Abstract: We have previously reported that dietary supplementation with purple laver(PL) Porphyra yezoensis,an edible red alga,for 28 days reduced the 24 hour ambulatory blood pressure(ABP) in 36 patients with essential hypertension(EH).However,the antihypertensive mechanism of PL remain obscure and the influence of PL on vascular endothelial function,an important factor in the development and the treatment of EH is also unclear.Thus,to elucidate the mechanisms,we investigated the influence of dietary supplementation with PL on the vascular endothelial function as represented by the levels of two vasoactive materials endothelin(ET),a potent vasoconstrictor,and nitric oxide(NO),a strong vasodilator.A total of 36 patients with EH(24 male,55.0±7.9 years old;12 female,50.5±7.1 years old) were divided into 2 groups in a blank controlled cross-sectional trial with supplementation of PL(45 g/d) for 28 days.After enrollment,all the subjects were asked to finish a questionnaire of their lifestyle and to sign a written informed consent according to the Declaration of Helsinki of the World Medical Association(Edinburgh revision,2000) and then were matched according to sex,age,and lifestyle and divided into two groups.There were no statistically significant differences between groups in terms of baseline demographic or clinical characteristics,blood routine,and lipid profile.During the study,subjects were instructed not to modify their daily lifestyle,such as changing their diet otherwise and exercise,except for taking the supplementary PL in the form of a 3 g-sheet with everyday meal for three times a day.After a 7-day run-in period,subjects were randomized to the purple laver(PL,45 g/d) or blank group for 28 days.After that,both groups entered a 7-day wash-out period and then crossed over to the alternate treatment for another 28 days.At the begining and the end of each treatment period,subjects were evaluated by 24 h ambulatory blood pressure(ABP) monitoring and by seated cuff blood pressure(BP) measurements at trough.Blood serum samples were collected and measured for lipid profile,endothelin(ET),and nitric oxide(NO) concentration before and after each treatment periods.As a result,PL significantly decreased ABP as compared with the blank and the baseline.Mean reductions in ABP for the two groups were(7.4±2.3)/(3.7±1.2)mmHg and(9.2±3.3)/(6.4±2.3) mmHg respectively,with significant reductions in ambulatory systolic blood pressure for both groups(P<0.05).Serum lipid profile was not significantly changed.However,serum ET concentration decreased(16.3±8.6)ng/L and(22.2±8.8)ng/L in the two groups respectively after consuming Porphyra yezoensis for 28 days(P<0.05).Meanwhile,serum NO concentration,as determined by nitrate/nitrite(NO^2-/NO^3-) concentration,significantly increased(15.8±5.8)μmol/L and(12.7±9.2)μmol/L respectively in the two groups(P<0.05).Moreover,the differences of ET and NO between the supplementation and the blank control group were both statistically significant(P<0.05).Furthermore,it should be noted that when the consumption of PL had been ceased for 28 days,serum ET and NO level also returned to their baseline level(101.5±13.2 ng/L and 63.9±13.9 μmol/L,respectively).In conclusion,our findings suggest that long-term dietary supplementation with PL can improve vascular endothelial dilatory function and then decrease 24 h ambulatory blood pressure in essential hypertensives.

Key words: Porphyra yezoensis, essential hypertension, endothelin, nitric oxide