Appearance and metabolic development of diabetes mellitus in the sand rat, Psammomys obesus

The aim of this study was to examine the long-term effects of synthetic chow diet on the metabolic pattern of diabetic syndrome in a large group of sand rats. Few animals had a fulminating reaction with markedly decreased glucose tolerance, low plasma insulin levels and death within 3-4 weeks. But the most of sand rats developed obesity and elevated plasma insulin levels. From the third month, 40% of sand rats presented a diabetic syndrome with hyperinsulinemia, hyperglycemia, markedly decreased glucose tolerance and insulin resistance. Plasma lipids were increased; the lipid and glycogen accumulation in the liver was high. So this diabetic syndrome can be compared to maturity onset diabetes. If this synthetic chow diet lasted more than 6 months, the most of animals lost considerable weight with a strong lipid depletion of fat stores. Serum immunoreactive insulin levels fall and the blood glucose rose over 500 mg/100 ml with glycosuria and ketonuria . The elevated triglyceride content of plasma and the lipid deposits in the liver were exaggerated; glycogen had disappeared. Animals developed an overtly insulin- dependent diabetes, the latter phase of the disease. The sand rat appears to us as a potentially interesting model for investigation both maturity onset and ketotic-type diabetic syndrome.     

Control of hyperglycemia and retardation of cataract by mulberry (Morus indica L.) leaves in streptozotocin diabetic rats

Dried leaf powder of mulberry (M. indica L.) when given along with the diet at 25% level to streptozotocin induced diabetic male Wistar albino rats for 8 weeks, controlled hyperglycemia, glycosuria, albuminuria and retarded onset of retinopathy. Untreated diabetic rats showed hyperglycemia, glycosuria, albuminuria and developed lenticular opacity after 8 weeks of experimental period.     

Cardiac function in spontaneously diabetic BB rats treated with low and high dose insulin

Cardiac abnormalities observed in animals with drug-induced diabetes may be due to the direct cardiotoxic effect of the drugs or factors not related to the diabetic state. The purpose of this investigation was to examine cardiac sarcoplasmic reticular (SR) calcium transport and heart function in the BB rat, a strain in which diabetes occurs spontaneously and clearly resembles insulin-dependent diabetes in humans. Complete insulin withdrawal for 2 or 4 days from BB diabetic rats leads to a spectrum of metabolic derangements including a loss of body weight, hyperglycemia, and elevated triglyceride levels confirming the insulin dependence of this model. The present study involved treating BB diabetic rats with a low (hyperglycemic) and high (normoglycemic) insulin dose for 12 weeks after the detection of glycosuria. The hearts from these animals were then isolated, and SR Ca2+ transport and heart function (using isolated perfused working hearts) were examined and compared with BB nondiabetic littermates or Wistar controls. Strain-related differences were found in ATP-dependent SR Ca2+ transport between the Wistar and BB rats. There were, however, no significant diabetes-related differences in SR Ca2+ transport between the low dose insulin treated diabetic group (LD) and the high dose insulin treated diabetic group (HD) or the nondiabetic littermates. Plasma lipid concentrations of the LD and HD BB rats and nondiabetic littermates were also generally higher than those of control Wistar rats indicating strain-related but not diabetes-related differences. In addition, there were no differences in cardiac function between the LD and BB nondiabetic littermates or Wistar controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of sex hormones on the onset of diabetic syndrome in WBN/Kob rats]

The effects of sex hormone on diabetic conditions were investigated in WBN/Kob strain rats, i.e., castrated or spayed, hormone-treated, and non-treated rats. The effects of sex hormone on glycosuria, body-weight change, glucose tolerance and histopathology of the pancreas were compared among these animals. There were no abnormal changes in these parameters in the non-treated females and estrogen-treated males. The glycosuria began to be observed from the age of about 30 weeks in the non-treated group and from the age of 52 weeks in the castrated group. In the female animals, this symptom began to appear from the age of 55 weeks in the testosterone-treated group and from the age of 72 weeks in the spayed group. Before the onset of the diabetic symptoms, glucose tolerance was impaired in these animals. Body weights of the castrated and estrogen-treated males were lower than that of the non-treated males, especially in the estrogen-treated males. Those of the spayed and testosterone-treated females were much heavier than that of the non-treated females. Testosterone treatment accelerated body-weight gain in the spayed female animals. Histopathological examination of the pancreas revealed atrophy of the aciner tissue and atrophy and disappearance of the islet cells similar to those of the non-treated WBN/Kob male rats in the castrated males, spayed females and testosterone-treated females. However, these changes were not observed in the non-treated females or estrogen-treated males. These findings suggest that female hormone suppressed the onset of hyperglycemia along with glycosuria and male hormone accelerates the onset of hyperglycemia in the WBN/Kob rats.     

非肥胖型糖尿病小鼠成年神经发生的实验研究

目的:探讨异常免疫反应介导的糖尿病(DM)对大脑神经干/祖细胞(NSC/NPC)增殖的影响。方法:依据尿糖测定结果将非肥胖型糖尿病(NOD)小鼠分为发病组和未发病组,观察两组小鼠的体重变化和胰岛炎的严重程度。通过5-溴-2'-脱氧尿苷(BrdU)掺入和免疫荧光染色方法,观察两组小鼠海马齿状回(DG)和侧脑室下区(SVZ)的BrdU阳性细胞数量的变化,以评估NSC/NPC增殖情况。结果:发病组小鼠呈现出多饮、多食、多尿等糖尿病典型症状,体重较未发病组明显减低。发病组小鼠胰腺组织中炎症评分为3分的胰岛数量明显多于未发病组,且胰岛炎症的平均评分显著高于未发病组(P0.05)。与未发病组比较,发病组小鼠大脑海马DG区BrdU阳性细胞显著降低(P0.01);SVZ区的BrdU阳性细胞数量亦明显少于未发病组(P0.001)。结论:异常免疫反应介导的DM可抑制小鼠大脑NSC/NPC的增殖。     

Non-Diabetic Hyperglycemia Exacerbates Disease Severity in Mycobacterium tuberculosis Infected Guinea Pigs

Hyperglycemia, the diagnostic feature of diabetes also occurs in non-diabetics associated with chronic inflammation and systemic insulin resistance. Since the increased risk of active TB in diabetics has been linked to the severity and duration of hyperglycemia, we investigated what effect diet-induced hyperglycemia had on the severity of Mycobacterium tuberculosis (Mtb) infection in non-diabetic guinea pigs. Post-prandial hyperglycemia was induced in guinea pigs on normal chow by feeding a 40% sucrose solution daily or water as a carrier control. Sucrose feeding was initiated on the day of aerosol exposure to the H37Rv strain of Mtb and continued for 30 or 60 days of infection. Despite more severe hyperglycemia in sucrose-fed animals on day 30, there was no significant difference in lung bacterial or lesion burden until day 60. However the higher spleen and lymph node bacterial and lesion burden at day 30 indicated earlier and more severe extrapulmonary TB in sucrose-fed animals. In both sucrose- and water-fed animals, serum free fatty acids, important mediators of insulin resistance, were increased by day 30 and remained elevated until day 60 of infection. Hyperglycemia mediated by Mtb infection resulted in accumulation of advanced glycation end products (AGEs) in lung granulomas, which was exacerbated by sucrose feeding. However, tissue and serum AGEs were elevated in both sucrose and water-fed guinea pigs by day 60. These data indicate that Mtb infection alone induces insulin resistance and chronic hyperglycemia, which is exacerbated by sucrose feeding. Moreover, Mtb infection alone resulted in the accumulation tissue and serum AGEs, which are also central to the pathogenesis of diabetes and diabetic complications. The exacerbation of insulin resistance and hyperglycemia by Mtb infection alone may explain why TB is more severe in diabetics with poorly controlled hyperglycemia compared to non-diabetics and patients with properly controlled blood glucose levels.     

Effect of long-term and short-term diabetes on the parathyroid hormone sensitive rat renal adenylate cyclase: correlation with vitamin D metabolism

In short-term experiments, male Wistar rats were made diabetic for 10 days with a single injection of streptozotocin (65 mg/kg body weight). One group of diabetic rats was treated with insulin for 3 days prior to sacrifice. In long-term experiments, vitamin D replete or vitamin D depleted rats were made diabetic for 6 weeks. Criteria for diabetes were loss of weight, glycosuria (Tes-Tape), and hyperglycemia. In long-term diabetic rats the activity of renal mitochondrial 25-hydroxyvitamin D3 (25-(OH)D3) 1 alpha-hydroxylase was significantly decreased and that of 25-(OH)D3 24-hydroxylase increased. However, the parathyroid hormone (PTH) sensitive renal adenylate cyclase activity of diabetic rats was not different from that of the nondiabetic rats in either the vitamin D replete group or the vitamin D depleted group. On the other hand, the PTH-sensitive renal adenylate cyclase activity was significantly higher in short-term diabetic rats than in control and insulin-treated rats. These differences were observed at doses of 10(-8) to 10(-5) M of PTH. This study has demonstrated for the first time that there are differences in the PTH-sensitive adenylate cyclase response between long-term and short-term diabetic rats. The hypersensitivity to PTH of the renal adenylate cyclase observed in short-term diabetic rats probably represents a response to insulin deficiency during the early development of diabetes mellitus in the rats.     

Effects of plasmid DNA injection on cyclophosphamide-accelerated diabetes in NOD mice

Type 1 diabetes results in most cases from the destruction of insulin-secreting beta cells by the immune system. Several immunization methods based on administration of autoantigenic polypeptides such as insulin and glutamic acid decarboxylase (GAD) have been used to prevent autoimmune diabetes in the non-obese diabetic (NOD) mouse. In the work presented here, a gene-based approach was taken for a similar purpose. A plasmid carrying different cDNAs was used to investigate the effects of injecting naked DNA on cyclophosphamide-accelerated diabetes in female NOD mice. Four-week-old animals received intramuscular injections of plasmid DNA encoding either intracellular GAD, a secreted form of GAD, or a secreted form of a soft coral luciferase. Monitoring of glycosuria and hyperglycemia indicated that injection of plasmid DNA encoding secreted GAD and secreted luciferase could prevent and delay diabetes, respectively. In contrast, injection of DNA encoding intracellular GAD did not suppress the disease significantly. Analysis of anti-GAD IgG(1) antibody titers in animal sera indicated that diabetes prevention after injection of GAD-encoding DNA was possibly associated with increased Th2-type activity. These results suggest that cellular localization of GAD is a factor to consider in the design of GAD-based genetic vaccines for the prevention of autoimmune diabetes.     

Effect of hypertension on the development of diabetic cardiomyopathy

The effect of hypertension on the progression of diabetic cardiomyopathy was examined by attempting to induce a similar level of diabetes in both spontaneously hypertensive rats (SHR) and Wistar rats. Streptozotocin (STZ) was injected into SHR (45 mg/kg) and Wistar rats (55 mg/kg) before (eight weeks of age) and after (twelve weeks of age) the development of hypertension in the SHR. For both groups of animals, induction of diabetes resulted in depressed weight gain, increased food and fluid consumption, hypoinsulinemia, hyperglycemia, and hypertriglyceridemia. For the rats injected at eight weeks of age, an oral glucose tolerance test (OGTT) demonstrated that although the SHR were significantly less diabetic than Wistar rats, the degree of cardiac dysfunction was equivalent in both strains. These results suggest that hypertension was interacting with the diabetic condition to impair cardiac performance. Injecting SHR at twelve weeks of age increased the severity of diabetes but interestingly did not depress heart function compared with the non-diabetic SHR group. Injecting Wistar rats at this age also increased the severity of diabetes, but unlike the SHR diabetic animals, these rats still had impaired cardiac performance. These results suggest that hypertension exacerbates the cardiac dysfunction seen during diabetes, especially when SHR rats are injected with STZ prior to the elevation of blood pressure. Moreover, in the SHR, the development of LV hypertrophy at the time of STZ injection may have compensated for the damaging effects of diabetes on the myocardium, thereby enabling the heart to perform normally.     

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。     

Combined effect of nicotinamide and streptozotocin on diabetic status in partially pancreatectomized adult BALB/c mice.

Pancreatic regeneration after pancreatectomy has been well documented in the animal models. We have recently reported that STZ diabetic animals operated for partial pancreatectomy showed normoglycemic status after the operation as compared to uncontrolled hyperglycemia and even death in the diabetic sham operated animals. In drug and virus-induced experimental diabetic models there is a high mortality of animals due to uncontrolled destruction of the beta-cells. In order to destroy sufficient beta-cell mass so as to induce diabetes but prevent mortality, we designed present studies to investigate the combined effect of pancreatectomy, nicotinamide, and streptozotocin (STZ) on diabetic status of BALB/c mice. BALB/c mice of either sex were subjected to 50% pancreatectomy. These were then treated with nicotinamide (350 mg/kg body weight) before and after streptozotocin (200 mg/kg body weight) administration. The changes in body weight, blood glucose levels, serum and pancreatic insulin contents of these animals were monitored in experimental and control group for 12 weeks, and follow up studies were made of these animals for further 12 weeks. It was found that there was a drastic loss of body weight, decreased serum and pancreatic insulin levels coupled with sustained and low levels of hyperglycemia in the experimental group as opposed to the control group. The results indicate that partial pancreatectomy followed by nicotinamide and streptozotocin treatment leads to a long-lasting hyperglycemic state, depicting the clinical symptom of NIDDM without mortality. The study probably reveals a new model for experimental diabetes.     

Formononetin Ameliorates Diabetic Neuropathy by Increasing Expression of SIRT1 and NGF

Diabetic neuropathy is commonly observed complication in more than 50 % of type 2 diabetic patients. Histone deacetylases including SIRT1 have significant role to protect neuron from hyperglycemia induced damage. Formononetin (FMNT) is known for its effect to control hyperglycemia and also activate SIRT1. In present study, we evaluated effect of FMNT as SIRT1 activator in type 2 diabetic neuropathy. Type 2 diabetic neuropathy was induced in rats by modification of diet for 15 days using high fat diet and administration of streptozotocin (35 mg/kg/day, i. p.). FMNT treatment was initiated after confirmation of type 2 diabetes. Treatment was given for 16 weeks at 10, 20 and 40 mg/kg/day dose orally. FMNT treatment‐controlled hypoglycemia and reduced insulin resistance significantly in diabetic animals. FMNT treatment reduced oxidative stress in sciatic nerve tissue. FMNT treatment also reduced thermal hyperalgesia and mechanical allodynia significantly. It improved conduction velocity in nerve and unregulated SIRT1 and NGF expression in sciatic nerve tissue. Results of present study indicate that continuous administration of FMNT protected diabetic animals from hyperglycemia induced neuronal damage by controlling hyperglycemia and increasing SIRT1 and NGF expression in nerve tissue. Thus, FMNT can be an effective candidate for treatment of type 2 diabetic neuropathy.     

Development and characterization of a novel rat model of type 2 diabetes mellitus: the UC Davis type 2 diabetes mellitus UCD-T2DM rat

The prevalence of type 2 diabetes (T2DM) is increasing, creating a need for T2DM animal models for the study of disease pathogenesis, prevention, and treatment. The purpose of this project was to develop a rat model of T2DM that more closely models the pathophysiology of T2DM in humans. The model was created by crossing obese Sprague-Dawley rats with insulin resistance resulting from polygenic adult-onset obesity with Zucker diabetic fatty-lean rats that have a defect in pancreatic beta-cell function but normal leptin signaling. We have characterized the model with respect to diabetes incidence; age of onset; longitudinal measurements of glucose, insulin, and lipids; and glucose tolerance. Longitudinal fasting glucose and insulin data demonstrated progressive hyperglycemia (with fasting and fed glucose concentrations >250 and >450 mg/dl, respectively) after onset along with hyperinsulinemia resulting from insulin resistance at onset followed by a progressive decline in circulating insulin concentrations, indicative of beta-cell decompensation. The incidence of diabetes in male and female rats was 92 and 43%, respectively, with an average age of onset of 6 mo in males and 9.5 mo in females. Results from intravenous glucose tolerance tests, pancreas immunohistochemistry, and islet insulin content further support a role for beta-cell dysfunction in the pathophysiology of T2DM in this model. Diabetic animals also exhibit glycosuria, polyuria, and hyperphagia. Thus diabetes in the UC Davis-T2DM rat is more similar to clinical T2DM in humans than in other existing rat models and provides a useful model for future studies of the pathophysiology, treatment, and prevention of T2DM.     

Effect of antilymphocyte serum and neonatal thymectomy upon onset of diabetes in the Chinese hamster

Prediabetic Chinese hamsters were treated with antilymphocyte serum (ALS), or thymectomized in order to test the hypothesis that beta-cell loss leading to diabetes in this animal model was related to cell-mediated autoimmunity. In addition, passive transfer of diabetes from the Chinese hamster to the nude mouse was attempted by transplantation of lymphocytes. Treatment of prediabetic Chinese hamsters with ALS or thymectomy did not alter development or severity of diabetes in this animal model. Lymphocytes from newly diagnosed diabetic Chinese hamsters did not cause hyperglycemia in nude mice. These three lines of evidence suggest that cell-mediated autoimmunity does not contribute to the etiology of diabetes in the Chinese hamster. The Chinese hamster remains a good model for the study of those forms of diabetes not related to cell-mediated autoimmune phenomena.     

Induction of diabetes with signs of autoimmunity in primates by the injection of multiple-low-dose streptozotocin

Aim

To develop a preclinical large animal model of autoimmune diabetes to facilitate the translational research of autoimmune diabetes in human.

Materials and methods

Nine young rhesus monkeys received multiple-low-dose (MLD) intravenous injections of streptozotocin for five consecutive days, followed by two additional boosting injections of STZ given 1 week apart. The induction of autoimmune diabetes was evaluated by regular metabolic testing, serological assessment of islet-reactive autoantibodies and histological examination of pancreatic tissues.

Results

Seven of nine treated animals became diabetic with moderate hyperglycemia initially and more severe hyperglycemia thereafter. All diabetic animals exhibited severely impaired glucose tolerance, limited islet function, and required insulin therapy to maintain relatively normal glucose metabolism and healthy status. Serological tests showed that all diabetic monkeys developed autoantibodies specifically against insulin and islet antigens. Furthermore, histological examination of the pancreata from diabetic animals revealed evidence of specific destruction of islet β cells and islets infiltrated with T lymphocytes. Overt and persistent diabetes can be induced in young rhesus monkeys by the injection of MLD-STZ, and autoimmune responses to pancreatic islet cells seem to be involved in the development of glucose intolerance and diabetes.

Conclusion

These data indicate for the first time that autoimmune diabetes can be induced in primates; this may serve as a valuable preclinical model for studying the pathogenesis of and potential therapies for autoimmune diabetes in humans.     

CD8+ T cell homing to the pancreas in the nonobese diabetic mouse is CD4+ T cell-dependent.

The adoptive transfer of type I diabetes in nonobese diabetic mice requires the contribution of both CD4+ and CD8+ T cells. To further elucidate the cellular pathway(s) of beta-cell destruction and the responsibility of each subset, high doses of committed T cells from diabetic mice purified to single subsets, were injected into syngeneic nonobese diabetic neonates. The recipients of single or mixed subsets were followed for clinical manifestations of diabetes and examined at 30 days of age for in situ lesions. None of the animals injected with either CD4+ or CD8+ T cells became overtly diabetic during the 30 days of observation whereas 8 of 23 mice inoculated with a mixture of the two subsets developed glycosuria and hyperglycemia. However, insulitis was found in 6 of the 13 mice injected with CD4+ T cells whereas only 1 of the 9 mice injected with CD8+ T cells showed marginal infiltration of the pancreas. The lesions initiated by CD4+ T cells alone were considerably less severe than those induced by the mixture of both subsets, corroborating the fact that overt disease did not occur in the former group. Together, these results suggest a distinct function for each diabetogenic T cell subset. CD4+ T cells, which have the capacity to home to the pancreas, promote in turn the influx of CD8+ effector T cells that do not by themselves accumulate in this organ. These results illustrate a novel form of T-T cell interactions leading to organ specific autoimmune lesions.     

Hyperglycemia and loss of ovarian hormones mediate atheroma formation through endothelial layer disruption and increased permeability

The overall goal of this project was to examine the interactions of hyperglycemia and loss of ovarian hormones on the artery wall in a type I diabetic mouse model. Intact or ovariectomized (OVX) female BALB/C mice were fed a high-cholesterol diet. Half the animals were treated with steptozotocin to induce insulin-deficient diabetes mellitus, generating four treatment groups: control, intact; control, ovariectomized; diabetic, intact; diabetic, ovariectomized (DOVX). We examined arterial structure and function and found that 1) diabetes and ovariectomy additively increased endothelial layer permeability, 2) arterial stiffening was increased in DOVX, 3) DOVX synergistically increased atheroma formation, and 4) ultrastructural evaluation revealed that the basal lamina was often multilayered and formed convoluted aggregates separating endothelium from the internal elastic lamina in diabetic, but not control arteries or arteries from OVX mice. Endothelium overlying these regions formed thin cytoplasmic extensions between these aggregates and was often separated from the basal lamina by electron lucent spaces. Our studies showed that diabetes and loss of ovarian function have additive and synergistic effects to worsen arterial pathophysiology by disrupting the arterial endothelial layer with increased permeability and increased atheroma formation.     

Diabetes induced in male transgenic mice by expression of human H-ras oncoprotein in pancreatic beta cells.

Transgenic mice expressing an insulin-promoted H-ras hybrid gene in pancreatic beta cells developed beta-cell degeneration and diabetes. The disease was manifested in male mice by hyperglycemia, glycosuria, and reduced plasma insulin levels, which appeared around 5 months of age and led to premature death. Histological analyses revealed large holes within the islets of Langerhans and a reduced number of beta cells. The destruction of the islets was not associated with an obvious inflammatory activity. Ultrastructural analysis showed extensive engorgement in the endoplasmic reticulum of the residual beta cells from diabetic males. The females carrying the insulin-promoted ras gene did not manifest any of the physiological abnormalities observed in males and showed only minor histological and ultrastructural changes, even at much greater ages.     

Glomerular Basement Membrane Selective Permeability in Short-term Streptozotocin-induced Diabetic Rats

In diabetes, the glomerular basement membrane undergoes thickening and structural alterations with loss of glomerular permselectivity properties. However, the onset of the alterations at early phases of diabetes is unclear. Aiming to determine the functional and structural alterations of the glomerular wall in the early stages of diabetes, we have studied the distribution of endogenous circulating albumin and type IV collagen in the glomerular basement membrane, using the immunocytochemical approach. The streptozotocin-injected hyperglycemic rat was our animal model. Renal tissues were examined after 10 days, 2, 4 and 6 months of hyperglycemia. Upon immunogold labelings, changes in the glomerular permeability to endogenous albumin were found altered as early as upon ten days of hyperglycemia. In contrast, no structural modifications were detected at this time point. Indeed, glomerular basement membrane thickening and an altered type IV collagen labeling distribution were only observed after four months of hyperglycemia, suggesting that functional alterations take place early in diabetes prior to any structural modification. In order to evaluate the reversibility of the glomerular alterations, two-month-old diabetic animals were treated with insulin. These animals showed a significant restoring of their glomerular permselectivity. Our results suggest a link between glycemic levels and alteration of glomerular permeability in early stages of diabetes, probably through high levels of glycated serum proteins.     

The course of development of glucose intolerance in the monkey (Macaca mulatta).

Longitudinal studies of the rhesus monkey reveal a syndrome of diabetes mellitus in those that become middle-aged and obese. The sequence of events in the development of the disease progresses from normoinsulinemia with normoglycemia through stages of hyperinsulinemia followed by below normal insulin levels with hyperglycemia and glycosuria. We believe the rhesus to be an excellent nonhuman primate model for maturity-onset diabetes in humans.