tailieunhanh - Báo cáo khoa học: Tumour necrosis factor-a attenuates insulin action on phosphoenolpyruvate carboxykinase gene expression and gluconeogenesis by altering the cellular localization of Foxa2 in HepG2 cells

Circulating tumour necrosis factor-a(TNFa) levels, which are elevated in obesity-associated insulin resistance and diabetes, inhibit insulin signalling at several points in the signalling cascade. The liver is critical in maintaining cir-culating glucose levels and, in a preliminary investigation using the human hepatoma (HepG2) cell line in this study, we demonstrated the role of TNFa in the regulation of this phenomenon and determined the underlying molecular mechanisms. | ỊFEBS Journal Tumour necrosis factor-a attenuates insulin action on phosphoenolpyruvate carboxykinase gene expression and gluconeogenesis by altering the cellular localization of Foxa2 in HepG2 cells Amit K. Pandey Vikash Bhardwaj and Malabika Datta Institute of Genomics and Integrative Biology CSIR Delhi India Keywords diabetes Foxa2 insulin phosphoenolpyruvate carboxykinase PEPCK tumour necrosis factor-a TNFa Correspondence M. Datta Institute of Genomics and Integrative Biology MallRoad Delhi-110 007 India Fax 91 11 27667471 Tel 91 11 27667439 27667602 ext. 135 E-mail mdatta@ Present address SpecialCentre for Molecular Medicine JawaharlalNehru University New Delhi India Received 19 January 2009 revised 18 March 2009 accepted 12 May 2009 doi Circulating tumour necrosis factor-a TNFa levels which are elevated in obesity-associated insulin resistance and diabetes inhibit insulin signalling at several points in the signalling cascade. The liver is critical in maintaining circulating glucose levels and in a preliminary investigation using the human hepatoma HepG2 cell line in this study we demonstrated the role of TNFa in the regulation of this phenomenon and determined the underlying molecular mechanisms. As the transcription factor Foxa2 has been implicated in part in the regulation of gluconeogenic genes we studied the effects of TNFa and or insulin on its cellular status in hepatocytes followed by an assessment of its occupancy on the phosphoenolpyruvate carboxykinase PEPCK promoter. Preincubation of cells with TNFa followed by insulin significantly prevented insulin-mediated nuclear exclusion of Foxa2 and substantially increased its nuclear concentration. Foxa2 was subsequently found to occupy its binding element on the PEPCK promoter. TNFa alone however did not alter the status of cellular Foxa2 or its occupancy on the PEP-CK promoter. TNFa preincubation also significantly attenuated insulin-induced inhibition of the .