We performed OGTT in normal and STZ-diabetic rats and noticed that blood glucose only peak at 60 min post oral glucose loading instead of at 30 min as with most previous studies. Can you provide an explanation?
Hi Ayman,
Usually an OGTT should show a peak at 30min but I already got some animal models, especially in insulin resistant + glucose intolerant subjects, showing increased glucose levels till 60 min.
It could be due to an advanced beta cells damages couples to high glucose intolerance that should need more time for clearance...
I would sugest for you to evaluate HOMA-IR and to see urin glucose levels in these mice.
Recently I did a similar experiment where I got peak at 30 min in normal animals. But there was not much difference between glucose levels at 30 and 60 min time points (160 +/- 5 vs. 151 +/- 8). May be peak is between 30 and 60 min. In nSTZ animals peak was definitely at 60 mins. Glucose load was 2 g/kg.
Hope it is useful
Nagaraj
Glucose absorption may be modified by other factors
- STZ uses glucose transporters and intestinal cells may be damaged-
Natraj, serum or plasma glucose measurements represent the resultant amount between the two processes, increase through absorption and decrease through usage. Because the difference between 30 min and 60 min time points in STZ treated animals was not significant, it does not necessarily mean that the transport of glucose from intestine is impaired. A simpler and obvious reason is poor glucose usage in STZ diabetic animals causing the glucose to remain in circulation for longer period of time. This is why the observed glucose peak in STZ diabetic animals (with total destruction of beta cells) will never be as sharp as in normal animals.
@tauseef .. The data I shared was for normal animals not STZ animals. The point I wanted to make was, in OGTT the glucose peak could be between 30 and 60 min and it also depends on the glucose load and the type of the animals used (strain, sex, BW, age etc..).
one way to test whether inestinal absorption may be the cuase is to inject glcose intraperitoneally and/or intravenously (rat tail vein)
Natraj, you forgot one more factor, height and timing of glucose peak in OGTT has more inter-animal variability that depends on the experience of person who is giving the oral garage - it is a relatively very simple and straight forward procedure but not for everyone! ;)
From my observations, glucose peak in OGTT in STZ-induced diabetic rats is between 30 min and 60 min.
I am working on n-STZ animal model, used 1.5g/kg glucose and got peak at 30 mints but some of the animal with clear signs of retinopathy did not show changes in OGTT test. If my procedure is correct, one can not rely on OGTT to diagnose T2DM in n-STZ rats. FBG levels of n-STZ rats are in normal range.
What can be done in such situation to diagnose T2DM in rats?
Hi Mirza,
Thanks for your input.
In your experiment, the best would be insulin tolerance test.
Regards.
Ayman
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