INRA, UR1196, Génomique et Physiologie de la Lactation, Jouy-en-Josas, France.
Physiol Genomics. 2013 Aug 1;45(15):645-52. doi: 10.1152/physiolgenomics.00020.2013. Epub 2013 May 28.
Leptin is known as a cytokine mostly produced by fat cells and implicated in regulation of energy metabolism and food intake but has also been shown to be involved in many physiological mechanisms such as tissue metabolism and cell differentiation and proliferation. In particular, leptin influences the development of mammary gland. Although leptin expression in mammary gland has been studied in several species, no data are available in the rabbit. Leptin transcripts in this species have been described as being encoded by only two exons rather than three as in other species. Our focus was to clone and sequence the rabbit leptin cDNA and to prepare the recombinant biologically active protein for validation of the proper sequence and then to describe leptin expression in rabbit mammary gland during different stages of pregnancy and lactation. The leptin sequence obtained was compared with those of other species, and genome alignment demonstrated that the rabbit leptin gene is also encoded by three exons. Additionally, we analyzed the expression of leptin during pregnancy and lactation. Leptin mRNA was weakly expressed throughout pregnancy, whereas mRNA levels were higher during lactation, with a significant increase between days 3 and 16. Leptin transcripts and protein were localized in luminal epithelial cells, thus indicating that leptin synthesis occurs in this compartment. Therefore, mammary synthesized leptin may constitute a major regulator of mammary gland development by acting locally as an autocrine and/or paracrine factor. Furthermore, our results support the possible physiological role of leptin in newborns through consumption of milk.
瘦素是一种主要由脂肪细胞产生的细胞因子，参与调节能量代谢和食物摄入，但也被证明参与许多生理机制，如组织代谢、细胞分化和增殖。特别是，瘦素影响乳腺的发育。虽然在几种物种中已经研究了乳腺中的瘦素表达，但在兔子中没有数据。该物种的瘦素转录本被描述为仅由两个外显子编码，而不是其他物种的三个外显子。我们的重点是克隆和测序兔瘦素 cDNA，并制备重组生物活性蛋白以验证正确的序列，然后描述兔乳腺在不同妊娠和哺乳阶段的瘦素表达。获得的瘦素序列与其他物种进行了比较，基因组比对表明，兔瘦素基因也由三个外显子编码。此外，我们分析了妊娠和哺乳期的瘦素表达。瘦素 mRNA 在整个妊娠期间表达较弱，而在哺乳期表达水平较高，在第 3 天至第 16 天之间显著增加。瘦素转录本和蛋白定位于腔上皮细胞中，因此表明瘦素合成发生在这个部位。因此，乳腺合成的瘦素可能通过作为局部自分泌和/或旁分泌因子发挥作用，构成乳腺发育的主要调节剂。此外，我们的结果支持了瘦素通过消耗牛奶在新生儿中发挥可能的生理作用。
