Comparison Of The Effects Of Phospholipid Extracts From Heads Of Salmon And Silver Carp On High-fat Diet-induced Metabolic Syndrome And Analysis Of Related Metabolic Mechanism

Fish-derived lipids are rich in EPA/DHA-binding phospholipids,which have good effects on improving metabolic syndrome.In this study,the phospholipids of salmon head and silver carp head were isolated,prepared and structurally analyzed,and the effects of phospholipid extracts from heads of salmon and silver carp on the improvement of metabolic syndrome were elucidated through animal models and metabolomics,providing a theoretical basis for the comprehensive utilization of aquatic products processing by-products.The main research contents and conclusions are as follows.1.The total lipids in heads of salmon and silver carp were extracted by the Bligh-Dyer method,and the neutral lipids,glycolipids and phospholipids were separated by medium-pressure silica gel column chromatography.The composition characteristics of phospholipids in fish heads were analyzed by ultra-performance liquid chromatography-time-of-flight mass spectrometry(UPLC-Triple TOF-MS/MS).The results showed that the lipids in salmon and silver carp heads were mainly neutral lipids,but still contained a small amount of phospholipids.The proportion of phospholipid in the total lipid of salmon head was 2.61 %,and that of silver carp head was 5.13 %.n-3PUFA phospholipids in salmon head accounted for 31.35 % of the total phospholipids,and n-3PUFA phospholipids in silver carp head accounted for34.86 % of the total phospholipids.The total contents of PC and PE in salmon head and silver carp head accounted for more than 90 % of the total phospholipids,and they were the two phospholipids with the most n-3PUFA binding.The EPA in salmon head phospholipids is mainly bound to PC,while the binding ratio of DHA in PC and PE is similar.DHA and EPA in silver carp head are mainly combined with PC.The main molecular types combining EPA and DHA in salmon head phospholipids were PC 16:0/22:6 and PC 16:0/20:5,accounting for 6.63 % and 4.17 % of the total phospholipids,respectively.The main molecular species combining EPA and DHA in the phospholipid of silver carp head were PC 16:0/20:5 and PC16:0/22:6,accounting for 8.87 % and 5.92 % of the total phospholipid,respectively.2.Salmon head phospholipids extract(S-PLs)and silver carp head phospholipids extract(SC-PLs)were prepared from salmon and silver carp heads,and UPLC-Triple TOF-MS/MS was used to analyze the lipid molecular types and structural characteristics of the two phospholipid extracts.The results showed that the phospholipid contents of S-PLs and SC-PLs were 65.49 % and 66.16 %,respectively.PC,PE and triglycerides(TG)were the main lipid species in the two fish head phospholipid extracts.The n-3PUFA-type phospholipids(EPA+DHA)in S-PLs accounted for 20.84 % of the total lipids,and the n-3PUFA-type phospholipids in SC-PLs accounted for 21.95 % of the total lipids.The proportion of EPA phospholipids in SC-PLs to the total lipids(7.48 %)was higher than that in S-PLs(4.79 %).PC and PE were the two phospholipid components that most bound n-3PUFA.EPA and DHA in SC-PLs and S-PLs are mainly combined with PC.The EPA in S-PLs was mainly bound to PC,while the binding ratio of DHA in PE and PC was similar.The main molecular species combining EPA and DHA in SC-PLs were PC 16:0/20:5 and PC 16:0/22:6,accounting for 3.09 % and 1.67 % of the total lipids,respectively.The main molecular species combining EPA and DHA in S-PLs were PC16:0/22:6 and PC18:0/20:5,accounting for 4.26 % and 0.39 % of the total lipids,respectively.3.The effect of SC-PLs and S-PLs on high-fat diet-induced metabolic syndrome was studies.The model of metabolic syndrome mice was induced by the high-fat diet(40% energy from lipid).The results showed that both SC-PLs and S-PLs reduced body weight and white adiposity index in mice with metabolic syndrome(p<0.05).Total triglyceride(TG),total cholesterol(TC)and low density lipoprotein(LDL-C)in the liver of mice with metabolic syndrome were significantly reduced(p<0.05)after the intervention with S-PLs.The SC-PLs significantly reduced fasting blood glucose and serum insulin levels in mice with metabolic syndrome(p<0.05)and improved insulin resistance;it also reduced the content of serum TC and TG.At the same time,SC-PLs intake also increased liver TG content and reduced the formation of fatty liver.The level of liver inflammatory factors in mice with metabolic syndrome was significantly reduced after the intervention with SC-PLs,indicating that SC-PLs could inhibit liver inflammation.The above results showed that the SC-PLs significantly improved the disorder of glucolipid metabolism in mice with metabolic syndrome,and the effect was better than that of S-PLs.4.In order to explore the mechanism of SC-PLs and S-PLs in improving glycolipid metabolism,we analyzed the hepatic glycolipid metabolism pathways and metabonomers..The results showed that both the SC-PLs and S-PLs could down-regulate the lipid synthesis genes FAS,ME and ACC.Meanwhile,the fatty acidβ-oxidizing genes PPARα and CPT-1a were up-regulated to regulate liver lipid metabolism.Besides,it can up-regulate the m RNA expressions of IRS1,Akt1 and GLUT2 genes,promote the hepatic tissue to synthesize glycogen by glucose,and inhibit hepatic insulin resistance.Metabolomics analysis of the liver showed that the SC-PLs could improve glutathione metabolism in the liver and exert its anti-inflammatory effect by up-regulating the pro-inflammatory resolution lipid mediator 5-HEPE to inhibit arachidonic acid metabolism and reduce the release of pro-inflammatory factors.After intervention with the S-PLs,the pro-inflammatory regression lipid factor(±)17-HDHA was significantly increased,indicating that S-PLs also had a certain regulatory effect on liver lipid metabolism.It was speculated that the difference in liver metabolome was the reason for the different effects of SC-PLs and S-PLs on improving glycolipid metabolism,and the difference in metabolome was related to the different compositions of SC-PLs and S-PLs.