Year of Publication

2014

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department

Nutritional Sciences

First Advisor

Dr. Alan Daugherty

Abstract

Angiotensinogen is the only known precursor in the renin-angiotensin system, a hormonal system best known as an essential regulator of blood pressure and fluid homeostasis. Angiotensinogen is sequentially cleaved by renin and angiotensin- converting enzyme to generate angiotensin II. As the major effector peptide, angiotensin II mainly function through angiotensin type 1 receptor.

Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and more recently renin inhibitors are widely known as the 3 classic renin-angiotensin system inhibitory drugs against hypertension and atherosclerosis. Here, we developed an array of regents to explore the effects of angiotensinogen inhibition. First, we demonstrated that genetic deficiency of angiotensinogen not only protected against hypercholesterolemia- induced atherosclerosis but also prevented diet-induced obesity. Then we found weekly intraperitoneal injection of antisense oligonucleotides against angiotensinogen remarkably surpressed body weight gain in mice fed a western diet, which was absent from classic renin-angiotensin system inhibition. The suppressed body weight gain was attributable to diminished body fat mass gain and enhanced energy expenditure. More excitingly, angiotensinogen antisense oligonucleotides regressed body weight gain on obese mice. Together, our findings revealed a unique feature of angiotensinogen inhibition beyond classic renin angiotensin inhibition and demonstrated therapeutic potentials of angiotensinogen antisense oligonucleotides against hypertension, atherosclerosis, and obesity.

We also developed an in vivo system to explore the functional consequences of disrupting a conserved Cys18-Cys137 disulfide bridge in angiotensinogen. The formation of this disulfide bridge could trigger conformational changes in angiotensinogen, thereby facilitating renin cleavage of angiotensinogen. It was predicted that the redox-sensitive disulfide bridge might change the efficiency of angiotensinogen/renin reaction to release angiotensin II, thus modulate angiotensin II-dependent functions. We determined effects of the presence and absence of the disulfide bridge on angiotensin II concentrations and responses in mice expressing either native angiotensinogen or Cys18Ser, Cys137Ser mutated angiotensinogen in liver via adeno-associated viral vectors. Contrary to the prediction, disruption of Cys18-Cys137 disulfide bridge in angiotensinogen had no discernible effects on angiotensin II production and angiotensin II-dependent functions in mice.