Pharmacological treatment of chronic diabetes by stimulating pancreatic beta-cell regeneration with systemic co-administration of EGF and gastrin

The Adaptor Protein NumbL Is Involved in the Control of Glucolipotoxicity-Induced Pancreatic Beta Cell Apoptosis

Avoiding the loss of functional beta cell mass is critical for preventing or treating diabetes. Currently, the molecular mechanisms underlying beta cell death are partially understood, and there is a need to identify new targets for developing novel therapeutics to treat diabetes. Previously, our group established that Mig6, an inhibitor of EGF signaling, mediates beta cell death under diabetogenic conditions. The objective here was to clarify the mechanisms linking diabetogenic stimuli to beta cell death by investigating Mig6-interacting proteins. Using co-immunoprecipitation and mass spectrometry, we evaluated the binding partners of Mig6 under both normal glucose (NG) and glucolipotoxic (GLT) conditions in beta cells. We identified that Mig6 interacted dynamically with NumbL, whereas Mig6 associated with NumbL under NG, and this interaction was disrupted under GLT conditions. Further, we demonstrated that the siRNA-mediated suppression of NumbL expression in beta cells prevented apoptosis under GLT conditions by blocking the activation of NF-κB signaling. Using co-immunoprecipitation experiments, we observed that NumbL's interactions with TRAF6, a key component of NFκB signaling, were increased under GLT conditions. The interactions among Mig6, NumbL, and TRAF6 were dynamic and context-dependent. We proposed a model wherein these interactions activated pro-apoptotic NF-κB signaling while blocking pro-survival EGF signaling under diabetogenic conditions, leading to beta cell apoptosis. These findings indicated that NumbL should be further investigated as a candidate anti-diabetic therapeutic target.

Gastrin producing syngeneic mesenchymal stem cells protect non-obese diabetic mice from type 1 diabetes

Progressive destruction of pancreatic islet β-cells by immune cells is a primary feature of type 1 diabetes (T1D) and therapies that can restore the functional β-cell mass are needed to alleviate disease progression. Here, we report the use of mesenchymal stromal/stem cells (MSCs) for the production and delivery of Gastrin, a peptide hormone that is produced by intestinal cells and foetal islets and can increase β-Cell mass, to promote protection from T1D. A single injection of syngeneic MSCs that were engineered to express Gastrin (Gastrin-MSCs) caused a significant delay in hyperglycaemia in non-obese diabetic (NOD) mice compared to engineered control-MSCs. Similar treatment of early-hyperglycaemic mice caused the restoration of euglycemia for a considerable duration, and these therapeutic effects were associated with the protection of, and/or higher frequencies of, insulin-producing islets and less severe insulitis. While the overall immune cell phenotype was not affected profoundly upon treatment using Gastrin-MSCs or upon in vitro culture, pancreatic lymph node cells from Gastrin-MSC treated mice, upon ex vivo challenge with self-antigen, showed a Th2 and Th17 bias, and diminished the diabetogenic property in NOD-Rag1 deficient mice suggesting a disease protective immune modulation under Gastrin-MSC treatment associated protection from hyperglycaemia. Overall, this study shows the potential of production and delivery of Gastrin in vivo, by MSCs, in protecting insulin-producing β-cells and ameliorating the disease progression in T1D.

Short-Term Effect of Hypergastrinemia Following Esomeprazole Treatment On Well-Controlled Type 2 Diabetes Mellitus: A Prospective Study

Objective:

Proton pump inhibitor (PPI) drugs reduce gastric acid secretion and lead to an increase in serum gastrin levels. Many preclinical and some clinical researches have established some positive effects of gastrin or PPI therapy on glucose regulation. The aim of this study was to prospectively investigate the short term effects of esomeprazole on glycaemic control in patients with type 2 diabetes mellitus. In addition, the presence of an association between this effect and gastrin levels was evaluated.

Methods:

Thirty-two subjects with type 2 diabetes mellitus were enrolled and grouped as intervention (n=16) and control (n=16). The participants in the intervention group were prescribed 40 mg of esomeprazole treatment for three months. At the beginning of the study and at the 3rd month, HbA1c level (%) and gastrin levels (pmol/L) of participants were assessed. Then, the groups were compared in terms of their baseline and 3rd month values.

Results:

In the intervention group, the mean gastrin level increased significantly from 34.3±14.4 pmol/L to 87.4±43.6 pmol/L (p<0.001). The mean HbA1c level was similar to the pre-treatment level (6.3±0.7% vs. 6.4±0.9%, p=0.441). There were no statistically significant differences in all parameters of the control group. The majority of individuals were on metformin monotherapy (65.6 %). The subgroup analysis of metformin monotherapy revealed that, in intervention group, there was a significant increase in gastrin levels (39.9±12.6 vs. 95.5±52.5, p=0.026), but the HbA1c levels did not change (6.0±0.4 % vs. 5.9±0.6 %, p=0.288); and in control group, gastrin levels did not change (37.5 ± 26.7 vs. 36.1 ±23.3, p=0.367), but there was an increase in HbA1c levels (6.1 ± 0.50 vs. 6.4 ± 0.60, p=0.01).

Conclusion:

Our study demonstrates that esomeprazole has no extra benefit for the controlled diabetic patient in three months. However, in only the metformin-treated subgroup, esomeprazole may prevent the rise in HbA1c level.

Characterization and anti-diabetic effects of the oligosaccharide fraction isolated from Rosa canina in STZ-Induced diabetic rats

Diabetes mellitus is the most common metabolic disorder characterized by chronic hyperglycemia. There has been a surge of research studies aiming to use natural products in the management of diabetes. The objective of this study was to isolate and characterize the structure and anti-diabetic mechanisms of the main ingredient from Rosa canina. The oligosaccharide was isolated from Rosa canina fruits and characterized by a combination of FTIR, NMR and Mass spectrometry. Wistar rats were divided into negative control, diabetic (type 2), isolated oligosaccharide (IO)-treated diabetic and positive diabetic controls. Oral glucose tolerance, gluconeogenesis and α-glucosidase inhibitory tests as well as immunohistochemistry and quantitative real time-PCR were performed to elucidate the molecular anti-diabetic mechanisms of IO. Structural analyses confirmed the oligosaccharide structure of isolated fraction. Gluconeogenesis and α-glucosidase activity were inhibited by IO in diabetic rats. The oral glucose tolerance test was improved significantly in the group treated with the IO (P < 0.05). Pancreatic β-cells and tissue pathological examination showed a significant improvement after the treatment period. In addition, the expression of Ngn3, Nkx6.1 and insulin increased in oligosaccharide-treated compared to untreated diabetic rats. Owing to the verified anti-diabetic effects and regenerative potential, isolated oligosaccharide could be considered as the promising drug in the management of diabetes.

Gastrin analogue administration adds no significant glycaemic benefit to a glucagon-like peptide-1 receptor agonist acutely or after washout of both analogues

AIM

To determine if a 4-week course of 14 mg weekly GLP-1 agonist LY2428757 combined with 3 mg or 2 mg daily gastrin analogue TT223 (LY+TT223) results in long-term glycaemic changes.

MATERIALS AND METHODS

Patients with in adequately-controlled type 2 diabetes mellitus ±metformin (N=151) were randomized to a 4-week course of LY+TT223 (3 mg), LY+TT223 (2 mg), LY+TT223 placebo (LY-only) or LY placebo+TT223 placebo (placebo). The primary objective was change in HbA1c from baseline to 5 month safter completion of therapy (i.e. at 6 months) and safety and tolerability with LY+TT223 versus LY-only.

RESULTS

LY groups showed HbA1c reductions during the active treatment phase. These did not persist during follow-up phase. Combining TT223 with LY did not result in additional glycaemic effects during treatment or follow-up. At 6 months, LSM ± SE for change in HbA1c from baseline was: LY+TT223 (3 mg): -0.1 ± 0.2%; LY+TT223 (2 mg): 0.1 ± 0.2%; LY-only: -0.2 ± 0.2%; placebo: 0.04 ± 0.2%. Secondary analyses were consistent with primary results. LY+TT223 was not superior to LY for other time points or end points, including insulin secretory response to mixed meal tolerance tests. The most common adverse events (nausea and vomiting) were more frequent with LY+TT223 versus LY-only. The safety profile was consistent with previous findings.

CONCLUSION

GLP-1+gastrin combination therapy did not improve glycaemic control versus GLP-1 alone.

Culturing with modified EGM2 medium enhances porcine neonatal islet-like cell clusters resistance to apoptosis in islet xenotransplantation

BACKGROUND

Neonatal pig islet-like cell clusters (NICC) are an attractive source of insulin-producing tissue for potential transplantation treatment of type 1 diabetic patients. However, a considerable loss of NICC after their transplantation due to apoptosis resulted from islet isolation and instant blood-mediated inflammatory reaction remains to be overcome.

METHODS

EGM2 medium depleted with hydrocortisone and supplemented with 50 mmol/L isobutylmethylxanthine, 10 mmol/L nicotinamide, and 10 mmol/L glucose was used to culture NICC at day 1, the day after isolation and changed every other day. NICC cultured with EGM2 or control Ham's F-10 medium were collected at day 7 of culture for the following assays. The viability of NICC was evaluated by AO/EB staining and FACS. Static assay and oxygen consumption rate analysis were performed to assess the function of NICC. Insulin and glucagon gene expression were measured by real-time PCR. Tubing loops model and TUNEL assay were performed to confirm the apoptosis-resistant ability of NICC cultured with modified EGM2 medium. Serum starvation and hypoxia treatment were used to test the tolerant capability of NICC in the microenvironment of hypoxia/nutrient deficiency in vitro. The molecules involved in apoptosis pathways in NICC were analyzed by Western blotting.

RESULTS

Compared with Ham's F-10 medium, culturing NICC with EGM2 medium led to increased number and viability of NICC with higher stimulation index, upregulated gene expression of both insulin and glucagon, and enhanced mitochondria function. Furthermore, fewer modified EGM2 medium cultured NICC were found under apoptosis when evaluated in an in vitro tubing loop model of IBMIR. Moreover, EGM2 medium cultured NICC demonstrated much less apoptotic cells under either serum starvation or hypoxia condition than their Ham's F-10 medium cultured counterparts. The enhanced capability of EGM2 cultured NICC to resist apoptosis was associated with their elevated protein levels of anti-apoptotic Bcl-2 family member Mcl-1.

CONCLUSION

Culturing NICC with EGM2 provides a simple and effective approach not only to increase NICC yield, viability, and maturation but also to enhance their resistance to apoptosis to preserve the initial graft mass for successful islet xenotransplantation.

Maximizing endogenous β-cell regeneration

PURPOSE OF REVIEW

Inadequate insulin-producing pancreatic β-cell mass is a key feature of both type 1 and type 2 diabetes. Efforts to regenerate β-cell mass from pancreatic precursors may thus ameliorate absolute or relative insulin deficiency, thereby improving glucose homeostasis. A clear understanding of the processes that govern the generation of new β-cells in the mature pancreas will be fundamental to success in this effort. This review discusses the current state of knowledge regarding β-cell regeneration and emphasizes recent studies of significance.

RECENT FINDINGS

Recent reports demonstrate regenerative potential in the adult human pancreas. Further, they build on the strong existing evidence that proliferation of preexisting β-cells is the predominant source of new β-cells in adulthood by dissecting the cell cycle machinery components and critical signaling pathways required for β-cell proliferation. Finally, β-cell trophic peptides have demonstrated preclinical potential as pharmacologic regenerative agents and may form the basis for clinical interventions in the future.

SUMMARY

Efforts to augment β-cell regeneration by enhancing β-cell viability and proliferation may lead to novel therapeutic approaches for type 1 and type 2 diabetes. An intimate understanding of the molecular mechanisms underlying the regulation of β-cell proliferation and survival will be fundamental to the optimization of endogenous β-cell regeneration.

Bi-stability in type 2 diabetes mellitus multi-organ signalling network

Type 2 diabetes mellitus (T2DM) is believed to be irreversible although no component of the pathophysiology is irreversible. We show here with a network model that the apparent irreversibility is contributed by the structure of the network of inter-organ signalling. A network model comprising all known inter-organ signals in T2DM showed bi-stability with one insulin sensitive and one insulin resistant attractor. The bi-stability was made robust by multiple positive feedback loops suggesting an evolved allostatic system rather than a homeostatic system. In the absence of the complete network, impaired insulin signalling alone failed to give a stable insulin resistant or hyperglycemic state. The model made a number of correlational predictions many of which were validated by empirical data. The current treatment practice targeting obesity, insulin resistance, beta cell function and normalization of plasma glucose failed to reverse T2DM in the model. However certain behavioural and neuro-endocrine interventions ensured a reversal. These results suggest novel prevention and treatment approaches which need to be tested empirically.

Activation of GLP-1 and gastrin signalling induces in vivo reprogramming of pancreatic exocrine cells into beta cells in mice

AIMS/HYPOTHESIS

Lineage conversion of non-beta cells into insulin-producing cells has been proposed as a therapy for the cure of diabetes. Glucagon-like peptide-1 (GLP-1) and its derivatives can induce beta cell neogenesis in vitro and beta cell mass expansion in vivo, but GLP-1 signalling has not been shown to regulate cell fate decisions in vivo. We therefore tested the impact of GLP-1 receptor (GLP1R) expression on beta cell differentiation in vivo.

METHODS

Mice overexpressing GLP1R in pancreatic exocrine cells were generated by Cre-mediated recombination in sex-determining region Y-box 9 (SOX9)-expressing cells and then treated with exendin-4 and/or gastrin. Histological analysis was performed to detect cellular reprogramming from the exocrine lineage into insulin-producing cells.

RESULTS

Whereas no newly generated beta cells were detected in the mice treated with exendin-4 alone, treatment with gastrin only induced the conversion of exocrine cells into insulin-producing cells. Furthermore, the overexpression of GLP1R, together with gastrin and exendin-4, synergistically promoted beta cell neogenesis accompanied by the formation of islet-like clusters. These newly generated beta cells expressed beta cell specific transcription factors, such as pancreatic and duodenal homeobox 1 (PDX1), NK6 homeobox 1 (NKX6.1) and musculoaponeurotic fibrosarcoma oncogene family A (MafA). These mice showed no histological evidence of pancreatitis or pancreatic dysplasia in their acini and had normal plasma amylase levels.

CONCLUSIONS/INTERPRETATION

Activation of GLP-1 and gastrin signalling induces beta cell neogenesis in the exocrine lineage without any deleterious pancreatic changes, which may lead to a potential therapy to cure diabetes by generating surrogate beta cells.

Beta Cell Mass Restoration in Alloxan-Diabetic Mice Treated with EGF and Gastrin

One week of treatment with EGF and gastrin (EGF/G) was shown to restore normoglycemia and to induce islet regeneration in mice treated with the diabetogenic agent alloxan. The mechanisms underlying this regeneration are not fully understood. We performed genetic lineage tracing experiments to evaluate the contribution of beta cell neogenesis in this model. One day after alloxan administration, mice received EGF/G treatment for one week. The treatment could not prevent the initial alloxan-induced beta cell mass destruction, however it did reverse glycemia to control levels within one day, suggesting improved peripheral glucose uptake. In vitro experiments with C2C12 cell line showed that EGF could stimulate glucose uptake with an efficacy comparable to that of insulin. Subsequently, EGF/G treatment stimulated a 3-fold increase in beta cell mass, which was partially driven by neogenesis and beta cell proliferation as assessed by beta cell lineage tracing and BrdU-labeling experiments, respectively. Acinar cell lineage tracing failed to show an important contribution of acinar cells to the newly formed beta cells. No appearance of transitional cells co-expressing insulin and glucagon, a hallmark for alpha-to-beta cell conversion, was found, suggesting that alpha cells did not significantly contribute to the regeneration. An important fraction of the beta cells significantly lost insulin positivity after alloxan administration, which was restored to normal after one week of EGF/G treatment. Alloxan-only mice showed more pronounced beta cell neogenesis and proliferation, even though beta cell mass remained significantly depleted, suggesting ongoing beta cell death in that group. After one week, macrophage infiltration was significantly reduced in EGF/G-treated group compared to the alloxan-only group. Our results suggest that EGF/G-induced beta cell regeneration in alloxan-diabetic mice is driven by beta cell neogenesis, proliferation and recovery of insulin. The glucose-lowering effect of the treatment might play an important role in the regeneration process.

Differentiation of fetal pancreatic stem cells into neuron-like and islet-like cells in vitro

Pancreatic stem cells were isolated and cultured from aborted human fetal pancreases of gestational age 14–20 weeks. They were seeded at a density of 1 × 10⁴ in serum-free media for differentiation into neuron-like cells, expressing β-tubulin III and glial fibrillary acidic protein. These neuron-like cells displayed a synapse-like morphology and appeared to form a neuronal network. Pancreatic stem cells were also seeded at a density of 1 × 10⁵ for differentiation into islet-like cells, expressing insulin and glucagon, with an islet-like morphology. These cells had glucose-stimulated secretion of human insulin and C-peptide. Results suggest that pancreatic stem cells can be differentiated into neuron-like and islet-like cells.

Nerve growth factor neutralization suppresses β-cell proliferation through activin A and betacellulin

OBJECTIVE

The aim of this study was to investigate the effects of nerve growth factor (NGF) neutralization on synthesis and secretion of activin A (Act-A) and betacellulin (BTC) from primary β cells and the importance of these relations for β-cell proliferation.

METHODS

β Cells were isolated from euglycemic and streptozotocin-induced (75 mg/kg) hyperglycemic rats and treated with NGF neutralization antibody. The gene expression levels of Act-A and BTC in the primary β cells were evaluated using quantitative real-time polymerase chain reaction. The cellular and secreted levels of Act-A and BTC proteins were estimated using Western blot analysis.

RESULTS

Nerve growth factor neutralization (1) reduced β-cell proliferation, (2) decreased Act-A at gene expression and protein levels while increasing its secretion from β cells, and (3) increased BTC at gene expression level while mildly decreasing its cellular protein level and secretion from β cells. Nerve growth factor neutralization specifically affected β cells of hyperglycemic rats.

CONCLUSIONS

These findings indicate that NGF is an important regulator for the synthesis and secretion of Act-A and BTC from the β cells. Moreover, the results suggested that β-cell proliferation decreased through NGF neutralization is possibly related to decreased BTC and increased Act-A secretion from β cells of hyperglycemic rats.

Pancreatic insulin-producing cells differentiated from human embryonic stem cells correct hyperglycemia in SCID/NOD mice, an animal model of diabetes

Background

Human pancreatic islet transplantation is a prospective curative treatment for diabetes. However, the lack of donor pancreases greatly limits this approach. One approach to overcome the limited supply of donor pancreases is to generate functional islets from human embryonic stem cells (hESCs), a cell line with unlimited proliferative capacity, through rapid directed differentiation. This study investigated whether pancreatic insulin-producing cells (IPCs) differentiated from hESCs could correct hyperglycemia in severe combined immunodeficient (SCID)/non-obese diabetic (NOD) mice, an animal model of diabetes.

Methods

We generated pancreatic IPCs from two hESC lines, YT1 and YT2, using an optimized four-stage differentiation protocol in a chemically defined culture system. Then, about 5–7×10⁶ differentiated cells were transplanted into the epididymal fat pad of SCID/NOD mice (n = 20). The control group were transplanted with undifferentiated hESCs (n = 6). Graft survival and function were assessed using immunohistochemistry, and measuring serum human C-peptide and blood glucose levels.

Results

The pancreatic IPCs were generated by the four-stage differentiation protocol using hESCs. About 17.1% of differentiated cells expressed insulin, as determined by flow cytometry. These cells secreted insulin/C-peptide following glucose stimulation, similarly to adult human islets. Most of these IPCs co-expressed mature β cell-specific markers, including human C-peptide, GLUT2, PDX1, insulin, and glucagon. After implantation into the epididymal fat pad of SCID/NOD mice, the hESC-derived pancreatic IPCs corrected hyperglycemia for ≥8 weeks. None of the animals transplanted with pancreatic IPCs developed tumors during the time. The mean survival of recipients was increased by implanted IPCs as compared to implanted undifferentiated hESCs (P<0.0001).

Conclusions

The results of this study confirmed that human terminally differentiated pancreatic IPCs derived from hESCs can correct hyperglycemia in SCID/NOD mice for ≥8 weeks.

Combination treatment of db/db mice with exendin-4 and gastrin preserves β-cell mass by stimulating β-cell growth and differentiation

Aim/Introduction:  Preservation of β‐cell mass is crucial for maintaining long‐term glucose homeostasis. Therapies based on incretin and its mimetics are expected to achieve this goal through various biological functions, particularly the restoration of β‐cell mass. Here we tested the effects of gastrin and exendin‐4 in type 2 diabetic animals.

Materials and Methods:  The effects of exendin‐4 and gastrin on β‐cell function and mass were examined in 8‐week‐old db/db mice. INS‐1 beta cells and AR42J cells were used to determine the molecular mechanism underlying the effects of the two agents. Immunohistochemistry, western blotting and RT‐PCR assays were used to assess the biological effects of the two agents.

Results:  Two weeks of combination administration of exendin‐4 plus gastrin resulted in a significant improvement of glucose tolerance associated with a marked preservation of β‐cell mass in db/db mice. Immunohistochemical analysis showed that such treatment resulted in the appearance of numerous irregularly‐shaped small islets and single insulin‐positive cells. While gastrin had little biological effect on INS‐1 β‐cells consistent with low expression of its intrinsic receptor on these cells, it caused differentiation of AR42J cells into insulin‐producing cells. Co‐stimulation with exendin‐4 significantly enhanced gastrin‐induced endocrine differentiation of AR42J precursor cells. These findings were further supported by enhanced expression of key genes involved in β‐cell differentiation and maturation, such as neurogenin3 (Ngn3) and MafA.

Conclusions:  These results suggest that combination treatment of db/db mice with exendin‐4 and gastrin preserves β‐cell mass by stimulating β‐cell growth and differentiation. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.00044.x, 2010)

Baicalein Protects against Type 2 Diabetes via Promoting Islet β-Cell Function in Obese Diabetic Mice

In both type 1 (T1D) and type 2 diabetes (T2D), the deterioration of glycemic control over time is primarily caused by an inadequate mass and progressive dysfunction of β-cell, leading to the impaired insulin secretion. Here, we show that dietary supplementation of baicalein, a flavone isolated from the roots of Chinese herb Scutellaria baicalensis, improved glucose tolerance and enhanced glucose-stimulated insulin secretion (GSIS) in high-fat diet (HFD-) induced middle-aged obese mice. Baicalein had no effect on food intake, body weight gain, circulating lipid profile, and insulin sensitivity in obese mice. Using another mouse model of type 2 diabetes generated by high-fat diet (HFD) feeding and low doses of streptozotocin injection, we found that baicalein treatment significantly improved hyperglycemia, glucose tolerance, and blood insulin levels in these middle-aged obese diabetic mice, which are associated with the improved islet β-cell survival and mass. In the in vitro studies, baicalein significantly augmented GSIS and promoted viability of insulin-secreting cells and human islets cultured either in the basal medium or under chronic hyperlipidemic condition. These results demonstrate that baicalein may be a naturally occurring antidiabetic agent by directly modulating pancreatic β-cell function.

Omeprazole and PGC-formulated heparin binding epidermal growth factor normalizes fasting blood glucose and suppresses insulitis in multiple low dose streptozotocin diabetes model

PURPOSE

Our objective was to develop novel nanocarriers (protected graft copolymer, PGC) that improve the stability of heparin binding EGF (HBEGF) and gastrin and then to use PGC-formulated HBEGF (PGC-HBEGF) and Omeprazole (+/- PGC-gastrin) for normalizing fasting blood glucose (FBG) and improving islet function in diabetic mice.

METHODS

HBEGF, PGC-HBEGF, Omeprazole, Omeprazole + PGC-HBEGF, Omeprazole + PGC-gastrin + PGC-HBEGF and epidermal growth factor (EGF) + gastrin were tested in multiple low dose streptozotocin diabetic mice.

RESULTS

Omeprazole + PGC-HBEGF normalized FBG and is better than EGF + gastrin at improving islet function and decreasing insulitis. Groups treated with Omeprazole, Omeprazole + PGC-HBEGF, or EGF + gastrin have significantly improved islet function versus saline control. All animals that received PGC-HBEGF had significantly reduced islet insulitis versus saline control. Non-FBG was lower for Omeprazole + PGC-gastrin + PGC-HBEGF but Omeprazole + PGC-HBEGF alone showed better FBG and glucose tolerance.

CONCLUSIONS

Omeprazole + PGC-HBEGF provides a sustained exposure to both EGFRA and gastrin, improves islet function, and decreases insulitis in multiple low dose streptozotocin diabetic mice. Although HBEGF or EGF elevates non-FBG, it facilitates a reduction of insulitis and, in the presence of Omeprazole, provides normalization of FBG at the end of treatment. The study demonstrates Omeprazole and PGC-HBEGF is a viable treatment for diabetes.

The antidiabetic effect of mesenchymal stem cells is unrelated to their transdifferentiation potential but to their capability to restore Th1/Th2 balance and to modify the pancreatic microenvironment

Type 1 diabetes mellitus (T1DM) is a chronic metabolic disease that results from cell-mediated autoimmune destruction of insulin-producing cells. In T1DM animal models, it has been shown that the systemic administration of multipotent mesenchymal stromal cells, also referred as to mesenchymal stem cells (MSCs), results in the regeneration of pancreatic islets. Mechanisms underlying this effect are still poorly understood. Our aims were to assess whether donor MSCs (a) differentiate into pancreatic β-cells and (b) modify systemic and pancreatic pathophysiologic markers of T1DM. After the intravenous administration of 5 × 10(5) syngeneic MSCs, we observed that mice with T1DM reverted their hyperglycemia and presented no donor-derived insulin-producing cells. In contrast, 7 and 65 days post-transplantation, MSCs were engrafted into secondary lymphoid organs. This correlated with a systemic and local reduction in the abundance of autoaggressive T cells together with an increase in regulatory T cells. Additionally, in the pancreas of mice with T1DM treated with MSCs, we observed a cytokine profile shift from proinflammatory to antinflammatory. MSC transplantation did not reduce pancreatic cell apoptosis but recovered local expression and increased the circulating levels of epidermal growth factor, a pancreatic trophic factor. Therefore, the antidiabetic effect of MSCs intravenously administered is unrelated to their transdifferentiation potential but to their capability to restore the balance between Th1 and Th2 immunological responses along with the modification of the pancreatic microenvironment. Our data should be taken into account when designing clinical trials aimed to evaluate MSC transplantation in patients with T1DM since the presence of endogenous precursors seems to be critical in order to restore glycemic control.

Proton pump inhibitors: impact on glucose metabolism

Diabetes mellitus is a complex chronic disease associated with an absolute insulin deficiency in type 1 diabetes (T1D) and a progressive deterioration of β-cell function in type 2 diabetes (T2D). T2D pathophysiology has numerous defects including incretin deficiency/resistance. Gastrin has demonstrated to be an islet growth factor (like glucagon-like peptide-1, epidermal growth factor, transforming growth factor-α,…) and be able to restore a functional β-cell mass in diabetic animals. This hormone is likely to stimulate insulin secretion during an ordinary protein-rich meal, this is, to have an incretin-like effect. Proton pump inhibitors (PPIs) can raise serum gastrin concentration significantly and therefore, affect to glucose metabolism through promoting β-cell regeneration/expansion and also enhancing insulin secretion. The present paper aims to review studies concerning the effect of PPIs on glucose metabolism. Several research groups have recently explored the potential role of this class of drugs on glycemic control, mainly in T2D. The results show antidiabetic properties for the PPIs with a global glucose-lowering power around 0.6-0.7 % points of HbA1c, but the level of evidence for the available literature is still not high. If these data start to become demonstrated in the ongoing clinical trials, PPIs could become a new antidiabetic agent with a good and safe profile for T2D and even useful for T1D, particularly in the area of islet transplantation to preserve β-cell mass.

The relation among NGF, EGF and insulin is important for triggering pancreatic β cell apoptosis

BACKGROUND

Nerve growth factor (NGF) is a well-known mediator for maintaining the survival of neurons, while recent studies report that its absence induces apoptosis in cultured β cells of humans and rats. However, its relationship with other growth factors that have important roles in the survival and function of β cells such as epidermal growth factor (EGF) has not yet been elucidated. The aim of this study was to investigate the effects of NGF withdrawal on the synthesis and secretion of EGF, insulin with respect to β cell apoptosis in hyperglycemic rats.

METHOD

β cells were isolated from euglycemic and streptozotocin-induced hyperglycemic rats and treated with NGF neutralizing antibody for withdrawal of NGF in culture medium. NGF, EGF and insulin levels in cell lysates and secretion samples were measured by enzyme-linked immunosorbent assay, and their gene expressions were determined by real-time reverse transcription polymerase chain reaction assay. Apoptosis was quantitatively determined by cytoplasmic histone-associated DNA fragments.

RESULTS

Nerve growth factor neutralization triggered β cell apoptosis. In addition decreased insulin, increased NGF and EGF were observed at gene expression and protein levels by NGF neutralization. Moreover, NGF withdrawal decreased secretion of these peptides from β cells. Although the alterations seemed to be similar under euglycemic and hyperglycemic conditions, NGF withdrawal more strongly affected β cells of hyperglycemic rats.

CONCLUSIONS

These important findings indicate that NGF is an important regulator for the synthesis and secretion of EGF and insulin from the β cells. Moreover, results suggested that NGF withdrawal causes apoptosis by decreasing EGF, NGF and insulin secretion from β cells of hyperglycemic rats.

Mixed chimerism and growth factors augment β cell regeneration and reverse late-stage type 1 diabetes

Type 1 diabetes (T1D) results from an autoimmune destruction of insulin-producing β cells. Currently, islet transplantation is the only curative therapy for late-stage T1D, but the beneficial effect is limited in its duration, even under chronic immunosuppression, because of the chronic graft rejection mediated by both auto- and alloimmunity. Clinical islet transplantation is also restricted by a severe shortage of donor islets. Induction of mixed chimerism reverses autoimmunity, eliminates insulitis, and reverses new-onset but not late-stage disease in the nonobese diabetic (NOD) mouse model of T1D. Administration of gastrin and epidermal growth factor (EGF) also reverses new-onset but not late-stage T1D in this animal model. Here, we showed that combination therapy of induced mixed chimerism under a radiation-free nontoxic anti-CD3/CD8 conditioning regimen and administration of gastrin/EGF augments both β cell neogenesis and replication, resulting in reversal of late-stage T1D in NOD mice. If successfully translated into humans, this combination therapy could replace islet transplantation as a long-term curative therapy for T1D.

[Effect of "Pintes" white wine on metabolic parameters in patients with metabolic syndrome]

Moderate alcohol consumption has been associated with decreased cardiovascular mortality in the general population. Relatively few studies have been conducted to evaluate the effect of white wine on insulin sensitivity.

AIMS

The authors studied the impact of moderate Pintes white wine consumption on insulin sensitivity and other metabolic parameters.

METHODS

The prospective study involved 18 patients with metabolic syndrome. The patients consumed Pintes white wine for 4 weeks, and parameters were measured before and after consumption.

RESULTS

The HOMA-IR decreased significantly after white wine consumption (2.28±2.04 vs 1.08±0.6; p = 0.002). There were no changes in serum cholesterol, LDL-cholesterol, triglyceride and fasting plasma glucose levels.

CONCLUSION

White wine consumption improved insulin sensitivity in patients with metabolic syndrome.

Concise review: pancreas regeneration: recent advances and perspectives

The replacement of functional pancreatic β-cells is seen as an attractive potential therapy for diabetes, because diabetes results from an inadequate β-cell mass. Inducing replication of the remaining β-cells and new islet formation from progenitors within the pancreas (neogenesis) are the most direct ways to increase the β-cell mass. Stimulation of both replication and neogenesis have been reported in rodents, but their clinical significance must still be shown. Because human islet transplantation is limited by the scarcity of donors and graft failure within a few years, efforts have recently concentrated on the use of stem cells to replace the deficient β-cells. Currently, embryonic stem cells and induced pluripotent stem cells achieve high levels of β-cell differentiation, but their clinical use is still hampered by ethical issues and/or the risk of developing tumors after transplantation. Pancreatic epithelial cells (duct, acinar, or α-cells) represent an appealing alternative to stem cells because they demonstrate β-cell differentiation capacities. Yet translation of such capacity to human cells after significant in vitro expansion has yet to be achieved. Besides providing new β-cells, cell therapy also has to address the question on how to protect the transplanted cells from destruction by the immune system via either allo- or autoimmunity. Encouraging developments have been made in encapsulation and immunomodulation techniques, but many challenges still remain. Herein, we discuss recent advances in the search for β-cell replacement therapies, current strategies for circumventing the immune system, and mandatory steps for new techniques to be translated from bench to clinics.

Oreocnide integrifolia Flavonoids Augment Reprogramming for Islet Neogenesis and β-Cell Regeneration in Pancreatectomized BALB/c Mice

Agents which can either trigger proliferation of β-cells or induce neogenesis of β-cells from precursors would be of pivotal role in reversing diabetic manifestations. We examined the role of flavonoid rich fraction (FRF) of Oreocnide integrifolia leaves using a mice model of experimental regeneration. BALB/c mice were subjected to ~70% pancreatectomy (Px) and supplemented with FRF for 7, 14, and 21 days after pancreatectomy. Px animals displayed increased blood glucose levels and decreased insulin titres which were ameliorated by FRF supplementation. FRF-treated mice demonstrated prominent newly formed islets budding off from ducts and depicting increased BrdU incorporation. Additionally, transcripts levels of Ins1/2, Reg-3α/γ, Ngn-3, and Pdx-1 were upregulated during the initial 1 week. The present study provides evidence of a nutraceutical contributing to islet neogenesis from ductal cells as the mode of β-cell regeneration and a potential therapeutic for clinical trials in management of diabetic manifestations.

Insulin improves β-cell function in glucose-intolerant rat models induced by feeding a high-fat diet

Insulin therapy has been shown to contribute to extended glycemia remission in newly diagnosed patients with type 2 diabetes mellitus. This study investigated the effects of insulin treatment on pancreatic lipid content, and β-cell apoptosis and proliferation in glucose-intolerant rats to explore the protective role of insulin on β-cell function. A rat glucose-intolerant model was induced by streptozotocin and a high-fat diet. Plasma and pancreatic triglycerides, free fatty acids, and insulin were measured; and pancreatic β-cell cell apoptosis and proliferation were detected by a propidium iodide cell death assay and immunofluorescence for proliferating cell nuclear antigen. Relative β-cell area was determined by immunohistochemistry for insulin, whereas insulin production in pancreas was assessed by reverse transcriptase polymerase chain reaction. Islet β-cell secreting function was assessed by the index ΔI30/ΔG30. Glucose-intolerant rats had higher pancreatic lipid content, more islet β-cell apoptosis, lower β-cell proliferation, and reduced β-cell area in pancreas when compared with controls. Insulin therapy reduced blood glucose, inhibited pancreatic lipid accumulation and islet β-cell apoptosis, and increased β-cell proliferation and β-cell area in glucose-intolerant rats. Furthermore, impaired insulin secretion and insulin production in glucose-intolerant rats were improved by insulin therapy. Insulin can preserve β-cell function by protecting islets from glucotoxicity and lipotoxicity. It can also ameliorate β-cell area by enhancing β-cell proliferation and reducing β-cell apoptosis.

Betacellulin-induced beta cell proliferation and regeneration is mediated by activation of ErbB-1 and ErbB-2 receptors

Background

Betacellulin (BTC), a member of the epidermal growth factor family, is known to play an important role in regulating growth and differentiation of pancreatic beta cells. Growth-promoting actions of BTC are mediated by epidermal growth factor receptors (ErbBs), namely ErbB-1, ErbB-2, ErbB-3 and ErbB-4; however, the exact mechanism for beta cell proliferation has not been elucidated. Therefore, we investigated which ErbBs are involved and some molecular mechanisms by which BTC regulates beta cell proliferation.

Methodology/Principal Findings

The expression of ErbB-1, ErbB-2, ErbB-3, and ErbB-4 mRNA was detected by RT-PCR in both a beta cell line (MIN-6 cells) and C57BL/6 mouse islets. Immunoprecipitation and western blotting analysis showed that BTC treatment of MIN-6 cells induced phosphorylation of only ErbB-1 and ErbB-2 among the four EGF receptors. BTC treatment resulted in DNA synthetic activity, cell cycle progression, and bromodeoxyuridine (BrdU)-positive staining. The proliferative effect was blocked by treatment with AG1478 or AG825, specific tyrosine kinase inhibitors of ErbB-1 and ErbB-2, respectively. BTC treatment increased mRNA and protein levels of insulin receptor substrate-2 (IRS-2), and this was blocked by the ErbB-1 and ErbB-2 inhibitors. Inhibition of IRS-2 by siRNA blocked cell cycle progression induced by BTC treatment. Streptozotocin-induced diabetic mice injected with a recombinant adenovirus expressing BTC and treated with AG1478 or AG825 showed reduced islet size, reduced numbers of BrdU-positive cells in the islets, and did not attain BTC-mediated remission of diabetes.

Conclusions/Significance

These results suggest that BTC exerts proliferative activity on beta cells through the activation of ErbB-1 and ErbB-2 receptors, which may increase IRS-2 expression, contributing to the regeneration of beta cells.

Gastrin treatment stimulates β-cell regeneration and improves glucose tolerance in 95% pancreatectomized rats

β-Cell mass reduction is a central aspect in the development of type 1 and type 2 diabetes, and substitution or regeneration of the lost β-cells is a potentially curative treatment of diabetes. To study the effects of gastrin on β-cell mass in rats with 95% pancreatectomy (95%-Px), a model of pancreatic regeneration, rats underwent 95% Px or sham Px and were treated with [15 leu] gastrin-17 (Px+G and S+G) or vehicle (Px+V and S+V) for 15 d. In 95% Px rats, gastrin treatment reduced hyperglycemia (280 ± 52 mg vs. 436 ± 51 mg/dl, P < 0.05), and increased β-cell mass (1.15 ± 0.15 mg)) compared with vehicle-treated rats (0.67 ± 0.15 mg, P < 0.05). Gastrin treatment induced β-cell regeneration by enhancing β-cell neogenesis (increased number of extraislet β-cells in Px+G: 0.42 ± 0.05 cells/mm(2) vs. Px+V: 0.27 ± 0.07 cells/mm(2), P < 0.05, and pancreatic and duodenal homeobox 1 expression in ductal cells of Px+G: 1.21 ± 0.38% vs. Px+V: 0.23 ± 0.10%, P < 0.05) and replication (Px+G: 1.65 ± 0.26% vs. S+V: 0.64 ± 0.14%; P < 0.05). In addition, reduced β-cell apoptosis contributed to the increased β-cell mass in gastrin-treated rats (Px+G: 0.07 ± 0.02%, Px+V: 0.23 ± 0.05%; P < 0.05). Gastrin action on β-cell regeneration and survival increased β-cell mass and improved glucose tolerance in 95% Px rats, supporting a potential role of gastrin in the treatment of diabetes.

Incretin physiology beyond glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide: cholecystokinin and gastrin peptides

Gastrin and cholecystokinin (CCK) are homologous hormone systems known to regulate gastric acid secretion, gallbladder emptying, and cell growth in the pancreas and stomach. They are, however, also involved in the development and secretory functions of pancreatic islet cells. For instance, foetal and neonatal islets express significant amounts of gastrin, and human as well as porcine islet cells express the gastrin/CCK-B receptor abundantly. Therefore, exogenous gastrin and CCK peptides stimulate insulin and glucagon secretion in man. Accordingly, endogenous hypergastrinaemia is accompanied by islet cell hyperplasia and increased insulin secretion. Conventionally, the effect of gastrointestinal hormones on insulin secretion (the incretin effect) has been defined and quantified in relation to oral versus intravenous glucose loadings. Under these unphysiological conditions, the release of gastrin and CCK and, hence, their effect on insulin secretion are modest in comparison with the effects of glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1 (GLP-1). Consequently, the interest of CCK and gastrin in incretin research has for decades been limited. A few years ago, however, it was suggested that gastrin together with epidermal growth factor or later GLP-1 might stimulate beta cell growth and secretion. Recent studies have shown that the combination of gastrin and GLP-1 actually restores normoglycaemia in diabetic mice. Therefore, a short review of the incretin system in a broader functional context that includes gastrin and CCK peptides may be timely.

Pancreatic Islet Culture and Preservation Strategies: Advances, Challenges, and Future Outlook

Postisolation islet survival is a critical step for achieving successful and efficient islet transplantation. This involves the optimization of islet culture in order to prolong survival and functionality in vitro. Many studies have focused on different strategies to culture pancreatic islets in vitro through manipulation of culture media, surface modified substrates, and the use of various techniques such as encapsulation, embedding, scaffold, and bioreactor culture strategies. This review aims to present and discuss the different methodologies employed to optimize pancreatic islet culture in vitro as well as address their respective advantages and drawbacks.

Harnessing the pancreatic stem cell

Building on the elaborate research studies that have helped map out key decision points in the process of pancreas development, reprogramming of pluripotent embryonic stem cells or induced pluripotent stem cells offers the possibility of overcoming restrictions on tissue supply associated with transplantation of donor islets. In a healthy pancreas, the beta-cell mass can exhibit significant plasticity, as reflected in the normal adaptive response in beta-cell mass to offset the metabolic challenge associated with pregnancy and obesity. In this article, alternative strategies and potential sources of pancreatic stem cells are considered.

Gastrointestinal hormones and the regulation of β-cell mass

Type 2 diabetes occurs due to a relative deficit in β-cell mass or function. Glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), and gastrin are gastrointestinal hormones that are secreted in response to nutrient intake, regulating digestion, insulin secretion, satiety, and β-cell mass. In this review, we focus upon β-cell mass regulation. β-cell mass expands through β-cell proliferation and islet neogenesis; β-cell mass is lost via apoptosis. GLP-1 and GIP are well-studied gastrointestinal hormones and influence β-cell proliferation, apoptosis, and islet neogenesis. CCK regulates β-cell apoptosis and mitogenesis, and gastrin stimulates islet neogenesis. GLP-1 and GIP bind to G protein-coupled receptors and regulate β-cell mass via multiple signaling pathways. The protein kinase A pathway is central to this process because it directly regulates proliferative and anti-apoptotic genes and transactivates several signaling cascades, including Akt and mitogen-activated protein kinases. However, the signaling pathways downstream of G protein-coupled CCK receptors that influence β-cell mass remain unidentified. Gastrointestinal hormones integrate nutrient signals from the gut to the β-cell, regulating insulin secretion and β-cell mass adaptation.

Effects of atorvastatin on the regeneration of pancreatic {beta}-cells after streptozotocin treatment in the neonatal rodent

To investigate the role of statins in beta-cell regeneration a model of streptozotocin (STZ)-induced beta-cell injury was used in the neonatal rat. We hypothesized that beta-cell growth and regeneration would increase following treatment with atorvastatin and that this would be associated with intraislet vasculogenesis. Pregnant Wistar rats were gavaged with 20 or 40 mg/kg atorvastatin for 21 days commencing on gestation day 15. Atorvastatin was detected in the circulation of the offspring. On postnatal day 4, the pups were given either a control or STZ (70 mg/kg ip) injection. beta-Cell mass had partially recovered by postnatal day 44 following STZ treatment, and atorvastatin (20 mg/kg) significantly increased beta-cell mass in both STZ-treated and control animals. An increase in the numbers of small islets at postnatal day 44 was seen in STZ-treated animals following atorvastatin, suggestive of neogenesis, and glucose tolerance was improved. Treatment with atorvastatin caused an increase in the numbers of intraislet endothelial cells at postnatal day 14 and the percentage of endothelial cells undergoing DNA synthesis, suggesting that angiogenesis had preceded the increase in beta-cell mass. The results indicate that functional beta-cell mass was expanded with atorvastatin in both control and STZ-treated neonatal rats and suggests a novel effect of a statin in promoting islet plasticity.

Pdx-1 regulation of the INGAP promoter involves sequestration of NeuroD into a non-DNA-binding complex

OBJECTIVE

Islet neogenesis-associated protein (INGAP) can enhance beta-cell mass to offset progression of diabetes. Identifying how transcription factors regulate INGAP gene expression could reveal key checkpoints governing islet neogenesis.

METHODS

Protein complex interactions at the INGAP promoter were detected using a beta-galactosidase reporter, these protein-DNA complexes being validated in competitive electrophoresis mobility shift assays. The relevance of the revealed promoter interactions was confirmed in small interfering RNA (siRNA) gene knockdown studies.

RESULTS

Pdx-1 negatively regulates stimulation of the INGAP promoter by Pan-1/NeuroD. Independently, Pdx-1, Pan-1, and NeuroD bind to the INGAP promoter as revealed by electrophoresis mobility shift assay studies. In combination, Pdx-1 selectively displaces NeuroD from a DNA-binding complex with Pan-1 to form a non-DNA-binding unit. The importance of this interaction is shown in HIT cells that have a forced reduction of Pdx-1 expression. In siRNA/Pdx-1-depleted HIT cells, the interaction of Pan-1/NeuroD with the INGAP promoter is increased 6-fold. Furthermore, endogenous INGAP expression is detected in Pdx-1-depleted cells.

CONCLUSIONS

These data reveal a dynamic interaction between Pdx-1, NeuroD, and Pan-1 for the regulation of INGAP promoter activity. Modulating molecular regulators of DNA expression may be a consideration in diabetic therapies that translate exogenous stimuli into new endogenous beta-cell mass.

Gastrin, cholecystokinin and gastrointestinal tract functions in mammals

The aim of the present review is to synthesise and summarise our recent knowledge on the involvement of cholecystokinin (CCK) and gastrin peptides and their receptors in the control of digestive functions and more generally their role in the field of nutrition in mammals. First, we examined the release of these peptides from the gut, focusing on their molecular forms, the factors regulating their release and the signalling pathways mediating their effects. Second, general physiological effects of CCK and gastrin peptides are described with regard to their specific receptors and the role of CCK on vagal mucosal afferent nerve activities. Local effects of CCK and gastrin in the gut are also reported, including gut development, gastrointestinal motility and control of pancreatic functions through vagal afferent pathways, including NO. Third, some examples of the intervention of the CCK and gastrin peptides are exposed in diseases, taking into account intervention of the classical receptor subtypes (CCK1 and CCK2 receptors) and their heterodimerisation as well as CCK-C receptor subtype. Finally, applications and future challenges are suggested in the nutritional field (performances) and in therapy with regards to the molecular forms or in relation with the type of receptor as well as new techniques to be utilised in detection or in therapy of disease. In conclusion, the present review underlines recent developments in this field: CCK and gastrin peptides and their receptors are the key factor of nutritional aspects; a better understanding of the mechanisms involved may increase the efficiency of the nutritional functions and the treatment of abnormalities under pathological conditions.

Islet neogenesis-associated protein pentadecapeptide (INGAP-PP): mechanisms involved in its effect upon beta-cell mass and function

The effect of islet neogenesis-associated protein pentadecapeptide (INGAP-PP) administration to normal male hamsters upon serum glucose and triglyceride levels, beta-cell mass and function was studied. INGAP-PP (500 mug) or saline was injected twice daily during 10 days. Both groups showed comparable body weight, serum glucose and triglyceride levels. INGAP-PP treated animals had significantly higher HOMA-IR and HOMA-beta and their islets released more insulin in response to glucose; they had lower islet DNA content, significantly increased number of islets/unit area, beta-cell replication rate and mass, cells co-expressing Pdx-1/INGAP and islets in contact with ducts, and decreased beta-cell apoptosis rate. The percentage of cells expressing Pdx-1 alone or together with INGAP or insulin increased significantly in ducts. These animals also showed a significantly higher concentration of Pdx-1 and Ngn-3 mRNA and a lower number of INGAP-positive cells. In conclusion, INGAP-PP promoted a controlled and functionally active increase of beta-cell mass; our data demonstrate for the first time the mechanism responsible for such changes; that Ngn-3 would be involved in INGAP-PP-induced neogenesis; and the existence of a negative feedback loop with endogenous INGAP-producing cells. Accordingly, INGAP-PP could be used to induce these effects in people with or at risk of developing diabetes.

Type 1 diabetes mellitus: primary, secondary, and tertiary prevention

We have entered the era of clinical trials to prevent type 1 diabetes mellitus (T1DM). Before 1922, when insulin was first given to a patient with diabetes, a diagnosis of T1DM was considered a death sentence. Advances in treatment for subjects with diabetes are not yet sufficient to prevent the deleterious impact of diabetes on both day-to-day activities and the early morbidity and mortality still associated with the disease. We now understand a great deal about blood glucose regulation and potential health complications associated with long-term T1DM, but the mystery of why, or the pathogenesis of this devastating disease, remains elusive. Great strides toward unraveling this mystery have been made over the past several decades. Even without definitive answers, we are moving from the period of discovery and animal research to the era of clinical trials. In this review, we wish to convey the palpable excitement in the field. It is time to determine if we can safely change the course of T1DM.

Pancreatic adenocarcinoma patients with localised chronic severe pancreatitis show an increased number of single beta cells, without alterations in fractional insulin area

AIMS/HYPOTHESIS

Recent histological analysis of pancreases obtained from patients with long-standing type 1 diabetes identified chronic islet inflammation and limited evidence suggestive of beta cell replication. Studies in rodent models also suggest that beta cell replication can be induced by certain inflammatory cytokines and by gastrin. We therefore tested the hypothesis that beta cell replication is observed in non-autoimmune human pancreatic disorders in which localised inflammation or elevated gastrin levels are present.

METHODS

Resected operative pancreatic specimens were obtained from patients diagnosed with primary adenocarcinoma (with or without chronic severe pancreatitis) or gastrinoma. Additional pancreatic tissue was obtained from autopsy control patients. Immunohistochemistry was used to assess fractional insulin area, beta cell number and replication rate and differentiation factors relevant to beta cell development.

RESULTS

Fractional insulin area was similar among groups. Patients with pancreatic adenocarcinoma and localised chronic severe pancreatitis displayed significant increases in the number of single beta cells, as well as increased beta cell replication rate and levels of neurogenic differentiation 1 in islets. Patients with gastrinoma demonstrated significant increases in the number of single beta cells, but the beta cell replication rate and islet differentiation factor levels were similar to those in the control group.

CONCLUSIONS/INTERPRETATION

These findings indicate that chronic severe pancreatic inflammation can be associated with significant effects on beta cell number or replication rate, depending on the distribution of the cells. This information may prove useful for attempts seeking to design therapies aimed at inducing beta cell replication as a means of reversing diabetes.

Islet-derived progenitors as a source of in vitro islet regeneration

Current therapies do not prevent the complications of diabetes. Furthermore, these therapies do not address the underlying pathology; the lack of functional beta-cell mass that occurs in both types 1 and 2 diabetes. While pancreas and islet transplantation do serve to increase beta-cell mass, a lack of donor organs limits the therapeutic potential of these treatments. As such, expansion of beta-cell mass from endogenous sources, either in vivo or in vitro, represents an area of increasing interest. One potential source of islet progenitors is the islet proper, via the dedifferentiation, proliferation, and redifferentiation of facultative progenitors residing within the islet. We have developed a tissue culture platform whereby isolated adult human pancreatic islets form proliferative duct-like structures expressing ductal and progenitor markers. Short-term treatment with a peptide fragment of islet neogenesis-associated protein (INGAP) induces these structures to reform islet-like structures that resemble freshly isolated islets with respect to the frequency and distribution of the four endocrine cell types, islet gene expression and hormone production, insulin content, and glucose-responsive insulin secretion. As such, the plasticity of adult human islets has significant implications for islet regeneration.

Beta-cell replacement for insulin-dependent diabetes mellitus

Beta-cell replacement is considered the optimal treatment for type 1 diabetes, however, it is hindered by a shortage of human organ donors. Given the difficulty of expanding adult beta cells in vitro, stem/progenitor cells, which can be expanded in tissue culture and induced to differentiate into multiple cell types, represent an attractive source for generation of cells with beta-cell properties. In the absence of well-characterized human pancreas progenitor cells, investigators are exploring the use of embryonic stem cells and stem/progenitor cells from other tissues. Once abundant surrogate beta cells are available, the challenge will be to protect them from recurring autoimmunity.

The Reg family member INGAP is a marker of endocrine patterning in the embryonic pancreas

OBJECTIVE

Adult islet neogenesis is believed to recapitulate elements of pancreatic endocrine development. Identifying factors that regulate islet neogenesis-associated protein (INGAP) gene activity could provide links to pancreas development.

METHODS

Predicted transcriptional regulators of INGAP were screened in an INGAP-promoter-reporter assay. Based upon their temporal expression, the occurrence of INGAP-positive cells during pancreas embryonic development were studied.

RESULTS

Pancreatic transcription factors, PDX-1, Ngn3, NeuroD, and Isl-1, activated the INGAP promoter, but PAX4, PAX6, and Nkx2.2 did not. The INGAP-positive cells were present in the developing pancreatic bud of the mouse embryo. Emerging clusters of unorganized endocrine cells were INGAP positive. These cells coexpressed insulin or somatostatin, but glucagon-expressing cells remained distinct. The INGAP-positive cells were also detected in the maturing neonatal endocrine cells organized into islets. In direct contrast to the embryo, glucagon localized with most INGAP-positive cells in the postnatal endocrine cells. The INGAP-positive cells juxtaposed pancreatic duct cells. A subset of 5-bromo-2'-deoxyuridine-positive/INGAP-positive cells was detected in the neonatal pancreas.

CONCLUSIONS

These data implicate INGAP and/or Reg family proteins in endocrine cell patterning during embryonic development and suggest that INGAP immunoreactivity is a key marker associated with early endocrine cells.

Epidermal growth factor increases insulin secretion and lowers blood glucose in diabetic mice

Epidermal growth factor (EGF) is synthesized in the pancreas and diabetic animals have low levels of EGF. However, the role of EGF in regulating the major function of the pancreas, insulin secretion, has not been studied. Here, we show that EGF rapidly increased insulin secretion in mouse pancreatic islets, as well as in a pancreatic β-cell line. These events were dependent on a Ca²⁺ influx and phospholipase D (PLD) activity, particularly PLD2, as determined using pharmacological blockers and molecular manipulations such as over-expression and siRNA of PLD isozymes. In addition, EGF also increased plasma insulin levels and mediated glucose lowering in normal and diabetic mice. Here, for the first time, we provide evidence that EGF is a novel secretagogue that regulates plasma glucose levels and a candidate for the development of therapeutics for diabetes.

Pancreatic islet immunoreactivity to the Reg protein INGAP

The Reg-related protein family member INGAP (islet neogenesis-associated protein) is a pleiotropic factor enhancing islet neogenesis, neurite growth, beta-cell protection, and beta-cell function. Using an antibody to the N-termini of INGAP, we have identified that immunoreactivity to INGAP localized to the pancreatic endocrine cells in mouse. INGAP- and insulin-immunoreactive cells are mutually exclusive, with INGAP-immunoreactive cells being preserved after streptozotocin-mediated destruction of beta-cells. Glucagon- and INGAP-immunoreactive cells colocalize, although respective antigen expression occurs in different intracellular locations. These data suggest that INGAP-immunoreactive cells include alpha-cells; however, detection of single INGAP-immunoreactive/glucagon-negative cells indicates that this may not be exclusive. In addition to mouse, detection of islet endocrine cells that were INGAP immunoreactive/glucagon immunoreactive/insulin negative was also observed in islets from human, monkey, and rat. These findings reveal that INGAP and/or related group 3 Reg proteins have a conserved expression in the pancreatic islet.