ORAL GLUCOSE TOLERANCE TEST (OGTT)

Diabetes mellitus is a metabolic disorder characterized by disturbances in carbohydrate, protein, and lipid metabolism and by complications like retinopathy, microangiopathy, and nephropathy. The Glucose Tolerance Test (GTT), also referred to as the Oral Glucose Tolerance Test (OGTT), is a method which can help to diagnose instances of diabetes mellitus or insulin resistance. The test is a more substantial indicator of diabetes than finger prick testing.

Oral glucose tolerance test measures your body's response to sugar (glucose) ability to use a type of sugar, called glucose, that is the body's main source of energy. The glucose tolerance test can be used to screen for type 2 diabetes. More commonly, a modified version of the glucose tolerance test is used to diagnose gestational diabetes- a type of diabetes that develops during pregnancy. OGTT, a test of immense value and sentiment, in favour of using fasting plasma glucose concentration alone was seen as a practical attempt to simplify and facilitate the diagnosis of diabetes.

In humans, fasting blood glucose concentrations and an oral glucose tolerance test (OGTT) is used to monitor temporal blood glucose fluctuations in response to an oral glucose challenge. The OGTT is the primary test used in medical screening in the diagnosis of T2DM and gestational diabetes, but can also be used to detect an intermediate metabolic state between normal glucose homeostasis and impaired glucose tolerance. In the past several decades, mouse models have become an important resource for researchers and the pharmaceutical industry to identify molecular mechanisms implicated in T2DM pathophysiology and to systematically exploit treatment options. Glucose tolerance tests (GTTs) are among the most widely used tests to assess a diabetic phenotype and alterations in glucose homeostasis under in vivo conditions in mice. Many GTT variations have been devised for various purposes, with different routes of administration, glucose doses, blood-sampling sites, blood-sampling intervals, or test durations, and may include assessing various metabolites and hormones in addition to blood glucose concentrations.

Testing

IN Humans:

The patient is instructed not to restrict carbohydrate intake in the days or weeks before the test. The test should not be done during an illness, as results may not reflect the patient's glucose metabolism when healthy. A full adult dose should not be given to a person weighing less than 42.6 kg (94 lb), or excessive glucose may produce a false-positive result. Usually, the OGTT is performed in the morning as glucose tolerance can exhibit a diurnal rhythm with a significant decrease in the afternoon. The patient is instructed to fast (water is allowed) for 8–12 hours prior to the tests. Medication such as large doses of salicylates, diuretics, anticonvulsants, and oral contraceptives affect the glucose tolerance test.

ONE-STEP TESTING

You need to go to the lab one time for a 2-hour glucose tolerance test. For this test:

·         DO NOT eat or drink anything (other than sips of water) for 8 to 14 hours before your test. (You also cannot eat during the test.)

·         You will be asked to drink a liquid that contains glucose (75 g).

·         You will have blood drawn before you drink the liquid, and again 2 more times every 60 minutes after you drink it. Each time, your blood glucose level will be checked.

·         Allow at least 2 hours for this test.

In Rodents:

The Oral Glucose Tolerance Test (OGTT) was performed on overnight fasting normal rats. Distilled water & test items will be administered to three groups of rats, respectively. Glucose (2 g/kg) was fed 30 min after pre-treatment with distilled water, test items. Blood glucose levels were measured at -30, 0, 30, 60, 120, and 240 min after glucose load to access the effect of the extract on blood glucose levels of the glucose loaded animals. The blood glucose was measured using blood glucose test strips and a glucometer.