Abstract
The NASH (Nonalcoholic steato-hepatitis) is characterized by hepatic fat accumulation associated with insulin resistance, and thus is associated with alterations of glucose flux in hepatocytes. Fluxes of glucose in the hepatocyte (influx or efflux), the glucose transporter GLUT2 plays a key role, with the participation of co-enzymes of glucose metabolism. Increased expression of GLUT2 has been shown in HepG2 human hepatocytes that develop accumulation of triglycerides after culture at high concentration of oleic acid. So, we expect some alteration in the expression of SLC2A2 (GLUT2 gene encoding) in animals with NAFLD.In the liver, the balance between the activity of enzymes glicoquinase (GK), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), together with the GLUT2 represent an important control for the capture or release of hepatic glucose. Moreover, these enzymes have been described as involved in the framework of hepatic steatosis and may therefore be involved in NASH.It was identified that the transcription factors HNF-1 alpha, HNF-3 beta, HNF-4alpha (Hepatocyte Nuclear Factor) highly expressed in liver, and NFkB (Nuclear Factor), related to inflammatory activity, they regulate genes important for metabolism and transport of glucose. In relation to SLC2A2, our group has demonstrated in liver and kidney of diabetic animals an increase in mRNA expression, which was associated with increased binding activity of HNF-1 alpha, HNF-3 beta, HNF-4alpha in the promoter SLC2A2, an effect that was reversed by insulin treatment. These data underscore the importance of HNFs on SLC2A2 gene regulation.Our hypothesis is that NASH occurs in abnormal expression of SLC2A2, determined by changes in transcriptional activity of HNF-1 alpha, HNF-3 beta, HNF-4alpha, or NFkB (important mediator of inflammatory cytokines). Our goal is to investigate in an experimental model of NASH regulation of SLC2A2 gene expression, and participation of HNF-1 alpha, HNF-3 beta, HNF-4alpha and NFkB in this regulation. For this, in obese mice by treatment with monosodium glutamate and supplemented with high fat diet, will be investigated: the degree of steatohepatitis (liver histology), presence of inflammatory activity (evaluation of inflammatory cytokines in liver and plasma) and insulin resistance (glucose, insulin and insulin tolerance test), the mRNA expression of GLUT2, GK, G6Pase, PEPCK, HNF-1 alpha, HNF-3 beta, HNF-4alpha and NFkB in the liver (time PCR real), the binding activity of transcriptional factors to the SLC2A2 gene promoter in vitro (electrophoretic mobility assay, EMSA) and in vivo (chromatin immunoprecipitation assay (ChIP assay). Thus, it is expected to characterize the regulation of expression of SLC2A2 in NASH, which may help to establish preventive or therapeutic mechanisms that control hepatic glucose flux in this disease.
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