Streptozotocin-induced Hyperglycemic Mice Research Articles

Anti-hyperglycemic effect of herbal formula of Moringa oleifera, Vernonia amygdalina and Centella asiatica extracts in streptozotocin-induced hyperglycemic mice

IntroductionMoringa oleifera, Vernonia amygdalina, and Centella asiatica are herbs used in traditional Chinese medicine and are commonly used in Southeast Asian countries to treat a variety of diseases. The experimental evidence showed that M. oleifera leaves, V. amygdalina leaves, and C. asiatica had the effect of supporting their treatment of diabetes. This study investigated the anti-hyperglycemic effect of a novel herbal formula from M. oleifera leaf, V. amygdalina leaf, and C. asiatica aerial part extracts. MethodsThe extract was examined for anti-hyperglycemic capacity in oral glucose tolerance test in normal mice. To confirm their role in a higher model, the extract was studied in the streptozotocin (STZ)-induced hyperglycemic model. Plasma glucose concentration, body weight, organ weight, malondialdehyde, glutathione in liver and kidneys, and pancreatic histology were also evaluated. Besides, in vitro properties of the extract were tested including α-amylase and α-glucosidase inhibitory, and antioxidant activities. ResultsAfter 7-day of treatment, the extract showed strong anti-hyperglycemic activity in the STZ-induced hyperglycemic mice, plasma glucose levels were reduced by 48.75 % and 54.13 % in the group administered with 200 mg/kg and 400 mg/kg of the extract, respectively, compared with the hyperglycemic control. The extract had the effect to protect the liver and kidneys against oxidation stress by enhancing glutathione levels in the liver and decreasing malondialdehyde levels in the liver and kidneys. The pancreatic β-cell protection was also observed by improving the size and number of pancreatic islets by the extract compared to the hyperglycemic control. The extract showed a significant α-amylase and α-glucosidase inhibitory activities, and antioxidant activity through DPPH and ABTS quenching and reducing power abilities. DiscussionThese results demonstrated remarkable potential of the combined extract of M. oleifera leaves, V. amygdalina leaves, and aerial part of C. asiatica in the management of diabetes.

Continuous stimulation of dual-function peptide PGLP-1-VP inhibits the morbidity and mortality of NOD mice through anti-inflammation and immunoregulation

Multiple animal and human studies have shown that administration of GLP-1RA can enhance β-cell recovery, reduce insulin dosage, reduce HbA1c content in the blood, reduce the risk of hypoglycemia and reduce inflammation. In the NOD mouse model, peptide VP treatment can prevent and treat type 1 diabetes through immunomodulation. Therefore, we designed a new dual-functional PGLP-1-VP, which is expected to combine the anti-inflammatory effect of PGLP-1 and the immunomodulatory effect of VP peptide. In streptozotocin-induced hyperglycemic mice model, we demonstrated that PGLP-1-VP can act as a GLP-1R agonist to improve hyperglycemia and increase insulin sensitivity. In the NOD mouse model, PGLP-1-VP treatment reduced morbidity, mortality, and pancreatic inflammation, and showed superior effect to PGLP-1 or VP treatment alone, confirming that PGLP-1-VP may act as a dual-function peptide. PGLP-1-VP provided immunomodulatory effect through increasing Th2 cell percentage and balancing the ratio of Th2/Th1 in spleen and PLN, similar to P277 and VP. Additionally, PGLP-1-VP and PGLP-1 act the anti-inflammation by increasing Treg cells and TGF-β1 content like DPP-IV inhibitor. Taken together, our data shows that the dual-functional PGLP-1-VP reduces morbidity and mortality in the NOD model, suggesting a potential role in preventing and treating type 1 diabetes.

Selective Loss of Calretinin-Poor Cochlear Afferent Nerve Fibers in Streptozotocin-Induced Hyperglycemic Mice.

Hearing loss is one of the major complications of diabetes mellitus and significantly lowers the quality of life of diabetic patients. In studies using diabetic animal models hearing loss have been frequently associated with damages to cochlear afferent fibers. Recent studies suggested that cochlear afferent neurons are composed of heterogeneous populations and a subgroup of neurons equipped with low level of calretinin might be more vulnerable to various noxious stimuli such as noise and neurotoxins. Here, we tested if cochlear afferent neurons deficient in the Ca2+-buffering protein calretinin are more vulnerable to hyperglycemic insults. Streptozotocin-induced (50 mg/kg, i.p.) hyperglycemic mice (>250 mg/dl) were tested. The expression patterns of calretinin in peripheral processes and the cell bodies of cochlear afferent nerve fibers were examined using immunohistochemistry and confocal microscopy. The proportion of calretinin-poor cochlear afferent fibers was much lower in hyperglycemic mice compared to the normoglycemic control group. (30.0 vs. 55.5% in the peripheral process; 15.7 vs. 24.4 % in spiral ganglion neuron). The results suggest that calretinin-poor cochlear nerve fibers may be selectively lost after the hyperglycemic insults. The finding also supports a calretinin's neuroprotective role against diabetic neuropathy in cochlear afferent neurons.

Neuroprotective effects of the peel of Citrus kawachiensis (Kawachi Bankan) and auraptene in the hippocampus of hyperglycemia mice and global cerebral ischemia/reperfusion injury mice

The peel of Citrus kawachiensis (Kawachi Bankan), a citrus species grown in Ehime, Japan, is abundant in auraptene. Auraptene, a coumarin compound, have been shown to exert anti-inflammatory effects in peripheral tissues, but it was still unclear of the effect in the brain. Hyperglycemia and brain ischemia induce inflammation and oxidative stress and cause massive damage in the brain; therefore, we examined the anti-inflammatory and other effects of the dried peel powder of C. kawachiensis and auraptene in a hyperglycemia and global cerebral ischemia models. The C. kawachiensis treatment inhibited astroglial activation in the hippocampus and the hyperphosphorylation of tau protein in hippocampal neurons, and also relieved the suppression of neurogenesis in the dentate gyrus of the hippocampus in the type 2 diabetic db/db mice. The C. kawachiensis treatment inhibited microglial and astroglial activation, and neuronal cell death in the hippocampus of transient global cerebral ischemia mice. It was suggested that the dried peel powder of C. kawachiensis exerts anti-inflammatory and neuroprotective effects in the brain. We attempted to demonstrate the effect of auraptene in the brains in streptozotocin-induced hyperglycemic mice and transient global cerebral ischemia mice. Auraptene administration showed the similar effects as the peel of C. kawachiensis in the hippocampus of these mice models. These results suggested that auraptene have potential effects as a neuroprotective agent in the peel of C. kawachiensis.

Antidiabetic and oxidative stress assessment of bio-enzymatically synthesized zinc oxide nanoformulation on streptozotocin-induced hyperglycemic mice

Oxidative stress has significant contribution in on-set and progression of diabetes. The disease onset leads to elevated levels of free radicals rendering the oxidant-inducing mechanisms incapable of protecting cellular organelles from inflicted damage. Herein, β-galactosidase-mediated bio-enzymatic synthesis of zinc oxide nanoparticles (ZnO NPs) was pioneered and characterized. These obtained ZnO NPs were assessed for their antidiabetic activity against streptozotocin (STZ)-induced diabetic mice. For this objective, 36 male albino mice were separated into 6 groups. The diabetes was induced in mice with STZ (120 mg kg−1 body weight), and further treated with three different doses of ZnO NPs (0.5 mg kg−1, 1 mg kg−1, and 2 mg kg−1) for 28 days. The results unveiled protective effects in diabetic mice treated with ZnO NPs through restoration of changes in body weight and normal glucose levels. The effects of ZnO NPs on lipid peroxidation and carbonyl contents were protective in liver, kidney and pancreas of diseased groups. Levels of serum biomarkers such as cholesterol, triglycerides and HDL-C indicated ZnO NPs treatment caused these levels to plummet towards control parameters. Normal liver function markers and urea levels in serum indicated successful treatment of diabetic mice with ZnO NPs. Histopathological studies revealed protective and non-toxic effects of ZnO NPs over vital tissues of kidney, liver, and pancreas. The results divulge efficacious pharmaceutical potential of ZnO NPs against formation of reactive oxygen species by scavenging free radicals enhancing the functioning of antioxidant fortifying enzymes generating sustenance over hyperglycemic conditions.

32-OR: Coordination of Mitochondrial Uncoupling with Pyruvate Dehydrogenase Activation Safely Ameliorates Hyperglycemia through Preferential Glucose Oxidation

Type 2 diabetes (T2D), which is characterized by hyperglycemia and insulin resistance, has become global epidemic. Uncoupling of mitochondria by chemical uncoupler, 2,4-dinitrophenol (DNP), is an efficient way to ameliorate hyperglycemia and insulin resistance. However, DNP use ceased in 1930s due to the systemic toxicities including hyperlactacidemia, hyperthermia and even death, which were mainly resulted from uncoupling actions induced excessive fat combustion and anaerobic glycolysis. To relieve the adverse effects derived from uncoupling activity, here we identified an effect-enhancing and toxicity-reducing way linking activation of pyruvate dehydrogenase (PDH) with DNP to T2D therapy. Activation of PDH by its classical activator, dichloroacetic acid (DCA), protected mice from DNP-derived hyperlactacidemia, hyperthermia and even death. Meanwhile, DCA combined with DNP further promoted glucose disposal in streptozotocin-induced hyperglycemic mice and enhanced insulin signaling in high-fat diet mice. Mechanistically, PDH activation corrected the excessive fatty acid oxidation and anaerobic glycolysis by DNP that was strongly associated with the adverse effects, and preferentially promoted glucose oxidation to improve hyperglycemia. Based on the beneficial effects of DNP combined with DCA, a novel compound possessing both mitochondrial uncoupling and PDH activation effects, named 6j, was identified and confirmed to promote glucose oxidation preferentially in vitro and in vivo. Therefore, our study suggested that combination of mitochondrial uncoupling and PDH activation might be a novel effective pharmacological approach for safely treating T2D. Disclosure J. Li: None. J. Li: None. Funding National Natural Science Foundation of China; Chinese Academy of Sciences; Shanghai Science and Technology Commission; K.C. Wong Education Foundation

Topical Topiramate Improves Wound Healing in an Animal Model of Hyperglycemia.

Wound healing is severely affected in hyperglycemia and other metabolic conditions. Finding new therapeutic approaches that accelerate wound healing and improve the quality of the scar may reduce the morbidity commonly associated with skin lesions in diabetes. This study evaluated the effect of topical topiramate (TPM) on wound healing in C57 mice. Streptozotocin-induced hyperglycemic mice were subjected to a wound on the back and randomly allocated for treatment with either vehicle or topical TPM cream (2%) once a day for 14 days. Polymerase chain reaction, Western blotting, and microscopy were performed for the analysis. TPM improved wound healing (complete resolution at Day 10, 98% ± 5 for TPM vs. 81% ± 28 for vehicle), increased organization and deposition of collagen Type I, and enhanced the quality of the scars as determined by microscopy. In addition, TPM modulated the expression of cytokines and proteins of the insulin-signaling pathway: In early wound-healing stages, expression of interleukin-10, an anti-inflammatory marker, increased, whereas at the late phase, the pro-inflammatory markers tumor necrosis factor-α and monocyte chemoattractant protein-1 increased and there was increased expression of a vascular endothelial growth factor. Proteins of the insulin-signaling pathway were stimulated in the late wound-healing phase. Topical TPM improves the quality of wound healing in an animal model of hyperglycemia. The effect of TPM is accompanied by modulation of inflammatory and growth factors and proteins of the insulin-signaling pathway. Therefore, topical TPM presents as a potential therapeutic agent in skin wounds in patients with hyperglycemia.

Salmonella infection leads to severe intestinal inflammation and increased CD4+FoxP3+ Treg cells in streptozotocin‑induced hyperglycemic mice.

Hyperglycemia promotes the growth and reproduction of bacteria, thereby increasing the probability of infection, which also causes rebound hyperglycemia. Therefore, the interactions of infection and hyperglycemia lead to the progression and deterioration of these diseases. Type 1 diabetes mellitus (T1DM) is an autoimmune disease. Studies have shown that regulatory T cells (Tregs) play a key role in maintaining islet-specific tolerance. Treg deficiency may lead to the development of early pancreatitis and T1DM, and sufficient amounts of Tregs can restore this tolerance, thereby inhibiting the occurrence of T1DM. Moreover, different subpopulations of dendritic cells (DCs) play an important role in activating autoreactive T cells and inducing autoimmune tolerance to autoantigens, which are closely related to the functional diversity caused by different phenotypes, maturation status, and the immune microenvironment of DC subpopulations. In the present study, we used streptozotocin-induced hyperglycemic mice to model T1DM and induced a Salmonella infection in the mouse model, leading to aggravated inflammation, which resulted in an elevated proportion of CD103+CD11b+ DCs and a significantly elevated proportion of CD4+FoxP3+ Tregs in the intestinal lamina propria. After co-culturing CD4+ T cells and DCs, we found that CD103+CD11b+ DCs could significantly promote the proliferation of CD4+ T cells. The elevated proportions of CD4+FoxP3+ Tregs were considered to be correlated with the increased number of CD103+CD11b+ DCs.

Neuroprotective effects of the peel of <i>Citrus kawachiensis</i> (Kawachi Bankan) and auraptene in the hippocampus of hyperglycemia mice and global cerebral ischemia/reperfusion injury mice.

The peel of Citrus kawachiensis (Kawachi Bankan), a citrus species grown in Ehime, Japan, is abundant in auraptene. Auraptene, a coumarin compound, have been shown to exert anti-inflammatory effects in peripheral tissues, but it was still unclear of the effect in the brain. Hyperglycemia and brain ischemia induce inflammation and oxidative stress and cause massive damage in the brain; therefore, we examined the anti-inflammatory and other effects of the dried peel powder of C. kawachiensis and auraptene in a hyperglycemia and global cerebral ischemia models. The C. kawachiensis treatment inhibited astroglial activation in the hippocampus and the hyperphosphorylation of tau protein in hippocampal neurons, and also relieved the suppression of neurogenesis in the dentate gyrus of the hippocampus in the type 2 diabetic db/db mice. The C. kawachiensis treatment inhibited microglial and astroglial activation, and neuronal cell death in the hippocampus of transient global cerebral ischemia mice. It was suggested that the dried peel powder of C. kawachiensis exerts anti-inflammatory and neuroprotective effects in the brain. We attempted to demonstrate the effect of auraptene in the brains in streptozotocin-induced hyperglycemic mice and transient global cerebral ischemia mice. Auraptene administration showed the similar effects as the peel of C. kawachiensis in the hippocampus of these mice models. These results suggested that auraptene have potential effects as a neuroprotective agent in the peel of C. kawachiensis.

Inhibitory Effects of Auraptene and Naringin on Astroglial Activation, Tau Hyperphosphorylation, and Suppression of Neurogenesis in the Hippocampus of Streptozotocin-Induced Hyperglycemic Mice.

Auraptene, a citrus-related compound, exerts anti-inflammatory effects in peripheral tissues, and we demonstrated these effects in the brains of a lipopolysaccharide-injected systemic inflammation animal model and a brain ischemic mouse model. Naringin, another citrus-related compound, has been shown to exert antioxidant effects in several animal models. Hyperglycemia induces oxidative stress and inflammation and causes extensive damage in the brain; therefore, we herein evaluated the anti-inflammatory and other effects of auraptene and naringin in streptozotocin-induced hyperglycemic mice. Both compounds inhibited astroglial activation and the hyperphosphorylation of tau at 231 of threonine in neurons, and also recovered the suppression of neurogenesis in the dentate gyrus of the hippocampus in hyperglycemic mice. These results suggested that auraptene and naringin have potential effects as neuroprotective agents in the brain.

Pharmacological Effects of EGLP-1, a Novel Analog of Glucagon-Like Peptide-1, on Carbohydrate and Lipid Metabolism

Background/Aims: Abnormal glucose metabolism and lipid metabolism are two key issues in Type 1 diabetes mellitus (T1DM). Insulin can control carbohydrate metabolism adequately, but cannot regulate lipid metabolism well in patients with T1DM. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have cured type 2 diabetes mellitus in clinical trials and have improved T1DM glycemic control in preclinical studies. However, previous studies have not reported whether GLP-1 can lower the serum concentration of non-esterified fatty acids (NEFAs). In this study, we examine whether GLP-1 can affect serum NEFA levels. Methods: The bioactivity of EGLP-1 (a novel GLP-1 analog) in vitro was analyzed in CG-HEK293 cells and with high-performance liquid chromatography. An intraperitoneal glucose tolerance test (IPGTT) was used to analyze the acute and sustained hypoglycemic effects of EGLP-1 in normal C57BL/6J mice. Streptozotocin-induced hyperglycemic mice were used to study the effects of EGLP-1 on blood glucose and NEFAs as well as its mechanism. Results: EGLP-1 activated GLP-1R and resisted dipeptidyl peptidase-IV digestion in vitro. Additionally, EGLP-1 had an insulinotropic action in vivo that lasted for approximately 6 h. In Streptozotocin-induced hyperglycemic mice, EGLP-1 improved hyperglycemia, inhibited food intake, and increased β-cell area. Serum physiological indexes showed that insulin and C-peptide levels were increased, while NEFA and triacylglycerol concentrations were decreased. Western blot analysis revealed that EGLP-1 significantly reduced phosphorylated-hormone sensitive lipase (pHSL) levels in white adipose tissue. Conclusions: EGLP-1 can improve hyperglycemia by increasing islet β-cell area and improving β-cell function, possibly due to reduced NEFA content in serum by lowering pHSL levels.

Cyclocarya paliurus extract activates insulin signaling via Sirtuin1 in C2C12 myotubes and decreases blood glucose level in mice with impaired insulin secretion.

Diabetes is caused by the lack of release or action of insulin. Some foods and supplements can compensate for this deficiency; thus, they can aid in the prevention or treatment of diabetes. The aim of this study was to investigate the effects of Cyclocarya paliurus extract (CPE) on insulin signaling and its capacity to correct hyperglycemia in the absence of insulin. To investigate the hypoglycemic effects of CPE, C2C12 cells were exposed to CPE (50 and 100 μg/mL). CPE promoted 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2NBDG) uptake into the cells via translocation of glucose transporter 4 (Glut4) to the plasma membrane. In addition, CPE enhanced tyrosine phosphorylation of insulin receptor substrate and activated phosphatidylinositol 3-kinase and protein kinase B (Akt) via sirtuin1 in C2C12 cells. Moreover, we found that oral administration of CPE (1 g/kg) to streptozotocin-induced hyperglycemic mice produced a progressive decrease in plasma glucose levels at 1 h after single dosing. At that point, CPE significantly increased the expression of skeletal muscle membrane Glut4 and enhanced the phosphorylation of Akt. These results suggest that CPE exerts antidiabetic effects similar to those of insulin, and may be an oral therapeutic alternative for the management of diabetes.

The Hepatic Protection Effects of Hepassocin in Hyperglycemic Crisis.

High glucose generates reactive oxygen species (ROS) and contributes to glucotoxicity in hepatocytes, and hyperglycemia causes structural and functional damage to the liver. However, only a mild hepatic dysfunction was observed in subjects with hyperglycemic crisis, implying a factor exists to exert a hepatic protective effect. Hepassocin is a hepatokine that modulates the proliferation and metabolism of hepatocytes and also exerts protective activity in liver injury. However, its role in hyperglycemic crisis-induced hepatic dysfunction remains unknown. To investigate the possible hepatic protection effects of hepassocin in hyperglycemic crisis. Plasma hepassocin concentrations and routine biochemistry were measured in 21 patients with hyperglycemic crisis before and after standard treatments. The effects of hepassocin on hepatic functions were evaluated in streptozotocin-induced hyperglycemic mice (STZ mice). HepG2 cells were used to clarify the possible mechanisms regulating hepassocin expression. Plasma hepassocin concentrations decreased significantly in subjects with hyperglycemic crisis after standard treatment accompanied by improved hepatic functions. Correction of hyperglycemia in STZ mice also decreased the hepatic hepassocin expression. Injection of recombinant hepassocin improved hepatic functions and histologic changes and increased the expression of antioxidative stress proteins, including superoxide dismutase 1 (SOD1). In HepG2 cells, high glucose increased hepassocin expression through signal transducer and activator of transcription 3 and hepatocyte nuclear factor-related pathways. We also demonstrated that hepassocin increased SOD1 expression through an extracellular signal-regulated kinase 1/2 nuclear factor erythroid-2-related factor 2 pathway, decreasing ethyl acetate-induced ROS production and improving cell viability. Increased hepassocin secretion in hyperglycemic crisis might offset the deleterious effects of hyperglycemia on hepatocytes.

Broad Infiltration of Macrophages Leads to a Proinflammatory State in Streptozotocin-Induced Hyperglycemic Mice.

Chronic diseases are often associated with altered inflammatory response, leading to increased host vulnerability to new inflammatory challenges. Employing streptozotocin (STZ)-induced diabetes as a model, we further investigate mechanisms leading to enhanced neutrophil (polymorphonuclear leukocytes [PMN]) responses under hyperglycemia and compare them with those under chronic colitis. We show that, different from colitis under which the PMN response is significantly potentiated, the existence of a proinflammatory state associated with broad increases in macrophages in various organs plays a dominant role in promoting the PMN inflammatory response in diabetic mice. Studies of PMN infiltration during zymosan-induced peritonitis reveal that hyperglycemia enhances PMN recruitment not through inducing a high level of IL-17, which is the case in colitis, but through increasing F4/80+ macrophages in the peritoneal cavity, resulting in elevations of IL-6, IL-1β, TNF-α, and CXCL1 production. Insulin reversal of hyperglycemia, but not the neutralization of IL-17, reduces peritoneal macrophage numbers and ameliorates PMN infiltration during peritonitis. Significantly increased macrophages are also observed in the liver, kidneys, and intestines under hyperglycemia, and they are attributable to exacerbated nephropathy and colitis when inflammatory conditions are induced by doxorubicin and dextran sulfate sodium, respectively. Furthermore, analyses of monocyte production and macrophage proliferation in tissues suggest that significant monocytosis of inflammatory F4/80+Gr-1+ monocytes from the spleen and macrophage proliferation in situ synergistically contribute to the increased macrophage population under hyperglycemia. In conclusion, our results demonstrate that STZ-induced hyperglycemic mice develop a systemic proinflammatory state mediated by broad infiltration of macrophages.

Enhanced alpha-kinase 1 accelerates multiple early nephropathies in streptozotocin-induced hyperglycemic mice

Alpha-kinase 1 (ALPK1) is associated with chronic kidney disease (CKD), type 2 diabetes mellitus and gout. Elevated ALPK1 levels have been observed in the kidneys of patients with diabetes and the white blood cells of patients with gout. As renal injury is a common outcome of CKD, diabetes and gout, the aim of this study was to investigate the effect of ALPK1 in the development of renal injury in a hyperglycemic condition. Hyperglycemia was induced in wild-type and ALPK1 transgenic mice by an intraperitoneal injection of streptozotocin (STZ). Functional and histological examinations were performed after 3weeks. STZ-treated ALPK1 transgenic mice exclusively showed arteriolar sclerosis and fibrous thickening of the Bowman's capsule in the kidney. This was accompanied by body weight loss, severe hyperglycemia, and low serum insulin levels. Renal renin and serum renin protein levels were higher in STZ-treated ALPK1 transgenic mice, whereas cGKII protein level was decreased by ALPK1 in human embryonic kidney 293 (HEK293) cells. ALPK1 up-regulated TGF-beta1 levels and transcription of fibrosis-related genes, including MMP-9, FIBRONECTIN, and TIMP1. MSU crystals increased ALPK1 transcription in cultured kidney cells. Finally, ALPK1 enhanced production of MSU crystals-induced IL-1beta in mice. Stimulation of soluble sodium urate induced IL-1beta and Alpk1 mRNA production in mice kidney. Taken together, these data show that an increase in ALPK1 results in accelerated fibrotic nephropathies, primarily through the enhancement of renin, TGF-beta1, and IL-1beta. Renal or blood ALPK1 levels are involved in the induction of fibrotic renal injury in an experimental model of hyperglycemia.

Chronic Elevation of Tumor Necrosis Factor-α Mediates the Impairment of Leptomeningeal Arteriogenesis in db/db Mice.

Leptomeningeal collateral growth is a key factor that defines the severity of ischemic stroke. Patients with stroke generally have vascular risk factors, such as diabetes mellitus; however, consensus is lacking on how diabetes mellitus affects leptomeningeal arteriogenesis. We investigate the influence of diabetes mellitus on the leptomeningeal arteriogenesis. We measured the vessel diameter of the leptomeningeal anastomoses 14 days after the common carotid artery occlusion in db/db, db/+, and streptozotocin-induced hyperglycemic mice. In another set of these mice, we measured the infarct volume attributed to subsequent middle cerebral artery occlusion 14 days after the common carotid artery occlusion. Mac-2-positive cells on the dorsal brain surface and the mRNA expression of several macrophage-related factors in the cerebral cortex were examined. Finally, we tested whether the leptomeningeal arteriogenesis could be restored by pharmaceutical intervention in the db/db mice. Cerebral hypoperfusion led to significant ipsilateral leptomeningeal collateral growth in db/+ mice and streptozotocin-induced hyperglycemic mice. The collateral growth contributed to reduced infarct volume. In contrast, leptomeningeal arteriogenesis was impaired in the db/db mice. The number of Mac-2-positive cells was increased and tumor necrosis factor-α mRNA expression was induced after common carotid artery occlusion in the db/+ mice. However, these responses were not observed in the db/db mice. Administration of the tumor necrosis factor-α inhibitor etanercept before common carotid artery occlusion restored the hypoperfusion-induced leptomeningeal collateral growth in db/db mice. These results indicate that leptomeningeal arteriogenesis is impaired in db/db mice and that suppression of the tumor necrosis factor-α response to hypoperfusion is the major contributing factor.

Effects of Grifola frondosa non-polar bioactive components on high-fat diet fed and streptozotocin-induced hyperglycemic mice

Context: Consumption of medicinal mushrooms for disease prevention and maintaining health has a very long history in Asia. Grifola frondosa (Fr) S.F. Gray (GF) (Meripilaceae) is a medicinal fungus popularly used for enhancing immune systems, lowering blood glucose, and improving spleen, stomach, and nerve functions.Objective: This study examines the hypoglycemic effects of GF in vitro and in vivo, and analyzes the chemical profiles of its bioactive components.Materials and methods: In vitro hypoglycemic effects of GF was evaluated enzymatically using α-amylase and α-glucosidase inhibition assays, whereas in vivo study was conducted on high-fat diet fed and streptozotocin (HFD + STZ)-induced hyperglycemic mice. GC-MS was used to determine the chemical profiles of bioactive components.Results: The non-polar fraction of GF exhibited a stronger anti-α-glucosidase activity (IC50: 0.0332 mg/ml) than acarbose, but its anti-α-amylase activity (IC50: 0.671 mg/ml) was weaker. Oral administration of GF at 600 mg/kg (GF600) significantly lowered the blood glucose, HbA1c, average blood glucose, and serum total cholesterol levels in hyperglycemic mice. Although GF was found to contain mainly oleic acid and linoleic acid, their levels in the fungus were low, suggesting that the effects of GF on HFD + STZ-induced hyperglycemic mice could be due to factors other than these fatty acids.Conclusion: These results conclude that GF possesses anti-α-glucosidase activity, and hypoglycemic effect in HFD + STZ-induced hyperglycemic mice.

Efeito da goma guar parcialmente hidrolisada no metabolismo de lipídeos e na aterogênese de camundongos

OBJETIVO: Observar os efeitos da goma guar parcialmente hidrolisada no metabolismo de colesterol e na formação de placa aterosclerótica em aorta de camundongos deficientes no receptor LDL, euglicêmicos ou com hiperglicemia induzida por estreptozotocina. MÉTODOS: Trinta e seis camundongos deficientes para o receptor de LDL foram divididos em quatro grupos de nove animais: grupos euglicêmicos, alimentados com dieta aterogênica padrão (controle euglicêmico) ou suplementada com 7,5% de goma guar parcialmente hidrolisada (goma guar parcialmente hidrolisada euglicêmico) e grupos hiperglicêmicos alimentados com dieta aterogênica padrão (controle hiperglicêmico) ou suplementada com 7,5% de goma guar parcialmente hidrolisada (goma guar parcialmente hidrolisada hiperglicêmico). Após quatro semanas de experimento foram medidos: ingestão alimentar, ganho de peso, glicemia, colesterol plasmático e hepático, assim como lesão aterosclerótica na aorta torácica e abdominal. RESULTADOS: Os resultados mostram que a suplementação de goma guar parcialmente hidrolisada levou ao aumento do colesterol hepático e plasmático em animais euglicêmicos, mas sem aumento na área de lesão aterosclerótica na aorta. Em animais hiperglicêmicos, a redução no colesterol plasmático não foi estatisticamente significante, mas no que se refere à lesão da aorta, observou-se redução significante. CONCLUSÃO: Os resultados sugerem que a goma guar parcialmente hidrolisada pode reduzir a aterosclerose associada ao Diabetes Mellitus tipo 1.

Absence of inducible nitric oxide synthase reduces myocardial damage during ischemia reperfusion in streptozotocin-induced hyperglycemic mice.

We investigated the role of inducible nitric oxide synthase (iNOS) on ischemic myocardial damage and angiogenic process in genetically deficient iNOS (iNOS(-/-)) mice and wild-type littermates (iNOS(+/+)), with and without streptozotocin-induced (70 mg/kg intravenously) diabetes. After ischemia (25 min) and reperfusion (120 min), both iNOS(+/+) and iNOS(-/-) diabetic mice (blood glucose 22 mmol/l) had myocardial infarct size greater than their respective nondiabetic littermates (P < 0.01). Myocardial infarct size (P < 0.05), apoptotic index (P < 0.005), and tissue levels of tumor necrosis factor (P < 0.01), interleukin-6 (P < 0.01), and interleukin-18 (P < 0.01) were higher in nondiabetic iNOS(-/-) mice compared with nondiabetic iNOS(+/+) mice. As compared with diabetic iNOS(-/-) mice, diabetic iNOS(+/+) mice showed a greater infarct size (P < 0.01) associated with the highest tissue levels of nitrotyrosine and proinflammatory cytokines, as well as apoptosis. The beneficial role of iNOS in modulating defensive responses against ischemia/reperfusion injury seems to be abolished in diabetic mice.

The hypoglycemic effect of Phyllanthus sellowianus fractions in streptozotocin-induced diabetic mice.

Phyllanthus sellowianus Müller Arg. (Euphorbiaceae) is a plant used in folk medicine as a hypoglycemic and diuretic agent. The present study describes the hypoglycemic effect of fractions obtained from the stem barks of P. sellowianus using a bioassay-guided fractionation protocol and streptozotocin-induced hyperglycemic mice. The aqueous extract was partitioned between dichloromethane and butanol to yield the dichloromethane (D), butanol (B) and the remaining aqueous (A) fractions. Fractions B and A, administered at the dose of 200 mg/kg p.o., caused a significant reduction in blood glucose concentration at 6 and 9 h, while the same dose of fraction D was ineffective. The reduction in blood glucose levels obtained with the B and A fractions was similar to that observed with glibenclamide (10 mg/kg) which was used as a reference for the hypoglycemic activity. Phytochemical analysis of fractions B and A revealed the presence of flavonoid compounds, of which rutin and isoquercitrin were the major constituents, respectively. The possible involvement of these flavonoids in the hypoglycemic effect of the active fractions is discussed.