1. Volume 124, Issue 1, Pages 160-171 (January 2003)
Induction of hepatic ABC transporter expression is part of the PPARα–mediated fasting response in the mouse 
Tineke Kok, Henk Wolters, Vincent W. Bloks, Rick Havinga, Peter L.M. Jansen, Bart Staels, Folkert Kuipers 
Gastroenterology 
Volume 124, Issue 1, Pages (January 2003)
DOI: /gast
Copyright © 2003 American Gastroenterological Association Terms and Conditions

2. Fig. 1
Plasma concentrations of β-hydroxybutyrate (A), steady-state mRNA levels of Hmgs in liver (B), and hepatic triglyceride contents (C) of fed, fasted, and refed wild-type and Pparα| mice. Total mRNA was isolated from livers of wild-type (white bars) and Pparα| (black bars) mice, and 4.5 μg of RNA was transcribed into cDNA and subjected to real-time PCR analysis as described in Materials and Methods. Hepatic triglyceride concentrations were measured in liver homogenates and expressed per milligram of liver. aSignificant difference between wild-type and Pparα| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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3. Fig. 2
Steady-state mRNA levels of Pparα (A), Pparγ (B), Srebp1c (C), Lxrα (D), Fxr (E), and Shp (F) in livers of fed, fasted, and refed wild-type and Pparα| mice. Total mRNA was isolated from livers of wild-type (white bars) and Pparα| (black bars) mice, transcribed into cDNA, and subjected to real-time PCR analysis as described in Materials and Methods. The presence of a Pparα transcript in Pparα| mice, also described by Muoio et al.,39 is explained by the presence of residual, nonfunctional mRNA. The strategy used for targeted disruption of the Pparα gene results in a nonfunctional transcript in Pparα| mice, which is recognized by our primer set described in Table 1. aSignificant difference between wild-type and Pparα| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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4. Fig. 3
Steady-state mRNA levels of Mdr2 (A), Bsep (B), Mdr1a (C), Mdr1b (D), Ntcp (E), and Oatp1 (F) during fasting or refeeding in livers of wild-type and Pparα| mice. Total mRNA was isolated from the livers of wild-type (white bars) and Pparα| (black bars) mice, transcribed into cDNA, and subjected to real-time PCR analysis as described in Materials and Methods. aSignificant difference between wild-type and Pparα| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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5. Fig. 4
Western blot analysis of Mdr2 Pgp and Na+K+-adenosine triphosphatase (β-subunit) protein levels in total liver membrane fractions of fed, fasted, and refed wild-type and Pparα| mice. Several preparations (n = 3, each from 2 pooled livers) were tested in the same way, and similar results were obtained. Apparent molecular weights are indicated at the right side of the blots.
Gastroenterology  , DOI: ( /gast )
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6. Fig. 5
Steady-state mRNA levels of (A) Abca1, (B) Abcg5, and (C) Abcg8 during fasting or refeeding in livers of wild-type and Pparα| mice. Total mRNA was isolated from the livers of wild-type (white bars) and Pparα| (black bars) mice, transcribed into cDNA, and subjected to real-time PCR analysis as described in Materials and Methods. aSignificant difference between wild-type and Pparα| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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7. Fig. 6
Steady-state mRNA levels of (A) Cyp7a1 and (B) Cyp27 during fasting or refeeding in livers of wild-type and Pparα| mice. Total mRNA was isolated from livers of wild-type (white bars) and Pparα| (black bars) mice, transcribed into cDNA, and subjected to real-time PCR analysis as described in Materials and Methods. aSignificant difference between wild-type and Pparα| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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8. Fig. 7
Bile flow and biliary bile salt, phospholipid, and cholesterol secretion in fed and fasted wild-type mice during intravenous administration of increasing amounts of TUDC. The gallbladders of mice were cannulated, and, at 30 minutes after starting bile collection, TUDC was infused via a jugular vein in stepwise increasing dosages, as indicated by the numbers (nmol/min) in the figure. Open circles represent fed mice, and filled circles represent fasted mice. Data are presented as mean ± SD from 4 mice of each group. (A) Bile flow is expressed in μL/min per 100 g body weight during TUDC infusion in time. (B) Bile salt secretion is expressed in nmol/min per 100 g body weight during TUDC infusion in time. (C) Phospholipid secretion vs. bile salt secretion, both expressed in nmol/min per 100 g body weight during TUDC infusion. (D) Cholesterol secretion vs. bile salt secretion, both expressed in nmol/min per 100 g body weight during TUDC infusion. *Significant difference between fasted and fed wild-type mice.
Gastroenterology  , DOI: ( /gast )
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9. Fig. 8
Hepatic triglyceride contents of fed, 24-hour fasted, and 48-hour fasted wild-type and Mdr2| mice. Hepatic triglyceride concentrations were measured in liver homogenates of wild-type (white bars) and Mdr2| (black bars) mice and expressed as total amount per liver. aSignificant difference between wild-type and Mdr2| mice on the same treatment. bSignificant difference between fasted/refed and fed mice of the same genotype.
Gastroenterology  , DOI: ( /gast )
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10. Fig. 9
Proposed role of PPARα in the regulation of hepatic ABC transporters during fasting. During fasting, plasma insulin concentrations decrease, and triglycerides (TG) stored in adipose tissue are mobilized to yield glycerol and free fatty acids (FA). Part of these fatty acids are taken up by the liver to enter the β-oxidation pathway, allowing the formation of ketone bodies. FAs taken up by the liver in excess of requirements for direct oxidation are re-esterified into TG, which gives rise to fasting-associated development of a fatty liver. FAs stimulate expression of genes involved in their uptake, β-oxidation, and ketogenesis via activation of the ligand-activated transcription factor PPARα, which seems to be a critical event in the control of the metabolic fasting response. Enhanced expression of the Pparα gene itself provides a feed-forward loop to accelerate this response. This study shows that activation of PPARα by fasting also leads to a PPARα–dependent induction of Mdr2 gene expression, protein levels, and function, leading to increased phospholipid output into bile. Furthermore, fasting induces the expression of Abca1 and Abcg5/Abcg8, which could be a direct consequence of PPARα activation or an indirect consequence of PPARα–dependent induction of Lxrα, a nuclear receptor involved in control of Abca1 and Abcg5/Abcg8 expression. Besides LXR, fasting also induces the mRNA expression of the bile salt–activated nuclear receptor Fxr in a PPARα–dependent manner. Increased expression of Abcg5/Abcg8, encoding ABC transporters that have recently been implicated in cholesterol transport, did not affect basal biliary cholesterol excretion but seemed to be associated with decreased rather than increased maximal hepatobiliary cholesterol excretion. This suggests that other factors control the rate of cholesterol excretion under these conditions.
Gastroenterology  , DOI: ( /gast )
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