Diabetes, Vol 46, Issue 12 2017-2021, Copyright © 1997 by American Diabetes Association
Effects of insulin on blood flow and volume in skeletal muscle of patients with IDDM: studies using [15O]H2O, [15O]CO, and positron emission tomography
M Raitakari, P Nuutila, J Knuuti, OT Raitakari, H Laine, U Ruotsalainen, O Kirvela, TO Takala, H Iida and H Yki-Jarvinen
Turku Positron Emission Tomography Center, Department of Anesthesiology, University of Turku, Finland.
Exaggerated vasoconstriction and blunted vasodilation of peripheral
resistance arteries to various vasoactive agents characterize patients with
IDDM. We characterized the hemodynamic effects of insulin in skeletal
muscle in patients with IDDM. Muscle blood flow and blood volume were
measured basally and during a high-dose insulin infusion (5 mU x kg(-1) x
min[-1]) in seven normotensive patients with IDDM (age, 30 +/- 6 years;
BMI, 24.5 +/- 2.0 kg/m2; blood pressure, 124 +/- 12/78 +/- 11 mmHg) and
nine matched normal subjects, using [15O]H2O, [15O]CO, and positron
emission tomography (PET). Whole-body insulin sensitivity was determined
using the euglycemic insulin clamp technique. Insulin-stimulated whole-body
glucose uptake was significantly lower in the patients with IDDM (45 +/- 15
micromol x kg(-1) x min[-1]) than in the normal subjects (62 +/- 14
micromol x kg(-1) x min[-1]) (P < 0.05). Insulin increased muscle blood
flow by 111 +/- 69% above basal from 3.0 +/- 2.0 to 5.8 +/- 3.0 ml x 100
g(-1) muscle x min(-1) (P < 0.005) in the normal subjects, but only by
42 +/- 30% from 2.0 +/- 0.9 to 2.9 +/- 1.4 ml x 100 g(-1) muscle x min(-1)
(P < 0.005) in patients with IDDM (P < 0.05 for change in flow in
IDDM vs. normal subjects). The calculated muscle vascular resistances were
comparable basally, but higher during hyperinsulinemia in the patients with
IDDM (37 +/- 17 mmHg x 100 g x min x ml[-1]) than in the normal subjects
(16 +/- 7 mmHg x 100 g x min x ml[-l]) (P < 0.05). Muscle blood volume
increased significantly by insulin in both groups without any difference
between the groups. We conclude that the ability of supraphysiological
concentrations of insulin to stimulate muscle blood flow is blunted in
patients with IDDM, because of the inability of insulin to stimulate linear
flow velocity rather than blood volume in skeletal muscle. This defect adds
yet another defect to the list of abnormalities in vascular function in
IDDM, which might predispose these patients to develop hypertension.