The measure of insulin sensitivity relies on establishing a quantitative relationship between plasma insulin and measurable insulin actions. However, in vivo the ever present feedback relationship between glucose (to stimulate insulin secretion) and insulin (to lower blood glucose) complicates the analysis of individual contributions of insulin resistance and B cell unresponsiveness to diseases such as type 2 diabetes.
The euglycemic hyperinsulinemic clamp has been designed to open this loop, and provide quantitative measurements of insulin sensitivity in conditions where both glycemia and hyperinsulinemia are set at constant, measurable levels. The amount of glucose infused in order to maintain euglycemia in face of the achieved hyperinsulinemia is a direct measurement of insulin sensitivity.
Combined with the use of glucose tracers, the clamp technique allows assessment of whole-body and tissue-specific insulin action on glucose fluxes and glucose metabolism, including:
- Basal and insulin-stimulated hepatic glucose production.
- Insulin-stimulated whole-body glucose uptake, glycolysis, and glycogen/lipid synthesis.
- Insulin-stimulated glucose uptake, glycolysis, and glycogen synthesis in individual tissues (e.g., skeletal muscle, adipose tissue (WAT, BAT), heart, brain).
An indwelling femoral vein catheter is placed 4 to 7 days prior to the experiment. The clamp is performed in 5 hour-fasted, awake and free-moving mice. The rate of insulin infusion is tailored (between 2.5 and 20mU/kg.min) to the metabolic parameter of interest. Lowest doses of insulin are best suited to assess insulin sensitivity in the liver, whereas high doses are best to assess insulin sensitivity in muscle. Choice of the insulin dose will also take into account age, sex and strain differences.
Twelve mice per group should be sent to our facility, one week prior to the experiment. In some cases, an additional, smaller cohort might be required to complete the experiment.
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Seyer P, Vallois D, Poitry-Yamate C, Schütz F, Metref S, Tarussio D, Maechler P, Staels B, Lanz B, Grueter R, Decaris J, Turner S, da Costa A, Preitner F, Minehira K, Foretz M, Thorens B. Hepatic glucose sensing is required to preserve β cell glucose competence. J Clin Invest. 2013 Apr 1;123(4):1662-76.
Becattini B, Marone R, Zani F, Arsenijevic D, Seydoux J, Montani JP, Dulloo AG, Thorens B, Preitner B, Wymann MP, Solinas G. PI3Kγ within a nonhematopoietic cell type negatively regulates diet-induced thermogenesis and promotes obesity and insulin resistance. Proc Natl Acad Sci U S A. 2011 Oct 18;108(42):E854-63.
Minehira, K., Young, SG., Villanueva, CJ., Yetukuri, L., Oresic, M., Hellerstein, MK., Farese, RV. Jr, Horton, JD., Preitner, F., Thorens, B., and Tappy, L. Blocking VLDL secretion causes hepatic steatosis but does not affect peripheral lipid stores or insulin sensitivity in mice. J Lipid Res. 49(9):2038-44, 2008.
Preitner F, Mody N, Graham TE, Peroni OD, Kahn BB. Long-term Fenretinide treatment prevents high-fat diet-induced obesity, insulin resistance, and hepatic steatosis. Am J Physiol Endocrinol Metab. 2009 Dec;297(6):E1420-9