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1.  Epigenetic Modifications in Essential Hypertension 
Essential hypertension (EH) is a complex, polygenic condition with no single causative agent. Despite advances in our understanding of the pathophysiology of EH, hypertension remains one of the world’s leading public health problems. Furthermore, there is increasing evidence that epigenetic modifications are as important as genetic predisposition in the development of EH. Indeed, a complex and interactive genetic and environmental system exists to determine an individual’s risk of EH. Epigenetics refers to all heritable changes to the regulation of gene expression as well as chromatin remodelling, without involvement of nucleotide sequence changes. Epigenetic modification is recognized as an essential process in biology, but is now being investigated for its role in the development of specific pathologic conditions, including EH. Epigenetic research will provide insights into the pathogenesis of blood pressure regulation that cannot be explained by classic Mendelian inheritance. This review concentrates on epigenetic modifications to DNA structure, including the influence of non-coding RNAs on hypertension development.
PMCID: PMC4848907  PMID: 27023534
essential hypertension; epigenetics; DNA methylation; histone modifications; non-coding RNA; microRNAs
2.  Signatures of miR-181a on the Renal Transcriptome and Blood Pressure 
Molecular Medicine  2015;21(1):739-748.
MicroRNA-181a binds to the 3′ untranslated region of messenger RNA (mRNA) for renin, a rate-limiting enzyme of the renin-angiotensin system. Our objective was to determine whether this molecular interaction translates into a clinically meaningful effect on blood pressure and whether circulating miR-181a is a measurable proxy of blood pressure. In 200 human kidneys from the TRANScriptome of renaL humAn TissuE (TRANSLATE) study, renal miR-181a was the sole negative predictor of renin mRNA and a strong correlate of circulating miR-181a. Elevated miR-181a levels correlated positively with systolic and diastolic blood pressure in TRANSLATE, and this association was independent of circulating renin. The association between serum miR-181a and systolic blood pressure was replicated in 199 subjects from the Genetic Regulation of Arterial Pressure of Humans In the Community (GRAPHIC) study. Renal immunohistochemistry and in situ hybridization showed that colocalization of miR-181a and renin was most prominent in collecting ducts where renin is not released into the systemic circulation. Analysis of 69 human kidneys characterized by RNA sequencing revealed that miR-181a was associated with downregulation of four mitochondrial pathways and upregulation of 41 signaling cascades of adaptive immunity and inflammation. We conclude that renal miR-181a has pleiotropic effects on pathways relevant to blood pressure regulation and that circulating levels of miR-181a are both a measurable proxy of renal miR-181a expression and a novel biochemical correlate of blood pressure.
PMCID: PMC4818264  PMID: 26322847
4.  Contribution of microRNA to pathological fibrosis in cardio-renal syndrome: impact of uremic toxins 
Physiological Reports  2015;3(4):e12371.
Progressive reduction in kidney function in patients following myocardial infarction (MI) is associated with an increase in circulating uremic toxins levels leading to increased extracellular matrix deposition. We have recently reported that treatment with uremic toxin adsorbent AST-120 in rats with MI inhibits serum levels of uremic toxin indoxyl sulfate (IS) and downregulates expression of cardiac profibrotic cytokine transforming growth factor beta (TGF-β1). In this study, we examined the effect of uremic toxins post-MI on cardiac microRNA-21 and microRNA-29b expression, and also the regulation of target genes and matrix remodeling proteins involved in TGFβ1 and angiotensin II signaling pathways. Sixteen weeks after MI, cardiac tissues were assessed for pathological and molecular changes. The percentage area of cardiac fibrosis was 4.67 ± 0.17 in vehicle-treated MI, 2.9 ± 0.26 in sham, and 3.32 ± 0.38 in AST-120-treated MI, group of rats. Compared to sham group, we found a twofold increase in the cardiac expression of microRNA-21 and 0.5-fold decrease in microRNA-29b in heart tissue from vehicle-treated MI. Treatment with AST-120 lowered serum IS levels and attenuated both, cardiac fibrosis and changes in expression of these microRNAs observed after MI. We also found increased mRNA expression of angiotensin-converting enzyme (ACE) and angiotensin receptor 1a (Agtr1a) in cardiac tissue collected from MI rats. Treatment with AST-120 attenuated both, expression of ACE and Agtr1a mRNA. Exposure of rat cardiac fibroblasts to IS upregulated angiotensin II signaling and altered the expression of both microRNA-21 and microRNA-29b. These results collectively suggest a clear role of IS in altering microRNA-21 and microRNA-29b in MI heart, via a mechanism involving angiotensin signaling pathway, which leads to cardiac fibrosis.
PMCID: PMC4425975  PMID: 25896982
AST-120; indoxyl sulfate; microRNA 21; microRNA 29b; myocardial infarction; uremic toxin
5.  Leukocyte telomere length variation due to DNA extraction method 
BMC Research Notes  2014;7:877.
Telomere length is indicative of biological age. Shorter telomeres have been associated with several disease and health states. There are inconsistencies throughout the literature amongst relative telomere length measured by quantitative PCR (qPCR) and different extraction methods or kits used. We quantified whole-blood leukocyte telomere length using the telomere to single copy gene (T/S) ratio by qPCR in 20 young (18-25 yrs) men after extracting DNA using three common extraction methods: Lahiri and Nurnberger (high salt) method, PureLink Genomic DNA Mini kit (Life Technologies) and QiaAmp DNA Mini kit (Qiagen). Telomere length differences of DNA extracted from the three extraction methods was assessed by one-way analysis of variance (ANOVA).
DNA purity differed between extraction methods used (P = 0.01). Telomere length was impacted by the DNA extraction method used (P = 0.01). Telomeres extracted using the Lahiri and Nurnberger method (mean T/S ratio: 2.43, range: 1.57 – 3.02) and PureLink Genomic DNA Mini Kit (mean T/S ratio: 2.57, range: 2.24 – 2.80) did not differ (P = 0.13). Likewise, QiaAmp and Purelink-extracted telomeres were not statistically different (P = 0.14). The Lahiri-extracted telomeres, however, were significantly shorter than those extracted using the QiaAmp DNA Mini Kit (mean T/S ratio: 2.71, range: 2.32 – 3.02; P = 0.003). DNA purity was associated with telomere length.
There are discrepancies between the length of leukocyte telomeres extracted from the same individuals according to the DNA extraction method used. DNA purity could be responsible for the discrepancy in telomere length but this will require validation studies. We recommend using the same DNA extraction kit when quantifying leukocyte telomere length by qPCR or when comparing different cohorts to avoid erroneous associations between telomere length and traits of interest.
PMCID: PMC4289347  PMID: 25475541
Telomeres; Leukocyte; T/S ratio; qPCR; DNA extraction; High salt method
6.  Measurement of absolute copy number variation reveals association with essential hypertension 
BMC Medical Genomics  2014;7:44.
The role of copy number variation (CNV) has been poorly explored in essential hypertension in part due to technical difficulties in accurately assessing absolute numbers of DNA copies. Droplet digital PCR (ddPCR) provides a powerful new approach to CNV quantitation. The aim of our study was to investigate whether CNVs located in regions previously associated with blood pressure (BP) variation in genome-wide association studies (GWAS) were associated with essential hypertension by the use of ddPCR.
Using a “power of extreme” approach, we quantified nucleic acids using ddPCR in white subjects from the Victorian Family Heart Study with extremely high (n = 96) and low (n = 92) SBP, providing power equivalent to 1714 subjects selected at random.
A deletion of the CNVs esv27061 and esv2757747 on chromosome 1p13.2 was significantly more prevalent in extreme high BP subjects after adjustment for age, body mass index and sex (12.6% vs. 2.2%; P = 0.013).
Our data suggests that CNVs within regions identified in previous GWAS may play a role in human essential hypertension.
PMCID: PMC4107748  PMID: 25027169
Copy number variation; Blood pressure; Hypertension; Extreme phenotypes; Droplet digital PCR
7.  Acute Exercise Leads to Regulation of Telomere-Associated Genes and MicroRNA Expression in Immune Cells 
PLoS ONE  2014;9(4):e92088.
Telomeres are specialized nucleoprotein structures that protect chromosomal ends from degradation. These structures progressively shorten during cellular division and can signal replicative senescence below a critical length. Telomere length is predominantly maintained by the enzyme telomerase. Significant decreases in telomere length and telomerase activity are associated with a host of chronic diseases; conversely their maintenance underpins the optimal function of the adaptive immune system. Habitual physical activity is associated with longer leukocyte telomere length; however, the precise mechanisms are unclear. Potential hypotheses include regulation of telomeric gene transcription and/or microRNAs (miRNAs). We investigated the acute exercise-induced response of telomeric genes and miRNAs in twenty-two healthy males (mean age = 24.1±1.55 years). Participants undertook 30 minutes of treadmill running at 80% of peak oxygen uptake. Blood samples were taken before exercise, immediately post-exercise and 60 minutes post-exercise. Total RNA from white blood cells was submitted to miRNA arrays and telomere extension mRNA array. Results were individually validated in white blood cells and sorted T cell lymphocyte subsets using quantitative real-time PCR (qPCR). Telomerase reverse transcriptase (TERT) mRNA (P = 0.001) and sirtuin-6 (SIRT6) (P<0.05) mRNA expression were upregulated in white blood cells after exercise. Fifty-six miRNAs were also differentially regulated post-exercise (FDR <0.05). In silico analysis identified four miRNAs (miR-186, miR-181, miR-15a and miR-96) that potentially targeted telomeric gene mRNA. The four miRNAs exhibited significant upregulation 60 minutes post-exercise (P<0.001). Telomeric repeat binding factor 2, interacting protein (TERF2IP) was identified as a potential binding target for miR-186 and miR-96 and demonstrated concomitant downregulation (P<0.01) at the corresponding time point. Intense cardiorespiratory exercise was sufficient to differentially regulate key telomeric genes and miRNAs in white blood cells. These results may provide a mechanistic insight into telomere homeostasis and improved immune function and physical health.
PMCID: PMC3994003  PMID: 24752326
8.  The Relation of Rapid Changes in Obesity Measures to Lipid Profile - Insights from a Nationwide Metabolic Health Survey in 444 Polish Cities 
PLoS ONE  2014;9(1):e86837.
The impact of fast changes in obesity indices on other measures of metabolic health is poorly defined in the general population. Using the Polish accession to the European Union as a model of political and social transformation we examined how an expected rapid increase in body mass index (BMI) and waist circumference relates to changes in lipid profile, both at the population and personal level.
Through primary care centres in 444 Polish cities, two cross-sectional nationwide population-based surveys (LIPIDOGRAM 2004 and LIPIDOGRAM 2006) examined 15,404 and 15,453 adult individuals in 2004 and 2006, respectively. A separate prospective sample of 1,840 individuals recruited in 2004 had a follow-up in 2006 (LIPIDOGRAM PLUS).
Two years after Polish accession to European Union, mean population BMI and waist circumference increased by 0.6% and 0.9%, respectively. This tracked with a 7.6% drop in HDL-cholesterol and a 2.1% increase in triglycerides (all p<0.001) nationwide. The direction and magnitude of the population changes were replicated at the personal level in LIPIDOGRAM PLUS (0.7%, 0.3%, 8.6% and 1.8%, respectively). However, increases in BMI and waist circumference were both only weakly associated with HDL-cholesterol and triglycerides changes prospectively. The relation of BMI to the magnitude of change in both lipid fractions was comparable to that of waist circumference.
Moderate changes in obesity measures tracked with a significant deterioration in measures of pro-atherogenic dyslipidaemia at both personal and population level. These associations were predominantly driven by factors not measureable directly through either BMI or waist circumference.
PMCID: PMC3908946  PMID: 24497983
9.  Urotensin-II System in Genetic Control of Blood Pressure and Renal Function 
PLoS ONE  2013;8(12):e83137.
Urotensin-II controls ion/water homeostasis in fish and vascular tone in rodents. We hypothesised that common genetic variants in urotensin-II pathway genes are associated with human blood pressure or renal function. We performed family-based analysis of association between blood pressure, glomerular filtration and genes of the urotensin-II pathway (urotensin-II, urotensin-II related peptide, urotensin-II receptor) saturated with 28 tagging single nucleotide polymorphisms in 2024 individuals from 520 families; followed by an independent replication in 420 families and 7545 unrelated subjects. The expression studies of the urotensin-II pathway were carried out in 97 human kidneys. Phylogenetic evolutionary analysis was conducted in 17 vertebrate species. One single nucleotide polymorphism (rs531485 in urotensin-II gene) was associated with adjusted estimated glomerular filtration rate in the discovery cohort (p = 0.0005). It showed no association with estimated glomerular filtration rate in the combined replication resource of 8724 subjects from 6 populations. Expression of urotensin-II and its receptor showed strong linear correlation (r = 0.86, p<0.0001). There was no difference in renal expression of urotensin-II system between hypertensive and normotensive subjects. Evolutionary analysis revealed accumulation of mutations in urotensin-II since the divergence of primates and weaker conservation of urotensin-II receptor in primates than in lower vertebrates. Our data suggest that urotensin-II system genes are unlikely to play a major role in genetic control of human blood pressure or renal function. The signatures of evolutionary forces acting on urotensin-II system indicate that it may have evolved towards loss of function since the divergence of primates.
PMCID: PMC3877024  PMID: 24391740
10.  Longer Leukocyte Telomeres Are Associated with Ultra-Endurance Exercise Independent of Cardiovascular Risk Factors 
PLoS ONE  2013;8(7):e69377.
Telomere length is recognized as a marker of biological age, and shorter mean leukocyte telomere length is associated with increased risk of cardiovascular disease. It is unclear whether repeated exposure to ultra-endurance aerobic exercise is beneficial or detrimental in the long-term and whether it attenuates biological aging. We quantified 67 ultra-marathon runners’ and 56 apparently healthy males’ leukocyte telomere length (T/S ratio) using real-time quantitative PCR. The ultra-marathon runners had 11% longer telomeres (T/S ratio) than controls (ultra-marathon runners: T/S ratio = 3.5±0.68, controls: T/S ratio = 3.1±0.41; β = 0.40, SE = 0.10, P = 1.4×10−4) in age-adjusted analysis. The difference remained statistically significant after adjustment for cardiovascular risk factors (P = 2.2×10−4). The magnitude of this association translates into 16.2±0.26 years difference in biological age and approximately 324–648bp difference in leukocyte telomere length between ultra-marathon runners and healthy controls. Neither traditional cardiovascular risk factors nor markers of inflammation/adhesion molecules explained the difference in leukocyte telomere length between ultra-marathon runners and controls. Taken together these data suggest that regular engagement in ultra-endurance aerobic exercise attenuates cellular aging.
PMCID: PMC3729964  PMID: 23936000
11.  Salt Loading in Canola Oil Fed SHRSP Rats Induces Endothelial Dysfunction 
PLoS ONE  2013;8(6):e66655.
This study aimed to determine if 50 days of canola oil intake in the absence or presence of salt loading affects: (1) antioxidant and oxidative stress markers, (2) aortic mRNA of NADPH oxidase (NOX) subunits and superoxide dismutase (SOD) isoforms and (3) endothelial function in SHRSP rats. SHRSP rats were fed a diet containing 10 wt/wt% soybean oil or 10 wt/wt% canola oil, and given tap water or water containing 1% NaCl for 50 days. Without salt, canola oil significantly increased RBC SOD, plasma cholesterol and triglycerides, aortic p22phox, NOX2 and CuZn-SOD mRNA, and decreased RBC glutathione peroxidase activity. With salt, canola oil reduced RBC SOD and catalase activity, LDL-C, and p22phox mRNA compared with canola oil alone, whereas plasma malondialdehyde (MDA) was reduced and RBC MDA and LDL-C were higher. With salt, the canola oil group had significantly reduced endothelium-dependent vasodilating responses to ACh and contractile responses to norepinephrine compared with the canola oil group without salt and to the WKY rats. These results indicate that ingestion of canola oil increases O2− generation, and that canola oil ingestion in combination with salt leads to endothelial dysfunction in the SHRSP model.
PMCID: PMC3676377  PMID: 23762494
12.  Consumption of a low glycaemic index diet in late life extends lifespan of Balb/c mice with differential effects on DNA damage 
Caloric restriction is known to extend the lifespan of all organisms in which it has been tested. Consequently, current research is investigating the role of various foods to improve health and lifespan. The role of various diets has received less attention however, and in some cases may have more capacity to improve health and longevity than specific foods alone. We examined the benefits to longevity of a low glycaemic index (GI) diet in aged Balb/c mice and examined markers of oxidative stress and subsequent effects on telomere dynamics.
In an aged population of mice, a low GI diet extended average lifespan by 12%, improved glucose tolerance and had impressive effects on amelioration of oxidative damage to DNA in white blood cells. Telomere length in quadriceps muscle showed no improvement in the dieted group, nor was telomerase reactivated.
The beneficial effects of a low GI diet are evident from the current study and although the impact to telomere dynamics late in life is minimal, we expect that earlier intervention with a low GI diet would provide significant improvement in health and longevity with associated effects to telomere homeostasis.
PMCID: PMC3922916  PMID: 24472560
13.  Genetic Dissection of a Blood Pressure Quantitative Trait Locus on Rat Chromosome 1 and Gene Expression Analysis Identifies SPON1 as a Novel Candidate Hypertension Gene 
Circulation research  2007;100(7):992-999.
A region with a major effect on blood pressure is located on rat chromosome 1. We have previously isolated this region in reciprocal congenic strains (WKY.SHR-Sa and SHR.WKY-Sa) derived from a cross of the spontaneously hypertensive rat (SHR) with the Wistar-Kyoto rat (WKY) and shown that there are two distinct BP quantitative trait loci (QTLs), BP1 and BP2, in this region. Sisa1, a congenic sub-strain from the SHR.WKY-Sa animals carrying an introgressed segment of 4.3Mb, contains BP1. Here, we report further dissection of BP1 by the creation of two new mutually exclusive congenic sub-strains (Sisa1a and Sisa1b) and interrogation of candidate genes by expression profiling and targeted transcript sequencing. Only one of the sub-strains (Sisa1a) continued to demonstrate a BP difference but with a reduced introgressed segment of 3Mb. Exonic sequencing of the twenty genes located in the Sisa1a region did not identify any major differences between SHR and WKY. However, microarray expression profiling of whole kidney samples and subsequent quantitative RT-PCR identified a single gene, Spon1 that exhibited significant differential expression between the WKY and SHR genotypes at both 6 and 24 weeks of age. Western blot analysis confirmed an increased level of the Spon1 gene product in SHR kidneys. Spon1 belongs to a family of genes with anti-angiogenic properties. These findings justify further investigation of this novel positional candidate gene in BP control in hypertensive rat models and humans.
PMCID: PMC3533402  PMID: 17332427
hypertension; genetics; rats; gene expression; quantitative trait locus
Hypertension  2011;58(6):1073-1078.
Variants in the gene encoding the γ-subunit of the epithelial sodium channel (SCNN1G) are associated with both Mendelian and quantitative effects on blood pressure. Here, in four cohorts of 1611 white European families comprising a total of 8199 individuals, we undertook staged testing of candidate SNPs for SCNN1G (supplemented with imputation based on data from the 1000 Genomes Project) followed by a meta-analysis in all families of the strongest candidate. We also examined relationships between the genotypes and relevant intermediate renal phenotypes as well as expression of SCNN1G in human kidneys. We found that an intronic SNP of SCNN1G (rs13331086) was significantly associated with age-, sex- and BMI-adjusted blood pressure in each of the four populations (P < 0.05). In an inverse variance-weighted meta-analysis of this SNP in all four populations each additional minor allele copy was associated with a 1 mmHg increase in systolic blood pressure and 0.52 mmHg increase in diastolic blood pressure (SE = 0.33, P = 0.002 for SBP; SE = 0.21, P = 0.011 for DBP). The same allele was also associated with higher 12-h overnight urinary potassium excretion (P = 0.04), consistent with increased epithelial sodium channel activity. Renal samples from hypertensive subjects showed a non-significant (P = 0.07) 1.7-fold higher expression of SCNN1G compared with normotensive controls. These data provide genetic and phenotypic evidence in support of a role for a common genetic variant of SCNN1G in blood pressure determination.
PMCID: PMC3220739  PMID: 22006290
blood pressure; genetics; meta-analysis; risk factors; cardiovascular diseases
15.  Inheritance of coronary artery disease in men: an analysis of the role of the Y chromosome 
Lancet  2012;379(9819):915-922.
A sexual dimorphism exists in the incidence and prevalence of coronary artery disease—men are more commonly affected than are age-matched women. We explored the role of the Y chromosome in coronary artery disease in the context of this sexual inequity.
We genotyped 11 markers of the male-specific region of the Y chromosome in 3233 biologically unrelated British men from three cohorts: the British Heart Foundation Family Heart Study (BHF-FHS), West of Scotland Coronary Prevention Study (WOSCOPS), and Cardiogenics Study. On the basis of this information, each Y chromosome was tracked back into one of 13 ancient lineages defined as haplogroups. We then examined associations between common Y chromosome haplogroups and the risk of coronary artery disease in cross-sectional BHF-FHS and prospective WOSCOPS. Finally, we undertook functional analysis of Y chromosome effects on monocyte and macrophage transcriptome in British men from the Cardiogenics Study.
Of nine haplogroups identified, two (R1b1b2 and I) accounted for roughly 90% of the Y chromosome variants among British men. Carriers of haplogroup I had about a 50% higher age-adjusted risk of coronary artery disease than did men with other Y chromosome lineages in BHF-FHS (odds ratio 1·75, 95% CI 1·20–2·54, p=0·004), WOSCOPS (1·45, 1·08–1·95, p=0·012), and joint analysis of both populations (1·56, 1·24–1·97, p=0·0002). The association between haplogroup I and increased risk of coronary artery disease was independent of traditional cardiovascular and socioeconomic risk factors. Analysis of macrophage transcriptome in the Cardiogenics Study revealed that 19 molecular pathways showing strong differential expression between men with haplogroup I and other lineages of the Y chromosome were interconnected by common genes related to inflammation and immunity, and that some of them have a strong relevance to atherosclerosis.
The human Y chromosome is associated with risk of coronary artery disease in men of European ancestry, possibly through interactions of immunity and inflammation.
British Heart Foundation; UK National Institute for Health Research; LEW Carty Charitable Fund; National Health and Medical Research Council of Australia; European Union 6th Framework Programme; Wellcome Trust.
PMCID: PMC3314981  PMID: 22325189
16.  FGF21 signalling pathway and metabolic traits – genetic association analysis 
European Journal of Human Genetics  2010;18(12):1344-1348.
Fibroblast growth factor 21 (FGF21) is a novel master regulator of metabolic profile. The biological actions of FGF21 are elicited upon its klotho beta (KLB)-facilitated binding to FGF receptor 1 (FGFR1), FGFR2 and FGFR3. We hypothesised that common polymorphisms in the FGF21 signalling pathway may be associated with metabolic risk. At the screening stage, we examined associations between 63 common single-nucleotide polymorphisms (SNPs) in five genes of this pathway (FGF21, KLB, FGFR1, FGFR2, FGFR3) and four metabolic phenotypes (LDL cholesterol – LDL-C, HDL-cholesterol – HDL-C, triglycerides and body mass index) in 629 individuals from Silesian Hypertension Study (SHS). Replication analyses were performed in 5478 unrelated individuals of the Swiss CoLaus cohort (imputed genotypes) and in 3030 directly genotyped individuals of the German Myocardial Infarction Family Study (GerMIFS). Of 54 SNPs that met quality control criteria after genotyping in SHS, 4 (rs4733946 and rs7012413 in FGFR1; rs2071616 in FGFR2 and rs7670903 in KLB) showed suggestive association with LDL-C (P=0.0006, P=0.0013, P=0.0055, P=0.011, respectively) and 1 (rs2608819 in KLB) was associated with body mass index (P=0.011); all with false discovery rate q<0.5. Of these, only one FGFR2 polymorphism (rs2071616) showed replicated association with LDL-C in both CoLaus (P=0.009) and men from GerMIFS (P=0.017). The direction of allelic effect of rs2071616 upon LDL-C was consistent in all examined populations. These data show that common genetic variations in FGFR2 may be associated with LDL-C in subjects of white European ancestry.
PMCID: PMC2988092  PMID: 20717167
fibroblast growth factor 21; fibroblast growth factor receptor 2; cholesterol; single-nucleotide polymorphism; genome-wide association studies
Hypertension  2010;56(6):1069-1076.
Genetic determinants of blood pressure are poorly defined. We undertook a large-scale gene-centric analysis to identify loci and pathways associated with ambulatory systolic and diastolic blood pressure.
We measured 24-hour ambulatory BP in 2020 individuals from 520 white European nuclear families (the GRAPHIC Study) and genotyped their DNA using the Illumina HumanCVD BeadChip array which contains approximately 50000 single nucleotide polymorphisms in >2000 cardiovascular candidate loci. We found a strong association between rs13306560 polymorphism in the promoter region of MTHFR and CLCN6 and mean 24-hour diastolic blood pressure - each minor allele copy of rs13306560 was associated with 2.6 mmHg lower mean 24-hour diastolic blood pressure (P=1.2×10−8). rs13306560 was also associated with clinic diastolic blood pressure in a combined analysis of 8129 subjects from the GRAPHIC Study, the CoLaus Study and the Silesian Cardiovascular Study (P=5.4×10−6). Additional analysis of associations between variants in Gene Ontology-defined pathways and mean 24-hour blood pressure in the GRAPHIC Study showed that cell survival control signalling cascades could play a role in blood pressure regulation. There was also a significant over-representation of rare variants (minor allele frequency <0.05) amongst polymorphisms showing at least nominal association with mean 24-hour blood pressure indicating that a considerable proportion of its heritability may be explained by uncommon alleles.
Through a large scale gene-centric analysis of ambulatory blood pressure, we identified an association of a novel variant at the MTHFR/CLNC6 locus with diastolic blood pressure and provided new insights into the genetic architecture of blood pressure.
PMCID: PMC3035934  PMID: 21060006
gene; genetics; blood pressure; single nucleotide polymorphism; association; heritability
18.  FGF21 signalling pathway and metabolic traits - genetic association analysis 
Fibroblast growth factor 21 (FGF21) is a novel master regulator of metabolic profile. The biological actions of FGF21 are elicited upon its klotho beta (KLB)-facilitated binding to FGF receptor 1 (FGFR1), FGF receptor 2 (FGFR2) and FGF receptor 3 (FGFR3). We hypothesised that common polymorphisms in the FGF21 signalling pathway may be associated with metabolic risk. At the screening stage we examined associations between 63 common single nucleotide polymorphisms (SNPs) in 5 genes of this pathway (FGF21, KLB, FGFR1, FGFR2, FGFR3) and 4 metabolic phenotypes (LDL cholesterol - LDL-C, HDL-cholesterol, triglycerides and body mass index - BMI) in 629 individuals from Silesian Hypertension Study. Replication analyses were performed in 5,478 unrelated individuals of the Swiss CoLaus cohort (imputed genotypes) and in 3,030 directly genotyped individuals of the German Myocardial Infarction Family Study. Of 54 SNPs that met quality control criteria after genotyping in Silesian Hypertension Study, four (rs4733946 and rs7012413 in FGFR1; rs2071616 in FGFR2 and rs7670903 in KLB) showed suggestive association with LDL-C (p=0.0006, p=0.0013, p=0.0055, p=0.011, respectively) and one (rs2608819 in KLB) was associated with BMI (p=0.011); all with false discovery rate q<0.5. Of these, only one FGFR2 polymorphism (rs2071616) showed replicated association with LDL-C in both the CoLaus cohort (p=0.009) and men from the German Myocardial Infarction Family Study (p=0.017). The direction of allelic effect of rs2071616 upon LDL-C was consistent in all examined populations. These data show that common genetic variation in FGFR2 may be associated with LDL-C in subjects of white European ancestry.
PMCID: PMC2988092  PMID: 20717167
fibroblast growth factor 21; fibroblast growth factor receptor 2; cholesterol; single nucleotide polymorphism; genome-wide association studies
19.  Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study 
Fox, Ervin R. | Young, J. Hunter | Li, Yali | Dreisbach, Albert W. | Keating, Brendan J. | Musani, Solomon K. | Liu, Kiang | Morrison, Alanna C. | Ganesh, Santhi | Kutlar, Abdullah | Ramachandran, Vasan S. | Polak, Josef F. | Fabsitz, Richard R. | Dries, Daniel L. | Farlow, Deborah N. | Redline, Susan | Adeyemo, Adebowale | Hirschorn, Joel N. | Sun, Yan V. | Wyatt, Sharon B. | Penman, Alan D. | Palmas, Walter | Rotter, Jerome I. | Townsend, Raymond R. | Doumatey, Ayo P. | Tayo, Bamidele O. | Mosley, Thomas H. | Lyon, Helen N. | Kang, Sun J. | Rotimi, Charles N. | Cooper, Richard S. | Franceschini, Nora | Curb, J. David | Martin, Lisa W. | Eaton, Charles B. | Kardia, Sharon L.R. | Taylor, Herman A. | Caulfield, Mark J. | Ehret, Georg B. | Johnson, Toby | Chakravarti, Aravinda | Zhu, Xiaofeng | Levy, Daniel | Munroe, Patricia B. | Rice, Kenneth M. | Bochud, Murielle | Johnson, Andrew D. | Chasman, Daniel I. | Smith, Albert V. | Tobin, Martin D. | Verwoert, Germaine C. | Hwang, Shih-Jen | Pihur, Vasyl | Vollenweider, Peter | O'Reilly, Paul F. | Amin, Najaf | Bragg-Gresham, Jennifer L. | Teumer, Alexander | Glazer, Nicole L. | Launer, Lenore | Zhao, Jing Hua | Aulchenko, Yurii | Heath, Simon | Sõber, Siim | Parsa, Afshin | Luan, Jian'an | Arora, Pankaj | Dehghan, Abbas | Zhang, Feng | Lucas, Gavin | Hicks, Andrew A. | Jackson, Anne U. | Peden, John F. | Tanaka, Toshiko | Wild, Sarah H. | Rudan, Igor | Igl, Wilmar | Milaneschi, Yuri | Parker, Alex N. | Fava, Cristiano | Chambers, John C. | Kumari, Meena | JinGo, Min | van der Harst, Pim | Kao, Wen Hong Linda | Sjögren, Marketa | Vinay, D.G. | Alexander, Myriam | Tabara, Yasuharu | Shaw-Hawkins, Sue | Whincup, Peter H. | Liu, Yongmei | Shi, Gang | Kuusisto, Johanna | Seielstad, Mark | Sim, Xueling | Nguyen, Khanh-Dung Hoang | Lehtimäki, Terho | Matullo, Giuseppe | Wu, Ying | Gaunt, Tom R. | Charlotte Onland-Moret, N. | Cooper, Matthew N. | Platou, Carl G.P. | Org, Elin | Hardy, Rebecca | Dahgam, Santosh | Palmen, Jutta | Vitart, Veronique | Braund, Peter S. | Kuznetsova, Tatiana | Uiterwaal, Cuno S.P.M. | Campbell, Harry | Ludwig, Barbara | Tomaszewski, Maciej | Tzoulaki, Ioanna | Palmer, Nicholette D. | Aspelund, Thor | Garcia, Melissa | Chang, Yen-Pei C. | O'Connell, Jeffrey R. | Steinle, Nanette I. | Grobbee, Diederick E. | Arking, Dan E. | Hernandez, Dena | Najjar, Samer | McArdle, Wendy L. | Hadley, David | Brown, Morris J. | Connell, John M. | Hingorani, Aroon D. | Day, Ian N.M. | Lawlor, Debbie A. | Beilby, John P. | Lawrence, Robert W. | Clarke, Robert | Collins, Rory | Hopewell, Jemma C. | Ongen, Halit | Bis, Joshua C. | Kähönen, Mika | Viikari, Jorma | Adair, Linda S. | Lee, Nanette R. | Chen, Ming-Huei | Olden, Matthias | Pattaro, Cristian | Hoffman Bolton, Judith A. | Köttgen, Anna | Bergmann, Sven | Mooser, Vincent | Chaturvedi, Nish | Frayling, Timothy M. | Islam, Muhammad | Jafar, Tazeen H. | Erdmann, Jeanette | Kulkarni, Smita R. | Bornstein, Stefan R. | Grässler, Jürgen | Groop, Leif | Voight, Benjamin F. | Kettunen, Johannes | Howard, Philip | Taylor, Andrew | Guarrera, Simonetta | Ricceri, Fulvio | Emilsson, Valur | Plump, Andrew | Barroso, Inês | Khaw, Kay-Tee | Weder, Alan B. | Hunt, Steven C. | Bergman, Richard N. | Collins, Francis S. | Bonnycastle, Lori L. | Scott, Laura J. | Stringham, Heather M. | Peltonen, Leena | Perola, Markus | Vartiainen, Erkki | Brand, Stefan-Martin | Staessen, Jan A. | Wang, Thomas J. | Burton, Paul R. | SolerArtigas, Maria | Dong, Yanbin | Snieder, Harold | Wang, Xiaoling | Zhu, Haidong | Lohman, Kurt K. | Rudock, Megan E. | Heckbert, Susan R. | Smith, Nicholas L. | Wiggins, Kerri L. | Shriner, Daniel | Veldre, Gudrun | Viigimaa, Margus | Kinra, Sanjay | Prabhakaran, Dorairajan | Tripathy, Vikal | Langefeld, Carl D. | Rosengren, Annika | Thelle, Dag S. | MariaCorsi, Anna | Singleton, Andrew | Forrester, Terrence | Hilton, Gina | McKenzie, Colin A. | Salako, Tunde | Iwai, Naoharu | Kita, Yoshikuni | Ogihara, Toshio | Ohkubo, Takayoshi | Okamura, Tomonori | Ueshima, Hirotsugu | Umemura, Satoshi | Eyheramendy, Susana | Meitinger, Thomas | Wichmann, H.-Erich | Cho, Yoon Shin | Kim, Hyung-Lae | Lee, Jong-Young | Scott, James | Sehmi, Joban S. | Zhang, Weihua | Hedblad, Bo | Nilsson, Peter | Smith, George Davey | Wong, Andrew | Narisu, Narisu | Stančáková, Alena | Raffel, Leslie J. | Yao, Jie | Kathiresan, Sekar | O'Donnell, Chris | Schwartz, Steven M. | Arfan Ikram, M. | Longstreth, Will T. | Seshadri, Sudha | Shrine, Nick R.G. | Wain, Louise V. | Morken, Mario A. | Swift, Amy J. | Laitinen, Jaana | Prokopenko, Inga | Zitting, Paavo | Cooper, Jackie A. | Humphries, Steve E. | Danesh, John | Rasheed, Asif | Goel, Anuj | Hamsten, Anders | Watkins, Hugh | Bakker, Stephan J.L. | van Gilst, Wiek H. | Janipalli, Charles S. | Radha Mani, K. | Yajnik, Chittaranjan S. | Hofman, Albert | Mattace-Raso, Francesco U.S. | Oostra, Ben A. | Demirkan, Ayse | Isaacs, Aaron | Rivadeneira, Fernando | Lakatta, Edward G. | Orru, Marco | Scuteri, Angelo | Ala-Korpela, Mika | Kangas, Antti J. | Lyytikäinen, Leo-Pekka | Soininen, Pasi | Tukiainen, Taru | Würz, Peter | Twee-Hee Ong, Rick | Dörr, Marcus | Kroemer, Heyo K. | Völker, Uwe | Völzke, Henry | Galan, Pilar | Hercberg, Serge | Lathrop, Mark | Zelenika, Diana | Deloukas, Panos | Mangino, Massimo | Spector, Tim D. | Zhai, Guangju | Meschia, James F. | Nalls, Michael A. | Sharma, Pankaj | Terzic, Janos | Kranthi Kumar, M.J. | Denniff, Matthew | Zukowska-Szczechowska, Ewa | Wagenknecht, Lynne E. | Fowkes, Gerald R. | Charchar, Fadi J. | Schwarz, Peter E.H. | Hayward, Caroline | Guo, Xiuqing | Bots, Michiel L. | Brand, Eva | Samani, Nilesh J. | Polasek, Ozren | Talmud, Philippa J. | Nyberg, Fredrik | Kuh, Diana | Laan, Maris | Hveem, Kristian | Palmer, Lyle J. | van der Schouw, Yvonne T. | Casas, Juan P. | Mohlke, Karen L. | Vineis, Paolo | Raitakari, Olli | Wong, Tien Y. | Shyong Tai, E. | Laakso, Markku | Rao, Dabeeru C. | Harris, Tamara B. | Morris, Richard W. | Dominiczak, Anna F. | Kivimaki, Mika | Marmot, Michael G. | Miki, Tetsuro | Saleheen, Danish | Chandak, Giriraj R. | Coresh, Josef | Navis, Gerjan | Salomaa, Veikko | Han, Bok-Ghee | Kooner, Jaspal S. | Melander, Olle | Ridker, Paul M. | Bandinelli, Stefania | Gyllensten, Ulf B. | Wright, Alan F. | Wilson, James F. | Ferrucci, Luigi | Farrall, Martin | Tuomilehto, Jaakko | Pramstaller, Peter P. | Elosua, Roberto | Soranzo, Nicole | Sijbrands, Eric J.G. | Altshuler, David | Loos, Ruth J.F. | Shuldiner, Alan R. | Gieger, Christian | Meneton, Pierre | Uitterlinden, Andre G. | Wareham, Nicholas J. | Gudnason, Vilmundur | Rettig, Rainer | Uda, Manuela | Strachan, David P. | Witteman, Jacqueline C.M. | Hartikainen, Anna-Liisa | Beckmann, Jacques S. | Boerwinkle, Eric | Boehnke, Michael | Larson, Martin G. | Järvelin, Marjo-Riitta | Psaty, Bruce M. | Abecasis, Gonçalo R. | Elliott, Paul | van Duijn , Cornelia M. | Newton-Cheh, Christopher
Human Molecular Genetics  2011;20(11):2273-2284.
The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10−8) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10−8). The top IBC association for SBP was rs2012318 (P= 6.4 × 10−6) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10−6) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity.
PMCID: PMC3090190  PMID: 21378095
20.  A common variant in low density lipoprotein receptor-related protein 6 gene (LRP6) is associated with LDL-cholesterol 
A rare mutation in low density lipoprotein receptor-related protein 6 gene (LRP6) was identified as the primary molecular defect underlying monogenic form of coronary artery disease. We hypothesised that common variants in LRP6 could predispose subjects to elevated LDL-cholesterol (LDL-C).
Methods and Results
12 common (minor allele frequency ≥0.1) single nucleotide polymorphisms in LRP6 were genotyped in 703 individuals from 213 Polish pedigrees (Silesian Cardiovascular Study families). The family-based analysis revealed that the minor allele of rs10845493 clustered with elevated LDL-C in offspring more frequently than expected by chance (p=0.0053). The quantitative analysis restricted to subjects free of lipid-lowering treatment confirmed the association between rs10845493 and age-, sex- and BMI-adjusted circulating levels of LDL-C in families as well as 2 additional populations - 218 unrelated subjects from Silesian Cardiovascular Study replication panel and 1138 individuals from Young Men Cardiovascular Association cohort (p=0.0268, p=0.0476 and p=0.0472, respectively). In the inverse variance weighted meta-analysis of the 3 populations each extra minor allele copy of rs10845493 was associated with 0.14 mmol/L increase in age-, sex- and BMI-adjusted LDL-C (SE=0.05, p=0.0038).
Common polymorphism in the gene underlying monogenic form of coronary artery disease impacts on risk of LDL-C elevation.
PMCID: PMC2814817  PMID: 19667113
gene; genetics; LDL-cholesterol; lipids; association
21.  Association between lipid profile and circulating concentrations of estrogens in young men 
Atherosclerosis  2008;203(1):257-262.
Men show higher rates of cardiovascular morbidity and mortality than pre-menopausal women and this sexual dimorphism may be related to sex-specific effects of sex steroids on cardiovascular risk factors. Unlike androgens, estrogens were not extensively investigated in relation to cardiovascular phenotypes in men.
We examined associations of estradiol and estrone and their precursors (total testosterone and androstenedione) with traditional cardiovascular risk factors (lipids, blood pressure, body mass) in 933 young (median age – 19 years), apparently healthy Polish men.
Total estradiol was associated with total cholesterol (p=0.006) and HDL-cholesterol (p<0.001) and estrone showed the strongest associations with both total cholesterol (p<0.001) and LDL-cholesterol (p<0.001) in the unadjusted ANOVA analysis. In the multivariable adjusted models in which other independent variables were held as constant one standard deviation increase in estradiol level was associated with 6%-standard deviation increase in total cholesterol (standardized B=0.06, p=0.038) and 6%-standard deviation decrease in HDL-cholesterol (standardized B=-0.06, p=0.036). An increase in estrone levels by one standard deviation was associated with respective 12%- and 13%-standard deviation increases in total cholesterol (standardized B=0.12, p<0.001) and LDL-cholesterol levels (standardized B=0.12, p<0.001) after controlling for other predictors of lipids. Estrone correlated linearly with androstenedione (r=0.28, p<0.001) but there was no correlation between estradiol and testosterone. Estrogens retained their independent associations with lipids after adjustment for their biochemical precursors in the multivariable analysis.
Increased levels of estrogens are associated with unfavourable lipid profile in men and that this association is apparent early in life, before cardiovascular disease manifestations.
PMCID: PMC2693280  PMID: 18639879
lipids; estrogens; sex steroids; association; risk factors
22.  Inverse Associations Between Androgens and Renal Function: The Young Men Cardiovascular Association (YMCA) Study 
American journal of hypertension  2008;22(1):100-105.
Men exhibit higher risk of nondiabetic renal diseases than women. This male susceptibility to renal disease may be mediated by gender-specific factors such as sex hormones.
We have undertaken a cross-sectional examination of associations between renal function (creatinine clearance estimated based on Cockcroft–Gault equation) and circulating levels of sex steroids (total testosterone, total estradiol, estrone, androstenedione, dehydroepiandrosterone sulfate (DHEA-S), and dihydrotestosterone) in 928 young (mean age: 18.5 ± 1.2 years) men.
Both androstenedione and DHEA-S showed inverse linear associations with renal function in the crude analysis of lean men (those with body mass index (BMI) less than median). However, only DHEA-S retained its association with renal function in lean subjects after adjustment—assuming no changes in other independent variables 1 s.d. increase in DHEA-S was associated with 13%-s.d. decrease in creatinine clearance (P = 0.004). Testosterone decreased across tertiles of creatinine clearance only in the crude analysis of nonlean (BMI greater than median) subjects (P < 0.001). The adjusted regression analysis that assumed no changes in other independent variables showed that 1 s.d. increase in total testosterone was associated with 11%-s.d. decrease in creatinine clearance of nonlean men (P = 0.006). Factor analysis confirmed an inverse association of renal function with both sex steroids and a different pattern of their loadings on glomerular filtration–related factors in lean (DHEA-S) and nonlean (testosterone) subjects.
Our data may suggest that androgens are inversely associated with estimated renal function in apparently healthy men without history of cardiovascular disease.
PMCID: PMC2808108  PMID: 19096379
23.  SLC2A9 Is a High-Capacity Urate Transporter in Humans 
PLoS Medicine  2008;5(10):e197.
Serum uric acid levels in humans are influenced by diet, cellular breakdown, and renal elimination, and correlate with blood pressure, metabolic syndrome, diabetes, gout, and cardiovascular disease. Recent genome-wide association scans have found common genetic variants of SLC2A9 to be associated with increased serum urate level and gout. The SLC2A9 gene encodes a facilitative glucose transporter, and it has two splice variants that are highly expressed in the proximal nephron, a key site for urate handling in the kidney. We investigated whether SLC2A9 is a functional urate transporter that contributes to the longstanding association between urate and blood pressure in man.
Methods and Findings
We expressed both SLC2A9 splice variants in Xenopus laevis oocytes and found both isoforms mediate rapid urate fluxes at concentration ranges similar to physiological serum levels (200–500 μM). Because SLC2A9 is a known facilitative glucose transporter, we also tested whether glucose or fructose influenced urate transport. We found that urate is transported by SLC2A9 at rates 45- to 60-fold faster than glucose, and demonstrated that SLC2A9-mediated urate transport is facilitated by glucose and, to a lesser extent, fructose. In addition, transport is inhibited by the uricosuric benzbromarone in a dose-dependent manner (Ki = 27 μM). Furthermore, we found urate uptake was at least 2-fold greater in human embryonic kidney (HEK) cells overexpressing SLC2A9 splice variants than nontransfected kidney cells. To confirm that our findings were due to SLC2A9, and not another urate transporter, we showed that urate transport was diminished by SLC2A9-targeted siRNA in a second mammalian cell line. In a cohort of men we showed that genetic variants of SLC2A9 are associated with reduced urinary urate clearance, which fits with common variation at SLC2A9 leading to increased serum urate. We found no evidence of association with hypertension (odds ratio 0.98, 95% confidence interval [CI] 0.9 to 1.05, p > 0.33) by meta-analysis of an SLC2A9 variant in six case–control studies including 11,897 participants. In a separate meta-analysis of four population studies including 11,629 participants we found no association of SLC2A9 with systolic (effect size −0.12 mm Hg, 95% CI −0.68 to 0.43, p = 0.664) or diastolic blood pressure (effect size −0.03 mm Hg, 95% CI −0.39 to 0.31, p = 0.82).
This study provides evidence that SLC2A9 splice variants act as high-capacity urate transporters and is one of the first functional characterisations of findings from genome-wide association scans. We did not find an association of the SLC2A9 gene with blood pressure in this study. Our findings suggest potential pathogenic mechanisms that could offer a new drug target for gout.
Editors' Summary
Blood is continually pumped around the human body to deliver the chemicals needed to keep the body's cells alive and to take cellular waste products to the kidneys where they are filtered out of the blood and excreted in the urine. In healthy people, the levels of nutrients and waste products in serum (the liquid part of blood) fall within “normal” ranges but in ill people these levels can be very different. For example, serum uric acid (urate) levels are usually increased in people with gout. In this arthritic condition, uric acid crystallizes in the joints (often those in the big toe) and causes swelling and intense pain. Increased serum urate levels, which are also associated with high blood pressure, diabetes, and several other important conditions, can be caused by eating food that is rich in chemicals called purines (for example, liver, dried beans, and port). The body also converts its own purines into uric acid so genetic variations in the enzymes involved in purine breakdown can alter serum urate levels, as can variations in the rate of urate removal from the body by the kidneys. Urinary urate excretion is controlled by urate transporters, proteins that carry urate into and out of the kidney cells. Uricosuric drugs, which are used to treat gout, reduce serum urate levels by inhibiting a urate transporter that reabsorbs urate from urine.
Why Was This Study Done?
Several urate transporters have already been identified but recently, using an approach called genome-wide association scanning, scientists found that some genetic variants of a human gene called SLC2A9 are more common in people with high serum urate levels than in people with normal levels. SLC2A9 encodes a glucose transporter (a protein that helps to move the sugar glucose through cell membranes) and is highly expressed in the kidney's main urate handling site. Given these facts, could SLC2A9 (the protein made from SLC2A9) be a urate transporter as well as a glucose transporter? In this study, the researchers investigate this possibility and also ask whether genetic variations in SLC2A9 might be responsible for the association between serum urate levels and high blood pressure.
What Did the Researchers Do and Find?
The researchers first expressed SLC2A9 in frog eggs, a type of cell that does not have its own urate transporter. They found that urate rapidly moved into eggs expressing SLC2A9 but not into control eggs, that SLC2A9 transported urate about 50 times faster than glucose, and that glucose stimulated SLC2A9-mediated urate transport. Similarly, overexpression of SLC2A9 in human embryonic kidney cells more than doubled their urate uptake. Conversely, when the researchers used a technique called RNA interference to reduce the expression of mouse SLC2A9 in mouse cells that normally makes this protein, urate transport was reduced. Next, the researchers looked at two small parts of SLC2A9 that vary between individuals (so-called single polynucleotide polymorphisms) in nearly 900 men who had had their serum urate levels and urinary urate excretion rates measured. They found that certain genetic variations at these two sites were associated with increased serum urate levels and decreased urinary urate excretion. Finally, the researchers used a statistical technique called meta-analysis to look for an association between one of the SLC2A9 gene variants and blood pressure. In two separate meta-analyses that together involved more than 20, 000 participants in several studies, there was no association between this gene variant and blood pressure.
What Do These Findings Mean?
Overall, these findings indicate that SLCA9 is a high capacity urate transporter and suggest that this protein plays an important part in controlling serum urate levels. They provide confirmation that common genetic variants in SLC2A9 affect serum urate levels to a marked degree, although they do not show exactly which genetic variant is responsible for increasing serum urate levels. They also provide important new insights into how the kidneys normally handle urate and suggest ways in which this essential process may sometimes go wrong. Thus, these findings could eventually lead to new treatments for gout and possibly for other diseases that are associated with increased serum urate levels.
Additional Information.
Please access these Web sites via the online version of this summary at
The UK National Health Service Direct health encyclopedia provides detailed information for patients about gout
MedlinePlus provides links to many sources of information about gout (in English and Spanish), including “What is gout?”, an easy-to-read guide from the US National Institutes of Arthritis and Musculoskeletal and Skin Diseases
Wikipedia also has pages on gout, uric acid, and SCL2A9 (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The Arthritis Research Campaign also has information on gout
Mark Caulfield and colleagues show that theSLC2A9 gene, which encodes a facilitative glucose transporter, is also a high-capacity urate transporter.
PMCID: PMC2561076  PMID: 18842065

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