K. J. Schjoedt

Time course of the antiproteinuric and antihypertensive effects of direct renin inhibition in type 2 diabetes

Inhibition of renin with an active site inhibitor, aliskiren, lowers blood pressure (BP) in diabetic patients. Here, we studied the time course of the antihypertensive and antiproteinuric effect of renin inhibition in 15 patients with type 2 diabetes and elevated urinary albumin/creatinine ratios (UACRs) to check whether aliskiren can decrease proteinuria. After a 4-week washout of previous medications, patients received aliskiren and furosemide daily for 28 days followed by a 4-week withdrawal period. Twenty-four-hour BPs were measured at baseline throughout treatment and withdrawal periods. The UACR was significantly reduced after 2-4 days of treatment with another significant reduction after 28 days. Systolic blood pressure (SBP) was significantly lower after 7 days with no further reduction after 28 days. The BP returned toward baseline 3 days after withdrawal, whereas the UACR was still significantly reduced compared with baseline 12 days after withdrawal. Our study shows that aliskiren reduced 24 h SBP, and this was associated with a reduction in albuminuria in type 2 diabetic patients.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Kidney Injury Molecule 1 (KIM1) in patients with diabetic nephropathy: a cross-sectional study and the effects of lisinopril.

Diabet. Med. 27, 1144–1150 (2010)

Tubular and glomerular injury in diabetes and the impact of ACE inhibition.

OBJECTIVE We studied tubular and glomerular damage in type 1 diabetic patients by measuring urinary–liver fatty acid binding protein (U-LFABP) and albuminuria. Subsequently, we evaluated the effect of ACE inhibition on U-LFABP in patients with diabetic nephropathy. RESEARCH DESIGN AND METHODS We studied Caucasians with type 1 diabetes: 58 with normoalbuminuria (urinary albumin <30 mg/24 h), 45 with persistent microalbuminuria (30–300 mg/24 h), and 45 with persistent macroalbuminuria (≥300 mg/24 h). A control group consisted of 57 healthy individuals. The groups were matched by sex and duration of diabetes. In addition, U-LFABP was measured in 48 type 1 diabetic patients with diabetic nephropathy in a randomized crossover trial consisting of 2 months of treatment with 20, 40, and 60 mg lisinopril once daily in random order. RESULTS In the cross-sectional study, levels of U-LFABP were significantly higher in normoalbuminuric patients versus those in the control group (median 2.6 [interquartile range 1.3–4.1] vs. 19 [0.8–3.0] μg/g creatinine, P = 0.02) and increased with increasing levels of albuminuria (microalbuminuric group 4.2 [1.8–8.3] μg/g creatinine and nephropathy group 71.2 [8.1–123.4], P < 0.05 for all comparisons). U-LFABP correlates with the urinary albumin-to-creatinine ratio (R2 = 0.54, P < 0.001). In the intervention study, all doses of lisinopril significantly reduced urinary albumin excretion rate and U-LFABP from baseline. The reductions in U-LFABP were 43, 46, and 40% with increasing doses of lisinopril (NS). CONCLUSIONS An early and progressive increase in tubulointerstitial damage as reflected by increased U-LFABP levels occurs in type 1 diabetic patients and is associated with albuminuria. Furthermore, ACE inhibition reduces the tubular and glomerular damage and dysfunction.

Levels of NT-proBNP, markers of low-grade inflammation, and endothelial dysfunction during spironolactone treatment in patients with diabetic kidney disease

Renin-angiotensin-aldosterone system (RAAS) blockade may reduce levels of biomarkers of chronic low-grade inflammation and endothelial dysfunction. We investigated the effect of spironolactone added to standard RAAS blockade on these biomarkers in an analysis of four original studies. Materials and methods: The studies were double-blind, randomised, placebo-controlled studies in 46 type 1 and 23 type 2 diabetic patients with micro- or macroalbuminuria treated with angiotensin-converting enzyme inhibitor (ACE inhibitor) or angiotensin receptor blocker (ARB), and randomised to additional treatment with spironolactone 25 mg and placebo daily for 60 days. Outcome measures: Changes in inflammatory (hsCRP, s-ICAM, TNFα, IL-6, IL-8, Serum amyloid A, IL1β), endothelial dysfunction (sE-selectin, s-ICAM1, s-VCAM1, VWF, p-selectin, s-thrombomodulin) and NT-proBNP after each treatment period. Results: During spironolactone treatment, u-albumin excretion rate was reduced from 605 (411–890) to 433 (295–636) mg/24 h, as previously reported. Markers of inflammation and endothelial dysfunction did not change; only changes in NT-proBNP (reduced by 14%, p=0.05) and serum amyloid A (reduced by 62%, p=0.10) were borderline significant. Discussions: Our results indicate that the renoprotective effect of spironolactone when added to RAAS blockade is not mediated through anti-inflammatory pathways since markers of inflammation and endothelial dysfunction are not affected during treatment.

Autoregulation of glomerular filtration rate during spironolactone treatment in hypertensive patients with type 1 diabetes: a randomized crossover trial

BACKGROUND Autoregulation of GFR, i.e. maintenance of relative constancy of GFR despite variations in mean arterial pressure (MAP) >80 mmHg, is impaired in diabetic kidney disease; furthermore, some antihypertensive drugs may jeopardize autoregulation. The aim of our study was to establish if spironolactone affects the ability to autoregulate GFR. METHODS Sixteen hypertensive type 1 diabetic patients with persistent normoalbuminuria (presumed normal autoregulation) completed this randomized, double-masked, crossover trial. After a 4-week wash-out period, patients received spironolactone 25 mg o.d. and matched placebo for 4 weeks in random order. After each treatment period, the ability to autoregulate GFR was determined by measuring GFR ((51)Cr-EDTA clearance) before (basal) and after acute blood pressure reduction by intravenous injection of clonidine. RESULTS During placebo, the mean (SE) basal GFR was 115 (5) ml/min/1.73 m(2) and the BP was 146 (4)/81 (2) mmHg corresponding to a MAP of 103 (2) mmHg. Spironolactone did not significantly reduce GFR or BP. Injection of clonidine induced a significant reduction in the MAP of 17 (2) and 19 (1) mmHg during placebo and spironolactone treatment, respectively, and an overall reduction in GFR of 11 and 15 ml/min/1.73 m(2) (both comparisons NS between treatment periods). Signs of impaired autoregulation were present in nine patients during placebo and in nine patients during spironolactone treatment. Relative changes in GFR on placebo treatment correlated with diabetes duration (R = 0.67, P < 0.01) but were not related to duration of hypertension, baseline BP, GFR, HbA1c or to changes in BP. CONCLUSION Spironolactone did not change the overall ability to autoregulate GFR in 16 hypertensive type 1 diabetic patients with normoalbuminuria. Our data are suggestive that the ability to autoregulate GFR is gradually impaired with increasing diabetes duration, a phenomenon not previously described in normoalbuminuric patients.

Aldosterone synthase (CYP11B2) -344T/C polymorphism is not associated with the initiation and progression of diabetic nephropathy in Caucasian Type 1 diabetic patients.

Aims  Aldosterone is one of the main effectors of the renin–angiotensin–aldosterone system regulating blood pressure. Previous studies have shown that the aldosterone synthase promoter polymorphism −344T/C influences aldosterone levels and is associated with hypertension, a risk factor for the initiation and progression of diabetic nephropathy. Therefore, we investigated whether the −344T/C polymorphism is associated with the development and progression of diabetic nephropathy in Type 1 diabetes mellitus.

Aldosterone synthase (CYP11B2)­344T/C polymorphism and renoprotective response to losartan treatment in diabetic nephropathy

Objective. It has been suggested that an aldosterone synthase gene polymorphism (CYP11B2 344T/C) is predictive of the blood pressure lowering effect of angiotensin II receptor blockers in essential hypertension. We investigated whether this polymorphism is predictive of reductions in blood pressure and albuminuria and preservation of glomerular filtration rate (GFR) during short‐term and long‐term treatment with losartan in 57 hypertensive type‐1 diabetic patients with diabetic nephropathy. Material and methods. After a 4‐week washout period, patients received losartan (100 mg o.d.) and were followed for a mean follow‐up of 36 months. At baseline, after 2 and 4 months, and every 6 months thereafter, GFR (51Cr‐EDTA‐clearance), albuminuria and 24‐h blood pressure were determined. The CYP11B2 344T/C polymorphism was determined by standard polymerase chain reaction (PCR). Results. The TT, CT and CC genotypes were found in 28 %, 58 % and 14 % of patients, respectively. At baseline albuminuria and blood pressure did not differ between genotype groups. Plasma aldosterone levels (geometric mean (95 % CI)) were similar at baseline: 87 (60–125), 77 (53–112), and 89 (49–161) pg mL−1 and during follow‐up (not significant). After initiation of losartan treatment, comparable mean (SE) reductions in blood pressure and albuminuria were seen in patients with TT, CT and CC genotypes (p >0.6 between groups). After long‐term follow‐up, there was a tendency towards a difference in systolic blood pressure reduction (p = 0.07, one‐way ANOVA), suggesting a poorer response in patients with the CC genotype. No significant difference in rate of decline in GFR (median (range)) was seen between groups (TT, CT, CC): 4.2 (−1.0 to 16.0), 3.2 (−1.6 to 13.8) and 2.6 (−0.1 to 11.0) mL min−1year−1, respectively (p = 0.5). Conclusions. Compared to a previous smaller study of angiotensin II receptor blockade in essential hypertension, we could not confirm that CYP11B2 344T/C genotypes contribute towards explaining the observed variability in response to treatment with angiotensin II receptor blockers, which could be due to lack of power.