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Constitutive androstane receptor mediates the induction of drug metabolism in mouse models of type 1 diabetes.

ABSTRACT: Untreated type 1 diabetes increases hepatic drug metabolism in both human patients and rodent models. We used knockout mice to test the role of the nuclear xenobiotic receptors constitutive androstane receptor (CAR) and pregnane and xenobiotic receptor (PXR) in this process. Streptozotocin-induced diabetes resulted in increased expression of drug metabolizing cytochrome P450s and also increased the clearance of the cytochrome P450 substrate zoxazolamine. This induction was completely absent in Car(-/-) mice, but was not affected by the loss of PXR. Among the many effects of diabetes on the liver, we identified bile acid elevation and activated adenosine monophosphate-activated protein kinase as potential CAR-activating stimuli. Expression of the CAR coactivator peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha was also increased in mouse models of type 1 diabetes.The CAR-dependent induction of drug metabolism in newly diagnosed or poorly managed type 1 diabetes has the potential for significant impact on the efficacy or toxicity of therapeutic agents.

SUBMITTER: Dong B

PROVIDER: S-EPMC2721020 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Constitutive androstane receptor mediates the induction of drug metabolism in mouse models of type 1 diabetes.

Dong Bingning B Qatanani Mohammed M Moore David D DD

Hepatology (Baltimore, Md.) 20090801 2

<h4>Unlabelled</h4>Untreated type 1 diabetes increases hepatic drug metabolism in both human patients and rodent models. We used knockout mice to test the role of the nuclear xenobiotic receptors constitutive androstane receptor (CAR) and pregnane and xenobiotic receptor (PXR) in this process. Streptozotocin-induced diabetes resulted in increased expression of drug metabolizing cytochrome P450s and also increased the clearance of the cytochrome P450 substrate zoxazolamine. This induction was com ...[more]

PMID: 19489075

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Project description:Background and aimsConstitutive androstane receptor (CAR) agonists, such as 1,4-bis [2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP), are known to cause robust hepatocyte proliferation and hepatomegaly in mice along with induction of drug metabolism genes without any associated liver injury. Yes-associated protein (Yap) is a key transcription regulator that tightly controls organ size, including that of liver. Our and other previous studies suggested increased nuclear localization and activation of Yap after TCPOBOP treatment in mice and the potential role of Yap in CAR-driven proliferative response. Here, we investigated a direct role of Yap in CAR-driven hepatomegaly and hepatocyte proliferation using hepatocyte-specific Yap-knockout (KO) mice.Approach and resultsAdeno-associated virus 8-thyroxine binding globulin promoter-Cre recombinase vector was injected to Yap-floxed mice for achieving hepatocyte-specific Yap deletion followed by TCPOBOP treatment. Yap deletion did not decrease protein expression of CAR or CAR-driven induction of drug metabolism genes (including cytochrome P450 [Cyp] 2b10, Cyp2c55, and UDP-glucuronosyltransferase 1a1 [Ugt1a1]). However, Yap deletion substantially reduced TCPOBOP-induced hepatocyte proliferation. TCPOBOP-driven cell cycle activation was disrupted in Yap-KO mice because of delayed (and decreased) induction of cyclin D1 and higher expression of p21, resulting in decreased phosphorylation of retinoblastoma protein. Furthermore, the induction of other cyclins, which are sequentially involved in progression through cell cycle (including cyclin E1, A2, and B1), and important mitotic regulators (such as Aurora B kinase and polo-like kinase 1) was remarkably reduced in Yap-KO mice. Microarray analysis revealed that 26% of TCPOBOP-responsive genes that were mainly related to proliferation, but not to drug metabolism, were altered by Yap deletion. Yap regulated these proliferation genes through alerting expression of Myc and forkhead box protein M1, two critical transcriptional regulators of CAR-mediated hepatocyte proliferation.ConclusionsOur study revealed an important role of Yap signaling in CAR-driven hepatocyte proliferation; however, CAR-driven induction of drug metabolism genes was independent of Yap.

Project description:The constitutive androstane receptor (CAR) is a xenosensing nuclear receptor and regulator of cytochrome P450s (CYPs). However, the role of CAR as a basal regulator of CYP expression nor its role in sexually dimorphic responses have been thoroughly studied. We investigated basal regulation and sexually dimorphic regulation and induction by the potent CAR activator TCPOBOP and the moderate CAR activator Nonylphenol (NP). NP is an environmental estrogen and one of the most commonly found environmental toxicants in Europe and the United States. Previous studies have demonstrated that NP induces several CYPs in a sexually dimorphic manner, however the role of CAR in regulating NP-mediated sexually dimorphic P450 expression and induction has not been elucidated. Therefore, wild-type and CAR-null male and female mice were treated with honey as a carrier, NP, or TCPOBOP and CYP expression monitored by QPCR and Western blotting. CAR basally regulates the expression of Cyp2c29, Cyp2b13, and potentially Cyp2b10 as demonstrated by QPCR. Furthermore, we observed a shift in the testosterone 6alpha/15alpha-hydroxylase ratio in untreated CAR-null female mice to the male pattern, which indicates an alteration in androgen status and suggests a role for androgens as CAR inverse agonists. Xenobiotic-treatments with NP and TCPOBOP induced Cyp2b10, Cyp2c29, and Cyp3a11 in a CAR-mediated fashion; however NP only induced these CYPs in females and TCPOBOP induced these CYPs in both males and females. Interestingly, Cyp2a4, was only induced in wild-type male mice by TCPOBOP suggesting Cyp2a4 induction is not sensitive to CAR-mediated induction in females. Overall, TCPOBOP and NP show similar CYP induction profiles in females, but widely different profiles in males potentially related to lower sensitivity of males to either indirect or moderate CAR activators such as NP. In summary, CAR regulates the basal and chemically inducible expression of several sexually dimorphic xenobiotic metabolizing P450s in a manner that varies depending on the ligand.

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Constitutive androstane receptor mediates the induction of drug metabolism in mouse models of type 1 diabetes.

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Constitutive androstane receptor mediates the induction of drug metabolism in mouse models of type 1 diabetes.

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