Effect Of Medium And Long Chain Triglyceride Structures On The Lifespan Of Caenorhabditis Elegans

The medium and long chain triglycerides mainly have structured triglycerides(STG)and physical mixtures of medium and long chain triglycerides(MCT/LCT).The total fatty acid compositions of the MCT/LCT and STG are the same,but the fatty acids has different position in the triglycerides.MCT/LCT and STG are different in digestion and absorption,lipid metabolism,immune inflammation.Lifespan is a comprehensive indicator of health.Studies have shown that fatty acids ingested by organisms can affect their lifespan,but the effect of the position of fatty acids in triglycerides on lifespan has rarely been reported.Caenorhabditis elegans is an ideal model for studying life mechanisms.However,the water-soluble culture environment in the laboratory limits Caenorhabditis elegans the application to study the nutrition of lipids.In this paper,the protein emulsion embedding technique was used to successfully deliver lipids to the Caenorhabditis elegans and the effects of MCT/LCT and STG on the lifespan of Caenorhabditis elegans were evaluated.The main findings are as follows:Firstly,a lipid delivery method for Caenorhabditis elegans was established based on protein emulsion embedding technology.The protein emulsions with particle size of 200-400 nm were prepared by high-pressure homogenization method.Fluorescent label method showed that the emulsions could be ingested by Caenorhabditis elegans successfully.The fatty acid analysis of Caenorhabditis elegans cultured in protein emulsions showed that the effect of emulsion particle sizes and oil concentrations in the medium on ingestion.The results showed that when the particle size in the range of 200-400 nm,the smaller particle sizes contributed to the ingestion of Caenorhabditis elegans.When the oil concentration is in the range of 0.01-10 mmol/L,the higher the oil concentration contributed to the ingestion of Caenorhabditis elegans.In addition,the method was also verified by conjugated linoleic acid triglycerides.The results showed that the conjugated linoleic acid triglyceride was successfully metabolized by Caenorhabditis elegans,which reduced the fat accumulation.Secondly,STG was synthesized by interesterification of medium chain triglycerides and trioleins.The enzyme amount,reaction temperature and reaction time of the enzymatic interesterification were optimized.The optimum conditions for preparation of STG were as follows: Lipozyme 435 of 6% as catalyst,heating temperature of 90oC,reaction time of 6 h.The physical and chemical indexes of STG and MCT/LCT were studied.Compared with MCT/LCT,the oxidative stability of STG increased by 38.41%,the melting point decreased by 16.44%,the type of triglycerides increased by 24 kinds,the medium chain fatty acids in sn-2 decreased by 7.71%,long-chain fatty acids in sn-2 decreased by 7.71%,the ratio of saturated and unsaturated fatty acids did not change.Finally,the effects of MCT/LCT and STG on the lifespan of Caenorhabditis elegans were studied.The effects of MCT/LCT and STG on the physiological and biochemical indexes of Caenorhabditis elegans were studied.Compared with STG group,the lifespan of Caenorhabditis elegans in the MCT/LCT group was reduced by 20.19%,the fat accumulation increased by 15.29%,and the active oxygen increased by 28.17%,malondialdehyde increased by 55.99%,superoxide dismutase activity decreased by 29.84%,and catalase activity decreased by 36.28%.There was no significant change in glutathione peroxidase activity.The changes of mRNA levels of key genes related to Caenorhabditis elegans lifespan were analyzed.The results showed that the transcription level of the aak-2 gene of the AMPK ? subunit in the MCT/LCT group was decreased by 33.33% compared with the STG group,the superoxide dismutase and catalase related genes sod-3 and cat-1 transcriptional levels were decreased by 14.08% and 43.16%,while the glutathione peroxidase-related gpx-1 gene was no significant change,the key gene of calorie restriction pathway sir-1.2,Insulin/Insulin-like growth factor signaling pathway key gene daf-16 and daf-2 were no significant change in the transcription levels.The above pathway was further verified by the gene-deficient Caenorhabditis elegans.The results showed that the MCT/LCT and STG affects the lifespan of Caenorhabditis elegans by aak-2 gene.