Comparative Studies of the Effects of Egg Yolk, Oats, Apple, and Wheat Bran on Serum Lipid Profile of Wistar Rats

Excess consumption of egg especially its yolk has been implicated in hyperlipidaemia (high level of cholesterol and triglyceride in the blood). Conversely, soluble dietary fibers, probably due to their ability to bind free lipid molecules, appear to play an important role in protecting against hyperlipidaemia. This study sought to evaluate the comparative effects of selected sources of fibers: apple, oats, and wheat bran, on serum lipid profile in physiologically normal Wistar rats. Twenty rats were used for the study and were randomized into four groups, with each containing five animals (n  =  5). A group which serves as control was fed with egg yolk while the other three groups were fed with apple, oats, and wheat bran, respectively. After two weeks of feeding, the animals were fasted overnight and blood samples from the retro-orbital sinus of the eye were collected for analyses of lipid profile. The results obtained showed that the group fed with oats had the lowest level of total cholesterol (82.9 ± 1.8 mg), low density lipoprotein (LDL) cholesterol (49.3 ± 1.4 mg), and triglycerides (TG) (75.1 ± 1.7 mg), as well as the highest level of HDL cholesterol (33.9 ± 0.9 mg). On the contrary, the group fed with egg yolk showed the highest level of total cholesterol (117.1 ± 4.4 mg), LDL cholesterol (96.4 ± 1.5 mg), and triacylglyceride (109 ± 2.6 mg), as well as the lowest level of HDL cholesterol (18.5 ± 0.9 mg). There was no significant difference (P  <  0.05) between oats and apple in their effects on blood lipid profile of Wistar rats. Wheat bran, being an insoluble dietary fibre, had less significant (P  <  0.05) effect on the blood lipid profile when compared to oats and apple. Findings from this study may assist physicians and dieticians in recommending appropriate diet for individuals desiring to normalize their blood lipids levels.


Introduction
Cardiovascular diseases and related disorders are a major cause of mortality both in men and women all over the world [1]. ey are commonly characterized by high levels of total cholesterol, triglyceride, and low density lipoprotein (LDL) cholesterol in the blood. Large amount of triglyceride and total cholesterol, more importantly LDL cholesterol in the blood, is oen associated with the etiology of cardiovascular diseases and is seen as primary risk factors [2]. High level of lipids in the blood has been associated with hypertension, stroke, and lipid peroxidation [3]. Epidemiological studies support the view that consuming diets rich in soluble �bers (fruits, grains, nuts, and vegetables) reduce the incidence of chronic diseases such as cardiovascular disorders, obesity, and diabetes [4]. A signi�cant correlation between consump� tion of �bers and serum concentration of lipids has been noted [5]. Meals rich in �ber have been associated with the propensity to reduce the risk of developing cardiovascular diseases and related disorders. Apples, oats, and wheat bran are food products with high �ber content [6] and are likely to reduce the total cholesterol, TG, and LDL cholesterol as well as possibly increase HDL cholesterol in the blood, a condition that lowers the risk of cardiovascular diseases and attendant mortality [5,7]. ere is an inverse correlation between HDL cholesterol and cardiovascular disorders, the higher the HDL cholesterol in the blood the lower the risk of cardiovascular disorder and vice versa. Conversely, LDL cholesterol and TG have direct correlation with susceptibility to cardiovascular disorders. e more these lipids are in the blood, the more prone an individual is to cardiovascular diseases, atherosclerosis, and hypertension. e present study therefore sought to compare the antilipidemic and anticholesteremic effects of oat, apple, and wheat bran in physiologically normal Wistar rats.

Materials and Methods
2.1. Materials. Twenty (20) Wistar rats of opposite sex were obtained from a local breeder in Ibadan, southwest of Nigeria. Egg yolk was obtained by separating the yolk from the albumin and dried in a hot air oven at 80 ∘ C for 3 hours to constant moisture content. Healthy apples, canned oats, and wheat bran were purchased from appropriate commercial centers in Ibadan, southwest of Nigeria.

Experimental Design. Twenty (20) male and female
Wistar rats weighing between 150 and 160 g were randomly assigned to four groups (A, B, C, and D), . ey were housed in individual cage and fed with grower's mash for two (2) weeks aer which the rats in different groups were fed as follows for another two weeks. Rats in groups A, B, C, and D were fed with apple, oats, wheat bran, and egg yolk, respectively. Group D serves as negative control (diet without �ber). e daily amounts of food intake by the rats in all the groups were determined and their body weights were measured on weekly basis. Aer the last food treatment, the rats were fasted for 12 h; blood samples were collected from the retro orbital sinus of the eye by ocular puncture into nonheparinised tubes and allowed to clot at room temperature for 30 min. e blood samples were then centrifuged at 3,000 rpm for 15 min and the serum obtained in each case was used for lipid pro�le analysis.

Biochemical
Analyses. e concentrations of high density lipoprotein cholesterol, low density lipoprotein cholesterol, trilglyceride, and total cholesterol were determined using commercial kits from Randox Laboratories, United Kingdom. e principle underlining each assay is given below.

Determination of Total Cholesterol.
Cholesterol is determined aer enzyme hydrolysis and oxidation. e indicator quinoneimine is formed from Hydrogen Peroxide and 4-aminoantipyrine in the presence of phenol and Peroxidase.

Results and Discussion
e mean gains in body weight and food intake of the experimental rats at the end of four weeks are shown in Table  1. Rats fed with egg yolk, oats, and wheat bran increased in body weight by 32.6 28.6 and 25.7 g, respectively, while those fed with apple reduced in body weight by 24.1 g. e relative higher gain in body weight of rats fed with egg yolk is probably due to the high fat content of egg yolk.
Fruits are known to help in body weight reduction through ease of excretion [8]. is tends to explain the loss in body weight observed in rats fed with apple in this study.
Animals fed with oats consumed the highest amount of food, and those placed on with wheat bran consumed the lowest amount of food. Similar quantities of food were consumed by animals in the control group fed with egg yolk and those fed with apple (Table 1). e palatability of the diets obviously affected the rate of consumption of each food and partly accounts for the trend in the �nal body weights of the animals. Table 3 presents the serum lipid pro�le of rats fed with different diets. As anticipated, the group of rats fed with egg yolk expressed the highest levels of LDL cholesterol (96.4 mg/dL), total cholesterol (117.4 mg/dL), and triglycerides (109.8 mg/dL) as well as the lowest level of HDL cholesterol (18.5 mg/dL). Egg yolk is rich in cholesterol (117.1 mg/dL) and its involvement in the incidence of cardiovascular diseases and atherosclerosis is popular [9]. On the contrary, rats fed with oats recorded the lowest level of total cholesterol (82.9 ± 1.8 mg), low density lipoprotein (LDL), cholesterol (49.3 ± 1.4 mg), and triglycerides (TG) (7 .1 ± 1.7 mg), as well as the highest level of HDL cholesterol (33.9 ± 0.9 mg).
ere was no signi�cant difference ( 0.0 ) between oats and apple in their effects on blood lipid pro�le of Wistar rats, with the chief constituent of these �bers being pectin and responsible for the hypocholesterolemic effect [10,11]. Rats fed with apple exhibited increased level of triglycerides (96.9 mg/dL) but exhibited lower levels of LDL cholesterol (57.9 mg/dL) and total cholesterol (88.5 mg/dL) when compared with rats fed with oats egg yolk. Lipogenesis may have accounted for the high triglycerides level observed in rats fed with apple when compared with those fed with oats and wheat bran [8]. e results observed with oat and apple in this study corroborate previous reports [6,7]. Wheat bran, though has the highest amount of crude �ber (9.9%) ( Table 2), had the least effect in improving the lipid pro�le of rats when compared to oats and apple. e reason for this is obvious in that wheat is chie�y composed of cellulose and lignin which are insoluble dietary �bers [11]. is observation agrees with the report of Jenkins and his colleagues, who reported in one of their studies [9] that wheat bran did not have any signi�cant effect on the serum lipids of individuals fed with it.
Soluble dietary �bers have been demonstrated to be bene�cial in the management or treatment of diabetes and cardiovascular disorders [5]. e actual role of these �bers in the entire process is unclear. Possibly, foods rich in soluble dietary �ber either reduced the �uantity or facilitate the elimination of other foods which may be risk factors for these diseases. Moreover, diets that are high in �ber tend to be low in energy and these diets can be useful in the control of body weight [12,13], a critical factor in individual's susceptibility to hyperlipidamia related disorders.

Conclusion and Recommendation
Overall, feeding of oats and apple to rats signi�cantly improves the serum lipid pro�le in this study. Consumption of foods rich in soluble dietary �bers such as oats and apple is highly encouraged. Dietary �ber is found only in plant foods such as fruits, vegetables, nuts, and grains. Milk, meat, and egg do not contain dietary �bers [14]; hence their intake should be minimized especially among adults. Moreover, excessive processing of �ber foods should be avoided. e removal of seed coat, peel, or hull reduces the �ber content of foods. For instance whole tomatoes have more �ber than peeled tomatoes; likewise, whole wheat bread contains more �ber than white bread [15].