The Relationship Between Plasma Lipid Composition And Inflammatory Gene Expression Of Mammary Tissue In Rats During The Peripartum Period

The objective of the present study was to investigate the change pattern of plasma fatty acid composition and concentration in different reproductive and physiological stages of rats, and inflammation-related genes or enzyme in mammary glands, to discuss the relationship between peripartum lipid mobilization and inflammation in mammary glands.Two experiments were designed in our study, Experiment 1:30 SD female rats (pregnancy:nonpregnancy=4:1) were selected to fed homozygous diet which recommended by ANI-93G (containing 7% soybean oil) from Od the rats determined pregnancy.On day 1,14 of pregnancy and day 3 after parturition, collected blood samples of pregnant and non-pregnant rats; on day 14 of pregnancy,6 pregnant rats were slaughtered to collect samples of mammary tissue; on day 3 after parturition,6 rats were injected with LPS diluent, the other 6 rats were injected with saline in mammary tissue,9h after injection, all experimental rats (including non-pregnant rats 6) were slaughtered and collected samples of mammary tissue. The concentration of plasma free fatty acids, the composition and concentration of plasma fatty acid; and mRNA expression of TLR-4, IL-1β, IL-6, TNF-αand XOR in the mammary tissue were determined in our study. The results were as follows:1,Compared to the rats on day 14 of pregnancy, the plasma free fatty acid concentration of day 3 after parturition was elevated,and no significant change was observed in nonpregnancy rats during the whole experiment.2. From 14d of pregnancy to 3d after parturition, the total fatty acids, the total absolute concentration of saturated fatty acid (SFA) and unsaturated fatty acid (PUFA) were increased. The absolute concentrationΣSFA, mainly C16:0 and C18:0,Σn-3PUFA, mainly C22:6n3,Σn-6PUFA,mainly C20:4n-6 were increased, respectively. But on day 3 after parturition, there were no siginificant differences between LPS group and physiological saline group in composition and concentration of fatty acid.3,During the peripartum period, the cytokines in mammary gland had a increasing trend, but less than LPS group. Compared to the rats on day 14 of pregnancy, the mRNA of IL-1β(P<0.001), TNF-a(P<0.05) expression of day 3 after parturition were increased. Although the mRNA expression of IL-6 (P<0.10) and TNF-α(P<0.05) were slightly elevated in peripartum period, the level of IL-6 (P<0.05), TNF-αin day 14 of pregnancy were lower than the nonpregnancy rats. Compared with physiological saline group, LPS significantly inducing the expression of IL-6 (P<0.05), the expression of IL-1β, TNF-αhad a increasing trend.4,Compared to the nonpregnancy and day 14 of pregnancy rats, the mRNA expression of XOR in day 3 after parturition was siginificantly elevated.Experiment 2 was conducted to investigate the effects of different oil source in diet on the composition and concentration of plasma fatty acid compositions and inflammation gene expression in mammary gland. The experiment used two-factor randomized complete-block design, fed two diets, including soybean oil group(7% soybean oil), lard group(5% lard+2% soybean oil) at Od of pregnancy, Od to14d of pregnancy and from Od of pregnancy until 3d after parturition. Six treatment groups were formed,6 pregnancy rat were choosen for each group.The concentration of plasma free fatty acids, the composition and concentration of plasma fatty acid at the 0d,14d of pregnancy and 3d after parturition, and the mRNA expression of TLR-4, IL-1β,IL-6, TNF-a and XOR in mammary gland were measured. The results were as follows:1,Comparied to the lard group, the soybean oil group increased C18:1n9,ΣMUFA concentration of day14 of pregnancy and day 3 after parturition. As the pregnancy perid inceasing, C20:4n6, C22:6n3,Σn-3PUFA concentration were elevated siginificantly.2,Comparied to the lard group, the mRNA expression of TLR-4 in mammary gland of soybean oil group had a higher trend. On day 3 after parturition, the mRNA expression of TLR-4 in both groups was siginificanly higher than the nonpregnancy rats, and the mRNA expression of IL-6 and TNF-αwere higher than day 14 of pregnancyBased on the results above, we can conclud that:1,During the peripartum period, lipid mobilization increased, resulting a variety of fatty acids increased, especially saturated fatty acids.2,During the peripartum period, the mRNA expression of IL-6, IL-1β, TNF-a increased in mammary gland, to enhanced inflammation levels in mammary gland. 3. On day 3 after parturition, injection of LPS enhanced the expression of cytokine in the mammary tissue, aggravated the extent of mammary gland inflammation, and it suggested that LPS caused expression of inflammatory cytokines and SFA enhanced this effect.4,The different oil in the diets can change the the composition and concentration of plasma fatty acid, thereby casuing the expression of inflammatory cytokines; Supplentation of lard had a stronger effect in inducing IL-1 (3, IL-6 expression.Based on the conclusions above, this study make it clear the change pattern of plasma lipid fatty acid composition of perinatal rats fed with different diets, and the change pattern of inflammation-relateds gene in mammary tissue, this study provided basic data to reveal the relationship betwwen nutrition of fatty acid and inflammatory response in mammary tissue, which offers the new ideas for further study the molecular mechanism of high incidence of mastitis in peripartum dams.