Istituto di Ingegneria Biomedica     
Brehm A., Thomaseth K., Bernroider E., Nowotny P., Waldhäusl W., Pacini G., Roden M. The role of endocrine counterregulation for estimating insulin sensitivity from intravenous glucose tolerance tests. In: Journal of Clinical Endocrinology and Metabolism, vol. 91 pp. 2272 - 8. The Endocrine Society, 2006.
Context. During insulin-modified frequently sampled intravenous glucose tolerance tests (IM-FSIGT), which allows assessment of insulin action, plasma glucose can markedly decrease. Objective. This study aimed to assess the counterregulatory impact of the insulin-induced fall of glucose on minimal model derived indices of insulin sensitivity (SI) and glucose effectiveness (SG). Participants. Thirteen nondiabetic volunteers (7 male, 6 female, age: 26 +/- 1 yr, body mass index: 22.1 +/- 0.7 kg/m(2)) were studied. Design. All participants were studied in random order during IM-FSIGT (0.3 g/kg glucose; 0.03 U/kg insulin at 20 min) and during identical conditions but with a variable glucose infusion preventing a decrease of plasma glucose concentration below euglycemia (IM-FSIGT-CLAMP). Five participants additionally underwent euglycemic-hyper-insulinemic (1 mU*kg(-1)min(-1)) clamp tests. Results. Plasma glucose declined during IM-FSIGT to its nadir of 50 +/- 3 mg/dl at 60 min in parallel to a rise (P < 0.05 vs. basal) of plasma glucagon, cortisol, epinephrine and growth hormone. Glucose infusion rates of 4.6 +/- 0.5 mg*kg(-1)*min(-1) between 30 and 180 min during IM-FSIGT-CLAMP prevented the decline of plasma glucose and the hypoglycemia counterregulatory hormone response. SI was approximately 68% lower during IM-FSIGT (3.40 +/- 0.36 vs. IM-FSIGT-CLAMP: 10.71 +/- 1.06 10(-4)*min(-1)*microU(-1)ml, P < 0.0001) whereas SG did not differ between both protocols (0.024 +/- 0.002 vs. 0.021 +/- 0.003 min(-1), P=NS). Compared with the euglycemic hyperinsulinemic clamp test, insulin sensitivity expressed in identical units from IM-FSIGT was approximately 66% (P < 0.001) lower but did not differ between the euglycemic hyperinsulinemic clamp test and the IM-FSIGT-CLAMP (P=NS). Conclusions. The transient fall of plasma glucose during IM-FSIGT results in lower estimates of insulin sensitivity which can be explained by hormonal response to hypoglycemia.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16595595&query_hl=1&itool=pubmed_docsum
DOI: 10.1210/jc.2006-0019
Subject insulin sensitivity
intravenous glucose tolerance tests

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