1771-P: Upregulation of RETN, TNFα, and CCL2 mRNAs in Adipocytes by Intermittent Hypoxia and Its MicroRNA-Mediated Mechanism

Abstract

Sleep apnea syndrome (SAS), characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]), is a risk factor for insulin resistance/type 2 diabetes. IH is considered to cause adipose tissue inflammation, leading to insulin resistance. In this study, we exposed mouse 3T3-L1 and human SW872 adipocytes to experimental IH (1% O2, 5% CO2 [5 min], 21% O2, 5% CO2 [10 min]) or normoxia (21% O2, 5% CO2) for 24 h, and analyzed mRNA expression of adipokines (leptin, adiponectin, resistin [RETN], tumor necrosis factor α [TNFα], IL-6, and C-C motif chemokine ligand 2 [CCL2]). We found that the mRNA levels of RETN, TNFα and CCL2 in SW872 cells (P=0.0257, P=0.0312, and P<0.0001, respectively) and 3T3-L1 adipocytes (P=0.0498, P=0.0237, and P=0.0002, respectively) were significantly increased by IH. RETN, TNFα, and CCL2 in IH-treated cell medium were also increased (P=0.0256, P=0.0215, and P<0.0001, respectively). We next prepared reporter plasmids containing human RETN (-979∼+20), TNFα (-966∼+19) and CCL2 (-3455∼+25) upstream of luciferase reporter gene, and transfected them into SW872 cells. The promoter activities of these genes were not increased by IH. Target mRNA search of microRNA (miR)s using MicroRNA.org program revealed that all the mRNAs have a potential target sequence for miR-452. The miR-452 level of IH-treated cells was significantly decreased than that of normoxia-treated cells (P=0.0458). To clarify the role of miR-452, miR-452 mimic and non-specific control RNA (miR-452 mimic NC) were introduced into SW872 cells, and the IH-induced up-regulation of RETN, TNFα, and CCL2 was abolished by introduction of miR-452 mimic but not by miR-452 mimic NC. These results indicate that IH stress down-regulates the miR-452 in adipocytes, resulting in the increased levels of RETN, TNFα, and CCL2 mRNA via the inhibition of the miR-452-mediated mRNA degradation, leading SAS patients to insulin resistance. Disclosure T. Uchiyama: None. A. Itaya-Hironaka: None. A. Yamauchi: None. M. Makino: None. S. Sakuramoto-Tsuchida: None. R. Shobatake: None. H. Ota: None. M. Takeda: None. C. Ohbayashi: None. S. Takasawa: None.