Oral insulin improves metabolic parameters in high fat diet fed rats

ABSTRACT Introduction/Aim: The gut has shown to have a pivotal role on the pathophysiology of metabolic disease. Food stimulation of distal intestinal segments promotes enterohormones secretion influencing insulin metabolism. In diabetic rats, oral insulin has potential to change intestinal epithelium behavior. This macromolecule promotes positive effects on laboratorial metabolic parameters and decreases diabetic intestinal hypertrophy. This study aims to test if oral insulin can influence metabolic parameters and intestinal weight in obese non-diabetic rats. Methods: Twelve weeks old Wistar rats were divided in 3 groups: control (CTRL) standard chow group; high fat diet low carbohydrates group (HFD) and HFD plus daily oral 20U insulin gavage (HFD+INS). Weight and food consumption were weekly obtained. After eight weeks, fasting blood samples were collected for laboratorial analysis. After euthanasia gut samples were isolated. Results: Rat oral insulin treatment decreased body weight gain (p<0,001), fasting glucose and triglycerides serum levels (p<0,05) an increased intestinal weight of distal ileum (P<0,05). Animal submitted to high fat diet presented higher levels of HOMA-IR although significant difference to CT was not achieved. HOMA-beta were significantly higher (p<0.05) in HFD+INS. Visceral fat was 10% lower in HFD+INS but the difference was not significant. Conclusions: In non-diabetic obese rats, oral insulin improves metabolic malfunction associated to rescue of beta-cell activity.

Antioxidant, anti-alpha-glucosidase and pancreatic beta-cell protective effects of methanolic extract of Ensete superbum Cheesm seeds

Objective: To investigate the antioxidant, anti-a-glucosidase and pancreatic b-cell protective potential of Ensete superbum (E. superbum) seeds. Methods: A variety of in vitro assays including radical scavenging, reducing power potential, phenolic content determination, a-glucosidase assay and pancreatic b-cell (1.4E7 cells) viability were employed for assessing the effect of methanolic extract of E. superbum seeds. Results: The radical scavenging and reducing power effects comparable with the stan-dard rutin were obtained while the enzyme inhibitory activity of the extract was 68-fold better than the standard antidiabetic drug, acarbose. The seed extract of E. superbum was packed-full of polyphenols with mean percentage gallic acid equivalent value of (38.2 ± 1.8) (n = 3). The protection of pancreatic cells from massive onslaught of hydrogen peroxide was far superior to that obtained for rutin. Conclusions: The reputed antidiabetic therapeutic uses of the seeds extract of E. superbum may be justified on the basis of inhibition of carbohydrate enzymes, anti-oxidant effects and pancreatic b-cell protection.

Antioxidant, anti-alpha-glucosidase and pancreatic beta-cell protective effects of methanolic extract of Ensete superbum Cheesm seeds

Objective To investigate the antioxidant, anti-α-glucosidase and pancreatic β-cell protective potential of Ensete superbum (E. superbum) seeds. Methods A variety of in vitro assays including radical scavenging, reducing power potential, phenolic content determination, α-glucosidase assay and pancreatic β-cell (1.4E7 cells) viability were employed for assessing the effect of methanolic extract of E. superbum seeds. Results The radical scavenging and reducing power effects comparable with the standard rutin were obtained while the enzyme inhibitory activity of the extract was 68-fold better than the standard antidiabetic drug, acarbose. The seed extract of E. superbum was packed-full of polyphenols with mean percentage gallic acid equivalent value of (38.2 ± 1.8) (n = 3). The protection of pancreatic cells from massive onslaught of hydrogen peroxide was far superior to that obtained for rutin. Conclusions The reputed antidiabetic therapeutic uses of the seeds extract of E. superbum may be justified on the basis of inhibition of carbohydrate enzymes, antioxidant effects and pancreatic β-cell protection.

Dynamic associations of mitochondria-endoplasmic reticulum in maintenance of pancreatic beta cell homeostasis / 药学学报

The appropriate regulation of intracellular bioenergy and nutrient metabolism is a basic requirement for proper function and survival of pancreatic beta cells, where mitochondria-endoplasmic reticulum (ER)-associations play crucial roles. Mitochondria are changed dynamically according to intracellular energy and nutrients, which provides material foundation for energy homeostasis; while ER regulates metabolic enzymes and protein synthesis in different pathways. This review sheds light upon the development of mitochondria-ER associations and its role in the regulation of insulin secretion in pancreatic beta cell. The impact on beta cell viability is discussed. Interruption of calcium and redox oxidative species results in reduction of glucose-stimulated insulin secretion, while intracellular calcium levels could be partial altered by depleting calcium from the ER. Given the tight link between ER and mitochondria, the association are crucial to the homeostasis and are an indicator of overall beta cell status, with a potential as a novel drug target for treatment of type 2 diabetes mellitus.

Effect and Mechanism of Cortex Lycii Radicis Extracts on the Proliferation and Apoptosis of Pancreatic Beta Cell / 浙江中医药大学学报

Objective] Observing Cortex Lycii Radicis' effect(Cortex Lycii) on rat insulinoma cells(INS-1) proliferation and apoptosis. To explore the mechanism of Cortex Lycii on Pancreatic Beta Cell Proliferation and apoptosis.[ Methods] After primary culture, cells were randomly divided into blank control group:control,11.1mmol·L-1 glucose,HG,30mmol·L-1 glucose, HG+Cortex Lycii(1g·L-1), HG+Cortex Lycii(2g·L-1), HG+Cortex Lycii(4g·L-1), the survival rate of cells was observed by cell counting kit-8(CCK-8);the apoptosis rate was observed by Annexin V stammg. [Results] ①Compared with HG the better effect of cell proliferation groups of Cortex Lycii(P<0.01), the best is group of Cortex Lycii(2g·L-1)(P<0.05) ②Compared with HG group the higher survival rate is group of Cortex Lycii(P<0.01), the lower apoptosis rate of Cortex Lycii(2g·L-1) compared with Cortex Lycii(1g·L-1). [Conclusion] Cortex Lycii can promote the proliferation of pancreatic beta cell, inhibit the apoptosis to protect the pancreatic beta cell. The optimal concentration is 2g·L-1.

Differential Gene Expression in GPR40-Overexpressing Pancreatic beta-cells Treated with Linoleic Acid

"G protein-coupled receptor 40" (GPR40), a receptor for long-chain fatty acids, mediates the stimulation of glucose-induced insulin secretion. We examined the profiles of differential gene expression in GPR40-activated cells treated with linoleic acid, and finally predicted the integral pathways of the cellular mechanism of GPR40-mediated insulinotropic effects. After constructing a GPR40-overexpressing stable cell line (RIN-40) from the rat pancreatic beta-cell line RIN-5f, we determined the gene expression profiles of RIN-5f and RIN-40. In total, 1004 genes, the expression of which was altered at least twofold, were selected in RIN-5f versus RIN-40. Moreover, the differential genetic profiles were investigated in RIN-40 cells treated with 30 microM linoleic acid, which resulted in selection of 93 genes in RIN-40 versus RIN-40 treated with linoleic acid. Based on the Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG, http://www.genome.jp/kegg/), sets of genes induced differentially by treatment with linoleic acid in RIN-40 cells were found to be related to mitogen-activated protein (MAP) kinase- and neuroactive ligand-receptor interaction pathways. A gene ontology (GO) study revealed that more than 30% of the genes were associated with signal transduction and cell proliferation. Thus, this study elucidated a gene expression pattern relevant to the signal pathways that are regulated by GPR40 activation during the acute period. Together, these findings increase our mechanistic understanding of endogenous molecules associated with GPR40 function, and provide information useful for identification of a target for the management of type 2 diabetes mellitus.

Padina arborescens extract protects high glucose-induced apoptosis in pancreatic beta cells by reducing oxidative stress

BACKGROUND/OBJECTIVES: This study investigated whether Padina arborescens extract (PAE) protects INS-1 pancreatic beta cells against glucotoxicity-induced apoptosis. MATERIALS/METHODS: Assays, including cell viability, lipid peroxidation, generation of intracellular ROS, NO production, antioxidant enzyme activity and insulin secretion, were conducted. The expressions of Bax, Bcl-2, and caspase-3 proteins in INS-1 cells were evaluated by western blot analysis, and apoptosis/necrosis induced by high glucose was determined by analysis of FITC-Annexin V/PI staining. RESULTS: Treatment with high concentrations of glucose induced INS-1 cell death, but PAE at concentrations of 25, 50 or 100 microg/ml significantly increased cell viability. The treatment with PAE dose dependently reduced the lipid peroxidation and increased the activities of antioxidant enzymes reduced by 30 mM glucose, while intracellular ROS levels increased under conditions of 30 mM glucose. PAE treatment improved the secretory responsiveness following stimulation with glucose. The results also demonstrated that glucotoxicity-induced apoptosis is associated with modulation of the Bax/Bcl-2 ratio. When INS-1 cells were stained with Annexin V/PI, we found that PAE reduced apoptosis by glucotoxicity. CONCLUSIONS: In conclusion, the present study indicates that PAE protects against high glucose-induced apoptosis in pancreatic beta cells by reducing oxidative stress.

Antidiabetic and Beta Cell-Protection Activities of Purple Corn Anthocyanins

Antidiabetic and beta cell-protection activities of purple corn anthocyanins (PCA) were examined in pancreatic beta cell culture and db/db mice. Only PCA among several plant anthocyanins and polyphenols showed insulin secretion activity in culture of HIT-T15 cells. PCA had excellent antihyperglycemic activity (in terms of blood glucose level and OGTT) and HbA1c-decreasing activity when compared with glimepiride, a sulfonylurea in db/db mice. In addition, PCA showed efficient protection activity of pancreatic beta cell from cell death in HIT-T15 cell culture and db/db mice. The result showed that PCA had antidiabetic and beta cell-protection activities in pancreatic beta cell culture and db/db mice.

Neonatal Diabetes Caused by Activating Mutations in the Sulphonylurea Receptor

Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels in pancreatic beta-cells play a crucial role in insulin secretion and glucose homeostasis. These channels are composed of two subunits: a pore-forming subunit (Kir6.2) and a regulatory subunit (sulphonylurea receptor-1). Recent studies identified large number of gain of function mutations in the regulatory subunit of the channel which cause neonatal diabetes. Majority of mutations cause neonatal diabetes alone, however some lead to a severe form of neonatal diabetes with associated neurological complications. This review focuses on the functional effects of these mutations as well as the implications for treatment.

Zinc y diabetes: un nutriente inportante en su prevención y tratamiento / Zinc in the prevention and treatment of diabetes

Zinc (Zn) is an essential micronutrient for humans and other organisms. It participates in the activity of more than 300 enzymes and in important cellular processes such as cell division and apoptosis, as well as cellular signaling. The concentration of Zn in humans is highly regulated, and alterations in Zn homeostasis have been associated with several diseases including diabetes. Zn supplementation in humans and other mammals has been associated with improved glycemic control in both type 1 and t type 2 diabetes mellitus, however the underlying molecular mechanisms involved in this process have not yet been fully elucidated. Zn appears to have a key role in insulin biosynthesis and activity, mainly by decreasing the production of certain cytokines such as IL-1beta and IL-6, associated with pancreatic beta cell death during the inflammatory process characteristic of type 2 diabetes. It also improves insulin mediated signal transduction in target cells, improving metabolic control. Zn could play an important role in the development of diabetes mellitus, since a genetic polymorphism of the Zn transporter ZnT-8 may be associated with an increased risk of type 2 diabetes. In this article we analyze the available information supporting the therapeutic use of Zn as a coadjutant in the metabolic control of diabetes mellitus.

Effect of PRX-1 Downregulation in the Type 1 Diabetes Microenvironment

Type 1 diabetes (T1D) is caused by dysregulation of the immune system in the pancreatic islets, which eventually leads to insulin-producing pancreatic beta-cell death and destabilization of glucose homeostasis. One of the major characteristics of T1D pathogenesis is the production of inflammatory mediators by macrophages that result in destruction or damage of pancreatic beta-cells. In this study the inflammatory microenvironment of T1D was simulated with RAW264.7 cells and MIN6 cells, acting as macrophages and pancreatic beta-cells respectably. In this setting, peroxiredoxin-1, an anti-oxidant enzyme was knocked down to observe its functions in the pathogenesis of T1D. RAW264.7 cells were primed with lipopolysaccharide and co-cultured with MIN6 cells while PRX-1 was knocked down in one or both cell types. Our results suggest that hindrance of PRX-1 activity or the deficiency of this enzyme in inflammatory conditions negatively affects pancreatic beta-cell survival. The observed decrease in viability of MIN6 cells seems to be caused by nitric oxide production. Additionally, it seems that PRX-1 affects previously reported protective activity of IL-6 in pancreatic beta cells as well. These results signify new, undiscovered roles for PRX-1 in inflammatory conditions and may contribute toward our understanding of autoimmunity.

Decreased Expression and Induced Nucleocytoplasmic Translocation of Pancreatic and Duodenal Homeobox 1 in INS-1 Cells Exposed to High Glucose and Palmitate

BACKGROUND: Type 2 diabetes mellitus (T2DM) is often accompanied by increased levels of circulating fatty acid. Elevations in fatty acids and glucose for prolonged periods of time have been suggested to cause progressive dysfunction or apoptosis of pancreatic beta cells in T2DM. However, the precise mechanism of this adverse effect is not well understood. METHODS: INS-1 rat-derived insulin-secreting cells were exposed to 30 mM glucose and 0.25 mM palmitate for 48 hours. RESULTS: The production of reactive oxygen species increased significantly. Pancreatic and duodenal homeobox 1 (Pdx1) expression was down-regulated, as assessed by reverse transcription-polymerase chain reaction and Western blot analyses. The promoter activities of insulin and Pdx1 were also diminished. Of note, there was nucleocytoplasmic translocation of Pdx1, which was partially prevented by treatment with an antioxidant, N-acetyl-L-cysteine. CONCLUSION: Our data suggest that prolonged exposure of beta cells to elevated levels of glucose and palmitate negatively affects Pdx1 expression via oxidative stress.

Effects of glimepiride on plasma glucose and beta-cell function in newly diagnosed type 2 diabetic patients / 中国基层医药

Objective To study the effects of glimepiride and short-term intensive therapy with insulin on plasma glucose and beta-cell function in newly diagnosed type 2 diabetic patients.Methods 80 newly diagnosed type 2 diabetic patients were divided into two groups of 40 patients each and randomly treated with insulin or glimepiride plus metformin for 8 weeks.The FBG,2hPBG,HbA_1c,improvement of beta-cell function were measured before and after intensive therapy in each group.Results After the treatment,FBG,2hPBG,HbA_1c were significantly decreased (all P<0.001) in each group;FCP and 2hPCP were increased(P<0.05)in each group.Conclusion Glimepiride or short-term intensive therapy with insulin plus metformin could effectively improve glycemic control and beta-cell function in newly diagnosed type 2 diabetic patients.

The role of autophagy in maintaining pancreatic beta-cell function / 第二军医大学学报

Disrupted pancreatic β-cell function and decreased β-cell number are two of the main causes of type 2 diabetes mellitus. Recent studies have indicated that autophagy plays an important role in protecting pancreatic β-cell and in maintaining the structure, number, and secretive function of pancreatic β-cell. Although autophagy has been a focus of study in recent years, including areas such as tumor, neural diseases and aging, but its relationship with pancreatic β-cell was not included. In this paper we review the concept of autophagy and its role in maintaining the normal function of pancreatic β-cells.

Transdifferentiation of Enteroendocrine K-cells into Insulin-expressing Cells / 당뇨병

BACKGROUND: Despite a recent breakthough in human islet transplantation for treating type 1 diabetes mellitus, the limited availability of donor pancreases remains a major obstacle. Endocrine cells within the gut epithelium (enteroendocrine cells) and pancreatic beta cells share similar pathways of differentiation during embryonic development. In particular, K-cells that secrete glucose-dependent insulinotropic polypeptide (GIP) have been shown to express many of the key proteins found in beta cells. Therefore, we hypothesize that K-cells can be transdifferentiated into beta cells because both cells have remarkable similarities in their embryonic development and cellular phenotypes. METHODS: K-cells were purified from heterogeneous STC-1 cells originating from an endocrine tumor of a mouse intestine. In addition, a K-cell subclone expressing stable Nkx6.1, called "Kn4-cells," was successfully obtained. In vitro differentiation of K-cells or Kn4-cells into beta cells was completed after exendin-4 treatment and serum deprivation. The expressions of insulin mRNA and protein were examined by RT-PCR and immunocytochemistry. The interacellular insulin content was also measured. RESULTS: K-cells were found to express glucokinase and GIP as assessed by RT-PCR and Western blot analysis. RT-PCR showed that K-cells also expressed Pdx-1, NeuroD1/Beta2, and MafA, but not Nkx6.1. After exendin-4 treatment and serum deprivation, insulin mRNA and insulin or C-peptide were clearly detected in Kn4-cells. The intracellular insulin content was also increased significantly in these cells. CONCLUSION: K-cells are an attractive potential source of insulin-producing cells for treatment of type 1 diabetes mellitus. However, more experiments are necessary to optimize a strategy for converting K-cells into beta cells.

Type 1 Diabetes Mellitus

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by selective autoimmune- mediated destruction of pancreatic islet beta- cells leading gradually to absolute insulin deficiency. T1D is under polygenic control. The HLA complex attributes 50% of the genetic risk for T1D while as many as 20 genes influence susceptibility to T1D. The autoimmune beta-cell destruction could be triggered by environmental factors. While the exact trigger of anti-islet autoimmunity remains elusive, it can lead to an imbalance between regulatory T cells and autoimmune effector T cells. During the initiation of insulitis, emerging evidences suggest that the infiltrating macrophages via toll-like receptor 2 (TLR2) activation lead to induction and amplification of insulitis. Following the priming of diabetogenic T-cells, autoreactive T effector cells destroy the beta cells by direct contact- dependent cytolysis or by soluble mediators secreted from macrophages or CD4 T effector cells. The hyperglycemia occurs late in its course after 80% of the beta cells have been destroyed. Although no current cure exists, refinement of genetic studies and islet autoantibodies has improved the ability to predict the risk of T1D and aid the establishment of rationally designed preventive therapies. Other strategies involve beta-cell replacement by islet transplantation. Extensive and long-term research on the efficacy of islet transplantation and preservation of beta-cell function is keenly needed.

Type 1 Diabetes Mellitus

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by selective autoimmune- mediated destruction of pancreatic islet beta- cells leading gradually to absolute insulin deficiency. T1D is under polygenic control. The HLA complex attributes 50% of the genetic risk for T1D while as many as 20 genes influence susceptibility to T1D. The autoimmune beta-cell destruction could be triggered by environmental factors. While the exact trigger of anti-islet autoimmunity remains elusive, it can lead to an imbalance between regulatory T cells and autoimmune effector T cells. During the initiation of insulitis, emerging evidences suggest that the infiltrating macrophages via toll-like receptor 2 (TLR2) activation lead to induction and amplification of insulitis. Following the priming of diabetogenic T-cells, autoreactive T effector cells destroy the beta cells by direct contact- dependent cytolysis or by soluble mediators secreted from macrophages or CD4 T effector cells. The hyperglycemia occurs late in its course after 80% of the beta cells have been destroyed. Although no current cure exists, refinement of genetic studies and islet autoantibodies has improved the ability to predict the risk of T1D and aid the establishment of rationally designed preventive therapies. Other strategies involve beta-cell replacement by islet transplantation. Extensive and long-term research on the efficacy of islet transplantation and preservation of beta-cell function is keenly needed.

Pathogenesis of Type 1 Diabetes / 한양의대학술지

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by selective destruction of pancreatic islet betacells causing insulin deficiency. T1D has been shown to be a polygenic trait, associated with several loci, among which the human leukocyte antigen (HLA) region accounts for 40% of the genetic risk to develop T1D. The betacell autoimmune response is triggered by environmental or unknown events in the predisposing genetic background. The triggers of autoimmunity can lead to a localized imbalance between regulatory T cells and autoimmune effector T cells. The macrophages and autoreactive lymphocytes infiltrate the islets and the interaction of betacells and immune cells leads to inductionamplification of insulitis and loss of betacells. T cells destroy betacells in a direct cytotoxic manner or influence the induction of betacell apoptosis through the release of cytotoxic molecules, such as cytokines. The autoimmune process progresses subclinically for many years in the majority of patients, and clinical symptom do not appear until more than 80% of betacells have been destroyed. Although no current "cure" exists, there is a major effort to develop immunotherapies to prevent or halt the disorder that still requires much research to fully understand exact triggering events leading toautoimmune activation. Other strategies involve beta- cell replacement by islet transplantation, but researchs to enhance the islet mass transplanted and preserve beta-cell function are necessary.

Beta Cells Preservation in Diabetes using GLP-1 and Its Analog / 한양의대학술지

Diabetes Mellitus is a metabolic disease caused by impaired insulin secretion of pancreatic beta cells and increased insulin resistance of peripheral tissues. In Asian T2DM, progressive loss of beta cells mass and concomitant reduction of insulin secretion are more fundamental problems than peripheral insulin resistance. To solve this problem, research fields about investigation how stimulated islet cell growth and block the islet cell death is getting more important. Recently introduced drug, Glucagon like peptide-1 (GLP-1) has many beneficial roles in treatment of diabetes. GLP-1 stimulated glucose dependent insulin secretion and also can preserve beta cell mass through stimulation of beta cell growth and differentiation and protection of beta cell death from hyperglycemic stress. After treatment of GLP-1 or Exendin-4 (GLP-1 receptor agonist), beta cell mass is increased in animal models. This can be achieved through beta cell proliferation in islet or differentiation from intrapancreatic progenitor cells like ductal epithelium. The mechanism of beta cell proliferation is mediated by the PKA-CREB pathway. After activation of GLP-1 receptor, intracellular cAMP is elevated and then it activates PKA and CREB phosphorylation. Translocation of CREB into the nucleus up-regulates PDX-1 andIRS-2. Another pathway for beta cell proliferation is trans-activation of EGFR via c-Src after GLP-1 receptor activated. The notch pathway, major determinant of pancreas development in the embryonic stage, can be participate beta mass preservation through activation of gamma secretase in the beta cell membrane. Cleaved intracellular part of the notch translocates to the nucleus and binds to the pdx-1 promoter region. In hyperglycemia, oxidative and endoplasmic reticulum (ER) stress can be caused by apoptosis of the beta cell. Protection of apoptosis is another tool for beta cell mass preservation. After treatment of GLP-1 or exendin-4, beta cell apoptosis induced by oxidative and ER stress can be protected. GLP-1 can modulate JNK and GSK 3beta activation and ER chaperone and ER stress response. In treatment of diabetes, GLP-1 increases insulin secretion with glucose dependent manner and also preserves beta cell mass against progressive beta cell loss

Mediators and mechanisms of pancreatic beta-cell death in type 1 diabetes

Type 1 diabetes mellitus (T1D) is characterized by severe insulin deficiency resulting from chronic and progressive destruction of pancreatic beta-cells by the immune system. The triggering of autoimmunity against the beta-cells is probably caused by environmental agent(s) acting in the context of a predisposing genetic background. Once activated, the immune cells invade the islets and mediate their deleterious effects on beta-cells via mechanisms such as Fas/FasL, perforin/granzyme, reactive oxygen and nitrogen species and pro-inflammatory cytokines. Binding of cytokines to their receptors on the beta-cells activates MAP-kinases and the transcription factors STAT-1 and NFkappa-B, provoking functional impairment, endoplasmic reticulum stress and ultimately apoptosis. This review discusses the potential mediators and mechanisms leading to beta-cell destruction in T1D.

O diabetes melito tipo 1 (DM1) tem como característica uma grave deficiência de insulina que resulta da destruição da célula-beta, crônica e progressiva, pelo sistema imune. O desencadeamento da autoimunidade contra a célula-beta é causado, provavelmente, por agentes ambientais que atuam quando existe predisposição genética. Uma vez ativadas, células imunes invadem as ilhotas, e os efeitos deletérios sobre as células-beta são mediados por mecanismos relacionados a Fas/FasL, perforina/granzima, espécies reativas de oxigênio e nitrogênio, e a citocinas pró-inflamatórias. A ligação de citocinas a seus receptores na célula-beta ativa MAP-quinase e fatores de transcrição STAT-1 e NFkapaB, provocando prejuízo funcional, estresse de retículo endoplasmático e, por fim, apoptose. Esta revisão discute os mecanismos e os mediadores potenciais que levam à destruição da célula-beta no DM1.