Effect of Different Vegetable Fats on Lipid Profile and Risk of Atherosclerosis in Rats

Abstract

Atherosclerotic vascular diseases (AVDs) are presently increasing rapidly in incidence and have become key contributors to the burden of disease in most developing countries like Ghana. The condition has been projected to more than double by 2025. The type and amount of dietary fat has been associated with several disorders including AVDs and it complications. Diet, as one of the most important modifiable risk factors of Coronary Heart Disease (CHD) modulates the other known risk factors. Excessive intake of dietary saturated fat and cholesterol has been found to increase serum cholesterol, thus leading to a high risk of cardiovascular diseases. Saturated fats, both of animal and vegetable or plant origin, have been discredited. This study was carried out to investigate the effect of vegetable fats including olive oil (OO), red palm oil (RdPO) and refined palm oil or palm olein (RfPO) on lipid profile and risk of Atherosclerosis in rat model. Three months old male Sprague-Dawley (S-D) rats (n=56) were divided into four groups: control, olive, red palm and refined palm oil groups (n=14 per group) received water and feed ad libitum. The controls were fed the standard rat chow whilst the treatment (oil) groups received diet enriched with extra 6% by weight of the corresponding oil. During the 16 weeks of dietary intervention, 7 rats were randomly selected from each group and sacrificed at two months intervals, and blood samples collected for biochemical analysis. Plasma lipid profile comprising of Total Cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), Apolipoprotein-A1 (Apo-A1), and Apolipoprotein-B100 (Apo-B100) were determined at baseline and at the end of every two months by the enzymatic technique using the Enzyme-Linked Immuno Sorbant Assay (ELISA). Pro- inflammatory markers including Interleukin-2 (IL-2), Interleukin-6 (IL-6), Tumor Necrosis Factor Alpha (TNF-α) and Total Antioxidant Status (TAS) were also determined by the ELISA method at baseline and at 2 and 4 months. There was no significant difference in the lipid profile of the treatment rats compared to the controls. However, there was a significant effect of the intake of the different oils on the inflammatory markers TNF-α and IL-6. There were also significant differences in the TAS of the rats from the different groups at month 2. Olive oil diet caused a significant decrease in the TNF-α and IL-6 mean concentrations (p=0.008) and (0.0041) respectively and an increase in the TAS mean concentrations (p=0.005). The two palm oil diets (RdPO and RfPO) caused an increase in both TNF-α and IL-6 concentrations. The red palm oil diet resulted in an increase in the TAS, whilst the refined palm oil diet caused a decrease in the TAS. However these effects were not statistically significant. The results suggest that the 3 different oils had different effects on the parameters investigated in this study. The increase in levels of the inflammatory indicators and reduction in total antioxidants levels recorded among rats fed RfPO enriched diet shows a likelihood of the oil enhancing inflammation and leading to oxidative stress and subsequent oxidative damage respectively, hence may have a potential of increasing the risk of development of atherosclerosis in rats. The intake of the red palm oil diet, although to some extent improved TAS of the rats, yet was associated with increased inflammation (TNF-α and IL-6). Therefore prolonged use may probably be associated with increased risk of developing atherosclerosis and other inflammatory diseases. On the contrary, intake of olive oil as a major source of fat may reduce the risk of atherosclerotic development due to its association with significant increase in TAS and a decrease in both IL-6 and TNF- α production in rats. The above findings therefore suggest that, olive oil may be most protective against atherosclerosis compared to the other oils. Also the red palm oil though unrefined, turned out to have a better antioxidant capacity than the refined form.