Effects of Heated Vegetable Oils on Serum Lipids and Aorta of Ovariectomized Rats

Abstract

This study examined the effects of heated vegetable oils in estrogen deficient rats. Eighty female Sprague-Dawley rats were divided equally into eight groups and given treatment as follows: (I) intact (non-ovariectomised), basal diet (control group); (II) ovariectomised, basal diet; (III) ovariectomised, basal diet fortified with 15% weight/weight (w/w) fresh soya bean oil (FSO); (IV) ovariectomised, basal diet fortified with 15% weight/weight (w/w) soya bean oil heated once (1H-SO); (V) ovariectomised, basal diet fortified with 15% weight/weight (w/w) soya bean oil heated five times (5H-SO); (VI) ovariectomised, basal diet fortified with 15% weight/weight (w/w)fresh palm oil (FPO); (VII) ovariectomised, basal diet fortified with 15% weight/weight (w/w) palm oil heated once (1H-PO); (VIII) ovariectomised, basal diet fortified with 15% weight/weight (w/w) palm oil heated five times (5H-PO). Duration of treatment was 6 months. Blood was taken at baseline and monthly interval for 6 months for determination of serum lipid profiles and malondialdehyde (MDA) levels. Serum homocystein and interleukin-6 were assayed at baseline and after 6 months of study. At the end of the study the rats were killed and consistent segments of the ascending aorta were taken for histopathological examination. The specimens were sectioned transervely and stained with haematoxylin-eosin and Verhoeff van Gieson for light microscopy. Measurements of the intimal thickness and the ratio between tunica intima / tunica media were calculated using computerised image analyser. Heated and fresh palm oil cause transient changes in lipid profiles, whereas soya oil; fresh, heated once and heated five times as well as heated once palm oil caused an increase in serum LDL-cholesterol. Fresh and heated vegetable oils diet did not alter the ratio between tunica intima and tunica media, serum MDA and homocystein level. Histological study showed no obvious focal or diffuse atherosclerotic plague formation with an intact internal elastic lamina and no evidence of smooth muscle cell migration.