Resistin is a key mediator of glucose-dependent insulinotropic polypeptide (GIP) stimulation of lipoprotein lipase (LPL) activity in adipocytes.
Studies on the physiological roles of the incretin hormone, glucose-dependent insulinotropic polypeptide (GIP) have largely focused on its insulinotropic action and ability to regulate beta-cell mass. In previous studies on the stimulatory effect of GIP on adipocyte lipoprotein lipase (LPL), a pathway was identified involving increased phosphorylation of protein kinase B (PKB) and reduced phosphorylation of LKB1 and AMP-activated protein kinase (AMPK). The slow time of onset of the responses suggested that GIP may have induced release of an intermediary molecule, and the current studies focused on the possible contribution of the adipokine resistin. In differentiated 3T3-L1 adipocytes, GIP, in the presence of insulin, increased resistin secretion through a pathway involving p38 mitogen-activated protein kinase (p38 MAPK) and the stress-activated protein kinase/Jun amino-terminal kinase (SAPK/JNK). The other major incretin hormone, glucagon-like peptide-1 (GLP-1), exhibited no significant effects. Chronic elevation of circulating GIP levels in the Vancouver Diabetic Fatty (VDF) Zucker rat resulted in increases in circulating resistin levels and activation of p38 MAPK or SAPK/JNK in epididymal fat tissue, suggesting the existence of identical pathways in vivo as well as in vitro. Administration of resistin to 3T3-L1 adipocytes mimicked the effects of GIP on the PKB/LKB1/AMPK/LPL pathway: increasing phosphorylation of PKB, reducing levels of phosphorylated LKB1 and AMPK, and increasing LPL activity. Knockdown of resistin using RNA interference attenuated the effect of GIP on the PKB/LKB1/AMPK/LPL pathway in 3T3-L1 adipocytes, supporting a role for resistin as a mediator.
Kim
Su-Jin
SJ
Department of Cellular and Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.
Nian
Cuilan
C
McIntosh
Christopher H S
CH
D016475:3T3 Cells; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; D017667:Adipocytes / Q000166:cytology / Q000201:enzymology*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004822:Epididymis / Q000201:enzymology; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism* / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000201:enzymology; D008071:Lipoprotein Lipase / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D011924:Rats, Zucker; D052243:Resistin / Q000378:metabolism* / Q000494:pharmacology; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D007328:Insulin; D009097:Multienzyme Complexes; D052243:Resistin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C491654:Stk11 protein, mouse; C488755:Stk11 protein, rat; D048051:p38 Mitogen-Activated Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D008071:Lipoprotein Lipase