Control of spontaneous glucose intolerance, hyperinsulinemia, and islet hyperplasia in nonobese C3H.SW male mice by Y-linked locus and adrenal gland

SPECT/CT Imaging of Mycobacterium tuberculosis Infection with [125I]anti-C3d mAb

PURPOSE

Diagnosis and therapeutic monitoring of chronic bacterial infection requires methods to detect and localize sites of infection accurately. Complement C3 activation fragments are generated and covalently bound to selective bacterial pathogens during the immune response and can serve as biomarkers of ongoing bacterial infection. We have developed several probes for detecting tissue-bound C3 deposits, including a monoclonal antibody (mAb 3d29) that recognizes the tissue-bound terminal processing fragments iC3b and C3d but does not recognize native circulating C3 or tissue-bound C3b.

PROCEDURES

To determine whether mAb 3d29 could be used to detect chronic Mycobacterium tuberculosis infection non-invasively, aerosol-infected female C3HeB/FeJ mice were injected with [¹²⁵I]3d29 mAb and either imaged using single-photon emission computed tomography (SPECT)/X-ray computed tomography (CT) imaging at 24 and 48 h after radiotracer injection or being subjected to biodistribution analysis.

RESULTS

Discrete lesions were detected by SPECT/CT imaging in the lungs and spleens of infected mice, consistent with the location of granulomas in the infected animals as detected by CT. Low-level signal was seen in the spleens of uninfected mice and no signal was seen in the lungs of healthy mice. Immunofluorescence microscopy revealed that 3d29 in the lungs of infected mice co-localized with aggregates of macrophages (detected with anti-CD68 antibodies). 3d29 was detected in the cytoplasm of macrophages, consistent with the location of internalized M. tuberculosis. 3d29 was also present within alveolar epithelial cells, indicating that it detected M. tuberculosis phagocytosed by other CD68-positive cells. Healthy controls showed very little retention of fluorescent or radiolabeled antibody across tissues. Radiolabeled 3d29 compared with radiolabeled isotype control showed a 3.5:1 ratio of increased uptake in infected lungs, indicating specific uptake by 3d29.

CONCLUSION

3d29 can be used to detect and localize areas of infection with M. tuberculosis non-invasively by 24 h after radiotracer injection and with high contrast.

Adaptive genetic variation, stress and glucose regulation

Elevated glucose levels in the presence of insulin are indicative of type 2 diabetes and the more inclusive metabolic syndrome. Alleles conferring susceptibility to these and other common conditions may be adaptations to past environments. It is possible that other mammals exhibiting environmental diversity harbor similar variants; therefore, we assessed glucose regulation in two species of deer mice (Peromyscus), a diverse endemic North American group. The prairie deer mouse, P. maniculatus bairdii (BW), and the Oldfield mouse, P. polionotus subgriseus (PO) differ in sexual dimorphism, behavior and habitat. PO animals exhibit better regulatory ability than BW animals, particularly among males, although both species display equivalent insulin levels/responses and non-fasted glucose levels. Hybrid males exhibit a PO glucose challenge response and subsequent analysis of consomic animals implicates Y chromosome variation as the genetic cause. Two pieces of evidence indicate that the male glucose regulatory differences are mediated by stress response: (1) fasting and handling alone account for most of the variation; (2) an inhibitor of glucocorticoid (GC) stress hormone synthesis eliminates these differences. PO males have GC levels that are twice those of BW males, indicating the presence of alleles that attenuate the GC response. We hypothesize that the interspecific physiological and behavioral differences are interrelated and that similar human variants exist.

Are the available experimental models of type 2 diabetes appropriate for a gender perspective?

Several experimental models have so far been developed to improve our knowledge of the pathogenetic mechanisms of type 2 diabetes mellitus (T2D), to determine the possible pharmacological targets of this disease and to better evaluate diabetes-associated complications, e.g. the cardiovascular disease. In particular, the study of T2D gained the attention of several groups working with different animal species: rodents, cats or pigs, as well as other non-human primate species. Each of these species provided useful and different clues. However, T2D has to be considered as a gender-associated disease: sex differences play in fact a key role in the onset as well as in the progression of the disease and a higher mortality for cardiovascular diseases is detected in diabetic women with respect to men. The results obtained from all the available animal models appear to only partially address this issue so that the search for more precise information in this respect appears to be mandatory. In this review we summarize these concepts and literature in the field and propose a reappraisal of the various animal models for a study of T2D that would take into consideration a gender perspective.

The genetic landscape of type 2 diabetes in mice

Inbred mouse strains provide genetic diversity comparable to that of the human population. Like humans, mice have a wide range of diabetes-related phenotypes. The inbred mouse strains differ in the response of their critical physiological functions, such as insulin sensitivity, insulin secretion, beta-cell proliferation and survival, and fuel partitioning, to diet and obesity. Most of the critical genes underlying these differences have not been identified, although many loci have been mapped. The dramatic improvements in genomic and bioinformatics resources are accelerating the pace of gene discovery. This review describes how mouse genetics can be used to discover diabetes-related genes, summarizes how the mouse strains differ in their diabetes-related phenotypes, and describes several examples of how loci identified in the mouse may directly relate to human diabetes.

Using Obese Mouse Models in Research: Special Considerations for IACUC Members, Animal Care Technicians, and Researchers

The mouse is the animal most commonly used to study the underlying causes of and treatments for obesity. The author reviews many of the issues that should be considered by all involved in research with mice expressing this phenotype, and describes some procedures exclusive to obesity research.

Successful allogeneic neonatal bone marrow transplantation devoid of myeloablation requires costimulatory blockade

A significant number of nonmalignant, progressive childhood disorders respond to bone marrow transplantation (BMT). Toxic myeloablative pretreatment regimens, graft failure, and graft-vs-host disease complicate the utility of BMT for neonatal treatment. We recently demonstrated high-dose BMT in neonatal animals enables chimeric engraftment without toxic myeloablation. Reagents that block T cell costimulation (anti-CD40L mAb and/or CTLA-4Ig) establish tolerant allogeneic engraftment in adult recipients. Donor lymphocyte infusion (DLI) re-establishes failing grafts and treats malignant relapse via a graft-vs-leukemia response. In this study, we tested the hypothesis that combining these approaches would allow tolerant allogeneic engraftment devoid of myeloablation in neonatal normal and mutant mice with lysosomal storage disease. Tolerant chimeric allogeneic engraftment was achieved before DLI only in the presence of both anti-CD40L mAb and CTLA-4Ig. DLI amplified allografts to full donor engraftment long-term. DLI-treated mice either maintained long-term tolerance or developed late-onset chronic graft-vs-host disease. This combinatorial approach provides a nontoxic method to establish tolerant allogeneic engraftment for treatment of progressive childhood diseases.

Sex steroids influence pancreatic islet hypertrophy and subsequent autoimmune infiltration in nonobese diabetic (NOD) and NODscid mice

Female nonobese diabetic (NOD) mice more frequently develop autoimmune diabetes than NOD males. Orchidectomy of the latter aggravates insulitis and diabetes. Because clear differences in immune function have not been observed between prediabetic females and males, before or after castration, we hypothesized that sex-related differences in diabetes incidence are related to target organ-specific actions of sex steroids. Previously, we showed that prediabetic NOD females develop hyperinsulinemia and subsequently mega-islets. Infiltration of the first inflammatory leukocytes is predominantly associated with these mega-islets. Here, we determined the relationship between sex hormones, mega-islet formation, and infiltrating cells in NOD and nonobese diabetic/severe combined immune-deficient (NODscid) mice. Mega-islet formation was reduced in NOD males compared with NOD females, and orchidectomy increased it, indicating a relationship between androgen levels and mega-islet formation. Moreover, enhanced mega-islet formation in castrated NOD males was associated with increased numbers of infiltrating leukocytes. Castrated NODscid males also exhibited increased mega-islet formation and dendritic cell infiltration, indicating that lymphocytes are not required for castration-induced effects. In conclusion, we show that androgens influence pancreatic islets and autoimmune infiltration in NOD and NODscid mice. This suggests that the gender difference in diabetes incidence in NOD mice is related to target organ-specific androgen effects.

Characterization of hyperinsulinemic recombinant inbred (RI) strains (SMXA-5 and SMXA-9) derived from normoinsulinemic SM/J and A/J mice

We discovered two mouse strains (SMXA-5 and SMXA-9) with hyperinsulinemia among the substrains and progenitor strains (SM/J and A/J) of the SMXA recombinant inbred (RI) strains, and characterized the two strains at 20 weeks of age. SMXA-5 (mean +/- S.E.M: 9.6 +/- 1.7 ng/ml) and SMXA-9 (7.7 +/- 1.3 ng/ml) males had higher serum immunoreactive insulin levels than SM/J (1.4 +/- 0.3 ng/ml) and A/J (1.1 +/- 0.1 ng/ml) males in the nonfasting condition. The hypoglycemic response to insulin at 30 min after injection was significantly less in SMXA-5 males than in SM/J mice. Glucose tolerance test revealed that the incidence of impaired glucose tolerant males was 58% (11/19) in SMXA-5 and 42% (10/24) in SMXA-9 strains, but none in SM/J and A/J strains. SMXA-5 (209 +/- 29 mg/dl) and SMXA-9 (235 +/- 31 mg/dl) had higher serum triglyceride levels than SM/J (126 +/- 14 mg/dl) and A/J (89 +/- 5 mg/dl) males in the nonfasting condition. Histologic examination revealed enlarged islets in the pancreas of hyperinsulinemic SMXA-5 male mice. Moreover, SMXA-5 and SMXA-9 mice exhibited mild obesity. SMXA-5 and SMXA-9 males were therefore characterized by hyperinsulinemia, impaired glucose tolerance, hypertriglyceridemia and mild obesity which resembled some of the phenotypes of human Syndrome X, although both progenitor strains were normal so far as we examined. Since the RI strains are a powerful tool to facilitate polygenic-trait analysis, SMXA-5 and SMXA-9 mice will be useful materials to investigate the genetic basis of complex diseases, and are possible new metabolic models in relation to hyperinsulinemia.

Environmental risk factors for multifactorial epilepsy in EL mice

PURPOSE

The epileptic EL mouse has been studied extensively as a model of multifactorial epilepsy. Although EL mice have a seizure occasionally during routine handling associated with cage changing, most studies have used vigorous tossing or shaking procedures for seizure induction. A new seizure testing procedure was developed that involved gentle handling and simulated situations associated with emotional stress in rodents. This new testing procedure was used to identify and characterize several environmental risk factors that influence seizure predisposition in EL mice.

METHODS

Ten adult EL mice were monitored for 7 days under 24-h light/dark video surveillance to assess the frequency of spontaneous seizures. The development of handling-induced seizures also was studied in EL mice, in nonepileptic ABP and DDY mice, and in reciprocal ABP x EL F1 hybrids from ages 30-180 days.

RESULTS

Seizure induction was necessary in EL mice, as spontaneous clinical seizures were not observed. Handling-induced seizure susceptibility was strongly age and gender dependent in naive EL mice (not previously handled) and peaked approximately 90 days, with males significantly more susceptible than females. No seizures were induced by handling in the nonepileptic mouse strains (ABP and DDY) over the testing period. Handling and seizures at young ages in EL and EL x ABP F1 hybrid mice significantly enhanced their seizure susceptibility when they were tested again 1 month later. A significant "Gowers effect" was seen also in EL mice. Furthermore, susceptibility was higher in ABP x EL F1 hybrids than in their reciprocal EL x ABP F1 hybrids at 90-150 days.

CONCLUSIONS

Seizure susceptibility in EL mice was significantly influenced by a number of environmental factors including age, gender, maternal/paternal effects, prior handling, and seizure history. The emotional stress/fear response is the likely trigger for seizure induction in EL mice. An early life experience stress-diathesis model, similar to that proposed for major depression in humans, was applicable to the development of seizure susceptibility in EL mice. The new seizure test will be useful for defining gene-environment interactions and in identifying susceptibility genes for multifactorial epilepsy.

Physiologic and endocrinologic characterization of male sex-biased diabetes in C57BLKS/J mice congenic for the fat mutation at the carboxypeptidease E locus

The fat gene in mice represents a recessive mutation at the carboxypeptidase E (Cpe) locus. The mutant allele (Cpe(fat)) encodes a highly unstable enzyme and produces an obesity phenotype characterized by attenuated processing of prohormones such as proinsulin that require this exopeptidase for full maturation. This article presents a preliminary physiologic and endocrinologic characterization of the stock of C57BLKS/LtJ-Cpe(fat)/Cpe(fat) mice at the backcross generation (N10) currently distributed by The Jackson Laboratory. Although previously reported not to be diabetogenic at N5, an additional five backcrosses to the C57BLKS/J background resulted in a male-biased development of both obesity and diabetes. Major differences distinguishing this mutant stock from the phenotypes produced by either the diabetes (Lepr(db)) or obese (Lep(ob)) mutations on the same inbred strain background are lack of hyperphagia and hypercorticism, sensitivity of diabetic males to exogenous insulin, and a milder and male-biased diabetes syndrome that is not associated with widespread beta-cell necrosis and islet atrophy, and that often remits with age.

Induction of diabetes in standard mice by immunization with the p277 peptide of a 60-kDa heat shock protein

We previously reported that immunity to the p277 peptide of the human 60-kDa heat shock protein (hsp60) was a causal factor in the diabetes of non-obese diabetic (NOD) mice, which are genetically prone to develop spontaneous autoimmune diabetes. The present study was done to test whether immunization with the p277 peptide could cause diabetes in standard strains of mice. We now report that a single administration of the p277 peptide conjugated to carrier molecules such as bovine serum albumin or ovalbumin can induce diabetes in C57BL/6 mice and in other strains not genetically prone to develop diabetes. The diabetes was marked by hyperglycemia, insulitis, insulin autoantibodies, glucose intolerance and low blood levels of insulin. The diabetes could be transferred to naive recipients by anti-p277 T cell lines. Similar to other experimentally induced autoimmune diseases, the autoimmune diabetes remitted spontaneously. After recovery, the mice were found to have acquired resistance to a second induction of diabetes. Susceptibility to induced diabetes in C57BL/6 mice was influenced by sex (males were much more susceptible than were females) and by class II genes in the major histocompatibility complex (B6.H-2bm12 mice with a mutation in the MHC-II molecule were relatively resistant). Other strains of mice susceptible to induced diabetes were C57BL/KSJ, C3HeB/FeJ, and NON/Lt. BALB/c and C3H/HeJ strains were relatively resistant. Immunization to p277-carrier conjugates could also induce transient hyperglycemia in young NOD mice, but upon recovery from the induced diabetes, the NOD mice were found to have acquired resistance to later development of spontaneous diabetes. Thus, T cell immunity to the p277 peptide can suffice to induce diabetes in standard mice, and a short bout of induced diabetes can affect the chronic process that would otherwise lead to spontaneous diabetes in diabetes-prone NOD mice.

Steroid sulfatase and the Y chromosome hypertensive locus of the spontaneously hypertensive rat

The spontaneously hypertensive rat (SHR) has a Y chromosome locus that increases blood pressure. This locus requires an androgen receptor and testosterone for maximum expression. Steroid sulfatase (STS) catalyzes the conversion of steroid sulfates to their active nonconjugated form. In some mammals the steroid sulfatase locus (Sts) is on the Y chromosome, although the rat Sts is on the X chromosome. We measured STS activity levels in SHR and normotensive Wistar Kyoto (WKY) males. SHR had significantly higher STS activity in testes, adrenal gland, liver, and hypothalamus. The Km values for STS in the two strains were not significantly different; thus, activity differences were likely due to differences in enzyme amounts. STS activity was measured in the backcross strains SHR/y and SHR/a to test and/or confirm a Y chromosome influence on STS. STS activity levels in these strains were intermediate between those of SHR and WKY. Because the blood pressures of SHR/y and SHR/a were also intermediate between SHR and WKY, the STS activity could be a secondary response to the hypertension. An alternative hypotheses is that a regulatory locus in addition to the structural locus is responsible for STS activity levels, and this regulatory locus is on the rat Y chromosome. Further study is needed to discriminate between these possibilities, and until the second hypothesis can be eliminated, the Sts locus or its modifier loci remain a potential component of the Y chromosome hypertensive locus.

Pancreatic islet hypertrophy in spontaneous maturity onset obese-diabetic CBA/Ca mice

Mature male CBA/Ca mice develop a spontaneous mild diabetes-obesity syndrome which is characterized by hyperglycaemia, hyperinsulinaemia and insulin resistance, and resembles human Type II diabetes mellitus. Immunocytochemical staining of pancreas sections for insulin showed that the pancreas from mature obese mice possessed significantly enlarged islets compared to those from age-matched control (lean) mice. The pancreatic insulin content was significantly greater in 24-week-old obese mice (1.78 +/- 0.14 mU/mg) compared with lean controls (0.92 +/- 0.09 mU/mg). This increase was still apparent at 48 weeks of age. We conclude that, unlike most other rodent models of Type II diabetes, there is no chronic degeneration of beta cells in these mice, so that circulating insulin levels remain high throughout their life. We suggest, therefore, that the male CBA/Ca mouse represents a valuable model for investigating maturity onset diabetes.

Glucose, insulin, and open field responses to immobilization in nonobese diabetic (NOD) mice

Numerous studies have suggested that stress precipitates type I diabetes. Because stress-elicited hyperglycemia may play a role in this effect, we measured the influence of acute immobilization (90 min) upon plasma glucose and insulin levels in nonobese diabetic (NOD) mice, a spontaneous model of type I diabetes. To this end, prediabetic 8-week-old mice of both sexes were compared to age- and sex-matched C57BL/6 control mice. Baseline plasma glucose levels and immobilization-elicited hyperglycemia were both lower in male and female NOD mice compared to their C57BL/6 counterparts. However, the maximal effects of immobilization upon plasma insulin (and corticosterone) levels were not different between NOD and C57BL/6 mice. When subjected to a metabolic stressor, such as 2-deoxyglucose-induced neuroglucopenia, both strains responded with similar increases in plasma glucose levels. This change was associated with hyperinsulinemia, whose amplitude was lower in NOD than in C57BL/6 females. Lastly, administration of the alpha 2-adrenergic agonist, clonidine, elicited a marked increase in plasma glucose levels, whose amplitude was independent of the strain. The results from this study indicate that the two strains differed in their glycemic response to a psychological, but not to a metabolic, stressor. Because NOD mice were found to exhibit increased locomotion when placed for the first time in an open field, it is suggested that behavioral differences contribute to this differential effect of immobilization upon circulating glucose levels in NOD and C57BL/6 mice.

Reduced insulin binding to liver plasma membranes in inherently obese diabetic CBA/Ca mice

Insulin binding to isolated liver plasma membranes was measured in mice from C57BL and LACG strains, and in normal and obese diabetic mice from the Bristol CBA/Ca colony. A simple and rapid three-step method for the preparation and purification of liver plasma membranes, using Percoll density gradient centrifugation was used. Both high and low affinity binding was detected in membranes from all four groups of mice. The Kd values for binding were similar in all groups, but the insulin binding capacity (Bmax) at low and high affinity was significantly reduced in obese CBA mice compared to age-matched lean controls. It is proposed that insulin receptor down-regulation may account for the insulin resistance observed in spontaneously obese diabetic CBA mice.

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.

Neuropeptide content in pancreas and pituitary of obese and diabetes mutant mice: strain and sex differences

The nature of the primary genetic defects in ob/ob and db/db mice are unknown. Both the obese (ob) and diabetes (db) mutations produce similar, multicomponent obese-hyperinsulinemic syndromes when maintained in the same strain of mouse. In an attempt to find differences between these mutations in neuroendocrine function affecting the islets of Langerhans or the pituitary, tissue content of four neuropeptides that are known to be capable of influencing the rate of insulin secretion was examined in obese (ob/ob) and diabetes (db/db) mice. In the first study, C57BL/6Job/ob and control males were studied at 3, 4, and 11 weeks of age. In the second study, db/db mice of both sexes and two inbred strains (C57BL/6J and C57BL/KsJ), which differ markedly in the severity of expression of the diabetes phenotype, were studied at 3 weeks of age, before the development of hyperglycemia and secondary consequences thereof. Immunoreactive peptides were measured in acetic acid extracts of pancreas and pituitary. No differences between male ob/ob and db/db mice of the C57BL/6J strain were found. Marked sex differences in lean control mice were found at 3 weeks of age in pancreatic Met-enkephalin-LI and galanin-LI (with two- to threefold higher content in males). Low pancreatic content (50% to 70% lower than in control mice) of galanin-LI, Met-enkephalin-LI and Leu-enkephalin-LI was associated with hyperinsulinemia in male B6 ob/ob and db/db mice at 3 weeks of age, though not in B6 db/db females and not in BKs db/db mice of either sex.(ABSTRACT TRUNCATED AT 250 WORDS)

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.