The impact of lipoic acid on endothelial function and proteinuria in quinapril-treated diabetic patients with stage I hypertension: results from the QUALITY study.

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. 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). 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. 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.