不同血糖水平对缺氧缺血新生大鼠脑内葡萄糖转运蛋白基因表达的影响研究

Effect of different blood glucose levels on the expression of cerebral GLUT3 mRNA in neonatal rats with hypoxia-ischemia

摘要:

目的：葡萄糖转运蛋白(GLUT)基因及其产物在调节脑内能量代谢方面有重要作用,近来葡萄糖在围产期缺氧缺血损伤中的作用正日益受到关注。该研究拟探讨不同血糖水平对缺氧缺血新生大鼠脑内GLUT3基因表达的影响,评估葡萄糖的缺氧缺血脑保护作用。方法：对7日龄SD新生大鼠通过调节25%葡萄糖的注射次数及时间或禁食12h,分别建立单纯低血糖组,缺氧缺血(HI)组,HI前低血糖组,HI后低血糖组,HI前轻度高血糖组,HI后轻度高血糖组,HI前重度高血糖组以及HI后重度高血糖组;另设正常组和假手术组。应用RT-PCR方法,分别在HI后2,24,48,72h及7d对各组新生大鼠脑内GLUT3基因进行测定。结果：正常组GLUT3基因表达量随日龄增加而表达量增高,HI可引起GLUT3基因表达量的短期上调,至HI后72h及7d则非常显著低于正常组(均P<0.01)。HI前低血糖组GLUT3基因表达量在各缺氧缺血组中为最低,尤其在HI后72h显著低于HI组(P<0.05)。HI前重度高血糖可明显上调GLUT3基因表达量,在HI后大部分时段的GLUT3基因表达量均显著高于其余各组(P<0.05或0.01)。HI前轻度高血糖对GLUT3基因表达的影响不如HI前重度高血糖组。在HI后无论轻或重度高血糖组以及HI后低血糖组,其GLUT3基因的表达时相均与HI前低血糖组类似。结论：结果提示HI前低血糖可使GLUT3基因表达和产物合成明显下调、脑病理改变加重;HI前重度高血糖则使GLUT3基因表达和产物合成明显上调、脑病理改变显著改善;在缺氧缺血前预先补充足量葡萄糖,有可能在一定程度上提高脑内应对缺氧缺血的侵袭、改善缺氧缺血程度的能力。

Abstract:

OBJECTIVE: Concerns of the effect of glucose on perinatal hypoxic-ischemic brain damage are increasing. It was previously considered that the glucose transporter (GLUT)genes and their productions played an important role in the regulation of cerebral energy metabolism. The present study aimed to explore the effect of different blood glucose levels on the expression of cerebral GLUT3 mRNA in neonatal rats with hypoxia-ischemia (HI), and to evaluate the neuroprotective effect of glucose against HI insults. METHODS: A total of 250 7-day-old neonatal SD rats were randomly divided into 10 groups (n=25 each): Normal control, Sham-operated, HI, Hypoglycemia, Hypoglycemia pre- and post-HI, Mild hyperglycemia pre- and post-HI, Severe hyperglycemia pre- and post-HI. Blood glucose levels of normal, hypoglycemia, mild hyperglycemia and severe hyperglycemia were defined as 5- 7 mmol/L, 3- 4 mmol/L, 10-15 mmol/L and 16-25 mmol/L, respectively. The expression of GLUT3 mRNA was detected with RT-PCT technique at 2, 24, 48 and 72 hrs and at 7 days after HI. RESULTS: There was a correlation between increases in GLUT3 mRNA expression and postnatal age in the Normal control group. HI significantly enhanced the expression of GLUT3 mRNA from 2 hrs, peaking at 24 hrs after HI, and then significantly decreased at 72 hrs and 7 days after HI when compared with the Normal Control group (P< 0.01 ). GLUT3 mRNA expression in the Hypoglycemia pre-HI group was the lowest among all groups with HI at each time point after HI, and a statistically significant difference was found at 72 hrs after HI when compared with the HI group (P<0.05). The expressional levels of GLUT3 mRNA in the Severe hyperglycemia pre-HI group were striklingly higher than those in any other groups with HI (P<0.05 or 0.01). The GLUT3 mRNA expression patterns in the Mild and Severe hyperglycemia post-HI and the Hypoglycemia post-HI groups were similar to the Hypoglycemia pre-HI group. CONCLUSIONS: GLUT3 mRNA expression and the synthesis of GLUT3 can be down-regulated by hypoglycemia pre-HI, coupled with aggravation of cerebral pathology, but up-regulated by higher hyperglycemia pre-HI, coupled with improvement of cerebral pathology. This suggested that adepuate glucose supplement before HI can improve the cerebral function against HI insults in neonatal rats.