Jennifer L. Sherr

Effect of Pramlintide on Prandial Glycemic Excursions During Closed-Loop Control in Adolescents and Young Adults With Type 1 Diabetes

OBJECTIVE Even under closed-loop (CL) conditions, meal-related blood glucose (BG) excursions frequently exceed target levels as a result of delays in absorption of insulin from the subcutaneous site of infusion. We hypothesized that delaying gastric emptying with preprandial injections of pramlintide would improve postprandial glycemia by allowing a better match between carbohydrate and insulin absorptions. RESEARCH DESIGN AND METHODS Eight subjects (4 female; age, 15–28 years; A1C, 7.5 ± 0.7%) were studied for 48 h on a CL insulin-delivery system with a proportional integral derivative algorithm with insulin feedback: 24 h on CL control alone (CL) and 24 h on CL control plus 30-μg premeal injections of pramlintide (CLP). Target glucose was set at 120 mg/dL; timing and contents of meals were identical on both study days. No premeal manual boluses were given. Differences in reference BG excursions, defined as the incremental glucose rise from premeal to peak, were compared between conditions for each meal. RESULTS CLP was associated with overall delayed time to peak BG (2.5 ± 0.9 vs. 1.5 ± 0.5 h; P < 0.0001) and reduced magnitude of glycemic excursion (88 ± 42 vs. 113 ± 32 mg/dL; P = 0.006) compared with CL alone. Pramlintide effects on glycemic excursions were particularly evident at lunch and dinner, in association with higher premeal insulin concentrations at those mealtimes. CONCLUSIONS Pramlintide delayed the time to peak postprandial BG and reduced the magnitude of prandial BG excursions. Beneficial effects of pramlintide on CL may in part be related to higher premeal insulin levels at lunch and dinner compared with breakfast.

Reduced Hypoglycemia and Increased Time in Target Using Closed-Loop Insulin Delivery During Nights With or Without Antecedent Afternoon Exercise in Type 1 Diabetes

OBJECTIVE Afternoon exercise increases the risk of nocturnal hypoglycemia (NH) in subjects with type 1 diabetes. We hypothesized that automated feedback-controlled closed-loop (CL) insulin delivery would be superior to open-loop (OL) control in preventing NH and maintaining a higher proportion of blood glucose levels within the target blood glucose range on nights with and without antecedent afternoon exercise. RESEARCH DESIGN AND METHODS Subjects completed two 48-h inpatient study periods in random order: usual OL control and CL control using a proportional-integrative-derivative plus insulin feedback algorithm. Each admission included a sedentary day and an exercise day, with a standardized protocol of 60 min of brisk treadmill walking to 65–70% maximum heart rate at 3:00 p.m. RESULTS Among 12 subjects (age 12–26 years, A1C 7.4 ± 0.6%), antecedent exercise increased the frequency of NH (reference blood glucose <60 mg/dL) during OL control from six to eight events. In contrast, there was only one NH event each on nights with and without antecedent exercise during CL control (P = 0.04 vs. OL nights). Overnight, the percentage of glucose values in target range was increased with CL control (P < 0.0001). Insulin delivery was lower between 10:00 p.m. and 2:00 a.m. on nights after exercise on CL versus OL, P = 0.008. CONCLUSIONS CL insulin delivery provides an effective means to reduce the risk of NH while increasing the percentage of time spent in target range, regardless of activity level in the mid-afternoon. These data suggest that CL control could be of benefit to patients with type 1 diabetes even if it is limited to the overnight period.

Effect of insulin feedback on closed-loop glucose control: a crossover study.

Background: Closed-loop (CL) insulin delivery systems utilizing proportional-integral-derivative (PID) controllers have demonstrated susceptibility to late postprandial hypoglycemia because of delays between insulin delivery and blood glucose (BG) response. An insulin feedback (IFB) modification to the PID algorithm has been introduced to mitigate this risk. We examined the effect of IFB on CL BG control. Methods: Using the Medtronic ePID CL system, four subjects were studied for 24 h on PID control and 24 h during a separate admission with the IFB modification (PID + IFB). Target glucose was 120 mg/dl; meals were served at 8:00 AM, 1:00 PM, and 6:00 PM and were identical for both admissions. No premeal manual boluses were given. Reference BG excursions, defined as incremental glucose rise from premeal to peak, and postprandial BG area under the curve (AUC; 0–5 h) were compared. Results are reported as mean ± standard deviation. Results: The PID + IFB control resulted in higher mean BG levels compared with PID alone (153 ± 54 versus 133 ± 56 mg/dl; p < .0001). Postmeal BG excursions (114 ± 28 versus 114 ± 47 mg/dl) and AUCs (285 ± 102 versus 255 ± 129 mg/dl/h) were similar under both conditions. Total insulin delivery averaged 57 ± 20 U with PID versus 45 ± 13 U with PID + IFB (p = .18). Notably, eight hypoglycemic events (BG < 60 mg/dl) occurred during PID control versus none during PID + IFB. Conclusions: Addition of IFB to the PID controller markedly reduced the occurrence of hypoglycemia without increasing meal-related glucose excursions. Higher average BG levels may be attributable to differences in the determination of system gain (Kp) in this study. The prevention of postprandial hypoglycemia suggests that the PID + IFB algorithm may allow for lower target glucose selection and improved overall glycemic control.

Prevention of type 1 diabetes: the time has come

Improved understanding of the pathogenesis of type 1 diabetes mellitus has completely changed our view of this disease in the past 25 years—from an acute, fulminant disease, to a chronic, autoimmune process. Information on genetic and serologic markers has increased our ability to identify individuals at risk. Prospectively gathered data indicate that, with a combination of immunologic and metabolic studies, children with a 6-year risk of disease higher than 90% can be identified due to an ongoing immune process. They differ from children with overt disease only in the time it will take for glucose levels to rise above a diagnostic threshold. Therapies to change the progression of β-cell loss have been tested in patients with newly diagnosed type 1 diabetes. With improved predictive capabilities and agents that can have longer-lasting effects than those tested more than 10 years ago, new prevention studies are underway. These studies are large and costly but the risks posed by such interventions compare favorably with those of developing hyperglycemia and of future complications portended by the diagnosis of diabetes. In this Review we discuss risk-stratification techniques and how they are applied, other diagnostic criteria, and outcomes from diabetes-prevention trials.

Acute Metabolic Effects of Exenatide in Patients With Type 1 Diabetes With and Without Residual Insulin to Oral and Intravenous Glucose Challenges

OBJECTIVE Glucagon-like peptide 1 (GLP-1) is an incretin hormone that is released from the gastrointestinal tract. Treatment with GLP-1 analogs has proven to be of clinical use for patients with type 2 diabetes. Patients with type 1 diabetes, particularly those with residual β-cell function, may also respond to treatment, but the acute metabolic effects of GLP-1 analogs on these patients in reaction to both oral and intravenous glucose challenges are not well understood. RESEARCH DESIGN AND METHODS Seventeen patients with type 1 diabetes, half of whom had residual insulin production, underwent two mixed-meal tolerance tests (MMTTs) and two intravenous glucose tolerance tests (IVGTTs), with and without pretreatment with exenatide. No exogenous bolus insulin was administered for the studies. Glucose excursions, insulin secretion rates (ISRs), and levels of glucagon, endogenous GLP-1, and gastric inhibitory polypeptide were measured after the meal or glucose loads. RESULTS During the MMTT, glucose levels were suppressed with exenatide in patients with or without residual insulin production (P = 0.0003). Exenatide treatment did not change the absolute ISR, but the ISR to glucose levels were increased (P = 0.0078). Gastric emptying was delayed (P = 0.0017), and glucagon was suppressed (P = 0.0015). None of these hormonal or glucose changes were detected during the IVGTT with exenatide administration. CONCLUSIONS Exenatide showed a significant antidiabetogenic effect prior to an oral meal in patients with type 1 diabetes involving glucagon suppression and gastric emptying, while preserving increased insulin secretion. GLP-1 analogs may be useful as an adjunctive treatment in type 1 diabetes.

New-generation diabetes management: glucose sensor-augmented insulin pump therapy

Diabetes is one of the most common chronic disorders with an increasing incidence worldwide. Technologic advances in the field of diabetes have provided new tools for clinicians to manage this challenging disease. For example, the development of continuous subcutaneous insulin infusion systems have allowed for refinement in the delivery of insulin, while continuous glucose monitors provide patients and clinicians with a better understanding of the minute to minute glucose variability, leading to the titration of insulin delivery based on this variability when applicable. Merging of these devices has resulted in sensor-augmented insulin pump therapy, which became a major building block upon which the artificial pancreas (closed-loop systems) can be developed. This article summarizes the evolution of sensor-augmented insulin pump therapy until present day and its future applications in new-generation diabetes management.

Acceleration of insulin pharmacodynamic profile by a novel insulin infusion site warming device.

Subcutaneously injected rapid‐acting insulin analogs do not replicate physiologic insulin action due to delays in their onset and peak action resulting in postprandial glucose excursions. The InsuPatch (IP) is a novel insulin infusion site warming device developed to accelerate insulin action by increasing blood flow to the area of insulin absorption. Thirteen adolescents with type 1 diabetes (T1D, mean age 14 ± 4 yr) were enrolled in this study to investigate the effect of the IP on the pharmacodynamics and pharmacokinetics of a 0.2 unit/kg bolus dose of aspart insulin using the euglycemic clamp technique.

Safety of Nighttime 2-Hour Suspension of Basal Insulin in Pump-Treated Type 1 Diabetes Even in the Absence of Low Glucose

OBJECTIVE An integrated sensor-augmented pump system has been introduced that interrupts basal insulin infusion for 2 h if patients fail to respond to low-glucose alarms. It has been suggested that such interruptions of basal insulin due to falsely low glucose levels detected by sensor could lead to diabetic ketoacidosis. We hypothesized that random suspension of basal insulin for 2 h in the overnight period would not lead to clinically important increases in blood β-hydroxybutyrate levels despite widely varying glucose values prior to the suspension. RESEARCH DESIGN AND METHODS Subjects measured blood glucose and blood β-hydroxybutyrate levels using a meter each night at 9:00 p.m., then fasted until the next morning. On control nights, the usual basal rates were continued; on experimental nights, the basal insulin infusion was reprogrammed for a 2-h zero basal rate at random times after 11:30 p.m. RESULTS In 17 type 1 diabetic subjects (mean age 24 ± 9 years, diabetes duration 14 ± 11 years, A1C level 7.3 ± 0.5% [56 mmol/mol]), blood glucose and blood β-hydroxybutyrate levels were similar at 9:00 p.m. on suspend nights (144 ± 63 mg/dL and 0.09 ± 0.07 mmol/L) and nonsuspend nights (151 ± 65 mg/dL and 0.08 ± 0.06 mmol/L) (P = 0.39 and P = 0.47, respectively). Fasting morning blood glucose levels increased after suspend nights compared with nonsuspend nights (191 ± 68 vs. 141 ± 75 mg/dL, P < 0.0001), and the frequency of fasting hypoglycemia decreased the morning following suspend nights (P < 0.0001). Morning blood β-hydroxybutyrate levels were slightly higher after suspension (0.13 ± 0.14 vs. 0.09 ± 0.11 mmol/L, P = 0.053), but the difference was not clinically important. CONCLUSIONS Systems that suspend basal insulin for 2 h are safe and do not lead to clinically significant ketonemia even if the blood glucose level is elevated at the time of the suspension.

The Alteration of Aspart Insulin Pharmacodynamics When Mixed With Detemir Insulin

OBJECTIVE Mixing rapid acting insulin analogs with detemir insulin to minimize daily injections has been adopted as a common regimen, especially for some children with type 1 diabetes, despite the manufacturing company’s caution against mixing these analogs in the same syringe. The effect of this practice on the pharmacodynamics (PD) of rapid-acting insulin has not been widely studied. This crossover, randomized study was undertaken to determine whether mixing aspart with detemir insulin has an adverse effect on the early glucodynamic action of rapid-acting insulin analog in humans. RESEARCH DESIGN AND METHODS Eight adolescents with type 1 diabetes (age 17.3 ± 0.6 years and A1C 7.3 ± 0.3%) had two euglycemic glucose clamps during which 0.2 units/kg aspart and 0.4 units/kg detemir insulin were injected either as a separate or single mixed injection in random order. RESULTS Mixing the two insulins diminished the peak and overall early aspart insulin action with significantly lower maximum glucose infusion rate (GIRmax separate 6.1 ± 0.7 mg/kg/min vs. mix 4.5 ± 0.5 mg/kg/min; P = 0.03) values and the area under curve for GIR during the first 3 h of the insulin action study (separate 757 ± 105 mg/kg vs. mix 491 ± 66 mg/kg; P = 0.04). CONCLUSIONS These data demonstrate that mixing aspart with detemir insulin markedly lowers the early PD action of aspart and prolongs its time-action profile as compared with the separate injection of these analogs. These changes in insulin PD should be weighed against the added convenience of mixing when considering such unlicensed use of these insulins in youth with type 1 diabetes.

Past, present, and future of insulin pump therapy: better shot at diabetes control

With the advent of continuous subcutaneous insulin infusion therapy and the findings of the Diabetes Control and Complications Trial, the management of type 1 diabetes has changed drastically. Over the past 30 years since its development, the effectiveness of continuous subcutaneous insulin infusion has been assessed in comparison with other modes of intensive treatment. Additionally, improvements in pump delivery systems have been made. Here, the findings of the studies on pump therapy are reviewed. Selection criteria of patients for pump use and how to initiate pump therapy are presented. Finally, newer findings on continuous glucose sensors are discussed as the next era of pump therapy continues to focus on the goal of developing an artificial pancreas.