Streptozotocin-Induced Diabetes in a Mouse Model (BALB/c) Is Not an Effective Model for Research on Transplantation Procedures in the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is characterized by the destruction of over 90% of the β-cells. C-peptide is a parameter for evaluating T1D. Streptozotocin (STZ) is a standard method of inducing diabetes in animals. Eight protocols describe the administration of STZ in mice; C-peptide levels are not taken into account. The aim of the study is to determine whether the STZ protocol for the induction of beta-cell mass destruction allows for the development of a stable in vivo mouse model for research into new transplant procedures in the treatment of type 1 diabetes. Materials and methods: Forty BALB/c mice were used. The animals were divided into nine groups according to the STZ dose and a control group. The STZ doses were between 140 and 400 mg/kg of body weight. C-peptide was taken before and 2, 7, 9, 12, 14, and 21 days after STZ. Immunohistochemistry was performed. The area of the islet and insulin-/glucagon-expressing tissues was calculated. Results: Mice who received 140, 160, 2 × 100, 200, and 250 mg of STZ did not show changes in mean fasting C-peptide in comparison to the control group and to day 0. All animals with doses of 300 and 400 mg of STZ died during the experiment. The area of the islets did not show any differences between the control and STZ-treated mice in groups below 300 mg. The reduction of insulin-positive areas in STZ mice did not exceed 50%. Conclusions: Streptozotocin is not an appropriate method of inducing a diabetes model for further research on transplantation treatments of type 1 diabetes, having caused the destruction of more than 90% of the β-cell mass in BALB/c mice.

On the mechanisms of damaging effect of diabetogenic chelators on the endothelium of blood capillaries in pancreatic islets

Authors showed that administration of diabetic zinc binders (DZC) to animals is accompanied not only by destruction and death of B cells, but also by the development of morphological changes in the capillaries of pancreatic islets at the site of contact with B cells (destruction of the capillary endothelium sites, change in the shape of the capillary lumen, erythrocytes adhesion, perivascular edema, hyperemia). Vascular changes are usually late complications of diabetes. To answer the question: are the described changes in islet capillaries a late complication of diabetes (1) or is it the result of the direct damaging effect of DZC (2), low doses of DZC that do not cause diabetes in animals are used, forming a toxic zinc-dithizone complex only at B-pole cells in contact with the capillary wall. It was shown that in this case, the capillary wall is damaged in the absence of diabetes, which indicates a direct damaging effect of DZC not only on B-cells but also on the endothelium of islet capillaries. This is not a direct cause of the development of these forms of diabetes, but may be accompanied by circulatory disorders in pancreatic islets and a worsening of the course of the disease.

Application of Propolis in Protecting Skeletal and Periodontal Health—A Systematic Review

Chronic inflammation and oxidative stress are two major mechanisms leading to the imbalance between bone resorption and bone formation rate, and subsequently, bone loss. Thus, functional foods and dietary compounds with antioxidant and anti-inflammatory could protect skeletal health. This review aims to examine the current evidence on the skeletal protective effects of propolis, a resin produced by bees, known to possess antioxidant and anti-inflammatory activities. A literature search was performed using Pubmed, Scopus, and Web of Science to identify studies on the effects of propolis on bone health. The search string used was (i) propolis AND (ii) (bone OR osteoporosis OR osteoblasts OR osteoclasts OR osteocytes). Eighteen studies were included in the current review. The available experimental studies demonstrated that propolis could prevent bone loss due to periodontitis, dental implantitis, and diabetes in animals. Combined with synthetic and natural grafts, it could also promote fracture healing. Propolis protects bone health by inhibiting osteoclastogenesis and promoting osteoblastogenesis, partly through its antioxidant and anti-inflammatory actions. Despite the promising preclinical results, the skeletal protective effects of propolis are yet to be proven in human studies. This research gap should be bridged before nutraceuticals based on propolis with specific health claims can be developed.

A review on experimental methods for diabetes induction and therapeutic efficacy of anti- diabetic drug loaded nanoformulation

Background: Different experimental methods have been used to induce the diabetes in animals. There are number of anti-diabetic drug loaded nano-formulations with high therapeutic value used to target diabetes with high therapeutic efficacy. Methods: From this review,various anti-hyperglycemic agents have been screened for their activity. The use of nanoformulation in diabetes treatment due to the possibility of incorporation of both hydrophilic and hydrophobic substances. Results: The clinical symptoms of diabetes arelike hyperglycemia, glucosuria, polydipsia, polyphagia, and polyuria and these symptoms were produced in experimental animal models through various diabetogens. The treatment by using nano-formulation lead to enhance the therapeutic efficacy due to increase in high carrier capacity. Conclusion: The characteristic features of the disease and pathological changes during disease in small animals (rats or mice) are similar to that of human beings. The use of synthetic as well as herbal drugs have shown greater therapeutic efficacy by encapsulating into nano drug delivery system.

Endothelium-Dependent Hyperpolarization (EDH) in Diabetes: Mechanistic Insights and Therapeutic Implications

Diabetes mellitus is one of the major risk factors for cardiovascular disease and is an important health issue worldwide. Long-term diabetes causes endothelial dysfunction, which in turn leads to diabetic vascular complications. Endothelium-derived nitric oxide is a major vasodilator in large-size vessels, and the hyperpolarization of vascular smooth muscle cells mediated by the endothelium plays a central role in agonist-mediated and flow-mediated vasodilation in resistance-size vessels. Although the mechanisms underlying diabetic vascular complications are multifactorial and complex, impairment of endothelium-dependent hyperpolarization (EDH) of vascular smooth muscle cells would contribute at least partly to the initiation and progression of microvascular complications of diabetes. In this review, we present the current knowledge about the pathophysiology and underlying mechanisms of impaired EDH in diabetes in animals and humans. We also discuss potential therapeutic approaches aimed at the prevention and restoration of EDH in diabetes.

DIFFERENT EXPERIMENTAL MODELS USED TO INDUCE DIABETES MELLITUS IN RODENTS: A REVIEW

Diabetes is a metabolic disease characterized by the presence of hyperglycemia resulting from either defects in insulin secretion or action or both. Various processes are involved in the development of diabetes. These range from autoimmune destruction of the insulin-producing cells, β-cells of the pancreas, a dysfunction of the pancreatic β-cell, and impaired insulin action through insulin resistance. Experimental diabetes in animals are widely induced by administration of alloxan and streptozotocin at a proper dose. The mechanism of their action in pancreatic β-cells has been extensively investigated. Reactive oxygen species are responsible for the cytotoxic action of both these diabetogenic agents. However, the source of their generation is different in the case of alloxan (ALX) and streptozotocin (STZ). In one of the study, it is also showed that the administration of a high-fat diet (HFD) to rats for 16 w showed a progressive increase in body weight, energy intake, abdominal fat deposition, and abdominal circumference along with impaired glucose tolerance, dyslipidemia and hyperinsulinemia. Administration of alloxan or streptozotocin in addition with HFD is also able to induce diabetes in an experimental rat model.

Direct Evidence for Glucose Consumption Acceleration by Carbonates in Cultured Cells

Established Py-3Y1-S2 rat fibroblast cells were used to evaluate whether NaHCO3 or Na2CO3 influences glucose metabolism in vitro, because factors that contribute to metabolic pathways are much simpler to evaluate in cultured cells than in whole animal bodies. The effects of the carbonates on glucose consumption decreased at high concentrations, >5 mg/ml for Na2CO3 and >7 mg/ml for NaHCO3, because of the increased pH of the culture medium. The effects of the carbonates on glucose consumption were additive with those of vanadium and concanavalin A. Streptozotocin, alloxan, and nicotinamide, which induce diabetes in animals, reduced glucose consumption by Py-3Y1-S2 cells, and the inhibitory effects of these reagents were abolished by both Na2CO3 and NaHCO3. Finally, the carbonates increased lactate production from glucose in the cells, followed by acceleration of lactate secretion into the culture medium. The present study clarified that NaHCO3 and Na2CO3 directly regulate glucose metabolism.

Microscopic changes in the liver, heart, and kidneys in alloxan diabetes rats

To make future researches of the results of treatment of diabetes possible, it is necessary to create a model of this pathology in experimental animals. It is crucial to trace the correlation between changes in organs when this pathology occurs in clinical cases and when it occurs in experimental cases. Today we have a number of methods used to form alloxan diabetes in animals, but alloxan monohydrate is the most frequently used. Thus, the purpose of our study was to: study microscopic changes in the liver, heart, and kidneys of alloxan diabetes rats. The experimental model of diabetes was reproduced by a 150 mg/kg single-dose subcutaneous administration of alloxan monohydrate in the form of a 5% solution per citrate buffer (pH 4.5). To prove the development of diabetes, blood glucose levels were measured by a Rightest GM500 blood glucose meter on the 20th day after administration of alloxan. There were used animals with medium severity diabetes (fasting glucose test showings 10 to 20 mmol/l). The experimental animals were euthanized by ethereal anesthesia decapitation. Samples of the liver, heart, and kidneys for histological examination were taken on the 20th day after administration of alloxan. Histologic sections were prepared according to the standard method, coloring was made by hematoxylin and eosin and based on Van Gizon method. We have found that on the 20th day after the simulation of alloxan diabetes, the liver showed microscopic signs of hepatitis with dystrophic changes in hepatocytes and intracellular cholestasis. The kidneys showed destruction of all structural components of the glomeruli with subsequent necrosis and dystrophic changes and destruction of the epithelium of the curvy and straight tubules. The heart showed granular degeneration of cardiocytes, in some areas, and distinct swelling between the muscle fibers bundles and inside the muscle fibers bundles, infiltration of the connective tissue stroma by erythrocytes in others. We believe that it is possible to obtain the most optimal spectrum of signs peculiar for type 1 diabetes by administration of alloxan as evidenced by microscopic changes in organs. Further, this model of diabetes will be used to study the influence of cell transplantation upon the development of the disease.

Guava Leaf Extract Diminishes Hyperglycemia and Oxidative Stress, Prevents β-Cell Death, Inhibits Inflammation, and Regulates NF-kB Signaling Pathway in STZ Induced Diabetic Rats

Traditional Chinese medication has been utilized by Chinese medical practitioners to treat the varied symptoms of diabetes mellitus (DM). Notably, guava leaf has been used to treat diabetes in Asia. Our present study has been designed to analyze the action of guava leaf extract (GLE) at the molecular level in treating DM. A low dose of streptozotocin (STZ) was used to induce experimental diabetes in animals. Rats were treated with GLE at different concentrations (100, 200, and 400 mg/kg b.w.). The standard drug glibenclamide (GB) (600 μg/kg b.w.) was used for comparison. The diabetic rats showed a reduced level of insulin, accompanied by exaggerated levels of blood glucose, lipid peroxidation product, and augmented expressions of inflammatory cytokines, and showed reduced levels of antioxidants compared to the control rats. Supplementation with GLE counteracted the consequences of STZ. It suppresses the oxidative stress and inhibits the state of inflammation and the results are almost similar to that of standard drug group (GB group 5). Our present research, therefore, provides useful data concerning guava leaf extract by a thorough assessment in diabetes management. Being a natural product, additional analysis on GLE can shed light on finding effective phytochemicals within the field of diabetes mellitus.

Evaluation of Urinary Tryptophan Metabolite Levels in Non-diabetic Compared to Diabetic Rats

Diabetes mellitus is one of the most common metabolic disorders in animals. Thus, currently, it is imperative to introduce non-invasive, economical and rapid methods for the investigation of diabetes in animals. In this study, the urine samples collected from 10 non-diabetic and 10 streptozotocin-induced diabetic rats were investigated by the spectrofluorimetric technique. Emission spectra for the urine samples were obtained following an excitation wavelength of 280 and 400 nm. The investigated fluorophores were mainly tryptophan metabolites, and significant differences resulted between the mean heights of the emission bands attributed to these fluorophore compounds in diabetic compared to non-diabetic rats. The shape of the spectral windings after the utilization of these two excitation wavelengths was almost similar for diabetic and non-diabetic rats; however, there were some discriminatory elements between the two types of investigated samples. In conclusion, the obtained urine fluorescence spectra allow a clear differentiation between diabetic and non-diabetic rats.