Full-length adiponectin attenuates insulin signaling and inhibits insulin-stimulated amino Acid transport in human primary trophoblast cells.
OBJECTIVE
Maternal adiponectin levels are reduced and placental nutrient transporters are upregulated in obesity and gestational diabetes mellitus; however, the effects of adiponectin on placental function are unknown. We hypothesized that adiponectin regulates placental amino acid transport.


METHODS
Human primary trophoblast cells were cultured and incubated with globular adiponectin (gAd) or full-length adiponectin (fAd) alone or in combination with insulin. System A and L amino acid transport and SNAT1, SNAT2, and SNAT4 isoform expression was measured. The activity of the AMP-activated protein kinase (AMPK), phosphatidylinositol 3 kinase-AKT, and peroxisome proliferator-activated receptor-alpha (PPARalpha) signaling pathways was determined.


RESULTS
In the absence of insulin, gAd stimulated AMPK Thr172 phosphorylation, SNAT2 protein expression, and system A activity. This effect appeared to be mediated by interleukin-6 release and signal transducer and activator of transcription 3 (STAT3) signaling because gAd failed to stimulate system A in cells in which STAT3 had been silenced using small interfering RNA. fAd alone had no effect on system A activity or SNAT expression. Insulin increased AKT and insulin receptor substrate 1 (IRS-1) phosphorylation, system A activity, and SNAT2 expression. When combined with insulin, gAd did not affect system A activity or SNAT expression. In contrast, fAd abolished insulin-stimulated AKT Thr308 and IRS-1 Tyr612 phosphorylation, system A activity, and SNAT2 expression. Furthermore, fAd increased PPARalpha expression and PPARalpha (Ser21) phosphorylation.


CONCLUSIONS
In contrast to the insulin-sensitizing actions of adiponectin in liver and muscle reported in the literature, fAd attenuates insulin signaling in primary human trophoblast cells. As a result, fAd inhibits insulin-stimulated amino acid transport, which may have important implications for placental nutrient transport and fetal growth in pregnancy complications associated with altered maternal adiponectin levels.
Department of Obstetrics and Gynecology, University of Cincinnati, Cincinnati, Ohio, USA. helen.jones@cchmc.org
Helen N
HN
Jones
Thomas
T
Jansson
Theresa L
TL
Powell
D052242:Adiponectin / Q000494:pharmacology*; D000596:Amino Acids / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects*; D015153:Blotting, Western; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D047493:PPAR alpha / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D015398:Signal Transduction / Q000187:drug effects*; D014327:Trophoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*
D052242:Adiponectin; D000596:Amino Acids; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047493:PPAR alpha