INGAP peptide improves nerve function and enhances regeneration in streptozotocin-induced diabetic C57BL/6 mice

Novel treatment modalities for painful diabetic neuropathy

BACKGROUND AND AIMS

Painful diabetic neuropathy significantly affects the quality of life in people with diabetic peripheral neuropathy (DPN). Existing pharmacological agents have limited efficacy and development of tolerance is a limitation.

METHODS

The present review focuses on novel pharmacological (systemic and topical) and non-pharmacological modalities for the alleviation of pain in people with DPN. We identified English language articles concerning studies with novel agents (animal or human) targeting symptomatic relief of painful diabetic neuropathy.

RESULTS

Though the pathophysiology of pain in DPN is complex, a better understanding of pain pathways (peripheral and central) have helped to identify potential targets for therapeutic success. Studies of pharmacological agents acting on various aspects of pain pathways including μ-opioid receptor agonist- norepinephrine reuptake inhibitor (MONRI), cannabinoid receptor, dual serotonin-nor-adrenergic (SNRI)-and triple dopamine reuptake inhibitor (SNDRI), purinergic receptors and sodium channel v1.7 blockers have undergone trials in humans and shown to improve pain symptoms and quality of life in people with DPN. A few other investigational agents targeting acetylcholine receptor, vanilloid channel, chemokine signaling, micro-RNA or mesenchymal stem cell based therapies (animal studies) have demonstrated promise in alleviation of pain. Topical agents like high-dose lidocaine, capsaicin, clonidine, amitriptyline and ketamine may benefit refractory neuropathic pain.

CONCLUSIONS

Novel MONRI, SNRI and cannabinoid receptor agonists have shown some promise for neuropathic pain relief in human trials, but await regulatory approvals. However, most of the novel pharmacological agents (systemic or topical) require appropriately powered placebo-controlled studies for clinical usage in painful diabetic neuropathy.

Effects of Reg3 Delta Bioactive Peptide on Blood Glucose Levels and Pancreatic Gene Expression in an Alloxan-Induced Mouse Model of Diabetes

OBJECTIVE

The endocrine regeneration of the pancreas holds great potential for stable diabetes therapy. The Regeneration (Reg) family of proteins has been associated with pancreas regeneration. Hence, the Reg3 delta bioactive peptide from a mouse was evaluated to see whether it can reverse hyperglycemia in a mouse model of diabetes with any effects on pancreatic gene expression.

METHODS

In this study, we administrated the synthetic Reg3 delta bioactive peptide to healthy mice and to alloxan-induced mouse models of diabetes for 30 days, with weekly measurements of body weight and blood glucose levels. After 1 month, pancreatic gene profiling of these mice was performed for the Ngn-3, Pdx-1, MapK8, IGF-1, IGF2bp2, Reg3 beta and Reg3 delta genes.

RESULTS

The glycemic levels in mice with diabetes were decreased significantly, restored almost to normal. Furthermore, the gene expression levels measured by quantitative polymerase chain reaction (qPCR) showed that messenger RNA (mRNA) levels of 2 important transcription factors (Ngn-3 and Pdx-1) were increased during the Reg3 delta peptide treatment.

CONCLUSIONS

This study shows that Reg3 delta has the potential to reverse hyperglycemia by modulating gene expression in pancreatic endocrine precursor markers Pdx-1 and Ngn-3, which require further investigation at the protein and immunohistology levels.

Mouse models of diabetic neuropathy

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes and is associated with significant morbidity and mortality. DPN is characterized by progressive, distal-to-proximal degeneration of peripheral nerves that leads to pain, weakness, and eventual loss of sensation. The mechanisms underlying DPN pathogenesis are uncertain, and other than tight glycemic control in type 1 patients, there is no effective treatment. Mouse models of type 1 (T1DM) and type 2 diabetes (T2DM) are critical to improving our understanding of DPN pathophysiology and developing novel treatment strategies. In this review, we discuss the most widely used T1DM and T2DM mouse models for DPN research, with emphasis on the main neurologic phenotype of each model. We also discuss important considerations for selecting appropriate models for T1DM and T2DM DPN studies and describe the promise of novel emerging diabetic mouse models for DPN research. The development, characterization, and comprehensive neurologic phenotyping of clinically relevant mouse models for T1DM and T2DM will provide valuable resources for future studies examining DPN pathogenesis and novel therapeutic strategies.

Islet neogenesis-associated protein-related pentadecapeptide improves the function of allograft after islets transplantation

OBJECTIVE

To investigate the protective effects of a pentadecapeptide of islet neogenesis-associated protein (INGAP-PP) on transplanted islets function.

METHODS

Islets were cultured in RPMI 1640 with or without INGAP-PP (10 μg/mL). After 24 h, the viability of the islets and glucose-stimulated insulin secretion (GSIS) were measured. The expression of genes B cell lymphoma/lewkmia2 (Bcl2) and protein kinase B (Akt) were detected by RT-PCR assay. Healthy rats transplanted with islets under the renal capsule were injected with INGAP-PP or saline in in the abdominal cavity. One week later, the expression of insulin nestin pancreatic (nestin) and duodenal homeobox 1 (Pdx1) and proliferating cell nuclear antigen (PCNA) in the transplanted islets were observed by immunohistochemistry. After that they were transplanted to the renal capsule of diabetic rats.

RESULTS

1. The amount of insulin released was increased in co-cultured group in concentration of 16.7 mmol/L glucose, which was (185.00±20.01 μU/mL) vs. (58.67±17.03 μU/mL). Gene expression of Bcl2 (0.61±0.22 vs. 0.50±0.21) and Akt (1.12±0.19 vs. 0.94±0.16) in the co-cultured group were increased compared with that of the control group. Islets viability in the co-cultured group (683.9±7.08) was higher than that of control group (547.9±8.02). The stimulating index (SI) of the co-cultured group was also higher than that of the control group. 2. The group of islets under the renal capsule which were co-cultured and injected with INGAP-PP had the more nestin expression in the islets.

CONCLUSIONS

The function of islet can be protected by the INGAP-PP, which will promote the viability, differentiation and regeneration of islet before transplantation. And it will be beneficial for the function of allograft after islets transplantation.

Diabetic neuropathy

Diabetic neuropathy (DN) is the most common and troublesome complication of diabetes mellitus, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care. The clinical assessment of diabetic peripheral neuropathy and its treatment options are multifactorial. Patients with DN should be screened for autonomic neuropathy, as there is a high degree of coexistence of the two complications. A review of the clinical assessment and treatment algorithms for diabetic neuropathy, painful neuropathy, and autonomic dysfunction is provided.

Identification of new altered genes in rat cochleae with noise-induced hearing loss

Because genes that are highly expressed in the cochlea after noise stress may have crucial regulatory roles in hearing, the identification of these genes may be useful for restoring normal auditory function. This study assessed altered gene expression at 1h following the cessation of noise exposure by using microarrays and real-time polymerase chain reaction (qPCR) in rats. In addition, the auditory threshold shifts and morphological changes of hair cells were observed. This study indicated that applied noise induced outer hair cell loss and a 40-50 dB hearing loss. Totally 239 altered genes were involved in the immune system process, response to stress, or response to stimulus. The expression of five up-regulated genes (Reg3b, Lcn2, Serpina3n, Nob1 and Hamp) was confirmed by qPCR. Future experiments will focus on several of these new candidate genes and may provide insight into the underlying auditory pathophysiology.

Short-term effects of INGAP and Reg family peptides on the appearance of small β-cells clusters in non-diabetic mice

The Reg3 peptides INGAP-PP and human Reg3α/β (HIP) have been hypothesized to stimulate β-cell neogenesis in the pancreas. Administration of INGAP-PP has been shown to cause an increase in β-cell mass in multiple animal models, reverse streptozotocin (STZ) induced diabetes in mice and reduces HbA1c levels in type 2 diabetic humans. In this study, we have examined the ability of the INGAP-PP and HIP peptides to induce β-cell formation in vivo in normal mice through short-term administration of the peptides. We assessed the peptides ability to induce an increase in extra-islet insulin-positive cell clusters by looking at β-cell number by point counting morphometry on pancreata that had been randomized using the smooth fractionator principle in non-diabetic NMRI mice after short-term injections of the peptides (5 d). Five day continuous BrdU labeling was used to determine if the new β-cells were derived from replicating β-cells. Real time quantitative RT-PCR and immuno-histochemistry was used to analyze changes in pancreatic transcription factor expression. A 1.5- to 2-fold increase in the volume of small extra-islet insulin-positive clusters post 5 d treatment with INGAP-PP and HIP as compared with mice treated with a non-peptide control or scrambled peptide (p<0.05) (n = 7) was found. Five day continuous BrdU infusion during the 5 d period showed little or no incorporation in islets or small insulin clusters. Five days of treatment with INGAP-PP or HIP, showed a tendency toward increased levels of pancreatic progenitor markers such as Ngn3, Nkx6.1, Sox9 and Ins. These are the first studies to compare and indicate that the human Reg3 α/β (HIP) peptide has similar bioactivity in vivo as INGAP by causing formation of small β-cell clusters in extra-islet pancreatic tissue after only 5 d of treatment. Upregulation of pancreatic transcription factors may be part of the mechanism of action.

Regenerating proteins and their expression, regulation and signaling

The regenerating (Reg) protein family comprises C-type lectin-like proteins discovered independently during pancreatitis and pancreatic islet regeneration. However, an increasing number of studies provide evidence of participation of Reg proteins in the proliferation and differentiation of diverse cell types. Moreover, Reg family members are associated with various pathologies, including diabetes and forms of gastrointestinal cancer. These findings have led to the emergence of key roles for Reg proteins as anti-inflammatory, antiapoptotic and mitogenic agents in multiple physiologic and disease contexts. Yet, there are significant gaps in our knowledge regarding the regulation of expression of different Reg genes. In addition, the pathways relaying Reg-triggered signals, their targets and potential cross-talk with other cascades are still largely unknown. In this review, the expression patterns of different Reg members in the pancreas and extrapancreatic tissues are described. Moreover, factors known to modulate Reg levels in different cell types are discussed. Several signaling pathways, which have been implicated in conferring the effects of Reg ligands to date, are also delineated. Further efforts are necessary for elucidating the biological processes underlying the action of Reg proteins and their involvement in various maladies. Better understanding of the function of Reg genes and proteins will be beneficial in the design and development of therapies utilizing or targeting this protein group.

Update on the management of diabetic polyneuropathies

The prevalence of diabetic polyneuropathy (DPN) can approach 50% in subjects with longer-duration diabetes. The most common neuropathies are generalized symmetrical chronic sensorimotor polyneuropathy and autonomic neuropathy. It is important to recognize that 50% of subjects with DPN may have no symptoms and only careful clinical examination may reveal the diagnosis. DPN, especially painful diabetic peripheral neuropathy, is associated with poor quality of life. Although there is a better understanding of the pathophysiology of DPN and the mechanisms of pain, treatment remains challenging and is limited by variable efficacy and side effects of therapies. Intensification of glycemic control remains the cornerstone for the prevention or delay of DPN but optimization of other traditional cardiovascular risk factors may also be of benefit. The management of DPN relies on its early recognition and needs to be individually based on comorbidities and tolerability to medications. To date, most pharmacological strategies focus upon symptom control. In the management of pain, tricyclic antidepressants, selective serotonin noradrenaline reuptake inhibitors, and anticonvulsants alone or in combination are current first-line therapies followed by use of opiates. Topical agents may offer symptomatic relief in some patients. Disease-modifying agents are still in development and to date, antioxidant α-lipoic acid has shown the most promising effect. Further development and testing of therapies based upon improved understanding of the complex pathophysiology of this common and disabling complication is urgently required.

Emerging drugs for diabetic neuropathy

IMPORTANCE OF THE FIELD

Diabetic neuropathy (DN) is a very common and disabling diabetes-related complication. DN is associated with significant morbidity and mortality. Diabetic peripheral neuropathy (DPN) can be painful in the earlier stages of the disease before becoming painless. Most of the currently available therapies are symptomatic (focusing on pain relief) rather than disease-modifying. With the exception of good glycemic control, there is currently no effective treatment to slow the progression of or reverse DPN.

AREAS COVERED IN THIS REVIEW

In this article, we review the epidemiology, pathogenesis, currently available and future treatments for DPN, and the potential development issues/challenges related to such new therapies. Literature search was performed using PubMed, Medline and Pharmaprojects from 1950 onwards. Search terms include a combination of terms such as diabetic neuropathy, pathogenesis, pathophysiology, mechanisms, treatment, therapy, oxidative/nitrosative stress, anti-oxidants, serotonin, nitrotyrosine, protein kinase C, aldose reductase, sodium channels, taurine, lipoic acid and poly (ADP-ribose) polymerase.

WHAT THE READER WILL GAIN

The reader will gain an overview of the epidemiology, clinical features and risk factors of DN. In addition, the reader will have a better understanding of the mechanisms that underpin the development of DPN and their relationships to the current and future therapies. The reader will also develop an insight into the limitations of the current approach to DPN treatment and the potential avenues for future research.

TAKE HOME MESSAGE

DN is a very common and disabling complication that currently has no effective treatments other than diabetes control. The pathogenesis of DPN is complex and multi-factorial. Several disease-modifying and symptomatic treatments are currently under development. Oxidative and nitrosative stress have been identified as key pathogenic factors in the development of DPN and new treatments target these pathways and/or their downstream consequences. Gene therapy and growth factors have also emerged as potential new therapies that target particular cellular compartments as opposed to being delivered systemically. The recognition of the difficulty in reversing established DN has focused efforts on slowing its progression.

Islet neogenesis-associated protein-related pentadecapeptide enhances the differentiation of islet-like clusters from human pancreatic duct cells

The differentiation of pancreatic ductal epithelial cells into beta-cells has been considered as an alternative method for increasing the number of islets for transplantation. Critical factors have been introduced into the in vitro differentiation protocol for pancreatic duct cells in order to enhance the production of beta-cells. Islet neogenesis-associated protein (INGAP) is an initiator of islet neogenesis and the peptide sequence 104-118 of INGAP has been shown to stimulate an increase in beta-cell mass in animals and also found in human pathological states involving islet neogenesis. To establish a novel method for the differentiation of beta-cells from human pancreatic duct cells with INGAP-related pentadecapeptide (INGAP-PP), the pancreatic duct cells were isolated, purified and expanded in vitro and differentiated using a four-step protocol that included nicotinamide, exendin-4, transforming growth factor beta(1) and INGAP-PP/Scrambled peptide (Scrambled-P). The production of islet-like clusters (ILCs) in the INGAP-PP group was significantly higher than that in the Scrambled-P control group after differentiation from an equal number of duct cells. The duct cells showed positive staining and expression for cytokeratin 19, pancreatic duodenal homeobox-1, nestin, and were negative for insulin and glucagon, as detected by both immunofluorescence and RT-PCR. Following differentiation the cells became insulin and glucagon positive. In addition, the ILCs from the INGAP-PP group secreted higher levels of insulin and C-peptide than the Scrambled-P group under a high glucose challenge. We conclude that INGAP peptide enhances the in vitro differentiation of pancreatic duct cells into islet-like clusters.

Increased tau phosphorylation and cleavage in mouse models of type 1 and type 2 diabetes

As the population of the United States ages, the incidence of age-related neurodegenerative and systemic diseases including Alzheimer's disease (AD) and diabetes is increasing rapidly. Multiple studies report that patients with diabetes have a 50-75% increased risk of developing AD compared with age- and gender-matched patients without diabetes. Abnormally phosphorylated tau is a major building block of neurofibrillary tangles, a classic neuropathological characteristic of AD. In addition, proteolytic tau cleavage promotes AD progression due to cleaved tau serving as a nucleation center for the pathological assembly of tau filaments. The current study examines tau modification in type 1 (streptozotocin-injected) and type 2 (db/db) mouse models of diabetes. Tau phosphorylation is increased in the cortex and hippocampus of db/db mice compared with db+ control mouse brain. Interestingly, there is an age-dependent increase in tau cleavage that is not observed in age-matched control db+ animals. Streptozotocin injection also increased tau phosphorylation; however, the increase was less significant compared with the type 2 mouse model, and more importantly, no tau cleavage was detected. Our results suggest tau modification caused by insulin dysfunction and hyperglycemia may contribute to the increased incidence of AD in diabetes. We hypothesize that type 1 and type 2 diabetes may contribute to AD through different mechanisms; in type 2 diabetes, hyperglycemia-mediated tau cleavage may be the key feature, whereas insulin deficiency may be the major contributing factor in type 1 diabetes.

Deletion of the mouse RegIIIbeta (Reg2) gene disrupts ciliary neurotrophic factor signaling and delays myelination of mouse cranial motor neurons

A large number of cytokines and growth factors support the development and subsequent maintenance of postnatal motor neurons. RegIIIbeta, also known as Reg2 in rat and HIP/PAP1 in humans, is a member of a family of growth factors found in many areas of the body and previously shown to play an important role in both the development and regeneration of subsets of motor neurons. It has been suggested that RegIIIbeta expressed by motor neurons is both an obligatory intermediate in the downstream signaling of the leukemia inhibitory factor/ciliary neurotrophic factor (CNTF) family of cytokines, maintaining the integrity of motor neurons during development, as well as a powerful influence on Schwann cell growth during regeneration of the peripheral nerve. Here we report that in mice with a deletion of the RegIIIbeta gene, motor neuron survival was unaffected up to 28 weeks after birth. However, there was no CNTF-mediated rescue of neonatal facial motor neurons after axotomy in KO animals when compared with wild-type. In mice, RegIIIbeta positive motor neurons are concentrated in cranial motor nuclei that are involved in the patterning of swallowing and suckling. We found that suckling was impaired in RegIIIbeta KO mice and correlated this with a significant delay in myelination of the hypoglossal nerve. In summary, we propose that RegIIIbeta has an important role to play in the developmental fine-tuning of neonatal motor behaviors mediating the response to peripherally derived cytokines and growth factors and regulating the myelination of motor axons.

Criteria for creating and assessing mouse models of diabetic neuropathy

Diabetic neuropathy (DN) is a serious and debilitating complication of both type 1 and type 2 diabetes. Despite intense research efforts into multiple aspects of this complication, including both vascular and neuronal metabolic derangements, the only treatment remains maintenance of euglycemia. Basic research into the mechanisms responsible for DN relies on using the most appropriate animal model. The advent of genetic manipulation has moved mouse models of human disease to the forefront. The ability to insert or delete genes affected in human patients offers unique insight into disease processes; however, mice are still not humans and difficulties remain in interpreting data derived from these animals. A number of studies have investigated and described DN in mice but it is difficult to compare these studies with each other or with human DN due to experimental differences including background strain, type of diabetes, method of induction and duration of diabetes, animal age and gender. This review describes currently used DN animal models. We followed a standardized diabetes induction protocol and designed and implemented a set of phenotyping parameters to classify the development and severity of DN. By applying standard protocols, we hope to facilitate the comparison and characterization of DN across different background strains in the hope of discovering the most human like model in which to test potential therapies.

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.

Mouse models of diabetic neuropathy

Diabetic neuropathy (DN) is a debilitating complication of type 1 and type 2 diabetes. Rodent models of DN do not fully replicate the pathology observed in human patients. We examined DN in streptozotocin (STZ)-induced [B6] and spontaneous type 1 diabetes [B6Ins2(Akita)] and spontaneous type 2 diabetes [B6-db/db, BKS-db/db]. Despite persistent hyperglycemia, the STZ-treated B6 and B6Ins2(Akita) mice were resistant to the development of DN. In contrast, DN developed in both type 2 diabetes models: the B6-db/db and BKS-db/db mice. The persistence of hyperglycemia and development of DN in the B6-db/db mice required an increased fat diet while the BKS-db/db mice developed severe DN and remained hyperglycemic on standard mouse chow. Our data support the hypothesis that genetic background and diet influence the development of DN and should be considered when developing new models of DN.

Clinical Manifestations and Current Treatment options for Diabetic Neuropathies

OBJECTIVE

To review the clinical manifestations and current treatment options for diabetic neuropathies, one of the most common complications of diabetes mellitus.

METHODS

We performed a MEDLINE search of the English-language literature using a combination of words (diabetic neuropathy, diabetic autonomic neuropathy, diagnosis and treatment) to identify original studies, consensus statements, and reviews on diabetic neuropathies published in the past 25 years. Emphasis was placed on clinical manifestations of distal polyneuropathy and its treatment, especially new therapies.

RESULTS

Distal symmetric polyneuropathy, the most common form of diabetic neuropathy, usually involves small and large nerve fibers. Small-nerve fiber neuropathy often presents with pain and loss of intraepidermal nerve fibers, but without objective signs or electrophysiologic evidence of nerve damage. This type of neuropathy is a component of impaired glucose tolerance and the metabolic syndrome. The greatest risk from small-fiber neuropathy is foot ulceration and subsequent gangrene and amputation. Large-nerve fiber neuropathy produces numbness, ataxia, and incoordination, thus impairing activities of daily living and causing falls and fractures. Successfully treating diabetic neuropathy requires addressing the underlying pathogenic mechanisms, treating symptoms to improve quality of life, and preventing progression and complications of diabetes mellitus. Two new drugs, duloxetine hydrochloride and pregabalin, have recently been approved for treatment of neuropathic pain associated with diabetes mellitus.

CONCLUSION

Symptomatic therapy has become available and newer and better treatment modalities, based on etiologic factors, are being explored with potential for clinically significant reduction of morbidity and mortality. Preventive strategies and patient and physician education still remain key factors in reducing complication rates and mortality.

Intramuscular injection of islet neogenesis-associated protein peptide stimulates pancreatic islet neogenesis in healthy dogs

OBJECTIVES

Diabetes is a serious health problem. It has been proposed that islet neogenesis from pancreatic progenitor cells may restore insulin secretion in diabetic mammals. Islet neogenesis- associated protein (INGAP) stimulates islet neogenesis; therefore, we hypothesized that it would stimulate islet neogenesis in dogs.

METHODS

Forty nondiabetic beagle dogs were randomly divided into 4 groups. Group 1 received daily intramuscular injections of vehicle, whereas the other 3 groups received daily INGAP injections of 0.5, 1.5, or 10 mg/kg. After 30 days, pancreatic tissues were collected, and RNA and histological sections were analyzed.

RESULTS

In dogs treated with 1.5 mg/kg INGAP, there was a significant (P < 0.001) increase in the percentage of insulin-positive cells (P < 0.001) and insulin gene expression. There was a trend to increased insulin-positive cells and gene expression with treatments of 0.5 and 10 mg/kg peptide. Protein gene product 9.5-positive cells were increased with treatment.

CONCLUSIONS

These results indicate that INGAP stimulates cells in the pancreatic duct epithelium of healthy dogs (putative islet progenitor cells) to develop along a neuroendocrine pathway and form new islets in response to INGAP peptide. The INGAP might be an effective therapy for diabetes.

Reg2 inactivation increases sensitivity to Fas hepatotoxicity and delays liver regeneration post-hepatectomy in mice

Reg2/RegIIIbeta is the murine homologue of the human secreted HIP/PAP C-type lectin. HIP/PAP transgenic mice were protected against acetaminophen-induced acute liver failure and were stimulated to regenerate post-hepatectomy. To assess the role of Reg2, we used Reg2-/- mice in a model of fulminant hepatitis induced by Fas and in the post-hepatectomy regeneration. Within 4 hours of J0-2 treatment (0.5 microg/g), only 50% of the Reg2-/- mice were alive but with an increased sensitivity to Fas-induced oxidative stress and a decreased level of Bcl-xL. In contrast, HIP/PAP transgenic mice were resistant to Fas, with HIP/PAP serving as a sulfhydryl buffer to slow down decreases in glutathione and Bcl-xL. In Reg2-/- mice, liver regeneration was markedly impaired, with 29% mortality and delay of the S-phase and the activation of ERK1/2 and AKT. Activation of STAT3 began on time at 3 hours but persisted strongly up to 72 hours despite significant accumulation of SOCS3. Thus, Reg2 deficiency induced exaggerated IL-6/STAT-3 activation and mito-inhibition. Because the Reg2 gene was activated between 6 and 24 hours after hepatectomy in wild-type mice, Reg2 could mediate the TNF-alpha/IL-6 priming signaling by exerting a negative feed-back on STAT3/IL-6 activation to allow the hepatocytes to progress through the cell cycle. In conclusion, Reg2 deficiency enhanced liver sensitivity to Fas-induced oxidative stress and delayed liver regeneration with persistent TNF-alpha/IL6/STAT3 signaling. In contrast, overexpression of human HIP/PAP promoted liver resistance to Fas and accelerated liver regeneration with early activation/deactivation of STAT3. Reg2/HIP/PAP is therefore a critical mitogenic and antiapoptotic factor for the liver.

Pancreatic islet transplantation for treating diabetes

Pancreatic islet transplantation is one of the options for treating diabetes and has been shown to improve the quality of life of severe diabetic patients. Since the Edmonton protocol was announced, islet transplantation have advanced considerably, including islet after kidney transplantation, utilisation of non-heart-beating donors, single-donor islet transplantation and living-donor islet transplantation. These advances were based on revised immunosuppression protocols, improved pancreas procurement and islet isolation methods, and enhanced islet engraftment. Further improvements are necessary to make islet transplantation a routine clinical treatment. To synergise efforts towards a cure for type 1 diabetes, a Diabetes Research Institute (DRI) Federation is currently being established to include leading diabetes research centres worldwide, including DRIs in Miami, Edmonton and Kyoto among others.

Neurite outgrowth in dorsal root ganglia induced by islet neogenesis-associated protein peptide involves protein kinase A activation

Islet neogenesis-associated protein (INGAP) peptide is a candidate therapeutic for diabetes and corrects sensory dysfunction in experimental diabetes in mice. In this study, we investigated the mechanism of action by which INGAP peptide promotes neurite outgrowth in sensory neurons of the dorsal root ganglia. Treatment of dorsal root ganglia primary dispersed cultures with INGAP peptide led to the displacement of fluorescently labeled forskolin from adenylate cyclase, the cyclic AMP-generating enzyme that has been implicated in neuritogenesis. The addition of forskolin or dibutyryl cyclic AMP enhanced the effects of INGAP peptide on neurite outgrowth in dorsal root ganglia explant cultures. Furthermore, pharmacological inhibition of adenylate cyclase with SQ22,536 or of protein kinase A with H89 or KT5720 significantly reduced the neurite-promoting effects of INGAP peptide. These results suggest that INGAP peptide-induced neurite outgrowth in the dorsal root ganglia partially involves cyclic AMP-dependent activation of protein kinase A.

Dual-action peptides: a new strategy in the treatment of diabetes-associated neuropathy

Peripheral neuropathy is one of the most common and debilitating complications of type 1 and type 2 diabetes mellitus. Recent studies have shown that several small, non-neural peptides possess neurotrophic activity and exert beneficial effects on nervous system function in experimental and clinical diabetes. Two of these, C-peptide and islet neogenesis-associated protein peptide, are derived from pancreatic proteins and use related signal transduction mechanisms. Derivatives of erythropoietin possess similar properties in the nervous system. As a group, these peptides are of increasing interest as leads to potential new approaches in the treatment of diabetes-associated neuropathies and other neurodegenerative conditions. This review addresses the recent advances made with these peptides in the context of diabetic neuropathy, and highlights similarities and differences in their mechanisms of action from the perspective of combination therapy.

HIP/PAP accelerates liver regeneration and protects against acetaminophen injury in mice

Human hepatocarcinoma-intestine-pancreas/pancreatic-associated protein HIP/PAP is a secreted C-type lectin belonging to group VII, according to Drickamer's classification. HIP/PAP is overexpressed in liver carcinoma; however, its functional role remains unclear. In this study, we demonstrate that HIP/PAP is a paracrine hepatic growth factor promoting both proliferation and viability of liver cells in vivo. First, a low number of implanted hepatocytes deriving from HIP/PAP-transgenic mice (<1:1,000) was sufficient to stimulate overall recipient severe combined immunodeficiency liver regeneration after partial hepatectomy. After a single injection of HIP/PAP protein, the percentages of bromodeoxyuridine-positive nuclei and mitosis were statistically higher than after saline injection, indicating that HIP/PAP acts as a paracrine mitogenic growth factor for the liver. Comparison of the early events posthepatectomy in control and transgenic mice indicated that HIP/PAP accelerates the accumulation/degradation of nuclear phospho-signal transducer activator transcription factor 3 and tumor necrosis factor alpha level, thus reflecting that HIP/PAP accelerates liver regeneration. Second, we showed that 80% of the HIP/PAP-transgenic mice versus 25% of the control mice were protected against lethal acetaminophen-induced fulminate hepatitis. A single injection of recombinant HIP/PAP induced a similar cytoprotective effect, demonstrating the antiapoptotic effect of HIP/PAP. Comparison of Cu/Zn superoxide dismutase activity and glutathione reductase-like effects in control and transgenic liver mice indicated that HIP/PAP exerts an antioxidant activity and prevents reactive oxygen species-induced mitochondrial damage by acetaminophen overdose. In conclusion, the present data offer new insights into the biological functions of C-type lectins. In addition, HIP/PAP is a promising candidate for the prevention and treatment of liver failure.

Tolerance induction and endogenous regeneration of pancreatic beta-cells in established autoimmune diabetes

Studies aimed at the understanding of the multifactorial development of autoimmune diabetes have made substantial contributions toward elucidating the molecular mechanisms that open the road to an effective prevention of defective immune responses. Immunomodulatory regimens capable of inducing tolerance are shown to be effective even in the reversal of established autoimmune diabetes in animal models. Experimental trials including the reeducation of autoreactive T cells, depletion of macrophages, dendritic cells, and T cells, as well as the use of monoclonal antibodies, have yielded encouraging results, but have not yet been translated into beneficial clinical outcomes. In addition, we are now seeing an emergence of promising new directions aimed at the induction of islet regeneration by endogenous factors, suggesting that the repair of pancreatic tissue is possible without the need for an engraftment of donor tissue. These recent waves of technological progress have injected new hope for a combined therapy to offer diabetic patients long-term benefits of insulin independence. This article reviews the latest findings on diabetic pathogenesis and discusses promising avenues to tolerance induction and islet regeneration.