Long-Term Improvement in Glucose Control and Counterregulation by Islet Transplantation for Type 1 Diabetes

Context: Islet transplantation has been shown to improve glucose counterregulation and hypoglycemia symptom recognition in patients with type 1 diabetes (T1D) complicated by severe hypoglycemia episodes and symptom unawareness, but long-term data are lacking. Objective: To assess the long-term durability of glucose counterregulation and hypoglycemia symptom responses 18 months after intrahepatic islet transplantation and associated measures of glycemic control during a 24-month follow-up period. Design, Setting, and Participants: Ten patients with T1D disease duration of approximately 27 years were studied longitudinally before and 6 and 18 months after transplant in the Clinical &amp; Translational Research Center of the University of Pennsylvania and were compared to 10 nondiabetic control subjects. Intervention: All 10 patients underwent intrahepatic islet transplantation according to the CIT07 protocol at the Hospital of the University of Pennsylvania. Main Outcome Measures: Counterregulatory hormone, endogenous glucose production, and autonomic symptom responses derived from stepped hyperinsulinemic-hypoglycemic and paired hyperinsulinemic-euglycemic clamps with infusion of 6,6-2H2-glucose. Results: Near-normal glycemia (HbA1c ≤ 6.5%; time 70–180 mg/dL ≥ 95%) was maintained for 24 months in all patients, with one returning to low-dose insulin therapy. In response to insulin-induced hypoglycemia, glucagon secretion was incompletely restored at 6 and 18 months, epinephrine was improved at 6 months and normalized at 18 months, and endogenous glucose production and symptoms, absent before, were normalized at 6 and 18 months after transplant. Conclusions: In patients with T1D experiencing problematic hypoglycemia, intrahepatic islet transplantation can lead to long-term improvement of glucose counterregulation and hypoglycemia symptom recognition, physiological effects that likely contribute to glycemic stability after transplant. </jats:sec

359-OR: a- or ß-Adrenergic Blockade Does Not Affect Transplanted Islet Responses to Hypoglycemia in Type 1 Diabetes (T1D)

Recipients of intrahepatic islet transplantation for T1D exhibit appropriate suppression of endogenous insulin and activation of glucagon secretion in response to insulin-induced hypoglycemia with restored glucose counterregulation and protection against clinically significant hypoglycemia. Whether sympathetic activation of adrenergic receptors on transplanted islets is required for these responses is not known. To evaluate the adrenergic contribution to post-transplant glucose counterregulation, we performed a randomized, double-blind crossover study of responses during a hyperinsulinemic (1 mU·kg-1·min-1) euglycemic (EU, ∼90 mg/dL)-hypoglycemic (HYPO, ∼50 mg/dL) clamp conducted under phentolamine (0.95 µg·kg-1·min-1; α-adrenergic blockage), propranolol (0.48 µg·kg-1·min-1; β-adrenergic blockage), or placebo infusion. Subjects were 5F/4M with median (range) age 53 (34 - 63) years, T1D duration 29 (18 - 56) years, post-transplant 7 (2 - 8) years, HbA1c 5.8 (4.5 - 6.8) %, insulin in-/dependent 5/4, on tacrolimus-based immunosuppression, and spent 97 (76 - 99) % time in range 70 - 180 mg/dL and 1 (0 - 3) % time with hypoglycemia &amp;lt; 70 mg/dL by CGM. During the EU-HYPO clamp, blood pressure was lower with phentolamine and heart rate lower with propranolol vs. placebo (P &amp;lt; 0.05). There was no difference in suppression of C-peptide or activation of glucagon with phentolamine or propranolol vs. placebo. Pancreatic polypeptide was greater with phentolamine vs. placebo during EU (P &amp;lt; 0.05), and free fatty acids were lower and the glucose infusion rate higher with propranolol vs. placebo during HYPO (P &amp;lt; 0.05) with no differences seen for endogenous glucose production. These results indicate physiologic α- and β-adrenergic blockage had no effect on transplanted islet responses to hypoglycemia. Sympathetic re-innervation, as occurs with re-vascularization of intrahepatic islets, may not be necessary for post-transplant recovery of glucose counterregulation in T1D. Disclosure M.R. Rickels: Consultant; Self; Semma Therapeutics, Inc. Research Support; Self; Xeris Pharmaceuticals, Inc. M. Bellin: Research Support; Self; Dexcom, Inc., Viacyte, Inc. Other Relationship; Self; Insulet Corporation. D. Stefanovski: None. A.J. Peleckis: None. C.V. Dalton-Bakes: None. E. Markmann: None. H.T. Nguyen: None. A. Naji: None. Funding National Institutes of Health (R01DK091331, UL1TR001878, P30DK19525) </jats:sec

Improvement in β-Cell Secretory Capacity After Human Islet Transplantation According to the CIT07 Protocol

The Clinical Islet Transplantation 07 (CIT07) protocol uses antithymocyte globulin and etanercept induction, islet culture, heparinization, and intensive insulin therapy with the same low-dose tacrolimus and sirolimus maintenance immunosuppression as in the Edmonton protocol. To determine whether CIT07 improves engrafted islet β-cell mass, our center measured β-cell secretory capacity from glucose-potentiated arginine tests at days 75 and 365 after transplantation and compared those results with the results previously achieved by our group using the Edmonton protocol and normal subjects. All subjects were insulin free, with CIT07 subjects receiving fewer islet equivalents from a median of one donor compared with two donors for Edmonton protocol subjects. The acute insulin response to glucose-potentiated arginine (AIRpot) was greater in the CIT07 protocol than in the Edmonton protocol and was less in both cohorts than in normal subjects, with similar findings for C-peptide. The CIT07 subjects who completed reassessment at day 365 exhibited increasing AIRpot by trend relative to that of day 75. These data indicate that engrafted islet β-cell mass is markedly improved with the CIT07 protocol, especially given more frequent use of single islet donors. Although several peritransplant differences may have each contributed to this improvement, the lack of deterioration in β-cell secretory capacity over time in the CIT07 protocol suggests that low-dose tacrolimus and sirolimus are not toxic to islets.</jats:p

Racial Differences in the Relationship of Glucose Concentrations and Hemoglobin A1c Levels

Background: Debate exists as to whether the higher hemoglobin A1c (HbA1c) levels observed in black persons than in white persons are due to worse glycemic control or racial differences in the glycation of hemoglobin. Objective: To determine whether a racial difference exists in the relationship of mean glucose and HbA1c. Design: Prospective, 12-week observational study. Setting: 10 diabetes centers in the United States. Participants: 104 black persons and 104 white persons aged 8 years or older who had had type 1 diabetes for at least 2 years and had an HbA1c level of 6.0% to 12.0%. Measurements: Mean glucose concentration, measured by using continuous glucose monitoring and compared by race with HbA1c, glycated albumin, and fructosamine values. Results: The mean HbA1c level was 9.1% in black persons and 8.3% in white persons. For a given HbA1c level, the mean glucose concentration was significantly lower in black persons than in white persons (P = 0.013), which was reflected in mean HbA1c values in black persons being 0.4 percentage points (95% CI, 0.2 to 0.6 percentage points) higher than those in white persons for a given mean glucose concentration. In contrast, no significant racial differences were found in the relationship of glycated albumin and fructosamine levels with the mean glucose concentration (P \u3e 0.20 for both comparisons). Limitation: There were too few participants with HbA1c levels less than 6.5% to generalize the results to such individuals. Conclusion: On average, HbA1c levels overestimate the mean glucose concentration in black persons compared with white persons, possibly owing to racial differences in the glycation of hemoglobin. However, because race only partially explains the observed HbA1c differences between black persons and white persons, future research should focus on identifying and modifying barriers impeding improved glycemic control in black persons with diabetes. Primary Funding Source: Helmsley Charitable Trust

Improved Health-Related Quality of Life in a Phase 3 Islet Transplantation Trial in Type 1 Diabetes Complicated by Severe Hypoglycemia

OBJECTIVE Attaining glycemic targets without severe hypoglycemic events (SHEs) is a challenging treatment goal for patients with type 1 diabetes complicated by impaired awareness of hypoglycemia (IAH). The CIT Consortium Protocol 07 (CIT-07) trial showed islet transplantation to be an effective treatment for subjects with IAH and intractable SHEs. We evaluated health-related quality of life (HRQOL), functional health status, and health utility before and after pancreatic islet transplantation in CIT-07 trial participants. RESEARCH DESIGN AND METHODS Four surveys, the Diabetes Distress Scale (DDS), the Hypoglycemic Fear Survey (HFS), the Short Form 36 Health Survey (SF-36), and the EuroQoL 5 Dimensions (EQ-5D), were administered repeatedly before and after islet transplantation. Summary statistics and longitudinal modeling were used to describe changes in survey scores from baseline and to characterize change in relation to a minimally important difference (MID) threshold of half an SD. RESULTS Improvements in condition-specific HRQOL met the MID threshold. Reductions from baseline in the DDS total score and its four DDS subscales (all P ≤ 0.0013) and in the HFS total score and its two subscales (all P &amp;lt; 0.0001) were observed across all time points. Improvements were observed after both 1 and 2 years for the EQ-5D visual analog scale (both P &amp;lt; 0.0001). CONCLUSIONS In CIT-07, 87.5% of the subjects achieved the primary end point of freedom from SHE along with glycemic control (HbA1c &amp;lt;7% [&amp;lt;53 mmol/mol]) at 1 year post–initial islet transplantation. The same subjects reported consistent, statistically significant, and clinically meaningful improvements in condition-specific HRQOL as well as self-assessments of overall health. </jats:sec

The Contemporary Prevalence of Diabetic Neuropathy in Type 1 Diabetes: Findings From the T1D Exchange

OBJECTIVE To evaluate the contemporary prevalence of diabetic peripheral neuropathy (DPN) in participants with type 1 diabetes in the T1D Exchange Clinic Registry throughout the U.S. RESEARCH DESIGN AND METHODS DPN was assessed with the Michigan Neuropathy Screening Instrument Questionnaire (MNSIQ) in adults with ≥5 years of type 1 diabetes duration. A score of ≥4 defined DPN. Associations of demographic, clinical, and laboratory factors with DPN were assessed. RESULTS Among 5,936 T1D Exchange participants (mean ± SD age 39 ± 18 years, median type 1 diabetes duration 18 years [interquartile range 11, 31], 55% female, 88% non-Hispanic white, mean glycated hemoglobin [HbA1c] 8.1 ± 1.6% [65.3 ± 17.5 mmol/mol]), DPN prevalence was 11%. Compared with those without DPN, DPN participants were older, had higher HbA1c, had longer duration of diabetes, were more likely to be female, and were less likely to have a college education and private insurance (all P &amp;lt; 0.001). DPN participants also were more likely to have cardiovascular disease (CVD) (P &amp;lt; 0.001), worse CVD risk factors of smoking (P = 0.008), hypertriglyceridemia (P = 0.002), higher BMI (P = 0.009), retinopathy (P = 0.004), reduced estimated glomerular filtration rate (P = 0.02), and Charcot neuroarthropathy (P = 0.002). There were no differences in insulin pump or continuous glucose monitor use, although DPN participants were more likely to have had severe hypoglycemia (P = 0.04) and/or diabetic ketoacidosis (P &amp;lt; 0.001) in the past 3 months. CONCLUSIONS The prevalence of DPN in this national cohort with type 1 diabetes is lower than in prior published reports but is reflective of current clinical care practices. These data also highlight that nonglycemic risk factors, such as CVD risk factors, severe hypoglycemia, diabetic ketoacidosis, and lower socioeconomic status, may also play a role in DPN development. </jats:sec