Abstract 352: Adeno-Associated Virus-mediated Restoration of Angiotensinogen Function in Mice With Hepatocyte-specific Deficiency

Abstract

Background and Objective We have reported previously that genetic or pharmacological inhibition of angiotensinogen (AGT) leads to resistance to dietary fat-induced body weight gain. This phenotype has not been observed in mice subject to pharmacological inhibitors of other components of the renin angiotensin system including renin, ACE, and AT1 receptors. To investigate whether restoration of AGT reverses this lean phenotype, we injected an adeno-associated virus (AAV) 2/8 vector carrying wild type AGT to mice with hepatocyte-specific deficiency of AGT (hepAGT -/-). Methods and Results HepAGT -/- mice were generated by disrupting AGT gene in hepatocytes via albumin promoter driven Cre recombinase expressed in mice with floxed AGT alleles. An AAV AGT vector was constructed with the insertion of wild type AGT. AAV null vector was used as control. AAV expression was driven by hepatocyte-specific thyroxine-binding globulin promoter. Five groups of male LDL receptor -/- mice at age of 8 - 10 weeks were studied: wild type (hepAGT +/+) mice received either no AAV (PBS) or null AAV, and hepAGT -/- mice received low dose (1 x 1010 genome copy), high dose (3 x 1010 genome copy), or null AAV. Four weeks after AAV injection (i.p.), all mice were fed a saturated fat-enriched diet (42% calories from milk fat) for 12 weeks. Plasma samples were collected through retro-orbital bleeding at weeks 2, 4, 8, and 16 after AAV injection. Plasma AGT concentrations peaked between weeks 2 and 4, then declined modestly, irrespective of dosage. However, at the high dose, plasma AGT concentrations in hepAGT -/- mice were comparable to those in hepAGT +/+ mice. Plasma total cholesterol concentrations, body weight gains, and systolic blood pressures were not different between hepAGT +/+ and hepAGT -/- mice receiving either dose of AGT AAV. Atherosclerosis, quantified as percent lesion area covering the intima of the aortic arch, was equivalent between hepAGT -/- mice receiving either dose of AGT AAV and hepAGT +/+ mice, whereas it was nearly absent in hepAGT -/- mice receiving null AAV. Conclusions AGT in an AAV 2/8 vector efficiently recovers plasma AGT concentration in hepAGT -/- mice in a dose-dependent manner. This approach permits the elucidation of structural mutations on AGT function.