The present study attempted to clarify the antihypertensive effect and its mechanism when alpha-linolenic acid (ALA) is administered orally. For this purpose, 1 mL of flaxseed oil, which is rich in ALA, and high oleic safflower oil was administered orally to spontaneously hypertensive rats (SHR) of a control and an ALA group on days 1 and 5. Systolic blood pressure was measured on day 1, and blood and liver were collected on day 5. Four hours after the oral administration on day 1, systolic blood pressure of the ALA group was lower than that of the control group. Levels of plasma vasodilators, such as prostaglandin I(2) metabolite, nitric oxide metabolites, and bradykinin, in the ALA group were significantly higher than those in the control group, but levels of vasoconstrictors, such as angiotensin II and thromboxane A(2) metabolite, did not differ significantly. It is known that bradykinin induces prostaglandin I(2) and nitric oxide. The present study shows that ALA reduced the systolic blood pressure of SHR, and its mechanism may be related to increases of prostaglandin I(2) and nitric oxide through bradykinin stimulation.
Adiponectin, an adipose-specific secretory protein, exhibits antidiabetic and antiatherogenic properties. The effect of alpha-linolenic acid (ALA) on adiponectin has not been revealed. ALA is included abundantly in vegetable oils such as flaxseed oil. In this study, we attempted to clarify the effect of ALA-rich flaxseed oil (FSO) intake on the adiponectin level in rats. Seven-week-old male Sprague-Dawley rats were fed test diets containing high oleic safflower oil (HOSO) or FSO for 4 weeks. After the experimental period, the plasma adiponectin concentration in the FSO-fed group was higher than that in the HOSO-fed group. The adiponectin content of perirenal adipose tissue in the FSO-fed group was also significantly higher than that in the HOSO-fed group. However, the adiponectin mRNA level in the perirenal adipose tissue did not differ significantly between the HOSO-fed and FSO-fed groups. In this study, we clarified the effect of the ALA-rich FSO ingestion on the plasma adiponectin concentration in rats. It was suggested that the ALA-rich FSO intake might exhibit beneficial effects through an increase of the adiponectin level.
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