Lanosterol Synthase Genetic Variants, Endogenous Ouabain, and Both Acute and Chronic Kidney Injury.

RATIONALE & OBJECTIVE: Studies of humans and animals have suggested that endogenous ouabain (EO) and related genes are mediators of acute (AKI) and chronic kidney injury. We sought to examine the relationship among EO levels, genetic variants in lanosterol synthase (LSS; an enzyme that catalyzes synthesis of cholesterol, a precursor of EO), and both AKI and chronic kidney injury. STUDY DESIGN: 2 prospective observational cohort studies and a cross-sectional study of kidney tissue. SETTING & PARTICIPANTS: (1) A prospective cohort study of patients undergoing cardiovascular surgery, (2) measurement of EO concentration in kidney tissue removed because of an adjacent tumor, and (3) a prospective cohort study of patients with newly diagnosed essential hypertension. EXPOSURE: Missense variant in LSS (A instead of C allele at rs2254524), which leads to a valine to leucine substitution at amino acid 642. OUTCOMES: Development of postoperative AKI in the cardiovascular surgery cohort, EO concentration in kidney tissue, and estimated glomerular filtration rate (eGFR) reductions in the essential hypertension cohort. ANALYTICAL APPROACH: Logistic regression for analysis of postoperative AKI, analysis of variance for EO concentration in kidney tissue, and generalized linear models for changes in eGFR over time. RESULTS: AKI incidence following cardiovascular surgery was greater among those with the LSS rs2254524 AA genotype (30.7%) than in those with the CC genotype (17.4%; P=0.001). LSS rs2254524 AA kidneys had higher EO concentrations than CC kidneys (2.14±0.29 vs 1.25±0.08ng/g; P<0.001). In the longitudinal study of patients with essential hypertension (median follow-up, 4 years; range, 1-15 years), eGFR decline was greater among the LSS rs2254524 AA genotype group (-4.39±1.18mL/min/1.73m2 per year) than in the AC or CC genotype groups (-1.07±0.55 and -2.00±0.45mL/min/1.73m2 per year respectively; P = 0.03). LIMITATIONS: These associations do not necessarily represent causal relationships; LSS rs2254524 variants may have effects on other steroid hormones. CONCLUSIONS: These findings support the potential value of LSS rs2254524 genotype-based risk stratification to identify patients at high risk for AKI before cardiovascular surgery, as well as predict accelerated eGFR in the setting of hypertension. These findings also suggest that LSS may in part drive EO-mediated kidney damage. EO may represent a new potential therapeutic target for the prevention of AKI and slowing of kidney damage in the setting of hypertension.

Endogenous ouabain and aldosterone are coelevated in the circulation of patients with essential hypertension.

OBJECTIVE: In the setting of normal sodium (Na) intake, many patients with hypertension have inappropriately elevated plasma aldosterone (Aldo) levels and may be at increased risk for tissue damage. Moreover, other adrenocortical steroids, including endogenous ouabain can stimulate tissue damage. As endogenous ouabain is often elevated in chronically Na-loaded states, is a vasoconstrictor, raises blood pressure (BP), and also promotes tissue fibrosis, we investigated the extent to which plasma Aldo and endogenous ouabain were coelevated among naïve hypertensive patients (NHP). We also investigated the impact of an acute salt load on these steroids, BP, and renal function. METHODS: NHP (590) were grouped in tertiles based on their baseline plasma Aldo (mean ±â€ŠSEM first 7.59 ±â€Š0.18, versus third 24.15 ±â€Š0.31 ng/dl). Baseline plasma renin activity (2.4 ±â€Š0.1 versus 1.2 ±â€Š0.1 ng/ml per h, P < 0.001), endogenous ouabain (268 ±â€Š14.9 pmol/l versus 239.0 ±â€Š13.6 pmol, P < 0.01) and DBP (91.9 ±â€Š0.76 versus 89.6 ±â€Š0.71 mmHg, P = 0.017) were higher in NHP in the third versus the first Aldo tertile, respectively. RESULTS: Acute Na loading showed that the BP of the third Aldo tertile NHP was especially salt-sensitive (slope of pressure-natriuresis relationship 0.015 ±â€Š0.002 versus 0.003 ±â€Š0.001 µEq/mmHg per min, P = 0.00024 after adjustment for sex, BMI, and age). Regression analyses showed that plasma Aldo and endogenous ouabain were linearly related (ß = 0.181, P = 0.0003). CONCLUSION: Among patients with essential hypertension, circulating endogenous ouabain and Aldo are typically coelevated and their BP is salt-sensitive. In conditions where Aldo is inappropriately elevated, both Aldo and endogenous ouabain may contribute to adverse cardiovascular and renal outcomes.

ADDing a piece to the puzzle of cognition in schizophrenia.

The biological bases of cognitive impairment in schizophrenia are poorly understood and may lie in insults in neurodevelopment, leading to alterations in critical structures. Synapses proteins are claimed to have etiopathogenic roles and more direct effects on core cognitive functions. Adducins family proteins seem of great interest, as they are fundamental constituents of synapses, involved in actin cytoskeleton assembly-disassembly, responsible of synaptic plasticity. ADD2 is more prominently expressed in brain tissues and influences memory and learning, commonly impaired in schizophrenia. In the present study we tested 342 patients with schizophrenia for three common adducins genetic variants, ADD1 rs4961, ADD2 rs4984 and ADD3 rs3731566, reported to have significant effects on circulatory system in humans. Neuropsychological measures were evaluated with the Brief Assessment of Cognition in Schizophrenia (BACS), a broad battery evaluating core cognitive domains. The analysis showed significant effects of ADD2 genotype on almost every cognitive domain. Moreover, significant interactions between ADD1 and ADD3 were also observed on some BACS subtests, namely Symbol Coding and Verbal Memory. Our findings suggest that adducins are involved in cognitive impairment in schizophrenia. This effect may result both from a direct mechanism affecting synaptic building and plasticity and indirectly as a consequence of vascular insults.

Lanosterol Synthase Gene Polymorphisms and Changes in Endogenous Ouabain in the Response to Low Sodium Intake.

Circulating levels of endogenous ouabain (EO), a vasopressor hormone of adrenocortical origin, are increased by sodium depletion. Furthermore, lanosterol synthase, an enzyme involved in cholesterol biosynthesis, has a missense polymorphism (rs2254524 V642L) that affects EO biosynthesis in adrenocortical cells. Here, we investigated the hypothesis that lanosterol synthase rs2254524 alleles in vivo impact the blood pressure (BP) and EO responses evoked by a low dietary Na intake (<100 mEq/d, 2 weeks) among patients with mild essential hypertension. During the low salt diet, the declines in both systolic BP (SBP: -8.7±1.7 versus -3.0±1.5; P=0.013) and diastolic BP (DBP: -5.1±0.98 versus -1.4±0.94 mm Hg; P<0.05), and the slope of the long-term pressure-natriuresis relationship affected significantly the presence of the lanosterol synthase rs2254524 A variant (AA: 0.71±0.22, AC 0.09±0.13, and CC 0.04±0.11 mEq/mm Hg/24 h; P=0.028). In addition, BP rose in ≈25% of the patients in response to the low salt diet and this was associated with increased circulating EO. Lanosterol synthase gene polymorphisms influence both the salt sensitivity of BP and changes in circulating EO in response to a low salt diet. The response of BP and EO to the low salt diet is markedly heterogeneous. Approximately 25% of patients experienced adverse effects, that is, increased BP and EO when salt intake was reduced and may be at increased long-term risk. The augmented response of EO to the low salt diet further supports the view that adrenocortical function is abnormal in some essential hypertensives.

Endogenous Ouabain: An Old Cardiotonic Steroid as a New Biomarker of Heart Failure and a Predictor of Mortality after Cardiac Surgery.

Cardiovascular diseases remain the main cause of mortality and morbidity worldwide; primary prevention is a priority for physicians. Biomarkers are useful tools able to identify high-risk individuals, guide treatments, and determine prognosis. Our aim is to investigate Endogenous Ouabain (EO), an adrenal stress hormone with hemodynamic effects, as a valuable biomarker of heart failure. In a population of 845 patients undergoing elective cardiac surgery, we have investigated the relationships between EO and echocardiography parameters/plasmatic biomarker of cardiac function. EO was found to be correlated negatively with left ventricular EF (p = 0.001), positively with Cardiac End-Diastolic Diameter (p = 0.047), and positively with plasmatic NT-proBNP level (p = 0.02). Moreover, a different plasmatic EO level (both preoperative and postoperative) was found according to NYHA class (p = 0.013). All these results have been replicated on an independent cohort of patients (147 subjects from US). Finally, a higher EO level in the immediate postoperative time was indicative of a more severe cardiological condition and it was associated with increased perioperative mortality risk (p = 0.023 for 30-day morality). Our data suggest that preoperative and postoperative plasmatic EO level identifies patients with a more severe cardiovascular presentation at baseline. These patients have a higher risk of morbidity and mortality after cardiac surgery.

TRPC6 gene variants and neuropsychiatric lupus.

Neuropsychiatric manifestations of systemic lupus erythematosus (NPSLE) influence patients' quality of life and their survival. Little is known about the pathophysiological bases of NPSLE and accordingly there are no specific therapeutic agents to be employed in this setting. Genetic research in systemic lupus erythematosus (SLE) is rapidly evolving as a tool to find clues about the pathogenic determinants of the disease and of its manifestations. Here, we describe the association of a single nucleotide polymorphic variant of the transient receptor potential cation channel, subfamily C, member 6 (TRPC6) gene with protection from the development of NPSLE in a cohort of 106 patients with SLE. TRPC6 is involved in the regulation of N-methyl-d-aspartate (NMDA) receptor signalling, a major player in post-ischemic neuronal injury and in the pathogenesis of NPSLE. TRPC6 genetic variants are promising candidate predictors of nervous system involvement in SLE, whereas the TRPC6 pathway might constitute a potential novel therapeutic target.

Beta-adducin and sodium-calcium exchanger 1 gene variants are associated with systemic lupus erythematosus and lupus nephritis.

Genetic research in systemic lupus erythematosus (SLE) is rapidly developing, and numerous sets of genes are being associated with specific clinical subphenotypes in the setting of SLE. On the other hand, basic science studies are revealing strong connections between salt-water balance and inflammation. The aim of this study was to evaluate whether variants of genes known to influence the individual susceptibility to hypertension also influence the renal function in a cohort of SLE patients with and without lupus nephritis (LN). This study is a case-control study with candidate gene approach. A total of 111 patients with SLE (50 with SLE without nephritis, 55 with LN and 6 with simple urinary sediment abnormalities) and 62 healthy controls (HC) were genotyped for NCX1 rs11893826 (NCX1a) and rs434082 (NCX1b) and ADD2 rs4984 SNPs. Patients with ADD2 CT genotype were protected from LN and skin involvement; ADD2 CC | NCX1a AA/AG genotypes were associated with the presence of anti-cardiolipin antibodies; NCX1a AA genotype was slightly more frequent in lupus patients than in HC and associated with relapse risk and higher creatinine in patients with LN. NCX1b GG patients with LN had increased chances to reach complete remission. NCX1b GG | NCX1a GG genotype is associated with joint involvement. ADD2 and NCX1 variants influence the risk and the clinical features of SLE and LN, highlighting their potential role in regulating systemic inflammation and/or the local response to immune-mediated injury.

A new clinical multivariable model that predicts postoperative acute kidney injury: impact of endogenous ouabain.

BACKGROUND: Acute kidney injury (AKI) is an important complication of cardiac surgery. Recently, elevated levels of endogenous ouabain (EO), an adrenal stress hormone with haemodynamic and renal effects, have been associated with worse renal outcome after cardiac surgery. Our aim was to develop and evaluate a new risk model of AKI using simple preoperative clinical parameters and to investigate the utility of EO. METHODS: The primary outcome was AKI according to Acute Kidney Injury Network stage II or III. We selected the Northern New England Cardiovascular Disease Study Group (NNECDSG) as a reference model. We built a new internal predictive risk model considering common clinical variables (CLIN-RISK), compared this model with the NNECDSG model and determined whether the addition of preoperative plasma EO improved prediction of AKI. RESULTS: All models were tested on >800 patients admitted for elective cardiac surgery in our hospital. Seventy-nine patients developed AKI (9.9%). Preoperative EO levels were strongly associated with the incidence of AKI and clinical complication (total ICU stay and in-hospital mortality). The NNECDSG model was confirmed as a good predictor of AKI (AUC 0.74, comparable to the NNECDSG reference population). Our CLIN-RISK model had improved predictive power for AKI (AUC 0.79, CI 95% 0.73-0.84). Furthermore, addition of preoperative EO levels to both clinical models improved AUC to 0.79 and to 0.83, respectively (ΔAUC +0.05 and +0.04, respectively, P < 0.01). CONCLUSION: In a population where the predictive power of the NNECDSG model was confirmed, CLIN-RISK was more powerful. Both clinical models were further improved by the addition of preoperative plasma EO levels. These new models provide improved predictability of the relative risk for the development of AKI following cardiac surgery and suggest that EO is a marker for renal vascular injury.

Quantitative proteomics reveals novel therapeutic and diagnostic markers in hypertension.

Hypertension is a prevalent disorder in the world representing one of the major risk factors for heart attack and stroke. These risks are increased in salt sensitive individuals. Hypertension and salt sensitivity are complex phenotypes whose pathophysiology remains poorly understood and, remarkably, salt sensitivity is still laborious to diagnose. Here we present a urinary proteomic study specifically designed to identify urinary proteins relevant for the pathogenesis of hypertension and salt sensitivity. Despite previous studies that underlined the association of UMOD gene variants with hypertension, this work provides novel evidence showing different uromodulin protein level in the urine of hypertensive patients compared to healthy individuals. Notably, we also show that patients with higher level of uromodulin are homozygous for UMOD risk variant and display a decreased level of salt excretion, highlighting the essential role of UMOD in the regulation of salt reabsorption in hypertension. Additionally, we found that urinary nephrin 1, a marker of glomerular slit diaphragm, may predict a salt sensitive phenotype and positively correlate with increased albuminuria associated with this type of hypertension.

Left ventricular radial function associated with genetic variation in the cGMP-dependent protein kinase.

cGMP-dependent protein kinase type I is a major mediator of cGMP signaling in the cardiovascular system. Recent studies on cardiac-specific PRKG1 knockout mice demonstrated that cGMP-dependent protein kinase type I mediates the negative inotropic effect of cGMP in the myocardium. We therefore investigated the association between left ventricular (LV) function and common polymorphisms in the PRKG1 gene in a general population. In 609 randomly selected participants (51.2% women; mean age, 48.8 years; 36.6% hypertensive) who were free from overt cardiac disease, we performed echocardiography and genotyped intronic tag single-nucleotide polymorphisms (SNPs) rs1904694, rs7897633, and rs7905063 in PRKG1. On the basis of color Doppler myocardial motion data, we calculated end-systolic longitudinal and radial deformation (strain) of the LV inferolateral wall. In multivariable-adjusted analyses accounting for confounders and relatedness, systolic radial strain was significantly (P ≤ 0.005) higher in homozygotes for rs1904694 (GG), rs7897633 (AA), and rs7905063 (TT) compared with heterozygotes or noncarriers. Haplotype analysis confirmed that LV radial strain was significantly higher in GAT homozygotes than in noncarriers (62.3% versus 56.0%; P = 0.0005). Transmission of the PRKG1 GAT haplotype to informative offspring was associated with higher LV radial strain (effect size, 6.11%; P = 0.017). For other LV phenotypes, none of the phenotype-genotype associations reached statistical significance. In conclusion, LV systolic radial function was associated with common polymorphisms in PRKG1. If experimental studies and longitudinal follow-up of LV function confirm the causality of this association, interference with cGMP-dependent protein kinase type I function might be a target for pharmacological intervention.

Preoperative endogenous ouabain predicts acute kidney injury in cardiac surgery patients.

OBJECTIVES: Acute kidney injury is a frequent complication of cardiac surgery and increases morbidity and mortality. As preoperative biomarkers predicting the development of acute kidney injury are not available, we have tested the hypothesis that preoperative plasma levels of endogenous ouabain may function as this type of biomarker. RATIONALE AND DESIGN: Endogenous ouabain is an adrenal stress hormone associated with adverse cardiovascular outcomes. Its involvement in acute kidney injury is unknown. With studies in patients and animal settings, including isolated podocytes, we tested the above mentioned hypothesis. PATIENTS: Preoperative endogenous ouabain was measured in 407 patients admitted for elective cardiac surgery and in a validation population of 219 other patients. We also studied the effect of prolonged elevations of circulating exogenous ouabain on renal parameters in rats and the influence of ouabain on podocyte proteins both "in vivo" and "in vitro." MAIN RESULTS: In the first group of patients, acute kidney injury (2.8%, 8.3%, 20.3%, p < 0.001) and ICU stay (1.4±0.38, 1.7±0.41, 2.4±0.59 days, p = 0.014) increased with each incremental preoperative endogenous ouabain tertile. In a linear regression analysis, the circulating endogenous ouabain value before surgery was the strongest predictor of acute kidney injury. In the validation cohort, acute kidney injury (0%, 5.9%, 8.2%, p < 0.0001) and ICU stay (1.2±0.09, 1.4±0.23, 2.2±0.77 days, p = 0.003) increased with the preoperative endogenous ouabain tertile. Values for preoperative endogenous ouabain significantly improved (area under curve: 0.85) risk prediction over the clinical score alone as measured by integrate discrimination improvement and net reclassification improvement. Finally, in the rat model, elevated circulating ouabain reduced creatinine clearance (-18%, p < 0.05), increased urinary protein excretion (+ 54%, p < 0.05), and reduced expression of podocyte nephrin (-29%, p < 0.01). This last finding was replicated ex vivo by incubating podocyte primary cell cultures with low-dose ouabain. CONCLUSIONS: Preoperative plasma endogenous ouabain levels are powerful biomarkers of acute kidney injury and postoperative complications and may be a direct cause of podocyte damage.

Left ventricular structure and function in relation to steroid biosynthesis genes in a white population.

BACKGROUND: Both endogenous ouabain (EO) and aldosterone are steroid hormones which might play a role in the pathogenesis of left ventricular (LV) hypertrophy and cardiac remodeling. Cholesterol side-chain cleavage enzyme (CYP11A1) and 3ß-hydroxysteroid dehydrogenase (HSD3B1) are two key enzymes in the pathway of steroid biosynthesis. METHODS: We investigated in 532 individuals (mean age, 50.3 years; 51.5% women) randomly recruited from a white European population whether LV structure and function were related to genetic variations in CYP11A1 and HSD3B1. We measured LV structure by conventional echocardiography and LV diastolic function by Doppler imaging of the transmitral blood flow and the mitral annular movement. We genotyped tag single nucleotide polymorphisms (SNPs) rs2279357, rs11638442 and rs2073475 in CYP11A1, and rs2236780, rs3765945, and rs6203 in HSD3B1. RESULTS: While adjusting for covariables and accounting for family clusters, LV mass index decreased (P ≤ 0.049) across the CYP11A1 genotypes in rs2279357 (CC vs. CT vs. TT), rs11638442 (GG vs. GC vs. CC), and rs2073475 (GG vs. GA+AA). Carriers of the CYP11A1 TCG haplotype had lower (P ≤ 0.017) LV mass and LV mass index than noncarriers. Carriers of HSD3B1 GCC haplotype had lower peak early (Ea; P = 0.004) and higher peak late (Aa; P = 0.066) diastolic mitral annular velocities and therefore a lower Ea/Aa ratio (P = 0.041) as compared with noncarriers. Neither plasma endogenous ouabain nor 24-h urinary aldosterone were related to any of the SNPs or haplotypes (P ≥ 0.07). CONCLUSIONS: Pending confirmation in other studies, LV mass and LV diastolic function seem to be related to genetic variation in the steroid biosynthesis.

Genes involved in vasoconstriction and vasodilation system affect salt-sensitive hypertension.

The importance of excess salt intake in the pathogenesis of hypertension is widely recognized. Blood pressure is controlled primarily by salt and water balance because of the infinite gain property of the kidney to rapidly eliminate excess fluid and salt. Up to fifty percent of patients with essential hypertension are salt-sensitive, as manifested by a rise in blood pressure with salt loading. We conducted a two-stage genetic analysis in hypertensive patients very accurately phenotyped for their salt-sensitivity. All newly discovered never treated before, essential hypertensives underwent an acute salt load to monitor the simultaneous changes in blood pressure and renal sodium excretion. The first stage consisted in an association analysis of genotyping data derived from genome-wide array on 329 subjects. Principal Component Analysis demonstrated that this population was homogenous. Among the strongest results, we detected a cluster of SNPs located in the first introns of PRKG1 gene (rs7897633, p = 2.34E-05) associated with variation in diastolic blood pressure after acute salt load. We further focused on two genetic loci, SLC24A3 and SLC8A1 (plasma membrane sodium/calcium exchange proteins, NCKX3 and NCX1, respectively) with a functional relationship with the previous gene and associated to variations in systolic blood pressure (the imputed rs3790261, p = 4.55E-06; and rs434082, p = 4.7E-03). In stage 2, we characterized 159 more patients for the SNPs in PRKG1, SLC24A3 and SLC8A1. Combined analysis showed an epistatic interaction of SNPs in SLC24A3 and SLC8A1 on the pressure-natriuresis (p interaction = 1.55E-04, p model = 3.35E-05), supporting their pathophysiological link in cellular calcium homeostasis. In conclusions, these findings point to a clear association between body sodium-blood pressure relations and molecules modulating the contractile state of vascular cells through an increase in cytoplasmic calcium concentration.

Endogenous ouabain and the renin-angiotensin-aldosterone system: distinct effects on Na handling and blood pressure in human hypertension.

OBJECTIVE: To evaluate whether the renin-angiotensin-aldosterone system (RAAS) and endogenous ouabain system differently affect renal Na handling and blood pressure. METHODS: Three hundred and one patients in whom we compared blood pressure, and renal Na tubular reabsorption in the basal condition and 2 h (T120) after saline infusion. RESULTS: Following multivariate-adjusted linear and quartiles analysis, baseline mean blood pressure (MBP) was significantly higher (113.7 ± 1.33 mmHg) in the fourth versus the first endogenous ouabain quartile (103.8 ± 1.04 mmHg) and the trend across the quartiles was highly significant (ß = 0.23, P = 3.53e-04). In contrast, an inverse relationship was present in the renin activity (PRA) quartiles with MBP highest in the first (112.5 ± 1.26) and lowest in the fourth PRA quartile (107.6 ± 1.48, P = 0.039). Following an acute saline load, changes in MBP and the slope of the pressure-natriuresis relationship were inversely related across the PRA quartiles. The fractional excretion of sodium (FENa) showed a negative linear trend going from the first to the third endogenous ouabain quartiles (2.35 ± 0.17 and 1.90 ± 0.14%, P = 0.05). Patients in the fourth endogenous ouabain quartile (>323 pmol/l) showed increased FENa T120 (2.78 ± 0.18%, P < 0.01) and increased Na tubular rejection fraction (P = 0.007) after Na load. After the saline load, there was a biphasic relationship between plasma endogenous ouabain and FENa favoring Na retention at low endogenous ouabain and Na excretion at high endogenous ouabain levels. CONCLUSION: The RAAS and endogenous ouabain system are two independent and complementary systems having an inverse (RAAS) or a direct (endogenous ouabain system) relationship with hemodynamic parameters.

Endogenous ouabain in renal Na(+) handling and related diseases.

The Na(+) pump and its Endogenous modulator Ouabain (EO) can be considered as an ancestral enzymatic system, conserved among species ranging from Drosophila to humans, related to Na handling. In this review, we examine how EO is linked with vascular function in hypertension and if it impacts the pathogenesis of heart and renal failure. Moreover, the molecular mechanism of endogenous ouabain-linked hypertension involves the sodium pump/sodium-calcium exchanger duet. Biosynthesis of EO occurs in adrenal glands and is under the control of angiotensin II, ACTH and epinephrine. Elevated concentrations of EO and in the sub-nanomolar concentration range were found to stimulate proliferation and differentiation of cardiac and smooth muscle cells. They may have a primary role in the development of cardiac dysfunction and failure. Experimental data suggest that the Na/K-ATPase α(2)-catalytic subunit causes EO-induced vasoconstriction. Finally, maneuvers that promote Na depletion, as diuretic therapy or reduced Na intake, raise the EO levels. Taken together, these findings suggest a key role for EO in body Na homeostasis.

Endogenous ouabain in Ménière's disease.

OBJECTIVE: Endogenous Ouabain (EO) has been demonstrated to modulate the activity of Na+, K+ -ATPase. Our purpose was to measure plasma levels of EO in Ménière's Disease (MD) subjects as a possible predisposing factor to developing and maintaining hydrops. STUDY DESIGN: Case-control study. SETTINGS: University hospital. PATIENTS: Thirty-nine MD subjects and 29 controls with a lifetime negative history for vertigo and dizziness. MAIN OUTCOME MEASURES: Plasma levels of EO. RESULTS: Plasma EO in MD subjects was in the range between 33 and 504 pmol/L (median, 135.5 pmol/L), whereas in the control group, plasma EO varied between 70 and 724 pmol/L (median, 205 pmol/L). The Mann-Whitney U test detected a statistically significant difference (p = 0.0001). CONCLUSION: Low plasma levels of EO have been proposed to augment Na-K pump activity, whereas high EO levels show an inhibitory effect on the pump activity. A proper pump activity may be necessary to keep the right ionic amount and osmolarity in endolymph. Although other possibilities may be considered, we suggest that altered control mechanisms of pump activity may be related to the pathogenesis and maintenance of MD.

Arterial properties in relation to genetic variations in the adducin subunits in a white population.

BACKGROUND: Adducin is a membrane skeleton protein, which consists of either alpha- and beta- or alpha- and gamma-subunits. We investigated whether arterial characteristics might be related to the genes encoding ADD1 (Gly460Trp-rs4961), ADD2 (C1797T-rs4984), and ADD3 (IVS11+386A>G-rs3731566). METHODS: We randomly recruited 1,126 Flemish subjects (mean age, 43.8 years; 50.3% women). Using a wall-tracking ultrasound system, we measured the properties of the carotid, femoral, and brachial arteries. We studied multivariate-adjusted phenotype-genotype associations, using a population- and family-based approach. RESULTS: In single-gene analyses, brachial diameter was 0.15 mm (P = 0.0022) larger, and brachial distensibility and cross-sectional compliance were 1.55 x 10(-3)/kPa (P = 0.013) and 0.017 mm(2)/kPa (P = 0.0029) lower in ADD3 AA than ADD3 GG homozygotes with an additive effect of the G allele. In multiple-gene analyses, the association of brachial diameter and distensibility with the ADD3 G allele occurred only in ADD1 GlyGly homozygotes. Otherwise, the associations between the arterial phenotypes in the three vascular beds and the ADD1 or ADD2 polymorphisms were not significant. In family-based analyses, the multivariate-adjusted heritability was 0.52, 0.38, and 0.30 for brachial diameter, distensibility, and cross-sectional compliance, respectively (P < 0.001). There was no evidence for population stratification (0.07 < or = P < or = 0.96). Transmission of the mutated ADD3 G allele was associated with smaller brachial diameter in 342 informative offspring (-0.12 +/- 0.04 mm; P = 0.0085) and in 209 offspring, who were ADD1 GlyGly homozygotes (-0.14 +/- 0.06 mm; P = 0.018). CONCLUSIONS: In ADD1 GlyGly homozygotes, the properties of the brachial artery are related to the ADD3 (A386G) polymorphism, but the underlying mechanism needs further clarification.

Effects of genetic variation in adducin on left ventricular diastolic function as assessed by tissue Doppler imaging in a Flemish population.

BACKGROUND: We investigated the possible association between left ventricular diastolic function and the ADD1 Gly460Trp and ADD3 IVS11 +386A>G polymorphisms alone and in combination. METHODS: In a family-based population study (473 subjects; 50.5% women; mean age 50.5 years), we measured early (Ea) and late (Aa) diastolic peak velocities of the mitral annulus by tissue Doppler imaging. In multivariate-adjusted analyses, we investigated phenotype-genotype associations, while accounting for confounders and family structure. RESULTS: Lateral Ea/Aa ratio was higher in ADD1 Trp allele carriers than in GlyGly homozygotes (1.51 vs. 1.40; P = 0.005) and was lower in ADD3 A allele carriers than in GG homozygotes (1.42 vs. 1.55; P = 0.005). The effects of ADD1 on the lateral Ea and Ea/Aa weakened with older age (P < 0.05). The best fitting model for lateral Ea and Ea/Aa included ADD1, ADD3, and the three-way interaction term of both genes with age. Below the age of 50 years, the lateral Ea/Aa ratio was higher in ADD1 Trp allele carriers than in GlyGly homozygotes (1.91 vs. 1.73; P = 0.006), particularly in the presence of ADD3 GG homozygosity (2.46 vs. 1.80; P = 0.0008). In older subjects, these phenotype-genotype associations were not significant (P > 0.20). Transmission of the ADD1 Trp allele to offspring was associated with higher lateral Ea (+0.91; P = 0.026) and Ea/Aa ratio (+0.23; P = 0.0008). CONCLUSION: Our population-based study demonstrated that left ventricular diastolic relaxation is modulated by genetic variation in ADD1 and ADD3. This association was more prominent in younger subjects in whom longstanding environmental factors and ageing are less likely to mask genetic effects.

Relationships among endogenous ouabain, alpha-adducin polymorphisms and renal sodium handling in primary hypertension.

OBJECTIVE: The basolateral Na pump drives renotubular reabsorption. In cultured renal cells, mutant adducins, as well as sub-nanomolar ouabain concentrations, stimulate the Na-K pump. METHODS: To determine whether these factors interact and affect Na handling and blood pressure (BP) in vivo, we studied 155 untreated hypertensive patients subdivided on the basis of their plasma endogenous ouabain or alpha-adducin genotype (ADD1 Gly460Trp-rs4961). RESULTS: Under basal conditions, proximal tubular reabsorption and plasma Na were higher in patients with mutated Trp ADD1 or increased endogenous ouabain (P = 0.002 and 0.05, respectively). BPs were higher in the high plasma endogenous ouabain group (P = 0.001). Following volume loading, the increment in BP (7.73 vs. 4.81 mmHg) and the slopes of the relationship between BP and Na excretion were greater [0.017 +/- 0.002 vs. 0.009 +/- 0.003 mmHg/(muEq min)] in ADD1 Trp vs. ADD1 Gly carriers (P < 0.05). BP changes were similar, whereas the slopes of the relationship between BP and Na excretion were lower [0.016 +/- 0.003 vs. 0.008 +/- 0.002 mmHg/(muEq min)] in patients with low vs. high endogenous ouabain (P < 0.05). In patients with high endogenous ouabain, volume loading increased the BP in the ADD1 Trp group but not in the Gly group (P < 0.05). Thus, patients with ADD1 Trp alleles are sensitive to salt and tubular Na reabsorption remains elevated after volume expansion. CONCLUSION: With saline loading, BP changes are similar in high and low endogenous ouabain patients, whereas tubular Na reabsorption increases in the high endogenous ouabain group. Saline loading unmasks differences in renal Na handling in patients with mutant adducin or high endogenous ouabain and exposes an interaction of endogenous ouabain and Trp alleles on BP.