Identification of a Copy Number Variation on Chromosome 20q13.12 Associated with Osteoporotic Fractures in the Korean Population

Osteoporotic fractures (OFs) are critical hard outcomes of osteoporosis and are characterized by decreased bone strength induced by low bone density and microarchitectural deterioration in bone tissue. Most OFs cause acute pain, hospitalization, immobilization, and slow recovery in patients and are associated with increased mortality. A variety of genetic studies have suggested associations of genetic variants with the risk of OF. Genome-wide association studies have reported various single-nucleotide polymorphisms and copy number variations (CNVs) in European and Asian populations. To identify CNV regions associated with OF risk, we conducted a genome-wide CNV study in a Korean population. We performed logistic regression analyses in 1,537 Korean subjects (299 OF cases and 1,238 healthy controls) and identified a total of 8 CNV regions significantly associated with OF (p < 0.05). Then, one CNV region located on chromosome 20q13.12 was selected for experimental validation. The selected CNV region was experimentally validated by quantitative polymerase chain reaction. The CNV region of chromosome 20q13.12 is positioned upstream of a family of long non-coding RNAs, LINC01260. Our findings could provide new information on the genetic factors associated with the risk of OF.

Response: Genome-Wide Association Study Identifies Two Novel Loci with Sex-Specific Effects for Type 2 Diabetes Mellitus and Glycemic Traits in a Korean Population (Diabetes Metab J 2014;38:375-87)

No abstract available.

Genome-Wide Association Study Identifies Two Novel Loci with Sex-Specific Effects for Type 2 Diabetes Mellitus and Glycemic Traits in a Korean Population

BACKGROUND: Until recently, genome-wide association study (GWAS)-based findings have provided a substantial genetic contribution to type 2 diabetes mellitus (T2DM) or related glycemic traits. However, identification of allelic heterogeneity and population-specific genetic variants under consideration of potential confounding factors will be very valuable for clinical applicability. To identify novel susceptibility loci for T2DM and glycemic traits, we performed a two-stage genetic association study in a Korean population. METHODS: We performed a logistic analysis for T2DM, and the first discovery GWAS was analyzed for 1,042 cases and 2,943 controls recruited from a population-based cohort (KARE, n=8,842). The second stage, de novo replication analysis, was performed in 1,216 cases and 1,352 controls selected from an independent population-based cohort (Health 2, n=8,500). A multiple linear regression analysis for glycemic traits was further performed in a total of 14,232 nondiabetic individuals consisting of 7,696 GWAS and 6,536 replication study participants. A meta-analysis was performed on the combined results using effect size and standard errors estimated for stage 1 and 2, respectively. RESULTS: A combined meta-analysis for T2DM identified two new (rs11065756 and rs2074356) loci reaching genome-wide significance in CCDC63 and C12orf51 on the 12q24 region. In addition, these variants were significantly associated with fasting plasma glucose and homeostasis model assessment of beta-cell function. Interestingly, two independent single nucleotide polymorphisms were associated with sex-specific stratification in this study. CONCLUSION: Our study showed a strong association between T2DM and glycemic traits. We further observed that two novel loci with multiple diverse effects were highly specific to males. Taken together, these findings may provide additional insights into the clinical assessment or subclassification of disease risk in a Korean population.

Identification of a genetic locus on chromosome 4q34-35 for type 2 diabetes with overweight

The incidence of type 2 diabetes is rising rapidly because of an increase in the incidence of being overweight and obesity. Identification of genetic determinants for complex diseases, such as type 2 diabetes, may provide insight into disease pathogenesis. The aim of the study was to investigate the shared genetic factors that predispose individuals to being overweight and developing type 2 diabetes. We conducted genome-wide linkage analyses for type 2 diabetes in 386 affected individuals (269 sibpairs) from 171 Korean families and association analyses with single-nucleotide polymorphisms of candidate genes within linkage regions to identify genetic variants that predispose individuals to being overweight and developing type 2 diabetes. Through fine-mapping analysis of chromosome 4q34-35, we detected a locus potentially linked (nonparametric linkage 2.81, logarithm of odds 2.27, P=6 x 10-4) to type 2 diabetes in overweight or obese individuals (body mass index, BMI> or =23 kg m-2). Multiple regression analysis with type 2 diabetes-related phenotypes revealed a significant association (false discovery rate (FDR) P=0.006 for rs13144140; FDR P=0.002 for rs6830266) between GPM6A (rs13144140) and BMI and waist-hip ratio, and between NEIL3 (rs6830266) and insulin level from 1314 normal individuals. Our systematic search of genome-wide linkage and association studies, demonstrate that a linkage peak for type 2 diabetes on chromosome 4q34-35 contains two type 2 diabetes-related genes, GPM6A and NEIL3.

Genome-Wide Association Study of Liver Enzymes in Korean Children

Liver enzyme elevations, as an indicator of liver function, are widely associated with metabolic diseases. Genome-wide population-based association studies have identified a genetic susceptibility to liver enzyme elevations and their related traits; however, the genetic architecture in childhood remains largely unknown. We performed a genome-wide association study to identify new genetic loci for liver enzyme levels in a Korean childhood cohort (n = 484). We observed three novel loci (rs4949718, rs80311637, and rs596406) that were multiply associated with elevated levels of alanine transaminase and aspartate transaminase. Although there are some limitations, including genetic power, additional replication and functional characterization will support the clarity on the genetic contribution that the ST6GALNAC3, ADAMTS9, and CELF2 genes have in childhood liver function.

Interaction Effects of Lipoprotein Lipase Polymorphisms with Lifestyle on Lipid Levels in a Korean Population: A Cross-sectional Study

Lipoprotein lipase (LPL) plays an essential role in the regulation of high-density lipoprotein cholesterol (HDLC) and triglyceride levels, which have been closely associated with cardiovascular diseases. Genetic studies in European have shown that LPL single-nucleotide polymorphisms (SNPs) are strongly associated with lipid levels. However, studies about the influence of interactions between LPL SNPs and lifestyle factors have not been sufficiently performed. Here, we examine if LPL polymorphisms, as well as their interaction with lifestyle factors, influence lipid concentrations in a Korean population. A two-stage association study was performed using genotype data for SNPs on the LPL gene, including the 3' flanking region from 7,536 (stage 1) and 3,703 (stage 2) individuals. The association study showed that 15 SNPs and 4 haplotypes were strongly associated with HDLC (lowest p = 2.86 x 10(-22)) and triglyceride levels (lowest p = 3.0 x 10(-15)). Interactions between LPL polymorphisms and lifestyle factors (lowest p = 9.6 x 10(-4)) were also observed on lipid concentrations. These findings suggest that there are interaction effects of LPL polymorphisms with lifestyle variables, including energy intake, fat intake, smoking, and alcohol consumption, as well as effects of LPL polymorphisms themselves, on lipid concentrations in a Korean population.

Interaction Effects of Lipoprotein Lipase Polymorphisms with Lifestyle on Lipid Levels in a Korean Population: A Cross-sectional Study

Lipoprotein lipase (LPL) plays an essential role in the regulation of high-density lipoprotein cholesterol (HDLC) and triglyceride levels, which have been closely associated with cardiovascular diseases. Genetic studies in European have shown that LPL single-nucleotide polymorphisms (SNPs) are strongly associated with lipid levels. However, studies about the influence of interactions between LPL SNPs and lifestyle factors have not been sufficiently performed. Here, we examine if LPL polymorphisms, as well as their interaction with lifestyle factors, influence lipid concentrations in a Korean population. A two-stage association study was performed using genotype data for SNPs on the LPL gene, including the 3' flanking region from 7,536 (stage 1) and 3,703 (stage 2) individuals. The association study showed that 15 SNPs and 4 haplotypes were strongly associated with HDLC (lowest p = 2.86 x 10(-22)) and triglyceride levels (lowest p = 3.0 x 10(-15)). Interactions between LPL polymorphisms and lifestyle factors (lowest p = 9.6 x 10(-4)) were also observed on lipid concentrations. These findings suggest that there are interaction effects of LPL polymorphisms with lifestyle variables, including energy intake, fat intake, smoking, and alcohol consumption, as well as effects of LPL polymorphisms themselves, on lipid concentrations in a Korean population.

Effect of Genetic Predisposition on Blood Lipid Traits Using Cumulative Risk Assessment in the Korean Population

Dyslipidemia, mainly characterized by high triglyceride (TG) and low high-density lipoprotein cholesterol (HDL-C) levels, is an important etiological factor in the development of cardiovascular disease (CVD). Considering the relationship between childhood obesity and CVD risk, it would be worthwhile to evaluate whether previously identified lipid-related variants in adult subjects are associated with lipid variations in a childhood obesity study (n = 482). In an association analysis for 16 genome-wide association study (GWAS)-based candidate loci, we confirmed significant associations of a genetic predisposition to lipoprotein concentrations in a childhood obesity study. Having two loci (rs10503669 at LPL and rs16940212 at LIPC) that showed the strongest association with blood levels of TG and HDL-C, we calculated a genetic risk score (GRS), representing the sum of the risk alleles. It has been observed that increasing GRS is significantly associated with decreased HDL-C (effect size, -1.13 +/- 0.07) compared to single nucleotide polymorphism combinations without two risk variants. In addition, a positive correlation was observed between allelic dosage score and risk allele (rs10503669 at LPL) on high TG levels (effect size, 10.89 +/- 0.84). These two loci yielded consistent associations in our previous meta-analysis. Taken together, our findings demonstrate that the genetic architecture of circulating lipid levels (TG and HDL-C) overlap to a large extent in childhood as well as in adulthood. Post-GWAS functional characterization of these variants is further required to elucidate their pathophysiological roles and biological mechanisms.

Effect of Genetic Predisposition on Blood Lipid Traits Using Cumulative Risk Assessment in the Korean Population

Dyslipidemia, mainly characterized by high triglyceride (TG) and low high-density lipoprotein cholesterol (HDL-C) levels, is an important etiological factor in the development of cardiovascular disease (CVD). Considering the relationship between childhood obesity and CVD risk, it would be worthwhile to evaluate whether previously identified lipid-related variants in adult subjects are associated with lipid variations in a childhood obesity study (n = 482). In an association analysis for 16 genome-wide association study (GWAS)-based candidate loci, we confirmed significant associations of a genetic predisposition to lipoprotein concentrations in a childhood obesity study. Having two loci (rs10503669 at LPL and rs16940212 at LIPC) that showed the strongest association with blood levels of TG and HDL-C, we calculated a genetic risk score (GRS), representing the sum of the risk alleles. It has been observed that increasing GRS is significantly associated with decreased HDL-C (effect size, -1.13 +/- 0.07) compared to single nucleotide polymorphism combinations without two risk variants. In addition, a positive correlation was observed between allelic dosage score and risk allele (rs10503669 at LPL) on high TG levels (effect size, 10.89 +/- 0.84). These two loci yielded consistent associations in our previous meta-analysis. Taken together, our findings demonstrate that the genetic architecture of circulating lipid levels (TG and HDL-C) overlap to a large extent in childhood as well as in adulthood. Post-GWAS functional characterization of these variants is further required to elucidate their pathophysiological roles and biological mechanisms.

Association of an Anti-inflammatory Cytokine Gene IL4 Polymorphism with the Risk of Type 2 Diabetes Mellitus in Korean Populations

Chronic inflammation has been implicated as one of the important etiological factors in insulin resistance and type 2 diabetes mellitus (T2DM). To investigate the role of anti-inflammatory cytokines in the development of T2DM, we conducted a case-control study to assess the association between IL4/IL4R polymorphisms and disease risk. We firstly identified single nucleotide polymorphisms (SNP) at IL4 and IL4RA loci by sequencing the loci in Korean participants. Case-control studies were conducted by genotyping the SNPs in 474 T2DM cases and 470 non-diabetic controls recruited from community-based cohorts. Replication of the associated signals was performed in 1,216 cases and 1,352 controls. We assessed effect of IL4-IL4RA interaction on T2DM using logistic regression method. The functional relevance of the SNP associated with disease risk was determined using a reporter expression assay. We identified a strong association between the IL4 promoter variant rs2243250 and T2DM risk (OR=0.77; 95% CI, 0.67~0.88; p=1.65x10-4 in the meta-analysis). The reporter gene expression assay demonstrated that the presence of rs2243250 might affect the gene expression level with ~1.5-fold allele difference. Our findings contribute to the identification of IL4 as a T2D susceptibility locus, further supporting the role of anti-inflammatory cytokines in T2DM disease development.

Genome-wide Association Study Identified TIMP2 Genetic Variant with Susceptibility to Osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disorder in the elderly population. To identify OA-associated genetic variants and candidate genes, we conducted a genome-wide association study (GWAS). A total 3,793 samples (476 cases: wrist + knee and 3317 controls) from a community-based epidemiological study were genotyped using the Affymetrix SNP 5.0. An intronic SNP (rs4789934) in the TIMP2 (tissue inhibitor of metalloproteinase-2) showed the most significance with OA (odd ratio [OR] = 2.06, 95% confidence interval [CI] = 1.52-2.81, p = 4.01 x 10(-6)). Furthermore, a polymorphism (rs1352677) in the NKAIN2 (Na+/K+ transporting ATPase interacting 2) was suggestively associated with OA (OR = 1.43, CI = 1.22-1.66, p = 7.01 x 10(-6)). The present study provides new insights into the identification of genetic predisposing factors for OA.

Genome-wide Survey of Copy Number Variants Associated with Blood Pressure and Body Mass Index in a Korean Population

Hypertension is the major factor of most death and high blood pressure (BP) can lead to stroke, myocardial infarction and cardiac failure. Moreover, hypertension is strongly correlated with body mass index (BMI). Although the exact causes of hypertension are still unclear, some of genetic loci were discovered from genome-wide association study (GWAS). Therefore, it is essential to study genetic variation for finding more genetic factor affecting hypertension. The purpose of our study is to conduct a CNV association study for hypertension-related traits, BP and BMI, in Korean individuals. We identified 2,206 CNV regions from 3,274 community-based Korean participants using the Affymetrix Genome-Wide Human SNP Array 6.0 platform and performed a logistic regression analysis of CNVs with two hypertension-related traits, BP and BMI. Moreover, the 4,692 participants in an independent cohort were selected for respective replication analyses. GWAS of CNV identified two loci encompassing previously known hypertension-related genes: LPA (lipoprotein) on 6q26, and JAK2 (Janus kinase 2) on 9p24, with suggestive p-values (0.0334 for LPA and 0.0305 for JAK2). These two positive findings, however, were not evaluated in the replication stage. Our result confirmed the conclusion of CNV study from the WTCCC suggesting weak association with common diseases. This is the first study of CNV association study with BP and BMI in Korean population and it provides a state of CNV association study with common human diseases using SNP array.

Genome-wide Association Study Identification of a New Genetic Locus with Susceptibility to Osteoporotic Fracture in the Korean Population

Osteoporotic fracture (OF), along with bone mineral density (BMD), is an important diagnostic parameter and a clinical predictive risk factor in the assessment of osteoporosis in the elderly population. However, a genomewide association study (GWAS) on OF has not yet been clarified sufficiently. To identify OF-associated genetic variants and candidate genes, we conducted a GWAS in a population-based cohort (Korean Association Resource [KARE], n=1,427 [case: 288 and control: 1139]) and performed a de novo replication study in hospital-based individuals (Asan and Catholic Medical Center [ACMC], n=1,082 [case: 272 and control: 810]). In a combined meta-analysis, a newly identified genetic locus in an intergenic region at 10p11.2 (near genes FZD8 and ANKRD30A ) showed the most significant association (odd ratio [OR] = 2.00, 95% confidence interval [CI] = 1.47~2.74, p=1.27x10(-5)) in the same direction. We provide the first evidence for a common genetic variant influencing OF and genetic information for further investigation in bone metabolism.

Identification of Genetic Variations in CBL, SORBS1, CRK, and RHOQ,Key Modulators in the CAP/TC10 Pathway of Insulin Signal Transduction and Their Association with Type 2 Diabetes Mellitus in the Korean Population

Recent evidence has strongly suggested that the CAP/TC10 pathway is involved in the trafficking, docking,and fusion of vesicles containing the insulin- responsive glucose transporter Glut4 to the plasma membrane. However, little is known about how the genes employed in the CAP/TC10 pathway are associated with the development of type 2 diabetes mellitus. In this study, we sequenced 4 genes of the CAP/TC10 pathway [SORBS1, CBL, CRK, and RHOQ] in 24 individuals to identify genetic variations in these loci. A total of 48 sequence variants were identified, including 23 novel variations. To investigate the possible association with type 2 diabetes mellitus, 3 single nucleotide polymorphisms from SORBS1, 3 from CBL , and 4 from RHOQ were genotyped in 1122 Korean type 2 diabetic patients and 1138 nondiabetic controls. Using logistic regression analysis, 1 significant association between SNP rs1376405 in RHOQ and type 2 diabetes mellitus [OR = 8.714 (C.I. 1.714-44.29), p = 0.009] was found in the recessive model. Our data demonstrate a positive association of the RHOQ gene in the CAP/TC10 pathway with T2DM in the Korean population.

Association between Single Nucleotide Polymorphisms of the Fibrinogen Alpha Chain (FGA) Gene and Type 2 Diabetes Mellitus in the Korean Population

Fibrinogen alpha chain (FGA), a subunit of fibrinogen, might be a potential player for type 2 diabetes mellitus (T2DM), since the plasma levels of fibrinogen is known to be related to the incidence of T2DM. To elucidate the potential role of FGA in T2DM, we investigated whether FGA genetic variations are relevant in T2DM in the Korean population. Seven FGA single nucleotide polymorphisms (SNPs) were genotyped in Ansung and Ansan cohorts (474 T2DM subjects and 470 normal controls) in Korea. The association between SNPs and T2DM was determined by logistic regression analysis. Genetic relevance of SNPs to T2DM-related phenotypes was investigated by multiple linear regression analysis. Statistical analysis revealed that among seven FGA SNPs, significant associations with T2DM were observed in FGA rs2070011 (p=0.013-0.034, OR=0.72~ 0.79), rs6050 (p=0.026~0.048, OR=1.24~1.37), and rs2070022 (p=0.016~0.039, OR=0.70~0.72). Two SNPs, rs2070011 and rs6050, also showed significant association with T2DM-related phenotypes such as triglyceride (p=0.005~0.011 for rs2070011 and p=0.003~0.008 for rs6050), total cholesterol (p=0.01 for rs2070011 and p=0.024 for rs6050) and fasting glucose (p=0.035~ 0.036 for rs2070011 and p=0.048 for rs6050) in 470 normal controls. Our association study implies that FGA might be an important genetic factor in T2DM pathogenesis in the Korean population by affecting plasma lipid and glucose levels.

Association of Common Vitamin D Receptor Gene Variations with Fracture Risk and Bone Mineral Density in Postmenopausal Korean Population

Osteoporosis is characterized by impaired osteogenesis. BMD is a major determinant of bone strength. The role of the VDR gene in predisposition to primary osteoporosis has been recognized. However, population-based case-control studies have been reported controversial results for known candidate genes in an ethnically distinct group. To determine the genetic effects of VDR variants on osteoporosis and BMD, we directly sequenced the VDR gene in 24 unrelated Korean individuals and identified eighteen sequence variants. We investigated the potential involvement of eight SNPs in osteoporosis in postmenopausal women (n = 729). Two SNPs (LD) in intron 2, -5294G > C (rs2238135) and -4817G > A (rs17882443) showed the evidence of association with enhanced BMD of the femoral neck (p(additive) =0.031 for rs2238135; p(additive)=0.017 and p(dominant)= 0.019 for 17882443). Moreover, VDR -4817G > A was significantly associated with protective effect on all fracture risk (p(recessive)=0.035, OR=0.2, 95% CI=0.05~0.89), and tended to be higher BMD values at various proximal femur sites. Therefore, we suggest that the -4817G > A may be useful genetic marker for vitamin D-related metabolism and may have an important role in the increased BMD of the proximal femur in postmenopausal Korean women.

Association of lipoprotein lipase (LPL) single nucleotide polymorphisms with type 2 diabetes mellitus

The etiology and pathogenesis of type 2 diabetes mellitus (T2DM) are not completely understood although it is often associated with other conditions such as obesity, hypertension, and dyslipidemia. Lipoprotein lipase (LPL) is a key enzyme in human lipid metabolism that facilitates the removal of triglyceride-rich lipoproteins from the bloodstream. LPL hydrolyzes the core of triglyceride-rich lipoproteins (chylomicrons and very low density lipoprotein) into free fatty acids and monoacylglycerol. To gain insight into the possible role of LPL in T2DM, nine single nucleotide polymorphisms (SNPs) of LPL were analyzed for the association with T2DM using 944 unrelated Koreans, including 474 T2DM subjects and 470 normal healthy controls. Of the nine LPL SNPs we analyzed, a significant association with multiple tests by the false discovery rate (FDR) was observed between T2DM and SNP rs343 (+13836C>A in intron 3). SNP rs343 was also marginally associated with some of T2DM-related phenotypes including total cholesterol, high density lipoprotein cholesterol (HDLc), and log transformed glycosylated hemoglobin in 470 normal controls, although no significant association was detected by multiple tests. In total, our results suggest that the control of lipid level by LPL in the bloodstream might be an important factor in T2DM pathogenesis in the Korean population.

Analysis of the Relative Effects of SNPs within a Gene to Serum Lipid Profiles Using Stepwise Linear Regression

BACKGROUND AND OBJECTIVES: It is very important to distinguish between the primary and secondary genetic effects at different sites within a small genetic region. Therefore, we evaluated the relative effects of single nucleotide polymorphisms (SNPs) within a gene on the serum lipid profiles by using individual data. SUBJECTS AND METHODS: To evaluate the contributions of SNPs in a region to the serum lipid profiles (total cholesterol, triglyceride, low density lipoprotein, high density lipoprotein), we used data that consisted of 808 individuals (327 males and 481 females) who did not have cardiovascular disease. In this study, we used a stepwise regression procedure to analyze the relative effects of four single nucleotide polymorphisms (ACE6, ACE7, ACE8, ACE10) in a gene region on the development of the serum lipid profiles in each gender group. RESULTS: In the males, there were epistatic interaction effects between two loci (ACE6xACE7, ACE6xACE8, ACE6xACE10, ACE8xACE10 and ACE7xACE8) and among three loci (ACE6xACE7xACE8, ACE6xACE7xACE10 and ACE6xACE8xACE10). Also, there are interaction effects between two loci (ACE6xACE7, ACE6xACE8, ACE6xACE10, ACE7xACE10 and ACE8xACE10) and among three loci (ACE6xACE7xACE8, ACE6xACE7xACE10, ACE6xACE8xACE10 and ACE7xACE8xACE10) in the females. CONCLUSION: The results suggested that each of these loci is important in causing a relative change of the serum lipid profiles, even with simultaneously accounting for the effects at the other loci. In the results of the analysis, there existed the effects of individual loci and significant interaction between the loci on the serum lipid profiles in each gender group. It was confirmed that this stepwise regression method can be suitable for evaluating the relative effects of SNPs and it is easily performed.