associations for diet (Ca, vitamin D, magnesium, phosphorus, and protein intake) and BMD. Increases of vitamin D, Ca, and protein intakes by 1 SD were associated with mean increases in the femoral neck BMD (0.083 SD, 0.064 SD, and 0.130 SD, respectively). Multiple significant interactions were identified between several loci (CYP2R1, CYP24A1, CYP27B1, VDR, and DHCR7/NADSYN1) and diet for BMDs (femoral neck, hip, and lumbar spine), mainly for protein intake.

CONCLUSIONS

Our data support associations of vitamin D, Ca, protein, phosphorous, and magnesium consumption with BMD in Mexican postmenopausal women and suggest possible gene-diet interactions. These results could facilitate future personalized nutrition recommendations to help prevent low BMD.

Using Mendelian Randomization to Decipher Mechanisms of Bone Disease

PURPOSE OF REVIEW

This review summarizes the basic principles of Mendelian randomization (MR) and provides evidence for the causal effect of multiple modifiable factors on bone outcomes.

RECENT FINDINGS

Several studies using MR approach have provided support for the causal effect of obesity on bone mineral density (BMD). Strikingly, studies have failed to prove a causal association between elevated 25(OH) D concentrations and higher BMD in community-dwelling individuals. The MR approach has been successfully used to evaluate multiple factors related to bone mineral density variation and/or fracture risk. The MR approach avoids some of the classical observational study limitations and provides more robust causal evidence, ensuring bigger success of the clinical trials. The selection of interventions based on genetic evidence could have a substantial impact on clinical practice.

Understanding Personalized Training Responses: Can Genetic Assessment Help?

Background:

Traditional exercise prescription is based on the assumption that exercise adaptation is predictable and standardised across individuals. However, evidence has emerged in the past two decades demonstrating that large inter-individual variation exists regarding the magnitude and direction of adaption following exercise.

Objective:

The aim of this paper was to discuss the key factors influencing this personalized response to exercise in a narrative review format.

Findings:

Genetic variation contributes significantly to the personalized training response, with specific polymorphisms associated with differences in exercise adaptation. These polymorphisms exist in a number of pathways controlling exercise adaptation. Environmental factors such as nutrition, psycho-emotional response, individual history and training programme design also modify the inter-individual adaptation following training. Within the emerging field of epigenetics, DNA methylation, histone modifications and non-coding RNA allow environmental and lifestyle factors to impact genetic expression. These epigenetic mechanisms are themselves modified by genetic and non-genetic factors, illustrating the complex interplay between variables in determining the adaptive response. Given that genetic factors are such a fundamental modulator of the inter-individual response to exercise, genetic testing may provide a useful and affordable addition to those looking to maximise exercise adaption, including elite athletes. However, there are ethical issues regarding the use of genetic tests, and further work is needed to provide evidence based guidelines for their use.

Conclusion:

There is considerable inter-individual variation in the adaptive response to exercise. Genetic assessments may provide an additional layer of information allowing personalization of training programmes to an individual’s unique biology.

SNP rs11185644 of RXRA gene is identified for dose-response variability to vitamin D3 supplementation: a randomized clinical trial

The level of serum 25-Hydroxyvitamin D [25(OH)D] has high heritability, suggesting that genes may contribute to variations in serum 25(OH)D level and vitamin D dose-response. As vitamin D deficiency has been linked to numerous diseases, understanding how genetic variation contributes to vitamin D dose-response is important for personalized vitamin D treatment and cost-effective disease prevention. To identify genetic variants responsible for vitamin D status and dose-response, we performed two vitamin D3 and calcium clinical supplementation trials in 2,207 postmenopausal Caucasian women. We examined the association of 291 SNPs with baseline serum 25(OH)D levels and 25(OH)D dose-response. Five SNPs, rs10500804 (P = 4.93 × 10⁻⁷), rs2060793 (P = 6.63 × 10⁻⁷), rs10741657 (P = 1.49 × 10⁻⁶), rs10766197 (P = 1.05 × 10⁻⁵) and rs11023380 (P = 7.67 × 10⁻⁵) in the CYP2R1 gene, as well as 6 SNPs, rs4588 (P = 7.86 × 10⁻⁷), rs2298850 (P = 1.94 × 10⁻⁶), rs1155563 (P = 6.39 × 10⁻⁶), rs705119 (P = 2.80 × 10⁻⁵), rs705120 (P = 1.08 × 10⁻⁴) and rs222040 (P = 1.59 × 10⁻⁴) in the GC gene were associated with baseline serum 25(OH)D levels. SNP rs11185644 near the RXRA was significantly associated with 25(OH)D dose-response (P = 1.01 × 10⁻⁴). Our data suggest that polymorphisms in the CYP2R1 and GC gene may contribute to variation in baseline serum 25(OH)D concentration, and that polymorphism rs11185644 may contribute to variation in 25(OH)D dose-response in healthy postmenopausal Caucasian women.

The influence of osteoporosis in trauma

Osteoporosis is a descriptive term for a loss of bone mass and structure which predisposes to fracture in response to minimal trauma. These fractures cause pain, disability and significant mortality, with enormous resource costs to health and other services. Proximal femoral (hip) fractures account for most of the mortality and cost, and an estimated six million osteoporosis-related hip fractures occur world-wide each year, a number likely to increase dramatically due to changes in population demographics. The diagnosis of osteoporosis should be considered in all patients over the age of 50 years who sustain a fracture, unless there is obvious major trauma. Not only will this inform immediate management but it also allows measures aimed at prevention of further fractures to be implemented. Early surgery is often effective in limiting morbidity from osteoporotic fractures and in older people is best planned in collaboration with other health care professionals.

Lower bone mineral density in Somali women living in Sweden compared with African-Americans

Vitamin D deficiency can lead to osteomalacia. Bone mineral density was lower in Somali women, living in Sweden, in relation to both the American and the African-American reference populations. The majority, 73 %, had vitamin D deficiency, and supplementation should be considered to prevent from osteomalacia, osteoporosis and future fractures.

PURPOSE

Low vitamin D can lead to osteomalacia. The hypothesis was that bone mineral density (BMD) in Somali women living in Sweden was lower in comparison with different ethnic reference populations.

METHODS

Women from Somalia, n = 67, median age 35.8 years (range 18 to 56), latitude 0-10° North living in Gothenburg, Sweden, latitude 57° North, >2 years were studied. All wore traditional Islamic clothing and had skin photo type V. BMD was recorded as the Z-score and compared with white American and African-American women, respectively, using standard data from the dual energy X-ray absorptiometry (DXA) manufacturer (Lunar Prodigy enCORETM, GE Healthcare, LU44663). A fasting blood test was drawn for analysis of serum 25(OH)D.

RESULTS

The median Z-score compared with the American white population was -0.9 SD of the lumbar spine (p < 0.00001), 0.1 SD of the left hip and 0.0 SD of the right hip (ns). The median Z-score compared with the African-American population was -1.6 SD of the lumbar spine (p < 0.00001), -0.9 SD of the left hip and -0.9 SD of the right hip (p < 0.001). The majority, 73 %, had vitamin D deficiency, serum 25(OH)D <25 nmol/l (<10 ng/ml). BMD did not correlate to vitamin D levels or to the number of years in Sweden. One wrist fracture was reported.

CONCLUSIONS

BMD was lower in these fairly young immigrant women from Somalia, living in Sweden, in relation to both the American and the African-American reference populations. Vitamin D supplementation should be considered to prevent from osteomalacia, osteoporosis and future fractures.

Vitamin D supplementation for prevention of mortality in adults

BACKGROUND

Available evidence on the effects of vitamin D on mortality has been inconclusive. In a recent systematic review, we found evidence that vitamin D3 may decrease mortality in mostly elderly women. The present systematic review updates and reassesses the benefits and harms of vitamin D supplementation used in primary and secondary prophylaxis of mortality.

OBJECTIVES

To assess the beneficial and harmful effects of vitamin D supplementation for prevention of mortality in healthy adults and adults in a stable phase of disease.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index-Expanded and Conference Proceedings Citation Index-Science (all up to February 2012). We checked references of included trials and pharmaceutical companies for unidentified relevant trials.

SELECTION CRITERIA

Randomised trials that compared any type of vitamin D in any dose with any duration and route of administration versus placebo or no intervention in adult participants. Participants could have been recruited from the general population or from patients diagnosed with a disease in a stable phase. Vitamin D could have been administered as supplemental vitamin D (vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol)) or as an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol) or 1,25-dihydroxyvitamin D (calcitriol)).

DATA COLLECTION AND ANALYSIS

Six review authors extracted data independently. Random-effects and fixed-effect meta-analyses were conducted. For dichotomous outcomes, we calculated the risk ratios (RRs). To account for trials with zero events, we performed meta-analyses of dichotomous data using risk differences (RDs) and empirical continuity corrections. We used published data and data obtained by contacting trial authors.To minimise the risk of systematic error, we assessed the risk of bias of the included trials. Trial sequential analyses controlled the risk of random errors possibly caused by cumulative meta-analyses.

MAIN RESULTS

We identified 159 randomised clinical trials. Ninety-four trials reported no mortality, and nine trials reported mortality but did not report in which intervention group the mortality occurred. Accordingly, 56 randomised trials with 95,286 participants provided usable data on mortality. The age of participants ranged from 18 to 107 years. Most trials included women older than 70 years. The mean proportion of women was 77%. Forty-eight of the trials randomly assigned 94,491 healthy participants. Of these, four trials included healthy volunteers, nine trials included postmenopausal women and 35 trials included older people living on their own or in institutional care. The remaining eight trials randomly assigned 795 participants with neurological, cardiovascular, respiratory or rheumatoid diseases. Vitamin D was administered for a weighted mean of 4.4 years. More than half of the trials had a low risk of bias. All trials were conducted in high-income countries. Forty-five trials (80%) reported the baseline vitamin D status of participants based on serum 25-hydroxyvitamin D levels. Participants in 19 trials had vitamin D adequacy (at or above 20 ng/mL). Participants in the remaining 26 trials had vitamin D insufficiency (less than 20 ng/mL).Vitamin D decreased mortality in all 56 trials analysed together (5,920/47,472 (12.5%) vs 6,077/47,814 (12.7%); RR 0.97 (95% confidence interval (CI) 0.94 to 0.99); P = 0.02; I(2) = 0%). More than 8% of participants dropped out. 'Worst-best case' and 'best-worst case' scenario analyses demonstrated that vitamin D could be associated with a dramatic increase or decrease in mortality. When different forms of vitamin D were assessed in separate analyses, only vitamin D3 decreased mortality (4,153/37,817 (11.0%) vs 4,340/38,110 (11.4%); RR 0.94 (95% CI 0.91 to 0.98); P = 0.002; I(2) = 0%; 75,927 participants; 38 trials). Vitamin D2, alfacalcidol and calcitriol did not significantly affect mortality. A subgroup analysis of trials at high risk of bias suggested that vitamin D2 may even increase mortality, but this finding could be due to random errors. Trial sequential analysis supported our finding regarding vitamin D3, with the cumulative Z-score breaking the trial sequential monitoring boundary for benefit, corresponding to 150 people treated over five years to prevent one additional death. We did not observe any statistically significant differences in the effect of vitamin D on mortality in subgroup analyses of trials at low risk of bias compared with trials at high risk of bias; of trials using placebo compared with trials using no intervention in the control group; of trials with no risk of industry bias compared with trials with risk of industry bias; of trials assessing primary prevention compared with trials assessing secondary prevention; of trials including participants with vitamin D level below 20 ng/mL at entry compared with trials including participants with vitamin D levels equal to or greater than 20 ng/mL at entry; of trials including ambulatory participants compared with trials including institutionalised participants; of trials using concomitant calcium supplementation compared with trials without calcium; of trials using a dose below 800 IU per day compared with trials using doses above 800 IU per day; and of trials including only women compared with trials including both sexes or only men. Vitamin D3 statistically significantly decreased cancer mortality (RR 0.88 (95% CI 0.78 to 0.98); P = 0.02; I(2) = 0%; 44,492 participants; 4 trials). Vitamin D3 combined with calcium increased the risk of nephrolithiasis (RR 1.17 (95% CI 1.02 to 1.34); P = 0.02; I(2) = 0%; 42,876 participants; 4 trials). Alfacalcidol and calcitriol increased the risk of hypercalcaemia (RR 3.18 (95% CI 1.17 to 8.68); P = 0.02; I(2) = 17%; 710 participants; 3 trials).

AUTHORS' CONCLUSIONS

Vitamin D3 seemed to decrease mortality in elderly people living independently or in institutional care. Vitamin D2, alfacalcidol and calcitriol had no statistically significant beneficial effects on mortality. Vitamin D3 combined with calcium increased nephrolithiasis. Both alfacalcidol and calcitriol increased hypercalcaemia. Because of risks of attrition bias originating from substantial dropout of participants and of outcome reporting bias due to a number of trials not reporting on mortality, as well as a number of other weaknesses in our evidence, further placebo-controlled randomised trials seem warranted.

What is the optimal dietary intake of vitamin D for reducing fracture risk?

Vitamin D has long been known to be important for bone health, but there is currently no consensus on the amount of vitamin D needed or how it varies with age, race/ethnicity, body size, absorption efficiency, season, and other factors. This review describes the effects of vitamin D on calcium absorption, parathyroid hormone levels, and changes in bone mineral density briefly and focuses in more detail on the results and interpretation of double-blind randomized controlled trials with fracture outcomes in older adults. Based on these trials, 400 IU/day, bringing 25-hydroxyvitamin D (25OHD) levels to 60-65 nmol/L, is not effective at lowering fracture risk in community-dwelling elders or in elders with prior fractures. Several large trials indicate that doses in the range of 700-1,000 IU/day can lower fracture risk by ~20 %. From these trials, it appears that a 25OHD level of 65 nmol/L is needed to reduce nonvertebral fracture risk and 75 nmol/L may be needed to lower hip fracture risk. Trials testing additional doses of vitamin D in different segments of the population are needed.

Skeletal effects of vitamin D supplementation in postmenopausal black women

Black women have lower serum 25-hydroxyvitamin D (25[OH]D) levels and higher parathyroid hormone (PTH) levels than white peers but lower bone turnover, suggesting skeletal resistance to PTH. Our objective was to determine if vitamin D supplementation (1,000 IU/day) would prevent bone loss and whether vitamin D receptor (VDR) polymorphisms modify the response. We performed a 2-year randomized, controlled, double-blind study of 1,000 IU vitamin D(3) vs. placebo in postmenopausal black women with serum 25(OH)D levels <20 ng/mL (n = 103). Measurements of 25(OH)D, PTH, and bone turnover were evaluated at baseline and 3, 6, 12, 18, and 24 months. DNA was extracted from peripheral blood leukocytes, and genotyping was conducted using standard techniques. Spine and hip bone mineral density (BMD) was measured at baseline and every 6 months. Serum 25(OH)D increased 11 ng/mL with vitamin D supplementation (p < 0.001), with no change in the placebo group. Vitamin D supplementation produced a significant decline in PTH at 3 months only, with no differences in bone turnover between placebo and vitamin D at any time point. Two-year changes in BMD were not significantly different between placebo- and vitamin D-treated black women at any skeletal site. Despite similar elevations in 25(OH)D, femoral neck BMD was only responsive to vitamin D supplementation in FF subjects (n = 47), not Ff/ff subjects (n = 31). Vitamin D supplementation does not appear to influence bone loss in black women. However, in the FF polymorphism of the VDR gene group, vitamin D supplementation may retard the higher rate of bone loss.

Efficacy of optimization of vitamin D in preventing osteoporosis and osteoporotic fractures: A systematic review

Increased intake or supplementation of vitamin D is often recommended for normal bone health; however, its preventive effect on osteoporosis has not been fully evaluated. The aim of this review is to gather evidence of the efficacy of the optimization of vitamin D nutrition in preventing osteoporosis and osteoporotic fractures. PubMed was used for searching the relevant literature using the MeSH terms "Bone Density (limited to "human", "female", and "English" literature)" or "Fractures (limited to "human", "age ≥45 years", and "English" literature)", and "Vitamin D". The searches yielded 19 randomized controlled trials (RCTs), nine cohort studies, 19 case-control studies, 19 cross-sectional studies, and one meta-analysis. We attempted to answer three questions: 1) does increased vitamin D intake prevent bone loss in peri- and postmenopausal women?, 2) does increased vitamin D intake prevent osteoporotic fractures in the elderly?, and 3) does increased vitamin D in take positively affect peak bone mass attainment in young women? The answer to questions 1 and 2 is that a vitamin D intake of 10-17.5 μg/day (400-700 IU/day) or more is effective in preventing bone loss in late postmenopausal women and an intake of 17.5-20 μg/day (700-800 IU/day) or more together with a calcium supplement reduces the risk of osteoporotic fractures. For question 3, some lines of evidence support the negative effect of low vitamin D nutrition on the attainment of peak bone mass in young women. Further studies are needed to clarify the effect of vitamin D in this age group.

Vitamin D supplementation for prevention of mortality in adults

BACKGROUND

The available evidence on vitamin D and mortality is inconclusive.

OBJECTIVES

To assess the beneficial and harmful effects of vitamin D for prevention of mortality in adults.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science (to January 2011). We scanned bibliographies of relevant publications and asked experts and pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included randomised trials that compared vitamin D at any dose, duration, and route of administration versus placebo or no intervention. Vitamin D could have been administered as supplemental vitamin D (vitamin D(3) (cholecalciferol) or vitamin D(2) (ergocalciferol)) or an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol) or 1,25-dihydroxyvitamin D (calcitriol)).

DATA COLLECTION AND ANALYSIS

Six authors extracted data independently. Random-effects and fixed-effect model meta-analyses were conducted. For dichotomous outcomes, we calculated the risk ratios (RR). To account for trials with zero events, meta-analyses of dichotomous data were repeated using risk differences (RD) and empirical continuity corrections. Risk of bias was considered in order to minimise risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors.

MAIN RESULTS

Fifty randomised trials with 94,148 participants provided data for the mortality analyses. Most trials included elderly women (older than 70 years). Vitamin D was administered for a median of two years. More than one half of the trials had a low risk of bias. Overall, vitamin D decreased mortality (RR 0.97, 95% confidence interval (CI) 0.94 to 1.00, I(2) = 0%). When the different forms of vitamin D were assessed separately, only vitamin D(3) decreased mortality significantly (RR 0.94, 95% CI 0.91 to 0.98, I(2) = 0%; 74,789 participants, 32 trials) whereas vitamin D(2), alfacalcidol, or calcitriol did not. Trial sequential analysis supported our finding regarding vitamin D(3), corresponding to 161 individuals treated to prevent one additional death. Vitamin D(3) combined with calcium increased the risk of nephrolithiasis (RR 1.17, 95% CI 1.02 to 1.34, I(2) = 0%). Alfacalcidol and calcitriol increased the risk of hypercalcaemia (RR 3.18, 95% CI 1.17 to 8.68, I(2) = 17%). Data on health-related quality of life and health economics were inconclusive.

AUTHORS' CONCLUSIONS

Vitamin D in the form of vitamin D(3) seems to decrease mortality in predominantly elderly women who are mainly in institutions and dependent care. Vitamin D(2), alfacalcidol, and calcitriol had no statistically significant effect on mortality. Vitamin D(3) combined with calcium significantly increased nephrolithiasis. Both alfacalcidol and calcitriol significantly increased hypercalcaemia.

Vitamin D status in relation to obesity, bone mineral density, bone turnover markers and vitamin D receptor genotypes in healthy Saudi pre- and postmenopausal women

The various factors that may contribute to vitamin D deficiency or insufficiency were examined among healthy Saudi pre- and postmenopausal women. Vitamin D deficiency was highly prevalent among studied Saudi women with obesity, poor sunlight exposure, poor dietary vitamin D supplementation and age as the main risk factors.

INTRODUCTION

The various factors that may contribute to vitamin D deficiency or insufficiency in relation to bone health among Saudi women are not known. The main objectives of the present study were to determine the factors influencing vitamin D status in relation to serum 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone (PTH), bone turnover markers (BTMs), bone mineral density (BMD), and vitamin D receptor genotype (VDR) in healthy Saudi pre- and postmenopausal women.

METHODS

A total number of 1,172 healthy Saudi women living in the Jeddah area were randomly selected and studied. Anthropometric parameters, socioeconomic status, sun exposure index together with serum levels of 25(OH)D, calcitriol, intact PTH, Ca, PO4, Mg, creatinine, albumin, and biochemical BTMs were measured. BMD was measured by a dual energy X-ray absorptiometry and VDR genotypes were also determined.

RESULTS

About 80.0% of Saudi women studied exhibited vitamin D deficiency (serum 25(OH)D<50.0 nmol/L) with only 11.8% of all women were considered with adequate vitamin D status (serum 25(OH)D>75 nmol/L). Secondary hyperparathyroidism was evident in 18.5% and 24.6% in pre- and postmenopausal women with 25(OH)D<50 nmol/L. Serum 25(OH)D was lower (P<0.001) and intact PTH higher (P<0.001) in the upper quintiles of body mass index (BMI) and waist-to-hip ratio (WHR). Multiple linear regression analysis showed that BMI, sun exposure index, poor dietary vitamin D supplementation, WHR, and age were independent positive predictors of serum 25(OH)D values.

CONCLUSIONS

Vitamin D deficiency is highly prevalent among healthy Saudi pre-and postmenopausal women and largely attributed to obesity, poor exposure to sunlight, poor dietary vitamin D supplementation, and age.

Association of vitamin D receptor gene polymorphisms with BMD and their effect on 1, 25-dihydroxy vitamin D3 levels in pre- and postmenopausal South Indian women from Andhra Pradesh

BACKGROUND

Osteoporosis is a multifactorial disorder with a strong genetic component and vitamin D receptor gene has been suggested as a candidate gene for osteoporosis. Therefore the present study was aimed to investigate the role of the VDR Fok 1 gene polymorphism and its influence on vitamin D3 levels and BMD in pre- and postmenopausal osteoporotic women of Indian ethnicity.

METHODS

427 osteoporotic women and 460 age matched controls were included in the study. VDR FOK1 gene polymorphism was assessed by the PCR-RFLP method. Serum vitamin D3 was measured by the HPLC method.

RESULTS

The frequency of ff genotype and f allele was significantly high in pre- and postmenopausal osteoporotic women in comparison with controls (p<0.001).In each case individuals with ff genotype had significantly low BMD in comparison with Ff and FF genotypes. No significant association was found between the genotypes and vitamin D3 levels.

CONCLUSION

The VDR Fok 1 gene is associated with low bone mass in all our study subjects. The genotype ff of the VDR Fok 1 gene is associated with osteoporosis. Further ff genotype associated significantly with low bone mass. Therefore the f allele of VDR Fok1 gene is an important risk factor for osteoporosis.

Genetics of osteoporosis

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass, defects in the microarchitecture of bone tissue, and an increased risk of fragility fractures. Twin and family studies have shown high heritability of bone mineral density (BMD) and other determinants of fracture risk such as ultrasound properties of bone, skeletal geometry, and bone turnover. Osteoporotic fractures also have a heritable component, but this reduces with age as environmental factors such as risk of falling come into play. Susceptibility to osteoporosis is governed by many different genetic variants and their interaction with environmental factors such as diet and exercise. Notable successes in identification of genes that regulate BMD have come from the study of rare Mendelian bone diseases characterized by major abnormalities of bone mass where variants of large effect size are operative. Genome-wide association studies have also identified common genetic variants of small effect size that contribute to regulation of BMD and fracture risk in the general population. In many cases, the loci and genes identified by these studies had not previously been suspected to play a role in bone metabolism. Although there has been extensive progress in identifying the genes and loci that contribute to the regulation of BMD and fracture over the past 15 yr, most of the genetic variants that regulate these phenotypes remain to be discovered.

Nutritional genomics era: opportunities toward a genome-tailored nutritional regimen

There is increasing evidence indicating that nutritional genomics represents a promise to improve public health. This goal will be reached by highlighting the mechanisms through which diet can reduce the risk of monogenic and common polygenic diseases. Indeed, nutrition is a very relevant environmental factor involved in the development and progression of metabolic disorders, as well as other kind of diseases. The revolutionary changes in the field of genomics have led to the development and implementation of new technologies and molecular tools. These technologies have a useful application in the nutritional sciences, since they allow a more precise and accurate analysis of biochemical alterations, in addition to filling fundamental gaps in the knowledge of nutrient-genome interactions in both health and disease. Overall, these advances will open undiscovered ways in genome-customized diets for disease prevention and therapy. This review summarizes the recent knowledge concerning this novel nutritional approach, paying attention to the human genome variations, such as single-nucleotide polymorphisms and copy number variations, gene expression and innovative molecular tools to reveal them.

Cholecalciferol supplementation throughout winter does not affect markers of bone turnover in healthy young and elderly adults

Although there have been several studies of the effect of vitamin D status on bone turnover in the elderly, the findings are unclear, and, furthermore, to date very few have investigated this in young adults. The objective of these randomized, placebo-controlled, double-blind, 2-center intervention studies was to investigate the effect of cholecalciferol supplementation (0, 5, 10, and 15 microg cholecalciferol/d) throughout winter time on indices of vitamin D status and bone turnover in young (aged 20-40 y; n = 215) and elderly (aged > or = 64 y; n = 204) adults, with relatively high mean calcium intakes of 976 and 874 mg/d, respectively. Fasting serum concentrations of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, bone-specific alkaline phosphatase, and carboxyterminal collagen crosslinks were measured by enzyme immunoassays at baseline and endpoint. Fok I and Taq I vitamin D receptor (VDR) genotypes were determined by real-time PCR. Endpoint serum 25(OH)D increased (P < 0.0001) in a dose-related manner with increasing supplemental cholecalciferol (up to 15 microg/d) in 20-40-y olds and up to 10 microg/d in > or = 64-y olds. Endpoint serum PTH was lower (P < 0.05) in the 3 cholecalciferol-supplemented groups compared with that in the placebo group in > or = 64-y olds, but cholecalciferol supplementation did not affect other markers in either cohort and there was no significant interaction with VDR genotype. In conclusion, cholecalciferol supplementation alone throughout winter did not affect bone turnover markers in apparently healthy young and elderly adults, even when stratified by VDR genotype.

Does vitamin D supplementation of healthy Danish Caucasian girls affect bone turnover and bone mineralization?

INTRODUCTION

A high peak bone mass may be essential for reducing the risk of osteoporosis later in life and a sufficient vitamin D level during puberty may be necessary for optimal bone accretion and obtaining a high peak bone mass. Dietary intake and synthesis during winter of vitamin D might be limited but the effect of vitamin D supplementation in adolescence on bone mass is not well established.

OBJECTIVE

To investigate the effect of supplementation with 5 and 10 microg/day vitamin D(3) for 12 months in 11- to 12-year-old girls on bone mass and bone turnover as well as the possible influence of VDR and ER genotype on the effect of the supplementation.

METHODS

The girls (n=221) were randomized to receive either 5 microg or 10 microg vitamin D(3) supplementation per day or placebo for 12 months. Whole body and lumbar spine bone mass measured by DXA and pubertal status were determined at baseline and after 12 months whereas physical activity and dietary intake of calcium and vitamin D were assessed at baseline. Serum (S) 25-hydroxyvitamin D (25OHD), S-osteocalcin, S-parathyroid hormone, S-calcium, S-inorganic phosphate, urinary (U) pyridinoline (Pyr) and deoxpyridinoline (Dpyr) were measured at baseline and after 6 and 12 months.

RESULTS

The S-25OHD concentration increased (p<0.001) relative to the baseline values in the groups receiving either 5 microg/day (mean+/-SD; 11.0+/-10.3 nmol/l, baseline 41.9+/-17.6 nmol/l) or 10 microg/day (13.3+/-11.8 nmol/l, baseline 44.4+/-16.6 nmol/l) vitamin D(3) for 12 months compared to placebo (-3.1+/-9.8 nmol/l, baseline 43.4+/-17.1 nmol/l). There was no effect of vitamin D-supplementation on biomarkers for bone turnover or on whole body or spine bone mineral augmentation. However, vitamin D supplementation increased whole body bone mineral density (BMD) (p=0.007) and bone mineral content (BMC) (p=0.048) in the FF VDR genotype but not in the Ff or ff VDR genotypes.

CONCLUSION

Supplementation with vitamin D (5 or 10 microg/day) over 12 months increased the S-25OHD concentration but there was no effect on indices of bone health in the entire group of girls. However, there was an effect on BMD for a subgroup with the FF VDR genotype indicating an influence of genotype.

Vitamin D receptor gene polymorphisms modulate the skeletal response to vitamin D supplementation in healthy girls

OBJECTIVES

Vitamin D receptor (VDR) gene plays an important role in bone mass regulation. We have previously shown a beneficial effect of vitamin D supplementation on bone mass in girls. This study investigated whether the musculo-skeletal response to Vitamin D was modulated by polymorphisms in VDR gene.

DESIGN

Randomized placebo-controlled trial.

METHODS

179 girls (10-17 years), were randomly assigned to placebo or Vitamin D3 for one year. VDR genotypes were determined in 167 girls using BsmI, TaqI and ApaI restriction enzymes. Bone mass at the spine, hip, forearm and total body, and lean mass were measured by DXA at baseline and at one year.

RESULTS

After one year, VDR gene polymorphisms using Bsm1 and TaqI restriction enzymes were associated with percent changes in bone area, BMC and BMD at multiple skeletal sites in the Vitamin D3 group but not in the placebo group. The least increments were observed in the BB and tt genotypes. No similar effect was observed with ApaI enzyme. This relationship between VDR genotypes and changes in BMD and BMC remained significant after adjustment for puberty, changes in lean mass, height and bone area.

CONCLUSION

VDR gene polymorphisms influence the skeletal response to vitamin D supplementation in healthy adolescent girls.

Update on the pharmacogenetics of the vitamin D receptor and osteoporosis

Vitamin D and calcium are essential for normal skeletal growth and for maintaining the mechanical and structural integrity of the skeleton. Reduced intake of calcium and vitamin D may be associated with reduced bone mass and osteoporosis while a chronic and severe vitamin D deficiency may lead to osteomalacia. Given the importance of vitamin D in bone homeostasis, common polymorphisms in the vitamin D receptor gene were the first to be investigated as possible determinants of bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain in part to be investigated, an additional important issue is represented by their potential pharmacogenomic and pharmacogenetic implications. This review analyzes major pharmacogenetic studies of polymorphisms in the vitamin D receptor gene and osteoporosis.

Pharmacogenetics of osteoporosis: future perspectives

Drug response is known to be highly variable among treated patients and affected by many factors, such as age, sex, ethnicity, concomitant diseases, and pharmacological therapy. However, sequence variants in the human genome are now considered an important cause of differences in drug responses. Pharmacogenetics, which is the utilization of individual genetic data to predict the outcome of drug treatment with respect to both beneficial and adverse effects, represents an emerging field of genetics with the potential to become useful for the identification of the most effective drug and the most beneficial dose for a given individual. On the basis of these considerations and thanks to recent advances in genetics and molecular biology, pharmacogenetics is becoming a flowering field in both basic and clinical research. Nevertheless, to date the opportunity to apply pharmacogenetic approaches to drug response and the possibility to use genetic screenings to tailor decisions about pharmacological treatments have limited applications. And this is even truer in the field of osteoporosis, in which pharmacogenetic studies are in their infancy. In this paper we review the most recent data on pharmacogenetics of osteoporosis, highlighting the presentations at the Second International Meeting on Pharmacogenetics of Osteoarticular Disorders held in Florence in April 2008.

Does vitamin D make the world go 'round'?

Abstract Vitamin D has emerged from obscurity, and its effects on various organ systems throughout the body down to the cellular level are being discovered. What was once thought to be a simple hormone affecting only bone and calcium metabolism has shifted. We no longer see vitamin D as a "vitamin" important only in childhood, but as a complex hormone that is involved not only in calcium homeostasis but also in the integrity of the innate immune system. Vitamin D deficiency is linked to inflammatory and long-latency diseases such as multiple sclerosis, rheumatoid arthritis, tuberculosis, diabetes, and various cancers, to name a few. In this review, we trace how we came to view vitamin D and how that view led to one of the largest epidemics of nutrient deficiency beginning in the late 20(th) century. We then discuss the needs of vitamin D in the context of the breastfeeding mother and her infant and child, why breastfed infants are particularly at risk, and what to do about it.

Post-fracture management of patients with hip fracture: a perspective

BACKGROUND

Hip fracture creates a worldwide morbidity, mortality and economic burden. After surgery, many patients experience long-term disability or die as a consequence of the fracture. A fracture is a major risk factor for a subsequent fracture, which may occur within a short interval.

METHODS

A literature search on post-fracture management of patients with hip fracture was performed on the Medline database. Key experts convened to develop a consensus document.

FINDINGS

Management of hip-fracture patients to optimize outcome after hospital discharge requires several stages of care co-ordinated by a multidisciplinary team from before admission through to discharge. Further studies that specifically assess prevention and post-fracture management of hip fracture are needed, as only one study to date has assessed an osteoporosis medication in patients with a recent hip fracture. Proper nutrition is vital to assist bone repair and prevent further falls, particularly in malnourished patients. Vitamin D, calcium and protein supplementation is associated with an increase in hip BMD and reduction in falls. Rehabilitation is essential to improve functional disabilities and survival rates. Fall prevention and functional recovery strategies should include patient education and training to improve balance and increase muscle strength and mobility. Appropriate management can prevent further fractures and it is critical that high-risk patients are identified and treated. To foster this process, clinical pathways have been established to support orthopaedic surgeons.

CONCLUSION

Although hip fracture is generally associated with poor outcomes, appropriate management can ensure optimal recovery and survival, and should be prioritized after a hip fracture to avoid deterioration of health and prevent subsequent fracture.

Pharmacogenetics of bone treatments: the VDR and ERalpha gene story

Osteoporosis is a common skeletal disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Although osteoporosis is a worldwide problem, there are many differences in human ethnics regarding both disease morbidity and drug treatment efficacy. Polymorphisms of vitamin D receptor (VDR) and estrogen receptor-alpha (ERalpha) loci are proposed as genetic determinants of bone quality, skeletal geometry and bone turnover markers. Furthermore, varying responsiveness to vitamin D and estrogen-based treatments may reflect allele variation in their signaling pathway genes (e.g., VDR or ERalpha). Because of their specific ethnic distribution, VDR and ERalpha polymorphisms may be involved in reported human differences of osteoporosis treatment responses.

Menopause: developing a rational treatment plan

In recent years, growing importance has been afforded to assisting women in coping with the menopausal transition. Menopause is a normal stage of development and a woman's attitude toward this transition embodies biological, psychological and social influences. An enlarging body of conflicting data concerning menopausal hormone therapy (MHT) demands reassessment of established paradigms of disease prevention and menopausal health. Currently, a woman's decision to participate in or abstain from menopausal HT is personal. It involves not only consideration of risk stratification of potential harm and benefit, but also involves her expectations and attitudes toward perceived physical and emotional changes associated with this change. Through the use of extensive patient history, quality-of-life questionnaires and powerful biological profiling, we may be able to develop a rational approach to menopausal HT that safely guides our patients through this transition.

Long-term 1,25(OH)2 vitamin D therapy increases bone mineral density in osteopenic women. Comparison with the effect of plain vitamin D

BACKGROUND AND AIMS

Although the bone protective effect of vitamin D has been studied intensively, the usefulness of 1,25(OH)2D3 in treating osteoporosis is still questionable. The aim of the present prospective study was to evaluate the effect of a standard pharmacological dose of 1,25(OH)2D3 in postmenopausal unsubstituted women.

METHODS

Our study group comprised 52 post-menopausal women with low normal or osteopenic values of bone mineral density (BMD). Thirty-two of them were treated with 1,25(OH)2D3 for 3 years. In parallel, another group of women was treated with cholecalciferol (n=20). Vitamin D adequacy before administration of 1,25(OH)2D3 and compliance with treatment were checked by serum PTH levels, which were assessed at the start and three times in the course of treatment.

RESULTS

Increase in BMD at the spine at the end of the 1st, 2nd and 3rd years of treatment with 1,25(OH)2D3 (expressed as a percentage of the value before treatment) was higher, but did not significantly differ from the effect of plain vitamin D. A significant increase in BMD at the hip at the end of the 3rd (but not the 1st and 2nd) year of treatment with 1,25(OH)2D3 was found (p<0.05, compared with the effect of plain vitamin D). The protective effect of cholecalciferol was found only on spine but not hip BMD.

CONCLUSION

The study supports the hypothesis that long-term administration of 1,25(OH)2D3 is effective in treating low bone mass in postmenopausal women.

Improved weight management using genetic information to personalize a calorie controlled diet

Background

Gene-environment studies demonstrate variability in nutrient requirements depending upon individual variations in genes affecting nutrient metabolism and transport. This study investigated whether the inclusion of genetic information to personalize a patient's diet (nutrigenetics) could improve long term weight management.

Methods

Patients with a history of failures at weight loss were offered a nutrigenetic test screening 24 variants in 19 genes involved in metabolism. 50 patients were in the nutrigenetic group and 43 patients attending the same clinic were selected for comparison using algorithms to match the characteristics: age, sex, frequency of clinical visits and BMI at initial clinic visit. The second group of 43 patients did not receive a nutrigenetic test. BMI reduction at 100 and > 300 days and blood fasting glucose were measured.

Results

After 300 days of follow-up individuals in the nutrigenetic group were more likely to have maintained some weight loss (73%) than those in the comparison group (32%), resulting in an age and gender adjusted OR of 5.74 (95% CI 1.74–22.52). Average BMI reduction in the nutrigenetic group was 1.93 kg/m²(5.6% loss) vs. an average BMI gain of 0.51 kg/m²(2.2% gain) (p < 0.023). Among patients with a starting blood fasting glucose of > 100 mg/dL, 57% (17/30) of the nutrigenetic group but only 25% (4/16) of the non-tested group had levels reduced to < 100 mg/dL after > 90 days of weight management therapy (OR for lowering glucose to < 100 mg/dL due to diet = 1.98 95%CI 1.01, 3.87, p < 0.046).

Conclusion

Addition of nutrigenetically tailored diets resulted in better compliance, longer-term BMI reduction and improvements in blood glucose levels.

Osteoporosis, schizophrenia and antipsychotics: the need for a comprehensive multifactorial evaluation

Osteoporosis is recognised as a major public health issue leading to bone fractures, pain and disability. Awareness of an elevated risk of osteoporosis in individuals with schizophrenia is increasing. An accelerated decrease in bone mineral density (BMD) in patients with schizophrenia may be disease related or drug induced. A drug-induced decrease in BMD has been attributed mostly to hyperprolactinaemia and its consequences. However, as demonstrated in this review, decreased BMD and osteoporosis are multifactorial processes, and abnormal bone structure and functions are not limited to BMD. Multiple dynamic processes may lead to impairment of bone homeostasis and eventually to bone abnormalities. Many of these processes may be abnormal in treated as well as untreated patients with schizophrenia. Despite many publications, the epidemiology of abnormal bone structure, mineralisation and dynamics in patients with schizophrenia is still not fully determined. Comprehensive studies of bone dynamics in individuals with first-episode schizophrenia, as well as in patients treated with various current medications, are needed in order to characterise the problem(s) and then to develop relevant treatment and prevention strategies.

Association between Vitamin D Receptor Gene Polymorphisms and Susceptibility to Chronic Kidney Disease and Periodontitis

BACKGROUND/AIMS

Chronic kidney disease (CKD) and periodontitis (PD) are serious public-health concerns. Vitamin D is a fat-soluble steroid hormone that interacts with its nuclear receptor (VDR) to regulate a variety of biological processes, such as bone metabolism, immune response modulation and transcription of several genes involved in CKD and PD disease mechanisms. The aim of this work was to investigate the association between polymorphisms in the VDR gene and end-stage renal disease (ESRD) and PD.

METHODS

222 subjects with and without ESRD (in hemodialysis) were divided into groups with and without PD. Polymorphisms TaqI and BsmI in the VDR gene were analyzed by PCR restriction fragment length polymorphism. The significance of differences in allele, genotype and haplotype frequencies between groups was assessed by the chi2 test (p value <0.05) and odds ratio (OR).

RESULTS

Allele G was associated with protection against ESRD: groups without versus with ESRD (GG) x (GA+AA): OR = 2.5, 95% CI = 1.4-4.6, p = 0.00; (G x A): OR = 1.5, 95% CI = 1.0-2.3, p = 0.02; (TG + CG) x (TA + CA): OR = 1.5, 95% CI = 1.0-2.3, p = 0.02. No association was observed between the study polymorphisms and susceptibility to or protection against PD.

CONCLUSION

Allele G of the VDR BsmI polymorphism was associated with protection against ESRD.

Genetics and osteoporosis

Over the past 10 years, many advances have been made in understanding the mechanisms by which genetic factors regulate susceptibility to osteoporosis. It has become clear from studies in man and experimental animals that different genes regulate BMD at different skeletal sites and in men and women. Linkage studies have identified several chromosomal regions that regulate BMD, but only a few causative genes have been discovered so far using this approach. In contrast, significant advances have been made in identifying the genes that cause monogenic bone diseases, and polymorphic variation is some of these genes has been found to contribute to the genetic regulation of BMD in the normal population. Other genes that have been investigated as possible candidates for susceptibility to osteoporosis because of their role in bone biology, such as vitamin D, have yielded mixed results. Many candidate gene association studies have been underpowered, and meta-analysis has been used to try to confirm or refute potential associations and gain a better estimate of their true effect size in the population. Most of the genetic variants that confer susceptibility to osteoporosis remain to be discovered. It is likely that new techniques such as whole-genome association will provide new insights into the genetic determinants of osteoporosis and will help to identify genes of modest effect size. From a clinical standpoint, genetic variants that are found to predispose to osteoporosis will advance our understanding of the pathophysiology of the disease. They could be developed as diagnostic genetic tests or form molecular targets for design of new drugs for the prevention and treatment of osteoporosis and other bone diseases.

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

Osteoporosis is a common skeletal disorder with a strong genetic component. In recent years, significant progress has been made in understanding the genetic basis of osteoporosis. Given the biological significance of signalling through steroid hormone receptors, bone biology and calcium homeostasis, alleles of steroid hormone receptor genes have been postulated to contribute to the well-documented genetic predisposition to osteoporosis; and in different studies, these alleles have been associated with variation in bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain, in part, to be investigated, an additional important issue is represented by potential pharmacogenomic (the investigation of variations of DNA or RNA characteristics as related to drug response) or pharmacogenetic (the influence of variations of DNA sequence on drug response) implications. In fact, steroid hormone receptors actually mediate the action of several compounds known to positively or negatively affect bone homeostasis, such as vitamin D, estrogen and glucocorticoids. This review analyses major pharmacogenetic studies of polymorphisms in steroid hormone receptor genes.

Impact of genetic variation on metabolic response of bone to diet

There is compelling evidence to suggest that both the development of bone to peak bone mass at maturity and subsequent loss depend on the interaction between genetic, hormonal, environmental and nutritional factors. The major part (≤80%) of the age-specific variation in bone turnover and bone density is genetically determined. However, the notion of genetic determinant is of little value unless the specific genes that are involved can be identified. Most work in this area of osteoporosis research has focused on the candidate gene approach, which has identified several candidate genes for osteoporosis, including genes encoding the vitamin D receptor (VDR), oestrogen receptors (α and β), apolipoprotein E, collagen type I α 1 and methylenetetrahydrofolate reductase, amongst many others. However, in general, findings from numerous studies of the association between such genes and various bone variables have been inconsistent. In addition to possible gene—gene interactions it is likely that there are interactions between these genes and certain environmental factors, especially nutrition, that may mediate expression of bone-related phenotypes. While these potential interactions add a level of complexity to our understanding of these apparent genetic effects on bone, identification of a role for genetic factors without knowledge of their interaction with nutrients can do little to advance prevention and treatment of osteoporosis. This information is especially important because, unlike genotype, diet and nutrition can be modified. The aim of the present review is to critically evaluate current knowledge relating to candidate genes for osteoporosis, with particular emphasis on their interaction with nutrients and dietary factors in determining bone health.

Moderate alcohol consumption and increased bone mineral density: potential ethanol and non-ethanol mechanisms

Mounting epidemiological evidence indicates an association between the moderate ingestion of alcoholic beverages and higher bone mineral density (v. abstainers). More limited findings provide some evidence for translation of this association into reduced fracture risk, but further studies are required. Here, these data are reviewed and caveats in their assimilation, comparison and interpretation as well as in the use and application of bone health indices are discussed. Whilst it is concluded that evidence is now strong for the moderate alcohol-bone health association, at least in relation to bone mineral density, mechanisms are less clear. Both ethanol and non-ethanol components have been implicated as factors that positively affect bone health in the light of moderate consumption of alcoholic beverages, and four particular areas are discussed. First, recent findings suggest that moderate ethanol consumption acutely inhibits bone resorption, in a non-parathyroid hormone- and non-calcitonin-dependent fashion, which can only partly be attributed to an energy effect. Second, critical review of the literature does not support a role for moderate ethanol consumption affecting oestrogen status and leading to a knock-on effect on bone. Third, Si is present at high levels in certain alcoholic beverages, especially beer, and may have a measurable role in promoting bone formation. Fourth, a large body of work indicates that phytochemicals (e.g. polyphenols) from alcoholic beverages could influence bone health, but human data are lacking. With further work it is hoped to be able to model epidemiological observations and provide a clear pathway between the magnitude of association and the relative contribution of these mechanisms for the major classes of alcoholic beverage.

The positive effect of dietary vitamin D intake on bone mineral density in men is modulated by the polyadenosine repeat polymorphism of the vitamin D receptor

INTRODUCTION

Few studies have considered the dietary influence of vitamin D intake on bone mineral density (BMD). Numerous studies have examined the association between VDR polymorphism and BMD, but no previous study has examined the joint influence of dietary vitamin D intake and VDR polymorphism on BMD.

METHODS

We therefore conducted a study in 230 men aged 41-76 years of age. BMD was measured with DXA. A second bone scan was performed on average 2.7 years after the first investigation. Dietary habits were assessed by 14 dietary 24-h recall interviews. The polyadenosine (A) VDR genotypes were determined.

RESULTS

Dietary vitamin D intake was associated with BMD at all sites, also after multivariate adjustment. Those in the highest quintile of intake had 9% higher femoral neck BMD (p = 0.004), 6% higher BMD at the lumbar spine (p = 0.06) and 5% higher total body BMD (p = 0.003) compared to men in the lowest quintile of dietary vitamin D intake. However, the positive association between vitamin D intake and BMD was especially apparent among those with the L/L polyadenosine (A) VDR genotype explaining between 10 and 15% of the variability in BMD depending on site (p < 0.004). There was furthermore a trend, in the lumbar spine, of less reduction in BMD with increasing vitamin D intake (p = 0.07) but not at the other sites. Calcium intake conferred no association with BMD.

CONCLUSIONS

Our results indicate that the extent of positive association between dietary vitamin D intake and BMD in men is dependent on VDR polymorphism, a novel conceivable important gene-environmental interaction.

Vitamin D insufficiency in congestive heart failure: why and what to do about it?

This article gives an overview of the current knowledge on vitamin D status in patients with congestive heart failure (CHF). A serum 25-hydroxyvitamin D level below 50 nmol/l (20 ng/ml) is generally regarded as insufficient. Available data indicate that the majority of CHF patients have 25-hydroxyvitamin D levels in the insufficiency range. Skin synthesis of vitamin D after solar ultraviolet B exposure is the most important vitamin D source for humans. However, CHF patients have relatively low outdoor activities. Consequently, a disease-related sedentary lifestyle is an important cause for the insufficient vitamin D status in CHF patients. There is also evidence from a recently performed case-controlled study that indicators of ultraviolet B exposure are already reduced in CHF patients during childhood, adolescence, and early adulthood compared to healthy controls. We present results indicating that an insufficient vitamin D status may contribute to the etiology/pathogenesis of CHF. Data include a vitamin D-mediated reduction of elevated blood pressure as well as a vitamin D-mediated prevention of enhanced parathyroid hormone levels, a pathophysiological state that contributes to cardiovascular disease. Based on population attributable risks, hypertension and cardiovascular disease have a high impact, accounting for the majority of CHF events.Theoretically, vitamin D status can be improved by adequate skin synthesis of vitamin D and/or adequate oral vitamin D intake. At present, daily oral intake of 50-100 microg vitamin D seems to be the most effective way to improve vitamin D status in CHF patients.

Predictors and relationships of serum 25 hydroxyvitamin D concentration with bone turnover markers, bone mineral density, and vitamin D receptor genotype in Emirati women

OBJECTIVES

To determine factors influencing serum 25 hydroxyvitamin D (25OHD) concentration and relationships between serum 25OHD concentration, bone turnover markers, bone mineral density (BMD), and vitamin D receptor (VDR) genotype in Emirati women.

METHODS

Serum 25OHD, parathyroid hormone (PTH), osteocalcin (OC), vitamin D binding protein (VDBP), and urinary deoxypyrdinoline (UDPD) concentrations and VDR genotype were determined in Emirati women volunteers who were participating in a study aiming at establishing a reference database for BMD.

RESULTS

Serum 25OHD concentration in the 259 women volunteers was 25.3 +/- 10.8 nmol/l (mean +/- SD), and all had vitamin D deficiency (25OHD <80 nmol/l). Mean serum 25OHD was highest in April (29.2 +/- 13.0 nmol/l), which marks the end of the short and cooler winter season, and lowest in August (18.2 +/- 5.9 nmol/l). No significant difference in 25OHD concentration was noted among Emirati women wearing different dress styles, but the mean serum 25OHD was significantly lower in comparison with non-Arab Caucasian women volunteers who dressed in a Western style (P < 0.001). Serum 25OHD correlated positively with age (r = 0.2), number of pregnancies (r = 0.16), dietary vitamin D intake (r = 0.15), serum calcium (r = 0.14), phosphorus (r = 0.14), VDBP (r = 0.15), and urinary calcium/creatinine (r = 0.2), and inversely with PTH (r = -0.22), OC (r = -0.13), and UDPD/creatinine (r = -0.15); P < 0.05 for all correlations. Multiple linear regression analysis showed that age, dietary vitamin D intake, multivitamin intake, and cooler season were independent positive predictors of serum 25OHD concentration (R(2) = 0.18). The frequencies of VDR genotypes were 36% GG, 44.1% AG, and 19.9% AA. Allele frequencies were 58% for G allele and 42% for A allele and were in Hardy-Weinberg equilibrium (x(2) = 1.44; P > 0.1). There was no statistically significant influence of VDR genotype on bone turnover or BMD.

CONCLUSIONS

Vitamin D deficiency is highly prevalent in Emirati women and appears largely attributable to insufficient sunlight exposure. It is associated with increased bone turnover. VDR genotype does not appear to influence bone turnover markers or BMD in Emirati women.

Vitamin D receptor gene polymorphisms and bone mineral density in postmenopausal Indian women

OBJECTIVES

Osteoporosis is a common condition in postmenopausal women. Bone mineral density (BMD), the major determinant of osteoporotic fracture risk, has a particular genetic background. However, consensus on the association of BMD with specific gene locus has not been reached. The race and ethnicity specific divergence in association studies must be assessed to predict the susceptibility and therapeutic response of associated genes. We investigated the potential association of Vitamin D receptor (VDR) gene polymorphisms ApaI, BsmI, FokI and TaqI with BMD in 246 postmenopausal Indian women (average age 54.2+/-3.4 years).

METHODS

The subjects were genotyped by PCR-RFLP and underwent BMD measurements at spine and hip by dual energy X-ray absorptiometery.

RESULTS

The average BMD at spine and hip of women with genotypes aa, bb (presence of restriction sites for ApaI and BsmI), FF and TT (absence of restriction sites for FokI and TaqI) was more than 10% higher than those with genotypes AA, BB, ff and tt, respectively. The interaction between BsmI, ApaI and TaqI genotypes showed significant effect of BsmI-ApaI genotypes (p=0.052) in this combination on BMD. However, presence of T allele in combination showed positive influence on BMD. Within the group, genotypes BB, ff and tt were significantly prevalent in women with osteoporotic bone mass, tt and BB had significantly higher adjusted odd ratio (OR) for age more than 55years.

CONCLUSION

Study reveals that VDR gene polymorphisms are associated with BMD in Indian women and perhaps, influence some determinant of bone metabolism. Ethnicity may attribute to frequency variation, however, allele impact remains same.

BsmI vitamin D receptor genotypes influence the efficacy of antiresorptive treatments in postmenopausal osteoporotic women. A 1-year multicenter, randomized and controlled trial

Vitamin D receptor (VDR) gene polymorphisms could be considered one of the factors influencing the efficacy of the anti-osteoporotic treatments. In this multicenter, prospective, randomized and controlled trial we evaluated whether BsmI vitamin D receptor (VDR) genotypes influence the efficacy of antiresorptive treatment regimes (administered alone or in combination) in postmenopausal osteoporotic women. Using restriction endonuclease, we identified the BsmI VDR polymorphism in 1,100 postmenopausal women with osteoporosis. The women were randomized, taking account of genotype, into five treatment groups: (1) alendronate (Aln, 10 mg/day) plus raloxifene (Rlx, 60 mg/day); (2) Aln plus hormone replacement therapy (HRT, 0.625 mg/day conjugated equine estrogens plus 2.5 mg/day medroxyprogesterone acetate); (3) Aln alone; (4) HRT alone; and (5) Rlx alone. Lumbar-spine bone mineral density (BMD) and bone turnover markers were measured at study entry and after 1 year of treatment. Using the general linear model (GLM) repeated-measures procedure, the means of BMD and bone turnover markers significantly differed from baseline after a period of treatment. In particular, the mean change from baseline for BMD was -0.034 (95% confidence interval [CI]: -0.037 to -0.031, P <0.001); for serum osteocalcin (OC) it was 1.369 (95% CI: 1.289 to 1.448, P <0.001); and for urinary deoxypyridinoline (DPD) it was 1.322 (95% CI: 1.242 to 1.401, P <0.001), indicating a considerable variation before and after treatment of these indicators. In all three cases these effects appeared significantly influenced by treatments, genotypes, and the treatments*genotypes interaction term (P <0.001 each, except for the BMD and genotype effect with P =0.02), and not by the investigational centers involved in the study. In conclusion, in postmenopausal osteoporotic women, BsmI VDR genotypes influence the efficacy of antiresorptive drugs particularly when used in combination.

Vitamin D receptor genotypes influence the success of calcitriol therapy for recurrent vertebral fracture in osteoporosis

Osteoporosis is a complex multi-factorial disease where environment, diet and genetics play a role in determining susceptibility. Patients with existing vertebral fracture have a heightened risk of further recurrent vertebral fracture. The efficacy of new osteoporosis therapies is often compared to calcium supplementation. 1,25-dihydroxyvitamin D3 (calcitriol) acts through the vitamin D receptor (VDR) and is effective at reducing recurrent vertebral fracture risk. Because the VDR controls calcium metabolism, we hypothesized that genetic variation at the VDR locus may influence response to both calcium and calcitriol therapy. Postmenopausal women with osteoporosis from a 3-year study comparing calcitriol versus calcium for prevention of vertebral fractures were genotyped for VDR alleles detected by FokI, BsmI, ApaI and TaqI. Data were analysed by hierarchical log-linear analysis and robust analysis of variance for relationships to fracture outcomes. Significant differences in the vertebral fracture rate in response to calcium therapy were observed between VDR genotypes (P<0.001). Calcium appeared to be equally effective as calcitriol in particular genotypes. The response to calcitriol therapy was most pronounced in patients carrying the TaqI t allele in combination with the FokI f initiation codon variant: f+t+ carriers were 11.3-fold less likely to sustain recurrent vertebral fracture in the last 2 years of the trial while on calcitriol therapy compared to calcium (P=1.4x10(-5)). Response to both calcium and calcitriol therapy is dependent on genetic variation at the VDR locus and two loci in the VDR gene may contribute to this effect.

Association of vitamin D receptor gene polymorphism and Parkinson's disease in Koreans

1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3), which is the biologically active form of vitamin D, has anti-inflammatory effects and can prevent experimental Parkinson's disease (PD). 1,25(OH)2D3 exerts most of its actions only after it binds to its specific nuclear receptors. Eighty-five Korean patients with PD and 231 unrelated healthy individuals were evaluated to determine if vitamin D receptor gene (VDRG) BsmI polymorphisms were markers for the susceptibility to PD in Korean patients. Each polymorphism was detected using polymerase chain reaction (PCR)-based restriction analysis. In addition, the relationship between the BsmI polymorphisms and the clinical manifestations of PD was evaluated. Overexpression of the b allele (91.2 vs. 85.7%; p=0.069) and homozygote bb (84.7 vs. 72.7%; p=0.043) was found in the PD patients compared with the controls. These results show for the first time an association between PD and a VDRG polymorphism, which might be involved in the pathogenesis of PD, or in the linkage disequilibrium of the VDRG to another pathogenic gene locus.