Effects of long-term intake of edible oils on hypertension and myocardial and aortic remodelling in spontaneously hypertensive rats

BACKGROUND: The nature of dietary lipid intake contributes to blood pressure control. OBJECTIVE: To test whether different edible lipid compounds are either beneficial or harmful to blood pressure and cardiac and aortic structure. METHODS: Six groups of 3-month-old male spontaneously hypertensive rats (n = 5) received different edible oils (fish, canola, palm, olive and soybean oils, 1.5 g/kg per day + 1 IU/ml vitamin E) or a placebo (water) by gavage for 13 weeks. Stereology was used to analyse left ventricular cardiomyocytes, intramyocardial vessels, connective tissue, aortic lamellae and tunica media smooth muscle cells. RESULTS: Fish oil decreased blood pressure, and increases in blood pressure were prevented by both canola and palm oils. The cardiomyocyte and intramyocardial vessel indices were greater in the fish-, canola- and palm-oil groups and smaller in the soybean-oil, olive-oil and control groups; the opposite effects were found in interstitial connective tissue. The number of lamellae was smaller in the fish-oil group but greater in the soybean-oil, canola-oil, and olive-oil groups. Canola oil reduced aortic wall thickness, but palm oil did not. The number of smooth muscle cells was smaller in the groups given fish, canola and olive oils. CONCLUSION: The most beneficial cardiac and aortic structural effects occurred in the fish-oil group. Both canola oil and palm oil were also effective in reducing blood pressure, favouring myocardial remodelling, although they produced contrasting effects with regard to aorta wall structure. Soybean oil and olive oil had mild effects on myocardial and aortic structure.