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Paradoxical relationship between alpha‐adrenergic tone and muscle sympathetic nerve activity in human metabolic syndrome
Author(s) -
Mckenna Edward Joseph,
Limberg Jacqueline,
Sebranek Joshua,
Walker Benjamin,
Hagen Scott,
Morgan Barbara,
Schrage William
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1091.33
Subject(s) - microneurography , medicine , adrenergic , phentolamine , endocrinology , vasoconstriction , blood pressure , blood flow , vasodilation , propranolol , heart rate , sympathetic nervous system , baroreflex , receptor
Animal models of metabolic syndrome (MS) exhibit greater basal adrenergic tone that may contribute to impaired blood flow. We hypothesized humans with MS would exhibit greater α‐adrenergic tone that correlated with higher muscle sympathetic nerve activity (mSNA). Phentolamine (PH, α‐adrenergic antagonist) was infused intra‐arterially into the forearm of MS adults (n=11) and healthy controls (n=16). mSNA was measured (microneurography) in a subset of subjects (n=15). Forearm blood flow (Doppler ultrasound) was normalized for higher blood pressure (BP) in MS and relative changes in vascular conductance (VC = blood flow/BP) were assessed. VC increased with PH infusion similarly between groups. MS exhibited greater mSNA compared to controls (66±9 vs 35±4 bursts/100 heart beats, p<0.01). Greater α‐adrenergic tone was inversely related to mSNA (r = 0.5, p= 0.07), thus adults with higher mSNA had less increase in VC with PH infusion. In summary, despite higher mSNA, adults with MS do not exhibit greater α‐adrenergic tone. These results suggest physiological adaptations occur with higher mSNA that blunt sympathetically‐mediated vasoconstriction at rest. This may be due to reduced adrenergic responsiveness or norepinephrine release. Support: AHA 10PRE3870000, NIH HL091397 , APS Summer Undergraduate Research Fellowship.