The Establishment And Utilization Of Hyperinsulinemic Uglycemic Clamps In Conscious, Unrestrained Mice

1.Type2diabetes is characterized by defect in insulin action and islet β cellfunction. The hyperinsulinemic euglycemic clamp, or insulin clamp, is widelyconsidered as the"gold standard" method for assessing insulin action in vivo. Theminiaturization of the insulin clamp used in genetic mouse models of metabolicdisease has led to significant advances in diabetes research. In the first part of thisstudy we aims at establishing the hyperinsulinemic-euglycemic clamps in conscious,unrestrained mice.2. Many studies have compared surrogate indexes of insulin sensitivity andresistance with glucose clamp estimates in human. However, there is difference inmetabolic physiology between human and rodent, surrogate indexes data are almostfrom human study, and have not been directly evaluated by insulin clamp in rodentpreviously. In the second part of this study we compared insulin clamp-derivedmeasurements of insulin sensitivity (GIR) with surrogate indexes, including QUICKI,HOMA, ISI, Ln(G15/G0) in mice.methodPart I: Establishment of hyperinsulinemic euglycemic Clamps in evaluatinginsulin sensitivity in mice. First, hyperinsulinemic euglycemic clampwas eset up inanesthetized mice, conscious unrestrained mice. Evaluation the appropriateanesthetics and optimization dosage of sodium pentobarbital to anesthetize animals,finding the proper position for cannulation, catheter length and insertion depth, theliquid filled in catheters, catheter fixation after surgery in conscious animalmethods. PartII:Insulin tolerance test (ITT), oral glucose tolerance test(OGTT), were used toget surrogate indexes, including QUICKI, HOMA-IR, ISI, Ln(G15/G0),comparedwith hyperinsulinemic euglycemic clamp-derived measurements of insulinsensitivity (GIR)in mice.We evaluated simple linear correlations and performedcalibration model analyses to evaluate the predictive accuracy of each surrogate.ResultsPartI:1.Hyperinsulinemic-euglycemic clamp was successfully established inanesthetized and conscious C57BL/6J mice (C57).2. Glucose and GIR achieve at steady-state period between60~80min. Glucoseinfusion rate clamp from anesthetized mice was23.3士2.7mg/(kg·min), coefficientof variation was4.9%. Glucose infusion rate from clamp in conscious, unrestrainedC57mice was30.3士1.6mg/(kg·min), coefficient of variation was5.2%PartII: The Pearsons’ linear correlation coefficient between GIR and (r=-0.536，P<0.001), HOMA-IR (r=-0.575，P<0.01), QUICK index (r=0.611，P<0.01) and ISIindex (r=0.609) and Ln(G15/G0) index (r=-0.786=) were statistically significant.Conclusion1. We have successfully established the gold standard of assessing insulinsensitivity hyperinsulinemic-euglycemic clamp in anesthetized mice as well as inconscious unrestrained mice.2. Ln (G15/G0) index, HOMA-IR index, the QUICK index and ISI index aresignificantly associated with GIR obtained from hyperinsulinemic-euglycemic clamptest and can be used for preliminary evaluation of insulin sensitivity in mice.