Distinct roles of β-cell mass and function during type 1 diabetes onset and remission

The anterior chamber of the eye technology and its anatomical, optical, and immunological bases

The anterior chamber of the eye (ACE) is distinct in its anatomy, optics, and immunology. This guarantees that the eye perceives visual information in the context of physiology even when encountering adverse incidents like inflammation. In addition, this endows the ACE with the special nursery bed iris enriched in vasculatures and nerves. The ACE constitutes a confined space enclosing an oxygen/nutrient-rich, immune-privileged, and less stressful milieu as well as an optically transparent medium. Therefore, aside from visual perception, the ACE unexpectedly serves as an excellent transplantation site for different body parts and a unique platform for noninvasive, longitudinal, and intravital microimaging of different grafts. On the basis of these merits, the ACE technology has evolved from the prototypical through the conventional to the advanced version. Studies using this technology as a versatile biomedical research platform have led to a diverse range of basic knowledge and in-depth understanding of a variety of cells, tissues, and organs as well as artificial biomaterials, pharmaceuticals, and abiotic substances. Remarkably, the technology turns in vivo dynamic imaging of the morphological characteristics, organotypic features, developmental fates, and specific functions of intracameral grafts into reality under physiological and pathological conditions. Here we review the anatomical, optical, and immunological bases as well as technical details of the ACE technology. Moreover, we discuss major achievements obtained and potential prospective avenues for this technology.

Mouse models and human islet transplantation sites for intravital imaging

Human islet transplantations into rodent models are an essential tool to aid in the development and testing of islet and cellular-based therapies for diabetes prevention and treatment. Through the ability to evaluate human islets in an in vivo setting, these studies allow for experimental approaches to answer questions surrounding normal and disease pathophysiology that cannot be answered using other in vitro and in vivo techniques alone. Intravital microscopy enables imaging of tissues in living organisms with dynamic temporal resolution and can be employed to measure biological processes in transplanted human islets revealing how experimental variables can influence engraftment, and transplant survival and function. A key consideration in experimental design for transplant imaging is the surgical placement site, which is guided by the presence of vasculature to aid in functional engraftment of the islets and promote their survival. Here, we review transplantation sites and mouse models used to study beta cell biology in vivo using intravital microscopy and we highlight fundamental observations made possible using this methodology.

Glycemic Variability Patterns Strongly Correlate With Partial Remission Status in Children With Newly Diagnosed Type 1 Diabetes

OBJECTIVE

To evaluate whether indexes of glycemic variability may overcome residual β-cell secretion estimates in the longitudinal evaluation of partial remission in a cohort of pediatric patients with new-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS

Values of residual β-cell secretion estimates, clinical parameters (e.g., HbA1c or insulin daily dose), and continuous glucose monitoring (CGM) from 78 pediatric patients with new-onset type 1 diabetes were longitudinally collected during 1 year and cross-sectionally compared. Circadian patterns of CGM metrics were characterized and correlated to remission status using an adjusted mixed-effects model. Patients were clustered based on 46 CGM metrics and clinical parameters and compared using nonparametric ANOVA.

RESULTS

Study participants had a mean (± SD) age of 10.4 (± 3.6) years at diabetes onset, and 65% underwent partial remission at 3 months. β-Cell residual secretion estimates demonstrated weak-to-moderate correlations with clinical parameters and CGM metrics (r2 = 0.05-0.25; P < 0.05). However, CGM metrics strongly correlated with clinical parameters (r2 >0.52; P < 0.05) and were sufficient to distinguish remitters from nonremitters. Also, CGM metrics from remitters displayed specific early morning circadian patterns characterized by increased glycemic stability across days (within 63-140 mg/dL range) and decreased rate of grade II hypoglycemia (P < 0.0001) compared with nonremitters. Thorough CGM analysis allowed the identification of four novel glucotypes (P < 0.001) that segregate patients into subgroups and mirror the evolution of remission after diabetes onset.

CONCLUSIONS

In our pediatric cohort, combination of CGM metrics and clinical parameters unraveled key clinical milestones of glucose homeostasis and remission status during the first year of type 1 diabetes.

The Theory of Hyperlipidemic Memory of Type 1 Diabetes

A literature search was conducted to identify publications addressing the early phases of lipid phenotypes in children and adults with either type 1 diabetes or type 2 diabetes. Medline, EMBASE, and Ovid were searched using the following search terms: clinical remission, partial remission, partial clinical remission, honeymoon phase, C-peptide, type 1 or 2 diabetes, children, pediatric type 1 or 2 diabetes, and paediatrics type 1 or 2 diabetes, adults, adult type 1 or type 2 diabetes. Partial clinical remission (PR) of type 1 diabetes (T1D) is characterized by continued endogenous production of insulin and C-peptide following the diagnosis and the introduction of exogenous insulin therapy. PR is associated with improved glycemic control and reduced prevalence of diabetes complications. The theory of hyperglycemic memory was proposed to explain this concept of improved glycemic outcomes in remitters (those who experienced PR) versus non-remitters (those who did not experience PR). However, this theory is incomplete as it does not explain the dichotomy in early lipid phenotypes in T1D based on PR status, which is an understudied area in diabetology and lipidology. To fill this knowledge gap, we propose the Theory of Hyperlipidemic Memory of T1D. This theory is premised on our 5-year research on early post-diagnostic dichotomy in lipid phenotypes between remitters and non-remitters across the lifespan. It provides a more rigorous explanation for the differences in lifelong atherosclerotic cardiovascular disease (ASCVD) risk between remitters and non-remitters. We conducted 4 clinical studies in pediatric and adult subjects with diabetes mellitus to characterize the particulars of the hyperlipidemic memory. In the first investigation, we explored the impact of the presence or absence of PR on lipid parameters in children and adolescents with T1D. In the second, we investigated whether pubertal maturation influenced our findings in T1D; and whether these findings could be replicated in healthy, non-diabetic children and adolescents. In the third, we leveraged our findings from T1D and controls to investigate the mechanisms of early lipid changes in T2D by comparing the earliest lipid phenotype of subjects with type 2 diabetes (T2D) to those of remitters, non-remitters, and controls. In the fourth, we investigated the impact of PR on the earliest lipid phenotypes in adults with T1D and compared these early lipid data to those of T2D subjects and controls. This body of work across the lifespan in children, adolescents, and adults supports the Theory of Hyperlipidemic Memory. This new theory clarifies why PR largely determines the risks for early-phase dyslipidemia, mid-term microvascular disease risk, and long-term ASCVD risk in subjects with T1D.

Cell Networks in Endocrine/Neuroendocrine Gland Function

Reproduction, growth, stress, and metabolism are determined by endocrine/neuroendocrine systems that regulate circulating hormone concentrations. All these systems generate rhythms and changes in hormone pulsatility observed in a variety of pathophysiological states. Thus, the output of endocrine/neuroendocrine systems must be regulated within a narrow window of effective hormone concentrations but must also maintain a capacity for plasticity to respond to changing physiological demands. Remarkably most endocrinologists still have a "textbook" view of endocrine gland organization which has emanated from 20^th century histological studies on thin 2D tissue sections. However, 21^st -century technological advances, including in-depth 3D imaging of specific cell types have vastly changed our knowledge. We now know that various levels of multicellular organization can be found across different glands, that organizational motifs can vary between species and can be modified to enhance or decrease hormonal release. This article focuses on how the organization of cells regulates hormone output using three endocrine/neuroendocrine glands that present different levels of organization and complexity: the adrenal medulla, with a single neuroendocrine cell type; the anterior pituitary, with multiple intermingled cell types; and the pancreas with multiple intermingled cell types organized into distinct functional units. We give an overview of recent methodologies that allow the study of the different components within endocrine systems, particularly their temporal and spatial relationships. We believe the emerging findings about network organization, and its impact on hormone secretion, are crucial to understanding how homeostatic regulation of endocrine axes is carried out within endocrine organs themselves. © 2022 American Physiological Society. Compr Physiol 12:3371-3415, 2022.

Autoimmunity in motion: Mechanisms of immune regulation and destruction revealed by in vivo imaging

Autoimmunity arises when mechanisms of immune tolerance fail. Here we discuss mechanisms of T cell activation and tolerance and the dynamics of the autoimmune response at the site of disease. Live imaging of autoimmunity provides the ability to analyze immune cell dynamics at the single-cell level within the complex intact environment where disease occurs. These analyses have revealed mechanisms of T cell activation and tolerance in the lymph nodes, mechanisms of T cell entry into sites of autoimmune disease, and mechanisms leading to pathogenesis or protection in the autoimmune lesions. The overarching conclusions point to stable versus transient T cell antigen presenting cell interactions dictating the balance between T cell activation and tolerance, and T cell restimulation as a driver of pathogenesis at the site of autoimmunity. Findings from models of multiple sclerosis and type 1 diabetes are highlighted, however, the results have implications for basic mechanisms of T cell regulation during immune responses, tumor immunity, and autoimmunity.

The β Cell in Diabetes: Integrating Biomarkers With Functional Measures

The pathogenesis of hyperglycemia observed in most forms of diabetes is intimately tied to the islet β cell. Impairments in propeptide processing and secretory function, along with the loss of these vital cells, is demonstrable not only in those in whom the diagnosis is established but typically also in individuals who are at increased risk of developing the disease. Biomarkers are used to inform on the state of a biological process, pathological condition, or response to an intervention and are increasingly being used for predicting, diagnosing, and prognosticating disease. They are also proving to be of use in the different forms of diabetes in both research and clinical settings. This review focuses on the β cell, addressing the potential utility of genetic markers, circulating molecules, immune cell phenotyping, and imaging approaches as biomarkers of cellular function and loss of this critical cell. Further, we consider how these biomarkers complement the more long-established, dynamic, and often complex measurements of β-cell secretory function that themselves could be considered biomarkers.

Modeling plasticity and dysplasia of pancreatic ductal organoids derived from human pluripotent stem cells

Personalized in vitro models for dysplasia and carcinogenesis in the pancreas have been constrained by insufficient differentiation of human pluripotent stem cells (hPSCs) into the exocrine pancreatic lineage. Here, we differentiate hPSCs into pancreatic duct-like organoids (PDLOs) with morphological, transcriptional, proteomic, and functional characteristics of human pancreatic ducts, further maturing upon transplantation into mice. PDLOs are generated from hPSCs inducibly expressing oncogenic GNAS, KRAS, or KRAS with genetic covariance of lost CDKN2A and from induced hPSCs derived from a McCune-Albright patient. Each oncogene causes a specific growth, structural, and molecular phenotype in vitro. While transplanted PDLOs with oncogenic KRAS alone form heterogenous dysplastic lesions or cancer, KRAS with CDKN2A loss develop dedifferentiated pancreatic ductal adenocarcinomas. In contrast, transplanted PDLOs with mutant GNAS lead to intraductal papillary mucinous neoplasia-like structures. Conclusively, PDLOs enable in vitro and in vivo studies of pancreatic plasticity, dysplasia, and cancer formation from a genetically defined background.

The Eye as a Transplantation Site to Monitor Pancreatic Islet Cell Plasticity

The endocrine cells confined in the islets of Langerhans are responsible for the maintenance of blood glucose homeostasis. In particular, beta cells produce and secrete insulin, an essential hormone regulating glucose uptake and metabolism. An insufficient amount of beta cells or defects in the molecular mechanisms leading to glucose-induced insulin secretion trigger the development of diabetes, a severe disease with epidemic spreading throughout the world. A comprehensive appreciation of the diverse adaptive procedures regulating beta cell mass and function is thus of paramount importance for the understanding of diabetes pathogenesis and for the development of effective therapeutic strategies. While significant findings were obtained by the use of islets isolated from the pancreas, in vitro studies are inherently limited since they lack the many factors influencing pancreatic islet cell function in vivo and do not allow for longitudinal monitoring of islet cell plasticity in the living organism. In this respect a number of imaging methodologies have been developed over the years for the study of islets in situ in the pancreas, a challenging task due to the relatively small size of the islets and their location, scattered throughout the organ. To increase imaging resolution and allow for longitudinal studies in individual islets, another strategy is based on the transplantation of islets into other sites that are more accessible for imaging. In this review we present the anterior chamber of the eye as a transplantation and imaging site for the study of pancreatic islet cell plasticity, and summarize the major research outcomes facilitated by this technological platform.

Mechanisms and early patterns of dyslipidemia in pediatric type 1 and type 2 diabetes

Objectives The is no consensus on the early patterns of lipid-based cardiovascular disease (CVD) risk in youth with either type 1 diabetes (T1D) or type 2 diabetes (T2D). The aim was todetermine the differences in CVD risk, using lipid profiles, in children and adolescents with either T1D or T2D at the time of their first lipid assessment, after stratifying the T1D cohort into remitters and non-remitters based on their honeymoon history. Methods A cross-sectional study of 249 subjects consisting of 73 controls, 53 T2D subjects, and 123 T1D subjects stratified into remitters (n=44), and non-remitters (n=79). Partial clinical remission (PCR) was defined as insulin-dose adjusted HbA1c of ≤9. Pubertal status was determined by Tanner staging. Results After adjusting for age, sex, BMI, race, and pubertal status, T2D patients had significantly higher LDL-C compared to the controls (p=0.022), the remitters (p=0.029), but not the non-remitters (103.1 ± 5.9 mg/dL vs. 91.4 ± 4.2 mg/dL, p=0.49). Similarly, T2D patients had significantly higher non-HDL-C compared to the controls (p=0.006), the remitters (p=0.0002), but not the non-remitters (137.6 ± 7.1 mg/dL vs. 111.71 ± 5.0 mg/dL, p=0.053). Total cholesterol was also significantly higher in T2D patients compared to the controls (p=0.0005), the remitters (p=0.006) but not the non-remitters (183.5 ± 6.6 mg/dL vs. 166.2 ± 4.8 mg/dL, p=0.27). Conclusions Lack of the honeymoon phase in children and adolescents with T1D confers early and significantly increased lipid-based cardiovascular risk to these patients that is similar to the elevated cardiovascular risk seen in T2D.

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.

RETRACTED: NF-κB inhibits the occurrence of type 1 diabetes through microRNA-150-dependent PUMA degradation

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy) This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 1D,E+H, 2E+H, 3F,H+K, and 4B+E which appear to have a similar phenotype as many other publications, as detailed here: https://pubpeer.com/publications/C6FD5C041268DBBCDA521AEC112FA4 and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. The journal requested the corresponding author comment on these concerns and provide the raw Western blot data. However, the authors were not able to satisfactorily fulfill this request and therefore the Editor-in-Chief decided to retract the article.

Longitudinal proteomics analysis in the immediate microenvironment of islet allografts during progression of rejection

The applicability and benefits of pancreatic islet transplantation are limited due to various issues including the need to avoid immune-mediated rejection. Here, we used our experimental platform of allogeneic islet transplant in the anterior chamber of the eye (ACE-platform) to longitudinally monitor the progress of rejection in mice and obtain aqueous humor samples representative of the microenvironment of the graft for accurately-timed proteomic analyses. LC-MS/MS-based proteomics performed on such mass-limited samples (~5 μL) identified a total of 1296 proteins. Various analyses revealed distinct protein patterns associated with the mounting of the inflammatory and immune responses and their evolution with the progression of the rejection. Pathway analyses indicated predominant changes in cytotoxic functions, cell movement, and innate and adaptive immune responses. Network prediction analyses revealed transition from humoral to cellular immune response and exacerbation of pro-inflammatory signaling. One of the proteins identified by this localized proteomics as a candidate biomarker of islet rejection, Cystatin 3, was further validated by ELISA in the aqueous humor. This study provides (1) experimental evidence demonstrating the feasibility of longitudinal localized proteomics using small aqueous humor samples and (2) proof-of-concept for the discovery of biomarkers of impending immune attack from the immediate local microenvironment of ACE-transplanted islets. SIGNIFICANCE: The combination of the ACE-platform and longitudinal localized proteomics offers a powerful approach to biomarker discovery during the various stages of immune reactions mounted against transplanted tissues including pancreatic islets. It also supports proteomics-assisted drug discovery and development efforts aimed at preventing rejection through efficacy assessment of new agents by noninvasive and longitudinal graft monitoring.

Functional analysis of islet cells in vitro, in situ, and in vivo

The islet of Langerhans contains at least five types of endocrine cells producing distinct hormones. In response to nutrient or neuronal stimulation, islet endocrine cells release biochemicals including peptide hormones to regulate metabolism and to control glucose homeostasis. It is now recognized that malfunction of islet cells, notably insufficient insulin release of β-cells and hypersecretion of glucagon from α-cells, represents a causal event leading to hyperglycemia and frank diabetes, a disease that is increasing at an alarming rate to reach an epidemic level worldwide. Understanding the mechanisms regulating stimulus-secretion coupling and investigating how islet β-cells maintain a robust secretory activity are important topics in islet biology and diabetes research. To facilitate such studies, a number of biological systems and assay platforms have been developed for the functional analysis of islet cells. These technologies have enabled detailed analyses of individual islets at the cellular level, either in vitro, in situ, or in vivo.

Transplantation of Islets of Langerhans into the Anterior Chamber of the Eye for Longitudinal In Vivo Imaging

Noninvasive in vivo imaging techniques are attractive tools to longitudinally study various aspects of islet of Langerhans physiology and pathophysiology. Unfortunately, most imaging modalities currently applicable for clinical use do not allow the comprehensive investigation of islet cell biology due to limitations in resolution and/or sensitivity, while high-resolution imaging technologies like laser scanning microscopy (LSM) lack the penetration depth to assess islets of Langerhans within the pancreas. Significant progress in this area was made by the combination of LSM with the anterior chamber of the mouse eye platform, utilizing the cornea as a natural body window to study cell physiology of transplanted islets of Langerhans. We here describe the transplantation and longitudinal in vivo imaging of islets of Langerhans in the anterior chamber of the mouse eye as a versatile tool to study different features of islet physiology in health and disease.

In vivo imaging of type 1 diabetes immunopathology using eye-transplanted islets in NOD mice

AIMS/HYPOTHESIS

Autoimmune attack against the insulin-producing beta cells in the pancreatic islets results in type 1 diabetes. However, despite considerable research, details of the type 1 diabetes immunopathology in situ are not fully understood mainly because of difficult access to the pancreatic islets in vivo.

METHODS

Here, we used direct non-invasive confocal imaging of islets transplanted in the anterior chamber of the eye (ACE) to investigate the anti-islet autoimmunity in NOD mice before, during and after diabetes onset. ACE-transplanted islets allowed longitudinal studies of the autoimmune attack against islets and revealed the infiltration kinetics and in situ motility dynamics of fluorescence-labelled autoreactive T cells during diabetes development. Ex vivo immunostaining was also used to compare immune cell infiltrations into islet grafts in the eye and kidney as well as in pancreatic islets of the same diabetic NOD mice.

RESULTS

We found similar immune infiltration in native pancreatic and ACE-transplanted islets, which established the ACE-transplanted islets as reliable reporters of the autoimmune response. Longitudinal studies in ACE-transplanted islets identified in vivo hallmarks of islet inflammation that concurred with early immune infiltration of the islets and preceded their collapse and hyperglycaemia onset. A model incorporating data on ACE-transplanted islet degranulation and swelling allowed early prediction of the autoimmune attack in the pancreas and prompted treatments to intercept type 1 diabetes.

CONCLUSIONS/INTERPRETATION

The current findings highlight the value of ACE-transplanted islets in studying early type 1 diabetes pathogenesis in vivo and underscore the need for timely intervention to halt disease progression.

New automatic quantification method of immunofluorescence and histochemistry in whole histological sections

Immunofluorescent staining is a widespread tool in basic science to understand organ morphology and (patho-) physiology. The analysis of imaging data is often performed manually, limiting throughput and introducing human bias. Quantitative analysis is particularly challenging for organs with complex structure such as the kidney. In this study we present an approach for automatic quantification of fluorescent markers and histochemical stainings in whole organ sections using open source software. We validate our novel method in multiple typical challenges of basic kidney research and demonstrate its general relevance and applicability to other complex solid organs for a variety of different markers and stainings. Our newly developed software tool "AQUISTO", applied as a standard in primary data analysis, facilitates efficient large scale evaluation of cellular populations in various types of histological samples. Thereby it contributes to the characterization and understanding of (patho-) physiological processes.

Operational immune tolerance towards transplanted allogeneic pancreatic islets in mice and a non-human primate

AIMS/HYPOTHESIS

Patients with autoimmune type 1 diabetes transplanted with pancreatic islets to their liver experience significant improvement in quality of life through better control of blood sugar and enhanced awareness of hypoglycaemia. However, long-term survival and efficacy of the intrahepatic islet transplant are limited owing to liver-specific complications, such as immediate blood-mediated immune reaction, hypoxia, a highly enzymatic and inflammatory environment and locally elevated levels of drugs including immunosuppressive agents, all of which are injurious to islets. This has spurred a search for new islet transplant sites and for innovative ways to achieve long-term graft survival and efficacy without life-long systemic immunosuppression and its complications.

METHODS

We used our previously established approach of islet transplant in the anterior chamber of the eye in allogeneic recipient mouse models and a baboon model of diabetes, which were treated transiently with anti-CD154/CD40L blocking antibody in the peri-transplant period. Survival of the intraocular islet allografts was assessed by direct visualisation in the eye and metabolic variables (blood glucose and C-peptide measurements). We evaluated longitudinally the cytokine profile in the local microenvironment of the intraocular islet allografts, represented in aqueous humour, under conditions of immune rejection vs tolerance. We also evaluated the recall response in the periphery of the baboon recipient using delayed-type hypersensitivity (DTH) assay, and in mice after repeat transplant in the kidney following initial transplant with allogeneic islets in the eye or kidney.

RESULTS

Results in mice showed >300 days immunosuppression-free survival of allogeneic islets transplanted in the eye or kidney. Notably, >70% of tolerant mice, initially transplanted in the eye, exhibited >400 days of graft survival after re-transplant in the kidney without immunosuppression compared with ~30% in mice that were initially transplanted in the kidney. Cytokine and DTH data provided evidence of T helper 2-driven local and peripheral immune regulatory mechanisms in support of operational immune tolerance towards the islet allografts in both models.

CONCLUSIONS/INTERPRETATION

We are currently evaluating the safety and efficacy of intraocular islet transplantation in a phase 1 clinical trial. In this study, we demonstrate immunosuppression-free long-term survival of intraocular islet allografts in mice and in a baboon using transient peri-transplant immune intervention. These results highlight the potential for inducing islet transplant immune tolerance through the intraocular route. Therefore, the current findings are conceptually significant and may impact markedly on clinical islet transplantation in the treatment of diabetes.

Partial Clinical Remission of Type 1 Diabetes Mellitus in Children: Clinical Applications and Challenges with its Definitions

The honeymoon phase, or partial clinical remission (PCR) phase, of Type 1 diabetes mellitus (T1DM) is a transitory period that is marked by endogenous insulin production by surviving β cells following a diabetes diagnosis and the introduction of insulin therapy. It is a critical window in the course of the disease that has short and long-term implications for the patient, such as a significant reduction in the risk of long-term complications of T1DM. To promote long-term cardiovascular health in children with newly diagnosed T1DM, three key steps are necessary: the generation of a predictive model for non-remission, the adoption of a user-friendly monitoring tool for remission and non-remission, and the establishment of the magnitude of the early-phase cardiovascular disease risk in these children in objective terms through changes in lipid profile. However, only about 50% of children diagnosed with T1DM experience the honeymoon phase. Accurate and prompt detection of the honeymoon phase has been hampered by the lack of an objective and easily applicable predictive model for its detection at the time of T1DM diagnosis, the complex formulas needed to confirm and monitor PCR, and the absence of a straightforward, user-friendly tool for monitoring PCR. This literature review discusses the most up-to-date information in this field by describing an objective predictive model for non-remission, an easy tool for monitoring remission or non-remission, and objective evidence for the cardiovascular protective effect of PCR in the early phase of the disease. The goal is to present non-remission as an independent clinical entity with significantly poorer long-term prognosis than partial remission.

Pubertal Lipid Levels Are Significantly Lower in Youth With Type 1 Diabetes Who Experienced Partial Clinical Remission

Importance

The physiologic changes in lipids during puberty in type 1 diabetes (T1D) are unclear because subjects in previous studies were not stratified by partial clinical remission status.

Aim

To determine the effect of partial clinical remission on lipid changes during puberty in youth with T1D.

Subjects and Methods

A retrospective cross-sectional study of 194 subjects consisting of 71 control subjects of age 12.9 ± 1.3 years and 123 subjects with T1D stratified into remitters (n = 44; age, 13.0 ± 0.8 years) and nonremitters (n = 79; age, 11.2 ± 0.6 years). Partial clinical remission was defined as insulin-dose adjusted HbA1c of ≤9. Pubertal status was determined by Tanner staging.

Results

Among the pubertal cohort, low-density lipoprotein cholesterol concentration was significantly higher in the nonremitters compared with remitters (91.1 ± 25.6 vs 77.2 ± 25.8 mg/dL, P = 0.018) and with normal-weight control subjects (91.1 ± 25.6 vs 70.4 ± 22.9 mg/dL, P = 0.009) but was similar between overweight/obese control subjects and nonremitters (89.7 ± 28.9 vs 91.1± 25.6 mg/dL, P = 0.81) and between normal-weight control subjects and remitters (70.4 ± 22.9 vs 77.2 ± 25.8 mg/dL, P = 0.39). Total cholesterol was also significantly higher in nonremitters compared with remitters (167.8 ± 30.5 vs 149.8 ± 32.1 mg/dL, P = 0.012) and with normal-weight control subjects (167.8 ± 30.5 vs 143.2 ± 30.1 mg/dL, P = 0.011) but was similar between nonremitters and overweight/obese control subjects (P = 0.098) and between remitters and normal-weight control subjects (P = 0.51). Non-high-density lipoprotein cholesterol was equally significantly higher in nonremitters compared with remitters (111.3 ± 30.1 vs 95.9 ± 29.1 mg/dL, P = 0.028) and normal-weight control subjects (111.3 ± 30.1 vs 86.2 ± 32.2 mg/dL, P = 0.028) but was similar between nonremitters and overweight/obese control subjects (P = 0.48) and between remitters vs normal-weight control subjects (P = 0.39).

Conclusions

Puberty-related reductions in low-density lipoprotein, total cholesterol, and non-high-density lipoprotein occur in remitters and normal-weight control subjects but not in nonremitters and overweight/obese control subjects.

The eye as a novel imaging site in diabetes research

Diabetes develops due to deficient functional β cell mass, insulin resistance, or both. Yet, various challenges in understanding the mechanisms underlying diabetes development in vivo remain to be overcome owing to the lack of appropriate intravital imaging technologies. To meet these challenges, we have exploited the anterior chamber of the eye (ACE) as a novel imaging site to understand diabetes basics and clinics in vivo. We have developed a technology platform transplanting pancreatic islets into the ACE where they later on can be imaged non-invasively for long time. It turns out that the ACE serves as an optimal imaging site and provides implanted islets with an oxygen-rich milieu and an immune-privileged niche where they undergo optimal engraftment, rich vascularization and dense innervation, preserve organotypic features and live with satisfactory viability and functionality. The ACE technology has led to a series of significant observations. It enables in vivo microscopy of islet cytoarchitecture, function and viability in the physiological context and intravital imaging of a variety of pathological events such as autoimmune insulitis, defects in β cell function and mass and insulin resistance during diabetes development in a real-time manner. Furthermore, application of the ACE technology in humanized mice and non-human primates verifies translational and clinical values of the technology. In this article, we describe the ACE technology in detail, review accumulated knowledge gained by means of the ACE technology and delineate prospective avenues for the ACE technology.

Pancreas Pathology During the Natural History of Type 1 Diabetes

PURPOSE OF REVIEW

We provide an overview of pancreas pathology in type 1 diabetes (T1D) in the context of its clinical stages.

RECENT FINDINGS

Recent studies of pancreata from organ donors with T1D and non-diabetic donors expressing T1D-associated autoantibodies reveal pathological changes/disease mechanisms beyond the well-known loss of β cells and lymphocytic infiltrates of the islets (insulitis), including β-cell stress, dysfunction, and viral infections. Pancreas pathology evolves through disease stages, is asynchronous, and demonstrates a chronic disease that remains active years after diagnosis. Critically, β-cell loss is not complete at onset, although young age is associated with increased severity. The recognition of multiple pathogenic alterations and the chronic nature of disease mechanisms during and after the development of T1D inform improved clinical trial design and reveal additional targets for therapeutic manipulation, in the context of an expanded time window for intervention.

Diet-induced β-cell insulin resistance results in reversible loss of functional β-cell mass

Although convincing in genetic models, the relevance of β-cell insulin resistance in diet-induced type 2 diabetes (T2DM) remains unclear. Exemplified by diabetes-prone, male, C57B1/6J mice being fed different combinations of Western-style diet, we show that β-cell insulin resistance occurs early during T2DM progression and is due to a combination of lipotoxicity and increased β-cell workload. Within 8 wk of being fed a high-fat, high-sucrose diet, mice became obese, developed impaired insulin and glucose tolerances, and displayed noncompensatory insulin release, due, at least in part, to reduced expression of syntaxin-1A. Through reporter islets transplanted to the anterior chamber of the eye, we demonstrated a concomitant loss of functional β-cell mass. When mice were changed from diabetogenic diet to normal chow diet, the diabetes phenotype was reversed, suggesting a remarkable plasticity of functional β-cell mass in the early phase of T2DM development. Our data reinforce the relevance of diet composition as an environmental factor determining different routes of diabetes progression in a given genetic background. Employing the in vivo reporter islet–monitoring approach will allow researchers to define key times in the dynamics of reversible loss of functional β-cell mass and, thus, to investigate the underlying, molecular mechanisms involved in the progression toward T2DM manifestation.—Paschen, M., Moede, T., Valladolid-Acebes, I., Leibiger, B., Moruzzi, N., Jacob, S., García-Prieto, C. F., Brismar, K., Leibiger, I. B., Berggren, P.-O. Diet-induced β-cell insulin resistance results in reversible loss of functional β-cell mass.

Non-Invasive Multiphoton Imaging of Islets Transplanted Into the Pinna of the NOD Mouse Ear Reveals the Immediate Effect of Anti-CD3 Treatment in Autoimmune Diabetes

We present a novel and readily accessible method facilitating cellular time-resolved imaging of transplanted pancreatic islets. Grafting of islets to the mouse ear pinna allows non-invasive, in vivo longitudinal imaging of events in the islets and enables improved acquisition of experimental data and use of fewer experimental animals than is possible using invasive techniques, as the same mouse can be assessed for the presence of islet infiltrating cells before and after immune intervention. We have applied this method to investigating therapeutic protection of beta cells through the well-established use of anti-CD3 injection, and have acquired unprecedented data on the nature and rapidity of the effect on the islet infiltrating T cells. We demonstrate that infusion of anti-CD3 antibody leads to immediate effects on islet infiltrating T cells in islet grafts in the pinna of the ear, and causes them to increase their speed and displacement within 20 min of infusion. This technique overcomes several technical challenges associated with intravital imaging of pancreatic immune responses and facilitates routine study of beta islet cell development, differentiation, and function in health and disease.

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.

Early prediction of autoimmune (type 1) diabetes

Underlying type 1 diabetes is a genetic aetiology dominated by the influence of specific HLA haplotypes involving primarily the class II DR-DQ region. In genetically predisposed children with the DR4-DQ8 haplotype, exogenous factors, yet to be identified, are thought to trigger an autoimmune reaction against insulin, signalled by insulin autoantibodies as the first autoantibody to appear. In children with the DR3-DQ2 haplotype, the triggering reaction is primarily against GAD signalled by GAD autoantibodies (GADA) as the first-appearing autoantibody. The incidence rate of insulin autoantibodies as the first-appearing autoantibody peaks during the first years of life and declines thereafter. The incidence rate of GADA as the first-appearing autoantibody peaks later but does not decline. The first autoantibody may variably be followed, in an apparently non-HLA-associated pathogenesis, by a second, third or fourth autoantibody. Although not all persons with a single type of autoantibody progress to diabetes, the presence of multiple autoantibodies seems invariably to be followed by loss of functional beta cell mass and eventually by dysglycaemia and symptoms. Infiltration of mononuclear cells in and around the islets appears to be a late phenomenon appearing in the multiple-autoantibody-positive with dysglycaemia. As our understanding of the aetiology and pathogenesis of type 1 diabetes advances, the improved capability for early prediction should guide new strategies for the prevention of type 1 diabetes.

Human beta cell mass and function in diabetes: Recent advances in knowledge and technologies to understand disease pathogenesis

Background

Plasma insulin levels are predominantly the product of the morphological mass of insulin producing beta cells in the pancreatic islets of Langerhans and the functional status of each of these beta cells. Thus, deficiency in either beta cell mass or function, or both, can lead to insufficient levels of insulin, resulting in hyperglycemia and diabetes. Nonetheless, the precise contribution of beta cell mass and function to the pathogenesis of diabetes as well as the underlying mechanisms are still unclear. In the past, this was largely due to the restricted number of technologies suitable for studying the scarcely accessible human beta cells. However, in recent years, a number of new platforms have been established to expand the available techniques and to facilitate deeper insight into the role of human beta cell mass and function as cause for diabetes and as potential treatment targets.

Scope of Review

This review discusses the current knowledge about contribution of human beta cell mass and function to different stages of type 1 and type 2 diabetes pathogenesis. Furthermore, it highlights standard and newly developed technological platforms for the study of human beta cell biology, which can be used to increase our understanding of beta cell mass and function in human glucose homeostasis.

Major Conclusions

In contrast to early disease models, recent studies suggest that in type 1 and type 2 diabetes impairment of beta cell function is an early feature of disease pathogenesis while a substantial decrease in beta cell mass occurs more closely to clinical manifestation. This suggests that, in addition to beta cell mass replacement for late stage therapies, the development of novel strategies for protection and recovery of beta cell function could be most promising for successful diabetes treatment and prevention. The use of today's developing and wide range of technologies and platforms for the study of human beta cells will allow for a more detailed investigation of the underlying mechanisms and will facilitate development of treatment approaches to specifically target human beta cell mass and function.

Intraocular in vivo imaging of pancreatic islet cell physiology/pathology

Background

Diabetes mellitus has reached epidemic proportions and requires new strategies for treatment. Unfortunately, the efficacy of treatment regimens on maintaining/re-gaining functional beta cell mass can, at the present, only be determined indirectly. Direct monitoring of beta cell mass is complicated by the anatomy of the endocrine pancreas, which consists of thousands to a million of discrete micro-organs, i.e. islets of Langerhans, which are scattered throughout the pancreas.

Scope of review

Here, we review the progress made over the last years using the anterior chamber of the eye as a transplantation site for functional imaging of pancreatic islet cells in the living organism. Islets engrafted on the iris are vascularized and innervated and the cornea, serving as a natural body-window, allows for microscopic, non-invasive, longitudinal evaluation of islet/beta cell function and survival with single-cell resolution in health and disease.

Major conclusions

Data provided by us and others demonstrate the high versatility of this imaging platform. The use of ‘reporter islets’ engrafted in the eye, reporting on the status of in situ endogenous islets in the pancreas of the same animal, allows the identification of key-events in the development and progression of diabetes. This will not only serve as a versatile research tool but will also lay the foundation for a personalized medicine approach and will serve as a screening platform for new drugs and/or treatment protocols. ‘Metabolic’ islet transplantation, in which islets engrafted in the eye replace the endogenous beta cells, will allow for the establishment of islet-specific transgenic models and ‘humanized’ mouse models as well as serving as the basis for a new clinical transplantation site for the cure of diabetes.

Vessel Network Architecture of Adult Human Islets Promotes Distinct Cell-Cell Interactions In Situ and Is Altered After Transplantation

Islet-cell hormone release is modulated by signals from endothelial and endocrine cells within the islet. However, models of intraislet vascularization and paracrine cell signaling are mostly based on the rodent pancreas. We assessed the architecture and endocrine cell interaction of the vascular network in unperturbed human islets in situ and their potential to re-establish their endogenous vascular network after transplantation in vivo. We prepared slices of fresh pancreas tissue obtained from nondiabetic patients undergoing partial pancreatectomy. In addition, we transplanted human donor islets into the anterior chamber of the mouse eye. Next, we performed three-dimensional in situ and in vivo imaging of islet cell and vessel architecture at cellular resolution and compared our findings with mouse and porcine islets. Our data reveal a significantly different vascular architecture with decreased vessel diameter, reduced vessel branching, and shortened total vessel network in human compared with mouse islets. Together with the distinct cellular arrangement in human islets, this limits β to endothelial cell interactions, facilitates connection of α and β cells, and promotes the formation of independent β-cell clusters within islets. Furthermore, our results show that the endogenous vascular network of islets is significantly altered after transplantation in a donor age-related mechanism. Thus, our study provides insight into the vascular architecture and cellular arrangement of human islets with apparent consequences for intercellular islet signaling. Moreover, our findings suggest that human islet engraftment after transplantation can be improved by using alternative, less mature islet-cell sources.

A predictive model for lack of partial clinical remission in new-onset pediatric type 1 diabetes

IMPORTANCE

>50% of patients with new-onset type 1 diabetes (T1D) do not enter partial clinical remission (PCR); early identification of these patients may improve initial glycemic control and reduce long-term complications.

AIM

To determine whether routinely obtainable clinical parameters predict non-remission in children and adolescents with new-onset T1D.

SUBJECTS AND METHODS

Data on remission were collected for the first 36 months of disease in 204 subjects of ages 2-14 years with new-onset type 1 diabetes. There were 86 remitters (age 9.1±3.0y; male 57%), and 118 non-remitters (age 7.0±3.1y; male 40.7%). PCR was defined as insulin-dose adjusted hemoglobin A1c of ≤9.

RESULTS

Non-remission occurred in 57.8% of subjects. Univariable analysis showed that the risk for non-remission was increased 9-fold in patients with 4 diabetes-associated auto-antibodies (OR = 9.90, p = 0.010); 5-fold in patients <5 years old (odds ratio = 5.38, p = 0.032), 3-fold in those with bicarbonate of <15 mg/dL at diagnosis (OR = 3.71, p = 0.008). Combined estimates of risk potential for HC03 and the number of autoantibodies by multivariable analysis, adjusted for BMI standard deviation score, showed HC03 <15 mg/dL with a clinically significant 10-fold risk (OR = 10.1, p = 0.074); and the number of autoantibodies with a 2-fold risk for non-remission (OR = 1.9, p = 0.105). Male sex and older age were associated with decreased risk for non-remission. A receiver-operating characteristic curve model depicting sensitivity by 1-specificity for non-remission as predicted by bicarbonate <15 mg/dL, age <5y, female sex, and >3 diabetes-associated autoantibodies had an area under the curve of 0.73.

CONCLUSIONS

More than 50% of children and adolescents with new-onset T1D do not undergo partial clinical remission and are thus at an increased risk for long-term complications of diabetes mellitus. A predictive model comprising of bicarbonate <15 mg/dL, age <5y, female sex, and >3 diabetes-associated autoantibodies has 73% power for correctly predicting non-remission in children and adolescents with new-onset T1D. Early identification of these non-remitters may guide the institution of targeted therapy to limit dysglycemia and reduce the prevalence of long-term deleterious complications.

Immunotherapy for Type 1 Diabetes: Why Do Current Protocols Not Halt the Underlying Disease Process?

T cell-directed immunosuppression only transiently delays the loss of β cell function in recent-onset type 1 diabetes. We argue here that the underlying disease process is carried by innate immune reactivity. Inducing a non-polarized functional state of local innate immunity will support regulatory T cell development and β cell proliferation.

The biomechanical properties of an epithelial tissue determine the location of its vasculature

An important question is how growing tissues establish a blood vessel network. Here we study vascular network formation in pancreatic islets, endocrine tissues derived from pancreatic epithelium. We find that depletion of integrin-linked kinase (ILK) in the pancreatic epithelial cells of mice results in glucose intolerance due to a loss of the intra-islet vasculature. In turn, blood vessels accumulate at the islet periphery. Neither alterations in endothelial cell proliferation, apoptosis, morphology, Vegfa expression and VEGF-A secretion nor ‘empty sleeves' of vascular basement membrane are found. Instead, biophysical experiments reveal that the biomechanical properties of pancreatic islet cells, such as their actomyosin-mediated cortex tension and adhesive forces to endothelial cells, are significantly changed. These results suggest that a sorting event is driving the segregation of endothelial and epithelial cells and indicate that the epithelial biomechanical properties determine whether the blood vasculature invades or envelops a growing epithelial tissue.

Vasculature is denser in soft than in stiff tissues. Kragl et al. suggest a mechanistic link between biomechanical tissue properties and vascularization by showing that integrin-linked kinase reduces the contractile forces of the cell cortex in endocrine pancreatic cells, facilitating their adhesion to blood vessels and enabling pancreatic islet vascularization.

Stimulated urine C-peptide creatinine ratio vs serum C-peptide level for monitoring of β-cell function in the first year after diagnosis of Type 1 diabetes

AIMS

To determine if urine C-peptide/creatinine ratio is a useful tool for monitoring β-cell function in new-onset Type 1 diabetes.

METHODS

Data were obtained from a prospective immunomodulation study in people with Type 1 diabetes ≤ 3 months from diagnosis, with a standard mixed-meal tolerance test and measurement of urine C-peptide/creatinine ratio carried out at 0, 3, 6, 9 and 12 months. The change in the insulin-dose-adjusted HbA_1c level was also correlated with the change in serum/urine C-peptide level during the 12-month follow-up period.

RESULTS

A significant reduction in urine C-peptide/creatinine ratio, measured after a mixed-meal, was reached at 9 months (-45.4%), whilst the reduction in stimulated serum C-peptide level reached significance after 3 months (-54.7%) in placebo-treated participants. Neither change in stimulated serum C-peptide nor change in urine C-peptide level correlated with each other, and nor did change in insulin-dose-adjusted HbA_1c level in the first 6 months, but all measures correlated significantly in the second half of the 12-month follow-up period.

CONCLUSION

Mixed-meal-stimulated urine C-peptide/creatinine ratio was similar to, although less sensitive than, stimulated serum C-peptide level in monitoring β-cell function during the first year after diagnosis. Because the former is significantly less invasive, it warrants inclusion in further studies in Type 1 diabetes and may represent an attractive alternative outcome measure in cohort studies and in children.

Label-free fast 3D coherent imaging reveals pancreatic islet micro-vascularization and dynamic blood flow

In diabetes, pancreatic β-cells play a key role. These cells are clustered within structures called islets of Langerhans inside the pancreas and produce insulin, which is directly secreted into the blood stream. The dense vascularization of islets of Langerhans is critical for maintaining a proper regulation of blood glucose homeostasis and is known to be affected from the early stage of diabetes. The deep localization of these islets inside the pancreas in the abdominal cavity renders their in vivo visualization a challenging task. A fast label-free imaging method with high spatial resolution is required to study the vascular network of islets of Langerhans. Based on these requirements, we developed a label-free and three-dimensional imaging method for observing islets of Langerhans using extended-focus Fourier domain Optical Coherence Microscopy (xfOCM). In addition to structural imaging, this system provides three-dimensional vascular network imaging and dynamic blood flow information within islets of Langerhans. We propose our method to deepen the understanding of the interconnection between diabetes and the evolution of the islet vascular network.

Quantitative Impact of Plasma Clearance and Down-regulation on GLP-1 Receptor Molecular Imaging

PURPOSE

Quantitative molecular imaging of beta cell mass (BCM) would enable early detection and treatment monitoring of type 1 diabetes. The glucagon-like peptide-1 (GLP-1) receptor is an attractive target due to its beta cell specificity and cell surface location. We quantitatively investigated the impact of plasma clearance and receptor internalization on targeting efficiency in healthy B6 mice.

PROCEDURES

Four exenatide-based probes were synthesized that varied in molecular weight, binding affinity, and plasma clearance. The GLP-1 receptor internalization rate and in vivo receptor expression were quantified.

RESULTS

Receptor internalization (54,000 receptors/cell in vivo) decreased significantly within minutes, reducing the benefit of a slower-clearing agent. The multimers and albumin binding probes had higher kidney and liver uptake, respectively.

CONCLUSIONS

Slow plasma clearance is beneficial for GLP-1 receptor peptide therapeutics. However, for exendin-based imaging of islets, down-regulation of the GLP-1 receptor and non-specific background uptake result in a higher target-to-background ratio for fast-clearing agents.

Alterations in β-Cell Calcium Dynamics and Efficacy Outweigh Islet Mass Adaptation in Compensation of Insulin Resistance and Prediabetes Onset

Emerging insulin resistance is normally compensated by increased insulin production of pancreatic β-cells, thereby maintaining normoglycemia. However, it is unclear whether this is achieved by adaptation of β-cell function, mass, or both. Most importantly, it is still unknown which of these adaptive mechanisms fail when type 2 diabetes develops. We performed longitudinal in vivo imaging of β-cell calcium dynamics and islet mass of transplanted islets of Langerhans throughout diet-induced progression from normal glucose homeostasis, through compensation of insulin resistance, to prediabetes. The results show that compensation of insulin resistance is predominated by alterations of β-cell function, while islet mass only gradually expands. Hereby, functional adaptation is mediated by increased calcium efficacy, which involves Epac signaling. Prior to prediabetes, β-cell function displays decreased stimulated calcium dynamics, whereas islet mass continues to increase through prediabetes onset. Thus, our data reveal a predominant role of islet function with distinct contributions of triggering and amplifying pathway in the in vivo processes preceding diabetes onset. These findings support protection and recovery of β-cell function as primary goals for prevention and treatment of diabetes and provide insight into potential therapeutic targets.

Identification of proliferative and mature β-cells in the islets of Langerhans

Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of β-cells. Pancreatic β-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential; understanding the mechanisms that underlie this functional heterogeneity might make it possible to develop new regenerative approaches. Here we show that Fltp (also known as Flattop and Cfap126), a Wnt/planar cell polarity (PCP) effector and reporter gene acts as a marker gene that subdivides endocrine cells into two subpopulations and distinguishes proliferation-competent from mature β-cells with distinct molecular, physiological and ultrastructural features. Genetic lineage tracing revealed that endocrine subpopulations from Fltp-negative and -positive lineages react differently to physiological and pathological changes. The expression of Fltp increases when endocrine cells cluster together to form polarized and mature 3D islet mini-organs. We show that 3D architecture and Wnt/PCP ligands are sufficient to trigger β-cell maturation. By contrast, the Wnt/PCP effector Fltp is not necessary for β-cell development, proliferation or maturation. We conclude that 3D architecture and Wnt/PCP signalling underlie functional β-cell heterogeneity and induce β-cell maturation. The identification of Fltp as a marker for endocrine subpopulations sheds light on the molecular underpinnings of islet cell heterogeneity and plasticity and might enable targeting of endocrine subpopulations for the regeneration of functional β-cell mass in diabetic patients.

Longitudinal three-dimensional visualisation of autoimmune diabetes by functional optical coherence imaging

AIMS/HYPOTHESIS

It is generally accepted that structural and functional quantitative imaging of individual islets would be beneficial to elucidate the pathogenesis of type 1 diabetes. We here introduce functional optical coherence imaging (FOCI) for fast, label-free monitoring of beta cell destruction and associated alterations of islet vascularisation.

METHODS

NOD mouse and human islets transplanted into the anterior chamber of the eye (ACE) were imaged with FOCI, in which the optical contrast of FOCI is based on intrinsic variations of the index of refraction resulting in a faster tomographic acquisition. In addition, the phase sensitivity allows simultaneous label-free acquisition of vascularisation.

RESULTS

We demonstrate that FOCI allows longitudinal quantification of progressive autoimmune insulitis, including the three-dimensional quantification of beta cell volume, inflammation and vascularisation. The substantially increased backscattering of islets is dominated by the insulin-zinc nanocrystals in the beta cell granules. This translates into a high specificity for the functional beta cell volume of islets. Applying FOCI to a spontaneous mouse model of type 1 diabetes, we quantify the modifications of the pancreatic microvasculature accompanying the progression of diabetes and reveal a strong correlation between increasing insulitis and density of the vascular network of the islet.

CONCLUSIONS/INTERPRETATION

FOCI provides a novel imaging technique for investigating functional and structural diabetes-induced alterations of the islets. The label-free detection of beta cell volume and infiltration together with vascularisation offers a unique extension to study ACE-transplanted human islets. These results are contributing to a deeper understanding of human islet transplant rejection and label-free in vivo monitoring of drug efficacy.

Combination Therapy Reverses Hyperglycemia in NOD Mice With Established Type 1 Diabetes

An increasing number of therapies have proven effective at reversing hyperglycemia in the nonobese diabetic (NOD) mouse model of type 1 diabetes (T1D), yet situations of successful translation to human T1D are limited. This may be partly due to evaluating the effect of treating immediately at diagnosis in mice, which may not be reflective of the advanced disease state in humans at disease onset. In this study, we treated NOD mice with new-onset as well as established disease using various combinations of four drugs: antithymocyte globulin (ATG), granulocyte-colony stimulating factor (G-CSF), a dipeptidyl peptidase IV inhibitor (DPP-4i), and a proton pump inhibitor (PPI). Therapy with all four drugs induced remission in 83% of new-onset mice and, remarkably, in 50% of NOD mice with established disease. Also noteworthy, disease remission occurred irrespective of initial blood glucose values and mechanistically was characterized by enhanced immunoregulation involving alterations in CD4+ T cells, CD8+ T cells, and natural killer cells. This combination therapy also allowed for effective treatment at reduced drug doses (compared with effective monotherapy), thereby minimizing potential adverse effects while retaining efficacy. This combination of approved drugs demonstrates a novel ability to reverse T1D, thereby warranting translational consideration.