Androgen receptor promotes hepatitis B virus-induced hepatocarcinogenesis through modulation of hepatitis B virus RNA transcription

Role of nuclear receptors in hepatitis B and C infections

Nuclear receptors are key regulators of many cellular functions including energy supply by the direct control of the expression of target genes. They constitute a super-family of transcription factors activated by ligands, hormones or metabolites, and therefore, sensible to host metabolic stimuli. Viral replication and production requires energy and elementary building blocks from the infected cells. Hepatitis B and C virus replication is modulated in part by liver nuclear receptors that regulate the glucose and lipid metabolism. However, nuclear receptors control the two viruses' replication by different mechanisms. The expression of hepatitis B virus genes is directly under the control of nuclear receptors, which bind to the viral genome regulatory regions. Viral replication and production may, therefore, be optimal when cells receive the correct metabolic signals. Hepatitis C virus replication and production depend to a large extent on lipidogenesis and lipoprotein secretion. The role of nuclear receptors in controlling hepatitis C replication may be to turn on the cellular mode that would provide the appropriate metabolic environment for viral replication.

Sex differences in nuclear receptor-regulated liver metabolic pathways

Liver metabolism is markedly sex-dimorphic; accordingly, the prevalence of liver diseases is different between sexes. The superfamily of nuclear receptors (NRs) governs the proper expression of key liver metabolism genes by sensing lipid-soluble hormones and dietary lipids. When the expression of those genes is deregulated, disease development is favored. However, we lack a comprehensive picture of the differences between NR actions in males and females. Here, we reviewed explorative studies that assessed NR functions in both sexes, and we propose a first map of sex-dimorphic NR expression in the liver. Our analysis suggested that NRs in the female liver exhibited cross-talk with more liver-protective potential than NRs in male liver. This study provides empirical support to the hypothesis that women are more resilient to some liver diseases than men, based on a more compensative NR network. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Tissue-specific knockout of androgen receptor in mice

Androgen acting through the androgen receptor (AR) is known to be essential for male sexual differentiation and development. Using Cre-lox technology, we have generated the floxed AR mice, which have been bred with general or tissue-specific Cre expressing transgenic mice to knock out the AR gene in specific target cells. Our findings indicated that AR is required for sexual development and that loss of AR can have significant effects on many aspects of physiological functions and disease progression, such as immune function, metabolism, and tumorigenesis. Furthermore, our strategy can generate AR knockout (ARKO) in female mice, which allows researchers to study the AR function in the female. In brief, our floxed AR mouse model provides a powerful tool to study in vivo AR functions in selective tissues and cell types and has made possible several research breakthroughs in the field of endocrinology.