Effect Of Maternal Dietary Protein Level On Fat Deposition In The Piglets At Weaning And The Research Of Lipid Metabolism Regulation Mediated By Leptin

The study aimed at (1) the determination of the effects of maternal protein restriction on lipid metabolism of piglets at weaning (2) the effect and mechanism of leptin on primary adipocytes of pigs in vitro. In order to study the lipometabolic status, we detect the mRNA, protein expression of perilipin and lipolytic enzyme (HSL and ATGL) and other related index.1 Effect of maternal dietary protein restriction on fat deposition of piglets at weaningSows in control group were fed with diets containing 12% and 14% of protein during pregnancy and lactation respectively, whereas protein levels reduced by half in treated group. Piglets born to sows in both control and treated groups were sacrificed after weaning. Back fat thickness of weaned piglets was measured. The leptin concentration in subcutaneous fat was determined by RIA assay. Gene expression of leptin, LepR, HSL, ATGL and FAS were quantitated with relative quantitative real time RT-PCR.We used western blot analysis to detect the content of perilipin and phosphorylated perilipin.The activity of lipases was also determined. The results showed that the body weight and back fat thickness of piglets in treated group were significantly smaller than that in control group. The leptin concentrations demonstrated a decreased tendency in maternal protein restriction group. Piglets in treated group exhibited significantly lower expression of ATGL, leptin, FAS mRNA (P<0.05). The phosphorylated perilipin content displayed a promoted trend in MPR offspring piglets than that in control piglets. Besides, the activity of lipases in subcutaneous fat was sigficanlty higher in MPR piglets than that in control group. The results suggest that the effect of maternal dietary protein restriction on fat deposition acted not only by reducing fat synthesis, but also by improving the ability of lipolytic.2 Effect and mechanism of leptin on primary cultured adipocytes of pigs SV cells were separated from subcutaneous adipose tissue of weaned piglet. Cells were cultured to 80% confluence followed by differentiation for 3 days. The cells were treated with 10-8 M and 10-7 M leptin respectively for 4h (acute treatment) or 48h (chronic treatment). We used oil-red O and immunofluorescence histochemistry to identify adipocytes, lipid droplets and perilipin. Cultured media were collected for quantitation of glycerol content. Perilipin, HSL and ATGL mRNA levels were determined by Real-time RT-PCR. Activity of lipases (HSL and ATGL) was determined. Perilipin and phosphorylated perilipin protein levesls were quantitated by Western blot analysis. After Leptin acute treatment for 4h,the viability of cells was increased significantly in 10-7M leptin treatment group; cells in both experimental groups released much more glycerol than in the control group; Perilipin, HSL and ATGL mRNA expression were significantly increased by 10-7 M leptin treatment, whereas 10-8 M Leptin treatment increased the mRNA expression of ATGL only; there was no alteration of lipase activity and perilipin content, and the phosphorylation of perilipin wasn't detected. After Leptin chronic treatment for 48h, Perilipin mRNA was down-regulated by 10-8 M leptin; 10-7 M leptin treatment could significantly down-regulate the expression of perilipin mRNA whereas up-regulate ATGL mRNA expression;importantly the phosphorylated perilipin were higher than control group in both treatement groups. The results indicate that acute treatment leptin may influence mRNA expression of related genes, and chronic leptin treatment activated phosphorylation of perilipin and increased lipolytic activity of mature adipocytes.