Hello,
I'm conducting an IPGTT experiment on WT and KO mice (mice which we have shown to have improved glucose tolerance) and I have a serious issue of glucose levels plummeting after 30-60min.
I get a nice spike at 15min but at the 30 min mark some mice drop there levels 100-150 points and at 60 min the mice are pretty much back at baseline. My lab has previously shown gradual decreases in glucose levels and levels reaching baseline around 240 min after IP injection. I'm very confused as to what I'm doing wrong.
I use a 1g/kg protocol and fast the mice for 6 hours. I take blood from the tip of the tail and keep the mice tethered to a mouse restrainer during the experiment.
Any help would be appreciated.
Might you be having a situation similar to 'reactive hypoglycemia' in humans. An overproduction of insulin (and with your mouse model being less insulin resistant) might create this faster drop. I know that it is about 30-45 minutes in humans for a hypoglycemic event to occur in people after ingestion of sugar, especially if sugar dose is not as high as the usual amounts ingested.
Thank you for your comment. However, for the WT condition I shouldn't see a drop in blood glucose levels that quickly. Is it possible that they are losing too much blood from the tail during the procedure?
Hi Marko,
Maybe the issue does not come from your mice or your IPGTT protocol but from your measurement method of glucose... What is it? Do you use the same method than your colleagues previously did? Are you sure it is repeatable/reproducible? Or could it come from the pre-analytical steps? In what biological matrix do you assay glucose concentration? serum/plasma I guess...? If so, are you paying attention to promptly separate by centrifugation (not more than 30 min) serum/plasma from the red blood cells after blood drawing? Indeed, red blood cells can continue consuming glucose in your tube and so artificially decrease your glucose measurements. That is why it it recommended to use grey cap tubes to recover blood with sodium fluoride as a glycolysis inhibitor and potassium oxalate as anticoagulants.
Maybe all what I said seems obvious to you and you already take into account all these aspects, but sometimes, "the devil is in the details" or at least in the things seeming unsignificant...
Hope it helps,
Good luck,
Cécile
Stress....catecholamine release increases glucose clearance .....measure epinephrine and norepinephrine levels bet they are really high......try making a tail cut and let the mouse recover for 2 hours before milking the tail for your baseline measure