HOMA-IR for insulin sensitivity have been shown to have a modest and weaker correlation for estimating insulin sensitivity in mice and rats in comparison to humans and it may be due to a considerable difference in murine physiology. If insulin sensitivity is the primary outcome of whatever you are studying it is recommended that you use the clamp studies instead. There are interesting articles pairing the two methods that you could take a look at:
https://www.ncbi.nlm.nih.gov/pubmed/23492513
Article Combined Effects of 19 Common Variations on Type 2 Diabetes ...
Article Validation of simple indexes to assess insulin sensitivity d...
HOMA-IR for insulin sensitivity have been shown to have a modest and weaker correlation for estimating insulin sensitivity in mice and rats in comparison to humans and it may be due to a considerable difference in murine physiology. If insulin sensitivity is the primary outcome of whatever you are studying it is recommended that you use the clamp studies instead. There are interesting articles pairing the two methods that you could take a look at:
https://www.ncbi.nlm.nih.gov/pubmed/23492513
Article Combined Effects of 19 Common Variations on Type 2 Diabetes ...
Article Validation of simple indexes to assess insulin sensitivity d...
Perform an ITT (insulin tolerance test). Fast rats for 3-5h (usually morning at beginning of light cycle) to normalize their blood glucose levels and challenge them with 0.75-1U insulin/Kg BW by IP injection. Measure their glucose levels by tail vein puncture at minutes 0, 15, 30, 60 (and if you want 120) after insulin injection. Plot data as % of their initial blood glucose levels and calculate AUC.
Article Loss of Insulin Signaling in Hepatocytes Leads to Severe Ins...