In both developed and developing countries, incidence of type 2 diabetes is rapidly increasing due to occurrences of obesity and unhealthy lifestyles. A line of previous studies has shown that unbalanced diet and physical inactivity are also risk factors of diabetes. The development of diabetes is preceded by symptoms such as resistance to insulin and disturbances of glucose metabolism. Therefore, long-term monitoring of glucose metabolism is crucial to investigate the physiological basis of the symptoms and further find a method to prevent the pathogenesis of the disease. However, there are no realistic methods to continuously monitor glucose metabolism for days in laboratory conditions. Because periodical (e.g., every 4 minutes) sampling of blood from laboratory animals is stressful to the animal and laborious for the experimenters, we developed a novel wireless system to chronically monitor glucose levels.
In our system, a monitoring device is implanted subcutaneously in inguinal area of adult rats. Using the implanted device, blood glucose levels were measured every 4 minutes for up to 1 week. With the monitoring system, we observed an increase in the blood glucose level with oral administration of 15% glucose solution and decrease with subcutaneous injection of insulin aspart (0.5 µl/kg).
Continuous monitoring of glucose metabolism is applicable to human subjects, but it does not allow us to experimentally reveal the molecular and physiological mechanism underlying the glucose metabolism. Our system is applicable to laboratory animals and thus allows for a large variety of experiments such as pharmacological interventions in glucose metabolism and insulin-independent manipulation of glucose levels.