BioMed Research International

BioMed Research International / 2018 / Article

Research Article | Open Access

Volume 2018 |Article ID 4398086 | 13 pages | https://doi.org/10.1155/2018/4398086

Effects of Chinese Dietary Pattern of Fat Content, n-6/n-3 Polyunsaturated Fatty Acid Ratio, and Cholesterol Content on Lipid Profile in Rats

Academic Editor: Ernesto S. Nakayasu
Received26 Oct 2017
Revised29 Jan 2018
Accepted08 Feb 2018
Published18 Mar 2018

Abstract

This study aims to investigate the effect of Chinese diet pattern of fat content (30% or 36.06%), n-6/n-3 polyunsaturated fatty acid (PUFA) ratio (5 : 1 or 9 : 1), and cholesterol content (0.04 or 0.057 g/kg total diet) on lipid profile using a rat model. Results showed that rats’ body weights (BWs) were controlled by the simultaneous intakes of cholesterol level of 0.04 g/kg total diet and n-6/n-3 ratio of 5 : 1. In addition, under high-fat diet, increased cholesterol feeding led to increased total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) levels and decreased triacylglycerols (TG) in rats’ plasma. However, high density lipoprotein cholesterol (HDL-C) level and the ratios of HDL-C/LDL-C and HDL-C/TC in rats’ plasma increased in response to simultaneous intakes of low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) even under high-fat diet. Moreover, as the n-6/n-3 PUFA ratio in the diet decreased, the proportion of n-3 PUFAs increased in plasma, liver, and muscle and resulted in the decrease of n-6/n-3 PUFA ratio.

1. Introduction

The amount and type of dietary fats largely influence plasma lipid content and play an important role in diseases prevention and development [1, 2]. In recent decade years, the number of obese and/or overweight people in China was up to 2,600 million and the data are increasing, which was largely associated with the unhealthy diet of high fat and cholesterol [3]. Data from National Nutrition and Health Survey in China showed that the average intake of fat was 76.2 g/60 kg·body weight (BW)·d in the whole country (30% total calories) and 85.6 g/60 kg·BW·d in the urban areas (36.06% total calories) [4]. And the consumption ratio of n-6/n-3 was 9 : 1 in both the whole country and the urban areas [5]. Moreover, the average cholesterol consumption in the whole country and the urban areas was 0.04 and 0.057 g/kg total diet, respectively [4, 5]. It is obvious that the Chinese dietary pattern of fat and cholesterol has surpassed the recommended level and the ratio of n-6/n-3 almost reached the upper level of FAO/WHO standards [6]. Besides, it was found that the increased Chinese dietary pattern of fat and cholesterol was positively associated with the increased morbidity and mortality of cardiovascular disease, with value of 0.98 and 1.00, respectively [5]. However, to the best of our knowledge, little has been reported regarding the influence of Chinese dietary pattern of fat and cholesterol on lipid metabolism.

Currently, there are many studies, using rat models, investigating the effects of different fatty acid ratios with or without cholesterol treatment on rats’ lipid metabolism. For example, Parrish et al. [7] found that there were attenuated perirenal and epididymal fat accumulation and reduction in adipocyte size in rats fed with a high-fat diet consisting of fish oil, compared to those fed with lard. Wong et al. [8] and Balasubramaniam et al. [9] reported that, in rats, dietary long-chain n-3 polyunsaturated fatty acid (PUFA) could reduce both triacylglycerols (TG) and cholesterol plasma concentrations. Yang et al. [10] found that comparing with rat group fed with n-6/n-3 ratio of 20 : 1, rat groups with the ratios of 1 : 1 and 5 : 1 had significantly decreased serum levels of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), and proinflammatory cytokines. Besides, Huang et al. [11] reported that the cholesterol-added diet (1%) did not impair the response to long-chain n-3 PUFA but increased the plasma cholesterol content and the liver weight. Moreover, Lu and Wu [12] found that added 1% cholesterol to diets led to a reduction of plasma TG and high density lipoprotein (HDL) levels and an increase of liver TG and cholesterol levels.

Therefore, the aim of this study was to investigate the influence of different fat intake, n-6/n-3 ratio, and cholesterol on lipids metabolism using a rat model according to the Chinese diet pattern. BWs, plasma lipid levels, and fatty acid compositions in rats’ plasma and tissues were determined and analyzed.

2. Methods and Materials

2.1. Materials and Chemicals

A total of 72 young male Sprague-Dawley rats (two or three months, 270 ± 33 g at the beginning of the experiment) were purchased from Experimental Animal Center of Jiangxi Medical College, China (approval number: 02196-02). They were randomly divided into 6 groups with 12 rats per group (Table 1) according to the different consumption of fat energy (30 or 36.06%), n-6/n-3 ratio (5 : 1 or 9 : 1), and cholesterol (0.04 or 0.057 g/kg total diet) and then were housed in the individual cages at a constant temperature of 22 ± 1°C with a normal 12 : 12 hours of light dark cycles. The six groups were Experimental Groups 1, 2, 3, and 4 (EG 1, 2, 3, and 4) and Control Groups 1 and 2 (CG 1 and 2). Except for different contents of palm oil and cholesterol in different groups, the compositions of other nutrients in the diet given to rats were identical (Table 2). Besides, rats in each group was intragastric gavage administered with blended oil of 0.8 mL/100 g·BW·d (EG 1, 2, 3, and 4) or 0.6 mL/100 g·BW·d (CG 1 and 2), so as to maintain the dietary consumption of fat energy and n-6/n-3 ratio in different group. The physical blended oil administered in each group consists of different proportions of camellia oil, sunflower oil, and linseed oil (fatty acid compositions shown in Table 3), and their formula in each group was shown in Table 4. All procedures involving animals were approved by the Ethics Committee, Nanchang University, and conducted in accordance with the guidelines of China for the care and use of laboratory animals.


energy proportion of fat (%) dose for oral administration of the blended oil in rats (mL/100 g⋅BW⋅d) cholesterol level (g/kg total diet)n-6/n-3

136.060.80.049 : 1
EG 236.060.80.0579 : 1
EG 336.060.80.045 : 1
EG 436.060.80.0575 : 1
CG 1300.60.049 : 1
CG 2300.60.0579 : 1

was experimental group and CG was control group. energy of fat consumed in the urban areas (36.06%) and in the whole country (30%), respectively. intake of blended oils in rats converted from Chinese dietary consumption per day in the urban areas (40 g/60 kg⋅BW⋅d) and in the whole country (30 g/60 kg⋅BW⋅d), respectively. cholesterol proportion of total diet in the whole country (0.04 g/kg total diet) and the urban areas (0.057 g/kg total diet), respectively.

Basal components (g/kg)Groups
EG1EG2EG3EG4CG1CG2

Corn flour480480480480480480
Soybean flour210210210210210210
Wheat bran170170170170170170
Wheat flour505050505050
Fish meal505050505050
CaH2PO4151515151515
Limestone power151515151515
Salt555555
Bean oil666666
Nutrient compositions (%)
 Carbohydrate52.58
 Fat3.50
 Protein21.2
 Moisture8.80
 Ash6.78
 Fiber2.80
Additional components
 Palm oil909086866161
 Cholesterol (mg/kg)405740574057

EG was experimental group and CG was control group. Different dietary treatments for groups: EG1 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); EG2 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1); EG3 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 5 : 1); EG4 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 5 : 1); CG1 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); CG2 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1). Different proportions of blended oil (g/100 g) for groups: EG1/EG2 (camellia oil 10 g, sunflower oil 74 g, and linseed oil 16 g); EG3/EG4 (camellia oil 18.6 g, sunflower oil 53.5 g, and linseed oil 27.9 g); CG1/CG2 (camellia oil 10.2 g, sunflower oil 73.5 g, and linseed oil 16.3 g).

Fatty acidsPalm oilCamellia oilSunflower oilLinseed oil

14:01.190.040.060.05
16:060.288.796.345.19
9c16:10.110.090.060.06
18:05.662.295.673.52
9t18:10.182.331.711.55
9c18:1 OA23.9876.4619.1220.35
11c18:11.41ND1.411.35
9c12c18:2n-6 LA5.516.8858.6614.31
20:00.360.050.300.23
18:3n-6NDNDND0.83
5c20:1ND0.02ND0.17
11c20:10.070.370.115.73
18:3n-3 ALA0.210.280.2134.65
21:0ND0.020.19ND
22:00.050.010.560.07
22:1n-9ND0.03ND0.31
23:00.030.01NDND
24:00.060.030.11ND
TSFA67.7311.3113.239.06
TMUFA25.5776.9520.7427.66
TPUFA5.737.2658.8750.28
n-6/n-326.2924.64279.330.44

OA, oleic acid; LA, linoleic acid; ALA, alpha-linolenic acid; TSFAs, total saturated fatty acids, the sum of (C14:0 + C16:0 + C18:0 + C20:0 + C21:0 + C22:0 + C23:0 + C24:0 + ⋯); TMUFAs, total monounsaturated fatty acids, the sum of (C16:1 + C18:1 + C20:1 + C22:1 + ⋯); TPUFAs, total polyunsaturated fatty acids, the sum of (C18:2n-6 + C18:3n-6 + C18:3n-3 + ⋯). ND, not detected. Different dietary treatments for groups: EG1 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); EG2 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1); EG3 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 5 : 1); EG4 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 5 : 1); CG1 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); CG2 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1). Different proportions of blended oil (g/100 g) for groups: EG1/EG2 (camellia oil 10 g, sunflower oil 74 g, and linseed oil 16 g); EG3/EG4 (camellia oil 18.6 g, sunflower oil 53.5 g, and linseed oil 27.9 g); CG1/CG2 (camellia oil 10.2 g, sunflower oil 73.5 g, and linseed oil 16.3 g).

Oil (g/100 g)EG1/EG2EG3/EG4CG1/CG2

Camellia oil1018.610.2
Sunflower oil7453.573.5
Linseed oil1627.916.3
Total100100100
Final fatty acid ratios administered to rats considering the oils in the chow
S : M : P1 : 1.22 : 11 : 1.19 : 11 : 1.21 : 1.03
n-6/n-39.125.049.07

EG was experimental group and CG was control group. S: total saturated fatty acids; M: total monounsaturated fatty acids; TPUFA: total polyunsaturated fatty acids. Different dietary treatments for groups: EG1 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); EG2 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1); EG3 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 5 : 1); EG4 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 5 : 1); CG1 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); CG2 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1). Different proportions of blended oil (g/100 g) for groups: EG1/EG2 (camellia oil 10 g, sunflower oil 74 g, and linseed oil 16 g); EG3/EG4 (camellia oil 18.6 g, sunflower oil 53.5 g, and linseed oil 27.9 g); CG1/CG2 (camellia oil 10.2 g, sunflower oil 73.5 g, and linseed oil 16.3 g).
2.2. Animal Treatment and Sampling

Before treatment, blood samples (about 0.5–1.0 mL) were collected from rats’ tail vein to measure the biochemical indices, such as TC, TG, LDL-C, and HDL-C. TC and TG were measured enzymatically on the automatic biochemistry analyzer (Beckman, CX4) because of their methodology, calibrators, and controls [13]. The very low density lipoprotein cholesterol (VLDL-C) and LDL-C were precipitated using dextran sulfate and magnesium sulfate before HDL-C was measured enzymatically on the same instrument. LDL-C was calculated from these values (TC, HDL-C, and TG) using the formula of Friedewald et al. [14] when the TG level was <4.52 mmol/L.

After 7-day basal chow, there was no difference in BWs or serum lipid profile among the six groups. Then, each group was maintained on the experimental diet for 60 days. Rats had free access to water. BWs were monitored weekly. After 60 days’ treatment, rats were fasted overnight (about 12 h, with water ad libitum) to reduce the feeding impact and then sacrificed under diethyl ether anesthesia. Blood samples were collected by cardiac puncture into clean test tubes containing 1% heparin sodium solution (w/w), centrifuged (4°C, 2500 r/min for 15 min) to get the plasma fraction, and then promptly stored at −80°C until analysis. The main organs and tissues (brain, heart, liver, and muscle) were removed and immediately rinsed in phosphate-buffered saline twice and then stored at −80°C until analysis.

2.3. Measurement of Biochemical Indices

Plasma lipid levels of TG, TC, LDL-C, and HDL-C after treatment were determined by automatic biochemistry analyzer (CX4, Beckman) as described above.

2.4. Fatty Acid Composition Analysis in Blood and Tissues

Total lipids were extracted with chloroform/methanol (v/v, 1 : 1) from the liver, brain, heart, muscle, and plasma according to the method of Folch et al. [15]. The obtained lipids were converted to fatty acid methyl esters (FAMEs) following the method of Lei et al. [16] and then analyzed by gas chromatography (model 6890N, Agilent Technologies, USA) equipped with an autoinjector, a fused-silica capillary column (CP-Sil 88, 100 m × 0.25 mm × 0.2 μm i.d.), and a flame ionization detector (FID) and operated on in splitless mode. The injector and detector temperatures were maintained at 250 and 260°C, respectively. The column temperature was held at 45°C for 3 min and then programmed to 175°C for 27 min at the rate of 13°C/min. The temperature was then further increased to 215°C at the rate of 4°C/min and held for 35 min. The oven temperature program was sustained for 86 min in total. The carrier gas was nitrogen, and the total gas flow rate was 52 mL/min. The injecting sample volume was 1 μL. Analysis of all peaks was accomplished by comparison of their retention times with FAME standards.

2.5. Statistical Analysis

Data were presented as mean ± SD and carried out using the Kruskal-Wallis one-way analysis by Statistical Package for the Social Sciences (SPSS) to compare differences between groups. values less than 0.05 () were considered significant.

3. Results

3.1. BWs

Under different diet of fat, n-6/n-3 ratio, and cholesterol, the change of BWs among six groups showed difference from the fourth week (Table 5). Compared with CG2 fed with fat energy of 30%, average BW in EG2 fed with higher fat energy of 36.06% was significantly increased (). Besides, with the same fat energy of 36.06% and n-6/n-3 ratio of 9 : 1, but different cholesterol level of 0.04 or 0.057 g/kg total diet, there was no significant difference () of BWs in EG1 and EG2. Also, with the same fat energy of 30% and n-6/n-3 of 9 : 1, but different cholesterol level of 0.04 or 0.057 g/kg total diet, there was no significant difference () of BWs in CG1 and CG2. However, with the same fat energy of 36.06% and n-6/n-3 of 5 : 1, the average BW in EG3 feeding cholesterol of 0.04 g/kg total diet was significantly lower than that in EG4 feeding cholesterol of 0.057 g/kg total diet (). Rats in EG4 fed with low n-6/n-3 ratio (5 : 1) but high cholesterol (0.057 g/kg total diet) showed no significant difference in BWs compared to those in EG1 feeding high n-6/n-3 ratio (9 : 1) but low cholesterol (0.04 g/kg total diet). Interestingly, rats in EG3 taking low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) showed significantly decreased BWs compared to those in EG2 taking high n-6/n-3 ratio (9 : 1) and cholesterol (0.057 g/kg total diet). All these results suggested that rats’ BW increased as the increase of fat energy, whereas the increase slowed down by reducing the intake of cholesterol under low intake of n-6/n-3 ratio.


The weekEG1EG2EG3EG4CG1CG2

0th
1st
2nd
3rd
4th
5th
6th
7th
8th
9th

Values presented as means () ± SD. Mean values within each row followed by different letters (a, b, c) are significantly () different. Different dietary treatments for groups: EG1 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); EG2 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1); EG3 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 5 : 1); EG4 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 5 : 1); CG1 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); CG2 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1). Different proportions of blended oil (g/100 g) for groups: EG1/EG2 (camellia oil 10 g, sunflower oil 74 g, and linseed oil 16 g); EG3/EG4 (camellia oil 18.6 g, sunflower oil 53.5 g, and linseed oil 27.9 g); CG1/CG2 (camellia oil 10.2 g, sunflower oil 73.5 g, and linseed oil 16.3 g).
3.2. The Plasma Lipid Levels

As shown in Table 6, for the groups with the same contents of fat energy (36.06%) and n-6/n-3 (9 : 1), rats in EG2 fed with cholesterol level of 0.057 g/kg total diet showed significantly () higher levels of TC (1.73 mmol/L) in plasma than those in EG1 fed with cholesterol level of 0.04 g/kg total diet (1.28 mmol/L). Likewise, with the same contents of fat energy (36.06%) and n-6/n-3 (5 : 1), the TC content in EG4 (cholesterol of 0.057 g/kg total diet) was  mmol/L, which was significantly higher () than that in EG3 (cholesterol of 0.04 g/kg total diet),  mmol/L. Besides, significant difference () was found between CG2 (cholesterol of 0.057 g/kg total diet) and CG1 (cholesterol of 0.04 g/kg total diet), containing 1.58 and 1.23 mmol/L of TC, respectively. Moreover, rats in EG3 taking low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) showed significantly decreased TC compared to those in EG2 taking high n-6/n-3 ratio (9 : 1) and cholesterol (0.057 g/kg total diet). From these results, it is clear that no matter the fat content in the diet, the higher cholesterol feeding might cause the higher plasma TC in rats. However, TC content in EG3 fed with 5 : 1 n-6/n-3 was similar to that in EG1 fed with 9 : 1 n-6/n-3, suggesting that n-6/n-3 ratio of 5 : 1 could not reduce plasma TC levels.


EG 1EG 2EG 3EG 4CG 1CG 2

TCB
A
TGB
A
HDL-CB
A
LDL-CB
A
HDL-C/LDL-CB
A
HDL-C/TCB
A

Values presented as means () ± SD. B and A represented before and after treatment, respectively. TC, total cholesterol; TG, triacylglycerols; VLDL-C, very low density lipoprotein cholesterol; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol. Mean values within each row followed by different letters (a, b, c) are significantly () different. B and A. Different dietary treatments for groups: EG1 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); EG2 (0.8 mL blended oil, 9% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1); EG3 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 5 : 1); EG4 (0.8 mL blended oil, 8.6% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 5 : 1); CG1 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.04 g/kg total diet, and n-6/n-3 9 : 1); CG2 (0.6 mL blended oil, 6.1% palm oil, cholesterol of 0.057 g/kg total diet, and n-6/n-3 9 : 1). Different proportions of blended oil (g/100 g) for groups: EG1/EG2 (camellia oil 10 g, sunflower oil 74 g, and linseed oil 16 g); EG3/EG4 (camellia oil 18.6 g, sunflower oil 53.5 g, and linseed oil 27.9 g); CG1/CG2 (camellia oil 10.2 g, sunflower oil 73.5 g, and linseed oil 16.3 g).

The TG contents in EG1, EG2, EG3, and EG4 were 0.43, 0.35, 0.46, and 0.38 mmol/L, respectively. The data showed that, with the same fat energy (36.06%) for EG2/EG4 and EG3, TG contents in EG2/EG4 fed with cholesterol of 0.057 g/kg total diet were significantly lower () than that in EG3 fed with cholesterol of 0.04 g/kg total diet. However, TG contents in CG1 (cholesterol of 0.04 g/kg total diet) and CG2 (cholesterol of 0.057 g/kg total diet), with the same fat energy of 30%, were 0.45 and 0.44 mmol/L, respectively, showing no significant difference (). There is a possibility that increased intake of cholesterol under high-fat diet could reduce plasma TG.

The contents of LDL-C in EG1, EG2, EG3, EG4, CG1, and CG2 were 0.39, 0.42, 0.28, 0.67, 0.36, and 0.39 mmol/L, respectively. The level of LDL-C in EG4 (cholesterol of 0.057 g/kg total diet) was significantly higher () compared to that in EG3/EG1 (cholesterol of 0.04 g/kg total diet). It can be inferred that the increasing cholesterol content in diet could increase level of LDL-C in plasma.

With the same n-6/n-3 (9 : 1) in EG1/EG2, the content of HDL-C in both was 0.61 mmol/L, showing no significant differences (). Similarly, the contents of HDL-C in CG1 and CG2 (9 : 1 n-6/n-3) were 0.54 and 0.50 mmol/L, respectively, showing no significant differences (). However, it was 0.63 and 0.99 mmol/L in EG3 and EG4 (5 : 1 n-6/n-3), respectively, which were higher than those in EG1, EG2, CG1, and CG2 (9 : 1 n-6/n-3). Results indicated that the HDL-C level increased with the increase of n-3 PUFAs in the diet.

Furthermore, HDL-C/TC were decreased significantly () in all groups after treatments. Besides, except for EG3, the ratios of HDL-C/LDL-C were also reduced significantly () in all groups after treatments. With n-6/n-3 ratio of 9 : 1, fat energy of 36.06% in EG1 and EG2, or 30% in CG1 and CG2, there was no significant difference in HDL-C/LDL-C. However, with the same fat energy of 36.06% and n-6/n-3 ratio of 5 : 1, the rats in EG3 fed with cholesterol of 0.04 g/kg total diet showed significantly higher ratio of HDL-C/LDL-C () than EG4 fed with cholesterol of 0.057 g/kg total diet (). Besides, under high-fat diet (36.06%), the ratios in EG4 () were relatively higher than in EG2 (), but significantly higher in EG3 () than in EG1 (), respectively, at the same level of cholesterol, difference in n-6/n-3 with 9 or 5. Moreover, rats in EG3 taking low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) showed significantly increased HDL-C/LDL-C and HDL-C/TC compared to those in EG2 taking high n-6/n-3 ratio (9 : 1) and cholesterol (0.057 g/kg total diet). These results demonstrated that decreased ratio of n-6/n-3 in diet could increase the ratio of HDL-C/LDL-C in plasma of rats under high-fat diet, and the increase level was significant accompanying low cholesterol feeding.

As shown in Table 7, negative correlations were found between HDL-C/LDL-C and TC (−0.423, 0.000), between HDL-C/LDL-C and LDL-C (−0.634, 0.000), between HDL-C/LDL-C and TG (−0.539, 0.010), and between TC and LDL-C (−0.253, 0.013). Besides, a negative correlation (−0.679, 0.031) was detected between HDL-C and BWs only in EG3 (not shown in the table). However, there was a positive correlation between TC and TG (0.210, 0.042).


Dependent variableIndependent variableCorrelation coefficient value

HDL-C/LDL-CTC0.000
TG0.010
LDL-C0.000
TCTG0.042
LDL-C0.013

lower than 0.01 () was very significantly different, and lower than 0.05 () was significantly different; TC, total cholesterol; TG, triacylglycerols; VLDL-C, very low density lipoprotein cholesterol; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol.
3.3. Effects of Dietary Fat and Cholesterol on FA Compositions in Plasma

The FAs profile in the diet could affect the FA compositions in rats’ plasma (Table 8). When the n-6/n-3 PUFA ratio in the diet decreased (EG 3 and 4), the proportion of n-3 PUFA in plasma increased, thus resulting in the decrease of n-6/n-3 PUFA ratio. Besides, rats fed with n-6/n-3 ratio of 9 : 1 (EG 1 and 2; CG 1 and 2) had significantly higher level of arachidonic acid (ARA) in the plasma compared to that in rats fed with n-6/n-3 ratio of 5 : 1 (EG 3 and 4). Moreover, the proportions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in rats feeding n-6/n-3 ratio of 5 : 1 (EG 3 and 4) were higher than those in rats feeding n-6/n-3 ratio of 9 : 1 (EG 1 and 2; CG 1 and 2). Cholesterol in diet can also affect the FA compositions in plasma. Rats fed with higher cholesterol (0.057 g/kg total diet) increased the TMUFAs (mainly oleic acid), but decreased the TSFAs (mainly stearic acid) compared to those in rats feeding cholesterol of 0.04 g/kg total diet. Further, rats in EG3 taking low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) showed higher EPA and DHA and lower ARA compared to those in EG2 taking high n-6/n-3 ratio (9 : 1) and cholesterol (0.057 g/kg total diet).


Fatty acidsEG1EG2EG3EG4CG1CG2

14:0
16:0
9c16:1
18:0
9t18:1
9c18:1 OA
11c18:1
9c12c18:2 LA
20:0
18:3n-6
5c20:1
11c20:1
18:3n-3 ALA
20:2n-6
22:0
20:4n-6 ARA
22:2n-6
20:5n-3 EPA
24:0