A New Method for Targeted and Sustained Induction of Type 2 Diabetes in Rodents

Xiaoke Bitong capsule alleviates inflammatory impairment via inhibition of the TNF signaling pathway to against diabetic peripheral neuropathy

BACKGROUND

Xiaoke Bitong capsule (XBC) is a crude herbal compound believed to tonify qi, improve blood circulation, and alleviate blood stasis. It has been used as an herbal formula for the prevention and treatment of diabetic peripheral neuropathy (DPN) under the guidance of traditional Chinese medicine (TCM). However, the pharmacological mechanisms by which XBC ameliorates DPN remain poorly understood. The interaction between pro-inflammatory factors and the activation of tumor necrosis factor (TNF) plays a critical role in the underlying mechanisms of DPN. XBC may protect against DPN through the regulation of the TNF pathway.

PURPOSE

Many studies show the association between DPN and nerve dysfunction, however, treatment options are limited. To identify specific therapeutic targets and active components of XBC that contribute to its anti-DPN effects, our study aimed to investigate the potential mechanism of action of XBC during the progression of DPN using a system pharmacology approach.

METHODS

An approach involving UPLC-Q-TOF/MS and network pharmacology was used to analyze the compositions, potential targets, and active pathways of XBC. Further, models of streptozocin (STZ) induced mouse and glucose induced RSC96 cells were established to explore the therapeutic effects of XBC. High glucose induced RSC96 cells were pretreated with small interfering RNA (siRNA) to identify potential therapeutic targets of DPN.

RESULTS

Seventy-one active compositions of XBC and five potential targets, including mitogen-activated protein kinase 8 (MAPK), interleukin-6 (IL-6), poly-ADP-ribose polymerase-1 (PARP1), vascular endothelial growth factor A (VEGFA), and transcription factor p65 (NF-κB), were considered as the potential regulators of DPN. In addition, the results revealed that the TNF signaling pathway was closely related to DPN. Moreover, DPN contributed to the decreased expressions of PI3K and AKT, increased TNF-α and IL-1β in RSC96 cells, which were both reversed by XBC or TNF-α siRNA.

CONCLUSION

XBC could protect against DPN by inhibiting the release of pro-inflammatory cytokines and regulating the activation of the TNF signaling pathway, further accelerating neurogenesis, and alleviating peripheral nerve lesions. Therefore, this study highlights the therapeutic value of XBC for DPN.

Comparative Screening of the Liver Gene Expression Profiles from Type 1 and Type 2 Diabetes Rat Models

Experimental animal models of diabetes can be useful for identifying novel targets related to disease, for understanding its physiopathology, and for evaluating emerging antidiabetic treatments. This study aimed to characterize two rat diabetes models: HFD + STZ, a high-fat diet (60% fat) combined with streptozotocin administration (STZ, 35 mg/kg BW), and a model with a single STZ dose (65 mg/kg BW) in comparison with healthy rats. HFD + STZ- induced animals demonstrated a stable hyperglycemia range (350-450 mg/dL), whereas in the STZ-induced rats, we found glucose concentration values with a greater dispersion, ranging from 270 to 510 mg/dL. Moreover, in the HFD + STZ group, the AUC value of the insulin tolerance test (ITT) was found to be remarkably augmented by 6.2-fold higher than in healthy animals (33,687.0 ± 1705.7 mg/dL/min vs. 5469.0 ± 267.6, respectively), indicating insulin resistance (IR). In contrast, a more moderate AUC value was observed in the STZ group (19,059.0 ± 3037.4 mg/dL/min) resulting in a value 2.5-fold higher than the average exhibited by the control group. After microarray experiments on liver tissue from all animals, we analyzed genes exhibiting a fold change value in gene expression <-2 or >2 (p-value <0.05). We found 27,686 differentially expressed genes (DEG), identified the top 10 DEGs and detected 849 coding genes that exhibited opposite expression patterns between both diabetes models (491 upregulated genes in the STZ model and 358 upregulated genes in HFD + STZ animals). Finally, we performed an enrichment analysis of the 849 selected genes. Whereas in the STZ model we found cellular pathways related to lipid biosynthesis and metabolism, in the HFD + STZ model we identified pathways related to immunometabolism. Some phenotypic differences observed in the models could be explained by transcriptomic results; however, further studies are needed to corroborate these findings. Our data confirm that the STZ and the HFD + STZ models are reliable experimental models for human T1D and T2D, respectively. These results also provide insight into alterations in the expression of specific liver genes and could be utilized in future studies focusing on diabetes complications associated with impaired liver function.

Analysis of immunohistomorphological changes in the colonic mucosa in a high-saturated fat and high-cholesterol fed streptozotocin/nicotinamide diabetic rat model

The mucosal surface of gastrointestinal tract is lined with epithelial cells that establish an effective barrier between the lumen and internal environment through intercellular junctions, preventing the passage of potentially harmful substances. The "intestinal barrier function" consist of a defensive system that prevent the passage of antigens, toxins, and microbial products, while maintains the correct development of the epithelial barrier, the immune system and the acquisition of tolerance toward dietary antigens and intestinal microbiota. Intestinal morphology changes subsequent to nutritional variations, stress, aging or diseases, which can also affect the composition of the microbiota, altering the homeostasis of the intestine. A growing body of evidence suggests that alterations in intestinal barrier function favor the development of exaggerated immune responses, leading to metabolic endotoxemia, which seems to be the origin of many chronic metabolic diseases such as type 2 diabetes mellitus (T2DM). Although the mechanisms are still unknown, the interaction between dietary patterns, gut microbiota, intestinal mucosa, and metabolic inflammation seems to be a key factor for the development of T2DM, among other diseases. This chapter details the different techniques that allow evaluating the morphological and molecular alterations that lead of the intestinal barrier dysfunction in a T2DM experimental model. To induce both diabetic metabolic disturbances and gut barrier disruption, Wistar rats were fed a high-saturated fat and high-cholesterol diet and received a single dose of streptozotocin/nicotinamide. This animal model may contribute to clarify the understanding of the role of intestinal barrier dysfunction on the late-stage T2DM etiology.

Restoring glucose balance: Conditional HMGB1 knockdown mitigates hyperglycemia in a Streptozotocin induced mouse model

Diabetes mellitus (DM) poses a significant global health burden, with hyperglycemia being a primary contributor to complications and high morbidity associated with this disorder. Existing glucose management strategies have shown suboptimal effectiveness, necessitating alternative approaches. In this study, we explored the role of high mobility group box 1 (HMGB1) in hyperglycemia, a protein implicated in initiating inflammation and strongly correlated with DM onset and progression. We hypothesized that HMGB1 knockdown will mitigate hyperglycemia severity and enhance glucose tolerance. To test this hypothesis, we utilized a novel inducible HMGB1 knockout (iHMGB1 KO) mouse model exhibiting systemic HMGB1 knockdown. Hyperglycemic phenotype was induced using low dose streptozotocin (STZ) injections, followed by longitudinal glucose measurements and oral glucose tolerance tests to evaluate the effect of HMGB1 knockdown on glucose metabolism. Our findings showed a substantial reduction in glucose levels and enhanced glucose tolerance in HMGB1 knockdown mice. Additionally, we performed RNA sequencing analyses, which identified potential alternations in genes and molecular pathways within the liver and skeletal muscle tissue that may account for the in vivo phenotypic changes observed in hyperglycemic mice following HMGB1 knockdown. In conclusion, our present study delivers the first direct evidence of a causal relationship between systemic HMGB1 knockdown and hyperglycemia in vivo, an association that had remained unexamined prior to this research. This discovery positions HMGB1 knockdown as a potentially efficacious therapeutic target for addressing hyperglycemia and, by extension, the DM epidemic. Furthermore, we have revealed potential underlying mechanisms, establishing the essential groundwork for subsequent in-depth mechanistic investigations focused on further elucidating and harnessing the promising therapeutic potential of HMGB1 in DM management.

Network based approach to identify interactions between Type 2 diabetes and cancer comorbidities

High blood sugar and insulin insensitivity causes the lifelong chronic metabolic disease called Type 2 diabetes (T2D) which has a higher chance of developing different malignancies. T2D with comorbidities like Cancers can make normal medications for those disorders more difficult. There may be a significant correlation between comorbidities and have an impact on one another's health. These associations may be due to a number of direct and indirect mechanisms. Such molecular mechanisms that underpin T2D and cancer are yet unknown. However, the large volumes of data available on these diseases allowed us to use analytical tools for uncovering their interrelated pathways. Here, we tried to present a system for investigating potential comorbidity relationships between T2D and Cancer disease by looking at the molecular processes involved, analyzing a huge number of freely accessible transcriptomic datasets of various disorders using bioinformatics. Using semantic similarity and gene set enrichment analysis, we created an informatics pipeline that evaluates and integrates Gene Ontology (GO), expression of genes, and biological process data. We discovered genes that are common in T2D and Cancer along with molecular pathways and GOs. We compared the top 200 Differentially Expressed Genes (DEGs) from each selected T2D and cancer dataset and found the most significant common genes. Among all the common genes 13 genes were found most frequent. We also found 4 common GO terms: GO:0000003, GO:0000122, GO:0000165, and GO:0000278 among all the common GO terms between T2d and different cancers. Using these genes and GO term semantic similarity, we calculated the distance between these two diseases. The semantic similarity results of our study showed a higher association of Liver Cancer (LiC), Breast Cancer (BreC), Colorectal Cancer (CC), and Bladder Cancer (BlaC) with T2D. Furthermore we found KIF4A, NUSAP1, CENPF, CCNB1, TOP2A, CCNB2, RRM2, HMMR, NDC80, NCAPG, and IGFBP5 common hub proteins among different cancers correlated to T2D. AGE-RAGE signaling pathway in diabetic complications, Osteoclast differentiation, TNF signaling pathway, IL-17 signaling pathway, p53 signaling pathway, MAPK signaling pathway, Human T-cell leukemia virus 1 infection, and Non-alcoholic fatty liver disease are the 8 most significant pathways found among 18 common pathways between T2D and selected cancers. As a result of our technique, we now know more about disease pathways that are critical between T2D and cancer.

Induction of experimental diabetes and diabetic nephropathy using anomer-equilibrated streptozotocin in male C57Bl/6J mice

Streptozotocin (STZ) is widely used to induce experimental diabetes in murine models. However, the ability to induce diabetic nephropathy (DN) is more challenging. It has been recommended to inject STZ at multiple low doses within 15 min after dissolution due to its alleged instability. However, some studies suggest that STZ is stable for days due to equilibration of its two anomers (α and β), 90 min after dissolution, and that this anomer-equilibrated STZ leads to higher survival rates and persistent hyperglycaemia with minimal weight loss. The aim of this study was to determine an optimal dose of anomer-equilibrated STZ to induce kidney tubular damage and compare it with the more commonly used freshly prepared STZ. We hypothesised that anomer-equilibrated STZ provides a better, reproducible experimental model of diabetes-induced kidney damage with improved animal welfare. Body measurements, fasting glycaemia, insulinemia and renal histology were assessed in male C57Bl/6J at two and six months of age treated with fresh (50 mg/kg) or anomer-equilibrated (dose ranging 35-50 mg/kg) STZ or vehicle control. We demonstrated a dose-dependent effect of anomer-equilibrated STZ on the induction of hypo-insulinaemia and hyperglycaemia, as well as body weight in two-month-old mice. Interestingly, in six-month-old mice STZ leads to body weight loss, independently of STZ preparation mode. Anomer-equilibrated STZ provoked moderate to severe kidney tubule structural damage, resulting in significant kidney hypertrophy, whereas freshly prepared STZ only caused mild alterations. In conclusion, our study proposes that anomer-equilibrated STZ provides a robust murine model of diabetes and early-stage diabetic nephropathy, which can be used to test therapeutic approaches to treat and/or prevent renal damage.

A high-sucrose diet exacerbates the left ventricular phenotype in a high fat-fed streptozotocin rat model of diabetic cardiomyopathy

Left ventricular (LV) dysfunction is an early, clinically detectable sign of cardiomyopathy in type 2 diabetes mellitus (T2DM) that precedes the development of symptomatic heart failure. Preclinical models of diabetic cardiomyopathy are essential to develop therapies that may prevent or delay the progression of heart failure. This study examined the molecular, structural, and functional cardiac phenotype of two rat models of T2DM induced by a high-fat diet (HFD) with a moderate- or high-sucrose content (containing 88.9 or 346 g/kg sucrose, respectively), plus administration of low-dose streptozotocin (STZ). At 8 wk of age, male Sprague-Dawley rats commenced a moderate- or high-sucrose HFD. Two weeks later, rats received low-dose STZ (35 mg/kg ip for 2 days) and remained on their respective diets. LV function was assessed by echocardiography 1 wk before end point. At 22 wk of age, blood and tissues were collected postmortem. Relative to chow-fed sham rats, diabetic rats on a moderate- or high-sucrose HFD displayed cardiac reactive oxygen species dysregulation, perivascular fibrosis, and impaired LV diastolic function. The diabetes-induced impact on LV adverse remodeling and diastolic dysfunction was more apparent when a high-sucrose HFD was superimposed on STZ. In conclusion, a high-sucrose HFD in combination with low-dose STZ produced a cardiac phenotype that more closely resembled T2DM-induced cardiomyopathy than STZ diabetic rats subjected to a moderate-sucrose HFD.NEW & NOTEWORTHY Left ventricular dysfunction and adverse remodeling were more pronounced in diabetic rats that received low-dose streptozotocin (STZ) and a high-sucrose high-fat diet (HFD) compared with those on a moderate-sucrose HFD in combination with STZ. Our findings highlight the importance of sucrose content in diet composition, particularly in preclinical studies of diabetic cardiomyopathy, and demonstrate that low-dose STZ combined with a high-sucrose HFD is an appropriate rodent model of cardiomyopathy in type 2 diabetes.

Induction of Type 2 Diabetes in Mice to Understand Vascular Changes That Drive Diabetic Retinopathy

Diabetic retinopathy is a common complication of type 2 diabetes. Research into this comorbidity is challenging due to the slow progression of pathological changes and the limited transgenic models available to study disease progression and mechanistic changes. Here, we describe a non-transgenic mouse model of accelerated type 2 diabetes using a high-fat diet in combination with streptozotocin delivered via osmotic mini pump. This model, when subjected to fluorescent gelatin vascular casting, can be used to study vascular changes in type 2 diabetic retinopathy.

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.

Combined analysis of whole-exome sequencing and RNA sequencing in type 2 diabetes mellitus patients with thirst and fatigue

BACKGROUND

The principal objective of this study was to gain a better understanding of the mechanisms of type 2 diabetes mellitus (T2DM) patients with fatigue (D-T2DM) through exome and transcriptome sequencing.

METHODS

After whole-exome sequencing on peripheral blood of 6 D-T2DM patients, the consensus mutations were screen out and analyzed by a series of bioinformatics analyses. Then, we combined whole-exome sequencing and transcriptome sequencing results to find the important genes that changed at both the DNA and RNA levels.

RESULTS

The results showed that a total of 265,393 mutation sites were found in D-T2DM patients compared with normal individuals, 235 of which were consensus mutations shared with D-T2DM patients. These genes significantly enriched in HIF-1 signaling pathway and sphingolipid signaling pathway. At the RNA level, a total of 375 genes were identified to be differentially expressed. After the DNA-RNA joint analysis, eight genes were screened that changed at both DNA and RNA levels. Among these genes, FUS and LMNA were related to carbohydrate metabolism, energy metabolism, and mitochondrial function. Subsequently, we predicted the herbs, including Qin Pi and Hei Zhi Ma, that might play a therapeutic role in D-T2DM through the SymMap database.

CONCLUSION

These findings have significant implications for understanding the mechanisms of D-T2DM and provide potential targets for D-T2DM diagnosis and treatment.

DPP-4 inhibition mediated antidiabetic potential of phytoconstituents of an aqueous fruit extract of Withania coagulans (Stocks) Dunal: in-silico, in-vitro and in-vivo assessments

The DPP-4 inhibition is an interesting target for the development of antidiabetic agents which promotes the longevity of GPL-1(Glucagon-like peptide 1). The current study was intended to assess DPP-4(Dipeptidyl Peptidase-4) inhibition mediated antidiabetic effect of phytocompounds of an aqueous fruit extract of Withania coagulans (Stocks) Dunal by in-vitro, in-silico and in-vivo approaches. The phytoconstituents screening was executed by LCMS (Liquid Chromatography with tandem mass spectrometry). The in-vitro and in-vivo, DPP-4 assays were performed by using available kits. The in-vitro DPP-4 activity was inhibited up to 68.3% by the test extract. Accordingly, in-silico determinations of molecular docking, molecular dynamics and pharmacokinetics were performed between the target enzyme DPP-4 and leading phytocompounds. The molecular dynamics authenticated the molecular docking data by crucial parameters of cytosolic milieu by the potential energy, RSMD (Root Mean Square Deviation), RSMF (Root Mean Square Fluctuation), system density, NVT (Number of particles at fixed volume, ensemble) and NPT (Number of particles at fixed pressure, ensemble). Accordingly, ADMET predictions assessed the druggability profile. Subsequently, the course of the test extract and the sitagliptin (positive control), instigated significant (p ≤ 0.001) ameliorations in HOMA indices and the equal of antioxidants in nicotinamide-streptozotocin induced type 2 diabetic animal model. Compassionately, the histopathology represented increased pancreatic cellular mass which caused in restoration of histoarchitectures. It has been concluded that phytoconstituents in W. coagulans aqueous fruit extract can regulate DPP-4, resulting in improved glucose homeostasis and enhanced endocrinal pancreatic cellular mass.Communicated by Ramaswamy H. Sarma.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

Type 2 Diabetes Mellitus: Pathogenic Features and Experimental Models in Rodents

Type 2 diabetes mellitus (T2DM) is the most common endocrine disorder (90%) in the world; it has numerous clinical, immunological, and genetic differences from type 1 diabetes mellitus. The pathogenesis of T2DM is complex and not fully clear. To date, animal models remain the main tool by which to study the pathophysiology and therapy of T2DM. Rodents are considered the best choice among animal models, because they are characterized by a small size, short induction period, easy diabetes induction, and economic efficiency. This review summarizes data on experimental models of T2DM that are currently used, evaluates their advantages and disadvantages vis-a-vis research, and describes in detail the factors that should be taken into account when using these models. Selection of a suitable model for tackling a particular issue is not always trivial; it affects study results and their interpretation.

Development and characterisation of a rat model that exhibits both metabolic dysfunction and neurodegeneration seen in type 2 diabetes

Abstract

Accurate modelling type 2 diabetes and diabetic complications in rodents has proven a challenge, largely as a result of the long‐time course of disease development in humans. In the present study, we aimed to develop and comprehensively characterise a new rodent model of type 2 diabetes. To do this, we fed Sprague–Dawley rats a high fat/high sugar diet (HFD) to induce obesity and dyslipidaemia. After 3 weeks, we s.c. implanted osmotic mini pumps to enable a 14 day, slow infusion of streptozotocin (STZ; lower dose = 100 mg kg⁻¹; higher dose = 120 mg kg⁻¹) to dose‐dependently reduce pancreatic beta cell mass. After removing the mini pumps, we monitored animals for 4 months using a battery of tests to assess both metabolic and neurodegenerative changes across time. Our data demonstrate the combination of the HFD and lower dose STZ leads to induction of early‐stage type 2 diabetes defined by moderate hyperglycaemia, hyperinsulinaemia and impaired glucose tolerance, at the same time as the retention of an obese phenotype. By contrast, combining the HFD and higher dose STZ leads to induction of later‐stage type 2 diabetes defined by frank hyperglycaemia, hypoinsulinaemia (but not insulin depletion) and severely impaired glucose tolerance, at the same time as retaining an obese phenotype. Regardless of dose of STZ (and level of hyperglycaemia), all diabetic rats exhibited signs of peripheral neurodegeneration in the skin and muscle. Thus, this model recapitulates many of the complex metabolic disturbances seen in type 2 diabetes and provides an excellent platform for investigating the pathophysiological mechanisms that lead to diabetic complications such as peripheral neuropathy.

Key points

Type 2 diabetes is a major health concern and markedly increases risk cardiovascular and neurodegenerative diseases.

Accurate modelling of type 2 diabetes is a major challenge and has impeded our ability to understand the mechanisms that contribute to complications of type 2 diabetes.

We have developed a method of inducing different stages of type 2 diabetes using a high fat/high sugar diet and 14 day infusion of streptozotocin to dose‐dependently destroy pancreatic beta cell mass.

Over 4 months, we comprehensively characterised these animals and confirmed that they develop sustained metabolic dysfunction and progressive peripheral neurodegeneration as seen in type 2 diabetes.

This new model will improve our ability to investigate the pathophysiological mechanisms that link type 2 diabetes with complications such as neurodegeneration.

Clinically relevant experimental rodent models of diabetic foot ulcer

Chronic wounds are a substantial clinical problem in diabetes and nearly 6% of diabetics suffer from foot disease including ulceration, infection, and tissue necrosis. Wound healing in diabetes is impaired and delayed and is augmented by diabetic complications. Wound healing involves complex cellular, molecular, and biochemical processes and animal models are the most suitable prototype to investigate and understand the underlying pathological changes in the process of wound healing. Animal models are also useful in evaluating the safety and efficacy of newer therapeutic agents and improving the clinical approaches for human patients with chronic ulcers. The wound healing strategies get more complicated in the presence of diabetes and its associated complication. Despite the advancement in methods of wound healing, the healing of the chronic diabetic foot ulcer (DFU) remains an important clinical problem resulting in costly and prolonged treatment and poses a risk for major amputation. Saying that it is important to elucidate the newer therapeutic targets and strategies via an in-depth understanding of the complicated cascade of the chronic DFU. A major challenge in translating lab findings to clinics is the lack of an optimal preclinical model capable of properly recapitulating human wounds. Both small and large animal models of wound healing involving rodents, rabbits, and pigs have been discussed. Mouse and rats as small animal models and pig as large animal models have been discussed in association with the diabetic wound but there are advantages and limitations for each model. In this review, we critically reviewed the pros and cons of experimental models of diabetic wound healing with a focus on type II diabetes rodent models.

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.

Hippocampus kuda protein hydrolysate improves male reproductive dysfunction in diabetic rats

The global prevalence of diabetes mellitus is rapidly increasing. This disease is associated with many complications including male reproductive dysfunctions and infertility. Seahorse ( Hippocampus kuda) is a marine teleost fish well known for its beneficial effects on the reproductive system in traditional Chinese medicine books. Recently, several studies have been shown that the enzymatic hydrolysate of seahorse has multiple pharmacological activities. This study aimed to investigate the seahorse peptide hydrolysate (SH) ameliorative effects on the diabetic-induced male reproductive dysfunction in rat models. The in vivo studies were carried out with three different doses of SH (4, 8, and 20 mg/kg) and the diabetes condition was induced by administrating with streptozotocin (35 mg/kg) and fed a 40% high-fat diet. Seahorse hydrolysate (20 mg/kg) inhibited lipid peroxidation, increased antioxidant enzyme activity, and restored seminiferous tubules morphology in testis. Moreover, it improved reproductive dysfunction by increasing the level of testosterone, follicle-stimulating hormone, luteinizing hormone, sperm count, and motility. According to these results, we suggested that SH exhibited amelioration effects on the reproductive dysfunction.

Carob fruit extract-enriched meat, as preventive and curative treatments, improves gut microbiota and colonic barrier integrity in a late-stage T2DM model

Epidemiological and experimental studies have suggested that dietary fiber and proanthocyanidins play an important role on gut microbiota (GM), colonic integrity and body health. Type 2 Diabetes Mellitus (T2DM) is a prevalent disease in which the modifications in the GM and colonic markers stand out. This manuscript hypothesizes the consumption of functional meat enriched in carob fruit extract [CFE; CFE-restructured meat (RM)] ameliorates the dysbiosis and colonic barrier integrity loss in a late-stage T2DM rat model induced by the conjoint action of a high-saturated-fat/high-cholesterol diet (Chol-diet) and a low dose of streptozotocin (STZ) plus a nicotinamide (NAD) injection. Three groups of eight rats were used: (1) D group, a T2DM control group, fed the Chol-diet; (2) ED group, a T2DM preventive strategy group fed the CFE-Chol-diet since the beginning of the study; and (3) DE group, a T2DM curative treatment group, fed the CFE-Chol-diet once the diabetic state was confirmed. The study lasted 8 weeks. Amount and variety of GM, feces short-chain-fatty acids (SCFAs), colonic morphology [crypt depth and density, goblet cells, proliferating cell nuclear antigen (PCNA) and transferase dUTP nick end labelling (TUNEL) indexes] and tight junctions were evaluated. A global colonic index combining 17 markers (GC_index) was calculated. ED rats displayed higher levels of GM richness, SCFAs production, crypt depth, and goblet cells than the D group. DE group showed lower Enterobacteriaceae abundance and greater TUNEL index and occludin expression in the distal colon than D counterpart. GC_index differentiated the colonic health status of the experimental groups in the order (ED > DE > D; P < 0.001) as a 17-51 range-quotation, ED, DE, and D groups displayed the values 43, 32.5, and 27, respectively. Thus, CFE-RM used as a T2DM preventive therapy could induce higher GM richness, more adequate SCFAs production, and better colonic barrier integrity. Furthermore, CFE-RM used with curative purposes induced more modest changes and mainly at the distal colonic mucosa. Further studies are needed to confirm this study's results, to ascertain the benefits of consuming proanthocyanidins-rich fiber during different T2DM stages.

Novel Short-Chain Quinones to Treat Vision Loss in a Rat Model of Diabetic Retinopathy

Diabetic retinopathy (DR), one of the leading causes of blindness, is mainly diagnosed based on the vascular pathology of the disease. Current treatment options largely focus on this aspect with mostly insufficient therapeutic long-term efficacy. Mounting evidence implicates mitochondrial dysfunction and oxidative stress in the central etiology of DR. Consequently, drug candidates that aim at normalizing mitochondrial function could be an attractive therapeutic approach. This study compared the mitoprotective compounds, idebenone and elamipretide, side-by-side against two novel short-chain quinones (SCQs) in a rat model of DR. The model effectively mimicked type 2 diabetes over 21 weeks. During this period, visual acuity was monitored by measuring optokinetic response (OKR). Vision loss occurred 5–8 weeks after the onset of hyperglycemia. After 10 weeks of hyperglycemia, visual function was reduced by 65%. From this point, the right eyes of the animals were topically treated once daily with the test compounds. The left, untreated eye served as an internal control. Only three weeks of topical treatment significantly restored vision from 35% to 58–80%, while visual acuity of the non-treated eyes continued to deteriorate. Interestingly, the two novel SCQs restored visual acuity better than idebenone or elamipretide. This was also reflected by protection of retinal pathology against oxidative damage, retinal ganglion cell loss, reactive gliosis, vascular leakage, and retinal thinning. Overall, mitoprotective and, in particular, SCQ-based compounds have the potential to be developed into effective and fast-acting drug candidates against DR.

Effects of Nigella sativa seed polysaccharides on type 2 diabetic mice and gut microbiota

Effect of Nigella sativa seed polysaccharides (NSSP) on type 2 diabetic mice and its gut microbiota was investigated on the type 2 diabetic mice model feed by high-fat diet. Fasting blood glucose (FBG), biochemical parameters, expression levels of cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and phosphor-AKT (p-AKT) protein, membrane glucose transporter 4 (GLUT4) in skeletal muscles, as well as the change of gut microbiota profile in mice model were measured. Results showed that the high-dose NSSP could significantly lower the levels of FBG, glycosylated serum protein (GSP), triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), malondialdehyde (MDA), TNF-α, IL-6 and IL-1β, and significantly increased insulin (INS), high-density lipoprotein cholesterol (HDLC), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT) and the expression levels of p-AKT and GLUT4 in mice. Besides, the high-dose NSSP has significantly increased the abundance of f_Muribaculaceae_Unclassified and Bacteroides, which were significantly suppressed in the mice gut after the treatment of streptozotocin (STZ). These results indicated that NSSP could improve the abnormal state of diabetic mice by regulating the PI3K/AKT signaling pathway with simultaneous changes of the gut microbiota profile.

M2 macrophage immunotherapy abolishes glucose intolerance by increasing IL-10 expression and AKT activation

Aim: Glucose intolerance associates with M1/M2 macrophage unbalance. We thus wanted to examine the effect of M2 macrophage administration on mouse model of glucose intolerance. Materials & methods: C57BL/6 mice fed a high-fat diet (HFD) for 12 weeks and then received thrice 20 mg/kg streptozotocin (HFD-GI). Bone marrow-derived stem cells were collected from donor mice and differentiated/activated into M2 macrophages for intraperitoneal administration into HFD-GI mice. Results: M2 macrophage treatment abolished glucose intolerance independently of obesity. M2 macrophage administration increased IL-10 in visceral adipose tissue and serum, but showed no effect on serum insulin. While nitric oxide synthase-2 and arginase-1 remained unaltered, M2 macrophage treatment restored AKT phosphorylation in visceral adipose tissue. Conclusion: M2 macrophage treatment abolishes glucose intolerance by increasing IL-10 and phosphorylated AKT.

Development and characterization of late-stage diabetes mellitus and -associated vascular complications

Preclinical investigation is the key mark of medical research, as the major breakthroughs including treatment of devastating diseases in biomedical research have been led by animal studies. Type 2 diabetes mellitus (T2DM) is a predominant metabolic disorder having high prevalence of morbidity worldwide which create an urgent need to understand the pathogenesis, complication and other possible influences by development of appropriate animal model. High-fat diet (HFD) fed animals (21 days) were treated with single cycle of repetitive dose (SCRD) of streptozotocin (STZ; 40, 30 and 20 mg/kg/per day in three respective group at 1st, 3rd, and 5th day) and double cycle of repetitive dose (DCRD) of streptozocin (STZ) (20, 10 and 5 mg/kg/per day in three respective group at 1st, 3rd, and 5th day in one cycle and 21st, 23rd, 25th day in second cycle of treatment) to induce late-stage diabetic complications. Induction of hyperglycemia was assessed by fasting and postprandial blood glucose, HbA1c, insulin, C-peptide, pancreatic β-cells and dyslipidaemia up to 12 weeks. Combined treatment of HFD and STZ (20 mg/kg) in the DCRD manner were significantly induced late-stage diabetic complication with sustained hyperglycaemia, no mortality, increased HbA1c and dyslipidaemia, reduced insulin, C-peptide and beta cells. Moreover, biochemical and histological assessment of micro and macrovascular tissues confirmed the significant cardio-renal injury, endothelial and hepatic damage. The study confirmed the development of chronic diabetic model in rat mimicked to clinical pathology with associated micro and macrovascular abnormalities which can further explore the molecular aspects of diseases.