Physiological hyperinsulinaemia increases intramuscular microvascular reactive hyperaemia and vasomotion in healthy volunteers.
OBJECTIVE
Insulin possesses vasodilatory actions that may be important in regulating its access to insulin-sensitive tissues. Our study aims to directly measure changes in response to insulin in the human skeletal muscle microcirculation. Measurement was by an implanted laser Doppler probe.


METHODS
We investigated changes in intramuscular and skin microvascular perfusion in 12 healthy individuals during a hyperinsulinaemic and a control clamp. We determined leg blood flow with plethysmography, finger skin functional capillary recruitment with capillaroscopy, endothelium-(in)dependent vasodilation by iontophoresis of acetylcholine and sodium nitroprusside, and leg intramuscular reactive hyperaemia and vasomotion with laser Doppler measurements.


RESULTS
Compared to the control study, hyperinsulinaemia (416+/-82 pmol/l) caused: (i) an increase in leg blood flow (1.0+/-1.0 vs 0.1+/-0.6 ml.min(-1).100 ml, p<0.05); (ii) an increase in finger skin capillary recruitment (14.9+/-10.1 vs -5.6+/-11.0%, p<0.01); (iii) no change in baseline laser Doppler perfusion either in finger skin or leg muscle; (iv) a tendency to increase acetylcholine-mediated vasodilation (475+/-534 vs 114+/-337%, p=0.07) with no change in sodium-nitroprusside-mediated vasodilation ( p=0.2) in finger skin; (v) an increase in intramuscular reactive hyperaemia (423+/-507 vs 0+/-220%, p<0.01); and (vi) a decrease in time needed to reach peak intramuscular perfusion (-3.6+/-3.0 vs 1.1+/-3.1 s, p<0.01). In addition, hyperinsulinaemia induced an increase in intramuscular vasomotion by increasing the contribution of frequencies between 0.01 and 0.04 Hz ( p<0.05 for all), which probably represents increased endothelial and neurogenic activity.


CONCLUSIONS
Physiological hyperinsulinaemia not only stimulates total blood flow and skin microvascular perfusion, but also augments human skeletal muscle microvascular recruitment and vasomotion as detected directly by laser Doppler measurements.
de Jongh
R T
RT
Department of Internal Medicine and Institute for Cardiovascular Research, VU University Medical Center, De Boelelaan 1117, PO Box 7057, 1007 MB Amsterdam, The Netherlands.
Clark
A D H
AD
IJzerman
R G
RG
Serné
E H
EH
de Vries
G
G
Stehouwer
C D A
CD
D000328:Adult; D015374:Biosensing Techniques; D001786:Blood Glucose / Q000737:chemistry / Q000187:drug effects; D005260:Female; D015309:Glucose Clamp Technique / Q000379:methods; D006801:Humans; D006940:Hyperemia / Q000150:complications* / Q000503:physiopathology; D006946:Hyperinsulinism / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D008722:Methods; D008833:Microcirculation / Q000503:physiopathology*; D020678:Microscopic Angioscopy / Q000379:methods; D018482:Muscle, Skeletal / Q000098:blood supply / Q000503:physiopathology*; D013977:Tibia; D014661:Vasoconstriction; D014664:Vasodilation; D014666:Vasomotor System / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin