Animal models of diabetes mellitus

Jinmaitong alleviates diabetic neuropathic pain by inhibiting JAK2/STAT3 signaling in microglia of diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Jinmaitong (JMT) is a prescription of Traditional Chinese Medicine that is composed of 12 crude drugs. It has been used in the treatment of diabetic neuropathic pain (DNP) for more than 30 years.

AIM OF STUDY

Microglia are thought to play an important role in neuropathic pain. This study aimed to evaluate the protective effect of JMT against DNP and to investigate the underlying mechanisms in which the microglia and JAK2/STAT3 signaling pathway were mainly involved.

MATERIALS AND METHODS

The chemical composition of JMT was analyzed using liquid chromatography tandem mass spectrometry. The diabetes model was constructed using 11 to 12-week-old male Zucker diabetic fatty (ZDF) rat (fa/fa). The model rats were divided into 5 groups and were given JMT at three dosages (11.6, 23.2, and 46.4 g/kg, respectively, calculated as the crude drug materials), JAK inhibitor AG490 (positive drug, 10 μg/day), and placebo (deionized water), respectively, for eight weeks (n = 6). Meanwhile, Zucker lean controls (fa/+) were given a placebo (n = 6). Body weight was tested weekly and blood glucose was monitored every 2 weeks. The mechanical allodynia and heat hyperalgesia were assessed using mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. After treatment, the microglia activation marker Iba-1, CD11B, CD68, neuroinflammatory mediators, and mediators of the JAK2/STAT3 signaling pathway were compared between different groups. The mRNA and protein levels of target genes were assessed by quantitative real-time PCR and Western Blot, respectively.

RESULTS

We found that JMT significantly inhibited the overactivation of microglia in spinal cords, and suppressed neuroinflammation of DNP model rats, thereby ameliorating neurological dysfunction and injuries. Furthermore, these effects of JMT could be attributed to the inhibition of the JAK2/STAT3 signaling pathway.

CONCLUSIONS

Our findings suggested that JMT effectively ameliorated DNP by modulating microglia activation via inhibition of the JAK2/STAT3 signaling pathway. The present study provided a basis for further research on the therapeutic strategies of DNP.

Effects of paradoxical sleep deprivation on oxidative parameters in the serum and brain of mice submitted to the animal model of hyperglycemia

The present study aimed to investigate the effects of paradoxical sleep deprivation (PSD) on behavioral and oxidative stress parameters in the brain and serum of mice submitted to the animal model of hyperglycemia induced by alloxan, mimicking the main symptom of diabetes mellitus (DM). Adults C57BL/6 male and female mice received an injection of alloxan, and ten days later, the animals were submitted to the PSD for 36 h. The animals' behavioral parameters were evaluated in the open-field test. Oxidative stress parameters [Diacetyldichlorofluorescein (DCF), Thiobarbituric acid reactive substances (TBARS), Superoxide dismutase (SOD), and Glutathione] were assessed in the frontal cortex, hippocampus, striatum, and serum. The PSD increased the male and female mice locomotion, but the alloxan's pre-administration prevented the PSD-induced hyperactivity. In addition, the male mice receiving alloxan and submitted to the PSD had elevated latency time in the first quadrant and the number of fecal boli, demonstrating increased anxiety-like behavior. The HPA-axis was hyperactivating in male and female mice pre-administered alloxan and/or PSD-submitted animals. The oxidative stress parameters were also increased in the serum of the animals administered alloxan and/or sleep-deprived mice. Despite alloxan or PSD leading to behavioral or biochemical alterations, the one did not potentiate the other in mice. However, more studies are necessary to identify the link between sleep and hyperglycemia.

Progress in experimental models to investigate the in vivo and in vitro antidiabetic activity of drugs

Diabetes mellitus is one of the world's most prevalent and complex metabolic disorders, and it is a rapidly growing global public health issue. It is characterized by hyperglycemia, a condition involving a high blood glucose level brought on by deficiencies in insulin secretion, decreased activity of insulin, or both. Prolonged effects of diabetes include cardiovascular problems, retinopathy, neuropathy, nephropathy, and vascular alterations in both macro- and micro-blood vessels. In vivo and in vitro models have always been important for investigating and characterizing disease pathogenesis, identifying targets, and reviewing novel treatment options and medications. Fully understanding these models is crucial for the researchers so this review summarizes the different experimental in vivo and in vitro model options used to study diabetes and its consequences. The most popular in vivo studies involves the small animal models, such as rodent models, chemically induced diabetogens like streptozotocin and alloxan, and the possibility of deleting or overexpressing a specific gene by knockout and transgenic technologies on these animals. Other models include virally induced models, diet/nutrition induced diabetic animals, surgically induced models or pancreatectomy models, and non-obese models. Large animals or non-rodent models like porcine (pig), canine (dog), nonhuman primate, and Zebrafish models are also outlined. The in vitro models discussed are murine and human beta-cell lines and pancreatic islets, human stem cells, and organoid cultures. The other enzymatic in vitro tests to assess diabetes include assay of amylase inhibition and inhibition of α-glucosidase activity.

Induction of diabetes by Tacrolimus in a phenotypic model of obesity and metabolic syndrome

Introduction

The pathogenesis of Post-Transplant Diabetes Mellitus (PTDM) is complex and multifactorial and it resembles that of Type-2 Diabetes Mellitus (T2DM). One risk factor specific to PTDM differentiates both entities: the use of immunosuppressive therapy. Specifically, Tacrolimus interacts with obesity and insulin resistance (IR) in accelerating the onset of PTDM. In a genotypic model of IR, the obese Zucker rats, Tacrolimus is highly diabetogenic by promoting the same changes in beta-cell already modified by IR. Nevertheless, genotypic animal models have their limitations and may not resemble the real pathophysiology of diabetes. In this study, we have evaluated the interaction between beta-cell damage and Tacrolimus in a non-genotypic animal model of obesity and metabolic syndrome.

Methods

Sprague Dawley rats were fed a high-fat enriched diet during 45 days to induce obesity and metabolic dysregulation. On top of this established obesity, the administration of Tacrolimus (1mg/kg/day) during 15 days induced severe hyperglycaemia and changes in morphological and structural characteristics of the pancreas.

Results

Obese animals administered with Tacrolimus showed increased size of islets of Langerhans and reduced beta-cell proliferation without changes in apoptosis. There were also changes in beta-cell nuclear factors such as a decrease in nuclear expression of MafA and a nuclear overexpression of FoxO1A, PDX-1 and NeuroD1. These animals also showed increased levels of pancreatic insulin and glucagon.

Discussion

This model could be evidence of the relationship between the T2DM and PTDM physiopathology and, eventually, the model may be instrumental to study the pathogenesis of T2DM.

Hyperglycemia and circadian disruption lead to retinal dysfunction in a stabilized colony of the fat sand rat Psammomys obesus

PURPOSE

The Fat Sand Rat (Psammomys obesus) recapitulates several features of human pre-proliferative diabetic retinopathy, but data are restricted to wild animals, incompatible with stringent biomedical research criteria. To overcome this barrier, we characterized retinal changes in a colony of P. obsesus maintained under strictly controlled housing conditions.

METHODS

Animals were maintained on low or high caloric energy diets, and raised under either standard (12 h light/12 h dark) or shortened (5 h light/5 h dark) photoperiods. Visual responses were tested by electroretinography, while structural/molecular changes were assayed by immunochemistry and molecular biology (RNAseq and qPCR).

RESULTS

Whereas high calorie diet alone did not induce hyperglycemia, coupled with short photoperiod >80 % animals developed severe hyper-insulinemia by 15 weeks, and 16 % animals further developed hyperglycemia. In these groups, electroretinography showed significant declines in visual responses in both hyper-insulinemic and hyperglycemic animals, especially in photopic (cone) responses. Transcriptomics analysis of hyperglycemic compared to low caloric controls revealed major upregulation in pathways involved in glial activation, extracellular matrix remodeling, inflammation, cytokine production, partial ischemic responses and angiogenesis. Western blotting against rhodopsin and cone opsin also showed decreased levels in both groups, overall decreases being greater for cones than rods in hyperglycemic animals.

CONCLUSIONS

P. obesus maintained in rigorously monitored captive conditions, albeit showing attenuated responses to dietary overload compared to wild counterparts, nevertheless do develop some retinal features of diabetic retinopathy-like degeneration. Such a colony with known sanitary status opens their broader use for biomedical research.

Effects of Diabetes Mellitus on Corneal Immune Cell Activation and the Development of Keratopathy

Diabetes mellitus (DM) is one of the most prevalent diseases globally, and its prevalence is rapidly increasing. Most patients with a long-term history of DM present with some degree of keratopathy (DK). Despite its high incidence, the underlying inflammatory mechanism of DK has not been elucidated yet. For further insights into the underlying immunopathologic processes, we utilized streptozotocin-induced mice to model type 1 DM (T1D) and B6.Cg-Lepob/J mice to model type 2 DM (T2D). We evaluated the animals for the development of clinical manifestations of DK. Four weeks post-induction, the total frequencies of corneal CD45+CD11b+Ly-6G- myeloid cells, with enhanced gene and protein expression levels for the proinflammatory cytokines TNF-α and IL-1β, were higher in both T1D and T2D animals. Additionally, the frequencies of myeloid cells/mm2 in the sub-basal neural plexus (SBNP) were significantly higher in T1D and T2D compared to non-diabetic mice. DK clinical manifestations were observed four weeks post-induction, including significantly lower tear production, corneal sensitivity, and epitheliopathy. Nerve density in the SBNP and intraepithelial terminal endings per 40x field were lower in both models compared to the normal controls. The findings of this study indicate that DM alters the immune quiescent state of the cornea during disease onset, which may be associated with the progressive development of the clinical manifestations of DK.

A concept for human use of real-time and remote monitoring of diabetic subjects using intermittent scanned continuous glucose measurement

BACKGROUND

Flash glucose monitoring systems like the FreeStyle Libre (FSL) sensor have gained popularity for monitoring glucose levels in people with diabetes mellitus. This sensor can be paired with an off-label converted real-time continuous glucose monitor (c-rtCGM) plus an ad hoc computer/smartphone interface for remote real-time monitoring of diabetic subjects, allowing for trend analysis and alarm generation.

OBJECTIVES

This work evaluates the accuracy and agreement between the FSL sensor and the developed c-rtCGM system. As real-time monitoring is the main feature, the system's connectivity was assessed at 5-min intervals during the trials.

METHODS

One week of glucose data were collected from 16 type 1 diabetic rats using the FSL sensor and the c-rtCGM. Baseline blood samples were taken the first day before inducing type 1 diabetes with streptozotocin. Once confirmed diabetic rats, FSL and c-rtCGM, were implanted, and to improve data matching between the two monitoring devices, the c-rtCGM was calibrated to the FSL glucometer readings. A factorial design 2 × 3^3 and a second-order regression was used to find the base values of the linear model transformation of the raw data obtained from the sensor. Accuracy, agreement, and connectivity were assessed by median absolute relative difference (Median ARD), range averaging times, Parkes consensus error grid analysis (EGA), and Bland-Altman analysis with a non-parametric approach.

RESULTS

Compared to the FSL sensor, the c-rtCGM had an overall Median ARD of 6.58%, with 93.06% of results in zone A when calibration was not carried out. When calibration frequency changed from every 50 h to 1 h, the overall Median ARD improved from 6.68% to 2.41%, respectively. The connectivity evaluation showed that 95% of data was successfully received every 5 min by the computer interface.

CONCLUSIONS AND CLINICAL IMPORTANCE

The results demonstrate the feasibility and reliability of real-time and remote subjects with diabetes monitoring using the developed c-rtCGM system. Performing calibrations relative to the FSL readings increases the accuracy of the data displayed at the interface.

Inulin prebiotic ameliorates type 1 diabetes dictating regulatory T cell homing via CCR4 to pancreatic islets and butyrogenic gut microbiota in murine model

Gut dysbiosis is linked to type 1 diabetes mellitus (T1D). Inulin (INU), a prebiotic, modulates the gut microbiota, promoting beneficial bacteria that produce essential short-chain fatty acids for immune regulation. However, how INU affects T1D remains uncertain. Using a streptozotocin-induced (STZ) mouse model, we studied INU's protective effects. Remarkably, STZ + INU mice resisted T1D, with none developing the disease. They had lower blood glucose, reduced pancreatic inflammation, and normalized serum insulin compared with STZ + SD mice. STZ + INU mice also had enhanced mucus production, abundant Bifidobacterium, Clostridium cluster IV, Akkermansia muciniphila, and increased fecal butyrate. In cecal lymph nodes, we observed fewer CD4+Foxp3+ regulatory T cells expressing CCR4 and more Foxp3+CCR4+ cells in pancreatic islets, with higher CCL17 expression. This phenotype was absent in CCR4-deficient mice on INU. INU supplementation effectively protects against experimental T1D by recruiting CCR4+ regulatory T cells via CCL17 into the pancreas and altering the butyrate-producing microbiota.

Animal Models of Type 2 Diabetes Complications: A Review

Diabetes mellitus is a multifactorial metabolic disease, of which type 2 diabetes (T2D) is one of the most common. The complications of diabetes are far more harmful than diabetes itself. Type 2 diabetes complications include diabetic nephropathy (DN), diabetic heart disease, diabetic foot ulcers (DFU), diabetic peripheral neuropathy (DPN), and diabetic retinopathy (DR) et al. Many animal models have been developed to study the pathogenesis of T2D and discover an effective strategy to treat its consequences. In this sense, it is crucial to choose the right animal model for the corresponding diabetic complication. This paper summarizes and classifies the animal modeling approaches to T2D complications and provides a comprehensive review of their advantages and disadvantages. It is hopeful that this paper will provide theoretical support for animal trials of diabetic complications.

Affective and Cognitive Impairments in Rodent Models of Diabetes

Diabetes and related acute and long-term complications have a profound impact on cognitive, emotional, and social behavior, suggesting that the central nervous system (CNS) is a crucial substrate for diabetic complications. When anxiety, depression, and cognitive deficits occur in diabetic patients, the symptoms and complications related to the disease worsen, contributing to lower quality of life while increasing health care costs and mortality. Experimental models of diabetes in rodents are a fundamental and valuable tool for improving our understanding of the mechanisms underlying the close and reciprocal link between diabetes and CNS alterations, including the development of affective and cognitive disorders. Such models must reproduce the different components of this pathological condition in humans and, therefore, must be associated with affective and cognitive behavioral alterations. Beyond tight glycemic control, there are currently no specific therapies for neuropsychiatric comorbidities associated with diabetes; animal models are, therefore, essential for the development of adequate therapies. To our knowledge, there is currently no review article that summarizes changes in affective and cognitive behavior in the most common models of diabetes in rodents. Therefore, in this review, we have reported the main evidence on the alterations of affective and cognitive behavior in the different models of diabetes in rodents, the main mechanisms underlying these comorbidities, and the applicable therapeutic strategy.

Observation of the neuroprotective efficacy of vitamin K in a streptozocin-induced diabetes model in chick embryos

Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia due to insulin deficiency and/or resistance. Vitamin K (VK) is a group of fat-soluble molecules, including naturally occurring vitamin K1 (phylloquinone). vitamin K2 (menaquinone), and synthetic vitamin K3 (menadione). Beyond coagulation, the health benefits of VK have been described to play different roles in both physiological and pathological processes such as inflammation, energy metabolism, neuroprotection, cellular growth, and survival. It was aimed to observe the antioxidant and/or neuroprotective activity of vitamin K1 in our model of chick embryo diabetic neuropathy (DN) induced by streptozotocin (STZ). Ninety White Leghorn, fertile and 0-day-old SPF (specific pathogen-free) eggs (57 ± 4 gr) were used in the study. Chick embryo blood brain tissues were taken for biochemical evaluation. Plasma insulin and glucose levels were measured. In addition, brain tissue total antioxidant level (TAS), total oxidant level (TOS), malondialdehyde (MDA), and vascular endothelial growth factor (VEGF) levels were measured. Plasma glucose levels were higher in the STZ-treated groups and lower in the treatment groups. Plasma insulin levels were observed to be higher in STZ groups in groups treated with high VK. Low TAS, high MDA, TOS, and VEGF levels were recorded in brain tissue STZ groups. Low VEGF, TOS, and MDA levels were recorded in the group treated with the highest VK, while high TAS levels were observed. In our STZ-induced chick embryo diabetic neuropathy model, we observed that VK1 reduced oxidant damage by showing antioxidant properties or by modulating antioxidant enzymes.

In Vivo Hypolipidemic, Hypoglycemic, Antihyperglycemic, and In Vitro Antioxidant Effects of Podocarpus gracilis Leaf Extract and Fractions in Diabetic Mice

Background

Podocarpus gracilis is an evergreen, dioecious tree found in Ethiopia and other African nations. It can reach a height of 60 meters. Without any scientific validation, ethnobotanical studies conducted in Ethiopia revealed that the Podocarpus gracilis plant's leaf is consumed orally to treat diabetes mellitus. Hence, this study aims to evaluate the in vivo blood glucose level lowering, lipid-lowering, and in vitro-free radical scavenging responses of Podocarpus gracilis leaf extract and fractions on experimental mice induced with diabetes.

Methods

The in vitro antioxidant activity of PGC (Podocarpus gracilis) leaf extract was assessed by using a diphenyl-2-picrylhydrazyl (DPPH) assay. The oral glucose-loaded, normoglycemic, and streptozotocin- (STZ-) induced diabetic mouse models were employed. In the STZ-induced mice model, the leaf extract and solvent fractions activity on serum lipid and weight were also measured. The extract and fractions were tested at 100, 200, and 400 mg/kg dosages. One-way ANOVA was used to determine the statistical significance of BGL (blood glucose level) changes within and between groups, and Tukey's post hoc multiple comparisons were then performed.

Results

In the acute toxicity study of Podocarpus gracilis leaf extract and fractions, there was no evidence of animal mortality at the maximum dose of 2 g/kg during the observation period. The extract-treated group with normoglycemia revealed a significant lowering in BGL at the 4-hour mark of 27.4% (p < 0.001) and 25.2% (p < 0.01) at doses of 200 mg/kg and 400 mg/kg, respectively, compared to that in negative control. In the oral glucose tolerance test (OGTT) model, only 400 mg/kg treated groups at 120 min after exposure showed a BGL reduction of 31.17% which was statistically significant (p < 0.05) in comparison to the negative control. In the single-dose STZ-induced model, eighth-hour BGL measurements from CE 100, CE 200, CE 400, and GLC5 showed drops in BGL of 43.1%, 44.1%, 45%, and 47.3% from baseline fasting BGL values. In the repeated streptozotocin (STZ)-induced model, at all doses of leaf extract and fractions, the fasting BGL was significantly (p < 0.001) reduced. Moreover, the leaf extract and solvent fractions have shown a significant (p < 0.001) reduction of serum lipids such as LDL, TC, and VLDL, and at the same time, it increases HDL at 14 days with body weight gained. In the test for antioxidant activity, the half-maximal inhibitory concentrations (IC50) for leaf extract and the standard medication (ascorbic acid) were 8.2 μg/ml and 3.3 μg/ml, respectively. The IC50 value denotes the concentration of the sample required to scavenge 50% DPPH radicals.

Conclusion

The 80% hydromethanolic leaf extract and fractions of Podocarpus gracilis exhibited blood glucose lowering, lipid-lowering activity in normoglycemic, oral glucose tolerance test (OGTT) mode, and STZ-induced diabetic mice with weight gains. There is scientific support for the alleged traditional use as an antidiabetic, lipid-lowering, and antioxidant activity. The results need to be confirmed by future studies.

Metformin beyond an anti-diabetic agent: A comprehensive and mechanistic review on its effects against natural and chemical toxins

In addition to the anti-diabetic effect of metformin, a growing number of studies have shown that metformin has some exciting properties, such as anti-oxidative capabilities, anticancer, genomic stability, anti-inflammation, and anti-fibrosis, which have potent, that can treat other disorders other than diabetes mellitus. We aimed to describe and review the protective and antidotal efficacy of metformin against biologicals, chemicals, natural, medications, pesticides, and radiation-induced toxicities. A comprehensive search has been performed from Scopus, Web of Science, PubMed, and Google Scholar databases from inception to March 8, 2023. All in vitro, in vivo, and clinical studies were considered. Many studies suggest that metformin affects diseases other than diabetes. It is a radioprotective and chemoprotective drug that also affects viral and bacterial diseases. It can be used against inflammation-related and apoptosis-related abnormalities and against toxins to lower their effects. Besides lowering blood sugar, metformin can attenuate the effects of toxins on body weight, inflammation, apoptosis, necrosis, caspase-3 activation, cell viability and survival rate, reactive oxygen species (ROS), NF-κB, TNF-α, many interleukins, lipid profile, and many enzymes activity such as catalase and superoxide dismutase. It also can reduce the histopathological damages induced by many toxins on the kidneys, liver, and colon. However, clinical trials and human studies are needed before using metformin as a therapeutic agent against other diseases.

Contribution of animal models to diabetes research: Its history, significance, and translation to humans

Diabetes mellitus is still expanding globally and is epidemic in developing countries. The combat of this plague has caused enormous economic and social burdens related to a lowered quality of life in people with diabetes. Despite recent significant improvements of life expectancy in patients with diabetes, there is still a need for efforts to elucidate the complexities and mechanisms of the disease processes to overcome this difficult disorder. To this end, the use of appropriate animal models in diabetes studies is invaluable for translation to humans and for the development of effective treatment. In this review, a variety of animal models of diabetes with spontaneous onset in particular will be introduced and discussed for their implication in diabetes research.

Diabetic Neuropathic Pain and Serotonin: What Is New in the Last 15 Years?

The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) is involved in numerous physiological functions and plays a key role in pain modulation including neuropathic pain. Diabetic neuropathy is a common complication of diabetes mellitus often accompanied by chronic neuropathic pain. Animal models of diabetes offer relevant tools for studying the pathophysiological mechanisms and pharmacological sensitivity of diabetic neuropathic pain and for identifying new therapeutic targets. In this review, we report data from preclinical work published over the last 15 years on the analgesic activity of drugs acting on the serotonergic system, such as serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressants, and on the involvement of certain serotonin receptors-in particular 5-HT_1A, 5-HT_2A/2c and 5-HT₆ receptors-in rodent models of painful diabetic neuropathy.

Chronic Wound Healing Models

In this paper, we review and analyze the commonly available wound healing models reported in the literature and discuss their advantages and issues, considering their relevance and translational potential to humans. Our analysis includes different in vitro and in silico as well as in vivo models and experimental techniques. We further explore the new technologies in the study of wound healing to provide an all encompassing review of the most efficient ways to proceed with wound healing experiments. We revealed that there is not one model of wound healing that is superior and can give translatable results to human research. Rather, there are many different models that have specific uses for studying certain processes or stages of wound healing. Our analysis suggests that when performing an experiment to assess stages of wound healing or different therapies to enhance healing, one must consider not only the species that will be used but also the type of model and how this can best replicate the physiology or pathophysiology in humans.

From Determining Brain Insulin Resistance in a Sporadic Alzheimer's Disease Model to Exploring the Region-Dependent Effect of Intranasal Insulin

Impaired response to insulin has been linked to many neurodegenerative disorders like Alzheimer's disease (AD). Animal model of sporadic AD has been developed by intracerebroventricular (icv) administration of streptozotocin (STZ), which given peripherally causes insulin resistance. Difficulty in demonstrating insulin resistance in this model led to our aim: to determine brain regional and peripheral response after intranasal (IN) administration of insulin in control and STZ-icv rats, by exploring peripheral and central metabolic parameters. One month after STZ-icv or vehicle-icv administration to 3-month-old male Wistar rats, cognitive status was determined after which rats received 2 IU of fast-acting insulin aspart intranasally (CTR + INS; STZ + INS) or saline only (CTR and STZ). Rats were sacrificed 2 h after administration and metabolic and glutamatergic parameters were measured in plasma, CSF, and the brain. Insulin and STZ increased amyloid-β concentration in plasma (CTR + INS and STZ vs CTR), while there was no effect on glucose and insulin plasma and CSF levels. INS normalized the levels of c-fos in temporal cortex of STZ + INS vs STZ (co-localized with neurons), while hypothalamic c-fos was found co-localized with the microglial marker. STZ and insulin brain region specifically altered the levels and activity of proteins involved in cell metabolism and glutamate signaling. Central changes found after INS in STZ-icv rats suggest hippocampal and cortical insulin sensitivity. Altered hypothalamic metabolic parameters of STZ-icv rats were not normalized by INS, indicating possible hypothalamic insulin insensitivity. Brain insulin sensitivity depends on the affected brain region and presence of metabolic dysfunction induced by STZ-icv administration.

An older diabetes-induced mice model for studying skin wound healing

Advances in wound treatment depend on the availability of animal models that reflect key aspects of human wound healing physiology. To this date, the accepted mouse models do not reflect defects in the healing process for chronic wounds that are associated with type two diabetic skin ulcers. The long term, systemic physiologic stress that occurs in middle aged or older Type 2 diabetes patients is difficult to simulate in preclinical animal model. We have strived to incorporate the essential elements of this stress in a manageable mouse model: long term metabolic stress from obesity to include the effects of middle age and thereafter onset of diabetes. At six-weeks age, male C57BL/6 mice were separated into groups fed a chow and High-Fat Diet for 0.5, 3, and 6 months. Treatment groups included long term, obesity stressed mice with induction of diabetes by streptozotocin at 5 months, and further physiologic evaluation at 8 months old. We show that this model results in a severe metabolic phenotype with insulin resistance and glucose intolerance associated with obesity and, more importantly, skin changes. The phenotype of this older age mouse model included a transcriptional signature of gene expression in skin that overlapped that observed with elderly patients who develop diabetic foot ulcers. We believe this unique old age phenotype contrasts with current mice models with induced diabetes.

Metabolomics-Based Profiling via a Chemometric Approach to Investigate the Antidiabetic Property of Different Parts and Origins of Pistacia lentiscus L

Pistacia lentiscus L. is a medicinal plant that grows spontaneously throughout the Mediterranean basin and is traditionally used to treat diseases, including diabetes. The aim of this work consists of the evaluation of the α-glucosidase inhibitory effect (i.e., antidiabetic activity in vitro) of different extracts from the leaves, stem barks and fruits of P. lentiscus harvested on mountains and the littoral of Tizi-Ouzou in Algeria. Metabolomic profiling combined with a chemometric approach highlighted the variation of the antidiabetic properties of P. lentiscus according to the plant's part and origin. A multiblock OPLS analysis showed that the metabolites most involved in α-glucosidase inhibition activity were mainly found in the stem bark extracts. The highest inhibitory activity was found for the stem bark extracts, with averaged inhibition percentage values of 84.7% and 69.9% for the harvested samples from the littoral and mountain, respectively. On the other hand, the fruit extracts showed a lower effect (13.6%) at both locations. The UHPLC-ESI-HRMS characterization of the metabolites most likely responsible for the α-glucosidase-inhibitory activity allowed the identification of six compounds: epigallocatechin(4a>8)epigallocatechin (two isomers), (epi)gallocatechin-3'-O-galloyl-(epi)gallocatechin (two isomers), 3,5-O-digalloylquinic acid and dihydroxy benzoic acid pentoside.

Influence of Murraya koenigii extract on diabetes induced rat brain aging

Food supplements are used to improve cognitive functions in age-related dementia. This study was designed to determine the Murraya koenigii leaves' effect on Alloxan-induced cognitive impairment in diabetic rats and the contents of oxidative stress biomarkers, catalase, reduced glutathione, and glutathione reductase in brain tissue homogenates. Wistar rats were divided into seven groups (six rats per group). Group I received saline water (1 ml, p.o.), Diabetes was induced in Groups II-VII with Alloxan (120 mg/kg/p.o). Group III was provided with Donepezil HCl (2.5 mg/kg/p.o.), Group IV, V, VI, and VII with Murraya koenigii ethanol extract (200 and 400 mg/kg/p.o.) and aqueous extract (200 and 400 mg/kg/p.o.), respectively, for 30 days. Behavior, acetylcholinesterase (AChE) activity, oxidative stress status, and histopathological features were determined in the hippocampus and cerebral cortex. Administration of Murraya koenigii ethanolic and aqueous extracts significantly (P<0.05, P<0.001) increased the number of holes crossed by rats from one chamber to another. There was an increase in the (1) latency to reach the solid platform, (2) number of squares traveled by rats on the 30^th day, and (3) percentage of spontaneous alternation behavior compared to the control group. Administration for successive days markedly decreased AChE activity (P<0.05), decreased TBARS level, and increased catalase, GSH, and GR levels. Murayya koenigii could be a promising food supplement for people with dementia. However, more research into sub-chronic toxicity and pharmacokinetic and pharmacodynamics interactions is essential.

Understanding Insulin in the Age of Precision Medicine and Big Data: Under-Explored Nature of Genomics

Insulin is amongst the human genome's most well-studied genes/proteins due to its connection to metabolic health. Within this article, we review literature and data to build a knowledge base of Insulin (INS) genetics that influence transcription, transcript processing, translation, hormone maturation, secretion, receptor binding, and metabolism while highlighting the future needs of insulin research. The INS gene region has 2076 unique variants from population genetics. Several variants are found near the transcriptional start site, enhancers, and following the INS transcripts that might influence the readthrough fusion transcript INS-IGF2. This INS-IGF2 transcript splice site was confirmed within hundreds of pancreatic RNAseq samples, lacks drift based on human genome sequencing, and has possible elevated expression due to viral regulation within the liver. Moreover, a rare, poorly characterized African population-enriched variant of INS-IGF2 results in a loss of the stop codon. INS transcript UTR variants rs689 and rs3842753, associated with type 1 diabetes, are found in many pancreatic RNAseq datasets with an elevation of the 3'UTR alternatively spliced INS transcript. Finally, by combining literature, evolutionary profiling, and structural biology, we map rare missense variants that influence preproinsulin translation, proinsulin processing, dimer/hexamer secretory storage, receptor activation, and C-peptide detection for quasi-insulin blood measurements.

A Review on Experimental Models to Test Medicinal Plants on Postprandial Blood Glucose in Diabetes

Due to the gravity of postprandial hyperglycemia in the development of microvascular and macrovascular diseases in diabetics, many medicinal plants are tested to determine their effectiveness in glycemic control and the mechanisms of action of the products. Consequently, various diabetic models have been developed and enhanced over the years. The objective of this review is to describe some of the experimental models to study the effect of medicinal plants used to control postprandial hyperglycemia. Data was collected from PubMed, ScienceDirect, Scopus, and Google scholar (1953-2021). Fiftyseven (57) studies were included in this review article. Ten models were identified and described. For each model, we described the targets involved and their roles in postprandial blood glucose control. The experimental design and procedures described the targets such as an α-glucosidase enzyme, SGLT1, GLUT2, DPP-IV, Na+/K+ ATPase pump, or intestinal motility in the models, experiment design and procedures were described. This review will facilitate the selection of the most appropriate model for studying agents used to investigate postprandial blood glucose.

The evaluation of early stage oxidative status in streptozotocin induced diabetes in rats

Early-stage diabetes can be defined as the stages before absolute insulin deficiency in patients. In this study, the early stage oxidative effect of streptozotocin(STZ) induced diabetes mellitus was evaluated. 28 male adult Sprague-Dawley rats were divided into four groups; control group and 7th, 14th, 21st days diabetic groups. Diabetic groups received single 65 mg/kg STZ injection intraperitoneally. Rats were decapitated at 7th, 14th and 21st days, liver tissues were taken. Nitric oxide(NO), malondialdehyde(MDA) levels and catalase, arginase activities were measured. MDA and NO levels were increased (respectively p < .001 and p < .01), mainly 14 and 21 days after STZ administration; moreover, while liver catalase activity was progressively decreased (p < .001), oppositely arginase was increased in the same time period (p < .01). Results show that MDA and nitric oxide together with catalase and arginase switch at an early stage of diabetes and they may contribute to subsequent complications related to diabetes via increased oxidative damage.

Histomorphometry Changes and Decreased Reactivity to Angiotensin II in the Ileum and Colon of Streptozotocin-Induced Diabetic Rats

Diabetes mellitus (DM) is a chronic progressive metabolic disorder associated with several gastrointestinal complications, affecting up to 75% of patients. Knowing that Angiotensin II (AngII) also regulates intestinal contraction, we decided to evaluate changes in ileum and colon histomorphometry and AngII reactivity in a rat model of DM. Streptozotocin (STZ, 55 mg/kg) was administered to induce DM to 24 adult male Wistar rats. Diabetic rats displayed all the characteristic signs of type 1 DM (T1DM) and fecal excretion increased about 4-fold over 14 days, while the excretion of controls remained unaltered. Compared to controls, diabetic ileum and colon presented an increase in both macroscopic (length, perimeter and weight) and microscopic (muscular wall thickness) parameters. Functionally, AngII-induced smooth muscle contraction was lower in diabetic rats, except in the distal colon. These differences in the contractile response to AngII may result from an imbalance between AngII type 1 (antagonized by candesartan, 10 nM) and type 2 receptors activation (antagonized by PD123319, 100 nM). Taken together, these results indicate that an early and refined STZ-induced T1DM rat model already shows structural remodelling of the gut wall and decreased contractile response to AngII, findings that may help to explain diabetic dysmotility.

Efficacy of methanolic extracts of some medicinal plants on wound healing in diabetic rats

Background

Materials and methods

Results

Conclusion

Date fruit as a promising source of functional carbohydrates and bioactive compounds: A review on its nutraceutical potential

From the past decade, consumption of ready-to-eat food and ease of access to fast food increased the onset of several diseases. Thus, there is a need to shift the trend from consumption of unhealthy food item to natural and healthy alternatives. In this context, fruits can be considered as functional food, which have ability to provide essential nutrients and bioactive compounds. These compounds when consume in adequate amount would have the potential to lower the onset of diseases. In this regard, Phoenix dactylifera or date fruit is an important source of functional carbohydrates and bioactive compounds for their use as functional foods. The major functional carbohydrate in date fruit are in the form of dietary fiber, such as β-glucan, cellulose and fructans along with other bioactive compounds. Additionally, it is also a good source of other important nutrients such as sugars, minerals, along with minor quantities of proteins and lipids. Due to these functional compounds, date fruit have shown a wide range of pharmaceutical properties such as antioxidant, anti-inflammatory, anti-diabetic, hepatoprotective and anticancer. This review provides latest information regarding functional and nutraceutical carbohydrates of date fruits along-with mechanism of action on different diseases reported in recent years. PRACTICAL APPLICATIONS: This will provide information to food industries for the development of innovative food products by using date fruit. Moreover, bioactive components from date fruit may prove to enhance global health and wellness. However, further research is needed on clinical trials for the development of functional food products by using date fruit for functional foods and pharmaceutical applications.

Understanding main pregnancy complications through animal models

Since human pregnancy is an inefficient process, achieving desired and pleasant outcome of pregnancy - the birth of a healthy and fit baby - is the main goal in any pregnancy. Spontaneous pregnancy failure is actually the most common complication of pregnancy and Most of these pregnancy losses are not known. Animal models have been utilized widely to investigate the system of natural biological adaptation to pregnancy along with increasing our comprehension of the most important hereditary and non-hereditary factors that contribute to pregnancy disorders. We use model organisms because their complexity better reproduces the human condition. A useful animal model for the disease should be pathologically similar to the disease conditions in humans. Animal models deserve a place in research because of the ethical limitations that apply to pregnant women's experiments. The present review provides insights into the overall risk factors involved in recurrent miscarriage, recurrent implant failure and preeclampsia and animal models developed to help researchers identify the source of miscarriage and the best research and treatment strategy for women with Repeated miscarriage and implant failure.

The attenuation effect of potassium 2-(1-hydroxypentyl)-benzoate in a mouse model of diabetes-associated cognitive decline: The protein expression in the brain

Aims

dl‐PHPB (potassium 2‐(1‐hydroxypentyl)‐benzoate) has been shown to have neuroprotective effects against acute cerebral ischemia, vascular dementia, and Alzheimer's disease. The aim of this study was to investigate the effects of dl‐PHPB on memory deficits and preliminarily explore the underlying molecular mechanism.

Methods

Blood glucose and behavioral performance were evaluated in the KK‐A^y diabetic mouse model before and after dl‐PHPB administration. Two‐dimensional difference gel electrophoresis (2D‐DIGE)‐based proteomics was used to identify differentially expressed proteins in brain tissue. Western blotting was used to study the molecular mechanism of the related signaling pathways.

Results

Three‐month‐old KK‐A^y mice were given 150 mg/kg dl‐PHPB by oral gavage for 2 months, which produced no effect on the level of serum glucose. In the Morris water maze test, KK‐A^y mice treated with dl‐PHPB showed significant improvements in spatial learning and memory deficits compared with vehicle‐treated KK‐A^y mice. Additionally, we performed 2D‐DIGE to compare brain proteomes of 5‐month KK‐A^y mice treated with and without dl‐PHPB. We found 14 altered proteins in the cortex and 11 in the hippocampus; two of the 25 altered proteins and another four proteins that were identified in a previous study on KK‐A^y mice were then validated by western blot to further confirm whether dl‐PHPB can reverse the expression levels of these proteins. The phosphoinositide 3‐kinase/protein kinase B/glycogen synthase kinase‐3β (PI3K/Akt/GSK‐3β) signaling pathway was also changed in KK‐A^y mice and dl‐PHPB treatment could reverse it.

Conclusions

These results indicate that dl‐PHPB may play a potential role in diabetes‐associated cognitive impairment through PI3K/Akt/GSK‐3β signaling pathway and the differentially expressed proteins may become putative therapeutic targets.

Globularia arabica methanolic leaf extract has higher efficacy on burn wound healing in diabetic rats compared to Malva slyvestries methanolic leaf extract

This study aimed to see how effective Globulari. arabica and Malva. slyvestries-based cream formulations were at healing scald burn wounds in rats. Depending on ointment preparations of 1%, 5%, and 10% w/w were created. For comparison, an ointment base and a regular burn cream composed soframycine were utilized. Rats introduced a burn by solidifying equipment at 100°C on a 14 mm 2 shaved dorsal region. A deep second-degree burn was created, and the percentage of wound contraction was measured over the next 15 days. The rats were euthanized on days 8 and 15, and histological slides were prepared using hematoxylin and eosin staining. Compared to the control group, a substantial increase in wound contraction and a significant decrease in the duration of epithelialization in the based ointment-treated groups. However, as paralleled to Globularia arabica, significant (P < 0.05) results were observed with 10% Globularia. arabica cream, whereas Malva. slyverstries indicate minimal healing. Soframycine causes a substantial increase in wound contraction (P <0.05). Soframycine cream with 10% Globularia arabica therapy resulted in practically complete re-epithelialization and re-structuring of wound tissue on histological examination, whereas Malva slyversries treatment resulted in low epithelization during treatment days. The findings suggest that Globularia arabica-based cream has the wound-healing capability.

High glucose-induced ROS-accumulation in embryo-larval stages of zebrafish leads to mitochondria-mediated apoptosis

In recent decades, diabetes mellitus has become a major chronic disease threatening human health worldwide, and the age of patients tends to be younger; however, the pathogenesis remains unclear, resulting in many difficulties in its treatment. As an ideal model animal, zebrafish can simulate the processes of human diabetes well. In this study, we successfully established a model of diabetic zebrafish larvae in a previous work. Furthermore, transcriptome analysis was completed, and the results suggested that 10.59% of differentially expressed genes (DEGs) related to the apoptosis pathway need to be considered. Then, glucose-induced developmental toxicity, reactive oxygen species (ROS) accumulation, antioxidant system function, apoptosis and mitochondrial dysfunction were measured in zebrafish larvae. We hope that this study will provide valuable reference information for type 2 juvenile diabetes treatment.

A Rat Experimental Model for Investigation of the Effect of Diabetes on Submandibular Salivary Glands Treated with Epidermal Growth Factor

Background: Despite the plethora of research around the negative effects of diabetes on different body organs, this topic still attracts a lot of attention in order to find potential remedies that could counteract or reverse the damaging effect of diabetes. Aim: In this study, we developed a reliable experimental rat model that can be used for investigation of the ability of epidermal growth factor (EFG) in restoring the normal architecture of oral tissues after being damaged by diabetes. Methods: Eighty adult male albino rats (average weight ±220 gm) were used in the current study. Twenty rats served as control and received no treatment. Diabetes was induced in forty rats using a single injection of 65mg/kg of Streptozotocin (STZ). Out of the forty diabetic rats, twenty rats received a single daily intraperitoneal injection of EGF (10 µg/Kg) for 8 weeks. Furthermore, twenty healthy rats received the same dose of EGF and served as positive controls. The submandibular salivary glands of all rats were examined for Immunohistochemical detection of myosin in the glandular structure. Results: The EGF treated group showed comparable myosin expression to the control group. The diabetic group revealed deterioration of all components of the submandibular salivary glands. Finally, the diabetic + EGF group has demonstrated restoration of the myosin expression levels in the submandibular salivary glands to a level that is not significantly different from healthy (non-diabetic) rats in the control group (p>0.05) and significantly higher than the diabetic group (p<0.0001). Conclusion: The findings of the present study confirm previous studies and validates the use of our animal model as predictable experimental tool to investigate the effects of diabetes and EGF on different oral tissues. It also highlights the importance of further research investigating EGF as a promising treatment modality for restoration of the condition and functions of tissues damaged by diabetes not only in the oral cavity but also around the whole body.  

Intrauterine exposure of mice to arsenite induces abnormal and transgenerational glycometabolism

The adverse, transgenerational effects on health caused by environmental pollutants are receiving increasing attention. For humans and mice, inorganic arsenic (iAs), a widespread environmental contaminant, is associated with diabetic phenotypes. However, the transgenerational effects of arsenite-induced changes in glucose metabolism in mice have not been fully investigated. In the present study, F0 pregnant mice were exposed to arsenite via drinking water (0, 0.5, 5, or 50 ppm NaAsO₂) from gestational day 0 (GD0) until parturition. We examined the effects of arsenite exposure on the metabolic phenotypes and the levels of proteins and genes related to glucose metabolism of dams and their offspring (F1∼F4). Arsenite exposure altered the glucose tolerance of offspring. Notably, glucose transporter-2 (GLUT2) and insulin receptor substrate-1 (IRS1), which are related to the maintenance of glucose homeostasis, were also changed. The homeostasis assessment-insulin resistance (HOMA-IR), an indicator of insulin resistance, was higher in the offspring from the F0 female mice exposed to arsenite. Furthermore, imprinted genes, insulin-like growth factor 2 (IGF2) and potassium voltage-gated channel subfamily Q member 1 (KCNQ1), related to glycometabolism across multiple generations, were lower in the offspring. In sum, arsenite exposure during pregnancy transgenerationally affects glucose metabolism, which is related to altered levels of IGF2 and KCNQ1.

Obesity-Associated Cancers: Evidence from Studies in Mouse Models

Obesity, one of the major problems in modern human society, is correlated with various diseases, including type 2 diabetes mellitus (T2DM). In particular, epidemiological and experimental evidence indicates that obesity is closely linked to at least 13 different types of cancer. The mechanisms that potentially explain the link between obesity and cancer include hyperactivation of the IGF pathway, metabolic dysregulation, dysfunctional angiogenesis, chronic inflammation, and interaction between pro-inflammatory cytokines, endocrine hormones, and adipokines. However, how the largely uniform morbidity of obesity leads to different types of cancer still needs to be investigated. To study the link between obesity and cancer, researchers have commonly used preclinical animal models, particularly mouse models. These models include monogenic models of obesity (e.g., ob/ob and db/db mice) and genetically modified mouse models of human cancers (e.g., Kras-driven pancreatic cancer, Apc-mutated colorectal cancer, and Her2/neu-overexpressing breast cancer). The experimental results obtained using these mouse models revealed strong evidence of a link between obesity and cancer and suggested their underlying mechanisms.

Cognitive impairments in type 1 diabetes mellitus model mice are associated with synaptic protein disorders

An association between type 1 diabetes mellitus (T1DM) and cognitive impairment was recently reported. However, the mechanisms by which T1DM induces cognitive impairment are still unknown. Here, we confirmed that T1DM mice induced by streptozotocin (STZ) injection had impaired working memory and spatial memory. We observed long-term potentiation (LTP) induction defects and synaptic loss in mice 20 weeks after STZ injection. We also found decreased levels of synaptic proteins, including the N-methyl-D-aspartic acid receptor (NMDAR) subunit NR2A, synaptophysin (SYP), and postsynaptic density 95 (PSD95), in the hippocampus and prefrontal cortex, revealing similarities in the alteration patterns of these synaptic proteins in aged Alzheimer's disease (AD) APP/PS1 mice and T1DM mice. Taken together, these findings expand our understanding of the mechanisms underlying T1DM-induced cognitive impairment.

Pulsed Electro-Magnetic Field (PEMF) Effect on Bone Healing in Animal Models: A Review of Its Efficacy Related to Different Type of Damage

Simple Summary

Pulsed electromagnetic fields (PEMFs) are a type of biophysical stimulation that has been shown to be effective in improving bone regeneration and preventing bone loss. Their use dates back to the 1970s, but a gold standard treatment protocol has not yet been defined. PEMF efficacy relies on the generation of biopotentials, which activate several molecular pathways. There is currently no clear understanding of the effects on bone healing and, in addition, there are several animal models relevant to this issue. Therefore, drawing guidelines and conclusions from the analysis of the studies is difficult. In vivo investigations on PEMF stimulation are reviewed in this paper, focusing on molecular and morphological improvements in bone. Currently, there is little knowledge about the biological mechanism of PEMF and its effect on bone healing. This is due to the variability of crucial characteristics of electro-magnetic fields, such as amplitude and exposure frequency, which may influence the type of biological response. Furthermore, a different responsiveness of cells involved in the bone healing process is documented. Heterogeneous setting parameters and different outcome measures are considered in various animal models. Therefore, achieving comparable results is difficult.

Abstract

Biophysical energies are a versatile tool to stimulate tissues by generating biopotentials. In particular, pulsed electromagnetic field (PEMF) stimulation has intrigued researchers since the 1970s. To date, many investigations have been carried out in vivo, but a gold standard treatment protocol has not yet been defined. The main obstacles are represented by the complex setting of PEMF characteristics, the variety of animal models (including direct and indirect bone damage) and the lack of a complete understanding of the molecular pathways involved. In the present review the main studies about PEMF stimulation in animal models with bone impairment were reviewed. PEMF signal characteristics were investigated, as well as their effect on molecular pathways and osseous morphological features. We believe that this review might be a useful starting point for a prospective study in a clinical setting. Consistent evidence from the literature suggests a potential beneficial role of PEMF in clinical practice. Nevertheless, the wide variability of selected parameters (frequency, duration, and amplitude) and the heterogeneity of applied protocols make it difficult to draw certain conclusions about PEMF effectiveness in clinical implementation to promote bone healing. Deepening the knowledge regarding the most consistent results reported in literature to date, we believe that this review may be a useful starting point to propose standardized experimental guidelines. This might provide a solid base for further controlled trials, to investigate PEMF efficacy in bone damage conditions during routine clinical practice.

Amelioration of diabetes and its complications by Manilkara zapota (L) P. Royen fruit peel extract and its fractions in alloxan and STZ-NA induced diabetes in Wistar rats

Purpose

This study aims to evaluate the effects of Manilkara zapota (L) P. Royen fruit peel extract (EMZFP) and its fractions in ameliorating diabetes and its complications in alloxan and STZ-NA induced diabetes in Wistar rats.

Methods

Antidiabetic effects of EMZFP were assessed in alloxan (150 mg kg^-1) induced diabetes in differently grouped rats (n=6). Diabetic rats were treated with EMZFP 150, 300, and 600 mg kg^-1 while, glimepiride (0.09 mg kg^-1) was used as a reference standard. Treated animals were assessed for various biological parameters i.e. blood glucose, serum lipids, nephroprotective markers, cardiovascular risk indices, liver glycogen, neuropathy, body weight, and histopathology of kidneys. However, for evaluating antidiabetic effects of fractions (chloroform, acetone, ethyl acetate, and remaining ethanol fraction) of EMZFP, diabetes was induced by streptozotocin (60 mg kg^-1)-nicotinamide (120 mg kg^-1/ml) in differently grouped male rats (n=6). Diabetic rats were treated with EMZFP fractions 200 mg kg^-1 however; glibenclamide (10 mg kg^-1) was a reference standard and evaluated for blood glucose, serum lipids, cardiovascular risk indices, and diabetic neuropathy.

Results

EMZFP 300 and 600 mg kg^-1/day demonstrated significant antihyperglycemic effects with augmentation in glycogen content, perfection in serum lipid profile, cardiovascular risk indices, body weight enhancement, nephroprotective effects, beneficial in peripheral neuropathy, and histopathological evidence of reversal of glomerulosclerosis. EMZFP-Et and EMZFP-EA fractions depicted a significant improvement in blood glucose, serum lipid profile, cardiovascular risk indices, and peripheral neuropathy.

Conclusion

EMZFP and its Et and EA fractions ameliorated diabetes and its complications by improving glycemic control and associated biochemical alteration.

Highlights

• Manilkara Zapota (L.) P. Royen fruit peel 70% ethanolic extract exert antidiabetic effects• EMZFP significantly ameliorated diabetic biochemical parameters and its complications.• EMZFP-Et and EMZFP-EA fractions exert potential antihyperglycemic, hypolipidemic effects and significantly improved cardiovascular risk indices, and peripheral neuropathy.• Studied MZFP can be used as promising natural herbal source of antidiabetic principles.

Glucose-Stimulated Calcium Dynamics in Beta Cells From Male C57BL/6J, C57BL/6N, and NMRI Mice: A Comparison of Activation, Activity, and Deactivation Properties in Tissue Slices

Although mice are a very instrumental model in islet beta cell research, possible phenotypic differences between strains and substrains are largely neglected in the scientific community. In this study, we show important phenotypic differences in beta cell responses to glucose between C57BL/6J, C57BL/6N, and NMRI mice, i.e., the three most commonly used strains. High-resolution multicellular confocal imaging of beta cells in acute pancreas tissue slices was used to measure and quantitatively compare the calcium dynamics in response to a wide range of glucose concentrations. Strain- and substrain-specific features were found in all three phases of beta cell responses to glucose: a shift in the dose-response curve characterizing the delay to activation and deactivation in response to stimulus onset and termination, respectively, and distinct concentration-encoding principles during the plateau phase in terms of frequency, duration, and active time changes with increasing glucose concentrations. Our results underline the significance of carefully choosing and reporting the strain to enable comparison and increase reproducibility, emphasize the importance of analyzing a number of different beta cell physiological parameters characterizing the response to glucose, and provide a valuable standard for future studies on beta cell calcium dynamics in health and disease in tissue slices.

Leveraging the strengths of mice, human stem cells, and organoids to model pancreas development and diabetes

Diabetes is an epidemic with increasing incidence across the world. Most individuals who are afflicted by this disease have type 2 diabetes, but there are many who suffer from type 1, an autoimmune disorder. Both types of diabetes have complex genetic underpinnings that are further complicated by epigenetic and environmental factors. A less prevalent and often under diagnosed subset of diabetes cases are characterized by single genetic mutations and include Maturity Onset Diabetes of the Young (MODY) and Neonatal Diabetes Mellitus (NDM). While the mode of action and courses of treatment for all forms of diabetes are distinct, the diseases all eventually result in the dysfunction and/or death of the pancreatic β cell - the body's source of insulin. With loss of β cell function, blood glucose homeostasis is disrupted, and life-threatening complications arise. In this review, we focus on how model systems provide substantial insights into understanding β cell biology to inform our understanding of all forms of diabetes. The strengths and weaknesses of animal, hPSC derived β-like cell, and organoid models are considered along with discussion of GATA6, a critical transcription factor frequently implicated in pancreatic dysfunction with developmental origins; experimental studies of GATA6 have highlighted the advantages and disadvantages of how each of these model systems can be used to inform our understanding of β cell specification and function in health and disease.

Impact of maternal hyperglycemia on cardiac development: Insights from animal models

Congenital heart disease (CHD) is the leading cause of birth defect-related death in infants and is a global pediatric health concern. While the genetic causes of CHD have become increasingly recognized with advances in genome sequencing technologies, the etiology for the majority of cases of CHD is unknown. The maternal environment during embryogenesis has a profound impact on cardiac development, and numerous environmental factors are associated with an elevated risk of CHD. Maternal diabetes mellitus (matDM) is associated with up to a fivefold increased risk of having an infant with CHD. The rising prevalence of diabetes mellitus has led to a growing interest in the use of experimental diabetic models to elucidate mechanisms underlying this associated risk for CHD. The purpose of this review is to provide a comprehensive summary of rodent models that are being used to investigate alterations in cardiac developmental pathways when exposed to a maternal diabetic setting and to summarize the key findings from these models. The majority of studies in the field have utilized the chemically induced model of matDM, but recent advances have also been made using diet based and genetic models. Each model provides an opportunity to investigate unique aspects of matDM and is invaluable for a comprehensive understanding of the molecular and cellular mechanisms underlying matDM-associated CHD.

Role of Glucose-6-Phosphate in Metabolic Adaptation of Staphylococcus aureus in Diabetes

Diabetic foot ulcer (DFU) is the most common and costly sequela of diabetes mellitus, often leading to lower-extremity amputation with poor 5-year survival rates. Staphylococcus aureus is the most prevalent pathogen isolated from DFU, suggesting adaptation of S. aureus to the unique metabolic conditions of diabetes. Diabetes is a complex metabolic disorder with increases not only in serum glucose levels but also in levels of other sugars, including fructose, mannose, and glucose-6-phosphate (G6P). However, the effect of metabolism of these sugars on the pathogenesis of S. aureus is not fully understood. In this study, we demonstrated that metabolism of G6P, fructose, and mannose induced greater expression of staphylococcal virulence factors than did glucose metabolism, but only G6P effects were independent of glucose-mediated carbon catabolite repression, suggesting a physiologically relevant role in diabetes. Our in vivo studies further demonstrated that G6P was highly present in skin adipose tissues of diabetic TALLYHO/JngJ mice, and subcutaneous infection with S. aureus caused significantly greater tissue necrosis and bacterial burden, compared to nondiabetic SWR/J mice. Finally, enhanced pathogenesis of S. aureus in diabetic TALLYHO/JngJ mice was significantly attenuated by deletion of the hexose phosphate transport (HPT) system. These results suggest that G6P is an important metabolic signal for S. aureus, enhancing the virulence in diabetes. A better understanding of how G6P metabolism is linked to the virulence of S. aureus will lead to the development of novel alternative therapeutics. IMPORTANCE Sugars are essential nutrients for S. aureus to survive and proliferate within the host. Because elevated serum glucose levels are a hallmark of diabetes, most studies have focused on the effect of glucose metabolism, and very little is known regarding the effects of metabolism of other sugars on the pathogenesis of S. aureus in diabetes. In this study, we demonstrated that G6P, which is highly present in diabetes, can induce expression of staphylococcal virulence factors that cause severe tissue necrosis and bacterial burden in skin infections. Our results highlight the importance of nutritional control of blood sugar levels, not only glucose but also other highly metabolizable sugars such as G6P. A better understanding of how activation of the HPT system is linked to the virulence of S. aureus will guide development of novel alternative therapeutics.

Effect of Chemically-Induced Diabetes Mellitus on Phenotypic Variability of the Enteric Neurons in the Descending Colon in the Pig

Gastrointestinal neuropathy in diabetes is one of numerous diseases resulting in abnormal functioning of the gastrointestinal tract (GIT), and it may affect any section of the GIT, including the descending colon. In the gastrointestinal system, the neurons are arranged in an interconnecting network defined as the enteric nervous system (ENS) which includes the myenteric plexus and the submucosal plexuses: inner and outer. Regular functioning of the ENS is determined by normal synthesis of the neurotransmitters and neuromodulators. This paper demonstrates the effect of hyperglycaemia on the number of enteric neurons which are immunoreactive to: neural isoform of nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), galanin (GAL), calcitonin generelated peptide (CGRP) and cocaine amphetamine-regulated transcript (CART) in the porcine descending colon. It was demonstrated that there was a statistically significant increase in the number of neurons within the myenteric plexus immunoreactive to all investigated substances. In the outer submucosal plexus, the CART-positive neurons were the only ones not to change, whereas no changes were recorded for nNOS or CART in the inner submucosal plexus. This study is the first study to discuss quantitative changes in the neurons immunoreactive to nNOS, VIP, GAL, CGRP and CART in the descending colon in diabetic pigs.

In Vitro Disease Models of the Endocrine Pancreas

The ethical constraints and shortcomings of animal models, combined with the demand to study disease pathogenesis under controlled conditions, are giving rise to a new field at the interface of tissue engineering and pathophysiology, which focuses on the development of in vitro models of disease. In vitro models are defined as synthetic experimental systems that contain living human cells and mimic tissue- and organ-level physiology in vitro by taking advantage of recent advances in tissue engineering and microfabrication. This review provides an overview of in vitro models and focuses specifically on in vitro disease models of the endocrine pancreas and diabetes. First, we briefly review the anatomy, physiology, and pathophysiology of the human pancreas, with an emphasis on islets of Langerhans and beta cell dysfunction. We then discuss different types of in vitro models and fundamental elements that should be considered when developing an in vitro disease model. Finally, we review the current state and breakthroughs in the field of pancreatic in vitro models and conclude with some challenges that need to be addressed in the future development of in vitro models.

Corosolic acid and its structural analogs: A systematic review of their biological activities and underlying mechanism of action

BACKGROUND

The corosolic acid (CA), also known as plant insulin, is a pentacyclic triterpenoid extracted from plants such as Lagerstroemia speciosa. It has been shown to have anti-diabetic, anti-inflammatory and anti-tumor effects. Its structural analogs ursolic acid (UA), oleanolic acid (OA), maslinic acid (MA), asiatic acid (AA) and betulinic acid (BA) display similar individual pharmacological activities to those of CA. However, there is no systematic review documenting pharmacological activities of CA and its structural analogues. This study aims to fill this gap in literature.

PURPOSE

This systematic review aims to summarize the medical applications of CA and its analogues.

METHODS

A systematic review summarizes and compares the extraction techniques, pharmacokinetic parameters, and pharmacological effects of CA and its structural analogs. Hypoglycemic effect is one of the key inclusion criteria for searching Web of Science, PubMed, Embase and Cochrane databases up to October 2020 without language restrictions. 'corosolic acid', 'ursolic acid', 'oleanolic acid', 'maslinic acid', 'asiatic acid', 'betulinic acid', 'extraction', 'pharmacokinetic', 'pharmacological' were used to extract relevant literature. The PRISMA guidelines were followed.

RESULTS

At the end of the searching process, 140 articles were selected for the systematic review. Information of CA and five of its structural analogs including UA, OA, MA, AA and BA were included in this review. CA and its structural analogs are pentacyclic triterpenes extracted from plants and they have low solubilities in water due to their rigid scaffold and hydrophobic properties. The introduction of water-soluble groups such as sugar or amino groups could increase the solubility of CA and its structural analogs. Their biological activities and underlying mechanism of action are reviewed and compared.

CONCLUSION

CA and its structural analogs UA, OA, MA, AA and BA are demonstrated to show activities in lowering blood sugar, anti-inflammation and anti-tumor. Their oral absorption and bioavailability can be improved through structural modification and formulation design. CA and its structural analogs are promising natural product-based lead compounds for further development and mechanistic studies.

Phenolics from Physalis peruviana fruits ameliorate streptozotocin-induced diabetes and diabetic nephropathy in rats via induction of autophagy and apoptosis regression

The objective of our study was to evaluate the effect of Physalis peruviana L. fruits in the management of diabetes and diabetic nephropathy in relation to its metabolic profile. In-vitro α-amylase, β-glucosidase, and lipase inhibition activities were assessed for the ethanolic extract (EtOH) and its subfractions. Ethyl acetate (EtOAc) fraction showed the highest α-amylase, β-glucosidase, and lipase inhibition effect. In vivo antihyperglycemic testing of EtOAc in streptozotocin (STZ)-induced diabetic rats showed that it decreased the blood glucose level, prevented the reduction in body weight, improved serum indicators of kidney injury (urea, uric acid, creatinine), and function (albumin and total protein). EtOAc increased autophagic parameters (LC3B, AMPK) and depressed mTOR contents. Histopathology revealed that EtOAc ameliorated the pathological features and decreased the glycogen content induced by STZ. The immunohistochemical analysis showed that EtOAc reduced P53 expression as compared to the STZ-diabetic group. UPLC-ESI-MS/MS metabolite profiling of EtOAc allowed the identification of several phenolic compounds. Among the isolated compounds, gallic acid, its methylated dimer and the glycosides of quercetin had promising α-amylase and β-glucosidase inhibition activity. The results suggest that the phenolic-rich fraction has a protective effects against diabetic nephropathy presumably via enhancing autophagy (AMPK/mTOR pathway) and prevention of apoptosis (P53 suppression).

A novel model of early type 1 diabetes mellitus: The chick embryo air sack model

Diabetes Mellitus (DM) is a metabolic disease characterized by hyperglycemia. Chronic hyperglycemia is associated with long-term dysfunction such as retinopathy, nephropathy, neuropathy and cardiovascular diseases. These complications increase rates of death and disability worldwide. Due to the negative effects of DM on the quality of life, the mechanism and treatments of the disease should be investigated in more detail. Most of the research in diabetes is performed in experimental animals. Experimental animal models contributed to the advancement of clinical research, the development of new therapeutic approaches, the discovery of insulin and the purification of insulin. There are many animal models of DM in the literature. But there are a few DM model studies created with chick embryos. In these studies, it was seen that there were differences in STZ doses and STZ administration techniques. The objective of this study was to create a more acceptable and easier DM model. 180 specific pathogen free (SPF) fertilized chicken eggs (White Leghorn chicken) were used in this study. STZ was administered to 160 SPF eggs for an induced DM model. The remaining 20 SPF eggs were separated as a control group. We used two different DM models (Air sack model (ASM) and Chorioallantoic membrane model (CAMM)) and blood sampling technique in our study. 160 SPF eggs were divided into two groups with 80 eggs in each group, according to the model in which STZ was administered. When the relationship between blood glucose and blood insulin levels were examined, it was determined that there was a significantly strong negative correlation in the control group and ASM 1 group; and a significantly very strong negative correlation was found in the ASM 2 group and ASM 3 group. Our data indicate that the optimal STZ dose to create a DM model was 0.45 mg/egg and the best DM model was ASM. The second technique to be the best blood sampling technique for determining blood glucose levels. We believe that ASM can be used in DM studies and anti-DM drug studies in terms of its easebly, applicability, reproducibility and low cost.

Local Immunomodulatory Strategies to Prevent Allo-Rejection in Transplantation of Insulin-Producing Cells

Islet transplantation has shown promise as a curative therapy for type 1 diabetes (T1D). However, the side effects of systemic immunosuppression and limited long-term viability of engrafted islets, together with the scarcity of donor organs, highlight an urgent need for the development of new, improved, and safer cell-replacement strategies. Induction of local immunotolerance to prevent allo-rejection against islets and stem cell derived β cells has the potential to improve graft function and broaden the applicability of cellular therapy while minimizing adverse effects of systemic immunosuppression. In this mini review, recent developments in non-encapsulation, local immunomodulatory approaches for T1D cell replacement therapies, including islet/β cell modification, immunomodulatory biomaterial platforms, and co-transplantation of immunomodulatory cells are discussed. Key advantages and remaining challenges in translating such technologies to clinical settings are identified. Although many of the studies discussed are preliminary, the growing interest in the field has led to the exploration of new combinatorial strategies involving cellular engineering, immunotherapy, and novel biomaterials. Such interdisciplinary research will undoubtedly accelerate the development of therapies that can benefit the whole T1D population.

Complications in the spine associated with type 2 diabetes: The role of advanced glycation end-products

Type 2 diabetes mellitus (T2D) is an increasingly prevalent disease with numerous comorbidities including many in the spine. T2D is strongly linked with vertebral fractures, intervertebral disc (IVD) degeneration, and severe chronic spinal pain. Yet the causative mechanism for these musculoskeletal impairments remains unclear. The chronic hyperglycemic state in T2D promotes the formation of advanced glycation end-products (AGEs) in tissues, and the accumulation of AGEs may play a role in musculoskeletal complications by modifying the extracellular matrix, impairing cellular homeostasis, and perpetuating an inflammatory cascade via its receptor (RAGE). The AGE and RAGE associated alterations in extracellular matrix composition and morphological features of the vertebral bodies and IVDs are likely contributors to the incidence and severity of spinal pathologies in T2D. This review will broadly examine the effects of AGEs on tissues in the spine in the context of T2D, with an emphasis on the changes in the vertebrae and the IVD. Along with the clinical and epidemiological findings, we will provide an overview of preclinical rodent models of T2D that exhibit deficits in the IVD and vertebral bone. Elucidating the role of AGEs and RAGE will be crucial for understanding the disease mechanisms and translation therapies of musculoskeletal pathologies in T2D.

Experimental animal models for diabetes and its related complications-a review

Diabetes mellitus, a very common and multifaceted metabolic disorder is considered as one of the fastest growing public health problems in the world. It is characterized by hyperglycemia, a condition with high glucose level in the blood plasma resulting from defects in insulin secretion or its action and in some cases both the impairment in secretion and also action of insulin coexist. Historically, animal models have played a critical role in exploring and describing malady pathophysiology and recognizable proof of targets and surveying new remedial specialists and in vivo medicines. In the present study, we reviewed the experimental models employed for diabetes and for its related complications. This paper reviews briefly the broad chemical induction of alloxan and streptozotocin and its mechanisms associated with type 1 and type 2 diabetes. Also we highlighted the different models in other species and other animals.

Preclinical models of diabetic wound healing: A critical review

The treatment of diabetic wounds (DWs) is always challenging for the medical community because of its multifaceted pathophysiology. Due to practical and ethical considerations, direct studies of therapeutic interventions on human subjects are limited. Thus, it is ideal for performing studies on animals having less genetic and biological variability. An ideal DW model should progress toward reproducibility, quantifiable interpretation, therapeutic significance, and effective translation into clinical use. In the last couple of decades, various animal models were developed to examine the complex cellular and biochemical process of skin restoration in DW healing. Also, these models were used to assess the potency of developed active pharmaceutical ingredients and formulations. However, many animal models lack studying mechanisms that can appropriately restate human DW, stay a huge translational challenge. This review discusses the available animal models with their significance in DW experiments and their limitations, focusing on levels of proof of effectiveness in selecting appropriate models to restate the human DW to improve clinical outcomes. Although numerous newer entities and combinatory formulations are very well appreciated preclinically for DW management, they fail in clinical trials, which may be due to improper selection of the appropriate model. The major future challenge could be developing a model that resembles the human DW environment, can potentiate translational research in DW care.