A Functional 12T-insertion polymorphism in the <i>ATP1A1</i> promoter confers decreased susceptibility to hypertension in a male Sardinian population

Identification of susceptibility genes for essential hypertension in humans has been a challenge due to its multifactorial pathogenesis complicated by gene-gene and gene-environment interactions, developmental programing and sex specific differences. These concurrent features make identification of causal hypertension susceptibility genes with a single approach difficult, thus requiring multiple lines of evidence involving genetic, biochemical and biological experimentation to establish causal functional mutations. Here we report experimental evidence encompassing genetic, biochemical and in vivo modeling that altogether support ATP1A1 as a hypertension susceptibility gene in males in Sardinia, Italy. ATP1A1 encodes the α1Na,K-ATPase isoform, the sole sodium pump in vascular endothelial and renal tubular epithelial cells. DNA-sequencing detected a 12-nucleotide long thymidine (12T) insertion(ins)/deletion(del) polymorphism within a poly-T sequence (38T vs 26T) in the ATP1A1 5’-regulatory region associated with hypertension in a male Sardinian population. The 12T-insertion allele confers decreased susceptibility to hypertension (P = 0.035; OR = 0.50 [0.28–0.93]) accounting for 12.1 mmHg decrease in systolic BP (P = 0.02) and 6.6 mmHg in diastolic BP (P = 0.046). The ATP1A1 promoter containing the 12T-insertion exhibited decreased transcriptional activity in in vitro reporter-assay systems, indicating decreased α1Na,K-ATPase expression with the 12T-insertion, compared with the 12T-deletion ATP1A1 promoter. To test the effects of decreased α1Na,K-ATPase expression on blood pressure, we measured blood pressure by radiotelemetry in three month-old, highly inbred heterozygous knockout ATP1A1+/− male mice with resultant 58% reduction in ATP1A1 protein levels. Male ATP1A1+/− mice showed significantly lower blood pressure (P &#60; 0.03) than age-matched male wild-type littermate controls. Concordantly, lower ATP1A1 expression is expected to lower Na-reabsorption in the kidney thereby decreasing sodium-associated risk for hypertension and sodium-induced endothelial stiffness and dysfunction. Altogether, data support ATP1A1 as a hypertension susceptibility gene in a male Sardinian population, and mandate further investigation of its involvement in hypertension in the general population

Sex-specific effects of NLRP6/AVR and ADM <i>loci</i> on susceptibility to essential hypertension in a Sardinian population

Coronary artery disease, heart failure, fatal arrhythmias, stroke, and renal disease are the most common causes of mortality for humans, and essential hypertension remains a major risk factor. Elucidation of susceptibility loci for essential hypertension has been difficult because of its complex, multifactorial nature involving genetic, environmental, and sex- and age-dependent nature. We investigated whether the 11p15.5 region syntenic to rat chromosome 1 region containing multiple blood pressure quantitative trait loci (QTL) detected in Dahl rat intercrosses harbors polymorphisms that contribute to susceptibility/resistance to essential hypertension in a Sardinian population. Initial testing performed using microsatellite markers spanning 18 Mb of 11p15.5 detected a strong association between D11S1318 (at 2.1 Mb, P = 0.004) and D11S1346 (at 10.6 Mb, P = 0.00000004), suggesting that loci in close proximity to these markers may contribute to susceptibility in our Sardinian cohort. NLR family, pyrin domain containing 6/angiotensin-vasopressin receptor (NLRP6/AVR), and adrenomedullin (ADM) are in close proximity to D11S1318 and D11S1346, respectively; thus we tested single nucleotide polymorphisms (SNPs) within NLRP6/AVR and ADM for their association with hypertension in our Sardinian cohort. Upon sex stratification, we detected one NLRP6/AVR SNP associated with decreased susceptibility to hypertension in males (rs7948797G, P = 0.029; OR = 0.73 [0.57-0.94]). For ADM, sex-specific analysis showed a significant association between rs4444073C, with increased susceptibility to essential hypertension only in the male population (P = 0.006; OR = 1.44 [1.13-1.84]). Our results revealed an association between NLRP6/AVR and ADM loci with male essential hypertension, suggesting the existence of sex-specific NLRP6/AVR and ADM variants affecting male susceptibility to essential hypertension

Sardinians genetic background explained by runs of homozygosity and genomic regions under positive selection

The peculiar position of Sardinia in the Mediterranean sea has rendered its population an interesting biogeographical isolate. The aim of this study was to investigate the genetic population structure, as well as to estimate Runs of Homozygosity and regions under positive selection, using about 1.2 million single nucleotide polymorphisms genotyped in 1077 Sardinian individuals. Using four different methods - fixation index, inflation factor, principal component analysis and ancestry estimation - we were able to highlight, as expected for a genetic isolate, the high internal homogeneity of the island. Sardinians showed a higher percentage of genome covered by RoHs&gt;0.5 Mb (FRoH%0.5) when compared to peninsular Italians, with the only exception of the area surrounding Alghero. We furthermore identified 9 genomic regions showing signs of positive selection and, we re-captured many previously inferred signals. Other regions harbor novel candidate genes for positive selection, like TMEM252, or regions containing long non coding RNA. With the present study we confirmed the high genetic homogeneity of Sardinia that may be explained by the shared ancestry combined with the action of evolutionary forces

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

11ß-hydroxysteroid dehydrogenase type 2 activity is associated with left ventricular mass in essential hypertension

Aims: Left ventricular mass (LVM) is under the control of aldosterone and angiotensin II in experimental hypertension, but the effect of aldosterone on LVM is controversial in essential hypertension (EH). Some EH patients show a mild impairment of 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) activity without clinical features of the syndrome of apparent mineralocorticoid excess, where the incomplete cortisol-to-cortisone conversion leads to glucocorticoid-mediated mineralocorticoid effects. The mineralocorticoid receptor and 11ß-HSD2 are co-expressed in human heart. We investigated whether LVM may be regulated by glucocorticoids in EH patients. Methods and results: The ratio between 24 h urinary tetrahydro derivatives of cortisol and cortisone (THFs/THE), plasma renin activity, 24 h urinary aldosterone, blood pressure, and LVM indexed for height2.7 (LVMh2.7) were analysed in 493 never-treated hypertensives and 98 normotensives. THFs/THE was associated with LVMh2.7 in hypertensives and normotensives (r=0.32, P&lt;0.001, and r=0.17, P=0.04, respectively) and persisted after adjusting for confounders (multiple regression analysis). Body mass index, sex, recumbent plasma renin activity, and THFs/THE accounted for 26.1% of LVMh2.7 variation. Urinary aldosterone was not correlated with LVMh2.7. Conclusion: We suggest that glucocorticoids may take part in the regulation of LVM in EH patients as a function of 11ß-HSD2 activity, and contribute to the target organ damage associated with essential hypertension

Effect of the HMG-CoA reductase inhibitors on blood pressure in patients with essential hypertension and primary hypercholesterolemia

Certain hydroxymethylglutaryl coenzyme A reductase inhibitors, ie, statins, may cause vasodilation by restoring the endothelial dysfunction that frequently accompanies hypertension and hypercholesterolemia. Several studies have found that a blood pressure reduction is associated with the use of statins, but conclusive evidence from controlled trials is lacking. After an 8-week placebo and diet run-in period, 30 persons with moderate hypercholesterolemia and untreated hypertension (total cholesterol 6.29±0.52 mmol/L, systolic and diastolic blood pressure 149±6 and 97±2 mm Hg) were randomized in a double-blind manner to placebo or pravastatin (20 to 40 mg/d) in a crossover design. In 25 participants who completed the 32-week trial, pravastatin decreased total and LDL cholesterol (both -1.09 mmol/L, P=0.001), systolic and diastolic blood pressure (-8 and -5 mm Hg, both P=0.001), and pulse pressure (-3 mm Hg, P=0.011) and blunted the blood pressure increase caused by the cold pressor test (-4 mm Hg, P=0.005) compared with placebo. It also reduced the level of circulating endothelin-1 (P=0.001). The blood pressure results were virtually unchanged in stratified analyses according to gender and age and in intention-to-treat analyses that included the 5 patients who dropped out of the study. When the participants were taking either placebo or pravastatin, blood pressure was not significantly correlated with total or LDL cholesterol or with circulating endothelin-1. Pravastatin decreases systolic, diastolic, and pulse pressures in persons with moderate hypercholesterolemia and hypertension. This antihypertensive effect may contribute to the documented health benefits of certain statins

α-Adducin 460Trp Allele Is Associated With Erythrocyte Na Transport Rate in North Sardinian Primary Hypertensives

Erythrocyte membrane alterations mirror those of vascular smooth muscle and renal tubular cell membrane. The interaction between adducin and Na-K pump is the most likely biochemical mechanism responsible for the increased tubular Na reabsorption and hypertension in Milan hypertensive strain (MHS) rats. To substantiate this hypothesis in humans, we tested to see if α-adducin Gly460Trp genotype is associated with erythrocyte sodium transport rate in a new cohort of n=268 never-treated North Sardinian primary hypertensives. Plasma renin activity and blood pressure response to hydrochlorothiazide were also measured to evaluate the relationship between sodium transport rate and two intermediate phenotypes with a higher degree of genetic complexity. Na-K pump, Na-K-Cl cotransport, and Li-Na countertransport at Vmax were faster (P&lt;0.0001), whereas intracellular Na concentration was lower (P&lt;0.0001) in patients carrying one or two 460Trp alleles. Such behavior was mirrored by opposite changes of intracellular Na concentration. Plasma renin activity and blood pressure response to diuretic treatment, on the other hand, showed a weaker association with the sodium transport rate. In conclusion, our findings are consistent with the hypothesis that the Gly460Trp α-adducin polymorphism may affect renal Na handling through an alteration in ion transport across the cell membrane mirrored by erythrocytes. These results may also have clinical relevance because the Gly460Trp α-adducin polymorphism may explain, at least in part, the variability of blood pressure response to diuretics in primary hypertensive patients

Alpha-adducin 460Trp allele is associated with erythrocyte Na transport rate in north Sardinian primary hypertensives

Erythrocyte membrane alterations mirror those of vascular smooth muscle and renal tubular cell membrane. The interaction between adducin and Na-K pump is the most likely biochemical mechanism responsible for the increased tubular Na reabsorption and hypertension in Milan hypertensive strain (MHS) rats. To substantiate this hypothesis in humans, we tested to see if α-adducin Gly460Trp genotype is associated with erythrocyte sodium transport rate in a new cohort of n268 never-treated North Sardinian primary hypertensives. Plasma renin activity and blood pressure response to hydrochlorothiazide were also measured to evaluate the relationship between sodium transport rate and two intermediate phenotypes with a higher degree of genetic complexity. Na-K pump, Na-K-Cl cotransport, and Li-Na countertransport at Vmax were faster (P&lt;0.0001), whereas intracellular Na concentration was lower (P&lt;0.0001) in patients carrying one or two 460Trp alleles. Such behavior was mirrored by opposite changes of intracellular Na concentration. Plasma renin activity and blood pressure response to diuretic treatment, on the other hand, showed a weaker association with the sodium transport rate. In conclusion, our findings are consistent with the hypothesis that the Gly460Trp α-adducin polymorphism may affect renal Na handling through an alteration in ion transport across the cell membrane mirrored by erythrocytes. These results may also have clinical relevance because the Gly460Trp α-adducin polymorphism may explain, at least in part, the variability of blood pressure response to diuretics in primary hypertensive patients