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Originally published online as doi:10.2353/ajpath.2009.080697 on February 26, 2009

Published online before print February 26, 2009
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(American Journal of Pathology. 2009;174:1329-1337.)
© 2009 American Society for Investigative Pathology
DOI: 10.2353/ajpath.2009.080697

Oxidative Stress-Mediated Mitochondrial Dysfunction Contributes to Angiotensin II-Induced Nonalcoholic Fatty Liver Disease in Transgenic Ren2 Rats

Yongzhong Wei*{dagger}, Suzanne E. Clark*{dagger}, John P. Thyfault*{dagger}, Grace M.E. Uptergrove*{dagger}, Wenhan Li*{dagger}, Adam T. Whaley-Connell*{dagger}, Carlos M. Ferrario{ddagger}, James R. Sowers*{dagger} and Jamal A. Ibdah*{dagger}

From the Department of Internal Medicine,* University of Missouri School of Medicine, Columbia, Missouri; the Harry Truman Veterans Administration Medical Center,{dagger} Columbia, Missouri; and Wake Forest University School of Medicine,{ddagger} Winston-Salem, North Carolina

Emerging evidence indicates that impaired mitochondrial fatty acid β-oxidation plays a key role in liver steatosis. We have recently demonstrated that increased angiotensin (ANG) II causes progressive hepatic steatosis associated with oxidative stress; however, the underlying mechanisms remain unclear. We hypothesized that ANG II causes hepatic mitochondrial oxidative damage and impairs mitochondrial β-oxidation, thereby leading to hepatic steatosis. We used the Ren2 rat with elevated endogenous ANG II levels to evaluate mitochondrial ultrastructural changes, gene expression levels, and β-oxidation. Compared with Sprague-Dawley littermates, Ren2 livers exhibited mitochondrial damage and reduced β-oxidation, as evidenced by ultrastructural abnormalities, decrease of mitochondrial content, percentage of palmitate oxidation to CO2, enzymatic activities (β-HAD and citrate synthase), and the expression levels of cytochrome c, cytochrome c oxidase subunit 1, and mitochondrial transcription factor A. These abnormalities were improved with either ANG II receptor blocker valsartan or superoxide dismutase/catalase mimetic tempol treatment. Both valsartan and tempol substantially attenuated mitochondrial lipid peroxidation in Ren2 livers. Interestingly, there was no difference in the expression of key enzymes (ACC1 and FAS) for fatty acid syntheses and their transcription factors (SREBP-1c and ChREBP) between Sprague-Dawley, untreated Ren2, and valsartan- or tempol-treated Ren2 rats. These results document that ANG II induces mitochondrial oxidative damage and impairs mitochondrial β-oxidation, contributing to liver steatosis.






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