Enzymatic Preparation Of Medium-and Long-Chain Triacylglycerol And Its Effect On Animal Lipid Metabolism And Related Diseases

Nowadays,the epidemic of obesity is a global public health issue.According to the World Health Organization,more than 39%of adults worldwide are overweight,and more than 13%of them reached obesity standards.Obesity often causes in vivo disorders of lipid metabolism and inflammations,and is closely related to a series of complications such as type 2 diabetes,liver steatosis and cardiovascular disease.Excessive fat intake caused by an unreasonable diet is one of the main causes of obesity.The development of functional fats that have fat-reducing effects and nutritional values as well as improve body fat metabolism can be an important way to prevent obesity.Medium-and long-chain triacylglycerols(MLCT)are structured lipids(SL)obtained from natural oils through modification or structural reorganization.They have both long chain fatty acids and medium chain fatty acids on one glycerol molecule.As a functional oil,MLCT is widely used in the fields of food and medicine.In this study.MLCT was prepared using medium-chain triacylglycerols(MCT)rich in C8:0 and C10:0 and high oleic rapeseed oil(HORO),and its effects on lipid metabolism,inflammation and related metabolic diseases in animals were explored.The research and its results are as follows:1.MCT and HORO were mixed at a molar ratio of 1:1 with 10%of Lipozyme RM IM,and the interesterification reaction was performed under a water bath at 60℃to obtain products containing MLCT.The product was purified by molecular distillation through first-stage molecular distillation(feed rate 2 mL/min,90℃ scraper speed 250 r/min)and second-stage molecular distillation(feed rate 1 mL/min,180℃,scraper speed 250 r/min)to remove free fatty acids,monoglycerides and diglycerides to obtain products with higher triglyceride content.The composition,physical and chemical properties of the product were analyzed.HPLC showed that the triglyceride content of the product reached 92.99%.The total/Sn-2 fatty acid composition of the product was determined.The main LCFAs in the product were oleic acid,linoleic acid and linolenic acid,and the main MCFAs were caprylic acid and capric acid,which was similar to the fatty acid composition on Sn-2.Analysis of triglyceride composition by high performance liquid chromatography-mass spectrometry analysis showed that the content of MLCT in the product was more than 50%,and the Equivalent Carbon Number(ECN)was 32～38.The above analysis results show that oils rich in MLCT can be effectively produced through the method of interesterification.2.The effect of MLCT on lipid metabolism in livers of rats in the short term was studied.Four-year-old male SD rats were randomly divided into a Control group,a MLCT group,a MCT group and a HORO group.The specific lipids were orally administered daily at a dose of 1 g/100 g for 2 weeks.The results showed that compared with HORO,MLCT significantly reduced plasma triacylglycerol(TG),total cholesterol(TC)and low density lipoprotein-cholesterol(LDL-C)levels;MLCT significantly inhibited the increase in liver weight,reduced hepatic TC and TG content and significantly increased the apolipoprotein A1/apolipoprotein B ratio.Gas chromatography showed significant changes in fatty acid composition of hepatic triglycerides and phospholipids,indicating that the intake of lipids could cause effective changes in the fatty acid composition in livers.Detection of hepatic lipid metabolism-related enzymes by ELISA revealed that hormone-sensitive triglyceride lipase(HSL),cyclic adenosine monophosphate(cAMP),and protein kinase A(PKA)levels were the highest in MCT rats,while the adipose triacylglyceride lipase(ATGL)levels were the lowest.In contrast,the HORO group had the lowest levels of HSL,cAMP and PKA,with the highest levels of ATGL.The levels of the above enzymes in the MLCT group were between those of MCT and HORO groups,and were higher than those in the Control group.The results show that MLCT improved lipid metabolism in rats in the short term with increased efficiency of lipid metabolism in the liver,thereby reducing the risk of related diseases.3.The effects of MLCT on long-term high-fat diet-induced lipid metabolism and metabolic diseases in obese rats were explore.Forty 4-week-old SD rats were randomly divided into 5 groups:Control group,HFD group,MLCT group,MCT group and HORO group.The control group was given a standard feed daily and normal saline at a dose of 1 g/100g body weight(BW),the HFD group was given a high fat diet and normal saline at a dose of 1 g/100 g BW,and the other three groups were given a high fat diet with specific lipids orally administered at a dose of 1 g/100 g BW for 6 weeks.The results showed that compared with HORO,MLCT significantly inhibited the body weight gain and tissue fat accumulation,reduced plasma TG and TC levels,increased HDL-C/LDL-C ratio,and reduced atherosclerosis risk.MLCT also significantly reduced the content of TG and TC in the liver and the apolipoprotein B/apolipoprotein A1 ratio,with reduced levels of fatty acid synthase and acetyl-CoA carboxylase.While the level of lipoprotein lipase increased.Oil red O staining of liver tissues showed that the number of lipid droplets in MLCT group was significantly reduced compared with HFD group.Gas chromatography also found that liver fatty acid content in MLCT group was lower than that in HFD group,but there was no statistical difference between the HORO and HFD group.The results showed that MLCT improved lipid metabolism in obese rats.High-fat diets also caused metabolic-related diseases in rats.The results showed that HORO significantly reduced fasting glucose tolerance and insulin sensitivity in rats,while MLCT and MCT effectively improved the blood glucose metabolism and insulin sensitivity.Compared with HORO group,the blood tumor necrosis factor-α(TNF-α),monocyte chemoattractant protein-1(MCP-1)and endotoxin levels in MLCT group were significantly reduced,while lower interleukin 6 and TNF-α levels and higher interleukin 10 levels were detected in the liver and white adipose tissue(WAT)of rats in MLCT group.An increase in plasma MCP-1 would cause more macrophages to invade WAT.This study showed that MLCT could effectively alleviate the lipid metabolism disorder and inflammatory response caused by high-fat diet,which might reduce the incidence of related metabolic diseases,indicating that MLCT could improve lipid metabolism and metabolic diseases under a long-term high-fat diet better than traditional oils.