橙皮苷对STZ糖尿病大鼠肾脏功能和形态的影响

观察橙皮苷对链脲佐菌素导致的糖尿病大鼠肾脏功能和形态的影响,并与氨基胍进行比较。结果表明:（1）两治疗组大鼠尿蛋白排泄量显著低于对照组P<0.05）;（2）两治疗组肾组织AGEs和LPO含量显著低于对照组（P<0.01,P<0.05）:（3）治疗组肾小球系膜增生和基底膜增厚明显减轻。提示橙皮苷在抑制蛋白非酶糖基化、预防糖尿病肾脏并发症方面具有与氨基胍相似的作用。     

槲皮素对糖尿病大鼠主动脉胶原非酶糖化的抑制作用

观察了槲皮素（Qu）对不同病程糖尿病（DM）大鼠主动脉胶原非酶糖化的抑制作用，并与氨基胍（AG）作对比。结果：Qu（100mg·kg-1／d）灌胃治疗9周，能明显抑制主动脉胶原及胶原交联的AGEs含量，与等剂量AG作用相近，但起效要晚。Qu有一定的降压作用，但对血糖及血清果糖胺无影响。提示Qu能通过抑制胶原非酶糖化来防治DM血管病变。     

糖尿病肾脏胶原非酶糖化与氨基胍阿斯匹林的治疗作用

本实验系统观察了ＳＴＺ所致糖尿病鼠在１、３、６个月后肾脏组织胶原发生非酶糖化的情况，及氨基胍、阿斯匹林对肾脏胶原非酶糖化的阻断作用。结果表明：各病程糖尿病动物肾组织的胶原含量和非酶糖化早期产物（５－ＨＭＦ）及胶原相联荧光值均明显高于正常对照。氨基胍能够减弱糖尿病动物肾组织胶原含量的增加和荧光产物的生成，但对５－ＨＭＦ含量无影响。阿斯匹林未显示出对胶原非酶糖化的影响。     

维生素E对不同病程糖尿病鼠主动脉胶原非酶糖化的影响

为探讨维生素Ｅ对非酶糖化的影响，本研究观察了糖尿病大鼠喂饲维生素Ｅ后主动脉胶原Ａｍａｄｏｒｉ产物、高级糖基化终末产物（ＡＧＥｓ）、ＡＧＥｓ—交联量及胶原含量的改变，发现喂饲维生素Ｅ的病鼠与相应年龄未喂饲维生素Ｅ的病鼠相比，其主动脉胶原Ａｍａｄｏｒｉ产物、ＡＧＥｓ、ＡＧＥｓ—交联量、胶原含量均明显下降，且治疗时间越长、疗效越明显，但均未能达到正常水平。说明维生素Ｅ能够抑制糖尿病患鼠主动脉胶原发生非酶糖化和棕色变，能增强胶原的可溶性，减少胶原在血管壁基底膜的沉积，从而可能有利于延缓糖尿病慢性血管病变的发生和发展     

葡萄籽多酚抗糖尿病大鼠非酶糖基化实验研究

目的观察葡萄籽多酚(GSPE)对糖尿病大鼠体内非酶糖基化反应的影响,评价其对糖尿病慢性并发症(DCC)的干预效果,并探讨其作用机制。方法Wistar大鼠腹腔注射链脲佐菌素(STZ)60mg/kg造成糖尿病模型,随机分为空白对照组、氨基胍(150mg·kg-1·d-1)治疗组、GSPE低、中、高3个剂量(50、150、450mg·kg-1·d-1)治疗组,每组12只,另12只设为正常对照组。常规喂养12周后取大鼠血清及脏器,比较各组肾重/体重比值,用荧光法比较各组肾皮质非酶糖基化终产物(AGEs),全自动生化仪检测血糖、总胆固醇(TC)和甘油三酯(TG)。结果与空白对照组比较,GSPE可以显著降低糖尿病大鼠肾重/体重比值(P<001),减少肾皮质AGEs(P<001),GSPE中、高剂量组与氨基胍治疗组作用相似;GSPE对血糖、TG无显著影响,仅GSPE中剂量组TC与正常对照组比较差异有显著性(P<001)。结论GSPE能够抑制体内非酶糖基化反应,是其防治DCC的主要作用机制之一。     

氨基胍对糖尿病大鼠心肌保护作用的超微结构研究

目的观察氨基胍对糖尿病大鼠心肌的保护作用。方法糖尿病SD大鼠模型22只，随机分为氨基胍治疗（AG）组10只和糖尿病组12只。给予AG组大鼠氨基胍50mg／kgVI服，日一次。同龄雄性SD大鼠作为正常对照（NC）组。全部大鼠给予普通饮食。10周后测血糖，麻醉后处死大鼠，留取心肌标本，超薄切片，透射电镜盲法观察。结果与糖尿病组大鼠相比，AG组大鼠的心肌肌原纤维排列整齐，肌膜完整，边缘整齐，纤维间脂滴增多；线粒体大体形态完整，排列整齐，嵴密集，断裂减少；血管基底膜增厚不明显，管腔无明显狭窄；间质中的胶原纤维减少，未定形物质无明显减少。结构与正常组大鼠差异无统计学意义。结论应用氨基胍可抑制或延缓糖尿病大鼠的心肌超微结构病变，提示晚期糖基化终末产物在糖尿病心肌病变的发生中发挥一定的作用。     

蛋白质的糖基化及其在肾脏病变中的作用

晚期糖基化终产物(AGE)是蛋白质的氨基与糖的醛基发生非酶性糖基化反应的终产物，在慢性肾功能衰竭和糖尿病肾病并发症的发生和发展中起重要作用。本文就AGE和AGE受体在肾脏病变中的作用作一综述。     

糖基化终末期产物的基础与临床

糖基化终末期产物的基础与临床胡伟新，唐政关键词糖基化产物；糖尿病并发症大量证据表明，持续的高血糖状态是各种糖尿病并发症发生的始动因素。在高血糖条件下，葡萄糖与蛋白质等大分子物质的氨基发生非酶糖基化反应，自发形成具有高度反应性的中期和晚期糖基化产物（统...     

卡托普利对糖尿病大鼠主动脉胶原非酶糖化的抑制作用

在链脲佐菌素所致糖尿病大鼠模型中，观察了卡托普利对糖尿病大鼠主动脉胶原非酶糖化的影响。     

糖尿病大鼠糖基化终产物与主动脉细胞外基质成分的关系

为探讨糖基化终产物在糖尿病大鼠动脉粥样硬化发生中对主动脉细胞外基质成分生成增加所起的作用,本实验将糖尿病大鼠、糖尿病＋ 氨基胍治疗大鼠和正常大鼠分别喂养１、２、３ 和４ 个月后,测定其血红蛋白－ 糖基化终产物及主动脉壁Ⅲ型前胶原、Ⅳ型胶原、Ⅳ型胶原－ 糖基化终产物及层粘蛋白含量。结果发现,糖尿病组大鼠各时相点血红蛋白－ 糖基化终产物（１ ～４ 个月分别为６．８８±１ ．２３、１０ ．２６±０．６３、１５．３±１．４９ 和１８．５７ ±２．９０ ｋｕｇ, 与血糖水平相关）、Ⅲ型前胶原（１ ～４个月分别为１５．２０±３．０３ 、２１．４４ ±１．７９、２７．１９±３ ．２８ 和３３．９９±４ ．９６ μｇＬ, 与血红蛋白－ 糖基化终产物和Ⅳ型胶原－ 糖基化终产物相关） 、Ⅳ型胶原（１～４ 个月分别为２３．６７±１．４９、３０．３７ ±２ ．８６、３６．６５ ±１．９８ 和４５．４６±５．７７ μｇＬ, 与血红蛋白－ 糖基化终产物和Ⅳ型胶原－ 糖基化终产物相关）、Ⅳ型胶原－ 糖基化终产物（１～４ 个月分别为０．７９ ±０．１５、１．２５ ±０．２２ 、１．５４ ±０．０６ 和１．８０±０ ．１４ Ｍｕｇ, 与血红蛋白－ 糖基化终产物和Ⅳ型胶原相关）      

糖尿病大鼠主动脉糖化终产物的免疫组化研究

目的　研究糖尿病时主动脉壁非酶糖化的程度以及非酶糖化机制在糖尿病血管重建和慢性并发症发生发展中的作用。方法　应用抗糖化终产物（ＡＧＥｓ） 多克隆抗体,对糖尿病大鼠和氨基胍治疗后的糖尿病大鼠进行主动脉壁ＡＧＥｓ 的免疫组化研究,计算机图像处理系统定量分析。结果糖尿病时主动脉壁中膜ＡＧＥｓ 的相对面积呈进行性增加,４ 周时其相对面积就显著大于对照组（ Ｐ＜０．０１）,氨基胍治疗４ 周后主动脉壁中膜ＡＧＥｓ 的相对面积较糖尿病组显著降低（ Ｐ＜ ０．０５）,治疗２４周后降低更为明显（Ｐ＜ ０．０１）。结论　主动脉壁ＡＧＥｓ 的免疫组化定量研究能更直观地反映血管组织非酶糖化的程度,非酶糖化是引起血管重建的重要机制之一。     

Prevention of glomerular basement membrane thickening by aminoguanidine in experimental diabetes mellitus

The etiology of diabetic glomerulopathy appears to be related, at least in part, to the degree of hyperglycemia, the resultant nonenzymatic glycosylation of proteins, and the eventual formation of advanced glycosylation end products in long-lived structural proteins. To investigate the relationship between the glomerular basement membrane (GBM) changes of diabetic nephropathy and the formation of advanced glycosylation end products, we studied control rats, diabetic rats, and control and diabetic rats who received aminoguanidine, a compound that pharmacologically inhibits formation of advanced glycosylation end products. After 9 months, rat weight was smaller and kidney weight larger in both diabetic groups compared with both control groups. GBM width was increased in the diabetic group compared with the control group. Aminoguanidine administration to diabetic rats ameliorated this increase in GBM. Thus, aminoguanidine administration from the onset of experimental diabetes prevented the widening of the GBM that is typical of diabetes.     

Aminoguanidine treatment reduces the increase in collagen stability of rats with experimental diabetes mellitus

Summary Alterations in the biophysical properties of connective tissues in diabetes mellitus have been attributed to the nonenzymatic glycation of the collagens and the subsequent formation of browning products, cross-linking the proteins. Aminoguanidine may bind to carbonyl groups of these nonenzymatic glycation products and thereby block the process. Rats with streptozotocin-induced diabetes were treated with aminoguanidine, 25mg·kg^–1·day^–1, for 120 days. The aminoguanidine treatment did not counteract the increase in blood glucose concentrations, nor did it prevent the arrest in weight gain of diabetic rats. The increased stability in 7 mol/l urea and increased tensile strength of tail tendons from the diabetic rats, however, were prevented by the aminoguanidine treatment. Aminoguanidine did not reduce the formation of early nonenzymatic glycation products (aldimine and Amadori rearrangement products), whereas the amount of browning products (fluorescent compounds) was reduced in the tail tendon collagen of the diabetic rats. Aminoguanidine treatment of intact rats did not influence these parameters. These findings indicate that the biophysical alterations of collagens induced by experimental diabetes are caused by cross-links derived from the nonenzymatic glycation, and furthermore, that aminoguanidine treatment may prevent the concomitant changes in biophysical properties of connective tissues.     

Increased endocytosis in retinal vascular endothelial cells grown in high glucose medium is modulated by inhibitors of nonenzymatic glycosylation

Summary We sought to determine if hyperglycaemia is responsible for increased retinal vascular endothelial-cell (RVEC) endocytosis in diabetes and to assess the role of nonenzymatic glycosylation in mediation of this novel endothelial-cell pathology. RVECs were propagated in media containing either 5 or 25 mmol/l glucose for up to 10 days after which they were exposed to the protein tracer horseradish peroxidase for 30 min. The level of RVEC endocytosis was quantified in intact cell monolayers by electron microscopic stereology, and in cell lysates by a simple spectrophotometric method. The effect of the nonenzymatic glycosylation inhibitors, aminoguanidine and d-lysine, on high-glucose medium induced changes in RVEC endocytosis was tested by inclusion of these agents in the culture medium. RVECs exposed to 25 mmol/l glucose showed a stepwise increase in endocytosis of horseradish peroxidase culminating in a two- to threefold increase after 10 days. Endocytosis returned to normal levels after a further 10 days in 5 mmol/l glucose medium. The increase in RVEC endocytosis was markedly reduced, but not completely normalised, by aminoguanidine and d-lysine. Exposure of cultured RVECs to 25 mmol/l glucose causes an increase in endocytosis of similar magnitude to that experienced by RVEC in early diabetes, and implicates hyperglycaemia in the latter situation. A significant component of the increase in RVEC endocytosis appears to be mediated by nonenzymatic glycosylation.Abbreviations HRP Horseradish peroxidase - RVEC retinal vascular endothelial cells - DMEM Dulbecco's modified Eagle's medium - AGE advanced glycosylation end products     

Prevention of endothelial dysfunction in streptozotocin-induced diabetic rats by gliclazide treatment

The aim of the present work was to analyze whether the oral hypoglycemic drug gliclazide affects diabetic endothelial dysfunction in streptozotocin-induced diabetic rats. Gliclazide was compared with glibenclamide, ascorbic acid, and aminoguanidine. An insulin-dependent model of diabetes was selected to exclude insulin-releasing effects of the drugs. Both in isolated aortic segments and mesenteric microvessels, endothelium-dependent relaxation evoked by acetylcholine (ACh, 1 nM to 10 microM) was significantly reduced in vessels from diabetic animals. This impairment was reversed when the segments were previously incubated with 100 U/ml superoxide dismutase. When streptozotocin-induced diabetic rats were orally treated from the time of diabetes induction with gliclazide (10 mg/kg) or ascorbic acid (250 mg/kg), ACh-induced endothelium-dependent relaxation was well preserved both in aortic segments and mesenteric microvessels. In addition, the impaired vasodilatation to exogenous nitric oxide (NO) in aortic segments was also improved in gliclazide-treated diabetic rats. On the other hand, oral treatment with glibenclamide (1 and 10 mg/kg) or aminoguanidine (250 mg/kg) did not produce significant improvements in diabetic endothelial dysfunction. We conclude that gliclazide reverses the endothelial dysfunction associated with diabetes. This effect appears to be due not to the metabolic actions of the drug but rather to its antioxidant properties, as it can be mimicked by other antioxidants. We propose that the mechanism involved is the inactivation of reactive oxygen species, which are increased in diabetes probably as a result of increased early protein glycosylation products, such as glycosylated hemoglobin (HbA(1c)). These effects of gliclazide are not shared by other oral hypoglycemic agent such as glibenclamide, or by blockade of advanced glycosylation end product (AGE) generation with aminoguanidine.     

Pioglitazone, a PPARgamma agonist, restores endothelial function in aorta of streptozotocin-induced diabetic rats

OBJECTIVE: To study the effect of pioglitazone (a PPAR gamma agonist) treatment on blood pressure, endothelial function, and oxidative stress in streptozotocin (STZ)-induced diabetic rats. METHODS: Sprague-Dawley rats were randomized into control (n=32) and STZ-diabetic (n=32) groups. Rats were further randomized to receive pioglitazone (10 mg/kg) or placebo for 4 weeks, and the following protocols were carried out. Blood pressure, blood glucose level, and body weight were measured. Thoracic aorta was isolated and the dose-response curve of phenylephrine (PE) in the presence or absence of Nomega-nitro-L-arginine-methyl ester (L-NAME) was recorded. The dose-response curve of acetylcholine (Ach) in the presence or absence of indomethacin, L-NAME, and methylene blue was recorded. Tone-related basal nitric oxide release experiments were carried out. Lipid peroxidation, superoxide dismutase, catalase, and reduced glutathione were estimated in liver, kidney, and aorta. Aortic nitrite levels were also measured. Further, in vitro effects of PE and Ach in the presence of pioglitazone (0.1 M-10 mM) were measured in aortic rings of nondiabetic and STZ-diabetic rats. Pioglitazone-induced relaxations were recorded in PE-contracted rings (with intact and denuded endothelium) in the presence of L-NAME and in KCl-contracted rings. RESULTS: Pioglitazone treatment reduced blood pressure without having any significant effect on blood glucose level and body weight of STZ-diabetic rats. Enhanced PE-induced contraction and impaired Ach-induced relaxations in STZ-diabetic rats were restored to normal by pioglitazone treatment. The presence of L-NAME but not indomethacin blocked Ach-induced relaxation in pioglitazone-treated STZ-diabetic rats. Basal nitric oxide release was significantly higher in pioglitazone-treated STZ-diabetic rats. Oxidative stress was significantly higher in STZ-diabetic rats and pioglitazone treatment significantly reduced it. High aortic nitrite levels of STZ-diabetic rats were significantly reduced by pioglitazone treatment. The presence of pioglitazone at higher concentrations (>10 muM), but not at lower concentrations, significantly changed the dose-response curve of PE or Ach. Pioglitazone relaxations at lower concentrations but not at higher concentrations were blocked by endothelium removal or by the presence of L-NAME. CONCLUSION: Pioglitazone administration reduced oxidative stress, which prevented the breakdown of nitric oxide and increased nitric oxide levels, thereby restoring the endothelial function in aorta of STZ-diabetic rat. Hence, from the present study it can be concluded that pioglitazone administration in STZ-diabetic rats lowers blood pressure, protects against oxidative stress, and restores endothelial function.