Gene therapy in diabetes

Diabetes Mellitus and Associated Vascular Disease: Pathogenesis, Complications, and Evolving Treatments

Diabetes mellitus is a metabolic disorder, characterized by elevated blood sugar levels (hyperglycemia) and insulin dysregulation. This disease is associated with morbidity and mortality, including significant potential vascular complications. High levels of hyperglycemia lead to not only elevated levels of reactive oxygen species but also advanced glycation end products, which are detrimental to the vascular endothelium and reduce protective compounds such as nitric oxide and prostacyclin. This damage contributes to the development of both macrovascular and microvascular complications. The present investigation explores the pathophysiological mechanisms of diabetic vascular complications and evaluates current management strategies, including lifestyle modifications, pharmacological treatments, and emerging therapies. The review underscores the importance of ongoing progress in diabetes management and patient education to lead to optimal patient-health outcomes and quality of life for individuals with diabetes mellitus.

Cell Therapies and Gene Therapy for Diabetes: Current Progress

The epidemic of diabetes continues to be an increasing problem, and there is a need for new therapeutic strategies. There are several promising drugs and molecules in synthetic medicinal chemistry that are developing for diabetes. In addition to this approach, extensive studies with gene and cell therapies are being conducted. Gene therapy is an existing approach in treating several diseases, such as cancer, autoimmune diseases, heart disease and diabetes. Several reports have also suggested that stem cells have the differentiation capability to functional pancreatic beta cell development in vitro and in vivo, with the utility to treat diabetes and prevent the progression of diabetes-related complications. In this current review, we have focused on the different types of cell therapies and vector-based gene therapy in treating or preventing diabetes.

Current approaches in CRISPR-Cas systems for diabetes

In the face of advancements in health care and a shift towards healthy lifestyle, diabetes mellitus (DM) still presents as a global health challenge. This chapter explores recent advancements in the areas of genetic and molecular underpinnings of DM, addressing the revolutionary potential of CRISPR-based genome editing technologies. We delve into the multifaceted relationship between genes and molecular pathways contributing to both type1 and type 2 diabetes. We highlight the importance of how improved genetic screening and the identification of susceptibility genes are aiding in early diagnosis and risk stratification. The spotlight then shifts to CRISPR-Cas9, a robust genome editing tool capable of various applications including correcting mutations in type 1 diabetes, enhancing insulin production in T2D, modulating genes associated with metabolism of glucose and insulin sensitivity. Delivery methods for CRISPR to targeted tissues and cells are explored, including viral and non-viral vectors, alongside the exciting possibilities offered by nanocarriers. We conclude by discussing the challenges and ethical considerations surrounding CRISPR-based therapies for DM. These include potential off-target effects, ensuring long-term efficacy and safety, and navigating the ethical implications of human genome modification. This chapter offers a comprehensive perspective on how genetic and molecular insights, coupled with the transformative power of CRISPR, are paving the way for potential cures and novel therapeutic approaches for DM.

Advancements in oral insulin: A century of research and the emergence of targeted nanoparticle strategies

With the growing prevalence of diabetes, there is an urgent demand for a user‐friendly treatment option that minimizes side effects related to the use of subcutaneous injections. Scientists have dedicated over a century to developing an oral dosage form of insulin that can be administrated orally. The oral route of administration is the most desirable route for regularly dosed drugs in terms of safety and patient compliance. However, oral delivery of insulin remains a formidable challenge due to its intrinsically limited ability to cross the intestinal epithelium membrane and susceptibility to enzymatic degradation. This article reviews oral insulin research over the past decade, with a particular focus on surface modifications of nanoparticles (NPs). Various strategies involving controlling surface charges, utilizing protective proteins, and targeting specific receptors with ligands have been explored. Notably, surface modifications of the NPs for targeting specific intestinal receptors have shown promise in enhancing insulin oral absorption and bioavailability. Advanced technologies such as oral microneedles and gene therapy have also been developed, but their safety requires further assessment. Despite encouraging preclinical results across numerous strategies, the current clinical evidence is less optimistic. In summary, the present findings highlight the substantial journey that still lies ahead before achieving successful oral delivery of insulin.

Practical Applications: This review provides a summary of recent progress in oral insulin delivery, particularly highlighting surface‐modified functional nanoparticles serving as an effective drug delivery system, which offers valuable information to the researchers. Due to the limited effectiveness of oral protein drugs caused by biological barriers, innovative technologies and drug delivery systems have been developed to overcome these obstacles and achieve therapeutic goals. This review concluded that surface modifications to nanoparticles can improve insulin stability and permeability, thereby enhancing oral bioavailability. It could assist researchers in developing more effective and patient‐friendly oral drug delivery systems.

Nanomedicine in the Treatment of Diabetes

Nanomedicine could improve the treatment of diabetes by exploiting various therapeutic mechanisms through the use of suitable nanoformulations. For example, glucose-sensitive nanoparticles can release insulin in response to high glucose levels, mimicking the physiological release of insulin. Oral nanoformulations for insulin uptake via the gut represent a long-sought alternative to subcutaneous injections, which cause pain, discomfort, and possible local infection. Nanoparticles containing oligonucleotides can be used in gene therapy and cell therapy to stimulate insulin production in β-cells or β-like cells and modulate the responses of T1DM-associated immune cells. In contrast, viral vectors do not induce immunogenicity. Finally, in diabetic wound healing, local delivery of nanoformulations containing regenerative molecules can stimulate tissue repair and thus provide a valuable tool to treat this diabetic complication. Here, we describe these different approaches to diabetes treatment with nanoformulations and their potential for clinical application.

Advances and challenges of the cell-based therapies among diabetic patients

Diabetes mellitus is a significant global public health challenge, with a rising prevalence and associated morbidity and mortality. Cell therapy has evolved over time and holds great potential in diabetes treatment. In the present review, we discussed the recent progresses in cell-based therapies for diabetes that provides an overview of islet and stem cell transplantation technologies used in clinical settings, highlighting their strengths and limitations. We also discussed immunomodulatory strategies employed in cell therapies. Therefore, this review highlights key progresses that pave the way to design transformative treatments to improve the life quality among diabetic patients.

Novel gene-based therapeutic approaches for the management of hepatic complications in diabetes: Reviewing recent advances

Diabetes mellitus is a chronic metabolic disorder marked by hyperglycemia and systemic complications, including hepatic dysfunction, significantly contributing to disease progression and morbidity. This article reviews recent advances in gene-based therapeutic strategies targeting hepatic complications in diabetes, offering a promising approach for precision medicine by addressing underlying molecular mechanisms. Traditional treatments for hepatic complications in diabetes often manage symptoms rather than molecular causes, showing limited efficacy. Gene-based therapies are poised to correct dysfunctional pathways and restore hepatic function. Fundamental gene therapy approaches include gene silencing via small interfering RNAs (siRNAs) to target hepatic glucose production, lipid metabolism, and inflammation. Viral vectors can restore insulin sensitivity and reduce oxidative stress in diabetic livers. Genome editing, especially CRISPR-Cas9, allows the precise modification of disease-associated genes, offering immense potential for hepatic complication treatment. Strategies using CRISPR-Cas9 to enhance insulin receptor expression and modulate aberrant lipid regulatory genes are explored. Safety challenges in gene-based therapies, such as off-target effects and immune responses, are discussed. Advances in nanoparticle-based delivery systems and targeted gene editing techniques offer solutions to enhance specificity and minimize adverse effects. In conclusion, gene-based therapeutic approaches are a transformative direction in managing hepatic complications in diabetes. Further research is needed to optimize efficacy, safety, and long-term outcomes. Nevertheless, these innovative strategies promise to improve the lives of individuals with diabetes by addressing hepatic dysfunction's genetic root causes.

Current Landscape of Various Techniques and Methods of Gene Therapy through CRISPR Cas9 along with its Pharmacological and Interventional Therapies in the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is frequently referred to as a "lifestyle illness". In 2000, India (31.7 million) had the greatest global prevalence of diabetes mellitus, followed by China (20.8 million), the United States (17.7 million), and other countries. In recent years, the treatment of gene therapy (T2DM) has attracted intensive interest.

OBJECTIVE

We aimed to critically review the literature on the various techniques and methods, which may be a possible novel approach through the gene therapy CRISPR Cas9 and some other gene editing techniques for T2DM. Interventional and pharmacological approaches for the treatment of T2DM were also included to identify novel therapies for its treatment.

METHOD

An extensive literature survey was done on databases like PubMed, Elsevier, Science Direct and Springer.

CONCLUSION

It can be concluded from the study that recent advancements in gene-editing technologies, such as CRISPR Cas9, have opened new avenues for the development of novel therapeutic approaches for T2DM. CRISPR Cas9 is a powerful tool that enables precise and targeted modifications of the genome.

Novel targets for potential therapeutic use in Diabetes mellitus

Future targets are a promising prospect to overcome the limitation of conventional and current approaches by providing secure and effective treatment without compromising patient compliance. Diabetes mellitus is a fast-growing problem that has been raised worldwide, from 4% to 6.4% (around 285 million people) in past 30 years. This number may increase to 430 million people in the coming years if there is no better treatment or cure is available. Ageing, obesity and sedentary lifestyle are the key reasons for the worsening of this disease. It always had been a vital challenge, to explore new treatment which could safely and effectively manage diabetes mellitus without compromising patient compliance. Researchers are regularly trying to find out the permanent treatment of this chronic and life threatening disease. In this journey, there are various treatments available in market to manage diabetes mellitus such as insulin, GLP-1 agonist, biguanides, sulphonyl ureas, glinides, thiazolidinediones targeting the receptors which are discovered decade before. PPAR, GIP, FFA1, melatonin are the recent targets that already in the focus for developing new therapies in the treatment of diabetes. Inspite of numerous preclinical studies very few clinical data available due to which this process is in its initial phase. The review also focuses on the receptors like GPCR 119, GPER, Vaspin, Metrnl, Fetuin-A that have role in insulin regulation and have potential to become future targets in treatment for diabetes that may be effective and safer as compared to the conventional and current treatment approaches.

PDX1 is the cornerstone of pancreatic β-cell functions and identity

Diabetes has been a worldwide healthcare problem for many years. Current methods of treating diabetes are still largely directed at symptoms, aiming to control the manifestations of the pathology. This creates an overall need to find alternative measures that can impact on the causes of the disease, reverse diabetes, or make it more manageable. Understanding the role of key players in the pathogenesis of diabetes and the related β-cell functions is of great importance in combating diabetes. PDX1 is a master regulator in pancreas organogenesis, the maturation and identity preservation of β-cells, and of their role in normal insulin function. Mutations in the PDX1 gene are correlated with many pancreatic dysfunctions, including pancreatic agenesis (homozygous mutation) and MODY4 (heterozygous mutation), while in other types of diabetes, PDX1 expression is reduced. Therefore, alternative approaches to treat diabetes largely depend on knowledge of PDX1 regulation, its interaction with other transcription factors, and its role in obtaining β-cells through differentiation and transdifferentiation protocols. In this article, we review the basic functions of PDX1 and its regulation by genetic and epigenetic factors. Lastly, we summarize different variations of the differentiation protocols used to obtain β-cells from alternative cell sources, using PDX1 alone or in combination with various transcription factors and modified culture conditions. This review shows the unique position of PDX1 as a potential target in the genetic and cellular treatment of diabetes.

Current Advances in the Management of Diabetes Mellitus

Diabetes mellitus (DM) underscores a rising epidemic orchestrating critical socio-economic burden on countries globally. Different treatment options for the management of DM are evolving rapidly because the usual methods of treatment have not completely tackled the primary causes of the disease and are laden with critical adverse effects. Thus, this narrative review explores different treatment regimens in DM management and the associated challenges. A literature search for published articles on recent advances in DM management was completed with search engines including Web of Science, Pubmed/Medline, Scopus, using keywords such as DM, management of DM, and gene therapy. Our findings indicate that substantial progress has been made in DM management with promising results using different treatment regimens, including nanotechnology, gene therapy, stem cell, medical nutrition therapy, and lifestyle modification. However, a lot of challenges have been encountered using these techniques, including their optimization to ensure optimal glycemic, lipid, and blood pressure modulation to minimize complications, improvement of patients' compliance to lifestyle and pharmacologic interventions, safety, ethical issues, as well as an effective delivery system among others. In conclusion, lifestyle management alongside pharmacological approaches and the optimization of these techniques is critical for an effective and safe clinical treatment plan.

Diabetes mellitus and diabetic foot ulcer: Etiology, biochemical and molecular based treatment strategies via gene and nanotherapy

Diabetes mellitus (DM) is a collection of metabolic and pathophysiological disorders manifested with high glucose levels in the blood due to the inability of β-pancreatic cells to secrete an adequate amount of insulin or insensitivity of insulin towards receptor to oxidize blood glucose. Nevertheless, the preceding definition is only applicable to people who do not have inherited or metabolic disorders. Suppose a person who has been diagnosed with Type 1 or Type 2DM sustains an injury and the treatment of the damage is complicated and prolonged. In that case, the injury is referred to as a diabetic foot ulcer (DFU). In the presence of many proliferating macrophages in the injury site for an extended period causes the damage to worsen and become a diabetic wound. In this review, the scientific information and therapeutic management of DM/DFU with nanomedicine, and other related data were collected (Web of Science and PubMed) from January 2000 to January 2022. Most of the articles revealed that standard drugs are usually prescribed along with hypoglycaemic medications. Conversely, such drugs stabilize the glucose transporters and homeostasis for a limited period, resulting in side effects such as kidney damage/failure, absorption/gastrointestinal problems, and hypoglycemic issues. In this paper, we review the current basic and clinical evidence about the potential of medicinal plants, gene therapy, chemical/green synthesized nanoparticles to improving the metabolic profile, and facilitating the DM and DFU associated complications. Preclinical studies also reported lower plasma glucose with molecular targets in DM and DFU. Research is underway to explore chemical/green synthesized nanoparticle-based medications to avoid such side effects. Hence, the present review is intended to address the current challenges, recently recognized factors responsible for DM and DFU, their pathophysiology, insulin receptors associated with DM, medications in trend, and related complications.

Therapeutic Approaches for the Management of Autoimmune Disorders via Gene Therapy: Prospects, Challenges, and Opportunities

BACKGROUND

Autoimmune diseases are the diseases that result due to the overactive immune response, and comprise systemic autoimmune diseases like rheumatoid arthritis (RA), sjӧgren's syndrome (SS), and organ-specific autoimmune diseases like type-1 diabetes mellitus (T1DM), myasthenia gravis (MG), and inflammatory bowel disease (IBD). Currently, there is no long-term cure; but, several treatments exist which retard the evolution of the disease, embracing gene therapy, which has been scrutinized to hold immense aptitude for the management of autoimmune diseases.

OBJECTIVE

The review highlights the pathogenic mechanisms and genes liable for the development of autoimmune diseases, namely T1DM, type-2 diabetes mellitus (T2DM), RA, SS, IBD, and MG. Furthermore, the review focuses on investigating the outcomes of delivering the corrective genes with their specific viral vectors in various animal models experiencing these diseases to determine the effectiveness of gene therapy.

METHODS

Numerous review and research articles emphasizing the tremendous potential of gene therapy in the management of autoimmune diseases were procured from PubMed, MEDLINE, Frontier, and other databases and thoroughly studied for writing this review article.

RESULTS

The various animal models that experienced treatment with gene therapy have displayed regulation in the levels of proinflammatory cytokines, infiltration of lymphocytes, manifestations associated with autoimmune diseases, and maintained equilibrium in the immune response, thereby hinder the progression of autoimmune diseases.

CONCLUSION

Gene therapy has revealed prodigious aptitude in the management of autoimmune diseases in various animal studies, but further investigation is essential to combat the limitations associated with it and before employing it on humans.

Focus on the Lymphatic Route to Optimize Drug Delivery in Cardiovascular Medicine

While oral agents have been the gold standard for cardiovascular disease therapy, the new generation of treatments is switching to other administration options that offer reduced dosing frequency and more efficacy. The lymphatic network is a unidirectional and low-pressure vascular system that is responsible for the absorption of interstitial fluids, molecules, and cells from the peripheral tissue, including the skin and the intestines. Targeting the lymphatic route for drug delivery employing traditional or new technologies and drug formulations is exponentially gaining attention in the quest to avoid the hepatic first-pass effect. The present review will give an overview of the current knowledge on the involvement of the lymphatic vessels in drug delivery in the context of cardiovascular disease.

Lentivirus Mediated Pancreatic Beta-Cell-Specific Insulin Gene Therapy for STZ-Induced Diabetes

Autoimmune destruction of pancreatic beta cells is the characteristic feature of type 1 diabetes mellitus. Consequently, both short- and intermediate-acting insulin analogs are under development to compensate for the lack of endogenous insulin gene expression. Basal insulin is continuously released at low levels in response to hepatic glucose output, while post-prandial insulin is secreted in response to hyperglycemia following a meal. As an alternative to multiple daily injections of insulin, glucose-regulated insulin gene expression by gene therapy is under development to better endure postprandial glucose excursions. Controlled transcription and translation of proinsulin, presence of glucose-sensing machinery, prohormone convertase expression, and a regulated secretory pathway are the key features unique to pancreatic beta cells. To take advantage of these hallmarks, we generated a new lentiviral vector (LentiINS) with an insulin promoter driving expression of the proinsulin encoding cDNA to sustain pancreatic beta-cell-specific insulin gene expression. Intraperitoneal delivery of HIV-based LentiINS resulted in the lowering of fasting plasma glucose, improved glucose tolerance and prevented weight loss in streptozoticin (STZ)-induced diabetic Wistar rats. However, the combinatorial use of LentiINS and anti-inflammatory lentiviral vector (LentiVIP) gene therapy was required to increase serum insulin to a level sufficient to suppress non-fasting plasma glucose and diabetes-related inflammation.

Modification of a Constitutive to Glucose-Responsive Liver-Specific Promoter Resulted in Increased Efficacy of Adeno-Associated Virus Serotype 8-Insulin Gene Therapy of Diabetic Mice

We have previously used a hepatotropic adeno-associated viral (AAV) vector with a modified human insulin gene to treat diabetic mice. The HLP (hybrid liver-specific promoter) used was constitutively active and non-responsive to glucose. In this study, we examined the effects of addition of glucose responsive elements (R3G) and incorporation of a 3' albumin enhancer (3'iALB) on insulin expression. In comparison with the original promoter, glucose responsiveness was only observed in the modified promoters in vitro with a 36 h lag time before the peak expression. A 50% decrease in the number of viral particles at 5 × 10⁹ vector genome (vg)/mouse was required by AAV8-R3GHLP-hINSco to reduce the blood sugar level to near normoglycemia when compared to the original AAV8-HLP-hINSco that needed 1 × 10¹⁰ vg/mouse. The further inclusion of an 860 base-pairs 3'iALB enhancer component in the 3' untranslated region increased the in vitro gene expression significantly but this increase was not observed when the packaged virus was systemically injected in vivo. The addition of R3G to the HLP promoter in the AAV8-human insulin vector increased the insulin expression and secretion, thereby lowering the required dosage for basal insulin treatment. This in turn reduces the risk of liver toxicity and cost of vector production.

Type 1 and 2 diabetes mellitus: A review on current treatment approach and gene therapy as potential intervention

Type 1 and type 2 diabetes mellitus is a serious and lifelong condition commonly characterised by abnormally elevated blood glucose levels due to a failure in insulin production or a decrease in insulin sensitivity and function. Over the years, prevalence of diabetes has increased globally and it is classified as one of the leading cause of high mortality and morbidity rate. Furthermore, diabetes confers a huge economic burden due to its management costs as well as its complications are skyrocketing. The conventional medications in diabetes treatment focusing on insulin secretion and insulin sensitisation cause unwanted side effects to patients and lead to incompliance as well as treatment failure. Besides insulin and oral hypoglycaemic agents, other treatments such as gene therapy and induced β-cells regeneration have not been widely introduced to manage diabetes. Therefore, this review aims to deliver an overview of the current conventional medications in diabetes, discovery of newer pharmacological drugs and gene therapy as a potential intervention of diabetes in the future.

Silencing of transgene expression in mammalian cells by DNA methylation and histone modifications in gene therapy perspective

DNA methylation and histone modifications are vital in maintaining genomic stability and modulating cellular functions in mammalian cells. These two epigenetic modifications are the most common gene regulatory systems known to spatially control gene expression. Transgene silencing by these two mechanisms is a major challenge to achieving effective gene therapy for many genetic conditions. The implications of transgene silencing caused by epigenetic modifications have been extensively studied and reported in numerous gene delivery studies. This review highlights instances of transgene silencing by DNA methylation and histone modification with specific focus on the role of these two epigenetic effects on the repression of transgene expression in mammalian cells from integrative and non-integrative based gene delivery systems in the context of gene therapy. It also discusses the prospects of achieving an effective and sustained transgene expression for future gene therapy applications.

The rise and potential fall of pancreas transplantation

BACKGROUND

The aim of this review is to bring pancreatic transplantation out of the specialist realm, informing practitioners about this important procedure, so that they feel better equipped to refer suitable patients for transplantation and manage, counsel and support when encountering them within their own speciality.

SOURCES OF DATA

Narrative review conducted in May 2017. OVID interface searching EMBASE and MEDLINE databases, using Timeframe: Inception to June 1, 2017. Articles were assessed for clinical relevance and most up to date content with articles written in english as the only inclusion criteria. Other sources, used included conference proceedings/presentations, unpublished data from our institution (Oxford Transplant Centre).

AREAS OF AGREEMENT

Pancreas transplantation has evolved from an experimental procedure to the gold standard of care for patients with type 1 diabetes and uraemia. Currently, it remains the most effective method of establishing and maintaining euglycemia over the longer term, halting and potentially reversing many of the secondary complications associated with diabetes. Significant improvements to quality of life and better life expectancy make it in the longer term, a lifesaving procedure compared to waiting candidates.

AREAS OF CONTROVERSY

The future of solid organ pancreas transplantation remains uncertain, with extensive comorbidity and advances in alternative therapies makes the long-term growth of the procedure questionable.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

Therapies to alleviate problems associated with ischaemia reperfusion injury, graft pancreatitis and more effective monitoring methods for detecting and treating organ rejection are the key areas of growth.

Effects of Icariside II on corpus cavernosum and major pelvic ganglion neuropathy in streptozotocin-induced diabetic rats

Diabetic erectile dysfunction is associated with penile dorsal nerve bundle neuropathy in the corpus cavernosum and the mechanism is not well understood. We investigated the neuropathy changes in the corpus cavernosum of rats with streptozotocin-induced diabetes and the effects of Icariside II (ICA II) on improving neuropathy. Thirty-six 8-week-old Sprague-Dawley rats were randomly distributed into normal control group, diabetic group and ICA-II treated group. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (60 mg/kg). Three days later, the diabetic rats were randomly divided into 2 groups including a saline treated placebo group and an ICA II-treated group (5 mg/kg/day, by intragastric administration daily). Twelve weeks later, erectile function was measured by cavernous nerve electrostimulation with real time intracorporal pressure assessment. The penis was harvested for the histological examination (immunofluorescence and immunohistochemical staining) and transmission electron microscopy detecting. Diabetic animals exhibited a decreased density of dorsal nerve bundle in penis. The neurofilament of the dorsal nerve bundle was fragmented in the diabetic rats. There was a decreased expression of nNOS and NGF in the diabetic group. The ICA II group had higher density of dorsal nerve bundle, higher expression of NGF and nNOS in the penis. The pathological change of major pelvic nerve ganglion (including the microstructure by transmission electron microscope and the neurite outgrowth length of major pelvic nerve ganglion tissue cultured in vitro) was greatly attenuated in the ICA II-treated group (p < 0.01). ICA II treatment attenuates the diabetes-related impairment of corpus cavernosum and major pelvic ganglion neuropathy in rats with Streptozotocin-Induced Diabetes.

Deletion of ARNT (Aryl hydrocarbon receptor nuclear translocator) in β-cells causes islet transplant failure with impaired β-cell function

Background

Replacing β-cells by islet-transplantation can cure type 1 diabetes, but up to 70% of β-cells die within 10 days of transplantation. ARNT (Aryl hydrocarbon Receptor Nuclear Translocator) regulates β-cell function, and potentially survival. Lack of ARNT impairs the ability of β-cells to respond to physiological stress and potentiates the onset of diabetes, but the exact role of ARNT in graft outcome is unknown.

Aim

To investigate the effect of β-cell deletion of ARNT on graft outcomes.

Methods

Islets were isolated from donor mice which had β-cell specific ARNT-deletion (β-ARNT) or littermate floxed controls. The islets were transplanted into diabetic SCID recipients in ratios of (a) 3 donors: 1 recipient, (b) 1 donor: 1 recipient or (c) ½ of the islets from 1 donor: 1 recipient. After 28 days, the kidney containing the graft was removed (nephrectomy) to exclude regeneration of the endogenous pancreas.

Results

In the supra-physiological-mass model (3∶1), both groups achieved reasonable glycaemia, with slightly higher levels in β-ARNT-recipients. In adequate-mass model (1∶1), β-ARNT recipients had poor glucose control versus floxed-control recipients and versus the β-ARNT donors. In the low-β-cell-mass model (½:1) β-ARNT transplants completely failed, whereas controls had good outcomes. Unexpectedly, there was no difference in the graft insulin content or β-cell mass between groups indicating that the defect was not due to early altered β-cell survival.

Conclusion

Outcomes for islet transplants lacking β-cell ARNT were poor, unless markedly supra-physiological masses of islets were transplanted. In the 1∶1 transplant model, there was no difference in β-cell volume. This is surprising because transplants of islets lacking one of the ARNT-partners HIF-1α have increased apoptosis and decreased islet volume. ARNT also partners HIF-2α and AhR (aryl hydrocarbon receptor) to form active transcriptional complexes, and further work to understand the roles of HIF-2α and AhR in transplant outcomes is needed.

Generating insulin-producing cells for diabetic therapy: existing strategies and new development

Type 1 and 2 diabetes are characterized by a deficiency in β-cell mass, which cannot be reversed with existing therapeutic strategies. Therefore, restoration of the endogenous insulin-producing cell mass holds great promise for curing diabetes in the future. Since the initial induction of insulin-producing cells (IPCs) from embryonic stem (ES) cells in 1999, several strategies and alternative cell sources have been developed to generate β-like cells, including direct differentiation from ES cells or induced pluripotent stem (iPS) cells, proliferation of existing adult β-cells, and reprogramming of non-pancreatic adult stem/mature cells or pancreatic non-β-cells to β-like-cells. However, several barriers persist in the translation of the aforementioned strategies into clinically applicable methods for IPC induction. We briefly review the most relevant studies for each strategy, and discuss the comparative merits and drawbacks. We propose that ex vivo patient-specific IPCs generated from iPS cells may be practical for cell transplantation in the near future, and in situ regeneration of IPCs from cells within the pancreas may be preferable for diabetes therapy.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

Insulin gene therapy from design to beta cell generation

Despite the fact that insulin injection can protect diabetic patients from developing diabetes-related complications, recent meta-analyses indicate that rapid and long-acting insulin analogues only provide a limited benefit compared with conventional insulin regarding glycemic control. As insulin deficiency is the main sequel of type-1 diabetes (T1D), transfer of the insulin gene-by-gene therapy is becoming an attractive treatment modality even though T1D is not caused by a single genetic defect. In contrast to human insulin and insulin analogues, insulin gene therapy targets to supplement patients not only with insulin but also with C-peptide. So far, insulin gene therapy has had limited success because of delayed and/or transient gene expression. Sustained insulin gene expression is now feasible using current gene-therapy vectors providing patients with basal insulin coverage, but management of postprandial hyperglycaemia is still difficult to accomplish because of the inability to properly control insulin secretion. Enteroendocrine cells of the gastrointestinal track (K cells and L cells) may be ideal targets for insulin gene therapy, but cell-targeting difficulties have limited practical implementation of insulin gene therapy for diabetes treatment. Therefore, recent gene transfer technologies developed to generate authentic beta cells through transdifferentiation are also highlighted in this review.