Renal protection by antihypertensive drugs: insights from microalbuminuria studies

Microvascular Dysfunction Is Associated With Worse Cognitive Performance

Microvascular dysfunction may be associated with worse cognitive performance. Most previous studies did not adjust for important confounders, evaluated only individual measures of microvascular dysfunction, and showed inconsistent results. We evaluated the association between a comprehensive set of measures of microvascular dysfunction and cognitive performance in the population-based Maastricht Study. We used cross-sectional data including 3011 participants (age 59.5±8.2; 48.9% women; 26.5% type 2 diabetes mellitus [oversampled by design]). Measures of microvascular dysfunction included magnetic resonance imaging features of cerebral small vessel disease, plasma biomarkers of microvascular dysfunction, albuminuria, flicker light-induced retinal arteriolar and venular dilation response and heat-induced skin hyperemia. These measures were summarized into a microvascular dysfunction composite score. Cognitive domains assessed were memory, processing speed, and executive function. A cognitive function score was calculated as the sum of the scores on these 3 cognitive domains. The microvascular dysfunction score was associated with a worse cognitive function score (standardized β, −0.087 [95% CI, −0.127 to −0.047]), independent of age, education level, sex, type 2 diabetes mellitus, smoking, alcohol use, hypertension, total/HDL (high-density lipoprotein) cholesterol ratio, triglycerides, lipid-modifying medication, prior cardiovascular disease, depression and plasma biomarkers of low-grade inflammation. The fully adjusted β-coefficient of the association between the microvascular dysfunction score and the cognitive function score was equivalent to 2 (range, 1–3) years of aging for each SD higher microvascular dysfunction score. The microvascular dysfunction score was associated with worse memory and processing speed but not with worse executive function. The present study shows that microvascular dysfunction is associated with worse cognitive performance.

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.

RAAS and stress markers in acute ischemic stroke: preliminary findings

OBJECTIVES

Angiotensin II type 1 receptor blockade has neuroprotective effects in animal stroke models, but no effects in clinical stroke trials. We evaluated cerebral and peripheral changes in the renin angiotensin aldosterone system (RAAS) and stress responses in acute ischemic stroke patients.

MATERIALS AND METHODS

Blood from a jugular and cubital vein was collected within 48 h of stroke onset, after 24 and 48 h, and renin, angiotensin I, angiotensin II, aldosterone, norepinephrine, epinephrine, and cortisol were measured. Post-stroke cubital vein samples were collected after 8 (4.7-10) months.

RESULTS

The acute systolic blood pressure was significantly increased, 148 (141-168) vs 140 (130-147) mmHg post-stroke. Angiotensin I, renin and aldosterone levels were significantly lower, angiotensin II was unchanged, and ACE activity was higher in the acute phase compared to post-stroke. No differences in RAAS were detected between jugular and cubital plasma levels. Jugular venous plasma levels of epinephrine and cortisol were elevated in the acute phase compared to cubital levels (P < 0.05).

CONCLUSION

Increased epinephrine and cortisol levels in the jugular vein blood may reflect a higher peripheral turnover. The observed changes in RAAS in the acute stroke phase are consistent with responses to increased blood pressure.

Correlation of 24-hour urinary protein quantification with spot urine protein:creatinine ratio in lupus nephritis

OBJECTIVES

Twenty-four hour urine collection has been the foundation for monitoring patients with lupus nephritis. However, the use of protein to creatinine ratios in spot urine samples is now widely used. We aimed to evaluate the validity of this method cross-sectionally and longitudinally.

METHODS

A cross-sectional retrospective study was conducted. Records of 486 lupus nephritis patients were searched for paired results of 24-h quantification of urinary protein and a random spot urine protein to creatinine ratio and were examined over a three-year period.

RESULTS AND CONCLUSIONS

Ninety-five lupus nephritis patients had paired results and were included in the final analysis, male/female 14/81, mean age 36.5 years. Over a three-year period there were a total of 137 samples from 95 patients. For the entire dataset, there was a significant correlation between protein:creatinine ratio and 24-h urine collection protein (mg), Spearman Rho correlation coefficient was 0.869, p < 0.0001 with (R (2 )= 0.504). There was also a strong correlation for longitudinal data, n = 14 at two-years Rho 0.910, p < 0.0001 with (R (2 )= 0.878), n = 8 at three-years Rho 0.909, p < 0.0001 and (R (2 )= 0.73). We have shown for the first time in a UK population of lupus nephritis patients, well trained in producing 24-h collection, that the spot protein:creatinine ratio correlates well with 24-h urinary total protein excretion. Having a simple, reliable, reproducible and cost-effective test such as the spot urine protein:creatinine ratio is therefore a valuable tool with which to monitor disease progression.

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.

Angiotensin Receptor Blockade in Acute Stroke. the Scandinavian Candesartan Acute Stroke Trial: Rationale, Methods and Design of a Multicentre, Randomised- and Placebo-Controlled Clinical Trial (NCT00120003)

Background

Elevated blood pressure following acute stroke is common, and yet early antihypertensive treatment is controversial. ACCESS suggested a beneficial effect of the angiotensin receptor blocker candesartan in the acute phase of stroke, but these findings need to be confirmed in new, large trials.

Aims and design

The Scandinavian Candesartan Acute Stroke Trial is an international randomised, placebo-controlled, double-blind trial of candesartan in acute stroke. We plan to recruit 2500 patients presenting within 30 h of stroke (ischaemic or haemorrhagic) and with systolic blood pressure ≥ 140 mmHg. The recruited patients are randomly assigned to candesartan or placebo for 7-days (doses increasing from 4 to 16mg once daily). Randomisation is performed centrally via a secure web interface. The follow-up period is 6-months. Patients are included from the following nine North-European countries: Norway, Sweden, Denmark, Belgium, Germany, Poland, Lithuania, Estonia and Finland.

Study outcomes

There are two co-primary effect variables:

Funding

The Scandinavian Candesartan Acute Stroke Trial receives basic funding from Norwegian health authorities. AstraZeneca supplies the trial drugs, and AstraZeneca and Takeda support the trial with limited, unrestricted grants.

Summary

The Scandinavian Candesartan Acute Stroke Trial is the first large trial of angiotensin receptor blockers in patients with elevated blood pressure and acute stroke, and aims to answer whether treatment with angiotensin receptor blockers is beneficial for this indication.

Antiproteinuric effects of antihypertensive agents in non-diabetic hypertensive population

Arterial hypertension and proteinuria are important factors associated with the progression of both diabetic and nondiabetic chronic kidney disease. The objective of the present study was to determine the influence of different antihypertensive drug groups on urinary albumin excretion (UAE) as related to blood pressure in non-diabetic population. Subjects (n=39) with chronic renal disease accompanied by mild to moderate hypertension and varying degrees of proteinuria were divided into 3 groups based on UAE values and placed on nonpharmacological and/or treatment with an antihypertensive drug regimen (consisting of one or more antihypertensive drugs [beta blocker, ACE inhibitor or calcium-channel blocker]) to achieve a target blood pressure ≤ 130/85 mmHg. Periodic UAE measurements were performed. A reduction was observed over time in most patients, however, it reached statistical significance only in the microalbuminuric group (P<0.01). Patients were further stratified into 5 groups depending on assigned therapy: 0, nonpharmacological treatment; 1-drug group 1; 12-drug groups 1 and 2; 13-drug groups 1 and 3; 123-all 3 drug groups (1-ACE inhibitors, 2-beta blockers, 3-calcium channel blockers). A statistically significant change in mean UAE values at the start and end of the study period in patients assigned to drug groups 12, 13, and 123 was achieved (P < 0.05). Also, there was a statistically significant difference in the average reduction of proteinuria under varying antihypertensive drug regimens (P < 0.05). In conclusion, in patients with hypertension, changes in UAE depend on initial UAE values and administered antihypertensive treatment. ACE inhibitors combined with calcium channel blockers resulted in a higher UAE reduction than other drug groups.

Development of microalbuminuria in essential hypertension

During the past few years, microalbuminuria has become a prognostic marker for cardiovascular and/or renal risk in diabetic and nondiabetic subjects. In essential hypertensives, an increased transglomerular passage of albumin may result from several mechanisms--hyperfiltration, glomerular basal membrane abnormalities, endothelial dysfunction, and nephrosclerosis. Cross-sectional studies have demonstrated that the main factors related to microalbuminuria are blood pressure (BP) values and hyperinsulinemia, as an expression of insulin resistance. Genetics, obesity, and smoking, however, have also been implicated as determinants of microalbuminuria in some of the studies. Follow-up studies support the role of BP values and subtle alterations in glucose metabolism, although contributing roles need to be assessed in further studies. It seems that the significance of microalbuminuria in essential hypertension is much broader than expected, and several factors may influence the presence of microalbuminuria. Thus, to reverse microalbuminuria, and to reduce urine albumin excretion and cardiovascular and renal risk, a strategy of multiple approaches may be needed. Whether or not the multiple approaches need to be implemented from the beginning or step by step in an individual approach should be established in the near future.

Antihypertensive treatment: should it be titrated to blood pressure reduction or to target organ damage regression?

PURPOSE OF REVIEW

The success of an antihypertensive treatment is difficult to estimate by the extent of blood pressure reduction alone. Above and beyond blood pressure values in an individual patient, it is necessary to monitor the impact of antihypertensive treatment on the development or regression of hypertension-induced early end-organ damage. The intermediate objectives or surrogate endpoints may provide additional valuable information about the level of success of a given therapy in a particular patient. Moreover, monitoring intermediate objectives may provide scientific evidence for delineating the best antihypertensive treatment.

RECENT FINDINGS

The importance of assessing left ventricular mass, microalbuminuria, carotid wall thickness and the development of new-onset diabetes during antihypertensive treatment has been stressed. Left ventricular hypertrophy during antihypertensive therapy is associated with a lower likelihood of cardiovascular morbidity and mortality, independent of blood pressure lowering and treatment modalities in people with essential hypertension. Likewise, a reduction in urinary albumin excretion seems to be followed by a reduction in cardiovascular morbidity and mortality. Risk implications of reducing carotid wall thickness or of developing new-onset diabetes have been more controversial, although it seems to be that both can have a desirable effect.

SUMMARY

The available findings support the necessity to monitor intermediate objectives, aside from blood pressure measurement, during the follow-up of hypertensives.

Use of protein:creatinine ratio measurements on random urine samples for prediction of significant proteinuria: a systematic review

BACKGROUND

Proteinuria is recognized as an independent risk factor for cardiovascular and renal disease and as a predictor of end organ damage. The reference test, a 24-h urine protein estimation, is known to be unreliable. A random urine protein:creatinine ratio has been shown to correlate with a 24-h estimation, but it is not clear whether it can be used to reliably predict the presence of significant proteinuria.

METHODS

We performed a systematic review of the literature on measurement of the protein:creatinine ratio on a random urine compared with the respective 24-h protein excretion. Likelihood ratios were used to determine the ability of a random urine protein:creatinine ratio to predict the presence or absence of proteinuria.

RESULTS

Data were extracted from 16 studies investigating proteinuria in several settings; patient groups studied were primarily those with preeclampsia or renal disease. Sensitivities and specificities for the tests ranged between 69% and 96% and 41% and 97%, respectively, whereas the positive and negative predictive values ranged between 46% and 95% and 45% and 98%, respectively. The positive likelihood ratios ranged between 1.8 and 16.5, and the negative likelihood ratios between 0.06 and 0.35. The cumulative negative likelihood ratio for 10 studies on proteinuria in preeclampsia was 0.14 (95% confidence interval, 0.09-0.24).

CONCLUSION

The protein:creatinine ratio on a random urine specimen provides evidence to "rule out" the presence of significant proteinuria as defined by a 24-h urine excretion measurement.

Long-Term Impact of Systolic Blood Pressure and Glycemia on the Development of Microalbuminuria in Essential Hypertension

The objective was to assess the temporal impact of factors related to the development of microalbuminuria during the follow-up of young adult normoalbuminurics with high-normal blood pressure or at stage 1 of essential hypertension. Prospective follow-up was conducted on 245 normoalbuminuric hypertensive subjects (mean age 40.9 years; 134 men; blood pressure 139.7/88.6 mm Hg; body mass index 28.5 kg/m2) never treated previously with antihypertensive drugs, with yearly urinary albumin excretion measurements, until the development of microalbuminuria. After enrollment, patients were placed on usual care including nonpharmacological treatment or with an antihypertensive drug regime to achieve a blood pressure of <135/85 mm Hg. Thirty subjects (12.2%) developed microalbuminuria after a mean follow-up of 29.9 months (range 12 to 144 months), 2.5 per 100 patients per year. Baseline urinary albumin excretion (hazard ratio, 1.07; P=0.006) and systolic blood pressure during the follow-up (hazard ratio, 1.03; P=0.008) were independent factors related to the follow-up urinary albumin excretion in a Cox proportional hazard model. A significant increase in the risk of developing microalbuminuria for urinary albumin excretion at baseline >15 mg per 24-hour systolic blood pressure >139 mm Hg and a positive trend in fasting glucose were observed in the univariate analyses. However, in the multivariate analysis, only the baseline urinary albumin excretion and the trend of fasting glucose were independently related to the risk of developing microalbuminuria. In mild hypertensives, the development of microalbuminuria was linked to insufficient blood pressure control and to a progressive increment of glucose values.

Reduced renal ClC-5 Cl− channel expression in spontaneously hypertensive rats with microalbuminuria

Mutations in a renal-specific Cl(-) channel, ClC-5, result in low-molecular-weight proteinuria. Herein we studied ClC-5 expression in the kidneys of spontaneously hypertensive rats (SHR) to identify possible causes of their increased urinary excretion of albumin. The amount of ClC-5 protein was significantly reduced in 3-month-old SHR as compared with normotensive Wistar/Kyoto (WKY) rats. The ClC-5 protein level was partially restored by short term administration of perindopril, an inhibitor of angiotensin-converting enzyme. Corresponding to the increase in ClC-5 expression, the albuminuria in SHR improved to the control level. These results implicate the ClC-5 Cl(-) channel reduction in the development of albuminuria in the early stage of essential hypertension.

Cerebrovascular protection and antihypertensive therapy

PURPOSE OF REVIEW

Our aim is to review the association between blood pressure and stroke and analyse data from randomized controlled trials involving diverse therapies, especially those regarding the renin-angiotensin system. In addition, an overview of stroke pathogenesis is given and its relationship with treatment action mechanisms reviewed.

RECENT FINDINGS

Stroke is a leading cause of death worldwide. In addition, many survivors of stroke suffer different degrees of disability. Because of the ageing of the global population, especially in regions of rapid economic growth, stroke will remain the second leading cause of death and in terms of disability it will be among the five most important causes in both developing and developed countries. High blood pressure is the most important risk factor for stroke, either ischemic or haemorrhagic, and established hypertension is the most prevalent modifiable risk factor. Data from controlled trials of blood-pressure-lowering treatment have demonstrated that treatment considerably lowers the risk of stroke within a few years of starting treatment. However, there exists controversy about the most efficient treatment regimen for primary and secondary prevention of stroke among the different blood-pressure-lowering treatments.

SUMMARY

Debate rages as to whether the benefits of treating high blood pressure are simply determined by the quality of blood-pressure control, or whether the choice of drug therapy adds or detracts from the expected benefits of blood-pressure reduction. The desirable future interventional comparative studies should consent to determine specific effects of drug classes on cardiovascular risk in the absence of the confounding effect of a relevant blood-pressure reduction that may counteract the potential blood-pressure-independent benefits of specific drug classes.

Microalbuminuria and oxidative stress in essential hypertension

OBJECTIVE

To assess the relationship between microalbuminuria and oxidative stress in mononuclear peripherals cells in essential hypertension.

METHODS

A total of 123 hypertensive patients in absence of antihypertensive treatment were included. A 24-h ambulatory blood pressure (BP) monitoring was performed using a Spacelabs 90207 monitor, and microalbuminuria was measured in 24-h urine collections. Oxidized/reduced glutathione ratio and the content of malondialdehide and damaged base 8-oxo-2'-deoxyguanosine in genomic and mitochondrial DNA were measured in peripheral mononuclear cells.

RESULTS

In the 29 (24%) microalbuminuric subjects, the amount of reduced glutathione was significantly lower and the ratio oxidized/reduced glutathione was significantly higher than in the normoalbuminuric subjects. In contrast, the simultaneous measurement of the levels of malondialdehide and 8-oxo-2'-deoxyguanosine from both genomic and mitochondrial DNA oxidation did not achieve statistical significance between the two groups. Subjects with the highest oxidized/reduced glutathione ratio tertile showed the highest urinary albumin excretion (UAE) (P = 0.04 for trend). In a stepwise multiple regression analysis, oxidized/reduced glutathione ratio was the main significant determinant of UAE accounting for the 9% of the variance when 24-h mean BP, age, sex, body mass index, glucose and total cholesterol were included in the model.

CONCLUSIONS

Oxidative stress seems to be a determinant of UAE independent of BP levels even in hypertensive subjects.

Polymorphisms of the angiotensinogen gene and the outcome of microalbuminuria in essential hypertension: a 3-year follow-up study

BACKGROUND

The objective of this study was to analyse the relationship of polymorphisms of the angiotensinogen (AGT) gene with the changes in microalbuminuria during 3 years of antihypertensive treatment in a group of young adults with essential hypertension.

METHODS

Essential hypertensives, less than 50 years old, never previously treated with antihypertensive drugs and in the absence of diabetes mellitus were included. After the initial evaluation, patients were treated using only nonpharmacological measures (n=23), only beta-blockers (n=26), only angiotensin-converting enzyme inhibitors (ACEi) (n=57) or a combination of treatments (n=25). The office blood pressure, biochemical profile and urinary albumin excretion (UAE) were measured at the beginning and then yearly. The polymorphism A-6G of the AGT gene located in the promoter region was analysed.

RESULTS

In total, 131 patients, 35 (27%) microalbuminurics, were included. Although no significant differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting glucose and UAE were observed among genotypes at the initial examination, during the 3 years of antihypertensive treatment the slope values for the DBP, fasting glucose and UAE differed significantly despite no differences in the distribution of treatments being present. The subjects carrying the AA-6 genotype had the largest DBP decrease, but the lowest UAE reduction and the highest slope of glucose. Out of 35 initially microalbuminuric patients, 24 became normoalbuminuric and the lowest reduction rates were observed in subjects who carried the allele A-6. No interaction between the type of treatment and genotype was observed on the changes in UAE, BP or glucose values. In the subset of 57 patients treated with ACEi, the changes in UAE, BP and glucose had the same trend as was observed in the total population.

CONCLUSIONS

Subjects carrying the AA genotype of the A-6G AGT gene polymorphism are resistant to a reduction of microalbuminuria. Whether this can be attributed to a predisposition to glucose metabolic disturbance or not needs to be confirmed in further studies.

The ACCESS Study: evaluation of Acute Candesartan Cilexetil Therapy in Stroke Survivors

BACKGROUND AND PURPOSE

The Acute Candesartan Cilexetil Therapy in Stroke Survivors (ACCESS) study was designed to assess the safety of modest blood pressure reduction by candesartan cilexetil in the early treatment of stroke. The study was also designed to provide an estimate of the number of cases required to perform a larger phase III efficacy study.

METHODS

Five hundred patients were recruited in a prospective, double-blind, placebo-controlled, randomized, multicenter phase II study.

RESULTS

This safety trial was stopped prematurely when 342 patients (339 valid) had been randomized because of an imbalance in end points. Demographic data, cardiovascular risk factors, and blood pressure on admission, on study onset, and within the whole study period were not significantly different between the 2 groups. However, the cumulative 12-month mortality and the number of vascular events differed significantly in favor of the candesartan cilexetil group (odds ratio, 0.475; 95% CI, 0.252 to 0.895). There were no significant differences in concomitant medication and in number or type of side effects.

CONCLUSIONS

Although the mechanisms by which angiotensin type 1 (AT1) receptor blockade affects cardiovascular morbidity and mortality are still unresolved, the present study shows that early neurohumoral inhibition has similar beneficial effects in cerebral and in myocardial ischemia. The fact that no cardiovascular or cerebrovascular event occurred as a result of hypotension is of significant clinical importance. When there is need for or no contraindication against early antihypertensive therapy, candesartan cilexetil is a safe therapeutic option according to the ACCESS results.

Microalbuminuria in hypertension

A body of evidence indicates that microalbuminuria is a well-recognized marker of cardiovascular complications and increased cardiovascular risk in hypertension. However, the prognostic significance of microalbuminuria remains controversial because only the results of a few prospective studies performed in small groups of hypertensive subjects without diabetes mellitus are available. Several factors can affect the prevalence of microalbuminuria in hypertension including age, sex, race, severity of the disease, and concomitant risk factors. This accounts for the large differences in the prevalence of microalbuminuria that can be found in the literature, with prevalence rates going from a low of 4.7% to a high of 46%. The main determinant of albumin excretion rate in subjects with mild hypertension and no cardiovascular complications seems to be the hemodynamic load, whereas in subjects with more severe hypertension and associated target organ damage, the augmented urinary albumin leak is probably the consequence of glomerular damage. Inhibition of the renin-angiotensin system with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists is particularly effective at reducing the albumin excretion rate, but whether these classes of drugs are more beneficial in patients with microalbuminuria remains to be determined. There is general consensus that evaluation of microalbuminuria is useful for the assessment of overall cardiovascular risk in hypertension, since albumin excretion rate appears to be a cost-effective way to identify patients at higher risk for whom additional preventive and therapeutic measures are advisable.

Drug-induced renal function impairment: a population-based survey

PURPOSE

The knowledge that drugs can affect renal function is mainly based on experimental studies or case reports. Thus, it has only been investigated in selected populations. Here we describe drug groups associated with altered renal function in the general population.

METHODS

To study this, we used baseline data of 8592 subjects of a population-based cohort. Hyper- and hypofiltration were defined as a filtration above or below the 90% confidence interval of age-and-sex-corrected creatinine clearance. Drug use was measured in the year preceding the kidney function measurement.

RESULTS

The prevalence of hyperfiltration (4.6% in the general population) was higher among subjects using anti-diabetics (11.7%), dermatological corticosteroids (5.9%) and sex hormones (5.8%), but lower in subjects using anti-thrombotics (2.4%) and diuretics (2.1%). Hypofiltration (4.3% in the general population) was seen more often in users of beta blockers (6.2%), ACE inhibitors (7.1%), statins (7.2%), anti-thrombitics (6.8%), trimethoprim (7.9%), vaccines (9.4%), NSAIDs (5.2%), anti-ulcer agents (6.3%), laxatives (7.7%) and eyedrops (6.7%).

CONCLUSIONS

Several drug groups found in this overview were to be expected, since patients with kidney disease often use them (e.g. cardiovascular drugs). Several other drug groups were somewhat unexpected and deserve further attention.

Factors related to the occurrence of microalbuminuria during antihypertensive treatment in essential hypertension

The objective of the study was to assess the factors related to the occurrence of microalbuminuria during the follow-up of a young adult group with essential hypertension that had not been previously treated. Normo-albuminuric essential hypertensives, <50 years old, who had not been previously treated with antihypertensive drugs and who did not have diabetes mellitus were included. After the initial evaluation, patients were treated using only nonpharmacological measures (n=62), beta-blockers (n=38), ACE inhibitors (n=64), calcium channel blockers (n=8), and several classes (n=15). Measurements were taken for office blood pressure, biochemical profile, and 24-hour urinary albumin excretion at the beginning of the study and were measured yearly during an average of 2.7+/-1.2 years of follow-up. Among the 187 patients included, 22 (11,7%) developed microalbuminuria (progressors, 4.4/100 patients/y). No differences were present between progressors and those who remained normo-albuminuric (nonprogressors) in terms of age, gender, body mass index, disease duration, blood pressure values, biochemical profile, familial history of diabetes or hypertension, smoking habits, or the presence of EKG left ventricular hypertrophy. The group with the lowest progression rate was the patients treated with ACE inhibitors (n=5; 2.9/100 patients/y), followed by the diet group (n=5; 3.3/100 patients/y) and the beta-blockers group (n=5; 4.1/100 patients/y). When we excluded patients treated with calcium channel blockers or those who changed over time between different classes of treatment, no significant differences in the incidence of microalbuminuria were observed among the groups. Progressors showed higher slopes of fasting glucose (4.78+/-11.4 versus 0.50+/-6.8 mg/y, P<0.02) and uric acid (0.58+/-0.93 versus 0.05+/-1.10 mg/y, P<0.03) compared with the slopes of nonprogressors. Both the slopes for glucose and systolic blood pressure over time were associated independently with the slope of the logarithm of urinary albumin excretion when adjusted for age, gender, and treatment groups. Cox proportional hazard model for progression of microalbuminuria showed that baseline urinary albumin excretion (risk ratio [RR]=1.06; confidence interval [CI] 95%, 1.01 to 1.11), slope for systolic blood pressure (RR=1.11; CI 95%, 1.03 to 1.20), and slope for glucose (RR=1.08; CI 95%, 1.03 to 1.14) were independently associated to the development of microalbuminuria. In conclusion, in a group of young adults with essential hypertension that had not been previously treated, the main factors influencing the occurrence of microalbuminuria during antihypertensive treatment were the values of microalbuminuria at baseline and the slopes for systolic blood pressure and fasting glucose.

Microalbuminuria in essential hypertension

Microalbuminuria (urinary albumin excretion equal to 30-300 mg/24 h) is a reliable indicator of premature cardiovascular mortality in diabetic patients and in the general population. In insulin-dependent and non-insulin-dependent diabetes mellitus microalbuminuria is a marker of initial diabetic nephropathy and predicts the evolution toward renal insufficiency. In essential hypertension the clinical and prognostic role of microalbuminuria is more controversial. While it is a recognised marker of cardiovascular complications and a reliable predictor of ischaemic heart disease, its prognostic value on the risk of progressive renal alterations is still uncertain because no prospective studies, taking microalbuminuria as a selection criterion and renal insufficiency as an end point, are available. Blood pressure control with antihypertensive drugs is accompanied by a reduction in urinary albumin excretion. The favourable effects of antihypertensive agents on microalbuminuria appear to be proportional to blood pressure reduction, but angiotensin-converting enzyme inhibitors and angiotensin-II-receptor antagonists show an additional beneficial effect on urinary albumin excretion. Whether the reduction of microalbuminuria obtained through pharmacological intervention has favourable prognostic implications remain to be demonstrated. However, screening for microalbuminuria is a relatively easy and inexpensive procedure and reveals a potentially treatable abnormality. Thus, considering that microalbuminuria identifies hypertensive subjects at higher risk than standard, urinary albumin excretion should be routinely measured in hypertensive patients and, in the presence of microalbuminuria, antihypertensive treatment should be intensified in order to obtain an optimal blood pressure control.

The impact of antihypertensive drug groups on urinary albumin excretion in a non-diabetic population

AIMS

Microalbuminuria (30-300 mg 24 h-1) is recognized to be independently associated with renal and cardiovascular risk. Antihypertensives may lower microalbuminuria. We questioned whether the use of different antihypertensive drug classes in general practice influences microalbuminuria as related to blood pressure in nondiabetic subjects.

METHODS

To study this, we used the data from 6836 subjects of an on-going population based study, focused on the meaning of microalbuminuria (PREVEND). Odds ratios, adjusted for age, sex, blood pressure, cholesterol level, smoking and the use of other antihypertensive or cardiovascular drugs, were calculated to determine the association of drug groups with microalbuminuria. Influence of antihypertensives on the relation between blood pressure and (log) urinary albumin excretion was determined by comparing linear regression lines.

RESULTS

Microalbuminuria was significantly associated with the use of dihydropyridine calcium channel blockers (odds ratio: 1.76 [1.22-2.54]), but not with other antihypertensive drug groups. The linear regression line of the relation between blood pressure and (log) urinary albumin excretion was significantly steeper (P = 0.0047) for users of calcium channel blockers, but not for other antihypertensives, compared with subjects using no antihypertensive. Users of a combination of renin-angiotensin system inhibitors and diuretics however, had a less steep regression line (P = 0.037).

CONCLUSIONS

This study suggests a disadvantageous effect of dihydropyridine calcium channel blockers on microalbuminuria compared with other antihypertensive drug groups. Thus, if microalbuminuria is causally related to an increased risk for cardiovascular morbidity and mortality, dihydropyridines do not seem to be agents of choice to lower blood pressure. Furthermore, the combination of renin-angiotensin system inhibition and diuretics seems to act synergistically.

Urinary excretion of type IV collagen as a specific indicator of the progression of diabetic nephropathy

AIMS AND METHODS

This study was carried out to clarify whether the urinary excretion of type IV collagen (u-IV collagen) detected by specific radioimmunoassay, can be used as an indicator for the progression of diabetic nephropathy.

RESULTS

u-IV collagen was higher in diabetic subjects with microalbuminuria and overt proteinuria than those with normoalbuminuria, IgA nephropathy, membranoproliferative glomerulonephritis, membranous nephropathy, or control normal subjects. u-IV collagen was positively correlated with serum and urinary beta(2)-microglobulin and negatively with creatinine clearance only in diabetic patients, but not in patients with other glomerular diseases. The serum type IV collagen was not different between all the groups, and not correlated with its urinary excretion. In the advanced diabetic nephropathy, immunoreactive type IV collagen was detected in glomerular basement membrane (GBM), tubular basement membrane and Bowman's capsule much more than that in the normal kidney.

CONCLUSION

These findings indicated increased production and degeneration of type IV collagen in diabetic nephropathy. It is suggested that augmented turnover of type IV collagen in GBM and tubular basement membrane results in increased concentrations of free u-IV collagen. Therefore, measurement of u-IV collagen may be a useful, specific indicator of the progression of diabetic nephropathy.

Effect of antihypertensive therapy on renal injury in type 2 diabetic rats with hypertension

In a previous study, we demonstrated that doxazosin (DZN), an alpha(1)-adrenergic blocker, prevented proteinuria in streptozotocin diabetic rats. In this study, we investigated whether DZN would lower established proteinuria by improving glomerular sclerosis in spontaneously hypertensive corpulent rats with type 2 diabetes mellitus. DZN treatment was compared with treatment with angiotensin-converting enzyme inhibitor, lisinopril (LIS) alone, and DZN in combination with LIS. Combination therapy was used to examine any additive effect of either drug alone in the reduction of proteinuria and glomerular sclerosis. Both male and female rats age 6 months with established proteinuria were used. The rats were allocated randomly to 1 of 4 groups: untreated, DZN treated, LIS treated, or a combination of DZN and LIS treatment. Drug treatment was continued for 16 weeks. The results show that (1) either drug alone or in combination significantly lowered systolic blood pressure; (2) DZN, LIS, or combination therapy reduced albuminuria at 16 weeks of treatment from baseline by 38.61+/-5.77%, 30.70+/-4. 21%, and 42.17+/-4.77% (mean+/-SE), respectively. No difference in albuminuria was observed among the 3 groups of rats; (3) the fractional mesangial area, which was 20.55+/-3.77% in untreated rats, was significantly reduced to 11.18+/-1.32% in DZN-treated rats, with a further reduction to 8.72+/-0.64% in LIS-treated rats and to 3.48+/-0.35% in rats treated with DZN+LIS; and (4) DZN but not LIS significantly improved plasma glucose levels in spontaneously hypertensive corpulent rats (untreated 21.06+/-0.97 mmol/L versus DZN treated 15.81+/-0.93 mmol/L or DZN+LIS treated 17.38+/-1.10 mmol/L; P<0.025 to 0.005). Thus, the data suggest that 16-week treatment with either DZN or LIS improves established proteinuria and glomerular sclerosis, but combination therapy is superior to either DZN or LIS alone in preventing glomerular sclerosis in type 2 diabetic rats with hypertension.

Clinical value of microalbuminuria in hypertension

Microalbuminuria (MA) is a well recognized marker of cardiovascular complications in hypertension, but whether MA can predict adverse outcome in this clinical condition is still a subject for debate. The fact that in hypertensive cohorts those patients who showed an increase in albumin excretion rate also manifested an increased incidence of morbid events indicates that the presence of MA in hypertension may carry an increased cardiovascular risk. However, the prognostic significance of MA remains controversial because no results of prospective studies performed in hypertensive subjects without diabetes mellitus are available. Several factors can affect the prevalence of MA in hypertension, including severity of the disease, selection procedures, concomitant risk factors, degree of obesity, age, and sex distribution. This accounts for the large differences in the prevalence of MA that can be found in the literature, with prevalence rates going from a low of 4.7% to a high of 40%. There is still conflict over whether MA in hypertension is due to increased intraglomerular pressure or to glomerular damage. The data from the literature suggest that in subjects with mild hypertension the main determinant of albumin excretion rate is the haemodynamic load. In subjects with more severe hypertension and hypertensive complications, the augmented urinary albumin leak is probably the consequence of a systemic microvascular disturbance which involves the glomeruli. In this respect, the insulin resistance state often associated to high blood pressure appears as one of the main pathogenetic factors. Whether management of hypertensive populations may be improved by monitoring of albumin excretion rate and whether antihypertensive drugs which are more effective in decreasing urinary albumin can be more beneficial in patients with MA remains to be determined.

Influence of the I/D polymorphism of the angiotensin-converting enzyme gene on the outcome of microalbuminuria in essential hypertension

The objective of the present study was to analyze the influence of the I/D polymorphism of the ACE gene on the outcome of microalbuminuria in essential hypertensive patients who were receiving antihypertensive treatment. One hundred thirty-six essential hypertensive patients who were <50 years old and had never previously received treatment with antihypertensive drugs were included in the study. During a 3-year period, patients received nonpharmacological treatment consisting of moderate salt restriction and a low-calorie diet they were obese, with or without a regimen of antihypertensive drugs based on beta-blockers or ACE inhibitors. Hydrochlorothiazide was added when necessary to maintain the blood pressure goal of <135/85 mm Hg. At the beginning of the study and at yearly intervals, systolic and diastolic blood pressures (SBP and DBP, respectively), 24-hour urinary albumin excretion (UAE), renal function, and biochemical profile measurements were made. The insertion/deletion (I/D) polymorphism of the ACE gene was determined through the use of polymerase chain reaction. The variables used in the statistical analysis were the measurements at the start of the study and the increase or decrease detected during the follow-up, estimated as individual specific regression line slope values. At baseline, no differences in blood pressure or UAE values were observed among genotypes. Likewise, the genotype or allele frequency was not significantly different between normoalbuminurics and microalbuminurics. After the 3 treatment years, significant reductions in SBP, DBP, and UAE were found (SBP 151.6+/-17.3 reduced to 137.2+/-14.3 mm Hg, P<0.001; DBP 96.6+/-8.9 reduced to 84.5+/-9.8 mm Hg, P<0.001; UAE 36.7+/-71.5 reduced to 28.3+/-78.6 mg/24 h, P<0. 05). The slopes of these parameters over time did not differ significantly among genotypes. The slope of SBP was the main factor related to the slope of logUAE (P<0.003). A significant positive correlation coefficient between the SBP and logUAE slopes was observed for the DD patients (r=0.57, P<0.0001) but was absent in patients carrying the I allele (II r=-0.03, P=NS; I/D r=0.01, P=NS). Follow-up studies should be used to achieve a better understanding of the impact of candidate gene polymorphisms on the development of hypertension-induced organ damage. Assessment of the I/D polymorphism of the ACE gene may identify subjects who require a greatly lowered blood pressure to prevent organ damage and to reduce hypertension-associated complications and death.