Sympathetic overactivity not uniformly distributed over the cardiovascular system in metabolic syndrome
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Sympathetic activation is associated with hypertension and/or insulin resistance, two characteristic features of the metabolic syndrome. The study aimed to determine whether activation of the sympathetic nervous system observed in metabolic syndrome is generalized to the entire cardiovascular system or rather confined to selected vascular beds. To this end, blood pressure, heart rate, venous plasma norepinephrine, and postganglionic sympathetic nerve traffic in skeletal muscle and skin districts were measured in 16 untreated metabolic syndrome patients, 12 essential hypertensive subjects, 12 obese subjects, and 14 lean normotensive controls. In hypertensive and obese subjects, muscle sympathethic nerve traffic values were significantly higher than in controls. In subjects with metabolic syndrome, a further significant increase in muscle sympathetic nerve traffic was detected. However, both skin sympathetic nerve traffic and skin sympathetic responses to an acoustic stimulus were not significantly different in the four groups. These results provide the first direct evidence that sympathetic activation is not uniformly distributed over the cardiovascular system in patients with a metabolic syndrome phenotype.
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