Microalbuminuria, an integrated marker of cardiovascular risk in essential hypertension

Association of 24-h urinary sodium excretion with microalbuminuria in a Chinese population

To assess the relationship of sodium, potassium and the ratio of sodium to potassium (Na/K) with albuminuria, a cross-sectional study was carried out in China in 2017. Sodium, potassium and albumin excretions were examined in a 24-h (h) urine sample collected from 1486 participants. Microalbuminuria was defined as 24-h urinary albumin excretion between 30 and 300 mg/24 h. The participants had an average age of 46.2 ± 14.1 years old, and 48.9% were men. The proportion of patients with microalbuminuria was 9.0%. As illustrated by the adjusted generalized linear mixed model, sodium concentration increased significantly with the increase in 24-h urinary albumin (β = 1.16, 95% confidence interval (CI) 0.38-1.93; P = 0.003). Multivariable-adjusted logistic regression analyses demonstrated that the odds ratio (OR) of microalbuminuria increased with the quartiles of sodium [OR = 2.20, 95% CI 1.26-3.84 (the maximum quartile vs. the minimum quartile), P_{for trend} = 0.006]. Potassium and the Na/K ratio did not have any association with outcome indicators. A high amount of sodium intake was potentially correlated with early renal function impairment.

Evaluation of Arterial Stiffness and Carotid Intima-Media Thickness in Children with Primary and Renal Hypertension

Hypertension is an increasing disease in children and the risk of endothelial damage and target organ damage increases in the presence of additional risk factors such as obesity. In our study, the effect of hypertension on early atherosclerotic changes and target organ damage in children was investigated. Twenty four-hour ambulatory pulse wave analysis was performed by oscillometric method in 71 children aged 8-18 years, 17 of whom were diagnosed with primary hypertension without obesity, 18 had both primary hypertension and obesity, and 16 had renal hypertension. Twenty healthy normotensive children were included as the control group. Carotid intima-media thickness (CIMT) and Left Ventricular Mass Index were measured. Central systolic blood pressure (cSBP), central diastolic blood pressure (cDBP), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were higher in the primary hypertension group compared to controls (p = 0.001, p = 0.005, p = 0.001, p = 0.009, respectively), cSBP was higher in the renal hypertension group than the control group (p = 0.018). There was no difference between the groups in terms of pulse wave analysis parameters, CIMT, or left ventricular mass index (p > 0.05). Pulse wave velocity was positively correlated with SBP, DBP, cSBP, cDBP (p < 0.001). Augmentation index was positively correlated with DBP and cDBP (p = 0.01, p = 0.002, respectively). Our findings show that high blood pressure is associated with arterial stiffness and target organ damage beginning in childhood. The detection of early atherosclerotic vascular changes using pulse wave analysis allows to take necessary precautions such as lifestyle changes to prevent target organ damage in hypertensive children.

Comparing the associations of clinic vs. ambulatory blood pressure with subclinical organ damage in young healthy adults: the African-PREDICT study

Raised blood pressure (BP) causes pathophysiological cardiovascular changes resulting in target organ damage. Although ambulatory and central BP relate more strongly to outcomes than clinical brachial BP in the elderly population, it is unknown which measure of BP is most strongly associated with markers of organ damage in younger populations. We compared the strength of associations between different BPs and measures of subclinical organ damage and investigated whether ethnic differences exist between these associations. The design was a cross-sectional analysis of the African-PREDICT study, including young black and white men and women (aged 20-30, N = 1202). We obtained clinic, ambulatory, and central BP readings, as well as measures of subclinical organ damage: central retinal arteriolar equivalent (CRAE) from fundus images, echocardiography to determine left ventricular mass index (LVMi), carotid intima media thickness (CIMT), carotid-femoral pulse wave velocity (PWV), and albumin-to-creatinine ratio (ACR) determined from spot urine samples. Overall, weak correlations were evident between CIMT, ACR, and BP, whereas CRAE, LVMi, and PWV correlated strongly with BP. In the total group, clinic brachial BP had stronger associations with CRAE, LVMi, and PWV (all p < 0.001) than ambulatory and central BP. Although the ethnic groups showed similar correlations between CRAE, LVMi, CIMT, and the various BPs, PWV correlated more strongly with ambulatory systolic BP (p < 0.001) in white participants. In young healthy adults, clinic brachial BP correlated more strongly with measures of early target organ damage than central or ambulatory BP. No differences were observed between correlations of BP and measures of target organ damage in the two ethnic groups.

Decreased Urinary Levels of SIRT1 as Non-Invasive Biomarker of Early Renal Damage in Hypertension

Sirtuins have become important players in renal damage in hypertension and diabetes, but their value as biomarkers is poorly assessed. The aims of the study were to evaluate the levels of sirtuin1 (SIRT1), and two miRNAs that regulate SIRT1 expression in hypertensive patients with incipient renal damage with and without diabetes. We quantified urinary SIRT1 and claudin 1 (CLDN1) mRNA and miR34-a and miR-200a levels by quantitative real-time polymerase chain reaction (RT-qPCR) from patients and in cultured podocytes treated with high glucose and angiotensin II. Western blot and fluorescence analyses were also performed. We found decreased SIRT1 levels in patients with increased urinary albumin excretion (UAE), the lowest with diabetes presence, and a strong association with UAE, discriminating incipient renal damage. In vitro experiments also showed SIRT1 overall decreases in podocyte cultures under treatment conditions. In urine samples, miR-34a was reduced and miR-200a increased, both related to UAE levels. However, both miRNAs were generally increased in podocyte cultures under high glucose and angiotensin-II treatment. These results show a significant urinary SIRT1 decrease in albuminuric hypertensive patients, strongly associated with albuminuria, suggesting that SIRT1 could be a potential and non-invasive method to assess incipient renal damage in hypertensive patients.

Decreased Renal Function Is a Risk Factor for Subclinical Coronary Atherosclerosis in Korean Postmenopausal Women

OBJECTIVES

Decreased renal function is associated with increased cardiovascular risk. Our study was planned to verify the association of decreased renal function and subclinical coronary atherosclerosis in postmenopausal women.

METHODS

We performed a retrospective review of 251 Korean postmenopausal women who visited the health promotion center for a routine health checkup. Estimated glomerular filtration rate (eGFR) was used to show renal function, which was estimated by calculated using the Cockcroft-Gault (CG) and the modification of diet in renal disease (MDRD) formulas. Coronary atherosclerosis was assessed by 64-row multidetector computed tomography.

RESULTS

Women with reduced eGFR (< 60 mL/minute/1.73 m2) had significantly higher brachial-ankle pulse wave velocity (baPWV) than women with normal eGFR (≥ 60 mL/minute/1.73 m2). The eGFR was negatively correlated with baPWV (r = -0.352, P < 0.001), significantly. The eGFR was lower in women with coronary atherosclerosis than in normal control women, markedly. Reduced eGFR was significantly associated with the presence of coronary atherosclerosis (odds ratio [OR] = 7.528, 95% confidence interval [CI] = 2.728-20.772, P < 0.001).

CONCLUSIONS

Decreased eGFR was closely associated with increased arterial stiffness and coronary atherosclerosis in postmenopausal women. Evaluating subclinical atherosclerosis by screening the renal function in postmenopausal women may be helpful screening high risk group and considering starting menopausal hormone therapy before atherosclerosis development.

Microalbuminuria in primary hypertension: a guide to optimal patient management?

Accurate assessment of the global risk profile is considered a prerequisite for the optimal management of hypertensive patients. In particular, the evaluation of subclinical organ damage, namely left ventricular hypertrophy, peripheral atherosclerosis and renal function, plays a key role in optimizing therapeutic targets and strategy in individual patients. Urine albumin excretion is a low-cost, easy-to-use test and a powerful predictor of cardiovascular diseases. The search for albuminuria has, therefore, become routine in the evaluation of hypertensive patients. Moreover, albuminuria has been shown to be associated with early signs of extra-renal organ damage such as left ventricular hypertrophy, and carotid atherosclerosis. Under effective antihypertensive treatment, changes in subclinical organ damage over time, especially regression of left ventricular hypertrophy, are paralleled by modification of risk status and may serve as intermediate endpoints for treatment. More recently, changes in albuminuria have also been proposed to reflect changes in the risk of cardiovascular events. If this is confirmed by large well-designed studies, microalbuminuria may not simply be regarded as a risk predictor but become itself an independent target for treatment.

Subclinical Kidney Damage in Hypertensive Patients: A Renal Window Opened on the Cardiovascular System. Focus on Microalbuminuria

The kidney is one of the major target organs of hypertension.Kidney damage represents a frequent event in the course of hypertension and arterial hypertension is one of the leading causes of end-stage renal disease (ESRD).ESRD has long been recognized as a strong predictor of cardiovascular (CV) morbidity and mortality. However, over the past 20 years a large and consistent body of evidence has been produced suggesting that CV risk progressively increases as the estimated glomerular filtration rate (eGFR) declines and is already significantly elevated even in the earliest stages of renal damage. Data was supported by the very large collaborative meta-analysis of the Chronic Kidney Disease Prognosis Consortium, which provided undisputable evidence that there is an inverse association between eGFR and CV risk. It is important to remember that in evaluating CV disease using renal parameters, GFR should be assessed simultaneously with albuminuria.Indeed, data from the same meta-analysis indicate that also increased urinary albumin levels or proteinuria carry an increased risk of all-cause and CV mortality. Thus, lower eGFR and higher urinary albumin values are not only predictors of progressive kidney failure, but also of all-cause and CV mortality, independent of each other and of traditional CV risk factors.Although subjects with ESRD are at the highest risk of CV diseases, there will likely be more events in subjects with mil-to-moderate renal dysfunction, because of its much higher prevalence.These findings are even more noteworthy when one considers that a mild reduction in renal function is very common in hypertensive patients.The current European Society of Hypertension (ESH)/European Society of Cardiology (ESC) guidelines for the management of arterial hypertension recommend to sought in every patient signs of subclinical (or asymptomatic) renal damage. This was defined by the detection of eGFR between 30 mL/min/1.73 m² and 60 mL/min/1.73 m² or the presence of microalbuminuria (MAU), that is an amount of albumin in the urine of 30-300 mg/day or an albumin/creatinine ratio, preferentially on morning spot urine, of 30-300 mg/g.There is clear evidence that urinary albumin excretion levels, even below the cut-off values used to define MAU, are associated with an increased risk of CV events. The relationships of MAU with a variety of risk factors, such as blood pressure, diabetes and metabolic syndrome and with several indices of subclinical organ damage, may contribute, at least in part, to explain the enhanced CV risk conferred by MAU. Nonetheless, several studies showed that the association between MAU and CV disease remains when all these risk factors are taken into account in multivariate analyses. Therefore, the exact pathophysiological mechanisms explaining the association between MAU and CV risk remain to be elucidated. The simple search for MAU and in general of subclinical renal involvement in hypertensive patients may enable the clinician to better assess absolute CV risk, and its identification may induce physicians to encourage patients to make healthy lifestyle changes and perhaps would prompt to more aggressive modification of standard CV risk factors.

Kidney and cardiovascular risk in primary hypertension

In patients with primary hypertension, therapeutic strategies should be based on global cardiovascular risk profile rather than on the severity of blood pressure alone. Accurate assessment of concomitant risk factors and especially of the presence and extent of subclinical organ damage is of paramount importance in defining individual risk. Given the high prevalence of hypertension in the population at large, however, extensive diagnostic evaluation is often impractical or unfeasible in clinical practice. Low cost, easy to use markers of risk are needed to improve the clinical management of patients with hypertension. Early renal abnormalities such as a slight reduction in glomerular filtration rate and/or the presence of microalbuminuria are well known and powerful predictors of cardio-renal morbidity and mortality and provide a useful, low cost tools to optimize cardiovascular risk assessment. A greater use of these tests should therefore be implemented in clinical practice in order to optimize the management of hypertensive patients.

Genomic and metabolomic profile associated to microalbuminuria

To identify factors related with the risk to develop microalbuminuria using combined genomic and metabolomic values from a general population study. One thousand five hundred and two subjects, Caucasian, more than 18 years, representative of the general population, were included. Blood pressure measurement and albumin/creatinine ratio were measured in a urine sample. Using SNPlex, 1251 SNPs potentially associated to urinary albumin excretion (UAE) were analyzed. Serum metabolomic profile was assessed by 1H NMR spectra using a Brucker Advance DRX 600 spectrometer. From the total population, 1217 (mean age 54 ± 19, 50.6% men, ACR>30 mg/g in 81 subjects) with high genotyping call rate were analysed. A characteristic metabolomic profile, which included products from mitochondrial and extra mitochondrial metabolism as well as branched amino acids and their derivative signals, were observed in microalbuminuric as compare to normoalbuminuric subjects. The comparison of the metabolomic profile between subjects with different UAE status for each of the genotypes associated to microalbuminuria revealed two SNPs, the rs10492025_TT of RPH3A gene and the rs4359_CC of ACE gene, with minimal or no statistically significant differences. Subjects with and without microalbuminuria, who shared the same genotype and metabolomic profile, differed in age. Microalbuminurics with the CC genotype of the rs4359 polymorphism and with the TT genotype of the rs10492025 polymorphism were seven years older and seventeen years younger, respectively as compared to the whole microalbuminuric subjects. With the same metabolomic environment, characteristic of subjects with microalbuminuria, the TT genotype of the rs10492025 polymorphism seems to increase and the CC genotype of the rs4359 polymorphism seems to reduce risk to develop microalbuminuria.

Interaction of obesity and central obesity on elevated urinary albumin-to-creatinine ratio

Background

Microalbuminuria was much more common among obese individuals indicating a probable association with obesity. However, association of microalbuminuria with interaction between obesity and central obesity has not yet been studied.

Design and Methods

A cross-sectional study was conducted in a 2889 general population aged ≥30 years. Obesity was defined as body mass index ≥28.0 kg/m² and central obesity was defined as waist-to-hip ratio ≥0.85 for females and ≥0.90 for males. Both additive and multipliable interactions between obesity and central obesity on elevated urinary albumin-to-creatinine ratio (UACR) were evaluated.

Results

After controlling for potential covariates, participants with both obesity and central obesity have significantly increased risk for elevated UACR (OR = 1.82 P<0.001) compared to those with neither. Additive interaction analysis indicated that about 43.9% of the risk of elevated UACR in participants with both obesity and central obesity was attributed to the interaction between obesity and central obesity (the attributable proportion because of the interaction: 0.439; 95% CI: 0.110–0.768). The multipliable interactive effect between obesity and central obesity on elevated UACR was not found significant (OR = 1.82, P = 0.078).

Conclusions

Microalbuminuria was significantly associated with the interaction between obesity and central obesity. Our results indicated that individuals with both obesity and central obesity should be intensively managed to prevent renal diseases.

Low-Grade Albuminuria Is Associated with Metabolic Syndrome and Its Components in Middle-Aged and Elderly Chinese Population

BACKGROUND

Micro-albuminuria has been well established as one of the risk factors of metabolic syndrome (MetS). However, the association of MetS and its components with low-grade albuminuria among those with normal urinary albumin excretion has not been clearly elucidated in Chinese population.

METHODOLOGY AND FINDINGS

A cross-sectional study was conducted among 9,579 participants with normal urinary albumin excretion, who were recruited from Jia Ding District, Shanghai, China. The single-void first morning urine sample was collected for urinary albumin and creatinine measurements, and urinary albumin-to-creatinine ratio (UACR) was calculated as urinary albumin divided by creatinine. Low-grade albuminuria was classified as sex-specific upper UACR quartile in this population. MetS was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria. The prevalence of MetS and its components increased across the UACR quartiles (all P trend <0.01). A multivariable adjusted logistic regression analysis revealed that the prevalence of MetS was gradually elevated according to the UACR quartiles (adjusted odds ratios [ORs] were 1.14, 1.24 and 1.59 for UACR quartiles 2, 3 and 4, compared with the lowest quartile; P trend<0.0001). In the further stratified logistic regression analyses, the associations between low-grade albuminuria and MetS were significant in both sex strata (male and female), both age strata (<60 and ≥60 years), both body mass index strata (<24 and ≥24 kg/m(2)), and both diabetes strata (yes and no). Compared to the lowest UACR quartile, the participants in the highest quartile of UACR had the highest prevalence of central obesity (OR = 1.43; 95%CI = 1.25-1.63), high blood pressure (OR = 1.64; 95%CI = 1.43-1.87), hyperglycemia (OR = 1.52; 95%CI = 1.30-1.78) and high triglycerides (OR = 1.19; 95%CI = 1.04-1.37).

CONCLUSIONS AND SIGNIFICANCE

Low-grade albuminuria was significantly associated with the increasing prevalence of MetS and its components in the middle-aged and elderly Chinese population with normal urinary albumin excretion.

Metabolic syndrome, C-reactive protein and microalbuminuria in a rural Chinese population: a cross-sectional study

Background

Microalbuminuria is an early marker of chronic kidney disease (CKD). Previous studies have shown that either metabolic syndrome (MetS) or chronic inflammation is related to renal impairment. The aim of this study was to investigate the association between MetS, C-reactive protein (CRP) and microalbuminuria in a rural Chinese population.

Methods

This was a cross-sectional study using data from the Handan Eye Study. MetS was defined according to the Chinese Diabetes Society (CDS) criteria. CRP levels ≥ 3 mg/L were classified as high CRP. Microalbuminuria was defined as a urinary albumin/creatinine ratio (ACR) of 30–300 mg/g.

Results

We included 4191 subjects aged ≥ 30 years in this analysis. The prevalence of MetS and microalbuminuria in the group was 25.7% and 15.6%, respectively. The odds ratio (OR) of microalbuminuria in subjects with MetS was 1.25 (95% confidence interval (CI): 1.03 − 1.51) compared with those without microalbuminuria. In multivariate logistic regression analysis, high blood pressure (OR 1.36, 95% CI: 1.10 − 1.67) and high fasting blood glucose (OR 1.44, 95% CI: 1.17 − 1.76) were independently associated with microalbuminuria. Subjects with high CRP and MetS had a 1.46-fold greater risk of having microalbuminuria compared with those with low CRP without MetS (95% CI: 1.06 − 2.01).

Conclusions

In this rural Chinese population aged ≥30 years, MetS and microalbuminuria were independently related and the combination of high CRP and MetS was associated with an increased risk of microalbuminuria.

Dietary salt intake is related to inflammation and albuminuria in primary hypertensive patients

BACKGROUND/OBJECTIVES

In this study, we hypothesized that dietary salt intake may be related with inflammation and albuminuria independently from blood pressure (BP) in non-diabetic hypertensive patients.

SUBJECTS/METHODS

A total of 224 patients with primary hypertension were included in the study. Serum C-reactive protein (CRP) levels, 24-h urine sodium and albumin excretion were measured in all patients. The subjects were divided into tertiles according to the level of 24-h urinary sodium excretion: low-salt-intake group (n = 76, mean urine sodium: 111.7 ± 29.1 mmol/24 h), medium-salt-intake group (n = 77, mean urine sodium: 166.1 ± 16.3 mmol/24 h) and high-salt-intake group (n = 71, mean urine sodium: 263.6 ± 68.3 mmol/24 h).

RESULTS

Systolic and diastolic BP measurements of patients were similar in the three salt-intake groups. CRP and urinary albumin levels were significantly higher in high-salt-intake group compared with medium- and low-salt-intake groups (P = 0.0003 and P = 0.001, respectively). CRP was positively correlated with 24-h urinary sodium excretion (r = 0.28, P = 0.0008) and albuminuria, whereas albuminuria was positively correlated with 24-h urinary sodium excretion (r = 0.21, P = 0.0002). Multiple regression analysis revealed that urinary sodium excretion was an independent predictor of both CRP and albuminuria.

CONCLUSIONS

These findings suggest that high salt intake is associated with enhanced inflammation and target organ damage reflected by increased albuminuria in treated hypertensive patients independent of any BP effect.

Inflammation and apoptosis in hypertension. Relevance of the extent of target organ damage

INTRODUCTION AND OBJECTIVES

To investigate the relationship between inflammatory and apoptotic parameters and the severity and extent of target organ damage in patients with essential hypertension.

METHODS

We studied 159 consecutive patients with treated essential hypertension. An exhaustive evaluation of damage to heart, kidney, and blood vessels was performed and plasma levels of inflammatory (interleukin 6 and soluble receptor of tumor necrosis factor-alpha type 2) and apoptotic markers (soluble receptor of tumor necrosis factor-alpha type 1 and soluble Fas receptor) were determined. Patients were categorized into four groups: a) no organ damage (33 patients); b) 1 organ damaged (52 patients); c) 2 organs damaged (44 patients), and d) 3 organs damaged (30 patients).

RESULTS

Serum levels of interleukin 6, soluble receptor of tumor necrosis factor-alpha type 1 and soluble receptor of tumor necrosis factor-alpha type 2 were higher in patients with target organ damage than in hypertensive patients without organ damage. Increasing levels of these molecules were progressively associated with an increase in the number of organs damaged, and the highest levels were observed in the group with damage to 3 organs (heart, kidney, and blood vessels). There were no differences in soluble Fas receptor levels between groups. Logistic regression analysis showed that age, smoking, diabetes mellitus, abdominal circumference, interleukin 6, and soluble receptor of tumor necrosis factor-alpha type 1 were independently related to the number of target organs damaged.

CONCLUSIONS

Extensive hypertensive disease with involvement of more target organs was associated with greater inflammatory and apoptotic activation in these hypertensive patients.

Relationship between inflammation and microalbuminuria in prehypertension

Inflammation is a pathogenic factor for target-organ damage (TOD) in hypertension. This study examined the relationship between inflammatory parameters and urinary albumin excretion (UAE) in prehypertension. A total of 65 prehypertensive subjects (blood pressure (BP) 120-139/80-89 mm Hg) and 26 healthy volunteers with BP <120/80 mm Hg were included. High-sensitivity C-reactive protein (hs-CRP), and serum and urinary tumor necrosis factor-α (TNF-α) were measured as inflammatory markers. Prehypertensive individuals had higher levels of inflammatory parameters and UAE than healthy subjects. Analyses carried out in prehypertensive participants showed that BP was similar between individuals with normoalbuminuria or microalbuminuria (MAB) (UAE between 30 and 299 mg per day). However, serum hs-CRP and urinary TNF-α excretion were higher in prehypertensives with MAB. Multiple regression analysis showed that systolic blood pressure (r=0.29, P<0.01), hs-CRP (r=0.20, P<0.001), and urinary TNF-α (r=0.69, P<0.001) were independently correlated with UAE (adjusted R(2)=0.73, P<0.001). Finally, logistic regression analysis performed in the prehypertensive group with the absence or presence of MAB as the dependent variable demonstrated that hs-CRP (3.92 (1.45-10.58), P=0.007) and urinary TNF-α (1.69 (1.20-2.37), P=0.002) were independent risk factors for the presence of MAB. Inflammatory parameters are significantly and independently associated with UAE in prehypertensive subjects, suggesting that inflammation may be a pathogenic factor for the early vascular or TOD in these individuals.

The metabolic syndrome in Africa: Current trends

Metabolic syndrome is a clustering of several cardiovascular risk factors. Contrary to earlier thoughts, metabolic syndrome is no longer rare in Africa. The prevalence is increasing, and it tends to increase with age. This increase in the prevalence of metabolic syndrome in the continent is thought to be due to departure from traditional African to western lifestyles. In Africa, it is not limited to adults but is also becoming common among the young ones. Obesity and dyslipidemia seem to be the most common occurring components. While obesity appears more common in females, hypertension tends to be more predominant in males. Insulin resistance has remained the key underlying pathophysiology. Though pharmacologic agents are available to treat the different components of the syndrome, prevention is still possible by reverting back to the traditional African way of life.

Status of end organs in newly detected rural essential hypertensives: a study from southern India

BACKGROUND

Hypertension is associated with end-organ damage (EOD). Since EOD is a risk factor for cardio- and cerebrovascular complications, it is a major requirement for these to be detected, prevented, and treated.

OBJECTIVE

The objectives of our study were to determine out the prevalence of EOD in newly detected rural essential hypertensives, identify the pattern of EOD involved, and also assess the interrelationship among them.

METHODS

A total of 147 consecutive patients with newly diagnosed essential hypertension and, attending the outpatient clinic, were included in this study based on a set of inclusion and exclusion criteria. Patients with comorbid illnesses were excluded from the investigation. The significance of a range of variables involved was evaluated using statistical software.

RESULTS

Amongst the cases, there were 79 males (M) and 68 females (F). Their mean and median ages were 55 (standard deviation (SD) = 9.90) and 54 years, respectively. Of these 86% (70 M and 56 F) had one or more EODs; an observation which was very close to statistically significant (P = .054). In our patients, microalbuminuria (35%), diastolic dysfunction (59%), increased left ventricular (LV) mass (68%) and retinopathy (69%) were particularly notable. Increased LV mass had a strong association with retinopathy, microalbuminuria, and diastolic dysfunction.

CONCLUSION

The presence of one or more EODs in newly detected hypertension indicates widespread vascular damage that carries a high risk for cardio- and cerebrovascular morbidity and mortality. Hence, there is an urgent requirement not only for complete evaluation but also to stimulate an increased awareness amongst physicians and the general public, regarding the control of blood pressure.

Renal resistive index and low-grade inflammation in patients with essential hypertension

In essential hypertension, increased renal resistive index (RRI) is associated to a reduction of renal function and microalbuminuria, and to renal tubulo-interstitial damage. A tubulo-interstitial inflammatory infiltration was found in experimental models of hypertension, and serum high-sensitive C-reactive protein (hsCRP) levels correlated with urinary markers of tubulo-interstitial damage in humans. We studied the relationship between RRI and serum hsCRP in hypertensives with preserved renal function, without microalbuminuria. We investigated hypertensive patients without diabetes, renal failure, microalbuminuria or major inflammatory disease. Serum levels of hsCRP were assayed. RRI was calculated by intrarenal Doppler ultrasound and considered pathologic when ≥0.70 or >95% of upper confidence limit expected for age decade. The renal volume-to-resistive index ratio (RV/RRI) was also calculated. We evaluated 85 patients (57±14 years, 61 males). Patients with pathologic RRI (n=21) were older and had significantly higher hsCRP levels (4.70±2.30 vs 2.93±2.09 mg l(-1), P<0.01) compared with patients with normal RRI, as well as patients with decreased RV/RRI (n=43). HsCRP was directly related with RRI (r=0.41, P<0.001) and inversely with RV/RRI (r=-0.35, P<0.001). HsCRP proved to be a significant predictor of both pathologic RRI and decreased RV/RRI, even after adjustment. In essential hypertension low-grade inflammation is associated with tubulo-interstitial damage evaluated by Doppler ultrasonography.

The progressive pathway of microalbuminuria: from early marker of renal damage to strong cardiovascular risk predictor

There is clear evidence that urinary albumin excretion levels, even below the cut-off values currently used to diagnose microalbuminuria, are associated with an increased risk of cardiovascular events. The relationships of microalbuminuria with a variety of risk factors, such as hypertension, diabetes and metabolic syndrome and with several indices of subclinical organ damage, may contribute, at least in part, to explain the enhanced cardiovascular risk conferred by microalbuminuria. Nonetheless, several studies showed that the association between microalbuminuria and cardiovascular disease remains when all these risk factors are taken into account in multivariate analyses. Therefore, the exact pathophysiological mechanisms explaining the association between microalbuminuria and cardiovascular risk remain incompletely understood. The simple search for microalbuminuria in hypertensive patients may enable the clinician to better assess absolute cardiovascular risk, and its identification may induce physicians to encourage patients to make healthy lifestyle changes and perhaps would prompt to more aggressive modification of standard cardiovascular risk factors.

Periodontal disease severity and urinary albumin excretion in middle-aged hypertensive patients

To address whether periodontal disease indexes are associated with urinary albumin-to-creatinine ratio (UACR) in conditions of high and low systemic inflammation as reflected by levels of high-sensitivity C-reactive protein (hs-CRP) in untreated hypertensive patients, we studied 242 hypertensive patients 51 ± 9 years old (24-hour systolic/diastolic blood pressure [BP] 132 ± 10/83 ± 8 mm Hg) with varying severity of periodontal disease evaluated by 3 periodontal disease indexes (PDIs) (i.e., mean clinical loss of attachment, maximum probe depth, and gingival bleeding index). Patients underwent BP measurements, echocardiography, and periodontal examination, and from fasting blood samples we assessed metabolic profile and hs-CRP. From 2 nonconsecutive overnight spot urine samples we evaluated UACR. With respect to median hs-CRP and UACR levels (1.67 mg/L and 10 mg/g, respectively), the total population was divided into patients with low-UACR/low-hs-CRP (n = 65), low-UACR/high-hs-CRP (n = 63), high-UACR/low-hs-CRP (n = 51), and high-UACR/high-hs-CRP (n = 63). PDIs differed among the 4 groups, and those with high UACR had significantly higher 24-hour systolic BP compared to those with low UACR. UACR was determined by all periodontal disease indexes, hs-CRP, and the interaction of each periodontal disease index with hs-CRP. In addition, mean clinical loss of attachment was the strongest determinant of the high-UACR/high-hs-CRP pattern among all studied periodontal disease indexes. In conclusion, in untreated middle-aged hypertensive patients, periodontal disease indexes and hs-CRP have a synergistic effect on UACR levels independently of the underlying hemodynamic load.

Urine albumin excretion, within normal range, reflects increasing prevalence of metabolic syndrome in patients with essential hypertension

Microalbuminuria is a prognostic marker of cardiovascular disease and is related to metabolic syndrome (MetS). For this purpose, the authors examined the relationship of low grade albuminuria to MetS, using 4 current definitions and a MetS score. They studied 6650 consecutive, nondiabetic, hypertensive patients with normal microalbumin excretion. MetS was defined by Adult Treatment Panel III, American Heart Association, World Heart Organization, International Diabetes Federation criteria, and MetS Gruppo Italiano per lo Studio della Streptochinasi nell'Infarcto Miocardico (GISSI) score. Urine microalbumin concentration was measured after a 24-hour urine collection by immunonephelometry. By all definitions, hypertensive patients with MetS had higher microalbumin levels. Significantly higher microalbumin levels were observed as the number of metabolic components rose. After adjustment for systolic blood pressure, the strength of this association was reduced to a nonsignificant level. Microalbumin levels, within normal range, are increased in patients with MetS, irrespective of the definition criteria.

Increased circulating CD31+/annexin V+ apoptotic microparticles and decreased circulating endothelial progenitor cell levels in hypertensive patients with microalbuminuria

OBJECTIVE

Microalbuminuria is associated with an increased risk for all-cause and cardiovascular mortality, but the pathophysiologic mechanism underlying the association between urinary albumin excretion and cardiovascular disease remains unclear. Here, we tested the hypothesis that enhanced endothelial apoptotic microparticles and decreased endothelial progenitor cell (EPC) levels might contribute to the pathophysiology of microalbuminuria or macroalbuminuria in cardiovascular disease.

METHODS

Flow cytometry was used to assess endothelial cell apoptosis and circulating EPC levels by quantification of circulating CD31/annexin V apoptotic microparticles and EPC markers (defined as KDRCD133, CD34CD133, CD34KDR) in peripheral blood.

RESULTS

In total, 125 patients with hypertension were enrolled in the study, of whom 80 patients (64%) were with normoalbuminuria (albumin excretion rate of <20 microg/min, overnight urine samples), 35 patients (28%) with microalbuminuria (an albumin excretion rate of 20-200 microg/min), and 10 patients (8%) with macroalbuminuria (an albumin excretion rate >200 microg/min). Compared to hypertensive patients with normoalbuminuria, patients with microalbuminuria or macroalbuminuria had significantly more diabetes (P = 0.005), higher systolic blood pressure (P = 0.018), and elevated serum creatinine levels (P < 0.001). Among the three groups, patients with microalbuminuria or macroalbuminuria had significantly increased CD31/annexin V apoptotic microparticles (1.8 +/- 2.2 versus 3.0 +/- 4.3 versus 5.2 +/- 6.2%, P = 0.044) and decreased circulating EPC numbers (P < 0.05). By multivariate analysis, CD31/annexin V apoptotic microparticle level was an independent predictor of urinary albumin excretion rate in hypertensive patients (P < 0.001). Microparticles isolated from hypertensive patients with microalbuminuria or macroalbuminuria attenuated EPC proliferation, migration, and increased H2O2 production, cellular senescence and apoptosis in comparison with those from hypertensive patients with normoalbuminuria.

CONCLUSION

These findings suggest that hypertensive patients with microalbuminuria or macroalbuminuria have increased endothelial apoptotic microparticles and decreased circulating EPC levels, which may contribute to atherosclerotic disease progression and enhanced cardiovascular risk in hypertensive patients with nephropathy.

Association of resistin with urinary albumin excretion in nondiabetic patients with essential hypertension

BACKGROUND

Evidence suggests that resistin, a recently described protein, is associated with subclinical atherosclerosis in different clinical settings. In this study, we investigated the relationship of increased resistin levels with urinary albumin excretion, expressed as the albumin-to-creatinine ratio (ACR), an established index of diffuse vascular damage, in hypertensives.

METHODS

Our population consisted of 132 untreated nondiabetic subjects with stage I-II essential hypertension (49 males, mean age = 54 years, mean office blood pressure (BP) = 159/100 mm Hg). In all patients, ACR was determined as the average of three nonconsecutive morning spot urine samples, and venous blood sampling was performed for estimation of resistin concentrations. The distribution of resistin was split by the median (4.63 ng/ml), and accordingly, subjects were stratified into those with high and low values.

RESULTS

Hypertensive patients with high (n = 66) compared to those with low resistin (n = 66) exhibited higher ACR values (21.8 + or - 15.3 vs. 10.3 + or - 3.8 mg/g, P < 0.01), even after adjustment for confounders. In the total population, resistin was associated with 24-h systolic BP (r = 0.244, P < 0.05), serum creatinine (r = 0.311, P = 0.007), and ACR (r = 0.499, P < 0.01). Multiple regression analysis revealed that age (b = 0.193, P = 0.02), body mass index (b = 0.237, P = 0.02), 24-h systolic BP (b = 0.338, P < 0.0001), 24-h heart rate (b = 0.169, P = 0.04), and resistin (b = 0.77, P < 0.01) were independently associated with ACR (R(2) = 0.471, P < 0.01).

CONCLUSIONS

Hypertensive subjects with augmented resistin levels exhibit higher albuminuria, independently of established risk factors. Moreover, the association of resistin with ACR suggests a link between resistin and microvascular disease in the early stages of essential hypertension.

ADMA, C-reactive protein, and albuminuria in untreated essential hypertension: a cross-sectional study

BACKGROUND

Asymmetric dimethylarginine (ADMA) and subclinical inflammation are associated with atherosclerosis progression, whereas microalbuminuria is an established index of hypertensive organ damage.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

In an outpatient hypertensive unit, 296 nondiabetic and untreated participants with hypertension were studied. Participants with atherosclerotic cardiovascular disease, severe valvulopathy, congestive heart failure, presence of neoplastic or other concurrent systemic disease, atrial fibrillation, serum creatinine level > 1.5 mg/dL in men and > 1.4 mg/dL in women, and urinary albumin excretion > 300 mg/24 h were excluded.

PREDICTORS

ADMA and high-sensitivity C-reactive protein (hs-CRP) levels.

OUTCOME VARIABLE

Albuminuria assessed using albumin-creatinine ratio (ACR).

MEASUREMENTS

Participants underwent ambulatory blood pressure monitoring, echocardiography, routine assessment of metabolic profile, ADMA, and hs-CRP, whereas ACR was determined as the mean of 3 values in nonconsecutive morning spot urine samples.

RESULTS

64 participants had an ACR of 30-300 mg/g. Stratification based on ADMA level showed that participants with hypertension in quartile [Q] 4 compared with those in Q3, Q2, and Q1 showed the highest ACRs (53.2 vs 31.2 vs 30.4 vs 16.7 mg/g; P < 0.008 for all). Moreover, stratification based on hs-CRP level showed that participants with hypertension in Q4 (69.8% had microalbuminuria) showed the highest ACRs (72.2 vs 25.6, 16.2, and 19.2 mg/g for Q3, Q2, and Q1, respectively; P < 0.008 for all). Stepwise regression analysis showed that age, 24-hour systolic blood pressure, hs-CRP level, ADMA level, and the interaction of hs-CRP with ADMA were independent predictors of ACR (R(2) = 0.674; P < 0.001).

LIMITATIONS

Cross-sectional study.

CONCLUSIONS

In patients with untreated essential hypertension, increased hs-CRP and ADMA levels are associated with microalbuminuria, suggesting the involvement of inflammation and endothelial dysfunction in vascular and kidney damage.

Clinical correlates of renal dysfunction in hypertensive patients without cardiovascular complications: the REDHY study

Our study was aimed to assess the clinical correlates of different degrees of renal dysfunction in a wide group of non-diabetic hypertensive patients, free from cardiovascular (CV) complications and known renal diseases, participating to the REDHY (REnal Dysfunction in HYpertension) study. A total of 1856 hypertensive subjects (mean age: 47+/-14 years), attending our hypertension centre, were evaluated. The glomerular filtration rate (GFR) was estimated by the simplified Modification of Diet in Renal Disease Study prediction equation. A 24-h urine sample was collected to determine albumin excretion rate (AER). Albuminuria was defined as an AER greater than 20 microg min(-1). We used the classification proposed by the US National Kidney Foundation's guidelines for chronic kidney disease (CKD) to define the stages of renal function impairment. In multiple logistic regression analysis, the probability of having stage 1 and stage 2 CKD was significantly higher in subjects with greater values of systolic blood pressure (SBP) and with larger waist circumference. SBP was also positively related to stage 3 CKD. Stage 3 and stages 4-5 CKD were inversely associated with waist circumference and directly associated with serum uric acid. Age was inversely related to stage 1 CKD and directly related to stage 3 CKD. The factors associated with milder forms of kidney dysfunction are, in part, different from those associated with more advanced stages of renal function impairment.

Protein and albumin-to-creatinine ratios in random urines accurately predict 24 h protein and albumin loss in patients with kidney disease

BACKGROUND

Random urine protein-to-creatinine (PCR) and albumin-to-creatinine (ACR) ratios have been proposed as alternatives to 24 h urine measurements to simplify sample collection and overcome errors. The aim of this study was to examine the ability of PCR and ACR to predict urinary 24 h protein and albumin loss, respectively, in patients with kidney disease, and determine the most appropriate time of collection.

METHODS

Eighty-three patients were recruited from a renal outpatient clinic. In a 24 h period, each collected an early-morning urine (EMU), second and third voids, and the remaining urine passed that day. PCR and ACR were determined in random urines and compared with the 24 h loss of protein and albumin, respectively.

RESULTS

For all patients, median (range) 24 h urine protein and albumin losses were 220 (30-15600) and 60 (<8-10,557) mg, respectively. Ratios derived from each of three random urines correlated well with 24 h protein or albumin loss (Spearman's r(s) > 0.87, P < 0.0001). Receiver operator characteristic (ROC) curve analysis showed PCR accurately predicted both an abnormal 24 h urine protein > or =150 mg/24 h (areas under curves [AUC] 0.90-0.92) and significant proteinuria above 300 mg/24 h (AUC between 0.97 and 1.00). ACR accurately predicted both an abnormal 24 h urine albumin > or =30 mg/24 h (AUC 0.98 to 0.99) and frank albuminuria at > or =300 mg/24 h or > or =700 mg/24 h (AUC between 0.99 and 1.00). EMU and random urines performed equally well in predicting proteinuria and albuminuria from PCR and ACR, respectively.

CONCLUSIONS

By careful choice of cut-offs, both PCR and ACR can be used in patients with kidney disease to rule in or rule out abnormal 24 h losses of protein and albumin. EMU and, importantly, random samples can be used as surrogates for 24 h urine collections.

Target organ damage in patients with rheumatoid arthritis: the role of blood pressure and heart rate

BACKGROUND

Rheumatoid arthritis (RA) is characterised by increased cardiovascular morbidity and mortality. Even though hypertension (HT) is highly prevalent in RA, the extent of target organ damage (TOD) caused by it remains unknown. Inflammation and sympathetic overdrive may also associate with TOD. We investigated the prevalence and associations of TOD in RA.

METHODS

In this cross-sectional, observational study, 251 RA patients with no overt cardiovascular or renal disease had extensive clinical and laboratory evaluations, including a 12-lead electrocardiogram and urine albumin:creatinine ratio. Pulse pressure (PP) was used as a proxy of arterial stiffness and heart rate (HR) of autonomic activity. TOD was defined as described in the European guidelines for the management of arterial hypertension. Binary logistic regression analysis was used to evaluate the independence of the variables that associated with the presence of TOD.

RESULTS

TOD prevalence was 23.5% (59/251). Of the 59 patients with TOD, 45.8% had suboptimally controlled HT, whereas 32.3% had undiagnosed HT. In univariable analysis, TOD was significantly associated with higher age (64.2+/-11.7 years vs. 58.0+/-12.4 years, p=0.001), HT prevalence (89.8% vs. 60.4%, p<0.001), systolic blood pressure (SBP) (150.3+/-18.8mmHg vs. 139.7+/-20.7mmHg, p=0.001), PP (70.6+/-16.6mmHg vs. 60.3+/-17.3mmHg, p<0.001), HR (77.1+/-15.4bpm vs. 72.2+/-12.2bpm, p<0.001), serum uric acid (320.6+/-88.8mumol/l vs. 285.0+/-74.9mumol/l, p=0.03) and type 2 diabetes mellitus prevalence (13.6% vs. 4.7%, p=0.019). Binary logistic regression analysis revealed that only hypertension indices and HR associated independently with TOD.

CONCLUSIONS

TOD is highly prevalent in patients with RA and associates independently with hypertension, arterial stiffness and heart rate. Further prospective studies are needed to confirm these findings and examine the role of beta-blockers in this particular population.

Albuminuria in children

PURPOSE OF REVIEW

Albuminuria is a marker of present and future cardiovascular and renal morbidity, and mortality, in adults. Because the roots of these diseases extend back into childhood, assessment of albuminuria has become relevant to child and adolescent clinical care.

RECENT FINDINGS

Normal levels of albumin excretion in children are well below the cut-off for microalbuminuria. In healthy children, albuminuria relates to fasting insulin, but not blood pressure, BMI, lipid levels, fasting glucose, or insulin resistance. In obese children, albuminuria relates to multiple measures of insulin resistance. In children with type 1 diabetes, hemoglobin A1c seems to be the most consistent clinical predictor of microalbuminuria although multiple mechanisms seem to be involved, including genetic polymorphisms. Children with type 2 diabetes and hypertension already exhibit microalbuminuria.

SUMMARY

When considering the population as a whole, children make ideal subjects in which to study the natural history of albuminuria given their relative lack of multiple morbidities commonly seen in adults. The unfortunate rise in 'adult' diseases in the pediatric age group makes this especially relevant. There is a need for longitudinal studies examining predictors of elevated urinary albumin levels as well as potential treatment strategies.

Relation of plasma midregional proatrial natriuretic peptide to target organ damage in adults with systemic hypertension

We tested the hypothesis that, in adults with essential hypertension, plasma levels of midregional proatrial natriuretic peptide (MR-proANP) are associated with target organ damage. MR-proANP is a newly described stable fragment of N-terminal proatrial natriuretic peptide. Participants included 1,919 adults with hypertension identified from the community (1,037 African-Americans, 65 +/- 9 years of age, 72% women; 882 non-Hispanic whites, 61 +/- 9 years of age, 55% women). We measured MR-proANP by an immunoluminometric assay. Measurements of target organ damage included the ankle-brachial index (ABI), urinary albumin-creatinine ratio (UACR), and left ventricular (LV) mass (available only in African-Americans). Generalized estimating equations were used to assess whether plasma MR-proANP was associated with measurements of target organ damage, independent of potential confounding variables. In African-Americans, higher MR-proANP was significantly associated with lower ABI (p <0.0001), higher UACR (p <0.0001), and greater LV mass (indexed to height to the power of 2.7, p <0.0001). After adjustment for age, gender, body mass index, systolic blood pressure, estimated glomerular filtration rate, smoking history, diabetes mellitus, total and high-density lipoprotein cholesterols, medication (blood pressure lowering, statin, and aspirin) use, and previous myocardial infarction or stroke, higher MR-proANP levels remained significantly associated with lower ABI (p = 0.01), higher UACR (p = 0.0007), and greater LV mass index (p <0.0001). In non-Hispanic whites, higher MR-proANP levels were significantly associated with lower ABI (p = 0.002) and greater UACR (p = 0.001), but not after adjustment for the covariates listed earlier. In conclusion, plasma MR-proANP may be a marker of target organ damage in the setting of hypertension, especially in African-Americans.

Lack of association between TGF-beta-1 genotypes and microalbuminuria in essential hypertensive men

BACKGROUND

Polymorphisms within the gene for transforming growth factor (TGF)-beta-1, a pro-fibrogenic cytokine pathophysiologically involved in hypertension and hypertensive target damage, might modulate the biological activity of the encoded protein. Through that mechanism, they might contribute to microalbuminuria, a marker of subclinical renal damage and a correlate of systemic inflammation and endothelial dysfunction in hypertension, a possibility never before tested. For this reason, we assessed the association of four TGF-beta-1 polymorphic variants (C-509T, Leu(10)-->Pro, Arg(25)-->Pro, Thr(263)-->Ile) with albuminuria in uncomplicated essential hypertensive men, using (circulating active + acid-activatable latent) TGF-beta-1 levels as an indirect index of their in vivo biological activity. Because of the close pathophysiological link of TGF-beta-1 with the renin-angiotensin system, we also tested the behaviour of the angiotensin converting enzyme (ACE) deletion/insertion (D/I) polymorphism.

METHODS

Albuminuria (three overnight collections), office and 24-h BP, left ventricular mass index (LVMI), BMI, renal function, glucose, lipids, plasma TGF-beta-1 (n = 162, ELISA) were measured in 222 genetically unrelated, never-treated, uncomplicated Caucasian hypertensive men. ACE D/I polymorphisms were analysed by the polymerase chain reaction technique or a 5' nuclease assay with further restriction analysis when required.

RESULTS

Urine albumin levels or microalbuminuria (albuminuria > or =15 microg/min) did not differ by TGF-beta-1 genotypes, but both parameters were more frequent in ACE D/D homozygotes. Plasma TGF-beta-1 was similar across genetic backgrounds and was unrelated to albuminuria. Cardiovascular, renal, metabolic parameters were homogeneously distributed across genotypes.

CONCLUSIONS

In contrast to its link with the ACE D/I genotype, microalbuminuria was independent of TGF-beta-1 polymorphism in this group of never-treated, uncomplicated essential hypertensive men.

Clinical Use and Pathogenetic Basis of Laboratory Tests for the Evaluation of Primary Arterial Hypertension

This review focuses on the laboratory biochemical tests that are useful in the diagnostic approach to the hypertensive patient. A "minimal" diagnostic laboratory work-up, including a small number of tests that are simple and relatively inexpensive, is first described. Because these tests provide basic information on the presence of major cardiovascular (CV) risk factors and target organ damage, and might give some clues to the presence of a secondary form of hypertension (HT), they should be performed on all patients presenting with HT. Other tests that are aimed at assessing the overall CV risk, a major determinant of prognosis that dictates the therapeutic strategy in the individual HT patient, are then discussed. They allow identification of major CV risk factors and associated clinical conditions which, if present, lead to a substantial change of therapeutic strategy. The role of C-reactive protein as a marker of atherosclerosis and its predictive value for CV events are also discussed. Finally, a section is devoted to tests that are currently confined to research purposes, such as markers of endothelial function including endothelin-1, homocysteine and genetic analysis.

Exercise blood pressure response, albuminuria, and arterial stiffness in hypertension

BACKGROUND

A hypertensive response to exercise is associated with high cardiovascular risk, whereas the data about its relation to surrogates of subclinical atherosclerosis are scarce. We investigated the relationships of a hypertensive response to exercise with urinary albumin excretion and arterial stiffness in hypertensives.

METHODS

There were 171 untreated males (mean age 52 years, all Caucasian) with stage I-II essential hypertension and a negative treadmill exercise test divided into those with a hypertensive response to exercise (n=48) (peak exercise systolic blood pressure > or =210 mm Hg) and to those with normal blood pressure response (n=123). Albumin-to-creatinine ratio values were determined as the mean of 3 nonconsecutive morning spot urine samples, and arterial stiffness was evaluated on the basis of carotid-to-femoral pulse wave velocity.

RESULTS

Patients with a hypertensive response to exercise compared with those with normal blood pressure response exhibited greater log albumin-to-creatinine ratio (1.52+/-0.59 vs 0.97+/-0.33 mg/g) and higher pulse wave velocity (8.7+/-1.6 vs 7.7+/-1.2 m/s), independent of potentially confounding demographic and clinical factors. Resting systolic blood pressure (odds ratio [OR] 1.11, 95% confidence interval [CI], 1.06-1.16), body mass index (OR 1.12, 95% CI, 1.02-1.23), resting heart rate (OR 0.96, 95% CI, 0.93-0.99), and albumin-to-creatinine ratio (OR 7.45, 95% CI, 2.54-21.83) were independently associated with a hypertensive response to exercise.

CONCLUSION

A hypertensive response to exercise is related to augmented albumin-to-creatinine ratio and arterial stiffness, reflecting accelerated subclinical atherosclerosis. The association of albumin excretion with exercise blood pressure response suggests that albuminuria constitutes an important factor in the interpretation of the hypertensive response to exercise-associated risk.

Cardiovascular biomarkers: increasing impact of laboratory medicine in cardiology practice

The practice of cardiology is in continual evolution, in parallel with the progress achieved by medical research in understanding the pathophysiology of cardiovascular disease and in developing new therapeutic procedures. Consequently, manufacturers of cardiac biomarkers are pressed with new demands to improve the performance of the existing and the development of novel ones. Several highly sensitive and/or specific assays for myocardial ischemic damage and myocardial function detection have already become commercially available. Moreover, an increasing number of novel risk factors have been added to the classical risk factors of cardiovascular disease. Finally, the recent surge of genetic analysis procedures will likely soon provide the clinical cardiologist with a number of laboratory tests for defining the molecular diagnosis, assessing new risk factors, and better targeting the pharmaceutical approaches in patients with cardiovascular disease. In this review, we first present the general characteristics of a biomarker followed by the analytical and clinical performance of assay methods.

Association of obstructive sleep apnea with urinary albumin excretion in essential hypertension: a cross-sectional study

BACKGROUND

Microalbuminuria reflects a state of widespread vascular dysfunction, whereas obstructive sleep apnea (OSA) further promotes atherosclerotic damage in hypertension.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

In an outpatient hypertensive unit, 62 untreated hypertensive patients (aged 48 +/- 7 years; office blood pressure [BP], 151 +/- 8/97 +/- 7 mm Hg) with OSA and 70 hypertensive patients without OSA (apnea hypopnea index [AHI] < or = 5) matched for age, sex, smoking status, body mass index, and 24-hour pulse pressure were studied.

PREDICTOR VARIABLE

Hypertension and OSA compared with hypertension without OSA. OSA defined as AHI greater than 5, documented by polysomnography.

OUTCOME VARIABLE

Albuminuria assessed by urinary albumin-creatinine ratio (ACR).

MEASUREMENTS

Participants underwent polysomnography, ambulatory BP monitoring, echocardiography, routine metabolic profile assessment, and glomerular filtration rate estimation, whereas ACR was measured from 2 nonconsecutive morning spot urine samples.

RESULTS

Hypertensive patients with OSA compared with those without OSA showed increased 24-hour diastolic BP (87 +/- 7 versus 85 +/- 7 mm Hg; P = 0.03) and nighttime pulse pressure (50 +/- 10 versus 45 +/- 10 mm Hg; P = 0.008), but did not differ regarding metabolic profile and estimated glomerular filtration rate. Albuminuria was greater by 57% in patients with OSA compared with those without OSA: log(10)ACR, 1.1 +/- 0.2 versus 0.7 +/- 0.4 mg/g; P < 0.001). In the entire study population, log10(ACR) correlated with log10(AHI) (r = 0.35; P < 0.001), minimum oxygen saturation during sleep (r = -0.33; P < 0.001), 24-hour pulse pressure (r = 0.38; P < 0.001), and nighttime pulse pressure (r = 0.21; P =0 .01). In a multivariable linear regression model, independent predictors of ACR were AHI (beta = 0.36; P < 0.001) and 24-hour pulse pressure (beta = 0.25; P = 0.01).

LIMITATIONS

Cross-sectional study.

CONCLUSIONS

Albuminuria increases within the normal range in hypertensive individuals with OSA compared with those without OSA proportionally to OSA severity independently of confounders. The association of upper-airway dysfunction with albuminuria and pulsatile hemodynamic load may provide an explanatory mechanism for the OSA-related risk in hypertension.

Importance of low-grade albuminuria

The well-described association between chronic kidney disease and cardiovascular disease is typically thought to originate from loss of renal function, as estimated by the glomerular filtration rate. However, recent data suggest that urinary albumin excretion has an important role in this association. Albuminuria is a marker of underlying vascular dysfunction and has been correlated with structural and functional integrity of the vasculature. Although the traditional upper limit of normal daily albumin excretion has been 30 mg/d, recent epidemiologic data suggest that levels in the general population are actually much lower. Further, within this range of low-grade albuminuria (LGA), increasing excretion rates are associated with increasing risk of cardiovascular disease. This association is independent of renal function, and in the earliest stages of chronic kidney disease, LGA seems to be a more important determinant than the glomerular filtration rate. This emerging association underscores the complexity of albumin excretion, in which subtle changes in albumin excretion reflect widespread vascular processes. Using the key words albuminuria, low-grade albuminuria, and microalbuminuria in a PubMed search of literature from January 1, 1995, to February 29, 2008, this review summarizes the most recent data on LGA and its association with cardiovascular and renal disease.

Microalbuminuria: risk factor and potential therapeutic target for stroke?

Microalbuminuria (MA), a microvascular irregularity of the blood-urine interface within kidney glomeruli, may reflect the renal sign of global endothelial dysfunction, and has been associated with an elevated risk of serious cardiovascular events including stroke. This relationship appears graded, with higher levels of MA being independently associated with a greater magnitude of vascular risk over time. Furthermore, the presence of MA appears to independently predict poorer clinical outcomes following acute stroke. Screening for MA is relatively easy and inexpensive and could be effective in identifying stroke patients at risk for unfavorable outcomes. Reduction of subclinical albuminuria in stroke patients could be a clinically relevant endpoint worthy of pursuit by pharmacological treatment since the antiproteinuric effects of several established therapies appear to parallel better cardiovascular prognosis including better stroke outcomes, among subjects at high vascular risk. This review depicts the compelling epidemiological and clinical evidence relating MA to stroke, and presents the rationale for conducting future studies to assess the role of MA as a potential therapeutic target in persons with, or at risk for stroke.

Albumin excretion rate in normal adolescents: relation to insulin resistance and cardiovascular risk factors and comparisons to type 1 diabetes mellitus patients

BACKGROUND AND OBJECTIVES

Although albumin excretion rates have been related to cardiovascular morbidity and mortality in both diabetic and nondiabetic adults, little is known about the relation between albuminuria and either cardiovascular risk factors or the insulin resistance syndrome in adolescents. A normal range for albumin excretion in adolescents was established, correlations between albumin excretion and cardiovascular risk factors were evaluated, and albumin excretion in normal adolescents was compared with that in type 1 diabetes mellitus adolescents.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Albumin excretion rate was measured in 368 normal and 175 diabetic adolescents. Multiple regression analysis was used to predict the relation of age, sex, Tanner stage, body mass index, and systolic blood pressure to albumin excretion in both cohorts. In addition, correlations between albumin excretion and age, blood pressure, body mass index, lipids, and measurements of insulin resistance were performed in the normal adolescents.

RESULTS

Mean albumin excretion was significantly lower in normal adolescents (4.0 microg/min) than in type 1 diabetic adolescents (5.0 microg/min). Albumin excretion increased with age in diabetics. Albumin excretion did not significantly correlate with any measure of cardiovascular risk or insulin resistance but did significantly correlate with fasting insulin.

CONCLUSIONS

Albumin excretion rate is not related to insulin resistance or traditional cardiovascular risk factors in adolescence but is related to fasting insulin. Diabetic adolescents have increased albumin excretion compared with normal adolescents.

Baseline albuminuria predicts the efficacy of blood pressure-lowering drugs in preventing cardiovascular events

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Albuminuria has been proven to be associated with cardiovascular morbidity and mortality. Such an association has been found not only in subjects with diabetes and hypertension, but also in the general population. It could therefore be expected that especially subjects with higher albuminuria levels may benefit from blood pressure-lowering agents to improve their cardiovascular outcome.

WHAT THIS STUDY ADDS

This study indicates that the efficacy of blood pressure-lowering agents to prevent cardiovascular events is dependent of the level of albuminuria before start of such treatment. The higher baseline albuminuria, the better the relative and absolute risk reduction for cardiovascular events with blood pressure-lowering drugs. The data also suggest a possible better cardiovascular protective effect of renin-angiotensin intervening agents compared with other blood pressure-lowering agents.

AIMS

Albuminuria has been proven to be associated with cardiovascular (CV) events in specific patient populations, but also in the general population. This study aimed to investigate whether the efficacy of blood pressure-lowering agents in preventing CV events depends on baseline urinary albumin excretion (UAE) and, if so, whether this holds true for blood pressure-lowering agents in general, or is limited to agents that interfere in the renin-angiotensin system.

METHODS

Data were used from a community-based cohort study and pharmacy dispensing records. Included were subjects with hypertension (systolic blood pressure >or=140 and/or diastolic blood pressure >or=90 mmHg), no cardiovascular disease history, and no previous use of blood pressure-lowering agents.

RESULTS

During study follow-up (7.1 +/- 1.6 years), 122 CV events were observed in 1185 subjects included. Start of blood pressure-lowering agents vs. non-use was associated with a difference in absolute CV event risk of 0.7%, 6% and 12.6% for all subjects, those with UAE >or= 15 mg day(-1) and >or=30 mg day(-1), respectively. Cox regression analysis showed that the relative risk for CV events after start of blood pressure-lowering agents was significantly dependent (P < 0.05) on baseline UAE; with hazard ratios of 0.87 [95% confidence interval (CI) 0.48, 1.60, P = NS], 0.58 (95% CI 0.36, 0.94, P < 0.05) and 0.37 (95% CI 0.20, 0.68, P < 0.05), for subjects with UAE < 15, >or=15 and >or=30 mg day(-1), respectively. Results adjusted for covariates were essentially similar. The use of angiotensin converting enzyme inhibitor/angiotensin-II receptor blocker (ACEi/ARB) treatment tended to be associated with a more favourable CV prognosis when compared with non-ACEi/ARB treatment (difference P = 0.06).

CONCLUSIONS

Our results suggest that the efficacy of blood pressure-lowering agents to prevent CV events is dependent on baseline albuminuria. The higher baseline albuminuria, the more absolute as well as relative risk reduction can be achieved. Our data suggest that this may especially be true for ACEi/ARBs. We caution that this is an observational study, and that these conclusions should therefore be regarded as hypothesis generating, rather than hypothesis testing.

Microalbuminuria screening in patients with hypertension: recommendations for clinical practice

INTRODUCTION

Correlations between renal and cardiovascular (CV) pathologies in advanced kidney or heart disease are well characterised, but less clearly defined in the early stages. Microalbuminuria, in addition to being an early sign of kidney damage, is often found in patients with essential hypertension, suggesting that it may reflect early vascular abnormalities.

EVIDENCE FROM LITERATURE

Studies have shown that even very low levels of microalbuminuria strongly correlate with CV risk: albumin excretion rates as low as 4.8 microg/min, well below the microalbuminuria thresholds stated in current clinical guidelines, are associated with increased risk of CV and cerebrovascular disease, independent of the presence of other risk factors. Increased microalbuminuria indicates endothelial dysfunction or developing atherosclerosis and predicts end-organ damage, major cardio or cerebrovascular events and death.

CLINICAL ASPECTS

Available tests for screening microalbuminuria are sensitive, reliable and accessible; current European and US guidelines advocate annual screening in patients with diabetes and wherever possible in non-diabetic patients with hypertension. Early identification of high-risk patients through detection of microalbuminuria allows selection of aggressive treatment to slow disease progression.

THERAPEUTIC IMPLICATIONS

Antihypertensive agents providing angiotensin II blockade are recommended for the treatment of hypertensive patients with microalbuminuria, regardless of diabetes and/or early or overt nephropathy. Treatment with angiotensin II receptor blockers provides effective reduction of microalbuminuria and blood pressure, and long-term prevention of CV events beyond blood pressure reduction. In addition, pharmacoeconomic studies have shown that these long-term benefits translate into a substantially reduced burden on healthcare resources.

ACE gene insertion/deletion polymorphism modulates capillary permeability in hypertension

A D/D (deletion/deletion) polymorphism within the ACE (angiotensin 1-converting enzyme) gene increases the risk of microalbuminuria, a predictor of atherosclerotic vascular disease, in essential hypertension. It is unknown, however, whether this genetic profile is accompanied by disturbed macromolecular permeability of systemic capillary endothelium, possibly in the context of generalized endothelial dysfunction. In the present study, the ACE gene polymorphism was determined by PCR in 79 never-treated uncomplicated hypertensive men and 16 normotensive men as controls. Evaluation variables were TERalb (transcapillary escape rate of albumin; the 1-h decline rate of intravenous (125)I-albumin, a measure of integrity of systemic capillary endothelium), albuminuria and forearm vasodilation to intra-arterial acetylcholine, an index of NO (nitric oxide)-mediated vasomotion, in addition to a series of sensitive parameters of albumin permeation (blood pressure, metabolic status and smoking habits). Analyses were done by comparing D/D homozygotes with grouped I/D (insertion/deletion) and I/I (insertion/insertion) subjects. TERalb was higher in D/D hypertensives, who had higher albuminuria, more frequent microalbuminuria and comparable forearm responsiveness to intra-arterial acetylcholine. Fasting glucose and insulin, insulin sensitivity, 24-h blood pressure, smoking habits and metabolic parameters did not differ between the two groups. TERalb and urine albumin values were positively associated in the hypertensive subjects. In conclusion, ACE D/D homozygosis, independently of several confounding factors, associates with higher TERalb in men with essential hypertension. This may reflect noxious genetic influences on systemic vascular permeability, a critical control mechanism for atherogenesis in the absence of grossly impaired NO-mediated arteriolar responsiveness. The parallel behaviour of TERalb and albuminuria suggests some shared genetically mediated determinant of renal and systemic microvascular abnormalities in hypertension.