IJCS | Volume 31, Nº2, March / April 2018

117 Martins et al. Flaxseed ReducesTNF-α Int J Cardiovasc Sci. 2018;31(2)114-122 Original Article Table 1 – Mean, median, minimum and maximum, standard deviation, and p values for total cholesterol in all groups Variable Group n Mean Median Minimum Maximum Standard deviation p value* Total cholesterol (baseline) Control (G1) 10 35.60 34.00 14.00 69.00 15.13 Cholesterol (G2) 10 24.60 24.50 12.00 43.00 9.51 Flaxseed (G3) 9 28.33 24.00 15.00 54.00 13.51 0.174 Total cholesterol (end of the study) Control (G1) 10 23.64 21.50 8.90 57.00 15.72 Cholesterol (G2) 10 62.09 24.54 12.90 336.00 100.23 Flaxseed (G3) 8 36.21 34.20 16.40 72.00 17.32 0.204 Difference (end of the study - baseline) Control (G1) 10 -11.96 -13.50 -31.00 6.00 12.50 Cholesterol (G2) 10 37.49 2.55 -28.00 305.00 97.79 Flaxseed (G3) 9 3.86 3.00 -19.00 18.00 10.83 0.029 *Nonparametric Kruskal-Wallis test, p < 0.05. Immunohistochemical analysis Immunohistochemistry was used to investigate the presence of ICAM-1 andTNF- α in all four aortic segments. The results indicated that ICAM-1 levels increased only in aortic segment 4 in group G3; however, there was no significant difference in relation to median levels (Figure 1). A similar result was found for TNF- α , that is, the level of this marker was significantly increased in the aortic segment 4 (Figure 2). TNF- α levels in group G3 were similar to those in the control group, while the levels in group G2 were greater than twice as those in the control group (p < 0.05). Discussion Atherosclerosis is a major cardiovascular disease, and the understanding of its development is required for its prevention and treatment. This knowledge can be acquired using experimental models. In this respect, several animal studies have shown that a high-fat diet leads to obesity, hypercholesterolemia, and other complications such as endothelial lesions. 11 The experimental protocol in the present study was an early model of atherosclerosis and involved the addition of 0.25% cholesterol from lyophilized eggs to the diet of rabbits aiming at causing atherosclerotic lesions. 12 The use of rabbits as an experimental model suits the objectives of this study because these animals develop aortic lesions fast. Th i s s tudy as s e s s ed t he b i ochemi ca l and immunochemical changes caused by a high-cholesterol diet with and without flaxseed, which is considered a functional food. The increase in TC found in the biochemical analysis in groups G2 and G3 was not expected in the group treated with flaxseed. A similar result was obtained by Dupasquier et al., 13 who observed no changes in TC in animals receiving a diet with 10% of flaxseed. This unexpected result may be explained by several factors, including the concentration of flaxseed used, the form of flaxseed administration (ground seeds), feed heating for the incorporation of components, and the duration of seed intake. Previous results have indicated that alpha‑linolenic and linoleic acids are sensitive to light, heating, and oxygen, and undergo oxidation when exposed to temperatures between 120°C and 270°C. 14 Therefore, the process of production of feed containing flaxseed in the present study may have caused a decrease in the level of these acids, thereby compromising their nutraceutical function. LDL-C levels increased in the groups treated with high cholesterol; however, the levels remained similar between these groups. Similar results were obtained in a study in humans involving the consumption of flaxseed, in which the levels of TC and LDL-C remained unchanged, 15 even though the experimental period of 4 weeks may not have been sufficient to cause this reduction. Zheng et al. 16 conducted a randomized clinical trial in individuals diagnosed with