Study On The Effect Of The Different Fatty Acid Compositions On The Lipid Metabolism Of Rats And Its Relative Molecular Mechanisms

As the economic development and the changes of the people's dietary structure, the Cardiovascular disease (cardiovascular disease, CVD) has become the main disease that harms the human health and occupies the first place of the disease which causes death in our country. In the late 1990s, the middle-aged crowd hypercholesterolemia detection rate had reached more than one third in our country. In 2004, the people in some domestic cities, suburbs and rural areas were taking more than 30% of dietary fat. There were 160 million people got domestic dyslipidemia and the population of overweight and obesity has reached 260 million. Research shows that with the increase in consumption of animal products and generally sub-standard of the total energy intake, elevated blood cholesterol level is an important reason of lipid metabolic disorder that caused atherosclerosis (atherosclerosis AS) and cardio - cerebral vascular diseases. Particularly the reduction of LDL-C lowering blood lipid levels and increased HDL-C level is an effective measure for preventing and treating of cardiovascular disease.The development of chronic diseases is tightly relates to diet and nutrition. Generally speaking, when we observe the relationship between diet and CVD from different economic levels and structure of the group, eloquent testimony to the prevalence of the CVD among different groups is quite different from the fact that these differences and total dietary fat intake and the proportion of closely relate to species. Different types of fat affect blood lipids differently. For example, the intake of saturated fatty acids (saturated fatty acid, SFA) will increase the blood lipids and the monounsaturated fatty acids (monounsaturated fatty acid, MUFA) and the polyunsaturated fatty acids (polyunsaturated fatty acid, PUFA) will reduce the role of lipids. In addition, under the same total fat content of various fatty acid composition is different from the regulation of blood lipids and the incidence of chronic diseases, such as CVD, the development and effects will not be the same. Therefore, a reasonable reduction of total dietary fat intake and actively explore dietary fatty acid composition is very significant for promoting the ideal of health and preventing the incidence of CVD and other chronic disease. This research discusses how the different composition and the allocated proportion fatty acid influence the animal model to the rat's blood fat level through the study on the daily meals characteristic. In the meantime, during the different dietary fat process of intervention the key enzyme in lipid metabolism of fatty acid synthase (Fatty acid synthase, FAS), 3-hydroxy-3-methyl-glutaric acid-coenzyme A reductase (HMG-CoA-Hydroxy-3-M ethylglutaryl CoA Reductase, HMG-CoA R), the PPARα(Paroxysm proliferator- activated receptor alpha, PPARα) and the SREBP-1c (Sterol regulatory element binding protein-1c, SREBP-1c) mRNA expression of different fatty acid composition compares to a preliminary study of the dietary lipid metabolism the molecular mechanism of regulation that provids a scientific basis for the rational consumption of fatty acids.The experiment sets up 15% of the fat content (by weight, than for approximately 33%) dietary intervention, select lard (primarily SFA), olive oil (primarily MUFA), sunflower oil (n-6 PUFA main), fish oil (n-3 PUFA main providers) and n-6/n-3 PUFA ratio of 1:1 mixed oil to observe the different components of feeding and oil mixture ratio of lipid and lipid metabolism of fatty acids on gene expression of critical process, the main results and conclusions are followings:1. During the experiment, all groups of rats were fed to make sure the energy intake would be considerable. After experiment 6weeks, compare to other groups, the food taking of the rats in the group n-3 PUFA decreased gradually, also the weight decreased very obviously. In case to ensure the rest of the group of rats will grow normally, we chose the one who take less food to be the benchmark and gave them the same amount of the feed. From the statistics, since the experiment 6w, the weight of n-3 PUFA rats was significantly lower than the other five groups and through the experimental period, the rest of the rats in each group had no significant difference in weight. In addition, the result shows that the group n-3 PUFA is the only expectation. Otherwise, all groups of rats feeding were controlled successfully and reached expected result. The result shows that when the concentration of fat intervention reaches 15%, the high concentrations of fish oil (n-3 PUFA content of nearly 70%) in rats feeding will affect the growth and function state adversely. But this situation did not found in the same concentration of lard (primarily SFA), olive oil (primarily MUFA), sunflower oil (n-6 PUFA main), fish oil (n-3 PUFA main providers) and n-6/n-3 PUFA ratio of with a mixture of 1:1;2. Because of all the antioxidant diet and rigorous standards in all groups of rats feeding were kept a considerable amount of nutrients energy intake, we can think that dietary intervention of rats in each group at different levels of lipid composition and the ratio of fatty acids from the diet lipid effects. The study shows that SFA feeding could increase serum TG, TC, LDL-C, TC/HDL-C, LDL-C/HDL-C significantly; in the meanwhile lower the level of HDL-C. However, the study shows that the MUFA, n-6 PUFA, n-3 PUFA, and 1:1 n-6/n-3 PUFA feeding could reduce serum TG, TC, LDL-C, TC/HDL-C, LDL-C/HDL-C significantly; and increase the level of HDL-C. Further research of the group finds that 1:1n-6/n-3 PUFA lipid-lowering effect of the whole is generally better than the terms of MUFA and n-6PUFA, but have no significant difference from n-3 PUFA. Although in this concentration of n-3 PUFA could reduce the blood-fat, however, due to the over taking of the n-6/n-3 PUFA was imbalanced, the malnutrition and the response of the immune decreases. So in this experiment, a dietary with the n-6/n-3 with a percentage of 1:1 is the most effective way to regulate lipids body. It will prevent the cardiovascular diseases conductively.3. Through the 8 weeks and 18 weeks RT-PCR experiment of the lipid metabolism in rat liver genes FAS, HMG-CoA R, PPARα, SREBP-1c mRNA level expression. We found that the main method that the SFA and the MUFA control the body is using the HMG-CoAR and FAS, but the PPARαand SREBP-1c don't effect on it. Compared to control groups, SFA increases the expression of HMG-CoA R and FAS mRNA significantly (P<0.01) and MUFA could significantly reduce the expression of HMG-CoA R and FAS gene (P <0.05). For PUFA, it regulates blood lipid more comprehensive and significantly reduce the key enzyme in lipid synthesis FAS, HMG-CoA R and the expression of SREBP-1c. Also can promote lipid metabolism and fatty acidβ- oxidation of the expression of the key enzyme PPARα.