Study On The Lipid-Lowering Activity Of Flaxseed Oil

Cardiovascular disease has become a leading cause which endangers human health and life, and the annual medical expense in China reaches almost 300 billion Yuan. Function oils are important materials for the prevention of cardiovascular disease. In order to increase their biological activity, many studies about the related factors have been conducted, including the physical and chemical quality, fatty acid composition and micronutrient composition. In this study, taking flaxseed oil as the research object, we focus on the fatty acid composition, processing technologies and exogenous micronutrient contents (vitamin E and phytosterols) on lipid-lowering activity of flaxseed oil, aiming for providing a theoretical basis for the development of high value-added functional food ingredients based on flaxseed oil or a-linolenic acid. The main results are as follows:(1) The effect of ALA content on lipid-lowering activity of flaxseed oilMale Wistar rats were divided into control group (Cont), high fat diet group (HFD), peanut oil group (PO),13%,27%and 55%α-linolenic acid blend oil (ALA-BO) groups. Except the Cont group, rats in other groups were fed with high fat feed and treated simultaneously with corresponding test oils (2 ml/kg, bw) for 6 weeks orally. The results showed that blend oils which contained 13%,27%and 55%a-linolenic acid (ALA) could regulate lipid metabolism through enhancing cholesterol secretion in hyperglycemic rats, and there was an accordant dose-response relationship between them. Plasma TC levels in 13%,27%and 55%ALA-BO groups decreased by 5%,12%and 19%(p<0.05) than PO group, TG levels decreased by 9%,19%,25%(p<0.05), and LDL-C levels decreased by 10%,16%,31%(P<0.05). Hepatic TC levels decreased by 14%,28%and 47%, TG levels decreased by 19%,45%,62%, and fecal cholesterol levels increased by 29%,43%,56% (p<0.05) respectively. But plasma MDA levels in 55% ALA-BO group increased by 11%, 14% when compared with 13%,27% ALA-BO groups. Therefore,13% and 27% ALA-BO groups had remarkable lipid-lowering activity, and also caused no oxidative damages on rats.Further studies on fatty acid composition in plasma, liver, brain, kidney and heart tissues of rats showed that high fat diet could reduce the n-3 PUFA levels in all tissues, but increasing ALA intake could result in an incorporation of n-3 PUFA in tissues and also showed a dose-effect relationship. There were some tissue-dependent differences in the increase of n-3 PUFA levels, the increase of ALA in kidney and heart was greater than that in plasma, brain and liver, and the EPA levels in brain and liver enhanced significantly, but no change was observed in DPA levels in kidney and heart, and there was no significant change in DHA levels in tissues. No difference was revealed in C18:3 (n-6) and C20:3 (n-6) levels among 13%,27% and 55%ALA-BO groups, but C20:4 levels decreased significantly in plasma, brain and kidney when compared with PO group. Our data suggested that oils rich in ALA could increase the levels of ALA and its metabolites in rat tissues and improve the relative proportion of EPA and DPA in brain, which may be one mechanism of ALA in reducing the risk of cardiovascular disease and promoting the growth of brain.(2) The effect of processing technology on lipid-lowering activity of flaxseed oilMale Wistar rats were divided into control group (Cont), high fat diet group (HFD), peanut oil group (PO), hot pressed and refining flaxseed oil group (HRFO) and cold-pressed flaxseed oil group (CFO). Except the Cont group, rats in other groups were fed with the high fat diet containing their respective oil for 4 weeks. The results showed that CFO could further reduce the plasma and hepatic TC, TG levels, and increase fecal cholesterol secretion when compared with the HRFO, in which the plasma TC levels in CFO group decreased by 19%(p<0.05), TG levels decreased by 8%(p>0.05) and LDL-C decreased by 11%(p>0.05), fecal cholesterol increased by 15%(p<0,05), and the hepatic TC levels decreased by 19%(p<0.05), TG levels decreased by 19%(p<0.05) when compared with HRFO group. And CFO could also further increase the T-AOC, GSH, SOD and VE content and reduce MDA levels in plasma and liver tissue(p<0.05), in which plasma and hepatic T-AOC levels increased by 11%,40%, GSH levels increased by 32%, 37%, SOD activity increased by 21%,26%, MDA levels reduced by 12%,27%, VE content increased by 27%,24%. Therefore, CFO has a more significant lipid-lowering activity when compared with the HRFO.(3)The effect of exogenous vitamin E and phytosterols on lipid-lowering activity of flaxseed oilMale Wistar rats were divided into hot pressed and refining flaxseed oil group (HRFO), low-dose VE enhanced flaxseed oil group (L-VE-HRFO), high-dose VE enhanced flaxseed oil group (H-VE-HRFO), low-dose phytosterols enhanced flaxseed oil group (L-PS-HRFO), high-dose phytosterols enhanced flaxseed oil group (H-PS-HRFO), low-dose VE and phytosterols enhanced flaxseed oil group (L-VE-PS-HRFO) and high-dose VE and phytosterols enhanced flaxseed oil group (H-VE-PS-HRFO), and the low and high doses of VE content were 100 and 200 mg/100g, the low and high doses of phytosterols contents were 1000 and 2000 mg/100g, and the experimental rats were fed with high fat diet containing the respective oil for 4 weeks. The results showed that increasing vitamin E levels in flaxseed oil could make the plasma and hepatic lipid levels of rats decrease to a certain extent, but no significant differences were observed (p>0.05). While the T-AOC, SOD, especially non-enzymatic antioxidant GSH and VE levels were significantly increased (p<0.05), and MDA levels were significantly lowered (p<0.05). Plasma T-AOC levels in L-VE-HRFO and H-VE-HRFO groups increased by 14%,22%, MDA levels decreased by 11%,19%, GSH levels increased by 35%,64%, and VE content increased by 79%,217%, respectively when compared with HRFO group. And the hepatic T-AOC levels in L-VE-HRFO and H-VE-HRFO groups increased by 18%,46%, MDA levels decreased by 17%,24%, GSH levels increased by 11%,59%, SOD activity increased by 12%,21%, VE content increased by 75%,124%when compared with HRFO group. Increasing the content of phytosterols in flaxseed oil could significantly reduce the plasma TG, TC and LDL-C levels, in which the plasma TG levels in L-PS-HRFO and H-PS-HRFO groups decreased by 15%,25%, TC levels decreased by 14%,26%, LDL-C levels reduced by 12%,28% than HRFO group, and hepatic TG, TC levels in L-PS-HRFO and H-PS-HRFO groups had significant differences when compared with the HRFO group(p<0.05). Combined addition of vitamin E and phytosterol had a significant influence on lipid-lowering activity of flaxseed oil which could optimize the plasma and hepatic lipid profiles and reduce the lipid per oxidation, and there was an accordant dose-response relationship.Thus, vitamin E and phytosterol enriched flaxseed oil could improve the lipid-lowering activity and inhibit the oxidative damage of body caused by high levels of ALA.