Analysis Of Effect Of Trans 10,cis 12-conjugated Linoleic Acid On Mice Growth And Metabolism

Trans-10,cis-12-conjugated linoleic acid(t10c12-CLA),one of the naturally occurring isomers of linoleic acid(LA,C18:2n-6)in milk and meat,has been reported to decrease body fat.However,a few studies suggested that CLA supplementation had no significant effect on the loss of fat,but could increase the risk of developing diabetes,non-alcoholic liver steatosis and cardiovascular disease.It is difficult to clarify these inconsistencies,because most animal experiments or clinical trials are based on the diet containing a variable fat content which supplied with CLA mixture containing an approximately equal amount of t10c12-and cis-9,trans-ll-CLA(c9t11-CLA).In addition,sources of industrial or natural CLA,host species(strain),age,gender,and nutritional status may also have an impact on the observed effects.This study aims to discuss the biological activity of t10c12-CLA and its influence on mammal lipid metabolism through two experiments.One is feeding mice with t10c12-producing recombinant food-grade Lactococcus lactis transformed with the pai isomerase gene.The other is analyzing physiological parameters of pai transgenic mice.In the first experiment,to investigate whether the dietary fat content has a role in the response of animals to t10c12-CLA,t10c12-producing recombinant food-grade Lactococcus lactis was used to feed slim,obesity-inducing,or obese mice.Compared with the non-CLA feeding mice,in the slim group the significant loss of body weight and abdominal adipose tissue were observed(P<0.05).The ratios of total cholesterol/HDL,and LDL/HDL were reduced(P<0.05),and the test group showed an early hepatic steatosis.In obesity-inducing mice,the body weight and abdominal adipose tissue were unexpectedly increased in company with an elevated(P<0.05)TG/HDL ratio.In obese mice,only the ratios of LDL/HDL and cholesterol/HDL were significantly reduced(P<0.05).In addition,within three groups,certain changes in fatty acid composition also occurred in various organs and tissues.In the second experiment,the code of the pai gene was optimized and cloned into pIRES2-AcGFP1 plasmid.This construct was introduced into murine NIH/3T3 fibroblast cells by lipofection.The intensity of GFP fluorescence and mRNA level indicated that pai could be highly expressed in mammalian cells.Total cellular lipid analysis showed that the pai expression resulted in an 223.7%increase(P<0.05)in tl0c12-CLA and inhibited the delta-6 fatty acid desaturase compared with the control.Then pCAGGS-pai plasmid was constructed and transgenic mice were generated.RT-qPCR analysis revealed that the pai gene was expressed in the transgenic tissues and organs.Gas chromatography showed that t10cl2-CLA could be detected in liver,kidney and muscle.The body weight of three weeks female F3 generation was obviously lowered in transgenic mice,and the ratio of LDL/HDL was aslo significantly reduced(P<0.05)in transgenic mice compared with wild type.These results suggest that endogenous expression of pai is beneficial for mammal in reducing body weight and the risk of cardiovascular disease.The dietary fat level and host obesity can alter the response to t10c12-CLA in animals.