羟基酪醇在2型糖尿病防治中的线粒体生成及二相酶激活机制研究

Type 2 diabetes is a serious health problem in China and the world. Though great efforts have been dedicated to type 2 diabetes study, so far the detailed mechanisms have not been well understood. There also have limited drugs with limited effects.One of the best strategies is to prevent type II diabetes with nutritional intervention. Previous studies showed that disturbance of mitochondrial biogenesis and degradation (especially decreased biogenesis) in insulin targeted cells might be a key contributing factor to type 2 diabetes. Hydroxytyrosol (HT) is a major active component of olive oil and olive leaf extract. A few animal studies found that olive leaf extract or HT could prevent type I diabetes. These studies have attributed the protective effects to the direct reaction with free radicals as a simple antioxidant. Our recent studies showed that HT could induce mitochondrial biogenesis and activate phase II enzymes in adipocytes and human retinal pigment epithelial cells. Therefore, we propose that HT may prevent type II diabetes by stimulating mitochondrial biogenesis (to ameliorate the decreased mitochondrial biogenesis and dysfunction) and activating phase II enzymes （to enhance the endogenous antioxidant defense system）. To prove this hypothesis, we will use both cellular and animal models of insulin resistance and type II diabetes to study the effects and molecular mechanisms of HT on stimulation of mitochondrial biogenesis and activation of phase II enzymes. This study will help to have better understanding the underlying mechanisms of type II diabetes, and find possible targets and pathways for effectively preventing type II diabetes.

我国2型糖尿病的防治形势异常严峻。从营养学角度入手进行防治是降低发病率、缓解糖尿病症状的有效手段之一。已有研究提示，2型糖尿病中胰岛素靶细胞线粒体生成代谢和分解代谢失衡，特别是生成降低导致的功能退变，是引发糖代谢紊乱的关键因素。羟基酪醇是橄榄油和橄榄叶中的主要活性成分之一。虽有少量动物实验发现橄榄叶提取物或羟基酪醇对I型糖尿病的预防有一定效果，但这些研究仅从自由基清除的抗氧化角度认识其保护机制。我们发现羟基酪醇能够有效提高脂肪细胞和人视网膜色素上皮细胞的线粒体生成，激活内源性二相酶抗氧化防御体系。 因此，我们假设，羟基酪醇可能会通过调控细胞线粒体稳态平衡，特别是促进线粒体生成而改善线粒体功能并通过激活二相酶系统提高细胞抗氧化防御能力而改善糖代谢紊乱，进而达到预防2型糖尿病的效果。我们将在胰岛素抵抗和2型糖尿病细胞及动物模型中，系统研究羟基酪醇的保护机制，为其防治2型糖尿病提供科学依据。

在本研究中我们利用高脂饮食诱导的肥胖、胰岛素抵抗小鼠模型和db/db糖尿病小鼠模型来验证羟基酪醇改善代谢综合征的作用效果，确认其线粒体和二项酶调节的作用机制。结果显示在高脂饮食模型中，10毫克/千克和50毫克/千克的羟基酪醇补充能够显著抑制体重的增加、肝脏和肌肉中脂肪的积累，有效恢复血糖、血脂的正常代谢水平。而在db/db糖尿病小鼠中，10毫克/千克的羟基酪醇具有显著降低血糖、血脂，提高胰岛素敏感性的能力，更为重要的是其作用效果与市场化药物二甲双胍在225毫克/千克的剂量效果类似，提示羟基酪醇在改善代谢紊乱中的较强应用前景。在高脂饮食模型和db/db糖尿模型鼠中，羟基酪醇都能有效调节肝脏、肌肉中线粒体的代谢和功能，通过激活二项酶体系来恢复机体氧化还原的稳态。以上发现证实羟基酪醇可调节线粒体代谢而改善线粒体功能，通过激活Nrf2介导的二相酶系统提高细胞抗氧化防御能力，最终改善糖代谢紊乱，达到预防2型糖尿病的效果, 为其防治2型糖尿病提供科学依据。所获结果符合预期,较为成功的实现了课题设想。共发表论文8篇（7篇SCI,1篇国内核心杂志），培养硕士生1名，博士生5名，博士后2名。