Rat Pancreatic Islets Research Articles

Effect of Sodium Aminophthalhydrazide on Structural and Functional Characteristics of Pancreatic Islands in Experimental Type 2 Diabetes Mellitus.

Under the influence of inflammation, pancreatic β cells can transdifferentiate into cells with a different phenotype. When inflammation decreases, the opposite process is possible. We studied the effect of intramuscular injection of 5-amino-2,3-dihydrophthalazine-1,4-dione sodium salt (APH) on the structural and functional characteristics of the pancreatic islets in rats with experimental type 2 diabetes mellitus. Insulin-producing, glucagon-producing, and proliferating cells were identified by immunohistochemistry. After APH administration, an increase in the number of β cells, a decrease in the number of α cells and cells synthesizing both insulin and glucagon (insulin-glucagon-positive) were observed; mitotic activity of β cells did not change. It is likely that APH promotes transdifferentiation of α cells into β cells by changing the microenvironment of endocrine cells and reducing inflammation in pancreatic islets.

Investigating the functional effects of the long-term ketogenic diet on pancreatic islets in epileptic rats

Ketogenic Diet is well studied and applied as a treatment in numerous nervous system diseases, such as epilepsy. However, KDs long term effect on the cells and the risk of potential insulin resistance are unclear. In this research, we aim to testify whether the usage of KD on patients with epilepsy would increase the risk of diabetes. In this research we firstly verified the cytotoxicity of the islet B cells which might be stimulated by the abundance of fats in the KD. We used a CCK-8 kit to conduct the experiment and obtained a result of higher IC50 values in the keto conditioned cells, which indicates that cells in keto face a higher cytotoxicity than cells in normal condition. Afterwards, we did both vivo and in vitro experiments on the rats. In the in vitro experiment, the islet cells in a keto-environment showed a higher apoptosis rate. In the in vivo experiment, Enzyme-linked immunosorbent assay (ELISA) was used to detect the insulin level and blood fat in plasma of rats. The result out of ELISA demonstrates a continuously decreasing level of insulin and lower body fat. In addition, oral glucose tolerance test (OGTT) was also used to find the blood sugar in the rats which came out as a result that the glucose metabolism has decreased. Although the experiments exhibit several side effects of KD, it might not be applicable to humans since we only had animal experiment. This research aims to reevaluate the benefits and side effects of application of KD to curing epilepsy.

Hyperglycemia influences the cell proliferation and death of the rat endocrine pancreas in the neonatal period

AimsTo evaluate the cell proliferation and death, and structural morphology of the pancreatic islet cells of the rats with hyperglycemia in the first month of life and compare to those of the control rats. Main methodsFemale Sprague-Dawley newborn rats received Streptozotocin (a beta-cytotoxic drug) at birth for diabetes induction. Control and hyperglycemic animals were euthanized on different days of life: 5, 10, 15, and 30. The pancreas was collected and processed for immunohistochemical analysis of cleaved Caspase-3 (cell death), Ki-67 (cell proliferation), PDX-1 (transcription factor responsible for insulin synthesis), and endocrine hormones (insulin, glucagon, and somatostatin). Key findingsControl females showed a higher percentage (%) of Ki-67-positive(+) cells on D10 and D15, a higher % of insulin+ and somatostatin+ cells on D15 and D30, a lower % of PDX-1+ cells on D10, and a higher % of glucagon+ cells on D10 and D30. Hyperglycemic females showed a lower % of Ki-67+ cells on D15, a higher % of cleaved Caspase-3+ cells on D15, and insulin+ cells on D15 and D30. In the comparison among the experimental groups, the hyperglycemic females showed an increased % of cleaved Caspase-3+ and Ki-67+ cells and a lower % of PDX-1+ cells. SignificanceThis study enabled a better understanding of the abnormal pancreas development regarding cellular proliferation, apoptosis, and hormonal synthesis in the neonatal period. Thus, the pancreatic islets of hyperglycemic rats do not reestablish the normal endocrine cell population, and cellular apoptosis overcame the proliferative activity of these cells.

Anti-Diabetic Potentials ofLactobacillus Strains by Modulating Gut Microbiota Structure and β-Cells Regeneration in the Pancreatic Islets of Alloxan-Induced Diabetic Rats.

Diabetes mellitus, a most common endocrine disorder of glucose metabolism, has become a global epidemic and poses a serious public health threat with an increased socio-economic burden. Escalating incidence of diabetes is correlated with changes in lifestyle and food habits that cause gut microbiome dysbiosis and β-cells damage, which can be addressed with dietary interventions containing probiotics. Hence, the search for probiotics of human origin with anti-diabetic, anti-AGE, and anti-ACE potentials has gained renewed interest for the effective management of diabetes and its associated complications. The present study used an alloxan (AXN)-induced diabetic rat model to investigate the effects of potential probiotic Lacticaseibacillus casei MKU1, Lactiplantibacillus pentosus MKU3, and Lactiplantibacillus plantarum MKU7 administration individually on physiochemical parameters related to diabetic pathogenesis. Experimental animals were randomly allotted into six groups viz. NCG (control), DCG (AXN), DGM (metformin), DGP1 (MKU1), DGP2 (MKU3), and DGP3 (MKU7), and biochemical data like serum glucose, insulin, AngII, ACE, HbA1c, and TNF-α levels were measured until 90days. Our results suggest that oral administration with MKU1, MKU3, or MKU7 significantly improved serum insulin levels, glycemic control, glucose tolerance, and body weight. Additionally, β-cell mass was increased by preserving islet integrity in Lactobacillus-treated diabetic rats, whereas TNF-α (~40%), AngII (~30%), and ACE levels (~50%) were strongly inhibited and enhanced sIgA production (5.8 folds) abundantly. Furthermore, Lactobacillus administration positively influenced the gut microbiome with a significant increase in the abundance of Lactobacillus species and the beneficial Bacteroides uniformis and Bacteroides fragilis, while decreased the pathogenic Proteus vulgaris and Parabacteroides distasonis. Among the probiotic treatment groups, L. pentosus MKU3 performed greatly in almost all parameters, indicating its potential use for alleviating diabetes-associated complications.

Involvement of interaction of Cav3.2 and nociceptive TRPA1 in pathological pain transmission.

T-type Ca2+ channels and TRPA1 expressed in sensory neurons are involved in pain. We previously demonstrated a functional interaction of these channels under physiological conditions. Here we investigated the possible involvement of these channels in inflammatory pain condition. We also evaluated the relationship of these channels endogenously expressed in RIN-14B, a rat pancreatic islet tumor cell line. In dorsal root ganglion (DRG) neurons innervated inflammatory side, [Ca2+]i increases induced by 15 mM KCl (15K) were enhanced in neurons responded to AITC. This enhancement was not observed in genetically TRPA1-deficient neurons. The T-type and AITC-induced currents were larger in neurons of the inflammatory side than in those of the control one. In DRGs of the inflammatory side, the protein expression of Cav3.2, but not TRPA1, was increased. In RIN-14B, 15K-induced [Ca2+]i increases were decreased by blockers of T-type Ca2+ channel and TRPA1, and by TRPA1-silencing. Immunoprecipitation suggested the coexistent of these channels in sensory neurons and RIN-14B. In mice with inflammation, mechanical hypersensitivity was suppressed by blockers of both channels. These data suggest that the interaction of Cav3.2 with TRPA1 in sensory neurons is enhanced via the augmentation of the activities of both channels under inflammatory conditions, indicating that both channels are therapeutic targets for inflammatory pain.

The Effects Of Simvastatin On Islets Of Langerhans In The Pancreas Of Rats: A Histological And Biochemical Study

Objective: This study explored the effect of simvastatin on the histomorphology of islets of Langerhans, glucose and insulin levels in rats. Study Design: The study was a one-year laboratory-based experimental control trial. Place and duration of study: It was conducted at Army Medical College Rawalpindi, in collaboration with the National Institute of Health Islamabad and Armed Force Institute of Pathology Rawalpindi. Methods: A one-year, laboratory-based, two-group experimental control trial was conducted. Thirty rats were assigned to each group: a control group receiving saline injections, and a simvastatin group receiving a simvastatin 60 mg/kg/day. Histological analysis of pancreatic islets, and measurements of blood glucose and insulin levels were performed. Statistical analysis was conducted using independent sample t-tests, with significance set at p < 0.005. Results: While simvastatin treatment did not affect the number of islets of Langerhans, The area of pancreatic islets of Langerhans was significantly higher in the simvastatin treatment group compared to control (52,664±38,871 μm2 vs 24,643±16,256 μm2, p=0.001). Serum insulin levels were also significantly elevated with simvastatin treatment (21.49±7.03 μIU/ml) compared to control (16.72±5.38 μIU/ml) (p=0.005). There were no significant differences in weekly fasting blood glucose levels at 4 or 12 weeks between groups (p>0.05). These findings suggest potential modulation of pancreatic islet function by simvastatin without affecting glycemic control in this model. Conclusions: These findings demonstrate that simvastatin treatment significantly impacts the morphology and function of pancreatic islets in rats, increasing insulin secretion without affecting blood glucose levels. Further research is necessary to elucidate the underlying mechanisms and clinical implications of these observations. Keywords: Simvastatin, islets of Langerhans, Sprague-Dawley rats, insulin, glucose, pancreas.

Hydrogel Alginate Considerations for Improved 3D Matrix Stability and Cell Graft Viability and Function in Studying Type 1 Diabetes In Vitro.

Biomedical devices such as islet-encapsulating systems are used for treatment of type 1 diabetes (T1D). Despite recent strides in preventing biomaterial fibrosis, challenges remain for biomaterial scaffolds due to limitations on cells contained within. The study demonstrates that proliferation and function of insulinoma (INS-1) cells as well as pancreatic rat islets may be improved in alginate hydrogels with optimized gel%, crosslinking, and stiffness. Quantitative polymerase chain reaction (qPCR)-based graft phenotyping of encapsulated INS-1 cells and pancreatic islets identified a hydrogel stiffness range between 600 and 1000Pa that improved insulin Ins and Pdx1gene expression as well as glucose-sensitive insulin-secretion. Barium chloride (BaCl2) crosslinking time is also optimized due to toxicity of extended exposure. Despite possible benefits to cell viability, calcium chloride (CaCl2)-crosslinked hydrogels exhibited a sharp storage modulus loss in vitro. Despite improved stability, BaCl2-crosslinked hydrogels also exhibited stiffness losses over the same timeframe. It is believed that this is due to ion exchange with other species in culture media, as hydrogels incubated in dIH2O exhibited significantly improved stability. To maintain cell viability and function while increasing 3D matrix stability, a range of useful media:dIH2O dilution ratios for use are identified. Such findings have importance to carry out characterization and optimization of cell microphysiological systems with high fidelity in vitro.

Stimulation of insulin secretion induced by low 4-cresol dose involves the RPS6KA3 signalling pathway.

4-cresol (4-methylphenol, p-cresol) is a xenobiotic substance negatively correlated with type 2 diabetes and associated with health improvement in preclinical models of diabetes. We aimed at refining our understanding of the physiological role of this metabolite and identifying potential signalling mechanisms. Functional studies revealed that 4-cresol does not deteriorate insulin sensitivity in human primary adipocytes and exhibits an additive effect to that of insulin on insulin sensitivity in mouse C2C12 myoblasts. Experiments in mouse isolated islets showed that 4-cresol potentiates glucose induced insulin secretion. We demonstrated the absence of off target effects of 4-cresol on a panel of 44 pharmacological compounds. Screening large panels of 241 G protein-coupled receptors (GPCRs) and 468 kinases identified binding of 4-cresol only to TNK1, EIF2AK4 (GCN2) and RPS6KA3 (RSK2), a kinase strongly expressed in human and rat pancreatic islets. Islet expression of RPS6KA3 is reduced in spontaneously diabetic rats chronically treated with 4-cresol and Rps6ka3 deficient mice exhibit reduction in both body weight and fasting glycemia, modest improvement in glycemic control and enhanced insulin release in vivo. Similar to low doses of 4-cresol, incubation of isolated rat islets with low concentrations of the RPS6KA3 inhibitor BIX 02565 stimulates both glucose induced insulin secretion and β-cell proliferation. These results provide further information on the role of low 4-cresol doses in the regulation of insulin secretion.

Clinacanthus nutans leaf extract reduces pancreatic β-cell apoptosis by inhibiting JNK activation and modulating oxidative stress and inflammation in streptozotocin-induced diabetic rats.

Controlling apoptosis induced by oxidative stress in pancreatic β-cells provides promising strategies for preventing and treating diabetes. Clinacanthus nutans leaves possess bioactive constituents with potential antioxidant and anti-diabetic properties. This study aimed to investigate the molecular mechanisms by which C. nutans extract protects pancreatic β-cells from apoptotic damage in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in male Wistar rats by intraperitoneal injection of 45 mg/kg STZ, followed by 28 days of treatment with C. nutans leaf extract and Glibenclamide as the standard drug. At the end of the study, blood samples were collected to measure glucose levels, oxidative stress markers, and inflammation. Pancreatic tissue was stained immunohistochemically to detect c-Jun N-terminal kinase (JNK) and Caspase-3 expression. The administration of C. nutans leaf extract to diabetic rats significantly reduced fasting blood glucose, malondialdehyde, and tumor necrosis factor-α levels, while concurrently enhancing the activity of superoxide dismutase. The immunohistochemical studies revealed a decrease in the expression of JNK and caspase-3 in the pancreatic islets of diabetic rats. Clinacanthus nutans exhibits the potential to protect pancreatic β-cells from apoptosis by suppressing oxidative stress and inflammation.

GIP_HUMAN [22-51] Peptide Encoded by the Glucose-Dependent Insulinotropic Polypeptide (GIP) Gene Suppresses Insulin Expression and Secretion in INS-1E Cells and Rat Pancreatic Islets.

GIP_HUMAN [22-51] is a recently discovered peptide that shares the same precursor molecule with glucose-dependent insulinotropic polypeptide (GIP). In vivo, chronic infusion of GIP_HUMAN [22-51] in ApoE-/- mice enhanced the development of aortic atherosclerotic lesions and upregulated inflammatory and proatherogenic proteins. In the present study, we evaluate the effects of GIP_HUMAN [22-51] on insulin mRNA expression and secretion in insulin-producing INS-1E cells and isolated rat pancreatic islets. Furthermore, we characterize the influence of GIP_HUMAN [22-51] on cell proliferation and death and on Nf-kB nuclear translocation. Rat insulin-producing INS-1E cells and pancreatic islets, isolated from male Wistar rats, were used in this study. Gene expression was evaluated using real-time PCR. Cell proliferation was studied using a BrdU incorporation assay. Cell death was quantified by evaluating histone-complexed DNA fragments. Insulin secretion was determined using an ELISA test. Nf-kB nuclear translocation was detected using immunofluorescence. GIP_HUMAN [22-51] suppressed insulin (Ins1 and Ins2) in INS-1E cells and pancreatic islets. Moreover, GIP_HUMAN [22-51] promoted the translocation of NF-κB from cytoplasm to the nucleus. In the presence of a pharmacological inhibitor of NF-κB, GIP_HUMAN [22-51] was unable to suppress Ins2 mRNA expression. Moreover, GIP_HUMAN [22-51] downregulated insulin secretion at low (2.8 mmol/L) but not high (16.7 mmol/L) glucose concentration. By contrast, GIP_HUMAN [22-51] failed to affect cell proliferation and apoptosis. We conclude that GIP_HUMAN [22-51] suppresses insulin expression and secretion in pancreatic β cells without affecting β cell proliferation or apoptosis. Notably, the effects of GIP_HUMAN [22-51] on insulin secretion are glucose-dependent.

Transcriptional signature of islet neogenesis-associated protein peptide-treated rat pancreatic islets reveals induction of novel long non-coding RNAs.

Diabetes mellitus is characterized by chronic hyperglycemia with loss of β-cell function and mass. An attractive therapeutic approach to treat patients with diabetes in a non-invasive way is to harness the innate regenerative potential of the pancreas. The Islet Neogenesis-Associated Protein pentadecapeptide (INGAP-PP) has been shown to induce β-cell regeneration and improve their function in rodents. To investigate its possible mechanism of action, we report here the global transcriptional effects induced by the short-term INGAP-PP in vitro treatment of adult rat pancreatic islets. Rat pancreatic islets were cultured in vitro in the presence of INGAP-PP for 4 days, and RNA-seq was generated from triplicate treated and control islet samples. We performed a de novo rat gene annotation based on the alignment of RNA-seq reads. The list of INGAP-PP-regulated genes was integrated with epigenomic data. Using the new gene annotation generated in this work, we quantified RNA-seq data profiled in INS-1 cells treated with IL1β, IL1β+Calcipotriol (a vitamin D agonist) or vehicle, and single-cell RNA-seq data profiled in rat pancreatic islets. We found 1,669 differentially expressed genes by INGAP-PP treatment, including dozens of previously unannotated rat transcripts. Genes differentially expressed by the INGAP-PP treatment included a subset of upregulated transcripts that are associated with vitamin D receptor activation. Supported by epigenomic and single-cell RNA-seq data, we identified 9 previously unannotated long noncoding RNAs (lncRNAs) upregulated by INGAP-PP, some of which are also differentially regulated by IL1β and vitamin D in β-cells. These include Ri-lnc1, which is enriched in mature β-cells. Our results reveal the transcriptional program that could explain the enhancement of INGAP-PP-mediated physiological effects on β-cell mass and function. We identified novel lncRNAs that are induced by INGAP-PP in rat islets, some of which are selectively expressed in pancreatic β-cells and downregulated by IL1β treatment of INS-1 cells. Our results suggest a relevant function for Ri-lnc1 in β-cells. These findings are expected to provide the basis for a deeper understanding of islet translational results from rodents to humans, with the ultimate goal of designing new therapies for people with diabetes.

Intraperitoneal injection of cell-engineered pancreas in rats with experimental type i diabetes (preliminary results)

Creation of a bioartificial pancreas, including a cell-engineered construct (CEC) formed from pancreatic islets (islets of Langerhans) and a biocompatible matrix mimicking the native microenvironment of pancreatic tissue, is one of the approaches to the treatment of type 1 diabetes mellitus (T1D).Objective: to conduct preliminary in vivo studies of the functional efficacy of intraperitoneal injection of a cell-engineered pancreatic endocrine construct and a suspension of rat pancreatic islets in an experimental T1D model.Materials and methods. Tissue-specific scaffold was obtained by decellularization of human pancreatic fragments. The viability and functional activity of rat islets isolated with collagenase were determined. Experimental T1D was modeled by intraperitoneal injection of low-dose streptozotocin and incomplete Freund’s adjuvant into rats. The rats were intraperitoneally injected twice with pancreatic CEC (n = 2) or islet suspension (n = 1). Glucose levels in the blood and urine of the rats were assessed. Histological examination of organs (pancreas and kidneys) of the experimental animals was carried out.Results. After the first injection, blood glucose levels gradually decreased in all animals by more than 47% of the initial values; by follow-up day 24, the glucose level rose to the initial hyperglycemic values. After repeated administration, a 63.4% decrease in glycemic level was observed in the rats with pancreatic CEC and a 47.5% decrease in the one with islet suspension. At week 5 of the experiment, blood glucose levels gradually increased in all animals. At the same time, the glycemic index of the rat with injected pancreatic CEC was 62% lower than the glycemic index of the rat with injected islets.Conclusion. Allogeneic pancreatic islets in pancreatic CEC increase the duration of stable glycemic level in T1D rats.

Dietary Supplementation with Yerba Mate (Ilex paraguariensis) Infusion Increases IRS-1 and PI3K mRNA Levels and Enhances Insulin Sensitivity and Secretion in Rat Pancreatic Islets.

"Yerba mate" (YM), an aqueous extract of Ilex paraguariensis, has antioxidant, diuretic, cardio-protective and hypoglycaemic properties. Since its effect on the pancreatic islets remains unclear, we evaluated insulin sensitivity and glucose-stimulated insulin secretion (GSIS) in rats consuming YM or tap water (C) for 21 days. Glucose tolerance, glycemia, triglyceridemia, insulinemia, TBARS and FRAP serum levels were evaluated. GSIS and mRNA levels of insulin signaling pathway and inflammatory markers were measured in isolated pancreatic islets from both groups. In C rats, islets were incubated with YM extract or its phenolic components to measure GSIS. YM improved glucose tolerance, enhanced GSIS, increased FRAP plasma levels and islet mRNA levels of IRS-1 and PI3K (p110), and decreased TBARS plasma levels and islet gene expression of TNF-α and PAI-1. Islets from C rats incubated with 100 µg/mL dry YM extract, 1 µM chlorogenic acid, 0.1 and 1 µM rutin, 1 µM caffeic acid or 1 µM quercetin showed an increase in GSIS. Our results suggest that YM enhances glucose tolerance because of its positive effects on GSIS, oxidative stress rate and insulin sensitivity in rat islets, suggesting that long-term dietary supplementation with YM may improve glucose homeostasis in pre-diabetes or type 2 diabetes.

A peptide triple agonist of GLP-1, neuropeptide Y1, and neuropeptide Y2 receptors promotes glycemic control and weight loss

Mechanisms underlying long-term sustained weight loss and glycemic normalization after obesity surgery include changes in gut hormone levels, including glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). We demonstrate that two peptide biased agonists (GEP44 and GEP12) of the GLP-1, neuropeptide Y1, and neuropeptide Y2 receptors (GLP-1R, Y1-R, and Y2-R, respectively) elicit Y1-R antagonist-controlled, GLP-1R-dependent stimulation of insulin secretion in both rat and human pancreatic islets, thus revealing the counteracting effects of Y1-R and GLP-1R agonism. These agonists also promote insulin-independent Y1-R-mediated glucose uptake in muscle tissue ex vivo and more profound reductions in food intake and body weight than liraglutide when administered to diet-induced obese rats. Our findings support a role for Y1-R signaling in glucoregulation and highlight the therapeutic potential of simultaneous receptor targeting to achieve long-term benefits for millions of patients.

The effects of trans fat diet intake on metabolic parameters and pancreatic tissue in offspring of prenatal bisphenol A exposed rats

Bisphenol A (BPA) is a plasticiser used in the manufacturing of many products and its effects on human health remain controversial. Up till now, BPA involvement in metabolic syndrome risk and development is still not fully understood. In this study, we aimed to investigate the effect of prenatal BPA exposure with postnatal trans-fat diet intake on metabolic parameters and pancreatic tissue histology. Eighteen pregnant rats were divided into control (CTL), vehicle tween 80 (VHC), and BPA (5 mg/kg/day) from gestational day (GD) 2 until GD 21, then their weaning rat’s offspring were fed with normal diet (ND) or trans-fat diet (TFD) from postnatal week (PNW) 3 until PNW 14. The rats were then sacrificed and the blood (biochemical analysis) and pancreatic tissues (histological analysis) were collected. Glucose, insulin, and lipid profile were measured. The study has shown that there was no significant difference between groups with regard to glucose, insulin, and lipid profiles (p > 0.05). All pancreatic tissues showed normal architecture with irregular islets of Langerhans in TFD intake groups compared to offspring that consumed ND. Furthermore, the pancreatic histomorphometry was also affected whereby the study findings revealed that there was a significant increase in the mean number of pancreatic islets in rats from BPA-TFD group (5.987 ± 0.3159 islets/field, p = 0.0022) compared to those fed with ND and BPA non-exposed. In addition, the results have found that prenatal BPA exposure resulted in a significant decrease in the pancreatic islets diameter of the BPA-ND group (183.3 ± 23.28 µm, p = 0.0022) compared to all other groups. In conclusion, prenatal BPA exposure with postnatal TFD in the offspring may affect glucose homeostasis and pancreatic islets in adulthood, and the effect may be more aggravated in late adulthood.

Efficiency of Bone Marrow-Derived Mesenchymal Stem Cells and Hesperetin in the Treatment of Streptozotocin-Induced Type 1 Diabetes in Wistar Rats.

Type 1 diabetes mellitus (T1DM) was established to be ameliorated by islet transplantation, but the shortage of the transplanted human islet tissue and the use of immunosuppressive drugs to inhibit the rejection of allogeneic grafts make this type of therapy is limited. Nowadays, therapy with stem cells is one of the most promising future treatments. This kind of therapy could have a profound impact on both replacement, as well as regenerative therapies, to improve or even cure various disorders, including diabetes mellitus. Flavonoids have also been shown to possess anti-diabetic effects. Thus, this study aims to evaluate the effectiveness of the bone marrow-derived mesenchymal stem cells (BM-MSCs) and hesperetin in the treatment of a T1DM rat model. T1DM was induced in male Wistar rats that had been starved for 16 h via intraperitoneal injection of STZ at a dose of 40 mg/kg body weight (b.wt.). After 10 days of STZ injection, the diabetic rats were allocated into four groups. The first diabetic animal group was considered a diabetic control, while the other three diabetic animal groups were treated for six weeks, respectively, with hesperetin (given orally at a dose of 20 mg/kg b.wt.), BM-MSCs (injected intravenously at a dose of 1 × 106 cells/rat/week), and their combination (hesperetin and BM-MSCs). The use of hesperetin and BM-MSCs in the treatment of STZ-induced diabetic animals significantly improved the glycemic state, serum fructosamine, insulin and C-peptide levels, liver glycogen content, glycogen phosphorylase, glucose-6-phosphatase activities, hepatic oxidative stress, and mRNA expressions of NF-κB, IL-1β, IL-10, P53, and Bcl-2 in pancreatic tissue. The study suggested the therapy with both hesperetin and BM-MSCs produced marked antihyperglycemic effects, which may be mediated via their potencies to ameliorate pancreatic islet architecture and insulin secretory response, as well as to decrease hepatic glucose output in diabetic animals. The improvement effects of hesperetin and BM-MSCs on the pancreatic islets of diabetic rats may be mediated via their antioxidant, anti-inflammatory, and antiapoptotic actions.

Identification of newly synthetized proteins by mass spectrometry to understand palmitate-induced early cellular changes in pancreatic islets.

Obesity and lipid metabolism dysregulation are often associated with insulin resistance, and can lead to type 2 diabetes. However, mechanisms linking insulin resistance, high levels of plasma free fatty acids (FFA), and β cell failure remain unclear. The aim of this work was to search for proteins whose synthesis was modified by a short exposure to FFA. This could help in the future to identify molecular mechanisms underlying islet dysfunction in the presence of FFA. Therefore, we assessed by mass spectrometry de novo protein synthesis of freshly isolated rat islets after palmitate short exposure. Quantitative proteome and secretome analyses were performed by combining metabolic incorporation of azidohomoalanine (AHA) and pulse labeling with stable isotope labeling by amino acids in cell culture (SILAC). We showed that pancreatic islets, in response to 4-h exposure to palmitate, increased the synthesis of ribosomal proteins and proteins of the cytoskeleton, and increased their secretion of proteins involved in insulin synthesis and insulin secretion, as well as insulin itself. First, these results show that de novo protein quantification analysis by LC-MS/MS is a useful method to investigate cellular modifications induced by FFA on pancreatic islets. Also, these results show that short exposure to palmitate increases the expression of ribosomal proteins and proteins involved in insulin secretion, and it remains to be determined if these effects are responsible or linked to the harmful effect of palmitate on β cells.NEW & NOTEWORTHY These results show that pancreatic rat islets cultured with palmitate mainly increase synthesis of ribosomal proteins and some proteins of the cytoskeleton. They also show a significant increase of secreted proteins involved in insulin synthesis and insulin secretion, as well as insulin itself. These data provide information to understand the mechanisms of β cell failure induced by lipotoxicity via the identification of all newly synthesized proteins in islets in response to short-term exposure to palmitate.

Trimetazidine Preconditioning Potentiates the Effect of Mesenchymal Stem Cells Secretome on the Preservation of Rat Pancreatic Islet Survival and Function In Vitro.

Islet transplantation offers improved glycemic control in individuals with type 1 diabetes mellitus. However, in vitro islet culture is associated with islet apoptosis and eventually will lose their functionality prior to transplantation. In this study, we examined the effects of mesenchymal stem cells (MSCs) secretome preconditioned with diazoxide (DZ) and trimetazidine (TMZ) on rat islet cells during pre-transplant culture. With and without preconditioned hAD-MSCs' concentrated conditioned media (CCM) were added to the culture medium containing rat islets every 12h for 24 and 48h, after testing for selected cytokine concentrations (interleukin (IL)-4, IL-6, IL-13). Insulin content, glucose-stimulated insulin secretion, islet cell apoptosis, and mRNA expression of pro-apoptotic (BAX, BAK-1, and PUMA) and anti-apoptotic factors (BCL-2,BCL-xL, and XIAP) in rat islets were assessed after 24 and 48h of culture. The protein level of IL-6 and IL-4 was significantly higher in TMZ-MSC-CM compared to MSC-non-CM. In rat isolated islets, normalized secreted insulin in the presence of 16.7mM glucose was significantly higher in treated islet groups compared to control islets at both 24 and 48h cultivation. Also, the percentage of apoptotic islet cells TMZ-MSC-CCM-treated islets was significantly lower compared to MSC-CM and MSC-CCM-treated islets in both 24 and 48h cultivation. Consistent with the number of apoptotic cells, after 24h culture, the expression of BCL-2 and BCL-xL genes in the control islets was lower than all treatment islet groups and in 48h was lower than only TMZ-MSC-CM-treated islets. Also, the expression of the XIAP gene in control islets was significantly lower compared to the TMZ-MSC-CCM-treated islets at both at 24 and 48h. In addition, mRNA level of the BAX gene in TMZ-MSC-CCM-treated islets was significantly lower compared to other groups at 48h. Our findings revealed that TMZ proved to be more effective than DZ and could enhance the potential of hAD-MSCs-CM to improve the function and viability of islets prior to transplantation.

Effects of a Ganoderma lucidum Proteoglycan on Type 2 Diabetic Rats and the Recovery of Rat Pancreatic Islets.

Type 2 diabetes (T2D) results from both insulin resistance and pancreatic β-cell dysfunction. A natural proteoglycan extracted from Ganoderma lucidum, namely, FYGL, has been demonstrated to be capable of ameliorating insulin resistance in previous work. In this work, a T2D rat model induced by streptozocin (STZ) and a high-fat diet was used to investigate the effects of FYGL on pancreatic functions, and the transcriptomics of the rat pancreas was used to investigate the biological processes (BP) and signal pathways influenced by FYGL on the gene basis. Furthermore, the results of transcriptomics were verified both by histopathological analyses and protein expression. The studies showed that FYGL positively regulated T2D-related BP and signaling pathways and recovered the pancreatic function, therefore ameliorating hyperglycemia and hyperlipidemia in vivo. Importantly, the recovery of the pancreatic function suggested a crucial strategy to radically treat T2D.

Cinchonine, a Potential Oral Small-Molecule Glucagon-Like Peptide-1 Receptor Agonist, Lowers Blood Glucose and Ameliorates Non-Alcoholic Steatohepatitis.

The glucagon-like peptide-1 receptor (GLP-1R) is an effective therapeutic target for type 2 diabetes mellitus (T2DM) and non-alcoholic steatohepatitis (NASH). Research has focused on small-molecule GLP-1R agonists because of their ease of use in oral formulations and improved patient compliance. However, no small-molecule GLP-1R agonists are currently available in the market. We aimed to screen for a potential oral small-molecule GLP-1R agonist and evaluated its effect on blood glucose and NASH. The Connectivity map database was used to screen for candidate small-molecule compounds. Molecular docking was performed using SYBYL software. Rat pancreatic islets were incubated in different concentrations glucose solutions, with cinchonine or Exendin (9-39) added to determine insulin secretion levels. C57BL/6 mice, GLP-1R-/- mice and hGLP-1R mice were used to conduct oral glucose tolerance test. In addition, we fed ob/ob mice with the GAN diet to induce the NASH model. Cinchonine (50 mg/kg or 100 mg/kg) was administered orally twice daily to the mice. Serum liver enzymes were measured using biochemical analysis. Liver tissues were examined using Hematoxylin-eosin staining, Oil Red O staining and Sirius Red staining. Based on the small intestinal transcriptome of geniposide, a recognized small-molecule GLP-1R agonist, we identified that cinchonine exerted GLP-1R agonist-like effects. Cinchonine had a good binding affinity for GLP-1R. Cinchonine promoted glucose-dependent insulin secretion, which could be attenuated significantly by Exendin (9-39), a specific GLP-1R antagonist. Moreover, cinchonine could reduce blood glucose in C57BL/6 and hGLP-1R mice, an effect that could be inhibited with GLP-1R knockout. In addition, cinchonine reduced body weight gain and food intake in ob/ob-GAN NASH mice dose-dependently. 100 mg/kg cinchonine significantly improved liver function by reducing the ALT, ALP and LDH levels. Importantly, 100 mg/kg cinchonine ameliorated hepatic steatosis and fibrosis in NASH mice. Cinchonine, a potential oral small-molecule GLP-1R agonist, could reduce blood glucose and ameliorate NASH, providing a strategy for developing small-molecule GLP-1R agonists.