The Impact of Lipoic Acid on Endothelial Function and Proteinuria in Quinapril-Treated Diabetic Patients With Stage I Hypertension

Abstract

Background: We sought to determine whether a combination of angiotensin-converting enzyme inhibitors (ACEIs) and the nutraceutical α-lipoic acid (ALA) regulates blood pressure, endothelial function, and proteinuria in diabetic patients with Stage I hypertension. Methods: A total of 40 diabetic patients with Stage I hypertension were treated in a crossover double-blinded manner. Patients were administered quinapril ([QUI] 40 mg/d) for 8 weeks or QUI + ALA (600 mg/d) for 8 weeks. Measurements included blood pressure, 24-hour collection of urinary albumin, and endothelial-dependent flow-mediated dilation (FMD). Results: There was a change of metabolic parameters in both study groups after 8 weeks of therapy. In comparison to baseline, the 24-hour urinary albumin significantly decreased by 30% in the QUI group ( P = .018, time comparison) and 53% in QUI + ALA group ( P < .005, time and group comparison). Also, when compared with baseline, FMD significantly increased by 58% in QUI group ( P < .005, time comparison) and by 116% in QUI + ALA group ( P < .005, time and group comparison). Systolic and diastolic blood pressure reduced significantly by 10% with QUI treatment. There was no further blood pressure reduction when patients were administered both QUI and ALA. Conclusions: In diabetic patients with hypertension, QUI reduces blood pressure, proteinuria, and improves endothelial function. Moreover, this effect is strongly potentiated with a combination of QUI and ALA. These results may attenuate the progression of vascular pathophysiology seen in patients with a combination of diabetes and hypertension.