Knockout of toll-like receptor-4 attenuates the pro-inflammatory state of diabetes

Type 1 diabetes (T1DM) is associated with increased vascular complications and is a pro-inflammatory state. Recent findings have shown increased TLR2 and 4 expression, signaling, ligands, and functional activation in T1DM subjects compared to controls and further accentuated in T1DM with microvascular complications. Thus, the aim of this study was to examine if genetic deficiency of TLR4 attenuates the increased inflammation associated with T1DM using the streptozotocin-induced diabetic mouse model. C57BL/6 and TLR4(-/-) mice were obtained and studied in the native state and following induction of diabetes using streptozotocin. Diabetic (WT+STZ) mice had increased expression of both TLR2 and TLR4, while TLR4(-/-) STZ mice had increased expression only of TLR2, but not TLR4 compared to the non-diabetic mice TLR2 expression was significantly increased with STZ-induced diabetes and was unaffected by knockout of TLR4. Also, levels of MyD88, IRAK-1 protein phosphorylation, Trif, IRF3, and NF-κB activity were significantly reduced in TLR4(-/-) +STZ mice compared to the WT+STZ mice. WT+STZ mice exhibited significantly increased levels of serum and macrophage IL-1β, IL-6, KC/IL-8, IP-10, MCP-1, IFN beta and TNF-α compared to WT mice and this was significantly attenuated in TLR4(-/-) +STZ mice (P<0.01). Thus, TLR4 contributes to the pro-inflammatory state and TLR4KO attenuates inflammation in diabetes.     

Alpha-phenyl-tert-butylnitrone (PBN) inhibits NFkappaB activation offering protection against chemically induced diabetes

Alpha-phenyl-tert-butylnitrone (PBN) is an effective spin trapping agent by reacting with and stabilizing free radical species. Reactive oxygen species (ROS) have been implicated in pancreatic beta cell death and the development of insulin-dependent diabetes mellitus (IDDM). We speculate that treatment with the PBN, will protect against diabetes development in two distinct chemically induced models for IDDM. Pretreatment with PBN (150 mg/kg ip) significantly reduced the severity of hyperglycemia in both alloxan- and streptozotocin (STZ) induced diabetes. To determine the mechanism by which PBN prevents hyperglycemia, we examined the ability of PBN to inhibit NFkappaB activation and to stabilize alloxan- and STZ-induced radicals. Both alloxan and STZ induced NFkappaB activation in the pancreas 30 min after their injection (50 mg/kg iv). PBN pretreatment inhibited both alloxan- and STZ-induced activation of NFkappaB and nitric oxide production. EPR studies showed that PBN could effectively trap alloxan-induced free radicals. It is clear that PBN can inhibit NFkappaB activation in the pancreas and reduce hyperglycemia in two distinct diabetogenic compounds. This research indicates that NFkappaB activation may be a key signal leading to beta cell death and IDDM. Understanding the cellular pathways leading to beta cell death may help in developing effective preventive or therapeutic targets for IDDM.     

The Chronological Characteristics of SOD1 Activity and Inflammatory Response in the Hippocampi of STZ-Induced Type 1 Diabetic Rats

Because it appears that oxidative stress and inflammation are implicated with disease pathogenesis in the diabetic brain, many researchers have used streptozotocin (STZ)-induced diabetic animals to study superoxide production and the effects of superoxide scavengers like Cu,Zn-superoxide dismutase (SOD1). However, many studies have been conducted without considering temporal changes after STZ injection. Interestingly, though SOD activities were not significantly different among the groups, SOD1 and 4-hydroxy-2-nonenal (4-HNE) immunoreactivities were significantly enhanced at 3 weeks after an STZ injection (STZ3w) versus only marginal levels in sham controls, whereas microglial activity was remarkably reduced in injected rats at this time. However, SOD1 immunoreactivity and microglial activities were only at the sham level at STZ4w. The present study provides important information concerning cell damage by ROS generated by STZ. Microglial response was found to be inactivated at STZ3w and neuronal cells (NeuN) showed a non-significant tendency to be reduced in number at STZ4w except in the dentate gyrus. We speculated that the above oxidative stress-related events should be accomplished at STZ3w in the brains of STZ-induced diabetes animal models. Therefore, the aim of the present study was to investigate chronological changes in SOD1 immunoreactivity associated with lipid peroxidation and inflammatory responses in the hippocampi of STZ-induced type I diabetic rats.     

Studies on the mechanism of testicular dysfunction in the early stage of a streptozotocin induced diabetic rat model

Streptozotocin (STZ) induced diabetic model has been widely used to study the effects of diabetes mellitus (DM) on male infertility, but it remains unclear whether the responses in this model are due to hyperglycemia or STZ per se. This study was designed to investigate the mechanism of STZ on testicular dysfunction. In the present study, sperm characteristics, serum testosterone, steroidogenic enzymes (StAR and 3β-HSD), and the vimentin apical extension of sertoli cells decreased significantly in the STZ group compared with those in the normal controls (p < 0.05), while Johnsen’s score, testicular lipid peroxidation, spermatogenic cell apoptosis, and the expressions of NF-κB and Wnt4 significantly increased (p < 0.05). Insulin replacement mainly restored the decreased serum testosterone and steroidogenic enzymes, but not other parameters. The results indicated that spermatogenic dysfunction in the early stage of STZ-induced diabetic rats was due to direct STZ cytotoxicity to sertoli cells, which could be regulated by Wnt4 and NF-κB, while steroidogenic dysfunction might be a direct or indirect consequence of insulin deficiency. The results suggested that STZ-induced diabetic model, at least in the early stage, is not suitable to study the diabetes-related spermatogenic dysfunction.     

Hexarelin Protects Rodent Pancreatic Β-Cells Function from Cytotoxic Effects of Streptozotocin Involving Mitochondrial Signalling Pathways In Vivo and In Vitro

Mitochondrial functions are crucial for pancreatic β-cell survival and glucose-induced insulin secretion. Hexarelin (Hex) is a synthetic small peptide ghrelin analogue, which has been shown to protect cardiomyocytes from the ischemia-reperfusion process. In this study, we used in vitro and in vivo models of streptozotocin (STZ)-induced β-cell damage to study the protective effect of Hex and the associated mechanisms. We found that STZ produced a cytotoxic effect in a dose- and time-dependent manner in MIN6 cells (a mouse β-cell line). Hex (1.0 μM) decreased the STZ-induced damage in β-cells. Rhodamine 123 assay and superoxide DHE production assay revealed that Hex ameliorated STZ-induced mitochondrial damage and excessive superoxide activity in β-cells. In addition, Hex significantly reduced STZ-induced expression of cleaved Caspases-3, Caspases-9 and the ratio of pro-apoptotic protein Bax to anti-apoptotic protein Bcl-2 in MIN6 cells. We further examined the in vivo effect of Hex in a rat model of type 1 diabetes induced by STZ injection. Hex ameliorated STZ-induced decrease in plasma insulin and protected the structure of islets from STZ-induced disruption. Hex also ameliorated STZ-induced expression of cleaved Caspase-9 and the Bax in β-cells. In conclusion, our data indicate that Hex is able to protects β-cell mass from STZ-caused cytotoxic effects involving mitochondrial pathways in vitro and in vivo. Hex may serve as a potential protective agent for the management of diabetes.     

A novel model of early type 1 diabetes mellitus: The chick embryo air sack model

Diabetes Mellitus (DM) is a metabolic disease characterized by hyperglycemia. Chronic hyperglycemia is associated with long-term dysfunction such as retinopathy, nephropathy, neuropathy and cardiovascular diseases. These complications increase rates of death and disability worldwide. Due to the negative effects of DM on the quality of life, the mechanism and treatments of the disease should be investigated in more detail. Most of the research in diabetes is performed in experimental animals. Experimental animal models contributed to the advancement of clinical research, the development of new therapeutic approaches, the discovery of insulin and the purification of insulin. There are many animal models of DM in the literature. But there are a few DM model studies created with chick embryos. In these studies, it was seen that there were differences in STZ doses and STZ administration techniques. The objective of this study was to create a more acceptable and easier DM model. 180 specific pathogen free (SPF) fertilized chicken eggs (White Leghorn chicken) were used in this study. STZ was administered to 160 SPF eggs for an induced DM model. The remaining 20 SPF eggs were separated as a control group. We used two different DM models (Air sack model (ASM) and Chorioallantoic membrane model (CAMM)) and blood sampling technique in our study. 160 SPF eggs were divided into two groups with 80 eggs in each group, according to the model in which STZ was administered. When the relationship between blood glucose and blood insulin levels were examined, it was determined that there was a significantly strong negative correlation in the control group and ASM 1 group; and a significantly very strong negative correlation was found in the ASM 2 group and ASM 3 group. Our data indicate that the optimal STZ dose to create a DM model was 0.45 mg/egg and the best DM model was ASM. The second technique to be the best blood sampling technique for determining blood glucose levels. We believe that ASM can be used in DM studies and anti-DM drug studies in terms of its easebly, applicability, reproducibility and low cost.     

Transduced Tat-glyoxalase protein attenuates streptozotocin-induced diabetes in a mouse model

Diabetes mellitus (DM) is characterized by hyperglycemia. Glyoxalase 1 (GLO) has considerable potential as a possible therapeutic agent for DM. However, the precise action of GLO remains unclear in DM. In this study, we examined the protective effects of GLO protein in a streptozotocin (STZ)-induced diabetes animal model using cell-permeable Tat-GLO protein. Purified Tat-GLO protein was efficiently transduced into RINm5F cells in a time- and dose-dependent manner and protected cells against sodium nitroprusside (SNP)-induced cell death and DNA fragmentation. Furthermore, Tat-GLO protein significantly inhibited blood glucose levels and altered the serum biochemical parameters in STZ-induced diabetic mice. These results demonstrate that transduced Tat-GLO protein protects pancreatic cells by the inhibition of STZ-mediated toxicity. Therefore, Tat-GLO protein could be useful as a therapeutic agent against DM.     

Streptozotocin directly impairs cardiac contractile function in isolated ventricular myocytes via a p38 map kinase-dependent oxidative stress mechanism

Streptozotocin (STZ) has long been used to induce experimental diabetes mellitus to study diabetic complications such as diabetic cardiomyopathy. However, direct impact of STZ on cardiac function is unknown. This study was designed to evaluate the cardiac contractile effect of STZ in isolated adult rat ventricular myocytes. Contractile properties were assessed with an IonOptix MyoCam system including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90), and maximal velocities of shortening/relengthening (+/-dL/dt). Intracellular Ca2+ handling was evaluated with the fluorescent dye fura-2. Acute exposure of STZ (10(-9)-10(-5) M) depressed PS, prolonged TR90, and decreased electrically stimulated intracellular Ca2+ rise in a concentration-dependent manner. TPS,+/-dL/dt, resting intracellular Ca2+ level, and intracellular Ca2+ clearing rate were unaffected. The STZ-induced mechanical alterations were alleviated by the antioxidant vitamin C (100 microM) and the p38 MAP kinase inhibitor SB203580 (1 microM). 2', 7'-Dichlorofluorescein diacetate staining revealed enhanced production of reactive oxygen species following STZ treatment, which was prevented by either vitamin C or SB203580. Collectively, our data provided convincing evidence that the tool drug for experimental diabetes STZ may itself cause deleterious cardiac contractile dysfunction via an oxidative stress and p38 MAP kinase-dependent mechanism. Thus, caution should be taken when assessing diabetic heart complications using STZ-induced diabetic models.     

Clinical and anti-aging effect of mud-bathing therapy for patients with fibromyalgia

This study focuses on two inflammatory diseases, viz., “diabetes mellitus (DM)” that causes serious complications such as retinopathy, nephropathy, and neuropathy, and “ischemic colitis” which is evoked by DM. Ischemic colitis originates from the reduction in mesenteric blood flow to the colon with existence of the occlusive or non-occlusive reasons. Our study objective was to provide early diagnostic approach for ischemic colitis in streptozotocin (STZ)-induced diabetic rats. Sprague-Dawley rats were divided into four groups: (i) control use of 0.1 M citrate buffer, the solvent of streptozotocin (C), (ii). induced ischemia (I), (iii) rats subjected to 60 mg/kg STZ intraperitoneally to induce type 1 diabetes (D) (48 h after STZ injection, blood glucose levels >200 mg/dl were considered as diabetic), and (iv) diabetic rats subjected to intestinal ischemia (D+I). The third diabetic group (D) was not operated. At the end of the experimental period, rats were sacrificed, C-reactive protein (CRP) and calprotectin levels were measured in the serum and colon tissue specimens. Tissue specimens were also analyzed histologically. We found that serum and colon calprotectin levels were elevated in the D+I group compared to the D and/or I group alone, but relatively calprotectin levels increased in I as compared to C group in colon tissues. CRP levels were significantly increased with ischemic colitis in diabetes, while colon CRP levels were decreased. These results provide evidence for the existence of inflammation in the STZ-induced diabetic rats with ischemic colitis. In conclusion, our measurements of serum calprotectin levels of STZ-induced diabetic rats with ischemic colitis provide a practical approach for an early diagnosis of ischemic colitis. Furthermore, these biochemical analyses correlate well with the histopathologic findings of STZ-induced diabetic rats with ischemic colitis. Future studies would be desirable to further strengthen the role of calprotectin in the early diagnosis of ischemic colitis in diabetics clinical settings.     

Islet Remodeling in Female Mice with Spontaneous Autoimmune and Streptozotocin-Induced Diabetes

Islet alpha- and delta-cells are spared autoimmune destruction directed at beta-cells in type 1 diabetes resulting in an apparent increase of non-beta endocrine cells in the islet core. We determined how islet remodeling in autoimmune diabetes compares to streptozotocin (STZ)-induced diabetes. Islet cell mass, proliferation, and immune cell infiltration in pancreas sections from diabetic NOD mice and mice with STZ-induced diabetes was assessed using quantitative image analysis. Serial sections were stained for various beta-cell markers and Ngn3, typically restricted to embryonic tissue, was only upregulated in diabetic NOD mouse islets. Serum levels of insulin, glucagon and GLP-1 were measured to compare hormone levels with respect to disease state. Total pancreatic alpha-cell mass did not change as autoimmune diabetes developed in NOD mice despite the proportion of islet area comprised of alpha- and delta-cells increased. By contrast, alpha- and delta-cell mass was increased in mice with STZ-induced diabetes. Serum levels of glucagon reflected these changes in alpha-cell mass: glucagon levels remained constant in NOD mice over time but increased significantly in STZ-induced diabetes. Increased serum GLP-1 levels were found in both models of diabetes, likely due to alpha-cell expression of prohormone convertase 1/3. Alpha- or delta-cell mass in STZ-diabetic mice did not normalize by replacement of insulin via osmotic mini-pumps or islet transplantation. Hence, the inflammatory milieu in NOD mouse islets may restrict alpha-cell expansion highlighting important differences between these two diabetes models and raising the possibility that increased alpha-cell mass might contribute to the hyperglycemia observed in the STZ model.     

Maturational impairment of thymic lymphocytes in streptozotocin-induced diabetes in rats

Streptozotocin (STZ)-induced diabetes in rats was associated with marked decreases in thymus weight and the number of thymic lymphocytes. Histologically, the cortical lymphocytes which were present near the cortico-medullary junction in the thymus seemed to be reduced selectively in the STZ-induced diabetes. Rosette-forming cells, which bind to guinea pig erythrocytes in the presence of fetal calf serum, were also significantly decreased. Insulin treatment allayed these intrathymic changes. Preincubation of thymic lymphocytes from diabetic rats with thymosin fraction 5 significantly enhanced the percentage of rosette-forming cells to near the control level. These results suggest that a maturational impairment of thymus cortical lymphocytes may be caused in STZ-induced diabetes with hypoinsulinemia and it may be intimately related to reductions in thymus weight and the number of thymic lymphocytes.     

Effect of sarpogrelate on altered STZ-diabetes induced cardiovascular responses to 5-hydroxytryptamine in rats

Sarpogrelate, a specific 5-HT_2A receptor antagonist is reported to produce a number of beneficial cardiovascular effects in diabetes mellitus. In the present investigation we have studied the effects of sarpogrelate on 5-HT receptors in heart and platelets in streptozotocin (STZ)-diabetic rats. Diabetes was induced by a single tail vein injection of STZ (45 mg/kg) and sarpogrelate (1 mg/kg, i.p.) was administered daily for 6 weeks. Injection of STZ produced significant loss of body weight, polyphagia, polydypsia, hyperglycemia, hypoinsulinemia, hypertension and bradycardia. Treatment with sarpogrelate significantly lowered fasting glucose levels with corresponding increase in insulin levels. It also significantly prevented STZ-induced polydypsia, hyperphagia, hypertension, and bradycardia but not the loss of body weight. 5-HT produced dose-dependent positive inotropic effect that was found to be decreased significantly in STZ-diabetic rats. Hearts obtained from sarpogrelate treated diabetic rats did not show any decrease in responsiveness to 5-HT. Relative platelet aggregation per se was found to be higher in STZ-diabetic rats as compared to control and this was significantly prevented by sarpogrelate treatment. 5-HT produced a dose-dependent increase in platelet aggregation in non-diabetic and sarpogrelate treated diabetic rats. However, 5-HT failed to produce any increase in platelet aggregation in untreated diabetic rats. Our data suggest that STZ-induced diabetes may produce down-regulation of cardiac 5-HT_2A receptors and increased platelet aggregation. Treatment with sarpogrelate seems to prevent STZ-induced down-regulation of 5-HT receptors and increase in platelet activity in diabetic rats.     

Protective effect of secoisolariciresinol diglucoside against streptozotocin-induced diabetes and its mechanism

Objectives: Reactive oxygen species (ROS) have been implicated in the development of streptozotocin (STZ)-induced diabetes mellitus. Secoisolariciresinol diglucoside (SDG) isolated from flaxseed is an antioxidant. An investigation was made of the effects of SDG on the development of STZ-induced diabetes in rat, to determine if SDG can prevent/reduce the development of diabetes and if this prevention/reduction is associated with reduction in oxidative stress.Design and Methods: The rats were divided into 4 groups: Group I, Control; Group II, SDG (22 mg/kg body wt, orally) for 24 days; Group III, STZ (80 mg/kg intraperitoneally); Group IV, SDG in the dose similar to Group II three days prior to STZ and 21 days thereafter. Oxidative stress was assessed by measuring serum and pancreatic lipid peroxidation product malondialdehyde (MDA), pancreatic antioxidant reserve (pancreatic-CL) and oxygen free radical producing activity of white blood cells (WBC-CL). A diagnosis of diabetes was made on the basis of glucosuria and was confirmed at the time of sacrifice (21 days after STZ treatment) by the presence of hyperglycemia. At the end of the protocol blood samples were collected for estimation of glucose, MDA and WBC-CL, and pancreas were removed for estimation of MDA and antioxidant reserve.Results: Incidence of diabetes was 100% in Group III and 25% in Group IV. SDG prevented the development of diabetes by 75%. Development of diabetes was associated with an increase in serum and pancreatic MDA, and in WBC-CL, and a decrease in pancreatic antioxidant reserve. Prevention of diabetes by SDG was associated with a decrease in serum and pancreatic MDA and WBC-CL and an increase in pancreatic antioxidant reserve.Conclusions: These results suggest that STZ-induced diabetes is mediated through oxidative stress and that SDG is effective in reducing the STZ-induced diabetes mellitus.     

Tangeretin inhibits streptozotocin-induced cell apoptosis via regulating NF-κB pathway in INS-1 cells

Oxidative stress is considered to play an important role in inducing the pancreatic β-cells apoptosis and promoting the development of diabetes mellitus. Tangeretin is a plant-derived flavonoid that retains antidiabetic effects. However, the role of tangeretin in streptozotocin (STZ)-induced β-cell apoptosis remains unclear. In this study, we aimed to examine the effects of tangeretin on STZ-induced cell apoptosis and the underlying mechanisms implicated in vitro. Our results showed that tangeretin improved the cell viability in STZ-induced INS-1 cells. Tangeretin reduced the increase of apoptosis ratio and revered the altered expressions of Bax and Bcl-2 caused by STZ induction. Furthermore, the impairment of insulin secretion ability as well as a reduction in messenger RNA levels of insulin 1 and 2 was significantly attenuated by tangeretin in STZ-induced INS-1 cells. Moreover, tangeretin resulted in a significant decrease in reactive oxygen species content, accompanied by an evident increase in the activities of superoxide dismutase, catalase, and glutathione peroxidase. Mechanistic studies further revealed that tangeretin inhibited the NF-κB pathway in STZ-induced INS-1 cells. These data indicated that tangeretin improved the cell apoptosis induced by STZ in INS-1 cells, which might be partly due to its antioxidant potential. Furthermore, NF-κB was found to be involved in the protective effect of tangeretin. Collectively, the results indicated that tangeretin could be used as a therapeutic approach for diabetes mellitus treatment.     

Phlorizin Pretreatment Reduces Acute Renal Toxicity in a Mouse Model for Diabetic Nephropathy

Streptozotocin (STZ) is widely used as diabetogenic agent in animal models for diabetic nephropathy (DN). However, it is also directly cytotoxic to kidneys, making it difficult to distinguish between DN-related and STZ-induced nephropathy. Therefore, an improved protocol to generate mice for DN studies, with a quick and robust achievement of the diabetic state, without direct kidney toxicity is required. To investigate the mechanism leading to STZ-induced nephropathy, kidney damage was induced with a high dose of STZ. This resulted in delayed gastric emptying, at least partially caused by impaired desacyl ghrelin clearance. STZ uptake in the kidneys is to a large extent mediated by the sodium/glucose cotransporters (Sglts) because the Sglt inhibitor phlorizin could reduce STZ uptake in the kidneys. Consequently, the direct toxic effects in the kidney and the gastric dilatation were resolved without interfering with the β-cell toxicity. Furthermore, pancreatic STZ uptake was increased, hereby decreasing the threshold for β-cell toxicity, allowing for single low non-nephrotoxic STZ doses (70 mg/kg). In conclusion, this study provides novel insights into the mechanism of STZ toxicity in kidneys and suggests a more efficient regime to induce DN with little or no toxic side effects.     

不同剂量链脲菌素对恒河猴某些常规生理指标的影响

目的　研究链脲菌素 (STZ)对恒河猴摄食、饮水、排尿、体重、血糖及尿糖等生理指标的影响 ,为建立糖尿病动物模型积累资料。方法　通过静脉给 7只恒河猴注射不同剂量的STZ。结果　使用不同剂量STZ后 ,7只恒河猴均在不同时间、不同程度出现与人糖尿病相类似的“三多一少”症状 ,同时对糖尿病猴使用不同剂量胰岛素可使其症状减轻。尤其是中、高剂量组的动物症状较为明显 ,而低剂量组体重有一个短时间的增加后又迅速下降。实验组中血糖和尿糖均出现不同程度的升高 ,以中、高 2个剂量组的动物变化较大。结论　采用中、高剂量组的STZ可诱导类似人类糖尿病的急性动物模型 ,而使用胰岛素治疗或低剂量STZ可使该动物模型疾病病程延长 ,有利于进行其并发症的研究。     

Effects of streptozotocin-induced diabetes on action potentials in the sinoatrial node compared with other regions of the rat heart

In vivo biotelemetry studies have demonstrated that heart rate (HR) is progressively and rapidly reduced after administration of streptozotocin (STZ) and that the reduction in HR can be partially normalized with insulin replacement. Reductions in HR have also been reported in isolated perfused heart and superfused right atrial preparations suggesting that intrinsic defects in the heart are at least partly responsible for the bradycardia. The regional effects of STZ-induced diabetes mellitus (DM) on action potentials (APs) in the sinoatrial node (SAN), right and left atria and ventricles have been compared in the spontaneously beating Langendorff perfused rat heart 10–12 weeks after treatment. HR was significantly reduced in STZ-induced diabetic rat heart (174 ± 9 BPM) compared to controls (241 ± 12 BPM). The duration of AP repolarization at 50% and 70% from peak AP was significantly prolonged in SAN, right atrium and right ventricle from STZ-induced diabetic rat compared to age-matched controls. In the SAN AP duration (APD) at 50% and 70% were 51.7 ± 2.2 and 59.5 ± 2.3 ms in diabetic rat heart compared to 45.2 ± 1.7 and 50.0 ± 1.6 ms in controls, respectively. In contrast APD at 50% and 70% were not significantly altered in the left atrium and left ventricle. Regional defects in the expression and/or electrophysiology of SAN ion channels, and in particular those involved in AP repolarization, might underlie heart rhythm disturbances in the STZ-induced DM rat.     

Real-time measurement of kidney tubule fluid nitric oxide concentrations in early diabetes: disparate changes in different rodent models.

There are several reports indicating that nitric oxide (NO) plays a role in the kidney hyperfiltration seen in the early stages of diabetes mellitus (DM). Whole kidney GFR and single nephron GFR (SNGFR) have been reported to decrease after nitric oxide synthase (NOS) inhibition. To date, no direct, in vivo, quantitative NO measurements have been made within the kidney in any models of early diabetes. To assess the possible association of changes in tubular fluid nitric oxide concentrations (TF [NO]) with early diabetes, a specially modified NO electrode with a tip diameter of about 7 microm was used to measure NO in single tubules in seven rodent groups. In the Sprague-Dawley (SD) rat model, TF [NO] increased by 50% after streptozotocin (STZ) induced DM1. In the B6129G2/J mouse, control TF [NO] was more than twice the rat control value and fell by 50% after STZ treatment. In three other groups of mice-db/db (B6.Cg-m+/+Lepr(db)/J) Type II diabetic (DM2) mouse, db/m (its heterozygote), and the corresponding wild type (WT)-TF [NO] was also much higher than in the rat, and unlike the B6129G2/J STZ diabetic mouse, did not change after the onset of diabetes. Blood glucose concentrations were similar in the three diabetic groups. Accordingly, in different rodent models of diabetes, in vivo TF [NO], measured in real time, varies significantly in control animals and directionally in different models of DM1 and DM2.     

Protective effects of the volatile oil of Nigella sativa seeds on β-cell damage in streptozotocin-induced diabetic rats: a light and electron microscopic study

The aim of this study was to evaluate the possible protective effects of the volatile oil of Nigella sativa (NS) seeds on insulin immunoreactivity and ultrastructural changes of pancreatic β-cells in STZ-induced diabetic rats. STZ was injected intraperitoneally at a single dose of 50 mg/kg to induce diabetes. The rats in NS treated groups were given NS (0.2 ml/kg) once a day orally for 4 weeks starting 3 days prior to STZ injection. To date, no ultrastructural changes of pancreatic β-cells in STZ induced diabetic rats by NS treatment have been reported. Islet cell degeneration and weak insulin immunohistochemical staining was observed in rats with STZ-induced diabetes. Increased intensity of staining for insulin, and preservation of β-cell numbers were apparent in the NS-treated diabetic rats. The protective effect of NS on STZ-diabetic rats was evident by a moderate increase in the lowered secretory vesicles with granules and also slight destruction with loss of cristae within the mitochondria of β-cell when compared to control rats. These findings suggest that NS treatment exerts a therapeutic protective effect in diabetes by decreasing morphological changes and preserving pancreatic β-cell integrity. Consequently, NS may be clinically useful for protecting β-cells against oxidative stress.     

Susceptibility to streptozotocin-induced diabetes is mapped to mouse chromosome 11

To study the contribution of beta-cell vulnerability to susceptibility to diabetes, we studied beta-cell vulnerability to a single high dose of streptozotocin (STZ) in an animal model of type 2 diabetes, the NSY mouse, a sister strain of the STZ-sensitive NOD mouse, in comparison with the STZ-resistant C3H mouse. NSY mice were found to be extremely sensitive to STZ. Introgression of a single Chr 11, where STZ-sensitivity was mapped in the NOD mouse, from NSY mice converted STZ-resistant C3H mice to STZ-sensitive. Two nucleotide substitutions were identified in the nucleoredoxin gene, a positional and functional candidate gene for STZ-induced diabetes on Chr 11. These data, together with the co-localization of type 1 (Idd4) and type 2 (Nidd1n) susceptibility genes on Chr 11, suggest that the intrinsic vulnerability of pancreatic beta cells is determined by a gene or genes on Chr 11, which may also contribute to susceptibility to spontaneous diabetes.