Vitamin D receptor genotypes in primary hyperparathyroidism

Accommodation-based interventions for individuals experiencing, or at risk of experiencing, homelessness

Background

Globally, almost 1.6 billion individuals lack adequate housing. Many accommodation-based approaches have evolved across the globe to incorporate additional support and services beyond delivery of housing.

Objectives

This review examines the effectiveness of accommodation-based approaches on outcomes including housing stability, health, employment, crime, wellbeing, and cost for individuals experiencing or at risk of experiencing homelessness.

Search Methods

The systematic review is based on evidence already identified in two existing EGMs commissioned by the Centre for Homelessness Impact (CHI) and built by White et al. The maps were constructed using a comprehensive three stage search and mapping process. Stage one mapped included studies in an existing systematic review on homelessness, stage two was an extensive search of 17 academic databases, three EGM databases, and eight systematic review databases. Finally stage three included web searches for grey literature, scanning reference lists of included studies and consultation with experts to identify additional literature. We identified 223 unique studies across 551 articles from the effectiveness map on 12th April 2019.

Selection Criteria

We include research on all individuals currently experiencing, or at risk of experiencing homelessness irrespective of age or gender, in high-income countries. The Network Meta-Analysis (NMA) contains all study designs where a comparison group was used. This includes randomised controlled trials (RCTs), quasi-experimental designs, matched comparisons and other study designs that attempt to isolate the impact of the intervention on homelessness. The NMA primarily addresses how interventions can reduce homelessness and increase housing stability for those individuals experiencing, or at risk of experiencing, homelessness. Additional outcomes are examined and narratively described. These include: access to mainstream healthcare; crime and justice; employment and income; capabilities and wellbeing; and cost of intervention. These outcomes reflect the domains used in the EGM, with the addition of cost.

Data Collection and Analysis

Due to the diverse nature of the literature on accommodation-based approaches, the way in which the approaches are implemented in practice, and the disordered descriptions of the categories, the review team created a novel typology to allow meaningful categorisations for functional and useful comparison between the various intervention types. Once these eligible categories were identified, we undertook dual data extraction, where two authors completed data extraction and risk of bias (ROB) assessments independently for each study. NMA was conducted across outcomes related to housing stability and health.Qualitative data from process evaluations is included using a "Best Fit" Framework synthesis. The purpose of this synthesis is to complement the quantitative evidence and provide a better understanding of what factors influenced programme effectiveness. All included Qualitative data followed the initial framework provided by the five main analytical categories of factors of influence (reflected in the EGM), namely: contextual factors, policy makers/funders, programme administrators/managers/implementing agencies, staff/case workers and recipients of the programme.

Main Results

There was a total of 13,128 people included in the review, across 51 reports of 28 studies. Most of the included studies were carried out in the United States of America (25/28), with other locations including Canada and the UK. Sixteen studies were RCTs (57%) and 12 were nonrandomised (quasi-experimental) designs (43%). Assessment of methodological quality and potential for bias was conducted using the second version of the Cochrane Risk of Bias tool for Randomised controlled trials. Nonrandomised studies were coded using the ROBINS- I tool. Out of the 28 studies, three had sufficiently low ROB (11%), 11 (39%) had moderate ROB, and five (18%) presented serious problems with ROB, and nine (32%) demonstrated high, critical problems with their methodology. A NMA on housing stability outcomes demonstrates that interventions offering the highest levels of support alongside unconditional accommodation (High/Unconditional) were more effective in improving housing stability compared to basic support alongside unconditional housing (Basic/Unconditional) (ES=1.10, 95% confidence interval [CI] [0.39, 1.82]), and in comparison to a no-intervention control group (ES=0.62, 95% CI [0.19, 1.06]). A second NMA on health outcomes demonstrates that interventions categorised as offering Moderate/Conditional (ES= 0.36, 95% CI [0.03, 0.69]) and High/Unconditional (ES = 0.22, 95% CI [0.01, 0.43]) support were effective in improving health outcomes compared to no intervention. These effects were smaller than those observed for housing stability. The quality of the evidence was relatively low but varied across the 28 included studies. Depending on the context, finding accommodation for those who need it can be hindered by supply and affordability in the market. The social welfare approach in each jurisdiction can impact heavily on support available and can influence some of the prejudice and stigma surrounding homelessness. The evaluations emphasised the need for collaboration and a shared commitment between policymakers, funders and practitioners which creates community and buy in across sectors and agencies. However, co-ordinating this is difficult and requires sustainability to work. For those implementing programmes, it was important to invest time in developing a culture together to build trust and solid relationships. Additionally, identifying sufficient resources and appropriate referral routes allows for better implementation planning. Involving staff and case workers in creating processes helps drive enthusiasm and energy for the service. Time should be allocated for staff to develop key skills and communicate engage effectively with service users. Finally, staff need time to develop trust and relationships with service users; this goes hand in hand with providing information that is up to date and useful as well making themselves accessible in terms of location and time.

Authors' Conclusions

The network meta-analysis suggests that all types of accommodation which provided support are more effective than no intervention or Basic/Unconditional accommodation in terms of housing stability and health. The qualitative evidence synthesis raised a primary issue in relation to context: which was the lack of stable, affordable accommodation and the variability in the rental market, such that actually sourcing accommodation to provide for individuals who are homeless is extremely challenging. Collaboration between stakeholders and practitioners can be fruitful but difficult to coordinate across different agencies and organisations.

Efficacy of weekly administration of cholecalciferol on parathyroid hormone in stable kidney-transplanted patients with CKD stage 1-3

Objectives

Kidney transplant (KTx) recipients frequently have deficient or insufficient levels of serum vitamin D. Few studies have investigated the effect of cholecalciferol in these patients. We evaluated the efficacy of weekly cholecalciferol administration on parathyroid hormone (PTH) levels in stable KTx patients with chronic kidney disease stage 1-3.

Methods

In this retrospective cohort study, 48 stable KTx recipients (37 males, 11 females, aged 52 ± 11 years and 26 months post-transplantation) were treated weekly with oral cholecalciferol (7500-8750 IU) for 12 months and compared to 44 untreated age- and gender-matched recipients. Changes in levels of PTH, 25(OH) vitamin D (25[OH]D), serum calcium, phosphate, creatinine and estimated glomerular filtration rate (eGFR) were measured at baseline, 6 and 12 months.

Results

At baseline, clinical characteristics were similar between treated and untreated patients. Considering the entire cohort, 87 (94.6%) were deficient in vitamin D and 64 (69.6%) had PTH ≥130 pg/mL. Serum calcium, phosphate, creatinine and eGFR did not differ between groups over the follow-up period. However, 25(OH)D levels were significantly higher at both 6 (63.5 vs. 30.3 nmol/L, p < 0.001) and 12 months (69.4 vs. 30 nmol/L, p < 0.001) in treated vs. untreated patients, corresponding with a significant reduction in PTH at both 6 (112 vs. 161 pg/mL) and 12 months (109 vs. 154 pg/mL) in treated vs. untreated patients, respectively (p < 0.001 for both).

Conclusions

Weekly administration of cholecalciferol can significantly and stably reduce PTH levels, without any adverse effects on serum calcium and renal function.

Assessment of Serum Vitamin B12 Levels and Other Metabolic Parameters in Subjects With Different Values of Bone Mineral Density

Background

Controversial experimental and clinical evidences have raised questions regarding the role of B12 and insulin-like growth factor 1 (IGF-1) on osteoblast function and bone health. In this study, we aimed to determine if the serum levels of B12, IGF-1 and procollagen type 1 N-terminal propeptide (P1NP) are associated with different degrees of bone mineral density (BMD).

Methods

A total of 287 subjects (190 women and 97 men; mean age 53 years) volunteered for evaluation of BMD and serum levels of B12, IGF-1 and P1NP; BMD at lumbar spine and proximal femur was evaluated by means of dual-energy X-ray absorption (DEXA) and expressed as T-score; serum concentrations of vitamin B12 and IGF1 were measured with a chemiluminescent immunoassay on Access II Beckman Coulter and DiaSorin Liaison XL analyzers, respectively; P1NP was assessed in 61 women and 35 men with reduced T-score on Roche Modular platform.

Results

A total of 101 subjects (66 women and 35 men) had a reduced BMD (T-score < -1) or osteoporosis with a T-score < -2.5, while 186 (124 women and 62 men) had a normal BMD. No significant difference in the B12 levels was observed between the subjects with reduced BMD (mean 265.15 pg/mL, 95% CI: 236 - 294.25) and those with normal BMD (mean 243.91, 95% CI: 225.78 - 262.03) (P = 0.1990); lower levels of IGF-1 were observed in the group with reduced BMD (mean 138.7 pg/mL, 95% CI: 126.75 - 150.83) than in that with normal BMD (mean 167.34, 95% CI: 136.49 - 198.18) (P< 0.001); serum levels of P1NP were significantly lower in 22 subjects younger than 50 years (mean 44.8 ng/mL, 95% CI: 36.4 - 53.1) vs. 74 subjects > 50 years old (mean 53.3, 95% CI: 34.3 - 72.3) (P < 0.001), and in women (mean 45.3, 95% CI: 37.6 - 52.9) vs. men (mean 62, 95% CI: 23 - 101) (P < 0.001).

Conclusion

We found no significant association between B12 levels and BMD, but significant associations of lower levels of IGF1 with reduced BMD and lower levels of P1NP with younger age and female sex were found; additional studies to further investigate the association of serum levels of B12, growth factors and biochemical turnover markers with human bone health are needed.

Genetic susceptibility to autoimmune thyroid diseases in a Chinese Han population: Role of vitamin D receptor gene polymorphisms

PURPOSE

Previous studies have found that some immune-related genes were associated with autoimmune thyroid diseases (AITDs). A couple of studies have explored the association between vitamin D (1,25-dihydroxyvitamin D3) receptor (VDR) gene polymorphisms and susceptibility to AITDs in different populations and found conflicting results. This case-control study was designed to evaluate the role of polymorphisms of VDR gene in the predisposition of AITDs in a Chinese Han population.

METHODS

A total of 417 patients with Graves' disease (GD), 250 patients with Hashimoto's thyroiditis (HT) and 301 healthy subjects were enrolled. The Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometer (MALDI-TOF-MS) Platform was applied to detect four SNPs (rs1544410, rs2228570, rs731236 and rs7975232) in the VDR gene.

RESULTS

In the rs7975232 allele A frequency showed a significant increase in GD patients (30.34% vs. 25.42% in controls; P=0.041, OR=1.278, 95%CI=1.010-1.617). However, no relationship was found between clinical phenotypes and the four SNPs.

CONCLUSIONS

This result suggests that the VDR gene may be one susceptibility gene which contributes to the risk of GD.

Vitamin D receptor gene polymorphisms and type 1 diabetes mellitus in a Korean population

BACKGROUND

Vitamin D receptor (VDR) has been suggested to play a role in the pathogenesis of type 1 diabetes mellitus (T1DM). There has been no case-control study examining the association between VDR polymorphisms and T1DM among Korean subjects with a low incidence of T1DM.

METHODS

Eighty-one T1DM patients and 113 unrelated healthy controls with no history of DM or other autoimmune diseases were investigated at either Pusan National University Children's Hospital or Korea University Anam Hospital between March 2009 and September 2013. Polymerase chain reaction-restriction fragment length polymorphism was utilized to genotype single nucleotide substitutions at TaqI, BsmI, and ApaI alleles.

RESULTS

All frequencies in T1DM and control subjects were in Hardy-Weinberg equilibrium, although ApaI in controls and TaqI in T1DM showed relatively weak equilibrium. TaqI and BsmI differences were significant (P = 0.045 and P = 0.012, respectively) after applying Bonferroni correction. The TT genotype carrier frequency among controls was higher than among the T1DM patients (P = 0.015; OR, 2.98; 95%CI: 1.19-7.42). T allele frequency was higher among controls than T1DM patients (P = 0.019; OR, 2.78; 95%CI: 1.15-6.72). The frequency of bb genotype carriers among controls was higher than among T1DM patients (P = 0.004; OR, 4.13; 95%CI: 1.4-12.10). The frequency of the b allele among controls was higher than that among T1DM patients (P = 0.016; OR, 3.20; 95%CI: 1.19-8.60).

CONCLUSIONS

T and b TaqI and BsmI alleles are protective against T1DM in Korean subjects.

Rapid and simultaneous detection of vitamin D receptor gene polymorphisms by a single ARMS-PCR assay

BACKGROUND

Vitamin D has various roles in many biological actions such as calcium homeostasis, cell proliferation, and cell differentiation to many target tissues. These effects are mediated by the active form of vitamin D, 1,25(OH)2D3, which binds to a cytoplasmic protein called vitamin D receptor (VDR). VDR gene has four common single nucleotide polymorphisms (SNPs) that are defined by the presence of restriction sites for FokI (F/f), TaqI (T/t), BsmI (B/b), and ApaI (A/a). The association of VDR gene polymorphisms with several diseases has been investigated. In most studies, VDR genotyping was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assays, which are cumbersome and time consuming, and their results are sometimes difficult to interpret.

OBJECTIVE

We modified previously reported primers for VDR genotyping and set up a single amplification-refractory mutation system (ARMS)-PCR method for simultaneous genotyping of four common VDR polymorphisms.

METHODS

In this study, 218 DNA samples were analyzed for VDR genetic variants by this ARMS-PCR technique; 136 of them were re-genotyped by PCR-RFLP assays to compare genotyping results.

RESULT

We obtained allelic frequencies of 69 vs. 31 % for F/f, 34 vs. 66 % for B/b, 70 vs. 30 % for T/t, and 52 vs. 48 % for A/a in this sample of the Iranian population. In addition, comparisons of the results of these two methods showed good uniformity in VDR genotypes; although, in some samples, ambiguity in restriction patterns was present.

CONCLUSION

As ARMS-PCR is more rapid, economic, and user friendly than PCR-RFLP, its substitution would be welcomed in disease association and pharmacogenetic studies of VDR variants.

Clinical phenotypes of Chinese primary hyperparathyroidism patients are associated with the calcium-sensing receptor gene R990G polymorphism

OBJECTIVE

The purpose of this study was to investigate the distribution of the A986S and R990G polymorphisms of the calcium-sensing receptor (CASR) gene in the Chinese population and whether there is an association between genetic variants and the risk of developing primary hyperparathyroidism (PHPT) and its associated clinical phenotypes.

METHODS

A total of 164 Chinese Han PHPT patients (M/F: 51/113) and 230 healthy controls (M/F: 50/180) were enrolled. The common clinical parameters of PHPT patients including biochemical markers, bone mineral density (BMD), kidney stone occurrence, and pathology results were analyzed. Genotyping was conducted for both the patients and controls, and it was carried out using standard procedures.

RESULTS

The R990G variant was more frequently present than the A986S variant in this group of Chinese PHPT patients. The R allele increased the risk of PHPT (odds ratio=1.134, 95% CI: 1.008, 1.277, and P=0.036). Patients with either the RR or RG genotype had lower blood calcium levels and higher alkaline phosphate levels than patients with the GG genotype. The lumbar BMD T-score was -2.20 (-2.63, -0.32) in patients with the GG genotype, and it was significantly lower in patients with the RR+RG genotype (-2.53 (-3.70, -1.72) P=0.036). Patients with the R allele had a significantly higher incidence of hyperplasia (25.0%) and carcinomas (7.1%) than those with the GG genotype (5.3 and 0% respectively; P=0.025). The prevalence of osteoporosis and parathyroid carcinomas was higher in Chinese PHPT patients with the R allele.

CONCLUSION

The R990G polymorphism is most frequently present in the Chinese population and among patients with PHPT. Additional studies in the Chinese population are needed to elaborate the relationship between genetics and PHPT.

Vitamin D and Tumor Necrosis Factor-Alpha Receptor Gene Polymorphisms in Various Hepatitis B Clinical Conditions in Turkey

Background

The aim is to define the role of single nucleotide polymorphism on the progress of hepatitis B virus (HBV) infection. We evaluated polymorphisms of TNF-α-308, Vitamin D receptor Apa I and Taq I gene in patients with HBV infection.

Methods

All subjects included were older than 18 years old. Sixty three patients had chronic HBV infection, 61 were HBsAg positive carriers and 59 were positive for anti-HBs and anti-HBc. Gene polymorphisms were evaluated by Amplification Refractory Mutation System PCR. For patients with chronic hepatitis, viral load, ALT levels, and histopathological evaluation of the liver were also compared.

Results

Gender distribution was not different among groups; however, anti-HBs positive patients were significantly older than the other patients. ALT levels and viral load were significantly higher in chronic hepatitis group than the asymptomatic carriers group. Vitamin D receptor Apa I gene and Taq I gene and TNF-α -308 gene variant alleles were not different in all three groups. Variant alleles of three genes were not different in subgroups of chronic hepatitis patients formed according to ALT levels, viral load, histological activity index, and fibrosis score.

Conclusions

Role of single nucleotide polymorphism in clinical status of various HBV infection states was not shown in this study. Considering the other studies performed with this aim, which strengthens the notion that ethnicity is an important factor, future studies with more patients from different ethnic groups may help to clear the role of polymorphisms in the clinical progress of HBV infection.

Vitamin D receptor BsmI polymorphism modulates soy intake and 25-hydroxyvitamin D supplementation benefits in cardiovascular disease risk factors profile

Vitamin D receptor polymorphisms may predispose that not all individuals could have benefits from the nutritional supplementation of 25-hydroxyvitamin D. Furthermore, vitamin D-related cardiovascular effects may also be influenced by soy isoflavones considered endocrine regulators of cardiovascular homeostasis. To find possible gene-diet interactions by evaluating individualized lipid metabolism benefits from an increase in soy and 25-hydroxyvitamin D intake, 106 healthy individuals, genotyped for vitamin D receptor (VDR) gene polymorphism rs1544410 (BsmI) were randomly assigned to either no intake, to daily 250 mL or 500 mL of a 25-hydroxyvitamin D supplemented SB for 2 months. The soybean beverage induced differences in cardiovascular risk factors (lipid profile, blood pressure, TNFα and MCP-1), as well as vitamin D metabolites in a dose-gene-dependent relation. Thus, VDR BsmI polymorphism affected individual response being the GG genotype the ones that showed dose-dependent manner responsiveness in the reduction in total cholesterol, LDL and triglycerides in comparison with the AA/AG genotype. These differences were associated with increased plasma levels of 1α,25-dyhydroxyvitamin D3 in the carriers of the GG genotype. It was concluded that metabolic response to 25-hydroxyvitamin D and soybean supplementation is dependent on VDR BsmI GG genotype due to a higher conversion rate from vitamin D precursors.

Racial differences in clinical use of cinacalcet in a large population of hemodialysis patients

BACKGROUND/AIMS

African-Americans with end-stage renal disease receiving dialysis have more severe secondary hyperparathyroidism than Whites. We aimed to assess racial differences in clinical use of cinacalcet.

METHODS

This retrospective cohort study used data from DaVita, Inc., for 45,589 prevalent hemodialysis patients, August 2004, linked to Centers for Medicare & Medicaid Services data, with follow-up through July 2007. Patients with Medicare as primary payer, intravenous vitamin D use, or weighted mean parathyroid hormone (PTH) level >150 pg/ml at baseline (August 1-October 31, 2004) were included. Cox proportional hazard modeling was used to evaluate race and other demographic and clinical characteristics as predictors of cinacalcet initiation, titration, and discontinuation.

RESULTS

Of 16,897 included patients, 7,674 (45.4%) were African-American and 9,223 (54.6%) were white; 53.2% of cinacalcet users were African-American. Cinacalcet was prescribed for 47.7% of African-Americans and 34.5% of Whites, and for a greater percentage of African-Americans at higher doses at each PTH strata. After covariate adjustment, African-Americans were more likely than Whites to receive cinacalcet prescriptions (hazard ratio 1.17, p < 0.001). The direction and magnitude of this effect appeared to vary by age, baseline PTH, and calcium, and by elemental calcium use. African-Americans were less likely than Whites to have prescriptions discontinued and slightly more likely to undergo uptitration (hazard ratio 1.09, 95% confidence interval 0.995-1.188), but this relationship lacked statistical significance.

CONCLUSION

Cinacalcet is prescribed more commonly and at higher initial doses for African-Americans than for Whites to manage secondary hyperparathyroidism.

Fok-I polymorphism of vitamin D receptor gene and the presence of renal dysfunction in patients with β-thalassemia major

Recent evidence supports the presence of renal dysfunction even among young patients with β-thalassemia major. However, the possible genetic contribution has never been investigated. The aim of this study was to correlate the presence of Fok-I polymorphism of the vitamin D receptor gene with abnormal levels of early markers of renal impairment in children and young adults with thalassemia. Thirty-four patients (19 male and 15 female) with β-thalassemia major on conventional treatment, with a mean decimal age of 14.62 ± 5.47 years (range: 5-22 years), were included in the study. Markers of renal function were determined in serum and in urine and patients were genotyped for Fok-I gene polymorphism. Genotype frequencies were similar to those previously reported for other populations: 47.06% of the patients were homozygous for the F allele, 41.18% were heterozygous, and 11.76% were homozygous for the f allele. A considerable number of patients demonstrated impaired renal function with increased serum cystatin C levels (29.41%), glomerular dysfunction with proteinuria (68%), as well as significant tubulopathy with hypercalciuria (73.08%), and increased levels of urinary β(2)-microglobulin (29.41%). When patients were stratified according to Fok-I polymorphism, a significantly higher prevalence of abnormally increased serum levels of cystatin C was observed in patients being homozygous for the f allele (75%) compared with those being heterozygous (Ff) or homozygous for the F allele (14.29% and 31.25%, respectively, P = .02). Further studies are needed to confirm these preliminary results and elucidate the possible mechanisms involved.

The effect of vitamin D receptor BsmI genotype on the response to osteoporosis treatment in postmenopausal women: a pilot study

AIM

The purpose of our study was to investigate the possible effect of BsmI vitamin D receptor (VDR's) polymorphism on changes in bone mineral density (BMD) and bone turnover markers in postmenopausal women receiving different treatments.

MATERIAL AND METHODS

This pilot study included 42 postmenopausal women with elevated fracture risk, randomized into 1-year treatment with weekly oral alendronate or daily subcutaneous teriparatide. Both groups received daily supplements of 1000 mg calcium and 800 IU vitamin D. Blood samples were obtained for biochemical evaluation and genotyping. BMD at the lumbar spine and femoral neck were assessed with dual energy X-ray absorptiometry. Baseline, follow-up BMD and markers of bone turnover were assessed according to the BsmI genotype.

RESULTS

BMD at the lumbar spine increased in patients carrying at least one b allele, while it decreased in patients with the BB genotype (P = 0.041). Whereas no gene-treatment interaction was observed in teriparatide-receiving patients, women with the BB genotype receiving alendronate resulted in negative BMD (-0.056 ± 0.032 g/m(2) ) and T-score (-0.295 ± 0.190) gradient, compared to carriers of the b allele (BMD: +0.020 ± 0.017 g/m(2) , P = 0.054; T-score: +0.217 ± 0.100, P = 0.030). No effect of genotype was apparent with respect to gradients of biochemical bone markers.

CONCLUSIONS

These preliminary results indicate that alendronate has a differential effect on BMD, depending on the VDR genotype. Carriers of the b allele may be more responsive to treatment compared to patients with the BB genotype. The interaction of VDR's BsmI polymorphism with the efficacy of the anti-osteoporotic treatment needs further investigation by larger prospective studies.

The DNA methylome of benign and malignant parathyroid tumors

The role of DNA methylation of CpG islands in parathyroid tumorigenesis has not been analyzed in an unbiased, systematic fashion. DNA was isolated from normal and pathologic parathyroid tissues, bisulphite modified and analyzed using the Infinium HumanMethylation27 BeadChip. Distinct hierarchical clustering of genes with altered DNA methylation profiles in normal and pathologic parathyroid tissue was evident. Comparing normal parathyroid tissue with parathyroid adenomas, 367 genes were significantly altered, while 175 genes significantly differed when comparing parathyroid carcinomas and normal parathyroid tissues. A comparison between parathyroid adenomas and parathyroid carcinomas identified 263 genes with significantly distinct methylation levels. Results were confirmed for certain genes in a validation cohort of 40 parathyroid adenomas by methylation-specific PCR. Genes of known or putative importance in the development of parathyroid tumors showed significant and frequent hypermethylation. DNA hypermethylation of CDKN2B, CDKN2A, WT1, SFRP1, SFRP2, and SFRP4 was associated with reduced gene expression in both benign and malignant parathyroid tumors. Treatment with 5-aza-2'-deoxycytidine of primary cell cultures restores expression of hypermethylated genes in benign and malignant parathyroid tumors. In conclusion, the unbiased, genome-wide study of the parathyroid tumor DNA methylome identified a number of genes with altered DNA methylation patterns of putative importance to benign and malignant parathyroid tumorigenesis.

Association between vitamin D receptor gene polymorphisms and type 1 diabetes mellitus in Iranian population

Type 1 diabetes mellitus (T1DM) is one of the T-cell mediated autoimmune diseases and vitamin D suppresses activation of T-cell and has immunomodulatory effects. In this study the association between four vitamin D receptor (VDR) gene polymorphisms, at positions FokI, BsmI, ApaI and TaqI, and susceptibility to T1DM was investigated. We assessed 87 Iranian patients with T1DM and one hundred healthy controls with no history of diabetes or other autoimmune diseases. Our results demonstrated that genotypes frequency of the TaqI VDR polymorphism differed significantly between T1DM patients and controls, TT genotype and T allele was more frequent in healthy controls compared with TIDM patients (P = 0.003; OR = 0.51, 95% CI = 0.31-0.84). Therefore, allele t is the risk-allele for developing TIDM in this study. No significant association was observed between others VDR SNPs and disease susceptibility. In conclusion, our case-control study indicated that the VDR TaqI polymorphism is associated with TIDM in Iranian population.

Hyperparathyroidism and malnutrition with severe vitamin D deficiency

BACKGROUND

Vitamin D deficiency and its associated problems are common in developing Asian countries and countries of the Middle East. Various factors, including poor nutritional status and other compounding factors such as dietary, cultural, ethnic, and environmental factors, play a major role in contributing to the poor calcium and vitamin D homeostasis. Vitamin D deficiency is thought to exacerbate signs and symptoms of hyperparathyroidism (HPT). In this overview, we present evidence of the impact of vitamin D and calcium deficiency on primary HPT (PHPT).

METHODS

We performed an evidence-based review of articles published in the English language between January 1960 and June 2008.

RESULTS

Level IV evidence suggests widespread calcium and vitamin D deficiency in developing countries (issue 1). Limited level IV evidence suggests malnutrition as a primary cause of calcium and vitamin D deficiency (issue 2). Level IV evidence suggests that calcium and vitamin deficiencies cause secondary HPT and possibly PHPT as well (issues 3 and 4). A literature search revealed only six studies that correlated vitamin D levels with clinical, biochemical, and pathologic features of PHPT (issue 5). These studies provide level IV evidence suggesting that vitamin D deficiency causes some specific clinical features of PHPT as well as exacerbating other features of the disease.

CONCLUSIONS

In the developing countries, which have severe vitamin D and calcium deficient population, PHPT patients present with advanced disease and particularly severe bone symptoms. There is presently only level IV evidence of vitamin D status affecting the clinical severity of PHPT.

Expression and somatic mutations of SDHAF2 (SDH5), a novel endocrine tumor suppressor gene in parathyroid tumors of primary hyperparathyroidism

To investigate the SDHAF2 gene and its effect on primary hyperparathyroidism. Parathyroid tumors causing primary hyperparathyroidism (pHPT) are one of the more common endocrine neoplasias. Loss of heterozygosity at chromosome 11q13 is the most common chromosomal aberration in parathyroid tumors occurring in about 40% of sporadic tumors. Only 15-19% display somatic mutations in the MEN1 gene, which suggest that this chromosomal region may harbor additional genes of importance in parathyroid tumor development. The SDHAF2 (formerly SDH5) gene is a recently identified neuroendocrine tumor suppressor gene at this locus, and inherited mutations of the SDHAF2 gene has been linked to familial paraganglioma. We demonstrate that the SDHAF2 gene is expressed in parathyroid tissue using RT-PCR. Because detection of inactivating mutations is the major criterion for validating a candidate tumor suppressor, we used automated sequencing of the coding region and intron/exon boundaries in 80 sporadic parathyroid adenomas from patients with pHPT. A known polymorphisms (A to G substitution; rs879647) was identified in 9/80 parathyroid tumors but no tumor-specific somatic mutational aberrations, such as nonsense, frameshift, or other inactivating mutations were identified. The SDHAF2 gene is expressed in parathyroid tissue. However, somatic mutations of the SDHAF2 tumor suppressor gene are unlikely to frequently contribute to parathyroid tumor development in sporadic pHPT.

Genomic and metabolomic patterns segregate with responses to calcium and vitamin D supplementation

Inter-individual response differences to vitamin D and Ca supplementation may be under genetic control through vitamin D and oestrogen receptor genes, which may influence their absorption and/or metabolism. Metabolomic studies on blood and urine from subjects supplemented with Ca and vitamin D reveal different metabolic profiles that segregate with genotype. Genotyping was performed for oestrogen receptor 1 gene (ESR1) and vitamin D receptor gene (VDR) in fifty-six postmenopausal women. Thirty-six women were classified as low bone density as determined by a heel ultrasound scan and twenty women had normal bone density acting as ‘controls’. Those with low bone density (LBD) were supplemented with oral Ca and vitamin D and were classified according to whether they were ‘responders’ or ‘non-responders’ according to biochemical results before and after therapy compared to controls receiving no supplementation. Metabolomic studies on serum and urine were done for the three groups at 0 and 3 months of therapy using NMR spectroscopy with pattern recognition. The ‘non-responder’ group showed a higher frequency of polymorphisms in the ESR1 (codons 10 and 325) and VDR (Bsm1 and Taq1), compared with to the ‘responders’. The wild-type genotype for Fok1 was more frequent in those with LBD (70 %) compared with the control group (10 %). Distinctive patterns of metabolites were displayed by NMR studies at baseline and 3 months of post-treatment, segregating responders from non-responders and controls. Identification of potential ‘non-responders’ to vitamin D and Ca, before therapy, based on a genomic and/or metabolomic profile would allow targeted selection of optimal therapy on an individual basis.

Vitamin D and primary hyperparathyroidism (PHPT)

Vitamin D deficiency and PHPT are two common conditions, especially in postmenopausal women. Vitamin D deficiency is said to be even more frequent in PHPT patients than in the general population due to an accelerated conversion of 25OHD into calcitriol or 24-hydroxylated compounds. Although several studies have reported worsening of PHPT phenotype (larger tumours, higher PTH levels, more severe bone disease) when vitamin D deficiency coexists whereas vitamin D supplementation in PHPT patients with a serum calcium level<3 mmol/L has been shown to be safe (no increase in serum or urinary calcium) and to decrease serum PTH concentration, that many physicians are afraid to give vitamin D to already hypercalcemic PHPT patients. On the other hand, it is possible that, in some patients, a persistent vitamin D deficiency induces, in the long-term, an autonomous secretion of PTH (i.e. tertiary hyperparathyroidism). The mechanism by which this could occur is unclear however. Finally, as many, otherwise normal, subjects with vitamin D insufficiency may have an increased serum PTH level we believe that those with vitamin D insufficiency should be excluded from a reference population for serum PTH levels. By doing that, we found that the upper normal limit for serum PTH was 25-30% lower than in the whole population.

Association of parathyroid adenoma and pregnancy with preeclampsia

OBJECTIVE

Case reports have described associations between calcium metabolism disturbances and primary hyperparathyroidism with preeclampsia, suggesting parathyroid involvement in preeclampsia etiology. This study examines whether parathyroid adenoma, the main cause of hyperparathyroidism, diagnosed and treated before pregnancy is associated with preeclampsia.

DESIGN

We conducted a register-based study to assess the association between parathyroid adenoma and subsequent preeclampsia.

SETTING

Births among Sweden's general population were studied.

POPULATION

The study population included 52 women with a diagnosis of parathyroid adenoma and 519 without, all of whom had a subsequent singleton pregnancy between 1973 and 1997.

METHODS

We performed a conditional logistic regression investigating the association of parathyroid adenoma with subsequent preeclampsia in the first singleton pregnancy with adjustment for potential confounding factors.

MAIN OUTCOME MEASURE

The main outcome was a diagnosis of preeclampsia that does not include women with prior chronic hypertension. To ensure that treatment of parathyroid adenoma was completed before pregnancy, those with a diagnosis of parathyroid adenoma made less than 2 yr before delivery (and the matched comparison women) were excluded.

RESULTS

Statistically, parathyroid adenoma prior to delivery is significantly (P < 0.001) associated with preeclampsia, producing an adjusted odds ratio of 6.89 (95% confidence interval, 2.30, 20.58).

CONCLUSION

A history of parathyroid adenoma should be viewed as a risk for preeclampsia.

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.

Vitamin D status affects osteopenia in postmenopausal patients with primary hyperparathyroidism

Controversy still exists about whether vitamin D status is related to the severity of primary hyperparathyroidism (pHPT), although vitamin D insufficiency is frequent in pHPT. The present study was therefore performed to examine the relationships between vitamin D status and various parameters in 30 postmenopausal pHPT patients. BMD values were measured by dual-energy x-ray absorptiometry at the lumbar spine (L(2-4)), femoral neck (FN) and distal one third of the radius (Rad 1/3). Serum levels of 25 hydroxy-vitamin D(3) [25(OH)D] and 1,25-dihydroxy vitamin D(3) [1,25(OH) (2)D(3)] were 15.8 +/- 3.5 microg/l and 69.3 +/- 33.3 ng/l in pHPT patients, respectively. Serum levels of calcium and PTH seemed to be negatively correlated to serum 25(OH)D levels, although the differences were not significant. However, when subjects with the highest serum PTH levels (PTH>1000 pg/ml) were excluded from the analysis, the correlation was significant between serum 25(OH)D levels and PTH, indicating that vitamin D status affects the severity of pHPT when severe cases were excluded. In addition, serum levels of 1,25(OH)(2)D(3) were significantly and negatively correlated to serum 25(OH)D levels. On the other hand, serum levels of 25(OH)D were significantly and positively correlated to BMD (Z-score) at the lumbar spine, but not at the radius and femoral neck; however, serum 25(OH)D levels were not correlated to the levels of any bone metabolic indices measured. Moreover, serum levels of 25(OH)D were not related to urinary calcium and the tubular reabsorption rate of phosphorus, and they were similar in groups with and without renal stones. In conclusion, vitamin D status seemed to be related to the severity of disease in postmenopausal patients with pHPT. In particular, the relationship between serum 25(OH)D level and BMD at the lumbar spine was predominant.

Vitamin d and its role in cancer and immunity: a prescription for sunlight

Vitamin D has been recognized for more than a century as essential for the normal development and mineralization of a healthy skeleton. More extensive roles for vitamin D were suggested by the discovery of the vitamin D receptor (VDR) in tissues that are not involved in calcium and phosphate metabolism. VDR has been discovered in most tissues and cells in the body and is able to elicit a wide variety of biologic responses. These observations have been the impetus for a reevaluation of the physiologic and pharmacologic actions of vitamin D. Here, we review the role of vitamin D in regulation of the immune system and its possible role in the prevention and treatment of cancer and 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.

Vitamin D receptor polymorphisms and diseases

The vitamin D endocrine system is central to the control of bone and calcium homeostasis. Thus, alterations in the vitamin D pathway lead to disturbances in mineral metabolism. Furthermore, a role for vitamin D has been suggested in other diseases, like cancer, diabetes and cardiovascular disease. Expression and nuclear activation of the vitamin D receptor (VDR) are necessary for the effects of vitamin D. Several genetic variations have been identified in the VDR. DNA sequence variations, which occur frequently in the population, are referred to as "polymorphisms" and can have biological effects. To test whether there is a linkage between VDR polymorphisms and diseases, epidemiological studies are performed. In these studies, the presence of a variation of the gene is studied in a population of patients, and then compared to a control group. Thus, association studies are performed, and a link among gene polymorphisms and diseases can be established. Since the discovery of VDR polymorphisms a number of papers have been published studying its role in bone biology, renal diseases, diabetes, etc. The purpose of this review is to summarize the vast amount of information regarding vitamin D receptor polymorphisms and human diseases, and discuss its possible role as diagnostic tools.

Parathyroid glands in calcium regulation and human disease

In humans and other land-living vertebrates, the parathyroids are known to have an overall regulatory role with action as a thermostat in the systemic calcium homeostasis to ensure tight regulation of serum calcium concentrations and appropriate skeletal mineralization. Parathyroid hormone (PTH) is an 84-amino-acid peptide, synthesized and released by parathyroid chief cells in response to hypocalcemia. PTH mobilizes calcium by increasing calcium resorption from bone and by raising calcium reabsorption in the proximal kidney tubule. Treatment with active vitamin D can increase vitamin D receptor expression, inhibit growth of parathyroid tumors, and reduce PTH levels in patients with hyperparathyroidism (HPT). Newly developed vitamin D analogues with reduced calcemic effects and with more pronounced antiproliferative effect may provide new favorable treatment for reversal of HPT.

Correlations between Vitamin D Status and Biochemical/Clinical and Pathological Parameters in Primary Hyperparathyroidism

BACKGROUND

To determine the prevalence of vitamin D deficiency and the effects of vitamin D status on parathyroid adenoma weight, clinical and biochemical indices in patients with primary hyperparathyroidism (pHPT) were studied.

METHODS

Eighty patients with pHPT who underwent surgical treatment and in whom the presence of parathyroid adenoma were confirmed histopathologically were studied retrospectively from recorded data files. Patients were divided into three groups: patients with 25-hydroxyvitamin D (25-OHD) concentrations < 15 ng/ml (group 1, n = 44), patients with 25-OHD concentrations > 15-25 ng/ml (group 2, n = 9), and patients with 25-OHD concentrations > 26 ng/ml (group 3, n = 27). Serum calcium, phosphate, alkaline phosphatase, creatinine, and albumin levels and urinary calcium excretion were determined by auto-analyzer. Plasma 25-OHD and parathyroid hormone (PTH) levels were determined by immunoradiometric assay using commercially available kits.

RESULTS

No statistically significant differences were observed with respect to serum calcium, phosphorus, albumin, and creatinine concentrations between these groups. Serum PTH, alkaline phosphatase concentrations, urinary calcium excretion, parathyroid adenoma weight, and postoperative sixth month PTH concentrations were significantly higher in group 1 patients than in group 2 and group 3 patients. Significant correlations were observed between parathyroid adenoma weight and serum 25-OHD concentrations (r = -0.348, P = 0.020); parathyroid adenoma weight and urinary calcium excretion (r = 0.348, P = 0.021). Multiple regression analysis revealed that parathyroid adenoma weight, serum 25-OHD, and preoperative PTH concentrations correlated independently and significantly with postoperative sixth month PTH concentrations.

CONCLUSIONS

Vitamin D deficiency leads to more severe bone disease, increased parathyroid tumor growth, and delayed postoperative recovery of parathyroid function in patients with primary hyperparathyroidism.

Vitamin D Receptor BsmI and TagI Gene Polymorphisms in a Turkish ESRD Population: Influences on Parathyroid Hormone Response

BACKGROUND

Clinical presentation and complications of end-stage renal disease patients are influenced by many environmental and genetic factors. In this study we sought to define the frequencies of BsmI and TagI vitamin D receptor gene polymorphisms and their influences on clinical presentations in the Turkish end-stage renal disease population.

METHODOLOGY AND PATIENTS

Hemodialyzed patients (n = 186; 111 male, 75 female) were genotyped for the insertion/deletion BsmI (B --> b, restriction site, exon VIII --> IX), TagI (T --> t, 352 exon IX) vitamin D receptor gene polymorphisms. The previous 12 months of laboratory values (C-reactive protein, intact parathyroid hormone, albumin, calcium, phosphorus, CaxP product) and clinical findings (vitamin D requirement, body weight) were analyzed retrospectively.

RESULTS

Mean age and follow-up periods were 42.1 +/- 12.6 years and 76.3 +/- 43.9 months, respectively. Polymorphism percentages were BsmI; BB/Bb/bb: 28.9/65.3/5.8% and TagI; TT/Tt/tt: 36.7/60.5/2.8%, respectively. Further analysis revealed that the TT variant of TagI was related to hyperparathyroidism (P < .05). Analysis of the data after regrouping patients according to iPTH levels (0 to 249; 250 to 499; > or =500 pg/mL) and hemodialysis duration (<60 versus > or =60 months) revealed an influence of TT variation on hyperparathyroidism as a function of increased hemodialysis duration and higher iPTH levels (P < .005).

CONCLUSION

TT variants of the TagI vitamin D receptor gene influence the development of hyperparathyroidism in hemodialysis patients, an influence that becomes more evident in patients with longer hemodialysis duration.

Secondary hyperparathyroidism is associated with vitamin D receptor polymorphism and bone density after renal transplantation

Immunosuppresive treatment and secondary hyperparathyroidism (SHPT) are considered among the most important pathogenetic factors for post-renal transplant bone disease. The aim of this study was to investigate the relationships among vitamin D receptor (VDR) gene polymorphism, parathyroid hormone (PTH) levels and bone density in renal transplant recipients. We enrolled 75 patients (50 male and 25 female, mean age 47+/-11 years) who had undergone kidney transplantation 53+/-4 months before. All patients underwent an evaluation of the main biochemical parameters of bone metabolism as well bone densitometry. VDR alleles were typed by a PCR assay based on a polymorphic BsmI restriction site. When patients were categorized according to the VDR genotype (BB, Bb, bb), serum creatinine and the cumulative doses of immunosuppressive drugs were similar across the groups. PTH levels higher than 80 pg/ml were found in 53.6% of the patients, with the highest values being detected in the bb VDR genotype (P<0.05). PTH was significantly correlated to urinary NTx values. Bone density was low in the whole population; however, spinal bone density was lower in the bb subgroup (P<0.02). In the whole population, only PTH (P<0.05) and body mass index (P<0.01) were independent predictors of spinal bone density. Grouping patients by the VDR gene polymorphism, only PTH continued to be an independent predictor of spinal bone density in the bb allele subgroup (R(2) Adj.=0.17). We can conclude that the VDR genotype polymorphism affects bone density of renal transplant recipients via its effects on the severity of SHPT.

Vitamin D

The vitamin D endocrine system plays an essential role in calcium homeostasis and bone metabolism, but research during the past two decades has revealed a diverse range of biological actions that include induction of cell differentiation, inhibition of cell growth, immunomodulation, and control of other hormonal systems. Vitamin D itself is a prohormone that is metabolically converted to the active metabolite, 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. This vitamin D hormone activates its cellular receptor (vitamin D receptor or VDR), which alters the transcription rates of target genes responsible for the biological responses. This review focuses on several recent developments that extend our understanding of the complexities of vitamin D metabolism and actions: the final step in the activation of vitamin D, conversion of 25-hydroxyvitamin D to 1,25(OH)(2)D in renal proximal tubules, is now known to involve facilitated uptake and intracellular delivery of the precursor to 1alpha-hydroxylase. Emerging evidence using mice lacking the VDR and/or 1alpha-hydroxylase indicates both 1,25(OH)(2)D(3)-dependent and -independent actions of the VDR as well as VDR-dependent and -independent actions of 1,25(OH)(2)D(3). Thus the vitamin D system may involve more than a single receptor and ligand. The presence of 1alpha-hydroxylase in many target cells indicates autocrine/paracrine functions for 1,25(OH)(2)D(3) in the control of cell proliferation and differentiation. This local production of 1,25(OH)(2)D(3) is dependent on circulating precursor levels, providing a potential explanation for the association of vitamin D deficiency with various cancers and autoimmune diseases.

Vitamin D receptor polymorphism and susceptibility to type 1 diabetes in Chilean subjects: a case-parent study

Several reports have found a relation between polymorphisms of the vitamin D receptor gene (VDR) and the development of type 1 diabetes. We have examined the association of three VDR polymorphism with type 1 diabetes in 59 Chilean case-parents trios. Genotyping for Bsm1, Apal and Taq1 polymorphism were performed. Transmission/ disequiibrium tests were used to assess gene-disease associations through the evaluation of allelic transmission to affected offspring. Non-significant increased transmissions of B allele (probability of transmission = 52.5%, p = 0.69), A allele (probability of transmission = 58.4%, p = 0.17) and T allele (probability of transmission = 52.0%, p = 0.77) were estimated in Bsml, Apal and Taql sites, respectively. Haplotype-based analyses showed non-significant preferential transmissions (global p = 0.52). The present study does not support the hypothesis of a significant contribution of VDR alleles in the etiology of type 1 diabetes of Chilean cases.

Distinction in gene expression profiles demonstrated in parathyroid adenomas by high-density oligoarray technology

OBJECTIVES

Somatic deletion of chromosome 11q13 is the most frequent genetic aberration in parathyroid adenoma. To gain further insight into the genetic etiology of parathyroid tumor development, we examined a comprehensive gene expression profile of parathyroid adenomas and normal parathyroid tissues. The results were then evaluated with respect to differences between adenomas and normal parathyroid tissue, and to the presence of loss of heterozygosity (LOH) in chromosomal region 11q13.

DESIGN AND METHODS

Sporadic parathyroid adenomas and normal parathyroids were hybridized against HG-U95Av2 oligonucleotide arrays (Affymetrix) containing a total of 12,625 probe sets. Quantitative real-time PCR (QRT-PCR) was performed in a larger series of parathyroid adenomas, in order to con-firm the microarray results.

RESULTS

Cyclin D1 and c-Jun showed increased expression in adenomas vs normal parathyroids by microarray analysis and QRT-PCR, suggesting an oncogenic role of these genes in parathyroid tumor development. At unsupervised hierarchical clustering, the adenomas fell into two groups: Group I adenomas were characterized by 11q13 LOH, while Group II adenomas lacked this abnormality. In addition, a t-test analysis identified largely non-overlapping genes with differential expression in the tumors subgroups; e.g. in Group I tumors the putative oncogene ENC 1 was found highly over-expressed vs Group II adenomas.

CONCLUSIONS

The microarray analyses revealed partly distinctive and partly common expression profiles in parathyroid adenomas with and without 11q13 LOH. In addition, approximately half of the under-expressed genes were mapped to chromosome 11, in agreement with a dose effect following loss of this chromosome.

Vitamin D receptor gene polymorphism in hypercalciuric children

Idiopathic hypercalciuria is a complex disease resulting from an interaction between environmental and genetic factors. Recently, the relationship between vitamin D receptor ( VDR) alleles and calcium homeostasis has been investigated. This study was conducted to explore the association of VDR gene polymorphism with the risk of absorptive hypercalciuria (AH). We investigated the VDR gene polymorphisms, ApaI, BsmI, and TaqI, in relation to intact parathormone (PTH), osteocalcin, and 25-hydroxyvitamin D in 80 children (42 males, 38 girls) with AH and in 86 healthy children without hypercalciuria. A significant difference in the ApaI genotype was observed between the AH group and the control group ( chi(2)=7.21, P=0.027). The AA genotype was associated with a 3.5-fold increased risk for idiopathic hypercalciuria compared with the Aa/aa genotype (odds ratio 3.5, 95% confidence interval 1.1-11). The BsmI and TaqI polymorphisms did not show any significant association with AH. Serum osteocalcin levels were significantly higher in the group with the AA genotype compared with those with the Aa or aa genotype ( P=0.02, P=0.05, respectively). The results indicate that the ApaI AA genotype of the VDR gene is not only associated with AH but is also related to differences in serum osteocalcin.

Association between AIDS disease progression rates and the Fok-I polymorphism of the VDR gene in a cohort of HIV-1 seropositive patients

In addition to its role in mineral metabolism, 1,25-dihydroxivitamin D3 (1,25(OH)2D3) also has immunomodulatory effects. Vitamin D receptor (VDR) mediates genomic actions of 1,25(OH)2D3, by acting as a transcription factor that modulates the expression of several 1,25(OH)2D3 response genes. Variations at the VDR locus have been associated with susceptibility and progression to several immune diseases. We investigated the association between rates of progression to acquired immunodeficiency syndrome (AIDS) and the Fok-I polymorphism, which is located at the initiation codon of the VDR gene. The study was performed with a cohort of 185 patients infected with human immunodeficiency virus type 1 (HIV-1): all belonged to the intravenous drug abuse risk group. Progression to AIDS was according to the Centers for Disease Control 1993 criterion (CDC-1993). In addition, a first drop in CD4 cell count to below 200 microL(-1) was considered as outcome. Patients who reached outcomes during follow-up were considered progressors. Non-progressors were those patients remaining outcome-free after a minimum follow-up of 8 years. Heterozygous at the Fok-I polymorphism were over-represented in the group of patients that progressed to AIDS CDC-1993 (50% of progressors versus 36% of non-progressors, P=0.061; risk ratio (RR)=1.38 (95% confidence interval (CI): 0.98-1.96)) and in the group of patients that showed a drop in CD4 cell count to below 200 microL(-1) (52% of progressors versus 36% of non-progressors, P=0.037; RR=1.44 (95% CI: 1.02-2.03)). Mean time to AIDS CDC-1993 was shorter for those with Ff genotype than for those with FF and ff genotypes (non-Ff genotype patients), (log rank test P=0.035; Cox hazard ratio (HR) for Ff versus non-Ff=1.53 (95% CI: 1.0-2.33), P=0.047). In addition the drop in CD4 cell count to below 200 microL(-1) was reached faster in Ff carriers than in non-Ff patients (log rank test P=0.015; HR for Ff versus non-Ff=1.77 (95% CI: 1.12-2.8), P=0.014). According to these results, HIV-1 seropositive patients carrying the Ff genotype could be considered prone to a faster progression to AIDS.

Primary hyperparathyroidism

PURPOSE OF REVIEW

This contribution presents research progress concerning primary hyperparathyroidism (pHPT), and the background for recent notable changes in treatment policy.

RECENT FINDINGS

Research has clarified that most patients with pHPT require surgery due to risk for osteoporosis, renal stones, and possibly silent complications of renal impairment, cardiovascular disease, and common psychiatric disability. Genetic studies have advanced, but the cause of the disease remains unclear for most patients. Localization methods for parathyroid tumors have improved and increased the interest for less invasive operative methods with shorter hospital stays and reduced costs for the patient. It is important to delineate when this really will imply progress and to use the new diagnostic methods in discussions of appropriate treatment strategies. It has also become evident that older pHPT patients especially could benefit from medical treatment of bone mineral deficit, and they may also need vitamin D or vitamin D analogues to prevent progress of the disease.

SUMMARY

pHPT is a common disorder among postmenopausal women, in whom most commonly applied surgical treatment has proven markedly efficient. There is now increased interest to better understand possible causes of the disease and schedule the most efficient surgical and medical treatment and discuss possible prophylaxis.

Update on genetic and clinical aspects of primary hyperparathyroidism

Primary hyperparathyroidism (pHPT) is a common endocrine disorder that predominantly affects postmenopausal women. It is mostly caused by solitary tumours within the parathyroid glands. Although the pathophysiology of pHPT is still incompletely understood, recent studies provide new clues on the development and cellular growth of tumours within the parathyroids associated with hypersecretion of parathyroid hormone and hypercalcaemia. The natural course of pHPT is rather benign. Nowadays, it has become an oligo- or asymptomatic disease often only detected by routine blood tests. These facts raise the question whether to perform parathyroidectomy on oligo- and asymptomatic patients with pHPT or whether it is possible to monitor these patients without surgery. The aim of this article is to review the literature as regards (i) the pathophysiological mechanisms that underlie parathyroid neoplasia and (ii) the defective calcium-sensing in patients with pHPT (iii) environmental and/or genetic risk factors that predispose to or promote parathyroid neoplasia, as well as (iv) alternative approaches to treat oligo- and asymptomatic patients with pHPT medically.

Parathyroid tumors

Parathyroid tumors causing primary hyperparathyroidism are common and often remain undiagnosed, despite that the diagnostic work-up is uncomplicated in most patients. The patients often do not receive the appropriate curative treatment, which is surgical. Recent studies show that surgery is beneficial in patients with mild asymptomatic disease, especially in the reversal of bone disease, neuropsychologic symptoms, and dyslipoproteinemia. All patients with the disease deserve a referral to an endocrine surgeon for discussions regarding surgical intervention. Minimally invasive techniques performed in the ambulatory setting have evolved rapidly and show an extraordinary high success rate, low-morbidity rate, and are likely to become the standard treatment for most patients with primary hyperparathyroidism.

Response of parathyroid glands to calcitriol in culture: Is this response mediated by the genetic polymorphisms in vitamin D receptor?

BACKGROUND

Recently, we have developed a model of parathyroid tissue culture that allows the study of the response of the parathyroid glands to long-term effectors, such as calcitriol, and that is also useful to study the likely effect of the genetic polymorphisms in the functionality of the glands. The aim of this study was to evaluate the response to calcitriol of cultured parathyroid tissue from patients with secondary hyperparathyroidism (HPT) and the possible effect of vitamin D receptor (VDR) gene polymorphisms on this response.

METHODS

Parathyroid glands (N = 37) from 34 parathyroidectomized patients (17 men, 17 women) were used. Several gland fragments were cultured for 60 hours in the presence of calcitriol 10(-9) mol/L or 10(-8) mol/L. DNA from each fragment was extracted to normalize the hormone secretion levels and to genotype the restriction sites ApaI, BsmI, TaqI, and FokI in the VDR gene.

RESULTS

The percentages of secretion observed in the response to calcitriol were: 69%+/- 28% (range, 3-100) and 46%+/- 19% (range, 8-78) for calcitriol 10(-9) mol/L and 10(-8) mol/L, respectively (P = 0.004). None of the polymorphisms showed statistical differences in response to calcitriol with any of the concentrations used.

CONCLUSION

Parathyroid glands cultured in vitro from patients with secondary HPT are able to respond to calcitriol decreasing PTH synthesis. These results, however, do not support the current hypothesis that VDR polymorphisms are involved in the modulation of the parathyroid gland response.

Nuclear receptor superfamily: Principles of signaling

Nuclear receptors (NRs) comprise a family of 49 members that share a common structural organization and act as ligand-inducible transcription factors with major (patho)physiological impact. For some NRs (“orphan receptors”), cognate ligands have not yet been identified or may not exist. The principles of DNA recognition and ligand binding are well understood from both biochemical and crystal structure analyses. The 3D structures of several DNA-binding domains (DBDs),in complexes with a variety of cognate response elements, and multiple ligand-binding domains (LBDs), in the absence (apoLBD)and presence (holoLBD) of agonist, have been established and reveal canonical structural organization. Agonist binding induces a structural transition in the LBD whose most striking feature is the relocation of helix H12, which is required for establishing a coactivator complex, through interaction with members of the p160 family (SRC1, TIF2, AIB1) and/or the TRAP/DRIP complex. The p160-dependent coactivator complex is a multiprotein complex that comprises histone acetyltransferases (HATs), such as CBP,methyltransferases, such as CARM1, and other enzymes (SUMO ligase,etc.). The agonist-dependent recruitment of the HAT complex results in chromatin modification in the environment of the target gene promoters, which is requisite to, or may in some cases be sufficient for, transcription activation. In the absence of ligands, or in the presence of some antagonists, certain NRs are bound to distinct multiprotein complexes through the interaction with corepressors, such as NCoR and SMRT. Corepressor complexes comprise histone deacetylases (HDACs) that have the capacity to condense chromatin over target gene promoters. Ligands have been designed that selectively modulate the interaction between NRs and their coregulators. Both HATs and HDACs can also modify the acetylation status of nonhistone proteins, but the significance in the context of NR signaling is unclear. NRs communicate with other intracellular signaling pathways on a mutual basis, and their functionality may be altered, positively or negatively, by post-translational modification. The majority of NRs act as retinoid X receptor (RXR) heterodimers in which RXR cannot a priori respond autonomously to its cognate ligand to activate target gene transcription. This RXR subordination allows signaling pathway identity for the RXR partner. The corresponding mechanism is understood and reveals cell and NR selectivity, indicating that RXR can, under certain conditions, act autonomously. NRs are regulators of cell life and death,and NR malfunction can be at the basis of both disease and therapy, as is impressively documented in the case of acute promyelocytic leukemia. Recently, several pathways have been uncovered that link NR action with cell proliferation and apoptosis.

The effects of vitamin D receptor polymorphism on secondary hyperparathyroidism and bone density after renal transplantation

Immunosuppresive treatment and secondary hyperparathyroidism (SHPT) are considered among the most important pathogenetic factors for postrenal transplant bone disease. The aim of this study was to investigate the relationships among vitamin D receptor (VDR) gene polymorphism, parathyroid hormone (PTH) levels, and bone density in renal transplant recipients. We enrolled 69 patients (47 men and 22 women; mean age, 47 +/- 11 years) who had undergone kidney transplantation 51 +/- 5 months before. All patients underwent an evaluation of the main biochemical parameters of bone metabolism as well as bone densitometry. VDR alleles were typed by a polymerase chain reaction (PCR) assay based on a polymorphic BsmI restriction site. When the patients were categorized according to the VDR genotype (BB, Bb, and bb), serum creatinine, and the cumulative doses of immunosuppressive drugs were similar across the groups. PTH levels higher than 80 pg/ml were found in 53.6% of the patients, with the highest values being detected in the bb VDR genotype (p < 0.05). PTH was significantly correlated to urinary type I collagen cross-linked N-telopeptide (NTx) values. Bone density was low in the whole population; however, spinal bone density was lower in the bb subgroup (p < 0.02). In the whole population, only PTH (p < 0.05) and body mass index (BMI; p < 0.01) were independent predictors of spinal bone density. When grouping the patients by the VDR gene polymorphism, only PTH continued to be an independent predictor of spinal bone density in the bb allele subgroup (R2 adj. = 0.17). We can conclude that the VDR genotype polymorphism affects bone density of renal transplant recipients via its effects on the severity of SHPT.

Multiple endocrine neoplasia type 1 polymorphism D418D is associated with sporadic primary hyperparathyroidism

BACKGROUND

Sporadic primary hyperparathyroidism (pHPT) occurs separately and in several hereditary disorders including multiple endocrine neoplasia type 1. Irradiation to the neck, female gender, and age are well-identified risk factors that predispose to pHPT. The multiple endocrine neoplasia type 1 gene is the most commonly deranged gene in parathyroid adenomas and contains several polymorphisms including D418D with a prevalence of roughly 50%.

METHODS

We genotyped 162 pHPT patients and control participants to evaluate if the D418D polymorphism is related to development of pHPT. One hundred fourteen of the pHPT patients and control participants were recruited from a health screening and were subjected to measurement of bone mineral density (BMD) at the lumbar spine, femoral neck, and total body.

RESULTS

The prevalence of each genotype (ie, MM, Mm, and mm) was for all pHPT patients: 62%, 29%, and 9%; and for all control participants: 32%, 43%, and 25% (P <.0004). For the screening-detected pHPT patients and control participants, the genotype distribution for MM, Mm, and mm was 60%, 30%, and 10%; and 31%, 44%, and 25%, respectively (P =.009). In the screening-recruited control participants, but not in pHPT patients, the MM genotype was also associated with higher total body BMD (P =.01) and BMD at the femoral neck (P =.02), whereas it failed to be significant for BMD at the lumbar spine (P =.08).

CONCLUSIONS

We report that the MM genotype was overrepresented in pHPT patients compared with control participants, suggesting a novel marker for pHPT. Furthermore, the MM genotype was associated with higher BMD at the femoral neck and in the total body in the screening-recruited control participants.

Current knowledge of Japanese type 1 diabetic syndrome

The Japanese have one of the lowest incidence of childhood type 1 diabetes in the world, but the incidence of this disease is clearly increasing within the Japanese population, as reported in several European countries. Latent autoimmune diabetes mellitus in adult (LADA) patients are also likely to have a lower incidence compared to Caucasians. Among the non-autoimmune (type 1B) diabetes in Japanese adults, there exists a novel subtype of type 1 diabetes characterized by extremely rapid onset and pancreatic exocrine inflammation. HLA and non-HLA gene associations to type 1 diabetes may vary depending on ethnic origin. Highly susceptible HLA haplotypes of type 1 diabetes observed in Caucasian patients are not found in Japanese patients, while protective HLA haplotypes are similar. Association studies of non-HLA genes have identified several candidate genes that influence the heterogeneity of disease phenotypes as well as disease susceptibility to type 1 diabetes. The INS-VNTR gene or polymorphisms of MICA gene are associated with susceptibility, whereas a certain allele of MICA gene and IL-10 gene polymorphism are associated with clinical heterogeneity of the disease. An expression of multiple autoantibodies to a biochemically determined autoantigen confers a high risk for progression to type 1 diabetes. The combined evaluation of multiple autoantibodies is more sensitive than is ICA testing for the diagnosis of type 1 diabetes. A high titer of GAD autoantibody has the predictive value of future insulin deficiency in patients with LADA. For accurate predictive strategies of future insulin deficiency, combinational multiple autoantibodies analysis or genetic determination should be considered for effective immune intervention.