Heart and kidney: fatal twins?

The association of echocardiographic parameters on renal outcomes in chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) often have structural abnormalities of the heart due to pressure and volume overload. The aim of this study was to evaluate associations between echocardiographic parameters and renal outcomes (estimated glomerular filtration rate [eGFR] slope and progression to dialysis) in patients with stage 3-5 CKD.

METHODS

This longitudinal study enrolled 419 patients. Changes in renal function were assessed using the eGFR slope. Rapid renal progression was defined as an eGFR slope < -3 mL/min/1.73 m²/year, and the renal endpoint was defined as commencing dialysis.

RESULTS

Increased left atrial diameter (LAD), ratio of left ventricular mass to body surface area (LVM/BSA), ratio of LVM to height^2.7 (LVM/ht^2.7), and ratio of observed to predicted LVM (o/p LVM) were associated with eGFR slope in an adjusted model, but left ventricular ejection fraction (LVEF) was not. Furthermore, LAD ≥ 4.7 cm, LVM/BSA > 115 g/m² in males and > 95 g/m² in females, and LVM/ht^2.7 > 48 g/ht^2.7 in males and > 44 g/ht^2.7 in females were correlated with progression to dialysis, but o/p LVM and LVEF were not. The maximum change in χ² change to predict renal outcomes was observed for LAD, followed by LVM/BSA and LVM/ht^2.7.

CONCLUSIONS

A large LAD and increased LVM, regardless of how it was measured (LVM/BSA, LVM/ht^2.7 and o/p LVM), were correlated with adverse renal outcomes in patients with CKD stage 3-5. LAD had superior prognostic value to LVM and LVEF.

The effects of Lycium barbarum water extract and fish collagen on milk proteolysis and in vitro angiotensin I-converting enzyme inhibitory activity of yogurt

Plain and Lycium barbarum yogurt were made in the presence and absence of fish collagen. Yogurt samples were analyzed for acidification, milk protein proteolysis, angiotensin I-converting enzyme (ACE) inhibitory activity, and sensory evaluation during refrigerated storage for up to 21 days. The o-phthaldialdehyde peptides amount of L. barbarum yogurt both in the presence and absence of fish collagen were significantly increased during 14 days of storage. SDS-PAGE showed improvement in whey proteins degradation of L. barbarum yogurt with/without fish collagen after 3 weeks of storage. L. barbarum yogurt in absence of fish collagen was acting as a great ACE inhibitor reached up to 85% on day 7 of storage. The incorporation of L. barbarum and/or fish collagen affected to a small extent the overall sensory characteristics of yogurt. Yogurt supplemented with L. barbarum and/or fish collagen may lead to the improvement in the production and formulation of yogurt differing in their anti-ACE activity.

Treatment of Urolithiasis with Medicinal Plant Salvia miltiorrhiza: A Nationwide Cohort Study

Salvia miltiorrhiza Bunge (Danshen), a common medicinal plant in traditional Chinese medicine, has been tested effectively to prevent urolithiasis in animals; nevertheless, the clinical application for urolithiasis remains unclear. We thus investigated the clinical effect of Danshen by analyzing the database from the Taiwan National Institute of Health. The cohort "Danshen-users" was prescribed Chinese herb medicine Danshen after the initial diagnosis of calculus. The control group (non-Danshen-users) was not given Danshen after the initial diagnosis of calculus. The date of first using Danshen after new diagnosis date of calculus was considered as index date. The outcome variables were categorized into two categories: the first category included calculus surgical treatment, including extracorporeal shock wave lithotripsy, ureteroscopy, percutaneous nephrostomy with fragmentation, and ureterolithotomy; the second category included any bleeding disorders, including gastrointestinal bleeding, intracranial hemorrhage, and blood transfusions. The incidence of calculus surgical treatment in the Danshen-users was less than that in the non-Danshen-users: 1.071% in 1,000 person-years (200 people followed up for 5 years) and 3.142% in 1,000 person-years, respectively. The adjusted hazard ratio for calculus surgical treatment in the Danshen-users was 0.34 (95% confidence intervals: 0.31-0.38) as compared to the non-Danshen-users. When stratified by sex, the incidence of calculus surgical treatment in Danshen-users was 0.685% in 1,000 person-years and 1.575% in 1,000 person-years for women and men, respectively, which was lower than that in non-Danshen-users. Danshen decreased the ratio of subsequent stone treatment after the first treatment in the study population; there was no increased bleeding risk due to long-term Danshen use.

P wave dispersion and maximum P wave duration are associated with renal outcomes in chronic kidney disease

P wave parameters measured by 12-lead electrocardiogram (ECG) are commonly used as a noninvasive tool to evaluate left atrial enlargement. This study was designed to assess whether P wave parameters were associated with renal outcomes in chronic kidney disease (CKD) patients. This longitudinal study enrolled 439 patients with CKD stages 3–5. Renal end points were defined as the commencement of dialysis or death. Change in renal function was measured using the estimated glomerular filtration rate (eGFR) slope. We measured two ECG P wave parameters corrected for heart rate, i.e., corrected P wave dispersion and corrected maximum P wave duration. The values of P wave dispersion and maximum P wave duration were 88.8±21.7 ms and 153.3±21.7 ms, respectively. During the follow-up period (mean, 25.2 months), 95 patients (21.6%) started hemodialysis and 30 deaths (6.8%) were recorded. Multivariate Cox regression analysis identified that increased P wave dispersion [hazard ratio (HR), 1.020; 95% confidence interval (CI), 1.009–1.032; P<0.001] and maximum P wave duration (HR, 1.013; 95% CI, 1.003–1.024; P = 0.012) were associated with progression to renal end points. Furthermore, increased P wave dispersion (unstandardized coefficient β = –0.016; P = 0.037) and maximum P wave duration (unstandardized coefficient β = –0.014; P = 0.040) were negatively associated with the eGFR slope. We demonstrated that increased P wave dispersion and maximum P wave duration were associated with progression to the renal end points of dialysis or death and faster renal function decline in CKD patients. Screening CKD patients on the basis of P wave dispersion and maximum P wave duration may help identify patients at high risk for worse renal outcomes.

Olmesartan medoxomil reverses glomerulosclerosis in renal tissue induced by myocardial infarction without changes in renal function

The aim of the present study was to investigate the effect of olmesartan medoxomil (OLM) on renal injury in mice with myocardial infarction (MI). A total of 33 male C57/BL/6 mice were divided into a sham surgery group (SHAM group), MI group (MI group) and OLM treatment group (OLM group). Experimental MI models were established in the mice of the MI and OLM groups by coronary artery ligation, and the mice in the OLM group were fed a daily dose of 10 mg/kg OLM for eight weeks. The results showed that MI induced a reduction in cardiac function and an increase in systolic blood pressure. In addition, increased periodic acid-Schiff (PAS) positive staining, combined with increased levels of angiotensin II (Ang II) in the plasma and kidneys, and increased expression levels of renin, angiotensin II type 1 receptor (AT1R) and angiotensinogen (AGT) in the kidney tissues was observed compared with those in the SHAM group. OLM treatment attenuated the injury by reducing the systolic blood pressure and PAS positive staining, and decreasing the expression levels of Ang II, renin, AT1R and AGT in the kidney compared with those in the MI group. It may be concluded that MI activates the intrarenal renin-angiotensin system and leads to glomerulosclerosis, and that OLM protects the kidney by inhibiting the effects of Ang II.

Association of chronic kidney disease and peripheral artery disease with inappropriate left ventricular mass

Inappropriate left ventricular mass index (LVM) may develop as a response to particular hemodynamic and metabolic alterations. Inappropriate LVM and peripheral artery disease (PAD) characterized by abnormally low or high ankle-brachial index (ABI) are common in chronic kidney disease (CKD) patients, in whom there may be a close and cause-effect relationship. The aim of this study is to assess whether CKD and abnormal ABI has an independent and additive association with inappropriate LVM. A total of 1110 patients were included in the study. Inappropriate LVM was defined as observed LVM more than 28% of the predicted value. The ABI was measured using an ABI-form device. PAD was defined as ABI <0.9 or >1.3 in either leg. Multivariate analysis showed that patients with estimated glomerular filtration rate (eGFR) <45 ml/min/1.73 m² (odds ratio [OR], 1.644; P = 0.011) and PAD (OR, 2.082; P = 0.002) were independently associated with inappropriate LVM. The interaction between eGFR <45 ml/min/1.73 m² and PAD on inappropriate LVM was statistically significant (P = 0.044). Besides, eGFR<45 ml/min/1.73 m² (change in observed/predicted LVM, 19.949; P<0.001) and PAD (change in observed/predicted LVM, 11.818; P = 0.003) were also significantly associated with observed/predicted LVM. Our findings show that eGFR <45 ml/min/1.73 m² and PAD are independently and additively associated with inappropriate LVM and observed/predicted LVM. Assessments of eGFR and ABI may be useful in identifying patients with inappropriate LVM.

Prevention of cardiovascular complications of the metabolic syndrome: focus on pharmacotherapy

The metabolic syndrome increases the risk of atherothrombotic cardiovascular disease (CVD) and diabetes. In turn, diabetes promotes the development of atheroma and is regarded as a coronary heart disease risk equivalent. A multifactorial therapeutic strategy is advocated for patients with the metabolic syndrome to improve cardiovascular risk factor profiles and to reduce the chances of developing type 2 diabetes. Individual components of the syndrome must be addressed using safe, efficacious, and cost-effective measures. There is general agreement that lifestyle modifications, including control of body weight, avoidance of central adiposity, adoption of an antiatherogenic diet, and regular physical activity, are crucial. However, as the magnitude of the individual components of the metabolic syndrome increases with time, lifestyle measures are often insufficient. An individual with metabolic syndrome will often require drug treatment for hyperglycemia, atherogenic dyslipidemia, and high blood pressure, together with antiplatelet therapy. Reducing the need for polypharmacy is an increasingly important consideration for clinicians and the pharmaceutical industry; to date, no single therapy has emerged that targets the root cause(s) of the syndrome. HMG-CoA reductase inhibitors are important agents that reduce CVD morbidity and mortality, in people with impaired fasting glucose or metabolic syndrome. Selective cannabinoid receptor antagonists appear promising because they improve or attenuate several key defects of the syndrome. Thiazolidinediones and metformin are presently licensed for treatment of type 2 diabetes but may prove to have a broader role in future. Novel insulin-sensitizing drugs are under investigation. Drugs that act to prevent or reverse endothelial dysfunction may be of particular utility in preventing cardiovascular disease, especially if initiated before tissue damage has become irreversible. Insulin therapy, which has antiinflammatory and endothelial protective properties, has been shown to reduce morbidity and mortality in high-risk nondiabetic patients during critical illness. Potential synergy between different classes of drugs with metabolic and/or cardiovascular protective properties merits further investigation.

Circulatory syndrome: an evolution of the metabolic syndrome concept!

The metabolic syndrome has been a useful, though controversial construct in clinical practice as well as a valuable model in order to understand the interactions of diverse cardiovascular risk factors. However the increasing importance of the circulatory system in particular the endothelium, in both connecting and controlling organ function has underlined the limitations of the metabolic syndrome definition. The proposed "Circulatory Syndrome" is an attempt to refine the metabolic syndrome concept by the addition of recently documented markers of cardiovascular disease including renal impairment, microalbuminuria, arterial stiffness, ventricular dysfunction and anaemia to more classic factors including hypertension, dyslipidemia and abnormal glucose metabolism; all of which easily measured in clinical practice. These markers interact with each other as well as with other factors such as aging, obesity, physical inactivity, diet and smoking. The final common pathways of inflammation, oxidative stress and hypercoagulability thereby lead to endothelial damage and eventually cardiovascular disease. Nevertheless, the Circulatory (MARC) Syndrome, like its predecessor the metabolic syndrome, is only a small step toward an understanding of these complex and as yet poorly understood markers of disease.

Microalbuminuria: causes and implications

Management strategies are increasingly focused on tackling the increasing burden of cardiovascular disease worldwide. Microalbuminuria is a powerful predictor of cardiovascular disease and mortality in adults. This holds true in the general adult population but is particularly recognized in those with diabetes, where it identifies those likely to develop progressive atherosclerotic vascular disease and renal impairment. The atherosclerotic process begins in childhood with likely consequences in later life. In-depth understanding of the mechanisms through which microalbuminuria occurs holds promise for designing therapies to arrest its development in the future. Microalbuminuria arises from increased leakage of albumin through the complex glomerular sieve known as the glomerular filtration barrier. This requires changes in the physio-chemical properties of components of this barrier. However, the increased glomerular permeability confirmed in disease does not necessarily correlate with recognized histological changes in the glomerulus, suggesting that perhaps more subtle ultrastructural changes may be relevant. The epidemiology of microalbuminuria reveals a close association between systemic endothelial dysfunction and vascular disease, also implicating glomerular endothelial dysfunction in microalbuminuria. This review discusses the mechanisms of microalbuminuria in disease, particularly the emerging role of the glomerular endothelium and its glycocalyx, and examines its implications for cardiovascular disease in the pediatric population.

Stepwise increases in left ventricular mass index and decreases in left ventricular ejection fraction correspond with the stages of chronic kidney disease in diabetes patients

AIMS

Patients with diabetic nephropathy are reported to have a high prevalence of left ventricular structural and functional abnormalities. This study was designed to assess the determinants of left ventricular mass index (LVMI) and left ventricular ejection fraction (LVEF) in diabetic patients at various stages of chronic kidney disease (CKD).

METHODS

This cross-sectional study enrolled 285 diabetic patients with CKD stages 3 to 5 from our outpatient department of internal medicine. Clinical and echocardiographic parameters were compared and analyzed.

RESULTS

We found a significant stepwise increase in LVMI (P < 0.001), LVH (P < 0.001), and LVEF <55% (P = 0.013) and a stepwise decrease in LVEF (P = 0.038) corresponding to advance in CKD stages.

CONCLUSIONS

Our findings suggest that increases in LVMI and decreases in LVEF coincide with advances in CKD stages in patients with diabetes.

Elevated Levels of N-Terminal Pro-Brain Natriuretic Peptide in Patients with Chronic Dyspnea and Moderate Renal Dysfunction: Decreased Clearance or Increased Cardiac Stress

BACKGROUND/AIMS

Serum levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) are often increased in patients with impaired renal function. The objective of this study was to investigate whether the increase in NT-proBNP is predominantly due to a reduced renal clearance or an increased cardiac secretion.

METHODS

A series of 697 outpatients (age: 57.5 ± 16.4 years) referred for evaluation of dyspnea were assigned to 4 groups according to their estimated glomerular filtration rate [eGFR (ml/min per 1.73 m2)]: group 1, eGFR <60 (n = 77); group 2, eGFR ≧60 to <75 (n = 139); group 3, eGFR ≧75 to <90 (n = 191), and group 4, eGFR ≧90 (n = 289). The patients were also grouped into 2 categories based on the presence (n = 176) or absence (n = 521) of heart disease.

RESULTS

In patients with heart disease, the adjusted values for NT-proBNP were higher in eGFR group 1 than in eGFR groups 2-4 (p ≤ 0.01). In patients without heart disease, eGFR group 1 membership had no effect on NT-proBNP.

CONCLUSION

A reduced renal clearance does not explain increased NT-proBNP levels in patients with moderate renal impairment and dyspnea. Our data suggest that a moderate reduction in renal function places additional stress on the heart in patients with established cardiac disease.

[Connection between the early phases of kidney disease and the metabolic syndrome]

INTRODUCTION AND OBJECTIVES

Advanced kidney disease is a major health problem due to its association with high cardiovascular morbidity and mortality. Early recognition of advanced kidney disease is the mainstay to avoid its progression. Since metabolic syndrome and insulin resistance are risk factors for both cardiovascular and advanced kidney disease, we investigated the relationship of early kidney disease (EKD) with metabolic syndrome and insulin resistance, and their association with surrogate markers of arteriosclerosis.

METHODS

We studied 1498 subjects. Insulin resistance was defined as HOMA ≥3.7 mmol (μU)/L(2) and EKD as stages 1 and 2 of the NKF-KDOQI. Carotid intima-media thickness was used as a surrogate marker of arteriosclerosis.

RESULTS

The presence of one trait of metabolic syndrome was associated with an odds ratio (OR) for EKD of 2.3 (95% confidence interval [CI], 1.18-4.48) that increased to 6.72 (95% CI, 3.56-13.69) in subjects with the syndrome. All the traits of the syndrome except low level of high-density lipoproteins showed an increased OR for EKD. Increasing HOMA was also directly correlated with higher OR for EKD, being as high as 3.89 (95% CI, 1.99-7.59) for subjects in the fourth quartile. Subjects with the syndrome plus EKD showed an increased intima-media thickness compared with those without kidney disease.

CONCLUSIONS

Insulin resistance and all metabolic syndrome traits except low level of high-density lipoproteins were significantly associated with an increased OR for EKD. Both metabolic syndrome and EKD were independently and additively related to the presence of surrogate markers of arteriosclerosis.

Distribution pattern of urine albumin creatinine ratio and the prevalence of high-normal levels in untreated asymptomatic non-diabetic hypertensive patients

BACKGROUND

Even high-normal albuminuria is reportedly associated with cardiovascular events.

OBJECTIVE

We determined the urine albumin creatinine ratio (UACR) in spot urine samples and analyzed the UACR distribution and the prevalence of high-normal levels.

PATIENTS AND METHODS

The UACR was determined using immunoturbidimetry in 332 untreated asymptomatic non-diabetic Japanese patients with hypertension and in 69 control subjects. The microalbuminuria and macroalbuminuria levels were defined as a UCAR ≥30 and <300 µg/mg·creatinine and a UCAR ≥300 µg/mg·creatinine, respectively.

RESULTS

The distribution patterns showed a highly skewed distribution for the lower levels, and a common logarithmic transformation produced a close fit to a Gaussian distribution with median, 25th and 75th percentile values of 22.6, 13.5 and 48.2 µg/mg·creatinine, respectively. When a high-normal UACR was set at >20 to <30 µg/mg·creatinine, 19.9% (66/332) of the hypertensive patients exhibited a high-normal UACR. Microalbuminuria and macroalbuminuria were observed in 36.1% (120/336) and 2.1% (7/332) of the patients, respectively. UACR was significantly correlated with the systolic and diastolic blood pressures and the pulse pressure. A stepwise multivariate analysis revealed that these pressures as well as age were independent factors that increased UACR.

CONCLUSION

The UACR distribution exhibited a highly skewed pattern, with approximately 60% of untreated, non-diabetic hypertensive patients exhibiting a high-normal or larger UACR. Both hypertension and age are independent risk factors that increase the UACR. The present study indicated that a considerable percentage of patients require anti-hypertensive drugs with antiproteinuric effects at the start of treatment.

High glucose causes dysfunction of the human glomerular endothelial glycocalyx

The endothelial glycocalyx is a gel-like layer which covers the luminal side of blood vessels. The glomerular endothelial cell (GEnC) glycocalyx is composed of proteoglycan core proteins, glycosaminoglycan (GAG) chains, and sialoglycoproteins and has been shown to contribute to the selective sieving action of the glomerular capillary wall. Damage to the systemic endothelial glycocalyx has recently been associated with the onset of albuminuria in diabetics. In this study, we analyze the effects of high glucose on the biochemical structure of the GEnC glycocalyx and quantify functional changes in its protein-restrictive action. We used conditionally immortalized human GEnC. Proteoglycans were analyzed by Western blotting and indirect immunofluorescence. Biosynthesis of GAG was analyzed by radiolabeling and quantified by anion exchange chromatography. FITC-albumin was used to analyze macromolecular passage across GEnC monolayers using an established in vitro model. We observed a marked reduction in the biosynthesis of GAG by the GEnC under high-glucose conditions. Further analysis confirmed specific reduction in heparan sulfate GAG. Expression of proteoglycan core proteins remained unchanged. There was also a significant increase in the passage of albumin across GEnC monolayers under high-glucose conditions without affecting interendothelial junctions. These results reproduce changes in GEnC barrier properties caused by enzymatic removal of heparan sulfate from the GEnC glycocalyx. They provide direct evidence of high glucose-induced alterations in the GEnC glycocalyx and demonstrate changes to its function as a protein-restrictive layer, thus implicating glycocalyx damage in the pathogenesis of proteinuria in diabetes.

Effect of cilnidipine on normal to marginally elevated urine albumin-creatinine ratio in asymptomatic non-diabetic hypertensive patients: an exponential decay curve analysis

BACKGROUND

High-normal urinary albumin excretion has been reported to have clinical significance with respect to progression of proteinuria and hypertension.

OBJECTIVE

We analysed the effect of cilnidipine (10 mg/day) on morning systolic blood pressure (SBP) and urine albumin-creatinine ratio (UACR) in 16 non-diabetic hypertensive patients with a normal to marginally elevated UACR (mean +/- SD 29.4 +/- 21.7; range 7.5-72.9 mg/g creatinine).

METHODS

Sequential home BP and UACR data were fitted to a simple exponential function as follows: where y is SBP (mmHg) or UACR (mg/g creatinine); alpha is the extent of the SBP (mmHg)- or UACR (mg/g creatinine)-lowering effect; beta (days) is the time-constant for SBP or UACR decrease; t is the number of days after the start of cilnidipine administration; and gamma is the finally stabilized SBP (mmHg) or UACR (mg/g creatinine).

RESULTS

Mean +/- SD morning SBP and UACR decreased by 20.4 +/- 11.4 mmHg and 15.2 +/- 13.1 mg/g creatinine, respectively, as determined by coefficient alpha. The mean +/- SD time-constant for UACR decrease was significantly longer than that for BP decrease (43.5 +/- 22.9 vs 15.4 +/- 7.1 days). UACR reduction correlated with pre-treatment UACR values (correlation coefficient [R] = 0.88, p < 0.01) but not with BP decrease.

CONCLUSIONS

The present study demonstrated that cilnidipine reduced UACR in hypertensive patients with normal to marginally elevated UACR independent of its BP-lowering effect.

Risk factors for development of cardiovascular complications in patients with chronic renal disease and diabetic nephropathy

INTRODUCTION

Cardiovascular diseases are the most frequent causes of morbidity and mortality in patients with chronic renal disease. The aim of our paper is to evaluate the risk factors of cardiovascular complications in patients with various stages of chronic renal disease (CRD), with or without diabetes mellitus (DM).

PATIENTS AND METHODS

The study included 98 patients with different stages of the CRD, with creatinine clearance <60 ml/min/1.73m2, and laboratory parameters monitored: homocysteine, BNP, cholesterol, LDL, HDL, HbA1c, Body Mass Index (BMI). First group comprised 49 patients with DM, age 50-82 years, M 28/F 21. Second group comprised 49 patients without DM, age 35-80 years, M 18/F 31. The IMT (intima media thickness) was measured by B-mode ultrasonography, and all patients had echocardiography examination done by 2D Doppler ultrasonography.

RESULTS

The IMT values in diabetic patients had statistically significant positive correlation with homocysteine values of r=0.9393, p<0.034, and cholesterol r=0.289, p<0.05, compared to non-diabetics. A significant negative correlation was found between the ejection fraction (EF) and BMI in both groups, more prominent in non-diabetics r=0.289, p<0.044 (diabetics r=0.162, p>0.05). 47.4% of diabetics had arteriosclerotic changes on carotid arteries, 8.5% had stenosis of ACC, and 22.0% had rhythm abnormalities on ECG. A positive correlation between IMT and BMI was found in diabetics, but was not statistically significant r=0.111, p>0.05. In the diabetics group a significantly higher (p<0.05) values of BNP, HbA1c, proteinuria, BMI, and cholesterol were found, and significantly lowered EF (p<0.0001).

CONCLUSION

Risk factors for cardiovascular complications in patients with DM are various, and the most pronounced significance was found in the values of homocysteine, BNP and cholesterol.

Obesity and changes in urine albumin/creatinine ratio in patients with type 2 diabetes: the DEMAND study

BACKGROUND AND AIMS

Obesity is a potential risk factor for renal disease in non-diabetic subjects. It remains unclear whether this also applies to diabetic patients. We investigated whether obesity predicted changes in albumin excretion rate in individuals with type 2 diabetes.

METHODS AND RESULTS

Fifty Italian diabetes outpatient clinics enrolled a random sample of 1289 patients. A morning spot urine sample was collected to determine urinary albumin/creatinine ratio (ACR) at baseline and after 1 year from the study initiation. Progression of albumin excretion was defined as a doubling in ACR, while regression was defined as a 50% reduction. Multivariate logistic regression analyses were used to evaluate correlates of these outcomes. Data are expressed as odds ratios (OR) with 95% confidence intervals (CI). The risk of progression increased by 7% (OR=1.07; 95%CI 1.00-1.15) for every 5-cm increase in waist circumference measured at baseline, and by 17% (OR=1.17; 95%CI 1.03-1.33) for every one-unit increase in BMI during follow-up. The likelihood of regression was not independently associated with any of the variables investigated. The effect of obesity on progression of ACR was independent of metabolic control, blood pressure, treatment, and baseline level of albumin excretion.

CONCLUSIONS

We found a tight link between obesity and changes in albumin excretion in diabetic subjects, suggesting potential benefits of interventions on body weight on end-organ renal damage.

Complementary effects of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in slowing the progression of chronic kidney disease

Chronic kidney disease (CKD) and end-stage renal disease continue to pose major healthcare challenges. Early initiation of therapy aimed at slowing the progression of CKD is essential. Increased renin-angiotensin-aldosterone-system activity and, in particular, elevated levels of angiotensin II (AII) play important roles in the development and progression of CKD. Therefore, pharmacologic therapies that block the effects of AII and reduce its pathogenic effects are cornerstones of clinical management. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) have been shown to have renoprotective effects in addition to their ability to control blood pressure. There is accumulating clinical evidence that the combination of an ACEI and an ARB provides greater renal protection, particularly in decreasing proteinuria, than does either agent alone.

The metabolic syndrome is related to albuminuria in Type 2 diabetes

AIMS

To determine the relationships between metabolic syndrome (MetS), diabetic nephropathy (DN) and renal function in Type 2 diabetes.

METHODS

In a clinic-based cohort of 1314 Type 2 diabetic patients (58% male; age 62 +/- 10 years), we analysed MetS, detected DN and estimated glomerular filtration rate (eGFR).

RESULTS

Prevalence of both microalbuminuria and macroalbuminuria were higher in subjects with MetS than in those without. Prevalence of DN (microalbuminuria and macroalbuminuria) increased with the number of MetS components. eGFR was lower in subjects with MetS than in those without (87 +/- 23 vs. 92 +/- 20 ml/min per 1.73 m2; P < 0.001). The lowest eGFR values were found in those with four or more components of the MetS. Prevalence of low eGFR increased with the stage of DN and was affected by MetS only in normoalbuminuric patients. MetS was independently associated with DN, also after adjustment for confounders [odds ratio (OR) 2.82, confidence interval (CI) 1.93, 4.11] and the presence of low eGFR in the model (OR 2.74, CI 1.87, 4.01). Similarly, MetS was a predictor of low eGFR (OR 1.93, CI 1.11, 3.36), but after adjustment for DN, the association was lost. Finally, MetS per se was independently associated with DN, but not with low eGFR after adjustment for all of the individual components of the MetS.

CONCLUSIONS

This study suggests a close and independent association between MetS and renal impairment. However, it is unclear whether and to what extent treating MetS by an intensive multifactorial therapeutic approach will prevent or delay progression to renal failure.

[Hypertension and the kidney]

Hypertension and proteinuria are common risk factors for cardiovascular morbidity and mortality, as well as for the progression of renal disease. Renal functional impairment represents an independent cardiovascular risk factor by itself. Strict antihypertensive therapy and measures to maximally reduce proteinuria can substantially improve the prognosis of renal patients. This review summarizes current evidence for the role of hypertension and proteinuria with regard to renal and cardiovascular outcomes and for the importance of intensive antihypertensive and anti-proteinuric measures.

Increased mast cell number in human hypertensive nephropathy

Mast cells have recently been related to nonallergic chronic organ damage and fibrosis. In the present study, we analyzed mast cell number, localization, and maturation in the kidney of a relatively unique group of middle-aged accident victims with primary essential hypertension and in normotensive controls (n=8 per group, Caucasians, predominantly male). Hypertensive kidneys showed a significantly higher degree of arteriolosclerosis. However, glomerular and tubulointerstitial matrix accumulation did not differ significantly to normotensive controls indicating a relatively early stage of hypertensive nephropathy. Using toluidine blue staining, renal mast cell number was found to be fivefold higher in hypertensive subjects compared with normotensive controls. Mast cells were primarily located in the peritubular interstitial spaces, some perivascular, but not in glomeruli. In a series of immunohistological staining studies, mast cell maturation grading showed that expression of early hematopoietic precursor cell marker CD34 did not differ between both groups. In contrast, mast cells were mostly positive for IgE receptor, tryptase, and chymase indicating a mature, differentiated cell phenotype in hypertensive nephropathy. Renal expression of stem cell factor was markedly upregulated in primary hypertension. Kidney macrophage and lymphocyte numbers were similar in both groups. In conclusion, human hypertensive kidney disease shows an early and conspicuous upregulation of stem cell factor along with an increased number of mature mast cells. The results suggest that renal mast cell accumulation may play a role in the pathogenesis of human hypertensive nephropathy.

Albumin transport and processing by the proximal tubule: physiology and pathophysiology

PURPOSE OF REVIEW

Significant epidemiological and clinical trial evidence supports the association between increased urinary albumin excretion, cardiovascular events and renal failure. An increase in albumin excretion has traditionally been considered to reflect a 'glomerular' leak of protein; however, it is now recognized that significant tubular reabsorption of albumin occurs under physiological conditions that may be modified by genetic determinants, systemic disease and drug therapies.

RECENT FINDINGS

The endocytosis of albumin by the proximal tubule is a highly regulated process depending on protein-protein interactions between several membrane proteins and scaffolding and regulatory molecules. The elucidation of these interactions is an ongoing research focus. There is also mounting evidence for a transcytotic pathway for retrieval of albumin from the tubular filtrate. The molecular basis for the role of albuminuria in both interstitial renal disease and cardiovascular pathology continues to be defined. The clinical implications of albuminuria due to a glomerular leak vs. reduced tubular reabsorption of albumin are, however, now under consideration. In particular, the prognostic implication of microalbuminuria induced by the more potent 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors is under study.

SUMMARY

The currently defined mechanisms underpinning the tubular reabsorption of albumin, how these are modified by pathology and pharmacology, and the clinical implications are the subject of this review.

Chip Electrophoresis as a Method for Quantifying Total Microalbuminuria

Background: Microalbuminuria is an important prognostic marker in diabetic nephropathy and cardiovascular disease. Initially, most commercial assays used immunoreactivity to quantify microalbuminuria; however, size-exclusion HPLC demonstrated the existence of nonimmunoreactive forms of albumin that may not be detected by immunoassay. Recent liquid chromatography tandem mass spectrometry analyses suggested that size-exclusion HPLC gave higher results attributable to other urine proteins coeluting with albumin. We describe an assay that measures total microalbuminuria (immunoreactive and nonimmunoreactive) without any discernable interference from other common urine proteins.

Methods: We used an automated chip electrophoresis system that utilized microfluidic separation technology and fluorescent sample detection. Each albumin specimen was mixed with the manufacturer’s sample buffer in addition to a chicken albumin internal calibrator and then electrophoresed without additional reducing agents.

Results: With variable concentrations of bovine serum albumin normalized to a chicken albumin internal calibrator, the electrophoresis system was best fit with a polynomial (R2 = 0.9997; concentration range, 5–300 mg/L). The lower limit of detection was 5 mg/L. Interchip and intrachip variation studies conducted on patient urine demonstrated CVs of 3%–13%. The introduction of potentially interfering agents (i.e., molecular analytes, nonalbumin proteins) did not alter precision. Compared with immunoassay, the chip electrophoresis identified higher microalbuminuria concentrations in all urine samples. The method also clearly resolved the albumin peak from interfering proteins.

Conclusions: Unlike immunoassay, chip electrophoresis can detect both immunoreactive and nonimmunoreactive forms of albumin. This system is a simple, robust method to quantify microalbuminuria with good sensitivity, precision, and accuracy.

Late referral of patients with chronic kidney disease: no time to waste

The prevalence of patients with chronic kidney disease (CKD) in the US population is approximately 11%, and because of the increase in life expectancy and in diabetic nephropathy incidence, an exponential increase is predicted for the next decades. During the past decade, evidence that the progression of CKD can be attenuated by a multifactorial therapeutic approach has been increasing. However, a substantial percentage of patients with CKD will have progression to CKD stage V (ie, need for renal replacement therapy). Late referral of these patients (ie, <1 to 6 months before the start of renal replacement therapy) has been shown to be associated with higher mortality, morbidity, and costs. However, up to 64% of patients with CKD are still referred late. This review presents the available data on the epidemiology, causes, and consequences of late patient referral. Furthermore, it offers information to prevent late referral, improve CKD patient care, and change clinical practice.

Imaging the renin-angiotensin system: an important target of anti-hypertensive therapy

Multiphoton fluorescence microscopy allows visualization, manipulation, and quantification of the structure-function relationships between pharmacological interventions and their physiological effects. The application of these methods to live animals permits direct observation of acute physical responses that lack chemically detectable signals in the blood or urine and would otherwise remain unknown. With the use of special fluorescent dyes, chemical/hormonal responses may also be detected. The delivery and site-specific effects of drugs can be monitored in real-time. The capacity to simultaneously visualize both proximal and distal segments of the nephron permits observation of the dynamic processes within the living kidney and a quantitative assessment of the various operations. Consequently, a clinically valuable and pending application for multi-photon microscopy will be to provide real-time, quantitative imaging of basic organ functions and their responses to therapeutic intervention. Imaging of the intra-renal renin content and enzymatic activity of renin in situ and in real-time is a new, more informative measure of RAS activity. Direct visualization of the molecular and cellular components of renin release signals and the interactions between the vascular endothelium, tubular epithelium, local mediators, and the renin producing cells provides great insight for drug development. Examples of how the effects of various RAS inhibitors can be visualized in the intact kidney are provided: including angiotensin converting enzyme inhibition (captopril), angiotensin II type 1 receptor blockade (olmesartan), and renin inhibition (aliskiren). The site-specific actions of diuretics, like furosemide, have also been visualized. Quantitative imaging of basic renal functions in health and disease can provide key information to assess the delivery and effects of pharmaceutical interventions.

Assessment of metabolic profile in a clinical setting

PURPOSE OF REVIEW

The metabolic syndrome, a clustering of abnormalities such as hyperglycemia, insulin resistance, hypertension, dyslipidemia, and central obesity, is a principal risk factor for cardiovascular disease, the leading cause of morbidity and mortality in the Western world. There are several definitions of the metabolic syndrome, all aiming at including as many persons at risk as possible. The assessment and, hence, the identification of such persons in a clinical setting is of utmost importance.

RECENT FINDINGS

Clinicians should document the presence of central obesity, assessed by waist circumference measurement or determination of body composition using dual X-ray absorptiometry or measurement of visceral fat using computed tomography or magnetic resonance imaging. The presence of dyslipidemia, insulin resistance, and arterial hypertension constitutes the full profile of the metabolic syndrome. Nevertheless, elevated uric acid levels or presence of nonalcoholic fatty liver, or the diagnosis of the polycystic ovary syndrome in women of reproductive age, all are reflected in high risk of later occurrence of the full metabolic syndrome and atherosclerotic cardiovascular disease.

SUMMARY

Although no unified definition for the metabolic syndrome exists, it is important to identify persons at risk, in order to reduce the resultant high morbidity and mortality rates.