title: Induction of mitochondrial uncoupling enhances VEGF₁₂₀ but reduces MCP-1 release in mature 3T3-L1 adipocytes: possible regulatory mechanism through endogenous ER stress and AMPK-related pathways.
abstract: Although white adipocytes contain a larger number of mitochondria per cytoplasmic volume, adipocyte mitochondrial uncoupling to reduce the efficiency of ATP production on cellular function including secretory regulation of bioactive molecules such as VEGF and MCP-1 remains to be elucidated. Here we induce mitochondrial uncoupling under hypoxia-independent conditions in mature 3T3-L1 adipocytes using a metabolic uncoupler, dinitrophenol (DNP). MCP-1 release was significantly decreased by 26% (p<0.01) in 24h DNP (30 μmol/L)-treated adipocytes compared to control cells. In contrast, secreted VEGF(120) lacking a heparin-binding domain was markedly increased 2.0-fold (p<0.01). CHOP content in these cells also were augmented (p<0.01), but no significant increase of endogenous oxidative stress was observed. Treatment with thapsigargin, which can induce exogenous endoplasmic reticulum (ER) stress, clearly attenuated MCP-1 release (p<0.01), but exhibited no effects on VEGF(120) secretion. On the other hand, exogenous H(2)O(2) amplified both MCP-1 and VEGF(120) secretion (p<0.05). In addition, under chronic activation of AMPK by AICAR, MCP-1 release was significantly diminished (p<0.05) but VEGF(120) secretion was increased (p<0.01). JNK phosphorylation in mature adipocytes was decreased by treatment with either DNP or AICAR (p<0.01). Enhanced VEGF(120) secretion with either DNP or AICAR was markedly suppressed by PI3K inhibitor LY294002 (p<0.01). Thus, induced mitochondrial uncoupling in adipocytes can reduce MCP-1 release through induction of endogenous ER stress and by reduced JNK activities via chronic activation of AMPK. Under this condition, VEGF(120) secretion was increased through PI3K-dependent pathways, which were chronically activated by AMPK, and not through ER stress. Because the decrease of MCP-1 secretion under mitochondrial uncoupling might attenuate chronic low-grade inflammation by suppressing macrophages recruitment to adipose tissue, clarification of the mechanism might reveal novel therapeutic targets for ameliorating obesity-associated insulin resistance in metabolic syndrome and type 2 diabetes.
authors.affiliation: Third Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Miyokawa-Gorin
authors.forename: Kazuto
authors.initials: K
authors.lastname: Takahashi
authors.forename: Keiko
authors.initials: K
authors.lastname: Handa
authors.forename: Atsuko
authors.initials: A
authors.lastname: Kitahara
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sumitani
authors.forename: Hidenori
authors.initials: H
authors.lastname: Katsuta
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Susumu
authors.initials: S
authors.lastname: Nishida
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yoshimoto
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohno
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ishida
mesh_terms: D041721:3T3-L1 Cells; D000091162:AMP-Activated Protein Kinase Kinases; D017667:Adipocytes / Q000378:metabolism / Q000502:physiology*; D050156:Adipogenesis; D000818:Animals; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D053858:Metabolic Networks and Pathways; D024821:Metabolic Syndrome / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D009765:Obesity / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases