Rizwan M Z, Harbid A A, Inglis M A, Quennell J H, Anderson G M
Centre for Neuroendocrinology and Department of Anatomy, University of Otago School of Medical Sciences, Dunedin, New Zealand.
J Neuroendocrinol. 2014 Apr;26(4):247-57. doi: 10.1111/jne.12140.
Leptin, a permissive hormonal regulator of fertility, provides information about the body's energy reserves to the hypothalamic gonadotrophin-releasing hormone (GnRH) neuronal system that drives reproduction. Leptin does not directly act on GnRH neurones, and the neuronal pathways that it uses remain unclear. RFamide-related peptide-3 (RFRP-3) neurones project to GnRH neurones and primarily inhibit their activity. We tested whether leptin could act via RFRP-3 neurones to potentially modulate GnRH activity. First, the effects of leptin deficiency or high-fat diet-induced obesity on RFRP-3 cell numbers and gene expression were assessed in male and female mice. There was no significant difference in Rfrp mRNA levels or RFRP-3-immunoreactive cell counts in wild-type versus leptin-deficient ob/ob animals, or in low-fat versus high-fat diet fed wild-type mice. Second, the presence of leptin-induced signalling in RFRP-3 neurones was examined in male and female wild-type mice and rats. Dual label immunohistochemistry revealed leptin-induced phosphorylated signal transducer and activator of transcription-3 in close proximity to RFRP-3 neurones, although there was very little (2-13%) colocalisation and no significant differences between vehicle and leptin-treated animals. Furthermore, we were unable to detect leptin receptor mRNA in a semi-purified RFRP-3 cell preparation. Because GABA neurones form critical leptin-responsive GnRH inputs, we also determined whether RFRP-3 and GABA cells were colocalised. No such colocalisation was detected. These results support the concept that leptin has little or no effects on RFRP-3 neurones, and that these neurones are unlikely to be an important neuronal pathway for the metabolic regulation of fertility by leptin.
瘦素是一种对生育有调节作用的激素，它将身体能量储备的信息传递给驱动生殖的下丘脑促性腺激素释放激素（GnRH）神经元系统。瘦素并不直接作用于GnRH神经元，其作用的神经通路尚不清楚。RF酰胺相关肽-3（RFRP-3）神经元投射到GnRH神经元并主要抑制其活性。我们测试了瘦素是否可以通过RFRP-3神经元发挥作用来潜在地调节GnRH活性。首先，在雄性和雌性小鼠中评估了瘦素缺乏或高脂饮食诱导的肥胖对RFRP-3细胞数量和基因表达的影响。在野生型与瘦素缺乏的ob/ob动物之间，或低脂与高脂饮食喂养的野生型小鼠之间，Rfrp mRNA水平或RFRP-3免疫反应性细胞计数没有显著差异。其次，在雄性和雌性野生型小鼠和大鼠中检查了RFRP-3神经元中瘦素诱导的信号传导。双重标记免疫组织化学显示，在靠近RFRP-3神经元的位置有瘦素诱导的磷酸化信号转导和转录激活因子-3，尽管共定位很少（2%-13%），并且在给予载体和瘦素处理的动物之间没有显著差异。此外，我们在半纯化的RFRP-3细胞制剂中未能检测到瘦素受体mRNA。由于GABA神经元形成关键的瘦素反应性GnRH输入，我们还确定了RFRP-3和GABA细胞是否共定位。未检测到这种共定位。这些结果支持这样一种观点，即瘦素对RFRP-3神经元几乎没有影响，并且这些神经元不太可能是瘦素对生育进行代谢调节的重要神经通路。
