橙皮苷与氨基胍对STZ－糖尿病大鼠主动脉胶原非酶糖化作用的比较

本文观察了天然黄酮类化合物──橙皮苷对ＳＴＺ－糖尿病大鼠主动脉胶原非酶糖基化作用的影响，并与氨基肌进行了比较。结果表明：用橙皮苷及氨基肌治疗１２０天后，糖尿病鼠动脉胶原ＡＧＥｓ含量明显降低（Ｐ＜０．０１），而血糖、体重无明显差别。提示橙皮苷对糖尿病大鼠蛋白非酶糖基化作用与氨基胍相似。     

Increased vascular permeability in pancreas of diabetic rats: detection with high resolution protein A-gold cytochemistry

Summary The role of the pancreatic microcirculation in the pathogenesis of Type 1 (insulin-dependent) diabetes mellitus remains poorly understood. Herein, a method is described for the ultrastructural investigation of the integrity of the pancreatic microvasculature. The method consists of histochemical detection and isolation of the islets followed by albumin and protein A-gold immunocytochemistry, whereby the distribution of endogenous albumin is used as a marker of endothelial integrity. This technique, applied to the study of spontaneously diabetic rats, reveals a selective increase in permeability of islet capillaries and post-capillary venules at the onset of diabetes, while acinar capillaries and arterioles remain intact. At 50 days of age, before the onset of diabetes, the microvasculature of diabetes-prone rats shows no alterations in permeability to albumin. When used in conjunction with morphometric analyses, this methodological approach may be useful for further studies in pathologic or experimental conditions involving the pancreatic microvasculature.     

Ocular vascular endothelial growth factor levels in diabetic rats are elevated before observable retinal proliferative changes

Summary Vascular endothelial growth factor (VEGF) is a potent angiogenic factor. VEGF levels in ocular tissue of 6-, 12-, 18- and 28-week-old Goto-Kakizaki (GK) rats, a well-known model of non-insulin-dependent diabetes, were evaluated by highly sensitive ELISA. VEGF concentrations in the GK rat as well as in non-diabetic Wistar rat significantly decreased from the age of 6 weeks to 18 weeks. However, although VEGF concentrations in the Wistar rat continued to fall significantly from 18 to 28 weeks of age, the levels were maintained between 18 and 28 weeks of age in GK rats. Levels were significantly different between the GK and Wistar rats at 28 weeks of age. Results of immunohistochemical studies of the eyes of Wistar and GK rats at 28 weeks of age suggest diffuse distribution of this cytokine in cells of neural origin. Weak to moderate VEGF immunoreactivity was exhibited mainly in the ganglion cell layer, inner plexiform layer and inner/outer nuclear layers in rats with and without diabetes. However, in the retinal optic nerve fiber layer, retinal pigment epithelium and choroid, strong VEGF immunoreactivity was noted only in the GK rat. In conclusion, increased VEGF production in certain ocular tissue, similar to that in humans, is observed quite early, at least before the appearance of observable retinal changes in the diabetic GK rat. This also suggests that the GK rat can be used as a model of initial or latent phase diabetic retinopathy. [Diabetologia (1997) 40: 726–730] Received: 14 January 1997 and in revised form 26 February 1997     

α-亚麻酸对糖尿病大鼠血管功能和氧化应激的影响

目的:观察α-亚麻酸（ALA）对糖尿病(DM)大鼠血管功能和氧化应激的影响,探讨ALA在DM血管并发症防治中的作用。方法: 将30只SD大鼠随机分为正常对照组、DM模型组和ALA治疗组［500 μg/(kg·d)］,每组10只。10只雄性SD大鼠以高脂饮食喂养4周后,腹腔注射链脲佐菌素（STZ）30 mg/kg建立Ⅱ型DM（T2DM）模型。4周后分离降主动脉,进行离体血管灌流观察血管的舒张功能,利用试剂盒测定灌流液中NO的含量以及血管组织中丙二醛（MDA）的含量、超氧化物岐化酶（SOD）和过氧化氢酶（CAT）的活性。结果: 与正常对照组相比,DM大鼠主动脉内皮依赖性舒张功能和NO的含量显著下降(P<0.01),ALA治疗可有效地减轻DM大鼠血管内皮功能障碍,增加NO的含量（均P<0.01）。另外,与正常对照组相比,DM大鼠血管组织中MDA的含量增加(P<0.01),抗氧化酶SOD和CAT的活性下降(P<0.01);ALA治疗可显著降低DM大鼠血管组织中MDA的含量(P<0.05),增加抗氧化酶SOD和CAT的活性(P<0.01)。结论: ALA可显著改善T2DM模型大鼠的血管内皮舒张功能障碍,其机制可能与减轻血管组织的氧化应激有关。     

Sucralfate attenuates gastric mucosal lesions and increased vascular permeability induced by ischaemia and reperfusion in rats

Recent evidence suggests that oxygen-derived free radicals are involved in mediating gastric microvascular and parenchymal cell injuries induced by ischaemia and reperfusion. Therefore, the effect of the locally acting anti-ulcer drug, sucralfate, was studied on ischaemia and reperfusion (e.g. induced gastric lesions, intraluminal bleeding, changes in vascular permeability and non-protein sulfhydryl levels in the rat stomach). Allopurinol was used as a known standard antioxidant drug. Rats were subjected to 30 min of gastric ischaemia in the presence of 100 mmol/L hydrochloric acid and reperfusion periods of 15, 30 or 60 min duration. The gastric lesions were assessed microscopically under an inverted microscope. The vascular permeability was quantified by measuring the extravasated Evans blue in the stomach. There were significantly greater numbers of gastric lesions, intraluminal bleeding and leakage of Evans blue during all reperfusion periods as compared with those of ischaemia, with maximum effects occurring at 60 min following reperfusion. Pretreatment with sucralfate (31.25–250 mg/kg, p.o.) or allopurinol (12.5–50 mg/kg, i.p.) 30 min before the procedure, dose-dependently reduced the gastric lesions, intraluminal bleeding, and decreased the vascular permeability induced by ischaemia and reperfusion. Furthermore, sucralfate dose-dependently reverses the ischaemia and reperfusion-induced depletion of mucosal non-protein sulfhydryl levels and inhibited the superoxide radical production in both cell-free xanthine-xanthine oxidase and in the stimulated polymorphonuclear cellular systems. These results suggest that the protection produced by sucralfate against gastric injury may be due to its antioxidant effects.     

Effects of interleukin‐6 treatment on neurovascular function,nerve perfusion and vascular endothelium in diabetic rats

Aim: Interleukin‐6 (IL‐6), a member of the neuropoietic cytokine family, participates in neural development and has neurotrophic activity. Recent research has also indicated actions to improve vasa nervorum function in diabetes. Both these facets are potentially relevant for treatment of diabetic neuropathy. The aim of this study was to determine whether IL‐6 treatment corrected changes in neurovascular function in streptozotocin‐induced diabetic rats. Methods: After 1 month of diabetes, rats were given IL‐6 for 1 month. The rats were subjected to sensory testing and measurements of nerve conduction velocities and nerve blood flow by hydrogen clearance microelectrode polarography. Further groups were used to study responses of the isolated gastric fundus and renal artery. Results were statistically analysed using ANOVA and post hoc tests. Results: Diabetic rats showed mechanical hyperalgesia, thermal hyperalgesia, and tactile allodynia. The former was unaffected by IL‐6 treatment, whereas the latter two measures were corrected. Immunohistochemical staining of dorsal root ganglia for IL‐6 did not reveal any changes with diabetes or treatment. The results showed that 22 and 17.4% slowing of sciatic motor and saphenous sensory nerve conduction velocities, respectively, with diabetes were improved by IL‐6. Sciatic endoneurial perfusion was halved by diabetes and corrected by IL‐6. A 40.6% diabetic deficit in maximal non‐adrenergic, non‐cholinergic relaxation of gastric fundus to nerve stimulation was unaffected by IL‐6. Renal artery endothelium‐dependent relaxation was halved by diabetes, the endothelium‐derived hyperpolarizing factor (EDHF) component being severely attenuated. IL‐6 did not affect nitric oxide‐mediated vasorelaxation, but markedly improved EDHF responses. Conclusions: IL‐6 improved aspects of small and large nerve fibre and vascular endothelium dysfunction in diabetic rats. The functional benefits related to increased nerve blood flow via an EDHF mechanism, and IL‐6 could have therapeutic potential in diabetic neuropathy and vasculopathy, which should be further evaluated.     

Nitric oxide and vascular endothelial growth factor concentrations are increased but not related in vitreous fluid of patients with proliferative diabetic retinopathy.

AIMS: Several reports have implicated nitric oxide (NO) in the angiogenic process. The assessment of NO stable end products, nitrite and nitrate (NOx), is commonly used as a measure of NO production in biological fluids. The aims of the study were to investigate NOx concentrations in the vitreous fluid of patients with proliferative diabetic retinopathy (PDR) and to evaluate the relationship between NOx and vascular endothelial growth factor (VEGF). PATIENTS AND METHODS: Serum and vitreous fluid samples were obtained simultaneously at the time of vitreoretinal surgery from 23 patients with PDR, and 17 control non-diabetic patients with non-proliferative ocular disease. NOx was determined by using the Griess reaction and VEGF levels were assessed by ELISA. RESULTS: The intravitreous concentration of NOx was significantly elevated in patients with PDR in comparison with the control group (31.6 +/- 2.96 micromol/l vs. 18 +/- 2.46 micromol/l; P = 0.01). However, we did not detect any differences between NOx serum concentrations. We observed a correlation between serum and vitreous levels of NOx in diabetic patients (r = 0.79; P < 0.001), but not in the control group. Intravitreous levels of VEGF in patients with PDR were higher than those obtained in serum (1.42 ng/ml (0.12-7.62) vs. 0.12 ng/ml (0.03-0.42); P < 0.01). Vitreal levels of VEGF were strikingly higher in patients with PDR than in the control subjects (1.42 ng/ml (0.12-7.62) vs. 0.009 ng/ml (0.009-0.04); P < 0.001). No correlation between vitreal concentrations of NOx and VEGF was observed, either in diabetic patients or in the control group. CONCLUSIONS: NOx and VEGF are increased but not related in the vitreous fluid of diabetic patients with PDR. Our results suggest that serum diffusion could play a significant role in explaining the increase of NOx. By contrast, intraocular production seems to be the main factor responsible for the intravitreous enhancement of VEGF.     

Suppression of transforming growth factor beta and vascular endothelial growth factor in diabetic nephropathy in rats by a novel advanced glycation end product inhibitor, OPB-9195

Aims/hypothesis. Advanced glycation end products (AGEs) participate in the pathogenesis of diabetic nephropathy. We reported earlier that OPB-9195, a synthetic thiazolidine derivative and novel inhibitor of advanced glycation, prevented progression of diabetic glomerulosclerosis by lowering serum concentrations of advanced glycation end products and reducing their deposition in the glomeruli. Here, we examined their contribution and that of growth factors, such as transforming growth factor-β (TGF-β) and vascular endothelial growth factor (VEGF), to the progression of diabetic nephropathy. We also investigated the expression of type IV collagen in the kidneys of Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats, a Type II (non-insulin-dependent) diabetes mellitus model, after treatment with OPB-9195. Methods. Using northern blots and immunohistochemical techniques, we determined the renal expression of TGF-β and type IV collagen mRNAs and proteins in OLETF rats. We also examined OPB-9195's effects on renal expression of VEGF mRNA and protein. Results. Concomitant increases in TGF-β and type IV collagen expression were observed at each point in time in OLETF rats not given OPB-9195. In contrast, OPB-9195 treatment greatly suppressed the renal expression of TGF-β, VEGF and type IV collagen mRNAs and proteins to that seen in non-diabetic rats. Conclusion/interpretation. Since OPB-9195, an AGE-inhibitor, prevented the progression of diabetic nephropathy by blocking type IV collagen production and suppressing overproduction of two growth factors, TGF-β and VEGF, in diabetic rats, this compound warrants further investigation. [Diabetologia (1999) 42: 579–588] Received: 2 October 1998 and in final revised form: 28 December 1998