Tavakkolizadeh Ali, Ramsanahie Anthony, Levitsky Lynne L, Zinner Michael J, Whang Edward E, Ashley Stanley W, Rhoads David B
Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Surg Res. 2005 Nov;129(1):73-8. doi: 10.1016/j.jss.2005.05.023. Epub 2005 Aug 8.
We have documented previously diurnal rhythms in intestinal sugar transporter expression. We set out to identify the role of the vagus nerve in these rhythms.
Sprague-Dawley rats underwent truncal vagotomy (V; n = 9) and were pair-fed with sham-operated (n = 4) and unoperated rats (n = 6). Rats were killed at ZT3 and ZT9 (ZT: Zeitgeber time with ZT0 set at lights-on), the time interval over which sucrase, SGLT1, GLUT2, and GLUT5 expression exhibit significant anticipatory increases. Jejunal RNA expression for the four genes were assessed by Northern blot analysis. SGLT1 and GLUT2 expression was further studied by Western blot analysis and in situ hybridization.
Control rats (sham-operated plus unoperated rats) exhibited the expected increase in RNA levels at ZT9 versus ZT3 for SGLT1, GLUT2, GLUT5, and sucrase (P < 0.01 for each). The diurnal rhythm of mRNA levels for GLUT2 and sucrase, but not for SGLT1 or GLUT5, were blunted in V rats. At protein level, SGLT1 was induced 4.3-fold in control rats (P < 0.01) and 3.8-fold in V rats (P < 0.01), whereas GLUT2 was induced 3.3-fold in control rats (P < 0.01) but only 1.4-fold in V rats (N.S.).
Our results indicate that signaling through the vagus nerve is necessary for the anticipatory induction of GLUT2 and sucrase. Persistence of normal rhythms in both SGLT1 and GLUT5 indicates that diurnal induction of these genes is independent of vagal innervation. Entrainment of anticipatory diurnal gene expression in the intestine occurs via two separate pathways that are differentially dependent on vagal input.
我们之前已记录了肠道糖转运蛋白表达的昼夜节律。我们着手确定迷走神经在这些节律中的作用。
对Sprague-Dawley大鼠进行迷走神经切断术（V组，n = 9），并将其与假手术组（n = 4）和未手术大鼠（n = 6）进行配对饲养。在ZT3和ZT9（ZT：授时时间，ZT0设定为开灯时间）处死大鼠，蔗糖酶、SGLT1、GLUT2和GLUT5表达在此时间间隔内呈现显著的预期增加。通过Northern印迹分析评估空肠中这四个基因的RNA表达。通过蛋白质印迹分析和原位杂交进一步研究SGLT1和GLUT2的表达。
对照大鼠（假手术组和未手术大鼠）在ZT9时SGLT1、GLUT2、GLUT5和蔗糖酶的RNA水平相对于ZT3呈现预期增加（各P < 0.01）。V组大鼠中GLUT2和蔗糖酶mRNA水平的昼夜节律减弱，但SGLT1或GLUT5未减弱。在蛋白质水平，SGLT1在对照大鼠中诱导增加4.3倍（P < 0.01），在V组大鼠中诱导增加3.8倍（P < 0.01），而GLUT2在对照大鼠中诱导增加3.3倍（P < 0.01），但在V组大鼠中仅诱导增加1.4倍（无统计学意义）。
我们的结果表明，通过迷走神经的信号传导对于GLUT2和蔗糖酶的预期诱导是必要的。SGLT1和GLUT5正常节律的持续存在表明这些基因的昼夜诱导独立于迷走神经支配。肠道中预期昼夜基因表达的同步化通过两条不同的途径发生，这两条途径对迷走神经输入的依赖性不同。
