The Role of Endocrine Counterregulation for Estimating Insulin Sensitivity from Intravenous Glucose Tolerance Tests.
From: Division of Endocrinology and Metabolism, Department of Internal Medicine 3, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
The Journal of clinical endocrinology and metabolism
- Publish Date: Jun 2006
- ISSN: 0021-972X
- Volume: 91
- Issue: 6
- Pages: 2272-8
- Medium: Print
- Language: English
- Citation (JAMA): Brehm Attila, Thomaseth Karl, Bernroider Elisabeth, et al. The Role of Endocrine Counterregulation for Estimating Insulin Sensitivity from Intravenous Glucose Tolerance Tests.. J. Clin. Endocrinol. Metab. Jun 2006;91:2272-8
Abstract
CONTEXT: During insulin-modified frequently sampled iv glucose tolerance tests (IM-FSIGT), which allow 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 (S(I)) and glucose effectiveness. PARTICIPANTS: Thirteen nondiabetic volunteers (seven males, six females, aged 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-hyperinsulinemic (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 GH. 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. S(I) was approximately 68% lower during IM-FSIGT (3.40 +/- 0.36 vs. IM-FSIGT-CLAMP: 10.71 +/- 1.06 10(-4).min(-1) per microU/ml, P < 0.0001), whereas glucose effectiveness 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, S(I) 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 S(I), which can be explained by hormonal response to hypoglycemia.
Mesh Headings (Keywords): Adult, Blood Glucose, Fatty Acids, Nonesterified, Female, Glucagon, Glucose Clamp Technique, Glucose Tolerance Test, Humans, Hydrocortisone, Insulin, Male, Norepinephrine
Check for Full Text / PubMed Unique Identifier (PMID): 16595595
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