The peel of Citrus kawachiensis (kawachi bankan) ameliorates microglial activation,tau hyper-phosphorylation,and suppression of neurogenesis in the hippocampus of senescence-accelerated mice

We previously reported that the dried peel powder of Citrus kawachiensis, one of the citrus products of Ehime, Japan, exerted anti-inflammatory effects in the brain of a lipopolysaccharide-injected systemic inflammation animal model. Inflammation is one of the main mechanisms underlying aging in the brain; therefore, we herein evaluated the anti-inflammatory and other effects of the dried peel powder of C. kawachiensis in the senescence-accelerated mouse-prone 8 (SAMP8) model. The C. kawachiensis treatment inhibited microglial activation in the hippocampus, the hyper-phosphorylation of tau at 231 of threonine in hippocampal neurons, and ameliorated the suppression of neurogenesis in the dentate gyrus of the hippocampus. These results suggest that the dried peel powder of C. kawachiensis exert anti-inflammatory and neuroprotective effects.     

Neuroprotective effect of Citrus kawachiensis (Kawachi Bankan) peels,a rich source of naringin,against global cerebral ischemia/reperfusion injury in mice

Cerebral ischemia/reperfusion is known to induce the generation of reactive oxygen species and inflammatory responses. Numerous studies have demonstrated that naringin (NGIN) has anti-oxidant and anti-inflammatory properties. We previously reported that Citrus kawachiensis contains a large quantity of NGIN in its peel. In the present study, we orally (p.o.) administered dried peel powder of C. kawachiensis to mice of a transient global ischemia model and found in the hippocampus region that it 1) suppressed neuronal cell death, 2) reversed the reduction in the level of phosphorylated calcium-calmodulin-dependent protein kinase II, 3) had the tendency to reverse the reduction in the level of glutathione, and 4) blocked excessive activation of microglia and astrocytes. These results suggested that the dried peel powder of C. kawachiensis had a neuroprotective effect against ischemic brain via anti-oxidative and anti-inflammatory effects. We also showed that these effects of the dried peel powder were more powerful than those obtained with a comparable amount of NGIN alone.     

Hepatic glycogen metabolism in the db/db mouse

Summary Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2–15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen synthase activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in V_max, and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios. Its use should clarify the regulation of hepatic glycogen metabolism and other metabolic processes known to be controlled by these hormones. The other animal models of type 2 diabetes, ob/ob mouse and fatty Zucker (fa/fa) rat, show similar impairment of hepatic glycogen metabolism. The concentrations of glycogen metabolizing enzymes are high and in vitro studies indicate enhanced rate of glycogen synthesis and breakdown. However, streptozotocin-induced diabetic animals and BB rats which resemble insulin-deficient type 1 diabetes are characterized by decreased glycogen turnover as a result of reduction in the levels of glycogen metabolizing enzymes.     

Gene Expression of Inflammatory Cytokines in Peripheral Leukocytes in db/db Mice Rose with Progression of Diabetes

Fourteen-week-old db/db mice showed significant higher blood glucose levels than 7 week-old mice. The mRNA levels of IL-1β and S100a4/a6/a9 in peripheral leukocytes were higher in 14 week-old mice than in 7 week-old mice. Together, inflammatory cytokine/cytokine-like factor mRNA levels in peripheral leukocytes were associated with progression of diabetes in db/db mice.     

Structural,metabolic and endocrine analysis of the diabetes (db/db) hypogonadal syndrome: relationship to hypophyseal hypercytolipidemia

Expression of the diabetes (db/db) mutation in C57BL/KsJ mice results in functional suppression of the female pituitary-gonadal axis accompanied by premature utero-ovarian cytolipoatrophy. Cellular gluco- and lipo-metabolic disturbances promoted by the db/db systemic hyperglycemic-hyperinsulinemic state suppress pituitary gonadotropin release in response to gonadotropin-releasing hormone and gonadal steroid stimulation and results in a hypogonadal-infertility syndrome. Adult female C57BL/KsJ control (+/+ and +/? genotypes) and db/db littermates were monitored for associations in systemic and cellular alterations in luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadal steroid (binding) levels, and pituitary glucometabolic indices associated with db/db-enhanced lipid imbibition and cytostructural disruption. Obesity, hyperglycemia, and hyperinsulinemia characterized all db/db mutants relative to controls. Serum and pituitary progesterone and estradiol concentrations were suppressed in db/db mutants, in association with serum LH and FSH levels, but not with pituitary LH and FSH concentrations, which were comparable between groups. Pituitary insulin receptor binding and glucose utilization rates were suppressed in db/db groups relative to +/? indices. Structural and cytochemical analysis of anterior (AP), intermediate (IL), and neuro-(NP) hypophyseal lobes demonstrated prominent hypercytolipidemia in db/db mutants relative to controls. Prominent cytolipidemia was localized within well-granulated basophilic gonadotrophs and within IL and NP pituicytes. Vasolipidemia and interstitial cytoadiposity were prominent throughout all db/db pituitary lobes. Thus, disturbances associated with pituitary hypercytolipidemia are functional components of the expressed diabetes-associated hypogonadal syndrome in db/db mutants. Progressive alterations in hypophyseal cytoarchitecture are correlated with suppression of pituitary metabolic and endocrine indices, alterations that contribute to functional disruption of the pituitary-hypogonadal axis in C57BL/KsJ-db/db mice.

     

过敏毒素受体(C3aR)在db/db糖尿病肾病小鼠肾脏中的表达及病理意义分析

利用半定量RT-PCR、免疫组化和Western blotting的方法,同时从mRNA水平和蛋白质水平对过敏毒素受体(C3aR)在不同病理阶段的2型糖尿病肾病模型小鼠——db/db小鼠肾脏中的表达情况进行了较为系统的分析．结果发现：a．在糖尿病前的db/db小鼠(4周龄的db/db小鼠),C3aR与作为正常对照的db/m小鼠相比没有明显差异．随着肥胖的加剧,高血糖、蛋白尿的发生和发展,C3aR在db/db小鼠肾脏中的表达显著升高．b．免疫组化分析显示,C3aR广泛地表达于db/m和db/db小鼠肾脏的皮质和髓质,分布于肾脏的上皮细胞中(包括肾小管上皮细胞、肾小球中的脏层上皮细胞(足细胞)和壁层上皮细胞)．从部位来看,皮髓交界处的肾小管中C3aR表达量明显要比其他部位的多．在肾小球,C3aR特异地存在于足细胞部位．在db/m小鼠,不同周龄小鼠肾脏中C3aR的表达量并没有明显变化,但在db/db小鼠,从8周龄开始,分布在db/db小鼠肾小管上皮细胞和小球足细胞中的C3aR均随小鼠周龄的增加而增加,至少在时间上,与小鼠糖尿病肾病的发生发展相关,其中尤以足细胞中和皮髓交界处肾小管上皮细胞中的变化最为明显． c．在糖尿病肾病小鼠中高表达C3aR的肾小管上皮细胞常有空泡变性的情况．上述工作印证了先前对2型糖尿病肾病患者肾小球基因表达谱的分析结果,更加明确了C3aR与糖尿病肾病的相关性,同时揭示了C3aR在正常小鼠和糖尿病肾病小鼠肾脏中的表达、分布和变化规律,有利于进一步揭示C3aR的功能及其在糖尿病肾病发生、发展过程中的可能作用,探讨糖尿病肾病的分子机制．     

Involvement of heparan sulfate in the renoprotective effects of imidapril,an angiotensin-converting enzyme inhibitor,in diabetic db/db mice

Abstract

We investigated the renoprotective effects of imidapril hydrochloride ((-)-(4?S)-3-[(2?S)-2-[[(1?S)-1-ethoxycarbonyl-3-phenylpropyl] amino] propionyl]-1-methyl-2-oxoimidazolidine-4-carboxylic acid hydrochloride, imidapril), an angiotensin-converting enzyme inhibitor, in a diabetic animal model. We used BKS.Cg-+Lepr^db/+Lepr^db (db/db) mice, a genetic animal model of obese type 2 diabetes. Diabetic db/db mice suffered from glomerular hyperfiltration, albuminuria and hypoalbuminemia. Oral administration of 5?mg/kg/day of imidapril for 3 weeks suppressed renal hyperfiltration, reduced albuminuria and normalized hypoalbuminemia. Imidapril did not influence body weights, blood pressure or blood glucose concentrations in db/db mice. Urinary excretion of heparan sulfate (HS) in non-treated 11-week-old db/db mice was significantly lower than that in age-matched non-diabetic db/+m mice. HS is a component of HS proteoglycans, which are present in glomerular basement membranes and glycocalyx of cell surfaces. Reduced urinary HS excretion indicated glomerular HS loss in db/db mice. Imidapril increased urinary excretion of HS to concentrations observed in db/+m mice, indicating that imidapril prevented the loss of renal HS. These results suggest that imidapril ameliorates renal hyperfiltration and loss of renal contents of HS. Improvement of filtration function and maintenance of HS, which is an important structural component of glomeruli, may contribute to renoprotective effects of imidapril.     

松果菊苷对db/db糖尿病小鼠心肌的保护作用

糖尿病心肌病（diabetic cardiomyopathy, DCM）是指发生于糖尿病患者,不能用冠心病、高血压性心脏病及其他心脏病变来解释的心肌疾病。目前,DCM的病因和发病机制尚未完全阐明,且缺乏特异性治疗手段。中药管花肉苁蓉提取物松果菊苷（echinacoside, ECH）对心肌细胞具有保护作用。以db/m小鼠为正常对照组（db/m组）,db/db小鼠分为模型组（db/db组）和ECH干预组（db/db+ECH组）,探讨了ECH对糖尿病db/db小鼠心肌的影响及机制。db/db+ECH组小鼠给予松果菊苷灌胃,db/m组和db/db组小鼠给予0.9%氯化钠溶液灌胃。心脏超声观察心脏功能,Masson染色观察组织胶原纤维含量,逆转录聚合酶链式反应检测Ⅰ型胶原和Ⅲ型胶原mRNA的表达,蛋白质免疫印迹技术检测转化生长因子-β1（transforming growth factor-β1, TGF-β1）、phospho-Smad2（p-Smad2）和phospho-Smad3（p-Smad3）的表达。结果显示,ECH能够改善db/db小鼠左心室肥大和心脏功能,降低胶原沉积（P<0.05）。ECH能够降低Ⅰ型和Ⅲ型胶原mRNA的表达（P<0.01）,下调TGF-β1、p-Smad2和p-Smad3蛋白的表达（P<0.05）。ECH对糖尿病心肌的保护作用可能与负反馈调节TGF-β1/Smads信号通路相关,研究结果为DCM的早期干预提供了新思路。     

Alterations of the Ca2+ signaling pathway in pancreatic beta-cells isolated from db/db mice

Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca²⁺-dependent manner. In diabetic animal models, different aspects of the calcium signaling pathway in beta-cells are altered, but there is no consensus regarding their relative contributions to the development of beta-cell dysfunction. In this study, we compared the increase in cytosolic Ca²⁺ ([Ca²⁺]_i) via Ca²⁺ influx, Ca²⁺ mobilization from endoplasmic reticulum (ER) calcium stores, and the removal of Ca²⁺ via multiple mechanisms in beta-cells from both diabetic db/db mice and nondiabetic C57BL/6J mice. We refined our previous quantitative model to describe the slow [Ca²⁺]_i recovery after depolarization in beta-cells from db/db mice. According to the model, the activity levels of the two subtypes of the sarco-endoplasmic reticulum Ca²⁺-ATPase (SERCA) pump, SERCA2 and SERCA3, were severely down-regulated in diabetic cells to 65% and 0% of the levels in normal cells. This down-regulation may lead to a reduction in the Ca²⁺ concentration in the ER, a compensatory up-regulation of the plasma membrane Na⁺/Ca²⁺ exchanger (NCX) and a reduction in depolarizationevoked Ca²⁺ influx. As a result, the patterns of glucosestimulated calcium oscillations were significantly different in db/db diabetic beta-cells compared with normal cells. Overall, quantifying the changes in the calcium signaling pathway in db/db diabetic beta-cells will aid in the development of a disease model that could provide insight into the adaptive transformations of beta-cell function during diabetes development.     

Dehydroepiandrosterone decreases elevated hepatic glucose production in C57BL/KsJ-db/db mice

Dehydroepiandrosterone (DHEA) is known to improve hyperglycemia in diabetic db/db mice that are obese and insulin resistant. In a previous study, we reported that DHEA suppresses the elevated hepatic gluconeogenic glucose-6-phosphatase (G6Pase) activity and gene expression in C57BL/KsJ-db/db mice. In the present study, we evaluated the total amount of gluconeogenesis using NaH[(14)C]CO(3) and hepatic glucose production using fructose as a substrate in primary cultured hepatocytes. Despite hyperinsulinemia, the glucose production of db/db mice in the total body and hepatocytes was elevated as compared to their heterozygote littermate C57BL/KsJ-db/+m mice. Administration of DHEA significantly decreased the blood glucose level and increased the plasma insulin level in db/db mice. Administration of DHEA decreased the elevated total body and hepatic glucose production in db/db mice. In addition, the glucose production in the primary cultured hepatocytes of db/db mice was decreased significantly by the direct addition of DHEA or DHEA-S to the medium. These results suggest that administration of DHEA suppresses the elevated total body and hepatic glucose production in db/db mice, and this effect on the liver is considered to result from increased plasma insulin and DHEA or DHEA-S itself.     

诱发性2型糖尿病小鼠模型与自发性db/db小鼠特性的比较

目的建立诱发性2型糖尿病小鼠模型,并将其与自发性2型糖尿病小鼠db/db进行比较分析。客观评价两种2型糖尿病小鼠模型,为糖尿病研究中动物模型的选择与实际应用提供实验依据。方法高脂饲料喂养C57BL/6J小鼠4周,腹腔连续3次注射STZ,建立诱发性2型糖尿病小鼠模型。感染后4周,大体肉眼观察小鼠的肝脏、肾脏,测定糖耐量,血清生化指标及血清细胞因子IL-2、IL-4、IL-6、IFN-γ、TNF-α、IL-17、IL-10表达量,将其与同龄的自发性2型糖尿病小鼠db/db进行比较分析。结果肉眼观察发现,两组模型小鼠的肝脏、肾脏与对照组均具有明显差异。糖耐量分析中,两组模型小鼠与对照组小鼠各时间点的血糖值均具有统计学差异（P〈0.05）,耐糖功能低下,两组模型小鼠间血糖值无统计学差异。血液生化指标中,与对照组小鼠相比,两组模型小鼠GLU、CHOL、LDLC明显升高（P〈0.05）;两组模型小鼠相互比较,诱发性2型糖尿病小鼠血脂水平较高（P〈0.05）。免疫指标比较显示：除IL-2外,两组模型小鼠血清中细胞因子水平均较对照组小鼠明显升高（P〈0.05）,而db/db小鼠血清中细胞因子表达较诱发性糖尿病小鼠高,其中IL-6、IFN-γ、TNF-α具有显著性差异（P〈0.05）。结论两组2型糖尿病模型小鼠均在一定程度上模拟了人类糖尿病患者症状,但由于糖尿病产生的原因不同而存在着一定的差异,研究者可根据实际需要参照相关数据进行选择。     

Citrus unshiu peel extract ameliorates hyperglycemia and hepatic steatosis by altering inflammation and hepatic glucose- and lipid-regulating enzymes in db/db mice

Insulin resistance in Type 2 diabetes leads to hepatic steatosis that can accompanied by progressive inflammation of the liver. Citrus unshiu peel is a rich source of citrus flavonoids that possess anti-inflammatory, anti-diabetic and lipid-lowering effects. However, the ability of citrus unshiu peel ethanol extract (CPE) to improve hyperglycemia, adiposity and hepatic steatosis in Type 2 diabetes is unknown. Thus, we evaluated the effects of CPE on markers for glucose, lipid metabolism and inflammation in Type 2 diabetic mice. Male C57BL/KsJ-db/db mice were fed a normal diet with CPE (2 g/100 g diet) or rosiglitazone (0.001 g/100 g diet) for 6 weeks. Mice supplemented with the CPE showed a significant decrease in body weight gain, body fat mass and blood glucose level. The antihyperglycemic effect of CPE appeared to be partially mediated through the inhibition of hepatic gluconeogenic phosphoenolpyruvate carboxykinase mRNA expression and its activity and through the induction of insulin/glucagon secretion. CPE also ameliorated hepatic steatosis and hypertriglyceridemia via the inhibition of gene expression and activities of the lipogenic enzymes and the activation of fatty acid oxidation in the liver. These beneficial effects of CPE may be related to increased levels of anti-inflammatory adiponectin and interleukin (IL)-10, and decreased levels of pro-inflammatory markers (IL-6, monocyte chemotactic protein-1, interferon-γ and tumor necrosis factor-α) in the plasma or liver. Taken together, we suggest that CPE has the potential to improve both hyperglycemia and hepatic steatosis in Type 2 diabetes.     

姜黄素对db/db小鼠基因组DNA甲基化的影响

目的:观察姜黄素对2型糖尿病模型db/db小鼠糖尿病症状的改善作用,并从表观遗传角度分析其对小鼠外周血DNA甲基化水平的影响。方法:2型糖尿病模型db/db小鼠随机分为糖尿病组和姜黄素干预组(给予250 mg/kg姜黄素溶液),连续灌胃8周。OGTT检测葡萄糖耐量,ELISA法测定空腹胰岛素并计算HOMA-IR和HOMA-β,RRBS技术检测外周血基因组DNA甲基化水平。结果:与糖尿病组相比,姜黄素干预小鼠的血糖、空腹胰岛素和HOMA-IR显著降低,葡萄糖耐量显著改善(P<0.05);且小鼠外周血基因组启动子区、CGI岸和5’-非编码区CpG甲基化水平显著降低(P<0.05);对两组间差异甲基化基因进行功能富集分析,筛选出前10位显著富集的可能与2型糖尿病相关的差异基因包括Hdac7、Micall1、Vangl2、Dhcr24、Kcnj8、Gnas、Tcf7l2、Dgkh、Dlgap1和Plekhg4。结论:姜黄素能够改善db/db小鼠的葡萄糖耐量及胰岛素抵抗,并且其外周血中存在显著低甲基化改变,提示姜黄素可能是通过抑制糖尿病小鼠中某些基因的异常甲基化修饰而发挥抗糖尿病作用。     

Expressional changes of ganglioside GM3 during ovarian maturation and early embryonic development in db/db mice

Diabetes and obesity cause abnormal development of reproductive processes in a variety of species, but the mechanisms that underlie this effect have not been fully elucidated. This study examined the expressional changes of ganglioside GM3 during ovarian maturation, in vitro fertilization (IVF) and early embryonic development in diabetic/obese db/db mice. In high-performance thin-layer chromatography studies, GM3 expression was conspicuously low in the ovaries of db/db mice compared to non-diabetic db/+ mice. Signal detected by anti-GM3 monoclonal antibody was greatly reduced in the primary, secondary and graffian follicles of db/db mice compared to control mice. Results from IVF with ova and sperm from db/db mice showed that GM3 expression during early embryonic development was obviously decreased compared to db/+ mice. This study also elucidated the effects of high glucose (20 and 30 mm) on early embryonic development in ICR strain mice. High glucose caused a decrease in GM3 expression during early embryonic development. Taken together, the results of this study indicate decreased GM3 expression during ovarian maturation and embryonic development of db/db mice, suggesting that alteration of ganglioside expression induced by the diabetic condition may be implicated in the abnormal follicular embryonic development.     

血管生成素样蛋白2在糖尿病肾病小鼠肾脏中的表达研究

利用半定量RT-PCR和免疫组化的方法同时从mRNA水平和蛋白质水平对血管生成素样蛋白2在不同病理阶段的2型糖尿病肾病模型小鼠--db/db小鼠肾脏中的表达情况进行了较为系统的分析.结果发现:a.在糖尿病前的db/db小鼠(4周龄的db/db小鼠),血管生成素样蛋白2与作为正常对照的db/m小鼠相比,差异不是很大,随着肥胖的加剧,高血糖、蛋白尿的出现,血管生成素样蛋白2在db/db小鼠肾脏中的表达无论从mRNA水平还是从蛋白质水平均显著升高.b.从免疫组化的分析结果来看,血管生成素样蛋白2主要分布于小鼠肾脏的肾小球部分,主要是沿毛细血管袢呈线性分布,其位置与足细胞的位置重叠,足细胞是小鼠肾脏中血管生成素样蛋白2的主要分泌细胞.c.小鼠肾脏血管生成素样蛋白2的表达水平似乎还与鼠龄相关:虽然变化幅度不是很大,但在周龄较大的小鼠(如20周龄以上),其表达水平相对较高.上述工作不仅印证了先前对2型糖尿病肾病患者肾小球基因表达谱的分析结果,更加明确了血管生成素样蛋白2与糖尿病肾病的相关性,同时揭示了血管生成素样蛋白2在正常小鼠和糖尿病肾病小鼠肾脏中的表达、分布和变化规律,有利于进一步揭示血管生成素样蛋白2的功能及其在糖尿病肾病发生、发展过程中的可能作用,探讨糖尿病肾病的分子机制.     

AL023001基因在2型糖尿病肾病小鼠中的差异表达分析

利用Affymetrix寡核苷酸基因表达谱芯片对2型糖尿病肾病模型动物——db/db小鼠的肾脏基因表达谱进行了研究.在此基础上,利用末端快速扩增法和RT-PCR的方法,对筛选出来的一个糖尿病肾病相关EST进行了cDNA克隆和表达分析.得到了一长为1.7 kb的cDNA片段.序列分析和网上数据库比对发现,此cDNA片段是小鼠表达序列AL023001的一部分.根据AL023001序列设计特异性引物,利用半定量RT-PCR的方法对AL023001在db/db小鼠肾脏、肝脏、脂肪、骨胳肌、脑等组织中的表达情况进行了分析,发现AL023001在db/db小鼠肾脏中的表达情况与基因芯片检测结果吻合,且AL023001在肝脏、脂肪、骨胳肌和脑等糖尿病肾病相关联组织中均有差异表达.这些结果提示：AL023001与db/db小鼠的糖尿病肾病具有相关性.上述工作有利于揭示AL023001基因的功能,探讨糖尿病肾病的分子机制.     

C-Fos在db/db自发性糖尿病小鼠颌下腺的表达

目的观察转基因糖尿病小鼠下颌下腺形态学改变与原癌基因C-fos蛋白表达的关系,为糖尿病的临床及基础研究提供依据。方法引进日本C57BL/ksj-db/ m表型正常隐性基因小鼠,其近亲交配所得纯合子后代,即为db/db(单基因遗传自然发病型)糖尿病小鼠。取3、4、6、8、10月龄db/db糖尿病小鼠及相应月龄的db/ m正常小鼠下颌下腺,行HE染色及SP免疫组化染色后进行图象分析,统计各组下颌下腺C-fos阳性表达的细胞数,观察其形态学改变。结果糖尿病小鼠下颌下腺腺泡萎缩,细胞缩小,形态不规则,排列不整齐。各月龄糖尿病小鼠颌下腺C-Fos阳性细胞明显低于相应对照组(P<0.01),且逐渐减少,呈下降趋势。结论db/db糖尿病状态下颌下腺细胞表达C-Fos蛋白明显降低,c-fos低表达可能与下颌下腺实质细胞的增殖减弱性形态学变化密切相关。     

Amelioration of accelerated diabetic mesangial expansion by treatment with a PKC beta inhibitor in diabetic db/db mice, a rodent model for type 2 diabetes.

Activation of protein kinase C (PKC) is implicated as an important mechanism by which diabetes causes vascular complications. We have recently shown that a PKC beta inhibitor ameliorates not only early diabetes-induced glomerular dysfunction such as glomerular hyperfiltration and albuminuria, but also overexpression of glomerular mRNA for transforming growth factor beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in streptozotocin-induced diabetic rats, a model for type 1 diabetes. In this study, we examined the long-term effects of a PKC beta inhibitor on glomerular histology as well as on biochemical and functional abnormalities in glomeruli of db/db mice, a model for type 2 diabetes. Administration of a PKC beta inhibitor reduced urinary albumin excretion rates and inhibited glomerular PKC activation in diabetic db/db mice. Administration of a PKC beta inhibitor also prevented the mesangial expansion observed in diabetic db/db mice, possibly through attenuation of glomerular expression of TGF-beta and ECM proteins such as fibronectin and type IV collagen. These findings provide the first in vivo evidence that the long-term inhibition of PKC activation in the renal glomeruli can ameliorate glomerular pathologies in diabetic state, and thus suggest that a PKC beta inhibitor might be an useful therapeutic strategy for the treatment of diabetic nephropathy.