摘要
目的 探讨脂毒性引起胰岛细胞凋亡在 β细胞功能异常中的作用。 方法 8周龄雄性SD大鼠随机分为两组 ,分别予总热量相同的正常脂肪含量饲料 (脂肪占总热量的 13% )和高脂饲料 (脂肪占总热量的 5 9% )饲养。 2 8周后 ,透射电镜观察胰岛细胞超微结构 ;进行胰岛素免疫组化染色光镜下定位 β细胞 ,图像分析测定平均每个胰岛内胰岛素的表达量 ;TUNEL法观察胰岛细胞凋亡情况并计数每个胰岛中 β细胞凋亡率 ,以Ki6 7单克隆抗体染色观察胰岛细胞的增生情况。 结果 高脂饲养组 (HF组 )胰岛细胞内可见明显脂质沉积 ,胰腺免疫组化染色图像分析显示平均每个胰岛内胰岛素染色阳性细胞面积和积分下光密度HF组均显著低于正常饲养组 (NC组 ) (HF :2 5 2 2 μm2vsNC :5 0 10 μm2 ,P =0 0 0 ;HF :12 10vsNC :2 4 4 7,P =0 0 0 )。HF组β细胞凋亡率明显高于NC组[(2 6± 8) %vs15± 5 ) % ,P <0 0 1]。两组增生的胰岛细胞数差异无显著意义 (0 5 0个 /胰岛vs 0 5 4个 /胰岛 ,P >0 0 5 )。 结论 高脂饲养对大鼠胰岛细胞的复制无明显改变 ,β细胞凋亡的增加可能是长期高脂饲养后大鼠胰岛功能改变的机制之一。
Objective In our previous study, we have observed that high fat feeding with normal total caloric intake for 28 weeks can induce higher fasting free fatty acids and the inhibited acute insulin secretary response(AIR) to intravenous glucose load in normal male Sprague Dawley rats The aim of this study is to investigate the effect of β cell apoptosis on the β cell function Methods Normal male Sprague Dawley rats were fed on a high fat diet (HF,59% of calories as fat, n =9) or isocaloric normal chow(NC,13% of calories as fat, n =10) for 28 weeks Then islet ultrastructure was studied by electron microscope The pancreatic slides were stained with insulin antibody The apoptotic β cells in islets were detected and quantified by the TUNEL technology(labeling of DNA strand breaks) A monoclonal antibody against rat Ki67 was used to study islet cell proliferation Results Image analysis of islet immunocytochemistry showed that both area and total density of insulin positive cells per islet were significantly lower in HF than in NC [HF:2522 μm 2 vs NC:5010 μm 2, P =0 00; HF: 1210 vs NC:2447, P =0 00] The frequency of β cell apoptosis was higher in HF than in NC[(26±8)% vs (15±5)% P <0 001] There was no difference in islet cell proliferation rate between the two groups At the ultrastructural level, the marked fat droplets and alterations of mitochondria were present in HF islet cells Conclusions β cell number is decreased after high fat feeding Increased β cell apoptosis may partially contribute to this process To arrest β cell apoptosis could be a new target to prevent β cell dysfunction induced by lipotoxicity
