Regeneration of islet β-cells in tree shrews and rats

Backgroud: Current understanding of injury and regeneration of islet β-cells in diabetes is mainly based on rodent studies. The tree shrew is now generally accepted as being among the closest living relatives of primates, and has been widely used in animal experimentation. However, there are few reports on islet cell composition and regeneration of β-cells in tree shrews.Methods: In this study, we examined the changes in islet cell composition and regeneration of β-cells after streptozotocin(STZ) treatment in tree shrews compared with Sprague-Dawley rats. Injury and regeneration of islet β-cells were observed using hematoxylin and eosin(HE) staining and immunohistochemical staining for insulin, glucagon, somatostatin and PDX-1.Results: Our data showed that in rats islet injury was most obvious on day 3 after injection, and islet morphologies were significantly restored by day 21. Regeneration of islet β-cells was very pronounced in rats, and mainly involved regeneration of centro-acinar cells and transformation of extra-islet ductal cells. In tree shrews, the regeneration of islet β-cells was not as significant. On days 3 and 7, only scattered regenerated cells were observed in the remaining islets. Further, no regeneration of centro-acinar cells was observed.Conclusion: The results suggest that the repair mechanism of islet β-cells in tree shrews is similar to that of humans.

Dietary Green Tea Extract and Antioxidants Improve Insulin Secretory Functions of Pancreatic β-Cells in Mild and Severe Experimental Rodent Model of Chronic Pancreatitis

Chronic pancreatitis (CP) is a progressive inflammatory disorder of the pancreas. It is predominantly idiopathic (with an unknown cause) in India and mostly due to alcohol in the West. Diabetes that occur secondary to chronic pancreatitis (T3c Diabetes) is often brittle, and is difficult to attain normoglycemia with conventional treatment requiring multiple doses of insulin. Mild and severe model of CP was induced in mice by repeated intraperitoneal injections of cerulein and L-arginine respectively with an intent to study islet dysfunction and develop therapeutic strategy in animal models of CP. Dietary intervention of epigallocatechin-3-gallate (EGCG) was tested in both the models of CP for its beneficial effects on insulin secretory functions. Pancreata collected upon euthanasia were used to study alterations in the morphology of pancreatic parenchyma and inflammation by staining with H&E and fibrotic changes by Masson’s trichrome and picrosirius staining. Insulin secretory functions of islets were evaluated to test the efficacy of the dietary intervention on β-cell functions. Intraperitoneal glucose tolerance test was performed to monitor the glucose homeostasis before and after the dietary intervention. Both the models resulted in CP with dispersed acini, inflammation and fibrosis. The loss of acini and extent of fibrosis was more in L-arginine model. 2-fold improvement in glucose-stimulated insulin secretory functions of islets was observed with 0.5% EGCG dietary intervention in cerulein model of CP and 1.6-fold in L-arginine model of CP. A further improvement in insulin secretion by 3.2-fold was observed with additional dietary supplements like N-acetyl cysteine, curcumin in combination with EGCG. Our results thus demonstrate and highlight the therapeutic potential of dietary green tea (EGCG) supplementation in reversing islet dysfunction and improving glucose homeostasis in experimental chronic pancreatitis in mice.

1.3 GHz 9-cell高性能超导腔高阶模耦合器电磁及热分析研究

中国科学院高能物理研究所于2023年6月完成了高品质因数1.3 GHz超导加速模组研发,在国际上率先实现了中温退火高品质因数超导腔模组技术路线。模组中集成了八只经过中温退火工艺处理的1.3 GHz9-cell超导腔,在模组的测试过程中超导腔的高阶模耦合器温升异常,导致超导腔无法在高梯度下稳定工作。通过HFSS软件和CST软件中的微波仿真模块对高阶模耦合器进行电磁分析,再通过理论和Ansys Workbench软件对高阶模耦合器进行热仿真分析,并结合模组的高功率实验,找到了超导腔性能异常的原因,并对超导腔高阶模耦合器的冷却方式进行了进一步的优化,解决了模组中超导腔高梯度下的不稳定性。

Fentanyl inhibits glucose-stimulated insulin release from β-cells in rat pancreatic islets

AIM： TO explore the effects of fentanyl on insulin release from freshly isolated rat pancreatic islets in static culture. METHODS： Islets were isolated from the pancreas of mature Sprague Dawley rats by common bile duct intraductal collagenase V digestion and were purified by discontinuous Ficoll density gradient centrifugation. The islets were divided into four groups according to the fentanyl concentration： control group （0 ng/mL）, group I （0.3 ng/mL）, group I （3.0 ng/mL）, and group III （30 ng/mL）. In each group, the islets were co-cultured for 48 h with drugs under static conditions with fentanyl alone, fentanyl ＋ 0.1 μg/mL naloxone or fentanyl ＋ 1.0 μg/mL naloxone. Cell viability was assessed by the MTT assay. Insulin release in response to low and high concentrations （2.8 mmol/L and 16.7 mmol/L, respectively） of glucose was investigated and electron microscopy morphological assessment was performed. RESULTS： Low- and high-glucose-stimulated insulin release in the control group was significantly higher than in groups I and II （62.33 ± 9.67 μIU vs 47.75 ± 8.47 μIU, 39.67 ± 6.18 μIU and 125.5 ± 22.04 μIU vs 96.17 ± 14.17 μIU, 75.17 ± 13.57 μIU, respectively, P 〈 0.01） and was lowest in group III （P 〈 0.01）. After adding 1 μg/mL naloxone, insulin release in groups II and II was not different from the control group. Electron microscopy studies showed that the islets were damaged by 30 ng/ml fentanyl. CONCLUSION： Fentanyl inhibited glucose-stimulated insulin release from rat islets, which could be prevented by naloxone. Higher concentrations of fentanyl significantly damaged β-cells of rat islets.

γ-aminobutyric acid secreted from isletβ-cells modulates exocrine secretion in rat pancreas

AIM： To investigate the role of endogenous γ-aminobutyric acid （GABA） in pancreatic exocrine secretion. METHODS： The isolated, vascularly perfused rat pancreas was employed in this study to eliminate the possible influences of extrinsic nerves and hormones. Cholecystokinin （CCK; 10 pmol/L） was intra-arterially given to stimulate exocrine secretion of the pancreas. RESULTS： Glutamine, a major precursor of GABA, which was given intra-arterially at concentrations of 1, 4 and 10 mmol/L, dose-dependently elevated the CCK-stimulated secretions of fluid and amylase in the normal pancreas. Bicuculline （10 μmol/L）, a GABAA receptor antagonist, blocked the enhancing effect of glutamine （4 mmol/L） on the CCK-stimulated exocrine secretions. Glutamine, at concentrations of 1, 4 and 10 mmol/L, dose-dependently increased the GABA concentration in portal effluent of the normal pancreas. The effects of glutamine on the CCK-stimulated exocrine secretion as well as the GABA secretion were markedly reduced in the streptozotocintreated pancreas. CONCLUSION： GABA could be secreted from β-cells into the isletoacinar portal system after administration of glutainine, and could enhance the CCK-stimulated exocrine secretion through GABAA receptors. Thus, GABA in islet β-cells is a hormone modulating pancreatic exocrine secretion.

Insufficient TRPM5 Mediates Lipotoxicity-induced Pancreaticβ-cell Dysfunction

Objective:While the reduction of transient receptor potential channel subfamily M member 5(TRPM5)has been reported in islet cells from type 2 diabetic(T2D)mouse models,its role in lipotoxicity-induced pancreaticβ-cell dysfunction remains unclear.This study aims to study its role.Methods:Pancreas slices were prepared from mice subjected to a high-fat-diet(HFD)at different time points,and TRPM5 expression in the pancreaticβcells was examined using immunofluorescence staining.Glucose-stimulated insulin secretion(GSIS)defects caused by lipotoxicity were mimicked by saturated fatty acid palmitate(Palm).Primary mouse islets and mouse insulinoma MIN6 cells were treated with Palm,and the TRPM5 expression was detected using qRT-PCR and Western blotting.Palm-induced GSIS defects were measured following siRNA-based Trpm5 knockdown.The detrimental effects of Palm on primary mouse islets were also assessed after overexpressing Trpm5 via an adenovirus-derived Trpm5(Ad-Trpm5).Results:HFD feeding decreased the mRNA levels and protein expression of TRPM5 in mouse pancreatic islets.Palm reduced TRPM5 protein expression in a time-and dose-dependent manner in MIN6 cells.Palm also inhibited TRPM5 expression in primary mouse islets.Knockdown of Trpm5 inhibited insulin secretion upon high glucose stimulation but had little effect on insulin biosynthesis.Overexpression of Trpm5 reversed Palm-induced GSIS defects and the production of functional maturation molecules unique toβcells.Conclusion:Our findings suggest that lipotoxicity inhibits TRPM5 expression in pancreaticβcells both in vivo and in vitro and,in turn,drivesβ-cell dysfunction.

Upregulation of α-ENaC induces pancreatic β-cell dysfunction,ER stress,and SIRT2 degradation

Islet beta cells(β-cells)produce insulin in response to high blood glucose levels,which is essential for preserving glucose homeostasis.Voltage-gated ion channels inβ-cells,including Na+,K+,and Ca2+channels,aid in the release of insulin.The epithelial sodium channel alpha subunit(α-ENaC),a voltage-independent sodium ion channel,is also expressed in human pancreatic endocrine cells.However,there is no reported study on the function of ENaC in theβ-cells.In the current study,we found thatα-ENaC was expressed in human pancreatic glandule and pancreatic isletβ-cells.In the pancreas of db/db mice and high-fat diet-induced mice,and in mouse isletβ-cells(MIN6 cells)treated with palmitate,α-ENaC expression was increased.Whenα-ENaC was overexpressed in MIN6 cells,insulin content and glucose-induced insulin secretion were significantly reduced.On the other hand,palmitate injured isletβ-cells and suppressed insulin synthesis and secretion,but increasedα-ENaC expression in MIN6 cells.However,α-ENaC knockout(Scnn1a−/−)in MIN6 cells attenuatedβ-cell disorder induced by palmitate.Furthermore,α-ENaC regulated the ubiquitylation and degradation of sirtuin 2 inβ-cells.α-ENaC also modulatedβ-cell function in correlation with the inositol-requiring enzyme 1 alpha/X-box binding protein 1(IRE1α/XBP1)and protein kinase RNA-like endoplasmic reticulum kinase/C/EBP homologous protein(PERK/CHOP)endoplasmic reticulum stress pathways.These results suggest thatα-ENaC may play a novel role in insulin synthesis and secretion in theβ-cells,and the upregulation ofα-ENaC promotes isletβ-cell dysfunction.In conclusion,α-ENaC may be a key regulator involved in isletβ-cell damage and a potential therapeutic target for type 2 diabetes mellitus.

The Effect of Tuberculosis Infection on Pancreatic Beta-Cell Function in Patients with Type 2 Diabetes Mellitus

Objective: The aim of this study is to investigate how individuals with type 2 diabetes mellitus’ pancreatic β-cell function index and insulin resistance index are affected by tuberculosis infection. Methods: The study group consisted of 89 patients with type 2 diabetes mellitus and tuberculosis infection who were admitted to Jingzhou Chest Hospital between March 2019 and March 2021. Gender and duration of diabetes were matching conditions. The control group was made up of 89 patients with type 2 diabetes who were admitted to Jingzhou Central Hospital’s endocrinology department during the same period. The two patient groups provided general information such as gender, age, length of diabetes, and blood biochemical indexes such as glycosylated hemoglobin (HbA1c), fasting glucose (FPG), and fasting C-peptide (FC-P). The HOMA calculator was used to calculate the HOMA-β and the HOMA-IR, and intergroup comparisons and correlation analyses were carried out. Results: Regarding gender, age, disease duration, FC-P, and HbA1c, the differences between the two groups were not statistically significant (P > 0.05). However, BMI, FPG, HOMA-β, and HOMA-IR showed statistically significant differences (P < 0.05). In comparison to the control group, the study group’s HOMA-β was lower and its HOMA-IR was greater. According to Spearman’s correlation analysis, HOMA-β had a negative association (P th FPG, HbA1c, and the length of the disease, and a positive correlation with BMI and FC-P. A positive correlation was found between HOMA-IR and BMI, FPG, and FC-P (P < 0.01), as well as a correlation with the length of the disease (P > 0.05) and HbA1c. Conclusions: In type 2 diabetes mellitus combined with tuberculosis infection, the patients had higher FPG levels and lower FC-P levels, the secretory function of pancreatic β-cells was more severely impaired, and insulin resistance was more obvious.

Mannogalactoglucan from mushrooms protects pancreatic islets via restoring UPR and promotes insulin secretion in TIDM mice

Type 1 diabetes mellitus(T1DM) lacks insulin secretion due to autoimmune deficiency of pancreaticβ-cells.Protecting pancreatic islets and enhancing insulin secretion has been therapeutic approaches.Mannogalactoglucan is the main type of polysaccharide from natural mushroom,which has potential medicinal prospects.Nevertheless,the antidiabetic property of mannogalactoglucan in T1DM has not been fully elucidated.In this study,we obtained the neutral fraction of alkali-soluble Armillaria mellea polysaccharide(AAMP-N) with the structure of mannogalactoglucan from the fruiting body of A.mellea and investigated the potential therapeutic value of AAMP-N in T1DM.We demonstrated that AAMP-N lowered blood glucose and improved diabetes symptoms in T1DM mice.AAMP-N activated unfolded protein response(UPR) signaling pathway to maintain ER protein folding homeostasis and promote insulin secretion in vivo.Besides that,AAMP-N promoted insulin synthesis via upregulating the expression of transcription factors,increased Ca^(2+) signals to stimulate intracellular insulin secretory vesicle transport via activating calcium/calmodulin-dependent kinase Ⅱ(CamkⅡ) and cAMP/PKA signals,and enhanced insulin secretory vesicle fusion with the plasma membrane via vesicle-associated membrane protein 2(VAMP2).Collectively,these studies demonstrated that the therapeutic potential of AAMP-N on pancreatic islets function,indicating that mannogalactoglucan could be natural nutraceutical used for the treatment of T1DM.

Roux-en-Y gastric bypass promotes expression of PDX-1 and regeneration of β-cells in Goto-Kakizaki rats

AIM:To study the effects of Roux-en-Y gastric bypass(RYGB) on the expression of pancreatic duodenal homeobox-1(PDX-1) and pancreatic β-cell regeneration/neogenesis,and their possible mechanisms in diabetics.METHODS:Three groups of randomly selected nonobese diabetic Goto-Kakizaki(GK) rats were subjected to RYGB,sham-RYGB and sham-operation(sham-op) surgery,respectively.The rats were euthanized at postoperative 1,2,4 and 12 wk.Their pancreases were resected and analyzed using reverse transcription polymerase chain reaction to detect the mRNA of PDX-1.Anti-PDX-1 immunohistochemical(IHC) staining and Western blotting were used to detect the protein of PDX-1.Double IHC staining of anti-Brdu and-insulin was performed to detect regenerated β-cells.The index of double Brdu and insulin positive cells was calculated.RESULTS:In comparison with sham-RYGB and sham-op groups,a significant increase in the expressions of PDX-1 mRNA in RYGB group was observed at all experimental time points(1 wk:0.378 ± 0.013 vs 0.120 ± 0.010,0.100 ± 0.010,F = 727.717,P < 0.001;2 wk:0.318 ± 0.013 vs 0.110 ± 0.010,0.143 ± 0.015,F = 301.509,P < 0.001;4 wk:0.172 ± 0.011 vs 0.107 ± 0.012,0.090 ± 0.010,F = 64.297,P < 0.001;12 wk:0.140 ± 0.007 vs 0.120 ± 0.010,0.097 ± 0.015,F = 16.392,P < 0.001);PDX-1 protein in RYGB group was also increased significantly(1 wk:0.61 ± 0.01 vs 0.21 ± 0.01,0.15 ± 0.01,F = 3031.127,P < 0.001;2 wk:0.55 ± 0.00 vs 0.15 ± 0.01,0.17 ± 0.01,F = 3426.455,P < 0.001;4 wk:0.39 ± 0.01 vs 0.18 ± 0.01,0.22 ± 0.01,F = 882.909,P < 0.001;12 wk:0.41 ± 0.01 vs 0.20 ± 0.01,0.18 ± 0.01,F = 515.833,P < 0.001).PDX-1 mRNA and PDX-1 protein production showed no statistical significance between the two sham groups.Many PDX-1 positive cells could be found in the pancreatic islets of the rats in RYGB group at all time points.In addition,the percentage of Brdu-insulin double staining positive cells was higher in RYGB group than in the other two groups(1 wk:0.22 ± 0.13 vs 0.03 ± 0.06,0.03 ± 0.06,P < 0.05;2 wk:0.28 ± 0.08 vs 0.00 ± 0.00,0.03 ± 0.06,P < 0.05;4 wk:0.24 ± 0.11 vs 0.07 ± 0.06,0.00 ± 0.00,P < 0.001;12 wk:0.20 ± 0.07 vs 0.03 ± 0.06,0.00 ± 0.00,P < 0.05).CONCLUSION:RYGB can increase the expression of pancreatic PDX-1 and induce the regeneration of β-cells in GK rats.The associated regeneration of islet cells may be a possible mechanism that how RYGB could improve type 2 diabetes mellitus.

Visfatin Protects Rat Pancreatic β-cells against IFN-γ-Induced Apoptosis through AMPK and ERK1/2 Signaling Pathways

Objective Interferon-γ （IFN-γ） plays an important role in apoptosis and was shown to increase the riskof diabetes. Visfatin, an adipokine, has anti-diabetic, anti-tumor, and regulating inflammatoryproperties. In this study we investigated the effect of visfatin on IFN-γ-induced apoptosis in ratpancreatic β-cells.Methods The RINm5F （rat insulinoma cell line） cells exposed to IFN-γ were treated with or withoutvisfatin. The viability and apoptosis of the cells were assessed by using MTT and flow cytometry. Theexpressions of mRNA and protein were detected by using real-time PCR and western blot analysis.Results The exposure of RINm5F cells to IFN-γ for 48 h led to increased apoptosis percentage of thecells. Visfatin pretreatment significantly increased the cell viability and reduced the cell apoptosisinduced by IFN-γ. IFN-γ-induced increase in expression of p53 mRNA and cytochrome c protein,decrease in mRNA and protein levels of anti-apoptotic protein Bcl-2 were attenuated by visfatinpretreatment. Visfatin also increased AMPK and ERK1/2 phosphorylation and the anti-apoptotic actionof visfatin was attenuated by the AMPK and ERK1/2 inhibitor.Conclusion These results suggested that visfatin protected pancreatic islet cells against IFN-γ-inducedapoptosis via mitochondria-dependent apoptotic pathway. The anti-apoptotic action of visfatin ismediated by activation of AMPK and ERK1/2 signaling molecules.

Intra-islet endothelial cell and β-cell crosstalk: Implication for islet cell transplantation

The intra-islet microvasculature is a critical interface between the blood and islet endocrine cells governing a number of cellular and pathophysiological processes associated with the pancreatic tissue. A growing body of evidence indicates a strong functional and physical interdependency of β-cells with endothelial cells(ECs), the building blocks of islet microvasculature. Intra-islet ECs, actively regulate vascular permeability and appear to play a role in fine-tuning blood glucose sensing and regulation. These cells also tend to behave as "guardians", controlling the expression and movement of a number of important immune mediators, thereby strongly contributing to the physiology of islets. This review will focus on the molecular signalling and crosstalk between the intra-islet ECs and β-cells and how their relationship can be a potential target for intervention strategies in islet pathology and islet transplantation.

Transdifferentiation of pancreatic α-cells into insulinsecreting cells: From experimental models to underlying mechanisms

Pancreatic insulin-secreting β-cells are essential regulators of glucose metabolism. New strategies are cur-rently being investigated to create insulin-producing β cells to replace deficient β cells, including the differentiation of either stem or progenitor cells, and the newly uncovered transdifferentiation of mature non-β islet cell types. However, in order to correctly drive any cell to adopt a new β-cell fate, a better understanding of the in vivo mechanisms involved in the plasticity and biology of islet cells is urgently required. Here, we review the recent studies reporting the phenomenon of transdifferentiation of α cells into β cells by focusing on the major candidates and contexts revealed to be involved in adult β-cell regeneration through this process. The possible underlying mechanisms of transdifferentiation and the interactions between several key factors involved in the process are also addressed. We propose that it is of importance to further study the molecular and cellular mechanisms underlying α- to β-cell transdifferentiation, in order to make β-cell regeneration from α cells a relevant and realizable strategy for developing cell-replacement therapy.

Relationship between Free Thyroxine and Islet Beta-cell Function in Euthyroid Subjects

Thyroid hormones have a specific effect on glucose-induced insulin secretion from the pancreas.We aimed to investigate the association between euthyroid hormones and islet betacell function in general population and non-treated type 2 diabetes mellitus(T2DM)patients.A total of 5089 euthyroid participants(including 4601 general population and 488 non-treated T2DM patients)were identified from a cross-sectional survey on the prevalence of metabolic diseases and risk factors in East China from February 2014 to June 2016.Anthropometric indices,biochemical parameters,and thyroid hormones were measured.Compared with general population,non-treated T2DM patients exhibited higher total thyroxine(TT4)and free thyroxine(FT4)levels but lower ratio of free triiodothyronine(T3):T4(P<0.01).HOMA-βhad prominently negative correlation with FT4 and positive relationship with free T3:T4 in both groups even after adjusting for age,body mass index(BMI)and smoking.When analyzed by quartiles of FT4 or free T3:T4,there were significantly decreased trend of HOMA-β going with the higher FT4 and lower free T3:T4 in both groups.Linear regression analysis showed that FT4 but not FT3 and free T3:T4 was negatively associated with HOMA-β no matter in general population or T2DM patients,which was independent of age,BMI,smoking,hypertension and lipid profiles.FT4 is independently and negatively associated with islet beta-cell function in euthyroid subjects.Thyroid hormone even in reference range could play an important role in the function of pancreatic islets.

The Influence of the Pro12Ala Mutation of PPARγ2 Receptor Gene on β-cells Restoration and Insulin Resistance in Type 2 Diabetes with Hypertension

The aim of this investigation was to determine whether a PPAR72 Prol2Ala polymorphism was associated with insulin resistance, β-cellfunction and hypertension in Chinese populations. 289 unrelated Chinese subjects first diagnosed Type 2 diabetes （HbAC1〈6.0） were investigated, including 132 hypertensive diabetic （HTD） subjects, 157 normotensive diabetic （NTD） subjects. Blood pressure and anthropometric measurements were collected from all participants, as well as several venous blood samples during oral glucose tolerance test （OGTT）. Biochemical measurements （high-density lipoprotein （HDL） and low-density lipoprotein-cholesterol （LDL）, triglycerides） and PPARγ2 Pro12Ala genotype were also determined. And insulin resistance and β-cells function was assessed by HOMA-IR and HOMA-β respectively. The frequency of subjects bearing the Pro12Ala was lower in the hypertension group （3. 03 %） than in the non-hypertension group （5.7 %） （P〈0.05） after adjusted for age, BMI and gender. Hypertensive diabetic Pro12Ala subjects had lower fasting plasma glucose level （P=0. 0127）, and better glucose tolerance 60 min after oral glucose （P=0. 0361）. Moreover, plasma insulin concentrations at 60 min was lower than those without A variant （P = 0. 0275）, and both hypertensive Ala/Pro in HOMA-β （P ： 0. 0455） and AUC for insulin （P=0. 0473） were higher, and HOMA-IR was lower （P=0. 0375） as compared with hypertensive Pro/Pro subjects. No association was observed between Prol2Ala genotype and BMI, total cholesterol, HDL- cholesterol or triglycerides in either group. Our findings suggested that the Ala 12 allele of the PPARγ2 gene may improve insulin resistance and ameliorate β-cell function reserves in T2DM with hypertension, and protect patients from hypertension in T2DM. As an important thrifty gene, environment factors may exerts an effect of PPARγ2 on glucose homeostasis and insulin resistance.

Implanting 1.1B4 human β-cell pseudoislets improves glycaemic control in diabetic severe combined immune deficient mice

AIM To investigate the potential of implanting pseudoislets formed from human insulin-releasing β-cell lines as an alternative to islet transplantation. METHODS In this study, the anti-diabetic potential of novel human insulin releasing 1.1B4 β-cells was evaluated by implanting the cells, either as free cell suspensions, or as three-dimensional pseudoislets, into the subscapular region of severe combined immune deficient mice rendered diabetic by single high-dose administration of streptozotocin. Metabolic parameters including food and fluid intake, bodyweight and blood glucose were monitored throughout the study. At the end of the study animals were given an intraperitoneal glucosetolerance test. Animals were then culled and blood and tissues were collected for analysis. Insulin and glucagon contents of plasma and tissues were measured by insulin radioimmunoassay and chemiluminescent enzyme-linked immunosorbance assay respectively. Histological analyses of pancreatic islets were carried out by quantitative fluorescence immunohistochemistry staining. RESULTS Both pseudoislet and cell suspension implants yielded well vascularised β-cell masses of similar insulin content. This was associated with progressive amelioration of hyperphagia(P < 0.05), polydipsia(P < 0.05), body weight loss(P < 0.05), hypoinsulinaemia(P < 0.05), hyperglycaemia(P < 0.05- P < 0.001) and glucose tolerance(P < 0.01). Islet morphology was also significantly improved in both groups of transplanted mice, with increased β-cell(P < 0.05- P < 0.001) and decreased alpha cell(P < 0.05- P < 0.001) areas. Whereas mice receiving 1.1B4 cell suspensions eventually exhibited hypoglycaemic complications, pseudoislet recipients displayed a more gradual amelioration of diabetes, and achieved stable blood glucose control similar to non-diabetic mice at the end of the study. CONCLUSION Although further work is needed to address safety issues, these results provide proof of concept for possible therapeutic applicability of human β-cell line pseudoislets in diabetes.

Cyclic nucleotide phosphodiesterase 3B is connected to osteopontin and protein kinase CK2 in pancreatic <i>β</i>-cells

Islets from RIP-PDE3B mice, exhibiting β-cell specific overexpression of the cAMP/cGMP-degrading enzyme phosphodiesterase 3B (PDE3B) and dysregulated insulin secretion, were subjected to microarray analysis. We show that osteopontin (OPN) mRNA is increased in a dose-dependent manner in islets from RIP-PDE3B mice, as compared to wild-type islets. In addition, in silico analysis shows that PDE3B and OPN are interacting. Furthermore, OPN interacts with protein kinase CK2 ina distinct submodule of the protein-protein interaction network. We studied PDE3B and OPN proteins and, in some cases, also PDE1B and PDE4C, under conditions of relevance for insulin secretion. In the presence of forskolin, PDE inhibitors, insulin, or a protein kinase CK2 inhibitor, similar alterations in protein levels of PDE3B and OPN are shown. In summary, results from using a number of strategies demonstrate a connection between PDE3B and OPNas well as a role for protein kinase CK2 inpancreatic β-cells.

Pancreaticβ-cell dysfunction in type 2 diabetes:Implications of inflammation and oxidative stress

Insulin resistance and pancreaticβ-cell dysfunction are major pathological mechanisms implicated in the development and progression of type 2 diabetes(T2D).Beyond the detrimental effects of insulin resistance,inflammation and oxidative stress have emerged as critical features of T2D that defineβ-cell dysfunction.Predominant markers of inflammation such as C-reactive protein,tumor necrosis factor alpha,and interleukin-1βare consistently associated withβ-cell failure in preclinical models and in people with T2D.Similarly,important markers of oxidative stress,such as increased reactive oxygen species and depleted intracellular antioxidants,are consistent with pancreaticβ-cell damage in conditions of T2D.Such effects illustrate a pathological relationship between an abnormal inflammatory response and generation of oxidative stress during the progression of T2D.The current review explores preclinical and clinical research on the pathological implications of inflammation and oxidative stress during the development ofβ-cell dysfunction in T2D.Moreover,important molecular mechanisms and relevant biomarkers involved in this process are discussed to divulge a pathological link between inflammation and oxidative stress duringβ-cell failure in T2D.Underpinning the clinical relevance of the review,a systematic analysis of evidence from randomized controlled trials is covered,on the potential therapeutic effects of some commonly used antidiabetic agents in modulating inflammatory makers to improveβ-cell function.

Glucose regulates LXRα subcellular localization and function in rat pancreatic β-cells

Liver X receptors(LXRs)are members of the nuclear receptor superfamily,which have been implicated in lipid ho-meostasis and more recently in glucose metabolism.Here,we show that glucose does not change LXRα protein level,but affects its localization in pancreatic β-cells.LXRα is found in the nucleus at 8 mM glucose and in the cytoplasm at4.2 mM.Addition of glucose translocates LXRα from the cytoplasm into the nucleus.Moreover,after the activation ofLXR by its synthetic non-steroidal agonist(T0901317),insulin secretion and glucose uptake are increased at 8 mM anddecreased at 4.2 mM glucose in a dose-dependent manner.Furthermore,at low glucose condition,okadaic acid reversedLXRα effect on insulin secretion,suggesting the involvement of glucose signaling through a phosphorylation-dependentmechanism.

Antioxidant Effects of Alperujo Extract (Arbequina and Frantoio Varieties) on MIN6 <i>β</i>-Cells Subjected to Stress with Glucose or H₂O₂

Alperujo, an antioxidant-rich by-product of olive oil extraction, could protect β-cells against oxidative damage. Our goal was to study the antioxidant effects of an alperujo extract (AE) on MIN6 β-cells challenged with glucose or hydrogen peroxide. MIN6 β-cells were challenged with glucose (100 mM) or H2O2 (0.15 mM), with or without AE (20 μM phenol). Reactive oxygen species, intracellular iron (Fe), insulin, glucose uptake, and mRNA gene expression of Uncoupling Protein-2 (UCP-2), Thioredoxin (TRDX), p47phox, and the ratio Bax/Bcl-2 were measured. ROS increased when the stressors were incubated with AE (p < 0.05 and p < 0.01, respectively). Intracellular Fe increased in glucose presence (100 mM p < 0.001). Insulin secretion improved when cells were pre-incubated with AE (p < 0.001) and glucose uptake increased when cells were pre-incubated with AE for 3 days and then further treated with glucose (p < 0.001). After 3 days of AE alone, mRNA relative expression of UCP-2 and TRDX increased (p < 0.001) and after 5 days p47phox, also increased. The Bax/Bcl-2 ratio tended to decrease in the samples pre-incubated with AE. The Alperujo extract,in vitro, had a pro-oxidant behavior, however pre-incubating MIN6 β-cells with AE tended to protect them against apoptosis, thereby enhancing insulin secretion.