Baseline plasma proinsulin response to glucose for predicting therapeutic response to otelixizumab in recent-onset type 1 diabetes

AIMS

In recent-onset type 1 diabetes, clamp-derived C-peptide predicts good response to anti-CD3. Elevated proinsulin and proinsulin/C-peptide ratio (PI/CP) suggest increased metabolic/inflammatory beta cell burden. We reanalyzed trial data to compare the ability of baseline acutely glucose-stimulated proinsulin, C-peptide and PI/CP to predict functional outcome.

METHODS

Eighty recent-onset type 1 diabetes patients participated in the placebo-controlled otelixizumab (GSK; NCT00627146) trial. Hyperglycemic clamps were performed at baseline, 6, 12 and 18 months, involving 3 h of induced euglycemia, followed by acutely raising and maintaining glycemia to ≥ 10 mmol/l for 140 min. Plasma proinsulin, C-peptide and PI/CP were determined after acute (minute 0 at 10 mmol/l; PI0, CP0, PI/CP0) and sustained glucose stimulation (AUC between minutes 60-140). Outcome was assessed as change in AUC60-140 C-peptide from baseline.

RESULTS

In multiple linear regression, higher baseline (≥median [P50]) PI0 independently predicted preservation of beta cell function in response to anti-CD3 and interacted significantly with IAA. During follow-up, anti-CD3 tempered a further increase in PI/CP0, but not in PI0. CP0 outperformed PI0 and PI/CP0 for post-treatment monitoring.

CONCLUSIONS

In recent-onset type 1 diabetes, elevated acutely glucose-stimulated proinsulin may complement or replace acutely or sustainedly stimulated C-peptide release for identifying good responders to anti-CD3, but not as outcome measure.

Comparison of Omentum and Subcutis as Implant Sites for Device-Encapsulated Human iPSC-Derived Pancreatic Endoderm in Nude Rats

Subcutaneous implants of device-encapsulated stem cell-derived pancreatic endoderm (PE) can establish a functional beta cell mass (FBM) with metabolic control in immune-compromised mice. In a study with human-induced pluripotent stem cell-PE, this outcome was favored by a preformed pouch which allowed lesion-free insertion of devices in a pre-vascularized site. This was not reproduced in nude rats, known to exhibit a higher innate reactivity than mice and therefore relevant as preclinical model: a dense fibrotic capsule formed around subcutis (SC) implants with virtually no FBM formation. Placement in omentum (OM) of nude rats provided a less fibrous, better vascularized environment than SC. It resulted in less donor cell loss (56% recovery at post-transplant-PT week 3 versus 16% in SC) allowing FBM-formation. At PT week 30, 6/13 OM-recipients exhibited glucose-induced plasma hu-C-peptide to 0.1-0.4 ng/ml, versus 0/8 in SC-recipients. These levels are more than 10-fold lower than in a state of metabolic control. This shortcoming is not caused by inadequate glucose responsiveness of the beta cells but by their insufficient number. The size of the formed beta cell mass (0.4 ± 0.2 µl) was lower than that reported in mice receiving the same cell product subcutaneously; the difference is attributed to a lower expansion of pancreatic progenitor cells and to their lower degree of differentiation to beta cells. This study in the nude rat model demonstrates that OM provides a better environment for formation of beta cells in device-encapsulated PE-implants than SC. It also identified targets for increasing their dose-efficacy.

Cell Mass Increase Associated with Formation of Glucose-Controlling β-Cell Mass in Device-Encapsulated Implants of hiPS-Derived Pancreatic Endoderm

Device-encapsulated human stem cell-derived pancreatic endoderm (PE) can generate functional β-cell implants in the subcutis of mice, which has led to the start of clinical studies in type 1 diabetes. Assessment of the formed functional β-cell mass (FBM) and its correlation with in vivo metabolic markers can guide clinical translation. We recently reported ex vivo characteristics of device-encapsulated human embryonic stem cell-derived (hES)-PE implants in mice that had established a metabolically adequate FBM during 50-week follow-up. Cell suspensions from retrieved implants indicated a correlation with the number of formed β cells and their maturation to a functional state comparable to human pancreatic β cells. Variability in metabolic outcome was attributed to differences in number of PE-generated β cells. This variability hinders studies on processes involved in FBM-formation. This study reports modifications that reduce variability. It is undertaken with device-encapsulated human induced pluripotent stem cell-derived-PE subcutaneously implanted in mice. Cell mass of each cell type was determined on intact tissue inside the device to obtain more precise data than following isolation and dispersion. Implants in a preformed pouch generated a glucose-controlling β-cell mass within 20 weeks in over 60% of recipients versus less than 20% in the absence of a pouch, whether the same or threefold higher cell dose had been inserted. In situ analysis of implants indicated a role for pancreatic progenitor cell expansion and endocrine differentiation in achieving the size of β- and α-cell mass that correlated with in vivo markers of metabolic control. Stem Cells Translational Medicine 2019;8:1296&1305.

Combined Analysis of GAD65, miR-375, and Unmethylated Insulin DNA Following Islet Transplantation in Patients With T1D

AIM

Several biomarkers have been proposed to detect pancreatic β cell destruction in vivo but so far have not been compared for sensitivity and significance.

METHODS

We used islet transplantation as a model to compare plasma concentrations of miR-375, 65-kDa subunit of glutamate decarboxylase (GAD65), and unmethylated insulin DNA, measured at subpicomolar sensitivity, and study their discharge kinetics, power for outcome prediction, and detection of graft loss during follow-up.

RESULTS

At 60 minutes after transplantation, GAD65 and miR-375 consistently showed near-equimolar and correlated increases proportional to the number of implanted β cells. GAD65 and miR-375 showed comparable power to predict poor graft outcome at 2 months, with areas under the curve of 0.833 and 0.771, respectively (P = 0.53). Using receiver operating characteristic analysis, we defined likelihood ratios (LRs) for rationally selected result intervals. In GADA-negative recipients (n = 28), GAD65 <4.5 pmol/L (LR = 0.15) and >12.2 pmol/L (LR = ∞) predicted good and poor outcomes, respectively. miR-375 could be used in all recipients irrespective of GAD65 autoantibody status (n = 46), with levels <1.4 pmol/L (LR = 0.14) or >7.6 pmol/L (LR = 9.53) as dual thresholds. The posttransplant surge of unmethylated insulin DNA was inconsistent and unrelated to outcome. Combined measurement of these three biomarkers was also tested as liquid biopsy for β cell death during 2-month follow-up; incidental surges of GAD65, miR-375, and (un)methylated insulin DNA, alone or combined, were confidently detected but could not be related to outcome.

CONCLUSIONS

GAD65 and miR-375 performed equally well in quantifying early graft destruction and predicting graft outcome, outperforming unmethylated insulin DNA.

Increase Functional β-Cell Mass in Subcutaneous Alginate Capsules With Porcine Prenatal Islet Cells but Loss With Human Adult Islet Cells

Alginate (Alg)-encapsulated porcine islet cell grafts are developed to overcome limitations of human islet transplantation. They can generate functional implants in animals when prepared from fetal, perinatal, and adult pancreases. Implants have not yet been examined for efficacy to establish sustained, metabolically adequate functional β-cell mass (FBM) in comparison with human islet cells. This study in immune-compromised mice demonstrates that subcutaneous implants of Alg-encapsulated porcine prenatal islet cells with 4 × 10⁵ β-cells form, over 10 weeks, a FBM that results in glucose-induced plasma C-peptide >2 ng/mL and metabolic control over the following 10 weeks, with higher efficiency than nonencapsulated, while failing in peritoneum. This intracapsular FBM formation involves β-cell replication, increasing number fourfold, and maturation toward human adult β-cells. Subcutaneous Alg-encapsulated human islet cells with similar β-cell number establish implants with plasma C-peptide >2 ng/mL for the first 10 weeks, with nonencapsulated cells failing; their β-cells do not replicate but progressively die (>70%), explaining C-peptide decline and insufficient metabolic control. An Alg matrix thus helps establish β-cell functions in subcutis. It allows formation of sustained metabolically adequate FBM by immature porcine β-cells with proliferative activity but not by human adult islet cells. These findings define conditions for evaluating its immune-protecting properties.

Accelerated Progression to Type 1 Diabetes in the Presence of HLA-A*24 and -B*18 Is Restricted to Multiple Islet Autoantibody-Positive Individuals With Distinct HLA-DQ and Autoantibody Risk Profiles

OBJECTIVE

We investigated the effect of HLA class I risk alleles on disease progression in various phases of subclinical islet autoimmunity in first-degree relatives of patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A registry-based group of siblings/offspring (aged 0-39 years) was monitored from single- to multiple-autoantibody positivity (n = 267) and from multiple-autoantibody positivity to clinical onset (n = 252) according to HLA-DQ, -A*24, -B*18, and -B*39 status. Genetic markers were determined by PCR sequence-specific oligotyping.

RESULTS

Unlike HLA-B*18 or -B*39, HLA-A*24 was associated with delayed progression from single- to multiple-autoantibody positivity (P = 0.009) but not to type 1 diabetes. This occurred independently from older age (P < 0.001) and absence of HLA-DQ2/DQ8 or -DQ8 (P < 0.001 and P = 0.003, respectively), and only in the presence of GAD autoantibodies. In contrast, HLA-A*24 was associated with accelerated progression from multiple-autoantibody positivity to clinical onset (P = 0.006), but its effects were restricted to HLA-DQ8⁺ relatives with IA-2 or zinc transporter 8 autoantibodies (P = 0.002). HLA-B*18, but not -B*39, was also associated with more rapid progression, but only in HLA-DQ2 carriers with double positivity for GAD and insulin autoantibodies (P = 0.004).

CONCLUSIONS

HLA-A*24 predisposes to a delayed antigen spreading of humoral autoimmunity, whereas HLA-A*24 and -B*18 are associated with accelerated progression of advanced subclinical autoimmunity in distinct risk groups. The relation of these alleles to the underlying disease process requires further investigation. Their typing should be relevant for the preparation and interpretation of observational and interventional studies in asymptomatic type 1 diabetes.

Functional Beta Cell Mass from Device-Encapsulated hESC-Derived Pancreatic Endoderm Achieving Metabolic Control

Human stem cells represent a potential source for implants that replace the depleted functional beta cell mass (FBM) in diabetes patients. Human embryonic stem cell-derived pancreatic endoderm (hES-PE) can generate implants with glucose-responsive beta cells capable of reducing hyperglycemia in mice. This study with device-encapsulated hES-PE (4 × 10⁶ cells/mouse) determines the biologic characteristics at which implants establish metabolic control during a 50-week follow-up. A metabolically adequate FBM was achieved by (1) formation of a sufficient beta cell number (>0.3 × 10⁶/mouse) at >50% endocrine purity and (2) their maturation to a functional state comparable with human pancreatic beta cells, as judged by their secretory responses during perifusion, their content in typical secretory vesicles, and their nuclear NKX6.1-PDX1-MAFA co-expression. Assessment of FBM in implants and its correlation with in vivo metabolic markers will guide clinical translation of stem cell-derived grafts in diabetes.

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Human stem cell-derived pancreatic precursors generate functional beta cell mass

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Cellular markers identify metabolically adequate human stem cell-generated implants

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Significance of determining beta cell number and maturation in implants

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Functional implants differ in endocrine composition from endocrine pancreas

HLA-A*24 Carrier Status and Autoantibody Surges Posttransplantation Associate With Poor Functional Outcome in Recipients of an Islet Allograft

OBJECTIVE

We investigated whether changes in islet autoantibody profile and presence of HLA risk markers, reported to predict rapid β-cell loss in pre-type 1 diabetes, associate with poor functional outcome in islet allograft recipients.

RESEARCH DESIGN AND METHODS

Forty-one patients received ≥2.3 million β-cells/kg body wt in one to two intraportal implantations. Outcome after 6-18 months was assessed by C-peptide (random and stimulated), insulin dose, and HbA1c.

RESULTS

Patients carrying HLA-A*24-positive or experiencing a significant autoantibody surge within 6 months after the first transplantation (n = 19) had lower C-peptide levels (P ≤ 0.003) and higher insulin needs (P < 0.001) despite higher HbA1c levels (P ≤ 0.018). They became less often insulin independent (16% vs. 68%, P = 0.002) and remained less often C-peptide positive (47% vs. 100%, P < 0.001) than recipients lacking both risk factors. HLA-A*24 positivity or an autoantibody surge predicted insulin dependence (P = 0.007).

CONCLUSIONS

HLA-A*24 and early autoantibody surge after islet implantation associate with poor functional graft outcome.

Relationship between glycaemic variability and hyperglycaemic clamp-derived functional variables in (impending) type 1 diabetes

AIMS/HYPOTHESIS

We examined whether measures of glycaemic variability (GV), assessed by continuous glucose monitoring (CGM) and self-monitoring of blood glucose (SMBG), can complement or replace measures of beta cell function and insulin action in detecting the progression of preclinical disease to type 1 diabetes.

METHODS

Twenty-two autoantibody-positive (autoAb(+)) first-degree relatives (FDRs) of patients with type 1 diabetes who were themselves at high 5-year risk (50%) for type 1 diabetes underwent CGM, a hyperglycaemic clamp test and OGTT, and were followed for up to 31 months. Clamp variables were used to estimate beta cell function (first-phase [AUC5-10 min] and second-phase [AUC120-150 min] C-peptide release) combined with insulin resistance (glucose disposal rate; M 120-150 min). Age-matched healthy volunteers (n = 20) and individuals with recent-onset type 1 diabetes (n = 9) served as control groups.

RESULTS

In autoAb(+) FDRs, M 120-150 min below the 10th percentile (P10) of controls achieved 86% diagnostic efficiency in discriminating between normoglycaemic FDRs and individuals with (impending) dysglycaemia. M 120-150 min outperformed AUC5-10 min and AUC120-150 min C-peptide below P10 of controls, which were only 59-68% effective. Among GV variables, CGM above the reference range was better at detecting (impending) dysglycaemia than elevated SMBG (77-82% vs 73% efficiency). Combined CGM measures were equally efficient as M 120-150 min (86%). Daytime GV variables were inversely correlated with clamp variables, and more strongly with M 120-150 min than with AUC5-10 min or AUC120-150 min C-peptide.

CONCLUSIONS/INTERPRETATION

CGM-derived GV and the glucose disposal rate, reflecting both insulin secretion and action, outperformed SMBG and first- or second-phase AUC C-peptide in identifying FDRs with (impending) dysglycaemia or diabetes. Our results indicate the feasibility of developing minimally invasive CGM-based criteria for close metabolic monitoring and as outcome measures in trials.

Preexisting insulin autoantibodies predict efficacy of otelixizumab in preserving residual β-cell function in recent-onset type 1 diabetes

OBJECTIVE

Immune intervention trials in recent-onset type 1 diabetes would benefit from biomarkers associated with good therapeutic response. In the previously reported randomized placebo-controlled anti-CD3 study (otelixizumab; GlaxoSmithKline), we tested the hypothesis that specific diabetes autoantibodies might serve this purpose.

RESEARCH DESIGN AND METHODS

In the included patients (n = 40 otelixizumab, n = 40 placebo), β-cell function was assessed as area under the curve (AUC) C-peptide release during a hyperglycemic glucose clamp at baseline (median duration of insulin treatment: 6 days) and every 6 months until 18 months after randomization. (Auto)antibodies against insulin (I[A]A), GAD (GADA), IA-2 (IA-2A), and ZnT8 (ZnT8A) were determined on stored sera by liquid-phase radiobinding assay.

RESULTS

At baseline, only better preserved AUC C-peptide release and higher levels of IAA were associated with better preservation of β-cell function and lower insulin needs under anti-CD3 treatment. In multivariate analysis, IAA (P = 0.022) or the interaction of IAA and C-peptide (P = 0.013) independently predicted outcome together with treatment. During follow-up, good responders to anti-CD3 treatment (i.e., IAA(+) participants with relatively preserved β-cell function [≥ 25% of healthy control subjects]) experienced a less pronounced insulin-induced rise in I(A)A and lower insulin needs. GADA, IA-2A, and ZnT8A levels were not influenced by anti-CD3 treatment, and their changes showed no relation to functional outcome.

CONCLUSIONS

There is important specificity of IAA among other diabetes autoantibodies to predict good therapeutic response of recent-onset type 1 diabetic patients to anti-CD3 treatment. If confirmed, future immune intervention trials in type 1 diabetes should consider both relatively preserved functional β-cell mass and presence of IAA as inclusion criteria.

Hyperglycemic clamp and oral glucose tolerance test for 3-year prediction of clinical onset in persistently autoantibody-positive offspring and siblings of type 1 diabetic patients

CONTEXT AND OBJECTIVE

In preparation of future prevention trials, we aimed to identify predictors of 3-year diabetes onset among oral glucose tolerance test (OGTT)- and hyperglycemic clamp-derived metabolic markers in persistently islet autoantibody positive (autoAb(+)) offspring and siblings of patients with type 1 diabetes (T1D).

DESIGN

The design is a registry-based study.

SETTING

Functional tests were performed in a hospital setting.

PARTICIPANTS

Persistently autoAb(+) first-degree relatives of patients with T1D (n = 81; age 5-39 years).

MAIN OUTCOME MEASURES

We assessed 3-year predictive ability of OGTT- and clamp-derived markers using receiver operating characteristics (ROC) and Cox regression analysis. Area under the curve of clamp-derived first-phase C-peptide release (AUC(5-10 min); min 5-10) was determined in all relatives and second-phase release (AUC(120-150 min); min 120-150) in those aged 12-39 years (n = 62).

RESULTS

Overall, the predictive ability of AUC(5-10 min) was better than that of peak C-peptide, the best predictor among OGTT-derived parameters (ROC-AUC [95%CI]: 0.89 [0.80-0.98] vs 0.81 [0.70-0.93]). Fasting blood glucose (FBG) and AUC(5-10 min) provided the best combination of markers for prediction of diabetes within 3 years; (ROC-AUC [95%CI]: 0.92 [0.84-1.00]). In multivariate Cox regression analysis, AUC(5-10 min)) (P = .001) was the strongest independent predictor and interacted significantly with all tested OGTT-derived parameters. AUC(5-10 min) below percentile 10 of controls was associated with 50-70% progression to T1D regardless of age. Similar results were obtained for AUC(120-150 min).

CONCLUSIONS

Clamp-derived first-phase C-peptide release can be used as an efficient and simple screening strategy in persistently autoAb(+) offspring and siblings of T1D patients to predict impending diabetes.

Clinical and biological characteristics of diabetic patients under age 40 in Cameroon: relation to autoantibody status and comparison with Belgian patients

AIMS

We investigated the prevalence of diabetes autoantibodies (Abs) in Cameroonian patients and controls, assessed their contribution in disease classification and compared results with data from Belgium.

METHODS

Abs against GAD (GADA), IA-2 (IA-2A) and zinc transporter 8 (ZnT8A) were assessed in 302 recently diagnosed Cameroonian patients with diabetes and 184 control subjects without diabetes aged below 40 years.

RESULTS

Only 27 (9%) Cameroonian patients were younger than 15 years. Overall, 29% of patients presented at least one diabetes-associated antibody vs 9% in healthy controls (24% vs 7% for GADA (p<0.001), 10% vs 3% for IA-2A (p<0.006), 4% vs 2% for ZnT8A). Ab(+) patients had lower C-peptide levels (p<0.001), were more often insulin-treated (p<0.002) and were as frequently diagnosed with type 1 diabetes as Ab(-) patients. Only 43% of Ab(+) patients aged 15-39 years were clinically classified as having type 1 diabetes in Cameroon vs 96% in Belgium (p<0.001). Not one Ab(+) Cameroonian patient carried HLA-DQ2/DQ8 genotype vs 23% of Belgian Ab(+) patients (p<0.001). Younger age at diagnosis and antibody positivity were independent predictors of insulin therapy. Ab(+) Cameroonian patients were older (p<0.001), had higher BMI (p<0.001) and lower Ab titers than Belgian Ab(+) patients. In ketonuric patients, prevalence of autoantibodies was similar as in non-ketonuric patients.

CONCLUSIONS

In Cameroonian patients with diabetes aged under 40 years, antibody-positivity is not clearly related to disease phenotype, but may help predict the need for insulin treatment.

In antibody-positive first-degree relatives of patients with type 1 diabetes, HLA-A*24 and HLA-B*18, but not HLA-B*39, are predictors of impending diabetes with distinct HLA-DQ interactions

AIMS/HYPOTHESIS

Secondary type 1 diabetes prevention trials require selection of participants with impending diabetes. HLA-A and -B alleles have been reported to promote disease progression. We investigated whether typing for HLA-B*18 and -B*39 may complement screening for HLA-DQ8, -DQ2 and -A*24 and autoantibodies (Abs) against islet antigen-2 (IA-2) and zinc transporter 8 (ZnT8) for predicting rapid progression to hyperglycaemia.

METHODS

A registry-based group of 288 persistently autoantibody-positive (Ab(+)) offspring/siblings (aged 0-39 years) of known patients (Ab(+) against insulin, GAD, IA-2 and/or ZnT8) were typed for HLA-DQ, -A and -B and monitored from the first Ab(+) sample for development of diabetes within 5 years.

RESULTS

Unlike HLA-B*39, HLA-B*18 was associated with accelerated disease progression, but only in HLA-DQ2 carriers (p < 0.006). In contrast, HLA-A*24 promoted progression preferentially in the presence of HLA-DQ8 (p < 0.002). In HLA-DQ2- and/or HLA-DQ8-positive relatives (n = 246), HLA-B*18 predicted impending diabetes (p = 0.015) in addition to HLA-A*24, HLA-DQ2/DQ8 and positivity for IA-2A or ZnT8A (p ≤ 0.004). HLA-B*18 interacted significantly with HLA-DQ2/DQ8 and HLA-A*24 in the presence of IA-2 and/or ZnT8 autoantibodies (p ≤ 0.009). Additional testing for HLA-B*18 and -A*24 significantly improved screening sensitivity for rapid progressors, from 38% to 53%, among relatives at high Ab-inferred risk carrying at least one genetic risk factor. Screening for HLA-B*18 increased sensitivity for progressors, from 17% to 28%, among individuals carrying ≥ 3 risk markers conferring >85% 5 year risk.

CONCLUSIONS/INTERPRETATION

These results reinforce the importance of HLA class I alleles in disease progression and quantify their added value for preparing prevention trials.

Sensitive and specific time-resolved fluorescence immunoassay of rat C-peptide for measuring hormone secretory and storage capacity of β-cells in vivo and in vitro

The limitations of current rat C-peptide assays led us to develop a time-resolved fluorescence immunoassay for measurements in plasma, incubation media, and tissue/cell extracts. The assay uses 2 monoclonal antibodies, binding to different parts of the C-peptide molecule, and allowing, respectively, capture of the peptide and its detection by europium-labeled streptavidin. It is performed on 25-μL samples for a dynamic range from 66pM up to 3900pM C-peptide and displays over 95% recovery of added peptide in the range of 111pM to 2786pM. Its inter- and intra-assay coefficients of variations are, respectively, lower than 7.6% and 4.8%. Cross-reactivities by rat insulin and by human and porcine C-peptide are negligible, and cross-reactivity by mouse C-peptide is 6% ± 2%. The assay has been validated for in vivo and in vitro measurements of C-peptide release and cellular content. Release patterns were similar to those for insulin and occurred in equimolar concentrations for both peptides. The molar C-peptide contents in purified β-cells and isolated islets were similar to the corresponding insulin contents. This was also the case for pancreatic extracts containing protease inhibitors.

Screening for insulinoma antigen 2 and zinc transporter 8 autoantibodies: a cost-effective and age-independent strategy to identify rapid progressors to clinical onset among relatives of type 1 diabetic patients

In first-degree relatives of type 1 diabetic patients, we investigated whether diabetes risk assessment solely based on insulinoma antigen 2 (IA-2) and zinc transporter 8 (ZnT8) antibody status (IA-2A, respectively, ZnT8A) is as effective as screening for three or four autoantibodies [antibodies against insulin (IAA), glutamate decarboxylase 65 kDa (GAD) glutamate decarboxylase autoantibodies (GADA) and IA-2A with or without ZnT8A] in identifying children, adolescents and adults who progress rapidly to diabetes (within 5 years). Antibodies were determined by radiobinding assays during follow-up of 6444 siblings and offspring aged 0-39 years at inclusion and recruited consecutively by the Belgian Diabetes Registry. We identified 394 persistently IAA(+) , GADA(+) , IA-2A(+) and/or ZnT8A(+) relatives (6·1%). After a median follow-up time of 52 months, 132 relatives developed type 1 diabetes. In each age category tested (0-9, 10-19 and 20-39 years) progression to diabetes was significantly quicker in the presence of IA-2A and/or ZnT8A than in their joint absence (P < 0·001). Progression rate was age-independent in IA-2A(+) and/or ZnT8A(+) relatives but decreased with age if only GADA and/or IAA were present (P = 0·008). In the age group mainly considered for immune interventions until now (10-39 years), screening for IA-2A and ZnT8A alone identified 78% of the rapid progressors (versus 75% if positive for ≥ 2 antibodies among IAA, GADA, IA-2A and ZnT8A or versus 62% without testing for ZnT8A). Screening for IA-2A and ZnT8A alone allows identification of the majority of rapidly progressing prediabetic siblings and offspring regardless of age and is more cost-effective to select participants for intervention trials than conventional screening.

Immune responses against islet allografts during tapering of immunosuppression--a pilot study in 5 subjects

Transplantation of isolated islet of Langerhans cells has great potential as a cure for type 1 diabetes but continuous immune suppressive therapy often causes considerable side effects. Tapering of immunosuppression in successfully transplanted patients would lower patients' health risk. To identify immune biomarkers that may prove informative in monitoring tapering, we studied the effect of tapering on islet auto- and alloimmune reactivity in a pilot study in five transplant recipients in vitro. Cytokine responses to the graft were measured using Luminex technology. Avidity of alloreactive cytotoxic T Lymphocytes (CTL) was determined by CD8 blockade. The influence of immunosuppression was mimicked by in vitro replenishment of tacrolimus and MPA, the active metabolite of mycophenolate mofetil. Tapering of tacrolimus was generally followed by decreased C-peptide production. T-cell autoreactivity increased in four out of five patients during tapering. Overall alloreactive CTL precursor frequencies did not change, but their avidity to donor mismatches increased significantly after tapering (P = 0·035). In vitro addition of tacrolimus but not MPA strongly inhibited CTL alloreactivity during tapering and led to a significant shift to anti-inflammatory graft-specific cytokine production. Tapering of immunosuppression is characterized by diverse immune profiles that appear to relate inversely to plasma C-peptide levels. Highly avid allospecific CTLs that are known to associate with rejection increased during tapering, but could be countered by restoring immune suppression in vitro. Immune monitoring studies may help guiding tapering of immunosuppression after islet cell transplantation, even though we do not have formal prove yet that the observed changes reflect direct effects of immune suppression on immunity.

An important minority of prediabetic first-degree relatives of type 1 diabetic patients derives from seroconversion to persistent autoantibody positivity after 10 years of age

AIMS/HYPOTHESIS

The appearance of autoantibodies (Abs) before diabetes onset has mainly been studied in young children. However, most patients develop type 1 diabetes after the age of 15 years. In first-degree relatives aged under 40 years, we investigated the frequency of seroconversion to (persistent) Ab positivity, progression to diabetes and baseline characteristics of seroconverters according to age.

METHODS

Abs against insulin (IAA), glutamate decarboxylase (GADA), insulinoma-associated protein 2 (IA-2A) and zinc transporter 8 (ZnT8A) were measured during follow-up of 7,170 first-degree relatives.

RESULTS

We identified 379 (5.3%) relatives with positivity for IAA, GADA, IA-2A and/or ZnT8A (Ab(+)) at first sampling and 224 (3.1%) at a later time point. Most seroconversions occurred after the age of 10 years (63%). During follow-up, Abs persisted more often in relatives initially Ab(+) (76%) than in seroconverters (53%; p < 0.001). In both groups diabetes developed at a similar pace and almost exclusively with Ab persistence (136 of 139 prediabetic individuals). For both groups, progression was more rapid if Abs appeared before the age of 10 years. Baseline characteristics at seroconversion did not vary significantly according to age.

CONCLUSIONS/INTERPRETATION

Seroconversion to (persistent) Ab(+) occurs regardless of age. Although the progression rate to diabetes is higher under age 10 years, later seroconverters (up to age 40 years) have similar characteristics when compared with age-matched initially Ab(+) relatives and generate an important minority of prediabetic relatives, warranting their identification and, eventually, enrolment in prevention trials.

Clusters of conserved beta cell marker genes for assessment of beta cell phenotype

Background and Methodology

The aim of this study was to establish a gene expression blueprint of pancreatic beta cells conserved from rodents to humans and to evaluate its applicability to assess shifts in the beta cell differentiated state. Genome-wide mRNA expression profiles of isolated beta cells were compared to those of a large panel of other tissue and cell types, and transcripts with beta cell-abundant and -selective expression were identified. Iteration of this analysis in mouse, rat and human tissues generated a panel of conserved beta cell biomarkers. This panel was then used to compare isolated versus laser capture microdissected beta cells, monitor adaptations of the beta cell phenotype to fasting, and retrieve possible conserved transcriptional regulators.

Principal Findings

A panel of 332 conserved beta cell biomarker genes was found to discriminate both isolated and laser capture microdissected beta cells from all other examined cell types. Of all conserved beta cell-markers, 15% were strongly beta cell-selective and functionally associated to hormone processing, 15% were shared with neuronal cells and associated to regulated synaptic vesicle transport and 30% with immune plus gut mucosal tissues reflecting active protein synthesis. Fasting specifically down-regulated the latter cluster, but preserved the neuronal and strongly beta cell-selective traits, indicating preserved differentiated state. Analysis of consensus binding site enrichment indicated major roles of CREB/ATF and various nutrient- or redox-regulated transcription factors in maintenance of differentiated beta cell phenotype.

Conclusions

Conserved beta cell marker genes contain major gene clusters defined by their beta cell selectivity or by their additional abundance in either neural cells or in immune plus gut mucosal cells. This panel can be used as a template to identify changes in the differentiated state of beta cells.

Contribution of antibodies against IA-2β and zinc transporter 8 to classification of diabetes diagnosed under 40 years of age

OBJECTIVE

We investigated whether measuring autoantibodies against zinc transporter 8 (ZnT8A) and IA-2β (IA-2βA) may improve classification of new-onset type 1 diabetic patients based on detection of autoantibodies against insulin (IAA), GAD (GADA), and IA-2 (IA-2A). In addition, we studied the correlation of IA-2βA and ZnT8A with other biological and demographic variables.

RESEARCH DESIGN AND METHODS

Circulating autoantibodies were determined by liquid-phase radiobinding assays from 761 healthy control subjects and 655 new-onset (<1 week insulin) diabetic patients (aged 0-39 years) with clinical type 1 diabetes phenotype consecutively recruited by the Belgian Diabetes Registry.

RESULTS

At diagnosis, IA-2βA and ZnT8A prevalences were 41 and 58%, respectively. In IAA-negative, GADA-negative, and IA-2A-negative patients, one IA-2βA-positive and eleven ZnT8A-positive individuals were identified at the expense of eight and seven additional positive control subjects (1%), respectively, for each test. ZnT8A or IA-2βA screening increased (P < 0.001; McNemar) the number of patients with ≥2 antibodies both under (from 78 to 87% for ZnT8A and 82% for IA-2βA) and above age 15 (from 51 to 63% for ZnT8A and 56% for IA-2βA) versus 0% in control subjects. IA-2βA and ZnT8A were preferentially associated with IA-2A, and with younger age at diagnosis. Unlike ZnT8A, IA-2βA levels were positively correlated with HLA-DQ8 and negatively with HLA-DQ2. ZnT8A could replace IAA for classification of patients above age 10 without loss of sensitivity or specificity.

CONCLUSIONS

ZnT8A, and to a lesser degree IA-2βA, may usefully complement GADA, IA-2A, and IAA for classifying insulin-treated diabetes under age 40 years.

Hyperglycaemic clamp test for diabetes risk assessment in IA-2-antibody-positive relatives of type 1 diabetic patients

AIMS/HYPOTHESIS

The aim of the study was to investigate the use of hyperglycaemic clamp tests to identify individuals who will develop diabetes among insulinoma-associated protein-2 antibody (IA-2A)-positive first-degree relatives (IA-2A(+) FDRs) of type 1 diabetic patients.

METHODS

Hyperglycaemic clamps were performed in 17 non-diabetic IA-2A(+) FDRs aged 14 to 33 years and in 21 matched healthy volunteers (HVs). Insulin and C-peptide responses were measured during the first (5-10 min) and second (120-150 min) release phase, and after glucagon injection (150-160 min). Clamp-induced C-peptide release was compared with C-peptide release during OGTT.

RESULTS

Seven (41%) FDRs developed diabetes 3-63 months after their initial clamp test. In all phases they had lower C-peptide responses than non-progressors (p < 0.05) and HVs (p < 0.002). All five FDRs with low first-phase release also had low second-phase release and developed diabetes 3-21 months later. Two of seven FDRs with normal first-phase but low second-phase release developed diabetes after 34 and 63 months, respectively. None of the five FDRs with normal C-peptide responses in all test phases has developed diabetes so far (follow-up 56 to 99 months). OGTT-induced C-peptide release also tended to be lower in progressors than in non-progressors or HVs, but there was less overlap in results between progressors and the other groups using the clamp.

CONCLUSIONS/INTERPRETATION

Clamp-derived functional variables stratify risk of diabetes in IA-2A(+) FDRs and may more consistently identify progressors than OGTT-derived variables. A low first-phase C-peptide response specifically predicts impending diabetes while a low second-phase response may reflect an earlier disease stage.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00654121

FUNDING

The insulin trial was financially supported by Novo Nordisk Pharma nv.

Differences in baseline lymphocyte counts and autoreactivity are associated with differences in outcome of islet cell transplantation in type 1 diabetic patients

OBJECTIVE

The metabolic outcome of islet cell transplants in type 1 diabetic patients is variable. This retrospective analysis examines whether differences in recipient characteristics at the time of transplantation are correlated with inadequate graft function.

RESEARCH DESIGN AND METHODS

Thirty nonuremic C-peptide-negative type 1 diabetic patients had received an intraportal islet cell graft of comparable size under an ATG-tacrolimus-mycophenolate mofetil regimen. Baseline patient characteristics were compared with outcome parameters during the first 6 posttransplant months (i.e., plasma C-peptide, glycemic variability, and gain of insulin independence). Correlations in univariate analysis were further examined in a multivariate model.

RESULTS

Patients that did not become insulin independent exhibited significantly higher counts of B-cells as well as a T-cell autoreactivity against insulinoma-associated protein 2 (IA2) and/or GAD. In one of them, a liver biopsy during posttransplant year 2 showed B-cell accumulations near insulin-positive beta-cell aggregates. Higher baseline total lymphocytes and T-cell autoreactivity were also correlated with lower plasma C-peptide levels and higher glycemic variability.

CONCLUSIONS

Higher total and B-cell counts and presence of T-cell autoreactivity at baseline are independently associated with lower graft function in type 1 diabetic patients receiving intraportal islet cells under ATG-tacrolimus-mycophenolate mofetil therapy. Prospective studies are needed to assess whether control of these characteristics can help increase the function of islet cell grafts during the first year posttransplantation.

Insulin treatment in IA-2A-positive relatives of type 1 diabetic patients

AIMS

We examined whether parenteral regular insulin can prevent diabetes in IA-2 antibody-positive (IA-2A+) relatives of type 1 diabetic patients, using a trial protocol that differed substantially from that of the Diabetes Prevention Trial-1.

METHODS

Twenty-five IA-2A+ relatives received regular human insulin twice a day for 36 months, during which time they were followed (median [interquartile range; IQR]: 47 [19-66] months) for glucose tolerance, HbA(1c) and islet autoantibodies, together with 25 IA-2A+ relatives (observation/control group) who fulfilled the same inclusion criteria, but were observed for 52 [27-67] months (P=0.58).

RESULTS

Twelve (48%) insulin-treated relatives and 15 (60%) relatives in the control group developed diabetes. There was no difference in diabetes-free survival between the two groups (P=0.97). Five-year progression (95% confidence interval) was 44% (25-69) in the insulin-treated group and 49% (29-70) in the observation group. At inclusion, progressors tended to have a higher pro-insulin/C-peptide ratio than non-progressors when measured 2 hours after a standardized glucose load (median [IQR]: 2.7% [1.8-4.3] vs. 1.6% [1.1-2.1]; P=0.01). No major hypoglycaemic episodes or significant increases in body mass index or diabetes autoantibodies were observed.

CONCLUSION

Prophylactic injections of regular human insulin were well tolerated, but failed to prevent type 1 diabetes onset in IA-2A+ relatives.

Relevance of cytotoxic alloreactivity under different immunosuppressive regimens in clinical islet cell transplantation

Islet or beta cell transplantation provides a promising cure for type 1 diabetes patients, but insulin-independency decreases frequently over time. Immunosuppressive regimens are implemented attempting to cope with both auto- and alloimmunity after transplantation. We analysed the influence of different immunotherapies on autoreactive and alloreactive T cell patterns and transplant outcome. Patients receiving three different immunosuppressive regimens were analysed. All patients received anti-thymocyte globulin induction therapy. Twenty-one patients received tacrolimus-mycophenolate mofetil maintenance immunosuppression, whereas the other patients received tacrolimus-sirolimus (SIR, n = 5) or SIR only (n = 5). Cellular autoreactivity and alloreactivity (CTL precursor frequency) were measured ex vivo. Clinical outcome in the first 6 months after transplantation was correlated with immunological parameters. C-peptide levels were significantly different between the three groups studied (P = 0.01). We confirm that C-peptide production was correlated negatively with pretransplant cellular autoreactivity and low graft size (P = 0.001, P = 0.007 respectively). Combining all three therapies, cellular autoimmunity after transplantation was not associated with delayed insulin-independence or C-peptide production. In combined tacrolimus-SIR and SIR-treated patients, CTL alloreactivity was associated with less insulin independence and C-peptide production (P = 0.03). The percentage of donors to whom high CTLp frequencies were measured was lower in insulin-independent recipients (P = 0.03). In this cohort of islet cell graft recipients, clinical outcome in the first 6 months after transplantation correlates with the applied immunosuppressive regimen. An association exists between insulin-independence and lower incidence of CTL alloreactivity towards donor human leucocyte antigen. This observational study demonstrates the usefulness of monitoring T cell reactivity against islet allografts to correlate immune function with graft survival.

Allograft-specific cytokine profiles associate with clinical outcome after islet cell transplantation

Islet cell transplantation can cure type 1 diabetes, but allograft rejection and recurrent autoimmunity may contribute to decreasing insulin independence over time. In this study we report the association of allograft-specific proliferative and cytokine profiles with clinical outcome. Peripheral blood mononuclear cells were obtained of 20 islet recipients. Cytokine values in mixed lymphocyte cultures (MLC) were determined using stimulator cells with graft-specific HLA class II. Qualitative and quantitative cytokine profiles were determined before and after islet transplantation, blinded from clinical outcome. Cytotoxic T Lymphocyte precursor (CTLp) assays were performed to determine HLA class I alloreactivity. Allograft-specific cytokine profiles were skewed toward a Th2 or regulatory (Treg) phenotype after transplantation in insulin-independent, but not in insulin-requiring recipients. IFNgamma/IL10 ratio and MLC proliferation decreased after transplantation in insulin-independent recipients (p = 0.006 and p = 0.01, respectively). Production of the Treg cytokine IL10 inversely correlated with proliferation in alloreactive MLC (p = 0.008) and CTLp (p = 0.005). Production of IL10 combined with low-MLC reactivity associated significantly with insulin independence. The significant correlation between allograft-specific cytokine profiles and clinical outcome may reflect the induction of immune regulation in successfully transplanted recipients. Islet donor-specific IL10 production correlates with low alloreactivity and superior islet function.

Simultaneous Measurement of Plasma Concentrations of Proinsulin and C-Peptide and Their Ratio with a Trefoil-Type Time-Resolved Fluorescence Immunoassay

Background: When the concentrations of 2 or more substances are measured separately, their molar ratios are subject to the additive imprecisions of the different assays. We hypothesized that the cumulative error for concentration ratios of peptides containing a common sequence might be minimized by measuring the peptides simultaneously with a “trefoil-type” immunoassay.

Methods: As a model of this approach, we developed a dual-label time-resolved fluorescence immunoassay (TRFIA) to simultaneously measure proinsulin, C-peptide, and the proinsulin–C-peptide ratio (PI/C). A monoclonal antibody captures all C-peptide–containing molecules, and 2 differently labeled antibodies distinguish between proinsulin-like molecules and true C-peptide.

Results: The trefoil-type TRFIA was capable of measuring plasma C-peptide and proinsulin simultaneously without mutual interference at limits of quantification of 48 and 8125 pmol/L, and 2.1 and 197 pmol/L, respectively. Within-laboratory imprecision values for the trefoil-type TRFIA ranged between 8.4% and 12% for the hormone concentrations. Unlike the hormone results obtained with separate assays, imprecision did not increase when PI/C was calculated from trefoil assay results (P &lt; 0.05). Peptide concentrations were highly correlated with results obtained in individual comparison assays (r2 ≥ 0.965; P &lt; 0.0001). The total error for PI/C obtained with the trefoil-type TRFIA remained ≤25% over a broader C-peptide range than with separate hormone assays (79–7200 pmol/L vs 590–4300 pmol/L C-peptide). Preliminary data indicate little or no interference by heterophile antibodies.

Conclusions: The developed trefoil-type TRFIA is a reliable method for simultaneous measurement of proinsulin, C-peptide, and PI/C and provides proof of principle for the development of other trefoil-type multiple-label immunoassays.

Cellular islet autoimmunity associates with clinical outcome of islet cell transplantation

Background

Islet cell transplantation can cure type 1 diabetes (T1D), but only a minority of recipients remains insulin–independent in the following years. We tested the hypothesis that allograft rejection and recurrent autoimmunity contribute to this progressive loss of islet allograft function.

Methodology/Principal Findings

Twenty-one T1D patients received cultured islet cell grafts prepared from multiple donors and transplanted under anti-thymocyte globulin (ATG) induction and tacrolimus plus mycophenolate mofetil (MMF) maintenance immunosuppression. Immunity against auto- and alloantigens was measured before and during one year after transplantation. Cellular auto- and alloreactivity was assessed by lymphocyte stimulation tests against autoantigens and cytotoxic T lymphocyte precursor assays, respectively. Humoral reactivity was measured by auto- and alloantibodies. Clinical outcome parameters - including time until insulin independence, insulin independence at one year, and C-peptide levels over one year- remained blinded until their correlation with immunological parameters. All patients showed significant improvement of metabolic control and 13 out of 21 became insulin-independent. Multivariate analyses showed that presence of cellular autoimmunity before and after transplantation is associated with delayed insulin-independence (p = 0.001 and p = 0.01, respectively) and lower circulating C-peptide levels during the first year after transplantation (p = 0.002 and p = 0.02, respectively). Seven out of eight patients without pre-existent T-cell autoreactivity became insulin-independent, versus none of the four patients reactive to both islet autoantigens GAD and IA-2 before transplantation. Autoantibody levels and cellular alloreactivity had no significant association with outcome.

Conclusions/Significance

In this cohort study, cellular islet-specific autoimmunity associates with clinical outcome of islet cell transplantation under ATG-tacrolimus-MMF immunosuppression. Tailored immunotherapy targeting cellular islet autoreactivity may be required. Monitoring cellular immune reactivity can be useful to identify factors influencing graft survival and to assess efficacy of immunosuppression.

Trial Registration

Clinicaltrials.gov NCT00623610

The age at diagnosis of type 1 diabetes continues to decrease in Belgian boys but not in girls: a 15-year survey

BACKGROUND

The age at clinical onset of type 1 diabetes is decreasing. Preliminary Belgian data suggested that this anticipation occurred preferentially in boys. We investigated whether this gender-specific anticipation could be confirmed over a 15-year observation period.

METHODS

In Antwerp, we studied incidence trends between 1989 and 2003 in 746 type 1 diabetic patients under age 40. For 2928 antibody-positive patients diagnosed nationwide during the same period, age at diagnosis was analysed according to gender and calendar year.

RESULTS

In Antwerp, the incidence of type 1 diabetes under age 15 increased significantly with time from 10.9/100 000/year in 1989-1993 to 15.8/100 000/year in 1999-2003 (p = 0.008). The rising incidence in children was largely restricted to boys under age 10 where the incidence more than doubled during the 15-year period (6.8/100 000/year in 1989-1993 vs 17.2/100 000/year in 1999-2003; p < 0.001). Such an increase was not found in girls under age 10 (p = 0.54). This selective trend toward younger age at diagnosis in boys was confirmed in the larger group of Belgian patients where the median age at diagnosis decreased in boys-but not in girls-from 20 years in 1989-1993 to 15 years in 1999-2003 (p < 0.001).

CONCLUSIONS

Over a 15-year observation period, a selective anticipation of clinical onset of type 1 diabetes was found in boys but not in girls. This suggests that an environmental factor may preferentially accelerate the sub-clinical disease process in young boys.

Adiponectin levels do not predict clinical onset of type 1 diabetes in antibody-positive relatives

AIMS/HYPOTHESIS

Insulin resistance has been proposed as a risk factor for type 1 diabetes. We investigated whether adiponectin, an insulin sensitiser, can serve as an additional predictive marker for type 1 diabetes in first-degree relatives of known patients.

METHODS

Adiponectin was followed in 211 persistently islet antibody-positive (Ab+) first-degree relatives of type 1 diabetic patients and in 211 age- and sex-matched persistently antibody-negative relatives, and correlated with antibody status, random proinsulin:C-peptide ratio and HLA-DQ genotype. During follow-up, 37 Ab+ relatives developed type 1 diabetes.

RESULTS

In the group of 422 relatives, baseline adiponectin correlated inversely with age and BMI and was lower in male than in female participants, especially after 15 years of age (p < 0.001). There was no correlation with antibody status or later development of diabetes. In 24 Ab+ relatives sampled fasted, adiponectin levels correlated significantly with homeostasis model assessment of insulin sensitivity (p = 0.006). In Ab+ relatives (n = 211), adiponectin levels could not predict type 1 diabetes nor complement risk assessment based on islet antibodies, HLA-DQ genotype and pancreatic hormones in Cox regression analysis.

CONCLUSIONS/INTERPRETATION

Adiponectin levels do not contribute to the prediction of type 1 diabetes in Ab+ relatives.

Identification of prediabetes in first-degree relatives at intermediate risk of type I diabetes

Prevention trials of type I diabetes are limited by recruitment of individuals at high risk of the disease. We investigated whether demographic and biological characteristics can identify rapid progressors among first-degree relatives of known patients at intermediate (< 10%) 5-year risk. Diabetes-associated antibodies, random proinsulin : C-peptide (PI/C) ratio and HLA DQ genotype were determined (repeatedly) in 258 islet antibody-positive IA-2Antibody-negative (Abpos/IA-2Aneg) normoglycaemic first-degree relatives. During follow-up (median 81 months), 14 of 258 Abpos/IA-2Aneg relatives developed type I diabetes; 13 (93%) of them had persistent antibodies conferring a 12% [95% confidence interval (CI): 5-19%] 5-year risk of diabetes. In Abpos/IA-2Aneg relatives with persistent antibodies (n = 126), the presence of >/= 1 HLA DQ susceptibility haplotype in the absence of a protective haplotype (P = 0.033) and appearance on follow-up of a high PI/C ratio (P = 0.007) or IA-2A-positivity (P = 0.009) were identified as independent predictors of diabetes. In persistently antibody-positive relatives with HLA DQ risk a recurrently high PI/C ratio or development of IA-2A identified a subgroup (n = 32) comprising 10 of 13 (77%) prediabetic relatives and conferred a 35% (95% CI: 18-53%) 5-year risk. Under age 15 years, 5-year progression (95% CI) was 57% (30-84%) and sensitivity 62%. In the absence of IA-2A, the combination of antibody persistence, HLA DQ risk and elevated PI/C ratio or later development of IA-2A and young age defines a subgroup of relatives with a high risk of type I diabetes (>/= 35% in 5 years). Together with initially IA-2A-positive relatives these individuals qualify for standardized beta cell function tests in view of prevention trials.

Species and epitope specificity of two 65 kDa glutamate decarboxylase time-resolved fluorometric immunoassays

The 65 kDa isoform of human glutamate decarboxylase (GAD65) is a major autoantigen in type 1 diabetes (T1D). In the present study, we have developed a sensitive sandwich time-resolved fluorescence immunoassay (TRFIA) for the quantification of GAD65 in cell extracts, cell media and serum. The monoclonal antibody GAD-6 is used to selectively capture GAD65 but not the slightly larger isoform GAD67, and the utilization of different detecting antibodies with distinct GAD65 epitope specificity allows modulating the specificity of the assay. To this effect we have biotinylated a recombinant antigen-binding fragment (rFab) with epitope specificity for the N-terminal region of rat and human GAD65 (rFab N-GAD65) and another rFab that selectively binds to the middle part of human GAD65 (rFab b96.11). In the assay the biotinylated rFabs are recognized by Europium labeled streptavidin. The obtained time-resolved fluorescence (TRF) is directly proportional to the concentration of GAD65 over a large measuring range (0.1 to >100 ng/mL). Based on total error estimation including both bias and imprecision, the lower limit of quantitation (LLOQ) of GAD65 in cell extracts is 0.33 ng/mL with the N-GAD65 TRFIA, and 0.10 ng/mL with the b96.11 TRFIA, but the latter is suitable for human GAD65 only, whereas the N-GAD65 TRFIA has equal sensitivity with rat and human GAD65. Specificity was further checked with GAD65/67 fusion proteins, confirming that the presence of intact capture as well as detection epitope on the analyte is a prerequisite for recognition in both assays. We show that the beta cell-specific marker GAD65 can be quantified in pancreatic cell extracts and in serum, allowing studies on discharge during cell death in vitro as well as in vivo.

Sex- and season-dependent differences in C-peptide levels at diagnosis of immune-mediated type 1 diabetes

AIMS/HYPOTHESIS

The incidence of type 1 diabetes varies according to age, sex and season of diagnosis. We investigated whether these and other clinical, biological and anthropometric parameters were correlated with residual beta cell function in newly diagnosed patients, since it is possible that the nature of external and/or genetic disease accelerators may be (partly) reflected in the inaugural disease presentation.

MATERIALS AND METHODS

The correlates of random C-peptide levels sampled shortly after diagnosis (median [interquartile range]: 3 [0-14] days) were studied by multivariate analysis in 1,883 islet-antibody-positive diabetic patients aged <40 years who were diagnosed between 1989 and 2000.

RESULTS

Higher C-peptide levels (above percentile 50 of patients) were associated with older age at diagnosis, female sex, diagnosis in the high-incidence season (October to March), less-decreased BMI (expressed as a standard deviation score), lower insulin requirements after stabilisation, lower prevalence of ketonuria and a less-increased glycaemia at diagnosis (all p < 0.001). C-peptide levels were not correlated with calendar year at diagnosis, duration of symptoms prior to diagnosis, HLA-DQ2/DQ8 genotype or islet antibody status.

CONCLUSIONS/INTERPRETATION

Sex- and season-dependent differences in residual functional beta cell mass and/or insulin resistance have been identified at diagnosis of type 1 diabetes. They may reflect differences in disease-precipitating external or lifestyle factors and should be further investigated longitudinally in prediabetes to further identify putative aetiological factors, which may provide targets for prevention.

Proinsulin levels and the proinsulin:c-peptide ratio complement autoantibody measurement for predicting type 1 diabetes

AIMS/HYPOTHESIS

We investigated whether random proinsulin levels and proinsulin:C-peptide ratio (PI:C) complement immune and genetic markers for identifying relatives at high risk of type 1 diabetes.

MATERIALS AND METHODS

During an initial sampling, random glycaemia, proinsulin, PI:C and HLA DQ genotype were determined in 561 non-diabetic first-degree relatives who had been positive for islet autoantibodies on one or more occasions and in 561 age- and sex-matched persistently antibody-negative relatives.

RESULTS

During follow-up (median 62 months), 46 relatives with antibodies at entry developed type 1 diabetes. At baseline, antibody-positive relatives (n=338) had higher PI:C values (p<0.001) than antibody-negative subjects with (n=223) or subjects without (n=561) later seroconversion. Proinsulin and PI:C were graded according to risk of diabetes as expressed by positivity for (multiple) antibodies or IA-2 antibodies, especially in persons carrying the high-risk HLA DQ2/DQ8 genotype and in prediabetic relatives. In the presence of multiple or IA-2 antibodies, a PI:C ratio exceeding percentile 66 of all antibody-negative relatives at entry (n=784) conferred a 5-year diabetes risk of 50% and 68%, respectively (p<0.001 vs 13% for same antibody status with PI:C<percentile 66). Cox regression analysis confirmed random PI:C as an independent predictor of the risk of diabetes (p< or =0.001).

CONCLUSIONS/INTERPRETATION

Random proinsulin and PI:C represent dynamic markers of the state of beta cell function that complement immune markers in identifying relatives who are at homogeneously high risk of contracting type 1 diabetes and are therefore eligible for secondary prevention trials.

Alloreactivity Against Repeated HLA Mismatches of Sequential Islet Grafts Transplanted in Non-Uremic Type 1 Diabetes Patients

BACKGROUND

Islet transplantation can restore insulin production in type 1 diabetes patients. However, survival of the islet allografts will face rejection or recurrence of autoimmunity or a combination of both. In a study on islet-after-kidney transplants, we previously reported that islet cell recipients presented low T-cell alloresponses for HLA mismatches that were shared by the islet cell graft and the prior kidney graft, that is, repeated mismatch, while vigorous responses were measured against novel HLA mismatches.

METHODS

We now investigated T-cell alloreactivity to repeated HLA-mismatches in three non-uremic type 1 diabetic patients each receiving three sequential islet cell implants.

RESULTS

These islet-after-islet recipients patients exhibited low or absent responses to repeated mismatches to the first graft which was accompanied by sustained graft function, and reduced responsiveness towards subsequent grafts. In one patient, T-cell responses towards these mismatches were noticed following new mismatches in subsequent grafts, with loss of graft function.

CONCLUSION

These case reports further support the view that subsequent islet implantations can reduce alloreactivity for repeated HLA mismatches. They demonstrate the usefulness of monitoring T-cell reactivity against islet allografts to correlate immune function with graft survival and to identify conditions for preservation of beta-cell function.

Combined positivity for HLA DQ2/DQ8 and IA-2 antibodies defines population at high risk of developing type 1 diabetes

AIMS/HYPOTHESIS

Prevention trials in first-degree relatives of type 1 diabetic patients are hampered by large interindividual differences in progression rate to diabetes. We investigated whether specific combinations of immune and genetic markers can identify subgroups with more homogeneous progression to clinical onset.

METHODS

Antibodies against islet cell cytoplasm (ICA), insulin (IAA), glutamate decarboxylase (GADA) and IA-2 protein (IA-2A) were measured in 790 non-diabetic control subjects and 4,589 first-degree relatives under age 40.

RESULTS

On first sampling, 11.1% of the siblings presented at least one antibody type (p<0.001 vs other relatives). During follow-up (median 52 months) 43 subjects developed type 1 diabetes (31 siblings, ten offspring of a diabetic father, two offspring of a diabetic mother). Using Kaplan-Meier survival analysis and Cox regression, IA-2A conferred the highest 5-year diabetes risk (>50%) irrespective of the number of antibodies present. In initially IA-2A-positive relatives (n=58) progression to hyperglycaemia depended more on HLA DQ status than on type of kinship (84% progression in the presence of DQ2/DQ8 vs 32% in its absence; p<0.003). In IA-2A-negative relatives (n=4,531) 5-year progression to diabetes increased with the number of other antibodies (ICA, GADA and/or IAA) (p<0.001) but overall did not exceed 10% even for two or more antibodies. Among relatives initially positive for one or more antibody type other than IA-2A (n=315), there was significantly more progression to diabetes (overall still <10%) in carriers of DQ2 (p<0.001 vs no DQ2), regardless of DQ8 status.

CONCLUSIONS/INTERPRETATION

These observations suggest that the HLA-DQ-inferred risk of diabetes can proceed through two distinct pathways distinguished by IA-2A status. Combined positivity for DQ2/DQ8 and IA-2A defines a more homogeneous high-risk population for prevention trials than those used so far.

HLA incompatibility and immunogenicity of human pancreatic islet preparations cocultured with blood cells of healthy donors

Type 1 diabetes mellitus (T1D) is a T-cell-mediated autoimmune disease characterized by the destruction of beta cells in the pancreas. An attractive novel therapy for type 1 diabetes is pancreatic islet transplantation, provided that recurrent islet autoimmunity and allograft rejection can be prevented. We analyzed the response of peripheral blood mononuclear cells (PBMC) from healthy blood donors to human islet-cell preparations with a composition similar to that of islet grafts used in clinical transplantation trials. It was examined whether the degree of major histocompatibility complex incompatibility between PBMC and donor islet cells is related to the degree of proliferative T-cell responses during coculture of human leukocyte antigen (HLA)-matched and mismatched PBMC with human islet cell-preparations (i.e., mixed islet/lymphocyte reaction). Prominent T-cell responses were observed in the vast majority of cases of double HLA class II mismatches. Intermediate T-cell responsiveness was observed in single HLA class II mismatches, whereas HLA matches did not induce a T-cell response. Our results identify the potential immunogenicity of islet preparations transplanted between HLA-DR incompatible subjects regardless of an autoimmune background of the recipient.

Heterogeneity in distribution of amyloid-positive islets in type-2 diabetic patients

Amyloid-containing (A+) islets are characteristic for type-2 diabetes (T2D), but their abundance seems variable among patients. It is unclear whether the distribution of A+ islets follows a certain pattern or occurs randomly throughout the pancreatic organ. We investigated the topography of A+ islets in eight pancreata of T2D patients and eight sex- and age-matched non-diabetic subjects. Transversal sections of head, body and tail segments were stained with synaptophysin combined with Congo red to map/quantify islet tissue and amyloid. In the eight T2D pancreata, the overall percentage of A+ islets varied from 4% to 85%. Further analysis in body and tail indicated that peripheral regions exhibited higher percentages of A+ islets than central regions (averages of, respectively, 30% and 17%, P<0.05). Non-diabetic control pancreata also exhibited A+ islets, albeit at a 25-fold lower frequency; a tendency towards higher percentage of A+ islets in peripheral versus central regions was also observed. The higher percentage A+ islets in peripheral regions was associated with a higher density and relative islet over exocrine surface area. These observations on heterogeneity in abundance and distribution of A+ islets need consideration when sampling tissue for studies on human islet amyloidosis. The present methodology allows us to further investigate the susceptibility to amyloidosis of islets in peripheral regions of the pancreas.

EGF-induced proliferation of adult human pancreatic duct cells is mediated by the MEK/ERK cascade

Human postnatal pancreatic duct cells are a potential source of new beta cells. Factors regulating proliferation of human pancreatic duct cells in vitro are unknown. In several other cell types, this process is influenced by ligands of the ErbB receptor family. The expression and functionality of the ErbB family members and their possible role in duct cell proliferation were determined. In cultured adult human pancreatic duct cells the different members of the ErbB family (ErbB1-4) were present at transcript and protein level. Stimulation of the duct cells with epidermal growth factor (EGF) and betacellulin results in Tyr-phosphorylation of ErbB1 and ErbB2, followed by activation of Shc, MEK1/2 and ERK1/2. Duct cells with activated ErbB signaling changed morphology and motility. EGF induced proliferation of a fraction of the duct cells and treatment with PD98059 prevented Ki67 expression in EGF-supplemented cells. When transduced with recombinant adenovirus expressing constitutively activated MEK1, duct cells proliferate and spread even in the absence of EGF. Importantly, the adult human duct cells retain their capacity to recapitulate ngn3-induced embryonic (neuro)endocrine differentiation after proliferation. Therefore, the present data support a possible role for human adult pancreatic duct cells, following expansion and transdifferentiation, as a source of insulin by transplantation to type I diabetes patients.

Seasonality in clinical onset of type 1 diabetes in belgian patients above the age of 10 is restricted to HLA-DQ2/DQ8-negative males, which explains the male to female excess in incidence

AIMS/HYPOTHESIS

Type 1 diabetes arises from an interplay between environmental and genetic factors. The reported seasonality at diagnosis supports the hypothesis that currently unknown external triggers play a role in the onset of the disease. We investigated whether a seasonal pattern is observed at diagnosis in Belgian Type 1 diabetic patients, and if so whether seasonality varies according to age, sex and genetic risk, all known to affect the incidence of Type 1 diabetes.

METHODS

The seasonal pattern at clinical diagnosis was assessed in 2176 islet antibody-positive diabetic patients aged 0 to 39 years diagnosed between 1989 and 2000. Additional stratification was performed for age, sex and HLA-DQ genotype.

RESULTS

Overall, a significant seasonal pattern at clinical diagnosis of diabetes was observed (p<0.001). More subjects were diagnosed in the period of November to February (n=829) than during the period of June to September (n=619) characterised by higher averages of maximal daily temperature and daily hours of sunshine. However, the seasonal pattern was restricted to patients diagnosed above the age of 10 (0-9 years: p=0.398; 10-19 years: p<0.001; 20-29 years: p=0.003; 30-39 years: p=0.015). Since older age at diagnosis is associated with a male to female excess and a lower prevalence of the genetic accelerator HLA-DQ2/DQ8, we further stratified the patients aged 10 to 39 years (n=1675) according to HLA-DQ genotype and sex, and we found that the seasonal pattern was largely restricted to male subjects lacking DQ2/DQ8 (n=748; p<0.00 vs all others: n=927; p=0.031).

CONCLUSIONS/INTERPRETATION

In a subgroup of male patients diagnosed over the age of 10, the later stages of the subclinical disease process may be more driven by sex- and season-dependent external factors than in younger, female and genetically more susceptible subjects. These factors may explain the male to female excess in diabetes diagnosed in early adulthood.

Epidemiology of type 1 and type 2 diabetes. The added value of diabetes registries for conducting clinical studies: the Belgian paradigm

Diabetes registries have documented that the lifetime risk of diabetes amounts to at least 10% in the western world. Moreover the prevalence of type 2 diabetes is increasing worldwide especially in developing countries. Furthermore there is a secular trend toward earlier clinical manifestation of both type 1 and type 2 diabetes. In the absence of a permanent cure for primary diabetes the present estimated number of at least 150 million diabetic patients worldwide is expected to double within the next 20 years. Consequently a sharp increase in the global burden of chronic diabetes complications is to be feared in the coming decades. Therefore it is absolutely mandatory to intensify research efforts aiming at identifying the etiological factors involved and designing effective strategies for prediction and prevention of the disease and its devastating complications. Diabetes registries constitute instruments of choice to conduct such studies because they are able to collect standardised clinical, demographic and biological information from sufficiently large representative groups of patients and risk groups such as first degree relatives. Since 1989, the Belgian Diabetes Registry is studying all types of diabetes presenting before age 40 in Belgium and provides a paradigm of how diabetes registries may also contribute to the advancement of knowledge on disease heterogeneity, etiology, prediction and prevention.

IA-2 autoantibodies predict impending type I diabetes in siblings of patients

AIMS/HYPOTHESIS

Multiple islet autoantibody positivity is currently believed to best predict progression to Type I (insulin-dependent) diabetes mellitus. We compared its predictive value with that of positivity for a particular type of islet autoantibody, directed against the IA-2 antigen.

METHODS

Autoantibodies against islet cell cytoplasm (ICA), insulin (IAA), GAD (GADA) and IA-2 (IA-2A) were measured at initial sampling in 1724 non-diabetic siblings (median age [range]:16 [0-39] years) of Type I diabetic patients with a median follow-up of 50 months.

RESULTS

On initial sampling 11% of siblings were positive for one antibody type or more and 2.1% for three of more types. During follow-up, 27 antibody-positive siblings developed diabetes. Using survival analysis, the risk for clinical onset within 5 years was 34% in subjects positive for three or more types compared with 13% in those with one type or more. Progression to diabetes amounted to 12% within 5 years among siblings positive for IAA, 20% for ICA, 19% for GADA but 59% for IA-2A (p<0.001 vs absence of the respective antibody). IA-2A were detected in 1.7% of all siblings and in 56% of the prediabetic subjects on first sampling. Initial positivity for two or three antibody markers was associated with a higher progression rate in IA-2A positive as compared to IA-2A negative siblings (p=0.001). In absence of IA-2A initial positivity for another antibody (IAA, ICA or GADA) conferred a low (<10% within 5 years) risk of diabetes compared to subjects lacking this antibody.

CONCLUSIONS/INTERPRETATION

In siblings of Type I diabetic patients, IA-2A positivity is a more direct predictor of impending clinical onset than multiple antibody positivity per se. Assessment of IA-2A status allows us to select subjects with homogeneously high risk of diabetes for participation in prevention trials.

Different regulated expression of the tyrosine phosphatase-like proteins IA-2 and phogrin by glucose and insulin in pancreatic islets: relationship to development of insulin secretory responses in early life

IA-2 and phogrin are tyrosine phosphatase-like proteins that may mediate interactions between secretory granules and cytoskeleton in islets and neuroendocrine tissues. We investigated factors that regulate IA-2 and phogrin expression and their relationship to maturation of insulin secretory responses that occur after birth. Islet content of IA-2, but not phogrin, increased during the first 10 days of life in rats, when insulin secretion in response to glucose increased to adult levels. In cultured 5-day-old rat islets, IA-2 protein and mRNA was increased by glucose and agents that potentiate insulin secretion by the cAMP pathway. Addition of insulin increased IA-2 protein levels and insulin biosynthesis without affecting IA-2 mRNA. Blocking insulin secretion with diazoxide or insulin action with insulin receptor antibodies inhibited glucose-induced increases in IA-2 protein, but not those of mRNA. Phogrin expression was unchanged by all agents. Thus, IA-2 is regulated at the mRNA level by glucose and elevated cAMP, whereas locally secreted insulin modulates IA-2 protein levels by stimulating biosynthesis. In contrast, phogrin expression is insensitive to factors that modify beta-cell function. These results demonstrate differential regulation of two closely related secretory granule components and identify IA-2 as a granule membrane protein subject to autocrine regulation by insulin.

Low density lipoprotein can cause death of islet beta-cells by its cellular uptake and oxidative modification

Islet beta-cells express receptors for low density (LDL) and very low density (VLDL) lipoproteins that are internalized by receptor-mediated endocytosis. The present study examined whether this process can affect the viability of isolated rat islet beta-cells. Culture with LDL (from 6 micro g/ml on), but not VLDL, causes necrosis of beta-cells within 2 d. No toxicity was observed when LDL binding and/or endocytosis was prevented by low temperature (8 C), or by addition of heparin or an excess of VLDL. The LDL toxicity did not occur in the presence of antioxidants (probucol or a mixture of glutathion, vitamins A, C, E plus dithiothreitol) or of the radical scavenger butylated hydroxytoluene. The degree of LDL-induced toxicity was correlated with an increase in the electrophoretic mobility of LDL, an index for its oxidative modification. Both LDL toxicity and oxidation were suppressed by omission or chelation of copper and iron in the medium. Addition of oxidized LDL was not cytotoxic to beta-cells, which lack oxidized LDL receptors. It is concluded that uptake of LDL by islet beta-cells and subsequent oxidative reactions can be damaging for the cells. This process can be counteracted by HDL and VLDL, and by antioxidants.

The incidence of type 1 diabetes in the age group 0-39 years has not increased in Antwerp (Belgium) between 1989 and 2000: evidence for earlier disease manifestation

OBJECTIVE

A worldwide increase in the incidence of childhood type 1 diabetes has been observed. Because in various countries the majority of new type 1 diabetic patients are diagnosed in adulthood, we investigated whether the rising incidence of this disorder in children reflects a global increase in the incidence of diabetes or a shift toward earlier clinical presentation.

RESEARCH DESIGN AND METHODS

The incidence of type 1 diabetes presenting before age 40 years was prospectively measured in the Antwerp district over a 12-year period (1989-2000). The completeness of ascertainment was evaluated by the capture-recapture method. Trends in incidence during the study period were analyzed by Poisson regression.

RESULTS

The incidence of type 1 diabetes diagnosed before age 40 years remained constant over the 12-year period, averaging 9.9 cases per 100,000 individuals per year. The incidence was similar in both sexes under age 15 years, but a marked male excess was noted for adult-onset disease, in particular after age 20 years, resulting in a male-to-female ratio of 0.9 under age 15 years vs. 1.6 thereafter (P = 0.001). During the 12-year observation period, there was a significant tendency toward increasing incidence under age 15 years at the expense of a decreasing incidence between ages 15 and 40 years (P = 0.025). The annual increase in incidence averaged 1.8% under age 15 years and 5.0% under age 5 years (P = 0.06).

CONCLUSIONS

Our results indicate that in Belgium, the increasing incidence of childhood type 1 diabetes-especially for children under age 5 years-is not attributable to a global increase in disease incidence, but rather to earlier clinical manifestation. The results suggest that an environmental factor may preferentially accelerate the subclinical disease process in young diabetes-prone subjects.

Troglitazone does not protect rat pancreatic beta cells against free fatty acid-induced cytotoxicity

Thiazolidinediones are a novel class of antidiabetic drugs that reduce insulin resistance through interaction with nuclear peroxisome proliferator-activated receptor (PPAR)gamma. One of these agents, troglitazone, was also proposed to protect beta cells against FFA-induced toxicity, but this effect has not yet been directly demonstrated. We recently reported in vitro conditions under which free fatty acids (FFA) cause beta cell death by necrosis or apoptosis. The present study investigates whether troglitazone (10 microM) interferes with this FFA-induced toxicity. Addition of this compound did not protect against oleate- or palmitate-induced toxicity. On the contrary, it increased palmitate-induced necrosis during the first two days of culture, and elevated (increase by 10-20%, P<0.05) both oleate- and palmitate-induced apoptosis after 8 days. These results do not support the view that troglitazone exerts a direct protective effect on beta cells that are exposed to cytotoxic FFA concentrations. They instead indicate that the agent may sensitize pancreatic beta cells to FFA-induced damage, raising the possibility that its use facilitates the deleterious effect of increased FFA levels on the pancreatic beta cell mass.