The islet endothelial cell: a novel contributor to beta cell secretory dysfunction in diabetes

Multifunctional Islet Transplantation Hydrogel Encapsulating A20 High-Expressing Islets

Islet transplantation is regarded as the most promising treatment for type 1 diabetes (T1D). However, the function of grafted islet could be damaged on account of transplant rejection and/or hypoxia several years later after transplantation. We proposed a hypothetical functionalized hydrogel model, which encapsulates sufficient A20 high-expressing islets and supporting cells, and performs as a drug release system releasing immunosuppressants and growth factors, to improve the outcome of pancreatic islet transplantation. Once injected in vivo, the hydrogel can gel and offer a robust mechanical structure for the A20 high-expressing islets and supporting cells. The natural biomaterials (eg, heparin) added into the hydrogel provide adhesive sites for islets to promote islets’ survival. Furthermore, the hydrogel encapsulates various supporting cells, which can facilitate the vascularization and/or prevent the immune system attacking the islet graft. Based on the previous studies that generally applied one or two combined strategies to protect the function of islet graft, we designed this hypothetical multifunctional encapsulation hydrogel model with various functions. We hypothesized that the islet graft could survive and maintain its function for a longer time in vivo compared with naked islets. This hypothetical model has a limitation in terms of clinical application. Future development work will focus on verifying the function and safety of this hypothetical islet transplantation hydrogel model in vitro and in vivo.

Paracrine regulation of insulin secretion

Pancreatic beta cells are the only cell type in our body capable of producing and secreting insulin to instruct the insulin-sensitive cells and tissues of our bodies to absorb nutrients after a meal. Accurate control of insulin release is of critical importance; too little insulin leads to diabetes, while an excess of insulin can cause potentially fatal hypoglycaemia. Yet, the pancreas of most people will control insulin secretion safely and effectively over decades and in response to glucose excursions driven by tens of thousands of meals. Because we only become aware of the important contributions of the pancreas when it fails to maintain glucose homeostasis, it is easy to forget just how well insulin release from a healthy pancreas is matched to insulin need to ensure stable blood glucose levels. Beta cells achieve this feat by extensive crosstalk with the rest of the endocrine cell types in the islet, notably the glucagon-producing alpha cells and somatostatin-producing delta cells. Here I will review the important paracrine contributions that each of these cells makes to the stimulation and subsequent inhibition of insulin release in response to a transient nutrient stimulation, and make the case that a breakdown of this local crosstalk contributes to the pathophysiology of diabetes. Graphical abstract.

Beta cell dysfunction in diabetes: the islet microenvironment as an unusual suspect

Cells in different tissues, including endocrine cells in the pancreas, live in complex microenvironments that are rich in cellular and acellular components. Intricate interactions with their microenvironment dictate most cellular properties, such as their function, structure and size, and maintain tissue homeostasis. Pancreatic islets are populated by endocrine, vascular and immune cells that are immersed in the extracellular matrix. While the intrinsic properties of beta cells have been vastly investigated, our understanding of their interactions with their surroundings has only recently begun to unveil. Here, we review current research on the interplay between the islet cellular and acellular components, and the role these components play in beta cell physiology and pathophysiology. Although beta cell failure is a key pathomechanism in diabetes, its causes are far from being fully elucidated. We, thus, propose deleterious alterations of the islet niche as potential underlying mechanisms contributing to beta cell failure. In sum, this review emphasises that the function of the pancreatic islet depends on all of its components. Graphical abstract.

Intricacies of the endothelin system in human obesity: role in the development of complications and potential as a therapeutic target

Activation of the vascular endothelin-1 (ET-1) system is a key abnormality in vascular dysfunction of human obesity, especially in patients developing complications, such as the metabolic syndrome, diabetes, and atherosclerosis. Vascular insulin resistance, an increased insulin-stimulated endothelial production of ET-1 combined with impaired nitric oxide availability, is the hallmark of obesity-related vasculopathy, but dysregulated adipokine release from obese adipose tissue may contribute to the predominance of ET-1-dependent vasoconstriction. ET-1, in turn, might determine unhealthy obese adipose tissue expansion, with visceral and perivascular adipose tissue changes driving the release of inflammatory cytokines and atherogenic chemokines. In addition, ET-1 might also play a role in the development of the metabolic complications of obesity. Studies have shown inhibition of lipoprotein lipase activity by ET-1, with consequent hypertriglyceridemia. Also, ET-1 in pancreatic islets seems to contribute to beta cell dysfunction, hence affecting insulin production and development of diabetes. Moreover, ET-1 may play a role in nonalcoholic steatohepatitis. Recent clinical trials using innovative design have demonstrated that antagonism of ET-type A receptors protects against some complications of obesity and diabetes, such as nephropathy. These findings encourage further investigation to evaluate whether targeting the ET-1 system could afford better protection against other consequences of the obesity epidemic.

Systemic AAV10.COMP-Ang1 rescues renal glomeruli and pancreatic islets in type 2 diabetic mice

INTRODUCTION

Diabetic hyperglycemia causes progressive and generalized damage to the microvasculature. In renal glomeruli, this results in the loss of podocytes with consequent loss of constitutive angiopoietin-1 (Ang1) signaling, which is required for stability of the glomerular endothelium. Repeated tail vein injection of adenovirus expressing COMP-Ang1 (a stable bioengineered form of Ang1) was previously reported to improve diabetic glomerular damage despite the liver and lungs being primary targets of adenoviral infection. We thus hypothesized that localizing delivery of sustained COMP-Ang1 to the kidney could increase its therapeutic efficacy and safety for the treatment of diabetes.

RESEARCH DESIGN AND METHODS

Using AAVrh10 adeno-associated viral capsid with enhanced kidney tropism, we treated 10-week-old uninephrectomized db/db mice (a model of type 2 diabetes) with a single dose of AAVrh10.COMP-Ang1 delivered via the intracarotid artery, compared with untreated diabetic db/db control and non-diabetic db/m mice.

RESULTS

Surprisingly, both glomerular and pancreatic capillaries expressed COMP-Ang1, compensating for diabetes-induced loss of tissue Ang1. Importantly, treatment with AAVrh10.COMP-Ang1 yielded a significant reduction of glycemia (blood glucose, 241±193 mg/dL vs 576±31 mg/dL; glycosylated hemoglobin, 7.2±1.5% vs 11.3±1.3%) and slowed the progression of albuminuria and glomerulosclerosis in db/db mice by 70% and 61%, respectively, compared with untreated diabetic db/db mice. Furthermore, COMP-Ang1 ameliorated diabetes-induced increases of NF-kBp65, nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase-2 (Nox2), p47phox and productions of myeloperoxidase, the inflammatory markers in both renal and pancreatic tissues, and improved beta-cell density in pancreatic islets.

CONCLUSIONS

These results highlight the potential of localized Ang1 therapy for treatment of diabetic visceropathies and provide a mechanistic explanation for reported improvements in glucose control via Ang1/Tie2 signaling in the pancreas.

Extracellular vesicles in diabetes mellitus induce alterations in endothelial cell morphology and migration

Background

Inflammation-related atherosclerotic peripheral vascular disease is a major end organ complication of diabetes mellitus that results in devastating morbidity and mortality. Extracellular vesicles (EVs) are nano-sized particles that contain molecular cargo and circulate in the blood. Here, we examined EV protein cargo from diabetic individuals and whether these EVs cause functional changes in endothelial cells.

Methods

We quantified inflammatory protein levels in plasma-derived EVs from a longitudinal cohort of euglycemic and diabetic individuals and used in vitro endothelial cell biological assays to assess the functional effects of these EVs with samples from a cross-sectional cohort.

Results

We found several significant associations between EV inflammatory protein levels and diabetes status. The angiogenic factor, vascular endothelial growth factor A (VEGF-A), was associated with diabetes status in our longitudinal cohort. Those with diabetes mellitus had higher EV VEGF-A levels compared to euglycemic individuals. Additionally, EV levels of VEGF-A were significantly associated with homeostatic model assessment of insulin resistance (HOMA-IR) and β-cell function (HOMA-B). To test whether EVs with different inflammatory cargo can demonstrate different effects on endothelial cells, we performed cell migration and immunofluorescence assays. We observed that EVs from diabetic individuals increased cell lamellipodia formation and migration when compared to EVs from euglycemic individuals.

Conclusions

Higher levels of inflammatory proteins were found in EVs from diabetic individuals. Our data implicate EVs as playing important roles in peripheral vascular disease that occur in individuals with diabetes mellitus and suggest that EVs may serve as an informative diagnostic tool for the disease.

MicroRNA-127 inhibits cell proliferation via targeting Kif3b in pancreatic β cells

MicroRNAs (miRNAs) have been implicated in β cells dysfunction. Previous studies indicated that miR-127 was specifically abundant in β cells and one of its target genes, Kif3b, promoted cell proliferation. However, the impact of the miR-127-Kif3b axis on β cells remains unknown. In this study, we revealed that miR-127 level was declined both in islets from the mice with a high-fat diet and in MIN6 cells with elevated glucose treatment. The elevated level of miR-127 attenuated β cell proliferation by repressing Kif3b expression without affecting apoptosis and cell cycle, and it dampened insulin secretion. Moreover, β cell-derived miR-127 could also affect the islet endothelial cell-line, MS1, in vitro via the transfer of extracellular vesicles (EVs). Treating MS1 cells with the EVs secreted by MIN6 cells exhibited a higher ability in cell migration and tube formation. However, this effect was abolished by the miR-127 inhibitor co-cultured with EVs-treated MS1 cells. Thus, we define that miR-127 is a crucial regulator of insulin secretion and cell proliferation in pancreatic β cells as well as a potential functional regulation factor in islet endothelial cells.

Mimicking nature-made beta cells: recent advances towards stem cell-derived islets

PURPOSE OF REVIEW

Stem cell-derived islets are likely to be useful as a future treatment for diabetes. However, the field has been limited in the ability to generate β-like cells with both phenotypic maturation and functional glucose-stimulated insulin secretion that is similar to primary human islets. The field must also establish a reliable method of delivering the cells to patients while promoting rapid in-vivo engraftment and function. Overcoming these barriers to β cell differentiation and transplantation will be key to bring this therapy to the clinic.

RECENT FINDINGS

The ability to generate stem cell-derived β-like cells capable of dynamic glucose-responsive insulin secretion, as well as β-like cells expressing key maturation genes has recently been demonstrated by several groups. Other groups have explored the potential of vascularized subcutaneous transplant sites, as well as endothelial cell co-transplant to support β cell survival and function following transplantation.

SUMMARY

The generation of stem cell-derived islets with dynamic glucose-responsive insulin secretion has brought the field closer to clinical translation, but there is still need for improving insulin content and secretory capacity, as well as understanding the factors affecting variable consistency and heterogeneity of the islet-like clusters. Other questions remain regarding how to address safety, immunogenicity and transplantation site moving forward.

Liraglutide ameliorates palmitate-induced oxidative injury in islet microvascular endothelial cells through GLP-1 receptor/PKA and GTPCH1/eNOS signaling pathways

In type 2 diabetes, lipotoxicity damages islet microvascular endothelial cells (IMECs), leading to pancreatic islet β cell dysfunction directly or indirectly. Glucagon-like peptide-1 (GLP-1) and its analogs have beneficial roles in endothelial cells. However, the protective effects of GLP-1 agents on IMECs and their potential mechanism remained obscure. In this study, exposure of MS-1 (a cell line derived from mouse IMECs) to different concentrations of palmitic acid (PA) was used to establish an injury model. The cells exposed to PA (0.25 mmol/L) were treated with a GLP-1 analog liraglutide (3, 10, 30, and 100 nmol/L). Reactive oxygen species (ROS) generation, apoptosis-related protein level, and endothelin-1 production were detected. The protein levels of signaling molecules were analyzed and specific inhibitors or blockers were used to identify involvement of signaling pathways in the effects of liraglutide. Results showed that PA significantly increased ROS generation and the levels of pro-apoptotic protein Bax, and decreased the levels of anti-apoptotic protein Bcl-2 and the mRNA expression and secretion of endothelin-1. Meanwhile, PA downregulated the protein levels of GLP-1 receptor (GLP-1R), phosphorylated protein kinase A (PKA), guanosine 5'-triphosphate cyclohydrolase 1 (GTPCH1), and endothelial nitric oxide synthase (eNOS). Furthermore, liraglutide ameliorated all these effects of PA in a dose-dependent manner. Importantly, GLP-1R antagonist exendin (9-39), PKA inhibitor H89, GTPCH1 inhibitor 2,4-diamino-6-hydroxypyrimidine, or NOS inhibitor N-nitro-l-arginine-methyl ester abolished the liraglutide-mediated amelioration in PA-impaired MS-1 cells. In conclusion, liraglutide ameliorates the PA-induced oxidative stress, apoptosis, and endothelin-1 secretion dysfunction in mouse IMECs through GLP-1R/PKA and GTPCH1/eNOS signaling pathways.

Islet Stellate Cells Regulate Insulin Secretion via Wnt5a in Min6 Cells

BACKGROUND

Type 2 diabetes mellitus is a serious public health problem worldwide. Accumulating evidence has shown that β-cell dysfunction is an important mechanism underlying diabetes mellitus. The changes in the physiological state of islet stellate cells (ISCs) and the effects of these cells on β-cell dysfunction is an important mechanism underlying diabetes mellitus. The changes in the physiological state of islet stellate cells (ISCs) and the effects of these cells on.

METHODS

Glucose-stimulated insulin secretion (GSIS) from Min6 cells was examined by estimating the insulin levels in response to high glucose challenge after culture with ISC supernatant or exogenous Wnt5a. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) analyses were used to observe changes in the β-cell dysfunction is an important mechanism underlying diabetes mellitus. The changes in the physiological state of islet stellate cells (ISCs) and the effects of these cells on.

RESULTS

We observed a significant increase in insulin secretion from Min6 cells cocultured in vitro with supernatant from db/m mouse ISCs compared to that from Min6 cells cocultured with supernatant from db/db mouse ISCs; The intracellular Ca²⁺ concentration in Min6 cells increased in cultured in vitro with supernatant from db/m mouse ISCs and exogenous Wnt5a compared to that from control Min6 cells. Culture of Min6 cells with exogenous Wnt5a caused a significant increase in pCamKII, pFoxO1, PDX-1, and Glut2 levels compared to those in Min6 cells cultured alone; this treatment further decreased Ror2 and Cask expression but did not affect β-cell dysfunction is an important mechanism underlying diabetes mellitus. The changes in the physiological state of islet stellate cells (ISCs) and the effects of these cells on.

CONCLUSION

ISCs regulate insulin secretion from Min6 cells through the Wnt5a protein-induced Wnt-calcium and FoxO1-PDX1-GLUT2-insulin signalling cascades.

The Role of the Islet Niche on Beta Cell Structure and Function

The islets of Langerhans or pancreatic islets are pivotal in the control of blood glucose and are complex microorgans embedded within the larger volume of the exocrine pancreas. Humans can have ~3.2 million islets [1] which, to our current knowledge, function in a similar manner to sense circulating blood glucose levels and respond with the secretion of a mix of different hormones that act to maintain glucose concentrations around a specific set point [2]. At a cellular level, the control of hormone secretion by glucose and other secretagogues is well-understood [3]. The key signal cascades have been identified and many details of the secretory process are known. However, if we shift focus from single cells and consider cells within intact islets, we do not have a comprehensive model as to how the islet environment influences cell function and how the islets work as a whole. This is important because there is overwhelming evidence that the structure and function of the individual endocrine cells are dramatically affected by the islet environment [4,5]. Uncovering the influence of this islet niche might drive future progress in treatments for Type 2 diabetes [6] and cell replacement therapies for Type 1 diabetes [7]. In this review, we focus on the insulin secreting beta cells and their interactions with the immediate environment that surrounds them including endocrine-endocrine interactions and contacts with capillaries.

Disruption of the pancreatic vasculature in zebrafish affects islet architecture and function

A dense local vascular network is crucial for pancreatic endocrine cells to sense metabolites and secrete hormones, and understanding the interactions between the vasculature and the islets may allow for therapeutic modulation in disease conditions. Using live imaging in two models of vascular disruption in zebrafish, we identified two distinct roles for the pancreatic vasculature. At larval stages, expression of a dominant negative version of Vegfaa (dnVegfaa) in β-cells led to vascular and endocrine cell disruption with a minor impairment in β-cell function. In contrast, expression of a soluble isoform of Vegf receptor 1 (sFlt1) in β-cells blocked the formation of the pancreatic vasculature and drastically stunted glucose response, although islet architecture was not affected. Notably, these effects of dnVegfaa or sFlt1 were not observed in animals lacking vegfaa, vegfab, kdrl, kdr or flt1 function, indicating that they interfere with multiple ligands and/or receptors. In adults, disrupted islet architecture persisted in dnVegfaa-expressing animals, whereas sFlt1-expressing animals displayed large sheets of β-cells along their pancreatic ducts, accompanied by impaired glucose tolerance in both models. Thus, our study reveals novel roles for the vasculature in patterning and function of the islet.

In vivo-mimicking microfluidic perfusion culture of pancreatic islet spheroids

Native pancreatic islets interact with neighboring cells by establishing three-dimensional (3D) structures, and are surrounded by perfusion at an interstitial flow level. However, flow effects are generally ignored in islet culture models, although cell perfusion is known to improve the cell microenvironment and to mimic in vivo physiology better than static culture systems. Here, we have developed functional islet spheroids using a microfluidic chip that mimics interstitial flow conditions with reduced shear cell damage. Dynamic culture, compared to static culture, enhanced islet health and maintenance of islet endothelial cells, reconstituting the main component of islet extracellular matrix within spheroids. Optimized flow condition allowed localization of secreted soluble factors near spheroids, facilitating diffusion-mediated paracrine interactions within islets, and enabled long-term maintenance of islet morphology and function for a month. The proposed model can aid islet preconditioning before transplantation and has potential applications as an in vitro model for diabetic drug testing.

Extracellular Vesicles in Type 1 Diabetes: Messengers and Regulators

PURPOSE OF REVIEW

Theories about the pathogenesis of type 1 diabetes (T1D) refer to the potential of primary islet inflammatory signaling as a trigger for the loss of self-tolerance leading to disease onset. Emerging evidence suggests that extracellular vesicles (EV) may represent the missing link between inflammation and autoimmunity. Here, we review the evidence for a role of EV in the pathogenesis of T1D, as well as discuss their potential value in the clinical sphere, as biomarkers and therapeutic agents.

RECENT FINDINGS

EV derived from β cells are enriched in diabetogenic autoantigens and miRNAs that are selectively sorted and packaged. These EV play a pivotal role in antigen presentation and cell to cell communication leading to activation of autoimmune responses. Furthermore, recent evidence suggests the potential of EV as novel tools in clinical diagnostics and therapeutic interventions. In-depth analysis of EV cargo using modern multi-parametric technologies may be useful in enhancing our understanding of EV-mediated immune mechanisms and in identifying robust biomarkers and therapeutic strategies for T1D.

β-Cell-Derived Angiopoietin-1 Regulates Insulin Secretion and Glucose Homeostasis by Stabilizing the Islet Microenvironment

Islets are highly vascularized for prompt insulin secretion. Although angiopoietin-1 (Ang1) is a well-known angiogenic factor, its role in glucose homeostasis remains largely unknown. The objective of this study was to investigate whether and how Ang1 contributes to glucose homeostasis in response to metabolic challenge. We used inducible systemic Ang1 knockout (Ang1^sys-/-) and β-cell-specific Ang1 knockout (Ang1^β-cell-/-) mice fed a high-fat diet for 24 weeks. Although the degree of insulin sensitivity did not differ between Ang1^sys-/- and Ang1^sys+/+ mice, serum insulin levels were lower in Ang1^sys-/- mice, resulting in significant glucose intolerance. Similar results were observed in Ang1^β-cell-/- mice, suggesting a critical role of β-cell-derived Ang1 in glucose homeostasis. There were no differences in β-cell area or vasculature density, but glucose-stimulated insulin secretion was significantly decreased, and PDX-1 expression and GLUT2 localization were altered in Ang1^β-cell-/- compared with Ang1^β-cell+/+ mice. These effects were associated with less pericyte coverage, disorganized endothelial cell ultrastructure, and enhanced infiltration of inflammatory cells and upregulation of adhesion molecules in the islets of Ang1^β-cell-/- mice. In conclusion, β-cell-derived Ang1 regulates insulin secretion and glucose homeostasis by stabilizing the blood vessels in the islet and may be a novel therapeutic target for diabetes treatment in the future.

Association between sarcopenia and erectile dysfunction in males with type II diabetes mellitus

BACKGROUND

The prevalence rates for both sarcopenia and erectile dysfunction (ED) gradually increase in middle-aged and elderly diabetic male population and they impair physical functioning, sexual functioning, and quality of life. The aim of the present study was to evaluate the sarcopenia in patients with diabetic ED.

METHODS

The study included 98 male patients with type II diabetes mellitus (DM) aged 18-80 years. Blood chemistry and hormone levels were obtained. The International Index of Erectile Function (IIEF-5) questionnaire was administered to the patients. The patients were divided into three groups according to the IIEF-5 score; a score of 5-10 points indicated severe ED, a score of 11-20 indicated moderate ED, and a score of 21-25 points indicated no ED. The muscle mass, handgrip strength, timed up and go test, upper mid-arm circumference, calf circumference, and body mass index were obtained. The statistical analysis was performed using MedCalc Statistical Software version 12.7.7. All parameters were compared between the three groups.

RESULTS

Of 98 patients included in the study, 84 patients had severe sarcopenia, 13 had moderate sarcopenia, while only one patient had normal muscle mass. The mean age was 56.59 ± 11.46 years. When patients were divided into three groups according to IIEF-5 score, 38 had severe ED, 39 had moderate ED, and 21 had no ED. There was a significant difference between the three groups in terms of handgrip strength, timed up and go test scores, upper mid-arm circumference, and calf circumference (p < .05 for all).

CONCLUSIONS

Although muscle mass remains unchanged, muscle strength and physical performance decrease in diabetic ED patients. Diabetic patients with severe and moderate ED have lower muscle strength and physical performance.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Adrb2 controls glucose homeostasis by developmental regulation of pancreatic islet vasculature

A better understanding of processes controlling the development and function of pancreatic islets is critical for diabetes prevention and treatment. Here, we reveal a previously unappreciated function for pancreatic β2-adrenergic receptors (Adrb2) in controlling glucose homeostasis by restricting islet vascular growth during development. Pancreas-specific deletion of Adrb2 results in glucose intolerance and impaired insulin secretion in mice, and unexpectedly, specifically in females. The metabolic phenotypes were recapitulated by Adrb2 deletion from neonatal, but not adult, β-cells. Mechanistically, Adrb2 loss increases production of Vascular Endothelial Growth Factor-A (VEGF-A) in female neonatal β-cells and results in hyper-vascularized islets during development, which in turn, disrupts insulin production and exocytosis. Neonatal correction of islet hyper-vascularization, via VEGF-A receptor blockade, fully rescues functional deficits in glucose homeostasis in adult mutant mice. These findings uncover a regulatory pathway that functions in a sex-specific manner to control glucose metabolism by restraining excessive vascular growth during islet development.

Microvascular Dysfunction and Hyperglycemia: A Vicious Cycle With Widespread Consequences

Microvascular and metabolic physiology are tightly linked. This Perspective reviews evidence that 1) the relationship between hyperglycemia and microvascular dysfunction (MVD) is bidirectional and constitutes a vicious cycle; 2) MVD in diabetes affects many, if not all, organs, which may play a role in diabetes-associated comorbidities such as depression and cognitive impairment; and 3) MVD precedes, and contributes to, hyperglycemia in type 2 diabetes (T2D) through impairment of insulin-mediated glucose disposal and, possibly, insulin secretion. Obesity and adverse early-life exposures are important drivers of MVD. MVD can be improved through weight loss (in obesity) and through exercise. Pharmacological interventions to improve MVD are an active area of investigation.

Danggui Sini Decoction Protected Islet Endothelial Cell Survival from Hypoxic Damage via PI3K/Akt/eNOS Pathway

Danggui Sini decoction (DSD) is a traditional Chinese decoction, which is wildly applied and showed to be effective in ameliorating ischemia-related symptoms. However, the mechanisms of DSD action in ischemic damage remain to be fully clarified. Pancreatic islet endothelial cells are pivotal constituent of islet microvasculature, with high vulnerability to hypoxic injuries. Here, using MST1 cell, a pancreatic islet endothelial cell-line, as a model, we investigated the effects of DSD on hypoxia-stimulated endothelial cell lesions and its underlying mechanisms. We found that DSD-Containing Serum (DSD-CS), collected from DSD-treated rats, could efficiently protect MST1 survival and proliferation from Cobalt chloride (CoCl₂) induced damage, including cell viability, proliferation, and tube formation. Furthermore, DSD-CS restored the activity of PI3K/Akt/eNOS signaling inhibited by CoCl₂ in MST1 cells. The protective effect of DSD-CS could be blocked by the specific PI3K/Akt/eNOS inhibitor LY294002, suggesting that DSD-CS protection of MST1 cell survival from hypoxia was mediated by PI3K/Akt/eNOS pathway. In conclusion, DSD treatment protected MST1 survival from hypoxic injuries via PI3K/Akt/eNOS pathway, indicating its role in protecting microvascular endothelial cells.

Islet Microvasculature Alterations With Loss of Beta-cells in Patients With Type 1 Diabetes

Islet microvasculature provides key architectural and functional roles, yet the morphological features of islets from patients with type 1 diabetes are poorly defined. We examined islet and exocrine microvasculature networks by multiplex immunofluorescence imaging of pancreases from organ donors with and without type 1 diabetes (n=17 and n=16, respectively) and determined vessel diameter, density, and area. We also analyzed these variables in insulin-positive and insulin-negative islets of 7 type 1 diabetes donors. Control islet vessel diameter was significantly larger (7.6 ± 1.1 μm) compared with vessels in diabetic islets (6.2 ± 0.8 μm; p<0.001). Control islet vessel density (number/islet) was significantly lower (5.3 ± 0.6) versus diabetic islets (9.3 ± 0.2; p<0.001). Exocrine vessel variables were not significantly different between groups. Islets with residual beta-cells were comparable to control islets for both vessel diameter and density and were significantly different from insulin-negative islets within diabetic donors (p<0.05). Islet smooth muscle actin area had a significant positive correlation with age in both groups (p<0.05), which could negatively impact islet transplantation efficiency from older donors. These data underscore the critical relationship of islet beta-cells and islet vessel morphology in type 1 diabetes. These studies provide new knowledge of the islet microvasculature in diabetes and aging.

Endothelial and beta cell composite aggregates for improved function of a bioartificial pancreas encapsulation device

INTRODUCTION

Encapsulation of pancreatic islets or beta cells is a promising strategy for treatment of type 1 diabetes by providing an immune isolated environment and allowing for transplantation in a different location than the liver. However, islets used for encapsulation often show lower functionality due to the damaging of islet endothelial cells during the isolation procedure. Factors produced by endothelial cells have great impact on beta cell insulin secretion. Therefore, mutual signaling between endothelial cells and beta cells should be considered for the development of encapsulation systems to achieve high insulin secretion and maintain beta cell viability. Here, we investigate whether co-culture of beta cells with endothelial cells could improve beta cell function within encapsulation devices.

MATERIALS AND METHODS

Mouse insulinoma MIN6 cells and human umbilical vein endothelial cells were used for creating composite aggregates on agarose microwell platform. The composite aggregates were encapsulated within flat poly(ether sulfone)/polyvinylpyrrolidone device. Their functionality was assessed by glucose-induced insulin secretion test and compared to non-encapsulated free-floating aggregates.

RESULTS

We created composite aggregates of 80-100 µm in diameter, closely mimicking pancreatic islets. Upon glucose stimulation, their insulin secretion is improved in comparison to aggregates consisting of only MIN6 cells. Moreover, the composite aggregates encapsulated within a device secrete more insulin than aggregates consisting of only MIN6 cells.

CONCLUSION

Composite aggregates of MIN6 cells with human umbilical vein endothelial cells have improved insulin secretion in comparison to MIN6 aggregates showing that the interaction of beta cell and endothelial cell is crucial for a functional encapsulation system.

Type I Interferon Is a Catastrophic Feature of the Diabetic Islet Microenvironment

A detailed understanding of the molecular pathways and cellular interactions that result in islet beta cell (β cell) destruction is essential for the development and implementation of effective therapies for prevention or reversal of type 1 diabetes (T1D). However, events that define the pathogenesis of human T1D have remained elusive. This gap in our knowledge results from the complex interaction between genetics, the immune system, and environmental factors that precipitate T1D in humans. A link between genetics, the immune system, and environmental factors are type 1 interferons (T1-IFNs). These cytokines are well known for inducing antiviral factors that limit infection by regulating innate and adaptive immune responses. Further, several T1D genetic risk loci are within genes that link innate and adaptive immune cell responses to T1-IFN. An additional clue that links T1-IFN to T1D is that these cytokines are a known constituent of the autoinflammatory milieu within the pancreas of patients with T1D. The presence of IFNα/β is correlated with characteristic MHC class I (MHC-I) hyperexpression found in the islets of patients with T1D, suggesting that T1-IFNs modulate the cross-talk between autoreactive cytotoxic CD8⁺ T lymphocytes and insulin-producing pancreatic β cells. Here, we review the evidence supporting the diabetogenic potential of T1-IFN in the islet microenvironment.