M. E. Cooper

OBJECTIVES: To assess and compare the effects of candesartan or lisinopril, or both, on blood pressure and urinary albumin excretion in patients with microalbuminuria, hypertension, and type 2 diabetes. DESIGN: Prospective, randomised, parallel group, double blind study with four week placebo run in period and 12 weeks' monotherapy with candesartan or lisinopril followed by 12 weeks' monotherapy or combination treatment. SETTING: Tertiary hospitals and primary care centres in four countries (37 centres). PARTICIPANTS: 199 patients aged 30-75 years. INTERVENTIONS: Candesartan 16 mg once daily, lisinopril 20 mg once daily. MAIN OUTCOME MEASURES: Blood pressure and urinary albumin:creatinine ratio. RESULTS: At 12 weeks mean (95% confidence interval) reductions in diastolic blood pressure were 9.5 mm Hg (7.7 mm Hg to 11.2 mm Hg, P<0.001) and 9.7 mm Hg (7.9 mm Hg to 11.5 mm Hg, P<0.001), respectively, and in urinary albumin:creatinine ratio were 30% (15% to 42%, P<0.001) and 46% (35% to 56%, P<0.001) for candesartan and lisinopril, respectively. At 24 weeks the mean reduction in diastolic blood pressure with combination treatment (16.3 mm Hg, 13.6 mm Hg to 18.9 mm Hg, P<0. 001) was significantly greater than that with candesartan (10.4 mm Hg, 7.7 mm Hg to 13.1 mm Hg, P<0.001) or lisinopril (mean 10.7 mm Hg, 8.0 mm Hg to 13.5 mm Hg, P<0.001). Furthermore, the reduction in urinary albumin:creatinine ratio with combination treatment (50%, 36% to 61%, P<0.001) was greater than with candesartan (24%, 0% to 43%, P=0.05) and lisinopril (39%, 20% to 54%, P<0.001). All treatments were generally well tolerated. CONCLUSION: Candesartan 16 mg once daily is as effective as lisinopril 20 mg once daily in reducing blood pressure and microalbuminuria in hypertensive patients with type 2 diabetes. Combination treatment is well tolerated and more effective in reducing blood pressure.

Transforming growth factor-beta (TGF-beta) and the renin-angiotensin system (RAS) have both been implicated in the pathogenesis of glomerulosclerosis in diabetic kidney disease. However, tubulointerstitial pathology may also be an important determinant of progressive renal dysfunction in diabetic nephropathy. In the present study, we investigated tubulointerstitial injury, TGF-beta1 expression, and the effect of blocking the RAS by inhibition of ACE. We randomized 36 male SD rats to control and diabetic groups. Diabetes was induced in 24 rats by administration of streptozotocin; 12 diabetic rats were further randomized to receive the ACE inhibitor ramipril (3 mg/l drinking water). At 6 months, experimental diabetes was associated with tubulointerstitial damage, a 70% increase in expression of TGF-beta1 (P < 0.05 vs. control), and a 120% increase in alpha1 (IV) collagen gene expression (P < 0.01 vs. control). In situ hybridization demonstrated a diffuse increase in both TGF-beta1 and alpha1 (IV) collagen mRNA in renal tubules. In addition, intense expression of both transcripts was noted in regions of focal tubular dilatation. Administration of the ACE inhibitor ramipril prevented tubulointerstitial injury and the overexpression of TGF-beta1 and alpha1 (IV) collagen mRNA. Changes in gene expression were accompanied by parallel changes in immunostaining for TGF-beta1 and type IV collagen. The observed beneficial effects of ramipril on the tubulointerstitium in experimental diabetes suggest that this mechanism may contribute to the therapeutic effect of ACE inhibitors in diabetic nephropathy.