Effects of a long-term treatment with aliskiren or ramipril on structural alterations of subcutaneous small resistance arteries of diabetic hypertensive patients

Structural alterations of subcutaneous small-resistance arteries are associated with a worse clinical prognosis in hypertension and non-insulin-dependent diabetes mellitus. The effects of the direct renin inhibitor aliskiren on microvascular structure were never previously evaluated. Therefore, we investigated the effects of aliskiren in comparison with those of an extensively used angiotensin-converting enzyme inhibitor, ramipril, on peripheral subcutaneous small-resistance artery morphology, retinal arteriolar structure, and capillary density in a population of patients with non-insulin-dependent diabetes mellitus. Sixteen patients with mild essential hypertension and with a previous diagnosis of non-insulin-dependent diabetes mellitus were included in the study. Patients were then randomized to 1 of the 2 active treatments (aliskiren 150 mg once daily, n=9; or ramipril 5 mg once daily, n=7). Each patient underwent a biopsy of the subcutaneous fat from the gluteal region, an evaluation of retinal artery morphology (scanning laser Doppler flowmetry), and capillary density (capillaroscopy), at baseline and after 1 year of treatment. Subcutaneous small arteries were dissected and mounted on a pressurized micromyograph, and the media-to-lumen ratio was evaluated. A similar office blood pressure-lowering effect and a similar reduction of the wall-to-lumen ratio of retinal arterioles were observed with the 2 drugs. Aliskiren significantly reduced media-to-lumen ratio of subcutaneous small-resistance arteries, whereas ramipril-induced reduction of media to lumen ratio was not statistically significant. No relevant effect on capillary density was observed. In conclusion, treatment with aliskiren or ramipril was associated with a correction of microvascular structural alterations in patients with non-insulin-dependent diabetes mellitus.