Impaired hepatic fatty acid oxidation in rats with short-term cholestasis: characterization and mechanism.
Rats with long-term cholestasis have reduced ketosis during starvation. Because it is unclear whether this is also the case in short-term cholestasis, we investigated hepatic fatty acid metabolism in rats with bile duct ligation for 5 days (BDL5, n = 11) or 10 days (BDL10, n = 11) and compared the findings with those made with pair-fed control rats (CON5 and CON10, n = 11). The plasma beta-hydroxybutyrate concentration was reduced in BDL rats (0.54 +/- 0.10 vs. 0.83 +/- 0.30 mM at 5 days and 0.59 +/- 0.24 vs. 0.88 +/- 0.09 mM at 10 days in BDL and control rats, respectively). In isolated liver mitochondria, state 3 oxidation rates for various substrates were not different between BDL and control rats. Production of ketone bodies from [(14)C]palmitate was reduced by 40% in mitochondria from BDL rats at both time points, whereas production of (14)CO(2) was maintained. These findings indicated intact function of the respiratory chain, Krebs cycle, and beta-oxidation and suggested impaired ketogenesis (HMG-CoA pathway). Accordingly, the formation of acetoacetate from acetyl-CoA by disrupted mitochondria was reduced in BDL rats at 5 days (2.1 +/- 1.0 vs. 4.8 +/- 1.9 nmol/min per mg protein) and at 10 days (1.7 +/- 1.0 vs. 6.2 +/- 1.9 nmol/min per mg protein). The principal defect could be localized at the rate-limiting enzyme of the HMG-CoA pathway, HMG-CoA synthase, which revealed decreased activity, and reduced hepatic mRNA and protein levels. We conclude that short-term cholestasis in rats leads to impaired hepatic fatty acid metabolism due to impaired ketogenesis. Ketogenesis is impaired because of decreased mRNA levels of HMG-CoA synthase, leading to reduced hepatic protein levels and to decreased activity of this key enzyme of ketogenesis. - Lang, C., M. Schäfer, D. Serra, F. G. Hegardt, L. Krähenbühl, and S. Krähenbühl. Impaired hepatic fatty acid oxidation in rats with short-term cholestasis: characterization and mechanism. J. Lipid Res. 2001. 42: 22;-30.
Lang
C
C
Institute of Clinical Pharmacology, University of Bern, Switzerland.
Schäfer
M
M
Serra
D
D
Hegardt
F
F
Krähenbühl
L
L
Krähenbühl
S
S
D000818:Animals; D002250:Carbon Radioisotopes; D002780:Cholestasis, Intrahepatic / Q000378:metabolism*; D002952:Citric Acid Cycle; D004195:Disease Models, Animal; D005227:Fatty Acids / Q000378:metabolism*; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000235:genetics / Q000378:metabolism; D008026:Ligation; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D002250:Carbon Radioisotopes; D005227:Fatty Acids; D012333:RNA, Messenger; D006904:Hydroxymethylglutaryl-CoA Synthase