Dietary effects of structured lipids and phytosteryl esters on cardiovascular function in spontaneously hypertensive rats

This study examined the dietary effects of sesame oil (SO)-based structured lipids (SL) and phytosteryl esters (PE) on cardiovascular function in conscious spontaneously hypertensive rats (SHR) fed high-fat (HF) diets (20% w/w fat). The dietary groups were as follows: normal diet (4.5% w/w fat), SO, SO fortified with PE (SOP), SL, and SL fortified with PE (SLP). Mean arterial blood pressures were similar in all groups, whereas resting heart rates (HR) were higher in all HF-fed groups. The pressor responses to the α 1 -adrenoceptor agonist, phenylephrine (5 μg/kg), were similar in all groups. However, the pressor responses to phenylephrine (10 μg/kg) were diminished in SO- or SL-fed SHR, whereas they were not diminished in SOP- or SLP-fed SHR. The depressor responses elicited by the nitric oxide (NO) donor, sodium nitroprusside (5 and 10 μg/kg), were not diminished in HF-fed rats. Baroreflex-mediated changes in HR were variously decreased in the HF-fed groups, and this decrease tended to be greater in SOP and SLP than in SO and SL groups. The depressor and tachycardic responses elicited by the β-adrenoceptor agonist, isoproterenol, were equivalent in all groups. The depressor responses elicited by the endothelium-dependent agonist, acetylcholine (0.1 μg/kg), and the hypertension elicited by the NO synthesis inhibitor, N G -nitro-L-arginine methylester (25 μmol/kg), were similar in all groups. These findings demonstrate that (1) HF diets increase resting HR and impair baroreflex function in SHR, whereas they do not obviously affect endothelium-dependent vasodilation, and (2) fortification with PE may be deleterious to cardiovascular function (eg, baroreflex activity) in SHR.