为了研究小鼠不同泌乳期乳脂肪合成相关基因的表达规律, 文章采用荧光定量PCR检测了小鼠乳腺中与脂肪合成和分泌相关20个基因的mRNA相对表达丰度和表达差异。结果表明, 在乳腺中脂蛋白脂酶(LPL)、乙酰辅酶A羧化酶(ACACA)、硬脂酰辅酶A去饱和酶(SCD)、黄嘌呤脱氢酶(XDH)、嗜乳脂蛋白(BTN)、脂肪酸分化蛋白(ADFP)基因都具有高mRNA表达丰度 (表达丰度>5%), 脂肪酸转运体(CD36)、脂肪酸合成酶(FASN)、1-酰基甘油磷酸酰基转移酶(AGPAT6)和甘油酰基转移酶(DGAT)基因具有中等mRNA表达丰度(5%>表达丰度>1%), 与妊娠期乳腺基因的mRNA表达相比, 在泌乳期这些基因的mRNA表达均有显著上调(P<0.05), 并且ACACA、SCD、FASN、AGPAT6和DGAT等脂肪合成酶基因的表达在泌乳中期(12 d)最高, 而在泌乳初期(6 d)和泌乳末期(18 d)较低, 呈现低-高-低的表达模式。转录因子固醇调节元件结合蛋白(SREBF)基因在泌乳开始时mRNA表达增加, 在泌乳中期(12 d)表达有10倍上调, 其变化规律与脂肪合成酶基因的表达模式相同, 说明SREBF基因在小鼠乳腺脂肪合成酶基因的表达调控中发挥重要调节作用。
To investigate the expression pattern of lipogenic genes in mammary gland of mouse in different lactation stages, the relative mRNA abundance and expression of 20 genes involved in milk fat synthesis and secretion of lactating mammary tissues were assessed using real-time PCR. Results revealed the significant upregulation of mRNA expression for both high abundant genes (abundance > 5%), such as LPL, ACACA, SCD, XDH, BTN, and ADFP and moderate abundant genes (5% > abundance > 1%), such as CD36, FASN, AGPAT6, and DGAT in lactation stages compared to pregnancy (P < 0.05). The mRNA expression of lipogenic enzyme genes for ACACA, SCD, FASN, AGPAT6, and DGAT exhibited lower expression lever in early (6 d) and late (18 d) lactation stages but higher expression level at middle stage (12 d), demonstrating a low-high-low pattern. Besides, the mRNA levels of some gene regulators were also measured. The mRNA expression of SREBF gene increased gradually along with the lactation, which showed a 10-fold elevation at middle stage (12 d). The expression pattern of SREBF gene was the same as lipogenic enzyme genes, suggesting that SREBF may play an important role in the regulation of lipogenic enzyme genes in the lactating mammary gland.
[1] Bauman DE, Mather IH, Wall RJ, Lock AL. Major advances associated with the biosynthesis of milk. J Dairy Sci, 2006, 89(4): 1235-1243.
[2] Bionaz M, Loor JJ. Gene Networks driving bovine milk fat synthesis during the lactation cycle. BMC Genomics, 2008, 9: 366.
[3] Wang CM, Li QZ. Identification of differentially expressed microRNAs during the development of Chinese murine mammary gland. J Genet Genomics, 2007, 34(11): 966-973.
[4] 孙杰, 罗军, 刘俊霞, 李大全. 不同泌乳期奶山羊乳腺OPN基因表达及其对MCF-7细胞生长的影响. 遗传, 2009, 31(8): 825-830.
[5] Schwertfeger KL, McManaman JL, Palmer CA, Neville MC, Anderson SM. Expression of constitutively activated akt in the mammary gland leads to excess lipid synthesis during pregnancy and lactation. J Lipid Res, 2003, 44(6): 1100-1112.
[6] Han LQ, Yang GY, Zhu HS, Wang YY, Wang LF, Guo YJ, Lu WF, Li HJ, Wang YL. Selection and use of reference genes in mouse mammary glands. Genet Mol Res, 2010, 9(1): 449-456.
[7] Fielding BA, Frayn KN. Lipoprotein lipase and the disposition of dietary fatty acids. Br J Nut, 1998, 80(6): 495-502.
[8] Jensen DR, Gavigan S, Sawicki V, Witsell DL, Eckel RH, Neville MC. Regulation of lipoprotein lipase activity and mRNA in the mammary gland of the lactating mouse. Biochem J, 1994, 298(Pt 2): 321-327.
[9] Doege H, Stahl A. Protein-mediated fatty acid uptake: Novel insights from in vivo models. Physiology, 2006, 21(4): 259-268.
[10] Stahl A. A current review of fatty acid transport proteins (SLC27). Eur J Physiol, 2004, 447(5): 722-727.
[11] Cases S, Zhou P, Shillingford JM, Wiseman BS, Fish JD, Angle CS, Hennighausen L, Werb Z, Farese RV Jr. Development of the mammary gland requires DGAT1 expression in stromal and epithelial tissues. Development, 2004, 131(13): 3047-3055.
[12] McManaman JL, Russell TD, Schaack J, Orlicky DJ, Robenek H. Molecular determinants of milk lipid secretion. J Mammary Gland Biol Neoplasia, 2007, 12(4): 259-268.
[13] Robenek H, Hofnagel O, Buers I, Lorkowski S, Schnoor M, Robenek MJ, Heid H, Troyer D, Severs NJ. Butyro-philin controls milk fat globule secretion. Proc Natl Acad Sci USA, 2006, 103(27): 10385-10390.
[14] Harvatine KJ, Bauman DE. SREBP1 and thyroid hormone responsive spot 14 (S14) are involved in the regulation of bovine mammary lipid synthesis during diet-induced milk fat depression and treatment with CLA. J Nutr, 2006, 136(10): 2468-2474.
[15] Cunningham BA, Moncur JT, Huntington JT, Kinlaw WB. "Spot 14" protein: a metabolic integrator in normal and neoplastic cells. Thyroid, 1998, 8(9): 815-825.
[16] Medina-Gomez G, Gray S, Vidal-Puig A. Adipogenesis and lipotoxicity: Role of peroxisome proliferator-activated receptor γ (PPARγ) and PPARγcoactivator-1 (PGC1). Public Health Nutr, 2007, 10(10A): 1132-1137.
