Carbohydrate ingestion, with transient endogenous insulinaemia, produces both sympathetic activation and vasodilatation in normal humans.
It has been shown that sustained insulin infusion causes an increase in sympathetic vasoconstrictor discharge but, despite this, also causes peripheral vasodilatation. The present study was designed to determine in healthy subjects the effect of ingestion of a carbohydrate meal, with its attendant physiological insulinaemia, on vascular resistance in and sympathetic vasoconstrictor discharge to the same vascular bed, and the relationship between these parameters. Fifteen healthy subjects were studied for 2 h following ingestion of a carbohydrate meal. Calf vascular resistance was measured by venous occlusion plethysmography, and muscle sympathetic nerve activity was assessed by peroneal microneurography. Five of the subjects also ingested water on a separate occasion, as a control. Following the carbohydrate meal, the serum insulin concentration increased to 588+/-72 pmol/l. This was associated with a 47% increase in skeletal muscle blood flow (P<0.001), a 39% fall in vascular resistance (P<0.001) and a 57% increase in sympathetic activity (P<0.001). There was a significant correlation between the increase in insulin and the changes in blood flow, vascular resistance and sympathetic activity. In conclusion, we have shown that ingestion of a carbohydrate meal, with its attendant physiological insulinaemia, was associated with overriding skeletal muscle vasodilatation, despite an increase in sympathetic vasoconstrictor discharge to the same vascular bed. These mechanisms may be important in ensuring optimal glucose uptake and maintenance of blood pressure postprandially.
Scott
Eleanor M
EM
Department of Endocrinology, St James's University Hospital, Beckett Street, Leeds LS9 7TF, UK. eleanorscott@doctors.org.uk
Greenwood
John P
JP
Vacca
Giovanni
G
Stoker
John B
JB
Gilbey
Stephen G
SG
Mary
David A S G
DA
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation*; D012039:Regional Blood Flow / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin