Induction of diabetes with signs of autoimmunity in primates by the injection of multiple-low-dose streptozotocin

Particle-Based therapies for antigen specific treatment of type 1 diabetes

Type 1 diabetes mellitus (T1D) is the leading metabolic disorder in children worldwide. Over time, incidence rates have continued to rise with 20 million individuals affected globally by the autoimmune disease. The current standard of care is costly and time-consuming requiring daily injections of exogenous insulin. T1D is mediated by autoimmune effector responses targeting autoantigens expressed on pancreatic islet β-cells. One approach to treat T1D is to skew the immune system away from an effector response by taking an antigen-specific approach to heighten a regulatory response through a therapeutic vaccine. An antigen-specific approach has been shown with soluble agents, but the effects have been limited. Micro or nanoparticles have been used to deliver a variety of therapeutic agents including peptides and immunomodulatory therapies to immune cells. Particle-based systems can be used to deliver cargo into the cell and microparticles can passively target phagocytic cells. Further, surface modification and controlled release of encapsulated cargo can enhance delivery over soluble agents. The induction of antigen-specific immune tolerance is imperative for the treatment of autoimmune diseases such as T1D. This review highlights studies that utilize particle-based platforms for the treatment of T1D.

Vitamin K2 Modulates Organelle Damage and Tauopathy Induced by Streptozotocin and Menadione in SH-SY5Y Cells

Vitamin K2, known for its antioxidative and anti-inflammatory properties, can act as a potent neuroprotective molecule. Despite its action against mitochondrial dysfunction, the mechanism underlying the links between the protective effects of vitamin K2 and endoplasmic reticulum (ER) stress along with basal levels of total tau protein and amyloid-beta 42 (Aβ42) has not been elucidated yet. To understand the neuroprotective effect of vitamin K2 during metabolic complications, SH-SY5Y cells were treated with streptozotocin for 24 h and menadione for 2 h in a dose-dependent manner, followed by post-treatment of vitamin K2 for 5 h. The modulating effects of vitamin K2 on cell viability, lactate dehydrogenase release, reactive oxygen species (ROS), mitochondrial membrane potential, ER stress marker (CHOP), an indicator of unfolded protein response (UPR), inositol requiring enzyme 1 (p-IRE1α), glycogen synthase kinase 3 (GSK3α/β), total tau and Aβ42 were studied. Results showed that vitamin K2 significantly reduces neuronal cell death by inhibiting cytotoxicity and ROS levels and helps in the retainment of mitochondrial membrane potential. Moreover, vitamin K2 significantly decreased the expression of CHOP protein along with the levels and the nuclear localization of p-IRE1α, thus showing its significant role in inhibiting chronic ER stress-mediated UPR and eventually cell death. In addition, vitamin K2 significantly down-regulated the expression of GSK3α/β together with the levels of total tau protein, with a petite effect on secreted Aβ42 levels. These results suggested that vitamin K2 alleviated mitochondrial damage, ER stress and tauopathy-mediated neuronal cell death, which highlights its role as new antioxidative therapeutics targeting related cellular processes.

Combined therapy of mesenchymal stem cells with a GLP-1 receptor agonist, liraglutide, on an inflammatory-mediated diabetic non-human primate model

AIMS

Immunomodulation concurrent with the promotion of β-cell function is a strategy used to develop innovative therapies for type 1 diabetes (T1D). Here, we assessed the therapeutic potential of co-administration of human clonal mesenchymal stem (stromal) cells (hBM-cMSCs) and liraglutide as a glucagon-like peptide-1 agonist in a non-human primate model with streptozotocin (STZ)-induced diabetes.

MAIN METHODS

Diabetes was induced through intravenous (i.v.) multiple low-dose (MLD) infusions of STZ at a dose of 30 mg/kg body weight (b.w.) for five consecutive days, followed by two booster injections of 35 mg/kg on days 12 and 19. After 90 days, the diabetic animals were randomly allocated to two groups: The combination therapy group (n = 4) received injections of 1.5 × 10⁶ hBM-cMSCs/kg b.w. through celiac artery by angiography on days 91 and 105 and daily subcutaneous injections of liraglutide (up to 1.8 mg/day) until day 160 while vehicle group received phosphate-buffered saline. The monkeys were assessed for functional, immunological, and histological analysis.

KEY FINDINGS

The combined treatment group had continued reduction in FBG levels up to day 160, which was accompanied by increased b.w., C-peptide, and β-cell function, and decreased HbA1c and fructosamine levels compared to vehicle group. The combined treatment increased Tregs, IL-4, IL-10, and TGF-β1 and decreased IL-6 and IL-1β. Stereological analysis of the pancreatic tissue exhibited more total volume of insulin-secreting islets in the combined treatment group compared to vehicle group.

SIGNIFICANCE

Our findings demonstrated this combined treatment impaired the clinical symptoms of diabetes in this animal model through immunomodulation and β-cell preservation.

Future Perspective of Diabetic Animal Models

Objective

The need of today’s research is to develop successful and reliable diabetic animal models for understanding the disease susceptibility and pathogenesis. Enormous success of animal models had already been acclaimed for identifying key genetic and environmental factors like Idd loci and effects of microorganisms including the gut microbiota. Furthermore, animal models had also helped in identifying many therapeutic targets and strategies for immune-intervention. In spite of a quite success, we have acknowledged that many of the discovered immunotherapies are working on animals and did not have a significant impact on human. Number of animal models were developed in the past to accelerate drug discovery pipeline. However, due to poor initial screening and assessment on inequivalent animal models, the percentage of drug candidates who succeeded during clinical trials was very low. Therefore, it is essential to bridge this gap between pre-clinical research and clinical trial by validating the existing animal models for consistency.

Results and Conclusion

In this review, we have discussed and evaluated the significance of animal models on behalf of published data on PUBMED. Amongst the most popular diabetic animal models, we have selected six animal models (e.g. BioBreeding rat, “LEW IDDM rat”, “Nonobese Diabetic (NOD) mouse”, “STZ RAT”, “LEPR Mouse” and “Zucker Diabetic Fatty (ZDF) rat” and ranked them as per their published literature on PUBMED. Moreover, the vision and brief imagination for developing an advanced and robust diabetic model of 21^st century was discussed with the theme of one mice-one human concept including organs-on-chips.

Elucidation of Molecular Mechanisms of Streptozotocin-Induced Oxidative Stress, Apoptosis, and Mitochondrial Dysfunction in Rin-5F Pancreatic β-Cells

Streptozotocin is a pancreatic beta-cell-specific cytotoxin and is widely used to induce experimental type 1 diabetes in rodent models. The precise molecular mechanism of STZ cytotoxicity is however not clear. Studies have suggested that STZ is preferably absorbed by insulin-secreting β-cells and induces cytotoxicity by producing reactive oxygen species/reactive nitrogen species (ROS/RNS). In the present study, we have investigated the mechanism of cytotoxicity of STZ in insulin-secreting pancreatic cancer cells (Rin-5F) at different doses and time intervals. Cell viability, apoptosis, oxidative stress, and mitochondrial bioenergetics were studied. Our results showed that STZ induces alterations in glutathione homeostasis and inhibited the activities of the respiratory enzymes, resulting in inhibition of ATP synthesis. Apoptosis was observed in a dose- and time-dependent manner. Western blot analysis has also confirmed altered expression of oxidative stress markers (e.g., NOS and Nrf2), cell signaling kinases, apoptotic protein-like caspase-3, PARP, and mitochondrial specific proteins. These results suggest that STZ-induced cytotoxicity in pancreatic cells is mediated by an increase in oxidative stress, alterations in cellular metabolism, and mitochondrial dysfunction. This study may be significant in better understanding the mechanism of STZ-induced β-cell toxicity/resistance and the etiology of type 1 diabetes induction.

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.

The Combined Extract of Zingiber officinale and Zea mays (Purple Color) Improves Neuropathy, Oxidative Stress, and Axon Density in Streptozotocin Induced Diabetic Rats

Based on the protective effect of the combined extract of purple waxy corn and ginger (PWCG) on oxidative stress related disorders in diabetic condition, we aimed to determine the effect of PWCG on the functional, biochemical, and structural change of the lesion nerve in streptozotocin- (STZ-) diabetic rats. PWCG at doses of 100, 200, and 300 mg·kg⁻¹ BW were orally given to STZ-diabetic rats which were subjected to chronic constriction (CCI) at right sciatic nerve for 21 days. The blood sugar was assessed before and at the end of study whereas the sciatic function index (SFI), paw withdrawal threshold intensity (PWTI), and paw withdrawal latency (PWL) were assessed every 3 days until the end of study. At the end of study, the determination of nerve conduction velocity (NCV), axon density, oxidative stress status, and aldose reductase (AR) activity of the lesion nerve were performed. It was found that PWCG improved SFI, PWTI, PWL, and NCV together with the improved oxidative stress status and the axon density in the lesion nerve. No changes of AR activity or blood sugar level were observed. Therefore, PWCG might improve the functional and structural changes in STZ-diabetic rats plus CCI via the improved oxidative stress status.

1H NMR-based metabonomic analysis of serum and urine in a nonhuman primate model of diabetic nephropathy

Diabetic nephropathy (DN) is a serious metabolic disease, and comprehensive understanding of its complex mechanism will help in preventing the onset and progression of DN. To reveal the systemic metabolic changes associated with renal injury, we performed 1H NMR-based metabonomic and multivariate analyses to analyze serum and urine obtained from a nonhuman primate model of DN. Our results indicated that DN monkeys exhibited a distinct metabolic profile, including higher levels of VLDL/LDL, lipids, unsaturated lipids, uric acid, allantoin, fumarate and hippurate, as well as lower levels of HDL, alanine, glutamate, pyruvate, formate, tyrosine, histidine and NAD+. The disturbed metabolic pathways were further identified, including NAD+ metabolism, purine metabolism, oxidative stress, lipid metabolism, and renal tubular reabsorption. This study highlights that NMR-based metabonomics provides insight into the underlying pathways in the pathogenesis and progression of DN at the metabolic level.

Molecular cloning and characterization of rhesus monkey platelet glycoprotein Ibα, a major ligand-binding subunit of GPIb-IX-V complex

INTRODUCTION

Through binding to von Willebrand factor (VWF), platelet glycoprotein (GP) Ibα, the major ligand-binding subunit of the GPIb-IX-V complex, initiates platelet adhesion and aggregation in response to exposed VWF or elevated fluid-shear stress. There is little data regarding non-human primate platelet GPIbα. This study cloned and characterized rhesus monkey (Macaca Mullatta) platelet GPIbα.

MATERIALS AND METHODS

DNAMAN software was used for sequence analysis and alignment. N/O-glycosylation sites and 3-D structure modelling were predicted by online OGPET v1.0, NetOGlyc 1.0 Server and SWISS-MODEL, respectively. Platelet function was evaluated by ADP- or ristocetin-induced platelet aggregation.

RESULTS

Rhesus monkey GPIbα contains 2,268 nucleotides with an open reading frame encoding 755 amino acids. Rhesus monkey GPIbα nucleotide and protein sequences share 93.27% and 89.20% homology respectively, with human. Sequences encoding the leucine-rich repeats of rhesus monkey GPIbα share strong similarity with human, whereas PEST sequences and N/O-glycosylated residues vary. The GPIbα-binding residues for thrombin, filamin A and 14-3-3ζ are highly conserved between rhesus monkey and human. Platelet function analysis revealed monkey and human platelets respond similarly to ADP, but rhesus monkey platelets failed to respond to low doses of ristocetin where human platelets achieved 76% aggregation. However, monkey platelets aggregated in response to higher ristocetin doses.

CONCLUSIONS

Monkey GPIbα shares strong homology with human GPIbα, however there are some differences in rhesus monkey platelet activation through GPIbα engagement, which need to be considered when using rhesus monkey platelet to investigate platelet GPIbα function.

Increasing glucagon secretion could antagonize the action of exogenous insulin for glycemic control in streptozocin-induced diabetic rhesus monkeys

Although intraislet insulin signaling is known to play a critical role in regulating glucagon secretion, it is unknown whether abnormal glucagon secretion influences the hypoglycemic effect of exogenous insulin with intraislet insulin deletion. We performed a longitudinal study using 16 streptozocin (STZ)-induced diabetic rhesus monkeys to explore α-cell function under the absence β-cells and to assess whether increasing glucagon secretion antagonizes the action of exogenous insulin for glycemic control. We found that although the α-cells were impaired and the basal secretion levels of glucagon decreased rapidly after STZ (80–90 mg/kg) administration, as based on long-term observation post-STZ injection, glucagon secretion and the number of α-cells were increased. Glycemic control was increasingly difficult, the insulin resistance (HOMA-IR) index was significantly higher, and the triglycerides (TG) levels were gradually decreased. Moreover, a significant correlation between the levels of glucagon and HOMA-IR was found. Under the long-term absence of β-cells, the inhibitory effect on α-cell activity is profoundly attenuated, leading to an increase in glucagon secretion and the amount of α-cells and even α-cell dysfunction. Increased glucagon levels have a serious impact on the insulin sensitivity in vivo and result in an antagonization of the hypoglycemic effect of exogenous insulin.

The use of animal models in diabetes research

Diabetes is a disease characterized by a relative or absolute lack of insulin, leading to hyperglycaemia. There are two main types of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes is due to an autoimmune destruction of the insulin-producing pancreatic beta cells, and type 2 diabetes is caused by insulin resistance coupled by a failure of the beta cell to compensate. Animal models for type 1 diabetes range from animals with spontaneously developing autoimmune diabetes to chemical ablation of the pancreatic beta cells. Type 2 diabetes is modelled in both obese and non-obese animal models with varying degrees of insulin resistance and beta cell failure. This review outlines some of the models currently used in diabetes research. In addition, the use of transgenic and knock-out mouse models is discussed. Ideally, more than one animal model should be used to represent the diversity seen in human diabetic patients.

Streptozotocin-induced cytotoxicity, oxidative stress and mitochondrial dysfunction in human hepatoma HepG2 cells

Streptozotocin (STZ) is an antibiotic often used in the treatment of different types of cancers. It is also highly cytotoxic to the pancreatic beta-cells and therefore is commonly used to induce experimental type 1 diabetes in rodents. Resistance towards STZ-induced cytotoxicity in cancer cells has also been reported. Our previous studies have reported organ-specific toxicity and metabolic alterations in STZ-induced diabetic rats. STZ induces oxidative stress and metabolic complications. The precise molecular mechanism of STZ-induced toxicity in different tissues and carcinomas is, however, unclear. We have, therefore, investigated the mechanism of cytotoxicity of STZ in HepG2 hepatoma cells in culture. Cells were treated with different doses of STZ for various time intervals and the cytotoxicity was studied by observing the alterations in oxidative stress, mitochondrial redox and metabolic functions. STZ induced ROS and RNS formation and oxidative stress as measured by an increase in the lipid peroxidation as well as alterations in the GSH-dependent antioxidant metabolism. The mitochondria appear to be a highly sensitive target for STZ toxicity. The mitochondrial membrane potential and enzyme activities were altered in STZ treated cells resulting in the inhibition of ATP synthesis. ROS-sensitive mitochondrial aconitase activity was markedly inhibited suggesting increased oxidative stress in STZ-induced mitochondrial toxicity. These results suggest that STZ-induced cytotoxicity in HepG2 cells is mediated, at least in part, by the increase in ROS/RNS production, oxidative stress and mitochondrial dysfunction. Our study may be significant for better understanding the mechanisms of STZ action in chemotherapy and drug induced toxicity.