Faculty Collaboration Database

Dissociation between sympathetic nerve traffic and sympathetically mediated vascular tone in normotensive human obesity. Hypertension 2008 Oct;52(4):687-95

Date

08/13/2008

Pubmed ID

18695151

Pubmed Central ID

PMC4222518

DOI

10.1161/HYPERTENSIONAHA.107.109603

Scopus ID

2-s2.0-54749109169 (requires institutional sign-in at Scopus site)   39 Citations

Abstract

Obesity increases the risk of hypertension and its cardiovascular complications. This has been partly attributed to increased sympathetic nerve activity, as assessed by microneurography and catecholamine assays. However, increased vasoconstriction in response to obesity-induced sympathoactivation has not been unequivocally demonstrated in obese subjects without hypertension. We evaluated sympathetic alpha-adrenergic vascular tone in the forearm by brachial arterial infusion of the alpha-adrenoreceptor antagonist phentolamine (120 microg/min) in normotensive obese (daytime ambulatory arterial pressure: 123+/-1/77+/-1 mm Hg; body mass index: 35+/-1 kg/m(2)) and lean (daytime ambulatory arterial pressure: 123+/-2/77+/-2 mm Hg; body mass index: 22+/-1 kg/m(2)) subjects (n=25 per group) matched by blood pressure, age, and gender. Microneurographic sympathetic nerve activity to skeletal muscle was significantly higher in obese subjects (30+/-3 versus 22+/-1 bursts per minute; P=0.02). Surprisingly, complete alpha-adrenergic receptor blockade by phentolamine (at concentrations sufficient to completely inhibit norepinephrine and phenylephrine-induced vasoconstriction) caused equivalent vasodilatation in obese (-57+/-2%) and lean subjects (-57+/-3%; P=0.9). In conclusion, sympathetic vascular tone in the forearm circulation is not increased in obese normotensive subjects despite increased sympathetic outflow. Vasodilator factors or mechanisms occurring in obese normotensive subjects could oppose the vasoconstrictor actions of increased sympathoactivation. Our findings may help to explain why some obese subjects are protected from the development of hypertension.

Author List

Agapitov AV, Correia ML, Sinkey CA, Haynes WG

Author

Alexei V. Agapitov MD Staff Physician in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adrenergic alpha-Antagonists
Adult
Blood Pressure
Brachial Artery
Female
Humans
Infusions, Intra-Arterial
Male
Obesity
Phentolamine
Severity of Illness Index
Sympathetic Nervous System
Vasoconstriction
Vasodilation