Effects of brown alga, Ecklonia cava on glucose and lipid metabolism in C57BL/KsJ-db/db mice, a model of type 2 diabetes mellitus

Recently, there has been a growing interest in alternative therapies of marine algae for diabetes. Therefore, the anti-diabetic effects of brown alga, Ecklonia cava was investigated in type 2 diabetic animal. Male C57BL/KsJ-db/db (db/db) mice were divided into control, dieckol rich extract of E. cava (AG-dieckol), or rosiglitazone (RG) groups. The blood glucose, blood glycosylated hemoglobin levels, and plasma insulin levels were significantly lower in the AG-dieckol and RG groups than in the control db/db mice group, while glucose tolerance was significantly improved in the AG-dieckol group. AG-dieckol markedly lowered plasma and hepatic lipids concentration compared to the control db/db mice group. The antioxidant enzyme activities were significantly higher in the AG-dieckol group than in the control db/db mice group, yet its TBARS level was markedly lower compared to the RG group. With regard to hepatic glucose regulating enzyme activities, glucokinase activity was enhanced in the AG-dieckol group mice, while glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities in the AG-dieckol group mice were significantly lowered than those in the control db/db mice group. These results suggest that AG-dieckol exert an anti-diabetic effect in type 2 diabetic mice by improving the glucose and lipid metabolism and antioxidant enzymes.     

Anti-diabetic and anti-oxidative effects of 4-hydroxypipecolic acid in C57BL/KsJ-db/db mice

Hypoglycemic effect of ethanol extracts of Peganum harmala (commonly known as 'Harmal') seeds has been reported on normal and streptozotocin-induced diabetic rats. In the present study, the authors determine anti-diabetic and anti-oxidative properties of 4-hydroxypipecolic acid (4-HPA) isolated from seeds of P. harmala in C57BL/KsJ-db/db mice. Twelve week old male mice were administered 50 mg/kg body weight (4-HPA suspension were made in 1% gum acacia) for the period of 10 days, and a significant reduction in the fasting blood glucose, plasma triglycerides (TG), cholesterol, free fatty acid, low-density lipoprotein-cholesterol and a significant increase in high-density lipoprotein-cholesterol level was observed with respect to vehicle-treated db/db mice. The anti-oxidant activity of 4-hydroxypipecolic acid was studied in liver and kidney tissues by assessing malondialdehyde levels for lipid peroxidation and enzyme activity of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). Treatment of 4-HPA significantly lowered the lipid peroxidation in hepatic and renal tissue and increased the activity of CAT, GSH-Px and SOD in treated mice.     

Antidiabetic and hypolipidemic effects of a novel dual peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonist, E3030, in db/db mice and beagle dogs

We investigated the antidiabetic effects of E3030, which is a potent dual activator of peroxisome proliferator-activated receptor (PPAR) alpha and PPARgamma, in an animal model of diabetes, C57BL/KsJ-db/db mice (db/db mice), and the lipidemic effects of E3030 in beagle dogs, whose PPARalpha and PPARgamma transactivation responses to E3030 were similar to those of humans. E3030 activated human PPARalpha, mouse PPARalpha, dog PPARalpha, human PPARgamma, mouse PPARgamma, and dog PPARgamma with EC(50) values of 65, 920, 87, 34, 73, and 34 nM, respectively, in the chimeric GAL4-PPAR receptor transactivation reporter assay. In db/db mice orally administered E3030 decreased blood glucose, triglyceride (TG), non-esterified fatty acids (NEFA), and insulin levels and increased blood adiponectin levels during a 14-day experimental period. Significant effects on blood glucose and adiponectin levels were observed at a dose of 3 mg/kg or greater. Furthermore, significant effects on blood TG, NEFA, and insulin levels were observed at doses of 1 mg/kg or more. An oral glucose tolerance test (OGTT) performed on Day 15 showed that E3030 at 3 mg/kg improved glucose tolerance in this model. Fourteen days of oral treatment with E3030 at a dose of 0.03 mg/kg or greater showed remarkable TG- and non high-density lipoprotein (non-HDL) cholesterol-lowering effects in beagle dogs. These results were similar to those observed for the PPARalpha agonist fenofibrate. E3030 also reduced apo C-III levels on Days 7 and 14, and elevated lipoprotein lipase (LPL) levels on Day 15. These results indicate that the TG- and non-HDL cholesterol-lowering actions of E3030 involve combined effects on reduction of apo C-III and elevation of LPL, resulting in increased lipolysis. The experimental results in animals suggest that E3030 has potential for use in the treatment of various aspects of metabolic dysfunction in type 2 diabetes, including dyslipidemia, hyperglycemia, hyperinsulinemia, and impaired glucose disposal.     

Impairment of the vascular relaxation and differential expression of caveolin-1 of the aorta of diabetic +db/+db mice

In this study, we compared the endothelium-dependent and -independent relaxation of the isolated thoracic aorta of control (+db/+m) and diabetic (+db/+db) (C57BL/KsJ) mice. The gene expression (mRNA and protein) level of the muscarinic M(3) receptors, endothelial nitric oxide synthase (eNOS) and caveolin-1 of the aorta was also evaluated. Acetylcholine caused a concentration-dependent, N(G)-nitro-L-arginine methyl-ester (20 microM)-sensitive relaxation, with approximately 100% relaxation at 10 microM, in +db/+m mice. In +db/+db mice, the acetylcholine-induced relaxation was significantly smaller (maximum relaxation: approximately 80%). The sodium nitroprusside-mediated relaxation was slightly diminished in +db/+db mice, compared to +db/+m mice. However, there was no significant difference in the isoprenaline- and cromakalim-induced relaxation observed in both species. The mRNA and protein expression levels of caveolin-1 were significantly higher in the aorta of +db/+db mice. In contrast, there was no difference in the mRNA and protein expression levels of eNOS and muscarinic M(3) receptors between these mice. Our results demonstrate that the impairment of the acetylcholine-induced, endothelium-dependent aortic relaxation observed in +db/+db mice was probably associated with an enhanced expression of caveolin-1 mRNA and protein.     

FR177391, a new anti-hyperlipidemic agent from Serratia. II. Pharmacological activity of FR177391

The pharmacological effect of FR177391, isolated from Serratia liquefaciens No. 1821, was studied in normal animals and various types of animal models of hypertriglyceridemia. Treatment of normal mice with FR177391 resulted in an increase in heparin-releasable lipoprotein lipase (LPL) activity in the blood and epididymal fat tissue. FR177391 treatment decreased triglyceride (TG) and increased high-density lipoprotein cholesterol in the blood in normal rats following 7 days treatment, suggesting potent LPL activating properties of FR177391. Both Triton WR1339-induced severe and fructose-induced mild hypertriglyceridemia in rats were attenuated by FR177391 treatment. Severely elevated levels of TG in db/db mice, an insulin resistant diabetic animal model, also significantly decreased from 14 days of treatment with FR177391. FR177391 treatment for 9 days caused a decrease in the elevated levels of TG in mice induced by intraperitoneal inoculation of murine lymphoma EL-4. Overall, this study demonstrated that FR177391 can be possibly a LPL activating agent and that FR177391 treatment improved hypertriglyceridemia in various rat and mouse animal models. These results suggest that FR177391 is a promising candidate compound for the management of hypertriglyceridemia.     

The anti-diabetic effects of ethanol extract from two variants of Artemisia princeps Pampanini in C57BL/KsJ-db/db mice.

The anti-diabetic effects of two variants of Artemisia princeps Pampanini, sajabalssuk (SB) and sajuarissuk (SS), were investigated in type 2 diabetic animal using their ethanol extracts. Male C57BL/KsJ-db/db (db/db) mice were divided into control, SB ethanol extract (SBE), SS ethanol extract (SSE), or rosiglitazone (RG) groups and their age-matched littermates (db/+) were used. Supplementation of the SBE (0.171 g/100g diet), SSE (0.154 g/100g diet), and RG (0.005 g/100g diet) improved glucose and insulin tolerance and significantly lowered blood glycosylated hemoglobin levels, as compared to the control group. Plasma insulin, C-peptide and glucagon levels in db/db mice were higher in the db/+ mice, however these values were significantly lowered by SBE, SSE or RG-supplement. Hepatic GK activity was significantly lower in the db/db mice than in the db/+ mice, while hepatic G6Pase activity was vice versa. Supplementation of SBE, SSE and RG reversed these hepatic glucose-regulating enzyme activities. In addition, SBE and SSE markedly increased the hepatic glycogen content and muscle ratio as compared to the control group, but they did not alter the food intake, body weight and plasma leptin level. The RG group, however, showed a significant increase in the food intake, body weight and plasma leptin. These results suggest that SBE and SSE exert an anti-diabetic effect in type 2 diabetic mice.     

Comparison of vascular relaxation, lipolysis and glucose uptake by peroxisome proliferator-activated receptor-gamma activation in +db/+m and +db/+db mice

In this study, we determined the in vitro effect of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activation on the aortic relaxation, lipolysis and insulin-induced [(3)H]-glucose uptake of the abdominal (omental) adipocytes of the non-diabetic (+db/+m) and obese/diabetic (+db/+db) mice. The expression of PPAR-gamma (mRNA and protein) in aorta and adipose tissues was evaluated and compared. Cumulative application of ciglitazone, pioglitazone and troglitazone (PPAR-gamma agonists) caused a concentration-dependent aortic relaxation (sensitive to 2-chloro-5-nitro-N-phenylbenzamide (GW9662) (1 microM, a selective PPAR-gamma antagonist) and N(omega)-nitro-l-arginine methyl ester (l-NAME) (20 microM, a nitric oxide synthase inhibitor)) with a maximum relaxation of approximately 30% (3 microM) in +db/+m mice, whereas no relaxation was observed in +db/+db mice. All PPAR-gamma agonists examined did not alter the basal lipolysis of both species, but forskolin caused a concentration-dependent lipolysis, with a greater magnitude observed in +db/+m mice. Insulin (0.1 and 1 microM) caused an enhancement of [(3)H]-glucose uptake into adipocytes with a greater magnitude in +db/+m mice. In contrast, none of the PPAR-gamma agonists tested (0.1, 1 and 10 microM) altered the basal and the insulin (0.1 microM)-induced [(3)H]-glucose uptake into adipocytes of both species. In addition, there was no difference in PPAR-gamma expression (mRNA and protein) in the aorta and adipose tissues between the species. In conclusion, our results demonstrate that PPAR-gamma is present in the abdominal (omental) adipose tissue and thoracic aorta. An acute activation of PPAR-gamma produced a small ( approximately 30%) aortic relaxation (nitric oxide/endothelium-dependent) of +db/+m mice. However, all PPAR-gamma agonists examined have no acute effect on lipolysis and the insulin-induced glucose uptake into adipocytes of both +db/+m and +db/+db mice.     

Mechanism of AVP release and synthesis in chronic salt-loaded rats.

Arginine vasopressin (AVP) is involved in osmotic regulation in the brain and peripheral tissues. To elucidate the regulatory mechanism that involves AVP release in hyperosmolality, we investigated the regulation of the synthesis and release of AVP in chronic salt-loaded rats. In chronic salt-loaded rats, which were generated by free access to water containing 2% NaCl for 7 days, plasma osmolality was significantly increased compared with control value. When tested, the AVP content was significantly higher in plasma but lower in the pituitary and whole brain (hypothalamus, cortex and striatum) than in control rats. The expression of AVP mRNA in the brain was significantly up-regulated compared with that in control rats. These data lead to the suggestion that hyperosmolality stimulates AVP release from the brain and subsequently induces AVP synthesis in the brain. On the other hand, mRNA levels of vasopressin V1a receptor (V1aR), whose down-regulation is known to be a counteraction to the V1aR activation, was not changed in the brain, suggesting that the AVP seems not to interact with the V1aR in the brain. These results suggest that hyperosmosis promotes the release of AVP into plasma, the subsequent induction of AVP mRNA in the brain and its action on the peripheral tissues.     

非诺贝特对衰老大鼠肝脏组织酰基辅酶A合成酶的影响

摘要目的观察非诺贝特对衰老大鼠肝脏组织酰基辅酶A（CoA）合成酶的影响,探讨衰老后出现脂质代谢异常的可能机制及非诺贝特对脂质代谢的调节作用。方法 雄性SD年轻大鼠（4～6周龄）和老年大鼠（24个月龄）各16只,随机分为对照组（常规喂养2周）和实验组（非诺贝特喂养2周）,测定大鼠血清三酰甘油和总胆固醇水平,采用半定量逆转录聚合酶链反应法检测大鼠肝脏组织酰基CoA合成酶水平。结果与年轻对照组比较,老年对照组三酰甘油和总胆固醇水平升高,老年大鼠肝脏组织酰基CoA合成酶水平表达降低。实验组与老年对照组比较三酰甘油和总胆固醇水平均下降;肝脏组织酰基CoA合成酶水平均升高。结论老年大鼠肝脏组织酰基CoA合成酶水平表达减少可能与老年脂质代谢异常有关;非诺贝特对老年脂质代谢异常有调节作用。     

丁苯酞对db/db小鼠学习记忆及海马NR2B受体的影响

目的 观察丁苯酞对2型糖尿病db/db小鼠学习记忆及海马N-甲基-D-天冬氨酸受体2B亚基(NR2B)表达的影响,探讨丁苯酞改善糖尿病认知功能障碍的机制.方法 将16只db/db小鼠按随机数字表法分为丁苯酞干预组(L-NBP组,n=8)和糖尿病对照组(DM组,n=8),同窝出生的db/m小鼠作为正常对照组(NC组,n=10).适应性喂养1周后,L-NBP组每日以溶于植物油中的丁苯酞灌胃,剂量为120 mg·kg-1,DM组与NC组则给予同等剂量的植物油灌胃,干预6周后,进行指标观察.应用Morris水迷宫检测小鼠的学习记忆能力.实时荧光定量PCR检测NR2B mRNA的表达情况.结果 与NC组比较,DM组小鼠逃避潜伏期延长和平均探索次数减少(P＜0.05),而L-NBP组小鼠较DM组上述学习记忆成绩明显改善(P＜0.05);与NC组相比,DM组和L-NBP组小鼠海马CA1区NR2B mRNA表达水平明显下降(P＜0.05),而L-NBP组较DM组NR2B mRNA表达水平明显增高(P＜0.05).结论 丁苯酞可改善糖尿病引发的认知功能障碍,推测其机制可能与上调海马NP,2B的表达有关.     

Hepatic metabolism of sulfur amino acids in db/db mice

To determine the effect of type-2 diabetes and obesity on the hepatic metabolism of sulfur amino acids, hepatic sulfur amino acid metabolism was determined in db/db mice. Hepatic methionine was markedly decreased in db/db mice, although the hepatic activity of betaine homocysteine methyltransferase was increased. The decrease in hepatic methionine was reflected by decreased sulfur-containing methionine metabolites, including S-adenosylmethionine, homocysteine, cysteine, and hypotaurine in liver and plasma. In contrast, S-adenosylhomocysteine, putrescine, and spermidine were increased in db/db mice. The hepatic level and activity of methionine adenosyltransferase I/III, an S-adenosylmethionine synthesizing enzyme, were significantly increased. These results suggest that increased polyamine synthesis, in conjunction with decreased hepatic methionine levels, is partly responsible for the reduction in hepatic S-adenosylmethionine. Decreased homocysteine in liver and plasma may be attributable to the decrease in hepatic methionine and upregulation of hepatic betaine homocysteine methyltransferase. Glutathione in liver and plasma did not change despite decreased γ-glutamylcysteine ligase activity. The decreased hepatic hypotaurine may be attributable to the downregulation of cysteine dioxygenase. The major finding of this study is that db/db mice exhibited decreases in hepatic methionine and its sulfurcontaining metabolites.     

Anti-diabetic effects of TongGuanWan, a Chinese traditional herbal formula, in C57BL/KsJ-db/db mice

In the present study, the anti-diabetic effects of a traditional Chinese medicinal formula extract, TongGuanWan, were investigated in type 2 diabetic animals. It was orally administered to C57BL/KsJ-db/db mice once a day for 4 weeks at the doses of 62, 125, and 250?mg/kg body weight. TongGuanWan significantly lowered the blood glucose and glycosylated haemoglobin levels as well as improved the glucose tolerance in db/db mice. The serum triglyceride levels in the db/db mice were significantly decreased, whereas the high-density lipoprotein cholesterol levels were significantly increased, after treatment with this herbal formula. TongGuanWan also markedly decreased the animals' body weights compared to those of the control db/db group but did not alter food intake. The effects of TongGuanWan were compared to those of the drug rosiglitazone. In addition, five main constituents of TongGuanWan, mangiferin, berberine, cinnamic aldehyde, timosaponin BII, and timosaponin AIII, were quantified using high performance liquid chromatography coupled with a diode array and an evaporative light scattering detector (HPLC-DAD-ELSD). These results suggest that TongGuanWan may be useful for the treatment of type 2 diabetes.     

FR258900, a novel glycogen phosphorylase inhibitor isolated from Fungus No. 138354. II. Anti-hyperglycemic effects in diabetic animal models

A novel glycogen phosphorylase inhibitor FR258900 was isolated from the cultured broth of a fungal strain No. 138354. We examined the hypoglycemic effects of FR258900 in diabetic animal models. FR258900 treatment significantly reduced the plasma glucose concentrations during oral glucose tolerance tests in diabetic mice models, including db/db mice and STZ-induced diabetic mice. Furthermore, FR258900 treatment resulted in rapid decrease in the plasma glucose levels in db/db mice. These improvements in glucose disposal were accompanied by increased liver glycogen contents, suggesting that the glucose lowering effects of FR258900 were attributed to suppressed hepatic glycogen breakdown and increased hepatic glycogen synthesis. Taken together, our results suggest that glycogen phosphorylase is a potentially useful target in new therapies against diabetes.     

益肾排毒丸调节AMPK/ACC信号通路对db/db小鼠肝损伤的保护作用研究

目的：探究益肾排毒丸（YSPDW）对db/db小鼠肝损伤的保护作用及其对脂代谢通路的影响机制。方法：C57BL/6小鼠作为空白对照组、8周龄的db/db小鼠分为非酒精性脂肪肝（non-alcoholic fatty liver disease,NAFLD）模型组、益肾排毒丸治疗组和二甲双胍阳性对照组。给药8周后检测小鼠肝脏系数、随机血糖、肝功能（丙氨转氨酶ALT、谷草转氨酶AST）、血脂（总胆固醇TC、三酰甘油TG、高密度脂蛋白胆固醇HDL-C、低密度脂蛋白胆固醇LDL-C）、肝脏脂质（TC、TG）、肝脏抗氧化因子（谷胱甘肽过氧化物酶GSH-Px、谷胱甘肽GSH、超氧化物歧化酶SOD、丙二醛MDA、过氧化氢酶CAT）、肝脏炎性因子（TNF-α、IL-6、IL-1β、MCP-1）等指标的变化。HE和PAS染色评估小鼠肝脏形态变化、脂肪变性和糖原沉积。Western blot检测脂代谢AMPK/ACC信号通路相关蛋白表达。结果：与模型组相比,益肾排毒丸给药组和二甲双胍组小鼠随机血糖和肝脏系数显著降低。生化指标检测结果显示益肾排毒丸可显著降低NAFLD模型小鼠血清AST、ALT、TC、TG水平和肝组织TC、TG、MDA水平,升高HDL-C含量,发挥肝保护作用;ELISA结果表明益肾排毒丸能明显升高NAFLD小鼠肝组织GSH-Px、GSH和SOD活性,显著降低肝脏炎性细胞因子TNF-α、IL-6、IL-1β和MCP-1的水平,表明益肾排毒丸可增加机体抗氧化能力,抑制炎症因子释放。HE和PAS结果显示益肾排毒丸可明显减轻肝组织脂肪变性和炎症细胞浸润,改善肝细胞的结构和形态完整。Western blot结果表明,益肾排毒丸能激活AMPK/ACC信号通路,显著增加模型小鼠肝脏p-AMPK和p-ACC蛋白表达。结论：益肾排毒丸可能通过促进AMPK/ACC信号通路来改善肝脏氧化应激、炎性反应,减少脂质合成,从而改善NAFLD的肝损伤。     

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。