Determinants of intra-individual variation in kidney function in normoalbuminuric insulin-dependent diabetic patients: importance of atrial natriuretic peptide and glycaemic control

The role of blood volume in cardiac dysfunction and reduced exercise tolerance in patients with diabetes

Blood volume is an integral component of the cardiovascular system, and fundamental to discerning the pathophysiology of multiple cardiovascular conditions leading to exercise intolerance. Based on a systematic search of controlled studies assessing blood volume, in this Personal View we describe how hypovolaemia is a prevalent characteristic of patients with diabetes, irrespective of sex, age, and physical activity levels. Multiple endocrine and haematological mechanisms contribute to hypovolaemia in diabetes. The regulation of intravascular volumes is altered by sustained hyperglycaemia and hypertension. Chronic activation of endocrine systems controlling fluid homeostasis, such as the renin-angiotensin-aldosterone system and vasopressin axis, has a role in progressive kidney desensitisation and diabetic nephropathy. Furthermore, albumin loss from the intravascular compartment reduces the osmotic potential of plasma to retain water. Hypovolaemia also affects the loading conditions and filling of the heart in diabetes. The elucidation of modifiable volumetric traits will plausibly have major health benefits in the diabetes population.

From ARB to ARNI in Cardiovascular Control

Coexistence of hypertension, diabetes mellitus and chronic kidney disease synergistically aggravates the risk of cardiovascular and renal morbidity and mortality. These high-risk, multi-morbid patient populations benefit less from currently available anti-hypertensive treatment. Simultaneous angiotensin II type 1 receptor blockade and neprilysin inhibition (‘ARNI’) with valsartan/sacubitril (LCZ696) might potentiate the beneficial effects of renin-angiotensin-aldosterone inhibition by reinforcing its endogenous counterbalance, the natriuretic peptide system. This review discusses effects obtained with this approach in animals and humans. In animal models of hypertension, either alone or in combination with myocardial infarction or diabetes, ARNI consistently reduced heart weight and cardiac fibrosis in a blood pressure-independent manner. Additionally, LCZ696 treatment reduced proteinuria, focal segmental glomerulosclerosis and retinopathy, thus simultaneously demonstrating favourable effects on microvascular complications. These results were confirmed in patient populations. Besides blood pressure reductions in hypertensive patients and greatly improved (cardiovascular) mortality in heart failure patients, ventricular wall stress and albuminuria were reduced particularly in diabetic patients. The exact underlying mechanism remains unknown, but may involve improved renal haemodynamics and reduced glomerulosclerosis, e.g. related to a rise in natriuretic peptide levels. However, the assays of these peptides are hampered by methodological artefacts. Moreover, since sacubitrilat is largely renally cleared, drug accumulation may occur in patients with impaired renal function and thus hypotension is a potential side effect in patients with chronic kidney disease. Further caution is warranted since neprilysin also degrades endothelin-1 and amyloid beta in animal models. Accumulation of the latter may increase the risk of Alzheimer’s disease.

Blood pressure-independent renoprotection in diabetic rats treated with AT1 receptor-neprilysin inhibition compared with AT1 receptor blockade alone

ARNI [dual AT1 (angiotensin II type 1) receptor-neprilysin inhibition] exerts beneficial effects on blood pressure and kidney function in heart failure, compared with ARB (AT1 receptor blockade) alone. We hypothesized that ARNI improves cardiac and kidney parameters in diabetic TGR(mREN2)27 rats, an angiotensin II-dependent hypertension model. Rats were made diabetic with streptozotocin for 5 or 12 weeks. In the final 3 weeks, rats were treated with vehicle, irbesartan (ARB) or irbesartan+thiorphan (ARNI). Blood pressure, measured by telemetry in the 5-week group, was lowered identically by ARB and ARNI. The heart weight/tibia length ratio in 12-week diabetic animals was lower after ARNI compared with after ARB. Proteinuria and albuminuria were observed from 8 weeks of diabetes onwards. ARNI reduced proteinuria more strongly than ARB, and a similar trend was seen for albuminuria. Kidneys of ARNI-treated animals showed less severe segmental glomerulosclerosis than those of ARB-treated animals. After 12 weeks, no differences between ARNI- and ARB-treated animals were found regarding diuresis, natriuresis, plasma endothelin-1, vascular reactivity (acetylcholine response) or kidney sodium transporters. Only ARNI-treated rats displayed endothelin type B receptor-mediated vasodilation. In conclusion, ARNI reduces proteinuria, glomerulosclerosis and heart weight in diabetic TGR(mREN2)27 rats more strongly than does ARB, and this occurs independently of blood pressure.

Protein- and diabetes-induced glomerular hyperfiltration: role of glucagon, vasopressin, and urea

A single protein-rich meal (or an infusion of amino acids) is known to increase the glomerular filtration rate (GFR) for a few hours, a phenomenon known as “hyperfiltration.” It is important to understand the factors that initiate this upregulation because it becomes maladaptive in the long term. Several mediators and paracrine factors have been shown to participate in this upregulation, but they are not directly triggered by protein intake. Here, we explain how a rise in glucagon and in vasopressin secretion, directly induced by protein ingestion, might be the initial factors triggering the hepatic and renal events leading to an increase in the GFR. Their effects include metabolic actions in the liver and stimulation of sodium chloride reabsorption in the thick ascending limb. Glucagon is not only a glucoregulatory hormone. It is also important for the excretion of nitrogen end products by stimulating both urea synthesis in the liver (along with gluconeogenesis from amino acids) and urea excretion by the kidney. Vasopressin allows the concentration of nitrogenous end products (urea, ammonia, etc.) and other protein-associated wastes in a hyperosmotic urine, thus allowing a very significant water economy characteristic of all terrestrial mammals. No hyperfiltration occurs in the absence of one or the other hormone. Experimental results suggest that the combined actions of these two hormones, along with the complex intrarenal handling of urea, lead to alter the composition of the tubular fluid at the macula densa and to reduce the intensity of the signal activating the tubuloglomerular feedback control of GFR, thus allowing GFR to raise. Altogether, glucagon, vasopressin, and urea contribute to set up the best compromise between efficient urea excretion and water economy.

Urinary biomarker N-acetyl-β-D-glucosaminidase can predict severity of renal damage in diabetic nephropathy

Background

Diabetic nephropathy is a clinical diagnosis where proteinuria is present in a patient with diabetes. Early intervention can significantly improve the prognosis. However, imprecision of the currently available biomarkers have impaired effective therapies in a timely manner. Urinary N-acetyl-β-D-glucosaminidase (NAG) is excreted in abnormally high amounts in many renal diseases. The aim of this study was to evaluate urinary NAG as an early biomarker in detection of diabetic nephropathy and whether it parallels the severity of kidney damage in different stages of diabetic nephropathy.

Methods

Fifty patients with type 2 DM were classified into 3 groups (normoalbuminurea, microalbuminurea and macroalbuminurea) and 10 healthy subjects served as a control group. Urinary NAG, albumin and creatinine were measured. Blood urea, serum creatinine, serum albumin, total proteins, serum cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), fasting and postprandial blood glucose, HbA1c and creatinine clearance were measured for all subjects.

Results

All diabetic patients had a significantly higher level of urinary NAG compared to control. NAG value increased in parallel with the severity of renal involvement.

Conclusion

Urinary NAG expresses the degree of renal impairment in diabetic nephropathy.

Vasopressin: a novel target for the prevention and retardation of kidney disease?

After several decades during which little attention was paid to vasopressin and/or urine concentration in clinical practice, interest in vasopressin has renewed with the availability of new, potent, orally active vasopressin-receptor antagonists--the vaptans--and with the results of epidemiological studies evaluating copeptin (a surrogate marker of vasopressin) in large population-based cohorts. Several experimental studies in rats and mice had previously shown that vasopressin, acting via vasopressin V2 antidiuretic receptors, contributes to the progression of chronic kidney disease; in particular, to autosomal dominant polycystic kidney disease. New epidemiological studies now suggest a role for vasopressin in the pathogenesis of diabetes mellitus and metabolic disorders via activation of hepatic V1a and/or pancreatic islet V1b receptors. The first part of this Review describes the adverse effects of vasopressin, as revealed by clinical and experimental studies in kidney diseases, hypertension, diabetes and the metabolic syndrome. The second part provides insights into vasopressin physiology and pathophysiology that may be relevant to the understanding of these adverse effects and that are linked to the excretion of concentrated nitrogen wastes and associated hyperfiltration. Collectively, the studies reviewed here suggest that more attention should be given to the vasopressin-thirst-urine concentration axis in clinical investigations and in patient care. Whether selective blockade of the different vasopressin receptors may provide therapeutic benefits beyond their present indication in hyponatraemia requires new clinical trials.

Serum cystatin C reflects the progress of albuminuria

BACKGROUND

Research on the relationship between urinary albumin excretion and serum cystatin C in diabetes is restricted to cross-sectional studies. In this study, we investigated how well serial measurements of serum cystatin C level reflect changes in the urinary albumin excretion rate.

METHODS

We enrolled and retrospectively collected data on 1,058 participants with type 2 diabetes who were older than 18 years and who had more than 3 years of follow-up with serial measurements of albuminuria and serum cystatin C at an outpatient clinic.

RESULTS

With the use of a linear mixed model, we found that the albuminuria level for each patient over time corresponded with the annual change in serum cystatin C-based estimated glomerular filtration rate (cysC-eGFR) but did not correspond with the creatinine-based eGFR calculated by the modification of diet in renal disease formula (MDRD-eGFR). The discrepancy in the direction of the trend was smaller with cysC-eGFR than with MDRD-eGFR.

CONCLUSION

Serum cystatin C level reflects the trend in albuminuria level more accurately than serum creatinine level in Korean type 2 diabetes mellitus patients.

Transgenic overexpression of brain natriuretic peptide prevents the progression of diabetic nephropathy in mice

AIMS/HYPOTHESIS

Brain natriuretic peptide (BNP) is a potent vasorelaxing and natriuretic peptide that is secreted from the heart and has cardioprotective properties. We have previously generated hypotensive transgenic mice (BNP-Tg mice) that overproduce BNP in the liver, which is released into the circulation. Using this animal model, we successfully demonstrated the amelioration of renal injury after renal ablation and in proliferative glomerulonephritis. Glomerular hyperfiltration is an early haemodynamic derangement, representing one of the key mechanisms of the pathogenesis of diabetic nephropathy. Based on the suggested involvement of increased endogenous natriuretic peptides, the aim of this study was to investigate their role in the development and progression of diabetic nephropathy.

MATERIALS AND METHODS

We evaluated the progression of renal injury and fibrogenesis in BNP-Tg mice with diabetes induced by streptozotocin. We also investigated the effect of BNP on high glucose-induced signalling abnormalities in mesangial cells.

RESULTS

After induction of diabetes, control mice exhibited progressively increased urinary albumin excretion with impaired renal function, whereas these changes were significantly ameliorated in BNP-Tg mice. Notably, diabetic BNP-Tg mice revealed minimal mesangial fibrogenesis with virtually no glomerular hypertrophy. Glomerular upregulation of extracellular signal-regulated kinase, TGF-beta and extracellular matrix proteins was also significantly inhibited in diabetic BNP-Tg mice. In cultured mesangial cells, activation of the above cascade under high glucose was abrogated by the addition of BNP.

CONCLUSIONS/INTERPRETATION

Chronic excess of BNP prevents glomerular injury in the setting of diabetes, suggesting that renoprotective effects of natriuretic peptides may be therapeutically applicable in preventing the progression of diabetic nephropathy.

Reduced plasma total homocysteine concentrations in Type 1 diabetes mellitus is determined by increased renal clearance

INTRODUCTION

Elevated plasma levels of total homocysteine are related to the development of vascular complications. Patients with diabetes mellitus are particularly at risk for the development of these complications. Several factors determine plasma total homocysteine including renal function.

AIMS

As early Type 1 diabetes is characterized by a relative glomerular hyperfiltration, increased renal clearance could contribute to decreased levels of homocysteine as observed in Type 1 diabetes mellitus. Therefore we investigated the relationship between plasma total homocysteine and the glomerular filtration rate (GFR).

METHODS

In 92 Type 1 diabetes patients and 44 control subjects, we measured GFR and effective renal plasma flow (ERPF) by means of continuous infusion of inulin and p-aminohippurate. Fasting plasma total homocysteine was measured using high performance liquid chromatography.

RESULTS

GFR (121 +/- 21 resp. 104 +/- 14 ml/min; P < 0.001) and ERPF (563 +/- 127 resp. 516 +/- 121 ml/min; P = 0.05) were significantly higher in Type 1 diabetes patients as compared with control subjects. Plasma total homocysteine was reduced in Type 1 diabetes patients as compared with control subjects (11.0 +/- 4.5 resp. 13.4 +/- 7 micromol/l; P = 0.01). Plasma total homocysteine was strongly correlated with GFR (Type 1 diabetes patients: r = -0.43, P < 0.001; control subjects: r = -0.39, P = 0.01).

CONCLUSION

GFR is a major determinant of plasma total homocysteine levels in Type 1 diabetes patients as well as control subjects. The reduced plasma total homocysteine levels in diabetes patients can be explained by an increased GFR.

Investigation of the human ANP gene in type 1 diabetic nephropathy: case-control and follow-up studies

The atrial natriuretic peptide gene (PND) is a candidate gene for diabetic nephropathy. We systematically analyzed five nonsynonymous PND polymorphisms and tested the association of genotype and haplotype distributions with diabetic nephropathy in a cross-sectional study and a 6-year follow-up study (489 and 301 type 1 diabetic patients, respectively). For this purpose, a new maximum-likelihood method dealing with haplotype-based association analysis for survival data was developed. None of the genotypes or haplotypes were associated with the disease in the case-control study. In the follow-up study, C708T and T2238C showed a weak association with disease progression, but T2238C was strongly associated with progression in poorly controlled subjects (mean HbA(1c) during follow-up was more than the median value [8.5%]; log-rank [TC or CC versus TT], P = 0.007; adjusted hazard ratio, TC or CC versus TT, 2.28, 95% CI 1.10-4.74; P = 0.027). The raw effect of the 2238C allele (hazard risk ratio 1.93, 95% CI 1.15-3.24; P = 0.012) was further confirmed by the haplotype analysis, suggesting that the 2238C allele of PND may affect the course of nephropathy in inadequately controlled type 1 diabetic patients.

BNP and congestive heart failure

Brain natriuretic peptide (BNP), a peptide hormone secreted chiefly by ventricular myocytes, plays a key role in volume homeostasis. The plasma concentration of BNP is raised in various pathological states, especially heart failure. Many studies suggest that measurement of plasma BNP has clinical utility for excluding a diagnosis of heart failure in patients with dyspnea or fluid retention and for providing prognostic information in those with heart failure or other cardiac disease. It may also be of value in identifying patients after myocardial infarction in whom further assessment of cardiac function is likely to be worthwhile. Preliminary evidence suggests that measuring the plasma concentration of BNP may be useful in fine tuning therapy for heart failure. Artificially raising the circulating levels of BNP shows considerable promise as a treatment for heart failure. With simpler assay methods now available, it is likely that many physicians will measure plasma BNP to aid them in the diagnosis, risk stratification, and monitoring of their patients with heart failure or other cardiac dysfunction.

Polymorphisms in the hANP (human atrial natriuretic peptide) gene, albuminuria, and hypertension

Atrial natriuretic peptide (ANP) jointly affects kidney function and blood pressure homeostasis and is a candidate susceptibility gene for both essential hypertension and kidney disease. We evaluated the relation between the ScaI and BstXI polymorphisms of the human ANP (hANP) gene, hypertension, and albuminuria in a clinical cohort of 1033 subjects, including type 1 and type 2 diabetic patients, nondiabetic subjects with essential hypertension, and nondiabetic normotensive control subjects. Microalbuminuria was present in 15%, 29%, and 2%, respectively, of type 1 diabetic, type 2 diabetic, and nondiabetic patients. Macroalbuminuria was present in 9% of type 1 diabetics, 21% of type 2 diabetics, and 31% of nondiabetics. Prevalence of hypertension was 31%, 58%, and 61% in normoalbuminuric, microalbuminuric, and macroalbuminuric subjects, respectively (P<0.0001). Genotype distributions were in Hardy-Weinberg equilibrium in all 4 patient subgroups. The frequency of the ScaI mutated allele (A(1)) was significantly lower in hypertensive than in control subjects (11% versus 19%, P=0.018) and in patients with macroalbuminuria (5%) as compared with normoalbuminuric subjects (16%; P<0.0001). In a nominal logistic model adjusting for gender, age, obesity, diabetes, micro/macroalbuminuria, and hypertension, the A(1) allele was independently associated with macroalbuminuria (odds ratio, 0.57; confidence interval, 1.39 to 3.59; P=0.003) but not with hypertension. In the same model, the frequency of the BstXI mutated allele (T(708)) was increased in the presence of microalbuminuria (odds ratio, 2.25; confidence interval, 1.39 to 3.59; P<0.001). We conclude that the mutated genotypes of the ScaI polymorphism are negatively associated with overt nephropathy, whereas the mutated genotypes of BstXI polymorphism are positively associated with microalbuminuria. hANP gene variants may exert a protective effect against the development and progression of kidney damage in diabetes.

Pronatriodilatin gene polymorphisms, microvascular permeability, and diabetic nephropathy in type 1 diabetes mellitus

Approximately 30% of diabetic patients develop nephropathy, the appearance of which is partially under genetic control. Atrial natriuretic peptide (ANP) has associated physiologic effects on the kidney. This study was conducted to examine the relationship between a newly identified and known polymorphism at the pronatriodilatin (PND) gene locus and renal involvement in type 1 diabetic subjects. Of 454 type 1 diabetic patients (219 men, 235 women), 323 showed no sign of nephropathy, 79 had incipient renal involvement, and 52 established nephropathy; 58 healthy control subjects were examined for comparison. Allele frequencies (C708 versus T708) were: 0.95 and 0.05 in normoalbuminuric patients, respectively; 0.88 and 0.12 in microalbuminuric patients; 0.96 and 0.04 both in those with overt nephropathy and in healthy control subjects (P = 0.011). Patients with incipient nephropathy were in disequilibrium compared with the total diabetic cohort (P = 0.02). In the same populations, an additional genotype for ScaI polymorphism of the PND gene was tested. The A1 and A2 allele frequencies were: 0.21 and 0.79 in normoalbuminuric patients; 0. 13 and 0.87 in microalbuminuric patients; 0.06 and 0.94 in type 1 diabetic subjects with overt nephropathy; and 0.20 and 0.80 in healthy control subjects, respectively (P < 0.0001). A subset of 55 normotensive patients with type 1 diabetes, well matched for clinical features, plasma ANP levels, and microvascular permeability to macromolecules, was investigated on the basis of the C708/T and A2/A1 polymorphisms. Both transcapillary escape rate of albumin (TERalb) and plasma ANP levels were significantly lower in patients with the T708 than with C708 allele, as well as in the A1 than in A2 allele (TERalb: T708 versus C708: 5.5+/-1.7 versus 7.8+/-2.0%/h, P = 0.0001; plasma ANP levels: 8.3+/-3.9 versus 15.3+/-7.7 pg/ml, P = 0.0003; A1 versus A2: 6.05+/-2.2 versus 7.3+/-2.1%/h, P = 0.044; 8.53+/-4.6 versus 14.5+/-7.4 pg/ml, P = 0.0024, respectively). Thus, in a large ethnically homogeneous cohort of diabetic subjects, our data show: (1) a significant association of C708/T polymorphism with microalbuminuria in long-term diabetes and with both lower plasma ANP levels and widespread albumin leakage; and (2) a strong association between ScaI polymorphism and both diabetic nephropathy and plasma ANP concentrations. These results suggest a possible role of PND gene in conferring protection from nephropathy and microvascular damage in type 1 diabetes.

Atrial natriuretic peptide increases albuminuria in type I diabetic patients: evidence for blockade of tubular protein reabsorption

BACKGROUND

It has been suggested that atrial natriuretic peptide (ANP) contributes to the glomerular hyperfiltration of diabetes mellitus. Infusion of ANP increases the urinary excretion of albumin in patients with type I diabetes mellitus (IDDM). Although the increased albuminuria is attributed to a rise in glomerular pressure, alterations in tubular protein handling might be involved.

PATIENTS AND METHODS

We have studied the effects of ANP in nine microalbuminuric IDDM patients. After obtaining baseline parameters, ANP was infused over a 1-h period (bolus 0.05 microgram kg-1, infusion rate 0.01 microgram kg-1 min-1). Renal haemodynamics, sodium and water clearance and tubular protein handling were studied.

RESULTS

The glomerular filtration rate (GFR) increased from 116.4 +/- 8.9 to 128.3 +/- 8.8 mL min-1 1.73 m-2, whereas the effective renal plasma flow (ERPF) decreased from 534.3 +/- 44.3 to 484.9 +/- 33.3 mL min-1 1.73 m-2 (P < 0.05). As a result, the filtration fraction was significantly higher during infusion of ANP. ANP attenuated proximal tubular sodium reabsorption. Urinary albumin excretion rose from 87.57 +/- 21.03 to 291.40 +/- 67.86 micrograms min-1 (P < 0.01). Changes in the urinary excretion of beta 2-microglobulin and free kappa light chains were more marked, the excretion of beta 2-microglobulin increasing from 0.28 +/- 0.21 to 51.87 +/- 10.51 micrograms min-1 (P < 0.01), and of free kappa-light chains from 4.73 +/- 1.74 to 46.14 +/- 6.19 micrograms min-1 (P < 0.01).

CONCLUSIONS

The observed rise in albuminuria during infusion of ANP does not simply reflect a change in glomerular pressure, but might at least partly result from an attenuation of tubular protein reabsorption.

An examination of the covariability of subclinical albuminuria in insulin-dependent diabetes mellitus: implications for monitoring microalbuminuria

We examined the covariability of subclinical albuminuria in a cohort of 160 insulin-dependent diabetics who underwent simultaneous measurements of overnight urinary albumin excretion rate (UAV) and several clinical variables on 7 occasions over a period of 18 months. After allowing for within-patient correlation between visits, significant within-patient associations were found between UAV and variations in tobacco consumption (regression coefficient = 0.006, S.E. = 0.002, P = 0.02), insulin dose (regression coefficient = 0.003, S.E. = 0.001, P = 0.01) and creatinine clearance (regression coefficient = 0.776, S.E. = 0.047, P < 0.0001); the association between UAV and creatinine clearance was not influenced by adjusting for urine flow rate. No significant associations were found between UAV and changes in blood pressure, glycaemic control or other variables. We then focused on 33 patients with intermittent microalbuminuria, defined as a UAV > 30 micrograms/min on at least one occasion, but not exceeding 3 consecutive occasions. These patients had a total of 52 episodes of microalbuminuria which were significantly associated at the 5% level with increases in creatinine clearance (P = 0.02), but not with changes in other variables. Our findings did not differ in patients with intermittent microalbuminuria defined with reference to a cut-off UAV of 20 micrograms/min. We conclude that changes in glomerular filtration rate (as reflected by creatinine clearance) may partly account for the within-patient variability in subclinical albuminuria in insulin-dependent diabetics, and that variables routinely measured in the clinic are not useful for deciding when to monitor patients for microalbuminuria.

Monitoring diabetic nephropathy: glomerular filtration rate and abnormal albuminuria in diabetic renal disease--reproducibility, progression, and efficacy of antihypertensive intervention

The principal end point in the evaluation of treatment in incipient and overt diabetic nephropathy is rate of decline in glomerular filtration rate (GFR). Therefore, information on reproducibility of GFR measurements is essential in the planning and evaluation of clinical trials. We studied reproducibility of GFR measurements in insulin-dependent and non-insulin-dependent diabetes mellitus patients using, respectively, a constant-infusion technique with urine collection and labeled iothalamate as a tracer marker and a single-shot procedure using Cr-EDTA, measuring the GFR from the decline in plasma level after bolus injection. The coefficient of variance in the insulin-dependent patients was from 7.5% to 8.8% with repeated measurements. In longitudinal studies with several measurements the mean coefficient of variances varied between 7.4% and 3.4%. In the non-insulin-dependent patients the coefficient of variances between two tests were 7.0% and 5.3% for normoalbuminuric and microalbuminuric patients, respectively. In cross-sectional studies as well as in longitudinal studies, it has been consistently shown that GFR is well preserved and at a supranormal level in patients with normoalbuminuria and microalbuminuria. A decline in GFR appears to start around the transition from microalbuminuria to overt diabetic renal disease, although more detailed studies are needed to support this finding. With regard to intervention trials, several studies document that microalbuminuria can be reduced by effective antihypertensive treatment, particularly with angiotensin-converting enzyme inhibitors, also in patients with normal or close to normal blood pressure. Preliminary results from long-term studies suggest that reduction in microalbuminuria in these patients is associated with preservation of GFR and, thus, apparently renoprotection. In patients with overt renal disease, it has been consistently shown that antihypertensive treatment reduces albuminuria as well as the rate of decline in GFR. This is also observed with combined treatment regimens, for instance beta blockers or angiotensin-converting enzyme inhibitors combined with diuretics, or the three types of drugs in combination.