Essential amino acid ratios and mTOR affect lipogenic gene networks and miRNA expression in bovine mammary epithelial cells

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.

Melatonin suppresses milk fat synthesis by inhibiting the mTOR signaling pathway via the MT1 receptor in bovine mammary epithelial cells

“…The data above preliminarily suggest that melatonin decreased cellular TAG levels via the PI3K‐Akt, mTOR, and AMPK signaling pathways during milk fat synthesis in BMECs. mTOR links with other proteins and serves as a core component of two distinct protein complexes, mTORC1 and mTORC2, which regulate different cellular processes and play significant roles in milk fat synthesis as the vitally important signaling pathway . The mTOR signaling pathway is regulated by two main upstream signaling pathways named PI3K‐Akt and AMPK .…”

“…mTOR links with other proteins and serves as a core component of two distinct protein complexes, mTORC1 and mTORC2, which regulate different cellular processes and play significant roles in milk fat synthesis as the vitally important signaling pathway. [52][53][54][55][56] The mTOR signaling pathway is regulated by two main upstream signaling pathways named PI3K-Akt and AMPK. 57,58 Phosphorylated Akt promotes the phosphorylation of the initially activated mTORC2 at the Ser473 site, allowing it to fully activate and promoting cell growth and protein synthesis.…”

Supply of methionine and arginine alters phosphorylation of mechanistic target of rapamycin (mTOR), circadian clock proteins, and α-s1-casein abundance in bovine mammary epithelial cells

“…In this study, we hypothesized that a greater supply of Met or Arg based on an ideal AA profile which has been used in cell culture studies from our laboratory 17,30,31 stimulates casein protein abundance in bovine mammary epithelial cells (BMEC). We used mRNA and protein abundance analyses to explore the potential molecular mechanisms involved in the coordination of upstream components of mTORC1 signaling and the circadian clock network.…”

Phosphorylation of AKT serine/threonine kinase and abundance of milk protein synthesis gene networks in mammary tissue in response to supply of methionine in periparturient Holstein cows

“…Recent in vitro and in vivo studies with ruminant mammary cells provided evidence that AKT regulates de novo fatty acid synthesis via the mTORC1/ sterol regulatory element binding transcription factor 1 (SREBF1) axis (Li et al, 2016(Li et al, , 2018Zhang et al, 2018). Thus, nutritional activation of mTORC1 or AKT could not only alter milk protein, but also mammary lipid synthesis, in part through upregulation of gene networks controlling those processes (Pauloin and Chanat, 2012;Caron et al, 2015;Zhang et al, 2018).…”