Association between vitamin D receptor gene polymorphisms, falls, balance and muscle power: results from two independent studies (APOSS and OPUS)

Exploring the impact of vitamin D-related genetic variants on muscular fitness changes in middle-aged and older adults in Kosovo

Introduction

Age-related decline in muscle strength and performance significantly impact morbidity and mortality. Various factors including genetics have been investigated to better understand this decline. This study aimed to investigate longitudinal changes in physical performance and strength and their association with genetic variants in genes involved in the vitamin D pathway.

Methods

This longitudinal study was conducted in the Prishtina region, Kosovo, with community-dwelling adults over 40 years of age. Genomic DNA was extracted from saliva samples to assess single nucleotide polymorphisms in the vitamin D receptor (VDR) gene (rs7975232, rs2228570, rs731236, also referred to as ApaI, FokI, and TaqI, respectively) and the vitamin D binding protein (GC) gene (rs4588, rs2282679). Physical performance was assessed by isometric handgrip strength, 30-s chair stand, timed up and go and 6-min walk test. Vitamin D levels were assessed from blood samples only at follow-up.

Results

A total of 138 participants (65.1 ± 9.0 years, 52.2% female) were included. Over a 2.7-year period, significant declines in the 30-s chair stand test (p < 0.001) and timed up and go performance (p < 0.001) were observed, whereas BMI increased. Only female participants experienced a decrease in handgrip strength (p < 0.001). Genotyping showed significant associations of the ApaI variant with changes in BMI and handgrip strength. Participants with the minor CC genotype showed a greater increase in BMI and a greater decrease in absolute and relative handgrip strength. No significant interactions were observed for FokI and TaqI in the VDR gene, or rs4588 and rs2282679 in the GC gene. Vitamin D deficiency (<50 nmol/L) was prevalent in 47.5% of participants, with significant differences in 25(OH)D levels observed between genotypes of the GC gene (rs4588, p = 0.039; rs2282679, p = 0.036).

Conclusion

Physical fitness declined significantly over time, with female participants experiencing a greater decline in handgrip strength. The ApaI variant in the VDR gene was associated with changes in muscle strength, while variants in the GC gene were associated with vitamin D levels. These findings suggest that genetic factors related to the vitamin D pathway may contribute to the age-related decline in muscle strength. Therefore, genetic predisposition should be considered when developing individual interventions for healthy aging.

Vitamin D supplementation and falls in residential aged care: A longitudinal multisite cohort study

Background

Vitamin D is vital for musculoskeletal health, and supplementation may lower risk of falls. Past research in residential aged care (RAC) settings on the effects of vitamin D on falls have reported inconclusive findings, partly due to study design limitations. We utilised a longitudinal study design to assess the association between the use of vitamin D and falls over 36 months in RAC.

Method

A longitudinal cohort study was conducted using routinely collected electronic data spanning 9 years from 27 RAC facilities in Sydney, New South Wales, Australia. The study included 4520 permanent residents aged 65 years or older who were admitted for the first time from 1 July 2014 and stayed for a minimum of one month. We identified daily vitamin D usage over 36 months, and measured adherence using the Proportion of Days Covered (PDC) metric. A PDC value of ≥80 % signifies optimal adherence. Primary outcomes were the number of all falls and injurious falls. A rolling time-varying predictor-outcome approach and Generalized Estimating Equations (GEE) were applied to determine the longitudinal link between vitamin D supplement use and subsequent risk of falls.

Results

Over two-thirds of residents (67.8 %; n = 3063) received vitamin D supplements during their stay, with a median PDC of 74.8 % among users, and 44.6 % (n = 1365) achieving optimal adherence. Increasing age, osteoporosis or fracture history, and dementia were associated with a greater likelihood of achieving optimal adherence. Crude fall incident rates were 8.05 and 2.92 incidents per 1000 resident days for all falls and injurious falls respectively. After accounting for relevant demographic and clinical factors, no significant links were observed between vitamin D supplement usage and fall outcomes: all falls (Incident Rate Ratio [IRR] 1.01; 95 % CI 1.00-1.02; P = 0.237) and injurious falls (IRR 1.01; 95 % CI 1.00-1.02; P = 0.091).

Conclusion

Vitamin D supplementation was not associated with a reduced risk of falls, suggesting it is not an effective intervention for preventing falls in RAC. While clinicians should ensure adequate vitamin D intake for residents' nutritional and bone health, it should not be a standalone falls prevention intervention in RAC populations.

The impact of genetic variation within the vitamin D pathway upon skeletal muscle function: A systematic review

Studies in vitro have demonstrated a key molecular role for 1,25-dihydroxyvitamin D (1,25D) in skeletal muscle function, with vitamin D-deficiency (low serum 25-hydroxyvitamin D, 25D) being associated with muscle pain and weakness. Despite this, an understanding of the overall role of vitamin D in muscle health (particularly the impact of vitamin D-related genetic variants) has yet to be fully resolved, relative to more well-studied targets such as the skeleton. Thus, we aimed to review existing studies that have investigated relationships between skeletal muscle function and single nucleotide polymorphisms (SNPs) within vitamin D-related genes. A systematic review of papers published between January 2000 and June 2022 on PubMed, EMBASE and Web of Science pertaining to association between functionally relevant vitamin D receptor genetic variants and variants within genes of the vitamin D pathway and skeletal muscle function/outcomes was performed. 21 articles were included in the review for final analysis, of which 20 only studied genetic variation of the VDR gene. Of the included articles, 81 % solely included participants aged ≥ 50 years and of the 9 studies that did not only include White individuals, only 2 included Black participants. Within the vitamin D system, the VDR gene is the primary gene of which associations between polymorphisms and muscle function have been investigated. VDR polymorphisms have been significantly associated with muscle phenotypes in two or more studies. Of note A1012G was significantly associated with higher handgrip strength, but the results for other SNPs were notably variable between studies. While the lack of definitive evidence and study heterogeneity makes it difficult to draw conclusions, the findings of this review highlight a need for improvements with regards to the use of more diverse study populations, i.e., inclusion of Black individuals and other people of colour, and expanding research scope beyond the VDR gene.

Genetic variants of the vitamin D receptor are related to dynapenia in postmenopausal women

BACKGROUND

Dynapenia increases with age and in the case of women is possibly influenced by menopause, yet whether vitamin D affects this increase remains controversial. The influence of genetic variants (single nucleotide polymorphisms) of the vitamin D receptor on dynapenia is an understudied area.

AIM

To analyze the association between genetic variants of the vitamin D receptor gene and dynapenia in a cohort of community-dwelling postmenopausal women.

METHODS

We performed a cross-sectional study of 463 women in a university hospital. Grip strength was used as an indicator of dynapenia. Differences in grip strength among single nucleotide polymorphisms rs11568820 and rs2228570 genotypes of the vitamin D receptor gene were assessed after adjusting for confounding variables, and the percentage of phenotypic variance was estimated by linear regression.

RESULTS

Dynapenia (grip strength <20 kg) was diagnosed in 178 of the women (38.45 %). A difference in grip strength, corresponding to variants of the vitamin D receptor gene single nucleotide polymorphism rs11568820, was found when using an additive model of inheritance, with lower grip strength for the TT genotype (ANOVA, p = 0.030, close to the 0.025 significance level determined by Bonferroni correction). Assuming a recessive inheritance model for allele T, the between-group difference in grip strength was significant (TT = 19.79 ± 3.10 kg vs. CC/CT = 21.58 ± 3.49 kg, p = 0.008) after adjusting for age, body mass index, comorbidities, and sociodemographic variables. More women with dynapenia had the TT genotype (60.71 %) than the CC or CT genotype (37.01 %) (p = 0.012).

CONCLUSION

This study demonstrates that the TT genotype of the rs11568820 SNP of the vitamin D receptor gene was associated with decreased grip strength in community-dwelling postmenopausal women.

Association between Polymorphisms in Vitamin D Pathway-Related Genes, Vitamin D Status, Muscle Mass and Function: A Systematic Review

An association between vitamin D level and muscle-related traits has been frequently reported. Vitamin D level is dependent on various factors such as sunlight exposure and nutrition. But also on genetic factors. We, therefore, hypothesize that single nucleotide polymorphisms (SNPs) within the vitamin D pathway-related genes could contribute to muscle mass and function via an impact on vitamin D level. However, the integration of studies investigating these issues is still missing. Therefore, this review aimed to systematically identify and summarize the available evidence on the association between SNPs within vitamin D pathway-related genes and vitamin D status as well as various muscle traits in healthy adults. The review has been registered on PROSPERO and was conducted following PRISMA guidelines. In total, 77 studies investigating 497 SNPs in 13 different genes were included, with significant associations being reported for 59 different SNPs. Variations in GC, CYP2R1, VDR, and CYP24A1 genes were reported most frequently, whereby especially SNPs in the GC (rs2282679, rs4588, rs1155563, rs7041) and CYP2R1 genes (rs10741657, rs10766197, rs2060793) were confirmed to be associated with vitamin D level in more than 50% of the respective studies. Various muscle traits have been investigated only in relation to four different vitamin D receptor (VDR) polymorphisms (rs7975232, rs2228570, rs1544410, and rs731236). Interestingly, all of them showed only very low confirmation rates (6-17% of the studies). In conclusion, this systematic review presents one of the most comprehensive updates of the association of SNPs in vitamin D pathway-related genes with vitamin D status and muscle traits in healthy adults. It might be used for selecting candidate SNPs for further studies, but also for personalized strategies in identifying individuals at risk for vitamin D deficiency and eventually for determining a potential response to vitamin D supplementation.

Prevalence of hypovitaminosis D in patients with juvenile osteochondritis dissecans

BACKGROUND

Juvenile osteochondritis dissecans (JOCD) is an acquired joint disease of unknown etiology that affects skeletally immature patients and has the potential to progress to osteoarthritis. Recent studies have reported a high prevalence of vitaminD deficiency in patients with osteochondral lesions. The aim of our study was to determine serum vitaminD levels in patients diagnosed with JOCD.

METHODS

Serum 25(OH)D levels of 31 patients (22 males) presenting 40 lesions (29 JOCD of the knee, and 11 of the ankle) were evaluated. The average age was 11.9±2.9years. HypovitaminosisD was defined as a value less than 30ng/mL and was divided into vitaminD insufficiency (20 to 30ng/mL) and vitaminD deficiency (<20ng/mL).

RESULTS

HypovitaminosisD was present in 45.2% of the evaluated patients (32.2% insufficiency and 13% deficiency). No significant differences were found in the mean values and incidence of hypovitaminosis between those patients in which the sample was taken in warm or cold season (P=.267 and P=.875, respectively). Patients who required surgery had a higher incidence of hypovitaminosis than those treated conservatively (60% versus 31%, P=.054). There was no correlation in the incidence of hypovitaminosis with sex, location, stability of the lesion, or if the lesion was uni- or bilateral.

CONCLUSION

In our series, almost half of the patients diagnosed with JOCD presented abnormal serum levels of vitaminD. A two-fold incidence of hypovitaminosis was observed in patients requiring surgical treatment compared to patients managed conservatively. The association found in this study does not imply causation, but it should be considered within the set of actions for the treatment of these injuries.

Genetic Associations with Aging Muscle: A Systematic Review

The age-related decline in skeletal muscle mass, strength and function known as 'sarcopenia' is associated with multiple adverse health outcomes, including cardiovascular disease, stroke, functional disability and mortality. While skeletal muscle properties are known to be highly heritable, evidence regarding the specific genes underpinning this heritability is currently inconclusive. This review aimed to identify genetic variants known to be associated with muscle phenotypes relevant to sarcopenia. PubMed, Embase and Web of Science were systematically searched (from January 2004 to March 2019) using pre-defined search terms such as "aging", "sarcopenia", "skeletal muscle", "muscle strength" and "genetic association". Candidate gene association studies and genome wide association studies that examined the genetic association with muscle phenotypes in non-institutionalised adults aged ≥50 years were included. Fifty-four studies were included in the final analysis. Twenty-six genes and 88 DNA polymorphisms were analysed across the 54 studies. The ACTN3, ACE and VDR genes were the most frequently studied, although the IGF1/IGFBP3, TNFα, APOE, CNTF/R and UCP2/3 genes were also shown to be significantly associated with muscle phenotypes in two or more studies. Ten DNA polymorphisms (rs154410, rs2228570, rs1800169, rs3093059, rs1800629, rs1815739, rs1799752, rs7412, rs429358 and 192 bp allele) were significantly associated with muscle phenotypes in two or more studies. Through the identification of key gene variants, this review furthers the elucidation of genetic associations with muscle phenotypes associated with sarcopenia.

The effects of vitamin D supplementation on muscle function among postmenopausal women: a systematic review and meta-analysis of randomized controlled trials

The loss of muscle mass and its strength is one of the most critical changes in aging which is associated with an increased risk of falls, osteoporotic fractures and mobility disability. Vitamin D, with its extra-skeletal benefits, might improve muscle function in elderly. The current systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize available relevant data and determine the effect of vitamin D supplementation on muscle function among postmenopausal women. We reached databases including; Cochrane library, Embase, PubMed, and Web of Science database until the end of May 2018 to identify relevant published RCTs. Heterogeneity among included studies was assessed using Q-test and I2 statistics. Random-effect model was applied to pool data and weighted mean difference (WMD) was calculated representing summary effect size. Outcomes of interest included the effects of vitamin D supplementation on hand grip strength (HGS), back muscle strength (BMS), and Timed Up and Go (TUG). Twelve RCTs out of 1739 potential reports were included in our meta-analysis. The pooled findings showed that vitamin D supplementation had no significant effect on HGS (WMD -0.03 kilogram (Kg); 95 % CI, -0.26, 0.20; P=0.78), BMS (WMD 7.21 newton (N); 95 % CI, -5.98, 20.40; P=0.28), and TUG (WMD 0.01 second (S); 95 % CI, -0.17, 0.18; P=0.93) in postmenopausal women. Overall, the current meta-analysis showed that taking vitamin D supplementation by postmenopausal women did not affect markers of muscle function. Further studies are required to confirm the effect of vitamin D supplementation on markers of muscle function.

Variations in the vitamin D receptor gene are not associated with measures of muscle strength, physical performance, or falls in elderly men. Data from MrOS Sweden

The vitamin D receptor (VDR) has been proposed as a candidate gene for several musculoskeletal phenotypes. However, previous results on the associations between genetic variants of the VDR with muscle strength and falls have been contradictory. The MrOS Sweden survey, a prospective population-based cohort study of 3014 elderly men (mean age 75 years, range 69-81) offered the opportunity to further investigate these associations. At baseline, data were collected on muscle strength and also the prevalence of falls during the previous 12 months. Genetic association analysis was performed for 7 Single Nucleotide Polymorphisms (SNPs), covering the genetic region surrounding the VDR gene in 2924 men with available samples of DNA. Genetic variations in the VDR were not associated with five different measurements of muscle strength or physical performance (hand grip strength right and left, 6 m walking test (easy and narrow) and timed-stands test). However, one of the 7 SNPs of the gene for the VDR receptor, rs7136534, was associated with prevalence of falls (33.6% of the AA, 14.6% of the AG and 16.5% of the GG allele). In conclusion, VDR genetic variants are not related to muscle strength or physical performance in elderly Swedish men. The role of the rs7136534 SNP for the occurrence of falls is not clear.

Predictors of presarcopenia in community-dwelling older adults: A 5-year longitudinal study

Objectives: Sarcopenia is an aging-induced decrease in muscle mass that increases frailty and fall in elderly people. Presarcopenia corresponds to the preliminary stage of sarcopenia. The purpose of this prospective study is to examine predictors of presarcopenia in health screening.Methods: The subjects were 124 community residents aged ≥60 years (55 males, 69 females, average age 70.2 years) who attended local government health checkups in 2010 and 2015, as part of the Yakumo study, and did not have presarcopenia in 2010. Body mass index (BMI), waist and hip circumferences, grip strength, bone mineral density (BMD), 10-m gait time, back muscle strength, and stride length were measured. Presarcopenia was defined using the appendicular skeletal muscle index (arm and leg skeletal muscle mass/height²).Results: The prevalences of presarcopenia in 2015 in males and females were 21.8% (12/55) and 30.4% (21/69), respectively. BMI, grip strength, BMD, back muscle strength, and osteoporosis deteriorated significantly more in the pre-sarcopenia group (n = 33) compared with controls (n = 91; no presarcopenia in 2015). In multivariate analysis, osteoporosis (OR 3.12, 95% CI 1.07-9.09; p < .05) was significantly associated with presarcopenia after 5 years.Conclusions: Establishment of risk factors for future pre-sarcopenia may allow development of evidence-based prevention strategies for this condition.

Vitamin D Status and Vitamin D Receptor Gene Polymorphisms Are Associated with Pelvic Floor Disorders in Women

Objectives

To investigate if vitamin D receptor (VDR) gene polymorphisms and circulating vitamin D levels are associated with pelvic floor disorders (PFDs).

Methods

In this case-control study, 25-hydroxy-vitamin D (25[OH]D) serum levels were analyzed in 47 females with PFDs and 87 healthy females (controls), respectively. The VDR gene polymorphisms were determined by using polymerase chain reaction and performing digestions with 4 restriction enzymes i.e., ApaI, TaqI, FokI, and BsmI. Vitamin D levels of patients were divided into <20 ng/mL, 20 to 30 ng/mL, and ≥30 ng/mL categories.

Results

Our correlative analysis of VDR polymorphisms as a function of the presence of PFD showed that ApaI and BsmI polymorphisms were significantly associated with PFD in vitamin-D-deficiency and insufficiency groups (P < 0.05). Mean vitamin D levels did not differ between the PFD case (13.01 ± 0.84 ng/mL) and control (15.11 ± 1.04 ng/mL) groups (P > 0.05). However, there was a significant difference in the distribution of vitamin D levels between study group and controls using Pearson's χ² test (<20 ng/mL, 20–30 ng/mL, and >30 ng/mL: 87.2%, 12.8%, and 0% in the study group and 75.9%, 16.1%, and 8.0% in controls, respectively, P < 0.05). Taken together, our observations suggest that vitamin D levels could be associated with PFDs and that 2 polymorphisms (i.e., ApaI and BsmI) in the VDR gene may contribute to an increased prevalence of PFDs in women with insufficient levels of vitamin D.

Conclusions

Examining vitamin D levels and performing a VDR genotype analysis may be helpful for assessing PFD risk.

Osteosarcopenia: where bone, muscle, and fat collide

As the world's population ages, the prevalence of chronic diseases increases. Sarcopenia and osteoporosis are two conditions that are associated with aging, with similar risk factors that include genetics, endocrine function, and mechanical factors. Additionally, bone and muscle closely interact with each other not only anatomically, but also chemically and metabolically. Fat infiltration, a phenomenon observed in age-related bone and muscle loss, is highly prevalent and more severe in sarcopenic and osteoporotic subjects. Clinically, when individuals suffer a combination of both disorders, negative outcomes such as falls, fractures, loss of function, frailty, and mortality increase, thus generating significant personal and socio-economic costs. Therefore, it is suggested that when bone mineral density loss is synchronic with decreased muscle mass, strength, and function, it should be interpreted as a single diagnosis of osteosarcopenia, which may be preventable and treatable. Simple interventions such as resistance training, adequate protein and calcium dietary intake, associated with maintenance of appropriate levels of vitamin D, have a dual positive effect on bone and muscle, reducing falls, fractures, and, consequently, disability. It is essential that fracture prevention approaches-including postfracture management-involve assessment and treatment of both osteoporosis and sarcopenia. This is of particular importance as in older persons the combination of osteopenia/osteoporosis and sarcopenia has been proposed as a subset of frailer individuals at higher risk of institutionalization, falls, and fractures. This review summarizes osteosarcopenia epidemiology, pathophysiology, diagnosis, outcomes, and management strategies.

Body mass index and the risk of low bone mass-related fractures in women compared with men: A PRISMA-compliant meta-analysis of prospective cohort studies

BACKGROUND

Body mass index (BMI) is inconsistently associated with the progression of low bone mass-related fractures. We conducted a systematic review and meta-analysis to summarize the evidence regarding the relationship between BMI and the risk of fracture in men and women separately. Furthermore, we analyzed the association between BMI and fracture risk in women compared with men.

METHODS

PubMed, EmBase, and the Cochrane Library were searched up to November 2015 to identify prospective cohort studies of low bone mass-related fractures. Prospective cohort studies that reported effect estimates of fracture risk for different BMI categories compared to normal weight were included. Relative risk (RR) and the ratio of relative risk (RRR) were calculated using a random-effect model to measure the relationship between BMI and fracture risk.

RESULTS

We analyzed 37 cohorts (32 articles), which included a total of 506,004 women and 118,372 men; overall, 38,200 incident cases were reported. Overall, a lower BMI was not associated with fracture risk in men (RR: 1.50, 95% confidence interval [CI]: 1.00-2.26; P = 0.051) or women (RR: 1.25, 95% CI: 0.97-1.62; P = 0.083). Although a higher BMI might play a beneficial impact in men (RR: 0.80, 95% CI: 0.69-0.93; P = 0.003), it has little effect in women (RR: 0.91, 95% CI: 0.74-1.11; P = 0.343). In addition, an increase in BMI by 5 kg/m decreased the risk of fractures in men (RR: 0.90, 95% CI: 0.83-0.98; P = 0.017) and women (RR: 0.85, 95% CI: 0.81-0.89; P < 0.001). Finally, there was no evidence of a sex difference in the RR for fractures between participants with different BMI categories compared with those with normal BMI. Finally, gender did not affect the risk of fracture for any category of BMI values.

CONCLUSION

Higher BMI may affect the risk of fractures regardless of the sex. This association may be due to the interaction between the participants' BMI and their bone mass density.

Vitamin-D measurement in patients with adolescent idiopathic scoliosis

Our retrospective study compared vitamin-D levels in 229 patients with adolescent idiopathic scoliosis (AIS) and 389 age-matched controls, and evaluated the correlation between vitamin-D levels and sex, Cobb's angle, and serum levels of calcium (Ca), phosphorus, and alkaline phosphatase in the AIS group. Vitamin-D levels were lower in the AIS group, with no sex-specific effects, indicative of a possible vitamin-D resistance in AIS. Vitamin-D levels correlated positively with Ca levels and negatively with Cobb's angle, indicative of a possible role of vitamin D in the etiopathogenesis of AIS. Patients with AIS should be monitored for vitamin-D deficiency/insufficiency.

Association between vitamin D receptor gene FokI polymorphism and skeletal fluorosis of the brick-tea type fluorosis: a cross sectional, case control study

BACKGROUND

Brick-tea type fluorosis is a public health concern in the north west area of China. The vitamin D receptor (VDR)-FokI polymorphism is considered to be a regulator of bone metabolism and calcium resorption. However, the association of VDR-FokI polymorphism with the risk of brick-tea type fluorosis has not been reported.

MATERIALS AND METHODS

A cross sectional, case control study was conducted in three provinces (Inner Mongolia, Qinghai and Sinkiang) in China. The fluoride content of Brick-tea water and urine was tested using the standards GB 1996-2005 and WS/T89-2006 (China), respectively. Skeletal fluorosis was diagnosed using the standard WS/192-2008 (China). The VDR-FokI polymorphism was detected by the Sequenom MassARRAY system.

RESULT

Compared with carriers of the CC genotype, participants with the CT/TT genotype had a significantly decreased risk of skeletal fluorosis (OR=0.761 (95% CI 0.580 to 0.997)), after adjustment for risk factors. When investigated among ethnic groups, the protective effect of the CT/TT genotype was limited in the Mongolian participants (OR=0.525 (95% CI 0.278 to 0.991)). Moreover, the interaction of VDR-FokI with risk factors was only found in Mongolian participants: the protective effect of the CT/TT genotype was limited to participants with >7.0 mg/day daily intake of tea fluoride (OR=0.085 (95% CI 0.009 to 0.851), participants with >3.2 mg/L urine fluoride (OR=0.103 (95% CI 0.017 to 0.633)) or participants aged 46-65 years (OR=0.404 (95% CI 0.177 to 0.922).

CONCLUSIONS

Our data suggest that the CT/TT genotype of VDR-FokI may be a protective factor for brick-tea type skeletal fluorosis, and this effect is pronounced in Mongolian participants.

Muscle strength is associated with vitamin D receptor gene variants

Vitamin D receptor (VDR) is an important candidate gene in muscle function. Scientific reports on the effect of its genetic variants on muscle strength are contradictory likely due to the inconsistent study designs. Hand grip strength (HGS) is a highly heritable phenotype of muscle strength but only limited studies are available on its genetic background. Association between VDR polymorphisms and HGS has been poorly investigated and previous reports are conflicting. We studied the effect of VDR gene variants on HGS in a sample of 706 schoolchildren. Genomic DNA was extracted from saliva samples and six candidate single nucleotide polymorphisms (SNPs) across the VDR gene were genotyped with Sequenom MassARRAY technique. HGS was measured with a digital dynamometer in both hands. Single marker and haplotype associations were adjusted for demographic parameters. Three SNPs, rs4516035 (A1012G; p = 0.009), rs1544410 (BsmI; p = 0.010), and rs731236 (TaqI; p = 0.038) and a 3' UTR haploblock constructed by three SNPs (Bsml-Taq1-rs10783215; p < 0.005) showed significantly associations with HGS of the dominant hand. In the non-dominant hand, the effects of the A1012G (p = 0.034) and the 3' UTR haploblock (p < 0.01) on HGS were also significant. Since the promoter SNP (A10112G) and the 3' UTR haplotype were proved to be associated with the expression and the stability of the VDR mRNA in earlier studies, VDR variants can be supposed to have a direct effect on muscle strength. The individual genetic patterns can also explain the inconsistency of the previously published clinical results on the association between vitamin D and muscle function. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2031-2037, 2016.

Replication study of the vitamin D receptor (VDR) genotype association with skeletal muscle traits and sarcopenia

Polymorphisms in the vitamin D receptor (VDR) gene are some of the most studied in relation to skeletal muscle traits and significant associations have been observed by multiple groups. One such paper by our group provided the first evidence of a genetic association with sarcopenia in men, but that finding has yet to be replicated in an independent cohort. In the present study, we examined multiple VDR polymorphisms in relation to skeletal muscle traits and sarcopenia in 864 men and women across the adult age span. In addition to VDR genotypes and haplotypes, measurements of skeletal muscle strength and fat-free mass (FFM) were determined in all subjects and a measure of sarcopenia was calculated. We observed significant associations between Fok1 and Bsm1 genotypes and skeletal muscle strength in men and women, though these associations were modest and no significant associations were observed for these polymorphisms and muscle mass traits nor for Bsm1-Taq1 haplotype with muscle strength. Fok1 FF genotype was associated with an increased the risk of sarcopenia in older women compared to f-allele carriers (1.3-fold higher risk). These results support previous findings that VDR genetic variation appears to impact skeletal muscle strength and risk for sarcopenia but the influence is modest.

Low 25(OH) D serum levels are related with hip fracture in postmenopausal women: a matched case-control study

Purpose

There is limited information on the prevalence of vitamin D deficiency among patients diagnosed with hip fracture in the Chinese Han population. Therefore, the aim of this study was to assess the effects of change in the serum levels of 25-hydroxyvitamin D [25(OH) D] and intact parathyroid hormone (iPTH) among postmenopausal women in North China with confirmed hip fracture.

Methods

This study was done from May 1, 2012 to April 30, 2014. Three hundred and forty-nine postmenopausal women who were diagnosed with first-ever hip fracture and 349 matched controls without fracture were used for this study. The 25(OH) D, iPTH, alkaline phosphatase, calcium, and phosphorus levels were measured in fasting venous blood samples collected from the subjects. A predesigned questionnaire was used to collect information on covariates for multivariate analyses to evaluate the hypothesized relationship between vitamin D deficiency and fracture risk.

Results

The serum 25(OH) D levels were found to be significantly (P < 0.0001) lower in hip fracture patients than in the controls [37.0 (interquartile range [IQR] 28.0–48.0) nmol/L vs. 41.3 (IQR 32.0–54.5) nmol/L; P < 0.0001], and the iPTH levels were significantly higher in the former group [10.2 (IQR 6.3–14.9) pmol/L vs. 5.8 (IQR 4.1–6.6) pmol/L; P < 0.0001]. Further, a 25(OH) D level ≤50 nmol/L was found to independently indicate the occurrence of hip fracture [odds ratio (OR), 3.023; 95 % confidence interval (CI) 2.154–4.298], as well as hip fracture with concomitant upper limb fracture (OR 4.473; 95 % CI 2.984–10.532). Similarly, a serum iPTH level ≥6.8 pmol/L independently indicated the development of hip fracture (OR 2.498; 95 % CI 1.764–3.942), as well as hip fracture with concomitant upper limb fracture (OR 3.254; 95 % CI 1.998–7.984).

Conclusions

Vitamin D insufficiency and secondary hyperparathyroidism were found to be common problems in the sample of postmenopausal women who had experienced hip fracture. Monitoring the alterations in the serum levels of 25(OH) D and iPTH could be applied clinically as independent risk factors for hip fracture.

Effect of vitamin D supplementation alone on muscle function in postmenopausal women: a randomized, double-blind, placebo-controlled clinical trial

The present study investigates the effects of vitamin D on muscle function in postmenopausal women. It has been shown that vitamin D supplementation in postmenopausal women with hypovitaminosis D provides significant protective factor against sarcopenia, with significant increases in muscle strength and control of progressive loss of lean mass.

INTRODUCTION

We aimed to evaluate the effect of supplementation of vitamin D (VITD) alone on muscle function in younger postmenopausal women.

METHODS

In this double-blind, placebo-controlled clinical trial, 160 Brazilian postmenopausal women were randomized into two groups: VITD group consisting of patients receiving vitamin D3 1000 IU/day orally (n = 80) or placebo group (n = 80). Women with amenorrhea for more than 12 months and age 50-65 years, with a history of falls (previous 12 months), were included. The intervention time was 9 months, with assessments at two points, start and end. Lean mass was estimated by total-body dual-energy X-ray absorptiometry (DXA) and muscle strength by handgrip strength and chair rising test. The plasma concentrations of 25-hydroxyvitamin D [25(OH)D] were measured by high-performance liquid chromatography (HPLC). Statistical analysis was by intention to treat (ITT), using ANOVA, Student's t test, and Tukey's test.

RESULTS

After 9 months, average values of 25(OH)D increased from 15.0 ± 7.5 to 27.5 ± 10.4 ng/ml (+45.4%) in the VITD group and decreased from 16.9 ± 6.7 to 13.8 ± 6.0 ng/ml (-18.5%) in the placebo group (p < 0.001). In the VITD group, there was significant increase in muscle strength (+25.3%) of the lower limbs by chair rising test (p = 0.036). In women in the placebo group, there was considerable loss (-6.8%) in the lean mass (p = 0.030).

CONCLUSION

The supplementation of vitamin D alone in postmenopausal women provided significant protective factor against the occurrence of sarcopenia, with significant increases in muscle strength and control of progressive loss of lean mass.

Serum Levels of 25-hydroxyvitamin D and Functional Outcome in Older Patients with Hip Fracture

The aim was to assess prognostic value of serum 25-hydroxyvitamin D (25[OH] D) levels in older Chinese patients with hip fracture. From June, 2012 to February, 2014, older patients with hip fracture were included. Serum 25(OH) D levels were measured at admission. The functional evaluation at the time of discharge was performed by the Barthel Index. In the 66 patients with an unfavorable outcome, serum 25(OH) D levels were lower compared with those with a favorable outcome. In multivariate analyses, there was an increased risk of unfavorable outcome associated with serum 25(OH) D levels ≤ 20 ng/ml (OR 5.25, 95% CI: 3.12-8.16). Our data supported an association between serum 25[OH] D levels at admission and short-term prognosis in Chinese older patients with hip fracture.

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.

Patterns of dietary intake and serum carotenoid and tocopherol status are associated with biomarkers of chronic low-grade systemic inflammation and cardiovascular risk

Dietary modification may affect inflammatory processes and protect against chronic disease. In the present study, we examined the relationship between dietary patterns, circulating carotenoid and tocopherol concentrations, and biomarkers of chronic low-grade systemic inflammation in a 10-year longitudinal study of Scottish postmenopausal women. Diet was assessed by FFQ during 1997-2000 (n 3237, mean age 54·8 (SD 2·2) years). Participants (n 2130, mean age 66·0 (SD 2·2) years) returned during 2007-11 for follow-up. Diet was assessed by FFQ (n 1682) and blood was collected for the analysis of serum high-sensitivity C-reactive protein (hs-CRP), IL-6, serum amyloid A, E-selectin, lipid profile and dietary biomarkers (carotenoids, tocopherols and retinol). Dietary pattern and dietary biomarker (serum carotenoid) components were generated by principal components analysis. A past 'prudent' dietary pattern predicted serum concentrations of hs-CRP and IL-6 (which decreased across the quintiles of the dietary pattern; P= 0·002 and P= 0·001, respectively; ANCOVA). Contemporary dietary patterns were also associated with inflammatory biomarkers. The concentrations of hs-CRP and IL-6 decreased across the quintiles of the 'prudent' dietary pattern (P= 0·030 and P= 0·006, respectively). hs-CRP concentration increased across the quintiles of a 'meat-dominated' dietary pattern (P= 0·001). Inflammatory biomarker concentrations decreased markedly across the quintiles of carotenoid component score (P< 0·001 for hs-CRP and IL-6, and P= 0·016 for E-selectin; ANCOVA). Prudent dietary pattern and carotenoid component scores were negatively associated with serum hs-CRP concentration (unstandardised β for prudent component: -0·053, 95% CI -0·102, -0·003; carotenoid component: -0·183, 95% CI -0·233, -0·134) independent of study covariates. A prudent dietary pattern (which reflects a diet high in the intakes of fish, yogurt, pulses, rice, pasta and wine, in addition to fruit and vegetable consumption) and a serum carotenoid profile characteristic of a fruit and vegetable-rich diet are associated with lower concentrations of intermediary markers that are indicative of CVD risk reduction.

Medication-induced osteoporosis: screening and treatment strategies

Drug-induced osteoporosis is a significant health problem and many physicians are unaware that many commonly prescribed medications contribute to significant bone loss and fractures. In addition to glucocorticoids, proton pump inhibitors, selective serotonin receptor inhibitors, thiazolidinediones, anticonvulsants, medroxyprogesterone acetate, aromatase inhibitors, androgen deprivation therapy, heparin, calcineurin inhibitors, and some chemotherapies have deleterious effects on bone health. Furthermore, many patients are treated with combinations of these medications, possibly compounding the harmful effects of these drugs. Increasing physician awareness of these side effects will allow for monitoring of bone health and therapeutic interventions to prevent or treat drug-induced osteoporosis.

Association between vitamin D receptor gene polymorphisms (Fok1 and Bsm1) and osteoporosis: a systematic review

Osteoporosis is a health concern characterized by reduced bone mineral density (BMD) and increased risk of fragility fractures. Many studies have investigated the association between genetic variants and osteoporosis. Polymorphism and allelic variations in the vitamin D receptor gene (VDR) have been found to be associated with bone mineral density. However, many studies have not been able to find this association. Literature review was conducted in several databases, including MEDLINE/Pubmed, Scopus, EMBASE, Ebsco, Science Citation Index Expanded, Ovid, Google Scholar, Iran Medex, Magiran and Scientific Information Database (SID) for papers published between 2000 and 2013 describing the association between Fok1 and Bsm1 polymorphisms of the VDR gene and osteoporosis risk. The majority of the revealed papers were conducted on postmenopausal women. Also, more than 50% studies reported significant relation between Fok1, Bsm1 and osteoporosis. Larger and more rigorous analytical studies with consideration of gene-gene and gene-environment interactions are needed to further dissect the mechanisms by which VDR polymorphisms influence osteoporosis.

Managing sarcopenia and its related-fractures to improve quality of life in geriatric populations

Sarcopenia, an aging-induced generalized decrease in muscle mass, strength, and function, is known to affect elderly individuals by decreasing mobile function and increasing frailty and imbalance that lead to falls and fragile fractures. Sarcopenia is a known risk factor for osteoporotic fractures, infections, and early death in some specific situations. The number of patients with sarcopenia is estimated to increase to 500 million people in the year 2050. Sarcopenia is believed to be caused by multiple factors such as disuse, malnutrition, age-related cellular changes, apoptosis, and genetic predisposition; however, this remains to be determined. Various methods have been developed, but no safe or effective treatment has been found to date. This paper is a review on the association between sarcopenia and its related-fractures and their diagnoses and management methods to prevent fractures.

Anteroposterior displacement behavior of the center of pressure, without visual reference, in postmenopausal women with and without lumbar osteoporosis

OBJECTIVE

The aims of this study were to evaluate the anteroposterior displacement behavior of the center of pressure without any visual reference and determine its relationship with knee muscle strength and reports of falls in postmenopausal women. Among those with osteoporosis, the specific objective was to evaluate the correlation of thoracic kyphosis and vitamin D with center of pressure displacement.

METHODS

This was a cross-sectional observational study without intervention. The assessments were performed on 126 postmenopausal women (aged 55-65 years) who were grouped according to their lumbar bone density into osteoporosis and control groups. Center of pressure was evaluated on a force platform (100 Hz frequency and 10 Hz filter), with the subjects standing on both feet with eyes closed for 60 seconds. Knee muscle strength was evaluated using an isokinetic dynamometer in concentric/concentric mode at a velocity of 60°/s. In the osteoporosis group, vitamin D was assayed, and the thoracic spine was radiographed.

RESULTS

In the control group, there was a correlation between the center of pressure and knee strength (r = 0.37; p<0.003). Reports of falls were not associated with center of pressure displacement (p = 0.056). In the osteoporosis group, thoracic kyphosis and vitamin D levels were not correlated with the center of pressure.

CONCLUSION

Anteroposterior center of pressure displacement without visual influence was not associated with falls, thoracic kyphosis or vitamin D in the osteoporosis group. Only knee muscle strength was associated with center of pressure displacement in the control group.

Genes and the ageing muscle: a review on genetic association studies

Western populations are living longer. Ageing decline in muscle mass and strength (i.e. sarcopenia) is becoming a growing public health problem, as it contributes to the decreased capacity for independent living. It is thus important to determine those genetic factors that interact with ageing and thus modulate functional capacity and skeletal muscle phenotypes in older people. It would be also clinically relevant to identify 'unfavourable' genotypes associated with accelerated sarcopenia. In this review, we summarized published information on the potential associations between some genetic polymorphisms and muscle phenotypes in older people. A special emphasis was placed on those candidate polymorphisms that have been more extensively studied, i.e. angiotensin-converting enzyme (ACE) gene I/D, α-actinin-3 (ACTN3) R577X, and myostatin (MSTN) K153R, among others. Although previous heritability studies have indicated that there is an important genetic contribution to individual variability in muscle phenotypes among old people, published data on specific gene variants are controversial. The ACTN3 R577X polymorphism could influence muscle function in old women, yet there is controversy with regards to which allele (R or X) might play a 'favourable' role. Though more research is needed, up-to-date MSTN genotype is possibly the strongest candidate to explain variance among muscle phenotypes in the elderly. Future studies should take into account the association between muscle phenotypes in this population and complex gene-gene and gene-environment interactions.

The roles of vitamin D in skeletal muscle: form, function, and metabolism

Beyond its established role in bone and mineral homeostasis, there is emerging evidence that vitamin D exerts a range of effects in skeletal muscle. Reports of profound muscle weakness and changes in the muscle morphology of adults with vitamin D deficiency have long been described. These reports have been supplemented by numerous trials assessing the impact of vitamin D on muscle strength and mass and falls in predominantly elderly and deficient populations. At a basic level, animal models have confirmed that vitamin D deficiency and congenital aberrations in the vitamin D endocrine system may result in muscle weakness. To explain these effects, some molecular mechanisms by which vitamin D impacts on muscle cell differentiation, intracellular calcium handling, and genomic activity have been elucidated. There are also suggestions that vitamin D alters muscle metabolism, specifically its sensitivity to insulin, which is a pertinent feature in the pathophysiology of insulin resistance and type 2 diabetes. We will review the range of human clinical, animal, and cell studies that address the impact of vitamin D in skeletal muscle, and discuss the controversial issues. This is a vibrant field of research and one that continues to extend the frontiers of knowledge of vitamin D's broad functional repertoire.

Vitamin D and its role in skeletal muscle

This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated with risk of falling. Clinical trials of vitamin D supplementation in older adults with low vitamin D status mostly report improvements in muscle performance and reductions in falls. The underlying mechanisms are probably both indirect via calcium and phosphate and direct via activation of the vitamin D receptor (VDR) on muscle cells by 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. VDR activation at the genomic level regulates transcription of genes involved in calcium handling and muscle cell differentiation and proliferation. A putative membrane-associated VDR activates intracellular signaling pathways also involved in calcium handling and signaling and myogenesis. Additional evidence comes from VDR knockout mouse models with abnormal muscle morphology and physical function, and VDR polymorphisms which are associated with differences in muscle strength. Recent identification of CYP27B1 bioactivity in skeletal muscle cells and in regenerating adult mouse muscle lends support to the direct action of both 25-hydroxyvitamin D and 1,25(OH)(2)D in muscle. Despite these research advances, many questions remain. Further research is needed to fully characterize molecular mechanisms of vitamin D action on muscle cells downstream of the VDR, describe the effects on muscle morphology and contractility, and determine whether these molecular and cellular effects translate into clinical improvements in physical function.

Genes, physical fitness and ageing

Persons aged 80 years and older are the fastest growing segment of the population. As more individuals live longer, we should try to understand the mechanisms involved in healthy ageing and preserving functional independence in later life. In elderly people, functional independence is directly dependent on physical fitness, and ageing is inevitably associated with the declining functions of systems and organs (heart, lungs, blood vessels, skeletal muscles) that determine physical fitness. Thus, age-related diminished physical fitness contributes to the development of sarcopenia, frailty or disability, all of which severely deteriorate independent living and thus quality of life. Ageing is a complex process involving many variables that interact with one another, including - besides lifestyle factors or chronic diseases - genetics. Thus, several studies have examined the contribution of genetic endowment to a decline in physical fitness and subsequent loss of independence in later life. In this review, we compile information, including data from heritability, candidate-gene association, linkage and genome-wide association studies, on genetic factors that could influence physical fitness in the elderly.

Developing novel prognostic biomarkers for multivariate fracture risk prediction algorithms

Multivariate prediction algorithms such as FRAX® and QFractureScores provide an opportunity for new prognostic biomarkers to be developed and incorporated, potentially leading to better fracture prediction. As more research is conducted into these novel biomarkers, a number of factors need to be considered for their successful development for inclusion in these algorithms. In this review, we describe two well-known multivariate prediction algorithms for osteoporosis fracture risk applicable to the UK population, FRAX and QFractureScores, and comment on the current prognostic tools available for fracture risk; dual X-ray assessment, quantitative ultrasonography, and genomic/biochemical markers. We also highlight the factors that need to be considered in the development of new biomarkers. These factors include the requirement for prospective data, collected in new cohort studies or using archived samples; the need for adequate stability data to be provided; and the need for appropriate storage methods to be used when retrospective data are required. Area under the receiver operating characteristic curve measures have been found to have limited utility in assessing the impact of the addition of new risk factors on the predictive performance of multivariate algorithms. New performance evaluation measures, such as net reclassification index and integrated discrimination improvement, are increasingly important in the evaluation of the impact of the addition of new markers to multivariate algorithms, and these are also discussed.

The genetic pleiotropy of musculoskeletal aging

Musculoskeletal aging is detrimental to multiple bodily functions and starts early, probably in the fourth decade of an individual's life. Sarcopenia is a health problem that is expected to only increase as a greater portion of the population lives longer; prevalence of the related musculoskeletal diseases is similarly expected to increase. Unraveling the biological and biomechanical associations and molecular mechanisms underlying these diseases represents a formidable challenge. There are two major problems making disentangling the biological complexity of musculoskeletal aging difficult: (a) it is a systemic, rather than "compartmental," problem, which should be approached accordingly, and (b) the aging per se is neither well defined nor reliably measurable. A unique challenge of studying any age-related condition is a need of distinguishing between the "norm" and "pathology," which are interwoven throughout the aging organism. We argue that detecting genes with pleiotropic functions in musculoskeletal aging is needed to provide insights into the potential biological mechanisms underlying inter-individual differences insusceptibility to the musculoskeletal diseases. However, exploring pleiotropic relationships among the system's components is challenging both methodologically and conceptually. We aimed to focus on genetic aspects of the cross-talk between muscle and its "neighboring" tissues and organs (tendon, bone, and cartilage), and to explore the role of genetics to find the new molecular links between skeletal muscle and other parts of the "musculoskeleton." Identification of significant genetic variants underlying the musculoskeletal system's aging is now possible more than ever due to the currently available advanced genomic technologies. In summary, a "holistic" genetic approach is needed to study the systems's normal functioning and the disease predisposition in order to improve musculoskeletal health.

A new active vitamin D3 analog, eldecalcitol, prevents the risk of osteoporotic fractures--a randomized, active comparator, double-blind study

BACKGROUND

Eldecalcitol is an analog of 1,25-dihydroxyvitamin D(3) that improves bone mineral density; however, the effect of eldecalcitol on the risk of fractures is unclear. The objective of this study is to examine whether eldecalcitol is superior to alfacalcidol in preventing osteoporotic fractures. This trial is registered with ClinicalTrials.gov, number NCT00144456.

METHODS AND RESULTS

This 3 year randomized, double-blind, active comparator, superiority trial tested the efficacy of daily oral 0.75 μg eldecalcitol versus 1.0 μg alfacalcidol for prevention of osteoporotic fractures. 1054 osteoporotic patients 46 to 92 years old were randomly assigned 1:1 to receive eldecalcitol (n=528) or alfacalcidol (n=526). Patients were stratified by study site and serum 25-hydroxyvitamin D level. Patients with low serum 25-hydroxyvitamin D levels (<50 nmol/L) were supplemented with 400 IU/day vitamin D(3). Primary end point was incident vertebral fractures. Secondary end points included any non-vertebral fractures and change in bone mineral density and bone turnover markers. Compared with the alfacalcidol group, the incidence of vertebral fractures was lower in eldecalcitol group after 36 months of treatment (13.4 vs. 17.5%; hazard ratio, 0.74; predefined 90% confidence interval [CI], 0.56-0.97). Eldecalcitol reduced turnover markers and increased bone mineral density more strongly than alfacalcidol. Eldecalcitol reduced the incidence of three major non-vertebral fractures, which was due to a marked reduction in wrist fractures by a post-hoc analysis (1.1 vs. 3.6%; hazard ratio, 0.29; 95% CI, 0.11-0.77). Among the adverse events, the incidence of increase in serum and urinary calcium was higher in the eldecalcitol group, without any difference in glomerular filtration rate between the two groups.

CONCLUSIONS

Eldecalcitol is more efficacious than alfacalcidol in preventing vertebral and wrist fractures in osteoporotic patients with vitamin D sufficiency, with a safety profile similar to alfacalcidol.

Molecular genetic studies of gene identification for sarcopenia

Sarcopenia, which is characterized by a progressive decrease of skeletal muscle mass and function with aging, is closely related to several common diseases (such as cardiovascular and airway diseases) and functional impairment/disability. Strong genetic determination has been reported for muscle mass and muscle strength, two most commonly recognized and studied risk phenotypes for sarcopenia, with heritability ranging from 30 to 85% for muscle strength and 45-90% for muscle mass. Sarcopenia has been the subject of increasing genetic research over the past decade. This review is designed to comprehensively summarize the most important and representative molecular genetic studies designed to identify genetic factors associated with sarcopenia. We have methodically reviewed whole-genome linkage studies in humans, quantitative trait loci mapping in animal models, candidate gene association studies, newly reported genome-wide association studies, DNA microarrays and microRNA studies of sarcopenia or related skeletal muscle phenotypes. The major results of each study are tabulated for easy comparison and reference. The findings of representative studies are discussed with respect to their influence on our present understanding of the genetics of sarcopenia. This is a comprehensive review of molecular genetic studies of gene identification for sarcopenia, and an overarching theme for this review is that the currently accumulating results are tentative and occasionally inconsistent and should be interpreted with caution pending further investigation. Consequently, this overview should enhance recognition of the need to validate/replicate the genetic variants underlying sarcopenia in large human cohorts and animal. We believe that further progress in understanding the genetic etiology of sarcopenia will provide valuable insights into important fundamental biological mechanisms underlying muscle physiology that will ultimately lead to improved ability to recognize individuals at risk for developing sarcopenia and our ability to treat this debilitating condition.

Effectiveness of simple balancing training program in elderly patients with history of frequent falls

OBJECTIVE

To study the effectiveness of simply-performed balancing exercises in fall prevention.

DESIGN

Pre- and post-trial.

SETTING

University hospital from January 2009 to May 2010.

PARTICIPANTS

Elderly with falls in the previous year.

INTERVENTION

Simple balancing exercise was performed at home every day and was recorded in the booklet.

MEASUREMENTS

New falling events and a battery of balancing abilities including the Timed Up and Go Test (TUGT), chair stand, functional reach, and Berg balance scale-short form were evaluated at baseline, 3-, 6-, 9-, and 12-month periods. Fear of falling and quality of life scores were assessed at baseline and 12-month periods.

RESULTS

146 subjects were recruited, 116 female (79.5%) with a mean age of 67.1 years. At the end of the study, 49% of participants had not fallen. All of the balancing abilities were compared between frequent and infrequent fallers and were significantly improved (P<0.001) except for functional reach in the frequent fall group. Most subjects (72%-79%) complied well with the exercise program. However, compliance had no effect on balancing abilities. About 36.4% of participants had adverse events from exercise, of which knee pain was the top ranked. The quality of life and the fall efficacy scores increased significantly at the end of the study. Factors affecting falling were compliance with exercise (adjusted odds ratio [OR]: 2.55, 95% confidence intervals [CI]: 1.04, 6.30) and a history of falling ≥3 times in the previous year (adjusted OR: 3.76, 95% CI: 1.18, 11.98).

CONCLUSION

Performing simply-designed balancing exercises, at least 3 days per week, can increase balancing abilities, and decrease fall rates in the elderly with a history of previous falls. However, strategies to encourage elderly compliance may prevent falling.

Low levels of 25-hydroxyvitamin D are associated with the occurrence of concomitant upper limb fractures in older women who sustain a fall-related fracture of the hip

OBJECTIVE

To investigate the association between serum levels of 25-hydroxyvitamin D and the occurrence of simultaneous fractures of the upper limb in older women who sustain a fall-related fracture of the hip.

STUDY DESIGN

Cross-sectional study.

MAIN OUTCOME MEASURES

We investigated 472 of 480 white women consecutively admitted to a rehabilitation hospital because of a fall-related hip fracture. Twenty-seven (5.7%) of the 472 women sustained a concomitant upper-limb fracture of either distal radius (20 women) or proximal humerus (seven women). We assessed serum levels of 25-hydroxyvitamin D 14.2 ± 4.1 (mean ± SD) days after surgical repair of the hip fracture in the 472 women by an immunoenzymatic assay.

RESULTS

Twenty-five-hydroxyvitamin D levels were significantly lower in the 27 women with concomitant fractures of both hip and upper limb than in the remaining 445 hip-fracture women: mean ± SD values were 6.5 ± 5.0 ng/ml and 11.7 ± 10.4 ng/ml respectively in the two groups (mean difference between groups 5.2 ng/ml: 95% CI 1.2-9.2; p=0.011). Low levels of 25-hydroxyvitamin D were significantly associated with concomitant fractures of the upper limb (p=0.017), after adjustment for eight potential confounders including age, height, weight, hip-fracture type, cognitive impairment, neurologic impairment, previous hip fracture, and previous upper-limb fracture.

CONCLUSIONS

Low levels of 25-hydroxyvitamin D were significantly associated with concomitant upper-limb fractures in our sample of older women with a fall-related fracture of the hip. Preventing vitamin D deficiency may lower the incidence of simultaneous fractures due to a singe fall in elderly women.

Pharmacogenetics of osteoporosis-related bone fractures: moving towards the harmonization and validation of polymorphism diagnostic tools

Osteoporosis is one of the most common skeletal chronic conditions in developed countries, hip fracture being one of its major healthcare outcomes. There is considerable variation in the implementation of current pharmacological treatment and prevention, despite consistent recommendations and guidelines. Many studies have reported conflicting findings of genetic associations with bone density and turnover that might predict fracture risk. Moreover, it is not clear whether genetic differences exist in relation to the morbidity and efficiency of the pharmacotherapy treatments. Clinical response, including beneficial and adverse events associated with osteoporosis treatments, is highly variable among individuals. In this context, the present article intends to summarize putative candidate genes and genome-wide association studies that have been related with BMD and fracture risk, and to draw the attention to the need for pharmacogenetic methodology that could be applicable in clinical translational research after an adequate validation process. This article mainly compiles analysis of important polymorphisms in osteoporosis documented previously, and it describes the simple molecular biology tools for routine genotype acquisition. Validation of methods for the easy, fast and accessible identification of SNPs is necessary for evolving pharmacogenetic diagnostic tools in order to contribute to the discovery of clinically relevant genetic variation with an impact on osteoporosis and its personalized treatment.

Vitamin D receptor genotypes are associated with bone mass in patients with Turner syndrome

BACKGROUND

Turner syndrome (TS) patients present low bone mineral density (BMD) and increased fracture risk, probably due to a genetic defect aggravated by hormonal deficiency.

AIM

To study the relationship between vitamin D receptor (VDR) gene polymorphisms and BMD and bone parameters in TS patients.

METHODS

DNA from 65 TS patients and 110 controls was amplified by PCR and digested with FokI, BsmI and ApaI restrictases. Lumbar and femoral BMD were determined by DEXA and serum intact parathyroid hormone, osteocalcin and beta-CrossLaps by electrochemiluminescence.

RESULTS

Genotype distribution within the ApaI site was different in both groups: genotype Aa was more abundant in TS (63.8% vs. 41.3%; p<0.01), whereas AA predominated in controls (33.9% vs. 15.5%; p<0.01). Patients carrying genotype bb (BsmI) or ff (FokI) had lower BMD than those with other genotypes (p<0.01 and p<0.05, respectively).

CONCLUSION

BsmI and FokI polymorphic sites of VDR could be genetic determinants of BMD in TS patients.

Evidence for pleiotropic factors in genetics of the musculoskeletal system

There are both theoretical and empirical underpinnings that provide evidence that the musculoskeletal system develops, functions, and ages as a whole. Thus, the risk of osteoporotic fracture can be viewed as a function of loading conditions and the ability of the bone to withstand the load. Both bone loss (osteoporosis) and muscle wasting (sarcopenia) are the two sides of the same coin, an involution of the musculoskeletal system. Skeletal loads are dominated by muscle action; both bone and muscle share environmental, endocrine and paracrine influences. Muscle also has an endocrine function by producing bioactive molecules, which can contribute to homeostatic regulation of both bone and muscle. It also becomes clear that bone and muscle share genetic determinants; therefore the consideration of pleiotropy is an important aspect in the study of the genetics of osteoporosis and sarcopenia. The aim of this review is to provide an additional evidence for existence of the tight genetic co-regulation of muscles and bones, starting early in development and still evident in aging. Recently, important papers were published, including those dealing with the cellular mechanisms and anatomic substrate of bone mechanosensitivity. Further evidence has emerged suggesting that the relationship between skeletal muscle and bone parameters extends beyond the general paradigm of bone responses to mechanical loading. We provide insights into several pathways and single genes, which apparently have a biologically plausible pleiotropic effect on both bones and muscles; the list is continuing to grow. Understanding the crosstalk between muscles and bones will translate into a conceptual framework aimed at studying the pleiotropic genetic relationships in the etiology of complex musculoskeletal disease. We believe that further progress in understanding the common genetic etiology of osteoporosis and sarcopenia will provide valuable insight into important biological underpinnings for both musculoskeletal conditions. This may translate into new approaches to reduce the burden of both conditions, which are prevalent in the elderly population.

Genetics of osteoporosis: accelerating pace in gene identification and validation

Osteoporosis is characterized by low bone mineral density and structural deterioration of bone tissue, leading to an increased risk of fractures. It is the most common metabolic bone disorder worldwide, affecting one in three women and one in eight men over the age of 50. In the past 15 years, a large number of genes have been reported as being associated with osteoporosis. However, only in the past 4 years we have witnessed an accelerated pace in identifying and validating osteoporosis susceptibility loci. This increase in pace is mostly due to large-scale association studies, meta-analyses, and genome-wide association studies of both single nucleotide polymorphisms and copy number variations. A comprehensive review of these developments revealed that, to date, at least 15 genes (VDR, ESR1, ESR2, LRP5, LRP4, SOST, GRP177, OPG, RANK, RANKL, COLIA1, SPP1, ITGA1, SP7, and SOX6) can be reasonably assigned as confirmed osteoporosis susceptibility genes, whereas, another >30 genes are promising candidate genes. Notably, confirmed and promising genes are clustered in three biological pathways, the estrogen endocrine pathway, the Wnt/beta-catenin signaling pathway, and the RANKL/RANK/OPG pathway. New biological pathways will certainly emerge when more osteoporosis genes are identified and validated. These genetic findings may provide new routes toward improved therapeutic and preventive interventions of this complex disease.