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

Streptozotocin as a tool for induction of rat models of diabetes: a practical guide

Streptozotocin (STZ) is the most used diabetogenic chemical for creating rat models of type 1 and type 2 diabetes. Despite ~60 years of using STZ in animal diabetes research, some prevailing views about STZ preparation and use are not supported by evidence. Here, we provide practical guides for using STZ to induce diabetes in rats. Susceptibility to the diabetogenic effect of STZ is inversely related to age, and males are more susceptible to STZ than females. Wistar and Sprague-Dawley rats, the most commonly-used rat strains, are sensitive to STZ, but some strains (e.g., Wistar-Kyoto rats) are less sensitive. STZ is mostly injected intravenously or intraperitoneally, but its intravenous injection produces more stable hyperglycemia. Despite the prevailing view, no fasting is necessary before STZ injection, and injection of its anomer-equilibrated solutions (i.e., more than 2 hours of dissolving) is recommended. Mortality following the injection of diabetogenic doses of STZ is due to severe hypoglycemia (during the first 24 h) or severe hyperglycemia (24 h after the injection and onwards). Some measures to prevent hypoglycemia-related mortality in rats include providing access to food soon after the injection, administration of glucose/sucrose solutions during the first 24-48 h after the injection, administration of STZ to fed animals, and using anomer-equilibrated solutions of STZ. Hyperglycemia-related mortality following injection of high doses of STZ can be overcome with insulin administration. In conclusion, STZ is a valuable chemical for inducing diabetes in rats, but some practical guides should be considered to perform well-conducted and ethical studies.

Comparison of Genetically Engineered Immunodeficient Animal Models for Nonclinical Testing of Stem Cell Therapies

For the recovery or replacement of dysfunctional cells and tissue—the goal of stem cell research—successful engraftment of transplanted cells and tissues are essential events. The event is largely dependent on the immune rejection of the recipient; therefore, the immunogenic evaluation of candidate cells or tissues in immunodeficient animals is important. Understanding the immunodeficient system can provide insights into the generation and use of immunodeficient animal models, presenting a unique system to explore the capabilities of the innate immune system. In this review, we summarize various immunodeficient animal model systems with different target genes as valuable tools for biomedical research. There have been numerous immunodeficient models developed by different gene defects, resulting in many different features in phenotype. More important, mice, rats, and other large animals exhibit very different immunological and physiological features in tissue and organs, including genetic background and a representation of human disease conditions. Therefore, the findings from this review may guide researchers to select the most appropriate immunodeficient strain, target gene, and animal species based on the research type, mutant gene effects, and similarity to human immunological features for stem cell research.

Research methodology for in vivo measurements of resting energy expenditure, daily body temperature, metabolic heat and non-viral tissue-specific gene therapy in baboons

A large number of studies have shown that the baboon is one of the most commonly used non-human primate (NHP) research model for the study of immunometabolic complex traits such as type 2 diabetes (T2D), insulin resistance (IR), adipose tissue dysfunction (ATD), dyslipidemia, obesity (OB) and cardiovascular disease (CVD). This paper reports on innovative technologies and advanced research strategies for energetics and translational medicine with this NHP model. This includes the following: measuring resting energy expenditure (REE) with the mobile indirect calorimeter Breezing®; monitoring daily body temperature using subcutaneously implanted data loggers; quantifying metabolic heat with veterinary infrared thermography (IRT) imaging, and non-viral non-invasive, tissue-specific ultrasound-targeted microbubble destruction (UTMD) gene-based therapy. These methods are of broad utility; for example, they may facilitate the engineering of ectopic overexpression of brown adipose tissue (BAT) mUCP-1 via UTMD-gene therapy into baboon SKM to achieve weight loss, hypophagia and immunometabolic improvement. These methods will be valuable to basic and translational research, and human clinical trials, in the areas of metabolism, cardiovascular health, and immunometabolic and infectious diseases.

Ectopic BAT mUCP-1 overexpression in SKM by delivering a BMP7/PRDM16/PGC-1a gene cocktail or single PRMD16 using non-viral UTMD gene therapy

Here we present our progress in inducing an ectopic brown adipose tissue (BAT) phenotype in skeletal muscle (SKM) as a potential gene therapy for obesity and its comorbidities. We used ultrasound-targeted microbubble destruction (UTMD), a novel targeted, non-viral approach to gene therapy, to deliver genes in the BAT differentiation pathway into rodent SKM to engineer a thermogenic BAT phenotype with ectopic mUCP-1 overexpression. In parallel, we performed a second protocol using wild-type Ucp-1-null knockout mice to test whether the effects of the gene therapy are UCP-1 dependent. Our main findings were a robust cellular presence of mUCP-1 immunostaining (IHC), significantly higher expression levels of mUCP-1 measured by qRT-PCR, and highest temperature elevation measured by infrared thermography in the treated thigh, achieved in rats after delivering the UTMD-PRDM16/PGC-1a/BMP7/hyPB gene cocktail. Interestingly, the weight loss obtained in the treated rats with the triple gene delivery, never recovered the levels observed in the controls in spite of food intake recovery. Our results establish the feasibility of minimally invasive UTMD gene-based therapy administration in SKM, to induce overexpression of ectopic mUCP-1 after delivery of the thermogenic BAT gene program, and describe systemic effects of this intervention on food intake, weight loss, and thermogenesis.

Use and Importance of Nonhuman Primates in Metabolic Disease Research: Current State of the Field

Obesity and its multiple metabolic sequelae, including type 2 diabetes, cardiovascular disease, and fatty liver disease, are becoming increasingly widespread in both the developed and developing world. There is an urgent need to identify new approaches for the prevention and treatment of these costly and prevalent metabolic conditions. Accomplishing this will require the use of appropriate animal models for preclinical and translational investigations in metabolic disease research. Although studies in rodent models are often useful for target/pathway identification and testing hypotheses, there are important differences in metabolic physiology between rodents and primates, and experimental findings in rodent models have often failed to be successfully translated into new, clinically useful therapeutic modalities in humans. Nonhuman primates represent a valuable and physiologically relevant model that serve as a critical translational bridge between basic studies performed in rodent models and clinical studies in humans. The purpose of this review is to evaluate the evidence, including a number of specific examples, in support of the use of nonhuman primate models in metabolic disease research, as well as some of the disadvantages and limitations involved in the use of nonhuman primates. The evidence taken as a whole indicates that nonhuman primates are and will remain an indispensable resource for evaluating the efficacy and safety of novel therapeutic strategies targeting clinically important metabolic diseases, including dyslipidemia and atherosclerosis, type 2 diabetes, hepatic steatosis, steatohepatitis, and hepatic fibrosis, and potentially the cognitive decline and dementia associated with metabolic dysfunction, prior to taking these therapies into clinical trials in humans.

Characterization of a PRISTANE-induced lupus-associated model in the non-human primate cynomolgus monkey

BACKGROUND

Lupus is an autoimmune disease with complex syndrome. Rodent models have limitations for recapitulating the spectrum of the disease. A more powerful translational model is desirable.

METHOD

Lupus-associated model in cynomolgus monkeys was induced by two intraperitoneal injections of 2, 6, 10, 14-tetramethylpentadecane (PRISTANE). Lupus-specific biomarkers and manifestations over a 246-day period were observed at multilevel. To visualize and quantify kidney function in real time, contrast-enhanced ultrasound was used.

RESULTS

The indicative biomarkers and manifestations fulfilled major diagnosis criteria according to the "Criteria of Lupus" of the American College of Rheumatology. Significant changes in time-intensity curve parameters were observed, indicating impaired renal function and the method as a feasible, non-invasive diagnostic method in primate model.

CONCLUSIONS

We successfully induced lupus-associated model with systemic lupus syndrome. This primate model can be a valuable translational model for further pathogenesis and symptomology studies and for exploring therapeutic candidates.

Changes in Cerebral Blood Flow during an Alteration in Glycemic State in a Large Non-human Primate (Papio hamadryas sp.)

Changes in cerebral blood flow (CBF) during a hyperglycemic challenge were mapped, using perfusion-weighted MRI, in a group of non-human primates. Seven female baboons were fasted for 16 h prior to 1-h imaging experiment, performed under general anesthesia, that consisted of a 20-min baseline, followed by a bolus infusion of glucose (500 mg/kg). CBF maps were collected every 7 s and blood glucose and insulin levels were sampled at regular intervals. Blood glucose levels rose from 51.3 ± 10.9 to 203.9 ± 38.9 mg/dL and declined to 133.4 ± 22.0 mg/dL, at the end of the experiment. Regional CBF changes consisted of four clusters: cerebral cortex, thalamus, hypothalamus, and mesencephalon. Increases in the hypothalamic blood flow occurred concurrently with the regulatory response to systemic glucose change, whereas CBF declined for other clusters. The return to baseline of hypothalamic blood flow was observed while CBF was still increasing in other brain regions. The spatial pattern of extra-hypothalamic CBF changes was correlated with the patterns of several cerebral networks including the default mode network. These findings suggest that hypothalamic blood flow response to systemic glucose levels can potentially be explained by regulatory activity. The response of extra-hypothalamic clusters followed a different time course and its spatial pattern resembled that of the default-mode network.

Nonhuman primate model in clinical modeling of diseases for stem cell therapy

Nonhuman primates (NHPs) are alike humans in size, behavior, physiology, biochemistry, and immunology. Given close similarities to humans, the NHP model offers exceptional opportunities to understand the biological mechanisms and translational applications with direct relevance to human conditions. Here, we evaluate the opportunities and limitations of NHPs as animal models for translational regenerative medicine. NHP models of human disease propose exceptional opportunities to advance stem cell-based therapy by addressing pertinent translational concerns related to this research. Nonetheless, the value of these primates must be carefully assessed, taking into account the expense of specialized equipment and requirement of highly specialized staff. Well-designed initial fundamental studies in small animal models are essential before translating research into NHP models and eventually into human trials. In addition, we suggest that applying a directed and collaborative approach, as seen in the evolution of stroke NHP models, will greatly benefit the translation of stem cell therapy in other NHP disease models.

Induction, management, and complications of streptozotocin-induced diabetes mellitus in rhesus monkeys

BACKGROUND

Diabetes mellitus (DM) model using streptozotocin (STZ) which induces chemical ablation of β cell in the pancreas has been widely used for various research purposes in non-human primates. However, STZ has been known to have a variety of adverse effects such as nephrotoxicity, hepatotoxicity, and even mortality. The purpose of this study is to report DM induction by STZ, toxicity associated with STZ and procedure and complication of exogenous insulin treatment for DM management in rhesus monkeys (Macaca mulatta) that are expected to be transplanted with porcine islets within 2 months.

METHODS

Streptozotocin (immediately dissolved in normal saline, 110 mg/kg) was slowly infused via central catheter for 10 minutes in 22 rhesus monkeys. Clinical signs, complete blood count and blood chemistry were monitored to evaluate toxicity for 1 week after STZ injection. Monkey basal C-peptides were measured and intravenous glucose tolerance test was performed to confirm complete induction of DM. Exogenous insulin was subcutaneously injected to maintain blood glucose in diabetic rhesus monkeys and the complications were recorded while in insulin treatment.

RESULTS

Severe salivation and vomiting were observed within 1 hour after STZ injection in 22 rhesus monkeys. One monkey died at 6 hours after STZ injection and the reason for the death was unknown. Pancreatitis was noticed in one monkey after STZ injection, but the monkey recovered after 5 days by medical treatment. Serum total protein and albumin decreased whereas the parameters for the liver function such as aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase significantly increased (P<.05) after STZ injection, but they were resolved within 1 week. Azotemia was not observed. Monkey fasting C-peptide levels after STZ injection were <0.1 ng/mL in 18 rhesus monkeys, but 0.34, 0.22, 0.16 ng/mL in three monkeys, respectively. The value of daily insulin requirement was 0.92±0.26IU/kg/d (range=0.45-1.29) in the monkeys. Diabetic ketoacidosis was observed in one rhesus monkeys, but the monkey recovered after 24 hours by fluid and insulin treatment.

CONCLUSIONS

Streptozotocin was effective for inducing DM in rhesus monkeys, but various adverse effects such as pancreatitis, liver toxicity or death were observed. Therefore, careful and suitable medical managements should be implemented to eliminate the risks of mortality and severe adverse effects.