title: QUICKI does not accurately reflect changes in insulin sensitivity with exercise training.
abstract: A novel index of insulin sensitivity, the quick insulin sensitivity check index, termed QUICKI (1/[log (insulin) + log (glucose)]), was recently developed. We examined whether QUICKI accurately reflects changes in insulin sensitivity after exercise training, a perturbation known to improve insulin sensitivity. Sedentary, nondiabetic adults underwent a frequently sampled iv glucose tolerance test before and after 6 months of training. Insulin sensitivity was estimated from the glucose tolerance test using Bergman's minimal model (insulin sensitivity-minimal model), and QUICKI was calculated from basal insulin and glucose. Exercise increased (P = 0.003) insulin sensitivity-minimal model but did not change (P = 0.12) QUICKI. Before and after training, the rank-correlation between QUICKI and insulin sensitivity-minimal model was significant (r = 0.79, P = 0.0005; r = 0.56, P = 0.03, respectively). However, the rank-correlation between fasting insulin alone with insulin sensitivity-minimal model was as good (before training r = -0.77, P = 0.0009; after training r = -0.55, P = 0.03) as that between QUICKI and insulin sensitivity-minimal model. Fasting glucose was not related to insulin sensitivity-minimal model at either time. When difference scores (i.e. after pretraining values) were examined, neither QUICKI nor fasting insulin correlated with insulin sensitivity-minimal model (QUICKI vs. insulin sensitivity-minimal model r = 0.24, P = 0.39; fasting insulin vs. insulin sensitivity-minimal model r = -0.40, P = 0.14). We conclude that fasting insulin is equivalent to fasting insulin plus glucose (i.e. QUICKI) at estimating basal insulin sensitivity in nondiabetic adults. However, QUICKI does not accurately reflect exercise-induced changes in insulin sensitivity within individual subjects.
authors.affiliation: Department of Medicine, University of Florida, Gainesville, Florida 32610, USA. gduncan@ufl.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Duncan
authors.forename: A D
authors.initials: AD
authors.lastname: Hutson
authors.forename: P W
authors.initials: PW
authors.lastname: Stacpoole
mesh_terms: D015415:Biomarkers; D001786:Blood Glucose / Q000032:analysis*; D015992:Body Mass Index; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance / Q000502:physiology*; D050356:Lipid Metabolism; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin