The mechanisms of alloxan- and streptozotocin-induced diabetes

Diabetic retinopathy: a comprehensive update on in vivo, in vitro and ex vivo experimental models

Diabetic retinopathy (DR), one of the leading causes of visual impairment and blindness worldwide, is one of the major microvascular complications in diabetes mellitus (DM). Globally, DR prevalence among DM patients is 25%, and 6% have vision-threatening problems among them. With the higher incidence of DM globally, more DR cases are expected to be seen in the future. In order to comprehend the pathophysiological mechanism of DR in humans and discover potential novel substances for the treatment of DR, investigations are typically conducted using various experimental models. Among the experimental models, in vivo models have contributed significantly to understanding DR pathogenesis. There are several types of in vivo models for DR research, which include chemical-induced, surgical-induced, diet-induced, and genetic models. Similarly, for the in vitro models, there are several cell types that are utilised in DR research, such as retinal endothelial cells, Müller cells, and glial cells. With the advancement of DR research, it is essential to have a comprehensive update on the various experimental models utilised to mimic DR environment. This review provides the update on the in vitro, in vivo, and ex vivo models used in DR research, focusing on their features, advantages, and limitations.

Identifying key genes for diabetic kidney disease by bioinformatics analysis

BACKGROUND

There are no reliable molecular targets for early diagnosis and effective treatment in the clinical management of diabetic kidney disease (DKD). To identify novel gene factors underlying the progression of DKD.

METHODS

The public transcriptomic datasets of the alloxan-induced DKD model and the streptozotocin-induced DKD model were retrieved to perform an integrative bioinformatic analysis of differentially expressed genes (DEGs) shared by two experimental animal models. The dominant biological processes and pathways associated with DEGs were identified through enrichment analysis. The expression changes of the key DEGs were validated in the classic db/db DKD mouse model.

RESULTS

The downregulated and upregulated genes in DKD models were uncovered from GSE139317 and GSE131221 microarray datasets. Enrichment analysis revealed that metabolic process, extracellular exosomes, and hydrolase activity are shared biological processes and molecular activity is altered in the DEGs. Importantly, Hmgcs2, angptl4, and Slco1a1 displayed a consistent expression pattern across the two DKD models. In the classic db/db DKD mice, Hmgcs2 and angptl4 were also found to be upregulated while Slco1a1 was downregulated in comparison to the control animals.

CONCLUSIONS

In summary, we identified the common biological processes and molecular activity being altered in two DKD experimental models, as well as the novel gene factors (Hmgcs2, Angptl4, and Slco1a1) which may be implicated in DKD. Future works are warranted to decipher the biological role of these genes in the pathogenesis of DKD.

Antidiabetic and antihyperlipidemic activities of Phyllanthus emblica L. extract in vitro and the regulation of Akt phosphorylation, gluconeogenesis, and peroxisome proliferator-activated receptor α in streptozotocin-induced diabetic mice

Background

The fruits of Phyllanthus emblica L. are high in nutrients and have excellent health care function and developmental value. There are many management strategies available for diabetes and hyperlipidemia. Nevertheless, there is a lack of an effective and nontoxic drug.

Objective

The present study was designed to first screen four extracts of P. emblica L. on insulin signaling target gene expression levels, including glucose transporter 4 (GLUT4) and p-Akt/t-Akt. The ethyl acetate extract of P. emblica L. (EPE) exhibited the most efficient activity among the four extracts and was thus chosen to explore the antidiabetic and antihyperlipidemic activities in streptozotocin (STZ)-induced type 1 diabetic mice.

Design

All mice (in addition to one control (CON) group) were administered STZ injections (intraperitoneal) for 5 consecutive days, and then STZ-induced mice were administered EPE (at 100, 200, or 400 mg/kg body weight), fenofibrate (Feno) (at 250 mg/kg body weight), glibenclamide (Glib) (at 10 mg/kg body weight), or vehicle by oral gavage once daily for 4 weeks. Finally, histological examination, blood biochemical parameters, and target gene mRNA expression levels were measured, and liver tissue was analyzed for the levels of malondialdehyde (MDA), a maker of lipid peroxidation.

Results

EPE treatment resulted in decreased levels of blood glucose, HbA1C, triglycerides (TGs), and total cholesterol and increased levels of insulin compared with the vehicle-treated STZ group. EPE treatment decreased blood levels of HbA1C and MDA but increased glutathione levels in liver tissue, implying that EPE exerts antioxidant activity and could prevent oxidative stress and diabetes. The EPE-treated STZ mice displayed an improvement in the sizes and numbers of insulin-expressing β cells. EPE treatment increased the membrane expression levels of skeletal muscular GLUT4, and also reduced hepatic mRNA levels of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase thereby inhibiting hepatic gluconeogenesis. This resulted in a net glucose lowering effect in EPE-treated STZ mice. Furthermore, EPE increased the expression levels of p-AMPK/t-AMPK in both the skeletal muscle and liver tissue compared with vehicle-treated STZ mice. EPE-treated STZ mice showed enhanced expression levels of fatty acid oxidation enzymes, including peroxisome proliferator-activated receptor α (PPARα), but reduced expression levels of lipogenic genes including fatty acid synthase, as well as decreased mRNA levels of sterol regulatory element binding protein 1c (SREBP1c), apolipoprotein-CIII (apo-CIII), and diacylglycerol acyltransferase-2 (DGAT2). This resulted in a reduction in plasma TG levels. EPE-treated STZ mice also showed reduced expression levels of PPAR γ. This resulted in decreased adipogenesis, fatty acid synthesis, and lipid accumulation within liver tissue, and consequently, lower TG levels in liver tissue and blood. Furthermore, EPE treatment not only displayed an increase in the Akt activation in liver tissue, but also in C2C12 myotube in the absence of insulin. These results implied that EPE acts as an activator of AMPK and /or as a regulator of the insulin (Akt) pathway.

Conclusions

Taken together, EPE treatment exhibited amelioration of the diabetic and hyperlipidemic state in STZ-induced diabetic mice.

Transient neonatal hyperglycemia induces metabolic shifts in the rat hippocampus: a 1H NMR-based metabolomics analysis

Diabetes has been reported to induce brain metabolic disturbance, but the effect of transient neonatal hyperglycemia (TNH) on brain metabolism remains unclear. Herein the rats were treated with a single intraperitoneal injection of 100 µg/g body weight of streptozotocin within 12 h after birth and displayed a typical clinical characteristic of TNH. Then we used NMR-based metabolomics to examine the metabolic changes in the hippocampus between TNH and normal control (Ctrl) rats at postnatal 7 days (P7) and 21 days (P21). The results show that TNH rats had significantly increased levels of N-acetyl aspartate, glutamine, aspartate and choline in the hippocampus relative to Ctrl rats at P7. Moreover, we found that the levels of alanine, myo-inositol and choline were significantly lower in TNH rats, although their blood glucose levels have been recovered to the normal level at P21. Therefore, our results suggest that TNH may have a long-term effect on hippocampal metabolic changes mainly involving neurotransmitter metabolism and choline metabolism.

Dental implants in large animal models with experimental systemic diseases: A systematic review

This systematic review aims to identify and discuss the most used methodologies in pre-clinical studies for the evaluation of the implementation of dental implants in systemically compromised pigs and sheep. This study provides support and guidance for future research, as well as for the prevention of unnecessary animal wastage and sacrifice. Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) was used as a guideline; electronic searches were performed in PubMed, Scopus, Scielo, Web of Science, Embase, Science Direct, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Directory of Open Access Journals, Database of Abstracts of Reviews of Effects, and gray literature until January 2022 (PROSPERO/CRD42021270119). Sixty-eight articles were chosen from the 2439 results. Most studies were conducted in pigs, mainly the Göttinger and Domesticus breeds. Healthy animals with implants installed in the jaws were predominant among the pig studies. Of the studies evaluating the effect of systemic diseases on osseointegration, 42% were performed in osteoporotic sheep, 32% in diabetic sheep, and 26% in diabetic pigs. Osteoporosis was primarily induced by bilateral ovariectomy and mainly assessed by X-ray densitometry. Diabetes was induced predominantly by intravenous streptozotocin and was confirmed by blood glucose analysis. Histological and histomorphometric analyses were the most frequently employed in the evaluation of osseointegration. The animal models presented unique methodologies for each species in the studies that evaluated dental implants in the context of systemic diseases. Understanding the most commonly used techniques will help methodological choices and the performance of future studies in implantology.

Extracellular Matrix Influences Gene Expression and Differentiation of Mouse Trophoblast Stem Cells

Trophoblast stem (TS) cells were first isolated from the mouse placenta; however, little is known about their maintenance and niche in vivo. TS cells, like other stem cells, have a unique microenvironment in which the extracellular matrix (ECM) is a component. Placental pathology is associated with ECM change. However, how these changes and the individual ECM components impact the maintenance or differentiation of TS cells has not been established. This study identified which ECM component(s) maintain the greatest expression of markers associated with undifferentiated mouse trophoblast stem (mTS) cells and which alter the profile of markers of differentiation based on mRNA analysis. mTS cells cultured on individual ECM components and subsequent quantitative polymerase chain reaction analysis revealed that laminin promoted the expression of markers associated with undifferentiated TS cells, fibronectin promoted gene expression associated with syncytiotrophoblast (SynT) layer II cells, and collagen IV promoted the expression of genes associated with differentiated trophoblast. To investigate whether pathological placental ECM influenced the expression of genes associated with different trophoblast subtypes, the mouse model of streptozotocin (STZ)-induced pancreatic β cell ablation and diabetes was used. Female mice administered STZ (blood glucose ≥300 mg/dL) or control (blood glucose ≤150 mg/dL) were mated. Placental pathology at embryonic day (E)14.5 was confirmed with reduced fetal blood space area, reduced expression of the pericyte marker αSMA, and decreased expression of ECM proteins. mTS cells cultured on ECM isolated from STZ placenta were associated with reduced expression of undifferentiated mTS markers and increased expression of genes associated with terminally differentiated trophoblast [Gcm-1 and SynA (SynT) and junctional zone Tpbpa and Prl2c2]. Altogether, these results support the value of using ECM isolated from the placenta as a tool for understanding trophoblast contribution to placental pathology.

A delve into the pharmacological targets and biological mechanisms of Paederia foetida Linn.: a rather invaluable traditional medicinal plant

Drug development from herbal medicines or botanical sources is believed to have a prominent role in the exploration of novel counteractive drugs that has sparked much interest in recent times. Paederia foetida is one such medicinal plant used in both traditional and folkloric medicine. Several parts of the herb are locally utilised as a natural curative agent for several ailments since time immemorial. Paederia foetida indeed possesses anti-diabetic, anti-hyperlipidaemic, antioxidant, nephro-protective, anti-inflammatory, antinociceptive, antitussive, thrombolytic, anti-diarrhoeal, sedative-anxiolytic, anti-ulcer, hepatoprotective activity, anthelmintic and anti-diarrhoeal activity. Furthermore, growing evidence shows many of its active constituents to be effective in cancer, inflammatory diseases, wound healing and spermatogenesis as well. These investigations shed light on possible pharmacological targets and attempts to establish a mechanism of action for these pharmacological effects. These findings contrast the significance of this medicinal plant for further research and for the exploration of novel counteractive drugs to establish a mechanism of action before being employed to healthcare. Pharmacological activities of Paederia foetida and their mechanism of action.

Bergenin ameliorates diabetic nephropathy in C57BL/6 J mice by TLR4/MyD88/NF-κB signalling pathway regulation

Bergenin (BG) is a polyphenolic substance which has therapeutic potential in the treatment of diabetic nephropathy (DN), a common complication of type II diabetes. However, the mechanisms underlying these effects remain unclear. We studied the protective effects and mechanisms of BG in DN mice, focusing on the TLR4/MyD88/NF-κB signalling pathway. C57BL/6 J mice were used as experiments (n=60), and 10 animals were randomly selected as normal control. The DN model was developed by administering an intraperitoneal injection of streptozotocin (40 mg/kg BW for three days) and a high-fat diet (n=50). BG (20, 40, and 80 mg/kg BW, once a day) was administered orally for four weeks. After BG treatment, the food and water intake of DN mice decreased, blood glucose levels decreased, and insulin resistance reduced. As a result, serum LDL-C, TC, and TG levels decreased; HDL-C levels increased; SOD, CAT, and GSH-Px levels decreased; and MDA levels increased. BG administration reduced AST, ALT, BUN, and CRE levels and inflammatory factors (including TNF-α, MCP-1, IL-1β, and IL-6). Histopathology revealed a significant improvement in pathological damage to the liver, kidney, and spleen of mice treated with BG, and TLR4, MyD88, and NF-κB p65 were down-regulated at both mRNA and protein levels in the BG-treated group. Based on these results, BG therapeutic type II DN by hypoglycaemia, improving liver and kidney function, and anti-oxidative stress; reducing inflammation; and inhibiting the TLR4/MyD88/NF-κB signalling pathway. The results of this study suggest that BG can be used as an effective treatment for type II DN.

Mitochondrial pyruvate metabolism and glutaminolysis toggle steady-state and emergency myelopoiesis

To define the metabolic requirements of hematopoiesis, we examined blood lineages in mice conditionally deficient in genes required for long-chain fatty acid oxidation (Cpt2), glutaminolysis (Gls), or mitochondrial pyruvate import (Mpc2). Genetic ablation of Cpt2 or Gls minimally impacted most blood lineages. In contrast, deletion of Mpc2 led to a sharp decline in mature myeloid cells and a slower reduction in T cells, whereas other hematopoietic lineages were unaffected. Yet MPC2-deficient monocytes and neutrophils rapidly recovered due to a transient and specific increase in myeloid progenitor proliferation. Competitive bone marrow chimera and stable isotope tracing experiments demonstrated that this proliferative burst was progenitor intrinsic and accompanied by a metabolic switch to glutaminolysis. Myeloid recovery after loss of MPC2 or cyclophosphamide treatment was delayed in the absence of GLS. Reciprocally, MPC2 was not required for myeloid recovery after cyclophosphamide treatment. Thus, mitochondrial pyruvate metabolism maintains myelopoiesis under steady-state conditions, while glutaminolysis in progenitors promotes emergency myelopoiesis.

Research progress of dihydromyricetin in the treatment of diabetes mellitus

Diabetic Mellitus (DM), a chronic metabolic disorder disease characterized by hyperglycemia, is mainly caused by the absolute or relative deficiency of insulin secretion or decreased insulin sensitivity in target tissue cells. Dihydromyricetin (DMY) is a flavonoid compound of dihydroflavonol that widely exists in Ampelopsis grossedentata. This review aims to summarize the research progress of DMY in the treatment of DM. A detailed summary of related signaling induced by DMY are discussed. Increasing evidence implicates that DMY display hypoglycemic effects in DM via improving glucose and lipid metabolism, attenuating inflammatory responses, and reducing oxidative stress, with the signal transduction pathways underlying the regulation of AMPK or mTOR/autophagy, and relevant downstream cascades, including PGC-1α/SIRT3, MEK/ERK, and PI3K/Akt signal pathways. Hence, the mechanisms underlying the therapeutic implications of DMY in DM are still obscure. In this review, following with a brief introduction of the absorption, metabolism, distribution, and excretion characteristics of DMY, we summarized the current pharmacological developments of DMY as well as possible molecular mechanisms in the treatment of DM, aiming to push the understanding about the protective role of DMY as well as its preclinical assessment of novel application.

Delineating mouse β-cell identity during lifetime and in diabetes with a single cell atlas

Although multiple pancreatic islet single-cell RNA-sequencing (scRNA-seq) datasets have been generated, a consensus on pancreatic cell states in development, homeostasis and diabetes as well as the value of preclinical animal models is missing. Here, we present an scRNA-seq cross-condition mouse islet atlas (MIA), a curated resource for interactive exploration and computational querying. We integrate over 300,000 cells from nine scRNA-seq datasets consisting of 56 samples, varying in age, sex and diabetes models, including an autoimmune type 1 diabetes model (NOD), a glucotoxicity/lipotoxicity type 2 diabetes model (db/db) and a chemical streptozotocin β-cell ablation model. The β-cell landscape of MIA reveals new cell states during disease progression and cross-publication differences between previously suggested marker genes. We show that β-cells in the streptozotocin model transcriptionally correlate with those in human type 2 diabetes and mouse db/db models, but are less similar to human type 1 diabetes and mouse NOD β-cells. We also report pathways that are shared between β-cells in immature, aged and diabetes models. MIA enables a comprehensive analysis of β-cell responses to different stressors, providing a roadmap for the understanding of β-cell plasticity, compensation and demise.

The functional maturity of grafted human pluripotent stem cell derived-islets (hSC-Islets) evaluated by the glycemic set point during blood glucose normalizing process in diabetic mice

Human pluripotent stem cell (hPSCs) derived-pancreatic islets (hSC-islets) are good candidates for cell replacement therapy for patients with diabetes as substitutes for deceased donor-derived islets, because they are pluripotent and have infinite proliferation potential. Grafted hSC-islets ameliorate hyperglycemia in diabetic mice; however, several weeks are needed to normalize the hyperglycemia. These data suggest hSC-islets require maturation, but their maturation process in vivo is not yet fully understood. In this study, we utilized two kinds of streptozotocin (STZ)-induced diabetes model mice by changing the administration timing in order to examine the time course of maturation of hSC-islets and the effects of hyperglycemia on their maturation. We found no hyperglycemia in immune-compromised mice when hSC-islets had been transplanted under their kidney capsules in advance, and STZ was administered 4 weeks after transplantation. Of note, the blood glucose levels of those mice were stably maintained under 100 mg/dl 10 weeks after transplantation; this is lower than the mouse glycemic set point (120-150 mg/dl), suggesting that hSC-islets control blood glucose levels to the human glycemic set point. We confirmed that gene expression of maturation markers of pancreatic beta cells tended to upregulate during 4 weeks after transplantation. Periodical histological analysis revealed that revascularization was observed as early as 1 week after transplantation, but reinnervation in the grafted hSC-islets was not detected at all, even 15 weeks after transplantation. In conclusion, our hSC-islets need at least 4 weeks to mature, and the human glycemic set point is a good index for evaluating ultimate maturity for hSC-islets in vivo.

Cross-Regulation Between Redox and Epigenetic Systems in Tumorigenesis: Molecular Mechanisms and Clinical Applications

Significance: Redox and epigenetics are two important regulatory processes of cell physiological functions. The cross-regulation between these processes has critical effects on the occurrence and development of various types of tumors. Recent Advances: The core factor that influences redox balance is reactive oxygen species (ROS) generation. The ROS functions as a double-edged sword in tumors: Low levels of ROS promote tumors, whereas excessive ROS induces various forms of tumor cell death, including apoptosis and ferroptosis as well as necroptosis and pyroptosis. Many studies have shown that the redox balance is influenced by epigenetic mechanisms such as DNA methylation, histone modification, chromatin remodeling, non-coding RNAs (microRNA, long non-coding RNA, and circular RNA), and RNA N6-methyladenosine modification. Several oxidizing or reducing substances also affect the epigenetic state. Critical Issues: In this review, we summarize research on the cross-regulation between redox and epigenetics in cancer and discuss the relevant molecular mechanisms. We also discuss the current research on the clinical applications. Future Directions: Future research can use high-throughput methods to analyze the molecular mechanisms of the cross-regulation between redox and epigenetics using both in vitro and in vivo models in more detail, elucidate regulatory mechanisms, and provide guidance for clinical treatment. Antioxid. Redox Signal. 39, 445-471.

Autophagy signaling in hypertrophied muscles of diabetic and control rats

Autophagy plays a vital role in cell homeostasis by eliminating nonfunctional components and promoting cell survival. Here, we examined the levels of autophagy signaling proteins after 7 days of overload hypertrophy in the extensor digitorum longus (EDL) and soleus muscles of control and diabetic rats. We compared control and 3-day streptozotocin-induced diabetic rats, an experimental model for type 1 diabetes mellitus (T1DM). EDL muscles showed increased levels of basal autophagy signaling proteins. The diabetic state did not affect the extent of overload-induced hypertrophy or the levels of autophagy signaling proteins (p-ULK1, Beclin-1, Atg5, Atg12-5, Atg7, Atg3, LC3-I and II, and p62) in either muscle. The p-ULK-1, Beclin-1, and p62 protein expression levels were higher in the EDL muscle than in the soleus before the hypertrophic stimulus. On the contrary, the soleus muscle exhibited increased autophagic signaling after overload-induced hypertrophy, with increases in Beclin-1, Atg5, Atg12-5, Atg7, Atg3, and LC3-I expression in the control and diabetic groups, in addition to p-ULK-1 in the control groups. After hypertrophy, Beclin-1 and Atg5 levels increased in the EDL muscle of both groups, while p-ULK1 and LC3-I increased in the control group. In conclusion, the baseline EDL muscle exhibited higher autophagy than the soleus muscle. Although TDM1 promotes skeletal muscle mass loss and strength reduction, it did not significantly alter the extent of overload-induced hypertrophy and autophagy signaling proteins in EDL and soleus muscles, with the two groups exhibiting different patterns of autophagy activation.

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.

Dose-dependent progression of multiple low-dose streptozotocin-induced diabetes in mice

This study investigated the effects of different multiple low doses of streptozotocin (STZ), namely 35 and 55 mg/kg, on the onset and progression of diabetes in mice. Both doses are commonly used in research, and although both induced a loss of beta cell mass, they had distinct effects on whole glucose tolerance, beta cell function, and gene transcription. Mice treated with 55 mg/kg became rapidly glucose intolerant, whereas those treated with 35 mg/kg had a slower onset and remained glucose tolerant for up to a week before becoming equally glucose intolerant as the 55 mg/kg group. Beta cell mass loss was similar between the two groups, but the 35 mg/kg-treated mice had improved glucose-stimulated insulin secretion in gold-standard hyperglycemic clamp studies. Transcriptomic analysis revealed that the 55 mg/kg dose caused disruptions in nearly five times as many genes as the 35 mg/kg dose in isolated pancreatic islets. Pathways that were downregulated in both doses were more downregulated in the 55 mg/kg-treated mice, whereas pathways that were upregulated in both doses were more upregulated in the 35 mg/kg-treated mice. Moreover, we observed a differential downregulation in the 55 mg/kg-treated islets of beta cell characteristic pathways, such as exocytosis or hormone secretion. On the other hand, apoptosis was differentially upregulated in 35 mg/kg-treated islets, suggesting different transcriptional mechanisms in the onset of STZ-induced damage in the islets. This study demonstrates that the two STZ doses induce distinctly mechanistic progressions for the loss of functional beta cell mass.

Feeding enhances fibronectin adherence of quiescent lymphocytes through non-canonical insulin signalling

Nutritional availability during fasting and refeeding affects the temporal redistribution of lymphoid and myeloid immune cells among the circulating and tissue-resident pools. Conversely, nutritional imbalance and impaired glucose metabolism are associated with chronic inflammation, aberrant immunity and anomalous leukocyte trafficking. Despite being exposed to periodic alterations in blood insulin levels upon fasting and feeding, studies exploring the physiological effects of these hormonal changes on quiescent immune cell function and trafficking are scanty. Here, we report that oral glucose load in mice and healthy men enhances the adherence of circulating peripheral blood mononuclear cells (PBMCs) and lymphocytes to fibronectin. Adherence to fibronectin is also observed upon regular intake of breakfast following overnight fasting in healthy subjects. This glucose load-induced phenomenon is abrogated in streptozotocin-injected mice that lack insulin. Intra-vital microscopy in mice demonstrated that oral glucose feeding enhances the homing of PBMCs to injured blood vessels in vivo. Furthermore, employing flow cytometry, Western blotting and adhesion assays for PBMCs and Jurkat-T cells, we elucidate that insulin enhances fibronectin adherence of quiescent lymphocytes through non-canonical signalling involving insulin-like growth factor-1 receptor (IGF-1R) autophosphorylation, phospholipase C gamma-1 (PLCγ-1) Tyr783 phosphorylation and inside-out activation of β-integrins respectively. Our findings uncover the physiological relevance of post-prandial insulin spikes in regulating the adherence and trafficking of circulating quiescent T-cells through fibronectin-integrin interaction.

Probiotic Escherichia coli Nissle 1917-derived outer membrane vesicles modulate the intestinal microbiome and host gut-liver metabolome in obese and diabetic mice

Introduction

Obesity and diabetes are common chronic metabolic disorders which can cause an imbalance of the intestinal flora and gut-liver metabolism. Several studies have shown that probiotics, including Escherichia coli Nissle 1917 (EcN), promote microbial balance and metabolic health. However, there are no studies on how EcN outer membrane vesicles (EcN-OMVs) influence the intestinal microflora and affect the metabolic disorders of obesity and diabetes.

Methods

In this study, we evaluated the effects of EcN-OMVs on high-fat diet (HFD)-induced obesity and HFD + streptozotocin (STZ)-induced diabetes.

Results

EcN-OMVs could reduce body weight, decrease blood glucose, and increase plasma insulin in obese mice. Similarly, EcN-OMVs treatment could modify the ratio of Firmicutes/Bacteroidetes in the gut, elevate intestinal short-chain fatty acid (SCFA)-producing flora, and influence the SCFA content of the intestine. Furthermore, the intestinal metabolites ornithine and fumaric acid, hepatic ω-6 unsaturated fatty acids, and SCFAs were significantly increased after administering EcN-OMVs.

Discussion

Overall, this study showed that EcN-OMVs might act as post-biotic agents that could modulate gut-liver metabolism and ameliorate the pathophysiology of obesity and diabetes.

Effect of Streptozocin on the Langerhans Islands in the pancreas of birds

In the current study, birds (Columba livia ) were used as a new model to study the effect of streptozotocin on the pancreas gland and the blood glucose level. Three concentrations of 75,65,55 mg/kg were adopted for five consecutive days with one IP dose daily. The experimental animals showed a gradual rise in blood glucose the average glucose in the first week of the experiment was usual for the three groups compared with the control group, while there was a significant change in the blood glucose level in the three groups at the end of the experiment (4th week), where the average glucose in the streptozotocin groups was 55 mg/kg (213.80 ± 12.43) mg/dl and the group 65 mg/kg(282.60 ± 16.78) mg/dl and a group of 75 mg/kg( 371.0 ± 38.39) mg/dl. Keywords: Streptozocin, Langerhans islands, pancreas.

Mitochondrial protein MPV17 promotes β-cell apoptosis in diabetogenesis

MPV17 is a mitochondrial inner membrane protein, and its deficiency can cause mitochondrial DNA (mtDNA) depletion, increase reactive oxygen species (ROS), and promote apoptosis in several cell types, suggesting that MPV17 plays a protective role in cells although the underlying mechanism remains unknown. To test whether MPV17 is also protective in diabetic kidney disease, we treated Mpv17-deficient mice with streptozotocin (STZ) and surprisingly found that they were resistant to diabetes. Mpv17 deficiency was also found to confer resistance to the diabetes induced by an insulin mutation (Ins2Akita), which represents a mouse model of monogenic diabetes characterized by proinsulin misfolding and β-cell failure. In both STZ and Ins2Akita models, Mpv17 mutants had significantly less severe β-cell loss and apoptosis compared with the wild-type mice. We next showed that MPV17 is expressed in β-cells of mice normally, suggesting that MPV17 acts β-cells autonomously to facilitate apoptosis. Consistently, Mpv17 knockdown improved the viability and ameliorated the apoptosis of cultured MIN6 cells treated with STZ and palmitic acid (PA), respectively, accompanied by prevention of caspase 3 activation. The proapoptotic effect of MPV17 in β-cells is in contrast with its known anti-apoptotic effect in other cell types. Thus, we have identified a novel regulator of β-cell death in diabetes development.

Protective effects and mechanisms of opuntia polysaccharide in animal models of diabetes mellitus: A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Opuntia speciesis used in traditional medicine to treat diabetes mellitus (DM). Polysaccharide is one of the main components of Opuntia. Opuntia polysaccharide (OPS) is a kind of natural active macromolecular substance, numerous animal experiments have been conducted to treat DM, however, its protective effect and mechanism in animal models of DM has not been clarified.

AIM OF THE STUDY

The aim of this study is to evaluate the efficacy of OPS on DM through a stematic review and meta-analysis of animal models, and whether its improves blood glucose (BG) levels, body weight (BW), food intake, water intake, and lipid levels, and to summarize the potential mechanism of OPS in the treatment of DM.

MATERIALS AND METHODS

We searched relevant Chinese and English databases from the date of construction to March 2022, including PubMed (MEDLINE), Embase, Cochrane Library, Scopus and Web of Science, China National Knowledge Infrastructure (CNKI), Chinese Biomedicine Literature Database (CBM), Chinese Science and Technology Periodicals Database (VIP), Wanfang Database. 16 studies were included for meta-analysis.

RESULTS

The results showed that compared with the model group, the OPS significantly improved BG, BW, food intake, water intake, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). Meta-regression and subgroup analysis showed that intervention dose, animal species, duration and modeling method may be the source of the heterogeneity. There was no statistical difference between the positive control group and the OPS treatment group in improving BW, food intake, water intake, TC, TG, HDL-C, and LDL-C.

CONCLUSIONS

OPS can effectively improve the symptoms of hyperglycemia, polydipsia, polyphagia, low body weight, and dyslipidemia in DM animals. The possible protective mechanisms of OPS on DM animals are immune regulation, repair of damaged pancreatic β cells, and inhibition of oxidative stress and cell apoptosis.

The Influence of Sildenafil-Metformin Combination on Hyperalgesia and Biochemical Markers in Diabetic Neuropathy in Mice

Background and objectives: Worldwide, approximately 500 million people suffer from diabetes and at least 50% of these people develop neuropathy. Currently, therapeutic strategies for reducing diabetic neuropathy (DN)-associated pain are limited and have several side effects. The purpose of the study was to evaluate the antihyperalgesic action of different sildenafil (phosphodiesterase-5 inhibitor) and metformin (antihyperglycemic agent) combinations in alloxan-induced DN. Methods: The study included 100 diabetic mice and 20 non-diabetic mice that were subjected to hot and cold stimulus tests. Furthermore, we determined the influence of this combination on TNF-α, IL-6 and nitrites levels in brain and liver tissues. Results: In both the hot-plate and tail withdrawal test, all sildenafil-metformin combinations administered in our study showed a significant increase in pain reaction latencies when compared to the diabetic control group. Furthermore, all combinations decreased blood glucose levels due to the hypoglycemic effect of metformin. Additionally, changes in nitrite levels and pro-inflammatory cytokines (TNF-α and IL-6) were observed after 14 days of treatment with different sildenafil-metformin combinations. Conclusions: The combination of these two substances increased the pain reaction latency of diabetic animals in a dose-dependent manner. Moreover, all sildenafil-metformin combinations significantly reduced the concentration of nitrites in the brain and liver, which are final products formed under the action of iNOS.

Comparative Antihyperglycemic and Antihyperlipidemic Effects of Lawsone Methyl Ether and Lawsone in Nicotinamide-Streptozotocin-Induced Diabetic Rats

Our previous study uncovered potent inhibitory effects of two naphthoquinones from Impatiens balsamina, namely lawsone methyl ether (2-methoxy-1,4-naphthoquinone, LME) and lawsone (2-hydroxy-1,4-naphthoquinone), against α-glucosidase. This gave us the insight to compare the hypoglycemic and hypolipidemic effects of LME and lawsone in high-fat/high-fructose-diet- and nicotinamide-streptozotocin-induced diabetic rats for 28 days. LME and lawsone at the doses of 15, 30, and 45 mg/kg, respectively, produced a substantial and dose-dependent reduction in the levels of fasting blood glucose (FBG), HbA1c, and food/water intake while boosting the insulin levels and body weights of diabetic rats. Additionally, the levels of total cholesterol (TC), triglycerides (TGs), high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), aspartate transaminase (AST), alanine transaminase (ALT), creatinine, and blood urea nitrogen (BUN) in diabetic rats were significantly normalized by LME and lawsone, without affecting the normal rats. LME at a dose of 45 mg/kg exhibited the most potent antihyperglycemic and antihyperlipidemic effects, which were significantly comparable to glibenclamide but higher than those of lawsone. Furthermore, the toxicity evaluation indicated that both naphthoquinones were entirely safe for use in rodent models at doses ≤ 50 mg/kg. Therefore, the remarkable antihyperglycemic and antihyperlipidemic potentials of LME make it a promising option for future drug development.

Type 2 diabetes mellitus in obesity promotes prolongation of cardiomyocyte contractile function, impaired Ca2+ handling and protein carbonylation damage

AIMS

To investigate whether the obesity associated to T2DM presented cardiomyocyte myocardial contractility dysfunction due to damage in Ca²⁺ handling, concomitantly with increased biomarkers of oxidative stress.

METHODS

Male Wistar rats were randomized into two groups: control (C): fed with standard diet; and obese (Ob) that fed a saturated high-fat. After the characterization of obesity (12 weeks), the Ob animals were submitted to T2DM induction with a single dose of intraperitoneal (i.p.) injection of streptozotocin (30 mg/kg). Thus, remained Ob rats that were characterized as to the presence (T2DMOb; n = 8) and/or absence (Ob; n = 10) of T2DM. Cardiac remodeling was measured by post-mortem morphological, isolated cardiomyocyte contractile function, as well as by intracellular Ca²⁺-handling analysis.

RESULTS

T2DMOb presented a significant reduction of all fat pads, total body fat and adiposity index. T2DMOb group presented a significant increase in protein carbonylation and superoxide dismutase (SOD) activity, respectively. T2DMOb promoted elevations in fractional shortening (15.6 %) and time to 50 % shortening (5.8 %), respectively. Time to 50 % Ca²⁺ decay was prolonged in T2DMOb, suggesting a possible impairment in Ca²⁺recapture and/or removal.

CONCLUSION

Type 2 diabetes mellitus in obesity promotes prolongation of cardiomyocyte contractile function with protein carbonylation damage and impaired Ca²⁺ handling.

Comparative Study of Cytokeratin Immunostaining of Parotid Gland Parenchyma in Normal, Diabetic, and Excretory Duct Ligation of Mongrel Dogs

OBJECTIVES

 The present study aimed to give a glimpse of the normal distribution of intermediate filaments within the parotid gland parenchyma of mongrel dogs and to reveal the pathological changes that may occur as a result of the effects of diabetes mellitus or atrophy of the gland caused by the ligation of the excretory duct to discover whether there is a similarity in these pathological behaviors.

MATERIALS AND METHODS

 Twelve healthy mongrel dogs were used in the experiment and were divided into three groups: group I (the control group), group II (dogs with alloxan-induced diabetes), and group III (dogs with the right-side duct-ligated parotid gland). The dogs were sacrificed 45 days after the parotid excretory duct were tied. The right parotid gland of all groups was dissected and prepared for histological and immunohistochemical expression of cytokeratin 17 assay.

RESULTS

 Histological findings confirmed that the parotid gland parenchyma of the diabetic group had glandular atrophy characterized by the loss of gland structure, degenerated acini, and dilatation of the duct system. Moreover, there is a predominance of the fibrous component with the presence of fat cells within the gland compartments. On the contrary, the excretory duct-ligated group undergoes severe glandular atrophy of the previous character with the presence of duct-like structure as well as extravasation and vasodilatation. Immunohistochemical expression of cytokeratin 17 in control parotid using an immunoperoxidase technique showed that cytokeratin expression varies from negative to mild in all ducts and some serous acinar cells. The gland parenchyma of the diabetic group showed mild to strong cytokeratin expression of duct cells more concentrated in the apical part with moderate to strong expression of diffuse type in some serous acini. The intensity of cytokeratin 17 in gland compartments of the excretory duct-ligated group revealed a variation in expression that ranged from negative to strong diffuse staining throughout the gland.

CONCLUSION

 The severity and prevalence of cytokeratin 17 in our results are predictive of the pathological influence of both diabetes mellitus and duct ligation on the cytokeratin intracellular filaments of the salivary gland parenchyma in a different way that interferes with saliva production and/or secretion leading to xerostomia.

Biochemical Changes Induced by the Administration of Cannabis sativa Seeds in Diabetic Wistar Rats

The present pilot study investigates the blood biochemical changes induced by hemp seeds in rats with diabetes. The composition of industrial hemp seeds, antioxidant activity, identification and quantification of phenols and fatty acids from hemp oil were determined. The Wistar adult rats used in the experiment were divided into three groups (n = 6) and kept under standard conditions. Group one, the control group (individuals without diabetes), and group two (diabetic individuals) received water and normal food ad libitum, while the third group, also including diabetic individuals, received specific food (hemp seeds) and water ad libitum. Subsequent blood biochemical parameters were determined. Hemp seeds had higher phenol (14 compounds), flavonoids and PUFA contents compared to other plants seeds. In addition, the antioxidant activity in Cannabis sativa was also increased. Moreover, the ratio between n-6 and n-3 was 4.41, ideal for different diseases. Additionally, all biochemical parameters showed significant changes following the treatment. It was shown that high doses of hemp seeds decreased diabetes-induced biochemical damage in rats most probably due to the high content of active compounds. In order to use these seeds in humans, it is essential to find out which hemp compounds are particularly responsible for these effects. Moreover, for the objective investigation of their effects, longer-term studies are needed.

Pancreatic islet protection at the expense of secretory function involves serine-linked mitochondrial one-carbon metabolism

Type 2 diabetes is characterized by insulin hypersecretion followed by reduced glucose-stimulated insulin secretion (GSIS). Here we show that acute stimulation of pancreatic islets with the insulin secretagogue dextrorphan (DXO) or glibenclamide enhances GSIS, whereas chronic treatment with high concentrations of these drugs reduce GSIS but protect islets from cell death. Bulk RNA sequencing of islets shows increased expression of genes for serine-linked mitochondrial one-carbon metabolism (OCM) after chronic, but not acute, stimulation. In chronically stimulated islets, more glucose is metabolized to serine than to citrate, and the mitochondrial ATP/ADP ratio decreases, whereas the NADPH/NADP+ ratio increases. Activating transcription factor-4 (Atf4) is required and sufficient to activate serine-linked mitochondrial OCM genes in islets, with gain- and loss-of-function experiments showing that Atf4 reduces GSIS and is required, but not sufficient, for full DXO-mediated islet protection. In sum, we identify a reversible metabolic pathway that provides islet protection at the expense of secretory function.

Small RNA Sequencing Analysis of STZ-Injured Pancreas Reveals Novel MicroRNA and Transfer RNA-Derived RNA with Biomarker Potential for Diabetes Mellitus

MicroRNAs (miRNAs) and transfer RNA-derived small RNAs (tsRNAs) play critical roles in the regulation of different biological processes, but their underlying mechanisms in diabetes mellitus (DM) are still largely unknown. This study aimed to gain a better understanding of the functions of miRNAs and tsRNAs in the pathogenesis of DM. A high-fat diet (HFD) and streptozocin (STZ)-induced DM rat model was established. Pancreatic tissues were obtained for subsequent studies. The miRNA and tsRNA expression profiles in the DM and control groups were obtained by RNA sequencing and validated with quantitative reverse transcription-PCR (qRT-PCR). Subsequently, bioinformatics methods were used to predict target genes and the biological functions of differentially expressed miRNAs and tsRNAs. We identified 17 miRNAs and 28 tsRNAs that were significantly differentiated between the DM and control group. Subsequently, target genes were predicted for these altered miRNAs and tsRNAs, including Nalcn, Lpin2 and E2f3. These target genes were significantly enriched in localization as well as intracellular and protein binding. In addition, the results of KEGG analysis showed that the target genes were significantly enriched in the Wnt signaling pathway, insulin pathway, MAPK signaling pathway and Hippo signaling pathway. This study revealed the expression profiles of miRNAs and tsRNAs in the pancreas of a DM rat model using small RNA-Seq and predicted the target genes and associated pathways using bioinformatics analysis. Our findings provide a novel aspect in understanding the mechanisms of DM and identify potential targets for the diagnosis and treatment of DM.

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

Preclinical biomedical models are a fundamental tool to improve the knowledge and management of diseases, particularly in diabetes mellitus (DM) since, currently, the pathophysiological and molecular mechanisms involved in its development are not fully clarified, and there is no treatment to cure DM. This review will focus on the features, advantages and limitations of some of the most used DM models in rats, such as the spontaneous models: Bio-Breeding Diabetes-Prone (BB-DP) and LEW.1AR1-iddm, as representative models of type 1 DM (DM-1); the Zucker diabetic fatty (ZDF) and Goto-kakizaki (GK) rats, as representative models of type 2 DM (DM-2); and other models induced by surgical, dietary and pharmacological-alloxan and streptozotocin-procedures. Given the variety of DM models in rats, as well as the non-uniformity in the protocols and the absence of all the manifestation of the long-term multifactorial complications of DM in humans, the researchers must choose the one that best suits the final objectives of the study. These circumstances, added to the fact that most of the experimental research in the literature is focused on the study of the early phase of DM, makes it necessary to develop long-term studies closer to DM in humans. In this review, a recently published rat DM model induced by streptozotocin injection with chronic exogenous administration of insulin to reduce hyperglycaemia has also been included in an attempt to mimic the chronic phase of DM in humans.

A flavonoid-rich fraction of Euphorbia peplus attenuates hyperglycemia, insulin resistance, and oxidative stress in a type 2 diabetes rat model

Background: Type 2 diabetes (T2D) is a metabolic disorder characterized by insulin resistance (IR) and hyperglycemia. Plants are valuable sources of therapeutic agents for the management of T2D. Euphorbia peplus has been widely used as a traditional medicine for the treatment of various diseases, but its beneficial role in T2D has not been fully explored. Methods: The anti-diabetic efficacy of E. peplus extract (EPE) was studied using rats with T2D induced by high-fat diet (HFD) and streptozotocin (STZ). The diabetic rats received 100, 200, and 400 mg/kg EPE for 4 weeks. Results: Phytochemical fractionation of the aerial parts of E. peplus led to the isolation of seven known flavonoids. Rats with T2D exhibited IR, impaired glucose tolerance, decreased liver hexokinase and glycogen, and upregulated glycogen phosphorylase, glucose-6-phosphatase (G-6-Pase), and fructose-1,6-bisphosphatase (F-1,6-BPase). Treatment with 100, 200, and 400 mg/kg EPE for 4 weeks ameliorated hyperglycemia, IR, liver glycogen, and the activities of carbohydrate-metabolizing enzymes. EPE attenuated dyslipidemia, serum transaminases, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and liver lipid accumulation, nuclear factor (NF)-κB p65, and lipid peroxidation, nitric oxide and enhanced antioxidants. All EPE doses upregulated serum adiponectin and liver peroxisome proliferator-activated receptor γ (PPARγ) in HFD/STZ-induced rats. The isolated flavonoids showed in silico binding affinity toward hexokinase, NF-κB, and PPARγ. Conclusion: E. peplus is rich in flavonoids, and its extract ameliorated IR, hyperglycemia, dyslipidemia, inflammation and redox imbalance, and upregulated adiponectin and PPARγ in rats with T2D.

Serum amyloid A and metabolic disease: evidence for a critical role in chronic inflammatory conditions

Serum amyloid A (SAA) subtypes 1-3 are well-described acute phase reactants that are elevated in acute inflammatory conditions such as infection, tissue injury, and trauma, while SAA4 is constitutively expressed. SAA subtypes also have been implicated as playing roles in chronic metabolic diseases including obesity, diabetes, and cardiovascular disease, and possibly in autoimmune diseases such as systemic lupus erythematosis, rheumatoid arthritis, and inflammatory bowel disease. Distinctions between the expression kinetics of SAA in acute inflammatory responses and chronic disease states suggest the potential for differentiating SAA functions. Although circulating SAA levels can rise up to 1,000-fold during an acute inflammatory event, elevations are more modest (∼5-fold) in chronic metabolic conditions. The majority of acute-phase SAA derives from the liver, while in chronic inflammatory conditions SAA also derives from adipose tissue, the intestine, and elsewhere. In this review, roles for SAA subtypes in chronic metabolic disease states are contrasted to current knowledge about acute phase SAA. Investigations show distinct differences between SAA expression and function in human and animal models of metabolic disease, as well as sexual dimorphism of SAA subtype responses.

Monitoring autophagic flux in vivo revealed its physiological response and significance of heterogeneity in pancreatic beta cells

Autophagy plays an essential role in preserving cellular homeostasis in pancreatic beta cells. However, the extent of autophagic flux in pancreatic islets induced in various physiological settings remains unclear. In this study, we generate transgenic mice expressing pHluorin-LC3-mCherry reporter for monitoring systemic autophagic flux by measuring the pHluorin/mCherry ratio, validating them in the starvation and insulin-deficient model. Our findings reveal that autophagic flux in pancreatic islets enhances after starvation, and suppression of the flux after short-term refeeding needs more prolonged re-starvation in islets than in the other insulin-targeted organs. Furthermore, heterogeneity of autophagic flux in pancreatic beta cells manifests under insulin resistance, and intracellular calcium influx by glucose stimulation increases more in high- than low-autophagic flux beta cells, with differential gene expression, including lipoprotein lipase. Our pHluorin-LC3-mCherry mice enable us to reveal biological insight into heterogeneity in autophagic flux in pancreatic beta cells.

Pharmacological effect of Heritiera fomes on Long Evans rats against Postprandial Hyperglycemia and adsorption in vitro

Background

Natural restoratives from traditional medicinal plants are considered to be a convenient, potent, and risk-free substitute treatment for hyperglycaemia. Our objective was to explore the activity of the crude extract of Heritiera fomes on postprandial hyperglycaemia by assessing relative measurements in a laboratory animal model.

Methods

The Streptozotocin induced diabetic rat (n = 88, twenty-two per group) was used for the glucose tolerance test as an initial support for the study. BaSO4 was administered orally as a marker to measure gut motility after one hour of methanolic extract (500 mg/kg body weight) administration where, only purified water (10 ml/kg) was used to treat the control group (n = 12) and a dose (500 mg/kg) of H. fomes extract was used for the test group (n = 12 in each group). After 60 min of incubation of the mixture of extract and glucose with 10% (v/v) yeast cell suspension, the absorbance was measured to determine the capacity of glucose absorption by yeast cells. Sixty Long Evans rats (n = 12 in each group) were used to assess disaccharidase enzyme activity as µmol/mg protein per hour by Lowry's protein estimation method. The carbohydrate absorption investigation was executed to evaluate the leftover sucrose content in the gastrointestinal system (n = 64).

Results

After oral administration of MHFL (71.84%), MHFB (71.41%), and MHFR (72.55%), GI motility (%) increased significantly (p < 0.001) compared to the control group (59.06%). A significant increase in glucose uptake and adsorption capacity measured by different concentrations of glucose ensures the decrease of glucose bound rate and a significant drop in blood glucose concentration. The significant (p < 0.001) decrease in intestinal disaccharidase activity of MHFL (1.40), MHFB (1.36), and MHFR (1.20) in comparison to the control group (1.50) indicates that the presence of H. fomes may reduce glucose absorption in the small bowel. Significant (p < 0.001 & p < 0.05) accumulation of sucrose content in the six different parts of the GI tract suggests the absorption of sucrose was decreased.

Conclusions

The findings of this study provide evidence on probable mechanisms for the anti-diabetic characteristics of H. fomes, and it is predicted that this plant will be studied further for the development of strong anti-hyperglycemic medicines.

The effects of hydroxytyrosol on Prdx6 and insulin expression in diabetic rat pancreases

Diabetes mellitus is a widespread endocrine disease worldwide, accompanying chronic hyperglycemia. In this study, we investigated the effect of hydroxytyrosol, which exerts an antioxidant effect, on the expressions of insulin and peroxiredoxin-6 (Prdx6), which protect cells against oxidative injury in diabetic rat pancreas. This experimental study had four groups with ten animals in each group: control (nondiabetic) group, hydroxytyrosol group [10 mg/kg/day intraperitoneal injection (ip) hydroxytyrosol for 30 days], streptozotocin group (single ip injection of 55 mg/kg streptozotocin), and streptozotocin + hydroxytyrosol group (single ip injection of streptozotocin and ip injection of 10 mg/kg/day hydroxytyrosol for 30 days). During the experiment, blood glucose levels were measured at regular intervals. Insulin expression was determined by immunohistochemistry and Prdx6 expression was determined by immunohistochemistry and western blot. Immunohistochemistry and western blot results were analyzed by one-way ANOVA with applied Holm-Sidak multiple comparison test, and blood glucose results were analyzed by two-way repeated measures ANOVA with applied Tukey's multiple comparison test. Blood glucose levels on days 21 and 28 were significantly lower in the streptozotocin + hydroxytyrosol group compared with the streptozotocin group (day 21, p = 0.049 and day 28, p = 0.003). Expression of both insulin and Prdx6 were lower in the streptozotocin and the streptozotocin + hydroxytyrosol groups compared with the control and hydroxytyrosol groups (p < 0.001). Insulin and Prdx6 expression in the streptozotocin + hydroxytyrosol group were higher compared with the streptozotocin group (p < 0.001). The immunohistochemical findings of Prdx6 and western blot were the same. In conclusion, hydroxytyrosol, which is an antioxidant compound, increased Prdx6 and insulin expression in diabetic rats. Insulin increased by hydroxytyrosol may have been effective in reducing blood glucose levels. Furthermore, hydroxytyrosol may exert its effect on insulin by increasing Prdx6 expression. Thus, hydroxytyrosol may decrease or prevent several hyperglycemia-dependent complications by increasing the expression of these proteins.

Regulation of PKC/TLR-4/NF-kB signaling by sulbutiamine improves diabetic nephropathy in rats

One of the serious complications of diabetes mellitus is diabetic nephropathy (DN) which may finally lead to renal failure. The current study aimed to explore the effect of sulbutiamine, a synthetic derivative of vitamin B1, in streptozotocin (STZ)-induced DN and related pathways. Experimental DN was successfully induced 8 weeks after a single low dose of STZ (45 mg/kg, I.P.). Four groups of rats were used in this study and divided randomly into: control group, diabetic group, sulbutiamine control (control + sulbutiamine) group, and sulbutiamine-treated (60 mg/kg) (diabetic + sulbutiamine) group. The fasting blood glucose level (BGL) and the levels of kidney injury molecule-1 (Kim-1), urea, creatinine in serum, and the renal content of malondialdehyde (MDA), protein kinase C (PKC), toll-like receptor-4 (TLR-4) and nuclear factor kappa B (NF-κB) were determined. Additionally, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) contents were evaluated immunohistochemically. Sulbutiamine treatment decreased fasting BGL and improved the kidney function tests compared to diabetic rats. Moreover, TLR-4, NF-κB, MDA and PKC contents were substantially reduced following sulbutiamine treatment compared to the diabetic group. Sulbutiamine managed to obstruct the production of the pro-inflammatory TNF-α and IL-1β and suppressed TGF-β1 level, in addition to attenuating the histopathological changes associated with DN. This study revealed, for the first time, the ability of sulbutiamine to ameliorate STZ-induced diabetic nephropathy in rats. This nephroprotective outcome of sulbutiamine against DN may be attributed to glycemic control in addition to its anti-oxidative, anti-inflammatory and anti-fibrotic effects.

Evaluation of Antidiabetic Effect of Combined Leaf and Seed Extracts of Moringa oleifera (Moringaceae) on Alloxan-Induced Diabetes in Mice: A Biochemical and Histological Study

Moringa oleifera (Moringaceae) is a medicinal plant rich in biologically active compounds. The aim of the present study was to screen M. oleifera methanolic leaf (L) extract, seed (S) extract, and a combined leaf/seed extract (2L : 1S ratio) for antidiabetic and antioxidant activities in mice following administration at a dose level of 500 mg/kg of body weight/day. Diabetes was induced by alloxan administration. Mice were treated with the extracts for 1 and 3 months and compared with the appropriate control. At the end of the study period, the mice were euthanized and pancreas, liver, kidney, and blood samples were collected for the analysis of biochemical parameters and histopathology. The oral administration of the combined L/S extract significantly reduced fasting blood glucose to normal levels compared with L or S extracts individually; moreover, a significant decrease in cholesterol, triglycerides, creatinine, liver enzymes, and oxidant markers was observed, with a concomitant increase in antioxidant biomarkers. Thus, the combined extract has stronger antihyperlipidemic and antioxidant properties than the individual extracts. The histopathological results also support the biochemical parameters, showing recovery of the pancreas, liver, and kidney tissue. The effects of the combined L/S extracts persisted throughout the study period tested. To the best of our knowledge, this is the first study to report on the antidiabetic, antioxidant, and antihyperlipidemic effects of a combined L/S extract of M. oleifera in an alloxan-induced diabetic model in mice. Our results suggest the potential for developing a natural potent antidiabetic drug from M. oleifera; however, clinical studies are required.

Treatment with Terminalia chebula Extract Reduces Insulin Resistance, Hyperglycemia and Improves SIRT1 Expression in Type 2 Diabetic Rats

BACKGROUND

Terminalia chebula Retz., Family Combretaceae (T. chebula) is one of the important plants mentioned in Ayurveda, a traditional system of medicine. The present work was designed to study the effect of the aqueous extract of T. chebula fruits in type 2 diabetic rats.

METHODS

The aqueous extract of the fruits was prepared by the double maceration technique. The extract was subjected to HPTLC analysis, which showed the presence of ellagic acid and gallic acid. Type 2 diabetes was induced in rats with a low dose of Streptozotocin (35 mg/kg) after administering a high-fat diet for fourteen days. Diabetic animals were treated with 500 and 1000 mg/kg of aqueous extract of T. chebula fruits for six weeks.

RESULTS

Diabetic rats showed a significantly (511.7 ± 17.6) (p < 0.001) high plasma glucose level compared to the normal group (106 ± 3.358). The T. chebula treatment group showed a significant (p < 0.001) reduction in plasma glucose at 500 mg/kg (394.3 ± 10.35) and 1000 mg/kg (368.6 ± 30.08) doses when compared with the diabetic control group. Treatment with aqueous extract significantly reduced lipid parameters in diabetic animals when compared to the animals in the diabetic control group. Treatment with extract at a dose of 500 mg/kg and 1000 mg/kg showed a significant reduction in AST (p < 0.01, p < 0.001) when compared with diabetic control rats. Treatment with extract significantly reduced ALT at 500 mg/kg (p < 0.05) and 1000 mg/kg (p < 0.001) doses when compared with diabetic control rats. The extract treatment improved insulin sensitivity and insulin sensitivity index (ISI) and significantly decreased HOMR-IR. Treatment with T. chebula aqueous extract at 1000 mg/kg significantly increased the level of GSH (p < 0.05) when compared to diabetic control rats. T. chebula treatment at 1000 mg/kg significantly increased levels of CAT (p < 0.01). Histopathology of pancreatic tissue revealed that the extract has a protective effect against the damage caused by hyperglycemia. Immunohistochemistry of pancreatic tissue showed increased expression of SIRT1 in diabetic animals treated with the extract.

CONCLUSIONS

The results of the present study indicate that the extract of T. chebula has significant effects in the management of type 2 diabetes.

Self-recovery in diabetic Sprague Dawley rats induced by intraperitoneal alloxan and streptozotocin

Alloxan and streptozotocin are the most popular diabetogenic agents in assessing antidiabetic activity. Self-recovery, indicated by unstable hyperglycemia conditions in animals induced by those agents, becomes a significant disturbance to accurate examination. This study aimed to evaluate and reveal the self-recovery incidence in Sprague Dawley rats induced with alloxan and streptozotocin. Each dose of alloxan (120, 150, 180 mg/kg) and streptozotocin (40, 50, 60 mg/kg) was administered through intraperitoneal injection. The results showed that each dose of alloxan induced self-recovery incidence. In rats given streptozotocin, self-recovery only occurred at a dose of 40 mg/kg. The other higher doses of streptozotocin induced stable hyperglycemia. Furthermore, this study revealed two types of self-recovery, namely temporary recovery and end recovery. Temporary recovery occurred in rats given alloxan, during end recovery in alloxan and streptozotocin. The examination of insulin levels showed a significant reduction in the temporary recovery and stable diabetic rats compared to the end recovery rats. Besides, the bodyweight of rats was also affected by different incidences of self-recovery. This study recommends paying more attention to the possibility of self-recovery in obtaining animal models of diabetes, emphasizing the determination of suitable diabetogenic agents and proper doses to reduce self-recovery incidences. The finding of temporary recovery in rats receiving alloxan indicates that alloxan induced delayed diabetes in rats.

Clonal Blumea lacera (Burm. f.) DC. ameliorates diabetic conditions by modulating carbohydrate and lipid hydrolases: a combine in vivo experimental and chemico-biological interaction study

Blumea lacera (Burm. f.) DC. is an aromatic annual herb that has traditionally been used to treat or protect against diabetes. Although it has infallible uses, its supply is limited due to its short lifespan. In this study, we aim to investigate the anti-diabetic potential of its micropropagated plants in type 2 diabetic mammalian (mouse) model and further expand the molecular mechanistic understanding of its activity. The water extract of the micropropagated plants was tested in mice with streptozotocin-induced diabetes. The extract effectively suppressed glucose levels prevented weight loss, and improved dyslipidemia in mice. Additionally, it improved liver injury as well as all investigated toxicity indicators, including serum glutamate-pyruvate transaminase, serum glutamic oxaloacetic transaminase, and serum anti-inflammatory marker C-reactive protein. The intramolecular interaction study revealed that the innate polyphenolic constituents of this plant more profoundly inhibited α-amylase, α-glucosidase, and lipase compared to the standard. The prolific bioactive compounds of the micropropagated plant could be attributed to these superior anti-diabetic effects, presumably via an elaborate inhibition of carbohydrate and lipid hydrolyzing enzymes. Thus, the obtained results provide solid experimental proof of the year-round utility of micropropagated plants as a standard source plant material of Blumea lacera (Burm. f.) DC. for drug research and therapeutic production.

Intra-gastrically administration of Stevia and particularly Nano-Stevia reversed the hyperglycemia, anxiety, and memory impairment in streptozotocin-induced diabetic rats

Type II diabetes mellitus is a group of metabolic disorders considered chronic hyperglycemia resulting from deficits in insulin secretion or insulin function. This disease usually links with various psychological problems such as anxiety and cognitive dysfunctions. Stevia (Stevia rebaudiana Bertoni) is a natural and healthy substitute sweetener for sugar and artificial sweeteners. It has become essential for human diets and food manufacturers. The aim of this research was to investigate the effects of Stevia and Nano-stevia on the regulation of anxiety and memory processes in male diabetic rats. The elevated plus-maze (EPM) test-retest procedure was used to assess anxiety and memory in male diabetic rats. The findings exhibited that induction of diabetes caused a distorted cellular arrangement in the liver tissue of male rats. On the other hand, intra-gastrically administration of Stevia (1 ml/kg) and nano-Stevia (1 ml/kg) indicated a normal appearance in the liver tissue of male diabetic rats. Moreover, induction of diabetes caused the augmentation of blood glucose, reduction in time spent in%open-arm time (%OAT) on the test day, and enhancement of%OAT on the retest day. Therefore, induction of diabetes in rats produced hyperglycemia, anxiogenic effect, and memory impairment and these responses were reversed by drug treatment. Furthermore, intra-gastrically application of Stevia (1 ml/kg) and nano-Stevia (1 ml/kg) reversed the hyperglycemia, anxiogenic effect, and memory impairment in male diabetic rats. Interestingly, Nano-Stevia exhibited the highest significant response rather than Stevia. In conclusion, the results of this research suggested the beneficial properties of Stevia and particularly Nano-Stevia on inducing anti-diabetic effects, anxiolytic behavior, as well as memory improvement in male diabetic rats.

Antihypertensive and antihyperglycemic effects of combinations of losartan with metformin and/or glibenclamide in desoxycorticosterone acetate and streptozotocin-induced hypertensive diabetic rats

BACKGROUND

Hypertension is a medical condition that often comorbidly exist in patients with type II diabetes. Therefore, it is very important to manage both conditions simultaneously to mitigate the complications and mortality connected with this comorbidity. Hence, this study investigated the antihypertensive and antihyperglycemic effects of combinations of losartan (LOS) with metformin (MET) and/or glibenclamide (GLB) in hypertensive diabetic rats. Hypertensive diabetic state was induced with desoxycorticosterone acetate (DOCA) and streptozotocin (STZ) in adult Wistar rats. The rats were divided into 5 groups (n = 5): control group (group 1), hypertensive diabetic (HD) control (group 2), treatment groups receiving LOS + MET (group 3), LOS + GLB (group 4), and LOS + MET + GLB (group 5). Group 1 comprised healthy rats while groups 2-5 were HD rats. The rats were treated orally once daily for 8 weeks. Fasted blood glucose (FBS) level, haemodynamic parameters, and some biochemical indices were thereafter assessed.

RESULTS

FBS level and blood pressure measurements were significantly (P < 0.05) increased following induction by DOCA/STZ. The drug treatment combinations, particularly combination of LOS + MET + GLB, significantly (P < 0.05) reduced the induced hyperglycemia and remarkably decreased systolic blood pressure and heart rate. There was significant (P < 0.05) reduction in raised lactate dehydrogenase and creatinine kinase levels by all drug treatment combinations except LOS + GLB.

CONCLUSIONS

Our findings suggest that LOS combinations with MET and/or GLB exhibited significant antidiabetic and antihypertensive effects against DOCA/STZ-induced hypertensive diabetic state in rats.

Catecholaminergic and Cholinergic Systems Mediate Beneficial Effect of Vortioxetine on Diabetes-Induced Neuropathic Pain

The therapeutic potential of vortioxetine on mechanical hyperalgesia/allodynia was investigated in rats with streptozotocin-induced diabetes, and its possible mechanism of action was elucidated in this study. The obtained findings demonstrated that subacute vortioxetine treatment (5 and 10 mg/kg for 2 weeks) increased the reduced paw-withdrawal thresholds of diabetic rats both in the Randall-Selitto and Dynamic plantar tests. Moreover, the falling latencies of animals did not change in the Rota-rod assessments. These results suggest that vortioxetine administration significantly improved diabetes-induced hyperalgesia and allodynia responses in the rats without affecting their motor coordination. The vortioxetine (5 mg/kg)-induced antihyperalgesic and antiallodynic effects were reversed by AMPT, yohimbine, ICI 118,551, sulpiride and atropine pre-treatments, suggesting the involvement of the catecholaminergic system, α₂- and β₂-adrenoceptors, D_2/3 dopaminergic receptors and cholinergic muscarinic receptors in the exhibited pharmacological activity, respectively. Moreover, the data from the immunohistochemical studies indicated that the inhibition of c-Fos overexpression in dorsal horn neurons also mediates the beneficial effect of this drug. Vortioxetine induced no difference in plasma glucose levels in diabetic rats. If clinical studies confirm these findings, the concomitant beneficial effect of vortioxetine on mood disorders and its neutral activity profile on glycemic control may make it an alternative drug for the treatment of neuropathic pain.

Pancreatic loss of Mig6 alters murine endocrine cell fate and protects functional beta cell mass in an STZ-induced model of diabetes

Background

Maintaining functional beta cell mass (BCM) to meet glycemic demands is essential to preventing or reversing the progression of diabetes. Yet the mechanisms that establish and regulate endocrine cell fate are incompletely understood. We sought to determine the impact of deletion of mitogen-inducible gene 6 (Mig6), a negative feedback inhibitor of epidermal growth factor receptor (EGFR) signaling, on mouse endocrine cell fate. The extent to which loss of Mig6 might protect against loss of functional BCM in a multiple very low dose (MVLD) STZ-induced model of diabetes was also determined.

Methods

Ten-week-old male mice with whole pancreas (Pdx1:Cre, PKO) and beta cell-specific (Ins1:Cre, BKO) knockout of Mig6 were used alongside control (CON) littermates. Mice were given MVLD STZ (35 mg/kg for five days) to damage beta cells and induce hyperglycemia. In vivo fasting blood glucose and glucose tolerance were used to assess beta cell function. Histological analyses of isolated pancreata were utilized to assess islet morphology and beta cell mass. We also identified histological markers of beta cell replication, dedifferentiation, and death. Isolated islets were used to reveal mRNA and protein markers of beta cell fate and function.

Results

PKO mice had significantly increased alpha cell mass with no detectable changes to beta or delta cells. The increase in alpha cells alone did not impact glucose tolerance, BCM, or beta cell function. Following STZ treatment, PKO mice had 18±8% higher BCM than CON littermates and improved glucose tolerance. Interestingly, beta cell-specific loss of Mig6 was insufficient for protection, and BKO mice had no discernable differences compared to CON mice. The increase in BCM in PKO mice was the result of decreased beta cell loss and increased beta cell replication. Finally, STZ-treated PKO mice had more Ins+/Gcg+ bi-hormonal cells compared to controls suggesting alpha to beta cell transdifferentiation.

Conclusions

Mig6 exerted differential effects on alpha and beta cell fate. Pancreatic loss of Mig6 reduced beta cell loss and promoted beta cell growth following STZ. Thus, suppression of Mig6 may provide relief of diabetes.

Dose-dependent progression of multiple low dose streptozotocin-induced diabetes in mice

This study investigated the effects of different multiple low doses of streptozotocin (STZ), namely 35 and 55 mg/kg, on the onset and progression of diabetes in mice. Both doses are commonly used in research, and while both induced a loss of beta cell mass, they had distinct effects on whole glucose tolerance, beta cell function and gene transcription. Mice treated with 55 mg/kg became rapidly glucose intolerant, whereas those treated with 35 mg/kg had a slower onset and remained glucose tolerant for up to a week before becoming equally glucose intolerant as the 55 mg/kg group. Beta cell mass loss was similar between the two groups, but the 35 mg/kg-treated mice had improved glucose-stimulated insulin secretion in gold-standard hyperglycemic clamp studies. Transcriptomic analysis revealed that the 55 mg/kg dose caused disruptions in nearly five times as many genes as the 35 mg/kg dose in isolated pancreatic islets. Pathways that were downregulated in both doses were more downregulated in the 55 mg/kg-treated mice, while pathways that were upregulated in both doses were more upregulated in the 35 mg/kg treated mice. Moreover, we observed a differential downregulation in the 55 mg/kg-treated islets of beta cell characteristic pathways, such as exocytosis or hormone secretion. On the other hand, apoptosis was differentially upregulated in 35 mg/kg-treated islets, suggesting different transcriptional mechanisms in the onset of STZ-induced damage in the islets. This study demonstrates that the two STZ doses induce distinctly mechanistic progressions for the loss of functional beta cell mass.

Gymnema Sylvestre Supplementation Restores Normoglycemia, Corrects Dyslipidemia, and Transcriptionally Modulates Pancreatic and Hepatic Gene Expression in Alloxan-Induced Hyperglycemic Rats

Gymnema sylvestre is traditionally used as an herbal remedy for diabetes. The effect of Gymnema sylvestre supplementation on beta cell and hepatic activity was explored in an alloxan-induced hyperglycemic adult rat. Animals were made hyperglycemic via a single inj. (i.p) of Alloxan. Gymnema sylvestre was supplemented in diet @250 mg/kg and 500 mg/kg b.w. Animals were sacrificed, and blood and tissues (pancreas and liver) were collected for biochemical, expression, and histological analysis. Gymnema sylvestre significantly reduced blood glucose levels with a subsequent increase in plasma insulin levels in a dosage-dependent manner. Total oxidant status (TOS), malondialdehyde, LDL, VLDL, ALT, AST, triglyceride, total cholesterol, and total protein levels were reduced significantly. Significantly raised paraoxonase, arylesterase, albumin, and HDL levels were also observed in Gymnema sylvestre treated hyperglycemic rats. Increased mRNA expression of Ins-1, Ins-2, Gck, Pdx1, Mafa, and Pax6 was observed, while decreased expression of Cat, Sod1, Nrf2, and NF-kB was observed in the pancreas. However, increased mRNA expression of Gck, Irs1, SREBP1c, and Foxk1 and decreased expression of Irs2, ChREBP, Foxo1, and FoxA2 were observed in the liver. The current study indicates the potent effect of Gymnema sylvestre on the transcription modulation of the insulin gene in the alloxan-induced hyperglycemic rat model. Enhanced plasma insulin levels further help to improve hyperglycemia-induced dyslipidemia through transcriptional modulation of hepatocytes.

The effect of phytoprotectors on the functioning of liver NAD⁺- and NADP⁺-maliс enzymes in rats with alloxan diabetes

The development of experimental alloxan diabetes in rats was accompanied by the increase the activity of liver NAD⁺- and NADP⁺-dependent malic enzymes (ME; NAD⁺-ME, EC 1.1.1.39 and NADP⁺-ME, 1.1.1.40) associated with an increase in the rate of transcription of genes encoding these enzymes. Oral administration of aqueous extracts of Jerusalem artichoke and olive to diabetic rats caused a noticeable decrease in blood glucose, a decrease in the rate of transcription of the studied genes; and a decrease in ME activity towards normal values. Thus, extracts of Jerusalem artichoke and olive can be used as additives to the standard therapy of diabetes mellitus.

Arabic gum ameliorates systemic modulation in Alloxan monohydrate-induced diabetic rats

Medicinal plants are considered an alternative therapy for diabetes mellitus as they regulate glucose levels. Moreover, a variety of plants offer a rich source of bioactive compounds that have potent pharmacological effects without any negative side effects. The present study aimed to clarify the effects of Arabic gum/Gum Acacia (GA) on the biochemical, histopathological, and immunohistochemical changes observed in diabetic rats. Further, the anti-inflammatory activity of GA in response to diabetes, through inflammatory mediators analysis. Male rats were divided into four groups: untreated control, diabetic, Arabic gum-treated, and Arabic gum-treated diabetic rats. Diabetes was induced using alloxan. Animals were sacrificed after 7 and 21 days of treatment with Arabic gum. Body weight, blood and pancreas tissue samples were collected for analysis. Alloxan injection significantly decreased body weight, increased glucose levels, decreased insulin levels, and caused depletion of islets of Langerhans and β-cell damage in the pancreas. Arabic gum treatment of diabetic rats significantly increased body weight, decreased serum glucose levels, increased insulin levels, exerts anti-inflammatory effect, and improved the pancreas tissue structure. Arabic gum has beneficial pharmacological effects in diabetic rats; therefore, it might be employed as diabetic therapy to reduce the hyperglycemic damage and may be applicable for many autoimmune and inflammatory diseases treatment. Further, the new bioactive substances, such as medications made from plants, have larger safety margins, and can be used for a longer period of time.

Antidiabetic activity of mango peel extract and mangiferin in alloxan-induced diabetic rats

Background

In diabetic animals, there is a significant increase in plasma glucose, serum total cholesterol, triglyceride, and low-density lipoprotein levels, and decreased body weight, liver and muscle glycogen, and high-density lipoprotein. Effective treatment of diabetes mellitus is not yet known, even though the management of diabetes mellitus is considered a global concern. Plants and herbs have played an important role in the healthcare of many societies throughout history. Today’s researchers are investigating the potential for using these nonpharmaceutical approaches to treat and control diabetes, either in conjunction with standard treatments or as an alternative to them. Herbal formulations are favored because to lower cost and fewer side effects compared to other methods for alleviating diabetes and its consequences. In ethnomedicinal practices, different parts of Mangifera indica are used to treatment of diabetes. The present investigation was undertaken to evaluate the antidiabetic activity of an ethanolic extract of Mangifera indica and mangiferin in alloxan-induced diabetic rats. This experiment was conducted in a set of two with four groups of animals namely control (Tc), treatment alloxan (Ta), treatment extract (Tae), and treatment mangiferin (Tam). To develop diabetes, Wistar rats treated with 150 mg/kg b.w. of alloxan monohydrate were injected intraperitoneally. Tae and Tam’s groups received a freshly prepared single dose of extract and mangiferin in distilled water via the oral route. All experimental groups received laboratory pallet feed diet and drinking water ad libitum. Diabetic rats were treated for 21 days with an ethanolic extract of mango peel and pure mangiferin orally daily at rates of 200 mg/kg b.w. and 20 mg/kg b.w.

Results

An alloxan-induced diabetic rat treated with mango peel extract and mangiferin significantly improved the overhead impact due to diabetes. There was a significant (p < 0.05) body weight loss in the alloxan-induced diabetic rats (Ta), whereas animals given mango peel extract and mangiferin showed a significant increase in body weight from 2 weeks onwards in comparison with control. Alloxan-induced rats (Ta) group have higher blood glucose levels and are significantly different (p < 0.01) from the control group. Mango peel extract and mangiferin significantly reduced the levels of fasting glucose after 21 days of treatment in comparison with diabetic animals. Mango peel extract and mangiferin influence the glycogen synthesis pathway in diabetes groups by increasing glycogen levels in muscle and liver. mango peel extract and mangiferin were found to have a nonsignificant impact on plasma cholesterol and HDL levels compared with the control group. Mango peel extract was found to have a significant difference (p < 0.05) in LDL levels compared with the control group. Mangiferin was found to have a significant difference (p < 0.05) in triglyceride and VLDL levels when compared with the control group. Histopathological examination of the pancreas in rats with type I diabetes caused by alloxan found that therapy with an ethanolic extract of mango peel and mangiferin restored beta cell function as well as rejuvenation of Islets of Langerhans.

Conclusions

Mango peel extract and mangiferin have antidiabetic, glycogenesis, and hypolipidemic properties when administered to alloxan-induced diabetic rats.

Graphical abstract

Characterization of gut microbial and metabolite alterations in faeces of Goto Kakizaki rats using metagenomic and untargeted metabolomic approach

BACKGROUND

In recent years, the incidence of type 2 diabetes (T2DM) has shown a rapid growth trend. Goto Kakizaki (GK) rats are a valuable model for the study of T2DM and share common glucose metabolism features with human T2DM patients. A series of studies have indicated that T2DM is associated with the gut microbiota composition and gut metabolites. We aimed to systematically characterize the faecal gut microbes and metabolites of GK rats and analyse the relationship between glucose and insulin resistance.

AIM

To evaluate the gut microbial and metabolite alterations in GK rat faeces based on metagenomics and untargeted metabolomics.

METHODS

Ten GK rats (model group) and Wistar rats (control group) were observed for 10 wk, and various glucose-related indexes, mainly including weight, fasting blood glucose (FBG) and insulin levels, homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of β cell (HOMA-β) were assessed. The faecal gut microbiota was sequenced by metagenomics, and faecal metabolites were analysed by untargeted metabolomics. Multiple metabolic pathways were evaluated based on the differential metabolites identified, and the correlations between blood glucose and the gut microbiota and metabolites were analysed.

RESULTS

The model group displayed significant differences in weight, FBG and insulin levels, HOMA-IR and HOMA-β indexes (P < 0.05, P < 0.01) and a shift in the gut microbiota structure compared with the control group. The results demonstrated significantly decreased abundances of Prevotella sp. CAG:604 and Lactobacillus murinus (P < 0.05) and a significantly increased abundance of Allobaculum stercoricanis (P < 0.01) in the model group. A correlation analysis indicated that FBG and HOMA-IR were positively correlated with Allobaculum stercoricanis and negatively correlated with Lactobacillus murinus. An orthogonal partial least squares discriminant analysis suggested that the faecal metabolic profiles differed between the model and control groups. Fourteen potential metabolic biomarkers, including glycochenodeoxycholic acid, uric acid, 13(S)-hydroxyoctadecadienoic acid (HODE), N-acetylaspartate, β-sitostenone, sphinganine, 4-pyridoxic acid, and linoleic acid, were identified. Moreover, FBG and HOMA-IR were found to be positively correlated with glutathione, 13(S)-HODE, uric acid, 4-pyridoxic acid and allantoic acid and ne-gatively correlated with 3-α, 7-α, chenodeoxycholic acid glycine conjugate and 26-trihydroxy-5-β-cholestane (P < 0.05, P < 0.01). Allobaculum stercoricanis was positively correlated with linoleic acid and sphinganine (P < 0.01), and 2-methyl-3-hydroxy-5-formylpyridine-4-carboxylate was negatively associated with Prevotella sp. CAG:604 (P < 0.01). The metabolic pathways showing the largest differences were arginine biosynthesis; primary bile acid biosynthesis; purine metabolism; linoleic acid metabolism; alanine, aspartate and glutamate metabolism; and nitrogen metabolism.

CONCLUSION

Metagenomics and untargeted metabolomics indicated that disordered compositions of gut microbes and metabolites may be common defects in GK rats.

Acacetin attenuates the pancreatic and hepatorenal dysfunction in type 2 diabetic rats induced by high-fat diet combined with streptozotocin

Acacetin is a natural flavonoid compound with multiple therapeutic potential in oxidative stress, inflammation, cancers, cardiovascular disease and infections. The present study aimed to detect the effect of acacetin on pancreatic and hepatorenal dysfunction in type 2 diabetic rats. The diabetic rats were induced by high-fat diet (HFD) followed by intraperitoneal injection of streptozotocin (STZ) at a dose of 45 mg/kg. Different doses of acacetin were orally administrated once a day for 8 weeks after the diabetic model was successfully established. The experimental results revealed that acacetin and acarbose displayed obvious attenuation in the levels of fasting blood glucose (FBG) and lipids compared to the untreated diabetic rats. In addition, the physiological function of liver and kidney was impaired in the persistent environment of hyperglycemia, while acacetin improved the damage of liver and kidney. Furthermore, hematoxylin-eosin (H&E) staining indicated that acacetin alleviated the pathological alterations of the pancreas, liver and kidney tissues. Besides, the increased levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-8 and malondialdehyde (MDA) were recused by acacetin treatment, while the reduction of superoxide dismutase (SOD) levels were suppressed by acacetin treatment. In conclusion, the experimental results demonstrated that acacetin improved the lipids and glucose levels, and hepatorenal antioxidant capacity, as well as ameliorated hepatorenal dysfunction in type 2 diabetic rats, and the potential mechanism might be associated with its antioxidant and anti-inflammatory activities.