Transgenic N-3 PUFAs Enrichment Leads To Weight Loss Via The Regulation Of Appetite-related Neuropeptides In Hypothalamus

Objective: At present,n-3 polyunsaturated fatty acids(PUFA)are effective against obesity,thus reduce the incidence of obesity related diseases.The fat-1 mice expressed the C.elegans fat-1 gene encoding an n-3 PUFA dehydrogenase that converts n-6 PUFA to n-3 PUFA.The fat-1 mice have significant amounts of n-3 PUFA,balanced n-6/n-3PUFA ratio which reduces the body weight.However,the detailed mechanism is not clear.With the model of fat-1 mice,we research the expression of appetite-related neuropeptides and uncoupling protein.The aim of this study is to explore the effect of fat-1 gene on body weight and possible mechanism.Methods: The fat-1 mice were a kind of gift from Professor Jingxuan Kang of Harvard Medical College and Jianbo Wan of University of Macau.Heterozygous transgenic fat-1mice were mated with C57BL/6 wild-type mice to produce wild-type(WT)and fat-1littermates.The mice were identified by PCR,all of the 6 weeks old healthy male mice were randomly divided into two groups: transgenic mice group and WT mice group.Body weight and length were recorded per week until the 8th week.At the end of the experiment,we killed the mice and weighed visceral around fat.We dyed the fat droplets in the liver by oil red O.Blood samples were taken to determine the content of the lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C)and total cholesterol(TC).NPY,Ag RP,CART,POMC,and Ghrelin neuropeptides in hypothalamus was measured by immunofluorescence.The m RNA of Leptin,UCP-1 and UCP-2 m RNA in adipose tissue were measured by q PCR.Leptin m RNA in blood was measured by q PCR.The protein of Leptin and UCP-2 in adipose tissue were measured by Western blotting.Results: We measured body weight and body length of the experimental animals weekly.The results showed that the body weight/length of fat-1 mice was lower than the WT mice(P<0.05).Fat weights of fat-1 mice were lower than that of the WT mice(P<0.05).The fat droplets in the liver were lower than the WT mice.The serum levels of HDL-C,LDL-C and TC in fat-1 mice were lower than the WT mice(P<0.05).Compared with wild-type mice,the levels of anorexigenic neuropeptide POMC/CART and growth peptide Ghrelin were higher,while the levels of feeding neuropeptide NPY/Ag RP were lower in fat-1 mice.UCP-1 and UCP-2 m RNA in adipose tissue were increased in fat-1mice,while Leptin decreased in fat-1 mice.Leptin m RNA in blood was of no significant difference.UCP-2 protein was increased in fat-1 mice,while Leptin protein was of no significant difference.Conclusion: The experimental results showed that the increase of endogenous n-3 PUFA level in fat-1 mice can improve energy metabolism and control the body weight.The mechanism might be achieved by modulating expression of appetite neuropeptides in the hypothalamus and UCP proteins in adipose.Leptin in two groups was of no significant difference.These results declared that body weight loss of fat-1 mice was not caused by Leptin.It may be caused by increased expression of UCP.The profound mechanisms need further research.