Objective To investigate the role of epigenetic regulations of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in the development of diabetic retinopathy and the metabolic memory phenomenon after hyperglycemia was terminated.Methods Diabetic rat model was established by intraperitoneal injection of streptozotocin (STZ).Sixty diabetic rats were randomly divided into 3 groups,poor glycemic control group rats were maintained in poor glycemic control for 4 months;semi glycemic control group rats were maintained in poor glycemic control for 2 months,followed by good glycemic control for 2 additional months;good glycemic control group rats were maintained in good glycemic control for 4 months.Twenty normal rats served as control group.The mRNA expression of PGC-1α and superoxide dismutase 2 (SOD2) of retina were measured by real-time PCR;the expression of PGC-1α and manganese superoxide dismutase (MnSOD) protein were measured by Western blot;the situation of DNA methylation in the promotor region of PPARGC1A was measured by bisulfite sequencing.Results The body-weight in the control group was significantly higher than that in the poor glycemic control group,semi glycemic control group and good glycemic control group (all at P =0.000).The blood glucose value in the poor glycemic control group was significantly higher than that in the control group (P =0.000).The expression levels of PGC-1 α mRNA were significantly lower and the expression levels of SOD2 mRNA were significantly higher in the good glycemic control group,semi glycemic control group and poor glycemic control group than those in the control group (all at P＜0.05).The expression levels of PGC-1α and SOD2 mRNA were significantly different between the good glycemic control group and poor glycemic control group (both at P＜0.05).Compared with the control group,the expression levels of PGC-1α and MnSOD protein were decreased in the diabetic model groups,with significant differences between them (all at P＜0.05).The expression level of PGC-1 α protein was significantly higher in the good glycemic control group than that in the poor glycemic control group (P＜0.05).Diabetes increased DNA methylation in the promotor region of PPARGC1A gene of retina.The DNA methylation level was significantly higher in the poor glycemic control group and semi glycemic control group than that in the control group (P =0.008,0.031).No statistical difference was found between the poor glycemic control group and semi glycemic control group (P ＞ 0.05).Conclusions The expressions of PGC-1o mRNA and protein and MnSOD protein in the retina of STZ induced diabetic rats are decreased,the expression of SOD2 mRNA is increased,the expression changes have metabolic memory characteristics.Increased DNA methylation in the promotor region of PPARGC1A when exposed to high glucose may have a role in the regulation of PGC-1 α expression and metabolic memory.%目的 通过检测糖尿病模型大鼠视网膜过氧化物酶体增生物激活受体γ辅助激活因子1α(PGC-1α)mRNA和蛋白表达以及PPARGC1A启动子区DNA甲基化的改变,探讨糖尿病发生和发展过程中PGC-1α的变化趋势、表观遗传学修饰改变及其在糖尿病视网膜病变(DR)代谢记忆中的作用.方法 取清洁级6～7周龄雄性SD大鼠80只,其中60只采用腹腔内注射链脲佐菌素(STZ)的方法建立糖尿病大鼠模型.将60只糖尿病模型大鼠应用随机数字表法随机分为3个组:血糖控制不佳组大鼠造模后4个月内血糖水平控制不佳;血糖半控制组大鼠造模后2个月内血糖水平控制不佳,2个月后维持正常血糖水平;血糖控制组大鼠造模后4个月内均保持正常血糖水平,每组各20只.对照组为周龄匹配的正常饲养大鼠20只.分离各实验组大鼠视网膜组织,应用实时荧光定量PCR法检测PGC-1α及超氧化物歧化酶2(SOD2) mRNA的表达,应用Western blot法检测PGC-1α及锰超氧化物歧化酶(MnSOD)蛋白的表达,应用亚硫酸氢钠测序法(BSP)检测PPARGC1A启动子区DNA甲基化状态的变化.结果 造模后4个月,对照组大鼠体质量明显高于血糖控制不佳组、血糖半控制组和血糖控制组,血糖控制不佳组血糖水平显著高于对照组,差异均有统计学意义(均P=0.000).血糖控制组、血糖半控制组和血糖控制不佳组大鼠视网膜组织中PGC-1 αmRNA相对表达量依次下降,均低于对照组,差异均有统计学意义(均P=0.000);血糖控制组PGC-1αmRNA相对表达量明显高于血糖控制不佳组,差异有统计学意义(P=0.002).血糖控制组、血糖半控制组和血糖控制不佳组大鼠视网膜组织中SOD2 mRNA表达依次增加,均高于对照组,差异均有统计学意义(P=0.006、0.000、0.000);血糖控制组与血糖控制不佳组SOD2 mRNA相对表达量比较,差异有统计学意义(P=0.001).血糖控制不佳组、血糖半控制组和血糖控制组大鼠视网膜中PGC-1α蛋白和MnSOD蛋白相对表达量显著低于对照组,血糖控制组大鼠视网膜PGC-1α蛋白相对表达量显著高于血糖控制不佳组,差异均有统计学意义(均P＜0.05).糖尿病模型大鼠视网膜组织中PPARGC1A启动子区DNA甲基化水平升高,血糖控制不佳组、血糖半控制组大鼠视网膜组织中PPARGC1A启动子区DNA甲基化的水平较对照组明显升高,差异均有统计学意义(P=0.008、0.031),血糖半控制组与血糖控制不佳组间比较,差异无统计学意义(P＞0.05).结论 糖尿病模型大鼠视网膜PGC-1αmRNA及蛋白表达均下降,视网膜SOD2 mRNA表达升高,MnSOD蛋白表达下降,具有代谢记忆的特点.PPARGC1A启动子区DNA甲基化水平的升高可能与PGC-1α表达受到抑制以及代谢记忆相关.
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