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Effect Of CLA On The Inhibition Of Lipogenic Gene Expression In Mammary Gland

Posted on:2012-03-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:L Q HanFull Text:PDF
GTID:1223330368487610Subject:Prevention of Veterinary Medicine
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ABSTRACT The molecular mechanism with regulation of milk fat synthesis in the mammary gland of lactating animals remain largely unknown.Recently, the characterization of lipogenic genes focused on the effect of lipid on mammary expression of these genes,especially the effect of Conjugated linoleic acid(CLA) on milk fat yield,composition and gene expression has largely been investigated in cows and mouse.Therefore,We test the lipogenic gene expression of mammary gland in lactating animal which received the CLA.(1)The mRNA expression and % relative mRNA abundance with 20 genes associated with lipid synthesis and secretion in mammary tissue was studied through the lactating period via quantitative PCR.The results indicated that: Genes involved in mammary FA uptake(LPL), FA synthesis (ACACA), desaturation (SCD) and lipid droplet formation (XDH, BTN1A1,ADFP) had the higher relative mRNA abundance and up-regulation in expression for the lactation.Moderate relative mRNA abundance were observed for genes associated with CD36,FASN and triacylglycerol synthesis (AGPAT6) .These genes expression was also up-regulation in lactation when compared with the pregnant period. Others genes are small amount.Change in SREBF mRNA expression during lactation,thought to be central for milk fat synthesis regulation, was >10-fold in magnitude and had a moderate % relative mRNA abundance, while expression of PPARγ, which the other regulators, was<1.5-fold and had a little mRNA abundance to SREBF.The effect of conjugated linoleic acid (CLA) supplements for reducing milk fat synthesis has been well documented in cows, but the molecular mechanisms involved in the mammary tissue are less convincing. Two experiments to study the effect of CLA on the milk fat synthesis was carried out on the farm.(2) Sixteen cows in lactation were randomly allocated to 4 treatments:grass hay plus concentrate either unsupplemented (control) or supplemented with Ca-CLA to provide 50 g/d (Low group),100 g/d (Medium group) and 200(High group) g/d for two weeks. The results showed that the milk yield didn’t changed in the cows of either control or supplemented with CLA. Compared with the control, CLA supplementation reduced milk fat content from 3.54 g/100ml to 2.94 g/100ml,2.58 g/100ml and 2.21 g/100ml respectively.Milk protein ,lactose content were unaffected by treatment. Gas-liquid chromatography analysis of the FAME revealed that Fatty acid composition of milk fat was markedly altered by CLA treatment. Supplementing the diet with Ca-CLA significant decreased the compozition of short and midium fatty acids(C6,C10,C12,C16), in which the concentration of stearic(C18:0),linoleic(C18:2) was significantly increased in milk fat (P<0.05). The yields of total milk fatty acids was reduced during the CLA treatment.(3)eight Holstein cows were blocked by parity and received a dietary fat supplement of either Ca-salts of palm oil fatty acids (control) or Ca-salts of Conjugated linoleic acid (CLA). Supplement provided about 200 g/d of fatty acids and continued for 14 d.Milk yield, and the content of protein and lactose in milk were unaffected by treatment. The cows receiving CLA supplement had a low milk fat content (2.21 versus 3.49%, P < 0.05).Milk fatty acid analysis indicated that CLA supplememnt reduced the secretion of all chains long fatty acids.The CLA diet also decreased mRNA expression of lipogenic enzyme of ACACA,FASN,LPL,SCD and expression of regulators of SREBF and INSIG1gene in cow mammary tissue. In addition, Our results indicated that CLA inbibit the de novo fatty acid synthesis and uptake of circulation fatty acid and provide evidence that SREBP is expected to be the predominant transcript expressed in mammary tissue.The effect of CLA on the lipid metabolism of lactating mouse and the molecular mechanisms involved in this process are unknown. Two experiments to study the effect of CLA on the lipid metabolism was carried out on the lactating mouse from lactation 4 to 15days .(4)Kunming (KM) mice are housed individually in polycarbonate cages under the conditions of 24°C, 40% humidity, and a 12-h light-dark cycle. The litters number was normalized to 8 at postpartum.All animals were fed the laboratory chow diet for the first 3 d.On day 4 postpartum,six lactating mice were randomly assigned to the control group (2% Peanut oil) or low lever CLA groups (LL group,0.5% CLA +1.5% Peanut oil); median lever CLA group (ML group, 1%CLA+1% Peanut oil); high lever CLA group (HL group, 1.5%CLA+0.5% Peanut oil) from day 4 to 15 postpartum.The results showed that dam body weight didn’t changed through the testing period, but the food significantly decreased of HL group compared with control group(14.51 vs 19.37), There were no differences in pup birth weights between control and CLA groups.After the intake of CLA food,The pups of HL group lost weight more rapidly, and from d 8 had significantly lower body weights than control pups (P<0.01) . At the end of the study,The pups weight of HL groups was significantly lower than those in control group (51.82 vs 67.93,P< 0.001) by d 15 of lactation.The milk weight obtained from the stomach ranged between 0·91 to 0·54 g/suckling pup.The milk lipid concentration of HL group was significantly lower than control(12.28 vs 15.42). There were no differences in the protein and lactose concentrations of milk from CLA and control groups. mRNA expression ratio of several lipogenic genes were analyzed in mammary tissue. Expression of ACC, SCD,LPL,FASN was significantly downregulated in mammary tissue in HL group compared with control (p<0.05).The regulators of SREBP,INSIG,PPARγandPPARGC1A mRNA gene expression was also down-regulated in mammary tissue in HL group com.(5) Twelve mouse was assigned to the control group (1.5% LA oil) or CLA groups (1.5% CLA oil) from day 4 to 15 postpartum ,and the results indicated that the dams food intake and pup body weight of CLA group was decreased when compared with control group by d 15 of lactation.The CLA group has a significantly lower milk volume,but the mammary and liver weight has no difference.Testing the blood and found that the content of CHO,HDL,LDL, Glucose,Insulin in CLA group had significant difference comparing with control group.The gene expression data showed that the mRNA expression of ACC,FASN,SREBP1-Cand PPARγwas down-regulated in the mammary of CLA group .mRNA expression of CD36,APOB100,FASN, SREBP1-Cand PPARγwas no significant differences ,but the mRNA expression of SCD was up-regulated and CPT1was down-regulated in the liver of CLA group.Based on these findings, we hypothesized that the effects of dietary CLA may be affect the lipid metabolism of liver and mammary in lactating...
Keywords/Search Tags:mammary gland, lactation, milk fat, gene expression, SREBF
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