Amir S, Lagiorgia M, Pollock R
Department of Psychology, Concordia University, Montreal, Que., Canada.
Brain Res. 1989 Feb 20;480(1-2):340-3. doi: 10.1016/0006-8993(89)90204-7.
Insulin can affect metabolic functions such as glucose production and fat mobilization through action in the ventromedial nucleus of the hypothalamus (VMH), and the VMH has been implicated in the regulation of heat generation in brown adipose tissue (BAT) in the rat. To study the role of insulin in modulating VMH mechanisms concerned with BAT thermogenic activity we evaluated the effect of intra-VMH microinjection of insulin on BAT (T(bat)) and core (T(core)) temperatures and BAT thermogenic activity (T(bat)-T(core)) in anaesthetized rats. Intra-VMH insulin (10 ng, 100 ng and 1 microgram) enhanced the decreases in T(bat) and T(core) resulting from exposure of the anaesthetized rats to mild cold, as well as diminished BAT thermogenic activity in a dose-dependent manner. This effect could be partially reversed by systemic treatment with norepinephrine (400 micrograms/kg). Intra-VMH injection of insulin analogs having reduced binding affinity to insulin receptors and diminished biological activity--i.e., acetyl3 insulin, succinyl3 insulin and TNB3 insulin--was much less effective at enhancing the decrease in T(bat) and T(core) or at inhibiting BAT thermogenic activity. These results demonstrate that insulin can modulate BAT thermogenesis in a specific manner through action in the VMH.
胰岛素可通过作用于下丘脑腹内侧核（VMH）来影响诸如葡萄糖生成和脂肪动员等代谢功能，并且VMH与大鼠棕色脂肪组织（BAT）的产热调节有关。为了研究胰岛素在调节与BAT产热活性相关的VMH机制中的作用，我们评估了向VMH内微量注射胰岛素对麻醉大鼠的BAT温度（T(bat)）、核心温度（T(core)）以及BAT产热活性（T(bat)-T(core)）的影响。向VMH内注射胰岛素（10纳克、100纳克和1微克）可增强麻醉大鼠暴露于轻度寒冷环境时T(bat)和T(core)的下降，并以剂量依赖的方式降低BAT产热活性。用去甲肾上腺素（400微克/千克）进行全身治疗可部分逆转这种效应。向VMH内注射与胰岛素受体结合亲和力降低且生物活性减弱的胰岛素类似物——即乙酰化胰岛素、琥珀酰化胰岛素和三硝基苯胰岛素——在增强T(bat)和T(core)的下降或抑制BAT产热活性方面效果要差得多。这些结果表明，胰岛素可通过在VMH中的作用以特定方式调节BAT产热。
