Urinary albumin excretion in a population based sample of 1011 middle aged non-diabetic subjects. The Copenhagen City Heart Study Group

Prevalence of Microalbuminuria and Its Association with Subclinical Carotid Atherosclerosis in Middle Aged, Nondiabetic, Low to Moderate Cardiovascular Risk Individuals with or without Hypertension

Microalbuminuria is closely associated with the risk of cardiovascular disease and all-cause mortality in the general population. Less is known about its relationship with subclinical atherosclerosis. We aimed to assess the prevalence of microalbuminuria and its relationship with subclinical atherosclerosis in middle-aged, nondiabetic, apparently healthy individuals (N = 187; 40.1% men, 59.9% women; aged 35–55 years) as well as to evaluate its potential associations with established risk modifiers, especially with the presence of carotid plaque. Clinical and laboratory parameters, the estimated 10-year fatal cardiovascular risk (SCORE), as well as circulating, functional (flow mediated vasodilation, ankle-brachial index, augmentation index, and pulse wave velocity), and morphological markers (mean carotid intima–media thickness, and carotid plaque) of subclinical atherosclerosis were analysed in group with vs. without microalbuminuria. Microalbuminuria was present in 3.8% of individuals with SCORE risk 0.43 ± 0.79%. Functional markers predominated in both groups. Carotid intima–media thickness (mean ± SD) in both groups was in range: 0.5–0.55 ± 0.09–0.14 mm. Carotid plaque was more frequent in group with (14.3%) vs. without (4.4%) microalbuminuria. Microalbuminuria had no statistically significant effect on most markers of subclinical atherosclerosis, but the increasing value of microalbuminuria was significantly associated with the occurrence of carotid plaque (p = 0.035; OR = 1.035; 95% CI = 1.002–1.07). Additional multiple logistic regression analysis, where variables belonged to microalbuminuria, number of risk factors, and family history, finally showed only two variables: microalbuminuria (p = 0.034; OR = 1.04; 95%CI = 1.003–1.09) and the number of risk factors (p = 0.006; OR = 2.15; 95% CI = 1.24–3.73) with independent and significant impact on the occurrence of carotid plaque. Our results may indicate an association of microalbuminuria with the presence of carotid atherosclerotic plaque; in addition, microalbuminuria and the number of risk factors appear to be possible predictors of the carotid plaque occurrence. Monitoring microalbuminuria may improve the personalized cardiovascular risk assessment in nondiabetic, low-to-moderate cardiovascular risk individuals with or without hypertension.

Urinary albumin excretion in healthy adults: a cross sectional study of 24-hour versus timed overnight samples and impact of GFR and other personal characteristics

Background

Urinary albumin can be measured in 24 h or spot samples. The 24 h urinary albumin excretion rate is considered the gold standard, but is cumbersome to collect. Instead, often an overnight sample is collected, and adjusted for dilution. Proxies for 24 h excretion rate have been studied in diabetics, but seldom in healthy individuals. Our aims were to compare 24 h and overnight albumin excretion, to assess the impact of personal characteristics, and to examine correlations between the 24 h excretion rate and proxies such as the albumin to creatinine ratio (ACR).

Methods

Separate 24 h and overnight urine samples were collected from 152 healthy kidney donors. Urinary creatinine, specific gravity, collection time, and sample volume determined. Differences between 24 h and overnight samples were examined, and the effects of age, sex, smoking, body mass, glomerular filtration rate, and urinary flow rate were assessed.

Results

The 24 h albumin excretion rate and ACR were both significantly higher than their overnight counterparts. Unadjusted albumin was unsurprisingly higher in the more concentrated overnight samples, while concentrations adjusted for specific gravity were similar. In multivariate analysis, the 24 h excretion rate and proxies were positively associated with glomerular filtration rate, as was ACR in overnight samples. There were positive associations between urinary albumin and body mass.

Conclusions

Proxies for the 24 h albumin excretion rate showed relatively high correlations with this gold standard, but differences due to sampling period, adjustment method, and personal characteristics were large enough to be worth considering in studies of albumin excretion in healthy individuals.

Effective CKD care in European countries: challenges and opportunities for health policy

Chronic kidney disease (CKD) is an important global public health problem that is associated with adverse health outcomes and high health care costs. Effective and cost-effective treatments are available for slowing the progression of CKD and preventing its complications, including cardiovascular disease. Although wealthy nations have highly structured schemes in place to support the care of people with kidney failure, less consideration has been given to health systems and policy for the much larger population of people with non-dialysis-dependent CKD. Further, how to integrate such strategies with national and international initiatives for control of other chronic noncommunicable diseases (NCDs) merits attention. We synthesized the various approaches to CKD control across 17 European countries and present our findings according to the key domains suggested by the World Health Organization framework for NCD control. This report identifies opportunities to strengthen CKD-relevant health systems and explores potential mechanisms to capitalize on these opportunities. Across the 17 countries studied, we found a number of common barriers to the care of people with non-dialysis-dependent CKD: limited work force capacity, the nearly complete absence of mechanisms for disease surveillance, lack of a coordinated CKD care strategy, poor integration of CKD care with other NCD control initiatives, and low awareness of the significance of CKD. These common challenges faced by diverse health systems reflect the need for international cooperation to strengthen health systems and policies for CKD care.

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.

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.

Differential impacts of adiponectin on low-grade albuminuria between obese and nonobese persons without diabetes

The goal of this study was to examine the association between adiponectin and low-grade albuminuria in nondiabetic persons and whether it differed between obese and nonobese individuals. Urinary albumin excretion (UAE) was assessed by overnight collection in 157 participants. Overall, as anticipated, 24-hour systolic blood pressure and fasting glucose levels were independent determinants of UAE (beta=0.254 and 0.176, respectively, P<.05). In obese persons (body mass index [BMI] >/=25 kg/m(2); n=63), adiponectin value was a significant negative determinant of UAE (beta=-0.256, P<.05) independent of blood pressure and glucose levels, whereas in nonobese participants (n=94) it was not. In an analysis of BMI and the median value of adiponectin (9.9 microg/mL), UAE was found to be significantly higher in obese persons with low adiponectin levels than in obese persons with high adiponectin levels (9.20 vs 5.11 microg/min; P<.05), even after adjustment for age, sex, blood pressure level, and glucose level. There was an inverse association between adiponectin and low-grade albuminuria in obese nondiabetic persons.

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.

Lack of association between endothelial nitric oxide synthase gene polymorphisms, microalbuminuria and endothelial dysfunction in hypertensive men

BACKGROUND

The Glu298Asp, T786C and 4a/4b genetic polymorphisms within the endothelial nitric oxide synthase (e-NOS) gene may predispose to hypertension, ischaemic heart disease and renal damage, possibly by reducing the generation of nitric oxide (NO), a fundamental substance in renal and cardiovascular biology. That same mechanism may contribute to raise albuminuria, a correlate of endothelial dysfunction and a marker of early kidney damage and poor cardiovascular prognosis in patients with hypertension. To assess that hypothesis, we evaluated the association of albuminuria with eNOS genotypes and their interacting potential with the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism. We also tested their impact on systemic NO availability, as reflected by endothelial-mediated forearm vasodilatation.

METHODS

Albuminuria (three overnight collections), blood pressure, body mass index, renal function, glucose, lipids and prevalence of the metabolic syndrome were measured in 235 genetically unrelated, never-treated, uncomplicated white men with essential hypertension. Endothelial function was assessed in a patient subgroup (n = 94) by measuring plethysmographic forearm blood flow vasodilatation in response to intra-arterial acetylcholine with sodium nitroprusside as a control. Polymerase chain reaction or a 5' nuclease assay were used to characterize the eNOS and ACE I/D variants.

RESULTS

Albuminuria or microalbuminuria (albuminuria > or = 15 microg/min) showed no association with eNOS polymorphisms either per se or after accounting for the co-existing ACE I/D genetic configuration. Forearm responses to acetylcholine did not differ by eNOS polymorphisms. Cardiovascular, renal, metabolic parameters were homogeneously distributed across different genetic backgrounds.

CONCLUSION

eNOS polymorphisms apparently play no role in promoting hypertensive renal damage, and do not influence endothelial-mediated vasodilatation in never-treated men with essential hypertension.

Microalbuminuria and risk for cardiovascular disease: Analysis of potential mechanisms

Microalbuminuria is a strong and independent indicator of increased cardiovascular risk among individuals with and without diabetes. Therefore, microalbuminuria can be used for stratification of risk for cardiovascular disease. Once microalbuminuria is present, cardiovascular risk factor reduction should be more "aggressive." The nature of the link between microalbuminuria and cardiovascular risk, however, remains poorly understood. There is no strong evidence that microalbuminuria causes atherothrombosis or that atherothrombosis causes microalbuminuria. Many studies have tested the hypothesis that a common risk factor underlies the association between microalbuminuria and cardiovascular disease but, again, have found no strong evidence in favor of this contention. At present, the most likely possibility is that a common pathophysiologic process, such as endothelial dysfunction, chronic low-grade inflammation, or increased transvascular leakage of macromolecules, underlies the association between microalbuminuria and cardiovascular disease, but more and prospective studies of these hypotheses are needed.

α-Adducin and angiotensin-converting enzyme polymorphisms in hypertension: evidence for a joint influence on albuminuria

BACKGROUND

A single-nucleotide polymorphism (Gly460Trp) within the alpha-adducin gene (ADD1) may influence several renal phenotypes, including salt sensitivity, susceptibility to renal failure, the renal haemodynamics and confer a worse cardiovascular risks profile. However, its relationship with microalbuminuria, a marker of early renal and cardiovascular damage and an independent predictor of morbid events in hypertension, is unknown. For this reason, we related the ADD1 genetic polymorphism to urine albumin levels and other clinical variables in essential hypertensive men. The angiotensin-converting enzyme (ACE) insertion/deletion (ID) polymorphism was also evaluated because of its interactive potential with the ADD1 genotype.

METHODS

Albuminuria (three overnight collections), echocardiographic left ventricular mass index, blood pressure, body mass index, renal function, glucose and lipids were measured in 238 genetically unrelated, never treated, uncomplicated Caucasian essential hypertensive men. Polymerase chain reaction or a 5' nuclease assay were used to characterize the ACE ID and ADD1 Gly460Trp variants, respectively.

RESULTS

Microalbuminuria (albuminuria >or= 15 microg/min) was more frequent in patients with the ACE DD variant, but only in those with a ADD1 Gly460Gly background. In contrast, urine albumin did not differ by ACE ID genotype in the presence of mutated ADD1 Trp alleles. ADD1 polymorphisms per se were not associated with albuminuria. Cardiovascular, renal, metabolic parameters were homogeneously distributed among different genetic backgrounds.

CONCLUSIONS

ACE DD and ADD1 Gly460Gly polymorphisms may jointly influence albuminuria in hypertensive men, 460Gly homozygosis facilitating or, possibly, the 460Trp allele mitigating the noxious renal impact of the ACE DD genotype. The data highlight further the complex pathophysiological implications of microalbuminuria in hypertension.

Urinary albumin excretion is a predictor of response to treatment and disease progression in low-grade non-Hodgkin's lymphoma

Slightly increased urinary albumin excretion (UAE) is frequently found in patients with malignant diseases and is associated with adverse prognostic factors. In the present study, the main objective was to elucidate the role of UAE as predictor of response to treatment and time to progression in low-grade non-Hodgkin's lymphoma. We included 52 patients with newly diagnosed follicular lymphoma grade 1 and 2. Pre- and post-treatment median UAE level was 17.5 and 12.0 microg/min, respectively (P < 0.01). Significantly more patients with a pre-treatment UAE below the median level were in CR after treatment (P < 0.05). Patients with a clinical response to treatment had a significantly lower frequency of UAE above the median post-treatment level (P < 0.05). UAE at the time of progression increased to a significantly higher level compared with the post-treatment level (26.5 vs. 16.0 microg/min; P < 0.0001). Median response duration and progression-free survival were significantly longer in patients with a post-treatment UAE below the median level (P < 0.001 and P < 0.0001, respectively). In conclusion, we found elevated UAE to be a highly sensitive indicator of clinical behavior in newly diagnosed low-grade lymphoma. Both response to treatment and time to progression were predicted by levels of UAE. Further studies are needed to confirm the clinical implications of UAE in lymphoma patients.

Very Low Levels of Microalbuminuria Are Associated With Increased Risk of Coronary Heart Disease and Death Independently of Renal Function, Hypertension, and Diabetes

Background— The aim of this study was to assess the level of urinary albumin excretion (microalbuminuria), which is associated with increased risk of coronary heart disease and death, in the population. Microalbuminuria has been suggested as an atherosclerotic risk factor. However, the lower cutoff level of urinary albumin excretion is unknown. It is also unknown whether impaired renal function confounds the association.

Methods and Results— In the Third Copenhagen City Heart Study in 1992 to 1994, 2762 men and women 30 to 70 years of age underwent a detailed cardiovascular investigation program, including a timed overnight urine sample. The participants were then followed up prospectively by registers until 1999 with respect to coronary heart disease and until 2001 with respect to death. During follow-up, 109 incident cases of coronary heart disease and 276 deaths were traced. A urinary albumin excretion above the upper quartile, ie, 4.8 μg/min, was associated with increased risk of coronary heart disease (RR, 2.0; 95% CI, 1.4 to 3.0; P <0.001) and death (RR, 1.9; 95% CI, 1.5 to 2.4; P <0.001) independently of age, sex, renal creatinine clearance, diabetes mellitus, hypertension, and plasma lipids. Lower levels of urinary albumin excretion were not associated with increased risk.

Conclusions— Microalbuminuria, defined as urinary albumin excretion >4.8 μg/min (corresponding to ≈6.4 μg/min during daytime), is a strong and independent determinant of coronary heart disease and death. Our suggestion is to redefine microalbuminuria accordingly and perform intervention studies.

Microalbuminuria in diabetic and hypertensive patients and the general population--consequences of various diagnostic criteria--the Nord-Trøndelag Health Study (HUNT)

OBJECTIVE

The purpose of this paper was to study the prevalence of microalbuminuria (MA) in males and females of various ages by applying various diagnostic criteria. Three groups of subjects were studied: apparently healthy individuals; self-reported hypertensives; and diabetics.

MATERIAL AND METHODS

A total of 9255 individuals (age > or =20 years), all of whom were identified from the large (n = 65 258) population-based Nord-Trøndelag Health Study (HUNT) performed in Norway between 1995 and 1997, delivered three morning urine samples for MA analysis. Of these individuals, 651 reported both diabetes and treated hypertension, 944 diabetes only and 5547 treated hypertension only. The remaining 2113 subjects without diabetes or treated hypertension were randomly selected. The albumin:creatinine ratio (ACR) was used as an expression of urine albumin excretion.

RESULTS

Applying the classical definition of MA of ACR > or =2.5 mg/mmol in at least two out of three urine samples, the prevalence of MA in those with both diabetes and hypertension was 42.2% in males and 25.9% in females; corresponding values for those with diabetes only were 27.8% and 22.4%, for the hypertensives 19.3% and 11.5% and for the randomly selected sample 5.2% and 4.7%. The prevalence of MA increased strongly with increasing age for both genders in all subgroups. The prevalence of MA changed considerably when applying different cut-off values of ACR and at least one, two or three urine samples with ACRs above the cut-off value.

CONCLUSIONS

This study, one of the largest cross-sectional screening studies of MA ever performed, clearly illustrates the consequences of applying different diagnostic criteria. The optimal cut-off levels of MA for the prediction of cardiovascular disease still remain to be properly defined, and more follow-up studies are therefore needed.

Microalbuminuria, a parameter independent of metabolic influences in hypertensive men

OBJECTIVE

To evaluate the relationship of albuminuria and microalbuminuria (overnight urine albumin > or = 15 micro g/min) with insulin resistance and related metabolic abnormalities in patients with essential hypertension.

DESIGN

Cross-sectional evaluation of 271 (age range, 19-77 years) never-treated, non-diabetic, uncomplicated hypertensive men.

MAIN OUTCOME MEASURES

Triplicate overnight urine albumin determination and homeostasis model assessment (HOMA) of insulin resistance as a surrogate measure of insulin sensitivity. Additional parameters were fasting and post-load circulating glucose and insulin, lipids, body mass index, blood pressure and echocardiographic left ventricular mass.

RESULTS

HOMA, fasting and post-challenge glucose and insulin, percentages of glucose-intolerant patients, triglycerides and high-density lipoprotein cholesterol levels did not differ across ascending urine albumin quartiles. Body mass index, blood pressure and ventricular mass were significantly greater in the upper quartiles, and the prevalence of obesity fivefold more frequent in the top as compared with the bottom urine albumin fourth. The statistical trend was unchanged after adjustment for HOMA, while accounting for systolic blood pressure and left ventricular mass by co-variance analysis abolished it. Eighty-eight patients bearing the phenotypic traits of the metabolic syndrome and a striking degree of insulin resistance and hyperinsulinemia showed urine albumin rates and prevalence of microalbuminuria comparable with the 183 patients who were not affected by that syndrome.

CONCLUSIONS

Albuminuria is independent of insulin resistance and other phenotypic components of the metabolic syndrome in never-treated, non-diabetic essential hypertensive men. Microalbuminuria is more frequent in obese hypertensives but this association is explained by higher blood pressure more than insulin resistance.

Mediators of inflammation correlate with microalbuminuria in patients with non-Hodgkin's lymphoma

Recent studies have demonstrated a high frequency of minor glomerular leakage of albumin in cancer patients. Pathogenic mechanisms of increased urinary albumin excretion (UAE) in malignancies remain to be clarified. We have attempted to identify whether microalbuminuria in lymphoma patients is associated with inflammatory mediators and the acute-phase response. UAE, urinary excretion of beta2-microglobulin and IgG, and serum levels of interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha) and C-reactive protein (CRP) were determined in 113 patients with newly diagnosed non-Hodgkin's lymphoma. We demonstrated a high frequency of microalbuminuria (>or= 20 microg/min) and UAE correlated strongly with serum levels of CRP, IL-6 and TNF-alpha. UAE, CRP, IL-6 and TNF-alpha were significantly higher in patients with advanced disease stage, B symptoms and in high-risk patients according to the International Prognostic Index. Urinary excretion of beta2-microglobulin was unaffected in patients with increased UAE. However, UAE was significantly correlated with urinary excretion of IgG, suggesting an altered size selectivity of the glomerular filtration barrier. This is the first study that shows a direct correlation between microalbuminuria and proinflammatory cytokines in malignancies, indicating a pathogenic relationship between inflammation and glomerular leakage of albumin. Future efforts should focus on the pathophysiological cause-effect mechanisms and larger studies are needed to confirm the clinical significance of UAE.

Microalbuminuria, an integrated marker of cardiovascular risk in essential hypertension

This paper reviews the existing epidemiological and clinical evidence about the relationships of non-diabetic microalbuminuria with cardiovascular risk factors such as elevated blood pressure (BP), systolic particularly, cardiac hypertrophy, adverse metabolic status, smoking habits, elevated angiotensin II levels, endothelial dysfunction, acute and perhaps subclinical inflammation. Because of that unique property of reflecting the influence of so many clinically relevant parameters, microalbuminuria may legitimately be defined as an integrated marker of cardiovascular risk, an unique profile among the several prognostic predictors available to stratify risk in hypertensive patients. Recent cohort studies also showed associations with cardiovascular morbidity and mortality independently from conventional atherogenic factors. This behaviour, whose understanding still needs further elucidation, suggests to measure albuminuria and to screen patients at a higher absolute risk in whom preventive treatment is expected to be more beneficial than in those with a lower absolute risk.

Urinary albumin excretion and transcapillary escape rate of albumin in malignancies

Transcapillary escape rate of albumin was determined in 22 patients with different malignancies. In addition, urinary albumin excretion rate was measured in 24-h urine samples using a sensitive immunoassay. Increased urinary albumin excretion was defined as >/=20 microg/min according to conventional standards. Renal glomerular filtration and tubular function was estimated by 51Cr-EDTA plasma clearance and urinary beta 2-microglobulin, respectively. Median urinary albumin excretion rate was 15.0 microg/min (range 6-510 microg/min) and the frequency of increased urinary albumin excretion was 41%. This agrees with other studies showing increased albuminuria in several types of malignant diseases. Patients with advanced disease (tumour, node, metastasis (TNM) stage II-IV) had a significantly higher urinary albumin excretion rate than patients with localized disease (TNM stage I). Serum creatinine, glomerular filtration rate and urinary beta 2-microglobulin were all within normal limits. Median transcapillary escape rate of albumin was 5.5 %/h (range 2-8 %/h) and this level is comparable with values in healthy subjects. There was no significant difference in transcapillary escape rate between patients with elevated urinary albumin excretion and the normoalbuminuric group. Median value of the absolut outflux of albumin was 10.6 g/h with similar levels in patients with increased urinary albumin excretion and patients with normoalbuminuria. Our results indicate a high prevalence of minor glomerular dysfunction with a slightly elevated urinary albumin excretion in patients with malignancies. The normal endothelial function, as estimated by the transcapillary escape rate of albumin, suggests an overall unaffected capillary permeability and increased urinary albumin loss appears to be an isolated renal phenomenon in cancer patients.

Arterial hypertension, microalbuminuria, and risk of ischemic heart disease

Albumin excretion in urine is positively correlated with the presence of ischemic heart disease and atherosclerotic risk factors. We studied prospectively whether a slight increase of urinary albumin excretion, ie, microalbuminuria, adds to the increased risk of ischemic heart disease among hypertensive subjects. In 1983 and 1984, blood pressure, urinary albumin/creatinine concentration ratio, plasma total and HDL cholesterol levels, body mass index, and smoking status were obtained in a population-based sample of 2085 subjects, aged 30 to 60 years, who were free from ischemic heart disease, diabetes mellitus, and renal or urinary tract disease. Untreated arterial hypertension or borderline hypertension was present in 204 subjects, who were followed until 1993 by the National Hospital and Death Certificate Registers with respect to development of ischemic heart disease. During 1978 person-years, 18 (9%) of the hypertensive subjects developed ischemic heart disease. Microalbuminuria, defined as a urinary albumin/creatinine ratio above the upper decile (1.07 mg/mmol), was the strongest predictor of ischemic heart disease, with an unadjusted relative risk of 4.2 (95% CI 1.5 to 11.9, P=0.006) and a relative risk of 3.5 (95% CI 1.0 to 12.1, P=0.05) when adjusted for all other atherosclerotic risk factors, including age and gender. In conclusion, microalbuminuria confers a 4-fold increased risk of ischemic heart disease among hypertensive or borderline hypertensive subjects. Urinary albumin excretion should be measured regularly in a hypertension clinic, and a rigorous control of blood pressure and of other atherosclerotic risk factors is recommended in hypertensive patients with microalbuminuria.

Microalbuminuria and pulse pressure in hypertensive and atherosclerotic men

To identify the biological covariates of microalbuminuria (albuminuria >/=15 microg/min) in nondiabetic subjects, brachial blood pressure, echocardiographic left ventricular mass, and other cardiovascular and metabolic parameters were evaluated in 211 untreated males (38 normal controls, 109 uncomplicated stage 1 to 3 essential hypertensives, and 64 patients with clinically stable atherosclerotic peripheral vascular disease either with [n=44] or without [n=20] essential hypertension) with normal cardiac and renal function. Compared with normoalbuminuric subjects, microalbuminuric subjects (n=67) were characterized by higher systolic blood pressure, comparable diastolic blood pressure, and, therefore, wider pulse pressure. Greater prevalence of hypertension, peripheral vascular disease, left ventricular hypertrophy, and reduced HDL cholesterol values further distinguished microalbuminuric from normoalbuminuric subjects in univariate comparisons. The risk of microalbuminuria increased by ascending pulse pressure quintiles in age-corrected logistic regression models, in which pulse pressure was more predictive than systolic pressure and was independent of mean pressure. When microalbuminuric status was regressed against a series of dichotomous (vascular and active smoker status) and continuous (age, pulse and mean pressure, left ventricular mass index, and HDL and LDL cholesterol) variables, only pulse pressure, left ventricular mass index, and smoking status were independent predictors. The association of increased albuminuria with wider pulse pressure, a correlate of the pulsatile hemodynamic load and conduit vessel stiffness as well as an important cardiovascular risk factor, may explain why microalbuminuria predicts cardiovascular events in nondiabetic subjects. The independence from concomitant vascular disease also suggests that wider pulse pressure, rather than representing a simple marker for atherosclerotic disease, influences albuminuria directly.

Microalbuminuria and transcapillary albumin leakage in essential hypertension

Microalbuminuria (an increased urinary albumin excretion that is not detectable by the usual dipstick methods for macroproteinuria) predicts cardiovascular events in essential hypertensive patients. A possible reason for this behavior is that albumin leaks through exaggeratedly permeant glomeruli exposed to the damaging impact of subclinical atherogenesis. To evaluate this possibility, the transcapillary escape rate of albumin (TER(alb), the 1-hour decline rate of intravenous (125)I-albumin), a parameter that estimates the integrity of systemic capillary permeability, albuminuria, blood pressure, echocardiographic left ventricular mass, lipids, and body mass index were measured in 73 uncomplicated, glucose-tolerant men with essential hypertension and normal renal function; 53 were normoalbuminuric, and 20 were microalbuminuric. Twenty-one normotensive age-matched male subjects were the controls. TER(alb) was higher in hypertensives, a behavior explained in part by a positive correlation with blood pressure values, although body mass index, lipids, and left ventricular mass showed no association. Transcapillary albumin leakage values did not differ between normoalbuminuric and microalbuminuric patients and were unrelated to albuminuria. Blood pressure, particularly systolic, and cardiac mass were higher in microalbuminuric patients in whom albuminuria correlated with both cardiovascular variables and indicated the influence of the hemodynamic load on urinary albumin levels. Thus, TER(alb), a parameter influenced by the permeability surface area product for macromolecules and the filtration power across the vascular wall, is altered in essential hypertensives. However, this abnormality is dissociated from the amount of albuminuria, which is contrary to the hypothesis that a higher albumin excretion reflects a greater degree of systemic microvascular damage in essential hypertension.

Urinary albumin excretion. An independent predictor of ischemic heart disease

Cross-sectional studies suggest that an increased urinary albumin excretion rate is associated with cardiovascular disease, dyslipidemia, and hypertension. The purpose of this study was to analyze prospectively whether the urinary albumin-to -creatinine (A/C) ratio can independently predict ischemic heart disease (IHD) in a population-based cohort. In 1983, urinary albumin and creatinine levels were measured, along with the conventional atherosclerotic risk factors, in 2085 consecutive participants without IHD, renal disease, urinary tract infection, or diabetes mellitus. The participants were followed up until death, emigration, or December 31, 1993. IHD was defined as a hospital discharge diagnosis or cause of death including the diagnoses ICD-8 and 410 to 414. Seventy-nine individuals developed IHD during the 21 130 person-years of follow-up. They were characterized by a preponderance of males and higher age, body mass index, blood pressure, lipoproteins, and proportion of current smokers. Microalbuminuria was defined as an A/C ratio) >90 percentile (>0.65 mg/mmol). When adjusted for other risk factors, the relative risk of IHD associated with microalbuminuria was 2.3 (95% CI, 1.3 to 3.9, P=0.002), and the 10-year disease-free survival decreased from 97% to 91% (P<0.0001) when microalbuminuria was present. An interaction between microalbuminuria and smoking was observed, and the presence of microalbuminuria more than doubled the predictive effect of the conventional atherosclerotic risk factors for development of IHD. It is concluded that microalbuminuria is not only an independent predictor of IHD but also substantially increases the risk associated with other established risk factors.

Normal values of overnight albumin excretion rate in a sample of healthy Italian children and adolescents

The aim of this study was to define normal values of albumin excretion rate (AER) in young people. We measured overnight timed AER (tAER, microgram/min) by a double-antibody radioimmunoassay in 281 healthy Italian children and adolescents (160 M and 121 F), aged 7-19 years. The frequency distribution of tAER deviated from normality, therefore percentiles were used: median and 95th percentile were 2.3 and 6.9 micrograms/min respectively. Log transformed tAER was not related to age or pubertal stage. "Borderline" AER refers to AER higher than normal 95th percentile in non-diabetic subjects but lower than microalbuminuria threshold level. Incipient nephropathy, expressed as "borderline" AER, has been reported in adult IDDM patients, and can be reversed by improving metabolic control. Because incipient diabetic nephropathy may be present in young IDDM patients without microalbuminuria, screening for AER should be recommended for pediatric diabetic patients, also before puberty, in order to detect early renal damage and the "borderline" AER state.

Ambulatory blood pressure and urinary albumin excretion in clinically healthy subjects

A slightly elevated urinary albumin excretion rate (UAER) is a predictor of atherosclerotic cardiovascular disease. The mechanism is unknown, but moderate office blood pressure elevation has been demonstrated as part of a clustering of known atherosclerotic risk factors in subjects with elevated UAER. Because 24-hour ambulatory blood pressure is a superior predictor of hypertensive target organ involvement, we aimed to investigate blood pressure profile in clinically healthy subjects with elevated UAER. Ambulatory blood pressure monitoring was performed with a portable recorder in 27 subjects with an elevated UAER (>6.6 microg/min, overnight urine collection) and 46 normoalbuminuric control subjects. Mean+/-SD systolic and diastolic ambulatory blood pressures (24-hour) were significantly higher in subjects with elevated UAER than in normoalbuminuric controls (134+/-12 versus 128+/-11 mm Hg and 78+/-7 versus 75+/-6 mm Hg, P<0.05), as were systolic and diastolic blood pressure loads [median (range): 42% (6 to 94%) versus 23% (1 to 89%) and 20% (0 to 68%) versus 6% (0 to 62%), P<0.05]. The circadian variation of blood pressure was normal in subjects with elevated UAER. However, the increased urinary loss of albumin could not be solely related to the higher blood pressure. In conclusion, apparently healthy subjects with elevated UAER had slightly but significantly higher 24-hour systolic and diastolic blood pressure levels in addition to increased blood pressure loads but normal circadian variation. The demonstrated differences in blood pressure may offer a partial explanation for the association between elevated urinary albumin excretion and atherosclerotic cardiovascular risk.

Insulin sensitivity in clinically healthy individuals with microalbuminuria

In epidemiologic studies microalbuminuria is associated with increased atherosclerotic risk profile, morbidity, and mortality. In order to examine whether such association could be explained by impaired insulin sensitivity, 23 clinically healthy subjects with microalbuminuria (urinary albumin excretion rate (UAER) of 6.6 to 150 micrograms/min) and 24 age- and sex-matched controls with normoalbuminuria (UAER < or = 6.6 micrograms/min) underwent a 3 h hyperinsulinaemic euglycaemic clamp investigation using an intravenous insulin infusion rate on 2 mU/(kg body weight x min). Insulin sensitivity (whole body glucose disposal) was similar in the two groups ((mean (95% C.I.)) 351 (321-381) vs. 364 (339-388) mg/(m2 x min); P = 0.51). Among urinary albumin excretion rate, blood pressure, serum lipid concentrations, body mass index waist-hip ratio, fasting concentrations of serum insulin and blood glucose, tobacco and alcohol consumption, physical activity, and age and sex, fasting serum insulin concentration was the only variable independently associated with insulin sensitivity (r = -0.55; P = 0.0001). It is concluded that microalbuminuria is not associated with impaired insulin sensitivity in clinically healthy individuals. The effect of microalbuminuria as predictor of atherosclerotic vascular disease may be mediated through other factors.

Reduced glomerular size- and charge-selectivity in clinically healthy individuals with microalbuminuria

The pathophysiologic mechanism behind microalbuminuria, a potential atherosclerotic risk factor, was explored by measuring fractional clearances of four endogenous plasma proteins of different size and electric charge (albumin, beta 2-microglobulin, immunoglobulin G, and immunoglobulin G4). Twenty-eight clinically healthy individuals with microalbuminuria, defined as a urinary albumin excretion of 6.6-150 micrograms min-1, and 60 matched control subjects were studied. Fractional immunoglobulin G clearance was higher (geometric means (95% confidence intervals)) 3.0 (2.3-3.9) x 10(-6), n = 28, vs. 2.1 (1.8-2.4) x 10(-6), n = 60; P = 0.02), whereas the ratio immunoglobulin G clearance/immunoglobulin G4 clearance was lower (geometric means (95% confidence intervals)) 1.8 (1.4-2.2), n = 28, vs. 2.3 (2.0-2.5), n = 60; P = 0.03) in microalbuminuric than in normoalbuminuric individuals. Fractional beta 2-microglobulin clearance was similar in the two groups. Since total IgG and the IgG4 subclass are of similar size and configuration but electrically neutral and negative, respectively; these findings indicate that microalbuminuria is associated with decreased size- and charge-selectivity of the glomerular vessel wall. Hypothetically, such alterations may reflect generalized vascular abnormalities linking microalbuminuria to atherogenesis.

Aspects of haemostatic function in healthy subjects with microalbuminuria--a potential atherosclerotic risk factor

Microalbuminuria, i.e., slightly elevated urinary albumin excretion rate (UAER), notifies increased risk for atherosclerotic disease and may reflect an early generalized vascular abnormality in healthy subjects. This study was designed in order to examine whether such abnormality is associated with a shift of the haemostatic balance in prothrombotic direction. The following haemostatic factors were measured in two representative groups of clinically healthy subjects, 28 with microalbuminuria (UAER of 6.6-150 micrograms/min) and 60 age- and sex-matched controls with normoalbuminuria (UAER < 6.6 micrograms/min): Coagulation factors: blood platelet count and mean volume, plasma Factor VII antigen concentration and coagulant activity, and plasma concentrations of prothrombin fragment 1 + 2, thrombin-antithrombin III complexes, fibrinogen, and fibrinopeptide A; fibrinolytic and endothelial factors: plasma concentrations of tissue plasminogen activator antigen and plasminogen activator inhibitor type 1 antigen; and endothelial factor: plasma von Willebrand factor antigen concentration. The fibrinolytic and endothelial factors were measured both before and after 10 minutes of venous occlusion of the arm. None of the haemostatic factors were significantly altered in the microalbuminuric group. Plasma fibrinogen concentration tended to be elevated but not statistically significant ((mean (95% C.I.) 7.8 (7.2-8.3) vs. 7.2 (6.9-7.5) mumol/l; p < 0.1). Neither did any of the haemostatic factors correlate with UAER in regression analyses. It is concluded that the haemostatic balance is unaltered in healthy subjects with microalbuminuria. It is unlikely that a prothrombotic state is present as an intermedial factor early in a causal chain between microalbuminuria and atherosclerotic vascular disease.

Atherosclerotic risk factors are increased in clinically healthy subjects with microalbuminuria

Increased morbidity and mortality from atherosclerotic vascular disease were observed in subjects with slightly elevated urinary albumin excretion rate (UAER), known as microalbuminuria. Therefore, the association between microalbuminuria and established atherogenic risk factors was studied in clinically healthy subjects. All healthy 40-65 year-old participants with microalbuminuria, examined within the first 21 months of The Copenhagen City Heart Study, were invited, and 28 were studied. An age- and sex-matched group of 60 randomly chosen subjects with normoalbuminuria served as control. Microalbuminuria was defined as a UAER of 6.6-150 micrograms/min, and normoalbuminuria as a UAER < or = 6.6 micrograms/min. In the microalbuminuric group, systolic and diastolic blood pressures were both elevated (mean (95% C.I.) 128 (123-134) vs. 119 (116-122) mmHg; P = 0.005, and 75 (71-78) vs. 69 (67-71) mmHg; P = 0.008, respectively), and serum apolipoprotein (apo) A-1 concentration was lower (1.30 (1.20-1.37) vs. 1.42 (1.36-1.47) milligrams; P = 0.02) in comparison with the normoalbuminuric group. Furthermore, serum HDL-cholesterol concentration tended to be lower, whereas body weight, body mass index and fasting serum insulin concentration were slightly elevated in the microalbuminuric group but not statistically significant. It is concluded that microalbuminuria in clinically healthy subjects is associated with increased levels of atherogenic risk factors. This may contribute to the increased vascular morbidity and mortality observed in these individuals.