Studies of the renal effects of angiotensin II receptor blockade: the confounding factor of acute water loading on the action of vasoactive systems.

The acute renal tubular effects of two pharmacologically distinct angiotensin II receptor antagonists have been evaluated in normotensive volunteers on various salt diets. In the first study, the renal response to a single oral dose of losartan (100 mg) was assessed in subjects on a low (50 mmol Na/d) and on a high (200 mmol Na/d) salt intake. In a second protocol, the renal effects of 50 mg irbesartan were investigated in subjects receiving a 100 mmol Na/d diet. Both angiotensin II antagonists induced a significant increase in urinary sodium excretion. With losartan, a modest, transient increase in urinary potassium and a significant increase in uric acid excretion were found. In contrast, no change in potassium and uric acid excretions were observed with irbesartan, suggesting that the effects of losartan on potassium and uric acid are due to the intrinsic pharmacologic properties of losartan rather than to the specific blockade of renal angiotensin II receptors. Assessment of segmental sodium reabsorption using lithium as a marker of proximal tubular reabsorption demonstrated a decreased distal reabsorption of sodium with both antagonists. A direct proximal tubular natriuretic effect of the angiotensin II antagonist could be demonstrated only with irbesartan. This apparent discrepancy allowed us to reveal the importance of acute water loading as a possible confounding factor in renal studies. The results of the present analysis show that acute water loading per se may enhance renal sodium excretion and hence modify the level of activity of the renin-angiotensin system expected from a given sodium diet. Since acute water loading is a common practice in clinical renal studies, this confounding factor should be taken into account when investigating the renal effects of vasoactive systems.

Bone metabolism and risk of secondary hyperparathyroidism 12 months after gastric banding in obese pre-menopausal women.

OBJECTIVE: To evaluate, during the first postoperative year in obese pre-menopausal women, the effects of laparoscopic gastric banding on calcium and vitamin D metabolism, the potential modifications of bone mineral content and bone mineral density, and the risk of development of secondary hyperparathyroidism. SUBJECTS: Thirty-one obese pre-menopausal women aged between 25 and 52 y with a mean body mass index (BMI) of 43.6 kg/m(2), scheduled for gastric banding were included. Patients with renal, hepatic, metabolic and bone disease were excluded. METHODS: Body composition and bone mineral density (BMD) were measured at baseline, 6 and 12 months after gastric banding using dual-energy X-ray absorptiometry. Serum calcium, phosphate, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, bilirubin, urea, creatinine, uric acid, proteins, parathormone, vitamin D(3), IGF-1, IGF-BP3 and telopeptide, as well as urinary telopeptide, were measured at baseline and 1, 3, 6, 9 and 12 months after surgery. RESULTS: After 1 y vitamin D3 remained stable and PTH decreased by 12%, but the difference was not significant. Serum telopeptide C increased significantly by 100% (P<0.001). There was an initial drop of the IGF-BP3 during the first 6 months (P<0.05), but the reduction was no longer significant after 1 y. The BMD of cortical bone (femoral neck) decreased significantly and showed a trend of a positive correlation with the increase of telopeptides (P<0.06). The BMD of trabecular bone, at the lumbar spine, increased proportionally to the reduction of hip circumference and of body fat. CONCLUSION: There is no evidence of secondary hyperparathyroidism 1 y after gastric banding. Nevertheless biochemical bone markers show a negative remodelling balance, characterized by an increase of bone resorption. The serum telopeptide seems to be a reliable parameter, not affected by weight loss, to follow up bone turnover after gastroplasty.

Mouse GLUT9: evidences for a urate uniporter.

GLUT9 (SLC2A9) is a newly described urate transporter whose function, characteristics, and localization have just started to be elucidated. Some transport properties of human GLUT9 have been studied in the Xenopus laevis oocyte expression system, but the type of transport (uniport, coupled transport system, stoichiometry ... .) is still largely unknown. We used the same experimental system to characterize in more detail the transport properties of mouse GLUT9, its sensitivity to several uricosuric drugs, and the specificities of two splice variants, mGLUT9a and mGLUT9b. [(14)C]urate uptake measurements show that both splice variants are high-capacity urate transporters and have a K(m) of approximately 650 microM. The well-known uricosuric agents benzbromarone (500 microM) and losartan (1 mM) inhibit GLUT9-mediated urate uptake by 90 and 50%, respectively. Surprisingly, phloretin, a glucose-transporter blocker, inhibits [(14)C]urate uptake by approximately 50% at 1 mM. Electrophysiological measurements suggest that urate transport by mouse GLUT9 is electrogenic and voltage dependent, but independent of the Na(+) and Cl(-) transmembrane gradients. Taken together, our results suggest that GLUT9 works as a urate (anion) uniporter. Finally, we show by RT-PCR performed on RNA from mouse kidney microdissected tubules that GLUT9a is expressed at low levels in proximal tubules, while GLUT9b is specifically expressed in distal convoluted and connecting tubules. Expression of mouse GLUT9 in the kidney differs from that of human GLUT9, which could account for species differences in urate handling.

Salt-dependent renal effects of an angiotensin II antagonist in healthy subjects.

This study was designed to evaluate in healthy volunteers the renal hemodynamic and tubular effects of the orally active angiotensin II receptor antagonist losartan (DuP 753 or MK 954). Losartan or a placebo was administered to 23 subjects maintained on a high-sodium (200 mmol/d) or a low-sodium (50 mmol/d) diet in a randomized, double-blind, crossover study. The two 6-day diet periods were separated by a 5-day washout period. On day 6, the subjects were water loaded, and blood pressure, renal hemodynamics, and urinary electrolyte excretion were measured for 6 hours after a single 100-mg oral dose of losartan (n = 16) or placebo (n = 7). Losartan induced no significant changes in blood pressure, glomerular filtration rate, or renal blood flow in these water-loaded subjects, whatever the sodium diet. In subjects on a low-salt diet, losartan markedly increased urinary sodium excretion from 115 +/- 9 to 207 +/- 21 mumol/min (P < .05). The fractional excretion of endogenous lithium was unchanged, suggesting no effect of losartan on the early proximal tubule in our experimental conditions. Losartan also increased urine flow rate (from 10.5 +/- 0.4 to 13.1 +/- 0.6 mL/min, P < .05); urinary potassium excretion (from 117 +/- 6.9 to 155 +/- 11 mumol/min); and the excretion of chloride, magnesium, calcium, and phosphate. In subjects on a high-salt diet, similar effects of losartan were observed, but the changes induced by the angiotensin II antagonist did not reach statistical significance. In addition, losartan demonstrated significant uricosuric properties with both sodium diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of SCH 34826, an orally active inhibitor of atrial natriuretic peptide degradation, in healthy volunteers.

Atrial natriuretic peptide is cleared from plasma by clearance receptors and by enzymatic degradation by way of a neutral metalloendopeptidase. Inhibition of neutral metalloendopeptidase activity appears to provide an interesting approach to interfere with metabolism of atrial natriuretic peptide to enhance the renal and haemodynamic effects of endogenous atrial natriuretic peptide. In this study, the effects of SCH 34826, a new orally active neutral metalloendopeptidase inhibitor, have been evaluated in a single-blind, placebo-controlled study involving eight healthy volunteers who had maintained a high sodium intake for 5 days. SCH 34826 had no effect on blood pressure or heart rate in these normotensive subjects. SCH 34826 promoted significant increases in excretion of urinary sodium, phosphate, and calcium. The cumulative 5-hour urinary sodium excretion was 15.7 +/- 7.3 mmol for the placebo and 22.9 +/- 5, 26.7 +/- 6 (p less than 0.05), and 30.9 +/- 6.8 mmol (p less than 0.01) for the 400, 800, and 1600 mg SCH 34826 doses, respectively. During the same time interval, the cumulative urinary phosphate excretion increased by 0.3 +/- 0.4 mmol after placebo and by 1.5 +/- 0.3 (p less than 0.01), 1.95 +/- 0.3 (p less than 0.01), and 2.4 +/- 0.4 mmol (p less than 0.001) after 400, 800, and 1600 mg SCH 34826, respectively. There was no change in diuresis or excretion of urinary potassium and uric acid. The natriuretic response to SCH 34826 occurred in the absence of any change in plasma atrial natriuretic peptide levels but was associated with a dose-dependent elevation of urinary atrial natriuretic peptide and cyclic guanosine monophosphate.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of interleukin 1α secretion by inflammasomes.

The crucial role of the proinflammatory cytokine interleukin 1β (IL-1β) in driving inflammatory disorders, such as Muckle-Wells syndrome and gout, has been extensively characterised. Owing to its high potency to induce inflammation the activation and secretion of IL-1β is tightly regulated. The sensing of various host 'dangers', including infections and metabolic deregulation, results in the formation of large protein complexes, termed inflammasomes. Formation of the inflammasomes leads to the cleavage and activation of caspase-1, which in turn proteolytically processes its substrates, including pro-IL-1β. Biologically active IL-1β is subsequently secreted by the cell. In contrast to IL-1β, little is known about mechanisms underlying the activation and secretion of its close homologue IL-1α. Moreover, the physiological role of IL-1α is still not well defined. Several studies hypothesise that IL-1α serves as a danger signal, which is passively released from dying cells. However, recent studies suggest a more complex function of this cytokine. Indeed, NLRP3 inflammasome agonists such as uric acid crystal or nigericin induce IL-1α cleavage and secretion, leading to the cosecretion of both IL-1β and IL-1α. Depending on the type of NLRP3 agonist, release of IL-1α is NLRP3-inflammasome/caspase-1 dependent or independent, but in both cases IL-1α processing depends on calpain protease activity. Taken together, these results suggest that the promotion and progression of inflammatory diseases is not solely due to IL-1β but also to its close relative IL-1α. This should be considered when IL-1 blockade is applied as a therapeutic strategy for diseases such as cryopyrin-associated periodic syndromes or gout.

ESRD caused by nephrolithiasis: prevalence, mechanisms, and prevention.

BACKGROUND: The contribution of nephrolithiasis-related end-stage renal disease (ESRD) to patients requiring renal replacement therapy has never been specifically evaluated. METHODS: Of the entire cohort of 1,391 consecutive patients who started maintenance dialysis therapy at our nephrology department between January 1989 and December 2000, a total of 45 patients (21 men) had renal stone disease as the cause of ESRD and constitute the study material. Type and cause of renal stone disease was determined in the 45 patients, as well as the change in prevalence of nephrolithiasis-related ESRD with time during this 12-year period. RESULTS: The overall proportion of nephrolithiasis-related ESRD was 3.2%. Infection (struvite) stones accounted for 42.2%; calcium stones, 26.7%; uric acid nephrolithiasis, 17.8%; and hereditary diseases (including primary hyperoxaluria type 1 and cystinuria), 13.3% of cases. Women were predominant among patients with infection and calcium stones, whereas men were predominant among patients with uric acid or hereditary stone disease. The proportion of patients with nephrolithiasis-related ESRD decreased from 4.7% in the triennial period 1989 to 1991 to 2.2% in the most recent period, 1998 to 2000 ( P = 0.07). This tendency to a decreasing prevalence mainly was caused by a rarefaction of infection and calcium stones with time, whereas frequencies of uric acid and hereditary stone disease remained essentially unchanged. CONCLUSION: Severe forms of nephrolithiasis remain an underestimated cause of potentially avoidable ESRD and need for renal replacement therapy. These findings highlight the crucial importance of accurate stone analysis and metabolic evaluation to provide early diagnosis and proper therapy for conditions that may lead to ESRD through recurrent stone formation and/or parenchymal crystal infiltration.

Cardiovascular effects in patrol officers are associated with fine particulate matter from brake wear and engine emissions

Background: Exposure to fine particulate matter air pollutants (PM2.5) affects heart rate variability parameters, and levels of serum proteins associated with inflammation, hemostasis and thrombosis. This study investigated sources potentially responsible for cardiovascular and hematological effects in highway patrol troopers. Results: Nine healthy young non-smoking male troopers working from 3 PM to midnight were studied on four consecutive days during their shift and the following night. Sources of in-vehicle PM2.5 were identified with variance-maximizing rotational principal factor analysis of PM2.5-components and associated pollutants. Two source models were calculated. Sources of in-vehicle PM2.5 identified were 1) crustal material, 2) wear of steel automotive components, 3) gasoline combustion, 4) speed-changing traffic with engine emissions and brake wear. In one model, sources 1 and 2 collapsed to a single source. Source factors scores were compared to cardiac and blood parameters measured ten and fifteen hours, respectively, after each shift. The "speed-change" factor was significantly associated with mean heart cycle length (MCL, +7% per standard deviation increase in the factor score), heart rate variability (+16%), supraventricular ectopic beats (+39%), % neutrophils (+7%), % lymphocytes (-10%), red blood cell volume MCV (+1%), von Willebrand Factor (+9%), blood urea nitrogen (+7%), and protein C (-11%). The "crustal" factor (but not the "collapsed" source) was associated with MCL (+3%) and serum uric acid concentrations (+5%). Controlling for potential confounders had little influence on the effect estimates. Conclusion: PM2.5 originating from speed-changing traffic modulates the autonomic control of the heart rhythm, increases the frequency of premature supraventricular beats and elicits proinflammatory and pro-thrombotic responses in healthy young men. [Authors]

Improving cardiovascular and renal outcomes in gout: what should we target?

Epidemiological and experimental studies have shown that hyperuricaemia and gout are intricately linked with hypertension, metabolic syndrome, chronic kidney disease and cardiovascular disease. A number of studies suggest that hyperuricaemia and gout are independent risk factors for the development of these conditions and that these conditions account, in part, for the increased mortality rate of patients with gout. In this Review, we first discuss the links between hyperuricaemia, gout and these comorbidities, and present the mechanisms by which uric acid production and gout might favour the development of cardiovascular and renal diseases. We then emphasize the potential benefit of urate-lowering therapies on cardiovascular and renal outcomes in patients with hyperuricaemia. The mechanisms that link elevated serum uric acid levels and gout with these comorbidities seem to be multifactorial, implicating low-grade systemic inflammation and xanthine oxidase (XO) activity, as well as the deleterious effects of hyperuricaemia itself. Patients with asymptomatic hyperuricaemia should be treated by nonpharmacological means to lower their SUA levels. In patients with gout, long-term pharmacological inhibition of XO is a treatment strategy that might also reduce cardiovascular and renal comorbidities, because of its dual effect of lowering SUA levels as well as reducing free-radical production during uric acid formation.

Clinical pharmacology of the angiotensin II receptor antagonist losartan potassium in healthy subjects

INTRODUCTION: The evaluation of a new drug in normotensive volunteers provides important pharmacodynamic and pharmacokinetic information as long as the compound has a specific mechanism of action which can be evaluated in healthy subjects as well as in patients. The purpose of the present paper is to discuss the results that have been obtained in normal volunteers with the specific angiotensin II receptor antagonist, losartan potassium. DOSE-FINDING: Over the last few years, studies in normotensive subjects have demonstrated that the minimal dose of losartan that produces maximal efficacy is 40-80 mg. Losartan has a long duration of action and its ability to produce a sustained blockade of the renin-angiotensin system is due almost exclusively to the active metabolite E3174. HORMONAL EFFECTS: Angiotensin II receptor blockade with losartan induces an expected increase in plasma renin activity and plasma angiotensin II levels. A decrease in plasma aldosterone levels has been found only with a high dose of losartan (120 mg). RENAL AND BLOOD PRESSURE EFFECTS: In normotensive subjects, losartan has little or no effect on blood pressure unless the subjects are markedly salt-depleted. Losartan causes no change in the glomerular filtration rate and either no modification or only a slight increase in renal blood flow. Losartan significantly increases urinary sodium excretion, however, and surprisingly produces a transient rise in urinary potassium excretion. Finally, losartan increases uric acid excretion and lowers plasma uric acid levels. CONCLUSIONS: These results suggest that losartan is an effective angiotensin II receptor antagonist in normal subjects. Its safety and clinical efficacy in hypertensive patients will be addressed in large clinical trials.

Interleukin-1 as a therapeutic target in gout.

PURPOSE OF REVIEW: To give an overview of current evidence for interleukin (IL)-1 blockade in the management of gout. RECENT FINDINGS: Three IL-1 blockers are currently available for clinical use: anakinra, rilonacept and canakinumab. Recent studies have focused on drugs with a long half-life: rilonacept and canakinumab. For treatment of acute gouty arthritis, three randomized controlled trials (RCTs) showed efficacy of canakinumab with some safety concerns and one RCT failed to show efficacy of rilonacept. For prevention of gout flare when starting uric acid lowering therapy (ULT), four RCTs showed efficacy of rilonacept and one RCT showed efficacy of canakinumab. SUMMARY: There is sufficient evidence supporting the use of IL-1 blockers for treatment of acute gouty arthritis or for prevention of gout flares when starting ULT in selected patients, with contraindications or intolerance to conventional therapy. More data are needed to assess safety and to specify their use in routine practice.

Meta-analysis identifies multiple loci associated with kidney function-related traits in east Asian populations.

Chronic kidney disease (CKD), impairment of kidney function, is a serious public health problem, and the assessment of genetic factors influencing kidney function has substantial clinical relevance. Here, we report a meta-analysis of genome-wide association studies for kidney function-related traits, including 71,149 east Asian individuals from 18 studies in 11 population-, hospital- or family-based cohorts, conducted as part of the Asian Genetic Epidemiology Network (AGEN). Our meta-analysis identified 17 loci newly associated with kidney function-related traits, including the concentrations of blood urea nitrogen, uric acid and serum creatinine and estimated glomerular filtration rate based on serum creatinine levels (eGFRcrea) (P < 5.0 × 10(-8)). We further examined these loci with in silico replication in individuals of European ancestry from the KidneyGen, CKDGen and GUGC consortia, including a combined total of ∼110,347 individuals. We identify pleiotropic associations among these loci with kidney function-related traits and risk of CKD. These findings provide new insights into the genetics of kidney function.

Double-blind comparison of indapamide with a placebo in hypertensive patients treated by practicing physicians.

The antihypertensive effect of indapamide (2.5 mg/day) was compared to that obtained with a placebo in a controlled trial carried out by 11 physicians in their private practice. Thirty-one patients with uncomplicated essential hypertension were included. After a run-in period of 3 weeks without any treatment, either indapamide (n = 16) or a placebo (n = 15) were administered for 8 weeks in double-blind fashion. Blood pressure decreased in both groups. In patients treated with indapamide, systolic pressure was significantly lower than in those given the placebo at 3 out of the 4 follow-up visits; diastolic pressure, however, was significantly lower only at the end of the trial. Both the active drug and the placebo were well tolerated. No significant change in body weight, plasma potassium and uric acid occurred during the study in either group of patients. It appears therefore that indapamide, at a dose which apparently has no major diuretic effect, may be useful for practitioners in managing patients with mild to moderate hypertension.

Adipocytokines, Hepatic and Inflammatory Biomarkers and Incidence of Type 2 Diabetes. The CoLaus Study.

CONTEXT: There is contradictory information regarding the prognostic importance of adipocytokines, hepatic and inflammatory biomarkers on the incidence of type 2 diabetes. The objective was to assess the prognostic relevance of adipocytokine and inflammatory markers (C-reactive protein - CRP; interleukin-1beta - IL-1β; interleukin-6- IL-6; tumour necrosis factor-α - TNF-α; leptin and adiponectin) and gamma-glutamyl transpeptidase (γGT) on the incidence of type 2 diabetes. METHODS: Prospective, population-based study including 3,842 non-diabetic participants (43.3% men, age range 35 to 75 years), followed for an average of 5.5 years (2003-2008). The endpoint was the occurrence of type 2 diabetes. RESULTS: 208 participants (5.4%, 66 women) developed type 2 diabetes during follow-up. On univariate analysis, participants who developed type 2 diabetes had significantly higher baseline levels of IL-6, CRP, leptin and γGT, and lower levels of adiponectin than participants who remained free of type 2 diabetes. After adjusting for a validated type 2 diabetes risk score, only the associations with adiponectin: Odds Ratio and (95% confidence interval): 0.97 (0.64-1.47), 0.84 (0.55-1.30) and 0.64 (0.40-1.03) for the second, third and forth gender-specific quartiles respectively, remained significant (P-value for trend = 0.05). Adding each marker to a validated type 2 diabetes risk score (including age, family history of type 2 diabetes, height, waist circumference, resting heart rate, presence of hypertension, HDL cholesterol, triglycerides, fasting glucose and serum uric acid) did not improve the area under the ROC or the net reclassification index; similar findings were obtained when the markers were combined, when the markers were used as continuous (log-transformed) variables or when gender-specific quartiles were used. CONCLUSION: Decreased adiponectin levels are associated with an increased risk for incident type 2 diabetes, but they seem to add little information regarding the risk of developing type 2 diabetes to a validated risk score.