Effect Of Oxidative Stress In Diabetic Rats Of Erectile Dysfunction The Mechanism And Treatment

Objective:To establish animal models of diabetic erectile dysfunction in rats, and make it in accordance with the pathophysiological changes of human diabetes mellitus type 2.Method:60 2-month old healthy male Wistar rats were selected and proved with normal erectile function by apomorphine(APO) function test. They were randomly divided into two groups:normal control group(10, given normal diet feeding) and diabetic model group(50, given self-made high-lipid diet feeding). After 8 weeks, oral glucose tolerance test and simultaneous insulin release test were performed. Blood sugar and insulin were determined by tail vein blood sampling. After 12-hour fasting of food and water, intra-abdominal injection of streptozotocin prepared with citric acid,35mg/kg/d was given the next day. After 9-day stabilization, oral glucose tolerance test and simultaneous insulin release test were re-performed. Lipid profile was determined by tail vein blood sampling. Blood insulin was determined by radioimmunoassay. Lipid profile (high-intensity lipoprotein cholesterol, free fatty acid, low-intensity lipoprotein cholesterol and triglyceride) was determined with spectrophotometer. APO function test was re-performed. Times of erection were recorded. And statistical analysis was done.Result:After 8-week of high-lipid diet feeding, the rats showed significant increase of weight as 133% as compared with those in normal diet group, with significant difference. Before injection of STZ, blood sugar was similar in two groups. After injection of STZ, blood sugar increased rapidly and stabilized at 15.8±3.9mmol/L, which was significantly higher than that before injection(p<0.05). Before injection of STZ, serum insulin was 8.7±1.1uu/ml in diabetic group. Then it was decreased to 7.3 ±1.5 after injection, which was still higher than that in normal group(4.3±0.7,p<0.05). Insulin sensitivity index was highest in normal group, then diabetic group before modeling, which was lowest in diabetic group. Free fatty acid, serum triglyceride, and low-intensity lipoprotein cholesterol were higher after modeling than before. Both were significantly higher than normal group. And high-intensity lipoprotein cholesterol showed opposite change. One rat died after injection of STZ. The rest 49 rats were performed APO test at week 9.5. APO test showed separated phenomenon in two groups. The changes of erectile function in normal diet group were not obvious, with erectile rate of 100%.24 rats out of 49 rats in diabetic group showed erection, with erectile rate of 48.9%, which was significantly lower than that in normal group.Conclusion:High-lipid feeding could induce weight increase, blood lipid abnormality and insulin resistance in rats. Low-dose STZ intra-abdominal injection could partly damage islet cells on the basis of this, which was similar to the pathogenesis of human diabetes mellitus type 2. APO test was performed at day 10 of modeling. Rats showed erectile rate of 42.8%. And the incidence of erectile dysfunction was increased to 53.2%, which showed the model could be established as rat model of diabetic type 2 erectile dysfunction. Objective:To explore the mechanism of erectile dysfunction induced by oxidative stress in type 2 diabetic rats.Method:Each 5 rats were randomly selected from normal control group, diabetic without ED group and diabetic ED group of Part One. They were killed after glutaraldehyde anesthesia. Blood sugar, insulin, NO, MDA, SOD and free fatty acid, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol were determined by vena cava sampling. Insulin sensitivity was determined by Homa-IR. Cavernous body of penis of rats was taken and HE stained to observe the changes of cell and histomorpholgy. PKC-αand eNOS expression was determined by immunohistochemistry. Western Blot was applied to quantitatively determine eNOS protein content. Then comparisons were done separately.Result:Blood sugar was increased in diabetic group as compared with normal control group(p<0.01).It was 19.8±3.2mmol/L in diabetic rats with ED and 17.4±5.2 mmol/L in diabetic rats without ED, which showed no significant difference between two groups(p>0.05). Serum insulin was correspondingly changed along with increasing of blood sugar. It was 9.5±4.2uU/ml in diabetic ED group, which was similar to diabetic without ED group(7.1±2.4 uU/ml). And both of them were higher than that in normal control group(p<0.05). Homa-IR was 8.89±3.64 in diabetic ED group, which was higher than that in diabetic without ED group(5.54±1.42, p<0.05). Both of them were higher than that in normal control group(1.26+0.77, p<0.01). The changes of FFA, LDL-C and TG were similar to Homa-IR(p>0.05). HDL-C showed the opposite change(p>0.05). MDA was increased in diabetic group, which was more obvious in±diabetic with ED group(p<0.05). And it was higher than that in normal control group(p<0.05). The changes of NO and SOD were similar to HDL-C(p<0.05). It was found in morphological study that the structure of cavernous body of penis in diabetic group was puffer as compared with normal control group. Cells were decreased significantly. Interspace was increased. Those changes were more obvious in diabetic rats with ED(p<0.05). Immunohistochemistry showed that PKC-αexpression was increased in cavernous body of penis in rats of diabetic group. eNOS expression in endothelial cell was decreased, which was related to with or without ED. And it showed significant difference as compared with normal control group(p<0.05). It was found in quantitative analysis that eNOS protein content in cavernous body of penis was lowest in diabetic ED group, then in diabetic without ED group. Both of them were lower than that in normal control group(p<0.05).Conclusion:High-lipid diet feeding combined with low-dose STZ induced oxidative damage such as anti-oxidizing material decreasing, oxidative damage product increasing and NO decreasing in rats, which was more obvious in diabetic rats with ED. And the severity of oxidative stress damage was in accordance with the changes of eNOS, PKC and NO. It suggested that erectile dysfunction in type 2 diabetic rats was related to oxidative stress damage. And oxidative stress might be the important reason of PKC activation, eNOS expression decreasing and NO production decreasing in cavernous body of penis of rats. Objective:To discuss if a-lipoic acid could improve the erection function of the rats with diabetic erection disorder(ED).Method:25 rats of the previous experiment were selected. There were 5 rats in normal control group. And 20 rats were in diabetic ED group, which were divided into DM control group(n=5), insulin group(n=5), a-lipoic acid group(n=5) and a-lipoic acid+insulin group(n=5). They were all free to feed and drink. The rats in insulin group were given Insulin Zinc Protamine 15u/kg.d, subcutaneous injection. The rats in a-lipoic acid group were given a-lipoic acid 35mg/kg.d, intraperitoneal injection. The rats in a-lipoic acid+insulin group were given both of the drugs. The rats in normal control group were given equivalent saline, intraperitoneal injection. APO test was re-performed after 4-week of treatment. The rats were killed by the previously mentioned method. Blood, corpus cavernosum penis and arteriae aorta were sampled to determine BS,INS,NO,SOD and MDA. HE staining was done to observe histomorphology. PKC and eNOS deposition were observed by immunohistochemistry. eNOS content was determined by Wester blot. Then comparisons were done.Results:There was no significant change of erectile function in normal control group, in which the erectile rate was still 100%. Time of erection in some rats was decreased as compared with previous test, without statistical difference. No erection occurred in any rats of diabetic control group after the treatment, with erectile rate of 0, which was the same as that before treatment. The erectile rate in insulin treatment group remained the same before and after the treatment. The erectile rate in a-lipoic acid group was increased from 0% before the treatment to 20% after the treatment. The erectile rate in a-lipoic acid+insulin group was increased to 40% after the treatment, with an obvious significance. NO was highest in normal control group, then a-lipoic acid+insulin group. Those were similar in a-lipoic acid group and insulin treatment group, which was higher in previous group. And that was lowest in diabetic control group. SOD showed the same changing tendency with NO. It was found by histological detection that PKC was over-expressed in diabetic group. eNOS was lowest. The change was the same with NO. eNOS protein expression confirmed this change.Conclusion:a-Lipoic acid could improve the oxidative stress in rats with diabetic erectile dysfunction, decrease penis PKC expression, and improve vascular endothelial cell function in diabetic rats. Synthesis inhibition of eNOS was relieved. NO content was increased. So the erectile function was improved.