Whether or not nutritionally-regulated foreign gene expression in vivo is achievable was examined in mouse liver after in vivo gene transfer by electroporation (EP). Electric pulses were applied to a left liver lobe immediately after injection of a luciferase reporter gene driven by the liver-type phosphoenolpyruvate carboxykinase (PEPCK) gene promoter. Cooling treatments especially with solid carbon dioxide in the transfection site prior to the in vivo gene EP increased reporter gene expression by a factor of 100. Body bioluminescence imaging also confirmed strong expression of the in vivo transferred reporter gene in a transfected area of the liver. Fasting conferred a 13-fold increase in the reporter gene expression in vivo in the liver when driven by the liver-type PEPCK promoter, whereas virtually no induction was found either by the SV40 promoter or by the same PEPCK promoter in the muscle when the mice were fasted. The administration of cAMP mimicked the fasting-induced reporter gene expression by the PEPCK promoter in the liver of fed mice. These results implicate that nutritionally-regulated foreign gene expression in vivo is attainable at least locally in the liver by a simple and convenient non-viral gene EP method.

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