Increased Insulin Production Research Articles

Functional Characterization of Wolfram Syndrome 1 Protein in ß-Cell Function and Viability

Endoplasmic reticulum (ER) homeostasis is crucial for proper β-cell function as evidenced by rare monogenic diabetic disorders, such as Wolfram syndrome, arising from genetic defects in key ER molecules. Wolfram syndrome stems from mutation of the ER transmembrane protein, Wolfram Syndrome 1 (WFS1), resulting in a recessive, progressive neurodegenerative disorder that first manifests as juvenile-onset diabetes mellitus (DM). While many WFS1 variants are associated with DM, the role of WFS1 in β-cell viability and function remains unclear. Our central hypothesis is that WFS1 regulates β-cell viability through downregulation of ER stress-responsive pro-apoptotic factors and β-cell function through modulation of key ER Ca2+ transporters. To test this hypothesis, we generated inducible β-cell models of WFS1 knockdown and overexpression using rat insulinoma cell lines to monitor β-cell function and β-cell death. We employed chemical and physiologic stimuli to model ER stress and monitored its downstream effects by real-time PCR, immunoblot and intracellular calcium mobilization. Our data indicate that β-cells depleted of WFS1 exhibit impaired insulin secretion and reduced insulin content. Additionally, knockdown of WFS1 is associated with decreased ER Ca2+, increased cytosolic Ca2+ and increased β-cell death. Conversely, increasing WFS1 expression in vitro increases insulin production and confers protection against ER stress-mediated β-cell death. Our data suggest that WFS1 may preserve β-cell viability by reducing the expression of pro-apoptotic factors CHOP and TRIB3. Future studies seek to clarify the mechanisms by which WFS1 protects β-cells against metabolic stressors and promotes insulin production. These studies will expand our understanding of the broader mechanisms by which ER dysfunction triggers β-cell pathology in more common forms of diabetes, and provide potential novel targets for intervention that center on preserving ER homeostasis. Disclosure D. Abreu: None. Z. Lavagnino: None. C.M. Brown: None. D.W. Piston: None. F. Urano: Research Support; Self; Eli Lilly and Company. Stock/Shareholder; Self; CytRx.

Insulin Metabolism and Assessment of Hepatic Insulin Extraction During Liver Regeneration. A Study in a Rat Model

ABSTRACTBackground: Liver regeneration is a complex procedure in which insulin metabolism has been implicated. The aim of this experimental study was to evaluate the role of insulin in rat hepatic regeneration following major hepatectomy (70%), employing an isolated perfused rat liver (IPRL) model to assess the extraction of insulin from the regenerating liver. Methods: Eighty-six male rats were randomized in 9 groups. A group of rats was studied at postoperative day (POD) 1 having a sham operation while control rats had no operation. All other animals were subjected to 70% hepatectomy. In phase B, at POD 1, 2, 3, 5, 7, and 14, the IPRL was applied. The regenerating liver was perfused with insulin (450 mu/ml) at a flow of 1.4 ml/gr liver/min for 20 min. Animal weight, liver weight, glucose, lactate, aspartate transferase (AST), alanine transferase (ALT), total bilirubin, albumin, prothrombin time (PT), insulin clearance, and tissue proliferating cell nuclear antigen (PCNA) expression were recorded. Results: We observed reduction of the liver's biochemical activities resulting in increase of AST (684%), ALT (532%), PT (27.7%), international normalized ratio (72%), and total bilirubin (82.8%) at first POD, while a normalization of the essential liver's functions occurs at fifth POD. Endogenous insulin concentration increased, while insulin extraction by the liver was reduced at the first POD in animals who underwent hepatectomy (13.94 ± 0.8 vs 7.97 ± 1.80 u/ml, p = 0.0005 and 71 ± 9.9 vs 165.88 µU/gr liver/min, respectively, p = 0.0005). Conclusions: Insulin seems to take part in hepatic regeneration, as the pancreas increases insulin production and the liver absorbs less despite the reduced hepatic mass and function.

Effect of Troglitazone (Tz) and N‐Acetyl Cysteine (Nac) Treatment on Beta Cells' Survival, and Insulin Production Under Hyperglycaemic Conditions

BackgroundType I diabetes mellitus is characterized by the deficiency of insulin‐producing beta cells but there is still a substantial number of beta cells found in the pancreas and secrete insulin at the time of diagnosis. The mTOR pathway can directly influence insulin production by affecting multiple translation factors, one of which is decreasing eIF‐4E inhibition which, in the same time, can be activated by the indirect insulin production enhancer, ERK phosphorylation pathway.AimThe purpose of this study is to find out the combined effects of TZ and NAC on Beta‐cells insulin production and survival under hyperglycemic conditions (24 hours and 72 hours) and explore the effect of different TZ concentrations under 72h hyperglycemic conditions.MethodsGRINCH cells were prepared, cultured, and divided into separate 24‐well plates (200,000 cell/well) and 96‐well plates (10,000 cell/well). The experiment was performed on a total of 8 wells, 4 for each type of well plates; 2 for 24hrs, and 2 for 72hrs treatments; 1 being normoglycemic and 1 being a hyperglycemic well for each time condition. Apart from the controls, each plate had 3 treatment groups. The first group was the cells treated with TZ (10μM). The second group was the cells treated with NAC (2mM). The third group was the combination of NAC with TZ along with the cells. All groups contained an adequate amount of media in relation to the treatment. To explore the effects of different TZ concentrations, two extra 24‐well plates with GRINCH cells were prepared, one for each environment (hyper and normoglycemic conditions). 3 different TZ concentrations were used, 10, 5, and 2.5μM along with their respective vehicle controls. measurements were taken at 24 and 72 hours.ResultsAll the three groups showed increased insulin production in normoglycemic 24hrs condition, however, in 24hrs hyperglycemia, only NAC and the combination of NAC and TZ showed an increase while TZ stayed the same. In 72hrs normoglycemia, TZ and NAC showed a decrease while their combination showed no change. While in 72hrs hyperglycemia both TZ and the combination decreased but NAC increased. The only 2 conditions with increased survival were NAC and TZ individual treatment in 72hrs normoglycemic conditions. Concerning the second part of the experiment; 2.5μM showed an increase in insulin production.ConclusionThere was no positive proof of the combination (TZ and NAC) effect in chronic 72hrs hyperglycemia which possibly excludes its use in diabetics, however, there positive effects in acute 24hrs hyperglycemia should be further investigated. Furthermore, the fact that at a certain concentration TZ was able to increase insulin proves that there is a point at which by using TZ, ERK and mTOR pathways both would be enhanced to increase insulin production which gives more incite of Thiazolidinediones effects in diabetic patients.Support or Funding InformationThis work was supported by the University of Sharjah and the Boehringer Ingelheim Pharmaceutical company.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Expression Differences of Cyclin Dependent Kinase Inhibitors In Aged and Young Pancreatic Beta Cells

The number of people affected by diabetes is continually rising, affecting over 400 million people worldwide. The insulin secreting pancreatic beta cells are essential to control proper glucose absorption and storage in insulin sensitive peripheral tissue. Both Type 1 and Type 2 diabetes are characterized by decreased functional beta cell mass and, consequently, decreased insulin production. One potential intervention is the use of beta cell transplantation from cadaveric donors. A major impediment to greater application of this treatment is the scarcity of transplant ready beta cells. Increasing the amount of functional beta cells will lead to increased insulin production and better management or a possible treatment strategy for the disease. Various genes have been defined that can induce beta cell replication. A major caveat of these findings, however, is that these factors induce replication in young beta cells and not aged beta cells. Given that the majority of beta cells that will be used for transplant will come from aged donors, it is imperative to understand why aged beta cells are refractory to these proliferative mechanisms. We aimed to determine why aged beta cells do not replicate as well as young beta cells. We hypothesized that one reason for why aged beta cells are refractory to genes that induce proliferation is greater expression of cell cycle inhibitors. The cell cycle is tightly regulated by cyclin‐dependent kinases. Cells also produce proteins known as cyclin‐dependent kinase inhibitors(CDKI's), which bind to cyclin dependent kinases, effectively shutting down cell proliferation. Here we demonstrate the expression of the INK4 and Cip/Kip family of CDKI's by mRNA, protein and histological expression in 5 week old and 5 month old primary rat beta cells. These results begin to define the functional changes that result in the inability of aged beta cells to replicate.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Structure Based Virtual Screening Studies to Identify Novel Potential Compounds for GPR142 and Their Relative Dynamic Analysis for Study of Type 2 Diabetes.

GPR142 (G protein receptor 142) is a novel orphan GPCR (G protein coupled receptor) belonging to “Class A” of GPCR family and expressed in β cells of pancreas. In this study, we reported the structure based virtual screening to identify the hit compounds which can be developed as leads for potential agonists. The results were validated through induced fit docking, pharmacophore modeling, and system biology approaches. Since, there is no solved crystal structure of GPR142, we attempted to predict the 3D structure followed by validation and then identification of active site using threading and ab initio methods. Also, structure based virtual screening was performed against a total of 1171519 compounds from different libraries and only top 20 best hit compounds were screened and analyzed. Moreover, the biochemical pathway of GPR142 complex with screened compound2 was also designed and compared with experimental data. Interestingly, compound2 showed an increase in insulin production via Gq mediated signaling pathway suggesting the possible role of novel GPR142 agonists in therapy against type 2 diabetes.

The role of single nucleotide polymorphisms in GIPR gene in the changes of secretion in hormones and adipokines in patients with obesity with type 2 diabetes

The relationship between the rs2302382, rs8111428 and Glu354Gln (rs1800437) polymorphisms in GIPR (glucosedependent insulinotropic polypeptide receptor) gene and plasma levels of mediators involved in the regulation of carbohydrate metabolism in obese patients with type 2 diabetes (before and after a test breakfast) was investigated. The contribution of polymorphic variants of rs2302382, rs8111428 in GIPR gene in the predisposition to type 2 diabetes in individuals belonging to the Slavic population of Russia was found. Polymorphisms rs2302382 and rs8111428 in the GIPR gene were characterized by the nonequilibrium cohesion. The decrease in the level of expression of the GIPR gene in adipose tissue of the small intestine mesentery in the carriers of the CC genotype rs2302382 and AA rs8111428 was associated with the increase in the plasma leptin level, whereas during normal expression, the plasma content of insulin, and GIP (in persons with the genotype of the polymorphism rs2302382 and AG polymorphism rs8111428), resistin and ghrelin (in individuals with the genotype of the polymorphism rs2302382) increased. We propose the stimulating effect of GIP on the secretion of resistin, leptin and ghrelin, with an increase in insulin production in obese patients with type 2 diabetes.

Insulinotropic and cytoprotective effect of L-theanine: An in vitro dose dependent study

Background: L-theanine is a natural bioactive amino acid present in tea (Camellia sinensis [L.] O. Kuntze) and consumed worldwide through tea decoction. Objective: The present work aims at evaluation of the insulin secretion and cytoprotective efficacy of L-theanine, a bioactive amino acid present in tea, on pancreatic β-cell line, RIN-m5F. Methods: RIN m5F cell were treated with L-theanine alone or prior to hydrogen peroxide (200 um) treatment and subsequently cell viability, cellular morphology, insulin secretion and insulin gene expression were analyzed. Results: Studies have shown that L-theanine dose dependently (0–300 μm) increases the β-cell mass as well as increases insulin production by RIN-m5F cell. It was also observed that pretreatment of the cell with L-theanine partially protected the oxidative stress of β-cells that were evident from cell viability, cellular morphology, and restoration of insulin-secreting ability. Conclusion: Results suggest that L theanine is an insulinotropic agent as well as effective in giving partial protection to pancreatic β-cells in oxidatively stressed condition. L-theanine can be used in the prevention or treatment of diabetes. Abbreviations used: EGCG: Epigallocatechin gallate; FBS: Fetal Bovine Serum; DMEM Dulbecco's Modified Eagle Medium

Hypoglycemic activity of Leaves of Bougainvillea spectabilis extract in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is a disease in which blood glucose levels are above normal. The β cells of the pancreas do not make sufficient insulin. Herbal drugs treat diabetes by improving insulin sensitivity, increasing insulin production and/or decreasing the amount of glucose in blood. The present study was aimed to investigate antidaibetic activity of methanolic leaf extract of Bougainvillea spectabilis (B. spectabilis) alone and in combination with glibencliamide in Streptozotocin induced diabetic rats. Primarily acute toxicity study and oral glucose tolerance test were performed. The powdered plant was successfully extracted with methanol by using soxhlet extractor. The Wister strains of male albino rats were used for present study. The methanol extracts of B. spectabilis (200mg/kg and 400mg/kg) were administered to both normal and streptozotocin induced diabetic rats at defined time intervals. Blood glucose levels were measured at 0, 30, 60, 120 minutes and 0, 7, 14, 21 and 28th day after oral administration of extracts. Of the doses test, highest anti-hyper glycemic effect was observed by the extract of leaves at 400mg/kg after a week treatment. B. spectabilis extract exhibited significant hypoglycemic activity at different doses and intervals. The toxicity study results showed that the medium lethal dose (LD50) of the extract is higher than 2g/kg body weight, and hence, in a single dose administration, the plant extract had no adverse effect. Bougainvillea spectabilis methanol extract exhibited potent hypoglycemic activity.

Research Highlights

Defining Total-body AIDS Virus Burden With Implications for Curative Strategies Estes JD, Kityo C, Ssali F, et al. [published online October 2, 2017]. Nat Med. doi: 10.1038/nm.4411. Human immunodeficiency virus (HIV) reservoirs have an important impact on the potential cure for the disease and will continue to be important in HIV transplant practices, especially when using HIV-positive donors. Despite having undetectable viral loads in serum, patients carry a significant amount of virus in lymphoid tissue (LT) which could result in reactivation of latent viral pools, thus making it very difficult to eradicate the virus. Furthermore, anti-retroviral therapy (ART) penetration into LT is poor. Therefore, viral load may be undetectable in serum; however, a significant amount of virus may still exist in LT, solid organs, and the brain. Interestingly, the penetration for ART into the brain is also limited, and many patients who have undetectable levels of virus in the serum will have high viral loads in the brain. The authors examined HIV reservoirs in humans as well as in rhesus macaques and looked for the virus in LT, gut, brain, heart, kidney, liver, lung, and spleen. To diagnose reservoirs, they looked for DNA, RNA, as well as virus-producing cells. They illustrated that the primary reservoir site was LT, where 98% of the RNA cells resided. Another organ with a high frequency of RNA-positive cells was the lung. Interestingly, the levels of ART in LT were significantly less than that in peripheral blood mononuclear cells and well below optimal concentration for viral suppression. Furthermore, there was a very large residual reservoir of DNA cells in individuals on ART, even in the presence of undetectable plasma viral loads. In the gut, there was almost no decrease of the DNA cell reservoir subsequent to ART. The authors demonstrated that even during effective ART, virus-producing cells persisted in the tissue, despite plasma viremia being less than 50 copies/mL. Ongoing viral production or reactivation of latently infected cells could be potential sources of virus that may reignite infection after treatment interruption. Inhibition of Y1 Receptor Signaling Improves Islet Transplant Outcome Loh K, Shi YC, Walters S, et al. Nat Commun. 2017;8(1):490. Clinical outcomes of pancreatic islet cell transplantation remain unsatisfactory with low survival rate of donor islets and compromised efficiencies of these cells. The authors investigated the effect of Y1 receptor blockers on islets after transplantation. Moreover, they tested the functional capacity of native beta cells at a time when type 1 diabetes becomes apparent, although patients are not yet fully insulin dependent, a condition referred by many as the “honeymoon period” for type 1 diabetics. The addition of Y1 receptor antagonists not only extended the period of normoglycemia in autoimmune-prone diabetic mice in their “honeymoon period,” but also improved outcomes in mice who received an islet cell transplant. Mechanistically, Y1 receptor stimulation reduced the intracellular cyclic adenosine monophosphate level resulting in reduced insulin secretion of pancreatic islet cells. Therefore, Y1 receptor blockers have the potential to increase insulin production, not only in transplanted islet cells but also in native pancreatic beta cells. The authors also investigated whether Y1 deficient islet transplants had a better outcome than wild type islet transplants in diabetic mice by manipulating Y1 receptors in islet cells before transplantation. Mice were either transplanted with a sufficient or a suboptimal number of islets (300 vs 60, respectively). An additional group of mice were transplanted with a minimal number of islets (60) where the Y1 receptor had been deleted. In the last group, the outcome was just as good as in the group of mice who received an adequate number of islets. In the other group who received a deficient number of islets, the outcome was poor, and the mice never became normoglycemic. This finding was repeated by blocking the Y1 receptor with a pharmacological agent (BIB03304). Interestingly, a transient inhibition over 5 days resulted in glycemic control in mice with a minimal islet mass (60). In mice receiving a minimal islet transplant (60) with an absent initial glycemic control could not be obtained initially, normoglycemia had been restored with a delayed Y1 receptor blockade starting from day 9. Similarly, human islet cultures enhanced insulin secretion when BIBO3304 was added to the culture, significantly improving glucose control. Thus, adding Y1 antagonists to the clinical treatment of islet cell transplants may reduce the number of beta cells to achieve normoglycemia.

Glutamine up-regulates pancreatic sodium-dependent neutral aminoacid transporter-2 and mitigates islets apoptosis in diabetic rats.

Glutamine aminoacid regulates insulin exocytosis from pancreatic β-cells. Liraglutide is a glucagon-like peptide-1 (GLP-1) analogue that has fascinated function in inhibiting β-cell apoptosis and preserving pancreatic β-cell mass. The present study investigated the benefit of adding glutamine to a regimen of liraglutide in diabetic rats focusing on their role in increasing insulin production and upregulation of the expression of sodium-dependent neutral aminoacid transporter-2 (SNAT2). In the present study, diabetes mellitus was induced in rats using streptozotocin (STZ, 50mg/kg, ip). Male rats were allocated into 5 groups, (i) vehicle group, (ii) STZ-diabetic rats, (iii) STZ-diabetic rats treated with liraglutide (150μg/kg, sc), (iv) STZ-diabetic rats treated with glutamine (po) and (v) STZ-diabetic rats treated with a combination of liraglutide and glutamine for four weeks. After finishing the therapeutic courses, the fasting blood glucose value was determined and rats were sacrificed. Pancreases were used for quantification of mRNA expression for SNAT2. Paraffin fixed samples were used for histologic staining and immunohistochemistry for insulin and apoptosis markers (activated caspase-3, BCL2 and BAX). Treatment with liraglutide and/or glutamine enhanced insulin production and hence glycemic control in diabetic male rats with favorable effects on apoptosis markers. Treatment with glutamine and its combination with liraglutide significantly increased pancreatic expression of SNAT2 by approximately 30-35 folds. Addition of glutamine to liraglutide regimen enhances the glycemic control and may have utility in clinical settings.

The role of polycarbonate monomer bisphenol-A in insulin resistance.

Bisphenol A (BPA) is a synthetic unit of polycarbonate polymers and epoxy resins, the types of plastics that could be found in essentially every human population and incorporated into almost every aspect of the modern human society. BPA polymers appear in a wide range of products, from liquid storages (plastic bottles, can and glass linings, water pipes and tanks) and food storages (plastics wraps and containers), to medical and dental devices. BPA polymers could be hydrolyzed spontaneously or in a photo- or temperature-catalyzed process, providing widespread environmental distribution and chronic exposure to the BPA monomer in contemporary human populations. Bisphenol A is also a xenoestrogen, an endocrine-disrupting chemical (EDC) that interferes with the endocrine system mimicking the effects of an estrogen and could potentially keep our endocrine system in a constant perturbation that parallels endocrine disruption arising during pregnancy, such as insulin resistance (IR). Gestational insulin resistance represents a natural biological phenomenon of higher insulin resistance in peripheral tissues of the pregnant females, when nutrients are increasingly being directed to the embryo instead of being stored in peripheral tissues. Gestational diabetes mellitus may appear in healthy non-diabetic females, due to gestational insulin resistance that leads to increased blood sugar levels and hyperinsulinemia (increased insulin production from the pancreatic beta cells). The hypothesis states that unnoticed and constant exposure to this environmental chemical might potentially lead to the formation of chronic low-level endocrine disruptive state that resembles gestational insulin resistance, which might contribute to the development of diabetes. The increasing body of evidence supports the major premises of this hypothesis, as exemplified by the numerous publications examining the association of BPA and insulin resistance, both epidemiological and mechanistic. However, to what extent BPA might contribute to the development of diabetes in the modern societies still remains unknown. In this review, I discuss the chemical properties of BPA and the sources of BPA contamination found in the environment and in human tissues. I provide an overview of mechanisms for the proposed role of bisphenol A in insulin resistance and diabetes, as well as other related diseases, such as cardiovascular diseases. I describe the transmission of BPA effects to the offspring and postulate that gender related differences might originate from differences in liver enzyme levels, such as UDP-glucuronosyltransferase, which is involved in BPA processing and its elimination from the organism. I discuss the molecular mechanisms of BPA action through nuclear and membrane-bound ER receptors, non-monotonic dose response, epigenetic modifications of the DNA and propose that chronic exposure to weak binders, such as BPA, may mimic the effects of strong binders, such as estrogens.

Molecular genetics of the transcription factor GLIS3 identifies its dual function in beta cells and neurons

The GLIS family zinc finger 3 isoform (GLIS3) is a risk gene for Type 1 and Type 2 diabetes, glaucoma and Alzheimer's disease endophenotype. We identified GLIS3 binding sites in insulin secreting cells (INS1) (FDR q<0.05; enrichment range 1.40–9.11 fold) sharing the motif wrGTTCCCArTAGs, which were enriched in genes involved in neuronal function and autophagy and in risk genes for metabolic and neuro-behavioural diseases. We confirmed experimentally Glis3-mediated regulation of the expression of genes involved in autophagy and neuron function in INS1 and neuronal PC12 cells. Naturally-occurring coding polymorphisms in Glis3 in the Goto-Kakizaki rat model of type 2 diabetes were associated with increased insulin production in vitro and in vivo, suggestive alteration of autophagy in PC12 and INS1 and abnormal neurogenesis in hippocampus neurons. Our results support biological pleiotropy of GLIS3 in pathologies affecting β-cells and neurons and underline the existence of trans‑nosology pathways in diabetes and its co-morbidities.

Nypa fruticans Wurmb. Vinegar's Aqueous Extract Stimulates Insulin Secretion and Exerts Hepatoprotective Effect on STZ-Induced Diabetic Rats.

Background: An aqueous extract (AE) of vinegar made from Nypa fruticans Wurmb. can improve postprandial glucose levels in normoglycaemic rats. The aim of this study was to evaluate its antihyperglycaemic activity further using in vivo and in vitro approaches. Methods: AE was administered to streptozotocin (STZ)-induced diabetic rats twice daily at three doses (1000, 500, and 250 mg/kg b.w.) for 12 days p.o. Several biochemical analyses and a histological study of the pancreas and liver were performed, accompanied by a cell culture assay. Results: As compared to diabetic control (DC), AE at the doses of 500 and 1000 mg/kg b.w. caused significant reduction (p < 0.05) of blood glucose, total cholesterol and triglycerides levels, with positive improvement of serum insulin levels. Interestingly, immunohistochemical staining of the pancreas suggested no β-cell regeneration, despite significant increase in insulin production. AE-treated groups, however, showed overall restoration of the hepatic histoarchitecture of STZ-induced liver damage, suggesting a possible hepatoprotective effect. The pancreatic effect of AE was further studied through RIN-5F cell culture, which revealed a positive stimulatory effect on insulin release at a basal glucose concentration (1.1 mM). Conclusion: Nypa fruticans Wurmb. vinegar’s aqueous extract exerts its antihyperglycaemic activity, at least in part, through insulin stimulatory and hepatoprotective effects.

Effects of Taurine Supplementation on Neuronal Excitability and Glucose Homeostasis.

In this study we examined the role of chronic taurine supplementation on plasma glucose homeostasis and brain excitability through activation of the insulin receptor. FVB/NJ male mice were supplemented with taurine in drinking water (0.05% w/v) for 4weeks and subjected to a glucose tolerance test (7.5mg/kg BW) after 12h fasting. We found that taurine-fed mice were slightly hypoglycemic prior to glucose injection and showed significantly reduced plasma glucose at 30 and 60 min post-glucose injection when compared to control mice. Previously, we reported that taurine supplementation induces biochemical changes that target the GABAergic system. Those studies show that taurine-fed mice are hyperexcitable, have reduced GABAA receptors expression and increased GAD and somatostatin expression in the brain. In this study, we found that taurine-fed mice had a significant increase in insulin receptor (IR) immuno-reactivity in the pancreas and all brain regions examined. At the mRNA level, we found that the IR showed differential regional expression. Surprisingly, we found that neurons express the gene for insulin and that taurine had a significant role in regulating insulin gene expression. We propose that increased insulin production and secretion in taurine-fed mice cause an increase activation of the central IR and may be partially responsible for the increased neuronal excitability observed in taurine supplemented mice. Furthermore, the high levels of neuronal insulin expression and its regulation by taurine implicates taurine in the regulation of metabolic homeostasis.

The Role of Hesperetin in the Management of Diabetes Mellitus and Its Complications

Diabetes mellitus is a chronic metabolic disease which is a serious global problem. Many antidiabetic therapies focus on improving insulin sensitivity, increasing insulin production, and/or decreasing the level of blood glucose. Hesperetin is a flavanoid commonly found in many herbal medicines and food. Hesperetin seem to demonstrate adequate properties. Animal studies were carried out for 45days and at the end of 45^th day blood samples were collected and various biochemical parameters were measured using autoanalyser. They can inhibit enzymes involved in glucose metabolism, prevent the development of insulin resistance and normalize plasma glucose and insulin levels. This synthetic drug apart from producing a hypoglycemic effect has also been found to manifest hypolipidemic and anti-obesity activity. Hesperetin is also promising agents in the prevention of diabetic complications. They have strong antioxidant activity and inhibit the formation of advanced glycation end products, implicated in the pathogenesis of diabetic nephropathy, embryopathy, and neuropathy or impaired wound healing. Until now very few clinical studies have been concerned with the application of Hesperetin in treating diabetes. Our experimental findings with respect to the mechanism of action of synthetic compound in Streptozotocin induced diabetic rats suggest that it enhances insulin secretion by the islets of langerhans and enhances glucose utilization. However, due to their great therapeutic potential, these compounds deserve special attention.

Intravenous Infusion of Human Adipose Tissue-Derived Mesenchymal Stem Cells to Treat Type 1 Diabetic Mellitus in Mice: An Evaluation of Grafted Cell Doses.

Mesenchymal stem cell (MSC) transplantation is a novel treatment for diabetes mellitus, especially type 1 diabetes. Many recent publications have demonstrated the efficacy of MSC transplantation on reducing blood glucose and increasing insulin production in both preclinical and clinical trials. However, the investigation of grafted cell doses has been lacking. Therefore, this study aimed to evaluate the different doses of MSCs on treatment of type 1 diabetes in mouse models. MSCs were isolated and expanded from human adipose tissue. Streptozotocin (STZ)-induced diabetic mice were divided into two groups that were intravenously transfused with two different doses of human MSCs: 106 or 2.106 cells/mouse. After transplantation, both grafted and placebo mice were monitored weekly for their blood glucose levels, glucose and insulin tolerance, pancreatic structural changes, and insulin production for 56days after transplantation. The results showed that the higher dose of MSCs (2.106 cells/mouse) remarkably reduced death rate. The death rates were 50%, 66%, and 0% in placebo group, low-dose (1.106 MSCs) group, and high-dose (2.106 MSCs) group, respectively, after 56 days of treatment. Moreover, blood glucose levels were lower for the high-dose group compared to other groups. Glucose and insulin tolerance, as well as insulin production, were significantly improved in mice transplanted with 2.106 cells. The histochemical analyses also support these results. Thus, a higher (e.g., 2.106) dose of MSCs may be an effective dose for treatment of type 1 diabetes mellitus.

Mesenchymal stem cells moderate immune response of type 1 diabetes.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by lack of insulin and irreversible destruction of islet β cells. In order to alleviate the symptoms, lifelong exogenous insulin administration has been the primary treatment of T1DM. In recent years, as a novel promising therapy, the transplantation of mesenchymal stem cells (MSCs) with or without pancreatic islets has achieved great therapeutic effects in animal models due to their multipotency along with their secretion of cytokines, angiogenic factors and immunomodulatory substances. There is plenty of evidence showing that MSCs can delay T1DM onset, reverse hyperglycemia after onset and increase insulin production. To date, the immunoregulation and immunosuppression of MSCs have been widely proved but the exact mechanisms are still not clear enough. Therefore, in this review, we mainly discuss the immunologic mechanism of MSCs in moderating the immune response of T1DM.

Pancreatic Islet Responses to Metabolic Trauma.

Carbohydrate, lipid, and protein metabolism are largely controlled by the interplay of various hormones, which includes those secreted by the pancreatic islets of Langerhans. While typically representing only 1% to 2% of the total pancreatic mass, the islets have a remarkable ability to adapt to disparate situations demanding a change in hormone release, such as peripheral insulin resistance. There are many different routes to the onset of insulin resistance, including obesity, lipodystrophy, glucocorticoid excess, and the chronic usage of atypical antipsychotic drugs. All of these situations are coupled to an increase in pancreatic islet size, often with a corresponding increase in insulin production. These adaptive responses within the islets are ultimately intended to maintain glycemic control and to promote macronutrient homeostasis during times of stress. Herein, we review the consequences of specific metabolic trauma that lead to insulin resistance and the corresponding adaptive alterations within the pancreatic islets.

Alterations in β-Cell Calcium Dynamics and Efficacy Outweigh Islet Mass Adaptation in Compensation of Insulin Resistance and Prediabetes Onset.

Emerging insulin resistance is normally compensated by increased insulin production of pancreatic β-cells, thereby maintaining normoglycemia. However, it is unclear whether this is achieved by adaptation of β-cell function, mass, or both. Most importantly, it is still unknown which of these adaptive mechanisms fail when type 2 diabetes develops. We performed longitudinal in vivo imaging of β-cell calcium dynamics and islet mass of transplanted islets of Langerhans throughout diet-induced progression from normal glucose homeostasis, through compensation of insulin resistance, to prediabetes. The results show that compensation of insulin resistance is predominated by alterations of β-cell function, while islet mass only gradually expands. Hereby, functional adaptation is mediated by increased calcium efficacy, which involves Epac signaling. Prior to prediabetes, β-cell function displays decreased stimulated calcium dynamics, whereas islet mass continues to increase through prediabetes onset. Thus, our data reveal a predominant role of islet function with distinct contributions of triggering and amplifying pathway in the in vivo processes preceding diabetes onset. These findings support protection and recovery of β-cell function as primary goals for prevention and treatment of diabetes and provide insight into potential therapeutic targets.

Proteasome inhibitors, including curcumin, improve pancreatic β-cell function and insulin sensitivity in diabetic mice.

Background:Type 2 diabetes stems from obesity-associated insulin resistance, and in the genetically susceptible, concomitant pancreatic β-cell failure can occur, which further exacerbates hyperglycemia. Recent work by our group and others has shown that the natural polyphenol curcumin attenuates the development of insulin resistance and hyperglycemia in mouse models of hyperinsulinemic or compensated type 2 diabetes. Although several potential downstream molecular targets of curcumin exist, it is now recognized to be a direct inhibitor of proteasome activity. We now show that curcumin also prevents β-cell failure in a mouse model of uncompensated obesity-related insulin resistance (Leprdb/db on the Kaliss background).Results:In this instance, dietary supplementation with curcumin prevented hyperglycemia, increased insulin production and lean body mass, and prolonged lifespan. In addition, we show that short-term in vivo treatment with low dosages of two molecularly distinct proteasome inhibitors celastrol and epoxomicin reverse hyperglycemia in mice with β-cell failure by increasing insulin production and insulin sensitivity.Conclusions:These studies suggest that proteasome inhibitors may prove useful for patients with diabetes by improving both β-cell function and relieving insulin resistance.