Collino Massimo, Aragno Manuela, Castiglia Sara, Tomasinelli Chiara, Thiemermann Christoph, Boccuzzi Giuseppe, Fantozzi Roberto
Department of Anatomy, Pharmacology, and Forensic Medicine, University of Turin, Turin, Italy.
Diabetes. 2009 Jan;58(1):235-42. doi: 10.2337/db08-0691. Epub 2008 Oct 7.
There is evidence that insulin reduces brain injury evoked by ischemia/reperfusion (I/R). However, the molecular mechanisms underlying the protective effects of insulin remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3beta (GSK-3beta). Here, we investigate the role of GSK-3beta inhibition on I/R-induced cerebral injury in a rat model of insulinopenic diabetes.
Rats with streptozotocin-induced diabetes were subjected to 30-min occlusion of common carotid arteries followed by 1 or 24 h of reperfusion. Insulin (2-12 IU/kg i.v.) or the selective GSK-3beta inhibitor TDZD-8 (0.2-3 mg/kg i.v.) was administered during reperfusion.
Insulin or TDZD-8 dramatically reduced infarct volume and levels of S100B protein, a marker of cerebral injury. Both drugs induced phosphorylation of the Ser9 residue, thereby inactivating GSK-3beta in the rat hippocampus. Insulin, but not TDZD-8, lowered blood glucose. The hippocampi of the drug-treated animals displayed reduced oxidative stress at 1 h of reperfusion as shown by the decreased generation of reactive oxygen species and lipid peroxidation. I/R-induced activation of nuclear factor-kappaB was attenuated by both drug treatments. At 24 h of reperfusion, TDZD-8 and insulin significantly reduced plasma levels of tumor necrosis factor-alpha; neutrophil infiltration, measured as myeloperoxidase activity and intercellular-adhesion-molecule-1 expression; and cyclooxygenase-2 and inducible-NO-synthase expression.
Acute administration of insulin or TDZD-8 reduced cerebral I/R injury in diabetic rats. We propose that the inhibitory effect on the activity of GSK-3beta contributes to the protective effect of insulin independently of any effects on blood glucose.
有证据表明胰岛素可减轻缺血/再灌注（I/R）诱发的脑损伤。然而，胰岛素保护作用的分子机制仍不清楚。胰岛素是糖原合酶激酶-3β（GSK-3β）的著名抑制剂。在此，我们在胰岛素缺乏型糖尿病大鼠模型中研究GSK-3β抑制对I/R诱导的脑损伤的作用。
用链脲佐菌素诱导糖尿病的大鼠，使其颈总动脉闭塞30分钟，然后再灌注1或24小时。在再灌注期间给予胰岛素（2-12 IU/kg静脉注射）或选择性GSK-3β抑制剂TDZD-8（0.2-3 mg/kg静脉注射）。
胰岛素或TDZD-8显著减小梗死体积并降低S100B蛋白水平，S100B蛋白是脑损伤的标志物。两种药物均诱导Ser9残基磷酸化，从而使大鼠海马体中的GSK-3β失活。胰岛素可降低血糖，但TDZD-8不能。如活性氧生成减少和脂质过氧化所示，药物治疗动物的海马体在再灌注1小时时氧化应激降低。两种药物治疗均减弱了I/R诱导的核因子-κB激活。在再灌注24小时时，TDZD-8和胰岛素显著降低血浆肿瘤坏死因子-α水平；以髓过氧化物酶活性和细胞间黏附分子-1表达衡量的中性粒细胞浸润；以及环氧合酶-2和诱导型一氧化氮合酶表达。
急性给予胰岛素或TDZD-8可减轻糖尿病大鼠的脑I/R损伤。我们提出，对GSK-3β活性的抑制作用有助于胰岛素的保护作用，而与对血糖的任何影响无关。
