链脲佐菌素致胰岛NO自由基损伤模型的建立和应用

以链脲佐菌素Streptozotocin（简称STZ）为糖尿病的诱因,以NO自由基含量为响应指标,建立了体外小鼠胰岛水平糖尿病药物筛选模型。当STZ作用浓度在0～50mmol/L内变化时,培养液中被检测到的NO大部分是来源于STZ溶于水后释放出的,而很小一部分是由胰岛培养物自身释放的,后者稳定在30～35mmol/L之间。另一方面,NO含量与胰岛素分泌量的剂量关系表明NO的增加伴随着胰岛素分泌量的下降,这标志着NO对胰岛功能的氧化性损伤,从而验证了NO作为该模型响应参量的可靠性。最终确定STZ致胰岛NO自由基损伤模型中STZ的作用浓度为5.0mmol/L,此时NO含量和胰岛素分泌量分别为STZ未加入前的10.81倍和0.43倍。最后应用该模型,快捷地考察了不同铬含量的魔芋葡甘露寡糖铬络合物（简称KOSCr）清除NO自由基的能力。     

Enhanced insulin sensitivity using electroacupuncture on bilateral Zusanli acupoints (ST 36) in rats

In this study, intravenous glucose tolerance test (ivGTT) and insulin challenge test (ICT) were applied to evaluate the influence of electroacupuncture (EA) on insulin sensitivity in rats. Firstly, hypoglycemic activity was confirmed on normal Wistar rats (36+/-12%) and streptozotocin (STZ)-induced diabetic rats (13+/-8%) after 60 min of 15 Hz EA on bilateral Zusanli acupoints. The rats were divided into the experiment group (EG) and control group (CG) randomly. After fasting, plasma glucose and insulin levels were assayed in the normal Wistar rats undergoing ivGTT. Plasma glucose levels and hypoglycemic activity were also evaluated in the normal Wistar rats and STZ diabetic rats during ICT. As the data showed, EA improved the glucose tolerance from 15 to 90 min (p<0.005 compared with the plasma glucose levels of the CG) during ivGTT. In addition, significant improvement in the Homeostasis Model Assessment (HOMA) index was found in the EG from 15 to 90 min (p<0.005 compared with the CG). More hypoglycemic activity was achieved in normal Wistar and STZ diabetic rats in the EG than in the CG (from 30 to 60 min) during ICT. In conclusion, the results suggest that 15 Hz EA at bilateral Zusanli acupoints improved glucose tolerance. Thus, EA should be considered as an alternative method for improving insulin sensitivity and/or increase insulin-hypoglycemic activity in rats.     

Galangin,a dietary flavonoid,improves antioxidant status and reduces hyperglycemia-mediated oxidative stress in streptozotocin-induced diabetic rats

Objective: To examine the effect of galangin on hyperglycemia-mediated oxidative stress in streptozotocin (STZ)-induced diabetic rats.

Methods: Diabetes was induced by intraperitoneal administration of low-dose STZ (40?mg/kg body weight (BW)) into male albino Wistar rats. Galangin (8?mg/kg BW) or glibenclamide (600?µg/kg BW) was given orally, once daily for 45 days to normal and STZ-induced diabetic rats.

Results: Diabetic rats showed significantly increased levels of plasma glucose, thiobarbituric acid reactive substances, lipid hydroperoxides, and conjugated dienes. The levels of insulin and non-enzymatic antioxidants (vitamin C, vitamin E, reduced glutathione) and the activity of enzymatic antioxidants (superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase (GST)) were decreased significantly in diabetic control rats. These altered plasma glucose, insulin, lipid peroxidation products, enzymatic and non-enzymatic antioxidants ions were reverted to near-normal level after the administration of galangin and glibenclamide.

Conclusion: The present study shows that galangin decreased oxidative stress and increased antioxidant status in diabetic rats, which may be due to its antidiabetic and antioxidant potential.     

Antidiabetic and antihyperlipidemic activity of asiatic acid in diabetic rats,role of HMG CoA: In vivo and in silico approaches

Hyperlipidemia is an associated complication of diabetes and also a major risk factor for cardiovascular diseases. The present study was designed to examine the antihyperlipidemic effect of asiatic acid (AA) in streptozotocin (STZ) induced diabetic rats. Diabetes was induced in male Wistar rats by a single intraperitoneal injection of STZ (40 mg/kg b.w.). Diabetic rats show increased plasma glucose, total cholesterol, triglycerides, free fatty acids, phospholipids, low density lipoprotein, very low density liprotein, atherogenic index and decreased insulin and high density lipoprotein in diabetic rats. The activity of 3-hydroxy 3-methylglutaryl coenzyme A (HMG CoA) reductase increased significantly in contrast to the activities of lipoprotein lipase and lecithin cholesterol acyltransferase. In addition, the molecular docking of AA against HMG CoA reductase involved in cholesterol biosynthesis using Argus software. Diabetic rats were treated with AA shifted all these parameters towards normalcy. AA has shown best ligand binding energy 11.8122 kcal/mol. The antihyperlipidemic effect of AA was compared with glibenclamide; a well-known antihyperglycemic drug. In conclusion, this study indicates that AA showed an antihyperlipidemic effect in addition to its antidiabetic effect in experimental diabetes.     

The study of renin–angiotensin–aldosterone in experimental diabetes mellitus

It is generally accepted that hypertension and other vascular pathologies increase in diabetes mellitus (DM) patients as a result of the renin–angiotensin–aldosterone (RAA) system. In this study, changes in the renin‐angiotensin‐aldosterone (RAA) system level was determined in Streptozotocin (STZ)‐injected rats. A total of 46 female Wistar albino rats (180–220 g body weight) was utilized in these experiments. STZ was given intraperitoneally to induce diabetes in rats. Streptozotocin (60 mg kg⁻¹ body weight) was dissolved in 0·1 m citrate–‐phosphate buffer (pH 4–5). The non‐diabetic rats were injected with sterilized buffer alone to act as a control group. Blood glucose levels were 398±8·2 mg dl⁻¹, 488±11·75 mg dl⁻¹ and 658±29·6 mg dl⁻¹ at days 3, 12 and 30 respectively. The level of plasma renin activity (PRA) was measured as 7·69±1·07 ng ml⁻¹ h⁻¹; 1·82±0·22 ng ml⁻¹ h⁻¹ and 0·67±0·12 ng ml⁻¹ h⁻¹ at days 3, 12 and 30, respectively. These values showed that the PRA levels are decreased with increased time period. Serum angiotensin converting enzyme (ACE, E.C. 3.4.15.1) levels were increased at days 12 and 30 (p<0·05 and p<0·005), whereas serum aldosterone levels were increased at days 3 and 12 (p<0·05). The level of urea and creatinine increased at days 12 and 30 (p<0·05 and p<0·005, respectively) when compared to the control group. The data from these experiments indicate that the PRA level decreased whereas ACE activity level increased in diabetic rats compared with the control. Aldosterone levels increased at the first stage of the experiment, but then decreased by the end of the experiment as a result of changes in renin and ACE levels. Copyright © 1999 John Wiley & Sons, Ltd.     

Brain Indoleamines in Alloxan- and Streptozotocin-Induced Diabetic Rats

Previous work by other authors has shown that alloxan-induced diabetes increases whereas streptozotocin-induced diabetes does not alter nonesterified fatty acid (NEFA) plasma levels. The present study replicates these results and demonstrates that fasted, streptozotocin-induced diabetic animals also have increased NEFA levels. In addition, brain levels of 5-hydroxytryptamine (5-HT) and of its immediate precursor and metabolite were measured. Alloxan- and fasted, streptozotocin-induced diabetic rats showed significant increases in brain indoleamine concentrations, whereas fed, streptozotocin-induced diabetic rats had unchanged levels of the same compounds. Levels of brain indoleamines exhibited a strong positive correlation with wet-dog shakes (an index of 5-HT activity) elicited by hippocampal stimulation. Blockade of wet-dog shakes by 5-HT receptor antagonists strengthens the proposal that this behavior is a good index of central 5-HT activity. The increased content of brain indoleamines in alloxan- and fasted, streptozotocin-induced diabetic rats may be related to the increased NEFA plasma levels seen in the same animals. This hypothesis is supported by the positive correlation demonstrated between NEFA and 5-HT levels. In conclusion, it is suggested that alloxan-induced diabetes may represent a useful model for studying the various behavioral changes known to occur in diabetics.     

Retinal capillary junctions: Ultrastructural tight junction artefacts induced by sodium ions and membrane reduction in streptozotocin diabetes

Summary Retinal capillary junctions were analysed in normal and diabetic rats and in a human retina with the electron microscope. Diabetes mellitus was induced with Streptozotocin. The retinae were fixed in Palade's osmium tetroxide containing sodium or calcium ions and block-stained in uranyl acetate.With Ca-fixation, no significant difference in interendothelial cleft width was detected between retinal layers or between normal and diabetic retinae. Diabetes caused a narrowing of the clefts in the Na-fixed tissue (X±SE, n=375; Normal: 78.6±3.00 Å; Diabetic: 57.7 ±2.42 Å; p0.001). A significant correlation was found between cleft width and the length of the tight junctions or zonulae occludentes (p<0.001). In the nerve fibre layer of the Nadiabetio retina, where cleft narrowing was greatest, there was an increase in length of the zonulae occludentes from 22.8±2.2% to 41.6±3.7% (p<0.001). Ca-fixation prevented these changes, indicating that at least some zonulae occludentes were interendothelial extraction artefacts.In the normal retina, endothelial cell membrane thickness was greater with Ca-than Na-fixation (p<0.001). Diabetes caused a decrease in membrane thickness of Ca-fixed tissue (p<0.001). The diabetic decrease in membrane thickness may explain the increased fragility and increased permeability of diabetic capillaries. Calcium binding by endothelial cell membranes is of primary importance in anticoagulation which is defective in diabetes.Work supported by a grant from the Taverna Estate and The Prince of Wales Hospital, Randwick, N.S.W., Australia. Presented in part at the 8th International Congress on Electron Microscopy held in Canberra, A.C.T., Australia, 1974.     

Regional Cerebral Glucose Utilization During Hyperglycemia

Previous data indicate that regional cerebral blood flow (rCBF) decreases during acute and chronic hyperglycemia. To test the hypothesis that the decrease in rCBF is secondary to a decrease in cerebral metabolic rate, the rate of regional cerebral glucose utilization (rCMRgl) was measured in awake-restrained rats during acute and chronic hyperglycemia. Acute hyperglycemia was produced by intraperitoneal injection of glucose, and chronic hyperglycemia was produced by treatment with streptozotocin. The rCMRgl was measured over a 10-min period using [6-14C]glucose. Glucose utilization was normal during acute hyperglycemia but decreased by 13% following 3 weeks of chronic hyperglycemia. The absence of a decrease in rCMRgl measured during acute hyperglycemia indicates that decreased rCBF cannot be explained by a change in the metabolic rate of the brain. The decrease in rCMRgl measured during chronic hyperglycemia does not necessarily indicate the presence of a drop in the metabolic rate of the brain because ketone bodies are available as an alternate fuel for oxidative metabolism. Therefore, it is unlikely that the decrease in rCMRgl measured during chronic hyperglycemia accounts for decreased rCBF.     

Streptozotocin-Induced Diabetes Reduces Brain Serotonin Synthesis in Rats

The rate of brain 5-hydroxytryptamine (serotonin) synthesis and turnover in streptozotocin-diabetic rats was assessed using three separate methods: the rate of 5-hydroxytryptophan accumulation following decarboxylase inhibition with Ro 4-4602; the decline in 5-hydroxyindoleacetic acid levels following monoamine oxidase inhibition with pargyline; and the rate of 5-hydroxyindoleacetic acid accumulation following blockade of acid transport with probenecid. Each of the three methods revealed that 5-hydroxytryptamine synthesis and turnover is decreased by 44-71% in diabetic rats with plasma glucose levels of between 500 and 600 mg%. In addition, the levels of free and bound plasma tryptophan were measured and the levels of the free amino acid were found to be the same in control and diabetic rats. Since diabetic rats exhibit a 40% decrease in brain tryptophan, the free tryptophan level in plasma does not predict brain tryptophan levels in diabetic rats. These data are discussed within the context of psychiatric disturbances experienced by diabetic patients.