Role of peroxisome proliferator-activated receptor-alpha in fasting-mediated oxidative stress
Aldehyde dehydrogenase; Biochemistry & Molecular Biology; differential expression; dismutase; Endocrinology & Metabolism; Fasting; fatty-acid oxidation; glutathione-s-transferase; hepatic steatosis; Lipid peroxidation; Lipid peroxidation; liver; manganese-superoxide-dismutase; mitochondrial aldehyde dehydrogenase; nitric-oxide; Null mice; oxidative stress; PPAR-alpha; PPAR-alpha; Protein nitration; Protein oxidation; rat-liver; Steatosis; Superoxide
The peroxisome proliferator-activated receptor-alpha (PPAR alpha) regulates lipid homeostasis, particularly in the liver. This study was aimed at elucidating the relationship between hepatosteatosis and oxidative stress during fasting. Fasted Ppara-null mice exhibited marked hepatosteatosis, which was associated with elevated levels of lipid peroxidation, nitric oxide synthase activity, and hydrogen peroxide accumulation. Total glutathione (GSH), mitochondrial GSH, and the activities of major antioxidant enzymes were also lower in the fasted Ppara-null mice. Consequently, the number and extent of nitrated proteins were markedly increased in the fasted Ppara-null mice, although high levels of protein nitration were still detected in the fed Ppara-null mice while many oxidatively modified proteins were only found in the fasted Ppara-null mice. However, the role of inflammation in increased oxidative stress in the fasted Ppara-null mice was minimal based on the similar levels of tumor necrosis factor-alpha change in all groups. These results with increased oxidative stress observed in the fasted Ppara-null mice compared with other groups demonstrate a role for PPAR alpha in fasting-mediated oxidative stress and that inhibition of PPAR alpha functions may increase the susceptibility to oxidative damage in the presence of another toxic agent. Published by Elsevier Inc.
Abdelmegeed M A; Moon K H; Hardwick J P; Gonzalez F J; Song B J
Free Radical Biology and Medicine
2009
2009-09
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1016/j.freeradbiomed.2009.06.017" target="_blank" rel="noreferrer noopener">10.1016/j.freeradbiomed.2009.06.017</a>
G-protein-coupled bile acid receptor plays a key role in bile acid metabolism and fasting-induced hepatic steatosis in mice.
*Gene Expression Regulation; Analysis of Variance; Animal; Animals; Bile Acids and Salts/*metabolism; Disease Models; Energy Metabolism/physiology; Fasting; Fatty Liver/*metabolism/pathology; G-Protein-Coupled/*genetics; Homeostasis/genetics; Inbred C57BL; Lipid Metabolism/genetics; Male; Mice; Oxygen Consumption/physiology; Random Allocation; Receptors; RNA-Binding Proteins/*metabolism; Signal Transduction
Bile acids are signaling molecules that play a critical role in regulation of hepatic metabolic homeostasis by activating nuclear farnesoid X receptor (Fxr) and membrane G-protein-coupled receptor (Takeda G-protein-coupled receptor 5; Tgr5). The role of FXR in regulation of bile acid synthesis and hepatic metabolism has been studied extensively. However, the role of TGR5 in hepatic metabolism has not been explored. The liver plays a central role in lipid metabolism, and impaired response to fasting and feeding contributes to steatosis and nonalcoholic fatty liver and obesity. We have performed a detailed analysis of gallbladder bile acid and lipid metabolism in Tgr5(-/-) mice in both free-fed and fasted conditions. Lipid profiles of serum, liver and adipose tissues, bile acid composition, energy metabolism, and messenger RNA and protein expression of the genes involved in lipid metabolism were analyzed. Results showed that deficiency of the Tgr5 gene in mice alleviated fasting-induced hepatic lipid accumulation. Expression of liver oxysterol 7alpha-hydroxylase in the alternative bile acid synthesis pathway was reduced. Analysis of gallbladder bile acid composition showed marked increase of taurocholic acid and decrease of tauro-alpha and beta-muricholic acid in Tgr5(-/-) mice. Tgr5(-/-) mice had increased hepatic fatty acid oxidation rate and decreased hepatic fatty acid uptake. Interestingly, fasting induction of fibroblast growth factor 21 in liver was attenuated. In addition, fasted Tgr5(-/-) mice had increased activation of hepatic growth hormone-signal transducer and activator of transcription 5 (GH-Stat5) signaling compared to wild-type mice. CONCLUSION: TGR5 may play a role in determining bile acid composition and in fasting-induced hepatic steatosis through a novel mechanism involving activation of the GH-Stat5 signaling pathway. (Hepatology 2017;65:813-827).
Donepudi Ajay C; Boehme Shannon; Li Feng; Chiang John Y L
Hepatology (Baltimore, Md.)
2017
2017-03
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/hep.28707" target="_blank" rel="noreferrer noopener">10.1002/hep.28707</a>