7.1 Metabolic Syndrome is Characterised by Sympathetic Activation Independently on the Obese State
Introduction: Several studies have previously shown that the metabolic syndrome is characterised by a marked sympathetic activation. Whether this adrenergic overdrive is mainly dependent on the obese state or it can be detected also in absence of this condition is unknown, however.
Methods: In 25 male patients (age 41.4±2.4 yrs, mean ± SEM) with metabolic syndrome (NCEP ATP III criteria) and in 12 age-matched healthy male controls, we measured along with body mass index (BMI), waist circumference (WC), plasma cholesterol and triglycerides, beat-to-beat arterial blood pressure (Finapres), heart rate (EKG), HOMA index and efferent postganglionic muscle sympathetic nerve traffic (microneurography, MSNA). Measurements were performed at rest and during arterial baroreceptor stimulation and deactivation via the vasoactive drug infusion technique.
Results: Based on BMI and WC values, patients with metabolic syndrome were classified as obese (MSO, n=16, BMI: 33.7±0.7 Kg/m2 and WC: 109.2±1.3 cm, means±SEM) and lean (MSL, n=9, BMI: 26.2±0.7 Kg/m2 and WC: 96.3±0.7 cm). With the exception of HOMA index, significantly greater in MSO than in MSL (5.1±0.3 vs 3.9±0.3, p<0,05) metabolic syndrome (including blood pressure) were altered to a similar extent in the 2 groups who also showed superimposable age. Both MSO and MSL displayed MSNA values significantly greater than C (62.4±1.5 and 52.8±1.7 vs. 39.7±1.2 bs/100hb, p±4 and −29.5±6 %, p±7 and −46.2±8%, p<0,05 to baroreceptor manipulation (MSL: − 26.6±5 and −39.4±7 %, MSO: −39.8±8 and −51.1±6 %, p<0,05.
Conclusions: These data provide the first evidence that the sympathetic activation and the baroreflex impairment characterising metabolic syndrome are independent on the presence of obesity. They also show that the obese state exerts potentiating effects on the sympathetic alterations seen in the metabolic syndrome, presumably because of the greater autonomic (baroreflex impairment) and metabolic (insulin resistance) alterations seen when the obese state and the metabolic syndrome are combined together.
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Seravalle, G.L., Dell’Oro, R., Arenare, F. et al. 7.1 Metabolic Syndrome is Characterised by Sympathetic Activation Independently on the Obese State. High Blood Press Cardiovasc Prev 14, 145 (2007). https://doi.org/10.2165/00151642-200714030-00123