Muscle sympathetic nerve activity and hemodynamic alterations in middle-aged obese women

Abstract

To study the relationship between the sympathetic nerve activity and hemodynamic alterations in obesity, we simultaneously measured muscle sympathetic nerve activity (MSNA), blood pressure, and forearm blood flow (FBF) in obese and lean individuals. Fifteen normotensive obese women (BMI = 32.5 ± 0.5 kg/m 2 ) and 11 agematched normotensive lean women (BMI = 22.7 ± 1.0 kg/m 2 ) were studied. MSNA was evaluated directly from the peroneal nerve by microneurography, FBF was measured by venous occlusion plethysmography, and blood pressure was measured noninvasively by an autonomic blood pressure cuff. MSNA was significantly increased in obese women when compared with lean control women. Forearm vascular resistance and blood pressure were significantly higher in obese women than in lean women. FBF was significantly lower in obese women. BMI was directly and significantly correlated with MSNA, blood pressure, and forearm vascular resistance levels, but inversely and significantly correlated with FBF levels. Obesity increases sympathetic nerve activity and muscle vascular resistance, and reduces muscle blood flow. These alterations, taken together, may explain the higher blood pressure levels in obese women when compared with lean age-matched women. Obesity is associated with hypertension, diabetes and dyslipidemia, and, in consequence, cardiovascular disease (1-4). In obese individuals, the hyperinsulinemia provoked by insulin resistance increases sympathetic nerve activity, which seems to link obesity to high blood pressure. Interesting, however, is the fact that not all obese individuals are hypertensive. The hypertensive effect of obesity is lower in Pima Indians, Hispanic Americans and African Americans than it is in Whites (5,6). Besides, even among Whites, not all obese individuals are hypertensive. Therefore, it is likely that the levels of blood pressure may be related to the etiology of obesity and/or the genetic mechanisms of obesity (7,8).It has been described that obese individuals have vascular dysfunction. The peripheral blood flow (9) and the vasodilatory re-

Vitamina C restaura pressão arterial e a resposta vasodilatadora no antebraço em crianças obesas

“…Additionally, we found that vasodilation during mental stress is markedly decreased in obese children. This finding corroborates previous findings, whose vasodilator response during reactive hyperemia or isometric exercise is reduced in obese children 7,19 . These changes are worrisome, since it is already known that endothelial dysfunction of blood vessels in childhood obesity is an early event for atherogenesis and for the formation of markers of arterial injury, which precedes the formation of platelets 19,20 .…”

“…We believe that increased blood pressure response during mental stress in obese children may be due to abnormal neurovascular control, since the existence of sympathetic overactivity, baroreflex dysfunction and muscular vasodilator dysfunction is already known 11,17 . In obese adults, sympathetic activation has been considered responsible for the increased peripheral vascular resistance and muscle as a result of pressure pressure 7 . Another possibility to explain an increased blood pressure could be by way of change in cardiac output.…”

“…Obese people present baroreflex dysfunction 4 , increased peripheral vascular resistance 5 , high oxidative stress 6 , as well as increased cardiac and muscular sympathetic activity 7,8 . These changes may lead to increased levels of blood pressure and decreased blood flow to muscles.…”

Sympathetic Vascular Tone in Human Obesity

“…Also, elevated mSNA coincides with increased vascular resistance in the forearm circulation of middle-aged obese women [Ribeiro et al, 2001]. However, the contribution of vascular α 1/2 -adrenergic receptors activation to increased vascular resistance has not been assessed in this study.…”

Respostas autonômicas cardíacas à manobra de tilt em adolescentes obesos

“…Indivíduos obesos têm atividade nervosa simpá-tica para o coração e vasos sangüíneos aumentada, hipersensibilidade quimiorreflexa e diminuição no controle barorreflexo arterial [1][2][3][4] . Esta constelação de alterações autonômicas contribui, também, para a disfunção vascular em obesos 5 6 , em que esses autores mostram que a obesidade provoca alterações na resposta vasodilatadora muscular durante o estresse mental e o exercício físico, em crianças de 8 a 12 anos, antecipando possíveis disfunções vasculares na idade adulta.…”