The oral glucose tolerance test (OGTT) is the most common test used for assessing of the body’s ability to breakdown glucose/ carbohydrate. The test evaluates the level of the clearance of glucose from the blood through measuring blood glucose from samples taken at intervals of 30 minutes against the initial glucose following an oral intake of a glucose solution (about 1.75g/kg body weight) after fasting for 8-12 hours. Impaired glucose metabolism, which is a sign of underlying disease states such as type 2 diabetes, insulin resistance, gestational diabetes etc., is indicated by elevated glucose levels (>140 mg/dl) after 2 hours (Kabaroğlu, C, et al).
Obesity is associated with an increased risk of impaired glucose homeostasis and diabetes type 2 (T2DM) often as a result of insulin resistance. In a study involving 80 obese adolescents (32 males and 48 females) glucose level of >140mg/dl was observed in some participants at 30 minutes during OGTT. The researchers compared the lipid profile, systemic inflammatory modulators and insulin resistance indices of this group against those of the normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) participants in a bid to determine the significance of the elevated levels of glucose at 30 minutes. Both the systemic inflammatory modulators and lipid profiles, mainly interlukin-6 (IL-6), neopterin and lipoprotein associated with phospholipas A2 (LP-PLA2 ) were found to be higher in obese participants with >140mg/dl glucose at 30 minutes than in the NGT and IGT obese adolescents. On the other hand, at 30 minutes there was no significant difference in the insulin levels among the three groups but in the group with >140 mg/dl, the insulin levels were found to be higher at 90 and 120 minutes than the other two groups (Kabaroğlu, C, et al).
The researchers established that a glucose level >140mg/dl at 30minutes in obese teenagers during OGTT is a significant indicator of a higher risk of cardiovascular diseases such as atherosclerosis, coronary heart disease and myocardial infarction. While obesity and IGT are often associated with higher risk of inflammation, the study identified a group that with NGT that was at a higher risk than the obese subjects with IGT. The higher levels of inflammatory modulators in the subjects with BG>140mg/dl than those in subjects with IGT is clinically significant as an indicator of an increased risk of cardiovascular disorders in obesity and thus should be considered in the evaluation of OGTT in of obese teenagers. From the results the researcher suggested that glucose levels >140mg/dl at 30 minutes during OGTT is probably a new glucose tolerance disorder in obesity. In other words, while findings of impaired fasting (IFG) and IGT in OGTT may be obvious predictors of alteration of glucose metabolism and the associated increased risk of cardiovascular diseases in obesity, BG> 140mg/dl at 30 minutes could be categorized as a new alteration of glucose metabolism that is different from IGT and IFG. Thus the evaluation of OGTT in obese adolescents should not rule out NGT but should give a special consideration to cases of NGT where BG> 140mg/dl at 30 minutes. The researchers also recommended the consideration of LP-PLA2 and neopterin as new systemic inflammation markers in obese teenagers. Despite the interesting findings, the researchers recommended further longitudinal studies to confirm their findings (Kabaroğlu, C, et al).
Work cited
Kabaroğlu, C, et al. "Elevated glucose level at 30 minutes during an oral glucose tolerance test in obese adolescents: a new disorder of glucose tolerance." Endocrine Journal 60.2 (2013): 197-205.
