Transforming growth factor-beta in human diabetic nephropathy: effects of ACE inhibition.

OBJECTIVE: Studies in rodent models have suggested that reduction in renal transforming growth factor (TGF)-beta1 may underlie the renoprotective effects of the renin-angiotensin system (RAS) blockade. However, the role of the RAS blockade in abrogating TGF-beta in human disease is unknown. Accordingly, we sought to examine TGF-beta gene expression and biological activity in human renal biopsies, before and after ACE inhibition. RESEARCH DESIGN AND METHODS: RNA was extracted from renal biopsies taken from participants in the Diabiopsies study, a randomized controlled 2-year trial of 4 mg/day perindopril versus placebo that reported a reduction in proteinuria and cortical matrix expansion in type 2 diabetic nephropathy. Biopsies taken at study entry and at 2 years were obtained in 12 patients (6 placebo and 6 taking perindopril). TGF-beta1 and its receptor mRNA were quantified by real-time PCR, and its biological activity was assessed by examining the activation of its intracellular signaling pathway (phosphorylated Smad2) and the expression TGF-beta-inducible gene H3 (betaig-H3). RESULTS: At baseline, TGF-beta1 expression was similar in both placebo- and perindopril-treated groups and was unchanged over a 2-year period in biopsies of placebo-treated subjects. In contrast, perindopril treatment led to a substantial diminution in TGF-beta1 mRNA (mean 83% reduction, P < 0.05). Phosphorylated Smad2 immunolabeling and betaig-H3 mRNA were similarly reduced with ACE inhibition (P < 0.05) but unchanged in the placebo group. No differences were noted in the gene expression of TGF-beta receptor II in biopsies of either placebo- or perindopril-treated subjects. CONCLUSIONS: This study demonstrates that over a 2-year period, treatment with perindopril in patients with type 2 diabetes and nephropathy leads to a reduction in both renal TGF-beta1 gene expression and its downstream activation.

Independent and additive impact of blood pressure control and angiotensin II receptor blockade on renal outcomes in the irbesartan diabetic nephropathy trial: clinical implications and limitations.

Elevated arterial pressure is a major risk factor for progression to ESRD in diabetic nephropathy. However, the component of arterial pressure and level of BP control for optimal renal outcomes are disputed. Data from 1590 hypertensive patients with type 2 diabetes in the Irbesartan Diabetic Nephropathy Trial (IDNT), a randomized, double-blind, placebo-controlled trial performed in 209 clinics worldwide, were examined, and the effects of baseline and mean follow-up systolic BP (SBP) and diastolic BP and the interaction of assigned study medications (irbesartan, amlodipine, and placebo) on progressive renal failure and all-cause mortality were assessed. Other antihypertensive agents were added to achieve predetermined BP goals. Entry criteria included elevated baseline serum creatinine concentration up to 266 micromol/L (3.0 mg/dl) and urine protein excretion >900 mg/d. Baseline BP averaged 159/87 +/- 20/11 mmHg. Median patient follow-up was 2.6 yr. Follow-up achieved SBP most strongly predicted renal outcomes. SBP >149 mmHg was associated with a 2.2-fold increase in the risk for doubling serum creatinine or ESRD compared with SBP <134 mmHg. Progressive lowering of SBP to 120 mmHg was associated with improved renal and patient survival, an effect independent of baseline renal function. Below this threshold, all-cause mortality increased. An additional renoprotective effect of irbesartan, independent of achieved SBP, was observed down to 120 mmHg. There was no correlation between diastolic BP and renal outcomes. We recommend a SBP target between 120 and 130 mmHg, in conjunction with blockade of the renin-angiotensin system, in patients with type 2 diabetic nephropathy.

Cost-effectiveness of irbesartan in diabetic nephropathy: a systematic review of published studies.

BACKGROUND: To review published studies on the cost-effectiveness of the use of irbesartan for treatment of advance overt nephropathy in patients with type 2 diabetes and hypertension. METHODS: Articles were identified based on a search of the PubMed databases using the keywords 'irbesartan', 'ESRD', 'cost-effectiveness', 'nephropathy' and 'costs', and by personal communication with the authors. Only studies published in the last 10 years were included. All costs data from the cost-effectiveness studies were inflated to 2003 Euros using published governmental conversion tables. RESULTS: Seven published studies were identified, spanning the following country settings: the US, Belgium and France, Germany, Hungary, Italy, Spain, and the UK. In each, the same pharmacoeconomic model was adapted using country-specific data to project and evaluate the clinical and cost outcomes of the treatment arms of the Irbesartan in Diabetic Nephropathy Trial (IDNT) (irbesartan, amlodipine or standard blood pressure control). Mean time to onset of ESRD was 8.23 years for irbesartan, 6.82 years for amlodipine and 6.88 years for the control (values were the same for Belgium, France, Germany, Hungary, Italy and Spain as transition probabilities for progression to ESRD were all derived from the IDNT). Mean cumulative incidence of ESRD was 36% with irbesartan, 49% with amlodipine and 45% with control treatment. Treatment with irbesartan was projected to improve life expectancy compared to both amlodipine and control in all seven published studies. Analysis of total lifetime costs showed that irbesartan treatment was cost saving compared to the other two treatment regimens, due to the associated reduction in ESRD cases. Cost savings with irbesartan became evident very early; after 2-3 years of treatment in most settings. CONCLUSIONS: Modelling studies based on the IDNT published to date suggest that irbesartan treatment in patients with type 2 diabetes, hypertension and advanced nephropathy is both life- and cost-saving compared to amlodipine or control.

An economic evaluation of irbesartan in the treatment of patients with type 2 diabetes, hypertension and nephropathy: cost-effectiveness of Irbesartan in Diabetic Nephropathy Trial (IDNT) in the Belgian and French settings.

BACKGROUND: In the Irbesartan in Diabetic Nephropathy Trial (IDNT), treatment with irbesartan demonstrated 23 and 20% reductions in the combined endpoint of doubling of serum creatinine (DSC), end-stage renal disease (ESRD) or death in patients with hypertension, type 2 diabetes and overt nephropathy compared with amlodipine and control, respectively. A simulation model was developed to project long-term cost consequences of the IDNT in Belgium and France. METHODS: A Markov model simulated progression from nephropathy to DSC, ESRD and death in patients with hypertension, type 2 diabetes and overt nephropathy. Treatment-specific probabilities were derived from IDNT. Country-specific ESRD-related data were retrieved from published sources. Delay in onset of ESRD, life expectancy and mean lifetime costs were calculated for patients with a baseline age of 59 years. Future costs were discounted at 3% per annum (p.a.), and clinical benefits were discounted at 0 and 3% p.a. Extensive sensitivity analyses were performed. RESULTS: Onset of ESRD was delayed with irbesartan by 1.41 and 1.35 years vs amlodipine and control, respectively. When a 10-year time horizon was considered, delay in ESRD onset led to anticipated improvements in life expectancy of 0.13 years vs amlodipine and 0.26 years vs control. Irbesartan was associated with cost savings of 14 949 and 9205/patient in Belgium, and 20 128 and 13 337 in France, vs amlodipine and control, respectively. The results were robust under a wide range of plausible assumptions. CONCLUSIONS: Treating patients with hypertension, type 2 diabetes and overt nephropathy using irbesartan was both cost- and life-saving compared with amlodipine and control.