Insulin Sensitivity, Impaired Counterregulation, and Glucose Variability

Insulin Sensitivity, Impaired Counterregulation, and Glucose Variability

This protocol will investigate physiological parameters including insulin sensitivity and counterregulatory function using a mixed meal test and induced hypoglycemia in subjects with type I diabetes.

The principal idea of the proposed research is: in order to be successful, closed-loop control of glucose in diabetes must adapt to individual physiologic characteristics and to the behavioral profile of each person. We propose to build a system that will use observers of patients' behavior and metabolic state and control modules that are responsible for insulin delivery and hypoglycemia prevention. In this phase of the project, we will investigate relationships of insulin sensitivity and impaired counterregulation with blood glucose variability, aiming to develop algorithmic physiology observers, which will track specific parameters of glucose variability and recurrent hypoglycemia as markers of change in a person's insulin sensitivity and counterregulatory ability.

Inclusion Criteria:

• Type I diabetes mellitus (TIDM) (as defined by the American Diabetes Association criteria or judgment of a physician) for at least two years prior to the enrollment in the study.
• Use of an insulin pump to treat their diabetes for at least six months prior to the study.
• Ability to use a bolus calculator function with the current insulin pump with pre-defined parameters for glucose goal, carbohydrate ratio, and insulin sensitivity factor.
• Age 21 - 64 years. Adults age 65 and over are likely to have medical exclusions for the follow-up Phase 2 study, which involves induced hypoglycemia.
• Completed Phase 1 of the Institutional Review Board (IRB) #14956 "Development of a Behavioral Observer for Type 1 Diabetes Mellitus"
• Willingness to use lispro (Humalog) insulin two days prior to and during inpatient admission.
• Willingness to perform Self-Monitoring Blood Glucose (SMBG) 4 times per day at times before meals and bedtime.
• Demonstration of proper mental status and cognition for completion of the study.

Exclusion Criteria:

• Pregnancy
• Psychiatric disorders that would interfere with study tasks (e.g. mental retardation, substance abuse)
• History of a systemic deep tissue infection with methicillin-resistant staph aureus or Candida albicans
• Known bleeding diathesis or dyscrasia
• Active enrollment in another clinical trial
• Medical condition that would make operating an insulin pump difficult (e.g. blindness, severe arthritis, extensive scar tissue at sites where devices are inserted).
• Anemia (hematocrit <36% [females], <38% [males]),
• Allergy or adverse reaction to lispro (Humalog) insulin
• Conditions which may increase the risk of induced hypoglycemia such as symptomatic heart disease, congestive heart failure, history of a cerebrovascular event, atrial fibrillation, renal insufficiency (creatinine >1.5) or uncontrolled hypertension (resting blood pressure >140/90).