Hepato-protective effects of loganin, iridoid glycoside from Corni Fructus, against hyperglycemia-activated signaling pathway in liver of type 2 diabetic db/db mice

Accumulating evidence indicates that uncontrolled diabetes leads to the progression of diabetic complications such as liver disorder. The present study was carried out to elucidate the protective role of loganin extracted from Corni Fructus against hepatic oxidative stress caused by type 2 diabetes. Loganin (20 or 100 mg/kg body weight/day, p.o.) was administered every day for 8 weeks to db/db mice, and its effect was assessed on comparison with vehicle-treated db/db and m/m mice. The administration of loganin led to a decrease in glucose and elevation of leptin in serum. The diabetic oxidative stress was attenuated by loganin through inhibitions of reactive oxygen species production and lipid peroxidation in the serum and liver. The expression of proteins induced by oxidative stress was significantly up-regulated in the liver of diabetic db/db mice; however, the expressions of both Nox-4 and p22^phox were decreased significantly by loganin administration. Loganin showed a crucial effect in the inflammation-activated signaling pathway through the regulation of NF-κB, COX-2, and iNOS. It was also found to regulate the anti-inflammatory factors Nrf-2 and HO-1 in hepatic tissue. Moreover, expression of MCP-1 was significantly down-regulated in the loganin-treated db/db mice. Furthermore, loganin administration showed a protective effect against apoptosis by the regulation of Bcl-2 and cytochrome c. The present study demonstrated that the administration of loganin isolated from Corni Fructus had a protective effect against hepatic oxidative stress under type 2 diabetes through regulations of protein expressions related to oxidative stress, inflammation, and apoptosis.     

Effects of morroniside isolated from Corni Fructus on renal lipids and inflammation in type 2 diabetic mice

Objectives The effects of morroniside isolated from Corni Fructus on renal lipids and inflammation provoked by hyperglycaemia were investigated using type 2 diabetic mice. Methods Morroniside was administered orally to db/db mice at 20 or 100 mg/kg daily for 8 weeks, and its effects were compared with those in vehicle‐treated db/db and m/m (non‐diabetic) mice. Serum and renal biochemical factors and protein expression related to lipid homeostasis and inflammation were measured. Key findings Morroniside produced significant dose‐dependent reductions in serum triglyceride and renal glucose and lipid levels. Morroniside altered the abnormal protein expression of sterol regulatory element binding proteins (SREBP‐1 and SREBP‐2). In addition, the formation of reactive oxygen species and lipid peroxidation were inhibited in the morroniside‐treated db/db mouse group, and the ratio of reduced glutathione to the oxidised form was significantly elevated. These results suggest that morroniside alleviated oxidative stress in the kidneys of db/db mice. Furthermore, 100 mg/kg morroniside down‐regulated the expression of nuclear factor‐κBp65, cyclooxygenase‐2 and inducible nitric oxide synthase augmented in db/db mice. Conclusions Morroniside may inhibit abnormal lipid metabolism and inflammation due to reactive oxygen species in the kidneys in type 2 diabetes.     

Evaluation of morroniside, iridoid glycoside from Corni Fructus, on diabetes-induced alterations such as oxidative stress, inflammation, and apoptosis in the liver of type 2 diabetic db/db mice

The present study was conducted to examine whether morroniside has an ameliorative effect on diabetes-induced alterations such as oxidative stress, inflammation, and apoptosis in the liver of type 2 diabetic db/db mice. Morroniside (20 or 100 mg/kg body weight/d, per os (p.o.)) was administered every day for 8 weeks to db/db mice, and its effect was compared with vehicle-treated db/db and m/m mice. The administration of morroniside decreased the elevated serum glucose concentration in db/db mice, and reduced the increased oxidative biomarkers including the generation of reactive oxygen species and lipid peroxidation in the liver. The db/db mice exhibited the up-regulation of nicotinamide adenine dinucleotide phosphate oxidase subunits, NF-E2-related factor 2 (Nrf2), heme oxygenase-1, nuclear factor-kappa B, cyclooxygenase-2, inducible nitric oxide synthase, monocyte chemotactic protein-1, and intracellular adhesion molecule-1 levels in the liver; however, morroniside treatment significantly reduced those expressions. Moreover, the augmented expressions of apoptosis-related proteins, Bax and cytochrome c, were down-regulated by morroniside administration. Hematoxylin-eosin staining showed that the increased hepatocellular damage in the liver of db/db mice improved on morroniside administration. Taking these into consideration, our findings support the therapeutic evidence for morroniside ameliorating the development of diabetic hepatic complications via regulating oxidative stress, inflammation, and apoptosis.     

Kinetic and molecular docking studies of loganin and 7-O-galloyl-d-sedoheptulose from Corni Fructus as therapeutic agents for diabetic complications through inhibition of aldose reductase

Archives of Pharmacal Research - Aldose reductase (AR) is a key enzyme in the polyol pathway that is strongly implicated in the pathogenesis of diabetic complications. AR inhibitors have been...     

自发性2型糖尿病小鼠db/db的生物学特性

目的观察自发性2型糖尿病小鼠C57BK/KsJ-db/db的生物学特性。方法从第5周起,每周测定db/db及db/+小鼠体质量、随机血糖;从第6周起,每2周测定血清胰岛素、甘油三酯、胆固醇水平;从第8周起,每4周测定糖化血清蛋白含量;20周龄处死,脏器、脂肪称质量,部分组织用体积分数10%中性甲醛固定,制作病理切片。结果 db/db小鼠体质量、血糖、胰岛素、GSP、甘油三酯及总胆固醇水平均明显高于同龄同性别对照组;与同龄同性别对照组相比,db/db小鼠各脂肪系数显著增高,而脾脏及肾脏则相对萎缩,脾脏及雄性小鼠的肾脏与对照组相比差异极显著;db/db小鼠胰岛细胞明显肥大;肝细胞大片坏死,且伴随炎细胞浸润及严重脂肪变性;肾小球肥大,可见炎性细胞浸润;心肌细胞间隙增大,且发生肥大变性。结论 db/db小鼠在生长发育过程中表现出肥胖、高血糖、高胰岛素血症,GSP、甘油三酯、总胆固醇水平升高,胰岛功能不足,肝脏、肾脏、心脏病变,适用于进行2型糖尿病研究。     

自发性2型糖尿病模型db/db小鼠生物学特性研究

目的对db/db小鼠进行生物学特性研究,满足糖尿病研究的需要。方法在试验周期内,测定db/db小鼠的空腹血糖、体质量及摄食饮水量,并测定21周龄模型动物的糖耐量、血中胰岛素、胰高血糖素、三酰甘油、总胆固醇等指标的水平,进行胰腺的免疫组化双重染色及主要脏器的病理学检查,并与db/m小鼠进行比较。结果与对照组db/m小鼠比较,db/db小鼠过度肥胖,伴有高血糖、胰岛素抵抗、脂质代谢紊乱,且肝脏和胰腺组织均出现明显病变,胰腺免疫组化双重染色结果与血液学测定结果一致,并可观察到胰岛中A细胞和B细胞的分布变化情况。结论对自发性2型糖尿病模型db/db小鼠所做的相关生物学特性检测,可供糖尿病研究参考。     

藻酸双酯钠对2型糖尿病db/db小鼠的糖脂代谢及糖尿病肾病的影响△

目的研究藻酸双酯钠(PSS)对2型糖尿病db/db小鼠模型高血糖、高血脂及糖尿病肾病的影响。方法取db/db小鼠随机分成5组(n=12),分别为模型对照组(db/db,蒸馏水)、阳性对照组(db/db,二甲双胍)、PSS低、中、高剂量组(db/db,PS25,PS50,PS100)以及正常对照组(C57/BL,蒸馏水),各组小鼠自由饮食进水90天。实验期间,每天记录进食量,每周记录体重,定期测定空腹血糖和糖化血红蛋白水平,末次给药后收集小鼠24h的尿液,用于检测尿白蛋白以及尿肌酐水平。实验结束后,测定小鼠血清中甘油三酯(TG)、低密度脂蛋白(LDL-c)、高密度脂蛋白(HDL-c)、总胆固醇(TC)含量。结果PSS可以显著降低空腹血糖和糖化血红蛋白水平,提高胰岛素敏感性,并减少db/db小鼠的脂肪累积,显著改善db/db小鼠的血脂水平,缓解db/db小鼠糖尿病肾病症状。结论PSS能够显著改善db/db小鼠的糖脂代谢紊乱以及糖尿病肾病症状。     

Urocortin ameliorates diabetic nephropathy in obese db/db mice

BACKGROUND AND PURPOSE: Hyperglycaemia induces overproduction of mitochondrial reactive oxygen species (ROS) in endothelial cells, which is believed to be a major molecular mechanism underlying complications of diabetes, including diabetic nephropathy. Impairment of endothelium-dependent vasodilatation is found in type 2 diabetes. Urocortin is a 40 amino-acid peptide related to the corticotrophin-releasing factor (CRF) family, which suppresses production of ROS in endothelial cells and sustains endothelium-dependent relaxations of rat coronary artery. However, it is not clear if urocortin has any effect on diabetic nephropathy. EXPERIMENTAL APPROACH: Possible mechanisms underlying the effects of urocortin on diabetic nephropathy were investigated in db/db mice and cultured rat mesangial cells. KEY RESULTS: Urocortin decreased body weight, plasma levels of advanced glycation end-products, blood urea nitrogen and creatinine levels. However, food intake, plasma insulin and glucose levels remained unaffected. Superoxide dismutase activity was increased markedly, whereas malonaldehyde levels in kidney homogenate and sorbitol concentrations in red blood cells were decreased significantly in urocortin-treated mice. Urocortin significantly decreased glomerular extracellular matrix expansion and accumulation in kidney. Moreover, urocortin inhibited the overexpression of transforming growth factor-beta 1 and connective tissue growth factor in rat mesangial cells induced by 25 mM glucose. All the effects of urocortin, except sorbitol accumulation, were abolished by the non-selective CRF receptor blocker, astressin. CONCLUSION AND IMPLICATIONS: Urocortin could significantly ameliorate diabetic nephropathy and this effect was mediated via the CRF receptor.     

NFAT2 inhibitor ameliorates diabetic nephropathy and podocyte injury in db/db mice

BACKGROUND AND PURPOSE

Podocyte injury plays a key role in the development of diabetic nephropathy (DN). We have recently shown that 11R-VIVIT, an inhibitor of cell-permeable nuclear factor of activated T-cells (NFAT), attenuates podocyte apoptosis induced by high glucose in vitro. However, it is not known whether 11R-VIVIT has a protective effect on DN, especially podocyte injury, under in vivo diabetic conditions. Hence, we examined the renoprotective effects of 11R-VIVIT in diabetic db/db mice and the possible mechanisms underlying its protective effects on podocyte injury in vivo and in vitro.

EXPERIMENTAL APPROACH

Type 2 diabetic db/db mice received i.p. injections of 11R-VIVIT (1 mg·kg⁻¹) three times a week and were killed after 8 weeks. Immortalized mouse podocytes were cultured under different experimental conditions.

KEY RESULTS

11R-VIVIT treatment markedly attenuated the albuminuria in diabetic db/db mice and also alleviated mesangial matrix expansion and podocyte injury. However, body weight, food and water intake, and glucose levels were unaffected. It also attenuated the increased NFAT2 activation and enhanced urokinase-type plasminogen activator receptor (uPA receptor) expression in glomerulor podocytes. In cultured podocytes, the increased nuclear accumulation of NFAT2 and uPA receptor expression induced by high glucose treatment was prevented by 11R-VIVIT or NFAT2-knockdown; this was accompanied by improvements in the filtration barrier function of the podocyte monolayer.

CONCLUSIONS AND IMPLICATIONS

The NFAT inhibitor 11R-VIVIT might be a useful therapeutic strategy for protecting podocytes and treating DN. The calcinerin/NFAT2/uPA receptor signalling pathway should be exploited as a therapeutic target for protecting podocytes from injury in DN.     

荞麦花叶发酵提取物对2型糖尿病db/db小鼠心肌损伤的影响

目的探讨荞麦花叶发酵提取物(EFBFL)对自发肥胖2型糖尿病db/db小鼠心肌损伤的保护作用及其可能的机制。方法 9周龄♂db/db小鼠随机分为EFBFL高(EFBFL-H,0.1 g·kg~(-1))、低(EFBFL-L,0.05 g·kg~(-1))剂量组,二甲双胍对照组,模型对照组,每组10只。同时以10只db/m小鼠为正常对照组。各组均每天灌胃给药1次,连续8周。于给药前及给药后第2、4、6、8周末检测小鼠随机血糖(RBG),8周后处死取血清检测肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)和糖基化终末代谢产物(AGEs)含量;HE染色光镜下观察心肌组织形态学改变,电镜下观察心肌超微结构;免疫组化法和Western blot法检测心肌组织葡萄糖转运蛋白4(Glut4)表达。结果 EFBFL能有效抑制db/db小鼠心肌细胞损伤及心肌纤维化的病理进程,降低小鼠血糖及血清中CK、CK-MB、AGEs的含量,增加小鼠心肌组织Glut4蛋白表达水平。结论 EFBFL对自发肥胖2型糖尿病db/db小鼠心肌损伤具有抑制作用,其机制可能与降低小鼠血糖、抑制AGEs的产生及促进心肌细胞Glut4蛋白的表达有关。     

Roles of coagulation pathway and factor Xa in the progression of diabetic nephropathy in db/db mice

The active type of coagulation factor X (factor Xa) activates various cell-types through protease-activated receptor 2 (PAR2). We previously reported that a factor Xa inhibitor could suppress Thy-1 nephritis. Considering that fibrin deposition is observed in diabetic nephropathy as well as in glomerulonephritis, this study examined the roles of the coagulation pathway and factor Xa in the development of diabetic nephropathy using type 2 diabetic model mice. Diabetic (db/db) and normoglycemic (m+/m+) mice were immunohistochemically evaluated for their expression/deposition of PAR2, transforming growth factor (TGF)-β, fibrin, extracellular matrix (ECM) proteins, and CD31 at week 20. Significantly greater numbers of PAR2-positive cells and larger amounts of fibronectin, and collagen IV depositions were observed in the glomeruli of db/db mice than those in m+/m+ mice. Next, expression of PAR2 versus deposition of collagen IV and fibronectin was compared between week 20 and week 30, and the number of PAR2-positive cells in the glomeruli decreased in contrast with the increased accumulation of ECM proteins. In an intervention study, fondaparinux, a factor Xa inhibitor, was subcutaneously administered for ten weeks from week 10 to 20. Fondaparinux treatment significantly suppressed urinary protein, glomerular hypertrophy, fibrin deposition, expression of connective tissue growth factor, and ECM proteins deposition together with CD31-positive capillaries. These results suggest that coagulation pathway and glomerular PAR2 expression are upregulated in the early phase of diabetes, together with the increase of profibrotic cytokines expression, ECM proteins deposition and CD-31-positive vessels. Factor Xa inhibition may ameliorate glomerular neoangiogenesis and ECM accumulation in diabetic nephropathy.     

Effect of 2-dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione,isolated from Averrhoa carambola L. (Oxalidaceae) roots,on advanced glycation end-product-mediated renal injury in type 2 diabetic KKAy mice

The roots of Averrhoa carambola L. (Oxalidaceae) have a long history of medical use in traditional Chinese medicine for treating diabetes and diabetic nephropathy. 2-Dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione (DMDD) was isolated from the tuberous roots of A. carambola L. The purpose of this study was to investigate the beneficial effect of DMDD on the advanced glycation end-product-mediated renal injury in type 2 diabetic KKAy mice with regard to prove its efficacy by local traditional practitioners in the treatment of kidney frailties in diabetics. KKAy mice were orally administrated DMDD (12.5, 25, 50 mg/kg body weight/d) or aminoguanidine (200 mg/kg body weight/d) for 8 weeks. Hyperglycemia, renal AGE formation, and the expression of related proteins, such as the AGE receptor, nuclear factor-κB, transforming growth factor-β1, and N^ε-(carboxymethyl)lysine, were markedly decreased by DMDD. Diabetes-dependent alterations in proteinuria, serum creatinine, creatinine clearance, and serum urea-N and glomerular mesangial matrix expansion were attenuated after treatment with DMDD for 8 weeks. The activities of superoxide dismutase and glutathione peroxidase, which are reduced in the kidneys of KKAy mice, were enhanced by DMDD. These findings suggest that DMDD may inhibit the progression of diabetic nephropathy and may be a therapeutic agent for regulating several pharmacological targets to treat or prevent of diabetic nephropathy.     

Akt/eNOS pathway activation in endothelium-dependent relaxation is preserved in aortas from female, but not from male, type 2 diabetic mice

Cardiovascular problems are major causes of morbidity and mortality, the main problems being coronary artery disease and atherosclerosis, in type 2 diabetes mellitus. However, female gender is a protective factor in the development of, for example, atherosclerosis and hypertension. Our aim was to investigate possible gender differences in the activation of Akt/eNOS signaling in aortas from a mouse type 2 diabetic model. Nonfasting plasma glucose was significantly above control in the diabetic mice (both males and females). Plasma insulin was not different between the age-matched controls and the diabetic mice (of either gender). In diabetic males (vs male controls and/or diabetic females): (a) systemic blood pressure was elevated, (b) the clonidine- and insulin-induced Akt-dependent aortic relaxations were impaired, but the ACh-induced Akt-independent and SNP-induced endothelium-independent aortic relaxations were not, (c) Akt and eNOS expression levels were lower, (d) both Akt phosphorylation at Ser(473) and eNOS phosphorylation at Ser(1177) in the aorta were lower under clonidine- or insulin-stimulation, but not under ACh-stimulation. These results suggest that in mice: (i) endothelial functions mediated via the Akt/eNOS pathway are abrogated in type 2 diabetes only in males and (ii) in females (vs males), eNOS expression is elevated and the endothelium resists dysfunction.     

Angiotensin II type 2 receptor-dependent increase in nitric oxide synthase activity in the endothelium of db/db mice is mediated via a MEK pathway

Angiotensin II type 2 receptor (AT(2)R) stimulation may cause vasodilation. It could thereby contribute to the antihypertensive effects of angiotensin II type 1 receptor (AT(1)R) antagonists since AT(1)R blockade reportedly increases endogenous levels of Ang II, and this may then bind to the unblocked AT(2)R. Because this is potentially an important consideration in diabetes, we examined whether or not AT(2)R mediates vasorelaxation in db/db diabetic mice. We also examined if AT(2)R-mediated vasorelaxation is preserved after long-term treatment with the AT(1)R antagonist losartan. The effects of AT(2)R stimulation, with either Ang II or the selective agonist CGP-42112A, were studied in aortas from db/db mice (a type 2 diabetic model). CGP-42112A induced a concentration-dependent relaxation in db/db aortas (not in Lean aortas), and this was significantly weakened by the MEK-inhibitor PD98059. CGP-42112A-induced relaxations were increased by Ang II-stimulation (by the organ-culture method) or by AT(1)R blockade (by long-term losartan treatment) only in Lean aortas. Basal AT(2)R expression, and Ang II-stimulated MEK and eNOS phosphorylations were all increased in aortas from db/db (vs. Lean) mice. Long-term losartan treatment increased Ang II-stimulated MEK and eNOS phosphorylations in aortas from Lean, but not db/db, mice. Therefore, this study has provided evidence that AT(2)R-mediated NO production and vasorelaxation through a MEK pathway are enhanced (under basal conditions) in aortas from db/db (vs. Lean) mice. The preservation of such AT(2)R function during AT(1)R blockade needs to be considered in the search for a physiological role for AT(2)R.     

基因缺陷型2型糖尿病模型动物db/db小鼠早期生物学特性研究

目的研究基因缺陷型2型糖尿病模型动物db/db小鼠的早期生物学特性,为db/db小鼠应用于降糖药物的研究奠定基础。方法采用db/db小鼠为模型组动物,db/m小鼠为对照组动物,测定两组小鼠的体质量、食量、饮水量、空腹血糖、正常饮食血糖、糖耐量、胰岛素耐量;于第14周眼底静脉丛取血,分离血清,测定糖化血清蛋白（GSP）、三酰甘油（TG）、总胆固醇（TC）;取肝、胰腺、腹部脂肪等主要脏器组织进行组织病理学检查。结果与对照组比较,db/db小鼠体质量、食量、饮水量显著增加;空腹血糖及正常饮食血糖显著升高,整个实验期血糖水平稳定;糖耐量异常、胰岛素耐量异常,对外源胰岛素敏感性显著降低;血清GSP、TG、TC含量显著升高,腹部脂肪质量显著增加,肝组织不同程度的空泡变性,脂肪组织中脂肪细胞体积增大,胰腺中胰岛细胞胞浆减少、血管扩张。结论 db/db小鼠早期脂质代谢紊乱,血糖、血脂显著升高,糖耐量及胰岛素耐量异常,血糖水平稳定,是研究2型糖尿病较为理想的模型。     

Total triterpene acids,active ingredients from Fructus Corni,attenuate diabetic cardiomyopathy by normalizing ET pathway and expression of FKBP12.6 and SERCA2a in streptozotocin‐rats

Total triterpene acids (TTAs) isolated from Cornus officinalis Sieb., one of the herbs contained in Liuwei Dihuang decoction, were aimed at alleviating diabetic cardiomyopathy. We hypothesized that the benefits of TTAs may result from suppressing the endothelin‐reactive oxidative species (ET‐ROS) pathway in the myocardium. Diabetes was produced by a single injection of streptozotocin (STZ, 60 mg kg⁻¹, i.p.) in rats. Assessment of cardiac function, calcium handling proteins, endothelin‐1 (ET‐1) and redox system was conducted 8 weeks after STZ injection. Medication with TTAs (50 mg kg⁻¹, i.g.) was installed in the last 4 weeks. The compromised cardiac function was characterized by depressed contractility (LVSP and LV+dp/dt_max) and relaxation (LVEDP and ‐LVdp/dt_min) in association with hyperglycaemia (30.2 ± 2.6 mmol L⁻¹) in STZ‐injected rats. Down‐regulated expression of FKBP12.6 (calstabin 2), sarcoplasmic reticulum Ca²⁺‐ATPase 2a (SERCA2a) and phospholamban (PLB) were also found. These changes occurred in connection with an increased ET‐1, up‐regulated mRNA of propreET‐1 and endothelin converting enzyme (ECE), and a state of oxidant stress was found by increased malondialdehyde (MDA), decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH‐px) activity, and an enhanced activity and expression of inducible nitric oxide synthase (iNOS) in the diabetic myocardium. After 4 weeks of treatment with TTAs, these changes were alleviated dramatically despite a mild reduction in hyperglycaemia (26.9 ± 3.4 mmol L⁻¹). In conclusion, TTAs, as active ingredients of Liuwei Dihuang decoction, alleviated diabetic cardiomyopathy by normalizing the abnormality of FKBP12.6 and SERCA2a and ET‐ROS pathway in the myocardium rather than by hypoglycaemic activity.     

Preservative effect of electrolyzed reduced water on pancreatic beta-cell mass in diabetic db/db mice

Oxidative stress is produced under diabetic conditions and involved in progression of pancreatic beta-cell dysfunction. Both an increase in reactive oxygen free radical species (ROS) and a decrease in the antioxidant defense mechanism lead to the increase in oxidative stress in diabetes. Electrolyzed reduced water (ERW) with ROS scavenging ability may have a potential effect on diabetic animals, a model for high oxidative stress. Therefore, the present study examined the possible anti-diabetic effect of ERW in genetically diabetic mouse strain C57BL/6J-db/db (db/db). ERW with ROS scavenging ability reduced the blood glucose concentration, increased blood insulin level, improved glucose tolerance and preserved beta-cell mass in db/db mice. The present data suggest that ERW may protects beta-cell damage and would be useful for antidiabetic agent.