Metabolic Control of Reproductive system by the brain

哺乳动物在禁食或营养不良条件下生殖功能受到抑制。胰腺葡萄糖激酶（Pancreatic glucokinase，GK）是胰岛β细胞葡萄糖敏感单位的重要组成部分，本研究旨在探讨上述条件下促性腺激素分泌的神经内分泌调节机制。我们采用GK免疫组织化学和共聚焦显微镜检查GK样免疫反应在大鼠脑内的解剖分布。我们发现室管膜细胞，内皮细胞和许多肾上腺素能神经元在整个心室系统的强烈GK样免疫反应。GK阳性室管膜细胞纤毛上有葡萄糖转运蛋白（GLUT）2样免疫反应。在肾上腺素能神经元中，GK样免疫反应见于胞质及其突起。目前的结果提出了这种可能性，这些GK样免疫阳性细胞包括一个巨大的葡萄糖敏感机制在brain.The在糖尿病条件下，有或没有胰岛素补充的脉冲促黄体生成素（LH）分泌的变化的一部分，也进行了调查。LH分泌抑制糖尿病羔羊没有胰岛素补充。另一方面，LH分泌持续在糖尿病羔羊与慢性胰岛素补充。这一发现支持了胰岛素和/或胰岛素依赖性葡萄糖可用性变化调节LH脉冲产生系统的论点。

The reproductive functions are suppressed under fasting or malnutritional condition in mammals. The present study was performed to determine the neuroendocrinological mechanism by which the secretion of gonadtropins are regulated under above-mentioned condition.Pancreatic glucokinase (GK) is considered an important element of glucose sensing unit in pancreatic β-cells. We employed GK immunohistochemistry and confocal microscopy to examine the anatomical distribution of GK-like immunoreactivities in the rat brain. We found strong GK-like immunoreactivities in the ependymocytes, endothelial cells and many serotonergic neurons throughout the ventricular system. The Gk-positive ependymocytes were found to have glucose transporter (GLUT) 2-like immunoreactivities on the cilia. In serotonergic neurons, GK-like immunoreactivity was found in the cytoplasm and their processes. The present results raise the possibility that these GK-like immunopositive cells comprise a part of a vast glucose-sensing mechanism in the brain.The changes in pulsatile luteinizing hormone (LH) secretion under diabetic conditions, with or without insulin supplementation, was also investigated. LH secretion was suppressed in diabetic lambs without insulin supplementation. On the other hand, LH secretion was sustained in diabetic lambs with chronical insulin supplementation. The finding supports the contention that insulin and/or insulin-dependent changes in glucose availability modulate LH pulse generating system.