Hanson E S, Levin N, Dallman M F
Department of Physiology, University of California, San Francisco 94143-0444, USA.
Endocrinology. 1997 Mar;138(3):1041-7. doi: 10.1210/endo.138.3.4995.
Fasting stimulates corticosterone (B) secretion and the expression and secretion of hypothalamic neuropeptide Y in rats. These studies tested the hypothesis that the rapid and marked fasting-induced increases in plasma B are responsible for stimulation of neuropeptide Y (NPY) gene expression. Plasma leptin and insulin were measured because they are also signals known to affect NPY messenger RNA (mRNA). Intact or adrenalectomized rats given a low fixed level of corticosterone (B replaced) were fasted for 48 h. NPY mRNA in the mediobasal hypothalamus, measured by nuclease protection assay, was elevated similarly above ad lib-fed controls in both intact and B replaced groups at 15 and 48 h after the onset of fasting. NPY immunoreactivity in the mediobasal hypothalamus increased between 3 and 48 h after onset of the fast in intact but not in B replaced groups. The fasting-induced decreases in leptin observed in intact rats at 48 h did not occur in B replaced rats. Fasting-induced decreases in insulin occurred in B replaced rats but not in intact rats. We conclude that: 1) elevated B is not required for fasting-induced increases in hypothalamic NPY gene expression; and 2) decreases in neither leptin nor insulin alone signal the changes that occur in NPY mRNA in fasted rats.
禁食可刺激大鼠体内皮质酮（B）的分泌以及下丘脑神经肽Y的表达和分泌。这些研究检验了如下假说：禁食快速且显著地引起血浆B升高，这是刺激神经肽Y（NPY）基因表达的原因。对血浆瘦素和胰岛素进行了测量，因为它们也是已知会影响NPY信使核糖核酸（mRNA）的信号。将给予低固定水平皮质酮（补充B）的完整或肾上腺切除大鼠禁食48小时。通过核酸酶保护分析测定，在禁食开始后的15小时和48小时，完整组和补充B组的中基底下丘脑NPY mRNA均同样高于自由进食对照组。禁食开始后3至48小时，完整组中基底下丘脑的NPY免疫反应性增加，而补充B组则未增加。完整大鼠在48小时时出现的禁食诱导的瘦素降低在补充B的大鼠中未出现。禁食诱导的胰岛素降低在补充B组大鼠中出现，而在完整大鼠中未出现。我们得出结论：1）禁食诱导的下丘脑NPY基因表达增加并不需要B升高；2）单独的瘦素或胰岛素降低均不能作为禁食大鼠中NPY mRNA发生变化的信号。
