Human beta cells are exceedingly resistant to streptozotocin in vivo

The functional maturity of grafted human pluripotent stem cell derived-islets (hSC-Islets) evaluated by the glycemic set point during blood glucose normalizing process in diabetic mice

Human pluripotent stem cell (hPSCs) derived-pancreatic islets (hSC-islets) are good candidates for cell replacement therapy for patients with diabetes as substitutes for deceased donor-derived islets, because they are pluripotent and have infinite proliferation potential. Grafted hSC-islets ameliorate hyperglycemia in diabetic mice; however, several weeks are needed to normalize the hyperglycemia. These data suggest hSC-islets require maturation, but their maturation process in vivo is not yet fully understood. In this study, we utilized two kinds of streptozotocin (STZ)-induced diabetes model mice by changing the administration timing in order to examine the time course of maturation of hSC-islets and the effects of hyperglycemia on their maturation. We found no hyperglycemia in immune-compromised mice when hSC-islets had been transplanted under their kidney capsules in advance, and STZ was administered 4 weeks after transplantation. Of note, the blood glucose levels of those mice were stably maintained under 100 mg/dl 10 weeks after transplantation; this is lower than the mouse glycemic set point (120-150 mg/dl), suggesting that hSC-islets control blood glucose levels to the human glycemic set point. We confirmed that gene expression of maturation markers of pancreatic beta cells tended to upregulate during 4 weeks after transplantation. Periodical histological analysis revealed that revascularization was observed as early as 1 week after transplantation, but reinnervation in the grafted hSC-islets was not detected at all, even 15 weeks after transplantation. In conclusion, our hSC-islets need at least 4 weeks to mature, and the human glycemic set point is a good index for evaluating ultimate maturity for hSC-islets in vivo.

Exocrine pancreas regeneration modifies original pancreas to alleviate diabetes in mouse models

Diabetes is a major public health issue because of its widely epidemic nature and lack of cure. Here, we show that pancreas-derived mesenchymal stem cells (PMSCs) are capable of regenerating exocrine pancreas when implanted into the kidney capsule of mice with streptozotocin (STZ)-induced diabetes. Mechanistically, we found that the regenerated exocrine pancreas elevated interleukin-6 (IL-6) in PMSC implants, which transiently activated tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) to inhibit IL-17, thereby rescuing damaged exocrine pancreas and islet β cells. In addition, we used knockout mouse models to show that global lack of IL-6, TNF-α, or IFN-γ resulted in increased severity of STZ-induced diabetes and resistance to PMSC implantation therapy, confirming the roles of these factors in safeguarding pancreatic β cells. Furthermore, removal of the kidney capsule PMSC implants at 28 days after implantation did not affect the PMSC-initiated therapeutic effect on diabetic mice. This study reveals a previously unknown role of exocrine pancreas regeneration in safeguarding β cells and demonstrates a "soil-rescues-seed" strategy for type 1 diabetes therapy.

Reduced calcium levels and accumulation of abnormal insulin granules in stem cell models of HNF1A deficiency

Mutations in HNF1A cause Maturity Onset Diabetes of the Young (HNF1A-MODY). To understand mechanisms of β-cell dysfunction, we generated stem cell-derived pancreatic endocrine cells with hypomorphic mutations in HNF1A. HNF1A-deficient β-cells display impaired basal and glucose stimulated-insulin secretion, reduced intracellular calcium levels in association with a reduction in CACNA1A expression, and accumulation of abnormal insulin granules in association with SYT13 down-regulation. Knockout of CACNA1A and SYT13 reproduce the relevant phenotypes. In HNF1A deficient β-cells, glibenclamide, a sulfonylurea drug used in the treatment of HNF1A-MODY patients, increases intracellular calcium, and restores insulin secretion. While insulin secretion defects are constitutive in β-cells null for HNF1A, β-cells heterozygous for hypomorphic HNF1A (R200Q) mutations lose the ability to secrete insulin gradually; this phenotype is prevented by correction of the mutation. Our studies illuminate the molecular basis for the efficacy of treatment of HNF1A-MODY with sulfonylureas, and suggest promise for the use of cell therapies.

Potential Ophthalmological Side Effects Induced by Anti-Neoplastic Regimens for the Treatment of Genitourinary Cancers: A Review

The outcomes of patients with genitourinary (GU) cancers have been steadily improving in recent years. Novel therapies have entered our armamentarium, while several other regimens are currently being studied in clinical trials. This recent explosion of new agents has improved patient survival and the quality of life for patients, but has also significantly increased the frequency of several side effects. The current review will focus on the potential ocular adverse reactions of GU neoplastic treatments. The broad spectrum of manifestations of ocular toxicity underscores the uniqueness and complexity of the anatomic, physiologic, and metabolic features of the human eye. Most side effects are mild in severity and transient, but some can be severe, disabling, and irreversible. Clinicians should be aware of complications that might be vision threatening and impact the patient's quality of life. In this review, we focused on the ocular toxicity of the antineoplastic regimens that are currently used for the treatment of GU, including prostate cancer, bladder cancer, renal cell carcinoma, testicular cancer, pheochromocytoma, adrenocortical carcinoma, and penile cancer.

Pathogenic Mechanism of Autoimmune Diabetes Mellitus in Humans: Potential Role of Streptozotocin-Induced Selective Autoimmunity against Human Islet β-Cells

Human type 1 diabetes mellitus is a chronic autoimmune disease characterized by the selective loss of insulin-producing β-cells in pancreatic islets of genetically susceptible individuals. In this communication, a new hypothesis is postulated which is based on the observations that streptozotocin (STZ), a chemically reactive and cytotoxic compound produced by certain gram-positive bacteria, can be preferentially taken up into islet β-cells and induce cytotoxicity and autoimmunity. It is hypothesized that humans might be occasionally exposed to STZ through opportunistic infections with the STZ-producing bacteria and/or through ingestion of certain food products that contain STZ. In addition, the potential presence of the STZ-producing bacteria in the gut microbiota of some individuals might be another source of long-term STZ exposure. Because of the high chemical reactivity of STZ and its breakdown products, these chemicals can covalently modify certain cellular macromolecules (e.g., DNA and proteins), and the covalently modified cellular components would serve as new antigens, potentially capable of inducing both humoral and cellular autoimmune responses in the islets of certain individuals. In addition to STZ exposure, the eventual development of autoimmunity against STZ-exposed islet β-cells also depends critically on the genetic predisposition of the susceptible individuals plus the opportunistic presence of a conducive, strong environmental trigger, which often is presented as severe febrile viral infections subsequently inducing strong aberrant reactions of the body’s immune system. The proposed pathogenic hypothesis is supported by a considerable body of direct and indirect evidence from laboratory animal studies and clinical observations. Certainly, more experimental and clinical studies are needed to carefully further examine each of the key components of the proposed pathogenic hypothesis.

Localized drug delivery graphene bioscaffolds for cotransplantation of islets and mesenchymal stem cells

In the present work, we developed, characterized, and tested an implantable graphene bioscaffold which elutes dexamethasone (Dex) that can accommodate islets and adipose tissue–derived mesenchymal stem cells (AD-MSCs). In vitro studies demonstrated that islets in graphene–0.5 w/v% Dex bioscaffolds had a substantial higher viability and function compared to islets in graphene-alone bioscaffolds or islets cultured alone (P < 0.05). In vivo studies, in which bioscaffolds were transplanted into the epididymal fat pad of diabetic mice, demonstrated that, when islet:AD-MSC units were seeded into graphene–0.5 w/v% Dex bioscaffolds, this resulted in complete restoration of glycemic control immediately after transplantation with these islets also showing a faster response to glucose challenges (P < 0.05). Hence, this combination approach of using a graphene bioscaffold that can be functionalized for local delivery of Dex into the surrounding microenvironment, together with AD-MSC therapy, can significantly improve the survival and function of transplanted islets.

Streptozotocin induces alpha-2u globulin nephropathy in male rats during diabetic kidney disease

BACKGROUND

Alpha-2u globulin nephropathy mainly shows toxicological pathology only in male rats induced by certain chemicals and drugs, such as levamisole (antiparasitic and anticancer drugs). Streptozotocin (STZ) is also an anticancer-antibiotic agent that has been used for decades to induce a diabetic kidney disease model in rodents. The purpose of this study is to determine if STZ causes alpha-2u globulin nephropathy in male rats during an advanced stage of diabetic kidney disease. Alpha-2u globulin nephropathy, water absorption and filtration capacities (via aquaporin [AQP]-1, - 2, - 4 and - 5) and mitochondrial function (through haloacid dehalogenase-like hydrolase domain-containing protein [HDHD]-3 and NADH-ubiquinone oxidoreductase 75 kDa subunit [NDUFS]-1 proteins) were examined in STZ-induced diabetic Wistar rat model.

RESULTS

More than 80% of severe clinical illness rats induced by STZ injection simultaneously exhibited alpha-2u globulin nephropathy with mitochondrial degeneration and filtration apparatus especially pedicels impairment. They also showed significantly upregulated AQP-1, - 2, - 4 and - 5, HDHD-3 and NDUFS-1 compared with those of the rats without alpha-2u globulin nephropathy.

CONCLUSIONS

STZ-induced alpha-2u globulin nephropathy during diabetic kidney disease in association with deterioration of pedicels, renal tubular damage with adaptation and mitochondrial driven apoptosis.

Proinflammatory Cytokine Interleukin 1β Disrupts β-cell Circadian Clock Function and Regulation of Insulin Secretion

Intrinsic β-cell circadian clocks are important regulators of insulin secretion and overall glucose homeostasis. Whether the circadian clock in β-cells is perturbed following exposure to prodiabetogenic stressors such as proinflammatory cytokines, and whether these perturbations are featured during the development of diabetes, remains unknown. To address this, we examined the effects of cytokine-mediated inflammation common to the pathophysiology of diabetes, on the physiological and molecular regulation of the β-cell circadian clock. Specifically, we provide evidence that the key diabetogenic cytokine IL-1β disrupts functionality of the β-cell circadian clock and impairs circadian regulation of glucose-stimulated insulin secretion. The deleterious effects of IL-1β on the circadian clock were attributed to impaired expression of key circadian transcription factor Bmal1, and its regulator, the NAD-dependent deacetylase, Sirtuin 1 (SIRT1). Moreover, we also identified that Type 2 diabetes in humans is associated with reduced immunoreactivity of β-cell BMAL1 and SIRT1, suggestive of a potential causative link between islet inflammation, circadian clock disruption, and β-cell failure. These data suggest that the circadian clock in β-cells is perturbed following exposure to proinflammatory stressors and highlights the potential for therapeutic targeting of the circadian system for treatment for β-cell failure in diabetes.

Imaging β-Cell Function Using a Zinc-Responsive MRI Contrast Agent May Identify First Responder Islets

An imaging method for detecting β-cell function in real-time in the rodent pancreas could provide new insights into the biological mechanisms involving loss of β-cell function during development of type 2 diabetes and for testing of new drugs designed to modulate insulin secretion. In this study, we used a zinc-responsive MRI contrast agent and an optimized 2D MRI method to show that glucose stimulated insulin and zinc secretion can be detected as functionally active "hot spots" in the tail of the rat pancreas. A comparison of functional images with histological markers show that insulin and zinc secretion does not occur uniformly among all pancreatic islets but rather that some islets respond rapidly to an increase in glucose while others remain silent. Zinc and insulin secretion was shown to be altered in streptozotocin and exenatide treated rats thereby verifying that this simple MRI technique is responsive to changes in β-cell function.

Human Pluripotent Stem Cells to Model Islet Defects in Diabetes

Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.

Noninvasive Monitoring of Glycemia-Induced Regulation of GLP-1R Expression in Murine and Human Islets of Langerhans

Glucagon-like peptide 1 receptor (GLP-1R) imaging with radiolabeled exendin has proven to be a powerful tool to quantify β-cell mass (BCM) in vivo. As GLP-1R expression is thought to be influenced by glycemic control, we examined the effect of blood glucose (BG) levels on GLP-1R-mediated exendin uptake in both murine and human islets and its implications for BCM quantification. Periods of hyperglycemia significantly reduced exendin uptake in murine and human islets, which was paralleled by a reduction in GLP-1R expression. Detailed mapping of the tracer uptake and insulin and GLP-1R expression conclusively demonstrated that the observed reduction in tracer uptake directly correlates to GLP-1R expression levels. Importantly, the linear correlation between tracer uptake and β-cell area was maintained in spite of the reduced GLP-1R expression levels. Subsequent normalization of BG levels restored absolute tracer uptake and GLP-1R expression in β-cells and the observed loss in islet volume was halted. This manuscript emphasizes the potency of nuclear imaging techniques to monitor receptor regulation noninvasively. Our findings have significant implications for clinical practice, indicating that BG levels should be near-normalized for at least 3 weeks prior to GLP-1R agonist treatment or quantitative radiolabeled exendin imaging for BCM analysis.

ATM and P53 differentially regulate pancreatic beta cell survival in Ins1E cells

Pancreatic beta cell death is a hallmark of type 1 and 2 diabetes (T1D/T2D), but the underlying molecular mechanisms are incompletely understood. Key proteins of the DNA damage response (DDR), including tumor protein P53 (P53, also known as TP53 or TRP53 in rodents) and Ataxia Telangiectasia Mutated (ATM), a kinase known to act upstream of P53, have been associated with T2D. Here we test and compare the effect of ATM and P53 ablation on beta cell survival in the rat beta cell line Ins1E. We demonstrate that ATM and P53 differentially regulate beta cell apoptosis induced upon fundamentally different types of diabetogenic beta cell stress, including DNA damage, inflammation, lipotoxicity and endoplasmic reticulum (ER) stress. DNA damage induced apoptosis by treatment with the commonly used diabetogenic agent streptozotocin (STZ) is regulated by both ATM and P53. We show that ATM is a key STZ induced activator of P53 and that amelioration of STZ induced cell death by inhibition of ATM mainly depends on P53. While both P53 and ATM control lipotoxic beta cell apoptosis, ATM but not P53 fails to alter inflammatory beta cell death. In contrast, tunicamycin induced (ER stress associated) apoptosis is further increased by ATM knockdown or inhibition, but not by P53 knockdown. Our results reveal differential roles for P53 and ATM in beta cell survival in vitro in the context of four key pathophysiological types of diabetogenic beta cell stress, and indicate that ATM can use P53 independent signaling pathways to modify beta cell survival, dependent on the cellular insult.

Use of Streptozotocin in Rodent Models of Islet Transplantation

Streptozotocin (STZ) selectively destroys beta cells and is widely used to induce experimental diabetes in rodents. Rodent beta cells are very sensitive to the toxic effects of STZ, while human beta cells are highly resistant to STZ. Taking advantage of this characteristic, here, we describe two protocols for the induction of STZ-diabetes. In the first model, hyperglycemia is induced prior to islet transplantation, whereas in the second model, STZ is injected after islet transplantation. The former model has many applications and thus is the most commonly used method. However, when implanting human islets into mice, there are clear benefits to administering STZ after the transplantation. It reduces the cost and burden of experiments and the number of human islets needed for transplantation and improves the welfare and survival of animals used in the experiments. In both methods, a key step in the experimental protocol is to remove the graft-bearing kidney at the end of the experiment and monitor onset of hyperglycemia. This can be used to demonstrate that the glycemic control of the animal is due to the engrafted islets and not regeneration of endogenous beta cells. This chapter outlines protocols of administering streptozotocin pre- and post-islet transplantation in mice as well as nephrectomy to remove the graft-bearing kidney.

Macroencapsulated Human iPSC-Derived Pancreatic Progenitors Protect against STZ-Induced Hyperglycemia in Mice

In type 1 diabetes, a renewable source of human pancreatic β cells, in particular from human induced pluripotent stem cell (hiPSC) origin, would greatly benefit cell therapy. Earlier work showed that pancreatic progenitors differentiated from human embryonic stem cells in vitro can further mature to become glucose responsive following macroencapsulation and transplantation in mice. Here we took a similar approach optimizing the generation of pancreatic progenitors from hiPSCs. This work demonstrates that hiPSCs differentiated to pancreatic endoderm in vitro can be efficiently and robustly generated under large-scale conditions. The hiPSC-derived pancreatic endoderm cells (HiPECs) can further differentiate into glucose-responsive islet-like cells following macroencapsulation and in vivo implantation. The HiPECs can protect mice from streptozotocin-induced hyperglycemia and maintain normal glucose homeostasis and equilibrated plasma glucose concentrations at levels similar to the human set point. These results further validate the potential use of hiPSC-derived islet cells for application in clinical settings.

A Model for Human Islet Transplantation to Immunodeficient Streptozotocin-Induced Diabetic Mice

Streptozotocin (STZ) is a cytotoxic glucose analogue that causes beta cell death and is widely used to induce experimental diabetes in rodents. The sensitivity of beta cells to STZ is species-specific and human beta cells are resistant to STZ. In experimental islet transplantation to rodents, STZ-diabetes must be induced before transplantation to avoid destruction of grafted islets by STZ. In human islet transplantation, injection of STZ before transplantation is inconvenient and costly, since human islet availability depends on organ donation and frail STZ-diabetic mice must be kept for unpredictable lapses of time until a human islet preparation is available. Based on the high resistance of human beta cells to STZ, we have tested a new model for STZ-diabetes induction in which STZ is injected after human islet transplantation. Human and mouse islets were transplanted under the kidney capsule of athymic nude mice, and 10–14 days after transplantation mice were intraperitoneally injected with five consecutive daily doses of STZ or vehicle. Beta-cell death increased and beta-cell mass was reduced in mouse islet grafts after STZ injection. In contrast, in human islet grafts beta cell death and mass did not change after STZ injection. Mice transplanted with rodent islets developed hyperglycemia after STZ-injection. Mice transplanted with human islets remained normoglycemic and developed hyperglycemia when the graft was harvested. STZ had no detectable toxic effects on beta cell death, mass and function of human transplanted islets. We provide a new, more convenient and cost-saving model for human islet transplantation to STZ-diabetic recipients in which STZ is injected after islet transplantation.

WTC rat has unique characteristics such as resistant to streptozotocin

Because we found that WTC rats might be resistant to streptozotocin (STZ), we have elucidated the mechanisms of resistant to the diabetogenic effects of STZ in the WTC rats. Dose response to STZ was evaluated with glucose levels. No significant changes in glucose level to STZ administration were observed in WTC rats. Insulin secretion by suppling glucose was preserved in WTC rats even after STZ administration. Although there was no significant difference in gene expression of both GLUT2 and Kir6.2, which were involved in STZ resistance, between WTC rats and Wistar rats, the expression of metallothionein 2a in pancreas and liver to STZ administration of WTC rats was significantly higher than that of Wistar rats. Moreover, alloxan did not induce diabetes in WTC rats as same as STZ. These results suggest that WTC rats might have powerful antioxidant property to protect β cells in pancreas. Because the STZ-resistant property is very close characteristics to human beings, WTC rats will become a useful animal model in diabetic researches.

Identification and Characterization of microRNAs Associated With Human β-Cell Loss in a Mouse Model

Currently there is no effective approach for monitoring early β-cell loss during islet graft rejection following human islet transplantation (HIT). Due to ethical and technical constraints, it is difficult to directly study biomarkers of islet destruction in humans. Here, we established a humanized mouse model with induced human β-cell death using adoptive lymphocyte transfer (ALT). Human islet grafts of ALT-treated mice had perigraft lymphocyte infiltration, fewer insulin⁺ β cells, and increased β-cell apoptosis. Islet-specific miR-375 was used to validate our model, and expression of miR-375 was significantly decreased in the grafts and increased in the circulation of ALT-treated mice before hyperglycemia. A NanoString expression assay was further used to profile 800 human miRNAs in the human islet grafts, and the results were validated using quantitative real-time polymerase chain reaction. We found that miR-4454 and miR-199a-5p were decreased in the human islet grafts following ALT and increased in the circulation prior to hyperglycemia. These data demonstrate that our in vivo model of induced human β-cell destruction is a robust method for identifying and characterizing circulating biomarkers, and suggest that miR-4454 and miR-199a-5p can serve as novel biomarkers associated with early human β-cell loss following HIT.

Zebrafish Pancreas Development and Regeneration: Fishing for Diabetes Therapies

The zebrafish pancreas shares its basic organization and cell types with the mammalian pancreas. In addition, the developmental pathways that lead to the establishment of the pancreatic islets of Langherhans are generally conserved from fish to mammals. Zebrafish provides a powerful tool to probe the mechanisms controlling establishment of the pancreatic endocrine cell types from early embryonic progenitor cells, as well as the regeneration of endocrine cells after damage. This knowledge is, in turn, applicable to refining protocols to generate renewable sources of human pancreatic islet cells that are critical for regulation of blood sugar levels. Here, we review how previous and ongoing studies in zebrafish and beyond are influencing the understanding of molecular mechanisms underlying various forms of diabetes and efforts to develop cell-based approaches to cure this increasingly widespread disease.

Human pluripotent stem cell based islet models for diabetes research

Although similar, mouse and human pancreatic development and beta cell physiology have significant differences. For this reason, mouse models present shortcomings that can obscure the understanding of human diabetes pathology. Progress in the field of human pluripotent stem cell (hPSC) differentiation now makes it possible to derive unlimited numbers of human beta cells in vitro. This constitutes an invaluable approach to gain insight into human beta cell development and physiology and to generate improved disease models. Here we summarize the main differences in terms of development and physiology of the pancreatic endocrine cells between mouse and human, and describe the recent progress in modeling diabetes using hPSC. We highlight the need of developing more physiological hPSC-derived beta cell models and anticipate the future prospects of these approaches.

Human Serum Versus Human Serum Albumin Supplementation in Human Islet Pretransplantation Culture: In Vitro and In Vivo Assessment

There is conflicting evidence favoring both the use of human serum (HS) and of human serum albumin (HSA) in human islet culture. We evaluated the effects of HS versus HSA supplementation on 1) in vitro β-cell viability and function and 2) in vivo islet graft revascularization, islet viability, β-cell death, and metabolic outcome after transplantation. Islets isolated from 14 cadaveric organ donors were cultured for 3 days in CMRL 1066 medium supplemented with HS or HSA. After 3 days in culture, β-cell apoptosis was lower in HS group (1.41 ± 0.27 vs. 2.38 ± 0.39%, p = 0.029), and the recovery of islets was 77 ± 11% and 54 ± 1% in HS- and HSA-cultured groups, respectively. Glucose-stimulated insulin secretion (GSIS) was higher in HS group (29.4, range 10.4-99.9, vs. 22.3, range 8.7-70.6, p = 0.031). In vivo viability and revascularization was determined in HS- and HSA-cultured islets transplanted into the anterior chamber of the eye of Balb/c mice (n = 14), and β-cell apoptosis in paraffin-embedded mouse eyes. Islet viability and β-cell apoptosis were similar in both groups. Revascularization was observed in one graft (HS group) on day 10 after transplantation. Islet function was determined in streptozotocin (STZ)-diabetic nude mice (n = 33) transplanted with 2,000 IEQs cultured with HS or HSA that showed similar blood glucose levels and percentage of normoglycemic animals over time. In conclusion, human islets cultured in medium supplemented with HS showed higher survival in vitro, as well as islet viability and function. The higher in vitro survival increased the number of islets available for transplantation. However, the beneficial effect on viability and function did not translate into an improved metabolic evolution when a similar number of HSA- and HS-cultured islets was transplanted.

mPGES-2 deletion remarkably enhances liver injury in streptozotocin-treated mice via induction of GLUT2

BACKGROUND & AIMS

Microsomal prostaglandin E synthase-2 (mPGES-2) deletion does not influence in vivo PGE2 production and the function of this enzyme remains elusive. The present study was undertaken to investigate the role of mPGES-2 in streptozotocin (STZ)-induced type-1 diabetes and organ injuries.

METHODS

mPGES-2 wild type (WT) and knockout (KO) mice were treated by a single intraperitoneal injection of STZ at the dose of 120 mg/kg to induce type-1 diabetes. Subsequently, glycemic status and organ injuries were evaluated.

RESULTS

Following 4 days of STZ administration, mPGES-2 KO mice exhibited severe lethality in contrast to the normal phenotype observed in WT control mice. In a separate experiment, the analysis was performed at day 3 of the STZ treatment in order to avoid lethality. Blood glucose levels were similar between STZ-treated KO and WT mice. However, the livers of KO mice were yellowish with severe global hepatic steatosis, in parallel with markedly elevated liver enzymes and remarkable stomach expansion. However, the morphology of the other organs was largely normal. The STZ-treated KO mice displayed extensive hepatocyte apoptosis compared with WT mice in parallel with markedly enhanced inflammation and oxidative stress. More interestingly, a liver-specific 50% upregulation of GLUT2 was found in the KO mice accompanied with a markedly enhanced STZ accumulation and this induction of GLUT2 was likely to be associated with the insulin/SREBP-1c pathway. Primary cultured hepatocytes of KO mice exhibited an increased sensitivity to STZ-induced injury and higher cellular STZ content, which was markedly blunted by the selective GLUT2 inhibitor phloretin.

CONCLUSIONS

mPGES-2 deletion enhanced STZ-induced liver toxicity possibly via GLUT2-mediated STZ uptake, independently of diabetes mellitus.

A review of piscine islet xenotransplantation using wild-type tilapia donors and the production of transgenic tilapia expressing a "humanized" tilapia insulin

Most islet xenotransplantation laboratories have focused on porcine islets, which are both costly and difficult to isolate. Teleost (bony) fish, such as tilapia, possess macroscopically visible distinct islet organs called Brockmann bodies which can be inexpensively harvested. When transplanted into diabetic nude mice, tilapia islets maintain long-term normoglycemia and provide human-like glucose tolerance profiles. Like porcine islets, when transplanted into euthymic mice, they are rejected in a CD4 T-cell-dependent manner. However, unlike pigs, tilapia are so phylogenetically primitive that their cells do not express α(1,3)Gal and, because tilapia are highly evolved to live in warm stagnant waters nearly devoid of dissolved oxygen, their islet cells are exceedingly resistant to hypoxia, making them ideal for transplantation within encapsulation devices. Encapsulation, especially when combined with co-stimulatory blockade, markedly prolongs tilapia islet xenograft survival in small animal recipients, and a collaborator has shown function in diabetic cynomolgus monkeys. In anticipation of preclinical xenotransplantation studies, we have extensively characterized tilapia islets (morphology, embryologic development, cell biology, peptides, etc.) and their regulation of glucose homeostasis. Because tilapia insulin differs structurally from human insulin by 17 amino acids, we have produced transgenic tilapia whose islets stably express physiological levels of humanized insulin and have now bred these to homozygosity. These transgenic fish can serve as a platform for further development into a cell therapy product for diabetes.

That which does not kill us makes us stronger--does Nietzsche's quote apply to islets? A re-evaluation of the passenger leukocyte theory, free radicals, and glucose toxicity in islet cell transplantation

In clinical islet transplantation, isolated islets are embolized into the liver via the portal vein (PV); however, up to 70% of the islets are lost in the first few days after transplantation (i.e., too quickly to be mediated by the adaptive immune system). Part of early loss is due to instant blood-mediated inflammatory reaction, an immune/thrombotic process caused by islets interacting with complement. We have shown that glucose toxicity (GT) also plays a critical role based upon the observation that islets embolized into the PVs of diabetic athymic mice are rapidly lost but, if recipients are not diabetic, the islet grafts persist. Using donor islets resistant to the β-cell toxin streptozotocin, we have shown that intraportal islets engrafted in non-diabetic athymic mice for as little as 3 days will maintain normoglycemia when streptozotocin is administered destroying the recipient's native pancreas β-cells. What is the mechanism of GT in β-cells? Chronic exposure to hyperglycemia over-exerts β-cells and their electron transport chains leak superoxide radicals during aerobic metabolism. Here we reinterpret old data and present some compelling new data supporting a new model of early intraportal islet graft loss. We hypothesize that diabetes stimulates overproduction of superoxide in both the β-cells of the islet grafts and the endothelial cells lining the intraportal microvasculature adjacent to where the embolized islets become lodged. This double dose of oxidant damage stresses both the islets, which are highly susceptible to free radicals because of inherent low levels of scavenging enzymes, and the adjacent hepatic endothelial cells. This, superimposed upon localized endothelial damage caused by embolization, precipitates inflammation and coagulation which further damages islet grafts. Based upon this model, we predict that pre-exposing islets to sub-lethal hyperoxia should up-regulate islet free radical scavenging enzyme levels and promote initial engraftment; reinterpretation of 30 years old "passenger leukocyte" data and preliminary new data support this. Other data suggests that pre-exposure of recipients to hyperoxia could up-regulate antioxidant enzymes in the hepatic endothelium. The combination of both effects could markedly enhance early intraportal islet graft survival and engraftment. Finally, if our model is correct, current in vitro and in vivo tests used to test batches of harvested islets for viability and function prior to transplantation are poorly conceived (n.b., it is already well-known that results using these tests often do not predict clinical islet transplantation success) and a different testing paradigm is suggested.

Regenerative medicine for diabetes: differentiation of human pluripotent stem cells into functional β-cells in vitro and their proposed journey to clinical translation

Diabetes is a group of metabolic diseases, rising globally at an alarming rate. Type 1 (juvenile diabetes) is the autoimmune version of diabetes where the pancreas is unable to produce insulin, whereas type 2 (adult onset diabetes) is caused due to insulin resistance of the cells. In either of the cases, elevated blood glucose levels are observed which leads to progressive comorbidity like renal failure, cardiovascular disease, retinopathy, etc. Metformin, sulphonyl urea group of drugs, as well as insulin injections are the available therapies. In advanced cases of diabetes, the drug alone or drug in combination with insulin injections are not able to maintain a steady level of blood glucose. Moreover, frequent insulin injections are rather cumbersome for the patient. So, regenerative medicine could be a permanent solution for fighting diabetes. Islet transplantation has been tried with a limited amount of success on a large population of diabetics because of the shortage of cadaveric pancreas. Therefore, the best proposed alternative is regenerative medicine involving human pluripotent stem cell (hPSC)-derived beta islet transplantation which can be obtained in large quantities. Efficient protocols for in vitro differentiation of hPSC into a large number of sustained insulin-producing beta cells for transplantation will be considered to be a giant leap to address global rise in diabetic cases. Although most of the protocols mimic in vivo pancreatic development in humans, considerable amount of lacuna persists for near-perfect differentiation strategies. Moreover, beta islets differentiated from hPSC have not yet been successfully translated under clinical scenario.

Generating β cells from stem cells-the story so far

Despite intensive research, a treatment for diabetic patients that completely restores normoglycemia for an indefinite period of time remains elusive. Although islet transplantation temporarily confers normoglycemia to patients, the lack of a renewable source of insulin-producing β cells hampers the use of this treatment option. Although significant hurdles remain, recent advances in stem cell biology indicate that generation of fully matured β cells from uncommitted progenitor cells, including human embryonic stem cells and induced pluripotent stem cells derived from somatic cell populations, is becoming an achievable goal.

Overexpression of intraislet ghrelin enhances β-cell proliferation after streptozotocin-induced β-cell injury in mice

Previously, we reported that exogenous administration of ghrelin ameliorates glucose metabolism in a neonate streptozotocin (STZ)-induced diabetic rat model through enhancement of β-cell proliferation. However, it was not clear whether the observed β-cell proliferation was a direct or indirect effect (e.g., via orexigenic or growth hormone-stimulated pathways) of ghrelin activity. Here, we aimed to investigate whether ghrelin directly impacts β-cell proliferation after STZ-induced injury in mice. Seven-week-old male rat insulin II promoter-ghrelin internal ribosomal sequence ghrelin O-acyltransferase transgenic (RIP-GG Tg) mice, which have elevated pancreatic ghrelin levels, but only minor changes in plasma ghrelin levels when fed a medium-chain triglyceride-rich diet, were treated with STZ. Then, serum insulin, pancreatic insulin mRNA expression, and islet histology were evaluated. We found that the serum insulin levels, but not blood glucose levels, of RIP-GG Tg mice were significantly ameliorated 14 days post-STZ treatment. Pancreatic insulin mRNA expression was significantly elevated in RIP-GG Tg mice, and β-cell numbers in islets were increased. Furthermore, the number of phospho-histone H3⁺ or Ki67⁺ proliferating β-cells was significantly elevated in RIP-GG Tg mice, whereas the apoptotic indexes within the islets, as determined by TUNEL assay, were not changed. These results indicate that ghrelin can directly stimulate β-cell proliferation in vivo after β-cell injury even without its orexigenic or GH-stimulating activities, although it did not have enough impact to normalize the glucose tolerance in adult mice.

Future detection and monitoring of diabetes may entail analysis of both β-cell function and volume: how markers of β-cell loss may assist

Disease heterogeneity is as major issue in Type II Diabetes Mellitus (T2DM), and this patient inter-variability might not be sufficiently reflected by measurements of glycated haemoglobin (HbA1c).Β-cell dysfunction and β-cell death are initiating factors in development of T2DM. In fact, β-cells are known vanish prior to the development of T2DM, and autopsy of overt T2DM patients have shown a 60% reduction in β-cell mass.As the decline in β-cell function and mass have been proven to be pathological traits in T2DM, methods for evaluating β-cell loss is becoming of more interest. However, evaluation of β-cell death or loss is currently invasive and unattainable for the vast majority of diabetes patients. Serological markers, reflecting β-cell loss would be advantageous to detect and monitor progression of T2DM. Biomarkers with such capacities could be neo-epitopes of proteins with high β-cell specificity containing post translational modifications. Such tools may segregate T2DM patients into more appropriate treatment groups, based on their β-cell status, which is currently not possible. Presently individuals presenting with adequately elevated levels of both insulin and glucose are classified as T2DM patients, while an important subdivision of those is pending, namely those patients with sufficient β-cell capacity and those without. This may warrant two very different treatment options and patient care paths.Serological biomarkers reflecting β-cell health status may also assist development of new drugs for T2DM and aid physicians in better characterization of individual patients and tailor individual treatments and patient care protocols.

Species incompatibilities in the pig-to-macaque islet xenotransplant model affect transplant outcome: a comparison with allotransplantation

BACKGROUND

Porcine islet transplantation into diabetic non-human primates is considered most relevant in translational research supporting a clinical application. Most studies have focused on immunosuppressive protocols, while metabolic aspects have mainly been utilized in graft monitoring. We evaluated data from our group regarding human and non-human primate (NHP) allotransplantation and pig-to-NHP xenotransplantation to identify incompatibilities in metabolic factors and their consequences for transplant outcomes.

METHODS

Basic gluco-metabolic parameters (fasting blood glucose, C-peptide, and response to stimulation with arginine or glucose) were derived from literature (humans), 72 macaques, and 47 adult Landrace pigs. Islet preparations from 15 human deceased donors, 61 macaques, and 23 adult pigs were compared with respect to yield, fractional viability assessed by oxygen consumption normalized for DNA, and in vitro glucose-induced insulin release. Metabolic parameters at day 75 after a single islet transplantation in the liver were compared for 19 patients and 9 macaques receiving an allotransplant and 11 macaques receiving a porcine xenotransplant: recipients received chronic immunosuppression.

RESULTS

Pigs differ from NHPs and humans by a much lower C-peptide level (0.42 vs. 1.3 to 2.0 ng/ml, respectively) and a 2- to 7-fold lower C-peptide response to arginine stimulation. In contrast, NHPs have the highest metabolic demand as evidenced by a high C-peptide and high C-peptide response to arginine stimulation; values are about twice higher than in humans. For manufactured islet preparations, these differences are reflected by glucose-stimulated insulin release (the stimulation index for pigs is 1.5, for humans 3.8, and for macaques 7.7), but not by fractional viability, which was in the same range. The day 75 outcome after transplantation assessed by C-peptide was similar for allotransplanted humans and NHPs (80 to 90% good graft function) and lower in xenografted NHPs (36% good graft function); gluco-metabolic parameters were in accordance with graft function, albeit different between species because normoglycemia under exogenous insulin is maintained more aggressively in patients than in NHPs. In xenografted NHPs, the shift in glycemic control with respect to normal values, combined with low values of circulating porcine C-peptide, resembled more the normal condition in a pig than that in a macaque.

CONCLUSIONS

The substantially lower glucose-induced insulin response in adult porcine islet preparations as opposed to islets manufactured from humans or macaques combined with the much higher need for insulin in macaques than in humans creates an imbalance between the metabolic demand and the engrafted islet mass in the pig-to-NHP xenograft recipient. Engrafted islet mass is affected by dose, suggesting that a much higher dose level of islets is necessary in the xenogeneic setting than in human or NHP allotransplantation, and pig islets need to be given at a higher dose in macaques than the anticipated effective dose in humans. To cope with differences in metabolic demand and presumably also metabolic dynamics, a liberal regime in supportive exogenous insulin might be essential to achieve long-term survival. These intrinsic characteristics of the NHP model deserve consideration to optimally design experimental studies with the perspective of translational value of results.

Streptozotocin-induced early thermal hyperalgesia is independent of glycemic state of rats: role of transient receptor potential vanilloid 1(TRPV1) and inflammatory mediators

Background

Streptozotocin (STZ) is used as a common tool to induce diabetes and to study diabetes-induced complications including diabetic peripheral neuropathy (DPN). Previously, we have reported that STZ induces a direct effect on neurons through expression and function of the Transient receptor potential vanilloid 1 (TRPV1) channel in sensory neurons resulting in thermal hyperalgesia, even in non-diabetic STZ-treated mice. In the present study, we investigated the role of expression and function of TRPV1 in the central sensory nerve terminals in the spinal cord in STZ-induced hyperalgesia in rats.

Results

We found that a proportion of STZ-treated rats were normoglycemic but still exhibited thermal hyperalgesia and mechanical allodynia. Immunohistochemical data show that STZ treatment, irrespective of glycemic state of the animal, caused microglial activation and increased expression of TRPV1 in spinal dorsal horn. Further, there was a significant increase in the levels of pro-inflammatory mediators (IL-1β, IL-6 and TNF-α) in spinal cord tissue, irrespective of the glycemic state. Capsaicin-stimulated release of calcitonin gene related peptide (CGRP) was significantly higher in the spinal cord of STZ-treated animals. Intrathecal administration of resiniferatoxin (RTX), a potent TRPV1 agonist, significantly attenuated STZ-induced thermal hyperalgesia, but not mechanical allodynia. RTX treatment also prevented the increase in TRPV1-mediated neuropeptide release in the spinal cord tissue.

Conclusions

From these results, it is concluded that TRPV1 is an integral component of initiating and maintaining inflammatory thermal hyperalgesia, which can be alleviated by intrathecal administration of RTX. Further, the results suggest that enhanced expression and inflammation-induced sensitization of TRPV1 at the spinal cord may play a role in central sensitization in STZ-induced neuropathy.

Comparison of metabolic and neuropathy profiles of rats with streptozotocin-induced overt and moderate insulinopenia

To assess the relative roles of insulinopenia, hyperglycemia and dyslipidemia in pathogenesis of diabetic neuropathy, we compared plasma insulin, glucose and lipid metabolism and peripheral nerve function in rats with streptozotocin (STZ)-induced overt and moderate insulinopenia (hyperglycemic, STZ-HG; random glucose>11 mM and normoglycemic, STZ-NG rats). While being slightly insulinopenic, STZ-NG rats are metabolically not different from control, naive animals, by having normal glucose tolerance and normal levels of plasma glucose, glycated HbA1c, cholesterol and triglycerides. Two weeks following injection of STZ, STZ-HG but not STZ-NG rats had suppressed motor nerve conduction velocity, F-wave prevalence, withdrawal responses to heat and von Frey filament stimuli. In apparent correlation with plasma insulin level, both STZ-HG and -NG rats manifested exaggerated responses in paw pressure and colorectal distension tests. These data suggest that insulinopenia may play a leading role in the diabetic impairment of deep muscle and visceral afferent pathways while hyperglycemia/dyslipidemia may represent a key requirement for the onset and progression of electrophysiological nerve impairment and loss of superficial heat and tactile perception. STZ-NG rats offer a convenient model for the investigation of the short-term effects of insulinopenia on peripheral nerve function.

The protective effect of testosterone on streptozotocin-induced apoptosis in beta cells is sex specific

OBJECTIVES

To investigate the protective role of steroid hormones on streptozotocin (STZ)-induced apoptosis in rat pancreatic beta cells.

METHODS

Two sets of experiments were performed. In the first, male rats were orchidectomized and substituted 72 hours later with testosterone, estradiol, or progesterone, and 24 hours later, administered with STZ. Subjects were killed 6 hours later, and apoptosis was determined in sections of the pancreas. In the second experiment, male or female rats were gonadectomized, were further substituted with testosterone, and then administered STZ. Six hours later, the animals were killed, and apoptosis, as well as immunoreactive expression of insulin, catalase, or Cu/Zn superoxide dismutase, was determined in sections of the pancreas. In addition, gonadectomized male or female subjects were substituted with testosterone and administered STZ, and 24 hours later, serum glucose and insulin were measured.

RESULTS

It was found that the cytoprotective effect was only shown in testosterone-treated male rats but not progesterone- or estradiol-treated male rats. In addition, the effect was seen in male rats but not in female rats, and there was an inverse correlation between apoptotic index and antioxidant enzyme immunoreactivity.

CONCLUSIONS

The cytoprotective effect of testosterone is sex specific and is related to the induction of antioxidant enzyme activities in pancreatic beta cells.

Lack of type VIII collagen in mice ameliorates diabetic nephropathy

OBJECTIVE

Key features of diabetic nephropathy include the accumulation of extracellular matrix proteins. In recent studies, increased expression of type VIII collagen in the glomeruli and tubulointerstitium of diabetic kidneys has been noted. The objectives of this study were to assess whether type VIII collagen affects the development of diabetic nephropathy and to determine type VIII collagen-dependent pathways in diabetic nephropathy in the mouse model of streptozotocin (STZ)-induced diabetes.

RESEARCH DESIGN AND METHODS

Diabetes was induced by STZ injections in collagen VIII-deficient or wild-type mice. Functional and histological analyses were performed 40 days after induction of diabetes. Type VIII collagen expression was assessed by Northern blots, immunohistochemistry, and real-time PCR. Proliferation of primary mesangial cells was measured by thymidine incorporation and direct cell counting. Expression of phosphorylated extracellular signal-regulated kinase (ERK1/2) and p27(Kip1) was assessed by Western blots. Finally, Col8a1 was stably overexpressed in mesangial cells.

RESULTS

Diabetic wild-type mice showed a strong renal induction of type VIII collagen. Diabetic Col8a1(-)/Col8a2(-) animals revealed reduced mesangial expansion and cellularity and extracellular matrix expansion compared with the wild type. These were associated with less albuminuria. High-glucose medium as well as various cytokines induced Col8a1 in cultured mesangial cells. Col8a1(-)/Col8a2(-) mesangial cells revealed decreased proliferation, less phosphorylation of Erk1/2, and increased p27(Kip1) expression. Overexpression of Col8a1 in mesangial cells induced proliferation.

CONCLUSIONS

Lack of type VIII collagen confers renoprotection in diabetic nephropathy. One possible mechanism is that type VIII collagen permits and/or fosters mesangial cell proliferation in early diabetic nephropathy.

Differential expression of GLUT2 in pancreatic islets and kidneys of New and Old World nonhuman primates

Diabetes is a growing public health concern, and animal models of this disease are necessary for a full understanding of disease pathogenesis, progression, clinical sequelae, and treatment options. In particular, nonhuman primate models of diabetes are important because of their close genetic relationship to humans. Although numerous Old World primate models have been described, few studies have examined the possibility of using New World monkeys as an animal model for this disease. Streptozotocin (STZ) is a common diabetogenic drug that selectively destroys beta cells after uptake via the GLUT2 glucose transporter. Induction of diabetes using STZ was attempted in common marmosets (Callithrix jacchus). These animals showed increases in blood glucose consistent with diabetes only at STZ doses markedly greater than those used in other primate species. Additionally, all animals showed pathological evidence of acute renal and liver toxicity secondary to the treatment. In a subsequent comparative study of various nonhuman primates, GLUT2 immunostaining in pancreatic islets was used as a marker for sensitivity to STZ. Immunostaining of islets from a variety of nonhuman primate species indicated a reduced expression of pancreatic GLUT2 in New compared with Old World monkeys; this finding explains their resistance to diabetic induction with STZ. Furthermore, there were age-dependent differences in GLUT2 expression, with aged and infant macaques showing reduced expression. We conclude that New World monkeys are an inappropriate model for diabetes induction with STZ and that, with all primate species, it is important to consider the animals' age before diabetic induction with STZ is attempted.

Pig islet xenotransplantation into non-human primate model

Allogeneic islet transplantation faces difficulties because (1) organ shortage is recurrent; (2) several pancreas donors are often needed to treat one diabetic recipient; and (3) the intrahepatic site of islet implantation may not be the most appropriate site. Another source of insulin-producing cells, therefore, would be of major interest, and pigs represent a possible and serious source for obtaining such cells. Pig islet grafts may seem difficult because of the species barrier, but recent reports demonstrate that pig islets may function in primates for at least 6 months. Pig islet xenotransplantation, however, must still overcome several hurdles before becoming clinically applicable. The actual consensus is to produce more preclinical data in the pig-to-primate model as a necessary requirement to envisage any pig-to-human transplantation of islets; therefore, a summary of the actual acquired knowledge of pig islet transplantation in primates seemed useful and is summarized in this overview.

Pancreatic endoderm derived from human embryonic stem cells generates glucose-responsive insulin-secreting cells in vivo

Development of a cell therapy for diabetes would be greatly aided by a renewable supply of human beta-cells. Here we show that pancreatic endoderm derived from human embryonic stem (hES) cells efficiently generates glucose-responsive endocrine cells after implantation into mice. Upon glucose stimulation of the implanted mice, human insulin and C-peptide are detected in sera at levels similar to those of mice transplanted with approximately 3,000 human islets. Moreover, the insulin-expressing cells generated after engraftment exhibit many properties of functional beta-cells, including expression of critical beta-cell transcription factors, appropriate processing of proinsulin and the presence of mature endocrine secretory granules. Finally, in a test of therapeutic potential, we demonstrate that implantation of hES cell-derived pancreatic endoderm protects against streptozotocin-induced hyperglycemia. Together, these data provide definitive evidence that hES cells are competent to generate glucose-responsive, insulin-secreting cells.

Streptozotocin-induced diabetes in large animals (pigs/primates): role of GLUT2 transporter and beta-cell plasticity

BACKGROUND

To induce irreversible diabetes in large animals, the efficiency of streptozotocin (STZ) was evaluated in pigs, primates and compared to the gold standard model in rats.

METHODS

Low (50 mg/kg) and high (150 mg/kg) doses of STZ were tested. Hepatic/renal function, glucose metabolism (intravenous glucose tolerance tests, fasting blood glucose) and histomorphometry were evaluated prior to, 1, and 4 weeks after STZ treatment.

RESULTS

In rats and primates, expressing a high level of GLUT2 expression on beta cells, a dose of 50 mg/kg STZ induced irreversible diabetes (due to the 97% destruction of beta cell mass) without provoking liver or renal failure. In pigs, despite the use of high STZ dose, partial correction of hyperglycaemia was observed four weeks after STZ injection (decreased fasting blood glucose and intravenous glucose tolerance tests; increased insulin production). The correction of hyperglycaemia was associated with significant hypertrophy of immature pig beta-cell clusters (+30%, P<0.05), whereas no hypertrophy was observed in rats/primates.

CONCLUSION

These results demonstrated that STZ might be used to induce irreversible diabetes in rats and primates. In contrast, the low STZ sensitivity in pigs related to a low expression of GLUT2, higher number of immature beta cells and compensatory beta-cell hypertrophy, renders STZ-induced diabetes inappropriate for studying islet allografts in swine.

Involvement of circadian clock geneClockin diabetes-induced circadian augmentation of plasminogen activator inhibitor-1 (PAI-1) expression in the mouse heart

Diabetes is associated with an excess risk of cardiac events, and one of the risk factors for infarction is the elevated-levels of plasminogen activator inhibitor-1 (PAI-1). To evaluate how the molecular clock mechanism is involved in the diabetes-induced circadian augmentation of PAI-1 gene expression, we examined the expression profiles of PAI-1 mRNA in the hearts of Clock mutant mice with streptozotocin-induced diabetes. Circadian expression of PAI-1 mRNA was blunted to low levels under both normal and diabetic conditions in Clock mutant mice, although the expression rhythm was augmented in diabetic wild-type (WT) mice. Furthermore, plasma PAI-1 levels became significantly higher in WT mice than in Clock mutant mice after STZ administration. Our results suggested that the circadian clock component, CLOCK, is involved in the diabetes-induced circadian augmentation of PAI-1 expression in the mouse heart.

Tissue-specific augmentation of circadian PAI-1 expression in mice with streptozotocin-induced diabetes

Diabetes is associated with an excess risk of cardiac events, and the risk for infarction is partly determined by plasminogen activator inhibitor-1 (PAI-1). We found that plasma total and active PAI-1 levels increased in a circadian manner in mice with streptozotocin (STZ)-induced diabetes. Circadian expression of PAI-1 mRNA in the lung, heart, liver, and kidney increased in a tissue-specific manner. Peak to peak comparisons revealed that the mRNA expression levels increased by 1.7, 1.7, 1.2, and 1.6-fold in the heart, lung, liver, and kidney, respectively. In contrast, the circadian expression of the clock gene, mPer2, was preserved in the diabetic mice, suggesting that the altered expression of PAI-1 mRNA did not arise due to impaired circadian clocks. Our results suggest that impairment of the coagulation and fibrinolytic systems induced by diabetes is partly due to impaired circadian PAI-1 fluctuation at the level of mRNA expression.

Gene- and tissue-specific alterations of circadian clock gene expression in streptozotocin-induced diabetic mice under restricted feeding

Circadian clocks are located in the suprachiasmatic nucleus (SCN) of the hypothalamus as well as in the peripheral tissues of mammals. Recent molecular studies have revealed that the phase of circadian gene expressions in peripheral clocks could entrain to time-imposed restricted feeding (RF) independently of the SCN. To elucidate whether endogenous insulin is involved in the entraining mechanisms of peripheral clocks to RF, we examined the expression profiles of clock genes in peripheral tissues of mice with diabetes induced by streptozotocin (STZ). The circadian expressing genes (mPer1, mPer2, and BMAL1) underwent a phase-shift induced by RF in the heart, liver, and kidney of both diabetic and normal animals. However, the expression phase of mPer1 in these tissues of the diabetic mice significantly differed from those in the normal animals under RF. The expression phase of the circadian output gene, albumin D-site binding protein (DBP), was completely shifted by RF both in normal and in diabetic mice, suggesting that the endogenous insulin is not essential for the entrainment of peripheral clocks to feeding cycles in mice.

Brain death significantly reduces isolated pancreatic islet yields and functionality in vitro and in vivo after transplantation in rats

Although approximately 1 million islets exist in the adult human pancreas, current pancreas preservation and islet isolation techniques recover <50%. Presently, cadaveric donors remain the sole source of pancreatic tissue for transplantation. Brain death is characterized by activation of proinflammatory cytokines and organ injury during preservation and reperfusion. In this study, we assessed the effects of brain death on islet isolation yields and functionality. Brain death was induced in male 250- to 350-g Lewis rats by inflation of a Fogarty catheter placed intracranially. The rats were mechanically ventilated for 2, 4, and 6 h before removal of the pancreas (n = 6). In controls, the catheter was not inflated (n = 6). Shortly after brain death induction, a significant increase in serum tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 was demonstrated in a time-dependent manner. Upregulation of TNF-alpha, IL-1beta, and IL-6 mRNA was noted in the pancreas. Brain death donors presented lower insulin release after glucose stimulation assessed by in situ perfusion of the pancreas. Islet recovery was reduced in brain death donors compared with controls (at 6 h 602.3 +/- 233.4 vs. 1,792.5 +/- 325.4 islet equivalents, respectively; P < 0.05). Islet viability assessed in dissociated islet cells and in intact cultured islets was reduced in islets recovered from brain death donors, an effect associated with higher nuclear activities of NF-kappaB p50, c-Jun, and ATF-2. Islet functionality evaluated in vitro by static incubation and in vivo after intraportal transplantation in syngeneic streptozotocin-induced diabetic rats was significantly reduced in preparations obtained from brain death donors. In conclusion, brain death significantly reduced islet yields and functionality. These observations may lead to strategies to reduce the effects of brain death on pancreatic islets and improve the results in clinical transplantation.