Poulaki Vassiliki, Qin Wenying, Joussen Antonia M, Hurlbut Peter, Wiegand Stanley J, Rudge John, Yancopoulos George D, Adamis Anthony P
Laboratory of Surgical Research, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
J Clin Invest. 2002 Mar;109(6):805-15. doi: 10.1172/JCI13776.
Acute intensive insulin therapy is an independent risk factor for diabetic retinopathy. Here we demonstrate that acute intensive insulin therapy markedly increases VEGF mRNA and protein levels in the retinae of diabetic rats. Retinal nuclear extracts from insulin-treated rats contain higher hypoxia-inducible factor-1alpha (HIF-1alpha) levels and demonstrate increased HIF-1alpha-dependent binding to hypoxia-responsive elements in the VEGF promoter. Blood-retinal barrier breakdown is markedly increased with acute intensive insulin therapy but can be reversed by treating animals with a fusion protein containing a soluble form of the VEGF receptor Flt; a control fusion protein has no such protective effect. The insulin-induced retinal HIF-1alpha and VEGF increases and the related blood-retinal barrier breakdown are suppressed by inhibitors of p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol (PI) 3-kinase, but not inhibitors of p42/p44 MAPK or protein kinase C. Taken together, these findings indicate that acute intensive insulin therapy produces a transient worsening of diabetic blood-retinal barrier breakdown via an HIF-1alpha-mediated increase in retinal VEGF expression. Insulin-induced VEGF expression requires p38 MAPK and PI 3-kinase, whereas hyperglycemia-induced VEGF expression is HIF-1alpha-independent and requires PKC and p42/p44 MAPK. To our knowledge, these data are the first to identify a specific mechanism for the transient worsening of diabetic retinopathy, specifically blood-retinal barrier breakdown, that follows the institution of intensive insulin therapy.
急性强化胰岛素治疗是糖尿病视网膜病变的一个独立危险因素。在此我们证明，急性强化胰岛素治疗可显著提高糖尿病大鼠视网膜中血管内皮生长因子（VEGF）的mRNA和蛋白水平。胰岛素治疗大鼠的视网膜核提取物中缺氧诱导因子-1α（HIF-1α）水平较高，并显示出HIF-1α依赖性与VEGF启动子中缺氧反应元件的结合增加。急性强化胰岛素治疗可使血视网膜屏障破坏显著增加，但用含可溶性VEGF受体Flt的融合蛋白治疗动物可使其逆转；对照融合蛋白则无此保护作用。p38丝裂原活化蛋白激酶（MAPK）和磷脂酰肌醇（PI）3激酶抑制剂可抑制胰岛素诱导的视网膜HIF-1α和VEGF增加以及相关的血视网膜屏障破坏，但p42/p44 MAPK或蛋白激酶C抑制剂则无此作用。综上所述，这些发现表明，急性强化胰岛素治疗通过HIF-1α介导的视网膜VEGF表达增加，导致糖尿病血视网膜屏障破坏出现短暂恶化。胰岛素诱导的VEGF表达需要p38 MAPK和PI 3激酶，而高血糖诱导的VEGF表达不依赖HIF-1α，需要PKC和p42/p44 MAPK。据我们所知，这些数据首次确定了强化胰岛素治疗后糖尿病视网膜病变短暂恶化的具体机制，特别是血视网膜屏障破坏的机制。
