The acute and chronic stimulatory effects of endothelin-1 on glucose transport are mediated by distinct pathways in 3T3-L1 adipocytes.
We have recently shown that pretreatment with endothelin-1 (ET-1) for 20 min stimulates GLUT4 translocation in a PI3-kinase-dependent manner in 3T3-L1 adipocytes (Imamura, T. et al., J Biol Chem 274:33691-33695). This study presents another pathway by which ET-1 potentiates glucose transport in 3T3-L1 adipocytes. ET-1 treatment (10 nM) leads to approximately 2.5-fold stimulation of 2-deoxyglucose (2-DOG) uptake within 20 min, reaching a maximal effect of approximately 4-fold at approximately 6 h, and recovering almost to basal levels after 24 h. Insulin treatment (3 ng/ml) results in an approximately 5-fold increase in 2-DOG uptake at 1 h, and recovering to basal levels after 24 h. The ETA receptor antagonist, BQ 610, inhibited ET-1 induced glucose uptake both at 20 min and 6 h, whereas the ETB receptor antagonist, BQ 788, was without effect. Interestingly, ET-1 stimulated 2-DOG uptake at 6 h, not at 20 min, was almost completely blocked by the protein-synthesis inhibitor, cycloheximide and the RNA-synthesis inhibitor, actinomycin D, suggesting that the short-term (20 min) and long-term (6 h) effects of ET-1 involve distinct mechanisms. GLUT4 translocation assay showed that 20 min, but not 6 h, exposure to ET-1 led to GLUT4 translocation to the plasma membrane. In contrast, 6 h, but not 20 min, exposure to ET-1 increased expression of the GLUT1 protein, without affecting expression of GLUT4 protein. ET-1 induced 2-DOG uptake and GLUT1 expression at 6 h were completely inhibited by the MEK inhibitor, PD 98059, and partially inhibited by the PI3-kinase inhibitor, LY 294002, and the G alpha i inhibitor, pertussis toxin. The PLC inhibitor, U 73122, was without effect. These findings suggest that ET-1 induced GLUT1 protein expression is primarily mediated via MAPK, and partially via PI3K in 3T3-L1 adipocytes.
Ishibashi
K
K
Department of Medicine, University of California, San Diego, La Jolla 92093-0673, USA.
Imamura
T
T
Sharma
P M
PM
Ugi
S
S
Olefsky
J M
JM
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007700:Kinetics; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D003513:Cycloheximide; D003609:Dactinomycin; D003847:Deoxyglucose; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D005947:Glucose; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D020928:Mitogen-Activated Protein Kinases; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D009842:Oligopeptides; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010880:Piperidines; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D010566:Virulence Factors, Bordetella; C495678:Slc2a1 protein, mouse; C495693:Slc2a4 protein, mouse; C087220:BQ 610; C086539:BQ 788