Role In Beta-cell Dysfunction Research Articles

#97 Study of association between post transplant diabetes mellitus (PTDM) and hypomagnesemia

Abstract Background and Aims New onset diabetes after transplantation (NODAT) or PTDM (Post-transplant Diabetes Mellitus) is associated with increased morbidity, renal graft loss, cardiovascular complications, mortality and increased health care costs. It has been shown that incidence of NODAT is rising in recent years. It is suggested that there is more prominent role of beta cell dysfunction rather than insulin resistance in patients with PTDM. Hypomagnesemia which is commonly seen in post-transplant patients is suggested to have a role in promoting beta cell dysfunction. Emerging modifiable risk factors for PTDM like hypomagnesemia need to be studied which may help to improve its prevalence and outcomes. Method This study was single centre study to assess association of PTDM or NODAT with hypomagnesemia. Other risk factors like body mass index (BMI) >25 kg/m2, higher age and sex of the recipient were also studied. This study was a prospective, non-randomised, comparative, observational study. Duration of the study was from 1st October 2016 to 28th February 2018. Recipients with age > 18 years with at least 2 fasting blood sugar readings of >126 mg/dl or 2 post prandial readings of >200 mg/dl or need for antidiabetic medications beyond 1-month post-transplant were studied as PTDM or NODAT. Patients with deceased donor transplant, second kidney transplant, simultaneous other organ transplant, active Hepatitis C infection, active cytomegalovirus infection, patients with acute rejection, patients with polycystic kidney disease and patients with basiliximab induction were excluded. Results After applying exclusion and exclusion criteria, 98 patients were studied in total. Among 98 patients around 40 patients developed PTDM. When assessed independently higher age of the patient (age more than 50 years) was associated with PTDM (p = .030) while sex of the recipient was not associated with PTDM (P = .188). BMI >25 kg/m2 was significantly associated with PTDM at 1 month (p = .0001), 2 month (p < .0001), 3 month (p < .0001), 6 month (p < .0001), 9 month (p = .0001) and 12 month (p = .003) post-transplant. No statistical difference between doses of steroids were seen in patients with or without PTDM. All 98 patients received tacrolimus as part of their immunosuppressant regime. Time varying serum tacrolimus trough levels were not associated with PTDM and was removed as confounder by using univariate cox proportional hazard model (p = 0.691). After univariate and subsequently multivariate logistic regression analysis only hypomagnesemia was significantly associated with PTDM (p = .0001). After using univariate and subsequently multivariate cox proportional hazard model to study time varying risk factors, both hypomagnesemia (HR, 0.099; 95% CI, 0.016-0.624, p = .014) and BMI >25 kg/m2 (HR, 3.435; 95% CI, 1.657-7.119, p = .001) were associated with PTDM. Significantly a greater number of patients with lower magnesium levels developed PTDM early as compared to patients with normal magnesium levels (Spearman's coefficient of rank correlation (rho) = 0.53; 95% CI, 0.261-0.722, p = .0004). Conclusion Hypomagnesemia and overweight are modifiable risk factors significantly associated with PTDM even after removing confounding factors. Early development of PTDM in patient with hypomagnesemia further corroborates its role. Active interventions should be sought to control hypomagnesemia and overweight which may improve the morbidity and mortality of kidney transplant patients in long run.

Prolonged culture of human pancreatic islets under glucotoxic conditions changes their acute beta cell calcium and insulin secretion glucose response curves from sigmoid to bell-shaped.

The rapid remission of type 2 diabetes by a diet very low in energy correlates with a marked improvement in glucose-stimulated insulin secretion (GSIS), emphasising the role of beta cell dysfunction in the early stages of the disease. In search of novel mechanisms of beta cell dysfunction after long-term exposure to mild to severe glucotoxic conditions, we extensively characterised the alterations in insulin secretion and upstream coupling events in human islets cultured for 1-3 weeks at ~5, 8, 10 or 20 mmol/l glucose and subsequently stimulated by an acute stepwise increase in glucose concentration. Human islets from 49 non-diabetic donors (ND-islets) and six type 2 diabetic donors (T2D-islets) were obtained from five isolation centres. After shipment, the islets were precultured for 3-7 days in RPMI medium containing ~5 mmol/l glucose and 10% (vol/vol) heat-inactivated FBS with selective islet picking at each medium renewal. Islets were then cultured for 1-3 weeks in RPMI containing ~5, 8, 10 or 20 mmol/l glucose before measurement of insulin secretion during culture, islet insulin and DNA content, beta cell apoptosis and cytosolic and mitochondrial glutathione redox state, and assessment of dynamic insulin secretion and upstream coupling events during acute stepwise stimulation with glucose [NAD(P)H autofluorescence, ATP/(ATP+ADP) ratio, electrical activity, cytosolic Ca2+ concentration ([Ca2+]c)]. Culture of ND-islets for 1-3 weeks at 8, 10 or 20 vs 5 mmol/l glucose did not significantly increase beta cell apoptosis or oxidative stress but decreased insulin content in a concentration-dependent manner and increased beta cell sensitivity to subsequent acute stimulation with glucose. Islet glucose responsiveness was higher after culture at 8 or 10 vs 5 mmol/l glucose and markedly reduced after culture at 20 vs 5 mmol/l glucose. In addition, the [Ca2+]c and insulin secretion responses to acute stepwise stimulation with glucose were no longer sigmoid but bell-shaped, with maximal stimulation at 5 or 10 mmol/l glucose and rapid sustained inhibition above that concentration. Such paradoxical inhibition was, however, no longer observed when islets were acutely depolarised by 30 mmol/l extracellular K+. The glucotoxic alterations of beta cell function were fully reversible after culture at 5 mmol/l glucose and were mimicked by pharmacological activation of glucokinase during culture at 5 mmol/l glucose. Similar results to those seen in ND-islets were obtained in T2D-islets, except that their rate of insulin secretion during culture at 8 and 20 mmol/l glucose was lower, their cytosolic glutathione oxidation increased after culture at 8 and 20 mmol/l glucose, and the alterations in GSIS and upstream coupling events were greater after culture at 8 mmol/l glucose. Prolonged culture of human islets under moderate to severe glucotoxic conditions markedly increased their glucose sensitivity and revealed a bell-shaped acute glucose response curve for changes in [Ca2+]c and insulin secretion, with maximal stimulation at 5 or 10 mmol/l glucose and rapid inhibition above that concentration. This novel glucotoxic alteration may contribute to beta cell dysfunction in type 2 diabetes independently from a detectable increase in beta cell apoptosis.

PAHSAs reduce cellular senescence and protect pancreatic beta cells from metabolic stress through regulation of Mdm2/p53

Senescence in pancreatic beta cells plays a major role in beta cell dysfunction, which leads to impaired glucose homeostasis and diabetes. Therefore, prevention of beta cell senescence could reduce the risk of diabetes. Treatment of nonobese diabetic (NOD) mice, a model of type 1 autoimmune diabetes (T1D), with palmitic acid hydroxy stearic acids (PAHSAs), a novel class of endogenous lipids with antidiabetic and antiinflammatory effects, delays the onset and reduces the incidence of T1D from 82% with vehicle treatment to 35% with PAHSAs. Here, we show that a major mechanism by which PAHSAs protect islets of the NOD mice is by directly preventing and reversing the initial steps of metabolic stress-induced senescence. In vitro PAHSAs increased Mdm2 expression, which decreases the stability of p53, a key inducer of senescence-related genes. In addition, PAHSAs enhanced expression of protective genes, such as those regulating DNA repair and glutathione metabolism and promoting autophagy. We demonstrate the translational relevance by showing that PAHSAs prevent and reverse early stages of senescence in metabolically stressed human islets by the same Mdm2 mechanism. Thus, a major mechanism for the dramatic effect of PAHSAs in reducing the incidence of type 1 diabetes in NOD mice is decreasing cellular senescence; PAHSAs may have a similar benefit in humans.

Differential expression of regulators of the canonical Wnt pathway during the compensatory beta-cell hyperplasia in prediabetic mice

We previously reported that the canonical Wnt signaling pathway is activated during compensatory islet hyperplasia in prediabetic mice. Here, we aimed to expand our knowledge concerning the Wnt signaling partners and modulators involved in this process. We report here that Axin1, Axin2, and DACT1, inhibitors of the canonical Wnt signaling pathway, displayed no change in their expression, while GSK-3β, a multi-functional kinase that acts as a negative regulator of this pathway as well as affects insulin secretion/action, was up-regulated in hyperplastic islets of prediabetic mice. We also observed that COUP-TFII, a protein that acts positively on Wnt-target genes related to cell proliferation, displays a significant increase in gene expression and protein content and is highly immunolabeled in islet cell nuclei of prediabetic mice compared to control islets. These findings suggest that GSK-3β and COUP-TFII may play a role in beta-cell dysfunction and hyperplasia during type 2 prediabetes.

In vitro effect of DDE exposure on the regulation of B-TC-6 pancreatic beta cell insulin secretion: a potential role in beta cell dysfunction and type 2 diabetes mellitus

Organochlorine compounds (OC) include synthetic insecticides previously used throughout the world before being banned for their adverse effects and environmental persistence; DDT (dichlorodiphenyltrichloroethane) was one of the most widely used. Epidemiological evidence suggests that higher levels of some OC, including metabolites of DDT, such as dichlorodiphenyldichloroethylene (DDE), are associated with type 2 diabetes mellitus (T2D). DDE exposure may affect pancreatic cellular functions associated with glucose control and possibly cause beta cell dysfunction. The in vitro effect of DDE exposure on pancreatic beta cell insulin secretion was investigated using Beta-Tumor Cell-6 (B-TC-6) murine pancreatic beta cells. DDE exposure significantly increased insulin secretion suggesting a role for DDE in altering insulin synthesis and secretion. Reactive oxygen species (ROS) levels were not significantly increased indicating that oxidative stress is not responsible for the DDE-induced insulin secretion. Pancreatic and duodenal homeobox factor-1 (PDX-1) levels were not significantly increased suggesting that DDE exposure does not alter insulin transcription, but prohormone convertase (PC) levels were increased suggesting a role for DDE in altering insulin translation. Based on these in vitro results, DDE may play a role in beta cell dysfunction by affecting mechanisms that regulate insulin secretion but it is not likely to be the major mechanism behind the DDE/T2D epidemiological association.

Inherent Beta Cell Dysfunction Contributes to Autoimmune Susceptibility.

The pancreatic beta cell is a highly specialized cell type whose primary function is to secrete insulin in response to nutrients to maintain glucose homeostasis in the body. As such, the beta cell has developed unique metabolic characteristics to achieve functionality; in healthy beta cells, the majority of glucose-derived carbons are oxidized and enter the mitochondria in the form of pyruvate. The pyruvate is subsequently metabolized to induce mitochondrial ATP and trigger the downstream insulin secretion response. Thus, in beta cells, mitochondria play a pivotal role in regulating glucose stimulated insulin secretion (GSIS). In type 2 diabetes (T2D), mitochondrial impairment has been shown to play an important role in beta cell dysfunction and loss. In type 1 diabetes (T1D), autoimmunity is the primary trigger of beta cell loss; however, there is accumulating evidence that intrinsic mitochondrial defects could contribute to beta cell susceptibility during proinflammatory conditions. Furthermore, there is speculation that dysfunctional mitochondrial responses could contribute to the formation of autoantigens. In this review, we provide an overview of mitochondrial function in the beta cells, and discuss potential mechanisms by which mitochondrial dysfunction may contribute to T1D pathogenesis.

The role of beta-cell dysfunction in early type 1 diabetes.

Emerging data have suggested that β-cell dysfunction may exacerbate the development and progression of type 1 diabetes (T1D). In this review, we highlight clinical and preclinical studies suggesting a role for β-cell dysfunction during the evolution of T1D and suggest agents that may promote β-cell health in T1D. Metabolic abnormalities exist years before development of hyperglycemia and exhibit a reproducible pattern reflecting progressive deterioration of β-cell function and increases in β-cell stress and death. Preclinical studies indicate that T1D may be prevented by modification of pathways impacting intrinsic β-cell stress and antigen presentation. Recent findings suggest that differences in metabolic phenotypes and β-cell stress may reflect differing endotypes of T1D. Multiple pathways representing potential drug targets have been identified, but most remain to be tested in human populations with preclinical disease. This cumulative body of work shows clear evidence that β-cell stress, dysfunction, and death are harbingers of impending T1D and likely contribute to progression of disease and insulin deficiency. Treatment with agents targeting β-cell health could augment interventions with immunomodulatory therapies but will need to be tested in intervention studies with endpoints carefully designed to capture changes in β-cell function and health.

2136-P: Effects of Cytokine Exposure on the Proteome of Human Islets as Evaluated by Shotgun and 2DE Analysis

Pro-inflammatory cytokines (CYT) lead to several changes in human islet (HI) protein expression, but few data are available on CYT-induced alterations at the whole proteome level, including post-translational modifications (PTM). We used label-free shotgun analysis (SG) and bi-dimensional gel electrophoresis (2DE) to explore how CYT modify the proteome of isolated HI. For this purpose, HI were isolated from the pancreas of 5 nondiabetic organ donors (age: 74±6 years; gender: 3M/2F; BMI: 27.9±3.6 kg/m2) and then cultured for 48h in the presence of 50 U/ml interleukin (IL)-1β + 1000 U/ml interferon (IFN)-γ. Then, 40 or 250 μg protein extracts were used respectively for SG or 2DE (to assess lysine-acetylation) analysis, with the SG mass spectrometry data acquired by nano-liquid chromatography tandem mass spectrometry. SG identified around 3000 proteins, of which 286 were differentially expressed after CYT exposure. Of these, 176 were upregulated and 110 downregulated. Among the former, we found mediators of inflammation, proteins of the ER and the immunoproteasome system and oxidative stress modulators (e.g., CXCL2, CXCL10, PSMB8, PSMB9, PSMB10, SOD2). Among the downregulated proteins, there were cathepsins, antioxidant molecules and enzymes of glycolysis and Krebs’ cycle (e.g., CTSH (a candidate gene for T1D), PRDX2, MDH). Ingenuity Pathway Analysis indicated that several upstream regulators were predicted to be differentially affected. Of them, 118 were presumably activated, including STAT1 and STAT2, NF-κB, JAK1, IRF1, HMGB1 and 36 inhibited, such as ACKR2, TRIM24, MAPK1, SUMO3. Bi-dimensional gel electrophoresis showed 151 spots that were lysine-acetylated, of which 2 were upregulated (PRDX3 and SOD1) and 4 downregulated (GDH, CTSD, ACAD9 and EIF4A1) by CYT. The present study shows novel proteomic changes, including specific PTM, induced in human islets by cytokine treatment that could play a role in beta cell dysfunction and demise and be the target for specific treatments. Disclosure F. Grano: None. F. Ciregia: None. M. Ronci: None. M. Mazzoni: None. L. Overbergh: None. C. De Luca: None. M. Suleiman: None. L. Marselli: None. P. De Simone: None. U. Boggi: None. C. Mathieu: Advisory Panel; Self; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Merck & Co., Inc., Novo Nordisk A/S, Roche Diabetes Care, Sanofi. Speaker's Bureau; Self; AstraZeneca, Novartis AG, Novo Nordisk A/S, Sanofi. D.L. Eizirik: None. A. Lucacchini: None. L. Giusti: None. P. Marchetti: None. M. Bugliani: None. Funding INNODIA

Class IIa HDACs do not influence beta-cell function under normal or high glucose conditions

ABSTRACTInhibiting Class IIa Histone Deacetylase (HDAC) function is a promising approach to therapeutically enhance skeletal and cardiac muscle metabolic health in several chronic diseases including type 2 diabetes. However, the importance of Class IIa HDACs in the beta-cell remains unknown. As beta-cell function is vital to maintaining glycaemia it is essential that the importance of Class IIa HDACs in the beta-cell is determined. Here we used the INS-1E cell line cultured in normal glucose (11.1 mM) or hyperglycaemic (20 mM) conditions for 48 hrs to represent cells in a normal and diabetic environment respectively. Cells cultured in high glucose showed significantly reduced insulin secretory function and increased apoptotic signalling compared to cells cultured in normal glucose. Class IIa HDACS, HDAC-4 and −5, were not regulated at the transcript or protein level under normal or hyperglycaemic conditions suggesting that they may not play a role in beta-cell dysfunction. Furthermore, overexpression of wild-type HDAC-4 and −5 or dominant negative HDAC-4 and −5 did not alter insulin secretion, insulin mRNA expression or apoptotic signalling under normal or hyperglycaemic conditions. This suggests that Class IIa Histone Deacetylases do not play an important physiological role in the beta-cell under normal or diabetic conditions. Thus, Class IIa Histone Deacetylase inhibitors are not likely to have a detrimental effect on beta-cells supporting the use of these inhibitors to treat metabolic diseases such as type 2 diabetes.

Changing the Concept of Type 2 Diabetes: Beta Cell Workload Hypothesis Revisited.

BackgroundDespite a number of innovations in anti-diabetic drugs and substantial improvement in diabetes care, the number of people with diabetes continues to increase, suggesting further need to explore novel approaches to prevent diabetes. Type 2 diabetes (T2DM) is characterized by beta cell dysfunction and insulin resistance. However, insulin resistance, usually a consequence of obesity, is often emphasized and the role of beta cell dysfunction in T2DM is less appreciated.Objective and ResultsThis paper summarizes recent evidence showing the importance of beta cell dysfunction in T2DM and refines the “beta cell workload hypothesis”, emphasizing the importance of beta cell preservation for the prevention and management of T2DM.ConclusionIt is hoped that this novel concept will foster a better understanding of the pathophysiology of T2DM by not only medical staff and patients with diabetes, but also the general population, and encourage more people to adhere to a healthy lifestyle, eventually resulting in “stopping diabetes”.

The long noncoding RNA Bsr in the genomically imprinted Dlk1-Dio3 region is suppressed in newborn rat pancreas by gestational obesity

Abstract Background: Fetal metabolic programming imposed by maternal obesity and impaired glucose tolerance predisposes the offspring to metabolic disease and beta cell dysfunction as adults. The aim of this study was to assess the whole pancreas RNA changes in neonatal offspring exposed to fetal programming. Methods: The outcome of fetal programming on offspring was tested using the selectively bred Diet Induced Obese (DIO) and the Diet Resistant (DR) strains. DIO and DR rats were fed either chow or high fat, high sucrose (high energy, HE) diet during gestation and the differences in pancreas RNA expression at two days after birth were measured by microarray. Pancreas sections were stained and analyzed for alpha and beta cell numbers. Neonatal islets were treated with cytotoxic cytokines and RNA measured by RT-Q-PCR. Results: Morphometric analyses revealed significant differences in alpha and beta cell numbers per pancreas or per islet by HE diet. Microarray analyses revealed 11 fold downregulation of the long noncoding RNA Bsr in whole pancreas by HE feeding of DIO rat dams. MicroRNAs from the same locus, the Dlk1- Dio3 imprinted region, were also decreased by HE diet. Moreover, treatment of isolated neonatal islets with inflammatory cytokines, IL-1β and IFN-γ, led to reduction of Bsr transcript in a time and dose dependent manner. Conclusions: Our data suggest that fetal programming of Bsr may play a role in beta cell dysfunction in obesity and type 2 diabetes.

IKKβ inhibition prevents fat-induced beta cell dysfunction in vitro and in vivo in rodents.

We have previously shown that oxidative stress plays a causal role in beta cell dysfunction induced by fat. Here, we address whether the proinflammatory kinase inhibitor of (nuclear factor) κB kinase β (IKKβ), which is activated by oxidative stress, is also implicated. Fat (oleate or olive oil) was infused intravenously in Wistar rats for 48h with or without the IKKβ inhibitor salicylate. Thereafter, beta cell function was evaluated in vivo using hyperglycaemic clamps or ex vivo in islets isolated from fat-treated rats. We also exposed rat islets to oleate in culture, with or without salicylate and 4(2'-aminoethyl)amino-1,8-dimethylimidazo(1,2-a)quinoxaline; BMS-345541 (BMS, another inhibitor of IKKβ) and evaluated beta cell function in vitro. Furthermore, oleate was infused in mice treated with BMS and in beta cell-specific Ikkb-null mice. 48h infusion of fat impaired beta-cell function in vivo, assessed using the disposition index (DI), in rats (saline: 1.41±0.13; oleate: 0.95±0.11; olive oil [OLO]: 0.87±0.15; p<0.01 for both fats vs saline) and in mice (saline: 2.51±0.39; oleate: 1.20±0.19; p<0.01 vs saline) and ex vivo (i.e., insulin secretion, units are pmol insulin islet-1h-1) in rat islets (saline: 1.51±0.13; oleate: 1.03±0.10; OLO: 0.91±0.13; p<0.001 for both fats vs saline) and the dysfunction was prevented by co-infusion of salicylate in rats (oleate+salicylate: 1.30±0.09; OLO+salicylate: 1.33±0.23) or BMS in mice (oleate+BMS: 2.25±0.42) in vivo and by salicylate in rat islets ex vivo (oleate+salicylate: 1.74±0.31; OLO+salicylate: 1.54±0.29). In cultured islets, 48h exposure to oleate impaired beta-cell function ([in pmol insulin islet-1h-1] control: 0.66±0.12; oleate: 0.23±0.03; p<0.01 vs saline), an effect prevented by both inhibitors (oleate+salicylate: 0.98±0.08; oleate+BMS: 0.50±0.02). Genetic inhibition of IKKβ also prevented fat-induced beta-cell dysfunction ex vivo ([in pmol insulin islet-1h-1] control saline: 0.16±0.02; control oleate: 0.10±0.02; knockout oleate: 0.17±0.04; p<0.05 control saline vs. control oleate) and in vivo (DI: control saline: 3.86±0.40; control oleate: 1.95±0.29; knockout oleate: 2.96±0.24; p<0.01 control saline vs control oleate). Our results demonstrate a causal role for IKKβ in fat-induced beta cell dysfunction in vitro, ex vivo and in vivo.

Serum Vitamin D Levels In Type 2 Diabetes Mellitus - A Missing Link

INTRODUCTION Type 2 diabetes, a significant global health care problem is the fifth leading cause of death and also a major cause of significant morbidity. Although our current methods of treating type 2 DM and its complications are improving, its prevention is preferable. Epidemiological data suggest 9 of 10 cases of type 2 DM are attributed to habits and form of modifiable behavior. Vitamin D has been traditionally known as anti ricketic factor or sunshine vitamin. It is unique because it is a vitamin synthesized by the body and functions as a hormone. Besides its pivotal role in calcium homeostasis and bone mineral metabolism, vitamin D endocrine system is now recognized to sub-serve a wide range of biological functions in cell differentiation, inhibition of cell growth and immunomodulation. 25-Hydroxyvitamin D serum level (measure of vitamin D status) of less than 20 ng/mL is vitamin D deficiency and 21 to 29 ng/mL is insufficiency. lt is currently recognized that. Systemic inflammation seen in type 2 DM has been linked primarily to insulin resistance, but elevated cytokines may also play a role in beta-cell dysfunction by triggering |3-cell apoptosis. Vitamin D may improve insulin sensitivity and promote beta-cell survival by directly modulating the generation and effects of cytokines. This raises important questions of association between vitamin D and type 2 diabetes hence the purpose of this current study.

Lepr(db) mouse model of type 2 diabetes: pancreatic islet isolation and live-cell 2-photon imaging of intact islets.

Type 2 diabetes is a chronic disease affecting 382 million people in 2013, and is expected to rise to 592 million by 2035 (1). During the past 2 decades, the role of beta-cell dysfunction in type 2 diabetes has been clearly established (2). Research progress has required methods for the isolation of pancreatic islets. The protocol of the islet isolation presented here shares many common steps with protocols from other groups, with some modifications to improve the yield and quality of isolated islets from both the wild type and diabetic Lepr(db) (db/db) mice. A live-cell 2-photon imaging method is then presented that can be used to investigate the control of insulin secretion within islets.

Role of beta-cell dysfunction, ectopic fat accumulation and insulin resistance in the pathogenesis of type 2 diabetes mellitus

In the natural history of type 2 diabetes (T2DM), individuals progress from normal glucose tolerance (NGT) to impaired glucose tolerance (IGT) to overt T2DM and this progression has been demonstrated in populations of diverse ethnic background. It is widely recognised that both insulin resistance and beta-cell dysfunction are important in the pathogenesis of glucose intolerance. In populations with a high prevalence of T2DM, insulin resistance is well established long before the development of any impairment in glucose homeostasis, particularly in subjects with ectopic fat accumulation. However, as long as the beta cell is able to secrete sufficient amounts of insulin to offset the severity of insulin resistance, glucose tolerance remains normal. This dynamic interaction between insulin secretion and insulin resistance is essential to the maintenance of NGT and interruption of this crosstalk between the beta cell and peripheral tissues results in the progressive deterioration of glucose homeostasis. In this paper the role of beta-cell function is reviewed, as well as the role of ectopic fat accumulation and insulin resistance in the development of type 2 diabetes.

Osteoprotegerin induces morphological and functional alterations in mouse pancreatic islets

Although serum osteoprotegerin (OPG) is significantly increased in diabetic subjects, its potential role in beta cell dysfunction has not been investigated. This study aimed to assess the effect of full-length OPG administered in vivo in mice on pancreatic islet structure and function and its interaction with the renin–angiotensin system (RAS). OPG-treated mice showed increased islet monocyte/macrophage infiltration, fibrosis and apoptosis with reduction of islet function. The remodeling of islet architecture was associated with increased pancreatic expression of components of the RAS, growth factor genes (transforming growth factor β and connective tissue growth factor) and inflammatory molecules (monocyte chemotactic protein-1 and vascular adhesion molecule type 1). Prevention of these changes with improvement of insulin secretion was observed in ramipril treated animals. Our data suggest that OPG might play an important role in promoting beta cell dysfunction and that the upregulation of the local RAS represents one possible mechanism responsible for the OPG-induced beta cell dysfunction.

Differences in insulin sensitivity, pancreatic beta cell function and circulating adiponectin across glucose tolerance status in Thai obese and non-obese women

Although adiponectin levels are associated with obesity and insulin insensitivity, the role of adiponectin in the progression to diabetes in non-obese subjects is unclear. Therefore, 289 women aged 50-80 years without previous history of diabetes or impaired glucose tolerance (IGT) were studied. They were classified as normal glucose tolerance (NGT), IGT or diabetes based on WHO criteria. Insulin sensitivity (S) and beta cell function (B) indices were calculated using homeostasis model assessment (HOMA). In obese women with BMI > or = 25 kg/m(2) (n = 161), there were declines in HOMA-%S (P < 0.001), HOMA-%B (P < 0.05) and circulating adiponectin (P < 0.001) across glucose tolerance status. In non-obese women with BMI < 25 kg/m(2) (n = 128), there was no significant change in HOMA-%S in women with IGT and diabetes as compared to women with NGT. However, HOMA-%B (P < 0.05) and serum adiponectin levels (P < 0.001) were significantly decreased across glucose tolerance. Serum adiponectin levels were correlated to HOMA-%S in both obese and non-obese women while negative correlations between circulating adiponectin and HOMA-%B were demonstrated only in obese women. We have demonstrated in the present study the predominant role of beta cell dysfunction as compared to that of insulin resistance in the deterioration of glucose tolerance in non-obese women. Circulating adiponectin appears to be inversely related to beta cell dysfunction in addition to insulin resistance only in obese women.

Proteomics Analysis of Cytokine-induced Dysfunction and Death in Insulin-producing INS-1E Cells: New Insights into the Pathways Involved

Cytokines released by islet-infiltrating immune cells play a crucial role in beta-cell dysfunction and apoptotic cell death in the pathogenesis of type 1 diabetes and after islet transplantation. RNA studies revealed complex pathways of genes being activated or suppressed during this beta-cell attack. The aim of the present study was to analyze protein changes in insulin-producing INS-1E cells exposed to inflammatory cytokines in vitro using two-dimensional DIGE. Within two different pH ranges we observed 2214 +/- 164 (pH 4-7) and 1641 +/- 73 (pH 6-9) spots. Analysis at three different time points (1, 4, and 24 h of cytokine exposure) revealed that the major changes were taking place only after 24 h. At this time point 158 proteins were altered in expression (4.1%, n = 4, p < or = 0.01) by a combination of interleukin-1beta and interferon-gamma, whereas only 42 and 23 proteins were altered by either of the cytokines alone, giving rise to 199 distinct differentially expressed spots. Identification of 141 of these by MALDI-TOF/TOF revealed proteins playing a role in insulin secretion, cytoskeleton organization, and protein and RNA metabolism as well as proteins associated with endoplasmic reticulum and oxidative stress/defense. We investigated the interactions of these proteins and discovered a significant interaction network (p < 1.27e-05) containing 42 of the identified proteins. This network analysis suggests that proteins of different pathways act coordinately in a beta-cell dysfunction/apoptotic beta-cell death interactome. In addition the data suggest a central role for chaperones and proteins playing a role in RNA metabolism. As many of these identified proteins are regulated at the protein level or undergo post-translational modifications, a proteomics approach, as performed in this study, is required to provide adequate insight into the mechanisms leading to beta-cell dysfunction and apoptosis. The present findings may open new avenues for the understanding and prevention of beta-cell loss in type 1 diabetes.

Awareness of pathophysiological concepts of type 2 diabetes—A survey in 847 physicians

Aims The aim of the study was to determine physicians’ knowledge of specific concepts generally implicated in the pathophysiology of type 2 diabetes (T2D). Methods A multiple choice online survey was completed by 847 physicians, of which 516 were engaged in primary care (PCP) and 331 in specialized care (SCP) in the US, the UK, Germany and France (3–30 years in practice, at least 40 patients with T2D). A continuous rating system was used to measure familiarity (“totally familiar” to “never heard of”) or agreement with a statement (from “totally agree” to “totally disagree”). Results The term “insulin resistance” was recognized by 74% of PCPs and 90% of SCPs ( p < 0.05) and 76% felt that it was “a key but not the sole determinant of T2D”. Only 47% agreed that “beta cell dysfunction is a key determinant of T2D onset” and 57% agreed with “beta cell dysfunction being a key determinant of T2D progression”. Even among SCPs, 6% were not familiar with the term “beta cell dysfunction” (16% among PCPs, p < 0.05). The overall familiarity with the following terms was: 55% with “beta cell dysfunction”, 56% with “beta cells”, 38% with “glucagon”, 32% with “alpha cells”, 55% with “hepatic glucose output”, 15% with “incretins” and 18% with “GLP-1”. SCPs were significantly more familiar with all terms than PCPs (all p-values <0.05). Conclusions The pathogenetic role of beta cell dysfunction in the onset and progression of T2D did not seem to be well established. “Insulin resistance” was a well known concept even among PCPs, while “hepatic glucose output”, “pancreatic alpha cells” and “glucagon” were not. Incretin hormones and GLP-1 were widely unknown. This may effect prescribing behaviour and how well an individual's therapy is based on pathophysiology.

Hypoadiponectinemia Predicts the Severity of Hepatic Fibrosis and Pancreatic Beta-Cell Dysfunction in Nondiabetic Nonobese Patients with Nonalcoholic Steatohepatitis

The relationships between the adipokines tumor necrosis factor (TNF)-alpha and adiponectin and the parameters of glucose homeostasis and severity of liver disease were assessed in nonobese nondiabetic subjects with nonalcoholic steatohepatitis (NASH). A frequently sampled intravenous glucose tolerance test, serum cytokine measurement, and 7-day alimentary record were performed in 20 biopsy-proven NASH patients and 45 age-, sex-, and BMI-matched controls (30 insulin sensitive and 15 insulin resistant). Patients with NASH had impaired pancreatic beta-cell function compared with both insulin-sensitive (adaptation index, AI: 97.7 +/- 17.7 vs 307.4 +/- 24.1 min(-2) mmol(-1) L; p= 0.00001) and insulin-resistant (adaptation index, AI: 97.7 +/- 17.7 vs 201.4 +/- 41.1 min(-2) mmol(-1) L; p= 0.001) controls. Serum adiponectin levels were also significantly lower in the NASH group than in the two control groups and correlated with adaptation index and with the severity of hepatic steatosis, necroinflammation, and fibrosis. When NASH patients were grouped according to the severity of histological liver damage, adiponectin was the only variable discriminating patients with higher necroinflammatory grade and fibrosis score from those with milder lesions. Beta-cell secretory impairment is present in nonobese patients with NASH before glucose intolerance appears and may contribute to their increased risk for developing diabetes. Hypoadiponectinemia is a feature of NASH and may have a pathogenetic role in beta-cell dysfunction and in hepatic necroinflammation and fibrosis, independently of insulin resistance, visceral fat accumulation, TNF-alpha axis activity, and dietary habits. Our findings provide further rationale for therapeutic approaches aimed at increasing adiponectin levels together with restoring beta-cell function and insulin sensitivity.