A single nucleotide polymorphism in the promoter region of the human gene for osteoprotegerin is related to vascular morphology and function

Association of rs2073618 polymorphism and osteoprotegerin levels with hypertension and cardiovascular risks in patients with type 2 diabetes mellitus

There are reports of link of osteoprotegerin (OPG) gene polymorphism to type-2 diabetes (T2D) and hypertension (HTN). The objective of the study was to assess the allele frequency of OPG (rs2073618) gene polymorphism and its association with heart rate variability (HRV) and blood pressure variability profile as CVD risks in diabetes mellitus patients with hypertension undergoing treatment. T2D patients on treatment without hypertension (n = 172), with hypertension (n = 177) and 191 healthy volunteers were recruited for the study. Their blood pressure variability including baroreflex sensitivity (BRS), heart rate variability (HRV), OPG, insulin, lipid profile, receptor-activator for NFkB (RANK), receptor-activator for NFkB-Ligand (RANKL), and tumor necrosis factor-α (TNF-α) were estimated. Allele frequency of OPG (rs2073618) gene polymorphism was assessed from the DNA samples. BRS and HRV indices were decreased, and RANKL/OPG and TNF-α were increased in T2D and T2D + HTN groups, respectively compared to healthy control group. The reduction in BRS was contributed by increased inflammation and reduced SDNN of HRV in GG genotype in T2D + HTN. In GG + GC subgroup, it was additionally contributed by rise in RANKL/OPG level (β - 0.219; p 0.008). Presence of mutant GG genotype contributed to the risk of hypertension among T2D patients (OR 3.004) as well as in general population (OR 2.79). It was concluded that CV risks are more in T2D patients with HTN expressing OPG rs2073618 gene polymorphism.

Tumor Necrosis Factor Family Members and Myocardial Ischemia-Reperfusion Injury: State of the Art and Therapeutic Implications

Ischemic heart disease is the principal cause of death worldwide and clinically manifests as myocardial infarction (MI), stable angina, and ischemic cardiomyopathy. Myocardial infarction is defined as an irreversible injury due to severe and prolonged myocardial ischemia inducing myocardial cell death. Revascularization is helpful in reducing loss of contractile myocardium and improving clinical outcome. Reperfusion rescues myocardium from cell death but also induces an additional injury called ischemia-reperfusion injury. Multiple mechanisms are involved in ischemia-reperfusion injury, such as oxidative stress, intracellular calcium overload, apoptosis, necroptosis, pyroptosis, and inflammation. Various members of the tumor necrosis factor family play a key role in myocardial ischemia-reperfusion injury. In this article, the role of TNFα, CD95L/CD95, TRAIL, and the RANK/RANKL/OPG axis in the regulation of myocardial tissue damage is reviewed together with their potential use as a therapeutic target.

Osteoprotegerin regulates vascular function through syndecan-1 and NADPH oxidase-derived reactive oxygen species

Osteogenic factors, such as osteoprotegerin (OPG), are protective against vascular calcification. However, OPG is also positively associated with cardiovascular damage, particularly in pulmonary hypertension, possibly through processes beyond effects on calcification. In the present study, we focused on calcification-independent vascular effects of OPG through activation of syndecan-1 and NADPH oxidases (Noxs) 1 and 4. Isolated resistance arteries from Wistar-Kyoto (WKY) rats, exposed to exogenous OPG, studied by myography exhibited endothelial and smooth muscle dysfunction. OPG decreased nitric oxide (NO) production, eNOS activation and increased reactive oxygen species (ROS) production in endothelial cells. In VSMCs, OPG increased ROS production, H2O2/peroxynitrite levels and activation of Rho kinase and myosin light chain. OPG vascular and redox effects were also inhibited by the syndecan-1 inhibitor synstatin (SSNT). Additionally, heparinase and chondroitinase abolished OPG effects on VSMCs-ROS production, confirming syndecan-1 as OPG molecular partner and suggesting that OPG binds to heparan/chondroitin sulphate chains of syndecan-1. OPG-induced ROS production was abrogated by NoxA1ds (Nox1 inhibitor) and GKT137831 (dual Nox1/Nox4 inhibitor). Tempol (SOD mimetic) inhibited vascular dysfunction induced by OPG. In addition, we studied arteries from Nox1 and Nox4 knockout (KO) mice. Nox1 and Nox4 KO abrogated OPG-induced vascular dysfunction. Vascular dysfunction elicited by OPG is mediated by a complex signalling cascade involving syndecan-1, Nox1 and Nox4. Our data identify novel molecular mechanisms beyond calcification for OPG, which may underlie vascular injurious effects of osteogenic factors in conditions such as hypertension and/or diabetes.

Association of osteoprotegerin gene T950C polymorphism with cardiometabolic risk factors in gestational diabetes mellitus in South Indian Tamilian women

BACKGROUND & AIMS

This study was designed to explore the relevance of Osteoprotegerin (OPG) and its polymorphism in the cardiometabolic risk in gestational diabetes mellitus patients before diet-therapy (GDMA1).

METHODS

South Indian Tamilian pregnant women were screened and 145 were grouped as GDMA1 (n = 73) and normal pregnancy (n = 72). Serum OPG, TNF α, lipid profile, insulin and blood pressure was compared. Genomic DNA was analysed for rs2073617 T950C polymorphism. Chi square test was done to analyze the frequency distribution of alleles. Multiple regression analysis was done to assess the association among cardiometabolic parameters.

RESULTS

TNF α (p < 0.01), Osteoprotegerin (p < 0.01), lipid profile (p < 0.01), atherogenic indices (p < 0.01), systolic and diastolic and blood pressure (<0.001) levels were higher in GDMA1 patients. TNF α (p < 0.01) and osteoprotegerin (p < 0.01) were higher in women with CT allele. Osteoprotegerin was independently contributed by BMI in all GDMA1 cases and diastolic blood pressure (DBP) in CT allele cases. There was significantly higher odd (OR = 3.63) in the distribution of CT genotype among the multiparous women.

CONCLUSIONS

Osteoprotegerin, atherogenic lipid risk factor and inflammation are higher in GDMA1 women. Rise in OPG is contributed by high BMI in GDMA1 women. Higher odds of CT allele distribution in multiparous women suggests that TT allele women are at higher risk of developing GDM in their first pregnancy. Further analysis of T950C polymorphism in a larger cohort is warranted to confirm its role.

Association of gene polymorphisms in RANKL/RANK/OPG system with hypertension and blood pressure in Chinese women

Recent studies have revealed that the receptor activator of nuclear factor-kappa B ligand/RANK/osteoprotegerin (RANKL/RANK/OPG) system has an important role in vascular calcification, which is contributory to various cardiovascular diseases and intimately linked to the regulation of blood pressure. Therefore, we performed a case-control study to investigate the associations of 21 single-nucleotide polymorphisms (SNPs) in the TNFSF11, TNFRSF11A and TNFRSF11B genes in the RANKL/RANK/OPG system with hypertension and blood pressure in post-menopausal Chinese women. In this study, 503 hypertensive patients and 509 normal controls were recruited. Genotyping was performed using the high-throughput Sequenom genotyping platform. The results showed that two SNPs (rs6567270 and rs4603673) in the TNFRSF11A were associated with hypertension (P=0.010 and P=0.013, respectively) and systolic blood pressure (P=0.024 and P=0.023, respectively). One SNP (rs9646629) in the TNFRSF11A showed significant association with diastolic blood pressure (P=0.031). The results of this study suggest that TNFRSF11A but not TNFSF11 and TNFRSF11B genetic variation is associated with hypertension and blood pressure in Chinese women. The findings provide additional support for the genetic role of RANKL/RANK/OPG system in hypertension and blood pressure regulation.

Meta-analysis of genome-wide association studies identifies two loci associated with circulating osteoprotegerin levels

Osteoprotegerin (OPG) is involved in bone homeostasis and tumor cell survival. Circulating OPG levels are also important biomarkers of various clinical traits, such as cancers and atherosclerosis. OPG levels were measured in serum or in plasma. In a meta-analysis of genome-wide association studies in up to 10 336 individuals from European and Asian origin, we discovered that variants >100 kb upstream of the TNFRSF11B gene encoding OPG and another new locus on chromosome 17q11.2 were significantly associated with OPG variation. We also identified a suggestive locus on chromosome 14q21.2 associated with the trait. Moreover, we estimated that over half of the heritability of OPG levels could be explained by all variants examined in our study. Our findings provide further insight into the genetic regulation of circulating OPG levels.

Role of osteoprotegerin and its gene polymorphisms in the occurrence of left ventricular hypertrophy in essential hypertensive patients

The aim of the study was to investigate the role of osteoprotegerin (OPG) in left ventricular hypertrophy (LVH) development in patients with essential hypertension (EH). A total of 1092 patients diagnosed with EH were recruited. The LVHs were determined and OPG gene polymorphisms were genotyped. Patients with LVH had a significantly higher mean serum OPG level than those without LVH. The 1181CC genotype carriers had significantly lower risk for LVH compared with GC and GG genotype carriers. The serum OPG level and OPG 1181 G>C polymorphism were found to be independent risk factors for the occurrence of LVH in hypertensive patients. In vitro study shows that OPG overexpression upregulates cell surface size, protein synthesis per cell, and hypertrophy- and fibrosis-related proteins in both cardiomyocytes and cardiac fibroblasts, whereas OPG inhibition can abolish the above-mentioned changes. Consistent with the in vitro data, our in vivo study revealed that the OPG administration induced the LVH in hypertensive rats. This study is the first to report the close association between OPG and LVH development in EH patients and the regulatory effect of OPG on cardiomyocytes and cardiac fibroblasts.

Role of osteoprotegerin gene variants in early-onset severe pre-eclampsia

AIM

The aim of this study was to detect the role of osteoprotegerin (OPG) gene variants in early-onset severe pre-eclampsia.

MATERIAL AND METHODS

The associations of 163A/G (rs3102735) and 950T/C (rs2073617) polymorphisms of OPG with pre-eclampsia (60 cases of early-onset severe pre-eclampsia and 91 cases of late-onset pre-eclampsia), as well as with the clinical manifestations of individuals, were evaluated.

RESULTS

Data showed lower frequencies of TC and TC + CC genotypes and C allele of 950T/C in the early-onset group than those of the control and late-onset groups (P = 0.003; P = 0.002; P = 0.005; P = 0.031; P = 0.021; P = 0.022). However, no significant differences were found in genotype and allele frequencies between the late-onset and control groups. Moreover, no significant differences were observed in the genotype and allele frequencies of 163A/G polymorphism among the three groups. In the early-onset group, 950T/C TC + CC genotype carriers exhibited significantly lower systolic blood pressure ([147.25 ± 11.89] mmHg) and 24-h urine protein ([2.46 ± 0.92] g) than the TT carriers ([165.88 ± 20.39] mmHg, [3.64 ± 0.81] g) (P = 0.003; P = 0.001, respectively). Serum creatinine was significantly higher in women with the 163A/G AG + GG genotypes ([82.31 ± 11.66] μmol/L) than in those with the AA genotype ([71.90 ± 16.85] μmol/L) (P = 0.003).

CONCLUSION

This study implicates that OPG gene variants may be associated with early-onset severe pre-eclampsia.

TNFRSF11B polymorphisms are associated with metabolic traits in Uyghur and Han ethnic groups

Abstract Introduction: To test whether genetic variants of osteoprotegerin gene (TNFRSF11B) affect metabolic traits (body mass index [BMI], glucose, triglyceride, total cholesterol) and bone mass traits.

METHODS

We conducted a population based association study to investigate associations of eight tagging single nucleotide polymorphisms (tSNPs) of the TNFRSF11B gene with the aforementioned traits in a Chinese Han population and an ethnic group admixed with Caucasians and Asians - Uyghur. The associations between the tSNPs and bone mass density (BMD) were also tested in Han population.

RESULTS

We found that SNP rs3102727, located in the first intron of the TNFRSF11B gene, was significantly associated with triglyceride levels in Uyghur population and Han population simultaneously. T allele of the rs3102727 variant was associated with a 0.10 mmol/L and 0.09 mmol/L lower level of triglyceride than C allele in Uyghur (p = 0.019) and Han subjects (p = 0.037), respectively. In addition, the T allele is also associated with a lower level of hip BMD (p = 0.025) and total BMD (p = 0.048). Further, we found significant associations between SNP rs11573869 and BMI in Uyghur subjects and SNP rs3134062 with hip BMD in Han sbujects. Rs11573869-T allele was associated with a 0.81 kg/m(2) lower level of BMI than C allele (p = 0.002) and the hip BMD decreases with the copy of rs3134062-T allele increases (p = 0.002).

CONCLUSION

We detected novel associations between TNFRSF11B polymorphisms and metabolic traits in Uyghur and Han populations. In addition, we found associations between TNFRSF11B polymorphisms and bone mass traits in Han population.

Osteoprotegerin (OPG) as a biomarker for diabetic cardiovascular complications

Osteoprotegerin (OPG) is a glycoprotein involved in bone metabolisms and with a regulatory role in immune, skeletal and vascular systems. Recently, circulating OPG levels have emerged as independent biomarkers of cardiovascular disease (CVD) in patients with acute or chronic heart disease, as well as in the healthy population. Furthermore, OPG has been implicated in various inflammations and linked to diabetes and poor glycaemic control. This review focuses on the relations between circulating OPG levels and cardiovascular complications, with special emphasis on diabetic patients. OPG levels were observed to increase concurrently with the severity of diabetic complications, that is, with the highest circulating OPG levels observed in diabetic patients dying from CVD. Although the clinical prognostic use of OPG may seem far away, OPG does look promising as a biomarker in order to help the cardiologist to a better risk-stratification of the patients.

Intima-media thickness of the carotid arteries is related to serum osteoprotegerin levels in healthy postmenopausal women

Osteoprotegerin (OPG) regulates bone mass by inhibiting osteoclast differentiation and activation, and also plays a role in vascular calcification. The objective of this study was to evaluate the relationship between serum OPG levels, and carotid artery intima-media thickness (IMT) and carotid plaque formation in healthy postmenopausal women. We recruited 68 healthy postmenopausal women for the study. Carotid plaque presence and IMT were evaluated by high resolution B-mode ultrasound. IMT was positively correlated with presence of plaque, age, menopause age and OPG, and inversely correlated with Apolipoprotein A1 (Apo A1). Serum OPG level was positively correlated with IMT (r = 0.366; p < 0.003) and age (r = 0.324; p < 0.008), and negatively correlated with Apo A1 (r = -0.481; p < 0.0001). We did not observe any significant relation between plaque occurrence and levels of serum OPG. In regression analysis OPG (p < 0.02) and menopause age (p < 0.05) were independent risk factors for IMT, and age (p < 0.05) and IMT (p < 0.05) were independent risk factors for plaque formation. Although the role of OPG in the vascular biology is poorly understood, our results suggest that elevated levels of serum OPG is associated with IMT and may play a role in the pathogenesis of atherosclerotic disease.

The role of osteoprotegerin in cardiovascular disease

Osteoprotegerin (OPG) is a 401 amino acid N-glycosylated protein, which is highly expressed in a large number of tissues. OPG mainly binds to two ligands, i.e. RANKL (receptor activator of nuclear factor κB ligand) and TRAIL (tumor necrosis factor- related apoptosis-inducing ligand). Upon binding to the former ligand, OPG inhibits the activation of osteoclasts and promotes apoptosis of osteoclasts, whereas the binding of OPG with TRAIL prevents apoptosis of tumor cells. There is now emerging evidence that OPG participates in the pathogenesis of atherosclerosis and cardiovascular diseases by amplifying the adverse effects of inflammation and several traditional risk factors such as hyperlipidemia, endothelial dysfunction, diabetes mellitus, and hypertension. Some epidemiological studies also showed a positive association between OPG levels and cardiovascular morbidity and mortality. The aim of this article is to provide an overview of the main biochemical, physiological, and pathological aspects of OPG biology in cardiovascular disease.

The roles of lipid oxidation products and receptor activator of nuclear factor-κB signaling in atherosclerotic calcification

This review focuses on the roles of oxylipids and receptor activator of nuclear factor-κB ligand signaling in calcific cardiovascular disease. Both intimal and valvular calcifications are closely associated with atherosclerosis, leading investigators to study the role of atherogenic oxidatively modified lipids (oxylipids). Results have identified the molecular signaling through which oxylipids induce osteogenic differentiation and calcification in vascular cells. A surprising concomitant finding was that, in bona fide osteoblasts from skeletal bone, oxylipids have the opposite effect, ie, inhibiting osteoblastic maturation. This is the basis for the lipid hypothesis of osteoporosis. Oxylipids also induce resorptive osteoclastic cells within the bone environment, raising the question of whether resorptive osteoclasts can be harnessed in the vascular context for cell-based therapy to remove artery wall mineral deposits. The challenge is that vascular cells produce antiosteoclastogenic factors, including the soluble decoy receptor for receptor activator of nuclear factor-κB ligand, possibly accounting for the paucity of resorptive cells and the dominance of mineral in atherosclerotic plaque. These factors may have therapeutic use in osteoclastogenic removal of mineral deposits from arteries.

(Sub)clinical cardiovascular disease is associated with increased bone loss and fracture risk; a systematic review of the association between cardiovascular disease and osteoporosis

Introduction

Both cardiovascular disease and osteoporosis are important causes of morbidity and mortality in the elderly. The co-occurrence of cardiovascular disease and osteoporosis prompted us to review the evidence of an association between cardiovascular (CV) disease and osteoporosis and potential shared common pathophysiological mechanisms.

Methods

A systematic literature search (Medline, Pubmed and Embase) was conducted to identify all clinical studies that investigated the association between cardiovascular disease and osteoporosis. Relevant studies were screened for quality according to guidelines as proposed by the Dutch Cochrane Centre and evidence was summarized.

Results

Seventy studies were included in this review. Due to a large heterogeneity in study population, design and outcome measures a formal meta-analysis was not possible. Six of the highest ranked studies (mean n = 2,000) showed that individuals with prevalent subclinical CV disease had higher risk for increased bone loss and fractures during follow-up compared to persons without CV disease (range of reported risk: hazard ratio (HR) 1.5; odds ratio (OR) 2.3 to 3.0). The largest study (n = 31,936) reported a more than four times higher risk in women and more than six times higher risk in men. There is moderate evidence that individuals with low bone mass had higher CV mortality rates and incident CV events than subjects with normal bone mass (risk rates 1.2 to 1.4). Although the shared common pathophysiological mechanisms are not fully elucidated, the most important factors that might explain this association appear to be, besides age, estrogen deficiency and inflammation.

Conclusions

The current evidence indicates that individuals with prevalent subclinical CV disease are at increased risk for bone loss and subsequent fractures. Presently no firm conclusions can be drawn as to what extent low bone mineral density might be associated with increased cardiovascular risk.

The relationship between Receptor Activator of Nuclear Factor-kappaB Ligand (RANKL) gene polymorphism and aortic calcification in Korean women

The aim of this study was to investigate the relationship between RANKL gene polymorphisms and aortic calcification in Korean women. In 237 healthy Korean women, aortic calcification in thoracic and abdominal aorta was examined in simple radiologic method and lumbar spine and femoral neck BMD were examined by dual energy X-ray absorptiometry. Serum OPG levels, bone turnover markers, such as ALP levels and urine deoxypyridinoline levels, and urine calcium excretion were measured. Genotyping of two RANKL gene polymorphisms, rs2277438 and rs9594782, was performed by allelic discrimination using the 5' nuclease polymerase chain reaction assay. The subjects with CT/CC genotypes of the rs9594782 polymorphism had a 3.9 times higher risk of aortic calcification compared with TT genotype. This significance was significant even after adjustment for age, BMI, blood pressure, fasting plasma glucose, serum high and low-density lipoprotein cholesterol levels. Mean levels of urine deoxypyridinoline were significantly higher in the subjects with AG/GG genotypes of the rs2277438 polymorphism compared with AA genotype, and this significance was persistent even after adjustment for age and BMI. There were no associations of mean values for age, BMI, serum OPG and ALP levels, urine calcium excretion, and BMD with RANKL gene polymorphisms. The RANKL gene rs9594782 polymorphism was associated with aortic calcification in Korean women. Rs2277438 polymorphism showed significant association with urine deoxypyridinoline levels, a bone resorption marker. These results suggest its role on vascular calcification and bone metabolism in humans.

A cohort study of the effects of serum osteoprotegerin and osteoprotegerin gene polymorphisms on cardiovascular mortality in elderly women

OBJECTIVE

To investigate the role of serum osteoprotegerin (OPG) and OPG gene polymorphisms in relation to cardiovascular (CV) and all-cause mortality in elderly women.

BACKGROUND

The OPG/RANK/RANKL plays a vital role in bone cell biology. It has also been detected in myocardial tissue and atherosclerotic plaques. In some population studies, OPG and OPG gene polymorphisms have been associated with CV disease risk.

DESIGN, MEASUREMENTS AND RESULTS

In an 8.5-year cohort population study of 1333 postmenopausal women mean age 75.2 ± 2.7 years, serum OPG concentrations above the median were associated with an increased risk of all-cause [odds ratio (OR) 1.39 (1.04-1.85)], and in particular CV mortality [OR 1.83 (1.10-3.05)], before and after adjusting for age, BMI, treated hypertension, diabetes, hypercholesterolemia, previous HRT use, calcium supplementation and smoking. Genotyping the OPG gene did not provide further information on the association between OPG and CV risk or mortality events.

CONCLUSIONS

Raised osteoprotegerin appears to be an independent risk factor for total and CV death and thus has potential as a useful biomarker of risk as well as a potential target for therapeutic intervention.

A single-nucleotide polymorphism in the gene encoding osteoprotegerin is associated with diastolic blood pressure in older men

BACKGROUND

Osteoprotegerin (OPG) has been associated with cardiovascular events but currently the mechanisms underlying this association are unknown. OPG is thought to play a role in controlling artery calcification and small studies have suggested that it may influence artery structure. We examined the association between single nucleotide polymorphisms (SNPs) in the gene encoding OPG (tumor necrosis factor receptor superfamily, member 11b, TNFRSF11B), with blood pressure in a large cohort of elderly men.

METHODS

21 tagging SNPs in the region encoded by TNFRSF11B were examined in 1,071 men recruited in a population-based study of elderly men. Genotyping was carried out using the Illumina Golden Gate assay. SNPs were investigated for their association with resting systolic and diastolic blood pressure after adjusting for other variables using linear regression. The association of SNPs in the region encoded by TNFRSF11B with plasma OPG was assessed in a random subset of 467 men.

RESULTS

One SNP, rs11573901, was significantly associated with diastolic blood pressure, after adjusting for other risk factors and multiple testing (coefficient -4.36, P = 0.001). Men with the TC genotype had lower diastolic blood pressure than those with the common cc variation. this snp was not associated with plasma opg in the 467 men in which this was examined.

CONCLUSIONS

This study suggests that a SNP within the region encoded by TNFRSF11B, which is believed to code for OPG, is associated with blood pressure. The mechanism underlying this observed association is currently unclear.

Genetic regulation of atherosclerotic plaque size and morphology in the innominate artery of hyperlipidemic mice

OBJECTIVE

We sought to determine the genetic factors contributing to atherosclerotic plaque size and cellular composition in the innominate artery, a murine model of advanced atherosclerosis.

METHODS AND RESULTS

We examined genetic contributions to innominate atherosclerotic plaque size and cellular composition in an intercross between C57BL/6J.Apoe(-/-), a strain susceptible to aortic lesions, and C3H/HeJ.Apoe(-/-), a strain resistant to aortic lesions. Surprisingly, total innominate lesion size was similar in the two strains. Genetic analyses identified one novel locus on Chromosome 2 for innominate artery lesion size, a significant locus for fibrous cap thickness on Chromosome 15, and several suggestive loci for cellular composition, all distinct from loci influencing aortic lesions. The Chromosome 2 locus contains a candidate, CD44. We show that CD44 is expressed in the innominate artery and differs strikingly in expression between the parental strains.

CONCLUSION

Multiple aspects of innominate lesion composition are genetically determined, but in a manner largely independent of the genetic contributions to aortic lesions.

Serum osteoprotegerin is associated with carotid intima media thickness in women with previous gestational diabetes

Circulating levels of osteoprotegerin (OPG) have been shown to be increased in patients with cardiovascular disorders and diabetes. The aim of this study was to determine serum OPG levels in women with previous gestational diabetes (GDM), and to investigate the relationship between OPG and carotid intima media thickness (IMT) and circulating cardiovascular risk factors. Serum OPG was measured in 46 women with previous GDM and 30 age-matched healthy controls. Carotid IMT was evaluated. Serum lipid, insulin and hsCRP levels, plasma fibrinogen, vWF and PAI-1 levels were measured. Serum OPG levels tended to be increased in women with previous GDM (p=0.058). Carotid IMT was increased in the study group. Women with previous GDM had elevated levels of hsCRP and PAI-1. OPG levels were positively correlated with age, fasting and post-load glucose levels, hsCRP, and carotid IMT. Multiple regression analysis showed that serum OPG was a statistically significant predictor for elevated carotid IMT. Our results revealed that OPG levels tended to be elevated in women with previous GDM. Significant association of OPG with carotid IMT suggested that OPG might play a role in the pathogenesis of endothelial dysfunction in women with previous GDM.

A genetic polymorphism of the osteoprotegerin gene is associated with an increased risk of advanced prostate cancer

Background

The purpose of this study was to evaluate the role of osteoprotegerin gene (OPG) polymorphisms as genetic modifiers in the etiology of prostate cancer (PCa) and disease progression.

Methods

Three hundred and sixty one patients with PCa and 195 normal controls were enrolled in the study, and two genetic polymorphisms, 149 T/C and 950 T/C in the putative promoter region of OPG, were genotyped.

Results

There was no significant difference in the genotype frequencies between PCa patients and controls (P = 0.939 and 0.294 for 149 T/C and 950 T/C polymorphisms, respectively). However, those patients with TC and TT genotypes in the 950 T/C polymorphism had a significantly increased risk of extraprostatic (age-adjusted odds ratio; aOR = 1.74 and 2.03 for TC and TT genotypes compared with the CC genotype, P = 0.028) and metastatic disease (aOR = 1.72 and 2.76 for TC and TT genotypes compared with the CC genotype, P = 0.009) compared with those with the CC genotype. In addition, analysis of the metastatic PCa patients (Stage D) showed that the presence of the T allele of the OPG 950 T/C polymorphism was an independent risk factor predicting survival by Cox proportional hazard regression analyses (P = 0.031).

Conclusion

Progression of PCa may be influenced by an intrinsic genetic factor of the host's bone metabolism. The variant C allele of 950 T/C in the OPG promoter may play a major role as a genetic safe guard against progression in patients with PCa.

Analysis of the association of polymorphism in the osteoprotegerin gene with susceptibility to chronic kidney disease and periodontitis

BACKGROUND AND OBJECTIVE

Chronic kidney disease (CKD) is a complex disorder, which results in several complications involving disturbance of mineral metabolism. Periodontal disease is an infectious disease that appears to be an important cause of systemic inflammation in CKD patients. Periodontal disease is characterized by clinical attachment loss (CAL) caused by alveolar bone resorption around teeth, which may lead to tooth loss. Osteoprotegerin (OPG) is a key regulator of osteoclastogenesis. Polymorphisms are the main source of genetic variation, and single nucleotide polymorphisms (SNPs) have been reported as major modulators of disease susceptibility. The aim of this study was to investigate the association of a polymorphism located at position -223 in the untranslated region of the OPG gene, previously known as -950, with susceptibility to CKD and periodontal disease.

MATERIAL AND METHODS

A sample of 224 subjects without and with CKD (in hemodialysis) was divided into groups with and without periodontal disease. The OPG polymorphism was analyzed by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

No association was found between the studied OPG polymorphism and susceptibility to CKD or periodontal disease.

CONCLUSION

It was concluded that polymorphism OPG-223 (C/T) was not associated with CKD and periodontal disease in a Brazilian population. Studies on other polymorphisms in this and other genes of the host response could help to clarify the involvement of bone metabolism mediators in the susceptibility to CKD and periodontal disease.

Determinants of endothelial function in a cohort of patients with peripheral artery disease

OBJECTIVES

Endothelial dysfunction assessed by brachial artery flow-mediated dilatation (FMD) has been associated with cardiovascular events. There have been relatively few studies examining FMD or other measures of endothelial function in patients with peripheral artery disease (PAD). The aim of this study was to examine determinants of FMD in a homogenous cohort of patients with PAD.

METHODS

We prospectively assessed patients presenting with life style-limiting intermittent claudication to establish the presence of cardiovascular risk factors, obesity and metabolic syndrome. Fasting serum was assayed for lipids, C-reactive protein, adiponectin, leptin, resistin and osteoprotegerin (OPG). FMD was measured by high-resolution ultrasound.

RESULTS

Serum concentrations of OPG were elevated in patients with obesity and metabolic syndrome. FMD was impaired in patients with obesity and metabolic syndrome and negatively correlated with serum concentrations of OPG. By multiple regression analysis, metabolic syndrome was independently associated with impaired FMD after adjustment for age, smoking, ischaemic heart disease, cerebrovascular disease and severity of PAD.

CONCLUSIONS

Our findings suggest that metabolic syndrome is an important determinant of endothelial function in patients with PAD, and OPG may be a useful biomarker of this effect.

Pathogenesis of calciphylaxis: Hans Selye to nuclear factor kappa-B

The clinical syndrome of calciphylaxis is characterized by arteriolar medial calcification, thrombotic cutaneous ischemia, necrotic skin ulceration, and a high mortality rate. This review integrates calciphylaxis risk factors with the molecular processes governing osseous and extraosseous mineralization. As the pathogenesis of calciphylaxis is better understood, targeted therapies aimed at disease prevention and reversal will follow.

Polymorphisms at the Osteoprotegerin and Interleukin-6 Genes in Relation to First-Ever Stroke

BACKGROUND

Arterial calcification and osteoporosis often coexist, especially in postmenopausal women. Osteoporosis associates with a substantially increased risk of stroke in elderly women, suggesting that impaired estrogen signaling may link stroke and osteoporosis. Osteoprotegerin (OPG, TNFRSF11B) and interleukin-6 (IL-6, IL6) are putative target genes for estrogen signaling and have been implicated in both cardiovascular diseases and osteoporosis. We hypothesized that specific polymorphisms in these genes may be associated with increased risk of ischemic stroke or intracerebral hemorrhage (ICH).

METHODS

We performed a population-based prospective nested case-control study, in which the relationships between polymorphisms (OPG-1181G/C, OPG-950T/C and IL6-174G/C) and ischemic stroke and ICH were examined. Definitive first-ever stroke events (n = 388), i.e. ischemic stroke (n = 320), ICH (n = 61) and unspecified stroke (n = 7) cases, and controls without cardiovascular disease (n = 773), matched for age, sex and geographical region were studied. Univariate and multivariate models using conditional logistic regression, which included traditional risk factors, were used to test for association.

RESULTS

Carriers of the OPG-1181C/C genotype had a significantly (p = 0.018) increased risk of ICH (OR, 2.69; 95% CI, 1.19-6.12) in the univariate analysis. After adjustments (hypertension, diabetes, BMI and triglycerides), this genotype remained significantly (p = 0.005) associated with ICH (OR, 6.04; 95% CI, 1.71-21.29). By contrast, no correlations were found between this genotype and ischemic stroke, nor between the OPG-950T/C or IL6-174G/C polymorphisms and stroke subtypes.

CONCLUSIONS

In this population, the OPG-1181C/C genotype associates with first-ever ICH, implying that alterations in OPG-mediated signaling in the vasculature may be involved in the pathophysiology of this disease.

Vascular calcification and osteoporosis--from clinical observation towards molecular understanding

Patients with osteoporosis frequently suffer from vascular calcification, which was shown to predict both cardiovascular morbidity/mortality and osteoporotic fractures. Various common risk factors and mechanisms have been suggested to cause both bone loss and vascular calcification, including aging, estrogen deficiency, vitamin D and K abnormalities, chronic inflammation and oxidative stress. Major breakthroughs in molecular and cellular biology of bone metabolism and the characterization of knockout animals with deletion of bone-related genes have led to the concept that common signaling pathways, transcription factors and extracellular matrix interactions may account for both skeletal and vascular abnormalities. For example, mice that lack the cytokine decoy receptor osteoprotegerin or the hormone Klotho display a combined osteoporosis-arterial calcification phenotype. In this review, we summarize the current data and evaluate potential mechanisms of the osteoporosis-arterial calcification syndrome. We propose a unifying hypothesis of vascular calcification that combines both active and passive mechanisms of vascular mineralization with aspects of bone resorption and age-related changes.

No associations between OPG gene polymorphisms or serum levels and measures of osteoporosis in elderly Australian women

Bone mass is the single most important risk factor for osteoporotic fractures in the elderly and is mainly influenced by genetic factors accounting for 40-75% of the inter-individual variation. Critical for the bone remodeling process is the balance between the newly discovered members of the tumor necrosis factor ligand and receptor superfamilies, osteoprotegerin (OPG) and receptor activator of nuclear factor-kappaB ligand, which mediate the effects of many upstream regulators of bone metabolism. In the present study, we evaluated the impact of sequence variations in the OPG gene on bone mass, bone-related biochemistry including serum OPG and fracture frequency in elderly Australian women. A total of 1101 women were genotyped for 3 different single nucleotide polymorphisms (SNP) within the OPG gene (G1181C, T950C and A163G). The effects of these SNPs and serum OPG on calcaneal quantitative ultrasound measurements, osteodensitometry of the hip and bone-related biochemistry were examined. We found no significant relationship between sequence variations in the OPG gene or serum OPG and bone mass, bone-related biochemistry or fracture frequency. Our findings confirm some recent publications investigating the same SNPs but diverge from others, indicating that generalization of the relationships found in this type of study must be done with caution and signify the importance of determining associations between polymorphisms and osteoporosis in different ethnic groups.

Osteoprotegerin inactivation accelerates advanced atherosclerotic lesion progression and calcification in older ApoE-/- mice

OBJECTIVE

Osteoprotegerin (OPG), a member of the tumor necrosis factor (TNF) superfamily of proteins, plays an important role in bone remodeling and is expressed in both mouse and human atherosclerotic lesions. The current study was designed to assess whether OPG plays a role in the progression and calcification of advanced atherosclerotic lesions in apoE(-/-) mice.

METHODS AND RESULTS

Atherosclerotic lesion area and composition and aortic calcium content were examined in mice deficient in both OPG and apolipoprotein E (OPG(-/-).apoE(-/-) mice) at 20, 40, and 60 weeks of age. Littermate OPG(+/+).apoE(-/-) mice were used as controls. The average cross-sectional area of lesions in the innominate arteries was increased in OPG(-/-).apoE(-/-) mice at 40 and 60 weeks of age. The increase in lesion area was coupled with a reduced cellularity and an increase in connective tissue including laminated layers of elastin. Sixty-week-old OPG(-/-).apoE(-/-) mice also had an increase in the area of calcification of the lesions. There were no differences in markers of plaque stability. In vitro, OPG induced matrix metalloproteinase-9 (MMP-9) activity in macrophages and smooth muscle cells and acted as a survival factor for serum-deprived smooth muscle cells.

CONCLUSIONS

OPG inhibits advanced plaque progression by preventing an increase in lesion size and lesion calcification. OPG may act as a survival factor and may modulate MMP9 production in vascular cells.

The relationship between four single nucleotide polymorphisms in the promoter region of the osteoprotegerin gene and aortic calcification or coronary artery disease in Koreans

OBJECTIVE

Osteoprotegerin (OPG) is a recently identified cytokine that acts as a decoy receptor for the receptor activator of the NF-kappaB ligand (RANKL). OPG has been shown to be an important inhibitor of osteoclastogenesis and arterial calcification in animal models. OPG has been proposed as a link molecule between osteoporosis and arterial calcification, but the relationship between the OPG gene and the cardiovascular system in human populations is unclear. Thus, the aim of this study was to investigate the relationship between OPG gene polymorphisms and aortic calcification or coronary artery disease in Koreans.

DESIGN AND PATIENTS

Genotyping of four polymorphisms, A163G, G209A, T245G and T950C, in the promoter region of the OPG gene was performed in 251 healthy Korean women (mean age 51.3 +/- 6.9 years) and in a second study population consisting of 100 patients who underwent coronary angiography (mean age 57.0 +/- 11.9 years), by allelic discrimination using the 5' nuclease polymerase chain reaction assay. Cardiovascular risk factors and serum OPG levels were measured and aortic calcification in thoracic and abdominal aorta was examined by simple radiological methods.

RESULTS

In the first study population, the prevalence of aortic calcification increased significantly as the subjects grew older. The frequencies of mutant alleles were significantly higher in the subjects with aortic calcification compared with those without aortic calcification in G209A and T950C polymorphisms, although these significances were lost after adjustment for age. No significant relationship was found between OPG gene polymorphisms and serum OPG levels or cardiovascular risk factors. In the second study group, there were no associations between OPG promoter genotypes and aortic calcification, serum OPG levels, or coronary artery disease.

CONCLUSIONS

We observed that the four polymorphisms in the promoter region of the OPG gene were not associated with aortic calcification or coronary artery disease in Koreans. Further studies are needed to clarify this relationship.

Serum levels of osteoprotegerin and osteoprotegerin polymorphisms in Gaucher disease

Bone involvement in Gaucher disease causes disability and reduced quality of life; loss of function and pain are important indications for enzyme replacement therapy. The purpose of this study was to ascertain whether osteoprotegerin (OPG), which decreases osteoclast activity, is indicative of incipient bone involvement by comparing OPG serum levels to Gaucher disease severity (SSI) and bone mineral density (BMD), and to correlate bone and disease markers to OPG polymorphisms: OPG1-2(A163G), OPG3-4(T129C) and OPG5-6(C1217T). Of 554 patients, 173 Ashkenazi Jewish patients with non-neuronopathic Gaucher disease were enrolled and 32 healthy Ashkenazi Jews served as controls. Serum OPG levels were detected by enzyme-linked immunosorbent assay and BMD was obtained by dual X-ray absorptiometry. OPG polymorphisms were determined in 63 randomly chosen patients. Serum OPG values for patients were not greater than in controls, but showed a statistically significant trend to increase with age (P = 0.057). No correlation existed between OPG levels and BMD or with genotype or other disease markers. A significant correlation was noted between OPG5-6 genotype and SSI. A significant difference was found between the allele distributions of each OPG polymorphism when compared with Caucasians and Ashkenazi Jews. OPG levels probably do not predict BMD in Gaucher disease and hence are not indicative of osteoporosis in Gaucher disease.

Osteoprotegerin (OPG)-a potential new role in the regulation of endothelialcell phenotype and tumour angiogenesis?

The progression of cancer depends on the establishment of a tumour blood supply, and therefore tumour angiogenesis has been identified as a major target for new anticancer agents. Recent reports have suggested that osteoprotegerin (OPG) is involved in the control of endothelial cell survival through the inhibition of the activity of tumour necrosis factor- (TNF) related apoptosis-inducing ligand (TRAIL). The role of OPG in human tumour development and angiogenesis is currently unknown. In the present study we demonstrate the ability of OPG to support endothelial cell survival, as well as the formation of cord-like structures in vitro using a matrigel tubule formation assay. Investigation of various human cancers demonstrated endothelial OPG expression in 59% of malignant tumours (n=512), but in contrast, OPG was absent in endothelial cells associated with benign tumours and normal tissues (n=178). In a series of 400 breast tumours, endothelial OPG expression was associated with high tumour grade and certain histological types. Our data show a clear separation in endothelial OPG expression between malignant tumours and nonmalignant tissues, supporting a potential biological role for this molecule in the development and/or maintenance of the tumour vasculature. This is the first study to report the proangiogenic effects of OPG in vitro, as well as correlating expression of OPG by tumour endothelial cells with clinicopathological data in human tumours.

The relationship between insulin resistance assessed by HOMA-IR and serum osteoprotegerin levels in obesity

AIM

We investigated the relationship between insulin resistance and serum osteoprotegerin (OPG) levels in healthy obese subjects and healthy lean controls.

METHODS

Fifty obese subjects (age: 31+/-8 years) and 24 lean controls (age: 30+/-7 years) were included in the study. We used the homeostasis model assessment for insulin resistance (HOMA-IR) index as the index of insulin resistance. OPG levels were measured with the commercial ELISA kit. Obese subjects were studied in three groups: Group I (n = 25) HOMA-IR index < 2.24, Group II (n = 13) index 2.24-3.59, Group III (n = 12) index > 3.59. Group IV (n = 24) was the lean controls with HOMA-IR index < 2.24.

RESULTS

Obese subjects with increased insulin resistance (Group III) had lower OPG values than other groups (11.88+/-7.43 pg/ml, 16.39+/-6.39 pg/ml, 17.37+/-9.61 pg/ml, and 18.1+/-6.65 pg/ml, respectively; Group I versus Group III p = 0.036; Group III versus Group IV p = 0.012). We also found significant inverse correlations between OPGc (corrected for BMI) and fasting glucose (r = -0.325, p = 0.005), fasting insulin (r = -0.404, p = 0.0001) as well as HOMA-IR (r = -0.428, p = 0.0001). Increased fibrinogen level was found in Group III than Group IV (9.32+/-1.97 micromol/l versus 7.47+/-1.65 micromol/l, respectively; p = 0.005). In conclusion, insulin resistance in obesity is associated with decreased serum OPG levels and increased fibrinogen levels. The relationship between serum OPG levels and HOMA-IR may provide an insight into vascular endothelial dysfunction in obesity.

Circulating amounts of osteoprotegerin and RANK ligand: genetic influence and relationship with BMD assessed in female twins

Osteoprotegerin (OPG) is a circulating receptor that inhibits osteoclastogenesis by binding to RANK ligand (RANKL). OPG knock-out animals develop severe osteoporosis. Treatment with OPG lowers bone resorption and increases BMD. OPG production is influenced by a wide range of hormones and cytokines. The influence of genetic factors on circulating amounts of OPG and RANKL is not known. BMD has been demonstrated to have a high heritability and there is evidence also that bone turnover and bone loss rates are controlled at least in part by genetic factors.

OBJECTIVE

Assessing the genetic impact on serum OPG and RANKL in women and estimation of the relative contribution of this inheritance to the total heritability of BMD.

METHODS

188 female twins (52 DZ and 42 MZ pairs) from the Danish Twin Registry were included in the study. Mean age was 35 years (range 19-64 years), average spine BMD was 1.04 +/- 0.11 g/cm2. Serum levels of OPG and RANKL were measured by ELISA (Biomedica, Vienna, Austria). This register covers twins born in Denmark since 1870. Heritability and environmental influence was assessed using a maximum-likelihood model for genetic pleiotropy.

RESULTS

RANKL levels showed a negative correlation with age and lower values in smokers. OPG levels were higher in postmenopausal women. Heritability (h(2)) was 85% for spine BMD and 52% for serum RANKL after adjustment for age, smoking and BMI. By contrast, there was no significant genetic influence on OPG levels (h(2) = 0, 95% CI: 0 to 0.31). Serum OPG was determined almost exclusively by individual environment (e(2) = 0.79), with a small, non-significant contribution from shared environment (c(2) = 0.21). Restricting analyses to the 158 premenopausal twins did not alter the findings.

CONCLUSIONS

Serum OPG and RANKL levels have only a weak relation to BMD in healthy women. Phenotype correlations indicate that the genes that contribute to twin similarity for BMD are not genes regulating serum levels of RANKL or OPG. The weak correlation with BMD appears to consist in shared environmental factors.

Deficiencies of physiologic calcification inhibitors and low-grade inflammation in arterial calcification: lessons for cartilage calcification

Apart from clinical parallels, similarities in the pathogenesis of arterial and articular cartilage calcification have come to light in recent years. These include the roles of aging, of chronic low-grade inflammation and of genetic and acquired dysregulation of inorganic pyrophosphate (PP(i)) metabolism. This review focuses on recent developments in understanding the pathogenesis of artery calcification pertinent to interpretation of the mechanistic basis for articular cartilage calcification in aging and osteoarthritis.

The molecular triad OPG/RANK/RANKL: involvement in the orchestration of pathophysiological bone remodeling

The past decade has seen an explosion in the field of bone biology. The area of bone biology over this period of time has been marked by a number of key discoveries that have opened up entirely new areas for investigation. The recent identification of the receptor activator of nuclear factor kappaB ligand (RANKL), its cognate receptor RANK, and its decoy receptor osteoprotegerin (OPG) has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK has been shown to be required for osteoclast differentiation. The third protagonist, OPG, acts as a soluble receptor antagonist for RANKL that prevents it from binding to and activating RANK. Any dysregulation of their respective expression leads to pathological conditions such as bone tumor-associated osteolysis, immune disease, or cardiovascular pathology. In this context, the OPG/RANK/RANKL triad opens novel therapeutic areas in diseases characterized by excessive bone resorption. The present article is an update and extension of an earlier review published by Kwan Tat et al. [Kwan Tat S, Padrines M, Theoleyre S, Heymann D, Fortun Y. IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology. Cytokine Growth Factor Rev 2004;15:49-60].

Decreased serum osteoprotegerin levels in patients with cardiac syndrome X

Receptor activator of nuclear factor KB (RANK) and osteoprotegerin (OPG) represent the ligand and decoy receptor, respectively, of a pleiotropic cytokine system that regulates bone metabolism and vascular biology. Several studies supported systemic microvascular abnormalities in patients with cardiac syndrome X (CSX). This study investigates serum OPG levels in healthy obese subjects and healthy lean controls affected by cardiac syndrome X.

METHODS

We compared the OPG levels in 8 patients with cardiac syndrome X [2 males, 6 females; age: 46+/-6 yr; body mass index (BMI): 30+/-5 kg/m2] with 24 obese subjects (8 males, 16 females; age: 38+/-5 yr; BMI: 35+/-5 kg/m2) and 15 healthy lean controls (6 males, 9 females; age: 36+/-5 yr; BMI: 23+/-2 kg/m2; BMI<25kg/m2).

RESULTS

Serum OPG levels in patients with cardiac syndrome X were lower than those in obese subjects and lean controls (11.45+/-8.36 pg/ml, 14.78+/-8.22 pg/ml, 19.24+/-6.96 pg/ml, respectively, cardiac syndrome X vs lean controls, p=0.039).

CONCLUSIONS

Serum OPG levels are lower in patients with CSX. Further studies on the mechanisms of OPG in microangiopathy may help to evaluate the OPG system role as a marker for disease activity, prognosis and response to therapy in cardiovascular diseases.

Genetics of Ultrasonographic Carotid Atherosclerosis

The search for genes related to the cause of common complex disorders such as cardiovascular disease has been frustrating, partly because of the many factors known to contribute to cardiovascular disease and the potential "distance" of cardiovascular disease as a phenotype from genes and gene products. Linkage and association studies for phenotypes more proximal in the pathway from DNA sequence variation to overt clinical disease, such as ultrasound-defined carotid atherosclerosis, may potentially be more enlightening. Only one genetic variant previously reported to be associated with atherosclerosis or clinically evident cardiovascular disease, matrix metalloproteinase (MMP) 3, has shown consistently positive associations with carotid disease, although it has not been studied widely. Another, PON1 L55M, is weakly associated in subgroups only, and 2, ApoE and MTHFR, are equivocal. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis. This may reflect the known inconsistency in associations of genetic variants with clinical cardiovascular disease itself. Alternatively, genetic determinants of ultrasound-defined carotid atherosclerosis may differ from those of clinically manifest cardiovascular disease and may require pursuit through large-scale genomic studies of carotid atherosclerosis as a distinct phenotype. Only 1 genetic variant, MMP 3, has shown consistently positive associations with ultrasonographic carotid disease, although it has not been studied widely. Another, PON1 L55 mol/L, is weakly associated in subgroups only. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis.

Osteoprotegerin and bone mineral metabolism in renal failure

PURPOSE OF REVIEW

This review focuses on the impact of a recent breakthrough in bone cell biology for understanding the pathophysiology of bone/vascular abnormalities associated with uraemia.

RECENT FINDINGS

Osteoprotegerin is a humoral osteoclastogenesis/osteoclast activation inhibitory factor, which belongs to the TNF-alpha receptor superfamily. Serum osteoprotegerin levels are elevated along with the deterioration of the glomerular filtration rate. The circulating osteoprotegerin molecules were likely to preserve the activity of osteoclastogenesis inhibition, and the levels in many dialysis patients were high enough to inhibit osteoclastogenesis. The higher serum osteoprotegerin levels were related to the development of vascular calcification.

SUMMARY

Osteoprotegerin is a potential uraemic toxin that increases the skeletal resistance to PTH. However, the roles of increased circulating osteoprotegerin on bone and/or vascular abnormalities in uraemia remain to be clarified.

Single nucleotide polymorphisms in the human gene for osteoprotegerin are not related to bone mineral density or fracture in elderly women

Osteoprotegerin (OPG), a secreted member of the tumor necrosis factor receptor family, is a potent inhibitor of osteoclast activation and differentiation. In animal models OPG prevents bone loss, and in humans bone resorption can be reduced by injections of OPG. OPG may also play a role in cardiovascular disease since mice lacking the OPG gene display arterial calcification. In a screening effort of the OPG gene, we recently discovered a single nucleotide polymorphism in the promoter region of OPG (T950C), and reported an association with vascular morphology and function in 59 healthy individuals. Due to the pronounced effect of OPG on bone turnover, the present study was conducted to investigate whether OPG polymorphisms are also associated with bone mineral density or with fracture. The relationship between single nucleotide polymorphisms in the promoter region of OPG (T950C) and the first intron (C1217T), and bone mineral density, measured by DXA in the hip or spine or ultrasound of the heel, was investigated in the Malmö OPRA-study of 1044 women, all 75 years old. The possible relation to fracture incidence was also analyzed. Among the 858 and 864 individuals respectively, genotyped, no significant associations between the investigated single nucleotide polymorphisms and bone mineral density measurements (T950C P = 0.50-0.64, C1217T P = 0.51-1.00), quantitative ultrasound measurements of the calcaneus, or fractures (T950C P = 0.61-0.66, C1217T P = 0.14-0.33) were found. Thus, our results show that polymorphisms in the OPG gene, one of which has previously been found to be associated with cardiovascular morphology and function, are not associated with bone mineral density in elderly Swedish women.

Genetics of intima-media thickness

PURPOSE OF REVIEW

Increased carotid artery intima-media thickness is associated with an increased risk of coronary heart disease or cerebrovascular disease and is a powerful predictor of cardiovascular and cerebrovascular outcomes. Consequently, the measurement is now used in a number of case control, cohort and familial and linkage studies as an intermediate phenotype for the investigation of the genetic and environmental determinants of atherosclerosis. The aim of this paper is to review the most recent available data on the genetic determinants of carotid intima-media thickness.

RECENT FINDINGS

Genes could account for a significant amount of variation in carotid intima-media thickness: up to 30-66%. Carotid intima-media thickness progressed more rapidly with age in familial hypercholesterolemia patients than in patients without his condition. Familial hypercholesterolemia patients with a null LDL receptor allele tended to have higher carotid intima-media thickness than patients carrying the LDL receptor defective allele. Small association studies showing positive or negative results with the angiotensinogen gene variants as well as with the angiotensin converting enzyme I/D polymorphism add to the confusion in this largely controversial area. Differing results may depend on the vascular territory and genetic background. New associations have been described in small studies.

SUMMARY

Studies on the association of polymorphisms and intima-media thickness are frequently disappointing and lead occasionally to conflicting results. Among study limitations is the fact that mostly single gene effects are considered; longitudinal cohort studies may be more appropriate than case control studies. Ongoing large prospective population studies and clinical trials have integrated the measurements of intima-media thickness and genotype determination with a genomic approach. As a result, in the near future we may see more important and robust results with significant consequences on our understanding of genetic determinants of atherosclerotic cardiovascular disease.