Sympathetic Neural Activation in Nondiabetic Metabolic Syndrome and Its Further Augmentation by Hypertension

Abstract

Abstract-Hypertension is a major cardiovascular risk factor in the metabolic syndrome (MS) in which the presence of insulin resistance, glucose intolerance, abnormal lipoprotein metabolism, and central obesity all confer an increased risk. Because essential hypertension (EHT), insulinemia, and visceral fat are associated with sympathetic hyperactivity, which is itself known to increase cardiovascular risk, the aim of this study was to see if MS is a state of sympathetic nerve hyperactivity and if the additional presence of EHT intensifies this hyperactivity. In 69 closely matched subjects, comprising hypertensive MS (MSϩEHT, 18), normotensive MS (MS-EHT, 17), hypertensives without MS (EHT, 16), and normotensive controls without MS (NC, 18), we measured resting muscle sympathetic nerve activity (MSNA) as assessed from multiunit discharges and from single units with defined vasoconstrictor properties (s-MSNA). The s-MSNA in MSϩEHT (76Ϯ3.1 impulses/100 beats) was greater (at least PϽ0.01) than in MS-EHT (62Ϯ3.2 impulses/100 beats) and in EHT (60Ϯ2.3 impulses/100 beats), and all these were significantly greater (at least PϽ0.01) than in NC (46Ϯ2.7 impulse/100 beats). The multi-unit MSNA followed a similar trend. These findings suggest that MS is a state of sympathetic nerve hyperactivity and that the additional presence of hypertension further intensifies this hyperactivity. The degree of sympathetic hyperactivity seen in this study could be argued at least partly to contribute to the higher cardiovascular risk and metabolic abnormalities seen in MSϩEHT patients. Key Words: sympathetic nervous system Ⅲ hypertension Ⅲ metabolism L ittle information exists on the level of sympathetic nerve activity in the metabolic syndrome (MS) and whether the presence of essential hypertension (EHT), which is itself a state of sympathetic nerve hyperactivity, 1-4 augments this activity. Sympathetic activation has already been associated with many of the individual components of the MS, such as visceral obesity, 5 insulinemia, 6 EHT, 1-4 and type 2 diabetes. 7 The majority of treated hypertensives have in addition at least one other MS component; 8 also, it is now widely recognized that MS constitutes a cluster of major cardiovascular risk factors, 9 represented mainly by insulin resistance and obesity in which hypertension as an individual component overlaps the least with the other components. 10 Hypertension is known to be one of the highest predictors of cardiovascular morbidity and mortality associated with the MS. 11,12 Furthermore, sympathetic activation in EHT is believed to contribute to cardiovascular risk. 13,14 We therefore tested the hypothesis that the level of sympathetic nerve activity would be increased in normotensive MS and that the additional presence of EHT would further amplify this sympathetic activation. Methods SubjectsA total of 72 white subjects were examined, comprising 18 subjects with hypertensive MS (MSϩEHT), 18 normotensive MS (MS-EHT), 18 hypertensives without MS (EHT), and 18 normotensive controls wi...

The effect of gender on the sympathetic nerve hyperactivity of essential hypertension

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Metabolic syndrome and left ventricular hypertrophy in a general population. Results from the Gubbio Study

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Metabolic Syndrome Increases Mortality in Heart Failure

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