Experimental Models to Study Diabetes Mellitus and Its Complications: Limitations and New Opportunities

Artificial intelligence in preclinical research: enhancing digital twins and organ-on-chip to reduce animal testing

Artificial intelligence (AI) is reshaping preclinical drug research offering innovative alternatives to traditional animal testing. Advanced techniques, including machine learning (ML), deep learning (DL), AI-powered digital twins (DTs), and AI-enhanced organ-on-a-chip (OoC) platforms, enable precise simulations of complex biological systems. AI plays a critical role in overcoming the limitations of DTs and OoC, improving their predictive power and scalability. These technologies facilitate early-stage, reliable evaluations of drug safety and efficacy, addressing ethical concerns, reducing costs, and accelerating drug development while adhering to the 3Rs principle (Replace, Reduce, Refine). By integrating AI with these advanced models, preclinical research can achieve greater accuracy and efficiency in drug discovery. This review examines the transformative impact of AI in preclinical research, highlighting its advancements, challenges, and the critical steps needed to establish AI as a cornerstone of ethical and efficient drug discovery.

Umbilical Cord Mesenchymal Stem Cells Attenuate Podocyte Injury in Diabetic Nephropathy Rats by Inhibiting Angpltl4/Integrin β3 in the Glomerulus

In this study, we investigated the therapeutic effects and mechanisms of umbilical cord mesenchymal stem cells (UCMSCs) in diabetic nephropathy (DN) ZDF (FA/FA) rats. The therapeutic effects were assessed by renal function tests, the urinary albumin-creatinine ratio, PAS staining, electron microscopy, and TGF-β1 expression in renal tissue. Subsequently, podocyte injury in renal tissue was detected by immunofluorescence staining for podocin. To further explore the underlying mechanism, serum Angptl4 levels were measured, and Angptl4, integrin β3, fibronectin, and podocin levels in renal tissue were analysed by Western blotting. In vitro, podocytes are stimulated with high glucose and then treated with UCMSCs, and podocyte activity and the expression of synaptopodin, Angptl4, and integrin β3 were observed. UCMSC significantly improve renal function, pathological injury, and podocyte injury in the ZDF (FA/FA) rats. Western blot revealed increased expression of Angptl4, integrin β3, and fibronectin in renal tissues of the DN group, and UCMSC treatment significantly downregulated those proteins. However, UCMSC showed no effects on serum Angptl4 concentration. Podocin expression in renal tissues was significantly restored by UCMSC treatment. In vitro, podocyte activity was decreased after high glucose stimulation and improved by UCMSC treatment. UCMSC restored the expression of synaptopodin, and Angptl4 and downstream integrin β3 were also inhibited. Our study suggested that UCMSC therapy could improve renal function and renal pathological changes in ZDF (FA/FA) rats. In addition, inhibition of the Angptl4/integrin β3 pathway is the potential mechanism by which UCMSC attenuates podocyte injury in the DN model.

Differential Responses of Articular Chondrocytes from Diabetic and Non-Diabetic Rats to Glucose Conditions and Inflammatory Stimuli: Influence of a Vitamin K2 Enriched Diet

ObjectiveMeanwhile, the association between osteoarthritis (OA) and type 2 diabetes mellitus (T2DM) is well known. However, it remains unclear whether vitamin K2 (vit.K2) could exert chondroprotective effects. Hence, this study investigates the interrelation between OA and T2DM under the influence of vit.K2 in chondrocytes.MethodsUsing an in vitro OA/T2DM model, articular chondrocytes were harvested from adult male Zucker diabetic fatty (ZDF) Leptfa/Crl rats, categorized as non-diabetic (heterozygous: fa/+) or diabetic (homozygous: fa/fa). Based on vit.K2 supplementation of the rats, four groups arose: control without or with vit.K2 and diabetic without or with vit.K2 supplementation. Inflammatory conditions simulating OA were induced by exposing chondrocytes to tumor necrosis factor alpha (TNFα) and C5a. Chondrocyte response was analyzed using proliferation, metabolic and wound healing assays, immunolabeling, as well as gene expression analyses.ResultsThe proliferation of chondrocytes from control rats with vit.K2 supplementation was significantly higher than those without vit.K2 feeding, under both normoglycemic (NG) and hyperglycemic (HG) conditions. The wound closure ability of chondrocytes was significantly higher in the non-diabetic compared with the diabetic chondrocyte donor group. TNFα and C5a exerted catabolic effects under HG conditions by significantly inducing Tnfα gene activity in chondrocytes of control rats without vit.K2 supplementation and a significant reduction of collagen type 2 gene expression in those cells of control rats with vit.K2 supplementation.ConclusionsThe response of chondrocytes derived from non-diabetic and diabetic donors differed. The vit.K2 supply of chondrocyte donor rats exerted anabolic effects on chondrocytes.

Impact on efficacy of target reduction of two FDA-approved ASO drugs by intracellular glucose levels in in vitro cell models

Antisense oligonucleotides (ASOs) have emerged as a new therapeutic modality for the treatment of both rare and common human diseases. A significant proportion of the patient population that may benefit from ASO therapy may also have common diseases, such as diabetes mellitus. The potential influence of prevalent diseases on the effectiveness of ASO drugs in silencing their target mRNAs remains largely unexplored. The present study utilized in vitro cell models to determine the impact on the efficacy of target reduction of two US Food and Drug Administration (FDA)-approved ASO drugs by intracellular glucose levels. Using inotersen and mipomersen as the FDA-approved ASO model drugs, this study demonstrated that a higher intracellular level of glucose resulted in decreased silencing efficacy of target reduction of inotersen and mipomersen in HepG2 cells. Reducing intracellular glucose levels in HepG2 cells, either by knocking down the glucose transporter GLUT2 or by treating with the antidiabetic drug metformin, reversed the decreased silencing efficacy of inotersen and mipomersen. This study brings to light the first indication about the significant impact of intracellular glucose levels on the silencing efficacy of the FDA-approved ASO drugs in an in vitro model.

Advanced glycation end products promote the progression of endometrial cancer via activating the RAGE/CHKA/PI3K/AKT signaling pathway

Endometrial cancer (EC) is a common malignant tumor that is closely associated with metabolic disorders such as diabetes and obesity. Advanced glycation end products (AGEs) are complex polymers formed by the reaction of reducing sugars with the amino groups of biomacromolecules, mediating the occurrence and development of many chronic metabolic diseases. Recent research has demonstrated that the accumulation of AGEs can affect the tumor microenvironment, metabolism, and signaling pathways, thereby affecting the malignant progression of tumors. However, the mechanism by which AGEs affect EC is unclear. Our research aimed to investigate how AGEs promote the development of EC through metabolic pathways and to explore their potential underlying mechanisms. Our experimental results demonstrated that AGEs upregulated the choline metabolism mediated by choline kinase alpha (CHKA) through the receptor for advanced glycation end products, activating the PI3K/AKT pathway and enhancing the malignant biological behavior of EC cells. Virtual screening and molecular dynamics simulation revealed that timosaponin A3 could target CHKA to inhibit AGE-induced progression of EC and that a newly discovered CHKA inhibitor could be a novel targeted inhibitor for the treatment of EC. This study provides new therapeutic strategies and contributes to the treatment of EC.

Molecular Findings Before Vision Loss in the Streptozotocin-Induced Rat Model of Diabetic Retinopathy

The streptozotocin-induced rat model of diabetic retinopathy presents similarities to the disease observed in humans. After four weeks following the induction of diabetes, the rats experience vision impairment. During this crucial four-week period, significant changes occur, with vascular damage standing out as a clinically significant factor, alongside neovascularization. While redox imbalance, activation of microglia, secretion of pro-inflammatory cytokines, and neuronal cell death are also observed, the latter remains an emerging hypothesis requiring further exploration. This review is a comprehensive and up-to-date chronological depiction of the progression of diabetic retinopathy within the initial four weeks of hyperglycemia, which precede the onset of vision loss. The data are structured in weekly changes. In the first week, oxidative stress triggers the activation of retinal microglia, which produces inflammation, leading to altered neurotransmission. The second week is characterized by leukostasis, which promotes ischemia, while neural degeneration begins and is accompanied by a simultaneous increase in vessel permeability. The progression of redox and inflammatory imbalances characterized the third week. Finally, in the fourth week, significant developments occur as vessels dilate and become tortuous, neovascularization develops, and retinal thickness diminishes, ultimately leading to vision loss. Through this clearly structured outline, this review aims to delineate a framework for the progression of streptozotocin-induced diabetic retinopathy.

Potentilla fulgens root extract rich in polyphenols ameliorate diabetic foot ulcers in wistar rats via regulating oxidative stress and connective tissue markers

BACKGROUND

Potentilla fulgens (Wall.) ex Hook. (Rosaceae), commonly known as 'Bajradanti' is native to the lower Himalayan regions inclusive of the North-East India. Traditionally, the plant is used to treat chronic ailments like diabetes and diverse wounds, including gastric and mouth ulcers, and injuries from tiger bites.

OBJECTIVE

This study aims to assess the efficacy of P. fulgens root extract rich in polyphenolics in healing diabetic foot ulcer (DFU) in rats.

METHODS

DFU was induced in streptozotocin-nicotinamide diabetic rat feet by open excision wound model. Rats were divided into eight groups (n = 6/group): normal, negative control, plain gel (placebo) control, 1% silver sulfadiazine, and P. fulgens treated with topical ethyl acetate (EAPF, 5% and 10%) and methanol extract (MEPF, 5% and 10%). The morphological, histological and various biochemical parameters associated with the wound healing process such as connective tissue repair and oxidative stress biomarkers were evaluated.

RESULTS

Topical application of EAPF 10% and MEPF 10% over 21 days significantly (p < 0.05) reduced ulcer area in DFU rats compared to negative control. Furthermore, the extracts treated group notably (p < 0.05) increased levels of connective tissue biomarkers (total protein, hydroxyproline, hexosamine, and hexuronic acid) and antioxidant components (SOD and GSH), while significantly (p < 0.05) decreasing levels of lipid peroxidation (LPO) in foot tissue homogenate. Histological analysis of rats treated with the extracts revealed significant evidence of tissue repair, characterised by enhanced epithelial and collagen formation, along with decreased polymorphonuclear infiltration and edema.

CONCLUSION

In summary, treatment with EAPF 10% significantly improved foot ulcers by modulating oxidative stress and connective tissue biomarkers in DFU animals.

The relevance of the heme oxygenase system in alleviating diabetes-related hormonal and metabolic disorders

Heme oxygenase (HO) is an enzyme that catalyzes heme degradation. HO dysfunction is linked to various pathological conditions, including diabetes. Results of animal studies indicate that HO expression and activity are downregulated in experimentally induced diabetes. This is associated with severe hormonal and metabolic disturbances. However, these pathological changes have been shown to be reversed by therapy with HO activators. In animals with experimentally induced diabetes, HO was upregulated by genetic manipulation or by pharmacological activators such as hemin and cobalt protoporphyrin. Induction of HO alleviated elevated blood glucose levels and improved insulin action, among other effects. This effect resulted from beneficial changes in the main insulin-sensitive tissues, i.e., the skeletal muscle, the liver, and the adipose tissue. The action of HO activators was due to positive alterations in pivotal signaling molecules and regulatory enzymes. Furthermore, diabetes-related oxidative and inflammatory stress was reduced due to HO induction. HO upregulation was effective in various animal models of type 1 and type 2 diabetes. These data suggest the possibility of testing HO activators as a potential tool for alleviating hormonal and metabolic disorders in people with diabetes.

Sustained release of nano-encapsulated glimepiride drug with chitosan nanoparticles: A novel approach to control type 2 diabetes in streptozotocin-induced Wistar albino rats

The objective of the present study was to encapsulate the effective antidiabetic glimepiride (GLM) drug with biodegradable chitosan nanoparticles (CS NPs) in order to reduce the risk of side effects, regulate and improve alternatives to therapy for people with type 2 Diabetes mellitus. The characterizations of the encapsulated EGLM-CS NPs were published in a previous paper. In continuation of the past study, here we report the in vitro and in vivo activities of EGLM-CS NPs in streptozotocin-induced diabetes Wistar albino rats orally treated for 28 days. Based on our results, the in vitro 3 T3-L1 cell lines observed that the highest concentration of 500 μg/mL exhibited 91.48 % cell viability after 24 h of treatment. The in vivo results of the EGLM-CS NPs treated rats group showed gradual control of the blood glucose level at 90 and 120 min compared to other groups because the drug showed a sustained release mechanism. A significant difference was observed in serum lipid profiles between diabetic treated and control rats. It is believed that the CS NPs served as a carrier system for the GLM drug, protected it from degradation, and enhanced its solubility as well as bioavailability. After 28 days of treatment, all the animal groups organs (pancreas, liver, and kidney) were dissected for histopathological analysis. The EGLM-CS NPs treated group displayed regeneration cells of the islets of Langerhans in the pancreas and normal cellular size with hyperplasia. The therapeutic potential was observed by the liver and kidney from rats reveals few tubule necrosis, improved bioavailability as compared to pure GLM drug treated rats. Hence, our formulated NPs are safe, no toxic effect on the vital organs, which will be helpful to improve the lives of diabetic patients and contribute to the overall health of the individuals.

Neuroprotective role of curcumin on the hippocampus against the oxidative stress and inflammation of streptozotocin-induced diabetes in rats

In recent years, it has gained importance to determine the effects of diabetes on central nervous system complications. This study aimed to assess the neuroprotective properties of curcumin against neuronal damage in the rat hippocampus caused by diabetes. In accordance with this purpose, we investigated the effects of curcumin on oxidative/antioxidative parameters and pro-inflammatory cytokines in the hippocampal tissue of diabetic Wistar rats. For this purpose, 32 adults, male and healthy Wistar Albino rats were used. Animals were randomly divided into four separate groups: control (C), curcumin(Cu), diabetes (D) and Diabetes + Curcumin (DCu)-treated groups. 60 mg/kg STZ i.p. A single dose was administered to D and DCu groups. Cu and DCu groups were given 50 mg/kg/day curcumin by gavage. After four weeks of treatment, the animals were decapitated under anesthesia and tissue samples were taken for analyses of the parameters (TNF-α, IL-6, IL-1, IL-10, MDA, SOD, catalase, and GSH activities) in the hippocampal tissue. TNF-α, IL-6, IL-1, and MDA levels were increased significantly (p < 0.05) in rats with diabetes compared to the other three groups. TNF-α, IL-6, IL-1, and MDA levels were lower in DCu group animals compared to the D group. It was determined that IL-10, SOD, Catalase, and GSH levels, which were significantly decreased in the D group, increased in the curcumin-supplemented diabetic group (DCu). The relevant sentence has been changed as follows. In conclusion, our findings from this study prove the protective effect of curcumin against diabetes-induced neuropathy in the hippocampus in rats with STZ-induced diabetes.

Diabetes mellitus and female sexual response: what do animal models tell us?

BACKGROUND

One of the less explored effects of diabetes mellitus (DM) is female sexual dysfunction. Females of different species have been used as models.

AIM

To analyze the information of animal models of DM and female sexual response (FSR).

METHODS

The literature of FSR in models of DM was reviewed.

OUTCOMES

Paradigm- and diabetes-dependent changes have been found in various aspects of the FSR.

RESULTS

Females in a type 1 DM (DM1) model show a decrease in the number of proestrus events, and ovariectomized females treated with sex hormones have been used. In these females, a reduction in lordosis has been reported; in proceptivity, the data are contradictory. These females present a decrease in sexual motivation that was restored after exogenous insulin. In the type 2 DM (DM2) model, females show regular estrous cycles, normal levels of lordosis behavior, and, depending on the paradigm, decreased proceptivity. These females display normal preference for sexually active males or their olfactory cues when having free physical contact; they lose this preference when tested in paradigms where physical interaction is precluded.

CLINICAL TRANSLATION

Preclinical data showing the high deleterious effects of a DM1 model and the less drastic effects under a DM2 model are in accordance with clinical data revealing a much higher prevalence of sexual dysfunction in women with DM1 than DM2.

STRENGTHS AND LIMITATIONS

The main strength is the analysis of the changes in various components of FSR in 2 models of DM. The main limitation is the difficulty in extrapolating the data on FSR from rats to women and that most studies focus on evaluating the impact of severe or chronic-moderate hyperglycemia/hyperinsulinemia on the sexual response, without considering other pathophysiologic alterations generated by DM.

CONCLUSION

Females with severe hyperglycemia have a decrease in FSR, while those with moderate hyperglycemia show much less drastic effects.

Effects of Some Olive Fruits-Derived Products on Oxidative Stress and Cardiovascular Biomarkers on Experimental Diabetes Mellitus

The aim of this study is to assess the possible effect of olive seed oil (OSO) and destoned and dehydrated olive oil (DDOO), in comparison with extra-virgin olive oil (EVOO), on some cardiovascular biomarkers in an experimental model of diabetes mellitus. Diabetic animals showed evident alterations in biomarkers involved in the evolution of diabetic vasculopathy, marked by increases in biomarkers that favor vascular damage, which was between 1.5 and five times as many as those in non-diabetic animals, and a smaller number of biomarkers that protect against such damage (25-75% less than in healthy controls) was observed. The three oils administered decreased the concentration of biomarkers of vascular damage (35-45% in the serum lipid profile, 15-40% in early biomarkers of vascular inflammation and 20-60% in platelet aggregation and in thromboxane/prostacyclin imbalance). The greatest effect was by the antioxidant, both in the inhibition of lipid peroxidation and in the increase of glutathione. DDOO showed a significantly greater effect on oxidative stress and on thromboxane/prostacyclin imbalance than those shown by OSO and EVOO. This greater effect may possibly be explained by its higher triterpenoid content (913 mg/kg, compared to 113 mg/kg in OSO and 75 mg/kg in EVOO). We conclude, in the light of the results of this study, that these oils meet two basic conditions: they could improve the yield of the olive industry, and they equal, and may even increase, the beneficial effects of EVOO on cardiovascular disease.

Cilostazol Ameliorates Motor Dysfunction and Schwann Cell Impairment in Streptozotocin-Induced Diabetic Rats

This study investigated the effects of cilostazol on motor dysfunction, spinal motor neuron abnormalities, and schwannopathy in rats with diabetes. Diabetes mellitus (DM) was induced in rats via femoral intravenous streptozotocin (STZ) injection (60 mg/kg). After successful DM induction, cilostazol was administered on day 15 via oral gavage (100 mg/kg/day) for 6 weeks until sacrifice. Behavioral assays, including motor function, were performed weekly. The sciatic nerve, L5 spinal cord, and spinal ventral root were collected to evaluate the expression of the glial fibrillary acidic protein (GFAP), myelin protein zero (P0), and choline acetyltransferase (ChAT) by immunofluorescence and Western blotting. DM rats displayed decreased running speeds, running distances, and toe spread but increased foot pressure. In addition, loss of non-myelinating Schwann cells and myelin sheaths was observed in the sciatic nerve and L5 spinal ventral root. Reduced numbers of motor neurons were also found in the L5 spinal ventral horn. Cilostazol administration significantly potentiated running speed and distance; increased hind paw toe spread; and decreased foot pressure. In the sciatic nerve and L5 spinal ventral root, cilostazol treatment significantly improved non-myelinated Schwann cells and increased myelin mass. ChAT expression in motor neurons in the spinal ventral horn was improved, but not significantly. Cilostazol administration may protect sensorimotor function in diabetic rats.

RatDEGdb: a knowledge base of differentially expressed genes in the rat as a model object in biomedical research

The animal models used in biomedical research cover virtually every human disease. RatDEGdb, a knowledge base of the differentially expressed genes (DEGs) of the rat as a model object in biomedical research is a collection of published data on gene expression in rat strains simulating arterial hypertension, age-related diseases, psychopathological conditions and other human afflictions. The current release contains information on 25,101 DEGs representing 14,320 unique rat genes that change transcription levels in 21 tissues of 10 genetic rat strains used as models of 11 human diseases based on 45 original scientific papers. RatDEGdb is novel in that, unlike any other biomedical database, it offers the manually curated annotations of DEGs in model rats with the use of independent clinical data on equal changes in the expression of homologous genes revealed in people with pathologies. The rat DEGs put in RatDEGdb were annotated with equal changes in the expression of their human homologs in affected people. In its current release, RatDEGdb contains 94,873 such annotations for 321 human genes in 836 diseases based on 959 original scientific papers found in the current PubMed. RatDEGdb may be interesting first of all to human geneticists, molecular biologists, clinical physicians, genetic advisors as well as experts in biopharmaceutics, bioinformatics and personalized genomics. RatDEGdb is publicly available at https://www.sysbio.ru/RatDEGdb.