A significant association exists between receptor tyrosine kinase-like orphan receptor 2 gene variants and the OPG/RANKL ratio in human plasma

SUMMARY

There is a paucity of studies investigating association between ROR2 gene variants and osteoporosis and osteoarthritis-related phenotypes. The published literature suggests that osteoprotegerin (OPG) and receptor activator of nuclear factor-kB ligand (RANKL) are essential for bone metabolism and correlate with osteoarthritis manifestation and progression. The present study provides evidence of the significant association between ROR2 variants and the OPG/RANKL ratio in human plasma. The present results also suggest significant association between ROR2 polymorphisms and severity of radiographic hand osteoarthritis.

INTRODUCTION

Despite the importance of the ROR-2 in skeletal physiology, there is a paucity of studies investigating the potential association of ROR2 gene variants with phenotypes relevant to osteoporosis and osteoarthritis. On the other hand, there is a considerable body of literature suggesting that OPG and RANKL and their ratio (OPG/RANKL) are essential for regulating bone resorption. This is also correlated with osteoarthritis manifestation and progression. The present study therefore examines whether ROR2 polymorphisms may be associated with the OPG/RANKL ratio and hand osteoarthritis (HOA).

METHODS

The study was conducted in a family-based sample of 1,515 Caucasian individuals, assessed for radiographic hand osteoarthritis, using the Kellgren/Lawrence score. Of these, 865 individuals were genotyped for 19 SNPs, relatively equally covering the ROR2 locus, and their plasma levels of OPG and RANKL were assayed. The association between the selected SNPs and OPG, along with the OPG/RANKL ratio and HOA, was explored using the pedigree disequilibrium test.

RESULTS

Of the total of 57 tests, 16 nominally significant results (p < 0.05) were obtained, which is considerably more than the three normally expected for type I error. The significant association signals for all three phenotypes were mapped to the intron 1 region. The most significant results were detected between OPG/RANKL and rs7048756 (p < 0.0005) and between adjacent rs4744107 and Kellgren/Lawrence score (p = 0.006).

CONCLUSIONS

The present study provides evidence of the significant association between ROR2 variants and the OPG/RANKL ratio in human plasma and also suggests ROR2 association with HOA.

Quantitative genetic study of the circulating osteopontin in community-selected families

The study assessed contribution of genetic factors to variability of osteopontin (OPN) levels. Evidence of association of OPN levels with polymorphisms in its structural gene and integrin-binding sialoprotein gene loci was obtained. The results motivate research of OPN-related proteins and genes with respect to biomineralization and other biological processes.

INTRODUCTION

OPN is a major phosphoprotein in bone, which plays key role in regulation of bone mineralization process. It is considered as a promising biomarker for osteoarthritis and osteoporosis, and various other pathological conditions. However, the contribution of genetics and other confounding factors to OPN circulating levels variation in general population has never been specifically determined. The main aims of the present study included (1) evaluation of the putative genetic and familial factors' effect on OPN variability and (2) testing the hypothesis that OPN plasma levels are associated with the genetic polymorphisms in its structural gene locus (SPP1) and in integrin-binding sialoprotein gene locus (IBSP).

METHODS

To address these questions, we used a family-based sample of 925 apparently healthy Caucasian individuals. Association of OPN levels with three SNPs in each of the two selected gene loci was explored using pedigree disequilibrium tests.

RESULTS

Some 58% and 13% of the OPN levels variability were attributable to genetic factors and common spouse environment, respectively. Three SNPs showed nominally significant association with OPN (p < 0.05). Of these, rs2616262 linked to IBSP promoter region remained significant after correction for multiple testing (p = 0.003). Significant association of this SNP and rs10516799 (distal segment of SPP1) with OPN was confirmed in several statistical tests. Using a special modification of variance component analysis, we examined gene-gene and gene-sex interaction effects, but found non-significant confirmation for these hypotheses.

CONCLUSIONS

Further studies are required to confirm the observed results and to explore the underlying molecular and physiological mechanisms.

Quantitative genetic study of amphiregulin and fractalkine circulating levels--potential markers of arthropathies

OBJECTIVE

Amphiregulin (AREG) and Fractalkine (FRACT), are involved in a variety of normal and pathological processes, and are both suggested to be relevant to joint degeneration. The aims of the present study included (1) testing association between circulating levels of these biomarkers and joint pathologies, (2) evaluation of the putative genetic and familial factors' effect on AREG and FRACT variability.

DESIGN

The study was conducted in the family-based sample of 923 Caucasian individuals. Variance component analysis was used to assess contribution of genetic and environmental factors to variability of AREG and FRACT concentration.

RESULTS

The mean levels of FRACT were significantly higher in the affected group with arthropathies (synovial joints osteoarthritis (OA) and disc degenerative disease, DDD) then in the control group (P<0.0004). Circulating AREG levels were higher in DDD (P=0.0272). Genetic factors constituted the main source of the interindividual differences of the AREG and FRACT levels in our sample, and explained 29.68% and 41.68% of the total variation, respectively. The phenotypic correlation between AREG and FRACT was substantial (r=0.55, P=0.0001) and was associated with both common genetic and environmental factors. Specifically, 30% of the phenotypic correlation between AREG and FRACT was due to common genetic effects.

CONCLUSIONS

Further studies are required to assess relevancy of FRACT to clinical diagnosis and prognosis of arthropathies, to investigate the mechanisms behind the observed phenotypic and genetic covariation among the studied biomarkers, and to explore specific genetic polymorphisms affecting AREG and FRACT variation.

Morphological and biochemical features of obesity are associated with mineralization genes' polymorphisms

BACKGROUND

Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) was recently extensively studied as a candidate gene for obesity phenotypes. As the human homologue of the mouse progressive ankylosis (ANKH) and alkaline phosphatase (ALPL) are known functional partners of ENPP1 in bone mineralization, we hypothesized that these genes may also be jointly involved in determining obesity features.

AIM

To examine the effects of the three genes, possible gene-sex and gene-gene interactions on variability of four obesity phenotypes: the body mass index (BMI), the waist-hip ratio (WHR), the epidermal growth factor receptor (EGFR), and leptin.

SUBJECTS AND METHODS

In all, 962 healthy individuals from 230 families were genotyped for 45 single nucleotide polymorphisms (SNPs). The association analysis was performed using two family based association tests (family based association test and pedigree disequilibrium test). The combined P-values of the two tests were estimated by Monte-Carlo simulations. Relative magnitude of the genetic and familial effects, gene-sex and gene-gene interactions were assessed using variance component models.

RESULTS

Associations were observed between ENPP1 polymorphisms and BMI (P=0.0037) and leptin (P=0.0068). ALPL markers were associated with WHR (P=0.0026) and EGFR (P=0.0001). The ANKH gene was associated with all four studied obesity-related traits (P<0.0184), and its effects were modulated by sex. Gene-gene interactions were not detected.

CONCLUSION

The observed pattern of association signals indicates that ANKH may have a generalized effect on adipose tissue physiology, whereas ENPP1 and ALPL affect distinct obesity features. The joint analysis of related genes and integration of the results obtained by different methods used in this research should benefit other studies of similar design.

Genetic determination of head-size-related anthropometric traits in an ethnically homogeneous sample of 373 Indian pedigrees of West Bengal

The substantial involvement of genetic factors in the determination of head-size and head-shape traits has been firmly established. However, there has been a lack of agreement on a number of specific issues concerning the pattern of inheritance of craniofacial features. In this study we examined some of these issues in a large, ethnically homogeneous sample of Indian pedigrees. The data included 1,263 individuals belonging to 373 nuclear families. Eleven raw head-size traits and two synthetic phenotypes, interpreted as horizontal and vertical head-size components (HOC and VEC, respectively), were used in the analysis. To establish the pattern of inheritance of head traits, we carried out univariate and bivariate analyses. Maximum heritability estimates ranged from 0.41 to 0.83 for the studied head-size phenotypes. The portion of the total residual variance attributable to putative additive genetic factors was 68.3% and 70.3% for HOC and VEC, respectively, and common familial factor effects were found to be nonsignificant. The extent of genetic influences did not differ significantly with respect to sex or between HOC and VEC. The results of bivariate variance decomposition analysis strongly suggest the existence of common genetic factors simultaneously affecting HOC and VEC; 41.8% of the two traits' total residual variance was attributable to the effect of these common genetic factors.

Family-based association study of polymorphisms in the RUNX2 locus with hand bone length and hand BMD

Osteoporosis is characterized by reduced bone strength. Bone size and bone mineral density (BMD) are major bone strength determinants. Identification of genes affecting the variability of these traits should improve prognosis and management of osteoporosis. This research was aimed to test the hypothesis of association of radiographic hand bone length (BL) and BMD with polymorphisms in the RUNX2 locus. Four SNPs linked to the two RUNX2 promoters were genotyped in 212 nuclear Caucasian families. These SNPs and four pairwise haplotypes were tested for association with eight BL and BMD traits, adjusted for covariates. We observed significant associations between polymorphisms linked to the RUNX2 P1 promoter and BL mean values for three studied bone groups: all 18 bones, proximal and medial bones (p = 0.0118, 0.0085, and 0.0056, respectively). Mean BMD values for all 18 bones, proximal and medial bones were associated with polymorphisms linked to the RUNX2 P2 promoter (p = 0.0032, 0.0077, 0.0007, respectively). Associations with BL and BMD mean values for medial and proximal bones remained significant even after correction for multiple testing. This study provides evidence of the association between polymorphisms linked to the two RUNX2 promoters and variability of hand BL and BMD. The results suggest independent roles for the two RUNX2 promoters in the determination of the traits studied.

Family-based association study of ROR2 polymorphisms with an array of radiographic hand bone strength phenotypes

For the first time the study provides evidence of association of radiographic hand bone length (BL) and bone mineral density (BMD) with polymorphisms in ROR2 gene that plays important role in skeletal development. This contributes to better understanding of bone physiology and may have application in clinical practice.

INTRODUCTION AND HYPOTHESIS

Bone size and bone mineral density (BMD) are major determinants of bone strength. Identification of genes affecting these traits' variability is important for better understanding of normal and pathological bone physiology and identification of the individuals at risk for bone fracture. This study tested the hypothesis of association of radiographic hand bone length (BL) and BMD with polymorphisms in ROR2 gene that is important in skeletal development.

METHODS

Nineteen ROR2 SNPs were genotyped in 705 individuals, belonging to 212 nuclear families. The four tagging SNPs (tSNPs) and the pairwise haplotypes between adjacent tSNPs were tested for association with series of hand BL and BMD measurements, adjusted for covariates, using family-based association tests.

RESULTS

We observed significant associations with BL and BMD mean values for all 18 studied hand bones (p = 0.0080, 0.0030), mean BL and BMD for proximal phalanges (p = 0.0218, 0.0060) and metacarpal bones (p = 0.0014, 0.0004). In the latter, the association remained significant after correction for multiple testing.

CONCLUSIONS

The region of the first through the second ROR2 introns is most likely to contain the functional polymorphism/s responsible for the observed associations. Further studies are required to identify the ROR2 functional polymorphism/s affecting bone size and BMD variation.

Pulmonary artery catheterization

After two decades, hemodynamic invasive monitoring using a flow-directed, balloon-tipped, pulmonary artery (PA) catheter has established itself as a significant component of acute clinical care. In spite of continued recommendations for limitations, restrictions, moratoria, and even abandonment, growth in catheter use continues. Attempts to replace it by competing technologies for routine clinical practice have not been successful thus far. More than one million PA catheters are inserted in the United States annually. The clinical utility and value of the pulmonary artery catheter depend largely on the interpretation of information obtained. Clinical interpretation of data is influenced by an understanding of cardiopulmonary hemodynamics, technical skills, and professional integrity of the physician using the device. After a brief history, this article focuses on the technical aspects of the insertion procedure, choice of hardware, and acquisition and analysis of information. Indications, contraindications, and clinical utility are briefly described. Major complications from PA catheterization reported in the literature since clinical introduction of the catheter are summarized.