Blood pressure (BP) response to cold pressor test (CPT) is associated with increased risk of cardiovascular disease. We performed a genome-wide linkage scan and regional association analysis to identify genetic determinants of BP response to CPT.
Methods and Results
A total of 1,961 Chinese participants completed the CPT. Multipoint quantitative trait linkage analysis was performed, followed by single-marker and gene-based analyses of variants in promising linkage regions (logarithm of odds, LOD ≥ 2). A suggestive linkage signal was identified for systolic BP (SBP) response to CPT at 20p13-20p12.3, with a maximum multipoint LOD score of 2.37. Based on regional association analysis with 1,351 SNPs in the linkage region, we found that marker rs2326373 at 20p13 was significantly associated with mean arterial pressure (MAP) responses to CPT (P = 8.8×10−6) after FDR adjustment for multiple comparisons. A similar trend was also observed for SBP response (P = 0.03) and DBP response (P = 4.6×10−5). Results of gene-based analyses showed that variants in genes MCM8 and SLC23A2 were associated with SBP response to CPT (P = 4.0×10−5 and 2.7×10−4, respectively), and variants in genes MCM8 and STK35 were associated with MAP response to CPT (P = 1.5×10−5 and 5.0×10−5, respectively).
Within a suggestive linkage region on chromosome 20, we identified a novel variant associated with BP responses to CPT. We also found gene-based associations of MCM8, SLC23A2 and STK35 in this region. Further work is warranted to confirm these findings.
Clinical Trial Registration
URL: http://www.clinicaltrials.gov; Unique identifier: NCT00721721.
blood pressure; linkage; genetic association
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 trans-ethnic 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 trans-ethnic 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 trans-ethnic 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 mmHg for mean arterial pressure and from 0.03 to 0.21 mmHg for pulse pressure. In conclusion, we present the first evidence of trans-ethnic replication of several mean arterial and pulse pressure loci in an East Asian population.
genetics; polymorphism; single nucleotide; blood pressure; hypertension; genome-wide association study; meta-analysis
To identify chromosomal regions harboring quantitative trait loci (QTL) for waist circumference (WC) and body mass index (BMI).
Design and Methods
We conducted a genome-wide linkage scan and regional association study WC and BMI among 633 Chinese families.
A significant linkage signal for WC was observed at 22q13.31–22q13.33 in the overall analysis (LOD=3.13). Follow-up association study of 22q13.31–13.33 revealed an association between the TBC1D22A gene marker rs16996195 and WC (false discovery rate (FDR)-Q<0.05). In gender-stratified analysis, suggestive linkage signals were attained for WC at 2p24.3–2q12.2 and 22q13.33 among females (LOD=2.54 and 2.15, respectively). Among males, 6q12–6q13 was suggestively linked to BMI (LOD= 2.03). Single marker association analyses at these regions identified male-specific relationships of 6 single nucleotide polymorphisms (SNPs) at 2p24.3–2q12.2 (rs100955, rs13020676, rs13014034, rs12990515, rs17024325 and rs2192712) and 5 SNPs at 6q12–6q13 (rs7747318, rs7767301, rs12197115, rs12203049, and rs9454847) with the obesity-related phenotypes (all FDR-Q<0.05). At chromosome 6q12–6q13, markers rs7755450 and rs11758293 predicted BMI in females (both FDR-Q<0.05).
We described genomic regions on chromosomes 2, 6, and 22 which may harbor important obesity-susceptibility loci. Follow-up study of these regions revealed several novel variants associated with obesity related traits. Future work to confirm these promising findings is warranted.
Obesity; genetics; linkage analysis; single nucleotide polymorphisms
Serum and glucocorticoid regulated kinase (SGK) plays a critical role in the regulation of renal sodium transport. We examined the association between SGK genes and salt sensitivity of blood pressure (BP) using single-marker and gene-based association analysis.
A 7-day low-sodium (51.3 mmol sodium/day) followed by a 7-day high-sodium intervention (307.8 mmol sodium/day) was conducted among 1,906 Chinese participants. BP measurements were obtained at baseline and each intervention using a random-zero sphygmomanometer. Additive associations between each SNP and salt-sensitivity phenotypes were assessed using a mixed linear regression model to account for family dependencies. Gene-based analyses were conducted using the truncated p-value method. The Bonferroni-method was used to adjust for multiple testing in all analyses.
In single-marker association analyses, SGK1 marker rs2758151 was significantly associated with diastolic BP (DBP) response to high-sodium intervention (P = 0.0010). DBP responses (95% confidence interval) to high-sodium intervention for genotypes C/C, C/T, and T/T were 2.04 (1.57 to 2.52), 1.79 (1.42 to 2.16), and 0.85 (0.30 to 1.41) mmHg, respectively. Similar trends were observed for SBP and MAP responses although not significant (P = 0.15 and 0.0026, respectively). In addition, gene-based analyses demonstrated significant associations between SGK1 and SBP, DBP and MAP responses to high sodium intervention (P = 0.0002, 0.0076, and 0.00001, respectively). Neither SGK2 nor SGK3 were associated with the salt-sensitivity phenotypes in single-maker or gene-based analyses.
The current study identified association of the SGK1 gene and BP salt-sensitivity in the Han Chinese population. Further studies are warranted to identify causal SGK1 gene variants.
We examined the association between 14 endothelial system genes and salt-sensitivity of blood pressure (BP).
After a 3-day baseline examination, during which time the usual diet was consumed, 1,906 Chinese participants received a 7-day low-sodium diet (51.3 mmol of sodium/day) followed by a 7-day high-sodium diet (307.8 mmol of sodium/day). BP measurements were obtained at baseline and at the end of each intervention using a random-zero sphygmomanometer.
The DDAH1 rs11161637 variant was associated with reduced BP salt sensitivity, conferring attenuated systolic BP (SBP) and mean arterial pressure (MAP) decreases from baseline to the low-sodium intervention (both P = 2×10−4). Examination of genotype–sex interactions revealed that this relation was driven by the strong associations observed in men (P for interactions = 1.10×10−4 and 0.008, respectively). When switching from the low- to high-sodium intervention, increases in diastolic BP (DBP) and MAP were attenuated by the COL18A1 rs2838944 minor A allele (P = 1.41×10−4 and 1.55×10−4, respectively). Conversely, the VWF rs2239153 C variant was associated with increased salt sensitivity, conferring larger DBP and MAP reductions during low-sodium intervention (P = 1.22×10−4 and 4.44×10−5, respectively). Ten variants from 3 independent SELE loci displayed significant genotype–sex interactions on DBP and MAP responses to low-sodium (P for interaction = 1.56×10−3 to 1.00×10−4). Among men, minor alleles of 4 correlated markers attenuated BP responses to low-sodium intake, whereas minor alleles of another 4 correlated markers increased BP responses. No associations were observed in women for these variants. Further, qualitative interactions were shown for 2 correlated SELE markers.
These data support a role for the endothelial system genes in salt sensitivity.
blood pressure; endothelial system; genes; hypertension; salt sensitivity.
The relation between parental history of hypertension and blood pressure response to potassium intake is unknown. A 7-day high-sodium followed by a 7-day high-sodium plus potassium dietary-feeding study was conducted from 2003 to 2005 among 1,871 Chinese participants. Those with a maternal history of hypertension had larger systolic blood pressure responses to potassium compared with those without: −4.31 (95% confidence interval (CI): −4.99, −3.62) mm Hg versus −3.35 (95% CI: −4.00, −2.70) mm Hg, respectively (Pdifference = 0.002). A consistent trend was observed for diastolic blood pressure responses: −1.80 (95% CI: −2.41, −1.20) mm Hg versus −1.35 (95% CI: −1.95, −0.74) mm Hg, respectively (P = 0.07). Stronger associations between early onset maternal hypertension and blood pressure responses were noted, with systolic blood pressure decreases of −4.80 (95% CI: −5.65, −3.95) mm Hg versus −3.55 (95% CI: −4.17, −2.93) mm Hg and diastolic blood pressure decreases of −2.25 (95% CI: −3.01, −1.50) mm Hg versus −1.42 (95% CI: −1.99, −0.85) mm Hg among those with early onset maternal hypertension versus those without, respectively (P = 0.001 and 0.009, respectively). Odds ratios for high potassium sensitivity were 1.36 (95% CI: 0.96, 1.92) and 1.60 (95% CI: 1.08, 2.36) for those with maternal hypertension and early onset maternal hypertension, respectively (P = 0.08 and 0.02, respectively). Potassium supplementation could help to reduce blood pressure among those with a maternal history of hypertension.
blood pressure; dietary potassium; family history; hypertension
Results from clinical trials examining the effect of intensive glucose control on cardiovascular disease have been conflicting.
To summarize clinical benefits and harms of intensive versus conventional glucose control for adults with type-2 diabetes.
Studies were retrieved by systematically searching the MEDLINE database (January 1950-April 2009) with no language restrictions.
Two independent reviewers screened abstracts or full text articles to identify randomized trials comparing clinical outcomes in type-2 diabetes patients treated with intensive compared to conventional glucose control.
Two investigators independently abstracted data on study variables and outcomes including severe hypoglycemia, cardiovascular disease, and all-cause mortality.
Five trials involving 27,802 adults were included. Intensive glucose targets were lower in the three most recent trials. Summary analyses showed that, compared with conventional control, intensive glucose control reduced the risk of cardiovascular disease (relative risk (RR): 0.90, 95% confidence interval (CI): 0.83, 0.98; risk difference per 1,000 patients per 5 years (RD): -15, CI: -24, -5) but not cardiovascular death (RR: 0.97, CI: 0.76, 1.24; RD: -3, CI: -14, 7) or all-cause mortality (RR: 0.98, CI: 0.84, 1.15; RD: -4, CI: -17, 10) and increased the risk of severe hypoglycemia (RR: 2.03, CI: 1.46, 2.81; RD: 39, CI: 7, 71). Similar to overall analyses, intensive glucose control reduced risk of cardiovascular disease and increased risk of severe hypoglycemia in pooled findings from early and more recent trials.
Summary rather than individual data were pooled across trials.
Intensive glucose control reduced risk for some cardiovascular disease (e.g., non-fatal myocardial infarction), but did not reduce risk for cardiovascular or all-cause mortality and increased risk of severe hypoglycemia.
intensive glucose control; cardiovascular disease; mortality; relative risk; randomized controlled trials; meta-analysis
To examine the association between renin-angiotensin-aldosterone system (RAAS) genes and salt-sensitivity of blood pressure (BP).
A 7-day low-sodium followed by a 7-day high-sodium dietary intervention was conducted among 1,906 participants living in a rural region of north China where habitual sodium-intake is high. BP measurements were obtained at baseline and following each intervention using a random-zero sphygmomanometer.
Diastolic BP (DBP) and mean arterial pressure (MAP) responses increased with the number of rs4524238 A alleles in the angiotensin II receptor, type 1 (AGTR1) gene. For example, mean DBP responses (95% CI) among those with genotypes G/G, G/A, and A/A were −2.53 (−2.89, −2.18), −3.49 (−4.13, −2.86), and −5.78 (−9.51, −2.06) mmHg, respectively, following the low-sodium intervention (p=0.0008). Carriers of the rare A allele of rs5479 in the hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2) gene had decreased DBP responses to low-sodium (p-value=0.00004). Those with the C/A and C/C genotypes had DBP responses of −0.70 (−6.62, 5.22) and −2.71 (−4.88, −0.54) mmHg, respectively. X-chromosome renin-binding protein (RENBP) gene markers rs1557501 and rs2269372 were associated with systolic BP (SBP) response to low-sodium in men (p=0.00004 and 0.0001, respectively). SBP responses (95% CI) were −6.13 (−6.68, −5.58) versus −4.07 (−4.88, −3.26) and −6.04 (−6.57, −5.52) versus −3.94 (−4.90, −2.99) mmHg among men with major versus those with minor alleles of rs1557501 and rs2269372, respectively. Haplotype analyses of these genes supported our single marker findings.
We identified RAAS variants that were predictive of salt-sensitivity in a Han population with habitually high-sodium intake.
blood pressure; genetics; polymorphism; dietary sodium; salt sensitivity; renin-angiotensin-aldosterone system
We examined the association between twelve single nucleotide polymorphisms (SNPs) in the alpha-adducin (ADD1) and guanine nucleotide binding protein (G protein) beta polypeptide 3 (GNB3) genes and systolic (SBP), diastolic (DBP), and mean arterial (MAP) pressure responses to salt-intake.
A 7-day low-sodium (51.3 mmol sodium/day) followed by a 7-day high-sodium intervention (307.8 mmol sodium/day) was conducted among 1,906 Han participants from rural north China. BP measurements were obtained at baseline and the end of each intervention period using a random-zero sphygmomanometer.
We identified a significant association between a rare ADD1 variant rs17833172 and SBP, DBP, and MAP responses to high-sodium (p-values<0.0001) and DBP response to low-sodium (p-value=0.002). Participants homozygous for the variant A allele of this marker had SBP, DBP, and MAP responses (95% confidence interval) to high-salt of 1.6 (−1.8, 4.9), −0.8 (−5.6, 4.0), and −0.1 (−4.0, 3.9) mmHg, respectively, versus corresponding responses of 4.6 (2.5, 6.6), 1.7 (−0.2, 3.6), and 2.7 (0.9, 4.4) mmHg, respectively, for those who were heterozygous or homozygous for the G allele. In addition, participants with at least one copy of the A allele of SNP rs1129649 of the GNB3 gene had significantly decreased MAP response to low-salt compared to homozygotes for the C allele (p-value=0.004) with responses of −3.4 (−3.8, −3.0) versus −4.2 (−4.6, −3.8) mmHg, respectively.
These data support a role for the ADD1 and GNB3 genes in BP salt-sensitivity. Future studies aimed at replicating these novel findings are warranted.
blood pressure; genetics; polymorphism; dietary sodium; salt sensitivity; ADD1; GNB3
Hypertension has become a major global health burden due to its high prevalence and associated increase in risk of cardiovascular disease and premature death. It is well established that hypertension is determined by both genetic and environmental factors and their complex interactions. Recent large-scale meta-analyses of genome-wide association studies (GWAS) have successfully identified a total of 38 loci which achieved genome-wide significance (P < 5×10−8) for their association with blood pressure (BP). Although the heritability of BP explained by these loci is very limited, GWAS meta-analyses have elicited renewed optimism in hypertension genomics research, highlighting novel pathways influencing BP and elucidating genetic mechanisms underlying BP regulation. This review summarizes evolving progress in the rapidly moving field of hypertension genetics and highlights several promising approaches for dissecting the remaining heritability of BP. It also discusses the future translation of genetic findings to hypertension treatment and prevention.
Blood pressure; Genetic association studies; Genetic linkage; Genome-wide association study; Hypertension; Rare variants; Sequencing; Risk prediction
Recent studies suggest that central obesity is an important predictor of cardiovascular disease (CVD) in addition to overall obesity. Both inflammation and endothelial dysfunction are associated with increased risk of CVD. We examined the association between body mass index (BMI) and waist circumference (WC) with plasma concentrations of biomarkers of inflammation and endothelial dysfunction.
We conducted a cross-sectional study of 2589 lean, moderately active participants aged 20 years and older in Inner Mongolia, China. Overnight fasting blood samples were obtained to measure the biomarkers including C-reactive protein (CRP), soluble inter-cellular adhesion molecule-1 (sICAM-1), soluble E-selectin (sE-selectin), and angiotensin II. Height, body weight, and WC were measured by trained staff and BMI was calculated (kg/m2).
In univariate analysis, CRP, sICAM-1, and sE-selectin were all significantly higher among individuals with a higher BMI and WC. In multivariate analysis, each standard deviation (SD) increase in WC (9.6 cm) was associated with about 46% higher risk (odds ratio [OR] 1.46, 95% confidence interval [CI] 1.21–1.76) of elevated CRP but a 1 SD increase in BMI (3.5 kg/m2) was not associated with the risk of elevated CRP (OR 0.96, 95% CI 0.80–1.16). However, each SD increase in BMI was associated with about 30% higher risk of having elevated E-selectin (OR 1.30, 95% CI 1.08–1.55).
WC is a stronger predictor of inflammation while BMI is a stronger predictor for endothelial dysfunction. These results suggest measuring both BMI and WC will help to assess the risk of CVD in the Chinese population.
Inflammation; Endothelial dysfunction; C-reactive protein; Body mass index; Waist circumference
Blood pressure (BP) responses to dietary sodium and potassium intervention and cold pressor test (CPT) vary considerably among individuals. We aimed to identify novel genetic variants influencing individuals’ BP responses to dietary intervention and CPT.
Methods and Results
We conducted a genome-wide association study of BP responses in 1,881 Han Chinese and de novo genotyped top findings in 698 Han Chinese. Diet-feeding study included a 7-day low-sodium (51.3 mmol/day), a 7-day high-sodium (307.8 mmol/day), and a 7-day high-sodium plus potassium-supplementation (60 mmol/day). Nine BP measurements were obtained during baseline observation and each intervention period. The meta-analyses identified eight novel loci for BP phenotypes, which physically mapped in or near PRMT6 (P=7.29×10−9), CDCA7 (P=3.57×10−8), PIBF1 (P=1.78×10−9), ARL4C (P=1.86×10−8), IRAK1BP1 (P=1.44×10−10), SALL1 (P=7.01×10−13), TRPM8 (P=2.68×10−8), and FBXL13 (P=3.74×10−9). There was a strong dose-response relationship between the number of risk alleles of these independent SNPs and the risk of developing hypertension over 7.5-year follow-up in the study participants. Compared to those in the lowest quartile of risk alleles, odds ratios (95% confidence intervals) for those in the second, third and fourth quartiles were 1.39 (0.97, 1.99), 1.72 (1.19, 2.47), and 1.84 (1.29, 2.62), respectively (P=0.0003 for trend).
Our study identified 8 novel loci for BP responses to dietary sodium and potassium intervention and CPT. The effect size of these novel loci on BP phenotypes are much larger than those reported by the previously published studies. Furthermore, these variants predict the risk of developing hypertension among individuals with normal BP at baseline.
blood pressure; genomics; sodium; potassium
Diabetes mellitus is associated with an increased incidence of colorectal cancer, but the impact of diabetes on colorectal cancer prognosis is not clear.
We conducted a meta-analysis of observational studies to examine the association between pre-existing diabetes and colorectal cancer all-cause mortality, cancer-specific mortality and recurrence.
Medline and Embase were searched through August 22, 2012.
We included studies reporting all-cause mortality, cancer-specific mortality, disease-free survival, or recurrence in colorectal cancer patients according to diabetic status.
Meta-analyses performed using random effects models.
Main Outcome Measures
All-cause mortality, cancer-specific mortality, diseases free survival.
Twenty-six articles met our inclusion criteria. Colorectal cancer patients with diabetes had a 17% increased risk of all-cause mortality (RR = 1.17; 95% CI: 1.09-1.25) and a 12% increased risk of cancer-specific mortality (RR = 1.12; 95% CI: 1.01-1.24) compared to those without diabetes. Those with diabetes also had poorer disease-free survival (RR = 1.54; 95% CI: 1.08-2.18) compared to their non-diabetic counterparts. In subgroup analyses, diabetes was associated with all-cause mortality in both rectal (RR = 1.24; 95% CI: 1.07-1.29) and colon cancer patients (RR = 1.17; 95% CI: 1.07-1.29). Sensitivity analyses including only patients with non-metastatic disease identified stronger associations between diabetes and both all-cause (RR = 1.32; 95% CI: 1.21-1.44) and cancer-specific (RR = 1.27; 95% CI: 1.06-1.52) mortality.
Some studies had short follow-up or did not report mean or median follow-up. The included studies were heterogeneous in study population, diabetes diagnostic criteria and outcome ascertainment.
Colorectal cancer patients with diabetes are at greater risk for all-cause and cancer-specific mortality and have worse disease-free survival compared to those without diabetes. Studies are warranted to determine if proper treatment could attenuate the excess mortality among diabetic colorectal cancer patients.
Colorectal neoplasms; diabetes mellitus; colorectal neoplasms metabolism; colorectal neoplasms prognosis; meta-analysis
Chronic kidney disease (CKD) can be a consequence of diabetes, hypertension, immunologic disorders, and other exposures, as well as genetic factors that are still largely unknown. Glomerular filtration rate (GFR), which is widely used to measure kidney function, has a heritability ranging from 25% to 75%, but only 1.5% of this heritability is explained by genetic loci that have been identified to date. In this study we tested for associations between GFR and 234 SNPs in 26 genes from pathways of blood pressure regulation in 3,025 rural Chinese participants of the “Genetic Epidemiology Network of Salt Sensitivity” (GenSalt) study. We estimated GFR (eGFR) using baseline serum creatinine measurements obtained prior to dietary intervention. We identified significant associations between eGFR and 12 SNPs in 6 genes (ACE, ADD1, AGT, GRK4, HSD11B1, and SCNN1G). The cumulative effect of the protective alleles was an increase in mean eGFR of 4 mL/min per 1.73 m2, while the cumulative effect of the risk alleles was a decrease in mean eGFR of 3 mL/min per 1.73 m2. In addition, we identified a significant interaction between SNPs in CYP11B1 and ADRB2. We have identified common variants in genes from pathways that regulate blood pressure and influence kidney function as measured by eGFR, providing new insights into the genetic determinants of kidney function. Complex genetic effects on kidney function likely involve interactions among genes as we observed for CYP11B1 and ADRB2.
We examined the association between 799 single-nucleotide polymorphisms in 39 sex hormone genes and blood pressure (BP) responses to a dietary-sodium intervention.
A 7-day low-sodium feeding study (51.3 mmol sodium/day) followed by a 7-day high-sodium feeding study (307.8 mmol sodium/day) was conducted among 1,906 Han Chinese participants. Nine BP measurements were obtained at baseline and the end of each intervention period using a random-zero sphygmomanometer.
Among men, absolute BP responses to sodium interventions decreased with the number of minor alleles of estrogen receptor 1 (ESR1) markers rs9340844, rs9397453, rs9371562, rs9397459, and rs9383951. For example, mean diastolic blood pressure (DBP) responses to low-sodium intervention (95% confidence interval) were –2.67 (–3.13, –2.22) mm Hg among those with the rs9397453 C/C genotype, –1.23 (–1.98, –0.48) mm Hg among those with the C/T genotype, and 0.08 (–2.31, 2.47) mm Hg among those with the T/T genotype (P = 1×10–4; false discovery rate (FDR)-q = 0.04). Mean DBP responses to high sodium according to the rs9397453 genotypes were 1.46 (1.03, 1.89) mm Hg among those with C/C, 0.19 (–0.54, 0.91) mm Hg among those with C/T, and –1.10 (–2.82, 0.61) mm Hg among those with T/T (P = 2×10–4; FDR-q = 0.04). Similar trends were noted for the association between these ESR1 variants and SBP responses to the dietary intervention. There were no significant associations between sex hormone gene variants and salt sensitivity in women, with genotype-gender interactions noted for the ESR1 markers that achieved significance in men.
We identified strong, consistent associations between ESR1 gene variants and salt sensitivity in men. Our results support a gender-specific role for ESR1 in the etiology of this complex trait.
blood pressure; genetics; polymorphism; dietary sodium; salt sensitivity; gender; hypertension.
The current study comprehensively examined the association between common genetic variants of the kallikrein-kinin system (KKS) and blood pressure salt sensitivity. A 7-day low-sodium followed by a 7-day high-sodium dietary intervention was conducted among 1,906 Han Chinese participants recruited from 2003 to 2005. Blood pressure was measured by using a random-zero sphygmomanometer through the study. A total of 205 single nucleotide polymorphisms (SNPs) covering 11 genes of the KKS were selected for the analyses. Genetic variants of the bradykinin receptor B2 gene (BDKRB2) and the endothelin converting enzyme 1 gene (ECE1) showed significant associations with the salt-sensitivity phenotypes even after adjustment for multiple testing. Compared with the major G allele, the BDKRB2 rs11847625 minor C allele was significantly associated with increased systolic blood pressure responses to low-sodium intervention (P = 0.0001). Furthermore, a haplotype containing allele C was associated with an increased systolic blood pressure response to high-sodium intervention (P = 0.0009). Seven highly correlated ECE1 SNPs were shown to increase the diastolic blood pressure response to low-sodium intervention (P values ranged from 0.0003 to 0.002), with 2 haplotypes containing these 7 SNPs also associated with this same phenotype (P values ranged from 0.0004 to 0.002). In summary, genetic variants of the genes involved in the regulation of KKS may contribute to the salt sensitivity of blood pressure.
blood pressure; genetics; kallikreins; kinins; polymorphism; sodium, dietary
The effects of low-carbohydrate diets (≤45% of energy from carbohydrates) versus low-fat diets (≤30% of energy from fat) on metabolic risk factors were compared in a meta-analysis of randomized controlled trials. Twenty-three trials from multiple countries with a total of 2,788 participants met the predetermined eligibility criteria (from January 1, 1966 to June 20, 2011) and were included in the analyses. Data abstraction was conducted in duplicate by independent investigators. Both low-carbohydrate and low-fat diets lowered weight and improved metabolic risk factors. Compared with participants on low-fat diets, persons on low-carbohydrate diets experienced a slightly but statistically significantly lower reduction in total cholesterol (2.7 mg/dL; 95% confidence interval: 0.8, 4.6), and low density lipoprotein cholesterol (3.7 mg/dL; 95% confidence interval: 1.0, 6.4), but a greater increase in high density lipoprotein cholesterol (3.3 mg/dL; 95% confidence interval: 1.9, 4.7) and a greater decrease in triglycerides (−14.0 mg/dL; 95% confidence interval: −19.4, −8.7). Reductions in body weight, waist circumference and other metabolic risk factors were not significantly different between the 2 diets. These findings suggest that low-carbohydrate diets are at least as effective as low-fat diets at reducing weight and improving metabolic risk factors. Low-carbohydrate diets could be recommended to obese persons with abnormal metabolic risk factors for the purpose of weight loss. Studies demonstrating long-term effects of low-carbohydrate diets on cardiovascular events were warranted.
carbohydrate-restricted diet; fat-restricted diet; meta-analysis; metabolic syndrome; obesity
The authors conducted a genome-wide linkage scan and positional association analysis to identify the genetic determinants of salt sensitivity of blood pressure (BP) in a large family-based, dietary-feeding study. The dietary intervention was conducted among 1,906 participants in rural China (2003–2005). A 7-day low-sodium intervention was followed by a 7-day high-sodium intervention. Salt sensitivity was defined as BP responses to low- and high-sodium interventions. Signals of the logarithm of the odds to the base 10 (LOD ≥ 3) were detected at 33–42 centimorgans of chromosome 2 (2p24.3-2p24.1), with a maximum LOD score of 3.33 for diastolic blood pressure responses to high-sodium intervention. LOD scores were 2.35–2.91 for mean arterial pressure (MAP) and 0.80–1.49 for systolic blood pressure responses in this region, respectively. Correcting for multiple tests, single nucleotide polymorphism (SNP) rs11674786 (2.7 kilobases upstream of the family with sequence similarity 84, member A, gene (FAM84A)) in the linkage region was significantly associated with diastolic blood pressure (P = 0.0007) and MAP responses (P = 0.0007), and SNP rs16983422 (2.8 kilobases upstream of the visinin-like 1 gene (VSNL1)) was marginally associated with diastolic blood pressure (P = 0.005) and MAP responses (P = 0.005). An additive interaction between SNPs rs11674786 and rs16983422 was observed, with P = 7.00 × 10−5 and P = 7.23 × 10−5 for diastolic blood pressure and MAP responses, respectively. The authors concluded that genetic region 2p24.3-2p24.1 might harbor functional variants for the salt sensitivity of BP.
allelic association; blood pressure; genetic linkage; salt sensitivity
An elevated blood pressure (BP) response to the cold pressor test (CPT) is associated with increased risk of hypertension and cardiovascular disease. However, it is still unclear whether BP response to the CPT is a stable and reproducible trait over time. Using the same study protocol, the authors repeated the CPT 4.5 years after initial administration among 568 Han Chinese in rural northern China (2003–2005 and 2008–2009). BP was measured using a standard mercury sphygmomanometer prior to and 0, 1, 2, and 4 minutes after the participants immersed their hand in ice water (3°C–5°C) for 1 minute. Absolute BP levels and BP responses during the CPT in the initial and repeated administrations were highly correlated. For example, the correlation coefficients were 0.67, 0.73, 0.71, and 0.72 for absolute systolic BP levels at 0, 1, 2, and 4 minutes after ice-water immersion (all P 's < 0.0001). The correlation coefficients for systolic BP response were 0.41 at 0 minutes, 0.37 at 1 minute, 0.42 for maximum response, and 0.39 for the area under the curve during CPT (all P 's < 0.0001). These data indicate that BP response to the CPT is a long-term reproducible and stable characteristic in the general population.
blood pressure; cardiovascular diseases; hypertension; reproducibility of results; stress, physiological
Rare mutations of the epithelial sodium channel (ENaC) lead to Mendelian forms of salt-sensitive hypertension or salt-wasting hypotension. We aimed to examine the association between common variants in the ENaC genes and salt-sensitivity of blood pressure (BP).
Methods and Results
A total of 1,906 Han Chinese participated in the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) study, which includes a 7-day low-sodium intake (51.3 mmol sodium/day) followed by a 7-day high-sodium intake (307.8 mmol sodium/day). Nine BP measurements were obtained at baseline and each intervention period using a random-zero sphygmomanometer. Single nucleotide polymorphisms (SNPs), both tagging and functional, from the three ENaC subunits, α, β, and γ (SCNN1A, SCNN1B, and SCNN1G), were genotyped. Multiple common SNPs in SCNN1G were significantly associated with BP response to low-sodium intervention (rs4073930, p=1.7×10-5; rs4073291, p=1.1×10-5; rs7404408, p=1.9×10-5; rs5735, p=3.0×10-4; rs4299163, p=0.004; and rs4499238, p=0.002) even after correcting for multiple testing. For example, under an additive model, the minor allele G of SNP rs4073291 was associated with 1.33 mmHg lower systolic BP (SBP) reduction during low-sodium intervention.
This large dietary sodium intervention study indicates that common variants of ENaC subunits may contribute to the variation of BP response to dietary sodium intake. Future studies are warranted to confirm these findings in an independent population and to identify functional variants for salt-sensitivity.
blood pressure; epithelial sodium channel; genetic variant; salt-sensitivity
The purpose of this study was to examine the association between genetic variants in the renin-angiotensin system (RAS) and blood pressure (BP) responses to cold pressor test (CPT).
The CPT was conducted among 1,998 Han Chinese participants. BP measurements were obtained before and after the CPT using a standard sphygmomanometer according to a standard protocol. The association between SNP genotypes and BP responses to the CPT was assessed using a mixed linear model.
Of 68 SNPs genotyped in 6 RAS genes, two were strongly associated with diastolic BP (DBP) responses to CPT (P ≤ 0.001; false discovery rate q-value < 0.05): rs2006765 and rs943580 in the angiotensinogen (AGT) gene. Compared to C allele carriers of rs2006765, the TT homozygotes had a significantly decreased DBP response to the CPT. For participants with the TT genotype, percent DBP responses were 5.68% (4.25%, 7.10%), compared to corresponding responses of 9.17% (8.66%, 9.68%) among participants with the CC+CT genotype. In addition, SNP rs4681443 of the angiotensin type 1 receptor (AGTR1) gene was significantly associated with percent SBP responses to CPT (P≤0.001; q-value <0.05).
Briefly, our study identified variants in the AGT and AGTR1 genes that may influence BP responses to CPT in Han Chinese population. These results show that genetic variants in the RAS play an important role in BP responses to CPT, and therefore in predicting future hypertension.
blood pressure; cold pressor test; renin-angiotensin system; genetics; polymorphism
Genetic determinants of BP response to potassium, or potassium sensitivity, are largely unknown. We conducted a genome-wide linkage scan and positional candidate gene analysis to identify genetic determinants of potassium sensitivity.
Methods and Results
1,906 Han Chinese participants took part in a 7-day high-sodium followed by a 7-day high-sodium plus potassium dietary intervention. BP measurements were obtained at baseline and following each intervention using a random-zero sphygmomanometer. Significant linkage signals (LOD>3) for BP responses to potassium were detected at chromosomal regions 3q24-q26.1, 3q28, and 11q22.3-q24.3. Maximum multipoint LOD scores of 3.09 at 3q25.2 and 3.41 at 11q23.3 were observed for absolute DBP and MAP responses, respectively. Linkage peaks of 3.56 at 3q25.1 and 3.01 at 11q23.3 for percent DBP response and 3.22 at 3q25.2, 3.01 at 3q28, and 4.48 at 11q23.3 for percent MAP response were also identified. AGTR1 SNP rs16860760 in the 3q24-q26.1 region was significantly associated with absolute and percent systolic (SBP) responses to potassium (p-values=0.0008 and 0.0006, respectively). Absolute SBP responses (95% CI) for genotypes C/C, C/T, and T/T were: −3.71 (−4.02, −3.40), −2.62 (−3.38, −1.85), and 1.03 (−3.73, 5.79) mmHg, respectively; and percent responses (95% CI) were: −3.07 (−3.33, −2.80), −2.07 (−2.74, −1.41), and 0.90 (−3.20, 4.99), respectively. Similar trends were observed for DBP and MAP responses.
Genetic regions on chromosomes 3 and 11 may harbor important susceptibility loci for potassium sensitivity. Furthermore, the AGTR1 gene was a significant predictor of BP responses to potassium intake.
Clinical Trial Registration Information
http://clinicaltrials.gov; Identifier: NCT00721721
blood pressure; potassium; genetics
We examined the association of biomarkers of inflammation and endothelial dysfunction with diabetes and metabolic syndrome (MetS) in persons from Inner Mongolia.
A cross-sectional study was conducted among 2,536 people aged 20 years and older from Inner Mongolia, China. Overnight fasting blood samples were obtained to measure plasma concentrations of high sensitivity C-reactive protein (hsCRP), soluble inter-cellular adhesion molecule-1 (sICAM-1), sE-selectin, angiotensin II, high density lipoprotein cholesterol, triglycerides, and blood glucose. Waist circumference and blood pressure were measured by trained staff. MetS was defined according to the modified ATP III definition for Asians. Elevated level of the biomarker was defined as values in the upper tertile of the distribution. Participants were categorized into one of four groups based on the presence or absence of metabolic and glycemic abnormalities: 1) free of prediabetes, diabetes and MetS (reference group), 2) prediabetes or diabetes only, 3) MetS without prediabetes or diabetes, and 4) MetS plus prediabetes or diabetes. The multivariable models are adjusted for age, gender, smoking, drinking, family history of hypertension, and body mass index.
Among study participants, 18.5% had prediabetes, 3.6% had diabetes, and 27.4% of the entire study population had 3 or more components of the MetS. Elevated hsCRP was associated with an increased odds of prediabetes or diabetes only, MetS without prediabetes or diabetes, and MetS plus prediabetes or diabetes with multivariable adjusted odds ratios (95% confidence intervals) of 2.3 (1.7-3.1), 3.0 (2.4-3.8), and 5.8 (4.5-7.5), respectively. Elevated sICAM-1 was associated with increased odds (95% CI) of prediabetes or diabetes only (2.1, 1.6-2.9) and MetS plus prediabetes or diabetes (4.2, 3.2-5.3) but was not associated with MetS alone. Elevated sE-selectin was associated with a modestly increased risk of MetS (OR 1.7, 95% CI 1.4-2.2). Elevated levels of Angiotensin II were not associated with the MetS plus prediabetes or diabetes in this study.
Diabetes and the MetS are common in the Inner Mongolia population. The biomarkers of inflammation and endothelial dysfunction are associated with increased risk for diabetes and MetS in this population. These results are consistent with results from other populations.
metabolic syndrome; diabetes; inflammation; endothelial dysfunction; C-reactive protein; intercellular adhesion molecule-1; E-selectin
We conducted a meta-analysis of genome-wide association studies of systolic (SBP) and diastolic (DBP) blood pressure in 19,608 subjects of East Asian ancestry from the AGEN-BP consortium followed by de novo genotypingin 2 stages of replication involving 10,518 and 20,247 East Asian samples. We identified novel genome-wide significant (P < 5 × 10−8) associations between SBP or DBP and variants at four novel loci: ST7L-CAPZA1, FIGN-GRB14, ENPEP, and NPR3, as well as a novel variant near TBX3. Except for NPR3, all novel findings were significantly replicated for SBP or DBP in independent samples. Sevenloci previously reported in populations of European descent were confirmed. On 12q24.13, we observed an ethnic specific association(implicating rs671 at the ALDH2 locus as the causal variant) that affected SBP, DBP and multiple traits related to coronary artery disease. These findings provide novel insights into blood pressure regulation and potential targets for intervention.
Although beneficial effects of potassium intake on blood pressure (BP) are well established, little is known about genetic factors that underlie interindividual variability in BP response to dietary potassium. In a previous study, we reported the first evidence for significant heritabilities for BP response in a dietary intervention study in rural Chinese. In this report, we extend our genetic studies to examine associations with polymorphisms in genes in vascular endothelial pathways.
We genotyped study participants for 23 SNPs in EDN1, NOS3, and SELE. We tested 17 of these SNPs for associations with BP response to potassium supplementation in 1,843 participants. Association tests used population based (GEE) and family based (QTDT) methods, as well as tests for gene by gene interaction (GMDR, GEE).
Single SNP analysis identified significant associations for several SNPs in EDN1 with multiple measures of BP response to potassium supplementation. The cumulative effects of the minor EDN1 alleles that showed significant associations were to reduce measures of BP response by 0.5 to 0.9 mm Hg. We found significant evidence for effects of gene by gene interactions between EDN1 and SELE, even in the absence of individual associations with SELE variants.
Our results implicate variability in EDN1 and SELE as genetic factors that influence BP response to potassium intake. While such epidemiological studies do not allow direct determination of physiologic mechanisms, our findings of joint effects identify EDN1 and SELE as targets for functional studies to determine their interactions in BP response to potassium intake.
potassium; blood pressure response; dietary intervention; hypertension; genetic association; gene by gene interaction