Glucose promotes cell growth and casein synthesis via ATF4/Nrf2-Sestrin2- AMPK-mTORC1 pathway in dairy cow mammary epithelial cells

In the dairy industry, glucose (Glu) is used as bioactive substance to increase milk yield. However, the molecular regulation underneath needs further clarification. Here, the regulation and its molecular mechanism of Glu on cell growth and casein synthesis of dairy cow mammary epithelial cells (DCMECs) were investigated. When Glu was added from DCMECs, both cell growth, β-casein expression and the mechanistic target of rapamycin complex 1 (mTORC1) pathway were increased. Overexpression and silencing of mTOR revealed that Glu promoted cell growth and β-casein expression through the mTORC1 pathway. When Glu was added from DCMECs, both Adenosine 5'-monophosphate-activated protein kinase α (AMPKα) and Sestrin2 (SESN2) expression were decreased. Overexpression and silencing of AMPKα or SESN2 uncovered that AMPKα suppressed cell growth and β-casein synthesis through inhibiting mTORC1 pathway, and SESN2 suppressed cell growth and β-casein synthesis through activating AMPK pathway. When Glu was depleted from DCMECs, both activating transcription factor 4 (ATF4) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression were increased. Overexpression or silencing of ATF4 or Nrf2 demonstrated that Glu depletion promoted SESN2 expression through ATF4 and Nrf2. Together, these results indicate that in DCMECs, Glu promoted cell growth and casein synthesis via ATF4/Nrf2-SESN2-AMPK-mTORC1 pathway.