Adiponectin secreted from adipose tissues plays a role in the regulation of energy homeostasis, food intake, and reproduction in the hypothalamus. We have previously demonstrated that adiponectin significantly inhibited GNRH secretion from GT1-7 hypothalamic GNRH neuron cells. In this study, we further investigated the effect of adiponectin on hypothalamic KISS1 gene transcription, which is the upstream signal of GNRH. We found that globular adiponectin (gAd) or AICAR, an artificial AMPK activator, decreased KISS1 mRNA transcription and promoter activity. Conversely, inhibition of AMPK by Compound C or AMPKα1-SiRNA augmented KISS1 mRNA transcription and promoter activity. Additionally, gAd and AICAR decreased the translocation of specificity protein-1 (SP1) from cytoplasm to nucleus; however, Compound C and AMPKα1-siRNA played an inverse role. Our experiments in vivo demonstrated that the expression of Kiss1 mRNA was stimulated twofold in the Compound C-treated rats and decreased about 60–70% in gAd- or AICAR-treated rats compared with control group. The numbers of kisspeptin immunopositive neurons in the arcuate nucleus region of Sprague Dawley rats mimicked the same trend seen in Ki ss 1 mRNA levels in animal groups with different treatments. In conclusion, our results provide the first evidence that adiponectin reduces Kiss1 gene transcription in GT1-7 cells through activation of AMPK and subsequently decreased translocation of SP1.
Jun-Ping Wen, Chune Liu, Wen-Kai Bi, Ya-Ting Hu, Qingshi Chen, Huibing Huang, Ji-Xing Liang, Lian-Tao Li, Li-Xiang Lin and Gang Chen
Sisi Luan, Wenkai Bi, Shulong Shi, Li Peng, Zhanbin Li, Jie Jiang, Ling Gao, Yifeng Du, Xu Hou, Zhao He and Jiajun Zhao
Subclinical hyperthyroidism, a condition characterized by decreased thyroid-stimulating hormone (TSH) and normal concentration of thyroid hormone, is associated with an elevated risk for cognitive impairment. TSH is the major endogenous ligand of the TSH receptor (TSHR) and its role is dependent on signal transduction of TSHR. It has not, however, been established whether TSHR signaling is involved in the regulation of cognition. Here, we utilized Tshr knockout mice and found that Tshr deletion led to significantly compromised performance in learning and memory tests. Reduced dendritic spine density and excitatory synaptic density as well as altered synaptic structure in CA1 subfield of the hippocampus were also noted. Furthermore, the synapse-related gene expression was altered in the hippocampus of Tshr -/- mice. These findings suggest that TSHR signaling deficiency impairs spatial learning and memory, which discloses a novel role of TSHR signaling in brain function.