Abstract
BackgroundThe objective of this study was to study how changing the ratio of Lys to Thr, Lys to His, and Lys to Val affects the expression of lipogenic genes and microRNA (miRNA) in bovine mammary epithelial cells.ResultsTriplicate cultures with the respective “optimal” amino acid (AA) ratio (OPAA = Lys:Met 2.9:1; Thr:Phe 1.05:1; Lys:Thr 1.8:1; Lys:His 2.38:1; Lys:Val 1.23:1) plus rapamycin (OPAARMC; positive control), OPAA, Lys:Thr 2.1:1 (LT2.1), Lys:Thr 1.3:1 (LT1.3), Lys:His 3.05:1 (LH3.0), or Lys:Val 1.62:1 (LV1.6) were incubated in lactogenic medium for 12 h. The expression of 15 lipogenic genes and 7 miRNA were evaluated. Responses to LT2.1, LT1.3, LH3.0, and LV1.6 relative to the control (OPAARMC) included up-regulated expression of ACSS2, FABP3, ACACA, FASN, SCD, LPIN1, INSIG1, SREBF1, PPARD, and NR1H3 (commonly known as LXR-α). Furthermore, LV1.6 up-regulated expression of ACSL1, DGAT1, and RXRA and down-regulated PPARG expression. Although no effect of OPAA on expression of PPARG was observed, compared with the control, OPAA up-regulated expression of the PPAR targets ACSS2, FABP3, ACACA, FASN, SCD, LPIN1, INSIG1, and SREBF1. Compared with the control, the expression of the anti-lipogenic MIR27AB was down-regulated by OPAA, LT2.1, LT1.3 and LH3.0. In contrast, compared with the control, the expression of the pro-lipogenic MIR21 was up-regulated by LT2.1, LT1.3, LH3.0, and LV1.6.ConclusionsThe observed up-regulation of lipogenic gene networks and the changes in expression of key miRNA involved in the control of lipogenic balance are indicative of a potentially important role of EAA ratios and mTOR signaling in the regulation of milk fat synthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s40104-016-0104-x) contains supplementary material, which is available to authorized users.
Highlights
The objective of this study was to study how changing the ratio of Lys to Thr, Lys to His, and Lys to Val affects the expression of lipogenic genes and microRNA in bovine mammary epithelial cells
The preliminary study was conducted to determine a suitable incubation time based on peak mRNA expression of the genes eukaryotic translation initiation factor 4E, eukaryotic translation initiation factor 4E-binding protein 1, mechanistic target of rapamycin (Ser/Thr kinase), ras homolog enriched in brain, ribosomal protein S6 kinase beta-1, and tuberous sclerosis 1
Treatment with OPAA led to greater expression of FABP3 compared with LH3.0 (P = 0.04) and LV1.6 (P < 0.01), while incubation with LV1.6 resulted in lower expression compared with LT2.1 (P < 0.01) and LT1.3 (P < 0.01)
Summary
The objective of this study was to study how changing the ratio of Lys to Thr, Lys to His, and Lys to Val affects the expression of lipogenic genes and microRNA (miRNA) in bovine mammary epithelial cells. Rulquin et al [2] proposed “ideal” values for intestinal absorption of EAA in dairy cows; after absorption, AA flow first to the liver where substantial and differential net removal occurs leading to marked alterations in the. Both Lys and Met, at supraphysiological concentrations, are known to stimulate β-casein synthesis in dairy cow mammary epithelial cells (MEC) [5, 6]. A putative role for AA on lipogenesis has been uncovered using non-ruminant hepatocytes where Met and Lys plus insulin altered mTOR signaling and the expression of fatty acid (FA) synthase (FASN) [11]. Leu and Gln increased activity of acetylCoA carboxylase (ACACA) [12] in rat hepatocytes
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