瘦素对小鼠脑缺血／再灌注损伤后脑血流和神经营养因子表达的影响

目的：研究瘦素（leptin）对脑缺血／再灌注损伤后血流变化和神经营养因子表达的影响。方法：45只雄性昆明小鼠随机分为假手术组、模型组和leptin治疗组，每组15只。采用大脑中动脉栓塞方法制备小鼠局灶性脑缺血／再灌注损伤模型。leptin治疗组和模型组于动脉栓塞（即缺血0min）的同时分别腹腔注射leptin 1μg／g或等体积磷酸盐缓冲液（PBS），假手术组未行栓塞。于MCAO前、缺血2h、再灌注5min和24h采用激光多普勒流量仪检测缺血侧脑组织大脑中动脉供血区血流量变化，免疫组化染色观察神经生长因子（NGF）和脑源性神经生长因子（BDNF）的表达。结果：模型建立后，大脑中动脉分支血流速度明显减慢；再灌注24h，leptin治疗组脑组织血流量较模型组明显改善（P〈0．01）。与假手术组相比，模型组缺血半影区NGF表达水平显著升高（P〈0．01），大部分NGF阳性细胞明显凋亡，而BDNF表达无明显升高（P〉0．05）；leptin治疗组NGF和BDNF表达水平均较假手术组显著升高（P〈0．01），NGF和BDNF阳性细胞形态接近正常。结论：leptin能够升高神经营养因子NGF、BDNF的表达水平，增加缺血区血流量，从而在脑缺血性损伤中发挥神经保护作用。

Effect of leptin on cerebral blood flow and expression of neurotrophic factors in mice with cerebral ischemia/reperfusion injury

Objective：To study the effect of leptin on cerebral blood flow and expression of neurotrophic factors in mice with cerebral isehemia/reperfusion injury. Methods： Forty-five male Kunming mice were randomly divided into sham operation group, model group and leptin-treatment group （n： 15 in each group）. Focal cerebral ischemia/reperfusion injury model was replicated by middle cerebral artery occlusion （MCAO） in model group and leptin-treatment group. After the arterial occlusion （ischemia 0 minutes）, mice in leptin-treatment group and model group received intraperitoneal injection of leptin 1 μg/g or an equal volume of phosphate buffer solution （PBS）, respectively. The cerebral blood flow was monitored with laser Doppler flowmetry （LDF） before MCAO, and after ischemia 0 minute, ischemia 2 hours/reperfusion 5 .minutes and 24 hours, respectively. The expression of nerve growth factor （NGF）, brain-derived neurotrophic factor （BDNF） were detected with immunohistochemistry. Resuits：The blood flow of the middle cerebral artery branch had slowed significantly after MCAO. Compared with model group, the volume of blood flow in leptin-treatment group increased significantly 24 hours after reperfusion （P〈0. 01）. Furthermore, compared with sham operation group, the expression of NGF in model group increased significantly, and, apoptosis occurred in most of the NGF positive cells. However, there was no evident change in the expression of BDNF （P〉0. 05）. On the other hand, compared with sham operation group, both expression of levels of NGF and BDNF in leptin-treatment group increased significantly （P〈0. 01）, and the morphology of positive cells was similar to that of normal cells. Conclusion： Leptin plays an important role in protection of neurons through up-regulating the expression of NGF and BDNF, and increasing the blood flow.