Subdiabetogenic Doses Of Streptozotocin Research Articles

Preferential effect of Montelukast on Dapagliflozin: Modulation of IRS-1/AKT/GLUT4 and ER stress response elements improves insulin sensitivity in soleus muscle of a type-2 diabetic rat model

AimsMontelukast (MNK), a leukotriene receptor antagonist, has proven its antioxidant/anti-inflammatory capacity to guard against diabetes-induced complications and to enhance metformin antidiabetic effect. Nevertheless, here we evaluated the involvement of endoplasmic reticulum (ER) stress and insulin signaling cascade in the effect of MNK and/or dapagliflozin (DAPA) using the soleus muscle of type 2 diabetic (T2D)/insulin resistant (IR) rats. Main methodsTo induce T2D/IR, rats were fed a westernized diet (WD) for 8 weeks followed by a sub-diabetogenic dose of streptozotocin (STZ). Animals were divided into control (receiving normal diet; ND), diabetic untreated, and diabetic treated for 4 weeks with DAPA, MNK, or their combination (DAPA+MNK). Blood glucose and serum lipid profile were determined, and the soleus muscle was tested for ER stress-induced IR, besides histopathological examination. Key findingsTreatment with DAPA, MNK, and especially their combination decreased the fasting plasma levels of glucose and insulin while improving insulin sensitivity and lipid profile. This was achieved via the activation of insulin signaling IRS-1/AKT/GLUT4 pathway in the soleus muscle consequent to the deactivation of the ER stress response elements, namely IRE1α, ATF6, and PERK to suppress p-JNK and p-eIF2α. SignificanceImproved insulin signaling along with the deactivation of the ER stress response by MNK comparable to the DAPA are partly responsible for the enhanced soleus muscle insulin sensitivity, effects that nominate MNK as an add-on to DAPA to enhance its antidiabetic efficacy.

202-LB: Reduced Glucose Effectiveness Exacerbates Impaired Glucose Tolerance in Prediabetic Dogs

The prodromal prediabetic state is characterized by glucose intolerance. Both insulin-dependent (sensitivity, secretion, clearance) and -independent factors (“glucose effectiveness”) contribute to glucose homeostasis. The relative importance of glucose effectiveness is not known. Healthy dogs (n=18) were tested at baseline (BL), after 6 wk on a high-fat diet (HFD), and 2 wk, after a sub-diabetogenic dose of streptozotocin (STZ, 18.5 mg/kg); HFD was continued. We performed intravenous glucose tolerance tests (IVGTTs)at 0, 6, and 8 wks. Minimal model analysis quantified insulin sensitivity (SI), acute insulin response to glucose (AIRg), disposition index (DI, = SI x AIRg), and glucose tolerance (KG). Glucose effectiveness (SG) was measured both by minimal model analysis and directly by multi-step hyperglycemic clamps at basal insulin in a subset of the dogs (n=5). Consumption of HFD induced 7.7±1.0% weight gain (P<0.001) and reduced SI (BL: 3.33±0.35; HFD: 2.01±0.38 x 104 min-1 per µU/ml; P=0.02). HFD elicited an increased AIRg (BL: 596±42; HFD: 1865±476 µU/ml, P=0.03) while maintaining KG (BL: 3.33±0.25; HFD: 3.67±0.33 min-1, P=0.69) as well as β-cell function expressed as DI (BL: 1939±236; HFD: 1882±199, P=0.97). SG was not changed by fat feeding per se (P=0.88). Prediabetes (STZ) conserved fasting glucose, but KG deteriorated (-45% from HFD to STZ) due to sustained insulin resistance with compromised β-cell function (DI decreased by 45±8%, P<0.01). Additionally, minimal model-based SG declined 37±8% from HFD to STZ (0.044±0.003 vs. 0.027±0.003 min-1, P<0.01), a result confirmed by glucose clamps (-30%). Impairments in both insulin-dependent and insulin-independent factors contribute to the glucose intolerance of experimental prediabetes. Rather than compensating for insulin resistance and beta-cell dysfunction, glucose effectiveness also declines, demonstrating that it exacerbates and contributes to glucose intolerance in the canine model of prediabetes. Disclosure C. M. Kolka: Research Support; Self; AstraZeneca. J. Porter: None. M. Ader: None. R. N. Bergman: None. Funding National Institutes of Health (DK27619, DK29867)

Escitalopram Ameliorates Cardiomyopathy in Type 2 Diabetic Rats via Modulation of Receptor for Advanced Glycation End Products and Its Downstream Signaling Cascades.

Type 2 diabetes mellitus (T2DM) has been recognized as a known risk factor for cardiovascular diseases. Additionally, studies have shown the prevalence of depression among people with diabetes. Thus, the current study aimed to investigate the possible beneficial effects of escitalopram, a selective serotonin reuptake inhibitor, on metabolic changes and cardiac complications in type 2 diabetic rats. Diabetes was induced by feeding the rats high fat-high fructose diet (HFFD) for 8 weeks followed by a subdiabetogenic dose of streptozotocin (STZ) (35 mg/kg, i. p.). Treatment with escitalopram (10 mg/kg/day; p. o.) was then initiated for 4 weeks. At the end of the experiment, electrocardiography was performed and blood samples were collected for determination of glycemic and lipid profiles. Animals were then euthanized and heart samples were collected for biochemical and histopathological examinations. Escitalopram alleviated the HFFD/STZ-induced metabolic and cardiac derangements as evident by improvement of oxidative stress, inflammatory, fibrogenic and apoptotic markers in addition to hypertrophy and impaired conduction. These results could be secondary to its beneficial effects on the glycemic control and hence the reduction of receptor for advanced glycation end products content as revealed in the present study. In conclusion, escitalopram could be considered a favorable antidepressant medication in diabetic patients as it seems to positively impact the glycemic control in diabetes in addition to prevention of its associated cardiovascular complications.

Insulin-like Growth Factor 2 Overexpression Induces β-Cell Dysfunction and Increases Beta-cell Susceptibility to Damage

The human insulin-like growth factor 2 (IGF2) and insulin genes are located within the same genomic region. Although human genomic studies have demonstrated associations between diabetes and the insulin/IGF2 locus or the IGF2 mRNA-binding protein 2 (IGF2BP2), the role of IGF2 in diabetes pathogenesis is not fully understood. We previously described that transgenic mice overexpressing IGF2 specifically in β-cells (Tg-IGF2) develop a pre-diabetic state. Here, we characterized the effects of IGF2 on β-cell functionality. Overexpression of IGF2 led to β-cell dedifferentiation and endoplasmic reticulum stress causing islet dysfunction in vivo. Both adenovirus-mediated overexpression of IGF2 and treatment of adult wild-type islets with recombinant IGF2 in vitro further confirmed the direct implication of IGF2 on β-cell dysfunction. Treatment of Tg-IGF2 mice with subdiabetogenic doses of streptozotocin or crossing these mice with a transgenic model of islet lymphocytic infiltration promoted the development of overt diabetes, suggesting that IGF2 makes islets more susceptible to β-cell damage and immune attack. These results indicate that increased local levels of IGF2 in pancreatic islets may predispose to the onset of diabetes. This study unravels an unprecedented role of IGF2 on β-cells function.

Genetic control of diabetes induction by complete Freund's adjuvant combined with subdiabetogenic doses of streptozotocin in Lewis rats--evidence for transient cytotoxicity against beta cells.

The non-specific activation of the immune system by administration of complete Freund's adjuvant (CFA) was examined in two congenic Lewis rat strains LEW. 1A (RT1a) and LEW. 1W (RT1u) as a possible mean of amplification of the specific immune response, directed to pancreatic beta cells induced by multiple non-diabetogenic injections of streptozotocin (STZ). Rats were given intraperitoneally 0.5 ml CFA and 1 day later 25 mg/kg body weight STZ. This combined treatment was repeated twice at weekly intervals. Control groups received vehicle, STZ or CFA only with the same doses and at the same times. Only CFA/STZ-treated rats developed a persisting hyperglycaemia (greater than 15 mmol/l glucose) namely 3/18 (17%) LEW. 1W and 47/76 (62%) LEW. 1A rats. The pancreatic insulin content in these hyperglycaemic rats was reduced by 96.6% in LEW. 1A rats and by 93% in LEW. 1W rats measured 8 weeks after the last CFA/STZ treatment. The response to CFA indicated by an increase of number of peripheral leucocytes and relative spleen weight gain at 7 days after CFA administration, was higher in LEW. 1A rats compared with those of LEW. 1W rats. Spleen cells harvested 72 h/48 h after the first and second CFA/STZ administration showed a cytotoxic reaction to isolated syngeneic islets as measured by 51Cr-release in vitro. Control rats receiving vehicle, STZ or CFA only showed no cellular anti-islet cytotoxicity. The anti-islet cytotoxicity of spleen cells was only transient and disappeared after the third CFA/STZ administration. Anti-islet cytotoxic antibodies were not detectable in this short-term study.(ABSTRACT TRUNCATED AT 250 WORDS)

Generation and partial characterization of monoclonal antibodies reactive with islet cell antigens.

Islet cell antibodies have been detected in more than 60% of newly diagnosed type I diabetics. Their pathogenetic role is still unclear. We have generated monoclonal antibodies (mc-ab) reactive with islet cell antigens by fusing mouse myeloma cells with spleen cells from Balb/c mice immunized with pancreatic islet cells. Hybridomas producing islet cell surface antibodies (ICSA) were detected by indirect immunofluorescence on viable cells from rat islets or rat insulinoma. Cytoplasmic islet cell antibodies (ICA) were detected by indirect immunofluorescence on Bouin-fixed sections of mouse pancreas. The ICSA- and/or ICA-producing hybridomas were cloned twice by limiting dilution. This paper describes six different mc-ab. All hybrid cell lines obtained produced IgM antibodies. Four of them mediate complement-dependent cytotoxicity to viable rat islet cells. In the present study the heterogeneity of circulating ICSA is demonstrated. Also, a monoclonal beta cell surface autoantibody K56aF3 was produced by fusion of spleen cells from a mouse treated with sub-diabetogenic doses of streptozotocin in combination with complete Freund's adjuvant. It was cytotoxic against islet cells up to a dilution of 1:1,000 and it could inhibit the insulin secretion from neonatal rat islets cultured in RPMI 1640 as stimulated by glucose or by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine common with glucose. The latter effect was reversible as indicated by the recovery of insulin secretion in a subsequent culture period without mc-ab. These results suggest that circulating ICSA in type I diabetics may alter beta cell function and thereby contribute to the pathogenesis of type I diabetes.

Early Enhanced Beta Cell Replication in Normoglycaemic Wistar Rats in Response to a Subdiabetogenic Dose of Streptozotocin

The effect of a single subdiabetogenic dose of streptozotocin (30 mg/kg body weight) on pancreatic insulin content and relative beta cell volume has been studied in normoglycaemic Wistar rats treated with streptozotocin either 2, 3 or 14 days after STZ was given. A single intravenous injection of streptozotocin caused a significant reduction of pancreatic insulin content, islet and beta cell volume, accompanied by a significantly diminished islet insulin content. The glucose- and 3-isobutyl-1-methylxanthine-stimulated insulin secretion was significantly lower in islets obtained 2 or 3 days after streptozotocin injection compared with those of vehicle-treated controls. 14 days after streptozotocin injection, beta cell volume and pancreatic insulin content partially recovered. At this time islet insulin content and secretory responsiveness were enhanced compared to the early phase following streptozotocin administration. The incorporation of [3H] thymidine into islet DNA was significantly enhanced at day 2 or 3 after streptozotocin application, whereas at day 14 the DNA synthesis corresponded to values from control rats. Despite persisting normoglycaemia, the beta cell volume of streptozotocin-treated rats was only 52% vs. control values, thus indicating the unresponsiveness of residual beta cells to compensate spontaneously for the beta cell loss.

Westernized-like-diet-fed rats: effect on glucose homeostasis, lipid profile, and adipocyte hormones and their modulation by rosiglitazone and glimepiride

Wersternized diet, containing high fat diet intake combined with high consumption of softdrinks, is accused with the emerge of modern epidemic obesity and diabesity. Therefore, we aimed to study the effect of this diet combination on the homeostasis of glucose, lipids, and some adipohormones in rats and to simulate the metabolic perturbations induced by the unhealthy Westernized diet intake, leading to the development of type 2 diabetes. To achieve this, we divided male Wistar rats (80–120 g) into two main groups: the first was fed commercial normal fat diet and the second received an in-house-prepared high-fat diet (HFD), combined with fructose in drinking water for a period of 6 weeks, followed by a subdiabetogenic dose of streptozotocin (STZ) (35 mg/kg) to produce frank hyperglycemia. The effect of this diet alone or after 2 weeks of treatment with rosiglitazone or glimepiride on glucose homeostasis, lipid profile, and levels of resistin and leptin was studied. The HFD/fructose/STZ diet elevated fasting plasma glucose, fructosamine, insulin, and homeostasis model assessment (HOMA) index, as well as serum triglycerides (TGs), total cholesterol (TC), and low-density lipoprotein cholesterol, with a decrease in high-density lipoprotein cholesterol. Hepatic TG and TC levels, as well as serum activities of aspartate transaminase (AST), alanine transaminase (ALT), and lactate dehydrogenase (LDH), were increased, suggesting a diet-induced hepatic steatosis, beside the increased levels of serum resistin and leptin. Rosiglitazone corrected the altered parameters measured, except for liver TGs; similarly, glimepiride reinstated the inverted parameters but raised insulin level and, consequently, the HOMA index. These results show that this diet could be used to induce an effect that mimics human type 2 diabetes with its metabolic disturbances and is suitable for screening the antidiabetic agents used for management of this disease.

Release of Glutamate Decarboxylase-65 into the Circulation by Injured Pancreatic Islet β-Cells

The enzyme glutamate decarboxylase-65 (GAD65) is a major autoantigen in autoimmune diabetes. The mechanism whereby autoreactivity to GAD65, an intracellular protein, is triggered is unknown, and it is possible that immunoreactive GAD65 is released by injured pancreatic islet beta-cells. There is a great need for methods by which to detect and monitor ongoing islet injury. If GAD65 were released and, furthermore, were able to reach the circulation, it could function as a marker of beta-cell injury. Here, a novel GAD65 plasma immunoassay is used to test the hypotheses that beta-cell injury induces GAD65 discharge in vivo and that discharged GAD65 reaches the bloodstream. Plasma GAD65 levels were determined in rats treated with alloxan, and with diabetogenic and low, subdiabetogenic doses of streptozotocin. beta-Cell injury resulted in GAD65 release into the circulation in a dose-dependent manner, and low-dose streptozotocin resulted in a more gradual increase in plasma GAD65 levels than did diabetogenic doses. Plasma GAD65 levels were reduced in rats that had undergone partial pancreatectomy and remained undetectable in mice. Together, these data demonstrate that GAD65 can be released into the circulation by injured beta-cells. Autoantigen shedding may contribute to the pathogenesis of islet autoimmunity in the multiple low-dose streptozocin model and perhaps, more generally, in other forms of autoimmune diabetes. These results demonstrate that, as is true with other tissues, islet injury, at least in some circumstances, can be monitored by use of discharged, circulating proteins. GAD65 is the first such confirmed protein marker of islet injury.

Protective effect of pioglitazone against multiple low-dose streptozotocin-induced diabetes in rats.

The autoimmune process is one of the etiological factors of diabetes in humans. Thiazolidinediones, which act through peroxisome proliferator-activated receptor-gamma, have been recently used to prevent diabetic-associated complications in patients with diabetes and insulin resistance. In the present study, we investigated the effect of pioglitazone on the diabetes induced by multiple low-dose streptozotocin (MLDS) in rats. When Sprague-Dawley rats were injected intraperitoneally with a sub-diabetogenic dose of streptozotocin (STZ; 40 mg/kg/day) for a period of 5 days, they developed hyperglycemia 2 days after posttreatment. Pioglitazone (6 mg/kg) administered orally for 7 days before the first dose of STZ prevented or delayed the development of MLDS-induced diabetes compared with the group treated only with STZ. Pioglitazone treatment showed no effect on plasma glucose levels in the control group. These findings suggest that pioglitazone prevented the autoimmune process involved in the development of MLDS-induced diabetes by decreasing glucose levels in rats.

Clusterin expression during regeneration of pancreatic islet cells in streptozotocin-induced diabetic rats.

Beta-cell regeneration has been reported after islet injury in an animal model for diabetes. Recently, we showed up-regulation of clusterin after islet injury and suggested that clusterin might be involved in cytoprotection and in the regeneration of islet cells. The aim of this study was to investigate the correlation of clusterin expression with islet regeneration and its effect on islet cell replication. Streptozotocin was administrated to rats to induce various types of diabetes. Islet regeneration and clusterin expression were examined after islet injuries. Clusterin cDNA was transfected to MIN6 cells and their proliferation activity was measured by a [3H]thymidine-incorporation assay. A diabetogenic dose of streptozotocin injected in rats provoked an immediate degeneration of beta cells. In this model, islets showed increased clusterin expression with extensive proliferation of alpha cells but showed poor beta-cell replication. A subdiabetogenic dose of streptozotocin, however, led to the proliferation of beta cells with clusterin up-regulation. In streptozotocin-treated neonatal rats, up-regulation of clusterin was noted during beta-cell proliferation. In all experimental models, clusterin was expressed in alpha cells in close correlation with islet cell proliferation, higher transcription of insulin mRNA and MAPKs activation. Cell replication was increased by 31 % in the MIN6 cells transfected by the clusterin cDNA. Up-regulation of clusterin in alpha cells might induce beta-cell proliferation and thus restore their population after islet injury. We suggest that clusterin could be considered as a growth factor-like molecule stimulating islet-cell proliferation by paracrine action.

Effects of aprotinin on the kallikrein–kinin system in type I diabetes (insulitis)

Sub-diabetogenic doses of streptozotocin (STZ) produce insulitis, β cell destruction and diabetes in mice. Since kinin have been proposed as an inflammatory mediator in several diseases, we decided to evaluate the role of the kallikrein–kinin system in the evolution of insulitis. Male C 57 BL/KsJ mdb mice were injected with STZ (40 mg/kg) for 5 consecutive d. Aprotinin (4000 KIU/d) was injected simultaneously with STZ during 10 d. Plasma and urine samples collected on day 15 were assayed for glucose concentration and proteins, nitrites and kallikrein. Diabetic mice showed hyperglycemia and increased diuresis, marked proteinuria, nitrites and kallikrein. Administration of aprotinin, a potent tissue kallikrein inhibitor, to STZ mice, reduced the hyperglycemia and the altered renal function of the diabetic mice to level no different from normal mice. The present studies are consistent with the hypothesis that the over-production of tissue kallikrein in insulitis could be controlled by the effect of aprotinin.

Activation of peritoneal macrophages during the prediabetic phase in low-dose streptozotocin-treated mice

Glucose metabolism and the production of O 2 − and NO 2 − have been studied in peritoneal macrophages from mice injected with 5 subdiabetogenic doses of streptozotocin. On day 12 after beginning of the treatment, peritoneal macrophages produced significantly higher amounts of lactate than macrophages from control mice. In addition, NO 2 − release and phorbol ester-induced O 2 − production were significantly augmented in macrophages from streptozotocin-treated mice. γ-Interferon induced in a dose-dependent manner the activity of NO synthase only in macrophages from streptozotocin-treated mice. These data show for the first time that peritoneal macrophages from streptozotocin-treated mice are activated and produce effector molecules such as O 2 − and NO which could participate in the destruction of pancreatic islets.

Predisposing effect of anti-Beta cell autoimmune process in NOD mice on the induction of diabetes by environmental insults

In NOD mice. 50-70% of females and 10-20% of males develop diabetes, although almost all the animals show insulitis. To see if environmental insults could induce diabetes in subjects with pre-clinical anti-Beta cell autoimmunity, non-diabetic NOD mice were selected and injected with a sub-diabetogenic dose of streptozotocin at 6 or 20 weeks of age. The streptozotocin failed to induce diabetes in 16 male and 16 female NOD mice within 4 weeks when they were injected at the age of 6 weeks. In contrast, 6 of 16 male and 10 of 16 female NOD mice developed diabetes within 4 weeks when they were injected at the age of 20 weeks. In untreated age-matched control NOD mice, none of the male and only 2 of 16 female mice became diabetic during the same 4 week period. On histologic examination, the degree of insulitis in streptozotocin-treated NOD mice (at the age of 24 weeks) was not significantly different from that of untreated control NOD mice. However, the streptozotocin-treated animals showed significantly lower pancreatic insulin content than the control mice. These results show that an anti-Beta cell autoimmune process in NOD mice has a predisposing effect on the induction of diabetes by a sub-diabetogenic dose of streptozotocin, and suggest that the precipitation of clinical diabetes by some environmental insults in subjects with pre-existing pre-clinical autoimmune Beta-cell destruction may be one mechanism of disease presentation in human Type 1 (insulin-dependent) diabetes.

Experimental diabetes impairs rat embryo development during the preimplantation period

Congenital malformations and early fetal losses are still the main complications of diabetic pregnancy. Whether the diabetic state affects the early embryo development during the preimplantation period is not known. To understand better the early steps of embryo growth, we collected the embryonic structures from the uterine horns of pregnant diabetic rats on day 5 of pregnancy. Diabetes was induced by streptozotocin (50 mg/kg) injection, 7, 14 or 21 days before mating. The morphological analysis revealed a lower rate of blastocysts (72% of all structures) and an increased rate of morulae (19.5%) in diabetic rats, compared to control animals (86.7 and 7.9% respectively). Hence, diabetic rats had fewer blastocysts (5.5 +/- 2.9 per rat) and more morulae (1.5 +/- 1.7) than control animals (7.2 +/- 2.7 and 0.66 +/- 1.2 respectively). Moreover, blastocysts from diabetic rats had fewer nuclei (26.9 +/- 7.3 per blastocyst) than blastocysts from control animals (31 +/- 6.1). In another set of experiments, subdiabetogenic doses of streptozotocin were administered. In rats injected with 25 mg/kg, neither the glycaemia, nor the morphological aspects of the embryos, nor the number of blastocyst nuclei differed from the control animals. In the animals receiving 35 mg/kg, the glycaemia was increased to approximately twice the control group value. However, the embryonic morphology and the nuclei counting of the blastocysts were similar to those of the fully diabetic group injected with 50 mg of streptozotocin. These results show that experimentally induced diabetes, even of a rather mild degree, affects the embryo development during the preimplantation period. The recovered embryos appear less mature and less developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes induction by subdiabetogenic doses of streptozotocin in BALB/cBOM mice. Noninvolvement of host B-lymphocyte functions

Diabetes induction by subdiabetogenic doses of streptozotocin in BALB/cBOM mice. Noninvolvement of host B-lymphocyte functions

Adrenergic receptors and the onset of streptozotocin-induced diabetes in mice

Abstract Treatment with yohimbine, an α 2 -adrenergic blocker, prior to the injection of a subdiabetogenic dose of streptozotocin (STZ) produced hyperglycemia and hypoinsulinemia in mice 7 days later. Prazosin, an α 1 -adrenergic blocker, was ineffective. The capacity of phentolamine and phenoxybenzamine to potentiate the diabetogenic effect of STZ was intermediate between that of yohimbine and prazosin. Propranolol and hexamethonium inhibited the potentiating action of yohimbine. Yohimbine enhanced the potentiating effect of isoproterenol on the STZ-induced diabetes. Acute changes in plasma glucose and insulin levels induced by STZ were potentiated by yohimbine but not by prazosin. The insulin releasing ability of the pancreatic islets 7 days after STZ was all but lost in mice pretreated with yohimbine but not with prazosin. These results suggest that the β- and α 2 -, not α 1 -, adrenergic system which modulates insulin release from pancreatic islets influences the response to the diabetogenic action of STZ in mice.

Induction of diabetes by cumulative environmental insults from viruses and chemicals.

Encephalomyocarditis virus (EMC) induces diabetes in certain inbred strains of mice by infecting and destroying pancreatic beta cells, the severity of the diabetes depending on the number of beta cells destroyed. In strains of mice resistant to EMC-induced diabetes, insufficient beta cells are damaged to alter glucose homeostasis. However, diabetes can be produced in many species by streptozotocin, a highly specific beta-cell toxin. Here, we used concentrations of streptozotocin that did not produce diabetes, but reduced the beta-cell reserve. When strains of mice normally resistant to EMC-induced diabetes were first treated with sub-diabetogenic doses of streptozotocin, then infected with EMC virus, diabetes developed. Furthermore, when mice were infected with viruses such as Coxsackie B3 and B5, which ordinarily produce little if any beta-cell damage, diabetes developed if the mice were first treated with sub-diabetogenic doses of streptozotocin. These findings suggest that diabetes may result from cumulative beta-cell damage induced by sequential environmental insults.

Complete protection from low-dose streptozotocin-induced diabetes in mice

STREPTOZOTOCIN (SZ) is a broad-spectrum antibiotic with oncolytic, oncogenic and diabetogenic properties1–4. To produce diabetes in experimental animals, SZ is administered as a single bolus, injected either intravenously (i.v.) or intraperitoneally (i.p.). Within 72 h, selective destruction of pancreatic beta cells and hyperglycaemia occur3,5. Subdiabetogenic doses of SZ cause only mild degranulation of the β-cells without hyperglycaemia during the first 72 h, unlike multiple (five) subdiabetogenic (i.v. or i.p.) doses of SZ to Charles River Laboratory (CD-1) mice, which produce marked glucose elevations within 5–6 days of the last injection of SZ, associated with morphological evidence of insulitis6,7. To dissociate direct β-cell toxicity of SZ from the delayed appearance of the insulitis and hyperglycaemia, we used antilymphocyte serum and 3-O-methyl-D-glucose (3-OMG), a nonmetabolised glucose analogue, which prevents the occurrence of hyperglycaemia for at least 72 h, when administered to mice or rats prior to a single diabetogenic dose of SZ8,9. Antilymphocyte serum (ALS), while not altering the multiple subdiabetogenic SZ-induced hyperglycaemia, does protect against the lymphocytic infiltration of the pancreatic islets, without changing the delayed hyperglycaemic response observed following the combination of 3-OMG and SZ injections10. We report here that injections of ALS (for 5 weeks), in combination with a regimen of 3-OMG and SZ, prevented the development of hyperglycaemia for the entire 14 weeks of the experiment, and that mice demonstrated essentially normal intraperitoneal glucose tolerance tests and pancreatic histology during the 3rd and 4th months following SZ.