BACKGROUND & AIMS:
:Male pigs are routinely castrated at a young age to prevent the formation of androstenone, a 16-androstene testicular steroid that is a major component of boar taint. The practice of castration has been increasingly viewed as unfavorable, due to both economic considerations and animal welfare concerns. Other means of controlling boar taint, including reducing the synthesis of androstenone in the testes, would eliminate the need for castration. In this study, we determined the effects of transactivation of three nuclear receptors, the constitutive androstane receptor (CAR), pregnane X receptor (PXR), and farnesoid X receptor (FXR), on gene expression and steroid hormone metabolism in primary porcine Leydig cells. Primary cells were isolated from mature boars, and transcript expression levels were assayed using real-time PCR. The transcripts of interest included porcine orthologs of common phase I and phase II metabolic enzymes, enzymes involved in steroidogenesis, and transcripts previously shown to be differentially expressed in boars with high androstenone and boar taint levels. Transactivation of CAR, PXR, or FXR increased the expression of several genes involved in steroidogenesis, including cytochrome B5A (CYB5A) and cytochrome B5 reductase 1 (CYB5R1), as well as hydroxysteroid (17-beta) dehydrogenase 4 (HSD17B4) and retinol dehydrogenase 12 (RDH12). Treatment with (6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO), a CAR agonist, or rifampicin (RIF), a PXR agonist, resulted in significantly (p<0.05) decreased sex steroid production and significantly (p<0.05) increased production of 16-androstene steroids. Treatment with the FXR agonist chenodeoxycholic acid (CDCA) resulted in significantly (p<0.05) decreased sex steroid production. These results indicate that transactivation of these nuclear receptors may lead to increased levels of 16-androstene steroids, likely by altering the activity of CYP17A1 through CYB5A and CYB5R1 to the andien-β synthase reaction and away from the 17α-hydroxylase and C17, 20 lyase reactions.
背景与目标:
: 公猪通常在幼年时就被阉割,以防止雄烯酮的形成,雄烯酮是一种16-雄烯酮睾丸类固醇,是公猪污染的主要成分。由于经济考虑和动物福利方面的考虑,阉割的做法越来越被认为是不利的。其他控制公猪污染的方法,包括减少睾丸中雄烯酮的合成,将消除去势的需要。在这项研究中,我们确定了组成型雄激素受体 (CAR),孕烷X受体 (PXR) 和法尼醇X受体 (FXR) 三种核受体的反式激活对原发性猪Leydig细胞的基因表达和类固醇激素代谢的影响。从成熟公猪中分离原代细胞,并使用实时PCR测定转录本表达水平。感兴趣的转录本包括常见的I期和II期代谢酶的猪直系同源物,与类固醇生成有关的酶以及先前显示在雄烯酮和公猪污染水平高的公猪中差异表达的转录本。CAR,PXR或FXR的反式激活增加了与类固醇生成有关的几个基因的表达,包括细胞色素B5A (CYB5A) 和细胞色素B5还原酶1 (CYB5R1) 以及羟基类固醇 (17-beta) 脱氢酶4 (HSD17B4) 和视黄醇脱氢酶12 (RDH12)。用 (6-(4-氯苯基) 咪唑并 [2,1-b][1,3) thiazole-5-carbaldehyde-O-(3,4-二氯苄基) 肟 (CITCO) (一种CAR激动剂) 或利福平 (RIF) (一种PXR激动剂) 治疗,导致性类固醇生成显著 (p<0.05) 减少,16-雄激素类固醇生成显著 (p<0.05) 增加。用FXR激动剂鹅去氧胆酸 (CDCA) 治疗导致性类固醇生成显著 (p<0.05) 减少。这些结果表明这些核受体的反式激活可能导致16-雄激素类固醇水平升高,可能通过将CYP17A1的活性通过CYB5A和CYB5R1改变为andien-β 合酶反应,并远离17α-羟化酶和C17,20裂解酶反应。