Chronic vitamin E treatment prevents defective endothelium-dependent relaxation in diabetic rat aorta

Summary We examined the effect in rats of 2 months of streptozotocin-induced diabetes mellitus on relaxation and contraction of aortas in vitro. A further diabetic group was treated from time of diabetes induction with a 1% dietary supplement of vitamin E. Diabetes caused a 26.5% deficit (p<0.001) in maximum endothelium-dependent relaxation to acetylcholine in phenylephrine-precontracted aortas. This was 64.3% attenuated (p<0.01) by vitamin E treatment; maximum relaxation was not significantly altered compared to non-diabetic rats. Vitamin E treatment of non-diabetic rats did not significantly affect acetylcholine-induced relaxation. Diabetes or treatment did not significantly alter acetylcholine sensitivity. Endothelium-independent relaxation response to glyceryl trinitrate was not affected by diabetes or vitamin E treatment, indicating that vascular smooth muscle responses to nitric oxide remained unaltered. There was a 35.4% reduction in the maximum contractile response to phenylephrine with diabetes (p<0.05) which was unaffected by vitamin E treatment. The data suggest that the chronic deficit in nitric oxide-mediated endothelium-dependent relaxation in diabetes depends largely upon excess activity of reactive oxygen species. Treatment with vitamin E to increase free radical scavenging specifically protected vascular endothelium although it had no effect on deficits in vascular smooth muscle contractile responses.Abbreviations NO Nitric oxide - ARI aldose reductase inhibitor - ACH acetylcholine - GTN glyceryl trinitrate - GSH reduced form of glutathione - EC₅₀ effective concentration for 50% of the maximal response     

The Changes in the Hypothalamo-Pituitary-Gonadal Axis of Streptozotocin-Treated Male Rats Depend from Age at Diabetes Onset

The influence of age at diabetes onset and of capillary microangiopathy on the severity and evolution of hypothalamo-pituitary-gonadal changes was studied morphologically and morphometrically in male rats 4 and 8 months after streptozotocin injection. At each time period we studied 2 groups of rats, one made diabetic before (age 1 month), the other after puberty (age 3 months), and compared them with corresponding controls. The size of hypothalamic axons, numerical density and size of pituitary gonadotrophs, size of testicular tubules, and basement membrane thickness of retinal capillaries were measured. Major differences were found at 8 months. Changes of pituitary glands (i.e. small and numerous gonadotrophs) and testes (i.e. small tubular size) were more important in pre- than in postpubertal diabetic rats. This was a consequence of the aggravating prepubertal diabetes between 4 and 8 months. On the contrary, these changes partially regressed in postpubertal diabetic animals. Pituitary and testicular changes were correlated. Other lesions, such as swollen axonal processes in the hypothalamus, increased thickness of seminiferous epithelium and of capillary basement membranes, though very evident in diabetics, were independent from age at induction. Neither microangiopathy nor glycemia were correlated with any other change which confirmed their secondary role in diabetic neuroendocrine disorders. Thus, two types of diabetic disorders of the hypothalamo-pituitary-gonadal axis could be distinguished: 1) those with irreversible effects on immature yet partially reversible effects on mature structures; and 2) those independent from age at induction.     

Transfected rat islet tumour cells express mouse major histocompatibility complex class I antigens functionally

Summary Rat insulinoma cells clone 5AH-B, were transfected by electroporation with the gene encoding the mouse major histocompatibility complex class I antigen H-2K^b, whereupon stable transfectants were selected and analysed. Data from flow cytometric analyses using three different H-2K^b specific monoclonal antibodies and functional assays using H-2K^b specific alloimmune cytotoxic T cells revealed that the encoded H-2 antigen was expressed in a functional manner. Similar experiments employing the monoclonal antibody OX-18, which recognizes rat major histocompatibility class I molecules, and xenoimmune cytotoxic T cells specific for the endogenously expressed RT1^g antigen showed that functional expression of the RT1^g antigen was maintained. However, a down-regulation of the expression was observed in H-2K^b positive transfectants, whereas normal expression was retained in K^b negative transfectants. The function of the native promoters of both the endogenous and the transfected class I genes was found to be preserved in the transfectants as assessed by the response to stimulation with interferon-. The present study was unable to confirm the reports of RIN specific lysis by T cells from multiple low dose streptozotocin diabetic mice. Even in the presence of the syngeneic restriction element no lysis was observed. We conclude, that rat insulinoma cells clone 5AH-B, are able to integrate a foreign class I antigen gene and express the encoded product functionally. The data also suggest the possibility of creating major histocompatibility antigen positive rat insulinoma cells which are RT1^g negative. Such transfectants will be of great potential value for the dissection of cell mediated B cell destructive processes.     

Gene expression of antioxidant enzymes in experimental diabetic neuropathy

Chronic hyperglycemia results in a large deficit in nerve blood flow. Both autoxidative- and ischemia-induced lipid peroxidation occurs, with resultant peripheral sensory neuropathy in streptozotocin-induced diabetes in the rat. Free radical defenses, especially involving antioxidant enzymes, have been suggested to be reduced, but scant information is available on chronic hyperglycemia. We evaluated the gene expression of glutathione peroxidase, catalase, and superoxide dismutase (cuprozinc and manganese separately) in L4,5 dorsal root ganglion (DRG) and superior cervical ganglion, as well as enzyme activity of glutathione peroxidase in DRG and sciatic nerve in experimental diabetic neuropathy of 3 months and 12 months durations. We also evaluated nerve electrophysiology of caudal, sciatic-tibial, and digital nerves. A nerve conduction deficit was seen in all nerves in experimental diabetic neuropathy at both 3 and 12 months. Gene expression of glutathione peroxidase, catalase, cuprozinc superoxide dismutase, and manganese superoxide dismutase were not reduced in experimental diabetic neuropathy at either 3 or 12 months. Catalase mRNA was significantly increased in experimental diabetic neuropathy at 12 months. Glutathione peroxidase enzyme activity was normal in sciatic nerve. We conclude that gene expression is not reduced in peripheral nerve tissues in very chronic experimental diabetic neuropathy. Changes in enzyme activity may be related to duration of diabetes or due to post-translational modifications.     

Attenuation of diabetic nephropathy by Chaihuang-Yishen granule through anti-inflammatory mechanism in streptozotocin-induced rat model of diabetics

Ethnopharmacological relevance

Traditional Chinese medical herbs have been used in China for a long time to treat different diseases. Based on traditional Chinese medicine (TCM) principle, Chaihuang-Yishen granule (CHYS) was developed and has been employed clinically to treat chronic kidney disease including diabetic nephropathy (DN). The present study was designed to investigate its mechanism of action in treatment of DN.

Materials and methods

Diabetic rats were established by having a right uninephrectomy plus a single intraperitoneal injection of STZ. Rats were divided into four groups of sham, diabetes, diabetes with CHYS and diabetes with fosinopril. CHYS and fosinopril were given to rats by gavage for 20 weeks. Samples from blood, urine and kidney were collected for biochemical, histological, immunohistochemical and molecular analyses.

Results

Rats treated with CHYS showed reduced 24 h urinary protein excretion, decreased serum TC and TG levels, but CHYS treatment did not affect blood glucose level. Glomerular mesangial expansion and tubulointerstitial fibrosis in diabetic rats were significantly alleviated by CHYS treatment. Moreover, CHYS administration markedly reduced mRNA levels of NF-κB p65 and TGF-β1, as well as decreased protein levels of NF-κB p65, MCP-1, TNF-α and TGF-β1 in the kidney of diabetic rats.

Conclusions

CHYS ameliorates renal injury in diabetic rats through reduction of inflammatory cytokines and their intracellular signaling.     

南瓜多糖对链脲菌素诱导的大鼠胰岛损伤的保护作用

目的:观察南瓜多糖(PP)对链脲菌素诱导的大鼠胰岛损伤的影响。方法:建立链脲菌素性糖尿病模型,PP(150,300,600mg·kg-1)灌胃3周进行治疗。检测大鼠空腹血糖值、血清胰岛素含量以及血清中超氧化物歧化酶(SOD)、丙二酰二醛(MDA)、一氧化氮(NO)的水平;观察链脲菌素性糖尿病大鼠胰岛细胞的超微结构的变化。结果:PP(300,600mg·kg-1)能显著降低STZ诱导的糖尿病大鼠的空腹血糖值;PP(600mg·kg-1)能升高糖尿病大鼠血清中的胰岛素值;PP(300,600mg.kg-1)治疗后,糖尿病大鼠血清中SOD值明显增加,MDA、NO的含量显著减少;大鼠胰岛细胞的超微结构显示PP对STZ损伤的胰岛细胞具有保护作用。结论:PP对链脲菌素诱导的大鼠胰岛损伤具有保护作用。     

卡托普利对糖尿病大鼠心肌组织肾素─血管紧张素系统的影响

在链脲霉素所致糖尿病大鼠模型（链脲霉素７０ｍｇ·ｋｇ－１，ｉＰ）观察了大鼠心肌组织肾素血管紧张素系统（ＲＡＳ）的变化以及血管紧张素转换酶抑制剂卡托普利的治疗作用（４．６ｍｍｏｌ·Ｌ－１卡托普利饮水给药４ｗｋ）。结果表明，糖尿病大鼠较正常大鼠心肌组织ＲＡ、ＡＣＥ活性显著升高（Ｐ＜０．０１），ＡｎｇⅠ、ＡｎｇⅡ、ＡＬＤ含量均明显增加（Ｐ＜０．０１）。卡托普利治疗组大鼠较糖尿病大鼠上述各项指标均有不同程度的降低，其中ＡＣＥ活性和ＡｎｇⅠ、ＡＭⅡ含量的改变有显著性差异（Ｐ＜０．０５，Ｐ＜０．０１），ＲＡ和ＡＬＤ含量改变差异无显著性（Ｐ＞０．０５）。提示：心肌组织ＲＡＳ功能亢进参与了糖尿病性心肌病发病过程。卡托普利对心肌组织ＲＡＳ的抑制作用可能是其减轻糖尿病心肌损害的主要作用机制。     

链脲佐菌素糖尿病模型动物血糖及体征动态变化的研究

目的 探讨链脲佐菌素(streptozotocin)糖尿病模型动物血糖和体征动态变化的特点.方法 链脲佐菌素1次或多次腹腔注射,分别建立大鼠和小鼠糖尿病模型;检测血糖变化,以进食量(g)/体质量(g),饮水量(ml)/体质量(g)计算进食量系数和饮水量系数.结果 雄性大鼠链脲佐菌素60 mg/kg糖尿病成模率为65.0%,血糖在注射后15 d达到高峰,15～25 d保持在较高水平,25d后出现明显的下降.小鼠链脲佐菌素200 mg/kg分5次建立糖尿病成模率为90.0%,血糖的动态变化与大鼠类似,但血糖下降不明显.在这两个糖尿病模型中,动物的饮水量系数变化与血糖水平变化的相关性最高,相关系数r＞0.97.结论 链脲佐菌素糖尿病模型动物的血糖水平在造模开始后的15～25 d维持在较高水平,可作为观察降血糖药物疗效的适宜时段.饮水量系数是反映血糖的水平变化的适宜指标.     

Animal models to test drugs with potential antidiabetic activity

Although medicinal plants have been historically used for diabetes treatment throughout the world, few of them have been validated by scientific criteria. Recently, a large diversity of animal models has been developed to better understand the pathogenesis of diabetes mellitus and new drugs have been introduced in the market to treat this disease. The aim of this work was to review the available animal models of diabetes and some in vitro models which have been used as tools to investigate the mechanism of action of drugs with potential antidiabetic properties. In addition, a MEDLINE/PUBMED search for articles on natural products, pancreatectomy and diabetes mellitus treatment published between 1996 and 2006 was done. In the majority of the studies, natural products mainly derived from plants have been tested in diabetes models induced by chemical agents. This review contributes to the researcher in the ethnopharmacology field to designs new strategies for the development of novel drugs to treat this serious condition that constitutes a global public health.     

建立糖尿病心肌病动物模型方法的实验研究

目的研究建立糖尿病心肌病动物模型的科学、实用的方法。方法应用链脲佐菌素对SD大鼠进行一次性腹腔注射,通过观察大鼠的一般状况、进食量、进水量、尿量、体重的变化,监测血糖、尿糖、心肌酶含量、胰岛素水平、心肌超微结构、心脏大血管内膜情况及心电图情况来评估糖尿病心肌病的发病情况。结果腹腔注射STZ 3周后,模型组大鼠出现病态表现,进食量、饮水量、尿量增加,体重下降。血糖值、尿糖值及肌酸激酶、乳酸脱氢酶值均较对照组大鼠升高。胰岛素水平较对照组明显降低,心肌超微结构符合糖尿病心肌病表现,心脏大血管未见纤维斑块和粥样斑块。结论对SD大鼠进行一次性腹腔注射链脲佐菌素(55mg/kg),大鼠于注射后第3周可出现稳定的糖尿病心肌病状态。这是一种可靠且实用性强的糖尿病心肌病动物模型的制备方法。