To determine whether mineralocorticoid receptor (MR) activation plays a role in diabetic renal injury and whether this role differs in types 1 and 2 diabetes mellitus, we examined the effect of a MR antagonist on renal injury in rodent models of type 1 (streptozotocin-treated rat) and type 2 (db/db mouse) diabetes. We studied three groups of 8-wk-old, uninephrectomized Wistar rats for 4 wk: diabetic streptozotocin- (55 mg/kg) treated rats (n = 11), diabetic streptozotocin-treated rats receiving the MR antagonist eplerenone (n = 15), and nondiabetic rats (n = 9). In addition, we studied three groups of 8-wk-old mice for 16 wk: diabetic db/db mice (n = 10), diabetic db/db mice treated with eplerenone (n = 8), and nondiabetic, db/+ littermates (n = 11). Diabetic rats and mice developed albuminuria and histopathological evidence of renal injury, including glomerular hypertrophy, mesangial expansion, and tubulointerstitial injury as well as increased renal cortical levels of MR protein, MR mRNA, TGFbeta mRNA, and osteopontin mRNA. All of these changes were significantly reduced by treatment with eplerenone except for the elevated MR levels. The beneficial effects of eplerenone were not attributable to changes in blood pressure or glycemia. In summary, MR expression was increased in kidneys of diabetic rodents, and MR antagonists effectively reduced diabetic renal injury irrespective of the species or specific cause of the diabetes. Thus, these data suggest that MR activation is a critical factor in the early pathogenesis of renal disease in both type 1 and type 2 diabetes mellitus.

The renin-angiotensin-aldosterone system plays an important role in large artery structure and blood pressure homeostasis. Among the genes coding for different components of this system, the aldosterone synthase (CYP11B2) gene could play an important role, but has been less investigated. We examined the role of two variations of the aldosterone synthase gene (CYP11B2), one located in the promoter of the gene, T-344C, the other in the 7th exon, the T4986C (Val/Ala), on plasma levels of renin and aldosterone, blood pressure, and arterial stiffness in subjects with essential hypertension. Subjects of European origin (n = 216) were examined during a 1-day hospitalization. Treatment, if any, was interrupted for at least 21 days before. Arterial stiffness was evaluated by measuring pulse wave velocity. Renin and aldosterone levels were evaluated by using a radioimmunoassay. The two polymorphisms were in complete linkage disequilibrium, as suggested by the presence of only three haplotypes in this population (T-344T4986, T-344C4986, and C-344T4986). The mean age and blood pressure values were similar in the different genotypes. Presence of the -344C allele was associated with elevated levels of plasma aldosterone: 90 +/- 8 pg/mL for TT (n = 67), 110 +/- 6 pg/mL for TC (n = 107), and 129 +/- 10 pg/mL for CC (n = 42) (test of codominant effect, P < .002 after adjustment for age and 24-h Na+ urine excretion). Pulse wave velocity was also increased in the -344C allele carriers: 11.3 +/- 0.4 m/sec, 12.7 +/- 0.3 m/sec, 12.0 +/- 0.5 m/sec in the TT, TC, and CC genotypes, respectively. No association was found between the T4986C polymorphism and the studied variables. In patients with essential hypertension, a variant on the promoter region of the aldosterone synthase gene is associated with significant differences in plasma aldosterone levels and arterial stiffness. These differences are not associated with variations in blood pressure levels.

Variations in the CAV1 gene are associated with IR and hypertension. CAV1 gene polymorphisms may be a biomarker for IR and hypertension, enabling earlier detection and improved treatment strategies.

The relationship between biological sex and aldosterone on blood pressure (BP) is unclear. We hypothesized that sex would modify the interaction between aldosterone and vascular responses to salt intake and angiotensin II (AngII). To test this hypothesis, in 1592 subjects from the well-controlled Hypertensive Pathotype cohort, we compared responses of women and men to chronic (BP and aldosterone levels in response to dietary salt) and acute (BP, renal plasma flow, and aldosterone responses to AngII infusion) manipulations. Women had a 30% higher salt sensitivity of BP than men (<0.0005) regardless of age or hypertension status, a greater BP response to AngII, and a 15% greater aldosterone response to AngII on both restricted and liberal salt diets (<0.005). Furthermore, there was an interaction (=0.003) between sex and aldosterone on BP response to AngII. Women also had a greater (<0.01) increment in renal plasma flow in response to AngII than men. To assess potential mechanisms for this sex effect, we compared aldosterone responses to AngII or potassium from rat zona glomerulosa cells and observed greater aldosterone production in female than male zona glomerulosa cells basally and in response to both agonists (<0.0001). In a rodent model of aldosterone-mediated cardiovascular disease induced by increased AngII and low NO, circulating aldosterone levels (<0.01), myocardial damage (<0.001), and proteinuria (<0.05) were greater in female than male rats despite having similar BP responses. Thus, increased aldosterone production likely contributes to sex differences in cardiovascular disease, suggesting that women may be more responsive to mineralocorticoid receptor blockade than men.

Observational studies in primary hyperaldosteronism (PA) suggest a positive relationship between aldosterone and parathyroid hormone (PTH); however, interventions to better characterize the physiologic relationship between the renin-angiotensin-aldosterone system (RAAS) and PTH are needed. We evaluated the effect of individual RAAS components on PTH using 4 interventions in humans without PA. PTH was measured before and after: Study 1) low-dose angiotensin II [AngII] infusion (1 ng/kg/min) and captopril administration (25 mg × 1); Study 2) high-dose AngII infusion (3 ng/kg/min); Study 3) blinded crossover randomization to aldosterone infusion (0.7 µg/kg/hr) and vehicle; and Study 4) blinded randomization to spironolactone (50mg/daily) or placebo for 6 weeks. Infusion of AngII at 1 ng/kg/min acutely increased aldosterone (+148%) and PTH (+10.3%), while AngII at 3 ng/kg/min induced larger incremental changes in aldosterone (+241%) and PTH (+36%) (P<0.01). Captopril acutely decreased aldosterone (−12%) and PTH (−9.7%) (P<0.01). In contrast, aldosterone infusion robustly raised serum aldosterone (+892%) without modifying PTH. However, spironolactone therapy over 6 weeks modestly lowered PTH when compared to placebo (P<0.05). In vitro studies revealed the presence of AngII type I and mineralocorticoid receptor mRNA and protein expression in normal and adenomatous human parathyroid tissues. We observed novel pleiotropic relationships between RAAS components and the regulation of PTH in individuals without PA: the acute modulation of PTH by the RAAS appears to be mediated by AngII, whereas the long-term influence of the RAAS on PTH may involve aldosterone. Future studies to evaluate the impact of RAAS inhibitors in treating PTH-mediated disorders are warranted.

Histone methylation, a determinant of chromatin structure and gene transcription, was thought to be irreversible, but recent evidence suggests that lysine-specific demethylase-1 (LSD1, Kdm1a) induces demethylation of histone H3 lysine 4 (H3K4) or H3K9 and thereby alters gene transcription. We previously demonstrated a human LSD1 phenotype associated with salt-sensitive hypertension. To test the hypothesis that LSD1 plays a role in the regulation of blood pressure (BP) via vascular mechanisms and gene transcription, we measured BP and examined vascular function and endothelial nitric oxide (NO) synthase (eNOS) expression in thoracic aorta of male wild-type (WT) and heterozygous LSD1 knockout mice (LSD1(+/-)) fed either a liberal salt (HS; 4% NaCl) or restricted salt diet (LS; 0.08% NaCl). BP was higher in LSD1(+/-) than WT mice on the HS diet but not different between LSD1(+/-) and WT mice on the LS diet. Further examination of the mechanisms of this salt-sensitive hypertension in LSD1(+/-) mice on the HS diet demonstrated that plasma renin activity and plasma levels and urinary excretion of aldosterone were less in LSD1(+/-) than WT, suggesting suppressed renin-angiotensin-aldosterone system. In contrast, phenylephrine (Phe)-induced aortic contraction was greater in LSD1(+/-) than WT mice on the HS diet. Treatment of aortic rings with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; a blocker of guanylate cyclase) enhanced Phe contraction in LSD1(+/-) compared with WT mice on the HS diet. Acetylcholine (Ach)-induced relaxation was less in LSD1(+/-) than WT mice on the HS diet. Endothelium removal or pretreatment with N(ω)-nitro-L-arginine methyl ester (blocker of NOS) or ODQ abolished Ach-induced relaxation in aorta of WT but had minimal effect in LSD1(+/-). Vascular relaxation to sodium nitroprusside, an exogenous NO donor and guanylate cyclase activator, was decreased in LSD1(+/-) vs. WT mice on the HS diet. RT-PCR and Western blots revealed decreased eNOS mRNA expression and eNOS and guanylate cyclase protein in the heart and aorta of LSD1(+/-) compared with WT mice on HS diet. Thus, during the HS diet, LSD1 deficiency is associated with hypertension, enhanced vascular contraction, and reduced relaxation via NO-cGMP pathway. The data support a role for LSD1-mediated histone demethylation in the regulation of NOS/guanylate cyclase gene expression, vascular function, and BP during the HS diet.

Context and objective We examined whether a prevalent caveolin-1 gene (CAV1) variant, previously related to insulin resistance, is associated with metabolic syndrome (MetS). Patients and methods We included subjects genotyped for the CAV1 variant rs926198 from two cohorts: 735 Caucasians from the HyperPATH multicenter study, and 810 Hispanic participants from the HTN-IR cohort. Results Minor allele carriers from HyperPATH cohort (57% of subjects) had higher Framingham risk scores, higher odds of diabetes (10.7% vs 5.7%, p=0.016), insulin resistance (44.3% vs 35.1%, p=0.022), low HDL (49.3% vs 39.6%, p=0.018) and MetS (33% vs 20.5%, p<0.001) but similar BMI. Consistently, minor allele carriers exhibited higher odds of MetS, even when adjusted for confounders and relatedness (OR 2.83 (1.73–4.63), p<0.001). The association with MetS was replicated in the Hispanic cohort HTN-IR (OR 1.61, [1.06–2.44], p=0.025). Exploratory analyses suggest that MetS risk is modified by a CAV1 variant - BMI status interaction, whereby the minor allele carrier status strongly predicted MetS (OR 3.86 [2.05–7.27], p<0.001) and diabetes (OR 2.27 [1.07–4.78], p=0.03) in non-obese, but not in obese subjects. In addition, we observed a familial aggregation for MetS diagnosis in minor allele carriers. Conclusion The prevalent CAV1 gene variant rs926198 is associated with MetS in separate Caucasian and Hispanic cohorts. These findings appear to be driven by an interaction between the genetic marker and obesity status, suggesting that the CAV1 variant may improve risk profiling in non-obese subjects. Additional studies are needed to confirm the clinical implications of our results.

Striatin is a novel protein that interacts with steroid receptors and modifies rapid, non-genomic activity in vitro. We tested the hypothesis that striatin would in turn affect mineralocorticoid receptor function and consequently sodium, water, and blood pressure homeostasis in an animal model. We evaluated salt sensitivity of blood pressure in novel striatin heterozygote knockout mice. When compared with wild type, striatin heterozygote exhibited a significant increase in blood pressure when sodium intake was increased from restricted (0.03%) to liberal (1.6%) sodium). Further, renal expression of mineralocorticoid receptor and its genomic downstream targets serum/glucocoticoid-regulated kinase 1 and epithelial sodium channel were increased in striatin heterozygote versus wild type mice on liberal sodium intake while the pAkt/Akt ratio, readout of mineralocoriticoid receptor's rapid, non-genomic pathway, was reduced. To determine the potential clinical relevance of these findings, we tested the association between single nucleotide polymorphic variants of striatin gene and salt sensitivity of blood presure in 366 Caucasian hypertensive subjects. HapMap derived tagging single nucleotide polymorphisms identified an association between rs2540923 with salt sensitivity of blood pressure (OR, 6.25; 95% CI 1.7-20; P=0.01). These data provide the first in vivo evidence in humans and rodents that associates striatin with markers of mineralocoriticoid receptor activity. The data also support the hypothesis that the rapid, non-genomic mineralocoriticoid receptor pathway (mediated via striatin) has a role in modulating the interaction between salt intake and blood pressure.