The Digestion And Absorption Characteristics And Effects On Lipid Metabolism Of Different Molecular Forms Of N-3 Long Chain Polyunsaturated Fatty Acids

Fish oil is abundant in n-3 series of long chain polyunsaturated fatty acids (n-3 LCPUFA), mainly EPA and DHA. The significant physiological activities of n-3 LCPUFA, such as preventing cardiovascular and cerebrovascular diseases, enhancing the visual and nervous system functions, anti-cancer, anti-inflammation and raising immune abilites, have been widely confirmed, which attracted increasing attention. Now, there are several molecular forms of n-3 LCPUFA-enriched products, involving free fatty acid (FFA), ethyl ester (EE), triglyceride (TG). FFA is highly unsaturated, making it susceptible to oxidative rancidity and EE is difficult to be digested and may cause alcohol intoxication. However, TG and phopholipid (PL), common in nature, is easily absorbed and safe to eat. Recently, PL is considered more conducive to absorption than TG and has superior physiological functions. But, the systematic comparation study on the digestion and absorption characteristics as well as nutritional benefits among PL, FFA, EE and TG is still scarce,In this study, we fisrt compared the effects of different types (FFA, EE, TG, PL) of n-3 LCPUFA and the compound of TG and egg yolk phospholipid (EGG-PL) on lipid metabolism in mice fed high-fat diet. The results showed that after short-term supplements of different molecular forms of n-3 LCPUFA, the lipid metabolism in mice was improved to varying degrees. In terms of lowering serum lipid, PL was the best and prevented the occurrence of atherosclerosis, while the compound could reduce the hepatic triglyceride content. TG enhanced the proportion of n-3 PUFA in liver, however, PL could significantly increase the level of DHA in brain. In the long-term experiment, in terms of decreasing the level of triglycerides, PL, the compound and TG is better than EE and FFA. In detail, PL worked best and TG took the second place, while the compoud showed the optimal cholesterol-lowering effect in mice. In additon, TG and PL were good sources of hepatic and cerebral DHA, respectively. The comparation of short-term and long-term experiments suggested that when DHA is used aiming at boosting mental development, short-term supplement might be enough effective. Meanwhile, we found that the DHA-bound PL differed from the simple mixture of TG and EGG-PL in the aspect of improving lipid metabolism and performed the best effect on reducing serum lipid level. Besides, DHA-enriched PL (DHA-PL) and EPA-enriched PL (EPA-PL) play different roles in improving lipid metabolism in obese mice. Whether the short or long term experiment, EPA-PL was more effective in anti-obesity and prevention of atherosclerosis, while DHA-PL could significantly increase the contents of DHA in tissues.The difference of the effects of n-3 LCPUFA which possess different molecular structures may be related to different characteristics of digestion and absorption. In our study, TG was hydrolyzed in the small intestine, releasing FFA and MG, while PL was degraded to FFA and lysophospholpids. TG was absorbed faster than PL, but after the gavage of PL, the serum DHA and EPA could be maintained at a high level for a long time. So far, a few studies have examined the influence of the galenic formulation of n-3 LCPUFA supplements on the digestion and absorption. Our study showed that the consumption of PL in a liposome form was significantly more effective compared to the consumption of the same PL in an emulsified form. The liposome form of PL remarkedly increased the content of serum n-3 LCPUFA, performing slow release and high efficiency. Besides, due to different fatty acid profiles or different nitrogenous bases, DHA-PL and EPA-PL were digested and absorbed in different ways. Our results demonstrated EPA-PL is absorbed more slowly than DHA-PL and EPA-PL could keep serum EPA content at a higher level.In conclusion, in this paper, the digestion and absorption characteristics and short-term and long-term effects on lipid metabolism of different molecular forms of n-3 LCPUFA have been studied systematically and comprehensively which provided a scientific basis for the assessment or development of n-3 LCPUFA.