Simple Continuous Glucose Monitoring in Freely Moving Mice

Our protocol offers a simple inexpensive method to monitor glucose levels in mice. The main advantage of this technique is that it does not require challenging microsurgery, and does not involve bleeding, or handling the mice. This method can be used to identify elusive glucose management phenotypes in mouse models of obesity and diabetes.

While attempting this protocol, the most critical step is the insertion of the cannula under the skin, and tightening of the inner sutures in order to keep the cannula in place. To begin shave the midline of the back of the anesthetized mouse, and use a depilatory cream to ensure complete hair removal. Open and load the sensor.

Then mount the sensor onto the sensor mounting device to expose the sensor's tape and cannula side. The cannula is void from the needle. Suture two 5-0 taper point sutures to the tape on both sides of the cannula.

For the dorsal skin preparation, make a two millimeter incision in the center of the shaved area above the spine using sharp scissors. Briefly insert small forceps with a blunt edge under the skin to form a small subcutaneous pocket, so that the cannula can be inserted easily into the pocket. Pass a suture through the skin on each side of the incision.

For the sensor insertion, remove the sensor completely from the sensor mounting device and hold the sensor with forceps to keep the surrounding tape from sticking to itself. Carefully insert the cannula into the subcutaneous pocket. Pull the sutures on each side, and tighten and tie them to attach the sensor firmly in place.

This will prevent the cannula from slipping out of the subcutaneous pocket once the adhesive tape loosens over time, Cut the ends of the sutures and discard them. Attach adhesive tape surrounding the sensor, and make eight discontinuous sutures around the sensor attaching the border of the sensors taped to the skin. Activate the sensor.

Once the cannula is inserted, and the CGM is successfully activated, collect the data using the receiver. The raw output data of three days from a single mouse using the code provided is shown here. The axis parameters, and all the other parameters can be modulated in the code.

Here, the data for three days are shown for clarity. Making a subcutaneous pocket and the addition of a few sutures allows the sensor's cannula to stay in place for a longer time. The continuous data acquired using this technique allowed us to uncover an elusive metabolic phenotype in a specific mouse strain.