Antidiabetic effects of cinnamon oil in diabetic KK-Ay mice

The hypoglycemic effect of cinnamon oil (CO) in a type 2 diabetic animal model (KK-A^y mice) was studied. The main component of CO was cinnamaldehyde, and other nineteen components were also determined. CO was administrated at doses of 25, 50 and 100 mg/kg for 35 days. It was found that fasting blood glucose concentration was significantly decreased (P < 0.05) with the 100 mg/kg group (P < 0.01) the most efficient compared with the diabetic control group. In addition, there was significant decrease in plasma C-peptide, serum triglyceride, total cholesterol and blood urea nitrogen levels while serum high density lipoprotein (HDL)-cholesterol levels were significantly increased after 35 days. Meanwhile, glucose tolerance was improved, and the immunoreactive of pancreatic islets β-cells was promoted. These results suggest that CO had a regulative role in blood glucose level and lipids, and improved the function of pancreatic islets. Cinnamon oil may be useful in the treatment of type 2 diabetes mellitus.     

Antidiabetic effects of corosolic acid in KK-Ay diabetic mice

The antidiabetic effects of corosolic acid (CA) were investigated in KK-Ay mice, an animal model of type 2 diabetes. CA (2 mg/kg body weight) reduced the blood glucose levels of KK-Ay mice 4 h after a single oral dose. CA (2 mg/kg) reduced the blood glucose levels in KK-Ay mice 2 weeks after a single oral dose and also significantly lowered plasma insulin levels were in KK-Ay mice under similar conditions. CA-treated KK-Ay mouse blood glucose significantly decreased in an insulin tolerance test. These results support the hypothesis that CA improves glucose metabolism by reducing insulin resistance. Therefore CA may be useful for the treatment of type 2 diabetes.     

Antidiabetic effect of glycyrrhizin in genetically diabetic KK-Ay mice

We, previously demonstrated that one shot administration of glycyrrhizin (Grz) reduced the postprandial blood glucose rise, using Std ddY mice. Subsequently, we evaluated the effects of long-term Grz treatment (2.7, 4.1 g/kg diet) on diabetic symptoms using genetically non-insulin dependent diabetic model mice (KK-Ay). Male KK-Ay mice were divided into 3 groups: the control group, 0.27% Grz diet (2.7 g of Grz/kg diet) group and 0.41% Grz diet (4.1 g of Grz/kg diet) group. The elevation of blood glucose concentration was almost entirely suppressed in mice fed the 0.41% Grz diet 7 weeks after the beginning of test feeding, although it was not suppressed in mice fed the control diet or the 0.27% Grz diet. Water intake in the control and 0.27% Grz diet groups increased gradually, whereas, this was not true in the 0.41% Grz diet group. Grz treatment significantly lowered blood insulin level. Throughout the experiment, Grz did not affect the food intake or body weight among the three groups. The mice fed the 0.41% Grz diet also improved their tolerance to oral glucose loading 9 weeks after the beginning of test feeding. This study shows that Grz has an antidiabetic effect in noninsulin-dependent diabetes model mice.     

Antidiabetic action of low molecular weight chitosan in genetically obese diabetic KK-Ay mice

Recently, we reported that low molecular weight (LMW) chitosan (chitosan lactate, average MW: 20,000) prevents the progression of low dose (100 mg/kg, i.p.) streptozotocin-induced slowly progressive diabetes mellitus in male ICR mice. The present study was designed to clarify the effects of LMW chitosan on hyperglycemia, hyperinsulinemia and hypertriglyceridemia in genetically obese diabetic male KK-Ay mice. LMW chitosan (0.05%, 0.2% or 0.8% water solution) was given daily as drinking water to male KK-Ay mice for 11 weeks, from 5 weeks of age. The non-fasting serum glucose levels of control mice continued to increase slowly throughout the experimental period. LMW chitosan lowered the serum glucose levels in a dose-dependent manner. In these diabetic mice, hyperinsulinemia and hypertriglyceridemia were observed, and LMW chitosan was dose-dependently effective in improving both serum biochemical parameters. LMW chitosan at three doses improved overdrinking and polyuria observed in these diabetic mice. It is concluded from these results that LMW chitosan may be useful for the treatment of obesity-related type 2 diabetes mellitus.     

Antidiabetic effect of polyphenols from brown alga Ecklonia kurome in genetically diabetic KK-Ay mice

Context: Prevalence of diabetes mellitus type 2 (DM-II) is increasing in Japan. Brown alga Ecklonia kurome Okamura (Laminariaceae) (kurome in Japanese) is rich in phlorotannins, a kind of polyphenol. Phlorotannins have been reported to possess various bioactivities; however, few studies have reported its effect on DM-II.

Objective: The present study was conducted to investigate the antidiabetic effect of polyphenols from E. kurome (KPP) on KK-A^y mice, the animal model for human DM-II.

Materials and methods: Inhibitory activities of KPP against α-amylase and α-glucosidase in vitro, and effects on oral carbohydrate tolerance test in vivo were investigated. KK-A^y mice were fed with 0.1% KPP containing water for 5 weeks. A glucose tolerance test was conducted at week 4 of the 5-week period. At the end of experiment, blood biochemical parameters, including blood glucose, insulin, glycoalbumin, and fructosamine were determined. Furthermore, the kidneys and pancreatic islets were histologically examined.

Results: KPP showed inhibitory activities on carbohydrate-hydrolyzing enzymes and decreased postprandial blood glucose levels. The body weight gain and blood glucose levels in the KPP group were lower than the control group during the experimental period. KPP improved glucose tolerance and decreased the fasting blood glucose and insulin levels, fructosamine and glycoalbumin levels compared with the control group. Furthermore, KPP contracted the pancreatic islet size and decreased renal mesangial matrix in KK-A^y mice.

Discussion and conclusion: These results suggest that KPP is effective against DM-II and might provide a source of therapeutic agents for DM-II.     

Antidiabetic effect of Nitobegiku, the herb Tithonia diversifolia, in KK-Ay diabetic mice

Nitobegiku (the herb of Tithonia diversifolia (HEMSL) A. GRAY) has been used as a medicinal plant for diabetes. The antidiabetic effect of an 80% ethanol extract of Nitobegiku (Td) was investigated in KK-Ay-mice, an animal model of type 2 diabetes. Td (500 mg/kg body weight) reduced the blood glucose of KK-Ay mice 7 h after a single oral dose. No change in blood glucose in Td-treated normal mice (ddY) was seen. Td (500 mg/kg) reduced blood glucose in KK-Ay mice 3 weeks after a single oral dose and also significantly lowered plasma insulin in KK-Ay mice under similar conditions. Td-treated KK-Ay mouse blood glucose was significantly decreased in an insulin tolerance test. These results support the hypothesis that Td improves glucose metabolism by reducing insulin resistance. Therefore, Nitobegiku may be useful for the treatment of type 2 diabetes.     

Increase in plasma fibrinogen and plasminogen activator inhibitor level in diabetic KK and KK-Ay mice

Coagulation activity in KK mice and KK-Ay mice produced by transferring the yellow obese gene (Ay) into KK mice, was studied to examine whether both mice are useful as a model of diabetic atherosclerosis. Plasma levels of hemoglobin A1c (HbA1c), insulin, fibrinogen, plasminogen activator inhibitor (PAI) and thrombomodulin were significantly high in KK and KK-Ay mice compared with age-matched non-diabetic mice (ddY mice). The changes in the plasma levels of fibrinogen at each time-point correlated with the increases in HbA1c levels. Pathological observation by Oil red O staining of aorta tissue from 4-month-old KK and KK-Ay mice revealed the early stages of atherosclerosis such as lipid deposition. These age-related increases in the plasma level of fibrinogen and PAI suggested that KK-Ay mice may contribute to help elucidate the early stages of diabetic atherosclerosis.     

Maslinic acid reduces blood glucose in KK-Ay mice

In the present study, we have examined the hypoglycemic effect of maslinic acid (MA) in KK-A(y) mice, an animal model of genetic type-2 diabetes. MA (10 mg/kg body wt) reduced the blood glucose levels in KK-A(y) mice at 4 h after a single oral dose. KK-A(y) mice receiving MA at daily dosages of 10 mg/kg and 30 mg/kg for 2 weeks showed a significant reduction in the blood glucose levels. Furthermore, the results also showed that MA might modulate glucose metabolism partially through reducing insulin resistance in KK-A(y) mice. Taken together, MA may hold great promise as a natural therapeutic agent for treatment of type 2 diabetes.     

Lipogenic action of the novel oral antidiabetic agent HQL-975 in genetically obese diabetic KK-Ay mice.

HQL-975 (3-{4-12-(5-methyl-2-phenyl-oxazol-4-yl)-ethoxyl-phenyl}-2S- propylamino-propionic acid) is a new oral antidiabetic agent which has been shown to be effective in insulin-resistant diabetic animals. In the present study, we examined the effects of HQL-975 on glucose utilization and insulin action in KK-Ay mice with genetically obese non-insulin diabetes. (1) Dietary administration of HQL-975 (19 mg/kg/d for 7 d) improved hyperglycemia, hyperlipidemia and hyperinsulinemia in the mice. (2) The HQL-975-treated mice showed enhanced net glucose utilization, that is, glucose was significantly incorporated into total lipids in the white adipose tissue (WAT) and liver, and into glycogen in the diaphragm for the last 24 h of the drug administration period. (3) Treatment improved the decreased stimulative action of insulin in the epididymal WAT and the agent increased insulin-stimulated lipogenesis from both glucose and acetate. (4) Treatment also increased the activity of lipogenic enzymes such as glycerol-3-phosphate dehydrogenase and fatty acid synthetase. (5) In vitro exposure of WAT to HQL-975 enhanced lipogenesis in the presence of insulin. From these findings, we conclude that HQL-975 improves glucose utilization of KK-Ay mice through the enhancement of insulin action, which is associated with its lipogenic effects.     

Hypoglycemic effects of turmeric (Curcuma longa L. rhizomes) on genetically diabetic KK-Ay mice

The turmeric (Curcuma longa L. rhizomes) EtOH extract significantly suppressed an increase in blood glucose level in type 2 diabetic KK-A(y) mice. In an in vitro evaluation, the extract stimulated human adipocyte differentiation in a dose-dependent manner and showed human peroxisome proliferator-activated receptor (PPAR)-gamma ligand-binding activity in a GAL4-PPAR-gamma chimera assay. The main constituents of the extract were identified as curcumin, demethoxycurcumin, bisdemethoxycurcumin, and ar-turmerone, which had also PPAR-gamma ligand-binding activity. These results indicate that turmeric is a promising ingredient of functional food for the prevention and/or amelioration of type 2 diabetes and that curcumin, demethoxycurcumin, bisdemethoxycurcumin, and ar-turmerone mainly contribute to the effects via PPAR-gamma activation.     

Hypoglycemic effects of clove (Syzygium aromaticum flower buds) on genetically diabetic KK-Ay mice and identification of the active ingredients

Clove (Syzygium aromaticum flower buds) EtOH extract significantly suppressed an increase in blood glucose level in type 2 diabetic KK-A^y mice. In-vitro evaluation showed the extract had human peroxisome proliferator-activated receptor (PPAR)-γ ligand-binding activity in a GAL4-PPAR-γ chimera assay. Bioassay-guided fractionation of the EtOH extract resulted in the isolation of eight compounds, of which dehydrodieugenol (2) and dehydrodieugenol B (3) had potent PPAR-γ ligand-binding activities, whereas oleanolic acid (4), a major constituent in the EtOH extract, had moderate activity. Furthermore, 2 and 3 were shown to stimulate 3T3-L1 preadipocyte differentiation through PPAR-γ activation. These results indicate that clove has potential as a functional food ingredient for the prevention of type 2 diabetes and that 2–4 mainly contribute to its hypoglycemic effects via PPAR-γ activation.     

Dietary corosolic acid ameliorates obesity and hepatic steatosis in KK-Ay mice

Corosolic acid (CRA), a constituent of Banaba leaves, has been reported to exert anti-hypertension, anti-hyperinsulinemia, anti-hyperglycemia, and anti-hyperlipidemia effects as well as to induce anti-inflammatory and anti-oxidative activities. The aim of this study was to investigate the inhibitory effects of CRA on the development of obesity and hepatic steatosis in KK-Ay mice, a genetically obese mouse model. Six-week-old KK-Ay mice were fed a high fat diet for 9 weeks with or without 0.023% CRA. Nine-week CRA treatment resulted in 10% lower body weight and 15% lower total fat (visceral plus subcutaneous fat) mass than in control mice. CRA treatment reduced fasting plasma levels of glucose, insulin, and triglyceride by 23%, 41%, and 22%, respectively. The improved insulin sensitivity in CRA-treated mice may be due on part to the increased plasma adiponectin and white adipose tissue (WAT) AdipoR1 levels. In addition, CRA treatment increased the expression of peroxisome proliferator-activated receptor (PPAR) alpha in liver and PPAR gamma in WAT. This is the first study to show that CRA treatment can contribute to reduced body weight and amelioration of hepatic steatosis in mice fed a high fat diet, due in part to increased expression of PPAR alpha in liver and PPAR gamma in WAT.     

中药降糖复方水提取物对KK-Ay糖尿病小鼠骨骼肌糖代谢PI3K/Akt信号通路的影响

目的 研究中药降糖复方水提取物（WEJTD）对自发性2型糖尿病（T2DM）模型KK-Ay小鼠骨骼肌糖代谢PI3K/Akt信号通路的影响。方法 将KK-Ay小鼠按随机数法随机分为5组：模型组、盐酸二甲双胍（MH,250 mg/kg）组和WEJTD低、中、高剂量（2、4、8 g/kg）组,C57BL/6J小鼠作为对照组,每天ig给药1次,共12周,对照组和模型组ig等体积蒸馏水。给药12周后,取小鼠血清,ELISA试剂盒法检测胰岛素水平;Trizol法提取肌肉组织中的RNA,荧光实时定量PCR（qRT-PCR）检测磷脂酰肌醇激酶-3（PI3K）、蛋白激酶B（Akt）、葡萄糖转运蛋白-4（GLUT-4）、糖原合成酶激酶-3β（GSK-3β）、糖原合成酶（GS）、胰岛素受体底物（IRS-1）mRNA水平。结果 与模型组比较,WEJTD高、中剂量显著上调小鼠血清胰岛素水平、骨骼肌中IRS-1 mRNA水平（P<0.05、0.001）;高、中、低剂量均显著下调骨骼肌中GSK-3β mRNA水平,显著上调PI3K、Akt、GLUT-4、GS mRNA水平（P<0.05、0.01、0.001）。结论 中药降糖复方通过上调PI3K/Akt信号通路,减少糖原沉积,刺激骨骼肌中葡萄糖转运。     

Glucose-lowering effect of powder formulation of African black tea extract in KK-Ay/TaJcl diabetic mouse

We observed the suppressive effect of a powder formulation of African black tea extract prepared from the leaves of Camellia sinensis on type 2 non-insulin dependent diabetic mice, KK-A(y)/TaJcl. Black tea extract significantly showed suppressive effect of the elevation of blood glucose on oral glucose tolerance test of 8 week-old KK-A(y)/TaJcl mice (P < 0.05). Long-term treatment with black tea extract showed significant suppression of post-prandial blood glucose and obesity (P < 0.05). The weight of the intestine of mice treated with black tea extract was significantly reduced (P < 0.05). From these results, African black tea used in this study showed a suppressive effect on the elevation of blood glucose during food intake and the body weight.     

Oral administration of quercetin inhibits bone loss in rat model of diabetic osteopenia

Diabetic osteopenia can result in an increased incidence of bone fracture and a delay in fracture healing. Quercetin, one of the most widely distributed flavonoids in plants, possesses antioxidant property and beneficial effect on osteoporosis in ovariectomized mice. All these properties make quercetin a potential candidate for controlling the development of diabetic osteopenia. Therefore, the present study was designed to investigate the putative beneficial effect of quercetin on diabetic osteopenia in rats. Diabetes mellitus was induced by streptozotocin. The diabetic rats received daily oral administration of quercetin (5 mg/kg, 30 mg/kg and 50 mg/kg) for 8 weeks, which was started at 4 weeks after streptozotocin injection. Quercetin at 5 mg/kg showed little effect on diabetic osteopenia, while quercetin at 30 mg/kg and 50 mg/kg could increase the decreased serum osteocalcin, serum alkaline phosphatase activity, and urinary deoxypyridinoline in diabetic rats. In addition, quercetin (30 mg/kg and 50 mg/kg) could partially reverse the decreased biomechanical quality and the impaired micro-architecture of the femurs in diabetic rats. Histomorphometric analysis showed that both decreased bone formation and resorption were observed in diabetic rats, which was partially restored by quercetin (30 mg/kg and 50 mg/kg). Further investigations showed that quercetin significantly lowered the oxidative DNA damage level, up-regulated the total serum antioxidant capability and the activity of serum antioxidants in diabetic rats. All those findings indicate the beneficial effect of quercetin on diabetic osteopenia in rats, and raise the possibility of developing quercetin as potential drugs or an ingredient in diet for controlling diabetic osteopenia.     

Naloxone-induced analgesia in diabetic mice

We evaluated the effects of s.c. administration of naloxone in mice with streptozotocin-induced diabetes, compared to those in age-matched naive mice. Naloxone injected s.c. produced a dose-related increase in tail-flick latency in diabetic mice but not in naive mice. Naloxone-induced analgesia in diabetic mice was significantly reduced by pretreatment with naltrindole, a selective antagonist of δ-opioid receptors. These results indicte that naloxone-induced ‘paradoxical’ analgesia in diabetic mice may be mediated by δ-opioid receptors.     

Anti-diabetic effect of an alpha-glucan from fruit body of maitake (Grifola frondosa) on KK-Ay mice

We have evaluated the anti-diabetic effect of a alpha-glucan (MT-alpha-glucan) from the fruit body of maitake mushrooms (Grifola frondosa) on KK-Ay mice (a kind of genetical type 2 diabetes animal model). The effects of MT-alpha-glucan (450 or 150 mg kg (-1)) on diabetic mice were investigated by observing the changes in body weight, the level of fasting plasma glucose, glycosylated serum protein (GSP), hepatic glycogen, serum insulin, triglycerides, cholesterol, free fatty acid, liver superoxide dismutase (SOD), glutathione peroxidase (GSHpx), reduced glutathione (GSH) and malondialdehyde (MDA). Moreover, the binding capacity of insulin receptors on liver crude plasma membranes was assayed and histopathological changes in the pancreas were observed. Treatment with MT-alpha-glucan significantly decreased the body weight, level of fasting plasma glucose, GSP, serum insulin, triglycerides, cholesterol, free fatty acid and MDA content in livers. Treatment with MT-alpha-glucan significantly increased the content of hepatic glycogen, GSH and the activity of SOD and GSHpx. Moreover, the insulin binding capacity to liver crude plasma membranes increased and histopathological changes in the pancreas were ameliorated in the treatment group. These data suggest that MT-alpha-glucan has an anti-diabetic effect on KK-Ay mice, which might be related to its effect on insulin receptors (i.e., increasing insulin sensitivity and ameliorating insulin resistance of peripheral target tissues).     

Socio-psychological stress-induced antinociception in diabetic mice

Rationale: Although it is well established that different forms of stress produce a pronounced antinociception, the effect of diabetes on psychological stress-induced antinociception is not yet clear. Objectives: The effect of diabetes on psychological stress-induced antinociceptive effect was assessed in mice. Methods: Animals were rendered diabetic by an injection of streptozotocin (200 mg/kg, IV). Mice were exposed to psychological stress in the compartment of a communication box. The antinociceptive response was evaluated by the tail-flick test, using radiant heat as a stimulus, which was performed before stress (pre-stress latency) and 0, 30 and 60 min after stress. Results: Exposure to socio-psychological stress for 5, 10 and 15 min produced duration-dependent antinociception in diabetic mice. However, in non-diabetic mice, no appreciable antinociception was found even in the case of socio-psychological stress for 15 min. Pretreatment with diazepam (0.3 mg/kg, IP) significantly attenuated socio-psychological stress-induced antinociception in diabetic mice (vehicle: 62.9±5.5%, n=10; diazepam: 22±1%, n=10). Furthermore, pretreatment with flumazenil (1 mg/kg, IV), a benzodiazepine receptor antagonist, also significantly reduced socio-psychological stress-induced antinociception in diabetic mice (vehicle: 77.9±5.0%, n=10; flumazenil: 5.8±1.2%, n=10). In contrast, pretreatment with methyl β-carboline-3-carboxylate (β-CCM, 2 mg/kg, IV), a benzodiazepine receptor inverse agonist, significantly enhanced socio-psychological stress-induced antinociception in non-diabetic mice (vehicle: 4.9±0.6%, n=10; β-CCM: 61.5±5.9%, n=10), but not in diabetic mice (vehicle: 50.7±4.5%, n=10; β-CCM: 64.4±7.2%, n=10). Conclusions: These results indicate that emotional stress can readily induce antinociception in diabetic mice. Furthermore, this enhanced emotional stress-induced antinociception might be attributable to an increase in the production and/or release of endogenous ligands for benzodiazepine receptors, such as diazepam binding inhibitor, which act as inverse benzodiazepine receptor agonists. Received: 1 September 1999 / Final version: 12 January 2000     

Antinociceptive effect of oxycodone in diabetic mice

The effect of oxycodone on thermal hyperalgesia in streptozotocin-induced diabetic mice was examined. The antinociceptive response was assessed by recording the latency in the tail-flick test using the radiant heat from a 50-W projection bulb on the tail. The tail-flick latency in diabetic mice was significantly shorter than that in non-diabetic mice. When diabetic mice were treated with oxycodone (5 mg/kg, s.c.), the tail-flick latency in diabetic mice was prolonged to the level considerably longer than the baseline latencies of non-diabetic mice. However, s.c. administration of morphine (5 mg/kg) did not produce a significant inhibition of the tail-flick response in diabetic mice. Oxycodone, at doses of 1.25-5.0 mg/kg administered s.c., produced a dose-dependent increase in the tail-flick latencies in both diabetic and non-diabetic mice. The antinociceptive effect of oxycodone was antagonized by pretreatment with a selective delta-opioid receptor antagonist, beta-funaltrexamine (20 mg/kg, s.c.), in both non-diabetic and diabetic mice. In non-diabetic mice, pretreatment with a selective kappa-opioid receptor antagonist, nor-binaltorphimine (20 mg/kg, s.c.) had no effect on the peak antinociceptive effect of oxycodone observed 30 min after administration, however, it slightly but significantly reduced oxycodone-induced antinociception observed 60 and 90 min after administration. On the other hand, pretreatment with nor-binaltorphimine practically abolished the peak (30 min) and persistent (60 and 90 min) antinociceptive effects of oxycodone in diabetic mice. Naltrindole (35 mg/kg, s.c.), a selective delta-opioid receptor antagonist, had no effects on the antinociceptive effect of oxycodone in both non-diabetic and diabetic mice. These results suggest that the antinociceptive effects of oxycodone may be mediated by mu- and kappa-opioid receptors in diabetic mice, whereas it may interact primarily with mu-opioid receptors in non-diabetic mice.     

Algogenic mediator-induced nociceptive response in diabetic mice

The duration of the somatostatin-, bradykinin- or prostaglandin F2alpha-induced nociceptive response was significantly less in diabetic mice than in non-diabetic mice. Subcutaneous injection of 7-benzylidenenaltrexone (0.1, 0.3 and 1 mg/kg), an antagonist of delta1-opioid receptors, had no significant effect on either somatostatin-, bradykinin- or prostaglandin F2alpha-induced nociceptive responses in non-diabetic mice. 7-Benzylidenenaltrexone (0.1 and 0.3 mg/kg, s.c.) also had no significant effect on somatostatin- or prostaglandin F2alpha-induced nociceptive responses in diabetic mice. However, the bradykinin-induced nociceptive response in diabetic mice was dose-dependently and significantly increased when 7-benzylidenenaltrexone (0.1, 0.3 and 1 mg/kg, s.c.) was injected 10 min before the injection of bradykinin. These results suggest that a spinal delta1-opioid receptor-mediated endogenous antinociceptive system may inhibit the bradykinin-mediated nociceptive responses in the second phase of the formalin-induced nociceptive response in diabetic mice.