Putrescine Stimulates the mTOR Signaling Pathway and Protein Synthesis in Porcine Trophectoderm Cells1

Abstract

Insufficient placental growth is a major factor contributing to intrauterine growth retardation in mammals. There is growing evidence that putrescine produced from arginine (Arg) and proline via ornithine decarboxylase is a key regulator of angiogenesis, embryogenesis, as well as placental and fetal growth. However, the underlying mechanisms are largely unknown. The present study tested the hypothesis that putrescine stimulates protein synthesis by activating the mechanistic target of rapamycin (mTOR) signaling pathway in porcine trophectoderm cell line 2 cells. The cells were cultured for 2 to 4 days in customized Arg-free Dulbecco modified Eagle Ham medium containing 0, 10, 25, or 50 μM putrescine or 100 μM Arg. Cell proliferation, protein synthesis, and degradation, as well as the abundance of total and phosphorylated mTOR, ribosomal protein S6 kinase 1, and eukaryotic initiation factor 4E-binding protein-1 (4EBP1), were determined. Our results indicate that putrescine promotes cell proliferation and protein synthesis in a dose- and time-dependent manner, which was inhibited by difluoro-methylornithine (an inhibitor of ornithine decarboxylase). Moreover, supplementation of culture medium with putrescine increased the abundance of phosphorylated mTOR and its downstream targets, 4EBP1 and p70 S6K1 proteins. Collectively, these findings reveal a novel and important role for putrescine in regulating the mTOR signaling pathway in porcine placental cells. We suggest that dietary supplementation with or intravenous administration of putrescine may provide a new and effective strategy to improve survival and growth of embryos/fetuses in mammals.

Glucocorticoids retard skeletal muscle development and myoblast protein synthesis through a mechanistic target of rapamycin (mTOR)-signaling pathway in broilers (Gallus gallus domesticus)

“…The results imply that the suppression of myoblast protein synthesis and muscle development induced by glucocorticoids is energy dependent, and that nutrition supplementation could relieve the stress response. These findings in chickens agree with a result in mammals (Kong et al, 2014), which revealed that AA administration promoted cell proliferation and protein synthesis by stimulating the mTOR-signaling pathway.…”

“…Leucine can stimulate the phosphorylation of S6K1 and eukaryotic initiation factor 4E binding protein1 (4EBP1) (Kimball et al, 1999;Kong et al, 2014), and increase tissue protein synthesis (Li et al, 2011;Yin et al, 2010). Shimizu et al (2011) reported that glucocorticoids inhibit mTOR activity via a distinct mechanism involving branched-chain amino acid transaminase 2 (BCAT2) gene activation.…”

Fetal and neonatal programming of postnatal growth and feed efficiency in swine

“…This leads to increased protein synthesis and whole-body growth [99]. Likewise, arginine or its metabolite putrescine activates mTOR to promote protein synthesis in placental cells and their proliferation [100]. In addition, dietary glutamine enhances intestinal integrity, cell survival, and villus height through the activation of mTOR cell signaling, while attenuating weaning-induced reduction in the abundances of occludin, claudin-1, zonula occluden (ZO)-2, and ZO-3 proteins [101].…”

Within-litter variation in birth weight: impact of nutritional status in the sow

“…et al, 2014a). Putrescine, which is a product of arginine catabolism in maternal tissues , can also stimulate protein synthesis in porcine placental cells (Kong et al, 2014). Of note, dietary supplementation of 0.8% L-arginine between Day 0 and Day 25 of gestation reduced litter size, uterine weight, total number of fetuses, number of corpora lutea and total fetal weights significantly at Day 25 .…”