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Concept: Renin

172

The kidney functions in key physiological processes to filter blood and regulate blood pressure via key molecular transporters and ion channels. Sex-specific differences have been observed in renal disease incidence and progression, as well as acute kidney injury in response to certain drugs. Although advances have been made in characterizing the molecular components involved in various kidney functions, the molecular mechanisms responsible for sex differences are not well understood. We hypothesized that the basal expression levels of genes involved in various kidney functions throughout the life cycle will influence sex-specific susceptibilities to adverse renal events.

Concepts: DNA, Renal failure, Kidney, Gene, Genetics, Gene expression, Blood pressure, Renin

170

BACKGROUND: To evaluated the prognostic significance of the pre-operative C-reactive protein (CRP) serum level in patients with renal cell cancer (RCC). METHODS: We evaluated 1,161 RCC patients with complete patient and tumour specific characteristics as well as information about their pre-operative CRP-level, who had undergone either radical nephrectomy or nephron-sparing surgery at two German high-volume centres (University Hospitals of Hannover and Ulm). The mean follow-up was 54 months. RESULTS: The CRP-level, stratified to three subgroups (CRP <= 4, 4--10, and >10 mg/l), correlated significantly with tumour stage (p < 0.001), the risk of presenting nodal disease (2.1, 3.1, and 16.4%) and distant metastasis (2.9, 8.6, and 30.0%; p < 0.001). The Kaplan-Meier 5-year cancer specific survival (CSS) rates were 89.4, 77.9, and 49.5%, respectively (p < 0.001). Multivariate analysis identified CRP as an independent prognosticator for CSS as well as overall survival (p < 0.001). Patients with a CRP of 4--10 and >10 mg/l had a 1.67 and 2.48 fold higher risk of dying due to their RCC compared to those with a pre-operative CRP <=4 mg/l, respectively. CONCLUSIONS: A high preoperative serum CRP level is an independent predictor of poor survival in patients with RCC. Its routine use could allow better risk stratification and risk-adjusted follow-up of RCC patients.

Concepts: Cancer, Lung cancer, Cancer staging, C-reactive protein, Renin, Renal cell carcinoma, Nephrectomy, Kidney cancer

163

Aliskiren is the newest antihypertensive drug and the first orally active direct renin inhibitor to become available for clinical use. Clinical data have substantiated that the antihypertensive effectiveness of aliskiren is similar to that of the other major antihypertensive agents. Furthermore, aliskiren has a similar safety profile to placebo. Combination treatment with aliskiren showed significant blood pressure and proteinuria reductions compared with monotherapy. Aliskiren decreases plasma renin activity in contrast to other renin-angiotensin-aldosterone related drugs. The efficacy of aliskiren in treating major cardiovascular events and the prevention of end-organ damage are being investigated in the ASPIRE HIGHER program. Although the first studies of the ASPIRE HIGHER program such as ALOFT, AVOID, AGELESS showed favorable findings, ASPIRE and AVANT-GARDE studies provided contradictory results. Subsequently, the ALTITUDE study was terminated early because of safety issues and lack of beneficial effects. Most recently, the ASTRONAUT trial showed no reduction in cardiovascular death or heart failure rehospitalization with the addition of aliskiren to standard therapy in patients who were hospitalized for heart failure and with reduced left-ventricular ejection fraction. The results of ongoing studies in other patient groups such as the ATMOSPHERE trial are awaited.

Concepts: Clinical trial, Blood, Myocardial infarction, Hypertension, Blood pressure, Effectiveness, Renin, Antihypertensive agents

154

Primary aldosteronism (PA) secondary to excessive and/or autonomous aldosterone secretion from the renin angiotensin system (RAS) accounts for approximately 10% of cases of hypertension and is primarily caused by bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenomas (APAs). Although the diagnosis has traditionally been supported by low serum potassium levels, normokalemic and even normotensive forms of PA have been identified expanding further the clinical phenotype. Morever, recent evidence has shown that serum aldosterone correlates with increased blood pressure in the general population and even moderately raised aldosterone levels are linked to increased cardiovascular morbidity and mortality. In addition, aldosterone antagonists are effective in blood pressure control even in patients without evidence of dysregulated aldosterone secretion. These findings indicate a higher prevalence of aldosterone excess among hypertensive patients than previously considered that could be attributed to disease heterogeneity, aldosterone level fluctuations related to an adrenocorticotropin (ACTH) effect, or inadequate sensitivity of current diagnostic means to identify apparent aldosterone excess. In addition, functioning aberrant receptors expressed in the adrenal tissue have been found in a subset of PA cases that could also be related to its pathogenesis. Recently a number of specific genetic alterations, mainly involving ion homeostasis across the membrane of zona glomerulosa, have been detected in approximately 50% of patients with APAs. Although specific genotype/phenotype correlations have not been clearly identified, differential expression of these genetic alterations could also account for the wide clinical phenotype, variations in disease prevalence and performance of diagnostic tests. In the present review, we critically analyze current means used to diagnose PA along with the role that ACTH, aberrant receptor expression and genetic alterations may exert, and provide evidence for an increased prevalence of aldosterone dysregulation in patients with essential hypertension and pre-hypertension.

Concepts: Kidney, Hypertension, Blood pressure, Aldosterone, Cortisol, Renin-angiotensin system, Renin, Hyperaldosteronism

111

Glyphosate-based herbicides (GBH) are the major pesticides used worldwide. Converging evidence suggests that GBH, such as Roundup, pose a particular health risk to liver and kidneys although low environmentally relevant doses have not been examined. To address this issue, a 2-year study in rats administering 0.1 ppb Roundup (50 ng/L glyphosate equivalent) via drinking water (giving a daily intake of 4 ng/kg bw/day of glyphosate) was conducted. A marked increased incidence of anatomorphological and blood/urine biochemical changes was indicative of liver and kidney structure and functional pathology. In order to confirm these findings we have conducted a transcriptome microarray analysis of the liver and kidneys from these same animals.

Concepts: Kidney, Liver, Renal cortex, Renin, Offal, Herbicide, Glyphosate, Roundup

37

Hypertension is a common and major risk factor for the leading U.S. killer, cardiovascular disease.(1)-(5) Reducing excess dietary sodium can lower blood pressure, with a greater response among persons with hypertension.(6)-(9) Nine of 10 Americans consume excess dietary sodium, defined as more than 2300 mg per day.(10),(11) Many leading medical and public health organizations recommend reducing dietary sodium to a maximum of 2300 mg per day on the basis of evidence indicating a public health benefit.(11)-(17) Yet this benefit has been questioned, mainly on the basis of studies suggesting that low sodium intake is also associated . . .

Concepts: Medicine, Public health, Epidemiology, Myocardial infarction, Cardiovascular disease, Sodium, Potassium, Renin

30

 To evaluate the outcomes with use of renin angiotensin system (RAS) blockers compared with other antihypertensive agents in people with diabetes.

Concepts: Hypertension, Diabetes mellitus, Randomized controlled trial, Blood pressure, Angiotensin, Renin-angiotensin system, Renin

28

For approximately six years, the only commercially available direct renin inhibitor aliskiren, which inhibits the renin-angiotensin-aldosterone system at the initial rate limiting step, has been marketed for the treatment of hypertension. Concurrently, much attention has been given the possibility that renin inhibition could hold potential for improved treatment in patients with chronic kidney disease, with diabetic nephropathy as an obvious group of patients to investigate, as the activity of the renin-angiotensin-aldosterone system is enhanced in these patients and as there is an unmet need for improved treatment and prognosis in these patients. Several short term studies have been performed in diabetic nephropathy, showing consistent effect on the surrogate endpoint lowering of albuminuria, both as monotherapy and in combination with other blockers of the renin-angiotensin-aldosterone system. In addition, combination treatment seemed safe and effective also in patients with impaired kidney function. These initial findings formed the basis for the design of a large morbidity and mortality trial investigating aliskiren as add-on to standard treatment. The study has just concluded, but was terminated early as a beneficial effect was unlikely and there was an increased frequency of side effects. Also in non-diabetic kidney disease a few intervention studies have been carried out, but there is no ongoing hard outcome study. In this review we provide the current evidence for renin inhibition in chronic kidney disease by reporting of the studies published so far as well as perspective on the future possibilites.

Concepts: Kidney, Nephrology, Medical terms, Hypertension, Blood pressure, Renin-angiotensin system, Renin, Renin inhibitor

28

Vasopressin modulates sodium reabsorption in the collecting duct through adenylyl cyclase-stimulated cyclic AMP, which exists as multiple isoforms; the specific isoform involved in vasopressin-stimulated sodium transport is unknown. To assess this, we studied mice deficient in adenylyl cyclase type VI specifically in the principal cells of the collecting duct. Knockout mice had increased urine volume and reduced urine sodium concentration, but regardless of the level of sodium intake, they did not exhibit significant alterations in urinary sodium excretion, arterial pressure, or pulse rate. Plasma renin concentration was elevated in knockout mice, however, suggesting a compensatory response. Valsartan significantly reduced arterial pressure in knockout mice but not in controls. Knockout mice had decreased renal cortical mRNA content of all three epithelial sodium channel (ENaC) isoforms, and total cell sodium channel isoforms α and γ were reduced in these animals. Patch-clamp analysis of split-open cortical collecting ducts revealed no difference in baseline activity of sodium channels, but knockout mice had abolished vasopressin-stimulated ENaC open probability and apical membrane channel number. In summary, these data suggest that adenylyl cyclase VI mediates vasopressin-stimulated ENaC activity in the kidney.

Concepts: Kidney, Nephron, Blood pressure, Renal physiology, Aldosterone, Sodium, Renin, Collecting duct system

28

The mode of renin release from renal juxtaglomerular cells into circulation is still unsolved in several aspects. Here we studied the intracellular organization of renin-storage vesicles and their changes during controlled stimulation of renin release. This was accomplished using isolated perfused mouse kidneys with 3-dimensional electron microscopic analyses of renin-producing cells. Renin was found to be stored in a network of single granules and cavern-like structures, and dependent on the synthesis of glycosylated prorenin. Acute stimulation of renin release led to increased exocytosis in combination with intracellular fusion of vesicles to larger caverns and their subsequent emptying. Renin release from the kidneys of SCID-beige mice, which contain few but gigantic renin-storage vesicles, was no different from that of kidneys from wild-type mice. Thus, our findings suggest that renin is released by mechanisms similar to compound exocytosis.Kidney International advance online publication, 12 December 2012; doi:10.1038/ki.2012.392.

Concepts: Kidney, Gene, Glucose, Cell membrane, Nephron, Renin, Juxtaglomerular cell, Juxtaglomerular apparatus