Journal of Clinical Endocrinology & Metabolism, Vol 81, 707-712, Copyright © 1996 by Endocrine Society
Insulin resistance in type I diabetes mellitus: a major role for reduced glucose extraction
S Makimattila, A Virkamaki, R Malmstrom, T Utriainen and H Yki-Jarvinen
Department of Medicine, University of Helsinki Central Hospital, Finland.
We determined whether insulin resistance in Type I diabetes is caused by a
defect in glucose extraction or blood flow and whether it is the rate of
glucose metabolism rather than insulin that increases blood flow in these
patients. To make this determination, 9 Type I diabetic patients (age 33
+/- 3 yr, body mass index 24 +/- 1 kg/m2, HbA1c 8.3 +/- 0.1%) and 10
matched normal subjects were first studied under normoglycemic
hyperinsulinemic conditions. The diabetic patients were then restudied
under similar conditions, but now whole body glucose uptake was normalized
by glucose mass-action (glucose 8.7 +/- 0.6 mmol/L). During normoglycemia,
rates of whole body (46 +/- 2 vs. 66 +/- 3 mumol/kg.min, P < 0.001) and
forearm (47 +/- 9 vs. 78 +/- 7 mumol/kg forearm.min, P < 0.05) glucose
uptake were decreased in the diabetic patients, because of a 32% decrease
in the glucose AV-difference (1.5 +/- 0.2 vs. 2.2 +/- 0.2 mmol/L, P <
0.05). Forearm blood flow was similar in the diabetic patients (3.6 +/- 0.7
mL/dl.min) and normal subjects (3.7 +/- 0.3 mL/dL.min). During matched
rates of whole body glucose uptake (68 +/- 1 vs. 66 +/- 3 mumol/kg.min,
normoglycemic study in controls vs. hyperglycemic study in the diabetic
patients), the glucose AV-difference across the forearm was 64% higher than
during normoglycemia (2.4 +/- 0.3 vs. 1.5 +/- 0.2 mmol/L, P < 0.05).
Forearm blood flow (3.6 +/- 0.4 mL/dL.min) under conditions of matched
glucose flux was similar to that during the normoglycemic study. We
conclude that a defect in glucose extraction rather than blood flow
characterizes insulin resistance in uncomplicated Type I diabetes. The
signal for the flow increase is insulin and not the rate of glucose
metabolism.