ADRENERGIC CONTRIBUTION TO GLUCOSE COUNTERREGULATION IN ISLET TRANSPLANTATION

Brief Description Of Study

In this protocol we aim to study how innervation affects transplanted islet cell responses to hypoglycemia. Our participants will all have received an islet cell transplant here at UPenn or at another national center. The purpose of this study is to test how a bodies’ nerves and hormones affect these islet cells and how they respond to low blood sugar (glucose). This study will provide important information about how the islets protect type 1 diabetics from low blood glucose.

Clinical Study Identifier: TX4755

Detailed Study Description

Group 1 subjects will include adult (ages 21 - 65 years) type 1 diabetic recipients of intrahepatic islet transplants with stable islet graft function defined by C-peptide > 0.5 ng/ml and insulin-independent or insulin-dependent with daily insulin requirement < 0.2 units/kg•d to maintain HbA1c < 7.0%. Subjects will be on standard immunosuppression consisting of tacrolimus with or without sirolimus or mychophenolic acid, and if receiving prednisone, no more than 5 mg daily. Subjects will be excluded for uncontrolled hypertension, history of cardiovascular disease, use of β-blockers, bronchial asthma, abnormal kidney, liver, or thyroid function, anemia, seizure disorder not related to prior severe hypoglycemia, pregnancy, and nursing. After informed consent, eligibility will be determined by a screening visit to include medical history, physical exam, EKG, urine pregnancy test, serum chemistries, TSH, cell counts, HbA1c and C-peptide. Detailed inclusion/exclusion criteria are provided below. Eligible Group 1 subjects will undergo placement of a 7 day blinded continuous glucose monitor (CGM; iPro®2 Professional Continuous Glucose Monitor, Medtronic, Northridge, CA) to characterize their hypoglycemia exposure, and be randomized to the order of receiving the α-adrenergic blocker phentolamine, the β-adrenergic blocker propranolol, or placebo in a double-blind cross-over fashion during each of three study visits. Subjects will avoid strenuous activity for three days prior to each study visit, with each visit occurring at least one week but not longer than one month apart. Subjects will be invited to spend the night in the Penn Center for Human Phenomic Science the evening prior to each study day, and will be required to do so if using insulin to maintain near-normoglycemia. Morning medications will be held until the completion of testing, with the exception of morning doses of twice daily immunosuppressants given after baseline blood samples are collected. Following 10-hours of overnight fasting, around 0700 at t = -120 min a primed (5 mg/kg ∙ fasting plasma glucose/90 for 5 min) continuous (0.05 mg/kg∙min for 355 min) infusion of 6,6-2H2-glucose (99% enriched; Cambridge Isotopes Laboratories, Andover, MA) will be administered to assess endogenous glucose production before and during the induction of hyperinsulinemia (Bernroider et al., 2005; Rickels et al., 2015). The phentolamine (0.95 μg/kg•min), propranolol (0.48 μg/kg•min), and placebo will each be administered intravenously, with the infusion starting at t = -30 min together with initiation of cardiac telemetry monitoring. These doses of phentolamine and propranolol have been shown to be effective in blocking blood pressure increases induced by phenylephrine (an α1-receptor agonist), and heart rate increases induced by isoproterenol (a β1-receptor agonist), respectively (Girdler et al., 1993). Heart rate and blood pressure will be recorded at least every fifteen minutes for protocol driven reduction, cessation, or reintroduction of the phentolamine, propranolol, or placebo infusion. After baseline blood samples at t = -15, and -1 min, at t = 0 min a continuous infusion of insulin (1.0 mU/kg∙min for 180 min) will be administered to produce hyperinsulinemia. Subsequently, a variable rate infusion of 20% glucose will be initiated to target the plasma glucose at ~ 90 mg/dl until 90 min (euglycemic phase), and then ~ 50 mg/dl until 180 min (hypoglycemic phase). To reduce changes in plasma enrichment during the clamp, the variable glucose infusion will be enriched to ~ 2.0 % with 6,6-2H2-glucose (Bernroider et al., 2005; Rickels et al., 2015). Blood samples will be taken every 5 min, centrifuged, and measured at bedside with an automated glucose analyzer (YSI 2300; Yellow Springs Instruments, Yellow Springs, OH) to adjust the glucose infusion rate and achieve the desired plasma glucose concentration. Additional blood samples will be taken at t = 30, 60, 75, 90, 120, 150, 165, and 180 min for biochemical analysis and verification of the plasma glucose levels. All samples will be collected on ice in chilled tubes containing EDTA and Protease Inhibitor Cocktail (Sigma-Aldrich, St. Louis, MO), centrifuged at 4°C, separated, and frozen at -80°C for subsequent analysis. The total amount of blood sampled will be 100 ml. A questionnaire will be administered every 15 - 30 min during the study in order to quantitate autonomic symptoms as the sum of scores ranging from 0 (none) to 5 (severe) for each of the following symptoms: anxiety, palpitations, sweating, tremor, hunger, and tingling (Towler et al., 1993; Rickels et al., 2015). To ensure complete α-blockade and complete β-blockade from the phentolamine and propranolol infusions, respectively, cardiovascular (heart rate and blood pressure) responses during the three testing conditions will be assessed after the first 3 subjects complete study. If no reduction in BP or increase in heart rate is evident during phentolamine administration, the infusion rate will be doubled for the next 3 subjects. If no reduction in heart rate or blood pressure is observed during propranolol administration, the infusion rate will be doubled for the next 3 subjects. Cardiovascular responses will again be assessed, and consideration made to reducing, but not further increasing, the rate of phentolamine or propranolol infusion. These assessments will be made by the PI together with the medical monitor, Dr. Raymond Townsend, Professor of Medicine in the Nephrology & Hypertension Division, who will also serve as DSMB chair. Conditions of testing will remain double-blind for each subject until their completion of all testing visits, unless for safety concerns, either the PI or medical monitor request an unblinding. Group 2 subjects will include adult (ages 21 - 65 years) type 1 diabetic recipients of extrahepatic islet transplants with stable islet graft function defined by C-peptide > 0.5 ng/ml and insulin-independent or insulin-dependent with daily insulin requirement < 0.2 units/kg•d to maintain HbA1c < 7.0%. Subjects will be on standard immunosuppression consisting of tacrolimus with or without sirolimus or mychophenolic acid, and if receiving prednisone, no more than 5 mg daily. Subjects will be excluded for uncontrolled hypertension, active cardiovascular disease, abnormal kidney, liver, or thyroid function, anemia, seizure disorder not related to prior severe hypoglycemia, pregnancy, and nursing. After informed consent, eligibility will be determined by a screening visit to include medical history, physical exam, EKG, urine pregnancy test, serum chemistries, TSH, cell counts, HbA1c and C-peptide. Detailed inclusion/exclusion criteria are provided below. Eligible Group 2 subjects will undergo placement of a 7 day blinded CGM (iPro®2 Professional) to characterize their hypoglycemia exposure, and participate in one study visit. Subjects will avoid strenuous activity for three days prior to the study visit. Subjects will be invited to spend the night in the Penn Center for Human Phenomic Science the evening prior to the study visit day, and will be required to do so if using insulin to maintain near-normoglycemia. Morning medications will be held until the completion of testing, with the exception of morning doses of twice daily immunosuppressants given after baseline blood samples are collected. Following 10-hours of overnight fasting, around 0700 at t = -120 min a primed (5 mg/kg ∙ fasting plasma glucose/90 for 5 min) continuous (0.05 mg/kg∙min for 355 min) infusion of 6,6-2H2-glucose (99% enriched; Cambridge Isotopes Laboratories) will be administered to assess endogenous glucose production before and during the induction of hyperinsulinemia (Bernroider et al., 2005; Rickels et al., 2015). At t = -30 min cardiac telemetry monitoring will be initiated, with every 30 min monitoring of heart rate and blood pressure documented during the glucose clamp procedure. After baseline blood samples at t = -15, and -1 min, at t = 0 min a continuous infusion of insulin (1.0 mU/kg∙min for 180 min) will be administered to produce hyperinsulinemia. Subsequently, a variable rate infusion of 20% glucose will be initiated to target the plasma glucose at ~ 90 mg/dl until 90 min (euglycemic phase), and then ~ 50 mg/dl until 180 min (hypoglycemic phase). To reduce changes in plasma enrichment during the clamp, the variable glucose infusion will be enriched to ~ 2.0 % with 6,6-2H2-glucose (Bernroider et al., 2005; Rickels et al., 2015). Blood samples will be taken every 5 min, centrifuged, and measured at bedside with an automated glucose analyzer (YSI 2300) to adjust the glucose infusion rate and achieve the desired plasma glucose concentration. Additional blood samples will be taken at t = 30, 60, 75, 90, 120, 150, 165, and 180 min for biochemical analysis and verification of the plasma glucose levels. All samples will be collected on ice in chilled tubes containing EDTA and Protease Inhibitor Cocktail, centrifuged at 4°C, separated, and frozen at -80°C for subsequent analysis. The total amount of blood sampled will be 100 ml. A questionnaire will be administered every 15 - 30 min during the study in order to quantitate autonomic symptoms as the sum of scores ranging from 0 (none) to 5 (severe) for each of the following symptoms: anxiety, palpitations, sweating, tremor, hunger, and tingling (Towler et al., 1993; Rickels et al., 2015). Group 3 subjects will include adult (ages 21 - 65 years) pancreatectomized recipients of intrahepatic islet auto-transplants with stable islet graft function defined by C-peptide > 0.5 ng/ml and insulin-independent or insulin-dependent with daily insulin requirement < 0.2 units/kg•d to maintain HbA1c < 7.0%. Subjects will be excluded for uncontrolled hypertension, active cardiovascular disease, abnormal kidney, liver, or thyroid function, anemia, seizure disorder, pregnancy, and nursing. After informed consent, eligibility will be determined by a screening visit to include medical history, physical exam, EKG, urine pregnancy test, serum chemistries, TSH, cell counts, HbA1c and C-peptide. Detailed inclusion/exclusion criteria are provided below. Eligible Group 3 subjects will undergo placement of a 7 day blinded CGM (iPro®2 Professional) to characterize their hypoglycemia exposure, and participate in one study visit. Subjects will avoid strenuous activity for three days prior to the study visit. Subjects will be invited to spend the night in the Penn Center for Human Phenomic Science the evening prior to the study visit day, and will be required to do so if using insulin to maintain near-normoglycemia. Morning medications will be held until the completion of testing. Following 10-hours of overnight fasting, around 0700 at t = -120 min a primed (5 mg/kg ∙ fasting plasma glucose/90 for 5 min) continuous (0.05 mg/kg∙min for 355 min) infusion of 6,6-2H2-glucose (99% enriched; Cambridge Isotopes Laboratories) will be administered to assess endogenous glucose production before and during the induction of hyperinsulinemia (Bernroider et al., 2005; Rickels et al., 2015). At t = -30 min cardiac telemetry monitoring will be initiated, with every 30 min monitoring of heart rate and blood pressure documented during the glucose clamp procedure. After baseline blood samples at t = -15, and -1 min, at t = 0 min a continuous infusion of insulin (1.0 mU/kg∙min for 180 min) will be administered to produce hyperinsulinemia. Subsequently, a variable rate infusion of 20% glucose will be initiated to target the plasma glucose at ~ 90 mg/dl until 90 min (euglycemic phase), and then ~ 50 mg/dl until 180 min (hypoglycemic phase). To reduce changes in plasma enrichment during the clamp, the variable glucose infusion will be enriched to ~ 2.0 % with 6,6-2H2-glucose (Bernroider et al., 2005; Rickels et al., 2015). Blood samples will be taken every 5 min, centrifuged, and measured at bedside with an automated glucose analyzer (YSI 2300) to adjust the glucose infusion rate and achieve the desired plasma glucose concentration. Additional blood samples will be taken at t = 30, 60, 75, 90, 120, 150, 165, and 180 min for biochemical analysis and verification of the plasma glucose levels. All samples will be collected on ice in chilled tubes containing EDTA and Protease Inhibitor Cocktail, centrifuged at 4°C, separated, and frozen at -80°C for subsequent analysis. The total amount of blood sampled will be 100 ml. A questionnaire will be administered every 15 - 30 min during the study in order to quantitate autonomic symptoms as the sum of scores ranging from 0 (none) to 5 (severe) for each of the following symptoms: anxiety, palpitations, sweating, tremor, hunger, and tingling (Towler et al., 1993; Rickels et al., 2015).

Additional Information About The Study

As previously stated, in this protocol we aim to study how innervation affects transplanted islet cell responses to hypoglycemia. The primary objective will be addressed by a double blind mechanistic non-interventional study in Type 1 diabetic recipients of intrahepatic islet transplantation (Group 1). This group will undergo 4 visits; a screening visit and 3 hyperinsulinemic clamps each with a randomly assigned condition: phentolamine (α blockade), propranolol (β blockade) or placebo. The secondary objective will be to compare islet cell hormonal responses to insulin-induced hypoglycemia between participants in Group 1 and Type 1 diabetic recipients of extrahepatic islet transplantation (Group 2), and Pancreatectomized recipients of intrahepatic islet auto-transplantation (Group 3). Groups 2 & 3 will undergo 2 visits; a screening visit and a single hyperinsulinemic clamp. We hope to enroll a maximum of 45 islet cell recipients. 12-15 participants will fall into each of the above three groups. A final component to this study will be to provide the participants with a Medtronic iPro®2 Professional Continuous Glucose Monitor which they will wear for 7 days. Participants will be compensated for their time + travel. Should participation require long-distance travel involving air or rail; economy or coach-fare tickets will be reimbursed via a check from the University of Pennsylvania. If travel is a short-distance; participants will receive $11.00 in cash at each visit to cover parking or regional rail ticket expense.

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