Unfavorable Reduction in the Ratio of Endothelin B to A Receptors in Experimental 5/6 Nephrectomy and Adenine Models of Chronic Renal Insufficiency

Chronic renal insufficiency (CRI) is characterized by increased endothelin 1 (ET-1) synthesis. We studied rat kidney endothelin receptor A (ETA) and receptor B (ETB) expressions after 12 and 27 weeks of 5/6 nephrectomy, and after 12 weeks of 0.3% adenine diet, representing proteinuric and interstitial inflammation models of CRI, respectively. Uric acid and calcium-phosphate metabolism were modulated after 5/6 nephrectomy, while ETA blocker and calcimimetic were given with adenine. Endothelin receptor mRNA levels were measured using RT-qPCR and protein levels using autoradiography (5/6 nephrectomy) or ELISA (adenine model). Both 12 and 27 weeks after 5/6 nephrectomy, kidney cortex ETA protein was increased by similar to 60% without changes in ETB protein, and the ETB:ETA ratio was reduced. However, the ETB:ETA mRNA ratio did not change. In the adenine model, kidney ETA protein was reduced by similar to 70%, while ETB protein was suppressed by similar to 95%, and the ETB:ETA ratio was reduced by similar to 85%, both at the protein and mRNA levels. The additional interventions did not influence the observed reductions in the ETB:ETAratio. To conclude, unfavorable reduction in the ETB:ETA protein ratio was observed in two different models of CRI. Therefore, ETA blockade may be beneficial in a range of diseases that cause impaired kidney function.Peer reviewe

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

Purpose: The underlying causes of primary hypertension are not fully understood. Evidence on the relation of plasma calcium concentration with blood pressure (BP) is inconsistent and relies largely on studies utilizing office BP measurements in populations using cardiovascular drugs. In many studies adjustment for confounders was not optimal. In this cross-sectional study we examined the association of plasma total calcium concentration with the haemodynamic determinants of blood pressure. Subjects and methods: Supine haemodynamics were recorded using pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis in 618 normotensive or never-treated hypertensive subjects (aged 19–72 years) without diabetes, cardiovascular or renal disease, or cardiovascular medications. Linear regression analysis was used to investigate factors associated with haemodynamic variables. Results: Mean age was 45.0 years, body mass index 26.8 kg/m2, seated office BP 141/89 mmHg, and 307 subjects (49.7%) were male. Mean values of routine blood and plasma chemistry analyses were within the reference limits of the tests except for low-density lipoprotein cholesterol (3.05 mmol/l). In the laboratory, mean supine radial BP was 131/75 mmHg, and both systolic and diastolic BP correlated directly with plasma total calcium concentration (r = 0.25 and r = 0.22, respectively, p < 0.001 for both). In regression analysis plasma total calcium concentration was an independent explanatory variable for radial and aortic systolic and diastolic BP, and systemic vascular resistance, but not for cardiac output, pulse wave velocity, or any of the heart rate variability parameters. Conclusion: Plasma total calcium concentration was directly associated with systolic and diastolic BP and systemic vascular resistance in normotensive or never-treated hypertensive subjects without comorbidities and cardiovascular medications. Higher plasma calcium concentration potentially plays a role in primary hypertension via an effect on vascular resistance

Changes in hemodynamics associated with metabolic syndrome are more pronounced in women than in men

The increase in cardiovascular risk associated with metabolic syndrome (MS) seems higher in women than in men. We examined hemodynamics during head-up tilt in 252 men and 250 women without atherosclerosis, diabetes, or antihypertensive medication, mean age 48 years, using whole-body impedance cardiography and radial pulse wave analysis. MS was defined according to Alberti et al. 2009. Men and women with MS presented with corresponding elevations of systolic and diastolic blood pressure (10-14%, p ≤ 0.001) versus controls. Supine pulse wave velocity (16–17%, p publishedVersionPeer reviewe

Moderate hyperuricaemia ameliorated kidney damage in a low-renin model of experimental renal insufficiency

Uric acid has promoted renal fibrosis and inflammation in experimental studies, but some studies have shown nephroprotective effects due to alleviated oxidative stress. We studied the influence of experimental hyperuricaemia in surgically 5/6 nephrectomized rats. Three weeks after subtotal nephrectomy or sham operation, the rats were allocated to control diet or 2.0% oxonic acid (uricase inhibitor) diet for 9 weeks. Then blood, urine and tissue samples were taken, and renal morphology and oxidative stress were examined. Inflammation and fibrosis were evaluated using immunohistochemistry and real-time PCR (RT-PCR). Remnant kidney rats ingesting normal or oxonic acid diet presented with similar to 60% reduction of creatinine clearance and suppressed plasma renin activity. Oxonic acid diet increased plasma uric acid levels by >80 mu mol/L. In remnant kidney rats, moderate hyperuricaemia decreased glomerulosclerosis, tubulointerstitial damage and kidney mast cell count, without influencing the fibrosis marker collagen I messenger RNA (mRNA) content. In both sham-operated and 5/6 nephrectomized rats, the mast cell product 11-epi-prostaglandin-F-2 alpha excretion to the urine and kidney tissue cyclooxygenase-2 (COX-2) levels were decreased. To conclude, hyperuricaemic remnant kidney rats displayed improved kidney morphology and reduced markers of oxidative stress and inflammation. Thus, moderately elevated plasma uric acid had beneficial effects on the kidney in this low-renin model of experimental renal insufficiency.Peer reviewe

Posture-Related Differences in Cardiovascular Function Between Young Men and Women : Study of Noninvasive Hemodynamics in Rural Malawi

Background Cardiovascular risk is higher in men than in women, but little information exists about sex-related differences in cardiovascular function from low-income countries. We compared hemodynamics between sexes in rural Malawi in a cohort followed up since their birth. Methods and Results Supine, seated, and standing hemodynamics were recorded from 251 women and 168 men (mean age, 21 years; body mass index, 21 kg/m2) using oscillometric brachial waveform analyses (Mobil-O-Graph). The results were adjusted for estimated glomerular filtration rate, and plasma potassium, lipids, and glucose. Men had higher brachial and aortic systolic blood pressure and stroke index regardless of posture (P<0.001), and higher upright but similar supine diastolic blood pressure than women. Regardless of posture, heart rate was lower in men (P<0.001), whereas cardiac index did not differ between sexes. Women presented with lower supine and standing systemic vascular resistance index (P<0.001), whereas supine-to-standing increase in vascular resistance (P=0.012) and decrease in cardiac index (P=0.010) were higher in women. Supine left cardiac work index was similar in both sexes, whereas standing and seated left cardiac work index was higher in men than in women (P<0.001). Conclusions In young Malawian adults, men had higher systolic blood pressure, systemic vascular resistance, and upright cardiac workload, whereas women presented with higher posture-related changes in systemic vascular resistance and cardiac output. These findings show systematic sex-related differences in cardiovascular function in a cohort from a low-income country with high exposure to prenatal and postnatal malnutrition and infectious diseases.publishedVersionPeer reviewe

Effects of oxonic acid-induced hyperuricemia on mesenteric artery tone and cardiac load in experimental renal insufficiency

Peer reviewe

Liquorice ingestion attenuates vasodilatation via exogenous nitric oxide donor but not via β2-adrenoceptor stimulation

We examined the effect of liquorice ingestion on haemodynamic responses to exogenous nitric oxide donor (nitroglycerin) and β2-adrenoceptor agonist (salbutamol), and 11β-hydroxysteroid dehydrogenase activity, in 21 volunteers and 21 reference subjects. Haemodynamic data was captured before and after sublingual nitroglycerin (0.25 mg) and inhaled salbutamol (400 μg) during orthostatic challenge utilising radial pulse wave analysis and whole-body impedance cardiography. The recordings were performed at baseline and following two weeks of liquorice intake (290–370 mg/d glycyrrhizin). Urinary cortisone and cortisol metabolites were examined. Liquorice intake elevated aortic systolic and diastolic blood pressure and systemic vascular resistance when compared with the reference group. Following research drug administration the liquorice-induced increase in systemic vascular resistance was observed in the presence of nitroglycerin (pPeer reviewe

The characteristics of elevated blood pressure in abdominal obesity correspond to primary hypertension : a cross-sectional study

Background: Obesity-related hypertension and the associated metabolic abnormalities are considered as a distinct hypertensive phenotype. Here we examined how abdominal fat content, as judged by waist:height ratio, influenced blood pressure and hemodynamic profile in normotensive subjects and never-treated hypertensive patients. Methods: The 541 participants (20–72 years) underwent physical examination and laboratory analyses and were divided into age and sex-adjusted quartiles of waist:height ratio. Supine hemodynamics were recorded using whole-body impedance cardiography, combined with analyses of radial tonometric pulse wave form and heart rate variability. Results: Mean waist:height ratios in the quartiles were 0.46, 0.51, 0.55 and 0.62. Radial and aortic blood pressure, systemic vascular resistance, pulse wave velocity, markers of glucose and lipid metabolism, leptin levels and C-reactive protein were higher in quartile 4 when compared with quartiles 1 and 2 (p < 0.05 for all). Cardiac index was lower in quartile 4 versus quartile 1, while no differences were seen in heart rate variability, augmentation index, plasma renin activity, and aldosterone concentration between the quartiles. Linear regression analyses showed independent associations of abdominal obesity with higher aortic systolic and diastolic blood pressure, systemic vascular resistance, and pulse wave velocity (p < 0.05 for waist:height ratio in all regression models). Conclusion: Higher waist:height ratio was associated with elevated blood pressure, systemic vascular resistance, and arterial stiffness, but not with alterations in cardiac sympathovagal modulation or activation of the circulating renin-angiotensin-aldosterone system. Although obesity-related elevation of blood pressure has distinct phenotypic features, these results suggest that its main characteristics correspond those of primary hypertension. Trial registration: ClinicalTrails.gov NCT01742702 (date of registration 5th December 2012).publishedVersionPeer reviewe

Hyperurikemian ja kalsium-fosfori -tasapainon vaikutukset hapetusstressiin ja reniini-angiotensiini-aldosteroni -järjestelmään kokeellisessa munuaisten vajaatoiminnassa

Krooninen munuaistauti aiheuttaa monia häiriöitä kehon normaalissa homeostaasissa. Edetessään munuaisvaurio vähentää munuaisten suodatuskapasiteettia, nostaa virtsahapon pitoisuutta verenkierrossa ja aiheuttaa verenkiertoelimistössä muutoksia, jotka suosivat tulehdustilaa, verisuonten rakenteellisia muutoksia (jäykistyminen, seinämän paksuuntuminen), kohonnutta verenpainetta ja lisääntynyttä hapetusstressiä. Jos munuaisten suodatuskapasiteetin lasku jatkuu esteittä, on seurauksena lopulta terminaalinen munuaisten vajaatoiminta. Kokeelliset mallit tarjoavat mahdollisuuden tutkimuksiin, joita ei voi toteuttaa soluviljelymalleissa tai kliinisissä hankkeissa. Tässä tutkimussarjassa käytettiin munuaisten vajaatoiminnan rottamallia, joka aiheutettiin vähentämällä kirurgisesti 5/6 munuaismassasta (NX). Verrokkien toimenpiteenä oli munuaiskapselien poisto (Sham). Tutkimusasetelmina olivat kokeellinen hyperurikemia, parikalsitolihoito, fosfaattilisä sekä fosforinsitomishoito 3.0% kalsiumkarbonaatilla. Hyperurikemia aiheutettiin ravinnon 2.0% oksonihappolisällä, joka estää virtsahappoa metaboloivaa urikaasi-entsyymiä. Vaikka hyperurikemian on esitetty olevan monien patofysiologisten prosessien taustalla, toimii virtsahappo myös hapetusstressiltä suojaavana antioksidanttina. D vitamiinireseptoria aktivoivalla parikalsitolilla hoidetaan sekundaarista hyperparatyreoosia, kun taas kalsiumperäisiä fosforinsitojia käytetään vähentämään elimistön fosforipitoisuutta. Tutkimuksessa selvitettiin reniini-angiotensiini-aldosteroni -järjestelmän (RAAS) komponenttien geeni-ilmentymisen muutoksia sekä muutoksia hapetusstressitasossa. Kokeellisissa hyperurikemiatutkimuksissa tärkeimpinä kohteina olivat kiertävä RAAS ja munuaiskudoksen reniini-angiotensiini -järjestelmä (RAS), kaulavaltimon tonus sekä hapetusstressi. Kolmannessa osatyössä tutkittiin parikalsitolihoidon vaikutusta munuaisen RAS-geenien luentaan. Kaksi viimeistä osatyötä käsittelivät kalsium-fosfori -tasapainon muutoksia kokeellisessa munuaisten vajaatoiminnassa, tutkimuskohteina munuaisten ja verisuoniston RAS-geeniekspression muutokset, verisuonen supistustilan säätely (suolilievevaltimo) ja verenkierron sekä virtsan typpioksimetaboliitit. Pääasiallisina mittausvälineinä käytettiin in vitro autoradiografiaa, Western blot -menetelmää, reaaliaikaista käänteis-PCR menetelmää, radioimmunoassay -menetelmää, histologista analyysiä sekä in vitro verisuonifunktion rekisteröintiä. Osatutkimusten kestona oli 12 tai 27 viikkoa, millä vaikutettiin munuaisten vajaatoiminnan asteeseen. Kokeelliset mallit toimivat odotetusti, ja niissä havaitut ominaisuudet olivat linjassa aiemman tiedon kanssa. Kokeellinen hyperurikemia aktivoi kiertävän RAAS:n eli lisäsi plasman reniiniaktiivisuutta ja aldosteronipitoisuutta. Samanaikaisesti se vähensi hapetusstressiä ja lisäsi antioksidanttikapasiteettia, mikä voitiin havaita vuorokausivirtsan vähentyneenä 8-iso-PGF2α -erityksenä sekä lisääntyneenä plasman TRAP-arvona. Vaikka hyperurikemia nosti verenpainetta ja lisäsi kaliumin hukkaa virtsaan, havaittiin samalla parantunut kaulavaltimon typpioksidivälitteinen verisuonen laajeneminen. Näiden 12 viikkoa kestäneiden tutkimusten löydökset viittaavat aldosteronin rooliin hyperurikemian aiheuttamien natriumretention ja kohonneen verenpaineen taustalla. Toisaalta löydökset osoittavat myös hyperurikemian aiheuttamia myönteisiä vaikutuksia hapetusstressin tasoon. Viidentoista viikon parikalsitolihoito, joka aloitettiin 12 viikkoa NX- ja Sham-leikkausten jälkeen, ei vaikuttanut munuaiskudoksen RAS-geenien luentaan, joka lisääntyi NX rotissa. Tämä löydös ei vastaa aiemmin julkaistua laajan huomion saanutta kokeellista tutkimusta, jossa parikalsitolihoito vähensi munuaisten RAS-geenien luentaa, kun hoito aloitettiin heti neljä päivää leikkausten jälkeen. Tutkimussarjaan kuuluvan osatyön asetelma muistuttaa enemmän kliinistä munuaistautia, mikä voi selittää eriävät löydökset. Ravinnon fosfaattilisä aiheutti lisääntynyttä munuaisten, sydämen ja valtimoiden angiotensiiniä konvertoivan entsyymin (ACE) ilmentymistä, lisäsi kudosvauriota ja vähensi angiotensiini II:n reseptori 1a:n luentaa NX rotissa. Fosforinsidonta aiheutti päinvastaisen vasteen tutkittujen kudosten ACE-ekspressiossa. Lisäksi se vähensi munuaisvaurioita ja nitroproteiinien määrää valtimoissa sekä paransi typpioksidivälitteistä verisuonen laajenemista. NX rottien kohonnut verenpaine oli yhteydessä typpioksidin metaboliittien lisääntymiseen plasmassa ja virtsassa sekä vähentyneeseen endoteelin typpioksidisyntaasi-entsyymiin. ACE-ekspressio ja nitroproteiinien määrä lisääntyi valtimoissa ja typpioksidivälitteinen vasorelaksaatio heikentyi suolilievevaltimossa. Kaikkiaan tutkimussarja mallintaa kroonisen munuaisten vajaatoiminnan tyypillisiä komplikaatioita ja niihin vaikuttavia tekijöitä. Tutkimuslöydökset korostavat veren fosfaattipitoisuuden hallinnan merkitystä munuaisten vajaatoiminnassa sekä komplikaatioiden taustalla olevan säätelyjärjestelmän monimuotoisuutta.Chronic kidney disease is linked to several disturbances of the normal homeostasis. Progressing kidney damage may lead to decreased renal filtration capacity and alter cardiovascular physiology in a way that favors inflammation, arterial remodeling, elevated blood pressure, and increased oxidative stress. When the loss of renal function continues unabated, chronic renal insufficiency (CRI) develops. Experimental models offer a flexible tool to study disorders that cannot be investigated in a cell culture, or are not feasible or ethical for a clinical setting. The present series of studies featured a rat model of experimental chronic renal insufficiency induced by the surgical ablation of 5/6 of total renal mass (NX). Decapsulation of both kidneys was performed in the sham rats (Sham). Dietary and pharmacological interventions included 2.0% oxonic acid-induced hyperuricemia, paricalcitol treatment, and phosphate loading or phosphate binding with 3.0% calcium carbonate. Elevated circulating level of uric acid, hyperuricemia, is commonly associated with the initiation of multiple pathophysiological processes, whereas uric acid also functions as an antioxidant protecting from oxidative stress. Paricalcitol is a vitamin D receptor activator, which is used to treat secondary hyperparathyroidism, while calcium-based phosphate binders have been traditionally used to lower serum phosphate levels. The studies were designed to mimic some of the most common complications associated with kidney disease. The aim of this investigation was to determine the potential changes in the renin-angiotensin-aldosterone (RAAS) system gene expression and in the markers of oxidative stress during stage 3 experimental CRI. The two studies on experimental hyperuricemia were designed to specifically focus on the circulating RAAS and the renal tissue renin-angiotensin system (RAS), carotid artery tone, and antioxidant capacity. In the third study, the effects of paricalcitol on the kidney RAS component gene transcription were studied. The final two studies examined altered calcium-phosphate metabolism in CRI, and concentrated on the kidney and vascular RAS gene expression, as well as the effects on vascular function and nitric oxide (NO) metabolites in conduit-size arteries. The principal measurement methods used in this series of studies were quantitative in vitro autoradiography, Western blotting, real-time quantitative RT-PCR, radioimmunoassay, histological analysis, and in vitro vascular function determinations. The duration of the studies was 12 or 27 weeks, which were chosen to influence the severity of CRI. The experimental models were found suitable for the study designs, and successfully produced the previously reported characteristics of each disorder. Experimental hyperuricemia activated the circulating RAAS, reflected as increased plasma renin activity and aldosterone concentration, as well as reduced oxidative stress and increased antioxidant capacity in vivo, as evidenced by reduced 24-hour urinary 8-isoprostaglandin F2α excretion and increased plasma total peroxyl radical-trapping capacity, respectively. Hyperuricemia also caused elevated K+ to Na+ ratio in the urine and enhanced NO-mediated vasorelaxation of the carotid artery in the NX rats. According to the findings of these two 12-week studies, the role of aldosterone seems pivotal in the hyperuricemia-induced Na+ retention and blood pressure elevation, whereas the increased uric acid level may contrarily provide beneficial effects on oxidative stress. Fifteen-week paricalcitol treatment, initiated 12 weeks after the initial insult, did not influence the transcription levels of the kidney RAS component genes, which were elevated in the NX rats. This result was contrary to an earlier experimental report, which found a suppressing influence on several kidney RAS components following initiation of paricalcitol treatment only four days after surgery. Without doubt, the situation in the included study more resembles the clinical renal disease, and may explain the inconsistency in comparison with the earlier findings. Dietary phosphate loading was associated with elevated kidney, cardiac, and aortic angiotensin-converting enzyme (ACE) expression, increased tissue damage, and lower angiotensin II receptor subtype 1a transcription in the NX rats. Phosphate binding had opposite effects on kidney, cardiac, and aortic ACE, as well as kidney damage and nitrated proteins in the aorta, while it also enhanced vasorelaxation via increased bioactivity of endothelium-derived NO. The hypertension in the NX rats was associated with elevated levels of plasma and urine NO metabolites, decreased endothelial NO synthase, increased ACE and nitrated proteins in the aorta, as well as impaired vasorelaxation via endothelium-derived NO in the mesenteric artery. These findings underline the importance of effective phosphate control in chronic kidney disease. In conclusion, the present studies provide a broad assessment of common complications associated with CRI. The differing effects on the RAAS and oxidative stress highlight the multifaceted metabolic modulation in stage 3 kidney disease