Hypoglycemia is a major barrier to the achievement of adequate glycemic control for most patients with insulin- dependent diabetes, both those with type 1 diabetes and advanced type 2 diabetes. Type 1 diabetic patients with absolute insulin deficiency (C-peptide negative) are at greatest risk for experiencing severe hypoglycemic events because the near total destruction of insulin producing islet beta-cells produces an associated defect in glucagon secretion from neighboring alpha-cells. Such patients then depend on the sympathoadrenal system as a final defense against hypoglycemia, but unfortunately, recurrent episodes of hypoglycemia blunt sympathoadrenal activation and produce a syndrome of hypoglycemia unawareness that is associated with a twenty-fold increased risk of life-threatening hypoglycemia. Without intact islet or sympathoadrenal (especially epinephrine) responses to hypoglycemia, these patients cannot increase endogenous (primarily hepatic) glucose production to prevent or correct low blood glucose. In the present application we propose to determine whether strict hypoglycemia avoidance by 2 novel therapeutic approaches for type 1 diabetes, namely islet cell transplantation (specific aim 1) or real-time continuous glucose monitoring (RT-CGM;
specific aim 2), can restore endogenous glucose production in response to hypoglycemia in patients with long standing disease.
Under specific aim 1, 12 subjects with long standing type 1 diabetes complicated by hypoglycemia unawareness will undergo assessment of the endogenous glucose production response to insulin-induced hypoglycemia using paired hyperinsulinemic eu- and hypoglycemic clamps with stable glucose isotope infusions before and at 6 and 18 months following islet cell transplantation.
Under specific aim 2, 12 similar type 1 diabetic subjects with hypoglycemia unawareness will undergo identical assessment of the endogenous glucose production response to insulin-induced hypoglycemia before and at 6 and 18 months following initiation of RT-CGM. Because islet transplant recipients may require some insulin to control hyperglycemia, and because RT-CGM may be interrupted or fail to arouse a sleeping patient, it is critical to understand what improvements in glucose counterregulation may be offered by either approach. While some patients may only be candidates for only one approach or the other, if both approaches are shown to restore glucose counterregulation, the data generated from this proposal will enable the design of future randomized trials of cell vs. mechanical therapy on long-term glucose counterregulatory responses and the protection thus offered against severe hypoglycemia.

Public Health Relevance

Impaired glucose counteregulation in long standing type 1 diabetes increases the risk for severe hypoglycemia, an important complication in itself and a significant barrier to the attainment of adequate glycemic control. This proposal will determine whether 2 novel approaches for the treatment of type 1 diabetes, namely islet cell transplantation (specific aim 1) or real-time continuous glucose monitoring (specific aim 2), can restore glucose counterregulation in response to insulin-induced hypoglycemia in patients with long standing disease.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Clinical and Integrative Diabetes and Obesity Study Section (CIDO)
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Arreaza-Rubin, Guillermo
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University of Pennsylvania
Internal Medicine/Medicine
Schools of Medicine
United States
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Rickels, Michael R; Peleckis, Amy J; Markmann, Eileen et al. (2016) Long-Term Improvement in Glucose Control and Counterregulation by Islet Transplantation for Type 1 Diabetes. J Clin Endocrinol Metab 101:4421-4430
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Rickels, Michael R; Fuller, Carissa; Dalton-Bakes, Cornelia et al. (2015) Restoration of Glucose Counterregulation by Islet Transplantation in Long-standing Type 1 Diabetes. Diabetes 64:1713-8
Choudhary, Pratik; Rickels, Michael R; Senior, Peter A et al. (2015) Evidence-informed clinical practice recommendations for treatment of type 1 diabetes complicated by problematic hypoglycemia. Diabetes Care 38:1016-29
Rickels, Michael R; Kong, Stephanie M; Fuller, Carissa et al. (2014) Insulin sensitivity index in type 1 diabetes and following human islet transplantation: comparison of the minimal model to euglycemic clamp measures. Am J Physiol Endocrinol Metab 306:E1217-24
Rickels, Michael R; Kong, Stephanie M; Fuller, Carissa et al. (2013) Improvement in insulin sensitivity after human islet transplantation for type 1 diabetes. J Clin Endocrinol Metab 98:E1780-5
Rickels, Michael R (2012) Recovery of endocrine function after islet and pancreas transplantation. Curr Diab Rep 12:587-96