Effect of isoflavone supplement on endothelial function: does efficacy vary with atherosclerotic burden?
نویسندگان
چکیده
Endothelial dysfunction is widely considered as a prognostic marker of future cardiovascular events in clinical settings, even in patients who do not have untoward symptoms of cardiovascular disease. Thus, treatments aimed at restoring endothelial dysfunction have important implications Many studies have demonstrated that supplementary treatments can improve endothelial function. These favourable effects may be due to improved abnormal nitric oxide metabolism, mediated by mechanisms such as antioxidant or anti-inflammatory effects. Isoflavones are contained in soy and are mainly phytooestrogens, which are chemically similar in structure to physiological oestrogens. It has been demonstrated that isoflavones can lower blood pressure and serum lipid levels, as well as function as antioxidant and anti-inflammatory agents in both laboratory and clinical settings. It is therefore apparent that treatment with isoflavones could ameliorate endothelial dysfunction. However, the effect of isoflavone supplements on endothelial function remains controversial. 15 The results of several studies regarding the effect of isoflavone supplementation on endothelial function, as determined by assessing brachial flow-mediated dilatation (FMD), are summarized in Table 1. Because of the oestrogen-like nature of isoflavones, the subjects in many of these studies were menopausal women. It has been demonstrated that endothelial dysfunction often develops in women after the menopause and that FMD values can range from ‘severely reduced’ to ‘normal’ in these subjects. –13 Therefore, it is not surprising that isoflavones had no effect on the endothelial function in subjects with normal FMD readings (.8.0%). On the other hand, isoflavone supplementation improved endothelial function in subjects with a reduced FMD (,6.0%), even if the patient was menopausal. Cuevas et al. demonstrated that isoflavones restored normal FMD readings, while both Simons et al. and Hallund et al. reported that isoflavones elevated FMD levels but also stated that these changes were not significant. Cupisti et al. reported that soy protein improves endothelial function in renal transplant patients with naturally reduced FMD values. This was the first study demonstrating the effect of isoflavone supplements on the endothelial function of patients with severe diseases. Unfortunately, this was not a randomized, double-blind, placebo-controlled study. Chan et al. demonstrated that oral isoflavone supplements, taken over 12 weeks, mildly but significantly restored FMD levels in patients with prior ischaemic stroke. This study therefore raised two important points that must be emphasized. First, this is the first study to confirm the effect of isoflavones on endothelial function in patients with established atherosclerosis in a randomized, double-blind, placebo-controlled trial. Secondly, this study demonstrated that the improved FMD measurements inversely correlated with baseline FMD levels with isoflavone treatment, indicating that isoflavones could restore endothelial function in patients with severe endothelial dysfunction. These findings imply that future clinical trials of isoflavone supplementation should be conducted mainly in patients with endothelial dysfunction. In this report, the isoflavone-induced change in FMD values was only 1.2%. However, measurements of brachial artery diameter and increased brachial blood flow after hyperaemia did not change with treatment. Furthermore, although this was a parallel-group design study, the number of subjects was sufficient to detect a small FMD change. Therefore, the small but significant change in the observed FMD values has important implications. Despite these promising findings, future studies that examine the
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ورودعنوان ژورنال:
- European heart journal
دوره 29 22 شماره
صفحات -
تاریخ انتشار 2008