Increased Beta-cell Mass Research Articles

Characterisation of Age-Dependent Beta Cell Dynamics in the Male db/db Mice

AimTo characterise changes in pancreatic beta cell mass during the development of diabetes in untreated male C57BLKS/J db/db mice. MethodsBlood samples were collected from a total of 72 untreated male db/db mice aged 5, 6, 8, 10, 12, 14, 18, 24 and 34 weeks, for measurement of terminal blood glucose, HbA1c, plasma insulin, and C-peptide. Pancreata were removed for quantification of beta cell mass, islet numbers as well as proliferation and apoptosis by immunohistochemistry and stereology. ResultsTotal pancreatic beta cell mass increased significantly from 2.1 ± 0.3 mg in mice aged 5 weeks to a peak value of 4.84 ± 0.26 mg (P < 0.05) in 12-week-old mice, then gradually decreased to 3.27 ± 0.44 mg in mice aged 34 weeks. Analysis of islets in the 5-, 10-, and 24-week age groups showed increased beta cell proliferation in the 10-week-old animals whereas a low proliferation is seen in older animals. The expansion in beta cell mass was driven by an increase in mean islet mass as the total number of islets was unchanged in the three groups. Conclusions/InterpretationThe age-dependent beta cell dynamics in male db/db mice has been described from 5-34 weeks of age and at the same time alterations in insulin/glucose homeostasis were assessed. High beta cell proliferation and increased beta cell mass occur in young animals followed by a gradual decline characterised by a low beta cell proliferation in older animals. The expansion of beta cell mass was caused by an increase in mean islet mass and not islet number.

Epidermal Growth Factor Signalling Promotes Pancreatic Beta-Cell Proliferation in Response to Nutrient Excess in Rats Through MTOR And FOXM1

A compensatory increase in beta-cell mass occurs in several physiological and pathophysiological situations, such as pregnancy, obesity and insulin resistance. We have previously observed that a 72-hour co-infusion of glucose and Intralipid (GLU+IL) in 6-month-old (6-mo) rats causes insulin resistance and beta-cell dysfunction, despite a marked increase in beta-cell proliferation and mass. Interestingly, none of these effects were observed in 2-month-old (2-mo) animals despite similar levels of circulating glucose, fatty acids and insulin. Islet gene expression profiling in 6-mo GLU+IL rats identified a transcriptional network associated with beta-cell proliferation and a central role for the forkhead transcription factor FoxM1. Expression of the heparin binding EGF-like growth factor (HB-EGF), a ligand of the EGF receptor (EGFR), was significantly induced in response to GLU+IL. First, we confirmed by RT-PCR the increased expression of HB-EGF, FoxM1 and its direct targets in islets from GLU+IL-infused 6-mo, but not 2-mo rats. Second, we observed that the expression of HB-EGF correlates significantly and positively with the expression of FoxM1 and its direct targets. Third, co-infusion of either the EGFR inhibitor, AG1478 or the mTOR inhibitor, rapamycin, blocked the increase in expression of FoxM1 and its targets in response to GLU+IL in 6-mo rats. Finally, HB-EGF induces the proliferation of insulin-secreting MIN6 cells, and this effect was blocked by AG1478 or rapamycin. We conclude that insulin resistance induced by nutrient excess in aging rats promotes beta-cell proliferation via a pathway that involved HB-EGF binding to EGFR, mTOR activation and FoxM1-mediated cell division.

Role of the Sik2-p35-Pja2 Complex in Pancreatic Beta Cell Functional Compensation

Metabolic syndrome and type 2 diabetes are increasingly prevalent global health risks. The transition from glucose intolerance/prediabetes to a diagnosis of diabetes occurs when pancreatic beta cells fail to compensate for the increasing demand for insulin. While mechanisms for increasing beta cell mass have been described, the molecular underpinnings of beta cell functional compensation remain largely unknown. Here we delineate a novel pathway featuring the Ser/Thr protein kinase Sik2 and E3 ubiqutin ligase Pja2 that is harnessed by the beta cell in both rodents and humans to enhance insulin secretion in response to hyperglycemia. Sik2 phosphorylates p35 at Ser91 to trigger p35 degradation by Pja2, which promotes insulin secretion through activation of voltage-dependent calcium channel (VDCC) and calcium ion influx. Loss of Sik2 in beta cells exacerbates high fat diet-induced glucose intolerance due to decreased plasma insulin levels. Sik2 protein accumulates in beta cells of obese models and human obese subjects, and is stabilized upon exposure to high concentration of glucose. Enhanced insulin secretion in islets from obese model mice is reverted by Sik2 knockdown. These findings demonstrate that the Sik2-Pja2-p35 complex is critical for beta cell functional compensation and maintenance of glucose homeostasis.

Weight Loss Intervention for Individuals with Diabetes and Serious Mental Illness: A Pragmatic Experiment in Community Settings

Metabolic syndrome and type 2 diabetes are increasingly prevalent global health risks. The transition from glucose intolerance/prediabetes to a diagnosis of diabetes occurs when pancreatic beta cells fail to compensate for the increasing demand for insulin. While mechanisms for increasing beta cell mass have been described, the molecular underpinnings of beta cell functional compensation remain largely unknown. Here we delineate a novel pathway featuring the Ser/Thr protein kinase Sik2 and E3 ubiqutin ligase Pja2 that is harnessed by the beta cell in both rodents and humans to enhance insulin secretion in response to hyperglycemia. Sik2 phosphorylates p35 at Ser91 to trigger p35 degradation by Pja2, which promotes insulin secretion through activation of voltage-dependent calcium channel (VDCC) and calcium ion influx. Loss of Sik2 in beta cells exacerbates high-fat diet-induced glucose intolerance, due to decreased plasma insulin levels. Sik2 protein accumulates in beta cells of obese models and human obese subjects, and is stabilized upon exposure to high concentration of glucose. Enhanced insulin secretion in islets from obese model mice is reverted by Sik2 knockdown. These findings demonstrate that the Sik2-Pja2-p35 complex is critical for beta cell functional compensation and maintenance of glucose homeostasis. ErrataCanadian Journal of DiabetesVol. 37Issue 6PreviewPlease note there were a few errors in the Canadian Journal of Diabetes October 2013 Supplement (CDA/CSEM professional conference abstract book). Please refer to the corrections below: Full-Text PDF

Nupr1 deletion protects against glucose intolerance by increasing beta cell mass.

The stress-activated nuclear protein transcription regulator 1 (NUPR1) is induced in response to glucose and TNF-α, both of which are elevated in type 2 diabetes, and Nupr1 has been implicated in cell proliferation and apoptosis cascades. We used Nupr1(-/-) mice to study the role of Nupr1 in glucose homeostasis under normal conditions and following maintenance on a high-fat diet (HFD). Glucose homeostasis in vivo was determined by measuring glucose tolerance, insulin sensitivity and insulin secretion. Islet number, morphology and beta cell area were assessed by immunofluorescence and morphometric analysis, and islet cell proliferation was quantified by analysis of BrdU incorporation. Islet gene expression was measured by gene arrays and quantitative RT-PCR, and gene promoter activities were monitored by measuring luciferase activity. Nupr1(-/-) mice had increased beta cell mass as a consequence of enhanced islet cell proliferation. Nupr1-dependent suppression of beta cell Ccna2 and Tcf19 promoter activities was identified as a mechanism through which Nupr1 may regulate beta cell cycle progression. Nupr1(-/-) mice maintained on a normal diet were mildly insulin resistant, but were normoglycaemic with normal glucose tolerance because of compensatory increases in basal and glucose-induced insulin secretion. Nupr1 deletion was protective against HFD-induced obesity, insulin resistance and glucose intolerance. Inhibition of NUPR1 expression or activity has the potential to protect against the metabolic defects associated with obesity and type 2 diabetes.

Glucagon-like peptide-1 receptor agonist treatment reduces beta cell mass in normoglycaemic mice

Incretin-based therapies improve glycaemic control in patients with type 2 diabetes. In animal models of diabetes, glucagon-like peptide-1 receptor agonists (GLP-1RAs) increase beta cell mass. GLP-1RAs are also evaluated in non-diabetic individuals with obesity and cardiovascular disease. However, their effect on beta cell mass in normoglycaemic conditions is not clear. Here, we investigate the effects of the GLP-1RA liraglutide on beta cell mass and function in normoglycaemic mice. C57BL/6J mice were treated with the GLP-1RA liraglutide or PBS and fed a control or high-fat diet (HFD) for 1 or 6 weeks. Glucose and insulin tolerance tests were performed after 6 weeks. BrdU was given to label proliferating cells 1 week before the animals were killed. The pancreas was taken for either histology or islet isolation followed by a glucose-induced insulin-secretion test. Treatment with liraglutide for 6 weeks led to increased insulin sensitivity and attenuation of HFD-induced insulin resistance. A reduction in beta cell mass was observed in liraglutide-treated control and HFD-fed mice at 6 weeks, and was associated with a lower beta cell proliferation rate after 1 week of treatment. A similar reduction in alpha cell mass occurred, resulting in an unchanged alpha to beta cell ratio. In contrast, acinar cell proliferation was increased. Finally, islets isolated from liraglutide-treated control mice had enhanced glucose-induced insulin secretion. Our data show that GLP-1RA treatment in normoglycaemic mice leads to increases in insulin sensitivity and beta cell function that are associated with reduced beta cell mass to maintain normoglycaemia.

Enhanced beta cell function and anti-inflammatory effect after chronic treatment with the dipeptidyl peptidase-4 inhibitor vildagliptin in an advanced-aged diet-induced obesity mouse model

Studies have shown that dipeptidyl peptidase-4 (DPP4) inhibitors stimulate insulin secretion and increase beta cell mass in rodents. However, in these models hyperglycaemia has been induced early on in life and the treatment periods have been short. To explore the long-term effects of DPP4 inhibition on insulin secretion and beta cell mass, we have generated a high-fat diet (HFD)-induced-obesity model in mice of advanced age (10 months old). After 1 month of HFD alone, the mice were given the DPP4 inhibitor vildagliptin for a further 11 months. At multiple time points throughout the study, OGTTs were performed and beta cell area and long-term survival were evaluated. Beta cell function and glucose tolerance were significantly improved by vildagliptin with both diets. In contrast, in spite of the long treatment period, beta cell area was not significantly different between vildagliptin-treated mice and controls. Mice of advanced age chronically fed an HFD displayed clear and extensive pancreatic inflammation and peri-insulitis, mainly formed by CD3-positive T cells, which were completely prevented by vildagliptin treatment. Chronic vildagliptin treatment also improved survival rates for HFD-fed mice. In a unique advanced-aged HFD-induced-obesity mouse model, insulin secretion was improved and the extensive peri-insulitis prevented by chronic DPP4 inhibition. The improved survival rates for obese mice chronically treated with vildagliptin suggest that chronic DPP4 inhibition potentially results in additional quality-adjusted life-years for individuals with type 2 diabetes, which is the primary goal of any diabetes therapy.

GLP-1 agonists in type 1 diabetes

Despite years of research in the field of type 1 diabetes, patients with the disease remain without a therapeutic agent that can alter the underlying immune response in a clinically beneficial way. Glucagon-like peptide 1 agonist therapies have shown some promising effects in terms of positively affecting overall beta cell health and increasing beta cell mass, primarily in mouse models. The three agents of this class currently available for patients with type 2 diabetes have shown beneficial clinical effects on glucose control in this patient population. The purpose of this article is to review the preclinical and clinical data of these agents to date with a focus on the potential immunological and clinical benefits these drugs may have on patients with type 1 diabetes.

Hyperplasia of Pancreatic Beta Cells and Improved Glucose Tolerance in Mice Deficient in the FXYD2 Subunit of Na,K-ATPase

Restoration of the functional potency of pancreatic islets either through enhanced proliferation (hyperplasia) or increase in size (hypertrophy) of beta cells is a major objective for intervention in diabetes. We have obtained experimental evidence that global knock-out of a small, single-span regulatory subunit of Na,K-ATPase, FXYD2, alters glucose control. Adult Fxyd2(-/-) mice showed significantly lower blood glucose levels, no signs of peripheral insulin resistance, and improved glucose tolerance compared with their littermate controls. Strikingly, there was a substantial hyperplasia in pancreatic beta cells from the Fxyd2(-/-) mice compared with the wild type littermates, compatible with an observed increase in the level of circulating insulin. No changes were seen in the exocrine compartment of the pancreas, and the mice had only a mild, well-adapted renal phenotype. Morphometric analysis revealed an increase in beta cell mass in KO compared with WT mice. This appears to explain a phenotype of hyperinsulinemia. By RT-PCR, Western blot, and immunocytochemistry we showed the FXYD2b splice variant in pancreatic beta cells from wild type mice. Phosphorylation of Akt kinase was significantly higher under basal conditions in freshly isolated islets from Fxyd2(-/-) mice compared with their WT littermates. Inducible expression of FXYD2 in INS 832/13 cells produced a reduction in the phosphorylation level of Akt, and phosphorylation was restored in parallel with degradation of FXYD2. Thus we suggest that in pancreatic beta cells FXYD2 plays a role in Akt signaling pathways associated with cell growth and proliferation.

PS2 - 8. Liraglutide decreases beta-cell mass in normoglycemic and high-fat diet-fed mice

Incretin-based therapies are used to treat patients with type 2 diabetes by stimulating insulin secretion. The incretin glucagon-like-peptide-1 (GLP-1) also increases beta-cell mass in diabetic animal models. GLP-1 receptor agonists also decrease body weight and may improve cardiovascular outcome.

Treatment of autoimmune diabetes in NOD mice by Toll-like receptor 2 tolerance in conjunction with dipeptidyl peptidase 4 inhibition

We have shown that chronic administration of the Toll-like receptor 2 (TLR2) agonist Pam3CSK(4) prevents diabetes in NOD mice by inducing TLR2 tolerance of dendritic cells (DCs). We have also reported that a novel dipeptidyl peptidase 4 (DPP4) inhibitor, DA-1229, could increase beta cell mass. Here we investigated whether a combination of DPP4 inhibition, with beneficial effects on beta cell mass, and TLR2 tolerisation, protecting beta cells from autoimmune destruction, could treat a model of established type 1 diabetes. Diabetic NOD mice were treated with 100μg Pam3CSK(4), administered three times a week for 3weeks, in combination with feeding with chow containing 0.3% DA-1229. Beta cell mass and proliferation were studied by immunohistochemistry. DC tolerance was assessed by studying diabetogenic CD4(+) T cell priming after adoptive transfer and expression of costimulatory molecules on DCs by flow cytometry. We observed reversal of diabetes in NOD mice by Pam3CSK(4)+DA-1229 but not by either Pam3CSK(4) or DA-1229 alone. Beta cell mass and the number of proliferating beta cells were significantly enhanced by Pam3CSK(4)+DA-1229, but not by either Pam3CSK(4) or DA-1229 alone. Diabetogenic T cell priming by DCs and upregulation of costimulatory molecules after ex vivo stimulation were attenuated in mice treated with Pam3CSK(4)+DA-1229, indicating DC tolerance. The relative proportions of CD4(+) T cells, CD8(+) T cells, B cells, DCs, macrophages and regulatory T cells, and T-helper polarisation were unchanged by treatment with Pam3CSK(4)+DA-1229. These data demonstrate that a combination of TLR2 tolerisation and DPP4 inhibition can reverse early-onset diabetes in NOD mice.

Beta Cell Count Instead of Beta Cell Mass to Assess and Localize Growth in Beta Cell Population following Pancreatic Duct Ligation in Mice

BackgroundPancreatic-tail duct ligation (PDL) in adult rodents has been reported to induce beta cell generation and increase beta cell mass but increases in beta cell number have not been demonstrated. This study examines whether PDL increases beta cell number and whether this is caused by neogenesis of small clusters and/or their growth to larger aggregates.MethodologyTotal beta cell number and its distribution over small (<50 µm), medium, large (>100 µm) clusters was determined in pancreatic tails of 10-week-old mice, 2 weeks after PDL or sham.Principal findingsPDL increased total beta cell mass but not total beta cell number. It induced neogenesis of small beta cell clusters (2.2-fold higher number) which contained a higher percent proliferating beta cells (1.9% Ki67+cells) than sham tails (<0.2%); their higher beta cell number represented <5% of total beta cell number and was associated with a similar increase in alpha cell number. It is unknown whether the regenerative process is causally related to the inflammatory infiltration in PDL-tails. Human pancreases with inflammatory infiltration also exhibited activation of proliferation in small beta cell clusters.Conclusions/significanceThe PDL model illustrates the advantage of direct beta cell counts over beta cell mass measurements when assessing and localizing beta cell regeneration in the pancreas. It demonstrates the ability of the adult mouse pancreas for neogenesis of small beta cell clusters with activated beta cell proliferation. Further studies should investigate conditions under which neoformed small beta cell clusters grow to larger aggregates and hence to higher total beta cell numbers.

The role of Raf-1 kinase inhibitor protein in the regulation of pancreatic beta cell proliferation in mice

Manoeuvres aimed at increasing beta cell mass have been proposed as regenerative medicine strategies for diabetes treatment. Raf-1 kinase inhibitor protein 1 (RKIP1) is a common regulatory node of the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) pathways and therefore may be involved in regulation of beta cell homeostasis. The aim of this study was to investigate the involvement of RKIP1 in the control of beta cell mass and function. Rkip1 (also known as Pebp1) knockout (Rkip1 (-/-)) mice were characterised in terms of pancreatic and glucose homeostasis, including morphological and functional analysis. Glucose tolerance and insulin sensitivity were examined, followed by assessment of glucose-induced insulin secretion in isolated islets and beta cell mass quantification through morphometry. Further characterisation included determination of endocrine and exocrine proliferation, apoptosis, MAPK activation and whole genome gene expression assays. Capacity to reverse a diabetic phenotype was assessed in adult Rkip1 (-/-) mice after streptozotocin treatment. Rkip1 (-/-) mice exhibit a moderately larger pancreas and increased beta cell mass and pancreatic insulin content, which correlate with an overall improvement in whole body glucose tolerance. This phenotype is established in young postnatal stages and involves enhanced cellular proliferation without significant alterations in cell death. Importantly, adult Rkip1 (-/-) mice exhibit rapid reversal of streptozotocin-induced diabetes compared with control mice. These data implicate RKIP1 in the regulation of pancreatic growth and beta cell expansion, thus revealing RKIP1 as a potential pharmacological target to promote beta cell regeneration.

Critical role of c-Kit in beta cell function: increased insulin secretion and protection against diabetes in a mouse model

The receptor tyrosine kinase, c-Kit, and its ligand, stem cell factor, control a variety of cellular processes, including pancreatic beta cell survival and differentiation as revealed in c-Kit ( Wv ) mice, which have a point mutation in the c-Kit allele leading to loss of kinase activity and develop diabetes. The present study further investigated the intrinsic role of c-Kit in beta cells, especially the underlying mechanisms that influence beta cell function. We generated a novel transgenic mouse model with c-KIT overexpression specifically in beta cells (c-KitβTg) to further examine the physiological and functional roles of c-Kit in beta cells. Isolated islets from these mice were used to investigate the underlying molecular pathway of c-Kit in beta cells. We also characterised the ability of c-Kit to protect animals from high-fat-diet-induced diabetes, as well as to rescue c-Kit ( Wv ) mice from early onset of diabetes. c-KitβTg mice exhibited improved beta cell function, with significantly improved insulin secretion, and increased beta cell mass and proliferation in response to high-fat-diet-induced diabetes. c-KitβTg islets exhibited upregulation of: (1) insulin receptor and IRSs; (2) Akt and glycogen synthase kinase 3β phosphorylation; and (3) transcription factors important for islet function. c-KIT overexpression in beta cells also rescued diabetes observed in c-Kit ( Wv ) mice. These findings demonstrate that c-Kit plays a direct protective role in beta cells, by regulating glucose metabolism and beta cell function. c-Kit may therefore represent a novel target for treating diabetes.

Combinatorial Human Progenitor Cell Transplantation Optimizes Islet Regeneration Through Secretion of Paracrine Factors

Transplanted human bone marrow (BM) and umbilical cord blood (UCB) progenitor cells activate islet-regenerative or revascularization programs depending on the progenitor subtypes administered. Using purification of multiple progenitor subtypes based on a conserved stem cell function, high aldehyde dehydrogenase (ALDH) activity (ALDH(hi)), we have recently shown that transplantation of BM-derived ALDH(hi) progenitors improved systemic hyperglycemia and augmented insulin secretion by increasing islet-associated proliferation and vascularization, without increasing islet number. Conversely, transplantation of culture-expanded multipotent-stromal cells (MSCs) derived from BM ALDH(hi) cells augmented total beta cell mass via formation of beta cell clusters associated with the ductal epithelium, without sustained islet vascularization. To identify paracrine effectors produced by islet-regenerative MSCs, culture-expanded BM ALDH(hi) MSCs were transplanted into streptozotocin-treated nonobese diabetic/severe combine immune deficient (SCID) mice and segregated into islet-regenerative versus nonregenerative cohorts based on hyperglycemia reduction, and subsequently compared for differential production of mRNA and secreted proteins. Regenerative MSCs showed increased expression of matrix metalloproteases, epidermal growth factor receptor (EGFR)-activating ligands, and downstream effectors of Wnt signaling. Regenerative MSC supernatant also contained increased levels of pro-angiogenic versus pro-inflammatory cytokines, and augmented the expansion of ductal epithelial but not beta cells in vitro. Conversely, co-culture with UCB ALDH(hi) cells induced beta cell but not ductal epithelial cell proliferation. Sequential transplantation of MSCs followed by UCB ALDH(hi) cells improved hyperglycemia and glucose tolerance by increasing beta cell mass associated with the ductal epithelium and by augmenting intra-islet capillary densities. Thus, combinatorial human progenitor cell transplantation stimulated both islet-regenerative and revascularization programs. Understanding the progenitor-specific pathways that modulate islet-regenerative and revascularization processes may provide new approaches for diabetes therapy.

Pdx1 Is Post-Translationally Modified In vivo and Serine 61 Is the Principal Site of Phosphorylation

Maintaining sufficient levels of Pdx1 activity is a prerequisite for proper regulation of blood glucose homeostasis and beta cell function. Mice that are haploinsufficient for Pdx1 display impaired glucose tolerance and lack the ability to increase beta cell mass in response to decreased insulin signaling. Several studies have shown that post-translational modifications are regulating Pdx1 activity through intracellular localization and binding to co-factors. Understanding the signaling cues converging on Pdx1 and modulating its activity is therefore an attractive approach in diabetes treatment. We employed a novel technique called Nanofluidic Proteomic Immunoassay to characterize the post-translational profile of Pdx1. Following isoelectric focusing in nano-capillaries, this technology relies on a pan specific antibody for detection and it therefore allows the relative abundance of differently charged protein species to be examined simultaneously. In all eukaryotic cells tested we find that the Pdx1 protein separates into four distinct peaks whereas Pdx1 protein from bacteria only produces one peak. Of the four peaks in eukaryotic cells we correlate one of them to a phosphorylation Using alanine scanning and mass spectrometry we map this phosphorylation to serine 61 in both Min6 cells and in exogenous Pdx1 over-expressed in HEK293 cells. A single phosphorylation is also present in cultured islets but it remains unaffected by changes in glucose levels. It is present during embryogenesis but is not required for pancreas development.

Ciliary neurotrophic factor (CNTF) protects non-obese Swiss mice against type 2 diabetes by increasing beta cell mass and reducing insulin clearance

Ciliary neurotrophic factor (CNTF) improves metabolic variables of obese animals with characteristics of type 2 diabetes, mainly by reducing insulin resistance. We evaluated whether CNTF was able to improve other metabolic variables in mouse models of type 2 diabetes, such as beta cell mass and insulin clearance, and whether CNTF has any effect on non-obese mice with characteristics of type 2 diabetes. Neonatal mice were treated with 0.1 mg/kg CNTF or citrate buffer via intraperitoneal injections, before injection of 250 mg/kg alloxan. HEPG2 cells were cultured for 3 days in the presence of citrate buffer, 1 nmol/l CNTF or 50 mmol/l alloxan or a combination of CNTF and alloxan. Twenty-one days after treatment, we determined body weight, epididymal fat weight, blood glucose, plasma insulin, NEFA, glucose tolerance, insulin resistance, insulin clearance and beta cell mass. Finally, we assessed insulin receptor and protein kinase B phosphorylation in peripheral organs, as well as insulin-degrading enzyme (IDE) protein production and alternative splicing in the liver and HEPG2 cells. CNTF improved insulin sensitivity and beta cell mass, while reducing glucose-stimulated insulin secretion and insulin clearance in Swiss mice, improving glucose handling in a non-obese type 2 diabetes model. This effect was associated with lower IDE production and activity in liver cells. All these effects were observed even at 21 days after CNTF treatment. CNTF protection against type 2 diabetes is partially independent of the anti-obesity actions of CNTF, requiring a reduction in insulin clearance and increased beta cell mass, besides increased insulin sensitivity. Furthermore, knowledge of the long-term effects of CNTF expands its pharmacological relevance.

Chemical Methods to Induce Beta-Cell Proliferation

Pancreatic beta-cell regeneration, for example, by inducing proliferation, remains an important goal in developing effective treatments for diabetes. However, beta cells have mainly been considered quiescent. This “static” view has recently been challenged by observations of relevant physiological conditions in which metabolic stress is compensated by an increase in beta-cell mass. Understanding the molecular mechanisms underlining these process could open the possibility of developing novel small molecules to increase beta-cell mass. Several cellular cell-cycle and signaling proteins provide attractive targets for high throughput screening, and recent advances in cell culture have enabled phenotypic screening for small molecule-induced beta-cell proliferation. We present here an overview of the current trends involving small-molecule approaches to induce beta-cell regeneration by proliferation.

Contribution of Different Mechanisms to Pancreatic Beta-cell Hyper-secretion in Non-obese Diabetic (NOD) Mice during Pre-diabetes

The development of insulin-dependent diabetes mellitus (IDDM) results from the selective destruction of pancreatic beta-cells. Both humans and spontaneous models of IDDM, such as NOD mice, have an extended pre-diabetic stage. Dynamic changes in beta-cell mass and function during pre-diabetes, such as insulin hyper-secretion, remain largely unknown. In this paper, we evaluated pre-diabetic female NOD mice at different ages (6, 10, and 14 weeks old) to illustrate alterations in beta-cell mass and function as disease progressed. We found an increase in beta-cell mass in 6-week-old NOD mice that may account for improved glucose tolerance in these mice. As NOD mice aged, beta-cell mass progressively reduced with increasing insulitis. In parallel, secretory ability of individual beta-cells was enhanced due to an increase in the size of slowly releasable pool (SRP) of vesicles. Moreover, expression of both SERCA2 and SERCA3 genes were progressively down-regulated, which facilitated depolarization-evoked secretion by prolonging Ca(2+) elevation upon glucose stimulation. In summary, we propose that different mechanisms contribute to the insulin hyper-secretion at different ages of pre-diabetic NOD mice, which may provide some new ideas concerning the progression and management of type I diabetes.

Emerging role of insulin with incretin therapies for management of type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a progressive disease warranting intensification of treatment, as beta-cell function declines over time. Current treatment algorithms recommend metformin as the first-line agent, while advocating the addition of either basal-bolus or premixed insulin as the final level of intervention. Incretin therapy, including incretin mimetics or enhancers, are the latest group of drugs available for treatment of T2DM. These agents act through the incretin axis, are currently recommended as add-on agents either as second-or third-line treatment, without concurrent use of insulin. Given the novel role of incretin therapy in terms of reducing postprandial hyperglycemia, and favorable effects on weight with reduced incidence of hypoglycemia, we explore alternative options for incretin therapy in T2DM management. Furthermore, as some evidence alludes to incretins potentially increasing betacell mass and altering disease progression, we propose introducing these agents earlier in the treatment algorithm. In addition, we suggest the concurrent use of incretins with insulin, given the favorable effects especially in relation to weight gain.