醛糖还原酶在非糖尿病疾病发生发展中作用

醛糖还原酶(aldose reductase,AR)属于醛-酮还原酶超家族成员,种类多且组织分布广,具有极广泛的底物[1]。AR是多元醇通路的限速酶,以NADPH为辅酶,将葡萄糖还原为山梨醇,继而在山梨醇脱氢酶(SDH)作用下,进一步将其氧化为果糖。在糖尿病(diabetes mellitus,DM)高血糖条件下,AR以及多元醇通路被激活,引起山梨醇蓄积于多种组织中,如晶状体、血管、神经及肾脏等,可引起相应的症状[2]。基于糖尿病实验动物模型基础上的广泛研究已证实:醛糖还原酶介导的多元醇糖代谢通路与糖尿病慢性并发症的发生和病变发展密切相关[3～5],AR活性增强是其主…     

醛糖还原酶:心肌缺血损伤干预的新靶点

醛糖还原酶是糖代谢多元醇通路的限速酶。最新研究表明：心肌缺血时醛糖还原酶活性增强，抑制醛糖还原酶可以通过保护糖酵解途径和抑制氧化应激，减轻心肌缺血损伤，改善缺血再灌注后心肌功能。醛糖还原酶抑制剂作为潜在的治疗心肌梗死的有效措施引起了研究者的关注。     

醛糖还原酶在神经系统疾病中的作用研究进展

醛糖还原酶(AR)是多元醇途径中的一种关键酶,其作用为将糖转化成多元醇。此反应过程带来烟酰胺腺嘌呤二核苷酸磷酸-烟酰胺腺嘌呤二核苷酸的转变对细胞内氧化还原反应以及炎性反应都可产生直接的影响。AR在神经系统疾病中的作用日益受到关注。本文对新近发表的有关文献进行综述,分析归纳了AR在糖尿病相关神经疾病、缺血缺氧性神经疾病、神经退行性疾病以及神经损伤中作用的研究报道,对AR可能成为神经系统疾病的治疗靶点进行分析,为相关神经系统疾病的诊疗提供新的思路。     

黄芩苷通过影响miR-141上调Sirt1表达而抑制高糖诱导的小鼠肾小球系膜细胞凋亡

目的:探讨黄芩苷在高糖环境下对小鼠肾小球系膜细胞凋亡的影响,并从微小RNA-141(miR-141)/沉默信息调节因子1(Sirt1)通路深入阐释黄芩苷对糖尿病肾病的治疗机制。方法:高糖(25 mmol/L葡萄糖)培养小鼠肾小球系膜细胞系SV40-MES-13模拟构建糖尿病肾病细胞模型,并分为正常对照组、高糖组、黄芩苷组和高糖+黄芩苷组。q PCR检测miR-141的表达水平,Western blot检测Sirt1的表达水平。双萤光素酶实验检测Sirt1与miR-141的调控关系。流式细胞术检测细胞凋亡。结果:与正常对照组相比,高糖条件下培养的系膜细胞内miR-141表达水平明显上调,Sirt1蛋白表达水平明显下调,细胞凋亡水平显著增加(P0.01);与高糖组比,高糖+黄芩苷组的细胞凋亡和miR-141表达水平明显降低,Sirt1蛋白表达水平明显升高(P0.01)。敲减Sirt1表达可以逆转下调miR-141对系膜细胞细胞凋亡和细胞内Sirt1蛋白水平的作用。过表达miR-141可以逆转黄芩苷抑制高糖对Sirt1蛋白水平和细胞凋亡的作用;过表达miR-141对系膜细胞的作用可以进一步被Sirt1的过表达所逆转。结论:黄芩苷可以通过抑制miR-141过表达,促进Sirt1表达水平上升,最终缓解高糖诱导的小鼠肾小球系膜细胞凋亡,达到治疗糖尿病肾病的作用。     

PKC信号通路与醛糖还原酶对转化生长因子β1诱导人肾系膜细胞纤连蛋白表达的影响

目的 探讨PKC信号通路与醛糖还原酶在非高糖条件下对转化生长因子(TGF)-β1诱导人肾系膜细胞(HMC)细胞外基质成分纤连蛋白表达的影响.方法 应用醛糖还原酶抑制剂、PKC信号通路抑制剂G(O)6983、转染pcDNA3-醛糖还原酶及siRNA分别作用于人系膜细胞后,再用TGF-β1刺激,观察刺激前后人系膜细胞表达纤连蛋白的情况.Western blot检测系膜细胞内纤连蛋白和醛糖还原酶的变化,即时RT-PCR鉴定转染和干扰效果.结果 系膜细胞在TGF-β1作用后,醛糖还原酶和纤连蛋白表达升高;单独使用醛糖还原酶抑制剂并不能下调纤连蛋白的表达;但预先使用醛糖还原酶抑制剂孵育后,再用TGF-β1刺激,纤连蛋白表达减少为对照组的34%(P<0.05).单独使用PKC信号通路抑制剂并不能下调纤连蛋白的表达;用PKC信号通路抑制剂后,再用TGF-β1刺激,纤连蛋白表达下降为对照组的42%(P<0.05).预先使用醛糖还原酶抑制剂、PKC抑制剂孵育细胞后,再用TGF-β1刺激,纤连蛋白表达下降;转染pcDNA3-醛糖还原酶后,系膜细胞中醛糖还原酶mRNA表达增多超过10倍,纤连蛋白表达增加了2.5倍(P<0.05),再用TGF-β1刺激,纤连蛋白表达增加了3.6倍(P<0.05);转染siRNA后,系膜细胞中醛糖还原酶mRNA表达减少为对照组的20%,纤连蛋白表达减少为对照组的6%(P<0.01),即使再用TGF-β1刺激,纤连蛋白表达仍然下降,为对照组的12%(P<0.01).结论 醛糖还原酶基因参与了系膜细胞中TGF-β1诱导纤连蛋白表达过程的调控,这一过程可能与PKC信号通路的活化有关.     

醛糖还原酶的研究进展

醛糖还原酶(AR)是糖代谢多元醇通路中的限速酶,除了将葡萄糖催化还原为山梨醇外,还可以催化还原大量脂质过氧化反应产生的醛及其衍生物。最近的研究显示,AR除在糖尿病并发症中发挥作用外,还在很多炎性疾病中发挥着重要作用,如动脉粥样硬化、脓毒症、哮喘、眼葡萄膜炎等。在发生炎症时,AR的存在可以促进促炎性因子如iNOS、CD86等的表达,进一步集中炎症反应。同时,也调节着组织损伤后,免疫系统的作用发挥。此外,AR在人类的肿瘤中如肺癌、结肠癌、肺癌、宫颈癌、卵巢癌中过度表达,提示在上述癌症的病理过程中,AR可能发挥作用。AR抑制剂(ARI)对糖尿病并发症的临床治疗,已经进入了3期实验,显示AR作为某些炎性疾病的治疗靶点,具有良好的应用前景。因此,本文对近年来AR的功能研究进展进行综述,并对其作为疾病治疗靶点的前景进行了展望。     

肾小球系膜细胞增殖在糖尿病肾病肾小球硬化中作用的研究进展

糖尿病肾病(DN)是糖尿病患者常见的微血管慢性并发症。系膜细胞(MC)是肾小球内主要的细胞成分。高糖刺激可通过降低细胞内源性硫化氢的浓度、激活转化生长因子β(TGF-β)超家族和影响长链非编码RNA(LncRNA)水平促进系膜细胞增殖。系膜细胞的异常激活在糖尿病肾小球硬化的进程中起重要推动作用。     

糖尿病大鼠肾小球产生转化生长因子β的研究

本文检测糖尿病大鼠肾小球产生的转化生长因子β的水平，并探讨体外高糖环境对系统膜细胞产生ＴＧＦβ的影响，建立ＳＴＺ诱发的糖尿病大鼠模型，４周后肾小球分泌的总量及活性ＴＧＦβ均比对照组明显增加，其中活性ＴＧＦβ增加为明显，体外高糖培养后的系膜细下降，而活性ＴＧＦβ却有上升。结果表明高糖环境下肾上球和系膜细胞确实存在着ＴＧＦβ分泌和激活的异常ＴＧＦβ分泌和激活的异常，ＴＧＦβ可能与了糖尿病肾病系膜区扩张     

茶多酚对高糖所致人肾小球系膜细胞活性氧和TGF-β1表达的影响

目的 探讨高糖对人肾小球系膜细胞活性氧(ROS)和转化生长因子β1，(TGF-β1)表达的影响及茶多酚的干预作用。方法 培养人肾小球系膜细胞，分为正常对照组、高糖组、茶多酚组和茶多酚干预组，培养0、12、36h后，用分光光度比色法测定细胞上清液超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量，用半定量RT-PCR和免疫细胞化学法检测细胞内TGF-β1，mRNA和蛋白表达的变化。结果 高糖导致系膜细胞SOD活性下降和MDA含量升高，上调TGF-β1，mRNA和蛋白表达，随时间延长更为明显；茶多酚干预可拮抗高糖时系膜细胞的上述改变。结论 高糖能促进人肾小球系膜细胞ROS产生增加，上调TGF-β1 mRNA和蛋白表达，茶多酚能抑制高糖对系膜细胞的作用。     

糖尿病肾病患者血浆一氧化氮、ET-1检测及其临床意义

糖尿病肾病(DN)是糖尿病(DM)的严重并发症，也是患者的主要死亡原因，以早期肾小球高灌注、肾小球肥大、系膜区扩张、基底膜增厚，晚期肾小球毛细血管腔闭塞、硬化为特征。近年来美、日和欧洲等发达国家和地区DN的发病率逐年增高，它已成为终末期肾脏疾病(ESRD)的首位病因(约占35%)[1]。然而DN的发病机制尚未完全明了，认为它主要与高血糖、蛋白非酶糖化、多元醇通道活性增高、肾小球滤过屏障功能障碍、血管活性物质参与等有关。其中一氧化氮(NO)和内皮素-1(ET-1)的作用，近年来受到广泛关注。为了解DN进展的可能机制，本文对DN患者不同阶段NO和ET-1的含量进行了检测，现报道如下。     

山梨醇增加糖尿病患者腰椎管狭窄症炎性反应因子的表达

目的探讨糖尿病腰椎管狭窄患者黄韧带增生肥厚的发生机制。方法 24例糖尿病和20例非糖尿病的腰椎管狭窄患者列为研究对象,观测黄韧带标本结构,D-Sorbitol/Xylitol试剂盒检测山梨醇水平。体外实验中使用小鼠成纤维细胞(NIH3T3)细胞系,用Western blot及q PCR分别检测高糖培养条件及醛糖还原酶抑制剂(ARI):依帕司他(EP)作用对细胞炎性反应因子及TGF-β表达水平的影响。结果糖尿病组较非糖尿病组的山梨醇水平更高、黄韧带平均厚度更大、标本弹力纤维降解、胶原纤维增生更为显著、免疫组化CD68阳性染色率更高(P0.01);体外实验中,NIH3T3细胞系在高糖培养与正常糖浓度培养相比山梨醇、促炎性细胞因子和TGF-β表达水平更高,而山梨醇、促炎性细胞因子和TGF-β增高的表达水平可被醛糖还原酶抑制剂所抑制并且呈剂量依赖(P0.05)。结论糖尿病腰椎管狭窄患者黄韧带中山梨醇水平显著增高,进而促进炎性反应因子及纤维化相关因子TGF-β表达增加,使得黄韧带炎性增生。     

Statin attenuates high glucose-induced and angiotensin II-induced MAP kinase activity through inhibition of NAD(P)H oxidase activity in cultured mesangial cells

An increased oxidative stress may contribute to the development of diabetic nephropathy. We have recently reported that high glucose level stimulated superoxide production through protein kinase C (PKC)-dependent activation of NAD(P)H oxidase in cultured vascular cells. Here we show that 3-hydroxy-3-methylglutaryl CoA reductase inhibitor (statin) attenuates both high glucose level-induced and angiotensin II (Ang II)-induced activation of p42/44 mitogen-activated kinase (MAP kinase) in cultured human mesangial cells through inhibition of NAD(P)H oxidase activity. The intracellular oxidative stress in cultured mesangial cells was evaluated by electron spin resonance (ESR) measurement. MAP kinase activity was evaluated by western blot analysis using anti phospho-specific MAP kinase antibody and anti-ERK-1 antibody. Exposure of the cells to high glucose level (450 mg/dl) for 72 hrs significantly increased MAP kinase activity as compared to normal glucose level (100 mg/dl). This increase was completely blocked by the treatment of pitavastatin (5x10(-7) M) as well as a NAD(P)H oxidase inhibitor (diphenylene iodonium, 10(-5) M) in parallel with the attenuation of oxidative stress. Ang II-induced activation of MAP kinase was also completely blocked by pitavastatin as well as a diphenylene iodonium in parallel with the attenuation of oxidative stress. In conclusion, pitavastatin attenuated high glucose-induced and Ang II- induced MAP kinase activity in mesangial cells through inhibition of NAD(P)H oxidase. Thus, statins may have a potential as a therapeutic tool for early diabetic nephropathy.     

The role of sorbitol pathway and treatment effect of aldose reductase inhibitor ONO2235 in the up-regulation of cardiac M2-muscarinic receptors in streptozotocin-induced diabetic rats

This study investigated the role of the sorbitol pathway on the genetic up-regulation of the cardiac M(2) muscarinic receptor (M(2)-mAChR) in streptozotocin (STZ)-induced diabetic rats. Three-month-old male Wistar rats were divided into five groups: (1) normal controls; (2) rats rendered diabetic by streptozotocin; (3) rats fed with glucose; (4) rats injected with sorbitol; and (5) diabetic rats treated with ONO-2235, an aldose reductase inhibitor. The M(2) muscarinic receptor (M(2)-mAChR) protein and mRNA densities of the heart tissue were measured by Western immunoblotting and Northern blotting, respectively. The densities of M(2)-mAChR protein and mRNA in the heart were significantly increased in diabetic rats, and rats given either glucose or sorbitol. When diabetic rats were treated with ONO-2235, the increases in heart M(2)-mAChR protein and mRNA were significantly reduced. The findings suggest that hyperglycemia and the sorbitol pathway are involved in the pathogenesis of diabetic heart disease in STZ-induced diabetic rats. Aldose reductase inhibitors may be useful in the treatment and prevention of cardiac complication in diabetes.     

白藜芦醇对糖尿病肾病大鼠醛糖还原酶的影响

目的:观察白藜芦醇对糖尿病肾病大鼠醛糖还原酶的影响。方法:将48只雄性SD大鼠随机分为空白对照组、模型组、白藜芦醇低、中、高剂量组和依帕司他组(n=8)。除正常对照组外,其余各组大鼠腹腔注射STZ(55 mg.kg-1),成功造模后白藜芦醇组分别给予5、154、5 mg.kg-1白藜芦醇,依帕司他组给予10 mg.kg-1依帕司他,连续灌胃6 w后,检测大鼠血糖、体重,HE染色检测肾脏病理改变,ELISA法检测醛糖还原酶(AR)活性。结果:与正常对照组相比,糖尿病组血糖与AR活性明显升高(P<0.05),与模型组比较,白藜芦醇各组血糖与AR活性明显降低(P<0.05)。结论:白藜芦醇可降低糖尿病大鼠血糖,其降糖效应可能与抑制AR活性有关。     

Glucose inhibition of human fibroblast proliferation and response to growth factors is prevented by inhibitors of aldose reductase

Diabetes mellitus is associated with premature senescence of cultured dermal fibroblasts. The present study investigated the effect of elevated glucose concentrations on cultured human fibroblasts from normal donors. Mean population doubling times, population doublings until senescence, saturation density at confluence (cells/cm2), tritiated thymidine incorporation, and response to platelet-derived growth factor (PDGF) were inhibited with the increasing glucose concentrations (11.0, 22, 44, or 55 mM glucose) (P less than 0.05). Replicative life span was markedly diminished by multiple passages in high glucose medium (5.5 mM glucose: 62.4 +/- 7.9 population doublings; 22 mM glucose: 22.8 +/- 3.4 population doublings: P less than 0.05). Aldose reductase activity was present in the cultured fibroblasts (3.9 +/- 0.5 nmol/min per mg protein), and inhibitors of aldose reductase, including sorbinil (10(-4) M--10(-6) M) and tolrestat (10(-6) M--10(-8) M), completely prevented glucose-mediated inhibition of fibroblast proliferation, restored the response to PDGF, and allowed a normal replicative life span. Myo-inositol (11 microM--5.5 mM) also reversed the adverse effects of glucose. These in vitro data demonstrate that elevated concentrations of glucose inhibit cell growth and promote premature senescence, effects which can be prevented with inhibitors of aldose reductase or supplemental myo-inositol. These aldose reductase-related effects may explain the impaired growth and premature senescence of cultured connective tissue from diabetic patients.     

The Saccharomyces cerevisiae aldose reductase is implied in the metabolism of methylglyoxal in response to stress conditions

The enzyme aldose reductase plays an important role in the osmo-protection mechanism of diverse organisms. Here, we show that yeast aldose reductase is encoded by the GRE3 gene. Expression of GRE3 is carbon-source independent and up-regulated by different stress conditions, such as NaCl, H2O2, 39 degrees C and carbon starvation. Measurements of enzyme activity and intracellular sorbitol in wild-type cells also indicate that yeast aldose reductase is stress-regulated. Overexpression of GRE3 increases methylglyoxal tolerance in Saccharomyces cerevisiae. Furthermore, high expression of GRE3 complements the deficiency of the glyoxalase system of a glo1delta mutant strain. Consistent with this, in vitro and in vivo assays of yeast aldose reductase activity indicate that methylglyoxal is an endogenous substrate of aldose reductase. Furthermore, addition of NaCl or H2O2 to exponential-phase cells triggers an initial transient increase in the intracellular level of methylglyoxal, which is dependent on the Gre3p and Glo1p function. These observations indicate that the metabolism of methylglyoxal is stimulated under stress conditions; and they support a methylglyoxal degradative pathway, in which this compound is metabolised by the action of aldose reductase.     

Sorbitol metabolism in inner medullary collecting duct cells of diabetic rats

Intracellular accumulation of sorbitol, generated fromd-glucose via the aldose reductase pathway, is thought to play an important role in diabetic complications such as lens cataracts and neuropathy. In order to elucidate the effect of diabetes on the renal inner medulla, another sorbitol-rich tissue, male Wistar rats were treated with a single dose of streptozotocin (60 mg/kg body weight, i.p.). Six wecks later total inner medullary tissue (IM) or isolated inner medullary collecting duct (IMCD) cells were prepared. In diabetic IM tissue, sorbitol content was 1.8-fold higher than in control IM tissue (134±17 vs. 74±22 mol/g tissue protein). Sorbitol production in both normal and diabetic IMCD cells was strongly dependent on extracellulard-glucose concentration. In normal cells, for example, sorbitol production was 90±9 mol sorbitol/g protein x h at 45 mMd-glucose compared to 13±1 mol/g protein x h at 5 mM. At identicald-glucose concentrations sorbitol synthesis in diabetic IMCD cells was, however, always significantly higher than in control cells (122% of control at 15 mM and 126% of control at 45 mM). In addition, aldose reductase activity in diabetic IM was found to be augmented. The maximal velocity was 4.2 times higher (97±22 U/g protein vs. 23±7 U/g protein) while theK _m of the enzyme remained unchanged. Membrane permeability for sorbitol or the response to changes in extracellular osmolarity was not significantly different in diabetic IMCD cells and normal cells with correspondingly high intracellular sorbitol concentrations. Similarly the kinetic parameters ofd-glucose uptake were not altered by streptozotocin treatment. These results suggest that increased medullary sorbitol content in diabetic rats is a result of increased sorbitol synthesis due to a higher extracellulard-glucose concentration and augmented aldose reductase activity in face of an unaltered sorbitol permeability of the plasma membrane.     

Regeneration and repair of myelinated fibers in sural-nerve biopsy specimens from patients with diabetic neuropathy treated with sorbinil

There is reason to believe that diabetic neuropathy may be related to the accumulation of sorbitol in nerve tissue through an aldose reductase pathway from glucose. Short-term treatment with aldose reductase inhibitors improves nerve conduction in subjects with diabetes, but the effects of long-term treatment on the neuropathologic changes of diabetic neuropathy are unknown. To determine whether more prolonged aldose reductase inhibition reverses the underlying lesions that accompany symptomatic diabetic peripheral polyneuropathy, we performed a randomized, placebo-controlled, double-blind trial of the investigational aldose reductase inhibitor sorbinil (250 mg per day). Sural-nerve biopsy specimens obtained at base line and after one year from 16 diabetic patients with neuropathy were analyzed morphometrically in detail and compared with selected electrophysiologic and clinical indexes. In contrast to patients who received placebo, the 10 sorbinil-treated patients had a decrease of 41.8 +/- 8.0 percent in nerve sorbitol content (P less than 0.01) and a 3.8-fold increase in the percentage of regenerating myelinated nerve fibers (P less than 0.001), reflected by a 33 percent increase in the number of myelinated fibers per unit of cross-sectional area of nerve (P = 0.04). They also had quantitative improvement in terms of the degree of paranodal demyelination, segmental demyelination, and myelin wrinkling. The increase in the number of fibers was accompanied by electrophysiologic and clinical evidence of improved nerve function. We conclude that sorbinil, as a metabolic intervention targeted against a specific biochemical consequence of hyperglycemia, can improve the neuropathologic lesions of diabetic neuropathy.     

Polyol Pathway Mediates Enhanced Degradation of Extracellular Matrix Via p38 MAPK Activation in Intervertebral Disc of Diabetic Rats

The aim of this study was to determine the significance of diabetes on degradation of intervertebral disc (IVD) extracellular matrix. Diabetic rats showed a significant increase in glucose and sorbitol contents in the IVD. The levels of aldose reductase, p38 and metalloproteinases, and degradation of metalloproteinase-derived aggrecan and type II collagen were increased, while tissue inhibitors of metalloproteinases levels were decreased in the IVD of diabetic rats. These changes were markedly affected by inhibition of aldose reductase or p38. Diabetes might contribute to enhanced matrix degradation in the IVD and the polyol pathway might mediate this process via p38 activation.     

Polymorphisms of sorbitol dehydrogenase (SDH) gene and susceptibility to diabetic retinopathy

The polyol pathway consists of two enzymes aldose reductase (AR) and sorbitol dehydrogenase (SDH); the former is the first enzyme in the polyol pathway, that catalyzes the reduction of glucose to sorbitol, the latter is the second one, that converts sorbitol to fructose using by NAD(+) as a cofactor. We along with others have recently found that SDH activity, the second step in the polyol pathway, might make a greater contribution to the etiology of diabetic retinopathy than does the first step involving AR. In this paper, we propose a novel hypothesis that polymorphisms of SDH gene may be correlated with SDH gene expression levels in diabetic retinas, thus being a valuable genetic marker for diabetic retinopathy.