Induction of diabetes in cynomolgus monkeys with high-dose streptozotocin: adverse effects and early responses

A Monovalent Mt10-CVB3 Vaccine Prevents CVB4-Accelerated Type 1 Diabetes in NOD Mice

Enteroviruses, which include Coxsackieviruses, are a common cause of virus infections in humans, and multiple serotypes of the group B Coxsackievirus (CVB) can induce similar diseases. No vaccines are currently available to prevent CVB infections because developing serotype-specific vaccines is not practical. Thus, developing a vaccine that induces protective immune responses for multiple serotypes is desired. In that direction, we created a live-attenuated CVB3 vaccine virus, designated mutant (Mt)10, that offers protection against myocarditis and pancreatitis induced by CVB3 and CVB4 in disease-susceptible A/J mice. Here, we report that the Mt10 vaccine protected against CVB4-triggered type 1 diabetes (T1D) in non-obese diabetic (NOD) mice but the expected subsequent development of spontaneous T1D in these genetically predisposed NOD mice was not altered. We noted that Mt10 vaccine induced significant amounts of neutralizing antibodies, predominantly of the IgG2c isotype, and the virus was not detected in vaccine-challenged animals. Furthermore, monitoring blood glucose levels-and to a lesser extent, insulin antibodies-was found to be helpful in predicting vaccine responses. Taken together, our data suggest that the monovalent Mt10 vaccine has the potential to prevent infections caused by multiple CVB serotypes, as we have demonstrated in various pre-clinical models.

Induction of diabetes in cynomolgus monkey with one shot of analytical grade streptozotocin

BACKGROUNDS

Streptozotocin (STZ)- induced diabetic monkey is a wide used preclinical animal model for the investigation of diabetes such as islet transplantation and development of diabetic drugs. There are serious side effects of this method, including nausea, emesis, weight loss, liver damage, renal failure, and metabolic acidosis. In order to reduce the side effects, diabetic monkeys were induced using clinical-grade STZ. However, clinical-grade STZ is not available in China. Here, we establised a method by using 100 mg/kg analytical-grade STZ to induce complete diabetes in cynomolgus monkey without generating adverse effects to liver and renal.

METHODS

Three cynomolgus monkeys were used in this study. 100 mg/kg STZ dissolved in normal saline and infused through vein line in 5 minutes after indwelling catheter in the carotid artery and jugular vein. After the STZ administration, blood glucose levels were examined every 1 or 2 hours in the first 48 hours. Then, blood glucose levels were examined twice per day during the first week after the STZ injection. Insulin and C-peptide levels were measured by ELISA. Blood chemistry of hepatic and renal function tests were performed. Insulin and glucagon expression in the islet of diabetic monkey and normal monkey were examined by immunohistochemistry assays.

RESULTS

The stimulated C-peptide level (Intravenous glucose tolerance test) which is less than 0.5 ng/mL, the triphasic blood glucose response and the destroyed β cell suggested the complete induction of diabetes model. No apparent adverse effects were observed including no signs of vomiting and toxicity after STZ injection.

CONCLUSION

In summary, we established a safe and reproducible STZ-induced diabetic cynomolgus monkey model for islet transplantation which will be used to develop novel approaches for the treatment of diabetes.

Taurine Increases Insulin Expression in STZ-Treated Rat Islet Cells In Vitro

This research aims at figure out the effects and the pathway of taurine on insulin in islet cells cultured in vitro treated by STZ. In the experiment, islet cells were isolated from pancreatic tissue by in situ perfusion with collagenase V. The pancreatic islet cells, maintained in RPMI 1640 culture medium were divided into six groups: C: control, E: supplemented with 10 mmol/L of taurine, group M, T1, T2 and T3 was treated with STZ (0.5 mmol/L), at the same time, taurine were added in group T1,T2 and T3 for 30 min, and then culture medium were collected by centrifugation and then insulin levels were detected by radioimmunoassay, the cells were then rinsed with Hanks, and 0,10, 0, 5, 10, 20 mmol/L of taurine in group C, E, M, T1, T2 and T3 were added for 24 h respectively. Total RNA was extracted, then insulin gene and its transcription regulator such as PDX-1, NeuroD1 were amplified by semi-quantitative RT-PCR. The results showed that, the release of insulin from islet cells treated by STZ could be inhibited by taurine, gene expression of insulin, PDX-1 and NeuroD1 in STZ group decreased significantly, which were up-regulated by taurine administration. In conclusion, taurine exerts a certain degree of protective and reconstructive effects on islet cells treated by STZ.

Simultaneous Subtotal Pancreatectomy and Streptozotocin Injection for Diabetes Modeling in Cynomolgus Monkeys

BACKGROUND

In an experimental animal model of islet transplantation, stable induction of insulin-dependent diabetes mellitus (IDDM) and islet isolation from donor pancreas are essential. Total pancreatectomy for IDDM induction and islet procurement in nonhuman primates leads to unwanted loss of exocrine function and may lead to morbidities associated with IDDM.

METHODS

IDDM induction with streptozotocin (STZ) is associated with drug toxicity of STZ and necessitates the killing of another animal for islet procurement. In this study, we performed a subtotal pancreatectomy combined with reduced STZ injection to induce IDDM and procure islets in a nonhuman primate model.

RESULTS

Twelve cynomolgus monkeys received low-dose STZ injections (60 mg/kg) simultaneously with subtotal pancreatectomy. All monkeys recovered from the procedure without complications. IDDM was induced in the animals. 57,691 ± 16,050 islets were isolated from the resected pancreas and transplanted into other monkeys.

CONCLUSIONS

Simultaneous subtotal pancreatectomy and low-dose STZ injection represent an effective and safe method to create an animal model of insulin dependence diabetes, while at the same time providing sufficient amounts of fresh islet cells for allotransplantation without requiring killing of additional animals.

Successful pharmaceutical-grade streptozotocin (STZ)-induced hyperglycemia in a conscious tethered baboon (Papio hamadryas) model

BACKGROUND

Non-human primate (NHP) diabetic models using chemical ablation of β-cells with STZ have been achieved by several research groups. Chemotherapeutic STZ could lead to serious adverse events including nephrotoxicity, hepatotoxicity, and mortality.

METHODS

We implemented a comprehensive therapeutic strategy that included the tether system, permanent indwelling catheter implants, an aggressive hydration protocol, management for pain with IV nubain and anxiety with IV midazolam, moment-by-moment monitoring of glucose levels post-STZ administration, and continuous intravenous insulin therapy.

RESULTS

A triphasic response in blood glucose after STZ administration was fully characterized. A dangerous hypoglycemic phase was also detected in all baboons. Other significant findings were hyperglycemia associated with low levels of plasma leptin, insulin and C-peptide concentrations, hyperglucagonemia, and elevated non-esterified fatty acids (NEFA) concentrations.

CONCLUSIONS

We successfully induced frank diabetes by IV administering a single dose of pharmaceutical-grade STZ safely and without adverse events in conscious tethered baboons.

Assessment of early renal damage in diabetic rhesus monkeys

The objectives of the study were to improve the model system of diabetic nephropathy in nonhuman primates and assess the early renal damage. Diabetes was induced in monkeys by streptozotocin, and the animals were administered exogenous insulin to control blood glucose (BG). Animals were divided into four groups, including the normal group (N = 3), group A (streptozotocin diabetic model with control of BG < 10 mmol/L, N = 3), group B (streptozotocin diabetic model with control of BG between 15 and 20 mmol/L, N = 4), and group C (streptozotocin diabetic model with control of BG between 15 and 20 mmol/L and high-sodium and high-fat diet, N = 4). The following parameters were evaluated: (1) blood biochemistry and routine urinalysis, (2) color Doppler ultrasound, (3) angiography, (4) renal biopsy, and (5) renal fibrosis-related gene expression levels. Animals in group C developed progressive histologic changes with typical diabetic nephropathy resembling diabetic nephropathy in human patients and exhibited accelerated development of diabetic nephropathy compared with other nonhuman primate models. Significant changes in the expression of the Smad2/3 gene and eNOS in renal tissue were also observed in the early stage of diabetic nephropathy. In conclusion, our model is an excellent model of diabetic nephropathy for understanding the pathogenesis of diabetic nephropathy.

Practical and critical instruction for nonhuman primate diabetic models

Diabetes mellitus, a disease of metabolic dysregulation, is characterized by inappropriate hyperglycemia resulting from progressive loss of insulin secretion or action. The potential of nonhuman primate (NHP) models in diabetes research has been well understood. NHPs have long been regarded as the "gold standard" for preclinical studies. However, there are persistent, severe obstacles to the development and application of these models. At present, a consensus for standardized strategies of diabetic induction has not been achieved. The different modeling methods of diabetes has led to various characterizations of the pathology of the disease; however, there are deficiencies of systemic evaluation programs for nonhuman primate diabetes models. In this scenario, experimental systemic programs provide the highly required guidelines for NHP diabetic models. Moreover, given the expensive and relatively small population of primates and the fatal diabetic complications, it is imperative to carefully manage the care and use of these animals in biomedical research studies. This article briefly reviews the technical and managerial aspects of NHP diabetes models providing practical and critical instruction on housing and care, routine management, development strategy, modeling diagnosis, evaluation, and disease control, as well as guidelines for model selection for various purposes. The present article sought to provide guidelines for NHP models of diabetes in their development and application. It is not intended to outline mandatory requirements for clinical accreditation.

Streptozotocin-associated lymphopenia in cynomolgus monkeys

Streptozotocin (STZ) is used to induce diabetes in experimental animals. It has a variety of adverse effects, ranging from nausea, emesis, and weight loss to liver damage, renal failure, and metabolic acidosis. STZ also has effects on the immune system, being associated with lymphopenia in rodents, the mechanism of which is not fully understood. We present data on a significant STZ-associated reduction in lymphocyte count in nonhuman primates. We report a significant reduction in absolute lymphocyte count; in 2 monkeys, the lymphopenia persisted for >100 d. However, a significant increase in absolute monocyte count was noted. Furthermore, an increase in serum monocyte chemoattractant protein-1 (MCP-1) was observed. The reduction in lymphocyte numbers may contribute to immunomodulation that may be beneficial to a subsequent islet graft, and may reduce the need for immunosuppressive therapy. The increase in monocytes and MCP-1, however, may be detrimental to the islet graft. Studies are warranted to explore the mechanism by which STZ has its effect.

Nonhuman primate models of type 1 diabetes mellitus for islet transplantation

Islet transplantation is an attractive treatment of type 1 diabetes mellitus (T1DM). Animal models of diabetes mellitus (DM) contribute a lot to the experimental studies of islet transplantation and to evaluations of isolated islet grafts for future clinical applications. Diabetic nonhuman primates (NHPs) represent the suitable models of DMs to better evaluate the effectiveness of islet transplantation, to assess new strategies for controlling blood glucose (BG), relieving immune rejection, or prolonging islet survival, and eventually to translate the preclinical data into tangible clinical practice. This review introduces some NHP models of DM, clarifies why and how the models should be used, and elucidates the usefulness and limitations of the models in islet transplantation.

Factors affecting transplant outcomes in diabetic nude mice receiving human, porcine, and nonhuman primate islets: analysis of 335 transplantations

BACKGROUND

In the absence of a reliable islet potency assay, nude mice (NM) transplantation is the criterion standard to assess islet quality for clinical transplantation. There are factors other than islet quality that affect the transplant outcome.

METHODS

Here, we analyzed the transplant outcomes in 335 NM receiving islets from human (n=103), porcine (n=205), and nonhuman primate (NHP; n=27) donors. The islets (750, 1000, and 2000 islet equivalents [IEQ]) were transplanted under the kidney capsule of streptozotocin-induced diabetic NM.

RESULTS

The proportion of mice that achieved normoglycemia was significantly higher in the group implanted with 2000 IEQ of human, porcine, or NHP islets (75% normoglycemic) versus groups that were implanted with 750 IEQ (7% normoglycemic) and 1000 IEQ (30% normoglycemic). In this study, we observed that the purity of porcine islet preparations (P≤0.001), islet pellet size in porcine preparations (P≤ 0.01), and mice recipient body weight for human islet preparations (P=0.013) were independently associated with successful transplant outcome. NHP islets of 1000 IEQ were sufficient to achieve normoglycemic condition (83%). An islet mass of 2000 IEQ, high islet purity, increased recipient body weight, and high islet pellet volume increased the likelihood of successful reversal of diabetes in transplanted mice. Also, higher insulin secretory status of islets at basal stimulus was associated with a reduced mouse cure rate. The cumulative incidence of graft failure was significantly greater in human islets (56.12%) compared with porcine islets (35.57%; P≤0.001).

CONCLUSION

Factors affecting NM bioassay were identified (islet mass, islet purity, pellet size, in vitro insulin secretory capability, and mouse recipient body weight) and should be considered when evaluating islet function.

A syndrome of severe hypoglycemia and acidosis in young immunosuppressed diabetic monkeys and pigs-association with sepsis

BACKGROUND

Large animals treated with immunosuppressive drugs for preclinical experiments of transplantation have increased risks of infection, which can be compounded by the induction of diabetes if islet transplantation is planned.

METHODS

We report our experience with severe sepsis in two young cynomolgus monkeys and five pigs that were subjected to diabetes induction, immunosuppressive therapy, or islet allotransplantation.

RESULTS

In two monkeys and five pigs, infection was associated with a syndrome of profound hypoglycemia accompanied by severe acidosis, which was resistant to treatment. We do not believe that this syndrome has been reported previously by others.

CONCLUSIONS

Despite treatment, this syndrome complicated the interpretation of blood glucose readings as a measure of islet graft function and resulted in death or the need for euthanasia in all seven animals. We tentatively suggest that the syndrome may be related to the presence of microorganisms that metabolize glucose and produce lactate.

The usefulness and limitations of the diabetic macaque model in evaluating long-term porcine islet xenograft survival

BACKGROUND

  Various groups have reported prolonged diabetes reversal and graft function after porcine islet transplantation into diabetic macaques using different experimental designs (macaque source, islet source, type of immunosuppression): subsequently, the International Xenotransplantation Association has published recommendations for entering a clinical trial. Our experiments showed limitations that affected consistent achievement of long-term survival. We aimed to identify these limitations and underlying causes to emphasize the translational value of this highly relevant type 1 diabetic macaque model.

METHODS

  We reviewed data from our institution and literature data on long-term porcine islet xenograft survival in the diabetic macaque model, especially focusing on aspects of incomplete diabetes reversal relative to macaque normal values. This phenomenon was compared with diabetes reversal in an allo-islet transplant model in macaques and with chronic insulin treatment of diabetic macaques, all with 180-day follow-up. This comparison enabled to identify potential model limitations and underlying causative factors.

RESULTS

  Especially in the xenograft model, the achievement of long-term graft survival revealed limitations including chronic, mild hyperglycemia and absence of body weight (BW) gain or even progressive BW loss. Metabolic incompatibilities in glycemic control (i.e., insulin kinetics) between the pig and macaque species underlie chronic, mild hyperglycemia. This phenomenon might not bear relevance for the pig-to-human species combination because the glycemic control in pigs and humans is similar and differs from that in nonhuman primates (NHP). Weight loss could be related to changes in the gastrointestinal tract related with local high exposure to orally administered immunosuppressants; these must be given at higher dose levels because of low bioavailability in macaques to achieve systemic exposure at therapeutic levels. This is aggravated by insufficient graft insulin production in proportion to the needs of macaques: this model limitation has no translational value to the pig-to-human setting. Nutritional deficits can result in incorrect interpretation of blood glucose levels and C-peptide levels regarding graft function. Likewise, nutritional status alters physiologic responses, influencing susceptibility to infectious and noninfectious complications.

CONCLUSION

  THE model-induced confounding described interferes with accurate interpretation of safety and efficacy studies, which affects the translational value of pig-to-NHP islet cell transplant studies to the pig-to-human transplant condition.

Management of adverse side-effects after chemotherapy in macaques as exemplified by streptozotocin: case studies and recommendations

The chemotherapeutic streptozotocin is used for induction of diabetes in animal models including non-human primates. Being a cytotoxic nitrosourea compound, it can be associated with adverse events (AEs), mainly nausea and emesis, nephrotoxicity, elevated liver transaminase levels, pulmonary oedema and, most prominently, metabolic acidosis: these can be severe in some cases. The incidence and gravity are to some extent related to the characteristics of the individual animal, diagnostic tools, prompt recognition of symptoms and supportive measures. Careful animal selection, dose adaptation and supportive actions such as renal protective hydration are the main tools in managing AEs, but do not fully eliminate unavoidable and sometimes life-threatening conditions. In our centre we have built experience in a cohort of 78 cynomolgus and rhesus macaques in which six cases manifested severe AEs (8%). This experience has prompted implementation of strategies for early detection and management of adverse effects, together with an animal refinement programme. We present here specific pretreatment regimens, post-infusion laboratory evaluations, and flow charts to assess/treat metabolic acidosis and precipitating factors. Case reports of the six animals with severe AEs are presented to illustrate management of AEs, especially metabolic acidosis, and criteria for early euthanasia where appropriate. We conclude that improved monitoring and validated tools allow for optimal management of adverse effects in an early stage of their manifestation. Reduced morbidity and mortality not only improve individual animal wellbeing but also avoid model-induced confounding that diminishes the translational value of the experimental protocol.

Characterizing the induction of diabetes in juvenile cynomolgus monkeys with different doses of streptozotocin

Juvenile (2-23 years old) cynomolgus monkeys are frequently used as recipients in non-human primate islet transplantation studies. The aim of this study was to examine the effects of different doses of streptozotocin (STZ), and find the optimal dose for inducing diabetes in these monkeys. Fifteen juvenile (2-3 years old) cynomolgus monkeys were separated into three groups and administered with different doses of STZ (100, 68 or 60 mg kg(-1)). Basal and glucose-stimulated blood glucose, insulin, and C-peptide levels, as well as body weights were monitored. Hepatic and renal function tests and pancreatic immunohistochemistry were performed before and after STZ treatment. Monkeys treated with both 100 and 68 mg kg(-1) of STZ exhibited continuous hyperglycemia, which coincided with a nearly complete loss of islet β-cells. Two monkeys received 60 mg kg(-1) of STZ, but only one became completely diabetic. During the first week following STZ treatment, hepatic and renal function slightly increased in these three groups. However, 24 hours post-STZ, serum total bile acid levels were significantly increased in monkeys treated with 100 mg kg(-1) than those treated with 68 mg kg(-1) of STZ (P<0.05). These data suggest that 100 mg kg(-1) and 68 mg kg(-1) of STZ can safely induce diabetes in cynomolgus monkeys aged 2-3 years, but 68 mg kg(-1) of STZ, rather than 100 mg kg(-1) of STZ, may be more appropriate for inducing diabetes in these monkeys. Furthermore, body surface area, rather than body weight, was a more reliable determinant of dosage, where 700 mg m(-2) of STZ should be the lower limit for inducing diabetes in juvenile monkeys.

Ultrastructural analysis, zinc transporters, glucose transporters and hormones expression in New world primate (Callithrix jacchus) and human pancreatic islets

The New world primates (NWP) Callithrix jacchus separated from man approximately 50 million years ago and is a potential alternative small non-human primate model for diabetes research. Ultrastructure, and gene expression of pancreatic islets and the recently described diabetes auto antigenic zinc transporters families in human, NWP and pig pancreas were studied. Morphologically NWP islets were larger than pig islets and similar in size to human islets. NWP islets alpha cells had high dense core surrounded by a limiting membrane, beta cells by the mixed morphology of the granule core, and delta cells by moderate opaque core. Antibody staining for insulin, glucagon, somatostatin and Glucagon-like peptide-1 (GLP-1) showed that the distribution pattern of the different cell types within islets was comparable to pig and human islets. In all three species protein expression of zinc transporter ZnT8 was detected in most of the insulin producing beta cells whereas Zip14 expression was widely expressed in alpha and beta cells. In both human and NWP little or no expression of Glut2 was observed compared to Glut1 and glucokinase at the protein level, however the messenger RNA level of Glut2 was greater than Glut1 and glucokinase. In contrast all three glucose transporters were expressed in pig islets at the protein level. The expression of Zip14 in islets is reported for the first time. In conclusion NWP pancreatic islets express comparable islet cell types and distribution to humans and pigs. Importantly, marmosets have a similar glucose transporter profile to humans, making this non-endangered primate species a useful animal model for pancreatic biology.

Refining the high-dose streptozotocin-induced diabetic non-human primate model: an evaluation of risk factors and outcomes

In preparation for islet transplantation, diabetes was induced using streptozotocin (STZ) in non-human primates ranging from juveniles to adults with diverse body types: we studied the process with respect to the diabetic state and emergence of adverse events (AEs) and their severity, and identified risk factors for clinical and laboratory AEs. Pharmaceutical-grade STZ was given based on body surface area (BSA) (1050–1250 mg/m2, equivalent to 80–108 mg/kg) or on body weight (BW) (100 mg/kg) to 54 cynomolgus and 24 rhesus macaques. AEs were related to risk factors, i.e. obesity parameters, BW and BSA, age and STZ dose in mg/m2. Clinical AEs during the first days after infusion prompted euthanasia of three animals. Except for those three animals, diabetes was successfully induced as shown by circulating C-peptide levels, the intravenous glucose tolerance test and/or arginine stimulation test. C-peptide after infusion weakly correlated ( P = 0.048) with STZ dose in mg/m2. Grade ≥3 nephrotoxicity or hepatotoxicity (serum markers >3× baseline or >5 × baseline, respectively) occurred in about 10% of cases and were generally mild and reversible. Grade ≥2 clinical AEs occurred in seven of 78 animals, reversed in four cases and significantly correlated with obesity parameters. Taking girth-to-height ratio (GHtR) as an indicator of obesity, with threshold value 0.92–0.95, the positive predictive value of obesity for AEs was 92% and the specificity 94%. We conclude that diabetes is successfully induced in non-obese animals using a 100 mg/kg pharmaceutical grade STZ dose. Obesity is a significant risk factor, and animals with a higher than normal GHtR should preferably receive a lower dose. The incidence of relevant clinical or laboratory AEs is low. Careful monitoring and supportive medical intervention can result in recovery of AEs.

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.

Hemoglobin A1C Percentage in Nonhuman Primates: A Useful Tool to Monitor Diabetes before and after Porcine Pancreatic Islet Xenotransplantation

Non-human primates (NHPs) are a very valuable experimental model for diabetes research studies including experimental pancreatic islet transplantation. In particular NHPs are the recipients of choice to validate pigs as possible source of pancreatic islets. The aim of this study was to quantify glycated hemoglobin percentage in NHPs and to assess whether changes in values reflect the metabolic trends after diabetes induction and islet transplantation. Sera from 15 NHPs were analyzed. 9 NHPs were rendered diabetic with streptozotocin (STZ), and 3 of them received porcine islet transplants. Hemoglobin A1c (HbA1c) percentage was measured with an assay based on a latex immunoagglutination inhibition methodology. Whereas diabetes and its duration were associated with increasing HbA1c levels, postislet transplantation blood glucose normalization was paralleled by a decrease in the HbA1c percentage. Our data provide evidence that HbA1c is a useful tool to monitor glucose metabolism in NHPs.

Treatment and risk factor analysis of hypoglycemia in diabetic rhesus monkeys

In order to anticipate and promptly treat hypoglycemia in diabetic monkeys treated with insulin or other glucose-lowering drugs, the relationships between the incidence and symptoms of hypoglycemia in these animals, and many factors involved in model development and sustainment were analyzed. Different procedures were performed on 22 monkeys for the induction of diabetes. The monkey models were evaluated by blood glucose, insulin, C-peptide levels and intravenous glucose tolerance tests. A glucose treatment program for the diabetic monkeys was administered and laboratory tests were regularly performed. A standard procedure of hypoglycemia treatment was established and the risk factors of hypoglycemia were analyzed by a logistic regression model. Furthermore, the relationships between the four methods of diabetes induction, renal function, glycemic control and hypoglycemia were studied using one-way analysis of variance and t-test. We found that the hypoglycemic conditions of diabetic monkeys were improved rapidly by our treatment. The statistical analysis suggested that the modeling methods, renal function and glycemic control were related to the incidence of hypoglycemia. In detail, the progress of diabetes, effects of glycemic control and, particularly, the severity of the hypoglycemia differed according to the induction strategy used. The models induced by partial pancreatectomy with low-dose streptozotocin were not prone to hypoglycemia and their glycemic controls were stable. However, the models induced by total pancreatectomy were more vulnerable to severe hypoglycemia and their glycemic controls were the most unstable. Moreover, the levels of blood creatinine and triglyceride increased after the development of diabetes, which was related to the occurrence of hypoglycemia. In conclusion, we suggested that total pancreatectomy and renal impairment are two important risk factors for hypoglycemia in diabetic monkeys. More attention should be paid to daily care of diabetic monkeys, particularly monitoring and protecting their renal function.

Characterization and validation of a streptozotocin-induced diabetes model in the vervet monkey

INTRODUCTION

Streptozotocin (STZ), preferentially toxic to pancreatic beta cells, is commonly used to model Type 1 diabetes mellitus (DM) in numerous species, including nonhuman primates.

METHODS

We induced DM in twenty vervet monkeys (Chlorocebus aethiops) by intravenous administration of either 45 (n=8, STZ-45) or 55 mg/kg STZ (n=12, STZ-55); ten control (CTL) monkeys received saline.

RESULTS

Overall there was 15% mortality, likely secondary to renal toxicity. Twice-daily insulin therapy was initiated to maintain comparable glycemic control, confirmed by comparable glycated hemoglobin levels. Exogenous insulin requirements increased rapidly for 4weeks; STZ-45 insulin doses stabilized thereafter while STZ-55 doses continued to increase through 16weeks. Glucose tolerance testing and arginine-stimulated insulin secretion confirmed 80-90% reduction in pancreatic beta cell function in both groups. Body weight was reduced in all STZ monkeys, with return to baseline only in STZ-45 at 16 wks. Elevated blood urea nitrogen (BUN) and creatinine were noted in the STZ-55 group. Alkaline phosphatase (ALKP) was also increased with STZ-55 (p < 0.05 vs. CTL) whereas STZ-45 ALKP elevation resolved by study end. Red cell parameters were reduced in all STZ monkeys, but more severely in the STZ-55 group.

DISCUSSION

We have demonstrated that a model of DM can be induced and maintained in vervets with a single dose of STZ. The lower dose of STZ (45 mg/kg) significantly improved the toxicity profile without altering efficacy in inducing DM. Finally, sufficient time following induction is recommended to allow transient renal, hepatic and hematologic parameters to resolve.

Comparison of single high-dose streptozotocin with partial pancreatectomy combined with low-dose streptozotocin for diabetes induction in rhesus monkeys

Monkeys with insulin-dependent diabetes are important experimental models for islet xenotransplantation. However, with regard to diabetes induction, total pancreatectomy is a difficult operation with a high complication rate, while streptozotocin (STZ) administration may cause serious toxic effects and individual difference in metabolism. We compared two strategies involving pancreatectomy and STZ to successfully and safely induce diabetes in rhesus monkeys. Thirteen rhesus monkeys were divided into two groups: single high-dose STZ administration (80, 100 and 120 mg/kg, n = 3 for each dose) (group 1) and partial pancreatectomy (70–75%) combined with low-dose STZ (15 mg/kg, n = 4) (group 2). Induction of diabetes was evaluated by blood glucose, insulin, C-peptide, intravenous glucose tolerance test (IVGTT) and arginine stimulation test (AST). Detection of hematological and serum biochemical parameters and biopsies of pancreas, liver and kidney were periodically performed. In our study, animals in both groups developed diabetes. Serum C-peptide levels in groups 1 and 2 decreased to 0.08 ± 0.07 and 0.35 ± 0.06 nmol/L, respectively. IVGTT and AST indicated severely impaired glucose tolerance. Immunohistochemistry demonstrated that rare insulin-positive cells remained in the pancreas. In terms of STZ toxicity, four monkeys died 8–14 days after STZ administration (3 with 120 mg/kg STZ and 1 with 100 mg/kg STZ). Group 1 animals developed liver and kidney injury evidenced by increased alanine aminotransferase, aspartate aminotransferase, total cholesterol, LDL, triglyceride and blood urea nitrogen for one month, and histological abnormality including hepatic steatosis, renal glomerulus and tubular injury. Nevertheless, moderate histological injuries were seen in animals with 80 mg/kg STZ, with subsequent recovery. In contrast, group 2 animals displayed normal biochemical parameters and histology, with generally less risk of postoperative complications. We conclude that injection of 80 mg/kg STZ could induce diabetes with moderate injuries. Partial pancreatectomy with low-dose STZ is a safer and more reproducible method for inducing diabetes in rhesus monkeys.

Recovery of endogenous beta-cell function in nonhuman primates after chemical diabetes induction and islet transplantation

OBJECTIVE

To describe the ability of nonhuman primate endocrine pancreata to reestablish endogenous insulin production after chemical beta-cell destruction.

RESEARCH DESIGN AND METHODS

Eleven monkeys (Macaca fascicularis) were rendered diabetic with streptozotocin. Eight diabetic monkeys received intraportal porcine islet transplantation.

RESULTS

Two monkeys transplanted after 75 days of type 1 diabetes showed recovery of endogenous C-peptide production a few weeks after transplantation, concomitant with graft failure. Histological analysis of the pancreas of these monkeys showed insulin-positive cells, single or in small aggregates, scattered in the pancreas and adjacent to ducts. Interestingly, numerous CK19(+) cells costained with proinsulin and PDX-1 antibodies. Furthermore, the peculiar double phenotype glucagon-positive/GLUT2(+) was observed. In these monkeys as well as in all others, the original islets showed no insulin staining.

CONCLUSIONS

Our data provide evidence that, in nonhuman primates, the pancreas can reestablish endogenous insulin production after chemical beta-cell destruction. This seems to be a nongeneralizable event with only 2 out of 11 monkeys recovering beta-cell function. In these two monkeys, younger age and islet graft behavior might have played a role in triggering endogenous beta-cell recovery.

Differential expression of GLUT2 in pancreatic islets and kidneys of New and Old World nonhuman primates

Diabetes is a growing public health concern, and animal models of this disease are necessary for a full understanding of disease pathogenesis, progression, clinical sequelae, and treatment options. In particular, nonhuman primate models of diabetes are important because of their close genetic relationship to humans. Although numerous Old World primate models have been described, few studies have examined the possibility of using New World monkeys as an animal model for this disease. Streptozotocin (STZ) is a common diabetogenic drug that selectively destroys beta cells after uptake via the GLUT2 glucose transporter. Induction of diabetes using STZ was attempted in common marmosets (Callithrix jacchus). These animals showed increases in blood glucose consistent with diabetes only at STZ doses markedly greater than those used in other primate species. Additionally, all animals showed pathological evidence of acute renal and liver toxicity secondary to the treatment. In a subsequent comparative study of various nonhuman primates, GLUT2 immunostaining in pancreatic islets was used as a marker for sensitivity to STZ. Immunostaining of islets from a variety of nonhuman primate species indicated a reduced expression of pancreatic GLUT2 in New compared with Old World monkeys; this finding explains their resistance to diabetic induction with STZ. Furthermore, there were age-dependent differences in GLUT2 expression, with aged and infant macaques showing reduced expression. We conclude that New World monkeys are an inappropriate model for diabetes induction with STZ and that, with all primate species, it is important to consider the animals' age before diabetic induction with STZ is attempted.

Metabolic aspects of pig-to-monkey (Macaca fascicularis) islet transplantation: implications for translation into clinical practice

AIMS/HYPOTHESIS

Attempts to use an alternative source of islets to restore glucose homeostasis in diabetic patients require preclinical islet xenotransplantation models to be tested. These models raise questions about metabolic compatibility between species and the most appropriate metabolic parameters to be used to monitor graft function. The present study investigated and compared relevant gluco-metabolic parameters in pigs, monkeys and the pig-to-monkey islet transplantation model to gain insight into the potential clinical outcome of pig-to-human islet transplantation.

METHODS

Basal and IVGTT-stimulated blood glucose, C-peptide, insulin and glucagon levels were assessed in non-diabetic pigs and monkeys. The same parameters were used to evaluate the performance of porcine islet xenografts in diabetic monkeys.

RESULTS

Non-diabetic cynomolgus monkeys showed lower levels of fasting and stimulated blood glucose but higher levels of C-peptide and insulin than non-diabetic pigs. The reported levels in humans lie between those of monkeys and pigs, and differences in metabolic parameters between pigs and humans appear to be smaller than those between pigs and cynomolgus monkeys. The transplantation data indicated that the degree of graft function (evaluated by the measurement of C-peptide levels) necessary to normalise blood glucose in the recipient was determined by the recipient levels rather than by the donor levels.

CONCLUSIONS/INTERPRETATION

The differences between donor and recipient species may affect the transplantation outcome and need to be considered when assessing graft function in xenotransplantation models. Given the differences between monkeys and humans as potential recipients of pig islets, it should be easier to reach glucose homeostasis in pig-to-human than in pig-to-non-human primate islet xenotransplantation.

Safe induction of diabetes by high-dose streptozotocin in pigs

OBJECTIVES

Streptozotocin (STZ) has been widely used to induce diabetes in rodents and nonhuman primates, but it has been found difficult to achieve a completely diabetic state in pigs in the absence of detrimental side effects. As a result, pancreatectomy has been advocated in this species. We have investigated the effects of 2 dosages of STZ to safely induce diabetes in pigs.

METHODS

Three pigs received Zanosar STZ at 150 mg/kg (group 1). Four pigs received Zanosar STZ at 200 mg/kg (group 2). The levels of glucose, insulin, and C-peptide when (a) fasting, (b) 30 minutes after eating, and (c) during intravenous glucose tolerance tests (IVGTTs) were measured in all pigs for 4 weeks after STZ injection. To confirm how long the diabetic state can be maintained after induction with STZ, levels were measured for 20 weeks in group 2.

RESULTS

One to 4 weeks after STZ administration, in group 1 (150 mg/kg) pigs, insulin and C-peptide levels were detected up to 7 microIU/mL and 0.4 ng/mL, respectively, both when fasting and after a meal test or IVGTT, indicating that the pigs had failed to become fully diabetic. In group 2 (200 mg/kg) pigs, insulin and C-peptide levels were less than the 2 microIU/mL and 0.25 ng/mL respective detection levels and did not increase after a meal test or IVGTT. Group 2 remained completely diabetic for the entire 20-week period of follow-up, without STZ-related hepatic or renal dysfunction.

CONCLUSIONS

High-dose (200 mg/kg) Zanosar STZ induces diabetes safely and completely in pigs without side effects. Pancreatectomy can, therefore, be avoided.