Liver-Specific siRNA Inhibition of Class 2a Histone Deacetylases (HDACs) Reduces Expression of Genes Regulating Gluconeogenesis in Primary Human and Mouse Hepatocytes, but Not in Mice

Gene expression control by histone-deacetylases Class 2a (HDACs 4,5,7,9) has been demonstrated to be involved in the negative regulation of hepatic gluconeogenesis and consequently inhibition of HDACs was shown to result in improved glucose and pyruvate tolerance in rodent type 2 diabetes (T2D) models. However, pan-inhibition of HDACs in all tissues leads also to severe side effects in various tissues, excluding this approach for treatment of T2D. Here, we have investigated in vitro and in vivo safety and efficacy of a liver-selective HDAC knock-down via single or combinatorial siRNAs for HDAC 4, 5 or 7. In primary mouse and human hepatocytes, specific siRNAs directed against HDAC 4, 5 or 7, as well as their combination led to a selective knock-down of the respective target gene(s) by about 80-90%, which paralleled with a significant reduction of genes involved in the regulation of gluconeogenesis. These siRNAs were administered in a liver-specific lipid-particle formulation for treatment of healthy C57BL/6J mice. Mice received five intravenous injections with either PBS, a control siRNA, one of the respective silencing siRNAs (0.75mg/kg) or all possible dual or triple combinations for 25 days. Quantitative real-time PCR demonstrated that siRNA treatment led to a significant downregulation of the respective HDACs in the liver. However no reduction of gluconeogenic genes (PCK1 and G6PC) was detected. Consequently, also no improvement in intraperitoneal pyruvate tolerance test (PTT) could be observed. In addition, no significant differences in fasting blood glucose or plasma insulin were observed between treatment groups. In summary, although active in cellular systems, liver-targeted siRNA knockdown of class 2a HDACs did not result in a clear inhibition of genes regulating gluconeogenesis in healthy mice suggesting no clear path forward for development of this approach for treatment of T2D. Disclosure S.W. Görgens: Employee; Self; Sanofi-Aventis Deutschland GmbH. S. Raichur: None. P. Wohlfart: Employee; Self; Sanofi-Aventis Deutschland GmbH. B. Brunner: Employee; Self; Sanofi. N. Tennagels: Employee; Self; Sanofi R&D. Stock/Shareholder; Self; Sanofi. M. Bielohuby: Employee; Self; Sanofi-Aventis Deutschland GmbH, Sanofi R&D.