[The Role of DNA Double-strain Damage Repairing Mechanisms in Diabetic Atheroscolersis].

OBJECTIVES: To identify the role of DNA double-strain damage repairing pathway in the development of diabetics atherosclerosis. METHODS: Wistar male rats were randomly divided into three groups: control group (group A), balloon injury group (group B) and diabetes + balloon injury group (group C). Streptozotocin (STZ) was injected into rat abdomen to induce diabetes. After stabilizing high glucose, rats in group B and group C were both under aortic balloon injury technique and fed high lipid forage post-operatively. Glucose levels and weight were observed weekly. Segments of aortoa of three groups were taken at 2, 4, 6 and 8 weeks, staining of senescent ß-galactosidase (SA-ß-gal) staining, HE and changes of aorta under light microscope were observed. The area of tunica intima (I) and tunica media (M) in aorta was measured, and their ratio (I/M) were analyzed. Expressions of gamma-histong family 2A variant (γ-H2AX), phosphorylated ataxia telangiectasia mutated (ATM), phosphorylated checkpoint kinasen 2 (CHK2) and phosphorylated P53 were detected by immunohistochemical staining. RESULTS: SA-ß-gal staining positive areas were dotted around in group B and group C [CM(155.3mm]but not in group A at two weeks.At the same time, a slight hyperlasia of aortic neointima was observed in HE staining of group B and group C. SA-ß-gal staining was positive scattered within the tunica intima of aorta of group B and group C at four weeks, and HE staining promted a significantly greater of aortic neointima in the group C than that in the other two group (P<0.05). Positive regions of SA-ß-gal staining were more in group C than group B at six weeks. Typical atherosclerotic plaques were formed, vascular smooth muscle cells were disordered arranged and foam cells were aggregated in the plaques of group C at six weeks post-operatively, and intimal membrane areas increased than group A and group B (P <0.05). At 8 weeks, SA-ß-gal positive areas in group C were greater than in group B. The arteriolar wall was markedly thickened and the lumen was narrowed. The area of intimal membrane and the I/M radio were significantly greater in group C than those in group A and group B (P <0.05). Positive expressed of γ-H2AX, phosphorylated ATM, phosphorylated CHK2 and phosphorylated P53 were observed in typical atherosclerotic foci of group C, and weaker expressed in group B. CONCLUSION: Cellular senescence of vascular edothelium is triggered and DNA double-strain damage is increased in diabetes. The DNA double-strain damage repairing machines may participate in the development of diabetic atherosclerosis.

Multiple low doses of erythropoietin delay the proliferation of hepatocytes but promote liver function in a rat model of subtotal hepatectomy.

PURPOSE: The impact of various doses of erythropoietin (EPO) on liver regeneration after partial hepatectomy (PH) in different animal models is still under debate. We investigated the impact of low doses of EPO on liver regeneration in a rat model of subtotal hepatectomy. METHODS: We established a 90 % PH rat model with perioperative injections of low-dose EPO (1,000 IU/kg). We analyzed survival and hepatocyte proliferation in animals treated with or without EPO and assessed liver function by blood ammonia measurement and the indocyanine green 15-min retention test. RESULTS: Low doses of EPO treatment improved the survival of rats after 90 % PH. Unexpectedly, during the first 24 h after the operation, liver regeneration in the EPO-treated rats was inhibited. DNA synthesis, cell proliferation, and the expression of cyclins and p-STAT3 peaked 48 h after PH, which was delayed by about 24 h vs. the control rats. Furthermore, EPO treatment increased the serum level of IL-6 and protected the hepatocytes from apoptosis. CONCLUSION: Low doses of EPO do not stimulate early hepatocyte proliferation in the regenerating liver, but contribute to liver protection by inducing IL-6 and inhibiting apoptosis.

[The role of DNA double strains damage repairing mechanisms in high glucose-induced endothelial senescence].

OBJECTIVE: To investigate the roles of DNA double stains damage repairing mechanisms in high glucose-induced cellular senescence. METHODS: Human umbilical vein endothelial cells (HUVECs) were incubated with different concentrations of glucose (5.5 mmol/L, 11 mmol/L, 22 mmol/L and 33 mmol/L) for 72 hrs before the assay of senescence-associated beta-galactosidase staining. The superoxides were detected by flow cytometry. The levels of NO were detected by enzyme assay. Gamma-H2AX and phosphorylated P53 protein were measured by Western blot. Changes after co-incubation with KU55993 (an inhibitor of ATM) were examined with methods mentioned above. RESULTS: Compared with control group, percentage of positive cells of senescence-associated beta-galactosidase staining increased significantly in high glucose groups. The corresponding levels of reactive oxygen increased and NO decreased in a concentration-dependent manner. Intra-cellular levels of gamma-H2AX and phosphorylated P53 protein were significantly increased in high glucose groups. Statistical significances were revealed between high-glucose group and control group, as well as among different high-glucose groups, but no significant difference was observed between mannitol and control group. KU55993, an inhibitor of ATM, significantly reduced the levels of gamma-H2AX, phosphorylated P53 protein, and positive rate of senescence-associated beta-galactosidase staining. CONCLUSION: High glucose may promote DNA double strains damage by enhancing oxidative stress and decreasing NO, and thus accelerate cellular senescence. ATM-P53 pathway, the key proteins related to DNA double strain damage repairing mechanisms, may play an important role in high glucose induced cellular senescence and atherosclerosis.

[Effects of testosterone substitution on metabolic syndrome-related factors in hypogonadal males: a meta-analysis].

OBJECTIVE: To conduct a meta-analysis on the effects of testosterone on the related factors of metabolic syndrome in hypogonadal males. METHODS: Based on the principles and methods of Cochrane systematic reviews, we searched the PubMed (1980 to August 2009), Embase (1980 to August 2009), the Cochrane Central Register of Controlled Trials and CNKI (1995 to August 2009) , and handsearched some relevant journals and conference proceedings as well. We also identified randomized controlled trials addressing the use of testosterone for the treatment of hypogonadism, screened the retrieved studies according to the predefined inclusion and exclusion criteria, evaluated the quality of the included studies, and performed a meta-analysis on the results of homogeneous studies using the Cochrane Collaboration's RevMan 5.0 software. RESULTS: Six randomized controlled trials were included. The results of analysis indicated that testosterone substitution could significantly ameliorate fasting blood glucose, total cholesterol and insulin resistance in hypogonadism patients, and it could also reduce LDL, HDL, triglyceride and systolic blood pressure, though with no significant difference from the controls. However, there was insufficient evidence to show the effects of testosterone on waist circumference, waist-hip ratio and diastolic blood pressure. CONCLUSION: Existing clinical evidence has demonstrated the positive effects of testosterone substitution on the improvement of insulin resistance, blood glucose and lipids, but due to the heterogeneity and high risk of bias in the included studies, the evidence might be insufficient to give full support to the demonstration. Further large-scale trials are required to define the metabolic effects of testosterone in the treatment of hypogonadism.