Oleic acid stimulates system A amino acid transport in primary human trophoblast cells mediated by toll-like receptor 4

We demonstrate that mTOR complex 1 modulates amino acid transport in primary human trophoblast cells by regulating Nedd4-2 mediated ubiquitination and plasma membrane trafficking of specific transporter isoforms, which may constitute a molecular mechanisms underlying abnormal human fetal growth.

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Regulation of amino acid transporters by glucose and growth factors in cultured primary human trophoblast cells is mediated by mTOR signaling

AJP Cell Physiology ◽

10.1152/ajpcell.00191.2009 ◽

2009 ◽

Vol 297 (3) ◽

pp. C723-C731 ◽

Cited By ~ 100

Author(s):

S. Roos ◽

O. Lagerlöf ◽

M. Wennergren ◽

T. L. Powell ◽

T. Jansson

Keyword(s):

Amino Acid ◽

Glucose Deprivation ◽

Mtor Signaling ◽

Amino Acid Transporters ◽

Trophoblast Cells ◽

Human Trophoblast ◽

System A ◽

System L ◽

Igf I ◽

Human Trophoblast Cells

Inhibition of mammalian target of rapamycin (mTOR) signaling in cultured human primary trophoblast cells reduces the activity of key placental amino acid transporters. However, the upstream regulators of placental mTOR are unknown. We hypothesized that glucose, insulin, and IGF-I regulate placental amino acid transporters by inducing changes in mTOR signaling. Primary human trophoblast cells were cultured for 24 h with media containing various glucose concentrations, insulin, or IGF-I, with or without the mTOR inhibitor rapamycin, and, subsequently, the activity of system A, system L, and taurine (TAUT) transporters was measured. Glucose deprivation (0.5 mM glucose) did not significantly affect Thr172-AMP-activated protein kinase phosphorylation or REDD1 expression but decreased S6 kinase 1 phosphorylation at Thr389. The activity of system L decreased in a dose-dependent manner in response to decreasing glucose concentrations. This effect was abolished in the presence of rapamycin. Glucose deprivation had two opposing effects on system A activity: 1) an “adaptive” upregulation mediated by an mTOR-independent mechanism and 2) downregulation by an mTOR-dependent mechanism. TAUT activity was increased after incubating cells with glucose-deprived media, and this effect was largely independent of mTOR signaling. Insulin and IGF-I increased system A activity and insulin stimulated system L activity, effects that were abolished by rapamycin. We conclude that the mTOR pathway represents an important intracellular regulatory link between nutrient and growth factor concentrations and amino acid transport in the human placenta.

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No evidence of attenuation of placental insulin-stimulated Akt phosphorylation and amino acid transport in maternal obesity and gestational diabetes mellitus

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00196.2019 ◽

2019 ◽

Vol 317 (6) ◽

pp. E1037-E1049 ◽

Cited By ~ 3

Author(s):

Marisol Castillo-Castrejon ◽

Thomas Jansson ◽

Theresa L. Powell

Keyword(s):

Insulin Resistance ◽

Amino Acid ◽

Gestational Diabetes ◽

Amino Acid Transport ◽

Pregnancy Complications ◽

Maternal Obesity ◽

Similar Degree ◽

Acid Transport ◽

Human Trophoblast ◽

Human Trophoblast Cells

Pregnancies complicated by obesity and/or gestational diabetes (GDM) are associated with peripheral insulin resistance; however, the insulin responsiveness of the placenta in these pregnancy complications remains largely unknown. We tested the hypothesis that primary human trophoblast cells and placental villous explants will be insulin responsive, characterized by amino acid transport, Akt and Erk activity with maternal obesity, and/or GDM. We evaluated term placentas from women with normal body mass index (BMI) (normal; n = 15), obesity (OB; n = 11), normal BMI with GDM (N-GDM; n = 11), and obesity with GDM (OB-GDM; n = 11). In a subgroup, primary human trophoblast cells (PHT) were isolated, and in an independent subgroup placental villous explants were exposed to varying concentrations of insulin. Amino acid transport capacity and insulin signaling activity were determined. Insulin significantly increased amino acid transport activity to a similar degree in PHT cells isolated from normal (+21%), N-GDM (+38%), OB (+37%), and OB-GDM (+35%) pregnancies. Insulin increased Akt and Erk phosphorylation in PHT cells (3-fold) and in villous explants (2-fold) in all groups to a similar degree. In contrast to the peripheral maternal insulin resistance commonly associated with obesity and/or GDM, we found that the placenta is insulin sensitive in these pregnancy complications. We suggest that elevated maternal insulin levels in pregnancies complicated by obesity and/or GDM promote critical placental functions, including amino acid transport. Insulin-stimulated placental nutrient delivery may contribute to the increased risk of fetal overgrowth and adiposity in these pregnancies. Moreover, our findings may inform efforts to optimize insulin regimens for women with GDM.

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Glucocorticoid regulation of amino acid transport in primary human trophoblast cells

Journal of Molecular Endocrinology ◽

10.1530/jme-19-0183 ◽

2019 ◽

Vol 63 (4) ◽

pp. 239-248 ◽

Cited By ~ 3

Author(s):

O.R. Vaughan ◽

T.L. Powell ◽

T. Jansson

Keyword(s):

Amino Acid ◽

Insulin Receptor ◽

Amino Acid Transport ◽

Mtor Signaling ◽

Acid Uptake ◽

Protein Abundance ◽

Acid Transport ◽

Human Trophoblast ◽

System A ◽

System L

Excess maternal glucocorticoids reduce placental amino acid transport and fetal growth, but whether these effects are mediated directly on the syncytiotrophoblast remains unknown. We hypothesised that glucocorticoids inhibit mechanistic target of rapamycin (mTOR) signaling and insulin-stimulated System A amino acid transport activity in primary human trophoblast (PHT) cells. Syncytialised PHTs, isolated from term placentas (n = 15), were treated with either cortisol (1 μM) or dexamethasone (1 μM), ± insulin (1 nM) for 24 h. Compared to vehicle, dexamethasone increased mRNA expression, but not protein abundance of the mTOR suppressor, regulated in development and DNA damage response 1 (REDD1). Dexamethasone enhanced insulin receptor abundance, activated mTOR complex 1 and 2 signaling and stimulated System A activity, measured by Na+-dependent 14C-methylaminoisobutyric acid uptake. Cortisol also activated mTORC1 without significantly altering insulin receptor or mTORC2 read-outs or System A activity. Both glucocorticoids downregulated expression of the glucocorticoid receptor and the System A transporter genes SLC38A1, SLC38A2 and SLC38A4, without altering SNAT1 or SNAT4 protein abundance. Neither cortisol nor dexamethasone affected System L amino acid transport. Insulin further enhanced mTOR and System A activity, irrespective of glucocorticoid treatment and despite downregulating its own receptor. Contrary to our hypothesis, glucocorticoids do not inhibit mTOR signaling or cause insulin resistance in cultured PHT cells. We speculate that glucocorticoids stimulate System A activity in PHT cells by activating mTOR signaling, which regulates amino acid transporters post-translationally. We conclude that downregulation of placental nutrient transport in vivo following excess maternal glucocorticoids is not mediated by a direct effect on the placenta.

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