Kato Keisuke, Oka Yoshitaka, Park Min Kyun
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Zoolog Sci. 2008 May;25(5):492-502. doi: 10.2108/zsj.25.492.
Despite the physiological and evolutionary significance of lipid metabolism in amniotes, the molecular mechanisms involved have been unclear in reptiles. To elucidate this, we investigated peroxisome proliferators-activated receptors (PPARs) in the leopard gecko (Eublepharis macularius). PPARs belong to a nuclear hormone-receptor family mainly involved in lipid metabolism. Although PPARs have been widely studied in mammals, little information about them is yet available from reptiles. We identified in the leopard gecko partial cDNA sequences of PPARalpha and beta, and full sequences of two isoforms of PPARgamma. This is the first report of reptilian PPARgamma mRNA isoforms. We also evaluated the organ distribution of expression of these genes by using RT-PCR and competitive PCR. The expression level of PPARalpha mRNA was highest in the large intestine, and moderate in the liver and kidney. The expression level of PPARbeta mRNA was highest in the kidney and large intestine, and moderate in the liver. Similarly to the expression of human PPARgamma isoforms, PPARgammaa was expressed ubiquitously, whereas the expression of PPARgammab was restricted. The highest levels of their expression, however, were observed in the large intestine, rather than in the adipose tissue as in mammals. Taken together, these results showed that the profile of PPARbeta mRNA expression in the leopard gecko is similar to that in mammals, and that those of PPAR alpha and gamma are species specific. This may reflect adaptation to annual changes in lipid storage due to seasonal food availability.
尽管脂质代谢在羊膜动物中具有生理和进化意义，但爬行动物中涉及的分子机制尚不清楚。为了阐明这一点，我们研究了豹纹守宫（Eublepharis macularius）中的过氧化物酶体增殖物激活受体（PPARs）。PPARs属于一个主要参与脂质代谢的核激素受体家族。尽管PPARs在哺乳动物中已得到广泛研究，但关于它们在爬行动物中的信息仍然很少。我们在豹纹守宫中鉴定出了PPARα和β的部分cDNA序列，以及PPARγ两种异构体的完整序列。这是关于爬行动物PPARγ mRNA异构体的首次报道。我们还通过逆转录聚合酶链反应（RT-PCR）和竞争性PCR评估了这些基因在各器官中的表达分布。PPARα mRNA的表达水平在大肠中最高，在肝脏和肾脏中中等。PPARβ mRNA的表达水平在肾脏和大肠中最高，在肝脏中中等。与人类PPARγ异构体的表达情况类似，PPARγa广泛表达，而PPARγb的表达受到限制。然而，它们表达水平最高的部位是大肠，而非像在哺乳动物中那样是脂肪组织。综上所述，这些结果表明，豹纹守宫中PPARβ mRNA的表达模式与哺乳动物相似，而PPARα和γ的表达模式具有物种特异性。这可能反映了对由于季节性食物供应导致的脂质储存年度变化的适应性。
