Exercise-induced hypoglycaemia and subcutaneous insulin infusion

Area of Science:

• Endocrinology
• Metabolic Disorders
• Exercise Physiology

Background:

• Continuous subcutaneous insulin infusion (CSII) is a common treatment for insulin-dependent diabetes.
• Exercise can lead to hypoglycemia (low blood glucose) in diabetic patients, particularly those using insulin therapy.
• Understanding the impact of insulin interruption on exercise-induced hypoglycemia is crucial for patient safety.

Purpose of the Study:

• To determine if a 3-hour interruption of insulin infusion could prevent exercise-induced hypoglycemia in patients with type 1 diabetes on CSII.
• To compare the effects of morning versus afternoon exercise on blood glucose levels after insulin interruption.

Main Methods:

• Seven insulin-dependent diabetic patients on CSII underwent bicycle exercise (45 min at 60% VO2 max) after a 3-hour insulin infusion pause.
• Studies were conducted after an overnight fast (morning) and 4 hours post-meal (afternoon).
• Blood glucose, free insulin, free fatty acids, and beta-hydroxybutyrate levels were monitored.

Main Results:

• Exercise caused a more significant blood glucose decline in the afternoon (2.2 mmol/l) compared to the morning (1.4 mmol/l) (p<0.01).
• Higher free insulin levels were observed during afternoon exercise.
• Three patients experienced symptomatic hypoglycemia during afternoon exercise, with no decrease in free insulin.

Conclusions:

• A 3-hour interruption of basal insulin infusion is insufficient to prevent exercise-induced hypoglycemia, particularly during afternoon postprandial exercise.
• Relative hyperinsulinism during exercise increases the risk of hypoglycemia even after insulin interruption.
• Individualized strategies are needed to manage hypoglycemia risk during exercise in diabetic patients on CSII.