Jingwen Zhu

A Genome-Wide Association Study Identifies GRK5 and RASGRP1 as Type 2 Diabetes Loci in Chinese Hans

Substantial progress has been made in identification of type 2 diabetes (T2D) risk loci in the past few years, but our understanding of the genetic basis of T2D in ethnically diverse populations remains limited. We performed a genome-wide association study and a replication study in Chinese Hans comprising 8,569 T2D case subjects and 8,923 control subjects in total, from which 10 single nucleotide polymorphisms were selected for further follow-up in a de novo replication sample of 3,410 T2D case and 3,412 control subjects and an in silico replication sample of 6,952 T2D case and 11,865 control subjects. Besides confirming seven established T2D loci (CDKAL1, CDKN2A/B, KCNQ1, CDC123, GLIS3, HNF1B, and DUSP9) at genome-wide significance, we identified two novel T2D loci, including G-protein–coupled receptor kinase 5 (GRK5) (rs10886471: P = 7.1 × 10−9) and RASGRP1 (rs7403531: P = 3.9 × 10−9), of which the association signal at GRK5 seems to be specific to East Asians. In nondiabetic individuals, the T2D risk-increasing allele of RASGRP1-rs7403531 was also associated with higher HbA1c and lower homeostasis model assessment of β-cell function (P = 0.03 and 0.0209, respectively), whereas the T2D risk-increasing allele of GRK5-rs10886471 was also associated with higher fasting insulin (P = 0.0169) but not with fasting glucose. Our findings not only provide new insights into the pathophysiology of T2D, but may also shed light on the ethnic differences in T2D susceptibility.

Genome-wide association study in Chinese identifies novel loci for blood pressure and hypertension

Hypertension is a common disorder and the leading risk factor for cardiovascular disease and premature deaths worldwide. Genome-wide association studies (GWASs) in the European population have identified multiple chromosomal regions associated with blood pressure, and the identified loci altogether explain only a small fraction of the variance for blood pressure. The differences in environmental exposures and genetic background between Chinese and European populations might suggest potential different pathways of blood pressure regulation. To identify novel genetic variants affecting blood pressure variation, we conducted a meta-analysis of GWASs of blood pressure and hypertension in 11 816 subjects followed by replication studies including 69 146 additional individuals. We identified genome-wide significant (P < 5.0 × 10(-8)) associations with blood pressure, which included variants at three new loci (CACNA1D, CYP21A2, and MED13L) and a newly discovered variant near SLC4A7. We also replicated 14 previously reported loci, 8 (CASZ1, MOV10, FGF5, CYP17A1, SOX6, ATP2B1, ALDH2, and JAG1) at genome-wide significance, and 6 (FIGN, ULK4, GUCY1A3, HFE, TBX3-TBX5, and TBX3) at a suggestive level of P = 1.81 × 10(-3) to 5.16 × 10(-8). These findings provide new mechanistic insights into the regulation of blood pressure and potential targets for treatments.

Genome-Wide Association Study Meta-Analysis Reveals Transethnic Replication of Mean Arterial and Pulse Pressure Loci

We conducted a genome-wide association study meta-analysis of mean arterial pressure and pulse pressure among 26 600 East Asian participants (stage 1) followed by replication study of up to 28 783 participants (stage 2). For novel loci, statistical significance was determined by a P<5.0×10–8 in joint analysis of stage 1 and stage 2 data. For loci reported by the previous mean arterial and pulse pressure genome-wide association study meta-analysis in Europeans, evidence of transethnic replication was determined by consistency in effect direction and a Bonferroni-corrected P<1.4×10–3. No novel loci were identified by the current study. Five independent mean arterial pressure variants demonstrated robust evidence for transethnic replication including rs17249754 at ATP2B1 (P=7.5×10–15), rs2681492 at ATP2B1 (P=3.4×10–7), rs11191593 at NT5C2 (1.1×10–6), rs3824755 at CYP17A1 (P=1.2×10–6), and rs13149993 at FGF5 (P=2.4×10–4). Two additional variants showed suggestive evidence of transethnic replication (consistency in effect direction and P<0.05), including rs319690 at MAP4 (P=0.014) and rs1173771 at NPR3 (P=0.018). For pulse pressure, robust evidence of replication was identified for 2 independent variants, including rs17249754 at ATP2B1 (P=1.2×10–5) and rs11191593 at NT5C2 (P=1.1×10–3), with suggestive evidence of replication among an additional 2 variants including rs3824755 at CYP17A1 (P=6.1×10–3) and rs2681492 at ATP2B1 (P=9.0×10–3). Replicated variants demonstrated consistency in effect sizes between East Asian and European samples, with effect size differences ranging from 0.03 to 0.24 mm Hg for mean arterial pressure and from 0.03 to 0.21 mm Hg for pulse pressure. In conclusion, we present the first evidence of transethnic replication of several mean arterial and pulse pressure loci in an East Asian population.

Associations of erythrocyte fatty acids in the de novo lipogenesis pathway with risk of metabolic syndrome in a cohort study of middle-aged and older Chinese

BACKGROUND Experimental studies suggest that elevated de novo lipogenesis (DNL) might be involved in the pathogenesis of metabolic disorders. Few prospective studies have been conducted, especially among populations with a high carbohydrate intake, to determine whether DNL fatty acids are associated with the risk of the metabolic syndrome (MetS). OBJECTIVE We aimed to investigate associations of erythrocyte fatty acids in the DNL pathway-including myristic acid (14:0), palmitic acid (16:0), palmitoleic acid (16:1n-7), hexadecenoic acid (16:1n-9), stearic acid (18:0), vaccenic acid (18:1n-7), and oleic acid (18:1n-9)-with the risk of MetS in a Chinese population with an average carbohydrate intake of >60% of energy. DESIGN A total of 1176 free-living Chinese men and women aged 50-70 y from Beijing and Shanghai were included in our analysis, giving rise to 412 incident MetS cases during 6 y of follow-up. Erythrocyte fatty acids and metabolic traits were measured in these participants. RESULTS Erythrocyte fatty acids in the DNL pathway were correlated with a high ratio of carbohydrate-to-fat intake, less favorable lipid profiles, and elevated liver enzymes at baseline. In comparison with the lowest quartile, RRs (95% CIs) of MetS in the highest quartile were 1.30 (1.04, 1.62; P-trend = 0.007) for 16:1n-7, 1.48 (1.17, 1.86; P-trend < 0.001) for 16:1n-9, 1.26 (1.01, 1.56; P-trend = 0.06) for 18:1n-7, and 1.51 (1.19, 1.92; P-trend < 0.001) for 18:1n-9 after multivariate adjustment for lifestyle factors and body mass index. Moreover, 16:0 and 16:1n-7 were associated with an elevated risk of diabetes. CONCLUSION Our findings suggest that fatty acids in the DNL pathway are independently associated with an elevated risk of metabolic disorders.

Dairy Consumption, Type 2 Diabetes, and Changes in Cardiometabolic Traits: A Prospective Cohort Study of Middle-Aged and Older Chinese in Beijing and Shanghai

OBJECTIVE To prospectively investigate associations of dairy consumption with risk of type 2 diabetes and changes of cardiometabolic traits. RESEARCH DESIGN AND METHODS In 2005, 2,091 middle-aged and older Chinese men and women were recruited and followed for 6 years. Baseline dairy consumption was assessed by a 74-item food frequency questionnaire. Erythrocyte fatty acids were analyzed by gas chromatography coupled with flame ion detector. Cardiometabolic traits were measured at both baseline and follow-up visits. RESULTS Only 1,202 (57.5%) participants reported any dairy consumption, with a median intake of 0.89 (interquartile range 0.19–1.03) serving/day. Compared with nonconsumers, the relative risks (RRs) of type 2 diabetes among those having 0.5–1 serving/day and >1 serving/day were 0.70 (95% CI 0.55–0.88) and 0.65 (0.49–0.85), respectively, after multivariate adjustment (Ptrend < 0.001), which were attenuated by further adjusting for changes in glucose during follow-up (Ptrend = 0.07). Total dairy consumption was associated with favorable changes in glucose, waist circumference, BMI, diastolic blood pressure (all Ptrend < 0.05), and systolic blood pressure (Ptrend = 0.05) after multivariate adjustment, including baseline values of dependent variables. Erythrocyte trans-18:1 isomers were significantly correlated with total dairy consumption (rs = 0.37, Ptrend < 0.001), and these dairy food biomarkers were associated with a lower risk of type 2 diabetes. The RR of type 2 diabetes comparing extreme quartiles of trans-18:1 isomers was 0.82 (0.65–1.04, Ptrend = 0.02), which was attenuated after adjustment for dairy consumption (Ptrend = 0.15). CONCLUSIONS Dairy consumption was associated with a significantly lower risk of type 2 diabetes and favorable changes of cardiometabolic traits in Chinese.

A meta-analysis of genome-wide association studies for adiponectin levels in East Asians identifies a novel locus near WDR11-FGFR2

Blood levels of adiponectin, an adipocyte-secreted protein correlated with metabolic and cardiovascular risks, are highly heritable. Genome-wide association (GWA) studies for adiponectin levels have identified 14 loci harboring variants associated with blood levels of adiponectin. To identify novel adiponectin-associated loci, particularly those of importance in East Asians, we conducted a meta-analysis of GWA studies for adiponectin in 7827 individuals, followed by two stages of replications in 4298 and 5954 additional individuals. We identified a novel adiponectin-associated locus on chromosome 10 near WDR11-FGFR2 (P = 3.0 × 10(-14)) and provided suggestive evidence for a locus on chromosome 12 near OR8S1-LALBA (P = 1.2 × 10(-7)). Of the adiponectin-associated loci previously described, we confirmed the association at CDH13 (P = 6.8 × 10(-165)), ADIPOQ (P = 1.8 × 10(-22)), PEPD (P = 3.6 × 10(-12)), CMIP (P = 2.1 × 10(-10)), ZNF664 (P = 2.3 × 10(-7)) and GPR109A (P = 7.4 × 10(-6)). Conditional analysis at ADIPOQ revealed a second signal with suggestive evidence of association only after conditioning on the lead SNP (Pinitial = 0.020; Pconditional = 7.0 × 10(-7)). We further confirmed the independence of two pairs of closely located loci (<2 Mb) on chromosome 16 at CMIP and CDH13, and on chromosome 12 at GPR109A and ZNF664. In addition, the newly identified signal near WDR11-FGFR2 exhibited evidence of association with triglycerides (P = 3.3 × 10(-4)), high density lipoprotein cholesterol (HDL-C, P = 4.9 × 10(-4)) and body mass index (BMI)-adjusted waist-hip ratio (P = 9.8 × 10(-3)). These findings improve our knowledge of the genetic basis of adiponectin variation, demonstrate the shared allelic architecture for adiponectin with lipids and central obesity and motivate further studies of underlying mechanisms.

A Genome Wide Association Study Identifies Common Variants Associated with Lipid Levels in the Chinese Population

Plasma lipid levels are important risk factors for cardiovascular disease and are influenced by genetic and environmental factors. Recent genome wide association studies (GWAS) have identified several lipid-associated loci, but these loci have been identified primarily in European populations. In order to identify genetic markers for lipid levels in a Chinese population and analyze the heterogeneity between Europeans and Asians, especially Chinese, we performed a meta-analysis of two genome wide association studies on four common lipid traits including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL) in a Han Chinese population totaling 3,451 healthy subjects. Replication was performed in an additional 8,830 subjects of Han Chinese ethnicity. We replicated eight loci associated with lipid levels previously reported in a European population. The loci genome wide significantly associated with TC were near DOCK7, HMGCR and ABO; those genome wide significantly associated with TG were near APOA1/C3/A4/A5 and LPL; those genome wide significantly associated with LDL were near HMGCR, ABO and TOMM40; and those genome wide significantly associated with HDL were near LPL, LIPC and CETP. In addition, an additive genotype score of eight SNPs representing the eight loci that were found to be associated with lipid levels was associated with higher TC, TG and LDL levels (P = 5.52×10-16, 1.38×10-6 and 5.59×10-9, respectively). These findings suggest the cumulative effects of multiple genetic loci on plasma lipid levels. Comparisons with previous GWAS of lipids highlight heterogeneity in allele frequency and in effect size for some loci between Chinese and European populations. The results from our GWAS provided comprehensive and convincing evidence of the genetic determinants of plasma lipid levels in a Chinese population.

Association of TMPRSS6 polymorphisms with ferritin, hemoglobin, and type 2 diabetes risk in a Chinese Han population

BACKGROUND Transmembrane protease serine 6 (TMPRSS6) regulates iron homeostasis by inhibiting the expression of hepcidin. Multiple common variants in TMPRSS6 were significantly associated with serum iron in recent genome-wide association studies, but their effects in the Chinese remain to be elucidated. OBJECTIVE The objective was to determine whether the TMPRSS6 single nucleotide polymorphisms (SNPs) rs855791(V736A) and rs4820268(D521D) were associated with blood hemoglobin and plasma ferritin concentrations and risk of type 2 diabetes in Chinese individuals. DESIGN The SNPs rs855791(V736A) and rs4820268(D521D) in the TMPRSS6 gene were genotyped and tested for their associations with plasma iron and type 2 diabetes risk in 1574 unrelated Chinese Hans from Beijing. RESULTS The 2 TMPRSS6 SNPs rs855791(V736A) and rs4820268(D521D) were both significantly associated with plasma ferritin (P ≤ 0.0058), hemoglobin (P ≤ 0.0013), iron overload risk (P ≤ 0.0068), and type 2 diabetes risk (P ≤ 0.0314). None of the associations with hemoglobin or plasma ferritin remained significant (P ≥ 0.1229) when the 2 variants were both included in one linear regression model. A haplotype carrying both iron-lowering alleles from the 2 TMPRSS SNPs showed significant associations with lower hemoglobin (P = 0.0014), lower plasma ferritin (P = 0.0027), and a reduced risk of iron overload (P = 0.0017) and of type 2 diabetes (P = 0.0277). CONCLUSIONS These findings suggest that TMPRSS6 variants were significantly associated with plasma ferritin, hemoglobin, risk of iron overload, and type 2 diabetes in Chinese Hans. The type 2 diabetes risk conferred by the TMPRSS6 SNPs is possibly mediated by plasma ferritin.

Associations of Genetic Risk Score with Obesity and Related Traits and the Modifying Effect of Physical Activity in a Chinese Han Population

Background/Objectives Recent large-scale genome-wide association studies have identified multiple loci robustly associated with BMI, predominantly in European ancestry (EA) populations. However, associations of these loci with obesity and related traits have not been well described in Chinese Hans. This study aimed to investigate whether BMI-associated loci are, individually and collectively, associated with adiposity-related traits and obesity in Chinese Hans and whether these associations are modified by physical activity (PA). Subjects/Methods We genotyped 28 BMI-associated single nucleotide polymorphisms (SNPs) in a population-based cohort including 2,894 unrelated Han Chinese. Genetic risk score (GRS), EA and East Asian ancestry (EAA) GRSs were calculated by adding BMI-increasing alleles based on all, EA and EAA identified SNPs, respectively. Interactions of GRS and PA were examined by including the interaction-term in the regression model. Results Individually, 26 of 28 SNPs showed directionally consistent effects on BMI, and associations of four loci (TMEM18, PCSK1, BDNF and MAP2K5) reached nominal significance (P<0.05). The GRS was associated with increased BMI, trunk fat and body fat percentages; and increased risk of obesity and overweight (all P<0.05). Effect sizes (0.11 vs. 0.17 kg/m2) and explained variance (0.90% vs. 1.45%) of GRS for BMI tended to be lower in Chinese Hans than in Europeans. The EA GRS and EAA GRS were associated with 0.11 and 0.13 kg/m2 higher BMI, respectively. In addition, we found that PA attenuated the effect of the GRS on BMI (P interaction = 0.022). Conclusions Our observations suggest that the combined effect of obesity-susceptibility loci on BMI tended to be lower in Han Chinese than in EA. The overall, EA and EAA GRSs exert similar effects on adiposity traits. Genetic predisposition to increased BMI is attenuated by PA in this population of Han Chinese.

Genome-wide meta-analyses identify novel loci associated with n-3 and n-6 polyunsaturated fatty acid levels in Chinese and European-ancestry populations

Epidemiological studies suggest that levels of n-3 and n-6 long-chain polyunsaturated fatty acids are associated with risk of cardio-metabolic outcomes across different ethnic groups. Recent genome-wide association studies in populations of European ancestry have identified several loci associated with plasma and/or erythrocyte polyunsaturated fatty acids. To identify additional novel loci, we carried out a genome-wide association study in two population-based cohorts consisting of 3521 Chinese participants, followed by a trans-ethnic meta-analysis with meta-analysis results from 8962 participants of European ancestry. Four novel loci (MYB, AGPAT4, DGAT2 and PPT2) reached genome-wide significance in the trans-ethnic meta-analysis (log10(Bayes Factor) ≥ 6). Of them, associations of MYB and AGPAT4 with docosatetraenoic acid (log10(Bayes Factor) = 11.5 and 8.69, respectively) also reached genome-wide significance in the Chinese-specific genome-wide association analyses (P = 4.15 × 10(-14) and 4.30 × 10(-12), respectively), while associations of DGAT2 with gamma-linolenic acid (log10(Bayes Factor) = 6.16) and of PPT2 with docosapentaenoic acid (log10(Bayes Factor) = 6.24) were nominally significant in both Chinese- and European-specific genome-wide association analyses (P ≤ 0.003). We also confirmed previously reported loci including FADS1, NTAN1, NRBF2, ELOVL2 and GCKR. Different effect sizes in FADS1 and independent association signals in ELOVL2 were observed. These results provide novel insight into the genetic background of polyunsaturated fatty acids and their differences between Chinese and European populations.