title: Cooling reduces cAMP-stimulated exocytosis and adiponectin secretion at a Ca2+-dependent step in 3T3-L1 adipocytes.
abstract: We investigated the effects of temperature on white adipocyte exocytosis (measured as increase in membrane capacitance) and short-term adiponectin secretion with the aim to elucidate mechanisms important in regulation of white adipocyte stimulus-secretion coupling. Exocytosis stimulated by cAMP (included in the pipette solution together with 3 mM ATP) in the absence of Ca2+ (10 mM intracellular EGTA) was equal at all investigated temperatures (23°C, 27°C, 32°C and 37°C). However, the augmentation of exocytosis induced by an elevation of the free cytosolic [Ca2+] to ~1.5 μM (9 mM Ca2+ + 10 mM EGTA) was potent at 32°C or 37°C but less distinct at 27°C and abolished at 23°C. Adiponectin secretion stimulated by 30 min incubations with the membrane permeable cAMP analogue 8-Br-cAMP (1 mM) or a combination of 10 μM forskolin and 200 μM IBMX was unaffected by a reduction of temperature from 32°C to 23°C. At 32°C, cAMP-stimulated secretion was 2-fold amplified by inclusion of the Ca2+ ionophore ionomycin (1μM), an effect that was not observed at 23°C. We suggest that cooling affects adipocyte exocytosis/adiponectin secretion at a Ca2+-dependent step, likely involving ATP-dependent processes, important for augmentation of cAMP-stimulated adiponectin release.
authors: Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
authors: Mickaël F
authors: MF
authors: El Hachmane
authors: Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
authors: Ali M
authors: AM
authors: Komai
authors: Department of Physiology/Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
authors: Charlotta S
authors: CS
authors: Olofsson
mesh_terms: D041721:3T3-L1 Cells; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D017667:Adipocytes / Q000378:metabolism*; D052242:Adiponectin / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003080:Cold Temperature; D000242:Cyclic AMP / Q000378:metabolism*; D005089:Exocytosis; D015759:Ionomycin / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological
chemical_list: D052242:Adiponectin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D015759:Ionomycin; C044258:8-chloro-cyclic adenosine monophosphate; D000242:Cyclic AMP; D002118:Calcium