Influence of dietary phytosterols and phytostanols on diastolic blood pressure and the expression of blood pressure regulatory genes in SHRSP and WKY inbred rats

Abstract

The aim of the present study was to determine the impact of increased consumption of phytosterols or phytostanols on blood pressure and renal blood pressure regulatory gene expression in stroke-prone spontaneously hypertensive (SHRSP) and normotensive Wistar-Kyoto (WKY) inbred rats. SHRSP and WKY inbred rats (10/group) were fed a control diet or a diet supplemented with phytosterols or phytostanols (2.0 g/kg diet). After 5 weeks, SHRSP rats demonstrated higher systolic and diastolic blood pressures than WKY inbred rats. SHRSP rats that consumed the phytosterol or phytostanol supplemental diets displayed a 2- or 3-fold respective increase in the diastolic blood pressure than those that consumed the control diet. Angiotensinogen (Agt), angiotensin I-converting enzyme 1 (Ace1), nitric oxide synthase (Nos) 1, Nos3, cyclooxygenase 2 (Cox2) and THUMP domain containing 1 were expressed at higher levels in SHRSP compared with WKY inbred rats. Renin and angiotensin II receptor type 1a were expressed at lower levels in SHRSP than WKY inbred rats. Phytostanol supplementation up-regulated the expression of Ace1 and Nos3 in SHRSP rats. Phytosterol supplementation increased the mRNA levels of Nos1 and spondin 1 (Spon1) in SHRSP and WKY inbred rats. Cox2 mRNA levels were elevated in both phytosterol- and phytostanol-supplemented SHRSP and WKY inbred rats. Therefore, the increased blood pressure in SHRSP rats may be partly due to altered renal expression of blood pressure regulatory genes. Specifically, up-regulation of Ace1, Nos1, Nos3, Cox2 and Spon1 were associated with the increased diastolic blood pressure observed in phytosterol- or phytostanol-supplemented SHRSP rats.