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Intrarenal Hemodynamic Changes After Captopril Test in Patients With Type 2 Diabetes

A duplex Doppler sonography study

¹ Department of Metabolism, Endocrinology, and Molecular Medicine, Osaka City University Graduate School of Medicine, Osaka, Japan
² Department of Nephrology, Osaka City University Graduate School of Medicine, Osaka, Japan
³ Department of Internal Medicine, Inoue Hospital, Inoue, Japan
⁴ Department of Urology, Osaka City University Graduate School of Medicine, Osaka, Japan

OBJECTIVE—ACE inhibitors are known to be effective in preventing the progression of diabetic nephropathy. Activation of the renin-angiotensin system (RAS) is reported to contribute to intrarenal hemodynamic abnormality in diabetic patients. We examined whether RAS blockade by captopril induces intrarenal hemodynamic changes in normotensive patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS—The patients ranged in age from 40 to 65 years (20 men and 20 women). A total of 15 age- and sex-matched healthy individuals served as control subjects. Resistive index (RI) of interlobar arteries was examined by duplex Doppler sonography before and after the oral captopril (25 mg) test.

RESULTS—At baseline, no significant differences in RI values or plasma renin activity (PRA) were seen between the patients and healthy subjects. In healthy subjects, the RI values after the captopril test were significantly higher than baseline values (P < 0.01). However, in patients with type 2 diabetes, both with normoalbuminuria and microalbuminuria, RI values after the test were significantly lower than baseline values (P < 0.001). There were significant negative correlations between RI value and HbA_1c (r = -0.458, P < 0.005) and between RI value and baseline PRA in diabetic patients (r = -0.339, P < 0.05). Multiple regression analysis showed that HbA_1c and baseline PRA significantly and independently affected the magnitude of decrease in RI values after captopril administration in diabetic patients (R² = 0.391, P < 0.0001).

CONCLUSIONS—These results indicate that the intrarenal RAS may be activated in diabetic patients, that such activation may be affected by poor glycemic control, and that blockade of RAS activation by ACE inhibitor reduces intrarenal vascular resistance in diabetic patients. The results emphasize the beneficial effects of ACE inhibition in improving intrarenal hemodynamics in diabetic patients.

Abbreviations: EDV, end-diastolic flow velocity • PA, plasma aldosterone • PRA, plasma renin activity • PSV, peak systolic flow velocity • RAS, renin-angiotensin system • RI, resistive index • UAE, urinary albumin excretion

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