Serum uric acid level and endothelial dysfunction in patients with nondiabetic chronic kidney disease

BACKGROUND

An elevated serum uric acid level is strongly associated with endothelial dysfunction and inflammation, both of which are common in chronic kidney disease (CKD). We hypothesized that endothelial dysfunction in subjects with CKD would correlate with uric acid levels.

MATERIALS AND METHODS

We evaluated the association between serum uric acid level and ultrasonographic flow-mediated dilatation (FMD) in 263 of 486 patients with recently diagnosed CKD (stage 3-5) (48% male, age 52 ± 12 years). To minimize confounding, 233 patients were excluded because they were diabetic, had established cardiovascular complications or were taking drugs (renin-angiotensin system blockers, statins) interfering with vascular function.

RESULTS

Serum uric acid level was significantly increased in all stages of CKD and strongly correlated with estimated glomerular filtration rate (eGFR-MDRD); FMD was inversely associated with serum uric acid (r = -0.49, p < 0.001). The association of serum uric acid with FMD remained after adjustment for age, gender, smoking, LDL cholesterol, eGFR, high-sensitivity C-reactive protein, systolic blood pressure, proteinuria, and homeostatic model assessment index (β = -0.27, p < 0.001).

CONCLUSION

Increased serum uric acid is an independent predictor of endothelial dysfunction in subjects with CKD.

Long-term morbidity and mortality related to falls in hemodialysis patients: role of age and gender - a pilot study

BACKGROUND

Patients with end-stage renal disease (ESRD) on hemodialysis (HD) are prone to falls. In this pilot study, we aimed to determine the incidence of falls in a cohort of HD patients during a 1-year period, to identify any specific risk factors that may predict falls in this cohort, and to assess whether falls can independently predict hospitalization, nursing home admissions and/or mortality over an additional 2 years.

MATERIALS AND METHODS

Baseline assessments followed by documentation of falls prospectively during a 1-year period were done on 76 HD patients. Patients were followed for an additional 2 years and four outcomes were recorded: all-cause death, nursing home admission, the number and duration of all hospitalizations.

RESULTS

20 patients (26.3%) fell over a 12-month period. Elderly and females had a higher risk of falls than the younger and male population (p = 0.034 and 0.006 respectively). During the 2-year follow-up, compared to non-fallers, fallers had a 2.13-fold increase in risk of death, a 3.5-fold increase in risk of nursing home admission, and nearly a 2-fold increase in the number and duration of hospitalizations.

CONCLUSIONS

Falls are common in HD patients, with a higher incidence in females and elderly, and are associated with worse outcomes, more so in recurrent fallers.

Screening for depression in elderly hemodialysis patients

BACKGROUND

Depression is common and associated with increased morbidity and mortality in elderly (≥65 years) hemodialysis patients. Beck's Depression Inventory (BDI) and the Geriatric Depression Scale (GDS) have been used in different cohorts to screen for depression.

OBJECTIVES

We aimed to evaluate the 15-item GDS (GDS-15) as such a tool in elderly hemodialysis patients and compare it with BDI, a previously validated tool in younger hemodialysis patients.

DESIGN

Cross-sectional study.

SETTING

Four out-patient hemodialysis units; 1 based in a university hospital and 3 based in the community.

PARTICIPANTS

Hemodialysis patients aged 65 years and older.

INTERVENTION

Both tools were administered to all participants, and a geriatric psychiatrist blinded to the results evaluated them for depression by the gold standard psychiatric interview.

MEASUREMENTS

The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for both tools were assessed against the psychiatric interview (n = 62).

RESULTS

Patients who were depressed according to the psychiatric interview had significantly higher GDS-15 and BDI scores compared to those not depressed (p < 0.01 both). ROC curves showed high predictive accuracy of the GDS-15 and BDI (area under the curve: 0.808 and 0.729) versus the psychiatric interview. The GDS-15 cutoff with the best diagnostic accuracy was 5 with a sensitivity of 63%, specificity of 82%, PPV of 60% and NPV of 83%. The BDI cutoff with the best diagnostic accuracy was 10 with a sensitivity of 68%, specificity of 77%, PPV of 57% and NPV of 85%.

CONCLUSION

These results provide evidence that the GDS-15 shows validity in comparison to a gold standard and can be used to screen for depression in the elderly hemodialysis population.

Potential new therapeutic agents for diabetic kidney disease

Diabetic nephropathy is the leading cause of end-stage renal disease, and both the incidence and prevalence of diabetic nephropathy continue to increase. Currently, various treatment regimens and combinations of therapies provide only partial renoprotection. It is obvious that new approaches are desperately needed to retard the progression of diabetic nephropathy. Recently, a number of new agents have been described that have the potential to delay the progression of diabetic kidney disease and minimize the growing burden of end-stage renal disease. These include inhibitors and breakers of advanced glycation end products, receptor antagonists for advanced glycation end products, protein kinase C inhibitors, NADPH (reduced nicotinamide adenine dinucleotide phosphate) oxidase inhibitors, glycosaminoglycans, endothelin receptor antagonists, antifibrotic agents, and growth factor inhibitors. This review addresses these promising new therapeutic agents for delaying the progression of diabetic kidney disease.

Renin-angiotensin-aldosterone system blockade effects on the kidney in the elderly: benefits and limitations

The proportion of the population that is elderly (age>or=65 years) is growing across the world. The increasing longevity of humans results in a higher number of elderly patients' presenting with multiple chronic diseases such as hypertension, diabetes, and chronic kidney disease (CKD). These problems increase morbidity and mortality in the elderly. Overactivity of the renin-angiotensin-aldosterone system (RAAS) is associated with the development of hypertension, cardiovascular events, and CKD, so targeting the RAAS is a logical therapeutic approach. Elderly patients present special concerns regarding the benefits versus risks of using RAAS blockers. Plasma renin activity declines with age, which has been attributed to the effect of age-associated nephrosclerosis. Plasma aldosterone is also reduced with age, resulting in a greater risk for hyperkalemia in older individuals, especially when coupled with the age-associated decline in GFR. Moreover, the elderly have a higher frequency of concurrent conditions and are on many medications, which may further increase the risk for adverse effects of RAAS blocking agents. Unfortunately, there is a paucity of literature that is specifically aimed at studying elderly using the RAAS blockers. We present in our in-depth review data regarding benefits and limitations of the use of the RAAS blockades on the various sites along the RAAS pathway for elderly patients. Specific attention was given to the role of combination RAAS blockade therapy and higher monotherapy dosing in the treatment of hypertension in the elderly.

Magnesium in Chronic Kidney Disease: Challenges and Opportunities

Cardiovascular disease is the leading cause of mortality and morbidity in patients with chronic kidney disease, which is partly explained by the fact that 40–70% of patients receiving dialysis have significant coronary artery disease. Recent clinical studies have shown that lower serum magnesium (Mg) levels are associated with vascular calcification and cardiovascular mortality among patients with end-stage renal disease (ESRD). On the other hand, hypermagnesemia inhibits parathyroid hormone secretion, which is considered an important independent risk factor for vascular calcification, left ventricular hypertrophy and mortality in ESRD patients. Finally, increasing evidence points towards a link between Mg and cardiovascular disease, even in subjects without chronic kidney disease. The purpose of this review was to critically review the current literature examining the effects of plasma Mg levels on cardiovascular disease and parathyroid hormone homeostasis in ESRD, and renal transplant patients.

Statin treatment for dyslipidemia in chronic kidney disease and renal transplantation: a review of the evidence

Patients with chronic kidney disease (CKD) have significantly increased risks of cardiovascular (CV) morbidity and mortality. Dyslipidemia is a common disorder in CKD patients. CKD patients have a different lipid profile with increased atherogenic lipid fractions, and serum low-density lipoprotein cholesterol (LDL-C) levels may underestimate the atherogenic effect of LDL-C in these patients. Dyslipidemia may contribute to the increased CV morbidity and mortality, and to the progression of kidney disease in CKD patients. Currently, statins are the pharmacologic intervention of first choice, if lifestyle changes fail adequately to lower LDL-C levels in the setting of normal or moderately elevated triglycerides. Statins have been extensively studied in a large variety of patient populations and have proven efficacy in the treatment of dyslipidemia, and in reducing CV mortality. Although much evidence supports the CV benefits of statins in patients with normal renal function, there are contradictory results for the beneficial effect of statin therapy on CV morbidity and mortality in CKD patients. While post hoc subgroup analyses of multiple randomized trials support statin use in early CKD patients, the only randomized trial conducted in diabetic dialysis patients found no evidence of benefit in overall mortality. Post transplant there is some definite CV benefit, albeit in a patient cohort selected to be at reduced CV risk by virtue of being eligible for organ transplant. The results from the AURORA and SHARP studies are awaited anxiously.

Circadian rhythm of blood pressure in patients with benign prostatic hyperplasia

OBJECTIVE

Nocturia, a common and bothersome symptom of benign prostatic hyperplasia (BPH), may cause sleep disturbances. Patients with nocturia may have difficulty returning to their normal sleep after repeated episodes of waking and voiding. Therefore, nocturia may have an impact on the circadian rhythm of blood pressure (BP). The association between nocturia and the circadian rhythm of BP was investigated in this study.

MATERIAL AND METHODS

A total of 100 male patients who had been diagnosed with BPH and 53 healthy male subjects were included in the study. Nocturnal urinary frequency was assessed by means of a questionnaire and recorded in both groups. Ambulatory BP monitoring was performed in all patients over a 24-h period.

RESULTS

Patient characteristics and laboratory parameters were similar in both groups. Seventy-five patients (75%) in the BPH group and 20 subjects (37.7%) in the control group were non-dippers, i.e. they did not have a normal nocturnal fall in BP, and this difference was statistically significant (p=0.001). Eighty-nine patients in the BPH group and 13 in the control group had nocturia. Seventy-one patients (79.8%) with nocturia were non-dippers and the difference compared to the patients without nocturia in the BPH group was significant (p=0.003), whereas four patients with nocturia (30.8%) were non-dippers in the control group.

CONCLUSIONS

Our findings indicate that non-dipping was more prevalent in elderly men with BPH and nocturia. BPH and nocturia may be etiological factors in the pathogenesis of non-dipping, which is an indicator of early cardiovascular disease. Further studies must focus on this relationship and, especially, on whether treatment of nocturia and BPH helps to treat non-dipping or not.

Sodium bicarbonate for the prevention of contrast-induced nephropathy: a meta-analysis of 17 randomized trials

BACKGROUND

Contrast-induced nephropathy (CIN) is a common cause of acute kidney injury. Several preventive therapies for this injury have been tested; however, there is still no consensus on the optimal protocol.

METHODS

We performed a systematic search of the National Library of Medicine and the Cochrane Library databases from January 1985 to November 2008 to identify randomized controlled studies examining sodium bicarbonate as a preventive measure for CIN in humans. We also reviewed conference abstracts from cardiology nephrology and radiology meetings from 2004 to 2008. A change in serum creatinine levels defined by an absolute (>or=0.5 mg/dl) or percentage (>or=25%) increase in the serum creatinine level is defined as CIN. The primary outcome measure was the incidence of CIN, and the secondary outcome measures were: change in serum creatinine from baseline, requirement for renal replacement therapy and death.

RESULTS

Seventeen randomized controlled trials have investigated the role of sodium bicarbonate for prophylaxis of CIN. The overall incidence of CIN was 11.3%. Using the results from all 17 studies that compared bicarbonate versus saline, the pooled relative risk of developing CIN was 0.54 (95% CI, 0.36-0.83) in the intervention arm, indicating a significant benefit from sodium bicarbonate. The pooled relative risk of CIN was 0.57 (95% CI, 0.35-0.95) when we analyzed for the studies that compared the effects sodium bicarbonate to NAC on development of CIN. There was no difference in the rates of requirement for renal replacement therapy and death.

CONCLUSIONS

The use of sodium bicarbonate appears to reduce the incidence of CIN when compared to other preventive strategies for CIN without a significant difference in the requirement of renal replacement therapy and mortality. There are study heterogeneity and publication biases. Further adequately powered randomized controlled studies are needed to determine whether sodium bicarbonate will reduce the clinically meaningful outcomes (e.g., need for dialysis or death) and optimal hydration strategy in high-risk patients.

Causes and mechanisms of nondipping hypertension

Growing evidence indicates that nondippers have worsened cardiovascular outcomes than dippers. Ambulatory blood pressure monitoring with a lack of nocturnal BP fall (nondipping) have also been shown to be more closely associated with target organ damage and worsened cardiovascular outcome than in patients with essential hypertension with dipping pattern. The underlying pathogenetic mechanisms potentially linking nondipping with cardiovascular disease are not fully understood. There are multiple possible underlying pathophysiologic mechanisms in the impaired BP decline during the night. Extrinsic and intrinsic factors including abnormal neurohormonal regulation, lack of physical activity, nutritional factors such as increased dietary sodium intake, and smoking of tobacco have been implicated for blunted circadian rhythm of BP. Certain diseases such as diabetes and chronic renal diseases also affect the circadian BP rhythm. Currently, the clinical importance of nondipping is known well; however, the relationship between certain disease states and nondipping has not been fully explained yet. This paper will attempt to address to clarify the underlying basis for nondipping and the specific associations with various disease states.

Antioxidant and protective effects of silymarin on ischemia and reperfusion injury in the kidney tissues of rats

BACKGROUND

Renal ischemia/reperfusion (I/R) injury is a major cause of acute renal failure. Silymarin is extracted from Silybum marianum and Cynara cardunculus seeds and fruits. The aim of this study is to investigate whether silymarin administration prevents the damage induced by I/R in rat kidneys.

MATERIALS AND METHODS

Thirty male Wistar rats were randomly divided into five experimental groups (n = 6, each) as follows; control group, sham-operated group, I/R group, silymarin group, and I/R + silymarin group. In the I/R and I/R + silymarin groups, both renal arteries were occluded using nontraumatic microvascular clamps for 45 min. Then, at the end of 24 h of reperfusion, the animals were killed. Kidney function tests, the serum and tissue antioxidant enzymes and oxidant products were determined.

RESULTS

Animals that were subjected to I/R exhibited significant increase in serum urea, creatinine, and cystatin C levels compared with the rats treated with silymarin prior to the I/R process (P < 0.001). The serum enzymatic activities of superoxide dismutase and glutathione peroxidase significantly decreased in the I/R group; however, this reduction was significantly improved by the treatment with silymarin (P < 0.001 and P < 0.05, respectively). Renal I/R produced a significant increase in serum and tissue malondialdehyde, nitric oxide, and protein carbonyl as compared with controls. Treatment with silymarin resulted in significant reduction in these markers (P < 0.001).

CONCLUSION

Based on our findings, silymarin protects the kidneys against I/R injury. This finding may provide a basis for the development of novel therapeutic strategies for protection against the damages caused by I/R.

Association of obesity with inflammation in occult chronic kidney disease

BACKGROUND

There are few studies concerning the development of chronic kidney disease (CKD) in obese patients independent of its relation with other risk factors. Also, the role of inflammation in this relationship is unclear. In this study we aimed to test the hypothesis that obesity is associated with risk for CKD and whether this risk is associated with serum C-reactive protein (CRP) levels in an apparently healthy obese population.

METHODS

Biochemical parameters and urinary protein excretion were determined in 110 patients with body mass index (BMI) >30.0 (calculated as kg/m2) and 50 age-matched healthy controls. Glomerular filtration rate was estimated by calculation of creatinine clearance.

RESULTS

Of the patients, 17.3% had CKD. They had higher CRP levels than controls (6.52 +/- 0.58 mg/L and 4.48 +/- 1.26 mg/L, respectively, p=0.001). Furthermore, CRP levels were positively correlated with BMI, waist circumference, waist to hip ratio and proteinuria, and negatively correlated with glomerular filtration rate (GFR). When GFR was considered as the dependent variable in a multiple regression analysis, CRP maintained its significant correlation with GFR.

CONCLUSION

Our study of apparently healthy obese individuals, has shown a significant association between BMI and CKD independent of other potential mediators. Furthermore, our findings suggest that inflammation may be the pathogenic mechanism of obesity-related CKD.

Improvement of endothelial dysfunction with simvastatin in patients with autosomal dominant polycystic kidney disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Endothelial dysfunction (ED), which is an early manifestation of vascular injury, has been shown in patients with ADPKD. Statins have a beneficial effect in the reversal of ED. The aim of this study was to investigate the effects of a statin, simvastatin, on ED in patients with ADPKD. Sixteen patients with ADPKD having well-preserved renal function were included in the study. Endothelial function of the brachial artery was evaluated by using high-resolution vascular ultrasound. Endothelial-dependent dilatation (EDD) was expressed as the percentage change in the brachial artery diameter from baseline to reactive hyperemia. After the baseline evaluations of EDDs, patients were started treatment with simvastatin at a dose of 40 mg/day and were treated for six months. EDDs were recalculated after one and six months of therapy. Interleukin-6 (IL-6) and high-sensitivity C-reactive protein were also measured as markers of inflammation. Baseline EDD was 11.3 +/- 6.9% in patients with ADPKD. After one month of simvastatin treatment, EDD increased significantly to 14.6 +/- 4.6 % (P = 0.016 versus baseline). Endothelial-dependent dilatation further increased significantly to 18.9 +/- 7.5 % (P = 0.011 versus baseline, P = 0.048 versus first month) after six months of therapy. There was also a significant decrease in the level of IL-6 from 21.6 +/- 21.7 pg/mL to 9.1 +/- 3.5 pg/mL (P= 0.002). Six months of simvastatin therapy resulted in a significant improvement of ED in patients with ADPKD. This finding may be in part related to the pleiotropic effects of simvastatin.

Ambulatory blood pressure and endothelial dysfunction in patients with autosomal dominant polycystic kidney disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Endothelial dysfunction (ED), which is an early manifestation of vascular injury, has been shown in patients with ADPKD. However, the association between ambulatory blood pressure and ED has not been investigated in these patients. Forty-one patients with ADPKD having well-preserved renal function were included in the study. Ambulatory blood pressure monitoring was performed in all patients. Patients were divided into dipper and non-dipper groups. Endothelial function of the brachial artery was evaluated by using high-resolution vascular ultrasound. Endothelial-dependent dilatation was expressed as the percentage change in the brachial artery diameter from baseline to reactive hyperemia. The mean 24-hour systolic blood pressure was similar in both groups (125.5 +/- 10.7 mmHg in dippers and 121.2 +/- 14.3 in non-dippers, p > 0.05). There was also no significant difference between the mean 24-hour diastolic blood pressures in both groups (82.3 +/- 9.6 mmHg in dippers and 77.1 +/- 8.6 mmHg in non-dippers, p > 0.05). The nocturnal fall rate in systolic blood pressure was 11.1 +/- 1.2% in dippers and 0.98 +/- 0.9% in non-dippers (p = 0.001). The nocturnal fall rate in diastolic blood pressure was 14.0 +/- 0.9% in dippers and 3.8 +/- 0.8% in non-dippers (p = 0.001). Endothelial-dependent dilatation was significantly higher in dippers compared to non-dippers (6.22 +/- 4.14% versus 3.57 +/- 2.52%, p = 0.025). Non-dipper patients with ADPKD show significant ED, which has an important impact on cardiovascular morbidity and mortality.

Membranoproliferative glomerulonephritis associated with pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is a multiorgan disorder affecting mainly the skin, the eyes, and the cardiovascular system. A 51-year-old woman was admitted to our clinic complaining of weakness and swelling of her legs for the past two years. She had a proteinuria of 7.29 g/24 h. Renal biopsy was performed, and the histological diagnosis was membranoproliferative glomerulonephritis. Four weeks later, she was admitted to the hospital due to pain in her left hand and necrosis in the fourth and fifth fingertips of the left hand. A skin biopsy was performed from the forearm and was reported as PXE. Herein, we present a case of membranoproliferative glomerulonephritis accompanying PXE.

Serum BNP concentration and left ventricular mass in CAPD and automated peritoneal dialysis patients

OBJECTIVE

To compare ultrafiltration under continuous ambulatory peritoneal dialysis (CAPD) and automated PD (APD), disclosing potential effects on serum B-type natriuretic peptide (BNP) levels and echocardiographic findings.

PATIENTS AND METHODS

This cross-sectional clinical study included 32 patients on CAPD and 30 patients on APD without clinical evidence of heart failure or hemodynamically significant valvular heart disease. Peritoneal equilibration tests, BNP levels, and echocardiographic measurements were performed in each subject. BNP measurements were also performed in 24 healthy control subjects.

RESULTS

Patients on APD had lower ultrafiltration and higher values of BNP and left ventricular mass index (LVMI) compared with patients on CAPD (respectively: 775 +/- 160 vs 850 +/- 265 mL, p = 0.01; 253.23 +/- 81.64 vs 109.42 +/- 25.63 pg/mL, p = 0.001; 185.12 +/- 63.50 vs 129.30 +/- 40.95 g/m(2), p = 0.001). This occurred despite higher mean dialysate glucose concentrations and far more extensive use of icodextrin in the APD group.

CONCLUSION

Treatment with APD is associated with higher plasma BNP levels and LVMI compared to CAPD. This may be the result of chronic fluid retention caused by lower ultrafiltration in APD patients.

Probrain natriuretic peptide for assessment of efficacy in heart failure treatment

N-terminal probrain natriuretic peptide (NT-proBNP) is elevated in patients with heart failure. Numerous clinical trials have evaluated the efficacy of spironolactone in heart failure; however, no studies have directly examined the effects of spironolactone treatment on NT-proBNP level. This study investigated whether NT-proBNP levels decrease with daily spironolactone treatment. The study consisted of 117 adult patients with heart failure. All participants were divided into 3 groups, class I, class II, and class III, according to the New York Heart Association classification system. Patients were randomly assigned to receive spironolactone or were treated with another drug, other than spironolactone, as placebo. NT-proBNP plasma samples were taken at baseline and after 6 mo of treatment. A total of 62 patients were treated with daily spironolactone; 55 patients were followed with available treatment without spironolactone. The baseline demographic and laboratory parameters were similar for patients in all groups. At the end of 6 mo, spironolactone-treated patients had significantly lower NT-proBNP levels and significantly better ejection fractions than did patients in all New York Heart Association classes who were not treated with spironolactone. Results suggest that spironolactone decreases plasma NT-proBNP concentrations, and that the measurement of plasma NT-proBNP levels may be helpful in assessing therapeutic efficacy in patients who are treated for heart failure.