生长激素释放激素受体激动剂MR409对db/db小鼠糖尿病肾病作用的研究

目的:探讨人工合成的生长激素释放激素受体激动剂MR409对db/db小鼠糖尿病肾病和肾脏纤维化的影响。方法:将db/db小鼠随机分为模型组和MR409治疗组,野生型小鼠为对照组,每组10只。MR409治疗组小鼠隔天皮下给予MR409(每只15μg),对照组和模型组小鼠隔天皮下给予等量溶剂对照,干预8周。取第8周末小鼠血清和尿液进行生化指标检测,HE、PAS、Masson和天狼星红染色用于评价肾损伤和肾纤维化程度,二氢乙啶(DHE)荧光染色检测评价肾脏中活性氧的含量,Western blot检测肾脏纤维化以及氧化应激相关蛋白的表达。结果:与db/db小鼠相比,MR409治疗可显著降低db/db小鼠尿蛋白/肌酐比、血清中胆固醇和甘油三脂含量以及肾间质纤维化和肾小球硬化面积(P0.05),MR409还可显著降低肾脏中活性氧水平及NADPH氧化酶亚基p22~(phox)和gp91~(phox)、纤连蛋白(FN)和转化生长因子β1(TGFβ1)蛋白的表达量(P0.05)。结论:生长激素释放激素受体激动剂MR409能有效减轻db/db小鼠糖尿病肾损伤,其机制可能与降低氧化应激和肾纤维化有关。     

小热休克蛋白家族和自噬相关蛋白 在自发性2型糖尿病db/db小鼠海马组织中的表达

目的观察自发性2型糖尿病db/db小鼠海马组织中小热休克蛋白家族(sHSPs)及自噬相关蛋白表达情况。方法正常db/m小鼠作为对照组,糖尿病db/db小鼠作为模型组,各10只。观察其体质量,空腹血糖(FBG);real-time PCR检测海马组织中小热休克蛋白家族、自噬相关基因mRNA的表达;Western blot检测HSPB8、BAG3、LC3、P62蛋白表达。结果 1)db/db小鼠体质量、空腹血糖均明显高于db/m小鼠(P0.01)。2)小热休克蛋白1-10(heat shock protein family B [small] member 1-10,HSPB 1-10)基因mRNA在小鼠海马组织中均有表达;其中HSPB1、HSPB3、HSPB5、HSPB6和HSPB8 db/db组明显低于db/m组(P0.05);HSPB2、HSPB9和HSPB10 db/db组高于db/m组(P0.05);而在db/db小鼠中LC3表达高于db/m组(P0.01),而P62反之(P0.01)。3)较db/m组,db/db组HSPB8、BAG3、LC3-Ⅱ蛋白表达均增高(P0.01),相反P62蛋白表达减低(P0.05)。结论 1)10种sHSPs均在小鼠海马组织中表达,但表达特点有所不同。2)8周龄糖尿病小鼠海马组织中存在HSPB8蛋白表达增强,且自噬激活。     

运动干预糖尿病心肌病的分子机制研究

目的:观察链脲佐菌素诱导的糖尿病大鼠心肌组织中NADPH氧化酶表达的变化,探讨运动对NADPH氧化酶的影响。方法:大鼠糖尿病模型建立成功1周后,测定糖尿病对心肌组织中NADPH氧化酶亚基表达的影响,测定8周的运动能否有效影响NADPH氧化酶亚基的表达;观测糖尿病对心肌胶原蛋白表达的影响,8周运动是否能够影响胶原蛋白的表达。结果:糖尿病导致心室NADPH氧化酶亚基p47~(phox)和gp91~(phox)表达增加,而8周运动能够抑制这2种亚基表达的增加;糖尿病引起心房肌p47~(phox)表达显著增加,运动抑制其增加;糖尿病大鼠心肌胶原蛋白Ⅲ水平显著增加,运动降低胶原蛋白的增加。结论:运动减低糖尿病大鼠心脏p47~(phox)和gp91~(phox)的表达。这可能是改善心内基质的重要机制,因此运动干预糖尿病心肌病的一个有效机制可能是通过抑制心肌氧化应激和降低胶原蛋白的表达。     

2型糖尿病模型db/db小鼠海马NOS阳性神经元变化

目的　观察人类 2型糖尿病模型———C5 7BL/KsJdb/db(db/db)小鼠海马NOS阳性神经元变化。方法　糖尿病组 :6周龄C5 7BL/KsJ(db +db +)小鼠 5只 ,尾静脉空腹血糖高于 11.1mmol/L且肥胖。对照组 :非糖尿病小鼠C5 7BL/KsJ(?+) 5只 ,尾静脉空腹血糖低于 6 .0mmol/L体重正常 ,于 30周龄 (成模第 6月末 )时 ,灌注固定取脑 ,以NADPH d组化法显示海马NOS阳性神经元。结果　与正常对照组相比 ,糖尿病组小鼠海马齿状回NOS阳性神经元密度显著减少 (P <0 0 1)。结论　糖尿病时NOS阳性神经元数量减少 ,NO的合成降低表明NO可能参与糖尿病中枢神经系统功能障碍     

运动通过下调烟酰胺腺嘌呤二核苷酸磷酸氧化酶亚基改善糖尿病心肌病

目的:探讨链脲霉素诱导的糖尿病对烟酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶的影响,测定运动的干预效应。方法:SD大鼠糖尿病建模成功1周后,检测心室和心房肌中NADPH氧化酶亚基的表达以及心血管紧张素Ⅱ的表达,测定8周的运动能否有效影响NADPH亚基以及血管紧张素Ⅱ的表达。结果:糖尿病导致心室肌NADPH氧化酶亚基p67~(Phox)和gp91~(phox)表达增加,而8周运动能够抑制两种亚基表达的增加。糖尿病心房肌p67~(phox)增加显著,运动抑制其增加。糖尿病心血管紧张素Ⅱ水平显著增加,运动降低血管紧张素Ⅱ的增加。结论:运动降低糖尿病大鼠心肌p67~(phox)和gp91~(phox)表达的增加,这可能是改善心内基质的机制之一,因此运动治疗和预防糖尿病心肌病的一个有效机制可能是通过抑制心肌氧化应激和降低血管紧张素Ⅱ的表达。     

二苯基碘和夹竹桃麻素通过降低早产儿外周血单个核细胞p47phox位移与水平减少活性氧的产生

目的观察NADPH氧化酶抑制剂二苯基碘(DPI)和夹竹桃麻素(apocynin)对NADPH氧化酶亚基p47phox介导的活性氧(ROS)产生的影响,探讨细胞在高氧条件下,p47phox介导ROS产生的机制。方法 32周以下早产儿,尚未吸氧前取外周血2 m L,分离纯化外周血单个核细胞(PBMC)将所得细胞分为对照组、高氧组、高氧联合DPI处理组、高氧联合apocynin处理组进行培养。对照组置于37℃、50 m L/L的CO2培养箱中,高氧及相应处理组置于950 m L/L的O2与50 m L/L的CO2混合气体中培养48 h。采用Mitosox Red标记结合激光共聚焦显微镜检测PBMC内ROS的生成量、硫代巴比妥酸比色法检测培养液丙二醛含量、免疫荧光检测p47phox在细胞内的定位及移位率、Western blot法检测p47phox的蛋白水平。结果与高氧组相比,其余三组ROS和丙二醛明显减少,p47phox移位率与含量也显著降低;与对照组相比,高氧联合DPI处理组及高氧联合apocynin处理组ROS、丙二醛、p47phox移位率与含量并无显著差异。结论 DPI和apocynin能通过降低p47phox移位与含量来减少高氧诱导的ROS升高。     

血管紧张素Ⅱ刺激高草酸尿症大鼠肾脏NADPH氧化酶的表达

目的： 观察肾素-血管紧张素系统（RAS）和NADPH氧化酶在高草酸尿症大鼠肾脏氧化应激（OS）形成中的相互作用。方法: 采用0.8%乙二醇饮水法诱导建立高草酸尿症大鼠模型。动物分6个组（n=8）,A组:空白组;B组：高草酸尿症组;C组：高草酸尿症+apocynin治疗组;D组：单纯apocynin治疗组;E组：高草酸尿症+losartan治疗组;F组：单纯losartan治疗组。后4组分别灌胃给予apocynin（0.2 g·kg-1·d-1）或losartan（30 mg·kg-1·d-1）。4周后检测大鼠尿液、肾组织中的OS指标（尿8-IP和肾组织SOD活性）,放免法检测肾组织血管紧张素Ⅱ（AngⅡ）的含量,免疫组化法观察NADPH氧化酶亚单位P47phox蛋白在肾脏中的表达位置,RT-PCR法检测肾组织p47phox mRNA的表达水平。结果: p47phox在各组大鼠肾脏中都有广泛表达,表达部位包括肾皮质、内髓、外髓。与A组比较,B组尿液8-IP明显增多,肾组织SOD活性降低,肾组织AngⅡ含量增多,p47phox mRNA在肾组织中的表达水平也明显增多。使用apocynin（C组）和losartan（E组）均可抑制肾组织p47phox mRNA的表达,同时肾脏的OS程度减轻。结论: 在高草酸尿症大鼠模型中,肾脏p47phox mRNA表达增多,导致肾脏OS;同时肾脏RAS也被激活,后者可通过刺激p47phox mRNA的表达而促进肾脏OS程度增加。     

甜菜碱对老龄db/db小鼠脂肪性肝损害的影响

 目的：通过高脂饮食诱发db/db小鼠非酒精性脂肪性肝病（NAFLD）模型,探索甜菜碱对遗传性小鼠脂肪肝脂质代谢的影响。方法：50只7月龄db/db鼠随机分为低、中、高剂量组、生理盐水对照组和阳性药物组。所有小鼠均饲以高脂饲料, 以诱发NAFLD 模型。 小鼠分别以200 mg/kg(低剂量组)、400 mg/kg(中剂量组)和800 mg/kg(高剂量组)甜菜碱溶液灌胃,连续6周。测定血清丙氨酸氨基转移酶(ALT)、甘油三酯(TG)、总胆固醇（TC）和低密度脂蛋白(LDL)水平,并行葡萄糖耐量测定和肝组织病理学观察。结果：甜菜碱可显著降低血清ALT、TC和LDL的水平(P<0.05或P<0.01)。组织学结果表明甜菜碱可显著减少小鼠肝细胞的脂肪样变性。结论: 甜菜碱可以显著改善老龄db/db小鼠的脂类代谢紊乱和肝功能,明显降低脂肪在肝细胞中的积蓄。     

SPARC在db/db小鼠肾脏组织中高表达

目的 检测db/db鼠肾脏组织中的富含半胱氨酸的酸性分泌蛋白(SPARC)的表达情况.方法 RT-PCR、Western blot及免疫荧光方法检测db/db鼠肾脏组织中的SPARC mRNA及蛋白的表达.结果 SPARC在db/db鼠肾脏组织中呈现高表达.结论 db/db鼠肾脏组织中的SPARC呈现高表达(P＜0.05),可能与糖尿病肾病的发生与发展有关.     

ACE2基因过表达减轻血管紧张素Ⅱ诱导的神经细胞氧化应激

目的:探讨过表达血管紧张素转换酶2(angiotensin-converting enzyme 2,ACE2)基因对血管紧张素Ⅱ(angiotensin Ⅱ,Ang Ⅱ)诱导的小鼠神经母细胞瘤Neuro-2A细胞氧化应激和NADPH氧化酶(NADPH oxidase, NOX)表达的影响。方法:构建ACE2重组慢病毒载体,以感染复数(multiplicity of infection,MOI)=10转染Neuro-2A细胞72 h,测定ACE2基因转染效率和ACE2蛋白表达,并检测神经细胞标志物以鉴定Neuro-2A细胞。Neuro-2A细胞分为7组:空白对照(control)组、慢病毒载体(eGFP)组、重组ACE2(ACE2-eGFP)组、AngⅡ刺激(Ang Ⅱ)组、 Ang Ⅱ+慢病毒载体(Ang Ⅱ-eGFP)组、Ang Ⅱ+ACE2(Ang Ⅱ-ACE2-eGFP)组和Ang Ⅱ+重组ACE2+A779(Ang Ⅱ-ACE2-eGFP-A779)组。采用酶联免疫吸附法(enzyme-linked immunosorbent assay, ELISA)测定Ang(1-7)水平,DHE染色法检测活性氧簇(reactive oxygen species,ROS)水平,Western blot检测MAS受体及NOX亚基(NOX2、NOX4、p47~(phox)和p67~(phox))蛋白表达。结果:AngⅡ显著增加Neuro-2A细胞ROS水平(P0.01),上调NOX2、NOX4、p47~(phox)和p67~(phox)蛋白表达(P0.01),但下调MAS蛋白表达(P0.01)。ACE2过表达抑制AngⅡ诱导的ROS增加(P0.05),下调NOX2、NOX4、p47~(phox)和p67~(phox)蛋白表达(P0.01),还可增加神经细胞Ang(1-7)含量(P0.01)和MAS受体表达(P0.01)。MAS受体拮抗剂A779能阻断ACE2下调NOX表达的作用(P0.05)。结论:ACE2过表达通过MAS受体对抗AngⅡ诱导的神经细胞氧化应激。     

厄贝沙坦通过诱导自噬减轻db/db小鼠肝脏脂肪变

目的:探讨厄贝沙坦对db/db小鼠脂肪肝的影响及自噬在这一过程中的作用。方法:雄性db/db小鼠24只随机分为模型组和厄贝沙坦组,另选取12只db/m小鼠作为正常对照组。各组分别干预16周后,观察体重、肝指数、血脂、肝功能以及肝脏病理的变化,检测肝组织PI3K/Akt/m TOR信号通路及自噬相关蛋白Atg-7、beclin-1和LC3B的表达情况,并利用电镜观察肝脏自噬小体的变化。结果:与模型组相比,应用厄贝沙坦干预后,db/db小鼠的体重、肝指数、血脂、丙氨酸转氨酶和天冬氨酸转氨酶与模型组相比显著降低(P0.05),肝脏病理改变明显减轻;肝组织p-PI3K、p-Akt和p-m TOR的表达明显减少,Atg-7、beclin-1和LC3B-Ⅱ的表达明显增加,肝脏自噬小体显著增多(P0.05)。结论:厄贝沙坦可能通过抑制PI3K/Akt/m TOR信号通路,上调自噬相关蛋白Atg-7、beclin-1和LC3B-Ⅱ表达,进而促进肝细胞自噬,减轻db/db小鼠肝脏脂肪变。     

Mibefradil reduces blood glucose concentration in db/db mice

OBJECTIVE:

Numerous recent studies suggest that abnormal intracellular calcium concentration ([Ca²⁺]_i) is a common defect in diabetic animal models and patients. Abnormal calcium handling is an important mechanism in the defective pancreatic β-cell function in type 2 diabetes. T-type Ca²⁺ channel antagonists lower blood glucose in type 2 diabetes, but the mechanism remains unknown.

METHODS:

We examined the effect of the Ca²⁺ channel antagonist mibefradil on blood glucose in male db/db mice and phenotypically normal heterozygous mice by intraperitoneal injection.

RESULTS:

Mibefradil (15 mg/kg, i.p., b.i.d.) caused a profound reduction of fasting blood glucose from 430.92±20.46 mg/dl to 285.20±5.74 mg/dl in three days. The hypoglycemic effect of mibefradil was reproduced by NNC 55-0396, a compound structurally similar to mibefradil but more selective for T-type Ca²⁺ channels, but not by the specific L-type Ca²⁺ channel blocker nicardipine. Mibefradil did not show such hypoglycemic effects in heterozygous animals. In addition, triglycerides, basal insulin and food intake were significantly decreased by mibefradil treatment in the db/db mice but not in the controls. Western blot analysis, immunohistochemistry and immunofluorescence staining showed a significantly increased expression of T-type Ca²⁺ channel α-subunits Cav3.1 and Cav3.2 in liver and brain tissues from db/db mice compared to those from heterozygous animals.

CONCLUSIONS:

Collectively, these results suggest that T-type Ca²⁺ channels are potential therapeutic targets for antidiabetic drugs.     

Thermoregulation in the diabetic-obese (db/db) mouse

1. Thermoregulation and non-shivering thermogenesis have been studied in the genetically diabeticobese (db/db) mouse.
2. At all environmental temperatures between 33 and 10°C the body temperature of the diabetic mice was lower than that of the normal littermates, the difference varying from 1.1°C at 33°C to 4.5°C at 10°C.
3. At 4°C the diabetic mice rapidly died (3.2 h) of hypothermia while the normal mice maintained their body temperature within the normal range.
4. At 23°C the diabetic animals exhibited a diurnal rhythm in body temperature which was similar in both phase and amplitude to the controls, but at every point throughout the 24h cycle the temperature of the mutants was lower by 1–2°C.
5. The resting metabolic rate at thermoneutrality (33°C) was higherper whole animal for the diabetics than for the normals. However, at temperatures below thermoneutrality the converse was observed; between 30 and 4°C the RMR of the mutants was lower than the controls by approximately 25%.
6. The capacity for non-shivering thermogenesis in diabetic mice was only one-half that found in normal animals.
7. The diabetic mouse has abnormalities in thermoregulation and non-shivering thermogenesis which are similar to those found in the genetically obese (ob/ob) mouse.

It is concluded that the high metabolic efficiency of the diabetic mouse, like that of the ob/ob mouse, can be explained by a reduced energy expenditure on thermoregulatory thermogenesis; this may represent a primary mechanism for the operation of the “thrifty genotype” associated with obesity and diabetes.     

Impaired liver regeneration after partial hepatectomy in db/db mice

Fatty liver is the most common hepatic disorder in humans and supposed to be a cause of poor prognosis after liver transplantation and hepatic resection which could be resulted from impaired liver regeneration. This study was carried out to analyze the process of liver regeneration in db/db mice which show severe steatosis because of abnormal leptin receptor. We performed 70% partial hepatectomy (PH) on db/db mice and normal +m/+m mice, and then sacrificed the animals 1, 2, 3, 5, 7 and 10 days later. The liver samples were weighed and examined histologically or immunohistochemically. As a result, the liver mass restitution was significantly inhibited in db/db mice compared with +m/+m mice. The BrdU labelling index peaked at 2 days after PH in both strains, although the value was lower in db/db mice. After that, interestingly, it decreased to the control level at 5 days in +m/+m mice while the recovery was delayed in db/db mice. Similar sequence was also observed in the PCNA labelling index. In addition, the peak time of the mitosis index was 2 days and 5 days after PH in +m/+m mice and in db/db mice, respectively. Thus, although not significant, the proliferative response of hepatocytes to PH occurred somewhat more transient and sharply in +m/+m mice while it lasted somewhat longer in db/db mice. This suggests that db/db mice may be valuable as one of the animal models for the investigation of the effects of steatosis on the liver regeneration.     

Differential effect of statins on diabetic nephropathy in db/db mice

Recent studies suggest a potential benefit of the lipid-lowering medication in the treatment of chronic kidney disease (CKD) such as diabetic nephropathy. Although statins have been widely used to lower serum cholesterol levels, the effect of these drugs on diabetic nephropathy has not been fully elucidated. In the present study, therefore, we addressed the role of different kinds of statins on diabetic nephropathy in db/db mice. Mice were fed with a standard diet with 0.005% (w/w) of pitavastatin, rosuvastatin, and pravastatin for 8 weeks starting from 8 weeks of age. The treatment with statins did not affect the food intake, body weight gain, adiposity, or blood pressure in db/db mice. Treatment with statins also had no effect on plasma lipid levels. In terms of the effect on albuminuria, pitavastatin and rosuvastatin reduced the urinary excretion of albumin by 60 and 40%, respectively, but not pravastatin, suggesting the effect of these two drugs on diabetic nephropathy. Furthermore, pitavastatin and rosuvastatin improved glomerular hypertrophy. All statins treatment improved insulin resistance. In addition, rosuvastatin and pravastatin treatment reduced oxidative stress measured by urinary 8-OHdG level, whereas the statins had no effect on the inflammatory response in the kidney of db/db mice. These results are not consistent with the renoprotective effect of statins. In conclusion, our data suggest that pitavastatin and rosuvastatin can improve diabetic nephropathy through the suppression of glomerular hypertrophy, independent of lipid-lowering or anti-oxidative effects.     

Ramipril improves oxidative stress-related vascular endothelial dysfunction in db/db mice

Endothelial dysfunction often precedes Type 2 diabetes-associated cardiovascular complications. One important cause of endothelial dysfunction is oxidative stress, which can lead to reduced nitric oxide (NO) bioavailability. In this study, we examined the effects of ramipril (an angiotensin-converting enzyme inhibitor, ACEI) on reactive oxygen species (ROS) production and endothelium-dependent vasodilation using a Type 2 diabetic (db/db) murine model. Plasma concentration of 8-isoprostane ([8-isoP]) was measured and used as an indication of the amount of ROS production. Six weeks of ramipril (10 mg/kg/day) treatment significantly reduced [8-isoP] and improved acetylcholine(ACh)-induced vasodilation in db/db mice without altering responses in wild-type (WT) mice. Responsiveness of smooth muscle cells to NO, assessed by sodium nitroprusside-induced vasodilation, was not different between db/db and WT mice regardless of ramipril or vehicle treatment. Our results suggest that ramipril specifically improved endothelium-dependent vasodilation in Type 2 diabetic mice, possibly by reducing ROS levels.