Glomerular hypertension as one cause of albuminuria in type II diabetic patients

Evaluation of glomerular hemodynamic changes by sodium-glucose-transporter 2 inhibition in type 2 diabetic rats using in vivo imaging

The mechanisms responsible for glomerular hemodynamic regulation with sodium-glucose co-transporter 2 (SGLT2) inhibitors in kidney disease due to type 2 diabetes remain unclear. Therefore, we investigated changes in glomerular hemodynamic function using an animal model of type 2 diabetes, treated with an SGLT2 inhibitor alone or in combination with a renin-angiotensin-aldosterone system inhibitor using male Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats. Afferent and efferent arteriolar diameter and single-nephron glomerular filtration rate (SNGFR) were evaluated in ZDF rats measured at 0, 30, 60, 90, and 120 minutes after the administration of a SGLT2 inhibitor (luseogliflozin). Additionally, we assessed these changes under the administration of the adenosine A1 receptor (A1aR) antagonist (8-cyclopentyl-1,3-dipropylxanthine), along with coadministration of luseogliflozin and an angiotensin II receptor blocker (ARB), telmisartan. ZDF rats had significantly increased SNGFR, and afferent and efferent arteriolar diameters compared to ZL rats, indicating glomerular hyperfiltration. Administration of luseogliflozin significantly reduced afferent vasodilatation and glomerular hyperfiltration, with no impact on efferent arteriolar diameter. Urinary adenosine levels were increased significantly in the SGLT2 inhibitor group compared to the vehicle group. A1aR antagonism blocked the effect of luseogliflozin on kidney function. Co-administration of the SGLT2 inhibitor and ARB decreased the abnormal expansion of glomerular afferent arterioles, whereas the efferent arteriolar diameter was not affected. Thus, regulation of afferent arteriolar vascular tone via the A1aR pathway is associated with glomerular hyperfiltration in type 2 diabetic kidney disease.

The proteinuria-lowering effects of dapagliflozin are associated with an initial decline in estimated glomerular filtration rate in patients with chronic kidney disease

AIM

Sodium-glucose co-transporter-2 inhibitor, dapagliflozin (DAPA) reduced albuminuria and slowed down the decline in estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease (CKD) in the DAPA-CKD trial. However, proteinuria (albuminuria) does not necessarily decrease in all patients in real-world clinical settings. Therefore, we aimed to identify the clinical characteristics of patients with CKD and decreased proteinuria in response to DAPA treatment.

METHODS

Of 106 patients with CKD, 54 patients were finally included who received 10 mg of DAPA once daily. Patients whose urinary protein-to-creatinine ratio (UPCR) decreased by >30% or ≤30% from baseline after 1 month of treatment were defined as responders and non-responders, respectively.

RESULTS

At baseline, median eGFR and UPCR were 45.3 mL/min/1.73 m2 (interquartile range [IQR], 29.7, 54.6) and 1.09 g/gCr (IQR, 0.52, 1.91), respectively. After 1 month of treatment, the mean decline in eGFR and reduction in UPCR was 6.5% (standard deviation [SD], 7.2%) and 6.6% (SD, 42.1%) from baseline, respectively. Moreover, the blood pressure, eGFR, and uric acid decreased significantly from baseline, but haemoglobin and serum potassium did not change. The median UPCR decreased significantly in patients with UPCR ≥0.5 g/gCr, but not <0.5 g/gCr at baseline. UPCR responders had a greater initial decline in eGFR at 1 month than non-responders.

CONCLUSION

The percent changes in UPCR were positively associated with the initial decline rate in eGFR in patients with CKD with a UPCR ≥0.5 g/gCr at baseline after 1 month of DAPA treatment.

Role of abnormal energy metabolism in the progression of chronic kidney disease and drug intervention

Chronic kidney disease (CKD) is a severe clinical syndrome with significant socioeconomic impact worldwide. Orderly energy metabolism is essential for normal kidney function and energy metabolism disorders are increasingly recognized as an important player in CKD. Energy metabolism disorders are characterized by ATP deficits and reactive oxygen species increase. Oxygen and mitochondria are essential for ATP production, hypoxia and mitochondrial dysfunction both affect the energy production process. Renin-angiotensin and adenine signaling pathway also play important regulatory roles in energy metabolism. In addition, disturbance of energy metabolism is a key factor in the development of hereditary nephropathy such as autosomal dominant polycystic kidney disease. Currently, drugs with clinically clear renal function protection, such as Angiotensin II Type 1 receptor blockers and fenofibrate, have been proven to improve energy metabolism disorders. The sodium-glucose co-transporter inhibitors 2 that can mediate glucose metabolism disorders not only delay the progress of diabetic nephropathy, but also have significant protective effects in non-diabetic nephropathy. Hypoxia-inducible factor enhances ATP production to the kidney by improving renal oxygen supply and increasing glycolysis, and the mitochondria targeted peptides (SS-31) plays a protective role by stabilizing the mitochondrial inner membrane. Moreover, several drugs are being studied and are predicted to have potential renal protective properties. We propose that the regulation of energy metabolism represents a promising strategy to delay the progression of CKD.

Association between Food Label Unawareness and Loss of Renal Function in Diabetes: A Cross-Sectional Study in South Korea

Objectives: To examine sex differences in the association between food label unawareness and loss of renal function among South Korean diabetic patients aged ≥30 year and determine whether reading food labels when choosing which food products to consume plays a potential role in slowing the progression of renal disease. Methods: Data from the 2016–2017 Korea National Health and Nutrition Examination Survey were used for the analysis. Renal function was determined by the Modification of Diet in Renal Disease estimated glomerular filtration rate, and food label unawareness was defined as being unaware of the food label when choosing a food product for consumption. Multiple regression analysis was used to investigate the association between food label unawareness and loss of renal function among South Korean diabetic patients. Results: Four hundred and eighty-seven diabetic patients (men: 274; women: 213) were enrolled. Loss of renal function was associated with food label unawareness in only male diabetic patients (men: β = –10.01, standard error (SE) = 5.08, p = 0.0506; women: β = –0.30, SE = 5.14, p = 0.9528). A strong association was found between loss of renal function and food label unawareness among socially isolated male diabetic patients who lived in a one-generational household, did not have a spouse, and ate alone. Conclusion: Cultivating habits of reading food labels and inducing social facilitation may play a potential role in managing loss of renal function among male diabetic patients.

Inhibition of Endocytosis of Clathrin-Mediated Angiotensin II Receptor Type 1 in Podocytes Augments Glomerular Injury

BACKGROUND

Inhibition of the renin-angiotensin system remains a cornerstone in reducing proteinuria and progression of kidney failure, effects believed to be the result of reduction in BP and glomerular hyperfiltration. However, studies have yielded conflicting results on whether podocyte-specific angiotensin II (AngII) signaling directly induces podocyte injury. Previous research has found that after AngII stimulation, β-arrestin-bound angiotensin II receptor type 1 (AT1R) is internalized in a clathrin- and dynamin-dependent manner, and that Dynamin1 and Dynamin2 double-knockout mice exhibit impaired clathrin-mediated endocytosis.

METHODS

We used podocyte-specific Dyn double-knockout mice to examine AngII-stimulated AT1R internalization and signaling in primary podocytes and controls. We also examined the in vivo effect of AngII in these double-knockout mice through renin-angiotensin system blockers and through deletion of Agtr1a (which encodes the predominant AT1R isoform expressed in kidney, AT1aR). We tested calcium influx, Rac1 activation, and lamellipodial extension in control and primary podocytes of Dnm double-knockout mice treated with AngII.

RESULTS

We confirmed augmented AngII-stimulated AT1R signaling in primary Dnm double-knockout podocytes resulting from arrest of clathrin-coated pit turnover. Genetic ablation of podocyte Agtr1a in Dnm double-knockout mice demonstrated improved albuminuria and kidney function compared with the double-knockout mice. Isolation of podocytes from Dnm double-knockout mice revealed abnormal membrane dynamics, with increased Rac1 activation and lamellipodial extension, which was attenuated in Dnm double-knockout podocytes lacking AT1aR.

CONCLUSIONS

Our results indicate that inhibiting aberrant podocyte-associated AT1aR signaling pathways has a protective effect in maintaining the integrity of the glomerular filtration barrier.

Effect of acupressure at Sanyinjiao on albuminuria in patients with early diabetic nephropathy: A single-blind, randomized, controlled preliminary study

BACKGROUND

Elevated urinary albumin excretion is a clinical manifestation of early-stage diabetic nephropathy (DN).

PURPOSE

To investigate effect of acupressure at Sanyinjiao on albuminuria in patients with early DN.

METHODS

Total included 53 patients with DN and albuminuria; 21 were assigned to the sham group without acupressure, and 32 were assigned to the experimental group with acupressure at Sanyinjiao (SP6) for 8weeks. The experimental group was divided into experiment A (acupressure <45 days) and experiment B (acupressure ≥45 days). The primary outcome measure was the urine albuminuria/creatinine ratio (UACR) or logarithmic transformed urine microalbumin creatinine ratio (log-UACR) changes, and the secondary outcome measures were the estimated glomerular filtration rate and hemoglobin A1c.

RESULTS

The difference in UACR and log-UACR before and after the study was higher in the experiment B group than in the experiment A and sham groups.

CONCLUSION

Acupressure at Sanyinjiao for 8 weeks may reduce albuminuria in patients with DN. However, this study was a preliminary design.

A Low-Protein Diet for Diabetic Kidney Disease: Its Effect and Molecular Mechanism, an Approach from Animal Studies

A low-protein diet (LPD) can be expected to retard renal function decline in advanced stages of chronic kidney disease (CKD), including diabetic kidney disease (DKD), and is recommended in a clinical setting. Regarding the molecular mechanisms of an LPD against DKD, previous animal studies have shown that an LPD exerts reno-protection through mainly the improvement of glomerular hyperfiltration/hypertension due to the reduction of intraglomerular pressure. On the other hand, we have demonstrated that an LPD, particularly a very-LPD (VLPD), improved tubulo-interstitial damage, inflammation and fibrosis, through the restoration of autophagy via the reduction of a mammalian target of rapamycin complex 1 (mTORC1) activity in type 2 diabetes and obesity animal models. Thus, based on animal studies, a VLPD may show a more beneficial effect against advanced DKD. Previous clinical reports have also shown that a VLPD, not a moderate LPD, slows the progression of renal dysfunction in patients with chronic glomerular nephritis. However, there is insufficient clinical data regarding the beneficial effects of a VLPD against DKD. Additionally, the patients with CKD, including DKD, are a high-risk group for malnutrition, such as protein–energy wasting (PEW), sarcopenia, and frailty. Therefore, an LPD, including a VLPD, should be prescribed to patients when the benefits of an LPD outweigh the risks, upon consideration of adherence, age, and nutritional status. As the future predicts, the development of a VLPD replacement therapy without malnutrition may be expected for reno-protection against the advanced stages of DKD, through the regulation of mTORC1 activity and adequate autophagy induction. However, further studies to elucidate detailed mechanisms by which a VLPD exerts reno-protection are necessary.

Association between gamma-glutamyltransferase and albuminuria in nondiabetic adults with normal renal function

BACKGROUND

Serum gamma-glutamyltransferase (GGT) has been associated with albuminuria in diabetes patients, but it has not been investigated in the general population. We aimed to investigate the association between serum GGT and albuminuria in the nondiabetic Korean population with normal kidney function.

METHODS

Study participants (3948; 1549 men and 2399 women) with an estimated glomerular filtration rate ≥60 mL/min/1.73 m² were analyzed from the fifth Korean National Health and Nutrition Examination Survey (2011). Albuminuria was defined as an albumin-creatinine ratio >30 mg/g. Serum GGT was analyzed by dividing into quartiles. Multiple logistic models were used to analyze the associations between GGT and albuminuria.

RESULTS

The prevalence of albuminuria was 5.1% and increased linearly according to increasing GGT quartiles (P for trend = 0.005). A linear regression analysis revealed that GGT was positively related with albuminuria (P = 0.008). After adjusting for confounding factors, the odds ratio for albuminuria was 1.80 (95% CI 1.079-3.010, P for trend = 0.029) for the highest quartile group compared with those observed in the lowest quartile of GGT. In addition, this independent relationship did not change when the cut-off value of GGT (30 IU/L) was applied to this analysis. Compared with GGT value ≤30 IU/L, the adjusted odds ratio of albuminuria in participants with GGT >30 IU/L was 1.96 (95% CI 1.319-2.906, P < 0.001).

CONCLUSION

Higher serum GGT levels within the reference range were significantly associated with albuminuria in nondiabetic Koreans with preserved kidney function, independently of traditional cardio-renal risk factors.

Capillary Rarefaction Associates with Albuminuria: The Maastricht Study

Albuminuria may be a biomarker of generalized (i.e., microvascular and macrovascular) endothelial dysfunction. According to this concept, endothelial dysfunction of the renal microcirculation causes albuminuria by increasing glomerular capillary wall permeability and intraglomerular pressure, the latter eventually leading to glomerular capillary dropout (rarefaction) and further increases in intraglomerular pressure. However, direct evidence for an association between capillary rarefaction and albuminuria is lacking. Therefore, we examined the cross-sectional association between the recruitment of capillaries after arterial occlusion (capillary density during postocclusive peak reactive hyperemia) and during venous occlusion (venous congestion), as assessed with skin capillaroscopy, and albuminuria in 741 participants of the Maastricht Study, including 211 participants with type 2 diabetes. Overall, 57 participants had albuminuria, which was defined as a urinary albumin excretion ≥30 mg/24 h. After adjustment for potential confounders, participants in the lowest tertile of skin capillary recruitment during postocclusive peak reactive hyperemia had an odds ratio for albuminuria of 2.27 (95% confidence interval, 1.07 to 4.80) compared with those in the highest tertile. Similarly, a comparison between the lowest and the highest tertiles of capillary recruitment during venous congestion yielded an odds ratio of 2.89 (95% confidence interval, 1.27 to 6.61) for participants in the lowest tertile. In conclusion, lower capillary density of the skin microcirculation independently associated with albuminuria, providing direct support for a role of capillary rarefaction in the pathogenesis of albuminuria.

Prevalence of and factors associated with albuminuria in the Korean adult population: the 2011 Korea National Health and Nutrition Examination Survey

BACKGROUND

Microalbuminuria is associated with increased risk of renal disease and cardiovascular diseases even in non-diabetic subjects. High incidence rates of microalbuminuria have been found in a number of population-based studies. However, the prevalence and risk factors associated with microalbuminuria in the general population in Korea are unclear.

OBJECTIVES

The present study was performed to estimate the prevalence of microalbuminuria and investigate the associated risk factors in the general adult population using the Fifth Korea National Health and Nutrition Examination Survey (KNHANES V-2) data from 2011.

METHODS

A total of 5,202 participants (mean age, 45.6 years; men, 2,337; women, 2,865) were included in the analysis. Microalbuminuria was evaluated in participants of KNHANES V-2 based on the urine albumin-creatinine ratio. Estimated glomerular filtration rate was calculated using the Modification of Diet in Renal Disease study equation.

RESULTS

The weighted prevalence of microalbuminuria was 5.2% (95% CI, 4.4-6.1) in the general population. The prevalence of albuminuria is increased with age. After adjustment for age and sex, the presence of albuminuria was associated with increased waist circumference, systolic and diastolic blood pressure, aspartate aminotransferase, triglyceride, fasting plasma glucose, and the presence of hypertension and diabetes. In logistic regression analyses, older age, female sex, diabetes, hypertension, and serum aspartate aminotransferase were independently associated with the presence of albuminuria.

CONCLUSION

The prevalence of microalbuminuria was found to be 5.2%, and conventional risk factors for cardiovascular diseases are closely related to the presence of microalbuminuria in Korea. Microalbuminuria may be a useful marker to identify individuals with increased risk of cardiovascular disease.

Release from glomerular overload by the addition of low-dose thiazide in patients with angiotensin receptor blocker-resistant hypertension

BACKGROUND/AIMS

This multicenter, prospective, observational study assessed the renoprotective effects of losartan/thiazide combination therapy in terms of lowering the estimated glomerular filtration rate (eGFR).

METHODS

Adult patients with angiotensin receptor blocker (ARB)-resistant essential hypertension (n = 104) were enrolled and switched to combination therapy with losartan (50 mg/day) and hydrochlorothiazide (12.5 mg/day).

RESULTS

eGFR values declined significantly during the first 3 months, and changes in eGFR were assessed according to tertiles of the eGFR decrease ratio at 3 months. Only the high eGFR decrease (1st tertile) group showed significantly greater decreases in baseline eGFR and albumin-to-creatinine ratio (ACR) during the first 3 months. Additionally, the assessment according to tertiles of the baseline eGFR showed a signifcant decrease in eGFR and ACR during the first 3 months in the high baseline eGFR (1st tertile) group, but not in the moderate (2nd tertile) and low baseline eGFR (3rd tertile) groups.

CONCLUSION

The present results revealed that losartan/thiazide combination therapy attenuated glomerular overload, indicating that this therapy may provide glomerular protection in patients with an elevated GFR without causing prolonged damage to renal function.

Angiotensin II blockade and renal protection

Current national guidelines have recommended the use of renin-angiotensin system inhibitors, including angiotensin II type 1 receptor blockers (ARBs), in preference to other antihypertensive agents for treating hypertensive patients with chronic kidney disease. However, the mechanisms underlying the renoprotective effects of ARBs are multiple and complex. Blood pressure reduction by systemic vasodilation with an ARB contributes to its beneficial effects in treating kidney disease. Furthermore, ARB-induced renal vasodilation results in an increase in renal blood flow, leading to improvement of renal ischemia and hypoxia. ARBs are also effective in reducing urinary albumin excretion through a reduction in intraglomerular pressure and the protection of glomerular endothelium and/or podocyte injuries. In addition to blocking angiotensin II-induced renal cell and tissue injuries, ARBs can decrease intrarenal angiotensin II levels by reducing proximal tubular angiotensinogen and production of collecting duct renin, as well as angiotensin II accumulation in the kidney. In this review, we will briefly summarize our current understanding of the pharmacological effects of an ARB in the kidney. We will also discuss the possible mechanisms responsible for the renoprotective effects of ARBs on type 2 diabetic nephropathy.

Renin-angiotensin-aldosterone system blockade and urinary albumin excretion in community-based patients with Type 2 diabetes: the Fremantle Diabetes Study

AIMS

To determine whether the reduction in urinary albumin excretion through renin-angiotensin-aldosterone system blockade found in intervention trials extends to community-based patients with Type 2 diabetes.

METHODS

We analysed data from 302 participants in the longitudinal observational Fremantle Diabetes Study who commenced angiotensin-converting enzyme inhibitor or angiotensin receptor blocker therapy during follow-up and who had an annual assessment on either side of this therapeutic change.

RESULTS

At baseline, the patients had a mean age of 63.8 years, a median diabetes duration of 4 years, a median HbA(1c) of 7.6% (60 mmol/mol) and a geometric mean (sd range) urinary albumin:creatinine ratio of 3.3 mg/mmol (0.8-13.1 mg/mmol). The percentages with normo-, micro- and macroalbuminuria were 49.0, 38.4 and 12.6%, respectively. During 6.1 ± 1.7 years of follow-up, initiation of renin-angiotensin-aldosterone system blockade was associated with a larger geometric mean (sd range) absolute albumin:creatinine ratio reduction in the patients with macroalbuminuria compared with those who had either normo- or microalbuminuria [-40.9 (-825.7 to 159.9) mg/mmol) vs. 1.7 (-1.6 to 20.0) mg/mmol and -0.5 (-23.0 to 39.5) mg/mmol, respectively; P < 0.001]. These changes remained significant after adjustment for changes in blood pressure and other potentially confounding variables, including drug dose and angiotensin-converting enzyme genotype. The post-treatment median albumin:creatinine ratios were 35.4 and 27.4% lower than before treatment in those with micro- or macroalbuminuria, respectively.

CONCLUSIONS

Usual-care initiation of renin-angiotensin-aldosterone system blockade confers a quantitatively similar renal benefit to that in intervention trials in Type 2 diabetes.

Microvascular complications and risk factors in patients with type 2 diabetes

AIM

To conduct a prospective study in patients with type 2 diabetes mellitus (T2DM) with no microvascular complications, analyzing the association between various baseline risk factors and development of microvascular complications at follow-up.

METHODS

A prospective, observational study in 376 patients with T2DM enrolled in 2004. The clinical end-point was urinary albumin excretion (UAE) > 30mg/24h and/or presence of retinopathy at follow-up in 2007. Baseline variables included age, gender, duration of T2DM, fasting plasma glucose, glycated hemoglobin (HbA(1c)), systolic and diastolic blood pressure, body weight, height, body mass index, waist circumference, total cholesterol, triglycerides, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), high sensitive C-reactive protein (hs-CRP), fibrinogen, UAE, creatinine, smoking status, exercise, alcohol consumption, use of hypoglycemic and lipid-lowering drugs, antihypertensive medications, and other data related to family history of diabetes and risk factors.

RESULTS

Ninety-five subjects (25.2%) developed a microvascular complication at the end of the follow-up period. In logistic regression analyses, the main independent risk factors were UAE >12mg/24h (odds ratio [OR]: 6.12; P=.000), hs-CRP> 3mg/L (OR: 3.00; P=.004), and hypertension (OR: 2.43; P=.023).

CONCLUSIONS

UAE levels higher than 12mg/24h, hs-CRP >3mg/L, and presence of hypertension were all independent risk factors for development of microvascular complications in patients with T2DM studied.

Renal effects of aliskiren compared with and in combination with irbesartan in patients with type 2 diabetes, hypertension, and albuminuria

OBJECTIVE

We investigated whether the antiproteinuric effect of the direct renin inhibitor aliskiren is comparable to that of irbesartan and the effect of the combination.

RESEARCH DESIGN AND METHODS

This was a double-blind, randomized, crossover trial. After a 1-month washout period, 26 patients with type 2 diabetes, hypertension, and albuminuria (>100 mg/day) were randomly assigned to four 2-month treatment periods in random order with placebo, 300 mg aliskiren once daily, 300 mg irbesartan once daily, or the combination using identical doses. Patients received furosemide in a stable dose throughout the study. The primary end point was a change in albuminuria. Secondary measures included change in 24-h blood pressure and glomerular filtration rate (GFR).

RESULTS

Placebo geometric mean albuminuria was 258 mg/day (range 84-2,361), mean +/- SD 24-h blood pressure was 140/73 +/- 15/8 mmHg, and GFR was 89 +/- 27 ml/min per 1.73 m(2). Aliskiren treatment reduced albuminuria by 48% (95% CI 27-62) compared with placebo (P < 0.001), not significantly different from the 58% (42-79) reduction with irbesartan treatment (P < 0.001 vs. placebo). Combination treatment reduced albuminuria by 71% (59-79), more than either monotherapy (P < 0.001 and P = 0.028). Fractional clearances of albumin were significantly reduced (46, 56, and 67% reduction vs. placebo). Twenty-four-hour blood pressure was reduced 3/4 mmHg by aliskiren (NS/P = 0.009), 12/5 mmHg by irbesartan (P < 0.001/P = 0.002), and 10/6 mmHg by the combination (P = 0.001/P < 0.001). GFR was significantly reduced 4.6 (95% CI 0.3-8.8) ml/min per 1.73 m(2) by aliskiren, 8.0 (3.6-12.3) ml/min per 1.73 m(2) by irbesartan, and 11.7 (7.4-15.9) ml/min per 1.73 m(2) by the combination.

CONCLUSIONS

The combination of aliskiren and irbesartan is more antiproteinuric in type 2 diabetic patients with albuminuria than monotherapy.

Aliskiren combined with losartan in type 2 diabetes and nephropathy

BACKGROUND

Diabetic nephropathy is the leading cause of end-stage renal disease in developed countries. We evaluated the renoprotective effects of dual blockade of the renin-angiotensin-aldosterone system by adding treatment with aliskiren, an oral direct renin inhibitor, to treatment with the maximal recommended dose of losartan (100 mg daily) and optimal antihypertensive therapy in patients who had hypertension and type 2 diabetes with nephropathy.

METHODS

We enrolled 599 patients in this multinational, randomized, double-blind study. After a 3-month, open-label, run-in period during which patients received 100 mg of losartan daily, patients were randomly assigned to receive 6 months of treatment with aliskiren (150 mg daily for 3 months, followed by an increase in dosage to 300 mg daily for another 3 months) or placebo, in addition to losartan. The primary outcome was a reduction in the ratio of albumin to creatinine, as measured in an early-morning urine sample, at 6 months.

RESULTS

The baseline characteristics of the two groups were similar. Treatment with 300 mg of aliskiren daily, as compared with placebo, reduced the mean urinary albumin-to-creatinine ratio by 20% (95% confidence interval, 9 to 30; P<0.001), with a reduction of 50% or more in 24.7% of the patients who received aliskiren as compared with 12.5% of those who received placebo (P<0.001). A small difference in blood pressure was seen between the treatment groups by the end of the study period (systolic, 2 mm Hg lower [P=0.07] and diastolic, 1 mm Hg lower [P=0.08] in the aliskiren group). The total numbers of adverse and serious adverse events were similar in the groups.

CONCLUSIONS

Aliskiren may have renoprotective effects that are independent of its blood-pressure-lowering effect in patients with hypertension, type 2 diabetes, and nephropathy who are receiving the recommended renoprotective treatment. (ClinicalTrials.gov number, NCT00097955 [ClinicalTrials.gov].).

Detailed glomerular ultrastructure in Japanese type 2 diabetic patients by the quick-freezing and deep-etching method

Mesangial expansion and glomerular basement membrane (GBM) thickening did not correlate with urinary albumin excretion (UAE) in type 2 diabetic patients in our previous studies; therefore, it was necessary to elucidate more detailed ultrastructural changes in the early stages of diabetic nephropathy (DN) in type 2 diabetic patients. The quick-freezing and deep-etching (QF-DE) method allows us to examine three-dimensional ultrastructures of human renal glomeruli in vivo at high resolution. The QF-DE method was applied to six type 2 diabetic patients without definable renal diseases other than DN. Four patients were normoalbuminuric (NA) and the other two were microalbuminuria (MA). Three control specimens were the normal parts from nephrectomies due to renal cell carcinomas. Electron microscopic morphometric analyses provided quantitative glomerular structural changes. Replica membranes were prepared by the QF-DE method, and diameters of mesh structures at the GBM and mesangial matrix (MM) were measured on electron micrographs as previously described. By the QF-DE method, both the GBM middle layer and MM were composed of polygonal meshwork structures. The mesh pores of the GBM and MM were more enlarged and irregular in shape in NA diabetic patients than those of the controls, and these ultrastructural changes became more obvious in MA patients. The mesh diameters of the GBM and MM in the diabetic patients were also larger than those of the controls. Such a mesh diameter of the GBM was well correlated with the amount of UAE, while the mesh diameter of MM showed a slight correlation with UAE. Although there were small number of subjects in the present study, the detailed ultrastructural changes in NA and MA type 2 diabetic patients, which had not been disclosed by conventional electron microscopy, were revealed by the QF-DE method. Increased mesh diameters of GBM might be related with the increase of UAE.

Proteinuria in diabetic kidney disease: a mechanistic viewpoint

Proteinuria is the hallmark of diabetic kidney disease (DKD) and is an independent risk factor for both renal disease progression, and cardiovascular disease. Although the characteristic pathological changes in DKD include thickening of the glomerular basement membrane and mesangial expansion, these changes per se do not readily explain how patients develop proteinuria. Recent advances in podocyte and glomerular endothelial cell biology have shifted our focus to also include these cells of the glomerular filtration barrier in the development of proteinuria in DKD. This review describes the pathophysiological mechanisms at a cellular level which explain why patients with DKD develop proteinuria.

Albuminuria, expression of nicotinamide adenine dinucleotide phosphate oxidase and monocyte chemoattractant protein-1 in the renal tubules of hypertensive Dahl salt-sensitive rats

In chronic renal diseases, experimental and human data suggest that excess albumin filtered through the glomerular capillary barrier is over-reabsorbed by proximal tubular cells, thereby activating these cells and upregulating the expression of chemokines. On the other hand, a high-salt diet has been shown to induce proteinuria in hypertensive Dahl salt-sensitive (DSS) rats, accompanied with the expression of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in the kidney. In the current study, we therefore examined albuminuria and the expressions of NADPH oxidase and monocyte chemoattractant protein-1 (MCP-1) in the renal tubular cells in hypertensive DSS rats, as well as the effects of the antioxidant N-acetylcysteine (NAC) on each of these parameters. DSS rats were fed a normal-salt diet (0.24% NaCl), a high-salt diet (8% NaCl), or a high-salt diet plus NAC supplementation (15 mg/mL drinking water) for 4 weeks. The high-salt diet provoked an increase in glomerular injuries accompanied with albuminuria and in urinary H2O2 and MCP-1 excretion. Immunohistochemical analysis showed the prominent expression of MCP-1 in the dilated tubular cells, where the NADPH oxidase subunit p47phox was also expressed. The current results suggest that albuminuria caused expression of NADPH oxidase and MCP-1 in the dilated renal tubules, resulting in interstitial inflammation and migration of mononuclear cells in DSS rats, because blockade of albuminuria by NAC counteracted the p47phox and MCP-1 expression.

Stratégies pour faire régresser les lésions de fibrose rénale

The deterioration of renal function in chronic kidney disease is related to the progression of renal fibrosis, which was long considered unavoidable. Today, the reversibility of renal fibrotic lesions is a reality, although still clinically rare. Because angiotensin II is highly profibrotic, blocking its action effectively protects the kidney, as numerous clinical trials have shown. The development of interstitial fibrosis is secondary to the epithelial-to-mesenchymal transition induced by transforming growth factor (TGF)-beta. Bone morphogenic protein-7 (BMP-7) and hepatocyte growth factor (HGF) induce the reverse transition and thus open up perspectives for treatment. Degradation of the extracellular matrix by matrix metalloproteinases or other enzymes is another therapeutic pathway. Renal regeneration may be promoted by modulation of hypoxia-inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF).

Microalbuminuria and the metabolic syndrome and its components in the Chinese population

BACKGROUND

Microalbuminuria and the metabolic syndrome (MetS) have both been linked to chronic kidney disease and cardiovascular disease. This study investigated the association between urinary albumin-to-creatinine ratio (ACR) and MetS and its components.

MATERIALS AND METHODS

A total of 2311 subjects aged 40 years and over were recruited in 2004 in a metropolitan city in Taiwan. The biochemical indices, such as fasting glucose levels, urinary albumin, urinary creatinine and anthropometric indices, were measured. We defined microalbuminuria as a urinary ACR ranging from 30 to 300 mg g(-1) creatinine. MetS was defined using the American Heart Association and the National Heart, Lung and Blood Institute (AHA/NHLBI) and the International Diabetes Federation (IDF) definitions. The relationship between MetS and microalbuminuria was examined using multiple logistical regression analysis.

RESULTS

Subjects with microalbuminuria had higher age, body mass index (BMI), waist circumference, blood pressure, fasting plasma glucose, triglycerides, total cholesterol (TCHOL)/high-density lipoprotein cholesterol (HDL-C) ratio, prevalence of diabetes mellitus and hypertension and lower HDL-C than subjects with normoalbuminuria. After adjusting for age and BMI, microalbuminuria was associated with the individual components of MetS, except in central obesity in women and elevated fasting glucose in men. After adjusting for age, BMI, smoking and alcohol consumption status, multiple logistical regressions revealed that microalbuminuria is strongly associated with MetS in both genders and according to both definitions. The odds ratio of having MetS using the AHA/NHLBI and IDF definition was 1.76 (1.16-2.67) and 1.73 (1.06-2.83) in men and 2.19 (1.38-3.50) and 2.09 (1.24-3.51) in women, respectively.

CONCLUSIONS

Microalbuminuria was strongly associated with MetS and its components. There is an increased likelihood of having MetS if subjects have microalbuminuria.

Decrease in tetrahydrobiopterin as a possible cause of nephropathy in type II diabetic rats

A decrease in renal synthesis of nitric oxide (NO) in the progression of diabetic nephropathy has been documented. As (6R)-5,6,7,8-tetrahydrobiopterin (BH4) is an essential cofactor of NO synthase, we investigated whether BH4 deficiency is involved in the pathogenesis of nephropathy. Ten-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats were used as a type II diabetic model, and Long-Evans Tokushima Otsuka (LETO) rats as the healthy controls. OLETF rats were orally treated with BH4 (10 mg/kg daily) or with water from 10 to 61 weeks of age. In another experiment, OLETF rats were treated orally with a calcium channel blocker, benidipine (5 mg/kg daily), or with 0.3% carboxymethyl cellulose (nontreated) from 10 to 52 weeks of age. Proteinuria was observed periodically, and at the end of the study, BH4 level and GTP cyclohydrolase I (GTPCH) activity in the kidney were measured. Proteinuria was observed at 13 weeks of age in the OLETF rats, and deteriorated until 61 weeks of age. Supplemental BH4 reduced the proteinuria. At 52 weeks of age, GTPCH activity and the BH4 level were decreased in the plasma and kidneys of OLETF rats, whereas they were significantly higher in the benidipine group than in the nontreated group. Proteinuria was milder in the benidipine group than in the nontreated group, without a concomitant decrease in blood pressure. Histologically observed glomerulosclerosis was mild in the BH4 and benidipine groups. In type II diabetic rats, renal BH4 is considered to play a crucial role in the pathogenesis of diabetic nephropathy. Benidipine was found to preserve BH4 levels, suggesting therapeutic renoprotective effects.

Glomerular hyperfiltration in non-proteinuric and non-hypertensive Japanese type 2 diabetic patients

Glomerular hyperfiltration (GHF) may be an important factor in the initiation of glomerular damage and in predisposing diabetic patients to the later development of diabetic nephropathy (DN). Previous reports show wide range of prevalence of GHF in type 2 diabetic patients. This cross-sectional study was designed to determine the prevalence of GHF at an early stage of DN in Japanese type 2 diabetic patients and to investigate the relationships between clinical variables and GHF. We measured the glomerular filtration rate (GFR) using the plasma clearance of iohexol in 56 control subjects and 93 type 2 diabetic patients without hypertension or overt proteinuria. We used Altman's method to calculate the age-adjusted 95% reference ranges for GFR from the data of control subjects and classified GHF in type 2 diabetics from the reference ranges. Hyperfiltrators (defined as GFR > mean GFR + 1.96 S.D. of control subjects) was found in 17% patients (16/93). Other 77 patients (83%) were normofiltrators (defined as GFR< or = mean GFR + 1.96 S.D. of control subjects). GFR values, both in hyperfiltrators and normofiltrators, were 140.5 +/- 14.6 and 98.8 +/- 14.0 ml/min/1.73 m2, respectively. Age, sex, BMI, blood pressure, albumin excretion rate, and frequency of microalbuminuria did not differ between the hyperfiltrators and normofiltrators. Fasting plasma glucose and hemoglobin A1c were significantly higher in the hyperfiltrators than the normofiltrators (P<0.001 and 0.004, respectively). GHF exists among Japanese type 2 diabetic patients with no evidence of overt proteinuria or hypertension. Glycemic control might be a significant determinant of GHF in these patients.

Enhanced renoprotective effects of ultrahigh doses of irbesartan in patients with type 2 diabetes and microalbuminuria

BACKGROUND

The purpose of this study was to evaluate the renoprotective effect as reflected by short-term changes in albuminuria of ultrahigh doses of irbesartan in type 2 diabetic patients with microalbuminuria.

METHODS

This double-masked randomized crossover trial included 52 (41 males) hypertensive type 2 diabetic patients with microalbuminuria on ongoing antihypertensive medication. At inclusion, previous antihypertensive treatment was discontinued and replaced with bendroflumethiazide, 5 mg once daily, for the entire study. Following 2 months wash-out (baseline), patients were treated randomly with irbesartan 300, 600, and 900 mg once daily, each dose for 2 months. End points evaluated at the end of each study period included urinary albumin excretion rate (UAE) (mean of three 24-hour collections), 24-hour ambulatory blood pressure, and glomerular filtration rate (GFR) [chromium 51 ethylenediaminetetraacetic acid (51Cr-EDTA)].

RESULTS

Baseline values were: 24-hour UAE [geometric mean (95% CI)] 134 (103 to 170) mg/24 hours, ambulatory blood pressure [mean (SD)] 140 (10)/77 (7) mm Hg, and GFR 103 (19) mL/min/1.73 m2. All doses of irbesartan significantly reduced UAE, ambulatory blood pressure, and GFR from baseline. Reductions in UAE from baseline were 52% (46% to 57%), 49% (43% to 54%), and 59% (54% to 63%) with increasing doses of irbesartan (P < 0.01). UAE was reduced significantly more by irbesartan 900 mg compared with lower doses with an additional reduction in UAE of 15% (2% to 26%) by irbesartan 900 mg compared with 300 mg (P = 0.02). The greater reduction in albuminuria by irbesartan 900 vs. 300 mg was more pronounced in patients with UAE during irbesartan 300 mg above vs. below the median [31% (18% to 42%) vs. -9% (-25% to 6%), respectively (P < 0.05)]. With increasing doses systolic ambulatory blood pressure was reduced from baseline by 8 (4 to 12), 9 (5 to 13), and 9 (5 to13) mm Hg, and diastolic ambulatory blood pressure by 6 (4 to 7), 7 (6 to 9), and 7 (6 to 9) mm Hg (NS between doses).

CONCLUSION

Ultrahigh dosing of irbesartan (900 mg once daily) is generally safe and offers additional renoprotection independent of changes in systemic blood pressure and GFR in comparison to the currently recommended dose of 300 mg.

Beneficial impact of spironolactone in diabetic nephropathy

BACKGROUND

Aldosterone has been suggested to play a role in the initiation and progression of diabetic nephropathy. Currently recommended treatment with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers [renin-angiotensin system (RAS) blockade] does not suppress circulating aldosterone sufficiently. We therefore aimed to evaluate the short-term effect of aldosterone antagonism with spironolactone on albuminuria and blood pressure in diabetic nephropathy.

METHODS

Twenty Caucasian type 1 diabetic patients with persistent macroalbuminuria despite antihypertensive treatment, including RAS blockade, completed this double-masked, randomized cross-over trial. Patients were treated in random order with spironolactone 25 mg once daily and matched placebo for two months, respectively, on top of usual antihypertensive treatment. After each treatment period albuminuria, 24-hour blood pressure, and glomerular filtration rate (GFR) were determined.

RESULTS

Spironolactone on top of usual antihypertensive treatment induced a 30% (95% CI 17 to 41) reduction in albuminuria from [geometric mean (95% CI)] 831 (624 to 1106) mg/24-hour on placebo treatment (P < 0.001), and a reduction in fractional albumin clearance of 35% (20 to 46, P < 0.001). Twenty-four-hour blood pressure showed an insignificant reduction of [mean reduction (95% CI)] 8 (-1 to 17)/3 (-0.2 to 7) mm Hg (P < 0.10). There was an insignificant reversible reduction in GFR during treatment with spironolactone. On spironolactone treatment, one patient was excluded due to hyperkalemia (plasma potassium 5.7 mmol/L) and one due to orthostatic dizziness. Otherwise treatment was well tolerated.

CONCLUSION

Our results suggest that spironolactone treatment on top of recommended antihypertensive treatment reduces blood pressure and may offer additional renoprotection in type 1 diabetic patients with diabetic nephropathy.

Preventing end stage renal disease in diabetic patients--genetic aspect (part I)

Diabetic nephropathy is a major cause of diabetes- related morbidity and mortality; however the clinical course of the disease and the renal prognosis is highly variable among individuals. The current review will discuss the genetic influence on the development of end stage renal disease (ESRD) in diabetic patients and potential improvements to the current treatment strategy to slow the loss of kidney function in these patients. In this first part, the growing evidence that glucose-induced activation of the intra-renal and systemic renin-angiotensin systems plays an essential role in processes leading to destruction of renal function is summarised. Genetic variations, especially the angiotensin-converting enzyme (ACE)/ID polymorphisms in the gene coding for ACE, are involved in activation of the renin-angiotensin system and seem to influence the clinical course of diabetic nephropathy during treatment with ACE inhibitors. In addition, this polymorphism may interact with other polymorphisms within the renin-angiotensin system, leading to high risk of ESRD. As new genetic approaches and methods develop, further understanding of diabetic nephropathy will evolve and genotyping will help prevent ESRD in diabetic patients.

Microalbuminuria and risk factors in type 1 and type 2 diabetic patients

A prospective study of normoalbuminuric diabetic patients was performed between 1997 and 2002 on 4097 type 1 and 6513 type 2 diabetic patients from the Swedish National Diabetes Register (NDR); mean study period, 4.6 years. The strongest independent baseline risk factors for the development of microalbuminuria (20-200 microg/min) were elevated HbA(1c) and diabetes duration in both types 1 and 2 diabetic patients. Other risk factors were high BMI, elevated systolic and diastolic BP in type 2 patients, and antihypertensive therapy in type 1 patients. A subsequent larger cross-sectional study in 2002 showed that established microalbuminuria was independently associated with HbA(1c), diabetes duration, systolic BP, BMI, smoking and triglycerides in types 1 and 2 diabetic patients, and also with HDL-cholesterol in type 2 patients. Relatively few types 1 and 2 patients with microalbuminuria achieved treatment targets of HbA(1c) < 6.5% (21-48%), BP < 130/85 mmHg (33-13%), cholesterol < 5 mmol/l (48-46%), triglycerides < 1.7 mmol/l (83-48%) and BMI < 25 kg/m(2) (50-18%), respectively. In conclusion, high HbA(1c), BP and BMI were independent risk factors for the development of microalbuminuria in types 1 and 2 diabetic patients. These risk factors as well as triglycerides, HDL-cholesterol and smoking were independently associated with established microalbuminuria. Treatment targets were achieved by a relatively few patients with microalbuminuria.

Microalbuminuria, renal function and development of sustained hypertension

OBJECTIVE

Microalbuminuria (MA) is a marker of adverse outcome in hypertension. The aim of this study was to investigate the association of MA with cardiovascular risk factors and glomerular hyperfiltration in the early stage of hypertension and to assess its predictive value for the development of sustained hypertension requiring antihypertensive treatment.

DESIGN AND PARTICIPANTS

We studied 1041 young stage 1 hypertensive subjects. Study variables were 24-h ambulatory blood pressure and heart rate, anthropometric measures, metabolic variables, creatinine clearance and lifestyle factors analyzed as a function of ascending urinary albumin measured from 24-h collections. Subjects were followed until they developed sustained hypertension and were eligible for antihypertensive medication according to current guidelines.

SETTING

Seventeen outpatient clinics in Italy.

RESULTS

Eighty-five percent of the subjects were normoalbuminuric, 9% had borderline MA, and 6% had overt MA. No between-group differences were found for age, body mass index, heart rate, lifestyle factors and biochemistry in both genders. Creatinine clearance was greater in the subjects with overt MA and borderline MA than in the normoalbuminuric subjects (P = 0.003 and 0.011, respectively). In a two-way ANCOVA, microalbuminuric subjects both with hyperfiltration (P < 0.001) and with normal filtration (P = 0.04) had higher 24-h systolic blood pressure than subjects with normoalbuminuria and normal filtration. In a Cox analysis, neither MA nor hyperfiltration were significant predictors of development of sustained hypertension.

CONCLUSION

MA is not associated with an adverse metabolic risk profile in the early stage of hypertension. MA is associated with greater hemodynamic load and with glomerular hyperfiltration in this clinical setting, but does not help in predicting those subjects destined to develop sustained hypertension requiring antihypertensive therapy.

Angiotensin receptor blockers in diabetic nephropathy: renal and cardiovascular end points

The activity of the renin-angiotensin-aldosterone system (RAAS) is elevated both in the circulation and in the renal tissue of diabetic and nondiabetic nephropathies. The increased RAAS activity plays an important role in the hemodynamic and nonhemodynamic pathogenetic mechanisms involved in kidney disease. Previous studies have demonstrated that albuminuria is not only a marker of glomerular lesions, but also a progression promoter, and finally a powerful predictor of the long-term beneficial effect of blood pressure-lowering therapy. Randomized crossover and parallel blind studies in patients with diabetic nephropathy have demonstrated that angiotensin II receptor blockers (ARB) induce favorable changes in systemic blood pressure, renal hemodynamics, and proteinuria similar to those induced by angiotensin-converting enzyme (ACE) inhibition. Studies have revealed the optimal renoprotective dose for some ARBs; however, additional dose titration studies are urgently needed to obtain the maximum benefit of this valuable new class of compounds. The combination of ARB and ACE inhibition is well tolerated and even more effective than monotherapy in reducing systemic blood pressure and albuminuria in diabetic nephropathy. In addition, dual RAAS blockade is safe and well tolerated. Impaired autoregulation of glomerular filtration rate (GFR); demonstrated with some blood pressure-lowering agents implies disturbances in the downstream transmission of the systemic blood pressure into the glomerulus, leading to capillary hypertension or hypotension depending of the level of blood pressure. ARB does not interfere with GFR autoregulation in hypertensive diabetic patients. In contrast to previous observational studies with ACE inhibition, long-term treatment with ARB has similar beneficial renoprotective effect on progression of diabetic kidney disease in hypertensive diabetic patients with ACE II and DD genotypes. ARB can prevent/delay development of diabetic nephropathy independently of its beneficial blood pressure-lowering effect in patients with type 2 diabetes and microalbuminuria. Recently, two landmark studies led to the following conclusion: "Losartan and Irbesartan conferred significant renal benefit in patients with type 2 diabetes and nephropathy. This protection is independent of the reduction in blood pressure it causes. The ARB is generally safe and well tolerated." A recent metaanalysis indicates that ARBs reduce cardiovascular events mainly because of reduction in first hospitalization for congestive heart failure in hypertensive type 2 diabetic patients with albuminuria. The studies mentioned here suggest that ARB represents a beneficial treatment of hypertension and proteinuria in incipient and overt diabetic nephropathy.

Effect of sodium intake on blood pressure and albuminuria in Type 2 diabetic patients: the role of insulin resistance

AIMS/HYPOTHESIS

This study was done to measure the effect of Na+ intake on blood pressure and albuminuria, in relation with insulin sensitivity and kidney haemodynamics, in Type 2 diabetic patients with and without microalbuminuria.

METHODS

Type 2 diabetic patients, 20 with microalbuminuria, 21 without, spent two consecutive 7-day periods, one on a high (250 mmol), the other on a low-Na+ (20 mmol) diet. Body weight, 24-h blood pressure and albuminuria were measured at the end of each period. At the end of high-Na+ diet insulin sensitivity (euglycaemic insulin clamp; 2 mU.kg(-1).min(-1)) and kidney haemodynamics were measured in nine patients from each group.

RESULTS

Switching from low to high-Na+ diet resulted in an increase in blood pressure (7.4+/-4.7 mmHg; p<0.001), body weight (1.9+/-0.4 kg; p<0.05) and albuminuria [from 80 (31-183) microg/min to 101 (27-965) microg/min; p<0.01) in patients with microalbuminuria. No changes occurred in patients without microalbuminuria. Patients with microalbuminuria also had greater intraglomerular pressure (44+/-1 mmHg vs 36+/-1; p<0.001), calculated from glomerular filtration rate, renal plasma flow, plasma protein concentration and the relationship between pressure and natriuresis. In these patients insulin sensitivity was lower (5.16+/-49 vs 7.36+/-0.63 mg.kg(-1).min(-1); p=0.007). Urinary albumin excretion (r=0.40; p=0.009) and insulin sensitivity (r=-0.59; p=0.01) were correlated with intraglomerular pressure.

CONCLUSION/INTERPRETATION

High salt intake increases blood pressure and albuminuria in Type 2 diabetic patients with microalbuminuria. These responses are associated with insulin resistance and increased glomerular pressure. Insulin resistance could contribute to greater salt sensitivity, increased glomerular pressure and albuminuria.

Kidney function during and after withdrawal of long-term irbesartan treatment in patients with type 2 diabetes and microalbuminuria

OBJECTIVE

Irbesartan is renoprotective in patients with type 2 diabetes and microalbuminuria. Whether the observed reduction in microalbuminuria is reversible (hemodynamic) or persistent (glomerular structural/biochemical normalization) after prolonged antihypertensive treatment is unknown. Therefore, the present substudy of the Irbesartan in Patients with Type 2 Diabetes and Microalbuminuria Study (IRMA-2) investigated the reversibility of kidney function changes after withdrawal of 2 years' antihypertensive treatment.

RESEARCH DESIGN AND METHODS

The substudy included 133 hypertensive type 2 diabetic patients with persistent microalbuminuria in IRMA-2, randomized to double-masked treatment with either placebo, irbesartan 150 mg, or irbesartan 300 mg o.d. for 2 years. Arterial blood pressure, overnight urinary albumin excretion rate, and glomerular filtration rate (GFR) were determined repeatedly.

RESULTS

Baseline characteristics were similar in the placebo, irbesartan 150-mg, and irbesartan 300-mg groups. At the end of the study, mean arterial blood pressure (MABP) was similarly lowered to 105 +/- 2 (mean +/- SE), 103 +/- 2, and 102 +/- 2 mmHg, respectively (P < 0.05 versus baseline), and urinary albumin excretion rate reduced by 8% (-16 to 27) (NS), 34% (95% CI 8-53), and 60% (46-70) (P < 0.05). Rates of decline in GFR were 1.3 +/- 0.7, 1.2 +/- 0.7, and 1.0 +/- 0.8 ml. min(-1). 1.73 m(-2) per month, respectively, during the initial 3 months of the study and 0.3 +/- 0.1, 0.3 +/- 0.1, and 0.4 +/- 0.1 ml. min(-1). 1.73 m(-2) per month in the remaining study period. One month after withdrawal of all antihypertensive medication, MABP remained unchanged in the placebo group, 105 +/- 2 mmHg, but increased significantly in the irbesartan groups, to 109 +/- 2 and 108 +/- 2 mmHg, respectively. Compared with baseline, urinary albumin excretion rate was increased by 14% (-17 to 54) in the placebo group and by 11% (-26 to 65) in the irbesartan 150-mg group but was persistently reduced by 47% (24-73) in the irbesartan 300-mg group (P < 0.05). GFR levels increased to baseline values in the placebo group and approached initial levels in irbesartan groups.

CONCLUSIONS

Persistent reduction of microalbuminuria after withdrawal of all antihypertensive treatment suggests that high-dose irbesartan treatment confers long-term renoprotective effects.

Effect of short-term hyperglycaemia on haemodynamics in type 1 diabetic patients

OBJECTIVES

Mechanisms underlying glucose-mediated development and progression of diabetic complications are incompletely understood. We tested the impact of short-term hyperglycaemia on systemic blood pressure and regulatory hormones in type 1 diabetic patients.

DESIGN AND METHODS

We included 18 patients [13 men, mean (SEM) diabetes duration 10 (1) years] without signs of autonomic neuropathy or renal complications in a randomized single-blinded cross-over trial using insulin-glucose clamp technique. Patients were clamped for 90 min to blood glucose of 5 mmol L(-1) (euglycaemia) and 15 mmol L(-1) (hyperglycaemia) in random order. Blood pressure was measured noninvasively every 5 min (Takeda TM2421 device). Regulatory hormones were determined at the end of each clamp period.

RESULTS

Systolic blood pressure increased [mean (95% CI)] 3 (1, 5) mmHg during hyperglycaemia from 123 (SEM 2) during euglycaemia, P=0.01. Diastolic blood pressure remained unchanged at 78 (2) mmHg. Hyperglycaemia reduced plasma concentrations of: renin [14 (4, 23)%, P=0.02], angiotensin II [17 (8, 25)%, P<0.01] and adrenaline [20 (10, 29)%, P<0.01]. Plasma concentration of atrial natriuretic peptide increased by 11 (6, 17) pg mL(-1) (P<0.01) from 43 (2) pg mL(-1). We calculated a median (range) increase in extracellular volume and plasma volume (PV) of 2.6 (0.7-5.3)% and 5.0 (-4.7 to 8.6)%, respectively.

CONCLUSIONS

In type 1 diabetic patients without signs of autonomic neuropathy short-term hyperglycaemia induced a modest increase in systolic blood pressure and suppression of the renin-angiotensin system, possibly caused by PV expansion because of fluid shift from intra- to extracellular compartment.

Renoprotective effects of adding angiotensin II receptor blocker to maximal recommended doses of ACE inhibitor in diabetic nephropathy: a randomized double-blind crossover trial

OBJECTIVE

We evaluated the renoprotective effects as reflected by short-term changes in albuminuria of dual blockade of the renin-angiotensin system (RAS) by adding an angiotensin II receptor blocker (ARB) to treatment with maximal recommended doses of an ACE inhibitor (ACEI) in patients with type 2 diabetes and nephropathy.

RESEARCH DESIGN AND METHODS

A total of 20 patients (17 men and 3 women) with type 2 diabetes along with hypertension and nephropathy were enrolled in this double-blind, randomized, two-period, crossover trial of 8 weeks of treatment with the ARB candesartan 16 mg daily and placebo added in random order to existing treatment with lisinopril/enalapril 40 mg daily or captopril 150 mg daily. At the end of each treatment period, we evaluated albuminuria in three 24-h urinary collections by turbidimetry, 24-h ambulatory blood pressure (ABP) using the Takeda-TM2420, and glomerular filtration rate (GFR) by the (51)Cr-EDTA plasma-clearance technique.

RESULTS

During monoblockade of the RAS by ACEI treatment, albuminuria was 706 (349-1,219) mg/24 h [geometric mean (IQR)]; 24-h ABP was 138 +/- 3/72 +/- 2 mmHg (mean +/- SE); and GFR was 77 +/- 6 ml x min(-1) x 1.73 m(-2) (mean +/- SE). During dual blockade of the RAS by addition of candesartan 16 mg daily, there was a mean (95% CI) reduction in albuminuria of 28 (17-38) compared with ACEI alone (P < 0.001). There was a modest reduction in systolic/diastolic 24-h ABP of 3/2 mmHg (-2 to 8 systolic, -2 to 5 diastolic; NS). Changes in albuminuria did not correlate to changes in ABP. Addition of candesartan 16 mg daily induced a small, insignificant decrease in GFR of 4 (-1 to 9) ml x min(-1) x 1.73 m(-2).

CONCLUSIONS

Dual blockade of the RAS provides superior short-term renoprotection independent of systemic blood pressure changes in comparison with maximally recommended doses of ACEI in patients with type 2 diabetes as well as nephropathy.

Microalbuminuria and hypertension with focus on type 1 and type 2 diabetes

Microalbuminuria and hypertension with Over the past decade, there has been considerable focus on the concept of microalbuminuria, not only because it predicts renal disease in type 1 and type 2 diabetes, but also because it relates to premature mortality in the diabetic and in the general population. More importantly, intervention at this stage is now possible with the perspective of preserving glomerular filtration rate (GFR) and ameliorating cardiovascular disease and ensuing strong end-points. INITIAL STUDIES: The concept of microalbuminuria was introduced about 20 years ago and since then there has been a multitude of studies and papers on this subject using the original definition, but not always, in the US. Before that time it was suggested, mainly from the US, that diabetic renal disease was an untreatable relentlessly progressive condition.

GENETIC STUDIES

There is an overwhelming number of studies on genetics and diabetes and also covering the genetics of diabetic complications including nephropathy. However, so far the results are extremely disappointing. Patients at risk cannot be identified and genetic analyses are of no value as a guide to treatment. The notion that the development of complications is controlled mainly by a special genetic pattern is increasingly doubtful. In genetic studies, it is rather phenotypic well-accepted risk factors that dominate. STRUCTURAL BASIS OF MICROALBUMINURIA: Patients with microalbuminuria have significant abnormalities in the kidney, including glomeruli. This is quite clear in patients with type 1 diabetes, but is also seen in type 2 diabetes, where on the other hand, other risk factors such as hypertension and dyslipidaemia also seem to be of importance, including loss of autoregulation. Renal biopsies are generally not indicated in the management of diabetic patients. MICROALBUMINURIA AND EARLY MORTALITY: It is quite clear that microalbuminuria predicts early mortality both in type 1 and type 2 diabetes. The association to other risk factors may partly explain this--but this does not account for the whole picture. Endothelial dysfunction as well as inflammatory and arteriosclerotic abnormalities in blood vessels may be a relevant hypothesis that needs to be further explored along with other possibilities. CLINICAL COURSE AND ASSOCIATED ABNORMALITIES: The risk factor for progression in normoalbuminuric patients to microalbuminuria is higher than normal albumin excretion (strongest factor), poor glycaemic control, elevated blood pressure, and to some extent smoking. The clinical course of microalbuminuria is usually progressive, but with the more effective intervention now available we encounter that the so-called natural history (without intervention) is increasingly difficult to study. Microalbuminuria is clearly associated with a number of abnormalities, almost in all organs, but GFR is generally well preserved in spite of more advanced structural lesions. Therefore, microalbuminuria is an important marker for more pronounced diabetic vascular disease in general as well as for nephropathy. Regression to normoalbuminuria only rarely occurs during standard unchanged nonintensive treatment. TREATMENT STRATEGIES: The best possible glycaemic control is important in preventing and ameliorating the course of normo- and micro-albuminuria. Another major treatment strategy, especially in microalbuminuric patients, is antihypertensive treatment including inhibition of the renal angiotensin aldosterone system. Numerous new studies are available, both in type 1 and type 2 diabetes, documenting that not only microalbuminuria but also renal and cardiovascular complications in these patient are also far better controlled by early detection and treatment. Therefore, screening for microalbuminuria should be a strategy in all diabetes management followed by effective intervention as outlined in this paper.

Capillary pressure in subjects with type 2 diabetes and hypertension and the effect of antihypertensive therapy

Raised capillary pressure has been implicated in the formation of diabetic microangiopathy in type I diabetes, in which it is elevated in those with the earliest signs of diabetic kidney disease but remains normal in those without complications. In subjects with type 2 diabetes without complications, capillary pressure is normal, although alterations in the pressure waveforms suggested enhanced wave reflections. The nature of skin capillary pressure in subjects with type 2 diabetes and hypertension remains to be elucidated, as does the effect of blood pressure-lowering therapy on capillary pressure in these subjects. Three studies were performed in well-matched groups. First, capillary pressure was elevated in hypertensive subjects with type 2 diabetes compared with normotensive subjects with type 2 diabetes (20.2 [17.4 to 22.7] mm Hg versus 17.7 [16.1 to 18.9] mm Hg, respectively, P<0.03, Mann-Whitney U test). Second, no significant difference was detected between hypertensive subjects with type 2 diabetes and hypertensive subjects without type 2 diabetes (19.4 [15.8 to 21.3] mm Hg versus 17.2 [15.1 to 19.8] mm Hg, respectively, P=0.5, Mann-Whitney U test). Finally, patients with type 2 diabetes were recruited to a case-control study. Seven subjects received blood pressure-lowering therapy and 8 did not. Therapy reduced capillary pressure from 18.2 [15.8 to 20.1] mm Hg to 15.9 [15.4 to 17.0] mm Hg (P=0.024 ANOVA), in contrast to the lack of effect of time alone. Mean arterial pressure was reduced from 110 [102 to 115] mm Hg to 105 [101 to 111] mm Hg (P=0.006, ANOVA). These findings provide a plausible mechanism by which reducing arterial hypertension may reduce the risk of microangiopathy in type 2 diabetes.

ACE inhibitor intervention in Type 1 diabetes with low grade microalbuminuria

Several clinical trials have consistently shown that antihypertensive treatment, particularly with angiotensin-converting enzyme inhibitors (ACE-I) reduces albuminuria in Type 1 diabetic patients. More recently, data on the beneficial effects of ACE-I on the preservation of glomerular filtration rate and renal ultrastructure have emerged. However, in general, these trials have recruited a wide spectrum of diabetics, including some patients with severe albuminuria. Thus, the question of the ideal stage at which to instigate what is likely to be lifelong therapy in young people still remains unanswered. Exercise is known to significantly increase both blood pressure (BP) and urinary albumin excretion (UAE), both of which are important determinants of progression of nephropathy in diabetes. Thus, it is possible that exercise may have an adverse effect on diabetic renal disease. The effects of ACE-I on exercise-BP and exercise-UAE in microalbuminuric Type 1 diabetic patients has not been examined in long-term placebo-controlled studies. In the second part of this two-part review, we examine the effects of the ACE-I, lisinopril, 20 mg o.d. for two years, in comparison with placebo, on UAE, 24-hour ambulatory BP, exercise-BP, exercise-UAE and renal haemodynamics in 22 patients with Type 1 diabetes and low-grade microalbuminuria. We further discuss the effects of ACE-I on nephropathy and other complications of diabetes.

The effect of ramipril on albumin excretion in diabetes and hypertension: the role of increased lysosomal activity and decreased transforming growth factor-beta expression

OBJECTIVES

Albumin excretion is modulated post-filtration by lysosomal processing that produces a spectrum of albumin-derived material in urine, much of which is not detected by conventional immunoassays. This study aimed to determine the efficacy of ramipril treatment (+ RAM) after 24 weeks on total albumin excretion (intact plus albumin-derived peptides) in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats with (d) and without (c) diabetes.

METHODS

Intact albumin excretion was analysed by radioimmunoassay and total albumin excretion was analysed by measuring radioactivity derived from circulating [ C]albumin. Renal lysosomal activity was determined by urinary [ H]dextran sulphate desulphation. Renal transforming growth factor-beta 1 (TGF-beta 1), TGF-beta inducible gene-h3 (beta ig-h3) and angiotensinogen mRNA production were analysed by real time reverse transcriptase-polymerase chain reaction.

RESULTS

Hypertension (SHR-c and SHR-d) resulted in a significant increase in intact albumin excretion, which was significantly reduced by ramipril treatment (P < 0.05 for SHR-c + RAM and 0.001 for SHR-d + RAM compared to non-treated). This was accompanied by a significant decrease in blood pressure (P < 0.001 for SHR-c + RAM and SHR-d + RAM), renal beta ig-h3 mRNA production (P < 0.05 for SHR-c + RAM and SHR-d + RAM), and an increase in lysosomal activity. Diabetes (WKY-d and SHR-d) primarily caused a significant increase in total albumin excretion, predominantly in the form of albumin-derived fragments in the WKY-d group and intact albumin in the SHR-d group. Ramipril treatment reduced total albumin excretion in the WKY-d + RAM group (P < 0.001).

CONCLUSIONS

Ramipril prevents increases in both intact albumin and total albumin excretion in hypertensive and diabetic states, respectively.

Optimal dose of candesartan for renoprotection in type 2 diabetic patients with nephropathy: a double-blind randomized cross-over study

OBJECTIVE

We evaluated the optimal dose of the angiotensin II receptor antagonist candesartan cilexetil for renoprotection as reflected by short-term changes in albuminuria in hypertensive type 2 diabetic patients with nephropathy.

RESEARCH DESIGN AND METHODS

A total of 23 hypertensive patients with type 2 diabetes and nephropathy were enrolled in this double-blind randomized cross-over trial with four treatment periods, each lasting 2 months. Each patient received placebo and candesartan: 8, 16, and 32 mg daily in random order. Antihypertensive medication was discontinued before enrollment, except for long-acting furosemide, which all patients received throughout the study in median (range) doses of 40 (30-160) mg daily. End points were albuminuria (turbidimetry), 24-h blood pressure (BP) (Takeda-TM2420), and glomerular filtration rate (GFR) (51Cr-labeled EDTA plasma clearance technique).

RESULTS

Values obtained during placebo treatment: albuminuria [geometric mean (95% CI)] 700 (486-1,007) mg/24-h, 24-h BP (mean +/- SE) 147 +/- 4/78 +/- 2 mmHg, and GFR 84 +/- 6 ml/min/1.73 m2. All three doses of candesartan significantly reduced albuminuria and 24-h BP compared with placebo. Mean (95% CI) reductions in albuminuria were 33% (21-43), 59% (52-65), and 52% (44-59) with increasing doses of candesartan. Albuminuria was reduced significantly more by the two highest doses than by the lowest dose (P < 0.01); 24-h systolic BP was reduced by 9 (2-16), 9 (2-16), and 13 (6-20) mmHg and 24-h diastolic BP was reduced by 5 (2-8), 4 (1-7), and 6 (3-9) mmHg with increasing doses of candesartan. There were no significant differences in the reductions in BP between the three doses. GFR was decreased by approximately 6 ml/min/1.73 m2 by all three doses of candesartan (P < 0.05 versus placebo).

CONCLUSIONS

The optimal dose of candesartan is 16 mg daily for renoprotection, as reflected by short-term reduction in albuminuria, in hypertensive type 2 diabetic patients with nephropathy.

Macular edema reflects generalized vascular hyperpermeability in type 2 diabetic patients with retinopathy

OBJECTIVE

Diabetic maculopathy (DMa) is the most prevalent sight-threatening type of retinopathy in type 2 diabetes and a leading cause of visual loss in the western world. The disease is characterized by hyperpermeability of retinal blood vessels and subsequent formation of hard exudates and macular edema, the degree of which can be estimated by measurement of retinal thickness. We examined associations between retinal thickness as evaluated by optical coherence tomography scanning (OCT), glomerular leakage as evaluated by urinary albumin excretion rate (UAE), and general vascular leakage as evaluated by the transcapillary escape rate of albumin (TER(alb)) in type 2 diabetic patients with and without DMa.

RESEARCH DESIGN AND METHODS

In 20 type 2 diabetic patients with DMa and 20 type 2 diabetic patients without retinopathy matched for age, sex, and duration of diabetes, we performed OCT, fundus photography, fluorescein angiography, and 24-h ambulatory blood pressure measurement. UAE was determined by radioimmunoassay. TER(alb) was determined as the initial disappearance of intravenously injected (125)I-labeled human serum albumin.

RESULTS

Patients with diabetic maculopathy had higher HbA(1c) (8.5 +/- 1.5 vs. 7.4 +/- 1.2%, P < 0.05) and higher total cholesterol (5.8 +/- 0.7 vs. 5.2 +/- 0.9 mmol/l, P < 0.05) than patients without retinopathy. UAE was higher in the DMa group than in the group with no retinopathy (9.3 x// 3.1 vs. 3.9 x// 1.9 micro g/min, P < 0.01). There was no difference in TER(alb) between the two groups (6.0 +/- 1.6 vs. 6.6 +/- 1.5%, NS). In the group with DMa, OCT, TER(alb), and UAE correlated significantly (OCT versus TER(alb): r = 0.55, P < 0.05; OCT versus UAE: r = 0.58, P < 0.01; UAE versus TER(alb): r = 0.81, P < 0.01). Conversely, there were no correlations between these three parameters in the group without retinopathy.

CONCLUSIONS

Macular edema seems to reflect a generalized vascular leakage in type 2 diabetic patients.

Effects of benidipine on glomerular hemodynamics and proteinuria in patients with nondiabetic nephropathy

Experimental studies suggest that some long-acting calcium antagonists decrease glomerular hypertension and suppress the progression of nephropathy, but clinical evidence is lacking. To investigate clinically whether a long-acting calcium antagonist, benidipine, lowers glomerular capillary hydraulic pressure via a decrease in efferent arteriolar resistance and decreases proteinuria, we examined hypertensive patients with nondiabetic nephropathy. The subjects were 7 patients with chronic glomerulonephritis or glomerulosclerosis. Before and during the administration of benidipine (4 mg/day), systemic pressure, glomerular hemodynamics, the sodium sensitivity index (reciprocal of the pressure-natriuresis curve), and urinary excretion of proteins (total protein, albumin, and immunoglobulin G) were investigated. The glomerular hemodynamics in terms of glomerular capillary hydraulic pressure and resistance of afferent and efferent arterioles were calculated from the renal clearance, plasma total protein concentration, and pressure-natriuresis relationship. Benidipine lowered the mean arterial pressure from 105 +/-5 to 99 +/- 4 mm Hg (p = 0.002; mean +/- SD) and glomerular pressure from 48 +/- 8 to 39 +/- 5 mmHg (p = 0.006) by decreasing the resistance of efferent arterioles. Benidipine made the pressure-natriuresis curve steeper and decreased the median sodium sensitivity index from 0.099 (0.084 and 0.117; 25th and 75th percentiles) to 0.048 (0.017 and 0.058; p = 0.018). Urinary excretion of proteins did not change. Our clinical study showed that benidipine lowered the glomerular pressure by decreasing the resistance of efferent arterioles and decreased the sodium sensitivity of blood pressure, but did not affect proteinuria in patients with nondiabetic nephropathy.

Diurnal variations of glomerular filtration rate and albuminuria in diabetic nephropathy

BACKGROUND

The aim of our study was to evaluate the diurnal variation in glomerular filtration rate (GFR), and the potential mechanisms responsible for such variations in GFR and albuminuria in diabetic nephropathy.

METHODS

In three 24-hour urine samples, divided into a night- and daytime portion, diurnal variation in albuminuria (ELISA) was assessed. Furthermore, during recumbency changes in albuminuria, GFR (51Cr-EDTA plasma clearance) and arterial blood pressure (TM2420) from nighttime (00:00 to 05:00 hours) to subsequent daytime (08:00 to 13:00 hours) were examined in 20 type 1 diabetic patients with diabetic nephropathy.

RESULTS

The 24-hour urine collections showed an average rise in albuminuria from night- to daytime of 51% (95% CI; 16 to 95; P < 0.01). During recumbency a non-significant rise was recorded from night- to daytime in albuminuria (22%, -8 to 61, P=0.15), simultaneously with an increase in GFR of 9.0% (3.4 to 14.5, P < 0.005) and mean arterial blood pressure (MABP) of 8.0% (4.3 to 11.7, P < 0.0001). No diurnal variation in fractional clearance of albumin was found. Significant associations between MABP and albuminuria were demonstrated during night- (R2=0.50; P < 0.001) and daytime (R2=0.48; P < 0.005). A linear regression analysis between diurnal variations in MABP and GFR showed that an increase in MABP (of 10%) from night- to daytime was associated with a significant increase in GFR (of 8.0%, 0.2 to 4.1, P < 0.02).

CONCLUSIONS

Our study revealed diurnal variations in GFR, albuminuria and MABP in diabetic nephropathy, with lowest values during sleep at night. The observed diurnal variation in albuminuria seems to be explained partly by mechanisms related to orthostasis, and partly by the diurnal variation in GFR and serum albumin concentration. The diurnal variation of blood pressure seems to play a role for the diurnal changes in GFR and albuminuria.

Long-term beneficial effect of ACE inhibition on diabetic nephropathy in normotensive type 1 diabetic patients

BACKGROUND

The purpose of this study was to assess whether long-term (8 years) inhibition of angiotensin-converting enzyme (ACE) protects kidney function in normotensive type 1 diabetic patients with diabetic nephropathy.

METHODS

We performed an open randomized follow-up study of normotensive type 1 diabetics with nephropathy either treated (N = 15) or not (N = 17) with captopril twice per day (average 74, range 12.5 to 125 mg/day). The main outcome measures were arterial blood pressure, albuminuria, and glomerular filtration rate (GFR; 51Cr-EDTA plasma clearance, twice yearly).

RESULTS

Arterial blood pressure (mm Hg) was kept constant in the captopril group, at baseline (mean, SEM), 128/78 (3/2) and during follow-up 129/77 (4/1) but increased significantly in the control group from 127/79 (2/1) to 137/84 (5/2) (P < 0.01). Furthermore, 8 out of the 17 control subjects required treatment with blood pressure-lowering drugs because they developed hypertension. The fractional albumin clearance (x10-5) remained unchanged in the captopril group: baseline [10.8 (1.25) geometric mean and antilog (SEM)] during the eight years [11.8 (1.47)], while a significant rise occurred in control patients: 13.3 (1.23) to 26.2 (1.42) (P < 0.05). Baseline GFR was nearly identical: 111 (6) and 115 (4) mL/min/1.73 m2 in the captopril and control group, respectively. The median (range) rate of decline in GFR (mL/min/year) was 1.7 (10.7 to -2.0) in the captopril group versus 2.8 (17.7 to -2.6) in the control group (P = NS).

CONCLUSIONS

The beneficial effect of captopril in arresting the rise in systemic blood pressure and albuminuria is long lasting. A loss in GFR is minimal in most patients with diabetic nephropathy if normotension is sustained by prospective treatment with ACE inhibitors or restored by implementation of other antihypertensive medications with the development of hypertension.