Glucose tolerance test and protocol
Glucose Tolerance Tests (GTT’s) determine how quickly glucose is cleared from the blood after glucose administration. Blood glucose levels are measured using Johnson and Johnson’s OneTouch® Ultra Blood Glucose Monitoring System immediately prior to glucose administration, and at 15, 30, 60, and 120 minutes after glucose administration (timing of glucose measurement can be modified on request). GTT’s are designed to evaluate effects of genetic mutations or novel compounds on glucose metabolism. These analyses are critically important for understanding mouse models of diabetes.
Standard Protocol
Johnson and Johnson’s OneTouch® Ultra Blood Glucose Monitoring System is minimally invasive, requiring only a tiny drop of blood (1 uL) and gives rapid and reliable results within 5 seconds. With the broadest range of operating temperatures of any system available, results are reliable and accurate. Calibration of the OneTouch® Ultra Blood Glucose Monitoring System is performed using control test solutions provided by the manufacturer.
We offer two forms of glucose administration in our glucose tolerance tests: Oral gavage (OGTT) and Intraperitoneal injection (IPGTT). OGTT is the most commonly requested procedure. We’ve performed 5000 OGTTs and 350 IPGTTs over the last 2.5 years.
Prior to glucose administration, mice undergo a 4 to 18 hour fast to achieve a baseline blood glucose level. After the fast, a 2 mm distal section of the mouse’s sterilized tail is snipped using a scalpel and gently squeezed to obtain two drops of blood, the first of which is discarded. The second drop is applied directly to a OneTouch® Glucometer test strip to obtain a baseline T0 blood glucose reading expressed as mg/dL. In our experience, one reading per time point is sufficient to obtain an accurate reading, but additional readings per time point may be performed upon request.
DIO mice tend to lose weight when subjected to repeat handling, which results in improved glucose tolerance. This is apparent in the vehicle group shown here, these animals had an 11.3% body weight loss with an associated improvement in glucose tolerance.
The advantage of oral gavage is that it allows for administration of a controlled amount of compound. The disadvantage is that this route of administration is stressful to the animal, which may result in weight loss, thus reducing the apparent therapeutic effect of the test compound. Where multiple daily compound administrations may be needed to maintain circulating levels of compound, administration via water or food may be considered, whilst consistency of drug administration cannot be assured, the reduction in stress may allow for a more clear result.
Effect of Rosiglitazone treatment on glucose levels in BKS.Cg-m +/+ Leprdb/J mice
Study Design and Timeline
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Following 0, 14 or 28 days of Rosiglitazone treatment at a therapeutic dose (25 mg/kg), db/db (BKS.Cg-m +/+ Leprdb/J) mice have a time-dependent decrease in both fasted glucose and GTT area under the curve (AUC) as compared to vehicle treated controls.
We also offer an insulin tolerance test (ITT). Our protocol is identical to the glucose tolerance test except that mice are fasted for up to 4 hours and human insulin diluted in sterile water is administered by IP injection in lieu of glucose administration at 1 U/kg. Blood glucose levels are monitored as above immediately prior to injection T0, and at 30, 60, and 90 minutes after injection. These data are expressed as % T0 blood glucose levels vs. time.
Customized Options
- Intravenous glucose administration
- Frequency of blood glucose measurements
- Duration of fast prior to T0 Glucometer reading
- Pairing of OGTT or IPGTT with insulin and/or enzymatic glucose blood draws
