title: Amylin and leptin activate overlapping signalling pathways in an additive manner in mouse GT1-7 hypothalamic, C₂C₁₂ muscle and AML12 liver cell lines.
abstract: OBJECTIVE
  It has been suggested that amylin amplifies leptin's effects and affects energy homeostasis synergistically with leptin in animals and humans. However, no previous study has reported on amylin and leptin signalling in hypothalamic, muscle and liver cells.
  
  
  METHODS
  Leptin and amylin signalling studies were performed in vitro in mouse GT1-7 hypothalamic, C₂C₁₂ muscle and AML12 liver cell lines.
  
  
  RESULTS
  Treatment of mouse GT1-7 and C₂C₁₂ cells with leptin or amylin increased signal transducer and activator of transcription 3 (STAT3) phosphorylation in a dose- and time-dependent manner. In mouse AML12 cells, leptin and amylin produced a biphasic response of STAT3 activity. Importantly, all leptin and amylin signalling pathways were saturable at leptin and amylin concentrations of ∼100 and ∼50 to 100 ng/ml, respectively. Leptin and amylin in combination activated STAT3, AMP-activated protein kinase (AMPK), extracellular signal-regulated kinase (ERK) 1/2 and Akt signalling pathways in an additive manner, effects that were abolished under endoplasmic reticulum (ER) stress. Leptin, but not amylin, increased IRS-1 phosphorylation in GT1-7 hypothalamic, but not in C₂C₁₂ muscle and AML12 liver cell lines.
  
  
  CONCLUSIONS
  Our data suggest that leptin and amylin have overlapping and additive, but not synergistic, effects in the activation of intracellular signalling pathways. ER stress may induce leptin and amylin resistance in hypothalamic, muscle and liver cell lines. These novel insights into the mode of action of leptin and amylin suggest that these hormones may play an additive role in regulating energy homeostasis in humans.
authors: Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors: H-S
authors: HS
authors: Moon
authors: J P
authors: JP
authors: Chamberland
authors: C S
authors: CS
authors: Mantzoros
mesh_terms: D000818:Animals; D002460:Cell Line; D004229:Dithiothreitol / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D058228:Islet Amyloid Polypeptide / Q000235:genetics / Q000378:metabolism*; D020738:Leptin / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D032342:Muscle Cells / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D034622:RNA Interference; D034741:RNA, Small Interfering; D011994:Recombinant Proteins / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D058228:Islet Amyloid Polypeptide; D020738:Leptin; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D014415:Tunicamycin; D004229:Dithiothreitol