Insulin acts via mitogen-activated protein kinase phosphorylation in rabbit blastocysts.
The addition of insulin during in vitro culture has beneficial effects on rabbit preimplantation embryos leading to increased cell proliferation and reduced apoptosis. We have previously described the expression of the insulin receptor (IR) and the insulin-responsive glucose transporters (GLUT) 4 and 8 in rabbit preimplantation embryos. However, the effects of insulin on IR signaling and glucose metabolism have not been investigated in rabbit embryos. In the present study, the effects of 170 nM insulin on IR, GLUT4 and GLUT8 mRNA levels, Akt and Erk phosphorylation, GLUT4 translocation and methyl glucose transport were studied in cultured day 3 to day 6 rabbit embryos. Insulin stimulated phosphorylation of the mitogen-activated protein kinase (MAPK) Erk1/2 and levels of IR and GLUT4 mRNA, but not phosphorylation of the phosphatidylinositol 3-kinase-dependent protein kinase, Akt, GLUT8 mRNA levels, glucose uptake or GLUT4 translocation. Activation of the MAPK signaling pathway in the absence of GLUT4 translocation and of a glucose transport response suggest that in the rabbit preimplantation embryo insulin is acting as a growth factor rather than a component of glucose homeostatic control.
Navarrete Santos
Anne
A
Department of Anatomy and Cell Biology, Martin Luther University Faculty of Medicine, Grosse Steinstrasse 52, D-06108 Halle (Saale), Germany.
Tonack
Sarah
S
Kirstein
Michaela
M
Pantaleon
Marie
M
Kaye
Peter
P
Fischer
Bernd
B
D000818:Animals; D001692:Biological Transport; D001755:Blastocyst / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D007150:Immunohistochemistry / Q000379:methods; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C057520:O-methylglucose polysaccharide; D011135:Polysaccharides, Bacterial; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011972:Receptor, Insulin; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D005947:Glucose