RESUMEN
Sumoylation of peroxisome proliferator-activated receptor γ (PPARγ) affects its stabilization, sublocalization, and transcriptional activity. However, it remains largely unknown whether PPARγ sumoylation inhibits the transactivation effect, leading to endothelium insulin resistance (IR). To test this possibility, human umbilical vascular endothelial cells (HUVECs) with a 90% confluence were randomly allocated to two batches. One batch was first pretreated with or without vitamin E for 24 hr and the other infected with adenoviruses containing either PIAS1-shRNA (protein inhibitor of activated STAT1-short hairpin RNA) or scramble shRNA. Cells were suffered from high glucose and palmitic acid (PA) exposure for further 48 hr. The levels of PPARγ, p-IKK, IKK, and NcoR (nuclear corepressors) were measured by western blot analysis. The interaction of IKK and PIAS1, as well as the PPARγ sumoylation, were examined by coimmunoprecipitation. The results showed that the exposure of high glucose and PA induced reactive oxygen species (ROS) production and IKK activation in HUVECs, promoting the interaction of IKK and PIAS1 and the sumoylation of PPARγ. However, vitamin E and PIAS1-shRNA partially decreased ROS production and IKK activation induced by high glucose and PA exposure. These data indicate that ROS-IKK-PIAS1 pathway mediates PPARγ sumoylation, leading to endothelium IR via stabilizing PPARγ-NcoR complex. These findings benefit understanding of regulatory networks of insulin signaling, which might provide a potential target to prevent and cure IR-related diseases.
Asunto(s)
Resistencia a la Insulina/genética , Insulina/genética , Co-Represor 1 de Receptor Nuclear/genética , PPAR gamma/genética , Factor de Transcripción STAT1/genética , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Redes Reguladoras de Genes/efectos de los fármacos , Glucosa/farmacología , Células Endoteliales de la Vena Umbilical Humana , Humanos , Insulina/metabolismo , Complejos Multiproteicos/genética , PPAR gamma/antagonistas & inhibidores , Ácido Palmítico/farmacología , Proteínas Inhibidoras de STAT Activados/genética , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/farmacología , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal/efectos de los fármacos , Proteínas Modificadoras Pequeñas Relacionadas con Ubiquitina/genética , Sumoilación/genética , Vitamina E/farmacologíaRESUMEN
Recent studies have shown that OPN (osteopontin) plays critical roles in cell survival, differentiation, bio-mineralization, cancer and cardiovascular remodeling. However, its roles in the differentiation of brown adipocytes and the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the roles of OPN in the brown adipogenesis and the underlying mechanisms. It was shown that the OPN successfully induced the differentiation of 3T3-L1 white preadipocytes into the PRDM16(+) (PRD1-BF1-RIZ1 homologous domain containing 16) and UCP-1(+) (uncoupling protein-1) brown adipocytes in a concentration and time-dependent manner. Also, activation of PI3K (phosphatidylinositol 3-kinase)-AKT pathway was required for the OPN-induced brown adipogenesis. The findings suggest OPN plays an important role in promoting the differentiation of the brown adipocytes and might provide a potential novel therapeutic approach for the treatment of obesity and related disorders.