Association and linkage analyses of interleukin-6 gene 634C/G polymorphism and bone phenotypes in Chinese

A systematic review and cross-database analysis of single nucleotide polymorphisms underlying hip morphology and osteoarthritis reveals shared mechanisms

OBJECTIVE

Understanding the mechanisms of hip disease, such as osteoarthritis (OA), is crucial to advance their treatment. Such hip diseases often involve specific morphological changes. Genetic variations, called single nucleotide polymorphisms (SNPs), influence various hip morphological parameters. This study investigated the biological relevance of SNPs correlated to hip morphology in genome-wide association studies (GWAS). The SNP-associated genes were compared to genes associated with OA in other joints, aiming to see if the same genes play a role in both hip development and the risk of OA in other lower limb joints.

METHODOLOGY

A systematic literature review was conducted to identify SNPs correlated with hip morphology, based on the Population, Intervention, Comparison, Outcome, and Study (PICOS) framework. Afterwards, Gene Ontology (GO) analysis was performed, using EnrichR, on the SNP-associated genes and compared with non-hip OA-associated genes, across different databases.

RESULTS

Reviewing 49 GWAS identified 436 SNPs associated with hip joint morphology, encompassing variance in bone size, structure and shape. Among the SNP-associated genes, SOX9 plays a pivotal role in size, GDF5 impacts bone structure, and BMP7 affects shape. Overall, skeletal system development, regulation of cell differentiation, and chondrocyte differentiation emerged as crucial processes influencing hip morphology. Eighteen percent of GWAS-identified genes related to hip morphology were also associated with non-hip OA.

CONCLUSION

Our findings indicate the existence of multiple shared genetic mechanisms across hip morphology and OA, highlighting the necessity for more extensive research in this area, as in contrast to the hip, the genetic background on knee or foot morphology remains largely understudied.

Association of interleukin-6 (rs1800796) but not transforming growth factor beta 1 (rs1800469) with serum calcium levels in osteoporotic patients

BACKGROUND

Osteoporosis is a multifactorial disease with a strong genetic influence. Recent studies have demonstrated that cytokines, such as TGF-β1 and interleukin 6 (IL-6) play complex roles in the normal bone metabolism and pathophysiology of osteoporosis. Here, we investigated the roles of 2 polymorphisms mapping to the promoters of TGF-β1and IL-6 genes on the genetic susceptibility to osteoporosis as well as calcium and vitamin D levels.

METHODS

A cohort of 297 elderly participants in northern Iran comprising 181 osteoporotic patients (mean age ± SD, 68.36 ± 7.21 years) and 116 unrelated healthy controls (mean age ± SD, 64 ± 5.44 years) was studied for TGF-β1(C-509T) and IL-6 (G-634C) polymorphisms using PCR-RFLP method.

RESULTS

A significant relationship was observed between calcium level and IL-6 genotypes in osteoporotic males (P = 0.011) and females (P = 0.020). No significant differences were observed between osteoporotic and control groups with respect to allele frequency or genotype distribution based on the 2 selected polymorphisms under different genetic models. The results remained the same after comparing the BMD values of either the femur neck or lumbar spine with the genotypes of the elderly men and women when analyzed separately.

CONCLUSION

IL-6 genotype influences serum calcium levels in osteoporotic patients. The lack of association between the common genetic variations of TGF-β1 and IL-6 genes, and BMD highlights the complex genetic background of osteoporosis in the north of Iran.

Interleukin 6 (IL-6) and IL-10 Promoter Region Polymorphisms Are Associated with Risk of Lumbar Disc Herniation in a Northern Chinese Han Population

AIM

This study assessed the association of single-nucleotide polymorphisms (SNPs) in the proinflammatory cytokines interleukin 6 (IL-6) and IL-10 with the risk of lumbar disc herniation in a Chinese Han population.

METHODS

We collected blood samples from 267 patients with lumbar disc herniation (case group) and 300 normals (control group) and performed analyses of the IL-6 572C/G and 174G/C SNPs as well as the IL-10 592A/C and 1082G/A SNPs using TaqMan technology.

RESULTS

The frequencies of the IL-6-572 GG, GC, and CC genotypes were 5.99%, 42.3%, and 51.6%, respectively, in the case group, and 1.6%, 24%, and 64.3%, respectively, in the control group. Thus, the relative risk of the IL-6-572 G genotype (GG plus GC) was 1.69-fold higher for developing lumbar disc herniation compared to the CC genotype (95% confidence interval: 1.16-2.39, p < 0.01). The risks associated with the IL-6-572 CG and GG genotypes were 1.55- and 4.48-fold higher, respectively, versus the CC genotype for developing lumbar disc herniation (p < 0.01). The IL-10-1082 AG genotype was significantly higher in the case group (26.22%) versus the control group (11.67%); whereas the AA genotype was lower in the case group (73.78%) versus the control group (88.33%; p < 0.05). The IL-10-1082 G allele frequency was significantly higher in the case group (13.11%) versus the control group (5.83%; p < 0.05).

CONCLUSION

This study demonstrates that genetic variants in the promoter regions of the IL-6 and IL-10 genes are associated with lumbar disc herniation risk in this Northern Chinese Han population.

Genome-wide association study identifies HMGN3 locus for spine bone size variation in Chinese

Bone size (BS) is one of the major risk factors for osteoporotic fractures. BS variation is genetically determined to a substantial degree with heritability over 50%, but specific genes underlying variation of BS are still largely unknown. To identify specific genes for BS in Chinese, initial genome-wide association scan (GWAS) study and follow-up replication study were performed. In initial GWAS study, a group of 12 contiguous single-nucleotide polymorphism (SNP)s, which span a region of ~25 kb and locate at the upstream of HMGN3 gene (high-mobility group nucleosomal binding domain 3), achieved moderate association signals for spine BS, with P values ranging from 6.2E-05 to 1.8E-06. In the follow-up replication study, eight of the 12 SNPs were detected suggestive replicate associations with BS in 1,728 unrelated female Caucasians, which have well-known differences from Chinese in ethnic genetic background. The SNPs in the region of HMGN3 gene formed a tightly combined haplotype block in both Chinese and Caucasians. The results suggest that the genomic region containing HMGN3 gene may be associated with spine BS in Chinese.

A susceptible haplotype within APOE gene influences BMD and intensifies the osteoporosis risk in postmenopausal women of Northwest India

BACKGROUND

The association of apolipoprotein E (APOE) genotypes with bone mineral density (BMD) and risk of osteoporosis have remained unclear. The influence of APOE gene polymorphisms on BMD as genetic mediators of osteoporosis risk needs to be explored in Indian postmenopausal females where this disease is rising rampantly.

METHODS AND RESULTS

The present study investigated the role and relevance of four pertinent APOE single nucleotide polymorphisms: 5'UTR G/C (rs440446), Int2 G/A (rs769450), Exon4 T/C (rs429358), Exon4C/T (rs7412) in DEXA verified 133 osteoporotic, 57 osteopenic and 83 normal postmenopausal females of India, who were not taking hormone replacement therapy. Minor allele frequencies of rs440446 and rs429358 were higher in osteoporotic females (0.31, 0.18) than osteopenic (0.29, 0.15) and females having normal bone mass (0.16, 0.07). Disease association analysis revealed a susceptibility haplotype CGTC (in order of rs440446, rs769450, rs429358, rs7412) and the carriers of this haplotype has higher risk of osteopenia (OR 3.53, 95% CI 1.21-11.0, P=0.017) and osteoporosis (OR 3.61, 95% CI 1.53-9.48, P=0.002) after adjusting the confounding effect of age, BMI and years since menopause. Females who possess either one copy or two copies of the haplotype have lesser BMD values of lumbar spine (0.88 and 0.85 g/cm(2)) and femoral neck (0.84 and 0.82 g/cm(2)) than those females who possess zero copy (0.9 and 0.87 g/cm(2), respectively).

CONCLUSIONS

The present study exposed a susceptibility haplotype CGTC, within APOE gene, which was found to be associated with BMD and risk of osteopenia and osteoporosis in postmenopausal females of India.

Interactions of interleukin-6 gene polymorphisms with calcium intake and physical activity on bone mass in pre-menarche Chinese girls

This study assessed independent associations and interactions of IL-6 promoter alleles (-174G/C and -634C/G), calcium intake and physical activity with bone mass among pre-menarche Chinese girls. The -634 CC carriers, greater calcium intake and physical activity were associated with better bone mass. The gene-bone association was more pronounced among girls with high physical activity or with low calcium intake.

INTRODUCTION

The association between interleukin (IL)-6 promoter polymorphisms and bone mass remains in debate. This cross-sectional study examined the association between the IL-6 promoter alleles (-174G/C and -634C/G) and bone mass, and assessed if the association could be modified by calcium intake or physical activity in pre-menarche Chinese girls.

METHODS

Two-hundred and twenty-eight healthy pre-menarche girls aged 9-11 years were recruited from primary schools in Guangzhou, China by sending letters to parents. None of them had diseases or medications known to affect bone metabolism. The IL-6 promoter genotypes were determined by PCR-RFLP, and BMD and BMC at the total body, lumbar spine, total hip and femoral neck were measured by DXA. Calcium intake and physical activity were assessed by face-to-face questionnaire interview.

RESULTS

One hundred and seventy-six subjects completed the entire study. We did not detect gene polymorphism at the IL-6 -174G/C locus, all were GG homozygotes. The IL-6 -634C/G polymorphism was significantly associated with both BMD and BMC even after adjusting for age and weight. Girls with CC genotype had higher levels of BMC and BMD than G allele carriers (+8.3% for the total body BMC, and +2.9%, +5.8%, and +5.7% for BMDs at the total body, total hip, and femoral neck, respectively; P < 0.05). The favorable effect of physical activity on BMDs at the total hip and femoral neck was much more pronounced in CC carriers than in G allele carriers, and the CC genotype associated higher BMDs at the total hip and femoral neck were observed only in girls with high level physical activity (P for interactions = 0.036 and 0.021, adjusted for age and weight). Calcium had a more benefit to the total body BMC in G allele carriers than in CC carriers, and the G allele-associated lower total body BMC was found only in subjects with low calcium intake.

CONCLUSION

The IL-6 -634C/G polymorphism was significantly associated with BMD and the association might be modified by calcium intake or physical activity in pre-menarche Chinese girls.

Molecular genetic studies of gene identification for osteoporosis

This review comprehensively summarizes the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of September 2007. It is intended to constitute a sequential update of our previously published reviews covering the available data up to the end of 2004. Evidence from candidate gene-association studies, genome-wide linkage and association studies, as well as functional genomic studies (including gene-expression microarray and proteomics) on osteogenesis and osteoporosis, are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. The major results of all studies are tabulated for comparison and ease of reference. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.

Interaction of interleukin-6 and estrogen receptor gene polymorphisms on bone mass accrual in Chinese adolescent girls

We assessed the main and interaction effects of interleukin-6 and estrogen receptor gene polymorphisms on bone mass accrual in Chinese adolescent girls. A total of 228 premenarche Chinese girls (9-11.5 years old) were recruited for a 2-year follow-up study. Bone mineral density (BMD) at the total body, lumbar spine (L1-L4), and total left hip were measured by dual-energy X-ray absorptiometry at baseline and follow-up. The -174G/C and -634C/G polymorphism of IL-6 gene, and PvuII and XbaI polymorphisms of the estrogen receptor (ER)-alpha gene, were determined. The -634C/G polymorphism of the IL-6 gene and PvuII polymorphism of ER-alpha gene were significantly associated with bone mass accrual after adjusting the potential confounding factors. Girls with pp genotype of ER-alpha gene had greater percentage accrual in BMD of total body (P = 0.010) and femoral intertrochanter (P = 0.038) than their PP and Pp counterparts. Girls with CC genotype of IL-6 -634G/C gene had higher percentage accrual in BMD of total body (P = 0.032) and femoral trochanter (P = 0.048) than their CG + GG counterparts. Significant interaction effects of IL-6 -634C/G polymorphism and ER-alpha PvuII polymorphism were observed on percentage change in BMD of total left hip (P = 0.009) and femoral intertrochanter (P = 0.007). The genotype CC (IL-6 -634C/G) x pp (ER-alpha PvuII) was associated with greater BMD accrual than other genotype combination in Chinese adolescent girls. We found that the IL-6 -634C/G and ER-alpha PvuII polymorphism were significantly associated with BMD accrual and that they have an interactional effect on BMD accrual in Chinese adolescent girls.