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.     

A possible Fourier transform infrared‐based plasma fingerprint of angiotensin‐converting enzyme inhibitor‐induced reversal of endothelial dysfunction in diabetic mice

Angiotensin‐converting enzyme inhibitors (ACE‐I) display vasoprotective activity and represent the cornerstone in the treatment of cardiovascular diseases. In this study, we tested whether Fourier transform infrared (FTIR)‐based analysis of blood plasma is sensitive to detect vasoprotective effects of treatment with perindopril including reversal of endothelial dysfunction in diabetes. For this purpose, plasma samples were collected from untreated db/db mice, db/db mice treated with 2 or 10 mg/kg perindopril and db+ mice. The effect of perindopril on endothelial function was examined in ex vivo aortic rings; 10 mg/kg but not 2 mg/kg of perindopril reversed endothelial dysfunction. In plasma of db/db mice, the balance between conformations of plasma proteins was noted, and treatment with perindopril at a high dose but not at a low dose reversed this effect. This was revealed by amide II/amide I ratio attributed to increased β‐sheet formation. Spectral markers at 3010, 1520/1238 cm^?1, representative for unsaturation degree of lipids and phosphorylation of tyrosine, respectively, were also affected by perindopril treatment. In conclusion, although metabolic abnormalities associated with type 2 diabetes mellitus such as hypertriglyceridemia and hyperglycemia strongly affected spectral FTIR profile of diabetic plasma, we identified FTIR features that seem to be associated with the vasoprotective activity of ACE‐I.      

Mechanisms of hepatic steatosis in mice fed a lipogenic methionine choline-deficient diet

The methionine choline-deficient (MCD) diet results in liver injury similar to human nonalcoholic steatohepatitis (NASH). The aims of this study were to define mechanisms of MCD-induced steatosis in insulin-resistant db/db and insulin-sensitive db/m mice. MCD-fed db/db mice developed more hepatic steatosis and retained more insulin resistance than MCD-fed db/m mice. Both subcutaneous and gonadal fat were reduced by MCD feeding: gonadal fat decreased by 23% in db/db mice and by 90% in db/m mice. Weight loss was attenuated in the db/db mice, being only 13% compared with 35% in MCD-fed db/db and db/m mice, respectively. Both strains had upregulation of hepatic fatty acid transport proteins as well as increased hepatic uptake of [14C]oleic acid: 3-fold in db/m mice (P < 0.001) and 2-fold in db/db mice (P < 0.01) after 4 weeks of MCD feeding. In both murine strains, the MCD diet reduced triglyceride secretion and downregulated genes involved in triglyceride synthesis. Therefore, increased fatty acid uptake and decreased VLDL secretion represent two important mechanisms by which the MCD diet promotes intrahepatic lipid accumulation in this model. Feeding the MCD diet to diabetic rodents broadens the applicability of this model for the study of human NASH.     

Suppressive effects of the peel of Citrus kawachiensis (Kawachi Bankan) on astroglial activation,tau phosphorylation,and inhibition of neurogenesis in the hippocampus of type 2 diabetic db/db mice

We previously reported that the dried peel powder of Citrus kawachiensis exerted anti-inflammatory effects in the brain in several animal models. Hyperglycemia induces inflammation and oxidative stress and causes massive damage in the brain; therefore, we herein examined the anti-inflammatory and other effects of the dried peel powder of C. kawachiensis in the streptozotocin-induced hyperglycemia mice model and in the type 2 diabetic db/db mice model. The C. kawachiensis administration inhibited microglial activation in the hippocampus in the streptozotocin-injected mice. Moreover, The C. kawachiensis treatment inhibited astroglial activation in the hippocampus and the hyperphosphorylation of tau at 231 of threonine and 396 of serine in hippocampal neurons, and also relieved the suppression of neurogenesis in the dentate gyrus of the hippocampus in the db/db mice. It was suggested that the dried peel powder of C. kawachiensis exerts anti-inflammatory and neuroprotective effects in the brain.     

Establishment of an Inflamed Animal Model of Diabetic Nephropathy

Aims Inflammatory stress plays a crucial role in the progression of diabetic nephropathy (DN). This study aimed to establish a novel inflamed animal model of DN and to evaluate its significance in DN.Methods Nondiabetic db/m mice and diabetic db/db mice were randomly divided into four groups: db/m, db/m+casein, db/db, and db/db+casein for eight weeks. Casein was subcutaneously injected to induce chronic inflammation. Body weight and albumin to creatinine ratio (ACR) in the urine were measured every week. The plasma levels of serum amyloid protein A (SAA) and tumour necrotic factor-α (TNF-α) were determined with the enzyme-linked immunosorbent assay. The morphological changes to the renal pathology and ultra-microstructures were checked by pathological staining and electron microscopy. Immunofluorescent staining and Western blotting were used to determine the protein expression of podocyte-specific molecules and inflammatory cytokines in kidneys.Results ACR, plasma levels of SAA and TNF-α, protein expression of inflammatory cytokines, mesangial expansion, collagen accumulation, and foot process effacement in kidneys of casein-injected db/db mice were significantly increased compared with the db/db mice. Casein injection markedly decreased the protein expression of Wilms'' tumor-1 and nephrin in kidneys of db/db mice, which are specific podocyte biomarkers, suggesting that chronic inflammation accelerates podocyte injuries in db/db mice. Interestingly, no obvious urinary protein, inflammatory cytokine expression, or histological changes in the kidneys of casein-injected db/m mice were found compared with the db/m mice.Conclusion An inflamed animal model of DN was successfully established and may provide a useful tool for investigating the pathogenesis of DN under inflammatory stress.     

The rate of degradation of liver glycogen phosphorylase is specifically decreased in the C57BL/KsJ — db/db mouse

Summary We have recently demonstrated that the activity of liver glycogen phosphorylase, the rate-limiting enzyme of glycogenolysis, is elevated in genetically diabetic (db/db) mouse and that it is primarily due to the presence of increased amounts of this enzyme. In the present study, we examined the turnover of glycogen phosphorylase in vivo in order to elucidate the mechanism for this specific increase. The rate of phosphorylase synthesis was slightly decreased in the diabetic mouse compared to controls. However, the relative rates of synthesis were similar in these two groups. The rate of degradation of this enzyme was decreased 20% (p<0.05) in the diabetic mouse compared to controls. More importantly, the relative rate of degradation of phosphorylase was found to be lower in the diabetic animals. This indicates that the elevated concentration of phosphorylase in the liver of the db/db mouse is likely due to a specific decrease in its rate of degradation.     

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.     

Design,synthesis and biological evaluation of 7-nitro-1H-indole-2-carboxylic acid derivatives as allosteric inhibitors of fructose-1,6-bisphosphatase

A series of novel indole derivatives was synthesized as inhibitors of fructose-1,6-bisphosphatase (FBPase). Extensive structure–activity relationships were conducted and led to a potent FBPase inhibitor 3.9 with an IC₅₀ of 0.99 μM. The binding mode of this series of indoles was predicted using CDOCKER algorithm. The results of this research will shed light on the further design and optimization of novel small molecules as FBPase inhibitors.     

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.     

大黄素降糖及改善脂质代谢的实验研究

目的：探讨大黄素对2型糖尿病模型db/db小鼠血糖及血脂水平的影响。方法：4周龄16只db/db雄性小鼠随机分为治疗组和对照组,每组8只;治疗组经灌胃每天给予100mg/kg大黄素;对照组灌胃给予相仿体积的生理盐水,开始10天每天算进食量,每周测空腹血糖及体重1次,连续干预8周,干预前及实验结束前1周测胰岛素耐量,干预结束后于颈动脉取血测血脂水平（HDL-C、LDL-C、TG、TC）。结果：①大黄素干预不影响db/db小鼠的进食量,与对照组比较,P〉0.05;②大黄素可显著减轻db/db小鼠体重,与对照组比较,P〈0.05;③大黄素可改善db/db小鼠胰岛素敏感性,降低小鼠的空腹血糖水平,与对照组比较,P〈0.05或P〈0.01;④大黄素可降低db/db小鼠血TG、TC、LDL-C水平,P〈0.01。结论：大黄素可有效地改善db/db小鼠的糖脂紊乱状态,其降糖及改善血脂代谢机制值得进一步深入研究。     

Hyperbaric oxygen therapy (HBOT) suppresses biomarkers of cell stress and kidney injury in diabetic mice

The disease burden from diabetic kidney disease is large and growing. Effective therapies are lacking, despite an urgent need. Hyperbaric oxygen therapy (HBOT) activates Nrf2 and cellular antioxidant defenses; therefore, it may be generally useful for treating conditions that feature chronic oxidative tissue damage. Herein, we determined how periodic exposure to oxygen at elevated pressure affected type 2 diabetes mellitus-related changes in the kidneys of db/db mice. Two groups of db/db mice, designated 2.4 ATA and 1.5 ATA, were treated four times per week with 100 % oxygen at either 1.5 or 2.4 ATA (atmospheres absolute) followed by tests to assess kidney damage and function. The sham group of db/db mice and the Hets group of db/+ mice were handled but did not receive HBOT. Several markers of kidney damage were reduced significantly in the HBOT groups including urinary biomarkers neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (CyC) along with significantly lower levels of caspase-3 activity in kidney tissue extracts. Other stress biomarkers also showed trends to improvement in the HBOT groups, including urinary albumin levels. Expressions of the stress response genes NRF2, HMOX1, MT1, and HSPA1A were reduced in the HBOT groups at the end of the experiment, consistent with reduced kidney damage in treated mice. Urinary albumin/creatinine ratio (ACR), a measure of albuminuria, was significantly reduced in the db/db mice receiving HBOT. All of the db/db mouse groups had qualitatively similar changes in renal histopathology. Glycogenated nuclei, not previously reported in db/db mice, were observed in these three experimental groups but not in the control group of nondiabetic mice. Overall, our findings are consistent with therapeutic HBOT alleviating stress and damage in the diabetic kidney through cytoprotective responses. These findings support an emerging paradigm in which tissue oxygenation and cellular defenses effectively limit damage from chronic oxidative stress more effectively than chemical antioxidants.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-015-0574-3) contains supplementary material, which is available to authorized users.     

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<...     

The effect of calcitonin on food intake in diabetic mice

The characteristic hyperphagia of the genetically obese diabetic (C57B1/Ks-db+/db+) mouse (db/db) is thought to be due to a defect in the satiety circuitry with a secondary overproduction of a circulating satiety factor to which they are insensitive. Recent studies have suggested that calcitonin may be a potent hormonal mediator of the satiety reflex. In this study it was shown that db/db mice were eight fold more sensitive to calcitonin than their heterozygote littermate controls. Mice with streptozotocin-induced diabetes were ten-fold more sensitive to calcitonin than their littermate controls. These results show that diabetes increases the sensitivity to the satiety effects of calcitonin.     

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。     

Synthesis,SAR, and X-ray structure of tricyclic compounds as potent FBPase inhibitors

With the aim of discovering a novel class of fructose-1,6-bisphosphatase (FBPase) inhibitors, a series of compounds based on tricyclic scaffolds was synthesized. Extensive SAR studies led to the finding of 8l with an IC₅₀ value of 0.013 μM against human FBPase. An X-ray crystallographic study revealed that 8l bound at AMP binding sites of human liver FBPase with hydrogen bonding interactions similar to AMP.     

大黄素降糖及改善脂质代谢的实验研究

目的:探讨大黄素对2型糖尿病模型db/db小鼠血糖及血脂水平的影响.方法:4周龄16只db/db雄性小鼠随机分为治疗组和对照组,每组8只;治疗组经灌胃每天给予100mg/kg大黄素;对照组灌胃给予相仿体积的生理盐水,开始10天每天算进食量,每周测空腹血糖及体重1次,连续干预8周,干预前及实验结束前1周测胰岛素耐量,干预结束后于颈动脉取血测血脂水平(HDLC、LDL-C、TG、TC).结果:①大黄素干预不影响db/db小鼠的进食量,与对照组比较,P＞0.05;②大黄素可显著减轻db/db小鼠体重,与对照组比较,P＜0.05;③大黄素可改善db/db小鼠胰岛素敏感性,降低小鼠的空腹血糖水平,与对照组比较,P＜0.05或P＜0.01;④大黄素可降低db/db小鼠血TG、TC、LDL-C水平,P＜0.01.结论:大黄素可有效地改善db/db小鼠的糖脂紊乱状态,其降糖及改善血脂代谢机制值得进一步深入研究.     

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．     

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.     

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.