Groups Of Diabetic Mice Research Articles

Reversal of New-Onset Type 1 Diabetes in Mice and Induction of FoxP3+ Regulatory T Cells by Syngeneic Bone Marrow Transplantation.

Objective: Autologous bone marrow transplantation (ABMT) was introduced as a novel strategy to treat new-onset type 1 diabetes (T1D). Induction of CD4+CD25+ FoxP3+T regulatory lymphocytes (Tregs) helps maintain self-tolerance in autoimmune diabetes. Here, we were tying to investigate the effects of syngeneic bone marrow transplantation (syn-BMT) in T1D mice models and to investigate the role of Tregs in this context.Research design and methods: Syn-BMT was used to mimic the ABMT to T1D patients in human. Fraternal inbred multiple low doses of streptozotocin (mld-SZ) induced diabetic mice were used as both donors (n = 7) and recipients (n = 20). And normal fraternal inbred mice were also used as donors (n=13). After total body irritation to recipient mice, syn-BMT was given either on day 10 or on day 40 of T1D. Blood and urine glucose was observed. On day120 after syn-BMT, glucose tolerance was tested and then mice were killed. Insulin levels in sera were tested by ELISA and pancreata histological and morphometry were analyzed by HE staining. Tregs in spleens were tested by Flow cytometry analysis, FoxP3 protein was tested by western blot, and FoxP3 mRNA was tested by real time PCR.Results: Syn-BMT, if applied when T1D is new-onset (10 d), can reverse blood glucose to close to normoglycemia without farther relapse, maintain blood insulin levels, improve glucose tolerance and ameliorate pancreata destruction. Syn-BMT leading to recovery of T1D results in the induction of Tregs, increased Foxp3 protein and mRNA expression in both the groups of diabetic mice receiving syn-BMT with either diabetic or normal donors. However, if given on a later disease stage (40 d), although syn-BMT helped reduce blood glucose for about 66 d and improved pancreata histological and morphometry, it showed relapse of diabetes further and decrement of insulin levels. Interestingly, this group did not show the increment of Tregs, Foxp3 protein or mRNA expression.Conclusions: This study provided a rationale to treat human new-onset T1D with autologous HSC. Syn-BMT, if given when T1D is new-onset, is safe and is able to reverse the diabetic status. The induction of Tregs and Foxp3 in both mRNA and protein levels as the results of syn-BMT, may contribute to the immune tolerance after syn-BMT, and the observed improvement of new-onset T1D.

Reversal of hyperglycemia by protein transduction of NeuroD in vivo

To test whether the neurogenic differentiation (NeuroD) protein could alleviate symptoms of diabetes mellitus by its transduction activity in vivo. Type 1 diabetes mellitus in mice was induced by ip (intraperitoneal) injection of streptozotocin (150 mg/kg). One group of diabetic mice were intravenously injected with the NeuroD-EGFP (Enhanced Green Fluorescent Protein) (5 mg/kg, n=6) and the other group with EGFP (5 mg/kg, n=5). After the transduction of NeuroD-EGFP, the distribution of the protein was examined by means of frozen section under fluorescent microscope observation. We conducted RT-PCR and Real-time quantitative PCR to measure the transcription levels of insulin mRNA. Immunohistochemistry was utilized to detect the insulin protein. Radioimmunoassay was conducted to determine the serum insulin levels. Blood glucose levels and body weights were regularly recorded after the protein administration. The NeuroD protein can be transduced into cells in vivo with a high efficiency of nearly 100%. Insulin mRNA was highly expressed in NeuroD-treated diabetic mice, 38-fold higher than that of control group (P<0.05). Immunohistochemistry revealed enteric insulin expression in the NeuroD-treated diabetic mice. The fasting serum insulin level of the NeuroD-EGFP group (n=6) was 337+/-39 pg/mL, significantly higher than that of the control diabetic mice (n=5) which was 84+/-23 pg/mL (P<0.01, t-test). Records of blood glucose level also displayed alleviation of hyperglycemia after NeuroD administration (P<0.01, t-test, n=6). In vivo-transduced NeuroD in the small intestine remained functionally active and could ameliorate the non-fasting glucose levels of streptozotocin-induced, diabetic mice by inducing enteric insulin expression.

Delayed functional maturation of neonatal porcine islets in recipients under strict glycemic control

The aim of this study was to compare the functional maturation of neonatal porcine islet (NPI) grafts exposed to long-term hyperglycemia with those implanted under euglycemic conditions. mice Neonatal porcine islets were transplanted under the left renal capsule of diabetic SCID mice (group H), or in diabetic SCID mice who were also implanted with 500 BALB/c islets under the right renal capsule (group N). On day 42, the right kidneys were removed in both groups. No animals in group H achieved euglycemia within 3 weeks after transplantation. Thus, these mice were exposed to long-term hyperglycemia. Mice in group N became euglycemic immediately after transplantation, however after removal of BALB/c grafts on day 42 they exhibited significantly higher blood glucose levels than in group H and showed glucose intolerance after glucose administration. Cellular insulin content of NPI grafts harvested on day 58 or 72 was significantly lower in group N mice compared to group H. These results suggest that tight control of glycemia reduces the functional maturation of NPI grafts.

REVERSAL OF DIABETIC COMPLICATIONS IN GENETIC MODEL OF TYPE I DIABETES (Akita mouse) BY TEMPOL

Type 1 diabetes is caused by autoimmune, chemical toxins, and genetic abnormalities. However, the mechanism by which the genetic abnormalities cause diabetic complications is largely unknown. Here we test the hypothesis that diabetic complications in Insulin-2 gene mutation (Akita) mouse are in part due to decrease in anti-oxidant capability. Two age groups of male Akita diabetic mice (4–9 weeks and 20–25 weeks of age) and age matched wild type control mice were divided into two groups (non-treatment controls and Tempol (antioxidant) treatment (250 mg/Kg body weight). Tempol was administrated in the drinking water for 6 weeks. The Akita mice were genotyped (to confirm mutation of the Ins 2 gene) using PCR primers specific for the mutant sequences. Diabetic mice in both age groups had blood glucose levels that were significantly elevated in comparison to control. Tempol produced no significant reduction in blood glucose levels of diabetic or control mice. However, at both age levels cardiac ejection fraction and left ventricular pressure were decrease in diabetic mice and the relaxation response of cardiac rings to acetylcholine was significantly attenuated. Cardiac tissue MMP-9 levels (indicator of tissue remodeling) were significantly elevated in both age groups. Tempol reversed the echocardiographic, acetylcholine relaxation and MMP-9 changes in the diabetic mice. These results suggest that oxidative stress is a primary mediator of the cardiac functional and structural changes in type 1 diabetes mellitus, and the treatment with anti-oxidant reversed these changes. A part of this work was supported by NIH grants.

Cardiac Metallothionein Synthesis in Streptozotocin-Induced Diabetic Mice, and Its Protection against Diabetes-Induced Cardiac Injury

Oxidative stress is involved in the pathogenesis of diabetes and its cardiovascular complications. Metallothionein (MT), a stress-response protein, is significantly increased in the liver and kidney of diabetic animals. We examined whether diabetes also induces cardiac MT synthesis through oxidative damage and whether MT overexpression protects the heart from injury. Diabetes was induced in mice by single injection of streptozotocin (STZ), and cardiac MT mRNA and protein levels were measured 2 weeks and 2 months after STZ treatment. Diabetes significantly increased cardiac MT synthesis 2 weeks and 2 months after STZ treatment, with no change in cardiac metals including zinc, copper, and iron. Serum and cardiac vasopeptide endothelin and inflammatory cytokine tumor necrosis factor-alpha were also significantly increased in diabetic hearts, as were the ratio of oxidized to reduced glutathione and the immunohistochemical staining of 3-nitrotyrosine and 4-hydroxynonenal. To explore the biological importance of increased MT synthesis in the heart, MT-overexpressing transgenic mice were treated with STZ and then examined 2 months later. A loss of inotropic reserve, uncovered during beta-adrenergic stimulation, and the presence of cardiac fibrosis, shown by increased Sirius red staining of collagen, were evident in the wild-type diabetic mice but not in the MT-overexpressing transgenic diabetic mice. These results suggest that diabetes-induced cardiac MT expression likely associates with systemic increases in endothelin-1 and tumor necrosis factor-alpha and the resulting cardiac oxidative stress. Overexpressing cardiac MT significantly protects the heart from diabetes-induced injury.

A Pentadecapeptide Fragment of Islet Neogenesis-Associated Protein Increases Beta-Cell Mass and Reverses Diabetes in C57BL/6J Mice

The objective of this study was to demonstrate that islet neogenesis-associated protein (INGAP) peptide, a pentadecapeptide containing the biologically active portion of native INGAP, increases functional beta-cell mass in normal animals and can be used therapeutically to reverse hyperglycemia in streptozotocin-induced diabetes. INGAP, a 175 amino acid pancreatic acinar cell protein, has been suggested to be implicated in beta-cell mass expansion. In the first part of this study, normoglycemic hamsters were administered either 500 microg INGAP peptide (n = 30) or saline (n = 20) intraperitoneally daily and sacrificed after 10 or 30 days of treatment. Blood glucose and insulin levels were measured, and a histologic and morphometric analysis of the pancreas was performed to determine the effect of INGAP peptide on the endocrine pancreas. In the second part of the study, 6- to 8-week-old C57BL/6J mice (n = 8) were administered multiple low doses of the beta-cell toxin streptozotocin (STZ) inducing insulitis and hyperglycemia. The mice were then injected with INGAP peptide (n = 4) or saline (n = 4) for 39 days and sacrificed at 48 days. Two additional groups of diabetic mice were administered either a peptide composed of a scrambled sequence of amino acids from INGAP peptide (n = 5) or exendin-4 (n = 5), an incretin that has been associated with amelioration of hyperglycemia. Islet cell neogenesis was stimulated in INGAP-treated hamsters by 10 days. At 30 days, the foci of new endocrine cells had the appearance of mature islets. There was a 75% increase in islet number, with normal circulating levels of blood glucose and insulin. Administration of INGAP peptide to diabetic mice reversed the diabetic state in all animals, and this was associated with increased expression of PDX-1 in duct cells and islet cell neogenesis with a reduction of insulitis in the new islets. Diabetic mice treated with exendin-4 or a scrambled INGAP peptide did not revert from hyperglycemia. Because there is a deficiency of beta-cell mass in both type-1 and type-2 diabetes, INGAP peptide stimulation of fully functional neoislet differentiation may provide a novel approach for diabetes therapy.

Elevated vascular endothelial growth factor production in islets improves islet graft vascularization.

Successful islet transplantation depends on the infusion of sufficiently large quantities of islets, of which only approximately 30% become stably engrafted. Rapid and adequate revascularization of transplanted islets is important for islet survival and function. Delayed and insufficient revascularization can deprive islets of oxygen and nutrients, resulting in islet cell death and early graft failure. To improve islet revascularization, we delivered human vascular endothelial growth factor (VEGF) cDNA to murine islets, followed by transplantation under the renal capsule in diabetic mice. Diabetic animals receiving a marginal mass of 300 islets that were pretransduced with a VEGF vector exhibited near normoglycemia. In contrast, diabetic mice receiving an equivalent number of islets that were transduced with a control vector remained hyperglycemic. Immunohistochemistry with anti-insulin and anti-CD31 antibodies revealed a relatively higher insulin content and greater degree of microvasculature in the VEGF vector-transduced islet grafts, which correlated with significantly improved blood glucose profiles and enhanced insulin secretion in response to glucose challenge in this group of diabetic recipient mice. These results demonstrate that VEGF production in islets stimulates graft angiogenesis and enhances islet revascularization. This mechanism might be explored as a novel strategy to accelerate islet revascularization and improve long-term survival of functional islet mass posttransplantation.

Differential hepatic gene expression in a polygenic mouse model with insulin resistance and hyperglycemia: evidence for a combined transcriptional dysregulation of gluconeogenesis and fatty acid synthesis.

New Zealand obese (NZO) mice exhibit severe insulin resistance of hepatic glucose metabolism. In order to define its biochemical basis, we studied the differential expression of genes involved in hepatic glucose and lipid metabolism by microarray analysis. NZOxF1 (SJLxNZO) backcross mice were generated in order to obtain populations with heterogeneous metabolism but comparable genetic background. In these backcross mice, groups of controls (normoglycemic/normoinsulinemic), insulin-resistant (normoglycemic/hyperinsulinemic) and diabetic (hyperglycemic/hypoinsulinemic) mice were identified. At 22 weeks, mRNA was isolated from liver, converted to cDNA, and used for screening of two types of cDNA arrays (high-density filter arrays and Affymetrix oligonucleotide microarrays). Differential gene expression was ascertained and assessed by Northern blotting. The data indicate that hyperinsulinemia in the NZO mouse is associated with: (i) increased mRNA levels of enzymes involved in lipid synthesis (fatty acid synthase, malic enzyme, stearoyl-CoA desaturase) or fatty acid oxidation (cytochrome P450 4A14, ketoacyl-CoA thiolase, acyl-CoA oxidase), (ii) induction of the key glycolytic enzyme pyruvate kinase, and (iii) increased mRNA levels of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase. These effects were enhanced by a high-fat diet. In conclusion, the pattern of gene expression in insulin-resistant NZO mice appears to reflect a dissociation of the effects of insulin on genes involved in glucose and lipid metabolism. The data are consistent with a hypothetical scenario in which an insulin-resistant hepatic glucose production produces hyperinsulinemia, and an enhanced insulin- and substrate-driven lipogenesis further aggravates the deleterious insulin resistance of glucose metabolism.

Regulation of the early subnormal retinal oxygenation response in experimental diabetes by inducible nitric oxide synthase.

We aimed to test the hypothesis that the inducible form of nitric oxide synthase (iNOS) contributes to the development of an early subnormal retinal oxygenation response in preclinical models of diabetic retinopathy. In urethane anesthetized Sprague Dawley rats or C57BL/6 mice, functional magnetic resonance imaging was used to noninvasively measure the change in retinal oxygen tension (Delta PO(2)) during a carbogen-inhalation challenge. In the rat experiments, the retinal Delta PO(2) of the following groups were compared: control rats (n = 9), 3-month diabetic rats (n = 5), and 3-month diabetic rats treated orally with L-N(6)-(1-iminoethyl)lysine 5-tetrazole amide, a prodrug of an inhibitor of iNOS (n = 6). In addition, the retinal Delta PO(2) of the following mouse groups were compared: C57BL/6 mice (n = 20), C57BL/6-Nos2(tm1 Lau) mice (n = 10), 4-month diabetic mice (n = 13), and 4-month diabetic knockout mice (n = 6). Only the Delta PO(2) of the superior hemiretina of the diabetic rat and mice groups were significantly subnormal (P < 0.05). The superior Delta PO(2) of the diabetic rats treated with the prodrug was not significantly (P > 0.05) different from their respective normal controls. In the mice experiments, the superior retinal Delta PO(2) of the iNOS null mice was not statistically different (P > 0.05) from that of normal control mice. iNOS is required for the development of an early subnormal Delta PO(2) in experimental diabetic retinopathy.

Short-term effect of acarbose on specific intestinal disaccharidase activities and hyperglycaemia in CBA diabetic mice.

The purpose of this study was to examine the short-term effects of 75, 100 and 150 mg of acarbose mixed in 100 g standard laboratory chow on specific intestinal disaccharidase activities and on hyperglycaemia in diabetic CBA strain mice on standard diet. The small intestine was excised and divided into three segments, from pylorus to duodenum, and two equal lengths of the jejunum and ileum of control and diabetic mice with or without added acarbose. Specific maltase and sucrase activities were determined using maltose and sucrose as substrates respectively. Increased specific activities of maltase and sucrase were detected in the intestines of CBA mice on standard laboratory diet seven days after alloxan-induced diabetes. Feeding for 7 days with 75, 100 or 150 mg acarbose uniformly mixed in 100 g standard laboratory chow, induced a decrease in the specific maltase and sucrase activities, compared with diabetic mice on standard laboratory diet. Feeding with 75 mg acarbose mixed in 100 g standard laboratory chow caused a statistically significant decrease of maltase in the duodenum and of sucrase in duodenum and jejunum, without a antihyperglycaemic effect. Feeding with 100 or 150 mg caused statistically significant decreases in specific maltase and sucrase activities in duodenum, jejunum and ileum. An antihyperglycaemic effect was observed only in the group of diabetic mice fed with 100 mg acarbose. This indicates that the antihyperglycaemic effect of acarbose involves factors other than these, related only to its inhibitory effect on disaccharidase activities.

Effect of intrathymic administration of mycobacterial heat shock protein 65 and peptide p277 on the development of diabetes in NOD mice: caution required in vaccination studies.

Heat shock protein 65 (hsp65) and a derived peptide, p277, are autoantigens reported in IDDM. I.p. injection of hsp65 reduced diabetes incidence in NOD mice and administration of p277 cured already diabetic mice. Also, intrathymic (i.t.) administration of whole islets or GAD65 prevented diabetes in NOD mice. The aim of this study was to evaluate whether i.t. injection of mycobacterial hsp65 or p277 can prevent diabetes in NOD mice. Three-week-old NOD female mice were injected intrathymically with 50 microg of hsp65 (n=30), 5 microg of p277 (n=30), and PBS (n=29). Diabetes incidence was observed for the following 300 days. Pancreas was then used for histological and immunohistological evaluation. No significant differences in diabetes incidence were observed among the three groups of mice. Interestingly, hsp65-treated mice developed diabetes slightly faster at 177+/-6 days compared to 202+/-8 days (p=0.015) for the p277-treated group and 197+/-7 days (p=0.033) for controls. The insulitis score and average islet size did not differ significantly among the three groups of diabetic mice. Scattered TCR-gamma/delta positive cells were found in the pancreas of all groups of mice. In contrast, a huge infiltrate of TCR-gamma/delta positive cells was detected in four out of eight (50%) p277-diabetic NOD mice. Thus, our data show an earlier onset of diabetes in hsp65-treated mice and no improvement in the incidence with either hsp65 or p277, suggesting that hsp65 acts in a different way from what was reported with GAD65. Caution is advised in future vaccination studies as hsp65 poses a potential danger.

Altered rhodopsin regeneration in diabetic mice caused by acid conditions within the rod photoreceptors

PURPOSE. The experiments were designed to provide details on the characteristics of rhodopsin regeneration in the rod photoreceptors of diabetic mice and to evaluate their mechanistic basis. METHODS. A genetically-derived diabetic albino mouse was developed. An excised albino mouse eye preparation was used. The preparation allows for direct measurements of rhodopsin concentration and other spectrally distinct intermediates, and maintains the structural integrity of the compartments involved in rhodopsin regeneration. The experiments were conducted at moderate bleaching levels, averaging 13–14%, with mice that exhibited moderate levels of blood glucose concentration. RESULTS. Rhodopsin regeneration was delayed in both genetically- derived and streptozotocin-injected diabetic mice when compared to non-diabetic mice. During the delay an intermediate of rhodopsin, N-Retinylidene Opsin (NRO440), that precedes the hydrolysis of the bleached chromophore from the opsin and that is associated with acidic conditions was observed. This intermediate was not observed in non-diabetic mice. The delay in rhodopsin regeneration of the diabetic mice was partially eliminated, and the relative concentration of NRO440 was decreased, when the internal pH of the rod photoreceptor was raised by modifying the perfusate composition. CONCLUSIONS. Following a bleach, both genetic and streptozotocin diabetic mice exhibited abnormalities in rhodopsin regeneration. When studied at moderate bleaching levels with animals that were moderately diabetic, both groups of diabetic mice exhibited a delay in the start of the rhodopsin regeneration. The delay appears to be caused by the formation of an acid intermediate of the bleached rhodopsin resulting from acid conditions within the rod photoreceptors.

Apoptosis down-regulates inflammation under the advancing epithelial wound edge: Delayed patterns in diabetes and improvement with topical growth factors

Background . Wound healing is involved in many aspects of care, ranging from anastomoses and skin incisions to foot ulcers and decubitus. Clinical healing failures are a major challenge to the physician and cause significant morbidity and mortality in select patient populations. As we are starting to understand more fully the mechanisms of impaired wound healing, the diabetic mouse (C5 7BL/KsJ-db/db) has been a good model for research. The diabetic wound exhibits significant delays in healing, previously identified as impaired cellular infiltration and granulation tissue formation. Apoptosis, or programmed cell death, is intimately involved in the regulation of inflammation and ultimately should play a role in the inflammatory phase of wound healing. Methods . To examine its role in wound healing, patterns of apoptosis in large, full-thickness cutaneous wounds were compared between groups of diabetic and nondiabetic mice. Results . Initially apoptosis was mainly limited to the wound edge and followed the advancing epithelial edge toward the center of the wound as healing progressed. Significant delays in the appearance of the apoptotic pattern were noted in the diabetic mice. Wounds in diabetic mice were then treated with topical application of growth factors. The delay in apoptotic pattern was reversed after treatment with the combination of insulin-like growth factor—II and platelet-derived growth factor, approaching levels in nondiabetic animals. Conclusions . Apoptosis appears concurrently with reepithelialization of the wound and may signal the end of the inflammatory phase of healing at that site in the wound. One can speculate that a signal for apoptosis and down-regulation of inflammation in the wound is derived from the epithelium.

P-604 - Two inbred groups of diabetic KK-CAy mice with high or low sensitivity of pulse rate to acetylcholine classified by higenamine response.

P-604 - Two inbred groups of diabetic KK-CAy mice with high or low sensitivity of pulse rate to acetylcholine classified by higenamine response.

XENOTRANSPLANTATION OF MICROENCAPSULATED FETAL RAT ISLETS

Fetal pancreatic islets were isolated from 21-day pregnant Wistar rats and enclosed in semipermeable alginate-polylysine-alginate capsules. Encapsulated islets that had been previously cultured for eight days in vitro were shown to secrete insulin in response to glucose challenge: low-glucose, high-glucose, and high-glucose + 3-isobutyl-1-methyl-xanthine (IBMX). Transplants of 800-1000 encapsulated cultured fetal islets into the peritoneal cavities of BALB/c mice with streptozotocin-induced diabetes restored normoglycemia for up to 171 days without immunosuppression. When the capsules were removed from 2 of the recipients they both quickly regressed to a diabetic state. Control groups of diabetic mice received unencapsulated, uncultured islets or empty capsules. The mortality rate among these animals was high and none experienced relief from hyperglycemia for longer than 6 days. These results demonstrate that cultured microencapsulated fetal rat islets of Langerhans can release insulin in response to an in vitro glucose challenge, and that transplants of these islets into diabetic mice can restore normoglycemia without the need for immunosuppressive therapy.

EFFECT OF GENETIC DIABETES AND ALCOHOL ON TISSUE CARNITINE AND INOSITOL CONCENTRATIONS IN MICE

Concentrations of acid-soluble L-carnitine and inositol were determined in heart, kidney, muscle, pancreas, liver, brain and blood of genetically diabetic obese db/db and their nondiabetic control C57BL/6J (CBL) mice. Results were compared to a group of diabetic and CBL mice fed ethanol (ETOH) 4 g/kg daily for 58-64 days. In CBL and db/db mice, heart muscle was found to have the greatest and brain the least content of carnitine. Diabetes caused a significant decrease in hepatic concentration of carnitine but did not affect carnitine concentration of heart, kidney, skeletal muscle, brain and pancreas. ETOH intake had no effect on carnitine content of any of the tissues studied. Free inositol content was highest in brain and lowest in skeletal muscle of CBL and db/db mice; diabetes or ETOH intake did not affect tissue inositol content. Except for liver, neither diabetes nor ETOH intake affects tissue carnitine or inositol concentration.

Effects of long-term diabetes and treatment with gangliosides on cardiac sympathetic innervation: A biochemical and functional study in mice

The effect of long-term diabetes on cardiac sympathetic innervation was investigated in genetically obese diabetic mice ( db db ). Previous studies have shown the presence of a peripheral neuropathy starting a few months after birth, and we recently reported a significant reduction of myocardial norepinephrine (NE) levels in the hearts of diabetic mice at the age of 6 months. In the present study, histofluorescence analysis of comparable sections of cardiac tissue of both control and diabetic animals confirmed the picture of a sympathetic denervated heart in this experimental model. Furthermore, functional studies in isolated atria revealed a difference between the two groups of animals: in fact heart rate increases induced by transmural stimulation were significantly lower in diabetic mice. Since a bovine brain ganglioside mixture (Cronassial ®) has been extensively studied for its effect on peripheral diabetic neuropathy, a group of diabetic mice was treated throughout the sixth month with this drug (10 mg/kg/day i.p.). The ganglioside treated animals showed a marked recovery of atrial function and cardiac NE concentration. The above results clearly indicate sympathetic neural damage in db db animals, likely related to an autonomic diabetic neuropathy and a possible protection by ganglioside of adrenergic nerves from this alteration.

Avoidance responding in mice with diabetes mellitus

In order to examine the behavioral concomitants of the neuroendocrine state of diabetes mellitus, the behavior of diabetic and normal male mice was compared in two behavioral paradigms. Diabetic mice were found to display significantly more passive avoidance to shock and significantly more submissive social behavior as compared to control mice. Furthermore, within the group of diabetic mice, mice showing the most passive avoidance also displayed the most submissive behavior. These findings suggest that diabetes mellitus may have effects on the neuroendocrine system that are manifested as changes in behavior.

Persistence of polymicrobial abscesses in the poorly controlled diabetic host.

Polymicrobial infections are frequently found in soft tissue infections of the lower extremities in diabetic patients. The relative susceptibility to and persistence of soft tissue polymicrobial infections of diabetic and nondiabetic mice using bacteria commonly found in clinical foot infections were studied. Subcutaneous abscesses were induced in three groups of diabetic and nondiabetic mice using: (1) E. coli and enterococcus, (2) enterococcus and Bacteroides fragilis (B. fragilis), and (3) E. coli and B. fragilis. Abscesses were removed at 1 and 2 wk for total colony counts. At 1 wk, there was a significantly greater bacterial growth in the abscesses of the diabetic mice compared with the nondiabetic mice only in the group injected with enterococcus and B. fragilis. There were significantly higher colony counts in the diabetic compared with the nondiabetic mice in all three groups at 2 wk after injection of the bacteria. Two weeks after injection of inocula containing B. fragilis, both in combination with E. coli or enterococcus, all nondiabetic mice had eradicated B. fragilis from the abscesses, but significant numbers of B. fragilis persisted in the abscesses of the diabetic mice. In the diabetic mice, the presence of enterococci was more synergistic for growth of B. fragilis than was the presence of E. coli. These studies demonstrate that the bacteria of polymicrobial soft tissue infections persist for a longer period of time in the diabetic compared with the nondiabetic host. In addition, B. fragilis has increased pathogenicity in the diabetic compared with the nondiabetic host, particularly in the presence of enterococci.

Influence of the diabetic state on isoproterenol-induced cardiac necrosis

Isoproterenol-induced myocardial necrosis was examined in male mice with alloxan-induced and genetically transmitted diabetes. Ten days after alloxan treatment, mice exhibited an elevation in blood glucose concentrations, weight loss, polyuria and decreased heart rates (510 +/- 15 v. 675 +/- 11 beats/min) compared with matched control mice. Similarly, genetically diabetic mice exhibited lower heart rates than the corresponding age-matched controls (383 +/- 30 v. 603 +/- 30 beats/min). In comparison to matched controls, both groups of diabetic mice had a significant decrease in the severity of the cardiac necrosis which was induced by the administration of isoproterenol. The reduction in isoproterenol-induced cardiac lesions was similar in mice with chemically induced diabetics and mice with genetically transmitted diabetes. Biochemical studies of ventricular slices revealed no change in basal cAMP levels and no differences in isoproterenol-induced changes in cAMP levels in mouse hearts from both models of diabetes. Insulin treatment corrected the chemically induced diabetic state and restored the cardiotoxic potential of isoproterenol.