糖尿病高血糖及糖代谢紊乱产生大量的羰基化合物，如甲基乙二醛(methylglyoxal，MG)、乙二醛（glyoxal），3-脱氧葡糖醛酮（3-deoxyglucosone，3-DG）。这些活泼的羰基化合物容易糖基化修饰生物大分子，与蛋白质、脂类及核酸发生羰-氨反应，形成晚期糖基化终末产物（advanced glycation endproducts，AGEs）。作为Maillard反应的中间体，MG具有两个高度活泼的羰基亲电中心，是AGEs形成的最重要前体，其糖基化活性是乙二醛的10倍，是还原糖的20,000～50,000倍，即使体内浓度很低，也极容易与生物大分子的末端氨基结合，使之发生分子内及分子间交联形成稳定的AGEs化合物。AGEs的富集被认为是导致糖尿病及其并发症发生发展的关键病理因素，在糖尿病及其并发症发病机制中起到重要作用。MG是细胞正常代谢过程中固有的毒副产物，可通过糖酵解、氨基酸降解以及脂类代谢等过程产生。乙二醛酶系统是清除胞浆内MG的最主要酶系统，该酶系统由乙二醛酶I（glyoxalase I，GLO1）、乙二醛酶II（glyoxalase I，GLO2）和一定催化剂量的还原型谷胱甘肽（glutathione，GSH）组成，其中GLO I是该酶系的限速酶，对MG 的代谢清除起到关键作用，能够减少糖基化产物AGEs的形成，有效抑制糖基化损伤。正常生理条件下，体内大约只有0．1％ ～0．4％ 的葡萄糖会转变成MG，成人体内每天产生3mmol MG，但仅有0.3%形成糖基化产物AGEs，剩余MG主要被体内GLO1酶系统及时清除，使体内MG维持在最低水平，从而抑制了生物大分子的糖基化修饰，减少AGEs的形成，使机体避免遭受MG及AGEs的毒性损伤。然而糖尿病病理条件下，糖尿病患者体内MG含量升高了2～4倍，同时乙二醛酶I活性下降，导致MG生成与清除不平衡，造成AGEs过度累积。AGEs通过破坏体内蛋白分子构象，改变酶的活性，影响受体的功能，对机体造成严重损伤。AGEs还能与其受体RAGE结合后，活化转录因子NFκB，激活炎症通路及氧化应激，释放大量的炎症因子及活性氧( reactive oxygen species，ROS)，诱导细胞凋亡及组织损伤，促进糖尿病肾病、脑病、眼病以及动脉粥样硬化等多种并发症的发生和发展。因此，减少MG的生成，提高MG的清除能力，抑制AGEs的形成，或阻断AGEs-RAGE介导的毒性效应将成为减缓糖尿病及其慢性并发症的有效手段。（一）糖尿病肾病（Diabetic Nephropathy，DN）是糖尿病微血管性并发症之一，成为糖尿病中最常见及危害性最严重的慢性并发症。其主要病理学特征为肾小球基底膜增厚、系膜细胞外基质扩增、肾小球肥大、足细胞丢失以及肾小球硬化，并且伴随着持续的尿白蛋白增多、血尿素升高以及肌酐清除率下降等临床表现。在糖尿病肾病的诸多发病机制中，高血糖是引起早期糖尿病肾病走向终末期肾病的始发因素，而微炎症以及随之引起的细胞外基质扩增是加快糖尿病肾病病变进程的关键。炎症通路中产生的大量生物分子包括转录因子、前炎症因子、炎症趋化因子、粘附分子、脂肪因子、Toll样受体以及核受体等，造成糖尿病微血管损伤，与糖尿病肾病的病变进程密切相关。糖代谢紊乱产生大量的AGEs，与其受体RAGE结合对慢性炎症反应进程起到关键的作用。肾脏结构包括肾小球基底膜、系膜细胞、内皮细胞、足细胞以及肾小管都有AGEs的沉积，AGEs除了自身的细胞毒性外，可以通过与肾小球细胞外基质中IV胶原、层粘蛋白以及其他蛋白分子间交联，导致肾小球细胞外基质扩增、基底膜增厚、肾小球肥大等肾脏结构异常，促进肾小球硬化。AGEs与其受体RAGE结合，活化转录因子NFκB及其上游IκB，促进炎症因子以及细胞生长因子的释放，促进血管内皮增生以及细胞外基质增生，改变肾小球细胞通透性，影响肾小球滤过功能。因此，寻求药物用于抑制AGEs的形成，阻断AGEs-RAGE-炎症通路介导的毒性效应，将成为防治糖尿病肾病的新策略。栀子苷具有一定的抗炎生物活性，以往研究发现栀子苷可以通过下调Aβ引起的RAGE-NFκB信号通路的活化，对阿尔茨海默病（Alzheimer’s disease，AD）神经炎性损伤具有明显改善作用。在本研究中，我们利用二型糖尿病db/db小鼠模型，从炎症角度探讨栀子苷对糖尿病肾病的保护作用及机制。我们发现栀子苷连续灌胃16周后：可以显著降低糖尿病小鼠血浆尿素及血肌酐水平，对其体重没有影响，栀子苷高剂量组可以稳定糖尿病小鼠的空腹血糖水平，控制其进一步增高，对糖尿病小鼠肾功能损伤具有保护作用；能够减少糖尿病小鼠肾小球细胞的丢失，抑制肾小球肥大及系膜细胞外基质增生，对糖尿病小鼠肾脏病理结构具有明显改善作用。其机制可能为：1）可以减少糖尿病小鼠肾脏MG的含量，并且通过体外实验证实栀子苷没有捕获MG的作用，肾脏中MG的减少可能与栀子苷控制血糖进一步增高的作用有关；2）能够降低糖尿病小鼠肾脏AGEs及RAGE的含量，抑制转录因子NFκB及其上游IκB、MAPK P38及ERK1/2的活化，减少TNF-α及IL-1β的含量。因此，本研究从AGEs-RAGE-炎症通路解释了栀子苷改善糖尿病肾病的作用机制，提示栀子苷有望成为预防和治疗糖尿病肾病的潜在药物。（二）线粒体是细胞能量代谢的主要场所，在细胞中发挥着重要功能，包括能量产生，脂肪酸代谢，嘧啶生物合成，钙离子稳态以及细胞信号传导等。线粒体各种生物大分子均会被MG、乙二醛等内源性羰基化合物糖基化修饰，糖基化修饰将对生物大分子造成严重损伤，导致线粒体结构及功能改变。研究表明，蛋白质赖氨酸及精氨酸糖基化水平达到0.1-1%，DNA糖基化水平达到1/107以及磷脂类糖基化水平达到0.1%时，糖基化修饰将对生物大分子造成严重损伤。蛋白质糖基化修饰后通过促进蛋白质分子内及分子间交联，改变蛋白质结构，影响蛋白质活性及功能；脂质糖基化修饰后通过增加膜流动性影响膜的功能，通过脂质过氧化作用，导致膜氧化损伤。DNA糖基化修饰后导致DNA链断裂，双螺旋结构解旋，DNA突变以及DNA与蛋白或核酸与核酸交联。其中，DNA糖基化修饰不仅影响基因的完整性，还会影响基因的表达。MG具有高度的糖基化修饰活性，是参与糖基化损伤的最主要前体。糖尿病病理条件下，高血糖及糖代谢紊乱产生大量MG，同时其胞内清除酶系统GLO1的酶活下降，导致胞内MG及AGEs大量积累。细胞内MG一旦产生，可以通过自由扩散穿越线粒体膜结构，进入线粒体，与线粒体生物大分子发生糖基化修饰，造成线粒体糖基化损伤，导致线粒体功能受损。当线粒体受损后，Ca2＋内流，诱发线粒体膜上的线粒体渗透性转变孔（mitochondrial permeability transition pore，mPTP）开放，mPTP 的开放程度对细胞的凋亡和坏死起到重要的作用。亲环素 D（Cyclophilin D，CypD）作为 mPTP的一个必不可少的组成成分，是调控mPTP开放的关键，其与线粒体内膜上的腺苷酸转运蛋白（adenine nucleotide translocator，ANT）结合，促进mPTP 的开放，导致线粒体功能紊乱。本研究发现糖尿病小鼠脑组织线粒体内具有较高水平的CypD蛋白表达，利用CypD基因缺陷型糖尿病小鼠模型，探讨CypD基因敲除后对线粒体糖基化损伤的保护作用及其作用机制。研究表明CypD基因敲除能通过减少MG、CML及AGEs的水平，抑制线粒体糖基化修饰，提高线粒体complex I 活性及ATP合成，减少脂质过氧化物生成，对线粒体功能损伤具有保护作用，其作用机制可能是通过上调GLO1的酶活及蛋白表达发挥作用的，提示CypD有可能成为防治线粒体糖基化损伤的潜在靶点。

Hyperglycemia and glycometabolic disorders associated with diabetes produce a large number of carbonyl compounds, such as methylglyoxal (MG), glyoxal and 3- deoxyglucosone (3-DG). These reactive carbonyl compounds easily make biological macromolecules glycated, and form to advanced glycation end products (AGEs) via the glycation of proteins, lipids and nucleotides with carbonyl-ammonia reaction. As the intermediate of Maillard reaction, MG containing two highly reactive carbonyl groups, is the most reactive precursor for forming AGEs which is up to 10-fold more reactive than glyoxal, and 20, 000 to 50, 000-fold more reactive than reducing glucose. Even MG at very low concentration can easily combine with N-terminal amino groups of biological macromolecules to form stable AGEs. The accumulation of AGEs is considered to be a key pathological factor leading to the development of diabetes and its complications, and plays an important role in the pathogenesis of diabetes and its complications.MG is a toxical product in normal cellular metabolic processes through glycolysis, amino acid degradation and lipid metabolism. Glyoxylase system, containing glyoxalase I (GLO 1), glyoxalase II (GLO 2) and reduced glutathione (GSH) considered as a catalyst, is the most important enzyme system to clear MG. Among them, GLO1 is the key enzyme of defense against MG glycation, which can reduce glycated products and inhibit glycation-induced damage. Under normal physiological condition, only 0.1% to 0.4% of glucose will be transformed into MG, and an adult body produces 3mmol MG per day, but only 0.3% of MG forms to AGEs, because the remaining of MG is metabolized promptly by GLO1 enzyme which can make MG maintained at a minimum level, inhibit the formation of AGEs, and protect against damage suffered from MG and AGEs. However, under diabetic condition, MG level is elevated two to four-fold, meanwhile glyoxylase I enzyme activity is decreased. MG under this imbalance of generation and clearation could result in excessive accumulation of AGEs. AGEs can cause serious body damage through changing protein conformation, lowering enzyme activity and influencing receptor function. AGEs-RAGE ligation can activate transcription factor NFκB, induce inflammatory pathway and oxidative stress, further produce large amounts of inflammatory cytokines and reactive oxygen species (ROS), leading to cell apoptosis and tissue damage, and promoting the development of various diabetic complications such as nephropathy, encephalopathy, eye disease and atherosclerosis. Therefore, reducing the generation of MG, improving the capacity of scavenging MG, inhibiting the formation of AGEs, or cutting off AGEs-RAGE-mediated toxic effects would be effective strategies for the prevention and treatment of diabetes and its complications. （I）Diabetic nephropathy (DN) is a very common microvascular complications of diabetes mellitus and has become a most serious disease of chronic diabetic complications. The major pathological characterizations of DN are glomerular basement membrane thickening, mesangial expansion, glomerular hypertrophy, podocyte loss and glomerulosclerosis with persistent albuminuria, enhanced blood urea nitrogen, and decreased creatinine clearance as clinical markers. Diabetic nephropathy has various pathogenesises. Upstream of these mechanisms, hyperglycaemia is the major driving force from the progression to end-stage renal disease of DN. Downstream of these mechanisms, microinflammation and subsequent extracellular matrix expansion are critical pathways for the progression of DN. Various molecules related to the inflammation pathway in diabetic nephropathy include transcription factors, pro-inflammatory cytokines, chemokines, adhesion molecules, Toll-like receptors, adipokines and nuclear receptors, which are candidates for the new molecular targets for the treatment of diabetic nephropathy.Prolonged glucose metabolic disorders lead to accumulate lots of AGEs considered to be the main initiation factors for inflammatory mechanisms in DN. AGEs with its receptor RAGE, played an important role in chronic inflammatory process. A growing body of evidence shows that almost all renal structures such as basement membranes, mesangial cells, endothelial cells, podocytes, and tubules, are susceptible to accumulate AGEs. AGEs promoted the intramolecular or intermolecular cross-linking of extracellular collagen, laminin and other proteins in glomeruli, subsequently caused glomerular basement membrane thickening, glomerular hypertrophy, mesangial expansion, and glomerulosclerosis which accelerated the progression of glomerular fibrosis. AGEs-RAGE interaction activated transcription factor NF-KB and IκB, promoted inflammatory cytokines release and cell growth factors, induces endothelial proliferation and extracellular matrix thickening, mesangial permeability changing, and affects glomerular filtration. Therefore, searching for drugs to inhibit the formation of AGEs, and block the toxic effects of AGEs-RAGE- mediated inflammatory pathways, will become a new strategy for the prevention and treatment of DN.Geniposide has significant anti-inflammatory activity. Pharmacological studies showed that geniposide could ameliorate Alzheimer’s disease-induced inflammatory respond via down-regulation of Aβ-mediated RAGE-NFκB signaling pathyway. In our study, we investigated the protective effects and the molecular mechanisms of geniposide focusing on the inflammatory pathway in type II diabetic db/db mice. After administration for 16 weeks, geniposide could notably low plasma creatinine and urea levels in diabetic db/db mice which showed the protective effects of geniposide on renal dysfunction. However, geniposide had no effect on body weight. the high dosage of geniposide significantly kept fasting blood glucose level without a further increase in diabetic mice. Geniposide could significantly reduce glomerular cells loss, and inhibit glomerular hypertrophy and mesangial expansion which showed the protective effects of geniposide on renal structure in diabetic mice. Renal MG was decreased by geniposide which showed no trapping effect on MG in vitro, possibly resulting from its role of controling blood glucose level. Geniposide significantly reduced renal AGEs and Rage levels, inhibited the phosphorylation of NF-KB and IκB, and suspended the activation of P38 and ERK1/2, as well as significantly decreased both TNF-α and IL-1β levels in diabetic mice. Based on these findings, we suggested that cutting off AGE–RAGE mediated inflammatory pathway played a critical role in the protective effects of geniposide against DN. Geniposide may become a new drug for the prevention and treatment of DN.（II）Mitochondria are the main place for cellular energy metabolism, and play a crucial role in cells, including energy production, fatty acid metabolism, pyrimidine biosynthesis, calcium homeostasis and cell signal transduction. Glycation of mitochondria biomolecules by MG, glyoxal and other carbonyl compounds might induce serious damage of all biological macromolecules and lead to mitochondria structure changes and biochemical dysfunction. Studies have shown that glycation of lysine and arginine residues on proteins with damage levels estimated at 0.1–1%, nucleotides on DNA at 1 in 107 and basic phospholipids at 0.1%, could cause serious biological macromolecules injury. Proteins glycation in arginine, lysine, and cysteine residues, are highly susceptible to form protein cross-links, change protein structure, as well as affect protein activity and function. Consequences of lipids glycation on the outer and inner mitochondrial membranes increase mitochondrial membrane fluidity and lead to mitochondrial dysfunction. Lipids glycation also cause membrane oxidative damage by lipid peroxidation. Nucleotides glycation in deoxyguanosine cause DNA strand breaks, double helix helicase, DNA mutations and DNA-proteins or nucleic acids-nucleic acid crosslinking. DNA glycosylation affects not only the integrity of the genes and also influences gene expression. MG has high glycated activity considered to be the main precursor of glycation damage. Under diabetic pathological conditions, high glucose produces a large number of MG, meanwhile glyoxylase I activity is decreased, the imbalance of generation and clearation could result in excessive accumulation of MG and AGEs. Cytosol MG can diffuse through mitochondrial lipid membranes and further enter mitochondria, and cause glycation of mitochondrial biological macromolecules.When mitochondria occurs glycation damage and Ca2+ concentration surpasses the normal physiological range, the mitochondrial membrane will form a channel that called mitochondrial permeability transition pore (mPTP), which is considered to be an important factor to determine cell apoptosis or necrosis. Cyclophilin D (CypD) as an essential component of mPTP plays a key role in regulating mPTP open. CypD transfers to the inner mitochondrial membrane, combines with adenine nucleotide translocator (ANT), and promotes mPTP open, leading to mitochondrial dysfunction. In our study, we found that CypD was significantly increased in diabetic brain mitochondria. Using CypD gene deficient diabetic mice, we investigated the effect of CypD deficiency on glycation-induced mitochondrial dysfunction and its mechanism. CypD deficiency significantly reduced renal MG, CML and AGEs levels, inhibited mitochondrial glycation, elevated mitochondrial complex I activity and ATP synthesis, decreased oxygen free radicals, and protected against mitochondrial dysfunction. The mechanism may be associated with upregulating GLO 1 activity and expression. CypD may become a potential target for the prevention and treatment of mitochondrial glycation.