Validation of the BETA-2 Score: An Improved Tool to Estimate Beta Cell Function After Clinical Islet Transplantation Using a Single Fasting Blood Sample

Defining Outcomes for β-cell Replacement Therapy in the Treatment of Diabetes: A Consensus Report on the Igls Criteria From the IPITA/EPITA Opinion Leaders Workshop

β-cell replacement therapy, available currently as pancreas or islet transplantation, has developed without a clear definition of graft functional and clinical outcomes. The International Pancreas and Islet Transplant Association and European Pancreas and Islet Transplantation Association held a workshop to develop consensus for an International Pancreas and Islet Transplant Association and European Pancreas and Islet Transplant Association Statement on the definition of function and failure of current and future forms of β-cell replacement therapy. There was consensus that β-cell replacement therapy could be considered as a treatment for β-cell failure, regardless of etiology and without requiring undetectable C-peptide, accompanied by glycemic instability with either problematic hypoglycemia or hyperglycemia. Glycemic control should be assessed at a minimum by glycated hemoglobin (HbA1c) and the occurrence of severe hypoglycemia. Optimal β-cell graft function is defined by near-normal glycemic control (HbA1c ≤6.5% [48 mmol/mol]) without severe hypoglycemia or requirement for insulin or other antihyperglycemic therapy, and with an increase over pretransplant measurement of C-peptide. Good β-cell graft function requires HbA1c less than 7.0% (53 mmol/mol) without severe hypoglycemia and with a significant (>50%) reduction in insulin requirements and restoration of clinically significant C-peptide production. Marginal β-cell graft function is defined by failure to achieve HbA1c less than 7.0% (53 mmol/mol), the occurrence of any severe hypoglycemia, or less than 50% reduction in insulin requirements when there is restoration of clinically significant C-peptide production documented by improvement in hypoglycemia awareness/severity, or glycemic variability/lability. A failed β-cell graft is defined by the absence of any evidence for clinically significant C-peptide production. Optimal and good function are considered successful clinical outcomes.

Assessment of simple indices based on a single fasting blood sample as a tool to estimate beta-cell function after total pancreatectomy with islet autotransplantation - a prospective study

We investigated six indices based on a single fasting blood sample for evaluation of the beta-cell function after total pancreatectomy with islet autotransplantation (TP-IAT). The Secretory Unit of Islet Transplant Objects (SUITO), transplant estimated function (TEF), homeostasis model assessment (HOMA-2B%), C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr) and BETA-2 score were compared against a 90-min serum glucose level, weighted mean C-peptide in mixed meal tolerance test (MMTT), beta score and the Igls score adjusted for islet function in the setting of IAT. We analyzed values from 32 MMTTs in 15 patients after TP-IAT with a follow-up of up to 3 years. Four (27%) individuals had discontinued insulin completely prior to day 75, while 6 out of 12 patients (50%) did not require insulin support at 1-year follow-up with HbA1c 6.0% (5.5-6.8). BETA-2 was the most consistent among indices strongly correlating with all reference measures of beta-cell function (r = 0.62-0.68). In addition, it identified insulin independence (cut-off = 16.2) and optimal/good versus marginal islet function in the Igls score well, with AUROC of 0.85 and 0.96, respectively. Based on a single fasting blood sample, BETA-2 score has the most reliable discriminant value for the assessment of graft function in patients undergoing TP-IAT.

Defining outcomes for β-cell replacement therapy in the treatment of diabetes: a consensus report on the Igls criteria from the IPITA/EPITA opinion leaders workshop

β-cell replacement therapy, available currently as pancreas or islet transplantation, has developed without a clear definition of graft functional and clinical outcomes. The International Pancreas & Islet Transplant Association (IPITA) and European Pancreas & Islet Transplantation Association (EPITA) held a workshop to develop consensus for an IPITA/EPITA Statement on the definition of function and failure of current and future forms of β-cell replacement therapy. There was consensus that β-cell replacement therapy could be considered as a treatment for β-cell failure, regardless of etiology and without requiring undetectable C-peptide, accompanied by glycemic instability with either problematic hypoglycemia or hyperglycemia. Glycemic control should be assessed at a minimum by glycated hemoglobin (HbA_1c ) and the occurrence of severe hypoglycemia. Optimal β-cell graft function is defined by near-normal glycemic control [HbA_1c  ≤ 6.5% (48 mmol/mol)] without severe hypoglycemia or requirement for insulin or other antihyperglycemic therapy, and with an increase over pretransplant measurement of C-peptide. Good β-cell graft function requires HbA_1c  < 7.0% (53 mmol/mol) without severe hypoglycemia and with a significant (>50%) reduction in insulin requirements and restoration of clinically significant C-peptide production. Marginal β-cell graft function is defined by failure to achieve HbA_1c  < 7.0% (53 mmol/mol), the occurrence of any severe hypoglycemia, or less than 50% reduction in insulin requirements when there is restoration of clinically significant C-peptide production documented by improvement in hypoglycemia awareness/severity, or glycemic variability/lability. A failed β-cell graft is defined by the absence of any evidence for clinically significant C-peptide production. Optimal and good functional outcomes are considered successful clinical outcomes.

External Validation of the Newly Developed BETA-2 Scoring System for Pancreatic Islet Graft Function Assessment

BACKGROUND

BETA-2 score using a single fasting blood sample was developed to estimate beta-cell function after islet transplantation (ITx) and was validated internally by a high ITx volume center (Edmonton). The goal was to validate BETA-2 externally, in our center.

METHODS

Areas under receiver operating characteristic curves (AUROCs) were obtained to see if beta score or BETA-2 would better detect insulin independence and glucose intolerance.

RESULTS

We analyzed values from 48 mixed meal tolerance tests (MMTTs) in 4 ITx recipients with a long-term follow-up to 140 months (LT group) and from 54 MMTTs in 13 short-term group patients (ST group). AUROC for no need for insulin support was 0.776 (95% confidence interval [CI] 0.539-1, P = .02) and 0.922 (95% CI 0.848-0.996, P < .001) for beta score and 0.79 (95% CI 0.596-0.983, P = .003) and 0.941 (95% CI 0.86-1, P < .001) for BETA-2, in LT and ST groups, respectively, and did not differ significantly. In LT group BETA-2 score ≥ 13.03 predicted no need for insulin supplementation with sensitivity of 98%, specificity of 50%, positive predictive value (PPV) of 93%, and negative predictive value (NPV) of 75%. In ST group the optimal cutoff was ≥13.63 with sensitivity of 92% and specificity, PPV, and NPV 82% to 95%. For the detection of glucose intolerance BETA-2 cutoffs were <19.43 in LT group and <17.23 in ST group with sensitivity > 76% and specificity, PPV, and NPV > 80% in both groups.

CONCLUSION

BETA-2 score was successfully validated externally and is a practical tool allowing for frequent and reliable assessments of islet graft function based on a single fasting blood sample.

Comparison of metabolic responses to the mixed meal tolerance test vs the oral glucose tolerance test after successful clinical islet transplantation

Following islet transplantation, mixed meal tolerance tests (MMTs) are routinely utilized to assess graft function, but how the 90-minute MMTT glucose value relates to a 120-minute glucose concentration of ≥11.1 mmol/L used to diagnose diabetes following a standardized 75 g-OGTT, is not known. We examined this relationship further. Thirteen subjects with Type 1 diabetes and stable transplant grafts, not on exogenous insulin with HbA1c < 7% (53 mmol/mol), were studied on 17 occasions with paired OGTTs and MMTTs. Receiver operating characteristic (ROC) curves were constructed to derive the 90-minute MMTT glucose threshold associated with a 120-minute glucose concentration following a 75 g-OGTT (OGTT₁₂₀ ) ≥11.1 mmol/L and their diagnostic accuracy. Studies with OGTT₁₂₀ ≥11.1 mmol/L (n = 5) had diminished C-peptide: glucose, greater integrated glucose and diminished insulin: glucose area under the curve (AUC) ratios (0-120 minutes) and disposition indices; all P < .05, contrasting with MMTTs where no difference in the 90-minute glucose concentrations, C-peptide:glucose, integrated glucose, C-peptide and C-peptide: glucose AUCs (0-90 minutes) was seen; all P > .05. A 90-minute MMTT glucose concentration ≥8.0 mmol/L demonstrated a sensitivity and specificity of ≥80% for the diagnosis of OGTT₁₂₀ ≥11.1 mmol/L; area under ROC curve (mean ± SEM) 73 ± 13%. A 90-minute MMTT glucose ≥8.0 mmol/L, identifies islet transplant recipients who may require closer monitoring for graft dysfunction.

Beta Cell Death by Cell-free DNA and Outcome After Clinical Islet Transplantation

BACKGROUND

Optimizing engraftment and early survival after clinical islet transplantation is critical to long-term function, but there are no reliable, quantifiable measures to assess beta cell death. Circulating cell-free DNA (cfDNA) derived from beta cells has been identified as a novel biomarker to detect cell loss and was recently validated in new-onset type 1 diabetes and in islet transplant patients.

METHODS

Herein we report beta cell cfDNA measurements after allotransplantation in 37 subjects and the correlation with clinical outcomes.

RESULTS

A distinctive peak of cfDNA was observed 1 hour after transplantation in 31 (83.8%) of 37 subjects. The presence and magnitude of this signal did not correlate with transplant outcome. The 1-hour signal represents dead beta cells carried over into the recipient after islet isolation and culture, combined with acute cell death post infusion. Beta cell cfDNA was also detected 24 hours posttransplant (8/37 subjects, 21.6%). This signal was associated with higher 1-month insulin requirements (P = 0.04), lower 1-month stimulated C-peptide levels (P = 0.01), and overall worse 3-month engraftment, by insulin independence (receiver operating characteristic-area under the curve = 0.70, P = 0.03) and beta 2 score (receiver operating characteristic-area under the curve = 0.77, P = 0.006).

CONCLUSIONS

cfDNA-based estimation of beta cell death 24 hours after islet allotransplantation correlates with clinical outcome and could predict early engraftment.

Comparative evaluation of simple indices using a single fasting blood sample to estimate beta cell function after islet transplantation

Six single fasting blood sample-based indices-Secretory Unit of Islet Transplant Objects (SUITO), Transplant Estimated Function (TEF), Homeostasis Model Assessment (HOMA)2-B%, C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr), and BETA-2 score-were compared against commonly used 90-minute mixed meal tolerance test (MMTT) serum glucose and beta score to assess which of them best recognizes the state of acceptable blood glucose control without insulin supplementation after islet allotransplantation (ITx). We also tested whether the indices could identify the success of ITx based on the Igls classification of beta cell graft function. We analyzed values from 47 MMTT tests in 4 patients with up to 140 months follow-up and from 54 MMTT tests in 13 patients with up to 42 months follow-up. SUITO, CP/G, HOMA2-B%, and BETA-2 correlated well with the 90-minute glucose of the MMTT and beta-score (r 0.54-0.76), whereas CP/GCr showed a modest performance (r 0.41-0.52) while TEF showed little correlation. BETA-2 and SUITO were the best identifiers and predictors of the need for insulin support, glucose intolerance, and ITx success (P < .001), while HOMA2-B% and TEF were unreliable. Single fasting blood sample SUITO and BETA-2 scores are very practical alternative tools that allow for frequent assessments of graft function.

Current issues in allogeneic islet transplantation

PURPOSE OF REVIEW

Transplantation of allogenic pancreatic islets is a minimally invasive treatment option to control severe hypoglycemia and dependence on exogenous insulin among type 1 diabetes (T1D) patients. This overview summarizes the current issues and progress in islet transplantation outcomes and research.

RECENT FINDINGS

Several clinical trials from North America and other countries have documented the safety and efficacy of clinical islet transplantation for T1D patients with impaired hypoglycemia awareness. A recently completed phase 3 clinical trial allows centres in the United States to apply for a Food and Drug Administration Biologics License for the procedure. Introduction of anti-inflammatory drugs along with T-cell depleting induction therapy has significantly improved long-term function of transplanted islets. Research into islet biomarkers, immunosuppression, extrahepatic transplant sites and potential alternative beta cell sources is driving further progress.

SUMMARY

Allogeneic islet transplantation has vastly improved over the past two decades. Success in restoration of glycemic control and hypoglycemic awareness after islet transplantation has been further highlighted by clinical trials. However, lack of effective strategies to maintain long-term islet function and insufficient sources of donor tissue still impose limitations to the widespread use of islet transplantation. In the United States, wide adoption of this technology still awaits regulatory approval and, importantly, a financial mechanism to support the use of this technology.

Integration of Routine Parameters of Glycemic Variability in a Simple Screening Method for Partial Remission in Children with Type 1 Diabetes

Although different criteria were used to define partial remission in type 1 diabetes, the IDAA1C formula has prevailed as it correlates with stimulated C-peptide levels. Our retrospective study evaluated clinical variables associated with the occurrence of IDAA1C-defined partial remission in a series of 239 pediatric patients. Diabetic ketoacidosis and age at diagnosis, but no other clinical feature, influenced the occurrence of remission. We then evaluated whether parameters of glycemic variability used in clinical routine may reliably define partial remission, as these would alleviate confounding factors related to insulin treatment. Using multiple linear regression, we observed that HbA_1C levels and percentage of normoglycemia were efficient and sufficient to predict partial remission. These parameters were entered into a formula, called glycemic target-adjusted HbA_1C (GTAA_1C), that corresponded to HbA_1C(%) - (3 × % of normoglycemic values_{(70-180 mg/dL)}). With a threshold of 4.5, this alternative formula predicted partial remission with a sensitivity and a specificity of 72.3% and 92%, respectively, and yielded strong correlation with IDAA1C levels and BETA-2 score, which is a correlate of β-cell function after islet transplantation. We propose GTAA_1C, based on routine and objective markers of glycemic variability, as a valid alternative for definition of partial remission in type 1 diabetes.

Validation of the BETA-2 Score: An Improved Tool to Estimate Beta Cell Function After Clinical Islet Transplantation Using a Single Fasting Blood Sample

The beta score, a composite measure of beta cell function after islet transplantation, has limited sensitivity because of its categorical nature and requires a mixed-meal tolerance test (MMTT). We developed a novel score based on a single fasting blood sample. The BETA-2 score used stepwise forward linear regression incorporating glucose (in millimoles per liter), C-peptide (in nanomoles per liter), hemoglobin A1c (as a percentage) and insulin dose (U/kg per day) as continuous variables from the original beta score data set (n = 183 MMTTs). Primary and secondary analyses assessed the score's ability to detect glucose intolerance (90-min MMTT glucose ≥8 mmol/L) and insulin independence, respectively. A validation cohort of islet transplant recipients (n = 114 MMTTs) examined 12 mo after transplantation was used to compare the score's ability to detect these outcomes. The BETA-2 score was expressed as follows (range 0-42): [Formula: see text] A score <20 and ≥15 detected glucose intolerance and insulin independence, respectively, with >82% sensitivity and specificity. The BETA-2 score demonstrated greater discrimination than the beta score for these outcomes (p < 0.05). Using a fasting blood sample, the BETA-2 score estimates graft function as a continuous variable and shows greater discrimination of glucose intolerance and insulin independence after transplantation versus the beta score, allowing frequent assessments of graft function. Studies examining its utility to track long-term graft function are required.

Research progress of mesenchymal stem cells combined with islet transplantation in treatment of type I diabetes mellitus

The most significant feature of type I diabetes is β-cell loss, which results in a series of complications. While β-cell loss occurs, β-cells are ultimately damaged by macrophages and T cells in the presence of inflammatory mediators. Because of this characteristic, five kinds of antibodies are commonly used in clinical practice to diagnose and evaluate β-cell loss, including islet cell antibody, insulin antibody, GAD65, IA-2 and IA-2b. In addition to the HLA gene related factors, environmental factors, such as infection, diet and physiological and psychological factors, are suspected to be causes of this disease. At present, there are many treatments for type I diabetes, and the clinical goal is to control blood glucose, prevent further damage of βcells and control patients' own immune response. In 1992, the discovery of insulin, which converts the fatal diabetes into a chronic disease, to some extent, delayed the progression of microvascular complications; however, it is not able to delay the progression of the disease. β-cell transplantation is currently the only minimally invasive means for reasonable control of blood glucose control disease related complications. Although whole pancreas transplantation can achieve a promising effect to some extent, it is accompanied by high incidence and mortality, as well as lifelong mandatory immune suppression. Bone marrow mesenchymal stem cells transplantation, lipopolysaccharideon (LPS) bone marrow mesenchymal stem cell pretreatment and islet cell exendin-4 liquid preservation reduce warm ischemia time damage and provide new avenues for islet cell transplantation.