From Turku PET Center (U.R., V.O., M.J.K.) and the Departments of
Medicine (H.L., P.N.), Clinical Physiology (M.L.), Clinical Chemistry (M.R.),
and Anesthesiology (O.K.) of the University of Turku (Finland); the Department
of Electronics and Informatics (P.V., C.C.), University of Padova (Italy); and
the Department of Medicine (T.U., H.Y.-J.), Division of Endocrinology and
Diabetology, University of Helsinki (Finland).
Correspondence to Hanna Laine, MD, Department of Medicine, University of Turku, Kiinamyllynk 4–8, FIN-20520 Turku, Finland. E-mail hannal{at}pet.tyks.fi
Background—We examined the integrity
of the effects of insulin on mean muscle blood flow, flow
heterogeneity, and blood volume in essential
hypertension.
Methods and Results—Positron emission tomography, combined with
[15O]H2O and [15O]CO as tracers
for direct measurement of blood flow and volume in skeletal muscle, and
a new bayesian iterative reconstruction algorithm allowing
pixel-by-pixel quantitation of blood flow and flow dispersion, were
used. Measurements were performed basally after an overnight fast and
under normoglycemic hyperinsulinemic conditions in 11
newly diagnosed, untreated mildly hypertensive men (age, 35±1 years;
body mass index, 25.2±0.4 kg/m2, blood pressure
141±4/96±2 mm Hg, mean±SE) and 11 matched normotensive
men. Insulin-stimulated whole body glucose uptake was significantly
decreased in the hypertensive men (41±4 µmol/kg per minute)
compared with the normotensive (59±4 µmol/kg per minute,
P<0.005) men. Mean blood flow in skeletal muscle was
significantly lower in the hypertensive than the normal subjects
basally (1.7±0.2 versus 2.7±0.4 mL/0.1 kg per minute,
P<0.05) and during hyperinsulinemia
(2.3±0.2 versus 4.2±0.8, P<0.05). The flow response
to insulin (0.6±0.2 versus 1.9±0.5 mL/0.1 kg per minute, hypertensive
versus normal subjects, P<0.05) was also significantly
blunted. Muscle blood volume was significantly lower in the
hypertensive than in the normal subjects, both basally (3.0±0.2 versus
3.5±0.2 mL/0.1 kg, P<0.05) and during
hyperinsulinemia (3.1±0.2 versus 4.0±0.2 mL/0.1
kg muscle, P<0.02). The increase in muscle blood volume
by insulin was significant in the normal (P<0.05) but
not the hypertensive subjects. Regional pixel-by-pixel analysis
within femoral muscles revealed significant spatial
heterogeneity of blood flow. Insulin increased absolute
dispersion of blood flow significantly more in the normal subjects than
in the hypertensive subjects (P<0.05).
Conclusions—True flow heterogeneity, as judged
from the coefficients of variation (relative dispersion), was
comparable between the groups basally and during
hyperinsulinemia. We conclude that mean flow, its
absolute dispersion, and blood volume exhibit insulin resistance in
patients with essential hypertension.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Preserved Relative Dispersion but Blunted Stimulation of Mean Flow, Absolute Dispersion, and Blood Volume by Insulin in Skeletal Muscle of Patients With Essential Hypertension
Key Words: blood pressure • insulin • glucose • tomography
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