The Effect Of Follicle-stimulating Hormone On Lipid Metabolism And Candidate Genes Expression In Chicken

Fat distribution is the process of differential accumulation of fat in different parts of the body.Abdominal fat and intramuscular fat are important economic traits in broiler chickens. Effects of thegonadotrophic hormone, FSH, on fat metabolism have been found recently; FSH significantly promotesdifferentiation and lipid deposition in preadipocytes. This study aims to verify the enhancing effect ofFSH on abdominal fat and intramuscular fat in vivo, and to understand the mechanism. We carried outthree experiments: the age-dependent changes in FSH secretion in chickens, the effect of FSH from twospecies on body fat deposition, and the effect of FSH on expression of genes related to fat metabolism.The results are given below with the details:1, Forty Beijing-You chicken (male: female=1:1) were used for testing normal FSH productionevery two weeks. There were no significant changes in content of FSH in female serum before6weeks,but a significant increase occurred at8weeks. There were no changes in males before8weeks. Theresults show that use of chickens younger than6weeks avoids possible confounding from endogenousproduction of FSH.2, Forty female chickens(1-d old) were randomly divided into4groups and subcutaneouslyinjected with4levels（0mIU/d，4mIU/d，17mIU/d，50mIU/d）of sheep FSH from d7to d14, thenweighted the body weight and also abdominal fat. Body weight and the proportion of abdominal fatwere not significantly changed in chickens injected with ovine FSH but were significantly increased inbirds treated with chicken FSH. The results confirm the stimulatory effect of chicken FSH on abdominalfat deposition and indicate specificity of the chicken FSHR.3, Sixty Beijing-You chickens (1-d old) were assigned into two groups, each with15males and15females, and the treated groups were subcutaneously injected with4mIU chicken FSH from d7to d14.Control groups were injected with the same volume of saline and weighted the body weight andabdominal fat to test the content of TG in breast muscle, the concentration of estrogen, luteinizinghormone, total cholesterol, high density lipoprotein and low density lipoprotein in serum as well as theexpression of genes related to lipid metabolism in breast muscle, liver and abdominal fat. After chickenFSH injection, the proportion of abdominal fat in male chicken has no significant difference comparedto the controls, the body weight and proportion of abdominal fat are significant higher in chiaken FSHinjecting group, and results indicate that the effect of FSH on lipid deposition is gender different. Infemales, the FSH content in serum and the TG content in breast muscle were significantly higher than incontrols after chicken FSH treatment, while the serum TG content was significantly lower, and therewere no differences in the serum contents of estrogen, LH, TC, HDL and LDL. The results show thatFSH may increase the intramuscular fat content in breast muscle, and the relative expression of DGAT2,FAS, H-FABP, EX-FABP, UCP3and PPARγwere significantly up-regulated in breast muscle. Treatmentwith FSH also significantly increased the relative expression of DGAT2, ACC, H-FABP, LPL, UCP3 and SREBP-1c in abdominal fat tissue. There were no significant effects of FSH on the expression ofthese genes in liver. The observed changes indicate that FSH promotes the accumulation of abdominalfat, probably by enhancing adipocyte differentiation, fatty acid synthesis, and transportof TG. FSHappears to increase the intramuscular fat content in breast muscle by enhancing fatty acid synthesis andlipid transport; none of these effects were found in liver.