Evaluation of metabolic control using a continuous subcutaneous glucose monitoring system in patients with type 1 diabetes mellitus who achieved insulin independence after islet cell transplantation

Glycemic variability indices can be used to diagnose islet transplantation success in type 1 diabetic patients

AIMS

High glycemic variability (GV) is the major indication for islet transplantation (IT) in patients with type 1 diabetes (T1D). The actual criteria used to assess graft function do not consider GV improvement. Our study aimed to describe GV indices' evolution in T1D patients who benefited from IT during the TRIMECO trial and to evaluate if thresholds might be defined to diagnose IT success.

METHODS

We collected data from 29 patients of the TRIMECO trial, a clinical trial (NCT01148680) comparing the metabolic efficacy of IT with intensive insulin therapy. Based on CGM data, we analyzed mean glucose level and four GV indices (standard deviation, coefficient of variation, MAGE and GVP) before (M0) and 6 months (M6) after IT.

RESULTS

Each GV index decreased significantly between M0 and M6: SD 53.9 mg/dL [44.6-61.5] versus 20.1 mg/dL [13.5-24.3]; CV 35.2% [30.6-37.7] versus 17.3% [12.0-20.5]; MAGE 134.9 mg/dl [111.2-155.8] versus 51.9 mg/dL [32.4-62.4]; GVP 35.3% [24.9-47.2] versus 12.2% [6.2-18.8] (p ≤ 0.0001). Thresholds diagnosing IT success at 6 months post-transplant were an SD at 22.76 mg/dL (sensibility 88.89%, specificity 80.00%), a CV at 17.47% (sensibility 88.89%, specificity 70.00%), a MAGE at 54.81 mg/dL (sensibility 88.89%, specificity 80.00%) and a GVP at 12.27% (sensibility 88.89%, specificity 70.00%).

CONCLUSIONS

This study confirms a positive impact of IT on GV. The proposed thresholds allow an easy evaluation of IT success using only CGM data and may be a clinical tool for the follow-up of transplanted patients.

Resolution of Neurotoxicity and β-Cell Toxicity in an Islet Transplant Recipient following Substitution of Tacrolimus with MMF

Calcineurin inhibitors such as tacrolimus have well-recognized efficacy in organ transplantation but side effects of nephrotoxicity, neurotoxicity, and β-cell toxicity that can be particularly detrimental in islet transplantation. Neuro- and nephrotoxicity have been demonstrated in multiple islet transplant recipients despite the relatively low serum maintenance levels typically used (3–5 ng/ml). We describe a single patient in whom symptoms and signs of neurotoxicity necessitated substitution of tacrolimus with mycophenolate mofetil (MMF), which resulted in complete symptom resolution over the subsequent 9 months. Concomitantly noted were an almost immediate improvement in glycemic control and an improved response to stimulation testing, suggesting remission of tacrolimus-induced β-cell toxicity and insulin resistance. At 18 months post-“switch,” 30 months posttransplant, the patient remains insulin independent with good glycemic control. The goal to remove calcineurin inhibitors from regimens of islet transplantation is a worthy one.

Demonstration of an intrinsic relationship between endogenous C-peptide concentration and determinants of glycemic control in type 1 diabetes following islet transplantation

OBJECTIVE

Maintenance of endogenous pancreatic β-cell function could be an important goal in the management of type 1 diabetes. However, the impact of stimulated C-peptide level on overall glycemic control is unknown. The relationship between C-peptide and parameters of glucose control was therefore characterized in a cohort with rapidly changing β-cell function following islet transplantation.

RESEARCH DESIGN AND METHODS

Standardized mixed-meal tolerance test was undertaken in 12 consecutive islet recipients at 1-6-month intervals, with graft function determined by 90-min stimulated C-peptide. Continuous glucose monitoring was undertaken in the week preceding each assessment and the relationship between C-peptide and glucose control evaluated by mixed Poisson regression.

RESULTS

Recipients completed 5 (1-14) [median (range)] clinical assessments over 18 (1-51) months posttransplant encompassing a wide range of stimulated C-peptide levels (7-2,622 pmol/L). Increasing β-cell function across predefined C-peptide groups was associated with reduced insulin dose, HbA1c, mean glucose (low [<200 pmol/L] 10.7 vs. excellent [>1,000 pmol/L] 7.5 mmol/L), and glucose SD (low, 4.4 vs. excellent, 1.4 mmol/L). Highly statistically significant continuous associations between stimulated C-peptide and mean interstitial glucose (lower by 2.5% [95% CI 1.5-3.5%] per 100 pmol/L higher C-peptide), glucose SD, time outside glucose target range, and measures of hyper-/hypoglycemia risk were confirmed.

CONCLUSIONS

Repeated assessment of islet transplant recipients has enabled modeling of the relationship between endogenous β-cell function and measures of glycemic control providing quantitative estimates of likely impact of an acute change in β-cell function in individuals with type 1 diabetes.

Continuous glucose monitoring analysis as predictor of islet yield and insulin requirements in autologous islet transplantation after complete pancreatectomy

We analyzed the pretransplant continuous glucose monitoring (CGM) data of 45 patients that underwent total pancreatectomy followed by autologous islet transplantation (AIT) at the University of Arizona Medical Center. Traditional and novel metrics of CGM time series were correlated to the total islet count (TIC), islet equivalents (IEQs), and weight-normalized IEQs (IEQ/kg). In a subset cohort (n = 26) we analyzed the relationship among the infused number of islets, the CGM indicators, and the first recorded insulin requirement after the procedure. We conclude that receiving a high islet yield is sufficient yet not necessary to achieve low or null insulin requirements within the first 50 days after surgery. Furthermore, CGM inertia and CGM length of curve (2 novel CGM indicators) are shown to be correlated to islet yield, and the CGMs normalized area (Ao) and time ratio above hyperglycemic level (To) are strongly correlated to insulin requirement. A screening test based on To is shown to have 100% sensitivity and 88% specificity discriminating insulin independence upon discharge.

Recommendations for standardizing glucose reporting and analysis to optimize clinical decision making in diabetes: the Ambulatory Glucose Profile (AGP)

Abstract Underutilization of glucose data and lack of easy and standardized glucose data collection, analysis, visualization, and guided clinical decision making are key contributors to poor glycemic control among individuals with type 1 diabetes. An expert panel of diabetes specialists, facilitated by the International Diabetes Center and sponsored by the Helmsley Charitable Trust, met in 2012 to discuss recommendations for standardization of analysis and presentation of glucose monitoring data, with the initial focus on data derived from CGM systems. The panel members were introduced to a universal software report, the Ambulatory Glucose Profile (AGP), and asked to provide feedback on its content and functionality, both as a research tool and in clinical settings. This paper provides a summary of the topics and issues discussed during the meeting and presents recommendations from the expert panel regarding the need to standardize glucose profile summary metrics and the value of a uniform glucose report to aid clinicians, researchers, and patients.

Recommendations for standardizing glucose reporting and analysis to optimize clinical decision making in diabetes: the ambulatory glucose profile

Underutilization of glucose data and lack of easy and standardized glucose data collection, analysis, visualization, and guided clinical decision making are key contributors to poor glycemic control among individuals with type 1 diabetes mellitus. An expert panel of diabetes specialists, facilitated by the International Diabetes Center and sponsored by the Helmsley Charitable Trust, met in 2012 to discuss recommendations for standardizing the analysis and presentation of glucose monitoring data, with the initial focus on data derived from continuous glucose monitoring systems. The panel members were introduced to a universal software report, the Ambulatory Glucose Profile, and asked to provide feedback on its content and functionality, both as a research tool and in clinical settings. This article provides a summary of the topics and issues discussed during the meeting and presents recommendations from the expert panel regarding the need to standardize glucose profile summary metrics and the value of a uniform glucose report to aid clinicians, researchers, and patients.

Impact of islet transplantation on diabetes complications and quality of life

Insulin represents a life-saving therapy for patients with type 1 diabetes but, despite appropriate treatment, it prevents only partially long-term diabetic complications, while generating fatal hypoglycemic episodes. Islet transplantation gained attention because of its safety, effectiveness, and minimal invasiveness; however it remains a procedure reserved for a selected group of patients. The introduction of the Edmonton Protocol in 2000, based on a newly designed steroid-free immunosuppressive protocol, revamped the course of islet transplantation. The main goal of islet transplantation remains insulin independence, although the effect of islet transplantation can be more comprehensively evaluated in terms of frequency of hypoglycemic episodes and impact on diabetic complications and quality of life. Islet transplantation was shown to have positive consequences on cardiovascular, renal, neurologic, and ocular diabetic complications. The proof of concept for cellular replacement therapy in diabetes has been established with islet transplantation, it only needs to be improved and rendered widely available.

Clinical use of fructosamine in islet transplantation

Many islet transplant recipients have medical conditions that could interfere with the accuracy of HbA1c measurements (e.g., anemia/dapsone use). Fructosamine is less prone to have clinical interferences and reflects glucose control in a shorter period of time than HbA1c. This study aimed to validate fructosamine use in islet transplant subjects and to evaluate its effectiveness as a predictor for islet graft dysfunction. Thirty-three islet transplant recipients who had concomitant fructosamine and HbA1c data available were retrospectively analyzed. HbA1c, fructosamine, mean capillary blood glucose, and islet graft function (fasting C-peptide/glucose ratio) were assessed. There was a significant and positive association between fructosamine and HbA1c (p < 0.0001). Both variables were also positively associated with mean overall and fasting capillary glucose. Neither fructosamine nor HbA1c was shown by ROC analysis to significantly discriminate between periods with and without subsequent graft dysfunction. HbA1c >6% was predictive of this outcome 1 month in advance (OR 2.95, p = 0.003). However, although significantly associated with graft dysfunction, use of this cutoff as a predictor of dysfunction has poor sensitivity (50%) and specificity (77.6%). Fructosamine above the normal range (>270 mumol/L Quest Diagnostics) was also predictive of ensuing dysfunction (OR 2.47, p = 0.03); however, it had similarly poor sensitivity (62%) and specificity (64%). Fructosamine can be used as an alternative to HbA1c for glycemic assessment in islet transplant recipients in situations with HbA1c assay interference. Neither HbA1c nor fructosamine are good predictors of islet graft dysfunction.

Blood glucose dynamics

Measurement of blood glucose concentration is central to the diagnosis and treatment of diabetes. Although there are large numbers of historic glucose measurements in individuals with diabetes, until recently there have been very few data sets that were recorded continuously or sampled frequently enough to reveal intrinsic blood glucose dynamics, or the change in blood glucose with time. There have even fewer such recordings from individuals not having diabetes to serve as a therapeutic target. As a result, blood glucose dynamics have generally not been used in the diagnosis or treatment of the disease. Although present blood glucose monitoring is based largely on discrete measurements, future monitoring will likely focus on analysis of blood glucose excursions. New measurements are now being obtained, and there is a need for new methods of analysis to extract the maximal information from the data. Several approaches are demonstrated here for characterization of blood glucose dynamics, and a patient profiling system is proposed. An example of new insights is the observation that there are four time scales of blood glucose variations in individuals without diabetes, and these time scales are modified or lost in diabetes.

Impact of islet transplantation on glycemic control as evidenced by a continuous glucose monitoring system

BACKGROUND

This study evaluated the effects of islet allotransplantation (ITx) on metabolic control utilizing a continuous glucose monitoring system (CGMS) and assessed its effectiveness as an indicator and predictor of graft dysfunction (GD).

METHODS

Glycemic control was assessed in 25 patients with type 1 diabetes mellitus (T1DM); 12 ITx recipients and 13 controls. Mean interstitial glucose, standard deviation (SD), glucose variability, and percentage of time in hyperglycemia (%GT >140 mg/dl), hypoglycemia (%GT <54 mg/dl), and normoglycemia (%GT 54-140 mg/dl) were measured in 72-hour time periods from CGMS recordings in the control group at baseline and in the ITx group at 3, 6, 9, 12, 15, and 18 months after ITx completion and were analyzed as predictors and indicators of GD. Hemoglobin A1c (HbA1c), 90-minute glucose after a mixed meal tolerance test, fasting C-peptide/glucose ratio, and insulin requirements were followed.

RESULTS

Compared to the control group, the percentage of time in hypoglycemia was significantly lower in the ITx group at all time points; time in normoglycemia was increased at all times except at 15 months; and time in hyperglycemia was significantly lower at 6, 9, 12, and 18 months. Mean glucose and glucose variability were significantly lower in the ITx group at all times except at 3 and 15 months, whereas HbA1c and 90-minute glucose were significantly lower in the ITx group at all time points. Mean glucose, SD, glucose variability, and %GT >140 mg/dl were significant as indicators but not as predictors of GD.

CONCLUSIONS

The CGMS demonstrated the benefits of ITx in T1DM, with improvements in glycemic control apparent up to 18 months after transplant. CGMS measures were found to be indicators of GD.

Toward maximizing the success rates of human islet isolation: influence of donor and isolation factors

In order to make islet transplantation a therapeutic option for patients with diabetes there is an urgent need for more efficient islet cell processing to maximize islet recovery. Improved donor management, organ recovery techniques, implementation of more stringent donor criteria, and improved islet cell processing techniques may contribute to enhance organ utilization for transplantation. We have analyzed the effects of donor and islet processing factors on the success rate of human islet cell processing for transplantation performed at a single islet cell processing center. Islet isolation outcomes improved when vasopressors, and in particular pitressin, and steroids were used for the management of multiorgan donors. Higher islet yields were obtained from adult male donors, BMI >25 kg/m2, adequate glycemic control during hospital stay, and when the pancreas was retrieved by a local surgical team. Successful isolations were obtained in 58% of the cases when > or = 4 donor criteria were met, and even higher success rates (69%) were observed when considering > or = 5 criteria. Our data suggest that a sequential, integrated approach is highly desirable to improve the success rate of islet cell processing.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.

Resolution of severe atopic dermatitis after tacrolimus withdrawal

Tacrolimus is an immunosuppressive agent used in solid organ and islet transplantation. Its topical form has shown benefit in the treatment of inflammatory skin conditions. Although tacrolimus has a wide spectrum of side effects, dermatological complications related to systemic tacrolimus therapy are limited in the literature. Atopic dermatitis (AD) is a chronic pruritic cutaneous condition that usually begins in infancy and is characterized by an increased Th2 response. We report the case of a patient with type 1 diabetes mellitus (T1DM) and history of AD latent for 10 years who developed severe dermatitis and alopecia 5 months after undergoing allogeneic islet transplantation and initiating a steroid-free immunosuppressive regimen with sirolimus and tacrolimus maintenance. After exclusion of other possible causes for the progression and exacerbation of the clinical presentation of AD, discontinuation of tacrolimus and introduction of mycophenolate mofetil resulted in full remission of the symptoms. The beneficial effects of tacrolimus withdrawal suggest a cause-effect relationship between this adverse event and the utilization of the drug. Islet graft function remained stable after modification of the therapeutic regimen (stable glycemic control and unchanged C-peptide).

Continuous glucose monitoring system for early detection of graft dysfunction in allogenic islet transplant recipients

BACKGROUND

There are no effective indicators of graft dysfunction in islet transplantation. This study evaluated the role of the Continuous Glucose Monitoring System (CGMS) as an early indicator of graft dysfunction in islet transplant recipients.

METHODS

In 5 islet allograft recipients, we retrospectively determined the date of graft dysfunction: 3 fasting blood glucose levels >7.8 mmol/L (140 mg/dL) and/or 3 postprandial blood glucose levels >10 mmol/L (180 mg/dL) in 1 week. We then determined 2 time points in respect to graft dysfunction, 5 to 9 months before (time point A) and 2 to 3 months before (time point B). For these 2 time points, we assessed the following: HbA1c, C-peptide (CP), C-peptide glucose ratio (CPGR), 90-minute glucose from mixed meal tolerance test, and percentage of capillary blood glucose levels >7.8 mmol/L (%CBG >7.8) in a 15-day interval (1 week before and after CGMS placement). From the CGMS recordings, we calculated the glucose variability and the percentage of time spent in hyperglycemia >7.8 mmol/L (%HGT >7.8) and >10 mmol/L (%HGT >10).

RESULTS

No difference was found between time points A and B for the following parameters: HbA1c, CP, CPGR, 90-minute glucose, %CBG >7.8, and %HGT >10. We observed a statistically significant increase from time point A to time point B in glucose variability (1.1 +/- 0.5 mmol/L to 1.6 +/- 0.6 mmol/L; P = .004), and in the %HGT >7.8 (11 +/- 12% to 22 +/- 18%; P = .036).

CONCLUSION

Glucose variability and %HGT >7.8 determined using CGMS are useful as early indicators of graft dysfunction in islet transplant recipients. Further studies with larger sample sizes will help validate these observations.

Glycemic thresholds for activation of counterregulatory hormone and symptom responses in islet transplant recipients

CONTEXT

In patients with type 1 diabetes and reduced awareness of hypoglycemia, the glycemic thresholds for activation of counterregulatory hormone and symptom responses to hypoglycemia are impaired, in part due to recurrent episodes of hypoglycemia. Islet transplantation can ameliorate occurrences of hypoglycemia in these patients.

OBJECTIVE

The objective of the study was to determine whether the avoidance of hypoglycemia achieved through islet transplantation results in improved glycemic thresholds for counterregulatory responses.

SETTING

The study was conducted at a general clinical research center.

PARTICIPANTS

Seven islet transplant recipients, six type 1 diabetic, and eight nondiabetic control subjects participated in the study.

INTERVENTION

We performed a stepped hyperinsulinemic hypoglycemic clamp and, in 12 subjects, a paired hyperinsulinemic euglycemic clamp to calculate the glycemic thresholds for and magnitude of counterregulatory responses.

RESULTS

The glycemic thresholds for all counterregulatory hormone and symptom responses in the islet transplant group were comparable with normal and higher than in the type 1 diabetes group (P < 0.01 for glucagon; P < 0.05 for epinephrine). The magnitude of the glucagon and epinephrine responses in the islet transplant group, although greater than in the type 1 diabetes group (P < 0.05 for both), remained less than normal (P < 0.01 for glucagon; P < 0.05 for epinephrine). The magnitude of GH secretion in the islet transplant group was comparable with normal and greater than in the type 1 diabetes group (P < 0.05).

CONCLUSIONS

The glycemic thresholds for activation of counterregulatory hormone and symptom responses appear normal after islet transplantation; however, the magnitudes of the glucagon and epinephrine responses remain impaired.

Monitoring of the islet graft

The Edmonton trials have brought about a marked improvement in the short-term rate of success of islet transplantation with rates of insulin-independence of 80% at 1-year being reported by several institutions worldwide. Unfortunately, this rate consistently decreases to 10-15% by 5 years post-transplantation. Several mechanisms have been proposed to explain this apparent 'islet exhaustion', but are difficult to pinpoint in a given patient. Understanding the reasons for islet graft exhaustion and its kinetics is a prerequisite for the improvement of islet transplantation outcome. In this regard, efficient monitoring tools for the islet graft have been conspicuously lacking and are required to detect islet damage and diagnose its mechanisms in a timely fashion, so as to initiate salvage therapy such as antirejection treatment. Tools for the monitoring of the islet graft include follow-up of metabolic function but mostly indicate dysfunction when it is too late to take action. Progress is likely to arise in the fields of immune monitoring, molecular monitoring and islet imaging, notably thanks to magnetic resonance (MR) or positron emission tomography (PET) technologies.

Overcoming the Challenges Now Limiting Islet Transplantation: A Sequential, Integrated Approach

Steady improvements in islet cell processing technology and immunosuppressive protocols have made pancreatic islet transplantation a clinical reality for the treatment of patients with Type 1 diabetes mellitus (T1DM). Recent trials are showing that improved glycemic metabolic control, prevention of severe hypoglycemia, and better quality of life can be reproducibly achieved after transplantation of allogeneic islets in patients with unstable T1DM. Despite these encouraging results, challenges ahead comprise obtaining adequate islet cells for transplant, enhancing islets engraftment, sustaining beta cell mass and function over time, and defining effective immune interventions, among others. In order to overcome the current hurdles to the widespread application of islet transplantation there is a need for implementation of integrated, sequential therapeutic approaches.