Genetics of osteoporosis: role of steroid hormone receptor gene polymorphisms

Biochemical markers and FokI and TaqI vitamin D receptor genes polymorphism in rheumatoid arthritis

BACKGROUND

Previous studies have reported the role of genes in different metabolic processes in the human body, and any variation in gene polymorphisms could lead to disturbances in these processes and different diseases.

OBJECTIVE

This study aimed to compare vitamin D receptor (VDR) FokI and TaqI genotypes in terms of parathyroid hormone (PTH) and some biomarkers of inflammation and susceptibility to rheumatoid arthritis (RA) disease.

METHODS

This study included 100 patients with rheumatoid arthritis (RA). Genotyping was performed by polymerase chain reaction (PCR) and examined by specific restriction enzymes using restriction fragment length polymorphism (RFLP). Serum intact PTH, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), and anti-cyclic citrullinated peptide antibodies (ACCPs) levels were measured.

RESULTS

An increased PTH level (> 65 pg/ml) was found in 8% of patients. No significant differences among FokI and TaqI vitamin D receptor genes polymorphism regarding positive and negative RF or ACCPs were found. A significant difference was found among FokI (p = 0.009) and none in TaqI genotypes regarding intact parathyroid hormone level categories. No significant correlation was found between the serum intact PTH level and ESR or CRP levels (P = 0.13 and 0.28, respectively). The parathyroid hormone level was not a good predictor for RF or ACCPs (P = 0.5 and 0.06, respectively).

CONCLUSION

The FokI gene may play a role in controlling PTH levels in patients with RA. There was no significant correlation found between the serum intact PTH level and RA severity according to ESR and CRP inflammatory biomarkers. There are no differences between VDR genes FokI and TaqI polymorphism in terms of RA susceptibility (for RF and ACCPs).

Drug Delivery and Therapy Strategies for Osteoporosis Intervention

With the advent of the aging society, osteoporosis (OP) risk increases yearly. Currently, the clinical usage of anti-OP drugs is challenged by recurrent side effects and poor patient compliance, regardless of oral, intravenous, or subcutaneous administration. Properly using a drug delivery system or formulation strategy can achieve targeted drug delivery to the bone, diminish side effects, improve bioavailability, and prolong the in vivo residence time, thus effectively curing osteoporosis. This review expounds on the pathogenesis of OP and the clinical medicaments used for OP intervention, proposes the design approach for anti-OP drug delivery, emphatically discusses emerging novel anti-OP drug delivery systems, and enumerates anti-OP preparations under clinical investigation. Our findings may contribute to engineering anti-OP drug delivery and OP-targeting therapy.

Evaluation of the Association of VDR rs2228570 Polymorphism with Elite Track and Field Athletes' Competitive Performance

The present study aimed to examine the vitamin D receptor (VDR), rs2228570 polymorphism, and its effect on elite athletes' performance. A total of 60 elite athletes (31 sprint/power and 29 endurance) and 20 control/ physically inactive, aged 18-35, voluntarily participated in the study. The International Association of Athletics Federations (IAAF) score scale was used to determine the performance levels of the athletes' personal best (PB). Whole exome sequencing (WES) was performed by the genomic DNA isolated from the peripheral blood of the participants. Sports type, sex, and competitive performance were chosen as the parameters to compare within and between the groups by linear regression models. The results showed no statistically significant difference between the CC, TC, and TT genotypes within and between the groups (p > 0.05). Additionally, our results underlined that there were no statistically significant differences for the association of rs2228570 polymorphism with PBs within the groups of the (p > 0.05) athletes. The genetic profile in the selected gene was similar in elite endurance, sprint athletes, and in controls, suggesting that rs2228570 polymorphism does not determine competitive performance in the analyzed athlete cohort.

Effects of sex, tobacco smoking, and alcohol consumption osteoporosis development: Evidence from Taiwan biobank participants

INTRODUCTION

Osteoporosis is major public health concern, but the long-term impacts of tobacco and alcohol consumption on its development are unclear. This study analyzed the relationship between tobacco and alcohol use and osteoporosis by using data from the Taiwan Biobank (TWB), established in 2012.

METHODS

Participants in TWB were included in our study, with a total of 18394 respondents included for analysis. To investigate the relationship between tobacco and alcohol use and osteoporosis, we surveyed their bone mineral density (BMD), consumption of tobacco and alcohol and other covariate data.

RESULTS

We found that participants in the tobacco smoking only group (OR=1.24; 95% CI: 1.08–1.42, p=0.003) and the group that both smoked and consumed alcohol (OR=1.39; 95% CI: 1.09–1.77, p=0.008) were more likely to develop osteoporosis than were participants who neither drank alcohol nor smoked. Menopause is strongly associated with osteoporosis in women, and we found that women who used alcohol or tobacco were not at a significantly higher risk than those in the reference group (tobacco only, OR=1.15; 95% CI: 0.86–1.53, p=0.345; both tobacco and alcohol, OR=0.61; 95% CI: 0.14–2.60, p=0.5040). However, men in these groups were at a significantly higher risk than the reference group (tobacco only, OR=1.26; 95% CI: 1.07–1.48, p=0.006; both tobacco and alcohol, OR=1.32; 95% CI: 1.03–1.70, p=0.030). Menopause was a significant risk factor for osteoporosis (OR=2.46; 95% CI: 1.77–3.41, p<0.001).

CONCLUSIONS

The influence of tobacco use on osteoporosis was significant, particularly in men, but the effects of alcohol consumption were equivocal in our study. The interactions between tobacco use, alcohol use, and menopausal status on osteoporosis should be considered in future studies.

Low serum 25-hydroxyvitamin D status in the pathogenesis of stress fractures in military personnel: An evidenced link to support injury risk management

Stress fractures are common amongst healthy military recruits and athletes. Reduced vitamin D availability, measured by serum 25-hydroxyvitamin D (25OHD) status, has been associated with stress fracture risk during the 32-week Royal Marines (RM) training programme. A gene-environment interaction study was undertaken to explore this relationship to inform specific injury risk mitigation strategies. Fifty-one males who developed a stress fracture during RM training (n = 9 in weeks 1-15; n = 42 in weeks 16-32) and 141 uninjured controls were genotyped for the vitamin D receptor (VDR) FokI polymorphism. Serum 25OHD was measured at the start, middle and end (weeks 1, 15 and 32) of training. Serum 25OHD concentration increased in controls between weeks 1-15 (61.8±29.1 to 72.6±28.8 nmol/L, p = 0.01). Recruits who fractured did not show this rise and had lower week-15 25OHD concentration (p = 0.01). Higher week-15 25OHD concentration was associated with reduced stress fracture risk (adjusted OR 0.55[0.32-0.96] per 1SD increase, p = 0.04): the greater the increase in 25OHD, the greater the protective effect (p = 0.01). The f-allele was over-represented in fracture cases compared with controls (p<0.05). Baseline 25OHD status interacted with VDR genotype: a higher level was associated with reduced fracture risk in f-allele carriers (adjusted OR 0.39[0.17-0.91], p = 0.01). Improved 25OHD status between weeks 1-15 had a greater protective effect in FF genotype individuals (adjusted OR 0.31[0.12-0.81] vs. 1.78[0.90-3.49], p<0.01). Stress fracture risk in RM recruits is impacted by the interaction of VDR genotype with vitamin D status. This further supports the role of low serum vitamin D concentrations in causing stress fractures, and hence prophylactic vitamin D supplementation as an injury risk mitigation strategy.

Association of Vitamin D Receptor Gene Polymorphisms with Hypercalcemia in Peritoneal Dialysis Patients

♦ Background

Some polymorphisms at the human vitamin D receptor (VDR) gene locus may influence calcium and bone metabolism. We investigated the roles of the BsmI and TaqI VDR gene polymorphisms in the development of hypercalcemia in Turkish peritoneal dialysis (PD) patients.

♦ Methods

We enrolled 132 PD patients treated with dialysate containing 1.75 mmol/L calcium. Serum levels of calcium, phosphorus, albumin, and intact parathyroid hormone (iPTH), and the cumulative doses of calcium-based phosphate binders and calcitriol were recorded every 3 months. The VDR BsmI and TaqI genotypes were determined by polymerase chain reaction.

♦ Results

When the patients were categorized according to these VDR genotypes, serum levels of phosphorus and iPTH and cumulative doses of calcium-based phosphate binders and calcitriol were similar across groups. The corrected serum calcium levels tended to increase in the patients with BsmI non- BB (Bb + bb) variants, but were significantly decreased in the BB variants (9.9 ± 0.7 vs 9.1 ± 0.6 mg/dL, p < 0.05). Hypercalcemia appeared in 21.2% of the patients during the follow-up period. The hypercalcemic patients had a significantly higher prevalence of the BsmI non- BB genotype than the normocalcemic patients (85.7% vs 59.6%, p < 0.007). On the contrary, the serum calcium levels were not affected by the TaqI VDR gene polymorphism ( p > 0.05).

♦ Conclusions

These findings suggest that the non- BB variants of the BsmI VDR gene polymorphism are associated with increased risk of developing hypercalcemia in PD patients.

Evaluation of the epidemiological and prognosis significance of ESR2 rs3020450 polymorphism in ovarian cancer

AIM

To investigate the correlation between the polymorphism of estrogen receptor β gene (ESR2) rs3020450 and cancer susceptibility, and explore the epidemiological significance and the effect of ESR2 expression levels on the prognosis of ovarian cancer.

METHODS

Based on meta-analysis the association between ESR2 rs3020450 polymorphism and cancer susceptibility was estimated and a case-control design was used to verify this result in ovarian cancer. The epidemiological effect of ESR2 rs3020450 polymorphism was assessed by attributable risk percentage (ARP) and population attributable risk percentage (PARP). Kaplan Meier plotters were used to evaluate overall survival (OS) and progression-free survival (PFS) in ovarian cancer patients and GEPIA for the differential expression of ESR2 levels in ovarian cancer and adjacent normal tissues.

RESULTS

The pooled analysis indicated no significant correlation between the ESR2 rs3020450 polymorphism and the cancer susceptibility. In the stratified analysis by cancer types, significantly decreased risk was found in ovarian cancer (AG vs GG: OR = 0.73, 95%CI: 0.53-0.97, P = 0.03). Unconditional logistic regression results of case-control study in ovarian cancer observed significant differences in all comparisons (AG vs GG: OR = 0.81, 95%CI: 0.62-0.98, P = 0.04; AA vs GG: OR = 0.63, 95%CI: 0.42-0.92, P = 0.01 and AG + AA vs GG: OR = 0.73, 95%CI: 0.53-0.96, P < 0.001). Based on meta-analysis and case-control pooled results, ARP and PARP were evaluated respectively in allele (21.95% and7.97%), heterozygote (36.99% and 12.11%) and dominant model (36.84% and 12.97%) of rs3020450 polymorphism in ovarian cancer. The expression levels of ESR2 in normal tissues was significantly higher than that in cancer tissues (OV, Median, 4.7:0.21), and significant correlations were observed between high ESR2 expression levels and long OS (HR = 0.80, 95%CI: 0.70-0.92, P = 0.002) and PFS (HR = 0.767, 95%Cl: 0.67-0.88, P < 0.001).

CONCLUSION

Our results indicated that ESR2 rs3020450 polymorphism was associated with ovarian cancer risk from epidemiological perspective, and high ESR2 expression levels was associated with long survival in patients with ovarian cancer.

DEVELOPMENT OF CLINICAL RISK ASSESSMENT TOOL FOR OSTEOPOROSIS (OSTEORISKAPP) USING A SYNDROMIC APPROACH

CONTEXT

DEXA is recommended for osteoporosis screening. However, the rate of screening with DEXA is very low. Therefore, methods that can be used more easily and cost effectively are needed.

OBJECTIVE

The objective of this study is to develop a clinical risk assessment tool of osteoporosis (OSTEORISKAPP) by using syndromic approach.

DESIGN

A methodological study was performed.

SUBJECTS AND METHODS

Three hundred and fifty-six participants who are above 50 years old are participants of study and take history and physical examination. Positive likelihood ratio (LR), pre and post test probability, is calculated. A logistic regression analysis and a ROC analysis are made with the model constructed by those criteria.

RESULTS

Eighteen different clinical risk indices are diagnosed. According to LR, 4 of these criteria are minimally effective, 11 of them are weakly effective and 3 of them are medium effective criteria According to results of logistic regression analysis, back pain, waist pain, and usage of cortisone for more than 3 months, vertebra tenderness in physical examination, having dorsal kyphosis and being obese are turned out to be statistically significant in 89.9% confidence interval. AUC is found to be 0.948 and diagnostic test is found to have perfect distinction ability.

CONCLUSION

Syndromic diagnostic criteria that will be used for osteoporosis screening of population and that is cost effective, no need to refer, practical, reliable and has tried to be developed.

Association of CYP1A1 and CYP1B1 polymorphisms with bone mineral density variations in postmenopausal Mexican-Mestizo women

Herein, we investigated potential associations between polymorphisms of genes related to estrogen metabolism and bone mineral density (BMD) in postmenopausal women. This was a cross-sectional study, in which two hundred and ninety postmenopausal Mexican-Mestizo women were studied. The BMD of the lumbar spine (LS), total hip (TH), and femoral neck (FN) was measured. The distribution of the genetic polymorphisms, including rs1799814 and rs1048943 at CYP1A1 as well as rs1056836 at CYP1B1, were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), single-stranded conformational polymorphism (SSCP), and DNA sequencing. Deviations from Hardy-Weinberg equilibrium (HWE) were tested, and linkage disequilibrium (LD) was calculated by direct correlation (r²). Moreover, haplotype analysis was performed. All polymorphisms were in HWE. The genotype and allele distributions of the three single nucleotide polymorphisms (SNPs) studied showed no significant differences. However, statistical significance was reached when constructing haplotypes. The CG haplotype in CYP1A1 was associated with variations in LS and FN BMD after adjustment for covariates (p = 0.021 and 0.045, respectively), but the association with TH BMD was not significant. These results suggested that the CG haplotype in CYP1A1 may play an important role in the mechanism of osteoporosis and may be useful as a genetic marker.

Association between the ACE gene I/D polymorphism and osteoporosis in a Turkish population

PURPOSE

The purpose of this study was to assess the relationship between osteoporosis and the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in a Turkish population.

METHODS

The study group consisted of 238 unrelated women with osteoporosis and 124 unrelated healthy female controls. All participants, patients and healthy controls, were of Turkish origin from the central region of Turkey. Genomic DNA was isolated from whole venous blood samples using a commercial DNA isolation kit. The ACE gene I/D polymorphism was analysed by polymerase chain reaction and gel electrophoresis.

RESULTS

Frequencies of the DD, ID and II genotypes in the patients were 44.5, 41.2 and 14.3 %, and in the controls they were 25.0, 51.6 and 23.4 %, respectively. A significant difference was observed between patients and controls according to genotype frequency (p=0.001). D and I allele frequencies of the I/D polymorphism were 65.1 and 34.9 % in the patient group and 50.8 and 49.2 % in the control group, respectively (p<0.001).

CONCLUSION

The ACE gene I/D polymorphism could be a genetic factor associated with osteoporosis.

Lifestyle and Genetic Predictors of Stiffness Index in Community-dwelling Elderly Korean Men and Women

PURPOSE

Differing lifestyle, nutritional, and genetic factors may lead to a differing stiffness index (SI) determined by quantitative ultrasound in elderly men and women. The purpose of this study was to determine SI and the gender-specific factors associated with low SI in a Korean elderly cohort.

METHODS

This was a cross-sectional descriptive study identifying the gender-specific factors related to SI in 252 men and women aged 65 years and greater from local senior centers in Seoul, Korea between January and February 2009.

RESULTS

The mean SI of elderly men was significantly higher than that of the women's. A multiple regression analysis reveals that age, nutritional status, and physical activity were predictive factors of lower SI in men, whereas age, alcohol consumption, educational level, and genetic polymorphism were predictive factors for elderly women.

CONCLUSIONS

Low SI was common in both elderly men and women. We found gender differences in factors linked to low SI. In multiple regression analysis, nutritional status and physical activity were more important factors in men, whereas alcohol consumption, educational level, and genetic polymorphism were significant factors predicting low SI in women. Gender-specific modifiable risk factors associated with low SI should be considered when developing osteoporosis prevention programs for the elderly.

Vitamin D receptor gene polymorphisms and the risk for female reproductive cancers: A meta-analysis

Vitamin D receptor (VDR) gene polymorphisms and the risks for various breast and ovarian cancers have been reported in many epidemiological studies. However, the associations between VDR gene polymorphisms and the risk for each type of cancer are unclear. The aim of this meta-analysis was to evaluate the associations between VDR gene polymorphisms and female reproductive cancers. A systematic review was performed with the PubMed Science Direct, Scopus, and Google Scholar databases up to April 2014 using the search terms "vitamin D receptor or VDR" and "variant or polymorphism or SNP" with terms for breast, ovarian, cervical, endometrial, uterine, and vaginal cancers. A meta-analysis with the pooled odds ratios and 95% confidence intervals was carried out to assess the associations between VDR polymorphisms (Cdx-2, FokI, BsmI, ApaI, and TaqI) and the risks for reproductive cancers under the heterozygous, homozygous, dominant, and recessive models with fixed or random effects models. Six ovarian cancer studies (13 individual studies involving 4107 cases and 6661 controls) and 29 breast cancer studies (38 individual studies involving 16,453 cases and 22,044 controls) were included in our meta-analysis. Our results indicate that the FokI polymorphism was related to increased risks for breast and ovarian cancers, whereas the BsmI polymorphism was associated with a decreased risk for developing these cancers. Our comprehensive meta-analysis indicated that the FokI and BsmI VDR gene polymorphisms may be significantly associated with gynecological cancers. We suggest monitoring VDR gene polymorphisms as potential biomarkers in patients with gynecological malignancy.

Association between single nucleotide polymorphisms of the estrogen receptor 1 and receptor activator of nuclear factor kappa B ligand genes and bone mineral density in postmenopausal Taiwanese

OBJECTIVE

To investigate the relationship between single nucleotide polymorphisms (SNPs) of the genes encoding the estrogen receptor 1 (ESR1) and the receptor activator of nuclear factor kappa B ligand (RANKL) and bone mineral density (BMD) in postmenopausal Taiwanese.

MATERIALS AND METHODS

Five ESR1 SNPs and three RANKL SNPs in 467 women were genotyped. Results of genotyping were correlated with BMD that had been adjusted for body mass index (BMI), age, and years after menopause.

RESULTS

Those with the ESR1 Crs1884054 allele were found to have a lower BMD at LS2-4/Lateral view (p = 0.005 and permutated p = 0.046), and those with the ESR1 haplotype Trs2234693-Ars922996 had a higher risk for low BMD also at LS2-4/Lat (OR = 1.8, 95% CI = 1.1-2.9). In addition, women without the RANKL haplotype Grs2148072-Crs2200287-Grs922996 had a higher risk for low BMD at LS1-4/AP (OR = 2.09, 95% CI = 1.21 ∼ 3.64). Stratification analyses revealed that those with ESR1 AArs1884054 and RANKL Ars2148072 (p = 0.032) or RANKL Trs2200287 (p = 0.007) had a lower BMD at LS1-4/AP.

CONCLUSION

Genotypes of these SNPs of ESR1 and RANKL may help us predict the osteoporosis risk in menopausal women.

Role of phytoestrogenic oils in alleviating osteoporosis associated with ovariectomy in rats

The objective of this study was to elucidate the effect of soybean oil (SbO) and sesame oil (SO) supplemented diets on bone biomarkers changes in OVX (ovariectomized) rats. The current data exhibited significant decrease in BMD (bone mineral density), accompanied with marked depletion in the level of Ca, P and Mg in both serum and bone of OVX rats. Also, serum estrogen, total protein, HDL-C (high density lipoprotein cholesterol), bone NO levels were decreased in OVX rats. However, a significant increase in the level of serum TL (total lipids), TC (total cholesterol), TG (triglycerides), LDL-C (low density lipoprotein cholesterol), VLDL-C (very low density lipoprotein cholesterol), urine minerals (Ca, P, Mg), as well as serum, bone and urine ALP (alkaline phosphatase) and ACP (acid phosphatase) activity were recorded in OVX rats. Further changes were also detected by the increased level of urine hydroxyproline, serum parathyroid hormone and osteocalcin, as well as urea and creatinine level in both serum and urine. On the other hand, when OVX rats were fed on SbO (soy bean oil) (15 % w/w) or SO (sesame oil) (10 % w/w) supplemented diets, the data recorded a significant improvement in all the above mentioned parameters. So, it can be concluded that consumption of SbO or SO supplemented diets might be considered as a functional food for retarding risks of osteoporosis associated with estrogen deficiency in OVX states.

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.

Association of vitamin D-related gene polymorphisms with manifestation of vitamin D deficiency in children

The prevalence of vitamin D deficiency, presenting as hypocalcemic seizures or rickets in children, is increasing worldwide due to insufficient vitamin D intake and lack of exposure to sunshine. However, considering that relatively few children with low 25-hydroxyvitamin D [25(OH)D] levels manifest symptoms, it is possible that genetic factors may predispose individuals to vitamin D deficiency. Recent twin studies have reported that the level of serum of 25(OH)D is influenced by genetic factors. In addition, genome-wide association studies and candidate gene studies have revealed that several vitamin D-related genes, including VDR, GC, NADSYN1, CYP2R1, CYP24A1, CYP27B1, and C10orf88 contribute to variations in serum 25(OH)D levels. To investigate whether genetic predisposition contributes to vitamin D deficiency, we analyzed polymorphisms in vitamin D-related genes in 30 Japanese patients with vitamin D deficiency presenting at less than 4 years of age, along with 66 controls. A χ(2) test showed that the genotype frequencies of BsmI polymorphism in VDR and rs10898191 in NADSYN1 were significantly different between the two groups. The allele frequencies of BsmI, ApaI, TaqI in VDR, rs10898191 in NADSYN1, and rs705117 in GC were also significantly different. In particular, the frequency of the BAtS haplotype in VDR was significantly increased in the patient group relative to controls (p = 0.0014; odds ratio, 5.61; 95% confidence interval 1.92 - 16.40). Although this is a small study, our findings suggest that VDR, NADSYN1, and GC polymorphisms may be linked to the manifestation of vitamin D deficiency in Japanese children.

Vitamin D receptor gene BsmI, FokI, ApaI, TaqI polymorphisms and bone mineral density in a group of Turkish type 1 diabetic patients

Previous studies have suggested an influence of vitamin D receptor alleles on bone metabolism and on susceptibility to type 1 diabetes mellitus in different ethnic populations. We aimed to investigate the distribution of vitamin D receptor (VDR) alleles in relation to biochemical bone turnover parameters and bone densitometry measurements in a group of Turkish type 1 diabetic patients. One hundred and seventeen patients (M/F 57/60, 27.6 ± 7.3 y duration of diabetes 8.1 ± 6.3 y) and 134 healthy controls (M/F 61/73, 26.2 ± 5.3 y) were included in the study. Bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry (DEXA). The vitamin D receptor gene (VDR) polymorphisms FokI, Bsm1, Apa1, and Taq1 were examined using a PCR-based restriction analysis. Serum levels of calcium, phosphor osteocalcin, intact parathyroid hormone, and C telopeptide were measured. Vitamin D receptor Bsm1 Fok1, Apa1, and Taq1 genotype distributions were not different between patient with diabetes and control groups. BMD was 0.77 ± 0.2 g/cm(2) vs. 0.97 ± 0.2 g/cm(2) (P = 0.0001) for the femur, 1.0 ± 0.1 g/cm(2) vs. 1.13 ± 0.1 g/cm(2) (P = 0.001) for type 1 diabetic patients and controls. Bone turnover markers were significantly lower in type 1 diabetic group. BMD measurements and bone metabolic markers were not different between the genotypes in either the patient with diabetes or the controls. The VDR gene polymorphisms, Bsm1, Fok 1, Apa1, and Taq1 showed no influence on bone metabolism in our group of type 1 diabetic patients.

Association of dental fluorosis with polymorphisms of estrogen receptor gene in Chinese children

Dental fluorosis (DF) is one of the important performances of endemic fluorosis. Some studies indicated that estrogen receptor (ESR) gene polymorphisms were associated with bone metabolism-related diseases. Therefore, it is possible that the variation in ESR genotypes will be associated with DF status. A case-control study was conducted among children aged 8-12 years with (n = 75) or without (n = 165) DF in China to investigate the relationship between ESR gene polymorphisms and DF. Gene polymorphisms were genotyped using the PCR-RFLP procedure. Children carrying R allele of ER RsaI had significantly increased risk of DF (Odds ratio (OR) = 1.821; 95% confidence interval (CI), 1.013-3.274) compared to children carrying r allele of ER RsaI in endemic fluorosis villages. For children with high-loaded fluoride status, carrying X allele of ESRα XbaI had a significantly decreased risk of DF (OR = 0.542; 95% CI, 0.314-0.936) compared to carrying x allele. This study provides the first evidence of an association between polymorphisms in the ESR gene with DF in high-fluoride-exposed populations. Further studies are needed to confirm the association.

The Role of Genetic Variation in Muscle Strength

Skeletal muscle is an important link to an individual’s health and quality of life. The primary clinical interest in skeletal muscle is muscle strength. Muscle strength is a complex trait, influenced by biological, morphological, psychological, and environmental factors. Muscle strength is highly variable among individuals and has a strong genetic component. Though several genetic variants have been associated with muscle strength, genes comprising this genetic component are generally unknown. Research examining associations between genetic variants and muscle strength suffers from scientific challenges such as lack of replication, population stratification, and complexity of defining muscle phenotypes. Additionally, non-scientific challenges such as privacy and protection of genetic information and the questionable value of direct-to-consumer genetic marketing exist. How these challenges will influence research examining genetics and muscle strength is uncertain. Findings from this research may lead to improved treatment for muscle-related disease as well as improved health and quality of life. This may be realized through the development of genetic profiles that clinicians can implement into personalized treatment plans. This review will summarize the current literature regarding genetic variation and muscle strength. The authors’ focus will be on the muscle strength response to resistance training. Additionally, the authors discuss challenges and implications of this research.

Evaluation of the effects of vitamin D receptor and estrogen receptor 1 gene polymorphisms on bone mineral density in postmenopausal women

The aim of this study is to evaluate the effects of estrogen receptor 1 (ESR1) and vitamin D receptor (VDR) gene polymorphisms on bone mineral density (BMD) in a group of previously untreated osteoporotic women. Effects of demographic, environmental, and hormonal factors were also evaluated in this context. Fifty women who did not have a prior diagnosis or treatment of osteoporosis were compared with 50 nonosteoporotic postmenopausal women. Demographic and morphometric characteristics, medical history, dietary habits, exercise history, and sunlight exposure were recorded. The diagnosis of osteoporosis was made with regard to BMD measurements with DEXA. Blood samples were obtained for serum biochemistry, bone turnover markers, and VDR and ESR1 gene polymorphism analysis. Polymorphic sites of VDR and ESR1 genes were amplified by polymerase chain reaction and examined using restriction fragment length polymorphism. Bb genotype was significantly higher in the osteoporotic group when compared to controls (p=0.022). Each 1 U decrease in the body mass index (BMI) increased the risk of osteoporosis by 8% independent of the genotype. We could not observe a significant effect of ESR1 polymorphism on BMD or osteoporosis risk. The interaction of ApaI and BsmI genotypes were found to be significant (p=0.041) and the AaBb genotype, when corrected for BMI, was shown to increase the risk of osteoporosis five times (p=0.005). However, the results demonstrated insignificant p values when correction for multiple testing was performed with the Bonferroni method in the logistic regression model. A predominance of Bb genotype of the VDR gene was evident in this group of postmenopausal Turkish women. Moreover, the combined genotype AaBb conferred a five times increased risk for osteoporosis when corrected for clinical variables.

Bone fractures after menopause

BACKGROUND

Every year 30% of individuals above age 65 fall, and falls are the principal cause of bone fractures. To reduce fracture incidence requires both prevention of falls and maintenance of bone strength.

METHODS

PubMed searches were performed, for studies of the epidemiology of fractures, bone physiology, endocrine effects, osteoporosis measurement, genetics, prevention and effectiveness. Topic summaries were presented to the Workshop Group and omissions or disagreements were resolved by discussion.

RESULTS

Ageing reduces bone strength in post-menopausal women because estrogen deficiency causes accelerated bone resorption. Bone mineral density (BMD) decreased more than 2.5 standard deviation below the mean of healthy young adults defines osteoporosis, a condition associated with an increased risk of fractures. Risk factors such as age and previous fracture are combined with BMD for a more accurate prediction of fracture risk. The most widely used assessment tool is FRAX™ which combines clinical risk factors and femoral neck BMD. General preventive measures include physical exercise to reduce the risk of falling and vitamin D to facilitate calcium absorption. Pharmacological interventions consist mainly in the administration of inhibitors of bone resorption. Randomized controlled trials show treatment improves BMD, and may reduce the relative fracture risk by about 50% for vertebral, 20-25% for non-vertebral and up to 40% for hip fractures although the absolute risk reductions are much lower.

CONCLUSIONS

Although diagnosis of osteoporosis is an important step, the threshold for treatment to prevent fractures depends on additional clinical risk factors. None of the presently available treatment options provide complete fracture prevention.

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.

Association between vitamin D receptor gene polymorphisms and severe chronic periodontitis in a Chinese population

BACKGROUND

Chronic periodontitis (CP) exhibits inflammation and alveolar bone loss, and severe forms of periodontitis are suggested to have a genetic basis. Vitamin D receptor (VDR) regulates bone metabolism and inflammation-related genes, and single nucleotide polymorphisms (SNPs) in the VDR gene may affect the functional activity of the VDR protein in CP. Therefore, the aim of this study was to investigate the association between VDR SNPs and severe CP in a Chinese population.

METHODS

DNA was obtained from 107 patients with severe CP and 121 control subjects. The BsmI, TaqI, ApaI, and FokI SNPs of VDR genes were investigated by restriction fragment length polymorphism of polymerase chain reaction (PCR) products. The digested PCR products were electrophoresed on an 8% polyacrylamide gel and developed by the DNA silver staining method.

RESULTS

The distribution of VDR TaqI genotypes and alleles between the two groups was significantly different (P = 0.019 and P = 0.039, respectively). The TT genotype and T allele seemed to increase the susceptibility of severe CP (odds ratio, 2.75; 95% confidence interval [CI]: 1.17 to 6.47; odds ratio, 2.28, 95% CI: 1.02 to 5.06, respectively) in Chinese populations. There was no significant difference in the genotype distribution or the allele frequencies of VDR BsmI, ApaI, or FokI between the two groups.

CONCLUSION

TaqI SNP of VDR gene might be associated with severe CP in Chinese patients.

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.

Vitamin D receptor gene polymorphism and osteoporosis in the Turkish population

Osteoporosis is one of the most important medical problems facing the aging population. It is defined as a decrease in the bone mass leading to an unacceptably high risk of fractures. Osteoporosis is a multifactorial disease. It is well established that genetic factors are involved in the pathogenesis of osteoporosis. Polymorphism of the vitamin D receptor (VDR) gene has been reported to play a major role in variations for genetic regulation of bone mass. Its role within various ethnic populations is not clear. The purpose of this project was to determine the frequencies of VDR genotypes in Turkey. Three polymorphisms of the VDR gene were analyzed using the polymerase chain reaction-restriction fragment length polymorphism technique. The sample for our study was comprised of postmenopausal women in Turkey, 100 of whom were diagnosed with osteoporosis. They were compared with 146 healthy controls. BsmI genotype frequencies in Turks resemble Caucasians rather than Asians, and Taq genotype frequencies in Turks neither resemble Caucasians nor Asians. The genotype frequencies of VDR were not statistically different between patients with osteoporosis and the control group. Among VDR haplotypes, bbAATT and bbTtAa are more frequent in the osteoporosis group than the control group.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

Vitamin D receptor gene polymorphisms predict acquired resistance to clodronate treatment in patients with Paget's disease of bone

Bisphosphonates are first-choice drugs for treatment of Paget's disease of bone (PDB); nevertheless, acquired resistance to bisphosphonate therapy has been described in PDB patients. The 1,25(OH)(2)D(3)/vitamin D receptor (VDR) system influences the effectiveness of antiresorptive treatments in metabolic bone disorders. This study evaluated the relationship between acquired resistance to clodronate treatment and BsmI, TaqI, and FokI VDR polymorphisms in Caucasian patients with polyostotic PDB (n = 84). We also evaluated the influence of mutations in exons 7 and 8 of the sequestosome 1 (SQSTM1) gene on the occurrence of this phenomenon. All patients were treated from diagnosis for several cycles with intravenous clodronate infusion (1500 mg/cycle). Acquired resistance to clodronate treatment was defined as the failure of total alkaline phosphatase serum levels to be suppressed to at least 50% of the patient's previous highest levels during a subsequent treatment course with the same compound, which produced a >50% response after the first exposure. During an observation period of 10.6 +/- 2.7 years, 31 PDB patients (36.9%) showed acquired resistance to clodronate. It was observed that the bb and TT VDR genotypes as well as a lower persistence of the biochemical response to the first treatment course were significantly and independently associated with the risk of developing resistance to clodronate treatment. SQSTM1 gene mutations, considered altogether, did not influence the occurrence of this phenomenon. Our results indicate that 3'VDR allelic variants and duration of biochemical response to the first treatment course are independent predictors of acquired resistance to clodronate treatment in patients with polyostotic PDB.

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.

An ENU-induced mutation in the Ankrd11 gene results in an osteopenia-like phenotype in the mouse mutant Yoda

The mechanisms that regulate bone mass are important in a variety of complex diseases such as osteopenia and osteoporosis. Regulation of bone mass is a polygenic trait and is also influenced by various environmental and lifestyle factors, making analysis of the genetic basis difficult. As an effort toward identifying novel genes involved in regulation of bone mass, N-ethyl-N-nitrosourea (ENU) mutagenesis in mice has been utilized. Here we describe a mouse mutant termed Yoda that was identified in an ENU mutagenesis screen for dominantly acting mutations. Mice heterozygous for the Yoda mutation exhibit craniofacial abnormalities: shortened snouts, wider skulls, and deformed nasal bones, underlined by altered morphology of frontonasal sutures and failure of interfrontal suture to close. A major feature of the mutant is reduced bone mineral density. Homozygosity for the mutation results in embryonic lethality. Positional cloning of the locus identified a missense mutation in a highly conserved region of the ankyrin repeat domain 11 gene (Ankrd11). This gene has not been previously associated with bone metabolism and, thus, identifies a novel genetic regulator of bone homeostasis.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

Long-term effects of progestins on bone quality and fractures

The effects of progestins on the quality of bone and their influence on the risk of fractures are reviewed. Data discussed are based on experimental studies in vivo that generally lasted for longer than one year. Information is given on the background of osteoporosis and on several means of inducing changes in bone quality. In young women who start using oral contraceptives based on progestins alone shortly after pubertal development, a significant decrease in bone quality has been documented. World Health Organization experts have concluded that this is not a real argument for restrictions on the use of these contraceptives. In postmenopausal women, no evidence has been found for a bone-protective or an estrogen-antagonistic effect of progestins. A wide range of estrogens have been used that have shown positive effects on bone, which are not antagonized by progestins. The therapeutic use of high-dose megestrol acetate may result in marked negative effects on bone, leading to severe osteoporosis, possibly due to the inherent glucocorticoid activity of this progestin. Other pharmacotherapeutic agents that can be used in postmenopausal therapy, and that clearly have beneficial effects on bone, are discussed.

Cross-sex pattern of bone mineral density in early onset gender identity disorder

Hormonally controlled differences in bone mineral density (BMD) between males and females are well studied. The effects of cross-sex hormones on bone metabolism in patients with early onset gender identity disorder (EO-GID), however, are unclear. We examined BMD, total body fat (TBF) and total lean body mass (TLBM) in patients prior to initiation of sex hormone treatment and during treatment at months 3 and 12. The study included 33 EO-GID patients who were approved for sex reassignment and a control group of 122 healthy Norwegians (males, n=77; females, n=45). Male patients (n=12) received an oral dose of 50 mug ethinylestradiol daily for the first 3 months and 100 mug daily thereafter. Female patients (n=21) received 250 mg testosterone enantate intramuscularly every third week. BMD, TBF and TLBM were estimated using dual energy X-ray absorptiometry (DXA). In male patients, the DXA measurements except TBF were significantly lower compared to their same-sex control group at baseline and did not change during treatment. In female patients, the DXA measurements were slightly higher than in same-sex controls at baseline and also remained unchanged during treatment. In conclusion, this study reports that body composition and bone density of EO-GID patients show less pronounced sex differences compared to controls and that bone density was unaffected by cross-sex hormone treatment.

Polymorphisms in the vitamin D receptor gene are associated with muscle strength in men and women

INTRODUCTION

Vitamin D receptor (VDR) polymorphisms have been associated with fracture risk and muscle strength, although evidence for the latter is limited and conflicting.

METHODS

BsmI, TaqI and FokI VDR polymorphisms were genotyped in 253 men (54.9 +/- 10.2 yr) and 240 women (41.5 +/- 13.2 yr). Haplotypes were constructed for BsmI and TaqI. Handgrip, isometric (at 60 degrees , 120 degrees and 180 degrees joint angle) and eccentric torques (60 degrees /s) of knee extension and flexion were analysed using AN(C)OVA. Torque-velocity curves were constructed for concentric torques at 60 degrees /s, 180 degrees /s and 240 degrees /s and analysed using multivariate AN(C)OVA. Age, height and fat-free mass were included as covariates.

RESULTS

Quadriceps isometric and concentric strength were higher in female f/f homozygotes compared to F allele carriers. Adjustment for confounding factors rendered results for quadriceps isometric strength at 120 degrees non-significant. No significant association was found with BsmI-TaqI haplotype in women. In contrast, male Bt/Bt homozygotes had higher isometric quadriceps strength at 150 degrees and higher concentric quadriceps strength than bT allele carriers without and with adjustment for confounding factors. No association was observed with FokI in men. In both genders, no interaction effect was present between BsmI-TaqI haplotype and FokI.

CONCLUSIONS

Different VDR gene polymorphisms are associated with quadriceps strength in men and women.

Genetics and pharmacogenetics of estrogen response

Estrogens are a steroid hormone group distributed widely in animals and human beings. Estrogens diffuse across cell phospholipidic membranes and interact with estrogen receptors. Their highest concentration is found in target tissues with reproductive function (breast, ovary, vagina and uterus). High estrogen levels are usually associated with tumor onset and progression, while loss of estrogen or its receptor(s) contributes to development and/or progression of various diseases (osteoporosis, neurodegenerative disease and cardiovascular disease). Despite the numerous efforts to highlight estrogen's mechanism of action, recent discoveries showed an unexpected degree of complexity of estrogenic response.

Effects of the interaction between lean tissue mass and estrogen receptor alpha gene polymorphism on bone mineral density in middle-aged and elderly Japanese

Because both genetic and environmental factors influence bone mass, it is important to examine the effect of gene-environment interactions on bone mineral density (BMD) for the prevention of osteoporosis at an individual level. Estrogen receptor alpha (ER alpha) plays an important role in increasing BMD via mechanical strain and muscle mass is a reflection of the forces the muscle applies to the bone. The aim of this study is to investigate the effect of the interaction between lean tissue mass (LTM) and the ER alpha polymorphisms T-->C (PvuII) [dbSNP: rs2234693] and A-->G (XbaI) [dbSNP: rs9340799] on BMD in middle-aged and elderly individuals. Subjects were 2209 community-dwelling Japanese men and women, ages 40 to 79 years. ER alpha polymorphisms in the first intron, T-->C and A-->G were identified and lumbar spine and femoral neck BMD and LTM were measured by dual-energy X-ray absorptiometry. Both T-->C and A-->G polymorphisms were divided into two genotype groups (TT vs. TC/CC; AA vs. AG/GG). In postmenopausal women, the effect of LTM on femoral neck BMD was significantly larger for those with the TC/CC genotype than for those with the TT genotype for the T-->C polymorphism, and larger for those with the AG/GG genotype than for those with the AA genotype for the A-->G polymorphism. This gene-LTM interaction was observed at the femoral neck, but not at the lumbar spine. For men and premenopausal women, no gene-LTM interaction was found. In conclusion, there was an interaction between LTM and the ER alpha T-->C and A-->G polymorphisms with respect to their effect on femoral neck BMD in postmenopausal women and those with the TC/CC and AG/GG genotypes had larger effects of LTM than those with TT and AA genotypes.

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.

The vitamin D receptor gene FokI polymorphism: functional impact on the immune system

1Alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) has important effects on the growth and function of multiple cell types. These pleiotropic effects of 1,25(OH)2D3 are mediated through binding to the vitamin D receptor (VDR). Several polymorphisms of the human VDR gene have been identified, with the FokI polymorphism resulting in VDR proteins with different structures, a long f-VDR or a shorter F-VDR. The aim of this study was to investigate the functional consequences of the FokI polymorphism in immune cells. In transfection experiments, the presence of the shorter F-VDR resulted in higher NF-kappaB- and NFAT-driven transcription as well as higher IL-12p40 promoter-driven transcription. Marginal differences were observed for AP-1-driven transcription, and no differential effects were observed for transactivation of a classical vitamin D-responsive element. Concordantly, in human monocytes and dendritic cells with a homozygous short FF VDR genotype, expression of IL-12 (mRNA and protein) was higher than in cells with a long ff VDR genotype. Additionally, lymphocytes with a short FF VDR genotype proliferated more strongly in response to phytohemagglutinin. Together, these data provide the first evidence that the VDR FokI polymorphism affects immune cell behavior, with a more active immune system for the short F-VDR, thus possibly playing a role in immune-mediated diseases.

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.

FokI polymorphism of the vitamin D receptor gene correlates with parameters of bone mass and turnover in a female population of the Italian island of Lampedusa

One of the most promising genetic approaches to dissecting a multifactorial disease is represented by genetically isolated population studies. We studied a genetic marker in a cohort of women living on the Mediterranean island of Lampedusa, a geographically isolated population. Lampedusa, located between the African coast and Sicily, consists of a young genetic isolate (<20 generations) with an exponential growth in the last generations. We analyzed the association between the FokI vitamin D receptor (VDR) gene polymorphism, previously proposed as a predictor of bone mass, with parameters of bone mass and turnover in a cohort of pre- and postmenopausal women living on Lampedusa. In 424 women (277 postmenopausal and 147 premenopausal), allelic frequencies were 49% for the F allele and 51% for the f allele. Using analysis of covariance, we found that subjects with ff genotype exhibited a significantly (P < 0.001) lower lumbar spine bone mass, by dual-energy X-ray absorptiometry, and lower values of bone ultrasonographic parameters (speed of sound and broadband ultrasound attenuation) relative to those with Ff and FF genotypes. Conversely, osteocalcin and serum cross-laps were significantly higher in ff and Ff compared to FF genotype. Our data suggest that FokI VDR polymorphism may contribute to the determination of bone mass and turnover in both pre- and postmenopausal women in this geographically isolated population.

The short vitamin D receptor is associated with increased risk for generalized aggressive periodontitis

BACKGROUND

Generalized aggressive periodontitis (GAP) exhibits severe inflammation and alveolar bone loss. Vitamin D receptor (VDR) regulates both bone metabolism and inflammation-related genes, and its polymorphisms and haplotypes may affect the functional activity of the VDR protein in GAP.

OBJECTIVE

We analysed the genetic effect of VDR start codon, intron, and exon polymorphisms, and their haplotypes on the development of GAP.

MATERIALS AND METHODS

The VDR start codon 27823C > T (rs2228570, FokI), intron 8 60890G > A (rs154410, BsmI), and exon 9 61968T > C (rs731236, TaqI) polymorphisms were determined by using the polymerase chain reaction-restriction fragment length polymorphism analysis among 93 GAP patients and 143 healthy controls.

RESULTS

The VDR start codon 27823*C/*C genotype was associated with an increased risk for GAP [odds ratio (OR) = 1.83, p = 0.028], but the intron 8 60880G > A and exon 9 61968T > C polymorphisms were not associated with GAP. The VDR haplotype homozygote ht1(C-G-T) carrying 27823*C allele was associated with a 1.8-fold increased risk of GAP (OR = 1.84, p = 0.030).

CONCLUSION

These results demonstrate that the short VDR (27823*C/*C) protein may influence GAP susceptibility.

Decreased responsiveness of naturally occurring mutants of human estrogen receptor alpha to estrogens and antiestrogens

Estrogen receptor alpha (ERalpha) is a ligand-inducible transcription factor that mediates the biological effects of estrogens and antiestrogens. Many point mutations in the human ERalpha gene have been reported to be associated with breast cancer, endometrial cancer, and psychiatric diseases. However, functional analyses for most mutants with amino acid changes are still lacking. In the present study, to investigate the effects of point mutations on the function, gel-shift assays and luciferase assays were performed for eight kinds of mutated ERalpha proteins, including a single nucleotide change of C207G (N69K), G478T (G160C), T887C (L296P), A908G (K303R), C926T (S309F), A1058T (E353V), A1186G (M396V), and G1231deletion (411fsX7). The mutated ERalpha expression plasmids were constructed by site-directed mutagenesis. With gel-shift assays using in vitro translated ERalpha proteins, binding to the consensus estrogen response element (ERE) was observed for the mutated ERalpha proteins except ERalpha (G160C) and ERalpha (411fsX7), the binding of which was comparable with that of the wild type. Western blot analyses showed that ERalpha (G160C) could not be efficiently translated with the in vitro transcription/translation system and that ERalpha (411fsX7) produced a truncated protein. To investigate the transactivation potency, wild-type or mutated ERalpha expression plasmids were co-transfected with pGL3-3EREc38 reporter plasmid into human breast adenocarcinoma MDA-MB-435 cells. The concentration-response curves (10pM-100nM E2) of the mutant ERalpha proteins except ERalpha (E353V) and ERalpha (411fsX7) were similar to that of wild-type ERalpha. However, at a low level of E2 (100pM), the mutants ERalpha (N69K), ERalpha (L296P), ERalpha (S309F), and ERalpha (M396V) showed a significant decrease of transactivation compared with that of the wild-type ERalpha. The mutants ERalpha (E353V) and ERalpha (411fsX7) did not show responsiveness to E2 and antiestrogens, 4-hydroxytamoxifen (4OHT) and ICI 182,780. The mutant ERalpha (S309F) showed decreased responsiveness for the antiestrogenicity of 4OHT. In conclusion, we found that some of the naturally occurring human ERalpha mutants with amino acid changes may have an altered responsiveness to estrogen and antiestrogens.

Gene polymorphisms involved in the regulation of bone quality

Osteoporotic fractures in subjects at advanced age constitute a tremendous and growing problem. Established lifestyle risk factors can explain only a modest proportion of the liability to osteoporotic fractures. Bone mineral density (BMD) is considered the best established risk factor for osteoporotic fractures. The importance of genetic factors in the quality of bone is substantial, but no consensus exists yet on the genes that are involved. However, concomitant diseases, balance disorders and lifestyle habits are more important for fractures in elderly subjects. The abundance of common sequence variations, so-called polymorphisms, in the human genome and their high frequency in the population have made them targets to explain variation in the risk. Some genes have been identified that appear to be involved in the regulation of bone mass and in the pathogenesis of osteoporosis. Among these are those coding for the two estrogen receptors (ERalpha and ERbeta), the androgen receptor (AR) and the vitamin D receptor (VDR). In addition, enzymes involved in the biogenesis of estrone and estradiol have attracted attention as well as polymorphisms in the regulatory region of the type I collagen gene, COLIA1, affecting the binding site for the transcription factor Specificity protein 1 (Sp1). Although evidence suggests that the quality of bone is determined to a large extent by genetic factors, research so far has not been able to unequivocally identify genes involved in this matter. Over the last years a large number of studies have pointed to the variability in many genes and their relation with BMD, bone-related symptoms or specific therapies. The findings emphasize the complexity of the genetics of bone mass and bone loss.

Vitamin D receptor genotype and risk of osteoporotic hip fracture in elderly women of Utah: an effect modified by parity

INTRODUCTION

The associations between vitamin D receptor (VDR) Bsm I and Fok I genotypes, parity, and risk of osteoporotic hip fracture were evaluated in a statewide population-based case-control study in Utah.

METHODS

Women age 50-89 years with hip fracture (n=882) were ascertained via surveillance of 18 Utah hospitals from 1997 to 2001. Age-matched controls were randomly selected (n=897). Participants were interviewed in their homes, and blood samples were collected for genotyping.

RESULTS

In logistic regression analyses that controlled for multiple confounders, Bsm I VDR genotype but not Fok I genotype was associated with risk of osteoporotic hip fracture (OR bb vs. BB genotype: 0.68; 95% CI: 0.50, 0.95). In similar analyses, no overall association was observed between parity status and risk of osteoporotic hip fracture. However, the effect of VDR genotype was modified by parity status. Among nulliparous women (n=140), Bsm I genotype was not associated with risk of hip fracture (OR bb vs. BB: 0.82; 95% CI: 0.28, 2.4); among primiparous women (n=133), bb genotype was associated with increased risk of hip fracture (OR bb vs. BB: 3.30; 95% CI: 0.96, 11.29); among multiparous women (n=1,400), bb genotype was associated with decreased risk of hip fracture (OR bb vs. BB: 0.59; 95% CI: 0.42, 0.84).

CONCLUSION

VDR Bsm I genotype was associated with risk of hip fracture in Utah women, and this effect was modified by parity status. Hormonal or lifestyle factors related to parity may underlie this interaction.

Vitamin D and estrogen receptor-alpha genotype and indices of bone mass and bone turnover in Danish girls

Peak bone mass is a major determinant of osteoporosis risk in later life. It is under strong genetic control; however, little is known about the identity of the genes involved. In the present study, we investigated the relationship between polymorphisms in the genes encoding the vitamin D receptor (VDR) (FokI, TaqI) and estrogen receptor-alpha (ERalpha) (PvuII, XbaI), and bone mineral density (BMD), bone mineral content (BMC), and markers of bone turnover in 224 Danish girls aged 11-12 years. BMD and BMC were measured by dual-energy X-ray absorptiometry. Serum osteocalcin, 25(OH)D, and parathyroid hormone (PTH) were measured by ELISA assays and urinary pyridinium cross-links by HPLC. Physical activity, dietary calcium, and Tanner stage were assessed by questionnaire. In general, there were no significant differences in anthropometrical variables, physical activity, dietary calcium, serum 25(OH)D, or PTH among genotype groups. BMD or BMC of lumbar spine or whole body (adjusted for body and bone size and pubertal status) were not associated with VDR or ERalpha genotypes or the combination of these genotypes. This lack of association remained even after adjustment for dietary and environmental factors. VDR genotypes had no effect on bone turnover markers. XX and PP ERalpha genotypes were associated (P < 0.05) with reduced levels of urinary pyridinium cross-links, whereas serum osteocalcin was similar among genotypes. These findings suggest that the rate of bone resorption was influenced by ERalpha genotypes, even though these biochemical differences were not evident in bone mass indices.